JP2002316875A - Silicon nitride sintered compact - Google Patents

Silicon nitride sintered compact

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Publication number
JP2002316875A
JP2002316875A JP2001118678A JP2001118678A JP2002316875A JP 2002316875 A JP2002316875 A JP 2002316875A JP 2001118678 A JP2001118678 A JP 2001118678A JP 2001118678 A JP2001118678 A JP 2001118678A JP 2002316875 A JP2002316875 A JP 2002316875A
Authority
JP
Japan
Prior art keywords
silicon nitride
sintered body
mass
nitride sintered
terms
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2001118678A
Other languages
Japanese (ja)
Inventor
Katsura Matsubara
桂 松原
Yasushi Hara
康 原
Masaya Ito
正也 伊藤
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Niterra Co Ltd
Original Assignee
NGK Spark Plug Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NGK Spark Plug Co Ltd filed Critical NGK Spark Plug Co Ltd
Priority to JP2001118678A priority Critical patent/JP2002316875A/en
Publication of JP2002316875A publication Critical patent/JP2002316875A/en
Pending legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To provide a silicon nitride sintered compact which has excellent dielectric strength and heat radia bility, and is suitable as ceramics, e.g. used for an insulated substrate for a semiconductor. SOLUTION: The silicon nitride sintered compact contains at least one kind of element selected from light rare earth elements in 3 to 14 mass% by an amount expressed in terms of oxide, and alkaline-earth metal elements in 4 to 10 mass% by an amount expressed in terms of oxides. The sintered compact further contains alkali metal elements by <=0.5 pts.mass, and a cobalt element or/and a nickel element in 0.05 to 2.0 mass% by an amount expressed in terms of oxides to 100 pts.mass of the balance obtained by removing the amount of the cobalt element or/and the nickel element expressed in terms of oxides and the amount of the alkali metal elements expressed in terms of oxides from the total amount of the components in the silicon nitride sintered compact. Also, its dielectric strength in a thickness of 0.3 mm is >=10 kV, and its thermal conductivity at a room temperature is >=54 W/m.K. The volume fraction of the above silicon nitride in the sintered compact is 90 to 95 vol.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明は、窒化珪素焼結体に
関し、更に詳しくは、絶縁耐力及び放熱性に優れ、半導
体用絶縁基板等に使用されるセラミックスとして好適な
窒化珪素焼結体に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride sintered body, and more particularly, to a silicon nitride sintered body having excellent dielectric strength and heat dissipation and suitable as a ceramic used for an insulating substrate for semiconductors.

【0002】[0002]

【従来の技術】窒化珪素焼結体は、機械的特性、耐熱
性、耐摩耗性及び耐食性等の諸性質に優れていることか
ら、従来より、ベアリングボールやタペット等の摺動部
材、切削工具等の耐摩耗部材、ターボチャージャーロー
ターやエンジンバルブ、セラミックグロープラグなどの
エンジン部材への実用化が検討されている。また、ハイ
ブリッド電気自動車のモーターを制御するインバーター
の半導体用絶縁基板として、従来は窒化アルミニウム焼
結体の適用が検討されていたが、窒化アルミニウム焼結
体では機械的強度が不十分であることから、近年では、
窒化珪素焼結体の優れた機械的特性に着目して、半導体
用絶縁基板としての適用が検討されている。
2. Description of the Related Art Sintered silicon nitride has excellent properties such as mechanical properties, heat resistance, abrasion resistance and corrosion resistance. Therefore, sliding members such as bearing balls and tappets and cutting tools have been conventionally used. Practical application to engine members such as wear-resistant members such as turbocharger rotors, engine valves, and ceramic glow plugs is being studied. Conventionally, the use of aluminum nitride sintered bodies as an insulating substrate for semiconductors in inverters that control motors of hybrid electric vehicles has been considered, but the mechanical strength of aluminum nitride sintered bodies is insufficient. ,in recent years,
Focusing on the excellent mechanical properties of the silicon nitride sintered body, application to an insulating substrate for a semiconductor has been studied.

【0003】そして、焼結体を半導体用絶縁基板として
用いる場合、半導体素子で発生する熱を効率よく外部へ
逃がすことが重要であるが、従来より用いられている窒
化アルミニウム焼結体と比べ、窒化珪素焼結体は熱伝導
特性の点に劣ることが指摘されており、半導体用絶縁基
板としての適用を妨げる要因となっていた。そこで、従
来より、窒化珪素焼結体の熱伝導率を向上させる数多く
の試みがなされており、その殆どは、窒化珪素粒子を粒
成長させることにより高熱伝導化を実現している。
When a sintered body is used as an insulating substrate for a semiconductor, it is important to efficiently release the heat generated in the semiconductor element to the outside. However, compared with a conventionally used aluminum nitride sintered body, It has been pointed out that the silicon nitride sintered body is inferior in heat conduction characteristics, which has been a factor hindering its application as an insulating substrate for semiconductors. Therefore, conventionally, many attempts have been made to improve the thermal conductivity of a silicon nitride sintered body, and most of them have realized high thermal conductivity by growing silicon nitride particles.

