Semiconductor substrate having a nitrided interface layer - Patents.com

Abstract

A method for producing a single crystalline semiconductor material of a nitride of a group 13 element is disclosed, which comprises the step of depositing by epitaxial growth on a starting substrate at least one isolation layer comprising an element (M) selected from Ge, Zr, Y, Si, Se, Sc, Mg, In, W, La, Ti, Ta and Hf, said method comprising a single crystalline semiconductor material of a nitride of a group 13 element having the chemical formula M v Al x O y N z an interfacial layer of the present invention is deposited between the starting substrate and the separating layer, characterized in that: - atomic indices (x and z) are greater than 0 and less than or equal to 1; - atomic indices (v and y) are between 0 and 1; - the sum (y+z) is greater than 0.9 and less than or equal to 1.5; - the sum (v+y) is greater than or equal to 0.3 and less than or equal to 1. [Representative diagram] Figure 1

Description

[Technical Field]

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

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

[0003] Current methods for producing semiconductor substrate materials based on nitrides of group 13 or group IIIA elements rely on deposition techniques, in particular heteroepitaxy, which consists of growing crystals, such as gallium nitride (GaN) crystals, on a starting substrate of different nature, such as a sapphire substrate.

[0004] Such methods use an injection system based on at least two different gas components that can interact prior to deposition.

[0005] Known methods include:

[0006] - MOVPE (metalorganic vapor phase epitaxy)

[0007] - HVPE (hydride vapor phase epitaxy),

[0008] - CSVT (close-spaced vapor transport),

[0009] - Ceramic deposition etc.

[0010] Heteroepitaxy remains the only solution for manufacturing components based on nitrides of group III elements. Industrially used substrates for gallium nitride epitaxy are sapphire (Al2O3), silicon, and silicon carbide (SiC). The difference in lattice parameters and thermal expansion coefficients between such substrates and nitrides of group III elements leads to the formation of numerous defects in the epitaxial layer, which reduces the performance of electronic components made with such materials. When the substrate is sapphire, a technique has been developed that involves inserting between the substrate and the epitaxial layer of nitrides of group III elements a nucleation layer, for example, made of GaN or AlN, deposited under separate growth conditions. This surface treatment makes it possible to limit the density of defects.

[0011] Various techniques are used to separate the group III nitride layer from its initial substrate in order to obtain a free-standing layer.

[0012] US 6,559,075 proposes, inter alia, laser ablation capable of decomposing GaN at the interface with the sapphire substrate, and EP 0966047A2 proposes chemical attack of the substrate supporting the layer of group III elements, which can also be used during or after the growth of the layer of group III elements.

[0013] EP 1245702A2 discloses, inter alia, a method for producing a free-standing layer of GaN, starting with a sapphire substrate onto which a metal layer is deposited and then an AlN film. The metal layer, which may contain an element selected from Al, Au, Ag, Cu, Pt, Ni, Ti, Zr, and Hf, facilitates the separation of the GaN layer from the substrate after epitaxial growth and acid or basic chemical attack. The metal layer must not react with or dissolve in ammonia or hydrogen gas during the growth stage. A preferred embodiment is proposed in which a mask is applied before or after depositing the metal layer.

[0014] EP 1246233A2 proposes depositing a first layer of group III nitride, followed by a metal film, on a growth substrate prior to a gas treatment in a growth chamber, particularly in a hydrogen-containing atmosphere. The metal layer may include Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Re, Fe, Ru, Os, Co, Cu, Pt, or Au. The gas treatment allows for the creation of voids in the first layer of group III nitride to facilitate subsequent separation of the second layer of group III nitride to form a free-standing layer.

[0015] WO 2005031045A2 proposes depositing on the substrate a silicon-based sacrificial intermediate layer intended to evaporate spontaneously at a later stage of the epitaxial growth of a nitride layer of a group III element, with the aim of creating a mechanically weak area at the interface between the substrate or growth seed and the future free-standing layer of such a nitride of a group III element, so that separation occurs during cooling due to high mechanical stresses (due to differences in thermal expansion coefficients) and consequently without the addition of any specific gas.

[0016] More recently, in US 2013 / 0178049 A1 it has been proposed to create an intermediate layer formed of NH4Cl which ensures automatic separation of the substrate and the free-standing layer during cooling after epitaxial growth.

[0017] However, NH4Cl decomposes at temperatures that are too low to allow growth at high temperatures, i.e., above 700° C. This leads, at the end of the growth, to too great a deformation of the coarse or monocrystalline layer intended to form wafers of nitrides of group 13 elements after separation of the starting substrate.

[0018] US 2016 / 0002822 A1 proposes producing a separation layer, the composition of which includes, for example, a carbon material or boron nitride. As in EP 1246233 A2, the separation is not instantaneous but requires the application of additional mechanical stress.

[0019] Therefore, the present invention provides substrates and wafers of nitride materials of Group 13 or Group III elements of the periodic table, particularly substrates and wafers of nitride materials of Group 13 or Group III elements, more specifically wafers and substrates made of GaN, which have a high thickness, typically greater than 100 μm, or 400 μm or more and less than 20 mm, preferably about 1 to 20 mm, and preferably about 5 to 10 mm, and a width of about 50.8 mm or more obtained by heteroepitaxy, and which have very high properties in terms of crystal quality, low defect density, low cracking rate, and / or significantly improved uniformity, particularly in relation to crystal quality and electrical resistivity. Summary of the Invention [Means for solving the problem]

[0020] In view of this, an object of the present invention is to provide a method for producing a single crystalline semiconductor material of a nitride of a group 13 element, particularly GaN, which comprises:

[0021] a) depositing by epitaxial growth on a starting substrate at least one separation layer comprising an element (M) selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, or an alloy of such elements;

