Method of manufacturing film on support having non-planar surface

Abstract

A method of making a film on a support having a non-planar surface. The invention relates to a method for producing a film (12) on a support (20) having a non-flat surface, characterized in that it comprises:-supplying a donor substrate (10) having a non-flat surface,-forming an embrittlement zone (11) in the donor substrate (10) to delimit said film (12) to be transferred,-forming a support (20) by deposition on the non-flat surface of the film (12) to be transferred,-forming the support (20) on the non-flat surface of the film (12) to be transferred, -separating the donor substrate (10) along the embrittlement zone (11) in order to transfer the film (12) onto the support (20).

Description

[0001] This application is a divisional application of the invention patent application with the original application number 201880070872.1 (international application number: PCT / EP2018 / 079797, application date: October 31, 2018, invention name: Method for manufacturing a membrane on a support having a non-flat surface). Technical Field

[0002] The invention relates to a method for producing a membrane on a support having a non-planar surface. Background Art

[0003] It is not easy to produce films, in particular single crystals, on a support when the film has a non-planar interface (interaction surface) with the support, that is to say said surface of the support comprises at least one curvature and / or a recessed or relief pattern.

[0004] This particular topology is not suitable for bonding and lamination methods, the general trend being towards techniques involving the formation of films by deposition on the support.

[0005] However, in addition to good mechanical strength of the film relative to the support, it is also necessary to ensure a sufficiently good crystalline quality of the film. However, the crystalline quality of the film depends strongly on the support on which the deposition takes place, in particular its surface. This is especially true when considering single-crystalline films formed by epitaxy. In this case, the nature of the support is particularly critical, since it needs to have the appropriate crystal structure and lattice parameters for the film that one wishes to deposit. The list of candidates that can play the role of support becomes so limited that in certain specification cases no solution can be found. Summary of the invention

[0006] One object of the present invention is therefore to conceive a method for manufacturing a film on a support having a non-planar surface while ensuring both a good crystalline quality of the film and a fairly wide choice as to the nature of the support.

[0007] To this end, the present invention proposes a method for manufacturing a film on a support having a non-flat surface, characterized in that the method comprises the following steps:

[0008] - supplying a donor substrate having a non-planar surface,

[0009] - forming an embrittled zone in the donor substrate to define said film to be transferred,

[0010] - forming the support by deposition on a non-planar surface of the film to be transferred,

[0011] - Separating the donor substrate along the embrittled zone to transfer the film to a support.

[0012] According to one embodiment, the method further comprises depositing an intermediate layer on the non-planar surface before depositing the support.

[0013] The formation of the embrittlement zone is advantageously performed by implanting ionic species in the donor substrate.

[0014] The implanted ion species may be hydrogen and / or helium.

[0015] According to one embodiment, the detachment of the donor substrate is caused by a thermal treatment.

[0016] In this case, the deposition of the support is advantageously carried out with a lower thermal budget than the separate heat treatment.

[0017] The transferred film may be made of a material selected from semiconductor materials, piezoelectric materials, magnetic materials, and functional oxides.

[0018] In a particularly advantageous manner, the transferred film is single-crystalline.

[0019] The thickness of the transferred film is generally between 100 nm and 10 μm, preferably between 100 nm and 1 μm.

[0020] The support may be made of a material selected from metal, glass and ceramic.

[0021] The support typically has a thickness between 1 μm and 50 μm.

[0022] Preferably, the material of the support is selected such that the absolute value of the difference in thermal coefficient with respect to the material of the transferred film is less than 5×10 -6 K -1 .

[0023] Deposition of the support may be achieved by one of the following techniques: physical vapor deposition, chemical vapor deposition, electrochemical deposition, spin coating, painting and spraying.

[0024] According to one embodiment of the present invention, the surface of the film to be transferred has at least one curved portion.

[0025] According to one embodiment of the invention, the surface of the film to be transferred has at least one recessed or embossed pattern.

[0026] According to one embodiment of the invention, the surface of the film to be transferred has a texture characterized by a roughness greater than 1 nmrms.

[0027] According to one embodiment, the non-planar surface of the film to be transferred is obtained after forming the embrittled zone (eg by etching the donor substrate).

[0028] According to one embodiment, the non-planar surface of the film to be transferred is obtained before forming the embrittled zone (eg by etching the donor substrate).

