Method for treating a substrate surface and method for transferring a portion of paving stones

Abstract

The invention relates to 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 being provided with a plurality of tiles (20, 20a), the treatment method comprising the steps of: - depositing a spacer (30) in the peripheral zone of the substrate, around the internal zone, and - polishing the surface of the substrate to obtain uniformity of the surface of the internal zone of the substrate. A method for transferring a portion of tiles from a donor substrate (10) to a receiving substrate is also described. Figure to be published with the abstract: Fig. 2

Description

Title of the invention: Method for treating a substrate surface and method 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 produced by transferring at least one layer onto a support. PRIORITY OF THE TECHNOLOGY

[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 used 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. It is therefore advantageous to use thin-film transfer solutions to fabricate composite structures comprising, in particular, 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. Such a process makes it possible, for example, to fabricate a composite structure comprising a thin film, for example of indium phosphide, taken from a donor substrate, in direct contact with a support substrate, for example of silicon or polycrystalline silicon carbide (p-SiC). The indium phosphide is, for example, in the form of blocks present on the donor substrate.

[0007] In order 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, for example chemical mechanical polishing (CMP for "Chemical Mechanical"), is used. "Polishing" according to the commonly used Anglo-Saxon terminology), can be implemented.

[0008] However, taking into account, in particular, the gaps between the blocks and the possible different geometries between the blocks, the surface to be polished is not completely flat and may exhibit marked roughness. Differences in surface uniformity then appear after polishing, especially on the edges of the outer blocks (the polishing speed being 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 uniformity of surface after a polishing step.

[0010] The invention relates to a method for treating a substrate surface, 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] - deposition of a spacer at the level of the peripheral zone of the substrate, around the internal zone, and

[0012] - polishing the surface of the substrate so as to obtain a uniformity of 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 of the paving stones. Furthermore, the spacer is easy to deposit in practice and remains an economical solution to implement for guaranteeing this surface uniformity.

[0014] Thus, at the end of the treatment process according to the invention, a paving substrate is obtained in which the paving stones have a uniform free surface (i.e., without defects in shape or roughness and with a substantially constant thickness for all the paving stones). 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] - the polishing is a mechano-chemical polishing;

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

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

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

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

[0021] - the plurality of paving stones comprising external paving stones positioned at the edge of the internal zone 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 a rectangular prism the plurality of paving stones;

[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] - after the polishing step, a step is planned for removing 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 one donor substrate on a recipient substrate, the process 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 furnished with a plurality of paving stones,

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

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

[0036] - bonding of the donor substrate to the recipient substrate via each a paving of the plurality of paving stones, a free surface of each paving stone forming a bonding interface, and

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

[0038] Advantageously, the method for transferring a portion of paving stones according to the invention makes it possible to transfer a portion of each paving stone from the donor substrate to the receiving substrate in a single iteration, following the gluing step and the step of detachment. This then makes it possible to reduce production times and therefore the production costs of semiconductor-type structures manufactured in this way compared to known processes.

[0039] Furthermore, the method of transferring a portion of paving stones according to the invention also makes it possible to transfer portions of paving stones from different substrates so as to transfer onto the receiving substrate portions of paving stones of different natures or different functionalities.

[0040] Furthermore, another advantage of the paving stone transfer method according to the invention is that the donor substrate can be reused several times without needing to be recycled. In other words, the donor substrate can be reused multiple 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.

[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 of the donor substrate and of the receiving substrate; 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, by way of example and not limitation, with reference to the accompanying figures, among which:

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

[0046] [Fig.2] represents a schematic view of a first example of a substrate equipped of a spacer conforming to the invention;

[0047] [Fig.3] represents a schematic view of a second example of a substrate equipped with a spacer according to the invention;

[0048] [Fig.4] represents a schematic view of a third example of a substrate equipped of a spacer conforming to the invention;

[0049] [Fig.5] represents a schematic view of a fourth example of a substrate equipped with a spacer according to the invention;

[0050] [Fig.6] represents a schematic view of a fifth example of a substrate equipped of a spacer conforming to the invention;

