Donor substrate for transferring thin layers and related transfer methods

Abstract

The invention relates to a donor substrate (100) for transferring a monocrystalline thin layer (1) made of a first material onto a receiver substrate (2), the donor substrate (100) having a front side (100a) and a rear side (100b) and comprising: - an embedded weakened surface (30) defining an upper part (101) and a lower part (102) of the donor substrate (100); - in the upper part (101), a first layer (10) on the side of the front side (100a), a second layer (20) adjacent to the embedded weakened surface (30) and a stop layer (20) interposed between the first layer (10) and the second layer (20). 15), in which the first layer (10) is made of a first material and the stop layer (15) is formed from a second material capable of providing a selective etching with respect to the first material; and an amorphized subpart (101', 101", 101"') amorphized by ion implantation and having a thickness strictly smaller than the thickness of the upper part (101) and comprising at least the first layer (10), the second layer (20) comprising at least one monocrystalline sublayer (22) adjacent to the buried weakened surface (30). The invention also relates to two embodiments of a method for transferring a monocrystalline thin layer (1) from a donor substrate (100).

Description

[Technical Field]

[0001] This invention belongs to the field of semiconductors and microelectronics. The invention relates to a donor substrate suitable for transferring thin layers onto a receiver substrate, and more particularly to low-temperature transfer onto a receiver substrate containing completed or partially completed electronic components. The invention also relates to a transfer method using the donor substrate. [Background technology]

[0002] The three-dimensional (3D) integration of circuits has been under intense development for several years because it allows for the association of different functions while minimizing the spatial requirements of the system. 3D integration is based on the vertical stacking of layers of electronic devices. Such stacks require the formation of layers of crystalline material on top of existing layers of the device. Such devices are neither homogeneous nor crystalline, which hinders the use of conventional crystalline thin-film growth techniques such as epitaxy. Furthermore, the layers of already fabricated devices often have limited temperature tolerance and must remain at low temperatures, especially since they may contain metallization levels.

[0003] Therefore, 3D integration selectively implements thin-film transfer techniques from a donor substrate to a receiver substrate that may have one or more layers of the device.

[0004] Several known layer transfer methods are based on assembly by directly bonding a donor substrate (from which a desired thin crystalline layer is obtained) onto a receiver substrate. The donor substrate then undergoes a thinning step, at which point a thin layer is formed. This thinning step is based on various techniques known in the prior art, particularly, - The Smart Cut® method is particularly suitable for forming very thin layers (typically having a thickness between a few nanometers and 1 micron), and is based on injecting a gas species into the assembled surface of the donor substrate before the assembly step to form an embedded weakening surface, and after assembly, during the fracture step, the donor substrate is separated along the weakening surface so that only the thin layer attached to the receiver substrate remains. -This may be carried out using a mechanochemical thinning method, including mechanical lapping, mechanochemical polishing, and chemical etching, which is particularly suitable for forming layers having a thickness of several microns to tens of microns, and even hundreds of microns.

[0005] Naturally, the techniques cited above are not exhaustive, and other known techniques may be used to thin the donor substrate.

[0006] As mentioned above, the Smart Cut™ method is particularly suitable for forming very thin layers. After transfer, several operations are required to make the transferred layer usable for manufacturing electronic devices, including repairing injection defects, smoothing fracture surfaces, thinning this same layer, and closing bond interfaces. These operations are usually performed at high temperatures, especially in relation to the fabrication of SOI (Silicon-on-Insulator) structures. In the case of 3D integration, which is of interest to us, they must be performed at low temperatures so as not to damage the underlying device layers.

[0007] French Patent No. 2978603 proposes a solution to facilitate the repair of injection defects at low temperatures. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] 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, especially when the receiver substrate is not suitable for high temperatures due to the presence of electronic devices. The present invention also relates to a method for transferring a thin layer from the donor substrate onto a receiver substrate. [Means for solving the problem]

[0009] The present invention relates to a donor substrate for transferring a single-crystal thin layer made from a first material onto a receiver substrate, wherein the donor substrate has a front side and a rear side. - Embedding weakening surfaces defining the upper and lower parts of the donor substrate, - In the upper part, a first layer is located at the front, a second layer is adjacent to the embedded weakening surface, and a stop layer is inserted between the first and second layers, 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 from a second material that can provide selective etching to the first material. - An amorphous sub-part comprising an amorphous sub-part having a thickness strictly less than the thickness of the upper part and comprising at least a first layer, wherein the second layer comprises at least one single-crystal sub-part adjacent to the embedded weakened surface, and the sub-part is intended to form a recrystallization seed for the amorphous sub-part.

