Manufacturing method of semiconductor device and the semiconductor device

Abstract

To provide a manufacturing method of a semiconductor device capable of reducing a resistance of a nitride semiconductor, and provide the semiconductor device.SOLUTION: A first nitride semiconductor layer is formed on a nitride semiconductor substrate containing Al under a condition of a wafer temperature Tnc of 850°C or more and 970°C or less and a reactor pressure Vnc of 150 mbar or more and 450 mbar or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a semiconductor device and a semiconductor device. [Background technology]

[0002] Conventionally, nitride semiconductors have been used as materials for forming light-emitting diodes (LEDs), laser diodes (LDs), and the like. Nitride semiconductors have a direct transition recombination mode, which allows high recombination efficiency and high optical gain to be obtained, making them suitable as materials for LEDs and LDs. As an example of a laser diode using such a nitride semiconductor, a technology for oscillating a current-injection type laser diode in the ultraviolet region has been disclosed (e.g., Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Zhang et al., Applied Physics Express 12, 124003(2019) Summary of the Invention [Problem to be solved by the invention]

[0004] In semiconductor devices, there have been cases where the resistance of nitride semiconductors has not been sufficiently reduced.

[0005] An object of the present disclosure is to provide a semiconductor device manufacturing method that enables the resistance of nitride semiconductors to be reduced, and a semiconductor device. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, in a semiconductor device manufacturing method according to one embodiment of the present disclosure, a first nitride semiconductor layer is formed on an Al-containing nitride semiconductor substrate under conditions where the wafer temperature Tnc is 850°C or higher and 970°C or lower, and the reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower.

[0007] A semiconductor device according to another aspect of the present disclosure includes a nitride semiconductor substrate containing Al, and a first nitride semiconductor layer disposed on the nitride semiconductor substrate, wherein the deviation α from alloy uniformity in a plane direction of the first nitride semiconductor layer is 130 meV or more and 350 meV or less.

[0008] It should be noted that the above summary of the invention does not list all of the features of the invention according to the present disclosure. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a semiconductor device manufacturing method and a semiconductor device that enable the resistance of nitride semiconductors to be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic plan view illustrating a configuration example of a semiconductor device according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating a configuration example of a semiconductor device according to an embodiment of the present disclosure. [Figure 3] 1 is a schematic cross-sectional view illustrating a configuration example of a semiconductor device according to an embodiment of the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a configuration example of a semiconductor device according to an embodiment of the present disclosure. [Figure 5] FIG. 1 is a cross-sectional view schematically illustrating a configuration example of a vertical power device according to an embodiment of the present disclosure. [Figure 6] 1 is a cross-sectional view schematically illustrating a configuration example of a lateral power device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] The semiconductor device according to the present disclosure will be described below through embodiments, but the following embodiments do not limit the scope of the invention according to the claims. Also, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0012] Furthermore, in the following description, "up" and "down" do not necessarily refer to the vertical direction relative to the ground. In other words, the "up" and "down" directions are not limited to the direction of gravity. "Up" and "down" are merely convenient expressions for specifying the relative positional relationship of surfaces, films, substrates, etc., and do not limit the technical idea of ​​the present disclosure. For example, if the paper is rotated 180 degrees, "up" will of course become "down" and "down" will become "up."

[0013] 1. First embodiment A semiconductor device according to a first embodiment of the present disclosure will be described. The semiconductor device according to the first embodiment is, for example, a laser diode. The following description will be given of the case where the semiconductor device is a laser diode.

[0014] (1.1) Laser diode structure The laser diode according to this embodiment includes a nitride semiconductor substrate containing aluminum (Al), a first nitride semiconductor layer of a first conductivity type disposed on the nitride semiconductor substrate, a light-emitting layer disposed on the first nitride semiconductor layer, a second nitride semiconductor layer of a second conductivity type disposed on the light-emitting layer, a first waveguide layer of the first conductivity type disposed between the first nitride semiconductor layer of the first conductivity type and the light-emitting layer to confine light in the light-emitting layer, and a second waveguide layer of the second conductivity type disposed between the light-emitting layer and the second nitride semiconductor layer of the second conductivity type to confine light in the light-emitting layer. The deviation α from alloy uniformity in the in-plane direction of the first nitride semiconductor layer is 130 meV or more and 350 meV or less. Each layer of the laser diode (the nitride semiconductor substrate and the semiconductor laminate formed thereon, including the first nitride semiconductor layer, the light-emitting layer, and the second nitride semiconductor layer) will be described in detail below.

[0015] <Nitride semiconductor substrate> The nitride semiconductor substrate (hereinafter sometimes referred to as substrate) contains a nitride semiconductor containing Al. The nitride semiconductor containing Al is, for example, AlN. That is, the substrate is preferably an AlN single crystal substrate. Furthermore, the nitride semiconductor containing Al is not limited to AlN, and may be, for example, AlGaN. For example, when the substrate is a nitride semiconductor single crystal substrate such as AlN or AlGaN, the difference in lattice constant with the nitride semiconductor layer formed on the substrate becomes small, and threading dislocations can be reduced by growing the nitride semiconductor layer in a lattice-matched system.

[0016] The threading dislocation density of the substrate is 5×10 4 cm -2 In particular, from the viewpoint of improving the emission intensity and reducing the oscillation threshold current, the threading dislocation density is preferably 1×10 3 More than 1×10 4 cm -2 More preferably, it is: The substrate may be formed on a heterogeneous substrate as long as it contains a nitride semiconductor containing Al. For example, AlN may be grown on a sapphire (Al2O3) substrate.

[0017] Here, the "contains" in the expression "contains AlxGa(1-x)N (0≦x≦1)" means that AlxGa(1-x)N (0≦x≦1) is mainly contained in the layer, but this expression also includes cases where other elements are contained. Specifically, this expression also includes cases where the composition of this layer is slightly changed by adding a small amount of an element other than AlxGa(1-x)N (0≦x≦1) (for example, Ga (when Ga is not the main element), In, As, P, or Sb, etc., in an amount of a few percent or less). The word "contains" has the same meaning when referring to "contains Al" or other layers. The amount of minor elements contained is not limited to the above.

[0018] The substrate preferably has a thickness of 100 μm or more and 600 μm or less. The surface orientation may be c-plane (0001), a-plane (11-20), or m-plane (10-10), with a c-plane (0001) substrate being more preferred. Furthermore, the substrate may be formed on a surface tilted at some angle (for example, -4° to 4°, preferably -0.4° to 0.4°) from the normal direction of the c-plane (0001), but is not limited thereto.

[0019] <Buffer layer> A buffer layer may be formed on the substrate, i.e., between the substrate and the first nitride semiconductor layer. The buffer layer is preferably formed on the entire surface of the substrate. By providing the buffer layer, a nitride semiconductor layer having small lattice constant differences and thermal expansion coefficient differences and few defects is formed on the buffer layer.

[0020] The buffer layer is preferably a nitride semiconductor layer containing Al, and is formed of a nitride semiconductor such as AlN, AlGaN, etc. The buffer layer may also contain impurities such as C, Si, Fe, Mg, etc.

[0021] The buffer layer has a thickness of, for example, several μm. Specifically, the thickness of the buffer layer is preferably greater than 10 nm and less than 10 μm. When the buffer layer is greater than 10 nm, the crystallinity of the nitride semiconductor such as AlN is enhanced. Furthermore, when the buffer layer is less than 10 μm thick, cracks are less likely to occur in the buffer layer formed by crystal growth over the entire wafer surface.

[0022] <First nitride semiconductor layer> A first conductivity type first nitride semiconductor layer is formed on a substrate. Here, for example, the word "on" in the expression "the first nitride semiconductor layer is formed on a substrate" means that the first nitride semiconductor layer is formed on one surface of the substrate. The above expression also includes cases where another layer exists between the substrate and the first nitride semiconductor layer. The word "on" has a similar meaning in relation to other layers. For example, the case where a second nitride semiconductor layer is formed on a first conductivity type first waveguide layer described later via an electron blocking layer is also included in the expression "the second nitride semiconductor layer is formed on the first waveguide layer."

[0023] In addition, in the description of this embodiment, the terms "first conductivity type" and "second conductivity type" refer to semiconductors that exhibit different conductivity types, and for example, if one is n-type conductivity, the other is p-type conductivity.

[0024] In the laser diode according to this embodiment, the first conductivity type first nitride semiconductor layer is, for example, a first conductivity type cladding layer (hereinafter referred to as a first conductivity type cladding layer). The first-conductivity-type cladding layer is a layer of a nitride semiconductor containing at least one of Al and Ga. The first-conductivity-type cladding layer is formed of, for example, AlxGa(1-x)N (0≦x≦1). That is, the first-conductivity-type cladding layer is, for example, an AlxGa(1-x)N (0≦x≦1) layer.

