JP4018935B2 - Plasma processing equipment - Google Patents

Description

【００７７】
これらの比（＝ｅ1／ｅ0）をｋとしたとき、ｋは、次式で表される。但し、ｍ：電子の質量，ｅ：電子の電荷，ｆ：印加周波数
Ｋ＝(１/２)(ν²＋ω²)｛１/(ν²＋(ω−ωｃ)²))
＋(１/(ν²＋(ω＋ωｃ)²))｝
但し、ν：衝突周波数， ω：励起角周波数，
ωｃ：サイクロトロン角周波数
一般に、ｋの値は、ガス圧が低い程、周波数が高い程大きくなる。図３は、Ａｒ（アルゴン）ガスの場合であり、圧力Ｐ＝１Ｐａにおいては、ｆ≧５０ＭＨｚでｋ≧１５０となり、磁場が無い時に比べて低ガス圧下においても解離が促進される。サイクロトロン共鳴効果は、圧力Ｐ＝１Ｐａにおいては、２０ＭＨｚ程度以下の周波数では急速に小さくなる。図２に示した特性でも分かるように、３０ＭＨｚ以下の周波数では、磁場無しの場合と差が少なく、サイクロトロン共鳴効果は小さい。
【００７８】
なお、ガス圧を低くすればサイクロトロン共鳴効果は高まるが、１Ｐａ以下ではプラズマの電子温度が高まり、解離が進み過ぎるという逆効果が大きくなる。ガスの過度の解離を抑えて、かつ、プラズマ密度を５×１０¹⁰cm^-3程度以上にするには、ガスの圧力として０．４Ｐａから４Ｐａ、好ましくは１Ｐａ程度から４Ｐａの間が良い。
【００７９】
サイクロトロン共鳴効果を発揮させるためには、ｋの値を数十以上とする必要がある。図２や図３からも明らかなように、過度にガスの解離を進めずにサイクロトロン共鳴効果を有効に利用するには、ガス圧が０．４Ｐａないし４Ｐａの圧力では、プラズマ生成用高周波電源として、３０ないし３００ＭＨｚ，好ましくは５０ないし２００ＭＨｚのＶＨＦを用いる必要がある。
【００８０】
図４は、従来のマグネトロン方式チャンバで上部電極を接地し、下部電極上に均一な横方向の磁界Ｂを与えると共に、６８ＭＨｚの高周波電力を印加した時の、試料に誘起されるイオン加速電圧Ｖ_DCと、試料内の誘起電圧Ｖ_DCのバラツキΔＶを示している。磁場Ｂの強度を上げると電子に働くローレンツ力によりイオン加速電圧Ｖ_DCが小さくなり、プラズマ密度が増加する。しかし、従来のマグネトロン放電型の場合、磁場Ｂの強度が２００ガウス程度と大きいため、プラズマ密度の面内の均一性が悪化し、誘起電圧のバラツキΔＶが大きくなり、試料のダメージが増大する欠点がある。
【００８１】
図４から、従来のマグネトロン放電型の２００ガウスの場合に比べ、ΔＶを１／５〜１／１０以下にするには、磁場Ｂの強度は、試料面付近において３０ガウス以下、好ましくは１５ガウス以下の小さな値とするのが、ダメージを無くす上から望ましい。
【００８２】
サイクロトロン共鳴領域は、上部電極１２と下部電極１５の中間で、かつ両電極の中間位置よりもやや上部電極側に形成される。図５は、横軸が試料面（下部電極１５）から上部電極１２までの距離、縦軸が磁場を示している。図５の例は、印加周波数ｆ1＝１００ＭＨｚ，Ｂｃ＝３７．５Ｇ、電極間隔＝５０mmの条件で、ＥＣＲ領域が、試料面から３０ｍｍ付近に形成されている。
【００８３】
このように本発明では、上部電極１２と下部電極１５との間で、下部電極１５（試料載置面）に平行な磁場成分の最大となる部分を、上部電極面、もしくは両電極の真中より上部電極側に設定する。これによって、下部電極面での試料に平行な磁場強度を３０ガウス以下好ましくは１５ガウス以下として、下部電極面付近で電子に働くローレンツカ（Ｅ×Ｂ）を小さい値とし、下部電極面でのローレンツカによる電子ドリフト効果によるプラズマ密度の面内の不均一性の発生をなくすことができる。
【００８４】
図１の実施例の磁場形成手段２００によれば、図６に示すように、ＥＣＲ領域が試料の中央部付近を除き、下部電極１５（試料載置面）からほぼ同じ高さの位置に形成される。従って、大口径の試料に対して、均一なプラズマ処理を行うことが出来る。ただし、試料の中心付近では、ＥＣＲ領域が試料載置面から高い位置に形成されている。ＥＣＲ領域と試料台間は、３０mm以上の距離があるため、この間でイオンやラジカル試は拡散し平均化されるので、通常のプラズマ処理には問題が無い。ただし、試料の全面を均一にプラズマ処理するためには、ＥＣＲ領域が試料の全面に亘り試料面から同じ高さの位置に、あるいは試料の外側のＥＣＲ領域が中心付近のＥＣＲ領域よりも若干試料台側に近くなるように形成されるのが望ましい。この対策については、後で詳細に述べる。
【００８５】
以上述べたように、図１に示す本発明の実施例では、プラズマ発生用高周波電源１６として、３０ないし３００ＭＨｚの高周波電力を用い、かつ電子サイクロトロン共鳴によりガスの解離を進めているため、処理室１０内のガス圧力が０．４Ｐａないし４Ｐａの低圧の下でも安定したプラズマが得られる。また、シース中でのイオンの衝突が少なくなるので、試料４０の処理に際して、イオンの方向性が増し垂直な微細加工性を向上させることができる。
【００８６】
処理室１０の周囲は、放電止じ込め用リング３７によってプラズマを試料４０付近に極在化させることにり、プラズマ密度の向上を図ると共に、放電止じ込め用リング３７より外の部分への不要なデポジット物の付着を最小とさせる。
【００８７】
なお、放電止じ込め用リング３７としては、カーボンやシリコンあるいはＳｉＣ等の半導体や導電材を用いる。この放電止じ込め用リング３７を高周波電源に接続しイオンによるスパッタを生じさせると、リング３７へのデポ付着を低減すると共にフッ素の除去効果も持たせることができる。
【００８８】
なお、試料４０の周辺の絶縁体１３上に、カーボンやシリコンあるいはこれらを含有するサセプタカバー３９を設けると、ＳｉＯ₂等の絶縁膜をフッ素を含有するガスを用いてプラズマ処理を行う場合、フッ素を除去出来るので、選択比の向上に役立つ。この場合、バイアス電源１７の電力の一部がサセプタカバー３９に印加されるように、サセプタカバー３９の下部分の絶縁体１３の厚みを０．５mm〜５mm程度に薄くすると、イオンによるスパッタ効果により上記効果が促進される。
【００８９】
また、直流電源２３の電位により、誘電体の静電吸着膜２２を挟んで下部電極１５（１５Ａ，１５Ｂ）と試料４０を介して静電吸着回路が形成される。この状態で試料４０は静電気力により下部電極１５に係止、保持される。静電気力により係止された試料４０の裏面には、ヘリウム、窒素、アルゴン等の熱伝導ガスが供給される。熱伝導ガスは、下部電極１５の凹部に充填されるが、その圧力は、数百パスカルから数千パスカル程度とする。なお、静電吸着力は、ギャップが設けられた凹部の間では、ほとんどゼロであり、下部電極１５の凸部においてのみ静電吸着力が発生しているとみなせる。しかし、後で述べるように、直流電源２３に電圧を適切に設定して、熱伝導ガスの圧力に十分耐えることのできる吸着力を設定することができるので、熱伝導ガスにより試料４０が動いたり飛ばされたりすることはない。
【００９０】
ところで、静電吸着膜２２は、プラズマ中のイオンに対するパルスバイアスのバイアス作用を減じる様に作用する。正弦波電源を用いてバイアスをしている従来の方法でもこの作用は生じているが、顕在化していない。しかし、パルスバイアスではイオンエネギー幅が狭いという特徴が犠牲になってしまうため、問題が大きくなる。
【００９１】
本発明では、パルスバイアスの印加に伴い静電吸着膜２２の両端間に発生する電圧の上昇を抑制し、パルスバイアスの効果を高めるために、電圧抑制手段を設けたことに１つの特徴がある。
【００９２】
電圧抑制手段の一例としては、パルスバイアスの印加に伴い静電吸着膜の両端間に生ずるバイアス電圧の一周期中の電圧の変化（Ｖ_CM）が、パルスバイアス電圧の大きさ(Ｖ_p)の１／２以下となるように構成するのが良い。具体的には、下部電極１５の表面に設けられた誘電体からなる静電吸着膜の膜厚を薄くしたり、誘電体を誘電率の大きい材料とすることにより、誘電体の静電容量を増す方法がある。
【００９３】
あるいはまた、他の電圧抑制手段として、パルスバイアス電圧の周期を短くして電圧Ｖ_CMの上昇を抑制する方法もある。さらに、静電吸着回路とパルスバイアス電圧印加回路を別な位置、例えば試料が配置保持される電極とは別の対向する電極、あるいは別に設けた第三の電極に、分離して設ける方法も考えられる。
【００９４】
次に、図７〜図１３を用いて、本発明における電圧抑制手段によりもたらされるべき、パルスバイアス一周期中の静電吸着膜の両端間に生じる電圧の変化（Ｖ_CM）とパルスバイアス電圧の関係について詳細に述べる。
【００９５】
まず、本発明のパルスバイアス電源１７において使用する望ましい出力波形の例を図７に示す。図中、パルス振幅：ｖ_p ，パルス周期：Ｔ₀ ，正方向パルス幅：Ｔ₁ とする。
【００９６】
図７（Ａ）の波形をブロッキングコンデンサ，静電吸着用誘電体層（以下、静電吸着膜と略称する）を経由して試料に印加した時、別の電源によりプラズマを発生させた状態での定常状態での試料表面の電位波形を図７（Ｂ）に示す。
ただし、波形の直流成分電圧 ：Ｖ_DC
プラズマのフローティングポテンシャル：Ｖ_f
静電吸着膜の両端間に生じる電圧の一周期中の最大電圧：Ｖ_CM とする。
【００９７】
図７（Ｂ）中、Ｖ_f より正電圧となっている（Ｉ）なる部分は、主に電子電流のみを引き込んでいる部分であり、Ｖ_f より負の部分は、イオン電流を引き込んでいる部分，Ｖ_f の部分は、電子とイオンとがつりあっている部分（Ｖ_f は通常数Ｖ〜十数Ｖ）である。
【００９８】
なお、図７（Ａ）および今後の説明では、ブロッキングコンデンサの容量や試料表面近辺の絶縁体による容量は静電吸着膜による容量（以下静電吸着容量と略称する）に比べて十分大きいと仮定している。
Ｖ_CMの値は次の式（数２）で表わされる。
【００９９】
【数２】

【０１００】
但し、ｑ：（Ｔ₀−Ｔ₁）期間に試料に流入するイオン電流密度（平均値）
ｃ：単位面積当りの静電吸着容量（平均値）
ｉ_i ：イオン電流密度， ε_r ：静電吸着膜の比誘電率
ｄ：静電吸着膜の膜厚 ε₀ ：真空中の誘電率（定数）
Ｋ：静電吸着膜の電極被覆率（≦１）
図８及び図９に、パルスデューティ比：（Ｔ₁／Ｔ₀）は一定のままＴ₀ を変化させた時の試料表面の電位波形とイオンエネルギーの確率分布を示す。但し、Ｔ₀₁，Ｔ₀₂：Ｔ₀₃：Ｔ₀₄：Ｔ₀₅＝１６：８：４：２：１とする。
【０１０１】
図８の（１）に示す様に、パルス周期Ｔ₀ が大きすぎると、試料表面の電位波形は矩形波から大きくはずれ、三角波になり、イオンエネルギーは図９に示すように、低い方から高い方まで一定の分布となり好ましくない。
【０１０２】
図８の（２）〜（５）に示す様に、パルス周期Ｔ₀ を小さくするにつれて、（Ｖ_CM／ｖ_p ）は１よりも小さな値となり、イオンエネルギー分布も狭くなってゆく。
【０１０３】
図８，図９においてＴ₀＝Ｔ₀₁，Ｔ₀₂：Ｔ₀₃：Ｔ₀₄：Ｔ₀₅は、
（Ｖ_CM／ｖ_p ）＝１，０.６３，０.３１，０.１６，０.０８に対応している。次に、パルスのオフ（Ｔ₀−Ｔ₁）期間と、静電吸着膜の両端間に生じる電圧の一周期中の最大電圧Ｖ_CMの関係を図１０に示す。
【０１０４】
静電吸着膜として、厚み０.３mmの酸化チタン含有アルミナ（ε_r＝１０）を用いて電極の約５０％を被膜（Ｋ＝０.５ ）した場合、イオン電流密度ｉ_i ＝５ｍＡ／cm² の中密度プラズマ中でのＶ_CMの値の変化を図１０の太線（標準条件の線）で示す。
【０１０５】
図１０から明らかなように、パルスのオフ（Ｔ₀−Ｔ₁）期間が大きくなるにつれ、静電吸着膜の両端間に生じる電圧Ｖ_CMはそれに比例して大きな値となり、通常使用されるパルス電圧ｖ_p 以上になってしまう。
【０１０６】
例えば、プラズマエッチング装置においては、ダメージ，下地やマスクとの選択性，形状等により通常、
ゲートエッチングでは ２０volt ≦ ｖ_p ≦１００volt
メタルエッチングでは ５０volt ≦ ｖ_p ≦２００volt
酸化膜エッチングでは ２５０volt ≦ ｖ_p ≦１０００volt
に制限される。
【０１０７】
後述の（Ｖ_CM ／ｖ_p ）≦０.５の条件を満たそうとすると標準状態では、（Ｔ₀−Ｔ₁）の上限は次のようになる。
ゲートエッチングでは （Ｔ₀−Ｔ₁）≦０.１５μｓ
メタルエッチングでは （Ｔ₀−Ｔ₁）≦０.３５μｓ
酸化膜エッチングでは （Ｔ₀−Ｔ₁）≦１．２μｓ
ところで、Ｔ₀ が０.１μｓ に近くなると、イオンシースのインピーダンスがプラズマのインピーダンスに近づくかそれ以下となるため、不要なプラズマの発生を生じると共に、バイアス電源がイオンの加速に有効に使われなくなってくる。このため、バイアス電源によるイオンエネルギーの制御性が悪化するため、Ｔ₀ は、０．１μｓ以上、好ましくは０．２μｓ以上が良い。
【０１０８】
従って、ｖ_pを低くおさえられるゲートエッチャ等においては、静電吸着膜の材料を比誘電率が１０〜１００と高いもの、（例えばＴａ₂Ｏ₃でε_r＝２５）に変えたり、絶縁耐圧を低下させず膜厚を薄く、例えば１０μｍ〜４００μｍ、望ましくは１０μｍ〜１００μｍにしたりする必要がある。
【０１０９】
図１０には、単位面積当りの静電容量ｃを、それぞれ２．５倍、５倍、１０倍に増加させた時のＶ_CMの値も併記した。静電吸着膜の改善を行っても現状では静電容量ｃを数倍にする改善が限度とみられ、Ｖ_CM≦３００ volt、ｃ≦１０ｃ₀とすると、
０.１μｓ≦（Ｔ₀−Ｔ₁）≦１０μｓとなる。
イオンの加速によりプラズマ処理に有効な部分は（Ｔ₀−Ｔ₁）の部分であり、パルスデューティ（Ｔ₁／Ｔ₀）としてはできるだけ小さい方が好ましい。
【０１１０】
時間平均も加味した、プラズマ処理の効率として（Ｖ_DC／ｖ_p)で見積ったのが、図１１である。（Ｔ₁／Ｔ₀）を小さくし、（Ｖ_DC／ｖ_p)を大きくするのが好ましい。
【０１１１】
プラズマ処理の効率として０．５≦（Ｖ_DC／ｖ_p)を仮定し、後述の条件、（Ｖ_CM／ｖ_p ）≦０.５を入れると、パルスデューディは、（Ｔ₁／Ｔ₀）≦０.４程度となる。
【０１１２】
なお、パルスデューディ（Ｔ₁／Ｔ₀）は小さいほどイオンエネルギーの制御に有効であるが、必要以上に小さくするとパルス幅Ｔ１が０．０５μｓ程度の小さい値となり、数十MHzの周波数成分を多く含むようになり、後述するような、プラズマ発生用高周波成分との分離も難しくなる。図１１に示すように、０≦（Ｔ₁／Ｔ₀）≦０．０５間での（Ｖ_DC／ｖ_p)の低下はわずかであり、（Ｔ₁／Ｔ₀）として０．０５以上で特に問題は生じない。
【０１１３】
ここで図１２に、ゲートエッチングの例として、塩素ガス１．３Ｐａをプラズマ化した時のシリコンと下地の酸化膜とのエッチングレートＥＳｉおよびＥＳｉＯ₂のイオンエネルギー依存性を示す。シリコンのエッチングレートＥＳｉは低イオンエネルギーでは一定値になる。イオンエネルギーが１０Ｖ程度以上では、イオンエネルギーの増加に従って、ＥＳｉも増加する。一方下地となる酸化膜のエッチングレートＥＳｉＯ₂は、イオンエネルギーが２０Ｖ程度以下では０であり、２０Ｖ程度を越えると、イオンエネルギーと共にＥＳｉＯ₂は増加する。
【０１１４】
その結果、イオンエネルギーが２０Ｖ程度以下では下地との選択比ＥＳｉ／ＥＳｉＯ₂が∞となる領域が存在する。イオンエネルギーが２０Ｖ程度以上では、下地との選択比ＥＳｉ／ＥＳｉＯ₂は、イオンエネルギーの増加と共に急速に低下する。
【０１１５】
図１３は、絶縁膜の一種である酸化膜（ＳｉＯ₂ ，ＢＰＳＧ，ＨＩＳＯ等）のエッチングの例として、Ｃ₄Ｆ₈ガス１.０Ｐａをプラズマ化した時の、酸化膜とシリコンとのエチングレートＥＳｉＯ₂および、ＥＳｉのイオンエネルギー分布を示すものである。
【０１１６】
酸化膜のエッチングレートＥＳｉＯ₂は、低イオンエネルギーでは負の値となり、デポを生じる。イオンエネルギーが４００Ｖ付近にてＥＳｉＯ₂が急速に正に立ち上がり、その後は、徐々に増加する。一方下地となるシリコンのエッチングレートＥＳｉは、ＥＳｉＯ₂よりイオンエネルギーの高い所で(−)（エッチング）から(＋)（エッチング）となり徐々に増加する。
【０１１７】
この結果、ＥＳｉＯ₂が(−)から(＋)に変化する付近にて、下地との選択比ＥＳｉＯ₂／ＥＳｉが ∞ となり、それ以上でＥＳｉＯ₂／ＥＳｉはイオンエネルギーの増加と共に急速に低下する。
【０１１８】
図１２、図１３で、実際のプロセスへの適用に対しては、ＥＳｉやＥＳｉＯ₂の値や、ＥＳｉ／ＥＳｉＯ₂や、ＥＳｉＯ₂／ＥＳｉの値の大きさを考慮して、バイアス電源を調整してイオンエネルギーを適正値にする。
【０１１９】
また、ジャストエッチング（下地膜が現われるまでのエッチング）まではエッチングレートの大きさを優先し、ジャストエッチ後は選択比の大きさを優先してイオンエネルギーをジャストエッチの前後に変更すれば、更に良い特性が得られる。
【０１２０】
ところで図１２、図１３に示した特性は、イオンのエネルギー分布が狭い部分に限定された時の特性である。イオンのエネルギー分布が広い場合の各エッチングレートはその時間平均値となるため、最適値に設定することが出来ず、選択比は大幅に低下してしまう。
【０１２１】
実験によると、（Ｖ_DC／ｖ_p）は０．３以下程度であれば、イオンエネルギーの広がりは±１５％程度以下となり、図１２や図１３の特性でも３０以上の高い選択比が得られた。また、（Ｖ_DC／ｖ_p）≦０．５であれば、従来の正弦波バイアス法に比べて選択比等の改善が図れた。
【０１２２】
このように、静電吸着膜の両端間に生じるパルス電圧の一周期中の電圧変化(Ｖ_CM)を抑える電圧抑制手段として、Ｖ_CMが、パルスバイアス電圧の大きさｖ_pの１／２以下となるように構成するのが良く、具体的には、下部電極１５の表面に設けられた誘電体の静電チャック膜２２の膜厚を薄くしたり、誘電体を誘電率の大きい材料とすることにより、誘電体の容量を増すことができる。あるいは、パルスバイアス電圧の周期を、０．１μｓ〜１０μｓ、好ましくは０．２μｓ〜５μｓ（繰り返し周波数：０．２MHz〜５MHzに対応）と短くし、パルスデューディ（Ｔ₁／Ｔ₀）を、０．０５≦（Ｔ₁／Ｔ₀）≦＝０．４として静電吸着膜の両端の電圧変化を抑制する。
【０１２３】
あるいはまた、上記誘電体の静電吸着膜の膜厚と、誘電体の比誘電率及びパルスバイアス電圧の周期の幾つかを組み合わせて、静電吸着膜の両端間に生じる電圧Ｖ_CMの変化が上記した（Ｖ_CM／ｖ_p ）≦０.５の条件を満たすようにしても良い。
【０１２４】
次に、図１の真空処理室を、絶縁膜（例えばＳｉＯ₂, ＳｉＮ，ＢＰＳＧ等）のエッチングに用いた実施例について述べる。
【０１２５】
ガスとしては、Ｃ₄Ｆ₈：１〜５％，Ａｒ：９０〜９５％，Ｏ₂：０〜５％
もしくは、Ｃ₄Ｆ₈：１〜５％，Ａｒ：７０〜９０％，Ｏ₂：０〜５％，ＣＯ：１０〜２０％，の組成のものを用いる。プラズマ発生用高周波電源１６としては、従来よりも高い周波数、例えば４０ＭＨｚのものを用い、１〜３Ｐａの低ガス圧領域での放電の安定化を計る。
【０１２６】
なお、プラズマ源用高周波電源１６の高周波化により必要以上の解離が進行する場合は、高周波電源１６の出力を高周波電源変調信号源１６１により、オンオフないしはレベル変調制御する。高レベルの時は、ラジカルの生成に比べてイオンの生成が盛んとなり、低レベルの時は、イオンの生成に比べてラジカルの生成が盛んとなる。オン（またはレベル変調時の高レベル）時間としては５〜５０μｓ程度、オフ時間（またはレベル変調時の低レベル）としては１０〜１００μｓ、周期２０μｓ〜１５０μｓ程度を用いる。これにより不必要な解離を防ぐとともに、所望のイオン−ラジカル比を得ることができる。
【０１２７】
また、プラズマ源用高周波電源の変調周期は、通常、パルスバイアスの周期に比べ長くなる。そこで、プラズマ源用高周波電源の変調周期をパルスバイアスの周期の整数倍にし、２つの間の位相を最適化することにより、選択比の改善ができた。
【０１２８】
