CHIP TRANSFER PROCESS

Abstract

The invention relates to a method for transferring chips onto a receiving substrate from tiles arranged on a support substrate, comprising: forming a substrate (10), called a donor pseudo-substrate, comprising the support substrate (2) and the tiles (1), in which two adjacent tiles are separated by a first distance (d1), carrying out chemical-mechanical polishing of the tiles, forming a weakening zone in at least a portion of the tiles so as to delimit a respective chip, bonding the donor pseudo-substrate to the receiving substrate via the tiles, detaching the tiles along the weakening zone so as to transfer a respective chip onto the receiving substrate, two adjacent chips being separated by a second distance greater than the first distance (d1), - before bonding, localized roughening of the surface of the tiles and / or of the receiving substrate to make regions of said surface unsuitable for bonding,so as to prevent the transfer of chips into said regions. Figure for abstract: Fig 2,

Description

Title of the invention: CHIP TRANSFER METHOD Technical field

[0001] The invention relates to a method for transferring chips from a substrate, called a donor pseudosubstrate, to a recipient substrate. STATE OF THE ART

[0002] 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 onto a support substrate or receiving substrate.

[0003] 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 tiles arranged in a pattern or at a predetermined location on the support substrate.

[0004] Such tiling may be made necessary by a difference in size between the donor substrate and the support substrate. Indeed, due to this difference in size, it is not possible to transfer a layer of the donor substrate covering the entire surface of the support substrate.

[0005] A well-known layer transfer method is the Smart Cut™ method, in which a weakening zone delimiting the layer to be transferred is formed by implantation of atomic species in the donor substrate, the donor substrate is bonded to the support substrate, and the donor substrate is detached along the weakening 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 have the same size.

[0006] However, if 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 massive substrates of smaller size, for example 10 or 15 cm in diameter. Furthermore, these materials of interest are sometimes particularly expensive, so that 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 binaries, indium phosphide (InP), gallium phosphide (GaP) and aluminum phosphide (A1P)).

[0007] Instead of transferring an entire layer of the donor substrate, a solution based on the Smart Cut™ process consists of taking 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 onto 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.

[0008] To allow the donor pseudo-substrate to be bonded to the receiving substrate, the free surface of all the blocks must extend in the same plane. For this purpose, before bonding, chemical mechanical polishing (CMP) can be carried out, preferably preceded by mechanical abrasion (called "grinding" in English) of the donor pseudo-substrate. Chemical mechanical polishing combines a mechanical action of a polishing pad and an abrasive powder and a chemical action of a polishing solution containing the abrasive powder (the combination of the abrasive powder and the solution being called slurry) to planarize the surface of all the blocks.

[0009] However, if the distance between the tiles is large, typically greater than or equal to 250 μm, the polishing pad, which has a certain flexibility, is partially inserted 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.

[0010] Conversely, the edges of the paving stones degrade the polishing pad very quickly, which requires frequent replacement of the polishing pad, increasing the cost of the chemical-mechanical polishing operation.

[0011] To avoid such rounding of the edges of the paving stones, it is therefore desirable to form a pseudo-donor substrate in which the distance between the paving stones is less than or equal to 250 pm.

[0012] However, depending on the applications of the final structure comprising the receiving substrate and the chips, it may be necessary to have a distance between the chips greater than 250 pm, for example greater than 1 mm, or even more.

[0013] One solution then consists of reducing the size of the chips transferred onto the donor substrate, by applying a photolithography mask to locally protect a part of the surface of the chips and expose another part of the surface of the chips. It is then possible to carry out localized etching of the part of the chips exposed by the mask, which has the effect of reducing the size of the chips and increasing the distance between adjacent chips.

[0014] This method is not, however, entirely satisfactory because it requires great precision in the placement of the mask and significantly increases the manufacturing time of the final structure. Furthermore, it consumes a significant quantity of chip material, which is generally expensive. This method is therefore not economically feasible on an industrial scale. Summary of the invention

[0015] An aim of the invention is therefore to design a chip transfer method making it possible to avoid rounding of the edge of the chips, even when the chips are distant from each other, which is easy to implement industrially and which minimizes the consumption of chip material.

