Method and system for detaching a semiconductor layer, and semi-finished product

Abstract

The invention relates to a method for detaching a semiconductor layer (4) from a layer stack (1), comprising the method steps of: A) providing the layer stack (1) of at least three layers, wherein a first layer is formed by a seed substrate (2), a second layer is formed by a parting layer (3) formed on the seed substrate (2) and a third layer is formed by the semiconductor layer (4) formed, preferably epitaxially, on the parting layer (3), and B) detaching the semiconductor layer (4) from the layer stack (1). The invention is distinguished in that, prior to and / or within method step B), a laser radiation (12) of a laser source (11) is focused into the semiconductor layer (4), wherein the laser radiation (12) is introduced into the semiconductor layer (4) along a lateral focusing line (6, 6') to create at least one modification region (7, 7') below a surface (9) of the semiconductor layer (4), wherein, in the modification region (7, 7'), a material of the semiconductor layer (4) is modified and a parting region (8) is creatable within the semiconductor layer (4) about the modification region (7, 7').

Description

[0001] Method and system for detaching a semiconductor layer, and semi-finished product

[0002] Description

[0003] The application relates to a method for detaching a semiconductor layer in accordance with the preamble of Claim 1, and to a method for producing a semiconductor layer in accordance with the preamble of claim 22. Furthermore, the invention relates to a system for detaching a semiconductor layer from a layer stack in accordance with the preamble of claim 23, and to a semi-finished product in accordance with the preamble of claim 24.

[0004] For large-surface electronic components, such as large-surface lighting elements or solar cells, but also for mass products such as semiconductor diodes, there is a need for cost- effective semiconductor wafers having high electronic quality, since in such components, the material cost of the semiconductor wafer is a substantial part of the cost of the overall product. To manufacture semiconductor wafers, methods are known, wherein semiconductor wafers are produced from silicon blocks ("ingots") by means of sawing methods. This allows high-quality, in particular monocrystalline, semiconductor wafers to be produced. The cost of manufacture is high, however, also due to the material loss caused by sawing of the silicon blocks.

[0005] Alternative methods have therefore been developed in which a semiconductor layer is deposited onto a seed substrate and subsequently detached from the carrier element. The detached semiconductor layer is thus the semiconductor wafer for the production of an electronic component.

[0006] It is known from the state of the art to create a porous parting layer on a partial surface of a seed substrate and subsequently to deposit a semiconductor layer on the seed substrate in an epitaxial process. To detach the semiconductor layer from the seed substrate, parting cuts are carried out by means of a laser beam, which completely penetrate the semiconductor layer and reach into the parting layer and / or the seed substrate, thus also damaging or diminishing the seed substrate.

[0007] However, it has proven disadvantageous that parts of the semiconductor layer remain on the seed substrate in the peripheral region of the seed substrate, parts of which are difficult to remove. Furthermore, the seed substrate, or the parting layer, are also compromised by the parting cuts, so that the seed substrates are frequently unsuitable to be reused for the production of a further semiconductor layer or have to be laboriously reprocessed thus limiting their ability to be reused.

[0008] An optimization of the prior art method for the production of a semiconductor layer is known, for example, from DE 10 2015 118 042 Al. Herein, a parting layer is created on a seed substrate on at least a processing side of the seed substrate over the full surface thereof prior to the deposition of the semiconductor layer, and the semiconductor layer is deposited on the processing side and on at least a side surface of the seed substrate in an overlapping manner, wherein, prior to parting of the semiconductor layer from the seed substrate, the overlapping regions of the semiconductor layer are removed.

[0009] Through the overlapping deposition, the semiconductor layer can be detached from the parting layer, or the seed substrate, in the intended size. To ensure reusability of the seed substrate, it is important for the seed substrate to not have any residues of the semiconductor layer after detachment. To ensure this, it is necessary to edge the seed substrate after detaching the overlapping regions and to remove a few micrometers so that the lateral dimensions of the seed substrates are diminished after each application. As soon as a dimension of the seed substrate is smaller than a minimum dimension, it can no longer be used as a seed substrate for the production of further semiconductor layers.

[0010] For industrial use, a cost reduction in the production of semiconductor layers is necessary, in particular through the reusability of seed substrates. At the same time, the detaching process is often very slow due to the necessity of having to remove the entire layers. The present invention is therefore based on the object of providing a simple and quick method of detaching a semiconductor layer from a seed substrate, wherein the reusability of seed substrates is ensured.

[0011] These and further objects are achieved by a method for detaching a semiconductor layer in accordance with Claim 1 and a method for producing a semiconductor layer in accordance with claim 22, and a system for detaching a semiconductor layer in accordance with claim 23. Furthermore, the object is also achieved by a semi-finished product in accordance with claim 24.

[0012] Advantageous embodiments of the method are shown in claims 1 to 21, advantageous embodiments of the semi-finished product are shown in claims 25 and 26.

[0013] The method according to the invention for detaching a semiconductor layer is provided, in particular, to be performed with a system according to the invention for detaching a semiconductor layer. The system according to the invention for detaching a semiconductor layer is provided, in particular, to perform a method according to the invention for detaching a semiconductor layer.

[0014] The method according to the invention for detaching a semiconductor layer comprises the following method steps:

[0015] A) providing a layer stack of at least three layers, wherein a first layer is formed by a seed substrate, a second layer by a parting layer formed on the seed substrate and a third layer by the semiconductor layer formed, preferably epitaxially, on the parting layer, and

[0016] B) detaching the semiconductor layer from the layer stack.

[0017] The invention is distinguished in that, prior to and / or within method step B), a laser radiation of a laser source is focused into the semiconductor layer, wherein the laser radiation is introduced into the semiconductor layer along a lateral focusing line to create at least one modification region below a surface of the semiconductor layer, wherein, in the modification region, a material of the semiconductor layer is modified and a parting region is formed within the semiconductor layer about the modification region.

[0018] By introducing the laser radiation, a modification region, or parting region, is created within the semiconductor layer in a simple manner, which facilitates detachment of the semiconductor layer from the layer stack, or from the parting layer. Herein, the laser radiation can be intentionally focused into the semiconductor layer without negatively affecting or changing the parting layer and / or the seed substrate in its properties. The seed substrate and / or the parting layer can thus be easily reused for the production of further semiconductor layers after the semiconductor layer has been detached.

[0019] According to the invention, the semiconductor layer is thus edged within the layer stack without directly edging the layer stack itself and thus reducing its dimension, in particular its longitudinal extension. Through not directly removing regions of the layer stack, such as during a sawing process or complete edging of the layer stack with a laser, particulate emission is also reduced and the semiconductor layer is less contaminated.

[0020] In the modification region, the material of the semiconductor layer is modified. By modifying, the semiconductor material is changed, in particular, in its crystalline structure. To achieve this, the material in the semiconductor layer is briefly molten or evaporated, and recrystallisation, or solidification, of the molten material is achieved. The introduction of laser radiation according to the invention in an epitaxial, preferably monocrystalline, silicon semiconductor layer can thus form, for example, the modification region from polycrystalline or amorphous silicon. According to the invention, the parting region is created about the modification region. The modification region can also be identical with the parting region.

[0021] The seed substrate is preferably of a crystalline material, in particular a monocrystalline material, preferably a semiconductor material. Alternatively, the seed substrate can also be of a polycrystalline or an amorphous material. The seed substrate can be, in particular, a carrier element, which comprises further regions or layers in addition to the actual seed substrate. A preferred embodiment is distinguished in that the focusing line is formed by the localized introduction of the laser radiation at a plurality of focusing points at a focusing depth and the at least one modification region is formed about each individual focusing point. It is therefore sufficient for the laser radiation to be introduced into the semiconductor layer only at individual points. The focusing depth depends, in particular, on a thickness of the semiconductor layer, wherein the creation of the modification region about the focusing point is to be considered when the focusing depth is adjusted. Preferably, the parting layer and, in particular the seed substrate, should not undergo modification so that they can be reused for the production of further semiconductor layers.

[0022] Preferably, the modification regions and / or the parting regions created about the modification regions of the focusing points overlap each other in the lateral direction and form a contiguous region. The overlapping and contiguous region along the focusing line ensures clean detachment of the semiconductor layer.

