Method for manufacturing a structure containing multiple embedded cavities

Abstract

The present invention relates to a method for manufacturing a structure comprising a plurality of cavities confined between a thin layer and a support substrate, the method comprising: a) preparing a donor substrate and a support substrate; b) injecting a first lightweight species into the donor substrate to form an embedded fragile surface defining a thin layer to be transferred; c) locally injecting a second species into the donor substrate to form a functional embedded fragile surface exhibiting a first zone without the second species and a second zone containing both species; d) forming a plurality of cavities opening to the front surface of the donor substrate or the support substrate; e) assembling the structure by directly bonding the donor substrate onto the support substrate to form a bond structure in which the cavities are positioned perpendicularly to either the first zone or the second zone; and f) heat-treating the bond structure to induce spontaneous separation along the functional embedded fragile surface to form the structure.

Description

[Technical Field]

[0001] The present invention relates to the fields of microelectronics and electromechanical microsystems. More specifically, the present invention relates to a method for manufacturing a plurality of cavities embedded in a structure comprising a support substrate and a thin layer, wherein the plurality of cavities are confined between the support substrate and the thin layer. [Background technology]

[0002] MEMS devices (MEMS is an acronym for Micro Electromechanical Systems) are widely used to manufacture a variety of sensors for numerous applications, including pressure sensors, microphones, high-frequency switches, and electroacoustic and ultrasonic transducers (e.g., piezoelectric microfabricated ultrasonic transducers (pMUTs)). Many of these MEMS devices are based on a flexible film overlaid on a cavity. During operation, the bending of the film, related to physical parameters (e.g., the propagation of acoustic waves in the case of pMUTs), is converted into an electrical signal (or vice versa, depending on whether the device is in receiving or transmitting mode).

[0003] Numerous layer transfer methods exist for obtaining structures containing thin layers (forming the aforementioned films) that protrude over multiple cavities. These advantageously rely on assembly by direct bonding (i.e., without the addition of adhesives) of the donor and support substrates along their respective front surfaces. One or the other substrate (conventionally the support substrate) contains cavities opening to its front surface. These cavities are sealed during the assembly step as a result of molecular bonding of the two substrates. A thinning step of the donor substrate transfers the thin layer onto the support substrate. This thinning step may, in particular, be based on Smart Cut™ technology, which utilizes an embedded brittle surface formed by injecting a lightweight species into the donor substrate. This brittle surface, along with the front surface of the donor substrate, can define the extent of the thin layer to be transferred (typically having a thickness of less than 2 μm). As is well known, thermal and / or mechanical activation causes microcracks to grow in the embedded brittle surface, resulting in separation along the surface and consequently transferring the thin layer onto the support substrate. The remaining portion of the donor substrate can be reused for subsequent layer transfer.

[0004] Nevertheless, obtaining high-quality thin-layer transfers is a complex problem because of the presence of cavities and the lack of reinforcing effect in their vertical direction. The reinforcing effect here is thought to be due to the presence of the front surface of the support substrate in contact with the thin layer.

[0005] Therefore, the growth of microcracks in the embedded fragile surface can cause irreversible damage to the thin layer perpendicular to the cavity, potentially leading to blisters equivalent to transfer defects, and even localized delamination.

[0006] The larger the cavity size, the more difficult it becomes to ensure transfer quality. The target lateral dimensions of the cavity are typically several microns to tens of microns, assuming the thin layer thickness is kept below 2 μm. Subject of the Invention

[0007] This invention proposes a method for batch fabricating a structure comprising multiple embedded cavities over which a high-quality thin layer, i.e., a layer with very few transfer defects, protrudes. This is based on the formation of a functionally called embedded fragile surface, whose features and properties differ between a first zone that benefits from a reinforcing effect and a second zone that does not, with the aim of making the growth (maturation) of microcracks in these two zones uncorrelated in order to improve the quality of layer transfer. [Overview of the project]

