N-doped semiconductor substrate

Abstract

1. A process for producing a monocrystalline semiconductor material of a Group 13 nitride, in particular gallium nitride, comprising the steps of depositing at least one monocrystalline layer on a starting substrate by three-dimensional epitaxial growth, said layer comprising regions resulting from growth of a basal facet and regions resulting from growth of facets with various orientations, called non-basal facets; and 2. Depositing an n-dopant gas having 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 said second chemical element in the region resulting from growth of the basal facet is 1.0×10 17 / cm 3 and the concentration of the first chemical element in the region resulting from the growth of the non-basal facet is 2.0×10 18 / cm 3 and providing the temperature so that the temperature is lower.

Description

Technical Field

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

[0002] These wafers are used as substrates for manufacturing semiconductor structures such as light-emitting diodes (LEDs), laser diodes (LDs), vertical transistors for power electronics, lateral transistors for power electronics or telecommunications (radio frequency), current rectifying diodes or sensors.

Background Art

[0003] The processes currently carried out for manufacturing semiconductor material substrates based on nitrides of Group 13 or IIIA elements are based on vapor deposition techniques, specifically heteroepitaxy techniques for growing crystals such as gallium nitride (GaN) crystals on starting substrates having different properties, such as sapphire substrates.

[0004] These methods involve systems that inject at least two different gas components that can interact before deposition.

[0005] For example, the following known methods can be mentioned. · Metalorganic vapor phase epitaxy (MOVPE) · Hydride vapor phase epitaxy (HVPE) · Closed-space vapor transport (CSVT) · Ceramic vapor phase growth

[0006] In so-called 3D growth processes, for example, methods of growing laterally in three dimensions, the dislocation density can be reduced to less than 10 7 / cm 2 .

[0007] Under the conditions of three-dimensional growth, the growth front by HVPE has a facet perpendicular to the growth front and a facet inclined with respect to the growth front. The facet perpendicular to this growth front is a facet formed by the basal plane (0001), and it is known that it contains less oxygen than various inclined facets (non-basal planes, indices hkil: h≠0 and k≠0 and i≠0). Due to this difference in n-type doping, a region with a higher resistivity than others, or a region with different optical properties, is generated. For example, after forming a two-dimensional surface by polishing and / or buffing, it can be observed that the optical and / or electrical properties are non-uniform.

[0008] In addition, the crystal lattice may have macro-inclusions with a size exceeding 10 μm mainly composed of twins, polarization inversions, or even polycrystals. Doping can lead to an increase in the presence of such defects in the crystal lattice.

[0009] Any of these defects generated during the growth process may induce imperfections (non-uniformity of doping and crystal defects, high dislocation density as it is) in the final wafer, which will induce problems in the manufacture of optoelectronic and / or electronic components.

[0010] To improve the optoelectronic properties of the substrate, US2006255339A1, for example, discloses an n-doped GaN crystal having a concentration of 0.7×10 18 ~about 3×10 18 / cm 3 and a thermal conductivity of at least 1.5 W / cm·K so that a device, specifically a diode with an output greater than 1 W, can be equipped. Only an example of Si doping is described in this application, but dopants such as Si, O, Ge, C, etc. can be used alone or in combination.

[0011] US20110175200A1 presents a HVPE growth process in which crystals are doped with Ge by adding GeCl4 into a reactor to obtain more electron-conductive crystals and compensate for the sharp increase in resistivity observed when the growth rate is higher than 450 μm / h. However, such a growth rate increases the surface concentration of macro-inclusions and degrades the crystal quality.

[0012] US9461121B2 claims a process for improving the dispersion state of n-dopants in GaN crystals by vapor-phase growth by mixing the introduced Ga and dopants. Uniform incorporation into the reactor is achieved by pre-mixing the dopant and Ga before the reaction with HCl or by mixing the dopant and gallium halide in a single tube into the reactor. The uniformity of the dopant concentration is measured by micro-Raman, microwave detection photoconductivity (MDP) or micro-photoluminescence. From the described method data, it is clear that the patent is a HVPE process involving 2D growth and thus does not present a solution for a 3D growth process.

Summary of the Invention

Problems to be Solved by the Invention

[0013] Thus, there is a need for wafers and substrates made of Group 13 or Group III nitride materials, specifically wafers and substrates made of Group 13 or Group III nitride materials, more specifically having a large thickness, usually exceeding 100 micrometers, and further 400 micrometers or more, obtained under three-dimensional growth conditions, with higher uniformity, and simultaneously having the following: · Usually less than 5 cm -2 Preferably less than 4 cm -2 Or even less than 1 cm -2 Low surface density of macro-inclusions · For example, the full width at half maximum (FWHM) of the X-ray diffraction (XRD) peak of the (002) line at an angle ω in a symmetric state with respect to the GaN (0001) plane is less than 130 arcsec, or, for example, the full width at half maximum (FWHM) of the X-ray diffraction (XRD) peak of the 201 line at an angle ω in an inclined state with respect to the GaN (0001) film is less than 240 arcsec, preferably less than 140 arcsec, better crystal quality, and · Improved electronic properties, usually an average electrical resistivity of less than 25 mohm·cm, or even less than 20 mohm·cm.

