Method for manufacturing a sheet-like donor substrate involving additive manufacturing technology

Abstract

The invention relates to a method for manufacturing a patch donor substrate, comprising the following steps: a) providing an initial structure comprising a carrier substrate having a front face and a back face and a plurality of patches made of a first monocrystalline material, wherein the patches are arranged on the front face and are spaced apart from each other; b) forming a complementary layer by means of an additive manufacturing technique, wherein the complementary layer: - is arranged between the patches, in contact with the front face of the carrier substrate; - is composed of a material called second material, which has a thermal expansion coefficient matching that of the first material; c) applying a mechanical and / or chemical-mechanical surface treatment to the complementary layer and the patches, to obtain the patch donor substrate, wherein the front face of the substrate has a flat and continuous surface at which the plurality of patches and the complementary layer are flush.

Description

Technical Field

[0001] This invention relates to the fields of microelectronics and semiconductors. In particular, the invention relates to a method for manufacturing a donor substrate having a working layer in the form of a pavé, the surface layer of which is intended to be transferred onto a receiving substrate. The method according to the invention relates to additive manufacturing technology. Background Technology

[0002] In the fields of microelectronics, optics, or optoelectronics, it can be advantageous to transfer thin layers (less than 1.5 μm) in discrete sheet form (e.g., made of group III-V materials) onto large-size receiving substrates (e.g., made of silicon). Thus, specific components can be produced (on the sheet-like thin layers), and these components can be co-integrated with silicon components, while benefiting from the device and substrate sizes common in the microelectronics industry.

[0003] Smart Cut TM The process (a well-known technique for transferring thin layers) can, in particular, create a composite structure comprising sheet-like thin layers on a receiving substrate, starting from a donor substrate having a working layer in sheet form. Recall that the smart lift-off process is based on forming a buried weakening surface in the sheet-like working layer of the donor substrate by injecting optical seeds: this buried weakening surface, together with the free surface of the sheet-like working layer, defines the sheet-like surface layer to be transferred. The process then involves assembly between the sheet-like working layer and the receiving substrate. Finally, separation occurs along the buried weakening surface to transfer the sheet-like surface layer onto the receiving substrate; the remaining portion of the donor substrate can be recycled, reprocessed, and used to transfer new sheet-like surface layers.

[0004] Therefore, in this case, the donor substrate has a carrier substrate on which discrete pieces are disposed, distributed on the surface of the carrier substrate according to the requirements of the target application of the final composite structure.

[0005] The fabrication of such donor substrates (also known as pseudo-donor substrates) typically involves assembling sheets of the working layer onto a carrier substrate via direct bonding or adhesive bonding. Each sheet typically has a thickness between tens and hundreds of micrometers and is endowed with a thickness of 1 mm. 2 Up to 400 mm 2 The lateral dimensions of the surface area between them. Considering their thickness, these pieces can be processed and assembled onto a carrier substrate using a "pick and place" technique.

[0006] Because the donor substrate sheets may have uneven thicknesses relative to each other, and excellent surface flatness is required for high-quality assembly and subsequent sheet-like thin-layer transfer, the steps for preparing the surface of the sheet-like working layer are particularly critical. Given the discontinuity of this layer, mechanical or chemical mechanical thinning steps tend to alter, collapse, or damage the edges of the sheets, which inevitably reduces the quality of subsequent assembly.

