JP4265201B2 - Super junction semiconductor device - Google Patents

Super junction semiconductor device Download PDF

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JP4265201B2
JP4265201B2 JP2002311509A JP2002311509A JP4265201B2 JP 4265201 B2 JP4265201 B2 JP 4265201B2 JP 2002311509 A JP2002311509 A JP 2002311509A JP 2002311509 A JP2002311509 A JP 2002311509A JP 4265201 B2 JP4265201 B2 JP 4265201B2
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JP2004146689A (en
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達司 永岡
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Fuji Electric Co Ltd
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Fuji Electric Device Technology Co Ltd
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    • H01L29/063—Reduced surface field [RESURF] pn-junction structures
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Description

【０００１】
【発明の属する技術分野】
本発明は、半導体素子の第１の電極側から第２の電極側へ向かって伸びる第１導電型半導体よりなるドリフト領域と、それと同様に伸びる第２導電型半導体よりなる仕切り領域とを、それらの伸びる方向に交差する方向に交互に繰り返し接合した構成（この構成を並列ｐｎ接合層または並列ｐｎ構造と称する）を有し、該並列ｐｎ接合層が、オン状態のときに電流を流し、かつオフ状態のときには空乏化するドリフト層となる半導体素子（これを超接合半導体素子と称する）に関し、特に、ＭＯＳＦＥＴ（絶縁ゲート型電界効果トランジスタ）やＩＧＢＴ（絶縁ゲート型バイポーラトランジスタ）やバイポーラトランジスタ等に適用可能な高耐圧化と大電流容量化を両立させることのできる超接合半導体素子に関する。
【０００２】
【従来の技術】
一般に、半導体素子は、電極が片面に形成された横型の素子と、両面に電極を有する縦型の素子に分類される。縦型半導体素子は、オン状態のときにドリフト電流が流れる方向と、オフ状態のときに逆バイアス電圧による空乏層が伸びる方向とが同じである。通常のプレーナ型のｎチャネル縦型ＭＯＳＦＥＴでは、高抵抗のｎ-ドリフト層の部分は、オン状態のときに、縦方向（深さ方向）にドリフト電流を流す領域として働く。したがって、このｎ-ドリフト層の電流経路を短くすれば、ドリフト抵抗が低くなるので ＭＯＳＦＥＴの実質的なオン抵抗が下がるという効果が得られる。
【０００３】
その一方で、高抵抗のｎ-ドリフト層の部分は、オフ状態のときには空乏化して耐圧を高める。したがって、ｎ-ドリフト層が薄くなると、ｐベース領域とドリフト領域との間のｐｎ接合から進行するドレイン−ベース間空乏層が広がる幅が狭くなり、シリコンの臨界電界強度に早く達するため、耐圧が低下してしまう。逆に、耐圧の高い半導体素子では、ｎ-ドリフト層が厚いため、順電圧やオン抵抗が大きくなり、損失が増えてしまう。このように、順電圧やオン抵抗（あるいは電流容量）と耐圧との間には、トレードオフ関係がある。
【０００４】
このトレードオフ関係は、ＩＧＢＴやバイポーラトランジスタやダイオード等の半導体素子においても同様に成立することが知られている。また、このトレードオフ関係は、オン状態のときにドリフト電流が流れる方向と、オフ状態のときの空乏層の伸びる方向とが異なる横型半導体素子にも共通である。
【０００５】
上述したトレードオフ関係による問題の解決法として、不純物濃度を高めた第１導電型半導体領域よりなるドリフト領域と、第２導電型半導体領域よりなる仕切り領域とを、交互に繰り返し接合した並列ｐｎ構造のドリフト層を有する超接合半導体素子が公知である（下記特許文献１〜４、非特許文献１などを参照。）。超接合半導体素子では、並列ｐｎ構造の不純物濃度が高くても、オフ状態のときに、空乏層が、並列ｐｎ構造の縦方向に伸びる各ｐｎ接合から横方向に広がり、ドリフト層全体を空乏化するため、高耐圧化を図ることができる。そして、並列ｐｎ構造のピッチ幅を狭くして不純物濃度を高くすることによって、上述したトレードオフが大幅に改善されることが知られている。
【０００６】
【特許文献１】
欧州特許出願第００５３８５４号明細書
【特許文献２】
米国特許第５２１６２７５号明細書
【特許文献３】
米国特許第５４３８２１５号明細書
【特許文献４】
特開平９−２６６３１１号公報
【非特許文献１】
Ｔａｔｓｕｈｉｋｏ Ｆｕｊｉｈａｒａ，「Ｔｈｅｏｒｙ ｏｆ ｓｅｍｉｃｏｎｄｕｃｔｏｒ Ｓｕｐｅｒｊｕｎｃｔｉｏｎ Ｄｅｖｉｃｅｓ」 Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３６（１９９７）ｐｐ．６２５４−６２６２ Ｐａｒｔ １，Ｎｏ．１０，Ｏｃｔｏｂｅｒ １９９７
【０００７】
【発明が解決しようとする課題】
しかしながら、並列ｐｎ構造のピッチ幅を狭くして不純物濃度を高くした場合、ドリフト領域の不純物濃度の増加にともなってキャリアの移動度が低下し、特にドリフト領域の不純物濃度がおおよそ１０15［ｃｍ-3］を超えるとキャリア移動度の低下傾向が強まるため、実際にはオン抵抗が十分に低くならず、上述したトレードオフの改善効果が小さいという問題点があった。
【０００８】
本発明は、上記問題点に鑑みてなされたものであって、不純物濃度が高い並列ｐｎ構造を有する超接合半導体素子において、オン抵抗を十分に低減し、それによって順電圧やオン抵抗と耐圧との間のトレードオフ関係を十分に改善することができる超接合半導体素子を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するため、本発明は、微細ピッチで、不純物濃度の高い並列ｐｎ構造を有する超接合半導体素子において、並列ｐｎ構造のｐ型半導体領域およびｎ型半導体領域のそれぞれの実効的な総不純物量を保持したまま、ドリフト領域の体積を大きくし、一方、仕切り領域の体積を小さくした構成であることを特徴とする。
【００１０】
この発明によれば、ドリフト領域の不純物濃度が下がるので、キャリア移動度が低下するのを防ぐことができる。ところで、超接合半導体素子では、並列ｐｎ構造を構成するｐ型半導体領域の実効的な総不純物量とｎ型半導体領域の実効的な総不純物量とが同じであれば、それらｐ型半導体領域とｎ型半導体領域の体積が異なっていても、それらの体積が同じ場合とほぼ同じ耐圧が得られることが知られている。したがって、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。
【００１１】
具体的には、単純に直方体のｐ型半導体領域とｎ型半導体領域とを交互に接合してできる縦型のストライプ状の並列ｐｎ構造の場合、ドリフト領域の幅をｄ1［μｍ］とし、仕切り領域の幅をｄ2［μｍ］とすると、ｄ1＋ｄ2の値が３６μｍ以下であり、かつｄ1＞ｄ2である。その理由は、ドリフト領域の不純物濃度をｎ１［ｃｍ-3］とし、仕切り領域の不純物濃度をｎ２［ｃｍ-3］とすると、高い耐圧と低いオン抵抗の両方が得られる概ね最適な不純物濃度は、それぞれつぎの（１）式および（２）式で与えられる。
【００１２】
【数５】

Figure 0004265201
【００１３】
【数６】
Figure 0004265201
【００１４】
ここで、簡単な場合として、ｄ1およびｄ2をともに１８μｍとすると、上記（１）式より、ドリフト領域の不純物濃度ｎ１は１．００×１０15ｃｍ-3となる。したがって、ｄ1＋ｄ2の値が３６μｍ以下であるような超接合半導体素子において、キャリア移動度の低下を防ぐことができる。
【００１５】
本発明は、並列ｐｎ構造が上述したストライプ状である場合に限らず、並列ｐｎ構造がセル状である場合にも同様に成り立つが、セル状の場合、最適な不純物濃度はセルの横断面形状やセルの配列の仕方などに依存するので、最適な不純物濃度の算出は複雑である。しかし、ドリフト領域の不純物濃度が１０15ｃｍ-3程度になる並列ｐｎ構造の寸法は、つぎのようなおおよその見積もりによって知ることができる。
【００１６】
簡単な場合として、直径ｄ1［μｍ］の円柱形状をしたドリフト領域を、互いの間をｄ2［μｍ］だけ開けて、三角格子状または四角格子状に配置したセル状の並列ｐｎ構造を想定し、ｄ1＝ｄ2＝ｄ［μｍ］とする。このときの円柱形ドリフト領域の中心間距離Ｄ1は、ｄ1＋ｄ2［μｍ］である。この円柱形状のドリフト領域を有する並列ｐｎ構造を、ドリフト領域および仕切り領域のそれぞれの幅をｄ1およびｄ2とし、ｄ1＝ｄ2＝ｄ［μｍ］となるストライプ状の並列ｐｎ構造であって、並列ｐｎ構造の接合長さが同じであるものと比較すると、ドリフト領域の体積は０．４倍程度になり、仕切り領域の体積は１．５倍程度になる。ここで、並列ｐｎ構造の接合長さとは、ドリフト電流が流れる方向の、ドリフト領域と仕切り領域との接触部分の寸法である。
【００１７】
つまり、並列ｐｎ構造がストライプ状である場合とセル状である場合のドリフト領域における総不純物量が同じであれば、セル状の場合のドリフト領域の不純物濃度は、ストライプ状の場合の１／０．４倍になる。そこで、セル状の並列ｐｎ構造のドリフト領域の濃度ｎ１が１０15ｃｍ-3となるときのｄの値を求めるにあたって、便宜的にｎ１を０．４×１０15ｃｍ-3として前記（１）式を用いれば、ｄの値は４０μｍとなる。したがって、セル状のドリフト領域を有する並列ｐｎ構造の場合には、ｄ1＋ｄ2の値が８０μｍ以下であるような超接合半導体素子において、キャリア移動度の低下を防ぐことができると考えられる。
【００１８】
なお、ドリフト領域のセル形状が円柱形ではなく、三角柱や四角柱状など、横断面形状が円形でない場合には、その断面積をｓ1［μｍ2］としたときの２√（ｓ1／３．１４）の値を直径ｄ1［μｍ］とする断面円形状で、かつ実際のドリフト領域と同じ体積の円柱形ドリフト領域に置き換えて考えればよい。そうすれば、上述した円柱形ドリフト領域の場合と同様にして、ドリフト領域の不純物濃度が１０15ｃｍ-3程度になる並列ｐｎ構造のおおよその寸法が求められる。
