Donor substrate for thin-layer transfer and associated transfer method

Abstract

The present invention relates to a donor substrate (100) for transferring a single-crystal thin layer (1) made of a first material onto a receiver substrate (2), wherein the donor substrate (100) has a front surface (100a) and a rear surface (100b), - a buried weakening plane (30) defining the upper surface (101) and lower surface (102) of the donor substrate (100), - a first layer (10) on the side of the front surface (100a) at the upper surface (101), a second layer (20) adjacent to the buried weakening plane (30), and a stop layer (15) inserted between the first layer (10) and the second layer (20), wherein the first layer (10) is composed of the first material and the stop layer (15) is formed of a second material capable of providing selective etching for the first material, the first layer, the second layer, and the stop layer, - amorphized by ion implantation, and strictly speaking, The invention comprises an amorphous sub-part (101', 101'', 101''') having a thickness thinner than that of the upper (101) and at least the first layer (10); and a second layer (20) adjacent to the embedded weakening plane (30) and comprising at least one single crystal sub-layer (22). The invention also relates to two embodiments of a method for transferring a single crystal thin layer (1) from a donor substrate (100).

Description

Technology Field

[0001] The present invention belongs to the field of semiconductors and microelectronics. The present invention relates to a donor substrate suitable for transferring a thin layer onto a receiver substrate, particularly to transfer at low temperature onto a receiver substrate comprising finished or partially finished electronic components. The present invention also relates to a method for transferring said donor substrate. Background Technology

[0002] Three-dimensional (3D) integration of circuits has been strongly developed over the years because it enables the association of different functions while minimizing the spatial requirements of the system. 3D integration is based on the vertical stacking of electronic device layers. Such stacking requires the formation of a crystalline material layer on top of existing device layers. Since these devices are neither homogeneous nor crystalline, conventional crystalline thin film growth techniques, such as epitaxy, cannot be used. Furthermore, existing device layers, particularly those that may contain metallization levels, often have limited temperature resistance and need to be maintained at low temperatures.

[0003] Therefore, 3D integration primarily implements a thin film transfer technology from a donor substrate to a receiver substrate that may include one or more device layers.

[0004] Some known layer transfer methods are based on assembly by direct bonding of a donor substrate (to which a desired thin crystalline layer is induced) onto a receiver substrate. Then, the donor substrate undergoes a thinning step, and finally, a thin layer is formed. This thinning step can be performed using various techniques known in the prior art. In particular:

[0005] - Smart Cut™ method particularly suitable for forming very thin layers (typically having a thickness of several nanometers to 1 micron): based on injecting a gas species into the donor substrate on its surface to be assembled before the assembly step to form a buried weakening plane; after assembly, during the crushing step, the donor substrate is separated along the weakening plane to leave only the thin layer attached to the receiver substrate.

[0006] - A mechanical-chemical thin film method comprising mechanical lapping, mechanical-chemical polishing and chemical etching, particularly suitable for forming layers having a thickness of several microns to tens or even hundreds of microns.

[0007] Of course, the techniques cited above are not exhaustive, and other known techniques may be used to thin the donor substrate.

[0008] As mentioned, the Smart Cut™ method is particularly suitable for forming very thin layers. After transfer, it is necessary to perform several operations to prepare the transferred layer for manufacturing electronic devices: repairing injection defects, smoothing fractured surfaces, thinning these same layers, and closing the bonding interfaces. These operations are typically performed at high temperatures, particularly in the context of manufacturing Silicon on Insulator (SOI) structures. For the 3D integration we are interested in, these operations must be performed at low temperatures to avoid damaging the underlying device layer.

[0009] Document FR2978603 proposes a solution that facilitates the repair of injection defects at low temperatures.

[0010] The present invention aims to improve the latest technology by proposing a donor substrate particularly suitable for transferring a high-quality single-crystal layer onto a receiver substrate, most particularly when the receiver substrate is incompatible with high temperatures due to the presence of an electronic device. The present invention also relates to a method for transferring a thin layer from the donor substrate onto a receiver substrate.

