Multilayer film structure and production method therefor

Abstract

The purpose of the present invention is to provide at least one of: a multilayer film structure having high crystallinity and flatness; and a method for producing the multilayer film structure. Furthermore, provided is at least one of: a multilayer film structure that has a SiC substrate and a nitride-based film formed on the substrate by sputtering, and that is applicable to a power device; and a method for producing the multilayer film structure. A multilayer film structure comprising: a SiC substrate; and a film that is formed on the SiC substrate and that contains a nitride-based material containing at least Ga, wherein the off angle of the (0001) plane of SiC monocrystal constituting the SiC substrate with respect to the silicon plane is 0.03-8°, and C and Cl in the film containing the nitride-based material are contained in amounts not more than 2×1019 atoms / cm3 and not more than 2×1018 atoms / cm3, respectively.

Description

Stacked film structure and method for manufacturing the same

[0001] The present invention relates to a laminated film structure and a method for manufacturing the same.

[0002] Nitride-based materials exhibit excellent semiconductor properties. For example, gallium nitride (GaN) has been put to practical use as a material for blue light-emitting diodes (LEDs) and blue laser diodes (LDs). Furthermore, gallium nitride has high breakdown voltage performance, making it suitable for applications such as power devices. Therefore, a laminated film structure in which a film of a nitride-based material (hereinafter also referred to as a "nitride-based film") is provided on a substrate is useful in the field of electronic devices.

[0003] Patent Documents 1 to 4 disclose techniques relating to the production of nitride-based films, including metal organic chemical vapor deposition (MOCVD) methods.

[0004] Patent Document 1 discloses a method for manufacturing a nitride film by MOCVD, in which a semiconductor crystal film (nitride film) is grown by injecting a pressure diffusion gas simultaneously with a reaction gas. The examples of Patent Document 1 specifically describe growing a gallium nitride film on a sapphire substrate using ammonia, hydrogen gas, and TMG (trimethylgallium) gas.

[0005] Patent Document 2 discloses growing a gallium nitride film on a GaAs (111) single crystal substrate using hydride vapor phase epitaxy (HVPE).

[0006] Patent Document 3 discloses a method for forming a gallium nitride film, in which a gallium nitride infiltrated gallium nitride molded product, in which gallium nitride and metallic gallium exist as separate phases in the molded product and the molar ratio of Ga / (Ga+N) in the entire molded product is 55% or more and 80% or less, is used as a sputtering target and sputtered onto a sapphire substrate.

[0007] Patent Document 4 discloses a silicon carbide (SiC) substrate for growing a gallium nitride compound semiconductor layer, characterized in that the epitaxial growth surface of the SiC substrate is a plane set at an off angle of 0.03° to 0.3° relative to the silicon plane of the C-plane (0001) of the SiC single crystal. The examples of Patent Document 4 describe growing a nitride film on the SiC substrate by MOCVD.

[0008] Japanese Patent Application Publication No. 4-164895 Japanese Patent Application Publication No. 2000-12900 Japanese Patent Application Publication No. 2014-159368 Japanese Patent Application Publication No. 2020-75839

[0009] The MOCVD methods of Patent Documents 1 and 4, and the HVPE method of Patent Document 2, are both chemical film formation methods. Furthermore, MOCVD and HVPE require metalorganic or chloride materials, respectively. Therefore, both methods are prone to the incorporation of impurities such as carbon and chlorine into the nitride-based films being formed. As a result, the resulting nitride-based films have high impurity concentrations, and devices constructed using such films suffer from significant performance degradation. In contrast, the sputtering method disclosed in Patent Document 3 is a physical film formation method in which raw material particles are deposited onto a substrate by physical impact from a sputtering target. Therefore, no metalorganic or chloride materials are required, and carbon and chloride impurity concentrations can be reduced. Furthermore, no equipment for detoxifying metalorganic or chloride materials is required, enabling the growth of nitride-based films with low environmental impact.

[0010] However, when applied to applications such as power devices, conventional nitride films formed on SiC substrates by sputtering do not have sufficient crystallinity.

[0011] In addition, the influence of the off-angle of the SiC substrate on the crystallinity of a nitride film formed by sputtering is unknown.

[0012] The present invention has been completed based on such findings, and aims to provide at least one of a laminated film structure having high crystallinity and flatness and a method for manufacturing the same, and a further aim to provide at least one of a laminated film structure having a SiC substrate and a nitride-based film formed on the substrate by sputtering, which can be applied to a power device, and a method for manufacturing the same.

[0013] The present inventors have found that the influence of the off-angle of the SiC substrate is significantly different between a nitride film obtained by MOCVD and a nitride film obtained by sputtering, and have found that by controlling the off-angle of the SiC substrate, a highly crystalline nitride film can be obtained on a SiC substrate by sputtering.

[0014] That is, the present invention is as set forth in the claims and also includes the following aspects (1) to (14). In this specification, the expression "to" includes the numerical values ​​at both ends. That is, "X to Y" is synonymous with "X or more and Y or less." Furthermore, "X and / or Y" is synonymous with "at least one of X and Y (one or both of X and Y, i.e., "X, Y, or X and Y")." (1) A laminated film structure having a SiC substrate and a film containing a nitride-based material containing at least Ga on the SiC substrate, wherein the off-angle of the (0001) plane of the SiC single crystal constituting the SiC substrate with respect to the silicon plane is 0.03° or more and 8° or less, and the C contained in the film containing the nitride-based material is 2×10 １９ pieces / cm ３ or less, and Cl is 2×10 １８ pieces / cm ３(2) The laminated film structure according to (1) above, wherein the rocking curve half-width of the (0002) plane of the surface is 5.30° or less. (3) The laminated film structure according to (1) above, wherein the nitride-based material is gallium nitride. (4) The laminated film structure according to any one of (1) to (3) above, wherein the arithmetic mean roughness (Ra) of the surface of the laminated film structure is 10.0 nm or less. (5) The method according to any one of (1) to (4) above, wherein the film containing the nitride-based material has a thickness of 20 nm or more. (6) The laminated film structure according to any one of (1) to (5) above, wherein the surface of the laminated film structure is composed of a hexagonal gallium nitride layer, and the surface of the gallium nitride layer has gallium (Ga) polarity. (7) The laminated film structure according to any one of (1) to (6) above, wherein an amorphous layer is present on the SiC substrate, and the thickness of the amorphous layer is 0 nm or more and less than 1.0 nm. (8) The laminated film structure according to (7) above, wherein the amorphous layer has a thickness of more than 0 nm and less than 1.0 nm. (9) The laminated film structure according to any one of (1) to (8) above, wherein the film containing a nitride-based material is a gallium nitride-based sputtered film. (10) A semiconductor element comprising the laminated film structure according to any one of (1) to (9) above. (11) An electronic device comprising the semiconductor element of (10) above. (12) A method for producing the laminated film structure according to any one of (1) to (9) above, comprising the steps of preparing a SiC substrate, immersing the SiC substrate in a cleaning solution, and depositing a film containing a nitride-based material on the SiC substrate after immersion by a sputtering method, wherein when depositing the film containing a nitride-based material, the formula: Es=[input power (unit: W / cm ２ ) / [introduced gas pressure (unit: Pa)] ２ The sputtering energy (Es) represented by ２ Pa ２ More than 150W / cm ２ Pa ２ (13) A method for manufacturing a laminated film structure, comprising: (a) performing the sputtering method at an ultimate vacuum of 5.0×10 －４ (14) When depositing the film containing the nitride-based material, the ultimate vacuum in the film deposition apparatus immediately before the film deposition is set to less than 1×10 Pa. －４(15) The method according to any one of (12) to (14), wherein the sputtering method is performed using a target having a carbon content of 1 mass % or less and a chlorine content of 100 ppm or less.

