Mother substrate, wafer complex, and method for manufacturing semiconductor device

Abstract

A mother substrate, a wafer complex, and a method for manufacturing a crystal substrate and a semiconductor device are disclosed. A mother substrate (100) including a central region (110) and an edge region (180) is provided. The edge region (180) surrounds the central region (110). A desorption layer (150) is formed in the central region (110). The desorption layer (150) extends parallel to the main surface (101, 102) of the mother substrate (100). The desorption layer (150) includes a modified substrate material. A groove (190) is formed in the edge region (180). The groove (190) surrounds the central region (110) in the lateral direction. The groove (190) runs vertically and / or obliquely with respect to the desorption layer (150).

Description

Technical Field

[0001] The present disclosure relates to a method of manufacturing a crystalline substrate (particularly a crystalline device substrate), to a method of manufacturing a semiconductor device, to a crystalline substrate, and to a wafer complex including a crystalline substrate. Background Art

[0002] Crystalline substrates such as crystalline semiconductor substrates are typically available in standard sizes, where the standard defines the diameter and thickness. On the other hand, attempts have been made to reduce the final thickness of thin semiconductor devices to improve device characteristics. For example, for power semiconductor devices with vertical load current flow between the front side and the back side, thinner semiconductor dies can result in lower on-state resistance. Other attempts aim to reduce substrate costs by using thin semiconductor slices as a basis for epitaxial growth. For example, a segmentation method horizontally segments thin slices from a semiconductor crystal block or horizontally segments standard wafers (wafer twins). Crystalline substrates such as semiconductor wafers can be slightly beveled, for example beveled and / or rounded, to avoid fragmentation and reduce the occurrence of cracks at the sharp edges of the crystal substrate.

[0003] There is a steady demand for improvements in the manufacture of crystalline substrates and semiconductor devices. Summary of the invention

[0004] Embodiments of the present disclosure relate to a method for manufacturing a device substrate. A mother substrate including a central region and an edge region is provided. The edge region surrounds the central region. A desorption layer is formed in the central region. The desorption layer extends parallel to the main surface. The desorption layer includes a modified substrate material. A groove is formed in the edge region. The groove surrounds the central region in the lateral direction. The groove runs vertically and / or obliquely with respect to the desorption layer.

[0005] A further embodiment of the present disclosure relates to a mother substrate. The mother substrate comprises a central region and an edge region. The edge region surrounds the central region. A groove in the edge region laterally surrounds the central region. The groove runs vertically and / or obliquely to the desorption layer. In the central region, the desorption layer extends parallel to the main surface and terminates at the groove. The desorption layer comprises a modified substrate material. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The accompanying drawings are included to provide a further understanding of embodiments, and are incorporated in and constitute a part of this specification.

[0007] The drawings illustrate embodiments of a crystal substrate, a wafer complex, a method of manufacturing a crystal substrate, and a method of manufacturing a semiconductor device and, together with the description, serve to explain the principles of the embodiments.

[0008] Further embodiments are described in the following detailed description and in the claims.

[0009] Figures 1A to 1C A schematic vertical cross-sectional view of a crystalline mother substrate according to an embodiment is shown for illustrating a method of manufacturing a device substrate using grooves in an edge region and a desorption layer in a central region.

[0010] Figure 2 is a schematic plan view of a mother substrate including a groove in an etched region according to an embodiment.

[0011] Figure 3 is a schematic plan view of a portion of a mother substrate from a semiconductor material including a groove between a central region and an edge region according to an embodiment.

[0012] FIG. 4A to FIG. 4E are schematic vertical cross-sectional views of edge regions of mother substrates having grooves of different shapes according to embodiments.

[0013] FIG. 5A to FIG. 5G is a schematic vertical cross-sectional view of a mother substrate based on a semiconductor material and a wafer composite including the mother substrate, for illustrating a method of manufacturing a semiconductor device according to an embodiment.

[0014] FIG. 6A to FIG. 6C is a schematic vertical cross-sectional view of a mother substrate based on a semiconductor material and a wafer composite including the mother substrate for illustrating a method of manufacturing a semiconductor device including layer transfer and epitaxial growth according to an embodiment.

[0015] FIG. 7A to FIG. 7B is a schematic vertical cross-sectional view of a mother substrate based on a semiconductor material and a wafer composite including the mother substrate for illustrating a method of manufacturing a semiconductor device in connection with forming a groove on a back side of a substrate according to an embodiment.

[0016] FIG. 8A to FIG. 8B is a schematic vertical cross-sectional view of a portion of a wafer composite and a trimming tool involving edge trimming according to an embodiment.

[0017] FIG. 9A to FIG. 9B is a schematic vertical cross-sectional view of a portion of a wafer composite involving forming a groove from the front side according to a further embodiment.

[0018] Fig.10 is a schematic vertical cross-sectional view of a wafer composite involving front-side processing according to an embodiment.

[0019] FIG. 11A to FIG. 11D is a schematic vertical cross-sectional view of a wafer composite involving backside processing according to an embodiment.

[0020] Fig.12is a schematic block diagram of a tool assembly suitable for performing front-side processing and / or back-side processing according to further embodiments. DETAILED DESCRIPTION

[0021] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and in which are shown by way of illustration specific embodiments in which device substrates, wafer composites, methods of manufacturing device substrates, and methods of manufacturing semiconductor devices may be practiced. It is to be understood that further embodiments may be utilized and that structural or logical changes may be made without departing from the scope of the present disclosure. For example, features illustrated or described for one embodiment may be used on or in conjunction with a further embodiment to produce yet another further embodiment. It is intended that the present disclosure includes such modifications and variations. Examples are described using specific language, which should not be interpreted as limiting the scope of the appended claims. The drawings are not to scale and are for illustrative purposes only. Unless otherwise stated, corresponding elements are indicated by the same reference numerals in different drawings.

[0022] The terms "having," "comprising," "including," and "comprising" are open ended, and the terms indicate the presence of stated structures, elements, or features, but do not exclude additional elements or features. The quantifiers "a," "an," and the pronoun "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0023] Ranges given for parameters include the boundary values. For example, a range from a to b for parameter y is read as a≤y≤b. Parameter y with a value of at least c is read as c≤y, and parameter y with a value of at most d is read as y≤d.

[0024] The main components of a layer or structure from a chemical composition or alloy are the elements whose atoms form the chemical composition or alloy. For example, nickel and silicon are the main components of a nickel silicide layer, and copper and aluminum are the main components of a copper-aluminum alloy.

[0025] The term "on" should not be interpreted as meaning only "directly on". On the contrary, if one element is "on" another element (e.g., a layer is "on" another layer or is "on" a substrate), further components (e.g., further layers) may be located between the two elements (e.g., if a layer is "on" a substrate, the further layer may be located between the layer and the substrate).

[0026] The term “power semiconductor device” refers to a semiconductor device having a high voltage blocking capability (eg, 30 V, 100 V, 600 V, 3.3 kV or higher) and having a nominal on-state current or forward current of at least 1 A (eg, 10 A or higher).

[0027] According to an embodiment, a method for manufacturing a device substrate may include providing a mother substrate. The mother substrate may be crystalline. That is, at least 90% or even at least 95% of the mother substrate may include crystalline materials, such as polycrystalline materials or single crystal materials. The mother substrate may include a central region and an edge region. The edge region may surround the central region. For example, at least 60% (or at least 70% or even at least 80%) of the mother substrate may be part of the central region.

[0028] The mother substrate (German: "Ausgangssubstrat") can be an ingot (chunk) of single-crystal material or a wafer-sized slice (e.g., wafer) of single-crystal material. The mother substrate can (in addition to the modified substrate material within the desorption layer) exclusively comprise single-crystal material, or can also comprise, in addition to the main part formed by single-crystal material, structures of modified substrate material and / or other materials in the desorption layer, such as conductive structures and / or insulating structures.

[0029] The single crystal material may be a ceramic, such as α-Al2O3 (sapphire), or may be a semiconductor material. By way of example, the semiconductor material may be any Group IV element semiconductor, such as silicon (Si) or germanium (Ge), any Group IV composite semiconductor, such as silicon carbide (SiC) or silicon germanium (SiGe), or any Group III / V composite semiconductor, such as gallium arsenide (GaAs) or gallium nitride (GaN).

[0030] For example, by way of example, the material of the mother substrate may be 15R-SiC (15R polytype of silicon carbide) or silicon carbide with a hexagonal polytype (e.g., 2H-SiC, 4H-SiC, or 6H-SiC). In addition to the main components of silicon and carbon, the mother substrate may also include dopant atoms such as nitrogen N, phosphorus P, beryllium Be, boron B, aluminum Al, and / or gallium Ga. Further, the mother substrate may include unwanted impurities such as hydrogen, fluorine, and / or oxygen.

[0031] For example, the mother substrate can be an original semiconductor wafer or a processed semiconductor wafer. The original semiconductor wafer can be a semiconductor wafer at a stage after it has been obtained from an ingot, for example by sawing, and before any treatment specifically for a particular type of semiconductor device. For example, the original semiconductor wafer may have been subjected to non-specialized treatments, such as edge rounding, beveling, heat treatment, and / or treatment to form a surface oxide. The processed semiconductor wafer can be a semiconductor wafer after having been subjected to at least one device-specific treatment (e.g., blanket doping or patterning). The processed semiconductor wafer may include spatially separated doped regions, insulator structures, and / or conductive structures, including polycrystalline semiconductor materials, metals, and / or metal composites.

[0032] The mother substrate may have two substantially parallel main surfaces of the same shape and size and a lateral outer surface connecting the edges of the two main surfaces. The mother substrate may extend laterally in a plane extending through a lateral direction. Thus, the mother substrate may have a surface extension along two lateral directions (also named horizontal directions below). The mother substrate may have a thickness along a vertical direction perpendicular to the lateral direction.

