CHIP TRANSFER METHOD

Abstract

The invention relates to a method for transferring chips onto a receiving substrate from tiles arranged on a support substrate, comprising: the formation of a substrate (10), called a pseudo-donor substrate, comprising the support substrate (2) and the tiles (1), in which two adjacent tiles are separated by a first distance (d1), the implementation of a mechano-chemical polishing of the tiles, the formation of a weakened zone in at least a part of the tiles so as to delimit a respective chip, the bonding of the pseudo-donor substrate onto the receiving substrate via the tiles, the detachment of the tiles along the weakened 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, a localized roughening of the surface of the tiles and / or the receiving substrate to render regions of said surface unsuitable for bonding,so as to prevent the transfer of chips into said regions. Figure for the abbreviation: Fig 2,

Description

Title of the invention: CHIP TRANSFER METHOD technical field

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

[0002] In the field of microelectronics, optics or optoelectronics, the design of multilayer structures sometimes requires transferring blocks in the form of portions of a layer from a donor substrate onto a support or receiving substrate.

[0003] This type of process is generally called a paving process, and involves a partial transfer of a layer taken from the donor substrate to form one or more paving stones arranged according to a pattern or at a predetermined location on the supporting substrate.

[0004] Such tiling may be necessary due to a size difference between the donor substrate and the support substrate. Indeed, because of this size difference, 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™ process, in which a weakened zone delimiting the layer to be transferred is formed by implanting atomic species in the donor substrate. The donor substrate is then bonded to the support substrate, and the donor substrate is detached along the weakened zone to transfer the layer from the donor substrate to the support substrate. However, this process assumes that the donor substrate and the support substrate are of identical size.

[0006] However, while silicon substrates are available in relatively large sizes, typically with a diameter of 300 mm, other materials of interest currently exist only as smaller, bulk substrates, 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 generated during transfer. This is particularly true of III-V semiconductor materials, including nitrides (for example, in the case of binary compounds, indium nitride (InN), gallium nitride (GaN), and aluminum nitride (Ain)), arsenides (for example, in the case of binary compounds, indium arsenide (InAs), gallium arsenide (GaAs), and aluminum arsenide (AlAs)), and phosphides (for example, in the case of compounds binary, indium phosphide (InP), gallium phosphide (GaP) and aluminium 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 so-called pseudo-donor substrate, forming by implantation of atomic species a zone of embrittlement in each block, gluing the pseudo-donor substrate onto a receiving substrate via the blocks, and detaching each block along the zone of embrittlement so as to transfer a portion of each block onto the receiving substrate.

[0008] 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, prior to bonding, chemical mechanical polishing (CMP) can 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 an abrasive powder with the chemical action of a polishing solution containing the abrasive powder (the abrasive powder and solution together being called the slurry) to flatten the surface of all the paving stones.

[0009] However, if the distance between the pads is large, typically greater than or equal to 250 pm, the polishing pad, which has a certain degree of flexibility, partially enters the gap between the pads and thus erodes the edges of the pads. This rounding of the edges, which is called "edge rounding" in English, reduces the effective surface area of ​​the chips transferred onto the receiving substrate.

[0010] Conversely, the edges of the paving stones degrade the polishing pad very quickly, which necessitates frequent replacement of the polishing pad, increasing the cost of the mechano-chemical 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 is to reduce the size of the chips transferred onto the donor substrate by applying a photolithography mask to locally protect part of the chip surface and expose another part. Localized etching can then be performed on the portion of the chips exposed by the mask. This has the effect of reducing the size of the chips and increasing the distance between adjacent chips.