[0022] b) By epitaxial growth, the chemical formula Al is grown such that the atomic indices obey the relationships: u=1 and r+s+t=1. r Ga s In t N u depositing at least one nucleation layer of

[0023] c) depositing by epitaxial growth at least one continuous monocrystalline layer of said semiconductor material of a nitride of a group 13 element having a thickness greater than 100 μm;

[0024] Chemical formula M v Al x O y N zan interfacial layer of the formula (I) is deposited between the separation layer and the nucleation layer and / or between the starting substrate and the separation layer,

[0025] - the atom indices (x and z) are greater than 0 and less than or equal to 1;

[0026] - atom indices (v and y) are between 0 and 1,

[0027] - the sum y+z is greater than 0.9 but less than or equal to 1.5,

[0028] - The sum v+y is greater than or equal to 0.3 and less than or equal to 1.

[0029] The method may also include the following steps:

[0030] d) separating the starting substrate;

[0031] e) grinding by removing at least one thickness of the monocrystalline layer to obtain wafers of nitrides of group 13 elements having a thickness between 200 μm and 2000 μm, preferably between 300 μm and 600 μm.

[0032] By way of indication, unless otherwise stated, indexes of chemical elements are atomic indexes and concentrations referred to in the text are atomic concentrations.

[0033] Advantageously, but optionally, the method according to the invention may further comprise at least one of the following features or any combination of such features:

[0034] - the separating layer has a thickness of less than 1 μm;

[0035] - the atomic index (r) is greater than 0, preferably greater than 0.5;

[0036] the sum of the indices s+t is less than 0.5; according to a possible embodiment, t is substantially equal to 0, preferably equal to 0;

[0037] - Chemical formula Al r Ga s In t N u The nucleation layer has a thickness of 50 to 1000 nm. Preferably, the nucleation layer is made of Al x Ga 1-x A crystalline layer of N, where x is 0.55 to 1:

[0038] - the separation step is carried out after step c) by chemical reaction or by physical transformation of the separation layer, preferably with little or no application of external energy;

[0039] the separation layer contains an element (M) preferably selected from Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, and more preferably selected from Ge, Si, B, Mg, In;

[0040] the separation layer may contain two or more elements (M1 and M2) preferably chosen from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, which may be deposited successively in a thin layer or in alloy form;

[0041] - the separation layer is formed as two or more successive layers containing an element (M) selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, each separation layer having an element different from that of the separation layer supporting it;

[0042] - the separation layer, nucleation layer and interface layer are deposited by MOVPE or MBE techniques with a growth rate of less than 10 μm per hour;

[0043] - index (y) is equal to 0 if said interface layer is deposited between a separation layer and a nucleation layer, and / or index (v) is equal to 0 if said interface layer is deposited between a starting substrate and a separation layer;

[0044] - the interfacial layer deposited between the separation layer and the nucleation layer is a crystalline layer and / or the interfacial layer deposited between the starting substrate and the separation layer is an amorphous layer;

[0045] - Chemical formula Al x O y N z The first interface layer (atomic indices x, y and z is 1 hereinafter) is deposited between the starting substrate and the separation layer, and the chemical formula M v Al y N z a second interfacial layer (wherein atomic indices v, y, and z are less than 1) is deposited between the separation layer and the nucleation layer;

[0046] - the separating layer is a monocrystalline layer;

[0047] - If it is formed by a crystal with cubic symmetry, this is the orientation <111> , <110> or <100> Preferably, the single crystalline layer is oriented along the direction <111> epitaxial at;

[0048] Optionally, a seed layer of gallium nitride may be deposited on the nucleation layer, preferably by MBE, MOVPE or HVPE.

[0049] Its thickness is preferably 0.5 to 10 μm;

[0050] A continuous monocrystalline layer of said semiconductor material of a nitride of a group 13 element is obtained by epitaxial growth by HVPE technique.

[0051] - the isolation, nucleation and seed layers and interface layers according to the invention are deposited at low growth rates using ALD (atomic layer deposition), PVD (physical vapor deposition), MOVPE or MBE (molecular beam epitaxy) techniques;

[0052] the thickness of the interface layer is more than 0.1 nm and / or less than 100 nm, preferably less than 50 nm, preferably less than or equal to 10 nm;

[0053] The interfacial layer deposited between the starting substrate and the separating layer is preferably crystalline. Preferably, its chemical formula M v Al x O y N z The index (v) is less than 0.1 and preferably substantially equal to 0.

[0054] Such an interfacial layer, referred to in the remainder of this application as "AlON," preferably consists essentially of oxygen, nitrogen, and aluminum. It is formed by annealing a sapphire substrate at temperatures above 700°C in an ammonia gas-containing environment. Its thickness, preferably between 0.1 nm and 100 nm, is obtained by annealing at 1000°C for approximately 5 minutes in an NH3-containing gas environment. The inventors have clearly discovered that, if covered with a separation layer composed of a material other than a group-13 nitride, the low-temperature (<700°C) stabilized interfacial layer is advantageously not sublimated during the growth stage of the nucleation layer or during the growth stage of the group-13 nitride monocrystalline layer, i.e., before the separation stage. It has also been observed that this interfacial layer, essentially composed of oxygen, nitrogen, and aluminum, contributes to reducing the risk of cracking of the subsequent separation and nucleation layer and the group-13 nitride layer before the separation stage d).

[0055] The interfacial layer deposited between the separation layer and the nucleation layer is preferably amorphous. Preferably, its chemical formula M v Al x O y N z The index (y) is less than 0.1, and preferably substantially 0.

