Composite structure including a monocrystalline iii-v compound material layer and associated manufacturing method

Abstract

The invention relates to a composite structure, comprising: - a support substrate, - a seed layer made of a monocrystalline III-V compound material arranged on the support substrate via a bonding interface, the III-V compound material being formed by at least one group III element, referred to as the first element, and by at least one group V element, referred to as the second element, - a useful layer at least partially covering a peripheral perimeter of the support substrate, the peripheral perimeter being without a seed layer, the useful layer being made of a material referred to as the third material, formed by at least one group III or group V element, having a melting point that is lower than a melting point of the III-V compound material of the seed layer. The invention also relates to a method for using and manufacturing a composite structure of this kind.

Description

Composite structure including a layer of single-crystal III-V composite material and associated manufacturing process FIELD OF 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 and 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] Document EP2945185A1 proposes a silicon substrate designed to receive a III-N material structure via epitaxial growth. For the fabrication of certain microelectronic or optoelectronic components, particularly HBT and HEMT transistors, lasers, and photodiodes, it is preferable to use composite substrates that provide a thin seed layer of single-crystal III-V composite material, deposited on a support substrate of a different material than the seed layer. This is done for economic reasons or to improve certain performance characteristics. As an example, consider an InP (indium phosphide) composite substrate on silicon, in which the single-crystal InP layer serves as a seed for the epitaxial growth of a functional stack of III-V layers, traditionally grown on a bulk InP substrate. The silicon substrate provides mechanical strength to the composite substrate and allows for optimized material costs.The III-V material seed layer of a composite substrate exhibits a crystalline quality far superior to the quality of a layer of the same nature formed by epitaxy on a silicon substrate.

[0003] Composite substrates can be manufactured in various ways, including by bonding a donor substrate to a support substrate and transferring the seed layer (from the donor substrate) to the support substrate via thinning, delamination, or separation steps along a buried brittle plane formed within the donor substrate, as is notably the case in the Smart Cut process. TM The assembled support and donor substrates having chamfers and a certain drop in edges at their periphery, the composite substrate generally presents a peripheral crown at the level of 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 in order to form 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 1c, which lacks a seed layer 4, is generally covered by a layer of silicon dioxide 2, thus preventing nucleation of the material in said ring 1c during epitaxial growth.

[0006] It is observed that material not deposited on the oxide layer 2 results in a higher growth rate in the region of the seed layer 4 near the crown 1c. Consequently, the thickness of the epitaxial layer 5 can increase by a factor of three to four at the edge (over a region typically less than or equal to 1 mm), and the composition of this edge layer can also be altered; these variations in thickness and composition are obviously not favorable to component manufacturing efficiency. This observation was reported, in particular, in document WO2018060570.

[0007] Another problem can arise with 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 composition of the edge layers. 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, as well as defects in subsequent component manufacturing steps. Furthermore, it causes contamination of the epitaxial growth matrix. SUBJECT OF THE INVENTION

[0008] The present invention proposes a composite structure comprising a support substrate on which a seed layer of a single-crystal III-V composite material is deposited, and comprising a useful layer deposited on the support substrate at the peripheral edge devoid of a seed layer. Such a composite structure reduces the overgrowth of the epitaxial layer at the edge of the seed layer during the epitaxial growth of the functional stack of layers. The invention also relates to a method for manufacturing the composite structure. BRIEF DESCRIPTION OF THE INVENTION

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

[0010] - a supporting substrate,

[0011] - a seed layer of single-crystal III-V composite material deposited on the substrate support via a bonding interface, the III-V composite material being formed of at least one element from group III, called the first element, and at least one element from group V, called the second element,

[0012] - a useful layer covering at least partially a peripheral perimeter of the support substrate, said peripheral perimeter being devoid of a seed layer, said useful layer being made of a material called third material, formed of at least one element of group III or group V, having a melting temperature lower than a melting temperature of the III-V compound material of the seed layer.