[0011] Brief description of the invention

[0012] The present invention relates to a donor substrate for transferring a single-crystal thin layer made of a first material onto a receiver substrate, wherein the donor substrate has a front surface and a back surface and comprises the following:

[0013] - Embedded weakening plane defining the upper and lower parts of the donor substrate,

[0014] - From the top, a first layer on the front side, a second layer adjacent to a buried weakening plane, and a stop layer inserted between the first layer and the second layer, wherein the first layer is composed of a first material and is intended to form a single-crystal thin layer, and the stop layer is formed of a second material that allows selective etching of the first material, a first layer, a second layer, and a stop layer,

[0015] - Amorphous sub-part comprising at least a first layer, which is amorphized through ion implantation and has a thickness that is strictly thinner than the thickness of the upper layer; and at least one single-crystal sub-layer, which is adjacent to a buried weakening plane, and the second layer which is intended to form a recrystallization seed for the amorphous sub-part.

[0016] According to the advantageous features of the present invention, the following are taken alone or in any feasible combination:

[0017] The amorphous sub-part includes a stationary layer;

[0018] The amorphous sub-part includes a portion of the second layer adjacent to the stationary layer;

[0019] The second layer consists of the first material;

[0020] The first material is selected from silicon, germanium, or a silicon / germanium alloy;

[0021] The second material is selected from silicon germanium or highly doped silicon;

[0022] The first layer has a thickness of 5 microns to 500 nm;

[0023] The stationary layer has a thickness of 2 to 100 nm;

[0024] The second layer has a thickness of 50 to 1000 nm;

[0025] The donor substrate includes an amorphous silicon junction layer disposed on a first layer;

[0026] The bonding layer has a thickness of 2 to 20 nm;

[0027] The donor substrate includes an intermediate layer made of silicon oxide interposed between a first layer and a bonding layer;

[0028] The intermediate layer has a thickness of 10 to 200 nm;

[0029] The present invention also relates to a method for transferring a single-crystal thin layer made of a first material onto a receiver substrate.

[0030] According to the first embodiment, the transfer method comprises the following steps:

[0031] a) a step of providing a donor substrate as described above,

[0032] b) a step of providing a receiver substrate;

[0033] c) A step of assembling by directly bonding the front surface of the donor substrate onto the receiver substrate,

[0034] d) a step of separating along an embedded weakening plane to transfer the upper part of the donor substrate onto the receiver substrate,

[0035] e) a step of recrystallizing an amorphous sub-part to form a thin single-crystal layer, thereby restoring single-crystal quality to the first layer,

[0036] f) A step of chemically etching the second layer, and then selectively chemically etching the stop layer for the single-crystal thin layer.

[0037] Advantageously, the recrystallization step e) includes heat treatment at a temperature of 450°C to 900°C, preferably 450°C to 550°C.

[0038] According to the second embodiment, the transfer method comprises the following steps:

[0039] a) a step of providing a donor substrate as described above,

[0040] a') locally recrystallizing an amorphous sub-part to restore single-crystal quality to the first layer without affecting the buried weakening plane, wherein the first recrystallized layer forms a single-crystal thin layer,

[0041] b) a step of providing a receiver substrate;

[0042] c) A step of assembling by directly bonding the front surface of the donor substrate onto the receiver substrate,

[0043] d) a step of separating along an embedded weakening plane to transfer the upper part of the donor substrate onto the receiver substrate,

[0044] f) A step of chemically etching the second layer, and then selectively chemically etching the stop layer for the single-crystal thin layer.

[0045] Advantageously, the recrystallization step a') includes heat treatment by a laser, which is applied to the front surface of the donor substrate and configured to induce solid-phase epitaxy of the amorphous sub-part.

[0046] Depending on the advantageous features of the transfer method according to the first or second embodiment of the present invention, the following are taken alone or in any feasible combination:

[0047] Separation step d) includes heat treatment at a temperature of 400°C or lower, preferably at a temperature of 250°C to 400°C;

[0048] Step a) of providing a donor substrate includes the step of implanting ions into the upper portion of the substrate, which is initially of single-crystal quality, to form an amorphous sub-part;

[0049] In step f), chemical etching of the second layer is optional for the stationary layer. Brief explanation of the drawing

