JP3764671B2

JP3764671B2 - Optical path changer, method for manufacturing the same, and optical module using the same

Info

Publication number: JP3764671B2
Application number: JP2001332133A
Authority: JP
Inventors: 重雄青野; 隆則安田
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2001-10-30
Filing date: 2001-10-30
Publication date: 2006-04-12
Anticipated expiration: 2021-10-30
Also published as: JP2003131088A

Description

【０００１】
【発明の属する技術分野】
本発明は、光通信及び光情報通信分野等において使用される光路変換体、及びその製造方法、並びにそれを用いた光モジュールに関する。
【０００２】
【発明の背景】
表面実装型の光伝送モジュールにおいて、動作電流や温度特性に優れた面発光レーザー（ＶｅｒｔｉｃａｌＣａｖｉｔｙＳｕｒｆａｃｅＥｍｉｔｔｉｎｇＬａｓｅｒ、以下、ＶＣＳＥＬともいう）の出射光を、所定形状の基体の反射面により光路を変えて、光ファイバ等の光素子に光学的接続を容易に行わせることが可能である。また、基体の反射面となる面に受光素子を搭載することで、ＶＣＳＥＬの出力監視が容易になる。
【０００３】
ところで、上述の光路変換体を、光伝送モジュールの基板として好適に用いられる単結晶シリコンで形成する場合、光路変換体の反射面は基板の異方性エッチングで形成することにより、高精度に平坦な反射面を作製できる。
【０００４】
しかし、基板を異方性エッチングにより高精度に平坦な反射面を作製するには、不純物の少ない基板を選択しなければならず、そのための製法が限定されしかもコスト高となる。すなわち、例えばＦＺ（フローティング・ゾーン）法によって製作された、コストの高いシリコン基板が選ばれる。これは、例えばＣＺ（チョコラルスキー）法などの比較的安価な手法によって製作されたシリコン基板は、製法プロセス上、不純物が混入し、結晶中に欠陥を作りやすいためである。このような欠陥は異方性エッチングの際に、エッチング面にピットを形成し、平坦な反射面が作製できない。
【０００５】
また、上記ＦＺ法で製作されたシリコン基板を用いた場合でも、高精度に平坦な反射面を作製するには、エッチング条件を最適化しなければならず、このような最適化は容易ではない。
【０００６】
また、受光素子のような光半導体素子を上記のような光路変換体を利用して搭載する場合、異方性エッチングで形成された面に搭載することになり、この面は基板表面に対し傾斜しているので、多数の光半導体素子を精度良く搭載するのが困難であるという問題が生じる。
【０００７】
さらに、光路変換体の実装基板への搭載時に、光路変換体を実装基板へ加圧・密着させることになるため、光路変換体のエッジ部で、受光素子に接続する電極配線が断線する恐れがあるという問題があった。
【０００８】
そこで本発明では、上述の問題を解消し、光反射面または素子配設面として平坦性の優れた面を備えた光路変換体を容易にかつ迅速に提供でき、さらに、面発光素子と光伝送体との光接続を高効率にできる、信頼性の高い光モジュールを提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために、本発明の光路変換体は、柱状をなし、単結晶シリコンから成る本体の上下面は、異方性エッチングで形成された（１１１）面またはその等価な、平坦面であり、前記本体の側面の非エッチング部は、（１００）面から［１１０］方向へ４．７°〜１４．７°傾斜させた面またはその等価な面であって、入射光を受光するとともに、その光の一部を反射させて所定方向へ光路変換させる受光素子が配設された素子配設面であり、前記本体の下面と前記素子配設面との間に、オーミックコンタクト用の不純物拡散領域が形成されていることを特徴とする。
【００１１】
また特に、前記受光素子が光を反射する面は、前記本体の下面に対して垂直方向であって前記下面側からの入射光に対して９０°の角度で光路変換させて略水平方向への出射光とすることを特徴とする。
【００１２】
また、特に前記受光素子は、ＩｎＧａＡｓ／ＩｎＰの化合物半導体材料からなることを特徴とする
【００１３】
また本発明の光路変換体の製造方法は、単結晶ウエハの両主面に対し異方性エッチングを施すことにより、前記両主面上に交互に位置するＶ溝を複数条に形成するとともに、前記Ｖ溝の両側に形成され断面が平行四辺形状で厚みが交互に異なる柱状部を形成する工程と、厚みの小さい方の柱状部を除去することにより、厚みの大きい方の柱状部を分離する工程とを含み、柱状をなす本体の非エッチング面の一部を入射光を受光するとともに、その光の一部を反射させて所定方向へ光路変換させる光半導体素子を設ける素子配設面としたことを特徴とする。
【００１４】
また本発明の光路変換体の製造方法は、単結晶ウエハの両主面に対し異方性エッチングを施すことにより、前記両主面上に交互に位置するＶ溝を複数条に形成するとともに、前記Ｖ溝の両側に形成され断面が平行四辺形状で厚みが交互に異なる柱状部を形成する工程と、厚みの小さい方の柱状部を除去することにより、厚みの大きい方の柱状部を分離する工程とを含み、柱状をなす本体の非エッチング面の一部を入射光を所定方向へ光路変換させるための光反射面としたことを特徴とする。
【００１５】
また本発明の光路変換体の製造方法は、前記単結晶ウエハの一主面と前記素子配設面との境界部分に半導体の不純物拡散領域を形成する工程と、前記素子配設面側の前記不純物拡散領域に前記光半導体素子をオーミック接合させる工程と、をさらに含むことを特徴とする。