[0013] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: the third material is made of the first element; the material composed of the seed layer is chosen from indium phosphide, gallium arsenide, gallium nitride, and their ternary or quaternary compounds; the support substrate is formed of a single-crystal or polycrystalline material chosen from silicon, sapphire, gallium arsenide, germanium, aluminum nitride and silicon carbide; the support substrate is made of silicon, the seed layer is made of indium phosphide and the useful layer is made of indium; the useful layer has a thickness of between 10 nm and 1000 nm.

[0014] According to another aspect, the invention relates to a method of using the composite structure which has just been presented and comprising the following steps: the supply of the composite substrate; the growth by epitaxy, under epitaxial conditions, of at least one functional layer on the seed layer of the composite structure at a temperature between the decomposition temperature of the useful layer and the decomposition temperature of the seed layer.

[0015] The usage process may include a step c), subsequent to step b) of growth, of removing a polycrystalline layer formed at the level of the useful layer, by mechanical lapping or by chemical etching.

[0016] The invention also relates to a method for manufacturing a composite structure comprising the following steps:

[0017] a) the supply of a composite substrate including a support substrate and a seed layer in a single-crystal III-V composite material disposed on the support substrate via a bonding interface, the support substrate having a peripheral perimeter devoid of the seed layer;

[0018] b) the formation of a useful layer on all or part of the peripheral perimeter of the supporting substrate, the useful layer being made of a so-called third material, formed of at least one element of group III or group V, and having a melting temperature lower than a melting temperature of the III-V compound material of the seed layer.

[0019] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: step a) comprises the following substeps: a1) the provision of a donor substrate in monocrystalline III-V composite material, a2) the formation of a fragile plane buried in the donor substrate, delimiting with a front face of said donor substrate, the seed layer to be transferred, a3) the bonding by molecular adhesion of the front face of the donor substrate to the support substrate, a4) the separation along the buried fragile plane to transfer the seed layer to the support substrate and obtain the composite substrate, on the one hand, and the remainder of the donor substrate, on the other hand;The process includes a step c) of growing by epitaxy at least one functional layer on the seed layer of the composite structure, said functional layer being formed of a single-crystal III-V composite material identical to or epitaxially compatible with that of the seed layer; step c) includes exposing the composite structure to a growth temperature and to gaseous precursors which include elements composing the III-V composite material of the functional layer; step c) further induces the formation of a polycrystalline layer comprising a composite material, based on the third material of the useful layer and at least one element composing the III-V composite material of the functional layer; the process includes a step d) of removing the polycrystalline layer, by mechanical lapping or by chemical etching. BRIEF DESCRIPTION OF THE FIGURES

[0020] 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:

[0021] The diagram schematically illustrates the overgrowth of an epitaxial layer, in a state-of-the-art composite substrate, at the edge of the germ layer, namely in the vicinity of the peripheral crown which is devoid of a germ layer and includes a silicon oxide layer;

[0022]

[0023] Laet and la present a first embodiment of a composite substrate forming part of a composite structure according to the present invention;

[0024]

[0025] Laet and la present a second embodiment of a composite substrate forming part of a composite structure according to the present invention;

[0026] This presents a variant embodiment of a composite substrate forming part of a composite structure according to the present invention;

[0027] The present is composite structures conforming to the present invention;

[0028] Presents composite structures according to the present invention after epitaxial growth of functional layers on the germ layer;

[0029]

[0030]

[0031]

[0032] La, la, laet la represent manufacturing steps of a composite structure, according to the present invention;

[0033] This presents the steps of a manufacturing process according to the present invention;

[0034]

[0035] Laet and la present other steps of a manufacturing process according to the present invention.

[0036] The same references in the figures can be used for elements of the same type. Some figures are schematic representations which, for the sake of clarity, are not drawn to scale. In particular, the layer thicknesses 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 are not necessarily to scale in the figures. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention relates to a composite structure 160 comprising 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.

