JP2698780B2 - Silicon nitride circuit board - Google Patents

Silicon nitride circuit board

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Publication number
JP2698780B2
JP2698780B2 JP7344238A JP34423895A JP2698780B2 JP 2698780 B2 JP2698780 B2 JP 2698780B2 JP 7344238 A JP7344238 A JP 7344238A JP 34423895 A JP34423895 A JP 34423895A JP 2698780 B2 JP2698780 B2 JP 2698780B2
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JP
Japan
Prior art keywords
silicon nitride
circuit board
substrate
thickness
thermal conductivity
Prior art date
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Expired - Lifetime
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JP7344238A
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Japanese (ja)
Other versions
JPH0969672A (en
Inventor
和男 池田
通泰 小松
信幸 水野谷
裕 小森田
孔俊 佐藤
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Toshiba Corp
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Toshiba Corp
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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】本発明は半導体装置等に使用
されるセラミックス回路基板に係り、特に放熱特性およ
び機械的強度を同時に改善し耐熱サイクル特性を向上さ
せた窒化けい素回路基板に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit board used for a semiconductor device and the like, and more particularly to a silicon nitride circuit board having improved heat radiation characteristics and mechanical strength and improved heat resistance cycle characteristics.

【０００２】[0002]

【従来の技術】従来からアルミナ（Ａｌ2 Ｏ3 ）焼結体
などのように絶縁性に優れたセラミックス基板の表面
に、導電性を有する金属回路層をろう材で一体に接合
し、さらに金属回路層の所定位置に半導体素子を搭載し
た回路基板が広く普及している。2. Description of the Related Art Conventionally, a conductive metal circuit layer is integrally joined to a surface of a ceramic substrate having excellent insulation properties, such as an alumina (Al 2 O 3 ) sintered body, with a brazing material, and further, a metal is formed. A circuit board having a semiconductor element mounted at a predetermined position on a circuit layer has been widely used.

【０００３】一方、窒化けい素を主成分とするセラミッ
クス焼結体は、一般に１０００℃以上の高温度環境下で
も優れた耐熱性を有し、かつ耐熱衝撃性にも優れている
ことから、従来の耐熱性超合金に代わる高温構造材料と
してガスタービン用部品、エンジン用部品、製鋼用機械
部品等の各種高強度耐熱部品への応用が試みられてい
る。また、金属に対する耐食性が優れていることから溶
融金属の耐溶材料としての応用も試みられ、さらに耐摩
耗性も優れていることから、軸受等の摺動部材，切削工
具への実用化も図られている。[0003] On the other hand, a ceramic sintered body containing silicon nitride as a main component generally has excellent heat resistance even in a high temperature environment of 1000 ° C or higher and also has excellent thermal shock resistance. As a high-temperature structural material replacing the heat-resistant superalloy, application to various high-strength heat-resistant parts such as parts for gas turbines, parts for engines, and mechanical parts for steelmaking has been attempted. In addition, because of its excellent corrosion resistance to metals, application of molten metal as a melting-resistant material has been attempted, and because of its excellent wear resistance, it has been put to practical use in sliding members such as bearings and cutting tools. ing.

【０００４】従来より窒化けい素セラミックス焼結体の
組成として、窒化けい素に酸化イットリウム（Ｙ
2 Ｏ3 ），酸化セリウム（ＣｅＯ），酸化カルシウム
（ＣａＯ）などの希土類元素あるいはアルカリ土類元素
の酸化物を焼結助剤として添加されたものが知られてお
り、これら焼結助剤により焼結性を高めて緻密化・高強
度化が図られている。[0004] Conventionally, as a composition of a silicon nitride ceramic sintered body, yttrium oxide (Y
It is known that an oxide of a rare earth element or an alkaline earth element such as 2 O 3 ), cerium oxide (CeO) and calcium oxide (CaO) is added as a sintering aid. Densification and high strength are achieved by improving sinterability.

【０００５】従来の窒化けい素焼結体は、窒化けい素原
料粉末に上記のような焼結助剤を添加し成形し、得られ
た成形体を１６００〜２０００℃程度の温度で焼成炉で
所定時間焼成した後に炉冷し、得られた焼結体を研削研
摩加工する製法で製造されている。A conventional silicon nitride sintered body is formed by adding the above-mentioned sintering aid to a silicon nitride raw material powder and molding the obtained molded body at a temperature of about 1600 to 2000 ° C. in a firing furnace. It is manufactured by a manufacturing method in which the sintered body obtained is calcined after sintering for an hour, and the obtained sintered body is ground and polished.

【０００６】[0006]

【発明が解決しようとする課題】しかしながら、上記従
来方法によって製造された窒化けい素焼結体では、靭性
値などの機械的強度は優れているものの、熱伝導特性の
点では、他の窒化アルミニウム（ＡｌＮ）焼結体、酸化
ベリリウム（ＢｅＯ）焼結体や炭化けい素(SiC)焼結体
などと比較して著しく低いため、特に放熱性を要求され
る半導体用回路基板などの電子用材料としては実用化さ
れておらず、用途範囲が狭い難点があった。However, although the silicon nitride sintered body manufactured by the above-mentioned conventional method has excellent mechanical strength such as toughness, it does not have the same thermal conductivity as other aluminum nitrides. AlN) sintered body, beryllium oxide (BeO) sintered body, silicon carbide (SiC) sintered body, etc., which are extremely low, so they are particularly suitable for electronic materials such as circuit boards for semiconductors that require heat dissipation. Has not been put into practical use, and has a drawback in that its application range is narrow.

【０００７】一方窒化アルミニウム焼結体は他のセラミ
ックス焼結体と比較して高い熱伝導率と低熱膨張係数の
特長を有するため、高速化、高出力化、多機能化、大型
化が進展する半導体素子（チップ）を搭載するための回
路基板部品やパッケージ材料として広く使用されてい
る。しかしながら、機械的強度の点で充分に満足できる
ものは得られていないため、回路基板の実装工程におい
て破損を生じたり、実装工程が煩雑になって半導体装置
の製造効率が低下する問題点があった。On the other hand, aluminum nitride sintered bodies have characteristics of high thermal conductivity and low coefficient of thermal expansion as compared with other ceramic sintered bodies, so that high-speed, high-output, multifunctional, and large-sized products are developed. It is widely used as a circuit board component and a package material for mounting a semiconductor element (chip). However, there has been no problem that a sufficiently satisfactory mechanical strength has been obtained, so that the circuit board may be damaged in the mounting process, or the mounting process may be complicated and the manufacturing efficiency of the semiconductor device may be reduced. Was.

【０００８】すなわち、上記窒化アルミニウム焼結体基
板や酸化アルミニウム焼結体基板などのセラミックス基
板を主たる構成材とする回路基板を、アッセンブリ工程
にて実装ボートにねじ止め等により固定しようとする
と、ねじの押圧力による僅かな変形やハンドリング時の
衝撃によって回路基板が破損し、半導体装置の製造歩留
りを大幅に低減させる場合がある。したがって、回路基
板においても、外力に耐える高強度特性と、高靭性特性
と、高出力化，高発熱量化に対応できる優れた放熱特性
とを兼ね備えたものが要請されている。That is, when a circuit board mainly composed of a ceramic substrate such as the aluminum nitride sintered body substrate or the aluminum oxide sintered body substrate described above is to be fixed to a mounting boat by a screw or the like in an assembly process, a screw is required. There is a case where the circuit board is damaged by a slight deformation due to the pressing force or an impact at the time of handling, and the production yield of the semiconductor device is largely reduced. Therefore, there is a demand for a circuit board that has both high strength characteristics to withstand external force, high toughness characteristics, and excellent heat radiation characteristics capable of coping with high output and high calorific value.

【０００９】また上記のような窒化アルミニウム基板表
面に金属回路層および半導体素子を一体に接合して形成
した回路基板においては、窒化アルミニウム基板自体の
機械的強度および靭性が不充分であったため、半導体素
子の作動に伴う繰り返しの熱サイクルを受けて、金属回
路層の接合部付近の窒化アルミニウム基板にクラックが
発生し易く、耐熱サイクル特性および信頼性が低いとい
う問題点があった。In a circuit board formed by integrally bonding a metal circuit layer and a semiconductor element on the surface of the aluminum nitride substrate as described above, the mechanical strength and toughness of the aluminum nitride substrate itself are insufficient, so The aluminum nitride substrate in the vicinity of the junction of the metal circuit layer is liable to crack due to repeated thermal cycling accompanying the operation of the element, and has a problem in that heat cycle characteristics and reliability are low.

【００１０】さらに窒化アルミニウムのように熱伝導率
が大きいセラミックス基板を使用して回路基板を製造し
た場合においても、ある程度の強度値および絶縁耐性を
確保するために、厚さが大きい窒化アルミニウム基板を
用いる必要があった。そのため、ＡｌＮ基板の高い熱伝
導率にも拘らず、回路基板全体としての熱抵抗値が増加
することになり、熱伝導率に比例した放熱性が得られな
いという問題点があった。Further, even when a circuit board is manufactured using a ceramic substrate having a high thermal conductivity such as aluminum nitride, an aluminum nitride substrate having a large thickness is required to secure a certain strength value and insulation resistance. Had to be used. Therefore, despite the high thermal conductivity of the AlN substrate, the thermal resistance value of the entire circuit board increases, and there is a problem that heat dissipation in proportion to the thermal conductivity cannot be obtained.

【００１１】本発明は上記のような課題要請に対処する
ためになされたものであり、窒化けい素焼結体が本来備
える高強度高靭性特性を利用し、さらに熱伝導率が高く
放熱性に優れるとともに耐熱サイクル特性を大幅に改善
した窒化けい素回路基板を提供することを目的とする。SUMMARY OF THE INVENTION The present invention has been made to address the above demands, and utilizes the high strength and toughness characteristics inherent in a silicon nitride sintered body, and has a high thermal conductivity and excellent heat dissipation. It is another object of the present invention to provide a silicon nitride circuit board having significantly improved heat cycle characteristics.

【００１２】[0012]

【課題を解決するための手段】本発明者は上記目的を達
成するために、回路基板の放熱性（熱伝導率）を劣化さ
せず、強度および靭性値を共に満足するような基板材料
を研究するとともに、回路基板のアッセンブリ工程にお
いて発生する締め付け割れや熱サイクル付加時に発生す
るクラックを防止する対策について鋭意研究を重ねた。
その結果、基板材料については、組成および製造条件を
適正に制御することにより、高い熱伝導率を有する窒化
けい素焼結体が得られたこと、この窒化けい素焼結体を
基板材料として使用し、基板表面に金属回路板などの回
路層を一体に形成するとともに、基板の厚さおよび金属
回路板の厚さを所定比率に設定して回路基板とした場
合、または回路基板のたわみ量や抗折強度値を所定値以
上に設定した場合に、アッセンブリ工程における回路基
板の締め付け割れ等を効果的に低減できること、耐熱サ
イクル特性を大幅に改善できること、特に基板の厚さを
低減できるために回路基板の放熱性を大幅に改善できる
こと、などを見出し本発明を完成するに至った。Means for Solving the Problems In order to achieve the above object, the present inventor has studied a substrate material which does not deteriorate the heat radiation (thermal conductivity) of a circuit board and satisfies both strength and toughness. At the same time, intensive research was conducted on measures to prevent tightening cracks generated during the assembly process of the circuit board and cracks generated when a heat cycle was applied.
As a result, for the substrate material, by appropriately controlling the composition and the manufacturing conditions, a silicon nitride sintered body having high thermal conductivity was obtained.Using this silicon nitride sintered body as a substrate material, When a circuit layer such as a metal circuit board is integrally formed on the surface of the board, and the thickness of the board and the thickness of the metal circuit board are set at a predetermined ratio to form a circuit board, or when the circuit board is bent or bent. When the strength value is set to a predetermined value or more, it is possible to effectively reduce tightening cracks and the like of the circuit board in the assembly process, significantly improve the heat cycle characteristics, and particularly to reduce the thickness of the circuit board, The inventors have found that heat dissipation can be greatly improved, and have completed the present invention.

【００１３】すなわち、基板材料自体に関して、本発明
者らは、従来使用されていた窒化けい素粉末の種類、焼
結助剤や添加物の種類および添加量、焼結条件に検討を
加え、従来の窒化けい素焼結体の有する熱伝導率の２倍
以上の高い熱伝導性を有する窒化けい素焼結体を開発し
た。さらに、この窒化けい素焼結体を基板材料として使
用し、その表面に、導電性を有する金属回路板を一体に
接合して回路基板を製造したときに、機械的強度、靭性
値、耐熱サイクル特性および放熱性を全て満足する窒化
けい素回路基板が得られることを実験により確認した。In other words, regarding the substrate material itself, the present inventors studied the types of silicon nitride powder, the types and amounts of sintering aids and additives, and the sintering conditions which were conventionally used. A silicon nitride sintered body having high thermal conductivity, which is at least twice the thermal conductivity of the silicon nitride sintered body, has been developed. Furthermore, when the silicon nitride sintered body is used as a substrate material, and a conductive metal circuit board is integrally joined to a surface of the substrate to produce a circuit board, the mechanical strength, toughness, and heat cycle characteristics are improved. Experiments have confirmed that a silicon nitride circuit board satisfying all of the heat dissipation properties can be obtained.

【００１４】具体的には、微細で高純度を有する窒化け
い素粉末に希土類元素酸化物等を所定量ずつ添加した原
料混合体を成形脱脂し、得られた成形体を所定温度で一
定時間加熱保持して緻密化焼結を実施した後、所定以下
の冷却速度で徐冷し、得られた焼結体を研削研摩加工し
て製造したときに熱伝導率が従来の窒化けい素焼結体の
２倍以上、具体的には６０Ｗ／ｍ・Ｋ以上と大きく向上
し、かつ常温（２５℃）における三点曲げ強度が６５０
ＭＰａ以上となるような高強度高靭性を有する窒化けい
素焼結体が得られることが判明し、放熱特性および強度
特性を共に満足する新規な窒化けい素材料を開発した。
そして、この窒化けい素材料を、回路基板の基板材料に
適用したときに、優れた放熱特性と耐久性と耐熱サイク
ル特性とを同時に改善できることが判明した。Specifically, a raw material mixture obtained by adding a predetermined amount of a rare earth element oxide or the like to fine and high-purity silicon nitride powder is molded and degreased, and the obtained molded body is heated at a predetermined temperature for a predetermined time. After carrying out the densification sintering while holding, it is gradually cooled at a predetermined cooling rate or less, and when the obtained sintered body is manufactured by grinding and polishing, the thermal conductivity is the same as that of a conventional silicon nitride sintered body. It is greatly improved by more than twice, specifically, more than 60 W / m · K, and the three-point bending strength at ordinary temperature (25 ° C.) is 650.
It has been found that a silicon nitride sintered body having high strength and toughness of not less than MPa can be obtained, and a novel silicon nitride material satisfying both heat radiation characteristics and strength characteristics has been developed.
It has been found that when this silicon nitride material is applied to a substrate material of a circuit board, excellent heat dissipation characteristics, durability and heat cycle characteristics can be simultaneously improved.

【００１５】また、酸素や高熱伝導化を阻害するＬｉ，
Ｎａ，Ｋ，Ｆｅ，Ｃａ，Ｍｇ，Ｓｒ，Ｂａ，Ｍｎ，Ｂと
いう特定の不純物陽イオン元素含有量を低減した高純度
の窒化けい素原料粉末を使用し、上記条件にて焼結する
ことにより、粒界相におけるガラス相（非晶質相）の生
成を効果的に抑制でき、粒界相における結晶化合物を２
０体積％以上（粒界相全体に対し）、より好ましくは５
０体積％以上とすることにより、希土類元素酸化物のみ
を原料粉末に添加した場合においても６０Ｗ／ｍ・Ｋ以
上、さらに好ましくは８０Ｗ／ｍ・Ｋ以上の高熱伝導率
を有する窒化けい素焼結体基板が得られるという知見を
得た。In addition, oxygen and Li, which inhibit high thermal conductivity,
By using a high-purity silicon nitride raw material powder having a reduced content of specific impurity cation elements such as Na, K, Fe, Ca, Mg, Sr, Ba, Mn, and B, and sintering under the above conditions. The formation of a glass phase (amorphous phase) in the grain boundary phase can be effectively suppressed,
0% by volume or more (based on the whole grain boundary phase), more preferably 5%
By setting the volume to 0% by volume or more, a silicon nitride sintered body having a high thermal conductivity of 60 W / m · K or more, more preferably 80 W / m · K or more, even when only a rare earth element oxide is added to the raw material powder. We have found that a substrate can be obtained.

【００１６】また、従来、焼結操作終了後に焼成炉の加
熱用電源をＯＦＦとして焼結体を炉冷していた場合に
は、冷却速度が毎時４００〜８００℃と急速であった
が、本発明者の実験によれば、特に冷却速度を毎時１０
０℃以下、好ましくは毎時５０℃以下に緩速に制御する
ことにより、窒化けい素焼結体組織の粒界相が非結晶質
状態から結晶相を含む相に変化し、高強度特性と高伝熱
特性とが同時に達成されることが判明した。Conventionally, when the sintered body is cooled by turning off the heating power supply of the sintering furnace after the sintering operation is completed, the cooling rate is as fast as 400 to 800 ° C. per hour. According to the experiment of the inventor, in particular, the cooling rate was set to 10
By slowly controlling the temperature to 0 ° C. or less, preferably 50 ° C./hour or less, the grain boundary phase of the silicon nitride sintered body structure changes from a non-crystalline state to a phase containing a crystalline phase. It has been found that the thermal properties are simultaneously achieved.