[0010] According to the advantageous features of the present invention, the following can be performed, either alone or in any feasible combination: The amorphous sub-part includes a stopping layer. The amorphous sub-part includes a portion of the second layer adjacent to the stopping layer. The second layer is made of the first material, The first material is selected from silicon, germanium, or a silicon / germanium alloy. The second material is selected from silicon germanium or highly doped silicon. The first layer has a thickness of 5 microns to 500 nm. The stopping layer has a thickness of 2 to 100 nm. · The second layer has a thickness of 50 to 1000 nm, · The donor substrate comprises an amorphous silicon bonding layer disposed on the first layer, · The bonding layer has a thickness of 2 to 20 nm, · The donor substrate comprises an intermediate layer made of silicon oxide inserted between the first layer and the bonding layer, · The intermediate layer has a thickness of 10 to 200 nm.

[0011] The present invention also relates to a method for transferring a single crystal thin layer made of a first material onto a receiver substrate.

[0012] According to the first embodiment, the transfer method is as follows: a) Providing a donor substrate as described above; b) Providing a receiver substrate; c) Assembling by directly bonding the front side of the donor substrate onto the receiver substrate; d) Separating along an embedded weakened plane in order to transfer the upper part of the donor substrate onto the receiver substrate; e) Recrystallizing the amorphized sub - part to restore the single crystal quality to the first layer, and then forming a single crystal thin layer; f) Chemically etching the second layer and then selectively chemically etching the stop layer with respect to the single crystal thin layer.

[0013] Advantageously, the recrystallization step e) includes a heat treatment at a temperature of 450 °C to 900 °C, preferably 450 °C to 550 °C.

[0014] According to the second embodiment, the transfer method is as follows: a) Providing a donor substrate as described above; a’) Locally recrystallizing the amorphized sub - part to restore the single crystal quality to the first layer without affecting the embedded weakened plane, wherein the first recrystallized layer forms a single crystal thin layer. b) providing a receiver substrate; c) assembling by directly bonding the front side of the donor substrate onto the receiver substrate; d) separating along an embedded weakened plane for transferring the upper part of the donor substrate onto the receiver substrate; f) chemically etching a second layer and then selectively chemically etching the stop layer with respect to the single crystal thin layer.

[0015] Advantageously, the recrystallization step a’) comprises a heat treatment by a laser applied to the front side of the donor substrate and configured to induce solid-phase epitaxy of the amorphized sub-part.

[0016] According to advantageous features of the transfer method according to the first or second embodiment of the invention, the following is done, alone or in any feasible combination: · The separation step d) comprises a heat treatment at a temperature of 400 °C or lower, optionally at a temperature of 250 °C to 400 °C; · The step a) of providing the donor substrate comprises implanting ions into the upper part of a substrate which is initially of single crystal quality in order to form an amorphized sub-part; · In step f), the chemical etching of the second layer is selective with respect to the stop layer.

Brief Description of the Drawings

[0017] Other features and advantages of the invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings. [Figure 1] FIG. showing donor substrates according to three variants of the invention. [Figure 2] FIG. showing donor substrates according to three variants of the invention. [Figure 3] FIG. showing donor substrates according to three variants of the invention. [Figure 4] FIG. showing a donor substrate according to an embodiment of the invention and its variants. [Figure 5]This figure shows a donor substrate according to one embodiment of the present invention and a modified version thereof. [Figure 6] This figure shows the manufacturing steps for a donor substrate according to the present invention. [Figure 7] This figure shows 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. [Figure 8] This figure shows 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. [Figure 9] This figure shows the deformation of a structure obtained by the transfer method according to the present invention. [Figure 10] This figure shows 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. [Figure 11] This figure shows 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.