[0029] The residue of the donor substrate at the end of the separation can be recycled with the aim of achieving a new film with a non-planar surface on the support; prior to said recycling, the residue of the donor substrate is subjected to an operation for regenerating its surface involving a material removal that is substantially zero or conformal to the topology of said residue.

[0030] According to one embodiment, the donor substrate comprises a plurality of pads laid on the surface of a wafer, each pad comprising a brittle zone defining a respective film to be transferred, and a support is deposited on the surface of all said pads.

[0031] According to a particular embodiment, the deposition of the support comprises the sequential deposition of at least two layers of different materials.

[0032] According to one embodiment, the method comprises, after detachment of the donor substrate, depositing an additional film on the side of the transferred film opposite to the support.

[0033] Another object relates to an intermediate structure obtained after depositing a support on a donor substrate. Said structure comprises:

[0034] - a donor substrate comprising a brittle zone defining a superficial film, and

[0035] - a support covering said membrane,

[0036] And the interface between the membrane and the support is not flat. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings, in which:

[0038] - Figure 1A is a schematic cross-sectional view of a donor substrate including a surface having a recessed pattern;

[0039] - Figure 1B and Figure 1C Shown schematically Figure 1A Two replacements for the embrittled zone formed in the donor substrate;

[0040] - Figure 1D The deposition is schematically shown in Figure 1B a support on a donor substrate;

[0041] - Figure 1E Show Figure 1D an alternative in which an intermediate layer has been deposited between the donor substrate and the support;

[0042] - Figure 1F Schematically showing the Figure 1E The structure obtained by separating the donor substrate along the embrittled zone;

[0043] - Figure 1G Schematically shows the process of depositing an additional film on the transferred film. Figure 1F structure;

[0044] - Figure 2A and Figure 2B The steps are shown in reverse order. Figure 1A to Figure 1B Alternatives;

[0045] - Figure 3A is a schematic cross-sectional view of a donor substrate including a curved surface;

[0046] - Figure 3B Schematically shown in Figure 2A forming a brittle zone in the donor substrate;

[0047] - Figure 3C Schematically shown in Figure 3B depositing a support member on a donor substrate;

[0048] - Figure 3D The structure obtained by separation of a donor substrate along the embrittled zone is shown in a schematic manner;

[0049] - Figure 4A is a schematic cross-sectional view of a donor substrate including a textured surface;

[0050] - Figure 4B Schematically shown in Figure 4A forming a brittle zone in the donor substrate;

[0051] - Figure 4C Schematically shown in Figure 4B depositing a support member on a donor substrate;

[0052] - Figure 4D The structure obtained by separation of a donor substrate along the embrittled zone is shown in a schematic manner;

[0053] - FIG. 5A to FIG. 5E The steps of the method implemented according to one embodiment of the present invention are shown in a schematic manner;

[0054] - FIG. 6A to FIG. 6D The steps of a method according to another embodiment of the present invention are shown in a schematic manner.

[0055] - FIG. 7A to FIG. 7G The steps of a method according to another embodiment of the present invention are shown in a schematic manner;

[0056] - FIG. 8A to FIG. 8C The steps of a method according to another embodiment of the invention are shown in a schematic manner.

[0057] For reasons of clarity in the drawings, various elements are not necessarily shown to scale. DETAILED DESCRIPTION

[0058] In general, the present invention provides for forming a support by deposition on a non-planar donor substrate that has been previously embrittled to define a thin film. The thin film is subsequently transferred to the support by separation of the donor substrate. The support may consist of a single material or a stack of at least two different materials deposited in sequence on a donor substrate.

[0059] The non-planarity of the surface of the donor substrate may be due to the curvature (concave or convex) of at least one portion of the surface, and / or the presence of at least one recessed or relief pattern extending from the surface, and / or surface texturing (whether voluntary or not).

[0060] Figure 1A A donor substrate 10 is shown, which comprises at least one superficial portion consisting of a material intended to form a thin film. Although the donor substrate is represented in the form of a bulk substrate, it can also be formed by a stack of different materials, wherein the superficial layer consists of the material intended to form a thin film. In particular, the thin film can correspond to a layer of this stack generated by epitaxy.

[0061] The surface 10a of the donor substrate 10 includes a certain number of recessed patterns 100 (or relief patterns (not shown here)) relative to a reference plane.

