JP4009044B2

JP4009044B2 - Thin-film birefringent element and method and apparatus for manufacturing the same

Info

Publication number: JP4009044B2
Application number: JP28843099A
Authority: JP
Inventors: 和憲藤井
Original assignee: Ricoh Optical Industries Co Ltd
Current assignee: Ricoh Optical Industries Co Ltd
Priority date: 1999-10-08
Filing date: 1999-10-08
Publication date: 2007-11-14
Anticipated expiration: 2019-10-08
Also published as: JP2001108832A

Description

【０００１】
【発明の属する技術分野】
本発明は、偏光素子に含まれる薄膜複屈折素子及びその製造方法及び製造装置に関する。
【０００２】
【従来の技術】
複屈折を利用して直線偏光・円偏光間の変換を初めとする光の偏光状態の調整、変換、回転を行う光学素子としては、従来、水晶や方解石といった結晶を加工したものがあるが、このような結晶を加工した光学素子は、材料費や加工コストがかかるという欠点がある。また、従来から斜め蒸着で形成された蒸着膜が異方性を持つことが知られており、蒸着膜は低コストで形成できることから、近年この斜め蒸着膜の異方性を波長板等の偏光素子として利用しようという提案がなされている。
【０００３】
ここで、図１６に斜め蒸着膜形成装置の一例を示すが、斜め蒸着を行う場合、斜め蒸着膜形成装置２５内で基板２６は蒸着材２８を備えた蒸発源２７に対して斜めに配置されているため、蒸発源２７と基板２６間の距離が基板位置で異なり、斜め蒸着により形成される蒸着膜は、同一基板内の上下方向において膜厚に差が生じる。この場合、複屈折量も膜厚に対応して異なっているため、基板内では位相差の分布が発生する。この基板内での位相差の分布を解消するため、斜め蒸着膜を多層構造とし、１層毎に基板への入射角を基板法線を中心として対称方向に変更する方法が知られている（特公平７−３４８６号公報）。
【０００４】
さらに斜め蒸着により形成される蒸着膜は、膜の縦方向と横方向で密度が異なり複屈折を示すが、この複屈折を目的として形成される斜め蒸着膜は、通常、金属酸化膜等の誘電体膜で形成されている。しかし、斜め蒸着により形成される誘電体膜はほとんどが柱状組成（コラム）として形成されるため密度が一様ではなく、内部応力も高く環境変化等により密着性が劣化し、基板から蒸着膜が剥離する、あるいは膜が白濁する不具合や、誘電体膜の吸収増加による分光透過率の低下などに見られる光学特性の劣化という不具合が生じる。
尚、この柱状組成（コラム）の成長方向では、蒸着角αとコラムの傾斜角βの間には、
β＝(1/2)tanα
の規則性があることが知られている（薄膜応用ハンドブック第２刷、（株）エヌ・ティー・エス発行）。
また、Ｔａ₂Ｏ₅の斜め蒸着において、柱状組成の傾斜角をα、蒸着角をθとしたときの両者の関係は、α＝0.5θの関係にあることが報告されている（Applied
optics/Vol.28,No.13/1 July 1989）。
【０００５】
【発明が解決しようとする課題】
上記従来技術（特公平７−３４８６号公報）に記載された方法により作成される斜め蒸着膜は、１層毎に基板の方向を変えて蒸着しなければならない多層膜構造であり、斜め蒸着膜の形成時に、１層毎に基板の方向を変更して蒸着する必要があるため加工時間の増長を招き、さらには製造装置への複雑で新規な機構の追加が必要となるため、コストがかかるという問題がある。加えて同一物質の分割蒸着となるため、各層での屈折率を均一に保つことは困難であり不均質膜と成りやすく、基板内での複屈折量にも誤差が生じ易くなるという問題がある。
また、上述したように、斜め蒸着により形成される誘電体膜はほとんどが柱状組成として形成されるため密度が一様ではなく、内部応力も高く環境変化等により密着性が劣化し、基板から蒸着膜が剥離する、あるいは膜が白濁する不具合や、誘電体膜の吸収増加による分光透過率の低下などに見られる光学特性の劣化という不具合が生じ、信頼性が劣るという問題がある。
【０００６】
本発明は上記事情に鑑みなされたものであり、加工コストが安く、量産が可能であり、且つ斜め蒸着膜の剥離及び白濁・吸収を防止し、斜め蒸着膜の密着性、耐環境性、光学特性及びその安定性等を向上させた信頼性の高い薄膜複屈折素子を提供すること、及び同一基板内での複屈折量の誤差を少なくさせた薄膜複屈折素子、もしくは基板内に任意の勾配を持たせた複屈折量を精度良く発現させた薄膜複屈折素子を提供することを目的とし、さらには、その薄膜複屈折素子の製造方法及び製造装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、本発明に係る薄膜複屈折素子は、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有する薄膜複屈折素子であって、上記斜め蒸着膜は膜厚及び複屈折量が制御された単層膜構造の蒸着膜であることを特徴としており、これにより、従来の多層膜構造の斜め蒸着膜に比べて加工コストを低減でき、量産性も確保できる。
また、本発明に係る薄膜複屈折素子は、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有する薄膜複屈折素子であって、上記斜め蒸着膜は膜厚及び複屈折量が制御された単層膜構造の蒸着膜であり、基板表面と上記斜め蒸着膜の間もしくは上記斜め蒸着膜上のいずれか一方もしくは両方に、密着性、耐環境性及び光学特性を向上させることを目的とする薄膜（アンダーコート膜またはオーバーコート膜）を有することを特徴としており、これにより、斜め蒸着膜の密着性、耐環境性及び光学特性の向上を図ることが可能となる。
さらに、本発明に係る薄膜複屈折素子は、上記の構成の薄膜複屈折素子において、上記斜め蒸着膜もしくは斜め蒸着膜上の薄膜に熱処理（アニール）を施して膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えたことを特徴としており、これにより、斜め蒸着膜の密着性、耐環境性、光学特性及びその安定性の向上を図ることが可能となる。
さらにまた、本発明に係る薄膜複屈折素子は、上記の構成の薄膜複屈折素子を、２個以上貼り合わせて構成したことを特徴としており、これにより、斜め蒸着膜の密着性、耐環境性、光学特性及びその安定性の向上をより一層図ることが可能となる。
そして上記のような本発明に係る薄膜複屈折素子は、以下のような製造方法あるいは製造装置で製造される。
【０００８】
請求項１に係る発明は、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有し、上記斜め蒸着膜は膜厚及び複屈折量が制御された単層膜構造の蒸着膜である薄膜複屈折素子を作製する際の薄膜複屈折素子の製造方法であって、１以上の基板を保持した円盤状の基板ホルダーを自転運動と公転運動からなる遊星回転機構で保持し、上記遊星回転機構により上記基板ホルダーを自転しながら上記蒸着装置内を公転運動させ、上記基板ホルダーで保持された１以上の基板を、蒸発物質を蒸発させる蒸発源の上部で半円状の軌跡を描くような回転運動で移動させるとともに、上記基板ホルダーと上記蒸発源の間の基板ホルダー近傍に開口部を有する遮蔽板を配置した状態で、上記蒸発源と、上記蒸発装置内にプラズマ状態を形成するプラズマ源もしくはイオン源を用いて蒸発物質をイオン化して基板方向に飛翔させ、上記遮蔽板の開口部を介して基板上に斜め方向から蒸発物質を入射させて斜め蒸着膜を形成することを特徴としており、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成することが可能となる。
また、請求項２に係る発明は、請求項１記載の薄膜複屈折素子の製造方法において、上記遮蔽板には、上記基板ホルダーの自転運動の中心と該遮蔽板の２つの開口部の中心が同一となるよう配置された状態で上記基板ホルダーの遊星回転機構による公転運動と同期させた公転運動が与えられることを特徴としている。
【００１０】
さらに請求項３に係る発明は、請求項１または２記載の薄膜複屈折素子の製造方法において、斜め方向からの蒸着により単層膜構造の斜め蒸着膜を形成すると共に、基板内において上記斜め蒸着膜の膜厚及び複屈折量を均一な状態に制御することを特徴としている。
【００１１】
請求項４に係る発明は、請求項１〜３のいずれか一つに記載の薄膜複屈折素子の製造方法において、上記基板上に目的とする膜厚及び／または複屈折量の蒸着膜を形成するために、上記蒸着装置内にダミー基板を配置し、さらに蒸着装置外部に監視窓で接する投光部と受光部からなる光学式膜厚計及び／または該光学式膜厚計と同等の光学系の投光部と受光部の途中に偏光子を追加した構成の複屈折量測定器を用いて、加工中のダミー基板もしくは基板の透過光量もしくは反射光量の変化を監視することにより、斜め蒸着中の蒸着膜の光学的膜厚及び／または複屈折量を監視し、所望の膜厚及び／または複屈折量と成るよう蒸着条件及び時間を制御することを特徴としており、これにより、斜め蒸着膜の膜厚及び／または複屈折量を均一な状態に制御することや、あるいは、斜め蒸着膜の基板内の位置と複屈折量の関係が勾配を持って分布するように制御することが可能となる。
【００１２】
請求項５に係る発明は、請求項１〜４のいずれか一つに記載の薄膜複屈折素子の製造方法において、上記斜め蒸着膜を形成する前の基板表面、もしくは斜め蒸着膜形成後の斜め蒸着膜上のいずれか一方もしくは両方に、密着性、耐環境性及び光学特性を向上させることを目的とする薄膜（アンダーコート膜またはオーバーコート膜）を蒸着膜もしくは塗膜により形成することを特徴としており、密着性、耐環境性及び光学特性が向上された薄膜複屈折素子を作製することが可能となる。
また、請求項６に係る発明は、請求項１〜４のいずれか一つに記載の薄膜複屈折素子の製造方法において、上記薄膜複屈折素子の斜め蒸着膜もしくは斜め蒸着膜上の薄膜に、レーザー光を走査しながら照射してレーザー熱処理（レーザーアニール）を行い膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えることを特徴としており、密着性、耐環境性、光学特性及びその安定性が向上された薄膜複屈折素子を作製することが可能となる。
さらにまた、請求項７に係る発明は、請求項１〜６のいずれか一つに記載の薄膜複屈折素子の製造方法において、上記薄膜複屈折素子を、２個以上貼り合わせることを特徴としており、密着性、耐環境性、光学特性及びその安定性がさらに向上された薄膜複屈折素子を作製することが可能となる。
【００１３】
請求項８に係る発明は、請求項１〜７のいずれか一つに記載の薄膜複屈折素子の製造方法に用いられる薄膜複屈折素子の製造装置であって、蒸発物質を蒸発させる蒸発源とプラズマ状態を形成するためのプラズマ源もしくはイオン源を有する蒸着装置と、その蒸着装置内において１以上の基板を保持する円盤状の基板ホルダーと、該基板ホルダーを自転運動と公転運動とにより上記蒸着装置内で回転させる遊星回転機構と、上記基板ホルダーと蒸発源の間の基板ホルダー近傍に配置され蒸発物質を通過させうる開口部を有する遮蔽板とを備え、上記遊星回転機構により上記基板ホルダーを自転しながら上記蒸着装置内を公転運動させ、上記基板ホルダーで保持された１以上の基板を、上記蒸発源の上部で半円状の軌跡を描くような回転運動で移動させるとともに、上記蒸発源とプラズマ源もしくはイオン源を用いて蒸発物質をイオン化して基板方向に飛翔させ、上記遮蔽板の開口部を介して基板上に斜め方向から蒸発物質を入射させて斜め蒸着膜を形成すること特徴としており、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成することが可能な製造装置を提供できる。
【００１５】
請求項９に係る発明は、請求項８記載の薄膜複屈折素子の製造装置において、上記蒸着装置の外部に設けられ監視窓で接する投光部と受光部からなる光学式膜厚計及び／または該光学式膜厚計と同等の光学系の投光部と受光部の途中に偏光子を追加した複屈折量測定器を備え、上記光学式膜厚計及び／または複屈折量測定器を用いて、加工中の基板の透過光量もしくは反射光量の変化を監視することにより、斜め蒸着中の蒸着膜の光学的膜厚及び／または複屈折量を監視し、所望の膜厚及び／または複屈折量と成るよう蒸着条件及び時間を制御することを特徴としており、斜め蒸着膜の膜厚及び／または複屈折量を均一な状態に制御することや、あるいは、斜め蒸着膜の基板内の位置と複屈折量の関係が勾配を持って分布するように制御することが可能な製造装置を提供できる。
請求項１０に係る発明は、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有し、上記斜め蒸着膜は膜厚及び複屈折量が制御された単層膜構造の蒸着膜である薄膜複屈折素子であって、請求項１〜７のいずれか一つに記載の薄膜複屈折素子の製造方法、あるいは請求項８または９に記載の薄膜複屈折素子の製造装置により製造されたことを特徴としている。
【００１６】
以下、本発明のより具体的な特徴について説明する。
本発明に係る薄膜複屈折素子は、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有するものであり、上記斜め蒸着膜は膜厚及び複屈折量が制御された単層膜構造の蒸着膜である。そして、本発明に係る薄膜複屈折素子の製造方法では、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成するが、単層膜構造で量産性を確保するため、例えば図１に示すような構成の製造装置により、基板ホルダー９で保持された１以上の基板６を、自転運動と公転運動からなる遊星回転機構を用いて、蒸着材３を蒸発させる蒸発源（例えば電子銃あるいは抵抗加熱源等）２の上部を半円状の回転運動で移動させ、さらに基板６と蒸発源２を結ぶ直線上の基板ホルダー近傍に、上下２箇所の開口部８を有する遮蔽板７を配置した状態で斜め蒸着膜を形成する。この時、基板法線２４に対して蒸発物質が４０〜８０度傾いた方向から飛翔するように基板ホルダー９及び遮蔽板７を設定する。
【００１７】
ここで、図６に示すような遊星回転機構４５により、円盤状の基板ホルダー４６は自転しながら蒸着装置内を公転運動するので、基板ホルダー４６に保持された基板４７には、軌跡４７ａで示すような半円状の回転運動が与えられる。
一方、図１に示すように、遮蔽板７には、基板ホルダー９の自転運動の中心と遮蔽板７の２つの開口部８の中心が同一となるよう配置された状態で基板ホルダー９の遊星回転機構による公転運動と同期させた公転運動が与えられる。すなわち、基板ホルダー９と遮蔽板７は同期して公転運動を行うが、この際、基板ホルダー９は自転しているので、基板ホルダー９上に保持された複数の基板６は、遮蔽板７の２箇所の開口部８を順次通過することになり、各基板６が開口部８を通過する時に蒸着されることになる。
【００１８】
そして、上記の状態で蒸発源２から蒸着材３の蒸発物質を蒸発させることにより、遮蔽板７の開口部８を通過した蒸発物質により基板６に蒸着膜が形成されるが、この時、遮蔽板７の上下２箇所の開口部８に位置した基板のみ蒸着膜が形成され、遮蔽部分に位置する基板には蒸着膜が形成されないので、基板に対する蒸着方向は一方向に規制されることになる。
すなわち、基板に対する蒸発物質の飛翔方向は、開口部８に位置する基板の中心と蒸発源２を結ぶ直線を基準とした上下方向に限定され、かつ基板はその直線に対して傾けて配置されているので、図２に示すように蒸着材３０からの蒸発物質は基板法線３１に対してαだけ傾いた方向から飛翔することになり、基板上に斜め蒸着膜が形成される。また、遮蔽板７の上下２箇所の開口部８の位置では、基板の上下の向きが逆となるため、遮蔽板７の上下２箇所の開口部８を順次通過する基板上には、基板の法線を中心として対称方向から蒸発物質が交互に入射することになり、膜厚が略均一な斜め蒸着膜膜が形成される。そして、この斜め蒸着膜は、上記の直線方向での蒸着膜の構造と同直線方向と直交する方向での膜の構造が異なるので、複屈折性を示す膜となる。
【００１９】
さらに上記遮蔽板７の上下２箇所の開口部８の形状を目的に応じて設定することにより、基板表面内における複屈折量の分布を任意に変更することが可能となる。具体的には基板内の同一面内において複屈折量を一様にするには、遮蔽板７の上下２箇所の開口部８の形状を基板ホルダー９の自転軸を基準とした円分形状とする。一方、基板内の一方向で複屈折量に勾配を持たせるには遮蔽板７の開口部８の形状を矩形を基準として中心側と外周側の開口部の幅を複屈折量の勾配に合わせて決定する。
【００２０】
尚、遮蔽板を用いないで複屈折量に勾配を持たせることも可能である。この場合には、図１１に示す構成の装置のように、公転冶具７１で保持された基板６９に公転機構にて円周状の回転運動を与える。この時、基板６９の法線７３に対して蒸発物質が６０〜８０度傾いた方向から飛翔するように基板６９の角度を設定する。この状態で基板上に蒸発物質を堆積させると、基板上には、蒸発源方向から反蒸発源方向にかけて膜厚が薄くなる勾配を持った単層構造の斜め蒸着膜を形成できる。
【００２１】
斜め蒸着膜を形成するための蒸着材は、斜め蒸着により異方性を示す物であれば良いが、特にＴａ₂Ｏ₅，ＳｉＯ₂，ＮｂＯ₅，ＷＯ₃，ＳｎＯ₂，ＴｉＯ₂等の金属酸化物系の誘電体膜は良好の結果を示す。しかし、単に斜め蒸着した場合には、密着性の劣化、白濁の発生、吸収の増加による分光特性の劣化等の問題が発生する。そのために本発明では、電子銃や抵抗加熱源等による蒸着材の蒸発に加えて、プラズマ源もしくはイオン源を用いて導入ガスをイオン化し装置内にプラズマ状態を形成させる。そして、そのプラズマ中を蒸発物質及び酸素などの反応性ガスが通過する際にイオン化し、蒸発物質と反応性ガスとの反応を促す。この時、あらかじめ基板ホルダーに前述のイオンと逆の電荷を与えておくことにより、プラズマ空間と基板の間に電界が形成され、イオン化された蒸発物質や導入ガスが電界に従い加速され基板表面に衝突するために、密着性が高く、吸収や白濁の少ない蒸着膜が形成される。
【００２２】
薄膜複屈折素子の複屈折量を所望の値とするためには蒸着膜の膜厚を制御する必要があり、本発明においては図１に示す装置のように、投光部である光源１４と、反射鏡１６及び受光部１５からなる光学式膜厚計を用いて蒸着中の光学的膜厚を連続的に監視し、光量の変化から斜め蒸着膜の屈折率と光学的膜厚を読み取り、所望の膜厚に形成するよう制御する。制御動作としては、蒸発源２上に設置したシャッター板１２の開閉動作により実行し、所望の膜厚が得られた時点でシャッター板１２で蒸発源２上を遮蔽することで蒸着膜の膜厚制御が可能となる。
【００２３】
さらに本発明では、図１に示す装置のように、複屈折量測定器を用いて蒸着中の複屈折量を監視しながら制御することも可能である。複屈折量測定器での制御は、上記の光学式膜厚計と同等の光学系構成で、投光部である光源２０と測定用基板６もしくはダミー基板１７の間、及び測定用基板６もしくはダミー基板１７と受光部２１もしくは受光部２２の間の計２箇所に偏光子１８を配置し、各々の偏光子１８の光学軸が９０度異なった方向とする。加えて光源２０からの出射光は目的とする複屈折に対応する波長の干渉フィルターで通過させる。制御動作としては、上記の膜厚制御と同様に蒸発源２上のシャッター板１２の開閉で実施する。そして、目的の波長と複屈折量に応じて光量の極大値もしくは極小値で蒸着を終了することで複屈折量の制御を行う。極大値と極小値の関係は複屈折の増加量に応じて、使用する干渉フィルターの１／２波長毎に極大値と極小値を繰り返す。
上記２種類の制御方法の何れか一方もしくは両方を用いることにより、高精度な複屈折量の制御が可能となる。
【００２４】
ところで、基板となる媒質と斜め蒸着膜の関係において、両者の組み合わせ次第では分子間の結合力が低下し密着性が劣る場合や、屈折率の違いにより分光透過率が低下する等の現象が発生する。そこで、蒸着膜と基板の密着性及び分光透過率をさらに向上させるためには、図５に示す構成の薄膜複屈折素子のように、斜め蒸着膜４２と基板４０の間に形成される蒸着膜もしくは塗膜によるアンダーコート４１、もしくは斜め蒸着膜上に形成される蒸着膜もしくは塗膜によるオーバーコート４３、のいずれか一方もしくは両方を形成することで達成できる。このアンダーコート及びオーバーコートの材料は、斜め蒸着膜の屈折率と基板の屈折率から振幅条件と位相条件を用いて求められる屈折率と膜厚で決定する。
また、斜め蒸着膜の密着性、耐環境性、光学特性及びその安定性をさらに向上させるためには、斜め蒸着膜もしくは斜め蒸着膜上の薄膜（オーバーコート）に熱処理（アニール）を施して膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えることにより達成することができる。より具体的には、斜め蒸着膜もしくは斜め蒸着膜上の薄膜に、レーザー光を走査しながら照射してレーザー熱処理（レーザーアニール）を行い膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えることにより、密着性、耐環境性、光学特性及びその安定性が向上された薄膜複屈折素子を作製することができる。また、斜め蒸着膜もしくは斜め蒸着膜上の薄膜にレーザーアニールを施すことにより、チップ化に伴う切断時の切削液の浸透による複屈折特性の変動を抑止することができる。
【００２５】
さらに、斜め蒸着膜を形成した２つ以上の薄膜複屈折素子を用い、基板上に形成された斜め蒸着膜を有する面同士を貼り合せることで位相差の分布を調整することができる。すなわち、１枚の基板内において位相差に分布を持つものであっても、基板内における位相差の分布傾向が同じ２つの薄膜複屈折素子を図１２に示すように非対称の状態で貼り合せることで位相差の分布が解消可能となる。また、上記の方法で位相差の分布傾向を揃えて図１３に示すように対称の状態で２つの薄膜複屈折素子を貼り合せることで位相差の分布の勾配をより強調したものが製作可能である。
一方、図１４に示すように、１枚の基板での位相差が少ないものを複数貼り合せることにより、任意の位相差を有する複屈折素子（例えば波長板）の製作が可能となる。また、前述したように、斜め蒸着膜の前後にアンダーコートとオーバコートの両方もしくは一方を形成した基板を２つ以上貼り合せることで、さらに分光透過率を向上させることが可能である。
これらの薄膜複屈折素子を貼り合せる場合には、斜め蒸着面側を向い合わせて貼り合せることにより、斜め蒸着面が外部に露出しないので、耐環境性に優れ、密着性及び位相差や分光特性といった各種特性の安定性に優れた信頼性の高い薄膜複屈折素子が作製可能となる。
【００２６】
【発明の実施の形態】
以下、本発明を実施するための具体的な構成及び動作についてより詳細に説明する。
本発明に係る薄膜複屈折素子は、図１に示すように遊星回転機構と中心部に開口部８を有する遮蔽板７を備えた構成に加えて、蒸発源２の蒸着材３からの蒸発物質と導入ガスをプラズマ源（もしくはイオン源）４を用いてイオン化する構成の装置を用いて、基板上に斜め蒸着膜を形成することで実現できる。ここで、図１は薄膜複屈折素子の斜め蒸着膜を形成する製造装置の第１の構成例を示し、（ａ）は製造装置内の概略構成を示す正面図、（ｂ）は側面図である。また、図１において符号１は蒸着装置、２は蒸発源（例えば、電子銃あるいは抵抗加熱源等）、３は蒸着材、４はプラズマ源（もしくはイオン源）、５は反応性ガス導入口、６は基板、７は遮蔽板、８は遮蔽板開口部、９は遊星回転機構に支持された基板ホルダー、１０は基板ホルダーの自転方向、１１は基板ホルダーの公転方向及び遮蔽板の公転方向、１２はシャッター板、１３は監視窓、１４は膜厚計の投光部である光源、１５は膜厚計の受光部、１６は膜厚計の反射鏡、１７はダミー基板、１８は複屈折測定器の偏光子、１９は複屈折測定器の反射鏡、２０は複屈折測定器の投光部である光源、２１は複屈折測定器の透過光受光部、２２は複屈折測定器の反射光受光部、２３は蒸発物質の飛翔方向、２４は基板法線である。
【００２７】
図１に示す装置では、１以上の基板６を保持した円盤状の基板ホルダー９を自転運動と公転運動からなる遊星回転機構で蒸着装置１内を回転させ、基板ホルダー９と蒸発源２の間の基板ホルダー近傍に、上下２箇所の開口部８を有する遮蔽板７を配置した状態で、蒸発物質を蒸発させる蒸発源２と蒸発装置内にプラズマ状態を形成するプラズマ源（もしくはイオン源）４を用いて蒸発物質をイオン化して基板方向に飛翔させ、上記遮蔽板７の開口部８を介して基板６上に斜め方向から蒸発物質を入射させて斜め蒸着膜を形成するものであり、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成することができる。また、基板上に目的とする膜厚及び複屈折量の蒸着膜を形成するために、蒸着装置１内にダミー基板１７を配置し、さらに蒸着装置１の外部に監視窓１３で接する投光部（光源）１４と受光部１５からなる光学式膜厚計及び該光学式膜厚計と同等の光学系の投光部（光源）２０と受光部２１，２２の途中に偏光子１８を追加した構成の複屈折量測定器を用いて、加工中のダミー基板１７もしくは基板６の透過光量もしくは反射光量の変化を監視することにより、斜め蒸着中の蒸着膜の光学的膜厚と複屈折量を監視し、所望の膜厚及び複屈折量と成るよう蒸着条件及び時間を制御することができ、斜め蒸着膜の膜厚及び複屈折量を均一な状態に制御することができる。
【００２８】
ここで、基板上に斜め方向から蒸発物質を入射させて形成した斜め蒸着膜を有する薄膜複屈折素子は、基板表面の法線方向から光線を入射した場合、偏光素子である波長板としての機能を有する。
図２に示すように、基板２９の法線３１に対して蒸着材３０からの蒸発物質を斜め方向から入射させて斜め蒸着膜を形成する場合、斜め蒸着の初期段階においては、通常の蒸着と同様に基板表面に核が形成されるが、基板２９上の斜め蒸着膜の核が成長するに従い、蒸発物質の飛翔方向の後ろに影ができて蒸発物質が到達せずに核が形成されない部分が出現し柱状構造となる。この現象は一般に「シャドーイング効果」と呼ばれている。
この斜め蒸着膜は、蒸着膜を形成する核の成長方向が図２において基板のＸ方向とＹ方向で異なり、Ｘ，Ｙ各方向を２次元の断面として捉えた場合、図４に示すＸ方向は、斜め蒸着膜３９の核の集合体が基板法線３７の方向に成長し、基板３６と平行な方向で核の集合体が密に接する。また、図３に示すＹ方向は、基板法線３３に対して蒸着物質入射方向３４に傾斜する微細で独立した柱状構造を形成するため、斜め蒸着膜３５の屈折率はＸ方向で最大となり、Ｙ方向で最小となる。
この屈折率と複屈折の関係は次のように表すことができる。すなわち、Ｘ方向の屈折率：ｎo 、Ｙ方向の屈折率：ｎe 、複屈折：Δｎとする場合、次式の関係が成り立つ。
Δｎ＝｜ｎo−ｎe｜
【００２９】
この斜め蒸着膜の柱状構造は基板表面に対する蒸発物質の入射方向に成長しているため、基板に対する蒸発物質の入射角αを４０〜８０度の範囲で調整することにより、基板のＸ方向とＹ方向の屈折率の差、すなわち「Δｎ」が調整可能となるが、この入射角は略７０度の時にΔｎが最も大きい値を示す。
薄膜複屈折素子を波長板として用いる場合、上記Δｎと膜厚を調整することにより任意の波長板が作製可能である。ここで、波長板の特性である位相遅れ（リタデーション）は次のように表すことができる。図７に示すように、直線偏光を波長板のｎe 方向とＹ方向の電気的振動成分４８が平行となる位置関係で透過させたとき、図８に示すように、基板のＹ方向を透過した電気的振動成分５０に対して基板のＸ方向を通過した電気的振動成分５１が図示したΓだけ遅れている。この位相遅れ（リタデーション）：Γ及びΔｎの関係は斜め蒸着膜の膜厚をｄとした場合、次式の関係が成り立つ。
Γ＝Δｎ・ｄ
【００３０】
Δｎと膜厚の両者を調整して目的の位相遅れを得ようとする場合、前述した蒸発物質の入射角を調整する方法の他にｎe 及びｎo の調整が必要となるが、この調整は、方向に偏らない膜全体としての屈折率、言い換えると複屈折を考慮しない膜の屈折率：ｎの調整方法と一致する。この屈折率：ｎの変化は、一般に▲１▼単位時間当り基板に形成される蒸着膜の膜厚（蒸着レート）、▲２▼蒸着中の圧力と導入ガスの量、▲３▼基板の温度、▲４▼イオンビームもしくはプラズマ形成の放電条件、の以上４項目が主な因子となるが、厳密にｎを任意の値に調整するのは困難であり、調整できる範囲も非常に限られるため膜厚を含めた調整が不可欠となるために、ｎの変化に合わせて膜厚を高精度に調整しなければならなくなり、製作過程が複雑となる。加えて基板上に形成される蒸着膜の屈折率を測定するためには、蒸着後にエリプソメータ等の測定器を用いなければならないために、蒸着中の屈折率に合わせた膜厚を決定するのは困難である。
【００３１】
しかし本発明では、図１に示す製造装置に設けた光学式膜厚計を用いて光量の変化を監視するため、光量の極大値と極小値から大凡の屈折率：ｎを読み取ることが可能となり、加えてこの光量変化から屈折率：ｎと膜厚：ｄの積である光学的膜厚：ｎｄを監視できるため、経験的に求められる位相遅れ（リタデーション）：Γと光学的膜厚：ｎｄの関係から、目標のｎｄに達した時に蒸着を終了すれば所望のΓを得ることが可能となる。加えてさらに高精度のΓを得ることも可能であり、この場合、上記光学式膜厚計と同等の光学系を有する複屈折量測定器の光路途中の光源２０と基板６の間と、基板６と透過光受光部２１もしくは反射光受光部２２の間の２箇所に偏光子１８を配置する。このとき各偏光子１８の光学軸は互いに直交させた状態でかつ基板６のｎo もしくはｎe となる方向と、偏光子１８の光学軸が±４５度で、各偏光子１８と基板６への光線を略垂直入射となるように配置したときに、クロスニコルの方式で蒸着中のΓを知ることが可能となり、蒸着中に所望のΓとなったときに蒸着を停止することにより、高精度の薄膜複屈折素子の製作が可能となる。尚、複屈折量測定器の光学系は透過型もしくは反射型のどちらでもよい。
【００３２】
ところで蒸発源から飛翔する蒸発物質は放射状に発散しながら蒸発するため、蒸発源からの距離が増すごとに蒸発物質の密度は広がりを持つこととなるが、図１６に示した従来の斜め蒸着における基板の配置方法では、蒸発源と基板との位置関係は蒸発物質の入射方向と基板法線を含む基板面内で距離に差が生じ、基板面内において膜厚分布を示す。
本発明の薄膜複屈折素子ではこの膜厚分布を単層膜構造で解決するために、図１に示す構成の装置を使用し、図６に示すような遊星回転機構４５により基板４７が半円状の軌跡４７ａを描くように移動させた状態で、図１に示す装置の遮蔽板開口部８から蒸発物質を基板法線２４に対し約７０度で入射させる。このとき蒸発源２に対する基板６の位置関係は、遮蔽板７の上下２箇所の開口部８の位置にきた基板６にのみ蒸発物質が入射するため、柱状構造の成長方向が図２に示す基板内でのＹ方向に限定される（但し、遮蔽板７の上側と下側の開口部位置では基板の向きは上下が逆となるため、蒸着膜は傾斜方向がＹ方向で逆向きの柱状構造が交互に重なる構造となる）。また、図１に示す装置の遮蔽板開口部８は上下方向で開口部の幅が異なり、前述した蒸発物質の密度を見かけ上均一に補正する働きを持ち、基板６に形成される斜め蒸着膜は基板面内での膜厚分布が解消され、基板表面の膜厚が一様となる。この方法で成膜された柱状組成の傾斜方向は、蒸着面と平行な面での柱状組成の成長角をβ、蒸着角をαとし、６０°≦α≦７０°の場合に、略｜β｜≦０．１５αの関係にある。
【００３３】
図１に示す装置の遮蔽板開口部８の形状は基板ホルダー９の中心を基準にθを５〜４５度の円分形状もしくは扇形とすることにより基板表面の膜厚を一様にできるが、円分の中心部を基板ホルダー９の中心より後方向に移動すれば基板の手前方向から後方向に膜厚分布の勾配を持たせることができる。
【００３４】
次に本発明の別の手段として、図１１に示す構成の製造装置を用いて斜め蒸着膜を成膜することにより、遮蔽板を用いないで基板内に膜厚分布を持たせることが可能となる。ここで、図１１は薄膜複屈折素子の斜め蒸着膜を形成する製造装置の第２の構成例を示し、製造装置内の概略構成を示す正面図である。また、図１１において符号６５は蒸着装置、６６はプラズマ源（もしくはイオン源）、６７は蒸発源（例えば、電子銃あるいは抵抗加熱源等）、６８は蒸着材、６９は基板、７０は基板ホルダー、７１は公転機構の公転冶具、７２は蒸発物質飛翔方向（蒸発源と基板間の距離：Ｌ）、７３は基板法線、７４は反応性ガス導入口である。図１１に示す装置においては、１以上の基板６９を公転機構の公転冶具７１で保持し、該公転機構の公転運動により基板６９を蒸着装置６５内で回転させた状態で、蒸着物質を蒸発させる蒸発源６７と蒸発装置内にプラズマ状態を形成するプラズマ源（もしくはイオン源）６６を用いて蒸発物質をイオン化して基板方向に飛翔させ、基板上に斜め方向から蒸発物質を入射させて斜め蒸着膜を形成するものであり、膜厚及び複屈折量の分布が制御された単層膜構造の斜め蒸着膜を形成することができる。尚、図１１の構成の場合にも、図１と同様の光学式膜厚計及び／または複屈折量測定器が必要に応じて設置されるが、これらの図示は省略する。
【００３５】
図１１において、基板６９は基板ホルダー７０を介して公転冶具７１に支持され、図示しない公転機構により円周状の回転運動を与えられる。この時、基板６９の法線に対して蒸発物質がα＝６０〜８０度傾いた方向から飛翔するように基板６９を設定する。この状態で基板上に蒸発物質を堆積させると、基板上には蒸発源方向から反蒸発源方向にかけての膜厚が薄い方向へ勾配を持った斜め蒸着膜を形成できる。
基板内における膜厚分布の勾配は、基板６９の法線７３に対する蒸発物質の飛翔方向７２の傾きと、蒸発源６７と基板６９間の距離：Ｌを変えることで調整が可能である。具体的には、基板法線７３に対する蒸発物質の飛翔する方向７２の角度：αを鋭角とし、蒸発源と基板間の距離：Ｌを長くすれば膜厚分布の勾配が緩やかとなり、前記のαを鈍角とし、Ｌを短くすれば膜厚分布の勾配をきつくすることができる。
【００３６】
