Method for manufacturing a tiled donor substrate, involving an additive manufacturing technique
Patent Information
- Application Number
- PCT/EP2025/053139
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-08
- Filing Date
- 2025-02-06
- Publication Date
- 2025-10-02
AI Technical Summary
The existing methods for manufacturing donor substrates with tiled thin layers face challenges in achieving uniform thickness and surface flatness, leading to degraded assembly quality due to mechanical or chemical-mechanical thinning steps that damage the edges of the pavers.
An additive manufacturing technique is employed to form a complementary layer between the pavers on the donor substrate, using a material with matched thermal expansion properties, followed by mechanical and/or mechano-chemical surface treatment to ensure a flat and continuous surface, thereby maintaining the integrity of the pavers.
The method ensures high-quality assembly and transfer of thin layers by maintaining uniformity and continuity between pavers, reducing edge damage and enhancing the overall assembly process.
Smart Images
Figure EP2025053139_02102025_PF_FP_ABST
Abstract
Description
Method of manufacturing a paved donor substrate, involving an additive manufacturing technique FIELD OF THE INVENTION
[0001] The present invention relates to the field of microelectronics and semiconductors. In particular, the invention relates to a method for manufacturing a donor substrate comprising a useful layer in the form of tiles, a surface layer of said tiles being intended to be transferred onto a receiving substrate. The method according to the invention involves an additive manufacturing technique. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0002] In the field of microelectronics, optics or optoelectronics, it may be interesting to transfer thin layers (less than 1.5µm), in the form of disjointed tiles (for example in III-V material), onto a large-sized receiving substrate (for example in silicon). Specific components (on the tiled thin layers) can thus be developed, and potentially co-integrated with silicon components, while benefiting from the equipment and substrate sizes of the conventional microelectronics industry.
[0003] The Smart Cut process TM, a well-known thin-film transfer technique, can notably produce a composite structure comprising thin layers paved on a receiving substrate, starting from a donor substrate which includes a useful layer in the form of paving stones. As a reminder, the Smart Cut process is based on the formation of a buried fragile plane in the useful paved layer of the donor substrate, by implantation of light species: this buried fragile plane defines, with the free surface of the useful paved layer, the paved surface layer which will be transferred. This process then involves an assembly between the useful paved layer and the receiving substrate. Finally, a separation takes place along the buried fragile plane to transfer the paved surface layer onto the receiving substrate; the remainder of the donor substrate can be recovered, conditioned and used for the transfer of a new paved surface layer.
[0004] The donor substrate, in such a case, therefore comprises a support substrate on which are arranged disjointed blocks, distributed over the surface of said support substrate according to the needs of the intended application for the final composite structure.
[0005] The manufacture of such a donor substrate (also called pseudo donor) is usually based on the assembly of the tiles of the useful layer on the support substrate by direct bonding or adhesive. Each tile typically has a thickness of between a few tens of micrometers and a few hundred micrometers, and lateral dimensions giving it a surface area of between 1mm 2 and 400mm 2 Given their thickness, these paving stones can be handled using “pick and place” techniques and assembled on the supporting substrate.
[0006] Since the pavers of the donor substrate may have non-uniform thicknesses between them and excellent surface flatness is required to obtain a high-quality assembly and transfer of the thin paved layer, the surface preparation step of the useful paved layer is particularly critical. Given the discontinuity of this layer, the mechanical or chemical-mechanical thinning steps tend to modify, collapse or damage the edges of the pavers, which inevitably degrades the quality of the subsequent assembly. SUBJECT OF THE INVENTION
[0007] The present invention addresses this problem and proposes a method for manufacturing a donor substrate comprising a useful paved layer particularly suitable for assembly on a receiving substrate for the purpose of transferring a thin paved surface layer. The method according to the invention implements an additive manufacturing step to form a layer complementary to the useful paved layer on the donor substrate, and to ensure continuity of material between the pavers, thus allowing quality surface preparation. BRIEF DESCRIPTION OF THE INVENTION
[0008] The present invention relates to a method of manufacturing a tiled donor substrate comprising the following steps:
[0009] a) providing an initial structure comprising a support substrate having a front face and a rear face, and a plurality of blocks made of a first, monocrystalline material, arranged on the front face and spaced apart from each other,
[0010] b) the formation of an additional layer by an additive manufacturing technique, the additional layer:
[0011] - being arranged between the paving stones, in contact with the front face of the supporting substrate,
[0012] - being composed of a material, called the second material, having a coefficient of thermal expansion matching that of the first material,
[0013] c) applying a mechanical and / or mechano-chemical surface treatment to the additional layer and to the paving stones, to obtain the paving donor substrate, a front face of which has a flat and continuous surface, at the level of which the plurality of paving stones and the additional layer are flush.
