n-co-doped semiconductor substrate

Abstract

A method for producing a single-crystal semiconductor material of a Group 13 nitride, in particular GaN, comprising the following steps: depositing at least one single-crystal layer on a starting substrate by three-dimensional epitaxial growth, the layer comprising a region resulting from basal plane growth and a region resulting from growth of a face of a different orientation, referred to as a non-basal plane; supplying an n-dopant gas containing a first chemical element selected from the chemical elements of Group 16 of the Periodic Table and at least one second chemical element selected from the chemical elements of Group 14 of the Periodic Table, such that the concentration of the second element in the region resulting from basal plane growth is greater than 1.0×10 17 / cm 3 , and the concentration of the first element in the region generated by non-basal plane growth is less than 2.0×10 18 / cm 3 .

Description

Technical Field

[0001] The present invention relates to the general technical field of manufacturing substrates and wafers of semiconductor materials based on elements of Groups 13 and 15 of the Periodic Table of the Elements, such as gallium nitride (GaN).

[0002] These wafers are used as substrates for the production of semiconductor structures, such as light emitting diodes (LEDs), laser diodes (LDs), vertical transistors for power electronics, horizontal transistors for power electronics or telecommunications (radio frequency), current rectifier diodes or sensors. Background Art

[0003] Current processes for manufacturing semiconductor material substrates based on nitrides of group 13 or IIIA elements rely on vapor deposition techniques, in particular heteroepitaxy, which consists in growing a crystal (for example a gallium nitride GaN crystal) on a starting substrate of different properties (for example a sapphire substrate).

[0004] These methods involve injection systems from at least two different gaseous components that are able to interact prior to deposition.

[0005] Well-known methods may be mentioned, for example:

[0006] -Metal-organic vapor phase epitaxy (MOVPE),

[0007] - Hydride Vapor Phase Epitaxy (HVPE),

[0008] - Closed Space Vapor Transfer (CSVT) extension,

[0009] -Ceramic vapor deposition, etc.

[0010] So-called 3D growth processes or, for example, three-dimensional lateral growth allow the dislocation density to be reduced to less than 10 7 / cm 2 .

[0011] Under three-dimensional growth conditions, the HVPE growth front has a face perpendicular to the growth front and a face inclined to the growth front. With respect to the faces perpendicular to the growth front, these are faces formed by the basal plane (0001). It is known that these faces contain less oxygen than various inclined faces (non-basal planes, index hkil, where h≠0 and k≠0 and i≠0). This difference in n-type doping causes some areas to be more resistant than others or to have different optical properties. After shaping to obtain a two-dimensional surface, for example by straightening and / or polishing, inhomogeneities in optical and / or electrical properties can be observed.

[0012] Furthermore, the lattice can have macroscopic inclusions with a size greater than 10 μm, consisting mainly of twins, domain inversions or even polycrystals. Doping leads to an increased presence of such defects in the lattice.

[0013] All these defects generated during the growth process lead to defects in the final wafer (doping heterogeneities and crystal defects, still high dislocation density), which will cause failures during the fabrication of optoelectronic and / or electronic devices.

[0014] In order to improve the photoelectric properties of the substrate, for example, US2006255339A1 discloses a concentration of 0.7×10 18 to about 3×10 18 / cm 3 At the same time, n-doped GaN crystals having a thermal conductivity of at least 1.5 W / cm.K are used to enable the provision of devices, particularly diodes with a power exceeding 1 W. Even though only examples with Si doping are provided in this application, dopants such as Si, O, Ge, and C may also be used alone or in combination.

[0015] US20110175200A1 proposes an HVPE growth process in which the crystal is doped with Ge by adding GeCl4 in the reaction chamber to obtain a more electronically conductive crystal to compensate for the sudden increase in resistivity observed when the growth rate exceeds 450μm / h. However, such growth rates result in a high surface density of macroscopic inclusions and lower crystal quality.

[0016] US9461121B2 claims a method for improving the distribution of n-dopants within GaN crystals, typically by mixing Ga and dopant inputs for vapor phase growth. Uniform introduction into the reactor can be achieved by pre-mixing the dopant and Ga before reacting with HCl or by mixing the dopant and gallium halide in a single channel within the reaction chamber. The uniformity of the dopant concentration is measured by micro-Raman, microwave probe photoconductivity (MDP) or micro-photoluminescence. The method data shows that this is clearly an HVPE process with 2D growth and therefore does not provide a solution for 3D growth processes.

