Composite structure including a layer of single-crystal III-V composite material and associated manufacturing process

Abstract

The invention relates to a composite structure comprising: - a seed layer of single-crystal III-V composite material extending in a principal plane, - a support substrate of crystalline material, on which the seed layer is deposited via a bonding interface, the support substrate comprising a peripheral rim devoid of a seed layer, the peripheral rim extending around an edge of the seed layer in the principal plane, - an intermediate layer of amorphous material, disposed between the seed layer and the support substrate and present on the peripheral rim, - at least one trench present in the peripheral rim, extending, along an axis normal to the principal plane, through the intermediate layer to the support substrate, or even into the support substrate, the trench being located less than 100 micrometers from the edge in the principal plane. The invention also relates to a method for manufacturing said structure.Figure to be published with the abbreviation: -.

Description

Title of the invention: Composite structure including a layer of single-crystal III-V composite material and associated manufacturing process. FIELD OF THE INVENTION

[0001] The present invention relates to the field of semiconductor materials for microelectronic components. It relates in particular to a composite structure comprising a support substrate and a seed layer, made of a III-V composite material, assembled via a bonding interface, said seed layer having been transferred from a donor substrate onto said support substrate. Such a structure is generally used to grow at least one epitaxial layer on the seed layer for the purpose of manufacturing components. The invention also relates to a method for manufacturing said composite structure. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] For the fabrication of certain microelectronic or optoelectronic components, particularly HBT and HEMT transistors, lasers, and photodiodes, it is desirable to use composite substrates that provide a thin seed layer of single-crystal IILV composite material, deposited on a support substrate of a different nature than the seed layer, for economic reasons or to improve certain performance characteristics. As an example, one can cite an InP (indium phosphide)-on-silicon composite substrate, in which the single-crystal InP layer serves as a seed for the epitaxial growth of a functional stack of IILV layers, traditionally grown on a bulk InP substrate. The silicon substrate provides mechanical robustness to the composite substrate and allows for optimization of material costs.

[0003] Composite substrates can be produced in various ways, including by bonding a donor substrate to a support substrate and transferring the seed layer (from the donor substrate) to said support substrate via thinning, delamination, or separation steps along a buried brittle plane formed in the donor substrate, as is notably the case in the Smart Cut™ process. Since the assembled support and donor substrates have chamfers and a certain degree of edge drop at their periphery, the composite substrate generally has a peripheral rim at which the seed layer is not transferred.

[0004] The composite substrate is then used to grow one or more epitaxial layer(s) on the seed layer with a view to forming the functional stack of III-V layers, intended for the manufacture of components.

[0005] Silicon dioxide is a material commonly used as a mask in the epitaxial growth technique known as Selective Area Growth (SAG). In a composite substrate S, the peripheral ring le, which lacks a seed layer 4, is generally covered by a layer of silicon dioxide 2, which prevents the deposition of material in said ring le during epitaxial growth.

[0006] It is observed that the material not deposited on the oxide layer 2 results in a higher growth rate in the region of the nucleus layer 4 near the crown ([Fig. 1]). Consequently, the thickness of the epitaxial layer 5 can increase by a factor of three to four at the edge, and the composition of this edge layer can also be modified; these variations in thickness and composition are obviously not favorable to the manufacturing yield of the components.

[0007] An additional problem can arise in the case of thick epitaxial layers (typically several micrometers): delamination of the layers is sometimes observed, induced by the stress accumulated in the structure due to the increased thickness and the change in layer composition. Delamination is a major drawback because it can lead to a significant reduction in the effective surface area of ​​functional layers in the composite substrate, and furthermore, it causes contamination of the epitaxial equipment enclosure. SUBJECT OF THE INVENTION

[0008] The present invention proposes a composite structure comprising a support substrate made of a crystalline material on which is disposed a seed layer made of a monocrystalline IILV composite material, an intermediate layer made of an amorphous material being interposed between the seed layer and the support substrate, and being present on a peripheral periphery of the support substrate lacking a seed layer. The composite structure comprises at least one trench formed in the peripheral periphery and extending through the intermediate layer and down to the support substrate: such a composite structure makes it possible to reduce the overgrowth of the epitaxial layer at the edge of the seed layer during the growth of the functional stack. The invention also relates to a method of manufacturing the composite structure. BRIEF DESCRIPTION OF THE INVENTION

[0009] The invention relates to a composite structure comprising:

[0010] - a seed layer of monocrystalline IILV compound material extending into a main plan,

[0011] - a crystalline material substrate on which the seed layer is disposed, via a bonding interface, the support substrate comprising a peripheral perimeter devoid of a seed layer, the peripheral perimeter extending around an edge of the seed layer in the principal plane,

[0012] - an intermediate layer of amorphous material, disposed between the seed layer and the supporting substrate is present on the peripheral perimeter,

[0013] - at least one trench present in the peripheral perimeter, extending, along an axis normal to the main plane, through the intermediate layer to the supporting substrate, or even into the supporting substrate, the trench being located less than 100 micrometers from the edge in the main plane.