Means for Solving the Problem

[0014] Therefore, an object of the present invention is a process for manufacturing a single-crystalline semiconductor material composed of a Group 13 nitride, particularly GaN, having the following steps. · Depositing at least one single-crystalline layer on a starting substrate by three-dimensional epitaxial growth, wherein the layer has a region having a facet perpendicular to the direction of the growth front formed by the basal plane (0001) due to the growth of basal facets, and a region having a facet non-perpendicular to the direction of the growth front due to the growth of facets having various orientations called non-basal facets. · Supplying an n-dopant gas having a first chemical element selected from chemical elements of Group 16 of the periodic table and at least one second chemical element selected from chemical elements of Group 14 of the periodic table such that the concentration of the second chemical element in the region due to the growth of basal facets is higher than 1.0×10 17 / cm 3 and the concentration of the first chemical element in the region due to the growth of non-basal facets is lower than 2.0×10 18 / cm 3 .

[0015] Unless otherwise specified, the chemical element concentrations described in the text are atomic concentrations as a method of representation.

[0016] Advantageously, but optionally, the process of the present invention may further include at least one of the following features. · The second chemical element of the n-dopant gas is germanium formed from solid sources of germanium tetrachloride, germane, tetramethylgermanium and isobutylgermanium, and their derivatives, and / or the second chemical element of the n-dopant gas is silicon formed from solid sources of silane, dichlorosilane and silicon tetrachloride, and their derivatives. · The first chemical element of the n-dopant gas is oxygen. · The supply and concentration of oxygen are controlled by controlling the purity of the Group III precursor and by performing one or more very thorough purges at a residual pressure of less than 10 Torr, followed by removing the N2 in the reactor one or more times.

[0017] In the presence of the simultaneous addition of the dopant and oxygen according to the present invention, the concentration of the n-dopant is no longer equally distributed between the (0001) facet and the non-basal facet. · The n-dopant gas is mixed with a gallium chloride gas stream in the gas phase. · The epitaxial growth is carried out by HVPE at a growth rate of less than 450 μm / h in order to reliably reduce the surface density of macro-inclusions and obtain satisfactory crystal quality. · The epitaxial growth is carried out by HVPE at a temperature of 910 °C to 1035 °C, preferably 925 °C to 1015 °C. Preferably, the molar flow rate ratio of the Group V precursor to the Group III precursor is 13 to 25. Preferably, the reactor is also maintained at a residual pressure of 100 to 500 Torr. Such conditions are particularly suitable for obtaining wafers in which the variation of the atomic ratio (silicon + germanium) / oxygen is controlled and a high atomic ratio is possible under substantially three-dimensional growth conditions, resulting in a wafer having a growth region with a surface composed of basal facets that is preferably less than 50%, or even less than 30%, and preferably 5 to 25% of the upper surface of the wafer.

[0018] The object of the present invention is also a process for manufacturing a semiconductor substrate made of a Group 13 nitride, in particular GaN, having the following steps. · A step of manufacturing a single-crystalline semiconductor material composed of a Group 13 nitride on a starting substrate according to the above characteristics. · A step of separating the single-crystalline semiconductor material from the starting substrate. · A step of adjusting the thickness of the single-crystalline material by removing it to obtain a Group 13 nitride wafer having a thickness of 250 μm to 2000 μm.

[0019] Further, an object of the present invention is also a wafer made of a two-dimensional Group 13 nitride, particularly gallium nitride, obtained by three-dimensional epitaxial growth. The wafer includes a region having a facet perpendicular to the direction of the growth front formed by the basal plane (0001) due to the growth of the basal facet, and a region having a facet with various orientations known as non-basal facets and having a facet non-perpendicular to the direction of the growth front due to the growth of the non-basal facets, and has the following characteristics. · The region due to the growth of the non-basal facet contains a first chemical element selected from the chemical elements of Group 16 of the periodic table, and the concentration of the first chemical element is 2.0×10 18 / cm 3 and less. · The region due to the growth of the basal facet contains at least one second chemical element selected from the chemical elements of Group 14 of the periodic table, and the concentration of the second chemical element is 1.0×10 17 / cm 3 and greater.

