JP3905980B2 - Metal oxide thin film pattern forming method and metal oxide thin film pattern forming composition - Google Patents

Description

（上記一般式（Ｉ），（II）中、Ｒ¹ およびＲ² は、水素原子、または炭素数１〜１５の置換もしくは非置換のアルキル基、アリール基、アラルキル基から選択され、同一でも異なっていてもよい。）
【００２６】
【化２】

（上記一般式（III ）、（IV）中、Ｒ³ およびＲ⁴ は、水素原子、または炭素数１〜１５の置換もしくは非置換のアルキル基、アリール基、アラルキル基から選択され、同一でも異なっていてもよい。）
前記一般式（Ｉ）〜（IV）中にＲ¹ 〜Ｒ⁴ として導入され得る非置換のアルキル基としては、例えば、メチル基、エチル基、イソプロピル基、ターシャリブチル基、イソブチル基、ノルマルブチル基、およびヘキシル基等が挙げられる。
【００２７】
これらのアルキル基に導入されて置換アルキル基を形成し得る置換基としては、例えば、トリフルオロメチル基、水酸基、アルコキシ基、カルボニル基、シアノ基、およびニトロ基等が挙げられる。
【００２８】
また、非置換のアリール基としては、例えばフェニル基およびナフチル基等が挙げられ、非置換のアラルキル基としては、例えば、フェニルエチル基およびフェニルプロピル基等が挙げられる。
【００２９】
こうした非置換のアリール基およびアラルキル基には、上述したような置換基が導入され得る。
また、側鎖として水素原子を有するポリシラン類またはポリシロキサン類は、加熱によりＳｉ−Ｈ結合が酸化されて架橋するので、有機基の残留量を少なくすることができる。
【００３０】
ケイ素系クラスターとしては、例えばシルセスキオキサン類などのかご状ポリシロキサンなどが用いられる。クラスターの分子量は特に限定されないが、３００〜３，０００であることが好ましく、４００〜１，０００であることがより好ましい。３００未満の場合には成膜性が充分でなく、昇華性有機金属錯体を昇華させるときに揮発してしまうおそれがある。一方、３，０００を越えると、塗布性、溶媒可溶性が悪化するおそれがある。
【００３１】
なお、本発明の組成物には、上述した成分に加えてさらに光酸発生剤や光塩基発生剤が含有されていてもよい。光酸発生剤とは、光の照射により酸を発生する化合物であり、例えばトリフェニルスルホニウムトリフレートのようなトリフェニルスルホニウム塩、ナフタルイミジルカンファースルフォネートのようなナフタルイミジル塩等が挙げられる。光酸発生剤を配合する場合は、その配合量は、ケイ素系高分子化合物に対して０．１〜５％程度とすることが好ましい。
【００３２】
また、光塩基発生剤は、光の照射により塩基を発生する化合物であり、例えばオルトニトロフェニルメチル基を有するみどり化学社製（商品名ＮＢＣ−１）のような光塩基発生剤等が挙げられる。光塩基発生剤を配合する場合は、その配合量は、ケイ素系高分子化合物に対して０．１〜５％程度とすることが好ましい。
【００３３】
本発明のパターン形成用組成物は、ケイ素系高分子化合物に所定の割合で昇華性有機金属錯体を配合し、必要に応じて光酸発生剤等を加えて、乳酸エチル、酢酸エチル、ＰＧＭＥＡ等のエステル類、キシレン、トルエン、アニソール、テトラヒドロフラン、および塩化メチレン等の溶媒に溶解して溶液として用いられる。この溶液をディッピング法、スピンコート法、ドクターブレード法、またはソルベントキャスト法などによって基材上に塗布して塗膜を形成し、得られた塗膜を６０〜１５０℃程度で０．５〜５分程度加熱することによって溶媒を除去して感光層が形成される。感光層の膜厚は、塗布溶液濃度、塗布条件や用途等に応じて適宜決定することができ、例えば、０．１〜１０μｍ程度とすることができる。
【００３４】
あるいは感光層は、上述したような昇華性有機金属錯体とケイ素系高分子化合物とを共蒸着することによって基材上に形成してもよい。
本発明の金属酸化物薄膜パターン形成方法においては、上述したように基材上に形成された感光層の所定の領域に光を照射するパターン露光、次いで加熱乾燥という処理が施される。
【００３５】
ここで図面を参照して、本発明のパターン形成方法を説明する。
図１は、本発明の金属酸化物薄膜パターン形成方法の一例の概略を表わす工程断面図である。
【００３６】
まず、図１（ａ）に示すように、基板１上に形成された感光層２に対し、例えば所定のパターンを有するマスク３を介して露光光４を照射してパターン露光を行なう。なお、マスクを用いずに、レーザー光源等で感光層２を直接走査してパターン露光を行なってもよい。
【００３７】
露光光４を照射する光源は、感光層２を感光させるものであれば任意の光源を用いることができる。換言すれば、露光に用いる光４は、感光層２中に含有される昇華性有機金属錯体を分解または変性して昇華性を消失または抑制するもの、あるいはケイ素系高分子化合物または別途添加した感光剤に光反応を生じさせて、この光反応が引き金となって昇華性有機金属錯体を分解または変性して昇華性を消失または抑制するものであればよい。具体的には、電子線などを露光光４として用いることができる。また、露光光４の露光量を制御して感光層の面内あるいは膜厚方向に露光量の傾斜を設けることによって、ＧＩ型の光導波路を形成することもできる。さらに複数の露光ビームの干渉などを利用することによって、感光層２内に干渉縞を形成して、フォトニックバンドや干渉鏡を形成してもよい。
【００３８】
昇華性有機金属錯体の吸収波長の光を露光光４として用いれば、この錯体を露光により直接分解することができる。例えば、Ａｌ（ＡＡ）₃ は２８０ｎｍ付近にピークをもつ吸収を示し、Ｚｒ（ＡＡ）₃ は３００ｎｍ付近にピークをもつ吸収を示すため、３００ｎｍ付近の紫外光を照射してパターン露光を行なうことによって露光部の金属錯体を分解することができる。また、Ｒｕ（ＡＡ）₃ などの可視光領域に吸収を有する金属錯体は、例えばケイ素系高分子化合物としてポリシランなどの紫外光領域に強い吸収を有するものを用いる場合に、ケイ素系高分子化合物の吸収に阻害されることなく、金属錯体を効率的に光分解することが可能である。また光分解を促進するために種々の増感剤を用いてもよい。各種増感色素を用いることが可能であり、その配合量は、ケイ素系高分子化合物に対して０．１〜５％程度とすることができる。
【００３９】
本発明のパターン形成方法において、昇華性有機金属錯体は、露光に起因して分解すればよく、必ずしも上述したように露光により直接分解する必要はない。光を照射することによって、まずケイ素系高分子化合物や他の感光性添加剤が光反応して光反応生成物を生じ、この光反応生成物が前述の昇華性有機金属錯体と反応して錯体の分解が引き起こされてもよい。例えば、Ａｌ（ＡＡ）₃ などのアセチルアセトナト錯体は、シラノール基やフェノール性水酸基などの水酸基によって配位子交換反応を起こす。そこで、ケイ素系高分子化合物や感光性添加剤として、このような水酸基を露光による光反応の結果生じるものを用いれば、水酸基が昇華性有機金属錯体を良好に分解して、その昇華性を消失させることができる。
【００４０】
例えば、ポリシラン類は光酸化によってシラノール基を生成し、ポリシラン類やポリシロキサン類のヒドロ基は、光反応によって効率的にシラノール基を生成する。また同じくポリシラン類やポリシロキサン類の側鎖に導入されたアルコキシ基は、加熱あるいは酸触媒などの存在下、シラノール基を生成する。この場合、酸触媒などとしては、上述したような光酸発生剤などが用いられる。
【００４１】
こうしたメカニズムで昇華性有機金属錯体の昇華性を消失させ得るポリシラン類としては、例えば、ポリジイソプロポキシシラン、ポリジターシャリブトキシシラン、ポリイソプロポキシメチルシラン、ポリターシャリブトキシメチルシラン、ポリターシャリブトキシシラン、ポリメチルシラン、およびポリフェニルシランが挙げられ、ポリシロキサン類としては、ポリジイソプロポキシシロキサン、ポリジターシャリブトキシシロキサン、ポリイソプロポキシメチルシロキサン、ポリターシャリブトキシメチルシロキサン、ポリターシャリブトキシシロキサン、ポリメチルシロキサン、およびポリフェニルシロキサンが挙げられる。
【００４２】
