JP3774354B2 - Intramembrane ion content measuring method and apparatus - Google Patents

Description

【００４５】
ここで、ε₀ は真空の誘電率、εoxは絶縁膜１０２の比誘電率、ρ₀ は膜内イオンの密度（個／ｃｍ³ ）、Ｇは絶縁膜１０２と測定用電極２０１とのギャップ、ｄoxは絶縁膜１０２の厚みである。
【００４６】
上記の式（１）において、膜内イオンの密度ρ₀ 以外の値は既知なので、電圧のシフト量ΔＶ_F1からρ₀ の値を決定することができる。なお、式（１）を用いた膜内イオン量の算出は、ホストコントローラ３９０（図１）内部の膜内イオン量決定部３９２によって実行される。
【００４７】
以上のようにして、図３（Ａ−１）に示す初期状態の絶縁膜１０２中に存在していた膜内イオンＭ⁺ の量を決定することができる。
【００４８】
なお、実際には、絶縁膜は、膜内イオンの他に固定電荷等も含んでいる。例えば、光照射を約１０分間行った場合に得られたシリコン酸化膜内の全電荷量は約５．６×１０¹⁰（個／ｃｍ² ）となっており、ナトリウムイオンＮａ⁺ が含まれていない場合のシリコン酸化膜中の全電荷量３×１０¹⁰（個／ｃｍ² ）とほぼ同等の値が得られる。このことから、絶縁膜中の膜内イオンは、ほぼ全て中和されていることが分かる。なお、光照射をさらに長時間行えば、さらに近似した値を得ることができる。
【００４９】
以上説明したように、本実施例においては、半導体ウエハを加熱することによって、絶縁膜中に存在する膜内イオンを絶縁膜の表面側に順次移動させるためのイオン移動処理を行いつつ、所定の波長範囲の光を照射することによって、絶縁膜の表面付近に存在する膜内イオンを順次中和する中和処理を実行している。これにより、絶縁膜中に存在する膜内イオンをほぼ全て中和することができるので、第１および第２のＣ−Ｖ曲線から、絶縁膜中の膜内イオンの量をより正確に求めることが可能となる。
【００５０】
なお、以上の説明からも分かるように、本実施例の膜内イオン量測定装置ＭＤ１（図１）における測定用電極２０１と金属製の試料台１７０と容量測定器３３０とホストコントローラ３９０との測定系が、本発明における電気特性測定部に相当する。また、光源装置３５０とホットプレート３６０とが、本発明における膜内イオン中和部に相当する。
【００５１】
Ｂ．第２実施例：
図５は、本発明の第２実施例としての膜内イオン量測定装置ＭＤ２を示す説明図である。この測定装置ＭＤ２も、図１に示す測定装置ＭＤ１と同様に、半導体ウエハ１００のＣ−Ｖ特性を非接触で測定する機能を有しているとともに、半導体ウエハ１００の絶縁膜中の膜内イオンを光照射によって中和する機能を有している。
【００５２】
測定装置ＭＤ２は、図１の測定装置ＭＤ１とほぼ同様の構成を有しているが、ホットプレート３６０（図１）が省略されている。本実施例においては、移動ステージ１９０が、試料台１７０に載置された半導体ウエハ１００を光源装置３５０の下部に搬送する。
【００５３】
図６は、第２実施例における半導体ウエハの絶縁膜中に存在する膜内イオン量の決定手順を示すフローチャートである。ステップＳ２０１においては、図２のステップＳ１０１と同様、半導体ウエハ１００について１回目の非接触Ｃ−Ｖ測定を行い、第１のＣ−Ｖ曲線を得る。
【００５４】
ステップＳ２０２ａでは、半導体ウエハ１００に所定の波長範囲の光を照射する。また、ステップＳ２０２ｂでは、半導体ウエハ１００に電圧を印加する。このステップＳ２０２ａ，Ｓ２０２ｂの処理を繰り返し行うことにより、絶縁膜１０２中の膜内イオンＭ⁺ は絶縁膜１０２の表面側に移動し、絶縁膜１０２の表面付近において中和される。この説明からも分かるように、このステップＳ２０２ａ，Ｓ２０２ｂが、図２のステップＳ１０２に対応する。
【００５５】
図７は、ステップＳ２０２ａ，Ｓ２０２ｂ（図６）において絶縁膜１０２中の膜内イオンＭ⁺ が中和される様子を示す説明図である。図７（Ａ−１），（Ａ−２）は、それぞれ、ステップＳ２０１における絶縁膜１０２中の膜内イオンＭ⁺ の分布を示しており、図４（Ａ−１），（Ａ−２）と同じである。
【００５６】
図７（Ｂ−１），（Ｂ−２）は、ステップＳ２０２ａにおける絶縁膜１０２中の膜内イオンＭ⁺ の分布を示している。ステップＳ２０２ａにおいて、図７（Ｂ−１）に示すように、半導体ウエハ１００に光を照射すると、半導体基板１０１中の電子が励起され、この結果、絶縁膜１０２の表面付近に存在する膜内イオンＭ⁺ が中和される。このとき、図７（Ｂ−２）に示すように、絶縁膜１０２の表面付近の膜内イオンＭ⁺ の密度が小さくなる。
【００５７】
図７（Ｃ−１），（Ｃ−２）は、ステップＳ２０２ｂにおける絶縁膜１０２中の膜内イオンＭ⁺ の分布を示している。ステップＳ２０２ｂにおいては、半導体ウエハ１００に電圧が印加される。具体的には、図７（Ｃ−１）に示すように、絶縁膜１０２と半導体基板１０１との界面付近に存在する膜内イオンＭ⁺ が、絶縁膜１０２の表面側に移動するように、絶縁膜１０２表面を負にバイアスする。このとき、図７（Ｃ−２）に示すように、絶縁膜１０２と半導体基板１０１との界面付近に残存する膜内イオンＭ⁺ の密度が小さくなり、逆に、絶縁膜１０２の表面付近に存在する膜内イオンＭ⁺ の密度が大きくなる。
【００５８】
ここで、ステップＳ２０２ａにおける光照射は、図５の光源装置３５０によって実行される。本実施例においても、約２３０ｎｍ〜約３００ｎｍの波長範囲を有する光が用いられている。半導体ウエハの表面１００ａでの光強度は約９ｍＷ／ｃｍ² に設定されており、照射時間は約２０秒間に設定されている。
【００５９】
一方、ステップＳ２０２ｂにおける電圧印加は、測定用電極２０１を用いて実行される。本実施例において、絶縁膜１０２に印加される電圧は、最大約４Ｖに設定されている。
【００６０】
ステップＳ２０２ａ，Ｓ２０２ｂの中和処理を繰り返し行うことにより、絶縁膜１０２中のほぼ全ての膜内イオンＭ⁺ は、絶縁膜１０２の表面付近で中和される。
【００６１】
ところで、本実施例において、ステップＳ２０２ａおよびステップＳ２０２ｂからなる一連の中和処理を繰り返し行っているのは、１回の中和処理だけでは、絶縁膜１０２中の膜内イオンＭ⁺ をほぼ全て中和することが困難なためである。
【００６２】
図８は、中和処理の回数と絶縁膜中に残存する膜内イオン量との関係を示す説明図である。図８の横軸は、処理回数を示しており、ステップＳ２０２ａとステップＳ２０２ａとの一連の処理が１回の処理を意味している。また、縦軸は、各回の処理が終了したときの絶縁膜１０２中の膜内イオン量Ｎ（個／ｃｍ² ）を示している。図示するように、各回の処理毎に、絶縁膜１０２中に残存する膜内イオンＭ⁺ の量Ｎは、徐々に減少している。仮に、４０回の処理で照射される光の照射量を、１回の処理で長時間照射した場合には、図８に示す１回処理後の膜内イオンＭ⁺ の量Ｎとほぼ同じ値しか得られない。このことから、光照射後に電圧を印加することによって、絶縁膜１０２と半導体基板１０１との界面付近に存在する膜内イオンＭ⁺ が絶縁膜１０２の表面側に移動すると考えられる。なお、図８において、処理回数を増加させれば、絶縁膜中に残存する膜内イオンの量Ｎをさらに減少させることができる。
【００６３】
上記のように、ステップＳ２０２ａおよびステップＳ２０２ｂの一連の中和処理を繰り返し実行することによって、絶縁膜１０２中の膜内イオンＭ⁺ が順次中和されることとなる。
【００６４】
図６のステップＳ２０３では、図２のステップＳ１０３と同様、２回目のＣ−Ｖ測定を行い、第２のＣ−Ｖ曲線を得る。
【００６５】