[0015] The present invention provides at least one of a laminated film structure having high crystallinity and flatness and a method for manufacturing the same, and a laminated film structure having a SiC substrate and a nitride-based film formed on the substrate by sputtering, which can be applied to a power device, and a method for manufacturing the same.

[0016] 1 is a schematic diagram showing an example of a cross section of a laminated film structure, a schematic diagram showing another example of a cross section of a laminated film structure, a schematic diagram showing an example of a semiconductor element, and a schematic diagram showing another example of a semiconductor element.

[0017] A specific embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described. Note that the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the present invention.

[0018] [Layered Film Structure] This embodiment relates to a layered film structure having a SiC substrate and a film containing a nitride-based material containing at least Ga on the SiC substrate, wherein the off-angle of the (0001) plane of the SiC single crystal constituting the SiC substrate with respect to the silicon plane is 0.03° or more and 8° or less, and the C contained in the film containing the nitride-based material is 2×10 １９ pieces / cm ３ or less, and Cl is 2×10 １８ pieces / cm ３ The laminated film structure of this embodiment is as follows. Silicon carbide (SiC) has a lattice constant close to that of nitride-based films, so that nitride-based films can easily grow epitaxially. Furthermore, since SiC has high thermal conductivity and excellent heat dissipation properties, by using silicon carbide as a support substrate for the nitride-based film, the laminated film structure of this embodiment is expected to exhibit characteristics suitable for applications that generate a large amount of heat, such as power devices.

[0019] The laminated film structure of this embodiment includes a SiC substrate as a so-called support substrate. The SiC substrate constituting the laminated film structure of this embodiment is a silicon carbide (SiC) substrate, and in particular, a substrate made of a silicon carbide single crystal (SiC single crystal substrate).

[0020] The SiC substrate has an off-angle (hereinafter simply referred to as "off-angle") of 0.03 degrees or more and 8 degrees or less (0.03° or more and 8° or less) with respect to the (0001) silicon plane of the SiC single crystal constituting the substrate. If the off-angle is too small, the terrace length (terrace width) of the atomic steps of the SiC single crystal becomes long. Therefore, it is thought that it becomes difficult to grow a film containing a nitride-based material with high crystallinity equivalent to that of the SiC substrate. On the other hand, if the off-angle is too large, the terrace length of the atomic steps becomes short. Therefore, although it becomes easier to obtain a film containing a nitride-based material with high crystallinity, the yield of SiC substrates obtained from SiC single crystal ingots decreases. As a result, it is thought that there are cost issues, such as high manufacturing costs for SiC substrates.

[0021] In this embodiment, the off angle is preferably 0.03° to 8°, 0.05° to 6°, 0.06° to 5°, 0.08° to 4°, 0.1° to 4°, or 0.1° to 2°. In another embodiment, the off angle may be 0.03° or more, 0.08° or more, or 1° or more, and may be 8° or less, or 5° or less.

[0022] The (0001) plane of a SiC single crystal (i.e., the equivalent plane corresponding to the C-axis of the SiC crystal) has a silicon plane (the so-called (0001) plane) and a carbon plane (the so-called (000-1) plane) on the opposite side. The silicon plane is the plane used to grow a gallium nitride film that functions as a gallium nitride-based compound semiconductor, that is, the plane on which a film containing a nitride-based material grows in the stacked film structure of this embodiment.

[0023] The off-angle is an angle relative to the direction of a reference crystal plane. The direction of the off-angle is not limited. The off-angle is, for example, an angle tilted from the (0001) plane direction to the (1-100) direction or the (11-20) direction, preferably an angle tilted from the (0001) plane direction to the (11-20) direction. As the SiC substrate constituting the stacked film structure of this embodiment, at least one of a SiC substrate in which the angle tilted from the (0001) plane direction to the (1-100) direction is the value of the off-angle described above and a substrate in which the angle tilted from the (0001) plane direction to the (11-20) direction is the value of the off-angle described above can be used, and a SiC substrate in which the angle tilted from the (0001) plane direction to the (11-20) direction is the value of the off-angle described above is preferred. More specifically, the SiC substrate constituting the stacked film structure of this embodiment may be a SiC substrate having an off angle from the (0001) plane direction to the (11-20) direction of 0.03° or more and 8° or less, further 0.05° or more and 8° or less, or even 3° or more and 6° or less.

[0024] The off-angle can be determined from 2θ / ω and ω scans using, for example, X-ray diffraction. The X-ray diffraction measurement for measuring the off-angle can be performed using a general X-ray diffraction device (for example, D8 DISCOVER, manufactured by Bruker AXS) under the following conditions.

[0025] Acceleration current / voltage: 50 mA / 50 kV Radiation source: CuKα radiation (λ = 1.5405 Å) Measurement mode: Continuous scan Scan conditions: 2 ° / min Measurement range: 2θ = 10 ° to 90 ° Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1 ° Receiving slit: open Receiving solar slit: 5 ° Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter XRD patterns can be measured using a general powder X-ray diffractometer (e.g., Ultima IV, manufactured by Rigaku Corporation). In addition, crystalline XRD peaks are peaks detected by identifying the 2θ of the peak top in the analysis of the XRD pattern using general analysis software (e.g., SmartLab Studio II, manufactured by Rigaku Corporation). The XRD pattern analysis conditions are as follows:

[0026]

[0033] Fitting conditions: automatic, background refinement, distributed pseudo-Voigt function (peak shape) Background removal method: fitting method Kα2 removal method: Kα1 / Kα2 ratio = 0.497 Smoothing method: B-Spline curve Smoothing conditions: second-order differential method, σ cut value = 3, χ threshold = 1.5 The SiC substrate constituting the stacked film structure of this embodiment may be a SiC substrate having the above-mentioned off-angle, and its manufacturing method is not limited. The SiC substrate may be a SiC substrate manufactured by a sublimation method or a melting method, or a SiC epitaxial substrate (SiC epitaxial substrate) in which a SiC single crystal layer is epitaxially grown on a SiC single crystal substrate manufactured by these methods.

[0027] The SiC substrate constituting the laminated film structure of this embodiment may be one or more selected from the group consisting of semi-insulating, n-type, and p-type, and is preferably at least one of semi-insulating and n-type, and more preferably n-type.

[0028] The SiC substrate may contain a dopant element such as a donor or an acceptor on its surface and / or inside. However, the SiC substrate does not necessarily contain a dopant element. Examples of the dopant element contained in the SiC substrate include one or more elements selected from the group consisting of boron, nitrogen, aluminum, and phosphorus.