[0038] The substrate support 10 can be chosen in particular for its mechanical properties, low cost, and compatibility with microelectronic processes and equipment. It is typically made of a single-crystal or polycrystalline material selected from silicon, sapphire, gallium arsenide, germanium, aluminum nitride, and silicon carbide. Its thickness can vary from a few tens to several hundred micrometers, for example, from 300 μm to 1000 μm.

[0039] The single-crystal seed layer 40 is selected according to the application and the intended components. It serves as a seed crystal 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 III-V composite material. This composite material consists of at least one element from group III, referred to as the first material, and at least one element from group V, referred to as the second material. The composite material for the seed layer 40 can be selected from indium phosphide, gallium arsenide, gallium nitride, and their ternary or quaternary compounds. Its thickness typically varies from a few nanometers to a few hundred nanometers, for example, from 10 nm to 1000 nm.

[0040] The seed layer 40 and the support substrate 10 are bonded together via a bonding interface 30. 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. Consequently, the seed layer 40 exhibits a crystalline quality far superior to that of a similar layer that would have been deposited, particularly in terms of dislocation density. The assembly including the support substrate 10 and the seed layer 40 is called the composite substrate 100.

[0041] In the composite substrate 100, the peripheral perimeter 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 on the peripheral perimeter 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 other), having a diameter of 50mm, 100mm, 150mm, 200mm, 300mm, or even more, as is common in the field of microelectronics (,).The peripheral perimeter 10c can have a width (measured radially between the edge of the support substrate 10 and the edge of the seed layer 40) of between a few hundred micrometers and a few millimeters, for example, between 200 μm and 5mm, more usually between 1mm and 3mm.

[0042] 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 seed layers 40, but substantially isolated from one another. 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 part of the support substrate 10 devoid of a seed layer 40, and bordering said 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 or even up to 5 mm.

[0043] The composite substrate 100 may optionally include an intermediate layer 20, placed on the support substrate 10 before its assembly with the seed layer 40, and thus sandwiched between said substrate 10 and the seed layer 40. Alternatively, the intermediate layer 20 may be located on the side of the seed layer 40, in which case the bonding interface 30 is situated between the intermediate layer 20 and the support substrate 10. Yet another option is that the intermediate layer 20 may be formed by two layers respectively placed on the seed layer 40 and the support substrate 10 before assembly: in this case, the bonding interface 30 is located between these two layers. The intermediate layer 20 may, in particular, enhance the quality and strength of the bonding interface 30. Specifically, it may be composed of silicon dioxide, silicon nitride, or other materials.

[0044] Returning to the general description, the composite structure 160 comprises, in addition to the composite substrate 100, a layer, called the useful layer 60, which at least partially covers the peripheral perimeter 10c of the support substrate 10 ( ). As stated previously, the peripheral perimeter 10c is devoid of a seed layer 40. At said perimeter 10c, the useful layer 60 is therefore disposed on the bare support substrate 10 ( (i)), or on the intermediate layer 20 (if the latter is present, as illustrated in (ii)).

[0045] The useful shell 60 is formed from at least one element of Group III or Group V of the Mendeleev periodic table. The material composing the useful shell 60 is called the third material. The third material may, in particular, include or be composed of an element of Group III, or an element of Group V, or even a metallic alloy of an element of Group III or Group V. The Group III or Group V element included in the third material is capable of reacting with the gaseous precursors used during the epitaxy of the functional shell 50 onto the seed shell 40.

[0046] This third material has a melting point lower than that of the seed layer 40. This characteristic allows the useful layer 60 to segment into islands during the epitaxial growth step required to form the functional layer 50 on the seed layer 40 of the composite structure 160, as will be explained later in this description. Advantageously, the melting point of the useful layer 60 is at least 100°C, and in some cases at least 200°C, lower than the melting point of the seed layer 40. Each island (composed of the third material) can then react with the gaseous precursors in the atmosphere within the epitaxial chamber and capture elements (from the gaseous precursors) that make up the III-V composite material of the functional layer 50.As will be described in the manufacturing process, a polycrystalline layer 65 comprising a composite material, based on the third material of the useful layer 60 and at least one element composing the III-V composite material of the functional layer 50, is thus formed on the support substrate 10, at the level of the peripheral perimeter 10c, during the epitaxial growth of the functional layer 50.

