Method of manufacturing an optoelectronic device comprising an intermetallic compound

Abstract

The method of the invention comprises epitaxy of a layer of interest in GeSn on a growth layer comprising GeSn with a tin concentration lower than that of the layer of interest; formation of an active region in the layer of interest, with a surface area lower than a first maximum surface area; removal of a portion of the growth layer so that the interface between the growth and interest layers opposite the active region is lower than a second maximum surface area or zero; formation of a metal portion comprising Ti or NiPt on a portion of the layer of interest; heating in a furnace at a temperature strictly higher than the epitaxy temperature, to produce an intermetallic compound from the metal portion; the first and second maximum surfaces being such that the tin in the active region does not segregate. Figure for abstract: Figure 2F

Description

Title of the invention: Method for manufacturing an optoelectronic device comprising an intermetallic compound Technical field

[0001] The field of the invention is that of producing a microelectronic or optoelectronic device based on an alloy of germanium and tin comprising an ohmic contact, in particular in the form of an intermetallic compound of NiPt and GeSn, or an intermetallic compound of Ti and GeSn. STATE OF THE PRIOR ART

[0002] Materials based on an alloy of germanium and tin (GeSn) can be used in light sources or photodetectors operating in the mid-infrared wavelength range (MWIR), for example at wavelengths greater than 1.6 pm. Several of these devices are generally manufactured in parallel on a plate on which rests at least one GeSn-based layer. They find applications in particular in the field of optical connections between chips or microprocessors, optical sensors of chemical species, or imagers.

[0003] Light sources and photodetectors based on a germanium and tin (GeSn) alloy comprise at least one GeSn-based active region in which photons are respectively emitted or absorbed. It is generally electrically connected to a reading or control or power supply circuit comprising metal lines and / or vias. It is therefore necessary to make an electrical connection between the GeSn-based material and the circuit. Very often, the electrical connection comprises an ohmic contact, in physical contact with the GeSn-based material. By definition, an electrical contact is said to be ohmic if a variation in the electric current flowing through it is proportional to a variation in a potential difference applied to its terminals.

[0004] One way to achieve a low-resistance ohmic contact is to form an intermetallic compound of GeSn. The intermetallic compound has other advantages, including good contact adhesion, low resistivity, good predictability of the ohmic contact resistance, and compatibility with CMOS processes.

[0005] An intermetallic compound of GeSn is typically obtained by heating a metal resting on the GeSn-based material to a temperature sufficient to allow a solid-state reaction leading to the formation of the compound, as well as a diffusion and / or inter-diffusion and / or nucleation process involving atoms of the metal. However, as soon as the concentration of tin is greater than 1% in germanium, it tends to segregate during heating, rendering the light source or photodetector inoperative. Tin segregation occurs particularly when the temperature exceeds the epitaxial temperature of the GeSn-based material. Segregation means that tin atoms leave the crystal lattice of the GeSn-based material to form a pure tin phase. A state of tin segregation can be visualized by X-ray diffraction.

[0006] Document EP 3 945 545 A1 proposes a solution for producing a Ni(GeSn) ohmic contact, limiting, or even eliminating, a tin segregation phenomenon at the ohmic contact. A layer of nickel (Ni) is deposited on a layer of germanium-tin alloy (GeSn). A layer of titanium nitride (TiN) is then deposited on the nickel layer. The TiN layer is illuminated by a pulsed laser beam. Most of the beam energy is absorbed by the TIN layer and the heat diffuses towards the Ni and GeSn layers, until it exceeds the melting temperature of the GeSn alloy. The laser emits 160 ns pulses at a wavelength of 308 nm, in an energy range between 0.4 J / cm2 and 0.7 J / cm2.

[0007] A laser such as that used in document EP 3 945 545 A1 typically has a beam cross-section equal to 1 cm2 and generally scans the plate. There is therefore a risk that the laser will heat the active region to a temperature higher than a temperature resulting in a tin segregation phenomenon. In addition, furnaces are generally preferred heating means in the semiconductor industry because they are versatile and allow manufacturing costs to be reduced. Among these, rapid thermal heating tools (or Rapid Thermal Annealing, RTA, in English), for example using a lamp, offer many advantages.

[0008] There is therefore a need for a method for producing an ohmic contact from an intermetallic compound which does not risk damaging the active zone of GeSn-based devices. It would also be advantageous if the method could be implemented in a rapid thermal heating tool. Statement of the invention

[0009] The invention aims to remedy at least in part the drawbacks of the prior art, and more particularly to propose a method for manufacturing an optoelectronic device comprising an active region based on an alloy of germanium and tin, and an intermetallic compound of low resistivity, without segregating the tin from the active region.

[0010] For this, the object of the invention is a method of manufacturing an optoelectronic device, comprising, successively, a step of epitaxy of a layer of interest based on a germanium and tin alloy on a growth layer comprising germanium, at an epitaxy temperature Te, such that a minimum tin concentration of the layer of interest is strictly greater than a maximum tin concentration of the growth layer, a step of forming an active region in the layer of interest, of surface area in a plane parallel to a principal plane of the layer of interest less than a first maximum surface, a step of removing at least part of the growth layer so that a surface area of ​​the growth layer in contact with the layer of interest and facing the active region is less than a second maximum surface area or zero, a metallization step to obtain a metallic portion comprising a metal chosen from titanium or an alloy of platinum and nickel, resting on a part of the layer of interest,a heating step in a furnace at a temperature Ti strictly higher than the epitaxy temperature Te, to produce an intermetallic compound from the metallic portion, comprising germanium, tin and the metal. The first maximum surface and the second maximum surface are such that the tin in the active region does not segregate during the heating step.

[0011] Some preferred but non-limiting aspects of this manufacturing method are as follows.

[0012] The removal step may release compressive mechanical stress in the active region.

[0013] A tin concentration in the active region may be greater than 13%, and a residual compression of the active region at the end of the removal step may be greater than or equal to -0.35%.

[0014] The removal step may comprise a transfer of the layer of interest onto an acceptor substrate, followed by a total removal of the growth layer.

[0015] The transfer can be carried out by bringing into contact a first bonding layer comprising a metal resting on the layer of interest, chosen from titanium or a nickel and platinum alloy, with a second bonding layer made of metal resting on the acceptor substrate.

[0016] The removal step may comprise an anisotropic etching of a through opening of the layer of interest, followed by an isotropic etching of the growth layer through the through opening, selective with respect to the layer of interest.

[0017] At the end of the isotropic etching, the growth layer and the layer of interest can define an interface not having a part facing the active region.

[0018] The anisotropic etching may define a peripheral portion of the layer of interest comprising the interface, and a structured portion of the layer of interest comprising a central portion comprising the active region, connected to the peripheral portion by at least two tension arms opposite each other with respect to the central portion, and the isotropic etching can induce a tensile stress of the central portion by the tension arms.

[0019] The surface extent of the active region can be delimited by an etching flank.

[0020] The etching flank may comprise a (110) or (HO) crystal plane of the layer of interest.

[0021] The metal may be titanium and the temperature T; of the heating step may be higher than a temperature at which a Ti6(GeSn)5 phase forms.

[0022] The metal may be an alloy of platinum and nickel and the temperature T; of the heating step may be higher than a temperature at which a NiPt(GeSn) phase forms.