[0016] To this end, the invention proposes a method for transferring chips onto a receiving substrate from tiles arranged on a support substrate, comprising: - the formation of a substrate, called a pseudo-donor substrate, comprising the support substrate and the paving stones, in which two adjacent paving stones are separated by a first distance, - the implementation of mechanical-chemical polishing of the paving stones, - the formation of a weakening zone in at least part of the blocks so as to delimit a respective chip, - bonding of the donor pseudo-substrate to the recipient substrate using the blocks, - detaching the tiles along the weakening zone so as to transfer a respective chip onto the receiving substrate, two adjacent chips being separated by a second distance greater than the first distance,

[0017] said method being characterized in that it comprises, before bonding, localized roughening of the surface of the tiles and / or of the receiving substrate to make regions of said surface unsuitable for bonding, so as to prevent the transfer of the chips into said regions.

[0018] Localized roughening makes it possible to form, at the bonding interface, regions in which adhesion between the tiles and the receiving substrate is insufficient to allow transfer of the chips into these regions. It therefore makes it possible to selectively transfer chips onto the receiving substrate, to go from a high density of tiles in the donor pseudo-substrate to a lower density of chips in the final structure. Since only the desired chips are transferred onto the receiving substrate, there is no waste of chip material.

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

[0020] - roughening is carried out by localized laser irradiation of the surface of the receiving substrate;

[0021] - the laser irradiation is carried out with a laser having a wavelength between 100 nm and 550 nm, preferably between 250 nm and 400 nm, according to pulses of a duration between 1 ns and 10 ps, ​​preferably between 10 ns and 500 ns;

[0022] - the method comprises applying a mask defining a pattern and irradiating from the surface through the mask;

[0023] - the pattern is chosen to delimit a plurality of zones of the receiving substrate separated by roughened areas opposite the same block, so as to allow the block to be divided into several chips according to said pattern;

[0024] - the first distance is less than or equal to 250 pm, preferably less than or equal to 100 pm;

[0025] - the second distance is greater than or equal to 1 mm, preferably greater or equal to 2 mm;

[0026] - the formation of the weakening zone is carried out by implantation of species ionic;

[0027] - the donor pseudo-substrate comprises a first group and a second group of paving stones;

[0028] - the method comprises a successive transfer of the blocks of the first group and of the paving stones of the second group on at least one receiving substrate;

[0029] - the method comprises: - a selective implantation of ionic species in the blocks of the first group to form a weakening zone so as to delimit a chip in said blocks of the first group, - localized roughening of a first receiving substrate opposite the paving stones of the second group, - bonding of the donor pseudo-substrate to the first recipient substrate, - detaching the tiles of the first group along the weakening zone to transfer the respective chips onto the first receiving substrate, - from the pseudo-donor substrate resulting from the detachment of the tiles of the first group, a selective implantation of ionic species in the tiles of the second group to form a weakening zone so as to delimit a chip in said tiles of the second group, - localized roughening of a second receiving substrate opposite the paving stones of the first group, - bonding of the donor pseudo-substrate to the second recipient substrate, - detaching the tiles of the second group along the weakening zone to transfer the respective chips onto the second receiving substrate;

[0030] - only the chips of the first group of tiles are transferred onto the substrate receiver and the donor pseudo-substrate is recycled for a new transfer of the chips from the first group of tiles;

[0031] - the paving stones of the first and second groups are made of different materials;

[0032] - the paving stones of the first group have a crystalline quality superior to that of the paving stones of the second group;

[0033] - the materials of the paving stones of the first and second groups have substantially a same material removal speed and the same chemical reactivity with respect to chemical-mechanical polishing;

[0034] - the paving stones include: - 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 (LiTaO3), lithium niobate (LiNbO3), potassium sodium niobate (KxNal-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 (AIN) or aluminum scandium nitride (AIScN), and / or - an electrically insulating material, such as diamond, strontium titanate, yttria zirconia or sapphire. BRIEF DESCRIPTION OF THE FIGURES

[0035] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

[0036] - [Fig.l] shows a top view and a sectional view of a pseudo-substrate donor according to one embodiment of the invention;

[0037] - [Fig.2] shows a top view and a sectional view of the pseudo-substrate donor of [Fig.l] and a receiving substrate, before their bonding;