[0033] Here and in the following, a first face and a second face may be “substantially parallel” if a mean plane approximating the first face encloses an angle of at most 5 degrees (or at most 2 degrees) with a mean plane approximating the second face.

[0034] The main surface may be oriented to be completely flat. The main surface and the lateral outer surface may be connected via a right-angled edge. Alternatively, the lateral outer surface may be chamfered, for example beveled and / or rounded in the direction of one of the main surfaces or in the direction of both main surfaces.

[0035] The lateral outer surface may include a vertical portion running in a vertical direction. In addition to the vertical portion, the lateral outer surface may also include one or more truncated portions between the vertical portion and the first main surface in the main surface. In addition, the lateral outer surface may further include one or more truncated portions between the vertical portion and the second main surface in the main surface. Each truncated portion may have another inclination angle with respect to the vertical portion. Alternatively, the lateral outer surface may include a rounded portion between the vertical portion and at least the first main surface in the main surface. The lateral outer surface may include one or more rounded portions between the vertical portion and the truncated portion, between adjacent truncated portions and / or between the truncated portion and the corresponding main surface.

[0036] The first major surface at the front side and the second major surface at the back side may have a polygonal (eg rectangular or hexagonal) shape with or without rounded edges or a circular shape with or without a cutout or flat portion along the periphery.

[0037] In vertical cross-section, the lateral outer surface may be flat, may be outwardly curved, and / or may include a chamfered portion at least at one of the transitions to the main surface. The chamfered portion may be beveled and / or rounded.

[0038] The main surface may extend laterally in a plane extending through the lateral direction.Thus, the mother substrate may have a lateral extension along two orthogonal lateral directions and may have a thickness along a vertical direction perpendicular to the lateral directions.

[0039] The mother substrate may be a semiconductor wafer, wherein the diameter and thickness of the mother substrate may correspond to production standards for semiconductor wafers. The diameter of the mother substrate may be 4 inches (100 mm), 6 inches (150 mm), 7 inches (175 mm), 200 mm (8 inches), or 300 mm (12 inches).

[0040] The central area of ​​the mother substrate can be a circular or almost circular area. In the case where the mother substrate is an original semiconductor wafer, at least the central area can be uniformly doped. In the case of a pre-processed semiconductor wafer, the central area can include a plurality of device areas separated in the lateral direction, wherein each device area can include a plurality of doped regions, conductive structures and / or insulating structures. The conductive structures and / or insulating structures can be formed on the mother substrate and / or can extend from the first main surface into the mother substrate. A grid-shaped cutout area can separate the device areas in the central area of ​​the mother substrate.

[0041] The edge region may be between the central region and the lateral outer surface of the mother substrate. The edge region may extend from the central region to the lateral outer surface. The edge region may be free of a device region. The edge region may completely surround the central region. The edge region may have an approximately uniform width. For example, the edge region may have an average width of at least 100 μm and at most 3 mm (e.g., at most 1 mm or at most 500 μm). It may be possible that the edge region includes or is defined by a chamfered (e.g., beveled and / or rounded) region of the mother substrate along the lateral outer surface. The chamfered region of the mother substrate may be defined by the lateral extension of the chamfered portion of the lateral outer surface. For example, the edge region may include, for example, may exclusively include a portion of the lateral outer surface, such as a chamfered portion of the lateral outer surface.

[0042] The desorption layer may be formed in the central region. The desorption layer may extend parallel to at least one of the main surfaces of the mother substrate or parallel to both main surfaces. The desorption layer may extend parallel to the lateral direction and / or may run parallel to the lateral direction.

[0043] The grooves may be formed in the edge region before or after the desorption layer is formed or even during the formation of the desorption layer. It may also be possible to form a portion of the groove before the desorption layer is formed and to form a further portion of the groove after the desorption layer is formed, or vice versa, to form a portion of the desorption layer before the groove is formed and to form a further portion of the desorption layer after the groove is formed. The grooves may consist of a single connected groove or a plurality of sub-grooves separated from each other in the transverse direction. The grooves may extend in a certain direction out of the layer in which the desorption layer is formed.

[0044] The groove may extend from one of the main surfaces up to the desorption layer or beyond the desorption layer. The vertical extension of the groove may be at least 80% (e.g. at least 95%) and at most 120% (e.g. 105%) of the distance between the desorption layer and the main surface in which the groove is formed. For example, the vertical extension of the groove and the distance between the desorption layer and the main surface in which the groove is formed may be equal or approximately equal.

[0045] In some embodiments, the groove may extend from at least one of the main surfaces into the mother substrate, or may extend from a portion of the lateral outer surface close to one of the main surfaces into the mother substrate. The groove may extend vertically and / or obliquely with respect to the desorption layer and / or with respect to the lateral direction. Here and below, "obliquely" may mean that the groove (e.g., the main axis of the groove) and the desorption layer and / or the lateral direction enclose an angle of at least 5 degrees and at most 90 degrees. For example, the groove and the desorption layer enclose an angle in the range of from 5 degrees to 85 degrees (e.g., in the range of from 5 degrees to 45 degrees).

[0046] For a "vertical" groove, an angle of 90 degrees is also satisfied. The main axis of the groove may be a direction along which the groove extends mainly away from the central region. For example, the groove may have its greatest extension away from the central region along the main axis. The main axis may run perpendicularly or at least obliquely to the peripheral direction of the mother substrate.

[0047] The groove may include a groove inner sidewall and a groove outer sidewall. The groove inner sidewall may be positioned closer to the central region than the groove outer sidewall. In some embodiments, the groove may terminate at the desorption layer, and the desorption layer may terminate at the groove. The desorption layer may contact the groove inner sidewall. According to some embodiments, the groove may taper, and the closed end of the groove and the outer edge of the desorption layer may merge.

[0048] The desorption layer may include a modified substrate material. The modified substrate material may form a plurality of modified zones separated in the transverse direction. Each modified zone may be arranged along a modification line. In some embodiments, the desorption layer may include a plurality of modified zones separated in the transverse direction, which are arranged along the modification line and separated by non-modified substrate material. For example, each modified zone may include a plurality of modified zones, which are generated from a single irradiation of the laser beam into the mother substrate. At least some or all of the modified zones may be connected to the modified zones adjacent to them and / or may overlap with the modified zones adjacent to them. In addition or as an alternative, it may be possible that at least some or all of the adjacent modified zones are separated from each other by non-modified substrate materials. That is, at least some of the modified zones or all of the modified zones may not overlap with the adjacent modified zones. The modification lines may run parallel to each other. The modified zones (e.g., modified lines) may terminate at the inner sidewalls of the groove. According to another example, the bottom of the modified zone and the groove may merge.

[0049] The modified substrate material may include the main component of the material of the parent substrate. For example, the modified substrate material may have a phase different from the phase of the non-modified material, for example, a phase different from the single crystal phase. For example, the modified zone may include the main component of the substrate material in polycrystalline form, in amorphous form and / or as a mixture of the basic components of the substrate material. For example, the modified substrate material may include elemental silicon in amorphous and / or polycrystalline form and / or carbon in amorphous and / or polycrystalline form.

[0050] According to some embodiments, the desorption layer may include a structure with a relatively high porosity (eg, a porosity of at least 20%) and / or a structure with implantation-induced crystal damage. The implantation-induced crystal damage may include crystal defects trimmed with, for example, hydrogen atoms.

[0051] The groove may surround the central area in the transverse direction. For example, the groove may completely surround the central area in the transverse direction. The groove may form a frame for the central area. The groove may have an approximately uniform radial extension (width) along the entire periphery. The groove may have an approximately uniform depth along the entire periphery. If the groove includes a plurality of sub-grooves, the sub-grooves may have approximately equal widths and / or equal depths along the entire periphery of the central area. In a horizontal plane, the groove may include a circular portion, or may approximate a circular portion with an orthogonal line portion.

[0052] For example, the groove may form a complete circle in a horizontal plane. The diameter of the circle may be smaller than the largest inscribed circle (German: "größter eingeschriebener Kreis") of a horizontal substrate shape, which may include one or more flat portions along the outer periphery. The groove may be vertical, or may be inclined in the direction of the center of the circle, wherein the angle between the main axis of the groove and the horizontal plane may be in the range of from 5 degrees to 45 degrees (e.g. from 15 degrees to 45 degrees). The groove may be formed exclusively in a portion of the edge region in which the main surfaces are parallel to each other. Alternatively, the groove may be formed partially or completely in a chamfered portion and / or a rounded portion of the edge region. For example, the groove may be formed completely or partially in the lateral outer surface.

[0053] According to another example, the groove may include one or more straight portions and one or more circular arcs, wherein the one or more straight portions and the one or more circular arcs complement each other into a closed form. The diameter of the circular arc may be less than, equal to or greater than the maximum inscribed circle of the horizontal substrate shape, which may include one or more flat portions along the outer periphery. Each straight portion of the groove may run parallel to a flat portion. The groove may be vertical, or may be tilted in the direction of the center of the circle, wherein the angle between the main axis of the groove and the horizontal plane may be in the range of from 5 degrees to 45 degrees (e.g., from 15 degrees to 45 degrees). The groove may be formed exclusively in the portion of the edge region where the main surfaces are parallel to each other. Alternatively, the groove may be partially or completely formed in the beveled portion and / or the rounded portion of the edge region. For example, the groove may be completely or partially formed in the lateral outer surface.

