Gallium nitride sputtering target, gallium nitride film, method for producing gallium nitride film, layered substrate, semiconductor element, and electronic equipment

Abstract

This gallium nitride sputtering target comprises a gallium nitride sintered compact containing a dopant. The dopant content of the sintered compact is at least 1 x 1021 atoms / cm3. The dopant can be an n-type dopant. The n-type dopant can be Si or Ge. The gallium nitride sputtering does not necessarily contain hydrogen.

Description

Gallium nitride sputtering target, gallium nitride film, method for producing gallium nitride film, laminated substrate, semiconductor element, and electronic device

[0001] The present disclosure relates to a gallium nitride sputtering target, a gallium nitride film, a method for producing a gallium nitride film, a laminated substrate, a semiconductor element, and an electronic device.

[0002] Gallium nitride films are used in semiconductor devices such as LEDs and transistors, and high conductivity is often required for such gallium nitride films. Gallium nitride films are sometimes formed by sputtering a gallium nitride sputtering target. Examples of such gallium nitride sputtering targets include, for example, a gallium nitride sputtering target having an area of ​​150 cm. ２ As described above, a gallium nitride sintered body having an oxygen content of 1 atm % or less is known (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-75851

[0004] However, when a gallium nitride film is formed by sputtering the gallium nitride sputtering target described in Patent Document 1, the gallium nitride film may not have sufficient conductivity. Even such a gallium nitride film can be made more conductive by subjecting it to a heat treatment such as annealing at a high temperature. However, in such a case, in a semiconductor device including a gallium nitride film, not only the gallium nitride film but also the electrodes, substrate, and other components are subjected to a heat treatment at a high temperature, which can easily cause melting of the electrodes, warping of the substrate, and distortion of the entire semiconductor device.

[0005] The present disclosure aims to provide a gallium nitride sputtering target capable of forming a gallium nitride film having high conductivity without heat treatment at high temperatures, a gallium nitride film, a method for manufacturing a gallium nitride film, a laminated substrate, a semiconductor element, and an electronic device.

[0006] The present invention provides a gallium nitride sintered body containing a dopant, wherein the content of the dopant in the sintered body is 1×10２１ atoms / cm ３ (2) The gallium nitride sputtering target according to (1), wherein the dopant is an n-type dopant. (3) The gallium nitride sputtering target according to (2), wherein the n-type dopant contains at least one of silicon and germanium. (4) The gallium nitride sputtering target according to (2), wherein the content of the dopant in the sintered body is 1×10 ２３ atoms / cm ３ (5) A gallium nitride sputtering target according to any one of (1) to (3), which is the following: (5) A gallium nitride sputtering target according to any one of (1) to (4), which does not contain hydrogen: (6) A gallium nitride film obtained by sputtering the gallium nitride sputtering target according to any one of (1) to (5), (7) A gallium nitride film obtained by sputtering the gallium nitride sputtering target according to any one of (1) to (5), which contains a dopant in an amount of 5×10 ２０ atoms / cm ３ (6) A gallium nitride film comprising the above. (8) The gallium nitride film according to (7), wherein the dopant is an n-type dopant. (9) The gallium nitride film according to (8), wherein the n-type dopant comprises at least one of silicon and germanium. (10) The gallium nitride film according to any one of (6) to (9), wherein the gallium nitride film does not contain hydrogen. (11) A method for producing a gallium nitride film, comprising a film formation step of producing a gallium nitride film by sputtering a gallium nitride sputtering target according to any one of (1) to (5). (12) A layered base material comprising a substrate and the gallium nitride film according to any one of (6) to (10). (13) A semiconductor element comprising the gallium nitride film according to any one of (6) to (10). (14) A semiconductor element comprising the layered base material according to (12). (15) An electronic device comprising the semiconductor element according to (13) or (14).

[0007] According to the present disclosure, there are provided at least one of a gallium nitride sputtering target capable of forming a gallium nitride film having high conductivity without heat treatment at high temperatures, a gallium nitride film, a method for manufacturing a gallium nitride film, a laminated substrate, a semiconductor element, and an electronic device.

[0008] Fig. 1 is a cross-sectional view showing an embodiment of a gallium nitride sputtering target of the present disclosure, Fig. 2 is a cross-sectional view showing an embodiment of a layered substrate of the present disclosure, and Fig. 3 is a schematic view showing an embodiment of an electronic device of the present disclosure.

[0009] 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.

[0010] <Gallium Nitride Sputtering Target> First, one embodiment of a gallium nitride sputtering target according to the present disclosure will be described.

[0011] The gallium nitride (hereinafter also simply referred to as "GaN") sputtering target 1 shown in FIG. 1 includes a gallium nitride sintered body 11 containing a dopant, and the content of the dopant in the sintered body 11 is 1×10 ２１ atoms / cm ３ The GaN sputtering target (hereinafter also simply referred to as "target") 1 may further include a support 13 bonded via a bonding layer 12.

[0012] By sputtering this target 1, a GaN film having high conductivity can be formed without high-temperature heat treatment. This eliminates the need for high-temperature heat treatment on the GaN film to increase its conductivity, thereby suppressing melting of the electrodes, warping of the substrate, and distortion of the entire semiconductor element. One of the reasons why the GaN film has high conductivity without high-temperature heat treatment is that the dopant content in the sintered body 11 is 1×10 ２１ atoms / cm ３In this case, it is believed that the dopant contained in a large amount in the GaN film produced using target 1 blocks defects in the crystal lattice of the GaN film, making it difficult for electrons to be trapped in the defects. In other words, a GaN film that is not heat-treated at high temperatures has low crystallinity and has many defects in the crystal lattice. When a voltage is applied to such a GaN film, electrons are trapped in the defects, preventing their movement. If the GaN film contains a large amount of dopant, the dopant blocks the defects, making it difficult for electrons to be trapped in the defects when a voltage is applied to the GaN film, and it is believed that this increases the conductivity of the GaN film.

[0013] The sintered body 11, the bonding layer 12, and the support 13 of the target 1 of this embodiment will be described in detail below.