【００１９】
また、セル状の並列ｐｎ構造において、直径ｄ2［μｍ］の円柱形状をした仕切り領域が、互いの間をｄ1［μｍ］だけ開けて、三角格子状または四角格子状に配置されている場合も、上述した円柱形状のドリフト領域が配置されている場合と同様にして、ドリフト領域の不純物濃度が１０15ｃｍ-3程度になる並列ｐｎ構造のおおよその寸法を見積もることができる。このときの円柱形仕切り領域の中心間距離Ｄ2は、ｄ1＋ｄ2［μｍ］である。
【００２０】
簡単な場合として、ｄ1＝ｄ2＝ｄ［μｍ］とし、この円柱形仕切り領域を有する並列ｐｎ構造を、ドリフト領域および仕切り領域の幅がそれぞれｄ1およびｄ2で、ｄ1＝ｄ2＝ｄ［μｍ］となるストライプ状の並列ｐｎ構造であって、並列ｐｎ構造の接合長さが同じであるものと比較すると、ドリフト領域の体積は１．５倍程度になり、仕切り領域の体積は０．４倍程度になる。
【００２１】
つまり、セル状の場合のドリフト領域の不純物濃度は、ストライプ状の場合の１／１．５倍に相当する。そこで、前記（１）式において、便宜的にｎ１を１．５×１０15ｃｍ-3とすると、ｄの値は１２．５μｍとなる。したがって、セル状の仕切り領域を有する並列ｐｎ構造の場合には、ｄ1＋ｄ2の値が２５μｍ以下であるような超接合半導体素子において、キャリア移動度の低下を防ぐことができると考えられる。
【００２２】
なお、仕切り領域のセル形状が円柱形ではなく、三角柱や四角柱状など、横断面形状が円形でない場合には、その断面積をｓ2［μｍ2］としたときの２√（ｓ2／３．１４）の値を直径ｄ2［μｍ］とする断面円形状で、かつ実際の仕切り領域と同じ体積の円柱形仕切り領域に置き換えて考えればよい。そうすれば、上述した円柱形仕切り領域の場合と同様にして、ドリフト領域の不純物濃度が１０15ｃｍ-3程度になる並列ｐｎ構造のおおよその寸法が求められる。
【００２３】
また、横型のストライプ状の並列ｐｎ構造の場合には、ドリフト領域および仕切り領域の幅をそれぞれｄ1［μｍ］およびｄ2［μｍ］とし、ドリフト領域および仕切り領域の不純物濃度をそれぞれｎ１［ｃｍ-3］およびｎ２［ｃｍ-3］とすると、高い耐圧と低いオン抵抗の両方が得られる概ね最適な不純物濃度ｎ１およびｎ２は、それぞれつぎの（３）式および（４）式で与えられる。
【００２４】
【数７】
Figure 0004265201
【００２５】
【数８】
Figure 0004265201
【００２６】
簡単な場合として、ｄ1およびｄ2をともに１２μｍとすると、上記（３）式より、ドリフト領域の不純物濃度ｎ１は１．００×１０15ｃｍ-3となる。つまり、ｄ1＋ｄ2の値が２４μｍ以下であるような超接合半導体素子において、キャリア移動度の低下を防ぐことができる。
【００２７】
なお、上記（１）式〜（４）式は、上記非特許文献１からの引用している。上記非特許文献１によれば、シリコンデバイスにおける最適濃度がＮD＝１．４１×１０12・α7/6・ｄ-7/5（ｃｍ-3） （４．１）において与えられ、上記αは、単位面積当たりのオン抵抗と耐圧とのトレードオフが最も良くなる値として、横型デバイスの場合にはα＝１／３、縦型デバイスの場合にはα＝１／２であることが示されている。ただし、上記非特許文献１では、ｄ1＝ｄ2＝ｄとしているため、本発明では、それを一般化するために、ｄを（ｄ1＋ｄ2）に置き換えている。そして、ＮD＊ｄ＝ｎ1＊ｄ1＝ｎ2＊ｄ2となるようにｎ1もしくはｎ2を求めている。さらに、ｄ1、ｄ2［μｍ］に対して、ｎ1、ｎ2［ｃｍ-3］が求まるような式に改めているので、上記（１）式〜（４）式には、単位を変換するための係数が存在する。
【００２８】
【発明の実施の形態】
以下に、本発明の実施の形態について図面を参照しつつ詳細に説明する。なお、本明細書において、ｎまたはｐを冠記した層や領域は、それぞれ電子または正孔を多数キャリアとする層や領域を意味している。また、ｎやｐに付した添字の＋は比較的高不純物濃度であり、−は比較的低不純物濃度であることを意味している。また、半導体素子の表面側から裏面側へ向かう方向を縦方向とし、これに交差する方向を横方向とする。また、以下の説明では、第１導電型をｎ型とし、第２導電型をｐ型とするが、その逆でも同様である。
【００２９】
実施の形態１．
図１は、本発明の実施の形態１にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図であり、図２は、その並列ｐｎ構造の上端面の構成を示す平面図である。図１に示すように、並列ｐｎ接合層２０は、縦方向に伸びるｎドリフト領域１と、縦方向に伸びるｐ+仕切り領域２とが、横方向に、交互に繰り返し接合された縦型ストライプ状の構成となっている。
【００３０】
図１または図２に示すように、ｎドリフト領域１の幅をｄ1［μｍ］とし、ｐ+仕切り領域２の幅をｄ2［μｍ］とすると、ｄ1とｄ2との和、すなわち並列ｐｎ構造の一対のｐｎ接合の繰り返しのピッチ幅は、３６μｍ以下であり、かつｄ1の方がｄ2よりも大きい。また、ｎドリフト領域１の実効的な総不純物量と、ｐ+仕切り領域２の実効的な総不純物量は、概ね同じである。そして、ｎドリフト領域１の実効的な不純物濃度ｎ１［ｃｍ-3］は、概ね前記（１）式で求められる濃度である。また、ｐ+仕切り領域２の実効的な不純物濃度ｎ２［ｃｍ-3］は、概ね前記（２）式で求められる濃度である。
【００３１】
図１に示すように、並列ｐｎ接合層２０と基板裏面の第２の電極であるドレイン電極３との間は、ｎ+半導体基板よりなる低抵抗層４となっている。また、基板表面側には、表面ｎドリフト領域５、ｐベース領域６、ｐ+コンタクト領域７、ｎ+ソース領域８、ゲート絶縁膜９、ゲート電極１０、層間絶縁膜１１および第１の電極であるソース電極１２よりなる表面素子構造が形成されている。
【００３２】
ここで、本発明者らがおこなったシミュレーションの結果を図３に示す。このシミュレーションでは、図２に示すように、並列ｐｎ接合層２０は、基板表面側から見てストライプ状であり、ｎドリフト領域１の幅ｄ1とｐ+仕切り領域２の幅ｄ2との和を６μｍとし、並列ｐｎ接合層２０の接合長さｌ（図１参照）を１１．５μｍとした。また、ｎドリフト領域１の不純物濃度およびｐ+仕切り領域２の不純物濃度を、それぞれ前記（１）式および前記(２)式より求まる濃度とした。また、素子表面のＭＯＳ構造を省いたダイオードまたは抵抗体で、耐圧と単位面積当たりのオン抵抗をシミュレーションにより調べた。
【００３３】
図３より、ｎドリフト領域１の幅ｄ1を広げてｎドリフト領域１の不純物濃度を低下させるのにともなって、単位面積当たりのオン抵抗が減少するという傾向が確認された。また、ｎドリフト領域１およびｐ+仕切り領域２の総不純物量がそれぞれ一定に保たれているため、ｎドリフト領域１の幅ｄ1が変化しても耐圧はほぼ一定であることが確認された。
【００３４】
上述した実施の形態１によれば、並列ｐｎ接合層２０のピッチ幅が、並列ｐｎ接合層２０のｎドリフト領域１の実効的な不純物濃度が１０15ｃｍ-3以上である従来の超接合半導体素子における並列ｐｎ接合層のピッチ幅と同じで、かつ並列ｐｎ接合層２０のｎドリフト領域１およびｐ+仕切り領域２のそれぞれの実効的な総不純物量が、従来の超接合半導体素子における並列ｐｎ接合層のｎドリフト領域およびｐ+仕切り領域のそれぞれの実効的な総不純物量と同じであっても、ｎドリフト領域１の幅を広げ、ｐ+仕切り領域２の幅を狭めることによって、ｎドリフト領域１の体積が大きくなり、ｎドリフト領域１ではより広範に不純物が分布することになるので、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができる。したがって、耐圧の低下を招くことなく、オン抵抗を小さくすることができるので、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。
【００３５】
実施の形態２．
図４は、本発明の実施の形態２にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。図４に示すように、実施の形態２は、実施の形態１において、並列ｐｎ接合層２０のｎドリフト領域１が絶縁体領域１３により分断された構成となっている。その他の構成は、実施の形態１と同じである。実施の形態１と同じ構成については、実施の形態１と同一の符号を付して説明を省略する。
【００３６】
実施の形態２では、ｎドリフト領域１が絶縁体領域１３により分断されているため、ｎドリフト領域１の幅ｄ1［μｍ］の定め方に注意が必要である。具体的には、絶縁体領域１３の両脇に、ｎドリフト領域１が半分ずつに分かれて構成されているので、その一つの幅はｄ1／２となる。
【００３７】
絶縁体領域１３は、たとえば半導体基板に形成されたトレンチ内を、酸化膜等の絶縁体で埋め込むことにより形成される。したがって、実施の形態２は、半導体基板にトレンチを設け、その側壁へドーピングをおこなった後、酸化膜等の絶縁体でトレンチを埋め込むことにより、並列ｐｎ接合層２０を形成する場合に有効である。
【００３８】
上述した実施の形態２によれば、実施の形態１と同様に、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。
【００３９】
実施の形態３．
図５は、本発明の実施の形態３にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。図５に示すように、実施の形態３は、実施の形態１において、並列ｐｎ接合層２０のｐ+仕切り領域２が、半導体基板に形成されたトレンチの側壁に沿って設けられている。このトレンチの内側領域は、酸化膜等の絶縁体よりなる絶縁体領域１３となっている。その他の構成は、実施の形態１と同じである。実施の形態１と同じ構成については、実施の形態１と同一の符号を付して説明を省略する。
【００４０】
実施の形態３は、実施の形態２と同様に、トレンチを利用して並列ｐｎ接合層２０を形成する場合に有効であるが、特に、トレンチ側壁から横方向への拡散距離が短くて済むので、並列ｐｎ接合層２０の形成工程が簡単になるという利点がある。なお、並列ｐｎ接合層２０は、ストライプ状に限らず、図６に示すように、市松模様状としてもよい。
【００４１】
上述した実施の形態３によれば、実施の形態１と同様に、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。
【００４２】
実施の形態４．
図７は、本発明の実施の形態４にかかる縦型トレンチＭＯＳＦＥＴの構成を示す縦断面図である。図７に示すように、実施の形態４は、実施の形態１において、ＭＯＳＦＥＴの表面素子構造がトレンチ構造となっている。トレンチは、基板表面から、ｐベース領域３６を貫通して、並列ｐｎ接合層２０のｎドリフト領域１内にまで達している。トレンチの内側には、ゲート絶縁膜３９を介してゲート電極４０が埋め込まれている。