[0007] The subject of this invention

[0008] This invention addresses this problem and proposes a method for manufacturing a donor substrate comprising a sheet-like working layer, particularly suitable for assembly onto a receiving substrate to achieve the transfer of sheet-like surface thin layers. The method according to the invention implements additive manufacturing steps to form layers complementary to the sheet-like working layer on the donor substrate and ensures material continuity between the sheets, thereby allowing for high-quality surface preparation. Summary of the Invention

[0009] This invention relates to a method for manufacturing a sheet-type donor substrate, the method comprising the following steps: a) Providing an initial structure comprising a carrier substrate having a front side and a back side, and a plurality of sheets made of a first single-crystal material, the plurality of sheets being disposed on the front side and spaced apart from each other. b) A supplementary layer is formed via additive manufacturing technology, wherein the supplementary layer: - Displaced between the pieces, in contact with the front side of the carrier substrate. - It is composed of a material referred to as the second material, which has a coefficient of thermal expansion that matches that of the first material. c) Apply mechanical and / or chemimechanical surface treatments to the supplementary layer and the pieces to obtain the piece-type donor substrate, the front side of which has a flat and continuous surface, on which the plurality of pieces and the supplementary layer are flush.

[0010] Advantageous features according to the invention, either alone or in any feasible combination: In step b), the supplementary layer is also formed on all or part of the sheet; The thickness of the supplementary layer is greater than or equal to the average thickness of the sheet; The additive manufacturing technology implemented in step b) is based on: - The powder of the second material is at least partially melted in a nozzle heated by a laser beam or electron beam. - Move the nozzle to deposit the molten powder between the sheets on the carrier substrate, and optionally deposit it on all or part of the sheets until the supplementary layer is formed; Step b) is based on: - A sub-step of additively manufacturing a template on a plate, the template having the same surface area as the carrier substrate and having a local opening at the location of the sheet of the initial structure. - An assembly sub-step between the template and the initial structure, where the template forms a supplementary layer; The carrier substrate is made of silicon; The first single-crystal material forming the sheet is selected from semiconductor materials, piezoelectric materials, and electrically insulating materials; The first single-crystal material forming the sheet is indium phosphide; The plates of the initial structure are spaced apart by a distance between 100 μm and 10 mm, or even 10 cm. The second material has the same properties as the first material; The second material is a composite material and includes an adhesive, the proportion of which is less than 30%.

[0011] The present invention also relates to the use of a sheet-type donor substrate obtained by the above manufacturing method for transferring the surface layer of each sheet onto a receiving substrate.

[0012] Advantageously, this application implements a thin-layer transfer technique, which involves the following steps: - Embedded weakening surfaces are formed in the sheet and the supplementary layer, the embedded weakening surfaces being substantially parallel to the front side of the sheet-type donor substrate. - Assemble the front side of the sheet-type donor substrate onto the receiving substrate. - Separate along the embedded weakened surface to form a composite structure comprising a receiving substrate and at least one thin layer derived from the respective pieces transferred onto the receiving substrate.

[0013] Preferably, after separation, the remaining portion of the sheet-like donor substrate is adjusted and then reused to transfer new thin layers onto a new receiving substrate. Attached Figure Description

[0014] Referring to the accompanying drawings, other features and advantages of the invention will become apparent from the following detailed description, wherein: [ Figure 1a ] [ Figure 1b ] Figure 1a and Figure 1b A sheet-type donor substrate obtained via the manufacturing method according to the invention is shown; [ Figure 2a ] [ Figure 2b ] Figure 2a and Figure 2b The initial structure provided in step a) of the manufacturing method according to the present invention is shown; [ Figure 3a ] [ Figure 3b ] Figure 3a and Figure 3b An example of an intermediate donor substrate obtained at the end of step b) of the manufacturing method according to the invention is shown; [ Figure 4 ] Figure 4 A first embodiment of step b) of the method according to the present invention is shown; [ Figure 5a ] [ Figure 5b ] [ Figure 5c ] [ Figure 5d ] Figure 5a , Figure 5b , Figure 5c and Figure 5d A sub-step of step b) of the manufacturing method according to the present invention is shown; [ Figure 6a ] [ Figure 6b ] [ Figure 6c ] [ Figure 6d ] Figure 6a , Figure 6b , Figure 6c and Figure 6d Step c) of the manufacturing method according to the present invention is shown. [ Figure 7a ] [ Figure 7b ] [ Figure 7c ] [ Figure 7d ] Figure 7a , Figure 7b , Figure 7c and Figure 7dThe steps for using a sheet-type donor substrate obtained by the manufacturing method according to the present invention are shown.