[0014] (1) Sintered body In this embodiment, the gallium nitride sintered body 11 is a sintered body having gallium nitride as the main component (also referred to as the "matrix" or "parent phase"), and may be a polycrystalline gallium nitride or a sintered body mainly composed of gallium nitride. However, the sintered body 11 of this embodiment may contain components other than gallium nitride, such as metallic gallium. The sintered body 11 of this embodiment may contain elements other than dopants and gallium nitride, such as inevitable impurities. Examples of inevitable impurities contained in the sintered body 11 of this embodiment include oxygen (O). Furthermore, the sintered body 11 of this embodiment may contain metal impurities as long as the effects of the sintered body 11 are not impaired. Examples of metal impurities include at least one of aluminum (Al) and indium (In). The metal impurities may be contained as metals or as metal compounds. In order to further improve the conductivity of the GaN film obtained from the sintered body 11 of this embodiment, the sintered body 11 of this embodiment preferably has a low content of elements other than dopants, nitrogen, and gallium, and preferably does not substantially contain metal impurities. Specifically, the content of metal impurities may be 50 mass ppm or less, 10 mass ppm or less, or 5 mass ppm or less, as the mass ratio [mass ppm] of metal impurities determined by glow discharge mass spectrometry relative to the total mass of elements determined by glow discharge mass spectrometry. The lower limit of the content of metal impurities may be 0 mass ppm or more, more than 0 mass ppm, or 1 mass ppm or more. Furthermore, the content of metal impurities may be 0 mass ppm or more and 50 mass ppm or less, or more than 0 mass ppm and 10 mass ppm or less. (Dopant) The sintered body 11 contains a dopant. The content of the dopant is 1×10 ２１ atoms / cm ３That's all. By including a large amount of dopant in the sintered body 11, the conductivity of the GaN film can be further improved when the sintered body 11 is sputtered to form a GaN film. The dopant may be an n-type dopant or a p-type dopant. Examples of n-type dopants include silicon, germanium, tin, and lead. From the viewpoint of substituting gallium atoms in the GaN film, the n-type dopant preferably includes at least one of silicon and germanium, which have an atomic radius close to that of gallium. Examples of n-type dopants include one or more selected from the group consisting of silicon, germanium, tin, and lead, and at least one of silicon and germanium. Examples of p-type dopants include magnesium, calcium, strontium, barium, and zinc. Examples of p-type dopants include one or more selected from the group consisting of magnesium, calcium, strontium, barium, and zinc, and at least one of magnesium and zinc. The sintered body 11 may contain a single dopant or two or more dopants.

[0015] The content of the dopant in the sintered body 11 is 1×10 ２１ atoms / cm ３ There are no particular limitations on the amount as long as it is equal to or greater than this, but from the viewpoint of further increasing the conductivity of the GaN film, it is preferably 1.5×10 ２１ atoms / cm ３ or more, more preferably 2 × 10 ２１ atoms / cm ３ or more, and even more preferably 4×10 ２１ atoms / cm ３ More preferably, 6 × 10 ２１ atoms / cm ３ The dopant content in the sintered body 11 is 1×10 ２３ atoms / cm ３ Below, 5 x 10 ２２ atoms / cm ３ or less, or 2 x 10 ２２ atoms / cm ３The upper and lower limits of the dopant content in the sintered body 11 may be any combination of the above, but may be 1×10 or less. ２１ atoms / cm ３ 1x10 or more ２３ atoms / cm ３ Below, 1.5 x 10 ２１ atoms / cm ３ 1x10 or more ２３ atoms / cm ３ Below, 2 x 10 ２１ atoms / cm ３ 1x10 or more ２３ atoms / cm ３ Below, 4 x 10 ２１ atoms / cm ３ 5x10 or more ２２ atoms / cm ３ or less, or 6 x 10 ２１ atoms / cm ３ 2x10 or more ２２ atoms / cm ３ It is preferable that:

[0016] The dopant content in the sintered body 11 refers to the smallest dopant content among the dopant contents measured continuously along the depth direction for the entire thickness of the sintered body 11 from the front surface to the back surface using secondary ion mass spectrometry (SIMS). The more measurement points in the SIMS measurement, the more preferable. Measurements are preferably performed at 5 or more or 10 or more points for the entire thickness, and more preferably at 20 or more, 30 or more, or 50 or more points per 100 nm of thickness. The unit of dopant content is "atoms / cm 3 " is 1 cm 3 is the number of dopant atoms contained in the sintered body 11 per 1000 .mu.m.

[0017] (Hydrogen) The sintered body 11 of this embodiment may or may not contain hydrogen (H). "Containing hydrogen" means that the hydrogen concentration is 5×10 in SIMS as described below. １８ atoms / cm ３ This means that hydrogen of 5×10 or more is detected by SIMS as described below, and "not containing hydrogen" means that hydrogen of 5×10 or more is detected by SIMS as described below.１８ atoms / cm ３ This means that less than 1000 ppm of hydrogen is detected.

[0018] The hydrogen content in the sintered body 11 of this embodiment is not particularly limited. However, from the viewpoint of further increasing the conductivity of the GaN film, it is preferable that the hydrogen content be 1×10 ２１ atoms / cm ３ Below, 5 x 10 ２０ atoms / cm ３ or less, or 1 x 10 ２０ atoms / cm ３ The hydrogen content in the sintered body 11 of this embodiment is preferably 1×10 １６ atoms / cm ３ That's it, 5 x 10 １６ atoms / cm ３ or more, or 1 x 10 １７ atoms / cm ３ The upper and lower limits of the hydrogen content in the sintered body 11 of this embodiment may be any combination of the above, but are not limited to 1×10 １６ atoms / cm ３ 1x10 or more ２１ atoms / cm ３ Below, 5 x 10 １６ atoms / cm ３ 5x10 or more ２０ atoms / cm ３ or less, or 1 x 10 １７ atoms / cm ３ 1x10 or more ２０ atoms / cm ３ It is preferable that:

[0019] The hydrogen content in the sintered body 11 of this embodiment refers to the smallest hydrogen content among the hydrogen contents measured continuously along the depth direction for the entire thickness of the sintered body 11 from the front surface to the back surface using SIMS secondary ion mass spectrometry. The number of measurement points in the SIMS measurement is preferably as large as possible. The number of measurement points is preferably 5 or more or 10 or more for the entire thickness, and more preferably 20 or more, 30 or more, or 50 or more per 100 nm thickness. The unit of hydrogen content is "atoms / cm 3 " is 1 cm3 is the number of hydrogen atoms contained in the sintered body 11 per unit area.

[0020] (Thickness) The thickness of the sintered body 11 of this embodiment is not particularly limited, and may be 5 cm or less, 3 cm or less, or 2 cm or less. Furthermore, the thickness of the sintered body 11 of this embodiment is preferably 2 mm or more, 5 mm or more, 7 mm or more, 8 mm or more, or 1 cm or more. The upper and lower limits of the thickness of the sintered body 11 may be any combination of the above, but are preferably 2 mm or more and 5 cm or less, 5 mm or more and 5 cm or less, or 7 mm or more and 3 cm or less. (Area) The area of ​​the sputtering surface (surface on which sputtering is performed) of the sintered body 11 of this embodiment is not particularly limited, and the lower limit of the sputtering surface area of ​​the sintered body 11 is 15 cm. ２ Above, 18cm ２ Above, 20cm ２ Above, 50cm ２ or more, or 100 cm ２ The upper limit of the area of ​​the sputtering surface of the sintered body 11 is 10,000 cm. ２ Below, 5000cm ２ or less than 1000 cm ２ The area of ​​the sputtering surface of the sintered body 11 is 15 cm ２ More than 10000cm ２ Below, 18cm ２ More than 5000cm ２ Below, 20cm ２ More than 5000cm ２ Less than or equal to 50 cm ２ More than 1000cm ２ The following can be exemplified.