[0014] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: - the trench is located less than 50 micrometers, or even less than 20 micrometers, from the edge of the germ layer; - the material composed of the seed layer is chosen from indium phosphide, gallium arsenide, gallium nitride, and their ternary or quaternary compounds; - the amorphous material of the intermediate layer is chosen from silicon oxide, silicon nitride, a silicon oxynitride, aluminium nitride, alumina; - the support substrate is formed from a single-crystal or polycrystalline material chosen from silicon, sapphire, gallium arsenide, germanium, aluminium nitride and silicon carbide; - the trench has a width, in the main plane, of between 500nm and 1mm, preferably from a few micrometers to 20qm; - the trench extends, in the main plane, all along the edge of the germ layer; - the composite structure comprises a plurality of trenches constructed in the peripheral perimeter of the supporting substrate; - the area occupied by said trenches in the main plane corresponds to at least 20% of the area of ​​the peripheral perimeter.

[0015] The invention also relates to a method for manufacturing a composite structure comprising the following steps:

[0016] a) the transfer of a seed layer made of a single-crystal III-V composite material onto a support substrate made of a crystalline material, via a bonding interface, an intermediate layer made of an amorphous material being interposed between the seed layer and the support substrate and being present on a peripheral periphery of the support substrate devoid of the germ layer, the peripheral perimeter extending around a border of the germ layer in a principal plane;

[0017] b) the formation of at least one trench in the peripheral perimeter, the trench extending, along an axis normal to the main plane, through the intermediate layer to the supporting substrate, or even into the supporting substrate, the trench being located less than 100 micrometers from the edge in the main plane. According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: - Step a) includes the following sub-steps: a1) the provision of a donor substrate in monocrystalline III-V composite material and a support substrate in a crystalline material, a2) the formation of a brittle plane buried in the donor substrate, delimiting, with a front face of said donor substrate, the seed layer to be transferred, a3) the formation of an intermediate layer, in an amorphous material, on a front face of the support substrate, a4) the molecular adhesion of the front face of the donor substrate to the intermediate layer of the support substrate, a5) the separation along the fragile buried plane to transfer the germ layer onto the supporting substrate, on the one hand, and to obtain the rest of the donor substrate, on the other hand. - step b) of forming the -at least one- trench is carried out between sub-step a3) and sub-step a4); - in which step b) of the formation of the -at least one- trench is carried out after sub-step a5); - the manufacturing process includes a step c) of growth by epitaxy of at least one functional layer on the germ layer of the composite structure. BRIEF DESCRIPTION OF THE FIGURES

[0018] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows with reference to the accompanying figures in which:

[0019] [Fig.1] Fig.1 schematically illustrates the overgrowth of an epitaxial layer (5), in a composite substrate (10) of the prior art, at the edge of the seed layer (4), namely in the vicinity of the peripheral crown devoid of a seed layer and comprising a layer of silicon oxide;

[0020] [Fig.2a]

[0021] [Fig.2b] [Fig.2a] and [Fig.2b] present a first embodiment of a composite substrate forming part of a composite structure according to the present invention;

[0022]

[0023] [Fig.3a] [Fig.3b] [Fig.3a] and [Fig.3b] present a second embodiment of a composite substrate forming part of a composite structure according to the present invention;

[0024]

[0025]

[0026] [Fig.4a] [Fig.4b] [Fig.4c] [Fig.4a], [Fig.4b] and [Fig.4c] illustrate composite structures according to the present invention;

[0027]

[0028]

[0029]

[0030]

[0031]

[0032] [Fig.5a] [Fig.5b] [Fig.5c] [Fig.5c'] [Fig.5d] [Fig.5e] Fig.5a, Fig.5b, Fig.5c, Fig.5c', Fig.5d and Fig.5e present a first method of implementing a process for manufacturing a composite structure, in accordance with the present invention;

