Method for treating a surface of a substrate and method for transferring a portion of tiles

Abstract

The invention relates to a treatment method for treating a surface (22) of a substrate (1), the substrate (1) comprising a peripheral zone (2) and an inner zone (4), the inner zone being provided with a plurality of tiles (20, 20a), the treatment method comprising steps of: - depositing a spacer (30) in the peripheral zone of the substrate, around the inner zone; and - polishing the surface of the substrate so as to obtain uniformity of a surface of the inner zone of the substrate. A method for transferring a portion of tiles from a donor substrate (10) to a receiver substrate is also described.

Description

DESCRIPTION TITLE: Process for treating a substrate surface and process for transferring a portion of paving stones TECHNICAL FIELD

[0001] The present invention relates generally to the field of semiconductor materials for microelectronic components.

[0002] The invention relates more particularly to a method for treating a substrate surface. The present invention also relates to a method for transferring a portion of paving stones from a donor substrate to a receiving substrate.

[0003] The invention finds a particularly advantageous application in the case of semiconductor substrates made by transferring at least one layer onto a support. STATE OF THE ART

[0004] Indium phosphide (InP) is increasingly used in photonics and power electronics applications, particularly to meet the needs of emerging areas of electronics. Power devices and integrated power supply systems using indium phosphide are especially popular for high-frequency and high-power electronic applications, due to the greater electron mobility of indium phosphide compared to traditional semiconductor materials such as silicon.

[0005] However, the use of indium phosphide for industrial microelectronic applications remains expensive and difficult to source for large substrates. Therefore, it is advantageous to use thin-film transfer solutions to fabricate composite structures that include an indium phosphide layer on a lower-cost substrate (e.g., silicon).

[0006] A well-known thin-film transfer solution is the Smart Cut™ process. This process allows, for example, the fabrication of a composite structure comprising a thin film, such as indium phosphide, taken from a donor substrate, in direct contact with a support substrate, such as silicon. or even in polycrystalline silicon carbide (p-SiC). Indium phosphide, for example, is present in the form of blocks on the donor substrate.

[0007] For the thin-film transfer process to be effective, and in particular the step of bonding paving stones, for example, to a receiving substrate, it is essential to ensure surface uniformity at the level of the thin film to be transferred. Specifically, a surface treatment is implemented to make it flat and reduce any roughness. For this purpose, a polishing step, such as chemical mechanical polishing (CMP), can be carried out.

[0008] However, due to the gaps between the paving stones and their potentially different geometries, the surface to be polished is not perfectly flat and may exhibit significant roughness. Differences in surface uniformity then appear after polishing, particularly on the edges of the outer paving stones (as the polishing speed is higher at these edges). SUMMARY OF THE INVENTION

[0009] The present invention therefore aims to improve the surface treatment of a substrate fitted with paving stones in order to guarantee a uniform surface after a polishing step.

[0010] The invention relates to a method for treating the surface of a substrate, the substrate comprising a peripheral zone and an internal zone, the internal zone being provided with a plurality of tiles, the treatment method comprising the following steps:

[0011] - placement of a spacer at the peripheral zone of the substrate, around the internal zone, and

[0012] - polishing the surface of the substrate to obtain uniformity of the surface of the internal zone of the substrate.

[0013] Thus, advantageously according to the invention, depositing the spacer in the peripheral zone of the substrate before the polishing step makes it possible to maintain a constant gap between a substrate support and a polishing head used during the polishing step, thereby ensuring uniform treatment of a free surface paving stones. Furthermore, the spacer is easy to install and remains an economical solution to ensure this surface uniformity.

[0014] Thus, following the treatment process according to the invention, a paving substrate is obtained in which the pavers have a uniform free surface (i.e., without shape defects or roughness and with a substantially constant thickness for all the pavers). This substrate can then be used for various applications.

[0015] In addition to the characteristics mentioned in the preceding paragraph, the treatment process according to the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations:

[0016] - polishing is a mechano-chemical polishing;

[0017] - the spacer is angularly equidistributed around the internal zone of the substrate;

[0018] - the spacer is placed around the perimeter of the internal zone of the substrate, the spacer covering at least 40% of a perimeter of the perimeter of the internal zone of the substrate;

[0019] - the spacer has a discontinuous shape around the internal zone of the substrate;

[0020] - the plurality of paving stones including external paving stones positioned at the edge of the internal area of ​​the substrate, a distance between the external paving stones and the spacer is greater than 200 micrometers;

[0021] - the plurality of paving stones including external paving stones positioned at the edge of the internal area of ​​the substrate, a distance between the external paving stones and the spacer is less than 30 millimeters;

[0022] - the thickness of the spacer is approximately on the order of the thickness of one block of the plurality of blocks;

[0023] - the thickness of the spacer is between 100 micrometers and 10 millimeters;

[0024] - the thickness of the spacer is between 100 and 1000 micrometers, or even between 50 and 10,000 micrometers;

[0025] - the spacer comprises a polymer material;

[0026] - The spacer placement step includes the following steps:

[0027] a) arrangement of the spacer on the peripheral area of ​​the substrate, and

[0028] b) crosslinking of the spacer so as to fix the spacer to the surface of the peripheral zone of the substrate;

[0029] - the spacer comprises a ceramic material;

[0030] - Following the polishing step, a step is planned to remove the spacer from the surface of the peripheral zone of the substrate; and

[0031] - the removal step includes a selective wet or dry etching step.