[0017] There is therefore a need for substrates and wafers of Group 13 or Group III nitride materials, in particular Group 13 or Group III nitride materials, and more particularly wafers and substrates composed of GaN, which have a large thickness, typically greater than 100 microns, or even 400 microns or more, obtained under three-dimensional growth conditions, are more uniform and simultaneously have:

[0018] - Low surface density of macroscopic inclusions, typically less than 5 cm -2 , preferably less than 4cm -2 , even less than 1cm -2 ,

[0019] - better crystal quality, for example as measured by: a half-width at half-maximum of the X-ray diffraction (XRD) peak of the (002) line of the GaN (0001) plane under symmetrical conditions around the angle ω, which is lower than 130 arc seconds; or a half-width at half-maximum of the X-ray diffraction (XRD) peak of the 201 line of the GaN (0001) film under tilted conditions around the angle ω, which is lower than 240 arc seconds, preferably lower than 140 arc seconds, and

[0020] - Improved electronic properties, typically with an average resistivity of less than 25 mohm.cm, or even less than 20 mohm.cm. Summary of the Invention

[0021] In this regard, the object of the present invention is a method for producing a single-crystalline semiconductor material of a Group 13 nitride, in particular GaN, comprising the following steps:

[0022] - depositing on a starting substrate by three-dimensional epitaxial growth at least one single-crystalline layer, said layer comprising regions resulting from basal growth, i.e. faces having a direction perpendicular to the growth front formed by the basal plane (0001), and regions, called non-basal planes, resulting from facet growth with a different orientation, i.e. faces not perpendicular to the direction of the growth front;

[0023] - supplying an n-dopant gas containing a first chemical element selected from the chemical elements of Group 16 of the periodic table and at least one second chemical element selected from the chemical elements of Group 14 of the periodic table, such that the concentration of the second element in the region resulting from the basal plane growth is higher than 1.0×10 17 / cm 3 , and the concentration of the first element in the region generated by non-basal plane growth is less than 2.0×10 18 / cm 3 .

[0024] As a guide, unless otherwise stated, all chemical element concentrations mentioned herein are atomic concentrations.

[0025] Advantageously, but optionally, the method according to the invention may also comprise at least one of the following features:

[0026] - the second chemical element of the n-dopant gas is germanium, formed from a solid source, GeCl4, germane, tetramethylgermanium and isobutylgermane and their derivatives, and / or, the second chemical element of the n-dopant gas is silicon, formed from a solid source, silane, dichlorosilane, silicon tetrachloride and their derivatives.

[0027] The first chemical element of the n-dopant gas is oxygen.

[0028] - Controlling the oxygen supply and concentration by controlling the purity of the Group III precursor and by subjecting the reactor to one or more very thorough purges at a residual pressure of less than 10 Torr, followed by one or more N2 purges.

[0029] In the case of simultaneous addition of dopants and oxygen according to the present invention, the concentration of the n-type dopant is no longer evenly distributed between the (0001) plane and the non-basal plane.

[0030] The n-dopant gas is mixed in the gas phase with the gallium chloride gas flow.

[0031] - Epitaxial growth is achieved by HVPE at a growth rate below 450 μm / h to ensure a low surface density of macroscopic inclusions and a satisfactory crystal quality.

[0032] Epitaxial growth is carried out by HVPE at a temperature between 910° C. and 1035° C., preferably between 925° C. and 1015° C. Preferably, the molar flow ratio of the Group V precursor to the Group III precursor is between 13 and 25. Preferably, the reactor is also maintained at a residual pressure between 100 and 500 Torr. Such conditions are particularly suitable for obtaining wafers with a controlled variation in the (silicon + germanium) / oxygen atomic ratio while allowing a high atomic ratio under essentially 3D growth conditions, i.e., resulting in a wafer with a growth area (having a surface consisting of a basal plane) preferably occupying less than 50% or even less than 30% and preferably between 5% and 25% of the upper surface of the wafer.

[0033] The present invention also has a further object of a method for producing a semiconductor substrate of Group 13 nitrides, in particular GaN, comprising the following steps:

[0034] - producing a single crystal semiconductor material of a Group 13 nitride on a starting substrate according to the above characteristics,

[0035] - Separating the starting substrate from the single crystal material;

[0036] - Correcting the thickness of the single crystal material by cleaning to obtain Group 13 nitride wafers with a thickness between 250 and 2000 microns.

[0037] The present invention also relates to a two-dimensional Group 13 nitride wafer, in particular GaN, obtained by three-dimensional epitaxial growth, comprising regions resulting from basal growth, i.e. faces having a direction perpendicular to the growth front formed by the basal (0001) planes, and regions resulting from facet growth of different orientations, known as non-basal planes, i.e. faces not perpendicular to the direction of the growth front, characterized in that:

[0038] - the region resulting from the non-basal plane growth comprises a first chemical element selected from Group 16 of the Periodic Table of Chemical Elements, the concentration of which is less than 2.0×10 18 / cm3 ,

[0039] - the region resulting from the basal plane growth comprises at least a second chemical element selected from the chemical elements of Group 14 of the Periodic Table, in a concentration greater than 1.0×10 17 / cm 3 .

[0040] Advantageously, but optionally, the wafer according to the invention may also comprise at least one of the following features:

[0041] - The concentration of the second element in the region produced by basal plane growth is greater than 2.0×10 17 / cm 3 , and the concentration of the first element in the region generated by non-basal growth is less than 1.0×10 18 / cm 3 .