[0018] The drawings are schematic diagrams, not to scale, for readability. In particular, the layer thickness along the z-axis is not to exact scale with respect to the lateral dimensions along the x and y axes. The same reference numerals in the drawings may be used for the same type of element. Different possibilities (modifications and embodiments described and / or detailed in the following description) should be understood as not mutually exclusive and may be combined together. [Modes for carrying out the invention]

[0019] The present invention relates to a donor substrate 100 for transferring a single-crystal thin layer 1, made from a first material, onto a receiver substrate 2. The first material is advantageously selected from silicon, germanium, or a silicon / germanium alloy. Where the term “first or second” material is used in the remainder of this specification, structural and crystallographic properties are not specified, only its properties are specified, and for example, amorphous, polycrystalline, or single-crystal silicon constitutes a material within the meaning of this specification.

[0020] The donor substrate 100 is typically 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 side 100a and a rear side 100b, as shown in Figure 1.

[0021] The embedded weakening surface 30 defines the upper 101 and lower 102 of the donor substrate 100. It extends parallel to the main surface (x,y) of the front side 100a of the donor substrate 100.

[0022] The embedded weakened surface 30 is formed by ion implantation of lightweight species performed on the front side 100a of the donor substrate 100, as is well known in the context of the Smart Cut™ method. The species to be implanted are preferably hydrogen, helium, or a combination of these two species. The weakened surface 30 is so named because it contains lens-shaped nanocracks generated by the implanted lightweight species.

[0023] The donor substrate 100 includes a stop layer 15 on its upper surface 101, extending in a plane parallel to the embedded weakening surface 30. The stop layer 15 is formed from a second material that can provide selective etching to the first material. Typically, the second material is selected from silicon germanium (SiGe) or highly doped silicon, the first material is suitable when the first material is made from silicon or germanium, and the second material is suitable when the first material is made from silicon, germanium, or silicon / germanium. In the case of the second silicon germanium material, the germanium content is typically between 10% and 40%. In the case of the second doped silicon material, for example, 1 E 18B / cm 3 ~1 E 20B / cm 3 P-type boron doping is preferred during this period.

[0024] The stopping layer 15 is interposed between the first layer 10 on the front side 100a and the second layer 20 adjacent to the embedded weakening surface 30. The stopping layer 15 typically has a thickness of 2 to 100 nm.

[0025] The first layer 10 and the second layer 20 are positioned on either side of the stop layer 15. The first layer 10 is made of the first material and is intended to constitute a single-crystal thin layer 1 that is transferred onto the receiver substrate 2. It can have a thickness of, for example, 5 nm to 500 nm, depending on the required thickness of the thin layer 1.

[0026] The thickness of the second layer 20 may be 50 to 1000 nm. It is understood that the sum of the thicknesses of the first layer 10, the stop layer 15, and the second layer 20 is equal to the depth of the embedded weakened surface 30.

[0027] The second layer 20 may be composed of the first material. Selectively, the donor substrate 100 is mainly composed of the first material in its single-crystal structure, with only the stop layer 15 formed within the second material to ensure selective etching during the transfer method.

[0028] The donor substrate 100 further includes amorphous sub-parts 101', 101'', and 101''' within the upper part 101. In the context of the present invention, amorphous means amorphous by ion implantation. This means that the sub-parts 101', 101'', and 101''' had a crystalline structure, or even a single-crystal structure, before having an amorphous structure. Therefore, the types of ions that can amorphous the sub-parts 101', 101'', and 101''' are described in detail below.

[0029] These amorphous sub-parts 101', 101'', 101''' include at least the first layer 10, extend more or less in the depth direction, and have a thickness strictly less than the thickness of the upper part 101. This means that the second layer 20 includes at least one single-crystal sub-layer 22 adjacent to the embedded weakened surface 30.