[0015] The accompanying drawings are schematic and not drawn to scale for clarity. In particular, the layer thickness along the z-axis is not drawn to scale relative to the lateral dimensions along the x and y axes.

[0016] In the accompanying drawings or description, the same reference numerals may be used for elements of the same nature. Detailed Implementation

[0017] This invention relates to a method for manufacturing such as Figure 1a and Figure 1b The method of the sheet-type donor substrate 100 illustrated herein.

[0018] The manufacturing method includes a first step a) of providing an initial structure 10, which includes a carrier substrate 1 and a plurality of sheets 2. Figure 2a and Figure 2b The carrier substrate 1 has a front side 1a and a back side 1b, and is preferably in the form of a wafer with a diameter of 200 mm, 300 mm or even larger. Its thickness is typically between 100 µm and 900 µm. Advantageously, the carrier substrate 1 is made of silicon or another semiconductor material that can be obtained in the form of large-diameter wafers.

[0019] The sheets 2 are formed of the first single-crystal material and are disposed on the front side 1a and spaced apart from each other. Typically, the sheets 2 are spaced apart by a distance between 100 µm and 10 mm, or even up to 10 cm. The thickness of each sheet can be greater than or equal to 100 µm, for example, between 300 µm and 600 µm, and the size is 1 mm. 2 Up to 20x20 mm 2 between.

[0020] The first material is advantageously selected from: - Semiconductor materials (e.g., III-V compounds, especially indium nitride (InN), gallium nitride (GaN), aluminum nitride (AlN), indium arsenide (InAs), gallium arsenide (GaAs), aluminum arsenide (AlAs), indium phosphide (InP), gallium phosphide (GaP) or aluminum phosphide (AlP), or for example, group IV or group IV-IV materials, especially germanium or silicon carbide (SiC)). - Piezoelectric materials (e.g., lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium sodium niobate (K... x Na 1-xNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), lead magnesium niobate and lead titanate complex (PMN-PT), zinc oxide (ZnO), aluminum nitride (AlN) or scandium aluminum nitride (AlScN)), and - Electrically insulating materials (e.g., diamond, strontium titanate, yttrium-stabilized zirconium oxide, or sapphire).

[0021] The initial structure 10 can be manufactured using any technique known to those skilled in the art. Typically, the sheet 2 originates from an initial substrate made of a first material, which has been cut by sawing, laser cutting, or the like. At the scale of the initial substrate, the thickness (TTV) can vary by several micrometers. Therefore, the sheets 2 can have these same thickness variations relative to each other.

[0022] The wafers 2 are then assembled onto the carrier substrate 1. A pick-and-place device, widely used for handling dies or chips, can be used to place them onto the carrier substrate 1. Assembly is preferably based on direct bonding via molecular adhesion, without the need for an intermediate adhesive layer. Surface treatment (cleaning, plasma activation, etc.) prior to assembly is recommended to obtain a high-quality bonding interface and provide significant mechanical strength.

[0023] Next, the manufacturing method includes step b), which corresponds to forming a supplementary layer 20 on one side of the front surface 1a of the initial structure 10 via additive manufacturing technology. Figure 3a , Figure 3b The supplementary layer 20 is disposed at least between the sheets 2 and contacts the front side 1a of the carrier substrate 1. It may also be formed on all or part of the sheets 2.

[0024] The supplementary layer 20 is made of a material referred to as the second material, which has a coefficient of thermal expansion that matches that of the first material. "Matching" is understood to mean that the difference between the coefficient of thermal expansion of the second material and the coefficient of thermal expansion of the first material is less than or equal to + / - 10%.

[0025] At the end of step b), an intermediate donor substrate 100' is obtained.

[0026] Advantageously, the first material and the second material have the same properties; as an example, for the first material made of monocrystalline InP, the second material can be made of polycrystalline or amorphous InP.