一方、パルスバイアス電圧の印加によって、プラズマ中のイオンを試料に加速、垂直入射させることにより、イオンエネルギーの制御を行う。パルスバイアス電源１７として、例えば、パルス周期：Ｔ＝０．６５μｓ、パルス幅：Ｔ₁＝０．１５μｓ、パルス振幅：Ｖ_p＝８００Ｖの電源を用いることにより、イオンエネルギーの分布幅は±１５％以下になり、下地のＳｉやＳｉＮとの選択比として２０〜５０の特性の良いプラズマ処理が可能になった。
【０１２９】
次に、図１４により本発明の他の実施例になる２電極型のプラズマエッチング装置を説明する。この実施例は、図１に示したと同様な構成であるが、試料４０を保持する下部電極１５が、単極式の静電チャック２０を備えた構成となっている点で異なる。下部電極１５の上表面に静電吸着用誘電体層２２が設けられ、下部電極１５には、高周波成分カット用のコイル２４を介して直流電源２３のプラス側が接続されている。また、２０Ｖ〜１０００Ｖの正のパルスバイアスを供給するパルスバイアス電源１７が、ブロッキングコンデンサ１９を介して接続されている。
【０１３０】
処理室１０の周囲には放電止じ込め用リング３７Ａ，３７Ｂを設置し、プラズマ密度の向上を図ると共に、放電止じ込め用リング３７Ａ，３７Ｂ外の部分への不要なデポジット物の付着を最小とさせる。図１４の放電止じ込め用リング３７Ａ，３７Ｂにおいて、下部電極側の放電止じ込め用リング３７Ａの土手部の直径は、上部電極側の放電止じ込め用リング３７Ｂの土手部の直径より小さくし、試料周辺での反応生成物の分布を一様にしている。
【０１３１】
なお、放電止じ込め用リング３７Ａ，３７Ｂの材料として、少なくとも処理室側に面する側に、カーボン、シリコンあるいはＳｉＣ等の半導体や導電体を用いる。また、下部電極側リング３７Ａにはコンデンサ１９Ａを介して１００Ｋ〜１３．５６ＭＨｚの放電止じ込めリング用バイアス電源１７Ａを接続し、上部電極側リング３７Ｂには高周電源１６の電力の一部が印加される様に構成し、イオンのスパッタ効果によるリング３７Ａ，３７Ｂへのデポ付着を低減すると共にフッ素の除去効果も持たせる。
【０１３２】
なお、図１４の１３Ａ，１３Ｃはアルミナ等で構成される絶縁体であり、１３ＢはＳｉＣ，グラッシーカーボン、Ｓｉ等の導電性を有する絶縁体である。
【０１３３】
リング３７Ａ，３７Ｂの導電性が低い場合には、金属等の導体をリング３７Ａ，３７Ｂ中に内蔵させリングの表面と内臓導体の距離を狭くすることにより、高周波電力がリング３７Ａ，３７Ｂの表面から放射され易くして、スパッタ効果を高めることができる。
【０１３４】
上部電極カバー３０は、通常その周辺のみがボルト２５０で上部電極１２に固定される。ガス供給部３６からガス導入室３４、ガス拡散板３２、上部電極１２を介して上部電極カバー３０にガスが供給される。上部電極カバー３０に設けられた孔は、孔中の異常放電を生成し難くするため、０．３〜１ｍｍ径の細孔になっており、上部電極カバー３０上部のガス圧は１気圧の数分の１から１／１０程度となる。例えば３００ｍｍ径の上部電極カバー３０に対して、全体として１００Ｋｇ程度以上の力が加わる。このため上部電極カバー３０が上部電極１２に対して凸状になり中央部付近では数百ミクロン以上の隙間を生じる。
【０１３５】
この場合、高周波源１６の周波数が３０ＭＨｚ程度以上高くなると、上部電極カバー３０の横方向抵抗が無視出来なくなり、特に中央部付近のプラズマ密度が低下する現象が出る。これを改善するには、上部電極カバー３０を周辺以外の中心寄りで上部電極１２に固定すれば良い。図１４の例では、ＳｉＣやカーボン等の半導体もしくはアルミナ等の絶縁体のボルト２５１で、上部電極カバー３０の中心寄りの数ケ所を上部電極１２に固定し、上部電極１２側から印加される高周波の分布を一様にしている。
【０１３６】
なお、上部電極カバー３０の少なくとも中心寄り部分を上部電極１２に固定する方法は、何ら上記ボルト２５１に限定されるものでなく、接着作用のある物質で上部電極カバー３０と上部電極１２とを全面でもしくは少なくとも中心寄りの部分で接着してもよい。
【０１３７】
図１４の実施例において、処理の対象物である試料４０は、下部電極１５の上に載置され、静電チャック２０、すなわち直流電源２３による正電荷とプラズマから供給される負電荷により静電吸着膜２２の両端間に生じるクーロン力により吸着される。
【０１３８】
この装置の作用は、図１に示した２電極型のプラズマエッチング装置と同様であり、エッチング処理を行う場合、処理を行なうべき試料４０を試料台１５に載置し、静電力で保持し、ガス供給系３６から処理室１０に処理ガスを所定の流量で導入しながら、他方真空ポンプ１８により真空排気することにより、処理室１０の圧力を試料の処理圧力、０．５〜４．０Ｐａに減圧排気する。次に、高周波電源１６をオンとし、両電極１２，１５間に２０MHｚ〜５００MHｚ、好ましくは３０MHｚ〜１００MHｚの高周波電圧を印加してプラズマを発生させる。他方、下部電極１５に、パルスバイアス電源１７から２０Ｖ〜１０００Ｖ、周期が０．１μs〜１０μs好ましくは０．２μs〜５μsの正のパルスバイアス電圧を印加し、処理室１０内のプラズマを制御して試料４０にエッチング処理を行う。
【０１３９】
このようなパルスバイアス電圧の印加によって、プラズマ中のイオンもしくはイオン及び及び電子を試料に加速、垂直入射させることにより、高精度の形状制御あるいは選択比制御を行う。パルスバイアス電源１７及び静電吸着膜２２に必要な特性は図１の実施例と同様であり、詳細は省略する。
【０１４０】
次に、図１５ないし図１７により本発明の他の実施例を説明する。この実施例は、図１に示した２電極型のプラズマエッチング装置と同様な構成であるが、磁場形成手段２００の構成が異なる。磁場形成手段２００のコア２０１は、偏心しており、試料４０の中心位置に相当する軸を中心にして、モータ２０４により駆動されて毎分数ないし数十回転の速度で回転するように構成されている。なお、コア２０１は接地されている。
試料の全面を高精度にプラズマ処理するためには、試料の中央部付近に比べ、試料の周辺部ないしはその外側付近のプラズマの生成が高まる様に、電子のサイクロトロン共鳴効果を中央に比べ、周辺部ないしはその外側で大きくするのがよい。しかし、図１の実施例の場合、図６に示したように、試料の中心付近ではＥＣＲ領域が無く、中心付近でプラズマ密度が低くなり過ぎる場合が出てくる。
【０１４１】
図１５の実施例では、磁場形成手段２００の偏心したコア２０１が回転することによって磁場の分布が変化し、試料の中心付近では時刻ｔ＝０，ｔ＝Ｔ₀では、ＥＣＲ領域が試料面から低い位置に形成され、時刻ｔ＝１／２Ｔ₀では試料面から高い位置に形成される。コア２０１が毎分数ないし数十回転の速度で回転する結果、図１７に示すように、両電極の中間部における試料面に平行な方向の磁場強度の平均値が、回転による時間平均化によりほぼ同じ値になる。すなわち、ＥＣＲ領域が試料の周辺部を除き試料面からほぼ同じ高さの位置に形成される。
【０１４２】
なお、図１５のコア２０１部に一点鎖線で示したように、偏心した中央部のコアに近い側の磁気回路を構成するコアはその厚さを薄く、遠い側の磁気回路を構成するコアはその厚さを厚くすれば、磁場強度の均一性はさらに向上する。
【０１４３】
次に、図１８ないし図１９により本発明の他の実施例を説明する。この実施例は、図１５に示した２電極型のプラズマエッチング装置と同様な構成であるが、磁場形成手段２００の構成が異なる。磁場形成手段２００のコア２０１は、処理室の中央に対応する位置に凹面のエッジ２０１Ａを有し、処理室の側方位置他のエッジ２０１Ｂを有している。凹面のエッジ２０１Ａの作用により、磁束Ｂは傾斜した方向成分を有する。その結果、磁場の分布が変化し、図１９に示したように、試料面に平行な成分の磁場強度が図１の実施例の場合に比べて、より均一化される。
【０１４４】
次に、図２０により本発明の他の実施例を説明する。この実施例は、図１５に示した２電極型のプラズマエッチング装置と同様な構成であるが、磁場形成手段２００の構成が異なる。磁場形成手段２００のコア２０１は固定式であり、処理室の中央に対応する位置に配置されたコア２０５と共に磁気回路を構成する。コア２０５は、絶縁体２０３と共に、エッジ２０１Ａの中心を通る軸の廻りを回転する。このような構成により、図１５の実施例と同様にして、試料の中心付近におけるＥＣＲ領域の平均的な位置が、試料面からほぼ同じ位置に形成される。すなわち、ＥＣＲ領域が試料の全面に亘り試料面からほぼ同じ高さの位置に形成される。
【０１４５】
次に、図２１ないし図２２により本発明の他の実施例になる２電極型のプラズマエッチング装置を説明する。この実施例では、磁場形成手段２００が、処理室１０の周囲に２対のコイル２１０，２２０を備えており、各対のコイルに置ける磁界の向きを矢印１，２，３，４のように順次切り替えることにより、回転磁界を形成するように構成されている。コイル２１０，２２０の中心位置Ｏ−Ｏは、両電極１２，１５の中間よりも上部電極１２側に位置している。これによって、試料４０上の磁場強度を３０ガウス以下、好ましくは１５ガウス以下になるように構成している。
コイル２１０，２２０の位置、外径を適宜選定することによって、試料の周辺部ないしはその外側付近のプラズマの生成がより高まる様に、磁場の強度分布を調整することができる。
【０１４６】
次に、図２３、図２４により、本発明の他の実施例になる２電極型のプラズマエッチング装置を説明する。この実施例では、磁場形成手段２００として、円形の処理室１０の周囲に沿って水平面内で円弧状に配置された一対のコイル２１０’を備えている。この一対のコイル２１０’に流れる電流を制御して、図２３に矢印（１）、（２）で示したように、一定周期毎に磁場の極性を変化させる。
【０１４７】
図２４に破線で示すように、磁束Ｂは、垂直面内では処理室中心部で拡がるため、処理室中心部の磁場強度は低下する。しかし、一対のコイル２１０’は、処理室に沿ってカーブしているため、水平面内では、処理室中心部に磁束Ｂが集まる様になっている。そのため、処理室中心部の磁場の強さを、図２２の実施例に比べて、高めることができる。すなわち、図２３の実施例では、図２２の実施例に比べて、処理室中心部における磁場強度の低下を抑制することができ、試料台の試料載置面における磁場強度の均一性を向上させることができる。
【０１４８】
また、一定周期毎に磁場の極性を変化させることによって、Ｅ×Ｂのドリフト効果を少なくしている。
【０１４９】
なお、磁場形成手段２００として、図２２の実施例と同様な、２対のコイルを採用しても良い。
【０１５０】
また、磁場形成手段２００として、円弧状コイル２１０’に代えて、図２５に示すように、円形の処理室１０の周囲に沿って配置された複数の直線コイル部分の組み合わせになる、凸型のコイル２１０’としても良い。この場合も、水平面内では、処理室中心部に磁束Ｂが集まる様になり、図２３の実施例と同じ効果が得られる。
【０１５１】
さらに、図２６の実施例のように、１対のコイルの中心軸を、処理室中心部で試料面に近づくように、垂直面内で傾斜させて配置しても良い。この実施例によれば、処理室中心部の磁場強度を上げ、処理室周辺部の磁場強度を下げることができるので、試料台の試料載置面における磁場強度の均一性を向上させることができる。なお磁場強度の均一化のためには、コイルの中心軸の傾斜角度θを、５度乃至２５度の範囲とするのが良い。
【０１５２】
また、図２７に示すように、一対のコイル２１０Ａの近傍に、コイル２１０Ｂを設置し、２組のコイルの電流を制御することにより、ＥＣＲ共鳴位置と共に、ＥＣＲ共鳴位置付近での磁場の勾配を変化させ、ＥＣＲ共鳴領域の幅を変化させることもできる。ＥＣＲ共鳴領域の幅をプロセス毎に最適化することにより、各プロセスに適したイオン／ラジカル比を得ることが可能となる。
【０１５３】
なお、以上述べた、図２３乃至図２７の実施例を、必要に応じて適宜組み合わせることにより、磁場強度分布の均一性と制御特性を更に向上させることが出来る。
【０１５４】
次に、図２８ないし図２９により本発明の他の実施例になる２電極型のプラズマエッチング装置を説明する。この実施例では、処理室壁の一部が導電体で構成されると共に接地されている。一方、磁場形成手段２００が、処理室１０の周囲及び上部にコイル２３０，２４０を備えている。コイル２３０で形成される磁束Ｂの向きと、コイル２３０で形成される磁束Ｂ’の向きは、矢印で示すように、処理室１０の中心部では互いに打消合い、処理室１０の周辺および外側では互いに重畳するように構成されている。その結果、試料面上の磁場の強度分布は図２９のようになる。しかも、試料４０の載置面部分では、上部電極１２と下部電極１５の間の、電界成分の向きと磁界成分の向きは平行である。一方、試料４０の載置面の外側部分では、上部電極１２の周辺部ないしは上部電極１２と処理室壁との部分で、横方向の電界成分と直交する縦方向の磁界成分が生じる。
【０１５５】
従って、図２８の実施例によれは、試料の中心付近における電子のサイクロトロン共鳴効果を下げ、試料の周辺部ないしはその外側付近のプラズマの生成を高めることができる。このようにして、試料の周辺部ないしはその外側付近のプラズマの生成をより高めることにより、プラズマ密度分布を均一化することができる。
【０１５６】
次に、図３０により本発明の他の実施例を説明する。この実施例は、図１に示した２電極型のプラズマエッチング装置において、高周波電源１６から上部電極１２に印加する高周波電力ｆ1では、充分なイオンエネルギーが得られない場合に、低周波電源１６３から上部電極１２に、例えば１ＭＨｚ程度以下の高周波ｆ３をバイアスとして印加することによって、イオンエネルギーを１００〜２００Ｖ程度増大させるものである。なお、１６４，１６５はフィルターである。
【０１５７】
次に、図３１により、無磁場型の２電極型のプラズマエッチング装置における、本発明の実施例を説明する。
【０１５８】
前にも述べたように、試料の微細加工性を向上させるには、プラズマ発生用高周波電源１６としてより高い周波数のものを用い、低ガス圧領域での放電の安定化を計るのがよい。本発明の実施例では、処理室１０における試料の処理圧力を０．５〜４．０Ｐａとしている。処理室１０内のガス圧力を４０mTorr以下の低圧にすることにより、シース中でのイオンの衝突が少なくなるので、試料４０の処理に際して、イオンの方向性が増し垂直な微細加工が可能になった。なお、５mTorr以下では、同じ処理速度を得るには、排気装置や高周波電源が大型化すると共に、電子温度の上昇による必要以上の解離が生じ、特性が劣化する傾向がある。
【０１５９】
一般に、一対の２電極を用いたプラズマ発生用の電源の周波数と安定的に放電が行われる最低のガス圧力との間には、図３２に示すように、電源の周波数が高くなるほど、電極間距離が大きくなるほど、安定放電最低ガス圧が低下するという関係がある。周囲の壁や放電閉込めリング３７へのデポ等の悪影響を避け、上部電極カバー３０やサセプタカバー３９や試料中のレジスト等によるフッ素や酸素を除去する効果を有効に機能させるために、最高ガス圧４０mTorr時の平均自由工程の２５倍以下に対応して、電極間距離を５０mm程度以下とするのが望ましい。また、電極間距離として、最高ガス圧（４０mTorr）時の平均自由工程の２〜４倍（４mm〜８mm）程度以上でないと、安定な放電が困難となる。
【０１６０】
図３１に示した実施例では、プラズマ発生用高周波電源１６として、２０MHｚ〜５００MHｚ、望ましくは３０MHｚ〜２００MHｚの高周波電力を用いるため、処理室内のガス圧力を、０．５〜４．０Ｐａの低圧にしても、安定したプラズマが得られ、微細加工性を向上させることができる。また、このような高周波電力を用いることによりガスプラズマの解離が良くなり、試料加工時の選択比制御が良くなる。
【０１６１】
以上述べた本発明の実施例において、パルスバイアス電源の出力とプラズマ発生用電源の出力との間に干渉が生ずる可能性も考えられる。そこで、以下、この対策についてのべる。
【０１６２】
まず、パルス幅：Ｔ₁，パルス周期：Ｔ₀で無限大の立上り／立下り速度をもつ理想的な矩形パルスにおいては、図３３に示す様に、ｆ≦３ｆ₀（ｆ₀＝（１／Ｔ₁)）の周波数範囲に７０〜８０％程度の電力が含まれる。実際に印加される波形は、立上り／立下り速度が有限となるため、電力の収束性は更に改善され、ｆ≦３ｆ₀の周波数範囲に９０％程度以上の電力が含まれる様にできる。
【０１６３】
３ｆ₀ なる高い周波数成分をもつパルスバイアスを試料面内に均一に印加される様にするためには、試料にほぼ平行な対向電極を設け、次式数３で求まる３ｆ₀に対して、ｆ≦３ｆ₀ なる範囲の周波数成分を接地することが望ましい。
【０１６４】
【数３】

【０１６５】
図３１に示した実施例は、上記パルスバイアス電源出力とプラズマ発生用電源出力との干渉の対策を行っている。すなわち、このプラズマエッチング装置において、試料４０と対向する上部電極１２には、プラズマ発生用高周波電源１６が接続される。この上部電極１２をパルスバイアスの接地レベルにするには、プラズマ発生用高周波電源１６の周波数ｆ₁ を上記の３ｆ₀ より大きくし、かつ、ｆ＝ｆ₁ 付近でのインピーダンスが大きく、他の周波数ではインピーダンスが低い、バンドエリミネータ１４１を上部電極１２と接地レベルとの間に接続する。
【０１６６】
一方、ｆ＝ｆ₁ 付近でのインピーダンスが低く、他の周波数はインピーダンスが高いバンドパスフィルタ１４２を、試料台１５と接地レベル間に設置する。このような構成を用いれば、パルスバイアス電源１７の出力とプラズマ発生用電源１６出力との間の干渉を、問題のないレベルに抑え、試料４０に良好なバイアスを加えることができる。
【０１６７】
図３４は、本発明を外部エネルギー供給放電方式のうち誘導結合型放電方式でかつ、無磁場タイプのプラズマエッチング装置へ適用した例である。５２は平面コイル、５４は平面コイルに１０MHｚ〜２５０MHｚの高周波電圧を印加する高周波電源である。誘導結合型放電方式は図１０に示した方式に比べ、低い周波数でかつ低圧での安定なプラズマ発生が可能になる。逆に、解離が進みやすくなるため、図１で示したように、高周波電源１の出力を高周波電源変調信号源１６１により変調し、不必要な解離を防ぐことが出来る。真空容器としての処理室１０は、静電吸着膜２２の上に試料４０が載置される試料台１５を備えている。
【０１６８】
エッチング処理を行う場合、処理を行なうべき試料４０を試料台１５に載置し、静電力で保持し、ガス供給系（図示せず）から処理室１０に処理ガスを所定の流量で導入しながら、他方真空ポンプにより真空排気することにより、処理室１０の圧力を０．５〜４．０Ｐａに減圧排気する。次に、高周波電源５４に１３．５６MHｚの高周波電圧を加えて処理室１０にプラズマを発生させる。このプラズマを用いて試料４０をエッチング処理する。他方、エッチング時には、下部電極１５に、周期が０．１μs〜１０μs好ましくは０．２μs〜５μsのパルスバイアス電圧を印加する。パルスバイアス電圧の振幅は、膜種により範囲が異なることは図１の実施例で述べたとおりである。このパルスバイアス電圧の印加によって、プラズマ中のイオンを試料に加速、垂直入射させることにより、高精度の形状制御あるいは選択比制御を行う。これにより、試料のレジストマスクパターンが極微細なものであっても、高精度のエッチング処理を行うことができる。
【０１６９】
また、図３５に示すように、誘導結合型放電方式無磁場タイプのプラズマエッチング装置において、誘導電高周波出力の処理室１０側に、隙間を有するファラデーシールド板５３と、０．５mm〜５mmの薄いシールド板保護用絶縁板５４を設置し、そのファラデーシールド板を接地してもよい。ファラデーシールド板５３の設置によって、コイルとプラズマ間の容量成分が少なくなり、図３４におけるコイル５２下の石英板やシールド板保護用絶縁板５４を叩くイオンのエネルギーを低下することが出来、石英板や絶縁板の損傷を少なくすると共に、プラズマ中への異物の混入を防ぐことが出来る。
