Silicon-doped gallium nitride film, manufacturing method of the same, laminate substrate, semiconductor element, and electronic device

Abstract

To provide a silicon-doped gallium film capable of improving a conductivity, a manufacturing method of the same, a laminate substrate, a semiconductor element, and an electronic device.SOLUTION: In a silicon-doped gallium nitride film containing gallium nitride and silicon, when a ratio R (C2 / C1) of a minimum value C2 to a maximum value C1 of silicon concentration in a range of 50 nm or more and A nm or less at a depth from a surface of the silicon-doped gallium nitride film, is 0.001 and more to less than 1, and then when the minimum value C2 is 1×1017 atoms / cm3 or more and a thickness of the silicon-doped gallium nitride is less 200 nm, A is a thickness of the silicon-doped gallium nitride, and when a thickness of the silicon-doped gallium nitride is 200 nm or more, A is 200 nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a silicon-doped gallium nitride film, a method for producing the same, a laminate substrate, a semiconductor device, and an electronic device. [Background technology]

[0002] Gallium nitride films are used in semiconductor devices such as LEDs and transistors, and such gallium nitride films are often required to have high electrical conductivity. As such a gallium nitride film, for example, a silicon-doped gallium nitride film is known, which is formed by forming a silicon film on an undoped gallium nitride film formed by chemical vapor deposition (CVD), and then diffusing the silicon in the silicon film into the gallium nitride film by heating (see, for example, Non-Patent Document 1 below). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] CFLin et al. “Improved contact performance of GaN film using Si diffusion”, APPLIEDPHYSICS LETTERS, vol.76, No.14, 1878-1880, April 3, 2000 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the silicon-doped gallium nitride film described in Non-Patent Document 1, silicon cannot be sufficiently diffused to a depth far from the surface, and there is room for improvement in terms of conductivity.

[0005] An object of the present disclosure is to provide at least one of a silicon-doped gallium nitride film capable of improving electrical conductivity, a method for producing the same, a laminate substrate, a semiconductor element, and an electronic device. [Means for solving the problem]

[0006] The contents of the present invention are as set forth in the claims, and the gist of the present disclosure is as follows.

[0007] (1) A silicon-doped gallium nitride film containing gallium nitride and silicon, a ratio R(C2 / C1) of a minimum value C2 of silicon concentration to a maximum value C1 in a range of a depth from the surface of the silicon-doped gallium nitride film of 50 nm or more and Anm or less, is 0.001 or more and less than 1; The minimum value C2 is 1×10 17 atoms / cm 3 That's all, When the thickness of the silicon-doped gallium nitride film is less than 200 nm, A is the thickness of the silicon-doped gallium nitride film, and when the thickness of the silicon-doped gallium nitride film is 200 nm or more, A is 200 nm. (2) The minimum silicon concentration C3 in the range of 50 nm to 300 nm in depth from the surface is 1 × 10 17 atoms / cm 3 The silicon-doped gallium nitride film according to (1) above. (3) The silicon-doped gallium nitride film according to (1) or (2), wherein the ratio R is 0.01 or more. (4) The silicon-doped gallium nitride film according to any one of (1) to (3), wherein the ratio R is 0.5 or less. (5) A method for producing a silicon-doped gallium nitride film according to any one of (1) to (4), comprising: A first step of preparing a gallium nitride film containing gallium nitride; a second step of forming a silicon film containing silicon on the gallium nitride film to obtain a first stack; and a third step of heating the first stack to diffuse the silicon contained in the silicon film into the gallium nitride film, thereby obtaining a second stack. (6) The method for producing a silicon-doped gallium nitride film according to (5), wherein the gallium nitride film is a sputtered film formed by sputtering. (7) The method for producing a silicon-doped gallium nitride film according to (5) or (6), wherein the first stack is heated to a temperature higher than 500° C. in the third step. (8) A layered substrate comprising the silicon-doped gallium nitride film according to any one of (1) to (4) and a substrate. (9) A semiconductor device comprising the laminated substrate according to (8). (10) An electronic device comprising the semiconductor element according to (9). [Effects of the Invention]

[0008] According to the present disclosure, there are provided at least one of a silicon-doped gallium nitride film capable of improving electrical conductivity, a method for producing the same, a laminate substrate, a semiconductor element, and an electronic device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view illustrating one embodiment of a laminated substrate according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described in detail using an example. However, the present disclosure is not limited to the following embodiment. In addition, the present disclosure includes any combination of the configurations and parameters disclosed herein, and any combination of the upper and lower limits of the numerical values ​​disclosed herein.

[0011] <Silicon-doped gallium nitride film> First, one embodiment of the silicon-doped gallium nitride film of the present disclosure will be described.