【0004】しかし、窒化珪素粒子の粒成長を促進する
と、アスペクト比の高い針状組織となり、微構造レベル
で立体障害が発生するために、緻密な焼結体を得ること
が困難となってくるという問題がある。これに対して従
来より、窒素ガス圧が10MPa程度のガス圧焼結(G
PS)や10〜300MPa程度の熱間静水圧加圧焼結
(HIP)や、あるいは機械的に一軸方向の圧力を加え
ながら焼結するホットプレス焼結(HP)といった加圧
焼結法が知られている。これらの焼結法によれば比較的
緻密な焼結体を得ることができるが、一般的に製造コス
トが高くなるため、低コストが要求される工業用材料の
製造プロセスとしては適していない。また、窒素雰囲気
圧力1MPa未満の広義の常圧焼結方法では、高密度の
焼結体を得ることは困難である。
However, when the grain growth of silicon nitride particles is promoted, a needle-like structure having a high aspect ratio is formed, and steric hindrance occurs at a microstructure level, so that it becomes difficult to obtain a dense sintered body. There is a problem. On the other hand, conventionally, gas pressure sintering (G
Pressure sintering methods such as PS), hot isostatic pressing sintering (HIP) of about 10 to 300 MPa, and hot press sintering (HP) sintering while applying mechanical uniaxial pressure are known. Have been. According to these sintering methods, a relatively dense sintered body can be obtained. However, since the production cost is generally high, it is not suitable as a production process of industrial materials requiring low cost. In addition, it is difficult to obtain a high-density sintered body by a normal-pressure sintering method in a nitrogen atmosphere pressure of less than 1 MPa.

【0005】更に、窒化珪素焼結体を半導体用絶縁基板
として用いる場合、焼結体の特性として絶縁耐圧が高い
ことが求められるが、上記のように熱伝導率を向上させ
るべく窒化珪素の粒成長を促進すると、絶縁耐力及び耐
電圧が低下する問題がある。そこで従来より、熱伝導率
を向上させると共に、経済的な方法で緻密化をすること
ができ、且つ優れた絶縁耐力を備える窒化珪素焼結体の
開発が望まれていた。
Further, when a silicon nitride sintered body is used as an insulating substrate for a semiconductor, a high dielectric strength voltage is required as a characteristic of the sintered body. However, as described above, particles of silicon nitride are required to improve thermal conductivity. When the growth is promoted, there is a problem that the dielectric strength and the withstand voltage decrease. Therefore, conventionally, there has been a demand for the development of a silicon nitride sintered body that can be densified by an economical method while improving the thermal conductivity and that has excellent dielectric strength.

【0006】[0006]

【発明が解決しようとする課題】本発明は上記実情に鑑
みてなされたものであり、絶縁耐力及び放熱性に優れ、
半導体用絶縁基板等に使用されるセラミックスとして好
適な窒化珪素焼結体を提供することを目的とする。
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has excellent dielectric strength and heat dissipation.
It is an object of the present invention to provide a silicon nitride sintered body suitable as a ceramic used for an insulating substrate for a semiconductor or the like.

【0007】[0007]

【課題を解決するための手段】本発明者等は、窒化珪素
焼結体において、窒化珪素の粒成長を促進した際に絶縁
耐力が低下する原因について詳細に検討した結果、窒化
珪素の粒成長により粒界三重点に残留気孔が生じ、この
気孔に電界が集中するためであることを発見した。そし
て、本発明者等は、窒化珪素焼結体中、軽希土類元素及
びアルカリ土類金属元素を所定量含有させることによ
り、残留気孔を除去あるいは低減し、熱伝導率及び絶縁
耐圧を向上させると共に、より繊密な焼結体とすること
ができることを見出して本発明を完成するに至った。
Means for Solving the Problems The inventors of the present invention have studied in detail the cause of a decrease in dielectric strength when silicon nitride grain growth is promoted in a silicon nitride sintered body. As a result, it was found that residual pores were generated at the grain boundary triple point, and the electric field was concentrated on these pores. The present inventors have found that by including a predetermined amount of a light rare earth element and an alkaline earth metal element in a silicon nitride sintered body, residual pores are removed or reduced, and thermal conductivity and dielectric strength are improved. The present inventors have found that a finer sintered body can be obtained, and have completed the present invention.

【0008】上記目的を達成するため、本発明が提供す
る窒化珪素焼結体は、軽希土類元素から選ばれた少なく
とも1種の元素を酸化物換算量で3〜14質量%及びア
ルカリ土類金属元素を酸化物換算量で3〜10質量%含
有し、且つ厚さ0.3mmにおける絶縁耐圧が10kV
以上であることを特徴とする。
In order to achieve the above object, a silicon nitride sintered body provided by the present invention contains at least one element selected from light rare earth elements in an amount of 3 to 14% by mass in terms of oxide and an alkaline earth metal. The element contains 3 to 10% by mass in terms of oxide and has a withstand voltage of 10 kV at a thickness of 0.3 mm.
It is characterized by the above.

【0009】本発明の窒化珪素焼結体における上記「軽
希土類元素」とは、ランタノイド系元素のうち、原子番
号57のLaから原子番号60のNdまでの元素の総称
である。また、本発明の窒化珪素焼結体における上記
「アルカリ土類金属元素」としては、例えば、Be、M
g、Ca、Sr、Ba等が挙げられる。そして、本発明
の窒化珪素焼結体では、上記「軽希土類元素」及び「ア
ルカリ土類金属元素」の両元素を少なくとも1種づつを
含んでいれば、2種以上の異なる軽希土類元素及びアル
カリ土類金属元素を含んでいてもよい。また、さらに軽
希土類元素以外の他の希土類元素を含有していてもよ
い。
The above-mentioned "light rare earth element" in the silicon nitride sintered body of the present invention is a general term for elements from La of atomic number 57 to Nd of atomic number 60 among lanthanoid elements. The “alkaline earth metal element” in the silicon nitride sintered body of the present invention includes, for example, Be, M
g, Ca, Sr, Ba and the like. In the silicon nitride sintered body of the present invention, two or more different light rare earth elements and alkali metals are contained as long as at least one of each of the above “light rare earth elements” and “alkaline earth metal elements” is included. It may contain an earth metal element. Further, a rare earth element other than the light rare earth element may be further contained.