【００１７】このような熱伝導率が６０Ｗ／ｍ・Ｋ以上
の高熱伝導性窒化けい素焼結体自体は、その一部が既に
本発明者により特許出願されており、さらに特開平６−
１３５７７１号公報および特開平７−４８１７４号公報
によって出願公開されている。そして、これらの特許出
願において記載されている窒化けい素焼結体は、希土類
元素を酸化物に換算して２．０〜７．５重量％含有する
ものである。しかしながら、本発明者はさらに改良研究
を進めた結果、含有される希土類元素は酸化物に換算し
て７．５重量％を超えた場合の方が焼結体の高熱伝導化
がさらに進み、焼結性も良好であるため、７．５重量％
を超えたものを用いることが好ましい。特に希土類元素
がランタノイド系列の元素である場合に、その効果は顕
著である。ちなみに粒界相中における結晶化合物相の粒
界相全体に対する割合が６０〜７０％である場合におい
ても、焼結体は１１０〜１２０Ｗ／ｍ・Ｋ以上の高熱伝
導率を達成することができる。A part of such a highly thermally conductive silicon nitride sintered body having a thermal conductivity of 60 W / m · K or more has already been applied for a patent by the present inventor.
The application is published by Japanese Patent Publication No. 1359771 and Japanese Patent Application Laid-Open No. 7-48174. The silicon nitride sintered bodies described in these patent applications contain 2.0 to 7.5% by weight of a rare earth element in terms of oxide. However, as a result of further improvement research, the present inventor has found that when the content of the rare earth element exceeds 7.5% by weight in terms of oxide, the sintered body has higher thermal conductivity, and 7.5% by weight
It is preferable to use one exceeding the above. In particular, when the rare earth element is a lanthanoid element, the effect is remarkable. Incidentally, even when the ratio of the crystalline compound phase in the grain boundary phase to the entire grain boundary phase is 60 to 70%, the sintered body can achieve a high thermal conductivity of 110 to 120 W / m · K or more.

【００１８】このように高強度特性および高伝熱特性を
共に満足する窒化けい素焼結体を基板材料とし、金属回
路板を基板材料表面に一体に接合して回路基板を形成す
ることにより、回路基板全体の靭性強度および熱伝導性
を改善することができ、特に回路基板のアッセンブリ工
程における締め付け割れや熱サイクルの付加によるクラ
ックの発生を効果的に防止できることが判明した。By using a silicon nitride sintered body that satisfies both high strength characteristics and high heat transfer characteristics as a substrate material and integrally bonding a metal circuit board to the surface of the substrate material to form a circuit board, It has been found that the toughness and thermal conductivity of the entire substrate can be improved, and in particular, the occurrence of cracks due to tightening cracks and the addition of a thermal cycle in the circuit board assembly process can be effectively prevented.

【００１９】特に上記窒化けい素焼結体は、高強度特性
と高熱伝導性とに加えて、優れた絶縁耐性を有している
ため、回路基板の基板材料とした場合に、基板厚さを従
来と比較して薄く形成することが可能となる。そして基
板厚さの減少により回路基板全体の熱抵抗を低減でき、
基板材料自体の高熱伝導性にも起因して回路基板の放熱
性を相乗的に改善できることが判明した。In particular, since the above silicon nitride sintered body has excellent insulation resistance in addition to high strength characteristics and high thermal conductivity, when the substrate material of the circuit board is used, the thickness of the substrate is conventionally reduced. It can be formed thinner as compared with. And the thermal resistance of the entire circuit board can be reduced by reducing the board thickness,
It has been found that the heat dissipation of the circuit board can be synergistically improved due to the high thermal conductivity of the board material itself.

【００２０】本発明は上記知見に基づいて完成されたも
のである。すなわち本願の第１の発明に係る窒化けい素
回路基板は、熱伝導率が６０Ｗ／ｍ・Ｋ以上で三点曲げ
強度（常温）が６５０ＭＰａ以上である高熱伝導性窒化
けい素基板上に酸化層を介して金属回路板を接合してな
る窒化けい素回路基板において、上記高熱伝導性窒化け
い素基板の厚さをＤS ，金属回路板の厚さをＤM とした
ときに関係式ＤS ≦２ＤM を満たすことを特徴とする。The present invention has been completed based on the above findings. That is, the silicon nitride circuit board according to the first invention of the present application has an oxide layer formed on a high thermal conductive silicon nitride substrate having a thermal conductivity of 60 W / m · K or more and a three-point bending strength (normal temperature) of 650 MPa or more. In a silicon nitride circuit board formed by joining metal circuit boards through the above, when the thickness of the high thermal conductive silicon nitride board is D S and the thickness of the metal circuit board is D M , the relational expression D S ≦ 2D M is satisfied.

【００２１】また本願の第２の発明に係る窒化けい素回
路基板は、熱伝導率が６０Ｗ／ｍ・Ｋ以上で三点曲げ強
度（常温）が６５０ＭＰａ以上である高熱伝導性窒化け
い素基板上にＴｉ，Ｚｒ，ＨｆおよびＮｂから選択され
る少なくとも１種の活性金属を含有する金属接合層を介
して金属回路板を接合してなる窒化けい素回路基板にお
いて、上記高熱伝導性窒化けい素基板の厚さをＤS ，金
属回路板の厚さをＤMとしたときに関係式ＤS ≦２ＤM
を満たすことを特徴とする。The silicon nitride circuit board according to the second aspect of the present invention has a high thermal conductivity silicon nitride substrate having a thermal conductivity of 60 W / m · K or more and a three-point bending strength (normal temperature) of 650 MPa or more. A high-thermal-conductivity silicon nitride substrate, wherein a metal circuit board is bonded via a metal bonding layer containing at least one active metal selected from Ti, Zr, Hf and Nb. Where D S is the thickness of the metal circuit board and D M is the thickness of the metal circuit board, and D S ≦ 2D M
Is satisfied.

【００２２】なお上記第１および第２の発明に係る窒化
けい素回路基板において、高熱伝導性窒化けい素基板の
厚さＤS および金属回路板の厚さＤM が関係式ＤM ≦Ｄ
S ≦（５／３）ＤM を満たすと更に好ましい。In the silicon nitride circuit boards according to the first and second aspects of the present invention, the thickness D S of the high thermal conductive silicon nitride board and the thickness D M of the metal circuit board are expressed by a relational expression D M ≦ D
Further preferably satisfy S ≦ (5/3) D M.

【００２３】また本願の第３の発明に係る窒化けい素回
路基板は、熱伝導率が６０Ｗ／ｍ・Ｋ以上である高熱伝
導性窒化けい素基板に回路層を一体に接合した回路基板
であり、回路基板を５０mmの支持間隔で保持した状態で
中央部に荷重を付加したときに窒化けい素基板が破断に
至るまでの最大たわみ量が０．６mm以上であることを特
徴とする。A silicon nitride circuit board according to a third invention of the present application is a circuit board in which a circuit layer is integrally joined to a high thermal conductive silicon nitride substrate having a thermal conductivity of 60 W / m · K or more. When a load is applied to a central portion of the silicon nitride substrate while the circuit substrate is held at a support interval of 50 mm, the maximum deflection amount before the silicon nitride substrate is broken is 0.6 mm or more.

【００２４】また他の態様として、熱伝導率が６０Ｗ／
ｍ・Ｋ以上である高熱伝導性窒化けい素基板に回路層を
一体に接合した回路基板であり、回路基板を５０mmの支
持間隔で保持した状態で抗折試験を実施したときに抗折
強度が５００ＭＰａ以上であることを特徴とする。In another embodiment, the thermal conductivity is 60 W /
This is a circuit board in which a circuit layer is integrally bonded to a high thermal conductive silicon nitride substrate having a m · K or more, and when a bending test is performed with the circuit board held at a support interval of 50 mm, the bending strength is increased. It is characterized by being at least 500 MPa.

【００２５】さらに高熱伝導性窒化けい素基板の厚さは
０．８mm以下に設定するとよい。また回路層が銅回路板
であり、この銅回路板がＣｕ−Ｏ共晶化合物によって窒
化けい素基板に直接接合されていることを特徴とする。
さらに回路層が銅回路板であり、Ｔｉ，Ｚｒ，Ｈｆおよ
びＮｂから選択される少なくとも１種の活性金属を含有
する活性金属ろう材層を介して上記銅回路板が窒化けい
素基板に接合されるように構成してもよい。また回路層
はＷあるいはＭｏにＴｉ，Ｚｒ，ＨｆおよびＮｂから選
択される少なくとも１種の活性金属を含有する高融点金
属メタライズ層から構成してもよい。Further, the thickness of the high thermal conductive silicon nitride substrate is preferably set to 0.8 mm or less. Further, the circuit layer is a copper circuit board, and the copper circuit board is directly bonded to the silicon nitride substrate by a Cu-O eutectic compound.
Further, the circuit layer is a copper circuit board, and the copper circuit board is bonded to the silicon nitride substrate via an active metal brazing material layer containing at least one active metal selected from Ti, Zr, Hf and Nb. You may comprise so that it may be. Further, the circuit layer may be formed of a refractory metal metallization layer containing at least one active metal selected from Ti, Zr, Hf and Nb in W or Mo.

【００２６】また高熱伝導性窒化けい素基板は、希土類
元素を酸化物に換算して２．０〜１７．５重量％、不純
物陽イオン元素としてのＬｉ，Ｎａ，Ｋ，Ｆｅ，Ｃａ，
Ｍｇ，Ｓｒ，Ｂａ，Ｍｎ，Ｂを合計で０．３重量％以下
含有する窒化けい素焼結体から成ることを特徴とする。The silicon nitride substrate having high thermal conductivity has a rare earth element content of 2.0 to 17.5% by weight in terms of oxide, and Li, Na, K, Fe, Ca, as impurity cation elements.
It is characterized by comprising a silicon nitride sintered body containing Mg, Sr, Ba, Mn, and B in total of 0.3% by weight or less.

【００２７】さらに高熱伝導性窒化けい素基板は、希土
類元素を酸化物に換算して２．０〜１７．５重量％含有
し、窒化けい素結晶および粒界相から成るとともに粒界
相中における結晶化合物相の粒界相全体に対する割合が
２０％以上である窒化けい素焼結体から構成してもよ
い。Further, the silicon nitride substrate having high thermal conductivity contains 2.0 to 17.5% by weight of a rare earth element in terms of oxide, and is composed of silicon nitride crystals and a grain boundary phase. It may be composed of a silicon nitride sintered body in which the ratio of the crystalline compound phase to the entire grain boundary phase is 20% or more.

【００２８】さらに高熱伝導性窒化けい素基板は、窒化
けい素結晶および粒界相から成るとともに粒界相中にお
ける結晶化合物相の粒界相全体に対する割合が５０％以
上である窒化けい素焼結体から構成することがさらに好
ましい。Further, the high thermal conductive silicon nitride substrate is a silicon nitride sintered body comprising a silicon nitride crystal and a grain boundary phase, wherein a ratio of a crystal compound phase in the grain boundary phase to the whole grain boundary phase is 50% or more. More preferably, it is constituted.

【００２９】上記第１の発明に係る窒化けい素回路基板
においては、ろう材などの接合剤を使用せず、窒化けい
素基板表面に酸化層を形成後、金属回路板と直接接合さ
れる例えば金属回路板が銅回路板の場合には、酸素を１
００〜１０００ｐｐｍ程度含有するタフピッチ電解銅が
使用され、銅と酸化銅との共晶化合物により接合界面に
おいて両部材が直接的に接合される（ＤＢＣ法）。即
ち、ＤＢＣ法においては、共晶化合物を形成するために
必要な酸素を含有したタフピッチ電解銅が使用される。In the silicon nitride circuit board according to the first aspect of the present invention, after an oxide layer is formed on the surface of the silicon nitride board without using a bonding agent such as a brazing material, the silicon nitride circuit board is directly bonded to the metal circuit board. If the metal circuit board is a copper circuit board, add 1 oxygen.
Tough pitch electrolytic copper containing about 00 to 1000 ppm is used, and both members are directly joined at a joining interface by a eutectic compound of copper and copper oxide (DBC method). That is, in the DBC method, tough pitch electrolytic copper containing oxygen necessary to form a eutectic compound is used.

【００３０】一方、第２の発明に係る窒化けい素回路基
板おいては、窒化けい素基板の表面に酸化層を形成せ
ず、活性金属を含有する金属接合層を接合剤として使用
して窒化けい素基板と金属回路板とを接合している。こ
の場合の金属回路板は酸素を含む必要がなく、無酸素銅
やリン酸銅や無電解銅で形成したものが使用される。On the other hand, in the silicon nitride circuit board according to the second aspect of the present invention, an oxide layer is not formed on the surface of the silicon nitride substrate, and a metal bonding layer containing an active metal is used as a bonding agent. The silicon substrate and the metal circuit board are joined. In this case, the metal circuit board does not need to contain oxygen, and one made of oxygen-free copper, copper phosphate, or electroless copper is used.

【００３１】なお、上記希土類元素としてランタノイド
系列の元素を使用することが、窒化けい素基板の熱伝導
率を向上させるために特に好ましい。It is particularly preferable to use a lanthanoid element as the rare earth element in order to improve the thermal conductivity of the silicon nitride substrate.

【００３２】また、高熱伝導性窒化けい素基板が窒化ア
ルミニウムおよびアルミナの少なくとも一方を１．０重
量％以下含有するように構成してもよい。さらにアルミ
ナを１．０重量％以下と窒化アルミニウムを１．０重量
％以下とを併用してもよい。Further, the high thermal conductive silicon nitride substrate may contain at least one of aluminum nitride and alumina in an amount of 1.0% by weight or less. Further, 1.0% by weight or less of alumina and 1.0% by weight or less of aluminum nitride may be used in combination.

【００３３】また本発明で使用する高熱伝導性窒化けい
素基板は、Ｔｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，
Ｍｏ，Ｗからなる群より選択される少なくとも１種を酸
化物に換算して０．１〜０．３重量％含有することが好
ましい。このＴｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃ
ｒ，Ｍｏ，Ｗから成る群より選択される少なくとも１種
は、酸化物、炭化物、窒化物、けい化物，硼化物として
窒化けい素粉末に添加することにより含有させることが
できる。Further, the high thermal conductive silicon nitride substrate used in the present invention is made of Ti, Zr, Hf, V, Nb, Ta, Cr,
It is preferable that at least one selected from the group consisting of Mo and W is contained in an amount of 0.1 to 0.3% by weight in terms of oxide. Ti, Zr, Hf, V, Nb, Ta, C
At least one selected from the group consisting of r, Mo, and W can be contained as an oxide, carbide, nitride, silicide, or boride by being added to the silicon nitride powder.

【００３４】本発明で使用する高熱伝導性窒化けい素基
板は、例えば以下の方法で製造される。すなわち、酸素
を１．７重量％以下、不純物陽イオン元素としてのＬ
ｉ，Ｎａ，Ｋ，Ｆｅ，Ｃａ，Ｍｇ，Ｓｒ，Ｂａ，Ｍｎ，
Ｂを合計で０．３重量％以下、α相型窒化けい素を９０
重量％以上含有し、平均粒径１．０μｍ以下の窒化けい
素粉末に、希土類元素を酸化物に換算して２．０〜１
７．５重量％と、必要に応じてアルミナおよび窒化アル
ミニウムの少なくとも一方を１．０重量％以下添加した
原料混合体を成形して成形体を調製し、得られた成形体
を脱脂後、温度１８００〜２１００℃で雰囲気加圧焼結
し、上記焼結温度から、上記希土類元素により焼結時に
形成された液相が凝固する温度までに至る焼結体の冷却
速度を毎時１００℃以下にして徐冷する。The high thermal conductive silicon nitride substrate used in the present invention is manufactured, for example, by the following method. That is, oxygen is 1.7% by weight or less, and L as an impurity cation element is
i, Na, K, Fe, Ca, Mg, Sr, Ba, Mn,
B in a total of 0.3% by weight or less and α-phase silicon nitride in an amount of 90%.
Wt.% Or more and a silicon nitride powder having an average particle size of 1.0 μm or less, and a rare earth element converted to an oxide of 2.0 to 1 in terms of oxide.
A raw material mixture containing 7.5% by weight and, if necessary, at least one of alumina and aluminum nitride added in an amount of 1.0% by weight or less is molded to prepare a molded body. Atmospheric pressure sintering at 1800 to 2100 ° C, the cooling rate of the sintered body from the sintering temperature to the temperature at which the liquid phase formed during sintering by the rare earth element solidifies is set to 100 ° C or less per hour. Cool slowly.

【００３５】さらに窒化けい素粉末に、さらにＴｉ，Ｚ
ｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔａ，Ｃｒ，Ｍｏ，Ｗの酸化物、
炭化物、窒化物、けい化物、硼化物からなる群より選択
される少なくとも１種を０．１〜３．０重量％添加する
とよい。Further, Ti, Z are added to the silicon nitride powder.
oxides of r, Hf, V, Nb, Ta, Cr, Mo, W;
At least one selected from the group consisting of carbides, nitrides, silicides, and borides may be added in an amount of 0.1 to 3.0% by weight.

【００３６】上記製造方法によれば、窒化けい素結晶組
織中に希土類元素等を含む粒界相が形成され、気孔率が
２．５％以下、熱伝導率が９０Ｗ／ｍ・Ｋ以上、三点曲
げ強度が室温で６５０ＭＰａ以上の機械的特性および熱
伝導特性が共に優れた窒化けい素焼結体が得られる。According to the above manufacturing method, a grain boundary phase containing a rare earth element or the like is formed in the silicon nitride crystal structure, the porosity is 2.5% or less, the thermal conductivity is 90 W / m · K or more, and A silicon nitride sintered body having a point bending strength of 650 MPa or more at room temperature and excellent in both mechanical properties and heat conduction properties is obtained.

【００３７】本発明において使用される高熱伝導性窒化
けい素基板の主成分となる窒化けい素粉末としては、焼
結性、強度および熱伝導率を考慮して、酸素含有量が
１．７重量％以下、好ましくは０．５〜１．５重量％、
Ｌｉ，Ｎａ，Ｋ，Ｆｅ，Ｍｇ，Ｃａ，Ｓｒ，Ｂａ，Ｍ
ｎ，Ｂなどの不純物陽イオン元素含有量が合計で０．３
重量％以下、好ましくは０．２重量％以下に抑制された
α相型窒化けい素を９０重量％以上、好ましくは９３重
量％以上含有し、平均粒径が１．０μｍ以下、好ましく
は０．４〜０．８μｍ程度の微細な窒化けい素粉末を使
用することができる。The silicon nitride powder used as the main component of the high thermal conductive silicon nitride substrate used in the present invention has an oxygen content of 1.7 weight in consideration of sinterability, strength and thermal conductivity. % Or less, preferably 0.5 to 1.5% by weight,
Li, Na, K, Fe, Mg, Ca, Sr, Ba, M
The total content of impurity cation elements such as n and B is 0.3
Α-type silicon nitride, which is suppressed to not more than 0.2% by weight, preferably not more than 0.2% by weight, contains not less than 90% by weight, preferably not less than 93% by weight, and has an average particle size of not more than 1.0 μm, preferably not more than 0.1% by weight. A fine silicon nitride powder of about 4 to 0.8 μm can be used.