[0032] The invention also relates to a method for transferring a portion of paving stones from a donor substrate to a receiving substrate, the method comprising the steps of:

[0033] - supply of a substrate comprising the donor substrate and a plurality of paving stones formed on the donor substrate, the substrate comprising a peripheral zone and an internal zone, the internal zone being provided with the plurality of paving stones,

[0034] - treatment of a substrate surface according to a treatment process as previously introduced,

[0035] - formation, by ion implantation, of a localized weakening plane in the paving stones,

[0036] - bonding of the donor substrate to the receiving substrate via each tile of the plurality of tiles, a free surface of each tile forming a bonding interface, and

[0037] - detachment of the donor substrate along the weakening plane in order to transfer the portion of each paving stone from the plurality of paving stones onto the receiving substrate.

[0038] Advantageously, the process for transferring a portion of a block according to the invention allows a portion of each block to be transferred from the donor substrate to the receiving substrate in a single iteration, following the bonding and detachment steps. This reduces production time and therefore the production costs of the semiconductor-type structures thus manufactured compared to known processes.

[0039] Furthermore, the paving portion transfer method according to the invention also allows paving portions from different substrates to be transferred so as to transfer paving portions of different types or functionalities onto the receiving substrate.

[0040] Furthermore, another advantage of the paving stone transfer process according to the invention is that the donor substrate can be reused multiple times without the need for recycling. In other words, the donor substrate can be reused several times to transfer other paving stone portions onto the same receiving substrate or onto a different receiving substrate. Such a transfer process therefore minimizes material loss.

[0041] In addition to the characteristics mentioned in the preceding paragraph, the method for transferring a portion of paving stones according to the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations:

[0042] - The bonding step includes a thermal annealing step for both the donor and recipient substrates; and

[0043] - the step of detaching the donor substrate is initiated thermally and / or mechanically by applying a mechanical force aimed at separating the donor substrate from the recipient substrate. BRIEF DESCRIPTION OF THE FIGURES

[0044] Other features and advantages of the invention will become clear from the description given below, which is by way of example and not limitation, with reference to the accompanying figures, including:

[0045] Figure 1 represents a schematic view of a substrate used in the present invention;

[0046] Figure 2 represents a schematic view of a first example of a substrate equipped with a spacer according to the invention;

[0047] Figure 3 shows a schematic view of a second example of a substrate equipped with a spacer according to the invention;

[0048] Figure 4 shows a schematic view of a third example of a substrate equipped with a spacer according to the invention;

[0049] Figure 5 shows a schematic view of a fourth example of a substrate equipped with a spacer according to the invention;

[0050] Figure 6 shows a schematic view of a fifth example of a substrate equipped with a spacer according to the invention;

[0051] Figure 7 shows a schematic view of a sixth example of a substrate equipped with a spacer according to the invention;

[0052] Figure 8 shows a schematic view of a seventh example of a substrate equipped with a spacer according to the invention;

[0053] Figure 9 shows a schematic view of an eighth example of a substrate equipped with a spacer according to the invention;

[0054] Figure 10 shows a schematic view of a ninth example of a substrate equipped with a spacer according to the invention;

[0055] Figure 11 represents a schematic view of a donor substrate and a receiving substrate in the context of a process for transferring a portion of paving stones according to the present invention;

[0056] Figure 12 shows a cross-sectional view of a substrate fitted with paving stones obtained after a polishing step according to the prior art; and

[0057] Figure 13 represents a cross-sectional view of a substrate fitted with paving stones obtained after implementation of the treatment process according to the invention.

[0058] For clarity, identical or similar elements are identified by identical reference symbols across all figures. DETAILED DESCRIPTION OF AT LEAST ONE IMPROVEMENT METHOD

[0059] The present invention aims to improve the surface treatment of a substrate, more particularly a semiconductor substrate, in order to improve surface uniformity after a polishing step. The invention specifically aims to prevent thickness variations that can be observed at substrate edges.

[0060] In this description, the term "surface uniformity" refers to a flat, smooth surface, free from any defect in shape, and whose roughness has been reduced or even completely eliminated. This uniform surface is then compatible with a direct bonding process (as described later in this description).

[0061] Figure 1 represents an example of substrate 1 according to the present invention.

[0062] The substrate 1 according to the invention comprises a donor substrate 10. This donor substrate 10 forms a basic part of the substrate 1. This donor substrate 10 It can, for example, be used in a thin-film transfer process. The donor substrate 10 includes, for example, silicon.