【０１７０】
また、ファラデーシールド板５３は、パルスバイアス電源１７の接地電極の役目も兼ねるため、試料４０とファラデーシールド板５３との間に均一にパルスバイアスを印加することが出来る。この場合、上部電極や試料台１５に設置するフィルタは不要である。
【０１７１】
図３６は、本発明をマイクロ波プラズマ処理装置に適用した装置の一部を縦断面した正面図である。静電吸着膜２２の上に試料４０が載置される試料台１５としての下部電極１５には、パルスバイアス電源１７及び直流電源１３が接続されている。４１はマイクロ波の発振源としてのマグネトロン、４２はマイクロ波の導波管であり、４３は、処理室１０を真空封止しマイクロ波を処理室１０に供給するための石英板である。４７は磁場を供給する第一のソレノイドコイル、４８は磁場を供給する第二のソレノイドコイルである。４９は処理ガス供給系であり、処理室１０内にエッチング、成膜等の処理を行なう処理ガスを供給する。また、処理室１０は、真空ポンプ（図示せず）により真空排気される。パルスバイアス電源１７及び静電チャック２０に必要な特性は図１の実施例と同様であり、詳細は省略する。
【０１７２】
エッチング処理を行う場合、処理を行なうべき試料４０を試料台１５に載置し、静電力で保持し、ガス供給系４９から処理室１０に処理ガスを所定の流量で導入しながら、他方真空ポンプにより真空排気することにより、処理室１０の圧力を０．５〜４．０Ｐａに減圧排気する。次に、マグネトロン４１及び第一、第二のソレノイドコイル４７、４８をオンとし、マグネトロン４１で発生したマイクロ波を導波管４２から処理室１０に導びいて、プラズマを発生させる。このプラズマを用いて試料４０にエッチング処理を行う。他方、エッチング時には、下部電極１５に、周期が０．１μs〜１０μs好ましくは０．２μs〜５μsのパルスバイアス電圧を印加する。
【０１７３】
このようなパルスバイアス電圧の印加によって、プラズマ中のイオンを試料に加速して、垂直に入射させることにより、高精度の形状制御あるいは選択比制御を行う。これにより、試料のレジストマスクパターンが極微細なものであっても、垂直入射によりマスクパターンに対応した高精度のエッチング処理が行える。
【０１７４】
なお、図１以下に示した本発明のプラズマエッチング装置において、静電吸着回路の直流電圧とパルスバイアス電源回路のパルス電圧を重畳して生成し、回路を共通に構成することもできる。また、静電吸着回路とパルスバイアス電源回路を別な電極に分離して設け、パルスバイアスが静電吸着に影響を及ぼさないようにすることもできる。
【０１７５】
図１に示したプラズマエッチング装置の実施例における静電吸着回路に代えて、他の吸着手段、例えば真空吸着手段を用いることもできる。
【０１７６】
以上述べた本発明の静電吸着回路とパルスバイアス電圧印加回路を備えたプラズマ処理装置は、エッチングガスに代えてＣＶＤガスを導入する等の変更を加えることにより、以上述べたエッチング処理に限らずＣＶＤ装置等のプラズマ処理装置にも適用できる。
【０１７７】
次に、図３７に示した本発明の他の実施例により、従来の欠点を改善し、イオンとラジカル生成の量と質を制御し、極微細なプラズマ処理を可能とするプラズマエッチング装置の他の実施例について述べる。
【０１７８】
すなわち、試料を設置している真空処理室の上流側で真空処理室とは別の場所に第一のプラズマ生成を行う場所を設定し、そこで生成した準安定原子を真空処理室に注入し、真空処理室にて第二のプラズマを生成する構成としている。図１に示したプラズマエッチング装置に加えて、イオン・ラジカル源用ガス供給部６０と、準安定原子発生用プラズマ発生室６２を備えている。また上部電極１２には、準安定原子を含むガスを真空処理室に導入するル−トのほかに、イオン・ラジカル源用ガス供給部に繋がっている導入ル−トを設けている。
【０１７９】
この実施例の特徴は、次の通りである。
▲１▼準安定原子発生用ガス供給部３６から供給されたガスを準安定原子発生用プラズマ発生室６２にて高周波電力を印加してプラズマ化し、あらかじめ所望の準安定原子を所望量発生させ処理室１０に流入させる。準安定原子発生用プラズマ発生室６２は、効率良く準安定原子を発生させるために、室内の圧力は、数百mTorr〜数十Torrの高い圧力に設定する。
【０１８０】
▲２▼他方、イオン・ラジカル源用ガス供給部６０からのガスを処理室１０に流入させる。
【０１８１】
▲３▼プラズマ発生用電源１６で比較的低電力の高周波を出力し、処理室１０にプラズマを発生させる。準安定原子の注入により、５ｅＶ程度以下の低エネルギ−の電子でもイオンを効率良く生成させることができるため、低電子温度（６ｅＶ程度以下、好ましくは４ｅＶ程度以下）で、かつ１５ｅＶ程度以上の高エネルギ−電子が大幅に少ないプラズマが得られる。このため、ラジカル源用ガスは過剰な解離を生じさせることなく必要な量と質を確保出来る。一方イオンの量は、準安定原子発生用プラズマ発生室６２にて発生する準安定原子の量と、イオン・ラジカル源用ガス供給部６０からのイオン源用ガスにて制御することができる。
【０１８２】
このようにしてイオンとラジカル生成の質や量を制御できる様になるため、極微細なプラズマ処理においても良好な性能が得られる。ラジカル源用ガスとしては、ＣＨＦ₃、ＣＨ₂Ｆ₂，Ｃ₄Ｆ₈あるいはＣＦ₄などのフルオロカ−ボンガスに、必要に応じてＣ，Ｈを含むガス（Ｃ₂Ｈ₄，ＣＨ₄，ＣＨ₃ＯＨなど）を混ぜてもちいる。準安定原子発生用ガスとしては、１種類ないしは２種類の希ガスをべ−スにしたものを用いる。イオン源用ガスとしては、下記の性質を持つ希ガス等を用いることにより、効率良くイオンを生成できる。
【０１８３】
前記準安定原子のエネルギ−凖位に対し、イオン源用ガスの電離凖位が低いもの、もしくは、イオン源用ガスの電離凖位の方が高いが、その差が小さい（５ｅＶ程度以下）ものが用いられる。
【０１８４】
尚、性能的には低下するがイオン源用ガスとして特に追加せず、上記準安定原子発生用ガスやラジカル源用ガスで代用することもできる。
【０１８５】
次に、図３８にイオンとラジカル生成の質や量を制御する本発明の他の実施例を示す。図３７と基本的考えは、同じであるが、図３７において、準安定原子発生用プラズマ室６２と真空処理室１０との間の距離が長く、この間での準安定原子の減衰が大きい場合の対策として実施する例である。４１はマイクロ波の発振源としてのマグネトロン、４２はマイクロ波の導波管であり、４３は第一のプラズマ生成室４５を真空封じして、マイクロ波を通過させるための石英板であり、４４はガス分散用の石英板である。第一のプラズマ生成室４５では、数１００ｍＴｏｒｒから数１０Ｔｏｒｒのガス圧で前記マイクロ波によりプラズマを発生させ、準安定原子を発生させる。
【０１８６】
図３８では、図３７に比較し準安定原子の発生場所と真空処理室間の距離を短く出来るため、高い密度で準安定原子を真空処理室に注入することができ、真空処理室１０におけるイオンの量を増加できる。処理室１０は５〜５０ｍＴorrの圧力に保ち、２０ＭＨｚ以上の高周波電源１６により、５ｅＶ好ましくは３ｅＶ以下で１０の１０乗から１１乗台／ｃｍ³の高密度低電子温度プラズマを発生させ、解離エネルギ−として８ｅＶ以上を必要とするＣＦ２の解離を避けつつ、イオン源用ガスの電離を進行させる。この結果、試料４０の表面上では、バイアス電源１７により数１００Ｖで加速されたイオンの入射でアシストされた下記反応が主に進行する。
ＳｉＯ₂＋２ＣＦ₂ → ＳｉＦ₄ ↑＋２ＣＯ ↑
なお、下地材料となるＳｉやＳｉＮは、ＣＦ₂ではエッチングされないため、高選択比の酸化膜エッチングが可能となった。
【０１８７】
また、ＣＦ₂の一部解離によるＦの増加は、シリコン、カ−ボンもしくはＳｉＣ等からなる上部電極カバ−３０により減少させている。
【０１８８】
上で述べたように、ラジカル源用ガスとイオン源用ガスとを調節することにより、処理室１０内でのイオンとラジカルとの比率をほぼ独立に制御でき、試料４０の表面での反応を所望のものにコントロ−ルすることが容易になった。
【０１８９】
本発明の、静電吸着回路とパルスバイアス電圧印加回路を備えたプラズマ処理装置は、エッチングガスに代えてＣＶＤガスを導入する等の変更を加えることにより、以上述べたエッチング処理に限らずＣＶＤ装置等のプラズマ処理装置にも適用できる。
【０１９０】
次に、図３９にイオンとラジカルとを独立に制御する本発明の他の実施例を示す。図３９において、ＣＨＦ₃、ＣＨ₂Ｆ₂，Ｃ₄Ｆ₈あるいはＣＦ₄などのフルオロカ−ボンガスに、必要に応じてＣ，Ｈを含むガス（Ｃ₂Ｈ₄，ＣＨ₃ＯＨなど）を混ぜ、図３９のＡなる部分よりバルブ７０を経由してラジカル発生用プラズマ発生室６２に入れる。
【０１９１】
ラジカル発生用プラズマ発生室６２では、数ＭＨｚないしは数１０ＭＨｚのＲＦ電源６３の出力をコイル６５に印加し、数１００ｍＴｏｒｒから数１０Ｔｏｒｒのガス圧でプラズマを発生させ、主にＣＦ２ラジカルを発生させる。同時に発生するＣＦ₃やＦはＨ成分により減少させる。
【０１９２】
なお、ラジカル発生用プラズマ発生室６２でＣＦやＯ等の成分を大幅に減少させることは困難なため、この後に不要成分除去室６５を設ける。ここでは、カ−ボンやＳｉを含む材質（カ−ボン、Ｓｉ，ＳｉＣ等）の内壁を設置し、不要な成分を減少、あるいは悪影響の少ない別のガスに変換させる。不要成分除去室６５の出口は、バルブ７１に接続し、ＣＦ₂が主成分のガス組成を供給する。
【０１９３】
なお、バルブ７０とバルブ７１との間は、デポ物等の堆積物が多く蓄積するため、比較的短期間で清掃や交換が必要である。このため、大気開放と交換とを容易にすると共に、再立ち上げ時の真空立ちあげ時間の短縮のため、バルブ７２を経由して排気装置７４に接続している。なお排気装置７４は、処理室１０用排気装置等と兼用してもよい。
【０１９４】
またイオン源用ガス（アルゴンガスやキセノンガス等の希ガス）Ｂはバルブ７３を経由し、前記のバルブ７１の出口と繋ぎ処理室に供給する。
【０１９５】
処理室１０は５〜４０ｍＴの圧力に保ち、変調を施した２０ＭＨｚ以上の高周波電源１６により、５ｅＶ好ましくは３ｅＶ以下で１０の１０乗から１１乗台／ｃｍ³の高密度低電子温度プラズマを発生させ、解離エネルギ−として８ｅＶ以上を必要とするＣＦ₂の解離を避けつつ、イオン源用ガスの電離を進行させる。この結果、試料４０の表面上では、バイアス電源１７により数１００Ｖで加速されたイオンの入射でアシストされた下記反応が主に進行する。
ＳｉＯ₂＋２ＣＦ₂ → ＳｉＦ₄ ↑＋２ＣＯ ↑
なお、下地材料となるＳｉやＳｉＮは、ＣＦ₂ではエッチングされないため、高選択比の酸化膜エッチングが可能となった。
【０１９６】
また、ＣＦ₂の一部解離によるＦの増加は、シリコン、カ−ボンもしくはＳｉＣ等からなる上部電極カバ−３０により減少させている。
【０１９７】
上で述べたように、ラジカル源用ガスＡとイオン源用ガスＢとを調節することにより、処理室１０内でのイオンとラジカルとの比率をほぼ独立に制御でき、試料４０の表面での反応を所望のものにコントロ−ルすることが容易になった。また、不必要なデポ成分等は、不要成分除去室６５で排除し、処理室１０には極力持ち込まないようにしているため、処理室１０内のデポは大幅に低減され、処理室１０を大気に開放して行う清掃の頻度も大幅に低減できた。
【０１９８】
次に、図４０にイオンとラジカルとを独立に制御する他の実施例を示す。酸化ヘキサフルオロプロピレンガス（ＣＦ₃ＣＦＯＣＦ₂，以下ＨＦＰＯと略す）をＡより、バルブ７０を経由して加熱パイプ部６６に通し、不要成分除去室６５とバルブ７１を経由し、イオン源ガスＢと混合し、処理室１０のほうに送る。加熱パイプ部６６では、８００℃〜１０００℃にＨＦＰＯを加熱し下記の熱分解によりＣＦ２を生成する。
ＣＦ₃ＣＦＯＣＦ₂ → ＣＦ₂＋ＣＦ₃ＣＦＯ
ＣＦ₃ＣＦＯは比較的安定な物質で分解しにくいが、一部分解し不要なＯやＦを発生するため、加熱パイプ部６６の後に不要成分除去室６５をもうけ不要成分を除去、あるいは悪影響のでない物質に変換している。一部のＣＦ₃ＣＦＯＣＦ₂は分解しないで処理室１０に流入するが、５ｅＶ以下の低電子温度のプラズマでは解離しないため問題とはならない。
【０１９９】
なお、バルブ７２、排気装置７４の用い方ならびに処理室１０内での反応は、図３９の場合と同じである。
【０２００】
本発明の、静電吸着回路とパルスバイアス電圧印加回路を備えたプラズマ処理装置は、エッチングガスに代えてＣＶＤガスを導入する等の変更を加えることにより、以上述べたエッチング処理に限らずＣＶＤ装置等のプラズマ処理装置にも適用できる。
【０２０１】
【発明の効果】
本発明によれば、φ３００ｍｍ以上の大口径の試料について微細パターンの精密な加工が容易で、また、微細加工時の選択比も向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。また、大口径の試料の全面にわたって均一かつ高速な処理、特に酸化膜処理を施すことができるプラズマ処理装置およびその処理方法を提供することができる。
【０２０２】
本発明によれば、さらに、試料中の絶縁膜（例えばＳｉＯ₂, ＳｉＮ，ＢＰＳＧ等）に対するプラズマ処理の選択性等を向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。
【０２０３】
また、制御性が良くかつ狭いイオンエネルギー分布を得て、プラズマ処理の選択性等を向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。
【０２０４】
また、静電吸着用誘電体層を有する試料台を使用する場合において、制御性良く、狭いイオンエネルギー分布を得て、プラズマ処理の選択性等を向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。
【０２０５】
また、イオンとラジカルの量や質を独立に制御することにより、プラズマ処理装置の処理室内の圧力を低くして、微細パターンの精密な加工が容易で、また、微細加工時の選択比も向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。
【０２０６】
さらにまた、イオンとラジカルの量や質を独立に制御することにより、試料中の絶縁膜（例えばＳｉＯ₂, ＳｉＮ，ＢＰＳＧ等）に対するプラズマ処理の選択性等を向上させたプラズマ処理装置及びプラズマ処理方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施例になる、２電極型のプラズマエッチング装置の縦断面図である。
【図２】電子のサイクロトロン共鳴を生じる磁場を加えた状態で、プラズマを発生させる高周波電源の周波数を変化させたときの、プラズマ密度の変化の一例を示す図である。
【図３】サイクロトロン共鳴時と無共鳴時とに電子が高周波電界から得るエネルギー利得ｋの状況を示す図である。
【図４】マグネトロン放電電極の上部電極を接地し、下部電極に磁界Ｂを与えると共に高周波電力を印加した時の、磁界強度と、試料に誘起されるイオン加速電圧Ｖ_DC及び試料内の誘起電圧のバラツキΔＶの関係を示す図である。
【図５】図１のプラズマエッチング装置の磁界特性の説明図である。
【図６】図１のプラズマエッチング装置のＥＣＲ領域の説明図である。
【図７】本発明のパルスバイアス電源において使用する望ましい出力波形の例を示す図である。
【図８】パルスデューティ比：（Ｔ₁／Ｔ₀）は一定のままＴ₀ を変化させた時の試料表面の電位波形とイオンエネルギーの確率分布を示す図である。
【図９】パルスデューティ比を一定のまま、Ｔ₀ を変化させた時の試料表面の電位波形とイオンエネルギーの確率分布を示す図である。
【図１０】パルスのオフ（Ｔ₀−Ｔ₁）期間と、静電吸着膜の両端間に生じる電圧の一周期中の最大電圧Ｖ_CMの関係を示す図である。
【図１１】パルスデューティ比と（Ｖ_DC／ｖ_p ）の関係を示す図である。
【図１２】塩素ガスをプラズマ化した時のシリコンと酸化膜とのエッチングレートＥＳｉおよびＥＳｉＯ₂のイオンエネルギー依存性を示す図である。
【図１３】酸化膜のエッチングの例としてＣ₄Ｆ₈ガスをプラズマ化した時の、酸化膜とシリコンとのエチングレートＥＳｉＯ₂および、ＥＳｉのイオンエネルギー分布を示す図である。
【図１４】本発明の他の実施例になる２電極型のプラズマエッチング装置の縦断面図である。
【図１５】本発明の他の実施例になる２電極型のプラズマエッチング装置の縦断面図である。
【図１６】図１５プラズマエッチング装置の磁場分布特性の説明図である。
【図１７】図１５のプラズマエッチング装置の、ＥＣＲ領域の説明図である。
【図１８】本発明の他の実施例になるプラズマエッチング装置の縦断面図である。
【図１９】図１８のプラズマエッチング装置の、磁場分布特性の説明図である。
【図２０】本発明の他の実施例になる、２電極型のプラズマエッチング装置の縦断面図である。
【図２１】本発明の他の実施例になる、２電極型のプラズマエッチング装置の縦断面図である。
【図２２】図２１のプラズマエッチング装置の、磁場分布特性の説明図である。
【図２３】本発明の他の実施例になる２電極型のプラズマエッチング装置の要部横断面図である。
【図２４】図２３のプラズマエッチング装置の縦断面図である。
【図２５】磁場形成手段の他の実施例を示す図である。
【図２６】本発明の他の実施例になる、２電極型のプラズマエッチング装置の縦断面図である。
【図２７】本発明の他の実施例になる、２電極型のプラズマエッチング装置の縦断面図である。
【図２８】本発明の他の実施例になる、２電極型プラズマエッチング装置の縦断面図である。
【図２９】図２８のプラズマエッチング装置の磁場分布特性の説明図である。
【図３０】本発明の他の実施例になる、２電極型プラズマエッチング装置の縦断面図である。
【図３１】図１に示した２電極型プラズマエッチング装置を改良した他の実施例の縦断面図である。
【図３２】プラズマ発生用電源の周波数と安定放電最低ガス圧の関係を示す図である。
【図３３】パルスバイアス電源の周波数と累積電力の関係を示した図である。
【図３４】本発明を、外部エネルギー供給放電方式のうち、誘導結合型放電方式でかつ、無磁場タイプのプラズマエッチング装置へ適用した例の縦断面図である。
【図３５】本発明の他の実施例になる、プラズマエッチング装置の縦断面図である。
【図３６】本発明をマイクロ波プラズマ処理装置に適用した装置の一部を縦断面した正面図である。
【図３７】本発明の他の実施例になる、プラズマエッチング装置の縦断面図である。
【図３８】本発明の他の実施例になる、プラズマ処理装置の一部を縦断面した正面図である。
【図３９】本発明の他の実施例になる、イオンとラジカルを独立して制御可能な、２電極プラズマエッチング装置の縦断面図である。
【図４０】本発明の他の実施例になる、イオンとラジカルを独立して制御可能な、２電極プラズマエッチング装置の部分詳細図である。
【符号の説明】
１０…処理室、１２…上部電極、１５…下部電極、１６…高周波電源、１７…パルスバイアス電源、１８…真空ポンプ、２０…静電チャック、２２…静電吸着膜、２３…直流電源、３０…上部電極カバー、３２…ガス拡散板３２、３６…ガス供給部３、４０…試料、１６１…高周波電源変調信号源、２００…磁場形成手段２００、２０１…コア、２０２…電磁コイル、２０３…絶縁体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and a processing method, and more particularly, to a plasma processing apparatus and a plasma processing method suitable for forming a fine pattern in a semiconductor manufacturing process.