【００４３】
ｐベース領域３６内の表面層の、トレンチ側壁の外側には、ｎ+ソース領域３８が設けられている。また、ｐベース領域３６内の表面層には、ｐ+コンタクト領域３７が設けられている。第１の電極であるソース電極４２は、ｎ+ソース領域３８およびｐ+コンタクト領域３７に接しており、層間絶縁膜４１によりゲート電極４０から絶縁されている。その他の構成は、実施の形態１と同じである。実施の形態１と同じ構成については、実施の形態１と同一の符号を付して説明を省略する。
【００４４】
上述した実施の形態４によれば、実施の形態１と同様に、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。
【００４５】
また、実施の形態４によれば、ｎドリフト領域１とｐベース領域３６との間の空乏化が促進されるので、オフ状態でのトレンチ底周辺における電界緩和が期待される。また、実施の形態４によれば、従来の超接合半導体素子における並列ｐｎ接合層のピッチ幅と同じピッチ幅で、ｎドリフト領域１の幅ｄ1を広げることができるので、ＭＯＳＦＥＴがオンしたときに、チャネルからｎドリフト領域１に流れ込んだオン電流が、ｎドリフト領域１内を放射状に広がりながら流れる際に有利であることが期待される。
【００４６】
実施の形態５．
図８は、本発明の実施の形態５にかかるダイオードの構成を示す斜視図である。図８に示すように、並列ｐｎ接合層２０は、縦方向に伸びる円柱形のｎドリフト領域１が三角格子状に配置され、その周りをｐ+仕切り領域２が囲む構成となっている。図８に示すように、ｎドリフト領域１の直径をｄ1［μｍ］とし、隣り合うｎドリフト領域１間の距離をｄ2［μｍ］とすると、隣り合うｎドリフト領域１の互いの中心間距離をＤ1［μｍ］は、ｄ1とｄ2との和になる。このとき、Ｄ1の値、すなわちｄ1＋ｄ2は８０μｍ以下であり、かつｄ1の方がｄ2よりも大きい。
【００４７】
図８に示すように、並列ｐｎ接合層２０と基板裏面の第２の電極であるカソード電極との間は、ｎ+半導体基板よりなる低抵抗層４となっている。また、基板表面には、ｐアノード層５６が設けられている。なお、図が煩雑になるのを避けるため、図８では、カソード電極および第１の電極であるアノード電極の図示を省略している。
【００４８】
上述した実施の形態５によれば、実施の形態１と同様に、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。なお、ｎドリフト領域１の配置を四角格子状にしても、ｎドリフト領域１を平面的に無駄なく均一に配置することができる。また、表面素子構造をＭＯＳＦＥＴの構造としても、同様の効果が得られる。
【００４９】
また、ｎドリフト領域１が円柱形ではなく、三角柱や四角柱状など、横断面形状が円形でない場合には、ｎドリフト領域１の断面積をｓ1［μｍ2］としたときに、２√（ｓ1／３．１４）で求まる値を直径ｄ1［μｍ］として考えればよい。
【００５０】
実施の形態６．
図９は、本発明の実施の形態６にかかるダイオードの構成を示す斜視図である。図９に示すように、並列ｐｎ接合層２０は、縦方向に伸びる円柱形のｐ+仕切り領域２が三角格子状に配置され、その周りをｎドリフト領域１が囲む構成となっている。図９に示すように、ｐ+仕切り領域２の直径をｄ2［μｍ］とし、隣り合うｐ+仕切り領域２間の距離をｄ1［μｍ］とすると、隣り合うｐ+仕切り領域２の互いの中心間距離をＤ2［μｍ］は、ｄ1とｄ2との和になる。このとき、Ｄ2の値、すなわちｄ1＋ｄ2は２５μｍ以下であり、かつｄ1の方がｄ2よりも大きい。
【００５１】
図９に示すように、並列ｐｎ接合層２０と基板裏面の第２の電極であるカソード電極（図示省略）との間は、ｎ+半導体基板よりなる低抵抗層４となっている。また、基板表面には、ｐアノード層５６および図示省略した第１の電極であるアノード電極が設けられている。
【００５２】
上述した実施の形態６によれば、実施の形態１と同様に、ｎドリフト領域１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。なお、ｐ+仕切り領域２の配置を四角格子状にしても、ｎドリフト領域１を平面的に無駄なく均一に配置することができる。また、表面素子構造をＭＯＳＦＥＴの構造としても、同様の効果が得られる。
【００５３】
また、ｐ+仕切り領域２が円柱形ではなく、三角柱や四角柱状など、横断面形状が円形でない場合には、ｐ+仕切り領域２の断面積をｓ2［μｍ2］としたときに、２√（ｓ2／３．１４）で求まる値を直径ｄ2［μｍ］として考えればよい。
【００５４】
実施の形態７．
図１０は、本発明の実施の形態７にかかる横型プレーナＭＯＳＦＥＴの構成を示す縦断面図であり、図１１は、その並列ｐｎ構造のドリフト電流が流れる方向に直交する断面（図１０のＡ−Ａ’における断面）の構成を示す縦断面図である。図１０に示すように、第１の電極であるソース電極７２と、第２の電極であるドレイン電極６３は、素子の同じ主面上に形成されている。そして、並列ｐｎ接合層８０は、ソース電極７２側からドレイン電極６３側へ伸びるｎドリフト領域６１およびｐ+仕切り領域６２が、ｎドリフト領域６１の伸びる方向に直交する方向に、交互に繰り返し接合された横型ストライプ状の構成となっている。
【００５５】
図１１に示すように、ｎドリフト領域６１の幅をｄ1［μｍ］とし、ｐ+仕切り領域６２の幅をｄ2［μｍ］とすると、ｄ1とｄ2との和は、２４μｍ以下であり、かつｄ1の方がｄ2よりも大きい。また、ｎドリフト領域６１の実効的な総不純物量と、ｐ+仕切り領域６２の実効的な総不純物量は、概ね同じである。そして、ｎドリフト領域６１の実効的な不純物濃度ｎ１［ｃｍ-3］は、概ね前記（３）式で求められる濃度である。また、ｐ+仕切り領域６２の実効的な不純物濃度ｎ２［ｃｍ-3］は、概ね前記（４）式で求められる濃度である。
【００５６】
図１０に示すように、ｐ-半導体基板８１上にｎ-層８２が設けられている。ｎ-層８２の表面層には、並列ｐｎ接合層８０を構成するｎドリフト領域６１およびｐ+仕切り領域６２と、ｐベース領域６６が形成されている。ｎドリフト領域６１の表面層には、ドレイン電極６３に接触し、ドレイン領域であるｎ+低抵抗領域６４が形成されている。また、ｐベース領域６６の表面層には、ソース電極７２に接触するｐ+コンタクト領域６７およびｎ+ソース領域６８が形成されている。ｐベース領域６６の、ｎ+ソース領域６８と並列ｐｎ接合層８０との間の表面上には、ゲート絶縁膜６９を介してゲート電極７０が形成されている。
【００５７】
上述した実施の形態７によれば、横型半導体素子においても、実施の形態１と同様に、ｎドリフト領域６１の不純物濃度が低くなり、キャリア移動度が低下するのを防ぐことができるので、耐圧の低下を招くことなく、オン抵抗を小さくすることができる。したがって、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。なお、図１２に示す部分断面図のように、ｐ-半導体基板８１上にｎ-層８２が設けられ、さらにその上にｐ-層８３が設けられたダブルリサーフ構造や、図１３に示す部分断面図のように、ｐ-半導体基板８１上に絶縁層８４が設けられたＳＯＩ（シリコン・オン・インシュレータ）構造とすれば、より特性のよい半導体素子が得られる。
【００５８】
以上において本発明は、耐圧領域を構成する超接合構造にかかわるものであるため、ソースやドレインの構造およびそれらの製造プロセス等については任意である。したがって、本発明は、ＭＯＳＦＥＴおよびダイオードに限らず、ＩＧＢＴ、バイポーラトランジスタまたはＧＴＯサイリスタ等にも適用され、それら半導体素子は縦型であってもよいし、横型であってもよい。また、本発明は、特開平１１−２２１８６１号公報に開示されているように、並列ｐｎ接合層２０，８０のｎドリフト領域１，６１とｐ+仕切り領域２，６２の不純物量が異なっている場合にも適用可能である。また、上述した各半導体領域の寸法や不純物濃度の値は一例であり、本発明はこれに限定されるものではない。
【００５９】
【発明の効果】
本発明によれば、微細ピッチで、不純物濃度の高い並列ｐｎ構造を有する超接合半導体素子において、並列ｐｎ構造のｐ型半導体領域およびｎ型半導体領域のそれぞれの実効的な総不純物量を保持したまま、ドリフト領域の体積を大きくし、一方、仕切り領域の体積を小さくすることにより、ドリフト領域の不純物濃度を下げることができるので、キャリア移動度が低下するのを防ぐことができる。したがって、耐圧の低下を招くことなく、オン抵抗を小さくすることができるので、順電圧やオン抵抗（あるいは電流容量）と耐圧との間のトレードオフ関係を十分に改善することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。
【図２】図１に示す素子の並列ｐｎ構造の上端面の構成を示す平面図である。
【図３】単位面積当たりのオン抵抗と並列ｐｎ構造のドリフト領域幅との関係を示すシミュレーション結果である。
【図４】本発明の実施の形態２にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。
【図５】本発明の実施の形態３にかかる縦型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。
【図６】図５に示す素子の並列ｐｎ構造の上端面の構成の他の例を示す平面図である。
【図７】本発明の実施の形態４にかかる縦型トレンチＭＯＳＦＥＴの構成を示す縦断面図である。
【図８】本発明の実施の形態５にかかるダイオードの構成を示す斜視図である。
【図９】本発明の実施の形態６にかかるダイオードの構成を示す斜視図である。
【図１０】本発明の実施の形態７にかかる横型プレーナＭＯＳＦＥＴの構成を示す縦断面図である。
【図１１】図１０に示す素子の並列ｐｎ構造のドリフト電流が流れる方向に直交する断面の構成を示す縦断面図である。
【図１２】図１０に示す素子の並列ｐｎ構造のドリフト電流が流れる方向に直交する断面の構成の他の例を示す縦断面図である。
【図１３】図１０に示す素子の並列ｐｎ構造のドリフト電流が流れる方向に直交する断面の構成のさらに他の例を示す縦断面図である。
【符号の説明】
１，６１ 第１導電型半導体領域（ｎドリフト領域）
２，６２ 第２導電型半導体領域（ｐ+仕切り領域）
３，６３ 第２の電極（ドレイン電極）
４ 第１導電型低抵抗層
１２，４２，７２ 第１の電極（ソース電極）
２０，８０ 並列ｐｎ接合層
６４ 第１導電型低抵抗領域[0001]
BACKGROUND OF THE INVENTION
