Gallium nitride sintered body

Abstract

The present invention provides a sintered gallium nitride body and at least one method for producing the same, which has high flexural strength despite containing 1.0 mass% or more of dopant elements, and which can directly form a p-type gallium nitride film. The sintered gallium nitride body is characterized by containing an alloy containing one or more dopant elements selected from the group of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), wherein the dopant element content is 1.0 mass% or more, and the oxygen content is 0.6 atm% or less.

Description

Technical Field

[0001] The present disclosure relates to a sintered body of gallium nitride from which a p-type gallium nitride film can be obtained.

Background Art

[0002] Gallium nitride (GaN) films are used as materials for LEDs and power semiconductors. A p-type gallium nitride film is required for fabricating semiconductor devices.

[0003] As a method for forming a p-type gallium nitride film, a method has been disclosed in which a gallium nitride film is formed by MOCVD and then a p-type dopant element is doped by pulse sputtering (for example, Patent Document 1). However, the method of Patent Document 1 is a multi-step film-forming method that requires, in addition to the gallium nitride film-forming step, a step of adding a dopant element to the gallium nitride film. On the other hand, in Patent Document 2, a sputtering target for a p-type gallium nitride thin film has been reported. By using such a target, a p-type gallium nitride film can be directly formed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the sputtering target for a p-type gallium nitride thin film of Patent Document 2 has a significant decrease in flexural strength as the content of the additive component increases, making it difficult to process the sputtering target. In addition, defects were likely to occur even during handling such as transfer.

[0006] In the present disclosure, an object is to provide at least one of a sintered body of gallium nitride and a method for producing the same, which has a high flexural strength and can directly form a p-type gallium nitride film despite containing a dopant element amount of 1.0 mass% or more.

Means for Solving the Problems

[0007] In the present disclosure, a sputtering target capable of directly forming a p-type gallium nitride film was studied by focusing on the state of the dopant element and the sinterability of the sintered body. As a result, it was found that by using a specific raw material as the dopant source, a sintered body of gallium nitride containing a dopant element capable of directly forming a p-type gallium nitride film with higher flexural strength than a conventional sputtering target capable of directly forming a p-type gallium nitride film can be obtained.

[0008] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows.

[0009] [1] A sintered body of gallium nitride, comprising an alloy containing one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), the content of the dopant element being 1.0 mass% or more, and the oxygen content being 0.6 atm% or less.

[0010] [2] The sintered body according to [1] above, wherein the alloy is an alloy of the dopant element and aluminum.

[0011] [3] The sintered body according to [1] or [2] above, wherein the total content of silicon, germanium, tin, and lead is 10 mass ppm or less.

[0012] [4] The sintered body according to any one of [1] to [3] above, having an actual measured density of 3.50 g / cm 3 or more.

[0013] [5] A sintered body according to any one of [1] to [4] above, wherein the bending strength is 55 MPa or more.

[0014] [6] A method for producing a sintered body according to any one of [1] to [5] above, comprising a gallium nitride source and a dopant source consisting of an alloy containing one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), wherein the dopant source content in terms of dopant elements is 1.0% by mass or more, and a firing step of hot pressing the raw material powder at a holding temperature of 400°C or higher and a holding pressure of 30 MPa or higher.

[0015] [7] The manufacturing method according to [6] above, wherein the oxygen content of the gallium nitride source is less than 0.4 atm%.

[0016] [8] A sputtering target comprising a sintered body as described in any one of [1] to [5] above.

[0017] [9] A method for manufacturing a sputtered film using the sputtering target described in [8] above. [Effects of the Invention]

[0018] This disclosure provides at least one of a gallium nitride sintered body, a sputtering target, and a method for manufacturing the same, which, despite containing 1.0 mass% or more of a dopant element, has high flexural strength and can directly form a p-type gallium nitride film. [Brief explanation of the drawing]

[0019] [Figure 1] SEM observation image of the sintered body of Example 1 (scale in the figure is 50 μm) [Figure 2] Elemental mapping of gallium (Ga) in the sintered body of Example 1 (scale in the figure is 50 μm) [Figure 3]Elemental mapping of magnesium (Mg) in the sintered body of Example 1 (scale in the figure is 50 μm) [Figure 4] Elemental mapping of aluminum (Al) in the sintered body of Example 1 (scale in the figure is 50 μm) [Figure 5] Secondary ion mass spectrometry (SIMS) results for the sputtered film obtained in Example 5 [Modes for carrying out the invention]

[0020] This disclosure will be described in detail with reference to one embodiment. However, this disclosure is not limited to the following embodiment. Furthermore, this disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein.