[0042] - The cumulative concentration of the first chemical element and the second chemical element is less than 2.0×10 19 / cm 3 , preferably less than 1×10 19 / cm 3 or even less than 5.0×10 18 / cm 3 , to obtain a good compromise between conductivity / resistivity and optical transparency.

[0043] - The second chemical element is germanium and / or silicon.

[0044] -(Silicon + Germanium) / Oxygen atomic ratio is between about 0.5 and 30, preferably between about 0.5 and 20, more preferably between about 0.5 and 15, more preferably between about 0.5 and 10, and most preferably between about 0.5 and 5.

[0045] - The basal growth area occupies less than 60%, preferably less than 50%, or less than 30%, preferably 5% to 25% of the upper surface of the wafer. Figure 4c In the view shown, the surface proportion of the area consisting of the base surface can be measured along plane c.

[0046] - Crystal quality as measured by: the half-width at half maximum of the X-ray diffraction (XRD) peak of the (002) line of the GaN (0001) plane under symmetrical conditions near the angle ω, which is lower than 130 arc seconds, preferably lower than 100 arc seconds, more preferably lower than 90 arc seconds, or even lower than 60 arc seconds; or the half-width at half maximum of the X-ray diffraction (XRD) peak of the 201 line of the GaN (0001) film under tilted conditions near the angle ω, which is lower than 240 arc seconds, preferably lower than 140 arc seconds, or even lower than 100 arc seconds.

[0047] -The average resistivity of the wafer material is less than 25 mohm.cm.

[0048] - The polished wafers are free of cracks longer than 200 microns, which correspond to intracrystalline cleavage.

[0049] The invention also relates to the use of a Group 13 or Group III nitride wafer according to one of the preceding features as a substrate for the production of optoelectronic and / or electronic components, such as light-emitting diodes, laser diodes, vertical transistors for power electronics, horizontal transistors for power electronics or telecommunications (radio frequency), current rectifier diodes or sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Other characteristics, objects and advantages of the invention will become apparent on reading the following detailed description and with reference to the accompanying drawings, given as non-limiting examples, in which:

[0051] [ Figure 1 ]

[0052] - Figure 1 The main possible steps of a substrate manufacturing process according to one embodiment of the present invention are summarized.

[0053] [ Figure 2 ]

[0054] - Figure 2 schematically depicts a semiconductor material consisting of a multilayer stack according to a possible embodiment of the present invention,

[0055] [ Figure 3 ]

[0056] - Figure 3 shows the correction and finishing steps according to one possible embodiment of the invention,

[0057] [ Figure 4a ]

[0058] [ Figure 4b ]

[0059] - Figure 4a and 4b It is shown from a vertical or ¾ view, respectively, that under these three-dimensional growth conditions, the growth front along the (0001) basal plane includes a plane perpendicular to the growth front of the GaN semiconductor material HVPE in a 3D mode.

[0060] [ Figure 4c ]

[0061] - Figure 4c The structure of a wafer according to the invention after rectification and polishing is depicted, showing a first region resulting from growth of non-basal planes and a region resulting from growth of basal planes.

[0062] [ Figure 5a ]

[0063] [ Figure 5b ]

[0064] - Figure 5a and 5b Represents the average variation of the Raman A1 (LO) peak measured by Raman spectroscopy on the (0001) facet region of the GaN material growth front in three-dimensional HVPE mode as a function of the doping precursor and the related free carrier density.

[0065] [ Figure 6 ]

[0066] - Figure 6 Shown is the average variation of the Raman peak A1(LO) on the faceted (0001) region of the growth front of GaN material by 3D-mode HVPE as a function of the volume flow ratio N2 / (N2+H2) during growth. DETAILED DESCRIPTION

[0067] refer to Figure 1 、 2 , illustrating the possible main stages of the GaN wafer manufacturing process.

[0068] In the following, the process according to the present invention will be described with reference to the manufacture of GaN wafers.

[0069] However, it will be apparent to those skilled in the art that the process described below can be used to grow materials including Group 13 nitride layers other than gallium nitride (GaN).

[0070] 1. Manufacturing process

[0071] The process includes:

[0072] - an optional growth stage 10 of a first layer 5a of a Group 13 nitride, preferably GaN;

[0073] - stage 20 of forming the separation zone 4;

[0074] - Stage 30 of resuming epitaxy to form a second thick GaN layer 5 b ;

[0075] - a separation stage 40 to obtain GaN crystals 5;

[0076] - a correction phase 45 to remove the thickness of the second GaN thick layer 5b;

[0077] A finishing phase 50 to form a GaN wafer from the GaN crystal 5 .

[0078] 1.1 Growth stage 10

[0079] The optional growth stage 10 comprises forming the first GaN layer 5a by lateral overgrowth.

[0080] The lateral overgrowth minimizes the defect density contained in the first GaN layer 5 a.

[0081] Methods for reducing the dislocation density in the first GaN layer 5a include:

[0082] - Start the island mode of GaN growth, and then

[0083] - Promote the coalescence of islands to obtain the first GaN layer 5a.

