COMBINED LASER TREATMENT OF A SOLID BODY TO BE SPLIT

Abstract

The invention relates to a method for detaching at least one solid body layer (14) from a solid body (1), wherein by means of the modifications (2) a crack guiding region (4) is provided for guiding a crack in order to detach a solid body portion (6), in particular a solid body layer, from the solid body (1). The invention preferably comprises at least the steps: moving the solid body (1) relative to a laser application device (8), successively producing laser beams (10) by means of the laser application device (8) in order to produce respectively at least one modification (2), wherein the laser application device (8) is adjusted for defined production of modifications depending on at least one parameter, in particular the transmission of the solid body at defined locations and for a defined solid body depth, wherein inhomogeneities of the solid body (1) in the region of the affected surface and/or in the region of the affected volume of the solid body (1) can be compensated for by the adjustment of the laser application device (8), detaching the solid body layer (14) from the solid body (1).

Claims

1. A method for detaching at least one solid body layer (14) from a solid body (1), wherein by means of the modifications (2) a crack guiding region (4) is provided for guiding a crack in order to detach a solid body portion (6), in particular a solid body layer, from the solid body (1), comprising at least the steps: moving the solid body (1) relative to a laser application device (8), successively producing laser beams (10) by means of the laser application device (8) in order to produce respectively at least one modification (2), wherein the laser application device (8) is adjusted for the defined production of modifications depending on at least one parameter, in particular the transmission of the solid body at defined locations and for a defined solid body depth, wherein inhomogeneities of the solid body in the region of the affected surface and/or in the region of the affected volume of the solid body are compensated by the adjustment of the laser application device (8), detaching the solid body layer (14) from the solid body (1).

2. The method according to claim 1, characterized in that data relating to the parameter or to a plurality of parameters are provided in a data storage device and are supplied to a control device at least before generating the modifications (2), wherein the control device adjusts the laser application device (8) depending on the respective location of the modification (2) to be produced and/or the laser beams (10) for generating modifications (2) have more energy in regions with low transmission than in regions with high transmission, wherein the laser application device (8) comprises a means, in particular an acousto-optic modulator for adjusting the laser beam energy.

3. The method according to one of the preceding claims, characterized in that the solid body layer (14) is detached from the solid body (1) along the crack guiding region (4) as a result of the production of modifications or the solid body (1) is acted upon thermally, in particular cooled, after the production of modifications and as a result of the thermal action the solid body layer (14) is detached from the solid body (1) along the crack guiding region (4) or a stress generating layer (18) in particular a polymer layer, is arranged or produced on the solid body (1), wherein the polymer layer is preferably arranged or produced on a surface of the solid body layer (14) to be detached, wherein the polymer layer is acted upon thermally, in particular cooled, wherein the polymer layer undergoes a change in its strength in response to the thermal action, with the result that as a result of the change in strength of the polymer layer, mechanical stresses are obtained in the solid body (1), wherein the mechanical stresses bring about a crack propagation along the crack guiding region in order to detach the solid body layer (14) from the solid body (1).

4. A method for producing at least one solid body layer (14) which is domed or curved at least in sections, at least comprising the steps: moving the solid body (1) relative to the laser application device (8), successively producing laser beams by means of the laser application device (8) in order to produce respectively at least one modification (2) inside the solid body, wherein as a result of the modifications (2) a crack guiding region (4) is provided for guiding a crack in order to detach a solid body portion (14), in particular a solid body layer, from the solid body (1), wherein the modifications bring about a pressure rise in the solid body (1), wherein the solid body layer (14) is detached from the solid body (1) due to the propagation of a crack as a result of the pressure rise along the crack guiding region (4), wherein at least a portion of the modifications (2) as part of the solid body layer (14) is separated from the solid body (1), wherein the solid body layer (14) is converted into a curved or domed shape as a result of the modifications (2), wherein the further surface portion of the solid body layer (14) resulting from the crack guiding region (4) is therefore convexly shaped at least in sections.

5. The method according to claim 4, characterized in that the laser beams (10) penetrate into the solid body (1) in the longitudinal direction of the solid body (1) or inclined at an angle of up to 60 with respect to the longitudinal direction (L) of the solid body (1) over an, in particular flat, surface which is preferably part of the solid body layer (14) and the crack guiding region (4) is formed from several layers of modifications (2), wherein the layers are produced spaced apart from one another or offset in the longitudinal direction (L), and/or at least a plurality of the modifications (2) have an extension in the longitudinal direction (L) which is between 1 and 50 m and/or the laser beams (10) for producing the modifications (2) are introduced into the solid body (1) in such a manner than the numerical aperture is less than 0.8.

6. A method for detaching at least one solid body layer (14), in particular a solid body wafer (14) from a solid body or donor substrate (1), at least comprising the steps: providing a solid body (1), producing modifications (2) inside the solid body (1) by means of laser beams (10), wherein as a result of the modifications (2) a crack guiding region (4) is predefined along which the solid body layer (14) is detached from the solid body (1), removing material of the solid body (1), in particular to produce a circumferential recess (12), wherein the removal of material takes place in the longitudinal direction of the solid body, wherein the crack guiding region (4) is exposed as a result of the removal of material, detaching the solid body layer (14) from the solid body, wherein the solid body is weakened by the modifications in the crack guiding region (4) in such a manner that the solid body layer (1) becomes detached from the solid body (1) as a result of the removal of material, or after the removal of material such a number of modifications is produced that the solid body is weakened in the crack guiding region in such a manner that the solid body layer (1) becomes detached from the solid body (1) or a stress generating layer (18) is produced or arranged on an in particular flat surface (16) of the solid body (1) aligned at an inclination to the circumferential surface and as a result of a thermal action on the solid body layer (14), mechanical stresses are generated in the solid body (1), wherein a crack for detaching a solid body layer (14) is produced as a result of the mechanical stresses, which crack propagates along the modifications (2) starting from the surface of the solid body exposed by the removal of material or the solid body is acted upon thermally, in particular cooled after the production of the modifications and as a result of the thermal action, the solid body layer (14) is detached from the solid body (1) along the crack guiding region (4).

7. The method according to claim 6, characterized in that the removal of material takes place starting from an exposed, in particular flat surface of the solid body (1), in particular parallel to the circumferential surface of the solid body (1), in the longitudinal direction (L) of the solid body (1) and spaced apart from the circumferential surface of the solid body (1) at least in sections and/or the removal of material takes place in the form of a trench (26) running continuously at least in sections, wherein the trench (26) is spaced apart from the circumferential surface preferably by at least 30 m or at least 100 m or at least 500 m or at least 1 mm.

8. The method according to one of claims 6 to 7, characterized in that after detachment of the solid body layer (14), at least the solid body portion (28) of the solid body (1) formed between the trench (26) and the circumferential surface, is removed at least in sections, in particular by the thickness of the previously detached solid body layer (14) or solid body layers (14), in particular is ground, lapped, etched or polished and/or the removal of material is brought about by means of laser ablation or water jet cutting or etching.

9. A method for detaching at least one solid body layer, in particular a solid body wafer (14) from a solid body or donor substrate (1), at least comprising the steps: providing a solid body (1), adjusting a flow behaviour of a gas, in particular air located between the solid body and the laser application device (8), in particular in the region of the radiation course, in order to prevent accumulations of dust in the region of the laser radiation, producing modifications (2) inside the solid body (1) by means of laser beams (10) of a laser application device (8), wherein a detachment region or crack guiding region is predefined by the modifications (2) along which a detachment of the solid body layer (14) from the solid body (1) takes place, detaching the solid body layer (14) from the solid body (1), wherein the solid body (1) is weakened by the modifications (2) in the crack guiding region (4) in such a manner that the solid body layer (14) is detached from the solid body (1) as a result of the removal of material or after the removal of material such a number of modifications is produced that the solid body is weakened in the crack guiding region in such a manner that the solid body layer (14) becomes detached from the solid body (1) or a stress generating layer (18) is produced or arranged on an in particular flat surface (16) of the solid body (1) aligned at an inclination to the circumferential surface and as a result of a thermal action on the solid body layer (14), mechanical stresses are generated in the solid body (1), wherein a crack for detaching a solid body layer (14) is produced as a result of the mechanical stresses, which crack propagates along the modifications (2) starting from the surface of the solid body exposed by the removal of material or the solid body (1) is acted upon thermally, in particular cooled after the production of the modifications and as a result of the thermal action, the solid body layer (14) is detached from the solid body (1) along the crack guiding region (4).

10. The method according to claim 9, characterized in that the adjustment of the flow behaviour is made by supplying a fluid, in particular ionized gas, in the region of the beam course between an objective and the solid body (1) or the adjustment of the flow behaviour is made by producing a negative pressure, in particular a vacuum in the region of the beam course between an objective and the solid body (1).