[0030] The amorphous sub-parts 101', 101'', and 101''' may include one or more of the layers described above. According to the first modification shown in Figure 1, the amorphous sub-part 101' includes only the first layer 10. According to the second modification (Figure 2), the sub-part 101'' includes the first layer 10 in addition to the stopping layer 15. Finally, according to the third modification shown in Figure 3, the amorphous sub-part 101''' includes a portion 21 of the second layer 20 adjacent to the stopping layer 15. In all modifications, a single-crystal sub-layer 22, which is a portion of the second layer 20 adjacent to the embedded weakening surface 30, is visible outside the amorphous sub-parts 101', 101'', and 101'''.

[0031] The donor substrate 100 is advantageous for direct bonding and good reinforcement of the bonding interface thanks to the presence of amorphous sub-parts 101', 101'', 101'''' on the front side 100a of the donor substrate 100, which is intended to be assembled on the receiver substrate 2. The amorphous surface deforms better than a single-crystal surface when the temperature rises and absorbs the bonding aqueous layer well. As a result, the presence of amorphous sub-parts 101', 101'', 101'''' allows for better closing of the bonding interface at lower temperatures, as shown below with respect to the transfer method according to the present invention.

[0032] According to a particular embodiment, the donor substrate 100 further includes an amorphous silicon bonding layer 50 disposed on the first layer 10 (Figure 4). Such a bonding layer 50 is preferably formed on the first layer 10 by CVD (Chemical Vapor Deposition). The bonding layer 50 has a thickness of 2 to 20 nm.

[0033] In a modified version of this embodiment, the donor substrate 100 further includes an intermediate layer 40 made of silicon dioxide, inserted between the first layer 10 and the bonding layer 50 (Figure 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 described below.

[0034] 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.

[0035] This method first includes step a) providing a donor substrate 100 as described above.

[0036] To this end, starting with an initial solid single crystal substrate 100' composed of a first material or an epitaxized initial substrate 100', a single crystal (not shown) composed of the first material and potentially of better quality on its front side 100a is obtained.

[0037] On the front side 100a of the initial substrate 100', the stop layer 15 also has a single-crystal structure (Figure 6(a)). The stop layer 15, made from SiGe, may be formed, for example, by epitaxial growth on the initial substrate 100'. For a stop layer 15 made of highly doped Si, if the initial substrate 100' is made of silicon, boron ion implantation can be performed into the initial substrate 100' to generate the layer 15. Alternatively, the stop layer 100' made from highly doped Si may also be formed by epitaxy. The stop layer 15 typically has a thickness of 2 to 100 nm.

[0038] Next, a surface layer 10 (referred to as the first layer 10) is preferably formed on the stop layer 15 by epitaxial growth (Figure 6(b)). The thickness is selected according to the intended application, and it is understood that this first layer 10 forms a single-crystal thin layer 1 that is transferred onto the receiver substrate 2 at the end of the transfer method according to the present invention.

[0039] In the case of a termination layer 15 whose lattice parameters differ from those of the first layer 10 and / or the initial substrate 100', the termination layer 15 preferably has a thickness smaller than the critical thickness (see JM. Hartmann et al., "Critical thickness for plastic relaxation of SiGe on Si(001) revised," Journal of Applied Physics 110, 083529 (2011)), for example, less than 50 nm, in order to prevent stress related to the difference in lattice parameters from degrading the crystallinity of the first layer 10.

[0040] Next, as shown in Figure 6(c), an amorphous step is performed from the front 100a on a sub-part 101''' which includes at least a first layer 10, optionally a stop layer 15, and a portion 21 of the initial substrate 100' located below the stop layer 15 (according to different modifications described with reference to Figures 1, 2, and 3).

[0041] Amorphization refers to the disorganization of the crystal lattice of subparts 10¹', 10¹'', and 10¹''', which amorphousizes the subparts. Amorphization is usually performed by ion implantation at room temperature or lower, using ions with atomic numbers greater than or equal to the atomic number of the first material, for example. As examples, the ions may be selected from silicon, germanium, xenon, and argon. Several sequential implantations can be performed with different implantation energies to amorphous subparts 10¹', 10¹'', and 10¹''' to a deeper and / or more uniform depth. The implantation dose is typically 2 e¹⁴ / cm². 2 From 1e16 / cm 2 It changes between these two points.