[0021] [Sintered body] The sintered body of this embodiment is a gallium nitride sintered body characterized by containing an alloy containing one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), wherein the dopant element content is 1.0% by mass or more. The sintered body of this embodiment has mechanical strength that makes it less susceptible to defects during handling such as transfer, and can be used as a sputtering target for directly depositing a p-type gallium nitride film (hereinafter also referred to as "p-type GaN film").

[0022] The sintered body of this embodiment relates to a sintered body of gallium nitride (GaN). The sintered body of gallium nitride in this embodiment is a sintered body mainly composed of gallium nitride, a so-called gallium nitride sintered body. The sintered body of this embodiment contains an alloy containing gallium nitride and one or more dopant elements selected from the group consisting of beryllium, magnesium, calcium, strontium, vanadium, zinc, and cadmium (hereinafter also referred to as "p-type dopant elements"). Furthermore, in addition to the alloy of gallium nitride and p-type dopant elements, metallic gallium may also be included.

[0023] The dopant element is one or more selected from the group consisting of beryllium, magnesium, calcium, strontium, vanadium, zinc, and cadmium. For ease of industrial application, the dopant element is more preferably at least one of magnesium and zinc, and even more preferably magnesium.

[0024] The dopant element content is 1.0% by mass or more, preferably 4.0% by mass or more, 4.5% by mass or more, or 6.0% by mass or more. Since the sintered body of this embodiment has a dopant alloy, a stable sintered body can be obtained even with such an amount of dopant element content. The more dopant element content there is, the easier it is to obtain a film exhibiting p-type properties, but the upper limit of the dopant element content in the sintered body of this embodiment is 20.0% by mass or less, 16.0% by mass or less, or 12.0% by mass or less. The dopant element content in the sintered body of this embodiment is 1.0% by mass or more and 20.0% by mass or less, 4.0% by mass or more and 20.0% by mass or less, 4.5% by mass or more and 16.0% by mass or less, or 6.0% by mass or more and 12.0% by mass or less.

[0025] The sintered body of this embodiment contains an alloy containing a p-type dopant element (hereinafter also referred to as "dopant alloy"). Including the p-type dopant element as an alloy improves the stability of the dopant element, and substantially suppresses the volatilization of the dopant element during the manufacture of the sintered body. As a result, a sintered body of this embodiment with a high dopant element content can be obtained. The dopant alloy may be any alloy consisting of a p-type dopant element and a metallic element that forms an alloy with the p-type dopant. Examples of metallic elements that form an alloy with the p-type dopant element include metallic elements of Group III, and it is preferable that at least one is selected from the group consisting of aluminum, indium, and thallium, and more preferably at least one of aluminum and indium, and even more preferably aluminum.

[0026] As the dopant alloy included in the sintered body of this embodiment, for example, an aluminum alloy of a p-type dopant element is preferred, and one or more aluminum alloys selected from the group consisting of zinc and magnesium are preferred, and a magnesium-aluminum alloy is even more preferred.

[0027] The dopant alloy content should be such that the dopant element content of the sintered body of this embodiment is the amount described above. For example, it is preferably 7.5% by mass or more, 8.0% by mass or more, or 10.0% by mass or more, and also preferably 35.0% by mass or less, 30.0% by mass or less, or 25.0% by mass or less. The dopant element content of the sintered body of this embodiment can be 7.5% by mass or more and 35.0% by mass or less, 8.0% by mass or more and 30.0% by mass or less, or 10.0% by mass or more and 25.0% by mass or less.

[0028] The sintered body of this embodiment preferably does not contain elements that may reduce the p-type properties of the resulting film (i.e., it should be 0 ppm by mass), preferably does not contain silicon (Si), more preferably does not contain one or more elements selected from the group of silicon, germanium (Ge), tin (Sn), and lead (Pb) (hereinafter also referred to as "n-type dopant elements"), and even more preferably does not contain group IV metallic elements. The total content of silicon, germanium, tin, and lead in the sintered body of this embodiment is preferably 10 ppm by mass or less, and more preferably 5 ppm by mass or less. On the other hand, the sintered body of this embodiment may contain n-type dopant elements as unavoidable impurities, for example, the content of n-type dopant elements may be 0 ppm by mass or more, or greater than 0 ppm by mass.

[0029] The sintered body of this embodiment may contain elements other than the dopant alloy and gallium nitride, such as unavoidable impurities, as long as they do not impair its effect.