【００３８】平均粒径が１．０μｍ以下の微細な原料粉
末を使用することにより、少量の焼結助剤であっても気
孔率が２．５％以下の緻密な焼結体を形成することが可
能であり、また焼結助剤が熱伝導特性を阻害するおそれ
も減少する。By using a fine raw material powder having an average particle size of 1.0 μm or less, it is possible to form a dense sintered body having a porosity of 2.5% or less even with a small amount of a sintering aid. Is also possible, and the possibility that the sintering aid impairs the heat transfer properties is reduced.

【００３９】またＬｉ，Ｎａ，Ｋ，Ｆｅ，Ｃａ，Ｍｇ，
Ｓｒ，Ｂａ，Ｍｎ，Ｂの不純物陽イオン元素は熱伝導性
を阻害する物質となるため、６０Ｗ／ｍ・Ｋ以上の熱伝
導率を確保するためには、上記不純物陽イオン元素の含
有量は合計で０．３重量％以下とすることにより達成可
能である。特に同様の理由により、上記不純物陽イオン
元素の含有量は合計で０．２重量％以下とすることが、
さらに好ましい。ここで通常の窒化けい素焼結体を得る
ために使用される窒化けい素粉末には、特にＦｅ，Ｃ
ａ，Ｍｇが比較的に多く含有されているため、Ｆｅ，Ｃ
ａ，Ｍｇの合計量が上記不純物陽イオン元素の合計含有
量の目安となる。Li, Na, K, Fe, Ca, Mg,
Since the impurity cation elements of Sr, Ba, Mn, and B are substances that hinder thermal conductivity, the content of the impurity cation element must be as follows in order to secure a thermal conductivity of 60 W / m · K or more. This can be achieved by making the total 0.3% by weight or less. Particularly for the same reason, the content of the impurity cation element is set to 0.2% by weight or less in total.
More preferred. Here, the silicon nitride powder used for obtaining a normal silicon nitride sintered body includes, in particular, Fe, C
a, Mg are contained in a relatively large amount, so that Fe, C
The total amount of a and Mg is a measure of the total content of the impurity cation element.

【００４０】さらに、β相型と比較して焼結性に優れた
α相型窒化けい素を９０重量％以上含有する窒化けい素
原料粉末を使用することにより、高密度の焼結体を製造
することができる。Furthermore, a high-density sintered body is manufactured by using a silicon nitride raw material powder containing 90% by weight or more of α-phase type silicon nitride which is superior in sinterability as compared with β-phase type. can do.

【００４１】また窒化けい素原料粉末に焼結助剤として
添加する希土類元素としては、Ｈｏ，Ｅｒ，Ｙｂ，Ｙ，
Ｌａ，Ｓｃ，Ｐｒ，Ｃｅ，Ｎｄ，Ｄｙ，Ｓｍ，Ｇｄなど
の酸化物もしくは焼結操作により、これらの酸化物とな
る物質が単独で、または２種以上の酸化物を組み合せた
ものを含んでもよいが、特に酸化ホルミウム（Ｈｏ2 Ｏ
3 ），酸化エルビウム（Ｅｒ2 Ｏ3 ）が好ましい。The rare earth elements to be added to the silicon nitride raw material powder as a sintering aid include Ho, Er, Yb, Y,
Oxides such as La, Sc, Pr, Ce, Nd, Dy, Sm, and Gd, or substances that become these oxides by sintering operation alone or in combination of two or more oxides are included. Good, but especially holmium oxide (Ho 2 O
3 ) Erbium oxide (Er 2 O 3 ) is preferred.

【００４２】特に希土類元素としてランタノイド系列の
元素であるＨｏ，Ｅｒ，Ｙｂを使用することにより、焼
結性あるいは高熱伝導化が良好になり、１８５０℃程度
の低温度領域においても十分に緻密な焼結体が得られ
る。したがって焼成装置の設備費およびランニングコス
トを低減できる効果も得られる。これらの焼結助剤は、
窒化けい素原料粉末と反応して液相を生成し、焼結促進
剤として機能する。In particular, by using Ho, Er, and Yb, which are lanthanoid series elements, as a rare earth element, sinterability or high thermal conductivity is improved, and sufficiently dense sintering can be performed even in a low temperature range of about 1850 ° C. Solidification is obtained. Therefore, the effect of reducing the equipment cost and running cost of the firing apparatus can be obtained. These sintering aids are
It reacts with the silicon nitride raw material powder to form a liquid phase and functions as a sintering accelerator.

【００４３】上記焼結助剤の添加量は、酸化物換算で原
料粉末に対して２．０〜１７．５重量％の範囲とする。
この添加量が２．０重量％未満の場合は、焼結体の緻密
化が不十分であり、特に希土類元素がランタノイド系元
素のように原子量が大きい元素の場合には、低強度で低
熱伝導率の焼結体が形成される。一方、添加量が１７．
５重量％を超える過量となると、過量の粒界相が生成
し、熱伝導率の低下や強度が低下し始めるので上記範囲
とする。特に同様の理由により４〜１５重量％とするこ
とが望ましい。The amount of the sintering aid to be added is in the range of 2.0 to 17.5% by weight in terms of oxide based on the raw material powder.
When the addition amount is less than 2.0% by weight, the sintered body is insufficiently densified. In particular, when the rare earth element is an element having a large atomic weight such as a lanthanoid-based element, low strength and low thermal conductivity are obtained. Rate sintered body is formed. On the other hand, the addition amount is 17.
If the amount exceeds 5% by weight, an excessive amount of the grain boundary phase is generated, and the thermal conductivity and strength begin to decrease. It is particularly desirable to set the content to 4 to 15% by weight for the same reason.

【００４４】また上記製造方法において他の選択的な添
加成分として使用するＴｉ，Ｚｒ，Ｈｆ，Ｖ，Ｎｂ，Ｔ
ａ，Ｃｒ，Ｍｏ，Ｗの酸化物，炭化物、窒化物、けい化
物、硼化物は、上記希土類元素の焼結促進剤の機能を促
進すると共に、結晶組織において分散強化の機能を果し
Ｓｉ3 Ｎ4 焼結体の機械的強度を向上させるものであ
り、特に、Ｈｆ，Ｔｉの化合物が好ましい。これらの化
合物の添加量が０．１重量％未満の場合においては添加
効果が不充分である一方、３．０重量％を超える過量と
なる場合には熱伝導率および機械的強度や電気絶縁破壊
強度の低下が起こるため、添加量は０．１〜３．０重量
％の範囲とする。特に０．２〜２重量％とすることが望
ましい。In addition, Ti, Zr, Hf, V, Nb, T
The oxides, carbides, nitrides, silicides, and borides of a, Cr, Mo, and W promote the function of the sintering accelerator of the rare earth element, and also have the function of strengthening the dispersion of Si 3 in the crystal structure. It is intended to improve the mechanical strength of the N 4 sintered body, and particularly, compounds of Hf and Ti are preferable. When the added amount of these compounds is less than 0.1% by weight, the effect of the addition is insufficient, while when the added amount exceeds 3.0% by weight, the thermal conductivity and mechanical strength and electric breakdown are caused. Since the strength is reduced, the amount of addition is in the range of 0.1 to 3.0% by weight. In particular, it is desirable that the content be 0.2 to 2% by weight.

【００４５】また上記Ｔｉ，Ｚｒ，Ｈｆ等の化合物は窒
化けい素焼結体を黒色系に着色し不透明性を付与する遮
光剤としても機能する。そのため、特に光によって誤動
作を生じ易い集積回路等を搭載する回路基板を製造する
場合には、上記Ｔｉ等の化合物を適正に添加し、遮光性
に優れた窒化けい素基板とすることが望ましい。The compounds such as Ti, Zr, and Hf also function as a light-shielding agent for coloring the silicon nitride sintered body to a black color and imparting opacity. Therefore, in particular, when manufacturing a circuit board on which an integrated circuit or the like which easily malfunctions due to light is mounted, it is desirable to appropriately add the compound such as Ti and the like to obtain a silicon nitride substrate excellent in light shielding properties.

【００４６】さらに上記製造方法において、他の選択的
な添加成分としてのアルミナ（Ａｌ2 Ｏ3 ）は、前記希
土類元素の焼結促進剤の機能を助長する役目を果すもの
であり、特に加圧焼結を行なう場合に著しい効果を発揮
するものである。このＡｌ2 Ｏ3 の添加量が０．１重量
％未満の場合においては、より高温度での焼結が必要に
なる一方、１．０重量％を超える過量となる場合には過
量の粒界相を生成したり、または窒化けい素に固溶し始
め、熱伝導の低下が起こるため、添加量は１重量％以
下、好ましくは０．１〜０．７５重量％の範囲とする。
特に強度、熱伝導率共に良好な性能を確保するためには
添加量を０．１〜０．５重量％の範囲とすることが望ま
しい。Further, in the above-mentioned production method, alumina (Al 2 O 3 ) as another optional additive component plays a role of promoting the function of the sintering accelerator for the rare earth element. This has a remarkable effect when sintering. When the addition amount of Al 2 O 3 is less than 0.1% by weight, sintering at a higher temperature is required. On the other hand, when the addition amount exceeds 1.0% by weight, an excessive amount of grain boundaries is required. Since a phase is formed or a solid solution starts to be formed in silicon nitride to cause a decrease in heat conduction, the amount of addition is set to 1% by weight or less, preferably 0.1 to 0.75% by weight.
In particular, in order to ensure good performance in both strength and thermal conductivity, it is desirable that the amount of addition be in the range of 0.1 to 0.5% by weight.

【００４７】また、後述するＡｌＮと併用する場合に
は、その合計添加量は１．０重量％以下にすることが望
ましい。When used in combination with AlN, which will be described later, it is desirable that the total amount thereof be 1.0% by weight or less.

【００４８】さらに他の添加成分としての窒化アルミニ
ウム（ＡｌＮ）は焼結過程における窒化けい素の蒸発な
どを抑制するとともに、上記希土類元素の焼結促進剤と
しての機能をさらに助長する役目を果すものである。Aluminum nitride (AlN) as another additive component serves to suppress the evaporation of silicon nitride during the sintering process and to further promote the function of the rare earth element as a sintering accelerator. It is.

【００４９】ＡｌＮの添加量が０．１重量％未満（アル
ミナと併用する場合では０．０５重量％未満）の場合に
おいては、より高温度での焼結が必要になる一方、１．
０重量％を超える過量となる場合には過量の粒界相を生
成したり、または窒化けい素に固溶し始め、熱伝導率の
低下が起こるため、添加量は０．１〜１．０重量％の範
囲とする。特に焼結性，強度，熱伝導率共に良好な性能
を確保するためには添加量を０．１〜０．５重量％の範
囲とすることが望ましい。なお前記Ａｌ2 Ｏ3と併用す
る場合には、ＡｌＮの添加量は０．０５〜０．５重量％
の範囲が好ましい。When the addition amount of AlN is less than 0.1% by weight (less than 0.05% by weight when used in combination with alumina), sintering at a higher temperature is required, while
If the amount exceeds 0% by weight, an excessive amount of the grain boundary phase is generated, or the solid solution starts to be dissolved in silicon nitride to cause a decrease in thermal conductivity. % By weight. In particular, in order to ensure good performance in sinterability, strength, and thermal conductivity, it is desirable that the addition amount be in the range of 0.1 to 0.5% by weight. When used in combination with Al 2 O 3 , the addition amount of AlN is 0.05 to 0.5% by weight.
Is preferable.

【００５０】また焼結体の気孔率は熱伝導率および強度
に大きく影響するため２．５％以下となるように製造す
る。気孔率が２．５％を超えると熱伝導の妨げとなり、
焼結体の熱伝導率が低下するとともに、焼結体の強度低
下が起こる。Since the porosity of the sintered body greatly affects the thermal conductivity and the strength, the sintered body is manufactured to be 2.5% or less. If the porosity exceeds 2.5%, it hinders heat conduction,
As the thermal conductivity of the sintered body decreases, the strength of the sintered body decreases.

【００５１】また、窒化けい素焼結体は組織的に窒化け
い素結晶と粒界相とから構成されるが、粒界相中の結晶
化合物相の割合は焼結体の熱伝導率に大きく影響し、本
発明において使用される高熱伝導性窒化けい素焼結体に
おいては粒界相の２０％以上とすることが必要であり、
より好ましくは５０％以上が結晶相で占めることが望ま
しい。結晶相が２０％未満では熱伝導率が６０Ｗ／ｍ・
Ｋ以上となるような放熱特性に優れ、かつ高温強度に優
れた焼結体が得られないからである。Although the silicon nitride sintered body is systematically composed of silicon nitride crystals and a grain boundary phase, the proportion of the crystalline compound phase in the grain boundary phase greatly affects the thermal conductivity of the sintered body. However, in the high thermal conductivity silicon nitride sintered body used in the present invention, it is necessary that the content be 20% or more of the grain boundary phase,
More preferably, it is desirable that the crystal phase accounts for 50% or more. When the crystal phase is less than 20%, the thermal conductivity is 60 W / m ·
This is because it is not possible to obtain a sintered body having excellent heat dissipation characteristics such as K or more and high temperature strength.

【００５２】さらに上記のように窒化けい素焼結体の気
孔率を２．５％以下にし、また窒化けい素結晶組織に形
成される粒界相の２０％以上が結晶相で占めるようにす
るためには、窒化けい素成形体を温度１８００〜２１０
０℃で２〜１０時間程度、加圧焼結し、かつ焼結操作完
了直後における焼結体の冷却速度を毎時１００℃以下に
して徐冷することが重要である。Further, as described above, the porosity of the silicon nitride sintered body is set to 2.5% or less, and the crystal phase accounts for 20% or more of the grain boundary phase formed in the silicon nitride crystal structure. The silicon nitride compact was heated to a temperature of 1800 to 210
It is important to perform pressure sintering at 0 ° C. for about 2 to 10 hours and gradually cool the sintered body immediately after completion of the sintering operation at a cooling rate of 100 ° C. or less per hour.

【００５３】焼結温度を１８００℃未満とした場合に
は、焼結体の緻密化が不充分で気孔率が２．５vol%以上
になり機械的強度および熱伝導性が共に低下してしま
う。一方焼結温度が２１００℃を超えると窒化けい素成
分自体が蒸発分解し易くなる。特に加圧焼結ではなく、
常圧焼結を実施した場合には、１８００℃付近より窒化
けい素の分解蒸発が始まる。If the sintering temperature is lower than 1800 ° C., the densification of the sintered body is insufficient, the porosity becomes 2.5 vol% or more, and both the mechanical strength and the thermal conductivity decrease. On the other hand, when the sintering temperature exceeds 2100 ° C., the silicon nitride component itself tends to be vaporized and decomposed. Especially not pressure sintering,
When normal-pressure sintering is performed, decomposition and evaporation of silicon nitride starts at about 1800 ° C.

【００５４】上記焼結操作完了直後における焼結体の冷
却速度は粒界相を結晶化させるために重要な制御因子で
あり、冷却速度が毎時１００℃を超えるような急速冷却
を実施した場合には、焼結体組織の粒界相が非結晶質
（ガラス相）となり、焼結体に生成した液相が結晶相と
して粒界相に占める割合が２０％未満となり、強度およ
び熱伝導性が共に低下してしまう。The cooling rate of the sintered body immediately after the completion of the above sintering operation is an important control factor for crystallizing the grain boundary phase, and when rapid cooling is performed such that the cooling rate exceeds 100 ° C./hour. Is that the grain boundary phase of the sintered body structure becomes non-crystalline (glass phase), the ratio of the liquid phase generated in the sintered body as a crystalline phase to the grain boundary phase is less than 20%, and the strength and thermal conductivity are reduced. Both will fall.

【００５５】上記冷却速度を厳密に調整すべき温度範囲
は、所定の焼結温度（１８００〜２１００℃）から、前
記の焼結助剤の反応によって生成する液相が凝固するま
での温度範囲で充分である。ちなみに前記のような焼結
助剤を使用した場合の液相凝固点は概略１６００〜１５
００℃程度である。そして少なくとも焼結温度から上記
液相凝固温度に至るまでの焼結体の冷却速度を毎時１０
０℃以下、好ましくは５０℃以下、さらに好ましくは２
５℃以下に制御することにより、粒界相の２０％以上、
特に好ましくは５０％以上が結晶相になり、熱伝導率お
よび機械的強度が共に優れた窒化けい素焼結体が得られ
る。The temperature range in which the cooling rate should be strictly adjusted is a temperature range from a predetermined sintering temperature (1800 to 2100 ° C.) to a temperature at which a liquid phase produced by the reaction of the sintering aid solidifies. Is enough. Incidentally, the liquidus freezing point when using the sintering aid as described above is approximately 1600 to 15
It is about 00 ° C. The cooling rate of the sintered body at least from the sintering temperature to the above-mentioned liquid phase solidification temperature is set to 10
0 ° C. or lower, preferably 50 ° C. or lower, more preferably 2 ° C.
By controlling the temperature to 5 ° C. or less, 20% or more of the grain boundary phase can be obtained.
Particularly preferably, 50% or more becomes a crystalline phase, and a silicon nitride sintered body excellent in both thermal conductivity and mechanical strength can be obtained.

【００５６】本発明において使用する高熱伝導性窒化け
い素基板は、例えば以下のようなプロセスを経て製造さ
れる。すなわち前記所定の微細粒径を有し、また不純物
含有量が少ない微細な窒化けい素粉末に対して所定量の
焼結助剤、有機バインダ等の必要な添加剤および必要に
応じてＡｌ2 Ｏ3 やＡｌＮ，Ｔｉ化合物等を加えて原料
混合体を調整し、次に得られた原料混合体を成形して所
定形状の成形体を得る。原料混合体の成形法としては、
汎用の金型プレス法、ドクターブレード法のようなシー
ト成形法などが適用できる。The high thermal conductive silicon nitride substrate used in the present invention is manufactured, for example, through the following process. That is, a predetermined amount of a sintering aid, a necessary additive such as an organic binder, and optionally Al 2 O are added to the fine silicon nitride powder having the predetermined fine particle size and a small impurity content. A raw material mixture is prepared by adding 3 or an AlN or Ti compound, and then the obtained raw material mixture is molded to obtain a molded body having a predetermined shape. As a molding method of the raw material mixture,
A general-purpose mold pressing method, a sheet forming method such as a doctor blade method, and the like can be applied.