[0002]
[Prior art]
Plasma processing is increasingly required to improve microfabrication and processing speed as semiconductor devices are highly integrated. In order to meet this demand, it is necessary to lower the processing gas pressure and the plasma density.
[0003]
(1) Using a cyclotron resonance phenomenon (abbreviated as ECR) between a microwave (2.45 GHz) electromagnetic field and a static magnetic field (875 G), (2) There are devices that generate plasma by exciting a coil with a power source of RF frequency to generate an induction electromagnetic field (abbreviated as ICP).
[0004]
By the way, when an oxide film is etched using a fluorocarbon gas, in the ECR shown in the above (1) and the ICP method shown in (2), the dissociation of the gas proceeds excessively, and the oxide film At present, it is difficult to increase the selection ratio with respect to the base (Si or SiN).
[0005]
On the other hand, it is difficult to stably discharge at a pressure of 10 Pa or less in the conventional method of generating plasma by applying an RF frequency voltage between parallel plates.
As countermeasures, (3) plasma is generated by a high frequency voltage of several tens of MHz or more as shown in Japanese Patent Laid-Open Nos. 7-297175 and 3-204925, and at a low frequency of several MHz or less. A two-frequency excitation method for controlling the bias of the sample, or (4) applying a magnetic field B in a direction intersecting with the self-bias electric field (E) induced on the sample surface as disclosed in Japanese Patent Laid-Open No. 2-312231. There is a magnetron RIE (abbreviated as M-RIE) method using an electron confinement action by an electron Lorentz force.
[0006]
As a method for increasing the plasma density under a low gas pressure, there is a method described in JP-A No. 56-13480. This utilizes electron cyclotron resonance (ECR) by microwaves (2.45 GHz) that are electromagnetic waves and static magnetic fields (875 Gauss), so that a high plasma density can be obtained even at a low gas pressure of 0.1 to 1 Pa. Is.
[0007]
On the other hand, in the technical field of performing etching processing or film formation processing of a semiconductor using plasma, ions in the plasma with respect to a sample table on which an object to be processed (for example, a semiconductor wafer substrate, hereinafter referred to as a sample) is arranged A processing apparatus including a high-frequency power source for accelerating the sample and an electrostatic adsorption film that holds the sample on the sample stage by electrostatic adsorption force is employed.
[0008]
For example, the apparatus described in US Pat. No. 5,320,982 generates plasma with microwaves, holds a sample on a sample stage by electrostatic adsorption force, and generates heat transfer gas between the sample and the sample stage. While controlling the temperature of the sample by interposing it, a high frequency power source with a sine wave output is used as a bias power source, and the power source is connected to the sample stage to control the ion energy incident on the sample.
[0009]
Japanese Patent Application Laid-Open No. 62-280378 discloses a distribution width of ion energy incident on a sample by generating and applying a pulsed ion control bias waveform for making the electric field strength between the plasma and the electrode constant. It is described that the processing dimensional accuracy of etching and the etching rate ratio between the film to be processed and the base material can be increased several times.
[0010]
In JP-A-6-61182, plasma is generated using electron cyclotron resonance, and a pulse bias having a pulse duty width of about 0.1% or more is applied to the sample to prevent the generation of notches. It is described.
[0011]
Note that as an example in which cyclotron resonance is caused by a VHF band electromagnetic wave and a static magnetic field to improve plasma density, Jap. J. et al. Appl. phys, Vol. 28, No. 10, October, 1989, PP. L 1860-L 1862. However, in this example, a high frequency of 144 MHz is applied to the coaxial central conductor, a 51 G magnetic field parallel to the central conductor is applied, cyclotron resonance is generated, and high-density plasma is generated, downstream of the plasma generating section. A grounded sample stage is installed.
[0012]
[Problems to be solved by the invention]
Among the prior arts described above, the plasma generation methods described in JP-A-7-288195 and JP-A-7-297175 generate plasma with a high frequency of 13.56 MHz or several tens of MHz. With a gas pressure of about several tens to 5 Pa (Pascal), good plasma can be generated for etching the oxide film. However, along with the miniaturization of pattern dimensions of about 0.2 μm or less, the verticalization of the processing shape has been strongly demanded. For this purpose, the gas pressure must be lowered. Yes.
[0013]
However, in the above-described two-frequency excitation method and M-RIE method, 5 × 10 at 4 Pa or less (0.4 to 4 Pa).^Tencm^-3It is difficult to stably generate a plasma having a desired density exceeding a certain level. For example, in the above-mentioned two-frequency excitation method, even if the plasma excitation frequency is increased, the plasma density does not increase so much at 50 MHz or more, or conversely decreases, and a low gas of 0.4 to 4 Pa appears. The plasma density is 5 × 10 by pressure^Tencm^-3This is difficult.
[0014]
In the M-RIE method, the plasma density generated by the electron confinement action due to the Lorentz force of electrons generated on the sample surface must be uniform over the entire surface of the sample. However, there is a drawback that in-plane deviation is generally caused in the plasma density due to drift of E × B. Since the deviation of the plasma density formed directly by the electron confinement action on the sample surface is generated near the sheath near the sample having a high electric field strength, it cannot be corrected by a method such as diffusion.
[0015]
As described in Japanese Patent Application Laid-Open No. 7-288195 as a solution to this problem, by arranging a magnet so that the magnetic field strength is weakened in the electron drift direction by E × B, the maximum value of the magnetic field parallel to the sample is obtained. As a result, even if 200 gauss is added, a uniform plasma gas with no bias can be obtained. However, once the magnetic field strength distribution is fixed, there is a drawback that it is difficult to easily follow changes in processing conditions because the conditions for plasma uniformity are limited to a specific narrow range. In particular, when the distance between the electrodes is narrow at about 20 mm or less for a large-diameter sample of φ300 or more, the pressure on the center of the sample is 10% or more higher than the pressure on the end of the sample, and the pressure difference on the sample is avoided. Therefore, when the distance between the sample stage and the counter electrode is set to 30 mm or more, the difficulty tends to increase particularly.
[0016]
Thus, in the above-described two-frequency excitation method and M-RIE method, 5 × 10 5 at a low pressure of 0.4 to 4 Pa.^Tencm^-3It is difficult to make the plasma density uniform within a sample surface of φ300 mm. Therefore, in the dual frequency excitation method and the M-RIE method, processing of a wafer having a diameter of 300 mm or more with a diameter of 0.2 microns or less with uniform and high-speed workability is performed on a base (Si, SiN, etc.). It is difficult to process with a high selection ratio.
[0017]
On the other hand, as a method for greatly increasing the plasma density due to the low gas pressure, there is one described in Japanese Patent Laid-Open No. 56-13480 in the above prior art. However, in this method, gas dissociation proceeds too much, and when a silicon oxide film or a nitride film is etched using a gas containing fluorine and carbon, a large amount of fluorine atoms / molecules and fluorine ions are generated. There is a disadvantage that the selection ratio with respect to the base (such as Si) cannot be obtained. The ICP method using an induction electromagnetic field of RF power also has a drawback that dissociation proceeds excessively as in the ECR method.
[0018]
In addition, a configuration is generally adopted in which the processing gas is exhausted from the periphery of the sample. In this case, the density in the central portion of the sample tends to be high, and the plasma density in the peripheral portion of the sample tends to be low. There was a fault that was missed. In order to remedy this drawback, an annular bank (focus ring) is provided near the periphery of the sample to stagnate the gas flow. However, reaction products adhere to this bank and become a source of foreign matter, resulting in a high yield. Had the disadvantage of decreasing.
[0019]
On the other hand, in order to control the energy of ions incident on the sample, a sinusoidal RF bias is applied to the electrode on which the sample is placed. As the frequency, several hundred KHz to 13.56 MHz are used, but in this frequency band, the ions follow the change of the electric field in the sheath, so that the energy distribution of the incident ions is low energy side and high energy side. It was a double peak type with two peaks. High energy ions have a high processing speed, but damage the sample. Low energy ions have a low processing speed. If you try to eliminate damage, the processing speed will decrease and the processing speed will increase. Then, there was a fault that damage would be a problem. On the other hand, if the RF bias frequency is set to a high value of, for example, about 50 MHz or more, the incident energy distributions are all close to a single peak, but most of the energy is used for plasma generation, and the voltage applied to the sheath is greatly reduced. There is a drawback that it is difficult to control the energy of incident ions independently.
[0020]
In the above prior art, the pulse bias power supply system described in Japanese Patent Application Laid-Open Nos. 62-280378 and 6-61182 uses a dielectric layer for electrostatic adsorption between the sample stage electrode and the sample. In the case of applying a pulse bias to the sample, if applied directly to the electrostatic adsorption method, the plasma and the sample surface are increased due to an increase in the voltage generated across the electrostatic adsorption film with the inflow of ion current. Since the ion acceleration voltage applied between them decreases and the ion energy distribution spreads, there is a drawback that it is impossible to cope with the processing of the necessary fine pattern while performing sufficient temperature control on the sample.
[0021]
In the conventional sine wave output bias power supply system described in US Pat. No. 5,320,982, the impedance of the sheath portion approaches or falls below that of the plasma itself as the frequency increases. As a result, unnecessary plasma is generated in the vicinity of the sheath in the vicinity of the sample, which is not used effectively for accelerating ions, and the plasma distribution is also deteriorated, so that the controllability of ion energy by the bias power source is lost.
[0022]
Furthermore, in plasma processing, it is important for the performance improvement to appropriately control the amount of ions, the amount of radicals and radical species. Conventionally, a gas serving as an ion source or radical source is allowed to flow into the processing chamber. Since the plasma is generated in the processing chamber to generate ions and radicals at the same time, the limit of the control is becoming clear as the processing of the sample is miniaturized.
[0023]
Also, as described in Jap. J. et al. Appl. In the example using the cyclotron resonance of VHF 帶 of phys, 28 and 10, there is no description of means for uniformly applying the installation bias voltage of the bias power source applied to the sample stage over the entire surface of the sample. Further, the height of the processing chamber is about 200 mm or more, and it is not configured to effectively utilize the surface reaction at the counter electrode, and it is difficult to obtain a high selection ratio with this configuration.
[0024]
An object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can easily process a fine pattern on a large-diameter sample easily by obtaining a uniform plasma with a large diameter of φ300 mm or more without excessively dissociating gas. It is to provide.
[0025]
Another object of the present invention is to provide a plasma processing apparatus and a processing method thereof capable of performing uniform and high-speed processing, particularly oxide film processing, over the entire surface of a large-diameter sample.
[0026]
Another object of the present invention is to provide an insulating film (eg, SiO 2) in a sample.₂, SiN, BPSG, etc.) to provide a plasma processing apparatus and a plasma processing method with improved plasma processing selectivity.
[0027]
Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method that can obtain a narrow ion energy distribution and can improve the selectivity of plasma processing stably with low damage and good controllability.
[0028]
Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method which improve temperature controllability by electrostatic adsorption of a sample and perform processing of a required fine pattern with high accuracy and stability.
[0029]
Another object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of independently controlling ions and radicals.
[0030]
[Means for Solving the Problems]
The present invention is characterized in that a vacuum processing chamber, plasma generating means including a pair of electrodes, a sample stage having a sample mounting surface on which a sample to be processed in the vacuum processing chamber is mounted, and the vacuum processing chamber being decompressed In a plasma processing apparatus having a decompression means for
The electrode includes a first electrode connected to a high-frequency power source, a second electrode that also serves as the sample stage, and a wall portion of the processing chamber that is located on the outer periphery of the first electrode and is grounded. The high-frequency power source is a power source that applies high-frequency power of VHFＭＨｚ of 30 MHz to 300 MHz between the pair of electrodes and between the first electrode and the wall portion of the processing chamber, and in the vicinity of the center of the processing chamber. Magnetic field forming means for forming a portion of a static magnetic field or low frequency magnetic field of 10 gauss or more and 110 gauss or less in a direction overlapping each other and overlapping each other at the periphery and outside of the processing chamber, and the periphery of the sample mounting surface An electron cyclotron resonance region is formed in the part or in the vicinity of the outside thereof by the interaction between the magnetic field and the electric field generated by the high-frequency power source.
[0031]
Another feature of the present invention is a plasma having a vacuum processing chamber, a plasma generating means including a pair of electrodes, and a sample stage for serving as one of the electrodes and for placing a sample to be processed in the vacuum processing chamber. In the processing device,
A high-frequency power source that applies a VHF power of 30 MHz to 300 MHz between the pair of electrodes, a decompression unit that depressurizes the vacuum processing chamber to 0.4 Pa to 4 Pa, and an electric field between or near the pair of electrodes. Magnetic field forming means for forming a static magnetic field or a low frequency magnetic field part of 10 gauss or more and 110 gauss or less in the direction to be connected, and the electrode comprises a first electrode connected to the high frequency power source and the sample stage. In addition, the second electrode connected to a bias power source for controlling ion energy has a distance between the pair of electrodes of 30 to 100 mm, and a period of 0.2 is used as the bias power source for controlling ion energy. Apply a pulse bias with a duty of 0.4 or less in the positive direction pulse portion to ~ 5 μs to the sample through a capacitive element, and the first electrode surface An electron cyclotron resonance region is formed by the interaction between the magnetic field and the electric field generated by the high-frequency power source on the first electrode side or above the center of both electrodes.
[0032]
Another feature of the present invention is that a plasma processing of a sample by a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generating means including a pair of electrodes. In the method
The electrode includes a pair of electrodes including a first electrode connected to the high-frequency power source and a second electrode serving as the sample stage and connected to a bias power source for ion energy control. The distance between the electrodes is 30 to 100 mm,
Depressurizing means for reducing the pressure in the vacuum processing chamber to 0.4 Pa to 4 Pa by a depressurizing means, and applying a static magnetic field or low frequency magnetic field of 10 to 110 gauss in a direction intersecting the electric field between the pair of electrodes by a magnetic field forming means. A step of forming a portion, and by applying a VHF band power of 30 MHz to 300 MHz between the pair of electrodes by a high frequency power source, and the interaction between the magnetic field and the electric field by the high frequency power source between the pair of electrodes. And forming a cyclotron resonance region of electrons, and processing the sample with a plasma generated by the cyclotron resonance of the electrons.
[0033]
According to the present invention, in order to obtain a uniform plasma with a large diameter of φ300 mm or more and a saturated ion current distribution of ± 5% or less without excessive gas dissociation, 30 MHz to 300 MHz, Preferably, 50 MHz to 200 MHz VHF is used. On the other hand, a static magnetic field or a low frequency magnetic field is formed in a direction crossing an electric field generated between the pair of electrodes by the high frequency power source. Thereby, an electron cyclotron resonance region due to the interaction between the magnetic field and the electric field is formed between the pair of electrodes on the opposite side of the sample table from the center of the pair of electrodes along the sample mounting surface of the sample table. It is formed. The sample is processed by the plasma generated by the cyclotron resonance of the electrons.
[0034]
The magnetic field has a portion of a static magnetic field or a low frequency (1 KHz or less) magnetic field of 10 to 110 Gauss, preferably 17 to 72 Gauss, and the gas has a low pressure of 0.4 Pa to 4 Pa. The distance between the electrodes is 30 to 100 mm, preferably 30 to 60 mm. Needless to say, each of the pair of electrodes has an area larger than the area of the sample to be processed.
[0035]
By using VHF of 50 MHz ≦ f ≦ 200 MHz as the frequency f of the high frequency power supply, the plasma density is reduced by about one or two digits compared to the case of the microwave ECR. In addition, gas dissociation is reduced, and generation of unnecessary fluorine atoms / molecules and ions is also reduced by an order of magnitude or more. By using this VHF band frequency and cyclotron resonance, the absolute value of the plasma density is 5 × 10 5.^Tencm^-3The above-described moderately high-density plasma can be obtained, and high-rate processing can be performed at a low pressure of 0.4-4 Pa. Further, since the gas dissociation does not proceed excessively, the selection ratio with the base such as Si or SiN is not greatly deteriorated.
[0036]
Compared to the conventional 13.56 MHz parallel plate electrode, the gas dissociation progresses a little, but the slight increase in fluorine atoms / molecules and ions caused by this means that a substance containing silicon or carbon is placed on the electrode surface or chamber wall surface. Furthermore, it can be improved by applying a bias to them or combining and discharging hydrogen and fluorine using a gas containing hydrogen.
[0037]
In addition, according to the present invention, between the two electrodes, the maximum magnetic field component parallel to the sample table is set on the opposite side of the sample table from the center of both electrodes, and the sample mounting surface of the sample table is By setting the magnetic field strength parallel to the sample to 30 gauss or less, preferably 15 gauss or less, the Lorentz force (E × B) acting on the electrons in the vicinity of the sample mounting surface is reduced, and the Lorentz force on the sample mounting surface is reduced. It is possible to eliminate the occurrence of plasma density non-uniformity due to the electron drift effect.
[0038]
According to another aspect of the present invention, the electron cyclotron resonance effect is compared with the central portion or the outside thereof so as to enhance the generation of plasma in the peripheral portion of the sample or near the outside of the sample as compared with the vicinity of the central portion of the sample. Make it bigger. Means for reducing the electron cyclotron resonance effect can be achieved by increasing the distance between the cyclotron resonance region and the sample, eliminating the cyclotron resonance region, or reducing the orthogonality between the magnetic field and the electric field.