[0063] The substrate 1 comprises an internal zone 4 and a peripheral zone 2. The internal zone 4 of the substrate 1 is provided with a plurality of paving stones 20, 20a.

[0064] The plurality of blocks 20, 20a takes the form of a plurality of portions of a bulk substrate or layer on which electronic components can be fabricated, or in which passive or active electronic components are already formed. This layer from which the blocks 20, 20a are formed comprises, for example, a bulk crystalline material (such as a semiconductor) or a layer with a functional structure (an epitaxial layer, a stack of epitaxial layers, a passive or active device, etc.).

[0065] In practice, the bulk substrate or layer from which the pavers 20, 20a are formed comprises a material that is not commercially available in the form of a large-dimension substrate. These are, for example, III-V semiconductor materials, including nitrides (for example, for binary compounds, indium nitride (InN), gallium nitride (GaN) and aluminium nitride (Ain)), arsenides (for example, for binary compounds, indium arsenide (InAs), gallium arsenide (GaAs) and aluminium arsenide (AlAs)), and phosphides (for example, for binary compounds, indium phosphide (InP), gallium phosphide (GaP) and aluminium phosphide (AIP)). Alternatively, it could also be IV or IV-IV semiconductor compounds, such as germanium and silicon carbide.The paving stones may also include a piezoelectric material, for example lithium tantalate (LiTaOs) or lithium niobate (LiNbOs), potassium-sodium niobate (KxNai-xNbOs or KNN), barium titanate (BaTiOs), quartz, lead titano-zirconiate (PZT), a lead-magnesium niobate and lead titanate compound (PMN-PT), zinc oxide (ZnO), aluminium nitride (AIN) or aluminium-scandium nitride (AIScN) (non-exhaustive list).

[0066] Alternatively, the pavés may include an electrically insulating material, such as diamond, strontium titanate (SrTiOs), yttria zirconia (YSZ), or sapphire.

[0067] Each block 20, 20a has a specific shape. Here, as can be seen in particular in Figure 1, each block 20, 20a has a square shape. The The present invention is not limited to the shape shown. Furthermore, the present invention applies equally if the paving stones have several different shapes.

[0068] As can be seen in Figure 1, two adjacent tiles 20, 20a are separated from each other by a gap 5. Furthermore, it is possible to define so-called "external" tiles (denoted "external tiles 20a" in this description) which are located at the edge of the internal zone 4 of the substrate 1. In other words, these external tiles 20a are those positioned closest to the peripheral zone 2.

[0069] In practice, the thickness of each 20, 20a block is on the order of a few hundred micrometers (pm). For example, the thickness of each 20, 20a block is between 100 and 1000 pm. In this description, the term "thickness" refers to a dimension of the element in question defined orthogonally to the surface of the substrate 1, for example, defined orthogonally to the surface 12 of the donor substrate 10.

[0070] Here, for a square shape, each 20, 20a block has a side dimension on the order of a few millimeters (mm). For example, the side of the square shape of each 20, 20a block is between 2 and 20 mm, preferably between 2 and 15 mm.

[0071] By design, the paving stones 20, 20a are raised relative to the surface 12 of the donor substrate 10 on which they are positioned. This raised area is on the order of the thickness of each paving stone 20, 20a. Each paving stone 20, 20a has a free surface 22 opposite the surface 12 of the donor substrate 10 on which the paving stones 20, 20a are positioned. The surface of the substrate 1 therefore includes the surface 12 of the donor substrate 10 and the free surface 22 of the paving stones 20, 20a.

[0072] The present invention aims to improve the surface uniformity of the substrate 1, and more particularly the uniformity of the free surface 22 of the paving stones 20, 20a. To this end, the invention relates firstly to a method of treating the surface of the substrate 1 (also referred to as the "treatment method" in this description).

[0073] This treatment process first comprises a step of depositing a spacer 30 in the peripheral zone 2 of the substrate 1. More specifically, the spacer 30 is deposited on the surface 12 of the peripheral zone 2 of the substrate 1. The spacer 30 is deposited around the internal zone 4 of the substrate 1. In other In terms of spacers, the spacer 30 is placed around the plurality of paving stones 20, 20a. It should be noted here that the term "around" means "in the surrounding space, nearby, encircling without necessarily being in direct contact." In other words, the spacer 30 is positioned to surround or encircle the plurality of paving stones (regardless of whether it is in contact with them). This also means that the spacer is not placed in the gaps 5 defined between two adjacent paving stones 20, 20a, nor on the paving stones 20, 20a themselves.

[0074] This arrangement is particularly advantageous because, despite the difference in coefficient of thermal expansion between the material in the spacer and those in the substrate and the blocks, it limits substrate deformation, especially if the substrate is primarily composed of silicon. Therefore, even if the substrate were to undergo further heat treatments after the process described above, the risks of deformation (whether bending or warping) or, more seriously, cracking of the substrate would be significantly minimized.

[0075] Furthermore, this arrangement of the spacer makes it easier to implement the treatment process according to the invention because it is not necessary to implement other treatment steps which would aim to remove portions of spacer which would have been deposited on the paving stones or in the gaps.

