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

Abstract

To manufacture a sputtering target for a gallium nitride thin film having a low oxygen content, a large area and a high strength.SOLUTION: Provided is a gallium nitride sintered body with an area of 150 cm2 or more and an oxygen content of 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 applications such as power devices in the future. Currently, gallium nitride thin films are generally manufactured by metalorganic chemical vapor deposition (MOCVD). The MOCVD method is a method of growing crystals by including the vapor of raw materials in a carrier gas, transporting it to the substrate surface, and decomposing the raw materials by reacting with the heated substrate.

[0002] Sputtering can be mentioned as a method for producing thin films other than the MOCVD method. This sputtering method physically collides positive ions such as Ar ions with a target installed at the cathode, releases the material constituting the target with the collision energy, and deposits a film with almost the same composition as the target material on a substrate installed opposite. There are a direct current sputtering method (DC sputtering method) and a radio frequency sputtering method (RF sputtering method).

[0003] Heretofore, a metal gallium target has been used as a method for forming a gallium nitride thin film by sputtering (see, for example, Patent Document 1). However, when using a metal gallium target, since the melting point of metal gallium is about 29.8 °C, it melts during sputtering, so it is difficult to obtain a gallium nitride film with highly stabilized characteristics such as crystallinity and permeability. In order to prevent this, an expensive cooling device has been attached, and a method of forming a film with low power has been proposed, but there are problems such as a decrease in productivity and an increase in the uptake of oxygen into the film.

[0004] In addition, a high-density gallium nitride sintered body has also been proposed (see, for example, Patent Document 2). According to this example, it is densified under extremely high pressure conditions of 58 Kbar (5.8 GPa). The apparatus for applying such pressure is extremely expensive and cannot produce large sintered bodies. Therefore, the sputtering target itself used in the sputtering method is extremely expensive, and it is difficult to increase its size, resulting in a problem that the film tends to be inferior in homogeneity.

[0005] In addition, as a method for reducing the oxygen content, a method has been proposed in which a gallium nitride sintered body containing oxygen is nitrided to reduce the oxygen content (see, for example, Patent Document 3). However, there is a problem that cracks may occur in the sintered body when the oxygen content is reduced by a certain amount or more.

[0006] In addition, when using the DC sputtering method, it is required that the resistivity of the sputtering target be low. As a method for this, a method has been proposed in which the resistivity of the sputtering target is reduced by infiltrating metallic gallium into a gallium nitride compact (see, for example, Patent Document 4). However, in this method, although the resistance is reduced, metallic gallium precipitates during bonding or sputtering, reacting with a solder material such as indium and causing the gallium nitride compact to peel off, resulting in a problem that stable discharge cannot be performed. As a countermeasure, a method has been proposed in which a thin film of tungsten is deposited on the back to suppress the precipitation of metallic gallium (see, for example, Patent Document 5). However, there are problems such as an increase in the target manufacturing process, which becomes complicated, and the need to use a special material such as an expensive tungsten material.

[0007] In recent years, research on film formation of gallium nitride on a large silicon substrate has been progressing, and larger sputtering targets will be required in the future, but such targets did not exist at present.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a large-sized gallium nitride-based sintered body having a low oxygen content and high strength, and a method for manufacturing the same.

Means for Solving the Problems

[0010] In view of such a background, the present inventors have conducted intensive studies. As a result, it has been found that a gallium nitride-based sintered body with a low oxygen content, high density, and large size can be produced by treating gallium nitride powder with a low oxygen content using a hot press mold with an appropriate holding time and a thermal expansion rate suitable for gallium nitride sintering, and the present invention has been completed.