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] [Fig.6a] [Fig.6b] [Fig.6c] [Fig.6d] [Fig.6e] [Fig.6e'] Fig.6a, Fig.6b, Fig.6e, Fig.5e, Fig.5e, Fig.5e, Fig.5e, Fig.5e, Fig.5a, Fig.5b, Fig.5c, Fig.5c', Fig.5d and Fig.5e present a first method of implementing a process for manufacturing a composite structure, in accordance with the present invention;

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] [Fig.6a] [Fig.6b] [Fig.6c] [Fig.6d] [Fig.6e] [Fig.6e'] Fig.6a, Fig.6b, Fig.5e ...[6c], [Fig. 6d], [Fig. 6e], and [Fig. 6e]' present a second embodiment of a manufacturing process for a composite structure according to the present invention;

[0039] [Fig. 7] [Fig. 7] presents a step of a manufacturing process according to the invention;

[0040] [Fig. 8] [Fig. 8] presents another step of a manufacturing process according to the invention.

[0041] The same reference numerals in the figures may be used for elements of the same type. Some figures are schematic representations which, for the sake of readability, are not to scale. In particular, the thicknesses of the layers along the z-axis are not to scale with respect to the lateral dimensions along the x and y axes; and the relative thicknesses of the layers with respect to each other are not necessarily to scale in the figures. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention relates to a composite structure 160 comprising in particular a support substrate 10 on which a seed layer 40 is disposed. The support substrate 10 and the seed layer 40 are formed of materials of different natures.

[0043] The substrate 10 can be chosen in particular for its properties (mechanical, electrical, thermal, etc.), its low cost, and / or its compatibility with microelectronic processes and equipment. It is made of a crystalline material (monocrystalline or polycrystalline), for example, silicon, sapphire, gallium arsenide, germanium, aluminum nitride, and silicon carbide. Its thickness can vary from a few tens to a few hundred micrometers, for example, from 50 µm to 800 µm.

[0044] The seed layer 40 is chosen according to the application and the components involved. It is intended to serve as a crystal seed for the epitaxy of a single-crystal functional layer 50 in and / or on which the components will be fabricated. The seed layer 40 is made of a single-crystal, type IILV composite material. This composite material can be chosen from indium phosphide, gallium arsenide, gallium nitride, and their ternary or quaternary compounds. The thickness of the seed layer 40 can typically vary from a few nanometers to a few hundred nanometers, for example, from 10 nm to 1000 nm.

[0045] The seed layer 40 and the support substrate 10 are bonded via a bonding interface 30, which extends along a principal plane (x,y). As will be described later with reference to the manufacturing process according to the invention, the seed layer 40 is assembled and transferred onto the support substrate 10, and not resulting from epitaxial growth or deposition on said substrate 10.

[0046] The assembly including the seed layer 40 and the support substrate 10 is called composite substrate 100 ([Fig.2a]).

[0047] In the composite substrate 100, the peripheral edge 10c of the support substrate 10 is devoid of a seed layer 40. This is a characteristic usually observed on a composite substrate 100 formed by assembly and layer transfer, given the presence of a chamfer and an edge drop at the periphery of the assembled substrates, which prevents the transfer of the seed layer 40 to the peripheral edge of the support substrate 10. According to a first embodiment, the composite substrate 100 can consist of a wafer, generally circular (but potentially square or otherwise), having a diameter of 50 mm, 100 mm, 150 mm, 200 mm, 300 mm, or even more, as is common in the field of microelectronics ([Fig. 2a], [Fig. 2b]). The peripheral edge 10c can exhibit a width (measured radially between the edge of the support substrate 10 and the edge 40b of the seed layer 40) of between a few hundred micrometers and a few millimeters, for example, between 200qm and 5mm, more usually between 1mm and 3mm.

[0048] According to a second embodiment, the composite substrate 100 may consist of a portion of a wafer 11, as illustrated in Figures 3a and 3b, or of a chip. The wafer 11 then comprises several adjacent but separated seed layers 40. Each seed layer 40 is disposed on a support substrate 10, a portion of the support 10' of the wafer 11. The peripheral rim 10c in this case is defined as the portion of the support substrate 10 devoid of a seed layer 40, and bordering the seed layer 40. The peripheral rim 10c may have a width ranging from a few hundred micrometers to a few millimeters, for example, from 200 µm to 1 mm.