[0014] According to advantageous characteristics of the invention, taken alone or in any feasible combination: in step b), the additional layer is also formed on all or part of the blocks; the additional layer has a thickness greater than or equal to an average thickness of the blocks; the additive manufacturing technique implemented in step b) is based on: - the at least partial melting of a powder of the second material, in a nozzle heated by a laser beam or an electron beam, - the movement of the nozzle to deposit the melted powder on the support substrate, between the blocks, and optionally on all or part of the blocks, until the additional layer is formed;step b) is based on:- a sub-step of additive manufacturing of a stencil on a plate, the stencil having a surface identical to that of the support substrate and comprising openings located at the locations of the blocks of the initial structure,- a sub-step of assembly between the stencil and the initial structure, the stencil forming the complementary layer;the support substrate is made of silicon;the first monocrystalline material forming the blocks is chosen from semiconductor materials, piezoelectric materials and electrical insulating materials;the first monocrystalline material forming the blocks is indium phosphide;the blocks of the initial structure are spaced apart by a distance of between 100µm and 10mm, or even 10cm;the second material is of the same nature as the first material;the second material is composite and comprises a binder, the proportion of binder being less than 30%.;
[0015] The invention also relates to a use of a paved donor substrate resulting from a aforementioned manufacturing method, for transferring a surface layer of each pavement onto a receiving substrate.
[0016] Advantageously, this use implements a thin layer transfer technique involving the following steps: - the formation of a buried fragile plane, substantially parallel to a front face of the paved donor substrate, in the pavers and in the complementary layer,
[0017] - assembly of the front face of the donor substrate paved on the recipient substrate,
[0018] - separation along the buried fragile plane, to form a composite structure comprising the receiving substrate and at least one thin layer from each paving stone transferred onto said receiving substrate.
[0019] Preferably, after separation, a remainder of the paved donor substrate is conditioned and then reused for a new thin layer transfer onto a new receiving substrate.
[0020] Other characteristics and advantages of the invention will emerge from the detailed description which follows with reference to the appended figures in which:
[0021]
[0022] Figures 1a and 1b show a paved donor substrate obtained by a manufacturing method according to the present invention;
[0023]
[0024] Figures 2a and 2b show an initial structure provided in step a) of a manufacturing method according to the invention;
[0025]
[0026] Figures 3a and 3b show examples of intermediate donor substrate obtained at the end of step b) of a manufacturing method in accordance with the invention;
[0027] This presents a first embodiment of step b) of a method in accordance with the invention;
[0028]
[0029]
[0030]
[0031] Figures 5a, 5b, 5c and 5d show sub-steps of a second embodiment of step b) of a manufacturing method according to the present invention;
[0032]
[0033]
[0034]
[0035] Figures 6a, 6b, 6c and 6d show step c) of a manufacturing method according to the invention;
[0036]
[0037]
[0038]
[0039] Figures 7a, 7b, 7c and 7d show steps in the use of a paved donor substrate resulting from a manufacturing process, in accordance with the invention.
[0040] The figures are schematic representations which, for readability purposes, are not to scale. In particular, the layer thicknesses along the z axis are not to scale with the lateral dimensions along the x and y axes.
[0041] The same references in the figures or in the description may be used for elements of the same nature. DETAILED DESCRIPTION OF THE INVENTION
[0042] The invention relates to a method of manufacturing a tile donor substrate 100 as illustrated in Figures 1a and 1b.
[0043] The manufacturing method comprises a first step a) of providing an initial structure 10 comprising a support substrate 1 and a plurality of blocks 2 (figures 2a and 2b). The support substrate 1 has a front face 1a and a rear face 1b and it is preferably in the form of a wafer with a diameter of 200mm, 300mm or even more. Its thickness is typically between 100μm and 900μm. Advantageously, the support substrate 1 is made of silicon, or other semiconductor material available in the form of a large diameter wafer.
[0044] The blocks 2 are formed from a first, monocrystalline material, arranged on the front face 1a and spaced apart from each other. Typically, the blocks 2 are spaced apart by a distance of between 100µm and 10mm, or even up to 10cm. Each block may have a thickness greater than or equal to 100µm, for example between 300µm and 600µm, and dimensions of between 1mm 2 up to 20x20mm2 .