[0023] The manufacturing method may comprise a preliminary procedure for determining the second maximum surface area comprising the following steps: epitaxy of a first GeSn-based layer of the same nature as the layer of interest, on a second layer of the same nature as the growth layer, removal of a portion of the second layer to produce a set of test structures each comprising an interface between the first and second layers, the interfaces having different surfaces, implementation of the heating step, identification of a subset of the set of test structures for which the tin in the test structure has segregated, definition of the second maximum surface area at a value strictly lower than all the surfaces of the interfaces of the test structures of the subset.

[0024] The first maximum surface area and the second maximum surface area may further be such that tin in the active region does not segregate upon healing annealing of the active region to remove dislocations from the active region.

[0025] The healing annealing and the heating step may be one and the same step. Brief description of the drawings

[0026] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0027] Figures 1A and 1B are schematic sectional views of process steps common to a first, a second and a fourth manufacturing process according to the invention;

[0028] Figures 2A to 2F are schematic sectional views of steps of a first manufacturing method according to the invention;

[0029] Figures 3A to 3C are schematic sectional views of steps of a second manufacturing method according to the invention;

[0030] Figures 4A to 4E are schematic sectional views of steps of a third manufacturing method according to the invention;

[0031] Figures 5A to 5C are schematic views of steps of a fourth manufacturing method according to the invention;

[0032] Figures 6A to 6C are schematic sectional views of steps of a procedure for obtaining a first threshold and a second surface threshold for tin segregation in a layer based on a germanium and tin alloy.

[0033] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0034] In the figures and in the remainder of the description, the same references represent identical or similar elements. In addition, the different elements are not shown to scale so as to favor the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and can be combined with each other. Unless otherwise indicated, the terms "substantially", "approximately", "of the order of" mean to within 10%, and preferably to within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are included, unless otherwise indicated.

[0035] The invention relates to a method for manufacturing an optoelectronic device. The latter comprises an active region made in a crystalline layer of interest based on an alloy of germanium and tin. The layer of interest is obtained by epitaxy on a crystalline growth layer based on germanium, optionally comprising a quantity of tin strictly less than a quantity of tin in the layer of interest. The active region extends along a surface area in a plane parallel to a principal plane of the layer of interest. A metallic portion made of a metal is deposited on the layer of interest. The assembly is heated in a furnace, which may be a rapid heating tool, to produce an intermetallic compound comprising GeSn and the metal.The heating temperature to form the intermetallic compound in a low-resistance phase is strictly higher than the epitaxy temperature, at the risk of segregating the tin contained in the active region. The growth layer is removed before heating, at least in part, in an area facing the active region and in contact with the layer of interest. If the growth layer is not removed entirely in the area, the layer of interest rests on a support surface of the growth layer facing the active region.

[0036] However, the inventors have found that there is a first threshold relating to the surface area of ​​the active region, independently of its geometric shape, beyond which, i.e. when the surface area of ​​the active region is greater than the first threshold, the tin segregates in the active region during heating to form the intermetallic compound. The inventors have also found that, if the layer of growth is not removed entirely in the area, there is a second threshold relating to the bearing surface, regardless of its geometric shape, beyond which tin segregates into the active region upon heating to form the intermetallic compound.

[0037] The method of the invention aims to produce a particular intermetallic compound by heating in a furnace an intermediate structure comprising the active region, the latter having a surface area and an arrangement preventing the segregation of tin during the production of the intermetallic compound. That is to say that the surface area of ​​the active region is below the first threshold, and the support surface is below the second threshold or non-existent, this in order to obtain the intermetallic compound from a metallic portion specifically comprising titanium or an alloy of nickel and platinum. Thus, the integrity of the active region is preserved, and the intermetallic compound is not very resistive.

[0038] The optoelectronic device may, for example, be a laser, a light-emitting diode, or a photodiode. It may be part of a larger assembly, such as an integrated photonic circuit. The intermetallic compound is, for example, part of an ohmic contact electrically connecting the active region to an electrical circuit.

[0039] By layer, we mean here and for the remainder of the description, an area consisting of one or more sub-layers of a material whose thickness along a Z axis is less, for example ten times, or even twenty times, than its longitudinal dimensions of width and length in a plane (X, Y) perpendicular to the Z axis. A layer can be structured.

[0040] Throughout the description, a layer or material is said to be “based” on a semiconductor when the layer or material comprises mainly the semiconductor, and possibly one or more additional chemical elements, such as for example doping atoms. Unless otherwise stated, the semiconductor is in a crystalline form. When the layer comprises several sub-layers, each sub-layer comprises mainly the semiconductor. The layer may for example comprise sub-layers each comprising mainly the semiconductor with different quantities of additional chemical element, and / or different additional chemical elements. Thus, a layer based on an alloy of germanium and tin may comprise an intrinsic germanium-tin sub-layer, intercalated between an n-doped germanium-tin sub-layer and a p-doped germanium-tin sub-layer.Similarly, a germanium-based layer may comprise a stack of sub-layers each comprising a majority of germanium and a concentration of tin atoms, the tin concentration of each sub-layer being, for example, increasing according to an ordering of the sub-layers along an axis perpendicular to a principal plane of the layer. Such a layer may serve as a . buffer layer for adapting a lattice parameter of a substrate to a lattice parameter of an epitaxial layer on the buffer layer.

[0041] By material or layer predominantly comprising a compound is meant a material or layer of which at least 50% of its volume is formed or comprises the compound. For example, a layer predominantly comprising an alloy of germanium (Ge) and tin (Sn) may be a layer of a material of empirical formula Si xGeySnz with x < (y + z) / 2.

[0042] A concentration of a chemical element in a material or layer is equal to the ratio of the number of atoms of that chemical element to the total number of atoms in the material or layer. Thus a layer of a germanium and tin alloy has a tin concentration of 13%, if the layer consists of 13% tin atoms and 87% germanium atoms.

[0043] Throughout the description, when a surface or surface area is compared to a value, it is intended to compare the surface or surface area to the value. Similarly, when one surface or surface area is compared to another surface or surface area, it is intended to compare the areas of the surfaces or surface areas.

[0044] An active region of an optoelectronic device is a part of the device intended to emit or detect light radiation of interest.

[0045] An example of a preliminary procedure for determining the first and second thresholds will now be described in connection with FIGS. 6A to 6C. The first and second thresholds are to be determined with regard to a concentration of tin in a first layer 620 based on an alloy of germanium and tin, and a thermal budget applied to the first layer 620 at least sufficient to create an intermetallic compound from a metallic portion resting on the first layer 620. The intermetallic compound is however not necessarily created during the procedure.

[0046] In [Fig.6A], a second layer 610 based on germanium is grown by epitaxy on a substrate 600, here made of silicon. A first layer 620 based on an alloy of germanium and tin is then grown by epitaxy at an epitaxy temperature Te, on the second layer 610. If the second layer 610 comprises tin, a minimum concentration of tin of the first layer 620 is strictly greater than a maximum concentration of tin of the second layer 610.

