Gallium nitride-based sintered body and method for manufacturing the same

Abstract

To manufacture a spattering target for a gallium nitride thin film which has high quality and is usable for light-emitting diodes and power devices of different colors.SOLUTION: A gallium nitride-based sintered body is provided in which a content of one or more kinds of group 13 elements selected from the group consisting of boron, aluminum and indium is not less than 0.001 atm% nor more than 25 atm% and an oxygen content is 1 atm% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Gallium nitride has attracted attention as a raw material for the light-emitting layer of blue light-emitting diodes (LEDs) and blue laser diodes (LDs). In recent years, it has been used in various applications such as white LEDs and blue LDs in the form of thin films and substrates, and is also attracting attention as a material for power devices in the future. Currently, gallium nitride thin films are generally manufactured by the metal-organic chemical vapor deposition (MOCVD) method. The MOCVD method involves transporting raw material vapors into a carrier gas to the substrate surface, and growing crystals by decomposing the raw materials through a reaction with the heated substrate.

[0002] Another method for fabricating thin films besides MOCVD is sputtering. In sputtering, positive ions such as Ar ions are physically collided with a target placed at the cathode, and the collision energy causes the material constituting the target to be ejected, depositing a film with almost the same composition as the target material onto a substrate placed opposite. There are two types: DC sputtering and RF sputtering.

[0003] Until now, metallic gallium targets have been used as a method for depositing gallium nitride thin films by sputtering (see, for example, Patent Document 1). However, when using metallic gallium targets, since metallic gallium has a melting point of approximately 29.8°C, it melts during sputtering, making it difficult to obtain a gallium nitride film with highly stable properties such as crystallinity and permeability. To prevent this, methods have been proposed that involve installing expensive cooling equipment and depositing the film at low power, but these methods have the drawbacks of reduced productivity and increased oxygen uptake into the film.

[0004] Furthermore, high-density gallium nitride sintered bodies have also been proposed (see, for example, Patent Document 2), but according to this example, densification occurs under extremely high pressure conditions of 58 kbar (5.8 gPa), and the equipment required to apply such pressure is very expensive, making it impossible to produce large sintered bodies. As a result, the sputtering targets used in the sputtering method are themselves very expensive and difficult to scale up, which has led to the problem of films that tend to have poor homogeneity.

[0005] Furthermore, as a method for reducing the oxygen content, a method has been proposed in which the oxygen-containing gallium nitride sintered body is subjected to nitriding treatment to reduce the oxygen content (see, for example, Patent Document 3). However, there was a problem that cracks may occur in the sintered body if the oxygen content was reduced beyond a certain level.

[0006] Furthermore, when using the DC sputtering method, a low resistivity of the sputtering target is required. One proposed method for reducing the resistivity of the sputtering target is to impregnate a gallium nitride molded product with metallic gallium (see, for example, Patent Document 4). However, this method reduces resistance, but during bonding and sputtering, metallic gallium precipitates, reacting with solder materials such as indium, causing the gallium nitride molded product to peel off and preventing stable discharge. As a countermeasure, a method has been proposed to suppress the deposition of metallic gallium by backing it with a thin film of tungsten (see, for example, Patent Document 5). However, this method has drawbacks such as increasing the number of target manufacturing steps, making it more complicated, and requiring the use of expensive tungsten material, a special material.

[0007] Furthermore, in recent years, research has progressed on depositing gallium nitride films onto large silicon substrates, which will require even larger sputtering targets in the future, but such targets did not currently exist.

[0008] Furthermore, gallium nitride-based LEDs require not only blue light, but also green and red light. To achieve this, the target must contain aluminum or indium, but such sputtering targets have not been available until now. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-172424 [Patent Document 2] Japanese Patent Publication No. 2005-508822 [Patent Document 3] Japanese Patent Publication No. 2012-144424 [Patent Document 4] Japanese Patent Publication No. 2014-159368 [Patent Document 5] Japanese Patent Publication No. 2014-91851 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a gallium nitride-based sintered body containing a group 13 element such as aluminum, which is high-strength and crack-free, and a sputtering target using the same. [Means for solving the problem]

[0011] In light of this background, the inventors conducted extensive research. As a result, they discovered that by processing gallium nitride powder with a low oxygen content using a hot press mold with an appropriate holding time and thermal expansion coefficient suitable for gallium nitride sintering, it is possible to produce a high-density, large gallium nitride-based sintered body with a low oxygen content, thus completing the present invention.