[0039]
Further, when the magnetic field gradient near the cyclotron resonance magnetic field BC is made steep and the ECR resonance region is narrowed, the cyclotron resonance effect can be weakened. The ECR resonance region is
Bc (1-a) ≦ B ≦ Bc (1 + a) where 0.05 ≦ a ≦ 0.1
It becomes the range of the magnetic field intensity B.
[0040]
Since dissociation proceeds in the ECR resonance region, the generation of ions is particularly active. On the other hand, in regions other than the ECR resonance region, dissociation does not proceed as compared with the ECR resonance region, and radical generation is more active. By adjusting the width of the ECR resonance region and the high-frequency power applied to the upper electrode, the generation of ions and radicals suitable for sample processing can be controlled more independently.
[0041]
Another feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generating means including a high-frequency power source. An electrostatic adsorption means for holding the sample on the sample stage by an electrostatic adsorption force, and a pulse bias application means for applying a pulse bias voltage to the sample, and applying a high frequency voltage of 10 MHz to 500 MHz as the high frequency power source, The vacuum processing chamber is configured to be depressurized to 0.5 to 4.0 Pa.
[0042]
Another feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generation means, wherein the sample is electrostatically adsorbed. Electrostatic adsorption means that is held on the sample stage by force, pulse bias application means that is connected to the sample stage and applies a pulse bias voltage to the sample stage, and the electrostatic adsorption means that accompanies the application of the pulse bias voltage And a voltage suppressing means for suppressing a change in voltage generated corresponding to the electrostatic adsorption capacity.
[0043]
Other features of the present invention include a step of placing a sample on one of a pair of opposed electrodes provided in a vacuum processing chamber, a step of holding the sample on the electrode by electrostatic attraction, and the placement of the sample A step of introducing an etching gas into the atmosphere, a step of evacuating the atmosphere to 0.5 to 4.0 Pa, a high frequency voltage of 10 MHz to 500 MHz is applied, and the etching gas is converted into plasma under the pressure. And a step of etching the sample with the plasma, and applying a pulse bias voltage to the one electrode.
[0044]
Other features of the present invention include a step of placing a sample on one of opposing electrodes, a step of holding the placed sample on the electrode by electrostatic attraction, and an atmosphere in which the sample is placed In addition, a step of introducing an etching gas, a step of converting the introduced etching gas into plasma, a step of etching the sample with the plasma, and a pulse amplitude of 250 V to 1000 V applied to the one electrode during the etching, And applying a pulse bias voltage having a duty ratio of 0.05 to 0.4, and comprising an insulating film (for example, SiO 2) in the sample.₂, SiN, BPSG, etc.).
[0045]
According to another feature of the present invention, the temperature controllability of the sample is sufficiently achieved by applying a pulsed bias power having a predetermined characteristic to a sample stage provided with an electrostatic adsorption means having a dielectric layer for electrostatic adsorption. Therefore, the necessary fine pattern processing can be stably performed. That is, an electrostatic adsorption means for holding the sample on the sample stage by electrostatic adsorption force and a pulse bias application means connected to the sample stage and applying a pulse bias voltage to the sample stage are provided. A pulse bias in which the duty of the positive direction pulse portion is ½ or less in 2 to 2 μs is applied to the sample through the capacitive element.
[0046]
According to another aspect of the present invention, as a voltage suppression unit that suppresses a change in voltage that occurs in response to the electrostatic adsorption capacity of the electrostatic adsorption unit as a pulse bias voltage is applied, A voltage change applied to both ends of the dielectric layer by electrostatic adsorption is configured to be ½ or less of the magnitude of the pulse bias voltage. Specifically, the thickness of the dielectric electrostatic chuck film provided on the surface of the lower electrode is reduced, or the dielectric is made of a material having a high relative dielectric constant. Alternatively, a method of suppressing a rise in voltage applied to both ends of the dielectric layer by shortening the cycle of the pulse bias voltage may be employed.
[0047]
According to another feature of the present invention, a pulse bias voltage having a pulse amplitude of 250 V to 1000 V and a duty ratio of 0.05 to 0.4 is applied to the one electrode during etching of the sample. , Insulating film in the sample (for example, SiO₂, SiN, BPSG, etc.) can be improved in plasma processing selectivity.
[0048]
Another feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generation means, wherein the sample is electrostatically adsorbed. Electrostatic adsorption means for holding the sample table by force, bias application means for applying a bias voltage to the sample, and means for predecomposing radical generating gas in the vacuum processing chamber, A radical supply means for supplying; means for supplying an ion generating gas to the vacuum processing chamber; and a plasma generating means for generating plasma in the vacuum processing chamber.₂Is to use.
[0049]
Another feature of the present invention is a plasma processing apparatus having a vacuum processing chamber, a sample stage for placing a sample to be processed in the vacuum processing chamber, and a plasma generating means including a high-frequency power source. In the sample stage by means of electrostatic attraction force, pulse bias application means for applying a pulse bias voltage to the sample, and the vacuum processing chamber in which the radical generating gas is pre-plasmaized into a desired amount. A plasma generating means for generating radicals for supplying radicals and a plasma generating means for generating plasma by supplying an ion generating gas to the vacuum processing chamber, and applying a high frequency voltage of 10 MHz to 500 MHz to the high frequency power source. At the same time, the vacuum processing chamber is configured to be depressurized to 0.5 to 4.0 Pa.
[0050]
According to another aspect of the present invention, a pulsed bias power having a predetermined characteristic is applied to a sample stage having an electrostatic attraction means having an electrostatic attraction dielectric layer, which independently controls the quantity and quality of ions and radials. By applying, the temperature controllability of the sample can be sufficiently performed, and the necessary fine pattern processing can be stably performed.
[0051]
Furthermore, the quantity and quality of ions and radials can be controlled independently, a narrow ion energy distribution can be obtained, and the selectivity of plasma treatment can be improved stably and with good controllability.
[0052]
In addition, as a voltage suppression means that controls the quantity and quality of ions and radials independently and suppresses the change in voltage that occurs in response to the electrostatic adsorption capacity of the electrostatic adsorption means as a pulse bias voltage is applied, A voltage change applied to both ends of the dielectric layer by electrostatic adsorption during the period is configured to be ½ or less of the magnitude of the pulse bias voltage. Specifically, the thickness of the dielectric electrostatic chuck film provided on the surface of the lower electrode is reduced, or the dielectric is made of a material having a high relative dielectric constant. Alternatively, a method of suppressing a rise in voltage applied to both ends of the dielectric layer by shortening the cycle of the pulse bias voltage may be employed.
[0053]
In addition, according to another aspect of the present invention, the amount and quality of ions and radials are controlled independently, and a pulse amplitude of 250 V to 1000 V and a pulse amplitude of 0.05 to 0.4 are applied to the one electrode during etching of the sample. By applying a pulse bias voltage having a duty ratio, an insulating film (for example, SiO 2) in the sample₂, SiN, BPSG, etc.) and the plasma processing selectivity with the substrate can be improved.
[0054]
According to still another aspect of the present invention, the quantity and quality of ions and radials are controlled independently, a high frequency voltage of 10 MHz to 500 MHz is used as a high frequency power source for plasma generation, and the gas pressure in the processing chamber is set to 0. The pressure is 5 to 4.0 Pa. Thereby, a stable plasma can be obtained. Further, by using such a high frequency voltage, ionization of the gas plasma is improved, and selection ratio control during sample processing is improved.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below. FIG. 1 shows a first embodiment in which the present invention is applied to a counter electrode type plasma etching apparatus.
In FIG. 1, a processing chamber 10 as a vacuum container is provided with a pair of opposed electrodes each composed of an upper electrode 12 and a lower electrode 15. A sample 40 is placed on the lower electrode 15. The gap between the electrodes 12 and 15 is preferably 30 mm or more so that the pressure difference on the sample surface when processing a sample having a large diameter of φ300 mm or more is 10% or less. Further, in order to reduce fluorine atoms, molecules and ions, from the viewpoint of effectively utilizing the reaction on the upper / lower electrode surfaces, it is desirable that the thickness is 100 mm or less, preferably 60 mm or less. A high-frequency power source 16 that supplies high-frequency energy is connected to the upper electrode 12 via a matching box 162. Reference numeral 161 denotes a high frequency power supply modulation signal source. A filter 165 having a low impedance for the frequency component of the bias power source 17 and a high impedance for the frequency component of the high frequency power source 16 is connected between the upper electrode 12 and the ground.
[0056]
The surface area of the upper electrode 12 placed substantially parallel to the sample stage is larger than the area of the sample 40 to be processed, and the voltage on the sheath on the sample surface is efficiently and uniformly applied by applying the bias power source 17. It is composed.
[0057]
On the lower surface of the upper electrode 12, an upper electrode cover 30 is provided as a fluorine removing plate made of silicon, carbon or SiC. A gas introduction chamber 34 having a gas diffusion plate 32 for diffusing gas into a desired distribution is provided above the upper electrode 12. Gas necessary for processing such as etching of the sample is supplied to the processing chamber 10 from the gas supply unit 36 through the gas diffusion plate 32 of the gas introduction chamber 34, the upper electrode 12, and the hole 38 provided in the upper electrode cover 30. Supplied. The outer chamber 11 is evacuated by a vacuum pump 18 connected to the outer chamber via a valve 14, and the processing chamber 10 is adjusted to the processing pressure of the sample. Reference numeral 13 denotes an insulator. Around the processing chamber 10, a discharge confining ring 37 is provided in order to increase the plasma density and to homogenize the reaction in the processing chamber. The discharge confinement ring 37 is provided with an exhaust gap.
[0058]
On the upper electrode 12, magnetic field forming means 200 for forming a magnetic field perpendicular to the electric field E formed between the electrodes and parallel to the surface of the sample 40 is provided. The magnetic field forming unit 200 includes a core 201, an electromagnetic coil 202, and an insulator 203. As a constituent material of the upper electrode 12, there is a non-magnetic material conductor such as aluminum or an aluminum alloy. Examples of the constituent material of the processing chamber 10 include nonmagnetic materials such as aluminum, aluminum alloys, alumina, quartz, SiC, and the like. The core 201 has a cross section approximately E having core portions 201A and 201B so as to form a magnetic field B in which the magnetic flux extends from the central upper part of the processing chamber 10 to the upper electrode 12 and extends along the upper electrode 12 approximately in parallel. It has a letter-shaped axially symmetric structure. The magnetic field formed between both electrodes by the magnetic field forming means 200 is a cyclotron resonance of a static magnetic field of 10 Gauss to 110 Gauss, preferably 17 Gauss to 72 Gauss, or a low frequency magnetic field (1 KHz or less). Has a part that occurs.
[0059]
As is well known, the magnetic field strength Bc (Gauss) that causes cyclotron resonance has a relationship of Bc = 0.357 × f (MHz) with respect to the frequency f (MHz) of the high frequency for plasma generation.
[0060]
In the present invention, the two electrodes 12 and 15 need only have a pair of opposing electrodes substantially parallel to each other, and the electrodes 12 and 15 have a slight concave or convex surface due to demands for plasma generation characteristics and the like. May be. In such a two-electrode type, the electric field distribution between the electrodes can be easily made uniform, and it is relatively easy to make the plasma generation by cyclotron resonance uniform by improving the uniformity of the magnetic field orthogonal to the electric field. It has the characteristics that
[0061]
The lower electrode 15 for mounting and holding the sample 40 has a configuration including a bipolar electrostatic chuck 20. That is, the lower electrode 15 is composed of an outer first lower electrode 15A and a second lower electrode 15B disposed on the inner upper side via an insulator 21, and on the upper surfaces of the first and second lower electrodes. An electrostatic adsorption dielectric layer (hereinafter abbreviated as an electrostatic adsorption film) 22 is provided. A DC power source 23 is connected between the first and second lower electrodes via coils 24A and 24B for cutting high-frequency components, and the second lower electrode 15B side is positive so that the two lower electrodes are positive. Apply DC voltage. Thereby, the sample 40 is adsorbed and held on the lower electrode 15 by the Coulomb force acting between the sample 40 and both lower electrodes via the electrostatic adsorption film 22. As the electrostatic adsorption film 22, for example, a dielectric such as aluminum oxide or a mixture of aluminum oxide and titanium oxide can be used. As the power source 23, a DC power source of several hundred volts is used.
[0062]
The lower electrode 15 (15A, 15B) is connected to a pulse bias power source 17 for supplying a pulse bias having an amplitude of 20V to 1000V via blocking capacitors 19A, 19B for cutting DC components.
[0063]
So far, the electrostatic chuck has been described using the two-pole type, but other types of electrostatic chucks, for example, a single-pole type or an n-pole type (n ≧ 3) may be used.
[0064]
When performing an etching process, the sample 40 which is a processing target is placed on the lower electrode 15 of the processing chamber 10 and is adsorbed by the electrostatic chuck 20. On the other hand, a gas necessary for the etching process of the sample 40 is supplied from the gas supply unit 36 to the processing chamber 10 through the gas introduction chamber 34. The outer chamber 11 is evacuated by a vacuum pump 18, and the processing chamber 10 is evacuated under reduced pressure so that the processing pressure of the sample becomes, for example, 0.4 to 4.0 Pa (pascal). Next, a high frequency power of 30 MHz to 300 MHz, preferably 50 MHz to 200 MHz is output from the high frequency power supply 16 to convert the processing gas in the processing chamber 10 into plasma.
[0065]
Electron cyclotron resonance is generated between the upper electrode 12 and the lower electrode 15 by the high frequency power of 30 to 300 MHz and the static magnetic field portion of 10 gauss or more and 110 gauss or less formed by the magnetic field forming means 200. , A plasma having a low gas pressure of 0.4 to 4.0 Pa and a high density is generated.
[0066]
On the other hand, the bias is applied to the lower electrode 15 from the pulse bias power supply 17 with a voltage of 20 V to 1000 V and a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs and a duty of a positive pulse part of 0.05 to 0.4. Is applied to control the electrons and ions in the plasma to perform the etching process on the sample 40.
[0067]
The etching gas is made to have a desired distribution by the gas diffusion plate 32 and then injected into the processing chamber 10 through the hole 38 opened in the upper electrode 12 and the upper electrode cover 30.
[0068]
The upper electrode cover 30 is made of carbon, silicon, or a material containing these, and the fluorine and oxygen components are removed to improve the selection ratio with the base such as resist or silicon.
[0069]
In order to improve the fine workability of a large-diameter sample, it is preferable to use a high frequency power source 16 for generating plasma to stabilize discharge in a low gas pressure region. In the present invention, 5 × 10 5 at a low pressure gas of 0.4 Pa to 4 Pa.^TenOr 5 × 10¹¹cm^-3The plasma generating high frequency power supply 16 is connected to the upper electrode 12 in order to obtain a uniform plasma having a large diameter without excessive gas dissociation. On the other hand, a bias power source 17 for controlling ion energy is connected to the lower electrode 15 on which the sample is placed, and the distance between these electrodes is set to 30 to 100 mm.
[0070]
Further, as the high frequency power source 16 for plasma generation, a VHF of 30 MHz to 300 MHz, preferably 50 MHz to 200 MHz is used, and a static magnetic field or a low frequency (1 KHz or less) magnetic field of 10 gauss to 110 gauss, preferably 17 gauss to 72 gauss. Electron cyclotron resonance occurs between the upper electrode 12 and the lower electrode 15 due to the interaction with the above portion.
[0071]
FIG. 2 shows an example of changes in plasma density when the frequency of a high-frequency power source that generates plasma is changed in a state where a magnetic field that causes electron cyclotron resonance is applied. The test gas was argon added with 2 to 10% of C4F8, and the pressure in the processing chamber was 1 Pa. The plasma density is standardized with 1 for the microwave ECR of f = 2450 MHz. In addition, the broken line has shown the case without a magnetic field.
[0072]
At 50 MHz ≦ f ≦ 200 MHz, the plasma density is reduced by about one or two orders of magnitude compared to the case of microwave ECR. In addition, gas dissociation is reduced, and generation of unnecessary fluorine atoms / molecules and ions is also reduced by an order of magnitude or more. By using this VHF band frequency and cyclotron resonance, the absolute value of the plasma density is 5 × 10 5.^Tencm^-3The above-described moderately high-density plasma can be obtained, and high-rate processing can be performed at a low pressure of 0.4 to 4 Pa. Furthermore, since the gas dissociation does not proceed excessively, SiO₂The selectivity with respect to a base such as Si or SiN with respect to an insulating film such as is not greatly deteriorated.
[0073]
At 50 MHz ≦ f ≦ 200 MHz, the gas dissociation proceeds slightly compared to the conventional 13.56 MHz parallel plate electrode, but the slight increase in fluorine atoms / molecules and ions caused by this occurs on the electrode surface and chamber wall surface. It can be improved by installing substances containing silicon and carbon. Or, further, by applying a bias to the electrode surface or chamber wall surface, fluorine is combined with carbon or silicon and discharged, or hydrogen and fluorine are combined and discharged using a gas containing hydrogen for improvement. Can do.
[0074]
When the frequency of the high-frequency power source is 200 MHz or higher, particularly 300 MHz or higher, the plasma density increases, but the gas dissociation becomes excessive and the increase of fluorine atoms / molecules and ions becomes too large, and selection with a base such as Si or SiN This is not preferable because the ratio is greatly deteriorated.
[0075]
FIG. 3 shows the energy gain k that an electron obtains from a high-frequency electric field during cyclotron resonance and when there is no resonance. When e0 is the energy obtained by electrons during one period of high frequency in the absence of a magnetic field and e1 is the energy obtained by electrons during one period of high frequency when a cyclotron resonance magnetic field Bc = 2πf · (m / e) is applied, e1 , e0 is as shown in Equation 1.
[0076]
[Expression 1]

[0077]
When these ratios (= e1 / e0) are k, k is expressed by the following equation. Where m: electron mass, e: electron charge, f: applied frequency
K = (1/2) (ν²+ Ω²) {1 / (ν²+ (Ω-ωc)²))
+ (1 / (ν²+ (Ω + ωc)²))}
Where ν: collision frequency, ω: excitation angular frequency,
ωc: cyclotron angular frequency
In general, the value of k increases as the gas pressure decreases and the frequency increases. FIG. 3 shows the case of Ar (argon) gas. At pressure P = 1 Pa, f ≧ 50 MHz and k ≧ 150, and dissociation is promoted even at a lower gas pressure than when no magnetic field is present. The cyclotron resonance effect decreases rapidly at a frequency of about 20 MHz or less at a pressure P = 1 Pa. As can be seen from the characteristics shown in FIG. 2, at a frequency of 30 MHz or less, there is little difference from the case without a magnetic field, and the cyclotron resonance effect is small.
[0078]
If the gas pressure is lowered, the cyclotron resonance effect is enhanced. However, at 1 Pa or less, the electron temperature of the plasma is increased, and the adverse effect that the dissociation proceeds excessively increases. Suppresses excessive gas dissociation and reduces plasma density to 5 × 10^Tencm^-3In order to make it more than about, the gas pressure is 0.4 Pa to 4 Pa, preferably about 1 Pa to 4 Pa.
[0079]
In order to exhibit the cyclotron resonance effect, the value of k needs to be several tens or more. As apparent from FIGS. 2 and 3, in order to effectively use the cyclotron resonance effect without excessively dissociating the gas, a gas pressure of 0.4 Pa to 4 Pa is used as a high frequency power source for plasma generation. , 30-300 MHz, preferably 50-200 MHz VHF is required.
[0080]
FIG. 4 shows the ion acceleration voltage V induced in the sample when the upper electrode is grounded in a conventional magnetron type chamber, a uniform lateral magnetic field B is applied to the lower electrode, and a high frequency power of 68 MHz is applied._DCAnd the induced voltage V in the sample_DCThe variation ΔV is shown. When the intensity of the magnetic field B is increased, the ion acceleration voltage V is generated by the Lorentz force acting on the electrons._DCDecreases and the plasma density increases. However, in the case of the conventional magnetron discharge type, since the intensity of the magnetic field B is as large as about 200 Gauss, the in-plane uniformity of the plasma density is deteriorated, the induced voltage variation ΔV is increased, and the sample is damaged. There is.
[0081]
From FIG. 4, in order to make ΔV 1/5 to 1/10 or less compared to the case of the conventional magnetron discharge type 200 gauss, the intensity of the magnetic field B is 30 gauss or less, preferably 15 gauss in the vicinity of the sample surface. The following small values are desirable in order to eliminate damage.