[0054] The groove may include a groove inner sidewall at a side oriented toward a central region (e.g., a lateral center) of the mother substrate. The groove may be formed at a distance from the central region. The distance between the groove and the central region may be uniform along the entire periphery. According to another example, the groove inner sidewall may mark a boundary or transition between the central region and the edge region. The width of the groove may be at least 10 μm. The depth of the groove (e.g., the extension of the groove along the main axis) may be in the range of from 10 μm to several hundred μm.

[0055] The combination of the peripheral groove and the desorption layer in contact with the inner sidewall of the groove can facilitate the later separation of the mother substrate into a device substrate and a recycling substrate, wherein the device substrate and the recycling substrate are separated along a separation surface extending through the desorption layer and / or along the desorption layer and / or substantially parallel to the desorption layer in the lateral direction. The groove can avoid or at least reduce edge effects that may adversely affect the formation of the portion of the desorption layer near the lateral outer surface.

[0056] According to an embodiment, the mother substrate can be split, for example, in the desorption layer by passing along the split surface. The split surface can vertically divide the desorption layer into a portion above the split surface (e.g., a first mother substrate portion) and into a portion below the split surface (e.g., a second mother substrate portion). The split divides the mother substrate into a first mother substrate portion (device substrate) and a second mother substrate portion (recovery substrate). The first mother substrate portion may include a mother substrate portion extending from the first main surface to the split surface. The second mother substrate portion may include a mother substrate portion extending from the split surface to the second main surface.

[0057] Due to the grooves, the segmentation process can be independent of edge effects, which can adversely affect the output of the segmentation process. Furthermore, it is possible to define the shape of the lateral outer surface of the device substrate or the shape of the lateral outer surface of the recycling substrate via the shape of the grooves. It is also possible to form a substrate portion whose lateral outer surface is not defined by the grooves, with an annular reinforcement portion. The reinforcement portion can have a larger vertical extension than the central portion of the associated substrate portion.

[0058] That is, the device substrate obtained from the segmentation process can have an inherently chamfered edge along the lateral outer surface and / or can be formed with a reinforcement ring. The formation of the chamfered edge and / or reinforcement ring does not require additional processing but is achieved by the segmentation process alone. The chamfered edge can reduce the occurrence of chipping and cracking along the lateral outer surface even for device substrates with thicknesses that cannot be achieved with standard chamfering tools. After the segmentation process, the reinforcement ring can mechanically stabilize the device substrate.

[0059] In addition or as an alternative, the recycled substrate obtained from the singulation process may have inherently chamfered edges and / or may include a reinforcement ring that stabilizes the recycled substrate after the singulation process. The lateral dimensions (e.g., diameter) of the recycled substrate may be identical to those of the parent substrate, so that reprocessing and / or reuse of the recycled substrate may use standard tools without changing or only not severely changing the settings of such standard tools.

[0060] For example, when the grooves can be formed completely or partially in the lateral outer surface and extend at an angle between 45 degrees and 5 degrees inclined to the horizontal plane, the diameters of both the recycled substrate and the device substrate can be approximately the same. Both the device substrate and the recycled substrate can be processed using the same tools, and the recycled substrate can be further processed in much the same manner as the device substrate or the mother substrate.

[0061] According to an embodiment, in the edge region, the distance between the main surfaces of the mother substrate may decrease as the distance to the lateral center of the mother substrate increases and / or as the distance to the central region increases. In other words, the mother substrate may be a semiconductor wafer having a lateral outer surface that is chamfered at a transition to at least one of the main surfaces. The chamfer may include a chamfered portion that may be rounded or not. The chamfer may contribute to reducing the occurrence of cracks and / or edge chipping effects during transportation or handling of the mother substrate. According to other examples, the distance between the main surfaces of the mother substrate may be constant in the edge region.

[0062] The peripheral grooves may decouple the formation of the desorption layer from the effects of the beveling on the process for forming the desorption layer. For example, due to the nature of laser-induced damage layer formation (optical constraints and microcrack lengths), it may be difficult to form a desorption layer containing laser-induced crystal damage in a manner that the laser-induced crystal damage reaches the lateral outer surfaces to a sufficient extent. In the event that the desorption layer does not reach the lateral outer surfaces to a sufficient extent, crack entry from the lateral outer surfaces during the segmentation process may be difficult, and the output may therefore be critical. In the event that the desorption layer terminates at the peripheral grooves, it may be possible to eliminate the need for the desorption layer to terminate at the lateral outer surfaces.

[0063] In addition to edge trimming processes, which can remove semiconductor material starting from the lateral outer surfaces, peripheral grooves extending from the direction of one of the main surfaces into the mother substrate can also be formed at an early stage of the process. In particular, the grooves can be formed using standard tools for wafer processing at the front side, such as dicing tools for separating device areas from each other, or edge trimming tools. The formation of the grooves can be easily integrated into existing production lines with low or medium effort.

[0064] In addition to performing a horizontal layer etching process that can remove the adhesive material that adheres the mother substrate to the auxiliary carrier, a peripheral groove extending from one of the main surfaces into the mother substrate can also be formed without removing the adhesive material and without residues of the adhesive material that could contaminate the mother substrate and / or the tool used to form the groove.

[0065] According to an embodiment, the groove can extend from the first main surface at the front side of the mother substrate into the mother substrate. The front side can be a side of the patterned substrate where the front side metallization of the semiconductor device (e.g., the source electrode and gate electrode of the power semiconductor device) is formed. In this case, by way of example, the groove can be formed with any tool adapted for the pre-slicing process in the DBG (before grinding dicing) process framework with low or medium additional effort. The output of the segmentation process can be significantly improved with only low or medium additional effort. According to other examples, the groove can extend from the second main surface opposite to the front side of the mother substrate into the mother substrate.

[0066] According to an embodiment, the groove may include an inner sidewall of the groove. The inner sidewall of the groove is oriented to the lateral center and / or central area of ​​the mother substrate. The inner sidewall of the groove may include a vertical or approximately vertical sidewall segment. In this context, the terms "vertical" and "inclined" may refer to the orientation of the sidewall segment relative to the lateral direction. The desorption layer may cut off the vertical sidewall segment. In other words, the desorption layer (e.g., a modified zone of the desorption layer including laser-induced crystal damage) may terminate at the vertical sidewall segment.

[0067] The inner sidewall of the groove can be cut orthogonally or nearly orthogonally using the desorption layer to support the propagation of cracks originating from the inner sidewall of the groove in a direction toward the lateral center of the mother substrate. It is possible to perform a singulation process with high reliability and high yield.

[0068] According to an embodiment, the groove may be spaced apart from the lateral outer surface of the mother substrate. In other words, the groove may be formed at a distance from the lateral outer surface. For example, the groove may be formed at a low additional cost using a cleaving blade and / or a laser ablation tool (e.g., a laser cleaving tool). The opening of the groove in the first main surface or the second main surface may have a width in the radial direction. The width of the groove opening may be in the range of from at least 10 μm (or at least 30 μm) to at most 1 mm (typically at most 300 μm or at most 100 μm). For example, the groove opening may have a width in the range of from 30 μm to 60 μm. The vertical extension of the groove may be selected so that the groove reaches the desorption layer. For example, the vertical extension of the groove may be in the range of from 10 μm to 200 μm, for example, in the range of from 20 μm to 120 μm (e.g., 60 μm to 120 μm or 30 μm to 60 μm).

[0069] According to an embodiment, the groove may extend inward from the lateral outer surface. In other words, the groove forms a single-sided recess, wherein the inner sidewall of the groove forms the only groove sidewall extending from the main surface into the mother substrate. Starting from the inner sidewall of the groove, the groove may have an approximately flat groove bottom extending from the inner sidewall of the groove to the lateral outer surface. The transition between the inner sidewall of the groove and the bottom of the groove may be curved. The radial extension of the groove corresponds to the distance from the inner sidewall of the groove to the outer periphery of the mother substrate. The radial groove extension may be at least 90% and at most 110% of the width of the edge region. For example, the radial extension of the groove may be at least 10 μm (or at least 30 μm) to at most 1 mm, typically at most 300 μm or at most 100 μm. The vertical extension of the groove may be in the range of from 10 μm to 200 μm, typically in the range of from 20 μm to 120 μm (e.g., 60 μm to 120 μm or 30 μm to 60 μm).

[0070] The groove bottom can be parallel to the main surface or can be inclined with respect to the main surface, so that the remainder of the mother substrate in the edge region is beveled, for example chamfered with or without rounded corners.

[0071] Forming the groove may include spiral cutting or a series of circular cuts with different diameters using a conventional cutting tool, such as a cutting blade for circular cutting, wherein material between the inner sidewall and the lateral outer surface of the groove may be completely removed.

[0072] According to another example, the edge beveling tool can remove material between the inner sidewall of the groove and the lateral outer surface (e.g., completely remove or remove at least 90% of the material). The edge beveling tool can be a grinding tool, wherein the shape of the notch of the grinding pad can be complementary to the vertical cross-sectional shape of the groove. The notch can be formed so that the device substrate is formed with a bevel along the lateral outer surface and / or so that the recycled substrate is formed with a bevel along the lateral outer surface.

[0073] According to an embodiment, forming the groove may include laser-assisted material removal. The laser-assisted material removal may include directing a laser beam in the direction of the first main surface and / or onto the first main surface. In an additional or alternative embodiment, the laser-assisted material removal may include directing a laser beam in the direction of the second main surface and / or onto the second main surface. In the latter case, the mother substrate may be attached to the auxiliary carrier with the front side facing downward.

[0074] In further additional or alternative embodiments, laser-assisted material removal may include directing a laser beam in the direction of and / or onto the first main surface. In the latter case, the mother substrate may be attached to the auxiliary carrier with the side opposite to the front side facing downwards.