【００５７】上記成形操作に引き続いて、成形体を非酸
化性雰囲気中で温度６００〜８００℃、または空気中で
温度４００〜５００℃で１〜２時間加熱して、予め添加
していた有機バインダ成分を充分に除去し、脱脂する。
次に脱脂処理された成形体を窒素ガス、水素ガスやアル
ゴンガスなどの不活性ガス雰囲気中で１８００〜２１０
０℃の温度で所定時間雰囲気加圧焼結を行う。Subsequent to the above molding operation, the molded body is heated in a non-oxidizing atmosphere at a temperature of 600 to 800 ° C. or in air at a temperature of 400 to 500 ° C. for 1 to 2 hours, and the organic binder previously added is heated. The components are sufficiently removed and degreased.
Next, the degreased compact is placed in an inert gas atmosphere such as nitrogen gas, hydrogen gas or argon gas in an atmosphere of 1800 to 210 g.
Atmospheric pressure sintering is performed at a temperature of 0 ° C. for a predetermined time.

【００５８】上記製法によって製造された高熱伝導性窒
化けい素基板は気孔率が２．５％以下、６０Ｗ／ｍ・Ｋ
（２５℃）以上、さらには１００Ｗ／ｍ・Ｋ以上の熱伝
導率を有し、また三点曲げ強度が常温で６５０ＭＰａ以
上、さらには８００ＭＰａ以上と機械的特性にも優れて
いる。The high thermal conductive silicon nitride substrate manufactured by the above-described method has a porosity of 2.5% or less and 60 W / m · K.
(25 ° C.) or more, furthermore, 100 W / m · K or more, and the three-point bending strength at room temperature is 650 MPa or more, and furthermore, 800 MPa or more, which is excellent in mechanical properties.

【００５９】なお、低熱伝導性の窒化けい素に高熱伝導
性のＳｉＣ等を添加して焼結体全体としての熱伝導率を
６０Ｗ／ｍ・Ｋ以上にした窒化けい素焼結体は本発明の
範囲には含まれない。しかしながら、熱伝導率が６０Ｗ
／ｍ・Ｋ以上である窒化けい素焼結体に高熱伝導性のＳ
ｉＣ等を複合させた窒化けい素系焼結体の場合には、窒
化けい素焼結体自体の熱伝導率が６０Ｗ／ｍ・Ｋ以上で
ある限り、本発明の範囲に含まれることは言うまでもな
い。It should be noted that the silicon nitride sintered body of which the thermal conductivity as a whole is 60 W / m · K or more by adding high thermal conductivity SiC or the like to low thermal conductivity silicon nitride is not limited to the present invention. Not included in range. However, the thermal conductivity is 60W
/ M · K or higher silicon nitride sintered body with high thermal conductivity S
In the case of a silicon nitride-based sintered body in which iC or the like is composited, it goes without saying that the silicon nitride-based sintered body itself is included in the scope of the present invention as long as the thermal conductivity of the sintered body itself is 60 W / m · K or more. .

【００６０】また上記高熱伝導性窒化けい素基板の厚さ
ＤS は、回路基板として使用した場合の要求特性に応じ
て種々の厚さに設定されるが、本発明では金属回路板の
厚さをＤM としたときに、関係式ＤS ≦２ＤM を満たす
ものとする。すなわち、高熱伝導性窒化けい素基板の厚
さＤS は金属回路板の厚さの２倍以下とする。窒化けい
素基板の厚さＤS が金属回路板の厚さＤM の２倍以下と
することにより、特定の熱伝導率を有する窒化けい素基
板の熱抵抗を小さくし、ひいては回路基板全体の熱抵抗
を小さくすることができる。なお高熱伝導性窒化けい素
基板の厚さＤSおよび金属回路板の厚さＤM が、関係式
ＤM ≦ＤS ≦（５／３）ＤM を満たすようにすることに
より、セラミックス回路基板としての強度特性および放
熱性を同時に満足することができるので、さらに好まし
い。The thickness D S of the high thermal conductive silicon nitride substrate is set to various thicknesses according to the required characteristics when used as a circuit board. Is D M , the relational expression D S ≦ 2D M is satisfied. That is, the thickness D S of the high thermal conductivity silicon nitride substrate is not more than twice the thickness of the metal circuit plate. By thickness D S of the silicon nitride substrate is more than 2 times the thickness D M of the metal circuit plate, to reduce the thermal resistance of the silicon nitride substrate having a specific thermal conductivity, and hence the circuit board whole Thermal resistance can be reduced. By setting the thickness D S of the high thermal conductive silicon nitride substrate and the thickness D M of the metal circuit board so as to satisfy the relational expression D M ≦ D S ≦ (5/3) D M , the ceramic circuit board is formed. It is more preferable because the strength characteristics and the heat dissipation can be simultaneously satisfied.

【００６１】この場合の高熱伝導性窒化けい素基板の具
体的な厚さは、０．２５〜０．８mmの範囲である。特
に、この窒化けい素基板の厚さを０．５mm以下、好まし
くは０．４mm以下に設定することにより、回路基板全体
の厚さを低減することができ、回路基板の上下面間の熱
抵抗差を、より効果的に減少させることが可能になり、
回路基板全体の放熱性を、より改善することができる。
但し、基板としての強度特性を確保するため、高熱伝導
性窒化けい素基板についても、厚さＤS は金属回路板の
厚さＤM 以上であることが望ましい。The specific thickness of the high thermal conductive silicon nitride substrate in this case is in the range of 0.25 to 0.8 mm. In particular, by setting the thickness of the silicon nitride substrate to 0.5 mm or less, preferably 0.4 mm or less, the thickness of the entire circuit board can be reduced, and the thermal resistance between the upper and lower surfaces of the circuit board can be reduced. The difference can be reduced more effectively,
The heat dissipation of the entire circuit board can be further improved.
However, in order to ensure the strength properties of the substrate, for the high thermal conductivity silicon nitride substrate, the thickness D S is desirably thickness D M or more metal circuit plate.

【００６２】本発明に係る窒化けい素回路基板は、上記
のように製造した高熱伝導性窒化けい素基板の表面に、
導電性を有する金属回路板などの回路層を一体に接合形
成し、さらにこの金属回路板上に半導体素子を搭載して
製造される。The silicon nitride circuit board according to the present invention is provided on the surface of the high thermal conductive silicon nitride substrate manufactured as described above.
A circuit layer such as a metal circuit board having conductivity is integrally formed, and a semiconductor element is mounted on the metal circuit board.

【００６３】上記金属回路板などの回路層の形成方法ま
たは接合方法は、特に限定されず、以下に説明する直接
接合法，活性金属法またはメタライズ法などを適用する
ことができる。The method for forming or joining the circuit layer such as the metal circuit board is not particularly limited, and a direct joining method, an active metal method, a metallizing method, or the like described below can be applied.

【００６４】直接接合法は、高熱伝導性窒化けい素基板
の表面に、厚さが０．５〜１０μｍ程度の酸化層を形成
し、この酸化層を介して、回路層となる金属回路板を上
記窒化けい素基板に直接接合する方法である。ここで上
記金属回路板は、ろう材などの接合剤を使用せずに窒化
けい素基板表面に直接的に一体に接合される。すなわ
ち、例えば金属回路板が銅回路板の場合、酸素を数１０
０ｐｐｍ含有する銅材が使用され、銅と酸化銅との共晶
化合物により、両部材が直接的に接合される。In the direct bonding method, an oxide layer having a thickness of about 0.5 to 10 μm is formed on the surface of a silicon nitride substrate having high thermal conductivity, and a metal circuit board serving as a circuit layer is formed via the oxide layer. This is a method of directly bonding to the silicon nitride substrate. Here, the metal circuit board is directly and integrally bonded to the surface of the silicon nitride substrate without using a bonding agent such as a brazing material. That is, for example, when the metal circuit board is a copper circuit board, oxygen
A copper material containing 0 ppm is used, and both members are directly joined by a eutectic compound of copper and copper oxide.

【００６５】なお、この直接接合法はＡｌ2 Ｏ3 などの
酸化物系セラミックスについてのみ適用可能であり、窒
化けい素基板にそのまま適用しても基板に対する濡れ性
が低いため、金属回路板の充分な接合強度が得られな
い。This direct bonding method can be applied only to oxide ceramics such as Al 2 O 3 , and even if applied directly to a silicon nitride substrate, the wettability to the substrate is low. High bonding strength cannot be obtained.

【００６６】そこで窒化けい素基板の表面に予め酸化層
を形成し、基板に対する濡れ性を高める必要がある。こ
の酸化層は上記高熱伝導性窒化けい素基板を、空気中な
どの酸化雰囲気中で温度１０００〜１４００℃程度で２
〜１５時間加熱して形成される。この酸化層の厚さが
０．５μｍ未満の場合には、上記濡れ性の改善効果が少
ない一方、１０μｍを超えるように厚く形成しても改善
効果が飽和するとともに、却って熱伝導率が低下し易く
なるため、酸化層の厚さは０．５〜１０μｍの範囲、よ
り好ましくは１〜５μｍの範囲に設定される。Therefore, it is necessary to form an oxide layer on the surface of the silicon nitride substrate in advance to enhance the wettability to the substrate. This oxide layer is formed by heating the high thermal conductive silicon nitride substrate at a temperature of about 1000 to 1400 ° C. in an oxidizing atmosphere such as air.
It is formed by heating for ~ 15 hours. When the thickness of the oxide layer is less than 0.5 μm, the effect of improving the wettability is small. On the other hand, when the thickness is increased to more than 10 μm, the effect of improvement is saturated and the thermal conductivity is reduced. The thickness of the oxide layer is set in the range of 0.5 to 10 μm, and more preferably in the range of 1 to 5 μm, to facilitate this.

【００６７】上記酸化層は、当初Ｓｉ3 Ｎ4 基板成分の
酸化物であるＳｉＯ2 のみから構成されているが、加熱
による金属回路板の接合操作時において、Ｓｉ3 Ｎ4 基
板に焼結助剤として添加されていた希土類元素酸化物が
酸化層方向に拡散移動する結果、希土類酸化物が酸化層
中に濃縮された構成となる。例えば焼結助剤としてＹ2
Ｏ3 を使用した場合には加熱接合操作後の酸化層は、Ｙ
2 Ｏ3 を１〜２０重量％程度含有するイットリアシリケ
ートなどのＳｉＯ2 −Ｙ2 Ｏ3 化合物から構成されるよ
うになる。The oxide layer is initially composed of only SiO 2 , which is an oxide of the Si 3 N 4 substrate component. However, during the joining operation of the metal circuit board by heating, the sintering aid is applied to the Si 3 N 4 substrate. As a result of the rare earth element oxide added as an agent diffusing and moving in the direction of the oxide layer, a structure is obtained in which the rare earth oxide is concentrated in the oxide layer. For example, Y 2 as a sintering aid
When O 3 is used, the oxide layer after the heat bonding operation is Y
Comes to be composed of SiO 2 -Y 2 O 3 compound such yttria silicate containing about a 2 O 3 1 to 20% by weight.

【００６８】また上記金属回路板を構成する金属として
は、銅，アルミニウム，鉄，ニッケル，クロム，銀，モ
リブデン，コバルトの単体またはその合金など、基板成
分との共晶化合物を生成し、直接接合法を適用できる金
属であれば特に限定されないが、特に導電性および価格
の観点から銅，アルミニウムまたはその合金が好まし
い。As the metal constituting the metal circuit board, a eutectic compound with a substrate component such as a simple substance of copper, aluminum, iron, nickel, chromium, silver, molybdenum, and cobalt or an alloy thereof is formed, and is directly connected. The metal is not particularly limited as long as it is a metal to which a legal method can be applied, but copper, aluminum or an alloy thereof is particularly preferable from the viewpoint of conductivity and cost.

【００６９】金属回路板の厚さは、通電容量等を勘案し
て決定されるが、窒化けい素基板の厚さを０．２５〜
１．２mmの範囲とする一方、金属回路板の厚さを０．１
〜０．５mmの範囲に設定して両者を組み合せると熱膨張
差による変形などの影響を受けにくくなる。The thickness of the metal circuit board is determined in consideration of the current carrying capacity and the like.
While the thickness of the metal circuit board is set to 0.1 mm,
If they are set in the range of about 0.5 mm and they are combined, the influence of deformation due to a difference in thermal expansion becomes less likely.

【００７０】そして、金属回路板が銅回路板である場合
には、以下のように接合操作が実施される。すなわち酸
化層を形成した高熱伝導性窒化けい素基板の表面の所定
位置に、銅回路板を接触配置して基板方向に押圧した状
態で、銅の融点（１０８３℃）未満の温度で、かつ銅−
酸化銅の共晶温度（１０６５℃）以上に加熱し、生成し
たＣｕ−Ｏ共晶化合物液相を接合剤として銅回路板が高
熱伝導性窒化けい素基板表面に直接的に接合される。こ
の直接接合法は、いわゆる銅直接接合法（ＤＢＣ：Dire
ct Bonding Copper 法）である。さらに直接接合した銅
回路板の所定位置に半導体素子（Ｓｉチップ）を半田接
合して搭載することにより、本発明に係るＳｉ3 Ｎ4 回
路基板が製造される。When the metal circuit board is a copper circuit board, the joining operation is performed as follows. That is, in a state in which a copper circuit board is in contact with a predetermined position on the surface of a high thermal conductive silicon nitride substrate on which an oxide layer is formed and pressed in the direction of the substrate, the temperature is lower than the melting point of copper (1083 ° C.). −
The copper circuit board is heated directly to a temperature higher than the eutectic temperature of copper oxide (1065 ° C.) and the resulting Cu—O eutectic compound liquid phase is used as a bonding agent to directly bond the copper circuit board to the surface of the silicon nitride substrate having high thermal conductivity. This direct bonding method is a so-called copper direct bonding method (DBC: Dire
ct Bonding Copper method). Further, the semiconductor element (Si chip) is soldered and mounted at a predetermined position on the directly bonded copper circuit board, whereby the Si 3 N 4 circuit board according to the present invention is manufactured.

【００７１】一方、金属回路板がアルミニウム回路板で
ある場合には、Ｓｉ3 Ｎ4 基板表面にＡｌ回路板を押圧
した状態でアルミニウム−けい素の共晶温度以上に加熱
し、生成したＡｌ−Ｓｉ共晶化合物を接合剤としてＡｌ
回路板がＳｉ3 Ｎ4 基板表面に直接的に接合される。そ
して直接接合したＡｌ回路板の所定位置に半導体素子を
半田接合して搭載することにより、本発明のＳｉ3 Ｎ4
回路基板が製造される。On the other hand, when the metal circuit board is an aluminum circuit board, the aluminum circuit board is heated to a temperature higher than the eutectic temperature of aluminum-silicon while the Al circuit board is pressed against the surface of the Si 3 N 4 substrate. Al with Si eutectic compound as bonding agent
A circuit board is directly bonded to the Si 3 N 4 substrate surface. And by mounting a semiconductor element on a predetermined position of the Al circuit plate directly bonded solder bonding to, Si 3 N 4 of the present invention
A circuit board is manufactured.

【００７２】このように直接接合法を使用して金属回路
板をＳｉ3 Ｎ4 基板表面に直接接合し、さらに半導体素
子を金属回路板上に搭載して形成した本発明に係るＳｉ
3 Ｎ4 回路基板によれば、金属回路板とＳｉ3 Ｎ4 基板
との間に、接着剤やろう材のような介在物が存在しない
ため、両者間の熱抵抗が小さく、金属回路板上に設けら
れた半導体素子の発熱を系外に迅速に放散させることが
可能である。As described above, according to the present invention, the metal circuit board is directly bonded to the surface of the Si 3 N 4 substrate by using the direct bonding method, and the semiconductor element is formed by mounting the semiconductor element on the metal circuit board.
According to 3 N 4 circuit board, between the metal circuit plate and the Si 3 N 4 substrate, for inclusions such as adhesive bastard material is not present, low thermal resistance therebetween, the metal circuit board It is possible to quickly dissipate the heat generated by the semiconductor element provided in the system outside the system.

【００７３】次に活性金属法による金属回路板の接合方
法を説明する。Next, a method of joining metal circuit boards by the active metal method will be described.

【００７４】活性金属法では、Ｔｉ，Ｚｒ，Ｈｆおよび
Ｎｂから選択される少なくとも１種の活性金属を含有し
適切な組成比を有するＡｇ−Ｃｕ−Ｔｉ系ろう材等で窒
化けい素基板表面に、厚さ２０μｍ前後の活性金属ろう
材層（金属接合層）を形成し、この金属接合層を介し
て、銅回路板などの金属回路板が接合される。活性金属
は、基板に対するろう材の濡れ性を改善し、接合強度を
高める作用を有する。活性金属ろう材の具体例として
は、重量％で上記活性金属を１〜１０％，Ｃｕを１５〜
３５％，残部が実質的にＡｇから成るろう材組成物が好
適である。上記金属接合層は、このろう材組成物を有機
溶媒中に分散して調製した接合用組成物ペーストを窒化
けい素基板表面にスクリーン印刷する等の方法で形成さ
れる。In the active metal method, an Ag—Cu—Ti brazing material containing at least one active metal selected from Ti, Zr, Hf and Nb and having an appropriate composition ratio is applied to the surface of a silicon nitride substrate. An active metal brazing material layer (metal bonding layer) having a thickness of about 20 μm is formed, and a metal circuit board such as a copper circuit board is bonded via the metal bonding layer. The active metal has an effect of improving the wettability of the brazing material to the substrate and increasing the bonding strength. As a specific example of the active metal brazing material, 1% to 10% of the active metal and 15% to
Preferred is a braze composition comprising 35%, with the balance substantially consisting of Ag. The metal bonding layer is formed by a method such as screen-printing a bonding composition paste prepared by dispersing the brazing material composition in an organic solvent on the surface of a silicon nitride substrate.

【００７５】そしてスクリーン印刷した金属接合層上
に、回路層となる金属回路板を接触配置した状態で、真
空中または不活性ガス雰囲気中で、例えばＡｇ−Ｃｕ共
晶温度（７８０℃）以上で、かつ金属回路板の融点（銅
の場合は１０８３℃）以下の温度に加熱することによ
り、金属回路板が金属接合層を介して窒化けい素基板に
一体に接合される。In a state where a metal circuit board to be a circuit layer is placed in contact with the screen-printed metal bonding layer in a vacuum or an inert gas atmosphere, for example, at a temperature higher than the eutectic temperature of Ag-Cu (780 ° C.). By heating the metal circuit board to a temperature equal to or lower than the melting point of the metal circuit board (1083 ° C. for copper), the metal circuit board is integrally bonded to the silicon nitride substrate via the metal bonding layer.