[0012] A silicon-doped gallium nitride film (hereinafter also referred to as "Si-doped GaN film") contains gallium nitride (hereinafter also referred to as "GaN") and silicon (hereinafter also referred to as "Si"). In the Si-doped GaN film, the ratio R(C2 / C1) of the minimum value C2 to the maximum value C1 of the Si concentration in the range of depth from the surface of the Si-doped GaN film to a depth of 50 nm or more and 50 nm or less is 0.001 or more and less than 1, and the minimum value C2 is 1×10 17 atoms / cm 3 That's all. The surface of the Si-doped GaN film refers to the side of the Si-doped GaN film on which the Si film described below was formed, i.e., the surface opposite to the substrate on which the GaN film is formed. When the Si-doped GaN film has a Si film on its surface, the depth from the surface refers to the depth from the interface between the Si film and the Si-doped GaN film toward the substrate. Furthermore, when the thickness of the Si-doped GaN film is smaller than 200 nm, A is the thickness of the Si-doped GaN film, and when the thickness of the Si-doped GaN film is 200 nm or more, A is 200 nm.

[0013] This Si-doped GaN film is suitable for cases where the ratio R is less than 0.001 or the minimum value C2 is 1×10 7 atoms / cm 3 The conductivity can be improved compared to when the thickness is less than 100 μm.

[0014] The Si-doped GaN film of this embodiment will be described in detail below.

[0015] (Maximum Si concentration C1) The Si concentration tends to decrease with increasing depth from the surface of the Si-doped GaN film. Therefore, the Si concentration at a depth of 50 nm from the surface of the Si-doped GaN film usually reaches a maximum value C1 when the depth from the surface of the Si-doped GaN film is in the range of 50 nm to Anm. The maximum Si concentration C1 is when the ratio R is 0.001 or more and less than 1 and C2 is 1×10 17 atoms / cm 3There is no particular limitation as long as the relationship of greater than or equal to 1 is satisfied. The lower limit of the maximum Si concentration C1 is 1×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , or 1×10 21 atoms / cm 3 Examples include: The upper limit of the maximum Si concentration C1 is 6 × 10 23 atoms / cm 3 , 5×10 23 atoms / cm 3 , or 3 × 10 23 atoms / cm 3 Examples include: The upper and lower limits of the maximum Si concentration C1 may be any of the above combinations, but the maximum Si concentration C1 is preferably 1×10 20 atoms / cm 3 More than 6 x 10 23 atoms / cm 3 , more preferably 5 × 10 20 atoms / cm 3 5x10 or more 23 atoms / cm 3 , particularly preferably 1 × 10 21 atoms / cm 3 3x10 or more 23 atoms / cm 3 is.

[0016] In this disclosure, the Si concentration refers to the concentration of Si measured using secondary ion mass spectrometry (SIMS). In SIMS, the Si concentration is measured by analyzing the mass of secondary ions ejected when the surface of the Si-doped GaN film is sputtered with primary ions. Specifically, first, data D1 showing the relationship between the Si ion intensity and the sputtering time is obtained. Next, the Si ion intensity and the sputtering time are converted into the Si concentration and the depth from the surface of the Si-doped GaN film, respectively, to obtain data D2 showing the relationship between the Si concentration and the depth from the surface of the Si-doped GaN film. Then, from data D2, the Si concentration when the depth from the surface of the Si-doped GaN film is 50 nm is determined as the maximum Si concentration C1. The unit of Si concentration is "atoms / cm". 3 " is 1 cm 3 is the number of Si atoms per

[0017] (Minimum Si concentration C2 from depth 50 nm to Anm) The Si concentration tends to decrease as the depth from the surface of the Si-doped GaN film increases (gets deeper), so the Si concentration at a depth Am from the surface of the Si-doped GaN film usually becomes the minimum value C2 of the Si concentration. The minimum value C2 of the Si concentration is set when the ratio R is 0.001 or more and less than 1 and C2 is 1×10 17 atoms / cm 3 There is no particular limitation as long as it is equal to or greater than this, and the lower limit of the minimum value C2 of the Si concentration is 1 × 10 18 atoms / cm 3 , 1×10 19 atoms / cm 3 , or 1×10 20 atoms / cm 3 Examples include: The upper limit of the minimum Si concentration C2 is 1 × 10 23 atoms / cm 3 , 5×10 22 atoms / cm 3 , or 2 × 10 22 atoms / cm 3Examples include: The upper and lower limits of the minimum value C2 of the Si concentration may be any of the above combinations, but the minimum value C2 of the Si concentration is preferably 1×10 18 atoms / cm 3 More than 1×10 23 atoms / cm 3 Less than 1×10, more preferably 19 atoms / cm 3 5x10 or more 22 atoms / cm 3 Below 1 × 10, particularly preferably 20 atoms / cm 3 Over 2×10 22 atoms / cm 3 The following is the result. The minimum value C2 of the Si concentration is the Si concentration when the depth from the surface of the Si-doped GaN film is Am in the above-mentioned data D2.

[0018] (ratio R) The ratio R is not particularly limited as long as it is 0.001 or more and less than 1, but the lower limit of the ratio R is preferably 0.002, more preferably 0.005, and particularly preferably 0.01. The upper limit of the ratio R can be, for example, 0.5, 0.2, or 0.1. The upper and lower limits of the ratio R may be any combination of the above, but the ratio R is preferably 0.002 or more and 0.5 or less, more preferably 0.005 or more and 0.2 or less, and particularly preferably 0.01 or more and 0.1 or less.

