Nitride semiconductor, semiconductor device, and method of manufacturing nitride semiconductor

Abstract

To provide a nitride semiconductor, a semiconductor device, and a method for manufacturing the nitride semiconductor.SOLUTION: According to an embodiment, a nitride semiconductor includes a substrate and a nitride member. The nitride member includes a first nitride region including Alx1Ga1-x1N (0<x1≤1) and a second nitride region including Alx2Ga1-x2N (0≤x2<1, x2<x1). The first nitride region is between the substrate and the second nitride region. The first nitride region includes a first portion and a second portion. The second portion is between the first portion and the second nitride region. The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion. The oxygen concentration in the second portion is equal to or less than 1×1018 / cm3. The first thickness of the first portion in the first direction from the first nitride region to the second nitride region is thinner than the second thickness of the second portion in the first direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a nitride semiconductor, a semiconductor device, and a method for manufacturing a nitride semiconductor.

Background Art

[0002] For example, a semiconductor device is manufactured using a wafer including a nitride semiconductor. Improvement in the quality of the nitride semiconductor is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments of the present invention provide a nitride semiconductor, a semiconductor device, and a method for manufacturing a nitride semiconductor that can improve quality.

Means for Solving the Problems

[0005] According to an embodiment of the present invention, the nitride semiconductor includes a substrate and a nitride member. The nitride member includes a first nitride region containing Al x1 Ga 1-x1 N (0 < x1 ≦ 1), and a second nitride region containing Al x2 Ga 1-x2 N (0 ≦ x2 < 1, x2 < x1). The first nitride region is between the substrate and the second nitride region. The first nitride region includes a first portion and a second portion. The second portion is between the first portion and the second nitride region. The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion. The oxygen concentration in the second portion is 1 × 10 18 / cm 3It is as follows. The first thickness of the first portion in the first direction from the first nitride region to the second nitride region is thinner than the second thickness of the second portion in the first direction.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0007] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationships between the thickness and width of each part, the ratio of the sizes between parts, etc. are not necessarily the same as those in reality. Even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In this specification and each figure, the same elements as those described above with respect to the previously presented figures are denoted by the same reference numerals, and detailed descriptions thereof are omitted as appropriate.

[0008] (First Embodiment) FIG. 1 is a schematic cross-sectional view illustrating a nitride semiconductor according to the first embodiment. As shown in FIG. 1, the nitride semiconductor 110 according to the embodiment includes a substrate 18s and a nitride member 10M. The wafer 210 includes the nitride semiconductor 110.

[0009] The substrate 18s includes, for example, silicon. The substrate 18s is, for example, a silicon substrate.

[0010] The nitride member 10M includes a first nitride region 11 and a second nitride region 12.

[0011] The nitride member 10M may include a third nitride region 13, a fourth nitride region 14, a fifth nitride region 15, and the like. The fourth nitride region 14 and the fifth nitride region 15 correspond to functional layers. The third nitride region 13, the fourth nitride region 14, and the fifth nitride region 15 are provided as necessary and may be omitted. At least any one of the third nitride region 13, the fourth nitride region 14, and the fifth nitride region 15 may be regarded as being included in the second nitride region 12.

[0012] The first nitride region 11 contains Al x1 Ga 1-x1 N (0 <x1 ≦ 1). The composition ratio x1 of Al in the first nitride region 11 is, for example, 0.35 or more and 1 or less. In one example, the first nitride region 11 contains AlN.

[0013] The second nitride region 12 contains Al x2 Ga 1-x2 N (0 ≦ x2 <1, x2 <x1). The second nitride region 12 contains AlGaN or GaN. The first nitride region 11 is between the substrate 18s and the second nitride region 12.

[0014] The direction from the first nitride region 11 to the second nitride region 12 is defined as the first direction. The first direction is the Z-axis direction. One direction perpendicular to the Z-axis direction is the X-axis direction. The direction perpendicular to the Z-axis direction and the X-axis direction is the Y-axis direction.

[0015] The substrate 18s, the first nitride region 11, and the second nitride region 12 are layered along the X-Y plane.

[0016] The first nitride region 11 includes a first portion 11a and a second portion 11b. The second portion 11b is located between the first portion 11a and the second nitride region 12. For example, the first portion 11a may be in contact with the substrate 18s. For example, the second portion 11b may be in contact with the second nitride region 12. The boundary between the first portion 11a and the second portion 11b may be unclear or clear.

[0017] The oxygen concentration in the first portion 11a is higher than the oxygen concentration in the second portion 11b. The oxygen concentration in the second portion 11b is 1×10 18 / cm 3 or less.

[0018] As shown in FIG. 1, the first thickness ta of the first portion 11a in the first direction (Z-axis direction) from the first nitride region 11 to the second nitride region 12 is thinner than the second thickness tb of the second portion 11b in the first direction. With such a configuration, it has been found that defects in the nitride member 10M can be suppressed. For example, leakage current caused by defects can be suppressed. According to the embodiment, a nitride semiconductor and a semiconductor device with improved quality can be provided.

[0019] For example, it is considered that the defect is formed due to dislocations in the nitride member 10M formed on the substrate 18s. The defect is, for example, a pit. By providing the first portion 11a with a high oxygen concentration, it is considered that, for example, the propagation of dislocations can be suppressed. For example, when the first portion 11a contains AlN, oxygen oxidizes Al. The oxidized Al suppresses, for example, the propagation of dislocations. The oxidized Al functions, for example, as a mask to stop dislocations. By providing the first portion 11a with a high oxygen concentration, the defect is reduced.

[0020] In the entire first nitride region 11, increasing the oxygen concentration is considered to inhibit the growth of AlN due to the high density of oxygen. As a result, for example, the flatness tends to be low. In addition to the first portion 11a with a high oxygen concentration, by providing the second portion 11b with a low oxygen concentration, the inhibition of the growth of AlN can be suppressed. For example, high flatness is easily obtained.