[0023] In a preferred embodiment, to create the focusing points, the layer stack is moved continuously, in particular at a continuous speed, relative to the laser source. Preferably, the layer stack is moved relative to the stationary laser source. Alternatively, or preferably additionally, a corresponding optics for the laser radiation can be moved instead of or in addition to the laser source in such a manner that the focusing points can be introduced into the semiconductor layer along the focusing line.

[0024] In a further preferred embodiment, to create the focusing points, the layer stack is intermittently moved relative to the laser source, preferably, the layer stack is moved relative to the stationary laser source. Alternatively or preferably additionally, instead or in addition to the laser source, a corresponding optics can also be moved in such a manner that the focusing points can be introduced into the semiconductor layer along the focusing line by means of the laser radiation.

[0025] Alternatively, the laser source or an optics for the laser radiation can also be moved relative to the stationary layer stack. Preferably, the laser source and / or the optical elements for the laser radiation can be moved relative to the surface of the semiconductor layer in the thickness direction towards or away from the surface of the semiconductor layer. By these means, irregularities and / or surface roughness can be compensated.

[0026] An advantageous embodiment of the method according to the invention is distinguished in that the laser radiation is pulsed. The pulsed laser radiation allows the individual focusing points to be intentionally introduced, and thus introduced in a limited manner, into the semiconductor layer.

[0027] Preferably, the pulsed laser radiation is short pulses in the range of nanoseconds. Particularly preferably, the short pulses have a pulse length in the range from 1 ns to 150 ns, preferably from 5 ns to 100 ns, particularly preferably from 10 ns to 30 ns. The short pulses ensure that sufficient energy, or a sufficiently high energy density, is provided to achieve localized melting of the semiconductor layer about the focusing point to create a modification region.

[0028] Alternatively, or preferably additionally, the pulsed laser radiation is ultrashort pulses in the range of picoseconds or femtoseconds. The ultrashort pulses ensure that the modification region can be more strictly reduced in its extension and can be smaller, in particular, so that the semiconductor layer overall is exposed to less influence.

[0029] Preferably, the pulsed laser radiation is only needed in the lower medium power range of the laser radiation of, for example, 100 mW to 10 W to create the modification regions.

[0030] A further preferred embodiment is distinguished in that a plurality of focusing points are created within the semiconductor layer one above each other in the thickness direction at different focusing depths. Alternatively or preferably additionally, a plurality of modification regions are created vertically above each other in the thickness direction. With thicker semiconductor layers, in particular, the creation of a parting region correspondingly extending in the thickness direction can be achieved, to ensure clean detachment of the semiconductor layer. Moreover, the plurality of focusing points ensures that the circumference and the extension of the modification region is minimized in relation to the parting region created. The semiconductor layer thus undergoes less modification due to a plurality of smaller modification regions.

[0031] The plurality of focusing points above each other in the thickness direction can be introduced in a plurality of successive processing steps so that, for example, the focusing points of a first focusing line are created first and, in a second step, the focusing points of a second focusing line are created, which are spaced from each other in the thickness direction and are situated vertically above each other in the thickness direction. Alternatively, the vertically superimposed focusing points can also be created immediately successively or simultaneously. This can be achieved, for example, by the use of corresponding optical elements in the beam path of the laser radiation. At least two focusing lines are thus created in parallel to each other.

[0032] Further, alternatively or preferably additionally, a plurality of focusing points are simultaneously created in the lateral direction in juxtaposition. By the simultaneous creation of a plurality of focusing points, the process of detachment of the semiconductor layer can be further accelerated.

[0033] In an advantageous embodiment, at the focusing points, the laser radiation is introduced in multiple succession. On the one hand, this can ensure that a modification of the material of the semiconductor layer is also carried out in the modification region. In particular, the modification region can also be influenced in its extension by the corresponding multiple introduction of pulsed laser radiation so that it has a desired extension and, as the case may be, shape.

[0034] A preferred embodiment is distinguished in that the semiconductor layer is essentially transparent to a wavelength of the laser radiation. This ensures intentional focusing of the laser radiation within the semiconductor layer on the focusing point without the radiation being first substantially absorbed as it penetrates the semiconductor layer and / or the further layers of the layer stack. Absorption in the region of the focusing point is essentially caused by the threshold energy density being exceeded in this region. Multi-photon absorption processes can also happen.

[0035] In particular, the wavelength of the laser radiation is in the range from 200 nm to 2000 nm, preferably in the range from 350 nm to 1600 nm, particularly preferably in the range from 500 nm to 1500 nm, most preferably in the range from 1000 nm to 1350 nm.

[0036] For a semiconductor layer of silicon, the wavelength of the laser radiation is preferably in the range from 800 nm to 2000 nm, preferably in the range from 900 nm to 1600 nm, particularly preferably in the range from 1000 nm to 1350 nm.

[0037] Advantageously, the parting region is formed within the semiconductor layer so that detachment of the semiconductor layer from the layer stack is easily achieved.

[0038] Preferably, the parting region extends up to the parting layer and / or the surface of the semiconductor layer. The particular extension of the parting region up to the parting layer in the thickness direction ensures that the semiconductor layer is easily detachable from the former. The extension of the parting region up to the surface of the semiconductor layer also ensures that it can be optically controlled, for example by means of a camera. When deviations from particular contours or malformations occur, the laser radiation to create the focusing points can be changed to influence or change the parting region or the optically visible part on the surface.

[0039] An advantageous embodiment is distinguished in that the laser radiation is introduced into the layer stack along the focusing line in such a manner that a predetermined breaking point, in particular a crack, is created within the semiconductor layer in the parting region comprising the modification region. In particular, the predetermined breaking point is formed through the parting region and / or the modification region.

[0040] Alternatively or preferably additionally, the laser radiation is introduced into the layer stack along the focusing line in such a manner that the semiconductor layer is parted from the rest of the layer stack, the residual stack, completely along the parting region. Complete parting of the semiconductor layer from the layer stack is thus enabled solely due to the laser radiation so that the semiconductor layer can be simply detached, for example, by means of a gripper as a type of detachment means.

[0041] In a preferred embodiment, the semiconductor layer includes an overlapping region larger than a flat side of the seed substrate and / or of the parting region, which is formed to preferably at least partially cover one or a plurality of side surfaces of the seed substrate and / or of the parting layer. The semiconductor layer thus has a larger extension than the flat side of the parting layer and overlaps on the side regions. This overlapping region can also extend along the side surfaces of the seed substrate or, when the parting layer is deposited along the latter, along the side surfaces of the parting layer. The overlapping region can be a result of the process and, due to its formation in the peripheral region, its crystalline quality is somewhat poorer, for example, due to defects or offsets as compared to the actual semiconductor layer. The creation of the semiconductor layer essentially corresponding to the area of the seed substrate is enabled by the overlapping region. Moreover, uniform thickness of the semiconductor layer is facilitated by the overlapping region.

[0042] The overlapping region can be of a poorer quality than the material of the semiconductor layer and can comprise, for example, defects or offsets. This helps to achieve, however, that the semiconductor layer relevant for the applications is spaced from these regions and has a higher grade and better quality.

[0043] Advantageously, the overlapping region is of the same material as the semiconductor layer. The overlapping region is thus automatically formed during the production of the semiconductor layer and thus forms part of the semiconductor layer.

[0044] Alternatively or preferably additionally, the overlapping region is detached from the semiconductor layer and / or from the layer stack in method step B). The overlapping region would be an obstruction to further use of the seed substrate for the production of semiconductor layers. Detaching the overlapping region thus improves reusability of the seed substrate. Moreover, it is ensured that all semiconductor layers are made on the basis of almost identical starting conditions, in particular in view of the shape and configuration of the seed substrates, thus facilitating series production.

[0045] A preferred embodiment of the method is distinguished in that the focusing line and / or the modification region and / or the parting region is formed at least in part within the overlapping region. In particular, when the overlapping region surrounds the side surfaces of the seed substrate or the parting layer, complete parting is achieved along the focusing line.

