TW201714857A - Silicon nitride sintered body and method for producing same - Google Patents

Abstract

A silicon nitride sintered body that contains silicon nitride, yttrium, magnesium and oxygen, and also contains a plurality of silicon nitride crystal grains and a grain boundary phase which constitutes a portion thereof other than the silicon nitride crystal grains, wherein: the grain boundary phase contains a Y20N4Si12O48 crystal phase, or the Y20N4Si12O48 crystal phase and a Y2Si3N3O4 crystal phase; and the ratio of the X-ray diffraction peak intensity of the (211) plane of the Y2Si3N3O4 crystal phase to the X-ray diffraction peak intensity of the (112) plane of the Y20N4Si12O48 crystal phase is 0 to 3.0, inclusive. As a result, the present invention provides a silicon nitride sintered body that exhibits high thermal conductivity and is favorable for use as a semiconductor device substrate or the like.

Description

Tantalum nitride sintered body and method of producing the same

The present invention relates to a tantalum nitride sintered body having a high thermal conductivity which can be suitably used for a substrate or the like of a semiconductor device, and a method for producing the same.

In the case of suppressing the leakage current of the power module, it is possible to greatly improve the insulation and the operation even when the power is increased and the capacitance is increased. The power module disclosed is a power module which is provided on a surface of a tantalum nitride sintered body having a thickness of 1.5 mm or less without a fine crack of 1 μm or more in width and a submicron crack having a width of less than 1 μm per unit. A current leakage value when an alternating current voltage of 1.5 kV to 100 Hz is applied between the front and back surfaces of the tantalum nitride sintered body at a temperature of 25 ° C and a humidity of 70% in an area of 100 μm ² and 0 to 2 sintered tantalum nitride sintered bodies. On a tantalum nitride ceramic substrate having a thermal conductivity of 50 W ‧ m ^-1 ‧ K ^-1 or more, a three-point bending strength of 500 MPa or more, and a residual carbon content of 500 ppm or less, a metal circuit board is provided and a semiconductor element is mounted thereon. In the above-described tantalum nitride ceramic substrate, Mg is contained in an amount of 0.5 to 3.0% by mass in terms of MgO.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-280494

Power module disclosed in Japanese Laid-Open Patent Publication No. 2009-280494 (Patent Document 1) In order to obtain a high thermal conductivity, a slow cooling rate of 100 ° C or less per hour after sintering is required, so that there is a problem of low productivity. Further, a tantalum nitride ceramic substrate having a further high thermal conductivity is strongly desired.

Accordingly, an object of the present invention is to provide a tantalum nitride sintered body having a high thermal conductivity which can be suitably used for a substrate or the like of a semiconductor device, and a method for producing the same.

A tantalum nitride sintered body which is one aspect of the present invention is a sintered body of tantalum nitride containing tantalum nitride, niobium, magnesium and oxygen. The tantalum nitride sintered body includes a plurality of tantalum nitride crystal grains and a grain boundary phase as a portion other than the tantalum nitride crystal grains. The grain boundary phase includes a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase. The intensity of the X-ray diffraction peak due to the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase relative to the intensity of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase The ratio is 0 or more and 3.0 or less.

A method for producing a tantalum nitride sintered body according to another aspect of the present invention is the method for producing a tantalum nitride sintered body according to the aspect of the invention, wherein the β-crystal phase ratio of the tantalum nitride powder of the raw material is 5% by mass or more And 40% by mass or less.

According to the above, a tantalum nitride sintered body having a high thermal conductivity which can be suitably used for a substrate or the like of a semiconductor device can be provided.

[Description of Embodiments of the Present Invention]

A tantalum nitride sintered body according to an embodiment of the present invention is a tantalum nitride sintered body containing tantalum nitride, niobium, magnesium, and oxygen. The tantalum nitride sintered body includes a plurality of tantalum nitride crystal grains and a grain boundary phase as a portion other than the tantalum nitride crystal grains. The grain boundary phase includes a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase. The intensity of the X-ray diffraction peak due to the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase relative to the intensity of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase The ratio is O or more and 3.0 or less. The tantalum nitride sintered body of the present embodiment has a high thermal conductivity.

The plurality of tantalum nitride crystal grains contained in the tantalum nitride sintered body of the present embodiment may have a short-axis particle diameter of 1.7 μm or more and 10.5 μm or less, and the long-axis particle diameter may be relative to the short-axis particle diameter. The aspect ratio is set to 2.0 or more and 7.7 or less. The tantalum nitride sintered body has a high thermal conductivity.

In the tantalum nitride sintered body of the present embodiment, the content ratio of various impurity metal elements other than cerium, lanthanum and magnesium can be made 0.5% by mass or less. The tantalum nitride sintered body has a high thermal conductivity.

In the tantalum nitride sintered body of the present embodiment, the magnesium oxide crystal phase can be prevented from being present. The tantalum nitride sintered body has a relatively high relative density and a high thermal conductivity.

In the tantalum nitride sintered body of the present embodiment, the thermal conductivity can be set to 95 W‧ m ^-1 ‧ K ^-1 or more. The tantalum nitride sintered body has a high thermal conductivity.

In the tantalum nitride sintered body of the present embodiment, the area ratio of the grain boundary phase to the tantalum nitride crystal grains in any specific cross section of the tantalum nitride sintered body can be made 10% or less. The tantalum nitride sintered body has a high thermal conductivity.

The method for producing a tantalum nitride sintered body according to another embodiment of the present invention is the method for producing a tantalum nitride sintered body according to the embodiment, wherein the β-crystal phase ratio of the raw material tantalum nitride powder is 5% by mass or more. 40% by mass or less. According to the method for producing a tantalum nitride sintered body of the present embodiment, a tantalum nitride sintered body having a high thermal conductivity can be obtained.

[Details of the embodiment of the present invention]

(cerium nitride sintered body)

The tantalum nitride sintered body of the present embodiment is a tantalum nitride sintered body containing tantalum nitride (Si ₃ N ₄ ), yttrium (Y), magnesium (Mg), and oxygen (O). The tantalum nitride sintered body includes a plurality of crystal grains of tantalum nitride (Si ₃ N ₄ ) and a grain boundary phase which is a portion other than the Si ₃ N ₄ grains. The grain boundary phase contains a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase. By Y ₂ Si ₃ N ₃ O ₄ crystalline phase of (211) plane of the X-ray intensity caused by diffraction peaks I _Y2 of the X-ray diffraction due to the relative Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of the (112) plane due to the the peak intensity ratio I _Y20 I _Y2 / I _Y20 is 0 or more and 3.0 or less. The tantalum nitride sintered body of the present embodiment has a high thermal conductivity.

The tantalum nitride sintered body of the present embodiment contains Si ₃ N ₄ , Y, Mg, and O. The progress of sintering of the crystal grains of Si ₃ N ₄ , that is, densification and particle growth, is carried out by initially forming a capillary agglomeration by liquid phase formation of a sintering aid, and then as a Si ₃ N ₄ crystal grain of α-Si ₃ The N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase are dissolved in the liquid phase of the sintering aid containing Y and Mg, and are further precipitated from the sintering aid liquid phase in the form of a β-Si ₃ N ₄ crystal phase. At the time of the reprecipitation, if the impurities remain in the Si ₃ N ₄ crystal grains, the thermal conductivity of the obtained tantalum nitride sintered body is lowered. Since Y traps solid solution oxygen, it can suppress the solid solution of oxygen (O) to Si ₃ N ₄ crystal grains, and therefore, the crystal structure of the β-Si ₃ N ₄ crystal phase is not disturbed. Further, since Y is not dissolved in the β-Si ₃ N ₄ crystal phase, the crystal structure of the β-Si ₃ N ₄ crystal phase is not disturbed. The disorder of the crystal structure hinders the conduction of heat, and therefore, disorder is not expected in order to increase the thermal conductivity. Therefore, the sintering aid containing Y is effective for improving the thermal conductivity. Mg can lower the melting point of an oxide such as SiO _x or an oxynitride such as SiON formed on the surface of Si ₃ N ₄ crystal grains, and thus is an essential element for liquid phase sintering of Si ₃ N ₄ crystal grains.

