Nitride semiconductors and semiconductor devices

Abstract

To provide a nitride semiconductor and a semiconductor device, capable of improving characteristics.SOLUTION: According to one embodiment, a nitride member of a nitride semiconductor includes: a first nitride region including Alx1Ga1-x1N (0<x1≤1); a second nitride region including Alx2Ga1-x2N (0≤x2<1, x2<x1); and a third nitride region including Alx3Ga1-x3N (0≤x3<1, x3<x1). The second nitride region is provided between the first nitride region and the third nitride region. The second nitride region includes carbon and oxygen. The first nitride region does not include carbon. Alternatively, a second carbon concentration in the second nitride region is higher than a first carbon concentration in the first nitride region. The second carbon concentration is higher than a third carbon concentration in the third nitride region. A ratio of the second oxygen concentration in the second nitride region to the second carbon concentration is equal to or greater than 1.0×10-4 and equal to or less than 1.4×10-3.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] For example, in a semiconductor device based on a nitride semiconductor, improvement in characteristics 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 and a semiconductor device capable of improving characteristics.

Means for Solving the Problems

[0005] According to an embodiment of the present invention, the nitride semiconductor includes a nitride member. The nitride member includes a first nitride region containing Al x1 Ga 1-x1 N (0 < x1 ≤ 1), a second nitride region containing Al x2 Ga 1-x2 N (0 ≤ x2 < 1, x2 < x1), and Al x3 Ga 1-x3It includes a third nitride region including N(0≦x3<1, x3<x1). The second nitride region is provided between the first nitride region and the third nitride region in a first direction from the first nitride region to the second nitride region. The second nitride region contains carbon and oxygen. The first nitride region does not contain carbon. Or, a second carbon concentration in the second nitride region is higher than a first carbon concentration in the first nitride region. The second carbon concentration is higher than a third carbon concentration in the third nitride region. A ratio of a second oxygen concentration in the second nitride region to the second carbon concentration is 1.0×10 -4 or more and 1.4×10 -3 or less.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a nitride semiconductor according to the first embodiment. [Figure 2] FIG. 2 is a graph illustrating a nitride semiconductor according to the first embodiment. [Figure 3] FIG. 3 is a graph illustrating characteristics of a nitride semiconductor. [Figure 4] FIG. 4 is a graph illustrating characteristics of a nitride semiconductor. [Figure 5] FIG. 5 is a graph illustrating characteristics of a nitride semiconductor. [Figure 6] FIG. 6 is a graph illustrating a nitride semiconductor according to the first embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating a semiconductor device according to the second embodiment.

Modes 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 relationship between the thickness and width of each part, the size ratio 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 reference numerals are assigned to elements similar to those described above with respect to the previously presented figures, 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 nitride member 10M.

[0009] The nitride member 10M includes a first nitride region 11, a second nitride region 12, and a third nitride region 13. The second nitride region 12 is provided between the first nitride region 11 and the third nitride region 13.

[0010] The first nitride region 11 contains Al x1 Ga 1-x1 N (0 < x1 ≦ 1). The first nitride region 11 includes, for example, AlGaN. For example, the composition ratio of Al in the first nitride region 11 is, for example, 0.05 or more and 0.6 or less. As shown in FIG. 1, the first nitride region 11 may have a laminated structure. In this case, the effective (e.g., average) composition ratio of Al in the first nitride region 11 is, for example, 0.15 or more and 0.55 or less. Examples of the laminated structure will be described later.

[0011] The second nitride region 12 contains Al x2 Ga 1-x2 N (0 ≦ x2 < 1, x2 < x1). The composition ratio of Al in the second nitride region 12 is, for example, 0 or more and 0.25 or less. The second nitride region 12 includes, for example, GaN. The second nitride region 12 contains carbon and oxygen.

[0012] The third nitride region 13 contains Al x3 Ga 1-x3It includes N(0≦x3<1, x3<x1). The composition ratio of Al in the third nitride region 13 is, for example, 0 or more and 0.25 or less. The third nitride region 13 includes, for example, GaN. The third nitride region 13 substantially does not contain carbon. Or, the carbon concentration in the third nitride region 13 is lower than the carbon concentration in the second nitride region 12.

[0013] Taking the first direction D1 from the first nitride region 11 to the second nitride region 12 as the Z-axis direction. One direction perpendicular to the Z-axis direction is taken as the X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as the Y-axis direction. The first nitride region 11, the second nitride region 12, and the third nitride region 13 are layered along the X-Y plane.

[0014] As shown in FIG. 1, the nitride semiconductor 110 may further include a substrate 18s. There is a first nitride region 11 between the substrate 18s and the second nitride region 12. The substrate 18s is, for example, a crystal substrate. The substrate 18s may include, for example, at least any one of a silicon substrate, a sapphire substrate, a SiC substrate, or a GaN substrate.