また、上述したメカニズムで昇華性有機金属錯体の昇華性を消失させる感光性添加剤としては、例えば、光酸発生剤とターシャリブトキシベンゼンなどのフェノール誘導体やイソプロポキシジフェニルシランなどのシラノール誘導体などとの混合物等が挙げられる。こうした感光性添加剤を配合する場合には、その配合量はケイ素系高分子化合物に対して１〜５％程度とすることが望まれる。
【００４３】
なお、ターシャリブトキシ基を側鎖に有するポリシラン類およびポリシロキサン類は、光酸発生剤などの潜在性触媒と組み合わせて用いることが好ましい。有機基は残留した場合には伝搬損失を増大させるおそれがあるが、膜収縮やひび割れを防ぐので厚膜を作製する際などには有機基は有効である。こうした場合、フッ素化した有機基を用いることによって、伝搬損失の増大をある程度抑制することができる。同様の理由から、成膜性を向上させる目的でポリイミドなどの有機ポリマーを添加する場合も、フッ素かポリイミドなどのフッ素化物を用いることが望まれる。
【００４４】
上述したようなパターン露光を施すことによって、感光層の露光部においては、昇華性有機金属錯体が変性して感光層に潜像が形成される。すなわち、感光層の露光部では昇華性有機金属錯体の昇華性が低減され、場合によっては露光部における昇華性は消失する。
【００４５】
こうして潜像が形成された感光層２に対し加熱乾燥を行なうことによって、図１（ｂ）に示すように未露光部２ｂの昇華性有機金属錯体５は、昇華して感光層２から除去される。ここでの加熱乾燥は、昇華性有機金属錯体の性状に応じて決定されることが好ましいが、一般に昇華温度より高く、分解温度以下に設定され、１分〜５時間程度行なうことが好ましく、５分〜１時間程度行なうことがより好ましい。加熱乾燥に当たっては、昇華性有機金属錯体を熱分解などさせることなく昇華させることが必要である。したがって、昇華温度が錯体の熱分解温度以下となるように、１ｔｏｒｒ以下程度の真空条件下で加熱乾燥を行なうことが最も好ましい。
【００４６】
なお、感光層の露光部２ａに昇華性を維持した金属錯体が残留している場合には、これも同様にして除去される。
その後、必要に応じて用いた露光源や紫外光源等を感光層２全面に照射する全面露光、あるいは２００〜５００℃程度の加熱などの処理を施して、図１（ｃ）に示すように感光層を無機化してもよい。これによって、錯体の分解物をケイ素系高分子化合物からなるマトリックスへ良好に定着させたり、ケイ素系高分子化合物マトリックスを無機化して光学特性を向上させることができる。例えば、ケイ素系高分子化合物マトリックスとしてポリシラン類を用いた場合には、全面露光と加熱乾燥とを行なうことによって、ＳｉＯ₂ 類似構造への無機化が進行する。
【００４７】
この工程を行なうことによって、昇華性有機金属錯体が分散するマトリックスが、多孔質ではない緻密な樹脂膜となるために、加工精度がよく微細なパターンも形成可能となる。
【００４８】
以上のように、本発明のパターン形成方法を用いることによって、ケイ素酸化物薄膜に他の金属元素がドープされてなるパターンを簡便に形成することができる。パターン状に形成された金属酸化物薄膜に対しＲＩＥ工程によりプラズマエッチングを行なった場合には、含有される金属種によってエッチング耐性が異なるため、このパターンをエッチングマスクとして用いることができる。こうして、パターンの下層に設けられた被加工薄膜を、形成したパターン通りのポジあるいはネガ像にエッチングすることができ、半導体微細加工に用いられる表面イメージング法への応用が可能である。
【００４９】
図２には、こうした方法の一例を模式的に表わす工程断面図を示す。
まず、図２（ａ）に示すように、基材１上に微細加工の対照となる薄膜（被加工薄膜）６、および上述したような感光層２を順次形成し、所定のパターンを有するマスク３を介して露光光４を照射してパターン露光を行なう。被加工薄膜６の材質は特に限定されず、例えばスピンコーティング法、ディップコーティング法、ＣＶＤ法、およびスパッタリング法等を用いて０．１〜１０μｍ程度の膜厚で形成することができる。次いで、加熱乾燥、必要に応じて後処理を行なって被加工薄膜６上の感光層２にパターンの潜像を形成する。しかる後、この潜像が形成された感光層２をエッチングマスクとして用いて、図２（ｂ）に示すように適切なエッチング方法によりプラズマ７でエッチングすることによって、図２（ｃ）に示すように微細加工された被加工薄膜６ａが得られる。エッチング方法としては加工精度が優れている点からドライエッチング法が好ましく、さらには異方性ドライエッチング法が好ましい。
【００５０】
あるいは、本発明のパターン形成方法によって形成された金属酸化物薄膜パターンを用いて、微細な金属配線パターンを形成することも可能である。感光層中に含有される金属種がＰｄ、Ｐｔ、Ｒｈ、またはＲｕの場合には、無電解めっきの触媒作用を有するので、次のようにして金属配線パターンを形成することができる。すなわち、前述の図１（ｃ）に示したようなケイ素酸化物薄膜中にこれらの金属種が含有された部分と含有されない部分とからなるパターンを、めっき浴に浸漬させることによって、金属種が含有されている部位では、この金属種が触媒となってケイ素酸化物薄膜の表面が無電解めっきされる。この場合、めっき浴は前述の金属種によって無電解めっきが進行するものであれば、任意のものが用いられる。一方、上記金属種が含有されない、あるいは非常に少ない部位は無電解めっきされず、これによって図３に示すような金属配線パターン９を形成することができる。このように金属配線パターンを形成する場合には、ケイ素酸化物薄膜は必ずしも無機化させる必要はない。
【００５１】
また、配線パターンがあまり微細でない場合には、ケイ素系高分子化合物と昇華性有機金属錯体との混合溶液を塗布して感光層を形成する代わりに、ケイ素系高分子化合物の微粒子からなる多孔質膜を形成し、この多孔質膜に昇華性有機金属錯体の溶液を含浸させるなどして吸着させたものを用いてもよい。また、こうした微粒子として、金属酸化物微粒子を用いることもできる。
【００５２】
本発明を用いると、以上述べたように伝搬損失が小さく、耐熱性に優れた微細屈折率パターンなどの金属酸化物薄膜パターンを、簡便に形成することが可能となる。
【００５３】
【発明の実施の形態】
以下に本発明を実施例に基づいて具体的に説明する。なお、以下の例は具体的に説明するためのものであって、本発明の実施態様や発明範囲を限定するものではない。
（実施例１）
本実施例では、光導波路幅２０μｍ、分岐導波路のピッチ２５０μｍの２分岐導波路パターンを有するフォトマスクを用いて、本発明の方法により２０×１μｍの矩形断面を有する２分岐光導波路素子を製造した。
【００５４】
まず、昇華性有機金属錯体としてのＺｒ（ＡＡ）₄ を、ケイ素系高分子化合物としてのポリジイソプロポキシシロキサンに対して１０ｗｔ％の割合で混合し、この混合物をトルエンに溶解してトルエン溶液を調製した。得られたトルエン溶液をガラス基板上にスピンコーティング法によって塗布し、１００℃で１分加熱することにより溶媒を除去して、膜厚約１μｍの感光層を作製した。
【００５５】
得られた感光層に上述したフォトマスクを用いて波長３００ｎｍの紫外光を照射（照射量：１Ｗ／ｃｍ² ）して、潜像を形成した。照射後、感光層の露光部においては、Ｚｒ（ＡＡ）₄ に起因する３００ｎｍ付近の吸収が消失したのを確認した。
【００５６】
潜像が形成された感光層は、１５０℃、１０^-2ｔｏｒｒで１時間、真空加熱乾燥を行なった。次いで、波長３００ｎｍの紫外光で全面露光（照射量：１Ｗ／ｃｍ² ）し、さらに４５０℃で３０分間加熱することにより、コア層を形成した。得られたコア層の上面にポリシラザン溶液をスピンコートし、４５０℃で３０分間加熱することにより上部クラッド層を形成して光導波路素子を得た。
【００５７】
作製した光導波路素子においては、露光部と未露光部との屈折率差が３．２％であった。波長６７０ｎｍでの伝送損失は、０．０６ｄＢ／ｃｍと比較的良好な値を示し、空気中で４５０℃、５時間加熱後も特性にほとんど変化がなかったことから、十分な耐熱性を有していることがわかった。さらに、導波路パターンと基板との熱膨張率の差も小さいことが確認された。
（実施例２）
ケイ素系高分子化合物としてポリジイソプロポキシシランを用いた以外は、前述の実施例１と同様にして光導波路を作製した。
【００５８】