[0050] Other features and advantages of the present invention will become apparent from the detailed description made with reference to the accompanying drawings. [Fig. 1] [Fig. 2] [Fig. 3] Figs. 1, 2 and 3 illustrate a donor substrate according to three variations of the present invention. [Fig. 4] [Fig. 5] Figs. 4 and 5 illustrate a donor substrate according to one embodiment and a variation of this embodiment according to the present invention. [Fig. 6] Fig. 6 illustrates the steps of manufacturing a donor substrate according to the present invention. [Fig. 7] [Fig. 8] Figs. 7 and 8 illustrate the steps of a method for transferring a single-crystal thin layer onto a receiver substrate according to a first embodiment of the present invention. [Fig. 9] Fig. 9 illustrates a variation of a structure generated from a transfer method according to the present invention. [Fig. 10] [Fig. 11] Figs. 10 and 11 illustrate the steps of a second embodiment of a method for transferring a single-crystal thin layer onto a receiver substrate according to the present invention. The drawings are not scaled schematics for readability. In particular, the thickness of the layer along the z-axis is not scaled according to the lateral dimension scale along the x-axis and y-axis. The same references in the drawings may be used for elements of the same type. It should be understood that different possibilities (variations and embodiments shown and / or described in detail in the following description) are not mutually exclusive and can be combined together. Specific details for implementing the invention

[0051] The present invention relates to a donor substrate (100) for transferring a single-crystal thin layer (1) made of a first material onto a receiver substrate (2). The first material is advantageously selected from silicon, germanium, or a silicon / germanium alloy. For the remainder of this specification, where the term “first or second” material is used, its structural and crystallographic properties are not specified, but only its properties: for example, amorphous, polycrystalline, or single-crystal silicon constitutes the material within the meaning of the present invention.

[0052] The donor substrate (100) is generally in the form of a wafer with a diameter of 150 mm to 450 mm or more and a thickness of typically 300 to 900 microns. It has a front surface (100a) and a back surface (100b) as shown in FIG. 1.

[0053] The embedded weakening plane (30) defines the upper (101) and lower (102) portions of the donor substrate (100). It extends parallel to the main plane (x, y) of the front surface (100a) of the donor substrate (100).

[0054] As is well known in the context of the Smart Cut™ method, the embedded weakening plane (30) is formed from the ion implantation of a hard mass species performed on the side of the front surface (100a) of the donor substrate (100). The implanted species are preferably hydrogen, helium, or a combination of these two species. The weakening plane (30) is so called because it contains lenticular-shaped nanocracks created by the implanted hard mass species.

[0055] A donor substrate (100) comprises a stop layer (15) extending in a plane parallel to an embedded weakening plane (30) within its upper portion (101). The stop layer (15) is formed of a second material capable of providing selective etching for a first material. Typically, the second material is selected from silicon germanium (SiGe) or highly doped silicon; the first is suitable if the first material is made of silicon or germanium, and the second is suitable if the first material is made of silicon, germanium, or silicon / germanium. In the case of the second silicon germanium material, the proportion of germanium is typically 10% to 40%. In the case of the second doped silicon material, for example 1 E 18 B / cm³ to 1 E 20 B / cm 3 P-type boron doping would be desirable.

[0056] A stop layer (15) is interposed between a first layer (10) on the side of the front surface (100a) and a second layer (20) adjacent to the embedded weakening plane (30). The stop layer (15) typically has a thickness of 2 to 100 nm.

[0057] The first layer (10) and the second layer (20) are arranged on both sides of the stationary layer (15). The first layer (10) is composed of a first material and is intended to form a single-crystal thin layer (1) to be transferred onto a receiver substrate (2). This can have a thickness of, for example, 5 nm to 500 nm depending on the thickness required for the thin layer (1).

[0058] The thickness of the second layer (20) may be 50 to 1000 nm. The sum of the thicknesses of the first layer (10), the stationary layer (15), and the second layer (20) is understood to be equal to the depth of the buried weakening plane (30).

[0059] The second layer (20) may be composed of the first material. Preferably, the donor substrate (100) is composed mainly of the first material within its single-crystal structure; and only the stop layer (15) is formed within the second material to ensure selective etching during the transfer method.

[0060] The donor substrate (100) further comprises an amorphous sub-part (101', 101'', 101''') within the upper portion (101). In the context of the present invention, the amorphous means is created by ion implantation; this implies that the sub-part (101', 101'', 101''') had a crystalline structure, and even a single-crystal structure, prior to having an amorphous structure. Accordingly, the type of ion capable of making the sub-part (101', 101'', 101''') amorphous will be described in detail below.