ところで、本発明の薄膜複屈折素子を構成する斜め蒸着膜は異方性を持つものであれば良いが、複屈折：Δｎが大きく機械強度に優れたものがより望ましく、Ｔａ₂Ｏ₅，ＳｉＯ₂，ＮｂＯ₅，ＷＯ₃，ＳｎＯ₂，ＴｉＯ₂等の金属酸化物系の誘電体膜は良好の結果を示す。しかし、これらの金属酸化物を蒸着材として基板上に斜め蒸着膜を形成した場合、高い内部応力により、そのままでは密着性が充分でなかったり、膜の白濁化や吸収の増加等の不具合が発生する。特に長波長域での１／４波長板もしくは１／２波長板としての複屈折量を得る場合、相当量の膜厚が必要となるために前記の問題が顕著に表れ、斜め蒸着膜が基板から剥離したり、白濁化による入射光の散乱や蒸着材が所望の組成から掛離れることによる吸収が発生し分光特性の低下等の不具合が発生する。
【００３７】
本発明では上記の問題を解決するために、通常の蒸着方式による蒸着材の蒸発に加えて、図１（あるいは図１１）に示す構成のように、蒸着装置１内にプラズマ源（もしくはイオン源）４を併用し、装置内に形成されるプラズマを積極的に活用する。具体的には蒸着装置１内を５×１０^-3Ｐａ以下に減圧した状態で不活性ガスであるアルゴン（Ａｒ）等の導入ガスを流量制御機構を用いて３〜５０ccm の範囲内で装置内のプラズマ発生機構に供給し放電を開始する。そのときプラズマ発生機構から供給される電子との衝突により導入ガスをイオン化し、さらに図示しない中間電極等によるイオン及び電子の引き出しにより蒸着装置内にプラズマ空間を形成する。そして、上記の状態で形成されたプラズマ中に、斜め蒸着膜との反応に最適な反応性ガス、例えば酸素を反応性ガス導入口５から導入することにより、蒸着材３の蒸発物質がプラズマ中を通過するときに、反応性ガスと蒸発物質がプラズマ中の電子やイオンとの衝突によりイオン化され、かつ両者間での反応が発生し、高いエネルギー状態で基板に突入するので、導入ガスと蒸着材が結合した蒸着膜が基板上に形成される。このとき基板（基板ホルダー）には負の電荷を与えておくことで、蒸着材の蒸発物質及び反応性ガスのイオンが電気的偏位状態にある基板に対して電界の効果で激突し基板上に核を形成する。この激突の繰り返しにより極めて密着性が高く光の吸収を軽減した斜め蒸着膜の形成が可能となる。
【００３８】
しかし、基板と斜め蒸着膜の組み合わせ次第では、双方の分子間の結合力低下や、過酷な使用環境に起因する密着力の低下が問題となる場合がある。さらに基板と斜め蒸着膜の間及び反基板側の斜め蒸着膜と接する媒質（例えば空気）の間で透過光の損失があり、分光透過率が低くなるという問題がある。
そこで上記の２つの問題を解決するために、本発明では図５に示す構成の薄膜複屈折素子のように、基板４０と斜め蒸着膜４２の間にアンダーコート４１を施し、斜め蒸着膜上にオーバーコート４３を施す。このアンダーコート４１及びオーバーコート４３の材料は、基板４０と斜め蒸着膜４２及び斜め蒸着膜４２と接する媒質の各屈折率から振幅条件と位相条件から求められる屈折率と膜厚で決定する。
【００３９】
上記アンダーコートやオーバーコートとなる薄膜の形成には真空蒸着やスパッタ等による蒸着膜あるいはスピンコート等による塗膜を用いる。このとき上記振幅条件のみで形成した膜に対して、振幅条件と位相条件の両者を考慮して形成した膜では分光透過率がさらに向上する。例えば硼硅酸ガラスを基板とし、Ｔａ₂Ｏ₅を斜め蒸着膜として用いた場合、アンダーコート及びオーバーコートの材料はシリコン系もしくはアルミニウム系の材料が最適となる。
ここで、形成する膜の屈折率：ｎ₁、光の入射する側の媒質の屈折率：ｎ₀、基板の屈折率：ｎ_Sとすると、単層膜構造の斜め蒸着膜における振幅条件は次のように表すことができる。
ｎ₁＝(ｎ₀・ｎ_S)^1/2
また、中心波長：λ₀、形成する膜厚：ｄ₁、ｍ＝１，２，３・・・（整数）とすると、単層膜における位相条件は次のように表すことができる。
ｎ₁・ｄ₁＝(２ｍ−１)・λ₀／４
【００４０】
一方、斜め蒸着膜が形成されない基板裏面側においても、そのままでは透過光の損失があるので、図５に示すように基板４０の裏面にも反射防止膜４４を形成することで分光透過率が向上する。この反射防止膜４４は上記と同様に振幅条件と位相条件から求められる屈折率と膜厚で決定し、真空蒸着法もしくはスパッタ法で薄膜を形成する。
【００４１】
また、斜め蒸着膜の密着性、耐環境性、光学特性及びその安定性をさらに向上させるためには、斜め蒸着膜もしくは斜め蒸着膜上の薄膜（オーバーコート）に熱処理（アニール）を施して膜の状態を改質すると良く、環境変化による複屈折量を始めとする光学特性の変動を抑えることができる。より具体的には、斜め蒸着膜もしくは斜め蒸着膜上の薄膜に、レーザー光を走査しながら照射してレーザー熱処理（レーザーアニール）を行い膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えることにより、密着性、耐環境性、光学特性及びその安定性が向上された薄膜複屈折素子を作製することができる。
【００４２】
ところで薄膜複屈折素子の基板上に形成された斜め蒸着膜が１枚の基板内において位相差に分布を持つものであっても、斜め蒸着膜を有する基板を複数枚貼り合せることにより位相差の分布を調整することができる。すなわち、基板内における位相差の分布傾向が同じである２つの薄膜複屈折素子を貼り合せることで位相差の分布が解消されたり、あるいは位相差の分布傾向を揃えて対称の状態で２つの薄膜複屈折素子を貼り合せることで、位相差の分布の勾配をより強調した薄膜複屈折素子が製作可能である。
また、１枚の基板内における位相差の分布が小さい薄膜複屈折素子を複数貼り合せることにより、任意の位相差を有する薄膜複屈折素子の製作が可能である。
これらの薄膜複屈折素子を製作する方法としては、同時に複数の基板を成膜した物もしくは、同じ条件で異なる時期に成膜したそれらの基板を、目的に応じて基板の方向を決めて貼り合せることで可能となる。
【００４３】
具体的には、斜め蒸着膜７７の膜厚あるいは位相差分布に勾配を有する薄膜複屈折素子でも、その勾配の向きを逆向きにして２枚の薄膜複屈折素子を図１２に示す構成のように接着剤７９で貼り合せることにより、基板内の位相差が均一な薄膜複屈折素子（例えば波長板）が作製できる。ここで、図１２に示す薄膜複屈折素子は、基板７５上にアンダーコート７６、斜め蒸着膜７７、オーバーコート７８を形成し、基板裏面に反射防止膜を設けた構成の薄膜複屈折素子を２つ形成した後、位相差分布の勾配の向きを逆向きにして接着剤７９で貼り合わせたものである。この場合、１枚の基板の位相差が例えば１／１６波長の位相差を有する場合には、２枚の薄膜複屈折素子の斜め蒸着膜７７の位相差分布の勾配の向きを逆向きにして貼り合せることで、基板内の位相差が均一な１／８波長の位相差を有する薄膜複屈折素子が製作できる。
同様に図１４に示すように、図１２の構成の薄膜複屈折素子をさらに２枚以上貼り付けた構成とした場合、１／８波長に貼り付けた薄膜複屈折素子の枚数を掛け合わせた位相差を有する１／４あるいは１／２波長の位相差を有する薄膜複屈折素子の製作が可能となる。
また、成膜時に取り付けた基板の上下方向を対称とし、図１３に示す構成のように、位相差分布の勾配の向きを同方向にして貼り合せることにより、基板内の位相差が一方向に勾配を持つ薄膜複屈折素子を製作することができる。
さらに、これらの基板を貼り合せる場合に、狭帯域フィルター等の各種フィルターを基板の接合面もしくは裏面に貼り合せることにより、位相差とフィルターの機能を併せ持つ薄膜複屈折素子の製作が可能となる。また、上記のように複数の薄膜複屈折素子を貼り合せて構成した薄膜複屈折素子においても、外側に位置する基板の裏面に反射防止膜８０を形成することにより、分光透過率を向上することができる。
【００４４】
【実施例】
次に本発明の具体的な実施例について説明する。
【００４５】
（実施例１）
図１に示す構成の装置を用い、蒸発源２に蒸着材３のＴａ₂Ｏ₅を入れ、蒸着材３からの蒸発物質の基板への入射角αが７０°となるように基板ホルダー９に５０×５０ｍｍのガラス基板６を複数配置し、遮蔽板７の開口部８のθを２０°とし、基板ホルダー９及び遮蔽板７を矢印１１で示す回転方向に公転運動させると共に基板ホルダー９を矢印１０で示す回転方向に自転させる。これにより、基板ホルダー９上の複数の基板６は、蒸着装置１内を公転運動しながら基板ホルダー９の自転により遮蔽板７の２箇所の開口部８の位置を順次通過することになり、その開口部８の位置を通過する時に蒸発物質が斜め蒸着されることになる。このとき予め蒸着装置１内を図示されない真空排気系を用いて１×１０^-4Ｐａ程度に減圧しておき、この状態からプラズマ源４に不活性ガスのＡｒを供給すると共に反応性ガス導入口５より酸素を導入した後、放電させ、装置内にプラズマ状態を形成し、例えば、電子銃からなる蒸発源２で蒸着材３を蒸発させて、基板上にＴａ₂Ｏ₅の斜め蒸着膜を約４μｍ形成する。蒸着中の膜厚制御は、光学式膜厚計を用いて干渉フィルターの中心波長：λを６３０ｎｍとし、ダミー用のガラス基板１７の光量変化を監視して、光学的膜厚：ｎｄが３３λとなった時点で蒸着を終了した。このようにして製作された薄膜複屈折素子は膜厚及び複屈折量が均一な単層膜構造の斜め蒸着膜を有し、１／４波長板として使用できる。
この薄膜複屈折素子をエリプソメータを用いて位相差：Δを測定した結果、Δ＝９０．４６°（波長：λ＝６３３ｎｍ）の測定結果が得られた。
【００４６】
（実施例２）
実施例１の基板と斜め蒸着膜の間に予めアンダーコートとしてＳｉＯを略９３ｎｍの厚さに形成し、実施例１と同一の方法と条件でＴａ₂Ｏ₅の斜め蒸着膜を形成し、その上にオーバーコートとしてＳｉＯ₂を略１０８ｎｍの厚さに形成した。さらに基板のＴａ₂Ｏ₅蒸着膜とは反対の面に３層反射防止膜を形成した（図５の構成）。
この薄膜複屈折素子を実施例１と同じ方法で位相差：Δを測定した結果、Δ＝９２．４３°の結果が得られた。
また、この薄膜複屈折素子の基板法線方向から垂直に光を入射し、分光透過率を測定した結果、λ＝６３３ｎｍで約９７％Ｔ以上の結果が得られた。
さらに、この薄膜複屈折素子を６０〜８５℃、９０％ＲＨの温・湿度雰囲気中に２００時間以上放置したが、蒸着膜の剥離は見られず、テープ試験においても放置前と何ら変わるものではなかった。
【００４７】
（実施例３）
実施例１または２の方法でＴａ₂Ｏ₅蒸着膜の膜厚を約８μｍに形成した。この薄膜複屈折素子は１／２波長板として使用できる。
この薄膜複屈折素子を実施例１と同じ方法で位相差：Δを測定した結果、Δ＝１７９．３５°の結果が得られた。
【００４８】
（実施例４）
実施例２の方法で製作された薄膜複屈折素子にレーザーアニールによる熱処理を実施した。具体的には、斜め蒸着膜上のオーバーコートにレーザー光を走査しながら照射してレーザーアニールを行い、膜の状態を改質した。
このレーザーアニール後の薄膜複屈折素子をダイシング装置を使用して５０×５０ｍｍから５×５ｍｍに切断したが、蒸着膜の剥離や位相差の変動は見られなかった。
さらに、５×５ｍｍに切断した薄膜複屈折素子を６０〜８５℃、９０％ＲＨの温・湿度雰囲気中に５００時間放置したが、蒸着膜の剥離や位相差の変動は見られなかった。
【００４９】
（実施例５）
実施例１または２または３で製作された薄膜複屈折素子を所望の大きさに切断し、図９の（ａ）に示す形状のプリズム５３の光の入射面と出射面に、位相差１／４波長の薄膜複屈折素子５４と位相差１／２波長の薄膜複屈折素子５５として配置し、図９の（ｂ）に示すプリズム正面５６から見た光学軸方向５７及び５８に合わせて各々貼り付けた。この薄膜複屈折素子５４，５５を貼り付けたプリズム５３は、２ビーム合成プリズムとして使用できる。
【００５０】
（実施例６）
実施例１または２または３と同一の方法で、ガラス基板の代わりに図９の（ａ）に示す形状のプリズム５３の光の入射面と出射面に直接、符号５４で示す位相差１／４波長の斜め蒸着膜を形成した後、符号５５で示す位相差１／２波長の斜め蒸着膜を形成する。そのとき図９の（ｂ）に示すプリズム正面５６から見た光学軸５７及び５８の方向が基板ホルダーの外周部と中心部を結ぶ線と平行となるように各々配置する。この位相差１／４波長と１／２波長の斜め蒸着膜５４，５５を形成したプリズム５３は、一体型の複合素子として波長板の機能を有する２ビーム合成プリズムとして使用できる。
【００５１】
（実施例７）
実施例１または２と同様の方法で、ガラス基板の代わりに図１０（ａ）に示す偏光ビームスプリッタ（ＰＢＳ）面６２を有するプリズム５９の一面に直接、符号６０で示す位相差１／４波長の斜め蒸着膜を形成する。そのとき図１０の（ｂ）に示す光学軸６３の方向が図１に示す装置の基板ホルダー９の外周部と中心部を結ぶ線と平行となるように配置する。この位相差１／４波長の斜め蒸着膜６０を形成したプリズム５９は、一体型の複合素子として波長板の機能を有するＰＢＳプリズムとして使用でき、コンパクトディスク（ＣＤ）、レーザーディスク（ＬＤ）、デジタルバーサタイルディスク（ＤＶＤ）等の記録媒体６１からの反射光を光源からの光束と分離する偏光分離素子として光ディスクドライブの光ピックアップ等に応用することができる。
【００５２】
（実施例８）
実施例２と同様の方法で基板７５上にアンダコート７６、斜め蒸着膜７７、オーバーコート７８を形成した薄膜複屈折素子（図５の構成）を２枚用い、図１５に示すように斜め蒸着膜７７側を向い合わせて接着剤７９を用いて貼り合せた。この薄膜複屈折素子の位相差：Δをエリプソメータを用いて測定した結果、Δ＝１７９．８３°の結果が得られた。この薄膜複屈折素子は１／２波長板として利用できる。
また、この薄膜複屈折素子を、６０〜８５℃、９０％ＲＨの温・湿度雰囲気中に２００時間放置したが、剥離や位相差：Δの変化は見られなかった。
【００５３】
（実施例９）
図１１に示す構成の装置を用い、蒸発源６７に蒸着材６８としてＴａ₂Ｏ₅を入れ、蒸着材６８からの蒸発物質の基板への入射角αが７０°となるように基板ホルダー７０に予めアンダーコートを形成した５０×５０ｍｍのガラス基板６９を数枚配置し、公転機構で公転冶具７１を回転させる。このとき予め装置内を図示されない真空排気系を用いて１×１０^-4Ｐａ程度に減圧しておき、この状態からプラズマ源６６に不活性ガスのＡｒを供給すると共に反応性ガス導入口７４より酸素を導入した後、放電させ、装置内にプラズマ状態を形成し、例えば、電子銃からなる蒸発源６７で蒸着材３を蒸発させ、基板上にＴａ₂Ｏ₅の蒸着膜を約２μｍ形成し、さらにＴａ₂Ｏ₅の蒸着膜上にオーバーコートを形成した。
このような作製方法で成膜中における基板ホルダー７０への固定方法を非対称にして膜厚に変化を持たせた斜め蒸着膜７７を有する薄膜複屈折素子を２枚作製し、この２枚の薄膜複屈折素子を、図１２に示す構成のように各蒸着膜側を向い合わせて接着剤７９で貼り合せた。この薄膜複屈折素子は１／４波長板として利用できる。
この薄膜複屈折素子の位相差：Δをエリプソメータで測定した結果、基板中心部の位相差はΔ＝９０．０２°（波長：λ＝６３３ｎｍ）であり、基板中心部と外周部のΔの差が２％以内という測定結果が得られた。
また、この薄膜複屈折素子を、６０〜８５℃、９０％ＲＨの温・湿度雰囲気中に２００時間放置したが、剥離や位相差：Δの変化は見られなかった。
【００５４】
【発明の効果】
以上説明したように、本発明の薄膜複屈折素子は、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を有するので、加工コストが安く、量産が可能であり、且つ光学特性が向上された薄膜複屈折素子を提供することができる。また、基板表面と上記斜め蒸着膜の間もしくは上記斜め蒸着膜上のいずれか一方もしくは両方に、密着性、耐環境性及び光学特性を向上させることを目的とする薄膜（アンダーコート膜またはオーバーコート膜）を有する構成とすることにより、斜め蒸着膜の剥離及び白濁・吸収を防止し、密着性と光学特性・耐環境性を向上させた薄膜複屈折素子を提供することができる。さらに、上記斜め蒸着膜もしくは斜め蒸着膜上の薄膜に熱処理（アニール）を施して膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えた構成とすることにより、密着性、耐環境性、光学特性及びその安定性が向上された薄膜複屈折素子を提供することができる。さらにまた、基板上に単層膜構造の斜め蒸着膜を形成した薄膜複屈折素子、あるいは基板表面と斜め蒸着膜の間もしくは斜め蒸着膜上のいずれか一方もしくは両方に薄膜（アンダーコート膜またはオーバーコート膜）を有する構成の薄膜複屈折素子、あるいは斜め蒸着膜もしくは斜め蒸着膜上の薄膜に熱処理（アニール）を施して膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えた構成の薄膜複屈折素子を、２個以上貼り合わせた構成とすることにより、密着性、耐環境性、光学特性及びその安定性がより一層向上された薄膜複屈折素子を提供することができる。
【００５５】
本発明の薄膜複屈折素子の製造方法によれば、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成することができるので、同一基板内での複屈折量の誤差を少なくさせた薄膜複屈折素子、もしくは基板内に任意の勾配を持たせた複屈折量を精度良く発現させた薄膜複屈折素子を製作することができる。また、密着性などの機械的強度に優れ、吸収の少ない光の利用効率の高い分光特性を有する斜め蒸着膜を単層構造で形成するため、生産性に優れ、かつ所望の複屈折量を精度良く達成できるため、各種光学系の幅広い波長への対応が可能な薄膜複屈折素子を製作できる。加えてレンズやプリズム等の光学素子へ直接蒸着して斜め蒸着膜を形成することもできるので、複屈折機能を有する複合素子の製作が可能となり、各種光学素子のさらなる小型化が可能となる。また、基板表面と斜め蒸着膜の間もしくは斜め蒸着膜上のいずれか一方もしくは両方に、密着性、耐環境性及び光学特性を向上させることを目的とする薄膜（アンダーコート膜またはオーバーコート膜）を蒸着膜や塗膜により形成することにより、斜め蒸着膜の剥離及び白濁・吸収を防止し、密着性と光学特性・耐環境性を向上させた薄膜複屈折素子を製作することができる。さらに、斜め蒸着膜もしくは斜め蒸着膜上の薄膜に、レーザー光を走査しながら照射してレーザー熱処理（レーザーアニール）を行い膜の状態を改質し、環境変化による複屈折量を始めとする光学特性の変動を抑えることにより、密着性、耐環境性、光学特性及びその安定性が向上された薄膜複屈折素子を製作することができる。また、斜め蒸着膜もしくは斜め蒸着膜上の薄膜にレーザーアニールを施すことにより、チップ化に伴う切断時の切削液の浸透による複屈折特性の変動を抑止することができる。さらにまた、基板上に単層膜構造の斜め蒸着膜を形成した薄膜複屈折素子、あるいは基板表面と斜め蒸着膜の間もしくは斜め蒸着膜上のいずれか一方もしくは両方に薄膜（アンダーコート膜またはオーバーコート膜）を有する構成の薄膜複屈折素子、あるいは斜め蒸着膜もしくは斜め蒸着膜上の薄膜に、レーザー光を走査しながら照射してレーザー熱処理（レーザーアニール）を行い膜の状態を改質し環境変化による複屈折量を始めとする光学特性の変動を抑えた薄膜複屈折素子を製作した後、これらの薄膜複屈折素子を２個以上接着剤で貼り合わせることにより、密着性、耐環境性、光学特性及びその安定性がより一層向上された薄膜複屈折素子を製作することができる。
【００５６】
本発明の薄膜複屈折素子の製造装置によれば、膜厚及び複屈折量が制御された単層膜構造の斜め蒸着膜を形成することができ、さらには、斜め蒸着膜の膜厚及び複屈折量を均一な状態に制御することや、あるいは、斜め蒸着膜の基板内の位置と複屈折量の関係が勾配を持って分布するように制御することができるので、同一基板内での複屈折量の誤差を少なくさせた薄膜複屈折素子、もしくは基板内に任意の勾配を持たせた複屈折量を精度良く発現させた薄膜複屈折素子を製作することができる。
【図面の簡単な説明】
【図１】本発明に係る薄膜複屈折素子の斜め蒸着膜を形成する製造装置の第１の構成例を示す図であって、（ａ）は製造装置内の概略構成を示す正面図、（ｂ）は製造装置の概略構成を示す側面図である。
【図２】本発明に係る薄膜複屈折素子の斜め蒸着膜を形成する際の、基板法線に対する蒸発物質の入射角αと基板の関係を示す図である。
【図３】図２のＹ方向側面から見た図であって、基板に対する蒸発物質の入射と斜め蒸着膜の柱状構造を模式的に示す図である。
【図４】図２のＸ方向側面から見た図であって、基板に対する蒸発物質の入射と斜め蒸着膜の柱状構造を模式的に示す図である。
【図５】本発明による薄膜複屈折素子の膜構造の一例を示す要部断面図である。
【図６】図１に示す製造装置に具備される遊星回転機構と該機構における基板移動の軌跡の例を示す図である。
【図７】直線偏光の成分状態を示す図である。
【図８】直線偏光が複屈折素子を通過した後の位相遅れを示す図である。
【図９】本発明の実施例４及び５の光学素子（２ビーム合成プリズム）を示す図であって、（ａ）は光学素子の平面図、（ｂ）は光学素子の側面図である。
【図１０】本発明の実施例６の光学素子（波長板の機能を有するＰＢＳプリズム）を示す図であって、（ａ）は光学素子の平面図、（ｂ）は光学素子の側面図である。
【図１１】本発明に係る薄膜複屈折素子の斜め蒸着膜を形成する製造装置の第２の構成例を示す概略構成図である。
【図１２】本発明に係る２つの薄膜複屈折素子を基板内の位相差が均一となるように貼り合せた構成の薄膜複屈折素子の要部断面図である。
【図１３】本発明に係る２つの薄膜複屈折素子を基板内の位相差が勾配を持つように貼り合せた構成の薄膜複屈折素子の要部断面図である
【図１４】本発明に係る複数の薄膜複屈折素子を基板内の位相差が均一となるように貼り合せた構成の薄膜複屈折素子の要部断面図である。
【図１５】本発明の実施例７の薄膜複屈折素子の構成例を示す要部断面図である。
【図１６】従来の斜め蒸着膜を形成する装置の一例を示す図であって、（ａ）蒸着膜形成装置の正面図、（ｂ）は蒸着膜形成装置の側面図である。
【符号の説明】
１蒸着装置
２蒸発源
３蒸着材
４プラズマ源（もしくはイオン源）
５反応性ガス導入口
６基板
７遮蔽板
８遮蔽板の開口部
９基板ホルダー
１０基板ホルダーの自転方向
１１基板ホルダーの公転方向及び遮蔽板の回転方向
１２シャッター板
１３監視窓
１４膜厚計の光源
１５膜厚計の受光部
１６膜厚計の反射鏡
１７ダミー基板
１８複屈折測定器の偏光子
１９複屈折測定器の反射鏡
２０複屈折測定器の光源
２１複屈折測定器の透過光受光部
２２複屈折測定器の反射光受光部
２３蒸発物質の飛翔方向
２４基板法線
２９基板
３０蒸着材
３１基板法線
３２基板
３３基板法線
３４蒸発物質入射方向
３５斜め蒸着膜
３６基板
３７基板法線
３８蒸発物質入射方向
３９斜め蒸着膜
４０基板
４１アンダーコート
４２斜め蒸着膜
４３オーバーコート
４４反射防止膜
４５遊星回転機構
４６基板ホルダー
４７基板
４７ａ基板の軌跡
４８Ｙ方向の電気的振動成分
４９Ｘ方向の電気的振動成分
５０Ｙ方向の電気的振動成分
５１Ｘ方向の電気的振動成分
５３プリズム
５４位相差１／４波長の薄膜複屈折素子
５５位相差１／２波長の薄膜複屈折素子
５６プリズム正面
５７薄膜複屈折素子の光学軸
５８薄膜複屈折素子の光学軸
５９ＰＢＳプリズム
６０位相差１／４波長の薄膜複屈折素子
６１記録媒体
６２ＰＢＳ面
６３薄膜複屈折素子の光学軸
６５蒸着装置
６６プラズマ源（もしくはイオン源）
６７蒸発源
６８蒸着材
６９基板
７０基板ホルダー
７１公転機構の公転冶具
７２蒸発物質の飛翔方向
７３基板法線
７４反応性ガス導入口
７５基板
７６アンダーコート
７７斜め蒸着膜
７８オーバーコート
７９接着層（接着剤）
８０反射防止膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin-film birefringent element included in a polarizing element, a manufacturing method thereof, and a manufacturing apparatus.
[0002]
[Prior art]
Optical elements that adjust, convert, and rotate the polarization state of light, including conversion between linearly polarized light and circularly polarized light using birefringence, have conventionally processed crystals such as quartz and calcite, An optical element obtained by processing such a crystal has a drawback that material costs and processing costs are high. In addition, it has been known that a deposited film formed by oblique deposition has anisotropy, and the deposited film can be formed at low cost. Proposals have been made to use it as an element.
[0003]
Here, FIG. 16 shows an example of an oblique vapor deposition film forming apparatus. When oblique vapor deposition is performed, the substrate 26 is disposed obliquely with respect to the evaporation source 27 having the vapor deposition material 28 in the oblique vapor deposition film forming apparatus 25. Therefore, the distance between the evaporation source 27 and the substrate 26 differs depending on the substrate position, and the vapor deposition films formed by oblique vapor deposition have a difference in film thickness in the vertical direction within the same substrate. In this case, since the amount of birefringence differs depending on the film thickness, a phase difference distribution occurs in the substrate. In order to eliminate this phase difference distribution in the substrate, a method is known in which the obliquely deposited film has a multilayer structure, and the incident angle to the substrate is changed for each layer in a symmetric direction with the substrate normal as the center ( Japanese Patent Publication No. 7-3486).
[0004]
Furthermore, the vapor deposition film formed by oblique vapor deposition has different density in the vertical and lateral directions of the film and exhibits birefringence. The oblique vapor deposition film formed for the purpose of this birefringence is usually a dielectric such as a metal oxide film. It is formed of a body membrane. However, the dielectric film formed by oblique deposition is mostly formed as a columnar composition (column), so the density is not uniform, the internal stress is high, and the adhesiveness deteriorates due to environmental changes, etc. Problems such as peeling or film turbidity and degradation of optical characteristics, such as a decrease in spectral transmittance due to increased absorption of the dielectric film, occur.
In addition, in the growth direction of this columnar composition (column), between the deposition angle α and the column inclination angle β,
β = (1/2) tanα
(Thin Film Application Handbook 2nd edition, issued by NTS Corporation).
Ta₂O_FiveIt has been reported that in the oblique deposition of α, the relationship between α and 0.5θ is the relationship between the columnar composition tilt angle α and the deposition angle θ (Applied).
optics / Vol.28, No.13 / 1 July 1989).
[0005]
[Problems to be solved by the invention]
The obliquely deposited film formed by the method described in the above prior art (Japanese Patent Publication No. 7-3486) has a multilayer structure in which the direction of the substrate must be changed for each layer, and the obliquely deposited film When forming the film, it is necessary to change the direction of the substrate for each layer to perform deposition, which increases the processing time, and further requires addition of a complicated and new mechanism to the manufacturing apparatus, which is costly. There is a problem. In addition, since the same material is divided and vapor-deposited, it is difficult to keep the refractive index uniform in each layer, which tends to be a heterogeneous film, and there is a problem that an error is likely to occur in the amount of birefringence in the substrate. .
In addition, as described above, the dielectric film formed by oblique deposition is mostly formed as a columnar composition, so the density is not uniform, the internal stress is high, and the adhesion deteriorates due to environmental changes, etc. There is a problem that the film is exfoliated or the film becomes cloudy, or the optical characteristics are deteriorated due to a decrease in spectral transmittance due to an increase in absorption of the dielectric film, resulting in poor reliability.
[0006]