【0010】本発明の窒化珪素焼結体において、上記
「軽希土類元素」の含有量は、少なくとも1種以上の元
素成分を酸化物換算量で3〜14質量%、好ましくは5
〜10質量%である。また、上記「アルカリ土類金属元
素」の含有量は、酸化物換算量で3〜10質量%、好ま
しくは5〜8質量%である。上記軽希土類元素の酸化物
換算量が3質量%未満、又は上記アルカリ土類金属元素
の酸化物換算量が3質量%未満であると、焼結体中の粒
界相の量が少なくなり残留気孔が増えて絶縁破壊電圧が
低下するので好ましくない。一方、上記軽希土類元素の
酸化物換算量が14質量%を超えるか、又は上記アルカ
リ土類金属元素の酸化物換算量が10質量%を超える
と、粒界相の量としては多くなる反面、針状組織が発達
しすぎるために、上記のように立体障害が発生する結
果、粒界三重点に残留気孔が発生し、やはり同様に絶縁
破壊電圧が低下してしまうので好ましくない。
In the silicon nitride sintered body of the present invention, the content of the “light rare earth element” is at least one element component in an amount of 3 to 14% by mass, preferably 5 to 14% by mass in terms of oxide.
To 10% by mass. The content of the “alkaline earth metal element” is 3 to 10% by mass, preferably 5 to 8% by mass in terms of oxide. If the amount of the light rare earth element in terms of oxide is less than 3% by mass or the amount of the alkaline earth metal element in terms of oxide is less than 3% by mass, the amount of the grain boundary phase in the sintered body is reduced and the residual It is not preferable because the number of pores increases and the dielectric breakdown voltage decreases. On the other hand, if the oxide equivalent of the light rare earth element exceeds 14% by mass or the oxide equivalent of the alkaline earth metal element exceeds 10% by mass, the amount of the grain boundary phase increases, Since the needle-like structure is excessively developed, steric hindrance occurs as described above, and as a result, residual pores are generated at the triple point of the grain boundary, and the dielectric breakdown voltage is similarly lowered, which is not preferable.

【0011】本発明の窒化珪素焼結体に含まれる上記軽
希土類元素及びアルカリ土類金属元素は、窒化珪素焼結
体を製造する工程において、通常は、それぞれ酸化物や
炭酸塩等の化合物として窒化珪素原料粉末と混合され
る。そして、焼成過程で窒化珪素原料粉末粒子の表面上
に存在する酸化膜と反応して液相を生成し、窒化珪素焼
結体を得るための焼結助剤としての働きを持つ。また、
焼結後は窒化珪素粒子間の粒界ガラス相あるいは粒界結
晶相の構成成分として存在する。
The light rare earth element and the alkaline earth metal element contained in the silicon nitride sintered body of the present invention are usually used as compounds such as oxides and carbonates in the step of producing the silicon nitride sintered body. It is mixed with silicon nitride raw material powder. Then, during the firing process, it reacts with an oxide film present on the surface of the silicon nitride raw material powder particles to generate a liquid phase, and has a function as a sintering aid for obtaining a silicon nitride sintered body. Also,
After sintering, it exists as a component of a grain boundary glass phase or a grain boundary crystal phase between silicon nitride particles.

【0012】本発明の窒化珪素焼結体は、厚さ0.3m
mにおける絶縁耐圧が10kV以上と高い値を有してい
る。ここで、特定の厚さにおける絶縁耐圧の値を規定し
たのは、絶縁耐圧と厚さとの間の相関性を一義的に定め
ることが困難である点を考慮したためである。例えば、
窒化珪素絶縁基板のような比較的薄い板状の焼結体の絶
縁耐圧特性は、2〜3mmを超える比較的肉厚の焼結体
を用いて測定された絶縁耐圧の値をそのまま適用しても
狙い通りの性能が得られないことが多い。従って、真に
絶縁耐力に優れた絶縁基板を得るためには、焼結体を特
定の厚さにした場合の絶縁耐圧の値を用いることが必要
であるとの観点に基づいている。本発明の窒化珪素焼結
体の絶縁耐圧を表すときの厚さは上記の0.3mmを基
準とするが、0.3±0.02mmの範囲であればよ
い。しかし、これに限定されるものではなく、例えば
0.32mmより厚い基板であれば、0.3±0.02
mmの厚さに研削加工した場合に10kV以上の絶縁破
壊電圧を示すものであればよく、一方、0.28mmよ
り薄い基板については、これと同様な製造方法により厚
さ0.3±0.02mmの基板を製造して絶縁耐圧を評
価する。尚、試料の表面状態については、特に限定され
ず、焼き肌面であっても研削加工面であってもよい。研
削加工面の目安としては、#170以上の砥石にて精研
削量(仕上げ研削量)10μmを1μm刻みで仕上げた
面とする。
The silicon nitride sintered body of the present invention has a thickness of 0.3 m
m has a high value of 10 kV or more. Here, the value of the withstand voltage at a specific thickness is defined because it is difficult to uniquely define the correlation between the withstand voltage and the thickness. For example,
The withstand voltage characteristics of a relatively thin plate-like sintered body such as a silicon nitride insulating substrate can be obtained by directly applying the value of the withstand voltage measured using a relatively thick sintered body exceeding 2 to 3 mm. In many cases, the desired performance cannot be obtained. Therefore, in order to obtain an insulating substrate having a truly excellent dielectric strength, it is necessary to use the value of the dielectric strength when the sintered body has a specific thickness. The thickness of the silicon nitride sintered body of the present invention when expressing the dielectric strength is based on the above 0.3 mm, but may be in the range of 0.3 ± 0.02 mm. However, the present invention is not limited to this. For example, if the substrate is thicker than 0.32 mm, 0.3 ± 0.02
Any substrate can be used as long as it exhibits a dielectric breakdown voltage of 10 kV or more when ground to a thickness of 0.3 mm. On the other hand, for a substrate thinner than 0.28 mm, a thickness of 0.3 ± 0.2 mm is obtained by the same manufacturing method. A substrate of 02 mm is manufactured and the withstand voltage is evaluated. The surface state of the sample is not particularly limited, and may be a burnt surface or a ground surface. As a guide for the grinding surface, a surface obtained by finishing a fine grinding amount (finish grinding amount) of 10 μm in 1 μm increments using a grindstone of # 170 or more.