[0042] For the first layer 10 and the second layer 20 made of silicon, and the stop layer 15 made of SiGe, the amorphous formation of the sublayer 101'' was performed, for example, for amorphous formation over a depth of 15 nm, at an energy of 5 keV. e 15 at / cm 2It can be obtained by implanting Ge with a dose of

[0043] Finally, at a depth deeper than the thickness of the amorphized sub-portions 101’, 101’’, 101’’’ (FIG. 6(d)), implantation of a light species, typically hydrogen, helium, or a combination of the two, is performed. In this way, an embedded weakened plane 30 that is more or less localized at the implantation peak is formed, defining the upper part 101 and the lower part 102 of the donor substrate 100. The single-crystal sub-layer 22 is held between the amorphized sub-portion 101’’’ and the embedded weakened plane 30.

[0044] The implantation energy is defined according to the target depth of the embedded weakened plane 30 in the donor substrate 100. Typically, it is several keV to 200 keV. The dose of the implanted species may vary from E 16 cm 2 ~1 E 17 / cm 2 and may change.

[0045] It should be noted that the steps of amorphization and implantation of the light species can be performed in the reverse order, that is, first implantation of the light species and then amorphization. [[ID=२२]]

[0046] At the end of step a) of the method according to the present invention, a donor substrate 100 according to one of the variants shown in FIGS. 1, 2, and 3 is obtained.

[0047] According to a particular embodiment, in order to obtain one of the variants shown in FIGS. 4 and 5, the bonding layer 50 and optionally the intermediate layer 40 are formed on the donor substrate 100.

[0048] These layers 40, 50 are selectively generated after the amorphization step, for example by chemical vapor deposition (CVD), to prevent the ion implantation of amorphization from causing impurities from these layers 40, 50 in the underlying layers (especially the first layer 10), making subsequent recrystallization more difficult. Of course, the deposition of layers 40, 50 must be carried out at a temperature lower than the recrystallization temperature of the amorphized sub-parts 101', 101'', 101'''. If a temperature is required for deposition that can modify the amorphized sub-parts 101', 101'', 101''' and / or alter the embedded weakened surface 30, it is also possible to choose to deposit one or more layers 40, 50 before the amorphization and / or lightweight species implantation step, which is undesirable at this stage of the method.

[0049] As shown below, the bonding layer 50, in particular, which is made from deposited amorphous silicon, improves the quality of the bonding interface generated in the subsequent assembly step c).

[0050] Next, the method includes step b) providing a support layer 2. This is typically in the form of a small plate, usually 150 mm to 450 mm in diameter and typically 300 to 900 microns thick. It can include a stack of various layers, particularly metallic, corresponding to layers of a device 2a (e.g., complementary CMOS, manufactured according to metal-oxide-semiconductor technology) placed on a solid portion made of a semiconductor material such as silicon. These metallic materials typically limit the temperature applicable to the receiver substrate 2 to 500°C or below.

[0051] The receiver substrate 2 may include a material that does not support high processing temperatures, either due to its properties or because its thermal expansion coefficient is very different from that of the transferred single-crystal thin layer 1, regardless of the presence or absence of a device layer.

[0052] Following steps a) and b), the transfer method includes step c) assembling by directly bonding the front side 100a of the donor substrate 100 onto the receiver substrate 2 to form an assembly bonded at the bonding interface 3 (Figure 7(a)). Direct bonding means 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 degree of cleanliness allow bonding to be carried out by molecular adhesion of the surface. To promote excellent bonding quality, surface cleaning and / or activation, which are well known in the field of molecular adhesion bonding, can be applied to the substrate before assembly. Assembly in a controlled atmosphere is also possible.

[0053] The receiver substrate 2 shown in Figure 7(a) includes a device layer 2a on its assembled surface. Generally, the surface film of this layer 2a is formed from silicon oxide or silicon nitride.