[0025] This makes it possible to improve the crystallinity of the light-emitting layer and the luminous efficiency when the light-emitting layer is formed from a material with a band gap energy in the deep ultraviolet region. From the viewpoint of realizing high luminous efficiency, the nitride semiconductor constituting the first-conductivity-type cladding layer is preferably a mixed crystal of AlN and GaN. Furthermore, from the viewpoint of growing the first-conductivity-type cladding layer and each layer formed above it with complete strain relative to the substrate, it is more preferable that the first-conductivity-type cladding layer be formed from AlxGa(1-x)N (0.7≦x≦1). Furthermore, the first conductivity type cladding layer preferably has n-type conductivity from the viewpoint of ease of film formation of the laminated structure and resistance.

[0026] The AlxGa(1-x)N (0≦x≦1) that constitutes the first conductivity type cladding layer is formed under low temperature and high pressure conditions, with a wafer temperature Tnc of 850°C to 970°C and a reactor pressure Vnc of 150mbar to 450mbar. This makes it possible to suppress the segregation of Al and Ga in the AlxGa(1-x)N (0≦x≦1). The deviation α from the alloy uniformity in the plane direction of AlxGa(1-x)N (0≦x≦1) can be made to be 130 meV or more and 350 meV or less, and the resistivity of AlxGa(1-x)N (0≦x≦1) can be made low.

[0027] From the viewpoint of reducing resistivity and maintaining surface flatness, it is preferable that the wafer temperature Tnc and reactor pressure Vnc are formed under conditions that satisfy the following ranges. -2Tnc+2050 <Vnc<-2Tnc+2350

[0028] Here, the "potential fluctuation of AlxGa(1-x)N (0≦x≦1)" is an index for specifying the distribution state of Ga in the plane direction of AlxGa(1-x)N (0≦x≦1). "α, which indirectly represents the potential fluctuation," is an index showing the deviation from the alloy uniformity in the plane direction of AlxGa(1-x)N (0≦x≦1). When the deviation α from the alloy uniformity in the plane direction of AlxGa(1-x)N (0≦x≦1) is between 130 meV and 350 meV, it indicates that Ga is distributed relatively uniformly in the plane direction of AlxGa(1-x)N (0≦x≦1), that is, Al and Ga are arranged relatively uniformly.

[0029] The dispersion of Al and Ga in AlxGa(1-x)N (0≦x≦1) constituting the first conductivity type cladding layer is, for example, 0.6 or more and 1 or less, where 1 represents a state in which they are completely uniformly dispersed.

[0030] The first-conductivity-type clad layer may be a gradient layer in which the Al composition increases as it moves away from the substrate for the purpose of controlling the longitudinal conductivity. In this case, the above-mentioned limitation on the Al composition can be the Al composition averaged over the film thickness of the first-conductivity-type clad layer for the Al composition at the position in the film thickness direction within the first-conductivity-type clad layer.

[0031] When the first-conductivity-type clad layer is an n-type conductive semiconductor layer, it may contain impurities such as group V elements other than N such as P, As, Sb, and impurities such as C, H, F, O, Mg, Si, etc., but the types of impurity elements are not limited to this. From the viewpoints of reducing electrical resistance and the availability of raw materials, the impurity contained in the first-conductivity-type clad layer is preferably Si, and the impurity concentration is 5×10 18 cm -3 or more and 5×10 19 cm -3 or less.

[0032] Further, the resistivity of the first-conductivity-type clad layer is preferably 1×10 -3 Ωcm or more and 5×10 -3 Ωcm or less. Thereby, carrier injection can be efficiently performed.

[0033] The first-conductivity-type clad layer preferably has a layer thickness of 250 nm or more and 800 nm or less, and more preferably has a layer thickness of 300 nm or more and 450 nm or less, from the viewpoints of lattice relaxation within the first-conductivity-type clad layer and film resistance.

[0034] <Light-emitting layer> The light-emitting layer is a layer of a nitride semiconductor containing Al and Ga. The nitride semiconductor contained in the light-emitting layer is preferably a mixed crystal of, for example, AlN and GaN from the viewpoint of realizing high luminous efficiency, for example, Al b Ga (1-b) N (0 < b < 1). The light-emitting layer may contain impurities such as group V elements other than N such as P, As, Sb, and impurities such as C, H, F, O, Mg, Si, etc., but the types of impurity elements are not limited to this.

[0035] In addition, the light-emitting layer can have either a multiple quantum well structure or a single quantum well structure. Although it depends on the vertical conductivity of the first conductivity type clad layer and the second conductivity type clad layer, the number of quantum well structures is preferably any one of 1 to 5.

[0036] <Waveguide layer> From the perspective of light confinement as a laser diode, the laser diode of the present embodiment may include a waveguide layer formed above and below the light-emitting layer so as to sandwich the light-emitting layer and having an effect of confining the light emitted from the light-emitting layer within the light-emitting layer. The waveguide layer is preferably composed of two layers, namely, a first conductivity type first waveguide layer (hereinafter referred to as the first conductivity type waveguide layer) disposed between the first conductivity type clad layer and the light-emitting layer, and a second conductivity type second waveguide layer (hereinafter referred to as the second conductivity type waveguide layer) disposed between the second conductivity type clad layer and the light-emitting layer.

[0037] That is, the laser diode of the present embodiment may include, for example, a first conductivity type waveguide layer disposed between the first conductivity type clad layer and the light-emitting layer and confining light to the light-emitting layer, and a second conductivity type waveguide layer disposed between the second conductivity type clad layer and the light-emitting layer and confining light to the light-emitting layer.

[0038] From the perspective of light confinement, the waveguide layer is preferably a nitride semiconductor containing Al and Ga having a bandgap higher in energy than the light-emitting layer. The waveguide layer preferably has an Al composition and a film thickness that increase the overlap of the electric field intensity distribution of the light standing in the device and the light-emitting layer. From the perspective of carrier confinement in the light-emitting layer, when the light-emitting layer is Al b Ga (1-b) N (0 < b < 1), and the waveguide layer is Al c Ga (1-c) N (0 < c < 1), it is more preferable that b < c and c ≧ b + 0.05. For example, when the light-emitting layer having an emission wavelength of 265 nm is taken as an example, b is 0.52, and c is preferably 0.57 or more. Also, from the perspectives of light confinement and sheet resistance, the total film thickness of the waveguide layer (the total film thickness of the first conductivity type waveguide layer and the second conductivity type waveguide layer) is preferably 70 nm or more and 150 nm or less.

[0039] The waveguide layer may contain impurities such as P, As, Sb, and other V group elements other than N, C, H, F, O, Mg, and Si, but the types of impurity elements are not limited to these. From the viewpoint of reducing electrical resistance and the ease of obtaining raw materials, the impurity contained in the first conductivity type waveguide layer is preferably Si, and the impurity concentration is 5×10 18 cm -3 5x10 or more 19 cm -3 It is preferable that:

[0040] The Al composition of each of the first-conductivity-type waveguide layer and the second-conductivity-type waveguide layer is preferably uniform in the film thickness direction, but is not limited to this. To avoid light absorption by a metal (e.g., a second electrode) present above the second-conductivity-type cladding layer described below, the Al composition of the second-conductivity-type waveguide layer may be higher than the Al composition of the first-conductivity-type waveguide layer. For the same purpose, the film thickness of the second-conductivity-type waveguide layer may be thicker than the film thickness of the first waveguide.

[0041] <Second nitride semiconductor layer> In the laser diode according to this embodiment, the second conductivity type second nitride semiconductor layer is, for example, a second conductivity type cladding layer (hereinafter referred to as a second conductivity type cladding layer). The second-conductivity-type cladding layer is a layer of a nitride semiconductor containing at least one of Al and Ga. The second-conductivity-type cladding layer is formed of, for example, AlyGa(1-y)N (0.1≦y≦1). That is, the second cladding layer is, for example, an AlyGa(1-y)N (0.1≦y≦1) layer. The second-conductivity-type cladding layer is formed on, for example, the light-emitting layer or the second-conductivity-type waveguide layer. This allows the second-conductivity-type cladding layer to easily lattice-match with the light-emitting layer or the second-conductivity-type waveguide layer, and makes it possible to suppress threading dislocation density.

[0042] The second-conductivity-type cladding layer is not particularly limited in its conductivity type, as long as it has sufficient conductivity to inject carriers (electrons or holes) into the light-emitting layer and can increase the overlap between the electric field intensity distribution of the optical mode existing in the device and the light-emitting layer (i.e., increase light confinement). The second-conductivity-type cladding layer may be, for example, p-type AlGaN doped with Mg. The second-conductivity-type cladding layer may also contain impurities such as P, As, Sb, and other Group V elements other than N, as well as C, H, F, O, Mg, and Si, but the types of impurity elements are not limited to these.