[0015] The first nitride region 11 does not contain carbon. Or, the carbon concentration in the second nitride region 12 is higher than the carbon concentration in the first nitride region 11. The carbon concentration in the second nitride region 12 is higher than the carbon concentration in the third nitride region 13.

[0016] In an embodiment, the ratio of the oxygen concentration (second oxygen concentration) in the second nitride region 12 to the second carbon concentration is 1.0×10 -4 or more and 1.4×10 -3The following is an explanation. It has been found that a semiconductor device including such a nitride semiconductor 110 can have a high punch-through voltage. The punch-through voltage corresponds to the voltage at which current suddenly starts to flow when a voltage is applied between the base 18s and the third nitride region 13. When the punch-through voltage is high, the semiconductor device including the nitride semiconductor 110 has a high breakdown voltage. According to the embodiment, it is possible to provide a nitride semiconductor and a semiconductor device that can have improved characteristics. Examples of semiconductor devices including the nitride semiconductor 110 will be described later.

[0017] The experimental results will be explained below. In the experiment, the nitride member 10M is formed by MOCVD (Metal Organic Chemical Vapor Deposition). In the experiment, the second nitride region 12 is formed on the first nitride region 11 at approximately 940°C. In forming the second nitride region 12, a source gas containing TMGa (Trimethyl Gallium) and ammonia is supplied in a hydrogen atmosphere. By forming the second nitride region 12 at a low temperature, the second nitride region 12 containing carbon and oxygen is obtained.

[0018] The third nitride region 13 is formed on the second nitride region 12 at approximately 1040° C. In forming the third nitride region 13, TMGa and ammonia are supplied in a hydrogen atmosphere. By forming the third nitride region 13 at a high temperature, the third nitride region 13 is obtained which is substantially free of carbon and oxygen.

[0019] Thereafter, a fourth nitride region 14 (see FIG. 1) is formed to form a semiconductor device. The fourth nitride region 14 includes AlGaN. Further, a source electrode, a drain electrode, and a gate electrode are formed, thereby obtaining a semiconductor device.

[0020] FIG. 2 is a graph illustrating the nitride semiconductor according to the first embodiment. FIG. 2 illustrates the results of SIMS (Secondary Ion Mass Spectrometry) analysis of the nitride member 10M. The horizontal axis of FIG. 2 represents the position pZ in the Z-axis direction. The vertical axis on the left side of FIG. 2 represents the carbon concentration CC and the oxygen concentration CO. The vertical axis on the right side of FIG. 2 represents the detection intensity Int_Al of Al secondary ions and the detection intensity Int_Ga of gallium secondary ions.

[0021] 2, the carbon concentration CC in the second nitride region 12 (second carbon concentration CC2) is higher than the carbon concentration CC in the first nitride region 11 (first carbon concentration CC1). The second carbon concentration CC2 is higher than the carbon concentration CC in the third nitride region 13 (third carbon concentration CC3). In this example, the first carbon concentration CC1 is about 1.7×10 19 / cm 3 The second carbon concentration CC2 is approximately 5.0 × 10 19 / cm 3 The third carbon concentration CC3 is approximately 4.0 × 10 16 / cm 3 is.

[0022] On the other hand, the oxygen concentration CO in the third nitride region 13 (third oxygen concentration CO3) is lower than the oxygen concentration CO in the first nitride region 11 (first oxygen concentration CO1). The oxygen concentration CO in the second nitride region 12 (second oxygen concentration CO2) is lower than the oxygen concentration CO in the first nitride region 11 (first oxygen concentration CO1). The oxygen concentration CO in the second nitride region 12 (second oxygen concentration CO2) is between the third oxygen concentration CO3 and the first oxygen concentration CO1. In this example, the first oxygen concentration CO1 is about 3.5×10 16 / cm 3 The second oxygen concentration CO2 is about 1.5 x 10 16 / cm 3 The third oxygen concentration CO3 is about 5.0 x 10 15 / cm 3 is.

[0023] Thus, the second nitride region 12 contains oxygen and has a high carbon concentration. It is believed that the inclusion of oxygen in the second nitride region 12 makes it easier for carbon to function as an acceptor. For example, the second nitride region 12 is more likely to have a high resistance. For example, the hole concentration increases in the second nitride region 12. It is believed that this can increase the punch-through voltage of the nitride semiconductor 110.

[0024] In the embodiment, the first carbon concentration CC1 may be, for example, an average value of the carbon concentration CC in the first nitride region 11. The second carbon concentration CC2 may be, for example, an average value of the carbon concentration CC in the second nitride region 12. The third carbon concentration CC3 may be, for example, an average value of the carbon concentration CC in the third nitride region 13.

[0025] The first oxygen concentration CO1 may be, for example, an average value of the oxygen concentration CO in the first nitride region 11. The second oxygen concentration CO2 may be, for example, an average value of the oxygen concentration CO in the second nitride region 12. The third oxygen concentration CO3 may be, for example, an average value of the oxygen concentration CO in the third nitride region 13.