The above-mentioned Si ₃ N ₄ , Y and Mg are respectively contained in a raw material of cerium nitride (Si ₃ N ₄ ) powder, yttrium oxide (Y ₂ O ₃ ) powder and magnesium oxide (MgO) powder, in order to The mixed powder is formed, degreased, and then sintered to be present. When the total amount of the inorganic raw material powder as the raw material is 100 parts by mass, for example, the Si ₃ N ₄ powder is 87.6 parts by mass or more and 98.5 parts by mass or less, and the Y ₂ O ₃ powder is 1.0 part by mass or more and 10.4 parts by mass. The amount of the MgO powder is 0.5 parts by mass or more and 2.0 parts by mass or less.

In the tantalum nitride sintered body of the present embodiment, when the mass of the whole is 100% by mass, the content ratio of Y is preferably 0.5% by mass or more and 10.4% by mass or less. Here, Y The content ratio is more preferably 0.6% by mass or more, and still more preferably 2.2% by mass or more. Further, the content of Y is more preferably 4.0% by mass or less, still more preferably 2.6% by mass or less. The content of Mg is preferably 0.05% by mass or more and 0.7% by mass or less. Here, the content of Mg is more preferably 0.07% by mass or more, and still more preferably 0.15% by mass or more. Further, the content of Mg is more preferably 0.5% by mass or less, still more preferably 0.24% by mass or less. The content of O is preferably 0.3% by mass or more and 2.0% by mass or less. Here, the content of O is more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. Further, the content of O is more preferably 1.5% by mass or less, still more preferably 1.1% by mass or less.

Here, when the content ratio of Y is less than 0.5% by mass, the content ratio of Mg is less than 0.05% by mass, or the content ratio of O is less than 0.3% by mass, the content ratio of these elements acting as a sintering aid Since it is insufficient, it is difficult to obtain a sufficient relative density as a sintered body because sintering does not progress. When the content of Y is more than 10.4% by mass, the content of Mg is more than 0.7% by mass, or the content of O is more than 2.0% by mass, the sintered body is increased due to an increase in the amount of grain boundary phase having a low thermal conductivity. The tendency of the thermal conductivity to become lower.

In the qualitative analysis of Si ₃ N ₄ , X-ray diffraction was performed using X'Pert PRO manufactured by PANalytical Co., Ltd. or an equivalent device, and then PDXL 2 or equivalent soft body of the integrated powder X-ray analysis software manufactured by Rigaku Corporation was used. In the qualitative analysis of the Si ₃ N ₄ , a sintered body having a surface of 500 μm × 500 μm or more was used. Here, Si ₃ N ₄ is considered to be at least any crystal form of the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase, and thus is utilized as an international diffraction data center as a powder X-ray diffraction database. Any of the crystal forms was identified by the powder diffraction data file, i.e., ICDD PDF-4+2014 No. 26191 and No. 79798. The X-ray diffraction system was scanned by the θ-2θ method using Cu-Kα rays excited at 45 kV and 40 mA, and was carried out at a step width of 0.03° and a cumulative time of 1 second.

Qualitative analysis and quantitative analysis of Y and Mg were performed by inductively coupled plasma-luminescence spectroscopic analysis (ICP-AES) using an ICPS-8100 or equivalent device manufactured by SHIMADZU. The order of the ICP-AES is exemplified below. As a pretreatment, it will be sintered The body is crushed by a mortar and mortar made of agate. In the analysis of Y and Mg, qualitative analysis is carried out according to the wavelength of light emitted when the element excited by the solution of the pretreated powder is sprayed into the Ar plasma and returned to the substrate state, and according to The intensity of the light is quantitatively analyzed. Thereby, the mass % of Y and Mg present in the sintered body is quantified. The pretreatment powder solution was prepared by adding 0.1 g of the pretreated powder together with an alkaline solvent containing 2 g of calcium carbonate and 0.5 g of boron oxide to a platinum crucible and melting at 1000 ° C. The melt was collected in an acidic solution containing 20 ml of 35 mass% hydrochloric acid and 20 ml of ion-exchanged water at 60 ° C, and then diluted to 200 ml with ion-exchanged water.

The qualitative analysis and quantitative analysis of O is carried out by an inert gas melting-non-dispersive infrared absorption (NDIR) method using EMGA650W manufactured by HORIBA Corporation or an equivalent device. The order of the analysis by the inert gas melting-NDIR method is exemplified below. As a pretreatment, the sintered body was pulverized by a mortar and mortar made of agate. In the analysis of O, qualitative analysis is carried out based on the fact that 0.03 g of the pretreated powder is charged into carbon crucible and the CO gas and/or CO ₂ gas generated when the temperature is raised to 1600 ° C at a high frequency is above the background level, and according to these The amount of gas produced was quantitatively analyzed. Thereby, the mass % of O present in the sintered body is quantified.

The tantalum nitride sintered body of the present embodiment includes a plurality of crystal grains of tantalum nitride (Si ₃ N ₄ ) and a grain boundary phase which is a portion other than the Si ₃ N ₄ crystal grains. The grain boundary phase contains a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase. By Y ₂ Si ₃ N ₃ O ₄ crystalline phase of (211) plane of the X-ray intensity caused by diffraction peaks I _Y2 of the X-ray diffraction due to the relative Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of the (112) plane due to the the peak intensity ratio I _Y20 I _Y2 / I _Y20 is 0 or more and 3.0 or less. The Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and the Y ₂ Si ₃ N ₃ O ₄ crystal phase are formed to capture solid solution oxygen in the Si ₃ N ₄ grains. The oxygen (O) dissolved in the Si ₃ N ₄ grains is responsible for lowering the thermal conductivity of the sintered body, but if yttrium oxide (Y ₂ O ₃ ) is added as a sintering aid, it is in the Si ₃ N ₄ crystal. In the case of the grain, O is stabilized in the form of a crystal phase such as Y ₂₀ N ₄ Si ₁₂ O ₄₈ or Y ₂ Si ₃ N ₃ O ₄ in the grain boundary phase, so that it can be lowered and lowered. The amount of solid solution oxygen in the Si ₃ N ₄ grains due to the thermal conductivity of the sintered body. In particular, in the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, the number of O atoms trapped by one Y atom is large, so that the grain boundary which is one of the causes of the decrease in the thermal conductivity of the sintered body is not increased. The amount of phase reduces the amount of solid solution oxygen in the Si ₃ N ₄ grains.

About the presence of silicon nitride sintered bodies Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and Y ₂ Si ₃ N ₃ O ₄ crystalline phase ratio, without increasing it by the amount of the grain boundary phase under reduced Si ₃ X-ray winding caused by the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase from the viewpoint of obtaining the amount of solid solution oxygen in the N ₄ crystal grains to obtain a tantalum nitride sintered body having a high thermal conductivity emission peak of intensity I _Y2 with respect to the result Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of the (112) than I _Y2 strength caused by the surface of the X-ray diffraction peaks of I _Y20 is / I _Y20 is 0 or more and 3.0 or less, preferably 0.1 or more, more preferably 0.5 or more, still more preferably 2.5 or less, further preferably 2.0 or less.