[0019] (Thickness) The thickness of the Si-doped GaN film is not particularly limited, but can be 500 nm or more. The lower limit of the thickness of the Si-doped GaN film can be 100 nm, 150 nm, 200 nm, 300 nm, 500 nm, or 700 nm. Since the Si-doped GaN film of this embodiment has Si diffused deep into it, it is useful when it has a thickness of 100 nm or more, and particularly useful when it has a thickness of 300 nm or more. As the upper limit of the thickness of the Si-doped GaN film, 5000 nm, 3000 nm, or 1000 nm can be exemplified. When the thickness of the Si-doped GaN film is less than 200 nm, A above is the thickness of the Si-doped GaN film, and when the thickness of the Si-doped GaN film is 200 nm or more, A above becomes 200 nm.

[0020] (Minimum value C3 of Si concentration at a depth from 50 nm to X nm (200 < X)) When the thickness of the Si-doped GaN film is greater than 200 nm, in the range where the depth from the surface of the Si-doped GaN film is 50 nm or more and X nm or less (200 < X), the minimum value C3 of the Si concentration is 1×10 17 atoms / cm 3 or more, or 1×10 18 atoms / cm 3 or more. Thereby, since Si diffuses deeply, the conductivity is likely to be improved even in a thick Si-doped GaN film. X is preferably larger as long as it exceeds 200, and 300, 400, or 500 can be exemplified. As the upper limit of the minimum value C3 of the Si concentration, 1×10 23 atoms / cm 3 , 5×10 22 atoms / cm 3 , or 2×10 22 atoms / cm 3 can be exemplified. The upper limit and the lower limit of the minimum value C3 of the Si concentration may be any combination of the above, but the minimum value C3 of the Si concentration is 1×10 17 atoms / cm 3 or more and 1×10 23 atoms / cm 3 or less, 1×10 18 atoms / cm 3 or more and 5×10 [[ID=4⑤]] 22 atoms / cm 3 or less, or 1×10 18 atoms / cm 3 or more and 2×10 22 atoms / cm 3 or less. (Resistivity) The resistivity of the Si-doped GaN film is 1×10 4 Ωcm or less, 1×10 3 Ωcm or less, 1×10 2 Ωcm or less, 1Ωcm or less, 8×10 -1 Ωcm or less, 5×10 -1 Ωcm or less, 1×10 -1 Ωcm or less, or 5 x 10 -2 Ωcm or less, and 1×10 -3 Ωcm or more, 5×10 -3 Ωcm or more, or 8×10 -3 The resistivity of a Si-doped GaN film is 1×10 -3 Ωcm or more and 1Ωcm or less, 1×10 -3 Ωcm or more 8×10 -1 Ωcm or less, 5×10 -3 Ωcm or more 5×10 -1 Ωcm or less, or 8 x 10 -3 Ωcm or more 5×10 -2 The resistance is Ωcm or less. In this embodiment, the resistivity of the Si-doped GaN film may be measured using a general Hall effect measurement device (for example, 8403 AC / DC Hall effect measurement device, manufactured by Toyo Corporation).

[0021] <Laminated base material> Next, one embodiment of the laminated base material of the present disclosure will be described with reference to FIG. 1, the layered base material 100 includes a substrate 10 and a Si-doped GaN film 20. The Si-doped GaN film 20 is made of the Si-doped GaN film described above. The above-described layered substrate 100 is useful for applications such as semiconductor devices, since it includes the Si-doped GaN film 20 that can improve electrical conductivity.

[0022] (substrate) The substrate 10 is not particularly limited. Examples of the substrate 10 include a sapphire substrate, a silicon substrate, a gallium nitride substrate, a silicon carbide substrate, a glass substrate, a quartz substrate, a polyimide substrate, or a polyethylene terephthalate substrate. A sapphire substrate, a silicon substrate, a gallium nitride substrate, or a silicon carbide substrate made of a single crystal is preferable, and a sapphire substrate, a gallium nitride substrate, or a silicon carbide substrate having a hexagonal crystal system is more preferable. The surface roughness Ra of the substrate 10 is not particularly limited, but is preferably 10 nm or less, 1 nm or less, or 0.5 nm or less. The surface roughness Ra of the substrate 10 may be 0 nm or more, or 0.01 nm or more, and may be exemplified as 0 nm or more and 10 nm or less, or 0.01 nm or more and 0.5 nm or less. Note that the surface roughness Ra represents the calculated average roughness and is measured by a method according to JIS B 0601.