[0062] The patterns can advantageously be formed by photolithography and etching of the donor substrate. They can also be obtained by deposition, for example using a mask.

[0063] Advantageously, the material intended to form a thin film is selected from: semiconductor materials (for example: silicon, silicon carbide, germanium, III-V compounds such as AsGa, InP, GaN, II-IV compounds such as CdTe, ZnO), piezoelectric materials (for example: LiNbO3, LiTaO3, PZT, PMN-PT), magnetic materials and functional oxides (for example: ZrO2, SrTiO3, YSZ, GaO2). These examples are not limiting.

[0064] Preferably, the material intended to form a thin film is single crystalline. It can also be polycrystalline, and in this case, the focus is often on optimizing its formation conditions in order to obtain, for example, a specific density and size of grains, and / or a preferred crystal orientation, and / or an optimized roughness.

[0065] A brittle zone 11 delimiting a superficial film 12 intended to be transferred is formed in the donor substrate 10. Although envisaged here to be performed after patterning, the formation of the brittle zone may be achieved before patterning.

[0066] The thickness of the transferred film is defined by the depth of the embrittled zone 11 in the donor substrate 10. Advantageously, this depth is between 100 nm and 10 μm, preferably between 100 nm and 1 μm.

[0067] The embrittled region 12 may be formed in the donor substrate 10 by implanting ion species ( Figure 1B The implantation is performed by passing the surface 10a of the substrate (schematically shown by arrows in FIG. 1 ). Advantageously, the implanted species are hydrogen ions and / or helium ions. The implantation energy makes it possible to define the depth of the implantation zone 11. The implantation dose is selected so that the film 12 can be separated after applying a suitable treatment. The implantation dose is selected to be low enough not to cause the formation of bubbles during the implantation step. The ion species, energy and implantation dose are selected according to the material of the donor substrate 10. These conditions have been the subject of numerous publications and are known to those skilled in the art.

[0068] If the implantation is performed through a surface that already has a pattern of depressions and / or reliefs, the embrittlement zone may follow substantially the same contours as these patterns, the thickness of the material between the surface and the embrittlement zone remaining substantially constant.

[0069] The continuity of the film and its quality near the transition between adjacent patterns may depend, among other things, on the thickness ratio between the thickness of the film and the amplitude of the relief. For thick films (e.g., 2 μm) and low steps (e.g., 0.05 μm), the film 12 may appear substantially continuous, as Figure 1B In contrast, for thin films (e.g., 0.05 μm) and high steps (e.g., 2 μm), the film 12 will most likely have discontinuities (see Figure 1C ), which may not necessarily be disadvantageous depending on the target application. In some cases, this phenomenon may be taken into account and it may be preferable to ensure that the angle between the surface of the pattern and the surface of the reference plane is less than or equal to 45°.

[0070] Alternatively (see Figure 2A ), if the implantation is performed through the surface 10a of the initially flat donor substrate 10 and the recessed and / or relief pattern is formed from this surface after the implantation, the embrittled zone is substantially flat. If discontinuities in the film 12 are not desired, etching of the pattern 100 must be performed later so that the etching depth is less than the depth of the embrittled zone 11 (see Figure 2B ).

[0071] In order to take into account the fact that several topological levels can play a role with respect to the embrittlement plane, it is conceivable that the embrittlement zone is not single, but multiple and / or extended. In the case of embrittlement by implantation, this can be easily accomplished by multiple or extended selection of the implantation energy.

[0072] Reference Figure 1D , a support 20 is formed on the surface of the film 12 (which, at this stage, still forms part of the donor substrate 10).

[0073] In contrast to the bonding techniques, the support is not pre-existing but is formed directly on the donor substrate. The following deposition techniques can be implemented for forming the support: physical vapor deposition (PVD), chemical vapor deposition (CVD), deposition by electrodeposition or electroforming, electroplating or electrochemical deposition (ECD), spin coating, painting and spraying. These techniques are known per se and will not be described in more detail here, the skilled person being able to select the most suitable technique depending on the material of the support to be deposited. In order not to cause premature detachment of the donor substrate, deposition techniques at relatively low temperatures are preferred.

[0074] According to the chosen deposition technique, the deposition may be conformal, that is to say the free surface of the support substantially follows the same contour as the pattern, the thickness of the material between the surface of the support and the surface of the donor substrate remaining substantially constant.