[0021] The thickness tr1 (see FIG. 1) of the first nitride region 11 in the first direction (Z-axis direction) from the first nitride region 11 to the second nitride region 12 may be the sum of the first thickness ta of the first portion 11a and the second thickness tb of the second portion 11b.

[0022] FIG. 2 is a graph illustrating a nitride semiconductor according to the first embodiment. FIG. 2 illustrates the SIMS (Secondary Ion Mass Spectrometry) analysis result of the nitride semiconductor 110. In FIG. 2, the horizontal axis is the position pZ in the Z-axis direction. The left vertical axis in FIG. 2 is the oxygen concentration C(O). The right vertical axis in FIG. 2 is the secondary ion intensity Int_Al of Al.

[0023] As shown in FIG. 2, the first nitride region 11 is provided between the substrate 18s and the second nitride region 12. The first nitride region 11 includes the first portion 11a and the second portion 11b. The first portion 11a is between the substrate 18s and the second portion 11b. The oxygen concentration C(O) in the first portion 11a is higher than the oxygen concentration C(O) in the second portion 11b.

[0024] As will be described later, such a plurality of portions with different oxygen concentrations C(O) can be formed by changing the temperature during the formation of the layer that becomes the first nitride region 11. In addition, a difference in oxygen concentration can also be formed by the growth rate or the partial pressure of ammonia gas during the formation of the layer that becomes the first nitride region 11. For example, when the temperature is low, the oxygen concentration C(O) becomes high. For example, when the growth rate is high, the oxygen concentration C(O) becomes high. For example, when the partial pressure of ammonia gas is high, the oxygen concentration C(O) becomes high.

[0025] Hereinafter, an example of the experimental results regarding the defect density when the oxygen concentration C(O) in the second portion 11b is changed will be described.

[0026] FIG. 3 is a graph illustrating a nitride semiconductor according to the first embodiment. The horizontal axis in FIG. 3 is the oxygen concentration C(O)1 in the second portion 11b. The vertical axis in FIG. 3 is the defect density DD1 that causes leakage. The defect density DD1 can be detected, for example, by observing the surface of the nitride member 10M using an optical microscope. For example, in the observation using an optical microscope, the number of pits per 1 cm 2 is calculated, and the defect density DD1 is obtained from the calculation.

[0027] As shown in FIG. 3, when the oxygen concentration C(O)1 in the second portion 11b is 3×10 16 / cm 3 or more and 1×10 18 / cm 3 or less, the defect density DD1 is low. When the oxygen concentration C(O)1 is less than 3×10 16 / cm 3 , the defect density DD1 is high. When the oxygen concentration C(O)1 exceeds 1×10 18 / cm 3 , the defect density DD1 is high.

[0028] As shown in FIG. 3, the characteristics of the oxygen concentration C(O)1 and the defect density DD1 in the second portion 11b are critical. When the oxygen concentration C(O)1 is about 3×10 13 / cm 3In the vicinity of, the defect density DD1 changes rapidly. The oxygen concentration C(O)1 is about 1×10 18 / cm 3 In the vicinity of, the defect density DD1 changes rapidly.

[0029] Hereinafter, an experimental example regarding the relationship between the magnitude relationship between the first thickness ta of the first portion 11a and the second thickness tb of the second portion 11b and the defect density will be described.

[0030] FIGS. 4(a) and 4(b) are graphs illustrating a nitride semiconductor according to the first embodiment. In these figures, the horizontal axis is the position pZ in the Z-axis direction. The vertical axis is the oxygen concentration C(O). FIG. 4(a) corresponds to the first sample SPL1. FIG. 4(b) corresponds to the second sample SPL2. In the first sample SPL1, the first thickness ta is thinner than the second portion 11b. In the second sample SPL2, the first thickness ta is thicker than the second portion 11b. As will be described below, it has been found that a lower defect density can be obtained when the first thickness ta is thinner than the second portion 11b.

[0031] FIG. 5 is a graph illustrating a nitride semiconductor according to the first embodiment. The horizontal axis of FIG. 5 is the thickness ratio Ct1. The thickness ratio Ct1 is the ratio of the first thickness ta of the first portion 11a to the second thickness tb of the second portion 11b. The vertical axis of FIG. 5 is the shape defect density DD2. A part of the shape defects becomes the defects causing leakage. In the experimental example of FIG. 5, the sum of the first thickness ta and the second thickness tb is 200 nm and is constant.

[0032] As shown in FIG. 5, when the thickness ratio Ct1 is low, the shape defect density DD2 is low. The thickness ratio Ct1 is preferably, for example, 0.8 or less. The thickness ratio Ct1 may be, for example, 0.5 or less. The thickness ratio Ct1 may be, for example, 0.3 or less. A low thickness ratio Ct1 results in a low shape defect density DD2. A low shape defect density DD2 results in a low defect density DD1. A low shape defect density DD2 reduces the density of the defects causing leakage.

[0033] As shown in FIG. 2, in the first portion 11a where the oxygen concentration C(O) is high, the oxygen concentration C(O) changes rapidly. In the second portion 11b where the oxygen concentration C(O) is low, the oxygen concentration C(O) does not change rapidly. For example, in the first portion 11a, it is considered that the inhibition of the growth of AlN can be effectively suppressed by the rapid decrease in the oxygen concentration C(O). Thereby, for example, high flatness can be effectively obtained.

[0034] For example, the rate of change of the oxygen concentration C(O) in the first portion 11a with respect to the first direction (Z-axis direction) is higher than the rate of change of the oxygen concentration C(O) in the second portion 11b with respect to the first direction. With such a profile, defects can be suppressed and high flatness can be obtained. For example, a nitride semiconductor and a semiconductor device with improved quality can be provided.

