Combined wafer production method with laser treatment and temperature-induced stresses

Abstract

A method for the production of layers of solid material is contemplated. The method may include the steps of providing a solid body for the separation of at least one layer of solid material, generating defects by means of at least one radiation source, in particular a laser, in the inner structure of the solid body in order to determine a detachment plane along which the layer of solid material is separated from the solid body, and applying heat to a polymer layer disposed on the solid body in order to generate, in particular mechanically, stresses in the solid body, due to the stresses a crack propagating in the solid body along the detachment plane, which crack separates the layer of solid material from the solid body.

Claims

1. A method for the production of layers of solid material comprising: providing a solid body for the separation of at least one layer of solid material, the solid body having a first level surface portion and a second level surface portion, wherein the second level surface is part of the layer of solid material, wherein the layer of solid material is thinner than the remaining part of the solid body, wherein the first level surface and the second level surface are opposing main surfaces of said solid material; then generating defects by means of laser beams of multiphoton excitation caused by at least one laser acting in the inner structure of the solid body in order to determine a detachment plane along which the layer of solid material is separated from the solid body, the laser beams penetrating into the solid body via the second level surface portion; then providing a receiving layer for holding the layer of solid material on the solid body, the receiving layer being disposed on the second level surface portion and the receiving layer being in the form of a polymer layer; then subjecting the receiving layer to temperature conditions in order to generate mechanical stresses in the solid body, including cooling of the receiving layer to a temperature below ambient temperature, the cooling taking place such that at least part of the polymer layer undergoes a glass transition and due to stresses a crack propagates in the solid body along the detachment plane, which crack separates the layer of solid material from the solid body; and wherein the defects are generated in different concentrations in the detachment plane.

2. The method of claim 1 further comprising at least one radiation source for providing the radiation to be introduced into the solid body being configured such that the rays irradiated by it generate the defects at predetermined locations within the solid body.

3. The method of claim 2 further comprising the radiation source being set up such that the rays irradiated by the radiation source generate the detachment plane penetrate into the solid body to a defined depth of less than 200 m.

4. The method of claim 2 further comprising the radiation source being set up such that the rays irradiated by the radiation source to generate the detachment plane penetrate into the solid body to a defined depth of more than 100 m.

5. The method of claim 2 further comprising the radiation source being a femtosecond laser.

6. The method of claim 5 further comprising energy of the femtosecond laser being chosen such that the damage propagation within the solid body is smaller than 3 times the Rayleigh length.

7. The method of claim 5 further comprising the wavelength of the femtosecond laser being chosen such that the absorption of the solid body is less than 10 cm.sup.1.

8. The method of claim 5 further comprising the defects respectively resulting from multiphoton excitation brought about by the femtosecond laser.

9. The method of claim 2 further comprising the radiation source having a pulse duration of less than 10 ps.

10. The method of claim 1 further comprising the solid body being disposed on a holding layer for holding the solid body, the holding layer being disposed on the first level surface portion of the solid body, the first level surface portion of the solid body being spaced apart from the second level surface portion of the solid body, the detachment plane being aligned parallel to the first level surface portion and/or the second level surface portion.

11. The method of claim 1 further comprising the solid body including silicon carbide and/or gallium arsenite and/or a ceramic material and the polymer layer, the polymer layer and/or a holding layer being made at least partially of PDMS, the holding layer being disposed on an at least partially level surface of a stabilisation device which is made at least partially of at least one metal.

12. The method of claim 1 further comprising the stresses in the solid body being set up such that the crack initiation and/or the crack propagation can be controlled in order to generate a pre-determined topography of the surface that is produced in the crack plane.

13. The method of claim 1 further comprising the solid body being a semiconductor material or a ceramic material.

14. The method of claim 1 further comprising the solid body being made of at least one semiconductor material or a ceramic material.