[0027] Advantageously, the carrier substrate 1 can also be selected to have a coefficient of thermal expansion close to that of the sheet material. For example, the carrier substrate 1 can also be formed by the same additive manufacturing technique and with the same material (second material) as the supplementary layer 20.

[0028] According to a variant, the second material is a composite material and includes an adhesive and a material with a coefficient of thermal expansion close to that of the first material. The proportion of the adhesive is less than 30%, less than 20%, or even less than 10%, such that the coefficient of thermal expansion of the composite second material differs as little as possible from that of the first material.

[0029] Preferably, the supplementary layer 20 also has a thickness greater than or equal to the average thickness of the sheet 2, so as to make it possible to limit the discontinuity of the material between the sheet 2 and the supplementary layer 20 as much as possible during the subsequent step c) of the method.

[0030] According to the first embodiment, the additive manufacturing technology implemented in step b) is based on: at least partially melting powder of a second material in a nozzle B heated by a laser beam or electron beam. Figure 4 Moving the nozzle B allows molten powder 20' to be deposited between the sheets 2 on the carrier substrate 1, and optionally on all or part of the sheets 2, until a supplementary layer 20 is formed. To achieve the desired thickness of the supplementary layer 20, multiple passes of the nozzle B at the same location may be required.

[0031] In particular, CLAD ("direct additive laser construction") type technology can be implemented.

[0032] As an example, if the second material constituting the powder is InP, the localized temperature between 650°C and 800°C generated by a laser beam or electron beam allows the powder grains to melt at least at the surface and thus agglomerate upon cooling into the form of supplementary layer 20. The temperature sensed by the initial structure 10 is much lower than this temperature, typically less than or equal to 100°C: this prevents any degradation of adjacent sheets 2, whose first material is, for example, single-crystal InP.

[0033] According to another example, the second material is a composite material and includes InP and a binder (a polymer compatible with the operating temperature): the localized temperature generated by a laser or electron beam (typically between 100°C and 800°C) allows the binder to melt, ensuring that the powder agglomerates in the form of supplementary layer 20. Similarly, the temperature perceived by the initial structure 10 remains low (typically less than 100°C), and this prevents its degradation. It should be noted that the use of the binder, even if its proportion is limited to 30%, 20%, or even 10%, involves shrinkage of supplementary layer 20, which should be taken into account when defining the initial deposition thickness of the supplementary layer.

[0034] Regardless of the specific example of this first embodiment, it is important to ensure that the supplementary layer 20 adheres well to the front side 1a of the carrier substrate 1. The presence of an adhesive in the second material facilitates this adhesion. Alternatively, an initial structure 10 comprising a surface layer on the carrier substrate 1 may be selected, wherein the properties of the surface layer are conducive to the adhesion of the supplementary layer 20.

[0035] Furthermore, texturing of the front side 1a may be advantageous in order to promote adhesion between the supplementary layer 20 and the carrier substrate 1; this could be, for example, a roughness level of the front side 1a greater than 1 nm RMS (measured by atomic force microscopy over a scanning area of ​​20 × 20 µm²).

[0036] According to the second embodiment, step b) includes a first sub-step of additively manufacturing template 20” on the plate. DMLS (“Direct Metal Laser Sintering”) type 3D printing technology can be specifically implemented.

[0037] Template 20'' has the same surface area as the carrier substrate 1, and has a local opening 3 at the location of the sheet 2 of the initial structure 10. Figure 5a , Figure 5b Next, step b) includes a second sub-step of assembling the template 20'' with the initial structure 10. Figure 5c Then template 20'' forms supplementary layer 20 ( Figure 5d ).

[0038] To achieve high-quality assemblies, especially when assemblies are envisioned to be performed via molecular adhesion (typically, deformation is expected to be less than 100 μm and the maximum variation in flatness is a few micrometers), good flatness of the template 20'' is important. It should be noted that any known type of assembly can be performed provided that the mechanical and thermal strength of the bonding is compatible with the rest of the method and the intended use of the sheet-like donor substrate 100.