【００１６】
また本発明の光モジュールは、高低差のある低位置面及び高位置面を形成した基板の低位置面に面発光素子及び該面発光素子の出射光を反射させる請求項１または２に記載の光路変換体を配設するとともに、前記高位置面に前記光路変換体からの反射光を入射させる光伝送体を配設したことを特徴とする。
【００１７】
【発明の実施の形態】
以下に、本発明に係る実施形態の例について模式的に示した図面に基づき詳細に説明する。
【００１８】
図１に本発明の光モジュールから受光素子を除いた参考形態の光モジュールＭ１の断面図を示す。
【００１９】
光モジュールＭ１は、高低差のある低位置面１ａ及び高位置面を形成した基板１の低位置面１ａに、面発光素子３、及び面発光素子３の出射光Ｌ１を反射させる光路変換体２をそれぞれ配設し、高位置面に形成され光軸に直交する断面形状がＶ字状を成す搭載用溝１ｂに、光路変換体２からの反射光Ｌ２を先端４ａに入射させる光ファイバやその他の光導波路体から成る光伝送体４を配設している。
【００２０】
ここで、光路変換体２は異方性エッチングが可能な材料から成り柱状である。そして、この本体の上下面２ａ，２ｂがアルカリ水溶液等を用いた異方性エッチングで形成されている。また、側面の非エッチング部である傾斜面２ｃが、面発光素子３からの入射光Ｌ１を所定方向へ光路変換させるための光反射面または受光素子等の光半導体素子を配設するための素子配設面としている。
【００２１】
この光路変換体２は本体が単結晶シリコンから成り、異方性エッチングを施す上下面２ａ，２ｂが（１１１）面またはその等価な面であり、かつ光反射面または素子配設面が、（１００）面から［１１０］方向へ４．７°〜１４．７°（最適には９．７°）傾斜させた面またはその等価な面であると、面発光素子３からのほぼ垂直な出射光を、光路変換体２の傾斜面２ｃでほぼ９０°角度で光路変換させて（略水平方向へ）水平に配設された光伝送体４へ入射させることができ、効率よく光接続できる。このように、光反射面は入射光に対して９０°の角度で光路変換させるように形成されているとよい。
【００２２】
光路変換体２は、以下のようにして製造される。
【００２３】
まず、図２に平面図、図３に図２のＡ−Ａ’線断面図にて示すように、単結晶ウエハＷの両主面１０，１３に対し、所定のフォトレジスト１１の形成面を保護し、露出面に対しアルカリ水溶液等による異方性エッチングを施すことにより、両主面１０，１３上に交互に位置するＶ溝１２を所定方向に複数条に形成する。これにより、Ｖ溝１２の両側に形成され断面が平行四辺形状で厚みが交互に異なる柱状部１４，１５が形成される。
【００２４】
なお、光路変換体２の傾斜面２ｃは光反射面または光半導体素子を高精度に配設するため、単結晶ウエハの両主面１０、１３は、ＭＣＰ（メカノケミカルポリッシュ）により鏡面（算術平均粗さが１０ｎｍ以下）に研磨されたものを用いる。
【００２５】
次に、厚みの小さい方の柱状部１５の両側に示したラインＤにおいてダイシングすることにより除去し、厚みの大きい方の柱状部１４を分離する。なお、図３において、θ１は４０°〜５０°、θ２は５９．４°〜６９．４°となる。（←θ１は４５°に対して±５°、θ２は６４．４°に対して±５°。光ファイバに光を有効に入射させるために、光ファイバの開口比を考慮して傾きの範囲を±５°とした。）
このようにして得た、柱状をなす本体の非エッチング面の一部を、入射光を所定方向へ光路変換させるための光反射面、または光半導体素子を設ける素子配設面とする。
【００２６】
面発光素子３は、例えばＶＣＳＥＬを用いるが、実装基板表面に対し法線方向に発光している形状であれば適用可能である。
【００２７】
光伝送体４は、光ファイバのほかに各種形状の光導波路体や基板１に直接形成した光導波路であってもよい。
【００２８】
かくして、異方性エッチング技術を用いた傾斜面を光反射用の斜面として用いず、鏡面研磨されたウエハの両主面を光反射面または光半導体素子の素子配設面とすることができ、平坦性の優れた光反射面または素子配設面を備えた、優れた光路変換体を提供できる。
【００２９】
また、光路変換体はウエハプロセスによる一括作製が可能なため、非常に低コストに作製可能である。
【００３０】
また、ウエハ面方位により入射光に対して所定角度で光路変換させる光路変換体を提供できるため、任意の傾斜角を形成でき、面発光素子からの出射光を効率的に入射光学系へ効率的に入射する光学系を提供できる。
【００３１】
さらに、光路変換体として単結晶シリコンを用いることにより、光半導体素子をシリコン基板上に直接形成したり、光半導体素子としてシリコンとは異なる化合物半導体材料を用いる場合、別の化合物半導体基板上に複数の光半導体素子を形成し、複数の光路変換体が形成されたシリコン基板表面へ、一括して貼り合わせる接着が可能なため、実装コストを削減した優れた受光素子付き光路変換体が実現される。
【００３２】
次に、本発明に係る実施形態について説明する。
【００３３】
図４に斜視図にて示すように、光路変換体２の非エッチング面である傾斜面（素子配設面）２ｃに、フォトダイオード等の受光素子である光半導体素子５を配設し、さらに、この光半導体素子５の電気信号線路，電流供給線路である電極パターン７，８を形成している。ここで、５ａは受光部、５ｂは電極パッドであり、電極パッド５ｂと電極パターン８とがボンディングワイヤ９で接続されている。
【００３４】
また、接着部材６を用いる場合は、ＡｕＳｉ系、ＡｕＳｕ系、ＰｂＳｎ系、Ｉｎ系の半田等を用いることにより、実装強度や信頼性に優れた実装が行える。但し、本文では、直接接合法と呼ばれる、半田や接着剤の接着部材６を用いることなく、光半導体素子５の表面の化学的性質を利用して接着できる。すなわち、クリーニングされた光半導体素子５の表面を光路変換体２の表面に接触させ水素結合により接着します。さらにアニールを行うことで水分子が蒸発し、酸素を介したより強固な結合へと変化し、信頼性を向上させることができる。