15. A method for the production of layers of solid material comprising: at a first instance in time, providing a solid body for the separation of at least one layer of solid material, the solid body having a first level surface portion and a second level surface portion, wherein the second level surface is part of the layer of solid material, wherein the layer of solid material is thinner than the remaining part of the solid body, wherein the first level surface and the second level surface are opposing main surfaces of said solid material; thereafter at a second instance in time occurring after the first instance, generating defects in the solid body with at least one laser producing laser beams of multiphoton within the inner structure of the solid body to produce a detachment plane along which the layer of solid material is separated from the solid body, the laser beams penetrating into the solid body via the second level surface portion; thereafter at a third instance in time occurring after the second instance, providing a receiving layer for holding the layer of solid material on the solid body, the receiving layer being disposed on the second level surface portion and the receiving layer being in the form of a polymer layer; thereafter at a fourth instance in time occurring after the second instance, subjecting the receiving layer to temperature conditions in order to generate mechanical stresses in the solid body, including cooling of the receiving layer to a temperature below ambient temperature, the cooling taking place such that at least part of the polymer layer undergoes a glass transition and a crack propagates in the solid body along the detachment plane due to stresses, the crack separating the layer of solid material from the solid body; and wherein the defects are generated in different concentrations in the detachment plane.

Description

[0047] The figures show as follows:

[0048] FIG. 1a a diagrammatic construction for generating defects in a solid body;

[0049] FIG. 1b a diagrammatic illustration of a layer arrangement before separating a layer of solid material from a solid body;

[0050] FIG. 1c a diagrammatic illustration of a layer arrangement after separating a layer of solid material from a solid body;

[0051] FIG. 2a a first diagrammatically illustrated variation for generating defects by means of light waves;

[0052] FIG. 2b a second diagrammatically illustrated variation for generating defects by means of light waves; and

[0053] FIG. 3a diagrammatic illustration of the detachment plane.

[0054] FIG. 1a shows a solid body 2 or a substrate that is disposed in the region of a radiation source 18, in particular a laser. The solid body 2 preferably has a first level surface portion 14 and a second level surface portion 16, the first level surface portion 14 preferably being aligned substantially or exactly parallel to the second level surface portion 16. The first level surface portion 14 and the second level surface portion 16 preferably delimit the solid body 2 in a Y direction that is preferably aligned vertically or perpendicularly. The level surface portions 14 and 16 preferably extend respectively in an X-Z plane, the X-Z plane preferably being aligned horizontally. Furthermore, it can be gathered from this illustration that the radiation source 18 irradiates rays 6 onto the solid body 2. The rays 6 penetrate by a defined depth into the solid body 2 depending on the configuration and generate a defect at the respective position or at a predetermined position.

[0055] FIG. 1b shows a multi-layered arrangement, the solid body 2 containing the detachment plane 8 and being provided in the region of the first level surface portion 14 with a holding layer 12 which is in turn preferably overlaid by an additional layer 20, the additional layer 20 preferably being a stabilisation device, in particular a metal plate. A polymer layer 10 is preferably disposed on the second level surface portion 16 of the solid body 2. The polymer layer 10 and/or the holding layer 12 are preferably made at least partially and particularly preferably entirely of PDMS.

[0056] FIG. 1c shows a state after a crack initiation and subsequent crack directing. The layer of solid material 4 adheres to the polymer layer 10 and is or can be spaced apart from the remaining part of the solid body 2.

[0057] FIGS. 2a and 2b show examples of the generation, shown in FIG. 1a, of a detachment plane 8 by introducing defects into a solid body 2 by means of light rays.

[0058] Therefore, the present invention relates to a method for the production of layers of solid material. This method according to the invention includes at the very least the steps of providing a solid body 2 for the separation of at least one layer of solid material 4, generating defects by means of at least one radiation source, in particular at least one laser, in particular at least one fs laser, in the inner structure of the solid body in order to determine a detachment plane along which the layer of solid material is separated from the solid body, and applying heat to a polymer layer 10 disposed on the solid body 2 in order to generate, in particular mechanically, stresses in the solid body 2, due to the stresses a crack propagating in the solid body 2 along the detachment plane 8, which crack separates the layer of solid material 4 from the solid body 2.