[0023] <Method for manufacturing Si-doped GaN film> The method for manufacturing the Si-doped GaN film of the present disclosure includes a first step of preparing a GaN film containing GaN, a second step of forming a Si film containing Si on the GaN film to obtain a first laminate, and a third step of heating the first laminate to diffuse Si contained in the Si film into the GaN film to obtain a second laminate. The obtained Si-doped GaN film is the above-described Si-doped GaN film and contains GaN and Si. In the Si-doped GaN film, the ratio R (C2 / C1) of the minimum value C2 to the maximum value C1 of the Si concentration in the range where the depth from the surface of the Si-doped GaN film is 50 nm or more and Anm or less is 0.001 or more and less than 1, and the minimum value C2 is 1×10 17 atoms / cm 3 or more. Here, when the thickness of the Si-doped GaN film is less than 200 nm, A is the thickness of the Si-doped GaN film, and when the thickness of the Si-doped GaN film is 200 nm or more, A is 2 nm.

[0024] Since the method for producing a Si-doped GaN film according to the present disclosure can produce a laminated substrate, the method for producing a Si-doped GaN film according to the present disclosure can also be called a method for producing a laminated substrate. The laminated substrate has a structure in which a Si-doped GaN film 20 is laminated on a substrate 10, and may further have a Si film on the Si-doped GaN film 20.

[0025] According to the method for producing a Si-doped GaN film of the present disclosure, the electrical conductivity of the resulting Si-doped GaN film can be improved. The GaN film is preferably a sputtered film formed by sputtering. In this case, Si can be diffused from the surface of the GaN film to a sufficiently deep position to increase the Si concentration. The main reasons for this are thought to be as follows. That is, in the first step, the sputtered film containing GaN formed by sputtering is composed of multiple columnar crystals extending in the thickness direction, and it is believed that gaps large enough for Si atoms to pass between these columnar crystals. Therefore, when a Si film is formed on the sputtered film to obtain a first stack in the second step, and then this first stack is heated in the third step to diffuse the Si contained in the Si film into the sputtered film, it is believed that the Si atoms can easily move through the gaps between the multiple columnar crystals, and the diffusion of Si atoms progresses. Therefore, Si can be diffused to a deep position sufficiently far from the surface of the resulting Si-doped GaN film, thereby increasing the Si concentration.

[0026] The first, second and third steps will be described in detail below, taking as an example a case where the GaN film is a sputtered film.

[0027] (1) First step The first step is a step of preparing a sputtered film containing GaN and formed by sputtering. In the first step, it is preferable to first evacuate the inside of the film forming apparatus before forming the sputtered film. The degree of vacuum (ultimate vacuum) in the film forming apparatus is not particularly limited, but is preferably 3×10 -5 Pa or less, and 1×10-5 It is more preferable to set the degree of vacuum to 3×10 Pa or less. -5 By setting the pressure to Pa or less, residual gases are less likely to be mixed in as impurities during film formation, and the crystallinity of the sputtered film is improved. In the film forming apparatus, it is preferable to perform a baking process before evacuating the film forming apparatus in order to remove residual gas. The degree of vacuum is greater than 0 Pa and is less than 1×10 -8 Pa or more, or 1×10 -7 For example, it can be exemplified as being equal to or greater than Pa.

[0028] In the first step, it is preferable to pretreat the substrate before forming the sputtered film, which removes organic layers and irregularities on the substrate surface, making epitaxial growth easier. Pretreatment methods include one or more selected from the group consisting of reverse sputtering, acid treatment, and UV treatment. However, reverse sputtering is preferred from the viewpoint of preventing re-adhesion of impurities after treatment. Reverse sputtering is a method of cleaning the surface by bombarding the substrate with plasma atoms rather than the sputtering target. By using this mechanism, the substrate surface is cleaned and sent to the film deposition chamber without exposure to the outside air, allowing film deposition to be performed while maintaining the cleanliness of the substrate surface. When reverse sputtering is performed, it is preferable to perform the treatment in a chamber different from the film-forming chamber in order to prevent reverse-sputtered impurities from adhering to the film-forming chamber. The gas species (sputtering gas) used in the reverse sputtering process can be at least one selected from the group consisting of argon, nitrogen, and oxygen, but in order to remove carbon-based impurities from the surface, it is preferable that the sputtering gas contains a certain amount of oxygen. The oxygen content in the sputtering gas is preferably 1% or more and 10% or less in terms of pressure ratio, with the total pressure of the entire composition gas being 100%. This makes it possible to efficiently remove carbon-based impurities from the surface. The treatment time for the reverse sputtering process is preferably 30 to 900 seconds, or 60 to 300 seconds. This allows for the removal of surface impurities while achieving a desirable surface roughness (Ra). Examples of reverse sputtering include a process performed for 60 seconds under the following conditions: 100 W, sputtering gas: Ar: 29 sccm (1 atm, 25°C), O2: 1 sccm (1 atm, 25°C).

[0029] Prior to forming the sputtered film, it is preferable to hold the substrate at the film formation temperature for a certain period of time. This reduces the temperature difference between the substrate and the sputtered film, improving the crystallinity of the resulting Si-doped GaN film. For example, the lower limit of the holding time is preferably 1 minute, 5 minutes, or 10 minutes. On the other hand, from the viewpoint of improving productivity, the upper limit of the holding time is preferably 1 hour or 30 minutes, and examples of the holding time include 1 minute to 1 hour, or 10 minutes to 30 minutes.