[0035] The oxygen concentration C(O) in the first portion 11a is, for example, 1×10 18 / cm 3 exceeds and is preferably 3.6×10 20 / cm 3 or less. If the oxygen concentration C(O) in the first portion 11a is excessively high, it is considered that the growth of AlN is inhibited. Thereby, for example, the flatness tends to be low.

[0036] The oxygen concentration C(O) in the first portion 11a is, for example, preferably 2.5×10 19 / cm 3 or more. Thereby, the propagation of dislocations can be effectively suppressed.

[0037] As shown in FIG. 2, the oxygen concentration C(O) in the second nitride region 12 is lower than the oxygen concentration C(O) in the second portion 11b. Thereby, high flatness is obtained in the second nitride region 12. A high-quality second nitride region 12 is easily obtained. The oxygen concentration C(O) in the second nitride region 12 is, for example, preferably 1×10 17 / cm 3 or less. A high-quality second nitride region 12 is easily obtained.

[0038] In an embodiment, the first thickness ta is preferably 5 nm or more and 150 nm or less. When the first thickness ta is 5 nm or more, for example, a low defect density can be easily obtained. When the first thickness ta is 150 nm or less, a homogeneous first portion 11a can be easily obtained.

[0039] In an embodiment, the second thickness tb is preferably 50 nm or more and 300 nm or less. As described above, the second thickness tb is thicker than the first thickness ta. When the second thickness tb is 50 nm or more, for example, a homogeneous second portion 11b can be easily obtained. When the second thickness tb is 300 nm or less, for example, a low defect density can be easily obtained.

[0040] The first nitride region 11 contains, for example, AlN. The second nitride region 12 contains, for example, AlGaN. The substrate 18s contains, for example, silicon.

[0041] As shown in FIG. 1, the nitride member 10M may include a third nitride region 13. The third nitride region 13 contains, for example, Al x3 Ga 1-x3 N (0 ≦ x3 ≦ 1). The third nitride region 13 contains, for example, AlGaN or GaN. As will be described later, the third nitride region 13 may have, for example, a laminated structure. The thickness of the third nitride region (third nitride region thickness tr3: see FIG. 1) is, for example, 1000 nm or more and 8000 nm or less.

[0042] As shown in FIG. 1 and as already described, the nitride member 10M may include a fourth nitride region 14 and a fifth nitride region 15. The fourth nitride region 14 contains Al x4 Ga 1-x4 N (0 ≦ x4 <1). The composition ratio x4 of Al in the fourth nitride region 14 is, for example, 0 or more and 0.5 or less. The fourth nitride region 14 contains, for example, GaN. The composition ratio x4 of Al in the fourth nitride region 14 is lower than the composition ratio of Al in the third nitride region 13. The thickness of the fourth nitride region (fourth nitride region thickness tr4 (see FIG. 1)) is, for example, 50 nm or more and 5000 nm or less.

[0043] As shown in FIG. 1, the fourth nitride region 14 may include a first film region 14a and a second film region 14b. The first film region 14a is between the third nitride region 13 and the second film region 14b. The first film region 14a contains carbon. The second film region 14b does not contain carbon. Or, the carbon concentration in the second film region 14b is lower than the carbon concentration in the first film region 14a. By providing the first film region 14a containing carbon, for example, it becomes easier to obtain a low dislocation density. The second film region 14b with a low carbon concentration makes it easier to obtain, for example, a high electron mobility. The thickness of the first film region 14a (the first film region thickness tr4a (see FIG. 1)) is, for example, 100 nm or more and 3000 nm or less. The thickness of the second film region 14b (the second film region thickness tr4b (see FIG. 1)) is, for example, 50 nm or more and 2000 nm or less.

[0044] The fifth nitride region 15 contains Al x5 Ga 1-x5 N (0 < x5 ≦ 1, x4 < x5). The composition ratio x5 of Al in the fifth nitride region 15 is, for example, 0.05 or more and 0.35 or less. The fifth nitride region 15 is, for example, AlGaN. The thickness of the fifth nitride region 15 (the fifth nitride region thickness tr5 (see FIG. 1)) is, for example, 15 nm or more and 50 nm or less. The second nitride region 12 is between the first nitride region 11 and the fifth nitride region 15. The third nitride region 13 is between the second nitride region 12 and the fifth nitride region 15. The fourth nitride region 14 is between the third nitride region 13 and the fifth nitride region 15.

[0045] For example, a carrier region is formed in a portion of the fourth nitride region 14 facing the fifth nitride region 15. The carrier region is, for example, a two-dimensional electron gas. In a semiconductor device based on the nitride semiconductor 110, the carrier region is used for the operation of the semiconductor device.

[0046] The nitride member 10M is formed, for example, by using a source gas containing a group III element (Al or Ga) and a source gas containing a group V element (N) by, for example, the MOCVD (metal organic chemical vapor deposition) method or the like.

[0047] The semiconductor device 110 according to the embodiment includes, for example, a substrate 18s and a nitride member 10M. The nitride member 10M includes a first nitride region 11 containing Al x1 Ga 1-x1 N (0 < x1 ≦ 1). The first nitride region 11 includes a first portion 11a and a second portion 11b. The first portion 11a is between the substrate 18s and the second portion 11b. The oxygen concentration in the first portion 11a is higher than the oxygen concentration in the second portion 11b. The oxygen concentration in the second portion 11b is 1 × 10 18 / cm 3 or less. The first thickness ta of the first portion 11a in the first direction from the substrate 18s to the first nitride region 11 is thinner than the second thickness tb of the second portion 11b in the first direction. A leakage current caused by defects can be suppressed. A nitride semiconductor and a semiconductor device with improved quality can be provided.