[0038] - [Fig.3] shows a sectional view and a bottom view of the receiving substrate after transfer of chips from the pseudo-donor substrate;

[0039] - [Fig.4] shows a sectional view and a top view of a pseudo-substrate donor according to an embodiment in which the paving stones are divided into two groups;

[0040] - Figures 5A to 5F schematically illustrate steps of two transfers successive arrays of chips from the donor pseudo-substrate of [Fig.4];

[0041] - [Fig.6] shows a sectional view and a top view of a pseudo-substrate donor according to an embodiment comprising interest tiles and sacrificial tiles;

[0042] - [Fig.7] shows a top view and a sectional view of the pseudo-substrate donor of [Fig.l] and a recipient substrate, before their bonding, in an embodiment in which an area of ​​the recipient substrate has been roughened so as to form a pattern opposite a block of the pseudo-donor substrate.

[0043] For reasons of readability of the figures, the different elements have not necessarily been represented to scale. The elements designated by the same reference sign from one figure to another designate similar elements, which are therefore not described each time. DETAILED DESCRIPTION OF EMBODIMENTS

[0044] Figures 1 to 3 illustrate the general principle of the invention.

[0045] Referring to [Fig.l], a pseudo-donor substrate 10 is formed by arranging the paving stones 1 on a support substrate 2.

[0046] The support substrate fulfills a role of mechanical support for the paving stones. The support substrate can be made of silicon, glass or sapphire (non-limiting list). The layer shown around the support substrate 2 in [Fig.l] is an oxide layer, which is generally present around silicon substrates, but such a layer is optional.

[0047] The support substrate advantageously has a diameter greater than or equal to 150 mm, preferably greater than or equal to 200 mm, and more preferably greater than or equal to 300 mm.

[0048] Preferably, at least some of the pavers are made of an expensive material available only in small dimensions. Optionally, the pavers may be made of a stack of such materials.

[0049] The blocks may advantageously comprise at least one of said materials:

[0050] - a semiconductor material, such as a III-V material, in particular nitride 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 material IV or IV-IV, including germanium or silicon carbide (SiC),

[0051] - a piezoelectric material, such as lithium tantalate (LiTaO3), lithium niobate (LiO3), lithium (LiNbO3), potassium sodium niobate (KxNai_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 (AIN) or aluminum scandium nitride (AIScN), and / or

[0052] - an electrically insulating material, such as diamond, strontium titanate, yttria-containing zirconia or sapphire.

[0053] As will be seen below, the paving stones can be identical or made of different materials.

[0054] In the illustrations shown, the paving stones have four straight edges and are arranged at regular intervals from each other to form a grid comprising a set of parallel lines and columns. It should be noted, however, that this arrangement of the paving stones is given for illustration purposes only; thus, the paving stones may possibly have different shapes, or be arranged at different distances from each other. Furthermore, the paving stones are not necessarily square, but may have any other shape suitable for the intended use, with or without a straight edge. For example, the paving stones may have a rectangular, circular shape, or any other shape composed of lines and / or curves.

[0055] The tiles are spaced apart from each other, with a distance dl between the facing edges of two adjacent tiles. The distance dl can be identical between all the tiles or variable.

[0056] The distance dl is less than or equal to 250 pm, preferably less than or equal to 100 pm.

[0057] To form the pseudo-donor substrate, the tiles may be cut from one or more respective donor substrates, and placed on a temporary support using a robot (a technique known as "Pick and Place"). Advantageously, the tiles have the same thickness as the respective donor substrate. In general, the thickness of the tiles is between 50 μm and 1 mm, for example of the order of 300 to 650 μm depending on the thickness of the donor material. The diameter of the donor substrate(s) is generally smaller than that of the temporary substrate and the support substrate.

[0058] The temporary support is for example formed from one of the following materials: an adhesive tape held by a frame, silicon, or glass (non-limiting list).

[0059] The pavers are then bonded to the support substrate, and then the temporary support is removed so as to expose the opposite surface of the pavers. Advantageously, the bonding of the pavers to the support substrate is direct, but it is possible to use a bonding layer between the pavers and the support substrate.