[0026] Hereinafter, experimental results regarding the carbon concentration CC and the oxygen concentration CO in the second nitride region 12 will be described.

[0027] In experiments, the carbon concentration CC and oxygen concentration CO in the second nitride region 12 are changed by changing the flow rate of the source gas during the formation of the second nitride region 12. For example, lowering the growth pressure tends to increase the carbon concentration CC. For example, increasing the growth rate tends to increase the carbon concentration CC. For example, increasing the ammonia partial pressure tends to increase the oxygen concentration CO. For example, decreasing the growth temperature tends to increase the oxygen concentration CO.

[0028] FIG. 3 is a graph illustrating the characteristics of nitride semiconductors. The horizontal axis of Fig. 3 is the ratio R2. The ratio R2 is the ratio (CO2 / CC2) of the second oxygen concentration CO2 to the second carbon concentration CC2. As already explained, the second carbon concentration CC2 is the concentration CC of carbon in the second nitride region 12. The second oxygen concentration CO2 is the concentration CO of oxygen in the second nitride region 12. The vertical axis of Fig. 3 is the punch-through voltage Vp1.

[0029] The punch-through voltage Vp1 is evaluated as follows: the voltage between the source electrode formed on the fourth nitride region 14 and the substrate 18s is changed, and the current flowing between the source electrode and the drain electrode is measured. In this example, the voltage at which the current value becomes 1 μA in the voltage-current characteristics is determined to be the punch-through voltage.

[0030] As shown in FIG. 3, when the ratio R2 is too low, the punch-through voltage Vp1 is low. When the ratio R2 is too high, the punch-through voltage Vp1 is low. When the ratio R2 is 1.0×10 -4 Over 1.4 x 10 -3 It has been found that a high punch-through voltage Vp1 can be obtained in the following cases: The punch-through voltage Vp1 changes critically with respect to the ratio R2. According to the embodiments, it is possible to provide a nitride semiconductor and a semiconductor device that can improve characteristics.

[0031] For example, if the oxygen concentration CO is too low in the second nitride region 12, it is thought that carbon has difficulty functioning as an acceptor. If the oxygen concentration CO is too high in the second nitride region 12, oxygen functions as a donor, making current leakage more likely to occur. In the second nitride region 12, a high punch-through voltage Vp1 can be obtained when the ratio R2 is appropriate.

[0032] FIG. 4 is a graph illustrating the characteristics of nitride semiconductors. The horizontal axis of Fig. 4 is the second carbon concentration CC2. As already explained, the second carbon concentration CC2 is the concentration CC of carbon in the second nitride region 12. The vertical axis of Fig. 4 is the punch-through voltage Vp1.

[0033] As shown in Figure 4, the second carbon concentration CC2 is 8 × 10 18 / cm 3 When the second carbon concentration CC2 is less than 8×10 18 / cm 3 When the second carbon concentration CC2 is 8×10 18 / cm 3 In this case, when the second carbon concentration CC2 increases, the punch-through voltage Vp1 increases. In this embodiment, the second carbon concentration CC2 is 8×10 18 / cm 3 It is preferable that the value is equal to or greater than this, and a high punch-through voltage Vp1 can be obtained.

[0034] If the second carbon concentration CC2 is excessively high, for example, defects are generated, and the crystal quality of the second nitride region 12 is likely to deteriorate. In the embodiment, the second carbon concentration CC2 is 5×10 20 / cm 3 The second carbon concentration CC2 is preferably 1×10 or less. 20 / cm 3 This makes it easier to suppress current leakage.

[0035] FIG. 5 is a graph illustrating the characteristics of nitride semiconductors. The horizontal axis of Fig. 5 is the second oxygen concentration CO2. As already explained, the second oxygen concentration CO2 is the concentration CO of oxygen in the second nitride region 12. The vertical axis of Fig. 4 is the punch-through voltage Vp1.

[0036] As shown in FIG. 5, when the second oxygen concentration CO2 is excessively low, the punch-through voltage Vp1 is low. When the second oxygen concentration CO2 is excessively high, the punch-through voltage Vp1 is low. When the second oxygen concentration CO2 is 7×10 15 / cm 3 Over 4×10 16 / cm 3 A high punch-through voltage Vp1 is obtained when: The punch-through voltage Vp1 changes critically with respect to the second oxygen concentration CO2.

[0037] In the embodiment, the second carbon concentration CC2 is preferably 2 to 200 times the first carbon concentration CC1. When the second carbon concentration CC2 is 2 or more times the first carbon concentration CC1, for example, the resistance of the second nitride region 12 is likely to be high. When the second carbon concentration CC2 is 200 times or less the first carbon concentration CC1, for example, defects in the second nitride region 12 are likely to be reduced.