[0030] (GaN sputtering target) The GaN sputtering target may contain GaN. In order to obtain the effect of the Si dopant in the GaN sputtering target, it is preferable that the amount of metal element impurities other than the Si dopant is small. Specifically, the content of metal element impurities in the GaN sputtering target is preferably less than 0.1 mass%, more preferably less than 0.01 mass%. The lower limit of the content of metal element impurities in the GaN sputtering target can be exemplified as more than 0 mass% and 0.001 mass% or more. The amount of metal element impurities in the GaN sputtering target can be measured by GDMS. Specific examples of metal impurity elements include Na, Mg, Al, Ti, Fe, Ni, Cu, and Zn. In order to improve the crystallinity of the entire sputtered film, the GaN sputtering target used preferably has an oxygen content of less than 3 at.%, more preferably 1 at.% or less. The oxygen content of the GaN sputtering target is preferably low. Theoretically, the oxygen content of a GaN sputtering target is 0 at.% or more, but the oxygen content of a practical GaN sputtering target can be, for example, more than 0 at.%, or 0.0001 at.% or more. The area of ​​the GaN sputtering target is not particularly limited, but the lower limit of the area of ​​the GaN sputtering target is preferably 18 cm 2 , more preferably 100 cm 2 The larger the area of ​​the GaN sputtering target, the more stable the discharge becomes, making it possible to perform sputtering at lower gas pressures and lower discharge densities. Furthermore, the uniformity of the film thickness and quality also improves. The upper limit of the area of ​​the GaN sputtering target is 10,000 cm. 2 , 5000cm 2 , or 1000 cm 2 Examples include:

[0031] (Sputtering) The sputtering method can be appropriately selected from DC sputtering, RF sputtering, AC sputtering, DC magnetron sputtering, RF magnetron sputtering, ECR sputtering, pulsed laser deposition, and ion beam sputtering. Among these, at least one of DC magnetron sputtering and RF magnetron sputtering is preferred because it allows for uniform film formation over a large area at high speed.

[0032] The gas pressure during sputtering (film formation pressure) is not particularly limited, but may be, for example, 1.0 Pa or less, and the upper limit of the film formation pressure is preferably 0.6 Pa, 0.4 Pa, 0.3 Pa, or 0.2 Pa. The lower the gas pressure during sputtering, the more easily particles emitted from the GaN sputtering target can reach the substrate while retaining their high energy, and the more easily they can be epitaxially rearranged. The lower limit of the gas pressure during sputtering can be 0 Pa or 0.1 Pa. The lower the gas pressure during sputtering, the more easily particles (sputtered particles) emitted from the GaN sputtering target reach the substrate while retaining their high energy, and the more easily the substrate is epitaxially rearranged. Examples of the gas pressure during sputtering include 0 Pa or more and 1.0 Pa or less, 0 Pa or more and 0.6 Pa or less, 0.1 Pa or more and 0.4 Pa or less, 0.1 Pa or more and 0.3 Pa or less, and 0.1 Pa or more and 0.2 Pa or less.

[0033] (substrate) The substrate may be the same as the substrate 10. The film is preferably formed on a heated substrate, which provides energy to the sputtered particles and makes the resulting sputtered film have a more stable crystalline state, thereby preventing cracks due to differences in thermal expansion coefficients during high-temperature heat treatment. The upper limit of the substrate temperature during film formation is preferably 600°C or 550°C. The lower limit of the substrate temperature can be, for example, room temperature, 100°C, or 400°C. When the substrate temperature is 100°C or higher, the crystallinity of the sputtered film tends to be high and defects tend to be reduced, which makes it easier to increase the conductivity of the sputtered film. Furthermore, when the substrate temperature is 400°C or higher, the sputtered particles, particularly GaN particles, can be arranged with good crystallinity in the sputtered film. The temperature of the substrate is preferably from room temperature to 600°C, from 100°C to 600°C, or from 400°C to 550°C.

[0034] (atmosphere) The atmosphere is not particularly limited, but preferably contains an inert gas from the viewpoint of suppressing reaction with the sputtered film. Examples of inert gases include argon and nitrogen, which may be used alone or in combination of two or more. The inert gas preferably contains nitrogen, which allows the production of a sputtered film with fewer nitrogen defects. The inert gas preferably consists of a mixture of argon and nitrogen.

[0035] The discharge density during discharge is 0.1W / cm 2 More than 5W / cm 2 Below, 0.3W / cm 2 More than 2.5W / cm 2 or less than 0.3W / cm 2 More than 1.5W / cm 2 The discharge density is calculated by dividing the power applied during discharge by the area of ​​the target surface of the sputtering target. 2 If the discharge density is less than 0.1 W / cm, the power applied to the target makes it difficult for coarse single crystal particles to peel off from the sputtering target. 2 When the above conditions are met, the plasma becomes stable, which facilitates discharge, and the film formation rate increases, improving film productivity. Furthermore, the energy during sputtering is high, which improves the adhesion of the sputtered film to the substrate during film formation.

[0036] The deposition time may be adjusted as appropriate depending on the thickness of the sputtered film. The longer the deposition time, the thicker the sputtered film can be.