[0029] Generally, when a SiC substrate is newly obtained, its surface is covered with a native oxide film or a native nitride film. This native oxide film is amorphous and has a thickness of approximately 1 to 3 nm. If a SiC substrate with a remaining native oxide film (amorphous layer) is used as is, the crystallinity of the nitride-based material film may be reduced. In contrast, if a SiC substrate from which the native oxide film has been more completely removed is used, the crystallinity of the gallium nitride film can be further improved. Therefore, it is preferable that the SiC substrate constituting the stacked film structure of this embodiment is a SiC substrate without a native oxide film (i.e., without an amorphous phase, or with an amorphous layer having a thickness of 0 nm). However, the stacked film structure of this embodiment may also include a SiC substrate having a native oxide film (amorphous phase) to such an extent that its effect is not impaired, and the SiC substrate may have an amorphous phase with a thickness of less than 1 nm or less than 0.5 nm.

[0030] The stacked film structure of this embodiment has a film containing a nitride-based material containing at least Ga (hereinafter also referred to as a "gallium nitride film"). The gallium nitride film contains a nitride-based material containing at least Ga (hereinafter also referred to as a "gallium nitride material"), and may further be made of a gallium nitride material.

[0031] The gallium nitride film is preferably a film formed by sputtering, a so-called sputtered film.

[0032] The gallium-containing nitride film is preferably one or more selected from the group consisting of gallium nitride film, aluminum gallium nitride film, indium gallium nitride film, and aluminum indium gallium nitride film. Furthermore, since it is useful as a material for light-emitting elements such as blue light-emitting diodes (LEDs) and blue laser diodes (LDs), and semiconductor elements such as power devices, the gallium-containing nitride film is more preferably a gallium nitride film. When the gallium nitride film is gallium nitride (GaN), the laminated film structure of this embodiment can be applied to electronic devices such as light-emitting elements and semiconductor elements. Furthermore, the laminated film structure of this embodiment can be used as a base substrate, and gallium nitride can be further formed thereon. Since the gallium nitride formed on the laminated film structure of this embodiment can be grown epitaxially, the laminated film structure of this embodiment containing this gallium nitride can be used as a device with excellent characteristics.

[0033] In this embodiment, the type of the gallium nitride material is not limited as long as it is a nitride-based material containing gallium (Ga). For example, the gallium nitride material may be a material that functions as a III-V semiconductor and contains at least gallium (Ga) as a group III element and nitrogen (N) as a group V element.

[0034] Specific examples of gallium nitride materials include one or more selected from the group consisting of gallium nitride, aluminum gallium nitride, and indium gallium nitride, with gallium nitride (GaN) being preferred.

[0035] The gallium nitride material is not limited to one whose composition is stoichiometric. For example, the stoichiometric composition of gallium nitride is a gallium (Ga) to nitrogen (N) ratio (atomic ratio) of 1:1. When the gallium nitride material contained in the gallium nitride film is gallium nitride, deviation from the stoichiometric composition is allowed as long as the crystal structure of gallium nitride is maintained, and the gallium nitride may be a gallium nitride that does not have a stoichiometric composition. For example, in this embodiment, when the gallium nitride material is gallium nitride, the composition of the gallium nitride is, for example, an atomic ratio of Ga:N of 0.9:1.0 to 1.1:1.0.

[0036] The gallium nitride material may contain a dopant element, such as one or more elements selected from the group consisting of Ar, O, Si, Fe, Mg, and Mn, or may not contain a dopant element.

[0037] When a dopant element is contained, the content of the dopant element is 1×10 １７ atoms / cm ３ or more (1 x 10 １７ pieces / cm ３ or more), and 1 × 10 １８ atoms / cm ３ More preferably, 1×10 １９ atoms / cm ３ In this embodiment, the dopant element may be contained in a range that provides the effects of this embodiment, and for example, the content of the dopant element is 1×10 ２２ atoms / cm ３ or less or 1 x 10 ２１ atoms / cm ３ The following are included: In this embodiment, for convenience, carbon (C) and chlorine (Cl) are not considered as dopant elements.

[0038] In the laminated film structure of this embodiment, the C contained in the gallium nitride film is 2×10 １９ pieces / cm ３ Below (2 x 10 １９ atoms / cm ３ (or less), and Cl is 2 × 10１８ pieces / cm ３ Below (2 x 10 １８ atoms / cm ３ (See below).

[0039] The gallium nitride film included in the stacked film structure of this embodiment has high crystallinity, and the C (carbon) and Cl (chlorine) contents in the gallium nitride film in contact with the SiC substrate are small. Specifically, the C content is 2.0 × 10 １９ atoms / cm ３ Hereinafter, the Cl content is 2.0 × 10 １８ atoms / cm ３ The following are the results. The low content of C and Cl increases the crystallinity of the gallium nitride film. Furthermore, the low impurity content (i.e., the content of C and Cl) of the gallium nitride film allows further epitaxial growth of a film thereon. This makes it possible to fabricate devices such as semiconductor elements with excellent characteristics.

[0040] The content of C is preferably 8.0×10 １８ atoms / cm ３ or less, more preferably 4.0 × 10 １８ atoms / cm ３ More preferably, 2.0 × 10 １８ atoms / cm ３ or less, and even more preferably 1.0 × 10 １８ atoms / cm ３ Particularly preferably, 8.0 × 10 １７ atoms / cm ３ The C content is preferably low, but it is not preferred that the C content is 0 atoms / cm ３ Above, 0 atoms / cm ３ Over 5.0 x 10 １７ atoms / cm ３ The above points can be mentioned.

[0041] The Cl content is preferably 8.0×10 １７ atoms / cm ３ or less, more preferably 4.0 × 10 １７ atoms / cm ３ More preferably, 2.0 × 10１７ atoms / cm ３ or less, and even more preferably 1.0 × 10 １７ atoms / cm ３ Particularly preferably, 8.0 × 10 １６ atoms / cm ３ The Cl content is preferably low, but it is not more than 0 atoms / cm ３ Above, 0 atoms / cm ３ Over 5.0 x 10 １６ atoms / cm ３ The above points can be mentioned.

[0042] The lower limit of the amount of impurities in the gallium nitride film is not limited. The content of C and Cl is 1.0×10 １４ atoms / cm ３ Above, and further 1.0 x 10 １５ atoms / cm ３ or more, or even 1.0 x 10 １６ atoms / cm ３ Anything above that is fine.

[0043] In this embodiment, the contents of C and Cl can be determined by secondary ion mass spectrometry (SIMS), for example, by secondary ion mass spectrometry using a secondary ion mass spectrometer (PCOR-SIMS; point by point correction-SIMS, EAG Laboratories).

[0044] The gallium nitride film contained in the laminated film structure of this embodiment preferably has high crystallinity. Here, "high crystallinity" refers to a state in which the crystal orientation within the film is highly aligned, and preferably refers to the gallium nitride film satisfying the FWHM described below. Due to the high crystallinity of the gallium nitride film, the laminated film structure of this embodiment can be suitably used as an underlayer when fabricating light-emitting elements such as LEDs and power device elements on a SiC substrate. Furthermore, the laminated film structure of this embodiment can be suitably used as a template substrate for growing a highly crystalline gallium nitride film.

[0045] The thickness of the gallium nitride film constituting this embodiment is not limited as long as it can be considered a film, even a thin film. The thickness of the gallium nitride film is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more. The upper limit of the film thickness is not limited, and may be 1000 nm or less, 500 nm or less, 250 nm or less, or 150 nm or less.