作製した光導波路素子においては、露光部と未露光部との屈折率差が３．４％であった。波長６７０ｎｍでの伝送損失は、０．０７ｄＢ／ｃｍと比較的良好な値を示し、空気中で４５０℃、５時間加熱後も特性にほとんど変化がなかったことから、十分な耐熱性を有していることがわかった。さらに、導波路パターンと基板との熱膨張率の差も小さいことが確認された。
（実施例３）
昇華性有機金属錯体として、Ｚｒ（ＡＡ）₄ の代わりにそれぞれ、Ａｌ（ＡＡ）₃ 、Ｉｎ（ＡＡ）₃ 、Ｌａ（ＡＡ）₃ 、Ｍｇ（ＡＡ）₂ 、およびＴｈ（ＡＡ）₄ を用いたほかは、前述の実施例１と同様にして光導波路素子を作製した。
【００５９】
作製した光導波路素子は、露光部と未露光部とでの屈折率差が３％以上あり、伝送損失は波長６７０ｎｍおよび１．３μｍにおいて、いずれも０．１ｄＢ／ｃｍ以下の良好な光伝送特性を示した。また、空気中で４５０℃、５時間加熱後も特性にほとんど変化がなかったことから、十分な耐熱性を有していることがわかった。さらに、導波路パターンと基板との熱膨張率の差も小さいことが確認された。
（実施例４）
昇華性有機金属錯体として、Ｚｒ（ＡＡ）₄ の代わりにそれぞれ、Ｉｎ（ＡＡ）₃ 、Ｌａ（ＡＡ）₃ 、Ｍｇ（ＡＡ）₂ 、およびＴｈ（ＡＡ）₄ を用いたほかは、前述の実施例２と同様にして光導波路素子を作製した。
【００６０】
作製した光導波路素子は、露光部と未露光部とでの屈折率差が３％以上あり、伝送損失は波長６７０ｎｍおよび１．３μｍにおいて、いずれも０．１ｄＢ／ｃｍ以下の良好な光伝送特性を示した。また、空気中で４５０℃、５時間加熱後も特性にほとんど変化がなかったことから、十分な耐熱性を有していることがわかった。さらに、導波路パターンと基板との熱膨張率の差も小さいことが確認された。
（実施例５）
昇華性有機金属錯体としてＺｒ（ＡＡ）₄ の代わりにＡｌ（ＡＡ）₃ を用いた以外は、前述の実施例１と同様にして光導波路素子を作製した。
【００６１】
作製した光導波路素子は、露光部と未露光部とでの屈折率差が１％以上あり、伝送損失は波長６７０ｎｍおよび１．３μｍにおいて、いずれも０．１ｄＢ／ｃｍ以下の良好な光伝送特性を示した。また、空気中で４５０℃、５時間加熱後も特性にほとんど変化がなかったことから、十分な耐熱性を有していることがわかった。さらに、導波路パターンと基板との熱膨張率の差も小さいことが確認された。
（実施例６）
本実施例においては、膜厚方向の微細屈折率分布パターンを形成した。
【００６２】
昇華性有機金属錯体としてのＡｌ（ＡＡ）₃ を、ケイ素系高分子化合物としてのポリジイソプロポキシシロキサンに対して１０ｗｔ％の割合で混合し、この混合物をトルエンに溶解してトルエン溶液を調製した。得られたトルエン溶液をガラス基板上にスピンコーティング法によって塗布し、１００℃で１分程度加熱することにより溶媒を除去して膜厚約５μｍの感光層を作製した。
【００６３】
光源として波長２６６ｎｍのレーザー光を用い、２軸のビーム光をそれぞれ感光層の両面から基板に対して入射角６０°、ビーム光軸の交差角１２０°で入射させて露光した。なお、照射スポット径は約１００μｍとした。
【００６４】
露光後の感光層は、１５０°、１０^-2ｔｏｒｒで１時間真空加熱乾燥した。真空加熱乾燥後、波長３００ｎｍの紫外光で全面露光（照射量：１Ｗ／ｃｍ² ）し、さらに４５０℃で３０分間加熱した。
【００６５】
得られた膜の照射部位におけるアルミニウム元素のＤｅｐｔｈ ＰｒｏｆｉｌｅをＸＰＳ測定により測定した。その結果、照射部位の膜厚方向に周期的なアルミニウム元素含有率の変化が観測され、感光層の膜厚方向にも屈折率分布を形成できることがわかった。
（実施例７）
本実施例においては、表面イメージング法により微細パターンを形成した。
【００６６】
昇華性有機金属錯体としてのＰｔ（ＡＡ）₂ を、ケイ素系高分子化合物としてのポリジイソプロポキシシロキサンに対して１０ｗｔ％の割合で混合し、この混合物をトルエンに溶解してトルエン溶液を調製した。
【００６７】
一方、シリコン基板上に膜厚０．７μｍの架橋ノボラック樹脂膜を形成し、この樹脂膜上に前述のトルエン溶液をスピンコーティング法によって塗布し、１００℃で１分程度加熱することにより溶媒を除去して膜厚約０．１μｍの感光層を作製した。
【００６８】
作製した感光層に０．５μｍのラインアンドスペースパターンのフォトマスクを用いて波長３００ｎｍの紫外光を照射（照射量：１Ｗ／ｃｍ² ）して、潜像を形成した。
【００６９】
潜像が形成された感光層は、１５０℃、１０^-2ｔｏｒｒで１時間真空加熱乾燥してパターンを形成した。このパターン形成した薄膜を塩素ガスを用いた反応性イオンエッチングによりドライエッチング処理して、ノボラック樹脂膜を微細加工を行なった。その結果、約０．５μｍのラインアンドスペースでノボラック樹脂膜をパターニングすることができた。
（実施例８）
本実施例においては、微細金属配線パターンを形成した。
【００７０】
昇華性有機金属錯体としてのＰｔ（ＡＡ）₂ を、ケイ素系高分子化合物としてのポリジイソプロポキシシロキサンに対して１０ｗｔ％の割合で混合し、この混合物をトルエンに溶解してトルエン溶液を調製した。得られたトルエン溶液をガラス基板上にスピンコーティング法によって塗布し、１００℃で１分程度加熱することにより溶媒を除去して膜厚約１μｍの感光層を作製した。
【００７１】
作製した感光層に５μｍのラインアンドスペースパターンのフォトマスクを用いて波長３００ｎｍの紫外光を照射（照射量：１Ｗ／ｃｍ² ）して、潜像を形成した。
【００７２】
潜像が形成された感光層は、１５０℃、１０^-2ｔｏｒｒで１時間真空加熱乾燥してパターンを形成した。このパターン形成した薄膜を、ニッケル無電界メッキ浴に浸漬して、Ｐｔを含有したパターン部位に膜厚１μｍのニッケル薄膜を析出させたところ、良好なニッケル電極パターンが形成された。
（実施例９）
まず、ガラス基板上にシリカ微粒子（平均粒子径約２０ｎｍ）をスキージ印刷法によって厚さ１μｍに塗布して多孔質膜を形成し、この多孔質膜にＰｔ（ＡＡ）₂ を吸着させて感光層を形成した。こうして得られた感光層を用いた以外は、前述の実施例８と同様にしてパターン形成を行ったところ、良好なニッケル電極パターンが形成された。
【００７３】
【発明の効果】
以上説明したように本発明によれば、伝搬損失が小さく、耐熱性に優れた無機系の光導波路やフォトニックバンド、干渉鏡などの屈折率分布を形成し得る、金属酸化物薄膜パターンを簡便に形成する方法およびこれに用いられるパターン形成用組成物が提供される。
【００７４】
本発明は、半導体微細加工プロセスに用いられる表面イメージング法や金属配線パターン形成などにも極めて好適に用いることができ、その工業的価値は絶大である。
【図面の簡単な説明】
【図１】本発明のパターン形成方法の一例を模式的に表わす工程断面図。
【図２】本発明のパターン形成方法の他の例を模式的に表わす工程断面図。
【図３】本発明の方法により形成された金属配線パターンの一例を模式的に表わす断面図。
【符号の説明】
１…基材
２…感光層
２ａ…露光部
２ｂ…未露光部
３…マスク
４…露光光
５…昇華性有機金属錯体
６…被加工薄膜
７…プラズマ
９…金属配線パターン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a metal oxide thin film pattern, and in particular, an optical waveguide optically coupled to an optical element such as an optical fiber, an optical waveguide, a semiconductor laser (LD), a photodiode (PD), or a lens, or a photonic. The present invention relates to a fine and periodic refractive index distribution pattern such as a band and an interference mirror, a metal oxide thin film pattern forming method applicable to a surface imaging method used for fine metal pattern formation and semiconductor fine processing, and a composition used therefor.