[0043] In order to inject carriers more efficiently into the light-emitting layer, the second conductivity type cladding layer is a compositionally graded layer formed of AlyGa(1-y)N (0.1≦y≦1) in which the Al composition y decreases with increasing distance from the substrate throughout the layer, but in some parts of the second conductivity type cladding layer, the Al composition y increases with increasing distance from the substrate.

[0044] The second-conductivity-type cladding layer preferably has a composition gradient in which the Al composition y changes from 1 to 0.7 with increasing distance from the nitride semiconductor substrate. The profile (gradient) of the Al composition y in the second-conductivity-type cladding layer may decrease continuously or intermittently. Here, "intermittently decreasing" means that the second-conductivity-type cladding layer includes a portion in which the Al composition y is constant (constant in the film thickness direction). In other words, the second-conductivity-type cladding layer may include a portion in which the Al composition y does not decrease with increasing distance from the substrate. The thickness of the second conductivity type cladding layer is preferably 500 nm or less from the viewpoint of lattice matching, and more preferably 250 nm to 500 nm from the viewpoint of optical confinement.

[0045] <Composition gradient layer> The laser diode according to this embodiment may have a compositionally graded layer between the light emitting layer (or the second conductivity type waveguide) and the second conductivity type cladding layer, the compositionally graded layer containing AlgGa(1-g)N (0.1≦g≦1) and having an Al composition g that increases with increasing distance from the nitride semiconductor substrate. By providing the compositionally graded layer as in this embodiment, the electric field is alleviated, improving the degradation suppression effect.

[0046] The thickness of the composition gradient layer is preferably 2 nm or more and 5 nm or less, and more preferably 2 nm or more and 3 nm or less, in which case the degradation suppression effect is further improved.

[0047] <Second-conductivity-type contact layer> The semiconductor laminate of the laser diode of this embodiment may further include a second-conductivity-type contact layer disposed on the second-conductivity-type cladding layer. The nitride semiconductor constituting the second-conductivity-type contact layer is preferably formed of, for example, GaN, AlN, or InN, or a mixed crystal containing these, and more preferably a nitride semiconductor containing GaN.

[0048] In the case of a p-type contact layer, the second conductivity type contact layer may contain impurities such as P, As, Sb, and other V group elements other than N, and C, H, F, O, Mg, Si, and Be. From the viewpoint of versatility of source gases, the impurity contained in the second conductivity type contact layer is preferably Mg. From the viewpoint of reducing contact resistance, the concentration of Mg is preferably 8×10 19 cm -3 5x10 or more 21 cm -3 Preferably, it is 5 x 10 or less. 20 cm -3 5x10 or more 21 cm -3 More preferably, it is:

[0049] The thickness of the second conductive type contact layer is preferably 1 nm or more and 20 nm or less. The thinner the second conductive type contact layer, the higher the carrier injection efficiency of the light emitting layer, and the thicker the layer, the lower the carrier injection efficiency.

[0050] <Electron Blocking Layer> The semiconductor laminate of the laser diode of this embodiment may further include an electron blocking layer above the light-emitting layer, the electron blocking layer having a bandgap larger than that of the light-emitting layer. The electron blocking layer may be provided, for example, on the light-emitting layer, inside the second-conductivity-type waveguide layer, between the second-conductivity-type waveguide layer and the light-emitting layer, or between the second-conductivity-type waveguide layer and the second-conductivity-type cladding layer. The thickness of the electron blocking layer is preferably 30 nm or less, and more preferably 20 nm or less, so that carriers (holes) can easily quantum-transport through the electron blocking layer.

[0051] <Electrode> The laser diode can emit light or oscillate by injecting a current through a second electrode disposed on the second conductivity type cladding layer and a first electrode disposed on the first nitride semiconductor layer, where the first electrode is formed so as to be in electrical contact with the first nitride semiconductor layer, and the second electrode is formed so as to be in electrical contact with the second conductivity type cladding layer.

[0052] The first electrode can be disposed, for example, on the back side of the substrate. Alternatively, the first electrode can be disposed on the first nitride semiconductor layer exposed by removing layers above the first nitride semiconductor layer in the semiconductor laminate by, for example, chemical etching or dry etching. In other words, the first electrode is disposed on a region of the first nitride semiconductor layer that does not form a mesa structure.

[0053] When the first nitride semiconductor layer is an n-type cladding layer, the first electrode is formed of a metal such as Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, or Zr, a mixed crystal of these metals, or a conductive oxide such as ITO or Ga2O3.

[0054] When the first nitride semiconductor layer is a p-type cladding layer, the first electrode is formed of a metal such as Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Ir, or Zr, a mixed crystal of these metals, or a conductive oxide such as ITO or Ga2O3.

[0055] When the second conductivity type cladding layer is an n-type cladding layer, the second electrode is formed of a metal such as Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, or Zr, a mixed crystal of these metals, or a conductive oxide such as ITO or Ga2O3.

[0056] When the second conductivity type cladding layer is a p-type cladding layer, the second electrode is formed from a metal such as Ni, Au, Pt, Ag, Rh, Pd, Pt, Cu, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Ir, or Zr, a mixed crystal of these metals, or a conductive oxide such as ITO or Ga2O3.

[0057] The arrangement area and shape of the first electrode and the second electrode are not limited as long as they are in electrical contact with the first nitride semiconductor layer and the second conductivity type cladding layer (or the second conductivity type contact layer if a second conductivity type contact layer is provided).

[0058] (1.2) Semiconductor device manufacturing methods The laser diode, which is the semiconductor device of this embodiment, is manufactured through a process of forming each layer on a substrate. The manufacturing method of the laser diode will be described below. (1.2.1) Laser diode manufacturing method (Formation of substrate) The substrate is formed by a general substrate growth method such as a vapor phase growth method such as sublimation or hydride vapor phase epitaxy (HVPE) or a liquid phase growth method.

[0059] (Formation of semiconductor laminate) Each layer of the semiconductor stack formed on the substrate can be formed by, for example, molecular beam epitaxy (MBE: Molecular Beam Epitaxy) method, hydride vapor phase epitaxy (HVPE) method, metal organic chemical vapor deposition (MOCVD: Metal Organic Chemical Vapor Deposition) method, or the like.

[0060] Here, among the layers formed on the substrate, the nitride semiconductor layer can be formed using, for example, an Al raw material containing trimethylaluminum (TMAl), a Ga raw material containing trimethylgallium (TMGa) or triethylgallium (TEGa), or an N raw material containing ammonia (NH3). [[ID=×]] [[ID=×]]

[0061] [[ID=×]] A semiconductor stack is formed on the substrate. At this time, an organometallic gas is introduced into the semiconductor stack formation space (reactor). First, a first nitride semiconductor layer containing a nitride semiconductor of the first conductivity type is formed on the substrate.

[0062] The formation conditions of the first nitride semiconductor layer (including the first conductivity type cladding layer) are low temperature and high pressure. Specifically, the wafer temperature Tnc is 850 °C or higher and 970 °C or lower, and the reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower. Thereby, it is possible to form AlxGa(1−x)N (0≦x≦1) in which the deviation α from the uniformity of the alloy in the plane direction is 130 meV or higher and 350 meV or lower.

[0063] The wafer temperature Tnc and the reactor pressure Vnc are preferably in the range satisfying -2Tnc + 2050 < Vnc < -2Tnc + 2350. Thereby, it is possible to form a first nitride semiconductor layer in which Ga is non-uniformly distributed in the plane direction of the first nitride semiconductor layer. Thereby, the resistivity can be reduced, and by increasing the carrier injection efficiency, it becomes easy to increase the light emission efficiency.

[0064] Next, after forming a first-conductivity-type waveguide layer made of a nitride semiconductor such as AlGaN on the first nitride semiconductor layer, a light-emitting layer is formed of a nitride semiconductor (such as AlGaN) including one or more quantum wells. Subsequently, a second-conductivity-type waveguide layer made of a nitride semiconductor such as AlGaN is formed on the light-emitting layer.

[0065] At this time, the formation of the first-conductivity-type waveguide layer, the light-emitting layer, and the second-conductivity-type waveguide layer is preferably performed under conditions satisfying -2Tw + 2050 < Vw < -2Tw + 2350 (850 °C < Tw < 970 °C), where Tw is the wafer temperature and Vw is the reactor pressure.