【００３５】
また、光路変換体２において、その本体の下面２ｂと素子配設面２ｃとの間、すなわち、素子配設面２ｃとエッチング面である下面２ｂとの境界部において、オーミックコンタクト用の不純物拡散領域が形成されている。
【００３６】
このようにして構成した光路変換体２を用い、図５に断面図にて示すように、光モジュールＭ２は、高低差のある低位置面及び高位置面を形成した基板１の低位置面１ａに、面発光素子３及びこれからの出射光を反射させる光路変換体２を配設するとともに、前記高位置面に光路変換体２からの反射光を入射させる光伝送体４を配設している。なお、光モジュールＭ２において、光路変換体２に光半導体素子５を配設すること以外の構成は、図１に示す光モジュールＭ１とほぼ同様であり、同一構成要素については同一符号を付し説明を省略する。
【００３７】
かくして、光モジュールＭ２によれば、光モジュールＭ１と同様な効果を奏する上に、素子配設面と光路変換体の下面との間に所定以上（例えば１×１０¹⁸ｃｍ^-3以上）の不純物濃度が拡散されているため、金属薄膜等で形成される受光素子の電気信号線路、電流供給線路を２面に形成する必要が無くなり、電気配線が光路変換体のエッジで断線することがない。
【００３８】
【実施例】
次に、本発明の光モジュールをより具体化した実施例について説明する。
＜参考例＞
図１に示す光モジュールＭ１において、単結晶シリコンから成り高低差のある基板１の低位置面１ａに光路変換体２及び面発光レーザー３が配設され、基板１の高位置面に形成された断面Ｖ字形状の搭載溝１ｂに光ファイバ４が配設されたものとした。
【００３９】
ここで、基板１は特に材質がＣＺ法で作製されたコストが安いことに特徴のあるシリコンを用い、段差は異方性エッチングにより形成した。また、光ファイバ４の搭載溝１ｂは異方性エッチングにより形成した。また、面発光レーザー３はＧａＡｓ系材料を用いた。
【００４０】
また、光路変換体２は以下のようにして作製した。
【００４１】
まず、図２に示すように、ＭＣＰにより鏡面に研磨された表裏面１０，１３が（１００）面から９．７°傾いた面を有するウエハＷを用い、表裏面において、フォトリソグラフィー技術により、［１１０］方向へ沿って直線状にフォトレジスト１１を等間隔に被着形成し、このウエハＷの露出部を水酸化カリウム水溶液に浸すことにより異方性エッチングを施した。これにより、（１１１）面及びそれに等価な面が斜面の断面Ｖ字状の溝１２が形成された。
【００４２】
図３に示すように、ウエハＷは（１００）から前記［１１０］方向へ９．７°傾いているので、傾斜角θ１は４５°、θ２は６４．４°となる。なお、θ１は光路を９０°変換するために、θ１＝４５°に設定する必要があり、この形成は異方性エッチングにより高精度に形成した。
【００４３】
また、４５°斜面を有する光路変換体用柱状体１４を形成するように、表面１０と裏面１３でフォトレジスト１１の形成領域をずらした。
【００４４】
次に、フォトレジスト１１をリムーバーにより除去し、その後、光路変換体用柱状体１４の上下面１０，１３に光反射膜を形成するべく金属薄膜を形成した。ここで、金属薄膜の最上層には反射率の高いＡｕを用いた。また、この最上層金属膜をウエハＷのシリコン基体上に有効に形成させるために、最上層金属薄膜とシリコン基体の間に下地金属膜としてＣｒ層を用い、シリコン基体表面にシリコン酸化膜層を形成した。金属薄膜の合計膜厚は約１μｍとした。
【００４５】
そして、図３に示すラインＤに沿って、ダイシングにより切断を行い、個々の光路変換体となるように切り分けた。その際に、エッチング残部である小さい方の柱状部１５が完全に除去され、所定形状の光路変換体が作製できた。
【００４６】
次に、こうして作製された光路反射体２は、図１に示すように、実装基板である基板１上の位置合わせマーカー（不図示）を利用して、正確に位置決めし実装固定した。この際の固定材にはＡｕＳｕ系の半田を用いた。
【００４７】
また、面発光レーザー３を加圧・密着させ、実装基板１に形成された薄膜半田（不図示）を溶解・冷却し、基板１上に実装固定し、次いで、光ファイバ４を搭載用溝１ｂ上に搭載し、例えば樹脂、或いはガラス板等の平板基板で押圧固定する等の方法で実装固定した。
【００４８】
かくして、光モジュールＭ１によれば、光反射面はミラー加工された｛１００｝面を利用するので、高精度に平坦化された反射面を実現できる。また、異方性エッチングにおいてエッチング面を高精度に平坦化する必要がないことにより、ＦＺ法、ＣＺ法等の各種の製法で作製したシリコン基板を用いることができ、また、エッチング中に超音波揺動などを行う必要がなく、エッチング条件の最適化が省けた。また、光路反射体はシリコンウエハの両面からエッチングを行うことにより、断面が略平行四辺形で、光路変換体の上面が平坦になることから、光路変換体は従来のフリップチップボンディング技術による高精度の実装も可能となった。
【００４９】
＜実施例＞
次に、図４及び図５に示した他の実施例について説明する。
【００５０】
光路変換体２の作製は参考例と同様にして行った。
【００５１】
そして、図４に示すように、光路変換体２の斜面２ｃに、光半導体素子５を以下のようにして配設した。
【００５２】
また、図５に示す光モジュールＭ２は、光路変換体２に光半導体素子５を配設し、その配線等を施した以外については、既に説明した光モジュールＭ１と同様に構成した。
【００５３】
この実施例では、光路変換体２の光反射面である傾斜面２ｃと下面２ｂの境界部分にＢ（ボロン）をイオン注入し、その不純物濃度を１×１０¹⁸ｃｍ^-3以上とした。なおこの時、Ａｌなど半導体の不純物であればＢ以外でも良い。
【００５４】
次いで、光半導体素子５用の電気信号線路７、電流供給線路８を金属薄膜で形成した。この金属薄膜は上層／下層で、Ａｕ／Ｃｒとし、その厚みは合計で約１μｍとした。このとき、各線路の一端は、不純物拡散領域２０，２１まで配置した。
【００５５】