[0051] [Fig.7] represents a schematic view of a sixth example of a substrate equipped of a spacer conforming to the invention;

[0052] [Fig.8] represents a schematic view of a seventh example of a substrate equipped of a spacer conforming to the invention;

[0053] [Fig.9] represents a schematic view of an eighth example of a substrate equipped of a spacer conforming to the invention;

[0054] [Fig. 10] represents a schematic view of a ninth example of a substrate equipped with a spacer according to the invention;

[0055] [Fig. 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] [Fig. 12] represents a cross-sectional view of a substrate fitted with paving stones obtained after a polishing step according to the prior art; and

[0057] [Fig. 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 signs throughout the figures.

[0059] DETAILED DESCRIPTION OF AT LEAST ONE IMPLEMENTATION

[0060] 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.

[0061] In this description, the expression "surface uniformity" refers to a flat, smooth surface, free from defects in shape and whose roughness has been reduced or even completely eliminated. This uniform surface can then be compatible with a direct bonding process (as described later in this description).

[0062] Fig. 1 represents an example of substrate 1 according to the present invention.

[0063] 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 can, for example, be used in a thin-film transfer process. The donor substrate 10 comprises, for example, silicon.

[0064] 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 tiles 20, 20a.

[0065] The plurality of paving stones 20, 20a takes the form of a plurality of portions of a solid substrate or layer on which can be manufactured electronic components, or in which passive or active electronic components are already formed. This layer from which the blocks 20, 20a are formed includes, 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.).

[0066] 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, with regard to binary compounds, indium nitride (InN), gallium nitride (GaN) and aluminium nitride (Ain)), arsenides (for example, with regard to binary compounds, indium arsenide (InAs), gallium arsenide (GaAs) and aluminium arsenide (AlAs)), and phosphides (for example, with regard to binary compounds, indium phosphide (InP), gallium phosphide (GaP) and aluminium phosphide (AlP)). 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 (LiTaO3) or lithium niobate (LiNbO3), potassium-sodium niobate (KxNai_xNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (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).

[0067] Alternatively, the pavés may comprise an electrically insulating material, such as, for example, diamond, strontium titanate (SrTiO3), yttria zirconia (YSZ), or sapphire.

[0068] Each block 20, 20a has a specific shape. Here, as can be seen in particular in [Fig. 1], each block 20, 20a has a square shape. The present invention is not limited to the shape shown. Moreover, the present invention applies in the same way if the blocks have several different shapes.

[0069] As can be seen in [Fig. 1], two adjacent blocks 20, 20a are separated from each other by a gap 5. Furthermore, it is possible to define so-called “external” blocks (denoted “external blocks 20a” in this description) which are located at the edge of the internal zone 4 of the substrate 1. In other words, these external blocks 20a are those which are positioned closest to the peripheral zone 2.

[0070] In practice, the thickness of each paver 20, 20a is on the order of a few hundred micrometers (pm). For example, the thickness of each paver 20, 20a is between 100 and 1000 pm. In this description, the term "thickness" refers to a dimension of the element concerned defined orthogonally to the surface of the substrate 1, for example defined orthogonally to the surface 12 of the donor substrate 10.

[0071] Here, for a square shape, each block 20, 20a has a side dimension on the order of a few millimeters (mm). For example, the side of the square shape of each block 20, 20a is between 2 and 20 mm, preferably between 2 and 15 mm.

[0072] 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 comprises the surface 12 of the donor substrate 10 and the free surface 22 of the paving stones 20, 20a.

[0073] 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).

[0074] This treatment process first includes a step of depositing a spacer 30 at the level of the peripheral zone 2 of the substrate 1. More particularly, 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 words, the spacer 30 is deposited around the plurality of tiles 20, 20a.

[0075] Figures 2 to 10 schematically represent several examples for the deposited spacer.

[0076] Advantageously, this spacer 30 makes it possible to maintain 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 makes it possible to maintain a constant gap between the polishing head and the surface 12 of the substrate 1.