ステップＳ２０４では、図２のステップＳ１０４と同様、第１のＣ−Ｖ曲線と第２のＣ−Ｖ曲線とから、初期状態の絶縁膜１０２中に存在した膜内イオンＭ⁺ の量を求める。
【００６６】
以上説明したように、本実施例においては、半導体ウエハに所定の波長範囲の光を照射することによって絶縁膜の表面付近に存在する膜内イオンを順次中和する中和処理と、半導体ウエハに電圧を印加することによって絶縁膜中に存在する膜内イオンを絶縁膜の表面側に順次移動させるイオン移動処理とを、繰り返し行っている。これにより、絶縁膜中に存在する膜内イオンをほぼ全て中和することができるので、第１および第２のＣ−Ｖ曲線から、絶縁膜中の膜内イオンの量をより正確に求めることが可能となる。
【００６７】
Ｃ．第３実施例：
ところで、第２実施例では、図６に示したように、ステップＳ２０２ｂで電圧を繰り返し印加し、ステップＳ２０３で非接触Ｃ−Ｖ測定を行っている。非接触Ｃ−Ｖ測定では、半導体ウエハ１００に電圧が印加される。したがって、ステップＳ２０２ｂにおける電圧印加は、非接触Ｃ−Ｖ測定を実行することによって実現することができる。第３実施例では、非接触Ｃ−Ｖ測定を実行することによって、半導体ウエハに電圧を印加し、絶縁膜中の膜内イオンを絶縁膜の表面側に順次移動させている。なお、第３実施例においても、第２実施例と同じ膜内イオン量測定装置ＭＤ２（図５）が用いられる。
【００６８】
図９は、第３実施例における半導体ウエハの絶縁膜中に存在する膜内イオン量の測定手順を示すフローチャートである。なお、ステップＳ３０１，Ｓ３０２ａ，Ｓ３０４については、第２実施例（図６）のステップＳ２０１，Ｓ２０２ａ，Ｓ２０４と同じである。
【００６９】
ステップＳ３０２ｂにおいては、非接触Ｃ−Ｖ測定が実行されることにより、半導体ウエハ１００に電圧が印加される。Ｃ−Ｖ測定時の電圧印加によって、図７（Ｃ−１），（Ｃ−２）と同様に、絶縁膜１０２と半導体基板１０１との界面付近に存在する膜内イオンＭ⁺ が絶縁膜１０２の表面側に移動する。ところで、Ｃ−Ｖ測定においては、図３（Ａ−１），（Ａ−２）に示すように、電圧は挿引される。したがって、絶縁膜１０２表面が負にバイアスされる場合もあるが、正にバイアスされる場合もある。しかしながら、電圧を挿引した場合にも、絶縁膜１０２中の膜内イオンＭ⁺ は、全体として絶縁膜１０２の表面側に移動する。これは、絶縁膜１０２中の膜内イオンＭ⁺ に、動きやすい方向（すなわち、絶縁膜１０２の表面側に向かう方向）があるためであると考えられている。なお、ステップＳ３０２ｂを繰り返し実行することによって複数のＣ−Ｖ曲線が得られるが、これらの測定結果から得られる絶縁膜中の膜内イオンの量は、図８と同じ傾向を示す。すなわち、ステップＳ３０２ａとステップＳ３０２ｂとの一連の処理回数が増加するにつれ、絶縁膜中の膜内イオン量は徐々に減少する。
【００７０】
ステップＳ３０３では、ステップＳ３０２ｂにおいて得られた複数のＣ−Ｖ曲線の中から、測定結果が収束したＣ−Ｖ曲線を第２のＣ−Ｖ曲線として求める。収束したＣ−Ｖ曲線とは、具体的には、絶縁膜中の膜内イオンの中和が進行し、フラットバンド電圧Ｖｆｂの値がほぼ一定の値に収束したＣ−Ｖ曲線を意味している。そして、ステップＳ３０４において、ステップＳ３０１で得られた第１のＣ−Ｖ曲線と、ステップＳ３０３で得られた第２のＣ−Ｖ曲線とから、膜内イオンの量が決定される。
【００７１】
図１０は、第３実施例の非接触Ｃ−Ｖ測定で得られた膜内イオン量の測定結果と、ＢＴ測定で得られた膜内イオン量の測定結果とを比較したグラフである。なお、ＢＴ（Bias Temperature）測定は、周知の接触測定であり、絶縁膜上に接触状態で設けられた電極が用いられる。ＢＴ測定では、高温状態の半導体ウエハに正電圧および負電圧を印加することにより、絶縁膜中に存在する膜内イオンを測定する。このＢＴ測定を用いれば、半導体ウエハが損傷してしまうが、かなり正確に膜内イオンの量を測定することが可能である。図１０では、膜内イオンの量が異なる４種類の半導体ウエハＷ１〜Ｗ４について、本実施例の非接触Ｃ−Ｖ測定とＢＴ測定とが実施されている。横軸は、ＢＴ測定で得られた膜内イオン量を示しており、縦軸は、本実施例の非接触Ｃ−Ｖ測定で得られた膜内イオン量を示している。そして、図中破線で示す直線上に各半導体ウエハＷ１〜Ｗ４がプロットされるときに、ＢＴ測定で得られた膜内イオン量と、本実施例の非接触Ｃ−Ｖ測定で得られた膜内イオン量とが一致することとなる。例えば、第２の半導体ウエハＷ２については、本実施例の非接触Ｃ−Ｖ測定およびＢＴ測定の双方において、膜内イオン量は約１．７×１０¹¹（個／ｃｍ² ）となっているので、破線で示す直線上にプロットされている。図１０に示すように、本実施例の非接触Ｃ−Ｖ測定の測定結果は、ＢＴ測定の測定結果と、かなり一致していることが分かる。
【００７２】
以上説明したように、本実施例においては、半導体ウエハに所定の波長範囲の光を照射することによって絶縁膜の表面付近に存在する膜内イオンを順次中和する中和処理と、半導体ウエハに対して非接触Ｃ−Ｖ測定を行うことによって絶縁膜中に存在する膜内イオンを絶縁膜の表面側に順次移動させるイオン移動処理とを、繰り返し行っている。また、繰り返し行われたイオン移動処理において得られた複数のＣ−Ｖ曲線のうち、収束したＣ−Ｖ曲線を第２のＣ−Ｖ曲線として求めている。これにより、絶縁膜中に存在する膜内イオンをほぼ全て中和することができ、第１および第２のＣ−Ｖ曲線から、絶縁膜中の膜内イオンの量をより正確に求めることが可能となる。
【００７３】
なお、第３実施例のようにすれば、絶縁膜１０２中に残存する膜内イオンＭ⁺ の量を確認しながら、膜内イオンＭ⁺ を中和することができるという利点がある。ただし、第２実施例のようにすれば、ステップＳ２０２ｂにおいて電圧を挿引しなくて済むので、膜内イオンの量の測定時間を短くすることができる。
【００７４】
第１ないし第３実施例から分かるように、本発明においては、絶縁膜中の膜内イオンを中和させる際に、絶縁膜中の膜内イオンを絶縁膜の表面側に順次移動させるための所定のイオン移動処理を行いつつ、半導体ウエハに所定の波長範囲の光を照射することによって、絶縁膜の表面付近に存在する膜内イオンを順次中和する中和処理を実行している。これにより、絶縁膜中に存在する膜内イオンをほぼ全て中和することができるので、この結果、絶縁膜中に存在していた膜内イオンの量をより正確に測定することが可能となる。
【００７５】
なお、この発明は上記の実施例や実施形態に限られるものではなく、その要旨を逸脱しない範囲において種々の態様において実施することが可能であり、例えば次のような変形も可能である。
【００７６】
（１）上記実施例では、半導体ウエハ１００に光を照射する際に、半導体ウエハ１００を光源装置３５０の下部に搬送しているが、搬送しないようにしてもよい。すなわち、光源装置３５０から射出される光が、プリズム１４０および透明電極である測定用電極２０１を通過して、半導体ウエハ１００を照射するようにしてもよい。この場合には、ステッピングモータ１１０と圧電アクチュエータ１２０と架台１３０の内側に光ファイバなどの導光路を設け、光源装置３５０から射出される光を半導体ウエハ１００上に導くようにすればよい。
【００７７】
（２）第２実施例では、測定用電極２０１を用いて半導体ウエハ１００に電圧を印加しているが、半導体ウエハ１００を帯電させるようにしてもよい。例えば、半導体ウエハ１００上にコロナ電荷を付加するようにすればよい。半導体ウエハ１００の表面を負電荷で帯電させれば、絶縁膜１０２中の膜内イオンＭ⁺ を絶縁膜１０２の表面側にうまく移動させることが可能である。半導体ウエハ１００の表面を負帯電させる帯電分子としては、炭酸イオンＣＯ₃ ^2-を用いることができる。