[0048] FIG. 6 is a schematic cross-sectional view illustrating a nitride semiconductor according to the first embodiment. As shown in FIG. 6, in the nitride semiconductor 111 and the wafer 211 according to the embodiment, the third nitride region 13 has a stacked structure.

[0049] For example, the third nitride region 13 includes a plurality of first regions 13a and a plurality of second regions 13b. In the first direction (Z-axis direction) from the first nitride region 11 to the second nitride region 12, one of the plurality of first regions 13a is between one of the plurality of second regions 13b and another one of the plurality of second regions 13b. The above-mentioned one of the plurality of second regions 13b is between the above-mentioned one of the plurality of first regions 13a and another one of the plurality of first regions 13a. For example, the first regions 13a and the second regions 13b are alternately provided along the Z-axis direction.

[0050] The first region 13a contains Al y1 Ga 1-y1 N (0 < y1 ≦ 1). The second region 13b contains Al y2 Ga 1-y2 N (0 ≦ y2 < y1).

[0051] The Al composition ratio (composition ratio y1) in the first region 13a is, for example, 0.75 or more and 1 or less. In one example, the first region 13a is AlN.

[0052] The Al composition ratio (composition ratio y2) in the second region 13b is, for example, 0.06 or more and 0.3 or less. In one example, the second region 13b is Al 0.13 Ga 0.87 N.

[0053] In one example, the composition ratio y1 is equal to or less than the composition ratio x1. In one example, the composition ratio y2 is higher than the composition ratio x2.

[0054] For example, one of the plurality of first regions 13a may be in contact with the second nitride region 12. For example, one of the plurality of second regions 13b may be in contact with the second nitride region 12. For example, one of the plurality of first regions 13a may be in contact with the fourth nitride region 14. For example, one of the plurality of second regions 13b may be in contact with the fourth nitride region 14. The plurality of first regions 13a and the plurality of second regions 13b may, for example, form a superlattice structure. The absolute value of the difference between the number of the plurality of first regions 13a and the number of the plurality of second regions 13b may be 0 or 1. The number of the plurality of first regions 13a is, for example, 10 or more and 200 or less. One of the plurality of first regions 13a may be regarded as the second nitride region 12.

[0055] Each of the plurality of first regions 13a has a first region thickness t1 along the first direction (Z-axis direction). For example, the first region thickness t1 is thinner than the second nitride region thickness tr2 of the second nitride region 12 along the first direction. Each of the plurality of second regions 13b has a second region thickness t2 along the first direction. For example, the second region thickness t2 is thinner than the second nitride region thickness tr2. For example, the first region thickness t1 is thinner than the second region thickness t2.

[0056] For example, the first region thickness t1 along the first direction of each of the plurality of first regions 13a is smaller than the first nitride region thickness tr1 along the first direction of the first nitride region 11. The second region thickness t2 along the first direction of each of the plurality of second regions 13b is smaller than the first nitride region thickness tr1.

[0057] The first region thickness t1 is, for example, 3 nm or more and 10 nm or less. In one example, the first region thickness t1 is 5 nm. The second region thickness t2 is, for example, 15 nm or more and 40 nm or less. In one example, the second region thickness t2 is 25 nm.

[0058] In the third nitride region 13 having such a structure, for example, at the interface between the first region 13a and the second region 13b, dislocations are likely to bend. A lower dislocation density is easily obtained. By providing a plurality of regions having different Al composition ratios, for example, a high breakdown voltage is easily obtained.

[0059] Hereinafter, an example of a method for manufacturing the nitride semiconductor 111 (wafer 211) will be described.

[0060] The substrate 18s is treated by organic cleaning and acid cleaning. The substrate 18s is introduced into an MOCVD apparatus. In a hydrogen atmosphere, the surface of the substrate 18s is heat-treated at 1000°C. By the heat treatment, for example, the oxide film on the surface of the substrate 18s is removed.

[0061] Thereafter, the first nitride region 11 is formed. For example, using trimethylaluminum (TMAl) and ammonia (NH3), an AlN layer that becomes the first portion 11a is formed at 780°C. The first thickness ta of the first portion 11a is, for example, 80 nm (for example, 5 nm or more and 150 nm or less). The growth temperature when forming the first portion 11a is, for example, 550°C or more and 800°C or less.

[0062] Thereafter, the substrate temperature is set to 1020 °C, and TMAI and NH3 are used to form an AlN layer that becomes the second portion 11b. The second thickness tb of the second portion 11b is, for example, 250 nm (for example, 90 nm or more and 300 nm or less). The growth temperature when forming the second portion 11b is, for example, 1000 °C or more and 1100 °C or less.

[0063] The oxygen concentration C(O) in the first portion 11a and the second portion 11b can be changed, for example, by temperature (the temperature of the substrate 18s) or ammonia partial pressure. By lowering the temperature, the oxygen concentration C(O) increases. By increasing the ammonia partial pressure, the oxygen concentration C(O) increases. For example, the ammonia partial pressure when forming the first portion 11a is 73 Pa, and the ammonia partial pressure when forming the second portion 11b is 6 Pa. For example, the ammonia partial pressure when forming the second portion 11b is 1 / 10 or less of the ammonia partial pressure when forming the first portion 11a.

[0064] For example, the second portion 11b substantially does not contain carbon. Or the concentration of carbon in the second portion 11b is, for example, lower than the concentration of carbon in the first portion 11a. For example, the ratio of the concentration of carbon in the second portion 11b to the concentration of carbon in the first portion 11a is 0.05 or less. By the first portion 11a containing carbon, for example, in the nitride member 10M, a low dislocation density is likely to be obtained. For example, in the first portion 11a containing carbon, the direction of the dislocations is likely to bend. Thereby, the dislocations propagating to the second portion 11b are reduced. For example, the ratio of the concentration of carbon in the second portion 11b to the concentration of carbon in the first portion 11a may also be 0.0001 or more.