[0020] Advantageously but optionally, the wafer according to the present invention may further include at least one of the following characteristics. · The concentration of the second chemical element in the region due to the growth of the basal facet is greater than 2.0×10 17 / cm 3 and the concentration of the first chemical element in the region due to the growth of the non-basal facet is less than 1.0×10 18 / cm 3 and less. · The cumulative concentration of the first and second chemical elements is less than 2.0×10 19 / cm 3 and preferably less than 1×10 19 / cm 3is less than, or even 5.0×10 18 / cm 3 less than, and good electrical conductivity / resistivity and light transmittance can be obtained. · The second chemical element is germanium and / or silicon. · The atomic ratio (silicon + germanium) / oxygen is about 0.5 to 30, preferably about 0.5 to 20, more preferably about 0.5 to 15, still more preferably about 0.5 to 10, and most preferably about 0.5 to 5. · The basal facet growth region is less than 60% of the upper surface of the wafer, preferably less than 50%, or less than 30%, and preferably 5% to 25%. The surface ratio of the region composed of the basal plane can be measured along plane c according to the figure shown in FIG. 4c, for example. · The crystal quality measured by the full width at half maximum of the X-ray diffraction (XRD) peak of the (002) line at an angle ω symmetric to the GaN(0001) plane is less than 130 arcsec, preferably less than 100 arcsec, preferably less than 90 arcsec, or even less than 60 arcsec, and the crystal quality measured by the full width at half maximum of the X-ray diffraction (XRD) peak of the 201 line at an angle ω inclined to the GaN film (0001) is less than 240 arcsec, preferably less than 140 arcsec, or even less than 100 arcsec. · The average electrical resistivity of the material of the wafer is less than 25 mohm·cm. · Cracks correspond to the cleavage inside the crystal, but there are no cracks exceeding 200 micrometers in the polished wafer.

[0021] The present invention also relates to the use of a group 13 or group III nitride wafer according to one of the aforementioned features as a substrate for manufacturing optoelectronic and / or electronic components such as light-emitting diodes, laser diodes, vertical transistors for power electronics, lateral transistors for power electronics or telecommunications (radio frequency), current rectifying diodes or sensors.

[0022] Other features, objects, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, which are by way of non-limiting illustration.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4a

Figure 4b

Figure 4c

Figure 5a

Figure 5b

Figure 6

Mode for Carrying Out the Invention

[0024] Referring to FIGS. 1 and 2, an example of the main stages of the GaN wafer manufacturing process is shown.

[0025] Hereinafter, the process according to the present invention will be described in relation to the manufacture of GaN wafers. However, it will be readily apparent to those skilled in the art that a material containing a layer of group 13 nitride other than gallium nitride GaN can be grown using the process described below.

[0026] 1. Manufacturing process This process consists of the following steps. · Step 10 of growing a first layer 5a made of a group 13 nitride, preferably GaN, which is optional · Step 20 of forming a separation region 4 · Step 30 of restarting epitaxy and forming a second thick layer 5b made of GaN · Separation step 40 for obtaining a GaN crystal 5 · Polishing step 45 for removing the thickness of the second thick layer 5b made of GaN · Finishing step 50 for forming a GaN wafer from the GaN crystal 5

[0027] 1.1. Growth stage 10 The growth step 10 is optional and is a step of forming the first GaN layer 5a by lateral overgrowth.

[0028] By laterally overgrowing, the density of defects contained in the first GaN layer 5a is minimized.

[0029] The methods used to reduce the dislocation density in the first GaN layer 5a consist of the following. · Start the island mode of GaN growth and then · Promote the coalescence of the islands to obtain the first GaN layer 5a.

[0030] Advantageously, the lateral overgrowth is carried out on a starting substrate 1 having a non-zero truncation angle.

[0031] By using a starting substrate 1 having a non-zero truncation angle, a first GaN layer 5a having a non-zero truncation angle can be grown.

[0032] 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 those skilled in the art on which gallium nitride can be grown.

[0033] The starting substrate 1 may have a thickness of several hundred micrometers, generally 350 micrometers.

[0034] Advantageously, the starting substrate 1 may be nitrided before the deposition step. This improves the quality of the resulting GaN crystal.

[0035] The truncation angle may be 0.1 to 5.0 degrees, preferably 0.2 to 0.8 degrees, and even more preferably 0.3 to 0.6 degrees (especially to limit the stacking error).

[0036] The growth of the first GaN layer 5a can be carried out in various modifications. In particular, the lateral overgrowth can be carried out based on the following. · Use of dielectric masks 3a, 3b having openings 3a on which islands are formed, as described in WO 99 / 20816. · Use of a dielectric layer without openings in which islands are spontaneously formed, as described in European Patent No. 1 338 683.