[0075] In general, laser-assisted material removal may include weakening and / or removing material of a mother substrate using a laser beam. Laser-assisted material removal may include or may be at least one of: laser-assisted ablation (e.g., laser dicing) or laser-assisted etching processes. Laser-assisted ablation typically utilizes material removal by melting and / or evaporating and / or sublimating material using a laser beam. Laser-assisted etching processes may include weakening and / or transforming material in an area of ​​a mother substrate where a groove is to be formed. The weakened material may then be removed, for example, via etching.

[0076] In general, the laser beam can be directed in the direction of the lateral center of the mother substrate. For example, the laser beam can be tilted relative to the horizontal direction or relative to both the vertical direction and the horizontal direction. The angle between the vertical direction and the propagation axis of the laser beam can be at least 30 degrees. In other embodiments, the angle between the vertical direction and the propagation axis of the laser beam can be at most 10 degrees, such as at most 5 degrees or 0 degrees. The laser beam can be a UV laser beam with a peak wavelength between at least 200 nm and at most 450 nm. In other embodiments, the laser beam can be a visible laser beam or an infrared laser beam, for example, with a wavelength of at least 1 μm and at most 1.8 μm. Larger wavelengths may also be possible.

[0077] Laser-assisted material removal can be controlled so as to form a groove having a curved groove inner sidewall. The groove inner sidewall can be curved inwardly relative to the groove. The ablation volume of the laser-assisted material removal can be small compared to the ablation volume of a process in which the groove is formed by means of a mechanical cleaving tool.

[0078] In some embodiments, the segmentation process can form a device substrate having an inherently outwardly curved lateral outer surface, which can be inherently less susceptible to edge chipping. The segmentation process can form a recycled substrate with a reinforcement ring, the sidewalls of which can advantageously be shallow and / or curved. In other words, it is possible that the reinforcement ring does not include steep sidewalls and / or rectangular outer edges so that the reinforcement ring can be inherently less susceptible to edge chipping. The reinforcement ring can facilitate reprocessing and / or reuse of thin recycled substrates with high yield.

[0079] In some embodiments, the segmentation process can form a recycled substrate having an inherently outwardly curved lateral outer surface that is inherently less susceptible to edge chipping. The device substrate can be formed with a reinforcement ring whose sidewalls can advantageously be shallow and / or curved. In other words, the reinforcement ring does not include steep sidewalls and / or rectangular outer edges so that the reinforcement ring can be inherently less susceptible to edge chipping. The reinforcement ring can facilitate further processing of very thin device substrates obtained from the device substrate with high yield.

[0080] The disassembly and handling stability for both the device substrate and the recycled substrate can be significantly improved.The formation of the groove from the second main surface can be performed without removing any or only a small amount of adhesive material used to temporarily mechanically connect the mother substrate to the auxiliary carrier.

[0081] According to an embodiment, the method includes connecting the auxiliary carrier and the mother substrate. The first main surface of the mother substrate is oriented to the working surface of the auxiliary carrier. In other words, the first main surface of the mother substrate faces the working surface of the auxiliary carrier. The auxiliary carrier and the mother substrate can be mechanically connected after the groove is formed in the first main surface and / or before the groove is formed in the second main surface. Forming the groove and dividing the mother substrate can make the auxiliary carrier completely unaffected. The auxiliary carrier can be reprocessed and reused with low or medium effort.

[0082] The auxiliary layer and the mother substrate may be directly bonded, or a bonding layer having high thermal stability may bond the first main surface of the mother substrate and the working surface of the auxiliary carrier.

[0083] According to an embodiment, connecting the auxiliary carrier and the mother substrate may include forming an adhesive structure between the working surface of the auxiliary carrier and the central area of ​​the mother substrate. For example, the adhesive material may be deposited on at least one of the working surface of the auxiliary carrier or the first main surface of the mother substrate. The adhesive material may be deposited in the central area of ​​the mother substrate and / or in the central part of the working surface, wherein the central part of the working surface corresponds to the central area of ​​the mother substrate in size and shape. It is possible that the adhesive material is not applied in the edge area. For example, the adhesive material may be deposited in a patterned deposition process, or the adhesive material may only be temporarily deposited in the edge area of ​​the mother substrate and removed from the edge area later.

[0084] In particular, the recesses can be completely or in most cases free of adhesive for the singulation process. The singulation process can remain unaffected by the adhesive and it is possible that no residues of adhesive material are released by the singulation process.

[0085] According to an embodiment, connecting the auxiliary carrier and the mother substrate may include forming an adhesive layer between the working surface of the auxiliary carrier and the first main surface of the mother substrate. For example, the adhesive layer may be formed across the entire first main surface. Before segmentation, the edge portion of the adhesive layer may be selectively released and / or removed relative to the central portion of the adhesive layer in the central region. An auxiliary irradiation beam that is effective only in the edge region may locally generate heat below the peripheral adhesive portion extending outward from the outer side wall of the groove and may release the peripheral adhesive portion. According to another example, adhesion may be released in the edge region (e.g., in the entire edge region and / or including the groove). After removing and / or releasing the peripheral adhesive portion, it is possible that the adhesive material does not block cracks from entering the desorption layer for segmentation processing.

[0086] According to an embodiment, a method of manufacturing a semiconductor device may include providing a device substrate, such as a crystalline device substrate, from a mother substrate according to a method as described above. The mother substrate may include a semiconductor material. The mother substrate may be a chamfered semiconductor wafer. The semiconductor device may be formed from a portion of the device substrate. A thin semiconductor device may be formed at low loss of expensive semiconductor materials.

[0087] According to an embodiment, the mother substrate may include a central region and an edge region. The edge region may surround the central region. The mother substrate may be any mother substrate as described above. By way of example, the mother substrate may include or may consist of a crystalline semiconductor material.

[0088] In the central region of the mother substrate, the desorption layer may extend parallel to the main surface. The desorption layer may include a modified substrate material. The desorption layer may be any desorption layer described above.

[0089] In the edge region of the mother substrate, the groove may surround and / or enclose the central region in the lateral direction. The groove (e.g., the main axis of the groove) may run vertically and / or obliquely with respect to the desorption layer. The groove may be any groove as described above or below. For example, the groove may have been formed using a method as described above or below. The desorption layer may terminate at the groove. For example, the desorption layer may terminate at the inner sidewall of the groove.

[0090] According to an embodiment, the distance between the main surfaces of the mother substrate may decrease as the distance to the lateral center of the mother substrate increases.

[0091] According to an embodiment, the groove may include a groove inner sidewall. The groove inner sidewall may include a vertical sidewall segment. The desorption layer may cut off the vertical sidewall segment. The groove may be spaced apart from the outer edge of the mother substrate. Alternatively, the groove may extend inward from the lateral outer surface of the mother substrate.

[0092] According to an embodiment, the inner sidewall of the groove may be bent inwardly relative to the groove. Therefore, the first substrate portion between the desorption layer and the first main surface may be bent outwardly. The groove may extend from the first main surface of the mother substrate or from the second main surface of the mother substrate into the mother substrate.

[0093] For example, the groove may form a complete circle in a horizontal plane. The diameter of the circle may be smaller than the maximum inscribed circle of the horizontal shape of the mother substrate, wherein the mother substrate may have one or more flat portions along the outer periphery. The groove may be vertical or may be inclined in the direction of the center of the circle, wherein the angle between the main axis of the groove and the horizontal plane may be in the range of from 15 degrees to 45 degrees. The groove may be formed exclusively in a portion of the mother substrate where the main surfaces run parallel to each other. Alternatively, the groove may be partially or completely formed in a portion where the distance between the front side and the opposite side is reduced, such as where the mother substrate shows a chamfer and / or a rounded corner. For example, the groove may be completely or partially formed in a chamfered portion and / or a rounded corner along the edge of the mother substrate.

[0094] According to another example, the groove may include one or more straight portions and one or more arcs, wherein the one or more straight portions and the one or more arcs complement each other into a closed form. The diameter of the arc may be less than, equal to or greater than the maximum inscribed circle of the horizontal shape of the mother substrate, and the mother substrate may include one or more flat portions along the outer periphery. Each straight portion of the groove may run parallel to a flat portion. The groove may be vertical, or may be tilted in the direction of the center of the circle, wherein the angle between the main axis of the groove and the horizontal plane may be in the range of from 15 degrees to 45 degrees. The groove may be formed exclusively in the portion of the edge region where the main surfaces are parallel to each other. Alternatively, the groove may be partially or completely formed in the beveled portion and / or the rounded portion of the mother substrate. For example, the groove may be completely or partially formed in the lateral outer surface.

[0095] According to an embodiment, the wafer complex may include a mother substrate and an auxiliary carrier as described above. The auxiliary carrier may be attached to the mother substrate, wherein the first main surface of the mother substrate is oriented to the working surface of the auxiliary carrier. In other words, the first main surface faces the working surface.

[0096] According to an embodiment, the wafer composite may include an adhesive structure between the auxiliary carrier and a central region of the mother substrate. There may be no adhesive structure between the auxiliary carrier and an edge region of the mother substrate.

[0097] According to a further embodiment, a processing device may include a profile sensor unit and a laser scanning unit. The profile sensor unit may obtain shape information about the mother substrate. For example, the profile sensor unit may obtain information about the horizontal shape of the mother substrate. In particular, the profile sensor unit may obtain information about the position and / or size of a cutout or a flat portion along the periphery of the mother substrate, and the mother substrate may have a circular horizontal shape in the remaining portion except for the cutout or the flat portion.

[0098] The laser scanning unit can direct the laser beam onto the mother substrate. The laser beam axis of the laser beam can be tilted with respect to the exposed main surface of the mother substrate. The angle between the exposed main surface and the laser beam axis can be at least 10 degrees and at most 90 degrees. The tilt angle is oriented so that the laser beam is directed in the direction of the lateral center of the mother substrate.