[0008] The present invention relates to a method for manufacturing a structure comprising a plurality of cavities confined between a thin layer and a support substrate, wherein the manufacturing method is a) A step of preparing a donor substrate and a support substrate, wherein each substrate has a front and a back surface, b) A step of injecting a first lightweight species into the donor substrate to form a uniform embedded fragile surface that defines the thin layer to be transferred, together with the front surface of the donor substrate, c) Inject the second seed locally into the donor substrate to introduce the second seed into a uniform embedded weak surface only in the second zone. A first zone including the first lightweight species but not including the second species, and The second zone includes the first lightweight species and the second species. The steps include forming a functional embedded vulnerability surface that exhibits the following characteristics: d) The step of forming a plurality of cavities that open on the front surface of the donor substrate or support substrate, e) Assembling by directly bonding the donor substrates to the support substrate along their respective front surfaces to form a bonded structure in which the multiple cavities are perpendicularly aligned with either the first or second zone of a functional embedded weak surface, f) A step of heat-treating the bond structure to induce spontaneous separation along the functional embedded weak surface, forming the structure on one side and the rest of the donor substrate on the other, Includes.

[0009] According to the advantageous features of the present invention, the injection in step c) is performed either alone or in any achievable combination, in the presence of a mask positioned in front of the donor substrate that is perpendicularly aligned with the first zone of the functionally embedded vulnerable surface.

[0010] The formation of the multiple cavities in step d) is performed, for example, by locally etching the front surface of the support substrate using the mask placed on the front surface.

[0011] Following step c), step d), which forms multiple cavities, includes etching the front surface of the donor substrate perpendicular to the second zone, while the first zone is protected from etching by a mask.

[0012] The method includes step c') injecting a third seed locally into the front surface of the donor substrate after step d) and after removing the mask, thereby injecting the third seed into a first zone of the functional embedding vulnerable surface and another embedding surface located below at a certain distance from the second zone of the functional embedding vulnerable surface. Step d), which forms multiple cavities, is performed before step c), The step of applying a mask positioned on the front surface of the donor substrate that is perpendicularly aligned with a second zone of a functional embedded vulnerable surface that is intended to be formed in a later step c), The process includes etching the front surface of a donor substrate perpendicular to a first zone, wherein the second zone is protected from etching by a mask, After step d) and after the mask has been removed from the front of the donor substrate, injection step c) is performed, thereby injecting the second seed into a second zone of the functional embedding vulnerable surface and into another embedding surface located below and at a certain distance from the first zone of the functional embedding vulnerable surface. The second zone of the functional embedded weakness plane is vertically aligned with a plurality of cavities in the bonding structure, the first light species is a hydrogen atom or ion, and the second species is a helium atom or ion. The first zone of the functional embedded weakness plane is vertically aligned with a plurality of cavities in the bonding structure, the first light species is a hydrogen atom or ion, or a helium atom or ion, or a hydrogen and helium atom or ion, and the second species is a silicon atom or ion that can slow down the growth rate of microcracks in the second zone of the functional embedded weakness plane compared to the growth rate of microcracks in the first zone. Assembly step e) includes at least one intermediate layer disposed on the donor substrate and / or the support substrate, and the intermediate layer is deposited after one of steps a) to d).

[0013] Other features and advantages of the present invention will become apparent from the following detailed description when referring to the accompanying drawings.

Brief Description of the Drawings

[0014] [Figure 1] FIG. showing two structures manufactured using the manufacturing method according to the present invention. [Figure 2a] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 2b] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 2c] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 2d] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 2e] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 2f] FIG. showing the steps of the manufacturing method according to the first embodiment of the present invention. [Figure 3a] FIG. showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 3b] It is a diagram showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 3c] It is a diagram showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 3d] It is a diagram showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 3e] It is a diagram showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 3f] It is a diagram showing the steps of the manufacturing method according to the second embodiment of the present invention. [Figure 4a] [Figure 4d] [Figure 4b] It is a diagram showing the steps of the manufacturing method according to the third embodiment of the present invention. Note that in this third embodiment, step d) (Fig. 4d) is performed before step c) (Fig. 4c). [Figure 4d] It is a diagram showing the steps of the manufacturing method according to the third embodiment of the present invention. [Figure 4c] It is a diagram showing the steps of the manufacturing method according to the third embodiment of the present invention. [Figure 4e] It is a diagram showing the steps of the manufacturing method according to the third embodiment of the present invention. [Figure 4f] It is a diagram showing the steps of the manufacturing method according to the third embodiment of the present invention. [Figure 5] It is an image seen from above an SOI structure having a cavity not according to the present invention, obtained after isothermal annealing at different temperatures. [Figure 6a] It is a diagram showing the steps of the manufacturing method according to a modification of the first embodiment of the present invention. Note that in this modification, an additional step c') is added after step d) as compared with the first embodiment shown in Figs. 2a to 2f. [Figure 6b] It is a diagram showing the steps of the manufacturing method according to a modification of the first embodiment of the present invention. [Figure 6c]This figure shows the steps of a manufacturing method according to a modified version of the first embodiment of the present invention. [Figure 6d] This figure shows the steps of a manufacturing method according to a modified version of the first embodiment of the present invention. [Figure 6c-2] Figure 6c' (Figure 6c-2) shows the steps of a manufacturing method according to a modified example of the first embodiment of the present invention. [Figure 6e] This figure shows the steps of a manufacturing method according to a modified version of the first embodiment of the present invention. [Figure 6f] This figure shows the steps of a manufacturing method according to a modified version of the first embodiment of the present invention. [Modes for carrying out the invention]