[0046] The film thickness can be determined by observing the cross section of the laminated film structure using a transmission electron microscope. Alternatively, multiple films sputtered under the same conditions may be prepared, and the film thicknesses may be measured using a contact film thickness meter or an optical film thickness meter, and the film thickness may be calculated using the film formation rate determined from these. A preferred method for measuring the film thickness is a method using a contact film thickness meter.

[0047] The stacked film structure of this embodiment includes a SiC substrate having a surface with an off-angle of 0.03 degrees or more and 8 degrees or less (0.03° or more and 8° or less), and at least one gallium nitride film provided on the SiC substrate.

[0048] In this embodiment, the "laminated film structure" is a structure that is composed of at least a substrate and one or more films laminated on the substrate.

[0049] The laminated film structure of this embodiment has a SiC substrate and a gallium nitride film on the SiC substrate. The SiC substrate only needs to have a gallium nitride film thereon, and further, the gallium nitride film only needs to be laminated on the SiC substrate. The gallium nitride film may be laminated directly on the SiC substrate, or may be laminated on the SiC substrate via another layer.

[0050] In the laminated film structure of this embodiment, when the gallium nitride film is laminated on the SiC substrate via another layer, the other layer can be an amorphous layer, and can be at least one of a natural oxide film and a natural nitride nitride film.In the laminated film structure of this embodiment, an amorphous layer can be present on the SiC substrate, and the SiC substrate and the gallium nitride can be laminated via an amorphous layer.That is, the laminated film structure of this embodiment can have an amorphous layer on the SiC substrate, or can be a laminated film structure configured by laminating a SiC substrate, an amorphous layer and a Ga-containing material film layer, or can be a laminated film structure having a configuration in which a SiC substrate, an amorphous layer and a Ga-containing material film layer are laminated in order.

[0051] The thickness of the amorphous layer is sufficient as long as it is less than 1.0 nm, and is preferably 0 nm or more and less than 1.0 nm, and more preferably 0 nm or more and 0.5 nm or less.

[0052] The amorphous layer can be, for example, a layer made of a reaction product between the surface of the SiC substrate and nitrogen, and can be, for example, an amorphous oxide layer, or a layer containing at least one amorphous material selected from silicon dioxide and silicon nitride, or a layer made of at least one of amorphous silicon dioxide and amorphous silicon nitride.

[0053] The laminated film structure of this embodiment preferably has a surface arithmetic mean roughness (Ra) of 10.0 nm or less, more preferably 5.0 nm or less, even more preferably 2.0 nm or less, and particularly preferably 1.0 nm or less. Having such an arithmetic mean surface roughness (Ra) makes it suitable as a substrate for constructing a device on its surface, and provides a substrate surface that exhibits sufficient smoothness for constructing a device. The arithmetic mean surface roughness (Ra) is ideally 0 nm. However, since a practical laminated film structure has surface roughness, the arithmetic mean surface roughness (Ra) of the laminated film structure of this embodiment can be, for example, greater than 0 nm, 0.5 nm or more, or 0.7 nm or more.

[0054] Similarly, the gallium nitride film constituting the laminated film structure of this embodiment also preferably has the above-mentioned arithmetic mean roughness (Ra).

[0055] The surface roughness may be measured using a scanning probe microscope (for example, NanoScope IIIa, manufactured by Bruker AXS).

[0056] The stacked film structure of this embodiment preferably has a rocking curve half-width (FWHM; hereinafter simply referred to as "FWHM") of the (0002) plane of its surface of 5.30° or less, 5.00° (°) or less, 3.00° (°) or less, 2.00° (°) or less, or 1.50° (°) or less. The smaller the FWHM, the higher the crystallinity, but examples of the FWHM include 0° or more, 0.1° or more, or 1.00° or more. When the stacked film structure of this embodiment is a stacked film structure composed of a SiC substrate and a gallium nitride film, the rocking curve half-width (FWHM) of the (0002) plane of the stacked film structure of this embodiment may be the rocking curve half-width (FWHM) of the (0002) plane of the gallium nitride film.

[0057] In this embodiment, the FWHM is a value evaluated by X-ray diffraction, and the evaluation conditions include the following.

[0058]

[0023] - Radiation source: CuKα radiation (λ = 0.15418 nm) - Monochromator: Ge (220) - Pathfinder: Crystal3B - Measurement mode: ω scan - Measurement interval: 0.01° (0.002° when the half-width is 0.1° or less) - Measurement time: 0.5 seconds - Measurement range: ω = 0° to 35°. In the laminated film structure of this embodiment, the surface thereof, for example, the surface of the gallium nitride film, is preferably composed of a hexagonal gallium nitride layer, and the surface of this gallium nitride layer preferably has a gallium (Ga) polarity. Having a gallium (Ga) polarity on the surface makes it less likely that hexagonal facets, which make device fabrication difficult, will be formed when gallium nitride (GaN) is further formed on the laminated film structure.

[0059] Hereinafter, as the laminated film structure of this embodiment, a laminated film structure without an amorphous layer (first embodiment) and a laminated film structure with an amorphous layer (second embodiment) will be described.

[0060] FIG. 1 is a cross-sectional schematic diagram of a laminated film structure in a first embodiment. In FIG. 1, the laminated film structure (1) comprises a SiC substrate (2) and a film of a nitride-based material (gallium nitride film) (3) provided on the SiC substrate (2). In the first embodiment, no amorphous layer is present. That is, the thickness of the amorphous layer is 0 nm, and the gallium nitride film (3) is in direct contact with the SiC substrate (2) without any other layer interposed therebetween.

[0061] The gallium nitride film (3) is in direct contact with the SiC substrate (2), i.e., the gallium nitride film is directly stacked on the SiC substrate (2), thereby increasing the crystallinity of the gallium nitride film (3) and the crystallinity of the surface of the stacked film. In other words, the gallium nitride film (3) is in direct contact with the highly crystalline SiC substrate (2), so that the gallium nitride film (3) grows in crystal form while having the same crystallinity as the SiC substrate (2). In terms of the manufacturing process, the gallium nitride film (3) grows epitaxially well.

[0062] In the first embodiment, other layers may be present on the gallium nitride film (3) as long as high crystallinity is maintained. That is, the gallium nitride film (3) in the stacked film structure of the first embodiment may be used as a buffer layer, and a highly crystalline layer may be stacked on the gallium nitride film (SiC substrate / gallium nitride film / highly crystalline layer). The highly crystalline layer may be a gallium nitride film, and the composition of the layer may be the same as or different from the gallium nitride film that is the buffer layer.

[0063] In the first embodiment, since no amorphous layer is present, the contrast of the amorphous layer between the SiC substrate and the gallium nitride film is not clearly observed in an observation image such as a cross-sectional TEM.