[0047] 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.

[0048] Advantageously, the useful layer 60 has a thickness between 10nm and 1000nm. Its thickness can be substantially the same as, less than, or greater than the thickness of the seed layer 40.

[0049] According to a preferred variant, the third material of the useful layer 60 is formed from the first element included in the III-V composite material of the seed layer 40. The polycrystalline layer 65 formed at the peripheral boundary 10c then has a structure and a lattice parameter close and consistent with the functional layer 50 elaborated on the seed layer 40; this limits the stresses at the boundary of the functional layer 50.

[0050] As an example, the composite structure 160 may include: a silicon support substrate 10, a seed layer 40 in InP (having a melting temperature of about 1050°C), 100nm thick, and a useful layer 60 in indium, 30nm thick and having a melting temperature of about 157°C.

[0051] To fabricate a short-wavelength infrared (SWIR) photodiode with a PIN structure, it is known to create a stack of layers (the functional layer 50) as shown below, by epitaxy, following the order indicated (1 = first layer 51 deposited on the seed layer, 2 = second layer 52 deposited on the first layer, etc.): InP, doped with N, with a typical thickness of 300 to 500 nm; In 0,53 Ga 0,47 As, intrinsic, with a typical thickness of 2.5 to 3 µm; InP, P-doped, with a thickness of 0.5 to 1 µm; In 0,53 Ga 0,47 As, doped P, with a typical thickness of 30 to 100nm.

[0052] During epitaxial growth, which takes place at around 600°C, the indium in the useful layer 60 will react with the phosphorus, brought by the gaseous precursors, from their introduction into the chamber and the temperature rise of the composite structure 160, and then during the deposition of the 1 èrelayer 51 on the seed layer 40, and form InP grains, then with arsenic, brought by the gaseous precursors during the deposition of the 2 ème layer 52, to form InAs grains, etc. (). The incorporation of V elements into the polycrystalline layer 65 formed on the peripheral perimeter 10c of the support substrate 10 of the composite structure promotes a uniform and good quality epitaxial growth of the different epitaxial layers (1 to 4 in this example) of the functional layer 50 on the seed layer 40, i.e. without overgrowth and without modification of composition at the edge.

[0053] The invention also relates to a method for manufacturing the composite structure 160. The method comprises a step a) corresponding to the supply of a composite substrate 100 including a support substrate 10 and a seed layer 40 disposed on the support substrate 10 via a bonding interface 30 (,). The support substrate 10 has a peripheral edge 10c devoid of the seed layer 40.

[0054] The seed layer 40 is made of a single-crystal III-V composite material (group III elements: In, Ga, Al, ...; group V elements: As, P, Sb, ...). Its thickness is 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 supporting substrate 1 can have a thickness between 300 μm and 1000 μm.

[0055] The single-crystal III-V compound material of the seed layer 40 is advantageously a binary compound, in particular indium phosphide (InP), gallium arsenide (GaAs) or gallium nitride (GaN). It may nevertheless be chosen from among ternary or quaternary III-V compounds.

[0056] The support substrate 1 can be formed from a single-crystal or polycrystalline material selected from silicon, sapphire, gallium arsenide, germanium, aluminum nitride and silicon carbide.

[0057] The composite substrate 10 can for example be of type InP (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.

[0058] The composite substrate 10 is produced by a thin film transfer technique, involving an assembly between said layer (seed layer 40) and the support substrate 10 via a bonding interface 30.