[0030] On the other hand, in order to improve the p-type properties of the film obtained from the sintered body of this embodiment, the oxygen content of the sintered body of this embodiment is 0.6 atm% or less. With such an oxygen content, leakage current is less likely to occur when the gallium nitride film obtained from the sintered body of this embodiment is used in applications such as light-emitting diodes and power devices. An ideal gallium nitride sintered body does not contain oxygen, so its oxygen content is 0 atm%. However, realistic gallium nitride sintered bodies do contain oxygen. It is preferable that the sintered body of this embodiment does not contain oxygen (i.e., the oxygen content is 0 atm%), but examples include 0 atm% or more, greater than 0 atm%, or 0.1 atm% or more. The oxygen content of the sintered body of this embodiment tends to decrease with increasing dopant alloy, but examples include 0.4 atm% or less, 0.35 atm% or less, or 0.3 atm% or less. The oxygen content of the sintered body in this embodiment may be 0 atm% or more and 0.6 atm% or less, greater than 0 atm% and 0.6 atm% or less, 0.1 atm% or more and 0.4 atm% or less, or 0.1 atm% or more and 0.3 atm% or less.

[0031] In this embodiment, the composition of the sintered body may be determined from the following formula.

[0032] 100 [mass%] = W Ga + W O + W N + W Alloy (1) In the above formula, W Ga , W O , W N and W Alloy are the mass ratios [mass%] of gallium, oxygen, nitrogen, and dopant alloy in the sintered body, respectively.

[0033] Note that W O and W N are the values [mass%] of oxygen and nitrogen measured by the thermal decomposition method in which the sintered body is thermally decomposed using a general oxygen and nitrogen analyzer (for example, LECO ON736, manufactured by Leco Corporation), respectively.

[0034] Also, when the sintered body contains elements such as inevitable impurities, the content thereof is the value [mass%] measured by glow discharge mass spectrometry. Due to the difference in the measurement method, when the sintered body of this embodiment contains elements such as inevitable impurities, its composition may apparently exceed 100 mass%.

[0035] In this embodiment, the oxygen content of the sintered body is measured by a method conforming to JIS H 1695 and is the value obtained from the following formula.

[0036] Oxygen content [atm%] =(W O / M O ) / {(W Ga / M Ga ) + (W N / M N ) +(W​​​​​​​​​​​​​​​​Alloy This is the same as equation (1), and also, M O The atomic weight of oxygen is 16.00 [g / mol], M Ga The atomic weight of gallium is 69.72 [g / mol], M N The atomic weight of nitrogen is 14.01 [g / mol]. Also, M Alloy The values ​​shown are the atomic weights of the dopant alloys. The atomic weights of the dopant elements contained in the dopant alloys are as follows: beryllium 9.01 [g / mol], magnesium 24.31 [g / mol], calcium 40.08 [g / mol], strontium 87.62 [g / mol], vanadium 50.94 [g / mol], zinc 65.39 [g / mol], and cadmium 112.41 [g / mol]. In addition, examples of metallic elements that form alloys with the p-type dopants contained in the dopant alloys include aluminum 26.98 [g / mol], indium 114.82 [g / mol], and thallium 204.38 [g / mol].

[0037] In this embodiment, the atomic ratio of gallium to the total amount of gallium and nitrogen in the sintered body (hereinafter also referred to as the "gallium ratio") [mol / mol] is preferably less than 0.55 or 0.50 or less. If the gallium ratio is 0.55 or higher, handling performance decreases. The gallium ratio is preferably 0 or higher, greater than 0, 0.10 or higher, or 0.30 or higher, and examples include 0 or more but less than 0.55, greater than 0 but less than 0.55, 0.10 or more but 0.50 or less, or 0.30 or more but 0.50 or less.

[0038] In this embodiment, the gallium ratio is obtained from the following equation.

[0039] Ga / (Ga+N) ratio = (W Ga / M Ga ) / {(W Ga / M Ga )+(W N / M N )} (3) In the above equation, the Ga / (Ga+N) ratio is the gallium ratio, and W Ga and W NThis is the mass percentage [mass%] of gallium and nitrogen in the sintered body, and also M Ga and M N This is the mass ratio [mass%] of gallium and nitrogen, and also M Ga The atomic weight of gallium is 69.72 [g / mol], and M N The atomic weight of nitrogen is 14.01 [g / mol].

[0040] The shape of the sintered body in this embodiment can be any shape depending on the purpose, for example, one or more selected from the group of plate-shaped, disc-shaped, cylindrical, cubic, rectangular parallelepiped-shaped, polyhedral-shaped, columnar, cylindrical, and conical shapes, and any other shape that can be used as a sputtering target. Furthermore, the sintered body in this embodiment is preferably a sintered body that has been sintered by a hot press process, a so-called hot-pressed body.