[0015] Certain diagrams are schematic representations, not to scale, for readability. In particular, the layer thickness along axis z is not to scale with respect to the lateral dimensions along axes x and y. In some drawings, elements of the same nature may be referred to by the same reference numeral.

[0016] The present invention relates to a method for manufacturing a structure 100 which includes a plurality of cavities 30 confined between a thin layer 10 and a support substrate 20, as shown in Figure 1. The structure 100 may potentially include at least one intermediate layer 50 between the thin layer 10 and the support substrate 20.

[0017] The first step a) of the manufacturing method is to prepare a donor substrate 11 onto which the thin layer 10 will be transferred, and a support substrate 20 (Figures 2a, 3a, 4a, and 6a).

[0018] The donor substrate 11 and support substrate 20 advantageously typically have the form of wafers with a diameter of more than 100 mm, for example, 150 mm, 200 mm, or 300 mm, and have front surfaces 11a, 20a and back surfaces 11b, 20b, respectively. Their thickness is typically 200 to 900 microns.

[0019] The donor substrate 11 can be formed from at least one material selected from silicon, germanium, III-V semiconductor compounds, silicon carbide, lithium tantalate, lithium niobate, or any other material of interest for the intended application. The support substrate 20 can be formed from at least one material selected from silicon, germanium, III-V semiconductor compounds, silicon carbide, lithium tantalate, lithium niobate, glass, ceramic, or any other material of interest for the intended application.

[0020] The next step b) of this method corresponds to injecting the first lightweight species into the donor substrate 11 through the entire front surface 11a of the donor substrate 11 (or in other words, full-surface injection or "full wafer" injection) to form a uniform embedded fragile surface 12' that defines the area of ​​the thin layer 10 to be transferred, together with the front surface 11a (Figures 2b, 3b, 4b, and 6b). Here, the term uniform means that the injection characteristics are the same across the entire area of ​​the embedded fragile surface 12'.

[0021] These lightweight species may be selected from hydrogen and / or helium atoms or ions in particular. As is well known with respect to the Smart Cut™ process, when these first species are injected into the donor substrate 11, they can form lenticular defects in a uniform embedded brittle surface 12', which are thermally activated and propagate in the form of microcracks through the diffusion of lightweight species and coalescence of lenticular defects. It should be noted that the lenticular defects are embedded within the donor substrate 11 and distributed in a thin layer determined by the injection Gaussian profile. For simplicity, this layer is referred to as the embedded brittle surface.

[0022] The injection energy determines the depth to which a uniform embedded weak surface 12' is generated in the donor substrate 11. Given the injection energy and the given material of the donor substrate 11, the injection dose of a lightweight material is an important parameter that determines the rate of microcrack propagation, i.e., the rate of blistering (in the absence of reinforcement) and the rate of fracture (when reinforcement is used).

[0023] The applicant has confirmed that, in a structure 100 having a cavity, the features and properties required for obtaining a transfer of a high-quality thin layer 10 differ depending on whether the surface is aligned perpendicular to the region that benefits from the reinforcing effect or perpendicular to the cavity (and therefore without reinforcing effect). In the region that benefits from the reinforcing effect, relatively high temperatures can be used in the heat treatment intended to bring about spontaneous separation of the embedded weak surface, and at the same time, it is considered advantageous to "slow down" the fracturing rate so as to maintain a controllable processing time, as higher temperatures also allow for placing microcracks under higher pressure, thereby promoting the continuity of the fracturing wave. In the region that does not benefit from the reinforcing effect (aligned perpendicular to the cavity), it is advantageous during the heat treatment described above for the propagation of microcracks to generate large-sized blisters without accelerating localized delamination.