【００７８】
また、第２および第３実施例では、独立して、あるいは、非接触Ｃ−Ｖ測定の際に、半導体ウエハに電圧を印加し、所定の波長範囲の光を照射することによって、膜内イオンを中和しているが、これに加えて、半導体ウエハを加熱するようにしてもよい。この場合には、イオン移動処理は、加熱する処理と電圧を印加する処理とを含むこととなる。
【００７９】
一般に、絶縁膜中の膜内イオンを中和する工程は、絶縁膜中の膜内イオンを絶縁膜の表面側に順次移動させるための所定のイオン移動処理を行いつつ、半導体ウエハに所定の波長範囲の光を照射することによって、絶縁膜の表面付近に存在する膜内イオンを順次中和する中和処理を実行するような工程であればよい。
【００８０】
（３）上記実施例では、電気的特性値として、Ｃ−Ｖ曲線から得られるフラットバンド電圧Ｖｆｂを用いているが、他の測定値を利用してもよい。例えば、半導体基板と絶縁膜との界面においてフェルミ準位と真性フェルミ準位とが一致する「ミッドギャップ電圧」と呼ばれる測定値を用いてもよい。
【００８１】
（４）上記実施例では、本発明の非接触測定手法として、Ｃ−Ｖ測定を用いているが、他の非接触測定手法を用いるようにしてもよい。例えば、半導体ウエハに断続光を照射することにより発生する半導体ウエハの表面光電圧（ＳＰＶ：Surface Photo Voltage）を非接触で測定する表面光電圧測定を用いることができる。また、測定用電極と半導体ウエハとのギャップを時間的に変化させつつ半導体ウエハの表面電位を測定する振動容量電位測定を用いてもよい。なお、この測定手法は、ケルビン法として周知であり、例えば、Z.Physin,115,296(1940年)に所載のB.ギゼ(Gysae)及びS.ワーゲナー(Wagener)の論文に詳細に開示されている。
【００８２】
一般に、本発明における非接触測定手法としては、半導体ウエハの絶縁膜中に含まれる膜内イオンに関連する半導体ウエハの電気的特性値を測定できるようなものであればよい。
【図面の簡単な説明】
【図１】本発明の第１実施例としての膜内イオン量測定装置ＭＤ１を示す説明図である。
【図２】第１実施例における半導体ウエハの絶縁膜中に存在する膜内イオン量の決定手順を示すフローチャートである。
【図３】半導体ウエハの絶縁膜中に存在する膜内イオンの量を測定する際の処理を示す説明図である。
【図４】ステップＳ１０２（図２）において絶縁膜１０２中の膜内イオンＭ⁺ が中和される様子を示す説明図である。
【図５】本発明の第２実施例としての膜内イオン量測定装置ＭＤ２を示す説明図である。
【図６】第２実施例における半導体ウエハの絶縁膜中に存在する膜内イオン量の決定手順を示すフローチャートである。
【図７】ステップＳ２０２ａ，Ｓ２０２ｂ（図６）において絶縁膜１０２中の膜内イオンＭ⁺ が中和される様子を示す説明図である。
【図８】中和処理の回数と絶縁膜中に残存する膜内イオン量との関係を示す説明図である。
【図９】第３実施例における半導体ウエハの絶縁膜中に存在する膜内イオン量の測定手順を示すフローチャートである。
【図１０】第３実施例の非接触Ｃ−Ｖ測定で得られた膜内イオン量の測定結果と、ＢＴ測定で得られた膜内イオン量の測定結果とを比較したグラフである。
【符号の説明】
１００…半導体ウエハ
１００ａ…半導体ウエハの表面
１０１…半導体基板
１０２…絶縁膜
１１０…ステッピングモータ
１２０…圧電アクチュエータ
１３０…架台
１４０…プリズム
１４０ａ…底面
１５０…発光素子
１６０…受光素子
１７０…試料台
１９０…移動ステージ
２０１…測定用電極
３１０…Ｚ位置制御装置
３２０…光量測定器
３３０…容量測定器
３５０…光源装置
３６０…ホットプレート
３８０…ステージ制御装置
３９０…ホストコントローラ
３９２…膜内イオン量決定部
Ｃｆｂ…フラットバンド容量
Ｖｆｂ…フラットバンド電圧
Ｇ…ギャップ
ＭＤ１，ＭＤ２…膜内イオン量測定装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for measuring the amount of ions in a film contained in an insulating film of a semiconductor wafer.
[0002]
[Prior art]
In the manufacturing process of a semiconductor wafer, alkali metal ions (Na⁺, K⁺, Li⁺) Or the like (hereinafter referred to as “in-film ions”). Since these in-film ions deteriorate the stability of the semiconductor wafer, there is a demand for measuring the amount of in-film ions.
[0003]
The amount of in-film ions present in the insulating film is the first electrical characteristic value in the state where the in-film ions are present in the insulating film and the second value in the state where the in-film ions are not present in the insulating film. It can be obtained by measuring the electrical characteristic value. Conventionally, the state in which no in-film ions exist in the insulating film has been realized by irradiating the semiconductor wafer with light to neutralize the in-film ions. Such a method for measuring the amount of ions in the membrane is described in detail in, for example, Japanese Patent Application Laid-Open No. 11-126811 disclosed by the applicant of the present application.
[0004]
[Problems to be solved by the invention]
However, in-film ions existing near the surface of the insulating film are almost neutralized by light irradiation, but in-film ions existing near the interface between the insulating film and the semiconductor substrate are not so neutralized. For this reason, it has been difficult to accurately determine the total amount of ions in the film existing in the insulating film.