[0014] However, this process is not entirely satisfactory because it requires high precision in mask placement and significantly increases the manufacturing time of the final structure. Furthermore, it consumes a significant amount of chip material, which is generally expensive. Therefore, this process is not economically viable on an industrial scale. Summary of the invention

[0015] An object of the invention is therefore to design a chip transfer method which avoids rounding of the edge of the chips, even when the chips are far apart 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 supporting substrate and the paving stones, in which two adjacent paving stones are separated by a first distance, - the implementation of a mechano-chemical polishing of the paving stones, - the formation of a weakened zone in at least part of the paving stones so as to delimit a respective chip, - the bonding of the donor pseudo-substrate to the receiving substrate via the paving stones, - the detachment of the paving stones 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, a localized roughening of the surface of the paving stones and / or the receiving substrate to render regions of said surface unsuitable for bonding, so as to prevent the transfer of chips in said regions.

[0018] Localized roughening allows the formation, at the bonding interface, of regions where adhesion between the tiles and the receiving substrate is insufficient to permit chip transfer into these regions. It therefore enables the selective transfer of chips onto the receiving substrate, transitioning from a high tile density in the donor pseudo-substrate to a lower chip density in the final structure. Since only the desired chips are transferred to the receiving substrate, there is no waste of chip material.

[0019] According to other advantageous but optional features, possibly combined where technically feasible:

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

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

[0022] - the method comprises the application of a mask defining a pattern and the irradiation of 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 the 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 achieved by planting 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 paving stones of the first group and of the paving stones of the second group on at least one receiving substrate;

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

[0030] - only the chips from the first group of tiles are transferred onto the substrate receiver and we recycle the pseudo-donor substrate for a new transfer of 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 exhibit a crystalline quality superior to that of the paving stones of the second group;

[0033] - the materials of the paving stones in the first and second groups exhibit substantially a same material removal rate and same chemical reactivity with respect to mechano-chemical polishing;

[0034] - the paving stones include: - a semiconductor material, such as a III-V material, in particular indium nitride (InN), gallium nitride (GaN), aluminium nitride (Ain), indium arsenide (InAs), gallium arsenide (GaAs), aluminium arsenide (AlAs), indium phosphide (InP), gallium phosphide (GaP) or aluminium phosphide (A1P), 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 lead-magnesium niobate-lead titanate compound (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 features and advantages of the invention will become apparent from the detailed description that follows, with reference to the accompanying drawings, in which:

[0036] - Fig. 1 presents a top view and a cross-sectional view of a pseudo-substrate donor according to an embodiment of the invention;

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

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

[0039] - Figure 4 presents a cross-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 in two transfers successive chips from the donor pseudo-substrate of the [Fig.4];

[0041] - Figure 6 presents a cross-sectional view and a top view of a pseudo-substrate donor according to an embodiment comprising interest blocks and sacrificial blocks;

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

[0043] For the sake of readability of the figures, the various elements have not necessarily been shown to scale. Elements designated by the same reference symbol from one figure to another designate similar elements, which are therefore not described each time. DETAILED DESCRIPTION OF IMPLEMENTATION METHODS

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

[0045] With reference to [Fig. 1], a pseudo-donor substrate 10 is formed by arranging the paving stones 1 on a supporting substrate 2.

[0046] The support substrate provides mechanical support for the paving stones. The support substrate can be made of silicon, glass, or sapphire (this list is not exhaustive). The layer shown around the support substrate 2 in [Fig. 1] 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 even more preferably greater than or equal to 300 mm.

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

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

[0050] - a semiconductor material, such as a III-V material, in particular nitride indium (InN), gallium nitride (GaN), aluminium nitride (AIN), indium arsenide (InAs), gallium arsenide (GaAs), aluminium arsenide (AlAs), indium phosphide (InP), gallium phosphide (GaP) or aluminium phosphide (A1P), or a material IV or IV-IV, including germanium or silicon carbide (SiC),