[0049] The composite substrate 100 further comprises an intermediate layer 20 made of an amorphous material, disposed on the support substrate 10 before its assembly onto the seed layer 40, and thus interposed between said substrate 10 and the seed layer 40 ([Fig. 2a], [Fig. 3a]). The intermediate layer 20 can, in particular, improve the quality and strength of the bonding interface 30. In particular, it can be composed of silicon oxide, silicon nitride, or another material. Its thickness can range from a few nanometers to several thousand nanometers, for example, from 50 nm to 2000 nm.

[0050] The intermediate layer 20 is also present on the peripheral perimeter 10c of the support substrate 10.

[0051] Returning to the general description, the composite structure 160 comprises, in addition to the composite substrate 100, at least one trench 60 present in the peripheral periphery 10c of the support substrate 10 ([Fig. 4a], [Fig. 4b], [Fig. 4c]). The trench 60 extends, along a z-axis normal to the principal plane (x,y), through the intermediate layer 20 and into the support substrate 10, or even into the support substrate 10. The bottom of the trench 60 therefore corresponds to a surface of the crystalline material forming the support substrate 10. The trench 60 has a depth greater than the thickness of the intermediate layer 20 so as to open onto or into the support substrate 10; its depth can be up to several micrometers, a few tens of micrometers, or even a few hundred micrometers.

[0052] The trench 60 is also located less than 100 micrometers from the edge 40b of the seed layer 40, in the principal plane (x,y).

[0053] The fact that trench 60 provides access to a crystalline material (the substrate support material 10) at its bottom allows for the nucleation of group III or group V elements contained in the gaseous precursors which will implemented during the epitaxy of a functional layer 50 on the seed layer 40. This nucleation can take place at the bottom of the trench 60 (crystalline material forming the support substrate 10) or possibly at the sides of the trench 60 when it penetrates the support substrate 10.

[0054] Since the trench is very close to the edge 40b of the seed layer 40, precursors are "consumed" in this area and are not over-concentrated as in the case where the peripheral perimeter 10c of the support substrate 10 is only covered by the intermediate layer 20 of amorphous material, which blocks any nucleation and growth of material.

[0055] By allowing the incorporation of elements of the gaseous precursors at the level of the peripheral perimeter 10c, the composite structure 160 strongly limits, or even avoids, the overgrowth of the functional layer 50 at the edge of the germ layer 40.

[0056] Advantageously, the trench 60 is located less than 50 micrometers, less than 20 micrometers, or even less than 10 micrometers from the edge 40b of the germ layer 40.

[0057] The trench 60 can have a width, in the main plane (x,y), of between 500nm and a few millimeters, in particular between 5qm and 2mm, or between 20qm and 1mm, or even between 100um and 500qm.

[0058] According to an advantageous embodiment, the trench 60 extends, in the principal plane (x,y), all along the edge 40b of the seed layer 40. In the example illustrated in figures 4a and 4b, the composite structure 160 is a circular plate and the edge 40b of the seed layer 40 is substantially circular: the trench 60 can then also extend in a circular shape.

[0059] In an alternative case where the composite structure 160 and the border 40b of the seed layer 40 has a square or rectangular shape in the principal plane (x,y), the trench 60 may extend in a similar shape, along the border 40b.

[0060] According to another advantageous embodiment, the composite structure 160 comprises a plurality of trenches 60, which may extend, in the principal plane (x,y), parallel to the boundary 40b of the seed layer 40 or parallel to the tangent to said boundary 40b, perpendicularly, or at any angle to the boundary 40b. In the example of [Fig. 4c], the two trenches 60 are concentric in the principal plane (x,y) and, for example, continuously follow the boundary 40b of the seed layer 40. They could optionally be discontinuous in the principal plane (x,y), and appear as dashed lines or as a network of holes, for example. A plurality of trenches 60 extending in radial directions in the principal plane (x,y) could also be envisaged.Let us recall that a trench 60 in the sense of the present invention is not necessarily attached to the notion of "line", each trench 60 can have a point shape (hole. rounded or polygon) or elongated (continuous or discontinuous), in the principal plane (x,y).

[0061] Preferably, the area occupied by said trenches 60 in the principal plane (x,y) corresponds to at least 20% of the area of ​​the peripheral perimeter 10c, so as to capture sufficient elements of the gaseous precursors at the level of said perimeter 10c and to avoid an overconcentration of precursors at the edge of the seed layer 40. The area occupied by the trenches 60 can be between 20% and typically 80%, 70% or even 60%.