[0059] Advantageously, and with reference to the Smart Cut process, step a) comprises the following sub-steps:

[0060] a1) the supply of a donor substrate 400 in monocrystalline III-V compound material, from which the seed layer 40 will be taken, and the supply of the support substrate 10 ();

[0061] 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 seed layer 40 to be transferred ();

[0062] a3) the bonding by molecular adhesion (i.e. any direct bonding, not involving adhesive material) of the front face of the donor substrate 400 on the support substrate 10, to form a bonded assembly 410 including a bonding interface 30 between the two substrates 400,10 ();

[0063] a4) the separation along the buried fragile plane 401 to transfer the seed layer 40 onto the support substrate 10 and obtain the composite substrate 100, on the one hand, and the remainder of the donor substrate 400', on the other hand ().

[0064] In step a1), 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 material availability. As mentioned previously with reference to the first embodiment of a composite substrate 100, the presence of chamfers and edge drops around the periphery of the assembled substrates 400, 10 (not shown in Figures 7) means that the bonding (step a3) is not effective all the way to the edges and that, consequently, the seed layer 40 is not transferred (step a4) to the peripheral edge 10c of the support substrate 10, in the composite substrate 100 (first embodiment).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 200μm and 5mm, more usually between 1mm and 3mm.

[0065] The second embodiment of a composite substrate 100 differs from the first in that the transferred seed layer 40 is not unique: at step a1), several donor substrates 400, for example in the form of vignettes, can be assembled on the support substrate 10 (portion of a support 10'), and give rise to the transfer of a plurality of seed layers 40, separated by a peripheral perimeter 10c bare of the support substrate 10, as illustrated in figures 3a and 3b.

[0066] Substep a2) can in particular be carried out by ion implantation of light species such as hydrogen and / or helium, as is known in reference to the Smart Cut process.

[0067] The front face of the donor substrate 400 and / or the front face (assembled) of the support substrate 10 may include an intermediate layer, insulating, conductive, or semiconducting, capable of facilitating bonding, improving the quality and strength of the interface, or providing interesting insulating or conductive properties for the future components to be developed. Cleaning and surface treatments (polishing, plasma, etc.) are usually applied to the substrates before assembly.

[0068] As a reminder, direct molecular adhesion bonding (substep a3) does not require an adhesive, as bonds are established at the atomic level between the surfaces being joined. Several types of molecular adhesion bonding exist, differing in particular by their temperature, pressure, atmospheric conditions, and pretreatments required before the surfaces are brought into contact. 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), and others.

[0069] Substep a4) of separation along the buried fragile plane is usually achieved by applying heat treatment at a temperature between 100°C and 900°C, depending on the materials involved. Such heat treatment induces the development of cavities and microcracks in the buried fragile plane 401, and their pressurization by the light gaseous species present, until a fracture propagates along said fragile plane. Alternatively or concurrently, mechanical stress can be applied to the bonded assembly, and in particular to the buried fragile plane 401, so as to propagate or mechanically assist the propagation of the fracture leading to separation.

[0070] The free surface of the germ layer 40 is usually rough after separation.

[0071] A finishing substep (a5) is preferably applied to the composite substrate 100 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 seed layer 40 compatible with a subsequent growth step by epitaxial growth of the functional layer 50. For this purpose, polishing and cleaning treatments, in particular, may be used.

[0072] As an example of implementation, one can refer 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.

[0073] Alternatively, the thin-film transfer technique can be based on bonding and mechanical and / or chemical thinning. Step a) may then include:

[0074] - the supply of a donor substrate 400 in single-crystal III-V material, having a front face and a back face,

[0075] - the molecular adhesion of the front face of the donor substrate 400 onto the support substrate 10, to form a bonded assembly including a bonding interface 30 between the two substrates 400,10,

[0076] - thinning of the back face of the donor substrate 400 to form a seed layer 40 and finally obtain the composite substrate 100.

[0077] Thinning can be achieved by all known techniques, including grinding (rectification), mechanical or mechano-chemical polishing, and / or chemical etching.

[0078] The process then includes a step b) corresponding to the formation of a layer, called the useful layer 60, on all or part of the peripheral perimeter 10c of the support substrate 10. The useful layer 60 is made of a material (called the third material) formed of at least one element of group III or group V.