[0054] When the donor substrate 100 is one of the configurations shown in Figures 1 to 3, the bonding interface 3 is established between the layer of device 2a and the amorphous sub-parts 101', 101'', 101''. The first amorphous layer 10 is particularly advantageous for the effective solidification of the bonding interface 3, even at low temperatures. In fact, with respect to a single-crystal surface, the amorphous surface deforms better as the temperature rises and better absorbs the water monolayer present at the interface during bonding by molecular adhesion. As a result, the presence of amorphous sub-parts 101', 101'', 101'' on the surface enables excellent closure of the bonding interface at low temperatures.

[0055] Therefore, bonding at ambient temperature, and optionally solidification annealing at temperatures below 350°C, already provide very good retention of the bonding interface 3, ensuring good progress of subsequent steps of the method, particularly separation step d).

[0056] When the donor substrate 100 is one of the configurations shown in Figures 4 and 5, the bonding interface 3 is established between the device layer 2a and the amorphous silicon bonding layer 50. For the same reasons mentioned above, the latter is extremely effective for closing (solidifying) the bonding interface at low temperatures, typically below 500°C. Alternatively, a solidification annealing method similar to that described above can also be applied.

[0057] Step d) separating the bonded assembly along the embedded weakened surface 30 allows the upper part 101 of the donor substrate 100 to be transferred onto the receiver substrate 2 (Figure 7(b)). Separation along the embedded weakened surface 30 is selectively performed by applying heat treatment at low temperatures, typically between 200°C and 500°C, due to the growth of microcracks caused by fusion and pressurization of gas species. Advantageously, the heat treatment is performed at temperatures below 400°C, and selectively between 250°C and 400°C.

[0058] Alternatively or in conjunction, separation may be caused by the application of mechanical stress to the combined assembly.

[0059] At the end of this separation, an intermediate SOI structure 150 is obtained on the one hand, and the lower part 102 of the donor substrate is obtained on the other hand.

[0060] Next, the transfer method according to the present invention includes step e) recrystallizing amorphous sub-parts 101', 101'', 101'''' in order to restore single-crystal quality to the first layer 10.

[0061] Recrystallization corresponds to imparting single-crystal properties to sublayers 101', 101'', and 101''''. This implements a solid-phase epitaxy (SPE) phenomenon. Such recrystallization is based on the application of heat treatment at a temperature in which the crystal lattices of sublayers 101', 101'', and 101'''' are rearranged based on the crystal lattice of the single-crystal sublayer 22 acting as a seed.

[0062] The recrystallization heat treatment may be performed at temperatures between 450°C and 900°C. Naturally, to address the aforementioned applications where the receiver substrate 2 is not suitable for high temperatures, the thermal recrystallization temperature is advantageously between 450°C and 550°C for 10 minutes to 50 hours under a non-oxidizing atmosphere. For example, annealing may be applied at 500°C for 2 to 4 hours to recrystallize amorphous silicon of 15 to 20 nm.

[0063] During heat treatment, the recrystallized plane moves from the single-crystal sublayer 22 (or from the single crystal portion of the second layer 20 of the upper 101 adjacent to the amorphous sublayer) toward the bonding interface 3.

[0064] At the end of recrystallization step e), the upper part 101 of the intermediate structure 150 is completely single-crystal (Figure 8(a)). Note that the heat treatment applied in separation step d) may be involved in the recrystallization of the amorphous sub-parts 101', 101'', 101'''', depending on its temperature and duration.

[0065] The first layer 10, whose single-crystal quality has been restored, corresponds to a single-crystal thin layer 1 that is then expected to be transferred onto the receiver substrate 2. Thus, the thin layer 1 has the physical and electrical properties expected for the manufacture of electronic components.

[0066] The thickness of the first layer 10 and good crystal recovery can be measured by ellipsometry, Raman, and / or transmission electron microscopy (TEM), respectively.

[0067] Depending on the properties of the stop layer 15, certain precautions must be taken to prevent damage to the stop layer 15 by the recrystallization step e). In particular, in the case of a stop layer 15 made from SiGe, the recrystallization temperature must be maintained below 700°C, and even below 600°C, so as not to plastically relax the SiGe.

[0068] Bonding interface 3 benefits from the heat treatment applied between the recrystallization step d) and the separation step e), because these treatments strengthen the interatomic bonds between the assembled surfaces.