[0011] That is, the aspects of the present invention are as follows. (1) A gallium nitride-based sintered body having an area of 150 cm 2 or more and an oxygen content of 1 atm% or less. (2) The gallium nitride-based sintered body according to (1), characterized in that the flexural strength is 50 MPa or more. (3) The gallium nitride-based sintered body according to (1) or (2), characterized in that the oxygen content is less than 0.3 atm%. (4) The gallium nitride-based sintered body according to any one of (1) to (3), characterized in that the total amount of impurity elements of Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, Cd is less than 10 wtppm. A gallium nitride-based sintered body according to any one of (1) to (4), characterized by containing a total amount of impurities of Mg and Si of less than 5 wtppm. A gallium nitride-based sintered body according to any one of (1) to (5), characterized by containing an amount of Si impurities of less than 1 wtppm. (7) The density is 3.0 g / cm 3 or more and 5.4 g / cm 3 or less, and is a gallium nitride-based sintered body according to any one of (1) to (6). A 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 pressing method, which uses gallium nitride powder having an oxygen content of 1 atm% or less as a raw material, and 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 material is within 15%, and is a method for producing a gallium nitride-based sintered body according to any one of (1) to (8). (10) A hot press mold for obtaining a disk, characterized in that the number of divisions of the sleeve is 3 or more, and is a method for producing a gallium nitride-based sintered body according to (9). (11) A sputtering target characterized by using a gallium nitride-based sintered body according to any one of (1) to (8). (12) A sputtering target according to (11), characterized in that there is no layer containing tungsten between the target member and the bonding layer. (13) A method for producing a gallium nitride-based thin film, characterized by using the sputtering target according to (11) or (12).

[0012] The gallium nitride-based sintered body of the present invention has an area of 150 cm 2 or more, preferably 175 cm 2 or more, and more preferably 200 cm 2The above is the case. By obtaining a large-area gallium nitride-based sintered body, it becomes possible to increase the size of the substrate on which a film can be formed. Further, it is characterized in that the oxygen content is 1 atm% or less, preferably 0.5 atm% or less, more preferably less than 0.3 atm%, still more preferably 0.2 atm% or less, and still 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 incorporation of oxygen as an impurity during film formation and obtain a film with higher crystallinity.

[0013] 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 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)).

[0014] 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 particularly preferably 70 MPa or more. By having such strength, it is possible to produce a sintered body with a large area of 150 cm 2 or more without cracking, and also when used as a sputtering target, it is possible to withstand the stress applied to the sintered body in the bonding process.

[0015] In order to be able to control the gallium nitride-based sintered body of the present invention into p-type and n-type semiconductors, it is preferable that the total amount of impurities of the elements Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, 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.

[0016] Among these impurities, the total amount of Mg and Si with a high activation rate is preferably contained in a total amount of 5 wtppm or less, more preferably 2 wtppm or less, and particularly preferably 1 wtppm. Further, the amount of Si impurities is preferably contained in 1 wtppm or less.

[0017] The gallium nitride-based sintered body of the present invention 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, particularly preferably 4.0 g / cm 3 or more and 5.4 g / cm 3 or less. The density of the gallium nitride-based sintered body described here refers to the density including open pores. Such a gallium nitride-based sintered body can be used as a sputtering target.

[0018] The gallium nitride-based sintered body of the present invention preferably has an average particle size (D50) of 1 μm or more and 150 μm or less, more preferably 5 μm or more and 100 μm or less, and particularly preferably 9 μm or more and 80 μm or less. By setting the particle size in this way, it is possible to obtain a gallium nitride-based sintered body with less oxygen content and high strength. Here, the average particle size (D50) refers to the 50% particle size in the area of primary particles observed with a scanning electron microscope or the like.

[0019] The gallium nitride-based sintered body of the present invention may contain Al, In, etc.

[0020] Next, a method for manufacturing the gallium nitride-based sintered body of the present invention will be described.

[0021] In order to obtain a large-sized sintered body with low oxygen without generating cracks in the gallium nitride-based sintered body, it is necessary to fire the gallium nitride-based sintered body without applying stress thereto.

[0022] That is, the method for manufacturing a gallium nitride-based sintered body of the present invention is a method for manufacturing a gallium nitride-based sintered body by a hot pressing method, characterized in that gallium nitride powder with an oxygen content of 1 atm% or less is used as a raw material, and 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 material is within 15%. With such a manufacturing method, it is possible to manufacture large sintered bodies of 150 cm 2 or more.

[0023] Hereinafter, the method for manufacturing a gallium nitride-based sintered body of the present invention will be described in more detail.