そして、別の半導体基板、例えばｎ⁺型ＧａＡｓ基板上に厚み１．０μｍ、不純物濃度１×１０¹⁸ｃｍ^-3のｎ型ＧａＡｓ層、厚み４．０μｍ、不純物濃度１×１０¹⁵ｃｍ^-3のｉ型ＧａＡｓ層、厚み０．５μｍ、不純物濃度１×１０¹⁵ｃｍ^-3のｉ型ＧａＡｓ層を形成し、最上層のｐ型ＧａＡｓ層の窓部からｐ型不純物のＺｎを約０．５μｍ拡散し、メサエッチ後、ｐ、ｎ電極を形成し、フォトダイオードである光半導体素子５を作製した。
【００５６】
その後、光ファイバへの反射する所望の光強度を得るために、上記の光半導体素子５上へ高屈折材料、低屈折材料を用いた誘電体多層膜を真空蒸着により作製しても良い。ここで、光半導体素子５は、ＧａＡｓ以外のＩｎＧａＡｓ／ＩｎＰなどの化合物半導体材料でも、また、ＰＩＮ型フォトダイオード以外のアバランシェ・フォト・ダイオードなど、フォトダイオードの機能を有するものであれば良い。
【００５７】
そして、光半導体素子５を形成したＧａＡｓ基板表面とガラス基板をＷＡＸで固定した後、光半導体素子形成領域を残し、ＧａＡｓ基板をエッチング除去した。
【００５８】
さらに、ガラス基板に固定された光半導体素子を、シリコン基板表面の反射面に位置合わせし、水素結合により接触させ、ＷＡＸを除去し、３００〜４００℃の熱処理を行い、光半導体素子５を水素結合だけでなく、酸素を介したさらに強固に接着させた。同時に、反射鏡素子の電気信号線路７、電流供給線路８と光路変換体２の不純物拡散領域２１，２６もアニールされ、オーミック接合された。
【００５９】
なお、ＡｕＳｉ系、ＡｕＳｕ系、ＰｂＳｎ系、Ｉｎ系の半田等の接着部材６を用いても、実装強度や信頼性に優れた実装が行えた。
【００６０】
このようにして得た受光素子付き光路変換体２は、実装基板１上の位置合わせマーカー（不図示）を用いて、正確に位置決めし実装した。その後、光半導体素子が搭載された光路変換体と実装基板に対して３００〜４００℃の熱処理を行い、実装基板上の電気信号線路、電流供給線路と反射鏡素子の不純物拡散領域をアニールすることによりオーミック接合された。
【００６１】
かくして、本発明の光モジュールＭ２によれば、参考例の光モジュールＭ１の作用・効果に加えて、以下のような効果を奏する。受光素子は、ダイシング・カット前のシリコン基板表面に基板同士の貼り合わせで一括接着させるために、従来、個々の受光素子をエッチングされた斜面に実装するのに比べて、実装時間の削減・高精度の実装が実現できた。
【００６３】
また、受光素子付き光路変換体の端部に存在する高濃度の不純物領域を介して、実装基板と受光素子付き光路変換体の電極が結合される。その結果、受光素子付き光路変換体のエッジ部に電極が配線されていないことから断線することがなくなる。
【００６４】
【発明の効果】
請求項１に記載の光路変換体によれば、異方性エッチング技術を用いた傾斜面を光反射用の斜面として用いず、鏡面研磨がしやすいウエハの両主面を光反射面または光半導体素子の素子配設面とすることができ、平坦性の優れた素子配設面を備えた優れた光路変換体を提供できる。
【００６５】
また、請求項４，５に記載の光路変換体の製造方法によれば、ウエハプロセスによる一括作製が可能なため、非常に低コストの光路変換体が作製可能である。
【００６６】
また、請求項２に記載の光路変換体によれば、ウエハ面方位により入射光に対して所定角度で光路変換させるようにできるため、面発光素子からの出射光を効率的に入射光学系へ効率的に光接続できる光モジュールを提供できる。
【００６７】
また、請求項１に記載の光路変換体において、素子配設面に受光素子が配設させることにより、面発光素子の出射光を精度よくモニタすることができるとともに、受光素子からの反射光を効率的に光伝送体へ入射させることが可能な優れた光モジュールを提供できる。
【００６８】
さらに、請求項１に記載の光路変換体によれば、光路変換体の下面と素子配設面との間に、オーミックコンタクト用の不純物拡散領域が形成されているので、金属薄膜で光半導体素子の電極パターンを光路変換体の２面に形成する必要が無くなり、光路変換体のエッジで金属薄膜の断線がない信頼性に優れた光モジュールを提供できる。
【００６９】
そして、請求項７に記載の光モジュールによれば、光伝送体に面発光素子からの出射光を効率よく光接続され、しかも信頼性の高い優れた光モジュールを提供できる。
【図面の簡単な説明】
【図１】本発明に係る光路変換体及び光モジュールから受光素子を除いた参考形態を模式的に説明する断面図である。
【図２】本発明に係る光路変換体の製造方法を模式的に説明するための平面図である。
【図３】図２におけるＡ−Ａ’線断面図である。
【図４】本発明に係る光路変換体を模式的に説明する斜視図である。
【図５】本発明に係る光モジュールを模式的に説明する斜視図である。
【符号の説明】
１：基板
１ａ：基板１の低位置面
１ｂ：搭載用溝
２：光路変換体
２ａ、２ｂ：光路変換体の上下面
２ｃ：光路変換体の傾斜面
３：面発光素子
４：光伝送体
４ａ：光伝送体の先端
５：光半導体素子（受光素子、フォトダイオード）
５ａ：受光部
５ｂ：電極パッド
６：接着部材（接着面）
７：電気信号線路
８：電流供給線路
９：ボンディングワイヤ
１０、１３：単結晶ウエハＷの両主面
１１：フォトレジスト
１２：Ｖ溝
１４，１５：光路変換体用柱状部
２０，２１：不純物拡散領域
Ｍ１，Ｍ２：光モジュール
Ｌ１：出射光
Ｌ２：反射光
Ｗ：単結晶ウエハ
θ１、θ２：エッチング面の傾斜角度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical path changer used in the fields of optical communication and optical information communication, a manufacturing method thereof, and an optical module using the same.