[0037] (2)Second process The second step is a step of forming a Si film containing Si on the sputtered film to obtain a first laminate.

[0038] The Si film may be formed by sputtering a Si target or by chemical vapor deposition (CVD), and from the viewpoint of easy formation of the Si film, it is preferable to form the Si film by sputtering a Si target.

[0039] In the second step, it is preferable to first evacuate the inside of the film forming apparatus before forming the Si film. The degree of vacuum (ultimate vacuum) in the film forming apparatus is not particularly limited, but is preferably 3×10 -5 Pa or less, and 1×10-5 It is more preferable that the degree of vacuum is 3×10 Pa or less. -5 By keeping the pressure below 0 Pa, residual gases are less likely to be mixed in as impurities during film formation. In order to remove residual gases, it is preferable to bake the film formation apparatus before evacuating the apparatus. The degree of vacuum should be above 0 Pa and below 1×10 -8 Pa or more, or 1×10 -7 For example, it can be exemplified as being equal to or greater than Pa.

[0040] Prior to forming the Si film, it is preferable to hold the sputtered film obtained in the first step at the Si film formation temperature for a certain period of time. This reduces the temperature difference between the sputtered film and the Si film. For example, the holding time is preferably 1 minute or more, 5 minutes or more, or 10 minutes or more. On the other hand, from the viewpoint of improving productivity, the holding time is preferably 1 hour or less, or 30 minutes or less, and examples of the holding time include 1 minute or more and 1 hour or less, or 10 minutes or more and 30 minutes or less.

[0041] (Si sputtering target) The Si sputtering target only needs to contain Si. In order to obtain the effect of the Si dopant in the Si sputtering target, it is preferable that the amount of metal element impurities other than Si is small. Specifically, the content of metal element impurities in the Si sputtering target is preferably less than 0.1 mass%, more preferably less than 0.01 mass%. The amount of metal element impurities in the Si sputtering target can be measured by GDMS.

[0042] (Sputtering) The sputtering method and gas pressure (film formation pressure) during sputtering may be the same as those in the first step.

[0043] (film formation) The deposition is preferably performed in a state where the sputtered film is heated, which provides energy to the sputtered particles and makes the Si film in a more stable crystalline state, thereby making it possible to prevent cracks due to differences in thermal expansion coefficients during heat treatment at high temperatures. The upper limit of the temperature of the sputtered film during film formation is preferably 600°C or 550°C. The lower limit of the temperature of the sputtered film can be, for example, room temperature, 100°C, or 400°C. When the temperature of the sputtered film is 100°C or higher, defects are reduced, making it easier to increase the conductivity of the Si film. Furthermore, when the temperature of the sputtered film is 400°C or higher, the sputtered particles, particularly Si particles, can be arranged with good crystallinity in the sputtered film. The temperature of the sputtered film is preferably from room temperature to 600°C, from 100°C to 600°C, or from 400°C to 550°C.

[0044] (atmosphere) The atmosphere is not particularly limited, but preferably contains an inert gas from the viewpoint of suppressing reaction with the Si film and the sputtered film. Examples of inert gases include argon and nitrogen, which may be used alone or in combination of two or more. The inert gas preferably contains nitrogen, which allows the production of a sputtered film with fewer nitrogen defects. The inert gas preferably consists of a mixture of argon and nitrogen.

[0045] The discharge density during discharge may be the same as in the first step.

[0046] The film formation time may be adjusted as appropriate depending on the thickness of the Si film, but the lower limit of the Si film thickness is preferably 10 nm, more preferably 50 nm, from the viewpoint of sufficiently diffusing Si in the Si film into the sputtered film. From the viewpoint of eliminating the need to remove the Si film in the second stack, the upper limit of the thickness of the Si film is preferably 1500 nm, more preferably 500 nm, and even more preferably 100 nm. The thickness of the Si film can be, for example, 10 nm to 1500 nm, 10 nm to 500 nm, or 50 nm to 100 nm.

[0047] The ratio R2 of the thickness of the Si film to the thickness of the sputtered film is not particularly limited, but the lower limit of the ratio R2 is preferably 1 / 100, and more preferably 1 / 50. From the viewpoint of eliminating the need to remove the Si film in the second stack, the upper limit of the ratio R2 is preferably 1 / 5, more preferably 1 / 10, and examples of the ratio R2 are 1 / 100 or more and 1 / 5 or less, or 1 / 50 or more and 1 / 10 or less.

[0048] (3rd step) The third step is a step of heating the first laminate to diffuse Si contained in the Si film into the sputtered film, thereby obtaining a second laminate.