[0056] Such an interfacial layer, referred to in the remainder of this application as "MAlN," preferably consists essentially of the elements (M), nitrogen, and aluminum. It is formed by contacting ammonia gas with the separation layer at temperatures above 700° C., followed by deposition of a crystalline nucleation layer of aluminum nitride and gallium nitride or indium nitride. During such deposition at temperatures above 700° C., the aluminum of the nucleation layer diffuses into the MAlN layer to form the MAlN.

[0057] The thickness of this interfacial layer is preferably between 0.1 and 100 nm. Such an interfacial layer significantly improves the coalescence of the nucleation layer and consequently reduces the misorientation of its grains.

[0058] The inventors have observed that the interfacial layer between the separation layer and the nucleation layer leads to an increase in the crystalline quality of the nucleation layer, which is better coalesced and uniform across the slab: the quality of the monocrystalline layer of group 13 nitrides is greatly improved (reduced dislocations or inclusions of group III nitrides with misorientations (>5°) of the major crystal axes relative to the crystalline matrix).

[0059] Furthermore, due to misorientation of the crystalline grains that make up the nucleation layer, the surface of the three-dimensional growth front of the group III element layer during HVPE growth can have local inconsistencies within the crystalline facets exposed at that surface. A direct consequence is local doping differences due to differences in dopant incorporation depending on the exposed crystalline facet. Therefore, it is important to have uniformity and reduced grain misorientation across the wafer to obtain similar electrical properties at different locations on the wafer after HVPE growth.

[0060] Also, a better-coalesced, weakly misoriented, and uniform nucleation layer across the wafer reduces variations that may occur at the surface of the three-dimensional growth front of the group III element layer during HVPE growth.

[0061] The direct consequence is that after grinding of the layer of group III elements resulting from growth by HVPE, a flat and continuous surface is obtained without voids or recesses having a diameter greater than 50 μm, preferably not greater than 25 μm.

[0062] Another object of the invention is the coarse crystals of nitrides of group 13 elements, preferably gallium nitride, that can be obtained by implementing the method described above, and that have the following characteristics:

[0063] - 11 m Larger crystal curvature radius,

[0064] - a width at half height of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions for the GaN (0001) plane that is less than 120 arc seconds, and a width at half height of the x-ray diffraction peak (XRD) of the 201 line around an angle (ω) under tilt conditions for the GaN (0001) film that is less than 240 arc seconds;

[0065] - 3cm -2 a surface macroscopic defect density of less than

[0066] - the half-width of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions for the GaN (0001) plane is less than 90 arc seconds, and the half-width of the x-ray diffraction peak (XRD) of the 201 line around an angle (ω) under tilt conditions for the GaN (0001) film is less than 150 arc seconds;

[0067] - a cracking ratio, measured by optical microscopy and corresponding to the sum of the lengths of each crack in the crystal divided by the diameter of the crystal, of less than 0.5;

[0068] - the ratio of the resistivity measured 40 mm from the center of the crystal to the resistivity measured at the center of the crystal being less than 1.6;

[0069] - the difference in absolute value between the half-width of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions of the GaN (0001) plane measured 40 mm from said center, which is less than 20 arc seconds, and such half-width measured at the center of the crystal.

[0070] Another object of the invention is a two-dimensional wafer of nitrides of group 13 elements, in particular GaN, obtained by epitaxial growth according to said method, characterized in that:

[0071] - Crystal curvature radius is 11 m Bigger,

[0072] - Surface macroscopic defect density is 6cm -2 Less than 5cm, preferably -2 Less than 3cm, preferably -2 is less than

[0073] - crystalline quality as measured by the half-width of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions of the GaN (0001) plane being less than 130 arc seconds, preferably less than 120 arc seconds, preferably less than 100 arc seconds, preferably less than 90 arc seconds, or preferably less than 60 arc seconds, and the half-width of the x-ray diffraction peak (XRD) of the 201 line around an angle (ω) under tilt conditions of the GaN (0001) film being less than 240 arc seconds, preferably less than 150 arc seconds, preferably less than 140 arc seconds, or preferably less than 100 arc seconds;

[0074] - the ratio of resistivity measured by the Hall effect at the periphery of the slab, especially at 40 mm from the center of the wafer, to such resistivity at the center of the wafer is less than 1.6;

[0075] - the difference in absolute value between the half-width of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions of the GaN (0001) plane measured 40 mm from the center of the wafer and such half-width measured at the center of the wafer is less than 20 arc seconds, preferably less than 15 arc seconds;

[0076] a cracking ratio, measured by optical microscopy and corresponding to the sum of the lengths of each crack in the crystal wafer divided by the diameter of the wafer, of less than 0.5, preferably less than 0.25;

[0077] In particular when the group 13 element is Ga, the continuous (0001) surface of the nitride of the group 13 element, i.e. the continuous Ga-face surface, does not have voids or recesses with a diameter larger than 50 μm, preferably does not have voids or recesses with a diameter larger than 25 μm.

[0078] Another object of the invention is the use of a two-dimensional wafer of nitrides of group 13 or group III elements according to one of the preceding features as a substrate for the manufacture of optoelectronic and / or electronic components such as light-emitting diodes, laser diodes, vertical transistors for power electronics, horizontal transistors for power electronics or (radio frequency) telecommunications, current rectifying diodes or sensors.

[0079] Other features, objects and advantages of the invention will become apparent from the detailed description that follows, given by way of non-limiting example and with reference to the drawings, in which: [Brief explanation of the drawings]

[0080] [Figure 1] FIG. 1 summarizes the possible main steps of a method for manufacturing a substrate according to an embodiment of the invention. [Figure 2] FIG. 2 shows a schematic representation of a semiconductor material made up of a stack of layers according to a possible embodiment of the invention. [Figure 3] FIG. 3 illustrates the grinding and finishing steps according to a possible embodiment to obtain a wafer of monocrystalline material of nitrides of group 13 elements according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0081] definition

[0082] The cracking ratio is measured by optical microscopy on a crystal or crystal wafer and corresponds to the sum of the length of each crack in the crystal or wafer divided by the diameter of the crystal or wafer.