[0005]
The present invention has been made to solve the above-described problems in the prior art, and provides a technique capable of more accurately measuring the amount of ions in a film existing in an insulating film of a semiconductor wafer. Objective.
[0006]
[Means for solving the problems and their functions and effects]
In order to solve at least a part of the problems described above, a method of the present invention is a method for measuring the amount of ions in a film existing in an insulating film formed on a surface of a semiconductor wafer, the method comprising: Obtaining a first electrical characteristic value of the semiconductor wafer according to a predetermined non-contact measurement method in a state where the in-film ions are included in the film, and (b) the in-film ions in the insulating film By irradiating the semiconductor wafer with light in a predetermined wavelength range while performing a predetermined ion movement process for sequentially moving to the surface side of the insulating film, the in-film ions existing near the surface of the insulating film are (C) a second electrical characteristic value of the semiconductor wafer obtained by the predetermined non-contact measurement method in a state in which the in-film ions are neutralized; A process to obtain; (d) Serial from the first and second electrical characteristic values, characterized in that it comprises the steps of determining the amount of the film within the ion that was present in the insulating film.
[0007]
In the method of the present invention, when the in-film ions in the insulating film are neutralized, the in-film ions are sequentially moved to the surface side of the insulating film, and the semiconductor wafer is irradiated with light, so that the vicinity of the surface of the insulating film is obtained. The existing membrane ions are sequentially neutralized. As a result, almost all the ions in the insulating film can be neutralized, so that the amount of ions in the insulating film can be measured more accurately. In addition, said ion movement process and neutralization process may be performed simultaneously, and may be performed separately.
[0008]
In the above method, the ion movement process may include a process of heating the semiconductor wafer.
[0009]
In this way, the ions in the film in the insulating film can be successfully moved sequentially to the surface side of the insulating film.
[0010]
In the above method, in the ion transfer treatment, the heating is preferably performed so that the temperature of the semiconductor wafer reaches a range of about 150 ° C. to about 230 ° C.
[0011]
In this way, the ions in the film can be moved to the vicinity of the surface of the insulating film in a relatively short time, and contamination due to organic substances or the like mixed into the semiconductor wafer can be reduced.
[0012]
In the above method, the semiconductor wafer is preferably heated in an inert gas atmosphere in the ion transfer treatment.
[0013]
In this way, contamination of the semiconductor wafer can be further reduced.
[0014]
In the above method, the ion movement treatment includes a process of applying a voltage to the semiconductor wafer, and the step (b) includes a step of repeatedly performing the neutralization treatment and the ion movement treatment. Good.
[0015]
Even in this case, the in-film ions in the insulating film can be successfully moved sequentially toward the surface side of the insulating film, and the in-film ions existing near the surface of the insulating film can be neutralized sequentially. .
[0016]
In the above method, the ion migration process includes a process of executing the predetermined non-contact measurement method on the semiconductor wafer, and the step (b) includes the neutralization process, the ion migration process, In the step (c), a converged value is selected from the plurality of electrical characteristic values obtained by the ion migration process repeatedly performed in the step (b). The step of obtaining the electrical characteristic value may be included.
[0017]
Even in such a case, the ions in the film in the insulating film can be sequentially moved to the surface side of the insulating film. In addition, since non-contact measurement is repeatedly performed, it is possible to neutralize the in-film ions while confirming the amount of in-film ions remaining in the insulating film.
[0018]
In the above method, the predetermined wavelength range is preferably a range including at least a part of a range of about 230 nm to about 300 nm.
[0019]
By using such light, in-film ions existing near the surface of the insulating film can be neutralized well.
[0020]
In the above method, the predetermined non-contact measurement method may be CV measurement.
[0021]
The apparatus of the present invention is an in-film ion amount measuring apparatus for measuring the amount of in-film ions present in an insulating film formed on the surface of a semiconductor wafer, and the electric power of the semiconductor wafer is measured according to a predetermined non-contact measurement method. An electrical property measurement unit for obtaining a physical property value, and a predetermined ion movement process for sequentially moving the in-film ions in the insulating film to the surface side of the insulating film. An in-film ion neutralization unit that performs neutralization treatment to sequentially neutralize the in-film ions existing near the surface of the insulating film by irradiating light in a wavelength range, and the electrical characteristic measurement unit The first electrical characteristic value of the semiconductor wafer measured according to the predetermined non-contact measurement method in a state where the in-film ions are included in the insulating film, and the in-film ion neutralization unit Io in the membrane The amount of ions in the film existing in the insulating film is determined from the second electrical characteristic value of the semiconductor wafer obtained by the predetermined non-contact measurement method in a state in which is neutralized. An in-film ion content determination unit is provided.
[0022]
Even when the apparatus of the present invention is used, the same operation and effect as the above method can be obtained, and the amount of ions in the insulating film can be measured more accurately.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
A. First embodiment:
FIG. 1 is an explanatory view showing an in-membrane ion amount measuring device MD1 as a first embodiment of the present invention. The measuring device MD1 has a function of measuring the CV characteristics of the semiconductor wafer 100 in a non-contact manner and also has a function of neutralizing ions in the insulating film of the semiconductor wafer 100 by light irradiation. ing.
[0024]
The measuring device MD1 includes a stepping motor 110, a piezoelectric actuator 120 installed below the stepping motor 110, and a gantry 130 installed further below the piezoelectric actuator 120. A prism 140 is installed on the bottom surface of the gantry 130. A light emitting element 150 such as a GaAlAs laser is fixed to one inclined surface of the gantry 130, and a light receiving element 160 is fixed to the other inclined surface.
[0025]
The bottom surface 140 a of the prism 140 is provided in parallel with the surface (a plane parallel to the XY plane) of the sample table 170 on which the semiconductor wafer 100 is placed. A measurement electrode 201 which is a transparent electrode is formed on the bottom surface 140a of the prism. Below the prism 140, the semiconductor wafer 100 is held on a metal sample stage 170 through a gap G, and the surface 100a of the semiconductor wafer 100 is set to be substantially parallel to the bottom surface 140a of the prism. Yes. In this measuring apparatus MD1, as detailed in Japanese Patent Laid-Open No. 4-132236, the tunnel effect of the laser light totally reflected by the bottom surface 140a of the prism is used, so that the non-contact CV measurement can be performed. The value of the gap G is measured. The semiconductor wafer 100 is adsorbed and held on a sample stage 170 by a vacuum pump (not shown). The sample stage 170 is fixed on the moving stage 190.
[0026]
A Z position control device 310 is connected to the stepping motor 110 and the piezoelectric actuator 120. The stepping motor 110 and the piezoelectric actuator 120 move the gantry 130 in the z direction (vertical direction) in accordance with a signal input from the Z position control device 310, thereby the measurement electrode 201 and the surface 100 a of the semiconductor wafer 100. The gap G is adjusted. The stepping motor 110 is used for movement (coarse movement) over a relatively large distance, and the piezoelectric actuator 120 is used for movement (fine movement) over a relatively small distance. A light amount measuring device 320 is connected to the light receiving element 160. The light quantity measuring device 320 measures the value of the gap G based on the signal value supplied from the light receiving element 160. Further, a capacitance measuring device 330 is connected to the measuring electrode 201 and the metal sample stage 170. The capacitance measuring device 330 measures the combined capacitance C between the measurement electrode 201 and the sample table 170 while applying a voltage between the measurement electrode 201 and the sample table 170. A stage controller 380 is connected to the moving stage 190. The moving stage 190 moves in the XY plane according to a signal input from the stage control device 380. The Z position control device 310, the light amount measuring device 320, the capacitance measuring device 330, and the stage control device 380 are connected to the host controller 390 and controlled by the host controller 390. The in-film ion amount determination unit 392 included in the host controller 390 determines the amount of in-film ions included in the insulating film of the semiconductor wafer 100 by processing the obtained data. As the host controller 390, for example, a personal computer is used.