[0049] The heating temperature of the first laminate is not particularly limited as long as it is a temperature at which the Si contained in the Si film diffuses into the sputtered film, but is preferably higher than 500°C, more preferably 600°C or higher, even more preferably higher than 700°C, and particularly preferably 800°C or higher. When the heating temperature of the first laminate is higher than 500°C, in the third step, Si in the silicon film not only passes through the gaps between the multiple columnar crystals in the sputtered film but also diffuses into the columnar crystals themselves, allowing Si to be more thoroughly diffused into the sputtered film. From the viewpoint of suppressing the reaction between Si and GaN in the sputtered film, the upper limit of the heating temperature of the first laminate is preferably 1000°C, more preferably 950°C, and particularly preferably 900°C. The heating temperature of the first laminate can be, for example, 600°C or higher and 1000°C or lower, 700°C or higher and 1000°C or lower, or 800°C or higher and 1000°C or lower. The heating time for the first laminate may be any time that allows the Si contained in the Si film to diffuse into the sputtered film, and may be 1 minute or more, 5 minutes or more, 10 minutes or more, 30 minutes or more, 1 hour or more, or 2 hours or more, or 6 hours or less, 5 hours or less, or 4 hours or less, for example, 1 minute to 6 hours, 5 minutes to 5 hours, 10 minutes to 5 hours, 30 minutes to 5 hours, 1 hour to 5 hours, or 1 hour to 4 hours. The heating time for the first laminate can be shortened as the heating temperature of the first laminate is higher.

[0050] The second stack includes at least a substrate and a Si-doped GaN film formed by doping Si into a sputtered film, and although at least a portion of the Si film may remain on the surface of the Si-doped GaN film, it is preferable that no Si film remains. If the Si film remains on the surface of the Si-doped GaN film, it is preferable to remove at least the Si film from the second stack.

[0051] The atmosphere in which the first stacked body is heated is not particularly limited, but preferably contains an inert gas from the viewpoint of suppressing deterioration of the Si-doped GaN film due to oxidation or the like.

[0052] Examples of a method for removing the Si film and the part of the sputtered film on the Si film side from the second stack include wet etching with an acidic mixture of hydrofluoric acid, nitric acid, and acetic acid.

[0053] <Semiconductor element> The semiconductor device of the present disclosure includes the above-described layered substrate, and the layered substrate includes the above-described Si-doped GaN film. The semiconductor device of the present disclosure may further include an electrode. The semiconductor device of the present disclosure includes the Si-doped GaN film 20 that can improve conductivity, and is therefore useful as a semiconductor device that requires high conductivity.

[0054] Examples of semiconductor elements include light-emitting elements such as blue light-emitting diodes (LEDs) and blue laser diodes (LDs), as well as power devices such as diodes and transistors.

[0055] <Electronic equipment> An electronic device according to the present disclosure includes the semiconductor element. The electronic device of the present disclosure can improve the performance of the electronic device by using a semiconductor element including a Si-doped GaN film that can improve the conductivity. Examples of electronic devices include mobile devices such as mobile phones, computers such as servers, power conversion devices such as AC-DC converters, transportation equipment such as automobiles, and aircraft such as drones. [Example]

[0056] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples.

[0057] Example 1 First, a sapphire substrate (off-axis angle: none, surface roughness Ra: 0.09 nm, diameter: 50.8 mm (2 inches)) manufactured by Shinkosha Co., Ltd. was prepared as a film-forming substrate. The surface of the sapphire substrate was set to the (0001) plane.

[0058] Meanwhile, a GaN sputtering target was prepared by sintering GaN powder. Then, the substrate and the GaN sputtering target were placed in a magnetron sputtering apparatus.

[0059] The target-substrate distance was set to 150 mm, and the ultimate vacuum was increased by baking the chamber before film formation.

[0060] Next, at the start of sputtering, plasma was ignited using nitrogen gas with the shutter on the substrate side closed, and pre-sputtering was carried out for 10 minutes under the same conditions as during film formation to stabilize the discharge. The distance between the shutter and the substrate was 5 mm. A shutter with a diameter of 3 inches was used. Then, the substrate was heated to a temperature of 500°C, and while Ar gas and nitrogen gas were introduced into the chamber as sputtering gases, a GaN sputtering target was sputtered under the film formation conditions listed in Table 1 to form a film on the substrate, forming a sputtered film (GaN sputtered film) made of GaN with a thickness of 1 μm, thereby obtaining a first stack. On the other hand, a Si sputtering target was prepared by sintering Si powder. The first laminate obtained as described above and a Si sputtering target were then placed in a magnetron sputtering device.

[0061] The target-substrate distance was set to 150 mm, and the ultimate vacuum was increased by baking the chamber before film formation.

[0062] Next, at the start of sputtering, plasma was ignited using nitrogen gas with the shutter on the substrate side closed, and pre-sputtering was carried out for 10 minutes under the same conditions as during film formation to stabilize the discharge. The distance between the shutter and the substrate was 5 mm. A shutter with a diameter of 3 inches was used. Then, the first stack was heated to a temperature of 500°C, and while Ar gas was introduced into the chamber as a sputtering gas, a Si sputtering target was sputtered under the film formation conditions listed in Table 2, thereby forming a film on the sputtered film of the first stack, thereby obtaining a second stack having a Si film with a thickness of 75 nm on the sputtered film of the first stack. Next, this second stack was placed in a heating furnace and heated at 1000° C. for 1 hour to diffuse Si constituting the Si film into the GaN film, thereby obtaining a Si-doped GaN film with a thickness of 1 μm.