[0065] Thereafter, the second nitride region 12 is formed. For example, using TMAI, trimethylgallium (TMGa), and ammonia, an AlGaN layer that becomes at least a part of the second nitride region 12 is formed at 960 °C. This AlGaN layer is, for example, carbon-doped Al 0.12 Ga 0.88It is an N layer. The thickness of the second nitride region 12 (second nitride region thickness tr2) is, for example, 250 nm (for example, 50 nm or more and 2000 nm or less). The carbon concentration in the second nitride region 12 is, for example, 4.0×10 18 / cm 3 . For example, the carbon concentration in the second nitride region 12 is higher than the carbon concentration in the first nitride region 11. By including carbon in the second nitride region 12, for example, in the nitride member 10M, a low dislocation density is easily obtained. For example, in the second nitride region 12 containing carbon, the direction of dislocations is likely to bend. As a result, the dislocations extending above the second nitride region 12 are reduced. The oxygen concentration in the second nitride region 12 is, for example, 7.9×10 15 / cm 3 . For example, the oxygen concentration in the second nitride region 12 is lower than the oxygen concentration in the first nitride region 11. Thereby, high flatness is obtained in the second nitride region 12. A high-quality second nitride region 12 is easily obtained.

[0066] Thereafter, a third nitride region 13 is formed. For example, the third nitride region 13 includes a plurality of first regions 13a and a plurality of second regions 13b. For example, in an atmosphere containing nitrogen and hydrogen, using TMAl and ammonia, an AlN layer serving as the first region 13a is formed. The temperature for forming the first region 13a is, for example, 940°C. The thickness of the first region 13a (first region thickness t1) is, for example, 5 nm (for example, 2 nm or more and 15 nm or less).

[0067] On the first region 13a, using TMAl, TMGa, and ammonia, an Al 0.13 Ga 0.87 N layer serving as the second region 13b is formed. The temperature for forming the second region 13b is, for example, 940°C. The thickness of the second region 13b (second region thickness t2) is, for example, 25 nm (for example, 15 nm or more and 40 nm or less). Such formation of the first region 13a and formation of the second region 13b are repeated 125 times in total. On the last second region 13b, the first region 13a is further formed. Thereby, the third nitride region 13 is formed.

[0068] The concentration of carbon in the third nitride region 13 is, for example, 1.5×10 19 / cm 3 (for example, 5×10 18 / cm 3 or more and 9×10 19 / cm 3 or less). The concentration of oxygen in the third nitride region 13 is, for example, 3.9×10 16 / cm 3 (for example, 5×10 15 / cm 3 or more and 1×10 17 / cm 3 or less). For example, the concentration of carbon in the third nitride region 13 is higher than the concentration of carbon in the second nitride region 12. The concentration of oxygen in the third nitride region 13 is higher than the concentration of oxygen in the second nitride region 12.

[0069] Thereafter, the temperature of the substrate 18s is set to, for example, 940°C, and TMGa and ammonia are used in a hydrogen atmosphere to form the first film region 14a. The first film region 14a is, for example, a GaN layer. The first film region 14a contains carbon. The thickness of the first film region 14a is, for example, 1000 nm (for example, 100 nm or more and 3000 nm or less). The concentration of carbon in the first film region 14a is, for example, 3×10 19 / cm 3 (for example, 5×10 18 / cm 3 or more and 9×10 19 / cm 3 or less).

[0070] Thereafter, the temperature of the substrate 18s is set to, for example, 1040°C, and TMGa and ammonia are used to form the second film region 14b. The second film region 14b is, for example, an undoped GaN layer. The thickness of the second film region 14b is, for example, 500 nm (for example, 50 nm or more and 2000 nm or less).

[0071] Thereafter, the temperature of the substrate 18s is set to, for example, 1020°C, and TMGa, TMAl and ammonia are used to form the fifth nitride region 15. The fifth nitride region 15 is, for example, an undoped Al0.2 Ga 0.8 It is a GaN layer. The thickness of the fifth nitride region 15 is, for example, 30 nm (for example, 15 nm or more and 50 nm or less).

[0072] The first film region 14a, the second film region 14b, and the fifth nitride region 15 form part of the functional layer.

[0073] (Second Embodiment) The second embodiment relates to a semiconductor device. FIG. 7 is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment. As shown in FIG. 7, the semiconductor device 120 according to the embodiment includes a nitride semiconductor according to the first embodiment (in this example, the nitride semiconductor 110), a first electrode 51, a second electrode 52, a third electrode 53, and an insulating member 61.

[0074] The direction from the first electrode 51 to the second electrode 52 is along a second direction that intersects the first direction (Z-axis direction). The second direction is, for example, the X-axis direction. The position of the third electrode 53 in the second direction is between the position of the first electrode 51 in the second direction and the position of the second electrode 52 in the second direction.

[0075] The nitride member 10M includes the first to fifth nitride regions 11 to 15. The fourth nitride region 14 includes a first partial region 10a, a second partial region 10b, a third partial region 10c, a fourth partial region 10d, and a fifth partial region 10e. The direction from the first partial region 10a to the first electrode 51 is along the first direction (Z-axis direction). The direction from the second partial region 10b to the second electrode 52 is along the first direction. The third partial region 10c is between the first partial region 10a and the second partial region 10b in the second direction (X-axis direction). The direction from the third partial region 10c to the third electrode 53 is along the first direction. The fourth partial region 10d is between the first partial region 10a and the third partial region 10c in the second direction. The fifth partial region 10e is between the third partial region 10c and the second partial region 10b in the second direction.

[0076] The fifth nitride region 15 includes a sixth sub-region 15f and a seventh sub-region 15g. The direction from the fourth sub-region 10d to the sixth sub-region 15f is along the first direction (Z-axis direction). The direction from the fifth sub-region 10e to the seventh sub-region 15g is along the first direction.