[0083] Macroscopic defects refer to macroscopic inclusions larger than 10 μm in size, primarily consisting of twins, domain inversions, or potentially polycrystallites within the crystalline matrix. Such defects can also be detected and measured by optical microscopy.

[0084] The crystal curvature is measured by the diffraction of light as described in the article "Curvature and bow of bulk GaN substrates" by Humberto M. Foronda et al., published in Journal of Applied Physics 120, 035104 (2016) [1]. Therefore, the crystal curvature radius (R c ) is the relation: R c =D 2 / (8f c ), where f c denotes the crystal flexure and D denotes the diameter of the wafer or crystal in meters.

[0085] The electrical resistivity is measured by the Hall effect using the van der Pauw method.

[0086] The resistivity ratio is the ratio between the resistivity measured 40 mm from the center of the wafer to such resistivity at the center of the crystal wafer.

[0087] 1 and 2 illustrate possible main steps of a method for producing a GaN wafer.

[0088] In the following, the method according to the invention will be explained with reference to the production of wafers of gallium nitride (GaN).

[0089] However, it will be apparent to one of ordinary skill in the art that the methods described below may be used to grow materials including layers of nitrides of Group 13 elements other than gallium nitride (GaN).

[0090] 1. Manufacturing method

[0091] The method comprises:

[0092] - providing (10) a starting substrate (1),

[0093] an optional step (20) in which a first interface layer (2), preferably aluminum oxynitride, preferably crystalline, is formed on the starting substrate (1), such optional step being particularly advantageous when it is desired to reduce the cracking rate or, more particularly, to improve the crystalline quality of the final monocrystalline layer of a group 13 element,

[0094] - forming (30) a separation region (3) comprising an element (M) selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, or an alloy of such elements, where M is preferably selected from the group consisting of Ge, Si, B, Mg, In. According to one embodiment, it is possible to deposit several different metals (M) successively.

[0095] a step (40) of depositing a second interface layer (4) of a nitride of element (M), preferably amorphous, which step (40) may be optional if step (20) is carried out,

[0096] - a step (50) of depositing a nucleation layer (5) of aluminum nitride and gallium nitride, preferably crystalline, during the deposition of this layer (5), aluminum may come into contact with the separation layer (3) and diffuse therein, converting the second interface layer (4) into a nitride of aluminum and element (M), MAlN, which improves the crystalline cohesion of the layer (5), the chemical formula of the final nucleation layer (5) being preferably Al x Ga 1-xN, where x is between 0.55 and 1,

[0097] - an epitaxy restart step (60) to form a thick layer of GaN (6),

[0098] - a separation step (70) to obtain free-standing coarse crystalline GaN (6a),

[0099] - a grinding step (80) for removing a thickness of the free-standing coarse crystalline GaN (6a),

[0100] a finishing step (90) for forming a GaN wafer (7) from said GaN crystal (6a), in particular a polishing step by CMP to make the surface of the wafer exchangeable for the resumption of epitaxy of nitrides of group III elements.

[0101] 1.1. Providing a substrate (10) and depositing an interfacial layer (2) of aluminum oxynitride (20):

[0102] The starting substrate (1) is a crystalline seed made of a material that can 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 of ordinary skill in the art for growing gallium nitride, preferably sapphire. It can have a thickness of several hundred microns, typically 350 microns. The miscut angle (especially to limit stacking faults) can be between 0.1° and 5.0°, preferably between 0.2° and 0.8°, and more preferably between 0.3° and 0.6°.

[0103] The growth of the interface layer (2) can be carried out by various alternatives. In particular, the substrate is first heated in a MOVPE (metalorganic vapor phase epitaxy) reactor chamber under nitrogen to a temperature of 800-1100°C at a pressure of 20-800 mbar, particularly preferably to a temperature of 850-1050°C at a pressure of about 100-150 mbar. Ammonia is then introduced into the chamber at a concentration of 10-30 slm for 5-30 minutes. The temperature is then reduced to below 850°C or below 700°C before forming the separation layer (3).

[0104] The interface layer (2) is preferably crystalline. Preferably, its chemical formula M v Al x O y N z The index (v) is less than 0.1 and preferably substantially equal to 0.

[0105] Such an interface layer (2), referred to in the remainder of this application as "AlON", consists essentially of oxygen, nitrogen and aluminum.

[0106] The thickness of the interface layer (2) is more than 0.1 nm and / or less than 100 nm, preferably less than 50 nm, preferably less than 10 nm.

[0107] 1.2. Formation of isolation regions (30):

[0108] The method also includes a step (30) of forming an isolation region (3), which may consist of depositing a sacrificial intermediate layer, for example, as described in documents US7790489B2; CN102226985A; EP2204477A1; WO2014114730A1; KR101117189B1; US2007082465A1; EP1 699 951A1 or US2011124139A1.

[0109] The layer is preferably continuous with a thickness of less than 10 μm.

[0110] It may have within its volume a closed cavity with a diameter of less than 200 nm.

[0111] The separation layer (3) preferably contains an element (M) selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, and Hf. The separation layer may contain two or more elements (M1 or M2) preferably selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, and Hf. These may be deposited successively as a thin layer or in the form of an alloy. The separation layer is preferably a monocrystalline layer.

