Silicon nitride sintered body, wear-resistant member, substrate for semiconductor device, and method for manufacturing silicon nitride sintered body

Abstract

The present invention provides a silicon nitride sintered body which enables firing at low temperatures, while having high strength. A silicon nitride sintered body according to one embodiment of the present invention contains 0.1% by mass to 10% by mass of zirconium in terms of oxide. With respect to the XRD analysis (2θ) of an any given cross-section of the silicon nitride sintered body, if I35.3 is the maximum peak intensity detected at 35.3° ± 0.2° on the basis of α-form silicon nitride crystal grains, I27.0 is the maximum peak detected at 27.0° ± 0.2° on the basis of β-form silicon nitride crystal grains, and I33.9 is the maximum peak detected at 33.9° ± 0.2° on the basis of zirconium nitride, 0.01 ≤ I35.3 / I27.0 ≤ 0.5 and 0 ≤ I33.9 / I27.0 ≤ 1.0 are satisfied.

Description

[Technical Field]

[0001] The embodiments described below generally relate to a silicon nitride sintered body, a wear-resistant member, a substrate for a semiconductor device, and a method for manufacturing a silicon nitride sintered body. [Background technology]

[0002] Silicon nitride sintered bodies are used in a variety of fields, taking advantage of their high strength. For example, in International Publication No. 2020 / 121752 (Patent Document 1), silicon nitride sintered bodies are used in wear-resistant components such as bearing balls. In International Publication No. 2020 / 044974 (Patent Document 2), silicon nitride sintered bodies are used in substrates for semiconductor devices. According to Patent Document 1, silicon nitride sintered bodies with a three-point bending strength of 900 MPa or more were obtained. According to Patent Document 2, silicon nitride sintered bodies with a three-point bending strength of 700 MPa or more were obtained.

[0003] In the manufacturing methods described in Patent Documents 1 and 2, silicon nitride sintered bodies are produced by firing at high temperatures of about 1600 to 2000°C. Generally, electric furnaces are used to fire silicon nitride sintered bodies. In recent years, there has been an increasing demand for decarbonization. In the production of silicon nitride sintered bodies, lowering the firing temperature is considered to be an effective way to reduce carbon dioxide emissions.

[0004] For example, Japanese Patent No. 5811391 (Patent Document 3) discloses a method of using packing powder in a firing chamber. In Patent Document 3, the use of packing powder suppresses the effects of SiO gas and Mg gas emitted from the degreased body. However, the firing temperature was 1550 to 1900°C. The firing temperature in the manufacturing method described in Patent Document 3 was approximately the same as the firing temperatures described in Patent Documents 1 and 2.

[0005] For example, Japanese Patent No. 5062402 (Patent Document 4) discloses firing at 1300 to 1375°C using reaction sintering. According to the manufacturing method described in Patent Document 4, firing is carried out at a low temperature, but the strength of the obtained silicon nitride sintered body is about 140 MPa. With such low strength, it is difficult to use the silicon nitride sintered body as a wear-resistant member or a substrate for a semiconductor device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 121752 [Patent Document 2] International Publication No. 2020 / 044974 [Patent Document 3] Patent No. 5811391 [Patent Document 4] Patent No. 5062402 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, there has not been a silicon nitride sintered body that can be fired at a low temperature and has high strength in the past. The embodiments of the present invention are intended to address this issue, and have an object to provide a silicon nitride sintered body that can be fired at a low temperature and has high strength. [Means for solving the problem]

[0008] The silicon nitride sintered body according to the embodiment contains 0.1% by mass or more and 10% by mass or less of zirconium, calculated as oxide. In an XRD analysis (2θ) of an arbitrary cross section of the silicon nitride sintered body, the strongest peak intensity detected at 35.3°±0.2° due to α-type silicon nitride crystal grains is defined as I 35.3 The strongest peak detected at 27.0°±0.2° is due to β-type silicon nitride crystal grains. 27.0The strongest peak detected at 33.9° ± 0.2° is based on zirconium nitride. 33.9 When 0.01≦I 35.3 / I 27.0 ≦0.5 and 0≦I 33.9 / I 27.0 ≦1.0. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram showing a bearing ball as an example of a wear-resistant member. [Figure 2] FIG. 1 is a schematic diagram showing an example of a substrate for a semiconductor device. [Figure 3] FIG. 2 is a top view showing an example of a baking chamber. [Figure 4] FIG. 10 is a side view showing another example of the baking chamber. [Figure 5] 2 is a graph showing an example of the results of XRD analysis of the silicon nitride sintered body according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The silicon nitride sintered body according to the embodiment contains 0.1% by mass or more and 10% by mass or less of zirconium, calculated as oxide. In an XRD analysis (2θ) of an arbitrary cross section of the silicon nitride sintered body, the strongest peak intensity detected at 35.3°±0.2° due to α-type silicon nitride crystal grains is defined as I 35.3 The strongest peak detected at 27.0°±0.2° is due to β-type silicon nitride crystal grains. 27.0 The strongest peak detected at 33.9° ± 0.2° is based on zirconium nitride. 33.9 When 0.01≦I 35.3 / I 27.0 ≦0.5 and 0≦I 33.9 / I 27.0 ≦1.0.

[0011] The silicon nitride sintered body according to the embodiment contains zirconium in an amount of 0.1% by mass to 10% by mass, calculated as oxide. Zirconium is calculated as ZrO2 (ZrO2). At least a portion of the zirconium (Zr) component forms a liquid phase at around 1300°C. Therefore, zirconium has the effect of lowering the firing temperature. Therefore, in order to perform firing at low temperatures, it is effective to include zirconium in an amount of 0.1% by mass to 10% by mass, calculated as oxide. If the zirconium content is less than 0.1% by mass, calculated as oxide, the effect of adding zirconium is small. If the zirconium content exceeds 10% by mass, calculated as oxide, a large amount of zirconium nitride is formed. In addition, voids may become larger. This may result in reduced strength and insulating properties. Therefore, the zirconium content is preferably in the range of 0.1% by mass to 10% by mass, calculated as oxide, and more preferably in the range of 0.5% by mass to 6% by mass.

[0012] In addition, an arbitrary cross section of the silicon nitride sintered body according to the embodiment is subjected to XRD analysis (2θ), and in the analysis results, the strongest peak intensity detected at 35.3°±0.2° based on α-type silicon nitride crystal grains is determined as I 35.3 The strongest peak intensity detected at 27.0°±0.2° based on β-type silicon nitride crystal grains is I 27.0 The strongest peak intensity detected at 33.9°±0.2° based on zirconium nitride is I 33.9 In this case, 0.01≦I 35.3 / I 27.0 ≦0.5 and 0≦I 33.9 / I 27.0 ≦1.0.

[0013] First, we will explain the method of XRD analysis (2θ). In XRD analysis, an arbitrary cross section of a silicon nitride sintered body is used as the measurement surface. A cross section with a surface roughness Ra of 1 μm or less is used as the measurement surface. For XRD analysis, a Cu target (Cu-Kα) is used. The XRD analysis is performed with the following settings: tube voltage 40 kV, tube current 40 mA, scan speed 2.0° / min, slit (RS) 0.15 mm, and scan range (2θ) 10° to 50°. XRD analysis can perform qualitative or quantitative analysis depending on the crystalline compound. Measurements are performed using a BRUKER D8 ADVANCE or an instrument with equivalent performance.

