Method for manufacturing a composite structure including a thin layer made of monocrystalline SiC on a carrier substrate made of polycrystalline SiC.

Abstract

A method for manufacturing a composite structure including a thin layer made of monocrystalline silicon carbide, comprising the steps of: a) providing an initial substrate made of monocrystalline silicon carbide and a carrier substrate made of polycrystalline silicon carbide; b) a porosification step applied to the initial substrate in order to form a porous layer on the front side of the initial substrate; c) a surface layer made of amorphous silicon carbide on the front side of the carrier substrate; d) bonding the initial substrate and the carrier substrate at their respective front sides to produce a first intermediate structure; e) a heat treatment step applied to the first intermediate structure at a temperature above 900° C. in order to form a thin layer, starting from the contact interface with the porous layer, thereby producing a second intermediate structure; and f) a separation step within the porous layer of the second intermediate structure in order to obtain, on the one hand, the composite structure and, on the other hand, the remaining part of the initial substrate.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to the field of semiconductor materials for microelectronic components. The present invention particularly relates to a method for producing a composite structure comprising a thin layer of monocrystalline silicon carbide on a carrier substrate made of polycrystalline silicon carbide. [Background technology]

[0002] (Technical Background of the Invention) SiC is being increasingly used to fabricate innovative power devices to meet the needs of the growing sector of electronics applications, particularly electric vehicles.

[0003] Power devices and integrated power systems based on monocrystalline silicon carbide can manage much higher power densities than their conventional silicon equivalents, and can do so with smaller sized active areas. To further limit the dimensions of power devices on SiC, it would be preferable to fabricate vertical components rather than horizontal components. To do this, the SiC structure must allow vertical electrical conduction between electrodes placed on the front and back sides of the structure.

[0004] Nevertheless, high-quality single-crystal SiC (c-SiC) substrates for the microelectronics industry are still expensive and difficult to supply in large sizes. Therefore, it is preferred to use layer transfer solutions to manufacture composite structures that typically include a thin layer of single-crystal SiC (derived from a high-quality c-SiC substrate) on a low-cost carrier substrate, e.g. made of polycrystalline SiC (p-SiC).

[0005] One well-known thin layer transfer solution is the Smart Cut® process, which uses implanting light ions into a single crystal donor substrate and bonding by direct bonding to the carrier substrate at the bonding interface. The transfer of a thin layer from the donor substrate to the carrier substrate is performed by fracture along a buried weakened plane created by the implantation of light ions.

[0006] Another known transfer solution, especially for silicon substrates, is the Eltran® process, which involves bonding by direct bonding to a carrier substrate, including a porous layer on which a thin monocrystalline layer is epitaxially grown. The transfer of the thin layer to the carrier substrate is carried out by separation within the porous layer. Objectives of the invention

[0007] The present invention relates to an alternative solution to the prior art solutions. The present invention relates to a method for manufacturing a composite structure comprising a thin layer made of monocrystalline SiC arranged on a carrier substrate made of polycrystalline SiC. The present invention also relates to an intermediate structure obtained during said manufacturing method. Summary of the Invention

[0008] BRIEF DESCRIPTION OF THE DRAWINGS The invention relates to a method for producing a composite structure comprising a thin layer made of monocrystalline silicon carbide arranged on a carrier substrate made of polycrystalline silicon carbide, the method comprising the steps of: a) providing an initial substrate made of monocrystalline silicon carbide having a front surface and a back surface, and a carrier substrate made of polycrystalline silicon carbide having a front surface and a back surface; b) a porosification step applied to the initial substrate in order to form a porous layer at least on the front side of the initial substrate; c) forming a surface layer made of amorphous silicon carbide on the front side of the carrier substrate and / or on the porous layer; d) bonding the initial substrate and the carrier substrate at their front sides to produce a first intermediate structure; e) a heat treatment step applied to the first intermediate structure at a temperature above 900° C. in order to crystallize the surface layer at least partially in the form of monocrystalline silicon carbide, starting from the contact interface with the porous layer, to form a thin layer, resulting in the production of a second intermediate structure; f) separation within the porous layer of the second intermediate structure in order to obtain, on the one hand, the composite structure and, on the other hand, the remainder of the initial substrate; The present invention relates to a method comprising the steps of:

[0009] According to other preferred, non-limiting features of the present invention, the following are taken into consideration, individually or in any technically feasible combination: At the end of step b), the porous layer has a thickness of 0.5 μm to 5 μm; At the end of step b), the porous layer contains pores with a size between 1 nm and 50 nm and has a porosity between 10% and 70%; At the end of c), the surface layer has a thickness of less than or equal to 10 μm; At the end of c), the surface layer has a thickness of 1 μm or less, typically of the order of one hundred to several hundred nanometers; Step c) comprises depositing an amorphous silicon carbide layer at least on the front side of the carrier substrate and / or at least on the porous layer to form a surface layer; The deposited amorphous silicon carbide layer is highly doped and has a 10 19 / cm 3 More than or equal to 10 20 / cm 3 having a concentration of dopant species greater than Step c) comprises amorphizing at least a surface layer on the front side of the carrier substrate to form a surface layer; step d) comprises, before bonding the initial substrate and the carrier substrate, forming a bonding layer on one and / or the other of the substrates on the side of their respective faces, the bonding layer having a total thickness of 10 nm or less after bonding; the bonding layer is comprised of at least one material selected from silicon, nickel, titanium, and tungsten; During step e), segmentation or dissolution of the bonding layer into nodules allows, at least locally, direct contact between the surface layer and the porous layer or between the surface layer and the carrier substrate; the heat treatment of step e) is carried out at a temperature of at least 1000°C, preferentially at least 1400°C or at least 1850°C; In step e), crystallization of the surface layer takes place starting from the contact interface with the carrier substrate to form an intermediate layer, at least partially in the form of polycrystalline silicon carbide; the fabrication method comprises, after step f), a finishing step g) involving a mechanical and / or chemical treatment of the composite structure in order to eliminate any residues of the porous layer from the front side of the thin layer and / or to correct the thickness uniformity of the composite structure; Step g) comprises a heat treatment applied to the composite structure at a temperature between 1000°C and 1900°C, before or after the mechanical and / or chemical treatment; The fabrication method includes reconditioning a remaining portion of the initial substrate for reuse as an initial substrate for fabricating a new composite structure.

[0010] The present invention also provides a carrier substrate made of polycrystalline silicon carbide; at least one surface layer made of amorphous silicon carbide arranged on a front side of the carrier substrate; A porous layer disposed on the surface layer; The initial substrate is made of single crystal silicon carbide on a porous layer. Equipped with the porous layer is disposed in direct contact with the surface layer or via a bonding layer such that a bonding interface exists between the porous layer and the surface layer; or the surface layer is arranged in direct contact with the carrier substrate or via a bonding layer, such that a bonding interface exists between the carrier substrate and the surface layer, or a surface layer on the porous layer side is arranged in direct contact with another surface layer on the carrier substrate side or via a bonding layer, and a bonding interface is present between the two surfaces; Regarding intermediate structures.

[0011] Other features and advantages of the present invention will become apparent from the following detailed description of the invention, when taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] 1 shows a composite structure manufactured using a fabrication method according to the present invention. [Figure 2a] 5 illustrates steps of a manufacturing method according to the invention. [Figure 2b] 5 illustrates different steps of the manufacturing method according to the invention. [Figure 2c] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2c-1] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2d] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2d-1] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2d-2] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2e] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2f] 4 illustrates a further step of the manufacturing method according to the invention. [Figure 2g] 4 illustrates a further step of the manufacturing method according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Detailed Description of the Invention The figures are schematic diagrams that are not drawn to scale for ease of reading: in particular, the thickness of the layers along the z-axis is not to scale relative to the lateral dimensions along the x- and y-axes, and the relative thicknesses of the layers with respect to one another are not necessarily taken into account in the figures.

[0014] The present invention relates to a method for the fabrication of a composite structure 100 (FIG. 1) comprising a thin layer 1 made of monocrystalline silicon carbide (in the following c-SiC is used to refer to monocrystalline silicon carbide) arranged on a silicon carbide carrier substrate 20. The carrier substrate 20 is polycrystalline (p-SiC).