[0047] In [Fig.6B], the first layer 620 is etched by anisotropic etching over its entire height to produce trenches 640.1 exposing the second layer 610. The trenches 640.1 delimit bases 640 in the first layer 620. The trenches may extend into the second layer 610, as shown in [Fig.6B]. Each base 640 has a surface area in a plane main plane of the first layer 620, delimited by the trenches, in all directions of the main plane. The bases 640 have surface areas of different surfaces, and can advantageously be homothetic to each other. The surface areas can for example be discs, rectangles or squares.

[0048] In [Fig.6C], the second layer 610 is etched isotropically through the trenches 640.1, selectively with respect to the first layer 620 and, advantageously selectively with respect to the substrate 600. A residual portion of the second layer 610 at the end of the isotropic etching constitutes pedestals 645 on which the bases 640 rest, each on a bearing surface 645.1 of the second layer 610. Each bearing surface 645.1 is a growth interface of the first layer 620 on the second layer 610. A pedestal 645 associated with a base 640 constitutes a test structure 650. The test structures 650 therefore have, on the one hand, different base surface areas, and on the other hand, also different bearing surfaces.

[0049] The steps of FIGS. 6A to 6C can be reproduced on successive substrates 600, by changing a parameter of the isotropic etching, such as for example an etching time, or a concentration of an etching solution, to obtain a set of test structures 650 having surface areas and support surfaces that are different and independent of each other.

[0050] All of the test structures 650 are then heated to a temperature T; strictly higher than the epitaxy temperature Te. This heating step is for example representative of a heating step for the production of an intermetallic compound, a healing annealing of an active region, or another step requiring a thermal budget, such as the production of a stack of interconnections, or the activation of dopant atoms, or a combination of these steps. Note that some of these steps may include common sub-steps.

[0051] The set of test structures 650 is then inspected with an optical microscope. The test structures 650 for which the tin of the base 640 has segregated are identified, and those for which the tin of the base has not segregated. It is then established that there is no segregation of the tin for the bases whose surface area is less than a first upper maximum surface and whose bearing surface 645.1 is less than a second maximum surface. The first maximum surface is strictly less than all the surface areas of the bases whose tin has segregated. The second maximum surface is strictly less than all the bearing surfaces of the bases whose tin has segregated.

[0052] A first method of manufacturing an optoelectronic device will be described in link with figures 1A, 1B, 2A to 2F. The optoelectronic device 1 can here be a light-emitting diode or a photodiode.

[0053] In [Fig. 1 A], a germanium-based buffer layer 110 is grown by epitaxy on a substrate 100, here made of silicon with a crystallographic orientation (100). The substrate 100 has a planar upper face substantially parallel and opposite to a lower face, also planar. The substrate 100 extends in a main plane.

[0054] Here and for the remainder of the description, a direct three-dimensional orthogonal reference frame (X, Y, Z) is defined, where the X and Y axes form a plane parallel to the main plane of the substrate 100, and where the Z axis is oriented from the substrate 100 towards the buffer layer 110, in a direction substantially orthogonal to the main plane of the substrate 100. In the remainder of the description, the terms “vertical” and “vertically” are understood as relating to an orientation substantially parallel to the Z axis, and the terms “horizontal” and “horizontally” as relating to an orientation substantially parallel to the (X, Y) plane. Furthermore, the terms “lower” and “upper” are understood as relating to an increasing positioning when moving away from the substrate 100, in the +Z direction.

[0055] The buffer layer 110 here comprises several sub-layers. In the order of appearance in the direction of the +Z axis, it may comprise a lower germanium sub-layer, a first germanium-tin sub-layer and a second germanium-tin sub-layer having an average tin concentration strictly greater than an average tin concentration of the first sub-layer. The thickness of the germanium sub-layer is here greater than the critical thickness, for example equal to 2.5 μm. A mechanical stress of the germanium sub-layer is then plastically released. The thickness of the first sub-layer is between 50 nm and 500 nm, with a tin concentration of between 5 and 8. The thickness of the second sub-layer is between 50 nm and 500 nm, with a tin concentration of between 8 and 12.

[0056] Alternatively, the buffer layer 110 may consist of the single lower germanium sub-layer or comprise any number of germanium-tin sub-layers, the tin concentration of each sub-layer then increasing in the order of appearance of the sub-layers in the direction of the +Z axis. It is also possible that the buffer layer 110 is a single layer comprising germanium and a gradually increasing tin concentration in the direction of the +Z axis.

[0057] A crystalline germanium-tin layer of interest 120 is then epitaxially grown on the buffer layer 110 at an epitaxy temperature Te. The buffer layer 110 is a so-called growth layer, because it is suitable for growing the crystalline layer of interest 120. The thickness of the layer of interest 120 may be strictly less than a critical thickness beyond which plastic deformation takes place. It has a concentration of tin atoms greater than 1% relative to the number of germanium atoms. The minimum concentration of tin atoms in the layer of interest 120 relative to the number of germanium atoms is in particular strictly greater than a maximum concentration of the buffer layer 110 relative to the number of germanium atoms. Thus, the layer of interest 120 is stressed in compression.

[0058] Throughout the description, if the optoelectronic device 1 is a photodiode, the minimum concentration of the layer of interest 120 may be between 2% and 20%. If the optoelectronic device 1 is a light-emitting diode or a laser, the minimum concentration of the layer of interest 120 may be between 6% and 20%.

[0059] Here and throughout the description, a minimum (respectively maximum) concentration of a compound in a layer is equal to the minimum (respectively maximum) reached by the average concentration of the compound in each plane parallel to the (X, Y) plane of the layer, along the Z axis.

[0060] An epitaxial growth method suitable for growing the buffer layer 110 is described in the document J. Aubin et al., “Growth and structural properties of step-graded, high Sn content GeSn layers on Ge”, Semiconductor Science and Technology 32, 094006 (2017).

[0061] The layer of interest 120 here consists of 3 sub-layers: an intrinsic or weakly doped active sub-layer 122 intercalated between a lower sub-layer 121 doped in-situ with a first conductivity type and an upper sub-layer 123 doped in-situ with a second conductivity type opposite to the first conductivity type. The first conductivity type is here n-type. An epitaxial growth method suitable for growing the layer of interest 120, with its in-situ doped sub-layers, is described in the document M. Frauenrath et al. “Advances in In Situ Boron and Phosphorous Doping of SiGeSn”, ECS J. Solid State Sci. Technol. 2023, 12 064001. The epitaxy temperature Te is typically between 301°C and 349°C. Epitaxy can, for example, be achieved by remote plasma-assisted chemical vapor deposition (RPCVD).It decreases with the tin concentration in the epitaxial layer.

[0062] In [Fig.lB], a first bonding layer 124.1 is deposited on the layer of interest 120 and a second bonding layer 124.2 is deposited on an acceptor substrate 150. On faces opposite, respectively, the layer of interest 120 and the acceptor substrate 150, the first and second bonding layers 124.1, 124.2 may both comprise a dielectric, preferably amorphous, such as for example silicon oxide (SiO) or silicon nitride (SiN), or, alternatively, both, a metal, for example chosen from titanium (Ti), copper (Cu), chromium (Cr), gold (Au) or an alloy of these metals. Thus, the first bonding layer 124.1 can be bonded to the second bonding layer 124.2 by a direct bonding technique.