[0021] (Shape) The shape of the sintered body 11 of this embodiment is arbitrary, and examples thereof include at least one of a flat plate shape and a cylindrical shape, as well as other shapes suitable for the intended use. (Bulk Density) The bulk density of the sintered body 11 of this embodiment is 4.0 g / cm3, which makes it easier to have mechanical properties suitable for a sputtering target. ３ or more than 4.2 g / cm ３The higher the bulk density, the more preferable it is, and the bulk density of the sintered body of this embodiment is, for example, 5.0 g / cm ３ Below, 4.8g / cm ３ or less than 4.6 g / cm ３ Preferably, it is 4.0 g / cm or less. ３ 5.0g / cm or more ３ Below, 4.2g / cm ３ 4.8g / cm or more ３ or less, or 4.2 g / cm ３ 4.6g / cm or more ３ In the present embodiment, the bulk density is the density [g / cm 3 ] measured by a method according to JIS R 1634:1998. ３ The pretreatment may be carried out by a vacuum method using distilled water. The flexural strength of the sintered body of this embodiment may be 10 MPa or more, and is preferably 15 MPa or more or 30 MPa or more. ２１ atoms / cm ３ Despite the high dopant content of 1000 or more, cracks, chips, etc. are less likely to occur when processed into a shape suitable for a sputtering target. High flexural strength is preferable, and examples include 60 MPa or less or 50 MPa or less. The flexural strength of the sintered body of this embodiment can be 15 MPa or more and 60 MPa or less, or 30 MPa or more and 50 MPa or less. In this embodiment, the flexural strength is the three-point bending strength of the sintered body measured by a method in accordance with JIS R 1601. Measurements are performed 3±1 times, and the average value is used as the flexural strength of this embodiment.

[0022] (2) Bonding Layer The bonding layer 12 of this embodiment may be composed of a solder containing one or more elements selected from the group consisting of tin, indium, and zinc. The bonding layer 12 is preferably composed of a solder containing indium, as this tends to increase the electrical conductivity and thermal conductivity of the target 1. When the bonding layer 12 is a solder containing indium, the target 1 may have a layer for improving wettability (hereinafter also referred to as a "barrier layer") between the gallium nitride sintered body 11 and the bonding layer 12. This improves the indium wettability of the sintered body 11, resulting in a stronger bond between the sintered body 11 and the bonding layer 12. The barrier layer may be composed of a component that is highly wettable to indium, and is preferably at least one of nickel and chromium.

[0023] (3) Support The material constituting the support 13 of this embodiment is not particularly limited, but is preferably one or more metals selected from the group consisting of copper, stainless steel, and titanium. The shape of the support 13 of this embodiment may be any desired shape corresponding to the shape of the sintered body 11, and examples thereof include at least one of a flat plate shape and a cylindrical shape, as well as other shapes suitable for the application.

[0024] <Method for Manufacturing Target> The method for manufacturing the target 1 of this embodiment includes a sintered body manufacturing step for manufacturing a gallium nitride sintered body 11 containing a dopant. The content of the dopant in the sintered body 11 is 1×10 ２１ atoms / cm ３ The method for manufacturing the target 1 according to the present embodiment may further include a bonding step of bonding the support 13 to the gallium nitride sintered body 11 via the bonding layer 12.

[0025] (Sintered body manufacturing process) The sintered body manufacturing process of this embodiment includes a molding process of molding a raw material powder containing gallium nitride and a dopant to obtain a molded body, and a sintering process of sintering the molded body to obtain the sintered body 11.

[0026] The raw material powder includes powdered gallium nitride and a dopant. The dopant is an element that imparts characteristics, such as semiconductor properties, depending on the application, and may be an n-type dopant or a p-type dopant. Examples of n-type dopants include silicon, germanium, tin, and lead. From the perspective of substituting gallium atoms in the GaN film, the n-type dopant preferably includes at least one of silicon and germanium, which have an atomic radius similar to that of gallium. The n-type dopant may be one or more selected from the group consisting of silicon, germanium, tin, and lead, or at least one of silicon and germanium. It may also be silicon or germanium. Examples of p-type dopants include magnesium, calcium, strontium, barium, and zinc. Examples of p-type dopants include one or more selected from the group consisting of magnesium, calcium, strontium, barium, and zinc, or at least one of magnesium and zinc. The sintered body 11 may contain a single dopant or two or more dopants.

[0027] The raw material powder preferably has a Ga / (Ga+N) ratio (atomic ratio) greater than 0.5 and contains gallium nitride and metallic gallium. The Ga / (Ga+N) ratio of the raw material powder is more preferably 0.51 or greater. Having such a composition of the raw material powder makes it easier to mold without a heated atmosphere. Furthermore, having such a composition of the raw material powder makes it easier to mold without a heated atmosphere, even if it contains a large amount of dopant. One reason for this is thought to be that the presence of metallic gallium between gallium nitride particles increases the bonding strength between the particles, resulting in increased shape stability of the molded body. The Ga / (Ga+N) ratio may be 0.6 or less or 0.55 or less. The Ga / (Ga+N) ratio may be greater than 0.5 and 0.6 or less, or 0.51 or more and 0.55 or less. The dopant content in the resulting sintered body 11 is preferably 1×10 ２１ atoms / cm ３ Make sure it is above that.

[0028] Since the strength of the obtained sintered body 11 tends to be high, the raw material powder has a loose bulk density of 1.0 g / cm ３ or more or 1.4 g / cm ３ Since moldability is easily improved, the loose bulk density is preferably 3.0 g / cm or more. ３ Less than or 2.5 g / cm ３ The loose bulk density is 1.0 g / cm ３ 3.0g / cm or more ３ or less than 1.4 g / cm ３ 2.5g / cm or more ３ The following points can be mentioned.

[0029] The loose bulk density of the raw material powder in this embodiment is a value measured by a method in accordance with JIS Z 2504.

[0030] The average particle size of the raw material powder is preferably 1 μm or more, 5 μm or more, or 9 μm or more, and is preferably 150 μm or less, 100 μm or less, or 80 μm or less. Examples of the average particle size of the raw material powder include 1 μm or more and 150 μm or less, 5 μm or more and 100 μm or less, or 9 μm or more and 80 μm or less.

[0031] The average particle diameter of the raw material powder in this embodiment is the average value of the circle-equivalent diameters determined from the areas of 1200±400 primary particles in a scanning electron microscope (hereinafter also referred to as "SEM") observation image obtained under the following conditions: Acceleration voltage: 10 kV Observation magnification: 50 to 5000 times

[0032] SEM observation in measuring the average particle size may be performed using a general SEM (for example, VE-9800, manufactured by KEYENCE Corp.). Alternatively, only primary particles whose entire particles can be confirmed in the SEM observation image may be measured, and multiple SEM observation images may be used so that the number of primary particles is the above-mentioned number (1200±400).

[0033] In the compacting step, the raw material powder is compacted to obtain a compact. The compacting method may be any method that can obtain a compact having a desired shape, and examples thereof include at least one of uniaxial press molding and cold isostatic pressing (hereinafter also referred to as "CIP") molding. A compact (green compact) is obtained by these compacting methods. In the compacting step, the raw material powder is preferably compacted without heating, and the raw material powder is preferably compacted at room temperature (25±10°C).

[0034] A particularly preferred molding method involves uniaxially pressing a raw material powder to obtain a primary compact, followed by CIP molding of the primary compact. The uniaxial press molding conditions may be any conditions that result in a primary compact having sufficient shape retention to prevent defects when subjected to CIP molding. For example, the pressure of the uniaxial press molding may be 10 MPa or more or 25 MPa or more, and 200 MPa or less or 300 MPa or less, such as 10 MPa to 200 MPa or 25 MPa to 300 MPa. The CIP molding conditions may be any conditions that result in a molded body as described below, such as 100 MPa or more or 200 MPa or more, and 400 MPa or less or 500 MPa or less, such as 100 MPa to 500 MPa or 200 MPa to 400 MPa.