[0012] In other words, embodiments of the present invention are as follows. (1) A gallium nitride-based sintered body, wherein the content of one or more Group 13 elements selected from the group consisting of boron, aluminum, and indium is 0.001 atm% or more and 25 atm% or less, and the oxygen content is 1 atm% or less. (2) The gallium nitride-based sintered body according to (1), wherein the oxygen content is less than 0.3 atm%. (3) The gallium nitride-based sintered body according to (1) or (2), characterized in that the total impurity content of elements of Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, Cd is less than 10 wtppm. (4) The gallium nitride-based sintered body according to any one of (1) to (3), characterized in that the total impurity content of Mg and Si is less than 5 wtppm. (5) The gallium nitride-based sintered body according to any one of (1) to (4), characterized in that the Si impurity content is less than 1 wtppm. (6) The gallium nitride-based sintered body according to any one of (1) to (5), characterized in that the density is 3.0 g / cm 3 or more and 5.4 g / cm 3 or less. (7) The gallium nitride-based sintered body according to any one of (1) to (6), characterized in that the maximum value of the peak attributable to gallium metal in the X-ray diffraction peak of the sintered body is 10% or less of the maximum value of the gallium nitride peak. (8) The gallium nitride-based sintered body according to any one of (1) to (7), characterized in that the average particle size of the sintered body is 1 μm or more and 150 μm or less. (9) A method for producing a gallium nitride-based sintered body by a hot press method, comprising using a gallium nitride powder having an oxygen content of 1 atm% or less and one or more Group 13 elements selected from the group consisting of boron, aluminum, and indium as raw materials, and characterized in that the difference between the linear thermal expansion coefficient in the direction perpendicular to the pressing direction of the hot press mold and the linear expansion coefficient of the raw materials is within 15%. (10) A hot press mold for obtaining a disk, characterized in that the number of divisions of the sleeve is 3 or more. (11) The characteristic feature is the use of a gallium nitride-based sintered body described in any of (1) to (8). A sputtering target. (12) The sputtering target according to (11), characterized in that there is no tungsten-containing layer between the target member and the bonding layer. A method for producing a gallium nitride-based thin film, characterized by using the sputtering target described in (13), (11), or (12).

[0013] The gallium nitride-based sintered body of the present invention is characterized in that the total content of one or more Group 13 elements selected from the group consisting of B, Al, and In is 0.001 atm% to 25 atm%, preferably 0.01 atm% to 25 atm%, and more preferably 0.1 atm% to 25 atm%. By obtaining such a gallium nitride-based sintered body containing B, Al, and In, it becomes possible to use it as a sputtering target and, after film formation, as a gallium nitride-based thin film for green or red LEDs or for power devices.

[0014] The gallium nitride-based sintered body of the present invention has an area of ​​150 cm². 2 It is preferable that it be greater than or equal to 175cm. 2 It is even more preferable that it be greater than or equal to 200 cm, and particularly preferable that it be 200 cm. 2 That concludes the explanation. By obtaining a large-area gallium nitride-based sintered body, it becomes possible to increase the size of the substrate on which the film can be deposited.

[0015] Furthermore, the oxygen content is characterized by being 1 atm% or less, preferably 0.5 atm% or less, more preferably less than 0.3 atm%, even more preferably 0.2 atm% or less, and even more preferably 0.1 atm% or less. By reducing the oxygen content in the gallium nitride-based sintered body, when used as a sputtering target, it is possible to reduce the inclusion of oxygen as an impurity during film formation and obtain a film with higher crystalline properties.