[0002]
[Prior art]
The development of surface-mounted optical waveguides for the purpose of application to optical interconnection technology and optical / electric mixed multi-chip modules for conventional high-speed broadband communication systems has been energetically performed. Such optical waveguides are expected to have a wide range of applications from in-chip wiring having a wiring length of several millimeters or less to in-module wiring of about several centimeters, and further to in-board optical wiring of about several tens of centimeters. Such an optical wiring is not easily affected by electromagnetic noise, and the generation amount of electromagnetic noise is very small. Moreover, it is expected that the importance will be further increased in the future, such as a significant reduction in processing speed due to signal delay and the like.
[0003]
Various surface mount type optical waveguides as described above have been studied from organic materials to inorganic materials. For example, an organic polymer such as an acrylic resin can be molded relatively easily, and has a merit that it can be processed at a low temperature without deteriorating nonlinear optical dyes. is doing. However, organic polymers such as acrylic resins are inferior in heat resistance, and at present, heat resistance is not sufficiently improved when polyimide or the like is used. Further, propagation loss in the infrared region is large due to infrared absorption caused by carbon-hydrogen bonds that are generally present in many organic compounds. Although the propagation loss can be reduced by substituting the carbon-hydrogen bond with the carbon-fluorine bond, this case has a problem in terms of cost.
[0004]
On the other hand, inorganic optical waveguides mainly composed of silicon dioxide have excellent characteristics such as excellent heat resistance and low propagation loss in the infrared region. However, a general silicon dioxide optical waveguide manufacturing method requires a multi-step complicated lithography process including a CVD process and an RIE process.
[0005]
In view of the above, there is a need for a processing process for producing an inorganic optical waveguide having excellent optical characteristics at a low cost and at a relatively low temperature. As such a processing process, for example, a metal oxide sol whose reactivity is suppressed by modification with an organic ligand such as acetylacetone is applied to a substrate to form a photosensitive layer, and the organic ligand is irradiated by pattern exposure. There has been proposed a method of obtaining a negative pattern of a metal oxide by decomposing and allowing the gel of an exposed part to proceed and washing and peeling off an unexposed part (Shinmo et al., Jpn. Appl. Phys., 33, L1181 (1994)). Furthermore, after pattern exposure of the polysilane film, the metal oxide sol is selectively infiltrated into the photooxidized exposed portion, and then the entire surface is exposed to oxidize the polysilane, and finally removed by washing to form a metal oxide thin film pattern. Has been disclosed (Japanese Patent Laid-Open No. 7-92695). Although these methods can form a metal oxide pattern by a relatively simple process, a cladding layer must be separately prepared except that the air layer is a cladding. In the latter method, hydrocarbon groups bonded to the side chain of polysilane may remain and propagation loss may increase, and a reactive group such as a hydroxyl group is required in the sol. Sex was a problem.
[0006]
Further, in the method using solvent development as described above, it is extremely difficult to manufacture an element that requires a periodic refractive index change in the film thickness direction, such as a photonic band structure or an interference mirror. For example, in the case of a multilayer type optical / electric hybrid chip, a reflecting mirror formed at an angle of 45 ° with respect to the substrate is indispensable in order to extract light in a direction perpendicular to the substrate. As such a reflecting mirror, an interference mirror having a periodic refractive index distribution is preferable in order to increase reflection efficiency. However, in order to install the interference mirror at 45 ° with respect to the substrate, it is necessary to form a fine refractive index distribution in a direction inclined by 45 ° from the film thickness direction at a desired portion of the waveguide film. However, it is very difficult to form such a three-dimensional refractive index distribution by a conventional method using a CVD process, an RIE process, or the like or a solvent development method.
[0007]
As a method for forming a refractive index distribution in an inorganic material without using solvent development, a method using a metal porous film impregnated with a photosensitive organometallic compound is disclosed (SPIE Proceedings, 2288, 580-588). (1994)). In this method, a photosensitive film is formed by impregnating a porous film of a metal oxide formed by a sol-gel method with a photoreactive organometallic compound, and this film is subjected to pattern exposure to expose a photosensitive organic film in an exposed area. Photolytic decomposition of metal compounds. The photodecomposed metal compound in the exposed area chemically bonds with the porous film, while the organometallic compound in the unexposed area is volatilized by a technique such as heating. For this reason, when it heats after exposure, the exposure part will be in the state in which the metal seed | species derived from an organometallic compound was doped in the metal oxide matrix, and can form a refractive index pattern.
[0008]
By using this method, it is possible to form a refractive index distribution in an inorganic substance without solvent development. However, the sol-gel solution for forming the sol-gel film is not sufficiently stable in storage, and a heat treatment at a high temperature of 700 ° C. or higher is necessary for densifying the metal porous film. could not.
[0009]
[Problems to be solved by the invention]
As described above, the conventional method for manufacturing an inorganic optical waveguide requires a complicated and relatively high-temperature process including a CVD process and an RIE process. In the case of a manufacturing method including a coating process, it is necessary to prepare a cladding layer separately, and the propagation loss is large due to the residual polysilane side chain. Also, since the sol solution does not have sufficient storage stability, process control and quality control are complicated, and in addition, a three-dimensional fine refractive index distribution in the film thickness direction such as a photonic band or an interference mirror is formed. It was extremely difficult to do.
[0010]
Therefore, the present invention can form a refractive index profile of an inorganic optical waveguide, a photonic band, an interference mirror, etc. with small propagation loss and excellent heat resistance, and can be used for surface imaging processes and fine metal wiring patterns in semiconductor microfabrication. An object of the present invention is to provide a method capable of easily forming a metal oxide thin film pattern useful for formation.
[0011]
Another object of the present invention is to provide a composition for forming a metal oxide thin film pattern as described above.
A further object of the present invention is to provide a method capable of easily forming a fine metal wiring pattern in semiconductor fine processing.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides:
Forming a photosensitive layer containing a sublimable organometallic complex and a silicon-based polymer compound on a substrate;
Selectively exposing a predetermined area of the photosensitive layer to form a latent image of a thin film pattern; and
The step of heating and drying the photosensitive layer on which the latent image of the thin film pattern is formed to remove the sublimable organometallic complex in the unexposed area.