【００７６】次に、メタライズ法による回路層の形成法
を説明する。メタライズ法では、例えばモリブデン（Ｍ
ｏ）やタングステン（Ｗ）などの高融点金属とＴｉやそ
の化合物とを主成分とするメタライズ組成物を窒化けい
素基板表面に焼き付けて、厚さ１５μｍ程度の回路層と
しての高融点金属メタライズ層を形成する方法である。Next, a method of forming a circuit layer by a metallizing method will be described. In the metallization method, for example, molybdenum (M
o) A refractory metal metallized layer as a circuit layer having a thickness of about 15 μm by baking a metallized composition mainly composed of a refractory metal such as tungsten (W) and Ti and its compound on the surface of a silicon nitride substrate. It is a method of forming.

【００７７】このメタライズ法により、回路層を形成す
る場合には、メタライズ層表面にさらにＮｉやＡｕから
成る厚さ３〜５μｍ程度の金属めっき層を形成すること
が好ましい。この金属めっき層を形成することにより、
メタライズ層の表面平滑性が改善され、半導体素子との
密着性がより改善されるとともに、半田濡れ性が向上す
るため、半田を使用した半導体素子の接合強度をより高
めることができる。When a circuit layer is formed by this metallization method, it is preferable to further form a metal plating layer having a thickness of about 3 to 5 μm made of Ni or Au on the surface of the metallized layer. By forming this metal plating layer,
The surface smoothness of the metallized layer is improved, the adhesion to the semiconductor element is further improved, and the solder wettability is improved, so that the bonding strength of the semiconductor element using solder can be further increased.

【００７８】上記のようにして製造した窒化けい素回路
基板の最大たわみ量は、回路基板のアッセンブリ工程に
おける締め付け割れの発生割合に大きな影響を及ぼす因
子であり、本発明では０．６mm以上、より好ましくは
０．８mm以上に設定される。上記最大たわみ量が０．６
mm未満では、アッセンブリ工程における回路基板の締め
付け割れが急増し、回路基板を使用した半導体装置の製
造歩留りが急減してしまう。The maximum amount of deflection of the silicon nitride circuit board manufactured as described above is a factor that has a great effect on the rate of occurrence of fastening cracks in the circuit board assembly process. Preferably, it is set to 0.8 mm or more. The maximum deflection is 0.6
If it is less than mm, the tightening crack of the circuit board in the assembly process will increase rapidly, and the production yield of the semiconductor device using the circuit board will decrease sharply.

【００７９】また回路基板の抗折強度も上記締め付け割
れの発生割合に影響を及ぼすとともに、窒化けい素基板
の薄型化の可否を支配する因子であり、本発明では５０
０ＭＰａ以上に規定される。この抗折強度が５００ＭＰ
ａ未満の場合では回路基板の締め付け割れが増加する。
また、従来の他のセラミックス基板よりも厚さを薄くす
ることが困難となり、薄型化に伴う回路基板全体の熱抵
抗値を相乗的に低減することが困難となる。したがって
回路基板の抗折強度は５００ＭＰａ以上に設定される
が、６００ＭＰａ以上に設定することが、より好まし
い。The bending strength of the circuit board also affects the rate of occurrence of the tightening cracks and is a factor that governs the possibility of thinning the silicon nitride substrate.
It is specified to be 0 MPa or more. This bending strength is 500MP
If it is less than a, the number of fastening cracks of the circuit board increases.
Further, it is difficult to make the thickness thinner than other conventional ceramic substrates, and it becomes difficult to synergistically reduce the thermal resistance value of the entire circuit board accompanying the thinning. Therefore, the bending strength of the circuit board is set to 500 MPa or more, and more preferably to 600 MPa or more.

【００８０】上記構成に係る窒化けい素回路基板によれ
ば、窒化けい素焼結体が本来的に有する高強度高靭性特
性に加えて特に熱伝導率を大幅に改善した高熱伝導性窒
化けい素基板表面に金属回路板を一体に接合して形成さ
れている。したがって、回路基板の靭性値が高いため、
最大たわみ量を０．６mm以上と大きく確保することがで
きる。また窒化けい素基板を従来より薄くすることが可
能であり、その場合でも回路基板の抗折強度が５００Ｍ
Ｐａ以上となる。そのため、アッセンブリ工程において
回路基板の締め付け割れが発生せず、回路基板を用いた
半導体装置を高い製造歩留りで量産することが可能にな
る。According to the silicon nitride circuit board having the above structure, in addition to the high strength and high toughness characteristics inherently possessed by the silicon nitride sintered body, the high thermal conductivity silicon nitride board has a particularly improved thermal conductivity. It is formed by integrally joining a metal circuit board to the surface. Therefore, since the toughness value of the circuit board is high,
The maximum deflection can be as large as 0.6 mm or more. Further, it is possible to make the silicon nitride substrate thinner than before, and even in that case, the flexural strength of the circuit board is 500M.
Pa or more. For this reason, the circuit board does not suffer from tightening cracks in the assembly process, and semiconductor devices using the circuit board can be mass-produced with a high production yield.

【００８１】また窒化けい素基板の靭性値が高いため、
熱サイクルによって基板に割れが発生することが少な
く、耐熱サイクル特性が著しく向上し、耐久性および信
頼性に優れた半導体装置を提供することができる。Further, since the silicon nitride substrate has a high toughness value,
It is possible to provide a semiconductor device in which a substrate is less likely to be cracked by a heat cycle, heat cycle characteristics are significantly improved, and durability and reliability are excellent.

【００８２】さらに従来では達成されていない高い熱伝
導率を有する窒化けい素基板を使用しているため、高出
力化および高集積化を指向する半導体素子を搭載した場
合においても、熱抵抗特性の劣化が少なく、優れた放熱
性を発揮する。Further, since a silicon nitride substrate having a high thermal conductivity, which has not been achieved conventionally, is used, even when a semiconductor element for high output and high integration is mounted, the thermal resistance characteristics are not improved. Deterioration is small and exhibits excellent heat dissipation.

【００８３】特に窒化けい素基板自体の機械的強度が優
れているため、要求される機械的強度特性を一定とした
場合に、他のセラミックス基板を使用した場合と比較し
て基板厚さをより低減することが可能となる。この基板
厚さを低減できることから熱抵抗値を相乗的に小さくで
き、放熱特性をさらに改善することができる。また要求
される機械的特性に対して、従来より薄い基板でも充分
に対応可能となるため、回路基板の高密度実装も可能と
なり、半導体装置をより小型化することが可能となる。In particular, since the mechanical strength of the silicon nitride substrate itself is excellent, when the required mechanical strength characteristics are fixed, the thickness of the substrate is more reduced than when other ceramic substrates are used. It becomes possible to reduce. Since the thickness of the substrate can be reduced, the thermal resistance value can be reduced synergistically, and the heat radiation characteristics can be further improved. In addition, since the required mechanical characteristics can be sufficiently coped with even a thinner substrate than before, a high-density mounting of a circuit board is also possible, and the semiconductor device can be further reduced in size.

【００８４】[0084]

【発明の実施の形態】次に本発明の実施形態について以
下に示す実施例を参照して具体的に説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be specifically described with reference to the following examples.

【００８５】実施例１〜３ 酸素を１．３重量％、不純物陽イオン元素としてＬｉ，
Ｎａ，Ｋ，Ｆｅ，Ｃａ，Ｍｇ，Ｓｒ，Ｂａ，Ｍｎ，Ｂを
合計で０．１５重量％含有し、α相型窒化けい素９７％
を含む平均粒径０．５５μｍの窒化けい素原料粉末に対
して、焼結助剤として平均粒径０．７μｍのＹ2 Ｏ
3 （酸化イットリウム）粉末５重量％、平均粒径０．５
μｍのＡｌ2 Ｏ3 （アルミナ）粉末１．０重量％を添加
し、エチルアルコール中で２４時間湿式混合した後に乾
燥して原料粉末混合体を調整した。 Examples 1 to 3 1.3% by weight of oxygen, Li, as impurity cation element
Na, K, Fe, Ca, Mg, Sr, Ba, Mn, and B are contained in a total of 0.15% by weight, and α-phase silicon nitride is 97%.
Of silicon nitride raw material powder having an average particle size of 0.55 μm containing Y 2 O having an average particle size of 0.7 μm as a sintering aid.
3 (yttrium oxide) powder 5% by weight, average particle size 0.5
1.0 wt% of Al 2 O 3 (alumina) powder having a thickness of μm was added, and the mixture was wet-mixed in ethyl alcohol for 24 hours and then dried to prepare a raw material powder mixture.

【００８６】次に得られた原料粉末混合体に有機バイン
ダを所定量添加して均一に混合した後に、１０００kg／
cm2 の成形圧力でプレス成形し、成形体を多数製作し
た。次に得られた成形体を７００℃の雰囲気ガス中にお
いて２時間脱脂した後に、この脱脂体を窒素ガス雰囲気
中９気圧にて１９００℃で６時間保持し、緻密化焼結を
実施した後に、焼結炉に付設した加熱装置への通電量を
制御して焼結炉内温度が１５００℃まで降下するまでの
間における焼結体の冷却速度がそれぞれ１００℃／hrと
なるように調整して焼結体を冷却し、さらに得られた各
焼結体を研摩加工して熱伝導率ｋが７０Ｗ／ｍ・Ｋであ
り、厚さがそれぞれ０．２５mm，０．４mm，０．６mmで
あり、縦２９mm×横６３mmである実施例１〜３用の窒化
けい素基板を調製した。上記窒化けい素基板の粒界相に
おいて結晶相が占める体積割合は３０％であり、基板の
気孔率は０．２％であった。Next, a predetermined amount of an organic binder was added to the obtained raw material powder mixture, and the mixture was uniformly mixed.
Press molding was performed at a molding pressure of cm 2 to produce a large number of compacts. Next, after the obtained compact was degreased in an atmosphere gas at 700 ° C. for 2 hours, the degreased body was held at 1900 ° C. for 6 hours at 9 atm in a nitrogen gas atmosphere, and after densifying and sintering, The amount of electricity supplied to the heating device attached to the sintering furnace was controlled so that the cooling rate of the sintered body until the temperature in the sintering furnace dropped to 1500 ° C was adjusted to 100 ° C / hr. The sintered bodies are cooled, and each of the obtained sintered bodies is polished to have a thermal conductivity k of 70 W / m · K and thicknesses of 0.25 mm, 0.4 mm, and 0.6 mm, respectively. Silicon nitride substrates for Examples 1 to 3 having a length of 29 mm and a width of 63 mm were prepared. The volume ratio of the crystal phase in the grain boundary phase of the silicon nitride substrate was 30%, and the porosity of the substrate was 0.2%.

【００８７】次に図１に示すように各窒化けい素基板２
表面の回路層を形成する部位および裏面の銅板を接合す
る部位に、３０ｗｔ％Ａｇ−６５％Ｃｕ−５％Ｔｉろう
材をスクリーン印刷し乾燥して厚さ２０μｍの活性金属
ろう材層７ａ，７ｂを形成した。この活性金属ろう材層
７ａ，７ｂの所定位置に、無酸素銅から成る厚さ０．３
mmの銅回路板４と厚さ０．２５mmの裏銅板５とを接触配
置した状態で、真空中で温度８５０℃で１０分間保持し
て接合体とした。次に各接合体をエッチング処理するこ
とにより、所定回路パターン（回路層）を形成した。さ
らに銅回路板４の中央部に、１６mm角×厚さ０．５mmの
半導体素子（出力：３００Ｗ）６を半田接合して実施例
１〜３に係る窒化けい素回路基板１を多数製造した。Next, as shown in FIG.
30 wt% Ag-65% Cu-5% Ti brazing material is screen-printed and dried on a portion where a circuit layer on the front surface is to be formed and a portion where the copper plate on the back surface is to be joined, and is dried to form a 20 μm-thick active metal brazing material layer 7 a, 7 b Was formed. At a predetermined position of the active metal brazing material layers 7a and 7b, a thickness of 0.3
In a state where the copper circuit board 4 having a thickness of 0.2 mm and the back copper plate 5 having a thickness of 0.25 mm were placed in contact with each other, the assembly was held at a temperature of 850 ° C. for 10 minutes in a vacuum. Next, a predetermined circuit pattern (circuit layer) was formed by performing an etching process on each bonded body. Further, a semiconductor element (output: 300 W) 6 of 16 mm square × 0.5 mm thickness was soldered to the center of the copper circuit board 4 to manufacture a large number of silicon nitride circuit boards 1 according to Examples 1 to 3.

【００８８】実施例４ 実施例３において使用した厚さ０．３mmおよび０．２５
mmの銅回路板に代えて表側に厚さ０．５mmの銅回路板お
よび裏側に厚さ０．３mmの裏銅板を使用した点以外は、
実施例３と同様に処理して実施例４に係るＳｉ3 Ｎ4 回
路基板を調製した。 Example 4 Thicknesses of 0.3 mm and 0.25 used in Example 3
Except for using a 0.5 mm thick copper circuit board on the front side and a 0.3 mm thick back copper sheet on the back side instead of the 0.5 mm copper circuit board,
The same processing as in Example 3 was performed to prepare a Si 3 N 4 circuit board according to Example 4.

【００８９】実施例５ 実施例２において使用した熱伝導率７０Ｗ／ｍ・Ｋの高
熱伝導性窒化けい素基板に代えて、焼結完了後における
冷却速度を調整して熱伝導率１００Ｗ／ｍ・Ｋの窒化け
い素基板を使用した以外は実施例２と同様に処理して実
施例５に係るＳｉ3 Ｎ4 回路基板を調製した。 Example 5 In place of the high thermal conductive silicon nitride substrate having a thermal conductivity of 70 W / m · K used in Example 2, the cooling rate after the completion of sintering was adjusted to adjust the thermal conductivity to 100 W / m · K. A Si 3 N 4 circuit board according to Example 5 was prepared in the same manner as in Example 2 except that a silicon nitride substrate of K was used.

【００９０】比較例１ 実施例３で使用した厚さ０．６mmの窒化けい素基板に代
えて、熱伝導率ｋが１７０Ｗ／ｍ・Ｋであり厚さが０．
８mmの窒化アルミニウム（ＡｌＮ）基板を使用した以外
は実施例３と同様に活性金属法によって基板表面に銅回
路板および裏銅板を一体に接合して比較例１に係る回路
基板を製造した。 Comparative Example 1 In place of the silicon nitride substrate having a thickness of 0.6 mm used in Example 3, the thermal conductivity k was 170 W / m · K and the thickness was 0.1 mm.
A circuit board according to Comparative Example 1 was manufactured by integrally bonding a copper circuit board and a back copper plate to the substrate surface by the active metal method in the same manner as in Example 3 except that an 8 mm aluminum nitride (AlN) substrate was used.

【００９１】比較例２ 実施例３で使用した厚さ０．６mmの窒化けい素基板に代
えて、厚さが０．８mmの窒化けい素基板を使用した以外
は実施例３と同様に活性金属法によって基板表面に銅回
路板および裏銅板を一体に接合して比較例２に係る回路
基板を製造した。 Comparative Example 2 An active metal was produced in the same manner as in Example 3 except that a silicon nitride substrate having a thickness of 0.8 mm was used instead of the silicon nitride substrate having a thickness of 0.6 mm used in Example 3. The circuit board according to Comparative Example 2 was manufactured by integrally joining a copper circuit board and a back copper board to the board surface by the method.

【００９２】このようにして調製した実施例１〜５およ
び比較例１〜２に係る回路基板の最大たわみ量および抗
折強度を測定したところ、実施例１〜５に係る窒化けい
素回路基板１は、従来の窒化アルミニウム基板を使用し
た比較例１の回路基板と比較して２倍以上の最大たわみ
量と抗折強度とを有することが判明した。また窒化けい
素基板の厚さを低減するに伴って、さらにたわみ量およ
び抗折強度が改善されることも確認できた。When the maximum deflection and flexural strength of the circuit boards according to Examples 1 to 5 and Comparative Examples 1 and 2 prepared as described above were measured, the silicon nitride circuit boards 1 according to Examples 1 to 5 were measured. Was found to have twice or more the maximum deflection and bending strength as compared with the circuit board of Comparative Example 1 using the conventional aluminum nitride substrate. In addition, it was confirmed that as the thickness of the silicon nitride substrate was reduced, the deflection amount and the bending strength were further improved.

【００９３】さらに各回路基板について放熱性評価試験
を実施した。放熱性評価試験は図３に示すように、出力
３００Ｗの半導体素子６を搭載した回路基板１を、１０
９０００Ｗ／ｍ2 ・Ｋの放熱容量を有する銅製ヒートシ
ンク８に接合した状態で半導体素子６に通電しながら半
導体素子６の表面温度Ｔｉを測定した。そして表面温度
Ｔｉが定常状態になった時点における外気温（Ｔ＝３０
０Ｋ）との差（ΔＴｉ＝Ｔｉ−Ｔ）を算出し、この半導
体素子６の温度上昇幅（ΔＴｉ）の大小によって放熱性
の良否を評価した。温度上昇幅（ΔＴｉ）の測定値を表
１に示す。Further, a heat radiation evaluation test was carried out for each circuit board. As shown in FIG. 3, the circuit board 1 on which the semiconductor element 6 having an output of 300 W was mounted was subjected to a heat radiation evaluation test.
The surface temperature Ti of the semiconductor element 6 was measured while energizing the semiconductor element 6 in a state of being joined to the copper heat sink 8 having a heat dissipation capacity of 9000 W / m 2 · K. Then, the outside air temperature (T = 30) when the surface temperature Ti is in a steady state.
0K) (ΔTi = Ti−T), and the degree of heat dissipation was evaluated based on the magnitude of the temperature rise (ΔTi) of the semiconductor element 6. Table 1 shows the measured values of the temperature rise width (ΔTi).