[0075] However, if the thickness of the deposition is important (eg greater than or equal to 50 μm) for the size of the topography (eg a step of 0.5 μm), the thickness of the deposition may appear constant and thus the free surface of the support will appear flat.

[0076] According to other embodiments, the deposition may have the effect of filling the depressions present on the surface of the donor substrate, thereby obtaining a substantially flat free surface of the support. In this case, the support has a variable thickness.

[0077] The support is advantageously made of a material selected from metals (e.g. Ni, Cu, Cr, Ag, Fe, Co, Zn, Al, Mo, W and alloys thereof), glass and ceramics (e.g. silicon dioxide (SiO2), aluminum oxide (Al2O3), polycrystalline AlN, polycrystalline silicon, polycrystalline SiC). These examples are not limiting.

[0078] The thickness of the support is typically between 1 μm and 50 μm (which is low enough so that the support can resemble a sheet), but can also be much larger.

[0079] Furthermore, care must be taken that the adhesion of the support on the donor substrate is sufficient to avoid detachment of the support during the film transfer process. This adhesion can be improved by depositing an adhesion layer on the donor substrate before depositing the support. For example, the adhesion layer can be made of one of the following materials: Ti, Cr, Pt, Ta, TiW, Si3N4, TiN, CrCu.

[0080] More generally, an intermediate layer 21 may be deposited on the membrane 12 before the support 20 is deposited (the final structure is shown in Figure 1E In addition to the potential adhesion function, such a layer may have the following functions: avoiding the diffusion of chemicals to the membrane 12 during the deposition of the support 20, and / or forming an electrical contact on the membrane 12, and / or forming a refractive index jump, and / or minimizing the discontinuity of the acoustic impedance. Naturally, a person skilled in the art will be able to select a suitable material and its thickness according to the mechanical, electrical, optical, thermal, acoustic or chemical function of the intermediate layer.

[0081] The thickness of said intermediate layer 21 is low enough so that the stiffness of this layer does not impair the flexibility of the support (when this criterion is important).

[0082] When there is an important difference between the thermal expansion coefficients of the support and the membrane (usually, greater than 5 × 10 -6 K -1 The material of the support is selected to exhibit sufficient toughness so that the transferred film does not suffer damage (e.g., crack type) during the transfer method. Sufficient toughness means that the elastic limit of the support is less than the product of the elastic limit of the film and the thickness ratio between the film and the support.

[0083] Reference Figure 1F , the donor substrate 10 is then separated along the embrittled zone 11 in order to transfer the film 12 to the support 20. At the end of this separation, a residue 10' of the donor substrate remains, which may be recycled for another use.

[0084] The separation is caused by treating the stack of support 20 on donor substrate 10. The treatment may be, for example, thermal, mechanical or a combination of these two types of treatment. This type of treatment is well known, in particular in Smart Cut TM In the context of the method, it will not be described in detail here. In the case of a thermal treatment, the thermal budget of the treatment is usually larger than the thermal budget of the support deposition.

[0085] The film 12 may be used as a seed for the deposition of an additional film 13 (see Figure 1G ).

[0086] The structure formed by the support 20 and the membrane 12 (and possible additional membranes) can be used to form a device that can be used in microelectronics, photonics or optics. This structure can also participate in the manufacture of sensors or transducers, or membranes for fuel cells.

[0087] FIG. 3A to FIG. 3D A further embodiment of the transfer method is shown in a schematic manner, in which the surface of the donor substrate has at least one curvature, concavity or convexity.

[0088] and Figures 1A to 2B The same reference numerals refer to the same elements and thus will not be described in detail. Figures 1A to 2B The materials and methods described also apply to FIG. 3A to FIG. 3D Implementation methods are not described herein, so they will not be described in detail.

[0089] Reference Figure 3A , the surface 10a of the donor substrate 10 is concave.

[0090] Reference Figure 3B , implanting atomic species through the surface 10a has the effect of forming an embrittled zone 11 within the donor substrate 10. The embrittled zone generally has a curvature substantially parallel to the surface of the donor substrate 10, the thickness of the film 12 to be transferred being substantially constant. As indicated previously, the surface of the donor substrate can be made concave or convex after the formation of the embrittled zone (which is then substantially flat).

[0091] Reference Figure 3C The support 20 is formed by deposition on the surface of the film 12 (which at this stage still forms part of the donor substrate 10). As indicated previously, an intermediate layer (not shown) may be deposited before depositing the support.