A method for forming a pattern of a metal oxide thin film comprising:
[0013]
The present invention also provides a metal oxide thin film pattern forming composition containing a sublimable organometallic complex and a silicon-based polymer compound.
Furthermore, the present invention provides
Forming a photosensitive layer containing a sublimable organometallic complex on a substrate;
Selectively exposing a predetermined area of the photosensitive layer to form a latent image of a thin film pattern;
Heating and drying the photosensitive layer on which the latent image of the thin film pattern is formed, and removing a sublimable organometallic complex in an unexposed portion; and
Provided is a method for forming a metal fine pattern comprising a step of depositing a metal on an exposed portion of a photosensitive layer after heat drying.
[0014]
Hereinafter, the present invention will be described in detail.
In the pattern formation method of the present invention, when a predetermined region of the photosensitive layer formed on the substrate is selectively exposed, the sublimable organometallic complex contained in the photosensitive layer of the exposed portion is sublimable by photolysis or the like. To lose. At the same time, through a reaction such as hydrolysis, the sublimable organometallic complex is bonded to the matrix silicon-based polymer compound, and a latent image is formed on the photosensitive layer. Thereafter, when the photosensitive layer is heat-dried, preferably vacuum heat-dried, the sublimable organometallic complex is sublimated and removed from the matrix made of the silicon-based polymer compound in the unexposed portion of the photosensitive layer. On the other hand, since the sublimable organometallic complex is decomposed in the exposed portion of the photosensitive layer, it does not sublime even when heated, and the central metal remains in the form of an oxide or the like. As a result, the exposed portion of the photosensitive layer is in a state where the silicon-based polymer compound is doped with the central metal element of the sublimable organometallic complex, and such a state does not occur in the unexposed portion. In this way, a pattern of a metal oxide thin film that can be applied to a refractive index distribution type optical waveguide pattern or the like can be formed between the exposed portion and the unexposed portion of the photosensitive layer. At this time, since the matrix in which the sublimable organometallic complex is dispersed is a fine resin layer that is not porous, the processing accuracy is good and a fine pattern can be formed.
[0015]
In the method for forming a metal oxide thin film pattern of the present invention, first, a photosensitive layer containing a sublimable organometallic complex and a silicon polymer compound is formed on a substrate. The substrate may be planar or curved, and the material is not limited at all. For example, any base material on which a metal oxide thin film pattern can be formed can be used, such as a silicon substrate or a quartz substrate.
[0016]
The photosensitive layer containing the sublimable organometallic complex and the silicon polymer compound can be formed using, for example, the metal oxide thin film pattern forming composition of the present invention.
Here, the composition for pattern formation of this invention is demonstrated.
[0017]
The sublimable organometallic complex that can be blended in the composition of the present invention is not particularly limited with respect to the structure of the ligand and the type of the central metal, but sublimates at a heating temperature of about 50 ° C. to 200 ° C. at room temperature or under reduced pressure. Things are desirable. Furthermore, it is preferable that it is stable in the air and the decomposition reaction does not proceed simultaneously at the sublimation temperature.
[0018]
Specifically, examples of the sublimable organometallic complex include β-diketone complexes such as an acetylacetone complex, and the following complexes are suitably used because they have appropriate sublimation properties. Al (AA)_Three , Be (AA)₂ , Ca (AA)₂ , Cd (AA)₂ , Co (AA)_Three , Cr (AA)_Three , Cu (AA)₂ , Eu (AA)_Three , Fe (AA)_Three , Ga (AA)_Three , In (AA)_Three , La (AA)_Three , Mg (AA)₂ , Mn (AA)₂ , Pb (AA)₂ , Pt (AA)₂ , Rh (AA)_Three , Ru (AA)_Three , Sc (AA)_Three , Th (AA)_Four ,UO₂ (AA)₂ Zn (AA)₂ , And Zr (AA)_Four Etc. AA represents an acetylacetonato ligand.
[0019]
In these acetylacetonato complexes, a trifluoropropyl group may be introduced instead of the terminal methyl group.
Among the above-mentioned complexes, Al (AA)_Three , In (AA)_Three , La (AA)_Three , Mg (AA)₂ , Th (AA)_Four , And Zr (AA)_Four Is particularly preferable from the viewpoint of excellent sublimation properties.
[0020]
The sublimable organometallic complex can be appropriately selected and used in accordance with the combination with the silicon-based polymer compound or the application. When the present invention is applied to a high-contrast pattern, for example, an optical waveguide, it is desired to increase the difference in refractive index between the exposed portion and the unexposed portion. For this purpose, the metal species of the sublimable organometallic complex should be as large as possible in the difference between the refractive index when the metal species alone forms a metal oxide and the refractive index of silicon oxide. preferable.
[0021]
The content of the sublimable organometallic complex in the pattern-forming composition of the present invention is not particularly limited, but when the content is too low, sufficient refraction occurs in the exposed and unexposed areas in the exposed photosensitive layer. The rate difference cannot be obtained. On the other hand, when the content is too large, the sublimable organometallic complex and the silicon-based polymer compound may be phase-separated and become non-uniform. Such non-uniformity significantly deteriorates the optical characteristics when used for an optical waveguide, for example. In addition, when the present invention is applied to the surface imaging method, the resolution of the lithography pattern is extremely lowered. In general, the content of the sublimable organometallic complex is preferably 1 to 50%, more preferably 5 to 15% with respect to the silicon-based polymer compound. However, this is not the case when the present invention is applied to the formation of a fine metal wiring pattern. Since the adhesion between the metal oxide thin film and the metal wiring pattern as the metal wiring base can be improved, it is desirable that the sublimable organometallic complex and the matrix such as the silicon-based polymer compound have some phase separation. It is. For phase separation, the content of the sublimable organometallic complex is preferably about 1 to 1000%, more preferably 50 to 200% with respect to the matrix component such as the silicon-based polymer compound.
[0022]
Examples of the silicon-based polymer that can be contained in the pattern forming composition of the present invention include inorganic or organic silicon-based polymer compounds and silicon-based clusters.
[0023]
Examples of the inorganic or organosilicon polymer compound include polysilanes, polysiloxanes, and polysilazanes, and the molecular weight thereof is not particularly limited, but is preferably 500 to 5,000,000. It is more preferable that it is 000-1,000,000. If it is less than 500, the film formability is not sufficient, and there is a risk of decomposition and volatilization. On the other hand, if it exceeds 5,000,000, the solubility in a solvent may be deteriorated during coating. The main chain of polysilanes or polysiloxanes may be linear, branched, ladder-like, or dendrimeric. However, in order to smoothly perform sublimation of the sublimable organometallic complex, the main chain of the polysilane is preferably linear or dendrimer, and forms a good pattern with higher contrast than the network. be able to. In addition, polysilanes are oxidized during exposure or heating and expand in volume. Since this simultaneously cancels the volume shrinkage due to the three-dimensional cross-linking, the occurrence of pattern distortion and cracks due to the volume change is suppressed, and a good pattern can be formed.
[0024]
In particular, polysilanes and polysiloxanes having an alkoxy group in the side chain are effective in improving the heat resistance of the film because the organic groups remaining in the film can be reduced. Further, when the present invention is applied to an optical waveguide, it is possible to reduce propagation loss. Polysilanes and polysiloxanes having an alkoxy group in the side chain include polysilanes having repeating units represented by the following general formulas (I) and (II), and the following general formulas (III) and (IV). Examples include polysiloxanes having repeating units.
[0025]
[Chemical 1]

(In the above general formulas (I) and (II), R¹ And R² Are selected from a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, an aryl group, and an aralkyl group, which may be the same or different. )
[0026]
[Chemical formula 2]

(In the above general formulas (III) and (IV), R^Three And R^Four Are selected from a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, an aryl group, and an aralkyl group, which may be the same or different. )
R in the general formulas (I) to (IV)¹ ~ R^Four Examples of the unsubstituted alkyl group that can be introduced as include a methyl group, an ethyl group, an isopropyl group, a tertiary butyl group, an isobutyl group, a normal butyl group, and a hexyl group.