【0013】また、本発明の窒化珪素焼結体は、上記軽
希土類元素及びアルカリ土類金属元素に加えて、コバル
ト元素又は/及びニッケル元素を含有するものとするこ
とができる。コバルト元素又はニッケル元素を含有する
ことにより、窒化珪素粒子の長軸方向への粒成長を抑制
することが可能となる。そのため、立体障害が原因とな
って発生する粒界三重点における気孔の残留をさらに抑
制することが可能となる。この場合、コバルト元素又は
/及びニッケル元素は化合物の形態で焼結体中に含ませ
ることができ、かかる化合物としては、酸化物、窒化
物、酸窒化物等が挙げられる。コバルト元素又は/及び
ニッケル元素の含有量は、上記窒化珪素焼結体の全成分
量からコバルト元素又は/及びニッケル元素の酸化物換
算量を除いた残部100質量部に対し、酸化物換算量で
0.05〜2.0質量部、好ましくは0.05〜0.5
質量部、更に好ましくは0.05〜0.1質量部であ
る。尚、コバルト元素又はニッケル元素を含有すること
により、焼結体の呈色が均一となる副次的効果も得るこ
とが可能である。
Further, the silicon nitride sintered body of the present invention may contain a cobalt element and / or a nickel element in addition to the light rare earth element and the alkaline earth metal element. By containing the cobalt element or the nickel element, it is possible to suppress the grain growth in the major axis direction of the silicon nitride particles. For this reason, it is possible to further suppress the residual pores at the grain boundary triple point due to steric hindrance. In this case, the cobalt element and / or the nickel element can be included in the sintered body in the form of a compound, and examples of such a compound include an oxide, a nitride, and an oxynitride. The content of the cobalt element or / and the nickel element is expressed in terms of an oxide conversion amount with respect to the remaining 100 parts by mass excluding the oxide conversion amount of the cobalt element and / or nickel element from the total component amount of the silicon nitride sintered body. 0.05 to 2.0 parts by mass, preferably 0.05 to 0.5
Parts by mass, more preferably 0.05 to 0.1 part by mass. Incidentally, by containing the cobalt element or the nickel element, it is also possible to obtain a secondary effect of making the coloration of the sintered body uniform.

【0014】また、本発明の窒化珪素焼結体は、アルカ
リ金属元素から選ばれた少なくとも1種以上の元素成分
を含有するものとすることができる。上記「アルカリ金
属元素」としては、例えば、Li、Na、K等が挙げら
れ、このうちの少なくとも1種を含んでいれば、2種以
上の異なるアルカリ金属元素を含んでいてもよい。かか
るアルカリ金属元素を含有することにより、粒界に生成
した液相の粘性を低下させ、その結果、焼結体の緻密化
を促進することができるので好ましい。上記「アルカリ
金属元素」の含有量については特に限定はないが、通常
は、上記窒化珪素焼結体の全成分量からアルカリ金属元
素の酸化物換算量を除いた残部100質量部に対し、酸
化物換算量で0.5質量部以下(但し、0質量部は含ま
ない。)、好ましくは0.01〜0.5質量部、更に好
ましくは0.01〜0.3質量部、特に好ましくは0.
01〜0.1質量部とすることができる。上記「アルカ
リ金属元素」の酸化物換算量をかかる範囲とすることに
より、焼結体の緻密化を促進すると共に、粒界相でのイ
オン伝導性の発現を抑え、絶縁性の低下を防止して優れ
た絶縁性を維持することができるので好ましい。尚、コ
バルト元素又は/及びニッケル元素を含有する場合の上
記「アルカリ金属元素」の含有量は、上記窒化珪素焼結
体の全成分量からコバルト元素又は/及びニッケル元素
の酸化物換算量並びにアルカリ金属元素の酸化物換算量
を除いた残部100質量部に対し、酸化物換算量で0.
5質量部以下(但し、0質量部は含まない。)、好まし
くは0.01〜0.5質量部、更に好ましくは0.01
〜0.3質量部、特に好ましくは0.01〜0.1質量
部とすることができる。
[0014] The silicon nitride sintered body of the present invention may contain at least one element component selected from alkali metal elements. Examples of the “alkali metal element” include Li, Na, K, and the like. If at least one of these elements is included, two or more different alkali metal elements may be included. By containing such an alkali metal element, the viscosity of the liquid phase generated at the grain boundary can be reduced, and as a result, the densification of the sintered body can be promoted, which is preferable. The content of the “alkali metal element” is not particularly limited, but is usually oxidized with respect to the remaining 100 parts by mass of the total content of the silicon nitride sintered body excluding the equivalent amount of the alkali metal element as oxide. 0.5 parts by mass or less (however, 0 parts by mass is not included), preferably 0.01 to 0.5 parts by mass, more preferably 0.01 to 0.3 parts by mass, particularly preferably 0.
It can be from 0.1 to 0.1 part by mass. By setting the amount of the above “alkali metal element” in terms of oxide to the above range, while promoting the densification of the sintered body, suppressing the expression of ionic conductivity in the grain boundary phase, and preventing a decrease in insulation properties. It is preferable because excellent insulating properties can be maintained. The content of the above-mentioned “alkali metal element” in the case of containing the cobalt element and / or the nickel element is calculated from the total amount of the components of the silicon nitride sintered body in terms of the oxide equivalent of the cobalt element and / or the nickel element and the alkali element. With respect to the remaining 100 parts by mass excluding the oxide equivalent amount of the metal element, the equivalent amount of the oxide is 0.1%.
5 parts by mass or less (however, 0 parts by mass is not included), preferably 0.01 to 0.5 parts by mass, more preferably 0.01 parts by mass.
To 0.3 part by mass, particularly preferably 0.01 to 0.1 part by mass.