[0061] These amorphous sub-parts (101', 101'', 101''') include at least a first layer (10) and extend to an approximate depth having a thickness smaller than that of the upper layer (101). This is equivalent to saying that the second layer (20) includes at least one single-crystal sub-layer (22) adjacent to the buried weakening plane (30).

[0062] The amorphous sub-part (101', 101'', 101''') may include one or more of the layers mentioned above. According to the first variation shown in FIG. 1, the amorphous sub-part (101') includes only the first layer (10). According to the second variation (Fig. 2), the sub-part (101'') includes a stationary layer (15) in addition to the first layer (10). Finally, according to the third variation shown in FIG. 3, the amorphous sub-part (101''') includes a portion (21) of the second layer (20) adjacent to the stationary layer (15). In all variations, outside the amorphous sub-part (101', 101'', 101'''), a single crystal sub-layer (22) is found as part of the second layer (20) adjacent to the buried weakening plane (30).

[0063] The donor substrate (100) is advantageous for direct bonding and good reinforcement of the bonding interface due to the presence of an amorphous sub-part (101', 101'', 101''') on the side of the front surface (100a), which is intended to be assembled onto the receiver substrate (2). The amorphous surface deforms better when the temperature increases and absorbs the bonding water layer better than a single-crystal surface. Consequently, the presence of the amorphous sub-part (101', 101'', 101''') makes it possible to close the bonding interface much better at lower temperatures, as shown below with reference to the transfer method according to the present invention.

[0064] According to a specific embodiment, the donor substrate (100) further comprises an amorphous silicon bonding layer (50) arranged on the first layer (10) (Fig. 4). This bonding layer (50) is preferably formed on the first layer (10) by chemical vapor deposition (CVD). The bonding layer (50) has a thickness of 2 to 20 nm.

[0065] According to a variation of this embodiment, the donor substrate (100) further comprises an intermediate layer (40) made of silicon oxide interposed between the first layer (10) and the bonding layer (50) (Fig. 5). The intermediate layer (40) typically has a thickness of 10 to 200 nm. The presence of an intermediate layer made of SiO2 may be useful for electrically insulating the single-crystal thin layer (1) when it is transferred onto the circuit layer (2a) of the receiver substrate (2) at the end of the transfer method, and the explanation thereof is as follows.

[0066] The present invention relates to a method for transferring a single-crystal thin layer (1) formed from a first material onto a receiver substrate (2).

[0067] The present method first includes step a) of providing a donor substrate (100) as described above.

[0068] To this end, starting from an initial solid single crystal substrate (100') composed of the first material or an initial substrate (100'), potentially better quality is obtained on the side of the first material single crystal (not shown) and its front surface (100a) through epitaxy.

[0069] On the front surface (100a) of the initial substrate (100'), the stationary layer (15) also has a single-crystal structure (Fig. 6a). The stationary layer (15) made of SiGe can be formed, for example, by epitaxial growth on the initial substrate (100'). For a stationary layer (15) of high-concentration doped Si, to produce said layer (15), if the latter is made of silicon, boron ion implantation can be performed on the initial substrate (100'). Alternatively, the stationary layer (100') made of high-concentration doped Si can also be formed by epitaxy. The stationary layer (15) typically has a thickness consisting of 2 to 100 nm.

[0070] Next, a surface layer (10) (referred to as the first layer (10)) is formed on the stationary layer (15), preferably by epitaxial growth (Fig. 6(b)). The thickness is selected according to the target application, and it is understood that this first layer (10) forms a single-crystal thin layer (1) that is transferred to a receiver substrate (2) at the end of the transfer method according to the present invention.

[0071] In the case of a stationary layer (15) in which the lattice parameters differ from those of the first layer (10) and / or the initial substrate (100'), the stationary layer (15) preferably has a thickness smaller than the critical thickness (cf. JM. Hartmann et al., "Critical thickness for plastic relaxation of SiGe on Si(001) revised" Journal of Applied Physics 110, 083529(2011)) to prevent stress associated with the difference in lattice parameters from degrading the crystallinity of the first layer (10), for example, a thickness of less than 50 nm.

[0072] As illustrated in FIG. 6(c), an amorphization step is then performed from the front (100a) on a sub-part (100''') comprising at least a first layer (10) (according to different variations mentioned with reference to FIG. 1, 2 and 3) and a portion (21) of an initial substrate (100') arranged below a stop layer (15) (according to different variations mentioned with reference to FIG. 1, 2 and 3).