[0027]
When performing non-contact CV measurement, the Z position control device 310 controls the stepping motor 110 and the piezoelectric actuator 120, and the gap G between the measurement electrode 201 and the surface 100a of the semiconductor wafer becomes a predetermined size. Thus, the measurement electrode 201 is positioned.
[0028]
The measuring device MD1 further includes a light source device 350 for irradiating the semiconductor wafer 100 with light and a hot plate 360 for heating the semiconductor wafer 100. As will be described later, the light source device 350 and the hot plate 360 move the ions in the insulating film formed on the surface of the semiconductor wafer 100 to the surface side of the insulating film and neutralize them by light irradiation. have. The light source device 350 includes a filter, a diffraction grating, and the like for limiting the wavelength range of light emitted from the light source. In this embodiment, a xenon flash lamp is used as the light source.
[0029]
The semiconductor wafer 100 is transferred by a transfer device (not shown) and placed on the sample stage 170 and the hot plate 360.
[0030]
FIG. 2 is a flowchart showing a procedure for determining the ion amount in the film existing in the insulating film of the semiconductor wafer in the first embodiment. In step S101, the first non-contact CV measurement is performed on the semiconductor wafer 100 to obtain a first CV curve.
[0031]
FIG. 3 is an explanatory diagram showing processing when measuring the amount of ions in the film existing in the insulating film of the semiconductor wafer. FIG. 3A-1 shows the vicinity of the surface of the semiconductor wafer 100 in step S101 of FIG. As shown in the drawing, an insulating film 102 is formed on the semiconductor substrate 101, and ions in the impurity film (in-film ions) M are formed in the insulating film 102.⁺It is included. In-membrane ion M⁺As sodium ion Na⁺And potassium ion K⁺Lithium ion Li⁺Etc. can be assumed. A measurement electrode 201 is disposed on the semiconductor wafer 100 with a gap G interposed therebetween.
[0032]
FIG. 3A-2 shows a first CV curve F1 when the first non-contact CV measurement is performed on the semiconductor wafer 100 shown in FIG. 3A-1. In the figure, the flat band voltage Vfb is a voltage corresponding to the flat band capacitance Cfb calculated from the film thickness dox of the insulating film 102 obtained from the CV curve. The flat band voltage Vfb is shifted by the amount of charge existing near the surface of the semiconductor wafer 100.
[0033]
When the first CV curve F1 is obtained in step S101 of FIG. 2, the semiconductor wafer 100 is heated and irradiated with light in a predetermined wavelength range in step S102. Thereby, the in-film ions M in the insulating film 102⁺Moves to the surface side of the insulating film 102 and is neutralized near the surface of the insulating film 102.
[0034]
FIG. 4 shows in-film ions M in the insulating film 102 in step S102 (FIG. 2).⁺It is explanatory drawing which shows a mode that is neutralized. FIG. 4A-1 shows in-film ions M in the insulating film 102 in step S101.⁺The spatial distribution of is schematically shown. FIG. 4 (A-2) shows the intramembrane ion M shown in FIG. 4 (A-1).⁺The density distribution in the thickness direction of the insulating film is shown. As shown, in-film ions M in the insulating film 102.⁺Are present in the vicinity of the surface of the insulating film 102 and in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101, and there is not so much between them. Such intramembrane ion M⁺This distribution is likely to occur when the insulating film 102 is formed while contaminating and oxidizing the semiconductor substrate, or when the resist formed on the insulating film 102 is ashed.
[0035]
Note that the density distribution as shown in FIG. 4A-2 can be confirmed by an etch-off method. That is, the insulating film 102 is gradually etched from its surface in a plurality of times, and the in-film ions M in the insulating film 102 are etched after each etching.⁺Measure the amount of Thereby, the in-film ions M in the insulating film 102⁺Can be known.
[0036]
4 (B-1), (B-2) and FIGS. 4 (C-1), (C-2) are similar to FIGS. 4 (A-1), (A-2) in the insulation in step S102. Intramembrane ion M in membrane 102⁺The distribution of is shown. As described above, in step S102, the semiconductor wafer 100 is heated and irradiated with light. As shown in FIG. 4 (B-1), when the semiconductor wafer 100 is irradiated with light, electrons in the semiconductor substrate 101 are excited. The excited electrons are ions M in the film existing near the surface of the insulating film 102.⁺Neutralize. At this time, as shown in FIG. 4B-2, in-film ions M near the surface of the insulating film 102⁺The density of becomes smaller. In-film ions M near the surface of the insulating film 102⁺When the density of the film becomes small, as shown in FIG. 4C-1, in-film ions M existing in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101.⁺However, it moves toward the surface side of the insulating film 102 so as to satisfy the equilibrium condition. By heating the semiconductor wafer 100 in this way, the in-film ions M⁺Can be easier to move. At this time, as shown in FIG. 4C-2, in-film ions M remaining in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101.⁺On the contrary, the in-film ions M present near the surface of the insulating film 102 are reduced.⁺The density of increases.
[0037]
By performing neutralization continuously as shown in FIGS. 4B-1 and 4B-2 and FIGS. 4C-1 and 4C-2, almost all of the insulating film 102 can be obtained. Intramembrane ion M⁺Is neutralized near the surface of the insulating film 102.
[0038]
Incidentally, in step S102 (FIG. 2), in-film ions M included in the insulating film 102 are obtained.⁺Is moved to the surface of the insulating film 102 because the in-film ions M⁺This is because neutralization tends to occur when it exists in the vicinity of the surface of the insulating film 102. This phenomenon can also be confirmed by the etch-off method as described above. That is, in-film ions M in the insulating film of the semiconductor wafer after light irradiation⁺In-film ions M in the insulating film in the semiconductor wafer not irradiated with light as described above⁺Compared to the distribution of the ions in the film M present in the vicinity of the surface of the insulating film⁺Can be easily neutralized by light irradiation.
[0039]
Here, the heating in step S102 is performed by the hot plate 360 of FIG. In this embodiment, the temperature of the semiconductor wafer 100 is heated to about 180 ° C., and the heating time is about 1 minute to about 10 minutes. The heating is preferably performed so that the temperature of the semiconductor wafer 100 reaches a range of about 150 ° C. to about 230 ° C. When heated at such a temperature, the in-film ions M can be obtained in a relatively short time.⁺Can be moved to the vicinity of the surface of the insulating film 102, and contamination due to organic substances or the like mixed into the semiconductor wafer 100 can be reduced. Further, the light source device 350 and the hot plate 360 may be provided in the housing, and the inside of the housing may be replaced with an inert gas such as nitrogen gas. If the semiconductor wafer 100 is heated in an inert gas atmosphere, contamination of the semiconductor wafer 100 can be further reduced.
[0040]
On the other hand, the light irradiation in step S102 is executed by the light source device 350 of FIG. In this embodiment, light having a wavelength range of about 230 nm to about 300 nm is used, and the light intensity at the surface 100a of the semiconductor wafer is about 4 mW / cm.²Is set to Further, light irradiation to the semiconductor wafer 100 is continuously performed during heating. In addition, it is preferable that the wavelength range of the light which irradiates the semiconductor wafer 100 is a range including at least a part of the range of about 230 nm to about 300 nm. If light having such a wavelength range is used, the electrons in the semiconductor substrate 101 can be excited well, and the in-film ions M present near the surface of the insulating film 102 can be obtained.⁺Can be neutralized.