[0037] 1.1.1. First modification example of lateral overgrowth In a first variant, the growth stage 10 consists of epitaxial lateral overgrowth (hereinafter referred to as ELO).

[0038] ELO includes the step of depositing a thick planar layer 2 on the starting substrate 1.

[0039] This deposition is preferably carried out by metalorganic vapor phase epitaxy (MOVPE) at a temperature of, for example, 500 to 700 °C, especially 600 °C.

[0040] By depositing layer 2, the stress between the starting substrate 1 and the first GaN layer 5a that will be epitaxially formed later is reduced. In fact, by depositing layer 2 on substrate 1, it becomes possible to "softly" transition between substrate 1 and the first GaN layer 5a, which have different crystal structures respectively.

[0041] Furthermore, by depositing layer 2, as will become clear from the following description, the separation of the GaN crystals 5 that will be carried out later becomes easier. Layer 2 is, for example, a GaN layer, an AlN layer or an AlGaN layer.

[0042] In another step, masks 3a, 3b including an opening 3a are formed. The opening 3a may be dot-shaped or strip-shaped and defines the position where GaN islands will grow selectively later.

[0043] The masks 3a, 3b are, for example, SiN xIt may also be a mask made of a dielectric material such as (SiN, Si3N4, etc.), or SiO2, or TiN. This minimizes the defects generated at the edges of the mask and improves the quality of the GaN layer epitaxially formed on the mask later. The formation of masks 3a and 3b can be performed by any technique known to those skilled in the art. For example, the formation of the mask may be composed of the following steps. · Depositing a dielectric layer 3a directly onto layer 2 from gaseous silane and ammonia precursors, and · Etching the dielectric layer 3a by photolithography to form an opening 3a.

[0044] In this way, a starting substrate 1 covered with layer 2 and masks 3a and 3b is obtained. Masks 3a and 3b not only improve the quality of the first GaN layer 5a (by removing through defects), but also smooth the interface between the starting substrate 1 and the first GaN layer 5a.

[0045] Another step is to form GaN islands through the openings 3a of the mask. The growth rate along the axis perpendicular to the main surface of the starting substrate 1 is kept higher than the lateral growth rate. This results in island-shaped or strip-shaped structures having a triangular cross-section (depending on the shape of the opening 3a). Within these strip-shaped structures having a triangular cross-section, the threading dislocations bend by 90 degrees.

[0046] Next, lateral overgrowth is performed, finally resulting in a flat ELO layer. At the end of this step in the process, a first GaN layer 5a with a dislocation density of less than 10 7 cm -2 is obtained.

[0047] 1.1.2. Second modification example of lateral overgrowth In the second embodiment, the growth stage 10 consists of Universal Lateral Overgrowth (hereinafter referred to as ULO) described in European Patent No. 1 977 028.

[0048] The ULO includes the step of depositing a nucleation layer on the starting substrate 1.

[0049] The nucleation layer is, for example, a very thin silicon nitride SiN film on the order of a few atomic planes, i.e., on the order of 10 nm to 20 nm in thickness. The deposition of SiN by silane and ammonia can continue for 360 seconds.

[0050] Next, a continuous buffer layer 2 made of, for example, GaN is deposited on this nucleation layer. By depositing the GaN buffer layer 2, crystal defects are removed, thereby minimizing the density of defects that will later be included in the first epitaxial GaN layer 5a from the initial stage of this process.

[0051] The thickness of this GaN buffer layer 2 may be 10 to 100 nm. The temperature during deposition can be 500 to 700 °C.

[0052] Next, annealing is performed at a high temperature of 900 to 1150 °C. Under the combined effect of the temperature rise, a sufficient amount of hydrogen in the gaseous carrier, and the presence of a very thin SiN film, the morphology of the GaN buffer layer 2 undergoes a significant modification from solid-phase recrystallization by mass transport. And the initially continuous GaN buffer layer 2 is converted into a discontinuous layer having a GaN pattern. In this way, GaN patterns, that is, islands, with very good crystal quality in which the epitaxial relationship with the starting substrate is maintained due to the very thin nucleation layer are obtained.

[0053] As a result, the region where silicon nitride SiN is exposed functions as a mask, and the GaN pattern functions as a GaN region located in the opening formed ex situ within the mask. Next, lateral overgrowth is performed, and finally a flat ULO layer is obtained.

[0054] This method in which a silicon nitride mask is spontaneously formed and has the same dislocation bending mechanism as ELO is called "ULO" (or "spontaneous ELO").

[0055] 1.2. Stage 20 of forming the separation region 4 This process further has a step 20 of forming a separation region 4.