[0073] Amorphization refers to the separation of the crystalline lattice of the sub-parts (101', 101'', 101'''), which makes the latter amorphous. Amorphization is generally performed at room temperature or lower temperatures, and by ion implantation, for example, from ions whose atomic number is greater than or equal to the atomic number of the first material. As an example, the ions may be selected from silicon, germanium, xenon, and argon. To amorphize the sub-parts (101', 101'', 101''') over greater depths and / or more uniform depths, multiple successive implantations may be performed at different implantation energies. The implanted dose is typically 2e14 / cm² to 1e16 / cm² 2 It is diverse.

[0074] For the first layer (10) and second layer (20) made of silicon, and the stationary layer (15) made of SiGe, the amorphization of the sublayer (101''') is, for example, 2.5 with an energy of 5 keV for amorphization over a depth of 15 nm. e This can be achieved by implanting Ge at a dose of 15 at / cm². It should be noted that most ion implantation simulation codes provide indications that enable the achievement of amorphousness of a single-crystal matrix, depending on the characteristics of the matrix, the characteristics of the implanted ions, energy, and implantation dose.

[0075] Finally, the injection of a hard mass species, typically hydrogen, helium, or a combination of both, is performed at a depth greater than the thickness of the amorphous sub-parts (101', 101'', 101''') (Fig. 6(d)). Thus, a buried weakening plane (30), somewhat localized at the injection peak, is formed and defines the upper (101) and lower (102) portions of the donor substrate (100). A single crystal sub-layer (22) is preserved between the amorphous sub-parts (101''') and the buried weakening plane (30).

[0076] The injection energy is defined according to the target depth for the embedded attenuation plane (30) within the donor substrate (100); this is typically several keV to 200 keV. The dose of the injected species is several 1 E 16 cm² to 1 E 17 / cm 2 It is diverse.

[0077] It should be noted that the steps of amorphization and injection of hard mass species can be performed in reverse order, that is, first injection of hard mass species and then amorphization.

[0078] At the end of step a) of the method according to the present invention, a donor substrate (100) according to one of the variations shown in FIG. 1, FIG. 2 and FIG. 3 is obtained.

[0079] According to a specific embodiment, to obtain one of the variations illustrated in FIGS. 4 and FIGS. 5, a bonding layer (50) and a potential intermediate layer (40) are formed on a donor substrate (100).

[0080] These layers (40, 50) are formed, for example, by chemical vapor deposition (CVD) and preferably after an amorphization step, to prevent ion implantation of the amorphization from causing impurities from these layers (40, 50) in the underlying layer (particularly the first layer (10)) and making subsequent recrystallization more difficult. Of course, the deposition of the layers (40, 50) must be possible at a temperature below the recrystallization temperature of the subsequent amorphized portion (101', 101'', 101'''). When the deposition requires a temperature at which the amorphized sub-part (101', 101'', 101''') can be modified and / or the buried weakening plane (30) can be altered, it is also possible to choose to deposit the layers or layers (40, 50) before the amorphization and / or implantation step of the hard mass species, which is not desirable at this stage of the method.

[0081] As shown below, the bonding layer (50), particularly made of deposited amorphous silicon, promotes the quality of the bonding interface created in the subsequent assembly step c).

[0082] Next, the method comprises step b) of providing a support layer (2). This is generally in the form of a small plate with a diameter of 150 mm to 450 mm and a thickness of typically 300 to 900 microns. It may comprise a stack of various layers, particularly including a metal material, corresponding to a layer (2a) of a device arranged in a solid portion (e.g., produced according to complementary CMOS, metal-oxide-semiconductor technology) made of a semiconductor material such as silicon. Such metal material typically limits the temperature applicable to the receiver substrate (2) to 500°C or lower.

[0083] The receiver substrate (2) may include a material that does not support high processing temperatures, whether or not it has a device layer, due to their properties, or due to their coefficient of thermal expansion being very different from that of the single crystal thin layer (1) to be transferred.

[0084] After steps a) and b), the transfer method includes an assembly step c) in which the front surface (100a) of the donor substrate (100) is directly bonded onto the receiver substrate (2) to form an assembly bonded at the bonding interface (3) (Fig. 7a). Direct bonding implies that no adhesive material is added between the assembled surfaces. The very low roughness of the surfaces (typically less than 0.5 nm RMS) and their high cleanliness allow for bonding by molecular adhesion of the surfaces. Surface cleaning and / or activation, which are well known in the field of molecular adhesion bonding, may be applied to the substrate before assembly to promote excellent bonding quality. Assembly in a controlled atmosphere is also possible.