[0066]

[0067] Thereby, a light-emitting layer in which Ga is unevenly distributed in the plane direction of the light-emitting layer can be formed. Similarly, a first-conductivity-type waveguide layer and a second-conductivity-type waveguide layer in which Ga is unevenly distributed in the plane direction of the first-conductivity-type waveguide layer and the second-conductivity-type waveguide layer can be formed. This increases the carrier recombination rate and improves the light-emitting efficiency. First, before forming a part of the second-conductivity-type cladding layer, the inflow of the organometallic gas into the reactor is temporarily stopped to interrupt the growth of the nitride semiconductor layer, and the film formation conditions are changed.

[0068] Subsequently, it is preferable to change the conditions to a wafer temperature of 900 °C or higher and 1000 °C or lower and a reactor pressure of 15 mbar or higher and 350 mbar or lower, resume the inflow of the organometallic gas, and form a part of the second-conductivity-type cladding layer from a second-conductivity-type nitride semiconductor. After forming a part of the second-conductivity-type cladding layer, before forming the remaining part of the second-conductivity-type cladding layer, the inflow of the organometallic gas into the reactor is temporarily stopped again to interrupt the growth of the nitride semiconductor layer, and the film formation conditions are changed.

[0069] ​Subsequently, the wafer temperature is changed to conditions of 1030°C or higher and 1100°C or lower, and the reactor pressure is changed to conditions of 15 mbar or higher and 350 mbar or lower. The inflow of the organometallic gas is restarted to form the remaining part of the second conductivity type clad layer.

[0070] As described above, by forming the first nitride semiconductor layer (first conductivity type clad layer) under low temperature and high pressure conditions, that is, under conditions where the wafer temperature Tnc is 850°C or higher and 970°C or lower, and the reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower, the deviation α from the uniformity of the alloy in the plane direction can be made 130 meV or higher and 350 meV or lower.

[0071] Further, when forming the first conductivity type waveguide layer, the light emitting layer, and the second conductivity type waveguide layer under conditions where the wafer temperature is Tw and the reactor pressure is Vw, satisfying -2Tw + 2050 < Vw < -2Tw + 2350 (850°C < Tw < 970°C), the resistivity can be reduced, the carrier recombination rate can be increased, point defects in each layer can be reduced, and deterioration suppression and light emission efficiency improvement can be achieved.

[0072] Also, if necessary, an intermediate layer may be formed of a nitride semiconductor such as AlGaN between the second conductivity type clad layer and the second conductivity type waveguide layer, a second conductivity type contact layer may be provided of a nitride semiconductor containing GaN or the like on the second conductivity type clad layer, and an electron blocking layer may be formed above the light emitting layer.

[0073] The laser diode is manufactured through a process of removing unnecessary portions of each layer of the semiconductor laminate formed on the substrate by etching (mesa structure forming process). The removal of the unnecessary portions of each layer of the semiconductor laminate can be performed by, for example, inductively coupled plasma (ICP) etching or the like. In the mesa structure forming process, by removing the unnecessary portions of each layer of the conductor laminate by etching, a part of the first nitride semiconductor layer is exposed.

[0074] (Formation of electrodes) Laser diodes can also be manufactured through a process of forming electrodes. Electrodes such as the first electrode and the second electrode can be formed by various methods, such as resistance heating evaporation, electron gun evaporation, or sputtering, in which metal is deposited by electron beam evaporation (EB) techniques, but are not limited to these methods. Each electrode can be formed as a single layer or as a multi-layer laminate. After the layers are formed, each electrode can be heat-treated in an oxygen, nitrogen, or air atmosphere.

[0075] Finally, the substrate on which the layers have been formed through the above-described steps is divided into individual pieces by dicing, thereby manufacturing the laser diodes. Specifically, a first electrode is formed on the surface of the first nitride semiconductor layer. The second electrode is formed on the top layer of a mesa structure (e.g., a second conductivity type cladding layer or a second conductivity type contact layer) that is part of the semiconductor laminate. The formed electrode is alloyed by heating with a rapid thermal annealing (RTA) device, which is a heat treatment using an infrared lamp, or by laser annealing, which is a heat treatment using a laser pulse, to obtain contact with the nitride semiconductor layer. The alloying method is not particularly limited as long as sufficient contact with the nitride semiconductor layer can be obtained. As described above, according to the method for manufacturing a laser diode according to this embodiment, it is possible to improve the carrier injection efficiency and increase the emission intensity.

[0076] (1.3) Measurement methods for the physical properties of laser diodes The physical properties of the laser diode described above can be measured as follows. (Layer thickness measurement method) The thickness of each layer constituting a laser diode can be measured by cutting a predetermined cross section perpendicular to the substrate, observing this cross section with a transmission electron microscope (TEM), and using the TEM's length measurement function. The measurement method involves first observing a cross section perpendicular to the main surface of the laser diode substrate using the TEM. Specifically, for example, within a TEM image showing a cross section perpendicular to the main surface of the laser diode substrate, an observation width of 2 μm or more is set in a direction parallel to the main surface of the substrate. Within this observation width, contrast is observed at the interface between two layers with different compositions, so the thickness up to this interface is observed in a continuous observation region 200 nm wide. The thickness of each layer can be obtained by calculating the average thickness of each layer included in this 200 nm wide observation region from five locations arbitrarily selected from the above-mentioned observation width of 2 μm or more.

[0077] (Measurement of impurity and doping concentrations) The concentration of dopants and impurities contained in each layer constituting the laser diode can be measured by secondary ion mass spectrometry (SIMS).

[0078] When measuring the concentration of dopants and impurities in each layer by SIMS after processing into a device, the measurement can be performed after removing the electrodes by chemical etching or physical polishing. The concentration of dopants and impurities in each layer can also be measured by sputtering from the substrate side where no electrodes are formed.

[0079] Specifically, SIMS measurements are performed under the measurement conditions provided by Evans Analytical Group (EAG), Inc. A cesium (Cs) ion beam with an energy of 14.5 keV is used to sputter the sample during the measurements.

[0080] (Method for measuring atomic concentration of each layer) One method for measuring the atomic concentration of each layer that constitutes a laser diode is reciprocal space mapping (RSM) using X-ray diffraction (XRD). Specifically, the lattice relaxation rate and Al composition relative to the substrate can be obtained by analyzing reciprocal lattice mapping data near the diffraction peak obtained using an asymmetric plane as the diffraction plane. Examples of diffraction planes include the (10-15) plane and the (20-24) plane.

[0081] Furthermore, layers and regions that do not provide sufficient reflection intensity by XRD, such as the light-emitting layer, gradient layer, and hillocks formed in each layer, can be measured by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and electron energy-loss spectroscopy (EELS).

[0082] EELS analyzes the composition of a sample by measuring the energy lost when an electron beam passes through the sample. Specifically, for example, the energy loss spectrum of the transmitted electron beam is measured and analyzed for a thin-sectioned sample used in TEM observation. The position of the peak that appears around 20 eV in energy loss varies depending on the composition of each layer, and the composition can be determined from the peak position.

[0083] In the same manner as the layer thickness calculation method using TEM observation described above, the Al composition of each layer is obtained by calculating the average value of the Al composition in an observation width of 200 nm from five points arbitrarily selected from an observation area of ​​2 μm or more.

[0084] EDX measures and analyzes the characteristic X-rays generated by an electron beam in a thin-sectioned sample used in the above-mentioned TEM observation, etc. In the same way as the method for calculating layer thickness using TEM observation described above, the Al composition of each layer is obtained by calculating the average value of the Al composition in an observation width of 200 nm from five points arbitrarily selected from an observation area of ​​2 μm or more.

[0085] XPS allows for depth profile evaluation by performing XPS measurements while performing sputter etching using an ion beam. While Ar+ is typically used as the ion beam, other ion species, such as Ar cluster ions, can be used as long as they can be irradiated by the etching ion gun installed in the XPS instrument. The depth profile of the Al composition in each layer can be obtained by measuring and analyzing the XPS peak intensities of Al, Ga, and N. Instead of sputter etching, the laser diode can be polished at an angle so that a cross section perpendicular to the main surface of the substrate is enlarged and exposed, and the exposed cross section can be measured by XPS.

[0086] In addition to XPS, Auger Electron Spectroscopy (AES) can also be used to measure the composition of each layer. In this case, the composition can be measured by Auger Electron Spectroscopy on a cross section exposed by sputter etching or angled polishing. The composition of each layer can also be measured by SEM-EDX measurement of a cross section exposed by angled polishing.

[0087] (Method for measuring potential fluctuations) α, which indirectly represents potential fluctuation, is calculated using the formula FWHM (meV) = αx + 10 meV, using the Al composition x of the nitride semiconductor layer and the full width at half maximum FWHM at the emission wavelength. Specifically, FWHM is obtained from the emission spectrum obtained by performing photoluminescence measurement on the nitride semiconductor layer. α can also be obtained using the Al composition x of the nitride semiconductor layer. In this case, photoluminescence measurement uses a light source with a wavelength shorter than the band gap of the nitride semiconductor layer to excite it. For example, a 213 nm YAG triple-harmonic laser is used. A more accurate value can be obtained by measuring while cooling the sample to 10 K or below.