[0063] Furthermore, advantageously, the first bonding layer 124.1 comprises titanium (Ti) or a nickel and platinum alloy (NiPt) or a bilayer of platinum (Pt) and nickel (Ni) in contact with the layer of interest 120, in the latter case, the platinum is preferentially in contact with the layer of interest 120. When the first bonding layer 124.1 comprises an alloy of platinum and titanium, the concentration of platinum atoms is typically between 5% and 15%, preferentially equal to 10%, relative to the number of nickel atoms. If the acceptor substrate 150 is made of silicon, the second bonding layer 124.2 may comprise a native, deposited or thermal silicon oxide, in contact with the acceptor substrate 150.

[0064] In this example, the first bonding layer 124.1 consists of 3 sub-layers, with in the order of appearance from the layer of interest 120, a 10 nm thick sub-layer of titanium (Ti), a 10 nm thick sub-layer of titanium nitride (TiN) and a Gold (Au) sub-layer of thickness greater than or equal to 200 nm, for example between 200 nm and 1 pm, or between 400 nm and 1 pm.

[0065] In this example, the acceptor substrate 150 is made of silicon and the second bonding layer 124.2 consists of 2 sub-layers, a chromium (Cr) sub-layer 10 nm thick, intercalated between a gold (Au) layer 200 nm thick and the acceptor substrate 150.

[0066] The first bonding layer 124.1 and the second bonding layer 124.2 are then brought into contact and adhere to each other to assemble the acceptor substrate 150 to the substrate 100 via the buffer layer 110, the layer of interest 120, the first bonding layer 124.1 and the second bonding layer 124.2. At the end of this step, the first bonding layer 124.1 and the second bonding layer 124.2 together define a metal layer 125. Consequently, the metal layer 125 advantageously comprises titanium (Ti) or an alloy of nickel and platinum (NiPt) or a bilayer of platinum (Pt) and nickel (Ni) in contact with the layer of interest 120, in the latter case, the platinum is preferentially in contact with the layer of interest 120. In this example, the assembly is carried out by thermocompression at 150°C for 60 minutes, applying a force equivalent to 1 tonne.

[0067] In [Fig.2A], the substrate 100 is removed. In this example, to remove the substrate 100, a grinding and / or polishing step is performed to leave a residual thickness of the substrate 100 of approximately 100 μm, followed by an etching step. The buffer layer 110 is then removed in its entirety, so as to remove lattice mismatch dislocations in the layer of interest 120, in the vicinity of an interface between the buffer layer 110 and the layer of interest 120. In this example, the buffer layer 110 is removed during isotropic etching by a sulfur hexafluoride (SF6) and / or carbon tetrafluoride (CF4) plasma. Note that, in Figures 2A to 2F, the Z axis of the direct orthogonal reference frame (X, Y, Z) is oriented from the layer of interest towards the acceptor substrate 150.

[0068] The inventors have found that misfit dislocations in the vicinity of the interface between the buffer layer 110 and the layer of interest 120 initiate an accumulation of tin under the effect of heating. The tin then migrates to the surface via the threading dislocation channel to diffuse along a

[110] direction of the layer of interest 120. A sustained phenomenon of tin segregation can then be established. This phenomenon can be, at least in part, avoided by the suppression of misfit dislocations induced by an at least partial removal of the buffer layer 110, here total, and can be stopped by the arrangement of an edge of the layer of interest 120 in a crystal plane orthogonal to the

[110] direction.

[0069] In [Fig.2B], the layer of interest 120 is locally etched over its entire thickness by anisotropic etching, to obtain a structured layer of interest 120.1. At the end of this step, the structured layer of interest 120.1 comprises an etching flank 140.1 substantially perpendicular to the plane (X, Y) which delimits a region of the layer of interest 120 intended to be an active region 140 of the optoelectronic device 1. The layer of interest 120 is here etched by a plasma of a gaseous mixture of CF4, N2 and O2, through a mask of photosensitive resin obtained by photolithography. The etching flank 140.1 also delimits a first doped region 141 of the first type of conductivity, originating from the lower sub-layer 121, and a second doped region 143 of the second type of conductivity, originating from the upper sub-layer 123.The first and second doped regions 141, 143 are intended to become the p and n doped regions of a PIN diode of the optoelectronic device 1.

[0070] A portion of the metal layer 125 in contact with the structured layer of interest 120.1 defines a metal portion 131 intended to create an intermetallic compound.

[0071] The structured layer of interest 120.1 may have over its entire height a rectangular or elliptical or circular section in a plane substantially parallel to the plane (X, Y). The etching flank 140.1 then has a shape, respectively, rectangular, elliptical or circular, in this plane. The active region 140 has a surface area in a plane parallel to the plane (X, Y) delimited by the etching flank 140.1.

[0072] Optionally, the structured layer of interest 120.1 may be subjected to annealing, called healing, in a furnace, for more than 5 minutes, at a temperature Tg strictly higher than the epitaxy temperature Te. The temperature Tg is for example greater than or equal to 350°C. Thus, crystalline defects of the structured layer of interest 120.1 and of the active region 140 are eliminated. Among these defects, taking into account for example the through dislocations and / or vacancies and / or interstitial atoms resulting from the epitaxy step of the layer of interest 120. The optional healing annealing is advantageously carried out following the obtaining of the structured layer of interest 120.1, but it may also be interesting to carry it out at other times in the process.

[0073] Alternatively, the anisotropic etching of the layer of interest 120 occurs after the deposition of the first bonding layer 124.1 and before the assembly of the acceptor substrate 150 with the substrate 100. For this alternative, the first bonding layer 124.1 is structured and forms a geometry substantially identical to the structured layer of interest 120.1 in a plane parallel to the plane (X, Y). The first bonding layer 124.1 thus structured, and the second bonding layer 124.2 are then brought into contact and adhere to each other to assemble the acceptor substrate 150 to the substrate 100 via the buffer layer 110, the layer of interest 120, the first bonding layer 124.1 and the second bonding layer 124.2. At the end of this step, the first structured bonding layer 124.1 and the second bonding layer 124.2 together define a structured metal layer 125.A portion of the metal layer 125 in contact with the structured layer of interest 120.1 defines a metal portion 131 intended to create an intermetallic compound. The assembly can be carried out by thermocompression at a temperature between 100°C and 250°C, for example equal to 150°C, for 60 minutes, applying a force equivalent to 1 ton. The substrate is then removed as described in connection with [Fig.2A]. Only the optional healing annealing can possibly be carried out at the step of [Fig.2B]. The method of this variant continues as described in connection with Figures 2C to 2F.

[0074] In [Fig.2C], an insulating coating 301 is deposited conformally on the structured layer of interest 120.1 and the metal layer 125. A first opening 301.1 and a second opening 301.2, both through, are made in the insulating coating 301 to expose, respectively, the layer of interest 120 and the metal layer 125. The first and second openings 301.1, 301.2 extend in planes substantially parallel to the plane (X, Y). The insulating coating 301 is advantageously a passivation layer of the structured layer of interest 120.1. It passivates in particular the active region 140 on the etching flank 140.1. The insulating coating 301 may be a dielectric. It typically has a thickness of 10 to 300 nm, preferably 150 to 200 nm. The insulating coating 301 is here made of silicon oxide, for example SiO2.