[0077] More specifically, the thickness difference between the surface to be polished and the surface 12 of the substrate 1 is offset by the spacer 30, thus allowing the free surface 22 of the paving stones 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 difference between the surface to be polished and the surface 12 of the substrate 1 is 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 difference at the paving stones. This then ensures uniform treatment of the surface of the paving stones 20, 20a during a polishing step (described below). Furthermore, the use of a spacer advantageously reduces substrate deformation in the area peripheral during the application of the polishing head. The spacer then acts as a stiffener for the substrate in the peripheral area.

[0078] 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.

[0079] Advantageously, the spacer 30 forms a support area for the polishing head around all the pads 20, 20a, making it possible to maintain a constant space between the polishing head and the substrate in the internal zone 4, thereby ensuring that all the pads 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.

[0080] 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 provided, enabling the evacuation of liquids involved, for example, when a mechano-chemical polishing process is carried out.

[0081] Alternatively, as shown in Figures 2, 3, and 6 to 10, the spacer 30 may have a continuous shape. A spacer with a continuous shape can be used regardless of the type of polishing employed. Furthermore, a spacer with a continuous shape is easier to deposit onto the substrate.

[0082] Advantageously, the spacer 30 is deposited around the perimeter of the internal zone 4 of the substrate 1. In this description, "perimeter" means a contour that delimits the zone concerned (here, for example, the internal zone 4 of the substrate 1). This perimeter can have different shapes.

[0083] 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 provided with the blocks 20, 20a.

[0084] In the example of [Fig.6], the spacer 30 is deposited along an octagonal perimeter.

[0085] In the example of [Fig.7], the spacer 30 is in the form of a double cord, one of annular shape and the other of octagonal shape.

[0086] Depositing the spacer 30 along a predefined perimeter allows for the use of a minimal amount of the deposition material required to form the spacer (this solution is therefore economical). Furthermore, such a spacer shape is easy to deposit.

[0087] 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 deposited 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 zone.

[0088] Alternatively, the spacer 30 is deposited so as to cover at least 40% of a surface around the perimeter of the internal zone 4 of the substrate 1

[0089] 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.

[0090] Preferably, the proportion of spacer 30 distributed over the perimeter of the peripheral zone 2 of the substrate 1 is greater than 50%. Alternatively, the proportion of spacer 30 distributed over the surface of the peripheral zone 2 of the substrate 1 is greater than 50%.

[0091] In the case of the variants shown in Figures 8 to 10, the distribution proportion of the spacer 30 is greater than 80% of the surface of the peripheral zone 2 of the substrate 1. These examples require the use of a larger quantity of deposition material but ensure an optimal spacing between the polishing head and the surface 12 of the substrate 1. The support of the polishing head, relative to the substrate support, is particularly stable here.

[0092] In practice, the spacer 30 is placed at a predefined minimum distance from the outer pads 20a. Preferably, this minimum distance is on the order of 200 pm. In other words, the distance between the outer pads 20a and the spacer 30 is greater than 200 pm. Such a minimum distance between the spacer 30 and the pads 20a ensures proper execution of the polishing step that follows (and is described later).

[0093] 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, on the order of 30 millimeters (mm). That is to say, the spacer 30 is positioned at a distance less than this predefined maximum distance from the outer pads 20a. This positioning with this predefined maximum distance ensures that the advantages provided by the spacer 30 for the polishing step are guaranteed.

[0094] 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).

[0095] A thickness of spacer 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.

[0096] Preferably, the thickness of the spacer 30 after the deposition step is substantially on the order of the thickness of a block 20, 20a. By "substantially," it is understood that a difference of less than 10% is observed with respect to the thickness of a block 20, 20a. The use of such a thickness for the spacer makes it possible to guarantee optimal surface uniformity for the blocks 20, 20a (a difference in thickness between the spacer and the blocks could induce 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 blocks 20, 20a).

[0097] In practice, to obtain such a thickness, it is possible to deposit a greater thickness of the spacer and to implement a grinding step (or "grinding" according to the commonly used Anglo-Saxon terminology) in order to obtain the desired thickness for the spacer.

[0098] 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.

[0099] In the case of a polymer material, the step of depositing 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.