The present invention has been made in view of the above circumstances, has low processing costs, can be mass-produced, prevents peeling of the obliquely deposited film, and prevents white turbidity / absorption, and adheres to the obliquely deposited film, environmental resistance, optical Providing highly reliable thin-film birefringent elements with improved characteristics and their stability, etc., and thin-film birefringent elements with reduced birefringence error in the same substrate, or any gradient in the substrate An object of the present invention is to provide a thin film birefringent element that accurately expresses the amount of birefringence imparted with the above, and further to provide a manufacturing method and a manufacturing apparatus for the thin film birefringent element.
[0007]
[Means for Solving the Problems]
  To achieve the above objective,Thin film birefringent element according to the present inventionIs a thin-film birefringent element having an obliquely deposited film formed by allowing an evaporating substance to enter from an oblique direction on a substrate, and the obliquely deposited film has a single layer film structure in which the film thickness and birefringence are controlled. The film is characterized by being a film, and as a result, the processing cost can be reduced and mass productivity can be ensured as compared with a conventional multilayered film having a multilayered structure.
  Also,Thin film birefringent element according to the present inventionIs a thin-film birefringent element having an obliquely deposited film formed by allowing an evaporating substance to enter from an oblique direction on a substrate, and the obliquely deposited film has a single layer film structure in which the film thickness and birefringence are controlled. A thin film (undercoat film or undercoat film) for improving adhesion, environmental resistance and optical properties between one of or both of the substrate surface and the oblique vapor deposition film or on the oblique vapor deposition film. This makes it possible to improve the adhesion, environmental resistance and optical characteristics of the obliquely deposited film.
  further,Thin film birefringent element according to the present inventionIsOf the above configurationIn thin-film birefringent elements, heat treatment (annealing) is applied to the above-mentioned obliquely deposited film or the thin film on the obliquely deposited film to modify the state of the film, thereby suppressing fluctuations in optical properties such as birefringence due to environmental changes. This makes it possible to improve the adhesion, environmental resistance, optical characteristics and stability of the obliquely deposited film.
  Furthermore,Thin film birefringent element according to the present inventionIsOf the above configurationIt is characterized in that two or more thin-film birefringent elements are bonded together, which makes it possible to further improve the adhesion, environmental resistance, optical characteristics and stability of the obliquely deposited film. Become.
  The thin film birefringent element according to the present invention as described above is manufactured by the following manufacturing method or manufacturing apparatus.
[0008]
  Claim1The invention according toAn obliquely deposited film formed by allowing an evaporating substance to enter from an oblique direction on a substrate, and the obliquely deposited film is a deposited film having a single layer structure in which the film thickness and birefringence are controlled.A method of manufacturing a thin film birefringent element for producing a thin film birefringent element, wherein one or more substrates are heldDiscoidThe substrate holder is a planetary rotation mechanism consisting of rotation and revolution.While holding and rotating the substrate holder by the planetary rotation mechanism,Inside the evaporation systemRevolutionLetOne or more substrates held by the substrate holder are moved in a rotational motion that draws a semicircular locus above the evaporation source that evaporates the evaporation substance, andWith the above substrate holderthe aboveWith a shielding plate having an opening in the vicinity of the substrate holder between the evaporation sources,the aboveEvaporation sourceAnd aboveThe vaporized substance is ionized by using a plasma source or ion source that forms a plasma state in the evaporation apparatus, and then the vaporized substance is caused to fly in the direction of the substrate, and the evaporated substance is incident on the substrate from an oblique direction through the opening of the shielding plate. An oblique vapor deposition film is formed, and an oblique vapor deposition film having a single layer film structure in which the film thickness and the birefringence amount are controlled can be formed.
  According to a second aspect of the present invention, in the method for manufacturing a thin film birefringent element according to the first aspect, the shielding plate has a center of rotation of the substrate holder and a center of two openings of the shielding plate. A revolving motion synchronized with a revolving motion by the planetary rotation mechanism of the substrate holder is provided in a state where they are arranged to be the same.
[0010]
  Further claims3The invention according to claim1 or 2In the manufacturing method of the thin film birefringent element described above, an oblique vapor deposition film having a single layer film structure is formed by vapor deposition from an oblique direction, and the film thickness and birefringence amount of the oblique vapor deposition film are controlled to be uniform in the substrate. It is characterized by.
[0011]
  Claim4The invention according to claim1-3In the method of manufacturing a thin film birefringent element according to any one ofthe aboveIn order to form a deposited film having a desired film thickness and / or birefringence amount on a substrate,the aboveA dummy substrate is disposed in the vapor deposition apparatus, and an optical film thickness meter and / or a light projection section having an optical system equivalent to the optical film thickness meter, comprising a light projecting portion and a light receiving portion that are in contact with the outside of the vapor deposition device by a monitoring window. And a birefringence measuring device with a polarizer added in the middle of the light receiving unit, by monitoring the change in the amount of transmitted or reflected light of the dummy substrate or substrate being processed, The optical film thickness and / or birefringence amount is monitored, and the deposition conditions and time are controlled so as to obtain a desired film thickness and / or birefringence amount. It is possible to control the birefringence amount to be uniform or to control the relationship between the position of the obliquely deposited film in the substrate and the birefringence amount with a gradient.
[0012]
  Claim5The invention according to claimAny one of 1-4DescriptionofMethod for manufacturing thin-film birefringent elementIn,the aboveA thin film (underlayer) for the purpose of improving adhesion, environmental resistance and optical properties on either or both of the substrate surface before forming the obliquely deposited film and / or the obliquely deposited film after forming the obliquely deposited film. The coating film or the overcoat film) is formed of a vapor-deposited film or a coating film, and a thin-film birefringent element with improved adhesion, environmental resistance, and optical characteristics can be produced.
  Claims6The invention according to claimAny one of 1-4DescriptionofMethod for manufacturing thin-film birefringent elementIn,the aboveLaser thin film birefringence element or thin film on oblique vapor deposition film is irradiated with laser light while scanning and laser heat treatment (laser annealing) is performed to modify the state of the film, and the amount of birefringence due to environmental changes It is possible to produce a thin film birefringent element with improved adhesion, environmental resistance, optical characteristics and stability.
  Furthermore, the claims7The invention according to claimAny one of 1-6DescriptionofMethod for manufacturing thin-film birefringent elementIn,the aboveIt is characterized in that two or more thin-film birefringent elements are bonded together, and a thin-film birefringent element with further improved adhesion, environmental resistance, optical characteristics and stability can be produced.
[0013]
  Claim8The invention according to claim 1 to claim 17Of the thin film birefringent element according to any one ofProduction methodAn apparatus for manufacturing a thin-film birefringent element for use in a vapor deposition apparatus having an evaporation source for evaporating an evaporation substance, a plasma source or an ion source for forming a plasma state, and at least one substrate in the evaporation apparatus. HoldDiscoidA substrate holder, a planetary rotation mechanism for rotating the substrate holder in the vapor deposition apparatus by rotation and revolving motion, and an opening disposed near the substrate holder between the substrate holder and the evaporation source to allow the evaporation material to pass therethrough And a shielding plate havingWhile rotating the substrate holder by the planetary rotation mechanism,Inside the evaporation systemRevolutionLetOne or more substrates held by the substrate holder are moved in a rotational motion that draws a semicircular locus above the evaporation source, andThe evaporation source is ionized using the evaporation source and the plasma source or the ion source to fly in the direction of the substrate, and the evaporation material is incident on the substrate from the oblique direction through the opening of the shielding plate to form an oblique deposition film. Therefore, it is possible to provide a manufacturing apparatus capable of forming an oblique vapor deposition film having a single layer film structure in which the film thickness and the birefringence amount are controlled.
[0015]
  Claim9The invention according to claim8In the manufacturing apparatus of the thin film birefringent element as described,the aboveAn optical film thickness meter comprising a light projecting portion and a light receiving portion, which are provided outside the vapor deposition apparatus and are in contact with a monitoring window, and / or a polarizer in the middle of a light projecting portion and a light receiving portion of an optical system equivalent to the optical film thickness meter During the oblique deposition by monitoring the change in transmitted light quantity or reflected light quantity of the substrate being processed using the above optical film thickness meter and / or birefringence quantity measuring device. The optical film thickness and / or birefringence amount of the deposited film is monitored, and the deposition conditions and time are controlled so as to obtain the desired film thickness and / or birefringence amount. And / or a production apparatus capable of controlling the amount of birefringence to be uniform, or controlling the relationship between the position of the obliquely deposited film in the substrate and the amount of birefringence to be distributed with a gradient. Can be provided.
  The invention according to claim 10 has an oblique vapor deposition film formed by allowing an evaporating substance to enter from an oblique direction on a substrate, and the oblique vapor deposition film has a single layer film structure in which the film thickness and birefringence are controlled. A thin-film birefringent element that is a film, which is manufactured by the method for manufacturing a thin-film birefringent element according to any one of claims 1 to 7, or the thin-film birefringent element manufacturing apparatus according to claim 8 or 9. It is characterized by that.
[0016]
Hereinafter, more specific features of the present invention will be described.
A thin-film birefringent element according to the present invention has an oblique vapor deposition film formed by allowing an evaporating substance to enter from an oblique direction on a substrate, and the oblique vapor deposition film is a single layer whose film thickness and birefringence amount are controlled. It is a deposited film having a film structure. And, in the method for manufacturing a thin film birefringent element according to the present invention, an oblique vapor deposition film having a single layer film structure in which the film thickness and the birefringence amount are controlled is formed, but in order to ensure mass productivity in the single layer film structure, For example, an evaporation source (evaporation source 3) that evaporates the vapor deposition material 3 on one or more substrates 6 held by the substrate holder 9 by using a planetary rotation mechanism composed of a rotation motion and a revolution motion by a manufacturing apparatus having a configuration as shown in FIG. (For example, an electron gun or a resistance heating source) 2 is moved by a semicircular rotational movement, and is further shielded with two openings 8 in the vicinity of a substrate holder on a straight line connecting the substrate 6 and the evaporation source 2. An obliquely deposited film is formed with the plate 7 disposed. At this time, the substrate holder 9 and the shielding plate 7 are set so that the evaporating substance flies from a direction inclined by 40 to 80 degrees with respect to the substrate normal 24.
[0017]
Here, since the disk-shaped substrate holder 46 revolves around the vapor deposition apparatus while rotating by the planetary rotation mechanism 45 as shown in FIG. 6, the substrate 47 held by the substrate holder 46 has a locus 47a. Such a semicircular rotational motion is given.
On the other hand, as shown in FIG. 1, the planetary plate of the substrate holder 9 is arranged on the shielding plate 7 so that the center of rotation of the substrate holder 9 and the center of the two openings 8 of the shielding plate 7 are the same. A revolving motion synchronized with the revolving motion by the rotating mechanism is given. That is, the substrate holder 9 and the shielding plate 7 revolve synchronously. At this time, since the substrate holder 9 is rotating, the plurality of substrates 6 held on the substrate holder 9 are separated from the shielding plate 7. Two openings 8 are sequentially passed, and each substrate 6 is deposited when passing through the openings 8.
[0018]
Then, by evaporating the evaporation material of the vapor deposition material 3 from the evaporation source 2 in the above state, a vapor deposition film is formed on the substrate 6 by the evaporation material that has passed through the opening 8 of the shielding plate 7. Since the vapor deposition film is formed only on the substrate located at the upper and lower openings 8 on the plate 7 and is not formed on the substrate located at the shielding portion, the vapor deposition direction with respect to the substrate is restricted to one direction. .