[0014] In the obtained analysis results, the strongest peak intensity detected at 35.3°±0.2° based on α-type silicon nitride crystal grains was determined as I 35.3 The strongest peak intensity detected at 27.0°±0.2° based on β-type silicon nitride crystal grains is I 27.0 The strongest peak intensity detected at 33.9°±0.2° based on zirconium nitride is I 33.9 Let's say.

[0015] The strongest peak refers to the peak with the greatest intensity among the peaks detected within a given range. "Intensity" refers to the intensity of the peak top. Furthermore, as long as the peak top is within the given range, the base of the peak may be outside the given range. Peaks due to α-type silicon nitride crystal particles also include α-type SiAlON. Peaks due to β-type silicon nitride crystal particles also include β-type SiAlON. The presence of α-type silicon nitride crystal particles and β-type silicon nitride crystal particles in a silicon nitride sintered body can be confirmed by other XRD peaks. For example, if α-type silicon nitride crystal particles are present, peaks are detected at 35.3°±0.2° and 31.0°±0.2°. Furthermore, if β-type silicon nitride crystal particles are present, peaks are detected at 27.0°±0.2° and 33.7°±0.2°. In other words, if peaks are detected at 35.3°±0.2° and 31.0°±0.2°, the silicon nitride sintered body is determined to contain α-type silicon nitride crystal grains. Similarly, if peaks are detected at 27.0°±0.2° and 33.7°±0.2°, the silicon nitride sintered body is determined to contain β-type silicon nitride crystal grains.

[0016] If necessary, the presence or absence of zirconium nitride shall be confirmed by qualitative analysis. If zirconium nitride is not detected by qualitative or quantitative analysis, 33.9 There is no peak of I 33.9 = 0. In simple terms, if the silicon nitride sintered body has been confirmed to contain zirconium by qualitative or quantitative analysis, the peak detected at 33.9° ± 0.2° is regarded as the peak due to zirconium nitride (I 33.9 ) may be recognized.

[0017] 0.01≦I 35.3 / I 27.0The fact that the ratio ≦0.5 indicates the presence of both α-type silicon nitride crystal grains and β-type silicon nitride crystal grains. α-type silicon nitride crystal grains are round particles that tend to have an aspect ratio of less than 2. β-type silicon nitride crystal grains tend to be elongated particles with an aspect ratio of 2 or more. α-type silicon nitride crystal grains fill the gaps between the elongated β-type silicon nitride crystal grains, thereby densifying the silicon nitride sintered body and improving its strength. As a result, as will be described later, a high-strength silicon nitride sintered body can be obtained even when sintered at a low temperature of less than 1650°C.

[0018] The main component of silicon nitride sintered body is silicon nitride. 35.3 / I 27.0 is 0.5 or less, this indicates that β-type silicon nitride crystal grains are contained in the largest amount by mass in the silicon nitride sintered body. In other words, the mass ratio of β-type silicon nitride crystal grains is greater than the mass ratio of α-type silicon nitride crystal grains. Furthermore, the peaks that appear in XRD analysis are affected by the composition, crystallinity, abundance, orientation, etc. Among the peaks related to β-type silicon nitride crystal grains, the peak detected at 27.0°±0.2° is likely to be the strongest. Furthermore, among the peaks related to α-type silicon nitride crystal grains, the peak detected at 35.3°±0.2° is likely to be the strongest. The maximum peak intensity I due to the β-type silicon nitride crystal grains, which are the main component, is 27.0 The maximum peak intensity I due to α-type silicon nitride crystal grains 35.3 By controlling the ratio of the maximum peak intensities based on the other components, optimization of the texture can be achieved.

[0019] I 35.3 / I 27.0 When the ratio is in the range of 0.01 to 0.5, the α-type silicon nitride crystal grains are distributed in the gaps between the β-type silicon nitride crystal grains. The elongated β-type silicon nitride crystal grains are intricately intertwined, and the gaps are filled by the α-type silicon nitride crystal grains, leading to improved strength. 35.3 / I 27.0If the ratio is less than 0.01, the amount of α-type silicon nitride crystal grains present may be insufficient. The gaps between β-type silicon nitride crystal grains may become large, causing a decrease in the strength of the silicon nitride sintered body. Furthermore, voids may be easily formed, which may decrease the insulating properties of the silicon nitride sintered body. 35.3 / I 27.0 If the value exceeds 0.5, the number of β-type silicon nitride crystal grains will be insufficient, and the long and thin β-type silicon nitride crystal grains will not be able to form a complex intertwined structure. As a result, the strength of the silicon nitride sintered body may decrease. Therefore, I 35.3 / I 27.0 is preferably in the range of 0.01 or more and 0.5 or less, and more preferably in the range of 0.05 or more and 0.4 or less.

[0020] I 33.9 is a peak due to zirconium nitride (ZrN). When the silicon nitride sintered body according to the embodiment is subjected to XRD analysis, 0≦I 33.9 / I 27.0 ≦1.0. 33.9 / I 27.0 The fact that the ratio is 1.0 or less indicates that the amount of zirconium nitride present in the β-type silicon nitride crystal grains is suppressed. 33.9 / I 27.0 If the ratio exceeds 1.0, the strength of the silicon nitride sintered body will decrease due to the high content of zirconium nitride. In addition, since zirconium nitride is a conductive material, the insulating properties of the silicon nitride sintered body will decrease. 33.9 / I 27.0 is preferably in the range of 0 or more and 1.0 or less, and more preferably in the range of 0 or more and 0.6 or less. 33.9 / I 27.0 = 0 means that ZrN is not present or I 33.9 indicates that no detection is possible (below the detection limit).

[0021] In the XRD analysis, the strongest peak intensity detected at 28.2°±0.2° based on zirconium oxide was I 28.2 When 0.01≦I 28.2 / I 27.0It is preferable that the maximum peak intensity detected at 30.1°±0.2° based on zirconium oxide satisfies I≦0.30. 30.1 When 0.02≦I 30.1 / I 27.0 It is preferable that the ratio satisfies ≦0.30.

[0022] The presence of a peak due to zirconium oxide indicates that at least a portion of the zirconium in the silicon nitride sintered body exists as zirconium oxide. Examples of zirconium oxide include ZrO2 and composite Zr oxides. For example, when aluminum oxide is used as a sintering aid, a Zr-Al-O compound may be formed as a composite Zr oxide. Similarly, when magnesium oxide is used as a sintering aid, a Zr-Mg-O compound may be formed as a composite Zr oxide. Composite Zr oxides also include partially stabilized zirconia and stabilized zirconia. Examples of partially stabilized zirconia and stabilized zirconia include oxides in which zirconium oxide is solid-dissolved with yttrium oxide, cerium oxide, magnesium oxide, or the like.