[0092] Depending on the chosen deposition technique, the deposition may be conformal, that is, the free surface of the support has substantially the same curvature as the donor substrate, the thickness of the material between the surface of the support and the surface of the donor substrate remaining substantially constant.

[0093] Reference Figure 3D , the donor substrate 10 is then separated along the embrittled zone 11 in order to transfer the film 12 to the support 20. At the end of this separation, a residue 10' of the donor substrate remains, which may be recycled for another use.

[0094] For the formation of the curved portion, FIG. 3A to FIG. 3D The methods of coating optical components such as diverging or converging lenses or parabolic reflectors are of particular interest. For example, they can be coatings for optical components such as diverging or converging lenses or parabolic reflectors. For example, they can also be optical lenses for glasses or augmented reality glasses, or curved screens, or windshields or cockpit elements.

[0095] FIG. 4A to FIG. 4D A further embodiment of the transfer method is schematically shown, in which the surface of the donor substrate has a textured topology. The topology may correspond in particular to the roughness of the surface of the donor substrate (whether voluntarily acquired or not).

[0096] and Figures 1A to 3D The same reference numerals refer to the same elements and thus will not be described in detail. Figures 1A to 2B The materials and methods described also apply to FIG. 4A to FIG. 4D Implementation methods are not described herein, so they will not be described in detail.

[0097] Reference Figure 4A , the surface 10a of the donor substrate 10 has a certain roughness (eg, greater than or equal to 1 nmrms).

[0098] Reference Figure 4B , implanting atomic species through the surface 10a has the effect of forming an embrittled zone 11 within the donor substrate 10. As previously indicated, the surface of the donor substrate may be textured after forming the embrittled zone.

[0099] Reference Figure 4C The support 20 is formed by deposition on the surface of the film 12 (which at this stage still forms part of the donor substrate 10). As indicated previously, an intermediate layer (not shown) may be deposited before depositing the support.

[0100] Depending on the chosen deposition technique, the deposition may be conformal, that is to say the free surface of the support has substantially the same texture as the donor substrate, the thickness of the material between the surface of the support and the surface of the donor substrate remaining substantially constant.

[0101] Reference Figure 4D , the donor substrate 10 is then separated along the embrittled zone 11 in order to transfer the film 12 to the support 20. At the end of this separation, a residue 10' of the donor substrate remains, which may be recycled for another use.

[0102] For example, for acoustic wave structures such as radio frequency (RF) filters, in particular to avoid reflections of parasitic waves on the back side of the substrate and / or layer under consideration, FIG. 4A to FIG. 4D The method is of particular interest.

[0103] Several application examples (non-limiting) of the method according to the invention are described below.

[0104] Example 1: Formation of lithium niobate film on copper sheet

[0105] Lithium niobate (LiNbO3) is a piezoelectric and pyroelectric material that is remarkable in that it retains its piezoelectric properties at high temperatures. Its Curie temperature is 1140°C, while many other materials lose their properties at temperatures ranging from about 100°C to 250°C.

[0106] It therefore represents an interesting material for systems that exploit piezoelectricity and / or pyroelectricity in these temperature ranges. For example, they can be systems that recover energy by recovering the energy of vibrations and other deformations of mechanical systems operating in harsh environments in a temperature range above 250°C. They can also be piezoelectric or pyroelectric sensors dedicated to measuring temperature, pressure or detecting gases.

[0107] The material is single-crystalline and has good quality when produced by drawing it from an ingot and then cutting it into bulk wafers of a few hundred μm thickness. In thin films, when they are produced by deposition, they are usually polycrystalline, at best quasi-single-crystalline, but very defective.

[0108] Many target structures must follow a specific topology (eg, a structured floating beam or floating platform that is horizontally displaced or set back relative to the substrate surface).

[0109] A LiNbO3 substrate 10 is provided. A trench 100 is created by etching in the substrate 10 in order to define the contour of the future suspended membrane (see Figure 1A ). Typically, the trench has a width of several tens of μm and a depth between 0.1 μm and 0.5 μm.

[0110] Helium ions are implanted into the substrate 10 to form a brittle region 11 and define a thin LiNbO3 film 12 (see Figure 1B ). The thickness of the film 12 is about 0.3 μm.