【0015】また、本発明の窒化珪素焼結体では、焼結
体中の窒化珪素の体積分率を90〜95vol%、好ま
しくは91〜94vol%とすることができる。上記窒
化珪素の体積分率を90vol%以上とすることによ
り、希土類元素−珪素−酸素−窒素を基本構成成分と
し、通常1W/m・K以下の低い熱伝導率を示す粒界相
成分、即ちガラス成分の生成を抑えることができる。そ
の結果、焼結体の熱伝導率の低下を防止でき、高い放熱
性が要求される半導体用絶縁基板としてへ好適に使用で
きるので好ましい。一方、上記窒化珪素の体積分率を9
5vol%以下とすることにより、窒化珪素成分に対し
て粒界相が不足することがないことから、残留気孔が多
数発生して熱伝導率が低下することを防止すると共に、
交流耐電圧の低下も防止して、厚さ0.3mmにおいて
10kV以上の絶縁耐圧特性が得られるので好ましい。
なお、本発明においては、上記の窒化珪素の体積分率は
以下のようにして求められる。窒化珪素焼結体の任意の
断面を鏡面研磨した後、その研磨面を走査型電子顕微鏡
により倍率3000倍にて高解像度で写真撮影する。得
られた写真の画像を二値化し、窒化珪素粒子の占める領
域を特定し、全視野面積に対する窒化珪素粒子の領域面
積の比(面積割合)を算出し、これを窒化珪素の体積分
率とする。
In the silicon nitride sintered body of the present invention, the volume fraction of silicon nitride in the sintered body can be 90 to 95 vol%, preferably 91 to 94 vol%. By setting the volume fraction of the silicon nitride to 90 vol% or more, a grain boundary phase component having a low thermal conductivity of usually 1 W / m · K or less, which is a rare earth element-silicon-oxygen-nitrogen as a basic component, that is, Generation of glass components can be suppressed. As a result, a decrease in the thermal conductivity of the sintered body can be prevented, and the sintered body can be suitably used as an insulating substrate for a semiconductor that requires high heat dissipation. On the other hand, the silicon nitride has a volume fraction of 9
By setting the content to 5 vol% or less, the grain boundary phase is not insufficient for the silicon nitride component, so that it is possible to prevent a large number of residual pores from being generated and lowering the thermal conductivity.
It is preferable because a decrease in AC withstand voltage is also prevented and a withstand voltage characteristic of 10 kV or more can be obtained at a thickness of 0.3 mm.
In the present invention, the volume fraction of silicon nitride is determined as follows. After an arbitrary cross section of the silicon nitride sintered body is mirror-polished, a photograph of the polished surface is taken with a scanning electron microscope at a magnification of 3000 times at a high resolution. The obtained photograph image is binarized, the area occupied by the silicon nitride particles is specified, the ratio of the area area of the silicon nitride particles to the entire viewing area (area ratio) is calculated, and this is calculated as the volume fraction of silicon nitride. I do.

【0016】本発明の窒化珪素焼結体は、上記構成を備
えることにより、従来の窒化珪素焼結体と比較して、優
れた絶縁耐圧と高い熱伝導率とを兼ね備えたものとする
ことができる。また、室温における熱伝導率を54W/
m・K以上、好ましくは60W/m・K以上、更に好ま
しくは65W/m・K以上とすることができる。室温に
おける熱伝導率をかかる範囲とすることにより、発生す
る熱を逃す必要のある半導体絶縁基板等として用いた場
合、効率的に放熱を促進することができるので好まし
い。
By providing the silicon nitride sintered body of the present invention with the above-described structure, the silicon nitride sintered body can have both excellent withstand voltage and high thermal conductivity as compared with a conventional silicon nitride sintered body. it can. In addition, the thermal conductivity at room temperature was 54 W /
m · K or more, preferably 60 W / m · K or more, more preferably 65 W / m · K or more. When the thermal conductivity at room temperature is in the above range, it is preferable to use it as a semiconductor insulating substrate or the like that needs to release generated heat, because heat can be efficiently promoted.