[0015] The method first comprises a step a) of providing an initial substrate 10 made of monocrystalline silicon carbide (Figure 2a). The initial substrate 10 is preferentially in the form of a wafer with a diameter of 100 mm, 150 mm, 200 mm or 300 mm and a thickness typically between 300 and 800 microns. It has a front face 10a and a rear face 10b. The surface roughness of the front face 10a is preferably chosen to be less than 1 nm Ra (average roughness), measured by atomic force microscope (AFM), for example on a scan of 20 microns x 20 microns. The initial substrate 10 may be of 4H or 6H polytype and may have n-type or p-type doping.

[0016] Step a) also includes providing a carrier substrate 20 made of polycrystalline silicon carbide having a front surface 20a and a back surface 20b (Figure 2a).

[0017] The carrier substrate 20 can be manufactured by conventional techniques such as sintering or chemical vapor deposition. It is preferentially in the same form as the initial substrate 10, typically in the form of a wafer having the typical diameter and thickness mentioned above for the initial substrate 10. The surface roughness of the front surface 20a of the carrier substrate 20 is preferably selected to be less than 1 nm Ra, at least if this surface is intended to be directly bonded in the subsequent step d) of the method.

[0018] The method then comprises a porosification step b) applied to the initial substrate 10 to form a porous layer 11 (FIG. 2b). Known porosification methods for SiC, some of which are described or referenced in the publications by Y. Shishkin et al. (“Photoelectrochemical etching of n-type 4H silicon carbide”, Journal of Applied Physics 96, 2311, 2004) and Gautier et al. (“Electrochemical formation of porous silicon carbide for micro-device applications”, Materials Science Forum, ISSN: 1662-9752, Vol. 924, pp. 943-946, 2018), can be applied to the initial substrate 10 to form the porous layer 11.

[0019] Preferably, the porous layer 11 has a thickness between 0.5 μm and 5 μm, a degree of porosity preferentially between 10% and 70% and a pore size typically between 1 nm and 50 nm.

[0020] These properties are, firstly, favorable for the crystallization (step e) of the method) of the layer 21 made of amorphous silicon carbide in monocrystalline form, intended to form the thin layer 1 of the composite structure 100, in contact with the porous layer 11; secondly, the properties of the porous layer 11 are suitable to enable and facilitate separation within this layer, in step f) of the method, while providing sufficient mechanical strength during the previous step.

[0021] The next step c) of the manufacturing method according to the invention corresponds to the formation, at least on the front surface 20a of the carrier substrate 20 or the front surface 10a of the initial substrate 10, of a surface layer 21, 12 made of amorphous silicon carbide.

[0022] According to a first embodiment, the substrate 20 is provided, at least on its front surface 20a, with said surface layer 21 made of amorphous silicon carbide (a-SiC) (FIG. 2c).

[0023] According to a second embodiment, a surface layer 12 made of amorphous silicon carbide is formed at least on the front side 10a of the initial substrate 10, ie on the porous layer 11 (FIG. 2c-1).

[0024] According to a third embodiment, a surface layer 21 is formed on the front side 20 a of the carrier substrate 20 and a further surface layer 12 is formed on the porous layer 11 , itself arranged on the initial substrate 10 .

[0025] In one or the other of the above embodiments, the front layer 21,12 can also be formed on the rear surface 20b,10b of the substrate 20,10 in question.

[0026] Regardless of the embodiment, the surface layers 21, 12 preferably have a total thickness of less than 10 μm.

[0027] To form this superficial layer 21, 12, step c) comprises, according to a first variant, depositing an a-SiC layer on the substrate 20, 10 in question. The deposition of amorphous SiC can be carried out by chemical vapor deposition (CVD) techniques, for example plasma-enhanced CVD (PECVD) or direct liquid injection CVD (DLI-CVD), by physical vapor deposition techniques or by any other known technique. For CVD deposition, deposition temperatures below 1100° C. or below 1000° C. are preferred and, with regard to the deposition precursors (methane or silane chemistry), the C / Si ratio is preferentially chosen to be greater than or equal to 1.