[0046] It is further preferred for the focusing line and / or the modification region and / or the parting region to be primarily formed outside of the overlapping region. This ensures that the overlapping region is cleanly and completely detached from the actual semiconductor layer, which is then used for further processing.

[0047] In a preferred embodiment, the focusing line and / or the modification region and / or the parting region is formed in a closed configuration. This ensures that the semiconductor layer can be intentionally and cleanly separated from the layer stack. The closed focusing line forms, in particular, a delimited area, which can then be detached from the layer stack as a semiconductor layer.

[0048] An advantageous embodiment is distinguished in that the laser radiation is introduced into the semiconductor layer from one or more flat sides of the layer stack. The focusing line can thus be intentionally introduced into the semiconductor layer, wherein only a relative movement of the layer stack and the laser radiation with respect to each other is required.

[0049] Preferably, the laser radiation can also be introduced into the semiconductor layer at a plurality of points simultaneously. For example, the laser radiation can be split up by means of optical elements to form the respective modification regions at opposite sides of the layer stack along parallel focusing lines.

[0050] Alternatively or preferably additionally, the laser radiation is introduced from a side surface of the layer stack into the semiconductor layer, in particular into the overlapping region. Detachment of the semiconductor layer with at least a part of the overlapping region from the parting layer or the seed substrate can thus be intentionally achieved.

[0051] In a further preferred embodiment, the focusing depth of the laser radiation is adjustable in the thickness direction in the range of a thickness of the semiconductor layer. The focusing points, or the focusing line, and thus the modification region, can thus be adjusted within the semiconductor layer as to their position and can be adjusted and varied according to the respective preconditions.

[0052] Preferably, the focusing depth in the thickness direction is in the range of half the thickness of the semiconductor layer and / or preferably in the range of 10 pm to 500 pm below the surface of the semiconductor layer. Preferably, the focusing depth is chosen thus that it is approximately in the middle of the thickness of the semiconductor layer.

[0053] In yet another embodiment of the method according to the invention, the focusing point is created with an essentially circular or oval-shaped cross-section. The cross-section can influence, in particular, the formation of the modification region and its configuration or extension. Preferably, the use of various optical elements in the beam path of the laser radiation can influence and change the cross-section of the focusing points.

[0054] Alternatively or preferably additionally, the modification region and / or the parting region is produced and / or created with an essentially circular or oval-shaped region cross-section. The region cross-section and generally the creation of the modification region is primarily determined by the cross-section and the configuration of the focusing point, which is situated in the modification region, as well as by the power applied to the semiconductor layer by the laser radiation. The absorption of the laser radiation and the heating of the semiconductor material about the focusing point leads to a change of the absorption properties of the semiconductor layer (free charge carrier absorption) thus leading to stronger absorption, for example, of the laser radiation by the focusing point and formation of an elongate modification region in the thickness direction. In particular, a longitudinal extension is created on the side of the modification region facing the laser radiation. The formation of the modification region also depends on the crystalline structure of the semiconductor layer about the region of the focusing point.

[0055] An advantageous embodiment is distinguished in that, in method step B), the laser radiation is introduced in such a manner that the seed substrate and / or the parting layer does not experience any influence by the laser radiation. The laser radiation can be adjusted, in particular, in such a way that modification only occurs in the semiconductor layer and, as the case may be, in the overlapping region.

[0056] Preferably, after method step B), in particular after a reprocessing step, the seed substrate, preferably together with the parting layer, is used for the production of at least one further semiconductor layer.

[0057] In a preferred embodiment, at least two focusing lines are created in the semiconductor layer at different focusing depths offset to each other in the transverse direction. In particular, the focusing lines are simultaneously or successively formed at different focusing depths. Creation of two modification regions one above the other is thus achieved in the transverse direction, which lead to the creation of a parting region extending at an angle to the thickness direction.

[0058] A further preferred embodiment is distinguished in that the laser radiation is incident into the layer stack in a direction perpendicular to the surface of the semiconductor layer. Alternatively, the laser radiation can also be incident into the layer stack at an angle of incidence to the normal on the surface of the semiconductor layer. The angle of incidence is formed between the normal on the surface of the semiconductor layer and the laser radiation. The angle of incidence is an angle different from 0°. The position and configuration of the parting regions can be influenced by the shape of the radiation of the laser radiation into the semiconductor layer or the layer stack. In particular, an incidence of the laser radiation at an angle of incidence leads to the formation of a parting region extending obliquely in the thickness direction. Preferably, the angle of incidence is in a range from ± 10° to ± 45°, in particular at ± 30°. Advantageously, the semiconductor layer and / or the seed substrate is silicon, in particular monocrystalline silicon. However, the invention is not limited in this way. The semiconductor layer can be any semiconductor, in particular crystalline material. In particular, the semiconductor layer can also be of germanium or any Ill-V-semiconductor, such as gallium nitride or gallium arsenide, or a semiconductor compound such as silicon carbide.

[0059] Alternatively or preferably additionally, the parting layer is porous silicon. Alternatively, the parting layer can be formed of any material which, on the one hand, is a good seeding layer for the semiconductor layer and / or, on the other hand, enables easy detachment of the semiconductor layer produced thereon.

[0060] The above object is further achieved by a method for producing a semiconductor layer, comprising the method steps of:

[0061] VI) providing a seed substrate;

[0062] V2) creating a parting layer on the seed substrate;

[0063] V3) depositing a semiconductor layer on the parting layer of the seed substrate, preferably by means of epitaxy, to create a layer stack of the seed substrate, the parting layer and the semiconductor layer; and

[0064] V4) detaching the semiconductor layer from the layer stack.

[0065] The method for producing a semiconductor layer is distinguished in that detaching of the semiconductor layer is done by a method for detaching a semiconductor layer or any advantageous embodiment thereof as described above. In particular, following method step V4), the method steps V2) to V4) are performed plural times with the seed substrate.

[0066] The above object is further achieved by a system for detaching a semiconductor layer from a layer stack, wherein the layer stack comprises at least a seed substrate, a parting layer formed on the seed substrate and the semiconductor layer preferably epitaxially produced on the parting layer, wherein the system comprises a support for the layer stack, preferably a detaching unit for the semiconductor layer, and a laser source to generate a laser radiation. The system is preferably configured for the execution of a method for detaching a semiconductor layer or any advantageous embodiment thereof as described above.

[0067] For the system it is essential that the laser radiation of the laser source is focused into the layer stack in such a manner that a modification region is created below a surface of the semiconductor layer along a lateral focusing line, in which a material of the semiconductor layer is modified, and preferably a parting region comprising the modification region is creatable and in that the semiconductor layer is formed to be detachable from the layer stack along the focusing line in particular by means of the detaching unit.

[0068] The above object is further achieved by a semi-finished product, comprising a layer stack of at least a seed substrate, a parting layer formed on the seed substrate and the semiconductor layer preferably epitaxially produced on the parting layer, in particular of silicon, wherein the semiconductor layer preferably includes an overlapping region larger than a flat surface of the seed substrate and / or the parting layer, which is preferably formed to at least partially cover one or more side surfaces of the seed substrate and / or the parting layer.

[0069] The semi-finished product according to the invention is distinguished in that, below a surface of the semiconductor layer, a modification region and preferably a parting region comprising the modification region is formed along a focusing line, wherein, in the modification region, a material of the semiconductor layer is modified.

[0070] In an advantageous embodiment, the parting region extends up to the parting layer and / or the surface of the semiconductor layer. It is thus ensured that the semiconductor layer is easily detachable from the layer stack or the parting layer.

[0071] Alternatively, or preferably additionally, a predetermined breaking point, in particular a crack, is formed through the parting region. In a preferred embodiment, the parting region extends within the semiconductor layer at an angle to the thickness direction. By providing that the parting region extends at an angle to the thickness direction, detaching the semiconductor layer from the remaining layer stack is simplified.