[0041]
In step S103 of FIG. 2, the second non-contact CV measurement is performed on the semiconductor wafer 100 to obtain a second CV curve.
[0042]
FIG. 3 (B-1) shows the intramembrane ion M shown in FIG. 3 (A-1) after step S102.⁺Shows a neutralized state. As shown in FIG.⁺Is neutralized after moving to the vicinity of the surface of the insulating film 102. FIG. 3B-2 shows a second CV curve F2 when the second non-contact CV measurement is performed on the semiconductor wafer 100 shown in FIG. 3B-1. FIG. 3B-2 also shows the first CV curve F1 obtained in step S101.
[0043]
In step S104 (FIG. 2), the first CV curve F1 obtained in step S101 and the second CV curve F2 obtained in step S102 are shown in FIG. 3 (A-1). In-film ions M present in the insulating film 102 in the initial state⁺Find the amount of. Specifically, in-membrane ion M⁺Is the shift amount ΔV of the flat band voltage Vfb of the first and second CV curves F1, F2._F1From this, it can be determined using the following equation (1).
[0044]
[Expression 1]

[0045]
Where ε₀Is the dielectric constant of vacuum, εox is the relative dielectric constant of the insulating film 102, ρ₀ Is the density of ions in the membrane (number / cm^Three ), G is a gap between the insulating film 102 and the measurement electrode 201, and dox is the thickness of the insulating film 102.
[0046]
In the above equation (1), the density ρ of ions in the membrane₀Since values other than are known, the voltage shift amount ΔV_F1To ρ₀The value of can be determined. The calculation of the in-film ion amount using the equation (1) is executed by the in-film ion amount determination unit 392 inside the host controller 390 (FIG. 1).
[0047]
As described above, the in-film ions M present in the insulating film 102 in the initial state shown in FIG.⁺The amount of can be determined.
[0048]
In practice, the insulating film contains fixed charges and the like in addition to ions in the film. For example, the total charge amount in the silicon oxide film obtained when light irradiation is performed for about 10 minutes is about 5.6 × 10 6.^Ten(Pieces / cm²) And sodium ion Na⁺The total amount of charges in the silicon oxide film when it is not included is 3 × 10^Ten(Pieces / cm²) Is almost the same value. From this, it is understood that almost all ions in the insulating film are neutralized. If light irradiation is performed for a longer time, a more approximate value can be obtained.
[0049]
As described above, in this embodiment, the semiconductor wafer is heated to perform predetermined ion movement processing for sequentially moving ions in the insulating film to the surface side of the insulating film. By irradiating light in the wavelength range, a neutralization process is performed to sequentially neutralize ions in the film existing near the surface of the insulating film. As a result, almost all the ions in the film existing in the insulating film can be neutralized, so that the amount of ions in the film in the insulating film can be obtained more accurately from the first and second CV curves. Is possible.
[0050]
As can be seen from the above description, measurement with the measurement electrode 201, the metal sample stage 170, the capacitance measuring device 330, and the host controller 390 in the in-membrane ion amount measuring device MD1 (FIG. 1) of the present embodiment. The system corresponds to the electrical property measuring unit in the present invention. Further, the light source device 350 and the hot plate 360 correspond to the in-membrane ion neutralization portion in the present invention.
[0051]
B. Second embodiment:
FIG. 5 is an explanatory view showing an in-membrane ion content measuring device MD2 as a second embodiment of the present invention. Similar to the measurement apparatus MD1 shown in FIG. 1, the measurement apparatus MD2 also has a function of measuring the CV characteristics of the semiconductor wafer 100 in a non-contact manner, and in-film ions in the insulating film of the semiconductor wafer 100. Has a function of neutralizing by irradiation with light.
[0052]
The measuring device MD2 has substantially the same configuration as the measuring device MD1 of FIG. 1, but the hot plate 360 (FIG. 1) is omitted. In this embodiment, the moving stage 190 transports the semiconductor wafer 100 placed on the sample stage 170 to the lower part of the light source device 350.
[0053]
FIG. 6 is a flowchart showing a procedure for determining the ion amount in the film existing in the insulating film of the semiconductor wafer in the second embodiment. In step S201, as in step S101 of FIG. 2, the first non-contact CV measurement is performed on the semiconductor wafer 100 to obtain a first CV curve.
[0054]
In step S202a, the semiconductor wafer 100 is irradiated with light in a predetermined wavelength range. In step S202b, a voltage is applied to the semiconductor wafer 100. By repeatedly performing the processes in steps S202a and S202b, the in-film ions M in the insulating film 102 are obtained.⁺Moves to the surface side of the insulating film 102 and is neutralized near the surface of the insulating film 102. As can be seen from this description, steps S202a and S202b correspond to step S102 in FIG.
[0055]
FIG. 7 shows in-film ions M in the insulating film 102 in steps S202a and S202b (FIG. 6).⁺It is explanatory drawing which shows a mode that is neutralized. FIGS. 7A-1 and 7A-2 illustrate the in-film ions M in the insulating film 102 in step S201, respectively.⁺This is the same as FIGS. 4A-1 and 4A-2.
[0056]
7B-1 and 7B-2 show in-film ions M in the insulating film 102 in step S202a.⁺The distribution of is shown. In step S202a, as shown in FIG. 7B-1, when the semiconductor wafer 100 is irradiated with light, electrons in the semiconductor substrate 101 are excited, and as a result, in-film ions existing near the surface of the insulating film 102. M⁺Is neutralized. At this time, as shown in FIG. 7B-2, in-film ions M near the surface of the insulating film 102⁺The density of becomes smaller.
[0057]
7C-1 and 7C-2 illustrate the in-film ions M in the insulating film 102 in step S202b.⁺The distribution of is shown. In step S202b, a voltage is applied to the semiconductor wafer 100. Specifically, as shown in FIG. 7C-1, in-film ions M present near the interface between the insulating film 102 and the semiconductor substrate 101.⁺However, the surface of the insulating film 102 is negatively biased so as to move to the surface side of the insulating film 102. At this time, as shown in FIG. 7C-2, in-film ions M remaining in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101.⁺On the contrary, the in-film ions M present near the surface of the insulating film 102 are reduced.⁺The density of increases.
[0058]
Here, the light irradiation in step S202a is performed by the light source device 350 of FIG. Also in this embodiment, light having a wavelength range of about 230 nm to about 300 nm is used. The light intensity at the surface 100a of the semiconductor wafer is about 9 mW / cm.²The irradiation time is set to about 20 seconds.
[0059]
On the other hand, the voltage application in step S202b is executed using the measurement electrode 201. In this embodiment, the voltage applied to the insulating film 102 is set to a maximum of about 4V.
[0060]
By repeatedly performing the neutralization process in steps S202a and S202b, almost all the in-film ions M in the insulating film 102 are obtained.⁺Is neutralized near the surface of the insulating film 102.
[0061]
By the way, in the present embodiment, the series of neutralization processes consisting of step S202a and step S202b are repeated, and the in-film ions M in the insulating film 102 are obtained only by one neutralization process.⁺This is because it is difficult to neutralize almost all of the above.
[0062]
FIG. 8 is an explanatory diagram showing the relationship between the number of neutralization treatments and the amount of in-film ions remaining in the insulating film. The horizontal axis in FIG. 8 indicates the number of processes, and a series of processes in step S202a and step S202a means one process. Also, the vertical axis represents the in-film ion amount N (number / cm / cm) in the insulating film 102 when each process is completed.²). As shown in the figure, in-film ions M remaining in the insulating film 102 for each treatment.⁺The amount N of is gradually decreasing. If the irradiation amount of light irradiated in 40 treatments is irradiated for a long time in one treatment, the in-film ion M after one treatment shown in FIG.⁺Only the same value as the amount N of is obtained. From this, by applying a voltage after light irradiation, in-film ions M present in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101.⁺Is considered to move to the surface side of the insulating film 102. In FIG. 8, if the number of treatments is increased, the amount N of in-film ions remaining in the insulating film can be further reduced.