[0077] The insulating member 61 is between the nitride member 10M and the third electrode 53. For example, the insulating member 61 includes a first insulating region 61p. The first insulating region 61p is provided between the third sub-region 10c and the third electrode 53 in the first direction (Z-axis direction).

[0078] The semiconductor device 120 may include a nitride semiconductor 111. In the semiconductor device 120, the current flowing between the first electrode 51 and the second electrode 52 can be controlled by the potential of the third electrode 53. The potential of the third electrode 53 is, for example, a potential based on the potential of the first electrode 51. The first electrode 51 functions as a source electrode, for example. The second electrode 52 functions as a drain electrode, for example. The third electrode 53 functions as a gate electrode, for example. In one example, the semiconductor device 120 is a HEMT (High Electron Mobility Transistor). According to the embodiment, a semiconductor device with improved characteristics can be provided.

[0079] In the semiconductor device 120, at least a part of the third electrode 53 is between the sixth sub-region 15f and the seventh sub-region 15g in the second direction (for example, the X-axis direction). At least a part of the third electrode 53 may be between the fourth sub-region 10d and the fifth sub-region 10e in the second direction (for example, the X-axis direction). The semiconductor device 120 is, for example, normally-off type.

[0080] FIG. 8 is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment. As shown in FIG. 8, the semiconductor device 121 according to the embodiment includes a nitride semiconductor according to the first embodiment (in this example, the nitride semiconductor 110), a first electrode 51, a second electrode 52, a third electrode 53, and an insulating member 61. In the semiconductor device 121, the third electrode 53 does not overlap with the sixth partial region 15f and the seventh partial region 15g in the second direction (for example, the X-axis direction). The third electrode 53 does not overlap with the fourth partial region 10d and the fifth partial region 10e in the second direction (for example, the X-axis direction). The semiconductor device 121 is, for example, a normally-on type.

[0081] (Third Embodiment) The third embodiment relates to a method for manufacturing a nitride semiconductor. The method for manufacturing a nitride semiconductor according to the third embodiment may be applied to a method for manufacturing a wafer or a method for manufacturing a semiconductor device.

[0082] FIG. 9 is a flowchart illustrating a method for manufacturing a nitride semiconductor according to the third embodiment. As shown in FIG. 9, in the method for manufacturing a nitride semiconductor according to the embodiment, a first portion 11a of a first nitride region 11 containing Al x1 Ga 1-x1 N (0 <x1 ≦ 1) is formed at a first temperature (step S120). After the formation of the first portion 11a, a second portion 11b of the first nitride region 11 is formed at a second temperature higher than the first temperature (step S130). After the formation of the second portion 11b, a second nitride region 12 containing Al x2 Ga 1-x2 N (0 ≦ x2 <1, x2 <x1) is formed (step S140). As shown in FIG. 9, before step S120, the substrate 18s may be heat-treated (step S110).

[0083] Due to the above temperature, the oxygen concentration C(O) in the first portion 11a becomes higher than the oxygen concentration C(O) in the second portion 11b.

[0084] The oxygen concentration C(O) in the second portion 11b is 1 × 10 18 / cm 3It is as follows. The first thickness ta of the first part 11a is thinner than the second thickness tb of the second part 11b.

[0085] By such a manufacturing method, a nitride semiconductor, a semiconductor device, and a method for manufacturing a nitride semiconductor capable of improving quality can be provided.

[0086] In an embodiment, the oxygen concentration C(O) in the second part 11b is preferably 3×10 16 / cm 3 or more. It is preferably more than 1×10 18 / cm 3 and preferably 3.6×10 20 / cm 3 or less.

[0087] The above-mentioned first temperature is, for example, 550°C or higher and 800°C or lower. The above-mentioned second temperature is, for example, 1000°C or higher. The second temperature is, for example, 1100°C or lower.

[0088] For example, the third temperature in the formation of the second nitride region 12 is higher than the above-mentioned first temperature. A low oxygen concentration C(O) is obtained in the second nitride region 12. The oxygen concentration C(O) in the second nitride region 12 is lower than the oxygen concentration C(O) in the second part 11b.

[0089] In an embodiment, information regarding the shape of the nitride region, etc. is obtained, for example, by electron microscope observation, etc. Information regarding the composition and element concentration in the nitride region is obtained, for example, by EDX (Energy Dispersive X-ray Spectroscopy), or SIMS (Secondary Ion Mass Spectrometry), etc. Information regarding the composition in the nitride region may be obtained, for example, by X-ray reciprocal lattice space mapping, etc.

[0090] According to an embodiment, a nitride semiconductor, a semiconductor device, and a method for manufacturing a nitride semiconductor capable of suppressing warpage can be provided.

[0091] The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, regarding the specific configurations of each element such as the nitride member, nitride region, and substrate included in the nitride semiconductor, those skilled in the art can appropriately select from the known range to similarly implement the present invention and obtain the same effects as long as they are included in the scope of the present invention.

[0092] In addition, combinations of any two or more elements of each specific example within a technically possible range are also included in the scope of the present invention as long as they include the gist of the present invention.

[0093] Furthermore, based on the nitride semiconductor, semiconductor device, and manufacturing method of the nitride semiconductor described above as embodiments of the present invention, all nitride semiconductors, semiconductor devices, and manufacturing methods of the nitride semiconductor that those skilled in the art can appropriately design and modify and implement also belong to the scope of the present invention as long as they include the gist of the present invention.

[0094] In addition, within the scope of the idea of the present invention, those skilled in the art can conceive of various modification examples and correction examples, and these modification examples and correction examples are also understood to belong to the scope of the present invention.

[0095] Some embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention and are also included in the scope of the invention described in the claims and its equivalents.