[0027]
Examples of the substituent that can be introduced into these alkyl groups to form a substituted alkyl group include a trifluoromethyl group, a hydroxyl group, an alkoxy group, a carbonyl group, a cyano group, and a nitro group.
[0028]
Examples of the unsubstituted aryl group include a phenyl group and a naphthyl group. Examples of the unsubstituted aralkyl group include a phenylethyl group and a phenylpropyl group.
[0029]
Such an unsubstituted aryl group and aralkyl group may be introduced with a substituent as described above.
In addition, polysilanes or polysiloxanes having a hydrogen atom as a side chain are crosslinked by oxidizing the Si—H bond by heating, so that the residual amount of organic groups can be reduced.
[0030]
As the silicon-based cluster, for example, a cage polysiloxane such as silsesquioxane is used. Although the molecular weight of a cluster is not specifically limited, It is preferable that it is 300-3,000, and it is more preferable that it is 400-1,000. If it is less than 300, the film-forming property is not sufficient, and there is a risk of volatilization when the sublimable organometallic complex is sublimated. On the other hand, if it exceeds 3,000, the coatability and solvent solubility may deteriorate.
[0031]
In addition to the above-described components, the composition of the present invention may further contain a photoacid generator or a photobase generator. The photoacid generator is a compound that generates an acid upon irradiation with light. Examples thereof include a triphenylsulfonium salt such as triphenylsulfonium triflate and a naphthalimidyl salt such as naphthalimidyl camphorsulfonate. When the photoacid generator is blended, the blending amount is preferably about 0.1 to 5% with respect to the silicon-based polymer compound.
[0032]
The photobase generator is a compound that generates a base when irradiated with light, and examples thereof include a photobase generator such as Midori Chemical Co., Ltd. (trade name NBC-1) having an orthonitrophenylmethyl group. . When the photobase generator is blended, the blending amount is preferably about 0.1 to 5% with respect to the silicon-based polymer compound.
[0033]
In the pattern forming composition of the present invention, a sublimable organometallic complex is blended with a silicon-based polymer compound at a predetermined ratio, and a photoacid generator or the like is added as necessary, and ethyl lactate, ethyl acetate, PGMEA, etc. These are used as a solution by being dissolved in a solvent such as xylene, toluene, anisole, tetrahydrofuran, and methylene chloride. This solution is applied onto a substrate by dipping, spin coating, doctor blade method, solvent casting method or the like to form a coating film, and the resulting coating film is about 0.5 to 5 at about 60 to 150 ° C. The photosensitive layer is formed by removing the solvent by heating for about a minute. The film thickness of the photosensitive layer can be appropriately determined according to the concentration of the application solution, application conditions, applications, and the like, and can be, for example, about 0.1 to 10 μm.
[0034]
Alternatively, the photosensitive layer may be formed on the substrate by co-evaporating a sublimable organometallic complex and a silicon-based polymer compound as described above.
In the metal oxide thin film pattern forming method of the present invention, as described above, a pattern exposure for irradiating a predetermined region of the photosensitive layer formed on the substrate with light, followed by heat drying is performed.
[0035]
Here, the pattern forming method of the present invention will be described with reference to the drawings.
FIG. 1 is a process sectional view showing an outline of an example of a metal oxide thin film pattern forming method of the present invention.
[0036]
First, as shown in FIG. 1A, pattern exposure is performed on the photosensitive layer 2 formed on the substrate 1 by irradiating exposure light 4 through a mask 3 having a predetermined pattern, for example. Note that pattern exposure may be performed by directly scanning the photosensitive layer 2 with a laser light source or the like without using a mask.
[0037]
As the light source for irradiating the exposure light 4, any light source can be used as long as it exposes the photosensitive layer 2. In other words, the light 4 used for exposure is obtained by decomposing or modifying a sublimable organometallic complex contained in the photosensitive layer 2 to eliminate or suppress sublimation, or a silicon-based polymer compound or a separately added photosensitivity. Any agent may be used as long as it causes a photoreaction and triggers the photoreaction to decompose or modify the sublimable organometallic complex to eliminate or suppress the sublimation property. Specifically, an electron beam or the like can be used as the exposure light 4. Also, a GI type optical waveguide can be formed by controlling the exposure amount of the exposure light 4 to provide an inclination of the exposure amount in the surface of the photosensitive layer or in the film thickness direction. Furthermore, by using interference of a plurality of exposure beams, interference fringes may be formed in the photosensitive layer 2 to form a photonic band or an interference mirror.
[0038]
If light having an absorption wavelength of the sublimable organometallic complex is used as the exposure light 4, this complex can be directly decomposed by exposure. For example, Al (AA)_Three Shows absorption with a peak near 280 nm, Zr (AA)_Three Shows absorption having a peak in the vicinity of 300 nm, so that the metal complex in the exposed portion can be decomposed by pattern exposure by irradiating with ultraviolet light in the vicinity of 300 nm. Ru (AA)_Three For example, when a metal complex having absorption in the visible light region such as polysilane having a strong absorption in the ultraviolet region is used as a silicon polymer compound, it is not hindered by the absorption of the silicon polymer compound. The metal complex can be efficiently photodecomposed. Various sensitizers may be used to promote photolysis. Various sensitizing dyes can be used, and the blending amount thereof can be about 0.1 to 5% with respect to the silicon-based polymer compound.
[0039]
In the pattern forming method of the present invention, the sublimable organometallic complex may be decomposed due to exposure, and does not necessarily have to be directly decomposed by exposure as described above. By irradiating with light, first, a silicon-based polymer compound or other photosensitive additive undergoes a photoreaction to produce a photoreaction product, which reacts with the sublimable organometallic complex described above to form a complex. Decomposition may be caused. For example, Al (AA)_Three In the acetylacetonate complex such as, a ligand exchange reaction is caused by a hydroxyl group such as a silanol group or a phenolic hydroxyl group. Therefore, if a silicon-based polymer compound or a photosensitive additive that uses such a hydroxyl group as a result of a photoreaction by exposure is used, the hydroxyl group decomposes the sublimable organometallic complex well and loses its sublimation properties. Can be made.
[0040]
For example, polysilanes generate silanol groups by photooxidation, and hydrosilanes of polysilanes and polysiloxanes efficiently generate silanol groups by photoreaction. Similarly, the alkoxy group introduced into the side chain of the polysilane or polysiloxane generates a silanol group in the presence of heating or an acid catalyst. In this case, as the acid catalyst, the photo acid generator as described above is used.
[0041]
Examples of polysilanes that can eliminate the sublimation property of the sublimable organometallic complex by such mechanism include, for example, polydiisopropoxysilane, polyditertiaryoxysilane, polyisopropoxymethylsilane, polytertiaryoxymethylsilane, polytertiaryoxy. Silanes, polymethylsilanes, and polyphenylsilanes, and polysiloxanes include polydiisopropoxysiloxane, polyditertiaryoxysiloxane, polyisopropoxymethylsiloxane, polytertiaryoxymethylsiloxane, polytertiaryoxysiloxane, Examples include polymethylsiloxane and polyphenylsiloxane.
[0042]
Examples of the photosensitive additive that eliminates the sublimation property of the sublimable organometallic complex by the mechanism described above include, for example, a photoacid generator and a phenol derivative such as tartariboxybenzene and a silanol derivative such as isopropoxydiphenylsilane. And the like. When blending such a photosensitive additive, the blending amount is desirably about 1 to 5% with respect to the silicon-based polymer compound.
[0043]
Note that polysilanes and polysiloxanes having a tertiary riboxy group in the side chain are preferably used in combination with a latent catalyst such as a photoacid generator. If the organic group remains, the propagation loss may increase. However, the organic group is effective in producing a thick film because it prevents film shrinkage and cracking. In such a case, an increase in propagation loss can be suppressed to some extent by using a fluorinated organic group. For the same reason, when an organic polymer such as polyimide is added for the purpose of improving film formability, it is desirable to use fluorine or a fluoride such as polyimide.