[0076] Finally, this prevents damage to the paving stones because the spacer is not placed on them.

[0077] Figures 2 to 10 schematically represent several examples for the deposited spacer.

[0078] Advantageously, this spacer 30 maintains a constant gap between a substrate support and a polishing head used during the polishing step (described below), thus ensuring uniform treatment of the free surface 22 of the paving stones 20, 20a. The spacer then forms a retaining material that maintains a constant gap between the polishing head and the surface 12 of the substrate 1.

[0079] More specifically, the thickness step between the surface to be polished and the surface 12 of the substrate 1 is offset here at the level of the spacer 30, thus allowing the free surface 22 of the pavers 20, 20a to be treated uniformly. In other words, the spacer 30 aims to offset the edge of the area to be polished so that the thickness step The space between the surface to be polished and the surface 12 of the substrate 1 is kept away from the paving stones 20, 20a. Thus, a polishing head, used in particular to polish the free surface 22 of the paving stones 20, will not encounter any thickness variation at the paving stones. This ensures uniform surface treatment of the paving stones 20, 20a during a polishing step (described below). Furthermore, the use of a spacer advantageously reduces substrate deformation in the peripheral zone during the application of the polishing head. The spacer then acts as a stiffener for the substrate in the peripheral zone.

[0080] In practice, as can be seen in Figures 2 to 10, the spacer 30 is distributed around the blocks 20, 20a. More specifically, the spacer 30 is angularly equidistributed around the blocks 20, 20a. By "angularly equidistributed," it is understood that the spacer 30 is evenly distributed around the internal zone 4, with respect to a center O of this internal zone 4. In other words, the spacer 30 is uniformly distributed around the internal zone 4, with respect to the center O of the internal zone 4. Put another way, the deposited spacer 30 exhibits symmetry with respect to the center O of the internal zone 4 of the substrate 1.

[0081] Advantageously, the spacer 30 forms a support zone for the polishing head around all the blocks 20, 20a, maintaining a constant gap between the polishing head and the substrate in the internal zone 4. This ensures that all the blocks 20, 20a will have a uniform free surface 22 after the polishing step. Furthermore, the use of a spacer advantageously reduces substrate deformation in the peripheral zone during the application of the polishing head.

[0082] As shown in Figures 4 and 5, the spacer 30 can have a discontinuous shape. This allows, in particular, for drainage spaces 31, 32 to be created, enabling the evacuation of liquids involved, for example, when a mechano-chemical polishing process is carried out.

[0083] Alternatively, as shown in Figures 2, 3, and 6 to 10, spacer 30 can have a continuous shape. A spacer with a continuous shape can be used regardless of the polishing method employed. Furthermore, a spacer with a continuous shape is easier to deposit onto the substrate.

[0084] Advantageously, the spacer 30 is deposited around the perimeter of the internal zone 4 of the substrate 1. In this description, it is understood by “perimeter” is a boundary that delimits the area concerned (here for example the internal zone 4 of substrate 1). This perimeter can have different shapes here.

[0085] As shown in Figures 2 to 4 and 8, the spacer 30 is, for example, deposited in an annular shape. In other words, in this case, the spacer 30 forms a (continuous or discontinuous) bead around the internal area 4 equipped with the blocks 20, 20a.

[0086] In the example in Figure 6, the spacer 30 is placed along an octagonal perimeter.

[0087] In the example in Figure 7, the spacer 30 is in the form of a double cord, one annular in shape and the other octagonal in shape.

[0088] Depositing the spacer 30 along a predefined perimeter allows for minimal use of the deposition material required to form the spacer (making this solution economical). Furthermore, this shape of spacer is easy to deposit.

[0089] In order to ensure optimal surface uniformity (i.e. to guarantee that the free surface of all the pavers 20, 20a undergoes the same treatment and presents the same result at the end of the treatment process), the spacer 30 is placed so as to cover at least 40% of a perimeter of the inner zone 4 of the substrate 1. In this description, "perimeter" means a length of the line that defines the contours of a concerned area.

[0090] Alternatively, the spacer 30 is deposited so as to cover at least 40% of a surface area around the perimeter of the internal zone 4 of the substrate 1

[0091] By combining this proportion of distribution of the spacer 30 and its angular equidistribution around the internal zone 4, the uniformity of the free surface 22 of the pavers 20, 20a is ensured.

[0092] Preferably, the proportion of spacer 30 distributed over the perimeter of the peripheral zone 2 of substrate 1 is greater than 50%. Alternatively, the proportion of spacer 30 distributed over the surface of the peripheral zone 2 of substrate 1 is greater than 50%.

[0093] In the case of the variants shown in Figures 8 to 10, the distribution proportion of spacer 30 is greater than 80% of the surface area of ​​the peripheral zone 2 of the substrate 1. These examples require the use of a larger quantity of deposition material but ensure optimal spacing between the head of polishing and the surface 12 of the substrate 1. The support of the polishing head, relative to the substrate support, is particularly stable here.

