Method for producing a substrate comprising a plurality of blocks

Abstract

The invention relates to a method for producing a substrate (100), referred to as a donor pseudo-substrate, comprising a plurality of first blocks (1) arranged at a distance from one another on a carrier substrate (3), wherein the method comprises: - arranging, on the carrier substrate (3), the first blocks (1) and a plurality of second blocks (2) arranged between the first blocks (1) such that each edge of each first block (1) faces at least one second block (2), wherein the first blocks (1) comprise a first material and the second blocks (2) comprise a second material different from the first material; and - chemical-mechanical polishing of the first and second blocks (1, 2).

Description

[0001] METHOD FOR MANUFACTURING A SUBSTRATE COMPRISING A PLURALITY OF PAVING PANELS

[0002] TECHNICAL FIELD

[0003] The invention relates to a method for manufacturing a substrate, called a pseudo-donor substrate, comprising a plurality of tiles, as well as a method for transferring chips from said tiles onto a receiving substrate.

[0004] STATE OF THE ART

[0005] In the field of microelectronics, optics or optoelectronics, the design of multilayer structures sometimes requires transferring tiles in the form of portions of a layer from a donor substrate to a support substrate or receiving substrate.

[0006] This type of process is generally referred to as a paving process, and involves a partial transfer of a layer taken from the donor substrate to form one or more paving stones arranged in a predetermined pattern or location on the supporting substrate.

[0007] Such tiling may be made necessary by a size difference between the donor substrate and the support substrate. Indeed, due to this size difference, it is not possible to transfer a layer of the donor substrate covering the entire surface of the support substrate.

[0008] A well-known layer transfer method is the Smart Cut™ method, in which an embrittlement zone is formed by implantation of atomic species into the donor substrate, delimiting the layer to be transferred, the donor substrate is bonded to the support substrate, and the donor substrate is detached along the embrittlement zone to transfer the layer from the donor substrate to the support substrate. However, this method assumes that the donor substrate and the support substrate are of identical size.

[0009] However, while silicon substrates are available with a relatively large size, typically a diameter of 300 mm, other materials of interest currently only exist in the form of bulk substrates of smaller size, for example 10 or 15 cm in diameter. Furthermore, these materials of interest are sometimes particularly expensive, so it is desirable to minimize any waste formed during transfer.This is particularly the case for III-V semiconductor materials, including nitrides (e.g., for binary compounds, indium nitride (InN), gallium nitride (GaN) and aluminum nitride (AIN)), arsenides (e.g., for binary compounds, indium arsenide (InAs), gallium arsenide (GaAs) and aluminum arsenide (AlAs)), and phosphides (e.g., for binary compounds, indium phosphide (InP), gallium phosphide (GaP) and aluminum phosphide (AlP)).

[0010] Instead of transferring an entire layer of the donor substrate, a solution based on the Smart Cut™ process consists of removing one or more blocks from at least one donor substrate and transferring said blocks onto an intermediate support, to form a substrate called a pseudo-donor substrate, forming by implantation of atomic species a weakening zone in each block, bonding the pseudo-donor substrate to a receiving substrate via the blocks, and detaching each block along the weakening zone so as to transfer a portion of each block onto the receiving substrate.

[0011] To allow the bonding of the donor pseudo-substrate to the receiving substrate, the free surface of all the paving stones must extend in the same plane. To this end, before bonding, chemical mechanical polishing (CMP) could be carried out, preferably preceded by mechanical abrasion (called "grinding") of the donor pseudo-substrate. Chemical mechanical polishing combines the mechanical action of a polishing pad and the chemical action of a polishing solution to planarize the surface of all the paving stones.

[0012] However, if the distance between the tiles is large, typically greater than or equal to 250 pm, the polishing pad, which has a certain flexibility, partially inserts itself into the gap between the tiles and thus erodes the edges of the tiles. This rounding of the edges, which is called "edge rounding" in English, reduces the useful surface area of ​​the chips transferred to the receiving substrate. Conversely, the edges of the tiles very quickly degrade the polishing pad, which must therefore be renewed frequently.

[0013] SUMMARY OF THE INVENTION

[0014] An aim of the invention is therefore to design a method for manufacturing a pseudo-donor substrate without rounding the edges of the paving stones, even when the paving stones are far from each other.

[0015] To this end, the invention proposes a method for manufacturing a substrate, called a donor pseudosubstrate, comprising a plurality of first blocks arranged at a distance from each other on a support substrate, comprising:

[0016] - arranging, on the support substrate, said first blocks and a plurality of second blocks arranged between the first blocks so that each edge of each first block faces at least one second block, the first blocks comprising a first material and the second blocks comprising a second material different from the first material, and

[0017] - chemical-mechanical polishing of the first and second blocks. In this text, “different material” means a material with a different composition and / or a different crystalline quality.