[0088] Furthermore, if there is a layer with a smaller band gap than the nitride semiconductor layer to be excited, it is possible to measure that specific layer by removing it by etching, etc. Specifically, if there is an emission layer above the first conductivity type waveguide layer, the quantized emission layer will be excited by the excitation light, so accurate values ​​can be obtained by removing the emission layer by etching and then measuring the first conductivity type waveguide layer.

[0089] (Application fields of semiconductor devices) The laser diode according to the present disclosure can be applied to devices in, for example, the fields of medicine and life science, the environment, industry and manufacturing, lifestyle and home appliances, agriculture, and other fields.The laser diode can be applied to devices for synthesizing and decomposing pharmaceuticals or chemical substances, devices for sterilizing liquids, gases, and solids (containers, food, medical equipment, etc.), devices for cleaning semiconductors, etc., devices for modifying the surface of films, glass, metals, etc., exposure devices for manufacturing semiconductors, FPDs (Flat Panel Displays), PCBs (Printed Wiring Boards), and other electronic products, printing and coating devices, adhesive and sealing devices, transfer and molding devices for films, patterns, mockups, etc., and devices for measuring and inspecting banknotes, wounds, blood, chemical substances, etc.

[0090] Examples of liquid sterilization equipment include, but are not limited to, automatic ice makers, ice trays and ice storage containers in refrigerators, water tanks for ice makers, freezers, ice makers, humidifiers, dehumidifiers, cold water tanks, hot water tanks and flow piping for water servers, stationary water purifiers, portable water purifiers, water supply units, hot water heaters, wastewater treatment equipment, garbage disposals, toilet drain traps, washing machines, dialysis water sterilization modules, peritoneal dialysis connector sterilizers, and disaster water storage systems.

[0091] Examples of gas sterilization devices include, but are not limited to, air purifiers, air conditioners, ceiling fans, floor or bedding vacuum cleaners, futon dryers, shoe dryers, washing machines, clothes dryers, indoor germicidal lamps, storage ventilation systems, shoe boxes, chests of drawers, etc.

[0092] Examples of solid sterilization equipment (including surface sterilization equipment) include, but are not limited to, vacuum sealers, belt conveyors, hand tool sterilizers for medical, dental, barber, and beauty salon use, toothbrushes, toothbrush holders, chopstick cases, cosmetic pouches, drain covers, toilet spot cleaners, and toilet lids.

[0093] 2. Second embodiment A semiconductor device according to a second embodiment of the present disclosure will be described. The semiconductor device according to the second embodiment is, for example, a light emitting element. Hereinafter, a case where the semiconductor device is a light emitting element will be described. (2.1) Structure of the light-emitting element The light-emitting device according to this embodiment includes a nitride semiconductor substrate containing Al (aluminum), a first nitride semiconductor layer of a first conductivity type disposed on the nitride semiconductor substrate, a light-emitting layer disposed on the first nitride semiconductor layer, and a second nitride semiconductor layer of a second conductivity type disposed on the light-emitting layer. The first nitride semiconductor layer contains AlxGa(1-x)N (0≦x≦1) in which the deviation α from alloy uniformity in the in-plane direction is 130 meV or more and 350 meV or less.

[0094] Hereinafter, each layer of the light emitting element (nitride semiconductor substrate and semiconductor laminated portion formed thereon, such as first nitride semiconductor layer, light emitting layer, second nitride semiconductor layer) will be described in detail. The light-emitting device of this embodiment differs from the laser diode of the first embodiment in that it does not include a first-conductivity-type waveguide layer and a second-conductivity-type waveguide layer. In addition, in the light-emitting device of this embodiment, the second-conductivity-type cladding layer may be used as a barrier layer.

[0095] Furthermore, the light-emitting device of this embodiment has a different configuration from the first nitride semiconductor layer (first conductivity type cladding layer) of the laser diode of Embodiment 1. Therefore, the first nitride semiconductor layer and second conductivity type cladding layer of the light-emitting device will be described in detail below. Note that the layers other than the first nitride semiconductor layer, ie, the nitride semiconductor substrate, buffer layer, and light emitting layer, are the same as those described in the first embodiment, and therefore description thereof will be omitted.

[0096] <First nitride semiconductor layer> In the light emitting device according to this embodiment, the first conductivity type first nitride semiconductor layer is, for example, a first conductivity type cladding layer. The first conductivity type cladding layer is a nitride semiconductor layer containing at least one of Al and Ga. The first conductivity type cladding layer is formed of AlxGa(1-x)N (0≦x≦1) in which the deviation α from alloy uniformity in the surface direction is 130 meV or more and 350 meV or less, and is preferably formed of AlxGa(1-x)N (0.7≦x≦1).

[0097] The first conductivity type cladding layer is preferably formed from an n-type semiconductor from the viewpoint of ease of film formation of a laminated structure and resistance. Furthermore, the thickness T0 of the first conductivity type cladding layer is preferably (3500x-2150) nm or more and (26500x-17850) nm or less (x is the Al composition x of AlxGa(1-x)N (0≦x≦1) that constitutes the first conductivity type cladding layer). Furthermore, the resistivity of the first conductivity type cladding layer is 1×10 -3 Ωcm or more 5×10-3 It is preferably Ωcm or less. Other than this, the structure is similar to that of the first nitride semiconductor layer (first conductivity type cladding layer) described in the first embodiment.

[0098] The deposition conditions for the first conductivity type cladding layer are also similar to those for the first nitride semiconductor layer (first conductivity type cladding layer) described in Embodiment 1. For example, AlxGa(1-x)N (0≦x≦1) constituting the first conductivity type cladding layer is formed under low temperature and high pressure conditions, in which the wafer temperature Tnc is 850°C or higher and 970°C or lower, and the reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower.

[0099] From the viewpoint of reducing resistivity and maintaining surface flatness, it is preferable that the wafer temperature Tnc and reactor pressure Vnc are formed under conditions that satisfy the following ranges. -2Tnc+2050 <Vnc<-2Tnc+2350

[0100] <Second nitride semiconductor layer> In the light-emitting device, instead of a second conductivity-type cladding layer with a graded Al composition, an electron blocking layer with a constant Al composition is provided on the light-emitting layer, and a second nitride semiconductor layer with a graded Al composition is provided on the electron blocking layer. From the viewpoint of lattice matching, the thickness of the second conductivity-type cladding layer is preferably 500 nm or less. Furthermore, from the viewpoint of carrier injection, the thickness is more preferably 30 nm or more and 100 nm or less. The thickness of the electron blocking layer is preferably 10 nm or more and 15 nm or less from the viewpoints of electron blocking and carrier injection.

[0101] Unlike the laser diode according to the first embodiment, the light-emitting device according to this embodiment does not include a first-conductivity-type waveguide layer and a second-conductivity-type waveguide layer. Therefore, it is difficult to evaluate α, which indirectly represents the potential fluctuation of the nitride semiconductor layer included in the light-emitting layer. This is because, when attempting to evaluate α, which indirectly represents the potential fluctuation, the quantized light-emitting layer is excited, preventing accurate results from being obtained. However, by forming a nitride semiconductor layer under the same conditions as those of the first embodiment, it is possible to form a nitride semiconductor layer having α, which indirectly represents the potential fluctuation.

[0102] 3. Third embodiment A semiconductor device according to a third embodiment of the present disclosure will be described. The semiconductor device according to the third embodiment is, for example, a power device. The following description will be given of a case where the semiconductor device is a power device. (3.1) Power device configuration The power device according to this embodiment includes a nitride semiconductor substrate containing aluminum (Al) and a first nitride semiconductor layer of a first conductivity type disposed on the nitride semiconductor substrate. The first nitride semiconductor layer contains AlxGa(1-x)N (0≦x≦1) in which the deviation α from alloy uniformity in the in-plane direction is 130 meV or more and 350 meV or less. Each layer of the power device will be described in detail below. The nitride semiconductor substrate is the same as the nitride semiconductor substrate described in the first embodiment, and therefore a description thereof will be omitted.

[0103] The power device of this embodiment differs from the laser diode of the first embodiment in that it does not include a waveguide layer and a light emitting layer. When the power device has a second nitride semiconductor layer, for example, the second nitride semiconductor layer has a different conductivity type from the first nitride semiconductor layer of the second conductivity type, and is a vertical device having a pn junction.

[0104] On the other hand, when the power device does not have a second nitride semiconductor layer, for example, a channel of a field effect transistor (MESFET) is formed in the first nitride semiconductor layer of the first conductivity type. That is, the power device includes a MESFET whose channel is formed in the first nitride semiconductor layer.