[0094] In practice, the spacer 30 is placed at a predefined minimum distance from the outer blocks 20a. Preferably, this minimum distance is approximately 200 pm. In other words, the distance between the outer blocks 20a and the spacer 30 is greater than 200 pm. Such a minimum distance between the spacer 30 and the blocks 20a ensures proper execution of the subsequent polishing step (described later).

[0095] Furthermore, the spacer 30 is not positioned at an excessively large distance from the outer pads 20a. In other words, a predefined maximum distance between the spacer 30 and the outer pads 20a can be defined here. Preferably, the predefined maximum distance is, for example, approximately 30 millimeters (mm). That is to say, the spacer 30 is positioned at a distance from the outer pads 20a that is less than this predefined maximum distance. This positioning at this predefined maximum distance ensures that the benefits provided by the spacer 30 for the polishing step are guaranteed.

[0096] As can be seen in figures 2 to 10, the spacer 30 is distributed at the edge of the peripheral zone 2 of the substrate (figures 2 and 8 to 10) or at a distance from the edge of the peripheral zone 2 of the substrate 1 (therefore at a distance from the edge of the substrate 1).

[0097] A spacer thickness of 30 is, for example, less than 10 millimeters (mm). For example, it is between 100 and 1000 pm, or even between 50 and 10,000 pm.

[0098] Preferably, the thickness of the spacer 30 after the deposition step is approximately the same as the thickness of a paver 20, 20a. By "approximately", it is understood that a difference of less than 10% is observed compared to the thickness of a paver 20, 20a. Using such a thickness for the spacer ensures optimal surface uniformity for the pavers 20, 20a (a difference in thickness between the spacer and the pavers could lead to an imbalance in the positioning of the polishing head and therefore present the risk that the polishing would not necessarily be carried out uniformly on all the pavers 20, 20a).

[0099] In practice, to obtain such a thickness, it is possible to deposit a greater thickness of the spacer and implement a grinding step (or "grinding" according to the commonly used Anglo-Saxon terminology) in order to obtain the desired thickness for the spacer.

[0100] Preferably, the spacer 30 comprises a polymer material. This is, for example, an epoxy resin. Preferably, it is a filled epoxy resin. The use of a polymer material is advantageous because it is easy to handle and inexpensive.

[0101] In the case of a polymer material, the deposition step of the spacer 30 includes, in practice, a step of arranging the spacer 30 on the peripheral zone 2 of the substrate 1 and a step of crosslinking the spacer 30 arranged so as to fix it on the surface 12 of the peripheral zone 2 of the substrate 1.

[0102] Alternatively, the spacer may be made of a ceramic material. Alternatively, the spacer may be made of an oxide.

[0103] More generally, any type of material with properties that allow the spacer to maintain its mechanical integrity during a polishing step, and particularly during a chemical polishing step, can be used. In other words, the spacer must be made of a material that is not attacked or degraded in aqueous, basic, or acidic environments.

[0104] Once the spacer 30 is placed on the surface 12 of the peripheral zone 2 of the substrate 1, the treatment process according to the invention includes a step of polishing the surface of the substrate 1 so as to obtain a uniformity of the surface of the internal zone 4 of the substrate 1. More particularly, this polishing step aims to obtain a uniformity of the free surface 22 of the pavers 20, 20a positioned in the internal zone 4 of the substrate 1.

[0105] The placement of the spacer 30 prior to this polishing step ensures a constant gap between the polishing head and the substrate support in the internal zone 4, thus guaranteeing that all the paving stones 20, 20a will have a uniform free surface 22 after polishing. Thanks to the spacer 30, the thickness difference step is offset at this spacer and is therefore further away from the paving stones. Furthermore, the use of a spacer advantageously reduces substrate deformation in the peripheral zone during the application of the polishing head. The spacer acts as a stiffener for the substrate in the peripheral zone. This allows for uniform polishing of the free surface 22 of the paving stones 20, 20a (even at the edges).

[0106] Preferably, the polishing method used here is a mechano-chemical polishing. This well-known polishing method is not described in detail here. Essentially, it relies on a combined action on the surface to be polished (here, the free surface 22 of the blocks 20, 20a): the polishing head (mechanical effect) and the chemical and abrasive effects of a polishing solution introduced onto the surface. In practice, the substrate 1, positioned on the substrate support, and the polishing head are rotated relative to each other, which removes material from the surface to be treated (here, the free surface 22 of the blocks 20, 20a) and then smooths the surface. This mechano-chemical polishing, combining chemical and mechanical effects, is particularly advantageous for planarizing a substrate, especially a semiconductor substrate.

[0107] Once the polishing step has been implemented, the treatment process may include a step of removing the spacer 30 from the surface 12 of the peripheral zone 2 of the substrate 1. This removal step is optional here.

[0108] In practice, this removal step includes, for example, an etching step to remove the spacer 30 from the surface 12 of the peripheral zone 2 of the substrate 1. This is, for example, a selective etching in wet or dry mode.