[0023] Zirconium oxide has either a monoclinic, tetragonal, or cubic crystal structure. 28.2 or I 30.1 The detection of a zirconium oxide peak indicates that the zirconium oxide is monoclinic or tetragonal. Monoclinic is a crystal structure that is stable at room temperature. Tetragonal is a crystal structure that is stable at around 1170°C. Cubic is a crystal structure that is stable at around 2370°C. The detection of a zirconium oxide peak in XRD analysis indicates the presence of crystalline zirconium oxide. In silicon nitride sintered bodies, zirconium oxide exists in the grain boundary phase. The presence of crystalline zirconium oxide compounds in the grain boundary phase can strengthen the grain boundary phase. This can further improve the strength of the silicon nitride sintered body.

[0024] 0.01≦I 28.2 / I 27.0 ≦0.30, or 0.02≦I30.1 / I 27.0 ≦0.30 indicates that the zirconium oxide is monoclinic or tetragonal. 28.2 / I 27.0 ≦0.30 and 0.02≦I 30.1 / I 27.0 ≦0.30 may be satisfied either in both cases or only one of them. Also, when only one of them is satisfied, I 28.2 or I 30.1 It is preferable that either one of the peaks is not detected (below the detection limit). 28.2 The detection of I indicates that the zirconium oxide is monoclinic. 30.1 The detection of ≈0.01 indicates that the zirconium oxide is tetragonal.

[0025] It is mainly composed of monoclinic or tetragonal crystals, which are stable between room temperature and around 1000°C. On the other hand, cubic crystals are stable around 2370°C. The fact that it is mainly composed of monoclinic or tetragonal crystals indicates that the structure is stable when fired at low temperatures below 1650°C. If there are a lot of cubic crystals, it indicates that the heat transferred to the sintered body during the firing process is not stable. This may cause the size of the zirconium oxide and voids to be difficult to control. In other words, it is preferable that there is little or no cubic zirconium oxide. Cubic zirconium oxide can be observed using a TEM (transmission electron microscope) or other similar device. Furthermore, the presence of tetragonal zirconium oxide is preferred. As will be described later, when zirconium oxide reacts with a sintering aid such as magnesium oxide during the sintering process, the zirconium oxide becomes tetragonal and stabilizes. In other words, the presence of tetragonal zirconium oxide indicates that zirconium oxide has reacted with other sintering aids to become stable. Examples of other sintering aids include components that form partially stabilized zirconia.

[0026] For this reason, I 28.2 / I 27.0is preferably in the range of 0.01 or more and 0.30 or less, and more preferably in the range of 0.05 or more and 0.20 or less. 30.1 / I 27.0 is preferably in the range of 0.02 or more and 0.30 or less, and more preferably in the range of 0.05 or more and 0.20 or less.

[0027] In addition, in the XRD analysis, the strongest peak intensity detected at 36.7°±0.2° was 36.7 The strongest peak intensity detected at 41.9°±0.2° is I 41.9 When 0≦I 36.7 / I 27.0 ≦0.50, or 0≦I 41.9 / I 27.0 It is preferable that 0≦I≦0.50. 36.7 / I 27.0 ≦0.50 and 0≦I 41.9 / I 27.0 ≦0.50, or only one of them may be satisfied.

[0028] The peaks detected at 36.7°±0.2° and 41.9°±0.2° are due to crystalline compounds in the grain boundary phase. The peaks observed in these two ranges are due to crystalline compounds other than zirconium oxide, indicating the presence of crystalline compounds other than zirconium oxide in the grain boundary phase. These crystalline compounds include compounds containing one or more elements selected from rare earth elements, aluminum, and magnesium. Rare earth elements include yttrium and lanthanoid elements. Crystalline compounds include oxides, nitrides, or oxynitrides containing elements selected from rare earth elements, aluminum, and magnesium. They may be composite oxides, composite nitrides, or composite oxynitrides, respectively.

[0029] As will be described later, examples of sintering aids include rare earth element oxides, magnesium oxides, and aluminum oxides. Rare earth elements and magnesium dissolve in zirconium oxide to form composite Zr oxides. The composite Zr oxides form a stable phase. Aluminum and oxygen may also dissolve in silicon nitride to form sialon.

[0030] 0≦I 36.7 / I 27.0 ≦0.50 or 0≦I 41.9 / I 27.0 The fact that the ratio of I to I is ≦0.50 indicates that the sintering aid contributes to the formation of a stable phase. In other words, the amount of crystalline compounds present in the grain boundary phase is suppressed. This allows the grain boundary phase to be strengthened by the pinning effect of the zirconium oxide particles. In other words, I 36.7 / I 27.0 or I 41.9 / I 27.0 It is preferable that the ratios do not exceed 0.50. If each of them exceeds 0.50, a large amount of crystalline compounds other than zirconium oxide, which have a low pinning effect, will be present. 36.7 / I 27.0 is preferably in the range of 0 or more and 0.50 or less, and more preferably in the range of 0 or more and 0.4 or less. 41.9 / I 27.0 ≦0.50 is preferably within the range of 0 or more and 0.5 or less, and more preferably within the range of 0 or more and 0.4 or less.

[0031] Furthermore, the presence of crystalline compounds in the grain boundary phase can improve the strength and hardness of the silicon nitride sintered body. This is because the crystalline compound phase is harder than the amorphous phase. The improvement in strength and hardness leads to the improvement in wear resistance. 36.7 / I 27.0 ≦0.50, 0 41.9 / I 27.0 ≦0.50, 0 36.7 / I 27.0 ≦0.50, and 0 41.9 / I 27.0 It is preferable that one or more of the following conditions be satisfied: ≦0.50. ​​​​

[0032] Fig. 5 is a graph showing an example of the results of XRD analysis of a silicon nitride sintered body according to an embodiment. In Fig. 5, peaks marked with triangles are peaks due to α-type silicon nitride crystal particles. Peaks marked with circles are peaks due to β-type silicon nitride crystal particles. Peaks marked with squares are peaks due to monoclinic zirconium oxide. Peaks marked with diamonds are peaks due to tetragonal zirconium oxide.

[0033] The analysis results shown in Figure 5 show that I 35.3 / I 27.0 is in the range of 0.01 to 0.5, and I 33.9 / I 27.0 is in the range of 0 to 1.0. 30.1 / I 27.0 is in the range of 0.02 to 0.30, and I 28.2 / I 27.0 is in the range of 0.01 to 0.30. In the analysis results shown in Figure 5, no peaks were detected in the range of 36.7°±0.2° and the range of 41.9°±0.2°. That is, I 36.7 / I 27.0 and I 41.9 / I 27.0 is zero.

[0034] The silicon nitride sintered body preferably contains zirconium oxide particles. For example, the zirconium oxide particles are dispersed in the grain boundary phase of the silicon nitride sintered body. In a measurement area of ​​100 μm × 100 μm in any cross section, the average particle size of the zirconium oxide particles is preferably 0.05 μm or more and 2 μm or less.