【００９４】表１に示す結果から明らかなように、各実
施例の回路基板によれば、従来のＡｌＮ基板（比較例
１）よりも熱伝導率が小さいＳｉ3 Ｎ4 基板を使用して
いるにも拘らず、Ｓｉ3 Ｎ4 基板の厚さを薄く形成でき
るため、回路基板全体の熱抵抗を低減することができ
る。したがって、半導体素子の温度上昇幅ΔＴｉは従来
のＡｌＮ回路基板とほぼ同等になり、優れた放熱性を示
すことが判明した。さらにＳｉ3 Ｎ4 基板厚さの低減化
により、熱抵抗が減少するため、回路基板全体としての
放熱特性をさらに改善できることも確認できた。As is clear from the results shown in Table 1, according to the circuit boards of the respective examples, the Si 3 N 4 substrate having a lower thermal conductivity than the conventional AlN substrate (Comparative Example 1) is used. Nevertheless, since the thickness of the Si 3 N 4 substrate can be reduced, the thermal resistance of the entire circuit substrate can be reduced. Therefore, the temperature increase width ΔTi of the semiconductor element was almost equal to that of the conventional AlN circuit board, and it was found that the semiconductor element exhibited excellent heat dissipation. Further, it was also confirmed that the heat resistance was reduced by reducing the thickness of the Si 3 N 4 substrate, so that the heat radiation characteristics of the entire circuit substrate could be further improved.

【００９５】一方、金属回路板の厚さの２倍を超える
０．８mm厚のＳｉ3 Ｎ4 基板を使用した比較例２におい
ては、半導体素子の温度上昇ΔＴｉが大きく、放熱特性
が相対的に低いことが判明した。On the other hand, in Comparative Example 2 using a 0.8 mm thick Si 3 N 4 substrate which is more than twice the thickness of the metal circuit board, the temperature rise ΔTi of the semiconductor element was large and the heat radiation characteristics were relatively low. It turned out to be low.

【００９６】上記各実施例の回路基板をアッセンブリ工
程においてボードに実装したところ、締め付け割れが発
生せず、回路基板を用いた半導体装置を高い製造歩留り
で量産することができた。When the circuit boards of the above embodiments were mounted on a board in the assembly process, no tightening cracks were generated, and the semiconductor devices using the circuit boards could be mass-produced with a high production yield.

【００９７】また各回路基板について−４５℃から室温
（ＲＴ）まで加熱し、引き続き室温から＋１２５℃まで
加熱した後に、室温を経て再び−４５℃に冷却するまで
を１サイクルとする昇温−降温サイクルを繰り返して付
加し、基板部にクラック等が発生するまでのサイクル数
を測定する耐熱サイクル試験を実施したところ、実施例
１〜５の回路基板では１０００サイクル経過後において
も、Ｓｉ3 Ｎ4 基板の割れや金属回路板（Ｃｕ回路板）
の剥離が皆無であり、優れた耐熱サイクル特性を示すこ
とが判明した。一方、比較例１のＡｌＮ回路基板におい
ては、１００サイクルでクラックが発生し、耐久性が低
いことが確認された。Further, each circuit board is heated from -45 ° C. to room temperature (RT), and subsequently heated from room temperature to + 125 ° C., and then heated and cooled in one cycle from the room temperature to cooling down to −45 ° C. A cycle was repeatedly added and a heat cycle test was performed to measure the number of cycles until cracks or the like occurred in the substrate portion. As a result, the circuit boards of Examples 1 to 5 showed that even after 1000 cycles, Si 3 N 4 Board cracks and metal circuit boards (Cu circuit boards)
No exfoliation was observed, indicating that the composition exhibited excellent heat cycle resistance. On the other hand, in the AlN circuit board of Comparative Example 1, cracks were generated in 100 cycles, and it was confirmed that the durability was low.

【００９８】実施例６〜１０ 活性金属法に代えて銅直接接合法（ＤＢＣ法）によって
金属回路板をＳｉ3 Ｎ4 基板に一体に接合し、実施例１
〜５に対応する同一寸法の実施例６〜１０に係るＳｉ3
Ｎ4 基板を下記要領で製造した。 Examples 6 to 10 Instead of the active metal method, a metal circuit board was integrally joined to a Si 3 N 4 substrate by a copper direct joining method (DBC method).
Si 3 according to Examples 6 to 10 of the same dimensions corresponding to
An N 4 substrate was manufactured as follows.

【００９９】すなわち、実施例１〜５において調製した
Ｓｉ3 Ｎ4 基板であり熱伝導率ｋが７０Ｗ／ｍ・Ｋまた
は１００Ｗ／ｍ・Ｋであり厚さがそれぞれ０．２５mm，
０．４mm，０．６mm，０．８mmである各Ｓｉ3 Ｎ4 基板
を酸化炉中で温度１３００℃で１２時間加熱することに
より、基板の全表面を酸化し、厚さ２μｍの酸化層を形
成した。酸化層はＳｉＯ2 皮膜で形成される。That is, the Si 3 N 4 substrate prepared in Examples 1 to 5, having a thermal conductivity k of 70 W / m · K or 100 W / m · K, a thickness of 0.25 mm,
By heating each of the 0.4 mm, 0.6 mm and 0.8 mm Si 3 N 4 substrates in an oxidation furnace at a temperature of 1300 ° C. for 12 hours, the entire surface of the substrates is oxidized to form an oxide layer having a thickness of 2 μm. Formed. The oxide layer is formed of a SiO 2 film.

【０１００】次に酸化層を形成した各Ｓｉ3 Ｎ4 基板表
面側に、表１に示すように、厚さ０．３mmまたは０．５
mmのタフピッチ電解銅から成る銅回路板を接触配置する
一方、背面側に厚さ０．２５mmまたは０．３mmのタフピ
ッチ電解銅から成る銅回路板を裏当て材として接触配置
させて積層体とし、この積層体を窒素ガス雰囲気に調整
した温度１０７５℃の加熱炉に挿入して１分間加熱する
ことにより、各Ｓｉ3 Ｎ4 基板の両面に銅回路板を直接
接合し、さらに半導体素子を半田接合して実施例６〜１
０に係るＳｉ3 Ｎ4 回路基板をそれぞれ調製した。Next, as shown in Table 1, a thickness of 0.3 mm or 0.5 mm was formed on the surface of each Si 3 N 4 substrate on which the oxide layer was formed.
A copper circuit board made of tough pitch electrolytic copper having a thickness of 0.2 mm is arranged in contact with the copper circuit board made of tough pitch electrolytic copper having a thickness of 0.25 mm or 0.3 mm on the back side as a backing material to form a laminate, This laminate was inserted into a heating furnace at a temperature of 1075 ° C. adjusted to a nitrogen gas atmosphere and heated for 1 minute, thereby directly bonding a copper circuit board to both surfaces of each Si 3 N 4 substrate and further soldering a semiconductor element. Examples 6 to 1
No. 0 Si 3 N 4 circuit boards were prepared.

【０１０１】各Ｓｉ3 Ｎ4 回路基板１ａは、図２に示す
ようにＳｉ3 Ｎ4 基板２の全表面にＳｉＯ2 から成る酸
化層３が形成されており、Ｓｉ3 Ｎ4 基板２の表面側に
金属回路板としての銅回路板４が直接接合される一方、
背面側に裏銅板としての銅回路板５が同様に直接接合さ
れ、さらに表面側の銅回路板４の所定位置に図示しない
半田層を介して半導体素子６がそれぞれ一体に接合され
た構造を有する。なおＳｉ3 Ｎ4 基板２の両面に銅回路
板４，５を接合した場合、裏銅板としての銅回路板５は
放熱促進および反り防止に寄与するので有効である。[0102] Each Si 3 N 4 circuit board 1a is oxidized layer 3 made of SiO 2 is formed on the entire surface the Si 3 N 4 substrate 2 as shown in FIG. 2, Si 3 N 4 surface of the substrate 2 While the copper circuit board 4 as a metal circuit board is directly joined to the side,
Similarly, a copper circuit board 5 as a back copper plate is directly bonded to the back side, and further, semiconductor elements 6 are integrally bonded to predetermined positions of the copper circuit board 4 on the front side via a solder layer (not shown). . When the copper circuit boards 4 and 5 are bonded to both sides of the Si 3 N 4 substrate 2, the copper circuit board 5 as the back copper plate is effective because it contributes to promoting heat radiation and preventing warpage.

【０１０２】上記のように直接接合法によって回路層を
形成した実施例６〜１０に係るＳｉ3 Ｎ4 回路基板の最
大たわみ量は０．８〜１．６mmの範囲であり、また抗折
強度は５５０〜９００ＭＰａの範囲であり、実施例１〜
５のように活性金属法で回路層を形成した場合と同等の
特性値が得られた。また耐熱サイクル試験において１０
００サイクル経過後においてもＳｉ3 Ｎ4 基板の割れや
金属回路板の剥離が皆無であり、優れた耐熱サイクル特
性を示した。The maximum deflection amount of the Si 3 N 4 circuit boards according to Examples 6 to 10 in which the circuit layers were formed by the direct bonding method as described above was in the range of 0.8 to 1.6 mm, and the bending strength was large. Is in the range of 550 to 900 MPa, and
As shown in FIG. 5, the same characteristic values as those obtained when the circuit layer was formed by the active metal method were obtained. In the heat cycle test, 10
Even after the lapse of 00 cycles, there was no cracking of the Si 3 N 4 substrate or peeling of the metal circuit board, indicating excellent heat cycle characteristics.

【０１０３】比較例３ 実施例８で使用した窒化けい素基板に代えて、熱伝導率
ｋが１７０Ｗ／ｍ・Ｋであり厚さが０．８mmの窒化アル
ミニウム（ＡｌＮ）基板を使用した以外は実施例８と同
様に銅直接接合法によって基板表面に銅回路板および裏
銅板を一体に接合して比較例３に係る回路基板を製造し
た。 Comparative Example 3 An aluminum nitride (AlN) substrate having a thermal conductivity k of 170 W / m · K and a thickness of 0.8 mm was used in place of the silicon nitride substrate used in Example 8. A circuit board according to Comparative Example 3 was manufactured by integrally joining a copper circuit board and a back copper sheet to the board surface by the copper direct joining method in the same manner as in Example 8.

【０１０４】比較例４ 実施例８で使用した厚さ０．６mmの窒化けい素基板に代
えて、厚さが０．８mmの窒化けい素基板を使用した以外
は実施例８と同様に銅直接接合法によって基板表面に銅
回路板および裏銅板を一体に接合して比較例４に係る回
路基板を製造した。COMPARATIVE EXAMPLE 4 The same procedure as in Example 8 was repeated except that the silicon nitride substrate having a thickness of 0.8 mm was used instead of the silicon nitride substrate having a thickness of 0.6 mm used in Example 8. A circuit board according to Comparative Example 4 was manufactured by integrally joining a copper circuit board and a back copper sheet to the board surface by a joining method.

【０１０５】上記のように製造した実施例６〜１０およ
び比較例３〜４に係る回路基板について、実施例１〜５
および比較例１〜２と同様に図３に示す放熱性評価試験
を実施し、出力３００Ｗの半導体素子の発熱に伴う温度
上昇幅ΔＴｉを測定して下記表１に示す結果を得た。ま
た窒化けい素基板等のセラミックス基板の厚さと半導体
素子の温度上昇ΔＴｉとの関係をグラフ化して図４に示
す。With respect to the circuit boards according to Examples 6 to 10 and Comparative Examples 3 and 4 manufactured as described above, Examples 1 to 5
A heat radiation evaluation test shown in FIG. 3 was performed in the same manner as in Comparative Examples 1 and 2, and the temperature increase width ΔTi accompanying the heat generation of the semiconductor element having an output of 300 W was measured, and the results shown in Table 1 below were obtained. FIG. 4 is a graph showing the relationship between the thickness of a ceramic substrate such as a silicon nitride substrate and the temperature rise ΔTi of a semiconductor element.

【０１０６】[0106]

【表１】 [Table 1]

【０１０７】上記表１および図４に示す結果から明らか
なように、窒化けい素基板の厚さを減少させるにつれ
て、回路基板全体の熱抵抗が減少し、半導体素子の温度
上昇ΔＴｉが一次的に減少して放熱性が改善されること
が確認できた。特に実施例６（◎印）と実施例１０（▽
印）と比較例３（●印）との比較から明らかなように、
熱伝導率が７０Ｗ／ｍ・Ｋで厚さが０．２５mmのＳｉ3
Ｎ4 基板または熱伝導率が１００Ｗ／ｍ・Ｋで厚さが
０．４mmのＳｉ3 Ｎ4 基板を使用して回路基板を形成す
ることにより、熱伝導率が１７０Ｗ／ｍ・Ｋで厚さが
０．８mmのＡｌＮ基板を使用して形成した回路基板と同
等の放熱性を確保することができた。そして基板厚さを
従来と比較して１／２以下に低減することが可能とな
り、基板の製造コストを低減することも可能となる。As is clear from the results shown in Table 1 and FIG. 4, as the thickness of the silicon nitride substrate is reduced, the thermal resistance of the entire circuit substrate is reduced, and the temperature rise ΔTi of the semiconductor element is temporarily reduced. It was confirmed that the heat dissipation was improved due to the decrease. In particular, Example 6 (◎) and Example 10 (▽)
) And Comparative Example 3 (●),
Si 3 with a thermal conductivity of 70 W / m · K and a thickness of 0.25 mm
By forming a circuit board using an N 4 substrate or a Si 3 N 4 substrate having a thermal conductivity of 100 W / m · K and a thickness of 0.4 mm, the thermal conductivity is 170 W / m · K and the thickness is Was able to secure heat radiation equivalent to that of a circuit board formed using a 0.8 mm AlN substrate. In addition, the thickness of the substrate can be reduced to 以下 or less as compared with the related art, and the manufacturing cost of the substrate can be reduced.

【０１０８】なお各Ｓｉ3 Ｎ4 基板は薄く形成した場合
においても絶縁耐性が良好であり、従来と同等以上の絶
縁破壊耐性を保持できることも判明した。一方、金属回
路板の厚さの２倍を超える０．８mm厚のＳｉ3 Ｎ4 基板
を使用した比較例４においては、半導体素子の温度上昇
ΔＴｉが大きく、放熱特性が相対的に低いことが判明し
た。It was also found that each Si 3 N 4 substrate had good insulation resistance even when formed thinly, and could maintain insulation breakdown resistance equal to or higher than the conventional one. On the other hand, in Comparative Example 4 using a 0.8 mm thick Si 3 N 4 substrate which is more than twice the thickness of the metal circuit board, the temperature rise ΔTi of the semiconductor element is large and the heat radiation characteristics are relatively low. found.

【０１０９】次に本発明で使用する窒化けい素基板の厚
さの大小が回路基板のたわみ量や抗折る強度に及ぼす影
響について、以下に示す実施例を参照して説明する。Next, the effect of the thickness of the silicon nitride substrate used in the present invention on the amount of deflection and the strength against bending of the circuit board will be described with reference to the following examples.

【０１１０】実施例１１〜１３ 酸素を１．３重量％、前記不純物陽イオン元素を合計で
０．１５重量％含有し、α相型窒化けい素９７％を含む
平均粒径０．５５μｍの窒化けい素原料粉末に対して、
焼結助剤として平均粒径０．７μｍのＹ2 Ｏ3 （酸化イ
ットリウム）粉末５重量％、平均粒径０．５μｍのＡｌ
2 Ｏ3 （アルミナ）粉末１．５重量％を添加し、エチル
アルコール中で２４時間湿式混合した後に乾燥して原料
粉末混合体を調整した。 Examples 11 to 13 Nitrides having an average particle size of 0.55 μm containing 1.3% by weight of oxygen and 0.15% by weight of the impurity cation element in total and containing 97% of α-phase type silicon nitride. For silicon raw material powder,
5% by weight of Y 2 O 3 (yttrium oxide) powder having an average particle size of 0.7 μm as an sintering aid, Al having an average particle size of 0.5 μm
1.5 wt% of 2 O 3 (alumina) powder was added, wet-mixed in ethyl alcohol for 24 hours, and dried to prepare a raw material powder mixture.

【０１１１】次に得られた原料粉末混合体に有機バイン
ダを所定量添加して均一に混合した後に、１０００kg／
cm2 の成形圧力でプレス成形し、長さ８０mm×幅５０mm
×厚さ１〜５mmの成形体を多数製作した。次に得られた
成形体を７００℃の雰囲気ガス中において２時間脱脂し
た後に、この脱脂体を窒素ガス雰囲気中９気圧にて１９
００℃で６時間保持し、緻密化焼結を実施した後に、焼
結炉に付設した加熱装置への通電量を制御して焼結炉内
温度が１５００℃まで降下するまでの間における焼結体
の冷却速度がそれぞれ１００℃／hrとなるように調整し
て焼結体を冷却し、さらに得られた各焼結体を研摩加工
してそれぞれ熱伝導率ｋが７０Ｗ／ｍ・Ｋであり、厚さ
が０．４mm，０．６mm，０．８mmである実施例１１〜１
３用の窒化けい素基板を調製した。Next, a predetermined amount of an organic binder was added to the obtained raw material powder mixture and uniformly mixed.
Press molding with a molding pressure of cm 2 , length 80mm x width 50mm
× Many molded bodies having a thickness of 1 to 5 mm were produced. Next, after the obtained molded body was degreased in an atmosphere gas at 700 ° C. for 2 hours, the degreased body was degreased in a nitrogen gas atmosphere at 9 atm.
After holding at 00 ° C. for 6 hours and performing densification sintering, sintering is performed until the temperature in the sintering furnace falls to 1500 ° C. by controlling the amount of electricity to the heating device attached to the sintering furnace. The sintered bodies were cooled by adjusting the cooling rates of the bodies to 100 ° C./hr, and the obtained sintered bodies were polished to obtain a thermal conductivity k of 70 W / m · K. Examples 11 to 1 having thicknesses of 0.4 mm, 0.6 mm and 0.8 mm
A silicon nitride substrate for No. 3 was prepared.