[0109] Alternatively, the removal step can be implemented by applying a plasma followed by a wet rinse.

[0110] Alternatively, the removal step can be implemented by applying ultraviolet radiation to degrade the spacer.

[0111] Alternatively, the removal step can be implemented by applying ozone molecules to degrade the spacer.

[0112] Advantageously, according to the invention, depositing the spacer 30 in the peripheral zone 2 of the substrate 1 before the polishing step makes it possible to maintain a constant gap between the donor substrate and a polishing head used during the polishing step, thus ensuring uniform treatment of the free surface 22 of the paving stones 20, 20a. Furthermore, the spacer is easy to deposit in practice and remains an economical solution for ensuring this surface uniformity.

[0113] Furthermore, the arrangement of the spacer around the plurality of paving stones is particularly advantageous because, despite the difference in coefficient of expansion The thermal barrier between the material within the spacer and the materials within the substrate and the blocks limits substrate deformation, particularly if the substrate is primarily composed of silicon. Furthermore, even if the substrate were to undergo further heat treatments after the treatment process according to the present invention, the risks of deformation (whether bending or warping) or, more seriously, cracking of the substrate would be significantly minimized.

[0114] Furthermore, this arrangement of the spacer makes it easier to implement the treatment process according to the invention and prevents the degradation of the paving stones because the spacer is not placed on them.

[0115] Thus, following the treatment process described above, a paved substrate is obtained in which the pavers have a uniform free surface (i.e., without shape defects or roughness and with a constant thickness for all the pavers). The advantages obtained are illustrated more specifically in Figures 12 and 13.

[0116] Figure 12 shows a cross-section of a substrate fitted with paving stones that has undergone a treatment process known in the prior art. As can be seen in this figure, the thickness (denoted y in Figure 12) of the paving stones obtained after the polishing step is not constant (the dashed line A highlights the differences in thickness between the paving stones after polishing). In particular, the outermost paving stone 20a has a thickness much less than the paving stones located in a more central area of ​​the substrate.

[0117] Figure 13 shows a cross-section of a substrate fitted with paving stones subjected to a treatment process according to the present invention. As this figure shows, the thickness (denoted y in Figure 13) of the paving stones obtained after the polishing step is generally constant (line B supports this point by illustrating that all the free surfaces 22 of the paving stones 20, 20a lie on this line B). Indeed, Figures 12 and 13 show a significant rounding of the corners of the paving stones near the peripheral zone (the rim) of the substrate without a spacer, with a paving stone thickness up to 20 µm thinner at the rim compared to the center of the substrate (Figure 12). In the case of the present invention (Figure 13), good thickness uniformity was obtained on the substrate fitted with a spacer, with significantly improved thickness uniformity over the entire surface of the substrate (Figure 13).

[0118] This substrate can then be used for various applications. In particular, this substrate can be used as a donor substrate in a process of transferring a portion of paving stones from a donor substrate to a receiving substrate.

[0119] The present invention also relates to a method of transferring a portion of paving stones from a donor substrate 10 to a receiving substrate 40 (visible in figure 11).

[0120] The process for transferring a portion of paving stones first involves supplying a substrate 1 comprising the donor substrate 10 and the plurality of paving stones 20, 20a. In practice, the paving stones 20, 20a are first cut. Any technique known to those skilled in the art can be used to cut the paving stones 20, 20a. Examples include sawing, cleaving, or laser cutting. This cutting can, for example, be combined with partial plasma engraving (or "plasma dicking" according to the Anglo-Saxon term) of the cut lines.

[0121] The paving stones 20, 20a thus cut are then placed on the donor substrate 10. The placement can be implemented by the "Pick and Place" technique, by which a robot picks up a paving stone, or a group of paving stones, previously cut and places it at a predetermined location on the donor substrate 10.

[0122] In practice, each paving stone 20, 20a adheres to the donor substrate 10 by molecular adhesion. To this end, surface treatments of the paving stones and / or the donor substrate can be carried out beforehand to promote good molecular adhesion. These treatments may include, in particular, cleaning, the deposition of an adhesive layer such as silicon dioxide (SiC>2), plasma activation prior to bonding, and annealing.

[0123] Alternatively, the bonding of the paving stones 20, 20a to the donor substrate 10 may involve an intermediate bonding layer, for example a polymer bonding layer, a eutectic bonding layer or a ceramic bonding layer.

[0124] In order to effectively implement the transfer of a portion 20', 20a' of each paver 20, 20a, the paver transfer process includes a treatment of the substrate surface 1 as previously described. More specifically, this treatment makes it possible to standardize the free surface 22 of the pavers 20, 20a (before their bonding and subsequent transfer) so as to guarantee the efficiency and success of the method of transferring portion 20', 20a' of each paving stone, and in particular the gluing step described below.