[0024] Progress toward this objective is achieved by implementing the manufacturing method according to the present invention, which envisions the creation of a functional embedded vulnerable surface 12 comprising a first zone Z1 that is different from a second zone Z2 in terms of the dose and / or properties of the injected species.

[0025] Step c) of this method corresponds to locally injecting a second seed into the donor substrate 11 to introduce the second seed into a uniform embedded weak surface 12' only in the second zone Z2. This makes it possible to form a functional embedded weak surface 12 (Figures 2c, 3c, 4c, and 6c). The latter surface is in the (x,y) plane of the front surface 11a, The first zone Z1 includes the first lightweight species but does not include the second species. The second zone, Z2, contains the first lightweight species and the second species.

[0026] The second species may have the same or different properties as the first species. The injection energy used to introduce the second species is adjusted so that the injection profile of the second species substantially overlaps with the injection profile of the first lightweight species. It is preferable that the maximum values ​​of the injection profiles of the first and second species are located at equal depths within + / - 20%, or more favorably, within + / - 10%.

[0027] Localized injection can be achieved in various ways. A first option, implemented in the first and second embodiments of the present invention (Figures 2c and 3c), involves using a mask (M) applied to the front surface 11a of the donor substrate 11 to protect the first zone Z1 from injection. Such masks are conventionally formed using deposition, lithography, and etching techniques. Another option, shown in Figure 4c with reference to a third embodiment of the present invention, involves utilizing the difference in undulation of the front surface 11a between a region perpendicular to the first zone Z1 and a region perpendicular to the second zone Z2 to place a second seed in the second zone Z2 of a functional embedding vulnerable surface 12, and introducing those seeds into another, but discontinuous, embedding surface 12" at a distance below the first zone of the surface 12. In this case, the second seed can contribute to the features and properties of the second zone Z2, but not to (or only to a very limited extent to) the features and properties of the first zone Z1.

[0028] During step d) of this method, a plurality of cavities 30 are formed on the front surface 11a of the donor substrate 11 (in the first and third embodiments, Figures 2d, 6d, and 4d), or on the front surface 20a of the support substrate 20 (in the second embodiment, Figure 3d).

[0029] It is important to note that step d) may be performed after step c) (First Embodiment, Figures 2d and 6d), or before step c) (Third Embodiment, Figure 4d), or even in parallel with step c) (Second Embodiment, Figure 3d).

[0030] Conventionally, the formation of a cavity on one side of the substrate is performed, for example, by locally etching the front surfaces 11a and 20a using masks (M, M') placed on the front surfaces 11a and 20a.

[0031] The depth of the cavity 30 may typically vary between 100 nm and 100 μm. The shape of the cavity in the (x, y) plane of the front surfaces 11a and 20a of the associated substrates 11 and 20 may be circular, square, rectangular, or polygonal. The characteristic dimensions (or lateral dimensions) of the cavity 30 in the (x, y) plane, i.e., its diameter (for a circle) or its side length (for a square), or its width and length (for a rectangle), are typically between 1 μm and 500 μm. The spacing between the cavities 30 may range from 1 μm to several hundred mm.

[0032] The first and third embodiments (Figures 2d and 4d), which assume the formation of a cavity 30 in the donor substrate 11, offer the advantage of requiring only one mask (M) to perform steps c) and d). Nevertheless, in these embodiments, the range of possible cavity depths is limited because the cavity depth must be kept smaller than the difference between the depth of the functional embedded fragile surface 12 and the target thickness of the thin layer 10 to be transferred.

[0033] The second embodiment assumes the formation of a cavity 30 in the support substrate 20 (Figure 3d). In this case, the mask M' used to define the position of the cavity 30 within the substrate 20 and the mask M used to define the positions of the first and second zones Z1 and Z2 must be such that the cavity 30 and the first or second zones Z1 and Z2 correspond to each other during the subsequent assembly steps.

[0034] The manufacturing method then includes step e) assembling by directly bonding the donor substrate 11 to the support substrate 20 at their respective front surfaces 11a, 20a to form a bonded structure 90 (Figures 2e, 3e, 4e, and 6e). A bonded interface 40 without adhesive is defined between the two assembled surfaces.