[0045] The first material is advantageously chosen from:
[0046] - semiconductor materials (such as a III-V compound, in particular indium nitride (InN), gallium nitride (GaN), aluminium nitride (AlN), indium arsenide (InAs), gallium arsenide (GaAs), aluminium arsenide (AlAs), indium phosphide (InP), gallium phosphide (GaP) or aluminium phosphide (AlP), or such as a IV or IV-IV material, in particular germanium or silicon carbide (SiC)),
[0047] - piezoelectric materials (such as lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium-sodium niobate (K x N / A 1-xNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), a compound of lead-magnesium niobate and lead titanate (PMN-PT), zinc oxide (ZnO), aluminum nitride (AlN) or aluminum scandium nitride (AlScN)), and
[0048] - electrical insulating materials (such as diamond, strontium titanate, yttria zirconia or sapphire).
[0049] This initial structure 10 can be produced by any technique known to those skilled in the art. In general, the blocks 2 are produced from an initial substrate consisting of the first material, which has been cut by sawing, laser cutting or other means. The thickness variation (TTV), on the scale of the initial substrate, can be several micrometers. The blocks 2 may therefore have these same thickness variations between them.
[0050] The tiles 2 are then assembled on the support substrate 1. Their placement on said support substrate 1 can be carried out by “pick and place” equipment, widely used for handling stickers or chips. The assembly is preferably based on direct bonding by molecular adhesion, not requiring the addition of intermediate adhesive layers. Surface treatments (cleaning, plasma activation, etc.) prior to assembly are recommended to obtain a good quality bonding interface and providing significant mechanical strength.
[0051] The manufacturing method then comprises a step b) corresponding to the formation of an additional layer 20, on the side of the front face 1a of the initial structure 10, by an additive manufacturing technique (figures 3a, 3b). The additional layer 20 is at least arranged between the blocks 2, in contact with the front face 1a of the support substrate 1. It can also be formed on all or part of the blocks 2.
[0052] The complementary layer 20 is composed of a material, called the second material, having a coefficient of thermal expansion matched to that of the first material. By “matched”, it is meant that the difference between the coefficient of thermal expansion of the second material and that of the first material is less than or equal to + / -10%.
[0053] At the end of step b), an intermediate donor substrate 100' is obtained.
[0054] Advantageously, the first material and the second material are of the same nature; for example, for a first material in monocrystalline InP, the second material may be in polycrystalline or amorphous InP.
[0055] Advantageously, the support substrate 1 can also be chosen so as to have an expansion coefficient close to the material of the paving stones. For example, the support substrate 1 can also be formed by the same additive manufacturing technique and with the same material (second material) of the additional layer 20.
[0056] According to a variant, the second material is composite and comprises a material whose coefficient of thermal expansion is close to that of the first material, and a binder. The proportion of binder being less than 30%, less than 20%, or even less than 10%, so as to keep the coefficient of thermal expansion of the second composite material as close as possible to that of the first material.
[0057] Preferably, the additional layer 20 also has a thickness greater than or equal to an average thickness of the blocks 2, this to make it possible to limit as much as possible the discontinuities of material between the blocks 2 and the additional layer 20, during the following step c) of the method.
[0058] According to a first embodiment, the additive manufacturing technique implemented in step b) is based on the at least partial melting of a powder of the second material, in a nozzle B heated by a laser beam or an electron beam (). The movement of the nozzle B makes it possible to deposit the melted powder 20' on the support substrate 1, between the blocks 2, and optionally on all or part of the blocks 2, until the complementary layer 20 is formed. Several passes of the nozzle B at the same location may be required to achieve the desired thickness of the complementary layer 20.
[0059] A CLAD type technique (Direct Additive Laser Construction) can be implemented in particular.
[0060] For example, if the second material constituting the powder is InP, a local temperature, generated by the laser beam or the electron beam, between 650°C and 800°C, allows the melting at least at the surface of the grains of the powder and consequently their agglomeration in the form of an additional layer 20 when they cool. The temperature felt by the initial structure 10 is well below this temperature, typically less than or equal to 100°C: this avoids any degradation of the adjacent blocks 2, the first material of which is for example monocrystalline InP.
[0061] According to another example, the second material is composite and comprises InP and a binder (polymer compatible with the operating temperatures): a local temperature, generated by the laser beam or the electron beam, typically between 100°C and 800°C can allow the melting of the binder, which ensures the agglomeration of the powder in the form of an additional layer 20. Here again, the temperature felt by the initial structure 10 remains low (typically less than 100°C), which prevents its degradation. It should be noted that the use of a binder, even if its proportion is limited to 30%, 20% or even 10%, involves a shrinkage of the additional layer 20, to be taken into account in the definition of the initial deposited thickness of the additional layer.