[0044]
By performing pattern exposure as described above, in the exposed portion of the photosensitive layer, the sublimable organometallic complex is modified to form a latent image on the photosensitive layer. That is, the sublimation property of the sublimable organometallic complex is reduced in the exposed portion of the photosensitive layer, and in some cases, the sublimation property in the exposed portion is lost.
[0045]
By heating and drying the photosensitive layer 2 on which the latent image is thus formed, the sublimable organometallic complex 5 in the unexposed portion 2b is sublimated and removed from the photosensitive layer 2 as shown in FIG. The The heat drying here is preferably determined according to the properties of the sublimable organometallic complex, but is generally set higher than the sublimation temperature and lower than the decomposition temperature, and is preferably performed for about 1 minute to 5 hours. It is more preferable to carry out for about minutes to 1 hour. In heat drying, it is necessary to sublimate the sublimable organometallic complex without thermal decomposition. Therefore, it is most preferable to perform heat drying under vacuum conditions of about 1 torr or less so that the sublimation temperature is lower than the thermal decomposition temperature of the complex.
[0046]
In addition, when the metal complex which maintained sublimation property remains in the exposure part 2a of a photosensitive layer, this is removed similarly.
Thereafter, the entire surface of the photosensitive layer 2 is irradiated with an exposure source, an ultraviolet light source, or the like as required, or a process such as heating at about 200 to 500 ° C. is performed to expose the photosensitive layer as shown in FIG. The layer may be mineralized. As a result, the decomposition product of the complex can be satisfactorily fixed to the matrix made of the silicon-based polymer compound, or the optical properties can be improved by making the silicon-based polymer compound matrix inorganic. For example, when polysilanes are used as the silicon-based polymer compound matrix, the entire surface exposure and heat drying are performed to obtain SiO.₂ Mineralization to a similar structure proceeds.
[0047]
By performing this step, the matrix in which the sublimable organometallic complex is dispersed becomes a dense resin film that is not porous, so that a fine pattern can be formed with high processing accuracy.
[0048]
As described above, by using the pattern forming method of the present invention, it is possible to easily form a pattern in which a silicon oxide thin film is doped with another metal element. When plasma etching is performed on the metal oxide thin film formed in a pattern by the RIE process, the etching resistance varies depending on the metal species contained therein, so that this pattern can be used as an etching mask. Thus, the thin film to be processed provided in the lower layer of the pattern can be etched into a positive or negative image according to the formed pattern, and can be applied to a surface imaging method used for semiconductor microfabrication.
[0049]
FIG. 2 is a process sectional view schematically showing an example of such a method.
First, as shown in FIG. 2 (a), a thin film (a thin film to be processed) 6 which is a fine processing contrast and a photosensitive layer 2 as described above are sequentially formed on a substrate 1, and a mask having a predetermined pattern. The pattern exposure is performed by irradiating the exposure light 4 through 3. The material of the thin film 6 to be processed is not particularly limited, and can be formed with a film thickness of about 0.1 to 10 μm using, for example, a spin coating method, a dip coating method, a CVD method, a sputtering method, or the like. Next, heat drying and post-processing as necessary are performed to form a latent image of the pattern on the photosensitive layer 2 on the thin film 6 to be processed. Thereafter, the photosensitive layer 2 on which the latent image is formed is used as an etching mask, and etching is performed with the plasma 7 by an appropriate etching method as shown in FIG. 2B, as shown in FIG. Thus, a thin film 6a to be processed is obtained. As an etching method, a dry etching method is preferable from the viewpoint of excellent processing accuracy, and an anisotropic dry etching method is more preferable.
[0050]
Or it is also possible to form a fine metal wiring pattern using the metal oxide thin film pattern formed by the pattern forming method of the present invention. When the metal species contained in the photosensitive layer is Pd, Pt, Rh, or Ru, since it has a catalytic action of electroless plating, a metal wiring pattern can be formed as follows. That is, by immersing a pattern composed of a portion containing these metal species and a portion not containing them in the silicon oxide thin film as shown in FIG. In the contained part, this metal seed | species serves as a catalyst and the surface of a silicon oxide thin film is electroless-plated. In this case, any plating bath may be used as long as electroless plating proceeds with the above-described metal species. On the other hand, the portion containing no or a small amount of the above metal species is not subjected to electroless plating, whereby a metal wiring pattern 9 as shown in FIG. 3 can be formed. Thus, when forming a metal wiring pattern, it is not necessary to make the silicon oxide thin film inorganic.
[0051]
In addition, when the wiring pattern is not very fine, instead of forming a photosensitive layer by applying a mixed solution of a silicon-based polymer compound and a sublimable organometallic complex, a porous material composed of fine particles of a silicon-based polymer compound is used. A film formed and adsorbed by impregnating the porous film with a solution of a sublimable organometallic complex may be used. Moreover, metal oxide fine particles can also be used as such fine particles.
[0052]
When the present invention is used, it is possible to easily form a metal oxide thin film pattern such as a fine refractive index pattern having a small propagation loss and excellent heat resistance as described above.
[0053]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described below based on examples. In addition, the following examples are for concrete description, and do not limit the embodiments and the scope of the invention.
Example 1
In this embodiment, a two-branch optical waveguide element having a rectangular cross section of 20 × 1 μm is manufactured by the method of the present invention using a photomask having a two-branch waveguide pattern with an optical waveguide width of 20 μm and a branching waveguide pitch of 250 μm. did.
[0054]
First, Zr (AA) as a sublimable organometallic complex_Four Was mixed at a rate of 10 wt% with respect to polydiisopropoxysiloxane as a silicon-based polymer compound, and this mixture was dissolved in toluene to prepare a toluene solution. The obtained toluene solution was applied onto a glass substrate by a spin coating method, and the solvent was removed by heating at 100 ° C. for 1 minute to produce a photosensitive layer having a thickness of about 1 μm.
[0055]
The obtained photosensitive layer was irradiated with ultraviolet light having a wavelength of 300 nm using the above-described photomask (irradiation amount: 1 W / cm² ) To form a latent image. After irradiation, Zr (AA) in the exposed part of the photosensitive layer_Four It was confirmed that absorption near 300 nm due to the disappearance occurred.
[0056]
The photosensitive layer on which the latent image is formed is 150 ° C., 10 ° C.^-2Vacuum drying was performed for 1 hour at torr. Next, the entire surface is exposed with ultraviolet light having a wavelength of 300 nm (irradiation amount: 1 W / cm² Then, the core layer was formed by heating at 450 ° C. for 30 minutes. A polysilazane solution was spin-coated on the upper surface of the obtained core layer, and the upper clad layer was formed by heating at 450 ° C. for 30 minutes to obtain an optical waveguide device.
[0057]
In the manufactured optical waveguide device, the difference in refractive index between the exposed portion and the unexposed portion was 3.2%. The transmission loss at a wavelength of 670 nm shows a relatively good value of 0.06 dB / cm, and there is almost no change in characteristics even after heating at 450 ° C. for 5 hours in air, so it has sufficient heat resistance. I found out. Furthermore, it was confirmed that the difference in coefficient of thermal expansion between the waveguide pattern and the substrate was also small.
(Example 2)
An optical waveguide was produced in the same manner as in Example 1 except that polydiisopropoxysilane was used as the silicon polymer compound.
[0058]
In the manufactured optical waveguide device, the refractive index difference between the exposed portion and the unexposed portion was 3.4%. The transmission loss at a wavelength of 670 nm shows a relatively good value of 0.07 dB / cm, and there is almost no change in characteristics even after heating at 450 ° C. for 5 hours in air, so it has sufficient heat resistance. I found out. Furthermore, it was confirmed that the difference in coefficient of thermal expansion between the waveguide pattern and the substrate was also small.
(Example 3)
As a sublimable organometallic complex, Zr (AA)_Four Instead of Al (AA)_Three , In (AA)_Three , La (AA)_Three , Mg (AA)₂ , And Th (AA)_Four An optical waveguide device was produced in the same manner as in Example 1 except that was used.
