Method for the material-saving production of wafers and processing of wafers

Abstract

The invention relates to a method for producing a multi-layer assembly. The method according to the invention comprises at least the following steps: providing a donor substrate (2) for removing a solid layer (4), in particular a wafer; producing modifications (12), in particular by means of laser beams (10), in the donor substrate (2) in order to specify a crack course; providing a carrier substrate (6) for holding the solid layer (4); bonding the carrier substrate (6) to the donor substrate (2) by means of a bonding layer (8), wherein the carrier substrate (6) is provided for increasing the mechanical strength of the solid layer (4) for the further processing, which solid layer is to be removed; arranging or producing a stress-producing layer (16) on the carrier substrate (6); thermally loading the stress-producing layer (16) in order to produce stresses in the donor substrate (2), wherein a crack is triggered by the stress production, which crack propagates along the specified crack course in order to remove the solid layer (4) from the donor substrate (2) such that the solid layer (4) is removed together with the bonded carrier substrate (6).

Claims

1. A method for producing a multi-layer assembly the method comprising: providing a donor substrate for removing a solid layer from the donor substrate; producing modifications in the donor substrate in order to specify a crack course; providing a carrier substrate for holding the solid layer; bonding the carrier substrate to the donor substrate by means of a bonding layer, wherein the carrier substrate is provided for increasing mechanical strength of the solid layer for further processing, which solid layer is to be removed; arranging or producing a stress-producing layer on the carrier substrate; thermally loading the stress-producing layer in order to produce stresses in the donor substrate, wherein a crack is triggered by the stress production, which crack propagates along the specified crack course in order to remove the solid layer from the donor substrate such that the solid layer is removed together with the bonded carrier substrate.

2. The method according to claim 1, wherein the bonding layer connects the solid layer and the carrier substrate to one another by means of a substance-to-substance bond and is destructible by means of radiation from a radiation source or a free-flowing substance.

3. The method according to claim 2, wherein the stress-producing layer is removed from the carrier substrate after removing the solid layer from the donor substrate and/or a material layer is produced on the solid layer, wherein a structural weakening of the carrier substrate and/or of the solid layer is effected prior to the production of the material layer.

4. The method according to claim 3, wherein the carrier substrate is used repeatedly to produce a multi-layer assembly, wherein the solid layer is removed from the carrier substrate prior to the repeated provision, and the carrier substrate is treated prior to the repeated provision.

5. The method according to claim 4, wherein a sacrificial layer is arranged or produced on the carrier substrate prior to the arrangement or production of the stress-producing layer on the carrier substrate, wherein the stress-producing layer is arranged or produced on the sacrificial layer.

6. The method according to claim 5, wherein the stress-producing layer comprises a polymer, wherein the stress-producing layer is temperature-controlled to a temperature below a glass transition temperature of the stress-producing layer.

7. The method according to claim 6, wherein the modifications are cracks in a crystal lattice and/or material portions of the donor substrate, and/or the modifications are produced by means of laser beams which are introduced via an outer surface of the donor substrate by a laser device.

8. The method according to claim 7, wherein the laser device is configured so that laser beams emitted by the laser device produce the modifications at predetermined locations within the donor substrate, wherein the laser device is adjusted so that the laser beams emitted by the laser device for producing the modifications penetrate into the donor substrate to a defined depth of less than 200 m, wherein the laser device has a pulse duration of below 10 ps.

9. The method according to claim 8, wherein: the laser device comprises a femtosecond laser and the energy of the laser beams of the femtosecond laser is chosen so that damage propagation of each modification in the donor substrate is smaller than 3-times the Rayleigh length; the wavelength of the laser beams of the femtosecond laser is chosen so that absorption by the donor substrate is smaller than 10 cm.sup.1; and/or the modifications in each case are produced as a result of a multi-photonic excitation effected by the femtosecond laser.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further advantages, goals and characteristics of the invention at hand will be discussed by means of drawings enclosed to the description below, in which the solutions according to the invention are illustrated in an exemplary manner. Components or elements of the solutions according to the invention, which correspond at least substantially with regard to their function in the figures, can hereby be identified with the same reference numerals, wherein these components or elements do not need to be numbered or explained in all figures.

(2) FIG. 1 shows, schematically, a method for producing a multi-layer assembly; and

(3) FIG. 2 shows, schematically, the treatment of a solid layer with the help of a carrier substrate.

DETAILED DESCRIPTION

(4) FIG. 1 shows, schematically, a plurality of states of a method for producing a multi-layer assembly 1. The first partial illustration shows a donor substrate 2, the surface of which, to which a carrier substrate 6, preferably of GaAs, is bonded in a further step, is preferably polished and cleaned. The donor substrate 2 can hereby preferably be an ingot or a thick wafer.

(5) The second partial illustration shows a radiation source, in particular a laser device 11, which emits beams, in particular one or a plurality of laser beams 10, by means of which modifications 12 are produced in the interior of the donor substrate 2, i.e. preferably spaced apart from all outer surfaces of the donor substrate 2, in particular in one plane.

(6) In the next partial illustration, reference numeral 8 identifies a bonding layer, which serves to fix the carrier substrate 6 to the donor substrate 2 by means of a substance-to-substance bond. It is conceivable hereby, e.g., for the bonding layer 8 to consist of an adhesive, in particular a light-absorbing adhesive, or to be produced by the local liquefication of the carrier substrate 6 and/or of the donor substrate 2, in particular as a result of a heat treatment. The bonding layer 8, however, preferably consists of a polymer material or, particularly preferably, has a polymer material, respectively.