[0024] First, the gallium nitride powder used as a raw material needs to have an oxygen content of 1 atm% or less. More preferably, it is less than 0.5 atm%, still more preferably less than 0.3 atm%, still more preferably 0.2 atm% or less, and still more preferably 0.1 atm% or less. In order to reduce oxygen, it is necessary to suppress surface oxidation, so the specific surface area of the powder is preferably small, more preferably 0.01 m 2 / g or more and 1.5 m 2 / g or less, and even more preferably 0.01 m 2 / g or more and less than 0.8 m 2 / g. When the specific surface area is smaller than 0.01 m 2 / g, the crystal particles are too large, so the adhesion force between the particles is weak, and it is difficult to maintain the shape during the final firing. Furthermore, generally, the sinterability decreases, making firing difficult.

[0025] Also, in order to obtain a gallium nitride-based sintered body with sufficient strength as a sputtering target, the loose bulk density of the gallium nitride powder as a raw material is preferably 1.0 g / cm 3 or more and less than 3.0 g / cm 3 , more preferably 1.4 g / cm 3 or more and less than 3.0 g / cm 3 . The loose bulk density is a value obtained by filling powder in a container having a certain volume without applying a load such as vibration and dividing the volume of the filled powder by the volume of the container. 3.0 g / cm 3If the loose bulk density is too high as described above, the strength of the granules constituting the powder becomes too high, and the granules remain without being crushed during molding and sintering, resulting in a significant decrease in the strength of the gallium nitride-based sintered body.

[0026] Also, the average particle size (D50) of the gallium nitride powder used as a raw material is preferably 1 μm or more and 150 μm or less. More preferably, it is 5 μm or more and 100 μm or less, and even more preferably 9 μm or more and 80 μm or less. By using such powder, it becomes possible to produce a gallium nitride-based sintered body that achieves both high strength and low oxygenation. Particularly in the case of gallium nitride, the sintering start temperature and the decomposition temperature are close, the sintering temperature range is narrow, and there is no significant grain growth during sintering. Therefore, the distribution of primary particles before sintering has a great influence on the gallium nitride-based sintered body. Note that the particle size of the primary particles refers to the diameter of the smallest unit of particles observed by SEM, the average particle size is measured by the diameter method, and it is measured for at least 100 or more particles, and then the value at the 50% particle size is referred to. Here, the particles for measuring the average particle size are measured for gallium nitride particles. In the case of a molded product using powder within this range, since the particle size is larger and the adhesion force is smaller than before, if there are open pores to the extent that they can be immersed, the binding force between particles is relatively weak. Therefore, when Ga immersion is performed, cracks will occur due to the stress generated during immersion and the difference in thermal expansion coefficient caused by heating and sputtering.

[0027] In addition, since changes in semiconductor characteristics occur by obtaining high crystallinity of the sputtering film or adding elements, it is preferable to use gallium nitride powder as a raw material that contains as few impurities as possible. However, to make 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 powder is less than 10 wtppm, more preferably 5 wtppm or less, and particularly preferably 3 wtppm or less.

[0028] Among these impurities, the total amount of Mg and Si with a high activation rate is preferably contained in a total amount of 5 wtppm or less, more preferably 2 wtppm or less, and particularly preferably 1 wtppm. Further, the amount of Si impurities is preferably contained in 1 wtppm or less.

[0029] The firing method uses the hot press method. The hot press method is a method of promoting sintering by applying temperature while pressurizing powder. It is a firing method that assists diffusion during firing by performing uniaxial pressing during heating, enabling sintering of materials with a low diffusion coefficient and difficult sintering.