[0060] Alternatively, it is possible to directly assemble the tiles on the support substrate with sufficient precision using the robot by using alignment marks arranged on the support substrate. This avoids the use of the temporary support and the transfer of the tiles from the temporary support to the support to form the pseudo-donor substrate.

[0061] A chemical-mechanical polishing of the free surface of the paving stones is then carried out.

[0062] Optionally, this chemical-mechanical polishing may be preceded by a step of planarization of the paving stones by mechanical abrasion (“grinding”). Such planarization may in particular be advantageous 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.

[0063] Chemical-mechanical polishing makes it possible to smooth the surface of the blocks to obtain a roughness compatible with bonding to a receiving substrate. Said roughness is typically less than 0.5 nm RMS. Such roughness is conventionally measured using an atomic force microscope (AFM) over a field of 1 pm x 1 pm. Other measurement methods, such as optical interferometry, can also be used.

[0064] When the distance between the paving stones is sufficiently small, the polishing pad 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 remain straight (not rounded). Otherwise, the edges of the paving stones may be rounded.

[0065] A weakening zone is formed in at least a portion of the tiles so as to delimit a chip to be transferred onto a receiving substrate.

[0066] The weakening zone is typically formed by ion implantation, preferably of hydrogen and / or helium. A person skilled in the art is able to define the operating conditions of this implantation, depending on the material of the blocks and the thickness of the chip to be transferred.

[0067] The formation of the weakening zone is preferably carried out after the chemical-mechanical polishing, but it can optionally be carried out before.

[0068] The receiving substrate may be a silicon substrate, but other materials may be considered. In particular, the choice of material may be guided by the intended application (for example to address issues of electrical and / or thermal conductivity in the final structure). The material of the receiving substrate may also be chosen according to its compatibility with the material of the blocks, for example with a coefficient of thermal expansion close to that of the paving stones. For example, the receiving substrate may include gallium arsenide, sapphire, or glass (non-limiting list).

[0069] The receiving substrate advantageously has a diameter identical to that of the support substrate of the donor pseudo-substrate, but it could possibly have a diameter greater than this.

[0070] To arrange the chips on the receiving substrate with an inter-chip distance greater than the inter-tile distance on the support substrate, localized bonding of the pseudo-donor substrate to the receiving substrate is carried out. By localized bonding, it is meant that the adhesion between the tiles and the receiving substrate does not take place over the entire surface of the tiles in contact with the receiving substrate, but only over a specific part of said surface. The transfer of the chips to the receiving substrate only occurs in the regions where the adhesion is sufficient.

[0071] To control the location of the transferred chips, the surface of the tiles or the receiving substrate is roughened in the regions where it is not desired to transfer chips. The roughened surface typically has a roughness greater than 0.5 nm RMS, preferably greater than 2 nm RMS, which makes it unsuitable for bonding. This allows selective bonding of the tiles only in the unroughened regions.

[0072] The roughening is advantageously carried out by laser irradiation. The wavelength of the laser used can be chosen between 100 nm and 550 nm, preferably between 250 nm and 400 nm. The irradiation is carried out in the form of pulses, the duration of which is typically between 1 ns and 10 ps, ​​more advantageously between 10 ns and 500 ns. For a silicon substrate treated at room temperature by a laser with a wavelength of 308 nm, with a pulse duration of 160 ns, the energy density provided is of the order of 1.9 J / cm2 over areas of 15x15 mm2. The energy density corresponds to the melting threshold of the irradiated material. A person skilled in the art is capable of adjusting the energy density according to the laser at his disposal and the material to be treated.

[0073] Preferably, the irradiation is applied to the receiving substrate rather than to the paving stones so as not to affect the properties of the paving stones, in particular when they are made of a III-V material.

[0074] The roughened areas can be defined solely by a controlled scan of the laser beam on the surface of the receiving substrate, in particular when the areas to be roughened have dimensions of the order of a few millimeters. Alternatively, in particular to more precisely control the size and / or shape of the areas to be roughened, it is possible to carry out the irradiation through a mask applied to the receiving substrate, the mask comprising openings facing the areas to be roughened.

[0075] [Fig.2] illustrates the receiving substrate 3 on which roughened regions 30 have been formed opposite certain blocks of the donor pseudo-substrate.