[0072] Further advantageous features and embodiments will be described in the following with reference to exemplary embodiments and the drawing figures. In the drawings:

[0073] Fig. la) shows a schematic sectional view of a layer stack using the method according to the invention;

[0074] Fig. lb) shows a perspective view of the layer stack of Fig. la);

[0075] Fig. lc) shows a schematic sectional view of a layer stack using the method according to the invention in a further embodiment;

[0076] Fig. 2a) and 2b) each show a schematic detail view of various embodiments of differently shaped focusing points;

[0077] Fig. 3a) and 3b) show top views of the layer stack of Fig. la) using the method according to the invention at different points in time;

[0078] Fig. 4a) shows a schematic sectional view of a layer stack using an alternative embodiment of the method according to the invention;

[0079] Fig. 4b) shows a schematic sectional view during detachment of the semiconductor layer;

[0080] Fig. 5 shows a schematic sectional view of a layer stack using yet another embodiment of the method according to the invention;

[0081] Fig. 6 shows a schematic sectional view of a layer stack using yet another embodiment of the method according to the invention;

[0082] Fig. 7 shows a schematic sectional view of a layer stack using yet another embodiment of the method according to the invention;

[0083] Fig. 8a) and 8b) each show a schematic sectional view of a layer stack using yet another embodiment of the method according to the invention;

[0084] Fig. 8c) shows a further schematic sectional view during detachment of the semiconductor layer after forming an obliquely extending parting region; Fig. 8d) and 8e) show schematic sectional views of a layer stack using yet another embodiment of the method according to the invention at different points in time;

[0085] Fig. 9a) shows a schematic sectional view of a layer stack using yet another embodiment of the method according to the invention; and

[0086] Fig. 9b) shows a further schematic sectional view during detachment of the semiconductor layer after forming a parting region of Fig. 9a).

[0087] All of the drawing figures are schematic views, not to scale. In the figures, the same reference numerals refer to the same or equivalent elements throughout.

[0088] Figures la) and lc) each show layer stacks 1 in a schematic sectional view, and Fig. lb) shows the layer stack 1 of Fig. la) in a perspective view. The layer stack 1 comprises three layers, which are arranged one above the other in the thickness direction 13. During the production of the layer stack 1, first a seed substrate 2 is provided which, in the present case, is made of silicon. By means of porosification, as known, for example from DE 10 2015 121 636 Al or DE 10 2018 111 858 Al, a parting layer 3 is created on the seed substrate 2, which covers the seed substrate 2 at least on one flat side. In the present case, the parting layer 3 surrounds the seed substrate 2 at the flat side 2a at the top in the thickness direction, as well as on the side regions of the seed substrate 2. Furthermore, a region of the bottom flat side 2b of the seed substrate 2 in the thickness direction can also be porosified at the regions of the parting layer 3 adjacent to the side regions. The parting layer 3 is thus also partially formed on the bottom flat side 2b of the seed substrate 2.

[0089] After forming the parting layer 3, a semiconductor layer 4 is formed on the parting layer 3 by means of epitaxy, which completely covers the parting layer 3 on the side of the parting layer 3 facing away from the top flat surface 2a of the seed substrate 2 and which has an overlapping region 10 in the lateral peripheral region. This method for the formation of a semiconductor layer is known from DE 10 2019 130745 Al.

[0090] Epitaxial deposition of the material of the semiconductor layer 4 is also carried out in the overlapping region 10. In the present case, this is also silicon. The seed substrate 2 is completely sheathed by the semiconductor layer 4 and the overlapping region 10 with the exception of the bottom flat surface 2b in the thickness direction 13.

[0091] To be able to detach the epitaxially created semiconductor layer 4 from the layer stack 1 and thus from the seed substrate 2, it is provided by the method in accordance with the invention to focus laser radiation 12 from a laser source 11 into the semiconductor layer 4. For this purpose, the laser radiation 12 is introduced at a plurality of positions for the creation of individual focusing points 5, which are situated within the semiconductor layer 4. The focusing points 5 are formed along a lateral focusing line 6 within the semiconductor layer 4 at a focusing depth 5a. The focusing depth 5a depends, in particular, on the thickness of the semiconductor layer 4 and, in the present case, is in the range of half the thickness of the semiconductor layer and thus, for example, in the range of about 70 pm.

[0092] A pulsed laser is used as the laser source 11, since this causes the focusing points 5 to be correspondingly formed. The laser radiation 12 is comprised of short pulses, the pulse length of which is in the range from 5 ns to 30 ns. The wavelength of the laser radiation 12 in the present case is at about 1064 nm or at about 1342 nm.

[0093] The laser radiation 12 of the laser source 11 is guided and focused by an optical element 15. For better clarity, only one optical element 15, in the present case, in the form of an optical lens, is shown in each of Figures la), lb) and lc). However, mirrors, partially transmitting mirrors, diffractive optical elements or apertures (diaphragms) could also be used as optical elements 15. As shown in Figures la) and lb), for focusing the laser radiation 12 into the semiconductor layer 4, the laser source 11 and the optical element 15 are arranged above the surface 9 of the semiconductor layer 4 in the thickness direction 13. The laser radiation 12 is introduced into the semiconductor layer 4 essentially in a direction perpendicular to the surface 9 thereof.

[0094] Fig. lc) shows a further embodiment of the method according to the invention, in which the laser radiation 12 is introduced into the semiconductor layer 4 at a focusing depth 5a for the formation of focusing points 5 from the bottom surface side 2b of the seed substrate 2. Again, the laser radiation 12 is focused into the layer stack 1 essentially in a direction perpendicular to the surface of the lower surface side 2b of the seed substrate 2. Depending on the materials chosen for the seed substrate 2, the parting layer 3 as well as the semiconductor layer 4, this type of radiation of the laser radiation 12 into the semiconductor layer 4 can also be possible. Furthermore, in Fig. lc), the parting layer 3 as well as the overlapping region 10 are only partially deposited along the side surfaces of the seed substrate 2.

[0095] To create the individual focusing points 5 in the semiconductor layer 4, in the present case, the layer stack 1 is moved relative to the laser source 11, or the laser radiation 12, which, in the present case, is essentially formed, or arranged, to be stationary in the lateral direction. Stationary arrangement of the laser radiation 12 is provided, for example, by using stationary optical elements 15, which focus the laser radiation 12 into the semiconductor layer 4 of the layer stack 1. The laser radiation 12 is pulsed during the uniform movement of the layer stack 1 into the semiconductor layer 4 and thus creates the individual focusing points 5. The lateral distance of the focusing points 5 depends on various factors and is influenced, in particular, by the relative speed of the layer stack 1 to the laser radiation 12, or the laser source 11, and the repeat frequency of the pulses of the laser source 11. By choosing the corresponding parameters, the distance of the focusing points 5 can be adjusted to ultimately enable detachment of the semiconductor layer 4. A short pulse length of the laser radiation 12 can help to accelerate the creation of focusing line 6 so that the semiconductor layer 4 can be subsequently rapidly detached.

[0096] The focusing line 6, in the present case, is formed in the semiconductor layer 4 as completely closed so that ultimately a semiconductor layer 4 to be detached is formed, which is detached from the layer stack 1 by means of a detachment unit and is then used for further processing, for example for the manufacture of solar cells and semiconductor components. The focusing line 6 formed in a closed configuration defines a region within the focusing line 6 which essentially corresponds to the semiconductor layer 4 to be detached.

[0097] A modification region 7 is created about each of the focusing points 5, in which the material of the semiconductor layer 4, in the present case silicon, is modified. The modification is a change in the crystalline structure of the semiconductor layer 4 which is created about the focusing points 5 by the introduction of the laser radiation 12. The laser radiation 12 focused into the semiconductor layer 4 causes at least short melting and, as the case may be, evaporation of the material of the semiconductor layer 4 at the focusing points 5 and in the modification region 7. During solidification of the molten material, the molten material assumes a different crystalline structure so that the crystalline structure differs significantly and, in particular, noticeably, from the rest of the semiconductor layer 4 about the modification region 7. Since, in the present case, the semiconductor layer 4 is crystalline silicon, the introduction of the laser radiation 12 into the semiconductor layer 4 modifies this to polycrystalline and / or partially amorphous silicon in the modification region 7.