[0059] Therefore, FIG. 2a shows diagrammatically how defects 34 can be generated in a solid body 2, in particular in order to generate a detachment plane 8 by means of a radiation source 18, in particular one or more lasers, in particular one or more fs lasers. Here the radiation source 18 emits radiation 6 with a first wavelength 30 and a second wavelength 32. The wavelengths 30, 32 are matched to one another here or the distance between the radiation source 18 and the detachment plane 8 to be generated is matched such that the waves 30, 32 converge substantially or precisely on the detachment plane 8 in the solid body 2, by means of which a defect is generated at the point of coinciding 34 as a result of the energies of the two waves 30, 32. The generation of defects can take place here by means of different or combined decomposition mechanisms such as e.g. sublimation or chemical reaction, the decomposition being able to be initiated here e.g. thermally and/or photochemically.

[0060] FIG. 2b shows a focussed light ray 6, the focal point of which preferably lies in the detachment plane 8. It is conceivable here for the light ray 6 to be focussed by one or more focussing bodies, in particular a lens/lenses (not shown). In this embodiment the solid body 2 is multi-layered in form and preferably has a partially transparent or transparent substrate layer 3 or material layer that is preferably made of sapphire or comprises sapphire. The light rays 6 pass through the substrate layer 3 onto the detachment plane 8 which is preferably formed by a sacrificial layer 5, the sacrificial layer 5 being exposed to radiation such that partial or complete destruction of the sacrificial layer 5 is brought about thermally and/or photochemically in the focal point or in the region of the focal point. It is also conceivable for the defects for the generation of the detachment layer 8 to be generated in the region of or precisely on a boundary surface between two layers 3, 4. It is therefore also conceivable for the layer of solid material 4 to be generated on a support layer, in particular a substrate layer 3, and for a detachment plane 8 for the detachment or separation of the layer of solid material 4 to be able to be generated by means of one or more sacrificial layers 5 and/or or by means of the generation of defects in a boundary surface, in particular between the layer of solid material 4 and the support layer.

[0061] FIG. 3 shows a detachment plane 8 which has regions with different concentrations of defects 82, 84, 86. It is conceivable here for a plurality or regions with different concentrations of defects to form a detachment plane 8, it also being conceivable for the defects 34 in the detachment plane 8 to be distributed substantially or exactly evenly over the surface. The different concentrations of defects per area can be of the same level or of different levels. Preferably, a first increased concentration of defects constitutes a crack initiation concentration 82 which is preferably generated in the region of the edge or extending towards the edge or adjacent to the edge. In addition or alternatively, a crack directing concentration 84 can be formed such that the crack separating the layer of solid material 4 from the solid body 2 can be controlled or regulated. Furthermore, in addition or alternatively, a concentration at the centre 86 is generated which preferably makes a very level surface possible in the region of the centre of the solid body 2. Preferably, the crack directing concentration 84 is made to be partially or entirely annular or encircling, and so preferably partially and particularly preferably entirely encircles the centre of the solid body 2 or the layer of solid material 4. Furthermore, it is conceivable for the crack directing concentration 84 to decrease step by step, constantly or fluently in a direction passing from the edge of the solid body 2 and towards the centre of the solid body 2. Furthermore, it is conceivable for the crack directing concentration 84 to be formed in bands and homogeneously or substantially or exactly homogeneously.

[0062] Therefore, the method according to the invention preferably includes the following steps:

[0063] Providing a workpiece for the detachment of at least one layer of solid material and/or at least one solid body, the workpiece having at least one exposed surface, generating defects within the workpiece by means of a radiation source, in particular a laser, in particular an fs laser, or a defect generation apparatus, the defects determining a crack directing layer, applying or generating a receiving layer on the exposed surface of the workpiece such as to form a composite structure, tempering the receiving layer in order to generate stresses within the workpiece, the stresses bringing about crack propagation within the workpiece, by means of the crack propagation a layer of solid material being separated from the workpiece along the crack directing layer.

LIST OF REFERENCE SIGNS

[0064] 2 solid body [0065] 3 substrate [0066] 4 layer of solid material [0067] 5 sacrificial layer [0068] 6 radiation [0069] 8 detachment plane [0070] 10 polymer layer [0071] 12 holding layer [0072] 14 first level surface portion [0073] 16 second level surface portion [0074] 18 radiation source [0075] 20 stabilisation device [0076] 30 first radiation portion [0077] 32 second radiation portion [0078] 34 location of the defect generation [0079] 82 crack initiation concentration [0080] 84 crack directing concentration [0081] 86 concentration at the centre [0082] X first direction [0083] Y second direction [0084] Z third direction