[0056] This step 20 of forming the separation region can be implemented by various modifications. Specifically, the step 20 of forming the separation region can be implemented in any of the following. · Before the growth step 10 of the first GaN layer (first modification) · After the growth step 10 of the first GaN layer (second modification) · During the growth step 10 of the first GaN layer (third modification)

[0057] 1.2.1. First modification example of forming the separation region 4 In the first embodiment, the step 20 for forming the separation region 4 may be to deposit a sacrificial intermediate layer before the growth step 10 of the first GaN layer 5a, as described in European Patent No. 1 699 951.

[0058] 1.2.2. Second modification example of forming the separation region In the second embodiment, the step 20 of forming the separation region 4 includes an implantation step that is performed after the growth step 10 of the first GaN layer 5a. By this implantation, a brittle region can be formed in the first GaN layer 5a.

[0059] Implantation means colliding ions with the first GaN layer 5a and forming a layer of microcavities (or bubbles) in the semiconductor at a depth close to the average penetration depth of these ions.

[0060] The ions to be implanted may be selected from tungsten, helium, neon, krypton, chromium, molybdenum, iron, hydrogen, or boron. Preferably, the implanted ions are tungsten ions. These have the specific characteristic of decomposing GaN.

[0061] Regarding the dose amount, when the ions to be implanted are H + is the case, the implantation dose amount is 10 16~10 17 cm -2 and the depth of implantation is from 0 to 50 nm from the free surface (referred to as the growth surface) of the first GaN layer 5a.

[0062] The implantation of embrittling ions may be carried out in one step or in successive steps. The temperature during implantation can be 4 to 1400 K.

[0063] Subsequent to implantation, annealing may be carried out to recover the crystal damage generated during ion implantation. The annealing can be performed at a temperature of 500 to 1500 °C.

[0064] 1.2.3. Third modification example of forming the separation region In the third embodiment, the separation region 4 can be formed during the growth stage 10 of the first GaN layer 5a.

[0065] Specifically, when the growth stage is carried out by a first variant embodiment known as ELO (i.e., deposition of the dielectric masks 3a, 3b), the step 20 of forming the separation region 4 can perform implantation of the buffer layer 2 before the deposition of the masks 3a, 3b.

[0066] Thereby, the separation region 4 can be accurately disposed at a desired depth. This is because the first GaN layer 5a deposited in the ELO step does not "interfere" with the ion implantation.

[0067] Of course, the implantation can be carried out at different aspects of the ELO (or ULO) stage, i.e., within the islands, at an intermediate stage where the islands are not fully merged, or after all the islands have merged.

[0068] 1.3. Epitaxy restart stage 30 At the end of the step 20 of forming the separation region 4 and the growth stage 10 of the first GaN layer 5a, the process has an epitaxial resumption step 30 for forming a thick GaN layer 5b.

[0069] Alternatively, this process may start directly from this step 30 by forming a thick GaN5b layer, in which case the growth stage 10 and the stage 20 of forming the separation region are optional. In the following description, it is assumed that these stages 10 and 20 are implemented.

[0070] This restart of epitaxy can be carried out by any of the following methods. · Metal-organic vapor phase epitaxy (MOVPE) · Hydride vapor phase epitaxy (HVPE) · Closed space vapor transport (CSVT) · Liquid phase epitaxial growth (LPE)

[0071] In this step, it is preferable to use the HVPE technology that enables mainly the following three advantageous effects. · The first effect is that the first GaN layer 5a is formed thick without degrading the crystal quality (no new dislocations or cracks occur). · The second effect is that during HVPE, the dislocation density is further reduced by at least a factor of 2 beyond 100 μm of GaN growth (0001) (Reference: https: / / doi.org / 10.1143 / APEX.5.095503). · The third effect is that when sublimation or mechanical breakdown occurs in the separation region 4 during HVPE growth, spontaneous separation from the starting substrate 1 can occur in the resulting thick GaN5 layer at the separation region 4.

[0072] More specifically, the restart of epitaxy is carried out by the following process. The temperature is raised in a mixed atmosphere of nitrogen, ammonia and hydrogen. When a stable temperature of about 1000 °C is reached, the growth stage of the thick GaN layer is started by introducing gallium chloride (GaCl) obtained by reacting HCl with liquid gallium maintained at a temperature of at least 800 °C into the gas phase. GaCl and ammonia are partially thermally decomposed in the growth chamber maintained at a temperature of about 1000 °C. In this way, single-crystalline GaN deposits are gradually formed at the nucleation substrate level (formed in the first growth stage).

[0073] It is necessary to obtain a GaN film that has a sufficient thickness to avoid the GaN layer breaking into pieces during separation and can be easily handled without the risk of damage, and thus is sufficiently resistant from a mechanical perspective. The growth continues for several hours under these experimental conditions, causing the GaN layer to reach a thickness of at least 200 microns, preferably exceeding 1 millimeter.