That is, the flying direction of the evaporation substance with respect to the substrate is limited to the vertical direction with respect to the straight line connecting the center of the substrate located at the opening 8 and the evaporation source 2, and the substrate is arranged to be inclined with respect to the straight line. Therefore, as shown in FIG. 2, the evaporated substance from the vapor deposition material 30 flies from a direction inclined by α with respect to the substrate normal line 31, and an oblique vapor deposition film is formed on the substrate. In addition, since the vertical direction of the substrate is reversed at the positions of the upper and lower two opening portions 8 of the shielding plate 7, the substrate is sequentially passed through the upper and lower two opening portions 8 of the shielding plate 7. The evaporating substance is alternately incident from the symmetric direction around the normal line, and an obliquely deposited film having a substantially uniform film thickness is formed. The obliquely deposited film is a film exhibiting birefringence because the structure of the deposited film in the linear direction is different from the structure of the film in the direction perpendicular to the linear direction.
[0019]
Furthermore, by setting the shapes of the openings 8 at the upper and lower portions of the shielding plate 7 according to the purpose, it is possible to arbitrarily change the distribution of birefringence in the substrate surface. Specifically, in order to make the amount of birefringence uniform within the same plane in the substrate, the shape of the openings 8 at the upper and lower portions of the shielding plate 7 is made to be a circular shape with respect to the rotation axis of the substrate holder 9. To do. On the other hand, in order to give a gradient to the birefringence amount in one direction in the substrate, the shape of the opening 8 of the shielding plate 7 is adjusted to match the gradient of the birefringence amount with the width of the opening on the center side and the outer peripheral side as a reference. To decide.
[0020]
It is also possible to give a gradient to the amount of birefringence without using a shielding plate. In this case, as in the apparatus having the configuration shown in FIG. 11, a circular rotational motion is given to the substrate 69 held by the revolution jig 71 by the revolution mechanism. At this time, the angle of the substrate 69 is set so that the evaporation substance flies from a direction inclined by 60 to 80 degrees with respect to the normal line 73 of the substrate 69. When the evaporation substance is deposited on the substrate in this state, a single layer structure oblique deposition film having a gradient in which the film thickness becomes thinner from the evaporation source direction to the anti-evaporation source direction can be formed on the substrate.
[0021]
The vapor deposition material for forming the oblique vapor deposition film may be any material that exhibits anisotropy by oblique vapor deposition.₂O_Five, SiO₂, NbO_Five, WO_Three, SnO₂, TiO₂A metal oxide based dielectric film such as the one shows good results. However, when only oblique deposition is performed, problems such as deterioration of adhesion, generation of white turbidity, and deterioration of spectral characteristics due to increased absorption occur. Therefore, in the present invention, in addition to evaporation of the vapor deposition material by an electron gun or a resistance heating source, the introduced gas is ionized using a plasma source or an ion source to form a plasma state in the apparatus. Then, when a reactive gas such as an evaporating substance and oxygen passes through the plasma, it is ionized to promote a reaction between the evaporating substance and the reactive gas. At this time, by applying a charge opposite to the aforementioned ions to the substrate holder in advance, an electric field is formed between the plasma space and the substrate, and the ionized evaporation substance and introduced gas are accelerated according to the electric field and collide with the substrate surface. Therefore, a deposited film with high adhesion and less absorption and cloudiness is formed.
[0022]
In order to set the birefringence amount of the thin film birefringence element to a desired value, it is necessary to control the film thickness of the deposited film. In the present invention, as in the apparatus shown in FIG. , Continuously monitoring the optical film thickness during vapor deposition using an optical film thickness meter comprising the reflecting mirror 16 and the light receiving unit 15, and reading the refractive index and the optical film thickness of the oblique vapor deposition film from the change in the amount of light; Control is performed to form a desired film thickness. The control operation is performed by opening and closing the shutter plate 12 installed on the evaporation source 2, and when the desired film thickness is obtained, the evaporation plate 2 is shielded by the shutter plate 12 so that the thickness of the deposited film is increased. Control becomes possible.
[0023]
Furthermore, in the present invention, as in the apparatus shown in FIG. 1, it is also possible to control while monitoring the birefringence amount during vapor deposition using a birefringence meter. The control with the birefringence measuring device is an optical system configuration equivalent to the optical film thickness meter described above, between the light source 20 as the light projecting unit and the measurement substrate 6 or the dummy substrate 17 and between the measurement substrate 6 or Polarizers 18 are arranged at a total of two locations between the dummy substrate 17 and the light receiving unit 21 or the light receiving unit 22, and the optical axes of the respective polarizers 18 are set in directions different by 90 degrees. In addition, the light emitted from the light source 20 is passed through an interference filter having a wavelength corresponding to the target birefringence. The control operation is performed by opening and closing the shutter plate 12 on the evaporation source 2 as in the above-described film thickness control. Then, the birefringence amount is controlled by terminating the vapor deposition at the maximum value or the minimum value of the light amount according to the target wavelength and the birefringence amount. The relationship between the maximum value and the minimum value repeats the maximum value and the minimum value for each half wavelength of the interference filter to be used according to the amount of increase in birefringence.
By using either one or both of the above two types of control methods, the birefringence amount can be controlled with high accuracy.
[0024]
By the way, in the relationship between the substrate medium and the obliquely deposited film, depending on the combination of the two, phenomena such as a decrease in the bonding force between molecules and poor adhesion, and a decrease in spectral transmittance due to a difference in refractive index occur. To do. Therefore, in order to further improve the adhesion between the deposited film and the substrate and the spectral transmittance, the deposited film formed between the obliquely deposited film 42 and the substrate 40 as in the thin film birefringent element having the configuration shown in FIG. Alternatively, it can be achieved by forming either one or both of an undercoat 41 with a coating film, or an overcoat 43 with a deposition film or coating film formed on an oblique deposition film. The material for the undercoat and overcoat is determined by the refractive index and film thickness obtained from the refractive index of the obliquely deposited film and the refractive index of the substrate using the amplitude condition and the phase condition.
In addition, in order to further improve the adhesion, environmental resistance, optical properties and stability of the obliquely deposited film, the film is subjected to heat treatment (annealing) on the obliquely deposited film or the thin film (overcoat) on the obliquely deposited film. This state can be improved by suppressing the fluctuation of optical characteristics including the amount of birefringence due to environmental changes. More specifically, laser deposition is applied to the obliquely deposited film or a thin film on the obliquely deposited film while scanning with laser light to modify the state of the film, and the amount of birefringence due to environmental changes is improved. By suppressing fluctuations in optical characteristics such as the beginning, a thin film birefringent element with improved adhesion, environmental resistance, optical characteristics and stability thereof can be produced. Further, by subjecting the obliquely deposited film or the thin film on the obliquely deposited film to laser annealing, it is possible to suppress fluctuations in the birefringence characteristics due to the penetration of the cutting fluid at the time of cutting accompanying chip formation.
[0025]
Furthermore, using two or more thin-film birefringent elements on which an obliquely deposited film is formed, the phase difference distribution can be adjusted by bonding the surfaces having the obliquely deposited film formed on the substrate. That is, two thin film birefringent elements having the same phase difference distribution tendency in the substrate are bonded in an asymmetric state as shown in FIG. Thus, the phase difference distribution can be eliminated. Further, by aligning the phase difference distribution tendency by the above method and bonding two thin film birefringent elements in a symmetrical state as shown in FIG. is there.
On the other hand, as shown in FIG. 14, it is possible to manufacture a birefringent element (for example, a wave plate) having an arbitrary phase difference by bonding a plurality of substrates having a small phase difference on a single substrate. Further, as described above, it is possible to further improve the spectral transmittance by bonding two or more substrates on which an undercoat and / or an overcoat are formed before and after the oblique deposition film.
When laminating these thin film birefringent elements, the oblique vapor deposition surface side is laminated and the oblique vapor deposition surface is not exposed to the outside, so it has excellent environmental resistance, adhesion, retardation and spectral characteristics. Thus, it is possible to manufacture a highly reliable thin film birefringent element excellent in stability of various characteristics.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific configurations and operations for carrying out the present invention will be described in more detail.
As shown in FIG. 1, the thin-film birefringent element according to the present invention includes a planetary rotation mechanism and a shielding plate 7 having an opening 8 at the center, and in addition, the evaporated substance from the vapor deposition material 3 of the evaporation source 2. Further, it can be realized by forming an obliquely deposited film on the substrate using an apparatus configured to ionize the introduced gas using a plasma source (or ion source) 4. Here, FIG. 1 shows a first configuration example of a manufacturing apparatus for forming an obliquely deposited film of a thin film birefringent element, (a) is a front view showing a schematic configuration in the manufacturing apparatus, and (b) is a side view. is there. In FIG. 1, reference numeral 1 denotes a vapor deposition apparatus, 2 denotes an evaporation source (for example, an electron gun or a resistance heating source), 3 denotes a vapor deposition material, 4 denotes a plasma source (or ion source), 5 denotes a reactive gas inlet, 6 is a substrate, 7 is a shielding plate, 8 is a shielding plate opening, 9 is a substrate holder supported by a planetary rotation mechanism, 10 is a rotation direction of the substrate holder, 11 is a revolving direction of the substrate holder and a revolving direction of the shielding plate, 12 is a shutter plate, 13 is a monitoring window, 14 is a light source that is a light projecting portion of the film thickness meter, 15 is a light receiving portion of the film thickness meter, 16 is a reflector of the film thickness meter, 17 is a dummy substrate, and 18 is birefringent. Polarizer of the measuring device, 19 is a reflecting mirror of the birefringence measuring device, 20 is a light source that is a light projecting portion of the birefringence measuring device, 21 is a transmitted light receiving portion of the birefringence measuring device, and 22 is a reflection of the birefringence measuring device. The light receiving unit 23 is a flight direction of the evaporated substance, and 24 is a normal line of the substrate.
[0027]
In the apparatus shown in FIG. 1, a disk-shaped substrate holder 9 holding one or more substrates 6 is rotated in the vapor deposition apparatus 1 by a planetary rotation mechanism composed of a rotation motion and a revolution motion, and the space between the substrate holder 9 and the evaporation source 2 is rotated. An evaporation source 2 that evaporates the evaporated substance and a plasma source (or ion source) 4 that forms a plasma state in the evaporation apparatus in a state where the shielding plate 7 having the upper and lower openings 8 is arranged in the vicinity of the substrate holder. The vaporized substance is ionized by using the ion beam to fly in the direction of the substrate, and the vaporized substance is incident on the substrate 6 from the oblique direction through the opening 8 of the shielding plate 7 to form an oblique vapor deposition film. An obliquely deposited film having a single layer film structure in which the thickness and birefringence are controlled can be formed. Further, in order to form a vapor deposition film having a desired film thickness and birefringence amount on the substrate, a dummy substrate 17 is disposed in the vapor deposition apparatus 1, and a light projecting unit that is in contact with the outside of the vapor deposition apparatus 1 through a monitoring window 13. A polarizer 18 is added in the middle of an optical film thickness meter (light source) 14 and a light receiving portion 15 and a light projecting portion (light source) 20 and light receiving portions 21 and 22 of an optical system equivalent to the optical film thickness meter. By monitoring the change in the amount of transmitted light or the amount of reflected light of the dummy substrate 17 or the substrate 6 being processed using the birefringence measuring device having the configuration, the optical film thickness and birefringence amount of the deposited film during oblique deposition can be determined. It is possible to monitor and control the deposition conditions and time so that the desired film thickness and birefringence amount are obtained, and the film thickness and birefringence amount of the obliquely deposited film can be controlled to be uniform.
[0028]