[0098] Fig. lb) shows a perspective view of a detail of the layer stack 1 of Fig. la). The individual focusing points 5 are essentially spherical in shape and are introduced into the semiconductor layer 4 along the focusing line 6. Modification regions 7 have formed about the individual focusing points 5, which have an elongate shape in the thickness direction 13, wherein the elongate extension is essentially on the side facing the laser radiation 12 above the focusing points 5.

[0099] Both the focusing points 5 and the modification region 7 can be variable in shape and configuration and depend, in particular, on the power of the laser source 11, the wavelength of the laser radiation 12, the pulse length of the laser radiation 12 and the optical properties of the semiconductor layer 4, such as the refractive index and the absorption coefficient, which are also generally temperature and time dependent. Figures 2a) and 2b), for example, show two embodiments of focusing points 5 and the modification region 7 created about the focusing points 5. As shown in Fig. 2a), the focusing point 5 was created with an essentially circular cross-section. The modification region 7 about the focusing point 5, has an oval-shaped cross-section, the main axis of which is essentially parallel to the thickness direction 13. The focusing point 5 itself only forms a small fraction of the modification region 7. The configuration of the modification region 7, in particular its shape and size, is also influenced by the crystalline quality of the semiconductor layer 4 and by the heating of the semiconductor layer 4 and the thus changed optical properties.

[0100] Fig. 2b) shows a further embodiment in view of the focusing point 5 and the modification region 7. By changing the laser radiation 12 during focusing of the latter into the semiconductor layer 4, for example by using further and / or different optical elements 15, in particular optical lenses, in the beam path of the laser radiation 12, the cross-section of the focusing point 5 can also have an oval-shaped configuration, wherein the main axis also extends essentially parallel to or in the thickness direction 13. The modification region 7 in this case, analogous to the focusing point 5 in its shape, is also formed to be oval-shaped or elliptical about the focusing point 5 with its main axis essentially parallel to the thickness direction 13. In contrast to Fig. 2a), the modification region 7 of Fig. 2b) is formed significantly larger or more elongate, wherein the elongate extension is essentially on the side facing the laser radiation 12. An elongate configuration of the focusing point 5 in the thickness direction 13 can be achieved, among other things, by focusing partial rays 12', 12" of the laser radiation 12 at different focusing depths, wherein the focusing points 5 for the partial rays 12', 12" of the laser radiation 12 can be situated in close proximity.

[0101] The focusing point 5 can generally have any particular cross-section, in particular, the focusing point 5 can also have an oval-shaped cross-section, the main axis of which essentially extends in the lateral direction 14 or at an angle to the thickness direction 13 and / or the lateral direction 14.

[0102] The individual focusing points 5, in the present case, are formed along the focusing line 6 so that the modification regions 7 of the focusing points 5 overlap with each other as shown in Figures la), lb), and lc). A contiguous region is thus created by the overlap of the individual modification regions 7, in which the material of the semiconductor layer 4 is modified.

[0103] During the formation of the modification region 7 about the focusing point 5, a further region is created about the modification region 7, which is referred to as a parting region 8. While there is no modification of the material of the semiconductor layer 4 within the parting region 8, stresses within the semiconductor layer 4 about the modification region 7 are created by the formation of the modification region 7 within the semiconductor layer 4. They cause the creation of a predetermined breaking point as a parting region 8 within the semiconductor layer 4 about the modification region 7. In the present case, the parting region 8 is already formed by a crack, which, as shown in Fig. 1, extends within the semiconductor layer 4. The parting region 8, in the exemplary embodiment shown, essentially extends along the lateral direction 14 and has only a small width in the transverse direction 17, which is perpendicular to the thickness direction 13 and the lateral direction 14 and, in the present case, extends into the image plane. The semiconductor layer 4 is detached from the layer stack 1 along the parting region 8.

[0104] By moving the layer stack 1 relative to the laser source 11, the focusing line 6 is fully introduced in the lateral direction 14 along the extension and the dimension of the semiconductor substrate 4. Focusing points 5 and corresponding modification regions 7 are thus also created in the overlapping region 10.

[0105] As shown in figures 3a) and 3b), the focusing line 6 and the parting region 8 formed along the focusing line 6 extends largely within the semiconductor layer 4 at a small distance to the overlapping region 10. The parting region 8, in the present case, can be seen, and is correspondingly shown, in a top view by the formation of a crack, which extends up to the surface 9 of the semiconductor layer 4. The focusing line 6, or the parting region 8, also "breaks through" the overlapping region 10 only in the peripheral area of the semiconductor layer 4 to the ends of the layer stack 1 in the lateral direction 14. Most of the focusing line 6, and thus also of the modification region 7 and the parting region 8, extends within the semiconductor layer 4. This serves to ensure that the semiconductor layer 4' to be detached is of high grade and quality. Offsets and crystallization defects, which have a negative effect on the grade and quality of the semiconductor layer 4, can occur at the peripheral areas of the semiconductor layer 4 and thus, in particular, in the overlapping region 10. The overlapping region 10 can also prevent mechanical detachment of the semiconductor layer 4, if the latter is not removed or, as suggested in the present method, is detached, or detachably modified, from the rest of the semiconductor layer 4. To avoid negative influences of these defects in a semiconductor component made later from the semiconductor layer 4, the focusing line 6, or the parting region 8, is formed in the semiconductor layer 4 mainly outside of the peripheral areas at a distance from the overlapping region 10.

[0106] To ultimately detach the semiconductor layer 4 from the layer stack 1, the focusing line 6 is introduced into the layer stack 1 and thus into the semiconductor layer 4 fully circumferentially and in a closed configuration, as shown in Fig. 3b). This serves to ensure that a semiconductor layer 4' to be detached and having high quality is formed within the semiconductor layer 4, which can also be completely detached from the layer stack 1. For this purpose, the focusing lines 6 with the focusing points 5 and the resulting parting regions 8 were first formed along the side surfaces so that the focusing line 6, or the parting regions 8 shown, are already formed in a closed configuration. Additionally, prior to detachment of the semiconductor layer 4' the laser radiation 11 is introduced at an angle to the side surfaces to create a chamfer. By beveling the corners of the semiconductor layer 4', the stability of the semiconductor layer 4' is increased, in particular. The semiconductor layer 4' to be detached has a somewhat smaller dimension than the semiconductor layer 4, which is determined by the extension of the focusing line 6 within the semiconductor layer 4.

[0107] Fig. 4a) shows a further embodiment of the method according to the invention, in which the laser radiation 12 is introduced into the semiconductor layer 4 simultaneously at two points. Two focusing points 5 and modification regions 7 corresponding to the focusing points 5 are thus created simultaneously or at a short time interval in the range of the pulse repeat frequency, which are created along two essentially parallel focusing lines 6, extending into the image plane in the present case. The essentially simultaneous creation of two focusing points 5, or modification regions 7, again substantially accelerates the process of detaching or releasing the semiconductor layer 4.

[0108] As shown in Fig. 4a) in the present case, the formation of the focusing points 5 for the creation of a respective focusing line 6 is performed at opposite regions of the layer stack 1. The lateral direction 14, along which the focusing points 5 are created, extends into the image plane in Fig. 4a). To completely part the semiconductor layer 4, after the creation of the two parallel focusing lines 6 with the corresponding modification region 7 and parting regions 8 along the sides of the layer stack 1, the layer stack 1 is only rotated by about 90° so that the focusing lines 6 with the corresponding modification region 7 and parting regions 8 can be subsequently created along the remaining two sides of the layer stack 1.

[0109] Fig. 4b) now shows the method step in which the semiconductor layer 4' is parted from the layer stack 1 by means of a detaching unit. After the complete formation of the parting regions 8, as described before, the semiconductor layer 4' is detached as shown in Fig. 4b) in such a manner that only the semiconductor layer 4', preferably with only part of the parting layer 3, is removed from the layer stack 1 and the regions about the overlapping region 10 first remain with the remaining residual stack 16.