(7) The fourth partial illustration shows a stress-producing layer 16, which, in the shown example, was initially produced so as to then be arranged on the carrier substrate 6. The carrier substrate 6 is preferably coated with a sacrificial layer 9 prior to the application of the stress-producing layer 16 to the carrier substrate 6, or prior to the production of the stress-producing layer 16 on the carrier substrate 6. The sacrificial layer 9 can hereby be provided, e.g. as adhesion promoter or for more easily removing the stress-producing layer 16. The stress-producing layer 16 preferably has a thickness, which is many times greater than the thickness of the sacrificial layer 9.

(8) According to the next partial illustration, provision is made for a temperature control device 17, which emits a coolant 19, in particular liquid nitrogen. The coolant 19 thereby effects a very quick cool-down of the stress-producing layer 16 to a temperature below the glass transition temperature of the material of the stress-producing layer 16. By cooling down the stress-producing layer 16, the stress-producing layer 16 contracts and thus introduces stresses into the donor substrate 2. When the stresses exceed a critical intensity, a crack forms in the area of the modifications 12 and thereby removes the solid layer 4 from the donor substrate 2, whereby a surface 15 of the donor substrate 2 is exposed on the one hand and whereby a surface 14 of the solid layer 4 is exposed on the other hand.

(9) Preferably after the removal of the solid layer 4 from the donor substrate 2, the stress-producing layer 16 and preferably also the sacrificial layer 9 is removed from the carrier substrate 6 according to the upper arrow, resulting in the multi-layer assembly 1 according to the invention. According to the lower arrow, the donor substrate 2 is used as donor substrate 2 again or the described method starts again, respectively. For this purpose, the donor substrate 2 is preferably treated, the exposed surface 15 is preferably in particular handled, in particular smoothed, in particular polished.

(10) The carrier substrate 6 serves to thin a donor substrate 2 and as stabilizer in response to the machining of the respective solid layer 4.

(11) The invention at hand thus refers to a method for producing a multi-layer assembly 1. The method according to the invention thereby preferably comprises at least the steps: providing a donor substrate 2 for removing a solid layer 4, in particular a wafer; producing modifications 12, in particular by means of laser beams 10, in the donor substrate 2 in order to specify a crack course; providing a carrier substrate 6 for holding the solid layer 4; bonding the carrier substrate 6 to the donor substrate 2 by means of a bonding layer 8, wherein the carrier substrate 6 is provided for increasing the mechanical strength of the solid layer 4 for the further processing, which solid layer is to be removed, arranging or producing a stress-producing layer 16 on the carrier substrate 6, thermally loading the stress-producing layer 16 in order to produce stresses in the donor substrate 2, wherein a crack is triggered by the stress production, which crack propagates along the specified crack course in order to remove the solid layer 4 from the donor substrate 2 such that the solid layer 4 is removed together with the bonded carrier substrate 6.

(12) A multi-layer assembly 1, as it was preferably produced according to the embodiments with regard to FIG. 1, is shown in FIG. 2

(13) In the second partial illustration shown next to the first partial illustration, the multi-layer assembly 1 is arranged in such a way with respect to a machining device 18 that the exposed surface 14 of the solid layer 4 can be treated by means of the machining device 18. It is conceivable hereby that the machining device 18 treats the exposed surface 14 mechanically, in particular by machining, optically, chemically and/or by means of plasma.

(14) A decomposition device 20, by means of which the bonding layer 8 is loaded, in particular destroyed, is illustrated in the third partial illustration. For this purpose, the decomposition device 20 emits radiation, e.g.. The radiation can hereby preferably be laser radiation or UV radiation. In the case of laser radiation, the radiation is preferably emitted by a picosecond or femtosecond laser. In the alternative, however, it is also conceivable for the decomposition device 20 to output a free-flowing substance, in particular a fluid, by means of which the bonding layer is dissolved. In the alternative or in addition, it is conceivable for the decomposition device 20 to produce a temperature, by means of which the bonding layer 8 is decomposed or dissolved.

(15) A state after the removal of the solid layer 4 from the carrier substrate 6 is shown in the fourth partial illustration. The carrier substrate 6 is then preferably treated, in particular cleaned and/or smoothed, in particular polished.

(16) The elliptical illustration shows the method illustrated by FIG. 1. The arrow hereby identifies that the exposed and preferably treated carrier substrate 6 is used again as a carrier substrate 6 in the method shown in FIG. 1.

(17) The invention is advantageous, because it reduces the material losses and provides a solution for producing extremely, in particular absolutely flat thin solid layers 4, in particular wear wafers. The solid layers 4 produced in this way thus have an extremely flat rear side, whereby they are in particular suitable for a 3D integration, because they do not have a warp, e.g., and preferably also no other deformations.

(18) TABLE-US-00001 List of Reference Numerals 1 multi-layer assembly 4 solid layer 2 donor substrate 6 carrier substrate 8 bonding layer 15 exposed surface of the donor substrate 9 sacrificial layer 16 stress-producing layer 10 laser beams 17 temperature control device 11 laser device 18 machining device 12 modifications 19 coolant 14 exposed surface of 20 decomposition device the solid layer