[0063]
As described above, the in-film ions M in the insulating film 102 are obtained by repeatedly executing the series of neutralization processes in steps S202a and S202b.⁺Will be sequentially neutralized.
[0064]
In step S203 of FIG. 6, the second CV measurement is performed similarly to step S103 of FIG. 2 to obtain a second CV curve.
[0065]
In step S204, as in step S104 of FIG. 2, the in-film ions M existing in the insulating film 102 in the initial state are obtained from the first CV curve and the second CV curve.⁺Find the amount of.
[0066]
As described above, in this embodiment, the semiconductor wafer is neutralized by sequentially irradiating the semiconductor wafer with light in a predetermined wavelength range to neutralize ions in the vicinity of the surface of the insulating film. Ion transfer treatment in which ions in the insulating film existing in the insulating film are sequentially moved to the surface side of the insulating film by applying a voltage is repeatedly performed. As a result, almost all the ions in the film existing in the insulating film can be neutralized, so that the amount of ions in the film in the insulating film can be obtained more accurately from the first and second CV curves. Is possible.
[0067]
C. Third embodiment:
By the way, in 2nd Example, as shown in FIG. 6, the voltage is repeatedly applied by step S202b, and the non-contact CV measurement is performed by step S203. In the non-contact CV measurement, a voltage is applied to the semiconductor wafer 100. Therefore, the voltage application in step S202b can be realized by performing non-contact CV measurement. In the third embodiment, by performing non-contact CV measurement, a voltage is applied to the semiconductor wafer to sequentially move ions in the insulating film to the surface side of the insulating film. In the third embodiment, the same in-membrane ion amount measuring device MD2 (FIG. 5) as in the second embodiment is used.
[0068]
FIG. 9 is a flowchart showing a procedure for measuring the amount of ions in the film existing in the insulating film of the semiconductor wafer in the third embodiment. Steps S301, S302a, and S304 are the same as steps S201, S202a, and S204 in the second embodiment (FIG. 6).
[0069]
In step S302b, a voltage is applied to the semiconductor wafer 100 by performing non-contact CV measurement. By applying a voltage during CV measurement, in-film ions M existing in the vicinity of the interface between the insulating film 102 and the semiconductor substrate 101 as in FIGS. 7C-1 and 7C-2.⁺Moves to the surface side of the insulating film 102. By the way, in the CV measurement, as shown in FIGS. 3A-1 and 3A-2, the voltage is inserted. Therefore, the surface of the insulating film 102 may be negatively biased or may be positively biased. However, the in-film ion M in the insulating film 102 is also present when a voltage is inserted.⁺Moves to the surface side of the insulating film 102 as a whole. This is because the ions M in the insulating film 102⁺It is thought that this is because there is a direction in which it is easy to move (that is, a direction toward the surface side of the insulating film 102). A plurality of CV curves are obtained by repeatedly executing step S302b. The amount of ions in the insulating film obtained from these measurement results shows the same tendency as in FIG. That is, as the number of times of a series of processing in step S302a and step S302b increases, the amount of ions in the insulating film gradually decreases.
[0070]
In step S303, a CV curve in which the measurement results converge is obtained as a second CV curve from the plurality of CV curves obtained in step S302b. Specifically, the converged CV curve means a CV curve in which neutralization of ions in the insulating film proceeds and the flat band voltage Vfb converges to a substantially constant value. Yes. In step S304, the amount of ions in the membrane is determined from the first CV curve obtained in step S301 and the second CV curve obtained in step S303.
[0071]
FIG. 10 is a graph comparing the measurement result of the in-film ion amount obtained by the non-contact CV measurement of the third example and the measurement result of the in-film ion amount obtained by the BT measurement. The BT (Bias Temperature) measurement is a well-known contact measurement, and an electrode provided in a contact state on the insulating film is used. In the BT measurement, in-film ions existing in the insulating film are measured by applying a positive voltage and a negative voltage to a semiconductor wafer in a high temperature state. If this BT measurement is used, the semiconductor wafer is damaged, but the amount of ions in the film can be measured fairly accurately. In FIG. 10, the non-contact CV measurement and the BT measurement of the present embodiment are performed on four types of semiconductor wafers W1 to W4 having different amounts of ions in the film. The horizontal axis shows the amount of ions in the membrane obtained by BT measurement, and the vertical axis shows the amount of ions in the membrane obtained by non-contact CV measurement of this example. And when each semiconductor wafer W1-W4 is plotted on the straight line shown with a broken line in a figure, the film | membrane obtained by the amount of ion in a film | membrane obtained by BT measurement, and the non-contact CV measurement of a present Example The amount of ions inside will match. For example, for the second semiconductor wafer W2, the amount of ions in the film is about 1.7 × 10 in both the non-contact CV measurement and the BT measurement of this example.¹¹(Pieces / cm²Is plotted on a straight line indicated by a broken line. As shown in FIG. 10, it can be seen that the measurement result of the non-contact CV measurement of this example is quite consistent with the measurement result of the BT measurement.
[0072]
As described above, in this embodiment, the semiconductor wafer is neutralized by sequentially neutralizing the ions in the vicinity of the surface of the insulating film by irradiating the semiconductor wafer with light in a predetermined wavelength range. On the other hand, by performing non-contact CV measurement, ion migration treatment is sequentially performed in which ions in the film existing in the insulating film are sequentially moved to the surface side of the insulating film. Moreover, the converged CV curve is calculated | required as a 2nd CV curve among the several CV curves obtained in the ion migration process performed repeatedly. Thereby, almost all the ions in the film existing in the insulating film can be neutralized, and the amount of ions in the film in the insulating film can be obtained more accurately from the first and second CV curves. It becomes possible.
[0073]
If the third embodiment is used, the in-film ions M remaining in the insulating film 102 will be described.⁺While confirming the amount of ions in the membrane⁺There is an advantage that can be neutralized. However, according to the second embodiment, since it is not necessary to insert a voltage in step S202b, the measurement time of the amount of ions in the membrane can be shortened.
[0074]
As can be seen from the first to third embodiments, in the present invention, when the ions in the insulating film are neutralized, the ions in the insulating film are sequentially moved to the surface side of the insulating film. While performing a predetermined ion migration process, the semiconductor wafer is irradiated with light in a predetermined wavelength range, thereby performing neutralization processing for sequentially neutralizing in-film ions existing near the surface of the insulating film. As a result, almost all ions in the film existing in the insulating film can be neutralized. As a result, the amount of ions in the film existing in the insulating film can be measured more accurately. .
[0075]
The present invention is not limited to the above examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0076]
(1) In the above embodiment, when the semiconductor wafer 100 is irradiated with light, the semiconductor wafer 100 is transferred to the lower part of the light source device 350, but it may not be transferred. That is, the light emitted from the light source device 350 may pass through the prism 140 and the measurement electrode 201 which is a transparent electrode, and irradiate the semiconductor wafer 100. In this case, a light guide such as an optical fiber may be provided inside the stepping motor 110, the piezoelectric actuator 120, and the gantry 130 so that the light emitted from the light source device 350 is guided onto the semiconductor wafer 100.
[0077]
(2) In the second embodiment, a voltage is applied to the semiconductor wafer 100 using the measurement electrode 201, but the semiconductor wafer 100 may be charged. For example, a corona charge may be added on the semiconductor wafer 100. If the surface of the semiconductor wafer 100 is charged with a negative charge, the in-film ions M in the insulating film 102⁺Can be successfully moved to the surface side of the insulating film 102. As charged molecules for negatively charging the surface of the semiconductor wafer 100, carbonate ions CO_Three ^2-Can be used.