[0035] In the sintering step of this embodiment, the compact is sintered to obtain the sintered body 11 .

[0036] The shape of the molded body may be any desired shape, such as one or more selected from the group consisting of disk, column, rectangle, polyhedron and cone, or any other shape depending on the purpose and use.

[0037] The measured density of the molded body is 3.0 g / cm ３ or more than 3.6 g / cm ３ or more, and 5.8 g / cm ３ or less than 5.5 g / cm ３ The following points can be mentioned.

[0038] The measured density of the molded body in this embodiment is a value measured by a method in accordance with JIS Z 8807.

[0039] In the sintering process, the sintering atmosphere is not particularly limited, but a nitride atmosphere is preferable. In this embodiment, a pre-shaped compact is sintered without pressure, so a sintering apparatus equipped with a mold is not required for sintering. That is, the shape of the compact does not depend on the mold equipped in the HP (Hot Press) apparatus. This increases the degree of freedom in the shape of the compact. Furthermore, carbon molds are mainly used in industrial HP processes. In contrast, the manufacturing method of this embodiment does not perform HP processing using a carbon mold, thereby preventing the incorporation of impurities, particularly carbon (C), from the carbon mold. As a result, when a GaN film is formed by sputtering a target including the sintered compact 11 of this embodiment, a GaN film with a lower carbon content is obtained. From the perspective of avoiding impurity incorporation, particularly carbon incorporation, the manufacturing method of this embodiment preferably does not include HP processing, particularly HP processing using a carbon mold.

[0040] The nitriding atmosphere in this embodiment is an atmosphere in which the nitriding reaction proceeds, particularly an atmosphere in which the nitriding reaction proceeds but the oxidation reaction does not proceed. Therefore, the nitriding atmosphere includes not only a nitrogen atmosphere but also an atmosphere containing elements other than nitrogen. An example of the nitriding atmosphere is an atmosphere containing at least one of nitrogen and a nitrogen compound. The gas constituting the nitriding atmosphere is preferably at least one selected from the group consisting of nitrogen gas, a nitrogen and hydrogen mixed gas, ammonia gas, hydrazine gas, and an alkylamine gas, further preferably at least one of ammonia gas and a nitrogen and hydrogen mixed gas, or further preferably ammonia gas.

[0041] Particularly preferred nitriding atmospheres include a flow atmosphere, a nitrogen compound flow atmosphere, and even an ammonia flow atmosphere. When the nitriding atmosphere is a flow atmosphere, i.e., an atmosphere in which an atmospheric medium such as a nitrogen compound-containing gas flows, the nitriding reaction of the metallic gallium is promoted when the raw material powder contains metallic gallium powder. This results in a more uniform composition of the resulting sintered body 11. The flow atmosphere may be one in which the atmospheric medium flows, and examples of such an atmosphere include a flow rate of 0.1 mL / min or more or 1 L / min or more. Meanwhile, the flow rate may be appropriately set depending on the molded body to be treated and the performance of the sintering furnace, and examples thereof include a flow rate of 20 L / min or less or 10 mL / min or less.

[0042] In the sintering step, it is preferable to sinter the compact (object to be sintered) without applying pressure, and it is more preferable to sinter the compact without applying molding pressure.

[0043] The holding temperature in the sintering process may be any temperature at which sintering of gallium nitride progresses. Furthermore, unlike HP processing, the molded body subjected to the sintering process already has a fixed shape at the start of the sintering process. Therefore, compared to sintering methods in which molding and sintering proceed simultaneously, such as HP processing, a high-density sintered body 11 can be obtained even at a lower holding temperature. Therefore, examples of holding temperatures include 1100°C or less, 1050°C or less, or 1000°C or less. On the other hand, examples of holding temperatures include 800°C or more, 900°C or more, or 950°C or more. Examples of holding temperatures include 800°C or more to 1100°C or less, 900°C or more to 1050°C or less, or 950°C or more to 1000°C or less.

[0044] The holding time at the holding temperature varies depending on the holding temperature, the size of the molded body, the performance of the sintering furnace used, etc., but at the above holding temperature, the holding time can be, for example, 1 hour or more and 20 hours or less, or even 2 hours or more and 10 hours or less.

[0045] In the manufacturing method of this embodiment, the upper and lower limits of parameters such as the Ga / (Ga+N) ratio, the surface area of ​​the molded body, the measured density of the molded body, the flow rate of the atmospheric medium, the holding temperature and the holding time may be any combination as described above.

[0046] <Gallium Nitride Film> One embodiment of the gallium nitride film (GaN film) of the present disclosure will be described.

[0047] The GaN film is a gallium nitride film obtained by sputtering the above-mentioned target 1. The GaN film is formed by sputtering a dopant at a concentration of 5×10 ２０ atoms / cm ３ The GaN film may be a gallium nitride film containing the above. This GaN film has high conductivity even without heat treatment at high temperatures. Therefore, it is not necessary to perform high-temperature heat treatment on the GaN film to increase its conductivity.

[0048] (Dopant) The GaN film contains a dopant. The dopant content is 5×10 ２０ atoms / cm ３ or more. The GaN film contains a large amount of dopant, which can further improve the conductivity of the GaN film. The dopant may be an n-type dopant or a p-type dopant. Examples of n-type dopants include silicon, germanium, tin, and lead. The n-type dopant preferably contains at least one of silicon and germanium, which have an atomic radius similar to that of gallium. The n-type dopant may be one or more selected from the group consisting of silicon, germanium, tin, and lead, and may further include at least one of silicon and germanium. Alternatively, it may be silicon or germanium. Examples of p-type dopants include magnesium, calcium, strontium, barium, and zinc. Examples of p-type dopants include one or more selected from the group consisting of magnesium, calcium, strontium, barium, and zinc, and further include at least one of magnesium and zinc. The GaN film may contain a single dopant, or may contain two or more dopants.

[0049] The dopant content in the GaN film is 5×10 ２０ atoms / cm ３ There are no particular limitations on the thickness as long as it is equal to or greater than this, but from the viewpoint of further increasing the conductivity of the GaN film, it is preferably 8×10 ２０ atoms / cm ３ or more, more preferably 1×10２１ atoms / cm ３ More preferably, 3×10 ２１ atoms / cm ３ The dopant content in the GaN film is 1×10 ２３ atoms / cm ３ Below, 5 x 10 ２２ atoms / cm ３ or less, or 2 x 10 ２２ atoms / cm ３ The upper and lower limits of the dopant content in the GaN film may be any combination of the above, but may be 5×10 ２０ atoms / cm ３ 1x10 or more ２３ atoms / cm ３ Below, 8 x 10 ２０ atoms / cm ３ 5x10 or more ２２ atoms / cm ３ or less, or 1 x 10 ２１ atoms / cm ３ 2x10 or more ２２ atoms / cm ３ It is preferable that:

[0050] The dopant content in the GaN film refers to the smallest dopant content among the dopant contents measured continuously along the depth direction for the entire thickness of the GaN film from the front surface to the back surface using secondary ion mass spectrometry (SIMS). The more measurement points there are for SIMS measurement, the more preferable. It is preferable to measure at 5 or more or 10 or more points for the entire thickness, and more preferably at 20 or more, 30 or more, or 50 or more points per 100 nm of thickness. The unit of dopant content is "atoms / cm". 3 " is 1 cm 3 is the number of dopant atoms contained in the GaN film per 1000 .mu.m.