[0099] The incident site of the laser beam may be close to the outer edge of the mother substrate. For example, the laser beam may be incident in the edge region of the exposed main surface, wherein the edge region is an annular strip of 3 mm including the outermost portion of the exposed main surface. Alternatively, the laser beam may be incident on the lateral outer surface of the mother substrate. Alternatively, the incident site of the laser beam may overlap both the edge region and the lateral surface region.

[0100] The trajectory of the laser beam on the master substrate is controllable as a function of the shape information obtained from the profile sensor unit. In particular, the laser beam can follow a kerf or a flat portion detected by the profile sensor unit.

[0101] According to an embodiment, the processing device may include a gantry unit adapted to be flippably connected to the main surface of the mother substrate. The gantry unit may be movable relative to the laser beam and / or the laser beam may be movable relative to the gantry unit so that the laser beam can follow a trajectory along the periphery of the mother substrate. The relative movement between the laser beam and the gantry unit may include rotational movement, radial movement and / or two orthogonal linear movements. The processing device is conducive to forming any type of groove as described above.

[0102] Embodiments of the methods described herein may be used to manufacture embodiments of the crystalline substrate as described herein. In at least some embodiments of the methods and / or crystalline substrates, the following features apply individually or in combination (if applicable):

[0103] (i) The desorption layer terminates at the groove and / or is in direct contact with the groove.

[0104] (ii) Forming the grooves comprises laser-assisted material removal, such as laser-assisted etching and / or laser ablation (eg laser dicing).

[0105] (iii) Laser-assisted material removal includes directing a laser beam into the first main surface or the second main surface of the mother substrate.

[0106] (iv) Laser-assisted material removal comprises directing a laser beam completely or partially into a lateral outer surface of the mother substrate, wherein the angle between the propagation direction of the laser beam and a horizontal plane is at least 20 degrees, such as at least 30 degrees.

[0107] (v) Laser-assisted material removal comprises directing a laser beam completely or partially into a lateral outer surface of the mother substrate, wherein the angle between the propagation direction of the laser beam and a horizontal plane is at most 75 degrees, such as at most 60 degrees.

[0108] (vi) The laser beam travels essentially parallel to the vertical direction.

[0109] (vii) The edge region is defined by and / or corresponds to a truncated outer region of the mother substrate.

[0110] (viii) The transition between the groove bottom and the inner sidewall of the groove may be rounded.

[0111] Figures 1A to 1C An embodiment having a groove 190 formed at the front side of the crystalline mother substrate 100 is illustrated.

[0112] Figure 1A The mother substrate 100 may include ceramics (e.g., sapphire α-Al2O3) or semiconductors (e.g., hexagonal polytype of silicon carbide). The mother substrate 100 may be an original substrate after being cut from a crystal block, or may be a processed substrate, such as a semiconductor wafer. The first main surface 101 at the front side and the second main surface 102 at the back side extend mainly parallel to each other. The second main surface 102 may have the same shape and size as the first main surface 101. The first main surface 101 and the second main surface 102 may be approximately flat or may be ribbed. The first main surface 101 and / or the second main surface 102 may be tilted off-axis by approximately 4 degrees with respect to the plane of the hexagonal lattice of the mother substrate 100. The lateral outer surface 103 connects the edge of the first main surface 101 and the edge of the second main surface 102.

[0113] The mother substrate 100 may include a central region 110 and an edge region 180 between the central region 110 and the outermost edge of the lateral outer surface 103. The central region 110 may include a plurality of device regions 115. The edge region 180 is free of the device region 115.

[0114] The device areas 115 are arranged in rows and columns. The cutout areas 116 of the grid shape separate the device areas 115 from each other in the lateral direction. Each device area 115 may include at least some of the structures defining the integrated circuit. The integrated circuit may be a power semiconductor device. Each device area 115 may include a structure formed on the semiconductor main part of the mother substrate. For example, the front side metallization may be formed on the semiconductor main part. The front side metallization may include a first load electrode of the power semiconductor device, and if applicable, a control electrode, such as a gate electrode of a MOSFET (metal oxide semiconductor field effect transistor), an IGBT (insulated gate bipolar transistor) or a JFET (junction field effect transistor).

[0115] The groove 190 is formed in the edge region 180. The desorption layer 150 is formed in the central region 110. The desorption layer 150 may be formed before or after the groove 190. For example, the desorption layer 150 may be formed before the groove 190 to avoid edge effects that may affect the formation of the desorption layer 150 in a region near the groove 190. According to another example, the groove 190 may be formed before the desorption layer 150, wherein the formation of the groove 190 may be combined with a front side process, and the formation of the desorption layer may be combined with a back side process (e.g., laser processing from the back side).

[0116] exist Figure 1B The desorption layer 150 shown in the figure may include a modified structure, which includes a material of the parent substrate in a modified form. The modified structure may include porous materials, injection-induced crystal damage and / or laser-induced material modification. The modified strips are separated in the laterally by strips of unmodified material. In addition, the desorption layer may include microcracks extending along the main crystal plane (e.g., along the a-plane). The microcracks may originate at the modified strips and / or may pass through the modified strips in a nearby manner.

[0117] The first distance d1 between the desorption layer 150 and the first main surface 101 can be less than the first vertical extension v1 of the groove 190. The groove 190 can be formed using a tool suitable for front-side processing in the field of manufacturing semiconductor devices. For example, the groove 190 can be formed using an edge trimming wheel, a cleaving blade and / or a patterned etching process (e.g., reactive ion beam etching). Alternatively, the groove can be formed using a dedicated tool designed to form the groove 190, such as by plasma etching using a vertical or inclined laser beam. The groove 190 (e.g., the main axis 194 of the groove 190) runs parallel to the vertical direction 104.

[0118] Before or after forming the grooves 190, a grid-shaped dicing grid (not shown) may be formed in the kerf region 116. The dicing grid may extend from the first main surface 101 into the mother substrate 100. The vertical extension of the dicing grid may be less than the first distance d1 between the first main surface 101 and the desorption layer 150.

[0119] In the illustrated example, the groove 190 extends from the first main surface 101 at the front side into the mother substrate 100. According to another example (not illustrated), the groove 190 extends from the second main surface 102 on the back side into the mother substrate 100.

[0120] In the illustrated example, the groove 190 extends vertically into the mother substrate 100. According to another example (not illustrated), the groove 190 is inclined relative to the vertical direction at an angle ranging from 5 degrees to 85 degrees in the direction of the lateral center of the mother substrate 100, wherein the groove 190 may extend into the mother substrate 100 from the first main surface 101 or from the second main surface 102.

[0121] In the illustrated example, the groove 190 extends from a horizontal surface section into the mother substrate 100. According to another example (not illustrated), the groove 190 extends partially or completely from a non-horizontal surface section of the first main surface or from a non-horizontal surface section of the second main surface 102 into the mother substrate 100, wherein the groove 190 may be vertical or inclined relative to the vertical direction at an angle ranging from 5 degrees to 85 degrees in the direction of the lateral center of the mother substrate 100. The non-horizontal surface section may be a chamfered and / or rounded surface portion.

[0122] The splitting process can split the crystalline mother substrate 100 along a ribbed splitting surface 155. The splitting surface 155 is formed in the desorption layer 150. In the case where the desorption layer 150 is based on a laser-induced modification of the material of the mother substrate 100, the splitting process can include applying a volume lattice stress. The volume lattice stress can be applied by ultrasound or by generating thermomechanical stress. For example, a polymer foil can be attached to the first main surface 101 or the second main surface 102. The mother substrate 100 and the polymer foil layer can be cooled below the glass transition temperature of the polymer foil. The polymer foil shrinks and induces volume lattice stress in the mother substrate 100. The mechanical stress induces macro-scale crack propagation along the main lattice plane (e.g., a-plane), wherein the still existing microcracks merge into the ribbed splitting surface 155 extending mainly in the lateral direction through the desorption layer 150. The generation of the splitting surface 155 starts at the exposed edge of the desorption layer 150 in the groove 190. The steep side walls of the grooves 190 that are not filled with solid material but may be filled with a fluid may facilitate a highly reproducible process of the singulation process.

[0123] As in Figure 1C As shown in Figure 1B The mother substrate 100 is divided into a first mother substrate portion and a second mother substrate portion. The first mother substrate portion (device substrate 410) includes the mother substrate 100 Figure 1B The second mother substrate portion (recovered substrate 420) includes the mother substrate 100 between the first main surface 101 and the split surface 155. Figure 1B The portion between the second major surface 102.

[0124] The device substrate 410 includes a first desorption layer portion 416 and a first substrate portion 415 having a lateral outer surface 413. The recycled substrate 420 includes a second substrate portion 425 and a second desorption layer portion 426. The recycled substrate 420 includes a reinforcement ring 427 protruding above the second desorption layer portion 426 along an outer periphery of the recycled substrate 420.

[0125] Figure 2 A schematic plan view of a cylindrical mother substrate 100 is shown. By way of example only, the lateral outer surface 103 of the mother substrate 100 includes a flat portion 106. In other embodiments, the lateral outer surface 103 may include a cut-out portion or may include more than one flat portion. The groove 190 may completely surround the central area 110. The groove 190 may include a circular portion 199 and a linear portion 198. The circular portion 199 may form or may be approximated as a portion of a circle, wherein the center of the circle coincides with the lateral center 105 of the mother substrate 100. The linear portion 198 may extend parallel to the flat portion 106 of the lateral outer surface 103. The circular portion 199 and the linear portion 198 may complement each other into a continuous frame without interruption.