[0038] In the embodiment, the first carbon concentration CC1 is 5.0×10 18 / cm 3 Over 1.0 x 10 20 / cm 3 It is preferable that the first carbon concentration CC1 is 5.0×10 or less. 18 / cm 3 When the first carbon concentration CC1 is 1.0×10 or more, the resistance of the first nitride region 11 is likely to be high. 20 / cm 3 By keeping the thickness below 100 nm, defects in the first nitride region 11 are likely to be reduced.

[0039] In the embodiment, the second carbon concentration CC2 is preferably 100 to 25,000 times the third carbon concentration CC3. When the second carbon concentration CC2 is 100 times or more the third carbon concentration CC3, for example, it becomes easier to suppress current leakage in the second nitride region 12. When the second carbon concentration CC2 is 25,000 times or less the third carbon concentration CC3, for example, it becomes easier to increase the resistance of the second nitride region 12.

[0040] In the embodiment, for example, the third carbon concentration CC3 is, for example, 3.0 × 10 16 / cm 3 It is preferable that the third carbon concentration CC3 is 3.0 × 10 or less. 16 / cm 3 By keeping the thickness below 1000 nm, for example, it is easy to obtain a third nitride region 13 with few defects.

[0041] In the embodiment, the first oxygen concentration CO1 is preferably higher than the second oxygen concentration CO2. For example, the first oxygen concentration CO1 is preferably 2 to 30 times the second oxygen concentration CO2. When the first oxygen concentration CO1 is 2 or more times the second oxygen concentration CO2, for example, the crystallinity of the second nitride region 12 is likely to be high. When the first oxygen concentration CO1 is 30 times or less the second oxygen concentration CO2, for example, the resistance of the first nitride region 11 is likely to be high.

[0042] In the embodiment, the second oxygen concentration CO2 is preferably higher than the third oxygen concentration CO3. For example, the second oxygen concentration CO2 is preferably 3 times or more and 20 times or less than the third oxygen concentration CO3. When the second oxygen concentration CO2 is 3 times or more than the third oxygen concentration CO3, for example, Nitride region 12 When the second oxygen concentration CO2 is 20 times or less than the third oxygen concentration CO3, for example, the crystallinity of the third nitride region 13 is likely to be high.

[0043] In the embodiment, the first oxygen concentration CO1 is, for example, 1.0×10 16 / cm 3 Over 5.0 x 10 17 / cm 3 It is preferable that the first oxygen concentration CO1 is 1.0×10 or less. 16 / cm 3 When the first oxygen concentration CO1 is 5.0×10 or more, current leakage in the first nitride region 11 is easily suppressed. 17 / cm 3 When the first oxygen concentration CO1 is 1.0×10 or less, the resistance of the first nitride region 11 is likely to be high. 17 / cm 3 The first oxygen concentration CO1 may be 1.0×10 or less. 17 / cm 3 When the thickness is equal to or less than this, the first nitride region 11 having high crystallinity is easily obtained.

[0044] In the embodiment, the third oxygen concentration CO3 is, for example, 5.0 × 10 15 / cm 3It is as follows. Thereby, it is easy to obtain the third nitride region 13 having high crystallinity.

[0045] In an embodiment, the composition ratio x2 is preferably less than 0.05, and the composition ratio x3 is preferably less than 0.05. For example, the second nitride region 12 contains GaN, and the third nitride region 13 contains GaN. By the low composition ratio x2, high crystallinity can be maintained, and the effect that carbon functions as an acceptor can be appropriately obtained easily. By the low composition ratio x3, high crystallinity can be maintained, the leakage current can be suppressed, and a high punch-through voltage Vp1 can be easily obtained.

[0046] As shown in FIG. 1, the first nitride region 11 may include a plurality of first layers 11a and a plurality of second layers 11b. In the first direction D1, one of the plurality of first layers 11a is between one of the plurality of second layers 11b and another one of the plurality of second layers 11b. One of the plurality of second layers 11b is between one of the plurality of first layers 11a and another one of the plurality of first layers 11a.

[0047] The first layer 11a contains Al y1 Ga 1-y1 N(0 < y1 ≦ 1). The first layer 11a contains, for example, AlN. The composition ratio of Al in the first layer 11a is preferably, for example, 0.75 or more and 1 or less.

[0048] The second layer 11b contains Al y2 Ga 1-y2 N(0 ≦ y2 < y1) 。 The second layer 11b contains, for example, Al 0.13 Ga 0.87 N. The composition ratio of Al in the second layer 11b is preferably, for example, 0 or more and 0.6 or less. The composition ratio of Al in the second layer 11b may be, for example, 0.06 or more and 0.35 or less. The second layer 11b may be GaN.