[0112] 1.3. Step (40) of depositing an interface layer of nitride of aluminum and element (M):

[0113] The interfacial layer (4) deposited between the separation layer (3) and the nucleation layer (5) is preferably amorphous. Preferably, its chemical formula M v Al x O y N z The index (y) is less than 0.1, and preferably substantially 0.

[0114] Such an interface layer (4), referred to in the remainder of this application as "MAlN", preferably consists essentially of the elements (M), nitrogen and aluminum.

[0115] The growth of the interfacial layer (4) can be performed by various alternatives. In particular, the substrate on which the separation layer has been deposited is heated to a temperature above approximately 700°C, preferably approximately 850°C to approximately 1100°C, under nitrogen at a pressure of approximately 50 to approximately 500 mbar, particularly less than 100 mbar. Ammonia is then introduced into the chamber for several seconds to activate the surface of the separation layer containing element (M). After forming the interfacial layer (4), an organic precursor of aluminum, preferably trimethylaluminum, is then introduced into the reactor chamber via nitrogen as a carrier gas to form a surface layer of aluminum and nitride of element (M) by reaction with element (M), followed by the formation of an AlN nucleation layer.

[0116] The thickness of this interface layer (4) is preferably greater than 0.1 nm and / or less than 100 nm, preferably less than 50 nm, preferably less than 10 nm, and this interface layer (4) significantly improves the coalescence of the aforementioned nucleation layer (5) and consequently reduces the misorientation of its grains.

[0117] 1.4. Nucleation layer formation step (50)

[0118] The preceding steps lead to the formation of a continuous layer of AlN having a thickness of about 50 to about 1000 nm, preferably about 50 to about 500 nm, called the nucleation layer (5), on which a thick layer of GaN can be formed by resuming epitaxy. During such deposition at temperatures above 700°C, the aluminum of the nucleation layer spreads into the MAlN layer to form MAlN. Preferably, the final chemical formula for the nucleation layer (5) is Al x Ga 1-x N, where x is between 0.55 and 1.

[0119] Alternatively and advantageously, an additional seed layer (5a) is deposited on the nucleation layer (5), in particular a layer of the formula Al x Ga y In zA layer of a nitride of a group III element of N, preferably a GaN layer with a (0001) orientation and a thickness of 0.5 to 10 μm, can be deposited, preferably by MOVPE. The deposition of this additional layer (5a) can reduce the stress between the AlN layer and the GaN HVPE layer subsequently epitaxially grown on the nucleation layer (5). Indeed, the deposition of such an additional layer (5a) can ensure the transition between the AlN layer and the GaN layer deposited by HVPE by limiting the number of crystal defects caused by differences in crystal structure. The growth of this GaN layer with a (0001) orientation can be preceded by the deposition of a dielectric SiNy layer, followed by the deposition of GaN at a temperature below 700°C, followed by annealing at a temperature above 900°C for recrystallization, as described in documents WO 99 / 020816 and EP 1338683 B1. Finally, the deposition of GaN at a temperature close to the annealing temperature can be performed on the recrystallized GaN layer.

[0120] Alternatively, the growth of the first GaN layer can be performed according to various alternatives. In particular, lateral overgrowth can be based on:

[0121] - the use of a dielectric mask containing openings in which the islets are formed, as described in document WO99 / 20816;

[0122] - The use of a dielectric layer without openings, in which islands form spontaneously, as described in document EP 1338683.

[0123] In particular, the masking step can be performed by optical photolithography (or by "nanoimprint"), which involves depositing a dielectric material, e.g., Si, with openings. x N y This involves the deposition of a mask made of (SiN, Si3N4, etc.) or SiO2 or TiN. The openings, which can be in the form of points or strips, make it possible to define locations for the selective subsequent growth of GaN islands.

[0124] The mask may be formed by any technique known to one of ordinary skill in the art. For example, the steps for forming the mask include:

[0125] - depositing a dielectric layer from vapor phase silane and ammonia precursors; and

[0126] - It consists of engraving the dielectric layer by photolithography to form openings.

[0127] The engraving of the group III nitride layer is then carried out by physicochemical means (for example by reactive ion etching, RIE), which must be interrupted before reaching the separation layer (3).

[0128] According to one possible method, the substrate or seed is masked before the step of restarting epitaxy consisting in the step of forming the GaN layer (6) or before the deposition of the aforementioned additional seed layer of GaN.

[0129] The masked and engraved seed is then introduced into a reactor for thickening the GaN layer (6) in step (60) and for separation in step (70).

[0130] 1.5. Epitaxy restart stage (60)

[0131] The method includes an epitaxy restart step (60) to form a thick layer of GaN.

[0132] The method can also begin immediately after the nucleation step by forming a thick layer of GaN (6), the seed step being optional.

[0133] Such resumption of epitaxy may be embodied by:

[0134] - MOVPE(Metalorganic vapor phase epitaxy);

[0135] - HVPE(Hydride vapor phase epitaxy);

[0136] - CSVT (close-spaced vapor transport); or again

[0137] - LPE (Liquid phase epitaxy).

[0138] During this stage it is advisable to use HVPE technology, which allows to obtain three main interesting effects:

[0139] The first effect is that the first GaN layer (6) thickens without losing its crystalline quality (no new dislocations or cracks appear).

[0140] - The second effect is that once the GaN(0001) growth exceeds 100 μm, the dislocation density decreases again by at least a factor of two during the resumption of HVPE epitaxy (see https: / / doi.org / 10.1143 / APEX.5.095503 ).

[0141] - The third effect is that the thick layer of GaN ( 6 ) can, in certain cases, allow spontaneous separation of the starting substrate (1) at the separation region (3) upon sublimation or mechanical cracking of the separation region (3) during growth by HVPE.