[0079] An example of implementing this step b) is illustrated in Figure 1. A mask 70 (for example, made of silicon oxide or silicon nitride) can be deposited only on the seed layer 40, leaving the peripheral edge 10c of the support substrate free in the composite substrate 100 ((i)). The working layer 60 is then deposited over the entire front face of the composite substrate 100, namely on the mask 70 and on the support substrate 10 at its peripheral edge 10c ((ii)). Finally, the mask 70 is removed (for example, by chemical etching), which also allows the removal of the portion of the working layer 60 deposited on the seed layer 40 ((iii)): thus, the composite structure 160 according to the present invention is obtained.

[0080] The third material of the useful layer 60 must have a melting temperature lower than the epitaxial growth temperature of the III-V composite material of the seed layer 40.

[0081] As an example, the useful layer 60 can be composed of indium, gallium, aluminum, whose melting temperatures are respectively 157°C, 29°C, 660°C.

[0082] The third material can also be a metallic alloy based on one of these elements.

[0083] The useful layer (60) preferentially has a thickness between 10nm and 1000nm.

[0084] The process may then include a step c) corresponding to the epitaxial growth of a functional layer 50 on the seed layer 40. The functional layer 50 is formed of a single-crystal III-V compound material identical to, or epitaxially compatible with, that of the seed layer 40. Epitaxially compatible means 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 intended components, comprise a stack of several epitaxially grown layers 51, 52.

[0085] Epitaxies of III-V compound materials, particularly those performed on InP or GaAs-based substrates, are usually carried out at temperatures between 500°C and 700°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 (TBCl) or (CH3)3CCl), AsH3, Trimethylindium (TMIn), Triethylgallium (TEGa). The epitaxial layers 51,52 of the functional layer 50 can be formed of binary, ternary, quaternary III-V compounds, or even comprising more than four elements, arranged according to a functional stacking for the development of microelectronic components such as HBT and HEMT transistors, lasers or photodiodes.

[0086] Under the specific conditions of the epitaxial formation of III-V composite materials in the functional layer 50 (pressure, nature and flow rates of precursor gases, etc.), the active layer and the seed layer are susceptible to decomposition when the composite structure 160 is heated to a temperature exceeding a so-called "decomposition temperature" for these layers. These decomposition temperatures are related to, but lower than, the melting temperatures of these layers. The epitaxial temperature (typically 500°C to 700°C, as previously explained) of the functional layer 50 is, of course, such that it does not lead to its decomposition. This temperature is also lower than the decomposition temperature of the seed layer.

[0087] The epitaxial temperature, according to the invention, is advantageously chosen to be higher than the decomposition temperature of the functional layer under the chosen epitaxial conditions. In some cases, the epitaxial temperature of the functional layer can be chosen to be higher than the melting temperature of the functional layer (while remaining lower than the decomposition temperature of the seed layer), but this condition is not mandatory, as the simple decomposition of the functional layer may be sufficient to produce the desired effect.

[0088] Thus, in step c), during the heating of the composite structure 160 in the epitaxial chamber, the useful layer 60 will segment into islands due to its decomposition temperature being lower than its epitaxial temperature. Each island, composed of the third material, will then react with the gaseous precursors in the atmosphere of the epitaxial chamber and capture elements (from the gaseous precursors) destined to form the III-V composite material of the functional layer 50. A polycrystalline layer 65 comprising a composite material, based on the third material of the useful layer 60 and at least one element composing the III-V composite material 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.

[0089] As an example, for a useful In layer 60, the following reactions can occur depending on the temperature:

[0090] - during the temperature rise, with the precursor PH3: 2In(I) + 2 PH3 (g) --> 2InP(s) + 3H2(g);

[0091] - once the growth temperature is reached, with the InCl precursor:

[0092] InCl(g) + PH3 (g) --> InP (s)+ HCl (g) + H2-.

[0093] 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.

[0094] Advantageously, the third material of the useful layer 60 is based on an element composing the seed layer 40, so that the polycrystalline layer 65 formed at the peripheral perimeter 10c has a structure and a lattice parameter close and / or consistent with the epitaxial layers 51,52 of the functional layer 50 elaborated on the seed layer 40; this limits the stresses at the boundary of the functional layer 50 and consequently the potential defects induced in said layer 50.