[0030] The difference in linear thermal expansion coefficient in the direction perpendicular to the pressing direction of the hot press mold and the thermal expansion coefficient of the input raw material is preferably within 15%, more preferably within 10%, and even more preferably within 5%. Even more preferably, it is +1% or less and -5% or more with respect to the thermal expansion coefficient of the raw material. Here, the linear thermal expansion coefficient of the hot press mold is the value for the mold in FIG. 1. When producing a gallium nitride-based sintered body, it is preferably 5.0×10 -6 / K or more and 7.0×10 -6 / K or less. More preferably, it is 5.0×10 -6 / K or more and 6.0×10 -6 / K or less. By using a material with a thermal expansion coefficient within that range, it becomes close to the linear thermal expansion coefficient of gallium nitride, making it possible to reduce the stress generated when it is enlarged. In the case of small sizes, even if the linear thermal expansion coefficients are different, sintering was possible because the dimensional difference was small, but it contained fine cracks and was a factor in reducing strength. When it is 150 cm 2 or more, the difference in dimensions due to the thermal expansion difference becomes large, stress is applied during firing, and cracks occur. Specifically, when it is 5.0×10 -6 / K or less, pressure sintering is performed at a predetermined temperature, and since the shrinkage of the hot press mold is smaller than the shrinkage of the gallium nitride-based sintered body during cooling, a large tensile stress is generated, causing cracks in the gallium nitride-based sintered body. Conversely, when it is 7.0×10 -6When it is at / K or higher, during cooling, the shrinkage of the hot press mold is larger than that of the gallium nitride sintered body, generating an external compressive stress, and similarly, the gallium nitride sintered body will also have a strength reduction and cracking due to crack generation.

[0031] An example of the hot press mold is shown in Fig. 1. It is preferable that the materials of the die, upper punch, lower punch, and sleeve in this figure are the same. By making the materials the same, the volume change during heating becomes the same, and it becomes possible to reduce the stress during thermal expansion and shrinkage.

[0032] The firing temperature is 1060 °C or higher and less than 1200 °C. 1060 °C or higher is necessary to promote the sintering of gallium nitride, and it must be less than 1200 °C to suppress the decomposition of gallium nitride into nitrogen and metallic gallium to a certain amount. Also, in order to improve the density of the gallium nitride sintered body, it is preferable that the pressure during firing is 30 MPa or higher and 100 MPa or lower, and more preferably 40 MPa or higher and 90 MPa or lower.

[0033] 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.

[0034] The holding time during firing is preferably 2 hours or more and 5 hours or less. More preferably, it is 3 hours or more and 4 hours or less. If it is less than 2 hours, even if the density is improved due to partial decomposition of gallium, the adhesion between particles does not progress. If firing is carried out for more than 5 hours, decomposition progresses and there are no fine particles, and even if the density is improved, the strength cannot be maintained. By firing within this range, it becomes possible to suppress decomposition while promoting sintering, and a gallium nitride sintered body with higher strength than before can be obtained.

[0035] The atmosphere in the hot press is carried out under vacuum. The degree of vacuum at the start of heating is 10 Pa or less, and 1×10 -1 Pa or less is preferable, 5×10 -2 Pa is more preferable, 1×10 -2It is particularly preferable that it is below Pa. This can reduce oxygen and oxygen elements such as water mixed from the atmosphere, and suppress oxidation during firing.

[0036] Also, when sintering under vacuum, the decomposition of gallium nitride powder gradually progresses from around 1060 °C. However, by sintering under vacuum, a part of the generated metallic gallium is discharged to the outside from the gallium nitride-based sintered body together with nitrogen which is a decomposition gas. For this reason, in the hot press mold, it is preferable that the clearance between the die and the upper punch is 0.2 mm or more. Or, it is preferable to use a material with a low density such as carbon felt between the powder and the upper and lower punches.

[0037] The hot press mold preferably includes a split sleeve 1. More preferably, the number of splits of the sleeve is preferably 3 or more, and even more preferably 4 or more. The maximum number of splits is preferably 6 or less. By splitting the sleeve in this way, it becomes easy to take out the gallium nitride-based sintered body, and it is possible to prevent cracking and chipping.

[0038] Also, in order to reduce the oxygen adsorbed on the hot press mold, it is preferable to perform a pre-firing dry run once. By doing so, it becomes possible to reduce the moisture adsorbed on the hot press apparatus and the mold before firing.