【０１１２】次に図５に示すように各窒化けい素基板２
表面の回路層を形成する部位および裏面の銅板を接合す
る部位に、３０ｗｔ％Ａｇ−６５％Ｃｕ−５％Ｔｉろう
材をスクリーン印刷し乾燥して厚さ２０μｍの活性金属
ろう材層７ａ，７ｂを形成した。この活性金属ろう材層
７ａ，７ｂの所定位置に、タフピッチ電解銅から成る厚
さ０．３mmの銅回路板４と厚さ０．２５mm値の裏銅板５
とを接触配置した状態で、真空中で温度８５０℃で１０
分間保持して接合体とした。次に各接合体をエッチング
処理することにより、所定回路パターンを形成した。さ
らに銅回路板４の中央部に半導体素子６を半田接合して
実施例１１〜１３に係る窒化けい素回路基板１ｂを多数
製造した。Next, as shown in FIG.
30 wt% Ag-65% Cu-5% Ti brazing material is screen-printed and dried on a portion where a circuit layer on the front surface is to be formed and a portion where the copper plate on the back surface is to be joined, and is dried to form a 20 μm-thick active metal brazing material layer 7 a, 7 b Was formed. A copper circuit board 4 made of tough pitch electrolytic copper and having a thickness of 0.3 mm and a back copper board 5 having a thickness of 0.25 mm are provided at predetermined positions of the active metal brazing layers 7a and 7b.
And 850 ° C. in a vacuum at 10 ° C.
The mixture was held for minutes. Next, a predetermined circuit pattern was formed by etching each of the joined bodies. Further, the semiconductor element 6 was soldered to the center of the copper circuit board 4 to manufacture a number of silicon nitride circuit boards 1b according to Examples 11 to 13.

【０１１３】比較例５ 実施例１１〜１３で使用した窒化けい素基板に代えて、
熱伝導率ｋが７０Ｗ／ｍ・Ｋであり厚さが０．８mmの窒
化アルミニウム（ＡｌＮ）基板を使用した以外は実施例
１１〜１３と同様に活性金属法によって基板表面に銅回
路板および裏銅板を一体に接合して比較例５に係る回路
基板を製造した。 Comparative Example 5 Instead of the silicon nitride substrate used in Examples 11 to 13,
Except for using an aluminum nitride (AlN) substrate having a thermal conductivity k of 70 W / m · K and a thickness of 0.8 mm, a copper circuit board and a backside were formed on the substrate surface by the active metal method in the same manner as in Examples 11 to 13. A circuit board according to Comparative Example 5 was manufactured by integrally joining the copper plates.

【０１１４】このようにして調製した実施例１１〜１３
および比較例５に係る回路基板の最大たわみ量および抗
折強度を測定して図６および図７に示す結果を得た。こ
こで最大たわみ量は、支持スパン５０mmで各回路基板を
支持した状態で中央部に荷重を付加し、Ｓｉ3 Ｎ4 基板
またはＡｌＮ基板が破断に至るまでの最大たわみ高さと
して測定した。また抗折強度は、破断時の荷重と基板断
面積とから算出した。Examples 11 to 13 thus prepared
The maximum deflection amount and bending strength of the circuit board according to Comparative Example 5 were measured, and the results shown in FIGS. 6 and 7 were obtained. Here, the maximum deflection amount was measured as a maximum deflection height until a Si 3 N 4 substrate or an AlN substrate was broken while a load was applied to the central portion while supporting each circuit board with a support span of 50 mm. The bending strength was calculated from the load at break and the cross-sectional area of the substrate.

【０１１５】図６および図７に示す結果から明らかなよ
うに、実施例１１〜１３に係る窒化けい素回路基板１ｂ
は、従来の窒化アルミニウム基板を使用した比較例５の
回路基板と比較して２倍以上の最大たわみ量と抗折強度
とを有することが判明した。また窒化けい素基板の厚さ
を低減するに伴って、さらにたわみ量および抗折強度が
改善されることも確認できた。さらに基板厚さの低減化
により、熱抵抗が減少するため、回路基板全体としての
放熱特性をさらに改善できることも確認できた。As is clear from the results shown in FIGS. 6 and 7, the silicon nitride circuit boards 1b according to Examples 11 to 13 are formed.
Was found to have twice or more the maximum deflection and bending strength as compared with the circuit board of Comparative Example 5 using the conventional aluminum nitride substrate. In addition, it was confirmed that as the thickness of the silicon nitride substrate was reduced, the deflection amount and the bending strength were further improved. Further, it was confirmed that the heat resistance was reduced by reducing the thickness of the substrate, so that the heat radiation characteristics of the entire circuit substrate could be further improved.

【０１１６】上記回路基板をアッセンブリ工程において
ボードに実装したところ、締め付け割れが発生せず、回
路基板を用いた半導体装置を高い製造歩留りで量産する
ことができた。When the above-mentioned circuit board was mounted on a board in an assembly process, no tightening cracks occurred, and mass production of semiconductor devices using the circuit board was possible with a high production yield.

【０１１７】また各回路基板について−４５℃から室温
（ＲＴ）まで加熱し、引き続き室温から＋１２５℃まで
加熱した後に、室温を経て再び−４５℃に冷却するまで
を１サイクルとする昇温−降温サイクルを繰り返して付
加し、基板部にクラック等が発生するまでのサイクル数
を測定する耐熱サイクル試験を実施したところ、実施例
１１〜１３の回路基板では１０００サイクル経過後にお
いても、Ｓｉ3 Ｎ4 基板の割れや金属回路板（Ｃｕ回路
板）の剥離が皆無であり、優れた耐熱サイクル特性を示
すことが判明した。一方、比較例５の回路基板において
は、１００サイクルでクラックが発生し、耐久性が低い
ことが確認された。Further, each circuit board is heated from -45 ° C. to room temperature (RT), then heated from room temperature to + 125 ° C., and then heated up and down in one cycle from room temperature to cooling down to −45 ° C. When a heat-resistant cycle test for measuring the number of cycles until cracks or the like were generated in the board portion was performed by repeatedly adding the cycles, the circuit boards of Examples 11 to 13 showed that even after 1000 cycles, Si 3 N 4 was obtained. It was found that there was no cracking of the substrate and no peeling of the metal circuit board (Cu circuit board), indicating excellent heat cycle characteristics. On the other hand, in the circuit board of Comparative Example 5, it was confirmed that cracks occurred in 100 cycles and durability was low.

【０１１８】実施例１４ 実施例１１〜１３において調製したＳｉ3 Ｎ4 基板であ
り熱伝導率ｋが７０Ｗ／ｍ・Ｋ，厚さがそれぞれ０．４
mm，０．６mm，０．８mmである各Ｓｉ3 Ｎ4基板を酸化
炉中で温度１３００℃で１２時間加熱することにより、
基板の全表面を酸化し、厚さ２μｍの酸化層を形成し
た。 Example 14 The Si 3 N 4 substrate prepared in Examples 11 to 13 had a thermal conductivity k of 70 W / m · K and a thickness of 0.4 W, respectively.
By heating each Si 3 N 4 substrate of mm, 0.6 mm and 0.8 mm in an oxidation furnace at a temperature of 1300 ° C. for 12 hours,
The entire surface of the substrate was oxidized to form an oxide layer having a thickness of 2 μm.

【０１１９】次に酸化層を形成した各Ｓｉ3 Ｎ4 基板表
面側に、厚さ０．３mmのタフピッチ電解銅から成る銅回
路板を接触配置する一方、背面側に厚さ０．２５mmのタ
フピッチ銅から成る銅回路板を裏当て材として接触配置
させて積層体とし、この積層体を窒素ガス雰囲気に調整
した温度１０７５℃の加熱炉に挿入して１分間加熱する
ことにより、図８に示すように各Ｓｉ3 Ｎ4 基板２の両
面に銅回路板を直接接合したＳｉ3 Ｎ4 回路基板をそれ
ぞれ調製した。Next, a copper circuit board made of tough pitch electrolytic copper having a thickness of 0.3 mm is placed in contact with the surface of each Si 3 N 4 substrate on which the oxide layer is formed, while a tough pitch having a thickness of 0.25 mm is provided on the back side. A copper circuit board made of copper is placed in contact with a backing material to form a laminate, and this laminate is inserted into a heating furnace at a temperature of 1075 ° C. adjusted to a nitrogen gas atmosphere and heated for 1 minute, thereby obtaining a structure shown in FIG. as the Si 3 N 4 circuit board directly bonded copper circuit board on both sides of the Si 3 N 4 substrate 2 were prepared.

【０１２０】各Ｓｉ3 Ｎ4 回路基板１ｃは、図８に示す
ようにＳｉ3 Ｎ4 基板２の全表面に酸化層３が形成され
ており、Ｓｉ3 Ｎ4 基板２の表面側に金属回路板として
の銅回路板４が直接接合される一方、背面側に裏銅板と
しての銅回路板５が同様に直接接合され、さらに表面側
の銅回路板４の所定位置に図示しない半田層を介して半
導体素子６が一体に接合された構造を有する。なおＳｉ
3 Ｎ4 基板２の両面に銅回路板４，５を接合した場合、
裏銅板としての銅回路板５は放熱促進および反り防止に
寄与するので有効である。[0120] Each Si 3 N 4 circuit board 1c is oxidized layer 3 is formed on the entire surface the Si 3 N 4 substrate 2 as shown in FIG. 8, the metal circuit on the front surface side the Si 3 N 4 substrate 2 While the copper circuit board 4 as a board is directly joined, the copper circuit board 5 as a back copper board is also directly joined to the back side in the same manner, and furthermore, at a predetermined position of the copper circuit board 4 on the front side via a solder layer (not shown). And the semiconductor element 6 is integrally joined. Note that Si
3 N 4 when bonding the copper circuit plates 4 and 5 on both sides of the substrate 2,
The copper circuit board 5 as the back copper plate is effective because it contributes to promoting heat radiation and preventing warpage.

【０１２１】上記のように直接接合法によって回路層を
形成した実施例４に係るＳｉ3 Ｎ4回路基板の最大たわ
み量は０．８〜１．６mmの範囲であり、また抗折強度は
５５０〜９００ＭＰａの範囲であり、実施例１１〜１３
のように活性金属法で回路層を形成した場合と同等の特
性値が得られた。また耐熱サイクル試験において１００
０サイクル経過後においてもＳｉ3 Ｎ4 基板の割れや金
属回路板の剥離が皆無であり、優れた耐熱サイクル特性
を示した。The maximum deflection of the Si 3 N 4 circuit board according to Example 4 in which the circuit layer was formed by the direct bonding method as described above was in the range of 0.8 to 1.6 mm, and the flexural strength was 550. To 900 MPa, and Examples 11 to 13
As described above, the same characteristic values as in the case where the circuit layer was formed by the active metal method were obtained. In the heat cycle test, 100
Even after the lapse of 0 cycles, there was no cracking of the Si 3 N 4 substrate or peeling of the metal circuit board, indicating excellent heat cycle characteristics.

【０１２２】実施例１５ 図９に示すように、実施例１１〜１３において調製した
Ｓｉ3 Ｎ4 基板であり熱伝導率ｋが７０Ｗ／ｍ・Ｋで、
厚さがそれぞれ０．４mm，０．６mm，０．８mmであるＳ
ｉ3 Ｎ4 基板２の表面に、モリブデン（Ｍｏ）と酸化チ
タン（ＴｉＯ2 ）との混合粉末に適量のバインダと溶剤
とを加えてペースト状にしたものをスクリーン印刷し、
加熱焼成して厚さ１５μｍの高融点金属メイタライズ層
１０を形成した。さらにメタライズ層１０の上に無電解
めっき法により厚さ３μｍのＮｉめっき層９を形成し、
所定パターンを有する回路層とした。次に回路層上に半
導体素子６を半田付けにより接合して実施例１５に係る
窒化けい素回路基板１ｄを多数製造した。 Example 15 As shown in FIG. 9, the Si 3 N 4 substrates prepared in Examples 11 to 13 had a thermal conductivity k of 70 W / m · K.
S whose thickness is 0.4mm, 0.6mm, 0.8mm respectively
On a surface of the i 3 N 4 substrate 2, a mixture of molybdenum (Mo) and titanium oxide (TiO 2 ) and an appropriate amount of a binder and a solvent added to form a paste are screen-printed,
By heating and baking, a high-melting-point metal metallized layer 10 having a thickness of 15 μm was formed. Further, a Ni plating layer 9 having a thickness of 3 μm is formed on the metallization layer 10 by an electroless plating method.
The circuit layer had a predetermined pattern. Next, a number of silicon nitride circuit boards 1d according to Example 15 were manufactured by bonding the semiconductor elements 6 to the circuit layer by soldering.

【０１２３】上記のようにメタライズ法によって回路層
を形成した実施例１５に係るＳｉ3 Ｎ4 回路基板の最大
たわみ量は１．０〜１．８mmの範囲であり、また抗折強
度は６５０〜９５０ＭＰａの範囲であり、実施例１１〜
１３のように活性金属法で回路層を形成した場合と同等
の特性値が得られた。また耐熱サイクル試験において１
０００サイクル経過後においてもＳｉ3 Ｎ4 基板の割れ
や金属回路板の剥離が皆無であり、めっき処理を施した
回路基板においても優れた耐熱サイクル特性を示した。The maximum deflection of the Si 3 N 4 circuit board according to Example 15 in which the circuit layer was formed by the metallization method as described above was in the range of 1.0 to 1.8 mm, and the transverse rupture strength was 650 to 650. In the range of 950 MPa, Examples 11 to
As shown in FIG. 13, the same characteristic values as those obtained when the circuit layer was formed by the active metal method were obtained. In heat cycle test, 1
Even after the lapse of 000 cycles, there was no cracking of the Si 3 N 4 substrate and no peeling of the metal circuit board, and the plated circuit board exhibited excellent heat cycle resistance.

【０１２４】次に種々の組成および特性値を有する他の
窒化けい素基板を使用した回路基板の実施形態について
以下に示す実施例１６を参照して具体的に説明する。Next, an embodiment of a circuit board using another silicon nitride substrate having various compositions and characteristic values will be specifically described with reference to Example 16 shown below.

【０１２５】実施例１６ まず回路基板の構成材となる各種窒化けい素基板を以下
の手順で製造した。 Example 16 First, various silicon nitride substrates to be used as components of a circuit board were manufactured by the following procedure.

【０１２６】すなわち酸素を１．３重量％、前記不純物
陽イオン元素を合計で０．１５重量％含有し、α相型窒
化けい素９７％を含む平均粒径０．５５μｍの窒化けい
素原料粉末に対して、表２〜４に示すように、焼結助剤
としてのＹ2 Ｏ3 ，Ｈｏ2 Ｏ3 などの希土類酸化物と、
必要に応じてＴｉ，Ｈｆ化合物，Ａｌ2 Ｏ3粉末，Ａｌ
Ｎ粉末とを添加し、エチルアルコール中で窒化けい素製
ボールを用いて７２時間湿式混合した後に乾燥して原料
粉末混合体をそれぞれ調整した。次に得られた各原料粉
末混合体に有機バインダを所定量添加して均一に混合し
た後に、１０００kg／cm2 の成形圧力でプレス成形し、
各種組成を有する成形体を多数製作した。That is, silicon nitride raw material powder containing 1.3% by weight of oxygen and 0.15% by weight of the impurity cation element in total and containing 97% of α-phase type silicon nitride and having an average particle size of 0.55 μm. respect, as shown in Table 2-4, and a rare earth oxide such as Y 2 O 3, Ho 2 O 3 as a sintering aid,
Ti, Hf compound, Al 2 O 3 powder, Al
N powder was added, and the mixture was wet-mixed in ethyl alcohol using a ball made of silicon nitride for 72 hours and then dried to prepare raw material powder mixtures. Next, after adding a predetermined amount of an organic binder to each of the obtained raw material powder mixtures and mixing them uniformly, the mixture was press-molded at a molding pressure of 1000 kg / cm 2 ,
A number of compacts having various compositions were manufactured.

【０１２７】次に得られた各成形体を７００℃の雰囲気
ガス中において２時間脱脂した後に、この脱脂体を表２
〜４に示す焼結条件で緻密化焼結を実施した後に、焼結
炉に付設した加熱装置への通電量を制御して焼結炉内温
度が１５００℃まで降下するまでの間における焼結体の
冷却速度がそれぞれ表２〜４に示す値となるように調整
して焼結体を冷却し、それぞれ試料１〜５１に係る窒化
けい素焼結体を調製した。Next, each of the obtained compacts was degreased in an atmosphere gas at 700 ° C. for 2 hours.
After the densification sintering is performed under the sintering conditions shown in ４ to ４, sintering is performed until the temperature in the sintering furnace falls to 1500 ° C. by controlling the amount of electricity to the heating device attached to the sintering furnace. The sintered bodies were cooled by adjusting the cooling rates of the bodies so as to have the values shown in Tables 2 to 4, respectively, to prepare silicon nitride sintered bodies according to Samples 1 to 51, respectively.

【０１２８】こうして得た試料１〜５１に係る各窒化け
い素焼結体について気孔率、熱伝導率（２５℃）、室温
での三点曲げ強度の平均値を測定した。さらに、各焼結
体についてＸ線回折法によって粒界相に占める結晶相の
割合（面積比）を測定し、下記表２〜４に示す結果を得
た。The average values of the porosity, the thermal conductivity (25 ° C.), and the three-point bending strength at room temperature of the silicon nitride sintered bodies according to Samples 1 to 51 thus obtained were measured. Further, the ratio (area ratio) of the crystal phase to the grain boundary phase was measured for each sintered body by the X-ray diffraction method, and the results shown in Tables 2 to 4 below were obtained.

【０１２９】[0129]

【表２】 [Table 2]

【０１３０】[0130]

【表３】 [Table 3]

【０１３１】[0131]

【表４】 [Table 4]

【０１３２】表２〜４に示す結果から明らかなように試
料１〜５１に係る窒化けい素焼結体においては、原料組
成を適正に制御し、従来例と比較して緻密化焼結完了直
後における焼結体の冷却速度を従来より低く設定してい
るため、粒界相に結晶相を含み、結晶相の占める割合が
高い程、高熱伝導率を有する放熱性の高い高強度窒化け
い素焼結体が得られた。As is clear from the results shown in Tables 2 to 4, in the silicon nitride sintered bodies according to Samples 1 to 51, the raw material composition was appropriately controlled, and the silicon nitride sintered body immediately after the completion of the densification sintering was compared with the conventional example. Since the cooling rate of the sintered body is set lower than before, the crystal phase is included in the grain boundary phase, and the higher the proportion of the crystal phase, the higher the heat conductivity and the higher the strength of the silicon nitride sintered body. was gotten.