[0062] Whatever the examples of this first embodiment, it is important to ensure that the complementary layer 20 adheres well to the front face 1a of the support substrate 1. The presence of a binder in the second material is favorable to this adhesion. It will also be possible to choose an initial structure 10 comprising a surface layer on the support substrate 1, a surface layer whose nature is favorable to the adhesion of the complementary layer 20.
[0063] Furthermore, to promote adhesion between the complementary layer 20 and the support substrate 1, texturing of the front face 1a may be advantageous; this could be, for example, a level of roughness of the front face 1a greater than 1nm RMS (on a 20x20μm scan). 2 in atomic force microscopy).
[0064] According to a second embodiment, step b) comprises a first sub-step of additive manufacturing of a 20'' stencil on a plate. A 3D printing technique of the DMLS ("direct metal laser sintering") type can in particular be implemented.
[0065] The stencil 20'' has a surface identical to that of the support substrate 1 and comprises localized openings 3 at the locations of the blocks 2 of the initial structure 10 (figures 5a, 5b). Step b) then comprises a second sub-step of assembly between the stencil 20'' and the initial structure 10 (), the stencil 20'' then forming the complementary layer 20 ().
[0066] Good flatness of the 20'' stencil is important to obtain a quality assembly, in particular when an assembly by molecular adhesion is envisaged (typically, a deformation of less than 100μm and a maximum variation in flatness of a few micrometers are expected). Note that any known type of assembly can be carried out, provided that the mechanical and thermal resistance of the bonding is compatible with the rest of the process and the intended use of the donor substrate 100 tile.
[0067] The method finally comprises a step c) corresponding to the application of a mechanical surface treatment (for example, grinding) and / or a mechanical-chemical surface treatment (for example, polishing) to the additional layer 20 and to the blocks 2 (figures 6a, 6b, 6c).
[0068] Whether the complementary layer 20 is of lesser thickness, substantially equal to or greater than the average thickness of the blocks 2, step c) aims to planarize the front face 100'a of the intermediate donor substrate 100', to obtain the block donor substrate 100 whose front face 100a has a flat and continuous surface, at the level of which the plurality of blocks 2 and the complementary layer 20 are flush (). By flat and continuous, we mean a surface devoid of reliefs (i.e. typically, less than 5nm, less than 1nm, or even less than 0.5nm of reliefs, in particular at the junctions between blocks 2 and complementary layer 20). The complementary layer 20 may optionally have a thickness substantially less than that of the blocks 2 after planarization, so as not to hinder the complete transfer of the paved surface layer from the blocks 2.
[0069] The removal of material carried out in step c) may vary according to the configuration of the intermediate donor substrate 100', and according to the thickness of the complementary layer 20. Typically the removal is between 1 µm and 200 µm, preferably between 20 µm and 60 µm.
[0070] As mentioned previously, the paving stones 2 may have thickness variations between them, linked to the TTV of the initial substrate from which they originate. Step c) makes it possible to rectify these thickness variations and to obtain a flat surface compatible with a thin layer transfer. In addition, the presence of the additional layer 20 facilitates planarization because it ensures the continuity of the treated surface 100'a and consequently avoids the phenomena of sagging of the edges of the paving stones ("corner rounding") during mechanical-chemical treatments.
[0071] Finally, the additional layer 20 being preferably mainly composed of a material of the same nature as the first material of the paving stones 2, the surface treatments are facilitated and do not come up against problems of polishing with double materials, in particular with different abrasion speeds.
[0072] According to the present invention, the tile donor substrate 100 can be used to transfer a surface layer of each tile 2 onto a receiving substrate 50. Preferably, a thin layer transfer technique involving the following steps is implemented. First, a buried fragile plane 4, substantially parallel to a front face 100a of the tile donor substrate 100, is formed in the tiles 2 and in the complementary layer 20 (). For this, an implantation of light species such as hydrogen, helium or a combination of these two species can be implemented. The next step consists of assembling the front face 100a of the tile donor substrate 100 onto the receiving substrate 50 (). Preferably, this assembly is based on molecular adhesion bonding, not requiring the presence of adhesive layers.As is well known per se, cleaning and other surface activations can be implemented to improve the quality and mechanical strength of the bonding interface 5. Finally, a separation along the buried fragile plane 4 occurs, to form a composite structure comprising the receiving substrate 50 and at least one thin layer 2i originating from each block 2 and transferred to said receiving substrate 50 (). Depending on the nature of the second material of the complementary layer 20, a complementary thin layer 20i, originating from the complementary layer 20, can also be transferred to the receiving substrate 50. In this case, a next step consists of locally etching this complementary thin layer 20i, so as to retain only the tiled thin layer 2i on the receiving substrate 50 ().