[0049] The effective Al composition ratio (e.g., the average Al composition ratio) in the first nitride region 11 corresponds to (y1·ta + y2·tb) / (ta + tb). "ta" is the thickness of the first layer 11a. "tb" is the thickness of the second layer 11b. The thickness is the length along the first direction D1. The effective Al composition ratio in the first nitride region 11 is, for example, 0.15 or more and 0.55 or less. The effective Al composition ratio in the first nitride region 11 may be, for example, 0.18 or more and 0.28 or less.

[0050] As shown in FIG. 1, the nitride semiconductor 110 may include a fifth nitride region 15. The fifth nitride region 15 contains Al x5 Ga 1-x5 N (0 < x5 ≤ 1). The fifth nitride region 15 contains, for example, AlN. The composition ratio x5 is preferably, for example, 0.5 or more and 1 or less.

[0051] As shown in FIG. 1, the nitride semiconductor 110 may include a sixth nitride region 16. The sixth nitride region 16 contains Al x6 Ga 1-x6 N (0 < x6 < 1, x6 < x5). The sixth nitride region 16 contains, for example, AlGaN. The composition ratio x6 is preferably, for example, 0.1 or more and 0.8 or less.

[0052] The nitride semiconductor 110 may include a fourth nitride region 14. The fourth nitride region 14 contains Al x4 Ga 1-x4 N (0 < x4 ≤ 1, x3 < x4). There is a third nitride region 13 between the second nitride region 12 and the fourth nitride region 14 in the first direction D1. The fourth nitride region 14 contains, for example, Al 0.2 Ga 0.8 N. The composition ratio x4 is preferably, for example, 0.05 or more and 0.35 or less.

[0053] For example, the third nitride region 13 includes a portion facing the fourth nitride region 14. For example, a carrier region is formed in this portion. 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.

[0054] The fourth nitride region 14 is substantially free of oxygen. Alternatively, the oxygen concentration in the fourth nitride region 14 is lower than the oxygen concentration CO (second oxygen concentration CO2) in the second nitride region 12. The fourth nitride region 14 is substantially free of carbon. Alternatively, the carbon concentration in the fourth nitride region 14 is lower than the carbon concentration CC (second carbon concentration CC2) in the second nitride region 12. The fourth nitride region 14 is substantially free of impurities that impart a conductivity type. The impurities that impart a conductivity type include, for example, Si or Mg.

[0055] The thickness t11 (see FIG. 1) of the first nitride region 11 is preferably, for example, 500 nm or more and 10,000 nm or less. The thickness ta of the first layer 11a is preferably, for example, 2 nm or more and 15 nm or less. The thickness tb of the second layer 11b is preferably, for example, 15 nm or more and 40 nm or less.

[0056] The thickness t12 (see FIG. 1) of the second nitride region 12 is preferably, for example, 500 nm or more and 5000 nm or less. The thickness t13 (see FIG. 1) of the third nitride region 13 is preferably, for example, 100 nm or more and 2000 nm or less. The thickness t14 (see FIG. 1) of the fourth nitride region 14 is preferably, for example, 15 nm or more and 50 nm or less.

[0057] The thickness t15 (see FIG. 1) of the fifth nitride region 15 is preferably, for example, not less than 50 nm and not more than 400 nm. The thickness t16 (see FIG. 1) of the sixth nitride region 16 is preferably, for example, not less than 50 nm and not more than 500 nm. The above thicknesses are lengths along the first direction D1.

[0058] Hereinafter, another example of the nitride semiconductor according to the embodiment will be described. FIG. 6 is a graph illustrating the nitride semiconductor according to the first embodiment. 6 illustrates the results of SIMS analysis of the nitride member 10M in the nitride semiconductor 111 according to the embodiment. The horizontal axis of FIG. 2 represents the position pZ in the Z-axis direction. The vertical axis on the left side of FIG. 2 represents the carbon concentration CC and the oxygen concentration CO. 6 The vertical axis on the right side represents the detected intensity Int_Al of Al secondary ions and the detected intensity Int_Ga of gallium secondary ions.

[0059] As shown in FIG. 6, the oxygen concentration CO in the nitride member 10M in the Z-axis direction (i.e., the first direction D1) reaches a peak value VO1 at a first position p1 between the first nitride region 11 and the second nitride region 12. For example, an intermediate region 11M is provided between the first nitride region 11 and the second nitride region 12. The first position p1 is included in the intermediate region 11M. The locally high oxygen concentration CO between the first nitride region 11 and the second nitride region 12 can bend dislocations, for example, in the intermediate region 11M. This can reduce the defect density in the region above the second nitride region 12. The provision of the intermediate region 11M reduces defects in the second nitride region 12 (and the third nitride region 13 thereover).

[0060] The peak value VO1 is, for example, 1.8 x 10 17 / cm 3 Over 5.0 x 10 18 / cm 3 It is preferable that the peak value VO1 is equal to or less than the first oxygen concentration CO1, for example. This makes it possible to effectively reduce the defect density in the second nitride region 12. It is preferable that the peak value VO1 is equal to or more than about 5 times the first oxygen concentration CO1, for example. This makes it possible to effectively reduce the defect density in the second nitride region 12. It is preferable that the peak value VO1 is equal to or more than 18 times the second oxygen concentration CO2, for example. This makes it possible to effectively reduce the defect density in the second nitride region 12.