11. A method for detaching at least one solid body layer (14), in particular a solid body wafer (14) from a solid body or donor substrate (1), at least comprising the steps: providing a solid body (1), wherein the solid body (1) has at least one coating (34) whose refractive index is different from the refractive index of the surface of the solid body (1) on which the coating (34) is arranged, or wherein a coating (34) is produced on the solid body (1) whose refractive index is different from the refractive index of the surface of the solid body (1) on which the coating (34) is arranged, producing modifications (2) inside the solid body (1) by means of laser beams (10) of a laser application device (8), wherein a crack guiding region is predefined by the modifications (2) along which a detachment of the solid body layer (14) from the solid body (1) is accomplished.

12. The method according to claim 11, characterized in that the coating (34) will be or is produced by means of spin coating, wherein the coating (34) comprises nanoparticles, in particular of at least one material selected from the list at least consisting of silicon, silicon carbide, titanium oxide, glass, in particular quartz glass or Al.sub.2O.sub.3 and/or a plurality of coatings (34) are arranged or produced above one another, wherein the refractive indices differ from one another, preferably a first coating which is arranged or produced on the solid body (1) has a larger refractive index than an additional coating which is produced on the first coating.

13. A method for detaching at least one solid body layer (14), in particular a solid body wafer (14) from a solid body or donor substrate (1), at least comprising the steps: providing a solid body (1), producing modifications (2) inside the solid body (1) by means of laser beams (10) of a laser application device (8), wherein a crack guiding region is predefined by the modifications (2) along which a detachment of the solid body layer (14) from the solid body (1) is accomplished, wherein the laser radiation is incident on the solid body at the Brewster angle or with a deviation in the range from 5 to +5 from the Brewster angle, detaching the solid body layer from the solid body, wherein the solid body is weakened in the crack guiding region (4) as a result of the modifications (2) in such a manner than the solid body layer (14) is detached from the solid body (1) as a result of the removal of material or after the removal of material such a number of modifications (2) is produced that the solid body is weakened in the crack guiding region in such a manner that the solid body layer (14) is detached from the solid body (1) or a stress generating layer (18) is produced or arranged on an in particular flat surface (16) of the solid body (1) aligned at an inclination to the circumferential surface and as a result of a thermal action on the solid body layer (14), mechanical stresses are generated in the solid (1), wherein a crack for detaching a solid body layer (14) is produced as a result of the mechanical stresses, which crack propagates along the modifications (2) starting from the surface of the solid body exposed by the removal of material or the solid body is acted upon thermally, in particular cooled after the production of the modifications and as a result of the thermal action, the solid body layer (14) is detached from the solid body (1) along the crack guiding region (4).

14. The method according to claim 13, characterized in that a compensating device, in particular an optical element such as a diffractive optical element or a continuous wedge is provided to compensate for a spherical aberration in the laser application device (8) resulting from the Brewster angle irradiation.

15. A method for detaching at least one solid body layer (14) from a solid body (1), wherein due to modifications (2) a crack guiding region (4) is predefined for guiding a crack for detaching a solid body portion (6), in particular a solid body layer, from the solid body (1), at least comprising the steps: moving the solid body (1) relative to a laser application device (8), successively producing laser beams (10) by means of the laser application device (8) to produce respectively at least one modification (2), detaching the solid body layer (14) from the solid body (1).

16. The method according to claim 15, characterized in that wherein the laser application device (8) is adjusted for the defined generation of modifications depending on at least one parameter, namely the transmission of the solid body (1) at defined points and for a defined solid body depth and/or wherein the modifications (2) bring about a pressure rise in the solid body (1), wherein the solid body layer (14) is detached from the solid body (1) as a result of the pressure rise along the crack guiding region due to a crack propagation, wherein at least one portion of the modifications (2) as part of the solid body layer (14) is detached from the solid body (1) and wherein the solid body layer (14) is preferably converted into a curved or domed form as a result of the modifications (2), wherein the further surface portion of the solid body layer (14) resulting from the crack guiding region (4) is therefore convexly shaped at least in sections and/or wherein the solid body (1) has at least one coating (34) whose refractive index is different from the refractive index of the surface of the solid (1) on which the coating (34) is arranged or wherein a coating (34) is produced on the solid (1), whose refractive index is different from the refractive index of the surface of the solid (1) on which the coating (34) is arranged and/or wherein the laser radiation is incident on the solid body (1) at the Brewster angle or with a deviation in the range from 10 to +10 from the Brewster angle, comprising one or more of the steps: removing material of the solid body (1), in particular to produce a circumferential recess (12), wherein the material is removed in the longitudinal direction of the solid body (1), wherein the crack guiding region (4) is exposed as a result of the removal of material or adjusting a flow behaviour of a gas, in particular air, located between the solid body (1) and the laser application device (8), in particular in the region of the radiation course, to prevent accumulations of dust in the region of the laser radiation (10).

17. The method according to claim 16 or claims 1 to 9, characterized in that a parameter is the degree of doping of the solid body at a predetermined location or in a predetermined region, in particular inside the solid body, in particular at a distance from the solid body surface, wherein the degree of doping is preferably determined by the analysis of back-scattered light having an inelastic scattering (Raman scattering), wherein the back-scattered light has a different wavelength or a different wavelength range from emitted light defined for triggering the back-scattering, wherein the back-scattered light is back-scattered from the predefined location or from the predefined region or wherein the degree of doping is preferably determined by means of an eddy current measurement, wherein conductivity differences in the solid body material are determined.

18. The method according to one of claims 16 to 17 or according to one of claims 1 to 9, further comprising the step: producing a composite structure by arranging or producing layers and/or components (150) on or above an initially exposed surface of the solid body (1), wherein the exposed surface is part of the solid body layer to be detached, wherein the modifications are produced to form the detachment plane before producing the composite structure.

19. The method according to claim 18, characterized in that before producing the detachment plane the solid body (1) is treated using at least one high-temperature method, wherein the high-temperature method is executed with a temperature between 70 C. and the melting point or evaporation temperature of the material of the solid body (1), wherein the at least one high-temperature method is an epitaxy method, a doping method or a method using plasma, wherein at least one layer (145) is produced on the solid body (1) by the high-temperature method, wherein the at least one generated layer (145) has predefined parameters, wherein at least one predefined parameter specifies a maximum degree of refraction and/or absorption and/or reflection of laser light waves, wherein the degree of refraction and/or absorption and/or reflection is less than 5% and preferably less than 1% and particularly preferably less than 0.1%.

20. The method according to one of the preceding claims, characterized in that the modifications are produced by means of multiphoton excitation, wherein initially at least a plurality of base modifications are produced on an in particular curved line, running homogeneously at least in sections, in particular in the homogeneously running section, wherein these base modifications are produced with predefined process parameters, wherein the predefined process parameters preferably comprise the energy per shot and/or the shot density, wherein at least one value of these process parameters and preferably both values or all the values of these process parameters or more than two values of these process parameters is specified depending on the crystal lattice stability of the solid body, wherein the value is selected so that the crystal lattice remains intact around the respective base modifications, wherein further trigger modifications are produced to trigger subcritical cracks, wherein at least one process parameter for generating trigger modifications is different from at least one process parameter for generating base modifications, preferably a plurality of process parameters are different from one another and/or the trigger modifications are produced in a direction which is inclined to or spaced apart from the course direction of the line along which the base modifications are generated, wherein the subcritical cracks propagate less than 5 mm.

21. The method according to one of the preceding claims, characterized in that the solid body material is silicon, wherein the numerical aperture lies between 0.5 and 0.8, in particular 0.65, the irradiation depth is between 200 m and 400 m, in particular 300 m, the pulse spacing is between 1 m and 5 m, in particular 2 m, the line spacing is between 1 m and 5 m, in particular 2 m, the pulse duration is between 50 ns and 400 ns, in particular 300 ns and the pulse energy is between 5 J and 15 J, in particular 10 J or the solid body material is SiC, wherein the numerical aperture lies between 0.5 and 0.8, in particular 0.4, the irradiation depth is between 100 m and 300 m, in particular 180 m, the pulse spacing is between 0.1 m and 3 m, in particular 1 m, the line spacing is between 20 m and 100 m, in particular 75 m, the pulse duration is between 1 ns and 10 ns, in particular 3 ns and the pulse energy is between 3 J and 15 J, in particular 7 J.

22. The method according to one of claim 20 or 21, characterized in that the subcritical cracks propagate between 5 m and 200 m, in particular between 10 m and 100 m or between 10 m and 50 m or between 10 m and 30 m or between 20 m and 100 m or between 20 m and 50 m or between 20 m and 30 m in the solid and/or tear sections between the regions of several lines in which the subcritical cracks have propagated as a result of the stresses that are produced by the glass transition.