[0035] As mentioned above, the zirconium oxide is preferably a crystalline compound having a predetermined XRD peak. The particle size of the zirconium oxide particles refers to the size of the zirconium oxide particles. The zirconium oxide particles may be either single crystal or polycrystalline. The average particle size of the zirconium oxide particles is preferably in the range of 0.05 μm to 2 μm. When the average particle size is in the range of 0.05 μm to 2 μm, the function of strengthening the grain boundary phase is enhanced. When the average particle size is less than 0.05 μm, the function of strengthening the grain boundary phase may be insufficient. Furthermore, when the average particle size exceeds 2 μm, the gaps between the silicon nitride crystal particles and the zirconium oxide particles may become large. Large gaps can cause voids to form. Therefore, the average particle size of the zirconium oxide particles is preferably in the range of 0.05 μm to 2 μm, more preferably in the range of 0.1 μm to 1 μm.

[0036] Furthermore, in a measurement area of ​​100 μm × 100 μm, the total area of ​​zirconium oxide particles is preferably in the range of 0.01% to 15%. By setting the area ratio to the measurement area of ​​100 μm × 100 μm at 0.01% to 15%, the zirconium oxide particles can be distributed more uniformly. The effect can be further enhanced by controlling the average particle size and area ratio of the zirconium oxide particles. More preferably, the total area of ​​the zirconium oxide particles is in the range of 0.01% to 15% in any measurement area measured on any cross section.

[0037] The method for measuring the average particle size and area ratio of zirconium oxide particles will be described below. First, a cross section of any desired size is obtained from a silicon nitride sintered body. There are no particular pretreatment requirements, as long as the cross section can be observed using a scanning electron microscope (SEM). For example, it is preferable to observe an ion-milled cross section using the SEM. For SEM observation, a cross section that has undergone XRD analysis may also be used. In this case, a magnified photograph (SEM photograph) of 1000 times or more is first taken using the SEM. A measurement area of ​​100 μm × 100 μm is randomly extracted from the magnified photograph. The particle size of each zirconium oxide particle in the measurement area is measured. The particle size is measured as the distance between the two most distant points on the outer edge of the particle. The average particle size measured in the 100 μm × 100 μm measurement area is taken as the average particle size. If zirconium oxide particles are difficult to distinguish in the SEM photograph, elemental mapping of zirconium and oxygen may be performed using energy dispersive X-ray analysis (EDX). When composite Zr oxide is included, zirconium oxide particles may be identified by also using mapping of the composite elements. For example, in EDX element mapping, the area where zirconium and oxygen overlap can be determined to be zirconium oxide particles.

[0038] The maximum diameter of voids in the silicon nitride sintered body is preferably 3 μm or less. To measure the maximum diameter of voids, an SEM photograph of any cross section of the silicon nitride sintered body is used. The SEM photograph used to measure the particle size of zirconium oxide particles may also be used to measure the maximum diameter of voids. The longest diameter of voids shown in the SEM photograph is measured. The longest diameter of voids is measured as the distance between the two most distant points on the outer edge of the void. The longest longest diameter of voids shown in a measurement area of ​​100 μm x 100 μm is defined as the maximum diameter of the void. It is more preferable that the maximum diameter of voids is 1 μm or less.

[0039] Voids can be observed by analyzing SEM photographs using image analysis software. Image J or equivalent software is used. In cross-sectional SEM photographs, contrast occurs between voids and other areas. For example, the color of voids appears darker and more intense than the color of areas other than voids. By utilizing this difference in contrast and binarizing the SEM photograph, it is possible to distinguish between voids and other areas.

[0040] The threshold value for binarization is determined by the "mode method" or "discriminant analysis binarization." If the image analysis software has a discriminant analysis binarization function, the discriminant analysis binarization method of that image analysis software is used. With discriminant analysis binarization, the threshold value is determined uniquely by the analysis software. This makes it easy to identify voids. For example, in an SEM image, the white area around a void is the boundary between the void and the silicon nitride sintered body. Therefore, the white area around a void should not be counted as a void. Also, in an SEM image, the silicon nitride sintered body is gray. Using the threshold value obtained by the "mode method" or "discriminant analysis binarization," voids can be displayed in black, and the white area around the void and the silicon nitride sintered body can be displayed in white. Using the binarized image, it is possible to distinguish between voids and other areas in the SEM image.

[0041] For example, in a measurement area of ​​100 μm×100 μm, it is preferable that the average particle size of the zirconium oxide particles is 0.05 μm to 2 μm, the total area of ​​the zirconium oxide particles is 0.01% to 15%, and the maximum diameter of the voids is 3 μm or less. More preferably, in a measurement area of ​​100 μm×100 μm, the average particle size of the zirconium oxide particles is 0.1 μm to 1 μm, the total area of ​​the zirconium oxide particles is 0.01% to 15%, and the maximum diameter of the voids is 1 μm or less.

[0042] A silicon nitride sintered body having the above-described structure can achieve a three-point bending strength of 600 MPa or more even when fired at a temperature below 1650°C. It can also achieve a dielectric strength of 13 kV / mm or more. The three-point bending strength is measured in accordance with JIS-R-1601 (2008). The dielectric strength is measured in accordance with the dielectric breakdown strength of JIS-C-2141 (1992). JIS-R-1601 corresponds to ISO 14704. JIS-C-2141 corresponds to IEC 672-2.

[0043] Such silicon nitride sintered bodies can be used in a variety of fields. The silicon nitride sintered bodies according to the embodiment can be used as wear-resistant members. FIG. 1 is a schematic diagram showing a bearing ball, which is an example of a wear-resistant member. In FIG. 1, 1 indicates a bearing ball. The bearing ball 1 is a spherical ball. The bearing ball 1 made of a silicon nitride sintered body has excellent wear resistance.

[0044] The bearing has a structure in which bearing balls 1 are arranged between an inner ring and an outer ring. Generally, the inner ring and outer ring are made of bearing steel. When a bearing rotates at high speed, electrolytic corrosion can occur. When the bearing ball 1 according to the embodiment is used, the occurrence of electrolytic corrosion can be suppressed due to the high insulating properties of the silicon nitride sintered body.

[0045] In addition, friction occurs on the surface of the bearing ball 1. The silicon nitride sintered body according to the embodiment has excellent wear resistance and therefore excellent durability. In addition to bearing balls, wear-resistant members include various roll materials for rolling mills, engine parts such as cam rollers, bearing members, compressor vanes, gas turbine blades, and friction stir welding tool members.

[0046] Furthermore, the silicon nitride sintered body according to the embodiment can be used as a substrate for a semiconductor device. Fig. 2 is a schematic diagram showing an example of a substrate for a semiconductor device. In Fig. 2, 2 is a substrate for a semiconductor device. Although Fig. 2 shows an example of a rectangular substrate, the shape of the substrate may also be circular, L-shaped, or U-shaped.

[0047] The substrate 2 for a semiconductor device is provided with a circuit section, a semiconductor element, and the like. The circuit section is a metal plate or a metallized layer, and the like. The circuit section is bonded to the substrate via a bonding layer, as necessary. A semiconductor device is obtained by mounting a semiconductor element, etc., on the circuit section. By using the silicon nitride sintered body according to the embodiment, a substrate 2 for a semiconductor device having excellent strength and insulating properties can be provided.