[0035] Depending on the embodiment, the cavity 30 is positioned to be perpendicularly aligned with either the first zone Z1 or the second zone Z2 of the functional embedded vulnerable surface 12.

[0036] The principle of direct bonding is well known in the prior art and will not be explained in detail here. Since this is based on molecular bonding between assembled surfaces, very good surface finish (cleanliness, low roughness, etc.) of the substrates 11 and 20 is required to obtain a good quality assembly.

[0037] Before assembly, the donor substrate 11 and the support substrate 20 are typically prepared. For example, a conventional sequence used in microelectronics, particularly for silicon-based substrates, includes ozone cleaning, SC1 cleaning (SC1 being an acronym for Standard Clean 1), and SC2 cleaning (SC2 being an acronym for Standard Clean 2), with rinsing in between. The surfaces to be assembled can also be activated, for example using plasma, before contact to promote high bonding energy between the surfaces.

[0038] Optionally, the donor substrate 11 and / or support substrate 20 may include an intermediate layer 50 on at least their respective front surfaces 11a, 20a to improve bonding quality and bonding energy at their interface, or to adapt to the purpose of the application (Figures 2e, 3e, 4e, and 6e). This intermediate layer may be formed from an insulating material, in particular, silicon oxide or silicon nitride. In a specific example where the donor substrate 11 and support substrate 20 are made of silicon, the resulting structure 100 is a silicon-on-insulator (SOI) structure with a recessed cavity 30.

[0039] The intermediate layer 50 located on the donor substrate 11 and / or the support substrate 20 can be formed by growth or deposition after one of steps a) to d) of this method.

[0040] The direct bonding in step e) may be performed in an ambient atmosphere or in a controlled atmosphere (e.g., in a low-pressure chamber).

[0041] The next step f) of the manufacturing method corresponds to heat-treating the bond structure 90 so that it brings about spontaneous separation along the functional embedded weak surface 12, forming structure 100 on one side and the rest of the donor substrate 11' on the other (Figures 2f, 3f, 4f, and 6f). Structure 100 includes a thin layer 10 assembled directly with the support substrate 20 or via an intermediate layer 50 along the bond interface 40, and an embedded cavity 30.

[0042] As previously stated, the applicant confirmed that the quality of the transfer of the thin layer 10 from the donor substrate 11 to the support substrate 20 is improved by applying a higher separation temperature. Figure 5 shows partial images of the surface of several SOI structures (not according to the present invention) with cavities after transfer, for various heat treatment temperatures (isothermal annealing) from 350°C to 450°C. It is clear that the density of transfer defects (appearing in black in the image) decreases with increasing heat treatment temperature in step f).

[0043] In the manufacturing method according to the present invention, the functional embedded fragile surface 12 is composed of two zones Z1 and Z2 having different injection characteristics, thereby promoting a transfer rate that is suitable for "high" temperatures (on the one hand, in the region that benefits from the reinforcing effect) and promoting the formation of large-sized blisters at these temperatures (on the other hand, in the region that is perpendicular to the cavity 30 that does not benefit from the reinforcing effect), and in some cases minimizing localized delamination.

[0044] According to one embodiment, a second zone Z2 of the functional embedded weak surface 12 is positioned to align perpendicularly with the cavity 30 within the joint structure 90.

[0045] In a particular case of an SOI-type target structure 100 having a cavity, the first lightweight species may be hydrogen atoms or ions, and the second species may be helium atoms or ions. Thus, in practice, the donor substrate 11 is made of single-crystal silicon, the support substrate 20 is made of silicon, and an intermediate layer 50 of silicon oxide (e.g., 200 nm thick) is placed on all or part of one and / or the other of the front surfaces 11a, 20a before assembly. As an example, the cavity 30 is formed in the donor substrate 11 and has a depth of 100 nm, a lateral dimension of 40 μm, and a gap of 7 μm. The injection energy of the first lightweight species (hydrogen) is 6 E 16 / cm 2 The dose is 140 keV, and the injection energy of the second seed (helium) is 2 E 16 / cm 2 This dose corresponds to 220 keV.

[0046] The first zone Z1 of the functionally embedded fragile surface 12 containing only hydrogen species is aligned perpendicularly to the region that benefits from the reinforcing effect, and the implantation characteristics in the first zone Z1 here are suitable for transfer in a higher temperature range (typically above 450°C).