[0075] In Figures 2D and 2E, metal portions 131 and an additional metal portion 132 are produced by a lift-off lithography process known to those skilled in the art. Note that the metal portions The metal portions 131 and the additional metal portion 132 can also be obtained by conventional photolithographic masking and dry etching steps. The additional metal portion 132 is optional.

[0076] In [Fig.2D], a bilayer of resins 302, 303 are exposed and developed, so as to define resin patterns having re-entrant flanks. A resin pattern and the insulating coating 301 together define a third opening 301.3 inside the first opening 301.1, exposing the structured layer of interest 120.1 in a plane substantially parallel to the (X, Y) plane. Optionally, the metal layer 125 is exposed at a fourth opening 301.4, inside the second opening 301.2.

[0077] A metal coating 304 is then deposited conformally. The metal coating 304 is then in contact with the structured layer of interest 120.1 at the third opening 301.3. It is also in contact with the metal layer 125 at the fourth opening 301.4, when the latter exists. The metal coating 304 advantageously comprises titanium (Ti) or a nickel and platinum alloy (NiPt) or a bilayer of platinum (Pt) and nickel (Ni) in contact with the structured layer of interest 120.1. In this example, the metal coating 304 consists of three undercoatings, a 7 nm undercoating of titanium nitride (TiN) sandwiched between a 10 nm undercoating of titanium (Ti) in contact with the structured layer of interest 120.1, and a 400 nm undercoating of gold (Au).

[0078] The resin patterns are then removed ([Fig.2E]), for example by dilution in acetone for 25 minutes, at 40°C, at the same time as parts of the metal coating 304 resting on the resin patterns. At the end of this step, each part of the metal coating 304 in contact with the structured layer of interest 120.1 in the third opening 301.3 defines a metal portion 131 intended to create an intermetallic compound. Here, the additional metal portion 132 consists of the part of the metal coating 304, initially positioned in the fourth opening 301.4, which rests on the metal layer 125.

[0079] [Fig.2F] is a step of producing an intermetallic compound 130. The intermediate structure obtained at the end of the process steps of [Fig.2E] is heated in a furnace. The thermal budget is sufficient to create the intermetallic compound 130 from each metal portion 131 in contact with the structured layer of interest 120.1, comprising germanium, tin and a metal of the metal portion 131. The heating step of [Fig.2F] is advantageously carried out in a rapid thermal heating tool (or Rapid Thermal Annealing, RTA, in English).

[0080] When the metal portion 131 comes from a metal coating 304 and / or a metal layer 125 comprising titanium (Ti) or an alloy of nickel and platinum (NiPt) or a bilayer of platinum (Pt) and nickel (Ni), the temperature T; of the heating step of [Fig.2F] is strictly higher than the epitaxy temperature Te. Thus, the heating step of [Fig.2F] participates in the suppression of crystalline defects of the structured layer of interest 120.1 and of the active region 140, in addition to or in replacement of the healing annealing. Among these defects, there are for example through dislocations and / or vacancies and / or interstitial atoms resulting from the epitaxy step of the layer of interest 120.

[0081] If the metal portion 131 comprises a platinum and nickel alloy (NiPt), the temperature T; is for example greater than or equal to 350°C, for a duration greater than 10 s, for example equal to 30 s, thus the intermetallic compound 130 comprises a NiPt(GeSn) phase which is not very resistive. If the metal portion 131 comprises titanium (Ti), as is the case in this example, the temperature T; is for example greater than or equal to 450°C, for a duration greater than 10 s, for example equal to 30 s, thus the intermetallic compound 130 comprises a Ti6 (GeSn)5 phase which is not very resistive.

[0082] The active region 140 has a surface area less than a first maximum surface area and the buffer layer 110 has been entirely removed, so that the tin of the active region 140 does not segregate during the step of producing the intermetallic compound 130. The first maximum surface area can be established by applying the prior procedure described in connection with FIGS. 6A to 6C, with a second layer 610 of the same nature as the buffer layer 110 and a first layer 620 of the same nature as the layer of interest 120. The thermal budget of the step of [Fig.2F] is applied for the heating of the step of [Fig.6C].

[0083] The etching flank 140.1 may advantageously comprise a (110) or (110) crystalline plane of the layer of interest 120 to avoid the possible sustained phenomenon of tin segregation. The trenches 640.1 during the production of the test structures of the prior procedure then all advantageously comprise a (110) or (110) crystalline plane.

[0084] The first maximum surface area is for example equal to 2.5.106 cm2, for an active region 140 comprising 13% tin and a thermal budget corresponding to a temperature of 400°C for 20 minutes.

[0085] In the optoelectronic device 1 produced with this first manufacturing method or the following ones, an intermetallic compound 130 in contact with the first doped region 141 is connected to an electrical circuit, for example a power supply or control or reading circuit, via a metal contact (not shown) formed on the intermetallic compound 130. The intermetallic compound 130 in contact with the second doped region 143 is connected to the electrical circuit via the metal layer 125 and an additional metal contact (not shown), formed on the additional metal portion 132. The metal contacts may comprise titanium (Ti), gold (Au), aluminum (Al), or an aluminum-copper alloy (AlCu). Alternatively, the intermetallic compounds 130 may be connected to the electrical circuit by a wire connection or tips, for example, tips of a tester.

[0086] A second method of manufacturing an optoelectronic device will be described in connection with figures 1A, 1B, 3A to 3C. The optoelectronic device 1 may here be a laser or a photodiode, capable of, respectively, emitting or receiving a luminous flux in a plane substantially parallel to the plane (X, Y). Only the differences with the first method will be explicitly described.

[0087] In [Fig.lB], the first and second bonding layers 124.1, 124.2 are made of a dielectric, here amorphous silicon oxide (SiOx). After assembly of the acceptor substrate 150 with the substrate 100, the first bonding layer 124.1 and the second bonding layer 124.2 together define an insulating layer 126.

[0088] In [Fig.3B], the layer of interest 120 is locally and partially etched by anisotropic etching, to obtain the structured layer of interest 120.1. The structured layer of interest 120.1 comprises an etching flank 140.1 substantially perpendicular to the plane (X, Y) which delimits a region of the layer of interest 120 intended to be an active region 140 of the optoelectronic device 1. The etching flank 140.1 also delimits a first doped region 141 of the first conductivity type, originating from the lower sub-layer 121. The upper sub-layer 123 is retained at least over a portion of its height, advantageously in its entirety. The first doped region 141 and a part of the upper sub-layer 123 opposite the first doped region 141 and the active region 140 are intended to become the p and n doped regions of a PIN diode of the optoelectronic device 1.The active region 140 has a surface area in a plane parallel to the (X, Y) plane delimited by the etching flank 140.1.

[0089] Metallic portions 131 are then produced using conventional photolithography and etching steps. At least one metallic portion 131 rests on the first doped region 141 and another metallic portion 131 rests on another exposed part of the layer of interest 120 located on the upper sub-layer 123.

[0090] [Fig.3C] is a step in producing an intermetallic compound 130. The intermediate structure obtained at the end of the process steps of [Fig.3B] is heated in a furnace. The thermal budget is sufficient to create the intermetallic compound 130 from each metal portion 131 in contact with the structured layer of interest 120.1, comprising germanium, tin and a metal of the metal portion 131. Intermetallic compounds are thus obtained on the sub-layer su- upper 123 and on the first doped region 141.