[0041] In this embodiment, a higher measured density of the sintered body is preferable, but this varies depending on the composition. For example, the measured density of the sintered body in this embodiment is 3.50 g / cm³. 3 More than 4.00g / cm 3 Above or above, or 4.20 g / cm³ 3 That's all, and also 5.00 g / cm³ 3 Below, 4.80g / cm 3 The following or 4.60 g / cm³ 3 The following are listed, and 3.50 g / cm³ 3 More than 5.00g / cm 3 Below 4.00g / cm 3 More than 4.80g / cm 3 The following, or 4.20 g / cm³ 3 More than 4.60g / cm 3 The following is preferable:

[0042] In this embodiment, "measured density" refers to the density [g / cm³] measured in accordance with JIS R 1634:1998. 3 The pretreatment can be performed using a vacuum method with distilled water.

[0043] The sintered body of this embodiment preferably has higher mechanical strength and flexural strength that is less prone to defects when used as a sputtering target, compared to conventional sintered bodies containing a similar amount of dopant elements. Specifically, the flexural strength is preferably 55 MPa or higher, and more preferably 60 MPa or higher or 80 MPa or higher. While a high flexural strength is preferable, its upper limit can be, for example, 200 MPa or less, 150 MPa or less, or 130 MPa or less. Examples of flexural strengths for the sintered body of this embodiment include 55 MPa to 200 MPa, 60 MPa to 150 MPa, or 80 MPa to 130 MPa.

[0044] In this embodiment, the flexural strength is the three-point bending strength of the sintered body measured according to the method in accordance with JIS R 1601. The measurement should be performed 3 ± 1 times, and the average value should be used as the flexural strength in this embodiment.

[0045] The sintered body of this embodiment can be used for known applications of gallium nitride sintered bodies, is preferably used as a sputtering target, and more preferably as a sputtering target for p-type GaN film deposition.

[0046] [Method for manufacturing sintered bodies] The manufacturing method for the sintered body of this embodiment is arbitrary as long as a sintered body satisfying the above-described configuration can be obtained. A preferred manufacturing method for the sintered body of this embodiment is a method for manufacturing a sintered body (hereinafter also referred to as "the manufacturing method of this embodiment") which includes a gallium nitride source and a dopant source consisting of an alloy containing one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), wherein the dopant source content in terms of dopant elements is 1.0% by mass or more, and a firing step of hot pressing the raw material powder at a holding temperature of 400°C or higher and a holding pressure of 30 MPa or higher.

[0047] The calcination process involves supplying raw material powders containing a gallium nitride source and a dopant source.

[0048] The gallium nitride source may be at least one of gallium nitride and its precursors, wherein the atomic ratio of gallium to the total amount of nitrogen and gallium (gallium ratio) is less than 0.55. Examples of gallium nitride precursors include one or more selected from the group consisting of gallium oxide, metallic gallium, and gallium chloride, and more preferably metallic gallium. The gallium nitride source is preferably one or more selected from the group consisting of gallium nitride, gallium oxide, metallic gallium, and gallium chloride, and more preferably gallium nitride, and more preferably gallium nitride powder. The gallium nitride powder preferred as a gallium nitride source is not particularly limited, but examples include gallium nitride powder produced by known methods, such as the method described in Japanese Patent Application Publication No. 2021-059483.

[0049] To reduce the oxygen content of the resulting sintered body, the oxygen content of the gallium nitride source is preferably less than 0.4 atm%, less than 0.3 atm%, or 0.2 atm% or less. It is preferable that the gallium nitride source does not contain oxygen (i.e., has an oxygen content of 0 atm%), but examples of oxygen content of the gallium nitride source include 0.005 atm% or more, 0.01 atm% or more, or 0.1 atm% or more. Examples of oxygen content of the gallium nitride source include 0.005 atm% or more and less than 0.4 atm%, 0.01 atm% or more and less than 0.3 atm%, or 0.1 atm% or more and 0.2 atm% or less.

[0050] The oxygen content of the gallium nitride source is the value calculated from the method described above and equation (3).

[0051] The gallium nitride source has a gallium ratio (atomic ratio of gallium to the total amount of nitrogen and gallium) of less than 0.55, preferably 0.50 or less, and preferably 0 or more, greater than 0, 0.10 or more, or 0.30 or more. The gallium ratio of the gallium nitride source can be 0 or more and less than 0.55, greater than 0 and less than 0.55, 0.10 or more and 0.50 or less, or 0.30 or more and 0.50 or less. In the manufacturing method of this embodiment, the gallium ratio of the gallium nitride source and the gallium ratio of the obtained sintered body are equivalent.

[0052] The dopant source may be at least one of an alloy containing one or more dopant elements selected from the group consisting of beryllium, magnesium, calcium, strontium, vanadium, zinc, and cadmium, and its precursors, and may be in powder form.

[0053] The dopant source tends to have a lower oxygen content in the resulting sintered body as the maximum particle size of the primary particles in the powder increases. Examples of maximum particle sizes include 500 μm or less, 300 μm or less, or 200 μm or less, as well as 100 μm or more. Alternatively, the maximum particle size may be between 100 μm and 500 μm, or between 100 μm and 200 μm.