[0110] To ensure reusability of the seed substrate 2 for the further production of semiconductor layers 4, it is advantageous to not only remove the semiconductor layer 4' to be detached but also the remaining parts of the semiconductor layer 4 as well as the overlapping region 10 from the residual stack 16. These remaining portions are also preferably detached during the detachment of the semiconductor layer 4 from the layer stack 1. The modification region 7, or the parting region 8, is formed in such a way that by detaching the semiconductor layer 4 the remaining portions such as the overlapping region 10 and the non-detached portion of the semiconductor layer 4 which is adjacent to the overlapping region 10 can also be detached from the layer stack 1.

[0111] In a method step subsequent to the state shown in Fig. 4b) the regions about the overlapping region 10 can be removed from the residual stack 16 so that the original seed substrate 2, with a portion of the parting layer 3, as the case may be, can be used for the production of a further semiconductor layer 4. Alternatively, the detachment of the semiconductor layer 4' from the layer stack 1 can also be performed in such a manner that the peripheral regions about the overlapping region 10 are also removed from the layer stack 1 simultaneously with the semiconductor layer 4'. The detachment of the semiconductor layer 4' and the peripheral areas are thus performed in one step.

[0112] Subsequently, the seed substrate 2 remains with a parting layer 3 which is complete or, as the case may be, which only remains in parts as shown in Fig. 4b). This seed substrate 2 can then be used in a later process for the production of further semiconductor layers 4, wherein, as the case may be, the parting layer 3 is reprocessed or newly produced on the seed substrate 2 for the production of the epitaxial semiconductor layer 4. However, the method according to the invention does not damage the seed substrate 2 in any way or substantially change its dimensions. What remains, rather, is always the same, high-quality, seed substrate 2 with its dimensions remaining essentially intact. By focusing the laser radiation 12 into the semiconductor layer 4, the seed substrate 2 does not undergo any modifications, nor is it edged at the peripheral areas, for example, by a laser completely penetrating the layer stack 1 or by means of sawing.

[0113] The introduction of the laser radiation 12 at two focusing points 5 formed simultaneously, at a distance to each other, as shown in Fig. 4a), can be implemented by means of various options. On the one hand, it is possible to split up the laser radiation 12 of a laser source 11 by means of one or more optical elements 15 and to guide it to the desired location of usage by means of further corresponding optical elements 15. This allows the introduction of the laser radiation 12 at different focusing points 5 simultaneously in a manner that is flexible and depends on the configuration of the optical elements 15. However, the beam path of the laser radiation 12 always requires checking so that it arrives at the intended focusing point 5.

[0114] Alternatively, a plurality of laser sources 11 can be used to produce laser radiation 12, wherein the laser radiation 12 of a laser source 11 is used to create a focusing point 5. A plurality of laser sources 11 is thus needed, which can be individually used, however, in a quick and flexible manner.

[0115] The position of the focusing point 5 as well as the creation of the modification region 7 can also be determined by the adjustment of the laser radiation 12. Depending on the thickness of the semiconductor layer 4 in the thickness direction 13, the focusing point 5 can thus be created closer to or further away from the surface 9 of the semiconductor layer 4. For this purpose, the focusing points 5 are introduced at a focusing depth 5a. It must be taken care, however, to create the focusing point 5 within the semiconductor layer 4 and not within the parting layer 3. The focusing depth 5a is thus always smaller than the thickness of the semiconductor layer 4, since otherwise modifications or changes in the parting layer 3 and, in particular, in the seed substrate 2 can occur.

[0116] The creation of the focusing points 5, in the present case, is caused by a short pulse of the pulsed laser radiation 12. Alternatively, however, there is also the possibility of introducing a plurality of short pulses in succession at a focusing point 5, and thus influencing, in particular, the configuration of the modification region 7 about the corresponding focusing point 5.

[0117] In the following Figures 5 to 7, further embodiments in view of the creation of focusing points 5, of focusing lines 6, of modification regions 7 and parting regions 8 are shown.

[0118] Fig. 5 shows a further embodiment of the method according to the invention, in which the individual focusing points are created further spaced from each other in the lateral direction 14. The modification regions 7 created about each focusing point 5 do not overlap each other due to the intervals of the focusing points 5. However, there is still an overlap, but only of the parting regions 8 created about each modification region 7. The respective parting regions 8 thus form a contiguous region with each other, along which the semiconductor layer 4 will be detached or released later on.

[0119] The individual modification regions 7 as well as the contiguous parting region 8 are completely situated within the semiconductor layer 4 as shown in Fig. 5. The parting region 8 thus neither reaches the parting layer 3 nor the surface 9 of the semiconductor layer 4 in the thickness direction 13. However, this is not absolutely necessary, since for the detachment of the semiconductor layer 4 it is sufficient that a corresponding parting region 8 as for example, in the present case, a predetermined breaking point, is formed within the semiconductor layer 4.

[0120] Fig. 6 shows a further embodiment substantially differing from Fig. 5 in view of the configuration of the parting region 8. In contrast to the exemplary embodiment of Fig. 5, the parting region 8 of Fig. 6 has been created in such a manner, or is formed in such a manner, that it extends up to the surface 9 of the semiconductor layer 4. Due to the focusing points 5 at the given focusing depth 5a which, in contrast to Fig. 5, are closer to the surface 9 of the semiconductor layer 4, in Fig. 6, the parting region 8 does not extend quite up to the parting layer 3. This different configuration of the parting regions 8 and, in particular, their extension in the thickness direction 13, is essentially determined by the number and configuration of the focusing points 5 and the focusing depth 5a. As shown in Fig. 6, the focusing points 5 along the focusing line 6 are closely spaced so that the modification regions 7 created about the focusing points 5 overlap each other in analogy to the parting region 8. The formation of the parting region 8 extending up to the surface 9 of the semiconductor layer 4 becomes apparent by the formation of a small crack or the like at the surface 9, which is formed during the processing of the layer stack 1. Due to the formation of the parting region 8 in the form of a crack up to the surface 9 of the semiconductor layer 4, it can be seen by the user, as the case may be, with the help of a camera or the like. An optical criterion is thus provided for the user or for a monitoring system, which can be used to determine whether the focusing points 5 and thus the modification region 7 and the parting region 8 have been properly created and, as the case may be, whether they are at the desired and proper places. The creation of the focusing points 5 for the detachment of the semiconductor layer 4 by the corresponding creation of the modification region 7 and the parting region 8 can thus be monitored. When the modification region 7 as well as the parting region 8 are only formed within the semiconductor layer 4, as is shown, for example, in the exemplary embodiment of Fig. 5, it is possible for the user or a monitoring system to determine, for example by means of an infrared camera, whether the focusing points 5 have been created with the corresponding modification regions 7 and whether the desired parting region 8 has been correspondingly created or formed. However, this will only become apparent later during the detachment of the semiconductor layer 4 from the layer stack 1.

[0121] In yet another exemplary embodiment of the method according to the invention, focusing points 5, 5' are created in the thickness direction 13 at different focusing depths 5a, 5a' above each other in the semiconductor layer 4, as is shown in Fig. 7. The creation of focusing points 5, 5' at different focusing depths 5a, 5a', in combination with the creation of two focusing lines 6, 6' spaced in the thickness direction 13, can be successively carried out in two operating steps. The laser radiation 12 for the different focusing points 5, 5' at the different focusing depths 5a, 5a' is successively introduced into the semiconductor layer 4, wherein a first focusing line 6 is first created at the first focusing depth 5a and subsequently, in an analogous fashion, the second focusing line 6' is created at the second focusing depth 5a'. Preferably, the laser radiation 12 is focused into the semiconductor layer 4 by means of optical elements 15 in such a manner that two focusing points 5, 5' are simultaneously created at two different focusing depths 5a, 5a'. By these means, a corresponding parting region 8 is created by the modification regions 7, 7' created about the two focusing lines 6, 6', which extends from the parting layer 3 to the surface 9 of the semiconductor layer 4. The modification regions 7, 7' of the individual focusing lines 6, 6' do not, however, overlap with each other. For semiconductor layers 4 formed thicker in the thickness direction 13 having a thickness of more than 200 pm, the introduction of a plurality of focusing lines 6, 6' above each other in the thickness direction 13 is particularly recommendable. The creation of a corresponding parting region 8 is thus ensured, which should also ensure complete detachment of the semiconductor layer 4 from the layer stack 1.