[0074] Next, the flow of HCl is diverted externally to finally complete the growth, and cooling is performed in an atmosphere consisting of nitrogen and ammonia.

[0075] The growth conditions for this second single-crystalline layer 5b are usually such that the growth temperature is 900 - 1200 °C, and the growth rate is 50 - 500 micrometers / h, preferably 70 - 200 micrometers / h.

[0076] The thickness of the thus-obtained self-supported GaN primary crystal is greater than 200 μm, preferably greater than 1 mm. The maximum thickness is less than 10 mm, or even less than 5 mm.

[0077] The diameter of the thus-obtained self-supported GaN primary crystal is greater than 50 mm, preferentially greater than 100 mm. Its maximum diameter is less than 250 mm, or even less than 200 mm.

[0078] Under these conditions, doping is carried out by adding an n-doping element according to the following process. · The supply and concentration of oxygen are controlled by controlling the purity of the group III precursor and by performing a very thorough purge of the reactor under a vacuum with a residual pressure of less than 500 torr before growth. · In the case of germanium, it is formed from solid sources, GeCl4, germane, tetramethylgermanium and isobutylgermanium, and their derivatives. Next, these dopant gases are vaporized in the reaction chamber. Preferably, these dopant gases may be premixed with the GaCl stream in the gas phase, and the doping stream in the growth chamber can be more uniformly dispersed.

[0079] In the case of gaseous precursors, the gas tank is maintained at a pressure of 1 to 3 bar, and a flow of carrier gas (N2 and / or H2) with a flow rate of 0.25 to 20 sccm is applied. · In the case of silicon, it is formed from silane, dichlorosilane and silicon tetrachloride, and their derivatives, which are vaporized in the reaction chamber. For dichlorosilane (diluted 1% in 99% N2 (or H2)), a flow of 1 to 20 sccm is applied. Preferably, these dopant gases may be mixed with the GaCl stream in the gas phase, and the doping stream in the growth chamber can be more uniformly dispersed. · Silicon and germanium can be introduced simultaneously, resulting in a three-dopant system.

[0080] 1.4. Separation stage 40 The separation stage 40 is also carried out according to a variant in which the stage 20 forming the separation region 4 is carried out.

[0081] In the case of ion implantation, the spontaneous separation stage 40 is caused by a thermal cycle (resumption of epitaxy and cooling at high temperature) that the thickly formed GaN layer 5 undergoes, i.e., a thermal cycle that generates stress causing separation due to the difference in the coefficient of thermal expansion between the starting substrate 1 and the thickly formed GaN layer 5.

[0082] When a sacrificial intermediate layer is deposited, this separation is caused during epitaxy by the spontaneous vaporization of this intermediate layer or by mechanical fracture at the level of the so-called sacrificial layer.

[0083] When separating after growth, the sacrificial layer may be vaporized using a laser.

[0084] A self-standing GaN crystal 5 as shown in FIG. 3 is obtained.

[0085] As is common in HVPE, the GaN crystal 5 includes projections 51 in the shape of a hexagonal pyramid on the front surface 52.

[0086] As shown in FIG. 3, such a crystal is curved and has a radius of curvature of less than 25 meters, preferably less than 20 meters (the radius of curvature of the front surface 52 and the radius of curvature of the crystal plane on the opposite side of the front surface 52).

[0087] In the example of FIG. 3, this radius of curvature is 5 meters or more, and further, the crystal 5 has a threading dislocation density of 10 7 cm -2 or less, preferably 5×10 6 cm -2 or less.

[0088] When the GaN crystal 5 is formed on a starting substrate having a non-zero truncation angle, the GaN crystal 5 will also have a non-zero truncation angle and has an orientation of the crystal plane that propagates from one layer to the next. For example, in the case of a sapphire substrate 1 having a truncation angle of 4 degrees, the growth surface of the crystal 5 has a truncation angle of 4 degrees over its entire surface, preferably an angle of 0.1 to 1 degree.

[0089] 1.5. Adjustment stage 45 When separated from the starting substrate 1, the GaN crystal 5 is polished. With current technology, the removal of the film thickness can be controlled with an error within 10 micrometers.

[0090] 1.6. Finishing stage 50 Next, finishing processing is performed to form a GaN wafer.

[0091] The back surface and side surfaces, i.e., the edges, of the insert are polished and polished to a surface finish acceptable for the application.

[0092] Thus, the process of the present application is particularly suitable for manufacturing wafers of semiconductor materials, particularly wafers made of elements of Group 13 and Group 15 of the periodic table, and more particularly wafers made of Group 13 nitrides, preferably GaN, with a diameter of 50 mm, or further 100 mm, or even larger than 150 - 200 mm.