【０１３３】これに対して酸素を１．３〜１．５重量
％，前記不純物陽イオン元素を合計で０．１３〜０．１
６重量％含有し、α相型窒化けい素を９３％含む平均粒
径０．６０μｍの窒化けい素原料粉末を用い、この窒化
けい素粉末に対してＹ2 Ｏ3 （酸化イットリウム）粉末
を３〜６重量と、アルミナ粉末を１．３〜１．６重量％
添加した原料粉末を成形，脱脂後、１９００℃で６時間
焼結し、炉冷（冷却速度：毎時４００℃）して得た焼結
体の熱伝導率は２５〜２８Ｗ／ｍ・Ｋと低く、従来の一
般的な製法によって製造された窒化けい素焼結体の熱伝
導率に近い値になった。On the other hand, 1.3 to 1.5% by weight of oxygen and 0.13 to 0.1 wt.
A silicon nitride raw material powder containing 6% by weight and containing 93% of α-phase silicon nitride and having an average particle diameter of 0.60 μm was used, and Y 2 O 3 (yttrium oxide) powder was added to the silicon nitride powder by 3%. To 6% by weight and 1.3 to 1.6% by weight of alumina powder
The added raw material powder is molded, degreased, sintered at 1900 ° C. for 6 hours, and cooled in a furnace (cooling rate: 400 ° C./hour) to obtain a sintered body having a low thermal conductivity of 25 to 28 W / m · K. The thermal conductivity was close to that of a silicon nitride sintered body manufactured by a conventional general manufacturing method.

【０１３４】次に得られた試料１〜５１に係る各窒化け
い素焼結体を研磨加工することにより、実施例１１〜１
３と同様に、厚さ０．４mm，０．６mm，０．８mmの窒化
けい素基板をそれぞれ調製した。次に調製した各窒化け
い素基板の表面に、実施例１１〜１３と同様に活性金属
法を使用して銅回路板等を一体に接合することにより図
５に示すような実施例１６に係る窒化けい素回路基板を
それぞれ調製した。Next, each of the obtained silicon nitride sintered bodies according to Samples 1 to 51 was polished to obtain Examples 11 to 1.
Similarly to 3, silicon nitride substrates having thicknesses of 0.4 mm, 0.6 mm and 0.8 mm were prepared, respectively. Next, a copper circuit board or the like is integrally joined to the surface of each prepared silicon nitride substrate by using the active metal method in the same manner as in Examples 11 to 13, thereby obtaining Example 16 as shown in FIG. Silicon nitride circuit boards were each prepared.

【０１３５】また各窒化けい素基板の表面に、実施例１
４と同様にＤＢＣ法を使用して銅回路板等を直接接合す
ることにより、図８に示すような実施例１６に係る窒化
けい素回路基板をそれぞれ調製した。Further, the surface of each silicon nitride substrate was placed on the surface of Example 1.
8, a silicon nitride circuit board according to Example 16 as shown in FIG. 8 was prepared by directly bonding a copper circuit board and the like using the DBC method.

【０１３６】さらに各窒化けい素基板の表面に、実施例
１５と同様にメタライズ法を使用して回路層を形成する
ことにより、図９に示すような実施例１６に係る窒化け
い素回路基板をそれぞれ調製した。Further, by forming a circuit layer on the surface of each silicon nitride substrate by using the metallization method in the same manner as in the fifteenth embodiment, the silicon nitride circuit substrate according to the sixteenth embodiment as shown in FIG. Each was prepared.

【０１３７】上記のように活性金属法，ＤＢＣ法，メタ
ライズ法によって回路層を形成した実施例１６に係る各
Ｓｉ3 Ｎ4 回路基板の最大たわみ量，抗折強度は実施例
１１〜１５と同等以上であり、また耐熱サイクル試験に
おいて１０００サイクル経過後においてもＳｉ3 Ｎ4 基
板の割れや回路層の剥離は皆無であり、優れた耐熱サイ
クル特性が得られた。The maximum deflection and flexural strength of each of the Si 3 N 4 circuit boards according to Example 16 in which the circuit layer was formed by the active metal method, the DBC method, and the metallizing method as described above were the same as in Examples 11 to 15. As described above, even after 1000 cycles in the heat cycle test, there was no cracking of the Si 3 N 4 substrate and no peeling of the circuit layer, and excellent heat cycle characteristics were obtained.

【０１３８】[0138]

【発明の効果】以上説明の通り、本発明に係る窒化けい
素回路基板によれば、窒化けい素焼結体が本来的に有す
る高強度高靭性特性に加えて特に熱伝導率を大幅に改善
した高熱伝導性窒化けい素基板表面に金属回路板を一体
に接合して形成されている。したがって、回路基板の靭
性値が高いため最大たわみ量および抗折強度を大きく確
保することができる。そのため、アッセンブリ工程にお
いて回路基板の締め付け割れが発生せず、回路基板を用
いた半導体装置を高い製造歩留りで量産することが可能
になる。As described above, according to the silicon nitride circuit board of the present invention, in particular, the thermal conductivity has been greatly improved in addition to the inherent high strength and toughness characteristics of the silicon nitride sintered body. It is formed by integrally joining a metal circuit board to the surface of a high thermal conductive silicon nitride substrate. Therefore, since the toughness value of the circuit board is high, the maximum deflection amount and the bending strength can be secured large. For this reason, the circuit board does not suffer from tightening cracks in the assembly process, and semiconductor devices using the circuit board can be mass-produced with a high production yield.

【０１３９】また窒化けい素基板の靭性値が高いため、
熱サイクルによって基板に割れが発生することが少な
く、耐熱サイクル特性が著しく向上し、耐久性および信
頼性に優れた半導体装置を提供することができる。Further, since the toughness value of the silicon nitride substrate is high,
It is possible to provide a semiconductor device in which a substrate is less likely to be cracked by a heat cycle, heat cycle characteristics are significantly improved, and durability and reliability are excellent.

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

【図１】本発明に係る窒化けい素回路基板の一実施例を
示す断面図。FIG. 1 is a sectional view showing one embodiment of a silicon nitride circuit board according to the present invention.

【図２】本発明に係る窒化けい素回路基板の他の実施例
を示す断面図。FIG. 2 is a sectional view showing another embodiment of the silicon nitride circuit board according to the present invention.

【図３】回路基板の放熱性評価試験要領を示す断面図。FIG. 3 is a cross-sectional view showing the procedure of a test for evaluating the heat dissipation of a circuit board.

【図４】放熱性評価試験におけるセラミックス基板厚さ
と半導体素子の温度上昇との関係を示すグラフ。FIG. 4 is a graph showing a relationship between a ceramic substrate thickness and a temperature rise of a semiconductor element in a heat radiation evaluation test.

【図５】本発明に係る窒化けい素回路基板の構成例を示
す断面図。FIG. 5 is a cross-sectional view illustrating a configuration example of a silicon nitride circuit board according to the present invention.

【図６】基板厚さと最大たわみ量との関係を示すグラ
フ。FIG. 6 is a graph showing a relationship between a substrate thickness and a maximum deflection amount.

【図７】基板厚さと抗折強度との関係を示すグラフ。FIG. 7 is a graph showing a relationship between substrate thickness and bending strength.

【図８】銅直接接合法によって回路層を形成した回路基
板の断面図。FIG. 8 is a sectional view of a circuit board on which a circuit layer is formed by a direct copper bonding method.

【図９】メタライズ法によって回路層を形成した回路基
板の断面図。FIG. 9 is a cross-sectional view of a circuit board on which a circuit layer is formed by a metallization method.

【符号の説明】[Explanation of symbols]

１，１ａ，１ｂ，１ｃ，１ｄ 窒化けい素回路基板（Ｓ
ｉ3 Ｎ4 回路基板） ２ 窒化けい素（Ｓｉ3 Ｎ4 ）基板 ３ 酸化層（ＳｉＯ2 皮膜） ４ 金属回路板（Ｃｕ回路板），回路層 ５ 金属回路板（裏銅板） ６ 半導体素子（チップ） ７ａ，７ｂ 活性金属層（金属接合層） ８ ヒートシンク ９ 金属めっき層（Ｎｉめっき層） １０ 高融点金属メタライズ層1,1a, 1b, 1c, 1d Silicon nitride circuit board (S
i 3 N 4 circuit board) 2 silicon nitride (Si 3 N 4 ) substrate 3 oxide layer (SiO 2 film) 4 metal circuit board (Cu circuit board), circuit layer 5 metal circuit board (back copper plate) 6 semiconductor element ( Chip) 7a, 7b Active metal layer (metal bonding layer) 8 Heat sink 9 Metal plating layer (Ni plating layer) 10 Refractory metal metallization layer

フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｈ０１Ｌ 23/12 Ｃ０４Ｂ 35/58 １０２Ｃ １０２Ｋ １０２Ｔ (72)発明者 小森田 裕 神奈川県横浜市鶴見区末広町２の４ 株 式会社東芝 京浜事業所内 (72)発明者 佐藤 孔俊 神奈川県横浜市磯子区新杉田町８番地 株式会社東芝 横浜事業所内Continued on the front page (51) Int.Cl. 6 Identification code Agency reference number FI Technical display location H01L 23/12 C04B 35/58 102C 102K 102T (72) Inventor Hiroshi Komorita 2 in Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa 4 Toshiba Corporation Keihin Works (72) Inventor Kotoshi Sato 8 Shinsugitacho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Corporation Yokohama Works

Claims (13)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 熱伝導率が６０Ｗ／ｍ・Ｋ以上で三点曲
げ強度（常温）が６５０ＭＰａ以上である高熱伝導性窒
化けい素基板上に酸化層を介して金属回路板を接合して
なる窒化けい素回路基板において、上記高熱伝導性窒化
けい素基板の厚さをＤS ，金属回路板の厚さをＤM とし
たときに関係式ＤS ≦２ＤM を満たすことを特徴とする
窒化けい素回路基板。1. A metal circuit board is bonded via an oxide layer to a high thermal conductivity silicon nitride substrate having a thermal conductivity of 60 W / m · K or more and a three-point bending strength (normal temperature) of 650 MPa or more. In the silicon nitride circuit board, when the thickness of the high thermal conductive silicon nitride board is D S and the thickness of the metal circuit board is D M , the relational expression D S ≦ 2D M is satisfied. Silicon circuit board. 【請求項２】 高熱伝導性窒化けい素基板の厚さＤS お
よび金属回路板の厚さＤM が関係式ＤM ≦ＤS ≦（５／
３）ＤM を満たすことを特徴とする請求項１記載の窒化
けい素回路基板。2. The thickness D S of the high thermal conductive silicon nitride substrate and the thickness D M of the metal circuit board are defined by the relational expression D M ≦ D S ≦ (5 /
3) The silicon nitride circuit board according to claim 1, wherein D M is satisfied. 【請求項３】 熱伝導率が６０Ｗ／ｍ・Ｋ以上で三点曲
げ強度（常温）が６５０ＭＰａ以上である高熱伝導性窒
化けい素基板上にＴｉ，Ｚｒ，ＨｆおよびＮｂから選択
される少なくとも１種の活性金属を含有する金属接合層
を介して金属回路板を接合してなる窒化けい素回路基板
において、上記高熱伝導性窒化けい素基板の厚さを
ＤS ，金属回路板の厚さをＤM としたときに関係式ＤS
≦２ＤMを満たすことを特徴とする窒化けい素回路基
板。3. At least one selected from Ti, Zr, Hf and Nb on a high thermal conductive silicon nitride substrate having a thermal conductivity of 60 W / m · K or more and a three-point bending strength (normal temperature) of 650 MPa or more. In a silicon nitride circuit board formed by bonding metal circuit boards via a metal bonding layer containing a kind of active metal, the thickness of the high thermal conductive silicon nitride board is set to D S , and the thickness of the metal circuit board is set to D S. When D M , the relational expression D S
A silicon nitride circuit board satisfying ≦ 2D M. 【請求項４】 高熱伝導性窒化けい素基板の厚さＤS お
よび金属回路板の厚さＤM が関係式ＤM ≦ＤS ≦（５／
３）ＤM を満たすことを特徴とする請求項３記載の窒化
けい素回路基板。4. The thickness D S of the high thermal conductive silicon nitride substrate and the thickness D M of the metal circuit board are defined by the relational expression D M ≦ D S ≦ (5 /
3) The silicon nitride circuit board according to claim 3, wherein D M is satisfied. 【請求項５】 熱伝導率が６０Ｗ／ｍ・Ｋ以上である高
熱伝導性窒化けい素基板に回路層を一体に接合した回路
基板であり、回路基板を５０mmの支持間隔で保持した状
態で中央部に荷重を付加したときに窒化けい素基板が破
断に至るまでの最大たわみ量が０．６mm以上であること
を特徴とする窒化けい素回路基板。5. A circuit board in which a circuit layer is integrally bonded to a high thermal conductivity silicon nitride substrate having a thermal conductivity of 60 W / m · K or more, and the circuit board is held at a supporting interval of 50 mm to form a central portion. A silicon nitride circuit board characterized in that the maximum amount of deflection before the silicon nitride board breaks when a load is applied to a portion is 0.6 mm or more. 【請求項６】 熱伝導率が６０Ｗ／ｍ・Ｋ以上である高
熱伝導性窒化けい素基板に回路層を一体に接合した回路
基板であり、回路基板を５０mmの支持間隔で保持した状
態で抗折試験を実施したときに抗折強度が５００ＭＰａ
以上であることを特徴とする窒化けい素回路基板。6. A circuit board in which a circuit layer is integrally bonded to a high thermal conductivity silicon nitride substrate having a thermal conductivity of 60 W / m · K or more, and the circuit board is held at a supporting interval of 50 mm. The bending strength is 500MPa when the bending test is performed.
A silicon nitride circuit board characterized by the above. 【請求項７】 高熱伝導性窒化けい素基板の厚さが０．
８mm以下であることを特徴とする請求項５または６記載
の窒化けい素回路基板。7. A high thermal conductive silicon nitride substrate having a thickness of 0.
7. The silicon nitride circuit board according to claim 5, wherein the thickness is 8 mm or less. 【請求項８】 回路層が銅回路板であり、この銅回路板
がＣｕ−Ｏ共晶化合物によって窒化けい素基板に直接接
合されていることを特徴とする請求項５記載の窒化けい
素回路基板。8. The silicon nitride circuit according to claim 5, wherein the circuit layer is a copper circuit board, and the copper circuit board is directly bonded to the silicon nitride substrate by a Cu—O eutectic compound. substrate. 【請求項９】 回路層が銅回路板であり、Ｔｉ，Ｚｒ，
ＨｆおよびＮｂから選択される少なくとも１種の活性金
属を含有する活性金属層を介して上記銅回路板が窒化け
い素基板に接合されていることを特徴とする請求項５記
載の窒化けい素回路基板。9. The circuit layer is a copper circuit board, and Ti, Zr,
6. The silicon nitride circuit according to claim 5, wherein the copper circuit board is bonded to the silicon nitride substrate via an active metal layer containing at least one active metal selected from Hf and Nb. substrate. 【請求項１０】 回路層はＷあるいはＭｏにＴｉ，Ｚ
ｒ，ＨｆおよびＮｂから選択される少なくとも１種の活
性金属を含有する高融点金属メタライズ層から成ること
を特徴とする請求項５記載の窒化けい素回路基板。10. The circuit layer is made of Ti or Z in W or Mo.
6. The silicon nitride circuit board according to claim 5, comprising a refractory metal metallized layer containing at least one active metal selected from r, Hf and Nb. 【請求項１１】 高熱伝導性窒化けい素基板は、希土類
元素を酸化物に換算して２．０〜１７．５重量％、不純
物陽イオン元素としてのＬｉ，Ｎａ，Ｋ，Ｆｅ，Ｃａ，
Ｍｇ，Ｓｒ，Ｂａ，Ｍｎ，Ｂを合計で０．３重量％以下
含有する窒化けい素焼結体から成ることを特徴とする請
求項１または３記載の窒化けい素回路基板。11. A silicon nitride substrate having a high thermal conductivity of 2.0 to 17.5% by weight of a rare earth element in terms of oxide, and Li, Na, K, Fe, Ca, as impurity cation elements.
4. The silicon nitride circuit board according to claim 1, comprising a silicon nitride sintered body containing a total of 0.3% by weight or less of Mg, Sr, Ba, Mn, and B. 【請求項１２】 高熱伝導性窒化けい素基板は、希土類
元素を酸化物に換算して２．０〜１７．５重量％含有
し、窒化けい素結晶および粒界相から成るとともに粒界
相中における結晶化合物相の粒界相全体に対する割合が
２０％以上である窒化けい素焼結体から成ることを特徴
とする請求項１または３記載の窒化けい素回路基板。12. A highly thermally conductive silicon nitride substrate contains 2.0 to 17.5% by weight of a rare earth element in terms of oxide and is composed of a silicon nitride crystal and a grain boundary phase. 4. The silicon nitride circuit board according to claim 1, wherein a ratio of the crystalline compound phase to the entire grain boundary phase is 20% or more. 【請求項１３】 高熱伝導性窒化けい素基板は、窒化け
い素結晶および粒界相から成るとともに粒界相中におけ
る結晶化合物相の粒界相全体に対する割合が５０％以上
である窒化けい素焼結体から成ることを特徴とする請求
項１または３記載の窒化けい素回路基板。13. A silicon nitride substrate comprising a silicon nitride crystal and a grain boundary phase, wherein a ratio of a crystalline compound phase to the whole grain boundary phase in the grain boundary phase is 50% or more. 4. The silicon nitride circuit board according to claim 1, wherein the silicon nitride circuit board comprises a body.
JP7344238A 1995-03-20 1995-12-28 Silicon nitride circuit board Expired - Lifetime JP2698780B2 (en)

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US6294244B1 (en) * 1997-12-22 2001-09-25 Kyocera Corporation Wiring board having excellent heat-radiating property
JP4346151B2 (en) * 1998-05-12 2009-10-21 株式会社東芝 High thermal conductivity sintered silicon nitride, circuit board and integrated circuit using the same
JP4649027B2 (en) * 1999-09-28 2011-03-09 株式会社東芝 Ceramic circuit board
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JP4854354B2 (en) * 2006-03-23 2012-01-18 京セラ株式会社 Silicon nitride bonded body, method for manufacturing the same, and member for semiconductor manufacturing apparatus using the same
DE102009015520A1 (en) * 2009-04-02 2010-10-07 Electrovac Ag Metal-ceramic substrate
JP2011067849A (en) * 2009-09-28 2011-04-07 Kyocera Corp Brazing filler metal, and heat radiation base body joined by using the same
JP7313105B2 (en) * 2019-09-17 2023-07-24 株式会社東芝 structures and junctions
JP7243888B1 (en) * 2022-03-29 2023-03-22 株式会社プロテリアル CERAMIC SUBSTRATE, CERAMIC SEGMENTED SUBSTRATE, AND METHOD FOR MANUFACTURING CERAMIC SUBSTRATE

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