Description

[0154] In the figures as an example:

[0155] FIG. 1 shows schematically the compensation for material properties by adaptation of the laser action depending on local property differences of the material;

[0156] FIG. 2a shows schematically the production of a modification, which is sufficient to guide a crack;

[0157] FIG. 2b shows schematically the production of a modification, which has a significantly stronger extension in the longitudinal direction of the solid body compared with the modification from FIG. 2a and after splitting of the solid body layer has the result that the solid body layer curves or bends;

[0158] FIG. 3 shows schematically the production of a trench in a solid body wherein the trench is preferably spaced apart from the outer circumferential surface of the solid body;

[0159] FIG. 4a shows schematically an arrangement in which particles such as, for example, dust collect in the course of the laser radiation, in particular at the point of intersection of the reflected beams;

[0160] FIG. 4b shows schematically an arrangement in which a flushing, in particular by means of gas such as for example ionized gas is provided, which removes particles from the point of intersection of the reflected beams;

[0161] FIG. 5 shows schematically an arrangement according to which one or more coatings are arranged on the solid body, wherein the coating/s preferably has or have at least one different optical property from the solid body;

[0162] FIG. 6a shows schematically the emission of laser beams at the Brewster angle;

[0163] FIG. 6b shows profiles to illustrate the relationship between angle of incidence and reflection;

[0164] FIGS. 7-18 each show examples for calculation of the optimal angle of incidence for a 1/e.sup.2 Gaussian profile and different numerical apertures taking into account the refractive index dependence of the surface reflection;

[0165] FIG. 19a shows schematically the progress of the cold split method;

[0166] FIG. 19b shows schematically the progress of the laser assisted spalling method;

[0167] FIG. 19c shows a photograph of an exposed surface of a solid body layer according to the method 19a;

[0168] FIG. 19d shows a photograph of an exposed surface of a solid body layer according to the method 19b;

[0169] FIGS. 20a-f SEM photographs of surfaces;

[0170] FIG. 21a shows a microscope photograph of a surface after spalling;

[0171] FIG. 21b shows Raman spectra of three different positions in 6H-silicon carbide;

[0172] FIG. 22 shows an example for a laser beam profile; and

[0173] FIG. 23a shows schematically an example for the bending of the solid body layer produced as a result of a first number of modifications and/or modification layers; and

[0174] FIG. 23b shows schematically a further example for the bending of the solid body layer produced as a result of a second number of modifications and/or modification layers, wherein the second number is greater than the first number

[0175] and

[0176] FIG. 24a shows a schematic structure of a Raman instrument as is preferably used according to the invention, in particular as is preferably part of the apparatus according to the invention;

[0177] FIG. 24b shows various exemplary vibration states of the lattice vibrations of SiC,

[0178] FIGS. 25a and 25b show two diagrams which show doping concentrations in a solid;

[0179] FIG. 26a shows a feed forward process according to the invention and

[0180] FIG. 26b shows a feedback process according to the invention.

[0181] FIG. 1 shows schematically a structure for executing a method for detaching at least one solid body layer 14 from a solid body 1. Due to the modifications 2 a crack-guiding region 4 for guiding a crack for detaching a solid body portion 14, in particular a solid body layer, from the solid body 1 is predefined. Since the laser beams 10, 11 are shown at various locations of the solid body 1, it is apparent that the solid body 1 is moved relative to a laser application device 8. The laser beams 10 and 11 shows thus represent situations at different times. In principle, the laser beams 10 are produced by means of the laser application device 8 to produce respectively at least one modification 2, wherein the laser application device 8 is adjusted for the defined production of modifications depending on at least one parameter, namely the transmission of the solid body 1 at defined locations and for a defined solid body depth. In the diagram according to FIG. 1 the laser beams 10, 11 thus represent laser beams having different properties or having at least one different property. The property changed from laser beam 10 to laser beam 11 takes account of the changed material properties in the respective affected region of the solid body 1. In the case shown for example, the laser beam 11 acts on a region of the solid body 1, which has a changed transmission, which for example can result from a doping spot.

[0182] Preferably after the modifications 2 have been produced the solid body layer 14 is detached from the solid body 1 according to the diagram in FIG. 19b.

[0183] FIG. 2a shows a situation in which modifications 2 having a first extension are produced in the longitudinal direction L of the solid body 1. The longitudinal extension L here preferably extends orthogonally or substantially orthogonally to the irradiated surface 17 of the solid body, wherein the irradiated surface 17 of the solid body 1 is part of the solid body layer 14 after detachment of the solid body layer 14. This particularly preferably relates to all the embodiments described in this step. The modifications 2 produced according to FIG. 2a are sufficient for guiding a crack for detaching the solid body layer 14.

[0184] FIG. 2b shows a modification according to which the modifications 2 produced have a greater extension in the longitudinal direction L compared with FIG. 2a. Additionally or alternatively, a plurality of, in particular two or three or more than two or three layers of modifications 2 can be produced at least in sections.

[0185] This is advantageous since as a result of a larger than necessary extension of the laser layer in the beam direction (depth or solid body length) the stress produced by the laser layer in the unmodified material can be increased. Thus, preferably more material can make a phase transformation or be amorphized or modified in another way than is necessary for the polymer split (cf. FIG. 19b). This increased stress serves to promote the spontaneous splitting of the material (without polymer). The laser parameters or laser beam parameters or parameters with which the laser application device is configuredfor the spontaneous splitting and the polymer processcan differ appreciably as a result. A greater extension of the laser layer here results in a higher pressure in the solid body with the result that the spontaneous splitting probability is increased. Furthermore, this embodiment is advantageous since a solid body layer 14 can be produced as a bent or curved solid body layer 14. Thus, this method can preferably also be used for producing at least one solid body layer 14 which is curved or bent at least in sections. In order to produce a curved or bent solid body layer (or bent or curved wafer), the method here preferably comprises at least the steps: moving the solid body 1 relative to the laser application device 8, successively producing laser beams 10 by means of the laser application device 8 in order to produce respectively at least one modification 2 inside the solid body, wherein as a result of the modifications 2 a crack guiding region 4 is provided for guiding a crack in order to detach a solid body portion 14, in particular a solid body layer, from the solid body 1, wherein the modifications bring about a pressure rise in the solid body 1, wherein the solid body layer 14 is detached from the solid body 1 due to the propagation of a crack as a result of the pressure rise along the crack guiding region 4, wherein at least a portion of the modifications 2 as part of the solid body layer 14 is separated from the solid body 1, wherein the solid body layer 14 is converted into a curved or domed shape as a result of the modifications 2, wherein the further surface portion of the solid body layer 14 resulting from the crack guiding region 4 is therefore convexly shaped at least in sections.

[0186] FIG. 3 shows an arrangement according to which preferably after a crack guiding region 4 has been produced in the solid body 1, a trench 26 is produced at least in sections and preferably circumferentially starting from the irradiated surface 17 in the longitudinal direction L of the solid body 1. After producing the trench 26, the solid body layer 14 can be detached from the solid body by producing further modifications 2 by means of laser beams 10, which are preferably also introduced via the irradiated surface 17. Alternatively a stress generating layer 18 is preferably arranged or produced on the region enclosed or surrounded or delimited by the trench 26, in particular on the surface of the subsequent solid body layer 14.

[0187] The stress generating layer preferably consists of a polymer material, in particular PDMS and in a further step is acted upon thermally, in particular cooled, in particular below its glass transition temperature at least in sections and particularly preferably completely. This preferably relates to all the embodiments described herein in which a stress generating layer is used or deployed.

[0188] As a result of the stress generation, a crack detaches the solid body layer 14 from the remaining solid body 1.

[0189] Preferably a surface treatment of the solid body 1 takes place in a further step. Preferably the frame 28 obtained between the trench 26 and the circumferential surface and/or the surface of the solid body 1 exposed by the detachment of the solid body layer 14 is smoothed, in particular ground, lapped, polished or etched.

[0190] Preferably the frame 28 and the exposed surface are treated in such a manner, in particular by cutting treatment that the surfaces lie in the same plane.

[0191] Thus, a method for detaching at least one solid body layer, in particular a solid body wafer 14 from a solid body or donor substrate 1 is provided, which preferably comprises at least the steps mentioned hereinafter: providing a solid body 1, producing modifications 2 inside the solid body 1 by means of laser beams 10, wherein as a result of the modifications 2 a detachment region or crack guiding region 4 is predefined along which the solid body layer 14 is detached from the solid body 1, removing material of the solid body 1, in particular to produce a circumferential recess 12, wherein the removal of material takes place in the longitudinal direction of the solid body, wherein the detachment region is exposed as a result of the removal of material, and detaching the solid body layer 14 from the solid body.