[0125] Next, the process of transferring a portion of paving stones includes a step of forming a localized weakening plane in the paving stones 20, 20a. This weakening plane aims to delimit a superficial portion 20', 20a' of each paving stone 20, 20a intended to be transferred onto the receiving substrate 40. This superficial portion 20', 20a' of each paving stone 20, 20a has, for example here, a thickness of less than 1.5 pm (i.e. the depth of the weakening plane).

[0126] In practice, to form the weakening plane, the pavers 20, 20a are exposed to a beam of ionic species. The ionic species penetrate the pavers 20, 20a and become embedded there (at a thickness determined by the placement parameters and corresponding to the target thickness for the layer to be transferred).

[0127] Preferably, the implanted ionic species are hydrogen ions and / or helium ions. A person skilled in the art is able to determine the implantation parameters, including the nature of the ionic species, the dose and the energy of the species, in order to implant the ionic species at the desired depth in the 20, 20a blocks.

[0128] The process for transferring a portion of paving stones then includes a step of bonding the donor substrate 10 to the receiving substrate 40. The donor substrate 10 and the receiving substrate 40 are first positioned opposite each other. Bonding is achieved via the paving stones 20 and 20a, which form a bonding interface. More precisely, bonding occurs only at the paving stones 20 and 20a. The peripheral zone 2 of the substrate 1 remains separate from the receiving substrate 40.

[0129] Preferably, this bonding step includes a thermal annealing step of the donor substrate 10 and the recipient substrate 40. This strengthens the bond between these two substrates.

[0130] Advantageously, each paver 20, 20a then adheres to the receiving substrate 40 by molecular adhesion. In practice, surface treatments of the pavers and / or the receiving substrate can be carried out beforehand to promote good molecular adhesion. These treatments may include, in particular, cleaning, the application of an adhesive layer such as silicon oxide. (SiC>2), plasma activation before bonding and annealing, preferably at low temperature (i.e. typically below 300°C).

[0131] The paving stones 20 and 20a are then detached along the weakening plane in order to transfer the portions 20' and 20a' delimited by the weakening plane onto the receiving substrate 40. More specifically, this detachment is carried out at the portions of the weakening plane located within the paving stones 20 and 20a. A fracture is initiated and then propagates along the weakening plane, which are by nature areas of greater fragility in the substrate. The portions 20' and 20a' of the paving stones 20 and 20a from the donor substrate 10 are thus transferred to the receiving substrate 40.

[0132] Alternatively, detachment can be initiated by heating the substrate assembly to a specific temperature, and / or triggered by applying mechanical stress to the donor substrate to separate it from the recipient substrate. This energy input allows the microcavities, after ion implantation, to "mature" in such a way as to cause detachment (or "splitting," according to the generally used Anglo-Saxon terminology).

[0133] Since the donor substrate 10 is fractured at the weakening plane, the other free surface 23 of the portions 20', 20a' of the pavers 20, 20a, which is opposite the receiving substrate 40 with respect to the portion 20', 20a', generally exhibits high roughness. A treatment step for this other free surface 23 of the portions 20', 20a' of the pavers 20, 20a can be implemented to smooth it and reduce its roughness. This treatment may include, for example, the treatment implemented via the treatment process introduced previously. Alternatively, it may be a chemical and / or thermal treatment.

[0134] At the end of the process of transferring a portion of paving stones, the receiving substrate 40 therefore includes the portions 20', 20a' of the paving stones 20, 20a (with, preferably, another free surface 23 of each portion 20', 20a' treated).

[0135] Advantageously, the paving portion transfer method according to the invention allows portions of paving stones 20, 20a to be transferred from substrate 1 to receiving substrate 40 in a single iteration, following the bonding and detachment steps. This reduces production time and therefore the production costs of the semiconductor-type structures thus manufactured compared to known methods.

[0136] Furthermore, the paving portion transfer method according to the invention also allows paving portions from different substrates to be transferred so as to transfer paving portions of different types or functionalities onto the receiving substrate.

[0137] Furthermore, another advantage of the paving stone transfer method according to the invention is that the donor substrate 10 can be reused multiple times without the need for recycling. In other words, the donor substrate can be reused several times to transfer other paving stone portions onto the same receiving substrate or onto a different receiving substrate. Such a transfer method therefore minimizes material loss.

[0138] In an alternative embodiment not shown, the substrate may be in the form of a large slab. In this case, it may comprise a plurality of paving stone groups as described above. In such a configuration, the spacer is placed around each of the paving stone groups. The processing method according to the invention is carried out, for example, on each of the paving stone groups.

[0139] In this embodiment, the transfer process according to the invention can also be implemented for each of the groups of paving stones.

[0140] Examples of applications

[0141] The present invention presents various particularly advantageous application cases, especially in the field of microelectronics.

[0142] In photonic applications, the active layer of the receiving substrate may include a photonic circuit comprising passive or active devices, for example one or more waveguides, one or more multiplexers, one or more microresonators, etc. The portions of the tiles transferred onto this layer may be made of indium phosphide (InP), which is a more suitable material than silicon for the epitaxial growth of an III-V material stack to form a laser arranged on said photonic circuit of the receiving substrate.