[0054] The dopant source content in the raw material powder should be 1.0% by mass or more when converted to dopant element content, and should be the same as the dopant element content in the sintered body of this embodiment described above [mass%]. In the manufacturing method of this embodiment, the dopant alloy and dopant element content in the dopant source in the raw material powder is equivalent to the dopant alloy and dopant element content in the resulting sintered body.

[0055] In the manufacturing method of this embodiment, the raw material powder is subjected to hot pressing at a holding temperature of 400°C or higher and a holding pressure of 30 MPa or higher.

[0056] In the firing process, the raw material powder is subjected to hot pressing. By hot pressing the raw material powder containing dopant elements as an alloy, densification progresses while suppressing the volatilization of the dopant elements, and the dispersion of the dopant elements is promoted. As a result, it becomes easier to obtain a sintered body with a flexural strength of 55 MPa or higher.

[0057] The holding temperature during the hot pressing process is 400°C or higher, preferably 500°C or higher. If the holding temperature is below 400°C, densification will not proceed, and it will not be possible to obtain a sintered body having the same dopant element content as the sintered body of this embodiment. Possible holding temperatures for the hot pressing process include less than 800°C or 700°C or lower. Alternatively, possible holding temperatures for the hot pressing process include 400°C or higher but less than 800°C, or 500°C or higher but 700°C or lower.

[0058] The holding pressure for the hot press treatment is 30 MPa or higher, preferably 35 MPa or higher. If the holding pressure is less than 30 MPa, side reactions will occur during the hot press treatment, resulting in a higher oxygen content. Examples of holding pressures for the hot press treatment include 80 MPa or less or 60 MPa or less, and examples of processing pressures for the hot press treatment include 30 MPa to 80 MPa or 35 MPa to 60 MPa.

[0059] The processing atmosphere for hot pressing is preferably a vacuum atmosphere. This suppresses the inclusion of impurities originating from the hot pressing process. Specific examples of a vacuum atmosphere include a reduced pressure atmosphere with a vacuum level of 0.01 Pa or less, or 0.005 Pa or less. Furthermore, a vacuum level of 0 Pa is preferable, but values ​​of 0 Pa or higher, greater than 0 Pa, or 0.0001 Pa or higher are also acceptable. Additionally, a vacuum level of 0 Pa or more and 0.01 Pa or less, or 0 Pa or more and 0.005 Pa or less is also acceptable.

[0060] The holding time for the hot press process can be adjusted as appropriate depending on the size of the hot press apparatus, the type and amount of raw material powder used, etc., but examples include 0.5 hours to 5.0 hours, or 0.5 hours to 3.0 hours.

[0061] A specific hot pressing process involves creating a vacuum atmosphere, raising the temperature to the holding temperature, and then holding the object under holding pressure.

[0062] [Sputtering target] The sintered body of this embodiment can be used as a sputtering target equipped with it (hereinafter also referred to as "the target of this embodiment"). The target of this embodiment may be the sintered body of this embodiment, that is, the sintered body of this embodiment may be used as a sputtering target as is, but it is preferable that the sintered body of this embodiment is a sputtering target bonded to a support via a bonding layer.

[0063] The shape of the target in this embodiment is arbitrary, and examples include at least one of a flat plate or a cylindrical shape, or other shapes suitable for the application.

[0064] The target of this embodiment preferably has a structure in which the sintered body of this embodiment is joined (i.e., bonded) to a support by a bonding layer. The bonding layer may be composed of solder containing one or more selected from the group consisting of tin, indium, and zinc. It is preferable that the bonding layer be composed of solder containing indium, as this tends to increase the conductivity and thermal conductivity of the target. If the bonding layer is solder containing indium, the target of this embodiment may have a layer that improves wettability (hereinafter also referred to as a "barrier layer") between the gallium nitride sintered body and the bonding layer. This improves the indium wettability of the sintered body, and as a result, the bond between the sintered body and the bonding layer becomes stronger. The barrier layer may be composed of a component with high wettability to indium, and is preferably at least one of nickel and chromium.

[0065] On the other hand, because it would increase costs, the target of this embodiment preferably does not have a layer containing tungsten (W), and it is particularly preferable that it does not have a layer containing tungsten as a barrier layer.

[0066] The support material in the target of this embodiment is preferably one or more selected from the group consisting of copper, stainless steel, and titanium. The shape of the support material may be any desired shape corresponding to the shape of the sintered body of this embodiment, and examples include at least one of a flat plate shape and a cylindrical shape, as well as other shapes suitable for the application.