Here, a thin-film birefringent element having an obliquely deposited film formed by allowing an evaporating substance to enter the substrate from an oblique direction functions as a wave plate that is a polarizing element when light is incident from the normal direction of the substrate surface. Have
As shown in FIG. 2, when an oblique deposition film is formed by causing the evaporation material from the deposition material 30 to enter the normal line 31 of the substrate 29 from an oblique direction, in the initial stage of the oblique deposition, Similarly, nuclei are formed on the surface of the substrate. As the nuclei of the obliquely deposited film on the substrate 29 grow, a shadow is formed behind the evaporating substance in the flight direction, and the evaporating substance does not reach and no nucleus is formed. Appears to form a columnar structure. This phenomenon is generally called “shadowing effect”.
In this obliquely deposited film, the growth direction of nuclei forming the deposited film is different between the X direction and the Y direction of the substrate in FIG. 2, and the X and Y directions shown in FIG. , The nucleus assembly of the obliquely deposited film 39 grows in the direction of the substrate normal 37, and the nucleus assembly is in close contact with the substrate 36 in a direction parallel to the substrate 36. Further, the Y direction shown in FIG. 3 forms a fine and independent columnar structure inclined in the vapor deposition substance incident direction 34 with respect to the substrate normal 33, so that the refractive index of the oblique vapor deposition film 35 is maximum in the X direction, Minimum in the Y direction.
The relationship between the refractive index and birefringence can be expressed as follows. That is, when the refractive index in the X direction: no, the refractive index in the Y direction: ne, and the birefringence: Δn, the following relationship is established.
Δn = | no−ne |
[0029]
Since the columnar structure of the obliquely deposited film grows in the incident direction of the evaporating substance with respect to the substrate surface, the incident angle α of the evaporating substance with respect to the substrate is adjusted in the range of 40 to 80 degrees to thereby adjust the X direction and Y of the substrate. The difference in refractive index in the direction, that is, “Δn” can be adjusted, but when the incident angle is approximately 70 degrees, Δn shows the largest value.
When the thin film birefringent element is used as a wave plate, an arbitrary wave plate can be produced by adjusting the Δn and the film thickness. Here, the phase lag (retardation), which is a characteristic of the wave plate, can be expressed as follows. As shown in FIG. 7, when linearly polarized light is transmitted in a positional relationship in which the ne direction of the wave plate and the electrical vibration component 48 in the Y direction are parallel to each other, the Y direction of the substrate is transmitted as shown in FIG. The electrical vibration component 51 that has passed through the X direction of the substrate is delayed by Γ shown in the figure with respect to the electrical vibration component 50. The relationship between the retardation (retardation): Γ and Δn is expressed by the following equation, where d is the thickness of the obliquely deposited film.
Γ = Δn · d
[0030]
In order to obtain the target phase delay by adjusting both Δn and the film thickness, it is necessary to adjust ne and no in addition to the method of adjusting the incident angle of the evaporating substance described above. This is consistent with the method of adjusting the refractive index of the entire film that does not deviate in direction, in other words, the refractive index of the film that does not consider birefringence: n. The change of the refractive index: n is generally (1) the film thickness (deposition rate) of the deposited film formed on the substrate per unit time, (2) the pressure during deposition and the amount of introduced gas, and (3) the temperature of the substrate. (4) The above four items of ion beam or plasma formation discharge conditions are the main factors, but it is difficult to strictly adjust n to an arbitrary value, and the adjustable range is very limited. Since adjustment including the film thickness is indispensable, the film thickness must be adjusted with high accuracy in accordance with the change of n, and the manufacturing process becomes complicated. In addition, in order to measure the refractive index of the deposited film formed on the substrate, it is necessary to use a measuring device such as an ellipsometer after the deposition, so determining the film thickness according to the refractive index during deposition is Have difficulty.
[0031]
However, in the present invention, since the change in the amount of light is monitored using the optical film thickness meter provided in the manufacturing apparatus shown in FIG. 1, it is possible to read the approximate refractive index: n from the maximum value and the minimum value of the light amount. In addition, since the optical film thickness: nd, which is the product of the refractive index: n and the film thickness: d, can be monitored from the change in the amount of light, the phase delay (retardation) required by experience: Γ and the optical film thickness: nd Therefore, if the deposition is terminated when the target nd is reached, a desired Γ can be obtained. In addition, it is possible to obtain Γ with higher accuracy. In this case, between the light source 20 and the substrate 6 in the optical path of the birefringence measuring device having an optical system equivalent to the optical film thickness meter, 6 and the polarizer 18 are arranged at two positions between the transmitted light receiving unit 21 or the reflected light receiving unit 22. At this time, the optical axes of the polarizers 18 are orthogonal to each other and the direction in which the optical axis of the polarizer 18 is no or ne and the optical axis of the polarizer 18 is ± 45 degrees. Can be known by the crossed Nicols method, and the deposition is stopped when the desired Γ is reached during the deposition. A thin-film birefringent element can be manufactured. The optical system of the birefringence measuring instrument may be either a transmission type or a reflection type.
[0032]
By the way, since the evaporated substance flying from the evaporation source evaporates while radiating radially, the density of the evaporated substance increases as the distance from the evaporation source increases. In the conventional oblique deposition shown in FIG. In the substrate arrangement method, the positional relationship between the evaporation source and the substrate has a difference in distance between the incident direction of the evaporation substance and the substrate surface including the substrate normal, and shows a film thickness distribution in the substrate surface.
In the thin-film birefringent element of the present invention, in order to solve this film thickness distribution with a single-layer film structure, an apparatus having the configuration shown in FIG. 1 is used, and the substrate 47 is made semicircular by a planetary rotation mechanism 45 as shown in FIG. In the state of moving so as to draw a locus 47a, the evaporating substance is made incident on the substrate normal 24 at about 70 degrees from the shielding plate opening 8 of the apparatus shown in FIG. At this time, the positional relationship of the substrate 6 with respect to the evaporation source 2 is that the evaporation substance is incident only on the substrate 6 located at the positions of the two openings 8 above and below the shielding plate 7, so that the growth direction of the columnar structure is the substrate shown in FIG. (However, since the orientation of the substrate is upside down at the opening positions on the upper and lower sides of the shielding plate 7, the deposited film has a columnar structure in which the inclination direction is opposite in the Y direction.) Are alternately stacked). In addition, the shielding plate opening 8 of the apparatus shown in FIG. 1 has an opening width different in the vertical direction, and has the function of correcting the density of the evaporating substance apparently and uniformly, and an obliquely deposited film formed on the substrate 6. The film thickness distribution in the substrate plane is eliminated, and the film thickness on the substrate surface becomes uniform. The inclination direction of the columnar composition formed by this method is approximately | β when the growth angle of the columnar composition on the plane parallel to the vapor deposition surface is β and the vapor deposition angle is α, and 60 ° ≦ α ≦ 70 °. | ≦ 0.15α.
[0033]
The shape of the opening 8 of the shielding plate of the apparatus shown in FIG. 1 can be made uniform by making the thickness of the substrate surface uniform by making a circular shape or fan shape of θ 5 to 45 degrees with respect to the center of the substrate holder 9. If the center of the circle is moved backward from the center of the substrate holder 9, the gradient of the film thickness distribution can be given from the front side of the substrate to the rear side.
[0034]
Next, as another means of the present invention, it is possible to provide a film thickness distribution in the substrate without using a shielding plate by forming an oblique vapor deposition film using the manufacturing apparatus having the configuration shown in FIG. Become. Here, FIG. 11 shows a second configuration example of the manufacturing apparatus for forming the obliquely deposited film of the thin film birefringent element, and is a front view showing a schematic configuration in the manufacturing apparatus. In FIG. 11, reference numeral 65 denotes a vapor deposition apparatus, 66 denotes a plasma source (or ion source), 67 denotes an evaporation source (for example, an electron gun or a resistance heating source), 68 denotes a vapor deposition material, 69 denotes a substrate, and 70 denotes a substrate holder. , 71 is a revolving jig of the revolving mechanism, 72 is an evaporating substance flight direction (distance between the evaporation source and the substrate: L), 73 is a substrate normal line, and 74 is a reactive gas inlet. In the apparatus shown in FIG. 11, one or more substrates 69 are held by a revolving jig 71 of a revolving mechanism, and the vapor deposition material is evaporated in a state where the substrate 69 is rotated in the vapor deposition apparatus 65 by the revolving motion of the revolving mechanism. The evaporation source 67 and the plasma source (or ion source) 66 that forms a plasma state in the evaporation apparatus are used to ionize the evaporation substance to fly toward the substrate, and the evaporation substance is incident on the substrate from an oblique direction to perform oblique deposition. An oblique vapor deposition film having a single-layer film structure in which the film thickness and the birefringence distribution are controlled can be formed. In the case of the configuration of FIG. 11 as well, an optical film thickness meter and / or a birefringence measuring device similar to those of FIG. 1 are installed as necessary, but these are not shown.
[0035]
In FIG. 11, a substrate 69 is supported by a revolving jig 71 via a substrate holder 70, and is given a circular rotational motion by a revolving mechanism (not shown). At this time, the substrate 69 is set so that the evaporated substance flies from a direction inclined by α = 60 to 80 degrees with respect to the normal line of the substrate 69. When the evaporating substance is deposited on the substrate in this state, an oblique vapor deposition film having a gradient from the evaporation source direction to the counter-evaporation source direction with a thin film thickness can be formed on the substrate.
The gradient of the film thickness distribution in the substrate can be adjusted by changing the gradient of the evaporating substance flight direction 72 with respect to the normal line 73 of the substrate 69 and the distance L between the evaporation source 67 and the substrate 69. Specifically, if the angle 72 in the direction 72 in which the evaporated substance flies with respect to the substrate normal line 73 is set to an acute angle and the distance L between the evaporation source and the substrate is increased, the gradient of the film thickness distribution becomes gentle. If the angle is made obtuse and L is shortened, the gradient of the film thickness distribution can be tightened.
[0036]
By the way, the obliquely deposited film constituting the thin film birefringent element of the present invention may be any film having anisotropy. However, it is more desirable that the birefringence: Δn is large and the mechanical strength is excellent.₂O_Five, SiO₂, NbO_Five, WO_Three, SnO₂, TiO₂A metal oxide based dielectric film such as the one shows good results. However, when these metal oxides are used as vapor deposition materials and an oblique vapor deposition film is formed on the substrate, due to high internal stress, problems such as insufficient adhesion or increased film turbidity or increased absorption occur. To do. In particular, when obtaining a birefringence amount as a quarter-wave plate or a half-wave plate in a long wavelength region, a considerable amount of film thickness is required, so that the above problem appears remarkably, and an obliquely deposited film is a substrate. , Or scattering of incident light due to white turbidity or absorption due to separation of the vapor deposition material from the desired composition, resulting in problems such as degradation of spectral characteristics.
[0037]
In the present invention, in order to solve the above problem, in addition to evaporation of a vapor deposition material by a normal vapor deposition method, a plasma source (or ion source) is provided in the vapor deposition apparatus 1 as shown in FIG. 1 (or FIG. 11). ) 4 is used together and the plasma formed in the apparatus is actively used. Specifically, the inside of the vapor deposition apparatus 1 is 5 × 10.^-3Introduced gas such as argon (Ar), which is an inert gas, is supplied to the plasma generation mechanism in the apparatus within a range of 3 to 50 ccm using a flow rate control mechanism in a state where the pressure is reduced to Pa or less. At that time, the introduced gas is ionized by collision with electrons supplied from the plasma generation mechanism, and a plasma space is formed in the vapor deposition apparatus by extracting ions and electrons by an intermediate electrode (not shown). Then, by introducing a reactive gas, for example, oxygen, which is optimal for reaction with the obliquely deposited film, into the plasma formed in the above state from the reactive gas inlet 5, the evaporated substance of the deposition material 3 is contained in the plasma. As the reactive gas and the evaporated substance are ionized by collision with electrons and ions in the plasma when passing through the substrate, a reaction occurs between the two and enters the substrate in a high energy state. A vapor deposition film in which the materials are bonded is formed on the substrate. At this time, by giving a negative charge to the substrate (substrate holder), the evaporation material of the vapor deposition material and the ions of the reactive gas collide with the substrate in the electric displacement state due to the effect of the electric field on the substrate. To form a nucleus. By repeating this collision, it is possible to form an obliquely deposited film with extremely high adhesion and reduced light absorption.