[0076] It will be noted that the non-roughened regions do not necessarily have the same size or the same shape as the tiles. Indeed, it is possible to roughen a part of the surface of the receiving substrate opposite a tile, for example corresponding to the periphery of said tile, in order to allow the transfer of a chip of a size smaller than that of the tile (the part of the tile in contact with the roughened area not being transferred due to the lack of adhesion).

[0077] In the sectional view of [Fig.2], the roughened regions 30 have been shown in slight relief relative to the rest of the surface of the receiving substrate 3 to facilitate their visualization, but they are generally coplanar with the rest of this surface.

[0078] The bonding comprises an alignment of the donor pseudo-substrate and the recipient substrate, in order to ensure that the roughened regions are opposite the blocks, then a contacting of the recipient substrate and the blocks.

[0079] For this alignment, the flat or notch which is generally present at the periphery of the substrates is in principle sufficient. Alternatively, the bonding machine can take into account the edges of the tiles to carry out the alignment, or use alignment patterns placed on the receiving substrate.

[0080] After bringing the blocks of the donor pseudo-substrate and the recipient substrate into contact, the chips are detached along the weakening zone. In a manner known per se (Smart Cut™ process), the detachment can be initiated by a heat treatment, a mechanical and / or chemical action at the weakening zone.

[0081] This detachment, and the transfer of the chips onto the receiving substrate, only occurs in the regions where the adhesion between the tiles and the receiving substrate is sufficient, i.e. in the non-roughened regions. In the roughened regions, the transfer does not occur, so that the tiles remain entirely on the support substrate.

[0082] Thus, as illustrated in [Fig.3], only a portion of the chips 1' have been transferred onto the receiving substrate 3. As a result, the distance d2 between two adjacent chips 1' on the receiving substrate 3 is greater than the initial distance dl between the tiles of the donor pseudo-substrate 10.

[0083] The distance d2 may be greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

[0084] The remainder of the donor pseudo-substrate, which includes the remainder of the tiles from which the chips have been detached, and the tiles from which the chips have not been detached, can possibly be recycled for the purpose of a new chip transfer.

[0085] We will now describe different embodiments of the invention.

[0086] In the case illustrated in Figures 2 and 3, only a portion of the chips were transferred. The remainder of the donor pseudo-substrate therefore comprises tiles of two different thicknesses.

[0087] To recycle the donor pseudo-substrate, it is therefore necessary to carry out mechanical abrasion to bring all the blocks to the same thickness, then mechanical-chemical polishing to obtain a surface that is sufficiently smooth for bonding.

[0088] However, this recycling involves consuming, on the paving stones which have not been glued, a thickness of material corresponding to the thickness of the chips.

[0089] Different solutions are possible to optimize the use of paving material and / or avoid wasting paving material, particularly when it is expensive.

[0090] A first solution consists of using the donor pseudo-substrate several times to transfer chips onto one or more recipient substrates.

[0091] As illustrated in [Fig.4], the blocks are distributed into two groups distributed over the surface of the support substrate. For example, the donor pseudo-substrate comprises an alternation of blocks 11 of a first group and blocks 12 of a second group. The distance dl between two adjacent blocks, in particular of two different groups, is less than or equal to 250 pm. On the other hand, the distance between two adjacent blocks of the same group is greater than 250 pm, preferably greater than 1 mm.

[0092] The tiles of the two groups may be formed from the same material or stack of materials. Alternatively, the tiles of the two groups may be formed from two different materials or stacks of different materials. For example, the tiles of the first group may comprise one semiconductor material and the tiles of the second group may comprise another semiconductor material, or a piezoelectric material.

[0093] The chips are transferred in two steps, depending on the group to which they belong.

[0094] In a first step, a weakening zone 110 is selectively formed in the blocks 11 of the first group. For this purpose, a mask 4, for example made of graphite, is placed opposite the surface of the blocks, the mask comprising openings opposite the blocks 11 of the first group ([Fig.5A]). Ion implantation is then carried out through the mask, so as to form the weakening zone 110 in the blocks 11 of the first group but not in the blocks 12 of the second group.

[0095] Furthermore, the surface of the receiving substrate is locally roughened, in the regions intended to be in contact with the blocks of the second group.