[0084] Advantageously, the lateral overgrowth is achieved on a starting substrate 1 having a non-zero cut-off angle.

[0085] Using a starting substrate 1 with a non-zero cutoff angle allows for growing a first GaN layer 5a with a non-zero cutoff angle.

[0086] The starting substrate 1 may be selected from Si, AlN, GaN, GaAs, Al2O3 (sapphire), ZnO, SiC, LiAlO2, LiGaO2, MgAl2O4, 4H-SiC, or any other type of starting substrate known to the skilled person for achieving gallium nitride growth.

[0087] It may have a thickness of several hundred microns, typically 350 microns. Advantageously, the starting substrate 1 may be treated by nitridation before any deposition step. This improves the quality of the GaN crystal obtained.

[0088] The cut-off angle may be comprised between 0.1 and 5.0 degrees, preferably between 0.2 and 0.8 degrees, even more preferably between 0.3 and 0.6 degrees (particularly in order to limit stacking errors).

[0089] The growth of the first GaN layer 5a can be achieved according to different variants. In particular, the lateral overgrowth can be based on:

[0090] - using a dielectric mask 3a, 3b comprising openings 3a in which islands are formed, as described in document WO 99 / 20816;

[0091] - using a dielectric layer without openings on which islands are formed spontaneously, as described in document EP 1 338 683.

[0092] 1.1.1. The first variant of lateral overgrowth

[0093] In a first variant, the growth stage 10 is an epitaxial lateral overgrowth (hereinafter referred to as ELO).

[0094] ELO comprises the steps of depositing a relatively thick planar layer 2 on a starting substrate 1 .

[0095] The deposition is preferably carried out by metal organic vapor phase epitaxy (MOVPE), for example at a temperature comprised between 500°C and 700°C, in particular at 600°C.

[0096] The deposition of layer 2 reduces the stress between the starting substrate 1 and the subsequently epitaxial first GaN layer 5a. In fact, the deposition of layer 2 on substrate 1 ensures a "soft" transition between substrate 1 and first GaN layer 5a (their crystal structures are different).

[0097] As will become apparent from the following description, the deposition of layer 2 further facilitates the subsequent separation of GaN crystals 5. Layer 2 is, for example, a GaN layer, an AlN layer or an AlGaN layer.

[0098] In a further step, masks 3a, 3b are formed comprising openings 3a. The openings 3a may be in the form of dots or stripes and define locations for the subsequent selective growth of GaN islands.

[0099] Masks 3a, 3b can be made of dielectric materials (such as SiN x The mask is made of silicon (SiN, Si3N4, etc.) or SiO2 or TiN). This minimizes defects generated at the edge of the mask, thereby improving the quality of the GaN layer subsequently grown on it.

[0100] The formation of the masks 3a, 3b can be performed by any technique known to those skilled in the art. For example, the formation of the masks may include:

[0101] Deposition of dielectric layer 3a directly on layer 2 from gaseous silane and ammonia precursors, and

[0102] The dielectric layer 3a is etched by photolithography to form an opening 3a.

[0103] A starting substrate 1 covered with layer 2 and masks 3a, 3b is thus obtained. Besides improving the quality of the first GaN layer 5a (by filtering out defects), the masks 3a, 3b also weaken the interface between the starting substrate 1 and the first GaN layer 5a.

[0104] Another step consists in forming GaN islands through the mask openings 3a. The growth rate along the axis perpendicular to the main plane of the starting substrate 1 is kept higher than the lateral growth rate. This results in islands or strips with a triangular cross section (depending on the shape of the openings 3a). In these strips with a triangular cross section, threading dislocations are bent by 90°.

[0105] Lateral overgrowth is then performed to finally form a planar ELO layer. At the end of this process step, a dislocation density of less than 10 7cm -2 The first GaN layer 5a.

[0106] 1.1.2. Second variant of lateral overgrowth

[0107] In a second embodiment, the growth stage 10 consists of a universal lateral overgrowth (hereinafter referred to as ULO) as described in document EP 1 977 028 .

[0108] ULO comprises the step of depositing a nucleation layer on a starting substrate 1 .

[0109] The nucleation layer is, for example, a very thin silicon nitride SiN film having a thickness of about a few atomic planes, ie about 10 nm to 20 nm. The SiN deposition based on silane and ammonia can last for 360 seconds.

[0110] A continuous buffer layer 2 (eg GaN) is then deposited on the nucleation layer. The deposition of the GaN buffer layer 2 filters out crystal defects and thus minimizes the defect density that will subsequently appear in the first epitaxial GaN layer 5a from the start of the process.

[0111] The thickness of the GaN buffer layer 2 may be between 10 and 100 nm. The temperature during this operation may be between 500 and 700°C.