[0192] This is advantageous since a laser treatment as far as the edge is problematical and therefore the solid body layer 14 produced also has very homogeneous properties in its edge zone. The basic concept presented here thus preferably comprises a laser ablation/grinding/removal of material from above to produce a notch or a trench, with the result that the previously produced laser layer is opened or exposed. Finally the solid body layer 14 or the target wafer is removed with the stress generating layer 18. The remaining edge or frame 28 can then be ground away again during a further surface preparation. Thus, the laser layer can be exposed and edge effects avoided during the polymer splitting by ablation from above, in particular be water jet cutting or laser ablation.

[0193] FIG. 4a shows an arrangement in which particles such as, for example, dust collect at the point of intersection of the reflected radiation characterized by the reference number 30 and thus negatively influence the production of modifications.

[0194] FIG. 4b shows an arrangement in which a flushing device 32 or flushing is provided. Thus, a fluid, in particular a gas and preferably an ionized gas is thus fed to the intersection point 30 in order to flush away particles collecting at the intersection point 30 by means of the fluid flow.

[0195] Thus, a method for detaching at least one solid body layer, in particular a solid body wafer 14 from a solid body or donor substrate 2 is provided which preferably comprises at least the steps mentioned hereinafter: providing a solid body 1, adjusting a flow behaviour of a gas, in particular air located between the solid body and the laser application device 8, in particular in the region of the radiation course, in order to prevent accumulations of dust in the region of the laser radiation, producing modifications 2 inside the solid body 1 by means of laser beams 10 of a laser application device 8, wherein a detachment region or crack guiding region is predefined by the modifications 2 along which a detachment of the solid body layer 14 from the solid body 1 takes place and detaching the solid body layer 14 from the solid body 1. This solution is advantageous since high laser intensities statically charge dust and this dust can be flushed out by the flushing, in particular with ionized gas, from the region between the objective and the workpiece. The gas flushing thus drives the dust out from the intermediate space between the objective 9 of the laser application device 8 and the workpiece or solid body 1. Additionally or alternatively the fluid flow, in particular the gas flow can be guided through the objective to produce a cooling effect towards absorbed power. Thus, the objective is preferably configured to guide a fluid, in particular the flushing fluid.

[0196] Furthermore or addition, a compensation of spherical aberrations at the objective can be accomplished. This changes the focus on the surface (incorporation of the material which has been passed through with a different refractive index), with the result that the focus in air deteriorates and thus has a lower intensity which in turn results in a lower particle suction effect or dust suction effect. Additionally or alternatively reduced reflection at the surface can be brought about. This can be brought about, for example by application of specific layers or coatings, in particular by spin coating, and/or by Brewster irradiation with polarized light.

[0197] FIG. 5 shows a schematic arrangement according to which the solid body 1 is provided with at least one coating 34. The coating 34 here can be single- or multilayer. Preferably the coating has a refractive index difference from the refractive index of the material of the solid body 1, in particular the refractive index of the material of the solid body 1 is preferably higher than that of the coating 34. It is also feasible that the coating 34 is constructed of several layers, wherein preferably two of the several layers have a refractive index difference. Preferably here the refractive index of the respective layer, which is arranged closest to the solid body is greater than the refractive index of a layer which is spaced further apart from the solid body 1.

[0198] This schematic structure therefore makes it possible to provide a method according to the invention for detaching at least one solid body layer, in particular a solid body wafer 14 from a solid body or donor substrate 1. Preferably this method here comprises at least the steps mentioned hereinafter: providing a solid body 1, wherein the solid body 1 has at least one coating 34 whose refractive index is different from the refractive index of the surface of the solid body 1 on which the coating 34 is arranged, or wherein a coating 34 is produced on the solid body 1 whose refractive index is different from the refractive index of the surface of the solid body 1 on which the coating 34 is arranged, producing modifications 2 inside the solid body 1 by means of laser beams 10 of a laser application device 8, wherein a crack guiding region 4 (cf. similarly FIG. 1) is predefined by the modifications 2 along which a detachment of the solid body layer 14 from the solid body 1 is accomplished.

[0199] The coating can be accomplished, for example, by means of spin coating. Thus, for example a solvent, mixed nanoparticles of materials having a high refractive index applies one or more thin (sub-wavelength) layers having a somewhat higher refractive index to the solid body 1 or the workpiece 1this results in an intermediate surface having reduced refractive index difference, lower reflection at the surface, lower contamination, more power in the material for more efficient material processing. Spin coating is advantageous since it is fast and favourable, cheap and fast, possible nanoparticles along with others or in addition to others are, for example silicon (n=3.55), silicon carb ide (n=2.6), titanium oxide (n=1.8), glass (n=1.5), Al.sub.2O.sub.3 (n=1.72). In the case of several layers with gradually increasing refractive index, a multilayer process is feasible for even more efficient refractive index matching and antireflection effect. Purely as an example, a layer arrangement could then be produced which consists of the layers mentioned hereinafter: 1st layer: Si, 2nd layer: SiC, 3rd layer: TiO.sub.2, each layer preferably 50-400 nanometres thick. This method is furthermore advantageous since by means of spin coating of such layers, extremely small roughnesses on the material surface can also be compensated (better material coupling-in), by less scattering at the interface, better wavefront overlapping at the focus in the depth and therefore a lower laser power is required, this results in more effective processing since a higher multiphoton transition probability is obtained. The spin coating layer or the production of a coating 34 can be applied in the course of the step for surface conditioning and re-preparation of the surface on the ingot or solid body 1 after splitting or detachment of the solid body layer 14. Therefore firstly a grinding/lapping/etching or polishing step can be accomplished and then or combined with one of the preceding steps, the spin coating step or the coating step which applies the thin layer or coating 34.

[0200] FIG. 6 shows schematically an arrangement for coupling-in laser beams 10, wherein the reflection is reduced in this arrangement. Preferably the laser beams 10 are coupled in at the Brewster angle. The Brewster angle is an angle of incidence for light of a specific polarization (the E vector points into the material not along the surface) at which no reflection occurs. The requirements for this are that the light is incident at an angle depending on the refractive index difference between air and the material. Furthermore, the light must be polarized (usually given in the case of laser light, requires single-mode lasers and no photonic crystal fibres). Coupling-in at the Brewster angle is therefore used to minimize back reflections. If irradiation takes place at the Brewster angle, the 30% surface reflection can be used almost completely for material processing in the depth of the material.

[0201] Irradiation at the Brewster angle is complex since the different beam components cover paths of different lengths in the highly refracting medium. The focus must be adapted accordingly by higher energy and/or by beam shaping. The beam shaping is preferably accomplished here, for example via one or more diffractive optical element/s (DOE) which compensate for this difference depending on the laser beam profile. The Brewster angle is relatively large, which in the case of high numerical aperture imposes requirements on the optics and their dimensions as well as working distance. Nevertheless this solution is advantageous since reduced reflections at the surface contribute to reduced surface damage since the light intensity is better coupled into the material. In the sense of this invention, laser beams 10 can also be emitted in all the other embodiments disclosed in this document at the Brewster angle or substantially at the Brewster angle. For coupling-in at the Brewster angle reference is herewith made to the document Optical Properties of Spin-Coated TiO2 Antireflection Films on Textured Single-Crystalline Silicon Substrates (Hindawi Publishing Corporation International Journal of Photoenergy, Volume 2015, Article ID 147836, 8 pages, http://dx.doi.org/10.1155/2015/147836). This document is made the subject of the present patent application in its full scope by reference. The aforementioned and included document discloses in particular calculations for the optimal angle of incidence for different materials and therefore refractive indices. The energy of the laser or the laser application device 8 is adapted not so much depending on the material but rather on the possible transmission at a specific angle. If therefore the optimal transmission is, for example, 93%, these losses must then be taken into account compared to experiments with perpendicular irradiation and losses of then, for example 17%, and the laser power adapted accordingly.

[0202] An example: 83% transmission perpendicular compared to 93% at an angle means that in order to achieve the same energy in the depth, only 89% of the laser power used for perpendicular irradiation is required (0.83/0.93=0.89). In the sense of the invention, the portion of the oblique irradiation therefore preferably serves to lose less light due to surface reflection and bring more into the depth. A possible subsequent problem which can occur as a result in certain arrangements is that the focus can acquire a skew profile in the depth and thus the intensities achievedthe key quantity for multiphoton processingare again lower, possibly even lower than in the case of perpendicular irradiation, where all the beam components cover the same optical path in the material. This can then preferably be accomplished by a diffractive optical element or by several diffractive elements or a continuous wedge or several continuous wedgesand/or other optical elementsin the beam path, which compensate for these additional paths and/or the influence on the individual beamsin particular different spherical aberrations over the beam profile. These DOEs can be calculated numerically using suitable software solutions (e.g. Virtuallab from Lighttrans, Jena) and then fabricated or prepared.