The X-ray diffraction system uses an X'Pert PRO manufactured by PANalytical Co., Ltd. or an equivalent device, and the X-ray system uses Cu-Kα rays having excitation conditions of 45 kV and 40 mA, and the scanning system utilizes the θ-2θ method. The step width is 0.03° and the cumulative time is 1 second. The analysis of the X-ray diffraction peak is performed using PDXL2 or equivalent soft body of the integrated powder X-ray analysis software manufactured by Rigaku Corporation. The X-ray diffraction peak caused by the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase refers to a peak existing on the low angle side where 2θ is 30 to 33°, and is used as a powder X-ray diffraction. The database was identified by ICDD PDF-4+2014 No.00-030-1462. The X-ray diffraction peak caused by the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase refers to a peak existing on the high angle side where 2θ is 30 to 33°, and the powder of the International Diffraction Data Center is used. The diffracted data file is identified by ICDD PDF-4+2014 No. 01-076-0724.

In order to increase the existence ratio of the above Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, it is preferable to use the high temperature of 1950 ° C or higher for sintering in the production of the tantalum nitride sintered body of the present embodiment, and the sintering temperature is The cooling rate of 100 ° C / min or more is rapidly cooled to 1000 ° C. By sintering at a high temperature of 1950 ° C or higher, the diffusion rate of Y is increased, so that the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is formed more efficiently, and the rapid cooling is performed at a cooling rate of 100 ° C/min or more. The metamorphosis of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase to the Y ₂ Si ₃ N ₃ O ₄ crystal phase is suppressed. That is, the discharge of O from the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase can be suppressed, and the re-solid solution of O from the grain boundary with respect to the Si ₃ N ₄ crystal grains can be suppressed. The cooling rate is more preferably 120 ° C / min or more.

Further, in the tantalum nitride (Si ₃ N ₄ ) powder of the raw material used in the production of the tantalum nitride sintered body of the present embodiment, the β crystal phase ratio (β-Si ₃ N ₄ crystal phase relative to α-Si _{3 )} When the mass percentage of the total of the N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase is 5% by mass or more and 40% by mass or less, the surface of the Y ₂ Si ₃ N ₃ O ₄ crystal phase is caused by the (211) plane. The ratio of the intensity of the X-ray diffraction peak to the intensity of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is 0 or more and 3.0 or less to obtain a nitride having a higher thermal conductivity. From the viewpoint of the sintered body, it is preferable. From this viewpoint, the β crystal phase ratio is more preferably 10% by mass or more, and still more preferably 20% by mass or more. Further, the β crystal phase ratio is more preferably 35% by mass or less, still more preferably 32% by mass or less. Here, the β crystal phase ratio is calculated by X-ray diffraction to identify the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase in the Si ₃ N ₄ powder of the raw material as described above. Thereafter, it was carried out using the RIR (reference intensity ratio) method.

Therefore, in the Si ₃ N ₄ powder of the raw material, it is preferred to use not only the yttrium imide decomposition powder previously used as the structural material but the direct nitriding powder or the mixed powder of the direct nitriding powder and the yttrium imide decomposition powder. . The β-crystal phase fraction in the direct nitriding powder is 20% by mass or more and 60% by mass or less, and the β-crystal phase fraction in the yttrium imide-decomposed powder is 1% by mass or less. Therefore, the niobium nitride powder of the raw material can be adjusted to have a β crystal phase ratio of 5 mass% or more and 40 mass% or less by adjusting the content of the direct nitride powder.

The quantitative analysis of the crystalline phase of the Si ₃ N ₄ powder of the raw material is carried out by X-ray diffraction using X'Pert PRO manufactured by PANalytical Co., Ltd. or an equivalent device, and PDXL2 of the integrated powder X-ray analysis software manufactured by Rigaku Co., Ltd. or the like is used. software. In the identification of the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase, No. 26191 and No. 79798 of ICDD PDF-4+2014, which is used as a powder X-ray diffraction database, respectively, by RIR (Reference intensity ratio) method is used for quantification. The X-ray diffraction system was scanned by the θ-2θ method using Cu-Kα rays excited at 45 kV and 40 mA, and was carried out at a step width of 0.03° and a cumulative time of 1 second.

Although the influence of the β crystal phase ratio of the raw material on the crystal phase of the grain boundary phase is unknown, it is currently considered as follows. Since the crystal phase of the grain boundary phase is in close contact with the Si ₃ N ₄ particles, it is affected by the Si ₃ N ₄ crystal system. The sintering of the Si ₃ N ₄ crystal grains is self-sintered by the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase in the liquid phase of the sintering aid and in the form of a β-Si ₃ N ₄ crystal phase. The re-precipitation of the auxiliary liquid phase proceeds. In this case the presence of the same, β crystalline silicon nitride powder in the raw materials and the fraction becomes β-Si ₃ N ₄ crystal phase from liquid phase sintering aid nucleation time of re-precipitated β-Si ₃ N ₄ crystal phase of rates. Therefore, at the time of sintering, the ratio of the α-Si ₃ N ₄ crystal phase to the β-Si ₃ N ₄ crystal phase changes. That different ratios β-Si ₃ N ₄ powder when the Si raw materials in the ₃ N ₄ crystal phase of, the β-Si under the respective time of sintering ₃ N ₄ crystal different ratios phases, the thus formed into a grain boundary phase of Crystallization is also different.

In view of having a high thermal conductivity, the tantalum nitride sintered body of the present embodiment preferably has a short-axis particle diameter of Si ₃ N ₄ crystal grains in the sintered body of 1.7 μm or more and 10.5 μm or less. The ratio of the major axis diameter of the Si ₃ N ₄ crystal grains to the short-axis particle diameter, that is, the aspect ratio is preferably 2.0 or more and 7.7 or less. In view of further improving the thermal conductivity of the tantalum nitride sintered body, the short-axis particle diameter of the Si ₃ N ₄ crystal grains in the sintered body is more preferably 1.8 μm or more, and further preferably 2.2 μm or more. Further, from the viewpoint of further improving the thermal conductivity of the tantalum nitride sintered body, the ratio of the major axis diameter of the Si ₃ N ₄ crystal grains to the short-axis particle diameter, that is, the aspect ratio is more preferably 2.5 or more, and further preferably It is 3.0 or more, more preferably 7.5 or less, further preferably 7.0 or less.

The analysis of the short-axis particle diameter and the aspect ratio (ratio of the long-axis particle diameter to the short-axis particle diameter) of the Si ₃ N ₄ crystal by SEM (scanning electron microscope)-EBSD (electron backscatter diffraction) Determination. The SEM observation was performed using a SUPRA 35 VP or equivalent device manufactured by Carl Zeiss, Inc., and the electron backscatter diffraction system utilized OIM 5.2 manufactured by TSL Solutions or an equivalent device.

The order of the SEM-EBSD measurement is exemplified below. As a pretreatment, a surface grinding disc was used and a surface of the sintered body was ground to a depth of 500 μm or more using a diamond grindstone (a diamond grinding grindstone #400 manufactured by Allied Materials Co., Ltd.), and then subjected to a lapping machine manufactured by KEMET Co., Ltd. finishing. First, the sintered body was ground to a depth of 10 μm or more using a copper platen and a diamond grindstone having a particle diameter of 3 μm, and then the sintered body was ground by a tin platen and a diamond grindstone having a particle diameter of 0.5 μm. The surface is ground to a depth of 3 μm or more. At this time, both of the polishing were carried out under the conditions of a rotation speed of 50 rpm and a load of 0.2 MPa. The surface processing can also be the same processing as described above.