[0051] - a piezoelectric material, such as lithium tantalate (LiTaO3), niobate lithium (LiNbO3), potassium-sodium niobate (KxNai_xNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), a lead-magnesium niobate-lead titanate compound (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, the yttria 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 blocks have four straight edges and are arranged at regular intervals to form a grid comprising a set of parallel lines and columns. It should be noted, however, that this arrangement of the blocks is given for illustrative purposes only; thus, the blocks may have different shapes or be arranged at different distances from each other. Furthermore, the blocks are not necessarily square, but may have any other shape suitable for the intended use, with or without a straight edge. For example, the blocks may be rectangular, circular, 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 opposite edges of two adjacent tiles. The distance dl can be the same for all 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 paving stones can 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 paving stones have the same thickness as the respective donor substrate. In general, the thickness of the paving stones is between 50 µm and 1 mm, for example, on 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 made of one of the following materials: an adhesive tape held by a frame, silicon, or glass (non-limiting list).

[0059] The paving stones are then glued to the substrate, and the temporary support is removed to expose the opposite surface of the paving stones. Advantageously, the paving stones are glued directly to the substrate, but it is also possible to use an adhesive layer between the paving stones and the substrate.

[0060] Alternatively, the tiles can be assembled directly onto the substrate with sufficient precision using a robot and alignment marks placed on the substrate. This avoids the need for temporary support and the transfer of the tiles from the temporary support to the substrate to form the donor pseudo-substrate.

[0061] Next, a mechano-chemical polishing of the free surface of the paving stones is implemented.

[0062] Optionally, this mechano-chemical polishing can be preceded by a planarization step of the paving stones by mechanical abrasion ("grinding"). Such planarization can be particularly advantageous when the paving stones have different thicknesses, in order to bring their free surfaces into a nearly uniform 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 proceed directly to mechano-chemical polishing.

[0063] Chemical-mechanical polishing makes it possible to smooth the surface of the paving stones to obtain a roughness compatible with bonding to a receiving substrate. This roughness is typically less than 0.5 nm RMS. Such roughness is conventionally measured using an atomic force microscope (AFM) over a 1 pm x 1 pm field. 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 them. 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 part of the tiles so as to delimit a chip to be transferred onto a receiving substrate.

[0066] The embrittlement zone is typically formed by an ion implantation, preferably of hydrogen and / or helium. Those skilled in the art can define the operating conditions for this implantation, depending on the material of the tiles and the thickness of the chip to be transferred.

[0067] The formation of the embrittlement zone is preferably carried out after the mechano-chemical polishing, but it can possibly be carried out before.

[0068] The receiving substrate can be a silicon substrate, but other materials can be considered. In particular, the choice of material can be guided by the intended application (for example, to address electrical and / or thermal conductivity issues in the final structure). The material of the receiving substrate can also be chosen based on its compatibility with the paving stone material, 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-exhaustive list).

[0069] The receiving substrate advantageously has the same diameter as the supporting substrate of the donor pseudo-substrate, but it could possibly have a diameter greater than the latter.

[0070] To arrange the chips on the receiving substrate with an inter-chip distance greater than the inter-pad distance on the support substrate, a localized bonding of the pseudo-donor substrate to the receiving substrate is performed. Localized bonding means that the adhesion between the pads and the receiving substrate does not occur over the entire surface of the pads in contact with the receiving substrate, but only over a specific portion of said surface. The transfer of the chips to the receiving substrate occurs only in the areas where the adhesion is sufficient.

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

[0072] Roughening is advantageously achieved 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 and a pulse duration of 160 ns, the energy density delivered is on the order of 1.9 J / cm² over areas of 15 x 15 mm². The energy density corresponds to the melting point of the irradiated material. A person skilled in the art is able to adjust the energy density according to the laser available and the material to be treated.

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

[0074] Roughened areas can be defined solely by a guided scan of the laser beam across the surface of the receiving substrate, particularly when the areas to be roughened are on the order of a few millimeters in size. Alternatively, especially for more precise control of the size and / or shape of the areas to be roughened, irradiation can be carried out through a mask applied to the receiving substrate, the mask having openings opposite the areas to be roughened.