[0203] The present invention thus provides a method for detaching at least one solid body layer, in particular a solid body wafer 14 from a solid body or donor substrate 1. The method according to the invention here preferably comprises at least the steps: providing a solid body 1, producing modifications 2 inside the solid body 1 by means of laser beams 10 of a laser application device 8, wherein a crack guiding region is predefined by the modifications 2 along which a detachment of the solid body layer 14 from the solid body 1 is accomplished, wherein the laser radiation is incident on the solid body 1 at the Brewster angle or with a deviation in the range from 10 to +10 from the Brewster angle. The method further comprises the step of detaching the solid body layer 14 from the solid body 1.

[0204] It was thus identified in the course of the present invention that a high refractive index difference between air/material means power losses of up to 30% with perpendicular irradiation. In the case of a 100 W laser, therefore 30 W is not available for the material processing or has other effects. Thus, it was further identified, for example, that contaminants can be formed on the optics, such as for example in the case of so-called optical pincers. In this case, extremely small particles both in air and in liquids always migrate to the focus of the laser beam (highest intensity)reflected power at the surface has the focus in the air or near the optics, the dust is driven/drawn to the optics. It was further identified that at the same time at 100 MW laser power and 97% transmission at the objective, significant heat (3 W) can enter into the objective, which must be removed/compensated to avoid thermal damage/modifications to the process. It was further identified that high powers bring with it the risk of surface damage. This is because the absorption of material can be increased due to surface states on the surface, extremely small dust particles can therefore only burn in the laser beam 10 and then form absorption nuclei which can then result in further damage due to absorption. It was further identified that high powers are distributed to several foci in the focal plane with diffractive optical elements (DOEs). DOEs show interference effects even before the focal plane, and it was identified that interference on the surface before the focal plane can produce local interference maxima which can result in damage to the surface and can result in a reduced transmissivity for laser radiation for processing in the depth. Furthermore, it was identified that some materials (for example: SiC) have local refractive index and other material property differences (e.g. absorption, transmission, scattering) e.g. due to the material doping (frequent occurrence: doping spot). It was further identified that depending on the surface roughness of the material on the laser coupling-in surface, the wavefront of the laser can be significantly impaired in the depth of the material so that the focus has reduced intensity (lower multiphoton transition probability) which in turn would involve higher intensities with the aforesaid problems.

[0205] Individual, several or all of these problems can be treated by individual ones or combinations of the methods disclosed here. Thus, the present invention can preferably be understood as a method for detaching at least one solid body layer from a solid body, wherein in this method by means of the modifications 2 a crack guiding region 4 is preferably provided for guiding a crack in order to detach a solid body portion 6, in particular a solid body layer, from the solid body 1. The method according to the invention preferably comprises at least the steps: moving the solid body 1 relative to a laser application device 8, successively producing laser beams 10 by means of the laser application device 8 in order to produce respectively at least one modification 2, detaching the solid body layer from the solid body.

[0206] According to the invention, a spalling process is thus described which in particular scales favourably for large-area semiconductor substrates having a diameter up to 300 mm or more than 300 mm. In order to eliminate the Wallner line pattern, a laser conditioning process is used, in particular with a high numerical aperture, with photon energies preferably below the material band gap energy. This process results in multiphoton interactions in the material and after the spalling process delivers a surface roughness of preferably Ra <1 m.

[0207] Preferably individual one or several of the aforesaid solutions according to the invention can be combined since as a result an even better solid body layer manufacture or solid body layer detachment can be brought about. Thus, according to the method according to the invention, the laser application device 8 is adjusted for the defined production of modifications depending on at least one parameter, i.e. the transmission of the solid body at defined points and for a defined solid body depth, and/or the modifications bring about a pressure rise in the solid body, wherein the solid body layer is detached from the solid body as a result of a pressure rise along the crack guiding region due to crack propagation, wherein preferably at least a portion of the modifications is detached from the solid body as part of the solid body layer and wherein the solid body layer is preferably converted into a curved or domed form as a result of the modifications, wherein the further surface portion of the solid body layer 14 resulting from the crack guiding region 4 is therefore convexly shaped at least in sections and/or wherein the solid body 1 has at least one coating 34 whose refractive index is different from the refractive index of the surface of the solid body on which the coating 34 is arranged or a coating 34 is produced on the solid body, whose refractive index is different from the refractive index of the surface of the solid body on which the coating is arranged and/or the laser radiation is incident on the solid body at the Brewster angle or with a deviation in the range from 5 to +5 from the Brewster angle, in particular with a deviation in the range from 4 to +4 or with a deviation in the range from 3 to +3 or with a deviation in the range from 2 to +2 or with a deviation in the range from 1 to +1 from the Brewster angle and/or the method additionally or alternatively comprises one or more of the steps: removing material of the solid body 1, in particular to produce a circumferential recess 12, wherein the material is removed in the longitudinal direction of the solid body, wherein the crack guiding region 4 is exposed as a result of the removal of material or adjusting a flow behaviour of a gas, in particular air, located between the solid body 1 and the laser application device 8, in particular in the region of the radiation course, to prevent accumulations of dust in the region of the laser radiation 10.

[0208] FIGS. 7-18 show examples for calculation of the optimal angle of incidence for a 1/e.sup.2 Gaussian profile and different numerical apertures taking into account the refractive index dependence of the surface reflection.

[0209] FIGS. 7-10 show the profiles when using silicon carbide (n=2.7).

[0210] Aim: to maximize the laser power coupled into the sample, ideally by using the Brewster angle for minimal surface reflection with p-polarized light. Result: for NA=0.8 Brewster coupling-in is not worthwhile (radiation cone couples in externally almost at the Brewster angle), smaller NA can benefit from this, in particular NA=0.2, higher NA have an intermediate ideal angle.

[0211] FIG. 7 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.2 (green), optimal angle of incidence 63.8.

[0212] FIG. 8 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.4 (green), optimal angle of incidence 52.5.

[0213] FIG. 9 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.6 (green), optimal angle of incidence here 35.6.

[0214] FIG. 10 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.8 (green), optimal angle of incidence here 0.

[0215] FIGS. 11-14 show the profiles when using silicon (n=3.6).

[0216] The aim here is to maximize the laser power coupled into the sample, ideally by using the Brewster angle for minimal surface reflection with p-polarized light. Result: for NA=0.8 Brewster coupling-in is not worthwhile (radiation cone couples in externally almost at the Brewster angle), smaller NA can benefit from this, in particular NA=0.2, higher NA have an intermediate ideal angle.

[0217] FIG. 11 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for silicon and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.2 (green), optimal angle of incidence here 67.9.

[0218] FIG. 12 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for silicon and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.4 (green), optimal angle of incidence here 57.4.

[0219] FIG. 13 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for silicon and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.6 (green), optimal angle of incidence here 43.6.

[0220] FIG. 14 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for silicon and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.8 (green), optimal angle of incidence here 0.

[0221] FIGS. 15-18 show the profiles when using sapphire/ALO (n=1.72).

[0222] The aim here is to maximize the laser power coupled into the sample, ideally by using the Brewster angle for minimal surface reflection with p-polarized light. Result: for NA=0.8 Brewster coupling-in is not worthwhile (radiation cone couples in externally almost at the Brewster angle), smaller NA can benefit from this, in particular NA=0.2, higher NA have an intermediate ideal angle, wherein NA=0.6 requires almost no angle for irradiation.

[0223] FIG. 15 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for ALO and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.2 (green), optimal angle of incidence here 54.9.

[0224] FIG. 16 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for ALO and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.4 (green), optimal angle of incidence here 41.2.

[0225] FIG. 17 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for silicon and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.6 (green), optimal angle of incidence here 14.5.

[0226] FIG. 18 shows in the upper diagram: relative coupled-in power over angle of incidence for a Gaussian profile for ALO and in the lower diagram: reflection coefficient for p-(red) and s-(blue) polarized light and angular Gaussian profile for mapped NA=0.8 (green), optimal angle of incidence here 0.

[0227] FIG. 19a outlines a standard method for laser-free spalling of large-area substrates. The wafer samples, which are usually used have sharp edges to avoid complications due to rounded edges. Rounded edges are used in conventional wafers to prevent the occurrence of cracks at the wafer edges, which can run inwards and then disturb the substrate and fabrication processes on this.

[0228] The process preferably proceeds as follows: after a standard cleaning process the wafers are coated with a primary layer to improve the surface adhesion and a sacrificial layer to improve the polymer-wafer separation at the end. The wafer is then coated with a PDMS (polydimethyl siloxane) polymer film of different thickness and a PDMS adhesivewith platinum polymerization catalyst.