[0018] The use of the second paving stones, which are advantageously made of a less expensive material than the first paving stones, makes it possible to protect the edges of the first paving stones during chemical-mechanical polishing. They therefore prevent the edges of the first paving stones from rounding off.

[0019] According to other advantageous but optional characteristics, possibly combined when technically possible:

[0020] - a distance between two first adjacent blocks is greater than or equal to 1 mm, preferably greater than or equal to 2 mm,

[0021] - a distance between each first tile and a second tile adjacent to said first tile is less than or equal to 250 pm, preferably less than or equal to 100 pm,

[0022] - the first material is a semiconductor material, such as a III-V material,

[0023] - the second material is a semiconductor material, such as silicon, said second material being chosen to have a difference in thermal expansion coefficient of zero or less than 40% in absolute value with the thermal expansion coefficient of the support substrate,

[0024] - the method comprises forming a weakening zone in the first blocks, so as to delimit in each first block a respective chip of the first material.

[0025] A donor pseudo-substrate obtainable by the method described above comprises a support substrate, a plurality of first tiles arranged at a distance from each other on the support substrate, and a plurality of second tiles arranged on the support substrate between the first tiles such that each edge of each first tile faces at least one second tile, the first tiles comprising a first material and the second tiles comprising a second material different from the first material, the free surface of each first tile being flush with the free surface of each second tile.

[0026] By "flush" we mean that the free surface of each first or second paver, which is flat, extends in the same plane. The free surface of a paver is the surface opposite the supporting substrate.

[0027] According to other advantageous but optional characteristics, possibly combined when technically possible:

[0028] - a distance between two first adjacent blocks is greater than or equal to 1 mm, preferably greater than or equal to 2 mm,

[0029] - a distance between each first tile and a second tile adjacent to said first tile is less than or equal to 250 pm, preferably less than or equal to 100 pm,

[0030] - the first material is a semiconductor material, such as a III-V material, - the second material is a semiconductor material, such as silicon, said second material having a difference in thermal expansion coefficient of zero or less than 40% in absolute value with the thermal expansion coefficient of the support substrate,

[0031] - each first block includes a weakening zone delimiting a respective chip of the first material.

[0032] According to another aspect, the invention provides a method of transferring chips onto a receiving substrate.

[0033] Said method comprises:

[0034] - the formation of a pseudo-donor substrate by the method described above, in which a weakening zone has been formed in the first tiles in order to delimit a respective chip therein,

[0035] - bonding said donor pseudo-substrate to a receiving substrate by means of the first blocks, and

[0036] - the detachment of each first tile along the weakening zone so as to transfer each chip onto the receiving substrate.

[0037] BRIEF DESCRIPTION OF THE FIGURES

[0038] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

[0039] - Figure 1 illustrates a top view and a sectional view of a donor pseudo-substrate according to a first embodiment of the invention;

[0040] - Figures 2A to 2E illustrate different steps in the manufacture of a donor pseudosubstrate according to the invention, respectively comprising the arrangement of the first and second blocks on a temporary support, the provision of the support substrate, the transfer of the first and second blocks from the temporary support to the support substrate, the implementation of chemical-mechanical polishing of the first and second blocks, and the formation of a weakening zone in the first blocks to delimit chips of the first material;

[0041] - figure 3 illustrates the bonding of the donor pseudo-substrate on a recipient substrate;

[0042] - Figure 4 illustrates the structure formed by the receiving substrate and the chips resulting from the detachment of the tiles along the weakening zone;

[0043] - Figure 5 illustrates a top view and a sectional view of a donor pseudo-substrate according to a second embodiment of the invention;

[0044] - Figure 6 illustrates a top view and a sectional view of a donor pseudo-substrate according to a third embodiment of the invention;

[0045] - Figure 7 illustrates a top view and a sectional view of a pseudo-donor substrate according to a fourth embodiment of the invention. For reasons of readability of the figures, the different elements have not necessarily been represented to scale.

[0046] DETAILED DESCRIPTION OF EMBODIMENTS

[0047] The donor pseudo-substrate comprises two types of tiles arranged on a support substrate:

[0048] - paving stones of interest comprising a first material,

[0049] - dummy paving stones (called “dummies” in English) comprising a second material different from the first material or of lower crystalline quality allowing it to be less expensive.

[0050] All of said paving stones have a free surface extending in the same plane parallel to the main surface of the supporting substrate. In other words, the surface of the dummy paving stones is flush with the surface of the paving stones of interest.