[0051] (Hydrogen) The GaN film of this embodiment may or may not contain hydrogen (H). "Containing hydrogen" means that the GaN film contains 5×10 １８ atoms / cm ３This means that hydrogen of 5×10 or more is detected by SIMS as described below, and "not containing hydrogen" means that hydrogen of 5×10 or more is detected by SIMS as described below. １８ atoms / cm ３ This means that less than 1000 ppm of hydrogen is detected.

[0052] The hydrogen content in the GaN film of this embodiment is not particularly limited, but from the viewpoint of further increasing the conductivity of the GaN film, it is preferable that the hydrogen content be 4×10 １８ atoms / cm ３ Below, 3 x 10 １８ atoms / cm ３ or less, or 2 x 10 １８ atoms / cm ３ In this embodiment, the hydrogen content in the GaN film is preferably 1×10 １６ atoms / cm ３ That's it, 5 x 10 １６ atoms / cm ３ or more, or 1 x 10 １７ atoms / cm ３ The upper and lower limits of the hydrogen content in the GaN film of this embodiment may be any combination of the above, but are not limited to 1×10 １６ atoms / cm ３ 4 x 10 or more １８ atoms / cm ３ Below, 5 x 10 １６ atoms / cm ３ 3x10 or more １８ atoms / cm ３ or less, or 1 x 10 １７ atoms / cm ３ 2x10 or more １８ atoms / cm ３ The hydrogen content in the GaN film of this embodiment is preferably 5×10 １８ atoms / cm ３ That's it, 1 x 10 １９ atoms / cm ３ That's it, 5 x 10 １９ atoms / cm ３ or more, or 1 x 10 ２０ atoms / cm ３ That is all, and 5 × 10 ２１ atoms / cm ３Below, 1 x 10 ２１ atoms / cm ３ or less, or 5 x 10 ２０ atoms / cm ３ The hydrogen content in the GaN film of this embodiment is 5×10 １８ atoms / cm ３ 5x10 or more ２１ atoms / cm ３ Below, 1 x 10 １９ atoms / cm ３ 1x10 or more ２１ atoms / cm ３ or less, or 5 x 10 １９ atoms / cm ３ 5x10 or more ２０ atoms / cm ３ It may be the following:

[0053] The hydrogen content in the GaN film of this embodiment refers to the smallest hydrogen content among the hydrogen contents measured continuously along the depth direction for the entire thickness of the GaN film from the front surface to the back surface using SIMS secondary ion mass spectrometry. The more measurement points there are in the SIMS measurement, the more preferable. The number of measurement points is preferably 5 or more or 10 or more for the entire thickness, and more preferably 20 or more, 30 or more, or 50 or more per 100 nm of thickness. The unit of hydrogen content is "atoms / cm 3 " is 1 cm 3 is the number of hydrogen atoms contained in the GaN film per unit area.

[0054] (Thickness) The thickness of the GaN film is not particularly limited, and may be 10 μm or less, 5 μm or less, or 1 μm or less. The thickness of the GaN film is preferably 1 nm or more, 5 nm or more, 10 nm or more, 50 nm or more, or 100 nm or more. The upper and lower limits of the thickness may be any combination of the above, but are preferably 1 nm or more and 10 μm or less, or 5 nm or more and 5 μm or less. (Resistivity) The resistivity of the GaN film is preferably 1 Ωcm or less, 8×10 －１ Ωcm or less, 5×10 －１ Ωcm or less, 3×10 －１ Ωcm or less, or 1 x 10 －１Ωcm or less, and 5×10 －４ Ωcm or more, 8 x 10 －４ Ωcm or more, 1×10 －３ Ωcm or more, or 3 x 10 －３ The resistivity of the GaN film is, for example, 5×10 －４ Ωcm or more and 1Ωcm or less, 8×10 －４ Ωcm or more 8 x 10 －１ Ωcm or less, 1×10 －３ Ωcm or more 5 x 10 －１ Ωcm or less, or 1 x 10 －３ Ωcm or more 3 x 10 －１ Ωcm or less, or 3 x 10 －３ Ωcm or more 1×10 －１ In this embodiment, the resistivity of the GaN film may be measured using a general Hall effect measuring device (for example, 8403 AC / DC Hall effect measuring device, manufactured by Toyo Corporation).

[0055] <GaN film manufacturing method> The GaN film manufacturing method of the present disclosure includes a film formation step of manufacturing a GaN film on a substrate by sputtering a target 1 including a GaN sintered body 11. The GaN film manufacturing method of the present disclosure may further include a preparation step before the film formation step. Note that, because a layered substrate is obtained by the GaN film manufacturing method of the present disclosure, the GaN film manufacturing method of the present disclosure can also be referred to as a layered substrate manufacturing method. According to the GaN film manufacturing method of the present disclosure, a GaN film having high conductivity can be manufactured without heat treatment at high temperatures. Furthermore, a GaN film having high conductivity can be manufactured even when the substrate temperature is low in the film formation step.

[0056] (1) Preparation Step In the preparation step, it is preferable to evacuate the inside of the film forming apparatus. 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 －５ It is more preferable to set the vacuum level to 3×10 Pa or less. －５By setting the pressure to 0 Pa or less, residual gases are less likely to be mixed in as impurities during film formation, improving the crystallinity of the GaN film. In the film formation apparatus, it is preferable to perform a baking process on the film formation apparatus before evacuating the apparatus in order to remove residual gases. The degree of vacuum should be greater than 0 Pa and less than 1×10 －８ Pa or more, or 1 x 10 －７ For example, the vacuum level is 1×10 Pa or more. －８ Pa or more 3×10 －５ Pa or less, or 1 x 10 －７ Pa or more 1×10 －５ Pa or less.

[0057] In addition, in the preparation process, it is preferable to pretreat the substrate. Pretreatment removes organic layers and irregularities on the substrate surface, facilitating epitaxial growth. Examples of 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 utilizing this mechanism, the substrate surface is cleaned and then sent to the film formation chamber without exposure to the outside air, allowing film formation while maintaining the cleanliness of the substrate surface. When performing reverse sputtering, it is preferable to perform the treatment in a chamber separate from the film formation chamber to prevent reverse sputtered impurities from adhering to the film formation chamber. Argon, nitrogen, oxygen, etc. can be used as the gas species (sputtering gas) used in reverse sputtering. However, it is preferable for the sputtering gas to contain a certain amount of oxygen in order to remove carbon-based impurities from the surface. The oxygen content is preferably 1% or more and 10% or less, with the pressure of the total composition gas being 100%. This makes it possible to efficiently remove carbonaceous impurities from the surface. Furthermore, the treatment time of the reverse sputtering treatment is preferably 30 seconds or more and 900 seconds or less, or 60 seconds or more and 300 seconds or less. This makes it possible to obtain a desirable surface roughness (Ra) while removing surface impurities. The reverse sputtering treatment is performed, for example, at 100 W, with sputtering gas Ar: 29 sccm (1 atm, 25°C), and O２ : 1 sccm (1 atm 25° C.) for 60 seconds.