[0229] The samples are then pre-cooled to a temperature just above the polymer glass transition temperature before they are dipped in liquid nitrogen. Depending on the size of the sample, the sample will have reached the temperature of liquid nitrogen up to 20 seconds later. At this time the system is in thermal equilibrium. The semiconductor layers are then separated in a spontaneously occurring spalling event. The spalling method is induced by the polymer glass transition and as a result, the Young's modulus in the polymer increases substantially. The additional difference in coefficients of thermal expansion (CTE) between semiconductor and polymer then induces sufficient stresses to horizontally separate the crystal. It is important that the method requires a relative contraction of the polymer in relation to the semiconductor. The next step is the dipping of the semiconductor parts with fastened PDMS films into a separating bath which finally dissolves the sacrificial layer and thereby enables recycling of the polymer as well as the preparation of the semiconductor wafers for further process steps.

[0230] FIG. 19a therefore shows a diagram of conventional spalling of substrates with an ensemble of preferably two stress layers, i.e. polymer films. The films are fastened to both sides of the substrate, followed by a rapid cooling step in order to induce temperature change stressing followed by crack formation and detachment of the substrate.

[0231] The laser-assisted spalling process shown in FIG. 19b is noticeably similar. The main difference is an additional laser processing step in which a laser beam is focussed on a defined plane or on a defined profile in the sample and then scans the sample. The laser layer produced in this way then defines the crack formation plane and therefore also the separation in the subsequent spalling process.

[0232] FIG. 19b therefore shows the laser-assisted spalling process. In addition to the process steps shown in FIG. 19a, by means of a modification layer produced by means of laser beams or laser system, in a further process step a structurally weakened layer is produced in the material which defines a preferred plane for spalling crack propagation.

[0233] A typical resulting wafer surface from laser-free spalling is shown in FIG. 19c. A pattern of Wallner lines is obtained from the crack propagation inside the material. Grooves can be made out on the surface of the material which reproduce the crack behaviour along the separating plane in the material. Cracks form at the edges of the sample and migrate inwards, with the result that a detailed pattern as in FIG. 19c is formed. The fourfold symmetry of the pattern is a consequence of the fourfold crystal symmetry in the silicon, with a singularity or a centre point of the crack waves in the centre of the sample. In order to technologically compete with wire sawing processes, however the surface quality after separation is of decisive importance for each spalling process. However, the resulting total thickness variation (TTV) of spalling surfaces without a laser process is usually far beyond the sector requirements. The typical TTV of spalling processes is of the order of magnitude of 50 m, wherein grinding steps would be required here before the further processing, which would make the costs too high. Instead, the use of LAS processes results in surface roughness values of Sa<1 m. Sa is the arithmetic mean of the absolute values of the surface coordinates z(x, y).

[0234] FIG. 19c thus shows a photograph of a half of a 30 mm silicon wafer after separation using conventional spalling. Wallner lines are clearly visible as crack grooves and indicative of high surface height variation (TTV).

[0235] FIG. 19d shows a photograph of a half of a 300 mm silicon wafer after laser-assisted spalling. The surface is homogeneous with a surface roughness of less than 1 m and without visible strips from the crack propagation. The vertical line on the left side of the substrate originates from a limitation of the travel of the substrate holding table of the laser system.

[0236] FIGS. 20a-f show an overview of the material surfaces after laser-assisted spalling. FIG. 20a shows a silicon surface of the sample shown in FIG. 19b with a surface roughness of

Sa=0.79 m. FIG. 20b shows a sapphire (Al.sub.2O.sub.3) substrate surface (C plane) after laser-assisted spalling with a surface roughness of Sa=1.96 m. FIG. 20c and FIG. 20d show surfaces of silicon carbide polymorphs 4H and 6H (both with N doping) after laser-assisted spalling with surface roughnesses Sa=1.85 m and Sa=1.29 m. FIG. 20e shows an example for spalling of non-crystalline material, surface of polycrystalline Al.sub.2O.sub.3, with a surface roughness Sa=3.89 m. FIG. 20f shows quartz glass, principle study, laser-assisted spalling experiment with surface roughness Sa=6.89 m.

[0237] FIG. 21a shows a microscopic photograph of a surface after spalling. FIG. 21b shows Raman spectra of three different points in 6H silicon carbide. The Raman spectra of the darker area (on the right-hand side of FIG. 21a) are curve K1 and curve K2, with curve K3 as the Raman spectrum of the lighter area on the left side in FIG. 21a. The peak height for the darker areas is reduced for almost all peaks and at position 2 in the darker area no more Raman peaks can be seen.

[0238] FIG. 22 shows a further additional or alternative beam profile. In the case of a Brewster application with high numerical apertures, the beam profile of the laser can be adapted according to the invention. Thus, at high NA this can result in a higher intensity in the flanks of the emitted laser beam profile. In extreme cases this is a type of doughnut profile with a clear intensity minimum in the centre. However, it is also feasible that the laser beam profile is configured as a Gaussian profile which is flattened in the centre. Preferably the circumstance is used that at high NA the edge zones of the laser profile can already enter into the vicinity of the Brewster angle. The example profile shown by FIG. 22 could thus be produced preferably with a relatively higher intensity fraction (compared with the other embodiments) in the flanks.

[0239] FIG. 23a describes a first solid body producing configuration. According to this configuration, it is possible to detach the solid body layer 14 from the solid body 1. According to this configuration, a first number of modifications 2 is produced in the solid body. The modifications 2 here preferably bring about a sagging of the cleaved solid body layer 14.

[0240] FIG. 23b shows a second solid body producing configuration. According to this configuration, it is also possible to detach the solid body layer 14 from the solid body 1. According to this configuration, however a second number of modifications 2 is produced in the solid body 1. Here the second number of modifications 2 is preferably greater than the first number of modifications. Additionally or alternatively it is possible that the configuration has several modification layers 2.1, 2.2 or more modification layers 2.1, 2.2 than the first configuration in which several modification layers can also be provided. Additionally or alternatively it is also feasible that individual ones or the majority of the modifications 2 according to the second configuration are configured to be stronger than in the first configuration. Configured to be stronger here preferably means that the individual modifications in each case extend over a larger volume than in the first configuration. The laser beams 10 here preferably penetrate into the solid body 1 in the longitudinal direction of the solid body 1 or inclined at an angle of up to 60 to the longitudinal direction L of the solid body over an, in particular flat, surface which is preferably part of the solid body layer and the crack guiding region 4 is then preferably formed of several layers of modifications 2. The layers are preferably produced spaced apart from one another or offset in the longitudinal direction L. Preferably at least several of the modifications 2 have an extension in the longitudinal direction L which is between 1 and 50 m and/or the laser beams 20 are preferably introduced into the solid body 1 to produce modifications 2 in such a manner that the numerical aperture is less than 1, preferably less than 0.9 or less than 0.7 or less than 0.6 or less than 0.5.

[0241] The invention thus describes a method for detaching at least one solid body layer from a solid body, wherein due to modifications a crack guiding region is predefined for guiding a crack for detaching a solid body portion, in particular a solid body layer, from the solid body, [0242] at least comprising the steps: moving the solid body relative to a laser application device, [0243] successively producing laser beams by means of the laser application device to produce respectively at least one modification, wherein the laser application device is adjusted for the defined generation of modifications depending on at least one parameter, namely the transmission of the solid body at defined points and for a defined solid body depth, wherein [0244] due to the adjustment of the laser application device, inhomogeneities of the solid body are compensated in the area of the affected surface and/or in the area of the affected volume of the solid body, detaching the solid body layer from the solid body.

[0245] FIG. 24a shows a Raman instrument 58. The Raman instrument 58 shown here has a laser 60 for emitting radiation. The radiation is preferably supplied by means of at least one optical fibre 61 for excitation preferably to an optical system and from this optical system, in particular a lens 64, is preferably focussed, in particular focussed into the solid body. This radiation is at least partially scattered, wherein preferably by means of a filter device or excitation filter 62, light components which have the same wavelength as the radiation emitted by the laser are filtered out. The other radiation components are then fed to a spectrograph 68 and recorded by means of a camera device, in particular a CCD detector 70 and evaluated or prepared by a control device 14, 72, in particular a computer.

[0246] Thus, atomic vibrations in the crystal are preferably excited by a preferably external or particularly preferably further laser. These vibrations are produced by light scattering at crystal atoms which results in observable scattered light, which has a photon energy changed by the amount of the vibration energy. In the case of several excitable vibrations, several peaks also appear in the spectrum of the scattered light. The resulting Raman scattering spectrum can then be investigated in detail using a spectrometer (lattice spectrometer) (so-called Raman spectroscopy). In this method the local conditions in the crystal are impressed on the individual Raman lines in their shape and the degree of doping can be concluded from an analysis of the shape of the Raman line.