The present invention provides a drift region made of a first conductivity type semiconductor extending from the first electrode side to the second electrode side of a semiconductor element, and a partition region made of a second conductivity type semiconductor extending in the same manner, Having a configuration in which the layers are alternately and repeatedly joined in a direction crossing the direction in which the parallel pn junction extends (this configuration is referred to as a parallel pn junction layer or a parallel pn structure), and when the parallel pn junction layer is in an on state, a current flows. Regarding a semiconductor element (this is referred to as a superjunction semiconductor element) which becomes a depletion drift layer in an off state, particularly in a MOSFET (insulated gate field effect transistor), an IGBT (insulated gate bipolar transistor), a bipolar transistor, etc. The present invention relates to a superjunction semiconductor element that can achieve both high breakdown voltage and large current capacity.
[0002]
[Prior art]
In general, semiconductor elements are classified into a horizontal element having electrodes formed on one side and a vertical element having electrodes on both sides. In the vertical semiconductor element, the direction in which the drift current flows in the on state is the same as the direction in which the depletion layer due to the reverse bias voltage extends in the off state. In a normal planar type n-channel vertical MOSFET, high resistance n - The portion of the drift layer functions as a region in which a drift current flows in the vertical direction (depth direction) when in the on state. Therefore, this n - If the current path of the drift layer is shortened, the drift resistance is lowered, so that the substantial on-resistance of the MOSFET is reduced.
[0003]
On the other hand, high resistance n - The drift layer portion is depleted in the off state to increase the breakdown voltage. Therefore, n - When the drift layer is thinned, the width of the drain-base depletion layer proceeding from the pn junction between the p base region and the drift region is narrowed, and the critical electric field strength of silicon is reached quickly, so that the breakdown voltage decreases. . Conversely, in a semiconductor device with a high breakdown voltage, n - Since the drift layer is thick, the forward voltage and the on-resistance increase, and the loss increases. Thus, there is a trade-off relationship between the forward voltage, on-resistance (or current capacity), and breakdown voltage.
[0004]
This trade-off relationship is also known to hold in semiconductor devices such as IGBTs, bipolar transistors, and diodes. This trade-off relationship is also common to lateral semiconductor elements in which the direction in which the drift current flows in the on state and the direction in which the depletion layer extends in the off state are different.
[0005]
As a solution to the above-described problem due to the trade-off relationship, a parallel pn structure in which a drift region composed of a first conductivity type semiconductor region with an increased impurity concentration and a partition region composed of a second conductivity type semiconductor region are alternately and repeatedly joined. There are known super junction semiconductor elements having a drift layer (see Patent Documents 1 to 4 and Non-Patent Document 1 below). In a superjunction semiconductor device, even when the impurity concentration of the parallel pn structure is high, the depletion layer extends laterally from each pn junction extending in the vertical direction of the parallel pn structure in the off state, and the entire drift layer is depleted. Therefore, a high breakdown voltage can be achieved. It is known that the trade-off described above is greatly improved by narrowing the pitch width of the parallel pn structure and increasing the impurity concentration.
[0006]
[Patent Document 1]
European Patent Application No. 0053854
[Patent Document 2]
US Pat. No. 5,216,275
[Patent Document 3]
US Pat. No. 5,438,215
[Patent Document 4]
JP-A-9-266611
[Non-Patent Document 1]
Tatsuhiko Fujihara, “Theory of semiconductor Superjunction Devices” Jpn. J. et al. Appl. Phys. Vol. 36 (1997) p. 6254-6262 Part 1, no. 10, October 1997
[0007]
[Problems to be solved by the invention]
However, when the impurity concentration is increased by narrowing the pitch width of the parallel pn structure, the carrier mobility decreases as the impurity concentration in the drift region increases, and in particular, the impurity concentration in the drift region is approximately 10%. 15 [Cm -3 ], The tendency of the carrier mobility to decrease increases, so that the on-resistance is not sufficiently low in practice, and the above-described trade-off improvement effect is small.