[0061] 6, the carbon concentration CC at the first position p1 is between the carbon concentration CC (first carbon concentration CC1) in the first nitride region 11 and the carbon concentration CC (second carbon concentration CC2) in the second nitride region 12. In this example, the Al concentration (composition ratio) at the first position p1 is between the Al concentration (composition ratio) in the first nitride region 11 and the Al concentration (composition ratio) in the second nitride region 12.

[0062] The intermediate region 11M is a transition region between the first nitride region 11 and the second nitride region 12. It is believed that the oxygen concentration CO peaks in the transition region, which allows dislocations to bend more effectively in the transition region. This effect is believed to reduce defects in the second nitride region 12.

[0063] The carbon concentration CC at the first position p1 is, for example, 2.8×10 19 / cm 3 Over 2.0 x 10 20 / cm 3 It is preferable that the carbon concentration CC is 2.8 × 10 or less. 19 / cm 3 Above this, the defect density DD becomes critically low. 20 / cm 3 If the temperature is higher than 1000 K, lattice relaxation is likely to occur at the interface between the intermediate region 11M and the second nitride region 12. As a result, the crystallinity of the second nitride region 12 is likely to decrease.

[0064] The ratio of the carbon concentration VC1 at the first position p1 to the peak value VO1 is preferably, for example, not less than 40 and not more than 200. In this range, the defect density in the second nitride region 12 is likely to be reduced effectively.

[0065] The defect density in the second nitride region 12 is lower than the defect density in the first nitride region 11. The defect density in the third nitride region 13 is lower than the defect density in the first nitride region 11. Information about the defect density can be obtained, for example, from a cross-sectional TEM image of the nitride member 10M. The provision of the intermediate region 11M reduces, for example, dislocations in the second nitride region 12 (and the third nitride region 13 thereon). For example, the dislocation density in the second nitride region 12 is lower than the dislocation density in the first nitride region 11. For example, the dislocation density in the third nitride region 13 is lower than the dislocation density in the first nitride region 11.

[0066] The intermediate region 11M contains, for example, aluminum. The aluminum concentration at the first position p1 is lower than the aluminum concentration (first aluminum concentration) in the first nitride region 11. For example, the second nitride region 12 does not contain aluminum. Alternatively, the aluminum concentration (second aluminum concentration) in the second nitride region 12 is equal to or lower than the aluminum concentration at the first position p1. For example, the aluminum concentration (composition ratio) at the first position p1 is between the aluminum concentration (composition ratio) in the first nitride region 11 and the aluminum concentration (composition ratio) in the second nitride region 12. In such an intermediate region 11M, the oxygen concentration CO peaks, thereby reducing the defect density.

[0067] The thickness of the intermediate region 11M is preferably, for example, not less than 5 nm and not more than 40 nm.

[0068] In the embodiment, the first nitride region 11 does not have to have a stacked structure. The first nitride region 11 may be a nitride semiconductor layer that does not substantially contain Al. In this case, the first nitride region 11 contains GaN. In this case, the composition ratio x1 is 0. In this case, the second nitride region 12 contains Al. x2 Ga 1-x2 N (0≦x2<1). The third nitride region 13 contains Al x3 Ga 1-x3N (0≦x3<1). In this case, the second nitride region 12 also contains carbon and oxygen. The first nitride region 11 does not contain carbon, or the second carbon concentration CC2 in the second nitride region 12 is higher than the first carbon concentration CC1 in the first nitride region 11. The second carbon concentration CC2 is higher than the third carbon concentration CC3 in the third nitride region 13. The ratio of the second oxygen concentration CO2 in the second nitride region 12 to the second carbon concentration CC2 is 1.0×10 -4 Over 1.4 x 10 -3 The following is the result.

[0069] (Second embodiment) The second embodiment relates to a semiconductor device. The semiconductor device according to the embodiment includes the nitride semiconductor according to the first embodiment. In the following, an example in which the semiconductor device includes a nitride semiconductor 110 will be described. The semiconductor device may also include a nitride semiconductor 111.

[0070] FIG. 7 is a schematic cross-sectional view illustrating the semiconductor device according to the second embodiment. As shown in FIG. 7, the semiconductor device 120 according to the embodiment includes the nitride semiconductor 110 according to the first embodiment, a first electrode 51, a second electrode 52, a third electrode 53, and an insulating member 61.

[0071] The direction from the first electrode 51 to the second electrode 52 is along a second direction D2 that intersects with the first direction D1. The second direction D2 is, for example, the X-axis direction. The position of the third electrode 53 in the second direction D2 is between the position of the first electrode 51 in the second direction D2 and the position of the second electrode 52 in the second direction D2.