[0122] In the above figures, the laser radiation 12 was introduced into the semiconductor layer 4 essentially in a direction perpendicular to the surface 9 of the semiconductor layer 4 for the creation of focusing points 5 and corresponding modification regions 7 and parting regions 8. The creation of modification regions 7 and parting regions 8, in this case, is primarily in the thickness direction 13 with a smaller extension or width in the transverse direction 17. The detached semiconductor layer 4' thus has side surfaces 9a essentially created perpendicular to the surface 9 of the semiconductor layer 4, as is also schematically shown in Fig. 4b).

[0123] Figures 8a) and 8b) show a further embodiment in which the semiconductor layer 4' to be detached is formed with a side surface 9a that is at an angle to the thickness direction 13. As shown in Fig. 8b), a parting region 8 extending at an angle to the thickness direction 13 is created by focusing points 5, 5' superimposed and offset with respect to each other in the transverse direction 17 and created at different focusing depths 5a, 5a'. Due to the offset arrangement of the two focusing points 5, 5', which are simultaneously created in the present case, and by the offset arrangement of the modification regions 7, 7', a parting region 8 is created which connects the two modification regions 7, 7' of the focusing points 5, 5' created offset from each other, thus extending obliquely to the thickness direction 13 in the semiconductor layer 4. Alternatively, the modification region 7 and / or the parting region 8, which extend obliquely with respect to the thickness direction 13, can already be created by the oblique incidence of the laser radiation 12 relative to the surface 9 of the semiconductor layer 4, which is shown in Fig. 8a). To achieve this, it is not absolutely necessary to have two offset focusing points 5, 5' as shown in Fig. 8b). Further alternatively, a modification region 7 and / or parting region 8 extending obliquely relative to the thickness direction 13 can be created by the oblique and / or perpendicular incidence of the laser radiation 12 relative to the surface 9 of the semiconductor layer 4 if a preferably mechanical stress is simultaneously applied to the semiconductor layer 4 or the layer stack 1, for example by means of bending forces.

[0124] To create the focusing points 5, 5', or the focusing lines 6, 6' resulting therefrom in the arrangement offset in the transverse direction 17, the laser radiation 12 is focused into the semiconductor layer 4 at an angle of incidence a to the normal on the surface 9 of the semiconductor layer 4. The angle of incidence a is formed between the normal on the surface of the semiconductor layer and the middle direction of the incident laser radiation 12 and does not at all comprise the perpendicular incidence of the laser radiation 12 which would represent an angle of incidence a of 0 degrees. Preferably, the angle of incidence a is in a range from ± 10° to ± 45°, in particular at ± 30°. By having the laser radiation 12 radiating at an angle, a plurality of focusing points 5, 5' can be simultaneously created, in analogy to the configuration of Fig. 7. Alternatively, the focusing points 5, 5' can also be successively created when the radiation is at an angle.

[0125] When the semiconductor layer 4' is detached from the layer stack 1, as is shown in Fig. 8c), the semiconductor layer 4' now has side surfaces 9a which are oblique with respect to the thickness direction 13 so that the flat surface at the bottom in the thickness direction 13 has a smaller surface area than the flat surface of the semiconductor layer 4' which is at the top in the thickness direction 13. A portion of the parting layer 3 remains on the semiconductor layer 4' to be detached when it is detached, as is shown in Fig. 8c). Chamfered side surfaces 9a simplify the process of removing the semiconductor layer 4' to be detached from the rest of the layer stack, the residual stack 16. The peripheral areas with the overlapping region 10 remaining on the residual stack 16 and the remainder of the semiconductor layer 4 are removed from the residual stack 16 in the subsequent method step so that the seed substrate 2 can be subsequently used for the production of a further semiconductor layer 4.

[0126] Figures 8d) and 8e) show a further embodiment for the creation of an obliquely extending parting region 8 within the semiconductor layer 4. The present is a two-stage method in which first a focusing point 5 with a corresponding modification region 7 is created at a first focusing depth 5a, as shown in Fig. 8d). To achieve this, as mentioned above, the laser radiation 12 is focused into the semiconductor layer 4 by means of optical elements 15. In a second step, a second focusing point 5' with a modification region 7' is created at a second focusing depth 5a' offset in the transverse direction 17, as shown in Fig. 8e). The parting regions thus created about the modification regions 7, 7' and the focusing points 5, 5' with their modification regions 7, 7' offset in the transverse direction 17 cause the creation of an obliquely extending parting region 8 in analogy to Fig. 8a).

[0127] In the present method according to Figures 8d) and 8e), as usual, the laser radiation 12 can be introduced in a direction perpendicular to the surface 9 of the semiconductor layer 4. There is therefore no need in this case for the oblique incidence of laser radiation 12 to create the focusing points 5, 5'. The extension of the parting region 8 in the semiconductor layer 4 at an angle, as well as the angle of the side surfaces 9a of the semiconductor layer 4 can be flexibly created by appropriately choosing a corresponding spacing of the focusing points 5, 5' in the transverse direction 17.

[0128] Figures 9a) and 9b) show yet another embodiment of the method according to the invention, in which the laser radiation 12 is laterally introduced into the overlapping regions 10 of the semiconductor layer 4 via optical elements 15. The focusing points 5 are created in the overlapping region 10 essentially at the level of the parting layer 3. This enables the creation of a peripheral, essentially horizontally extending parting region 8 along the focusing line 6 (not shown) by the incidence of the laser radiation 12 via the side surfaces of the layer stack 1, along which, as shown in Fig. 9b), the semiconductor layer 4' can be detached together with a portion of the parting layer 3. This embodiment provides not only for the detachment of the semiconductor layer 4', but also of the overlapping regions 10 embracing the detached semiconductor layer 4', as shown in Fig. 9b). The thus detached semiconductor layer 4' can then either be used to be further processed together with the overlapping regions 10. Alternatively, the peripheral areas 10 of the detached semiconductor layer 4' are removed in a further processing step, before it is used for further processing.

[0129] List of reference numerals

[0130] 1 layer stack

[0131] 2 seed substrate

[0132] 2a, 2b flat side

[0133] 3 parting layer

[0134] 4, 4' semiconductor layer

[0135] 5, 5' focusing point

[0136] 5a, 5a' focusing depth

[0137] 6, 6' focusing line

[0138] 7, 7' modification region

[0139] 8 parting region

[0140] 9 surface of semiconductor layer

[0141] 9a side surface of semiconductor layer

[0142] 10 overlapping region

[0143] 11 laser source

[0144] 12 laser radiation

[0145] 12', 12" partial rays of laser radiation

[0146] 13 thickness direction

[0147] 14 lateral direction

[0148] 15 optical element

[0149] 16 residual stack

[0150] 17 transverse direction a angle of incidence

Claims

Claims1. A method of detaching a semiconductor layer (4) from a layer stack (1), comprising the method steps of:A) providing the layer stack (1) of at least three layers, wherein a first layer is formed by a seed substrate (2), a second layer is formed by a parting layer (3) formed on the seed substrate (2) and a third layer is formed by the semiconductor layer (4) formed, preferably epitaxially, on the parting layer (3),B) detaching the semiconductor layer (4) from the layer stack (1), characterized in that prior to and / or within the method step B), focusing a laser radiation (12) of a laser source (11) into the semiconductor layer (4), wherein the laser radiation (12) is introduced into the semiconductor layer (4) along a lateral focusing line (6, 6') to create at least one modification region (7, 7') below a surface (9) of the semiconductor layer (4), wherein, in the modification region (7, 7'), a material of the semiconductor layer (4) is modified and a parting region (8) is created within the semiconductor layer (4) about the modification region (7, 7')-2. The method according to claim 1, characterized in that the focusing line (6, 6') is created by locally introducing the laser radiation (12) at a plurality of focusing points (5, 5') in a focusing depth (5a, 5a') and the at least one modification region (7, 7') is formed about each of the individual focusing points (5, 5'), wherein the modification regions (7, 7') and / or the parting regions (8) of the focusing points (5, 5') formed about the modification regions (7, 7') preferably overlap each other in the lateral direction (14) and form a contiguous region.