[0095] 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 perimeter 10c, generally involving prior protection of the surface of the functional layer 50. The resulting structure can then undergo the conventional steps required for the fabrication of components in and / or on the functional layer 50.

[0096] 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

Composite structure (160) comprising: - a support substrate (10), - a seed layer (40) of monocrystalline III-V composite material disposed on the support substrate (10) via a bonding interface (30), the III-V composite material being formed of at least one element of group III, called first element, and at least one element of group V, called second element, - a useful layer (60) covering at least partially a peripheral perimeter (10c) of the support substrate (10), said peripheral perimeter (10c) being devoid of seed layer (40), said useful layer (60) being of a material called third material, formed of at least one element of group III or of group V, having a melting temperature lower than a melting temperature of the III-V composite material of the seed layer (40). Composite structure (160) according to the preceding claim, wherein the third material is made up of the first element. 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. Composite structure (160) according to any one of the preceding claims, wherein the support substrate (10) is formed of a single-crystal or polycrystalline material selected from silicon, sapphire, gallium arsenide, germanium, aluminum nitride and silicon carbide. Composite structure (160) according to claim 1, wherein the support substrate (10) is made of silicon, the seed layer (40) is made of indium phosphide and the useful layer (60) is made of indium. Composite structure (160) according to any one of the preceding claims, wherein the useful layer (60) has a thickness between 10 nm and 1000 nm. Method of using a composite structure (160) comprising the following steps: supplying a composite substrate (100) according to one of the preceding claims; growing by epitaxy, under epitaxial conditions, at least one functional layer (50) on the seed layer (40) of the composite structure (160) at a temperature between the decomposition temperature of the useful layer (60) and the decomposition temperature of the seed layer (40). Method of use according to the preceding claim, comprising a step c), subsequent to the growth step b), of removal of a polycrystalline layer (65) formed at the level of the useful layer (60), by mechanical grinding or by chemical etching. A method for manufacturing a composite structure (160) comprising the following steps: a) supplying a composite substrate (100) including a support substrate (10) and a seed layer (40) of a single-crystal III-V composite material disposed on the support substrate (10) via a bonding interface (30), the support substrate (10) having a peripheral perimeter (10c) devoid of the seed layer (40); b) forming a useful layer (60) on all or part of the peripheral perimeter (10c) of the support substrate (10), the useful layer (60) being of a so-called third material, formed of at least one element of group III or group V, and having a melting temperature lower than a melting temperature of the III-V composite material of the seed layer (40). A manufacturing process according to the preceding claim, wherein step a) comprises the following substeps: a1) supplying a donor substrate (400) of single-crystal III-V composite material, a2) forming a buried brittle plane (401) in the donor substrate (400), delimiting with a front face of said donor substrate, the seed layer (40) to be transferred, a3) bonding by molecular adhesion of the front face of the donor substrate (400) to the support substrate (10), a4) separating along the buried brittle plane (401) to transfer the seed layer (40) to the support substrate (10) and obtain the composite substrate (100), on the one hand, and the remainder (400') of the donor substrate, on the other hand. A manufacturing method according to one of the two preceding claims, comprising a step c) of growing by epitaxy at least one functional layer (50) on the seed layer (40) of the composite structure (160), said functional layer (50) being formed of a single-crystal III-V composite material identical to or epitaxially compatible with that of the seed layer (40), in which: - step c) includes exposing the composite structure (160) to a growth temperature and to gaseous precursors which include elements composing the III-V composite material of the functional layer (50), - step c) further induces the formation of a polycrystalline layer (65) comprising a composite material, based on the third material of the useful layer (60) and at least one element composing the III-V composite material of the functional layer (50). Manufacturing process according to the preceding claim, comprising a step d) of removing the polycrystalline layer (65), by mechanical lapping or by chemical etching.

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