[0100] Alternatively, the spacer may comprise a ceramic material. Alternatively still, the spacer may comprise an oxide.

[0101] More generally, it is possible to use any type of material that has properties enabling the spacer to maintain its mechanical integrity during a polishing step, and more particularly during a chemical polishing step. In other words, the spacer comprises a material that is not attacked or deteriorated in aqueous, basic, or acidic media.

[0102] 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.

[0103] The placement of the spacer 30 prior to this polishing step makes it possible to maintain a constant gap between the polishing head and the substrate support in the internal zone 4, thus ensuring that all the blocks 20, 20a will have a uniform free surface 22 after the polishing step. Thanks to the spacer 30, the thickness difference step is offset at this spacer and is therefore away from the blocks. In addition, 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. This allows for uniform polishing of the free surface 22 of the blocks 20, 20a (even at the edges).

[0104] Preferably, the polishing employed here is a mechano-chemical polishing. This 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) of the polishing head (mechanical effect) and the chemical and abrasive effects of a polishing solution introduced at the surface to be polished. In practice, the substrate 1, positioned on the substrate support, and the polishing head are rotated relative to each other, which allows material to be removed from the surface to be treated (here, the free surface 22 of the blocks 20, 20a) and the surface to be smoothed. This mechano-chemical polishing, combining chemical and mechanical effects, is particularly advantageous for the planarization of a substrate, especially a semiconductor substrate.

[0105] 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.

[0106] In practice, this removal step includes, for example, an etching step so as 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 by wet or dry process.

[0107] Alternatively, the removal step can be implemented by applying a plasma followed by a wet rinse.

[0108] Alternatively, the removal step can be implemented by applying ultraviolet radiation so as to degrade the spacer.

[0109] Alternatively, the removal step can be implemented by applying ozone molecules so as to degrade the spacer.

[0110] 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. Moreover, the spacer is in practice easy to remove and also remains an economical solution to implement to guarantee this surface uniformity.

[0111] 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 particularly in Figures 12 and 13.

[0112] Figure 12 shows a cross-section of a substrate fitted with paving stones subjected to a process of known prior art treatment. As can be seen in this figure, the thickness (denoted y in [Fig. 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 outer paving stone 20a has a thickness much less than the paving stones located in a more central area of ​​the substrate.

[0113] Figure 13 shows a cross-section of a substrate fitted with paving stones subjected to a process of the treatment according to the present invention. As shown in this figure, the thickness (denoted y in [Fig. 13]) of the blocks obtained after the polishing step is generally constant (line B supports this point by illustrating that all the free surfaces 22 of the blocks 20, 20a lie on this line B). Indeed, Figures 12 and 13 show a significant rounding of the corners of the blocks near the peripheral zone (the rim) of the substrate without a spacer, with a block thickness up to 20 µm thinner at the rim compared to the center of the substrate ([Fig. 12]). In the case of the present invention ([Fig. 13]), good thickness uniformity was obtained on the substrate equipped with a spacer, with significantly improved thickness uniformity over the entire surface of the substrate ([Fig. 13]).

[0114] This substrate can then be used for various applications. In particular, this substrate can be used as a donor substrate in a process for transferring a portion of paving stones from a donor substrate to a receiving substrate.

[0115] 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 [Fig. 11]).

[0116] 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.

[0117] The paving stones 20, 20a thus cut are then placed on the donor substrate 10. The placement can be carried out by the "Pick and Place" technique, by which a robot picks up a paving stone, or a group of paving stones, previously cut out and places it at a predetermined location on the donor substrate 10.

[0118] 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 (SiO2), plasma activation before bonding, and annealing.

[0119] 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.

[0120] In order to efficiently transfer 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 uniformize 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 transfer process of the portion 20', 20a' of each paver, and in particular of the bonding step described below.

[0121] 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).

[0122] In practice, to form the embrittlement plane, the blocks 20, 20a are exposed to a beam of ionic species. The ionic species penetrate the blocks 20, 20a and become embedded there (at a thickness determined by the implantation parameters and corresponding to the target thickness for the layer to be transferred).