[0247] FIG. 24b shows how possible lattice vibrations appear in SiC, wherein these modes are predefined by crystal symmetry and directions and can also be excited simultaneously. The views shown have an extension along the crystal axis A. In this case, vibrations of the atoms are only possible in certain directions, wherein the directions are predefined by the symmetry of the crystal.

[0248] FIG. 25a shows a section of a Raman profile of a 4H silicon carbide solid body doped with nitrogen (example spectrum for Raman on doped SiC). Here the form of the LO(PC) mode is used for measurement of the doping concentration and fitted. Lower panel: fitting residual.

[0249] FIG. 25b shows a smaller section of the Raman profile.

[0250] As shown a direct method is obtained to determine the dopant concentration using Raman measurements from a measurement of the shape and following fit to the LO(PC) mode.

[0251] In general, the aim is therefore by adjusting the laser parameters, to adjust the optimal (smallest possible, shortest possible) crack profile in the material which still results in successful separation as a result of crack propagation by otherwise minimizes or reduces all material losses (even in grinding steps).

[0252] FIGS. 26a and 26b show two possibilities for configuring the lifting of individual wafers from the boule/ingot.

[0253] According to FIG. 26a this is configured as a feedforward loop and according to FIG. 26b as a feedback loop.

[0254] In the case of feedforward, the distribution is characterized before the laser process and from this a map or treatment instructions or parameter adaptations, in particular location-dependent is calculated for the laser process, in particular the production of modifications. Feedforward is preferably performed on the ingot/boule.

[0255] Alternatively, as shown in FIG. 26b, a feedback loop can be implemented according to which after each separation step the wafer formed is characterized and serves as a template for the next one.

[0256] Depending on the material and doping, different adaptations can thus be made during the laser process:

[0257] In the case of SiC material, different adaptations of the laser parameters can be made at different depths depending on the resulting doping. Under the boundary conditions mentioned hereinafter, this can result in the functions likewise mentioned hereinafter.

[0258] Depth 180 m, pulse duration 3 ns, numerical aperture 0.4

[0259] Low doping: 7 J-21 mOhmcm

[0260] High doping: 8 J-16 mOhmcm

[0261] Depth 350 m, pulse duration 3 ns, numerical aperture 0.4

[0262] Low doping: 9.5 J-21 mOhmcm

[0263] High doping: 12 J-16 mOhmcm

[0264] Formula for 180 m depth:

[0265] E Energy in J

[0266] E0 Offset energy at lowest doping

[0267] K Energy scaling factor

[0268] R Measured degree of doping

[0269] B Base degree of doping (21 mOhmcm)

E=E0+(BR)*K

[0270] Here

[0271] K=1/(21-16) J/mOhmcm=0.2 J/mOhmcm

[0272] E0=7 J

[0273] B=21 mOhmcm

[0274] Example: measured degree of doping of 19 mOhmcm: E=7.4 J

[0275] Formula for 350 m depth:

[0276] E Energy in J

[0277] E0 Offset energy at lowest doping

[0278] K Energy scaling factor

[0279] R Measured degree of doping

[0280] B Base degree of doping (21 mOhmcm)

E=E0+(BR)*K

[0281] Here

[0282] K=2.5/(21-16) J/mOhmcm=0.5 J/mOhmcm

[0283] E0=9.5 J

[0284] B=21 mOhmcm

[0285] Example: 19 mOhmcm: E=10.5 J

[0286] FIGS. 27a to 27i show various arrangements which can be provided after producing the further material layers or components 150 for initiating the crack.

[0287] FIGS. 27a-27i show various solid body arrangements 176 such as are advantageous for initiating crack guiding and/or crack initiating stresses.

[0288] FIG. 27a here shows a processed solid body 1 or wafer with structures or components 150.

[0289] Compared to the solid body 1 shown in FIG. 27a, in the solid body 1 shown in FIG. 27b, a receiving layer 140 is arranged or produced on the component side, in particular on the components 150 or the further material layers 150. The receiving layer 140 is here preferably arranged on the solid body layer to be detached. The receiving layer 140 can in this case also be designated as split film and is therefore preferably laminated on the structure side. In the following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0290] Compared to the diagram in FIG. 27b, according to FIG. 27c a retaining layer/bonded wafer is arranged on the underside of the solid body or on the exposed surface of the solid body. The retaining layer can also be a tool carrier or chuck 300. In a following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0291] FIG. 27d shows an arrangement compared with FIG. 27b according to which the solid body is provided with double-sided receiving layers 140, 146. The further receiving layer 146 is in this case arranged on a surface of the subsequently remaining residual solid body, wherein an adhesion promotion layer 148 and/or sacrificial layer 149 and/or protective layer 142 can be arranged or produced between the further receiving layer 146 and the solid body 1. The two receiving layers 140 and 146 are preferably laminated on. In the following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0292] FIG. 27e shows an arrangement according to which, compared with the arrangement known from FIG. 27d, no adhesion promotion layer 146 and/or sacrificial layer 149 and/or protective layer 142 is arranged or produced between the further receiving layer 146 and the solid body 1. In the following step, the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0293] FIG. 27f shows an arrangement which is constructed inversely to the arrangement known from FIG. 27d, i.e. the adhesion promotion layer 146 and/or sacrificial layer 149 and/or protective layer 142 are not arranged or produced between the further receiving layer 146 and the solid body 1 but between the receiving layer 140 and the solid body 1 and thus is/are produced or arranged on the solid body layer to be detached. One or more layers can be produced here on the components 150 or the structures for example by means of spin coating. In the following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0294] FIG. 27g shows an arrangement or implementation which corresponds to a combination of the arrangements from FIGS. 27d and 27f. The solid body is preferably laminated with split film on both sides, likewise a protective layer and/or adhesion promotion layer and/or sacrificial layer can be provided under the split film on both sides, furthermore, for example, spin coating is possible on the structures, In the following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0295] FIG. 27h shows an arrangement which is similar to the arrangement shown in FIG. 27b wherein the receiving layer is not arranged or laminated on one side on a surface of the solid body layer to be detached but on the residual solid body remaining after the detachment. The detachment then takes place as a result of cooling similar to the detachment from an ingot or as in an ingot process.

[0296] FIG. 27i shows an arrangement which is similar to the arrangement known from FIG. 27c wherein one or more of the layers or devices mentioned hereinafter is/are arranged or produced on the component side of the solid body or on or above the component 150. These layers or devices are preferably in this case: at least or precisely one adhesion promotion layer 148 and/or at least or precisely one sacrificial layer 149 and/or at least or precisely one protective layer 142 and/or at least one or precisely one stabilizing device 3, in particular a tool carrier or chuck 300 (preferably cooling device) or another wafer. In the following step the entire arrangement is then cooled, with the result that the split or the crack initiation and/or the crack guidance is brought about.

[0297] FIG. 28 shows an illustration of an example for a writing pattern with an X-Y processing:

[0298] Arrows 170, 172 represent the laser feed device, the black circles represent the different laser shots or modifications 9 which here do not overlap with their damaging effect in the material. It is preferred here if the laser initially travels in one direction and produces modifications 9 before it reverses and writes modifications 9 in the second (lower) direction.

[0299] FIGS. 29a to 29d show various cooling devices 174. The solid body arrangements 176 processed in these cooling devices 174 result from the different implementations or configurations of the solid body 1 provided with one or more receiving layers 140, 146 shown and described in FIGS. 27a to 27i. The cooling devices 174 shown herein all use a liquefied gas 178 as initial cooling medium for cooling. This initial cooling medium is either nebulized or vaporized depending on the embodiment.

[0300] Preferably the initial cooling medium is liquid nitrogen. Alternative cooling methods, e.g. by means of piezoelements are also conceivable and possible.

[0301] The cooling device 174 is preferably used here to cool the receiving layer 140, 146 to a temperature between 85 C. and 10 C., in particular to a temperature between 80 C. and 50 C.

[0302] According to FIG. 29a, the cooling device 174 comprises a nitrogen bath, wherein the receiving layer is positioned at a distance, in particular by means of an adjustable positioning device 180, to the liquid nitrogen held in the nitrogen bath. Thus, the solid body arrangement is preferably arranged on a positioning device or on a holder above a nitrogen bath. A temperature gradient over the chamber height thus results and the temperature at the solid body arrangement is adjustable via the filling level with the initial cooling medium of the position of the solid body arrangement 176 (distance from the base of the chamber).

[0303] According to the embodiments in FIGS. 29b to 29d the cooling device can preferably comprise a nebulizing means, in particular at least or precisely one perforated pipeline for nebulizing liquid nitrogen or a nebulizing means for nebulizing liquid nitrogen and the cooling effect can be produced by nebulized or vaporized nitrogen.