[0142] More precisely, the restart is carried out according to the following procedure: the temperature is increased in an atmosphere of a mixture of nitrogen, ammonia, and hydrogen. Once a temperature of approximately 1000°C has been reached in a stable manner, the growth stage of the GaN epitaxial layer is then triggered by introducing, in vapor form, gallium chloride (GaCl), obtained by reacting HCl with liquid gallium, maintained at a temperature of at least 800°C. GaCl and ammonia are partially pyrolyzed in the growth chamber, the temperature of which is maintained at approximately 1000°C. Thus, a monocrystalline deposit of GaN is gradually formed on the nucleation substrate (formed during the first growth stage).

[0143] During separation, it is necessary to obtain a GaN film that is thick enough, and therefore strong enough from a mechanical point of view, to prevent the GaN layer from cracking into small area pieces and to facilitate handling without risk of breakage. Growth then continues for several hours under these experimental conditions to achieve a thickness of at least 200 μm for the GaN layer, and preferably more than 1 mm.

[0144] Growth is then finally completed by switching the HCl flow to the outside and cooling occurs in an atmosphere formed by nitrogen and ammonia.

[0145] The growth conditions for this single crystalline layer (6) can typically be a growth temperature of 900 to 1200°C and a growth rate of 50 to 500µm / h, preferably 70 to 200µm / h.

[0146] The thus obtained free-standing coarse crystal of GaN (6a) has a thickness of more than 200 μm, preferably more than 1 mm, and its maximum thickness is less than 10 mm, or less than 5 mm.

[0147] The diameter of the thus obtained free-standing coarse crystal of GaN (6a) is greater than 50 mm, preferably greater than 100 mm, and the maximum diameter is less than 250 mm, or less than 200 mm.

[0148] 1.6. Separation Stage (70)

[0149] Also, a separation step (70) is implemented; this depends on the implemented alternative of step (30) for forming the separation region (3).

[0150] In the case of depositing an intermediate sacrificial layer, this separation occurs during the resumption of epitaxy by spontaneous evaporation of the intermediate layer or by mechanical cracking in the so-called sacrificial layer.

[0151] In the case of post-growth separation, a laser or other intense heat source is used to vaporize the sacrificial layer.

[0152] Thus, a free-standing crystal of GaN (6a) is obtained, as shown in FIG.

[0153] As is common in HVPE, the GaN crystal (6a) includes protrusions (61) in the form of hexagonal pyramids on its front surface (62).

[0154] Such crystals shown in FIG. 3 are hemispherical and have a crystal radius of curvature (crystal radius of front surface (62)) of less than 25 meters, preferably less than 20 meters, as does the crystal radius of curvature of the crystal face opposite said front surface (62).

[0155] In the example of FIG. 3, such a crystal radius of curvature is 5 meters or more; additionally, the crystal (6a) also has a radius of curvature of 10 7 cm -2 Less than or equal to 5 x 10 6 cm -2 has a density of through-dislocations less than

[0156] The crystal bending or curvature of the crystal or wafer is measured by diffraction of light as described in the article "Curvature and bow of bulk GaN substrates" by Humberto M. Foronda et al., published in Journal of Applied Physics 120, 035104 (2016) [1]. The crystal curvature radius R c is the relation:Rc =D 2 / (8f c ), where f c denotes the crystal curvature and D denotes the diameter of the crystal or wafer expressed in meters.

[0157] Furthermore, a free-standing coarse crystal of GaN (6a) formed on a starting substrate having a "miscut" angle other than 0 will have a miscut angle other than 0, and the orientation of the crystal plane will be propagated from one layer to another. For example, in the case of a sapphire substrate (1) having a miscut angle of 4°, the growth surface of the crystal (6a) will have a miscut angle of 4°, preferably 0.1 to 1°, over its entire surface.

[0158] 1.7. Grinding Stage (80)

[0159] Once the GaN crystal (6a) has been separated from the starting substrate (1), grinding begins. Current technology allows the layer thickness removal to be controlled to within 10 μm.

[0160] 1.8. Finishing stage (90)

[0161] Finishing operations are then performed to form the GaN wafer (7).

[0162] The rear surface is ground and the side or edge of the wafer (7) is polished to obtain a surface condition suitable for the application.

[0163] The proposed method is therefore particularly suitable for producing slices or wafers of semiconductor materials, in particular slices or wafers of materials from groups 13 and 15 of the periodic table, and more particularly slices or wafers composed of nitrides of group 13 elements, preferably GaN, with large diameters of more than 50 mm, more than 100 mm or even more than 150-200 mm.

[0164] The previous performance of stage (40) facilitates the obtaining at stage (90) of a continuous GaN surface, Ga-face or (0001), without voids or recesses larger than 25 μm in diameter.

[0165] Slices or wafers of semiconductor material (7) according to FIG. 3 formed by the method of the present invention have a thickness of 200 to 2000 μm and excellent crystalline quality, such that the half-width of the x-ray diffraction peak (XRD) of the (002) line around the angle (ω) under symmetric conditions of the GaN (0001) film is less than 130 arc seconds.

[0166] Advantageously, but optionally, the final wafer obtained by the method of the invention also has the following characteristics:

[0167] - Crystal curvature radius is 11 m Bigger,

[0168] - Surface macroscopic defect density is 6cm -2 Less than 3cm, preferably -2 is less than

[0169] crystalline quality as measured by the half-width of the x-ray diffraction peak (XRD) of the (002) line around an angle (ω) under symmetric conditions for the GaN (0001) plane being less than 130 arc seconds, preferably less than 100 arc seconds, preferably less than 90 arc seconds, or preferably less than 60 arc seconds, and the half-width of the x-ray diffraction peak (XRD) of the 201 line around an angle (ω) under tilt conditions for the GaN (0001) film being less than 240 arc seconds, preferably less than 140 arc seconds, or preferably less than 100 arc seconds;

[0170] - a cracking ratio, measured by optical microscopy and corresponding to the sum of the lengths of each crack in the crystalline wafer divided by the diameter of the wafer, of less than 0.5;

[0171] - A continuous Ga-face surface without voids or depressions larger than 50 μm in diameter.