[0085] As illustrated in FIG. 7a, the receiver substrate (2) includes a device layer (2a) on its assembled surface. Generally, the surface film of this layer (2a) will be formed of silicon oxide or silicon nitride.

[0086] When the donor substrate (100) is one of the forms shown in FIGS. 1 to 3, the bonding interface (3) is established between the device layer (2a) and the amorphous sub-parts (101', 101'', 101'''). The first amorphous layer (10) is particularly advantageous for the effective reinforcement of the bonding interface (3), even at low temperatures. In fact, with respect to a single-crystal surface, the amorphous surface deforms better when the temperature increases and better absorbs the water monolayer present at the interface during bonding by molecular adhesion. Consequently, the presence of the amorphous sub-parts (101', 101'', 101''') on the surface allows for excellent closure of the bonding interface at low temperatures.

[0087] Accordingly, bonding at ambient temperature, and optionally strengthening annealing at a temperature below 350°C, provides very good retention of the bonding interface (3), thereby ensuring good progress of the following steps of the method, particularly the separation step d).

[0088] When the donor substrate (100) is in one of the forms shown in FIGS. 4 and FIGS. 5, the bonding interface (3) is established between the device layer (2a) and the bonding layer (50) made of amorphous silicon. For the same reasons mentioned above, the latter is very effective at closing (strengthening) the bonding interface at low temperatures, typically below 500°C. The same type of strengthening annealing as described above may also be applied.

[0089] Step d) for separating the bonded assembly along the embedded weakening plane (30) enables the upper portion (101) of the donor substrate (100) to be transferred onto the receiver substrate (2) (Fig. 7(b)). Separation at the embedded weakening plane (30) is primarily performed by applying a heat treatment at a low temperature, typically between 200°C and 500°C, due to the growth of microcracks caused by the bonding and by pressurizing the gas species. Advantageously, the heat treatment is performed at a temperature of 400°C or lower, preferably at a temperature consisting of 250°C to 400°C.

[0090] Alternatively, or jointly, separation can occur by applying mechanical stress to the joined assembly.

[0091] At the end of this separation, on one hand, an intermediate SOI structure (150) is obtained, and on the other hand, the lower part (102) of the donor substrate is obtained.

[0092] Next, the transfer method according to the present invention includes step e) of recrystallizing amorphous sub-parts (101', 101'', 101''') to restore single crystal quality to the first layer (10).

[0093] Recrystallization corresponds to providing the sub-parts (101', 101'', 101''') with their single-crystal characteristics. This implements a solid-phase epitaxy (SPE) phenomenon. This recrystallization is based on the application of heat treatment at a temperature in which the crystalline lattice of the sub-parts (101', 101'', 101''') is reorganized on the base of the crystal lattice of the single-crystal sub-layer (22), which acts as a seed.

[0094] Recrystallization heat treatment can be performed at a temperature of 450°C to 900°C. Of course, to handle the aforementioned application where the receiver substrate (2) is not compatible with high temperatures, the thermal recrystallization temperature is advantageously 450°C to 550°C for a period of 10 minutes to 50 hours and under a non-oxidizing atmosphere. For example, to recrystallize amorphous silicon of 15 to 20 nm, annealing can be applied at 500°C for 2 to 4 hours.

[0095] During heat treatment, the recrystallization front moves toward the bonding interface (3) from the single crystal lower layer (22) (or from the single crystal, which is part of the second layer (20) of the upper (101) adjacent to the amorphous lower portion).

[0096] At the end of the recrystallization step e), the upper part (101) of the intermediate structure (150) is completely single crystal (Fig. 8(a)). It should be noted that the heat treatment applied in the separation step d) may participate in the recrystallization of the amorphous lower part (101', 101'', 101''') depending on its temperature and duration.

[0097] Next, the first layer (10) with restored single-crystal quality corresponds to a single-crystal thin layer (1) that is expected to be transferred onto a receiver substrate (2). Thus, the thin layer (1) will have expected physical and electrical properties for the creation of electronic components.

[0098] It is possible to measure the thickness and good crystalline restoration of the first layer (10) by ellipsometry, by Raman, and / or by transmission electron microscopy (TEM), respectively.