[0062] By way of example, the composite structure 160 may comprise: - a circular silicon substrate support 10 - an intermediate layer 20 of silicon oxide, 500 nm thick, - a 40-layer InP germ layer, 300 nm thick and with a border 40b circular, and - one, two or three trenches 60, 2000 nm deep, 50 pm wide, spaced 200 pm apart and having a continuous or discontinuous circular shape, concentric to the border 40b; the trench 60 closest to the border 40b of the seed layer 40 being spaced from said border 40b by about 70 pm.

[0063] According to another example, the composite structure 160 may comprise: - a silicon substrate support 10, in circular, square or rectangular shape, - an intermediate layer 20 of silicon oxide, 500 nm thick, - a GaN germ layer 40, 300 nm thick and with a border 40b of the same shape as the support substrate 10, and - 2 trenches 60, 1000 nm deep, 100 pm wide, spaced apart by 100 pm and having a circular shape, concentric to the border 40b; the trench 60 closest to the border 40b of the seed layer 40 being spaced from said border 40b by about 40 pm.

[0064] The invention also relates to a method of manufacturing the composite structure 160.

[0065] The process includes a step a) corresponding to the transfer of a seed layer (40) made of a single-crystal IILV composite material onto a support substrate 10 made of a crystalline material, via a bonding interface 30 extending along a principal plane (x,y) ([Fig. 2a], [Fig. 3a]). The support substrate 10 has a peripheral rim 10c devoid of the seed layer 40. The peripheral rim 10c extends around an edge 40b of the seed layer 40 in the principal plane (x,y).

[0066] The germ layer 40 is made of single-crystal IILV composite material (group III elements: In, Ga, Al,...; group V elements: As, P, Sb,...). It has a thickness typically between a few nanometers and 1 micrometer, preferably less than or equal to 1000 nm, 500 nm, 250 nm, or even 100 nm. The single-crystal III-V compound material of the germ layer 40 is advantageously a binary compound, in particular indium phosphide (InP), gallium arsenide (GaAs) or gallium nitride (GaN).

[0067] The support substrate 1 is formed from a single-crystal or polycrystalline material selected from silicon, sapphire, gallium arsenide, germanium, aluminum nitride, and silicon carbide. The support substrate 1 may have a thickness between 50 µm and 800 µm.

[0068] An intermediate layer 20, made of an amorphous material, is disposed between the seed layer 40 and the support substrate 10. This intermediate layer is also present on the peripheral periphery 10c of the support substrate 10, which lacks the seed layer 40. The amorphous material of the intermediate layer 20 is, for example, chosen from silicon dioxide, silicon nitride, silicon oxynitride (SiON), aluminum nitride, and alumina. The thickness of the intermediate layer 20 can range from a few nanometers to several thousand nanometers, for example, from 50 nm to 2000 nm.

[0069] The transfer of step a) can for example lead to an InP type structure (seed layer 40) on Si (support substrate 10), InP on sapphire, InP on GaAs, InP on Ge, InP on SiC, GaAs on Si, GaAs on Sapphire, GaAs on Germanium, GaAs on SiC, GaN on Si, etc., with an intermediate layer 20 in SiO2, SiN, SiON or other amorphous material mentioned above.

[0070] The method further includes a step b) corresponding to the formation of at least one trench 60 in the peripheral perimeter 10c, the trench 60 extending, along an axis z normal to the main plane (x,y), through the intermediate layer 20 and up to the support substrate 10, or even into the support substrate 10. According to the invention, the trench 60 is located less than 100 micrometers from the edge 40b in the main plane (x,y).

[0071] The -at least one- trench 60 can be created by a mechanical removal or cutting technique (for example, sawing by diamond wheel or laser, to the target depth of trench) or an engraving technique (dry or wet) which may in particular involve the conventional implementation of masking and optionally photolithography.

[0072] Advantageously, and with reference to the Smart Cut process, step a) of the process comprises the following substeps:

[0073] al) the supply of a donor substrate 400 in monocrystalline IILV composite material, from which the seed layer 40 will be taken, and the supply of the support substrate 10 in a crystalline material ([Fig.5a], [Fig.6a]);

[0074] a2) the formation of a fragile plane buried 401 in the donor substrate 400, delimiting with a front face of said donor substrate 400, the germ layer 40 to be transferred ([Fig.5b], [Fig.6b]);

[0075] a3) the formation of an intermediate layer 20, in an amorphous material, on a front face of the support substrate 10 ([Fig.5c], [Fig.6c]),

[0076] a4) the molecular adhesion of the front face of the donor substrate 400 on the intermediate layer 20 of the support substrate 10, to form a glued assembly 410 including a bonding interface 30 between the two substrates 400,10 ([Fig.5d], [Fig.6d]);

[0077] a5) the separation along the buried fragile plane 401 to transfer the germ layer 40 on the support substrate 10, on the one hand, and obtain the remainder of the donor substrate 400', on the other hand ([Fig.5e], [Fig.6e]).