[0047] The second zone Z2 of the functional embedded fragile surface 12, containing the first seed (hydrogen) and the second seed (helium), is aligned perpendicularly to the region (cavity 30) that does not benefit from the reinforcing effect, and the injection characteristics in the second zone Z2 here are suitable for the formation of large-sized blisters in the aforementioned "high" temperature range.

[0048] According to another embodiment, the first zone Z1 of the functional embedded weak surface 12 is positioned to align perpendicularly with the cavity 30 within the joint structure 90.

[0049] In the specific case of the SOI - type target structure 100 having a cavity, the first light species may be an atom or ion of hydrogen, or an atom or ion of helium, or an atom or ion of hydrogen and helium (in which case step c) involves co - implantation, i.e., two successive implantations of these two light species). The second species to be implanted locally is an atom or ion that can slow down the growth rate of micro - cracks in the second zone Z2 of the functional embedded weak plane 12 compared to the growth rate of micro - cracks in the first zone Z1. These second species may be, for example, atoms or ions of silicon, which damage the material of the donor structure 11 to achieve more or less amorphization, and thus change the growth rate of micro - cracks. Of course, to achieve the same purpose, second species of different properties can be implanted.

[0050] In practice, the donor substrate 11 is made of single - crystal silicon, the support substrate 20 is made of silicon, and before assembly, an intermediate layer 50 of silicon oxide (e.g., 200 nm thick) is located on the front surface 20a. As an example, the cavity 30 is formed in the donor substrate 11 and has a depth of 100 nm, a lateral dimension of the order of 40 μm, and a pitch of 7 μm. The implantation energy of the first light species (co - implanted hydrogen and helium) is 1 E 16 / cm 2 and 1.5 E 16 / cm 2 at 32 keV (H) and 52 keV (He) respectively, and the implantation energy of the second species (Si) is 10 E 14 / cm 2 at 360 keV with a dose of.

[0051] The first zone Z1 of the functional embedded weak plane 12 containing only the first species (hydrogen and helium) is aligned perpendicular to the region (cavity 30) that does not benefit from the reinforcement effect, and the implantation characteristics in the first zone Z1 here may be suitable for the formation of large - sized blisters with limited local delamination in the "high" temperature range desired in the separation heat - treatment step f).

[0052] The second zone Z2 of the functional embedded fragile surface 12, containing the first species (hydrogen and helium) and the second species (Si), is aligned perpendicularly to the region that benefits from the reinforcing effect, and the implantation characteristics in the second zone Z2 here are suitable for transfer in a "high" temperature range (typically above 450°C).

[0053] It should be noted that the manufacturing method may include, after step f), a conventional step (mechanical, chemically mechanical, chemical, or thermal) of finishing and / or polishing the free surface 10a of the thin layer 10 in order to achieve the required crystal quality and surface finish for the thin layer 10 in the completed structure 100.

[0054] According to a modification of the first embodiment of the present invention shown in Figures 6a to 6f, step c') can be performed to locally inject a third seed into the front surface 11a of the donor substrate 11. This step c') may be performed in particular after step d) of forming a cavity 30 in the donor substrate 11 and after removing the mask M (Figure 6c'). Thus, the third seed is injected into the first zone Z1 of the functional embedding vulnerable surface 12 and into another discontinuous embedding surface 12" located at a distance below the second zone Z2 of the functional embedding vulnerable surface 12. These third seeds contribute to altering the features and properties of the first zone Z1 of the functional embedding vulnerable surface 12, but have little to no effect on the features and properties of the second zone Z2.

[0055] At the end of the transfer of the thin layer 10, the discontinuous embedding surface 12" is located on the remaining portion 11' of the donor substrate (Figure 6f).

[0056] The present invention can be used in a wide range of MEMS or NEMS (nanoelectromechanical systems) devices, or in any other application that benefits from a thin layer 10 locally placed on a cavity 30 within a structure 100. As already described herein, a silicon-on-insulator (SOI) substrate with an embedded cavity is a known example of such a structure 100.

[0057] The present invention is not limited to the embodiments described, and modified embodiments may be adopted without departing from the scope of the invention as defined by the claims.