[0105] <First nitride semiconductor layer> The first nitride semiconductor layer is a nitride semiconductor layer containing at least one of Al and Ga. The first nitride semiconductor layer is formed of AlxGa(1-x)N (0≦x≦1) in which the deviation α from alloy uniformity in the in-plane direction is 130 meV or more and 350 meV or less. Furthermore, as shown below, there are preferred embodiments for both MESFETs and vertical power devices.

[0106] (3.2) Vertical power devices or MESFETs The first nitride semiconductor layer is preferably made of AlxGa(1-x)N (0.7≦x≦1). The first nitride semiconductor layer is preferably formed from an n-type semiconductor.

[0107] The thickness T0 of AlxGa(1-x)N (0≦x≦1) constituting the first nitride semiconductor layer is preferably (3500x−2150) nm or more and (26500x−17850) nm or less, where x is the Al composition x of AlxGa(1-x)N (0≦x≦1). The resistivity of AlxGa(1-x)N (0≦x≦1) constituting the first nitride semiconductor layer is 1×10 -3 Ωcm or more 5×10 -3 It is preferably Ωcm or less. Other than this, the structure is similar to that of the first nitride semiconductor layer (first conductivity type cladding layer) described in the first embodiment.

[0108] <Second nitride semiconductor layer> In the power device according to this embodiment, the second nitride semiconductor layer of the second conductivity type is a cladding layer of p-type conductivity type (hereinafter referred to as a second conductivity type cladding layer). The second-conductivity-type cladding layer is a layer of a nitride semiconductor containing at least one of Al and Ga. The second-conductivity-type cladding layer is formed of, for example, AlyGa(1-y)N (0.1≦y≦1). That is, the second cladding layer is, for example, an AlyGa(1-y)N (0.1≦y≦1) layer. The second-conductivity-type cladding layer is formed on the first-conductivity-type cladding layer. This allows the second-conductivity-type cladding layer to easily lattice-match with the first-conductivity-type cladding layer, making it possible to suppress threading dislocation density.

[0109] The conductivity type of the second conductivity type cladding layer is not particularly limited as long as it has sufficient conductivity to inject carriers (electrons or holes) into the first conductivity type cladding layer. The second conductivity type cladding layer may be, for example, p-type AlGaN doped with Mg. The second conductivity type cladding layer may also contain impurities such as P, As, Sb, and other Group V elements other than N, as well as C, H, F, O, Mg, and Si, but the types of impurity elements are not limited to these.

[0110] From the viewpoint of more efficient carrier injection, the second conductivity type cladding layer is a compositionally graded layer formed of AlyGa(1-y)N (0.1≦y≦1) in which the Al composition y decreases with increasing distance from the substrate throughout the layer, but in some parts of the second conductivity type cladding layer, the Al composition y increases with increasing distance from the substrate.

[0111] The second-conductivity-type cladding layer preferably has a composition gradient in which the Al composition y changes from 1 to 0.7 with increasing distance from the nitride semiconductor substrate. The profile (gradient) of the Al composition y in the second-conductivity-type cladding layer may decrease continuously or intermittently. Here, "intermittently decreasing" means that the second-conductivity-type cladding layer includes a portion in which the Al composition y is constant (constant in the film thickness direction). In other words, the second-conductivity-type cladding layer may include a portion in which the Al composition y does not decrease with increasing distance from the substrate.

[0112] The thickness of the second conductivity type cladding layer is preferably 1000 nm or less from the viewpoints of lattice matching and withstand voltage, and more preferably 400 nm to 700 nm from the viewpoint of on-resistance.

[0113] Furthermore, a layer made of AlzGa(1-z)N (0≦z≦1) may be included between the first conductivity type cladding layer and the second conductivity type cladding layer. By including AlzGa(1-z)N (0≦z≦1), it is expected that the breakdown voltage will be improved. From the viewpoint of breakdown voltage and on-resistance, the film thickness of AlzGa(1-z)N (0≦z≦1) is preferably 10 nm or more and 100 nm or less.

[0114] 4. Examples of semiconductor devices The semiconductor device of this embodiment will be described in more detail below with reference to Figures 1 to 6. The detailed configuration of each layer in each of the following examples is as described above. (4.1) First example Fig. 1 is a cross-sectional schematic diagram of a first example of a laser diode 1. As shown in Fig. 1, the laser diode 1 includes a substrate 11, a semiconductor laminate 10 disposed on the substrate 11, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 includes a first conductivity-type cladding layer 101 having an n-type conductivity (an example of a "first nitride semiconductor layer" in the present disclosure), a first conductivity-type waveguide layer 102, a light-emitting layer 103, a second conductivity-type waveguide layer 104, and a second conductivity-type cladding layer 105 having a p-type conductivity (an example of a "second nitride semiconductor layer" in the present disclosure).

[0115] (4.2) Second example Fig. 2 is a cross-sectional schematic diagram of a second example of a laser diode 2. As shown in Fig. 2, the laser diode 2 includes a substrate 11, a buffer layer 12, a semiconductor laminate 10 disposed on the substrate 11 (buffer layer 12), a first electrode 13, and a second electrode 14. The semiconductor laminate 10 includes a first conductivity-type cladding layer 101 having an n-type conductivity (an example of a "first nitride semiconductor layer" in the present disclosure), a first conductivity-type waveguide layer 102, a light-emitting layer 103, a second conductivity-type waveguide layer 104, and a second conductivity-type cladding layer 105 having a p-type conductivity (an example of a "second nitride semiconductor layer" in the present disclosure). That is, the laser diode 2 differs from the laser diode 1 in that the laser diode 2 includes a buffer layer 12 .

[0116] (4.3) Third example Fig. 3 is a cross-sectional schematic diagram of a laser diode 3 as a third example. As shown in Fig. 3, the laser diode 3 includes a substrate 11, a buffer layer 12, a semiconductor laminate 10 disposed on the substrate 11, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 includes a first conductivity-type cladding layer 101 having an n-type conductivity (an example of a "first nitride semiconductor layer" in the present disclosure), a first conductivity-type waveguide layer 102, a light-emitting layer 103, a second conductivity-type waveguide layer 104, a second conductivity-type cladding layer 105 having a p-type conductivity (an example of a "second nitride semiconductor layer" in the present disclosure), and a contact layer 106.

[0117] That is, the laser diode 3 differs from the laser diode 1 in that it includes a contact layer 106 . The laser diode of the present disclosure may have a configuration including the buffer layer 12 described in the second example and the contact layer 106 described in the third example.

[0118] (4.4) Fourth example FIG. 4 is a cross-sectional schematic diagram of a fourth example of a light-emitting element 4. As shown in FIG. 4, the light-emitting element 4 includes a substrate 11, a semiconductor laminate 10 disposed on the substrate 11, a first electrode 13, and a second electrode 14. The semiconductor laminate 10 includes a first-conductivity-type cladding layer 101 having n-type conductivity (an example of a "first nitride semiconductor layer" in the present disclosure), a light-emitting layer 103, and a second-conductivity-type cladding layer 105 having p-type conductivity (an example of a "second nitride semiconductor layer" in the present disclosure). Note that the light-emitting element 4 also includes an electron blocking layer and a second-conductivity-type contact layer that function as the second-conductivity-type cladding layer 105.

[0119] That is, the light-emitting element 4 differs from the laser diode 1 in that it does not include the first-conductivity-type waveguide layer 102 and the second-conductivity-type waveguide layer 104. The light-emitting element 4 also differs from the laser diode 1 in that it is provided with an electron blocking layer and a second-conductivity-type contact layer that serve as the second-conductivity-type cladding layer 105. The light-emitting device of the present disclosure may have a configuration including the buffer layer 12 described in the second example.

[0120] (4.5) Fifth Example Fig. 5 is a cross-sectional schematic diagram of a fifth example of a vertical power device. The vertical power device 5 shown in Fig. 5 is a diode having a pn junction, and includes an insulating substrate 11, an n-type first nitride semiconductor layer 101 disposed on the substrate 11, a fourth nitride semiconductor layer 114 disposed on the first nitride semiconductor layer 101, a second nitride semiconductor layer 105 disposed on the fourth nitride semiconductor layer 114, an electrode 41 provided on the front side of the first nitride semiconductor layer 101 and electrically connected to the second nitride semiconductor layer 105, and an electrode 42 provided on the back side of the first nitride semiconductor layer 101 and electrically contacting the first nitride semiconductor layer 101. The second nitride semiconductor layer 105 and the fourth nitride semiconductor layer 114 are partially etched to expose the front surface of the first nitride semiconductor layer 101, and the electrode 42 is disposed on this exposed surface. The n-type is an example of a first conductivity type, and the p-type is an example of a second conductivity type.