The EBSD measurement system has a measurement area of 30 μm × 100 μm, and the measurement conditions are, for example, an acceleration voltage of 15 kV, a working distance of 15 mm, a step size of 0.1 μm, an adjacent 8×8, and an accumulated time of 0.01 second. Thereby, an IQ (image quality) map is obtained. Within the obtained IQ image (field area: 30 μm × 100 μm), the Si ₃ N ₄ grain having the largest area is selected to the fifth largest Si ₃ N ₄ grain, and the five Si ₃ N ₄ grains are selected. The short-axis particle diameter, the major-axis particle diameter, and the aspect ratio were calculated using Image J software (open source code developed by Wayne Rasband; the same applies hereinafter) and equivalent software. In the Image J software, the selected Si ₃ N ₄ crystal grains were approximately elliptical, and the short-axis particle diameter and the long-axis grain diameter were calculated. The aspect ratio is calculated by dividing the major axis particle diameter by the minor axis particle diameter. The range of the short-axis particle diameters shown in Tables 1 to 3 is the range of the minimum and maximum values of the five Si ₃ N ₄ crystal grains. Further, the aspect ratios shown in Tables 1 to 3 are the average values of the five Si ₃ N ₄ crystal grains. The short-axis particle diameter of the Si ₃ N ₄ crystal grains in the tantalum nitride sintered body of the present embodiment is preferably 1.7 μm or more and 10.5 μm or less, more preferably 1.8 μm or more, and still more preferably 2.2 μm or more. The minimum and maximum values of the five Si ₃ N ₄ grains are included in the range. Further, the ratio of the major axis diameter of the Si ₃ N ₄ crystal grain to the minor axis particle diameter, that is, the aspect ratio is preferably 2.0 or more and 7.7 or less, more preferably 2.5 or more, still more preferably 3.0 or more, and further preferably 7.5 or less, and more preferably 7.0 or less means that the average value of the five Si ₃ N ₄ crystal grains is included in the range.

When the minimum value of the short-axis grain size of the Si ₃ N ₄ grains in the plurality of sintered bodies (specifically, the five selected in the above) is less than 1.7 μm, the particle growth of the Si ₃ N ₄ grains If it is insufficient, the removal of impurities in the Si ₃ N ₄ particles as a raw material is insufficient, so that it is difficult to increase the thermal conductivity of the sintered body. When the maximum value of the short-axis particle diameter of the plurality of Si ₃ N ₄ grains is more than 10.5 μm, a long-time sintering time is required in order to obtain high heat conduction, so that the productivity is lowered and the thermal conductivity of the sintered body is lowered. . Further, when the aspect ratio is more than 7.7, the increase in the sintered density is insufficient, and the thermal conductivity tends to decrease. When the aspect ratio is less than 2.0, it is difficult to increase the thermal conductivity of the sintered body.

Further, the tantalum nitride sintered body of the present embodiment can obtain a tantalum nitride having a high thermal conductivity by setting the β crystal phase ratio of the Si ₃ N ₄ powder of the raw material to 5 mass% or more and 40 mass% or less. Sintered body. The sintering of the Si ₃ N ₄ crystal grains is carried out by dissolving the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase in the liquid phase of the sintering aid, and crystallizing the phase with β-Si ₃ N ₄ The form is re-precipitated from the liquid phase of the sintering aid. Therefore, the β-Si ₃ N ₄ crystal phase in the Si ₃ N ₄ powder of the raw material becomes the core when the β-Si ₃ N ₄ crystal phase is reprecipitated from the liquid phase of the sintering aid. I.e., β crystalline silicon nitride powder in the raw materials and the fraction becomes β-Si ₃ N ₄ crystal nuclei of the same phase when the liquid phase sintering aid reprecipitation from β-Si ₃ N ₄ of the presence of crystalline phases.

Therefore, if the β crystal phase fraction of the Si ₃ N ₄ powder of the raw material is less than 5% by mass, the particles of the β-Si ₃ N ₄ crystal phase which becomes the core of the re-precipitation are reduced, and the β-Si ₃ N _{4 of} the small amount of the particles Since the crystal phase preferentially grows in one direction (abnormal particle growth), the aspect ratio becomes excessively large, and the sintered density of the sintered body becomes low, and it is also difficult to increase the thermal conductivity of the sintered body. When the β crystal phase ratio of the Si ₃ N ₄ powder of the raw material is more than 40% by mass, the particles of the β-Si ₃ N ₄ crystal phase which becomes the core of re-precipitation increase, and the β-Si ₃ N ₄ crystal of the large amount of particles When the particles grow at the same time, the particle growth becomes insufficient, so that the aspect ratio becomes excessively small, and it is difficult to increase the thermal conductivity of the sintered body.

In the tantalum nitride sintered body of the present embodiment, the content of various impurity metal elements other than cerium (Si), yttrium (Y), and magnesium (Mg) is preferably 0.5 from the viewpoint of improving thermal conductivity. The mass% or less is more preferably 0.3% by mass or less, and further preferably 0.1% by mass or less. As described above, the solid solution of the elemental metal and/or the compound of the impurity metal element to the Si ₃ N ₄ crystal grain causes a decrease in the thermal conductivity of the sintered body. For example, the elemental and/or compound of Al is readily soluble in the Si ₃ N ₄ grains, resulting in a Sialon with lower thermal conductivity (Si _6-Z Al _Z O _Z N _8-Z , where Z is A rational number of 0 to 4) is a hindrance factor for high thermal conductivity of the sintered body.

The quantitative analysis of the impurity metal elements in the raw material powder and the sintered body was carried out by luminescence spectroscopic analysis (AES) using ICP (Inductively Coupled Plasma) as a light source. The ICP-AES apparatus uses, for example, ICPS-8100 manufactured by SHIMADZU Co., Ltd. or an equivalent apparatus. The order of ICP-AES is exemplified below. As a pretreatment, the sintered body was first pulverized using a mortar made of agate and a mortar. Thereafter, 0.1 g of the pulverized powder of the sintered body was placed in a platinum crucible together with an alkaline solvent containing 2 g of calcium carbonate and 0.5 g of boron oxide, and melted at 1000 ° C to contain the melt. 20 ml of an acidic solution of 35 mass% hydrochloric acid and 20 ml of ion-exchanged water was recovered at 60 ° C, and then diluted to 200 ml with ion-exchanged water. The light emitted by the metal element excited by the sample solution obtained in this manner in a mist form and introduced into the Ar plasma is subjected to spectrometry, and quantitative analysis is performed based on the intensity thereof.

The tantalum nitride sintered body of the present embodiment preferably has no magnesium oxide (MgO) crystal phase. The tantalum nitride sintered body can have a relatively high relative density and a high thermal conductivity because the amount of the grain boundary phase which lowers the thermal conductivity can be lowered by evaporating magnesium oxide (MgO) during sintering.

X-ray diffraction is performed for the identification of the MgO crystal phase in the tantalum nitride sintered body. The X-ray diffraction system uses an X'Pert PRO manufactured by PANalytical Co., Ltd. or an equivalent device. The X-ray system uses Cu-Kα rays having excitation conditions of 45 kV and 40 mA, and the scanning system utilizes the θ-2θ method. The step width is 0.03° and the cumulative time is 1 second. The analysis of the X-ray diffraction peak is performed using PDXL2 or equivalent soft body of the integrated powder X-ray analysis software manufactured by Rigaku Corporation. When the X-ray diffraction peak due to the (200) plane of MgO is not observed between 22.5 and 43.1 °, or when it is not distinguishable from the background, it is considered that the MgO crystal phase is not present in the Si ₃ N ₄ sintered body.

In the tantalum nitride sintered body of the present embodiment, the thermal conductivity is preferably 95 W ‧ m ^-1 ‧ K ^-1 or more, more preferably 100 W ‧ m ^-1 ‧ K ^-1 or more, and still more preferably 110 W ‧ m ^-1 ‧K ^-1 or more. The tantalum nitride sintered system has high heat dissipation characteristics and can be used as a heat dissipation substrate of a semiconductor device. When the thermal conductivity of the Si ₃ N ₄ sintered body is less than 95 W·m ^-1 ‧ K ^-1 , the semiconductor device on the upper portion of the heat dissipation substrate cannot sufficiently dissipate heat, and therefore the semiconductor device is broken due to the heat resistance temperature or higher, and the semiconductor device cannot be sufficiently obtained. Device characteristics.