[0016] Here, "atm%" has the same meaning as "at%", and is represented by the ratio of the number of atoms of a specific element to the total number of atoms of all elements contained. For example, in gallium nitride containing oxygen, when gallium, nitrogen, and oxygen are each contained in wt%, the oxygen content (atm%) is calculated as follows: oxygen content (atm%) = (oxygen content (wt%) / oxygen atomic weight) / ((gallium content (wt%) / gallium atomic weight) + (nitrogen content (wt%) / nitrogen atomic weight) + (oxygen content (wt%) / oxygen atomic weight)).

[0017] In order to be able to control the gallium nitride-based sintered body of the present invention into a p-type or n-type semiconductor, it is preferable that the total impurity amount of elements such as Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, and Cd in the gallium nitride-based sintered body is less than 10 wtppm, more preferably 5 wtppm or less, and particularly preferably 3 wtppm or less.

[0018] Among these impurities, the total amount of Mg and Si with a high activation rate is preferably 5 wtppm or less in total, more preferably 2 wtppm or less, and particularly preferably 1 wtppm. Further, the Si impurity amount is preferably 1 wtppm or less.

[0019] The gallium nitride-based sintered body of the present invention preferably has a flexural strength of 50 MPa or more, more preferably 60 MPa or more, and still more preferably 70 MPa or more. By having such strength, it is possible to produce a sintered body with a large area without cracking, and also to withstand the stress applied to the sintered body in the bonding process when used as a sputtering target.

[0020] The gallium nitride-based sintered body of the present invention preferably has a density of 3.0 g / cm 3 or more and 5.4 g / cm 3 or less, more preferably 3.5 g / cm 3 or more and 5.4 g / cm 3 or less, and particularly preferably 4.0 g / cm 3 or more and 5.4 g / cm3 The following applies. The density of the gallium nitride-based sintered body mentioned here refers to the density including open pores. Such gallium nitride-based sintered bodies can be used as sputtering targets.

[0021] The gallium nitride-based sintered body of the present invention preferably has an average particle diameter (D50) of 1 μm to 150 μm, more preferably 5 μm to 100 μm, and particularly preferably 9 μm to 80 μm. By having such a particle diameter, it is possible to obtain a gallium nitride-based sintered body with a lower oxygen content and higher strength. Here, the average particle diameter (D50) refers to the 50% particle diameter in the area of ​​the primary particles observed with a scanning electron microscope or the like.

[0022] Furthermore, it is preferable that the sintered body contains a small amount of metallic gallium. In particular, it is preferable that the maximum value of the peak caused by metallic gallium in the X-ray diffraction peak is 10% or less of the maximum value of the gallium nitride peak, more preferably 5% or less, and even more preferably 1% or less. If metallic gallium is present in the sintered body, it alloys with one or more Group 13 elements selected from the group consisting of B, Al, and In, which lowers the melting point and causes liquefaction, resulting in the sintered body losing its shape or cracking. Also, when used as a sputtering target, Ga-(B,Al,In) alloy precipitates during sputtering, making stable film formation difficult.

[0023] Next, the method for producing the gallium nitride-based sintered body of the present invention will be described.

[0024] To obtain a large, low-oxygen sintered body without causing cracks in the gallium nitride-based sintered body, it is necessary to sinter the gallium nitride-based sintered body with as little stress as possible.

[0025] In other words, the present invention provides a method for producing a gallium nitride-based sintered body by a hot press method, characterized in that it uses gallium nitride powder with an oxygen content of 1 atm% or less and one or more Group 13 element powders selected from the group consisting of boron, aluminum, and indium as raw materials, and the difference between the linear thermal expansion coefficient in the direction perpendicular to the pressurizing direction of the hot press mold and the linear thermal expansion coefficient of the raw materials is within 15%.

[0026] The method for producing the gallium nitride-based sintered body of the present invention will be described in more detail below.

[0027] First, the gallium nitride powder used as the raw material must have an oxygen content of 1 atm% or less. More preferably, it is less than 0.5 atm%, even more preferably less than 0.3 atm%, even more preferably 0.2 atm% or less, and even more preferably 0.1 atm% or less. In order to reduce oxygen, it is necessary to suppress surface oxidation, so a small specific surface area of ​​the powder is preferable, more preferably 0.01 m². 2 / g or more 1.5m 2 Less than or equal to / g, more preferably 0.01m 2 / g or more 0.8m 2 It is less than / g. 0.01m 2 If the specific surface area is smaller than / g, the crystal grains are too large, resulting in weak adhesion between the grains. This makes it difficult to maintain the shape during final firing, and furthermore, the sinterability generally decreases, making firing difficult.