[0058] In the preparation step, it is preferable to hold the substrate at the temperature planned for film formation for a certain period of time. This makes the temperature of the substrate uniform before film formation, improving the crystallinity of the GaN film that is the film formed. 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. Examples of the holding time include 1 minute or more and 1 hour or less, or 5 minutes or more and 30 minutes or less.

[0059] (2) Film Formation Step (GaN Sputtering Target) The above-described GaN sputtering target 1 can be used as the GaN sputtering target. The area of ​​the sputtering surface (surface on which sputtering is performed) of the target 1 is not particularly limited, but it is preferable that the area be 15 cm ２ Above, 18cm ２ Above, 20cm ２ Above, 50cm ２ or more, or 100 cm ２ The above is preferable. The larger the area of ​​the sputtering surface, the more stable the discharge becomes, making it possible to perform sputtering at a lower gas pressure and lower discharge density. Furthermore, the uniformity of the film thickness and quality of the GaN film is improved. The area of ​​the sputtering surface is 10,000 cm ２ Below, 5000cm ２ or less than 1000 cm ２ The area of ​​the sputtering surface is 15 cm ２ More than 10000cm ２ Below, 18cm ２ More than 5000cm ２ Below, 20cm ２ More than 5000cm ２ Less than or equal to 50 cm ２ More than 1000cm ２ The following can be exemplified.

[0060] (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 and high-speed film formation over a large area.

[0061] The gas pressure (film formation pressure) during sputtering is not particularly limited, but may be, for example, 1.0 Pa or less, and preferably 0.6 Pa or less, 0.4 Pa or less, 0.3 Pa or less, or 0.2 Pa or less. The lower the gas pressure during sputtering, the more easily particles emitted from the target 1 reach the substrate while maintaining high energy, and the more easily they are epitaxially rearranged. The gas pressure during sputtering may be, for example, 0 Pa or more or 0.1 Pa or more. The lower the gas pressure during sputtering, the more easily particles emitted from the target 1 (sputtered particles) reach the substrate while maintaining high energy, and the more easily they are epitaxially rearranged on the substrate. The gas pressure during sputtering may be, for example, 0 Pa or more to 1.0 Pa or less, 0 Pa or more to 0.6 Pa or less, 0.1 Pa or more to 0.4 Pa or less, 0.1 Pa or more to 0.3 Pa or less, or 0.1 Pa or more to 0.2 Pa or less.

[0062] (Substrate) The substrate may be the same as the substrate 10 described later. Film formation is preferably performed while the substrate is heated. By forming the film while the substrate is heated, energy is imparted to the sputtered particles, making it possible to obtain a more stable crystalline state for the resulting GaN film, and cracking due to differences in thermal expansion coefficients during high-temperature heat treatment can be prevented. The substrate temperature during film formation is preferably 1000°C or less, 900°C or less, 800°C or less, 600°C or less, or 550°C or less. The substrate temperature may be room temperature or higher, 50°C or higher, 100°C or higher, or 400°C or higher. When the substrate temperature is 50°C or higher, the GaN film tends to have high crystallinity and fewer defects, making it easier to increase the conductivity of the GaN film even with a small amount of hydrogen. Furthermore, when the substrate temperature is 400°C or higher, the GaN particles, which are particularly sputtered particles, can be aligned with good crystallinity in the GaN film. The substrate temperature is preferably from room temperature to 600°C, from 50°C to 1000°C, from 50°C to 900°C, from 100°C to 800°C, from 100°C to 600°C, or from 400°C to 550°C.

[0063] (Atmosphere) The atmosphere may or may not contain hydrogen. However, from the viewpoint of enhancing safety, it is preferable that the atmosphere be composed of a gas that does not contain hydrogen. The atmosphere may further contain an inert gas. Since the inert gas is less reactive with the GaN film, impurities are less likely to be generated in the GaN film. Examples of the inert gas include argon and nitrogen. Examples of the inert gas include at least one of argon and nitrogen. These may be used alone or in combination. It is preferable that the inert gas contains nitrogen. In this case, a GaN film with fewer nitrogen defects can be produced. The inert gas is preferably composed of argon and nitrogen. When the inert gas is composed of argon and nitrogen, the nitrogen / (nitrogen + argon) partial pressure ratio (hereinafter also referred to as the "nitrogen partial pressure ratio") [Pa / Pa] is preferably 0.85 or less, 0.80 or less, or 0.75 or less. By setting the nitrogen partial pressure ratio within the above range, the crystallinity of the obtained GaN film is likely to be high and the number of defects is reduced, which makes it easier to lower the resistivity of the GaN film. The lower limit of the nitrogen partial pressure ratio can be 0.50 or more, 0.60 or more, or 0.70 or more. The nitrogen partial pressure ratio can be, for example, 0.50 to 0.85, 0.60 to 0.80, or 0.70 to 0.75. When only nitrogen gas is used, the nitrogen partial pressure ratio is 1.0. The flow rate of the sputtering gas can be, for example, 1 sccm or more or 5 sccm or more, and 80 sccm or less or 50 sccm or less, for example, 1 sccm to 80 sccm or 5 sccm to 50 sccm. When the sputtering gas is composed of argon gas and nitrogen gas, the flow rate of the argon gas is, for example, 1 sccm or more or 5 sccm or more, and 30 sccm or less or 20 sccm or less, such as 1 sccm or more and 30 sccm or less, or 5 sccm or more and 20 sccm or less, and the flow rate of the nitrogen gas is, for example, 1 sccm or more or 5 sccm or more, and 50 sccm or less or 40 sccm or less, such as 1 sccm or more and 50 sccm or more and 40 sccm or less, such as 1 sccm or more and 5 sccm or more and 40 sccm or less.

[0064] The discharge density during discharge was 0.1 W / cm ２ Above, 0.3W / cm ２ Above, 0.5W / cm ２ or more, or 1.0 W / cm ２ or more, and 5 W / cm ２ Below, 4W / cm ２ Below, 2.5W / cm ２ or less, or 1.5 W / cm ２ The discharge density during discharge is 0.1 W / cm ２ More than 5W / cm ２ Below, 0.3W / cm ２ More than 4W / cm ２ Below, 0.3W / cm ２ 2.5W / cm or more ２ Below, 0.5W / cm ２ 2.5W / cm or more ２ Below, 0.3W / cm ２ 1.5W / cm or more ２ or less, or 1.0 W / cm ２ 2.5W / cm or more ２ The discharge density is the power applied during discharge divided by the area of ​​the target surface of the sputtering target. ２ If the discharge density is less than 0.05 W / cm, coarse single crystal particles are less likely to peel off from the sputtering target due to the power applied to the target. ２ In this case, the plasma is stabilized, which facilitates discharge, and the film deposition rate is increased, improving film productivity. Furthermore, the energy during sputtering is high, which improves the adhesion of the GaN film to the substrate during film deposition.

[0065] The deposition time may be adjusted appropriately depending on the thickness of the GaN film, and the longer the deposition time, the thicker the GaN film can be.