In order to derive the thermal conductivity of the Si ₃ N ₄ sintered body, thermal diffusivity, specific gravity, and specific heat are required. The thermal diffusivity is measured by an optical alternating current method (scanning laser AC (Alternative Current) method, Angtrom method) or laser flash measurement method. The optical communication method uses a Laser-PIT device manufactured by ULVAC or an equivalent device. The measurement sequence using the device is exemplified below. The laser light is moved along the longitudinal direction of the sample by irradiating a strip of laser light having a uniform illumination frequency of 2.5 to 10 Hz, and the AC temperature response is measured by a thermocouple mounted on the back side of the sample, and responds according to the temperature. The thermal diffusivity was calculated from the attenuation rate corresponding to the amplitude and position. The sample shape has a width of 2.5 to 5 mm, a length of 30 mm, and a thickness of 0.5 mm or less, and the laser heating surface is blackened by a graphite spray only. The thermocouple and the sample system are followed by a silver paste. The laser flash measurement method uses a TC-7000 manufactured by ULVAC Corporation or an equivalent device. The thermal diffusivity was calculated based on the temperature history curve of the back surface of the test piece when the surface of the test piece was irradiated with a laser pulse (refer to JIS-R1611:2010). The sample shape was 10 mm in diameter and 3 to 6 mm in thickness, and the whole sample was blackened by graphite spray. The specific gravity was determined using the Archimedes method and the specific heat was 0.68 J ‧ g ^-1 ‧ K ^-1 .

In the tantalum nitride sintered body of the present embodiment, the portion other than the Si ₃ N ₄ crystal grains in any specific cross section of the tantalum nitride sintered body is the grain boundary phase with respect to the tantalum nitride (Si ₃ N ₄ ) crystal grain. The area ratio is preferably 10% or less, more preferably 9% or less, and still more preferably 6% or less. The tantalum nitride sintered body has a high thermal conductivity because the ratio of the area of the grain boundary phase to the Si ₃ N ₄ crystal grains is 10% or less.

The tantalum nitride sintered body is formed of Si ₃ N ₄ crystal grains and other grain boundary phases. The area S of the Si ₃ N ₄ crystal grain of any specific cross section of the tantalum nitride sintered body, and the area S _B of the grain boundary phase (the grain boundary phase exists between the Si ₃ N ₄ crystal grains) and the crystal The analysis of the area ratio of the boundary phase with respect to the Si ₃ N ₄ crystal grains of 100 × S _B /S was measured by SEM (Scanning Electron Microscope) - EBSD (electron beam backscatter diffraction). The SEM observation was performed using a SUPRA 35 VP or equivalent device manufactured by Carl Zeiss, Inc., and the electron backscatter diffraction system utilized OIM 5.2 manufactured by TSL Solutions or an equivalent device.

The order of the SEM-EBSD measurement is exemplified below. As a pretreatment, a surface grinding disc was used and a surface of the sintered body was ground to a depth of 500 μm or more using a diamond grindstone (a diamond grinding grindstone #400 manufactured by Allied Materials Co., Ltd.), and then subjected to a lapping machine manufactured by KEMET Co., Ltd. finishing. First, the sintered body was ground from the surface to a depth of 10 μm or more using a copper platen and a diamond grindstone having a particle diameter of 3 μm, and then the sintered body was ground from the sintered body using a tin platen and a diamond grindstone having a particle diameter of 0.5 μm. The surface is ground to a depth of 3 μm or more. At this time, both of the polishing were carried out under the conditions of a rotation speed of 50 rpm and a load of 0.2 MPa. The surface processing can also be processed in the same manner as described above.

In the EBSD measurement, the measurement area is set to 30 μm × 100 μm, and the measurement conditions are, for example, an acceleration voltage of 15 kV, a working distance of 15 mm, a step size of 0.1 μm, an adjacent 8×8, and an accumulated time of 0.01 second, thereby obtaining IQ ( Image quality) map. The obtained IQ image (viewing area: 30 μm × 100 μm) was binarized by Image J software, and the white tantalum sintered body was white as the Si ₃ N ₄ crystal grain, and the black dark portion was formed. As the grain boundary phase, the area S of the Si ₃ N ₄ crystal grain and the area S _{B of the} grain boundary phase were calculated, and the area ratio of the grain boundary phase to the Si ₃ N ₄ crystal grain was calculated as 100 × S _B /S. Further, the IQ image used for the calculation of the area ratio of the grain boundary phase to the Si ₃ N ₄ crystal grain may be shorter than the above-mentioned Si ₃ N ₄ crystal grain from the viewpoint of suppressing the analysis cost. The IQ image used for the calculation of the axial particle diameter and the aspect ratio is the same.

(Manufacturing method of tantalum nitride sintered body)

The method for producing the tantalum nitride sintered body of the present embodiment is not particularly limited, and includes, for example, preparing a raw material containing raw materials of tantalum nitride (Si ₃ N ₄ ), yttrium (Y), magnesium (Mg), and oxygen (O). In the preparation step, a raw material is molded to obtain a molding step of the molded body, and a sintering step of sintering the formed body to obtain a sintered body. According to the method for producing a tantalum nitride sintered body of the present embodiment, a tantalum nitride sintered body having a high thermal conductivity can be obtained with high productivity.

The raw material preparation step is not particularly limited. For example, as a raw material containing Si ₃ N ₄ , Y, Mg, and O, a tantalum nitride (Si ₃ N ₄ ) powder, a yttrium oxide (Y ₂ O ₃ ) powder, and a magnesium oxide can be prepared. (MgO) a mixed powder of powder. The mixing ratio of the tantalum nitride (Si ₃ N ₄ ) powder, the yttrium oxide (Y ₂ O ₃ ) powder, and the magnesium oxide (MgO) powder is not particularly limited, but the cause of the niobium nitride sintered body is Y ₂ Si _{3 .} The ratio of the intensity of the X-ray diffraction peak caused by the (211) plane of the N ₃ O ₄ crystal phase to the intensity of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is 0 or more In the case of obtaining a tantalum nitride sintered body having a high thermal conductivity, it is preferable that the Si ₃ N ₄ powder is 87.6 parts by mass in terms of 100 parts by mass of all the inorganic raw material powders as a raw material. The amount of the Y ₂ O ₃ powder is 1.0 part by mass or more and 10.4 parts by mass or less, and the MgO powder is 0.5 part by mass or more and 2.0 parts by mass or less.

The average particle diameter of the Si ₃ N ₄ powder used as a raw material is 0.8 μm or more and 1.3 μm or less, the average particle diameter of the Y ₂ O ₃ powder is 1.3 μm or more and 1.8 μm or less, and the average particle diameter of the MgO powder is 1.0 μm or more. Further, when it is 1.5 μm or less, it is preferable from the viewpoint of increasing the sintered density of the sintered body and improving the thermal conductivity. The average particle diameter of the Si ₃ N ₄ powder, the Y ₂ O ₃ powder, and the MgO powder was measured by Microtrac MT3300EX manufactured by MicrotracBEL Co., Ltd. or an equivalent device.

Here, the Si ₃ N ₄ powder is not particularly limited, but the intensity of the X-ray diffraction peak due to the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase in the tantalum nitride sintered body is relative to the Y The ratio of the intensity of the X-ray diffraction peak caused by the (112) plane of the ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is 0 or more and 3.0 or less, and from the viewpoint of obtaining a tantalum nitride sintered body having a high thermal conductivity, It is a direct nitriding powder obtained by direct nitriding of ruthenium monomer by ammonia or nitrogen in an active atmosphere such as high temperature or plasma, or by reacting ruthenium halide with ammonia. A bismuth imine compound such as sulfimine (Si(NH) ₂ ), decylamine (Si(NH ₂ ) ₄ ), or quinone imine (Si ₂ N ₂ NH) is thermally decomposed to obtain A mixed powder of an amine decomposed powder and a direct nitrided powder.