[0082]
The cyclotron resonance region is formed between the upper electrode 12 and the lower electrode 15 and slightly closer to the upper electrode than the intermediate position between the two electrodes. In FIG. 5, the horizontal axis indicates the distance from the sample surface (lower electrode 15) to the upper electrode 12, and the vertical axis indicates the magnetic field. In the example of FIG. 5, the ECR region is formed in the vicinity of 30 mm from the sample surface under the conditions of the applied frequency f1 = 100 MHz, Bc = 37.5 G, and the electrode interval = 50 mm.
[0083]
As described above, in the present invention, the portion where the maximum magnetic field component parallel to the lower electrode 15 (sample mounting surface) is located between the upper electrode 12 and the lower electrode 15 from the upper electrode surface or the middle of both electrodes. Set to the upper electrode side. As a result, the magnetic field intensity parallel to the sample on the lower electrode surface is set to 30 gauss or less, preferably 15 gauss or less, and the Lorentzka (E × B) acting on the electrons near the lower electrode surface is set to a small value. In-plane non-uniformity of plasma density due to the electron drift effect caused by Lorentzka can be eliminated.
[0084]
According to the magnetic field forming means 200 of the embodiment of FIG. 1, as shown in FIG. 6, the ECR region is formed at substantially the same height from the lower electrode 15 (sample mounting surface) except for the vicinity of the center of the sample. Is done. Therefore, uniform plasma treatment can be performed on a large-diameter sample. However, in the vicinity of the center of the sample, the ECR region is formed at a high position from the sample mounting surface. Since there is a distance of 30 mm or more between the ECR region and the sample stage, ions and radical samples are diffused and averaged during this distance, so that there is no problem in normal plasma processing. However, in order to perform plasma processing uniformly on the entire surface of the sample, the ECR region is located at the same height from the sample surface over the entire surface of the sample, or the ECR region outside the sample is slightly more than the ECR region near the center. It is desirable to be formed so as to be close to the table side. This countermeasure will be described in detail later.
[0085]
As described above, in the embodiment of the present invention shown in FIG. 1, the plasma generation high-frequency power source 16 uses a high-frequency power of 30 to 300 MHz and gas dissociation is advanced by electron cyclotron resonance. A stable plasma can be obtained even under a low gas pressure of 10 to 10 Pa. In addition, since the collision of ions in the sheath is reduced, the directionality of ions is increased during the processing of the sample 40, and the vertical fine workability can be improved.
[0086]
Around the processing chamber 10, the plasma is localized near the sample 40 by the discharge confinement ring 37, so that the plasma density is improved and the discharge confinement ring 37 is moved to a portion outside the discharge confinement ring 37. Minimize the deposition of unwanted deposits.
[0087]
As the discharge confinement ring 37, a semiconductor or conductive material such as carbon, silicon, or SiC is used. When this discharge confinement ring 37 is connected to a high-frequency power source to cause sputtering by ions, deposition of deposits on the ring 37 can be reduced and fluorine can be removed.
[0088]
If a susceptor cover 39 containing carbon, silicon, or these is provided on the insulator 13 around the sample 40, SiO 2₂In the case where the insulating film such as fluorine is subjected to plasma treatment using a gas containing fluorine, fluorine can be removed, which helps to improve the selectivity. In this case, if the thickness of the insulator 13 in the lower part of the susceptor cover 39 is reduced to about 0.5 mm to 5 mm so that a part of the power of the bias power supply 17 is applied to the susceptor cover 39, the sputtering effect by ions is caused. The above effects are promoted.
[0089]
Further, an electrostatic adsorption circuit is formed by the potential of the DC power source 23 through the lower electrode 15 (15A, 15B) and the sample 40 with the dielectric electrostatic adsorption film 22 interposed therebetween. In this state, the sample 40 is locked and held on the lower electrode 15 by electrostatic force. A heat conduction gas such as helium, nitrogen, or argon is supplied to the back surface of the sample 40 locked by the electrostatic force. The heat conduction gas is filled in the recesses of the lower electrode 15, and the pressure is about several hundred Pascals to several thousand Pascals. The electrostatic attraction force is almost zero between the concave portions provided with the gap, and it can be considered that the electrostatic attraction force is generated only at the convex portion of the lower electrode 15. However, as will be described later, it is possible to set an adsorbing force that can sufficiently withstand the pressure of the heat conduction gas by appropriately setting the voltage in the DC power source 23, and thus the sample 40 is moved by the heat conduction gas. It will never be skipped.
[0090]
By the way, the electrostatic adsorption film 22 acts so as to reduce the bias action of the pulse bias with respect to ions in the plasma. This effect also occurs in the conventional method of biasing using a sine wave power supply, but it has not become apparent. However, the problem of the pulse bias is increased because the feature of narrow ion energy is sacrificed.
[0091]
The present invention has one feature in that a voltage suppression means is provided in order to suppress an increase in voltage generated between both ends of the electrostatic adsorption film 22 due to the application of the pulse bias and to enhance the effect of the pulse bias. .
[0092]
As an example of the voltage suppressing means, a change in voltage during one cycle of the bias voltage (V_cm) Is the magnitude of the pulse bias voltage (V_pIt is good to constitute so that it becomes 1/2 or less. Specifically, the electrostatic capacitance film made of a dielectric provided on the surface of the lower electrode 15 is reduced in thickness, or the dielectric is made of a material having a high dielectric constant, thereby reducing the capacitance of the dielectric. There are ways to increase.
[0093]
Alternatively, as another voltage suppression means, the voltage V_cmThere is also a method to suppress the rise of Furthermore, a method of separately providing the electrostatic adsorption circuit and the pulse bias voltage application circuit at different positions, for example, an electrode opposite to the electrode on which the sample is arranged and held, or a third electrode provided separately is considered. It is done.
[0094]
Next, using FIG. 7 to FIG. 13, a change in voltage (V) generated between both ends of the electrostatic adsorption film during one cycle of the pulse bias, which should be provided by the voltage suppressing means in the present invention._cm) And the pulse bias voltage will be described in detail.
[0095]
First, an example of a desirable output waveform used in the pulse bias power supply 17 of the present invention is shown in FIG. In the figure, pulse amplitude: v_p , Pulse period: T₀ , Positive direction pulse width: T₁ And
[0096]
When the waveform of FIG. 7A is applied to a sample via a blocking capacitor and an electrostatic adsorption dielectric layer (hereinafter abbreviated as an electrostatic adsorption film), plasma is generated by another power source. FIG. 7B shows a potential waveform on the sample surface in the steady state.
However, DC component voltage of waveform: V_DC
Plasma floating potential: V_f
Maximum voltage during one cycle of voltage generated between both ends of the electrostatic adsorption film: V_cm And
[0097]
In FIG. 7B, V_f The portion (I) that is more positive voltage is a portion that mainly draws only the electron current, and V_f The more negative part is the part drawing the ionic current, V_f Is the part where electrons and ions are balanced (V_f Is usually several V to several tens V).
[0098]
In FIG. 7A and the following description, it is assumed that the capacity of the blocking capacitor and the capacity of the insulator near the sample surface are sufficiently larger than the capacity of the electrostatic adsorption film (hereinafter abbreviated as electrostatic adsorption capacity). is doing.
V_cmIs expressed by the following equation (Equation 2).
[0099]
[Expression 2]

[0100]
Where q: (T₀-T₁) Ion current density flowing into the sample during the period (average value)
c: Electrostatic adsorption capacity per unit area (average value)
i_i : Ion current density, ε_r : Relative permittivity of electrostatic adsorption film
d: film thickness of the electrostatic adsorption film ε₀ : Dielectric constant in vacuum (constant)
K: Electrode adsorption film electrode coverage (≦ 1)
8 and 9, the pulse duty ratio: (T₁/ T₀) T remains constant₀ The potential waveform on the sample surface and the probability distribution of the ion energy when V is changed are shown. However, T₀₁, T₀₂: T₀₃: T₀₄: T₀₅= 16: 8: 4: 2: 1.
[0101]
As shown in (1) of FIG.₀ Is too large, the potential waveform on the sample surface deviates greatly from the rectangular wave and becomes a triangular wave, and the ion energy has a constant distribution from low to high as shown in FIG.
[0102]
As shown in (2) to (5) of FIG.₀ (V_cm/ V_p ) Becomes a value smaller than 1, and the ion energy distribution becomes narrower.
[0103]
8 and 9, T₀= T₀₁, T₀₂: T₀₃: T₀₄: T₀₅Is
(V_cm/ V_p ) = 1, 0.63, 0.31, 0.16, 0.08. Next, pulse off (T₀-T₁) Period and maximum voltage V in one cycle of voltage generated between both ends of the electrostatic adsorption film_cmThe relationship is shown in FIG.
[0104]
As an electrostatic adsorption film, alumina containing titanium oxide having a thickness of 0.3 mm (ε_r= 10), when about 50% of the electrode is coated (K = 0.5), the ion current density i_i = 5mA / cm² V in medium density plasma_cmThe change in the value is shown by the thick line (standard condition line) in FIG.
[0105]
As is apparent from FIG. 10, the pulse is turned off (T₀-T₁) As the period increases, the voltage V generated across the electrostatic adsorption film_cmIs a proportionally larger value, and the normally used pulse voltage v_p That's it.
[0106]
For example, in a plasma etching apparatus, due to damage, selectivity to the base or mask, shape, etc.
For gate etching, 20 volts ≤ v_p ≦ 100volt
For metal etching, 50 volts ≤ v_p ≦ 200volt
For oxide film etching, 250 volts ≤ v_p ≦ 1000volt
Limited to
[0107]
(V_cm / V_p ) ≦ 0.5 if the condition is satisfied, (T₀-T₁) Is as follows.
In gate etching (T₀-T₁) ≦ 0.15μs
In metal etching (T₀-T₁) ≦ 0.35μs
In oxide film etching (T₀-T₁) ≦ 1.2μs
By the way, T₀ When is close to 0.1 μs, the impedance of the ion sheath approaches or becomes less than that of the plasma, so that unnecessary plasma is generated and the bias power source is not effectively used for accelerating ions. For this reason, since the controllability of ion energy by the bias power supply deteriorates, T₀ Is 0.1 μs or more, preferably 0.2 μs or more.
[0108]
Therefore, v_pIn a gate etcher or the like that can keep the film low, the material of the electrostatic adsorption film is a material having a high relative dielectric constant of 10 to 100 (for example, Ta₂O_ThreeΕ_r= 25), and the film thickness should be thin, for example, 10 μm to 400 μm, preferably 10 μm to 100 μm without reducing the withstand voltage.
[0109]
FIG. 10 shows V when the capacitance c per unit area is increased by 2.5 times, 5 times, and 10 times, respectively._cmThe values of are also shown. Even if the electrostatic adsorption film is improved, the improvement of the capacitance c several times is considered to be the limit at present._cm≦ 300 volt, c ≦ 10c₀Then,
0.1 μs ≦ (T₀-T₁) ≦ 10 μs.
The effective part for plasma treatment by ion acceleration is (T₀-T₁) And pulse duty (T₁/ T₀) Is preferably as small as possible.
[0110]
As the efficiency of plasma treatment, taking into account the time average (V_DC/ V_pFIG. 11 shows an estimate in (). (T₁/ T₀) Is reduced and (V_DC/ V_p) Is preferably increased.
[0111]
0.5 ≦ (V_DC/ V_p) And the following conditions (V_cm/ V_p ) ≦ 0.5, the pulse duty is (T₁/ T₀) ≦ 0.4.
[0112]
Pulse duty (T₁/ T₀) Is more effective for controlling the ion energy, but if it is made smaller than necessary, the pulse width T1 becomes a small value of about 0.05 μs and contains many frequency components of several tens of MHz. Separation from high-frequency components for plasma generation becomes difficult. As shown in FIG. 11, 0 ≦ (T₁/ T₀) ≤ 0.05 (V_DC/ V_p) Decreases slightly and (T₁/ T₀) 0.05 or more, no particular problem occurs.
[0113]
Here, in FIG. 12, as an example of gate etching, etching rates ESi and ESiO between silicon and the underlying oxide film when chlorine gas 1.3 Pa is turned into plasma.₂The ion energy dependence of is shown. The etching rate ESi of silicon becomes a constant value at low ion energy. When the ion energy is about 10 V or more, ESi increases as the ion energy increases. On the other hand, the etching rate ESiO of the underlying oxide film₂Is 0 when the ion energy is about 20 V or less, and when it exceeds about 20 V, ESiO is combined with the ion energy.₂Will increase.
[0114]
As a result, when the ion energy is about 20 V or less, the selection ratio ESi / ESiO with the substrate is low.₂There is a region where becomes ∞. When the ion energy is about 20 V or more, the selection ratio ESi / ESiO with the underlying layer₂Decreases rapidly with increasing ion energy.
[0115]
FIG. 13 shows an oxide film (SiO2) which is a kind of insulating film.₂ , BPSG, HISO, etc.)_FourF₈Etching rate ESiO between oxide film and silicon when gas of 1.0 Pa is turned into plasma₂And the ion energy distribution of ESi is shown.
[0116]
Oxide etching rate ESiO₂Becomes negative at low ion energies and produces a deposit. ESiO near 400V ion energy₂Rises rapidly to positive and then gradually increases. On the other hand, the etching rate ESi of the underlying silicon is ESiO.₂At higher ion energies, it gradually increases from (-) (etching) to (+) (etching).
[0117]
As a result, ESiO₂Near the change from (-) to (+)₂/ ESi becomes ∞, and beyond that, ESiO₂/ ESi decreases rapidly with increasing ion energy.
[0118]
In FIGS. 12 and 13, ESi and ESiO are applied to the actual process.₂Value, ESi / ESiO₂And ESiO₂In consideration of the value of / ESi, the bias power supply is adjusted to set the ion energy to an appropriate value.
[0119]
In addition, if the ion energy is changed before and after the just etch, priority is given to the magnitude of the etching rate until just etching (etching until the base film appears), and after the just etching, the magnitude of the selection ratio is given priority. Good characteristics can be obtained.
[0120]
The characteristics shown in FIGS. 12 and 13 are characteristics when the energy distribution of ions is limited to a narrow portion. Since each etching rate when the ion energy distribution is wide is the time average value, it cannot be set to an optimum value, and the selection ratio is greatly reduced.
[0121]
According to experiments, (V_DC/ V_p) Is about 0.3 or less, the spread of ion energy is about ± 15% or less, and a high selection ratio of 30 or more was obtained even in the characteristics of FIGS. Also, (V_DC/ V_p) ≦ 0.5, the selectivity and the like can be improved as compared with the conventional sine wave bias method.
[0122]
Thus, the voltage change (V) during one cycle of the pulse voltage generated between both ends of the electrostatic adsorption film._cmAs a voltage suppression means for suppressing_cmIs the magnitude of the pulse bias voltage v_pIt is preferable that the thickness of the dielectric electrostatic chuck film 22 provided on the surface of the lower electrode 15 is reduced, or the dielectric is made to have a dielectric constant. By using a large material, the capacity of the dielectric can be increased. Alternatively, the period of the pulse bias voltage is shortened to 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs (repetition frequency: corresponding to 0.2 MHz to 5 MHz), and pulse duty (T₁/ T₀) 0.05 ≦ (T₁/ T₀) ≦ = 0.4 to suppress the voltage change at both ends of the electrostatic adsorption film.
[0123]
Alternatively, the voltage V generated between both ends of the electrostatic adsorption film by combining the thickness of the electrostatic adsorption film of the dielectric, some of the dielectric constant of the dielectric and the period of the pulse bias voltage._cmChange as described above (V_cm/ V_p ) ≦ 0.5 may be satisfied.
[0124]
Next, the vacuum processing chamber of FIG.₂, SiN, BPSG, etc.) will be described.
[0125]
As gas, C_FourF₈: 1 to 5%, Ar: 90 to 95%, O₂: 0-5%
Or C_FourF₈: 1 to 5%, Ar: 70 to 90%, O₂: 0 to 5%, CO: 10 to 20%. As the high frequency power source 16 for plasma generation, a higher frequency than conventional one, for example, 40 MHz is used, and stabilization of discharge in a low gas pressure region of 1 to 3 Pa is measured.
[0126]
Note that when the dissociation more than necessary proceeds due to the high frequency of the plasma source high frequency power supply 16, the output of the high frequency power supply 16 is on / off or level modulated by the high frequency power supply modulation signal source 161. At a high level, generation of ions is more active than generation of radicals, and at a low level, generation of radicals is more active than generation of ions. The on time (or high level at the time of level modulation) is about 5 to 50 μs, the off time (or low level at the time of level modulation) is about 10 to 100 μs, and the period is about 20 μs to 150 μs. As a result, unnecessary dissociation can be prevented and a desired ion-radical ratio can be obtained.
[0127]
Further, the modulation cycle of the high frequency power source for plasma source is usually longer than the cycle of the pulse bias. Therefore, the selection ratio can be improved by optimizing the phase between the two by setting the modulation period of the high frequency power source for the plasma source to an integral multiple of the period of the pulse bias.
[0128]
On the other hand, by applying a pulse bias voltage, ions in plasma are accelerated and perpendicularly incident on the sample, thereby controlling ion energy. As the pulse bias power source 17, for example, pulse period: T = 0.65 μs, pulse width: T₁= 0.15 μs, pulse amplitude: V_pBy using a power supply of = 800 V, the ion energy distribution width becomes ± 15% or less, and plasma processing with a good characteristic of 20 to 50 as a selection ratio with the underlying Si or SiN becomes possible.
[0129]
Next, a two-electrode type plasma etching apparatus according to another embodiment of the present invention will be described with reference to FIG. This embodiment has the same configuration as shown in FIG. 1 except that the lower electrode 15 holding the sample 40 has a configuration including a monopolar electrostatic chuck 20. A dielectric layer 22 for electrostatic attraction is provided on the upper surface of the lower electrode 15, and the positive side of the DC power source 23 is connected to the lower electrode 15 via a coil 24 for cutting high frequency components. A pulse bias power source 17 that supplies a positive pulse bias of 20 V to 1000 V is connected via a blocking capacitor 19.
[0130]
Discharge confining rings 37A and 37B are installed around the processing chamber 10 to improve the plasma density and minimize the deposits of unnecessary deposits on portions outside the discharge confining rings 37A and 37B. Let me. In the discharge confinement rings 37A and 37B in FIG. 14, the diameter of the bank portion of the discharge confinement ring 37A on the lower electrode side is smaller than the diameter of the bank portion of the discharge confinement ring 37B on the upper electrode side. The distribution of reaction products around the sample is made uniform.
[0131]
As a material for the discharge confinement rings 37A and 37B, a semiconductor or a conductor such as carbon, silicon or SiC is used at least on the side facing the processing chamber. The lower electrode side ring 37A is connected to a discharge confinement ring bias power source 17A of 100K to 13.56 MHz via a capacitor 19A, and a part of the power of the high frequency power source 16 is connected to the upper electrode side ring 37B. It is configured so as to be applied, and it reduces deposition of deposits on the rings 37A and 37B due to the sputtering effect of ions and also has an effect of removing fluorine.
[0132]
14A and 14C are insulators made of alumina or the like, and 13B is an insulator having conductivity such as SiC, glassy carbon, or Si.
[0133]
When the conductivity of the rings 37A and 37B is low, a high-frequency power is generated from the surfaces of the rings 37A and 37B by incorporating a conductor such as a metal in the rings 37A and 37B and reducing the distance between the ring surface and the internal conductor. It is easy to radiate, and the sputtering effect can be enhanced.
[0134]
Normally, only the periphery of the upper electrode cover 30 is fixed to the upper electrode 12 with bolts 250. A gas is supplied from the gas supply unit 36 to the upper electrode cover 30 through the gas introduction chamber 34, the gas diffusion plate 32, and the upper electrode 12. The hole provided in the upper electrode cover 30 has a diameter of 0.3 to 1 mm in order to make it difficult to generate abnormal discharge in the hole, and the gas pressure above the upper electrode cover 30 is a number of 1 atm. From 1 to 1/10. For example, a force of about 100 kg or more is applied to the upper electrode cover 30 having a diameter of 300 mm as a whole. Therefore, the upper electrode cover 30 is convex with respect to the upper electrode 12, and a gap of several hundred microns or more is generated near the center.