[0099] Depending on the characteristics of the stationary layer (15), specific precautions must be taken to prevent it from being damaged by the recrystallization step e). In particular, in the case of a stationary layer (15) made of SiGe, the recrystallization temperature must be maintained below 700°C, or even below 600°C, so as not to plastically relax the SiGe.

[0100] The bonding interface (3) benefits from the heat treatment applied during the recrystallization step d) and the separation step e), because this treatment strengthens the interatomic bonds between the assembled surfaces.

[0101] Accordingly, the amorphous properties of the first layer (10) facilitate direct bonding between the donor substrate (100) and the receiver substrate (2) in step c) of the method; this also allows for recrystallization by solid-phase epitaxy at low temperatures, while allowing for effective repair of crystalline defects associated with the injection of hard mass species: thus, the first layer (10) recovers physical and electrical properties associated with its single-crystal quality.

[0102] Finally, the transfer method includes step f) of chemical etching of the second layer (20) followed by chemical etching of the first layer (10) and optionally the stop layer (15) (Fig. 8(b)). Advantageously, the constituent material of the second layer (20) also allows the latter to be optionally etched with respect to the stop layer (15).

[0103] The disclosed dry etching or wet etching techniques may be implemented. The chemical etching solutions that can be used are typically TMAH (tetramethylammonium hydroxide), TEAH (tetraethylammonium hydroxide), or KOH (potassium hydroxide) for silicon, a mixture of HF (hydrofluoric acid) / acetic acid / H2O2 (hydrogen peroxide) for SiGe, and a mixture of HF / acetic acid / H2O2 or H3PO4 (phosphoric acid) for germanium.

[0104] Step f) enables the removal of the second layer (20), which has a relatively high residual roughness (typically of about 10 nm RMS), due to crushing (step d) along the buried weakened plane (30).

[0105] Good surface conditions (roughness) can be restored due to the etching selectivity between the second layer (20) and the stop layer (15). The etching selectivity between the stop layer (15) and the first layer (10) provides very low surface roughness to the latter and maintains uniformity of thickness.

[0106] Accordingly, the transfer method makes it possible to obtain a structure (200) comprising a single-crystal thin layer (1) arranged on a receiver substrate (2), which may include a device layer incompatible with any high-temperature processing (Fig. 8(b)).

[0107] When the donor substrate (100) includes a bonding layer (50) or a stack composed of an intermediate layer (40) and a bonding layer (50), the obtained structure (200) is as in FIG. 9(a) and (b).

[0108] The present invention also relates to a second embodiment of a method for transferring a single crystal thin layer (1), as illustrated in FIGS. 10 and 11, onto a receiver substrate (2).

[0109] This embodiment differs from the previously described method by the positioning of the recrystallization step in the step sequence of the method. In fact, after step a) of supplying the donor substrate (100) (identical to the description above), step a') of local recrystallization of the amorphous sub-parts (101', 101'', 101''') is performed to restore single-crystal quality to the first layer (10) and subsequently cause separation in the method without affecting the buried weakening plane (30), that is, without affecting the capacity of the buried weakening plane (30).

[0110] Advantageously, the recrystallization step a') comprises a laser heat treatment applied to the front surface (100a) of the donor substrate (100) and configured to induce solid-phase epitaxy of the amorphous sub-parts (101', 101'', 101''') (Fig. 10(a)). For example, such heat treatment can be implemented by a UV excimer laser (λ=308 nm) having a pulse duration of about 200 ns and an energy density of about 0.8 J / cm².

[0111] At the end of step a'), the upper part (101) of the donor substrate (100) is completely single crystal, and the first recrystallized layer (10) forms a single crystal thin layer (1) intended to be transferred onto the receiver substrate (2).

[0112] Step b) providing a receiver substrate (2), step c) assembling by directly bonding the front surface (100a) of the donor substrate (100) onto the receiver substrate (2) (Fig. 10(b)), and step d) separating along the embedded weakening plane (30) to transfer the upper surface (101) of the donor substrate (100) onto the receiver substrate (2) (Fig. 11(a)) are performed in the second embodiment of the method according to the first embodiment described above.

[0113] There is no recrystallization step e), and the latter is performed before assembly.