[0028] The deposition techniques mentioned above make it possible to form the surface layers 21, 12, the thickness of which can typically vary between 100 nm and 10 μm, for example about 1 μm. Likewise, the doping of the surface layers 21, 12 made of a-SiC can be easily adjusted when formed by one of these techniques. In particular, they may be highly doped (usually n-type, but optionally p-type) and thus be 10 19 / cm 3 More than or equal to 10 20 / cm 3It should be noted that the surface layers 21, 12 are intended to be at least partially crystallized in monocrystalline form to form the thin layer 1 of the composite structure 100, and therefore may be highly doped to give rise to a thin layer 1 having a low resistivity, depending on the requirements of the intended application.

[0029] According to a second variant, step c) comprises amorphizing a surface layer of the substrate in question in order to form a surface layer 21, 12 made of a-SiC. This amorphization can be carried out by known techniques such as ion bombardment (for example with Si or C ions) or neutron bombardment, with an appropriate energy to form an amorphous layer 21, 12 having the desired thickness.

[0030] In the case of amorphization of the surface layer of the substrate 20 (first and third embodiments), the polycrystalline structure of the carrier substrate 20 may be made amorphous, for example by ion bombardment.

[0031] According to this second variant of the formation of the surface layers 21, 12, the thickness of the surface layers is preferentially less than 1 μm, typically of the order of one hundred to several hundred nanometers.

[0032] The manufacturing method according to the invention then comprises a step d) which comprises bonding the initial substrate 10 and the carrier substrate 20 at their respective front faces 10a, 20a (FIG. 2d, FIG. 2d-1, FIG. 2d-2).

[0033] Thus, in the first embodiment (FIG. 2d), the porous layer 11 and the surface layer 21 are bonded along the bonding interface 3, resulting in a first intermediate structure 30.

[0034] In a second embodiment (FIG. 2d-1), the surface layer 12 is bonded along a bonding interface 3' to a carrier substrate 20, resulting in a first intermediate structure 30'.

[0035] Finally, in the third embodiment (FIG. 2d-2), the surface layers 22, 12 formed on the carrier substrate 20 and the porous layer 11, respectively, are bonded along a bonding interface 3″ to obtain a first intermediate structure 30″.

[0036] As specified below, regardless of the embodiment, the bonding interface 3, 3', 3'' in step d) can comprise a direct contact between the joined surfaces or an indirect contact via a bonding layer between the joined surfaces.

[0037] The bonding of step d) is based on direct bonding by molecular adhesion. As is well known per se, such bonding does not require any adhesive material since the bond is made at the atomic level between the surfaces to be bonded. There are several types of molecular adhesive bonding that differ notably in terms of temperature, pressure, atmospheric conditions or treatments before bringing the surfaces into contact. These include room temperature bonding with or without prior plasma activation of the surfaces to be bonded, atomic diffusion bonding (ADB), surface activated bonding (SAB), etc.

[0038] The bonding step d) may involve a conventional sequence of chemical cleaning (e.g., RCA cleaning) and surface activation (e.g., with oxygen or nitrogen plasma) or other surface preparation (scrubbing, etc.) prior to bringing the surfaces to be bonded into contact, which is likely to enhance the quality (low defect density, high adhesion energy) of the bonding interface 3, 3', 3''.

[0039] As mentioned above, and optionally, step d) comprises forming a bonding layer on one and / or the other of the faces to be joined of the substrates 20, 10 before bringing said faces into contact. The bonding layer may thus be deposited (for example by chemical vapor deposition CVD) on the porous layer 11 and / or on the surface layer 21 (in a first embodiment), directly on the carrier substrate 20 and / or on the surface layer 12 (in a second embodiment), or on one and / or the other of the surface layers 22, 12 (in a third embodiment).

[0040] The bonding layer may be made of at least one material selected from silicon, nickel, titanium, tungsten, etc. The bonding layer is preferentially reduced in thickness, typically having a total thickness of 10 nm or less, or 5 nm or less. In a first embodiment, it is important that the bonding layer has a small thickness that allows its segmentation in the form of nodules or its dissolution during the subsequent heat treatment of step e), which results in at least locally direct contact between the porous layer 11 and the superficial layer 21, which direct contact is essential for the correct implementation of the crystallization carried out in the next step e). If the bonding layer is made of a semiconductor material (such as silicon in particular), it can be doped to promote vertical electrical conduction.