[0039] Finally, the method includes step c), which corresponds to applying mechanical surface treatment (e.g., grinding) and / or chemical mechanical surface treatment (e.g., polishing) to the supplementary layer 20 and the sheet 2. Figure 6a , Figure 6b , Figure 6c ).

[0040] Regardless of whether the thickness of the supplementary layer 20 is less than, substantially equal to, or greater than the average thickness of the cladding 2, step c) aims to planarize the front side 100'a of the intermediate donor substrate 100' to obtain a cladding donor substrate 100 with a flat and continuous surface on its front side 100a, where the plurality of cladding 2 and the supplementary layer 20 are flush. Figure 6dFlat and continuous is understood to mean a surface without undulations (i.e., typically having undulations of less than 5 nm, less than 1 nm, or even less than 0.5 nm, especially at the junction between sheet 2 and supplementary layer 20). After planarization, supplementary layer 20 may optionally have a thickness substantially less than that of sheet 2 so as not to impede the complete transfer of the sheet-like surface layer derived from sheet 2.

[0041] The material removal performed in step c) can vary depending on the configuration of the intermediate donor substrate 100' and the thickness of the supplementary layer 20. The removed material is typically between 1 μm and 200 μm, preferably between 20 μm and 60 μm.

[0042] As described above, the sheets 2 may have thickness variations relative to each other, which are associated with the TTV of the initial substrate from which they originate. Step c) can correct these thickness variations and obtain a flat surface compatible with thin-layer transfer. Furthermore, the presence of the supplementary layer 20 makes planarization easier because it ensures the continuity of the processed surface 100'a and thus prevents the phenomenon of sheet edge collapse ("corner rounding") during chemical mechanical processing.

[0043] Finally, since the supplementary layer 20 is preferably made of a material with the same properties as the first material of the sheet 2, surface treatment becomes easier and the polishing problem of two materials (especially those with different wear rates) is not encountered.

[0044] According to the present invention, the sheet-type donor substrate 100 can be used to transfer the surface layer of each sheet 2 onto a receiving substrate 50. Preferably, a thin-layer transfer technique involving the following steps is implemented. First, a buried weakening surface 4, substantially parallel to the front side 100a of the sheet-type donor substrate 100, is formed in the sheet 2 and the supplementary layer 20. Figure 7a For this purpose, implantation of light seeds such as hydrogen, helium, or a combination of both can be performed. The next step involves assembling the front side 100a of the sheet-like donor substrate 100 onto the receiver substrate 50. Figure 7b Preferably, the assembly is based on bonding via molecular adhesion, eliminating the need for an adhesive layer. As is well known per se, cleaning and other surface activation can be performed to improve the quality and mechanical strength of the bonding interface 5. Finally, separation occurs along the embedded weakening surface 4 to form a composite structure comprising a receiving substrate 50 and at least one thin layer 2i, which originates from the individual pieces 2 and is transferred onto the receiving substrate 50. Figure 7c Depending on the properties of the second material of the supplementary layer 20, a supplementary thin layer 20i derived from the supplementary layer 20 can also be transferred onto the receiving substrate 50. In this case, subsequent steps include locally etching the supplementary thin layer 20i to leave only the sheet-like thin layer 2i on the receiving substrate 50. Figure 7d ).

[0045] Before or after removing the supplementary thin layer 20i (if present), multiple polishing and cleaning processes can be applied to restore the good surface finish of the sheet-like thin layer 2i.

[0046] After the separation step, the remaining portion 100i of the sheet-type donor substrate 100 can be treated (mechanical grinding and / or chemical mechanical polishing and cleaning) and then reused to transfer new thin layers onto new receiving substrates.

[0047] Of course, the present invention is not limited to the described embodiments, and modified embodiments may be added thereto without departing from the scope of the present invention.