[0096] With reference to [Fig.5B], the donor pseudo-substrate is bonded to the receiving substrate. Given the roughening, adhesion only occurs between the blocks 11 of the first group and the receiving substrate 3.

[0097] The blocks 11 of the first group are detached along the respective weakening zone 110, so as to transfer the chips 11' onto the receiving substrate 3 ([Fig.5C]). The receiving substrate 3 therefore comprises chips 11' spaced apart by a distance d2 greater than d1.

[0098] The donor pseudo-substrate can be reused directly for a second chip transfer step.

[0099] A weakening zone 120 is selectively formed in the blocks 12 of the second group. For this purpose, a mask 4, for example made of graphite, is placed opposite the surface of the blocks, the mask comprising openings opposite the blocks 12 of the second group ([Fig.5D]). Ion implantation is then carried out through the mask, so as to form the weakening zone 120 in the blocks of the second group but not in the remainder of the blocks of the first group.

[0100] Furthermore, the surface of a receiving substrate is locally roughened, in the regions intended to be in contact with the tiles of the first group. The receiving substrate may be the same as the receiving substrate used in the first step, for example when the chips of the first and second groups are intended to be transferred into different areas of the receiving substrate. In this case, the relative orientation of the donor pseudo-substrate and the receiving substrate may be different between the two chip transfer steps, depending on the desired arrangement in the final structure. Alternatively, a receiving substrate different from that of the first step is used for the second step.

[0101] With reference to [Fig.5E], the donor pseudo-substrate is bonded to the receiving substrate. Given the roughening, adhesion only occurs between the blocks 12 of the second group and the receiving substrate 3.

[0102] The blocks 12 of the second group are detached along the respective weakening zone 120, so as to transfer the chips 12' onto the receiving substrate ([Fig.5F]). The receiving substrate 3 therefore comprises chips 12' spaced apart by a distance d2 greater than d1.

[0103] The surface of the blocks of the second group having been polished before the first chip transfer step, it is suitable for bonding and no chemical-mechanical polishing is therefore necessary between the two chip transfer steps.

[0104] At the end of the second step, the donor pseudo-substrate can be recycled, in particular by implementing chemical-mechanical polishing, to implement two new chip transfer steps as described above.

[0105] It would of course be possible to provide more than two groups of tiles and consequently more than two chip transfer steps.

[0106] A second solution to save pad material is to use a different material for pads not intended for chip transfer.

[0107] As illustrated in [Fig.6], the donor pseudo-substrate 10 is formed by arranging on the support substrate 2 tiles of interest 1, which are intended for the transfer of a chip onto the receiving substrate, and tiles 5 of another material, generally less expensive than the material of the tiles of interest. These other tiles 5 are sacrificial tiles, intended solely to fill the gaps between the tiles of interest to ensure that the distance dl between two adjacent tiles is less than 250 pm, in order to avoid rounding the edge of the tiles of interest during chemical-mechanical polishing, and to avoid damaging the polishing pad. Preferably, each tile of interest is surrounded by sacrificial tiles on each of its edges, in order to allow homogeneous polishing of said tile of interest.

[0108] The sacrificial tiles may be made of a material of the same composition as the tiles of interest, but have a lower crystalline quality. For example, if the tiles of interest are made of monocrystalline InP, the sacrificial tiles may be made of polycrystalline InP, or of monocrystalline InP having a high dislocation rate. An advantage of using the same material for the tiles of interest and the sacrificial tiles is that all of the tiles have the same behavior with respect to chemical-mechanical polishing, in particular the same hardness and the same material removal rate. It is therefore possible to achieve homogeneous polishing of all of the tiles.

[0109] Alternatively, the sacrificial blocks may be made of a material of different composition than that of the blocks of interest. In this case, the material of the sacrificial blocks must preferably be chosen to have a behavior close to that of the material of the blocks of interest with respect to chemical-mechanical polishing, in particular in terms of material removal rate (the ratio of the removal rates must typically be less than 2) and chemical reactivity with respect to the slurry. In practice, the person skilled in the art knows how to find suitable pairs of materials for the blocks of interest and the sacrificial blocks either by choosing the slurry and adapting the material of the sacrificial blocks accordingly, or by choosing the material of the sacrificial blocks and carrying out a study to determine or even tailor a slurry to have a similar material removal rate and chemical reactivity.