[0091] Just as for the first manufacturing method, the active region 140 has a surface area less than a first maximum surface area and the buffer layer 110 has been entirely removed, so that the tin of the active region 140 does not segregate during the step of producing the intermetallic compound 130. The etching flank 140.1 may advantageously comprise a crystalline plane (110) of the layer of interest 120 to avoid the possible sustained phenomenon of tin segregation.

[0092] The first maximum surface area is for example equal to 2.5.106 cm2, for an active region 140 comprising 13% tin.

[0093] A third method of manufacturing an optoelectronic device will now be described in connection with FIGS. 4A to 4C. The optoelectronic device 1 may here be a laser capable of emitting a luminous flux in a plane substantially parallel to the plane (X, Y). Only the differences with the first method will be explicitly described.

[0094] The step of [Fig.4A] is identical to that of [Fig.1A]. The first conductivity type is here of the p type. The substrate 100 further comprises a doped layer of the first conductivity type, made of silicon or based on germanium, on which the epitaxy of the buffer layer 110 is carried out. The buffer layer 110 is doped in situ with the first conductivity type.

[0095] In [Fig.4B], the layer of interest 120 is etched by anisotropic etching over its entire height to obtain at least one through opening 160 exposing the buffer layer 110. An etching flank 140.1 substantially perpendicular to the plane (X, Y) delimits a region of the layer of interest 120 intended to be an active region 140 of the optoelectronic device 1. The layer of interest 120 is here etched by a plasma of a gaseous mixture of CF4, N2 and O2, through a mask of photosensitive resin obtained by photolithography. The etching flank 140.1 also delimits a first doped region 141 of the first type of conductivity, originating from the lower sub-layer 121, and a second doped region 143 of the second type of conductivity, originating from the upper sub-layer 123. The first and second doped regions 141, 143 are intended to become the p and n doped regions of a PIN diode of the optoelectronic device 1.The active region 140 has a surface area in a plane parallel to the (X, Y) plane delimited by the etching flank 140.1.

[0096] In [Fig.4C], the buffer layer 110 is etched isotropically, selectively relative to the layer of interest 120 and advantageously, selectively relative to the substrate 100. A residual portion of the buffer layer 110 at the end of the isotropic etching constitutes a pedestal 145 on which the first doped region 141 rests, on a bearing surface 145.1 of the buffer layer 110. The bearing surface 145.1 is a growth interface of the layer of interest 120 on the buffer layer 110.

[0097] Selective isotropic etching is for example a plasma etching of CF4, N2 and O2 , in an etching chamber at a pressure of 50.103 Torr, with a gas flow rate of 30 sccm of CF4, 40 sccm of N2, 50 sccm of O2. Alternatively, isotropic etching by a sulfur hexafluoride (SF6) plasma can be used.

[0098] In [Fig.4D], a metal portion 131 is formed on the second doped region 143 and an additional metal portion 132 on the substrate 100, by conventional steps of the semiconductor industry, for example similar to FIGS. 2C to 2E.

[0099] [Fig.4E] is a step of producing an intermetallic compound 130. The intermediate structure obtained at the end of the process steps of [Fig.4D] is heated in a furnace. The thermal budget is sufficient to create the intermetallic compound 130 from the metal portion 131 in contact with the structured layer of interest 120.1, comprising germanium, tin and a metal of the metal portion 131. An intermetallic compound is thus obtained on the first doped region 141. During this step, an additional intermetallic compound 133 is also obtained on the substrate 100. If the substrate 100 is made of germanium, the additional intermetallic compound 133 may be Ni(Pt)Ge. If the substrate 100 is made of silicon, the additional intermetallic compound 133 may be Ni(Pt)Si.

[0100] As for the first and second manufacturing methods, the surface area of ​​the active region 140 is less than a first maximum surface area. The buffer layer 110 has also been partially removed, so that the support surface 145.1 is less than a second maximum surface area. The tin of the active region 140 then does not segregate during the step of producing the intermetallic compound 130. The etching flank 140.1 may also advantageously comprise a crystalline plane (110) or (110) of the layer of interest 120 to avoid the possible sustained phenomenon of tin segregation.

[0101] The first maximum surface area and the second maximum surface area can be established by applying the prior procedure described in connection with FIGS. 6A to 6C, with a second layer 610 of the same nature as the buffer layer 110 and a first layer 620 of the same nature as the layer of interest 120. The thermal budget of the step of [Fig.4E] is applied for the heating of the step of [Fig.6C].

[0102] The first maximum surface area and the second maximum surface area are for example respectively equal to 2.5.106 cm2, and to 3.108 cm2, for an active region 140 comprising 13% tin and a thermal budget corresponding to a temperature of 400°C for 20 minutes.

[0103] The active region 140 of the optoelectronic device 1 produced by any one of the first, second and third production methods may have a mechanical stress in compression, for example equal to -0.35%. The tin concentration to obtain a direct gap is then typically greater than 13%. average concentration of the layer of interest 120 and of the active region 140 is for example between 13% and 16%.

[0104] We will now describe a fourth method of manufacturing an optoelectronic device 1 according to the invention, which this time comprises an active region 140 having a mechanical tensile stress and a tin concentration greater than 8%.

[0105] The steps of [Fig.1A], 1B and 3A are carried out. The insulating layer 126 is here made of silicon oxide. A silicon nitride layer having a compressive mechanical stress is then deposited on the lower sub-layer 121. The silicon nitride layer is etched over its entire height to produce a pad 570 having a compressive mechanical stress.

[0106] The layer of interest 120 is then locally etched over its entire thickness by anisotropic etching, to produce a through opening 560 exposing the insulating layer 126. The insulating layer 126 is then etched isotropically, selectively relative to the layer of interest 120 and the acceptor substrate 150, for example under HF vapor or in an HF solution. At the end of this double etching, a structured layer of interest 120.1 is obtained ([Fig.5A]) which comprises a structured part 511 suspended above the acceptor substrate 150, and a peripheral part 512 resting on a non-etched part of the insulating layer 126. The structured part 511 comprises a central portion 520 connected to the peripheral part 512 by first lateral portions 530 forming tensioning arms, and by second lateral portions 540 forming electrical polarization arms.The structured portion 511 and the peripheral portion 512 together constitute a structured layer of interest 120.1 originating from the layer of interest 120. The pad 570 rests entirely on the central portion 520 and is centered thereon.

[0107] The central portion 520 has an elongated shape in the plane (X, Y), in the sense that it has a length along its longitudinal axis A-A' which is greater than its width. The length and the width are the dimensions of the central portion 520 in a plane parallel to the plane (X, Y). The shape of the central portion 520 in this plane may be rectangular, polygonal, oblong, or other. The length of the central portion 520 may be of the order of a few tens of microns, and the width may be of the order of a few microns. In the case where the local width of the central portion 520 varies along the longitudinal axis A-A', the length is then greater than the average width. The tensioning arms 530 are opposite each other with respect to the central portion 520 along the longitudinal axis A-A'.