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

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

[0077] In the cross-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 includes an alignment of the donor pseudo-substrate and the receiving substrate, in order to ensure that the roughened regions are opposite the paving stones, then a contacting of the receiving substrate and the paving stones.

[0079] For this alignment, the flat surface or notch that is generally present at the periphery of the substrates is in principle sufficient. Alternatively, the gluing machine can take into account the edges of the paving stones to perform the alignment, or use alignment patterns placed on the receiving substrate.

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

[0081] This detachment, and the transfer of the chips onto the receiving substrate, only occurs in 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 the tiles remain entirely on the supporting 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 can be greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

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

[0085] We will now describe different forms of embodiment 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 and then mechano-chemical polishing to obtain a surface smooth enough for bonding.

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

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

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

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

[0092] The blocks in both groups may be made of the same material or a stack of materials. Alternatively, the blocks in both groups may be made of two different materials or stacks of different materials. For example, the blocks in the first group may comprise a semiconductor material and the blocks in the second group may comprise another semiconductor material, or a piezoelectric material.

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

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

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

[0096] With reference to [Fig. 5B], the donor pseudo-substrate is bonded to the receiving substrate. Due to the roughening, adhesion occurs only 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 embrittlement 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 at a distance d2 greater than dl.

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

[0099] A weakened zone 120 is selectively formed in the blocks 12 of the second group. To this end, a mask 4, for example made of graphite, is placed opposite the surface of the blocks, the mask having 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 weakened zone 120 in the blocks of the second group but not in the remaining blocks of the first group.

[0100] Furthermore, the surface of a receiving substrate is locally roughened in the areas intended to be in contact with the chips 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 to different areas of the receiving substrate. In this case, the relative orientation of the donor pseudo-substrate and the receiving substrate may differ between the two chip transfer steps, depending on the desired arrangement in the final structure. Alternatively, a different receiving substrate is used for the second step than for the first step.

[0101] With reference to [Fig. 5E], the donor pseudo-substrate is bonded to the receiving substrate. Due to the roughening, adhesion occurs only 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 embrittlement zone 120, so as to transfer the chips 12' onto the receiving substrate ([Fig. 5F]). The receiving substrate 3 therefore comprises chips 12' spaced at a distance d2 greater than dl.

[0103] The surface of the second group's tiles having been polished before the first chip transfer step, it is suitable for bonding and therefore no mechano-chemical polishing is 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 a mechano-chemical polishing, to implement two new chip transfer steps as described above.

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

[0106] A second solution for saving the paving material is to use a different material for the paving stones which are not intended for the transfer of a chip.

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

[0108] Sacrificial blocks may be made of a material with the same composition as the blocks of interest, but with a lower crystalline quality. For example, if the blocks of interest are made of single-crystal InP, the sacrificial blocks may be made of polycrystalline InP, or of single-crystal InP with a high dislocation rate. One advantage of using the same material for the blocks of interest and the sacrificial blocks is that all the blocks exhibit 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 the blocks.

[0109] Alternatively, the sacrificial blocks may be made of a material with a different composition than the blocks of interest. In this case, the material of the sacrificial blocks should preferably be chosen to have behavior similar to that of the material of the blocks of interest with respect to chemical polishing, particularly in terms of material removal rate (the ratio of removal rates typically being less than 2) and chemical reactivity with respect to the slurry. In practice, those skilled in the art know how to find suitable material pairs 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 conducting 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 blocks of interest so as to delimit the chips to be transferred.

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

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

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

[0114] The receiving substrate is subjected to localized roughening, so as to roughen the surface in relation to the sacrificial paving stones.

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

[0116] During the detachment of the blocks along the embrittlement zone, only the chips of the blocks of interest 1 are transferred to the receiving substrate, whether the sacrificial blocks 5 have an embrittlement 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 reuse of the blocks of interest. For this purpose, mechanical abrasion is carried out, if necessary, to make the sacrificial blocks flush with the blocks of interest, followed by mechano-chemical polishing to make the surface of the blocks of interest suitable for bonding.