[0126] The circular portion 199 may form a portion of a circle and may be formed by point symmetry processing (e.g., rounding or edge trimming). Alternatively, the circular portion 199 may include orthogonal linear segments so that the groove 190 follows a stepped line that approximates a portion of a circle, and wherein the circular portion 199 may be formed by a processing tool using Cartesian coordinates, for example, for generating an etching mask on the first main surface 101.

[0127] According to another example (not shown), the groove 190 may be a circle.

[0128] Figure 3A central region 110 including device regions 115 and a grid-shaped dividing grid 117 is shown, which separates the device regions 115 from each other in the lateral direction. A groove 190 separating the device region 115 from the edge region 180 may include an orthogonal linear portion in the lateral projection of the line segments of the dividing grid 117. The groove 190 may have a greater vertical extension than the dividing grid. The groove 190 may have a greater lateral width than the line segments of the dividing grid 117 and / or may have another vertical cross-sectional shape like the line segments of the dividing grid 117. According to an embodiment, the groove 190 may be separated from the dividing grid 117 in the lateral direction.

[0129] FIG. 4A to FIG. 4E A vertical cross section of a groove 190 extending from the first main surface 101 into the mother substrate 100 and a possible position of the desorption layer 150 relative to the groove 190 is shown. The mother substrate 100 comprises a chamfer 185 between the outer edge of the first main surface 101 and the straight vertical portion at the outermost edge of the lateral outer surface 103. The chamfer 185 forms a part of the lateral outer surface 103. The main axis 194 of the groove 190 runs vertically or obliquely to the vertical direction 104.

[0130] exist Figure 4A 1 , the groove 190 extends inwardly from the lateral outer surface 103. The groove 190 has only a groove inner sidewall 191 oriented to the lateral center of the first main surface 101. The radial extension (width) of the groove 190 is equal to the distance of the groove inner sidewall to the outer periphery of the mother substrate. The radial groove extension can be at least 90% and at most 110% of the width of the edge region.

[0131] The groove bottom 195 may extend approximately in a plane parallel to the first main surface 101. According to other examples, the groove bottom 195 may slightly drop or may slightly rise as the distance to the lateral outer surface 103 decreases.

[0132] The transition between the groove bottom 195 and the inner sidewall 191 of the groove can be rounded, wherein the radius r1 of the rounding can be in the range of from 0.5 μm to 50 μm, typically in the range of from 1 μm to 15 μm or in the range of from 20 μm to 30 μm. The rounded transition between the groove bottom and the inner sidewall of the groove can be produced by the tool (e.g., a cutting tool, a trimming tool and / or a grinding tool) used to prepare the groove. Due to mechanical wear of the tool, the groove may not be accurately cut out but rounded. When preparing the groove, for example, when defining the width and / or vertical extension of the groove, the radius caused by the tool can be considered. Between the first main surface 101 and the rounding, the inner sidewall 191 of the groove may include a vertical or approximately vertical sidewall section 193. The desorption layer 150 can cut off the inner sidewall 191 of the groove in the vertical sidewall section 193.

[0133] Figure 4B and Figure 4C The present invention relates to a groove 190 having a groove inner sidewall 191 and a groove outer sidewall 192 formed symmetrically. The width of the groove 190 in the radial direction relative to the lateral center of the mother substrate may increase as the distance from the first main surface 101 increases. Figure 4B As shown in the figure, it can be gradually reduced or Figure 4C The opening of the groove 190 in the first main surface 101 has a width in the radial direction.

[0134] The portion of the groove inner sidewall 191 between the first main surface 101 and the desorption layer 150 defines a lateral outer surface 413 of the device substrate 410, which can be obtained from the mother substrate 100 by segmenting along a segmentation surface through the desorption layer 150. The stepped or inclined groove sidewall 191 produces an advanced etching profile for the device substrate 410. At least for processing steps that directly process the device substrate 410 after the segmentation process, the risk of edge chipping and damage during disassembly can be reduced. The inclined and / or stepped groove inner sidewall 191 can facilitate edge beveling of thin and ultra-thin substrate portions. The thin or ultra-thin substrate portion can have a diameter in the range of a typical wafer diameter and a thickness of up to 120 μm (e.g., up to 80 μm or even up to 60 μm). The groove outer sidewall 192 can define the shape of the inner sidewall of the reinforcement ring 427 of the recycled substrate 420.

[0135] FIG. 4D to FIG. 4E Asymmetric groove inner sidewalls 191 and groove outer sidewalls 192 are involved. For example, the groove inner sidewall 191 may include a steeper section than the groove outer sidewall 192. In the steep or nearly vertical sidewall section 193, the desorption layer 150 may cut the groove inner sidewall 191 orthogonally or nearly orthogonally for a reliable segmentation process induced by volume lattice stress. Above and / or below the vertical sidewall section 193, the groove inner sidewall 191 may be slightly rounded or beveled. The groove outer sidewall 192 may be significantly shallower than the groove inner sidewall 191. The chamfer 185 and the groove outer sidewall 192 define the sidewalls of the reinforcement ring 427. The reinforcement ring 427 with shallow sidewalls may be robust against chipping and may facilitate less complex processing of the recycled substrate 420.

[0136] exist Figure 4EIn the embodiment of the present invention, the groove 190 can be formed by plasma etching, which can use an inclined laser beam. The groove 190 can gradually become thinner as the distance from the first main surface 101 increases. The inner sidewall 191 of the groove can be curved. The curvature can extend inwardly relative to the groove 190 and outwardly relative to the device substrate 410. In addition, the outer sidewall 192 can be curved outwardly relative to the groove 190 and inwardly relative to the reinforcement ring 427. The desorption layer 150 can terminate at the closed end of the tapered groove 190 or terminate near the closed end of the tapered groove 190.

[0137] According to other examples (not shown), as shown in FIG. FIG. 4A to FIG. 4E The depicted recess 190 extends from the second major surface 102 into the mother substrate 100 .

[0138] FIG. 5A to FIG. 5G A method of manufacturing a semiconductor device, for example, a vertical silicon carbide power semiconductor device, is illustrated.

[0139] Figure 5A A mother substrate 100 is shown, which may be a processed beveled silicon carbide wafer having a standard diameter and having a standard thickness. The mother substrate 100 includes a central region 110 and an edge region 180 surrounding the central region 110. The edge region 180 separates the central region 110 from the lateral outer surface 103. In the edge region 180, the mother substrate 100 includes a beveled portion 185. The beveled portion may include a bevel section and / or a rounded corner, for example, between adjacent bevel sections and between a bevel section and a main surface 101, 102.

[0140] The central region 110 includes a plurality of device regions 115. The edge region 180 does not contain the device region 115. The device regions 115 are arranged in rows and columns, and the cutout regions 116 of the grid shape separate the device regions 115 from each other in the lateral direction. In each device region 115, several doping regions may be formed. For example, the mother substrate 100 may have a background doping of a first conductivity type, and each device region 115 may include one or more emitter regions 120 of a complementary second conductivity type. The emitter region 120 may be in contact with the first main surface 101. The emitter region 120 may be an anode region of a power semiconductor diode, or may include a body region of a power switching device, which includes a transistor unit. A front side metallization 171 may be formed on the first main surface 101. The front side metallization 171 may be in contact with the emitter region 120. A portion of the interlayer dielectric 160 may be formed between a portion of the front side metallization 171 and the first main surface 101. A passivation structure (not shown) may cover the edges of the front side metallization 171. A recess 190 may be formed in the edge region 180.

[0141] Figure 5B A groove 190 is shown extending from the first main surface 101 into the mother substrate 100. The groove 190 may be formed in a horizontal main section of the first main surface 101 and may have a shape as described with reference to FIG. FIG. 4A to FIG. 4E Furthermore, a grid-shaped dicing grid (not shown) may be formed in the cutout region 116 , wherein the vertical extension of the dicing grid may be smaller than the vertical extension of the grooves 190 .

[0142] The auxiliary carrier 300 can be attached to the front side of the mother substrate 100. For example, the adhesive layer 200 can adhere the auxiliary carrier 300 to the first main surface 101 with the front side metallization 171. The adhesive layer 200 can be formed by a temporary bonding / debonding adhesive. For example, a liquid glue can be applied to the front side of the mother substrate 100. The glue can at least partially fill the groove 190 and the gap between the adjacent parts of the front side metallization 171. Pre-baking can dry the glue and / or can remove a portion of the solvent contained in the glue. The auxiliary carrier 300 can be brought into contact with the exposed top surface of the dried glue. The dried glue can be cured, for example, by irradiation with ultraviolet radiation to form the adhesive layer 200.

[0143] The laser beam 800 may be directed to the exposed second main surface 102 of the mother substrate 100 to form the desorption layer 150 in the central region 110, such as in Figure 5A As shown in.

[0144] Figure 5C A wafer complex 890 is shown, which comprises a mother substrate 100 with the front side adhesively bonded to a working surface 301 of an auxiliary carrier 300. The auxiliary carrier 300 may be a glass plate, a sapphire plate, or a plate that may comprise a material from the main part of the mother substrate 100. For example, the auxiliary carrier 300 may comprise polycrystalline or crystalline silicon carbide. The adhesive layer 200 may fill the space between adjacent parts of the front side metallization 171. The adhesive layer 200 may fill the groove 190 and may form a meniscus extending from the chamfer 185 of the mother substrate 100 to the working surface 301 of the auxiliary carrier 300.

[0145] The laser beam 800 penetrates the second main surface 102 at the back side of the mother substrate 100 and forms a modified structure 151 in the desorption layer 150. The modified structure 151 may include another phase of the semiconductor material of the mother substrate 100, such as elemental silicon and elemental carbon, such as amorphous carbon. The modified structure 151 may form a modified strip extending orthogonally to the cross-sectional plane. In addition, the desorption layer 150 may include microcracks 154 generated by mechanical stress, which is caused by the heat generated by heating by the laser beam 800 and / or the volume expansion by the phase change of the semiconductor material. The desorption layer 150 cuts off the inner sidewall 191 of the groove. In other words, the microcracks 154 of the desorption layer 150 can terminate at the inner sidewall 191 of the groove.