[0039] When hot pressing is carried out under the above-mentioned conditions, during sintering, metallic gallium does not act as an inhibitor and an appropriate amount is contained. Therefore, as sintering progresses, it becomes possible to obtain a gallium nitride-based sintered body with high density and suppressed oxidation. Particularly in the region of 1090 °C or higher and 1150 °C or lower, metallic gallium is partially decomposed, but since the sintering of gallium nitride also progresses, by performing pressure sintering under high vacuum, the sintering of gallium nitride progresses without being inhibited by metallic gallium, and the density is improved. When using gallium nitride as a sputtering target, it is preferable that the gallium nitride-based sintered body has conductivity, and for this purpose, it is preferable that metallic gallium is present. And since gallium alloyizes with various metals and lowers the melting point, it becomes possible to discharge the impurity elements remaining inside the sintered body together with metallic gallium by partially decomposing and depositing gallium, resulting in a gallium nitride-based sintered body that contains as few impurities as possible.

[0040] The obtained gallium nitride-based sintered body is preferably in a disk shape. By being in a disk shape, the thermal expansion and contraction become uniform in the circumferential direction, and it becomes possible to suppress the stress applied to the gallium nitride-based sintered body.

[0041] The obtained gallium nitride-based sintered body may be processed into a predetermined dimension according to the application such as a sputtering target. The processing method is not particularly limited, and a surface grinding method, a rotary grinding method, a cylindrical grinding method, or the like can be used.

[0042] The gallium nitride-based sintered body may be fixed (bonded) to a flat or cylindrical support with an adhesive such as a soldering material as needed and used as a sputtering target. For the sputtering target, it is preferable that there is no layer containing tungsten between the target member and the bonding layer. By not using an expensive metal tungsten target, the cost is reduced and the tungsten film formation process becomes unnecessary, so the productivity is improved.

[0043] In addition, for the sputtering target of the present invention, it is preferable to use a tin-based solder material, an indium-based solder material, or a zinc-based solder material as the bonding layer. Among them, indium solder is particularly preferable because of its high conductivity, high thermal conductivity, and softness and ease of deformation.

[0044] In addition, for the sputtering target of the present invention, metals such as Cu, SUS, or Ti are preferable as the support because of their high thermal conductivity and high strength. For a flat-shaped molded product as the support, it is preferable to use a flat-shaped support, and for a cylindrical-shaped molded product, it is preferable to use a cylindrical-shaped support.

[0045] Next, a method for manufacturing the sputtering target of the present invention will be described.

[0046] The sputtering target of the present invention is manufactured by bonding a gallium nitride-based sintered body to a support via a bonding layer. For the bonding layer, a tin-based solder material, an indium-based solder material, a zinc-based solder material, etc. can be used. When using an indium-based solder material, in order to improve the indium wettability to the gallium nitride-based sintered body, a layer for improving wettability may be formed between the gallium nitride-based sintered body and the solder material. The material of that layer is preferably inexpensive and has high wettability to indium. For example, it is preferable to use a nickel-based or chromium-based material. This layer is preferably formed uniformly over the entire interface with the solder material. There is no particular limitation on the method for forming such a barrier layer, and sputtering, vapor deposition, coating, etc. can be used.

Effects of the Invention

[0047] The gallium nitride-based sintered body of the present invention is large-sized, has a low oxygen content, and high strength, and is suitable for use as a sputtering target for production.

Brief Description of the Drawings

[0048]

Figure 1

Figure 2

Examples

[0049] The following is an explanation with examples, but it is not limited thereto. (Bulk density) Measurement was carried out using a powder tester PT-N type (manufactured by Hosokawa Micron). (Density of gallium nitride sintered body) The density of the gallium nitride sintered body was measured according to the method for measuring bulk density in JIS R1634. (Oxygen content) The oxygen content was measured using an oxygen / nitrogen analyzer (manufactured by LECO). (Measurement of average particle diameter (D50)) The measurement of the average particle diameter (D50) was carried out by the diameter method from the observation images by SEM for at least 3 fields of view or more, and after measuring 100 or more particles, the 50% particle diameter was taken as the average particle diameter. The measurement targets were only gallium nitride powder and gallium nitride particles in the gallium nitride sintered body. (Flexural strength) The flexural strength of the sintered body was processed to appropriate dimensions and measured according to JIS R 1601. (Impurity analysis) Impurities other than gas components were analyzed using GDMS (glow discharge mass spectrometry).