[0123] 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, in particular 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 blocks 20, 20a.

[0124] The method 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. The bonding is achieved via the paving stones 20, 20a, which form a bonding interface. More Specifically, the bonding only takes place at the level of the paving stones 20, 20a. The peripheral zone 2 of the substrate 1 remains at a distance from the receiving substrate 40.

[0125] 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.

[0126] Advantageously, each paving stone 20, 20a then adheres to the receiving substrate 40 by molecular adhesion. In practice, surface treatments of the paving stones and / or the receiving 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 (SiO2), plasma activation before bonding, and annealing, preferably at low temperature (i.e., typically below 300°C).

[0127] The paving stones 20, 20a are then detached along the weakening plane in order to transfer the portions 20', 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 in the paving stones 20, 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', 20a' of the paving stones 20, 20a from the donor substrate 10 are thus transferred onto the receiving substrate 40.

[0128] Alternatively, detachment can be initiated by heating the substrate assembly to a given 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).

[0129] Since the donor substrate 10 is fractured at the embrittlement 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 of 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.

[0130] 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).

[0131] Advantageously, the method for transferring a portion of paving stones according to the invention makes it possible to transfer portions of paving stones 20, 20a from the substrate 1 onto the The receiving substrate is bonded in a single iteration, following both the bonding and detachment steps. This reduces production time and therefore the production costs of the resulting semiconductor-type structures compared to known processes.

[0132] Furthermore, the method of transferring a portion of paving stones according to the invention also makes it possible to transfer portions of paving stones from different substrates so as to transfer onto the receiving substrate portions of paving stones of different natures or different functionalities.

[0133] Furthermore, another advantage of the paving stone transfer method according to the invention is that the donor substrate 10 can be reused several times without needing to be recycled. 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.

[0134] Examples of applications

[0135] The present invention presents various particularly advantageous application cases, especially in the field of microelectronics.

[0136] 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 waveguide(s), one or more multiplexer(s), one or more micro-resonators, 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 a stack of III-V materials to form a laser arranged on said photonic circuit of the receiving substrate.

[0137] Given the relatively large size of the indium phosphide (InP) blocks, several circuits can possibly be made within each block.

[0138] According to an alternative embodiment, the aforementioned tiles can be subdivided into smaller tiles, each initial tile defining a cell comprising a plurality of chips, each chip formed within a smaller tile. It is thus possible to form two levels of tile arrangement on the substrate: a first level at the cell level, where the tiles are arranged on the substrate according to a first pattern, and a second level at the chip level, where the tiles are arranged within the respective cell according to a second pattern.

[0139] 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 size of the tiles can be up to 1 centimeter side length. The pavers are advantageously laid densely on the substrate, for example with a distance between pavers typically less than 300 pm.

[0140] In micro-LED applications, the size of gallium nitride (GaN) wafers is advantageously less than 50 pm.

Claims

Demands

1. Method of 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 blocks (20, 20a), the treatment method comprising steps of: - depositing a spacer (30) at the level of the peripheral zone (2) of the substrate (1), around the internal zone (4), and - polishing 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. Processing 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 treatment 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. Processing method according to claim 9, wherein the spacer (30) deposition step comprises steps of: - arranging the spacer (30) on the peripheral area (2) of the substrate (1), and - crosslinking the spacer (30) so as to fix the spacer (30) to the surface (12) of the peripheral area (2) of the substrate (1).

11. A treatment 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. Processing method according to claim 12, wherein the removal step includes a wet or dry selective 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: - supplying 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), - treating a surface (22) of the substrate (1) according to any one of claims 1 to 12, - forming, by ion implantation, a localized weakening plane in the paving stones (20, 20a), - bonding the donor substrate (10) to the receiving substrate (40) via each paving stone (20, 20a) of the plurality of paving stones, a free surface (22) of each block (20, 20a) forming a bonding interface, and - detachment of the donor substrate (10) along the embrittlement plane in order to transfer the portion (20',20a') of each paving stone (20, 20a) of the plurality of paving stones on 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). 19

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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