[0064] FIG. 2 is a cross-sectional schematic diagram of a laminated film structure according to a second embodiment. This laminated film structure (1) comprises a SiC substrate (2) and a film (3) of a nitride-based material containing at least Ga (gallium nitride film) provided on the SiC substrate (2). In the second embodiment, an amorphous layer (4) is present between the SiC substrate (2) and the gallium nitride film (3). The thickness of the amorphous layer (4) is greater than 0 nm and less than 1.0 nm, and even greater than 0.1 nm and less than 0.5 nm. By having the thickness of the amorphous layer (4) less than 1.0 nm, the crystallinity of the gallium nitride film (3) is increased even if the amorphous layer (4) is present. In contrast, if an amorphous layer having a thickness of 1.0 nm or more is present on the SiC substrate (2), the epitaxial growth of the gallium nitride film (3) is inhibited, and the crystallinity of the gallium nitride film (3) is reduced. Furthermore, if the thickness of the amorphous layer (4) is 1.0 nm or more, the crystal orientation of the gallium nitride film (3) will not be uniform, resulting in a polycrystalline film.

[0065] The material of the amorphous layer is not particularly limited, but is typically an amorphous oxide layer, further comprising silicon dioxide and / or silicon nitride, and more typically comprising silicon dioxide.

[0066] In the second embodiment, as long as the high crystallinity of the gallium nitride film (3) is maintained, other layers other than the amorphous layer (4) may be present between the SiC substrate (2) and the gallium nitride film (3). However, it is preferable that no other layers other than the amorphous layer (4) exist. Furthermore, as long as the high crystallinity is maintained, other layers may be present on the gallium nitride film (3).

[0067] In both the first and second aspects, the combination of gallium nitride materials constituting the gallium nitride film is not limited as long as it contains Ga, and a gallium nitride-based film is more preferred, with a gallium nitride film being particularly preferred. The gallium nitride film may be made up of a single gallium nitride material or two or more gallium nitride materials. That is, the gallium nitride film may contain two or more gallium nitride materials. Furthermore, the gallium nitride film may be made up of multiple layers.

[0068] Furthermore, it is believed that by forming a film of a nitride-based material on the silicon surface of a SiC substrate, it becomes easier to make the surface of gallium nitride (GaN) that constitutes the nitride-based material film gallium (Ga) polar.

[0069] The gallium nitride film is preferably a gallium nitride-based sputtered film.

[0070] A preferred embodiment of the present invention is a laminated film structure having a configuration in which a film containing a nitride-based material containing at least Ga is laminated on a SiC substrate, wherein the SiC substrate is made of SiC single crystal, and the off-angle with respect to the SiC (0001) plane is 0.03° or more and 8° or less, and the carbon content of the nitride-based material contained in the film is 2×10 １９ atoms / cm ３ or less, and the chlorine content is 2 x 10 １８ atoms / cm ３ The following laminated film structures are included:

[0071] As a more preferred embodiment of the present invention, there is provided a laminated film structure having a configuration in which a gallium nitride film is laminated on a single crystal SiC substrate, wherein an off-angle with respect to a (0001) plane of SiC constituting the single crystal SiC substrate is 0.03° or more and 8° or less, and a carbon content of the gallium nitride film is 2×10 １９ atoms / cm ３ or less, and the chlorine content is 2 x 10 １８ atoms / cm ３ The following laminated film structures are included:

[0072] A preferred embodiment of the present invention is a method for manufacturing a SiC substrate, comprising: a SiC substrate; and a nitride film containing gallium, wherein the nitride film is stacked on the SiC substrate directly or via an amorphous layer; the SiC substrate is made of SiC single crystal; the off-angle of the SiC substrate with respect to the SiC (0001) plane is 0.03° or more and 8° or less; and the carbon content of the nitride film is 2×10 １９ atoms / cm ３ or less, and the chlorine content is 2 x 10 １８ atoms / cm ３or less, and the rocking curve half width of the (0002) plane of the nitride film is 5.00° or less.

[0073] [Semiconductor Element and Electronic Device] The semiconductor element of this embodiment may include the laminated film structure of this embodiment.

[0074] The electronic device of this embodiment may include the semiconductor element of this embodiment. Examples of the semiconductor element include a light-emitting element such as a blue light-emitting diode (LED) or a blue laser diode (LD) ( FIG. 3 ), or a power device such as a diode or transistor ( FIG. 4 ). The semiconductor element may include a thin film and / or a thick film made of a nitride-based material such as gallium nitride (GaN) provided on the laminated film structure of this embodiment as a base layer. The semiconductor element and electronic device may also include functional components other than the laminated film structure. Due to the high crystallinity of the nitride-based film that constitutes the laminated film structure, the semiconductor element and electronic device exhibit excellent characteristics.

[0075] [Method for Manufacturing Laminated Film Structure] The laminated film structure of this embodiment can be manufactured by any method as long as it satisfies the above-described configuration, but can be suitably manufactured by the following manufacturing method.

[0076] That is, the method for manufacturing the stacked film structure of this embodiment includes a step of preparing a SiC substrate (hereinafter also referred to as a "substrate preparation step"), a step of immersing the SiC substrate in a cleaning solution (hereinafter also referred to as a "wet etching step"), and a step of forming a film containing a nitride-based material on the immersed SiC substrate by a sputtering method (hereinafter also referred to as a "film formation step"). When forming the film containing the nitride-based material, the formula: Es=[input power (unit: W / cm ２ ) / [introduced gas pressure (unit: Pa)] ２ The sputtering energy (Es) represented by ２ Pa ２ More than 150W / cm ２ Pa ２ The manufacturing method is as follows.

[0077] Preferably, the method for manufacturing the laminated film structure of the present embodiment includes the steps of: preparing a SiC substrate; immersing the SiC substrate in a cleaning solution for 3 seconds or more; and applying an ultimate vacuum of 5.0×10 to the SiC substrate after the immersion. －４ and then depositing a film containing a nitride-based material by a sputtering method using a sputtering target having a carbon content of less than 1 mass % and a chlorine content of less than 100 ppm, wherein when depositing the film containing the nitride-based material, the formula: Es=[input power (unit: W / cm ２ ) / [introduced gas pressure (unit: Pa)] ２ The sputtering energy (Es) represented by ２ Pa ２ More than 150W / cm ２ Pa ２ The details of each step of the manufacturing method will be described below.

[0078] <Substrate Preparation Step> In the substrate preparation step, a SiC substrate is prepared. The manufacturing method of the SiC substrate is not limited, and it may be manufactured by sublimation or melt growth, or it may be a SiC epitaxial substrate in which a SiC single crystal layer is epitaxially grown on a SiC single crystal substrate manufactured by these methods. In addition, the SiC substrate may or may not contain a dopant element such as a donor or acceptor on its surface and / or interior.

[0079] <Wet Etching Step> In the wet etching step, the prepared SiC substrate is immersed in a cleaning solution. The SiC substrate to be subjected to the wet etching step is preferably a SiC substrate having the above-described off-angle, and more preferably a SiC substrate made of a SiC single crystal having the above-described off-angle.

[0080] The SiC substrate may have any shape as long as it is similar to the desired laminated film structure, and may have, for example, a disk shape, a disk shape having a diameter of 10 mm to 150 mm, or even a disk shape having a diameter of 25 mm to 120 mm.

[0081] The thickness of the SiC substrate may be sufficiently thick relative to the thickness of the gallium nitride film, and may be, for example, 200 μm or more, or 300 μm or more, and 1000 μm or less, or 600 μm or less.