[0110] The pseudo-donor is subjected to ion implantation at least in the tiles of interest so as to delimit the chips to be transferred.

[0111] Depending on the behavior of the material of the sacrificial paving stones with respect to the implantation, in particular in terms of bubbling, the implantation can be carried out simultaneously in the sacrificial paving stones.

[0112] Alternatively, in particular if the material of the sacrificial tiles generates defects linked to bubbling, the implantation is carried out only in the tiles of interest, using a mask as described in the previous embodiment.

[0113] Bubbling is a phenomenon known to those skilled in the art, in which the ionic species implanted in the material generate a deformation of the free surface of the material under the effect of a heat treatment. The bubbles thus formed are therefore likely to harm the bonding.

[0114] The receiving substrate is subjected to localized roughening, so as to roughen the surface opposite the sacrificial blocks.

[0115] The donor pseudo-substrate is bonded to the receiving substrate. Given the roughening, adhesion only occurs between the blocks of interest and the receiving substrate.

[0116] When detaching the tiles along the weakening zone, only the chips of the tiles of interest 1 are transferred to the receiving substrate, whether the sacrificial tiles 5 have a weakening zone or not.

[0117] On the receiving substrate 3, the chips 1' are therefore separated by a distance d2 greater than dl.

[0118] The donor pseudo-substrate can be recycled for the purpose of reusing the paving stones of interest. For this purpose, mechanical abrasion is carried out if necessary to make the sacrificial paving stones flush with the paving stones of interest, then chemical-mechanical polishing is carried out to make the surface of the paving stones of interest suitable for bonding.

[0119] Another application of roughening is obtaining chips of shapes and / or dimensions different from those of the blocks. Indeed, since the transfer only occurs in sufficiently smooth regions, it is possible to decompose a block into a plurality of chips of smaller dimensions by sticking it on a surface having alternating smooth areas and roughened areas.

[0120] This principle is illustrated schematically in [Fig.7], which shows an enlarged view of two facing zones on the receiving substrate and on the donor pseudo-substrate. The zone of the donor pseudo-substrate corresponds to a single tile 1. The zone 32 of the receiving substrate 3, on the other hand, comprises several regions of different roughness: smooth regions 31, suitable for bonding the tile, and roughened regions 30 extending between the smooth regions, unsuitable for bonding. In the illustrated embodiment, these regions are arranged in a checkerboard pattern, but it goes without saying that they could take any other shape depending on the desired shape for the chips.

[0121] After bonding the block 1 to said zone 32 of the receiving substrate, and detaching the block along the weakening zone, only the portions of block actually bonded to the receiving substrate are transferred to the receiving substrate and form chips.

[0122] The minimum size of the roughened regions depends on the laser used.

[0123] It may be useful to use a mask to more precisely control the size and shape of the regions to be roughened, in particular when they have a size of less than 100 μm. The mask comprises openings corresponding to the regions to be roughened, so as to only allow irradiation of the surface of the receiving substrate at the level of these openings, and to protect the rest of the surface of the receiving substrate.

[0124] Naturally, the embodiments presented above can be combined.

[0125] Regarding the bonding conditions of the paving stones and the receiving substrate, a person skilled in the art may use any known and appropriate technique depending on the materials considered. Thus, for example, he may form a dielectric layer, for example SiO2, Al2O3, AlN or SiN on the surface of the paving stones and / or the receiving substrate, in order to carry out an oxide-on-oxide bonding. Alternatively, a person skilled in the art may use an intermediate bonding layer, such as a metal or a polymer. The bonding may preferably be carried out at atmospheric pressure, but if necessary, vacuum bonding may be carried out. A person skilled in the art may also carry out annealing in order to reinforce the bonding energy.