[0038]
However, depending on the combination of the substrate and the obliquely deposited film, there may be a problem of a decrease in the bonding force between the two molecules and a decrease in the adhesion due to a severe use environment. Furthermore, there is a problem that transmitted light is lost between the substrate and the obliquely deposited film and between the medium (for example, air) in contact with the obliquely deposited film on the opposite substrate side, and the spectral transmittance is lowered.
Therefore, in order to solve the above two problems, in the present invention, an undercoat 41 is applied between the substrate 40 and the obliquely deposited film 42 like the thin film birefringent element having the configuration shown in FIG. An overcoat 43 is applied. The material of the undercoat 41 and the overcoat 43 is determined by the refractive index and the film thickness obtained from the amplitude condition and the phase condition from the respective refractive indexes of the substrate 40, the obliquely deposited film 42, and the medium in contact with the obliquely deposited film 42.
[0039]
For the formation of the thin film to be the undercoat or overcoat, a deposited film by vacuum deposition or sputtering or a coating film by spin coating or the like is used. At this time, in contrast to the film formed only with the amplitude condition, the spectral transmittance is further improved in the film formed considering both the amplitude condition and the phase condition. For example, borosilicate glass is used as a substrate, Ta₂O_FiveIs used as the oblique deposition film, the material of the undercoat and overcoat is optimally silicon-based or aluminum-based.
Here, the refractive index of the film to be formed: n₁, Refractive index of medium on which light is incident: n₀, Substrate refractive index: n_SThen, the amplitude condition in the obliquely deposited film having the single layer film structure can be expressed as follows.
n₁= (N₀・ N_S)^1/2
Center wavelength: λ₀, Film thickness to be formed: d₁, M = 1, 2, 3,... (Integer), the phase condition in the single layer film can be expressed as follows.
n₁・ D₁= (2m-1) · λ₀/ 4
[0040]
On the other hand, even on the back side of the substrate where the oblique deposition film is not formed, there is a loss of transmitted light as it is, so that the spectral transmittance is improved by forming the antireflection film 44 on the back side of the substrate 40 as shown in FIG. To do. The antireflection film 44 is determined by the refractive index and the film thickness obtained from the amplitude condition and the phase condition in the same manner as described above, and a thin film is formed by vacuum deposition or sputtering.
[0041]
In addition, in order to further improve the adhesion, environmental resistance, optical properties and stability of the obliquely deposited film, the film is subjected to heat treatment (annealing) on the obliquely deposited film or the thin film (overcoat) on the obliquely deposited film. It is preferable to modify the above state, and fluctuations in optical characteristics such as birefringence due to environmental changes can be suppressed. More specifically, laser deposition is applied to the obliquely deposited film or a thin film on the obliquely deposited film while scanning with laser light to modify the state of the film, and the amount of birefringence due to environmental changes is improved. By suppressing fluctuations in optical characteristics such as the beginning, a thin film birefringent element with improved adhesion, environmental resistance, optical characteristics and stability thereof can be produced.
[0042]
By the way, even if the obliquely deposited film formed on the substrate of the thin film birefringent element has a distribution in the phase difference in one substrate, the retardation can be reduced by bonding a plurality of substrates having the obliquely deposited film. The distribution can be adjusted. That is, the two thin film birefringent elements having the same phase difference distribution tendency in the substrate are bonded together, or the phase difference distribution is eliminated, or the two phase difference distribution trends are aligned and the two thin films are symmetrical. By bonding the birefringent elements, it is possible to manufacture a thin film birefringent element that emphasizes the gradient of the phase difference distribution.
In addition, a thin film birefringent element having an arbitrary phase difference can be manufactured by bonding a plurality of thin film birefringent elements having a small phase difference distribution in one substrate.
As a method of manufacturing these thin film birefringent elements, a plurality of substrates formed at the same time or those substrates formed at different times under the same conditions are bonded together with the direction of the substrate determined according to the purpose. This is possible.
[0043]
Specifically, even in a thin film birefringent element having a gradient in the thickness of the obliquely deposited film 77 or the phase difference distribution, the two thin film birefringent elements are configured as shown in FIG. A thin film birefringent element (for example, a wave plate) having a uniform phase difference in the substrate can be produced by laminating with an adhesive 79. Here, the thin-film birefringent element shown in FIG. 12 has two thin-film birefringent elements in which an undercoat 76, an obliquely deposited film 77, and an overcoat 78 are formed on a substrate 75, and an antireflection film is provided on the back surface of the substrate. After the two layers are formed, they are pasted together with an adhesive 79 with the gradient of the phase difference distribution being reversed. In this case, when the phase difference of one substrate has a phase difference of 1/16 wavelength, for example, the gradient direction of the phase difference distribution of the obliquely deposited film 77 of the two thin film birefringent elements is reversed. By bonding, a thin film birefringent element having a phase difference of 1/8 wavelength with a uniform phase difference in the substrate can be manufactured.
Similarly, as shown in FIG. 14, when two or more thin film birefringent elements having the structure shown in FIG. 12 are pasted, the number of thin film birefringent elements pasted to 1/8 wavelength is multiplied. A thin-film birefringent element having a phase difference of 1/4 or 1/2 wavelength having a phase difference can be manufactured.
Further, the vertical direction of the substrate attached at the time of film formation is made symmetric, and the phase difference distribution in the substrate is bonded in the same direction as shown in FIG. A thin film birefringent element having a gradient can be manufactured.
Further, when these substrates are bonded together, it is possible to manufacture a thin film birefringent element having both a phase difference and a filter function by bonding various filters such as a narrow band filter to the bonding surface or back surface of the substrate. In addition, in the thin film birefringent element formed by bonding a plurality of thin film birefringent elements as described above, the spectral transmittance can be improved by forming the antireflection film 80 on the back surface of the substrate located outside. Can do.
[0044]
【Example】
Next, specific examples of the present invention will be described.
[0045]
Example 1
Using the apparatus having the configuration shown in FIG.₂O_FiveA plurality of 50 × 50 mm glass substrates 6 are arranged on the substrate holder 9 so that the incident angle α of the evaporated substance from the vapor deposition material 3 to the substrate is 70 °, and θ of the opening 8 of the shielding plate 7 is set to θ. The substrate holder 9 and the shielding plate 7 are revolved in the rotation direction indicated by the arrow 11 and the substrate holder 9 is rotated in the rotation direction indicated by the arrow 10. Thereby, the plurality of substrates 6 on the substrate holder 9 sequentially pass through the positions of the two openings 8 of the shielding plate 7 by the rotation of the substrate holder 9 while revolving in the vapor deposition apparatus 1. When passing through the position of the opening 8, the evaporated material is obliquely deposited. At this time, the inside of the vapor deposition apparatus 1 is used in advance by using a vacuum exhaust system (not shown).^-FourThe pressure is reduced to about Pa, and from this state, an inert gas Ar is supplied to the plasma source 4 and oxygen is introduced from the reactive gas inlet 5, and then discharged to form a plasma state in the apparatus. The evaporation material 3 is evaporated by the evaporation source 2 composed of an electron gun, and Ta is deposited on the substrate.₂O_FiveIs formed with a thickness of about 4 μm. Film thickness control during vapor deposition is performed by using an optical film thickness meter to set the center wavelength of the interference filter: λ to 630 nm, and monitoring the light amount change of the dummy glass substrate 17 so that the optical film thickness: nd is 33λ. At that time, the deposition was finished. The thin-film birefringent element manufactured in this way has an oblique vapor deposition film having a single-layer film structure with a uniform film thickness and birefringence, and can be used as a quarter-wave plate.
As a result of measuring phase difference: Δ of this thin film birefringent element using an ellipsometer, a measurement result of Δ = 90.46 ° (wavelength: λ = 633 nm) was obtained.
[0046]
(Example 2)
SiO is formed to a thickness of approximately 93 nm as an undercoat in advance between the substrate of Example 1 and the obliquely deposited film, and Ta is used under the same method and conditions as in Example 1.₂O_FiveAn obliquely deposited film is formed, and SiO is formed thereon as an overcoat.₂Was formed to a thickness of approximately 108 nm. Furthermore, Ta of the substrate₂O_FiveA three-layer antireflection film was formed on the surface opposite to the deposited film (configuration shown in FIG. 5).
The thin film birefringent element was measured for phase difference Δ by the same method as in Example 1, and as a result, Δ = 92.43 ° was obtained.
Further, light was incident perpendicularly from the normal direction of the substrate of the thin film birefringent element, and the spectral transmittance was measured. As a result, a result of about 97% T or more was obtained at λ = 633 nm.
Furthermore, this thin film birefringent element was left in a temperature / humidity atmosphere of 60 to 85 ° C. and 90% RH for 200 hours or more. There wasn't.
[0047]
(Example 3)
Ta in the method of Example 1 or 2₂O_FiveThe thickness of the deposited film was formed to about 8 μm. This thin film birefringent element can be used as a half-wave plate.
The thin film birefringent element was measured for the phase difference Δ by the same method as in Example 1, and as a result, Δ = 179.35 ° was obtained.
[0048]
Example 4
The thin film birefringent element manufactured by the method of Example 2 was subjected to heat treatment by laser annealing. Specifically, laser annealing was performed by irradiating the overcoat on the obliquely deposited film while scanning with laser light to modify the film state.
The thin film birefringent element after laser annealing was cut from 50 × 50 mm to 5 × 5 mm using a dicing apparatus, but no peeling of the deposited film and no change in phase difference were observed.
Further, the thin film birefringent element cut to 5 × 5 mm was left in a temperature / humidity atmosphere of 60 to 85 ° C. and 90% RH for 500 hours, but no peeling of the deposited film and fluctuation of the retardation were observed.
[0049]
(Example 5)
The thin-film birefringent element manufactured in Example 1 or 2 or 3 is cut to a desired size, and the phase difference 1 / is applied to the light incident surface and light exit surface of the prism 53 having the shape shown in FIG. The thin film birefringent element 54 having four wavelengths and the thin film birefringent element 55 having a phase difference of ½ wavelength are arranged in accordance with the optical axis directions 57 and 58 viewed from the prism front face 56 shown in FIG. I attached. The prism 53 to which the thin film birefringent elements 54 and 55 are attached can be used as a two-beam combining prism.
[0050]
(Example 6)
In the same manner as in the first, second, or third embodiment, instead of the glass substrate, the phase difference ¼ indicated by reference numeral 54 is directly applied to the light incident surface and the light exit surface of the prism 53 having the shape shown in FIG. After forming an oblique vapor deposition film having a wavelength, an oblique vapor deposition film having a phase difference of ½ wavelength indicated by reference numeral 55 is formed. At that time, the optical axes 57 and 58 viewed from the prism front surface 56 shown in FIG. 9B are arranged so that the directions of the optical axes 57 and 58 are parallel to the line connecting the outer peripheral portion and the central portion of the substrate holder. The prism 53 formed with the oblique vapor deposition films 54 and 55 having the phase difference of ¼ wavelength and ½ wavelength can be used as a two-beam combining prism having the function of a wavelength plate as an integrated composite element.
[0051]
(Example 7)
In the same manner as in the first or second embodiment, instead of the glass substrate, the phase difference ¼ wavelength indicated by reference numeral 60 is directly provided on one surface of the prism 59 having the polarization beam splitter (PBS) surface 62 shown in FIG. An obliquely deposited film is formed. At that time, the optical axis 63 shown in FIG. 10B is arranged so that the direction of the optical axis 63 is parallel to the line connecting the outer peripheral portion and the central portion of the substrate holder 9 of the apparatus shown in FIG. The prism 59 on which the oblique deposition film 60 having a phase difference of ¼ wavelength is formed can be used as a PBS prism having a function of a wave plate as an integrated composite element, and is a compact disc (CD), laser disc (LD), digital The present invention can be applied to an optical pickup of an optical disk drive or the like as a polarization separation element that separates reflected light from a recording medium 61 such as a versatile disk (DVD) from a light beam from a light source.