[0041] As shown in FIG. 2d, in a first embodiment of the invention, the first intermediate structure 30 resulting from step d) is formed starting from the carrier substrate 20, thus in a reverse order to that seen in the figure: a carrier substrate 20 made of polycrystalline silicon carbide having a back surface 20b; a surface layer 21 made of amorphous silicon carbide on the front side 20a of the carrier substrate 20; a porous layer 11 arranged in direct contact with a surface layer 21 or via a bonding layer, and a bonding interface 3 is present between the porous layer 11 and the surface layer 21; an initial substrate 10 made of monocrystalline silicon carbide on and in contact with the porous layer 11; Equipped with.

[0042] FIG. 2d-1 shows a first intermediate structure 30′ resulting from step d) in the second embodiment of the present invention, the first intermediate structure 30′ comprising: a carrier substrate 20 made of polycrystalline silicon carbide; a surface layer 12 made of amorphous silicon carbide arranged on the front surface 20a of the carrier substrate 20 in direct contact therewith or via a bonding layer, the surface layer 12 having a bonding interface 3' between the carrier substrate 20 and the surface layer 12; A porous layer 11 on a surface layer 12; an initial substrate 10 made of monocrystalline silicon carbide on and in contact with the porous layer 11; Equipped with.

[0043] Finally, FIG. 2d-2 shows a first intermediate structure 30″ resulting from step d) in the third embodiment of the present invention, the first intermediate structure 30″ being a carrier substrate 20 made of polycrystalline silicon carbide; a surface layer 21 made of amorphous silicon carbide on the front side 20a of the carrier substrate 20; a further surface layer 12 made of amorphous silicon carbide, arranged in direct contact with the surface layer 21 or via a bonding layer, such that a bonding interface 3 ″ exists between the two surfaces 21, 12; A porous layer 11 on a surface layer 12; an initial substrate 10 made of monocrystalline silicon carbide on and in contact with the porous layer 11; Equipped with.

[0044] The next step e) of the fabrication method comprises a heat treatment applied to the first intermediate structure 30, 30', 30'' at a temperature above 900° C. in order to crystallize the surface layers 21, 12 (FIG. 2e). The temperature of the heat treatment is preferably above 1000° C., or above 1400° C., or even above 1850° C. By way of example, for a 1 μm surface layer 21, 12 made of a-SiC, a heat treatment at 1700° C. for 30 minutes can be applied.

[0045] The surface layers 21, 12 crystallize in the form of monocrystalline silicon carbide by the phenomenon of solid phase epitaxy starting from the direct contact interface between the porous layer 11 (this SiC has a monocrystalline structure) and the surface layers 21, 12 made of a-SiC. The surface layers crystallized in monocrystalline form form the thin layer 1.

[0046] It may also happen that only a part of the surface layers 21, 12 crystallizes in monocrystalline form. This is because the crystallization can take place at least partially in the form of polycrystalline silicon carbide starting from the contact interface with the carrier substrate 20, and then an intermediate layer 22 is formed, the p-SiC of the carrier substrate 20 extending up to the thin layer 1 made of c-SiC. In other words, the intermediate layer 22 is interposed between the carrier substrate 20 and the thin layer 1. The interface between the intermediate layer 22 and the thin layer 1 has the advantage of being completely closed, since it is defined from the same a-Si material (the surface layers 21, 12) by the contact of the c-SiC and p-SiC crystallization fronts. This is an interesting advantage compared to the bonded interface between two materials of different crystallinity (for example p-SiC / c-SiC), the complete closure of which depends in particular on the roughness and surface finish of said materials before joining.

[0047] To obtain such an intermediate layer 22, in particular when there is no surface layer 21 present on the carrier substrate 20 (i.e. in the second embodiment), preparations are made so that the surface layer 12 made of a-Si (on the porous layer 11 side) is in direct contact with the carrier substrate 20, either in the absence of a bonding layer or by use of a discontinuous bonding layer, for example a bonding layer forming a set of nodules between which the carrier substrate 20 is in direct contact with the surface layer 12.

[0048] Step e), regardless of the embodiment carried out, leads to obtaining a second intermediate structure 40 in which all or part of the surface layers 21, 12 are crystallized in monocrystalline form to form a thin layer 1 (Figure 2e).