[0111] An adhesion layer 21 composed of a Cr / Cu alloy is deposited on the film 12 by PVD technology. Next, a copper sheet 20 is deposited on the adhesion layer 21 by electrochemical deposition technology (see Figure 1E ). The thickness of the sheet is about 20 μm.

[0112] Next, annealing is applied at a temperature of 300° C. in order to cause separation of the donor substrate 10 along the embrittled region 11 .

[0113] Example 2: Formation of Yttrium-stabilized Zirconia Film on Nickel Sheet

[0114] Yttrium-stabilized zirconia (YSZ) is usually in the form of a polycrystalline ceramic or, less commonly, a single crystal substrate.

[0115] One use of this material is based on its ion-conducting properties. It is therefore used as a solid diaphragm in SOFC (solid oxide fuel cell) systems to play the role of an electrolyte. These systems, when they must be miniaturized (this is called micro SOFC), are interested in evolving into diaphragms that are thin on the one hand (that is, typically less than a few μm thick) and single-crystalline on the other hand. These systems operate at high temperatures (typically 550-700° C.) and are subject to strong thermomechanical loads. In order to make the diaphragm more resistant, it is advantageously given a corrugated shape, thereby having a bellows topology, which makes it possible to better absorb deformations by a spring effect. In addition, such shaping can have the beneficial effect of maximizing the exposed surface available for the desired electrochemical reaction.

[0116] Supply single crystal YSZ substrate 10 (see Fig. 7A A network of grooves 100 is generated by etching in the substrate 10 in order to define the contour of the future bellows of the electrolyte membrane (see Figure 7B ). Typically, the groove 100 has a width of several tens of μm and its depth is about 2 μm. The sides 100a of the groove (which will define the transition between the high and low areas of the bellows) are advantageously controlled to be inclined at more than 45° relative to the normal to the surface 10a. The grooves are spaced several tens of μm apart from each other to form the desired corrugations.

[0117] Hydrogen ions are implanted into the substrate 10 to form a brittle region 11 and define a thin YSZ film 12 (see Figure 7C ). The thickness of the film 12 is about 1 μm.

[0118] An adhesion layer 21 consisting of a Cr / Cu alloy is deposited on the film 12 by PVD technology (see Fig.7D ). Next, a nickel sheet 20 is deposited on the adhesive layer 21 by electrochemical deposition technology (see Fig. 7E ). The thickness of the sheet is about 20 μm.

[0119] Next, annealing is applied at a temperature of 300° C. so as to cause the donor substrate 10 to separate along the embrittled zone 11 (see Figure 7F ).

[0120] Next, the support 20 may be etched to obtain the final bellows shape (see Figure 7G ).

[0121] Example 3: Formation of a single-crystal silicon film on a curved glass sheet

[0122] In the field of producing screens or other optical components (lenses, mirrors, etc.), the production of non-flat or curved parts makes it difficult to use thin films of single-crystalline materials such as silicon. This example aims to make it possible to use thin silicon films on glass sheets with a specific curvature. The silicon films are particularly useful for producing high-performance transistors (for example, in order to make high-definition ultra-compact curved screens).

[0123] A bulk single crystal silicon substrate 10 is provided.

[0124] The curved shape that one wishes to follow is created by etching in the silicon substrate. Figure 5A In the embodiment shown, the shape chosen is a concave shape with a more pronounced rise on the edges. Any other profile (parabolic, elliptical, corrugated, etc.) would be possible. This shape can be generated thanks to etching by mechanical processing. A person skilled in the art will know how to adjust the etching technique to best suit the desired shape and size.

[0125] The substrate 10 is subjected to thermal oxidation to produce a SiO2 layer 14 having a thickness of 0.2 μm (see Figure 5B ).

[0126] Next, hydrogen ions are implanted into the substrate 10 through the oxide layer 14 to form the embrittled region 11 and define the single crystal silicon thin film 12 (see Figure 5C ). The thickness of the film 12 is about 0.5 μm.

[0127] A sheet 20 made of silicon dioxide (glass) is deposited on the film 12 by a deposition technique at low temperature (generally below 200° C., so as not to cause premature separation along the brittle zone) (see Figure 5D ). The thickness of the sheet is about 20 μm. In cases where high thermomechanical stresses are likely to occur, doping the silicon dioxide, for example with phosphorus or boron ions, makes it possible to better adjust the thermal expansion coefficient of the glass to that of silicon. A person skilled in the art will know how to choose the doping level and the most suitable conditions and deposition techniques, especially in terms of temperature and desired final thickness.