[0082] The resistivity of the SiC substrate is arbitrary, but for example, 1.0×10 －３ Ω cm or more or 1.0 x 10 －２ Ω cm or more, and 1.0 × 10 ８ Ω・cm or more or less, 1.0×10 ７ Ω・cm or less or 1.0×10 －１ Ω·cm or less.

[0083] In the wet etching process, contaminants and oxide films on the surface of the SiC substrate are removed (cleaned).

[0084] The cleaning liquid may be at least one selected from the group consisting of an aqueous hydrofluoric acid solution, sulfuric acid, hydrochloric acid, hydrogen peroxide, ammonium hydroxide, trichloroethylene, acetone, methanol, and isopropanol, and is preferably an aqueous hydrofluoric acid solution. The immersion may be performed by immersing the SiC substrate in the cleaning liquid after ultrasonic treatment using an ultrasonic cleaner.

[0085] When a hydrofluoric acid aqueous solution is used as the cleaning solution, the hydrofluoric acid concentration of the hydrofluoric acid aqueous solution is preferably 1 to 10 mass % (1 mass % or more and 10 mass % or less), and more preferably 5 to 10 mass % (5 mass % or more and 10 mass % or less). By setting the hydrofluoric acid concentration to 5 mass % or more, it becomes possible to efficiently modify the surface with hydrogen. Furthermore, by setting the concentration to 10 mass % or less, the surface roughness of the SiC substrate after the wet etching process is less likely to increase.

[0086] The immersion time of the SiC substrate is preferably 3 seconds or more and 100 seconds or less, and more preferably 5 seconds or more and 100 seconds or less (5 to 100 seconds). By setting the immersion time to 5 seconds or more, the oxide film can be sufficiently removed, and the thickness of the amorphous layer in the laminated film structure after manufacture can be reduced. Furthermore, by setting the immersion time to 100 seconds or less, it is possible to suppress surface roughness during etching.

[0087] The immersion time may be 20 seconds or more and 100 seconds or less, or 20 seconds or more and 50 seconds or less. This makes it easier to prepare a laminated film structure of the first embodiment having an amorphous layer thickness of 0 nm (no amorphous material present). The immersion time may be 5 seconds or more and less than 20 seconds. This makes it possible to prepare a laminated film structure of the second embodiment having an amorphous layer thickness of more than 0 nm and less than 1.0 nm.

[0088] After immersion in the cleaning solution, residual droplets on the substrate surface are removed by a method such as blowing nitrogen gas over the surface.

[0089] The SiC substrate after the wet etching treatment preferably has the oxide film sufficiently removed and a flat surface. The SiC substrate after the wet etching treatment has an arithmetic mean roughness (Ra) of 0.5 nm or less, preferably 0.3 nm or less. The arithmetic mean roughness of the SiC substrate is preferably small, but can be, for example, 0 nm or more or 0.1 nm or more.

[0090] Since the substrate surface is susceptible to contamination by impurities in the atmosphere after the removal of the residual droplets, it is preferable to proceed to the nitride-based material film formation step within 24 hours or less, i.e., the transition time from the wet etching step to the film formation step is less than 24 hours, and even 12 hours or less, or 5 hours or less. A short transition time is preferable, but examples include 15 minutes or more, or 30 minutes or more.

[0091] Although a practical SiC substrate has a native oxide film, if a SiC substrate without a native oxide film is provided, the manufacturing method of this embodiment does not need to include the wet etching step.

[0092] <Film Forming Step> In the film forming step, a film of a nitride-based material, i.e., a film of a nitride-based material containing at least Ga (gallium nitride film) is formed by sputtering on the SiC substrate after the wet etching process. This forms a sputtered film of gallium nitride, and the stacked film structure of this embodiment is obtained.

[0093] The sputtering method may be any known method, and examples thereof include one or more selected from the group consisting of DC sputtering, RF sputtering, AC sputtering, DC magnetron sputtering, RF magnetron sputtering, pulse sputtering, and ion beam sputtering. Because it is possible to form a uniform film over a large area at high speed, the sputtering method is preferably magnetron sputtering, and more preferably at least one of DC magnetron sputtering and RF magnetron sputtering.

[0094] As the sputtering target (hereinafter also simply referred to as "target"), a known target used for depositing nitride-based films can be used. Such targets include at least one of a metal target and a nitride-based target.

[0095] From the viewpoint of improving the crystallinity of the entire film, the lower the C content and Cl content of the target, the more preferable. The sputtering method is preferably carried out using a target having a carbon content of 1 mass % or less, further 1000 mass ppm or less, or even 100 mass ppm or less, and a chlorine content of 100 ppm or less, further 10 ppm or less, as analyzed by, for example, glow discharge mass spectrometry (GDMS).

[0096] Furthermore, the C content and Cl content are preferably 100 ppm (weight ratio) or less, 50 ppm or less, or 10 ppm or less, respectively. Although it is preferable that the C content and Cl content are low, as long as the target can obtain the desired gallium nitride film, there are no lower limits for these. For example, the carbon content of the target may be 0 ppm or more, more than 0 ppm, or 10 ppm or more, and the chlorine content of the target may be 0 ppm or more, more than 0 ppm, or 0.5 ppm or more.

[0097] The larger the target area, the more easily it is possible to form a film on a large-area substrate, and the more uniform the film thickness and quality are. ２ More than 100 cm is preferable. ２The above is more preferable. The target area refers to the area of ​​one of the main surfaces of the target.

[0098] The sputtering method was carried out with an ultimate vacuum of 5.0 × 10 －４ Pa or even less than 1.0 × 10 －５ It is preferable to carry out the heating after the pressure has reached 0.2 Pa or less.

[0099] When forming a nitride film, the ultimate vacuum level in the film forming apparatus immediately before film formation is 1×10 －４ Pa or less, 7×10 －５ Pa or less, 2×10 －５ Pa or less, 9×10 －６ Pa or less, or 5 x 10 －６ The higher the degree of vacuum inside the apparatus before film formation, the more likely it is that the impurities remaining in the deposition film (nitride film) will be prevented from being mixed in. As a result, the crystallinity of the deposited film is further improved. The higher the degree of vacuum, the better. －６ Pa or more or 2 x 10 －６ Pa or more.

[0100] To remove residual gases, the device may be subjected to a baking process before film formation.

[0101] Furthermore, sputtering film formation is preferably carried out while the substrate is heated. This promotes migration of particles deposited on the substrate, allowing the formation of a deposited film in a stable crystalline state. The substrate heating temperature (also referred to as the "film formation temperature" or "substrate temperature") is preferably 100°C to 800°C, more preferably 200°C to 600°C. Furthermore, sputtering is preferably carried out at a substrate temperature of 400°C or higher and 850°C or lower.

[0102] As the gas introduced during sputtering, known gases used for forming nitride films can be used. Such gases include argon (Ar) and nitrogen (N ２ The gas preferably contains at least argon, and more preferably a mixed gas of argon and nitrogen. If necessary, other gases such as ammonia may be introduced.