[0067] [Film forming method] The sintered body and target of this embodiment can be used in a sputtering film deposition method. Using the sintered body of this embodiment, a sputtered film of p-type gallium nitride can be deposited directly. This sputtered film is a so-called laminated film formed by laminating it on a substrate by sputtering using the target of this embodiment.

[0068] The sputtering method is one or more selected from the group consisting of DC sputtering, pulsed DC sputtering, RF sputtering, AC sputtering, DC magnetron sputtering, RF magnetron sputtering, and ion beam sputtering, preferably at least one of DC magnetron sputtering and RF magnetron sputtering.

[0069] The sputtering gas can be any gas used for sputtering, and may include inert gases, and more specifically, at least one of argon gas and nitrogen gas. When sputtering using the target of this embodiment, the surface of the resulting sputtered film tends to be smooth, so the sputtering gas is preferably a nitrogen-containing gas, and preferably a mixed gas of argon and nitrogen. The mixed gas is preferably nitrogen-rich, and the nitrogen / (nitrogen + argon) partial pressure ratio [Pa / Pa] (hereinafter also simply referred to as "nitrogen partial pressure ratio") is preferably greater than 0.5, 0.7 or greater, or 0.9 or greater. The nitrogen partial pressure ratio may be 1.0 or less, or less than 1.0, and more preferably greater than 0.5 and less than 1.0, 0.7 or greater and less than 1.0, or 0.9 or greater and less than 1.0.

[0070] The flow rate of the sputtered gas may be 5 ml / min or more, or 10 ml / min or more, and also 100 ml / min or less, or 70 ml / min or less.

[0071] The gas pressure of the sputtering gas should be 0.05 Pa or higher, or 0.1 Pa or higher, and also 3 Pa or lower, or 2 Pa or lower. The gas pressure of the sputtering gas can be 0.05 Pa or higher and 3 Pa or lower, or 0.1 Pa or higher and 2 Pa or lower.

[0072] To generate a stable plasma, the discharge power density in sputtering is 0.1 W / cm². 2 Above or above, or 0.3 W / cm² 2 That's all, and also 5W / cm 2 The following is acceptable: The discharge power density is 0.1 W / cm². 2 More than 5W / cm 2 Below or above 0.1 Pa or 5 W / cm² 2 The following are some examples:

[0073] The substrate can be appropriately selected according to the target film and substrate laminate (hereinafter also simply referred to as "laminated laminate"), and examples include one or more selected from the group consisting of glass substrates, alumina substrates, silicon substrates, gallium nitride substrates, aluminum nitride substrates, and silicon carbide substrates, and furthermore, at least one of alumina substrates, silicon substrates, and gallium nitride substrates.

[0074] The sputtering method and conditions can be appropriately selected depending on the desired sputtered film.

[0075] The substrate temperature in sputtering deposition (hereinafter also referred to as the "deposition temperature") is arbitrary and may be 10°C or higher, 20°C or higher, or 800°C or lower. When increasing the deposition rate, the deposition temperature may be 100°C or higher, 300°C or higher, or 800°C or lower, or 500°C or lower.

[0076] The sputtering time (hereinafter also referred to as "deposition time") depends on the sputtering conditions. The deposition time can be set appropriately depending on the size of the substrate and the desired thickness of the sputtered film. For example, it can be 1 minute or more, or 10 minutes or more, or 5 hours or less, or 1 hour or less. The film deposition time can be 1 minute or more and 5 hours or 10 minutes or more and 1 hour or less. [Examples]

[0077] The present disclosure will be illustrated below with reference to examples. However, the present disclosure is not limited thereto. (oxygen content) The oxygen content of the sintered body was measured using an oxygen and nitrogen analyzer (instrument name: LECO ON736, manufactured by LECO) in accordance with JIS H 1695. (Measured density of sintered body) The measured density of the sintered body was determined in accordance with the method for measuring actual density specified in JIS R 1634. The mass was determined by weighing the sintered body after pretreatment using a vacuum method with distilled water, and the volume was determined from the shape measured using a micrometer. (flexural strength) The three-point bending strength of the sintered body was measured according to the method compliant with JIS R 1601. The measurement was performed twice, and the average value was used as the bending strength. (Tissue observation) The microstructure of the sintered body was observed by examining the cross-section using a SEM equipped with EDS (product name: JSM-IT800, manufactured by JEOL Ltd.). Furthermore, mapping images of the elements Ga, Mg, and Al were obtained for the observed cross-sections. Observation: Secondary electron images, backscattered electron images, elemental mapping Acceleration voltage: 15kV Irradiation current: 50nA Analysis area: 100×150μm Field of view: 1 field of view per sample

[0078] Example 1 A raw material powder was obtained by mixing gallium nitride powder, which has a gallium ratio of 0.5 and an oxygen content of 0.12 atm%, with aluminum-magnesium alloy powder (manufactured by Kanto Metal Co., Ltd.) having a maximum particle size of less than 150 μm, so that the aluminum-magnesium alloy content is 8.8 mass% (5.0 mass% as magnesium).