[0066] <Layered Base Material> Next, one embodiment of the layered base material of the present disclosure will be described with reference to FIG. 2 . As shown in FIG. 2 , the layered base material 100 includes a substrate 10 and a GaN film 20. The GaN film 20 is composed of the GaN film described above. With the layered base material 100, it is not necessary to perform high-temperature heat treatment on the GaN film 20 to increase its conductivity, and therefore it is not necessary to perform high-temperature heat treatment on the layered base material 100 including the GaN film 20. In other words, it is not necessary to perform high-temperature heat treatment on not only the GaN film 20 but also the substrate 10. Therefore, with the layered base material 100, it is possible to reduce the likelihood of warping of the substrate 10 and distortion throughout the layered base material 100.

[0067] (Substrate) The substrate 10 is not particularly limited, and 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, and a polyethylene terephthalate substrate. 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. The surface roughness Ra represents the calculated average roughness.

[0068] <Semiconductor Element> The semiconductor element of the present disclosure includes a GaN film. The semiconductor element of the present disclosure may further include electrodes, a substrate, and other components. When the semiconductor element includes a GaN film and a substrate, the semiconductor element includes a laminated base material. The substrate may be the same as substrate 10. According to the semiconductor element of the present disclosure, high-temperature heat treatment for increasing the conductivity of the GaN film is not required, and therefore high-temperature heat treatment is not required for the semiconductor element including the GaN film. In other words, high-temperature heat treatment is not required not only for the GaN film but also for the electrodes, substrate, and other components. Therefore, the semiconductor element can be made less susceptible to melting of the electrodes, warping of the substrate, and distortion of the entire semiconductor element.

[0069] The present disclosure is particularly useful for semiconductor devices having electrodes containing a low-melting-point metal such as aluminum, because if the electrodes contain a low-melting-point metal, the semiconductor device may not be heat-treated at high temperatures to avoid melting the electrodes.

[0070] Examples of semiconductor elements include light-emitting elements such as blue light-emitting diodes (LEDs) and blue laser diodes (LDs), and power devices such as diodes and transistors.

[0071] <Electronic Device> Next, one embodiment of an electronic device according to the present disclosure will be described with reference to Fig. 3. The electronic device 300 shown in Fig. 3 includes a semiconductor element 200, which includes a layered base material 100. According to the electronic device 300, the semiconductor element 200 can reduce the occurrence of electrode melting, substrate warpage, and distortion throughout the semiconductor element, thereby suppressing a decrease in performance of the electronic device 300. Examples of the electronic device 300 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.

[0072] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples.

[0073] Example 1 First, 50 g of a mixed powder (first mixed powder) of metallic gallium and gallium nitride was prepared. The Ga / (Ga+N) ratio (atomic ratio) of the first mixed powder was set to 0.49. The dopant content in the resulting sintered body was set to 1.5×10 ２１ atoms / cm ３ 0.58 g of silicon powder was prepared so that the first mixed powder and silicon powder were mixed to obtain a second mixed powder. Next, the second mixed powder was filled into a mold having a rectangular opening of 10 mm length x 40 mm width. After filling, the mold was uniaxially press-molded at room temperature at a pressure of 100 MPa to obtain a primary compact. The primary compact was cold isostatically pressed at a pressure of 300 MPa to obtain a CIP-treated body.

[0074] The CIP-treated body was placed on an alumina setter and sintered in an atmosphere furnace under the following conditions to obtain a target made of a sintered GaN body: Heat treatment atmosphere: Ammonia flow atmosphere (ammonia gas flow rate: 6000 mL / min) Holding temperature: 980°C Holding time: 5 hours

[0075] Example 2 First, 50 g of a mixed powder (first mixed powder) of metallic gallium and gallium nitride was prepared. The Ga / (Ga+N) ratio (atomic ratio) of the first mixed powder was set to 0.49. The dopant content in the resulting sintered body was set to 5.0×10 ２１ atoms / cm ３ 2.0 g of silicon powder was prepared so that the first mixed powder and silicon powder were mixed to obtain a second mixed powder. Next, the second mixed powder was filled into a mold having a rectangular opening of 10 mm length x 40 mm width. After filling, the mold was uniaxially press-molded at room temperature at a pressure of 100 MPa to obtain a primary compact. The primary compact was cold isostatically pressed at a pressure of 300 MPa to obtain a CIP-treated body.

[0076] The CIP-treated body was placed on an alumina setter and sintered in an atmosphere furnace under the following conditions to obtain a target consisting of a sintered GaN body. Heat treatment atmosphere: Ammonia flow atmosphere (ammonia gas flow rate: 6000 mL / min) Holding temperature: 980°C Holding time: 5 hours (Example 3) First, 50 g of a mixed powder (first mixed powder) of metallic gallium and gallium nitride was prepared. The Ga / (Ga+N) ratio (atomic number ratio) of the first mixed powder was set to 0.49. In addition, the dopant content in the obtained sintered body was 2.0 × 10 ２１2.0 g of germanium powder was prepared so that the above-mentioned first mixed powder and germanium powder were mixed to obtain a second mixed powder. Next, the above-mentioned second mixed powder was filled into a cylindrical mold having a diameter of 54 mm. After filling, the mold was subjected to uniaxial press molding at room temperature under a pressure of 100 MPa to obtain a primary compact. The primary compact was subjected to cold isostatic pressing at a pressure of 300 MPa to obtain a CIP-treated body. The CIP-treated body was placed on an alumina setter and sintered in an atmosphere furnace under the following conditions to obtain a target consisting of a sintered GaN body. Heat treatment atmosphere: ammonia flow atmosphere (ammonia gas flow rate 6000 mL / min) Holding temperature: 980°C Holding time: 5 hours

[0077] (Comparative Example 1) When obtaining the second mixed powder, 50 g of the first mixed powder and the dopant content in the obtained sintered body were 1.5 × 10 ２０ atoms / cm ３ A target made of a sintered body of GaN was obtained in the same manner as in Example 1, except that 0.057 g of silicon powder was mixed so as to obtain a sintered body of GaN.

[0078] <Characteristics> The thickness of the target, the hydrogen content in the GaN film, and the dopant (silicon) content were measured as follows.

[0079] (Thickness) The thickness of the target was measured using a micrometer. (Dopant Content of the Target) The dopant content was measured continuously along the depth direction from the surface of the target using SIMS. The smallest dopant content among the series of dopant contents measured over the entire thickness from the front surface to the back surface of the target was defined as the dopant content in the target. The number of measurement points was five for Examples 1 to 3 and five for Comparative Example 1. The results are shown in Table 1. (Bulk Density) The bulk density was measured in accordance with the bulk density measurement method specified in JIS R 1634. The mass of the sintered body was measured by weighing the mass of the sintered body after pretreatment using a vacuum method using distilled water, and the volume was calculated from the shape measured using a micrometer. (Flexural Strength) The three-point bending strength of the sintered body was measured using a method specified in JIS R 1601. The measurement was performed twice, and the average value was used as the flexural strength.