[0128] Next, annealing is applied at a temperature of 500° C. so as to cause the donor substrate 10 to separate along the embrittled zone 11 (see Figure 5E ).

[0129] Example 4: Formation of lithium tantalate film on glass sheet

[0130] This example targets, for example, acoustic wave structures such as radio frequency (RF) filters. In certain RF structures, attempts are made to avoid reflections of parasitic waves on the back side of the substrate and or layer under consideration. One approach consists in making the interface and the back surface geometrically imperfect, in particular by introducing active texturing or other roughness. If it is envisaged to use thin films of certain single crystal materials (e.g., LiTaO3), it is difficult or even impossible to meet this constraint, and this is the case without resorting to complex stacks that introduce additional intermediate layers.

[0131] A bulk single crystal LiTaO 3 substrate 10 is supplied.

[0132] Hydrogen ions are implanted into the substrate 10 through the surface 10a to form a brittle region 11 and define a single crystal LiTaO3 thin film 12 (see Fig. 6A ). The thickness of the film 12 is about 1.5 μm.

[0133] The surface 10a is textured by photolithography (see Figure 6B ). In this example, the implantation occurs before the texturing step, but it could also occur after, e.g. FIG. 4A to FIG. 4D As in the embodiment shown.

[0134] A person skilled in the art will know how to adjust the technique to best suit the desired shape and size of the texture. For example, a nanoimprint lithography technique may be chosen to define a pattern with features having slightly submicron lateral dimensions at a depth of about 0.05 μm. In one alternative, the texturing is obtained by roughening by the cathode sputtering effect. According to another alternative, preferably achieved before the implantation step, the texturing may be obtained by grinding the surface of the substrate 10.

[0135] A sheet 20 made of silicon dioxide is deposited on the film 12 by a deposition technique at low temperature (generally below 100° C. in order not to cause premature separation along the embrittled zone) (see Figure 6C ). The thickness of the sheet is about 10 μm. A person skilled in the art will know how to choose the most suitable deposition technique under these conditions, in particular in terms of temperature and desired final thickness. Alternatively, the sheet 20 may be made of metal instead of silicon dioxide.

[0136] Next, annealing is applied at a temperature of about 200° C. so as to cause the donor substrate 10 to separate along the embrittled zone 11 (see Fig.6D ).

[0137] Example 5: Case where the donor substrate includes multiple pads

[0138] According to one embodiment of the present invention, the non-planar topology of the donor substrate is caused by forming a plurality of pads 1001 laid on the surface of the wafer 1000 (see Fig. 8A ).

[0139] Advantageously, the pad is formed of a material selected from semiconductor material, piezoelectric material, magnetic material and functional oxide. Advantageously, the pad is single crystalline. Each pad can be arranged at an appropriate position on the wafer individually or collectively by bonding.

[0140] The pads may have any suitable size and shape depending on the target application.The pads may be laid out on the wafer in a regular manner, for example to form a grid pattern.

[0141] The main surface of each pad 1001 is parallel to the main surface of the wafer 1000. However, as long as the thickness of each pad is not controlled with sufficient accuracy, there may be slight thickness differences from one pad to the next (e.g., about 1 μm or 2 μm thickness). As a result, the surface composed of all pad surfaces has level differences, usually in the form of steps (the amplitude of these variations is in the range of Fig. 8A These different steps thus form a non-planar topology on the wafer surface.

[0142] Typically, the pads are intended for transferring a shallow monocrystalline film onto a final support, as described, for example, in documents FR 3 041 364 and US 6,562,127. To this end, before or after placing each pad in place on the wafer, an embrittled zone 1011 is formed in each pad to delimit the corresponding film 1012 to be transferred (for example, by implantation as described above).

[0143] Unlike the method described in the above-mentioned document, which involves bonding the main face of each pad to the final support, the present invention proposes depositing the support 20 on all the pads laid on the wafer surface (see Figure 8B ). Therefore, there are no assembly problems related to height differences of different pads.

[0144] Next, each gasket is separated along the corresponding embrittled zone 1011 to transfer the corresponding film 1012 to the support 20 (see Figure 8C ).

[0145] Whatever the embodiment considered, at the end of the separation of the donor substrate, a residue 10 ′ remains.