[0002]
BACKGROUND OF THE INVENTION
In a surface mount type optical transmission module, the light emitted from a surface emitting laser (Vertical Cavity Surface Emitting Laser (hereinafter also referred to as VCSEL)) excellent in operating current and temperature characteristics is changed by the reflecting surface of a substrate having a predetermined shape. It is possible to easily make an optical connection to an optical element such as an optical fiber. In addition, by mounting the light receiving element on the surface to be the reflecting surface of the base, it becomes easy to monitor the output of the VCSEL.
[0003]
By the way, when the above-mentioned optical path changer is formed of single crystal silicon that is preferably used as a substrate of an optical transmission module, the reflection surface of the optical path changer is formed by anisotropic etching of the substrate, so that it can be flattened with high accuracy. the reflection surface can be manufactured, such.
[0004]
However, to produce a flat reflection surface with high accuracy the substrate by anisotropic etching, it is necessary to select a low substrate impurity, and their preparation for the limited addition costly. That is, for example, a high-cost silicon substrate manufactured by the FZ (floating zone) method is selected. This is because, for example, a silicon substrate manufactured by a relatively inexpensive method such as the CZ (Chocoral Ski) method is likely to have a defect in the crystal because impurities are mixed in the manufacturing process. Such defects during the anisotropic etching, a pit is formed on the etched surface, it is unable to produce a flat reflection surface.
[0005]
Also, even when a silicon substrate fabricated by the FZ method, to produce a flat reflection surface with high accuracy, it is necessary to optimize the etching conditions, such optimization is not easy .
[0006]
When an optical semiconductor element such as a light receiving element is mounted using the optical path changer as described above, it is mounted on a surface formed by anisotropic etching, and this surface is inclined with respect to the substrate surface. Therefore, there arises a problem that it is difficult to mount a large number of optical semiconductor elements with high accuracy.
[0007]
Furthermore, when the optical path changer is mounted on the mounting substrate, the optical path changer is pressed and adhered to the mounting substrate, so that the electrode wiring connected to the light receiving element may be disconnected at the edge of the optical path changer. There was a problem that there was.
[0008]
Therefore, the present invention solves the above-described problems, and can easily and quickly provide an optical path changer having a surface with excellent flatness as a light reflecting surface or an element mounting surface. An object of the present invention is to provide a highly reliable optical module capable of highly efficient optical connection with a body.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the optical path changer of the present invention has a columnar shape , and the upper and lower surfaces of the main body made of single crystal silicon are (111) planes formed by anisotropic etching or equivalent flat surfaces thereof. , and the non-etched portion of the side surface of the body is a surface or a plane equivalent obtained by 4.7 ° ~14.7 ° inclined to the [110] direction from the (100) plane, for receiving the incident light together, a part of light by reflecting Ri element arrangement surface der the light receiving elements are arranged to the optical path conversion in a predetermined direction, between the element arrangement surface and the lower surface of the body, for the ohmic contact characterized Rukoto impurity diffusion region is not formed.
[0011]
Further, in particular, the surface on which the light receiving element reflects light is perpendicular to the lower surface of the main body, and is optically path-changed at an angle of 90 ° with respect to incident light from the lower surface side so as to extend in a substantially horizontal direction. It is characterized by being emitted light .
[0012]
In particular, the light receiving element is made of an InGaAs / InP compound semiconductor material.
The method of manufacturing an optical path changer according to the present invention includes anisotropic etching on both main surfaces of a single crystal wafer, thereby forming V grooves alternately positioned on both main surfaces in a plurality of strips, A step of forming columnar portions formed on both sides of the V-groove and having a parallelogram shape and different thicknesses alternately, and a columnar portion having a larger thickness are removed by removing the columnar portion having a smaller thickness. A part of the non-etched surface of the column-shaped main body that receives incident light and reflects the part of the light to change the optical path in a predetermined direction, thereby providing an element arrangement surface. It is characterized by that.
[0014]
The method of manufacturing an optical path changer according to the present invention includes anisotropic etching on both main surfaces of a single crystal wafer, thereby forming V grooves alternately positioned on both main surfaces in a plurality of strips, A step of forming columnar portions formed on both sides of the V-groove and having a parallelogram shape and different thicknesses alternately, and a columnar portion having a larger thickness are removed by removing the columnar portion having a smaller thickness. A part of the non-etched surface of the columnar main body is a light reflecting surface for changing the optical path of incident light in a predetermined direction.
[0015]
The method of manufacturing an optical path changer according to the present invention includes a step of forming an impurity diffusion region of a semiconductor at a boundary portion between one main surface of the single crystal wafer and the element disposition surface, and the element disposition surface side And an ohmic junction of the optical semiconductor element to the impurity diffusion region.