[0093] The wafer of semiconductor material described in FIG. 3 formed according to the process of the present invention has a thickness of 200 - 2000 micrometers and has excellent crystal quality with the full width at half maximum of the X-ray diffraction (XRD) peak of the (002) line at an angle ω symmetric to the GaN film (0001) being less than 130 arcsec.

[0094] According to another possible process, for the purpose of explanation and comparison with the above-described process, the single crystal material according to the present invention is preferably obtained by growing on a starting substrate or seed such as sapphire on which a layer of GaN nitride having a thickness of at least several micrometers and less than 10 micrometers has been previously deposited. The growth is carried out in a HVPE reactor. The epitaxial deposition is carried out under the same conditions as in step 30 described above, but is continued for a longer period to form a layer of several mm.

[0095] The crystal is trimmed and then cut into several wafers having a thickness of usually 100 - 600 micrometers using either a loose wire saw (abrasive particles in a slurry attached to the wire before cutting) or a fixed wire saw (abrasive particles pre-fixed on the wire). The finishing steps (polishing, lapping) are the same as in the above-described process.

[0096] The present invention and its advantages are illustrated by the following examples. The examples according to the present invention should not be regarded as limiting the implementation of the invention.

[0097] Embodiment examples In Example 1 (comparative example), the GaN growth is carried out by HVPE using a substrate, for example, according to the process described in step (iii) of WO / 03100839A2 which is preferably included, based on the substrate as described in WO / 03100839A2. The (volume) flow rate of N2 / (N2 + H2) is 0.2. Further, in this example, the growth temperature is maintained at 930 °C. The structure of the growth front surface FC observed by a scanning electron microscope is shown in FIGS. 4(a) and (b).

[0098] FIG. 4c is a structural view of the wafer after polishing and lapping according to the present invention, and is a view showing a first region caused by the growth of a non-basal facet and a region caused by the growth of a basal facet.

[0099] In Example 2 (comparative example), different from Example 1, during the HVPE growth step of step 30 shown in FIG. 1, oxygen is introduced into the gas phase (for example, an oxygen flow diluted 1% in 99% N2 sent at 0.2 to 10 sccm), and n-doping is introduced into the GaN material.

[0100] In Example 3 (according to the present invention), different from Example 2, germanium is also introduced. Germanium is introduced in the form of GeCl4 at a flow rate of 2 sccm until the end of HVPE for co-doping the GaN material.

[0101] From the SIMS measurements in the basal facet region (0001) and the non-basal region, the respective amounts of the included atoms could be estimated. For this purpose, an ion beam is irradiated onto the surface to locally ionize a part of the material. Thereby, it becomes possible to analyze the atoms (alloying, doping or impurities) constituting the material. The measurement line is performed with a length of about 0.9 mm. The selected incident ion beam enables the analysis of the composition of the material in a circle with a diameter of about 10 μm and a depth of about 1 μm. Each crater (or the beam collision point) of the measurement line is at an interval of about 50 μm.

[0102] At least one SIMS measurement is performed in the GaN region resulting from basal facet growth (0001) using this protocol and due to the density of the GaN region resulting from basal facet growth in comparison with the GaN region resulting from non-basal facet growth. Once the measurement is made, the analyzed region is imaged by cathodoluminescence to reliably attribute the SIMS measurement to different GaN regions.

[0103] Also, the free carrier density and the average resistivity of the GaN layer measured by the Van der Pauw method are shown in Table 1 below.

[0104]

Table 1

[0105] The XRD crystal quality is determined by measuring the full width at half maximum of the X-ray diffraction (XRD) peak of the (002) line at an angle ω that is symmetric with respect to the (0001) GaN plane.

[0106] The amount of oxygen element in the (0001) facet is observed to increase very slightly by doping, unlike in the non-basal three-dimensional growth region. When the germanium element is introduced, the obtained germanium concentration is the same in the growth region resulting from the (0001) facet and the growth region resulting from the non-basal facet.

[0107] Examples 2 and 3 generally have similar characteristics (free carrier density and resistivity) and are improved compared to Example 1. However, Example 3 according to the present invention shows a more uniform dopant distribution. At the same time, the crystal quality is of very satisfactory quality, and the surface density of macro-inclusions is within an acceptable range.