[0048] Next, a method for manufacturing the silicon nitride sintered body according to the embodiment will be described. The method for manufacturing the silicon nitride sintered body according to the embodiment is not particularly limited as long as it has the above-mentioned configuration. Here, a method for obtaining the silicon nitride sintered body with a good yield will be described.

[0049] A method for manufacturing a silicon nitride sintered body according to an embodiment includes a molded body preparation step, a degreased body preparation step, a degreased body placement step, a packing powder placement step, and a firing step. The molded body is prepared by mixing silicon nitride powder and at least a zirconium compound powder and molding the mixed powder. The degreased body is prepared by degreasing the molded body. The degreased body and packing powder are placed in a firing chamber. In the firing step, the degreased body is fired at less than 1650°C in the firing chamber in which the packing powder is placed.

[0050] Fig. 3 is a top view showing an example of a firing chamber. Fig. 4 is a side view showing another example of a firing chamber. In Fig. 3 and Fig. 4, reference numeral 3 denotes the firing chamber, reference numeral 4 denotes the outer wall, reference numeral 5 denotes the inner wall, reference numeral 6 denotes the packing powder, reference numeral 7 denotes the degreased body, reference numeral 8 denotes the lid, and reference numeral 9 denotes the floor. Fig. 3 and Fig. 4 are diagrams showing the inside of the firing chamber of a firing furnace.

[0051] First, a step of preparing a molded body is carried out. At least zirconium compound powder is mixed with silicon nitride powder. The silicon nitride contained in the silicon nitride powder is preferably α-type. The α-type silicon nitride rate is preferably 90% or more. The amount of oxygen contained in the silicon nitride is preferably 2 mass% or less, and the average particle size of the silicon nitride is preferably 3 μm or less. The α-type silicon nitride powder undergoes grain growth to β-type silicon nitride during the firing step. By allowing grain growth to occur, both α-type silicon nitride crystal particles and β-type silicon nitride crystal particles can be present. Note that β-type silicon nitride powder may be added as necessary.

[0052] Examples of the zirconium compound powder include zirconium oxide powder and composite Zr oxide. The proportion of zirconium oxide in the zirconium compound powder is preferably within the range of 90% by mass to 100% by mass. One or more of monoclinic zirconium oxide powder, tetragonal zirconium oxide powder, and cubic zirconium oxide powder can be used. Monoclinic zirconium oxide powder is preferably used as the raw material powder. Monoclinic crystals are stable at room temperature. Examples of composite Zr oxide include partially stabilized zirconia or stabilized zirconia. Partially stabilized zirconia or stabilized zirconia is preferably a tetragonal crystal. Tetragonal partially stabilized zirconia or stabilized zirconia is stable at room temperature. This reduces the variation in crystal change due to the heat influence during the firing process. The average particle size of the zirconium compound powder is preferably 3 μm or less. Zirconium oxide serves as a sintering aid for low-temperature firing below 1650°C. The amount of zirconium compound powder added is preferably within a range of 0.1% by mass to 10% by mass in terms of zirconium oxide, since this range makes it easier to control the XRD peaks described above.

[0053] The raw material powder may contain sintering aids other than zirconium oxide. For example, one or more elements selected from rare earth elements, aluminum, and magnesium are selected, and one or more sintering aids selected from oxides, nitrides, and oxynitrides of the selected elements are used. The oxides, nitrides, and oxynitrides may be composite oxides, composite nitrides, and composite oxynitrides, respectively. Examples of rare earth elements include yttrium and lanthanoid elements.

[0054] In particular, it is preferable to add an oxide as a sintering aid. Aluminum oxide or magnesium oxide reacts with zirconium oxide during the firing process to form a composite Zr oxide. Stabilized zirconia or partially stabilized zirconia is formed depending on the amount of magnesium dissolved. Stabilized zirconia or partially stabilized zirconia tends to become tetragonal.

[0055] Furthermore, when zirconium oxide reacts with aluminum oxide, a Zr-Al-O crystalline compound is formed. Aluminum oxide may also react with silicon nitride to form α-sialon or β-sialon. Zirconium oxide added in a monoclinic state reacts with other sintering aids to transform into a tetragonal crystal and become stable. Monoclinic zirconium oxide that does not completely react with other sintering aids may remain as is.

[0056] Rare earth elements dissolve in zirconium oxide to form a stabilizing phase. They are also effective sintering aids for improving sinterability. Rare earth elements can react with silicon nitride, aluminum, and magnesium to form crystalline compounds. Examples of such compounds include rare earth-Al-O, rare earth-Mg-O, rare earth-Al-Mg-O, rare earth-Al-ON, rare earth-Mg-ON, rare earth-Al-Mg-ON, rare earth-Si-Al-O, rare earth-Si-Mg-O, rare earth-Si-Al-Mg-O, rare earth-Si-Al-ON, rare earth-Si-Mg-ON, and rare earth-Si-Al-Mg-ON. These crystalline compounds are characterized by the presence of I. 36.7 or I 41.9 It is effective in controlling

[0057] The total amount of the compound of an element selected from rare earth elements, aluminum, and magnesium is preferably within the range of 1% by mass to 15% by mass. The compound is one or more selected from oxides, nitrides, and oxynitrides. In addition to Al2O3 and MgO, spinel (MgAl2O4) may also be used as the oxide of aluminum or magnesium.

[0058] Another example of a sintering aid is silicon oxide. Silicon oxide has the effect of lowering the eutectic temperature with zirconium oxide, which in turn lowers the firing temperature. The amount of silicon oxide added is preferably within the range of 0.1% by mass to 5% by mass. Impurity oxygen contained in silicon nitride powder may be added as silicon oxide.

[0059] Silicon nitride powder, zirconium oxide powder (including composite Zr oxide), and other sintering aid powders are mixed together. A binder and a solvent are then added to prepare a raw material powder slurry. A compact is then produced using the raw material powder slurry. A variety of methods can be used to produce the compact, including die pressing, cold isostatic pressing (CIP), and doctor blade pressing.

[0060] Next, the green body is degreased to produce a degreased body. The degreasing step is a step of removing or reducing the binder and solvent in the green body. The degreasing step is preferably carried out within a temperature range of 400°C or higher and 600°C or lower. The degreasing step can be carried out in nitrogen, air, or vacuum. By carrying out the degreasing step, a degreased body is obtained.

[0061] Next, the produced degreased body is placed in a sintering chamber. In the example shown in FIG. 4, the degreased body 7 is placed on the floor 9 in the sintering chamber. A sintering container may be used as needed. The degreased bodies 7 may be stacked on top of each other, or the sintering containers may be stacked. When stacking the degreased bodies 7, a base powder or base plate may be placed between the degreased bodies 7.

[0062] Next, a step of placing the packing powder in the sintering chamber is performed. The firing chamber 3 is a room inside the firing furnace, and is a room for firing the degreased body 7. The firing chamber 3 also has an outer wall 4 and an inner wall 5. The packing powder 6 is placed in the gap between the outer wall 4 and the inner wall 5. The space in which the degreased body 7 is placed is connected to the space between the outer wall 4 and the inner wall 5. The step of placing the packing powder 6 may be performed after the degreased body 7 is placed in the firing chamber 3, or may be performed before the degreased body 7 is placed in the firing chamber 3.