[0051] The dummy blocks are not intended to produce electronic, optical or optoelectronic components, but to at least partially fill the gaps between the blocks of interest. Thus, by increasing the coverage rate of the support substrate by the blocks, the polishing pad can be kept in the plane of the free surface of the blocks and prevented from being inserted between the blocks. Rounding of the edge of the blocks can therefore be avoided or at least minimized.

[0052] The use of such dummy blocks is particularly interesting when the distance between two adjacent blocks of interest is greater than or equal to 1 mm, and even more preferably greater than or equal to 2 mm.

[0053] Particularly advantageously, the distance between a paving stone of interest and an adjacent dummy paving stone is less than or equal to 250 pm, preferably less than or equal to 100 pm. Indeed, the polishing pad, even if flexible, cannot be significantly introduced between the paving stone of interest and the dummy paving stone. The polishing action is therefore limited to the free surface of the paving stones and does not cause rounding of the edges of the paving stones.

[0054] The interest pavers are usually made of an expensive material and available only in small dimensions. Optionally, the interest pavers can be made of a stack of such materials.

[0055] The paving stones of interest may advantageously comprise at least one of said materials:

[0056] - a semiconductor material, such as a III-V material, in particular indium nitride (InN), gallium nitride (GaN), aluminum nitride (AIN), indium arsenide (InAs), gallium arsenide (GaAs), aluminum arsenide (AlAs), indium phosphide (InP), gallium phosphide (GaP) or aluminum phosphide (AlP), or a IV or IV-IV material, in particular germanium or silicon carbide (SiC), - a piezoelectric material, such as lithium tantalate (LiTaCh), lithium niobate (LiNbCh), potassium sodium niobate (KxNai-xNbCh or KNN), barium titanate (BaTiCh), quartz, lead zirconate titano (PZT), a compound of lead-magnesium niobate and lead titanate (PMN-PT), zinc oxide (ZnO), aluminum nitride (AIN) or aluminum scandium nitride (AIScN), and / or

[0057] - an electrically insulating material, such as diamond, strontium titanate, yttria zirconia or sapphire.

[0058] Since the dummy paving stones are only intended to fill the gaps between the paving stones of interest, they are made of a material different from that of the paving stones of interest or of lower crystalline quality, which is advantageously less expensive than that of the paving stones of interest, and readily available.

[0059] Preferably, the material of the dummy paving stones is further chosen to exhibit behavior compatible with that of the paving stones of interest during chemical-mechanical polishing and / or during use of the donor pseudo-substrate.

[0060] Thus, for example, the material of the dummy paving stones advantageously exhibits behavior with respect to mechanical-chemical polishing (i.e. in particular in terms of polishing speed) comparable to that of the material of the paving stones of interest, so as not to cause a gap between the free surface of the paving stones of interest and the dummy paving stones during polishing.

[0061] Furthermore, the material of the dummy paving stones advantageously has a coefficient of thermal expansion close to that of the paving stones of interest, so as not to cause deformation of the support substrate during heat treatments undergone by the donor pseudo-substrate. By close coefficients of thermal expansion, we mean coefficients of thermal expansion that are equal or have a difference of less than 40% in absolute value.

[0062] For example, the dummy blocks can be made of silicon.

[0063] In other examples, the dummy paving stones may have a similar composition to the paving stones of interest, but a lower quality. For example, the paving stones of interest may be made of a monocrystalline III-V material and the dummy paving stones of a polycrystalline III-V material or of lower crystalline quality.

[0064] Figure 1 illustrates a top view and a sectional view of a donor pseudo-substrate according to a first embodiment.

[0065] The pseudo-donor substrate comprises a support substrate 3 on which are arranged tiles of interest 1 and dummy tiles 2.

[0066] The tiles of interest 1 are arranged at regular intervals, with a distance dl between the closest edges of two adjacent tiles. It should be noted, however, that this arrangement of the tiles of interest is given for illustrative purposes only; thus, the tiles of interest may possibly have different shapes, or be arranged at different distances from each other. Furthermore, the tiles of interest are not necessarily square as illustrated in Figure 1, but may have any other shape suitable for the intended use, with or without a straight edge. For example, the tiles of interest may have a rectangular, circular shape, or any other shape composed of lines and / or curves.

[0067] The distance dl is advantageously greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

[0068] Dummy tiles 2 are arranged between the tiles of interest 1, so that the edge of each tile of interest is opposite the edge of a dummy tile. We thus have a distance d2 between the edge of a tile of interest and the nearest edge of a dummy tile, which is much less than the distance dl.