[0135]
In this case, when the frequency of the high-frequency source 16 is increased by about 30 MHz or more, the lateral resistance of the upper electrode cover 30 cannot be ignored, and a phenomenon that the plasma density in the vicinity of the center portion is lowered is caused. In order to improve this, the upper electrode cover 30 may be fixed to the upper electrode 12 near the center other than the periphery. In the example of FIG. 14, several places near the center of the upper electrode cover 30 are fixed to the upper electrode 12 with bolts 251 of a semiconductor such as SiC or carbon or an insulator such as alumina, and a high frequency applied from the upper electrode 12 side. The distribution of is uniform.
[0136]
The method of fixing at least the center portion of the upper electrode cover 30 to the upper electrode 12 is not limited to the bolt 251 at all, and the upper electrode cover 30 and the upper electrode 12 are bonded to the entire surface with a substance having an adhesive action. Or at least at the center portion.
[0137]
In the embodiment of FIG. 14, a sample 40, which is an object to be processed, is placed on the lower electrode 15 and is electrostatically charged by a positive charge from the electrostatic chuck 20, that is, a DC power source 23, and a negative charge supplied from plasma. It is adsorbed by the Coulomb force generated between both ends of the adsorption film 22.
[0138]
The operation of this apparatus is the same as that of the two-electrode type plasma etching apparatus shown in FIG. 1, and when performing the etching process, the sample 40 to be processed is placed on the sample stage 15 and held by electrostatic force, While the processing gas is introduced into the processing chamber 10 from the gas supply system 36 at a predetermined flow rate, the pressure in the processing chamber 10 is reduced to the processing pressure of the sample, 0.5 to 4.0 Pa by evacuating the vacuum with the vacuum pump 18. Exhaust under reduced pressure. Next, the high frequency power supply 16 is turned on, and a plasma is generated by applying a high frequency voltage of 20 MHz to 500 MHz, preferably 30 MHz to 100 MHz, between the electrodes 12 and 15. On the other hand, a positive pulse bias voltage of 20 V to 1000 V and a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs is applied to the lower electrode 15 from the pulse bias power source 17 to control the plasma in the processing chamber 10. The sample 40 is etched.
[0139]
By applying such a pulse bias voltage, ions in the plasma or ions and electrons are accelerated and perpendicularly incident on the sample, thereby performing highly accurate shape control or selectivity control. The characteristics required for the pulse bias power source 17 and the electrostatic adsorption film 22 are the same as those in the embodiment of FIG.
[0140]
Next, another embodiment of the present invention will be described with reference to FIGS. This embodiment has the same configuration as the two-electrode type plasma etching apparatus shown in FIG. 1, but the configuration of the magnetic field forming means 200 is different. The core 201 of the magnetic field forming means 200 is eccentric and is configured to rotate at a speed of several to several tens of revolutions per minute driven by the motor 204 about the axis corresponding to the center position of the sample 40. . The core 201 is grounded.
In order to perform plasma processing of the entire surface of the sample with high accuracy, the electron cyclotron resonance effect is compared with that in the center so that the generation of plasma in the periphery of the sample or in the vicinity of the outside of the sample is higher than in the vicinity of the center of the sample. It is better to enlarge the part or outside of it. However, in the embodiment of FIG. 1, as shown in FIG. 6, there is no ECR region near the center of the sample, and the plasma density may become too low near the center.
[0141]
In the embodiment of FIG. 15, the magnetic field distribution changes as the eccentric core 201 of the magnetic field forming means 200 rotates, and the time t = 0, t = T near the center of the sample.₀Then, the ECR region is formed at a position lower than the sample surface, and time t = 1 / 2T₀Then, it is formed at a high position from the sample surface. As a result of the core 201 rotating at a speed of several to several tens of revolutions per minute, as shown in FIG. 17, the average value of the magnetic field strength in the direction parallel to the sample surface at the intermediate part of both electrodes is almost equal to the time averaging by the rotation. It becomes the same value. That is, the ECR region is formed at substantially the same height from the sample surface except for the periphery of the sample.
[0142]
In addition, as shown by the alternate long and short dash line in the core 201 part of FIG. 15, the core constituting the magnetic circuit on the side close to the eccentric central part is thin, and the core constituting the far side magnetic circuit is If the thickness is increased, the uniformity of the magnetic field strength is further improved.
[0143]
Next, another embodiment of the present invention will be described with reference to FIGS. This embodiment has the same configuration as the two-electrode type plasma etching apparatus shown in FIG. 15, but the configuration of the magnetic field forming means 200 is different. The core 201 of the magnetic field forming unit 200 has a concave edge 201A at a position corresponding to the center of the processing chamber, and an edge 201B at the side of the processing chamber and other edges. Due to the action of the concave edge 201A, the magnetic flux B has an inclined directional component. As a result, the distribution of the magnetic field changes, and as shown in FIG. 19, the magnetic field intensity of the component parallel to the sample surface is made more uniform than in the embodiment of FIG.
[0144]
Next, another embodiment of the present invention will be described with reference to FIG. This embodiment has the same configuration as the two-electrode type plasma etching apparatus shown in FIG. 15, but the configuration of the magnetic field forming means 200 is different. The core 201 of the magnetic field forming means 200 is a fixed type, and constitutes a magnetic circuit together with the core 205 disposed at a position corresponding to the center of the processing chamber. The core 205, together with the insulator 203, rotates around an axis passing through the center of the edge 201A. With this configuration, the average position of the ECR region in the vicinity of the center of the sample is formed at substantially the same position from the sample surface, as in the embodiment of FIG. That is, the ECR region is formed at almost the same height from the sample surface over the entire surface of the sample.
[0145]
Next, a two-electrode type plasma etching apparatus according to another embodiment of the present invention will be described with reference to FIGS. In this embodiment, the magnetic field forming means 200 includes two pairs of coils 210 and 220 around the processing chamber 10, and the direction of the magnetic field placed on each pair of coils is indicated by arrows 1, 2, 3, and 4. By sequentially switching, a rotating magnetic field is formed. The center position OO of the coils 210 and 220 is located closer to the upper electrode 12 than the middle between the electrodes 12 and 15. Thus, the magnetic field intensity on the sample 40 is configured to be 30 gauss or less, preferably 15 gauss or less.
By appropriately selecting the positions and outer diameters of the coils 210 and 220, the intensity distribution of the magnetic field can be adjusted so that the generation of plasma in the periphery of the sample or in the vicinity of the outside thereof is further increased.
[0146]
Next, a two-electrode type plasma etching apparatus according to another embodiment of the present invention will be described with reference to FIGS. In this embodiment, the magnetic field forming means 200 includes a pair of coils 210 ′ arranged in an arc shape in the horizontal plane along the circumference of the circular processing chamber 10. By controlling the current flowing through the pair of coils 210 ', the polarity of the magnetic field is changed at regular intervals as shown by arrows (1) and (2) in FIG.
[0147]
As indicated by a broken line in FIG. 24, the magnetic flux B spreads in the central portion of the processing chamber in the vertical plane, so that the magnetic field strength in the central portion of the processing chamber decreases. However, since the pair of coils 210 ′ are curved along the processing chamber, the magnetic flux B is collected at the center of the processing chamber in the horizontal plane. Therefore, the strength of the magnetic field in the center of the processing chamber can be increased compared to the embodiment of FIG. That is, in the embodiment of FIG. 23, a decrease in the magnetic field strength in the central portion of the processing chamber can be suppressed compared to the embodiment of FIG. 22, and the uniformity of the magnetic field strength on the sample mounting surface of the sample stage is improved. be able to.
[0148]
In addition, the drift effect of E × B is reduced by changing the polarity of the magnetic field at regular intervals.
[0149]
As the magnetic field forming means 200, two pairs of coils similar to the embodiment of FIG.
[0150]
Further, as the magnetic field forming means 200, instead of the arc-shaped coil 210 ′, as shown in FIG. 25, a convex type that is a combination of a plurality of linear coil portions arranged along the circumference of the circular processing chamber 10 is used. The coil 210 'may be used. Also in this case, in the horizontal plane, the magnetic flux B is collected at the center of the processing chamber, and the same effect as the embodiment of FIG. 23 can be obtained.
[0151]
Furthermore, as in the embodiment of FIG. 26, the central axis of the pair of coils may be disposed in an inclined manner in the vertical plane so as to approach the sample surface at the center of the processing chamber. According to this embodiment, the magnetic field strength at the center of the processing chamber can be increased and the magnetic field strength at the periphery of the processing chamber can be decreased, so that the uniformity of the magnetic field strength on the sample mounting surface of the sample stage can be improved. . In order to make the magnetic field strength uniform, the inclination angle θ of the central axis of the coil is preferably in the range of 5 to 25 degrees.
[0152]
In addition, as shown in FIG. 27, a coil 210B is installed in the vicinity of a pair of coils 210A, and by controlling the currents of the two sets of coils, the gradient of the magnetic field in the vicinity of the ECR resonance position is set together with the ECR resonance position. It is also possible to change the width of the ECR resonance region. By optimizing the width of the ECR resonance region for each process, an ion / radical ratio suitable for each process can be obtained.
[0153]
It should be noted that the uniformity of the magnetic field strength distribution and the control characteristics can be further improved by appropriately combining the embodiments shown in FIGS. 23 to 27 as necessary.
[0154]
Next, a two-electrode type plasma etching apparatus according to another embodiment of the present invention will be described with reference to FIGS. In this embodiment, a part of the processing chamber wall is made of a conductor and grounded. On the other hand, the magnetic field forming unit 200 includes coils 230 and 240 around and above the processing chamber 10. The direction of the magnetic flux B formed by the coil 230 and the direction of the magnetic flux B ′ formed by the coil 230 cancel each other at the center of the processing chamber 10 as indicated by arrows, and at the periphery and outside of the processing chamber 10. It is comprised so that it may mutually overlap. As a result, the intensity distribution of the magnetic field on the sample surface is as shown in FIG. Moreover, in the mounting surface portion of the sample 40, the direction of the electric field component and the direction of the magnetic field component between the upper electrode 12 and the lower electrode 15 are parallel. On the other hand, in the outer portion of the mounting surface of the sample 40, a vertical magnetic field component perpendicular to the horizontal electric field component is generated in the peripheral portion of the upper electrode 12 or the portion of the upper electrode 12 and the processing chamber wall.
[0155]
Therefore, according to the embodiment of FIG. 28, the cyclotron resonance effect of electrons near the center of the sample can be lowered, and the generation of plasma around the sample or near the outside can be enhanced. In this way, the plasma density distribution can be made uniform by further increasing the generation of plasma in the periphery of the sample or in the vicinity of the outside thereof.
[0156]
Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, in the two-electrode type plasma etching apparatus shown in FIG. 1, the high-frequency power f1 applied from the high-frequency power supply 16 to the upper electrode 12 is not used to obtain sufficient ion energy. By applying a high frequency f3 of, for example, about 1 MHz or less as a bias to the upper electrode 12, the ion energy is increased by about 100 to 200V. Reference numerals 164 and 165 denote filters.
[0157]
Next, an embodiment of the present invention in a magnetic fieldless two-electrode type plasma etching apparatus will be described with reference to FIG.
[0158]
As described above, in order to improve the fine workability of the sample, it is preferable to use a high frequency power source 16 for generating plasma and stabilize the discharge in the low gas pressure region. In the embodiment of the present invention, the processing pressure of the sample in the processing chamber 10 is set to 0.5 to 4.0 Pa. By reducing the gas pressure in the processing chamber 10 to a low pressure of 40 mTorr or less, collision of ions in the sheath is reduced. Therefore, when the sample 40 is processed, the directionality of ions is increased and vertical fine processing is possible. . At 5 mTorr or less, in order to obtain the same processing speed, the exhaust device and the high-frequency power source increase in size, and dissociation more than necessary occurs due to an increase in the electron temperature, which tends to deteriorate the characteristics.
[0159]
In general, between the frequency of the power source for plasma generation using a pair of two electrodes and the lowest gas pressure at which stable discharge is performed, the higher the frequency of the power source, the higher the frequency between the electrodes, as shown in FIG. There is a relationship that the stable discharge minimum gas pressure decreases as the distance increases. In order to avoid adverse effects such as deposition on the surrounding walls and the discharge confinement ring 37 and to effectively function the effect of removing fluorine and oxygen by the upper electrode cover 30, the susceptor cover 39 and the resist in the sample, etc., the highest gas The distance between the electrodes is preferably about 50 mm or less, corresponding to 25 times or less of the mean free process at a pressure of 40 mTorr. Further, if the distance between the electrodes is not more than about 2 to 4 times (4 mm to 8 mm) of the mean free path at the maximum gas pressure (40 mTorr), stable discharge becomes difficult.
[0160]
In the embodiment shown in FIG. 31, since high frequency power of 20 MHz to 500 MHz, preferably 30 MHz to 200 MHz is used as the plasma generating high frequency power supply 16, the gas pressure in the processing chamber is set to a low pressure of 0.5 to 4.0 Pa. However, stable plasma can be obtained, and fine workability can be improved. Further, by using such high frequency power, the dissociation of the gas plasma is improved, and the selectivity control during sample processing is improved.
[0161]
In the embodiment of the present invention described above, there is a possibility that interference may occur between the output of the pulse bias power supply and the output of the plasma generating power supply. Therefore, this measure is described below.
[0162]
First, pulse width: T₁, Pulse period: T₀In an ideal rectangular pulse having an infinite rise / fall rate, f ≦ 3f as shown in FIG.₀(F₀= (1 / T₁)) About 70 to 80% of power is included in the frequency range. Since the actually applied waveform has a finite rise / fall rate, the power convergence is further improved, and f ≦ 3f₀In the frequency range, about 90% or more of electric power can be included.
[0163]
3f₀ In order to uniformly apply a pulse bias having a high frequency component to the sample surface, a counter electrode substantially parallel to the sample is provided, and 3f obtained by the following equation (3)₀F ≦ 3f₀ It is desirable to ground the frequency components in a certain range.
[0164]
[Equation 3]

[0165]
The embodiment shown in FIG. 31 takes measures against interference between the pulse bias power supply output and the plasma generation power supply output. That is, in this plasma etching apparatus, a plasma generating high frequency power supply 16 is connected to the upper electrode 12 facing the sample 40. In order to set the upper electrode 12 to the ground level of the pulse bias, the frequency f of the high frequency power source 16 for generating plasma is used.₁ The above 3f₀ Larger and f = f₁ A band eliminator 141 having a large impedance in the vicinity and a low impedance at other frequencies is connected between the upper electrode 12 and the ground level.
[0166]
On the other hand, f = f₁ A bandpass filter 142 having a low impedance in the vicinity and a high impedance at other frequencies is installed between the sample stage 15 and the ground level. If such a configuration is used, interference between the output of the pulse bias power source 17 and the output of the plasma generating power source 16 can be suppressed to a level without any problem, and a good bias can be applied to the sample 40.
[0167]
FIG. 34 shows an example in which the present invention is applied to a plasma etching apparatus of the inductively coupled discharge method and the non-magnetic field type among the external energy supply discharge methods. 52 is a planar coil, and 54 is a high-frequency power source for applying a high-frequency voltage of 10 MHz to 250 MHz to the planar coil. Compared with the method shown in FIG. 10, the inductively coupled discharge method can generate stable plasma at a low frequency and a low pressure. On the other hand, since dissociation easily proceeds, as shown in FIG. 1, the output of the high frequency power source 1 can be modulated by the high frequency power source modulation signal source 161 to prevent unnecessary dissociation. The processing chamber 10 as a vacuum container includes a sample stage 15 on which a sample 40 is placed on an electrostatic adsorption film 22.
[0168]
When performing the etching process, the sample 40 to be processed is placed on the sample stage 15 and held by an electrostatic force, while a processing gas is introduced into the processing chamber 10 from a gas supply system (not shown) at a predetermined flow rate. On the other hand, the pressure in the processing chamber 10 is reduced to 0.5 to 4.0 Pa by evacuating with a vacuum pump. Next, a high frequency voltage of 13.56 MHz is applied to the high frequency power source 54 to generate plasma in the processing chamber 10. The sample 40 is etched using this plasma. On the other hand, at the time of etching, a pulse bias voltage having a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs is applied to the lower electrode 15. As described in the embodiment of FIG. 1, the range of the amplitude of the pulse bias voltage varies depending on the film type. By applying this pulse bias voltage, ions in the plasma are accelerated and perpendicularly incident on the sample, thereby performing highly accurate shape control or selection ratio control. Thereby, even if the resist mask pattern of a sample is a very fine thing, a highly accurate etching process can be performed.
[0169]
As shown in FIG. 35, in the inductively coupled discharge type magnetic fieldless type plasma etching apparatus, a Faraday shield plate 53 having a gap and a thin thickness of 0.5 mm to 5 mm are provided on the processing chamber 10 side of the induction high frequency output. An insulating plate 54 for protecting the shield plate may be installed and the Faraday shield plate may be grounded. By installing the Faraday shield plate 53, the capacitance component between the coil and the plasma is reduced, and the energy of ions hitting the quartz plate under the coil 52 and the shield plate protection insulating plate 54 in FIG. 34 can be reduced. In addition, it is possible to reduce the damage to the insulating plate and to prevent foreign matters from being mixed into the plasma.
[0170]
Further, since the Faraday shield plate 53 also serves as a ground electrode of the pulse bias power supply 17, a pulse bias can be applied uniformly between the sample 40 and the Faraday shield plate 53. In this case, a filter installed on the upper electrode or the sample stage 15 is unnecessary.
[0171]
FIG. 36 is a front view of a longitudinal section of a part of an apparatus in which the present invention is applied to a microwave plasma processing apparatus. A pulse bias power source 17 and a DC power source 13 are connected to the lower electrode 15 as the sample stage 15 on which the sample 40 is placed on the electrostatic adsorption film 22. 41 is a magnetron as a microwave oscillation source, 42 is a microwave waveguide, and 43 is a quartz plate for vacuum-sealing the processing chamber 10 and supplying the microwave to the processing chamber 10. 47 is a first solenoid coil for supplying a magnetic field, and 48 is a second solenoid coil for supplying a magnetic field. A processing gas supply system 49 supplies a processing gas for performing processing such as etching and film formation into the processing chamber 10. The processing chamber 10 is evacuated by a vacuum pump (not shown). The characteristics required for the pulse bias power supply 17 and the electrostatic chuck 20 are the same as those of the embodiment of FIG.
[0172]
When performing the etching process, the sample 40 to be processed is placed on the sample stage 15 and held by an electrostatic force, while the processing gas is introduced from the gas supply system 49 into the processing chamber 10 at a predetermined flow rate, while the other vacuum pump The pressure in the processing chamber 10 is reduced to 0.5 to 4.0 Pa by evacuation. Next, the magnetron 41 and the first and second solenoid coils 47 and 48 are turned on, and the microwave generated by the magnetron 41 is guided from the waveguide 42 to the processing chamber 10 to generate plasma. An etching process is performed on the sample 40 using this plasma. On the other hand, at the time of etching, a pulse bias voltage having a period of 0.1 μs to 10 μs, preferably 0.2 μs to 5 μs is applied to the lower electrode 15.
[0173]
By applying such a pulse bias voltage, ions in the plasma are accelerated to the sample and incident vertically, thereby performing highly accurate shape control or selection ratio control. Thereby, even if the resist mask pattern of the sample is extremely fine, high-precision etching processing corresponding to the mask pattern can be performed by vertical incidence.
[0174]
In the plasma etching apparatus of the present invention shown in FIG. 1 and subsequent figures, the circuit can be configured in common by generating the DC voltage of the electrostatic adsorption circuit and the pulse voltage of the pulse bias power supply circuit in a superimposed manner. In addition, the electrostatic adsorption circuit and the pulse bias power supply circuit can be provided separately on separate electrodes so that the pulse bias does not affect the electrostatic adsorption.
[0175]
Instead of the electrostatic adsorption circuit in the embodiment of the plasma etching apparatus shown in FIG. 1, other adsorption means such as a vacuum adsorption means can be used.
[0176]
The plasma processing apparatus having the electrostatic adsorption circuit and the pulse bias voltage application circuit of the present invention described above is not limited to the etching process described above by adding a change such as introducing a CVD gas instead of the etching gas. The present invention can also be applied to a plasma processing apparatus such as a CVD apparatus.
[0177]
Next, according to another embodiment of the present invention shown in FIG. 37, a plasma etching apparatus which improves the conventional defects, controls the amount and quality of ion and radical generation, and enables ultrafine plasma processing. Examples will be described.