[0112] Annealing is then performed at a high temperature of 900 to 1150°C. The combined effects of the elevated temperature, the presence of sufficient hydrogen in the carrier gas, and the presence of a very thin SiN film cause the morphology of the GaN buffer layer 2 to undergo a profound change due to solid-phase recrystallization induced by mass transfer. The initially continuous GaN buffer layer 2 then transforms into a discontinuous GaN pattern layer. Due to the very small thickness of the nucleation layer, a GaN pattern or island is obtained that has very good crystalline quality and maintains an epitaxial relationship with the starting substrate.

[0113] The exposed areas of silicon nitride (SiN) are then used as a mask, and the GaN pattern is used as the GaN region located in the openings created ex situ in the mask. Lateral overgrowth is then performed to ultimately form a planar ULO layer.

[0114] This method, in which the silicon nitride mask forms spontaneously and involves the same dislocation bending mechanism as in ELO, is designated "ULO" (or "spontaneous ELO").

[0115] 1.2 Stage 20 of forming separation zone 4

[0116] The process also comprises a stage 20 of forming the separation zone 4 .

[0117] This stage 20 of forming the separation zone can be implemented according to different variants. In particular, the stage 20 of forming the separation zone can be implemented:

[0118] - before the growth stage 10 of the first GaN layer (first variant), or

[0119] - after the growth phase 10 of the first GaN layer (second variant), or

[0120] - During the growth phase 10 of the first GaN layer (third variant).

[0121] 1.2.1. First variant of forming the separation zone 4

[0122] In a first embodiment, the stage 20 of forming the separation zone 4 may consist in depositing a sacrificial intermediate layer before the stage 10 of growing the first GaN layer 5 a , as described in document EP 1 699 951 .

[0123] 1.2.2. Second variant of forming the separation zone

[0124] In the second embodiment, the stage 20 of forming the separation zone 4 comprises an implantation step performed after the stage 10 of growing the first GaN layer 5a. This implantation allows the creation of an embrittled zone in the first GaN layer 5a.

[0125] Implantation consists in bombarding the first GaN layer 5a with ions to create a layer of microcavities (or bubbles) in the semiconductor at a depth close to the average penetration depth of these ions.

[0126] The implanted ions may be selected from tungsten, helium, neon, krypton, chromium, molybdenum, iron, hydrogen, or boron. Preferably, the implanted ions are tungsten ions, which have specific characteristics for decomposing GaN.

[0127] In terms of dose, when the injected ions are H+ ions, the injected ion dose can be between 10 16 to 10 17 cm -2 The implantation depth may vary between 0 nm and 50 nm starting from the free surface (called the growth plane) of the first GaN layer 5 a.

[0128] The implantation of embrittlement ions can be performed in a single step or in successive steps. During the implantation step, the temperature can be between 4K and 1400K.

[0129] The implantation may be followed by an annealing phase to cure the crystal damage produced during the ion implantation, which annealing may be performed at a temperature comprised between 500°C and 1500°C.

[0130] 1.2.3. Third variant of forming the separation zone

[0131] In the third embodiment, the separation region 4 may be formed during the growth phase 10 of the first GaN layer 5 a .

[0132] In particular, when the growth phase is carried out according to the first variant embodiment known as ELO (ie deposition of dielectric masks 3 a , 3 b ), the phase 20 of forming the separation zone 4 may comprise the implantation of the buffer layer 2 before depositing the masks 3 a , 3 b .

[0133] This allows the separation zone 4 to be placed at the precisely desired depth, since the first GaN layer 5a deposited in the ELO step does not "interfere" with the ion implantation.

[0134] Of course, the injection can be performed at different stages of the ELO (or ULO) phase, either within the islands, at an intermediate stage before the islands are fully coalesced, or after the islands are fully coalesced.

[0135] 1.3 Epitaxial recovery stage 30

[0136] At the end of the phase 20 of forming the separation zone 4 and the growth phase 10 of the first GaN layer 5a, the process comprises an epitaxial recovery phase 30 to form a thick GaN layer 5b.

[0137] The process can also start directly at this stage 30 by forming the thick GaN layer 5b, the growth stage 10 and the stage 20 of forming the separation zone being optional. In the following, the application of these stages 10 and 20 is considered.

[0138] This epitaxial recovery can be achieved by:

[0139] -Metal-organic vapor phase epitaxy (MOVPE);

[0140] -Hydride vapor phase epitaxy (HVPE);

[0141] - Closed Space Vapor Transfer (CSVT) extension; or

[0142] -Liquid Phase Epitaxy (LPE).

[0143] In this step, HVPE technology is preferably used, which can achieve three main beneficial effects:

[0144] - The first effect is that the first GaN layer 5a is thickened without losing its crystalline quality (without generating new dislocations or cracks).

[0145] - A second effect is that the dislocation density is further reduced by a factor of at least 2 over 100 μm of GaN growth (0001) during HVPE (ref https: / / doi.org / 10.1143 / APEX.5.095503).

[0146] A third effect is that the thick GaN layer 5 thus obtained may, under certain circumstances, allow spontaneous detachment from its starting substrate 1 at the detachment zone 4 in the event of sublimation or mechanical fracture of said detachment zone during HVPE growth.