[0050] (Examples 1 to 7) 600 g of the gallium nitride powder shown in Table 1 was put into a 180 mmφ carbon mold having the thermal expansion rate of the die in Table 1 and then put into a hot press. The ultimate vacuum degree before the start of temperature rise was fired under the conditions shown in Table 2. The temperature was raised at 200 °C / h and finally increased to the temperature in Table 1. At that time, the pressure condition was increased to the pressure in Table 1 when maintaining the highest temperature, and the hot press treatment was carried out for 2 hours with the holding time of temperature and pressure. The temperature was lowered to about 50 °C in 5 hours, the mold was taken out, and the sintered body was recovered. All were 150 cm 2It was the above sintered body. The results of the density, average particle diameter (D50), oxygen content, flexural strength, and area of the obtained gallium nitride-based sintered body are shown in Table 3.

[0051] Also, the results of the impurity amounts in Examples 2, 6, and 7 are shown in Table 4.

[0052] Furthermore, the sintered body was processed, and after bonding to the backing plate, it was confirmed whether or not film formation was possible by DC or RF as a sputtering target. As a result, for all samples, it was confirmed that bonding was performed without problems and film formation was possible by DC / RF.

[0053] (Comparative Examples 1 to 4) Using the gallium nitride powder shown in Table 1, hot press treatment was performed under the same heating rate, holding time, and cooling conditions as in Example 1, except for the ultimate vacuum, firing temperature, holding time, and pressure shown in Table 2. As a result, the density, oxygen content, average particle diameter (D50), and heating test results of the obtained gallium nitride-based sintered body were as shown in Table 3. In Comparative Example 3, the fragments of the sintered body were small and the flexural test could not be performed.

[0054] Also, the results of the impurity amount in Comparative Example 4 are shown in Table 4.

[0055]

Table 1

[0056]

Table 2

[0057]

Table 3

[0058]

Table 4

Explanation of Symbols

[0059] 1 Sleeve 2 Dies 3 Upper Punch 4 Lower Punch

Claims

1. with a density of 3.5 g / cm ３ or more and 5.4 g / cm ３ or less, and in addition, an area of 150 cm ２ or more, an oxygen content of 1 atm% or less, and an average particle size of the sintered body of 5 μm or more and 150 μm or less, a gallium nitride-based sintered body characterized by that.

2. The gallium nitride-based sintered body according to claim 1, characterized in that the flexural strength is 50 MPa or more.

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

4. The gallium nitride-based sintered body according to any one of claims 1 to 3, characterized in that the total amount of impurities of the elements Si, Ge, Sn, Pb, Be, Mg, Ca, Sr, Ba, Zn, Cd is less than 10 wtppm.

5. The gallium nitride-based sintered body according to any one of claims 1 to 4, characterized in that the total amount of impurities of Mg and Si is less than 5 wtppm.

6. The gallium nitride-based sintered body according to any one of claims 1 to 5, characterized in that the amount of Si impurities is less than 1 wtppm.

7. The density is 4.0 g / cm ３ or more and 5.4 g / cm ３ or less, and the gallium nitride-based sintered body according to any one of claims 1 to 6, characterized in that it is as described above.

8. The gallium nitride-based sintered body according to any one of claims 1 to 7, characterized in that the area of the sintered body is 150 cm 2 or more.

9. A method for producing a gallium nitride-based sintered body by a hot pressing method, comprising using gallium nitride powder having an oxygen content of 1 atm% or less as a raw material, and the difference between the linear thermal expansion coefficient in a direction perpendicular to the pressing direction of the hot pressing die and the linear expansion coefficient of the raw material is within 15%. A method for producing a gallium nitride-based sintered body according to any one of claims 1 to 8.

10. A hot pressing die for obtaining a disk, characterized in that the number of divisions of the sleeve is 3 or more. A method for producing a gallium nitride-based sintered body according to claim 9.

11. A sputtering target characterized by using the gallium nitride-based sintered body according to any one of claims 1 to 8.

12. The sputtering target according to claim 11, characterized in that there is no layer containing tungsten between the target member and the bonding layer.

13. A method for producing a gallium nitride-based thin film, characterized by using the sputtering target according to claim 11 or 12.

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