[0016]
The optical module according to claim 1, wherein the surface light emitting element and the light emitted from the surface light emitting element are reflected on a low position surface of the substrate on which the low position surface and the high position surface having a height difference are formed. An optical path changing body is provided, and an optical transmission body for allowing reflected light from the optical path changing body to enter the high position surface.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment according to the present invention will be described in detail based on the drawings schematically shown.
[0018]
FIG. 1 shows a cross-sectional view of an optical module M1 of a reference form in which a light receiving element is removed from the optical module of the present invention.
[0019]
The optical module M1 includes a surface light emitting element 3 and an optical path changer 2 that reflects the emitted light L1 of the surface light emitting element 3 on a low position surface 1a having a height difference and a low position surface 1a of the substrate 1 on which the high position surface is formed. , And an optical fiber for allowing the reflected light L2 from the optical path changer 2 to be incident on the tip 4a into the mounting groove 1b formed in a high position plane and having a V-shaped cross section perpendicular to the optical axis, and the like. An optical transmission body 4 composed of the optical waveguide body is provided.
[0020]
Here, the optical path changer 2 is made of a material capable of anisotropic etching and has a columnar shape. The upper and lower surfaces 2a and 2b of the main body are formed by anisotropic etching using an alkaline aqueous solution or the like. An inclined surface 2c, which is a non-etched portion on the side surface, is an element for disposing an optical semiconductor element such as a light reflecting surface or a light receiving element for changing the optical path of incident light L1 from the surface light emitting element 3 in a predetermined direction. It is set as the arrangement surface.
[0021]
The optical path changer 2 has a main body made of single crystal silicon, and upper and lower surfaces 2a and 2b on which anisotropic etching is performed are (111) surfaces or equivalent surfaces thereof, and a light reflection surface or an element arrangement surface is ( The surface light emitting device 3 has a substantially vertical protrusion when the surface is inclined by 4.7 ° to 14.7 ° (optimally 9.7 °) in the [110] direction from the (100) surface or an equivalent surface thereof. The incident light can be converted into an optical path at an angle of approximately 90 ° on the inclined surface 2c of the optical path changer 2 (substantially in the horizontal direction) to be incident on the optical transmission member 4 disposed horizontally, and optical connection can be made efficiently. Thus, the light reflecting surface is preferably formed so as to change the optical path at an angle of 90 ° with respect to the incident light.
[0022]
The optical path changer 2 is manufactured as follows.
[0023]
First, as shown in a plan view in FIG. 2 and a cross-sectional view along line AA ′ in FIG. 2, a predetermined photoresist 11 formation surface is formed on both main surfaces 10 and 13 of the single crystal wafer W. By protecting the exposed surface and performing anisotropic etching with an alkaline aqueous solution or the like, a plurality of V-grooves 12 alternately positioned on both main surfaces 10 and 13 are formed in a predetermined direction. Thereby, the columnar parts 14 and 15 formed on both sides of the V-shaped groove 12 and having a cross-sectional parallelogram shape and different thicknesses are formed.
[0024]
The inclined surface 2c of the optical path changer 2 is provided with a light reflecting surface or an optical semiconductor element with high accuracy, so that both main surfaces 10 and 13 of the single crystal wafer are mirror surfaces (arithmetic average) by MCP (mechanochemical polishing). A material whose roughness is 10 nm or less is used.
[0025]
Next, dicing is performed on the line D shown on both sides of the columnar portion 15 having the smaller thickness, and the columnar portion 14 having the larger thickness is separated. In FIG. 3, θ1 is 40 ° to 50 °, and θ2 is 59.4 ° to 69.4 °. (← θ1 is ± 5 ° with respect to 45 °, θ2 is ± 5 ° with respect to 64.4 °. In order to make light incident on the optical fiber effectively, the range of the inclination is taken into account the aperture ratio of the optical fiber. Was set to ± 5 °.)
A part of the non-etched surface of the columnar main body obtained in this way is used as a light reflecting surface for changing the optical path of incident light in a predetermined direction, or an element arrangement surface on which an optical semiconductor element is provided.
[0026]
For example, a VCSEL is used as the surface light emitting element 3, but any shape that emits light in the normal direction to the surface of the mounting substrate is applicable.
[0027]
In addition to the optical fiber, the optical transmission body 4 may be an optical waveguide body of various shapes or an optical waveguide formed directly on the substrate 1.
[0028]
Thus, the inclined surface using the anisotropic etching technique is not used as the inclined surface for light reflection, and both main surfaces of the mirror-polished wafer can be used as the light reflecting surface or the element arrangement surface of the optical semiconductor element. It is possible to provide an excellent optical path changer having a light reflecting surface or an element arrangement surface with excellent flatness.
[0029]
Further, the optical path changer can be manufactured at a very low cost because it can be collectively manufactured by a wafer process.
[0030]
In addition, since an optical path changer that changes the optical path at a predetermined angle with respect to the incident light can be provided depending on the wafer surface orientation, an arbitrary inclination angle can be formed, and the outgoing light from the surface light emitting element can be efficiently transmitted to the incident optical system. Can be provided.
[0031]
Furthermore, by using single crystal silicon as the optical path changer, when an optical semiconductor element is formed directly on a silicon substrate, or when a compound semiconductor material different from silicon is used as the optical semiconductor element, a plurality of semiconductor elements are formed on another compound semiconductor substrate. Can be bonded to the silicon substrate surface on which a plurality of optical path changers are formed at once, so that an excellent optical path changer with a light receiving element can be realized with reduced mounting costs. .
[0032]
It will now be described engagement Ru implementation form the present invention.