[0079] 15 g of the obtained raw material powder was filled into a carbon mold measuring 17 mm x 45 mm and placed in a hot press machine. After placement, the pressure was reduced to 0.004 Pa, and then the hot press process was performed by raising the temperature and holding it under the following conditions.

[0080] Heating rate: 200°C / hour Holding temperature: 600℃ Holding pressure: 40 MPa Retention time: 1 hour After hot pressing, when the temperature was reduced to 500°C, a cooling gas (argon) was introduced, and after further reduction to 50°C, the sintered body was recovered from the hot pressing apparatus, yielding a sintered gallium nitride body containing an aluminum-magnesium alloy with a magnesium content of 5.0 mass%.

[0081] Figures 1 to 4 show SEM observation images of the sintered body of this embodiment, as well as elemental mappings of Ga, Mg, and Al. From Figures 1 and 2, it was confirmed that the crystalline grains of the sintered body of this embodiment have an irregular shape and that gallium (gallium nitride) forms the matrix. Furthermore, since Mg and Al have similar distributions, it was confirmed that magnesium and aluminum are included in the sintered body as an alloy.

[0082] Example 2 A sintered gallium nitride body containing aluminum-magnesium alloy and having a magnesium content of 7.0% was obtained by the same method as in Example 1, except that gallium nitride powder and aluminum-magnesium alloy powder were mixed so that the aluminum-magnesium alloy content was 12.3% by mass (7.0% by mass as magnesium).

[0083] Example 3 A sintered gallium nitride body containing aluminum-magnesium alloy and having a magnesium content of 9.6% was obtained by the same method as in Example 1, except that gallium nitride powder and aluminum-magnesium alloy powder were mixed so that the aluminum-magnesium alloy content was 16.6% by mass (9.6% by mass as magnesium).

[0084] Example 4 In the same manner as in Example 1, a sintered gallium nitride body containing aluminum-magnesium alloy and having a magnesium content of 15.1% was obtained, except that the gallium nitride powder and aluminum-magnesium alloy powder were mixed so that the aluminum-magnesium alloy content was 26.3% by mass (15.1% by mass as magnesium). Example 5 A sintered gallium nitride body containing an aluminum-magnesium alloy was obtained in the same manner as in Example 1, except that a powder of an aluminum-magnesium alloy with a maximum particle size of less than 300 μm was mixed to obtain a raw material powder, and the magnesium content was 5.0% by mass.

[0085] Comparative Example 1 A sintered gallium nitride body containing aluminum-magnesium alloy and having a magnesium content of 3.0% was obtained by the same method as in Example 1, except that gallium nitride powder and aluminum-magnesium alloy powder were mixed so that the aluminum-magnesium alloy content was 5.2% by mass (3.0% by mass as magnesium).

[0086] Comparative Example 2 A sintered gallium nitride body containing an aluminum-magnesium alloy and having a magnesium content of 5.0 mass was obtained using the same method as in Example 1, except that the holding pressure during the hot pressing process was set to 20 MPa.

[0087] Comparative Example 3 The hot pressing process was carried out in the same manner as in Comparative Example 1, except that the holding temperature was set to 300°C and the holding pressure to 20 MPa. However, cracks occurred during the hot pressing process, and a sintered body could not be obtained.

[0088] Comparative Example 4 Except for using magnesium powder with a particle size of 500 μm (manufactured by Kanto Metal Co., Ltd.) instead of aluminum-magnesium alloy powder, mixing gallium nitride powder and magnesium powder so that the magnesium powder content was 16.4% by mass, and setting the hot pressing temperature to 800°C, a magnesium-containing gallium nitride sintered body was obtained using the same method as in Example 1, with a magnesium content of 16.4% by mass.

[0089] Comparative Example 5 A sintered body was prepared using the method described in Example 6 of Patent Document 2. Specifically, magnesium nitride (Mg3N2) was used as the dopant source, and magnesium nitride was added to 100 g of gallium nitride powder at a concentration of 14,000 wt ppm. The mixture was then uniformly mixed to obtain the raw material powder. The obtained raw material powder was filled into a carbon mold with a diameter of 78 mm, placed in a hot press apparatus, and subjected to hot pressing under the following conditions.

[0090] Heating rate: 200°C / hour Holding temperature: 1090℃ Holding pressure: 50 MPa Retention time: 2 hours After hot pressing, the sintered body was cooled to 50°C and then recovered from the hot pressing apparatus to obtain a sintered gallium nitride body containing magnesium nitride with a magnesium content of 1.4% by mass.