[0008]
The present invention has been made in view of the above problems, and in a superjunction semiconductor device having a parallel pn structure with a high impurity concentration, the on-resistance is sufficiently reduced, whereby forward voltage, on-resistance and breakdown voltage are reduced. An object of the present invention is to provide a superjunction semiconductor device that can sufficiently improve the trade-off relationship between the two.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a superjunction semiconductor device having a parallel pn structure with a fine pitch and a high impurity concentration. The structure is characterized in that the volume of the drift region is increased while the volume of the partition region is decreased while the amount of impurities is maintained.
[0010]
According to the present invention, since the impurity concentration in the drift region is lowered, it is possible to prevent the carrier mobility from being lowered. By the way, in the super junction semiconductor element, if the effective total impurity amount of the p-type semiconductor region constituting the parallel pn structure is the same as the effective total impurity amount of the n-type semiconductor region, the p-type semiconductor region It is known that even if the n-type semiconductor regions have different volumes, substantially the same breakdown voltage can be obtained as when the volumes are the same. Therefore, the on-resistance can be reduced without causing a decrease in breakdown voltage.
[0011]
Specifically, in the case of a vertical stripe-shaped parallel pn structure that is simply formed by alternately joining a rectangular parallelepiped p-type semiconductor region and an n-type semiconductor region, the width of the drift region is defined as d. 1 [Μm] and the width of the partition region is d 2 If [μm], d 1 + D 2 Is 36 μm or less, and d 1 > D 2 It is. The reason is that the impurity concentration in the drift region is n 1 [Cm -3 ], And the impurity concentration of the partition region is n 2 [Cm -3 ], The substantially optimum impurity concentration that provides both high breakdown voltage and low on-resistance is given by the following equations (1) and (2), respectively.
[0012]
[Equation 5]
Figure 0004265201
[0013]
[Formula 6]
Figure 0004265201
[0014]
Here, as a simple case, d 1 And d 2 Is 18 μm, the impurity concentration n in the drift region is calculated from the above equation (1). 1 Is 1.00 × 10 15 cm -3 It becomes. Therefore, d 1 + D 2 In a superjunction semiconductor device having a value of 36 μm or less, a decrease in carrier mobility can be prevented.
[0015]
The present invention is not limited to the case where the parallel pn structure is the above-described stripe shape, but similarly holds when the parallel pn structure is a cell shape. In the case of the cell shape, the optimum impurity concentration is the cross-sectional shape of the cell. Calculation of the optimum impurity concentration is complicated. However, the impurity concentration in the drift region is 10 15 cm -3 The approximate size of the parallel pn structure can be found by the following approximate estimate.
[0016]
As a simple case, the diameter d 1 [Μm] cylindrical drift regions are d between each other. 2 Assuming a cell-like parallel pn structure that is opened in [μm] and arranged in a triangular lattice shape or a square lattice shape, d 1 = D 2 = D [μm]. The center distance D of the cylindrical drift region at this time 1 D 1 + D 2 [Μm]. The parallel pn structure having this cylindrical drift region is defined as the width of each of the drift region and the partition region being d. 1 And d 2 And d 1 = D 2 Compared to a stripe-shaped parallel pn structure in which = d [μm] and the junction length of the parallel pn structure is the same, the volume of the drift region is about 0.4 times, and the volume of the partition region Becomes about 1.5 times. Here, the junction length of the parallel pn structure is the dimension of the contact portion between the drift region and the partition region in the direction in which the drift current flows.
[0017]
That is, if the total impurity amount in the drift region is the same when the parallel pn structure is striped and in the cell shape, the impurity concentration in the drift region in the cell shape is 1/0 that in the stripe shape. .4 times. Therefore, the concentration n of the drift region of the cell-like parallel pn structure 1 10 15 cm -3 In calculating the value of d when 1 0.4 × 10 15 cm -3 If the above equation (1) is used, the value of d is 40 μm. Therefore, in the case of a parallel pn structure having a cellular drift region, d 1 + D 2 In a superjunction semiconductor element having a value of 80 μm or less, it is considered that a decrease in carrier mobility can be prevented.
[0018]
If the cell shape of the drift region is not cylindrical, but the cross-sectional shape is not circular, such as a triangular prism or a quadrangular prism, the cross-sectional area is s 1 [Μm 2 ] 2√ (s 1 /3.14) is the diameter d 1 What is necessary is just to consider replacing it with a cylindrical drift region having a circular cross section of [μm] and the same volume as the actual drift region. Then, the impurity concentration in the drift region is 10 as in the case of the cylindrical drift region described above. 15 cm -3 An approximate dimension of the parallel pn structure is required.
[0019]
In the cell-like parallel pn structure, the diameter d 2 [Μm] cylindrical partition regions are d between each other 1 Even in the case of being arranged in a triangular lattice shape or a quadrangular lattice shape by opening [μm], the impurity concentration of the drift region is 10 as in the case where the cylindrical drift region described above is disposed. 15 cm -3 The approximate size of the parallel pn structure can be estimated. The center distance D of the cylindrical partition region at this time 2 D 1 + D 2 [Μm].
[0020]
As a simple case, d 1 = D 2 = D [μm], and the parallel pn structure having the cylindrical partition region has a width of the drift region and the partition region of d 1 And d 2 And d 1 = D 2 Compared with a stripe-shaped parallel pn structure in which = d [μm] and the junction length of the parallel pn structure is the same, the volume of the drift region is about 1.5 times, and the volume of the partition region Becomes about 0.4 times.
[0021]
That is, the impurity concentration of the drift region in the case of the cell shape corresponds to 1 / 1.5 times that in the case of the stripe shape. Therefore, in the above formula (1), for convenience, n 1 1.5 × 10 15 cm -3 Then, the value of d is 12.5 μm. Therefore, in the case of a parallel pn structure having a cellular partition region, d 1 + D 2 In a superjunction semiconductor device having a value of 25 μm or less, it is considered that a decrease in carrier mobility can be prevented.
[0022]
If the cell shape of the partition region is not cylindrical, but the cross-sectional shape is not circular, such as a triangular prism or a quadrangular prism, the sectional area is s 2 [Μm 2 ] 2√ (s 2 /3.14) is the diameter d 2 What is necessary is just to consider replacing with a cylindrical partition region having a circular cross section of [μm] and the same volume as the actual partition region. Then, the impurity concentration of the drift region is 10 as in the case of the cylindrical partition region described above. 15 cm -3 An approximate dimension of the parallel pn structure is required.
[0023]
In the case of a horizontal stripe parallel pn structure, the widths of the drift region and the partition region are set to d, respectively. 1 [Μm] and d 2 [Μm], and the impurity concentration of the drift region and the partition region is n 1 [Cm -3 ] And n 2 [Cm -3 ], An approximately optimum impurity concentration n that provides both a high breakdown voltage and a low on-resistance. 1 And n 2 Are given by the following equations (3) and (4), respectively.
[0024]
[Expression 7]
Figure 0004265201
[0025]
[Equation 8]
Figure 0004265201
[0026]
As a simple case, d 1 And d 2 Is 12 μm, the impurity concentration n in the drift region is calculated from the above equation (3). 1 Is 1.00 × 10 15 cm -3 It becomes. That is, d 1 + D 2 In a superjunction semiconductor device having a value of 24 μm or less, a decrease in carrier mobility can be prevented.
[0027]
The above formulas (1) to (4) are cited from Non-Patent Document 1. According to Non-Patent Document 1, the optimum concentration in a silicon device is N. D = 1.41 × 10 12 ・ Α 7/6 ・ D -7/5 (Cm -3 ) Is given in (4.1), and α is the value at which the trade-off between on-resistance per unit area and breakdown voltage is the best, α = 1/3 for horizontal devices, and for vertical devices Indicates that α = ½. However, in the above non-patent document 1, d 1 = D 2 = D, in the present invention, in order to generalize it, d is replaced by (d 1 + D 2 ). And N D * D = n 1 * D 1 = N 2 * D 2 N to be 1 Or n 2 Seeking. And d 1 , D 2 For [μm], n 1 , N 2 [Cm -3 ] Has been changed to an equation such that a coefficient for converting a unit exists in the equations (1) to (4).
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in this specification, a layer or region with n or p is a layer or region having electrons or holes as majority carriers. Further, the subscript + attached to n or p means a relatively high impurity concentration, and-means a relatively low impurity concentration. In addition, a direction from the front surface side to the back surface side of the semiconductor element is defined as a vertical direction, and a direction intersecting this is defined as a horizontal direction. In the following description, the first conductivity type is n-type and the second conductivity type is p-type, and vice versa.
[0029]
Embodiment 1 FIG.
FIG. 1 is a longitudinal sectional view showing a configuration of a vertical planar MOSFET according to a first embodiment of the present invention, and FIG. 2 is a plan view showing a configuration of an upper end surface of the parallel pn structure. As shown in FIG. 1, the parallel pn junction layer 20 includes an n drift region 1 extending in the vertical direction and a p extending in the vertical direction. + The partition region 2 has a configuration of a vertical stripe shape that is alternately and repeatedly joined in the horizontal direction.
[0030]
As shown in FIG. 1 or 2, the width of the n drift region 1 is d 1 [Μm], p + The width of the partition area 2 is d 2 If [μm], d 1 And d 2 , That is, the repeated pitch width of a pair of pn junctions in a parallel pn structure is 36 μm or less, and d 1 Is d 2 Bigger than. Further, the effective total impurity amount of the n drift region 1 and p + The effective total amount of impurities in the partition region 2 is substantially the same. The effective impurity concentration n of the n drift region 1 1 [Cm -3 ] Is a concentration generally determined by the equation (1). P + Effective impurity concentration n of the partition region 2 2 [Cm -3 ] Is a concentration generally determined by the equation (2).