[0172] According to another possible method, which is exemplary and differs from the method described above, the monocrystalline material according to the invention is obtained by growth on a starting substrate or seed, for example sapphire, on which a layer of nitride GaN has been deposited beforehand, preferably at least a few μm and less than 10 μm. The growth is carried out in an HVPE reactor. The epitaxial deposition is carried out under the same conditions as in step (30) described above, but continues for a longer period to form a layer of several mm.

[0173] After the crystal (6a) has been trimmed, it is cut into slices or wafers, typically 100-600 μm thick, using either a loose wire top (abrasive particles in a slurry that impregnates the wire before cutting) or a fixed wire top (abrasive particles pre-fixed on the wire). The finishing step (pre-polishing, polishing) is similar to the method described above.

[0174] The invention and its advantages are illustrated by the following examples, which of course should not be considered as limiting the implementation of the invention.

[0175] Illustrative Examples

[0176] In the following examples, a starting sapphire substrate was loaded into a CVD reactor, followed by deposition of an element (M) selected from Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, Hf, or an alloy of such elements.

[0177] The deposition of Ge is carried out at about 950° C. at a pressure below 400 mbar for a thickness between 250 nm and 3 μm. The precursor used for the vapor deposition is GeCl 4 .

[0178] The deposition of Zr is carried out at a pressure of less than 400 mbar for a thickness between 250 nm and 3 μm at about 450° C. The precursor used for vapor phase deposition is Zr amidinate (Zr-AMD).

[0179] The deposition of Y is carried out at approximately 500° C. by a deposition method at a pressure of less than 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is yttrium β-diketone.

[0180] The deposition of Si is carried out at about 900 °C at a pressure below 400 mbar for thicknesses between 250 nm and 3 μm. The precursor used is SiH4.

[0181] The deposition of B is carried out at about 1300 °C at a pressure below 400 mbar for thicknesses of 250 nm to 3 μm. The precursor used is BCl3.

[0182] The deposition of Sc is carried out at approximately 1100° C. at a pressure below 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is tris(cyclopentadienyl)scandium.

[0183] The deposition of Mg is carried out at about 900 °C at a pressure below 400 mbar for thicknesses of 250 nm to 3 μm. The precursor used is Cp2Mg (bis(cyclopentadienyl)magnesium).

[0184] The deposition of In is carried out at about 500° C. at a pressure of less than 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is TMI (trimethyl-indium).

[0185] The deposition of W is carried out at about 650° C. at a pressure below 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is Cl4(PhCN)W(NPh).

[0186] The deposition of La is carried out at about 450° C. at a pressure of less than 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is lanthanum β-diketonate.

[0187] The deposition of Ti is carried out at approximately 600°C at a pressure below 400 mbar for thicknesses between 250 nm and 3 μm. The precursor used is TiCl2.

[0188] The deposition of Ta is carried out at a pressure of less than 400 mbar for a thickness between 250 nm and 3 μm at approximately 600° C. The precursor used is tert-butylimido-tris-ethylmethylamido-tantalum (TBTEMT).

[0189] The deposition of Hf is carried out at about 700° C. at a pressure below 400 mbar for a thickness between 250 nm and 3 μm. The precursor used is Hf(NMe2)4.

[0190] In the first part of the preceding example, a substrate, preferably sapphire, is preheated in a CVD reactor chamber under nitrogen at a pressure of about 130 mbar to a temperature of about 1000°C. Ammonia is then introduced into the chamber at a concentration of about 20 slm for 5 minutes. As previously mentioned, this first interfacial layer between the sapphire substrate and the layer of element (M) has a crystalline thickness of 0.5 to 5 nm.

[0191] In the second part of the preceding example, the second interfacial layer is obtained according to the following procedure: in particular, ammonia is again introduced into the chamber at a concentration of 2000-10,000 slm for a few seconds to activate the surface of the separation layer containing element (M), and then trimethylaluminum is introduced into the reactor chamber through nitrogen as a carrier gas to form a surface layer of aluminum and nitride of element (M) by reaction with element (M).

[0192] The amorphous interface layer has a thickness of approximately 0.5 to 5 nm.

[0193] In the third part of the preceding example, no first or second interfacial layers were deposited.

[0194] For all such series, a nucleation layer of AlN approximately 100 nm to 2 μm thick was subsequently deposited. After separation, the obtained crystals were ground according to the same procedure to obtain wafers.

[0195] The properties of such substrates show similar results regardless of the element (M) selected, which are presented in the following table.

[0196] [Table 1]

[0197] A large reduction in the surface density of macroscopic inclusions, typically 3 / cm, for Examples 3 and 4 (according to the invention) compared to Example 1 (comparative example). 2 It can be seen that the crystal quality measured by the half-width of the x-ray diffraction peak (XRD) of the (002) line around the angle (ω) under symmetric conditions of the GaN (0001) plane is improved by at least 15 arc seconds in the case of Example 2 (according to the present invention), and by more than 40 arc seconds for Examples 3 and 4 compared to Example 1. It was also observed that the crystal quality measured by XRD, just like the electrical resistivity, is very uniform between the center and the edge of the crystal wafer. The inventors have clearly discovered that, when covered with a separation layer (3) composed of a material other than a group III nitride, the low-temperature (<700°C) stabilized interfacial layer (2) is advantageously not sublimated during the growth stage of the nucleation layer (5), i.e., before the separation stage. It was also observed that this interfacial layer (2) formed of oxygen, nitrogen, and aluminum contributes to the subsequent separation and reduction of the risk of cracking of the nucleation layer and the group III nitride layer before the separation stage d).