[0078] In substep a1a), the donor substrate 400 and support 10 are usually in the form of circular plates, with diameters ranging from 50 mm to 300 mm, depending on the availability of materials. As mentioned previously with reference to the first embodiment of composite substrate 100, the presence of chamfers and edge drops around the periphery of the assembled substrates 400, 10 (not shown in Figures 5 and 6) implies that the bonding (substep a4) is not effective all the way to the edges and that, consequently, the seed layer 40 is not transferred (substep a5) to the peripheral edge 10c of the support substrate 10 ([Fig. 5e], [Fig. 6e]). Note that this peripheral perimeter 10c has a width (measured radially between the edge of the support substrate 10 and the edge of the seed layer 40) typically between a few hundred micrometers and a few millimeters, for example, between 200qm and 5mm, more usually between 1mm and 3mm.

[0079] The second embodiment of composite substrate 100 differs from the first in that the transferred seed layer 40 is not unique: during substep a1a), several donor substrates 400, for example in the form of vignettes, can be assembled on a support substrate 10', and give rise to the transfer of a plurality of seed layers 40, separated by a peripheral perimeter 10c of the individual support substrate 10, as illustrated in Figures 3a and 3b.

[0080] Substep a2) can notably be carried out by ion implantation of light species such as hydrogen and / or helium, as is known from the Smart Cut process. Note that the front face of the donor substrate 400 may include an additional layer, capable of protecting the substrate surface during ion implantation and / or of facilitating bonding, improving the quality and strength of the interface, or providing insulation or conductivity properties of interest for the future components to be developed.

[0081] During substep a3), the intermediate layer 20 is formed at least on the front face (to be assembled) of the support substrate 10, typically by thermal oxidation or deposition. The intermediate layer 20 may also be present on the rear face of the support substrate 10. This intermediate layer 20 is likely to facilitate bonding, improve the quality and strength of the interface, or provide interesting insulation or conductivity properties for the future components to be developed.

[0082] According to a first variant of the manufacturing process, step b) of forming the -at least one- trench 60 is carried out after substep a3), before substep a4) of gluing ([Fig.5c]').

[0083] According to a second embodiment variant, step b) is carried out after substep a5) of separation ([Fig.6e]').

[0084] Preferably, regardless of the implementation variant, chemical cleaning and / or surface treatments (polishing, plasma, etc.) are usually applied to the substrates before substep a4) of assembly.

[0085] As a reminder, direct molecular adhesion bonding (substep a4) does not require an adhesive material, as bonds are established at the atomic scale between the surfaces being joined. Several types of molecular adhesion bonding exist, which differ in particular in their temperature, pressure, atmospheric conditions, or pretreatments prior to contacting the surfaces. Examples include room-temperature bonding with or without prior plasma activation of the surfaces to be joined, atomic diffusion bonding (ADB), surface-activated bonding (SAB), etc.

[0086] Substep a5) of separation along the buried fragile plane 401 is usually achieved by applying a heat treatment at a temperature between 100°C and 900°C, depending on the materials involved. Such a heat treatment induces the development of cavities and microcracks in the buried fragile plane 401, and their pressurization by the light species present in gaseous form, until a fracture propagates along said fragile plane. Alternatively or concurrently, mechanical stress may be applied to the bonded assembly and in particular to the buried fragile plane 401, so as to propagate or help propagate mechanically the fracture leading to separation.

[0087] The free surface of the germ layer 40 is usually rough after separation.

[0088] A finishing substep a6) is preferably applied to the composite substrate 100, in order to restore the crystalline quality and surface condition of the seed layer 40, and to consolidate the bonding interface 30. The finishing may include thermal, mechanical and / or chemical treatments. It also aims to make the surface of the germ layer 40 compatible with a subsequent growth stage by epitaxy of the functional layer 50. As such, polishing and cleaning treatments in particular can be used.

[0089] In the second embodiment of the process (figures 6a to 6e'), the trench(s) can be made before or after substep a6).