[0028] Furthermore, in order to obtain a gallium nitride-based sintered body with sufficient strength to be used as a sputtering target, the bulk density of the gallium nitride powder used as the raw material should be 1.0 g / cm³. 3 More than 3.0g / cm 3 Preferably less than 1.4 g / cm³, and more preferably 1.4 g / cm³. 3 More than 3.0g / cm 3 It is less than 3.0 g / cm³. Note that the bulk density in light packaging is a value obtained by filling a container of a certain volume with powder without applying any load such as vibration, and then dividing the volume of the filled powder by the volume of the container. 3If the bulk density is excessively high, the strength of the granules constituting the powder becomes too high, and the granules remain uncrushed during molding and firing, resulting in a significant decrease in the strength of the gallium nitride-based sintered body.

[0029] Furthermore, the average particle size (D50) of the gallium nitride powder used as a raw material is preferably between 1 μm and 150 μm. More preferably between 5 μm and 100 μm, and even more preferably between 9 μm and 80 μm. By using such powder, it is possible to produce a gallium nitride-based sintered body that achieves both high strength and low oxygen content. In particular, with gallium nitride, the sintering start temperature and decomposition temperature are close, the sintering temperature range is narrow, and there is no significant grain growth during sintering, so the distribution of primary particles before sintering greatly affects the gallium nitride-based sintered body. The particle size of the primary particles refers to the diameter of the smallest unit particle observed by SEM, and the average particle size is measured by the diameter method, and the value at 50% particle size is expressed after measuring at least 100 or more particles. Here, the particles for which the average particle size is measured are gallium nitride particles. In the case of molded products using powders within this range, the particle size is larger and the adhesive force is weaker than before. Therefore, if there are open pores large enough to allow immersion, the bonding force between particles is relatively weak. When Ga is immersed, cracks occur due to the stress generated during immersion and the difference in thermal expansion coefficient caused by heating and sputtering.

[0030] Furthermore, in order to obtain high crystallinity in the sputtering film and because the semiconductor properties change when elements are added, it is preferable to use gallium nitride powder as a raw material that contains as few impurities as possible. However, in order to obtain p-type and n-type semiconductors, it is preferable that the gallium nitride powder contains less than 10 wtppm of impurity elements, more preferably 5 wtppm or less, and particularly preferably 3 wtppm or less.

[0031] Regarding the total amount of Mg and Si, which have high activation rates among the impurities, it is preferable that the total amount be 5 wt ppm or less, more preferably 2 wt ppm or less, and particularly preferably 1 wt ppm. Furthermore, it is preferable that the amount of Si impurities be 1 wt ppm or less.

[0032] Similarly, it is preferable to use boron, aluminum, and indium that contain as few impurities as possible. The purity of these materials with respect to metal impurities is preferably 99 wt% or higher, and more preferably 99.9 wt% or higher.

[0033] The forms of boron, aluminum, and indium to be included are not particularly limited, but it is preferable that the oxygen content be kept to a minimum and that other metallic elements are not included. Therefore, metallic boron, boron nitride, metallic aluminum, aluminum nitride, metallic indium, and indium nitride are preferred. More preferably, metallic aluminum, aluminum nitride, metallic indium, and indium nitride are preferred. The amount of oxygen contained in the raw material is preferably 3 atm% or less, more preferably 1.5 atm% or less, and even more preferably 1 atm% or less. By doing so, it is possible to obtain a gallium nitride-based sintered body with suppressed oxygen content.

[0034] The firing method used is the hot press method. The hot press method is a method of sintering by applying heat while pressurizing the powder. By applying uniaxial pressure during heating, diffusion during firing is assisted, making it possible to sinter materials that have a low diffusion coefficient and are difficult to sinter.