[0049] The manufacturing method finally comprises a step f) of separation within the porous layer 11 of the second intermediate structure 40 in order to obtain, on the one hand, the composite structure 100 and, on the other hand, the remaining part 10' of the initial substrate (FIG. 2f).

[0050] The separation step f) is carried out by applying a mechanical stress to the second intermediate structure 40. The stress can be exerted by pressing and / or inserting a tool (for example a blade or other inclined shape) on the edge of said intermediate structure 40 opposite the porous layer 11. Alternatively, the mechanical stress can be applied by a water jet or an air jet directed at the edge of the structure 40 also opposite the porous layer 11. Regardless of the separation technique used, the applied mechanical stress must be suitable to propagate a breaking wave in the porous layer 11, which has a lower mechanical strength compared to the other layers or interfaces of the second intermediate structure 40.

[0051] By taking care to protect the free faces of the second intermediate structure 40, the separation can optionally be facilitated by lateral chemical etching of the porous layer 11.

[0052] At the end of the separation step f), the free face 1a of the thin layer 1 of the composite structure 100 may bear remnants of a porous layer 11r (FIG. 2f), as may the front face 10'a of the remaining part 10' of the initial substrate.

[0053] The method according to the invention can therefore include a step g) of mechanical and / or chemical treatment of the composite structure 100 in order to remove residues 11r of the porous layer 11 from the front surface 1a of the thin layer 1 and / or to correct the thickness uniformity of the composite structure 100 (Figure 2g).

[0054] Step g) may include chemical mechanical polishing (CMP) and / or chemical or plasma treatment (etching or cleaning) and / or mechanical treatment (grinding) to remove residues 11r.

[0055] Step g) can also include cleaning operations of Caro (piranha etching) and / or SC1 / SC2 (Standard Clean 1, Standard Clean 2) and / or HF (hydrofluoric acid) type, or N2, Ar or CF4 plasma, in order to further improve the quality of the free surface 1a of the thin layer 1.

[0056] Step g) may comprise a treatment applied to the composite structure 100 at a temperature between 1000° C. and 1900° C., for about one hour to several hours. This heat treatment may be carried out before or after the mechanical and / or chemical treatment described above. Its purpose is to stabilize the composite structure 100, if appropriate by significantly developing the crystalline quality of the thin layers 1, so that the structure 100 is perfectly compatible with subsequent heat treatments at very high temperatures required for the fabrication of components on and / or in said layers 1.

[0057] Finally, the fabrication method may include a step of reconditioning the remaining portion 10' of the initial substrate for reuse as the initial substrate 10 of the new composite structure 100 (FIG. 2g). A mechanical and / or chemical treatment similar to the treatment applied to the composite structure 100 to remove the residues 11r may be applied to the front side 10'a of the remaining substrate 10'. The reconditioning step may also include one or more treatments of the edges of the remaining substrate 10' and / or its back side 10'b by chemical-mechanical polishing, grinding, and / or dry or wet chemical etching.

[0058] Naturally, the invention is not limited to the described embodiments and examples, and variants may be added without departing from the scope of the invention as defined by the claims.

Claims

1. A method for fabricating a composite structure (100) comprising a thin layer (1) made of single-crystalline silicon carbide, disposed on a carrier substrate (20) made of polycrystalline silicon carbide, comprising: a) providing an initial substrate (10) made of single-crystalline silicon carbide having a front surface (10a) and a back surface (10b), and a carrier substrate (20) made of polycrystalline silicon carbide having a front surface (20a) and a back surface (20b); b) a step of applying a porous treatment to the initial substrate (10) to form a porous layer (11) at least on the front surface (10a) side of the initial substrate (10); c) forming a surface layer (21, 12) made of amorphous silicon carbide on the front surface (20a) of the carrier substrate (20) and / or on the porous layer (11); d) joining the initial substrate (10) and the carrier substrate (20) at their respective front surfaces to produce a first intermediate structure (30, 30', 30''); e) a heat treatment step applied to the first intermediate structure (30, 30', 30'') at a temperature exceeding 900 °C to crystallize at least a portion of the surface layer (21, 12) in the form of single-crystalline silicon carbide, starting from the contact interface with the porous layer (11), to form the thin layer (1) and produce a second intermediate structure (40); f) separating the composite structure (100) on one hand and the remaining portion (10') of the initial substrate on the other hand within the porous layer (11) of the second intermediate structure (40). A method comprising the above steps.