[0119] Another application of roughening is obtaining chips of different shapes and / or dimensions than 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 smaller chips by gluing it onto a surface having alternating smooth and roughened areas.

[0120] This principle is schematically illustrated in [Fig. 7], which shows a magnified view of two opposing zones on the receiving substrate and the donor pseudo-substrate. The zone of the donor pseudo-substrate corresponds to a single pad 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 pad, 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 is understood that they could take any other form depending on the desired shape of the chips.

[0121] After the bonding of the paving stone 1 to said zone 32 of the receiving substrate, and detachment of the paving stone along the weakening zone, only the portions of the paving stone actually bonded to the receiving substrate are transferred onto 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 employ a mask that allows for more precise control of the size and shape of the areas to be roughened, particularly when they are smaller than 100 µm. The mask includes openings corresponding to the areas to be roughened, so as to allow irradiation of the surface of the receiving substrate only 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 employ any known and appropriate technique depending on the materials involved. For example, they may form a dielectric layer, such as SiO2, Al2O3, A1N, or SiN, on the surface of the paving stones and / or the receiving substrate to achieve oxide-on-oxide bonding. Alternatively, a person skilled in the art may use an intermediate bonding layer, such as a metal or a polymer. Bonding may preferably be carried out at atmospheric pressure, but if necessary, vacuum bonding may be performed. A person skilled in the art may also use annealing to increase the bond strength.

Claims

Demands

1. A method for transferring chips onto a receiving substrate from tiles arranged on a support substrate, comprising: - the formation of a substrate (10), called a pseudo-donor substrate, comprising the support substrate (2) and the tiles (1, 11, 12), in which two adjacent tiles are separated by a first distance (dl), - the implementation of a mechano-chemical polishing of the tiles (1), - the formation of a weakened zone (110, 120) in at least a portion of the tiles (1, 11, 12) so as to delimit a respective chip (1', 11', 12'), - the bonding of the pseudo-donor substrate (10) to the receiving substrate (3) via the tiles (1, 11, 12), - the detachment of the tiles (1, 11, 12) along the weakened zone (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 process being characterized in that it comprises, prior to bonding, a localized roughening of the surface of the paving stones (1, 11, 12) and / or the receiving substrate (3) to render regions (30) of said surface unsuitable for bonding, so as to prevent the transfer of 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. A 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, in 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 the application of a pattern-defining mask and the irradiation of the surface through the mask.

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

6. A method according to any one of claims 1 to 5, wherein the first distance (dl) is less than or equal to 250 pm, preferably less than or equal to 100 pm.

7. A method according to any one of claims 1 to 6, wherein the second distance (d2) is greater than or equal to 1 mm, preferably greater than or equal to 2 mm.

8. A method according to any one of claims 1 to 7, wherein the formation of the embrittlement zone is achieved by implanting ionic species.

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

10. A method according to claim 9, wherein the paving stones (11) of the first group and the paving stones (12) of the second group are successively transferred onto at least one receiving substrate.

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

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

13. A method according to any one of claims 9 to 12, wherein 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 crystalline quality superior to that of the paving stones (12) of the second group.

15. A method according to any one of claims 13 or 14, wherein the paving materials (11, 12) of the first and second groups exhibit the same rate of material removal and the same chemical reactivity towards mechano-chemical polishing.

16. A method according to any one of claims 1 to 15, wherein 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), or sodium potassium niobate (KxNal-xNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), a lead-magnesium niobate-lead titanate compound (PMN-PT), zinc oxide (ZnO), aluminium nitride (AIN) or aluminium-scandium nitride (AIScN), and / or - an electrically insulating material,such as diamond, strontium titanate, yttria-treated zirconia, or sapphire.

Images