[0031]
As shown in FIG. 1, the space between the parallel pn junction layer 20 and the drain electrode 3 as the second electrode on the back surface of the substrate is n + The low resistance layer 4 is made of a semiconductor substrate. Further, on the substrate surface side, a surface n drift region 5, a p base region 6, p + Contact region 7, n + A surface element structure including a source region 8, a gate insulating film 9, a gate electrode 10, an interlayer insulating film 11, and a source electrode 12 as a first electrode is formed.
[0032]
Here, the result of the simulation performed by the present inventors is shown in FIG. In this simulation, as shown in FIG. 2, the parallel pn junction layer 20 has a stripe shape as viewed from the substrate surface side, and the width d of the n drift region 1 1 And p + Width d of partition area 2 2 And the junction length l (see FIG. 1) of the parallel pn junction layer 20 was 11.5 μm. Further, the impurity concentration of the n drift region 1 and p + The impurity concentration of the partition region 2 was set to the concentration obtained from the equation (1) and the equation (2), respectively. In addition, the breakdown voltage and the on-resistance per unit area were examined by simulation with a diode or resistor without the MOS structure on the element surface.
[0033]
From FIG. 3, the width d of the n drift region 1 1 It was confirmed that the on-resistance per unit area decreased as the impurity concentration in the n drift region 1 was decreased by expanding the n drift region 1. Also, n drift region 1 and p + Since the total impurity amount of the partition region 2 is kept constant, the width d of the n drift region 1 1 It was confirmed that the withstand voltage was almost constant even when the value changed.
[0034]
According to the first embodiment described above, the pitch width of the parallel pn junction layer 20 is 10 and the effective impurity concentration of the n drift region 1 of the parallel pn junction layer 20 is 10. 15 cm -3 The same as the pitch width of the parallel pn junction layer in the conventional superjunction semiconductor device as described above, and the n drift region 1 and p of the parallel pn junction layer 20 + The effective total impurity amount of each partition region 2 is determined so that the n drift region and p of the parallel pn junction layer in the conventional super junction semiconductor device + Even if the effective total impurity amount of each partition region is the same, the width of the n drift region 1 is increased, and p + By narrowing the width of the partition region 2, the volume of the n drift region 1 is increased, and impurities are distributed more widely in the n drift region 1. The degree can be prevented from decreasing. Accordingly, since the on-resistance can be reduced without causing a decrease in the withstand voltage, the trade-off relationship between the forward voltage or the on-resistance (or current capacity) and the withstand voltage can be sufficiently improved.
[0035]
Embodiment 2. FIG.
FIG. 4 is a longitudinal sectional view showing the configuration of the vertical planar MOSFET according to the second embodiment of the present invention. As shown in FIG. 4, the second embodiment has a configuration in which the n drift region 1 of the parallel pn junction layer 20 is divided by the insulator region 13 in the first embodiment. Other configurations are the same as those of the first embodiment. About the same structure as Embodiment 1, the code | symbol same as Embodiment 1 is attached | subjected and description is abbreviate | omitted.
[0036]
In the second embodiment, since the n drift region 1 is divided by the insulator region 13, the width d of the n drift region 1 1 Care must be taken in determining [μm]. Specifically, since the n drift region 1 is divided in half on both sides of the insulator region 13, the width of one of the regions is d 1 / 2.
[0037]
Insulator region 13 is formed, for example, by burying a trench formed in a semiconductor substrate with an insulator such as an oxide film. Therefore, the second embodiment is effective when the parallel pn junction layer 20 is formed by providing a trench in a semiconductor substrate, doping the sidewall thereof, and then burying the trench with an insulator such as an oxide film. .
[0038]
According to the second embodiment described above, as in the first embodiment, it is possible to prevent the impurity concentration of the n drift region 1 from being lowered and the carrier mobility from being lowered, so that the breakdown voltage is not lowered. , The on-resistance can be reduced. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved.
[0039]
Embodiment 3 FIG.
FIG. 5 is a longitudinal sectional view showing the configuration of the vertical planar MOSFET according to the third embodiment of the present invention. As shown in FIG. 5, the third embodiment is different from the first embodiment in that the p of the parallel pn junction layer 20. + A partition region 2 is provided along the side wall of a trench formed in the semiconductor substrate. An inner region of the trench is an insulator region 13 made of an insulator such as an oxide film. Other configurations are the same as those of the first embodiment. About the same structure as Embodiment 1, the code | symbol same as Embodiment 1 is attached | subjected and description is abbreviate | omitted.
[0040]
The third embodiment is effective in the case where the parallel pn junction layer 20 is formed using a trench, similarly to the second embodiment, but in particular, the diffusion distance in the lateral direction from the trench sidewall can be shortened. There is an advantage that the process of forming the parallel pn junction layer 20 is simplified. The parallel pn junction layer 20 is not limited to a stripe shape, and may be a checkered pattern as shown in FIG.
[0041]
According to the third embodiment described above, as in the first embodiment, the impurity concentration of the n drift region 1 is reduced and the carrier mobility can be prevented from being lowered, so that the breakdown voltage is not lowered. , The on-resistance can be reduced. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved.
[0042]
Embodiment 4 FIG.
FIG. 7 is a longitudinal sectional view showing the configuration of the vertical trench MOSFET according to the fourth embodiment of the present invention. As shown in FIG. 7, in the fourth embodiment, the surface element structure of the MOSFET is a trench structure in the first embodiment. The trench extends from the substrate surface through the p base region 36 and into the n drift region 1 of the parallel pn junction layer 20. A gate electrode 40 is buried inside the trench through a gate insulating film 39.
[0043]
On the outside of the trench sidewall of the surface layer in the p base region 36, n + A source region 38 is provided. The surface layer in the p base region 36 has p + A contact region 37 is provided. The source electrode 42 which is the first electrode is n + Source region 38 and p + It is in contact with the contact region 37 and is insulated from the gate electrode 40 by the interlayer insulating film 41. Other configurations are the same as those of the first embodiment. About the same structure as Embodiment 1, the code | symbol same as Embodiment 1 is attached | subjected and description is abbreviate | omitted.
[0044]
According to the above-described fourth embodiment, as in the first embodiment, the impurity concentration of the n drift region 1 is reduced and the carrier mobility can be prevented from being lowered, so that the breakdown voltage is not lowered. , The on-resistance can be reduced. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved.
[0045]
Further, according to the fourth embodiment, depletion between n drift region 1 and p base region 36 is promoted, so that electric field relaxation around the trench bottom in the off state is expected. Further, according to the fourth embodiment, the width d of the n drift region 1 is equal to the pitch width of the parallel pn junction layer in the conventional super junction semiconductor element. 1 Therefore, when the MOSFET is turned on, it is expected that the on-current that flows from the channel into the n drift region 1 is advantageous when flowing in the n drift region 1 while spreading radially.
[0046]
Embodiment 5 FIG.
FIG. 8 is a perspective view showing a configuration of a diode according to the fifth exemplary embodiment of the present invention. As shown in FIG. 8, in the parallel pn junction layer 20, cylindrical n drift regions 1 extending in the vertical direction are arranged in a triangular lattice shape, and the periphery thereof is p. + The partition area 2 surrounds the structure. As shown in FIG. 8, the diameter of the n drift region 1 is d 1 [Μm], and the distance between adjacent n drift regions 1 is d 2 If [μm], the distance between the centers of the adjacent n drift regions 1 is D 1 [Μm] is d 1 And d 2 And the sum. At this time, D 1 The value of d 1 + D 2 Is 80 μm or less and d 1 Is d 2 Bigger than.
[0047]
As shown in FIG. 8, there is n between the parallel pn junction layer 20 and the cathode electrode as the second electrode on the back surface of the substrate. + The low resistance layer 4 is made of a semiconductor substrate. A p anode layer 56 is provided on the substrate surface. In addition, in order to avoid that a figure becomes complicated, illustration of the anode electrode which is a cathode electrode and a 1st electrode is abbreviate | omitted in FIG.
[0048]
According to the fifth embodiment described above, as in the first embodiment, the impurity concentration of the n drift region 1 is reduced and the carrier mobility can be prevented from being lowered, so that the breakdown voltage is not lowered. , The on-resistance can be reduced. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved. It should be noted that even if the n drift region 1 is arranged in a square lattice shape, the n drift region 1 can be uniformly disposed in a planar manner without waste. The same effect can be obtained even if the surface element structure is a MOSFET structure.
[0049]
In addition, when the n drift region 1 is not a cylinder and the cross sectional shape is not circular, such as a triangular prism or a quadrangular prism, the cross sectional area of the n drift region 1 is s 1 [Μm 2 ] 2√ (s 1 /3.14) is the diameter d 1 Think of it as [μm].
[0050]
Embodiment 6 FIG.