2. The method for fabrication according to claim 1, wherein at the end of step b), the porous layer (11) has a thickness of 0.5 µm to 5 µm.

3. The method for fabrication according to claim 1 or 2, wherein at the end of step b), the porous layer (11) contains pores, the size of the pores is 1 nm to 50 nm, and the porosity is 10% to 70%.

4. The method for fabrication according to claim 1 or 2, wherein at the end of step c), the surface layer (21, 12) has a thickness of 10 µm or less.

5. The method for fabrication according to claim 1 or 2, wherein at the end of step c), the surface layer (21, 12) has a thickness of 1 µm or less, typically on the order of hundreds to several hundred nanometers.

6. The method according to claim 1 or 2, wherein step c) includes depositing an amorphous silicon carbide layer on at least the front surface (20a) side of the carrier substrate (20) and / or at least on the porous layer (11) in order to form the surface layer (21, 12).

7. The deposited amorphous silicon carbide layer is highly doped and has a dopant species concentration exceeding 10 １９ / cm ３ or exceeding 10 ２０ / cm ３ A method for fabrication according to claim 6, having a dopant species concentration of

8. The method according to claim 1 or 2, wherein step c) includes amorphizing at least the surface layer on the front surface (20a) side of the carrier substrate (20) in order to form the surface layer (21).

9. Step d) includes forming a bonding layer on the front surface side of one and / or the other of the substrates before the step of bonding the initial substrate (10) and the carrier substrate (20), The method according to claim 1 or 2, wherein the bonding layer has a total thickness of 10 nm or less after bonding.

10. The method according to claim 9, wherein the bonding layer is composed of at least one material selected from silicon, nickel, titanium, and tungsten.

11. During step e), at least locally, by segmenting or dissolving the bonding layer into nodules, direct contact between the surface layer (21) and the porous layer (11) or between the surface layer (12) and the carrier substrate (20) is enabled. The method according to claim 9 for manufacturing.

12. The method according to claim 1 or 2, wherein the heat treatment in step e) is performed at a temperature of 1000 °C or higher, preferably 1400 °C or higher, or 1850 °C or higher.

13. In step e), the crystallization of the surface layer (21, 12) starts from the contact interface with the carrier substrate (20) in order to form an intermediate layer (22) and occurs at least partially in the form of polycrystalline silicon carbide. The method according to claim 1 or 2 for manufacturing.

14. After step f), a finishing step g) including mechanical and / or chemical treatment of the composite structure (100) is included in order to remove the residue (11r) of the porous layer (11) from the front surface (1a) of the thin layer (1) and / or to correct the thickness uniformity of the composite structure (100). The method according to claim 1 or 2 for manufacturing.

15. The method according to claim 14, wherein step g) comprises a heat treatment applied to the composite structure (100) at a temperature of 1000°C to 1900°C before and / or after the mechanical and / or chemical treatment.

16. The method according to claim 1 or 2, comprising the step of readjusting the remaining portion (10') of the initial substrate for reuse as an initial substrate (10) for manufacturing a new composite structure (100).

17. A carrier substrate (20) made of polycrystalline silicon carbide, At least one surface layer (21, 12) made of amorphous silicon carbide, disposed on the front surface (20a) side of the carrier substrate (20), A porous layer (11) disposed on the surface layer (21, 12), And an initial substrate (10) made of single crystal silicon carbide on the porous layer (11). Comprising The porous layer (11) is in direct contact with the surface layer (21) or is disposed via a bonding layer, and a bonding interface (3) exists between the porous layer (11) and the surface layer (21), or The surface layer (12) is in direct contact with the carrier substrate (20) or is disposed via a bonding layer, and a bonding interface (3') exists between the carrier substrate (20) and the surface layer (12), or The surface layer (12) on the porous layer (11) side is in direct contact with another surface layer (21) on the carrier substrate (20) side or is disposed via a bonding layer, and a bonding interface (3'') exists between the two surface layers (21, 12). An intermediate structure (30, 30').

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