[0304] According to FIG. 29b, a homogeneous spray device/nebulizer is provided for spraying or nebulizing. The spraying or nebulizing is preferably accomplished above the solid body arrangement 176. Furthermore preferably temperature measurements are made for temperature monitoring, the initial data are output for regulating a valve, in particular a nitrogen valve. The temperature measurements are preferably made on the substrate or on the solid body 1 or on the receiving layer 140.

[0305] The substrate or the solid body 1 or the solid body arrangement 176 preferably rests above the chamber bottom in order to avoid nitrogen deposition on the bottom of the chamber.

[0306] According to FIG. 29c, preferably a perforated pipeline is used as homogeneous spray device. Furthermore preferably temperature measurements are made for temperature monitoring, the initial data are output for regulating a valve, in particular a nitrogen valve. The temperature measurements are preferably made on the substrate or on the solid body 1 or on the receiving layer 140.

[0307] The substrate or the solid body 1 or the solid body arrangement 176 preferably rests above the chamber bottom in order to avoid nitrogen deposition on the bottom of the chamber. According to FIG. 29d, this shows a cooling device 176 which comprises a homogeneous spray device/nebulizer 182 for cooling preferably several or each side. Furthermore preferably temperature measurements are made for temperature monitoring, the initial data are output for regulating a valve, in particular a nitrogen valve. The temperature measurements are preferably made on the substrate or on the solid body 1 or on the receiving layer 140.

[0308] The substrate or the solid body 1 or the solid body arrangement 176 preferably rests above the chamber bottom in order to avoid nitrogen deposition on the bottom of the chamber.

[0309] The chamber 184 of the cooling device 174 is preferably closed to reduce a temperature gradient as far as possible by insulation.

[0310] FIG. 30 shows three examples for preferred relationships between the crystal lattice orientation and the production of modifications. This method is particularly appropriate for the detachment of solid body layers from a solid body consisting of SiC or comprising SiC. These relationships result in a further method according to the invention. This further method according to the invention is preferably used for detaching at least one solid body layer from at least one solid body 1, in particular of a wafer from an ingot or for thinning a wafer. The further method according to the invention preferably comprises at least the steps: producing a plurality of modifications 2 by means of laser beams inside the solid body 1 to form a detachment plane 4, and introducing an external force into the solid body 1 to produce stresses in the solid body 1, wherein the external force is so strong that the stresses bring about a crack propagation along the detachment plane 4.

[0311] According to the invention, the modifications are produced successively in at least one line or row or line, wherein the modifications 2 produced in a line or row or line are preferably produced at a distance X and with a height H so that a crack propagating between two successive modifications, in particular a crack propagating in the crystal lattice direction, the direction of propagation of which is aligned at an angle W with respect to the detachment plane, interconnects the two modifications. The angle W here preferably lies between 2 and 6, in particular at 4. Preferably the crack propagates from a region below the centre of a first modification to a region above the centre of a second modification. The essential relationship here is therefore that the size of the modification can or must be varied depending on the distance of the modifications and the angle W.

[0312] Furthermore this method can also comprise the step of producing a composite structure by arranging or producing layers and/or components 150 on or above an initially exposed surface of the substrate 1, wherein the exposed surface is preferably part of the solid body layer to be detached. Particularly preferably the modifications for forming the detachment plane 4 are formed before producing the composite structure.

[0313] In order to introduce the external force, for example by analogy with the previously described method a receiving layer 140 can be arranged on an exposed surface of the composite structure or the solid body.

[0314] The three diagrams 30a to 30c are intended to illustrate how the size of the damage/modification zone amorphized/phase-converted by the laser influences the height covered by the sawtooth pattern of the crack. In general, the crack therefore runs along the crystal planes between individual atoms of the crystal. In the modified zone these clear planes are no longer existent, the . . . therefore comes to a halt.

[0315] The damage zone along the beam direction and also laterally in the focal plane can be reduced by a numerical aperture which is preferably as high as possible. Since only the threshold intensity must be reached, a smaller pulse energy is then sufficient here.

[0316] If the damage zone is now configured to be suitably smaller, the laser modifications can be set more densely, which makes the sawtooth run shorter and overall causes a smaller height extension of the modified plane (first diagram).

[0317] If on the other hand, the damage zone is configured to be larger (higher energy and/or lower numerical apertureFIG. 30b), a larger microcrack is initiated by the increased pressure of the amorphized zone which can be intercepted (i.e. stopped in a controlled manner) by a damage zone of greater extension at a greater distance.

[0318] FIG. 30c finally shows the risk if the damage zone is not sufficiently large and cracks which run too widely are triggered by the laser modification, that the cracks on the one hand run too widelyi.e. the height difference produced by the cracks is greater than desiredand on the other hand the cracks are driven through under the further damage zones and not stopped by the amorphized material. This then again results in material losses since all the cracked material layers must be removed for the end product or renewed laser processing.

[0319] FIG. 31 shows a schematically depicted snapshot from a further method according to the invention. This further method is preferably used to detach at least one solid body layer from at least one solid body 1, in particular a wafer from an ingot or for thinning a wafer. The further method according to the invention preferably comprises at least the steps: producing a plurality of modifications 2 by means of laser beams inside the solid body 1 to form a detachment plane 4 and introducing an external force into the solid body 1 to produce stresses in the solid body 1, wherein the external force is so strong that the stresses bring about a crack propagation along the detachment plane 4.

[0320] According to the invention, in a first step the modifications are produced on a line 103 and preferably at the same distance from one another. Furthermore, it is conceivable that a plurality of these lines produced in the first step are produced. These first lines are particularly preferably produced parallel to the crack propagation direction and preferably rectilinearly or in a circular arc shape, in particular in the same plane. After producing these first lines, preferably second lines 105 are produced to trigger and/or drive preferably subcritical cracks. The second lines are also preferably produced rectilinearly. Particularly preferably the second lines are inclined with respect to the first lines, in particular aligned orthogonally. The second lines preferably extend in the same plane as the first lines or particularly preferably in a plane which is parallel to the plane in which the first lines extend. Preferably third lines are then produced to connect the subcritical cracks.

[0321] This method is particularly appropriate for detaching solid body layers from a solid body consisting of SiC or comprising SiC.

[0322] Furthermore the modifications can be produced successively in at least one line or row or line, wherein the modifications 2 produced in a line or row or line are preferably produced at a distance X and with a height H, so that a crack propagating between two successive modifications, in particular a crack propagating in the crystal lattice direction, the direction of propagation of which is aligned at an angle W to the detachment plane interconnects the two modifications. The angle W here lies preferably between 2 and 6, in particular 4. Preferably the crack propagates from a region below the centre of a first modification to a region above the centre of a second modification. The essential relationship here is therefore that the size of the modification can or must be varied depending on the distance of the modifications and the angle W.

[0323] Furthermore this method can also comprise the step of producing a composite structure by arranging or producing layers and/or components 150 on or above an initially exposed surface of the substrate 1, wherein the exposed surface is preferably part of the solid body layer to be detached. Particularly preferably the modifications for forming the detachment plane are formed before producing the composite structure.

[0324] In order to introduce the external force, for example by analogy with the previously described method a receiving layer 140 can be arranged on an exposed surface of the composite structure or the solid body.

[0325] Thus, in the further laser method according to the invention, lines parallel to the crack propagation direction (preferably called transverse lines) are preferably produced on SiC (but also other materials) in order to initially define a plane for the preferred crack initiation (crack initialization) before longitudinal lines drive the cracks. In this case, the cracks are firstly initialized transversely, then longitudinally before a final step sets lines between the longitudinal lines of the second step to initiate the cracks extensively. This enables shorter crack paths which minimizes the final surface roughness.

[0326] Example diagram for transverse lines (with the sawtooth) and crack initiation lines (on the wave crests of the sawtooth).

REFERENCE LIST

[0327] 1 Solid body

[0328] 2 Modification

[0329] 3 Location where modification produced

[0330] 4 Crack guiding region

[0331] 6 Solid body portion

[0332] 8 Laser application device

[0333] 9 Objektive

[0334] 10 Laser beams

[0335] 11 Modified laser beams

[0336] 12 Recess

[0337] 14 Solid body layer

[0338] 16 Surface of solid body layer

[0339] 17 Irradiated surface

[0340] 18 Stress generating layer or receiving layer 140

[0341] 19 Adhesive or further stress generating layer

[0342] 24 Local property variation of the solid body (e.g. the transmission)

[0343] 26 Trench

[0344] 28 Frame

[0345] 30 Point of intersection of reflected beams

[0346] 32 Flushing

[0347] 34 Coating

[0348] 300 Chuck

[0349] L Longitudinal direction of solid body