[0091] The results for the examples and comparative examples are shown in the table below.

[0092] [Table 1]

[0093] From the table above, it was confirmed that all of the sintered bodies in the examples contained magnesium, and therefore were sintered gallium nitride bodies capable of directly forming a p-type gallium nitride film. Furthermore, from Examples 1 to 4 and Comparative Example 1, it was confirmed that the sintered bodies in the examples were sintered bodies that possessed a flexural strength of 60 MPa or more and an oxygen content of 0.5 amt% or less, despite having a magnesium content of 1.0 mass% or more, and even 4.0 mass% or more. From Examples 3 and 5, it was confirmed that increasing the particle size of the dopant alloy (aluminum-magnesium alloy) reduced the oxygen content while having little effect on flexural strength and density. In addition, the total content of silicon, germanium, tin, and lead in all of the sintered bodies in the examples was 10 mass ppm or less.

[0094] Furthermore, Comparative Example 2 confirmed that the oxygen content increased when the holding pressure during the hot pressing process was less than 30 MPa, and Comparative Example 3 confirmed that a sintered body could not be obtained when the holding temperature during the hot pressing process was 300°C or lower. In addition, Examples 5 and Comparative Example 4 confirmed that in the case where magnesium was added instead of magnesium-aluminum alloy, the oxygen content increased and the flexural strength was low, despite the large particle size. Furthermore, the sintered body disclosed in Patent Document 2 was a sintered body containing magnesium and low oxygen content, but it also had low flexural strength.

[0095] Example 6 A sintered body was obtained in the same manner as in Example 5, except that 50 g of raw material powder was filled into a circular mold with a diameter of 53 mm. This was then ground down to form a disc-shaped sintered body with a diameter of 50.8 mm and a thickness of 3 mm. Using the obtained sintered body, indium solder as the bonding layer, and an oxygen-free copper backing plate as the support, a circular sputtering target with a backing plate was fabricated.

[0096] Using the obtained sputtering target, a film was deposited on the substrate by sputtering under the following conditions to obtain a laminated substrate having a magnesium-containing gallium nitride film (sputtered film). The sputtering apparatus used was a CMS-6400 (manufactured by Comet Corporation). Sputtering method: RF magnetron sputtering Substrate: Sapphire substrate Film forming temperature: 500℃ Sputtering gas: Nitrogen (i.e., nitrogen partial pressure ratio is 1.0) Gas pressure: 0.3 Pa Output: 3.8W / cm² 2

[0097] (Analysis of sputtered films) Secondary ion mass spectrometry (SIMS) was performed on the resulting sputtered laminated substrate. A Model 6600 Quadrupole SIMS instrument, manufactured by Physical Electronics PHI, was used. Figure 5 shows the SIMS results for magnesium, aluminum, and gallium concentrations of the obtained laminated substrate; the magnesium concentration is shown by a solid line, the aluminum concentration by a dotted line, and the gallium concentration by a dashed line. Figure 5 indicates that magnesium is continuously and uniformly present along the depth direction from the surface (Depth=0mm), and that its content is 7.8 × 10⁻⁶. 21 It was confirmed that the atom / cc (= 52,000 mass ppm = 5.2 mass%) concentration was high. Furthermore, since the aluminum content increased as Depth ≥ 90 nm, it was confirmed that the thickness of the magnesium-containing gallium nitride film was 90 nm.

[0098] The entire contents of the specification, claims, abstract, and drawings of Japanese Patent Application No. 2024-155023, filed on September 9, 2024, are incorporated herein by reference as part of the disclosure of this specification.

Claims

1. The alloy contains one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd). The dopant element content is 1.0% by mass or more. The oxygen content is 0.6 atm% or less, and The alloy is an alloy of the dopant element and aluminum. A sintered gallium nitride body characterized by the following features.

2. The sintered body according to claim 1, wherein the total content of silicon, germanium, tin, and lead is 10 ppm by mass or less.

3. The measured density was 3.50 g / cm³. ３ The sintered body according to claim 1 is as described above.

4. The sintered body according to claim 1, wherein the flexural strength is 55 MPa or more.

5. A method for producing a sintered body according to claims 1 to 4, comprising a firing step of hot-pressing a raw material powder, which includes a gallium nitride source and a dopant source made of an alloy containing one or more dopant elements selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), and cadmium (Cd), wherein the dopant source content in terms of dopant elements is 1.0% by mass or more, at a holding temperature of 400°C or higher and a holding pressure of 30 MPa or higher.

6. The manufacturing method according to claim 5, wherein the oxygen content of the gallium nitride source is less than 0.4 atm%.

7. A sputtering target comprising the sintered body according to claims 1 to 4.

8. A method for manufacturing a sputtered film using the sputtering target described in claim 7.

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