[0069] For example, the distance d2 is less than or equal to 250 pm, preferably less than or equal to 100 pm.

[0070] In the embodiment of Figure 1, the blocks of interest having four rectilinear edges, four dummy blocks with rectilinear edges are arranged around a block of interest. The edge of each dummy block is arranged opposite a respective edge of the block of interest, parallel to it in order to have a constant distance d2 between the block of interest and the respective dummy block. Thus, at any point of the perimeter of the block of interest, the distance with each adjacent block is at most equal to d2. The remaining free space between the blocks is then sufficiently restricted to prevent the polishing pad from being inserted between the blocks and eroding the edges of the blocks.

[0071] For example, the tiles of interest may be 3x3 mm in size 2 and be spaced by a distance dl equal to 7 mm. The dummy paving stones then advantageously have a size of 6.5x3 mm 2, so that the distance d2 between a tile of interest and a dummy tile is equal to 0.25 mm.

[0072] Figures 2A to 2E illustrate steps in the manufacture of the pseudo-donor substrate of Figure 1. To facilitate the alignment of the tiles of interest and the dummy tiles, it is advantageous to first assemble the tiles of interest and the dummy tiles on a temporary support and then transfer said tiles from the temporary support to the support substrate.

[0073] Referring to Figure 2 A, the interest paving stones 1 and the dummy paving stones 2 are first placed on a temporary support.

[0074] The temporary support is for example formed from one of the following materials: adhesive tape held by a frame, silicon substrate, glass substrate (non-limiting list).

[0075] The pavers of interest and the dummy pavers may be cut from one or more respective donor substrates and placed on the temporary support using a robot (a technique known as "Pick and Place"). Advantageously, the pavers have the same thickness as the respective donor substrate.

[0076] Referring to Figure 2B, the support substrate 3 is provided. Referring to Figure 2C, the paving stones 1, 2 are bonded to the support substrate 3 via their free surface, and then the temporary support is removed so as to expose the opposite surface of the paving stones. Advantageously, the bonding of the paving stones to the support substrate is direct, but it is possible to use a bonding layer between the paving stones and the support substrate.

[0077] Alternatively, it is possible to assemble the pavers directly onto the support substrate with sufficient precision using the robot by using alignment marks placed on the support substrate. This avoids the use of the temporary support and the transfer of the pavers from the temporary support to the support.

[0078] With reference to Figure 2D, a chemical-mechanical polishing of the free surface of the paving stones of interest and the dummy paving stones is carried out. As shown schematically, due to the small distance between the paving stones, the polishing pad 5 acts essentially in the plane of the free surface of the paving stones, without inserting itself between the paving stones. Consequently, the edges of the paving stones, in particular the paving stones of interest, remain straight (not rounded).

[0079] Optionally, this chemical-mechanical polishing may be preceded by a step of planarization of the paving stones by mechanical abrasion (“grinding”). Such planarization may be advantageous in particular when the paving stones have different thicknesses, in order to bring their free surface substantially into the same plane, or to reduce the thickness of the paving stones. However, if the paving stones have coplanar free surfaces, it is possible to dispense with such planarization and to implement chemical-mechanical polishing directly.

[0080] Optionally, before chemical-mechanical polishing, a layer of resin or polymer (not shown) can be deposited between the blocks of interest and the dummy blocks, so as to fill the gaps between said blocks.

[0081] With reference to Figure 2E, a weakening zone 10 is formed in the blocks of interest 1 (and possibly in the dummy blocks 2) delimiting a surface chip 11 in each block. Said weakening zone is advantageously obtained by implantation of ionic species (for example hydrogen and / or helium), shown diagrammatically by the arrows, in the blocks.

[0082] The formation of the weakening zone is preferably carried out after chemical-mechanical polishing, but it can possibly be carried out before.

[0083] This produces a pseudo-donor substrate 100 which can subsequently be bonded to a receiving substrate to transfer the chips. The receiving substrate is typically a semiconductor substrate, for example a silicon substrate, solid or comprising microelectronic or optoelectronic devices.

[0084] With reference to Figure 3, the free surface of the tiles is bonded to the receiving substrate 6. Advantageously, the bonding of the tiles to the receiving substrate is direct, but it is possible to use a bonding layer between the tiles and the receiving substrate. With reference to Figure 4, the tiles of interest 1 are detached along the weakening zone 10, so as to transfer the chips 11 to the receiving substrate 6 by the Smart Cut™ process. The detachment can be initiated by a heat treatment, a mechanical and / or chemical action at the weakening zone.

[0085] Figures 5 to 7 illustrate other embodiments of the pseudo-donor substrate.