Claims

Claims

1. A method for transferring chips onto a receiving substrate from tiles arranged on a support substrate, comprising: - forming a substrate (10), called a donor pseudo-substrate, comprising the support substrate (2) and the tiles (1, 11, 12), in which two adjacent tiles are separated by a first distance (dl), - carrying out chemical-mechanical polishing of the tiles (1), - forming a weakening zone (110, 120) in at least a portion of the tiles (1, 11, 12) so as to delimit a respective chip (1', 11', 12'), - bonding the donor pseudo-substrate (10) to the receiving substrate (3) via the tiles (1, 11, 12), - detaching the tiles (1, 11, 12) along the weakening zone (110, 120) in at least a portion of the tiles (1, 11, 12) so as to delimit a respective chip (1', 11', 12'), - gluing the donor pseudo-substrate (10) onto ... detaching the tiles (1, 11, 12) along the weakening zone (110, 120) in at least a portion of weakening (110, 120) so as to transfer a respective chip (1', 11', 12') onto the receiving substrate (3), two adjacent chips being separated by a second distance (d2) greater than the first distance (dl),said method being characterized in that it comprises, before bonding, a localized roughening of the surface of the tiles (1, 11, 12) and / or of the receiving substrate (3) to make regions (30) of said surface unsuitable for bonding, so as to prevent the transfer of the chips into said regions.

2. A method according to claim 1, wherein the roughening is carried out by localized laser irradiation of the surface of the receiving substrate (3).

3. Method according to claim 2, wherein the laser irradiation is carried out with a laser having a wavelength between 100 nm and 550 nm, preferably between 250 nm and 400 nm, according to pulses of a duration between 1 ns and 10 ps, ​​preferably between 10 ns and 500 ns.

4. A method according to claim 2, comprising applying a mask defining a pattern and irradiating the surface through the mask.

5. Method according to claim 4, in which the pattern is chosen to delimit a plurality of zones of the receiving substrate separated by roughened zones opposite the same tile, so as to allow the tile to be divided into several chips according to said pattern.

6. Method according to one of claims 1 to 5, in which the first distance (dl) is less than or equal to 250 pm, preferably less than or equal to 100 pm.

7. Method according to one of claims 1 to 6, in which the second distance (d2) is greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

8. Method according to one of claims 1 to 7, in which the formation of the weakening zone is carried out by implantation of ionic species.

9. A method according to one of claims 1 to 8, wherein the donor pseudosubstrate comprises a first group and a second group of tiles (11, 12).

10. Method according to claim 9, in which the blocks (11) of the first group and the blocks (12) of the second group are successively transferred onto at least one receiving substrate.

11. Method according to claim 10 in combination with claim 8, comprising: - selective implantation of ionic species in the tiles (11) of the first group to form a weakening zone (110) so as to delimit a chip (11') in said tiles of the first group, - localized roughening of a first receiving substrate (3) opposite the tiles (12) of the second group, - bonding of the donor pseudo-substrate on the first receiving substrate (3), - detaching the tiles (11) of the first group along the weakening zone (110) to transfer the respective chips (11') onto the first receiving substrate (3), - from the donor pseudo-substrate resulting from the detachment of the tiles of the first group, selective implantation of ionic species in the tiles (12) of the second group to form a weakening zone (120) so as to delimit a chip (12') in said blocks of the second group,- localized roughening of a second receiving substrate opposite the paving stones of the first group, - bonding of the donor pseudo-substrate to the second receiving substrate, - detachment of the tiles of the second group along the weakening zone to transfer the respective chips to the second receiving substrate.

12. Method according to claim 9, in which only the chips (11') of the first group of tiles are transferred onto the receiving substrate (3) and the pseudo-donor substrate (10) is recycled for a new transfer of the chips of the first group of tiles (H).

13. Method according to one of claims 9 to 12, in which the paving stones (11, 12) of the first and second groups are made of different materials.

14. A method according to claim 12, wherein the paving stones (11) of the first group have a higher crystalline quality than the paving stones (12) of the second group.

15. Method according to one of claims 13 or 14, in which the materials of the blocks (11, 12) of the first and second groups have the same material removal rate and the same chemical reactivity with respect to chemical-mechanical polishing.

16. Method according to one of claims 1 to 15, in which the blocks (1, 11, 12) comprise: - 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 (LiTaO3), lithium niobate (LiNbO3), potassium-sodium niobate (KxNal-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 (AIN) or aluminum scandium nitride (AIScN), and / or - an electrically insulating material,such as diamond, strontium titanate, yttria zirconia or sapphire.,

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