[0147] More precisely, the recovery is carried out according to the following process: the temperature is increased in a mixed atmosphere of nitrogen, ammonia and hydrogen. Once a stable temperature of about 1000°C is reached, the growth phase of the thick GaN layer is then initiated by introducing gaseous gallium chloride (GaCl) obtained by reacting HCl with liquid gallium maintained at at least 800°C. GaCl and ammonia are partially pyrolyzed in the growth chamber maintained at a temperature of about 1000°C. As a result, a single-crystalline GaN deposit gradually forms at the level of the nucleation substrate (formed during the first growth phase).

[0148] It is necessary to obtain a GaN film that is thick enough and therefore mechanically resistant enough to avoid the GaN layer from breaking into small pieces during the separation process and to facilitate its handling without the risk of breakage. Under these experimental conditions, the growth lasts several hours to achieve a GaN layer thickness of at least 200 microns, preferably greater than 1 mm.

[0149] The growth is then finalized by diverting the HCl flow externally, and cooling is carried out in an atmosphere composed of nitrogen and ammonia.

[0150] The growth conditions of the second single crystal layer 5b are generally a growth temperature between 900 and 1200°C, and a growth rate between 50 and 500 microns / hour, preferably between 70 and 200 microns / hour.

[0151] The thickness of the original free-standing GaN crystal thus obtained is greater than 200 micrometers, preferably greater than 1 mm, and its maximum thickness is less than 10 mm, or even less than 5 mm.

[0152] The original free-standing GaN crystal thus obtained has a diameter greater than 50 mm, preferably greater than 100 mm, and a maximum diameter less than 250 mm, or even less than 200 mm.

[0153] Under these conditions, doping is performed by adding n-doping elements according to the following method:

[0154] - By controlling the purity of the Group III precursors and by controlling the oxygen supply and concentration by very thoroughly purging the reactor before growth under vacuum at a residual pressure below 500 Torr.

[0155] For germanium: from solid sources, GeCl4, germanium, tetramethylgermanium, isobutylgermane, and their derivatives. These dopant gases are then evaporated in the reaction chamber. Preferably, these dopant gases can be pre-mixed with the GaCl stream in the vapor phase to improve the uniform distribution of the dopant stream in the growth chamber.

[0156] In the case of gaseous precursors, the gas tank is maintained at a pressure between 1 and 3 bar and a flow of carrier gas (N2 and / or H2) is applied at a flow rate between 0.25 and 20 sccm.

[0157] For silicon, silane, dichlorosilane, silicon tetrachloride, and their derivatives, evaporated in the reaction chamber. In the case of dichlorosilane (1%, diluted in 99% N2 (or H2)), a flow rate of between 1 and 20 sccm is applied. These dopant gases can preferably be mixed with the GaCl flow in the gas phase to improve the uniform distribution of the dopant flow in the growth chamber.

[0158] - Silicon and germanium can be introduced together to form a 3-dopant system.

[0159] 1.4 Separation stage 40

[0160] A separation stage 40 is also implemented, which depends on the variant implemented for the stage 20 of forming the separation zone 4 .

[0161] In the case of ion implantation, a spontaneous separation phase 40 occurs due to the thermal cycles (high temperature epitaxial recovery and cooling) experienced by the thickened GaN layer 5, which generates stress due to the difference in thermal expansion coefficients between the starting substrate 1 and the thickened GaN layer 5, leading to their separation.

[0162] In the case of deposited sacrificial intermediate layers, this separation occurs during the epitaxial process by spontaneous vaporization of the intermediate layer or by mechanical fracture at the level of the so-called sacrificial layer.

[0163] In the case of post-growth separation, a laser can be used to evaporate the sacrificial layer.

[0164] Get as Figure 3 The free-standing GaN crystal 5 is shown.

[0165] As is common in HVPE, the GaN crystal 5 comprises, on the front side 52 , protrusions 51 in the form of hexagonal pyramids.

[0166] Figure 3 The crystal shown in FIG5 is curved and has a radius of curvature (the radius of curvature of the front face 52 and the radius of curvature of the crystal face opposite said front face 52 ) of less than 25 meters and preferably less than 20 meters.

[0167] exist Figure 3In the example, the radius of curvature is 5 meters or more; in addition, the threading dislocation density of crystal 5 is 10 7 cm -2 or smaller, preferably smaller than 5×10 6 cm -2 .

[0168] GaN crystal 5 formed on a starting substrate having a non-zero cutoff angle also has a non-zero cutoff angle, with the orientation of the crystal planes propagating from one layer to the next. For example, in the case of a sapphire substrate 1 having a cutoff angle of 4 degrees, the growth plane of crystal 5 has a cutoff angle of 4 degrees, preferably between 0.1 and 1 degrees, across its entire surface.

[0169] 1.5 Correction Stage 45

[0170] The GaN crystal 5 is straightened once it has been separated from the starting substrate 1. Current technology allows controlled removal of layer thicknesses of around 10 microns.