[0146] If recycling of the donor substrate is envisaged, repair operations may be implemented, in particular aimed at regenerating the surface of the donor substrate that may have been damaged during separation. These operations may in particular include steps of cleaning, etching, annealing, smoothing and planarization (for example by polishing).

[0147] In case the topology of the donor substrate has been formed before the embrittlement step, the residue of the donor substrate has the same topology as the initial topology of the donor substrate. In terms of cost issues, it may seem advantageous to retain this topology (curvature, and / or recessed pattern and / or texturing) initially created in the donor substrate in order to avoid having to systematically reform it after each recycling. In this case, planarization methods are avoided and methods with conformal removal of material in thickness, or even substantially zero removal of material (that is, below 30 nm), such as plasma etching or smoothing annealing, are preferred.

Claims

1. A method for manufacturing a film (12) on a support (20), the surface of the support having at least a recessed or embossed pattern, characterized in that: The method comprises the following steps: supplying a donor substrate (10), the surface of which has at least a recessed or embossed pattern formed by a plurality of pads (1001) laid on the surface of a wafer (1000), forming a brittle zone (11) in each liner (1001) to define a corresponding film (12) to be transferred, forming the support member (20) on the surface of all the pads (1001) by deposition, The donor substrate (10) is separated along the embrittled zone (11) to transfer each respective film (12) to the support (20).

2. The method according to claim 1, further comprising: An intermediate layer (21) is deposited on the non-planar surface before depositing the support (20).

3. The method according to claim 1, wherein: The step of forming the embrittled zone in each pad (1001) is performed by implanting ion species in the donor substrate (10).

4. The method according to claim 3, wherein: The implanted ion species are hydrogen and / or helium.

5. The method according to one of claims 1 to 2, wherein: The separation of the donor substrate (10) is caused by heat treatment.

6. The method according to claim 5, wherein: Deposition of the support member (20) is achieved with a thermal budget that is less than that of the separate heat treatment.

7. The method according to one of claims 1 to 2, wherein: Each respective transferred film (12) is made of a material selected from the group consisting of a semiconductor material, a piezoelectric material, a magnetic material and a functional oxide.

8. The method according to one of claims 1 to 2, wherein: The transferred film (12) is single crystalline.

9. The method according to claim 1, wherein: The thickness of the transferred film (12) is between 100 nm and 10 μm, preferably between 100 nm and 1 μm.

10. The method according to one of claims 1 to 2, wherein: The support member (20) is made of a material selected from metal, glass and ceramic.

11. The method according to one of claims 1 to 2, wherein: The support (20) has a thickness between 1 μm and 50 μm.

12. The method according to one of claims 1 to 2, wherein: The material of the support (20) is selected to have a thermal coefficient difference of less than 5×10 -6 K -1 .

13. The method according to one of claims 1 to 2, wherein: The deposition of the support (20) is achieved by one of the following techniques: physical vapor deposition, chemical vapor deposition, electrochemical deposition, spin coating, painting and spraying.

14. The method according to one of claims 1 to 2, wherein: The plurality of pads (1001) are laid on the surface of the wafer (1000) after forming the embrittled zone in each pad (1001).

15. The method according to one of claims 1 to 2, wherein: The plurality of pads (1001) are laid on the surface of the wafer (1000) before forming the embrittled zone in each pad (1001).

16. The method according to one of claims 1 to 2, wherein: At the end of said separation, said residue (10') of said donor substrate is recovered with a view to achieving a new corresponding film (12) for each pad (1001) having a non-planar surface on a support (20), and before said recovery, said residue of said donor substrate is subjected to an operation for regenerating the surface of said residue involving a material removal which is substantially zero or conformal to the topology of said residue (10').

17. The method according to one of claims 1 to 2, wherein: The deposition of the support (20) comprises sequential deposition of at least two layers of different materials.

18. The method according to one of claims 1 to 2, further comprising: After said separation of said donor substrate, an additional film (13) is deposited on the face of each respective transferred film (12) opposite to said support (20).

19. A structure comprising: A donor substrate (10), the surface of which has at least a recessed or embossed pattern formed by a plurality of pads (1001) laid on the surface of a wafer (1000), each pad (1001) including a brittle zone (11) for defining a corresponding superficial film (12), and A support (20) is deposited on the surface of the donor substrate (10) having at least a recessed or relief pattern formed by the plurality of pads (1001).

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