Claims

1. A method for manufacturing a sheet-type donor substrate (100), the method comprising the following steps: a) Providing an initial structure (10) comprising a carrier substrate (1) having a front side (1a) and a back side (1b) and a plurality of sheets (2) made of a first single crystal material, the plurality of sheets (2) being disposed on the front side (1a) and spaced apart from each other. b) A supplementary layer (20) is formed via additive manufacturing technology, wherein the supplementary layer (20) is: - Displaced between the pieces (2), in contact with the front side (1a) of the carrier substrate (1), - It is composed of a material referred to as the second material, which has a coefficient of thermal expansion that matches that of the first material. c) Apply mechanical and / or chemimechanical surface treatments to the supplementary layer (20) and the pieces (2) to obtain the piece-type donor substrate (100), the front side (100a) of the piece-type donor substrate (100) having a flat and continuous surface, at which the plurality of pieces (2) and the supplementary layer (20) are flush.

2. The manufacturing method according to claim 1, wherein, In step b), the supplementary layer (20) is also formed on all or part of the piece (2).

3. The manufacturing method according to any one of the preceding claims, wherein, The thickness of the supplementary layer (20) is greater than or equal to the average thickness of the piece (2).

4. The manufacturing method according to any one of the preceding claims, wherein, The additive manufacturing technology implemented in step b) is based on: - In a nozzle (B) heated by a laser beam or electron beam, at least partially melt the powder of the second material. - Move the nozzle (B) to deposit the molten powder (20') between the pieces (2) on the carrier substrate, and optionally deposit it on all or part of the pieces (2) until the supplementary layer (20) is formed.

5. The manufacturing method according to any one of claims 1 to 3, wherein, Step b) is based on: - A sub-step of additively manufacturing a template (20'') on a board, the template (20'') having the same surface area as the carrier substrate (1) and having a partial opening at the location of the piece (2) of the initial structure (10). - An assembly sub-step between the template (20'') and the initial structure (10), wherein the template (20'') forms the supplementary layer (20).

6. The manufacturing method according to any one of the preceding claims, wherein, The carrier substrate (1) is made of silicon.

7. The manufacturing method according to any one of the preceding claims, wherein, The first single crystal material forming the sheet (2) is selected from semiconductor materials, piezoelectric materials and electrically insulating materials.

8. The manufacturing method according to any one of the preceding claims, wherein, The first single crystal material forming the sheet (2) is indium phosphide (InP).

9. The manufacturing method according to any one of the preceding claims, wherein, The pieces (2) of the initial structure (10) are spaced apart by a distance between 100 μm and 10 mm, or even 10 cm.

10. The manufacturing method according to any one of the preceding claims, wherein, The second material has the same properties as the first material.

11. The manufacturing method according to any one of the preceding claims, wherein, The second material is a composite material and includes an adhesive, the proportion of which is less than 30%.

12. Use of a sheet-type donor substrate (100) obtained by the manufacturing method according to claims 1 to 11 for transferring the surface layer of each sheet (2) onto a receiving substrate (50).

13. Use of the sheet-type donor substrate (100) according to claim 12, wherein the use implements a thin-layer transfer technique, the thin-layer transfer technique involving the following steps: - An embedded weakening surface (4) is formed in the sheet (2) and the supplementary layer (20), the embedded weakening surface (4) being substantially parallel to the front side (100a) of the sheet-type donor substrate (100). - The front side (100a) of the sheet-type donor substrate (100) is assembled onto the receiving substrate (50). - Separate along the embedded weakened surface (4) to form a composite structure comprising the receiving substrate (50) and at least one thin layer (2i) derived from the respective pieces (2) transferred onto the receiving substrate (50).

14. Use of the sheet-type donor substrate (100) according to claim 13, wherein, After separation, the remaining portion (100i) of the sheet-like donor substrate (100) is adjusted and then reused to transfer new thin layers onto a new receiving substrate.

Images