[0063] Example 2 A Si-doped GaN film was obtained in the same manner as in Example 1, except that the temperature at which the second stack was heated in the heating furnace (heating temperature of the second stack) was changed to 950°C and the heating time was changed to 4 hours. Example 3 A Si-doped GaN film was obtained in the same manner as in Example 1, except that the temperature at which the second stack was heated in the heating furnace (heating temperature of the second stack) was changed to 600°C and the heating time was changed to 7 hours.

[0064] (Comparative Example 1) A film was formed on the CVD film of a first stack consisting of a sapphire substrate (u-GaN-on-Sapphire Template, manufactured by Enkris Semiconductor) with a GaN film (CVD film) produced by the CVD method, using a Si sputtering target in the same manner as in Example 1, to produce a second stack having a 75 nm thick Si film on the CVD film, and the second stack was further heated in a heating furnace in the same manner as in Example 1. In this way, a Si-doped GaN film was obtained.

[0065] <Characteristics> (Thickness) The step height between the film-formed portion and the non-film-formed portion was measured as the thickness of the Si-doped GaN film using a step height gauge DektakXT (manufactured by Bruker). The results are shown in Table 3.

[0066] (Maximum Si concentration C1, minimum Si concentration C2, minimum Si concentration C3, and ratio R) The Si concentration of the Si-doped GaN film was measured continuously along the depth direction from the surface of the Si-doped GaN film using a TOF-SIMS (IONTOF, M6). The maximum Si concentration at a depth of 50 nm from the surface of the Si-doped GaN film was determined as C1, and the minimum Si concentration at a depth of 200 nm was determined as C2, and R (= C2 / C1) was calculated. Furthermore, the Si concentration at a depth of 300 nm from the surface of the Si-doped GaN film was determined as C3. The results are shown in Table 3.

[0067] <Conductivity> The conductivity of the Si-doped GaN film was measured using resistivity as an index. The resistivity of the Si-doped GaN film was measured using an 8403 AC / DC Hall effect measuring device (manufactured by Toyo Corporation). The results are shown in Table 3.

[0068] [Table 1] [Table 2] [Table 3]

[0069] From the results shown in Table 3, the resistivity of the Si-doped GaN films of Examples 1 to 3 was a maximum of 1.0E+04 (1.0×10 4 ) Ωcm, whereas the Si-doped GaN film of Comparative Example 1 had a resistivity of 2.4E+04 (2.4 × 10 4 In Examples 1 and 2, in which the heating temperature of the second laminate was 800°C or higher, the resistivity was 1.2E-02 (1.2 × 10 -2 ) Ωcm and 5.3E-01(5.3×10 -1 ) Ωcm, and it was confirmed that the resistivity was lower than that of Example 3 in which the heating temperature of the second laminate was less than 800°C. From the above, it was confirmed that the Si-doped GaN film of the present disclosure can improve electrical conductivity. [Explanation of symbols]

[0070] 10...substrate, 20...Si-doped GaN film, 100...layered substrate.

Claims

1. A silicon-doped gallium nitride film comprising gallium nitride and silicon, a ratio R(C2 / C1) of a minimum value C2 of silicon concentration to a maximum value C1 in a range of a depth from a surface of the silicon-doped gallium nitride film of 50 nm or more and A nm or less, is 0.001 or more and less than 1; The minimum value C2 is 1×10 １７ atoms / cm ３ That's all, A silicon-doped gallium nitride film, wherein A is the thickness of the silicon-doped gallium nitride film when the thickness of the silicon-doped gallium nitride film is less than 200 nm, and A is 200 nm when the thickness of the silicon-doped gallium nitride film is 200 nm or more.

2. The minimum silicon concentration C3 in the range of a thickness of 300 nm or more and a depth from the surface of 50 nm to 300 nm is 1×10 １７ atoms / cm ３ The silicon-doped gallium nitride film according to claim 1 .

3. The silicon-doped gallium nitride film of claim 1 , wherein the ratio R is 0.01 or greater.

4. The silicon-doped gallium nitride film of claim 1 , wherein the ratio R is 0.5 or less.

5. 10. A method for producing a silicon-doped gallium nitride film according to claim 1, comprising: A first step of preparing a gallium nitride film containing gallium nitride; a second step of forming a silicon film containing silicon on the gallium nitride film to obtain a first stack; and a third step of heating the first stack to diffuse the silicon contained in the silicon film into the gallium nitride film, thereby obtaining a second stack.

6. The method for producing a silicon-doped gallium nitride film according to claim 5 , wherein the gallium nitride film is a sputtered film formed by sputtering.

7. 6. The method for producing a silicon-doped gallium nitride film according to claim 5, wherein the first stack is heated to a temperature higher than 500[deg.] C. in the third step.

8. A layered substrate comprising the silicon-doped gallium nitride film according to claim 1 and a substrate.

9. A semiconductor device comprising the laminated substrate according to claim 8 .

10. An electronic device comprising the semiconductor device according to claim 9.

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