[0035] The linear thermal expansion coefficient of the hot press mold in the direction perpendicular to the pressing direction is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less compared to the thermal expansion coefficient of the raw material being introduced. Even more preferably, it is +1% or less and -5% or more relative to the thermal expansion coefficient of the raw material. The linear thermal expansion coefficient of the hot press mold here is the value for the mold shown in Figure 1. When producing a gallium nitride-based sintered body, 5.0 × 10 -6 / K or more 7.0×10 -6It is preferable that it is less than or equal to / K. More preferably 5.0 × 10 -6 / K or more 6.0×10 -6 It is below / K. By using materials with a thermal expansion coefficient within that range, the linear thermal expansion coefficient approaches that of gallium nitride, making it possible to reduce the stress incurred when the size is increased. In the case of small sizes, sintering was possible even if the linear thermal expansion coefficient was different because the dimensional difference was small, but microcracks were embedded, which was a factor in reducing strength. 150cm 2 In such cases, the dimensional difference due to thermal expansion becomes large, causing stress during firing and resulting in cracking. Specifically, 5.0 × 10 -6 Below 7.0 × 10⁻¹⁰°C, pressure sintering occurs at a predetermined temperature, and during cooling, the shrinkage of the hot-press type is smaller than the shrinkage of the gallium nitride-based sintered body, resulting in large tensile stress and cracking of the gallium nitride-based sintered body. -6 When the temperature is above / K, the shrinkage of the hot-pressed type is greater than that of the gallium nitride-based sintered body during cooling, generating external compressive stress, which in turn causes a decrease in strength and cracking in the gallium nitride-based sintered body due to crack formation.

[0036] An example of a hot press mold is shown in Figure 1. In this figure, it is preferable that the die, upper punch, lower punch, and sleeve are made of the same material. By using the same material, the volume change during heating will be similar, making it possible to reduce stress during thermal expansion and contraction.

[0037] The firing temperature should be between 1060°C and less than 1200°C. A temperature of 1060°C or higher is necessary to promote the sintering of gallium nitride, and the temperature must be kept below 1200°C to limit the decomposition of gallium nitride into nitrogen and metallic gallium to a certain extent. Furthermore, to improve the density of the gallium nitride-based sintered body, the firing pressure should preferably be between 30 MPa and 100 MPa, and more preferably between 40 MPa and 90 MPa.

[0038] The firing temperature depends on the particle size of the powder used; the larger the particle size, the higher the temperature that can be applied.

[0039] The preferred holding time during firing is 15 minutes to less than 1 hour. If the holding time is less than 15 minutes, even if the density increases due to partial decomposition of gallium, the adhesion between particles will not progress. If the firing time is longer than 1 hour, the decomposition progresses, alloying with the contained boron, aluminum, and indium, which lowers the melting point, and even if the density increases, the strength cannot be maintained. By firing within this range, it is possible to suppress decomposition while promoting sintering, and a gallium nitride-based sintered body with higher strength than before can be obtained.

[0040] The hot press operation is performed under vacuum. The vacuum level at the start of heating should be 10 Pa or less, and 1 × 10 -1 Preferably Pa or less, 5 × 10 -2 Pa is more preferred, 1 × 10 -2 It is particularly preferable that the pressure be below Pa. This reduces the amount of oxygen and other oxygen-containing elements such as water that are introduced from the atmosphere, thereby suppressing oxidation during firing.

[0041] Furthermore, when sintering under vacuum, the decomposition of gallium nitride powder gradually progresses from around 1060°C. However, by sintering under vacuum, some of the metallic gallium produced by the decomposition is discharged from the gallium nitride-based sintered body along with nitrogen, which is a decomposition gas. For this reason, it is preferable that the clearance between the die and the upper punch in the hot press mold be 0.2 mm or more. Alternatively, it is preferable to use a low-density material such as carbon felt between the powder and the upper and lower punches.

[0042] The hot press mold preferably includes a segmented sleeve. More preferably, the sleeve is segmented into three or more segments, and even more preferably into four or more segments. The maximum number of segments is preferably six or less. Segmenting the sleeve in this way makes it easier to remove the gallium nitride-based sintered body and prevents cracking and chipping.