【0017】[0017]

【発明の実施の形態】以下、本発明について、実験例に
より具体的に説明する。 (1)焼結体の調製 原料粉末として、Si34粉末(平均粒径1.0μm、
α率99%、不純物酸素量1.2質量%)と、希土類元
素化合物(CeO2、La23、Nd23及びPr611
〔平均粒径1〜3μm〕)と、SrCO3(平均粒径1
μm)と、アルカリ金属酸化物(Li2CO3、Na2
3及びK2CO3〔平均粒径 0.5〜2μm〕)と、
Co34(平均粒径1μm)と、NiO(平均粒径1μ
m)を用いた。これらを表1に示す組成の割合となるよ
うに配合して原料粉末混合物を調製した。尚、表1中、
Si34、希土類元素化合物及びSrOの量の値は質量
%である。また、Co化合物、Ni化合物及びアルカリ
金属酸化物の量の値は、Si 34、希土類元素化合物及
びSrOの合計量100質量部に対する質量部である。
そして、該原料粉末混合物をエタノールを分散媒として
樹脂製ポット中、樹脂製球石にて16時間混合粉砕した
後、泥漿を湯煎乾燥して混合粉末を得た。次いで、該混
合粉末を金型プレスでφ40mm×t5mmのペレット
形状にした後、CIP装置により150MPaの圧力で
成形して成形体を得た。その後、該成形体に離型剤とし
てボロンナイトライドを塗布した後、窒化珪素質の焼成
ケース中に入れ、以下の表1に示した条件により8時間
焼成を行って、実施例1〜7及び比較例1〜3の各焼結
体を得た。
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to experimental examples.
This will be described more specifically. (1) Preparation of sintered body As raw material powder, SiThreeNFourPowder (average particle size 1.0 μm,
α rate 99%, impurity oxygen content 1.2 mass%) and rare earth element
Elemental compound (CeOTwo, LaTwoOThree, NdTwoOThreeAnd Pr6O11
[Average particle size 1-3 μm]) and SrCOThree(Average particle size 1
μm) and an alkali metal oxide (LiTwoCOThree, NaTwoC
OThreeAnd KTwoCOThree[Average particle size 0.5-2 μm]),
CoThreeOFour(Average particle size 1 μm) and NiO (average particle size 1 μm).
m) was used. These have the composition ratios shown in Table 1.
Thus, a raw material powder mixture was prepared. In Table 1,
SiThreeNFour, Rare earth element compound and SrO amount are mass
%. Also, a Co compound, a Ni compound and an alkali
The value of the amount of metal oxide is Si ThreeNFour, Rare earth element compounds and
And 100 parts by mass of the total amount of SrO and SrO.
Then, using the raw material powder mixture as a dispersion medium with ethanol
In a resin pot, mixed and crushed with a resin ball for 16 hours
Thereafter, the slurry was dried in hot water to obtain a mixed powder. Then,
Pellet of φ40mm × t5mm by pressing the mixed powder
After the shape, the pressure is 150MPa by CIP device
The molded product was obtained by molding. Thereafter, a release agent is added to the molded body.
After applying boron nitride, baking silicon nitride
8 hours in a case, according to the conditions shown in Table 1 below
After sintering, sintering of each of Examples 1 to 7 and Comparative Examples 1 to 3
I got a body.

【0018】[0018]

【表1】 [Table 1]

【0019】(2)性能評価 上記方法により得られた実施例1〜7及び比較例1〜3
の各焼結体について、以下の方法により性能評価を行っ
た。理論密度比(%)は、アルキメデス法により焼結体
の密度を測定し、混合則で計算した理論密度に対する比
で表すことにより求めた。また、耐電圧値(kV)は、
上記方法により得られた実施例1〜7及び比較例1〜3
の各焼結体の厚さを0.3mmに研磨加工した後、Jl
S C2110「固体電気絶縁材料の絶縁耐力の試験方
法」に基づく常態油中耐電圧測定を行うことにより求め
た。ここで、絶縁破壊電圧測定の際に使用した電極形状
は図1に示すとおりである。尚、JlS規格での試料厚
さは2mmあるいは3mmであるが、半導体用絶縁基板
への適用においては、実際の基板が厚さ約0.3mmで
使用されることが多いために、本試験での試料厚さは
0.3mmとした。更に、室温(25℃)における熱伝
導率(W/m・K)は、上記方法により得られた実施例
1〜7及び比較例1〜3の各焼結体を用いて、これを別
途φ10mm×t2mmに研磨加工した試料を製造し、
JlS R1611「ファインセラミックスのレーザー
フラッシュ法による熱拡散率・比熟容量・熱伝導率試験
方法」に従って測定した。これらの評価結果を以下の表
2に示す。
(2) Performance evaluation Examples 1 to 7 and Comparative examples 1 to 3 obtained by the above method.
The performance of each sintered body was evaluated by the following method. The theoretical density ratio (%) was determined by measuring the density of the sintered body by the Archimedes method and expressing the ratio with respect to the theoretical density calculated by the mixing rule. The withstand voltage value (kV) is
Examples 1 to 7 and Comparative Examples 1 to 3 obtained by the above method
After polishing each sintered body to a thickness of 0.3 mm,
It was determined by performing a withstand voltage measurement in normal oil based on SC2110 “Test method for dielectric strength of solid electrical insulating material”. Here, the shape of the electrodes used in measuring the breakdown voltage is as shown in FIG. The sample thickness according to the JIS standard is 2 mm or 3 mm. However, in the case of application to an insulating substrate for a semiconductor, since an actual substrate is often used with a thickness of about 0.3 mm, the test was conducted in this test. Was 0.3 mm in thickness. Furthermore, the thermal conductivity (W / m · K) at room temperature (25 ° C.) was determined by separately using φ10 mm for each of the sintered bodies of Examples 1 to 7 and Comparative Examples 1 to 3 obtained by the above method. XT2mm to produce a sample polished,
It was measured according to JLS R1611 "Test method for thermal diffusivity, specific ripening capacity and thermal conductivity of fine ceramics by laser flash method". The results of these evaluations are shown in Table 2 below.