Claims

1. A method for manufacturing a structure (100) including a plurality of cavities (30) confined between a thin layer (10) and a support substrate (20), a) A step of preparing a donor substrate (11) and a support substrate (20), wherein each of the substrates (11, 20) has a front surface (11a, 20a) and a rear surface (11b, 20b), b) A step of injecting a first lightweight material into the donor substrate (11) to form a uniform embedded fragile surface (12') that defines the thin layer (10) to be transferred, together with the front surface (11a) of the donor substrate (11), c) Inject the second seed locally into the donor substrate (11) to introduce the second seed into the uniform embedded fragile surface (12') only in the second zone (Z2), A first zone (Z1) which includes the first lightweight species but does not include the second species, and A second zone (Z2) including the first lightweight species and the second species. The steps include forming a functional embedded vulnerability surface (12) that exhibits the following characteristics: d) The step of forming a plurality of cavities (30) that open on the front surface (11a, 20a) of the donor substrate (11) or the support substrate (20), e) Assembling by directly bonding the donor substrate (11) to the support substrate (20) along their respective front surfaces (11a, 20a) to form a bond structure (90) in which the plurality of cavities (30) are aligned perpendicularly to either the first zone (Z1) or the second zone (Z2) of the functional embedded fragile surface (12), f) The step of heat-treating the bonding structure (90) to induce spontaneous separation along the functional embedded weak surface (12), thereby forming the structure (100) on one side and the remaining portion (11') of the donor substrate on the other side. A manufacturing method that includes this.

2. The manufacturing method according to claim 1, wherein the injection in step c) is carried out in the presence of a mask (M) positioned on the front surface (11a) of the donor substrate (11) that is aligned perpendicularly to the first zone (Z1) of the functional embedded fragile surface (12).

3. The manufacturing method according to claim 2, wherein the formation of the plurality of cavities (30) in step d) is performed, for example, by locally etching the front surface (20a) of the support substrate (20) using a mask (M') placed on the front surface (20a).

4. The manufacturing method according to claim 2, wherein, after step c), step d) forming the plurality of cavities (30) includes etching the front surface (11a) of the donor substrate (11) that is aligned perpendicularly to the second zone (Z2), and the first zone (Z1) is protected from etching by the mask (M).

5. The manufacturing method according to claim 4, further comprising step c') of locally injecting a third seed into the front surface (11a) of the donor substrate (11) after step d) and after removing the mask (M), thereby injecting the third seed into the first zone (Z1) of the functional embedding vulnerable surface (12) and another embedding surface (12") located below the second zone (Z2) of the functional embedding vulnerable surface (12).

6. Step d) of forming the plurality of cavities (30) is performed before step c), The steps include applying a mask (M) positioned on the front surface (11a) of the donor substrate (11) that is perpendicularly aligned with the second zone (Z2) of the functional embedded fragile surface (12) that is intended to be formed in a later step c), A step of etching the front surface (11a) of the donor substrate (11) that is perpendicular to the first zone (Z1), wherein the second zone (Z2) is protected from etching by the mask (M), The manufacturing method according to claim 1, including

7. The manufacturing method according to claim 6, wherein after step d) and after the mask (M) has been removed from the front surface (11a) of the donor substrate (11), the injection step c) is performed, thereby injecting the second seed into the second zone of the functional embedding vulnerable surface (12) and into another embedding surface (12") located at a distance below the first zone (Z1) of the functional embedding vulnerable surface (12).

8. The second zone (Z2) of the functional embedded weak surface (12) is aligned perpendicularly with the plurality of cavities (30) within the joint structure (90), The first lightweight species is a hydrogen atom or ion, and the second species is a helium atom or ion. The manufacturing method according to any one of claims 1 to 5.

9. The first zone (Z1) of the functional embedded weak surface (12) is aligned perpendicularly to the cavity (30) within the joint structure (90), The first lightweight species is a hydrogen atom or ion, or a helium atom or ion, or a hydrogen and helium atom or ion. The second species is a silicon atom or ion that can slow down the growth rate of the microcracks in the second zone (Z2) of the functional embedded brittle surface (12) compared to the growth rate of the microcracks in the first zone (Z1). The manufacturing method according to any one of claims 1, 2, 3, 6, and 7.

10. The manufacturing method according to any one of claims 1 to 9, wherein assembly step e) includes at least one intermediate layer (50) disposed on the donor substrate (11) and / or the support substrate (20), the intermediate layer (50) being deposited after one of steps a) to d).

Images