[0063] As shown in FIG. 3, the packing powder 6 is placed in the space between the outer wall 4 and the inner wall 5. This space surrounds the degreased body 7 in the horizontal direction. Furthermore, as shown in FIG. 4, a lid 8 may be placed above the degreased body 7. When the lid 8 is placed, the packing powder 6 is also placed in the space inside the lid 8. The space in which the degreased body 7 is placed is connected to the space inside the lid 8. When it is not possible to place the packing powder 6 inside the lid 8, the packing powder 6 may be placed on top of the lid 8.

[0064] In the example shown in Figures 3 and 4, the packing powder 6 is placed between the outer wall 4 and the inner wall 5. If the baking chamber 3 does not have an outer wall 4 or an inner wall 5, the packing powder 6 may be placed around the baking container containing the degreased body 7. Similarly, if the lid 8 is not provided, the packing powder 6 may be placed on top of the baking container. Note that the outer wall 4, the inner wall 5, or the baking container do not need to form a completely sealed space within the baking chamber 3. Gases emitted from the degreased body 7 may escape to the outside from the outer wall 4, the inner wall 5, or the baking container. For this reason, holes or passages through which gases can flow may be provided in the outer wall 4, the inner wall 5, or the baking container.

[0065] The packing powder 6 is preferably one or more selected from silicon nitride, silicon oxide, magnesium oxide, and talc. The silicon nitride powder may be either α-type or β-type. Talc is a composite oxide represented by MgO·SiO2. These packing powders 6 are effective for controlling partial pressure during the firing process.

[0066] Next, a firing step is performed in which the degreased body 7 is fired at a temperature below 1650°C. The firing temperature is preferably below 1550°C. Here, "low-temperature firing" refers to firing the degreased body at a temperature below 1650°C, or even below 1550°C. The pressure during firing may be normal pressure, increased pressure, or reduced pressure. The firing atmosphere may be air, a non-oxidizing atmosphere, or a vacuum. The pressure change during the firing step is preferably 0.1 MPa or less. By using the packing powder 6, the pressure change during the firing step can be kept to 0.1 MPa or less.

[0067] As mentioned above, zirconium oxide powder is an effective sintering aid for firing at temperatures below 1650°C. However, zirconium oxide easily reacts with silicon nitride to form zirconium nitride. In particular, at temperatures around 1600°C, zirconium oxide and silicon nitride easily react to form zirconium nitride.

[0068] In addition, magnesium oxide (MgO), a sintering aid, can form a liquid phase at low temperatures. During the firing process, MgO volatilizes as Mg. The volatilized Mg has strong reducing properties. When the Mg contained in the degreased body 7 volatilizes, it exerts a strong reducing effect on ZrO2. As a result, ZrO2 is reduced to form Zr. Zr reacts with nitrogen to form ZrN (zirconium nitride). Although zirconium oxide or magnesium oxide is an effective sintering aid for low-temperature firing, in the past, a large amount of ZrN was formed, which deteriorated the properties. As a result, I 33.9 / I 27.0 There were cases where the value exceeded 1.0.

[0069] ZrN is primarily formed in the surface layer of silicon nitride sintered compacts. It is possible to remove the ZrN from the surface layer by scraping off a few tens of micrometers. However, removing the surface layer increases manufacturing costs. For this reason, it is preferable to suppress the formation of ZrN during the sintering process. Furthermore, ZrN is electrically conductive. When silicon nitride sintered compacts containing ZrN are used in bearing balls, they can cause electrolytic corrosion. When silicon nitride sintered compacts containing ZrN are used as semiconductor device substrates, they can cause poor insulation. The vapor pressures of rare earth oxides and aluminum oxide are lower than those of ZrO2 and MgO. Therefore, rare earth oxides and aluminum oxide are sintering aids with low reducibility.

[0070] By using the packing powder 6, it is possible to suppress the transformation of ZrO2 into ZrN, that is, it is possible to suppress the reduction of ZrO2, and it is also possible to suppress the reduction of MgO.

[0071] The use of packing powder 6 improves the airtightness inside the firing chamber 3. Improved airtightness leads to suppression of pressure changes inside the firing chamber 3. Furthermore, by using one or more materials selected from silicon nitride, silicon oxide, magnesium oxide, and talc as packing powder 6, pressure changes during the firing process can be kept to 0.1 MPa or less. The vapor pressures of silicon nitride, silicon oxide, magnesium oxide, and talc are equal to or greater than that of zirconium oxide. Because packing powder 6 is reduced first compared to zirconium oxide, the zirconium oxide in the degreased body 7 is less likely to be nitrided.

[0072] For example, if silicon nitride powder or silicon oxide powder is used for the packing powder 6, SiO (silicon monoxide) gas is emitted from the packing powder 6. When the space inside the firing chamber 3 is filled with SiO gas emitted from the packing powder 6, the zirconium oxide in the degreased body 7 is less likely to be nitrided. If magnesium oxide or talc is used for the packing powder 6, magnesium is emitted from the packing powder 6 during firing. The magnesium pressure in the space inside the firing chamber 3 increases. This suppresses the volatilization of magnesium from the degreased body 7 and the reduction of ZrO2 due to the volatilization of Mg from the degreased body 7. As a result, the XRD peaks of zirconium oxide and zirconium nitride can be controlled. Furthermore, the reduction of MgO, which is added as a sintering aid, can be suppressed. Experiments conducted by the present inventors confirmed that Mg present in the space inside the firing chamber 3 does not easily reduce ZrO2 contained in the degreased body 7. That is, it was confirmed that even when the partial pressure of Mg in the space inside the firing chamber 3 is high, by suppressing the volatilization of Mg from the degreased body 7, the reduction reaction of ZrO2 can be effectively suppressed.

[0073] Furthermore, if a large amount of degreased body 7 is fired at one time to increase mass productivity, gas will be generated from the large amount of degreased body 7 at the same time. As a result, the pressure change during the firing process will be large. By venting gas from the pack powder 6 and suppressing the amount of gas generated from the degreased body 7, the pressure change during the firing process can be controlled to 0.1 MPa or less.

[0074] The firing temperature is preferably less than 1650°C, more preferably less than 1550°C. As mentioned above, α-type silicon nitride powder is used as the raw material powder. The α-type silicon nitride powder undergoes grain growth into β-type silicon nitride crystal particles during the firing process. By lowering the firing temperature to less than 1650°C, the grain growth into β-type silicon nitride crystal particles can be suppressed. This makes it possible to control the ratio of α-type silicon nitride crystal particles to β-type silicon nitride crystal particles. As a result, I 35.3 / I 27.0 Furthermore, controlling the grain growth of β-type silicon nitride crystal grains also leads to controlling the distribution of zirconium oxide grains. Furthermore, the maximum diameter of voids in the silicon nitride sintered body can be reduced to 1 μm or less.

[0075] For example, when the firing process is carried out at 1650°C using the same firing furnace (batch-type electric furnace), it is possible to reduce electricity consumption by approximately 15% compared to when the firing process is carried out at 1800°C. Low-temperature firing also allows firing at normal pressure. Since pressure control is no longer necessary, costs can be reduced. The lifespan of setters, heat insulating materials, etc. inside the firing furnace can also be extended. Silicon nitride sintered bodies, which allow low-temperature firing, are effective in reducing electricity consumption and costs.