In addition, the β crystallinity of the Si ₃ N ₄ powder of the raw material is not particularly limited, but from the viewpoint of obtaining a tantalum nitride sintered body having a high thermal conductivity, it is preferably 5% by mass or more and 40% by mass. the following. The sintering of the Si ₃ N ₄ grains is carried out by dissolving the α-Si ₃ N ₄ crystal phase and the β-Si ₃ N ₄ crystal phase in the liquid phase of the sintering aid, and crystallizing the phase with β-Si ₃ N ₄ The form is re-precipitated from the liquid phase of the sintering aid. Therefore, the β-Si ₃ N ₄ crystal phase in the Si ₃ N ₄ powder of the raw material becomes a core when the β-Si ₃ N ₄ crystal phase is reprecipitated from the liquid phase of the sintering aid. I.e., β crystalline silicon nitride powder in the raw materials and the fraction becomes β-Si ₃ N ₄ crystal nuclei of the same phase when the liquid phase sintering aid reprecipitation from β-Si ₃ N ₄ of the presence of crystalline phases. Therefore, if the β crystal phase ratio of the Si ₃ N ₄ powder of the raw material is less than 5% by mass, the particles of the β-Si ₃ N ₄ crystal phase which becomes the core of the re-precipitation are reduced, and the β-Si ₃ N4 crystal of the small amount of the particles Since the aspect ratio is preferentially grown (abnormal particle growth), the aspect ratio becomes excessively large, and the sintered density of the sintered body is lowered, and it is also difficult to increase the thermal conductivity of the sintered body. When the β crystal phase ratio of the Si ₃ N ₄ powder of the raw material is more than 40% by mass, the number of particles of the β-Si ₃ N ₄ crystal phase which becomes the core of the re-precipitation increases, and the β-Si ₃ N ₄ crystal of the plurality of particles is the same. When the growth occurs, the particle growth becomes insufficient, so that the aspect ratio becomes excessively small, and it is difficult to increase the thermal conductivity of the sintered body.

Further, the impurity element contained in the Si ₃ N ₄ powder is not particularly limited, but from the viewpoint of obtaining a tantalum nitride sintered body having a high thermal conductivity, it is preferable that Al, Ca, Fe, and Mg are respectively 0.01. The mass% or less, and O is 1.0% by mass or less. Identification of impurity elements was performed using ICP-AES. Specifically, qualitative analysis is performed according to the wavelength of light emitted when the impurity element excited by the solution of the Si ₃ N ₄ powder is sprayed into the Ar plasma and returned to the substrate state, and according to The intensity of the light is quantitatively analyzed. Thereby, the mass % of Al, Ca, Fe, and Mg present in the Si ₃ N ₄ powder was obtained. A more specific order will be exemplified below. A solution of Si ₃ N ₄ powder was prepared by adding 0.1 g of the pretreated Si ₃ N ₄ powder together with an alkaline solvent containing 2 g of calcium carbonate and 0.5 g of boron oxide in a platinum crucible. The mixture was poured into a platinum crucible and melted at 1000 ° C, and the melt was recovered in an acidic solution containing 20 ml of 35 mass % hydrochloric acid and 20 ml of ion-exchanged water at 60 ° C, and then diluted with ion-exchanged water. Up to 200ml. Even if the intensity of light is equal to the background, it is also recorded as 0.01% by mass or less. Regarding O, qualitative analysis is carried out based on the presence of background gas or higher of CO gas and/or CO ₂ gas generated by charging 0.03 g of raw material tantalum nitride powder into carbon crucible and raising the temperature to 1600 ° C at a high frequency, and according to the gases The amount of production was quantitatively analyzed. Thereby, the mass % of O present in the sintered body is quantified.

As for the raw material, a sintering aid, an organic binder, a deagglomerating agent-dispersing agent, a dispersion medium, and the like may be further added from the viewpoint of producing a suitable sintered body.

Examples of the sintering aid include magnesium oxide (MgO) powder, yttrium oxide (Y ₂ O ₃ ) powder, and the like. Examples of the organic binder include polyvinyl butyral (PVB) and the like. Examples of the deagglomerating agent-dispersing agent include a polycarboxylic acid compound, a polyethyleneimine compound, and a polyoxyethylene derivative. Examples of the dispersion medium include alcohols such as ethanol, water, and the like. Further, the method of mixing the above raw materials is not particularly limited, and examples thereof include ball mill mixing, ultrasonic mixing, and the like. In the ball mill mixing, a ball and a container made of tantalum nitride are used from the viewpoint of preventing the incorporation of an impurity element such as iron (Fe). Further, a raw material slurry having a volume of 0.25 to 0.5 times the volume of the mixing container of the ball mill to be used is filled. The raw material slurry was homogenized by mixing for 30 minutes or more. In the ultrasonic mixing, the raw material slurry is homogenized by mixing for 10 minutes or more. Whether or not there is granulation.

The molding method in the molding step is not particularly limited, and examples thereof include a uniaxial pressure molding method and a CIP (cold pressure equalization) method. The molding pressure is preferably 0.5 tf/cm ² (weight ton/cm ² ) or more, and more preferably 0.8 tf/cm ² or more from the viewpoint of forming a high-density molded body.

The sintering step is not particularly limited, but from the viewpoint of obtaining a preferred sintered body, it is preferred to include a degreasing step, a sintering step, and a cooling step. The degreasing step is not particularly limited. For example, the degreasing can be carried out under an atmospheric atmospheric flow atmosphere of 800 ° C or lower until the residual carbon amount is 1000 ppm or less. The carbon content in the degreased body can be determined by using an infrared detector to discharge CO and/or CO ₂ by burning 0.1 g of the pulverized powder of the degreased body in a stream of oxygen at 1000 ° C for 1 minute. The amount is tested. The measurement was performed using CS-230 or equivalent equipment manufactured by LECO Corporation. The sintering step is not particularly limited. For example, sintering can be carried out under high pressure and high temperature conditions of 0.5 MPa or more and 1950 ° C or more in a nitrogen atmosphere. In the cooling substep, the intensity I _Y2 of the X-ray diffraction peak due to the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase in the tantalum nitride sintered body is relative to the Y ₂₀ N ₄ Si ₁₂ causing the intensity of O ₄₈ crystal phase of (112) plane of the X-ray diffraction peak ratio I _Y20 I _Y2 / I _Y20 is 0 or more and 3.0 or less silicon nitride sintered body is obtained the high thermal conductivity silicon nitride sintered From the viewpoint of the body, the cooling rate is preferably 100 ° C / min or more, more preferably 120 ° C / min or more. By the cooling step having a cooling rate of preferably 100 ° C / min or more, more preferably 120 ° C / min or more, a tantalum nitride sintered body having a high thermal conductivity can be obtained with high productivity.

According to the method for producing a tantalum nitride sintered body of the present embodiment, even if the holding time at the highest temperature during sintering is not extended, the holding time is 4 hours or longer, and even if it is 30 hours or shorter, more preferably 17 hours or shorter. A sintered tantalum nitride having a thermal conductivity of 95 W‧ m ^-1 ‧ K ^-1 or more can also be obtained.

[Examples]

1. Preparation of raw materials

With respect to Examples 1 to 13 and Comparative Examples 1 to 7, zinc nitride (Si ₃ N ₄ ) powder, yttrium oxide (Y ₂ O ₃ ) powder, and magnesium oxide of the types and mass parts shown in Tables 1 to 3 were prepared. (MgO) powder, a mixed slurry of PVB (polyvinyl butyral) as a mass part shown in Tables 1 to 3 as an organic binder, and a mass part of ethanol shown in Tables 1 to 3 as a dispersion medium. Further, in Examples 5 to 7, 1 part by mass of CELUNA F-216 and 3 parts by mass of CELUNA E503, which are manufactured as a de-agglomerating agent-dispersing agent, were added to CELUNA F-216. Here, the mass part of each raw material means all of the inorganic raw material powders which are raw materials, namely, tantalum nitride (Si ₃ N ₄ ) powder, yttrium oxide (Y ₂ O ₃ ) powder, and magnesium oxide (MgO) powder. The total mass parts are set to 100 parts by mass of each raw material.