Explanation of Reference Numerals

[0096] 10M... nitride member, 10a~10e... first to fifth partial regions, 11~15... first to fifth nitride regions, 11a, 11b... first and second parts, 13a, 13b... first and second regions, 14a, 14b... first and second film regions, 15f... sixth partial region, 15g... seventh partial region, 18s... substrate, 51~53... first to third electrodes, 61... insulating member, 61p... first insulating region, 110, 111... nitride semiconductors, 120, 121... semiconductor devices, 210, 211... wafers, C(O), C(O)1... oxygen concentration, Ct1... thickness ratio, DD1... defect density, DD2... shape defect density, Int_Al... secondary ion intensity, SPL1, SPL2... first and second samples, pZ... position, t1, t2... first and second region thicknesses, ta, tb... first and second thicknesses, tr1~tr5... first to fifth nitride region thicknesses, tr4a, tr4b... first and second film region thicknesses

Claims

1. a substrate, a nitride member, and comprising, the nitride member, Al ｘ１ Ga １－ｘ１ A first nitride region containing N (0 < x1 ≤ 1), where x1 is 1, and Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), comprising, the first nitride region is between the substrate and the second nitride region, the first nitride region includes a first portion and a second portion, the first portion and the second portion contain AlN, the second portion is between the first portion and the second nitride region, the oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, a nitride semiconductor in which a first thickness of the first portion in a first direction from the first nitride region to the second nitride region is thinner than a second thickness of the second portion in the first direction.

2. a substrate, a nitride member, and comprising, the nitride member, Al ｘ１ Ga １－ｘ１ a first nitride region containing N (0 < x1 ≤ 1), Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), comprising, the first nitride region is between the substrate and the second nitride region, the first nitride region includes a first portion and a second portion, an Al composition ratio in the first portion is the same as an Al composition ratio in the second portion, the second portion is between the first portion and the second nitride region, the oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, a nitride semiconductor in which a first thickness of the first portion in a first direction from the first nitride region to the second nitride region is thinner than a second thickness of the second portion in the first direction.

3. The nitride semiconductor according to claim 1 or 2, wherein the first thickness is 0.8 times or less of the second thickness.

4. The first thickness is 5 nm or more and 150 nm or less, The nitride semiconductor according to any one of claims 1 to 3, wherein the second thickness is 50 nm or more and 300 nm or less.

5. a substrate, a nitride member, and comprising, the nitride member, Al ｘ１ Ga １－ｘ１ a first nitride region containing N(0 < x1 ≤ 1), where x1 is 1, and Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), comprising, the first nitride region is between the substrate and the second nitride region, the first nitride region includes a first portion and a second portion, the first portion and the second portion contain AlN, the second portion is between the first portion and the second nitride region, the oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, a nitride semiconductor in which a change rate of the oxygen concentration in the first portion with respect to a first direction from the first nitride region to the second nitride region is higher than a change rate of the oxygen concentration in the second portion with respect to the first direction.

6. a substrate, a nitride member, and comprising, the nitride member, Al ｘ１ Ga １－ｘ１ a first nitride region containing N (0 < x1 ≤ 1), Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), comprising, The first nitride region is between the substrate and the second nitride region, The first nitride region includes a first portion and a second portion, The Al composition ratio in the first portion is the same as the Al composition ratio in the second portion, The second portion is between the first portion and the second nitride region, The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, For the nitride semiconductor, the rate of change of the oxygen concentration in the first portion in a first direction from the first nitride region to the second nitride region is higher than the rate of change of the oxygen concentration in the second portion in the first direction.

7. The oxygen concentration in the second part is 3×10 １６ / cm ３ or more. The nitride semiconductor according to any one of claims 1 to 6.

8. The oxygen concentration in the first part exceeds 1×10 １８ / cm ３ and is 3.6×10 ２０ / cm ３ or less. The nitride semiconductor according to any one of claims 1 to 7.

9. The oxygen concentration in the first part is 2.5×10 １９ / cm ３ or more. The nitride semiconductor according to claim 8.

10. A substrate, A nitride member, Comprising: The nitride member is A first nitride region containing Alx1Ga1 - x1N (0 < x1 ≤ 1), A second nitride region containing Alx2Ga1 - x2N (0 ≤ x2 < 1, x2 < x1), Including The first nitride region is between the substrate and the second nitride region, The first nitride region includes a first portion and a second portion, The first portion and the second portion contain AlN, The second portion is between the first portion and the second nitride region, The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second portion is 1 × 10^18 / cm^3 or less, The first thickness of the first portion in the first direction from the first nitride region to the second nitride region is thinner than the second thickness of the second portion in the first direction, The oxygen concentration in the second nitride region is lower than the oxygen concentration in the second portion, a nitride semiconductor.