[0171] 1.6 Finishing stage 50

[0172] Finishing operations are then performed to form the GaN wafer.

[0173] Straighten and polish the back and sides or edges of the insert to a surface finish acceptable for the application.

[0174] The proposed process is therefore particularly suitable for manufacturing wafers of semiconductor materials, in particular wafers of materials of elements from Groups 13 and 15 of the periodic table, more particularly wafers consisting of Group 13 nitrides, preferably GaN, with large diameters, the large diameter being greater than 50 mm, exceeding 100 mm or even 150 to 200 mm.

[0175] According to the process of the present invention, the Figure 3 The semiconductor material wafer has a thickness of 200 to 2000 microns and excellent crystal quality, so that the half-maximum width of the X-ray diffraction (XRD) peak of the (002) line of the GaN film (0001) near the angle ω under symmetric conditions is less than 130 arc seconds.

[0176] According to another possible process, by way of illustration and in contrast to the process described previously, the single-crystalline material according to the invention is obtained by growth on a starting substrate or seed crystal (for example sapphire) on which a GaN nitride layer, preferably at least a few microns and less than 10 microns, has preferably already been deposited. The growth is carried out in an HVPE type reactor. The epitaxial deposition is carried out under the same conditions as in stage 30 above, but for a longer time, so as to form a layer of several millimeters.

[0177] The crystal undergoes a trimming operation and is then cut into several wafers, typically 100 to 600 microns thick, using either a loose wire saw (abrasive grains immersed in a slurry of wire before cutting) or a fixed wire saw (abrasive grains pre-fixed to the wire). The finishing steps (pre-polishing, polishing) are similar to those described above.

[0178] The invention and its advantages are illustrated by the following examples. The examples according to the invention should not be considered as limiting its implementation.

[0179] Exemplary embodiments

[0180] In Example 1 (Comparative Example), GaN growth was carried out by HVPE based on a substrate such as that described in WO / 03100839A2, according to a method such as that described in the publication preferably incorporated in step (iii). The (volume) flow ratio of N2 / (N2+H2) was 0.2. In addition, in the present case, the growth temperature was maintained at 930°C. The structure of the growth front FC observed by scanning electron microscopy is shown in FIG. Figure 4a and 4b shown.

[0181] Figure 4c The structure of a wafer according to the invention after rectification and polishing is depicted, showing a first region resulting from growth of non-basal planes and a region resulting from growth of basal planes.

[0182] In Example 2 (Comparative Example), unlike the previous examples, Figure 1 During the HVPE growth phase shown in step 30 , oxygen is introduced into the gas phase (eg, 1% O 2 diluted in a 99% N 2 flow, delivered at 0.2 sccm to 10 sccm) to introduce n-type doping in the GaN material.

[0183] In Example 3 (according to the present invention), unlike the previous examples, germanium was also introduced in the form of GeCl4 at a flow rate of 2 seem to allow co-doping of the GaN material until the end of the HVPE growth.

[0184] From targeted SIMS measurements of the substrate facet area (0001) and non-substrate areas, we can estimate the corresponding atomic weights of incorporation. To this end, an ion beam is applied to the surface to locally ionize a portion of the material. This enables analysis of its constituent atoms (alloys, dopants, or impurities). The measurement line is spread over a length of approximately 0.9 mm. The selected incident ion beam allows analysis of the material's composition within a circle with a diameter of approximately 10 μm and a depth of approximately 1 μm. The spacing between each pit of the line (or impact point of the ion beam) is approximately 50 μm.

[0185] Using this scheme, and because GaN regions produced by basal-plane growth are denser than those produced by non-basal-plane growth, at least one SIMS measurement was performed in the GaN region (0001) produced by basal-plane growth. Once the measurement was completed, the analyzed area was imaged by cathodoluminescence in order to unambiguously attribute the SIMS measurements to the different GaN regions.

[0186] In addition, the free carrier density and average resistivity of the GaN layer measured by the Van der Pauw method are also shown in Table 1 below: [Table 1]

[0187]

[0188] Table 1: SIMS measurements of NID (or non-doped), O-doped, and O+Ge-doped samples; LOD = limit of detection (6*10 15 cm -3 )

[0189] The XRD crystal quality was determined by the half-width at half maximum of the X-ray diffraction peak of the (002) line near the angle ω under symmetric conditions of the (0001) GaN plane.

[0190] It is observed that, unlike the non-basal 3D growth region, the amount of oxygen in the (0001) plane increases only slightly with doping.

[0191] When Ge is introduced, a similar Ge concentration is obtained in the growth region of the (0001) plane compared to the growth region of the non-basal plane.

[0192] Examples 2 and 3 have similar properties (free carrier density and resistivity) on average and are improved compared to Example 1, but Example 3 according to the present invention shows a much more uniform dopant distribution while exhibiting very satisfactory crystalline quality and an acceptable surface density of macroscopic inclusions.