[0143] Given the relatively large size of indium phosphide (InP) blocks, several circuits can potentially be made within each block.

[0144] According to an alternative execution method, the aforementioned paving stones can be subdivided into smaller paving stones, each An initial tile defines a cell comprising a plurality of chips, each formed within a small tile. It is thus possible to form two levels of tile arrangement on the substrate: a first level at the cell level, where the chips are arranged on the substrate according to a first pattern, and a second level at the chip level, where the chips are arranged within the respective cell according to a second pattern.

[0145] In radio frequency (RF) applications, the active layer of the receiving substrate may comprise components operating at relatively low frequencies, while the tiles, which are advantageously made of indium phosphide (InP) or gallium nitride (GaN), may comprise the components operating at higher frequencies. For such applications, the tile size can be as small as 1 centimeter on each side. The tiles are advantageously arranged densely on the substrate, for example, with a typical tile spacing of less than 300 µm.

[0146] In micro-LED applications, the size of gallium nitride (GaN) wafers is advantageously less than 50 pm.

Claims

DEMANDS

1. A method for treating a surface (22) of a substrate (1), the substrate (1) comprising a peripheral zone (2) and an internal zone (4), the internal zone (4) being provided with a plurality of tiles (20, 20a), the treatment method comprising the steps of: - deposition of a spacer (30) at the level of the peripheral zone (2) of the substrate (1), around the internal zone (4), and - polishing of the surface (22) of the substrate (1) so as to obtain a uniformity of a surface (22) of the internal zone (4) of the substrate (1).

2. A treatment method according to claim 1, wherein the polishing is a mechano-chemical polishing.

3. Processing method according to claim 1 or 2, wherein the spacer (30) is angularly equidistributed around the internal zone (4) of the substrate (1).

4. A treatment method according to any one of claims 1 to 3, wherein the spacer (30) has a discontinuous shape around the internal zone (4) of the substrate (1).

5. Processing method according to any one of claims 1 to 4, wherein the spacer (30) is deposited along a perimeter of the internal zone (4) of the substrate (1), the spacer (30) covering at least 40% of a perimeter of the internal zone (4) of the substrate (1).

6. A processing method according to any one of claims 1 to 5, wherein, the plurality of blocks (20, 20a) comprising external blocks (20a) positioned at the edge of the internal zone (4) of the substrate (1), a distance between the external blocks (20a) and the spacer (30) is greater than 200 micrometers.

7. A treatment method according to any one of claims 1 to 6, wherein, the plurality of paving stones (20, 20a) comprising external paving stones (20a) positioned at the edge of the internal zone (4) of the substrate (1), a distance between the external paving stones (20a) and the spacer (30) is less than 30 millimeters.

8. Processing method according to any one of claims 1 to 7, wherein the thickness of the spacer (30) is between 100 micrometers and 10 millimeters.

9. A treatment method according to any one of claims 1 to 8, wherein the spacer (30) comprises a polymer material.

10. A processing method according to claim 9, wherein the spacer (30) deposition step comprises the following steps: - arrangement of the spacer (30) on the peripheral area (2) of the substrate (1), and - crosslinking of the spacer (30) so as to fix the spacer (30) to the surface (12) of the peripheral zone (2) of the substrate (1).

11. Processing method according to any one of claims 1 to 8, wherein the spacer (30) comprises a ceramic material.

12. Processing method according to any one of claims 1 to 11, comprising, after the polishing step, a step of removing the spacer (30) from the surface (12) of the peripheral zone (2) of the substrate (1).

13. A processing method according to claim 12, wherein the removal step comprises a selective wet or dry etching step.

14. A method for transferring a portion (20', 20a') of paving stones from a donor substrate (10) onto a receiving substrate (40), the method comprising the steps of: - supply of a substrate (1) comprising the donor substrate (10) and a plurality of paving stones (20, 20a) formed on the donor substrate (10), the substrate (1) comprising a peripheral zone (2) and an internal zone (4), the internal zone (4) being provided with the plurality of paving stones (20, 20a), - treatment of a surface (22) of the substrate (1) according to any one of claims 1 to 12, - formation, by ion implantation, of a localized weakening plane in the paving stones (20, 20a), - bonding of the donor substrate (10) to the receiving substrate (40) via each tile (20, 20a) of the plurality of tiles, a free surface (22) of each tile (20, 20a) forming a bonding interface, and - detachment of the donor substrate (10) along the weakening plane in order to transfer the portion (20', 20a') of each paving stone (20, 20a) of the plurality of paving stones onto the receiving substrate (40).

15. Method of transferring a portion of paving stones according to claim 14, wherein the bonding step includes a thermal annealing step of the donor substrate (10) and the receiving substrate (40).

16. Method of transferring a portion of paving stones according to claim 14 or 15, wherein the step of detaching the donor substrate (10) is initiated thermally and / or mechanically by applying a mechanical force aimed at separating the donor substrate (10) from the receiving substrate (40).

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