[0121] The fourth nitride semiconductor layer 114 is, for example, an un-AlGaN layer. Here, un-AlGaN refers to a layer that is not intentionally doped with a dopant. In the vertical power device 5 shown in FIG. 5, when a forward bias is applied between the electrode 41 and the electrode 42, a current flows from the electrode 41 to the electrode 42 via the p-type second nitride semiconductor layer 105, the i-AlGaN fourth nitride semiconductor layer 114, and the n-type first nitride semiconductor layer 101.

[0122] (4.6) Sixth Example Fig. 6 is a cross-sectional schematic diagram of a sixth example of a lateral power device. The lateral power device 6 shown in Fig. 6 is a MESFET. As shown in Fig. 6, the lateral power device 6 has an insulating substrate 11, an n-type first nitride semiconductor layer 101 disposed on the substrate 11, a gate electrode 32 disposed on the n-type layer 23, a source electrode 41, and a drain electrode 42.

[0123] When the lateral power device 6 is a MESFET, the lateral power device 6 does not have a second nitride semiconductor layer. In the case of a MESFET, the gate electrode 23 is made of metal and is connected to the n-type first nitride semiconductor layer 101 via a Schottky junction. The current flowing from the drain electrode 42 to the source electrode 41 is controlled by a depletion layer formed in the n-type first nitride semiconductor layer 101 immediately below the gate electrode 32.

[0124] Although not shown, an n+ type source region may be provided directly below the source electrode 41, and an n+ type drain region may be provided directly below the drain electrode 42. This may contribute to improving the ohmic characteristics and reducing the contact resistance of the junctions between the source electrode 41 and the drain electrode 42 and the n-type first nitride semiconductor layer 101. Furthermore, a gate insulating film may be provided below the gate electrode 23. This facilitates the design of the depletion layer.

[0125] 4.Effects The semiconductor device manufacturing method and the semiconductor device according to the embodiment of the present disclosure have the following advantages. (1) The method for manufacturing a semiconductor device according to an embodiment of the present disclosure forms a first nitride semiconductor layer on a nitride semiconductor substrate containing Al under the conditions that the wafer temperature Tnc is 850°C or higher and 970°C or lower, and the reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower. Thus, by growing the first nitride semiconductor layer in a low-temperature and high-pressure environment, the migration length difference between Al and Ga atoms becomes small, so that they can be alloyed uniformly, the potential fluctuation can be improved, and a first nitride semiconductor layer with low resistance can be obtained.

[0126] (2) In the method for manufacturing a semiconductor device according to an embodiment of the present disclosure, the wafer temperature Tnc and the reactor pressure Vnc may also be in the range satisfying -2Tnc + 2050 < Vnc < -2Tnc + 2350. Thereby, a first nitride semiconductor layer in which Ga is uniformly distributed in the plane direction of the first nitride semiconductor layer can be formed. (3) In the method for manufacturing a semiconductor device according to an embodiment of the present disclosure, a nitride buffer layer containing Al may be formed on the nitride semiconductor substrate before forming the first nitride semiconductor layer. The first nitride semiconductor layer may be formed on the nitride buffer layer. Thereby, a first nitride semiconductor layer with a small lattice constant difference and a small coefficient of thermal expansion difference and few defects can be formed on the buffer layer.

[0127] (4) The semiconductor device according to an embodiment of the present disclosure includes a nitride semiconductor substrate containing Al and a first nitride semiconductor layer disposed on the nitride semiconductor substrate. The first nitride semiconductor layer contains AlxGa(1 - x)N (0 ≤ x ≤ 1). The deviation α of the alloy in the plane direction of AlxGa(1 - x)N (0 ≤ x ≤ 1) is 130 meV or higher and 350 meV or lower. Thereby, Al and Ga are alloyed uniformly, and a low-resistance first nitride semiconductor layer can be obtained. (5) In the semiconductor device according to an embodiment of the present disclosure, the degree of dispersion of Al and Ga in AlxGa(1−x)N (0≦x≦1) may be 0.6 or more and 1.0 or less, assuming that the state where Al and Ga are completely uniformly dispersed is 1. Thereby, Al and Ga are uniformly alloyed, and a low-resistance first nitride semiconductor layer can be obtained.

[0128] (6) The semiconductor device according to an embodiment of the present disclosure may further include a light-emitting layer including one or more quantum wells disposed on the first nitride semiconductor layer, and a second nitride semiconductor layer of a second conductivity type disposed on the light-emitting layer. The first nitride semiconductor layer may have a first conductivity, and the second nitride semiconductor layer may have a second conductivity. Thereby, as a semiconductor device, for example, a laser diode or a light-emitting element can be provided. (7) The semiconductor device according to an embodiment of the present disclosure may include a second nitride semiconductor layer of a second conductivity type provided in the first nitride semiconductor layer of a first conductivity. The first nitride semiconductor layer may have a first conductivity, and the second nitride semiconductor layer may have a second conductivity. Thereby, as a semiconductor device, a light-emitting element or, for example, a vertical power device can be provided.

[0129] (8) In the semiconductor device according to an embodiment of the present disclosure, the first nitride semiconductor layer may be AlxGa(1−x)N (0.7≦x≦1). Thereby, the light emission intensity of the light-emitting element can be increased, or the breakdown voltage of the vertical power device can be increased. (9) In the semiconductor device according to an embodiment of the present disclosure, the first nitride semiconductor layer may be n-type. Thereby, the driving voltage of the light-emitting element can be reduced, or the driving voltage of the vertical power device can be reduced.

[0130] (10) In the semiconductor device according to an embodiment of the present disclosure, the film thickness T0 (nm) of the first nitride semiconductor layer may satisfy 3500x−2150<T0<26500x−17850. This makes it possible to provide a lattice-matched thin film, which can increase the emission intensity of a light-emitting device and increase the breakdown voltage of a vertical power device. (11) In the semiconductor device according to the embodiment of the present disclosure, the conductivity of the first nitride semiconductor layer is 1×10 ―3 Ωcm or more 5×10 ―3 It may be Ωcm or less. This makes it possible to reduce the driving voltage of the light emitting element and the driving voltage of the vertical power device. [Example]

[0131] <Sample 1> The laser diode of the present disclosure will be described below with reference to examples and comparative examples, but the laser diode of the present disclosure is not limited to these examples. The substrate used was a (0001) AlN single crystal substrate with a thickness of 550 μm.

[0132] Next, an AlN layer, which is a homoepitaxial layer, was formed on the substrate. The AlN layer was formed to a thickness of 500 nm in an environment of 1200°C. At this time, the ratio of the supply rate of the Group III element source gas to the supply rate of the nitrogen source gas (V / III ratio) was set to 50. The growth rate of the AlN layer was 0.5 μm / hr. Trimethylaluminum (TMAl) was used as the Al source, and ammonia (NH3) was used as the N source.

[0133] A first conductivity type first nitride semiconductor layer was formed on this substrate. The first nitride semiconductor layer was an n-type AlGaN layer (Al: 75%, i.e., Al) using Si as a dopant impurity. 0.75 Ga 0.25The first nitride semiconductor layer was formed to a thickness of 400 nm under the conditions of a temperature of 970°C, a reactor pressure of 200 mbar, and a V / III ratio of 4000. The growth rate of the first nitride semiconductor layer was 0.4 μm / hr. Trimethylaluminum (TMAl) was used as the Al source, triethylgallium (TEGa) was used as the Ga source, ammonia (NH3) was used as the N source, and monosilane (SiH4) was used as the Si source.

[0134] Next, an n-type waveguide layer, which is a first conductivity type waveguide layer, was formed on the first nitride semiconductor layer. The n-type waveguide layer was an n-type AlGaN layer (Al: 63%, i.e., Al) using Si as a dopant impurity. 0.63 Ga 0.37 The n-type waveguide layer was formed to a thickness of 40 nm under the conditions of a temperature of 970°C, a reactor pressure of 300 mbar, and a V / III ratio of 4000. The growth rate of the n-type waveguide layer was 0.35 μm / hr. Trimethylaluminum (TMAl) was used as the Al source, triethylgallium (TEGa) was used as the Ga source, and ammonia (NH3) was used as the N source.

[0135] Next, a light-emitting layer was formed on the n-type waveguide layer. The light-emitting layer was formed to have a multi-quantum well structure in which quantum well layers and barrier layers were stacked two times. Here, the quantum well layer was an AlGaN layer (Al: 52%, i.e., Al) with a thickness of 4.5 nm. 0.52 Ga 0.48 The barrier layer having a thickness of 6.0 nm was an AlGaN layer (Al: 63%, i.e., Al 0.63 Ga 0.37 N layer).