[0052]
(Example 8)
Two thin-film birefringent elements (configuration shown in FIG. 5) in which an undercoat 76, an obliquely deposited film 77, and an overcoat 78 are formed on a substrate 75 by the same method as in Example 2 are used, and obliquely deposited as shown in FIG. Bonding was performed using the adhesive 79 with the film 77 side facing. As a result of measuring the phase difference Δ of the thin film birefringent element using an ellipsometer, a result of Δ = 179.83 ° was obtained. This thin film birefringent element can be used as a half-wave plate.
The thin film birefringent element was allowed to stand in a temperature / humidity atmosphere of 60 to 85 ° C. and 90% RH for 200 hours, but no peeling or phase difference: Δ was observed.
[0053]
Example 9
Using an apparatus having the configuration shown in FIG.₂O_FiveAnd several 50 × 50 mm glass substrates 69 on which an undercoat has been previously formed are arranged on the substrate holder 70 so that the incident angle α of the evaporation material from the vapor deposition material 68 to the substrate is 70 °. The revolution jig 71 is rotated. At this time, the inside of the apparatus is preliminarily used by using a vacuum exhaust system (not shown).^-FourThe pressure is reduced to about Pa, and from this state, an inert gas Ar is supplied to the plasma source 66 and oxygen is introduced from the reactive gas inlet 74 and then discharged to form a plasma state in the apparatus. The evaporation material 3 is evaporated by an evaporation source 67 composed of an electron gun, and Ta is deposited on the substrate.₂O_FiveA deposited film of about 2 μm is formed, and Ta₂O_FiveAn overcoat was formed on the deposited film.
Two thin-film birefringent elements having an obliquely deposited film 77 having a change in film thickness by making the fixing method to the substrate holder 70 asymmetric during film formation by such a manufacturing method are manufactured. The birefringent element was bonded with an adhesive 79 so that the respective deposited films faced each other as shown in FIG. This thin film birefringent element can be used as a quarter wavelength plate.
As a result of measuring the phase difference: Δ of this thin film birefringent element with an ellipsometer, the phase difference at the center of the substrate is Δ = 90.02 ° (wavelength: λ = 633 nm), and the difference in Δ between the center of the substrate and the outer peripheral portion. A measurement result of 2% or less was obtained.
The thin film birefringent element was allowed to stand in a temperature / humidity atmosphere of 60 to 85 ° C. and 90% RH for 200 hours, but no peeling or phase difference: Δ was observed.
[0054]
【The invention's effect】
As described above, the thin-film birefringent element of the present invention has a single-layered oblique deposition film in which the film thickness and birefringence are controlled, so that the processing cost is low, mass production is possible, and optical A thin-film birefringent element with improved characteristics can be provided. Also, a thin film (undercoat film or overcoat) for the purpose of improving adhesion, environmental resistance and optical properties between the substrate surface and the obliquely deposited film or on or both of the obliquely deposited film. By having a structure having a film), it is possible to provide a thin-film birefringent element that prevents peeling of the obliquely deposited film and clouding / absorption, and has improved adhesion, optical characteristics, and environmental resistance. Furthermore, heat treatment (annealing) is applied to the above-mentioned obliquely deposited film or the thin film on the obliquely deposited film to modify the state of the film so that the variation in optical characteristics including the amount of birefringence due to environmental changes is suppressed. Thus, it is possible to provide a thin film birefringent element with improved adhesion, environmental resistance, optical characteristics and stability. Furthermore, a thin-film birefringent element in which a single layer film structure obliquely deposited film is formed on a substrate, or a thin film (undercoat film or overcoat) between the substrate surface and the obliquely deposited film, or on the obliquely deposited film, or both. A thin film birefringent element having a coating film), or an obliquely deposited film or a thin film on the obliquely deposited film is subjected to heat treatment (annealing) to modify the state of the film, and the birefringence due to environmental changes A thin-film birefringent element in which adhesion, environmental resistance, optical characteristics and stability thereof are further improved by combining two or more thin-film birefringent elements having a structure that suppresses fluctuations in characteristics. Can be provided.
[0055]
According to the method for manufacturing a thin film birefringent element of the present invention, an oblique vapor deposition film having a single layer film structure in which the film thickness and the birefringence amount are controlled can be formed, so that an error in the birefringence amount in the same substrate can be formed. It is possible to manufacture a thin film birefringent element in which the amount of birefringence with an arbitrary gradient in the substrate is accurately expressed. In addition, it forms a slanted vapor deposition film with a single-layer structure that has excellent mechanical strength such as adhesion and low-absorption light utilization efficiency and high spectral efficiency. Since this can be achieved well, a thin-film birefringent element capable of supporting a wide range of wavelengths of various optical systems can be manufactured. In addition, since an oblique deposition film can be formed by directly vapor-depositing on an optical element such as a lens or a prism, a composite element having a birefringence function can be manufactured, and various optical elements can be further miniaturized. Also, a thin film (undercoat film or overcoat film) for the purpose of improving adhesion, environmental resistance and optical properties between one or both of the substrate surface and the obliquely deposited film or on the obliquely deposited film. By forming the film with a vapor deposition film or a coating film, it is possible to produce a thin film birefringent element that prevents peeling of the oblique vapor deposition film and clouding / absorption, and has improved adhesion, optical properties, and environmental resistance. In addition, laser deposition is performed by irradiating obliquely deposited films or thin films on obliquely deposited films while scanning with laser light to modify the state of the film, and optics including birefringence due to environmental changes. By suppressing fluctuations in characteristics, it is possible to manufacture a thin film birefringent element with improved adhesion, environmental resistance, optical characteristics, and stability. Further, by subjecting the obliquely deposited film or the thin film on the obliquely deposited film to laser annealing, it is possible to suppress fluctuations in the birefringence characteristics due to the penetration of the cutting fluid at the time of cutting accompanying chip formation. Furthermore, a thin-film birefringent element in which a single layer film structure obliquely deposited film is formed on a substrate, or a thin film (undercoat film or overcoat) between the substrate surface and the obliquely deposited film, or on the obliquely deposited film, or both. A thin film birefringent element having a coating film), or an obliquely deposited film or a thin film on the obliquely deposited film is irradiated with a laser beam while scanning to perform a laser heat treatment (laser annealing) to modify the state of the film. After manufacturing thin-film birefringent elements that suppress fluctuations in optical properties such as the amount of birefringence due to changes, two or more of these thin-film birefringent elements are bonded together with an adhesive so that adhesion, environmental resistance, A thin-film birefringent element with further improved optical characteristics and stability can be manufactured.
[0056]
According to the thin-film birefringent element manufacturing apparatus of the present invention, it is possible to form an oblique vapor deposition film having a single-layer film structure in which the film thickness and birefringence are controlled. Since the refraction amount can be controlled to be uniform, or the relationship between the position of the obliquely deposited film in the substrate and the birefringence amount can be controlled so as to be distributed with a gradient, it is possible to control the refraction amount within the same substrate. A thin-film birefringent element in which an error in the amount of refraction is reduced, or a thin-film birefringent element in which a birefringence amount having an arbitrary gradient in the substrate is accurately expressed can be manufactured.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first configuration example of a manufacturing apparatus for forming an obliquely deposited film of a thin film birefringent element according to the present invention, wherein (a) is a front view showing a schematic configuration in the manufacturing apparatus; b) is a side view showing a schematic configuration of the manufacturing apparatus.
FIG. 2 is a diagram showing a relationship between an incident angle α of a vaporized substance with respect to a substrate normal and a substrate when forming an obliquely deposited film of a thin film birefringent element according to the present invention.
FIG. 3 is a diagram seen from the side surface in the Y direction of FIG. 2 and is a diagram schematically showing incidence of an evaporating substance on a substrate and a columnar structure of an obliquely deposited film.
4 is a view as seen from the side surface in the X direction of FIG. 2, and schematically shows the incidence of the evaporated substance on the substrate and the columnar structure of the obliquely deposited film.
FIG. 5 is a cross-sectional view of an essential part showing an example of a film structure of a thin film birefringent element according to the present invention.
6 is a diagram showing an example of a planetary rotation mechanism provided in the manufacturing apparatus shown in FIG. 1 and a substrate movement locus in the mechanism.
FIG. 7 is a diagram showing a component state of linearly polarized light.
FIG. 8 is a diagram showing a phase delay after linearly polarized light passes through a birefringent element.
FIGS. 9A and 9B are diagrams showing optical elements (two-beam combining prisms) according to Examples 4 and 5 of the present invention, in which FIG. 9A is a plan view of the optical element, and FIG. 9B is a side view of the optical element.
FIGS. 10A and 10B are diagrams showing an optical element (PBS prism having a function of a wave plate) according to Example 6 of the present invention, where FIG. 10A is a plan view of the optical element, and FIG. 10B is a side view of the optical element; is there.
FIG. 11 is a schematic configuration diagram showing a second configuration example of a manufacturing apparatus for forming an obliquely deposited film of a thin film birefringent element according to the present invention.
FIG. 12 is a cross-sectional view of the main part of a thin film birefringent element having a configuration in which two thin film birefringent elements according to the present invention are bonded together so that the phase difference in the substrate is uniform.
FIG. 13 is a cross-sectional view of the main part of a thin film birefringent element having a configuration in which two thin film birefringent elements according to the present invention are bonded so that the phase difference in the substrate has a gradient.
FIG. 14 is a cross-sectional view of a main part of a thin film birefringent element having a configuration in which a plurality of thin film birefringent elements according to the present invention are bonded so that the phase difference in the substrate is uniform.
FIG. 15 is a cross-sectional view showing a principal part of a configuration example of a thin-film birefringent element according to Example 7 of the present invention.
FIGS. 16A and 16B are diagrams showing an example of a conventional apparatus for forming an obliquely deposited film, where FIG. 16A is a front view of the deposited film forming apparatus, and FIG. 16B is a side view of the deposited film forming apparatus.
[Explanation of symbols]
1 Vapor deposition equipment
2 Evaporation source
3 Deposition material
4 Plasma source (or ion source)
5 Reactive gas inlet
6 Substrate
7 Shield plate
8 Shield plate opening
9 Substrate holder
10 Direction of rotation of substrate holder
11 Revolution direction of substrate holder and rotation direction of shielding plate
12 Shutter plate
13 Monitoring window
14 Light source for film thickness meter
15 Light-receiving part of film thickness meter
16 Reflector of film thickness meter
17 Dummy board
18 Birefringence measuring device polarizer
19 Reflector of birefringence measuring instrument
20 Light source of birefringence measuring instrument
21 Transmitted light detector of birefringence measuring instrument
22 Reflected light detector of birefringence measuring instrument
23 Flight direction of evaporation material
24 substrate normal
29 substrates
30 Deposition material
31 Substrate normal
32 substrates
33 Substrate normal
34 Evaporative substance incident direction
35 Obliquely deposited film
36 substrates
37 substrate normal
38 Evaporative material incident direction
39 Obliquely deposited film
40 substrates
41 Undercoat
42 Obliquely deposited film
43 Overcoat
44 Anti-reflective coating
45 Planetary rotation mechanism
46 Substrate holder
47 Substrate
47a Trace of substrate
48 Y-direction electrical vibration component
49 Electrical vibration component in X direction
50 Y-direction electrical vibration component
51 Electrical vibration component in X direction
53 Prism
54 Thin-film birefringent element with 1/4 phase difference
55 Thin-film birefringent element with retardation 1/2 wavelength
56 Prism front
57 Optical axis of thin-film birefringent element
58 Optical axis of thin-film birefringent element
59 PBS Prism
60 Thin-film birefringent element with 1/4 phase difference
61 Recording media
62 PBS surface
63 Optical axis of thin-film birefringent element
65 Vapor deposition equipment
66 Plasma source (or ion source)
67 Evaporation source
68 Vapor deposition material
69 substrates
70 Substrate holder
71 Revolution Jig of Revolution Mechanism
72 Flight direction of evaporating substances
73 Substrate normal
74 Reactive gas inlet
75 substrates
76 Undercoat
77 Obliquely deposited film
78 overcoat
79 Adhesive layer (adhesive)
80 Anti-reflective coating