[0103] The sputtering energy (Es) when depositing the nitride film is 0.1 W / cm ２ Pa ２ More than 150W / cm ２ Pa ２ Here, the sputtering energy (Es) is the energy of sputtered particles during sputtering film formation, and is expressed by the formula: Es = [input power density (unit: W / cm ２ ) / [introduced gas pressure (unit: Pa)] ２ is defined as:

[0104] The input power density (Es) is the input energy per unit area when the input power is divided by the area of ​​the target. This allows for the deposition of a film with high crystallinity. Although the detailed reasons are not clear, it is presumed that the magnitude of the sputtering energy (Es) changes the characteristics of the sputtered particles, such as the adhesion of the sputtered particles that reach the substrate, the diffusion length when the sputtered particles migrate on the substrate, and / or the penetration depth into the film that has already been deposited, which affects the crystallinity of the nitride film. Es is 0.1 W / cm ２ Pa ２ or more, and 0.5 W / cm ２ Pa ２ Above, 1W / cm ２ Pa ２ More than 2W / cm ２ Pa ２ or more or 10 cm ２ Pa ２ It is preferable that Es is 100 W / cm or more. ２ Pa ２ Below, 60W / cm ２ Pa ２ or less than 30 W / cm ２ Pa ２ The following is fine.

[0105] If necessary, a step of further laminating another nitride-based film on the nitride-based film may be provided. For example, a gallium nitride-based film may be formed as a nitride-based film by sputtering, and then another gallium nitride-based film may be formed thereon by MOCVD.

[0106] In this manner, the laminated film structure of this embodiment is manufactured.

[0107] The present invention will be further described using the following examples and comparative examples. However, the present invention is not limited to the following examples. (1) Evaluation The laminated film structures obtained in each example and comparative example were evaluated as follows. <Structural Analysis> The presence or absence of an amorphous layer and its thickness were determined by analyzing the interface between the SiC substrate and the nitride film. As a pretreatment, a carbon coating was applied to the surface of the laminated film structure, followed by focused ion beam (FIB) processing to prepare an observation sample. Next, a field emission transmission electron microscope (JEM-2100F, manufactured by JEOL Ltd.) was used to observe the cross section of the observation sample. The electron beam acceleration voltage was set to 200 kV. <Elements Contained in the Laminated Film Structure> The C and Cl contents in the nitride film were evaluated using a secondary ion mass spectrometer (Eurofins EAG, PCOR-SIMS). Analysis was performed while scraping the nitride film surface, and the lowest concentration was extracted from the profile up to the SiC substrate.

[0108] <Surface Roughness of Laminated Film Structure> The arithmetic mean roughness (Ra) of the surface of the laminated film structure was measured using a scanning probe microscope (Bruker AXS, NanoScope IIIa) in tapping mode AFM with a visual field of 2 μm×2 μm.

[0109] <Polarity of laminated film structure> The polarity and crystalline phase of the gallium nitride film were evaluated using a time-of-flight atom scattering surface analyzer (TOFLAS-3000, Pascal Corporation). The laminated film structure was set in the analyzer so that its film-formed surface was facing up, and measurements were performed. The polarity and crystalline phase of the gallium nitride film were determined by comparing the pole figures obtained by measurement with the pole figures of each crystalline phase and polarity of the first four outermost layers obtained by simulation. The detailed measurement conditions are as follows:

[0110] - Probe: He (atomic scattering) - Energy: 3 keV - Beam source-target distance: 805 mm - Target-detector distance: 395 mm - Analysis chamber vacuum level: 2 x 10 －３Pa or less <Crystallism of the laminated film structure> The crystallinity of the surface of the laminated film structure was evaluated using an X-ray diffractometer (D8 DISCOVER, manufactured by Bruker AXS). The analysis was performed in HIGH RESOLUTION mode under conditions of 40 kV and 40 mA. In addition, a monochromator was used to remove CuKα2, and an ω scan was performed. The rocking curve of the (0002) plane was measured to determine the full width at half maximum (FWHM), which was used as an index of the crystallinity of the film. The analysis conditions were as follows:

[0111] - Radiation source: CuKα radiation (λ = 0.15418 nm) - Monochromator: Ge (220) - Pathfinder: Crystal3B - Measurement mode: ω scan - Measurement interval: 0.01° (0.002° when the half-width is 0.1° or less) - Measurement time: 0.5 seconds - Measurement range: ω = 0° to 35° [Example 1] (Example) <Preparation step> An n-type SiC substrate (offset 4° from the silicon surface in the (11-20) direction, i.e., an off angle of 4°) was prepared as a SiC substrate. The substrate had a diameter of 50 ± 0.5 mm (50 mm), a thickness of 330 ± 25 μm (330 μm), and a resistivity of 0.015 Ω cm or more (0.015 Ω cm).

[0112] <Wet Etching Step> The SiC substrate was subjected to a wet etching process (cleaning process). First, hydrofluoric acid (Kanto Chemical Co., Ltd., Ultrapure grade) was diluted with ultrapure water (Kanto Chemical Co., Ltd., Ultrapure grade) to obtain a diluted hydrofluoric acid aqueous solution with a hydrogen fluoride concentration of 5 mass%. The SiC substrate was immersed in the diluted hydrofluoric acid aqueous solution for 30 seconds and then removed from the diluted hydrofluoric acid aqueous solution. Nitrogen gas was then blown onto the SiC substrate to remove any remaining droplets on the surface of the SiC substrate.

[0113] As a result, a cleaned SiC substrate (Ra: 0.15 nm) was obtained. Thereafter, without any time gap (within one hour), the obtained SiC substrate was subjected to a film formation step (a nitride film formation step described later).

[0114] <Nitride-Based Film Formation Process> Using a magnetron sputtering device, a nitride-based film was formed on a wet-etched SiC substrate by RF magnetron sputtering. That is, a gallium nitride (GaN) target (purity 99.99 mass%, carbon content 20 ppm, and chlorine content 1 ppm) was used as the sputtering target. The SiC substrate and the target were placed in the film formation chamber of the sputtering device, and the chamber was evacuated. The degree of vacuum in the film formation chamber (the ultimate vacuum before film formation) was 1.8 × 10 －６ After the pressure reached Pa, sputtering was started to form a gallium nitride film.

[0115] The film was formed using a mixed gas of nitrogen (flow rate: 20 sccm) and argon (flow rate: 3 sccm) as the gas introduced into the film formation chamber, with the substrate temperature at 800°C and the sputtering energy at 10 W / cm ２ Pa ２ As a result, a gallium nitride (GaN) film having a thickness of 50 nm was formed, and a laminated film structure (a laminated film structure having a SiC substrate and a gallium nitride film, with the gallium nitride film laminated on the SiC substrate) was fabricated.

[0116] Examples 2 to 5 (Examples) A ​​laminated film structure was produced in the same manner as in Example 1, except that the conditions for the nitride film formation process were as shown in Table 1.

[0117] [Example 6] (Example) A stacked film structure was produced in the same manner as in Example 1, except that the immersion time of the SiC substrate in the diluted hydrofluoric acid aqueous solution in the wet etching treatment was set to 5 seconds, and the conditions for the nitride film formation step were set to the conditions shown in Table 1.

[0118] Example 7 (Comparative Example) A laminated film structure was produced in the same manner as in Example 1, except that the immersion time of the SiC substrate in the diluted hydrofluoric acid aqueous solution in the wet etching treatment was set to 2 seconds, and the conditions for the nitride film formation step were set to the conditions shown in Table 1.