[0072] The nitride member 10M includes a first nitride region 11, a second nitride region 12, an intermediate region 11M, a third nitride region 13, and a fourth nitride region 14. The third nitride region 13 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 D1. The direction from the second partial region 10b to the second electrode 52 is along the first direction D1. The third partial region 10c is located between the first partial region 10a and the second partial region 10b in the second direction D2. The direction from the third partial region 10c to the third electrode 53 is along the first direction D1. The fourth partial region 10d is located between the first partial region 10a and the third partial region 10c in the second direction D2. The fifth partial region 10e is located between the third partial region 10c and the second partial region 10b in the second direction D2.

[0073] The fourth nitride region 14 includes a sixth sub-region 10f and a seventh sub-region 10g. The direction from the fourth sub-region 10d to the sixth sub-region 10f is along the first direction D1. The direction from the fifth sub-region 10e to the seventh sub-region 10g is along the first direction D1.

[0074] The insulating member 61 is located 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 partial region 10c and the third electrode 53 in the first direction (Z-axis direction).

[0075] The first electrode 51 is electrically connected to the sixth partial region 10f, and the second electrode 52 is electrically connected to the seventh partial region 10g.

[0076] 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, for example, a source electrode. The second electrode 52 functions as, for example, a drain electrode. The third electrode 53 functions as, for example, a gate electrode. The semiconductor device 120 is, for example, a HEMT (High Electron Mobility Transistor).

[0077] According to the embodiment, a high punch-through voltage Vp1 can be obtained. According to the embodiment, a semiconductor device capable of improving characteristics can be provided.

[0078] In the semiconductor device 120, at least a portion of the third electrode 53 is located between the sixth partial region 10f and the seventh partial region 10g in the second direction D2. At least a portion of the third electrode 53 may be located between the fourth partial region 10d and the fifth partial region 10e in the second direction D2. The first insulating region 61p may be located between the fourth partial region 10d and the fifth partial region 10e. The semiconductor device 120 is, for example, a normally-off type.

[0079] FIG. 8 is a schematic cross-sectional view illustrating the semiconductor device according to the second embodiment. As shown in FIG. 8 , the semiconductor device 121 according to the embodiment includes the nitride semiconductor 110 according to the first embodiment, 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 10f and the seventh partial region 10g in the second direction D2. The third electrode 53 does not overlap with the fourth partial region 10d and the fifth partial region 10e in the second direction D2. The semiconductor device 121 is, for example, a normally-on type. A high punch-through voltage Vp1 can also be obtained in the semiconductor device 121. A semiconductor device capable of improving characteristics can be provided.

[0080] In the embodiment, information about the shape of the nitride region is obtained by, for example, electron microscope observation. Information about the composition and element concentration in the nitride region is obtained by, for example, EDX (Energy Dispersive X-ray Spectroscopy) or SIMS (Secondary Ion Mass Spectrometry). Information about the composition in the nitride region may be obtained by, for example, X-ray reciprocal space mapping.

[0081] According to the embodiment, it is possible to provide a nitride semiconductor and a semiconductor device that can improve characteristics.

[0082] In this specification, "electrically connected" includes a state in which multiple conductors are physically in contact with each other and a current flows between these multiple conductors. "Electrically connected" also includes a state in which multiple conductors are connected to each other and a current flows between these multiple conductors.

[0083] 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, the specific configurations of the elements included in the nitride semiconductor, such as the nitride region and the substrate, are within the scope of the present invention as long as a person skilled in the art can implement the present invention in a similar manner and obtain similar effects by appropriately selecting them from known ranges.

[0084] Furthermore, any combination of two or more elements of each specific example within the scope of technical feasibility is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0085] In addition, all nitride semiconductors and semiconductor devices that can be implemented by a person skilled in the art by appropriately modifying the design based on the nitride semiconductors and semiconductor devices described above as embodiments of the present invention also fall within the scope of the present invention, as long as they include the gist of the present invention.

[0086] In addition, within the scope of the concept of the present invention, a person skilled in the art may come up with various modifications and alterations, and these modifications and alterations are also considered to fall within the scope of the present invention.