[0069] Therefore, the amorphous nature of the first layer 10 facilitates direct bonding between the donor substrate 100 and the receiver substrate 2 in step c) of the method. This also enables effective repair of crystal defects associated with the injection of lightweight species, while simultaneously allowing recrystallization by solid-phase epitaxy at low temperatures, thus restoring the single-crystal quality and associated physical and electrical properties of the first layer 10.

[0070] Finally, the transfer method includes step f) chemically etching the second layer 20, and then step f) selectively chemically etching the stop layer 15 relative to the first layer 10 (Figure 8(b)). Advantageously, the constituent material of the second layer 20 also allows the second layer 20 to be selectively etched relative to the stop layer 15.

[0071] Known dry etching or wet etching techniques can be employed. Typical chemical etching solutions that can be used are 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.

[0072] Step f) allows for the removal of the second layer 20, which has a relatively high residual roughness (typically around 10 nm RMS) due to fracture along the embedded weakened surface 30 (step d).

[0073] The etching selectivity between the second layer 20 and the stopping layer 15 allows for the restoration of a good surface condition (roughness). The etching selectivity between the stopping layer 15 and the first layer 10 provides the first layer 10 with very low surface roughness while maintaining its thickness uniformity.

[0074] Therefore, the transfer method makes it possible to obtain a structure 200 including a single-crystal thin layer 1 placed on a receiver substrate 2, which may include a layer of device that is not suitable for any high-temperature processing (Figure 8(b)).

[0075] When the donor substrate 100 includes a binding layer 50 or a stack composed of an intermediate layer 40 and a binding layer 50, the resulting structure 200 is as shown in Figures 9(a) and 9(b).

[0076] The present invention also relates to a second embodiment of a method for transferring a single-crystal thin layer 1 onto a receiver substrate 2, as shown in Figures 10 and 11.

[0077] This embodiment differs from the previously described method by arranging a recrystallization step in a series of steps of the method. In fact, after step a) (same as described above) of supplying the donor substrate 100, 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 without affecting the embedded weakened surface 30, that is, without affecting the ability of the embedded weakened surface 30 to subsequently cause separation in this method.

[0078] Advantageously, the recrystallization step a') includes heat treatment with a laser configured to be applied to the front side 100a of the donor substrate 100 and induce solid-phase epitaxy of the amorphous sub-parts 101', 101'', 101'''' (Figure 10(a)). As an example, this heat treatment is performed with pulses having a duration of about 200 ns and a load of 0.8 J / cm². 2 This can be carried out using a UV excimer laser with an energy density of approximately λ=308nm.

[0079] 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.

[0080] Step b) providing the receiver substrate 2, step c) assembling by directly bonding the front side 100a of the donor substrate 100 onto the receiver substrate 2 (Figure 10(b)), and step d) separating along the embedded weakening surface 30 to transfer the upper part 101 of the donor substrate 100 onto the receiver substrate 2 (Figure 11(a)) are performed in a second embodiment of the method according to the first embodiment described above.

[0081] There is no recrystallization step e), the latter of which is performed before assembly.

[0082] However, advantageously, step f) of selectively chemically etching the second layer 20 with respect to the termination layer 15, and then selectively chemically etching the termination layer 15 with respect to the single crystal thin layer 1, is carried out in the same manner (Figure 11(b)).

[0083] The donor substrate 100 according to the present invention enables the transfer (according to the first or second embodiment of the transfer method) of a single-crystal thin layer 1 with very high crystal quality suitable for the manufacture of electronic components, without requiring the application of high-temperature heat treatment to repair defects associated with the injection of lightweight species, smooth fracture surfaces, thin the transferred portion 101, and solidify the bonding interface 3.

[0084] The layer configuration of the donor substrate 100 further simplifies the method of transferring the thin layer 1 onto the receiver substrate 2 by limiting steps c) to f) to low-temperature heat treatment and selective chemical etching.

[0085] Naturally, the present invention is not limited to the embodiments described, and modified embodiments may be added thereto without departing from the scope of the invention as defined by the claims.