The average particle diameter of the Si ₃ N ₄ powder is 0.8 μm or more and 1.3 μm or less, and the average particle diameter of the Y ₂ O ₃ powder is 1.3 μm or more and 1.8 μm or less, and the average particle diameter of the MgO powder is 1.0 μm or more and 1.5 μm or less. . The average particle diameter of the powders was measured by a laser diffraction scattering method using a Microtrac MT3300EX manufactured by MicrotracBEL. Further, the β crystal phase ratio (% by volume) in the Si ₃ N ₄ powder is shown in Tables 1 to 3. The β crystal phase ratio is quantified by X-ray diffraction. In the Si ₃ N ₄ powder, Al, Ca, Fe, and Mg, which are impurity metal elements, are each contained in an amount of 0.1% by mass or less, and O as an impurity non-metal element is contained in an amount of 0.5% by mass or less.

The analysis of the impurity metal element is performed by ICP-AES according to the state in which the metal element excited by the sample solution containing the raw material Si ₃ N ₄ powder is sprayed and introduced into the Ar plasma to be restored to the substrate state. The wavelength of the light is qualitatively analyzed and quantitatively analyzed based on the intensity of the light. Thereby, the mass % of Al, Ca, Fe, and Mg existing in the raw material Si ₃ N ₄ powder is obtained. The solution of the raw material Si ₃ N ₄ powder was prepared by adding 0.1 g of the pretreated powder together with an alkaline solvent containing 2 g of calcium carbonate and 0.5 g of boron oxide to a platinum crucible at 1000 ° C. The melt was melted, and the melt was recovered in an acidic solution containing 20 ml of 35 mass% hydrochloric acid and 20 ml of ion-exchanged water at 60 ° C, and then diluted to 200 ml with ion-exchanged water. Even if the intensity of light is equal to the background, it is also recorded as 0.01% by mass or less.

As a raw material, Si ₃ N ₄ powder, Y ₂ O ₃ powder, MgO powder, PVB (polyvinyl butyral) as an organic binder, ethanol as a dispersion medium, and, if necessary, a decondensing agent - 1 part by mass of CELUNA F-216 manufactured by Beijing Oils and Fats Co., Ltd. and 3 parts by mass of CELUNA E503 were mixed by ultrasonic waves for 60 minutes to prepare a uniform mixed slurry.

2. Formation of the formed body

The mixed slurry of the raw materials obtained as described above was molded by a uniaxial pressing molding method at the molding pressures shown in Tables 1 to 3.

3. Formation of sintered body

The molded body obtained as described above was degreased at 800 ° C under atmospheric atmospheric flow atmosphere until the residual carbon amount became 200 ppm. Then, the degreased molded body was sintered under a nitrogen atmosphere at a sintering pressure, a sintering temperature, and a sintering time shown in Tables 1 to 3. Then, it was cooled from the sintering temperature to 1000 ° C at the cooling rate shown in Tables 1 to 3, and then slowly cooled.

For the sintered body obtained as described above, Si ₃ N ₄ crystal grains were identified, and the contents of Y, Mg, O, and Al and Fe as impurity metal elements were quantified to confirm the presence or absence of the MgO crystal phase, and the analysis factor Y ₂ Si ₃ N ₃ O ₄ crystalline phase of (211) to cause the surface of the X-ray diffraction peak of intensity I _Y2 relative intensity factor Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of (112) to cause the surface of the X-ray diffraction peaks of The ratio of I _Y20 to I _Y2 /I _Y20 is the ratio of the area of the grain boundary phase to the Si ₃ N ₄ grain on the analytical cross section, and the thermal conductivity is derived. The results are summarized in Tables 1 to 3.

Here, the identification of the Si ₃ N ₄ crystal grains was carried out by X-ray diffraction using No. 26191 and No. 79798 of ICDD PDF-4+2014, which is a powder X-ray diffraction database, respectively. The X-ray diffraction system was performed using Cu-Kα rays excited at 45 kV and 40 mA by scanning with the θ-2θ method, a step width of 0.03°, and a cumulative time of one second.

The analysis of Y, Mg, Al, and Fe was carried out using ICP-AES by ICPS-8100 manufactured by SHIMADZU. In the case of using this ICP-AES, the sintered body was pulverized by a mortar and mortar made of agate as a pretreatment. In the analysis of Y and Mg, qualitative analysis is performed according to the wavelength of light emitted when the element excited by the solution of the pretreated powder is sprayed into the Ar plasma and returned to the substrate state, and According to the intensity of the light Quantitative analysis. The pretreatment powder solution was prepared by adding 0.1 g of the pretreated powder together with an alkaline solvent containing 2 g of calcium carbonate and 0.5 g of boron oxide to a platinum crucible and melting at 1000 ° C. The melt was recovered in an acidic solution containing 20 ml of 35 mass% hydrochloric acid and 20 ml of ion-exchanged water at 60 ° C, and then diluted to 200 ml with ion-exchanged water.

The analysis of O was carried out by an inert gas melting-non-dispersive infrared absorption (NDIR) method using EMGA650W manufactured by HORIBA. When the analysis was carried out by the inert gas melting-NDIR method, the sintered substrate was pulverized by a mortar and mortar made of agate as a pretreatment. In the analysis of O, qualitative analysis was carried out based on the fact that 0.03 g of the pretreated powder was charged into carbon crucible and the CO gas and/or CO ₂ gas generated when the temperature was raised to 1600 ° C by a high frequency of 20±2 MHz was above the background level. Quantitative analysis is performed based on the amount of gas generated.

It was confirmed whether or not the MgO crystal phase was carried out by X-ray diffraction. The X-ray diffraction system uses X'Pert PRO manufactured by PANalytical Co., Ltd., and the X-ray system uses Cu-Kα rays having excitation conditions of 45 kV and 40 mA, and the scanning system utilizes the θ-2θ method. The step width is 0.03° and the cumulative time is 1 second. The analysis of the X-ray diffraction peak uses a comprehensive powder X-ray analysis software manufactured by Rigaku Corporation. When the X-ray diffraction peak due to the (200) plane of MgO is not observed between 22.5 and 43.1 °, or when it is not distinguishable from the background, it is considered that the MgO crystal phase is not present in the Si ₃ N ₄ sintered body.

By Y ₂ Si ₃ N ₃ O ₄ crystalline phase of (211) plane of the X-ray intensity caused by diffraction peaks I _Y2 of the X-ray diffraction due to the relative Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of the (112) plane due to the The analysis of the peak intensity I _Y20 ratio I _Y2 /I _Y20 uses X-ray diffraction. The X-ray diffraction system uses X'Pert PRO manufactured by PANalytical Co., Ltd., and the X-ray system uses Cu-Kα rays having excitation conditions of 45 kV and 40 mA, and the scanning system utilizes the θ-2θ method. The step width is set to 0.03° and the accumulated time is set to 1 second. The X-ray diffraction peak was analyzed using PDXL2, a comprehensive powder X-ray analysis software manufactured by Rigaku Corporation. The X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is a peak located on the low angle side between 2θ and 30 to 33°, and is used as a powder X-ray diffraction database. The powder diffraction data file of the International Diffraction Data Center is identified by ICDD PDF-4+2014 No.00-030-1462. The X-ray diffraction peak due to the (211) plane of the Y ₂ Si ₃ N ₃ O ₄ crystal phase is a peak located on the high angle side between 2θ and 30 to 33°, and the powder diffraction using the international diffraction data center The data file is identified by ICDD PDF-4+2014 No.01-076-0724. According to this method, the intensity of the X-ray diffraction peak caused by the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is I _Y20 and the (211) plane of the crystal phase of the Y ₂ Si ₃ N ₃ O ₄ The intensity of the induced X-ray diffraction peak I _Y2 is calculated as the ratio I _Y2 /I _Y20 .