[0059]
The manufactured optical waveguide device has a difference in refractive index of 3% or more between the exposed portion and the unexposed portion, and has good transmission characteristics with transmission loss of 0.1 dB / cm or less at wavelengths of 670 nm and 1.3 μm. showed that. In addition, since the characteristics hardly changed even after heating at 450 ° C. for 5 hours in air, it was found that the film had sufficient heat resistance. Furthermore, it was confirmed that the difference in coefficient of thermal expansion between the waveguide pattern and the substrate was also small.
(Example 4)
As a sublimable organometallic complex, Zr (AA)_Four Instead of In (AA)_Three , La (AA)_Three , Mg (AA)₂ , And Th (AA)_Four An optical waveguide device was produced in the same manner as in Example 2 except that was used.
[0060]
The manufactured optical waveguide device has a difference in refractive index of 3% or more between the exposed portion and the unexposed portion, and has good transmission characteristics with transmission loss of 0.1 dB / cm or less at wavelengths of 670 nm and 1.3 μm. showed that. In addition, since the characteristics hardly changed even after heating at 450 ° C. for 5 hours in air, it was found that the film had sufficient heat resistance. Furthermore, it was confirmed that the difference in coefficient of thermal expansion between the waveguide pattern and the substrate was also small.
(Example 5)
Zr (AA) as a sublimable organometallic complex_Four Al (AA) instead of_Three An optical waveguide device was produced in the same manner as in Example 1 except that was used.
[0061]
The produced optical waveguide device has a difference in refractive index of 1% or more between the exposed portion and the unexposed portion, and has good optical transmission characteristics with transmission loss of 0.1 dB / cm or less at wavelengths of 670 nm and 1.3 μm. showed that. In addition, since the characteristics hardly changed even after heating at 450 ° C. for 5 hours in air, it was found that the film had sufficient heat resistance. Furthermore, it was confirmed that the difference in coefficient of thermal expansion between the waveguide pattern and the substrate was also small.
(Example 6)
In this example, a fine refractive index distribution pattern in the film thickness direction was formed.
[0062]
Al (AA) as a sublimable organometallic complex_Three Was mixed at a rate of 10 wt% with respect to polydiisopropoxysiloxane as a silicon-based polymer compound, and this mixture was dissolved in toluene to prepare a toluene solution. The obtained toluene solution was applied onto a glass substrate by a spin coating method, and the solvent was removed by heating at 100 ° C. for about 1 minute to produce a photosensitive layer having a thickness of about 5 μm.
[0063]
Laser light having a wavelength of 266 nm was used as a light source, and exposure was performed by allowing biaxial light beams to enter the substrate from both sides of the photosensitive layer at an incident angle of 60 ° and a beam optical axis crossing angle of 120 °. The irradiation spot diameter was about 100 μm.
[0064]
The photosensitive layer after exposure is 150 °, 10 °^-2Vacuum-dried for 1 hour at torr. After vacuum drying, the entire surface is exposed with ultraviolet light having a wavelength of 300 nm (irradiation amount: 1 W / cm² And heated at 450 ° C. for 30 minutes.
[0065]
The depth profile of the aluminum element at the irradiated part of the obtained film was measured by XPS measurement. As a result, a periodic change in the aluminum element content in the film thickness direction of the irradiated part was observed, and it was found that a refractive index distribution could be formed in the film thickness direction of the photosensitive layer.
(Example 7)
In this example, a fine pattern was formed by the surface imaging method.
[0066]
Pt (AA) as a sublimable organometallic complex₂ Was mixed at a rate of 10 wt% with respect to polydiisopropoxysiloxane as a silicon-based polymer compound, and this mixture was dissolved in toluene to prepare a toluene solution.
[0067]
On the other hand, a crosslinked novolak resin film having a thickness of 0.7 μm is formed on a silicon substrate, and the above toluene solution is applied onto the resin film by a spin coating method, and the solvent is removed by heating at 100 ° C. for about 1 minute. Thus, a photosensitive layer having a thickness of about 0.1 μm was produced.
[0068]
The prepared photosensitive layer was irradiated with ultraviolet light having a wavelength of 300 nm using a photomask having a 0.5 μm line and space pattern (irradiation amount: 1 W / cm² ) To form a latent image.
[0069]
The photosensitive layer on which the latent image is formed is 150 ° C., 10 ° C.^-2A pattern was formed by vacuum heating and drying at torr for 1 hour. The patterned thin film was dry-etched by reactive ion etching using chlorine gas to finely process the novolac resin film. As a result, the novolac resin film could be patterned with a line and space of about 0.5 μm.
(Example 8)
In this example, a fine metal wiring pattern was formed.
[0070]
Pt (AA) as a sublimable organometallic complex₂ Was mixed at a rate of 10 wt% with respect to polydiisopropoxysiloxane as a silicon-based polymer compound, and this mixture was dissolved in toluene to prepare a toluene solution. The obtained toluene solution was applied onto a glass substrate by a spin coating method, and the solvent was removed by heating at 100 ° C. for about 1 minute to produce a photosensitive layer having a thickness of about 1 μm.
[0071]
The prepared photosensitive layer was irradiated with ultraviolet light having a wavelength of 300 nm using a photomask having a 5 μm line and space pattern (irradiation amount: 1 W / cm² ) To form a latent image.
[0072]
The photosensitive layer on which the latent image is formed is 150 ° C., 10 ° C.^-2A pattern was formed by vacuum heating and drying at torr for 1 hour. When this patterned thin film was immersed in a nickel electroless plating bath to deposit a 1 μm-thick nickel thin film on the pattern portion containing Pt, a good nickel electrode pattern was formed.
Example 9
First, silica fine particles (average particle diameter of about 20 nm) are coated on a glass substrate to a thickness of 1 μm by a squeegee printing method to form a porous film, and Pt (AA) is formed on the porous film.₂ Was adsorbed to form a photosensitive layer. When a pattern was formed in the same manner as in Example 8 except that the photosensitive layer thus obtained was used, a good nickel electrode pattern was formed.
[0073]
【The invention's effect】
As described above, according to the present invention, a metal oxide thin film pattern that can form a refractive index profile of an inorganic optical waveguide, a photonic band, an interference mirror, or the like with low propagation loss and excellent heat resistance can be easily used. And a pattern forming composition used therefor are provided.
[0074]
The present invention can be used very suitably for surface imaging methods and metal wiring pattern formation used in semiconductor microfabrication processes, and its industrial value is tremendous.
[Brief description of the drawings]
FIG. 1 is a process cross-sectional view schematically showing an example of a pattern forming method of the present invention.
FIG. 2 is a process cross-sectional view schematically showing another example of the pattern forming method of the present invention.
FIG. 3 is a cross-sectional view schematically showing an example of a metal wiring pattern formed by the method of the present invention.
[Explanation of symbols]
1 ... Base material
2 ... Photosensitive layer
2a: Exposure part
2b: Unexposed part
3 ... Mask
4 ... exposure light
5 ... Sublimable organometallic complex
6 ... Thin film
7 ... Plasma
9 ... Metal wiring pattern

Claims (4)

Forming a photosensitive layer containing a sublimable organometallic complex and a silicon-based polymer compound on a substrate;
A step of selectively exposing a predetermined region of the photosensitive layer to form a latent image of a thin film pattern; and a step of heating and drying the photosensitive layer on which the latent image of the thin film pattern is formed to sublimate the unexposed portion. A method for forming a pattern of a metal oxide thin film comprising a step of removing an organometallic complex. The method for forming a metal oxide thin film pattern according to claim 1, wherein the sublimable organometallic complex is an acetylacetone complex derivative. A metal oxide thin film pattern forming composition comprising a sublimable organometallic complex and a silicon polymer compound. Forming a photosensitive layer containing a sublimable organometallic complex on a substrate;
Selectively exposing a predetermined area of the photosensitive layer to form a latent image of a thin film pattern;
A step of heating and drying the photosensitive layer on which the latent image of the thin film pattern is formed, and removing a sublimable organometallic complex in an unexposed portion; and a step of depositing a metal on the exposed portion of the photosensitive layer after the heating and drying. A method for forming a fine metal pattern.

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