[0198] The inventors have also observed that the interfacial layer (4) between the separation layer (3) and the nucleation layer (5) leads to an increase in the crystalline quality of the nucleation layer (5), which coalesces better and is highly uniform across the wafer, and the quality of the monocrystalline layer of nitrides of group 13 elements is greatly improved (reduced dislocations or reduced inclusions in nitrides of group III elements with misorientations (>5°) of the major crystal axes relative to the crystalline matrix).

[0199] Furthermore, due to misorientation of the crystalline grains that make up the nucleation layer (5), during HVPE growth, the surface of the three-dimensional growth front of the group III element layer may have local inconsistencies within the crystalline facets exposed at that surface. A direct consequence is local doping differences due to differences in dopant incorporation depending on the exposed crystalline facet. Therefore, it is important to have uniformity and reduced grain misorientation across the wafer in order to obtain similar electrical properties at different locations on the wafer after HVPE growth.

[0200] Also, a better coalesced, slightly misoriented, and uniform nucleation layer (5) across the wafer reduces variations that may exist at the surface of the three-dimensional growth front of the layer of group III elements during HVPE growth.

[0201] The direct consequence is that after grinding of the layer of group III elements resulting from growth by HVPE, a flat and continuous surface is obtained without voids or recesses having a diameter greater than 50 μm, preferably not greater than 25 μm.

[0202] From the standpoint of performance and uniformity, such advantages are beneficial in use, as they improve current distribution in LEDs, lasers, and power transistors fabricated from the wafers. In optical applications, this also leads to improved absorption uniformity in the group III nitride layers.

Claims

1. 1. A method for producing a single crystalline semiconductor material of a nitride of a Group 13 element, comprising: The starting sapphire substrate is annealed at a temperature above 700° C. in an environment containing ammonia gas to form a compound of formula M on the starting substrate. ｖ Al ｘ O ｙ N ｚ forming a first interfacial layer comprising: element M selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, and Hf; forming, by epitaxial growth, on said first interface layer at least one separation layer comprising said element M or an alloy of said element M; Chemical formula Al ｒ Ga ｓ In ｔ N ｕ depositing by epitaxial growth at least one nucleation layer of the present invention, wherein the atomic indices obey the relationships: u=1 and r+s+t=1, and wherein said nucleation layer is deposited at a temperature above 700° C.; depositing by epitaxial growth at least one continuous monocrystalline layer of said semiconductor material of a nitride of said Group 13 element; The chemical formula M ｖ Al ｘ O ｙ N ｚ The first interface layer is the atom index v is less than 0.1, Atomic indices x and z are greater than 0 and less than or equal to 1; the atom index y ranges from 0 to 1; the sum y + z is greater than 0.9 and less than or equal to 1.5; the sum v+y is equal to or greater than 0.3 and equal to or less than 1, Furthermore, the chemical formula M ｖ Al ｘ O ｙ N ｚ depositing a second interfacial layer between the separation layer and the nucleation layer; The chemical formula M ｖ Al ｘ O ｙ N ｚ The second interface layer is Atomic indices x and z are greater than 0 and less than or equal to 1; the atom index v ranges from 0 to 1, the atomic index y is less than 0.1; the sum y + z is greater than 0.9 and less than or equal to 1.5; The sum v + y is greater than or equal to 0.3 and less than or equal to 1; method.

2. The method of claim 1, wherein the monocrystalline layer is deposited at a temperature between 900°C and 1200°C.

3. 3. The method of claim 1, wherein the separating layer has a thickness of less than 1 μm.

4. 4. The method according to claim 1, wherein the separation layer is formed as two or more continuous layers containing an element different from the element M selected from the group consisting of Ge, Zr, Y, Si, B, Sc, Mg, In, W, La, Ti, Ta, and Hf.

5. 5. The method according to claim 1, wherein the separation layer, the nucleation layer and the first interface layer are deposited by MOVPE or MBE techniques with a growth rate of less than 10 μm per hour, and the continuous monocrystalline layer of semiconductor material of a nitride of a group 13 element is obtained by epitaxial growth by HVPE techniques.

6. The method of claim 1 or 2, wherein the second interface layer is a crystalline layer and the first interface layer is an amorphous layer.

7. Chemical formula Al ｘ O ｙ N ｚ The method according to any one of claims 1 to 6, wherein the first interface layer has atomic indices x, y and z of 1 or less.

8. Chemical formula M ｖ Al ｘ N ｚ 3. The method of claim 1, wherein the second interface layer has atomic indices v, x, and z less than 1.

9. The method of claim 1 or 2, wherein the thickness of the first interface layer and the second interface layer is greater than 0.1 nm and less than 50 nm.

10. The nucleation layer is Al ｘ Ga １－ｘ 10. The method of claim 1, wherein the crystalline silicon is formed of N, where 0.55≦x≦1.

11. A method according to any one of claims 1 to 10, wherein a layer of SixNy is deposited on the nucleation layer before the step of depositing the at least one continuous monocrystalline layer.

12. The method according to any one of claims 1 to 11, further comprising the step of separating the starting substrate from the continuous monocrystalline layer to obtain a coarse crystal of the nitride of the group 13 element.

13. 13. The method of claim 12, further comprising grinding by removing at least one thickness of the coarse crystal of nitride of group 13 element to obtain a two-dimensional wafer of nitride of group 13 element having a thickness between 200 μm and 2000 μm.

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