[0146] According to FIG. 5A to FIG. 5C According to the example illustrated in FIG, the groove 190 is formed at the front side of the mother substrate 100 before the mother substrate 100 is attached to the auxiliary carrier 300 with the front side facing downward. According to another example (not illustrated), the groove 190 is formed at the back side of the mother substrate 100, for example after the mother substrate 100 is attached to the auxiliary carrier 300 with the front side facing downward.

[0147] The auxiliary irradiation beam 810 may be directed onto the peripheral bonding portion 280 of the bonding structure 200 before or after forming the desorption layer 150, such as in Figure 5D For example, the auxiliary irradiation beam 810 may be directed exclusively onto the peripheral bonding portion 280 through the auxiliary carrier 300 .

[0148] Figure 5E The wafer composite 890 including the mother substrate 100 and the auxiliary carrier 300 is shown after removing the peripheral adhesive portion 280. The central adhesive portion forms an adhesive structure 210 connecting the mother substrate 100 and the auxiliary carrier 300. The recess 190 does not contain solid material and may be filled with a fluid, for example with ambient air or a process gas.

[0149] A segmentation process induced by volume lattice stress is performed.The volume lattice stress may be induced by applying ultrasound or by a polymer foil attached to the second main surface 102 at the back side of the mother substrate 100 and cooled below the glass transition temperature of the polymer foil.

[0150] As in Fig. 5F As shown in the figure, Figure 5EThe desorbed layer 150 is divided along the rib-shaped dividing surface 155 that ends at the inner side wall 191 of the groove. The first mother substrate portion between the first main surface 101 and the dividing surface 155 can form a device substrate 410, which has a thickness of less than 200 μm, for example, less than 100 μm or less than 50 μm. A thin device substrate can be obtained from the device substrate 410 as described below. The second mother substrate portion between the second main surface 102 and the dividing surface 155 forms a recycled substrate 420. A further device substrate can be obtained from the recycled substrate 420 by appropriate treatment.

[0151] The rib-shaped segmented surface 155 may be planarized (e.g., ground and / or polished), for example, in a chemical / mechanical polishing process and / or by a heat treatment in a hydrogen-containing atmosphere. The planarization process may include exposing the diced grid if the diced grid is formed according to a DBG method. Backside processing for completing the vertical power conductor device may be performed. The backside processing may include implanting dopants of at least one conductivity type and forming backside metallization.

[0152] Figure 5G Shown from Fig. 5F The processed device substrate 450 is obtained by processing the device substrate 410 of the present invention. The processed device substrate 450 includes a heavily doped contact region 129 formed along a backside surface 452 and a voltage sustaining layer 121 formed between the contact region 129 and the emitter region 120. The voltage sustaining layer 121 may include a low-doped drift zone and / or a super junction structure having relatively heavily doped p-type columns and n-type columns extending in a vertical direction. A backside metallization 172 may be formed on the backside surface 452.

[0153] FIG. 6A to FIG. 6C It involves a layer transfer process combined with an epitaxial process, wherein the transferred layer may be obtained from a semiconductor wafer by a singulation process as described above.

[0154] The groove 190 is formed in the edge region 180 of the mother substrate 100, for example, by edge trimming. The first main surface 101 at the front side of the mother substrate 100 is attached to the auxiliary carrier 300. For example, the first main surface 101 and the working surface 301 of the auxiliary carrier 300 can be directly bonded to each other. According to the illustrated embodiment, a thermally stable bonding layer 250 can be provided between the first main surface 101 of the mother substrate 100 and the working surface 301 of the auxiliary carrier 300. As described above, the desorption layer 150 is formed in the mother substrate 100.

[0155] Fig. 6AThe desorption layer 150 is shown to terminate at the inner sidewall 191 of the groove. By way of example, the bonding layer 250 mechanically connecting the auxiliary carrier 300 and the mother substrate 100 may be or may include a silicon nitride layer, a structured layer containing silicon nitride, a layer including heavily doped crystalline silicon carbide and / or polycrystalline silicon carbide. The auxiliary carrier 300 may consist of or may include the material of the mother substrate 100. In the case where the mother substrate 100 is a silicon carbide crystal, the auxiliary carrier 300 may also be a silicon carbide crystal, for example a silicon carbide crystal with poor crystal quality.

[0156] The segmentation process described above extends horizontally through Fig. 6A The rib-shaped dividing surface 155 of the desorption layer 150 separates the second mother substrate portion (recovery substrate 420) from the first mother substrate portion (device substrate 410).

[0157] As in Figure 6B As shown in FIG. 1 , the rib-shaped segmented surface 155 of the device substrate 410 can be polished and / or planarized to a certain extent, wherein the height of each rib can be reduced. The device substrate 410 represents a transfer layer suitable as a starting layer for epitaxial processing. An epitaxial layer can be formed on the device substrate 410. Front-side processing can form the structure of the integrated circuit in and / or on the epitaxial layer.

[0158] Figure 6C A processed device substrate 450 is shown including a device substrate 410 and an epitaxial layer 430 obtained by epitaxial growth on the device substrate 410. The emitter region 120, the interlayer dielectric 160 and the front side metallization 171 may be formed in and / or on the epitaxial layer 430 as described above.

[0159] The processed device substrate 450 may be separated from the auxiliary carrier 300 . For example, the bonding layer 250 may be selectively removed, or a further laser-induced singulation process may be effective on the upper portion of the auxiliary carrier 300 .

[0160] FIG. 7A to FIG. 7B A method of forming the groove 190 after mounting the mother substrate 100 on the auxiliary carrier 300 is involved.

[0161] As in Fig. 7A As shown in FIG. 1 , the mother substrate 100 may be as shown in FIG. Figure 5A Such a mother substrate is described. The mother substrate 100 can be connected front-side down to the auxiliary carrier 300 via the adhesive layer 200. The inclined laser beam 800 can be directed onto the second main surface 102 from the back side.

[0162] The laser beam 800 may be incident vertically on the second main surface 102, wherein a vertical groove extending from the second main surface 102 into the mother substrate 100 may be formed. The groove 190 may have a Figure 2 and FIG. 4A to FIG. 4E Any shape is described for the groove extending from the first main surface 101 into the mother substrate 100 .

[0163] According to the illustrated embodiment, the propagation axis 801 of the laser beam 800 is tilted at an inclination angle β to the vertical direction 104. By way of example, the inclination angle β can be in the range from 10 degrees to 80 degrees. The laser beam 800 can induce plasma etching, which can be controlled to form a tapered groove 190 that terminates in the plane of the desorption layer 150. Alternatively, the groove 190 can cut through the plane of the desorption layer 150 and / or can be slightly shifted from the desorption layer 150 in the lateral direction by a few microns. For example, the vertical extension of the groove 190 relative to the second main surface 102 can be equal to or greater than the second distance d2 between the second main surface 102 and the desorption layer 150.

[0164] The shape of the groove inner sidewall 191 and the shape of the groove outer sidewall 192 can be controlled by the parameters of plasma etching (such as energy, angle and incident area). For example, the groove inner sidewall 191 can be bent inwardly relative to the groove 190, and bend outwardly relative to the portion of the mother substrate 100 between the second main surface 102 and the desorption layer 150. Therefore, the groove outer sidewall 192 can be formed to extend inwardly relative to the groove 190 and extend outwardly relative to the substrate portion between the first main surface 101 and the desorption layer 150.

[0165] According to FIG. 7A to FIG. 7B According to the example illustrated in FIG, the groove 190 is formed at the back side of the mother substrate 100 after the mother substrate 100 is attached front side down to the auxiliary carrier 300. According to another example (not illustrated), the groove 190 is formed at the front side of the mother substrate 100 before the mother substrate 100 is attached front side down to the auxiliary carrier 300.

[0166] Fig. 8A A portion of a wafer composite 890 is shown, which includes a mother substrate 100 with a chamfer 185, a groove 190, and a desorption layer 150 that cuts off a vertical sidewall section 193 of an inner sidewall 191 of the groove. The chamfer 185 is a portion of the lateral outer surface 103. An adhesive layer 200 formed between the first main surface 101 of the mother substrate 100 and the working surface 301 of the auxiliary carrier 300 mechanically connects the mother substrate 100 and the auxiliary carrier 300.

[0167] Forming the groove 190 before mounting the mother substrate 100 on the auxiliary carrier 300 avoids ablation of debris, and this can be performed using existing tools (e.g., conventional edge trimmers). The edge trimming process can be quite fast and inexpensive. Existing tools for edge trimming allow for rapid integration of the process in a processing line. The auxiliary carrier 300 remains intact and can be reused without extensive rework.

[0168] Figure 8B A polishing pad 850 of a bevel wheel etch dresser is shown. The shape of the notch 851 of the polishing pad 850 can be profiled to the lateral outer surface 103 of the mother substrate 100, wherein the groove 190 is formed at the front side of the mother substrate 100. In addition, the polishing pad 850 can be profiled with chamfers along the lateral outer surfaces of the device substrate 410 and the recycled substrate 420. Multiple notches 851 can reduce processing time.

[0169] exist Fig. 9A , the groove 190 extends from the first main surface 101 into the mother substrate 100. The groove 190 is formed at a certain distance from the lateral outer surface 103. Forming the groove 190 may include cutting using a circular cutting edge. In addition or as an alternative, forming the groove 190 may include linear cutting and / or grinding in a portion parallel to the flat portion of the lateral outer surface 103. Alternatively, the groove 190 may be formed by at least one of the following: (i) laser ablation processing or laser-assisted etching processing, such as by using UV (ultraviolet) laser irradiation; (ii) plasma and / or patterned etching processing, such as RIE (reactive ion beam etching); and / or (iii) electrical discharge machining (EDM) and / or electrochemical discharge machining (ECDM).