【0020】[0020]

【表2】 [Table 2]

【0021】(3)実験例の効果 表2より、本発明の範囲内である実施例1〜7の各焼結
体では、いずれも熱伝導率が54〜75W/m・Kと高
い値を示すと同時に、理論密度比が98.0〜99.0
%と高い値を示して緻密化を実現しており、更に0.3
mmの試料厚さにおいて耐電圧値が10kV以上の高い
耐電圧性を示している。かかる結果より、実施例1〜7
の各焼結体は、優れた熱伝導性及び絶縁耐圧を奏すると
共に、残留気孔を除去あるいは低減した緻密な焼結体で
あることが判る。特に、アルカリ金属元素を含む実施例
3、5〜7の各焼結体では、耐電圧値が11〜13kV
であり、実施例1、2及び4の焼結体より若干高い値を
示している。かかる結果より、アルカリ金属元素を含有
することにより、高い緻密性を示すとと共に、絶縁耐圧
に優れた焼結体とすることができることが判る。また、
窒化珪素の体積分率が90vol%以上である実施例
1、3、5〜7の各焼結体では、熱伝導率が57〜75
W/m・Kと高い値を示している。特に窒化珪素の体積
分率が大きい実施例3、5〜7では、65〜75W/m
・Kと更に優れた値を示している。この結果から、窒化
珪素の体積分率が90vol%以上とすると、熱伝導率
を向上させることができることが判る。
(3) Effects of Experimental Examples From Table 2, all the sintered bodies of Examples 1 to 7, which are within the scope of the present invention, have a high thermal conductivity of 54 to 75 W / m · K. At the same time, the theoretical density ratio is 98.0-99.0.
% To achieve high densification, and further 0.3%
It shows high withstand voltage with a withstand voltage value of 10 kV or more at a sample thickness of mm. From these results, Examples 1 to 7
It can be seen that each of the sintered bodies has excellent thermal conductivity and dielectric strength, and is a dense sintered body in which residual pores are removed or reduced. In particular, each of the sintered bodies of Examples 3 and 5 to 7 containing an alkali metal element has a withstand voltage of 11 to 13 kV.
Which is slightly higher than the sintered bodies of Examples 1, 2 and 4. From these results, it can be seen that by containing an alkali metal element, it is possible to obtain a sintered body having high denseness and excellent withstand voltage. Also,
In each of the sintered bodies of Examples 1, 3, 5 to 7 in which the volume fraction of silicon nitride is 90 vol% or more, the thermal conductivity is 57 to 75.
It shows a high value of W / m · K. In particular, in Examples 3 and 5 to 7 in which the volume fraction of silicon nitride is large, 65 to 75 W / m
-It shows K and a more excellent value. From this result, it is understood that when the volume fraction of silicon nitride is 90 vol% or more, the thermal conductivity can be improved.

【0022】これに対し、比較例1の焼結体は、焼結体
中の軽希土類元素の含有量が2質量%と低いことから、
理論密度比が90.1%と小さく、耐電圧値も3kVと
低い値を示している。この結果より、比較例1の焼結体
では、焼結体の緻密化が進んでおらず、絶縁耐圧にも劣
る焼結体であることが判る。また、比較例2の焼結体
は、理論密度比が95.0%と比較例1に比べて若干改
善されているものの、焼結体中の軽希土類元素が15質
量%と多いことから、耐電圧値も7kVと低く、依然と
して絶縁耐圧にも劣る焼結体であることが判る。この原
因については、軽希土類元素が多量に添加されているた
めに窒化珪素の粒成長が過度に進行し、粒界三重点に残
留気孔が残存したためと考えられる。更に、比較例3の
焼結体は、軽希土類元素含有量は本発明の範囲内である
が、SrO含有量が2質量%と少ないことから、理論密
度比が92.3%と小さく、耐電圧値も5kVと低い値
を示している。この結果より、比較例3の焼結体では、
焼結体の緻密化が進んでおらず、絶縁耐圧にも劣る焼結
体であることが判る。
On the other hand, in the sintered body of Comparative Example 1, the content of the light rare earth element in the sintered body was as low as 2% by mass.
The theoretical density ratio is as small as 90.1%, and the withstand voltage value is as low as 3 kV. From this result, it can be seen that the sintered body of Comparative Example 1 is a sintered body in which the densification of the sintered body has not progressed and the dielectric strength is inferior. The sintered body of Comparative Example 2 has a theoretical density ratio of 95.0%, which is slightly improved as compared with Comparative Example 1. However, the light rare earth element in the sintered body is as large as 15% by mass. It can be seen that the withstand voltage value is as low as 7 kV and the sintered body is still inferior in the withstand voltage. It is considered that the cause is that a large amount of the light rare earth element is added, so that the grain growth of silicon nitride excessively progresses and residual pores remain at the grain boundary triple point. Further, the sintered body of Comparative Example 3 had a light rare earth element content within the range of the present invention, but had a small SrO content of 2% by mass. The voltage value also shows a low value of 5 kV. From these results, in the sintered body of Comparative Example 3,
It can be seen that the densification of the sintered body has not progressed and the sintered body is inferior in dielectric strength.

【0023】尚、本発明においては、前記具体的実施例
に示すものに限られず、目的、用途に応じて本発明の範
囲内で種々変更した実施例とすることができる。
It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention in accordance with the purpose and application.

【0024】[0024]

【発明の効果】本発明の窒化珪素焼結体によれば、窒化
珪素焼結体中、軽希土類元素及びアルカリ土類金属元素
を所定量含有させることにより、優れた熱伝導性及び絶
縁耐圧を奏すると共に、残留気孔を除去あるいは低減し
た緻密な焼結体をより経済的な方法で得ることができ
る。そして、本発明の窒化珪素焼結体は、熱伝導性及び
絶縁耐力に優れていることから、例えば半導体用絶縁基
板等の半導体装置用やOA機器等の各種部品に使用され
るセラミックスとして好適に用いることができる。
According to the silicon nitride sintered body of the present invention, by including a predetermined amount of a light rare earth element and an alkaline earth metal element in the silicon nitride sintered body, excellent thermal conductivity and dielectric strength can be obtained. In addition, a dense sintered body in which residual pores are removed or reduced can be obtained by a more economical method. And, since the silicon nitride sintered body of the present invention is excellent in thermal conductivity and dielectric strength, it is suitable as a ceramic used for various parts such as semiconductor devices such as insulating substrates for semiconductors and OA equipment, for example. Can be used.