[0090] As an example of the realization of a 100 mm composite substrate (without trenching), reference may be made to the publication by B. Ghyselen et al. “Large-Diameter III-V on Si Substrates by the Smart Cut Process: The 200 mm InP Film on Si Substrate Example”, physica status solidi (a) Volume 219, Issue 4.

[0091] Alternatively, the thin-film transfer technique may be based on mechanical and / or chemical bonding and thinning. Step a) may then include:

[0092] - the supply of a donor substrate 400 in single-crystal III-V material, exhibiting a front face and a rear face, and the provision of a support substrate 10,

[0093] - the formation of an intermediate layer 20, in an amorphous material, on a face before the substrate support 10,

[0094] - the molecular adhesion bonding of the front face of the donor substrate 400 onto the substrate support 10, to form a bonded assembly including a bonding interface 30 between the two substrates 400,10,

[0095] - thinning the rear face of the donor substrate 400 to form a layer germ 40 transferred onto the support substrate 10.

[0096] Thinning can be achieved by all known techniques, including grinding (rectification), mechanical or mechano-chemical polishing, and / or chemical etching.

[0097] Step b) of forming the -at least one- trench 60 in the peripheral perimeter 10c can be carried out before bonding or after thinning.

[0098] Returning to the general description, the process may then include a step c) corresponding to the epitaxial growth of a functional layer 50 on the seed layer 40 of the composite structure 160 ([Fig. 7]). The functional layer 50 is formed of a single-crystal III-V composite material identical to, or epitaxially compatible with, that of the seed layer 40. By epitaxially compatible, we mean having an identical crystalline structure and a lattice parameter sufficiently close to allow proper epitaxial growth according to the knowledge of those skilled in the art. This functional layer 50 may, depending on its composition and the components involved, comprise a stack of several epitaxially grown layers 51, 52.

[0099] Epitaxies of III-V compound materials, in particular epitaxies carried out on InP, GaAs or GaN-based substrates, are usually performed at temperatures between 500°C and 1000°C, for example, by metal-organic chemical vapor deposition (MOCVD). The gaseous precursors used can be, for example, InCl, PH3, or other chlorinated precursors known to those skilled in the art (such as Chlorine Tert-Butyl (TBC1) or (CH3)3CC1), AsH3, Trimethylindium (TMIn), Triethylgallium (TEGa). The epitaxial layers 51, 52 of the functional layer 50 can be formed from binary, ternary, quaternary, or even IILV compounds, comprising more than four elements, arranged in a functional stacking configuration for the fabrication of microelectronic components such as HBT and HEMT transistors, lasers, or photodiodes.

[0100] In step c), during the heating of the composite structure 160 in the epitaxial chamber, the bottom (made of crystalline material) and possibly the sides of each trench 60 will react with the gaseous precursors in the atmosphere within the epitaxial chamber and capture elements (from the gaseous precursors) destined to form the composite material IILV of the functional layer 50 to form a polycrystalline material inside the trench 60: a filled trench 61 thus appears. The continuation of polycrystalline growth at the peripheral edge 10c induces the formation of a polycrystalline layer 65 ([Fig. 7] (i) and (ii)).A polycrystalline layer 65 comprising a composite material, based on the elements composing the composite material IILV of the first epitaxial layer 51 (then of the second, and so on), is thus formed on the support substrate 10, at the level of the peripheral perimeter 10c, in parallel with the epitaxial growth of the functional layer 50. .

[0101] By allowing the incorporation of elements of the gaseous precursors at the level of the peripheral periphery 10c, the composite structure 160 strongly limits, or even avoids, the overgrowth of the functional layer 50 at the edge of the germ layer 40. It thus promotes a uniform and good quality epitaxial growth of the different epitaxial layers 51,52 of the functional layer 50 on the germ layer 40.

[0102] The manufacturing process may finally include a step d) of removing the polycrystalline layer 65, in particular by mechanical grinding or by wet or dry chemical etching of the peripheral rim 10c ([Fig. 8] (i)). An advantage of the fact that the trenches 60 can be arranged in the peripheral rim 10c with relative freedom is that the location of the polycrystalline layer 65 can be chosen, and said polycrystalline layer 65 potentially more easily removed.

[0103] Optionally, the polycrystalline material contained in the -at least one- filled trench 61 can also be removed, to find one (or more) empty trenches 60.

[0104] The resulting structure can then follow the classic steps required for the development of components in and / or on the functional layer 50.