[0114] However, advantageously, step f) of chemically etching the second layer (20) with respect to the stationary layer (15) and then chemically etching the stationary layer (15) with respect to the single crystal thin layer (1) is performed in the same manner (Fig. 11(b)).

[0115] The donor substrate (100) according to the present invention enables the transfer of a single crystal thin layer (1) of very high crystalline quality (according to the first or second embodiment of the transfer method) that is compatible with the creation of electronic components, and enables the injection of hard mass species, smoothing of the fractured surface, thinning of the transferred portion (101), and repair of defects related to strengthening of the bonding interface (3) without requiring the application of high-temperature heat treatment.

[0116] The composition of the layers of the donor substrate (100) further simplifies the method of transferring the thin layer (1) to the receiver substrate (2) by limiting steps c) to f) to heat treatment and selective chemical etching at a low temperature.

[0117] Of course, the present invention is not limited to the described embodiments, and variations may be anticipated without departing from the scope of the invention as defined by the claims.

Claims

Claim 1 A method for transferring a single crystal thin layer (1) made of a first material onto a receiver substrate (2), comprising the step of a) providing a donor substrate (100) having a front surface (100a) and a rear surface (100b), wherein the donor substrate (100) comprises an embedded weakening plane (30) partitioning the upper surface (101) and the lower surface (102) of the donor substrate (100), wherein within the upper surface (101), there is a first layer (10) on the side of the front surface (100a), a second layer (20) adjacent to the embedded weakening plane (30), and a stop layer (15) inserted between the first layer (10) and the second layer (20), wherein the first layer (10) is composed of the first material and is intended to form the single crystal thin layer (1), and the stop layer (15) is formed of a second material capable of providing selective etching of the first material, and the donor A substrate (100) comprises an amorphous sub-part (101', 101'', 101''') which is amorphous through ion implantation and has a thickness that is strictly thinner than the thickness of the upper (101), and comprises at least the first layer (10), and the second layer (20) comprises at least one single-crystal sub-layer (22) adjacent to the buried weakening plane (30), and the sub-layer (22) is intended to form a recrystallization seed for the amorphous sub-part (101', 101'', 101'''), and the method comprises: a) the amorphous sub-part (101', 101'') to restore single-crystal quality to the first layer (10) without affecting the buried weakening plane (30), a) a step of locally recrystallizing 101''') - wherein the recrystallized first layer (10) forms the single crystal thin layer (1), b) a step of providing a receiver substrate (2), c) a step of directly bonding the front surface (100a) of the donor substrate (100) onto the receiver substrate (2),d) a step of separating along the embedded weakening plane (30) to transfer the upper portion (101) of the donor substrate (100) onto the receiver substrate (2), f) a step of chemically etching the second layer (20) and then optionally chemically etching the stop layer (15) with respect to the single crystal thin layer (1), comprising a transfer method. Claim 2 A transfer method according to claim 1, wherein the amorphous sub-part (101'', 101''') comprises the stop layer (15). Claim 3 A transfer method according to claim 1, wherein the amorphous sub-part (101''') comprises a portion (21) of the second layer (20) adjacent to the stop layer (15). Claim 4 In claim 1, the second layer (20) is composed of the first material, in a transfer method. Claim 5 A transfer method according to claim 1, wherein the first material is selected from silicon, germanium, or a silicon / germanium alloy. Claim 6 A transfer method according to claim 1, wherein the second material is selected from silicon germanium or highly doped silicon. Claim 7 A transfer method according to claim 1, wherein the donor substrate (100) comprises an amorphous silicon bonding layer (50) arranged on the first layer (10). Claim 8 A transfer method according to claim 1, wherein the recrystallization step a') comprises heat treatment by a laser applied to the front surface (100a) of the donor substrate (100) and configured to induce solid-phase epitaxy of the amorphous sub-parts (101', 101'', 101'''). Claim 9 A transfer method according to claim 1, wherein the separation step d) comprises heat treatment at a temperature of 400°C or lower, or between 250°C and 400°C. Claim 10 A transfer method according to claim 1, wherein step a) of providing the donor substrate (100) comprises the step of implanting ions into the upper portion (101) of the donor substrate (100), which is initially of single-crystal quality, to form the amorphous lower portion (101', 101'', 101'''). Claim 11 In claim 1, in step f), the chemical etching of the second layer (20) is optional for the stop layer (15), transfer method. Claim 12 delete Claim 13 delete Claim 14 delete

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