[0073] Polishing and cleaning sequences can be applied to restore a good surface condition to the paved thin layer 2i, before or after removal of the complementary thin layer 20i (when present).
[0074] After the separation step, the remainder 100i of the donor substrate 100 can be conditioned (mechanical grinding and / or chemical-mechanical polishing and cleaning) then reused for a new thin layer transfer onto a new receiving substrate.
[0075] Of course, the invention is not limited to the embodiments described and variant embodiments can be made without departing from the scope of the invention.
Claims
A method of manufacturing a tile donor substrate (100) comprising the following steps: a) providing an initial structure (10) comprising a support substrate (1) having a front face (1a) and a rear face (1b), and a plurality of tiles (2) made of a first, monocrystalline material, arranged on the front face (1a) and spaced apart from each other, b) forming a complementary layer (20) by an additive manufacturing technique, the complementary layer (20): - being arranged between the tiles (2), in contact with the front face (1a) of the support substrate (1), - being composed of a material, called the second material, having a coefficient of thermal expansion matched to that of the first material, c) applying a mechanical and / or mechanochemical surface treatment to the complementary layer (20) and to the tiles (2), to obtain the tile donor substrate (100) of which a front face (100a) has a flat surface and continue,at which the plurality of paving stones (2) and the additional layer (20) are exposed., Manufacturing method according to claim 1, wherein, in step b), the additional layer (20) is also formed on all or part of the blocks (2). Manufacturing method according to one of the preceding claims, in which the additional layer (20) has a thickness greater than or equal to an average thickness of the blocks (2). Manufacturing method according to one of the preceding claims, in which the additive manufacturing technique implemented in step b) is based on:- the at least partial melting of a powder of the second material, in a nozzle (B) heated by a laser beam or an electron beam,- the movement of the nozzle (B) to deposit the melted powder (20') on the support substrate, between the blocks (2), and optionally on all or part of the blocks (2), until the complementary layer (20) is formed. Manufacturing method according to one of claims 1 to 3, in which step b) is based on:- a sub-step of additive manufacturing of a stencil (20'') on a plate, the stencil (20'') having a surface identical to that of the support substrate (1) and comprising openings located at the locations of the blocks (2) of the initial structure (10),- a sub-step of assembly between the stencil (20'') and the initial structure (10), the stencil (20'') forming the complementary layer (20). Manufacturing method according to one of the preceding claims, in which the support substrate (1) is made of silicon. Manufacturing method according to one of the preceding claims, in which the first monocrystalline material forming the blocks (2) is chosen from semiconductor materials, piezoelectric materials and electrical insulating materials. Manufacturing method according to one of the preceding claims, in which the first monocrystalline material forming the blocks (2) is indium phosphide (InP). Manufacturing method according to one of the preceding claims, in which the blocks (2) of the initial structure (10) are spaced apart by a distance of between 100µm and 10mm, or even 10cm. Manufacturing method according to one of the preceding claims, in which the second material is of the same nature as the first material. Manufacturing method according to one of the preceding claims, in which the second material is composite and comprises a binder, the proportion of binder being less than 30%. Use of a donor tile substrate (100) resulting from a manufacturing method according to claims 1 to 11, for transferring a surface layer of each tile (2) onto a receiving substrate (50). Use of a paved donor substrate (100) according to the preceding claim, implementing a thin layer transfer technique involving the following steps: - the formation of a buried fragile plane (4), substantially parallel to a front face (100a) of the paved donor substrate (100), in the pavers (2) and in the complementary layer (20), - the assembly of the front face (100a) of the paved donor substrate (100) on the receiving substrate (50), - the separation along the buried fragile plane (4), to form a composite structure comprising the receiving substrate (50) and at least one thin layer (2i) from each pavement (2) transferred onto said receiving substrate (50). Use of a tiled donor substrate (100) according to the preceding claim, wherein, after separation, a remainder (100i) of the tiled donor substrate (100) is conditioned and then reused for a new thin layer transfer onto a new receiving substrate.