[0178]
That is, a place where the first plasma generation is performed at a location different from the vacuum processing chamber on the upstream side of the vacuum processing chamber in which the sample is installed, the metastable atoms generated there are injected into the vacuum processing chamber, The second plasma is generated in the vacuum processing chamber. In addition to the plasma etching apparatus shown in FIG. 1, an ion / radical source gas supply unit 60 and a metastable atom generation plasma generation chamber 62 are provided. In addition to the route for introducing a gas containing metastable atoms into the vacuum processing chamber, the upper electrode 12 is provided with an introduction route connected to the gas supply unit for the ion / radical source.
[0179]
The features of this embodiment are as follows.
(1) The gas supplied from the metastable atom generating gas supply unit 36 is converted into plasma by applying high-frequency power in the metastable atom generating plasma generation chamber 62 to generate a desired amount of metastable atoms in advance. Flow into chamber 10. In the metastable atom generation plasma generation chamber 62, the chamber pressure is set to a high pressure of several hundred mTorr to several tens of Torr in order to efficiently generate metastable atoms.
[0180]
(2) On the other hand, the gas from the ion / radical source gas supply unit 60 is caused to flow into the processing chamber 10.
[0181]
{Circle around (3)} A relatively low power high frequency is output from the plasma generating power source 16 to generate plasma in the processing chamber 10. By injection of metastable atoms, ions can be efficiently generated even with low energy electrons of about 5 eV or less, so that the electron temperature is low (about 6 eV or less, preferably about 4 eV or less) and high as about 15 eV or more. Plasma with significantly less energy electrons can be obtained. Therefore, the necessary amount and quality of the radical source gas can be secured without causing excessive dissociation. On the other hand, the amount of ions can be controlled by the amount of metastable atoms generated in the plasma generation chamber 62 for generating metastable atoms and the ion source gas from the ion / radical source gas supply unit 60.
[0182]
Since the quality and amount of ions and radicals can be controlled in this way, good performance can be obtained even in extremely fine plasma processing. As the radical source gas, CHF_Three, CH₂F₂, C_FourF₈Or CF_FourFluorocarbon gas such as gas containing C and H as necessary (C₂H_Four, CH_Four, CH_ThreeOH etc.) can be mixed. As the metastable atom generating gas, one or two kinds of rare gas based gas is used. By using a rare gas having the following properties as the ion source gas, ions can be generated efficiently.
[0183]
The ionization potential of the ion source gas is lower than the energy level of the metastable atom, or the ionization potential of the ion source gas is higher, but the difference is smaller (about 5 eV or less). Is used.
[0184]
Although the performance is lowered, it is not particularly added as the ion source gas, and the above-mentioned metastable atom generating gas or radical source gas can be substituted.
[0185]
Next, FIG. 38 shows another embodiment of the present invention for controlling the quality and quantity of ion and radical generation. The basic idea is the same as in FIG. 37, but in FIG. 37, the distance between the metastable atom generation plasma chamber 62 and the vacuum processing chamber 10 is long, and the attenuation of the metastable atoms between them is large. This is an example implemented as a countermeasure. 41 is a magnetron as a microwave oscillation source, 42 is a microwave waveguide, 43 is a quartz plate for vacuum-sealing the first plasma generation chamber 45 and allowing microwaves to pass through, 44 Is a quartz plate for gas dispersion. In the first plasma generation chamber 45, plasma is generated by the microwave at a gas pressure of several hundreds mTorr to several tens Torr, and metastable atoms are generated.
[0186]
In FIG. 38, since the distance between the generation place of the metastable atoms and the vacuum processing chamber can be shortened as compared with FIG. 37, metastable atoms can be injected into the vacuum processing chamber at a high density. The amount of can be increased. The processing chamber 10 is maintained at a pressure of 5 to 50 mTorr, and a high frequency power supply 16 of 20 MHz or more is used to provide a power of 10 e to 11 sq.^ThreeThe ion source gas is ionized while avoiding the dissociation of CF 2 that requires 8 eV or more as the dissociation energy. As a result, on the surface of the sample 40, the following reaction assisted mainly by the incidence of ions accelerated at several hundred volts by the bias power source 17 proceeds.
SiO₂+ 2CF₂ → SiF_Four ↑ + 2CO ↑
Si and SiN used as the base material are CF₂In this case, the oxide film can be etched with high selectivity.
[0187]
CF₂The increase in F due to the partial dissociation of is reduced by the upper electrode cover 30 made of silicon, carbon, SiC or the like.
[0188]
As described above, by adjusting the radical source gas and the ion source gas, the ratio of ions to radicals in the processing chamber 10 can be controlled almost independently, and the reaction on the surface of the sample 40 can be controlled. It became easier to control to the desired one.
[0189]
The plasma processing apparatus including the electrostatic adsorption circuit and the pulse bias voltage application circuit according to the present invention is not limited to the etching process described above by adding a change such as introducing a CVD gas instead of the etching gas. It can also be applied to plasma processing apparatuses such as the above.
[0190]
Next, FIG. 39 shows another embodiment of the present invention in which ions and radicals are controlled independently. In FIG. 39, CHF_Three, CH₂F₂, C_FourF₈Or CF_FourFluorocarbon gas such as gas containing C and H as necessary (C₂H_Four, CH_ThreeOH, etc.) are mixed and put into the radical generating plasma generating chamber 62 via the valve 70 from the portion A in FIG.
[0191]
In the radical generating plasma generating chamber 62, the output of the RF power source 63 of several MHz or several tens of MHz is applied to the coil 65, plasma is generated at a gas pressure of several hundred mTorr to several tens of Torr, and CF2 radicals are mainly generated. Simultaneously generated CF_ThreeAnd F are reduced by the H component.
[0192]
Since it is difficult to greatly reduce the components such as CF and O in the radical generating plasma generating chamber 62, an unnecessary component removing chamber 65 is provided after this. Here, the inner wall of a material containing carbon or Si (carbon, Si, SiC, etc.) is installed, and unnecessary components are reduced or converted to another gas with less adverse effects. The outlet of the unnecessary component removal chamber 65 is connected to the valve 71 and CF.₂Supplies the main gas composition.
[0193]
Since a large amount of deposits such as deposits accumulate between the valve 70 and the valve 71, cleaning and replacement are necessary in a relatively short period of time. For this reason, it is connected to the exhaust device 74 via the valve 72 in order to facilitate the opening to the atmosphere and replacement, and to shorten the vacuum startup time at the time of restarting. The exhaust device 74 may also be used as an exhaust device for the processing chamber 10 or the like.
[0194]
An ion source gas (rare gas such as argon gas or xenon gas) B is supplied to the processing chamber through the valve 73 and connected to the outlet of the valve 71.
[0195]
The processing chamber 10 is maintained at a pressure of 5 to 40 mT, and is modulated by a high frequency power source 16 of 20 MHz or higher, and 5 eV, preferably 3 eV or less, from the 10th power to the 11th power / cm.^ThreeOf high density and low electron temperature plasma and requires 8 eV or more as dissociation energy₂The ionization of the ion source gas proceeds while avoiding the dissociation of the ion source. As a result, on the surface of the sample 40, the following reaction assisted mainly by the incidence of ions accelerated at several hundred volts by the bias power source 17 proceeds.
SiO₂+ 2CF₂  → SiF_Four  ↑ + 2CO ↑
Si and SiN used as the base material are CF₂In this case, the oxide film can be etched with high selectivity.
[0196]
CF₂The increase in F due to the partial dissociation of is reduced by the upper electrode cover 30 made of silicon, carbon, SiC or the like.
[0197]
As described above, by adjusting the radical source gas A and the ion source gas B, the ratio of ions to radicals in the processing chamber 10 can be controlled almost independently, and the surface of the sample 40 can be controlled. It became easier to control the reaction to the desired one. Further, unnecessary depot components and the like are eliminated in the unnecessary component removal chamber 65 and are not brought into the processing chamber 10 as much as possible. Therefore, the deposits in the processing chamber 10 are greatly reduced, and the processing chamber 10 is kept in the atmosphere. The frequency of cleaning after opening the door was also greatly reduced.
[0198]
Next, FIG. 40 shows another embodiment in which ions and radicals are controlled independently. Hexafluoropropylene oxide gas (CF_ThreeCFOCF₂, Hereinafter referred to as HFPO) from A through the heating pipe 66 through the valve 70, through the unnecessary component removal chamber 65 and the valve 71, mixed with the ion source gas B, and sent to the processing chamber 10. . In the heating pipe portion 66, HFPO is heated to 800 ° C. to 1000 ° C., and CF 2 is generated by the following thermal decomposition.
CF_ThreeCFOCF₂  → CF₂+ CF_ThreeCFO
CF_ThreeCFO is a relatively stable substance that is difficult to decompose, but partially decomposes to generate unnecessary O and F. Therefore, an unnecessary component removal chamber 65 is provided after the heating pipe portion 66 to remove unnecessary components or to have no adverse effect. It has been converted. Some CF_ThreeCFOCF₂Flows into the processing chamber 10 without being decomposed, but is not a problem because it does not dissociate in a plasma having a low electron temperature of 5 eV or less.
[0199]
The use of the valve 72 and the exhaust device 74 and the reaction in the processing chamber 10 are the same as in the case of FIG.
[0200]
The plasma processing apparatus including the electrostatic adsorption circuit and the pulse bias voltage application circuit according to the present invention is not limited to the etching process described above by adding a change such as introducing a CVD gas instead of the etching gas. It can also be applied to plasma processing apparatuses such as the above.
[0201]
【The invention's effect】
According to the present invention, it is possible to provide a plasma processing apparatus and a plasma processing method in which precise processing of a fine pattern is easy for a sample having a large diameter of φ300 mm or more and the selection ratio at the time of micro processing is improved. In addition, it is possible to provide a plasma processing apparatus capable of performing uniform and high-speed processing, particularly oxide film processing, over the entire surface of a large-diameter sample, and a processing method thereof.
[0202]
According to the present invention, the insulating film in the sample (for example, SiO 2₂, SiN, BPSG, etc.) can be provided. A plasma processing apparatus and a plasma processing method with improved plasma processing selectivity and the like can be provided.
[0203]
In addition, it is possible to provide a plasma processing apparatus and a plasma processing method which have good controllability and obtain a narrow ion energy distribution and improve the selectivity of plasma processing.
[0204]
In addition, when using a sample stage having a dielectric layer for electrostatic adsorption, there is provided a plasma processing apparatus and a plasma processing method that provide a narrow ion energy distribution with good controllability and improve the selectivity of plasma processing. can do.
[0205]
In addition, by independently controlling the quantity and quality of ions and radicals, the pressure in the processing chamber of the plasma processing equipment can be lowered, making it easy to precisely process fine patterns and improving the selectivity during fine processing. A plasma processing apparatus and a plasma processing method can be provided.
[0206]
Furthermore, by independently controlling the quantity and quality of ions and radicals, an insulating film (eg, SiO 2) in the sample can be obtained.₂, SiN, BPSG, etc.) can be provided. A plasma processing apparatus and a plasma processing method with improved plasma processing selectivity and the like can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an example of a change in plasma density when the frequency of a high-frequency power source that generates plasma is changed in a state where a magnetic field that causes electron cyclotron resonance is applied.
FIG. 3 is a diagram showing a state of energy gain k obtained by electrons from a high-frequency electric field during cyclotron resonance and when there is no resonance.
FIG. 4 shows magnetic field strength and ion acceleration voltage V induced in a sample when an upper electrode of a magnetron discharge electrode is grounded, a magnetic field B is applied to the lower electrode and a high frequency power is applied._DCIt is a figure which shows the relationship of dispersion | variation (DELTA) V of the induced voltage in a sample.
FIG. 5 is an explanatory diagram of magnetic field characteristics of the plasma etching apparatus of FIG. 1;
6 is an explanatory diagram of an ECR region of the plasma etching apparatus of FIG.
FIG. 7 is a diagram showing an example of a desirable output waveform used in the pulse bias power supply of the present invention.
FIG. 8: Pulse duty ratio: (T₁/ T₀) T remains constant₀ It is a figure which shows the electric potential waveform of the sample surface when changing, and the probability distribution of ion energy.
FIG. 9 shows that the pulse duty ratio remains constant and T₀ It is a figure which shows the electric potential waveform of the sample surface when changing, and the probability distribution of ion energy.
FIG. 10: Pulse off (T₀-T₁) Period and maximum voltage V in one cycle of voltage generated between both ends of the electrostatic adsorption film_cmIt is a figure which shows the relationship.
FIG. 11 shows pulse duty ratio and (V_DC/ V_p FIG.
FIG. 12 shows etching rates ESi and ESiO between silicon and an oxide film when chlorine gas is turned into plasma.₂It is a figure which shows the ion energy dependence.
FIG. 13 shows C as an example of etching of an oxide film._FourF₈Etching rate ESiO between oxide film and silicon when gas is turned into plasma₂It is a figure which shows the ion energy distribution of ESi.
FIG. 14 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
FIG. 15 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
FIG. 16 is an explanatory diagram of magnetic field distribution characteristics of the plasma etching apparatus.
17 is an explanatory diagram of an ECR region of the plasma etching apparatus of FIG.
FIG. 18 is a longitudinal sectional view of a plasma etching apparatus according to another embodiment of the present invention.
19 is an explanatory diagram of magnetic field distribution characteristics of the plasma etching apparatus of FIG.
FIG. 20 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
FIG. 21 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
22 is an explanatory diagram of magnetic field distribution characteristics of the plasma etching apparatus of FIG. 21. FIG.
FIG. 23 is a cross-sectional view of an essential part of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
24 is a longitudinal sectional view of the plasma etching apparatus of FIG. 23. FIG.
FIG. 25 is a diagram showing another embodiment of the magnetic field forming means.
FIG. 26 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
FIG. 27 is a longitudinal sectional view of a two-electrode type plasma etching apparatus according to another embodiment of the present invention.
FIG. 28 is a longitudinal sectional view of a two-electrode plasma etching apparatus according to another embodiment of the present invention.
29 is an explanatory diagram of magnetic field distribution characteristics of the plasma etching apparatus of FIG. 28. FIG.
FIG. 30 is a longitudinal sectional view of a two-electrode plasma etching apparatus according to another embodiment of the present invention.
FIG. 31 is a longitudinal sectional view of another embodiment in which the two-electrode plasma etching apparatus shown in FIG. 1 is improved.
FIG. 32 is a diagram showing the relationship between the frequency of the power source for plasma generation and the stable discharge minimum gas pressure.
FIG. 33 is a diagram showing the relationship between the frequency of the pulse bias power supply and the accumulated power.
FIG. 34 is a longitudinal sectional view of an example in which the present invention is applied to an inductively coupled discharge method and a magnetic field type plasma etching apparatus among external energy supply discharge methods.
FIG. 35 is a longitudinal sectional view of a plasma etching apparatus according to another embodiment of the present invention.
FIG. 36 is a front view of a longitudinal section of a part of an apparatus in which the present invention is applied to a microwave plasma processing apparatus.
FIG. 37 is a longitudinal sectional view of a plasma etching apparatus according to another embodiment of the present invention.
FIG. 38 is a front view of a part of a plasma processing apparatus according to another embodiment of the present invention in a longitudinal section.
FIG. 39 is a longitudinal sectional view of a two-electrode plasma etching apparatus capable of independently controlling ions and radicals according to another embodiment of the present invention.
FIG. 40 is a partial detailed view of a two-electrode plasma etching apparatus capable of independently controlling ions and radicals according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Processing chamber, 12 ... Upper electrode, 15 ... Lower electrode, 16 ... High frequency power supply, 17 ... Pulse bias power supply, 18 ... Vacuum pump, 20 ... Electrostatic chuck, 22 ... Electrostatic adsorption film, 23 ... DC power supply, 30 ... upper electrode cover, 32 ... gas diffusion plate 32, 36 ... gas supply unit 3, 40 ... sample, 161 ... high frequency power source modulation signal source, 200 ... magnetic field forming means 200, 201 ... core, 202 ... electromagnetic coil, 203 ... insulation body

Claims (3)

A pair of flat plate electrodes that are installed in a vacuum processing chamber and that also serve as a sample stage that can hold a sample opposite to each other and having an insulating film;
An electrostatic adsorption film that is provided on one plate electrode that also serves as the sample stage, and to which a heat transfer gas is supplied between the back surface of the sample;
Decompression means for setting the gas pressure in the vacuum processing chamber to 0.5 to 4.0 Pa;
The gap between the pair of flat plate electrodes is 30 mm to 100 mm, the electrode cover provided on the other electrode of the pair of flat plate electrodes and made of a material containing Si or C;
Gas introduction means for introducing an etching gas containing fluorine into the vacuum processing chamber, having a plurality of pores provided in the electrode cover;
A bias power source for accelerating ions in the plasma connected to the one electrode;
A high-frequency power source that applies high-frequency power of 50 MHz or 200 MHz to the other electrode and converts the introduced gas into plasma;
Magnetic field forming means for forming a portion of a static magnetic field or a low frequency magnetic field of 10 gauss or more and 110 gauss or less in a direction overlapping each other near the center of the vacuum processing chamber and overlapping each other around and outside the vacuum processing chamber. Prepared,
The magnetic field forming means changes the magnetic field by rotating eccentrically with respect to the center of the sample surface, and sets the distance of the electron cyclotron resonance region to the sample by the interaction between the magnetic field and the electric field generated by the high-frequency power source. Including a continuously changing core,
A plasma processing apparatus , wherein the cyclotron resonance region is formed in a peripheral part of the sample stage or in the vicinity of the outside thereof . A pair of flat plate electrodes that are installed in a vacuum processing chamber and that also serve as a sample stage that can hold a sample having a diameter of 300 mm or more, with one electrode facing each other and having an insulating film;
An electrostatic adsorption film that is provided on one plate electrode that also serves as the sample stage, and to which a heat transfer gas is supplied between the back surface of the sample;
Decompression means for setting the gas pressure in the vacuum processing chamber to 0.5 to 4.0 Pa;
The gap between the pair of flat plate electrodes is 30 mm to 60 mm, the electrode cover is provided on the other electrode of the pair of flat plate electrodes and made of a material containing Si or C;
Gas introduction means for introducing an etching gas containing fluorine into the vacuum processing chamber, having a plurality of pores provided in the electrode cover;
A bias power source for accelerating ions in the plasma connected to the one electrode;
A high-frequency power source that applies high-frequency power of 50 MHz or 200 MHz to the other electrode and converts the introduced gas into plasma;
Magnetic field forming means for forming a portion of a static magnetic field or a low frequency magnetic field of 10 gauss or more and 110 gauss or less in a direction overlapping each other near the center of the vacuum processing chamber and overlapping each other around and outside the vacuum processing chamber. Prepared,
The magnetic field forming means changes the magnetic field by rotating eccentrically with respect to the center of the sample surface, and sets the distance of the electron cyclotron resonance region to the sample by the interaction between the magnetic field and the electric field generated by the high-frequency power source. Including a continuously changing core,
A plasma processing apparatus , wherein the cyclotron resonance region is formed in a peripheral part of the sample stage or in the vicinity of the outside thereof . A pair of flat plate electrodes that are installed in a vacuum processing chamber and that also serve as a sample stage that can hold a sample having a diameter of 300 mm or more, with one electrode facing each other and having an insulating film;
An electrostatic adsorption film that is provided on one plate electrode that also serves as the sample stage, and to which a heat transfer gas is supplied between the back surface of the sample;
Decompression means for setting the gas pressure in the vacuum processing chamber to 0.5 to 4.0 Pa;
The gap between the pair of flat plate electrodes is 30 mm to 60 mm, the electrode cover is provided on the other electrode of the pair of flat plate electrodes and made of a material containing Si or C;
Gas introduction means for introducing an etching gas containing fluorine into the vacuum processing chamber, having a plurality of pores provided in the electrode cover;
A bias power source for accelerating ions in the plasma connected to the one electrode;
A high-frequency power source that applies high-frequency power of 50 MHz or 200 MHz to the other electrode and converts the introduced gas into plasma;
A susceptor cover made of a material containing Si or C located in the vicinity of the sample;
Magnetic field forming means for forming a portion of a static magnetic field or a low frequency magnetic field of 10 gauss or more and 110 gauss or less in a direction overlapping each other near the center of the vacuum processing chamber and overlapping each other around and outside the vacuum processing chamber. Prepared,
The magnetic field forming means changes the magnetic field by rotating eccentrically with respect to the center of the sample surface, and sets the distance of the electron cyclotron resonance region to the sample by the interaction between the magnetic field and the electric field generated by the high-frequency power source. Including a continuously changing core,
A plasma processing apparatus , wherein the cyclotron resonance region is formed in a peripheral part of the sample stage or in the vicinity of the outside thereof .

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