[0108] In addition, according to the experiments of the present inventors, the minimum concentration of Ge atoms or Si atoms in the facet region (0001) is preferably 1.0×10 17 atoms / cm 3 or higher, and the maximum concentration of O atoms in the region due to the growth of non-basal facets is preferably 2.0×10 18 atoms / cm 3 or lower. As a result, it becomes possible to reach an average resistivity of the GaN layer of less than 25 mohm·cm, or even less than 20 mohm·cm. At the same time, the cumulative density of O, Si, and Ge atoms in the crystal consisting of two domains can be kept below 1.0×10 19 atoms / cm 3 In addition, the concentration of Ge+Si atoms is higher than 2.0×10 17 atoms / cm, and preferably can be higher than 8.0×10 17 atoms / cm 3 Furthermore, the density of O atoms can preferably be made less than 1.0×10 18 atoms / cm 3

[0109] Regarding the region due to facet growth (0001), Raman measurement was performed using a Thermo DXRxi Raman spectrometer. This spectrometer is for high-speed Raman imaging with a maximum acquisition capacity of 600 spectra / second. In one configuration, analysis is performed with a 532 nm laser and an output of 10 mW. The laser beam is focused on the sample through a microscope with a magnification level of 50 times.

[0110] ​Fluctuations in the free carrier density are known to affect the position of the A1(LO) peak in the Raman spectrum of GaN. As the wave number increases, the free carrier density of the sample becomes higher. Figures 5a and 5b show the variation of the A1(LO) peak position as a function of the doping rate related to the GeCl4 flow rate. It should be noted that when doping is carried out only with oxygen, the A1(LO) peak position in the facet region (0001) does not vary, so it can be inferred that the free carrier concentration in these regions is the same as that of the samples without intentional doping. In the case of mixed doping (here germanium + oxygen), since the peak position varies, it can be seen that the number of free carriers in the facet region (0001) has increased. Thus, the single crystal of Example 3 has a Raman peak A1(LO) larger than 734 cm -1 −1.

[0111] Example 4 and Figure 6 show that increasing the N2 / (N2 + H2) volume flow rate in the reactor increases the doping in the region due to facet growth (0001).

[0112] Thus, according to the present invention, the basal plane (0001) and the non-basal plane can coexist on the same three-dimensional growth front during the HVPE growth of GaN, and after forming the GaN layer to obtain a two-dimensional surface, it is possible to have more uniform optical and electrical properties than when simply doped with oxygen.

[0113] When the uniformity of the material properties is improved, the advantage is that the current distribution of the light-emitting diodes, lasers, and power transistors made from our products is also improved. Also, in the case of optical applications, the uniformity of the absorption rate of the GaN layer is also improved.

[0114] Since the latter do not have significant variations in their properties within the same wafer, both of these advantages are beneficial in the manufacture of devices.

Claims

1. A manufacturing process of a single-crystal semiconductor material composed of a Group 13 nitride, comprising: depositing at least one single-crystal layer on a starting substrate by three-dimensional epitaxial growth, wherein the single-crystal layer includes a region having a facet perpendicular to the direction of the growth front formed by the basal plane (0001) due to the growth of basal facets, and a region having a facet non-perpendicular to the direction of the growth front due to the growth of facets having various orientations called non-basal facets; An n-dopant gas having 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 is supplied such that the concentration of the second chemical element in the region due to the growth of the base facet is higher than 1.0×10 １７ atoms / cm ３ and the concentration of the first chemical element in the region due to the growth of the non-base facet is lower than 2.0×10 １８ atoms / cm ３ , and includes a step of supplying the gas in such a manner. the atomic ratio (silicon + germanium) / oxygen of the single-crystal semiconductor material is 0.5 to 5; the step of depositing the at least one single-crystal layer by epitaxial growth: is performed by hydride vapor phase epitaxy (HVPE) at a growth rate of less than 450 μm / h; is performed at a temperature of 910 °C to 1035 °C; is performed in a reactor maintained at a residual pressure of 100 to 500 Torr; supplying the Group III precursor and the Group V precursor with a molar flow rate ratio of the Group V precursor to the Group III precursor being 13 to 25; A manufacturing process of a single-crystal semiconductor material.

2. The second chemical element of the n-dopant gas is germanium formed from solid sources of germanium tetrachloride, germane, tetramethylgermanium, and isobutylgermanium, and their derivatives, and / or the second chemical element of the n-dopant gas is silicon formed from solid sources of silane, dichlorosilane, and silicon tetrachloride, and their derivatives. The manufacturing process according to Claim 1.

3. The first chemical element of the n-dopant gas is oxygen. The manufacturing process according to Claim 1 or 2.

4. The n-dopant gas is mixed with a gallium chloride gas stream in the gas phase. The manufacturing process according to any one of Claims 1 to 3.

5. A manufacturing process of a semiconductor substrate composed of a Group 13 nitride, comprising: manufacturing a single-crystal semiconductor material composed of a Group 13 nitride on a starting substrate, the steps according to any one of Claims 1 to 4; separating the single-crystal semiconductor material from the starting substrate; adjusting by removing the thickness of the single-crystal semiconductor material to obtain a Group 13 nitride wafer having a thickness of 250 to 2000 μm.

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