[0170] according to Fig. 9B A spiral cut or a plurality of circular cuts with different diameters may form a groove 190 extending outwardly to the lateral outer surface 103 .

[0171] Fig.10 A groove 190 formed by front-side micromachining is shown. This process can use UV ablation using an angled laser beam. The ablation volume can be quite small and can form both a beveled device substrate 410 and a recycled substrate 420 with a beveled reinforcement ring 427.

[0172] FIG. 11A to FIG. 11DEmbodiments involving backside micromachining are disclosed. The process may use UV ablation using an inclined laser beam. The process may be performed after the mother substrate 100 is mounted on the auxiliary carrier 300. The inclined laser beam 800 may be controlled to form both a beveled recycled substrate 420 and a device substrate 410 having a beveled reinforcement ring 417. The incident site for the ablation laser beam 800 may be selected to achieve both an advantageously beveled recycled substrate 420 and an advantageously configured reinforcement ring 417. Alternatively or in addition, the incident site for the ablation laser beam 800 may be selected to completely or highly avoid ablating a portion of the adhesive layer.

[0173] Forming the groove 190 may include laser-assisted material removal, wherein the laser-assisted material removal may include directing a laser beam completely or partially onto the lateral outer surface 103 of the mother substrate 100, and wherein the inclination angle between the propagation direction of the laser beam and the horizontal plane is at least 20 degrees, for example at least 30 degrees.

[0174] exist Fig.11A In the embodiment, the grooves 190 extend from the outermost edge of the second major surface 102 to the direction of the lateral ends of the desorption layer 150 .

[0175] exist Fig. 11B In FIG. 8 , the tilt angle β between the vertical direction 104 and the laser beam axis 801 of the laser beam 800 is approximately 30 degrees. The incident location is completely within the strictly horizontal main portion of the second main surface 102 .

[0176] exist Fig. 11C , the tilt angle β is about 30 degrees, and the incidence location is mainly in the slightly chamfered portion of the second main surface 102 and to some extent on the lateral outer surface 103.

[0177] exist Fig.11D In the embodiment, the tilt angle β is about 75 degrees. The incident position is completely on the lateral outer surface 103.

[0178] exist FIG. 11A to FIG. 11D In each of the examples illustrated in , the groove 190 is formed at the back side of the mother substrate 100 after the mother substrate 100 is attached front side down to the auxiliary carrier 300. According to other examples (not illustrated), the groove 190 is formed in the same manner as illustrated, but the groove 190 is formed at the front side of the mother substrate 100 before the mother substrate 100 is attached front side down to the auxiliary carrier 300.

[0179] Fig.12A processing apparatus 900 for inclined laser ablation along the periphery of a crystal mother substrate having an arbitrary horizontal cross section is schematically shown. The profile sensor unit 910 can obtain shape information about the shape of the mother substrate 100. The scanning unit 920 can generate a laser beam 800 incident on the mother substrate at an angle between 10 degrees and 80 degrees relative to the vertical direction, and can control the position of the incident portion of the laser beam 800 on the mother substrate. A wafer complex 890 including the mother substrate can be temporarily mounted on a stage unit 940. The stage unit 940 can allow the wafer complex 890 to rotate and / or linearly move relative to the profile sensor unit 910 and the scanning unit 930.

[0180] The control unit 920 can process information obtained from the contour sensor unit 910 and, if applicable, can process information obtained from the stage unit 940, and can control the relative movement between the scanning unit 920 and the stage unit 940 in such a way that the laser beam 800 follows a desired path on the surface of the wafer complex 890.

[0181] The processing device 900 allows forming any groove as described above, in particular as described with reference to FIG. 4A to FIG. 4E , Fig.10 as well as FIG. 11A to FIG. 11D The groove 190 is described.

Claims

1. A method for manufacturing a device substrate, the method comprising: Providing a mother substrate (100) including a central region (110) and an edge region (180), wherein the edge region (180) surrounds the central region (110); forming a desorption layer (150) in the central region (110), wherein the desorption layer (150) extends parallel to the major surfaces (101, 102) of the mother substrate (100), and wherein the desorption layer (150) comprises a modified substrate material; and A groove (190) is formed in the edge region (180), wherein the groove (190) surrounds the central region (110) in the lateral direction, wherein the groove (190) runs vertically and / or obliquely with respect to the desorption layer (150), The grooves delimit the desorption layer laterally, so that the desorption layer ends before reaching the edge region.

2. The method according to claim 1, further comprising: The mother substrate (100) is divided along a dividing surface (155) passing through the desorption layer (150), wherein a portion of the mother substrate (100) forms a device substrate (410).

3. The method according to any one of the preceding claims 1-2, wherein: In the edge region (180), the distance between the main surfaces (101, 102) of the mother substrate (100) decreases as the distance from the lateral center (105) of the mother substrate (100) increases.

4. The method according to any of the preceding claims 1 - 2, wherein the recess (190) extends from the first main surface (101) of the mother substrate (100) into the mother substrate (100).

5. A method according to any one of the preceding claims 1-2, wherein the groove (190) includes a groove inner sidewall (191) oriented to the lateral center (105) of the mother substrate (100), the groove inner sidewall (191) includes a vertical sidewall segment (193), and wherein the desorption layer (150) cuts off the vertical sidewall segment (193).

6. The method according to any of the preceding claims 1-2, wherein the groove (190) is spaced apart from a lateral outer surface (103) of the mother substrate (100).

7. The method according to any one of claims 1 to 2, wherein the groove (190) extends inwardly from the lateral outer surface (103).

8. A method according to any one of the preceding claims 1-2, wherein forming the groove (190) includes laser-assisted material removal, wherein the laser-assisted material removal includes directing a laser beam (800) onto a first main surface (101) of a mother substrate (100) and / or onto a second main surface (102) of the mother substrate (100), wherein the second main surface (102) is opposite to the first main surface (101).

9. A method according to any one of the preceding claims 1-2, wherein forming the groove (190) comprises laser-assisted material removal, wherein the laser-assisted material removal comprises directing a laser beam (800) completely or partially onto a lateral outer surface (103) of the mother substrate (100), wherein the lateral outer surface (103) connects the two main surfaces (101, 102), and wherein the angle between the propagation direction of the laser beam (800) and a horizontal plane is at least 30 degrees.

10. The method of claim 8, wherein the laser beam (800) is tilted in the direction of a lateral center (105) of the mother substrate (100), and wherein the angle between the vertical direction (104) and the laser beam (800) is at least 30 degrees.

11. The method according to any one of the preceding claims 1-2, further comprising: An auxiliary carrier (300) and a mother substrate (100) are connected, wherein a first main surface (101) of the mother substrate (100) faces a working surface (301) of the auxiliary carrier (300), and wherein the auxiliary carrier (300) and the mother substrate (100) are connected after a groove (190) is formed in the first main surface (101) and / or before a groove (190) is formed in the second main surface (102).

12. The method according to claim 11, wherein connecting the auxiliary carrier (300) and the mother substrate (100) comprises forming an adhesive structure (210) between a working surface (301) of the auxiliary carrier (300) and a central area (110) of the mother substrate (100).

13. The method according to claim 11, wherein Connecting the auxiliary carrier (300) and the mother substrate (100) comprises forming an adhesive layer (200) between the working surface (301) of the auxiliary carrier (300) and the first main surface (101) of the mother substrate (100), and Prior to singulation, the peripheral adhesive portion (280) of the adhesive layer (200) in the edge region (180) is released and / or removed.

14. A method for manufacturing a semiconductor device, the method comprising: The method according to any of the preceding claims 1 to 13, wherein the device substrate (410) is obtained from a mother substrate (100) by slicing the mother substrate (100) along a slicing surface (155) in the desorption layer (150), and wherein the mother substrate (100) comprises a crystalline semiconductor material; as well as A semiconductor device (600) is formed from a portion of a device substrate (410).

15. A mother substrate (100), comprising: a central region (110) and an edge region (180), wherein the edge region (180) surrounds the central region (110); a desorption layer (150) in the central region (110), the desorption layer (150) extending parallel to the major surfaces (101, 102), wherein the desorption layer (150) comprises a modified substrate material; as well as a groove (190) in the edge region (180), wherein the groove (190) laterally surrounds the central region (110), and wherein the groove (190) runs vertically and / or obliquely with respect to the desorption layer (150), The grooves delimit the desorption layer laterally, so that the desorption layer ends before reaching the edge region.

16. The mother substrate according to claim 15, wherein in the edge region (180) the distance between the main surfaces (101, 102) of the mother substrate (100) decreases with increasing distance to the lateral center (105) of the mother substrate (100).

17. The mother substrate according to any one of claims 15-16, wherein the groove (190) comprises a groove inner sidewall (191), the groove inner sidewall (191) comprises a vertical sidewall segment (193), and wherein the desorption layer (150) cuts off the vertical sidewall segment (193).

18. A wafer composite comprising: A mother substrate (100) according to any one of claims 15 to 17; and An auxiliary carrier (300) is attached to the mother substrate (100), wherein the first main surface (101) of the mother substrate (100) is oriented to the working surface (301) of the auxiliary carrier (300).

19. The wafer composite according to claim 18, further comprising: An adhesive structure (210) is provided between the auxiliary carrier (300) and the central region (110) of the mother substrate (100), wherein the adhesive structure (210) is not provided between the auxiliary carrier (300) and the edge region (180) of the mother substrate (100).

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