[0086] In the case of Figure 5, the blocks of interest have a very large spacing (typically greater than 10 mm) and the number and size of the dummy blocks has been minimized compared to the embodiment of Figure 1. Each block of interest is surrounded by four dummy blocks which protect each of its edges during chemical-mechanical polishing, but the gap between two blocks of interest is not entirely filled by the dummy blocks. There therefore remains a gap between two adjacent dummy blocks, between which the polishing pad can possibly be inserted, but the edge rounding effect will only apply to the dummy blocks and will therefore not be harmful to the blocks of interest.

[0087] To effectively protect the paving stones of interest, the dummy paving stones advantageously have a width (in the direction perpendicular to the edge of the paving stone of interest opposite which they are arranged) greater than or equal to 10 mm. The other dimension of the dummy paving stones (in the direction parallel to the edge of the paving stone of interest opposite which they are arranged) is advantageously equal to that of the paving stones of interest.

[0088] For example, if the tiles of interest have a size of 3x3 mm 2 and are spaced 20 mm apart, they can be surrounded by 10x3 mm dummy paving stones 2 .

[0089] According to another example, if the tiles of interest have a size of 10x10 mm 2 and are spaced 50 mm apart, they can be surrounded by dummy paving stones of 10 to 25 xlO mm 2 .

[0090] It should be noted that the corners of the paving stones are less prone to rounding during chemical-mechanical polishing. Therefore, it is sufficient to protect the edges of the paving stones of interest with the dummy paving stones to avoid their rounding and thus the reduction of the useful surface area of ​​the chips.

[0091] Figure 6 illustrates another embodiment, in which the dummy paving stones have different shapes and sizes.

[0092] In particular, in this embodiment, the dummy paving stones have a larger dimension than that of the paving stones of interest, in order to better protect the corner of the paving stones of interest against the action of the polishing pad.

[0093] Figure 7 illustrates another embodiment, in which the same dummy paving stone in the form of a single strip is arranged between two parallel rows of paving stones of interest.

[0094] This embodiment makes it possible to reduce the number of dummy paving stones required, since a single dummy paving stone in the form of a strip simultaneously protects the edge of several paving stones of interest. This reduces the assembly time of the dummy paving stones compared to the embodiment of Figure 1.

[0095] These different figures are only intended to illustrate different ways of arranging the dummy paving stones around the paving stones of interest in order to protect the edges of the paving stones of interest from erosion caused by the polishing pad, but the person skilled in the art may choose other arrangements of the dummy paving stones depending on the shape and arrangement of the paving stones of interest, provided that each edge of the paving stones of interest is opposite a sufficiently close dummy paving stone. This choice may in particular depend on a compromise between the quantity of material consumed to form the dummy paving stones and the time required to position the dummy paving stones between the paving stones of interest.

Claims

CLAIMS 1. Method for manufacturing a substrate (100), called a pseudo-donor substrate, comprising a plurality of first blocks (1) arranged at a distance from each other on a support substrate (3), comprising: - the arrangement, on the support substrate (3), of said first blocks (1) and of a plurality of second blocks (2) arranged between the first blocks (1) so that each edge of each first block (1) faces at least one second block (2), the first blocks (1) comprising a first material and the second blocks (2) comprising a second material having a different composition and / or a different crystalline quality from that of the first material, and - chemical-mechanical polishing of the first and second blocks (1, 2) by means of a polishing pad, the first and second blocks being separated by free intervals of a width less than or equal to 250 pm so as to minimize the insertion of the polishing pad between the blocks.

2. Method according to claim 1, in which a distance (dl) between two first adjacent blocks is greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

3. Method according to one of claims 1 or 2, in which a distance (d2) between each first block (1) and a second block (2) adjacent to said first block is less than or equal to 250 pm, preferably less than or equal to 100 pm.

4. Method according to one of claims 1 to 3, in which the first material is a semiconductor material, such as a III-V material.

5. Method according to one of claims 1 to 4, in which the second material is a semiconductor material, such as silicon, said second material being chosen to have a difference in thermal expansion coefficient of zero or less than 40% in absolute value with the thermal expansion coefficient of the support substrate.

6. Method according to one of claims 1 to 5, comprising the formation of a weakening zone (10) in the first blocks, so as to delimit in each first block a respective chip (11) of the first material.

7. Method for transferring chips (11) of a first material onto a receiving substrate (6), comprising: - the formation of a pseudo-donor substrate (100) by the method according to claim 6, - bonding said donor pseudo-substrate (100) to a receiving substrate (6) by means of the first blocks (1), and - detaching each first tile (1) along the weakening zone (10) so as to transfer each chip (11) onto the receiving substrate (6).

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