[0193] Furthermore, according to the inventors' experiments, the minimum concentration of Ge or Si atoms in the facet region (0001) is preferably higher than 1.0×10 17 atoms / cm 3 The maximum concentration of O atoms in the region resulting from non-basal growth is preferably less than 2.0 × 10 18 atoms / cm 3 Therefore, the average resistivity of the GaN layer can be reduced to less than 25 mohm.cm, or even less than 20 mohm.cm, while keeping the cumulative concentration of O, Si, and Ge atoms in the two domains below 1.0×10 19 atoms / cm 3 In addition, the concentration of Ge+Si atoms can be higher than 2.0×10 17 atoms / cm 3, preferably higher than 8.0×10 17 atoms / cm 3 In addition, the concentration of O atoms may preferably be less than 1.0×10 18 atoms / cm 3 .

[0194] Raman measurements of the region resulting from faceted growth (0001) were also performed using a Thermo DXRxi Raman spectrometer. This spectrometer is dedicated to fast Raman imaging, with a maximum acquisition capacity of 600 spectra per second. In one configuration, analysis was performed using a 532 nm laser with 10 mW power. The laser beam was focused on the sample through a microscope providing 50x magnification.

[0195] It is well known that changes in free carrier density affect the position of the A1(LO) peak in the GaN Raman spectrum. As the wave number increases, the sample has a higher free carrier density. Figure 5a and 5b The variation of the position of the Al(LO) peak as a function of the doping rate in relation to the GeCl4 flow rate is shown. It is noteworthy that the position of the Al(LO) peak in the faceted regions (0001) does not change when doping is performed solely by oxygen, so it can be estimated that the free carrier density in these regions is similar to that of a sample without intentional doping. When doping is performed in a mixed manner (germanium + oxygen in this case), the position of the peak changes, which indicates that the number of free carriers in the faceted regions (0001) increases. Thus, the single crystal according to Example 3 of the present invention has a density of >734 cm-1 over its entire surface. -1 The Raman peak A1(LO) of

[0196] Example 4 and Figure 6 It is shown that increasing the volume flow ratio of N2 / (N2+H2) in the reaction chamber increases the doping in the region resulting from facet (0001) growth.

[0197] Therefore, the present invention allows basal (0001) and non-basal planes to coexist within the same three-dimensional growth front during HVPE growth of GaN, while having more uniform optical and electrical properties than simple oxygen doping after shaping the GaN layer and obtaining a two-dimensional surface.

[0198] The advantage of increased uniformity in material properties is improved current distribution in LEDs, lasers, and power transistors made from our products. For optical applications, it also leads to improved uniformity in the absorption of GaN layers.

[0199] Both advantages are beneficial when manufacturing devices because the characteristics of the devices do not vary significantly within the same wafer.

Claims

1. A method for producing a single crystal semiconductor material of a Group 13 nitride, comprising the following steps: depositing at least one single-crystalline layer on a starting substrate by three-dimensional epitaxial growth, said single-crystalline layer comprising regions resulting from basal plane growth having faces perpendicular to the direction of a growth front formed by a basal plane (0001) and regions resulting from face growth of differently oriented faces, referred to as non-basal planes, having faces not perpendicular to the direction of the growth front; and supplying an n-dopant gas containing a first chemical element selected from the chemical elements of Group 16 of the periodic table and at least one second chemical element selected from the chemical elements of Group 14 of the periodic table so that the concentration of the second chemical element in the region produced by the basal plane growth is higher than 1.0×10 17 / cm 3 , and the concentration of the first chemical element in the region generated by non-basal plane growth is less than 2.0×10 18 / cm 3 , wherein the semiconductor material has a (silicon + germanium) / oxygen atomic ratio between 0.5 and 5, and wherein the depositing of at least one single crystal layer is carried out under the following conditions: growth rates below 450 μm / h via hydride vapor phase epitaxy; At temperatures between 910°C and 1035°C; in a reactor having a residual pressure between 100 and 500 Torr; and The Group V precursor and the Group III precursor are supplied at a molar flow ratio of the Group V precursor to the Group III precursor of between 13 and 25.

2. The manufacturing method according to claim 1, wherein the second chemical element of the n-dopant gas is germanium, formed from a solid source, GeCl4, germane, tetramethylgermanium and isobutylgermane and their derivatives, and the second chemical element of the n-dopant gas is silicon, formed from a solid source, silane, dichlorosilane, silicon tetrachloride and their derivatives. The manufacturing method according to claim 1 , wherein the first chemical element of the n-dopant gas is oxygen. The manufacturing method according to claim 1 , wherein the n-dopant gas is mixed with the gallium chloride gas flow in a gas phase.

5. A method for manufacturing a semiconductor substrate of a Group 13 nitride, comprising the following steps: The method for producing a single crystal semiconductor material of a Group 13 nitride according to claim 1, wherein the single crystal semiconductor material of the Group 13 nitride is produced on the starting substrate. separating the single crystal material from the starting substrate; and The thickness of the single crystal material is corrected by cleaning to obtain Group 13 nitride wafers having a thickness between 250 microns and 2000 microns.

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