[0119] Example 8 (Comparative Example) A stacked film structure was produced in the same manner as in Example 1, except that a GaN target having a C content of 100 ppm or more (1 mass %) was used and the conditions for the nitride film formation process were as shown in Table 1.

[0120] Example 9 (Comparative Example) A stacked film structure was produced in the same manner as in Example 1, except that a GaN target having a Cl content of 100 ppm or more (100 ppm by mass) was used and the conditions for the nitride film formation process were as shown in Table 1.

[0121] Examples 10 to 12 (Comparative Examples) Stacked film structures were fabricated in the same manner as in Example 1, except that the conditions for the nitride film formation process were as shown in Table 1.

[0122] Example 13 (Comparative Example) A GaN film was grown on a SiC substrate by metal organic chemical vapor deposition (MOCVD) to fabricate a laminated film structure.

[0123] Example 14 (Comparative Example) A GaN film was grown on a SiC substrate by hydride vapor phase epitaxy (HVPE) to fabricate a laminated film structure.

[0124] [Examples 15 and 16] (Examples) A ​​laminated film structure was fabricated in the same manner as in Example 1, except that a semi-insulating SiC substrate (offset by 0.1° from the silicon surface in the (11-20) direction, i.e., an off angle of 0.1°) was prepared as the SiC substrate, and the conditions shown in Table 1 were used. The substrate had a diameter of 101.6±0.5 mm, a thickness of 500±25 μm, and a resistivity of 1.0×10 ７ The value was Ω·cm.

[0125] [Examples 17 and 18] (Examples) A ​​stacked film structure was fabricated in the same manner as in Example 1, except that an n-type SiC substrate (offset by 4° in the (11-20) direction from the silicon surface, i.e., an off angle of 4°) was prepared as the SiC substrate, and the conditions shown in Table 1 were used. The substrate had a diameter of 101.6±0.5 mm, a thickness of 350±25 μm, and a resistivity of 0.01 Ω cm.

[0126] [Examples 19 and 20] (Examples) A ​​stacked film structure was produced in the same manner as in Example 1, except that an n-type SiC substrate (offset by 8° from the silicon plane in the (11-20) direction, i.e., an off angle of 8°) was prepared as the SiC substrate, and the conditions shown in Table 1 were used. The substrate had a diameter of 101.6±0.5 mm, a thickness of 350±25 μm, and a resistivity of 0.01 Ω cm. (3) Results The evaluation results obtained for Examples 1 to 20 are shown in Table 2. Examples 1 to 6 and 15 to 20 are examples, and Examples 7 to 14 are comparative examples.

[0127] In particular, in Examples 1 to 5, the C content is 1.9 × 10 １９ atoms / cm ３ The Cl content is 4.9 × 10 １７ atoms / cm ３ The thickness of the amorphous layer was small, at 0.2 nm or less. Furthermore, the arithmetic mean roughness (Ra) was small, at 1.8 nm or less, and the full width at half maximum (FWHM) was small, at 3.8° or less. Thus, in Examples 1 to 6, Ga-polar gallium nitride films (nitride-based films) were successfully produced that were low in impurities, highly flat, crystalline, and had hexagonal crystallinity.

[0128] In contrast, the comparative examples (Examples 7 to 14) had a high C or Cl content and were inferior in crystallinity and surface flatness. For example, in Example 7, in which the Si substrate was immersed for 2 seconds, an amorphous layer was present, and its thickness was 1.2 nm. In Examples 8 and 9, in which the C content or Cl content in the target was 100 ppm or more, the C content or Cl content on the surface of the obtained laminated film structure was high. The ultimate vacuum was 5.0 × 10 －４ Example 10 of Pa had a large FWHM and low crystallinity. ２ Pa ２ Example 11, where the ２ Pa ２ In Example 12, in which the GaN film was grown by MOCVD, the FWHM of the surface of the laminated film structure was large and the crystallinity was low. In Example 13, in which the GaN film was grown by MOCVD, the C content was high, and in Example 14, in which the GaN film was grown by HVPE, the Cl content was high.

[0129]

[0130]

[0131] The entire contents of the specification, claims, abstract, and drawings of Japanese Patent Application No. 2021-063918, filed on April 5, 2021, are hereby incorporated by reference as the disclosure of the specification of the present invention.

[0132] REFERENCE SIGNS LIST 1 laminated film structure 2 SiC substrate 3 nitride-based film 4 amorphous layer 5 light-emitting diode 6 drift layer 7 electrode 8 light-emitting layer 9 transistor 10 electron passage layer 11 electron generation layer 12 barrier layer

Claims

1. A laminated film structure having a SiC substrate and a film containing a nitride-based material containing at least Ga on the SiC substrate, wherein an off-angle of a (0001) plane of a SiC single crystal constituting the SiC substrate with respect to a silicon plane is 0.03° or more and 8° or less, and C contained in the film containing the nitride-based material is 2×10 １９ pieces / cm ３ or less, and Cl is 2×10 １８ pieces / cm ３ The laminated film structure is as follows:

2. 2. The laminated film structure according to claim 1, wherein the half-width of the rocking curve of the (0002) plane on the surface is 5.30° or less.

3. 2. The laminated film structure according to claim 1, wherein the nitride-based material is gallium nitride.

4. 3. The laminated film structure according to claim 1, wherein the arithmetic mean roughness (Ra) of the surface of the laminated film structure is 10.0 nm or less.

5. The method according to claim 1 or 2, wherein the film containing the nitride-based material has a thickness of 20 nm or more.

6. 3. The laminated film structure according to claim 1, wherein a surface of the laminated film structure is composed of a hexagonal gallium nitride layer, and the surface of the gallium nitride layer has a gallium (Ga) polarity.

7. 3. The laminated film structure according to claim 1, wherein an amorphous layer is present on the SiC substrate, and the thickness of the amorphous layer is 0 nm or more and less than 1.0 nm.

8. The laminated film structure according to claim 7 , wherein the thickness of the amorphous layer is greater than 0 nm and less than 1.0 nm.

9. 3. The laminate film structure according to claim 1, wherein the film containing a nitride-based material is a gallium nitride-based sputtered film.

10. A semiconductor device comprising the laminated film structure according to claim 1 or 2.

11. An electronic device comprising the semiconductor device of claim 10.

12. 2. A method for producing a laminated film structure according to claim 1, comprising the steps of: preparing a SiC substrate; immersing the SiC substrate in a cleaning solution; and depositing a film containing a nitride-based material on the SiC substrate after immersion by a sputtering method, wherein when depositing the film containing the nitride-based material, the formula: Es=[input power (unit: W / cm ２ ) / [Introducing gas pressure (unit: Pa)] ２ The sputtering energy (Es) represented by ２ P ２ More than 150W / cm ２ P ２ A method for producing a laminated film structure comprising the steps of:

13. The sputtering method was carried out at a vacuum level of 5.0×10 －４ The method according to claim 12, wherein the process is carried out after reducing the pressure to less than Pa.

14. When forming the film containing the nitride-based material, the ultimate vacuum in the film forming apparatus immediately before the film formation is set to 1×10 －４ The method according to claim 12 or 13, wherein the viscosity is set to 0.01 Pa or less.

15. The method according to claim 12 or 13, wherein the sputtering method is carried out using a target having a carbon content of 1 mass % or less and a chlorine content of 100 ppm or less.