[0108] These tension arms 530 are dimensioned so as to induce, in association with the pad 570, a tensile deformation in the central portion 520 along the longitudinal axis A-A'. They therefore extend longitudinally from the central portion 520, along the longitudinal axis A-A', and more precisely from the longitudinal ends of the latter. Also, the longitudinal axis AA' corresponds to a main deformation axis of the central portion 520.

[0109] The central portion 520 being stressed in tension by the tension arms 530, it therefore exhibits a deformation of its crystallographic structure by increasing its natural lattice parameter along the longitudinal axis A-A'. The tension arms 530 make it possible to increase the non-zero value of tension stress in the central portion 520 induced by the pad 570, preferably without themselves undergoing significant mechanical stress. For this, the tension arms 530 are dimensioned so that the average width "b" of the tension arms 30 is greater than the average width "a" of the central portion 520, preferably ten times greater than the latter. By width, or local width, is meant the local dimension of a portion or an arm, in the plane (X, Y), along a transverse axis orthogonal to the longitudinal axis A-A'. The average width of a portion can then be an average of its local width calculated over the length of the portion..

[0110] The tensioning arms 530 may have a shape in the plane (X, Y) that is substantially rectangular, with a sudden increase in its width from the central portion 520, or even a trapezoid shape with a width that increases continuously as one moves away from the central portion 520. Other shapes are of course possible, such as a triangular shape.

[0111] The structured part 511 further comprises second lateral portions, forming polarization arms 540. At least two polarization arms 540 are arranged on either side of the central portion 520, opposite each other along a transverse axis, parallel to the plane (X, Y) and orthogonal to the longitudinal axis A-A'. They therefore extend from the lateral edges of the central portion 520 along the transverse axis. In this embodiment, the polarization arms 540 participate, with the tensioning arms 530, in connecting the central portion 520 to the peripheral part 512.

[0112] Furthermore, each of the polarization arms 540 comprises a main part 541 and a plurality of connecting parts 542, these ensuring the mechanical and electrical connection between the main part 541 and the central portion 520. The main part 541 then has a width greater than that of each connecting part 542. The width of the main part 541 is here its dimension in a plane parallel to the plane (X, Y) and along the axis A-A'. In addition, the connecting parts 542 are distributed along the axis A-A', advantageously in a uniform manner. The connecting portions 542 extend from a lateral edge of the central portion 520 and together delimit a continuous region along the longitudinal axis A-A' of the active sub-layer 122 and the central portion 520, intended to be the active region 140 of the optoelectronic device 1. Consequently, the active region 140 has an extent surface in a plane parallel to the plane (X, Y) delimited laterally by lateral etching flanks 140.1 substantially orthogonal to the plane (X, Y) and parallel to the longitudinal axis A-A', and longitudinally by the first connecting part 542 and the last connecting part 542, encountered along the longitudinal axis A-A'. The mechanical stress and the tin concentration of the active region 140 are such that it has a direct gap.

[0113] A metal portion 131 is formed on a part of the layer of interest 120 at each main part 541 of each polarization arm 540. More precisely, a metal portion 131 is formed on a part of the upper sub-layer 123 made accessible by local etching of the lower sub-layer 121 and the active sub-layer 122. And, a metal portion 131 is formed on the lower sub-layer 121. Each metal portion 131 comprises titanium (Ti) or a nickel and platinum alloy (NiPt) or a bilayer of platinum (Pt) and nickel (Ni) in contact with a part of the layer of interest 120.

[0114] The step of producing an intermetallic compound 130 of [Fig.2F] is then carried out, applied to the structure obtained after the formation of the metal portions 131. An intermetallic compound 130 is then obtained (FIGS. 5B and 5C) on a part of the layer of interest 120 at the level of each main part 541 of each polarization arm 540. The main part 541 of each polarization arm 540 is intended to electrically polarize the active region 140 from the intermetallic compounds 130. FIGS. 5B and 5C are schematic views, in section, respectively, along the axis A-A' and the axis B-B', of the structured layer of interest 120.1 on the acceptor substrate 150 of [Fig.5A].

[0115] Preferably, to improve the quality of the electrical polarization of the active region 140, the intermetallic compounds 130 are each partially surrounded by an electrical insulation line (not shown). An insulation line extends around an intermetallic compound 130 between it and the peripheral portion 512, and does not extend between it and the polarization arm 540. The insulation lines may be through-trenches of the layer of interest 120.

[0116] Optical reflectors 505, for example Bragg mirrors, can be arranged in the tensioning arms 530, on either side of the central portion 520, in order to produce an electrically pumped laser diode.

[0117] In a first variant, it is possible not to carry out the steps of [Fig.lB] and 3A. The silicon nitride layer presenting a compressive mechanical stress is then deposited on the upper sub-layer 123. And, the buffer layer 110 is etched isotropically, selectively with respect to the layer of interest 120 and, advantageously, selectively with respect to the acceptor substrate 150, instead of etching the insulating layer 126. The part of the buffer layer 110 facing the active region 140 is therefore completely removed during the step of producing the intermetallic compounds 130.

[0118] In a second variant, it is possible to deposit a silicon nitride layer having a tensile mechanical stress instead of the silicon nitride layer having a compressive mechanical stress. The pad 570 is then replaced by two pads 571 from the silicon nitride layer resting this time on the tensioning arms 530, centered on the longitudinal axis A-A'. The second variant can be used in combination with the first variant.

[0119] In a third variant, the layer of interest 120 consists of a single layer based on an alloy of germanium and intrinsic tin. The polarization arms 540 are then previously implanted before the formation of the metal portions 131. The polarization arms 540 have different types of doping. It is then not necessary to carry out a partial local etching to make a sub-layer of the layer of interest 120 accessible before the formation of the metal portions 131. The third variant can be used in combination with the first variant and / or the second variant.

[0120] For the four manufacturing methods which have just been described, as well as for their variants, the metal portions 131 in contact with a part of the layer of interest 120 advantageously comprise titanium (Ti) or an alloy of nickel and platinum (NiPt) or a bilayer of platinum (Pt) and nickel (Ni) in contact with the layer of interest 120, in the latter case, the platinum is preferentially in contact with the layer of interest 120. The intermetallic compounds 130 are produced in a furnace at a temperature T; strictly higher than the epitaxy temperature Te of the layer of interest 120. The step of producing the intermetallic compounds 130 participates in the suppression of crystalline defects of the structured layer of interest 120.1, in addition to or in replacement of a healing annealing at a temperature strictly higher than the epitaxy temperature Te of the layer of interest 120.Among these defects, there are for example through dislocations and / or vacancies and / or interstitial atoms resulting from the epitaxy step of the layer of interest 120.

[0121] For the four manufacturing methods, as well as for their variants, if the metal portion 131 comprises a nickel and platinum alloy (NiPt), the temperature T; is for example greater than or equal to 350°C, for a duration greater than 10 s, for example equal to 30 s, thus the intermetallic compound 130 comprises a NiPt(GeSn) phase which is low resistivity. If the metal portion 131 comprises titanium (Ti), as is the case in this example, the temperature T; is for example greater than or equal to 450°C, for a duration greater than 10 s, for example equal to 30 s, thus the intermetallic compound 130 comprises a low resistivity Ti6(GeSn)5 phase. The step of producing the intermetallic compounds 130 is advantageously carried out in a rapid thermal annealing (RTA) tool.