[0136] The light-emitting layer was grown at a temperature of 950°C, a reactor pressure of 300 mbar, and a V / III ratio of 4000. The growth rate of the quantum well layer was 0.18 μm / hr, and the growth rate of the barrier layer was 0.15 μm / hr.

[0137] Next, a p-type waveguide layer, which is a second conductive type waveguide layer, was formed on the light emitting layer. The p-type waveguide layer was an AlGaN layer containing no dopant (Al: 63%, i.e., Al 0.63 Ga 0.37 The p-type waveguide layer was formed to a thickness of 70 nm under the conditions of a temperature of 950°C, a reactor pressure of 300 mbar, and a V / III ratio of 4000. The growth rate of the p-type waveguide layer was 0.35 μm / hr. Trimethylaluminum (TMAl) was used as the Al source, and triethylgallium (TEGa) was used as the Ga source. ) was used.

[0138] Next, a second conductivity type second nitride semiconductor layer was formed on the p-type waveguide layer. The second nitride semiconductor layer was a compositionally graded layer with a gradient Al composition ratio. The layer consisted of a 2.5 nm thick AlGaN layer with an Al composition distribution that varied from Al=0.63 to 1.0 in the direction away from the substrate, and a 330 nm thick p-type AlGaN layer with an Al composition distribution that varied from Al=1.0 to 0.7 in the direction away from the substrate.

[0139] Next, a p-type contact layer, which is a second conductivity type contact layer, was formed on the second nitride semiconductor layer. Here, the p-type contact layer was formed from an AlGaN layer and a GaN layer. The AlGaN layer was a p-type nitride semiconductor layer with a layer thickness of 30 nm, using Mg as a dopant impurity and with an Al composition distribution that varied from Al = 0.7 to 0.4 in the direction away from the substrate. The GaN layer was formed from GaN (i.e., Al: 0%) with a thickness of 10 nm.

[0140] The second conductivity type contact layer was formed under the conditions of a temperature of 950°C, a reactor pressure of 150 mbar, and a V / III ratio of 3650. The growth rate of the second conductivity type contact layer at this time was 0.2 μm / hr.

[0141] Various analyses were carried out on the nitride semiconductor laminate obtained as described above. As a result, α, which indirectly represents the potential fluctuation of the first nitride semiconductor layer, was 133 meV. The dispersion, which represents the uniformity of Al and Ga, was 0.61. The resistivity of the first nitride semiconductor layer was 4.8×10 -3 It was Ωcm.

[0142] The semiconductor laminate formed as described above was annealed in an N2 atmosphere at 700°C for 10 minutes or more to further reduce the resistance of the second conductivity-type contact layer. Dry etching was performed using an ICP with a gas containing Cl2 to form a mesa structure that exposed the first nitride semiconductor layer.

[0143] The formed mesa structure had a length of 700 μm in the <1-100> direction and a length of 40 μm in the <11-20> direction. The length in the <11-20> direction is the distance between the side faces of the mesa structure.

[0144] On the second conductivity-type contact layer of the mesa structure, Ni and Au films were sequentially deposited in a rectangular shape extending in the <1-100> direction to form multiple electrode metal regions, which served as p-type second electrodes. The width of the second electrode was 5 μm, and its length was 600 μm or more. Furthermore, in the region where the n-type cladding layer of the mesa structure was exposed, V, Al, Ni, Ti, and Au films were sequentially deposited in a rectangular shape extending in the <1-100> direction to form multiple electrode metal regions, which served as n-type first electrodes. The first and second electrodes were annealed at 550°C for 60 seconds in a nitrogen atmosphere using an RTA system.

[0145] Furthermore, the substrate was divided into stripes by cleaving multiple times parallel to the <11-20> direction within the electrode metal region, forming individual laser diodes. The length of the mesa structure in the <1-100> direction after division was 600 μm. The laser diode thus obtained was subjected to current injection and edge emission intensity measurements. The threshold voltage was 8.1 V and the oscillation threshold current was 3.6 kA / cm. 2 It was.

[0146] <Sample 2>~<Sample 18> Laser diodes of Samples 2 to 18 were fabricated in the same manner as Sample 1, except that the growth conditions (growth temperature, growth pressure) of the n-type AlGaN layer using Si as a dopant impurity that constitutes the first nitride semiconductor layer were changed as shown in Table 1.

[0147] <Sample 19> An LED of Sample 21 was formed under the same growth conditions for the first nitride semiconductor layer as in Sample 1. The light emitting device had a light emission intensity of 80 (mW). <Sample 20> The MESFET of Sample 23 was formed under the same growth conditions for the first nitride semiconductor layer as in Sample 1. Note that, since it was a MESFET, the light emitting layer and the second nitride semiconductor layer were not formed. <Sample 21> A vertical power device of Sample 24 was formed under the same growth conditions for the first nitride semiconductor layer as in Sample 1. Since it was a vertical power device, no light emitting layer was formed.

[0148] [Table 1]

[0149] In Table 1, it was confirmed that Samples 1, 2, 7 to 9, 11 to 13, 15 to 17, and 19 to 21 had lower resistivity than the other samples.

[0150] Although the embodiments of the present disclosure have been described above, the above embodiments are merely examples of devices and methods for embodying the technical ideas of the present disclosure, and the technical ideas of the present disclosure do not specify the materials, shapes, structures, arrangements, etc. of the components. The technical ideas of the present disclosure can be modified in various ways within the technical scope defined by the claims. [Explanation of symbols]

[0151] 1, 2, 3 Laser Diode 4 Light-emitting element 5 Vertical power devices 6 Lateral power devices (e.g., MESFETs) 10 Semiconductor laminated section 11 Circuit Board 12 Buffer layer 13 1st electrode 14 2nd electrode 21 Source Region 22 Drain region 23 n-type layer 25 well area 31 Gate insulating film 32 gate electrode 41 Source electrode 42 Drain electrode 101 First nitride semiconductor layer (first conductivity type cladding layer) 102 first conductive type waveguide layer 103 Light-emitting layer 104 Second conductivity type waveguide layer 105 Second nitride semiconductor layer (second conductivity type cladding layer) 106 Contact layer 114 Fourth nitride semiconductor layer

Claims

1. A method for manufacturing a semiconductor device, comprising forming a first nitride semiconductor layer on an Al-containing nitride semiconductor substrate under conditions where a wafer temperature Tnc is 850° C. or higher and 970° C. or lower and a reactor pressure Vnc is 150 mbar or higher and 450 mbar or lower.

2. The wafer temperature Tnc and the reactor pressure Vnc are expressed as follows:

2. The method for manufacturing a semiconductor device according to claim 1, wherein the range satisfies −2Tnc+2050<Vnc<−2Tnc+2350.

3. forming a nitride buffer layer containing Al on the nitride semiconductor substrate before forming the first nitride semiconductor layer; The method for manufacturing a semiconductor device according to claim 1 , wherein the first nitride semiconductor layer is formed on the nitride buffer layer.

4. a nitride semiconductor substrate containing Al; a first nitride semiconductor layer disposed on the nitride semiconductor substrate; the first nitride semiconductor layer includes AlxGa(1-x)N (0≦x≦1), A semiconductor device, wherein the alloy dissociation α in the plane direction of the AlxGa(1-x)N (0≦x≦1) is 130 meV or more and 350 meV or less.

5. 5. The semiconductor device according to claim 4, wherein the dispersion of Al and Ga in the AlxGa(1-x)N (0≦x≦1) is 0.6 or more and 1.0 or less, where 1 represents a state in which Al and Ga are completely uniformly dispersed.

6. a light emitting layer including one or more quantum wells disposed on the first nitride semiconductor layer; a second nitride semiconductor layer disposed on the light emitting layer, The semiconductor device according to claim 4 or 5, wherein the first nitride semiconductor layer has a first conductivity type and the second nitride semiconductor layer has a second conductivity type.

7. a second nitride semiconductor layer provided on the first nitride semiconductor layer, The semiconductor device according to claim 4 or 5, wherein the first nitride semiconductor layer has a first conductivity type and the second nitride semiconductor layer has a second conductivity type.

8. 8. The semiconductor device according to claim 6, wherein the first nitride semiconductor layer is AlxGa(1-x) (0.7≦x≦1).

9. 8. The semiconductor device according to claim 6, wherein the first nitride semiconductor layer is n-type.

10. 8. The semiconductor device according to claim 6, wherein the thickness T0 (nm) of the first nitride semiconductor layer satisfies 3500x-2150<T0<26500x-17850.

11. The conductivity of the first nitride semiconductor layer is 1×10 ―３ Ωcm or more 5 x 10 ―３ 8. The semiconductor device according to claim 6, wherein the resistivity is Ωcm or less.

Images