[0033]
As shown in a perspective view in FIG. 4, an optical semiconductor element 5 that is a light receiving element such as a photodiode is disposed on an inclined surface (element disposition surface) 2 c that is a non-etched surface of the optical path changer 2, and Electrode patterns 7 and 8 which are electric signal lines and current supply lines of the optical semiconductor element 5 are formed. Here, 5 a is a light receiving portion, 5 b is an electrode pad, and the electrode pad 5 b and the electrode pattern 8 are connected by a bonding wire 9.
[0034]
Further, when the adhesive member 6 is used, mounting with excellent mounting strength and reliability can be performed by using AuSi-based, AuSu-based, PbSn-based, In-based solder, or the like. However, in the present text, bonding can be performed using the chemical properties of the surface of the optical semiconductor element 5 without using the bonding member 6 of solder or adhesive, which is called a direct bonding method. That is, the cleaned surface of the optical semiconductor element 5 is brought into contact with the surface of the optical path changer 2 and bonded by hydrogen bonding. Further, by performing annealing, water molecules evaporate and change to stronger bonds via oxygen, and reliability can be improved.
[0035]
In the optical path changer 2, an impurity diffusion region for ohmic contact is formed between the lower surface 2b of the main body and the element disposition surface 2c, that is, at the boundary between the element disposition surface 2c and the lower surface 2b which is an etching surface. Is formed.
[0036]
Using the optical path changer 2 configured as described above, as shown in a cross-sectional view in FIG. 5, the optical module M2 includes a low position surface 1a of the substrate 1 on which a low position surface and a high position surface having a height difference are formed. In addition, a surface light emitting element 3 and an optical path changer 2 that reflects light emitted from the surface light emitting element 3 are disposed, and an optical transmission member 4 that causes reflected light from the optical path changer 2 to enter the high position surface. . The optical module M2 has substantially the same configuration as that of the optical module M1 shown in FIG. 1 except that the optical semiconductor element 5 is disposed in the optical path changer 2, and the same components are denoted by the same reference numerals and described. Is omitted.
[0037]
Thus, according to the optical module M2, the same effect as that of the optical module M1 is achieved, and more than a predetermined amount (for example, 1 × 10 ¹⁸ cm ⁻³ or more) of impurities between the element arrangement surface and the lower surface of the optical path changer. Since the concentration is diffused, it is not necessary to form the electric signal line and the current supply line of the light receiving element formed of a metal thin film on two surfaces, and the electric wiring is not disconnected at the edge of the optical path changer.
[0038]
【Example】
Next, a more specific example of the optical module of the present invention will be described.
<Reference example>
In the optical module M1 shown in FIG. 1, the optical path changer 2 and the surface emitting laser 3 are disposed on the low position surface 1a of the substrate 1 made of single crystal silicon and having a height difference, and formed on the high position surface of the substrate 1. It is assumed that the optical fiber 4 is disposed in the mounting groove 1b having a V-shaped cross section.
[0039]
Here, the substrate 1 is made of silicon, which is particularly characterized in that the material is manufactured by the CZ method and the cost is low, and the step is formed by anisotropic etching. The mounting groove 1b of the optical fiber 4 was formed by anisotropic etching. The surface emitting laser 3 was made of a GaAs material.
[0040]
Moreover, the optical path changer 2 was produced as follows.
[0041]
First, as shown in FIG. 2, a wafer W having front and back surfaces 10 and 13 polished to a mirror surface by MCP and having a surface inclined by 9.7 ° from the (100) surface is used. Photoresist 11 was deposited and formed linearly along the [110] direction, and anisotropic etching was performed by immersing the exposed portion of this wafer W in an aqueous potassium hydroxide solution. As a result, a groove 12 having a V-shaped cross-section with a (111) plane and an equivalent plane inclined.
[0042]
As shown in FIG. 3, since the wafer W is inclined 9.7 ° from (100) in the [110] direction, the inclination angle θ1 is 45 ° and θ2 is 64.4 °. Note that θ1 needs to be set to θ1 = 45 ° in order to convert the optical path by 90 °, and this formation was performed with high accuracy by anisotropic etching.
[0043]
Further, the formation region of the photoresist 11 was shifted between the front surface 10 and the back surface 13 so as to form the optical path changer columnar body 14 having a 45 ° slope.
[0044]
Next, the photoresist 11 was removed by a remover, and then a metal thin film was formed to form light reflecting films on the upper and lower surfaces 10 and 13 of the columnar body 14 for an optical path changer. Here, Au having a high reflectance was used for the uppermost layer of the metal thin film. In order to effectively form the uppermost metal film on the silicon substrate of the wafer W, a Cr layer is used as a base metal film between the uppermost metal thin film and the silicon substrate, and a silicon oxide film layer is formed on the silicon substrate surface. Formed. The total film thickness of the metal thin film was about 1 μm.
[0045]
And it cut | disconnected by dicing along the line D shown in FIG. 3, and it cut | divided so that it might become each optical path change body. At that time, the smaller columnar portion 15 which is an etching residue was completely removed, and an optical path changing body having a predetermined shape was produced.
[0046]
Next, as shown in FIG. 1, the optical path reflector 2 produced in this way was accurately positioned and mounted and fixed using an alignment marker (not shown) on the substrate 1 as a mounting substrate. In this case, AuSu solder was used as a fixing material.
[0047]
Further, the surface emitting laser 3 is pressed and adhered, and a thin film solder (not shown) formed on the mounting substrate 1 is melted and cooled to be mounted and fixed on the substrate 1, and then the optical fiber 4 is mounted on the mounting groove 1b. It was mounted and fixed by a method such as pressing and fixing with a flat substrate such as a resin or glass plate.