11. A substrate, A nitride member, Comprising: The nitride member is Al ｘ１ Ga １－ｘ１ A first nitride region containing N (0 < x1 ≤ 1), and Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), Including The first nitride region is between the substrate and the second nitride region, The first nitride region includes a first portion and a second portion, The first portion and the second portion contain AlN, The second portion is between the first portion and the second nitride region, The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, For the first portion, the rate of change of the oxygen concentration in a first direction from the first nitride region to the second nitride region is higher than the rate of change of the oxygen concentration in the second portion in the first direction. A nitride semiconductor in which the oxygen concentration in the second nitride region is lower than the oxygen concentration in the second portion. **Claim 12** A substrate, A nitride member, Comprising: The nitride member Al ｘ１ Ga １－ｘ１ a first nitride region containing N (0 < x1 ≤ 1), Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), Including The first nitride region is between the substrate and the second nitride region, The first nitride region includes a first portion and a second portion, The second portion is between the first portion and the second nitride region, The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, The first thickness of the first portion in the first direction from the first nitride region to the second nitride region is thinner than the second thickness of the second portion in the first direction, A nitride semiconductor in which the oxygen concentration in the second nitride region is lower than the oxygen concentration in the second portion. **Claim 13** A substrate, A nitride member, Comprising: The nitride member Al ｘ１ Ga １－ｘ１ a first nitride region containing N (0 < x1 ≤ 1), and Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), Including The first nitride region is between the substrate and the second nitride region, The first nitride region includes a first portion and a second portion, The second portion is between the first portion and the second nitride region, The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, The rate of change of the oxygen concentration in the first portion with respect to the first direction from the first nitride region to the second nitride region is higher than the rate of change of the oxygen concentration in the second portion with respect to the first direction, A nitride semiconductor in which the oxygen concentration in the second nitride region is lower than the oxygen concentration in the second portion. **Claim 14** The oxygen concentration in the second nitride region is 1×10 １７ / cm ３ or less. The nitride semiconductor according to any one of claims 10 to 13. **Claim 15** The nitride semiconductor according to claim 2 or 6 or 12 or 13, wherein the first nitride region contains AlN. **Claim 16** The nitride semiconductor according to any one of claims 1 to 15, wherein the substrate contains silicon. **Claim 17** The nitride member contains Al ｘ３ Ga １－ｘ３ and further includes a third nitride region containing N (0 ≦ x3 ≦ 1). The nitride semiconductor according to any one of claims 1 to 16, wherein the second nitride region is between the first nitride region and the third nitride region. **Claim 18** The third nitride region includes a plurality of first regions and a plurality of second regions, In the first direction, one of the plurality of first regions is between one of the plurality of second regions and another one of the plurality of second regions, and the one of the plurality of second regions is between the one of the plurality of first regions and another one of the plurality of first regions. The first region contains Al ｙ１ Ga １－ｙ１ N (0 < y1 ≤ 1), The second region contains Al ｙ２ Ga １－ｙ２ N (0 ≦ y2 < y1), the nitride semiconductor according to claim 17. **Claim 19** The nitride member Al ｘ４ Ga １－ｘ４ a fourth nitride region containing N (0 ≦ x4 < 1), and Al ｘ５ Ga １－ｘ５ a fifth nitride region containing N (0 < x5 ≤ 1, x4 < x5), Further including The third nitride region is between the first nitride region and the fifth nitride region, The fourth nitride region is between the third nitride region and the fifth nitride region, The nitride semiconductor according to claim 17.

20. The nitride semiconductor according to claim 19, A first electrode, A second electrode, A third electrode, An insulating member, Comprising, The direction from the first electrode to the second electrode is along a second direction that intersects the direction from the first nitride region to the second nitride region, The position of the third electrode in the second direction is between the position of the first electrode in the second direction and the position of the second electrode in the second direction, The fourth nitride region includes a first partial region, a second partial region, a third partial region, a fourth partial region, and a fifth partial region, The direction from the first partial region to the first electrode is along the first direction, The direction from the second partial region to the second electrode is along the first direction, The third partial region is between the first partial region and the second partial region in the second direction, and the direction from the third partial region to the third electrode is along the first direction, The fourth partial region is between the first partial region and the third partial region in the second direction, The fifth partial region is between the third partial region and the second partial region in the second direction, The fifth nitride region includes a sixth partial region and a seventh partial region, The direction from the fourth partial region to the sixth partial region is along the first direction, The direction from the fifth partial region to the seventh partial region is along the first direction, The insulating member is between the nitride member and the third electrode, a semiconductor device.

21. Al ｘ１ Ga １－ｘ１ Form a first portion of a first nitride region containing N (0 < x1 ≤ 1) at a first temperature, After the formation of the first portion, a second portion of the first nitride region is formed at a second temperature higher than the first temperature, After the formation of the second part, Al ｘ２ Ga １－ｘ２ form a second nitride region containing N (0 ≦ x2 < 1, x2 < x1), The oxygen concentration in the first portion is higher than the oxygen concentration in the second portion, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, The first thickness of the first portion is thinner than the second thickness of the second portion, The third temperature in the formation of the second nitride region is higher than the first temperature, a method for manufacturing a nitride semiconductor.

22. The first temperature is 550 °C or higher and 800 °C or lower, The second temperature is 1000 °C or higher, the method for manufacturing a nitride semiconductor according to claim 21.

23. Al ｘ１ Ga １－ｘ１ Form a first portion of a first nitride region containing N (0 < x1 ≤ 1) at a first temperature, After the formation of the first portion, a second portion of the first nitride region is formed at a second temperature higher than the first temperature, After the formation of the second part, Al ｘ２ Ga １－ｘ２ a second nitride region containing N (0 ≦ x2 < 1, x2 < x1) is formed, The oxygen concentration in the first part is higher than the oxygen concentration in the second part, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, The first thickness of the first part is thinner than the second thickness of the second part, The first temperature is 550 °C or higher and 800 °C or lower, The second temperature is 1000 °C or higher. A method for manufacturing a nitride semiconductor.

24. The oxygen concentration in the second part is 3×10 １６ / cm ３ or more. The method for manufacturing a nitride semiconductor according to any one of claims 21 to 23.

25. The oxygen concentration in the first part exceeds 1×10 １８ / cm ３ and is 3.6×10 ２０ / cm ３ or less. The method for manufacturing a nitride semiconductor according to any one of claims 21 to 24.

26. A substrate, A nitride member, Comprising, The nitride member contains Al ｘ１ Ga １－ｘ１ and includes a first nitride region containing N (0 < x1 ≤ 1). The first nitride region includes a first part and a second part, The Al composition ratio in the first part is the same as the Al composition ratio in the second part, The first part is between the substrate and the second part, The oxygen concentration in the first part is higher than the oxygen concentration in the second part, The oxygen concentration in the second part is 1×10 １８ / cm ３ or less, A nitride semiconductor in which the first thickness of the first part in the first direction from the substrate to the first nitride region is thinner than the second thickness of the second part in the first direction.

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