[0076] The manufacturing method described above allows for the production of silicon nitride sintered bodies with a relative density of 98% or more. The relative density can be determined by the Archimedes method. Even with low-temperature sintering at temperatures below 1650°C, a relative density of 98% or more can be achieved. Furthermore, silicon nitride sintered bodies with a three-point bending strength of 600 MPa or more can be produced. Silicon nitride sintered bodies with a dielectric strength of 13 kV / mm or more can be produced. While there is no particular lower limit for the sintering temperature, 1200°C or higher is preferred. At temperatures below 1200°C, the silicon nitride sintered body may not be sufficiently densified, making it impossible to reduce the maximum void diameter to 1 μm or less. For this reason, the sintering temperature is preferably between 1200°C and 1650°C, and more preferably between 1300°C and 1550°C.

[0077] The obtained silicon nitride sintered body may be subjected to an additional heat treatment if necessary. Examples of additional heat treatments include hot isostatic pressing (HIP) and a warping correction process. By performing HIP treatment, a silicon nitride sintered body with a relative density of 99% or more can be obtained. Furthermore, by performing HIP treatment, the three-point bending strength of the silicon nitride sintered body can be increased to 900 MPa or more. The heat treatment temperature in the additional heat treatment step is optional. The additional heat treatment step is preferably performed at a temperature of less than 1650°C, but may be performed at 1650°C or higher.

[0078] (Example) (Examples 1 to 14, Comparative Examples 1 to 4) Alpha-type silicon nitride powder was prepared as the raw material powder. The average particle size of the alpha-type silicon nitride powder was 3 μm or less, the impurity oxygen content was 1.3 mass%, and the alpha phase ratio was 90% or more. Zirconium oxide powder (including composite Zr oxide), yttrium oxide powder, aluminum oxide powder, magnesium oxide powder, spinel powder, and silicon dioxide powder were prepared as sintering aid powders. The average particle size of the sintering aid powder was 3 μm or less. The silicon nitride powder and sintering aid powder were mixed in the mixing ratios shown in Table 1. The mixing ratios are based on 100 mass% of the total silicon nitride powder and sintering aid powder. Regarding the crystal structure of the zirconium oxide powder (composite Zr oxide) listed in Table 1, "monoclinic" indicates that monoclinic zirconium oxide powder was used. "tetragonal" indicates that tetragonal yttrium-stabilized zirconia powder was used. The sintering aid spinel powder was MgAl2O4.

[0079] [Table 1]

[0080] In the examples, at least one of silicon nitride powder, zirconium oxide powder, yttrium oxide powder, aluminum oxide powder, magnesium oxide powder, spinel powder, and silicon dioxide powder is blended in a predetermined amount. In Comparative Example 1, no zirconium oxide is added. In Comparative Example 2, a large amount of zirconium oxide powder is added. In Comparative Example 3, as described below, firing is performed without using a packing powder. In Comparative Example 4, as described below, firing is performed at 1800°C.

[0081] The raw material powders were mixed, a binder and a solvent were added, and a raw material powder slurry was produced using a ball mill. Example 9 was produced using a planetary mill at 400 rpm for 1 hour. The slurry was dried and powdered, and a compact was produced using a mold press. The compact was then subjected to a debinding process at a temperature between 400°C and 600°C.

[0082] Next, the degreased body was placed in the firing chamber. In Examples 1 to 14, Comparative Examples 1 and 2, and Comparative Example 4, packing powder was placed between the outer and inner walls of the firing chamber. Furthermore, packing powder was placed on the lid of the firing chamber. On the other hand, in Comparative Example 3, no packing powder was placed. The firing process was carried out under the conditions shown in Table 2.

[0083] [Table 2]

[0084] Silicon nitride sintered bodies were produced by the above steps. In Examples 1 to 14 and Comparative Examples 3 and 4, the zirconium content, calculated as oxide, was within the range of 0.1% by mass or more and 10% by mass or less. In Comparative Example 1, the silicon nitride sintered body did not contain zirconium. In Comparative Example 2, the zirconium content in the silicon nitride sintered body, calculated as oxide, exceeded 10% by mass. In Comparative Example 3, no packing powder was used, so the pressure change during the firing process exceeded 0.1 MPa. In Comparative Example 4, the firing temperature was high, so the pressure change during the firing process exceeded 0.1 MPa even though a packing powder was used.

[0085] Next, an arbitrary cross section of each silicon nitride sintered body was subjected to XRD analysis. The conditions and method of XRD analysis were as described above. The relationship between the peak intensities observed in the XRD analysis is shown in Table 3.

[0086] [Table 3]

[0087] As can be seen from Table 3, for the silicon nitride sintered body according to the example, I 35.3 / I 27.0 and I 33.9 / I 27.0 was within the predetermined range. In addition, in the silicon nitride sintered body according to the example, zirconium was present as zirconium oxide. Note that a peak ratio of 0 indicates that the molecular peak intensity is below the detection limit.

[0088] In contrast, in Comparative Example 2, I 33.9 / I 27.0 The value exceeded 1.0. In Comparative Example 2, a large amount of zirconium oxide powder was added, resulting in the formation of a large amount of ZrN. In Comparative Example 3, a large amount of ZrN was formed, resulting in the absence of a packing powder. In Comparative Example 4, a high firing temperature resulted in the formation of silicon nitride and zirconium oxide inside the sintered body, and a large amount of zirconium nitride on the surface of the sintered body.

[0089] Next, an arbitrary cross section of the silicon nitride sintered body was photographed using an SEM. Using the obtained SEM photograph, the average particle size and total area of ​​zirconium oxide particles were measured. The maximum diameter of voids was also measured. Detailed conditions were as described above. The total area of ​​zirconium oxide particles was confirmed to be within the range of 0.01% to 15% in an arbitrary 100 μm x 100 μm measurement area. The relative density of the silicon nitride sintered body was also measured. The relative density was measured using the Archimedes method. The results are shown in Table 4.

[0090] [Table 4]

[0091] In the silicon nitride sintered body according to the example, the average particle size and total area of ​​the zirconium oxide particles were within the specified range. The maximum diameter of the voids was also 3 μm or less. The relative density was also 96% or more, and the sintered body was sufficiently densified.

[0092] On the other hand, in Comparative Example 1, since zirconium oxide was not added, voids were large and the relative density was low. In Comparative Example 2, since a large amount of zirconium oxide was added, voids were large and the relative density was low. In Comparative Example 3, since no packing powder was used, a large amount of zirconium nitride was formed, and as will be described later, the insulation properties were low. In Comparative Example 4, since the firing temperature was high, a large amount of zirconium nitride was formed. In other words, it was found that the compositions of the examples are not suitable for high-temperature firing.

[0093] Next, the three-point bending strength and dielectric strength of each silicon nitride sintered body were measured. The measurement conditions were as described above. The dielectric strength was measured to see if it was 14 kV / mm or more. The results are shown in Table 5.