The analysis of the short-axis particle diameter and the aspect ratio (ratio of the long-axis particle diameter to the short-axis particle diameter) of the Si ₃ N ₄ crystal grains was measured by SEM-EBSD. The SEM observation was performed using SUPRA 35 VP manufactured by Carl Zeiss, Inc., and the electron backscatter diffraction system used OIM 5.2 manufactured by TSL Solutions or an equivalent device. As a pretreatment for SEM-EBSD measurement, a surface of a sintered body was ground to a depth of 500 μm or more using a diamond grinding stone (diamond grinding stone #400 manufactured by Allied Materials Co., Ltd.), and then manufactured by KEMET Co., Ltd. Finishing machine for finishing. First, the sintered body was ground from the surface to a depth of 10 μm using a copper platen and a diamond grindstone having a particle diameter of 3 μm, and then the sintered body was ground from the surface thereof using a tin platen and a diamond grindstone having a particle diameter of 0.5 μm. A depth of 3 μm. At this time, both of the polishing were carried out under the conditions of a rotation speed of 50 rpm and a load of 0.2 MPa.

The EBSD measurement was performed under the conditions of a measurement area of 30 μm × 100 μm, an acceleration voltage of 15 kV, a working distance of 15 mm, a step size of 0.1 μm, an adjacent 8 × 8 time, and an accumulated time of 0.01 second, and an IQ (image quality) map was obtained. Within the obtained IQ image (field area: 30 μm × 100 μm), the Si ₃ N ₄ grain having the largest area is selected to the fifth largest Si ₃ N ₄ grain, and the five Si ₃ N ₄ crystals are selected. The particles were imaged using Image J software to calculate the short axis particle size, the major axis particle size, and the aspect ratio. In the Image J software, the selected Si ₃ N ₄ crystal grains were approximately elliptical, and the short-axis particle diameter and the long-axis grain diameter were calculated. The aspect ratio is calculated by dividing the major axis particle diameter by the minor axis particle diameter. The range of the short-axis particle diameters of Tables 1 to 3 is the range of the minimum and maximum values of the five Si ₃ N ₄ grains. The aspect ratios of Tables 1-3 are the average values for the five Si ₃ N ₄ grains.

The analysis of the ratio of the grain boundary phase on the cross section of the Si ₃ N ₄ sintered body to the Si ₃ N ₄ crystal grain was observed by SEM. The SEM observation was performed using SUPRA 35 VP manufactured by Carl Zeiss. As a pretreatment for analysis, a surface grinding machine was used, and a diamond grindstone (diamond grinding stone #400 manufactured by Allied Materials Co., Ltd.) was used to grind the surface of the sintered body to a depth of 500 μm or more, and then the fineness of KEMET was used. The processing machine performs finishing. First, the sintered body was ground from the surface to a depth of 10 μm using a copper platen and a diamond grindstone having a particle diameter of 3 μm, and then the sintered body was ground from the surface thereof using a tin platen and a diamond grindstone having a particle diameter of 0.5 μm. A depth of 3 μm. At this time, both of the polishing were carried out under the conditions of a rotation speed of 50 rpm and a load of 0.2 MPa. The SEM system uses an acceleration voltage of 5 kV and a working distance of 10 mm, and uses a reflected electron image for analysis. This image was binarized by Image J software. For the tantalum nitride sintered body, the bright portion which is white is regarded as Si ₃ N ₄ crystal grains, and the dark portion which appears black is regarded as a grain boundary phase.

The thermal conductivity of the Si ₃ N ₄ sintered body is derived based on the thermal diffusivity, specific gravity, and specific heat. The measurement of the thermal diffusivity is carried out by using an optical communication method. The optical communication method uses a Laser-PIT device manufactured by ULVAC. By using the device, the laser light is irradiated along the longitudinal direction of the sample while irradiating the band-shaped laser light having a uniform illumination frequency of 2.5 to 10 Hz, thereby measuring the AC temperature response by using a thermocouple attached to the back surface of the sample, and according to the The thermal diffusivity is calculated from the amplitude of the temperature response and the attenuation rate corresponding to the position. The sample shape has a width of 2.5 to 5 mm, a length of 30 mm, and a thickness of 0.5 mm or less, and the laser heating surface is blackened by a graphite spray only. The thermocouple and the sample system are followed by a silver paste. The specific gravity was determined using the Archimedes method and the specific heat was 0.68 J ‧ g ^-1 ‧ K ^-1 .

As shown in Examples 1 to 13 of Tables 1 to 2, the tantalum nitride, tantalum, magnesium, and oxygen are contained, and a plurality of tantalum nitride crystal grains and grain boundary phases other than the tantalum nitride crystal grains are included. The phase comprises a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase, which is a crystalline phase of Y ₂ Si ₃ N ₃ O ₄ (211) intensity to cause the surface of the X-ray diffraction peaks of I _Y2 with respect to the result Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of the (112) intensity caused by the surface of the X-ray diffraction peaks of I _Y20 ratio I _Y2 / I _Y20 is 0 or more and The tantalum nitride sintered body of 3.0 or less exhibits a high thermal conductivity of 95 W ‧ m ^-1 ‧ K ^-1 or more. On the other hand, as shown in Comparative Examples 1 to 7 of Table 3, since the intensity I _Y20 of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase was 0, Y _{2 was} Si ₃ N ₃ O ₄ crystalline phase of the (211) intensity caused by the surface of the X-ray diffraction peaks of I _Y2 relative intensity factor Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase of (112) to cause the surface of the X-ray diffraction peaks of I The ratio of _Y20 to I _Y2 /I _Y20 is ∞ (infinity) and the tantalum nitride sintered body of more than 3.0 shows only a low high thermal conductivity of less than 95 W ‧ m ^-1 ‧ K ^-1 .

The embodiments and examples disclosed herein are to be considered in all respects The scope of the present invention is defined by the scope of the invention, and is intended to be

Claims (7)

A tantalum nitride sintered body comprising tantalum nitride, niobium, magnesium, and oxygen, and the tantalum nitride sintered body includes a plurality of tantalum nitride crystal grains and crystals other than the tantalum nitride crystal grains The boundary phase, the grain boundary phase includes a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase, or a Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase and a Y ₂ Si ₃ N ₃ O ₄ crystal phase due to the above Y ₂ Si ₃ N ₃ The ratio of the intensity of the X-ray diffraction peak caused by the (211) plane of the O ₄ crystal phase to the intensity of the X-ray diffraction peak due to the (112) plane of the Y ₂₀ N ₄ Si ₁₂ O ₄₈ crystal phase is 0 or more 3.0 or less. The tantalum nitride sintered body according to claim 1, wherein the plurality of the tantalum nitride crystal grains contained in the tantalum nitride sintered body have a minor axis particle diameter of 1.7 μm or more and 10.5 μm or less, and the major axis diameter is relative to The aspect ratio of the short-axis particle diameter, that is, the aspect ratio is 2.0 or more and 7.7 or less. The tantalum nitride sintered body according to claim 1 or 2, wherein a content ratio of each of the impurity metal elements other than cerium, lanthanum and magnesium is 0.5% by mass or less. A tantalum nitride sintered body according to claim 1 or 2, wherein a magnesium oxide crystal phase is absent. The tantalum nitride sintered body of claim 1 or 2 has a thermal conductivity of 95 W ‧ m ^-1 ‧ K ^-1 or more. The tantalum nitride sintered body according to claim 1 or 2, wherein an area ratio of the grain boundary phase to the tantalum nitride crystal grain on any specific cross section of the tantalum nitride sintered body is 10% or less. The method for producing a tantalum nitride sintered body according to any one of claims 1 to 6, wherein the β-crystal phase ratio of the tantalum nitride powder of the raw material is 5% by mass or more and 40% by mass or less.