[0087] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0088] 10M...nitride member, 10a to 10g...first to seventh partial regions, 11 to 16...first to sixth nitride regions, 11M...intermediate region, 11a, 11b...first and second layers, 18s...substrate, 51 to 53...first to third electrodes, 61...insulating member, 61p...first insulating region, 110, 111...nitride semiconductor, 120, 121...semiconductor device, CC, CO...concentration, CC1 to CC3...first to third carbon concentrations, CO1 to CO3...first to third oxygen concentrations, D1, D2...first and second directions, Int_Al, Int_Ga...detection intensity, R2...ratio, VO1...peak value, Vp1...punch-through voltage, p1...first position, pZ...position, t11 to t16, ta, tb...thickness

Claims

1. Al ｘ１ Ga １－ｘ１ a first nitride region including N (0<x1≦1); a second nitride region comprising GaN; a third nitride region comprising GaN; a nitride member including the second nitride region is provided between the first nitride region and the third nitride region in a first direction from the first nitride region to the second nitride region; the second nitride region comprises carbon and oxygen; the first nitride region is carbon-free, or a second carbon concentration in the second nitride region is higher than a first carbon concentration in the first nitride region; the second carbon concentration is greater than a third carbon concentration in the third nitride region; The ratio of the second oxygen concentration in the second nitride region to the second carbon concentration is 1.0×10 －４ 1.4 x 10 －３ is as follows: A nitride semiconductor, wherein the concentration of oxygen in the second nitride region is between the concentration of oxygen in the third nitride region and the concentration of oxygen in the first nitride region.

2. The second carbon concentration is 8×10 １８ / cm ３ The nitride semiconductor according to claim 1 .

3. The second carbon concentration is 5×10 ２０ / cm ３ The nitride semiconductor according to claim 2, wherein:

4. The second oxygen concentration is 7×10 １５ / cm ３ The nitride semiconductor according to any one of claims 1 to 3.

5. The second oxygen concentration is 4×10 １６ / cm ３ The nitride semiconductor according to claim 4, wherein:

6. 6. The nitride semiconductor according to claim 1, wherein the second carbon concentration is at least 2 times and at most 200 times the first carbon concentration.

7. The first carbon concentration is 5×10 １８ / cm ３ 1x10 or more ２０ / cm ３ The nitride semiconductor according to any one of claims 1 to 6, wherein:

8. 8. The nitride semiconductor according to claim 1, wherein the second carbon concentration is 100 times or more and 25,000 times or less than the third carbon concentration.

9. The third carbon concentration is 3×10 １６ / cm ３ The nitride semiconductor according to any one of claims 1 to 8, wherein:

10. 10. The nitride semiconductor according to claim 1, wherein the first oxygen concentration in said first nitride region is at least 2 times and at most 30 times the second oxygen concentration.

11. The first oxygen concentration is 1×10 １６ / cm ３ 5x10 or more １７ / cm ３ The nitride semiconductor according to claim 10, wherein:

12. 12. The nitride semiconductor according to claim 1, wherein the second oxygen concentration is 3 to 20 times the third oxygen concentration in the third nitride region.

13. The nitride semiconductor according to any one of claims 1 to 12, wherein the second nitride region has a thickness of 500 nm or more and 5000 nm or less.

14. the first nitride region includes a plurality of first layers and a plurality of second layers; In the first direction, one of the plurality of first layers is between one of the plurality of second layers and another one of the plurality of second layers, and the one of the plurality of second layers is between the one of the plurality of first layers and another one of the plurality of first layers; The first layer is Al ｙ１ Ga １－ｙ１ N (0<y1≦1), The second layer is Al ｙ２ Ga １－ｙ２ The nitride semiconductor according to any one of claims 1 to 13, comprising N (0≦y2<y1).

15. Further comprising a substrate; The nitride semiconductor according to any one of claims 1 to 14, wherein the first nitride region is located between the substrate and the second nitride region.

16. The nitride member is Al ｘ５ Ga １－ｘ５ further comprising a fifth nitride region comprising N (0<x5≦1); The nitride semiconductor of claim 15 , wherein the fifth nitride region is between the substrate and the first nitride region in the first direction.

17. The nitride member is Al ｘ４ Ga １－ｘ４ further comprising a fourth nitride region comprising N (0<x4≦1, x3<x4); 17. The nitride semiconductor according to claim 1, wherein the third nitride region is located between the second nitride region and the fourth nitride region in the first direction.

18. The nitride semiconductor according to claim 17; A first electrode; A second electrode; A third electrode; An insulating member; Equipped with a direction from the first electrode to the second electrode is along a second direction intersecting the first direction; a position of the third electrode in the second direction is between a position of the first electrode in the second direction and a position of the second electrode in the second direction; the third nitride region includes a first partial region, a second partial region, a third partial region, a fourth partial region, and a fifth partial region; a direction from the first partial region to the first electrode is along the first direction; a direction from the second partial region to the second electrode is along the first direction; the third partial region is located between the first partial region and the second partial region in the second direction, and a direction from the third partial region to the third electrode is along the first direction; the fourth partial region is located between the first partial region and the third partial region in the second direction, the fifth partial region is located between the third partial region and the second partial region in the second direction, the fourth nitride region includes a sixth sub-region and a seventh sub-region; a direction from the fourth partial region to the sixth partial region is along the first direction; a direction from the fifth partial region to the seventh partial region along the first direction; The insulating member is between the nitride member and the third electrode.

19. The semiconductor device according to claim 18 , wherein at least a portion of the third electrode is located between the sixth partial region and the seventh partial region in the second direction.

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