[0105] Of course, the invention is not limited to the embodiments and examples described, and alternative embodiments can be made without departing from the scope of the invention.

Claims

Demands

1. Composite structure (160) comprising: - a seed layer (40) of single-crystal III-V composite material extending in a principal plane (x,y), - a support substrate (10) of crystalline material, on which the seed layer (40) is disposed via a bonding interface (30), the support substrate (10) comprising a peripheral rim (10c) devoid of a seed layer (40), the peripheral rim (10c) extending around an edge (40b) of the seed layer (40) in the principal plane (x,y), - an intermediate layer (20) of amorphous material, disposed between the seed layer (40) and the support substrate (10) and present on the peripheral rim (10c), - at least one trench (60) present in the peripheral rim (10c), extending, along an axis (z) normal to the principal plane (x,y), through the intermediate layer (20) down to the supporting substrate (10), or even into the supporting substrate (10),the trench (60) being located less than 100 micrometers from the edge (40b) in the principal plane (x,y).

2. Composite structure (160) according to the preceding claim, wherein the trench (60) is located less than 50 micrometers, or even less than 20 micrometers, from the edge (40b) of the seed layer (40).

3. Composite structure (160) according to any one of the preceding claims, wherein the material composed of the seed layer (40) is selected from indium phosphide, gallium arsenide, gallium nitride, and their ternary or quaternary compounds.

4. Composite structure (160) according to any one of the preceding claims, wherein the amorphous material of the intermediate layer (20) is selected from silicon oxide, silicon nitride, silicon oxynitride, aluminium nitride, alumina.

5. Composite structure (160) according to any one of the preceding claims, wherein the supporting substrate (10) is formed of a single-crystal or polycrystalline material selected from silicon, sapphire, gallium arsenide, germanium, aluminum nitride and silicon carbide.

6. Composite structure (160) according to any one of the preceding claims, wherein the trench (60) has a width, in the principal plane (x,y), of between 500nm and 1mm, preferably from a few micrometers to 20qm.

7. Composite structure (160) according to any one of the preceding claims, wherein the trench (60) extends, in the principal plane (x,y), all along the edge (40b) of the seed layer (40).

8. Composite structure (160) according to any one of the preceding claims, comprising a plurality of trenches (60) arranged in the peripheral perimeter (10c) of the supporting substrate 10.

9. Composite structure (160) according to the preceding claim, wherein the area occupied by said trenches (60) in the principal plane (x,y) corresponds to at least 20% of the area of ​​the peripheral perimeter (10c).

10. Method of manufacturing a composite structure (160) comprising the following steps: a) the transfer of a seed layer (40) in a single-crystal III-V composite material, onto a support substrate (10) in a crystalline material, via a bonding interface (30), an intermediate layer (20) in an amorphous material being interposed between the seed layer (40) and the support substrate (10) and being present on a peripheral perimeter (10c) of the support substrate (10) devoid of the seed layer (40), the peripheral perimeter (10c) extending around an edge (40b) of the seed layer (40) in a principal plane (x,y);b) the formation of at least one trench (60) in the peripheral perimeter (10c), the trench (60) extending, along an axis (z) normal to the main plane (x,y), through the intermediate layer (20) to the supporting substrate (10), or even into the supporting substrate (10), the trench (60) being located less than 100 micrometers from the edge (40b) in the main plane (x,y).;

11. A manufacturing method according to the preceding claim, wherein step a) comprises the following substeps: a) the provision of a donor substrate (400) of single-crystal III-V composite material and a support substrate (10) of a crystalline material, a2) the formation of a fragile plane buried (401) in the donor substrate (400), delimiting with a front face of said donor substrate, the seed layer (40) to be transferred, a3) the formation of an intermediate layer (20), in an amorphous material, on a front face of the support substrate (10), a4) the bonding by molecular adhesion of the front face of the donor substrate (400) on the intermediate layer (20) of the support substrate (10), a5) the separation along the fragile plane buried (401) to transfer the seed layer (40) onto the support substrate (10), on the one hand, and to obtain the remainder (400') of the donor substrate, on the other hand.

12. A manufacturing method according to the preceding claim, wherein step b) of forming the -at least one- trench (60) is carried out between substep a3) and substep a4).

13. A manufacturing method according to claim 11, wherein step b) of forming the -at least one- trench (60) is carried out after substep a5).

14. A manufacturing method according to one of the two preceding claims, comprising a step c) of epitaxial growth of at least one functional layer (50) on the seed layer (40) of the composite structure (160).

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