FIG. 9 is a perspective view showing a configuration of a diode according to the sixth exemplary embodiment of the present invention. As shown in FIG. 9, the parallel pn junction layer 20 has a cylindrical p extending in the vertical direction. + The partition region 2 is arranged in a triangular lattice shape, and the n drift region 1 surrounds the partition region 2. As shown in FIG. + The diameter of the partition area 2 is d 2 [Μm] and adjacent p + The distance between the partition areas 2 is d 1 When [μm], adjacent p + The distance between the centers of the partition areas 2 is D 2 [Μm] is d 1 And d 2 And the sum. At this time, D 2 The value of d 1 + D 2 Is 25 μm or less and d 1 Is d 2 Bigger than.
[0051]
As shown in FIG. 9, there is n between the parallel pn junction layer 20 and the cathode electrode (not shown) as the second electrode on the back surface of the substrate. + The low resistance layer 4 is made of a semiconductor substrate. A p anode layer 56 and an anode electrode, which is a first electrode (not shown), are provided on the substrate surface.
[0052]
According to the above-described sixth embodiment, as in the first embodiment, the impurity concentration of the n drift region 1 is reduced and the carrier mobility can be prevented from being lowered, so that the breakdown voltage is not lowered. , The on-resistance can be reduced. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved. P + Even if the partition regions 2 are arranged in a square lattice shape, the n drift regions 1 can be uniformly disposed in a plan view without waste. The same effect can be obtained even if the surface element structure is a MOSFET structure.
[0053]
P + If the partition area 2 is not cylindrical and the cross-sectional shape is not circular, such as a triangular prism or a quadrangular prism, p + The sectional area of the partition region 2 is s 2 [Μm 2 ] 2√ (s 2 /3.14) is the diameter d 2 Think of it as [μm].
[0054]
Embodiment 7 FIG.
FIG. 10 is a longitudinal sectional view showing a configuration of a lateral planar MOSFET according to a seventh embodiment of the present invention. FIG. 11 is a sectional view of the parallel pn structure perpendicular to the direction in which the drift current flows (A- in FIG. 10). It is a longitudinal cross-sectional view which shows the structure of the cross section in A '. As shown in FIG. 10, the source electrode 72 as the first electrode and the drain electrode 63 as the second electrode are formed on the same main surface of the element. The parallel pn junction layer 80 includes an n drift region 61 extending from the source electrode 72 side to the drain electrode 63 side and p + The partition region 62 has a horizontal stripe configuration in which the partition region 62 is alternately and repeatedly joined in a direction orthogonal to the direction in which the n drift region 61 extends.
[0055]
As shown in FIG. 11, the width of the n drift region 61 is d 1 [Μm], p + The width of the partition area 62 is d 2 If [μm], d 1 And d 2 And the sum is 24 μm or less and d 1 Is d 2 Bigger than. Further, the effective total impurity amount of the n drift region 61 and p + The effective total impurity amount of the partition region 62 is substantially the same. The effective impurity concentration n of the n drift region 61 is 1 [Cm -3 ] Is a concentration generally determined by the equation (3). P + Effective impurity concentration n of the partition region 62 2 [Cm -3 ] Is a concentration generally determined by the equation (4).
[0056]
As shown in FIG. - N on the semiconductor substrate 81 - A layer 82 is provided. n - The surface layer of the layer 82 includes n drift regions 61 and p constituting the parallel pn junction layer 80. + A partition region 62 and a p base region 66 are formed. The surface layer of the n drift region 61 is in contact with the drain electrode 63 and is the drain region n + A low resistance region 64 is formed. Further, the surface layer of the p base region 66 has a p in contact with the source electrode 72. + Contact region 67 and n + A source region 68 is formed. n of the p base region 66 + A gate electrode 70 is formed on the surface between the source region 68 and the parallel pn junction layer 80 via a gate insulating film 69.
[0057]
According to the above-described seventh embodiment, also in the horizontal semiconductor element, the impurity concentration in the n drift region 61 is reduced and the carrier mobility can be prevented from being lowered as in the first embodiment. On-resistance can be reduced without incurring a decrease. Therefore, the trade-off relationship between the forward voltage, on-resistance (or current capacity) and breakdown voltage can be sufficiently improved. As shown in the partial sectional view of FIG. - N on the semiconductor substrate 81 - A layer 82 is provided and further p - As shown in the double RESURF structure provided with the layer 83 and the partial cross-sectional view shown in FIG. - If an SOI (silicon-on-insulator) structure in which an insulating layer 84 is provided on a semiconductor substrate 81, a semiconductor element with better characteristics can be obtained.
[0058]
In the above, the present invention relates to the superjunction structure that constitutes the breakdown voltage region, and therefore the source and drain structures, the manufacturing process thereof, and the like are arbitrary. Therefore, the present invention is not limited to MOSFETs and diodes, but is also applied to IGBTs, bipolar transistors, GTO thyristors, and the like, and these semiconductor elements may be vertical or horizontal. Further, as disclosed in Japanese Patent Application Laid-Open No. 11-221861, the present invention provides n drift regions 1, 61 and p of parallel pn junction layers 20, 80. + The present invention is also applicable when the impurity amounts of the partition regions 2 and 62 are different. Further, the dimensions and impurity concentration values of the semiconductor regions described above are examples, and the present invention is not limited to these.
[0059]
【The invention's effect】
According to the present invention, the effective total impurity amount of each of the p-type semiconductor region and the n-type semiconductor region of the parallel pn structure is maintained in the superjunction semiconductor element having the parallel pn structure having a high impurity concentration at a fine pitch. The impurity concentration in the drift region can be lowered by increasing the volume of the drift region while decreasing the volume of the partition region, and thus the carrier mobility can be prevented from decreasing. Accordingly, since the on-resistance can be reduced without causing a decrease in the withstand voltage, the trade-off relationship between the forward voltage or the on-resistance (or current capacity) and the withstand voltage can be sufficiently improved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration of a vertical planar MOSFET according to a first embodiment of the present invention;
2 is a plan view showing a configuration of an upper end surface of the parallel pn structure of the element shown in FIG. 1. FIG.
FIG. 3 is a simulation result showing a relationship between an on-resistance per unit area and a drift region width of a parallel pn structure.
FIG. 4 is a longitudinal sectional view showing a configuration of a vertical planar MOSFET according to a second embodiment of the present invention.
FIG. 5 is a longitudinal sectional view showing a configuration of a vertical planar MOSFET according to a third embodiment of the present invention.
6 is a plan view showing another example of the configuration of the upper end surface of the parallel pn structure of the element shown in FIG. 5. FIG.
FIG. 7 is a longitudinal sectional view showing a configuration of a vertical trench MOSFET according to a fourth embodiment of the present invention.
FIG. 8 is a perspective view showing a configuration of a diode according to a fifth exemplary embodiment of the present invention.
FIG. 9 is a perspective view showing a configuration of a diode according to a sixth embodiment of the present invention.
FIG. 10 is a longitudinal sectional view showing a configuration of a lateral planar MOSFET according to a seventh embodiment of the present invention.
11 is a longitudinal sectional view showing a configuration of a cross section perpendicular to a direction in which a drift current of the parallel pn structure of the element shown in FIG. 10 flows.
12 is a longitudinal sectional view showing another example of the configuration of a cross section orthogonal to the direction in which the drift current of the parallel pn structure of the element shown in FIG. 10 flows.
13 is a longitudinal sectional view showing still another example of a cross-sectional configuration orthogonal to the direction in which the drift current of the parallel pn structure of the element shown in FIG. 10 flows.
[Explanation of symbols]
1,61 First conductivity type semiconductor region (n drift region)
2,62 Second conductivity type semiconductor region (p + Partition area)
3,63 Second electrode (drain electrode)
4 First conductivity type low resistance layer
12, 42, 72 First electrode (source electrode)
20,80 Parallel pn junction layer
64 First conductivity type low resistance region

Claims (8)

半導体素子の第１の主面側に形成された第１の電極と、半導体素子の第２の主面側に形成された第２の電極と、前記第１の電極と前記第２の電極との間に設けられた第１導電型低抵抗層と、前記第１の電極側から前記第２の電極側へ向かってそれぞれ伸びる複数の第１導電型半導体領域および複数の第２導電型半導体領域が、それらの伸びる方向に交差する方向に交互に繰り返し接合され、かつオン状態のときに電流を流し、オフ状態のときに空乏化する並列ｐｎ接合層と、を具備する超接合半導体素子において、
前記第１導電型半導体領域の不純物濃度が１０ 15 ｃｍ -3 以下であり、前記第１導電型半導体領域の実効的な総不純物量と、前記第２導電型半導体領域の実効的な総不純物量とを同じとして、前記各第１導電型半導体領域の幅をｄ1［μｍ］とし、前記各第２導電型半導体領域の幅をｄ2［μｍ］とすると、ｄ1＋ｄ2の値は３６μｍ以下であり、かつｄ1＞ｄ2であることを特徴とする超接合半導体素子。A first electrode formed on the first main surface side of the semiconductor element; a second electrode formed on the second main surface side of the semiconductor element; the first electrode and the second electrode; A first conductive type low resistance layer provided between the first conductive type semiconductor region, a plurality of first conductive type semiconductor regions and a plurality of second conductive type semiconductor regions respectively extending from the first electrode side toward the second electrode side In a superjunction semiconductor device comprising: a parallel pn junction layer that is alternately and repeatedly joined in a direction intersecting with the extending direction, and that conducts current when in an on state and is depleted when in an off state,
The impurity concentration of the first conductivity type semiconductor region is 10 15 cm −3 or less, and the effective total impurity amount of the first conductivity type semiconductor region and the effective total impurity amount of the second conductivity type semiconductor region. And the width of each of the first conductive semiconductor regions is d 1 [μm], and the width of each of the second conductive semiconductor regions is d 2 [μm], the value of d 1 + d 2 is 36 μm. A superjunction semiconductor device having the following configuration and d 1 > d 2 . 前記第１導電型半導体領域の実効的な不純物濃度ｎ 1 ［ｃｍ -3 ］は、つぎの式で求められる濃度であることを特徴とする請求項１に記載の超接合半導体素子。
Figure 0004265201
 2. The superjunction semiconductor device according to claim 1, wherein the effective impurity concentration n 1 [cm −3 ] of the first conductivity type semiconductor region is a concentration obtained by the following equation .