[0122] For the four manufacturing methods, as well as for their variants, during the step of producing the intermetallic compounds 130, the active region 140 has a surface area less than a first maximum surface area and the buffer layer 110 has an interface facing the active region 140 less than a second maximum surface area, so that the tin of the active region 140 does not segregate during the step of producing the intermetallic compound 130. For the first, second and fourth manufacturing methods with transfer to an acceptor substrate 150, the second condition is ensured by the fact that the buffer layer 110 is completely removed. For the first variant of the fourth manufacturing method, the active region 140 is in the suspended central portion 520, therefore, without a residual part of the buffer layer 110 facing the active region 140.

[0123] For the four manufacturing methods, as well as for their variants, the first maximum surface and the second maximum surface can be established by applying the preliminary procedure described in connection with FIGS. 6A to 6C, with a second layer 610 of the same nature as the buffer layer 110 and a first layer 620 of the same nature as the layer of interest 120. The thermal budget of the step of producing the intermetallic compound is applied for the heating of the step of [Fig.6C], possibly added to a thermal budget for healing defects in the active region 140.

[0124] For the four manufacturing methods, as well as for their variants, the active region 140 is delimited by at least one etching flank 140.1. The etching flank 140.1 may advantageously comprise a crystal plane (110) of the layer of interest 120 to avoid the possible sustained phenomenon of tin segregation. The trenches 640.1 during the production of the test structures of the prior procedure then all advantageously have a crystal plane (110) or (110).

[0125] For the four manufacturing methods, as well as for their variants, each test structure of the preliminary procedure advantageously has a geometric shape in a main plane of the layer of interest 120 homothetic to a shape of the structured layer of interest 120.1.

[0126] Finally, for the four manufacturing methods, the difference between the minimum tin concentration of the layer of interest 120 and the maximum tin concentration of the buffer layer 110 may be such that the buffer layer 110 can be removed, at least in part, by selective etching of the buffer layer 110 relative to the layer of interest 120. Isotropic etching by a sulfur hexafluoride (SF6) plasma can etch a buffer layer 110 with a maximum tin concentration of less than 7%, selectively relative to a layer of interest 120 with a concentration minimum tin concentration strictly greater than 7%, for example greater than or equal to 8%. Isotropic etching by a carbon tetrafluoride (CF4) plasma can etch a buffer layer 110 with a maximum tin concentration of less than 8%, selectively relative to a layer of interest 120 with a minimum tin concentration strictly greater than 8%, for example greater than or equal to 9%. Etching of a first material is selective relative to a second material if the first material is etched at least 5 times faster than the second material, preferably at least 10 times faster.

[0127] Particular embodiments have just been described. Different variants and modifications will be apparent to those skilled in the art. In particular, they will know how to perfectly apply the manufacturing methods to obtain an optoelectronic device 1 comprising a PN junction instead of a PIN junction, the active region 140 then being perfectly defined by its function. It will also be apparent to those skilled in the art that the active region 140 may comprise one or more quantum wells, for example by jumps in the tin concentration.

Claims

Claims

1. Method of manufacturing an optoelectronic device (1), comprising, successively: • a step of epitaxy of a layer of interest (120) based on an alloy of germanium and tin on a growth layer (110) comprising germanium, at an epitaxy temperature Te, such that a minimum tin concentration of the layer of interest (120) is strictly greater than a maximum tin concentration of the growth layer (110), • a step of forming an active region (140) in the layer of interest (120), of surface extent in a plane parallel to a main plane of the layer of interest (120) less than a first maximum surface, • a step of removing at least part of the growth layer (110) so that a surface (145.1) of the growth layer (110) in contact with the layer of interest (120) and facing the active region (140) is less than a second maximum or zero surface, • a metallization step to obtain a metallic portion (131) comprising a metal chosen from titanium or an alloy of platinum and nickel, resting on a part of the layer of interest (120), • a heating step in a furnace at a temperature T; strictly higher than the epitaxy temperature Te, to produce an intermetallic compound (130) from the metallic portion (131), comprising germanium, tin and the metal;

2.

3. the first maximum surface area and the second maximum surface area being such that the tin in the active region (140) does not segregate during the heating step. A method according to any preceding claim, wherein the removing step releases compressive mechanical stress in the active region. The method of claim 2, wherein a tin concentration in the active region (140) is greater than 13%, and a compression re- the active region (140) at the end of the removal step is greater than or equal to -0.35%.

4. A method according to any preceding claim, wherein the removing step comprises transferring the layer of interest (120) onto an acceptor substrate (150), followed by complete removal of the growth layer (110).

5. Method according to claim 4, in which the transfer is carried out by bringing into contact a first bonding layer (124.1) comprising a metal resting on the layer of interest (120), chosen from titanium (Ti) or a nickel and platinum alloy (NiPt), with a second bonding layer (124.2) of metal resting on the acceptor substrate (150).

6. A method according to any one of claims 1 to 3, wherein the removing step comprises anisotropic etching of a through opening (160, 560) of the layer of interest (120), followed by isotropic etching of the growth layer (110) through the through opening (160, 560), selective with respect to the layer of interest (120).

7. Method according to claim 6, in which, at the end of the isotropic etching, the growth layer (110) and the layer of interest (120) define an interface not having a part facing the active region.

8. The method of claim 7, wherein the anisotropic etching defines a peripheral portion (512) of the layer of interest (120) comprising the interface, and a structured portion (511) of the layer of interest (120) comprising a central portion (520) comprising the active region (140), connected to the peripheral portion (512) by at least two tension arms (530) opposite each other with respect to the central portion (520), and the isotropic etching induces a tensile stress of the central portion (520) by the tension arms (530).

9. A method according to any preceding claim, wherein the surface extent of the active region (140) is delimited by an etching flank (140.1).

10. The method of claim 9, wherein the etching flank (140.1) comprises a crystal plane (110) or (110) of the layer of interest (120).

11. A method according to any preceding claim, wherein the metal is titanium and the temperature T; of the heating step is above a temperature at which a Ti6(GeSn)5 phase forms.

12. A method according to any one of claims 1 to 10, wherein the metal is an alloy of platinum and nickel and the temperature T; of the heating step is higher than a temperature at which a NiPt(GeSn) phase forms.

13. Method according to any one of the preceding claims, comprising a preliminary procedure for determining the second maximum surface area comprising the following steps: • epitaxy of a first layer (620) based on GeSn of the same nature as the layer of interest (120), on a second layer (610) of the same nature as the growth layer (110), • removal of a part of the second layer (610) to produce a set of test structures (650) each comprising an interface (645.1) between the first and second layers (620, 610), the interfaces (645.1) being of different surfaces, • implementation of the heating step, • identification of a subset of the set of test structures for which the tin in the test structure (650) has segregated, • definition of the second maximum surface area at a value strictly lower than all the surfaces of the interfaces of the test structures (650) of the subset.

14. A method according to any preceding claim, wherein the first maximum surface area and the second maximum surface area are further such that tin in the active region (140) does not segregate upon a healing anneal of the active region to remove dislocations from the active region.

15. The method of claim 14, wherein the healing annealing and the heating step are one and the same step.

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