[0080] <Formation of GaN Film> (Example 4) A sapphire substrate (off-axis: 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 sapphire substrate's surface was set to the (0001) plane. The substrate and sputtering target were then placed in a magnetron sputtering apparatus. The sputtering target was prepared as follows. A sintered body was obtained in the same manner as in Example 1, except that 200 g of a mixed powder of metallic gallium and gallium nitride (first mixed powder) and 2.3 g of silicon powder were prepared, and a cylindrical mold with a diameter of 111 mm was used. This sintered body was then ground into a disk-shaped sintered body with a diameter of 101.6 mm and a thickness of 3.5 mm. A circular sputtering target with a backing plate was prepared using the obtained sintered body, indium solder as a bonding layer, and an oxygen-free copper backing plate as a support. The sputtering target-substrate distance was 150 mm, and the chamber was baked prior to film formation to achieve a higher ultimate vacuum. Next, at the start of sputtering, plasma was ignited using nitrogen gas with the substrate-side shutter closed. Pre-sputtering was performed for 10 minutes under the same conditions as film formation to stabilize the discharge. The shutter-substrate distance was 5 mm. A 3-inch diameter shutter was used. The substrate was then heated to 500°C, and while introducing nitrogen gas as the sputtering gas into the chamber, the target was sputtered under the film formation conditions listed in Table 2 to form a film on the substrate, forming a GaN film. (Example 5) A sintered body was obtained in the same manner as in Example 2, except that 200 g of a mixed powder of metallic gallium and gallium nitride (first mixed powder) and 8.0 g of silicon powder were prepared, and a cylindrical mold with a diameter of 111 mm was used. A GaN film of this example was obtained in the same manner as in Example 4, except that the obtained sintered body was used. Example 6 A sapphire substrate (off-angle: none, surface roughness Ra: 0.09 nm, diameter: 50.8 mm (2 inches)) manufactured by Kyocera Corporation was prepared as a film formation substrate. At this time, the surface of the sapphire substrate was set to be the (0001) plane.The substrate and sputtering target were then placed in a magnetron sputtering apparatus. The sputtering target was prepared as follows. A sintered body was obtained using the same method as in Example 3, and then ground to form a disk-shaped sintered body with a diameter of 50.8 mm and a thickness of 3.0 mm. A circular sputtering target with a backing plate was prepared using the obtained sintered body, indium solder as the bonding layer, and an oxygen-free copper backing plate as the support. The target-substrate distance was 185 mm, and the chamber was baked prior to film formation to achieve a higher ultimate vacuum. Next, the substrate was heated to a temperature of 800°C, and while Ar gas and nitrogen gas were introduced into the chamber as sputtering gases, the film formation conditions listed in Table 2 were adjusted. Then, plasma was ignited, and pre-sputtering was performed for 10 minutes with the shutter closed to stabilize the discharge. The shutter was then opened, and the sputtering target was sputtered under the film formation conditions listed in Table 2 to form a film on the substrate, forming a GaN film. (Example 7) The GaN film of this example was obtained in the same manner as in Example 6, except that the substrate was heated to a temperature of 500°C. (Example 8) The GaN film of this example was obtained in the same manner as in Example 6, except that the nitrogen partial pressure ratio was set to 1. (Comparative Example 2) A sintered body was obtained in the same manner as in Comparative Example 1, except that 200 g of a mixed powder of metallic gallium and gallium nitride (first mixed powder) and 0.2 g of silicon powder were prepared, and a cylindrical mold with a diameter of 111 mm was used. A GaN film of this example was obtained in the same manner as in Example 4, except that the obtained sintered body was used.

[0081] (Hydrogen Content in GaN Film) Using SIMS, the hydrogen content was measured continuously along the depth direction from the surface of the GaN film. The smallest hydrogen content among the series of hydrogen contents measured over the entire thickness from the surface to the back surface of the GaN film was taken as the hydrogen content in the GaN film. The number of measurement points was 5 for Example 4, 5 for Example 5, 5 for Example 6, 5 for Example 7, and 5 for Comparative Example 2. The results of the hydrogen content in the GaN film are shown in Table 3. Note that the hydrogen content in the GaN film was not measured for Example 8, and is therefore indicated as "-".

[0082] (Dopant Content in GaN Film) Using SIMS, the dopant content was measured continuously along the depth direction from the surface of the GaN film. The smallest dopant content among the series of dopant contents measured over the entire thickness from the surface to the back surface of the GaN film was taken as the dopant content in the GaN film. The number of measurement points was 5 for Example 4, 5 for Example 5, 5 for Example 6, 5 for Example 7, and 5 for Comparative Example 2. The results of the dopant content in the GaN film are shown in Table 3. Note that the dopant content in the GaN film of Example 8 was not measured, and is therefore indicated as "-".

[0083] <Conductivity of GaN Film> The conductivity of the GaN film was measured using resistivity. The resistivity of the GaN film was measured using an 8403 AC / DC Hall effect measurement device (manufactured by Toyo Corporation). The results are shown in Table 3.

[0084]

[0085] From the results shown in Table 3, the GaN films of Examples 4 to 8 had a resistivity of 4.1×10 －３ (Ωcm) ~2.5×10 －１ (Ωcm), whereas the GaN film of Comparative Example 2 had a resistivity of 6.8×10 ３ (Ωcm). Comparing Examples 6 and 8, it was confirmed that Example 6, which was obtained with a nitrogen partial pressure ratio of 0.75 as a film formation condition, had a lower resistivity. From the above, it was confirmed that the GaN sputtering target of the present disclosure can form a GaN film having high conductivity without heat treatment at high temperatures. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-032401, filed March 4, 2024, on which the priority claim of this application is based, are hereby incorporated by reference herein as the disclosure of the specification of the present disclosure.

[0086] REFERENCE SIGNS LIST 1 target, 11 sintered body, 12 bonding layer, 13 support, 10 substrate, 20 GaN film, 100 laminated base material, 200 semiconductor element, 300 electronic device

Claims

1. A gallium nitride sintered body containing a dopant, wherein the content of the dopant in the sintered body is 1×10 ２１ atoms / cm ３ This completes the gallium nitride sputtering target.

2. The gallium nitride sputtering target of claim 1, wherein the dopant is an n-type dopant.

3. The gallium nitride sputtering target of claim 2, wherein the n-type dopant comprises at least one of silicon and germanium.

4. The content of the dopant in the sintered body is 1×10 ２３ atoms / cm ３ 4. The gallium nitride sputtering target according to claim 1, wherein:

5. The gallium nitride sputtering target according to any one of claims 1 to 4, which does not contain hydrogen.

6. A gallium nitride film obtained by sputtering the gallium nitride sputtering target according to any one of claims 1 to 5.

7. Dopant 5x10 ２０ atoms / cm ３ The gallium nitride film according to claim 6, comprising the above.

8. The gallium nitride film of any one of claims 7, wherein the dopant is an n-type dopant.

9. The gallium nitride film according to claim 7 or 8, wherein the n-type dopant comprises at least one of silicon and germanium.

10. The gallium nitride film according to any one of claims 6 to 9, which does not contain hydrogen.

11. A method for producing a gallium nitride film, comprising a film formation step of producing a gallium nitride film by sputtering the gallium nitride sputtering target according to any one of claims 1 to 5.

12. A layered substrate comprising the gallium nitride film according to any one of claims 6 to 10 and a substrate.

13. A semiconductor device comprising the gallium nitride film according to any one of claims 6 to 10.

14. A semiconductor device comprising the laminated substrate according to claim 12.

15. An electronic device comprising the semiconductor element according to claim 13 or 14.

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