Figure 0004265201
 前記第２導電型半導体領域の実効的な不純物濃度ｎ 2 ［ｃｍ-3］は、つぎの式で求められる濃度であることを特徴とする請求項１または２に記載の超接合半導体素子。
Figure 0004265201
 The second conductivity type semiconductor region effective impurity concentration n 2 of [cm -3] is one super junction semiconductor device according to claim 1 or 2, characterized in that the concentration obtained by the expression technique.
Figure 0004265201
 半導体素子の第１の主面側に形成された第１の電極と、半導体素子の第２の主面側に形成された第２の電極と、前記第１の電極と前記第２の電極との間に設けられた第１導電型低抵抗層と、前記第１の電極側から前記第２の電極側へ向かって伸びるとともに、その伸びる方向に交差する方向に規則正しく配置された複数の第１導電型半導体領域の周りを、第２導電型半導体領域が囲み、かつオン状態のときに電流を流し、オフ状態のときに空乏化する並列ｐｎ接合層と、を具備する超接合半導体素子において、
前記第１導電型半導体領域の不純物濃度が１０ 15 ｃｍ -3 以下であり、前記第１導電型半導体領域の実効的な総不純物量と、前記第２導電型半導体領域の実効的な総不純物量とを同じとして、前記各第１導電型半導体領域の横断面の面積をｓ 1 ［μｍ 2 ］としたときに２√（ｓ 1 ／３．１４）の値をｄ 1 ［μｍ］とし、また隣り合う前記第１導電型半導体領域の互いの中心間距離をＤ 1 ［μｍ］としたときにＤ 1 −ｄ 1 の値をｄ 2 ［μｍ］とすると、ｄ 1 ＋ｄ 2 は８０μｍ以下であり、かつｄ 1 ＞ｄ 2 であることを特徴とする超接合半導体素子。 A first electrode formed on the first main surface side of the semiconductor element; a second electrode formed on the second main surface side of the semiconductor element; the first electrode and the second electrode; A first conductive type low resistance layer provided between the first conductive type low resistance layer and a plurality of first conductive layers that extend from the first electrode side toward the second electrode side and are regularly arranged in a direction intersecting the extending direction. A superjunction semiconductor device comprising: a parallel pn junction layer that surrounds a conductive semiconductor region, and that includes a parallel pn junction layer that surrounds the second conductive semiconductor region, allows a current to flow in an on state, and depletes in an off state.
The impurity concentration of the first conductivity type semiconductor region is 10 15 cm −3 or less, and the effective total impurity amount of the first conductivity type semiconductor region and the effective total impurity amount of the second conductivity type semiconductor region. And the value of 2√ (s 1 /3.14) is d 1 [μm] when the cross-sectional area of each of the first conductivity type semiconductor regions is s 1 [μm 2 ] , When the distance between the centers of the adjacent first conductive type semiconductor regions is D 1 [μm] and D 1 −d 1 is d 2 [μm], d 1 + d 2 is 80 μm or less. And a superjunction semiconductor element characterized by satisfying d 1 > d 2 . 半導体素子の第１の主面側に形成された第１の電極と、半導体素子の第２の主面側に形成された第２の電極と、前記第１の電極と前記第２の電極との間に設けられた第１導電型低抵抗層と、前記第１の電極側から前記第２の電極側へ向かって伸びるとともに、その伸びる方向に交差する方向に規則正しく配置された複数の第２導電型半導体領域の周りを、第１導電型半導体領域が囲み、かつオン状態のときに電流を流し、オフ状態のときに空乏化する並列ｐｎ接合層と、を具備する超接合半導体素子において、
前記第１導電型半導体領域の不純物濃度が１０ 15 ｃｍ -3 以下であり、前記第１導電型半導体領域の実効的な総不純物量と、前記第２導電型半導体領域の実効的な総不純物量とを同じとして、前記各第２導電型半導体領域の横断面の面積をｓ 2 ［μｍ 2 ］としたときに２ √（ｓ 2 ／３．１４）の値をｄ 2 ［μｍ］とし、また隣り合う前記第２導電型半導体領域の互いの中心間距離をＤ 2 ［μｍ］としたときにＤ 2 −ｄ 2 の値をｄ 1 ［μｍ］とすると、ｄ 1 ＋ｄ 2 は２５μｍ以下であり、かつｄ 1 ＞ｄ 2 であることを特徴とする超接合半導体素子。A first electrode formed on the first main surface side of the semiconductor element; a second electrode formed on the second main surface side of the semiconductor element; the first electrode and the second electrode; A first conductive type low resistance layer provided between the first conductive type low resistance layer and a plurality of second resistance layers regularly extending in a direction intersecting the extending direction while extending from the first electrode side toward the second electrode side. A superjunction semiconductor device comprising: a parallel pn junction layer that surrounds a conductive semiconductor region, and includes a parallel pn junction layer that energizes a current in an on state and depletes in an off state.
The impurity concentration of the first conductivity type semiconductor region is 10 15 cm −3 or less, and the effective total impurity amount of the first conductivity type semiconductor region and the effective total impurity amount of the second conductivity type semiconductor region. And the value of 2 √ (s 2 /3.14) is d 2 [μm] when the cross-sectional area of each of the second conductivity type semiconductor regions is s 2 [μm 2 ] , If the distance between the centers of the adjacent second conductivity type semiconductor regions is D 2 [μm], and D 2 −d 2 is d 1 [μm], d 1 + d 2 is 25 μm or less. And a superjunction semiconductor element characterized by satisfying d 1 > d 2 . 半導体素子の一主面側に形成された第１の電極および第２の電極と、前記第１の電極と前記第２の電極との間に設けられた第１導電型低抵抗領域と、前記第１の電極側から前記第２の電極側へ向かってそれぞれ伸びる複数の第１導電型半導体領域および複数の第２導電型半導体領域が、それらの伸びる方向に交差する方向に交互に繰り返し接合され、かつオン状態のときに電流を流し、オフ状態のときに空乏化する並列ｐｎ接合層と、を具備する超接合半導体素子において、
前記第１導電型半導体領域の不純物濃度が１０ 15 ｃｍ -3 以下であり、前記第１導電型半導体領域の実効的な総不純物量と、前記第２導電型半導体領域の実効的な総不純物量とを同じとして、前記各第１導電型半導体領域の幅をｄ 1 ［μｍ］とし、前記各第２導電型半導体領域の幅をｄ 2 ［μｍ］とすると、ｄ 1 ＋ｄ 2 の値は２４μｍ以下であり、かつｄ 1 ＞ｄ 2 であることを特徴とする超接合半導体素子。 A first conductive type low resistance region provided between the first electrode and the second electrode, the first electrode and the second electrode formed on one main surface side of the semiconductor element; A plurality of first conductivity type semiconductor regions and a plurality of second conductivity type semiconductor regions respectively extending from the first electrode side toward the second electrode side are alternately and repeatedly joined in a direction intersecting with the extending direction. And a parallel pn junction layer that allows a current to flow in the on state and is depleted in the off state,
The impurity concentration of the first conductivity type semiconductor region is 10 15 cm −3 or less, and the effective total impurity amount of the first conductivity type semiconductor region and the effective total impurity amount of the second conductivity type semiconductor region. And the width of each first conductive semiconductor region is d 1 [μm] and the width of each second conductive semiconductor region is d 2 [μm], the value of d 1 + d 2 is 24 μm. A superjunction semiconductor device having the following configuration and d 1 > d 2 . 前記第１導電型半導体領域の実効的な不純物濃度ｎ 1 ［ｃｍ -3 ］は、つぎの式で求められる濃度であることを特徴とする請求項６に記載の超接合半導体素子。
Figure 0004265201
 The superjunction semiconductor device according to claim 6 , wherein an effective impurity concentration n 1 [cm −3 ] of the first conductivity type semiconductor region is a concentration obtained by the following equation .
Figure 0004265201
 前記第２導電型半導体領域の実効的な不純物濃度ｎ 2 ［ｃｍ -3 ］は、つぎの式で求められる濃度であることを特徴とする請求項６または７に記載の超接合半導体素子。
Figure 0004265201
 The superjunction semiconductor element according to claim 6 or 7, wherein the effective impurity concentration n 2 [cm -3 ] of the second conductivity type semiconductor region is a concentration obtained by the following equation .
Figure 0004265201
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