Claims

Evaporation material from an oblique direction have a obliquely deposited film formed by incident on the substrate, the thin film birefringent element is a deposited film of the obliquely deposited film is a single layer film structure thickness and birefringence is controlled A manufacturing method of a thin film birefringent element when producing,
A disk-shaped substrate holder holding one or more substrates is held by a planetary rotation mechanism consisting of rotation and revolving motion, and the substrate holder is rotated by the planetary rotation mechanism and revolved in the deposition apparatus to rotate the substrate. One or more substrates held by the holder are moved in a rotational motion that draws a semicircular locus above the evaporation source that evaporates the evaporation substance, and in the vicinity of the substrate holder between the substrate holder and the evaporation source With the shielding plate having an opening disposed in the evaporation source, the evaporation source is ionized using the plasma source or the ion source that forms a plasma state in the evaporation apparatus, and then the evaporation substance is ionized to fly toward the substrate. A manufacturing method of a thin-film birefringent element, wherein an evaporated material is incident on a substrate from an oblique direction through an opening of a plate to form an obliquely deposited film .

In the manufacturing method of the thin film birefringent element according to claim 1,
The shield plate is arranged so that the center of rotation of the substrate holder and the center of the two openings of the shield plate are the same, and the revolution of the substrate holder synchronized with the revolution motion of the planetary rotation mechanism. A method of manufacturing a thin-film birefringent element , characterized in that motion is given .

In the manufacturing method of the thin film birefringent element according to claim 1 or 2,
A thin-film birefringent element characterized in that an obliquely deposited film having a single-layer film structure is formed by deposition from an oblique direction, and the thickness and birefringence amount of the obliquely deposited film are controlled to be uniform in a substrate . Manufacturing method .

In the manufacturing method of the thin film birefringent element as described in any one of Claims 1-3 ,
In order to form a vapor deposition film having a desired film thickness and / or birefringence on the substrate, a dummy substrate is disposed in the vapor deposition apparatus, and a light projecting unit and a light receiving unit that are in contact with the outside of the vapor deposition apparatus through a monitoring window And / or a birefringence measuring device having a configuration in which a polarizer is added in the middle of the light projecting part and the light receiving part of an optical system equivalent to the optical film thickness meter. By monitoring the change in the amount of transmitted light or reflected light of the dummy substrate or substrate, the optical film thickness and / or birefringence amount of the deposited film during oblique deposition is monitored, and the desired film thickness and / or birefringence amount A method for producing a thin-film birefringent element , characterized in that vapor deposition conditions and time are controlled so as to be.

In the manufacturing method of the thin film birefringent element as described in any one of Claims 1-4 ,
A thin film intended to improve adhesion, environmental resistance and optical properties on one or both of the substrate surface before forming the obliquely deposited film and / or the obliquely deposited film after forming the obliquely deposited film. A method for producing a thin-film birefringent element, comprising forming a vapor-deposited film or a coating film .

In the manufacturing method of the thin film birefringent element as described in any one of Claims 1-5 ,
Laser oblique heat treatment (laser annealing) is performed by irradiating the thin film birefringent element obliquely deposited film or the thin film on the obliquely deposited film while scanning with laser light to modify the state of the film, and the amount of birefringence due to environmental changes A method for manufacturing a thin-film birefringent element, characterized by suppressing fluctuations in optical characteristics such as the beginning .

In the manufacturing method of the thin film birefringent element as described in any one of Claims 1-6 ,
A method for producing a thin- film birefringent element, wherein two or more thin-film birefringent elements are bonded together .

It is a manufacturing apparatus of the thin film birefringent element used for the manufacturing method of the thin film birefringent element as described in any one of Claims 1-7 ,
A vapor deposition apparatus having an evaporation source for evaporating an evaporation substance, a plasma source or an ion source for forming a plasma state, a disk-shaped substrate holder for holding one or more substrates in the vapor deposition apparatus, and rotating the substrate holder A planetary rotation mechanism that rotates in the vapor deposition apparatus by movement and revolving movement, and a shielding plate that is disposed in the vicinity of the substrate holder between the substrate holder and the evaporation source and has an opening through which the evaporated substance can pass.
While rotating the substrate holder by the planetary rotation mechanism, the inside of the vapor deposition apparatus revolves so that one or more substrates held by the substrate holder rotate in a semicircular locus above the evaporation source. While moving by movement,
The evaporation source is ionized using the evaporation source and the plasma source or the ion source to fly in the direction of the substrate, and the evaporation material is incident on the substrate from an oblique direction through the opening of the shielding plate to form an oblique deposition film. An apparatus for manufacturing a thin-film birefringent element, characterized by comprising:

In the manufacturing apparatus of the thin film birefringent element according to claim 8 ,
Optical film thickness meter comprising a light projecting portion and a light receiving portion provided outside the vapor deposition apparatus and in contact with a monitoring window, and / or polarized light in the middle of a light projecting portion and a light receiving portion of an optical system equivalent to the optical film thickness meter. Equipped with a birefringence measuring device with an additional element, and by using the optical film thickness meter and / or birefringence measuring device to monitor the change in the amount of transmitted or reflected light of the substrate being processed, oblique deposition Production of a thin film birefringent element characterized in that the optical film thickness and / or birefringence amount of the deposited film is monitored and the deposition conditions and time are controlled so that the desired film thickness and / or birefringence amount is obtained. Equipment .

A thin-film birefringent element having a single-layer film structure in which a film thickness and a birefringence amount are controlled. There,
A thin-film birefringent element manufactured by the method for manufacturing a thin-film birefringent element according to any one of claims 1 to 7, or the thin-film birefringent element manufacturing apparatus according to claim 8 or 9. Child.