3. The method according to any one of the preceding claims, characterized in that, for creating the focusing points (5, 5'), the layer stack (1) is uniformly moved relative to the laser source (11), in particular at a continuous speed, or in that, for creating thefocusing points (5, 5'), the layer stack (1) is intermittently moved relative to the laser source (11), preferably in that the layer stack (1) is moved relative to the stationary laser source (11).

4. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is pulsed, in particular in that the pulsed laser radiation (12) is short pulses in the range of nanoseconds, preferably having a pulse length in the range of 1 ns to 150 ns, preferably from 5 ns to 100 ns, particularly preferably from 10 ns to 30 ns, or in that the pulsed laser radiation (12) is ultra-short pulses in the range of picoseconds or femtoseconds.

5. The method according to any one of the preceding claims, characterized in that a plurality of focusing points (5, 5') are formed in the thickness direction (13) vertically above each other at different focusing depths (5a, 5a') within the semiconductor layer (4), and / or in that a plurality of modification regions (7, 7') are vertically created one above the other in the thickness direction (13) and / or in that a plurality of focusing points (5, 5') are simultaneously created in the lateral direction juxtaposed to each other.

6. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is introduced plural times in succession at the focusing points (5, 5').

7. The method according to any one of the preceding claims, characterized in that the semiconductor layer (4) is essentially transparent to a wavelength of the laser radiation (12), in particular in that the wavelength is in the range from 100 nm to 2000 nm, preferably in the range from 350 nm to 1600 nm, particularly preferably in the range from 500 nm to 1500 nm, most preferably in the range from 1000 nm to 1350 nm.

8. The method according to any one of the preceding claims, characterized in that the parting region (8) is created within the semiconductor layer (4), preferably in that the parting region (8) extends up to the parting layer (3) and / or the surface (9) of the semiconductor layer (4).

9. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is introduced into the layer stack (1) along the focusing line (6, 6') in such a manner that a predetermined breaking point, in particular, a crack, is formed in the parting region (8) comprising the modification region (7, 7') within the semiconductor layer (4), in particular in that it is formed through the parting region (8) and / or the modification region (7, 7'), and / or in that the laser radiation (12) is introduced into the layer stack (1) along the focusing line (6, 6') in such a manner that the semiconductor layer (4) is completely parted from the residual stack (16) along the parting region (8).

10. The method according to any one of the preceding claims, characterized in that the semiconductor layer (4) includes an overlapping region (10) larger than a flat side of the seed substrate (2) and / or the parting layer (3), which is preferably formed at least partially covering one or more side surfaces of the seed substrate (2) and / or the parting layer (3).

11. The method according to claim 10, characterized in that the overlapping region (10) is formed of the same material as the semiconductor layer (4) and / or in that the overlapping region (10) is parted from the semiconductor layer (4) and / or from the layer stack (1) in method step B).

12. The method according to claim 10 or 11, characterized in that the focusing line (6, 6') and / or the modification region (7, 7') and / or the parting region (8) is formed at least partially within the overlapping region (10), preferably in that the focusing line (6, 6') and / or the modification region (7, 7') and / or the parting region (8) is mainly formed outside of the overlapping region (10).

13. The method according to any one of the preceding claims, characterized in that the focusing line (6, 6') and / or the modification region (7, 7') and / or the parting region (8) is formed in a closed configuration.

14. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is introduced into the semiconductor layer (4) from one or more flat sides of the layer stack (1) and / or in that the laser radiation (12) is introduced into the semiconductor layer (4), in particular is introduced into the overlapping region (10), from a side surface of the layer stack (1).

15. The method according to any one of the preceding claims, characterized in that the focusing depth (5a, 5a') of the laser radiation (12) is adjustable in the range of the thickness of the semiconductor layer (4) and is preferably in the range of half the thickness of the semiconductor layer and / or preferably in the range of 10 pm to 500 pm below the surface (9) of the semiconductor layer (4).

16. The method according to any one of the preceding claims, characterized in that the focusing point (5, 5') is created with an essentially circular or oval-shaped crosssection and / or in that the modification region (7, 7') and / or the parting region (8) is created and / or formed with an essentially circular or oval-shaped region crosssection.

17. The method according to any one of the preceding claims, characterized in that, in method step B), the laser radiation (12) is introduced in such a manner that the seed substrate (2) and / or the parting layer (3) is not subject to any influence by the laser radiation (12), preferably in that the seed substrate (2), preferably with the parting layer (3), is reused after method step B), in particular after a reprocessing step, for the production of at least one further semiconductor layer (4).

18. The method according to any one of the preceding claims, characterized in that at least two focusing lines (6, 6') are created in the semiconductor layer (4) at different focusing depths (5a, 5a') offset from each other in the transverse direction (17), inparticular in that the focusing lines (6, 6') are simultaneously or successively created at different focusing depths (5a, 5a').

19. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is radiated into the layer stack (1) in a direction perpendicular to the surface (9) of the semiconductor layer (4).

20. The method according to any one of the preceding claims, characterized in that the laser radiation (12) is radiated into the layer stack (1) at an angle of incidence (a) to the normal on the surface (9) of the semiconductor layer (4), wherein preferably the modification region (7, 7') and / or the parting region (8) is created to extend at an angle to the thickness direction (13).

21. The method according to any one of the preceding claims, characterized in that the semiconductor layer (4) and / or the seed substrate (2) is of silicon, in particular monocrystalline silicon and / or in that the parting layer (3) is of porous silicon.

22. A method for the production of a semiconductor layer (4), comprising the method steps of:VI) providing a seed substrate (2);V2) creating a parting layer (3) on the seed substrate (2);V3) depositing a semiconductor layer (4) on the parting layer (3) of the seed substrate (2), preferably by means of epitaxy, to create a layer stack (1) of the seed substrate (2), the parting layer (3) and the semiconductor layer (4); andV4) detaching the semiconductor layer (4) from the layer stack (1), characterized in that detaching of the semiconductor layer (4) is done by a method according to any one of claims 1 to 21, in particular in that, following method step V4), the method steps V2) to V4) are performed plural times with the seed substrate (2).

23. A system for detaching a semiconductor layer (4) from a layer stack (1), in particular for executing a method according to any one of claims 1 to 21, wherein the layer stack (1) comprises at least a seed substrate (2), a parting layer (3) formed on the seed substrate (2) and the semiconductor layer (4) preferably epitaxially created on the parting layer (3), wherein the system comprises a support for the layer stack (1), preferably a detaching unit for the semiconductor layer (4), and a laser source (11) to generate a laser radiation (12), characterized in that the laser radiation (12) of the laser source (11) is focused into the layer stack (1) in such a manner that a modification region (7, 7') is created below a surface (9) of the semiconductor layer (4) along a lateral focusing line (6, 6'), in which a material of the semiconductor layer (4) is modified, and a parting region (8) comprising the modification region (7, 7') is creatable and in that the semiconductor layer (4) is formed to be detachable from the layer stack (1) along the focusing line (6, 6') in particular by means of the detaching unit.

24. A semi-finished product, comprising a layer stack (1) of at least a seed substrate (2), a parting layer (3) formed on the seed substrate (2) and the semiconductor layer (4) preferably epitaxially created on the parting layer (3), in particular of silicon, wherein the semiconductor layer (4) includes an overlapping region (10) larger than a flat side of the seed substrate (2) and / or the parting layer (3), which is preferably formed at least partially covering one or more side surfaces of the seed substrate (2) and / or the parting layer (3), characterized in that, below a surface (9) of the semiconductor layer (4), a modification region (7, 7') and preferably a parting region (8) comprising the modification region (7, 7') is formed along a focusing line (6, 6'), wherein, in the modification region (7, 7'), a material of the semiconductor layer (4) is modified.

25. A semi-finished product according to claim 24, characterized in that the parting region (8) extends up to the parting layer (3) and / or the surface (9) of the semiconductor layer (4) and / or in that a predetermined breaking point, in particular a crack, is formed through the parting region (8).

6. A semi-finished product according to claim 24 or 25, characterized in that the parting region (8) extends within the semiconductor layer (4) at an angle to the thickness direction (13).

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