Claims

1. A donor substrate (100) for transferring a single-crystal thin layer (1) made from a first material onto a receiver substrate (2), wherein the donor substrate (100) has a front side (100a) and a rear side (100b), - An embedded weakening surface (30) that defines the upper (101) and lower (102) portions of the donor substrate (100), - In the upper part (101), a first layer (10) on the front side (100a), a second layer (20) adjacent to the embedded weakening surface (30), and a stop layer (15) inserted between the first layer (10) and the second layer (20), wherein the first layer (10) is made of the first material and intended to form the single crystal thin layer (1), and the stop layer (15) is made of the second material which can provide selective etching to the first material, - Amorphized sub-parts (101', 101'', 101'''') having a thickness strictly less than the thickness of the upper part (101) and comprising at least the first layer (10), wherein the second layer (20) comprises at least one single-crystal sub-layer (22) adjacent to the embedded weakened surface (30), the sub-layer (22) being intended to form a recrystallization seed for the amorphous sub-parts (101', 101'', 101''''), The amorphous sub-part (101'', 101''') includes the stop layer (15), or the amorphous sub-part (101''') includes the stop layer (15) and a portion (21) of the second layer (20) adjacent to the stop layer (15), wherein the donor substrate (100).

2. The donor substrate (100) according to claim 1, wherein the second layer (20) is made of the first material.

3. The donor substrate (100) according to claim 1 or 2, wherein the first material is selected from silicon, germanium, or a silicon / germanium alloy.

4. The donor substrate (100) according to any one of claims 1 to 3, wherein the second material is selected from silicon germanium or highly doped silicon.

5. A donor substrate (100) according to any one of claims 1 to 4, comprising an amorphous silicon bonding layer (50) disposed on the first layer (10).

6. A method for transferring a single-crystal thin layer (1) made from a first material onto a receiver substrate (2), a) the step of providing a donor substrate (100) according to any one of claims 1 to 5, b) The step of providing the receiver board (2), c) The step of directly bonding the front side (100a) of the donor substrate (100) onto the receiver substrate (2), d) A step of separating the upper part (101) of the donor substrate (100) along the embedded weakening surface (30) in order to transfer it onto the receiver substrate (2), e) Recrystallizing the amorphous sub-parts (101', 101'', 101''') to restore the single-crystal quality to the first layer (10), and then forming the single-crystal thin layer (1), f) The step of chemically etching the second layer (20), and then selectively chemically etching the stop layer (15) with respect to the single crystal thin layer (1), Methods that include...

7. The transfer method according to claim 6, wherein the recrystallization step e) includes a heat treatment at a temperature of 450°C to 900°C.

8. A method for transferring a single-crystal thin layer (1) made from a first material onto a receiver substrate (2), a) the step of providing a donor substrate (100) according to any one of claims 1 to 5, a') A step of locally recrystallizing the amorphous sub-parts (101', 101'', 101'''') in order to restore the single-crystal quality of the first layer (10) without affecting the embedded weakened surface (30), wherein the recrystallized first layer (10) forms the single-crystal thin layer (1), b) The step of providing the receiver board (2), c) The step of directly bonding the front side (100a) of the donor substrate (100) onto the receiver substrate (2), d) A step of separating the upper part (101) of the donor substrate (100) along the embedded weakening surface (30) in order to transfer it onto the receiver substrate (2), f) The step of chemically etching the second layer (20), and then selectively chemically etching the stop layer (15) with respect to the single crystal thin layer (1), Methods that include...

9. The transfer method according to claim 8, wherein the recrystallization step a') includes laser heat treatment applied to the front side (100a) of the donor substrate (100) and configured to induce solid-phase epitaxy of the amorphous sub-parts (101', 101'', 101'''').

10. The transfer method according to claim 6 or 8, wherein the separation step d) includes heat treatment at a temperature of 400°C or lower.

11. The transfer method according to claim 6 or 8, wherein step a) providing the donor substrate (100) includes implanting ions into the upper portion (101) of the substrate (100), which is initially of single-crystal quality, in order to form the amorphous sub-portions (101', 101'', 101'''').

12. The transfer method according to claim 6 or 8, wherein in step f), the chemical etching of the second layer (20) is selective with respect to the stop layer (15).

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