[0078]
In the second and third embodiments, in-film ions are applied by applying a voltage to a semiconductor wafer and irradiating light in a predetermined wavelength range independently or in non-contact CV measurement. In addition to this, the semiconductor wafer may be heated. In this case, the ion migration process includes a heating process and a voltage application process.
[0079]
In general, in the process of neutralizing ions in the insulating film, a predetermined wavelength is applied to the semiconductor wafer while performing a predetermined ion migration process for sequentially moving the ions in the insulating film to the surface side of the insulating film. Any process may be used as long as a neutralization process for sequentially neutralizing in-film ions existing near the surface of the insulating film by irradiating light in a range.
[0080]
(3) In the above embodiment, the flat band voltage Vfb obtained from the CV curve is used as the electrical characteristic value, but other measured values may be used. For example, a measurement value called “mid gap voltage” in which the Fermi level and the intrinsic Fermi level coincide with each other at the interface between the semiconductor substrate and the insulating film may be used.
[0081]
(4) In the above embodiment, CV measurement is used as the non-contact measurement method of the present invention, but other non-contact measurement methods may be used. For example, the surface photovoltage measurement which measures the surface photovoltage (SPV: Surface Photo Voltage) of the semiconductor wafer generated by irradiating the semiconductor wafer with intermittent light can be used. Further, vibration capacitance potential measurement may be used in which the surface potential of the semiconductor wafer is measured while changing the gap between the measurement electrode and the semiconductor wafer over time. This measurement method is known as the Kelvin method, and is disclosed in detail in, for example, the papers of B. Gysae and S. Wagener described in Z. Physin, 115, 296 (1940). Yes.
[0082]
In general, any non-contact measurement method in the present invention may be any method that can measure electrical characteristic values of a semiconductor wafer related to ions in the film contained in the insulating film of the semiconductor wafer.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an in-membrane ion amount measuring device MD1 as a first embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure for determining the amount of ions in the film existing in the insulating film of the semiconductor wafer in the first embodiment.
FIG. 3 is an explanatory diagram showing a process when measuring the amount of ions in a film existing in an insulating film of a semiconductor wafer.
FIG. 4 shows in-film ions M in the insulating film 102 in step S102 (FIG. 2).⁺It is explanatory drawing which shows a mode that is neutralized.
FIG. 5 is an explanatory view showing an in-membrane ion amount measuring device MD2 as a second embodiment of the present invention.
FIG. 6 is a flowchart showing a procedure for determining the amount of ions in a film existing in an insulating film of a semiconductor wafer in a second embodiment.
7 shows in-film ions M in the insulating film 102 in steps S202a and S202b (FIG. 6).⁺It is explanatory drawing which shows a mode that is neutralized.
FIG. 8 is an explanatory diagram showing the relationship between the number of neutralization treatments and the amount of in-film ions remaining in the insulating film.
FIG. 9 is a flowchart showing a procedure for measuring an ion amount in a film existing in an insulating film of a semiconductor wafer in a third embodiment.
FIG. 10 is a graph comparing the measurement result of the in-film ion amount obtained by the non-contact CV measurement of the third example and the measurement result of the in-film ion amount obtained by the BT measurement.
[Explanation of symbols]
100: Semiconductor wafer
100a ... surface of semiconductor wafer
101 ... Semiconductor substrate
102: Insulating film
110 ... Stepping motor
120: Piezoelectric actuator
130: Stand
140 ... Prism
140a ... bottom surface
150: Light emitting element
160. Light receiving element
170 ... Sample stage
190 ... Movement stage
201: Measuring electrode
310 ... Z position control device
320: Light quantity measuring device
330 ... Capacity measuring instrument
350 ... Light source device
360 ... Hot plate
380 ... Stage control device
390 ... Host controller
392: In-membrane ion content determination unit
Cfb: Flat band capacity
Vfb: Flat band voltage
G ... Gap
MD1, MD2 ... Intramembrane ion content measuring device

Claims (9)

A method for measuring the amount of ions in a film present in an insulating film formed on a surface of a semiconductor wafer,
(A) obtaining a first electrical characteristic value of the semiconductor wafer according to a predetermined non-contact measurement method in a state where the in-film ions are included in the insulating film;
(B) irradiating the semiconductor wafer with light in a predetermined wavelength range while performing a predetermined ion movement process for sequentially moving the in-film ions in the insulating film to the surface side of the insulating film; Performing a neutralization treatment for sequentially neutralizing the ions in the film existing near the surface of the insulating film;
(C) obtaining a second electrical characteristic value of the semiconductor wafer obtained by the predetermined non-contact measurement method in a state where the ions in the film are neutralized;
(D) determining the amount of ions in the film existing in the insulating film from the first and second electrical characteristic values;
A method for measuring the amount of ions in a membrane. A method for measuring the amount of ions in a membrane according to claim 1,
The in-film ion content measurement method, wherein the ion movement process includes a process of heating the semiconductor wafer. A method for measuring the amount of ions in a membrane according to claim 2,
In the ion moving process, the temperature of the heating the semiconductor wafer, no 1 50 ° C. to be performed to reach a range of 2 30 ° C., the film within the ion volume measurement method. A method for measuring the amount of ions in a membrane according to claim 2 or 3,
In the ion transfer process, the semiconductor wafer is heated in an inert gas atmosphere. A method for measuring the amount of ions in a membrane according to any one of claims 1 to 4,
The ion transfer process includes a process of applying a voltage to the semiconductor wafer,
The step (b) is an in-membrane ion content measurement method including a step of repeatedly performing the neutralization treatment and the ion transfer treatment. A method for measuring the amount of ions in a membrane according to any one of claims 1 to 4,
The ion movement process includes a process of executing the predetermined non-contact measurement method on the semiconductor wafer,
The step (b) includes a step of repeatedly performing the neutralization treatment and the ion transfer treatment,
The step (c) includes a step of obtaining a converged value as the second electrical property value among the plurality of electrical property values obtained by the ion migration process repeatedly performed in the step (b). Intramembrane ion content measuring method. A method for measuring the amount of ions in a membrane according to any one of claims 1 to 6,
The predetermined wavelength range, to 2 30 nm without a range including at least a portion of the range of 3 nm, film ion amount measurement method. A method for measuring the amount of ions in a membrane according to any one of claims 1 to 7,
The predetermined non-contact measurement method is a method for measuring the amount of ions in a membrane, which is CV measurement. A device for measuring the amount of ions in a film that measures the amount of ions in a film existing in an insulating film formed on the surface of a semiconductor wafer,
An electrical property measurement unit for obtaining electrical property values of the semiconductor wafer according to a predetermined non-contact measurement method;
By irradiating the semiconductor wafer with light in a predetermined wavelength range while performing a predetermined ion migration process for sequentially moving the ions in the insulating film to the surface side of the insulating film, the insulating film An in-film ion neutralization section for performing neutralization treatment for sequentially neutralizing the in-film ions existing near the surface of
With
The electrical property measuring unit is
The first electrical characteristic value of the semiconductor wafer measured according to the predetermined non-contact measurement method in a state where the in-film ions are included in the insulating film, and the in-film ion neutralization unit Based on the second electrical characteristic value of the semiconductor wafer obtained by the predetermined non-contact measurement method in a state where ions are neutralized, the amount of ions in the film existing in the insulating film is determined. An in-membrane ion amount measuring apparatus comprising an in-membrane ion amount determining unit for determining.

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