[0094] [Table 5]

[0095] As can be seen from Table 5, the silicon nitride sintered bodies according to the examples had excellent three-point bending strength and dielectric strength. Excellent properties were obtained even when fired at a low temperature of less than 1650°C. In the comparative examples, the silicon nitride sintered bodies were not densified, and therefore had low strength and insulation properties.

[0096] Next, the silicon nitride sintered bodies according to Examples 1 to 3 were subjected to HIP treatment. After the HIP treatment, the relative density and three-point bending strength were measured. The results are shown in Table 6.

[0097] [Table 6]

[0098] As can be seen from Table 6, the HIP treatment promoted densification and improved the strength of the silicon nitride sintered body.

[0099] Furthermore, according to the embodiment, the firing step can be carried out at a low temperature of less than 1650° C., thereby reducing energy consumption.

[0100] Embodiments of the invention include the following features. (Feature 1) A silicon nitride sintered body containing 0.1% by mass or more and 10% by mass or less of zirconium in terms of oxide, In the XRD analysis (2θ) of an arbitrary cross section, the strongest peak intensity detected at 35.3°±0.2° based on α-type silicon nitride crystal grains is defined as I 35.3 The strongest peak detected at 27.0°±0.2° is due to β-type silicon nitride crystal grains. 27.0 The strongest peak detected at 33.9° ± 0.2° is based on zirconium nitride. 33.9 In this case, 0.01≦I 35.3 / I 27.0 ≦0.5, and 0≦I 33.9 / I 27.0 ≦1.0, Silicon nitride sintered body that satisfies the above requirements. (Feature 2) In the XRD analysis (2θ), the strongest peak detected at 30.1°±0.2° due to zirconium oxide was determined as I 30.1 In this case, 0.02≦I 30.1 / I 27.0 ≦0.30 2. The silicon nitride sintered body according to Feature 1, which satisfies the above. (Feature 3) In the XRD analysis (2θ), the strongest peak detected at 28.2°±0.2° due to zirconium oxide was determined as I 28.2 In this case, 0.01≦I 28.2 / I 27.0 ≦0.30 3. The silicon nitride sintered body according to Feature 2, which satisfies the above. (Feature 4) In the XRD analysis (2θ), the strongest peak detected at 36.7°±0.2° was determined as I 36.7 The strongest peak detected at 41.9°±0.2° is I 41.9 In this case, 0≦I 36.7 / I 27.0 ≤ 0.50, or 0≦I 41.9 / I 27.0 ≦0.50 4. The silicon nitride sintered body according to any one of Features 1 to 3, which satisfies the above. (Feature 5) Contains zirconium oxide particles, The average particle size of the oxide particles is 0.05 μm or more and 2 μm or less, 5. The silicon nitride sintered body according to any one of Features 1 to 4, wherein the total area of ​​the oxide particles is within a range of 0.01% to 15% in a 100 μm×100 μm measurement area of ​​any cross section. (Feature 6) 6. The silicon nitride sintered body according to any one of Features 1 to 5, wherein the maximum diameter of voids is 3 μm or less in a measurement area of ​​100 μm×100 μm in any cross section. (Feature 7) 7. A wear-resistant member using the silicon nitride sintered body according to any one of Features 1 to 6. (Feature 8) A substrate for a semiconductor device using the silicon nitride sintered body according to any one of Features 1 to 6. (Feature 9) a step of mixing silicon nitride powder and at least zirconium compound powder and molding the mixture to prepare a molded body; a step of degreasing the compact to produce a degreased body; placing the degreased body in a baking chamber; placing a packing powder within the firing chamber; a firing step of firing the degreased body at a temperature lower than 1650°C in the firing chamber in which the packing powder is placed; A method for producing a silicon nitride sintered body comprising the steps of: (Feature 10) 10. The method for producing a silicon nitride sintered body according to Feature 9, wherein the firing temperature in the firing step is less than 1550°C. (Feature 11) The pressure change during the firing process is 0.1 MPa or less. 10 1. A method for producing the silicon nitride sintered body according to claim 1. (Feature 12) 12. The method for producing a silicon nitride sintered body according to any one of claims 9 to 11, wherein the packing powder is at least one selected from the group consisting of silicon nitride, silicon oxide, magnesium oxide, and talc.

[0101] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0102] 1...Bearing ball 2...Substrate for semiconductor device 3...Baking chamber 4...Exterior wall 5…Inner wall 6...Filling powder 7...Degreased body 8…Lid part 9…Floor part

Claims

1. A silicon nitride sintered body containing zirconium oxide particles, the zirconium content being 0.1% by mass or more and 10% by mass or less in terms of oxide, In the XRD analysis (2θ) of an arbitrary cross section, the strongest peak intensity detected at 35.3°±0.2° based on α-type silicon nitride crystal grains was determined as I ３５．３ The strongest peak intensity detected at 27.0°±0.2° based on β-type silicon nitride crystal grains is defined as I ２７．０ The strongest peak intensity detected at 33.9°±0.2° based on zirconium nitride is I ３３．９ In this case, 0.01≦I ３５．３ / I ２７．０ ≦0.5, and 0≦I ３３．９ / I ２７．０ ≦1.0、 Fulfilling The average particle size of the oxide particles is 0.05 μm or more and 2 μm or less, A silicon nitride sintered body, in which in a 100 μm×100 μm measurement area of ​​any cross section, the total area of ​​the oxide particles is in the range of 0.01% to 15% and the maximum diameter of voids is 3 μm or less.

2. In the XRD analysis (2θ), the strongest peak intensity detected at 30.1°±0.2° based on zirconium oxide was determined as I ３０．１ In this case, 0.02≦I ３０．１ / I ２７．０ ≦0.30 The silicon nitride sintered body according to claim 1, which satisfies the above.

3. In the XRD analysis (2θ), the strongest peak intensity detected at 28.2°±0.2° due to zirconium oxide was determined as I ２８．２ In this case, 0.01≦I ２８．２ / I ２７．０ ≦0.30 The silicon nitride sintered body according to claim 2, which satisfies the above.

4. In the XRD analysis (2θ), the strongest peak intensity detected at 36.7°±0.2° was determined as I ３６．７ , the strongest peak intensity detected at 41.9°±0.2° is I ４１．９ In this case, 0≦I ３６．７ / I ２７．０ ≦0.50, or 0≦I ４１．９ / I ２７．０ ≦0.50 4. The silicon nitride sintered body according to claim 1, which satisfies the following:

5. A silicon nitride sintered body described in any one of claims 1 to 3, having a relative density of 98% or more.

6. A silicon nitride sintered body as described in claim 4, having a relative density of 98% or more.

7. A wear-resistant member using the silicon nitride sintered body according to any one of claims 1 to 3.

8. A wear-resistant member using the silicon nitride sintered body according to claim 5.

9. A wear-resistant member using the silicon nitride sintered body according to claim 6.

10. A substrate for a semiconductor device, which uses the silicon nitride sintered body according to any one of claims 1 to 3.

11. A substrate for a semiconductor device, which uses the silicon nitride sintered body according to claim 5.

12. A substrate for a semiconductor device, which uses the silicon nitride sintered body according to claim 6.

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