[0043] Furthermore, in order to reduce the oxygen adsorbed on the hot press mold, it is preferable to preheat the mold once before firing. This makes it possible to reduce the moisture adsorbed on the hot press device and mold before firing.

[0044] The resulting gallium nitride-based sintered body is preferably disc-shaped. The disc shape ensures uniform thermal expansion and contraction in the circumferential direction, thereby suppressing stress on the gallium nitride-based sintered body.

[0045] The resulting gallium nitride-based sintered body may be processed to a predetermined size depending on its application, such as a sputtering target. The processing method is not particularly limited, but surface grinding, rotary grinding, or cylindrical grinding can be used.

[0046] The gallium nitride-based sintered body may be fixed (bonded) to a flat or cylindrical support using an adhesive such as solder, as needed, and used as a sputtering target. It is preferable that there is no tungsten-containing layer between the target member and the bonding layer in the sputtering target. This reduces costs by avoiding the use of expensive metallic tungsten targets and improves productivity by eliminating the need for a tungsten film deposition process.

[0047] Furthermore, the sputtering target of the present invention preferably uses a tin-based solder material, an indium-based solder material, or a zinc-based solder material as the bonding layer. Among these, indium solder is particularly preferred because it has high electrical and thermal conductivity, and is soft and easily deformable.

[0048] Furthermore, the sputtering target of the present invention preferably uses a metal such as Cu, SUS, or Ti as the support due to its high thermal conductivity and strength. For flat molded products, a flat support is preferred, while for cylindrical molded products, a cylindrical support is preferred.

[0049] Next, the method for manufacturing the sputtering target of the present invention will be described.

[0050] The sputtering target of the present invention is manufactured by bonding a gallium nitride-based sintered body to a support via a bonding layer. The bonding layer can be made of tin-based solder, indium-based solder, zinc-based solder, etc. When using indium-based solder, a wettability-improving layer may be formed between the gallium nitride-based sintered body and the solder to improve the wettability to the gallium nitride-based sintered body with indium. The material of this layer is preferably inexpensive and has high wettability to indium, for example, nickel-based or chromium-based materials are preferred. It is preferable that this layer is uniformly formed across the entire interface with the solder. There are no particular limitations on the method of forming such a barrier layer, and sputtering, vapor deposition, coating, etc., can be used. [Effects of the Invention]

[0051] The gallium nitride-based sintered body of the present invention is suitable for use as a sputtering target for LED thin films of various colors. [Brief explanation of the drawing]

[0052] [Figure 1] Hot press mold used in the examples and comparative examples [Figure 2] The four-part sleeve used in the example [Examples]

[0053] The following will be an explanation using examples, but it is not limited to these examples. (Lightweight bulk density) Measurements were performed using a PT-N type powder tester (manufactured by Hosokawa Micron). (Density of gallium nitride-based sintered body) The density of the gallium nitride-based sintered body was determined according to the bulk density measurement method specified in JIS R1634. (oxygen content) The oxygen content was measured using an oxygen and nitrogen analyzer (manufactured by LECO). (Measurement of average particle size (D50)) The average particle size (D50) was measured using the diameter method from SEM observation images for at least three fields of view, and after measuring 100 or more particles, the 50% particle size was taken as the average particle size. The measurement targets were limited to gallium nitride particles in gallium nitride powder and gallium nitride sintered bodies. (flexural strength) The flexural strength of the sintered body was measured in accordance with JIS R 1601 after processing it to the appropriate dimensions. (Impurity analysis) Impurities other than gaseous components were analyzed using GDMS (glow discharge mass spectrometry). (Confirmation of crystalline phase, measurement of intensity ratio) The standard measurement was performed using a general powder X-ray diffractometer (instrument name: UltimaIII, manufactured by Rigaku Corporation). The XRD measurement conditions were as follows:

[0054] Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: 2θ / θ scan Measurement interval: 0.01° Divergence slit: 0.5deg Scattering slit: 0.5deg Light-receiving slit: 0.3mm Measurement time: 1.0 seconds Measurement range: 2θ = 20° to 80° For the identification and analysis of the XRD patterns, XRD analysis software (product name: JADE7, manufactured by MID Corporation) was used. For the hexagonal phase, the gallium nitride crystal phase was confirmed by referring to JCPDS No. 00-050-0792, and for metallic gallium, the ratio of the highest peaks was confirmed by referring to, for example, JCPDS No. 00-005-0601. Peak intensity ratio (%) = Maximum peak intensity of metallic gallium / Maximum peak intensity of gallium nitride (Examples 1-6) Gallium nitride powder, with elements added in the proportions shown in Table 1, was used in 600g for Example 1 and 120g for Examples 2-6. These were placed in carbon molds with the thermal expansion coefficients shown in Table 2 and subjected to hot pressing. The vacuum level achieved before heating was as shown in Table 2. The firing was started under these conditions, and the temperature was increased at 200°C / h until it reached the temperature shown in Table 2. The pressure conditions were increased to the pressure shown in Table 2 during the maximum temperature holding period. The hot pressing process was performed with the temperature and pressure held for 2 hours. After cooling to approximately 50°C, the mold was removed and the sintered body was recovered. The area, X-ray peak intensity ratio, density, oxygen content, flexural strength, and average particle size (D50) of the obtained gallium nitride sintered body are shown in Table 3.

[0055] Furthermore, the results for the amount of impurities in Example 1 are shown in Table 4.

[0056] (Comparative Examples 1-3) Using the gallium nitride powder shown in Table 1, a hot press treatment was performed under the same conditions as in Example 2, except for the conditions shown in Table 2. The area, X-ray peak intensity ratio, density, oxygen content, flexural strength, and average particle size (D50) of the obtained gallium nitride-based sintered body are shown in Table 3. In Comparative Example 1, no sintered body was obtained, and therefore the area could not be measured.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] [Table 4] [Explanation of symbols]

[0061] 1 sleeve 2 dice 3. Upper punch 4. Lower punch

Claims

1. The content of one or more Group 13 elements selected from the group consisting of boron, aluminum, and indium is 0.001 atm% to 25 atm%, the oxygen content is 1 atm% or less, and the density is 3.0 g / cm³. ３ 5.4g / cm or more ３ The following are gallium nitride-based sintered bodies.

2. The gallium nitride-based sintered body according to claim 1, characterized in that the oxygen content is less than 0.3 atm%.

3. A gallium nitride-based sintered body according to claim 1 or 2, characterized in that it contains less than 10 wt ppm of total impurities of the elements Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, and Cd.

4. A gallium nitride-based sintered body according to any one of claims 1 to 3, characterized in that it contains less than 5 wt ppm of total impurities of Mg and Si.

5. A gallium nitride-based sintered body according to any one of claims 1 to 4, characterized in that it contains less than 1 wt ppm of Si impurities.

6. A gallium nitride-based sintered body according to any one of claims 1 to 5, characterized in that the maximum value of the peak attributable to gallium metal in the X-ray diffraction peak of the sintered body is 10% or less of the maximum value of the gallium nitride peak.

7. A method for producing a gallium nitride-based sintered body by a hot press method, characterized in that the raw materials are gallium nitride powder with an oxygen content of 1 atm% or less and one or more Group 13 element powders selected from the group consisting of boron, aluminum, and indium, the hot press atmosphere is under vacuum, and the difference between the linear thermal expansion coefficient of the hot press mold in the direction perpendicular to the pressurizing direction and the linear thermal expansion coefficient of the raw materials is 15% or less, as described in any one of claims 1 to 6.

8. The method for manufacturing a gallium nitride-based sintered body according to claim 7, characterized in that it is a hot press mold for obtaining a disc, wherein the number of divisions of the sleeve is three or more.

9. A sputtering target characterized by using a gallium nitride-based sintered body according to any one of claims 1 to 6.

10. The sputtering target according to claim 9, characterized in that there is no tungsten-containing layer between the target member and the bonding layer.

11. A method for producing a gallium nitride-based thin film, characterized by using the sputtering target described in claim 9 or 10.

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