【図面の簡単な説明】[Brief description of the drawings]

【図1】実験例において絶縁破壊電圧測定の際に使用し
た電極形状である。
FIG. 1 shows the shape of an electrode used for measuring a breakdown voltage in an experimental example.

【符号の説明】[Explanation of symbols]

1;試料、2:上部電極、3;下部電極。 1: sample, 2: upper electrode, 3: lower electrode.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 伊藤 正也 名古屋市瑞穂区高辻町14番18号 日本特殊 陶業株式会社内 Fターム(参考) 4G001 BA01 BA05 BA08 BA10 BA32 BB01 BB05 BB08 BB10 BB32 BC23 BD03 BD23 BD38  ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masaya Ito 14-18 Takatsuji-cho, Mizuho-ku, Nagoya F-term in Japan Special Ceramics Co., Ltd. 4G001 BA01 BA05 BA08 BA10 BA32 BB01 BB05 BB08 BB10 BB32 BC23 BD03 BD23 BD38

Claims (5)

【特許請求の範囲】[Claims] 【請求項1】 軽希土類元素から選ばれた少なくとも1
種の元素を酸化物換算量で3〜14質量%及びアルカリ
土類金属元素を酸化物換算量で3〜10質量%含有し、
且つ厚さ0.3mmにおける絶縁耐圧が10kV以上で
あることを特徴とする窒化珪素焼結体。
At least one selected from light rare earth elements
Containing 3 to 14% by mass of an element as an oxide and 3 to 10% by mass of an alkaline earth metal element in terms of an oxide;
A silicon nitride sintered body having a withstand voltage of 10 kV or more at a thickness of 0.3 mm.
【請求項2】 上記窒化珪素焼結体の全成分量からアル
カリ金属元素の酸化物換算量を除いた残部100質量部
に対し、アルカリ金属元素を酸化物換算量で0.5質量
部以下含有する請求項1記載の窒化珪素焼結体。
2. An alkali metal element is contained in an amount of 0.5 parts by mass or less in terms of an oxide with respect to 100 parts by mass of the total content of the silicon nitride sintered body excluding the amount of the alkali metal element in terms of oxide. The silicon nitride sintered body according to claim 1, wherein
【請求項3】 上記窒化珪素焼結体の全成分量からコバ
ルト元素又は/及びニッケル元素の酸化物換算量を除い
た残部100質量部に対し、コバルト元素又は/及びニ
ッケル元素を酸化物換算量で0.05〜2.0質量部含
有する請求項1記載の窒化珪素焼結体。
3. The amount of cobalt element and / or nickel element in terms of oxide relative to the remaining 100 parts by mass excluding the amount of cobalt element and / or nickel element in terms of oxide from the total amount of components of the silicon nitride sintered body. The silicon nitride sintered body according to claim 1, which contains 0.05 to 2.0 parts by mass.
【請求項4】 上記窒化珪素焼結体の全成分量からコバ
ルト元素又は/及びニッケル元素の酸化物換算量並びに
アルカリ金属元素の酸化物換算量を除いた残部100質
量部に対し、アルカリ金属元素を酸化物換算量で0.5
質量部以下含有する請求項1記載の窒化珪素焼結体。
4. An alkali metal element is added to the remaining 100 parts by mass of the total content of the silicon nitride sintered body excluding the oxide equivalent of the cobalt element and / or nickel and the oxide equivalent of the alkali metal element. In terms of oxide
The silicon nitride sintered body according to claim 1, which contains not more than parts by mass.
【請求項5】 焼結体中に占める窒化珪素の体積分率が
90〜95vol%であり、且つ室温における熱伝導率
が54W/m・K以上である請求項1乃至4のいずれか
に記載の窒化珪素焼結体。
5. The sintered body according to claim 1, wherein a volume fraction of silicon nitride in the sintered body is 90 to 95 vol%, and a thermal conductivity at room temperature is 54 W / m · K or more. Silicon nitride sintered body.
JP2001118678A 2001-04-17 2001-04-17 Silicon nitride sintered compact Pending JP2002316875A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009029665A (en) * 2007-07-27 2009-02-12 Kyocera Corp Circuit board and its manufacturing method
JP2010235335A (en) * 2009-03-30 2010-10-21 Kyocera Corp Ceramic sintered compact, heat dissipating substrate and electronic device
WO2014025062A1 (en) * 2012-08-10 2014-02-13 京セラ株式会社 Silicon nitride sintered compact and heat conduction member

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009029665A (en) * 2007-07-27 2009-02-12 Kyocera Corp Circuit board and its manufacturing method
JP2010235335A (en) * 2009-03-30 2010-10-21 Kyocera Corp Ceramic sintered compact, heat dissipating substrate and electronic device
WO2014025062A1 (en) * 2012-08-10 2014-02-13 京セラ株式会社 Silicon nitride sintered compact and heat conduction member
CN104470872A (en) * 2012-08-10 2015-03-25 京瓷株式会社 Silicon nitride sintered compact and heat conduction member
JPWO2014025062A1 (en) * 2012-08-10 2016-07-25 京セラ株式会社 Silicon nitride sintered body and heat conductive member

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