[0048]
Thus, according to the optical module M1, the light reflection surface because it utilizes a mirror processed {100} plane, it can be realized reflection surface that is planarized with high accuracy. Further, since it is not necessary to flatten the etching surface with high accuracy in anisotropic etching, a silicon substrate manufactured by various manufacturing methods such as FZ method and CZ method can be used. rocking like there is no need to perform and eliminates the optimization of etching conditions. In addition, the optical path reflector is etched from both sides of the silicon wafer, so that the cross section is substantially parallelogram and the top surface of the optical path converter is flattened. Can also be implemented.
[0049]
<Example>
Next, another embodiment shown in FIGS. 4 and 5 will be described.
[0050]
The optical path changer 2 was produced in the same manner as in the reference example .
[0051]
And as shown in FIG. 4, the optical semiconductor element 5 was arrange | positioned on the slope 2c of the optical path changer 2 as follows.
[0052]
Further, the optical module M2 shown in FIG. 5 is configured in the same manner as the optical module M1 already described, except that the optical semiconductor element 5 is disposed on the optical path changer 2 and wiring is provided.
[0053]
In this embodiment, B (boron) is ion-implanted into the boundary portion between the inclined surface 2c and the lower surface 2b, which is the light reflecting surface of the optical path changer 2, and the impurity concentration is set to 1 × 10 ¹⁸ cm ⁻³ or more. At this time, other than B, as long as it is a semiconductor impurity such as Al.
[0054]
Next, the electric signal line 7 and the current supply line 8 for the optical semiconductor element 5 were formed of a metal thin film. This metal thin film was an upper layer / lower layer, made of Au / Cr, and the total thickness was about 1 μm. At this time, one end of each line was disposed up to the impurity diffusion regions 20 and 21.
[0055]
Then, on another semiconductor substrate, for example, an n ⁺ -type GaAs substrate, an n-type GaAs layer having a thickness of 1.0 μm and an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ , a thickness of 4.0 μm and an impurity concentration of 1 × 10 ¹⁵ cm ⁻³ . An i-type GaAs layer having a thickness of 0.5 μm and an impurity concentration of 1 × 10 ¹⁵ cm ⁻³ is formed, and p-type impurity Zn is diffused by about 0.5 μm from the window of the uppermost p-type GaAs layer. After mesa etching, p and n electrodes were formed to produce an optical semiconductor element 5 that is a photodiode.
[0056]
Thereafter, in order to obtain a desired light intensity reflected to the optical fiber, a dielectric multilayer film using a high refractive material and a low refractive material may be formed on the optical semiconductor element 5 by vacuum deposition. Here, the optical semiconductor element 5 may be made of a compound semiconductor material such as InGaAs / InP other than GaAs, or may have a photodiode function such as an avalanche photodiode other than a PIN photodiode.
[0057]
Then, after fixing the surface of the GaAs substrate on which the optical semiconductor element 5 was formed and the glass substrate by WAX, the optical semiconductor element formation region was left and the GaAs substrate was removed by etching.
[0058]
Further, the optical semiconductor element fixed to the glass substrate is aligned with the reflective surface of the silicon substrate surface, brought into contact with hydrogen bonds, WAX is removed, heat treatment is performed at 300 to 400 ° C., and the optical semiconductor element 5 is hydrogenated. In addition to bonding, it was more strongly bonded via oxygen. At the same time, the electric signal line 7 of the reflecting mirror element, the current supply line 8 and the impurity diffusion regions 21 and 26 of the optical path changer 2 were also annealed and ohmic joined.
[0059]
Even when an adhesive member 6 such as AuSi-based, AuSu-based, PbSn-based, or In-based solder was used, mounting with excellent mounting strength and reliability could be performed.
[0060]
The optical path changer 2 with the light receiving element thus obtained was accurately positioned and mounted using an alignment marker (not shown) on the mounting substrate 1. After that, heat treatment at 300 to 400 ° C. is performed on the optical path changer and the mounting substrate on which the optical semiconductor element is mounted, and the impurity diffusion regions of the electric signal line, the current supply line and the reflector element on the mounting substrate are annealed. Was ohmic-bonded.
[0061]
Thus, according to the optical module M2 of the present invention, in addition to the operations and effects of the optical module M1 of the reference example , the following effects can be obtained. Since the light receiving elements are bonded together by bonding the substrates to the silicon substrate surface before dicing and cutting, mounting time is reduced compared to the conventional mounting of each light receiving element on an etched slope. Implementation of accuracy was achieved.
[0063]
In addition, the mounting substrate and the electrode of the optical path changer with the light receiving element are coupled to each other through a high concentration impurity region present at the end of the optical path changer with the light receiving element. As a result, since the electrode is not wired at the edge portion of the optical path changer with the light receiving element, disconnection does not occur.
[0064]
【The invention's effect】
According to the optical path converter according to 請 Motomeko 1, anisotropic etching technique without using a slope for the light reflecting inclined plane with the light reflecting surface or a light both main surfaces of easily wafer mirror-polished can be an element arrangement surface of the semiconductor device can provide excellent optical path converter having excellent element arrangement surface flatness.
[0065]
Further, according to the manufacturing method of the optical path converting element according to 請 Motomeko 4,5, for bulk manufacturing by the wafer process that can be a very low cost of the optical path converter can be produced.
[0066]
Further, according to the optical path converter according to 請 Motomeko 2, since it so as to convert the optical path at an angle to the incident light by the wafer surface orientation, effectively incident optical system the light emitted from the surface emitting element It is possible to provide an optical module that can be optically connected to the optical system efficiently.
[0067]
In the optical path converting element according to 請 Motomeko 1, the receiving element can be disposed on the element arrangement surface, it is possible to accurately monitor the light emitted from the surface light-emitting element, the reflected light from the light-receiving element It is possible to provide an excellent optical module that can efficiently enter the optical transmitter.
[0068]
Further, according to the optical path converter according to 請 Motomeko 1, between the lower surface and the element arrangement surface of the optical path conversion member, since the impurity diffusion region for ohmic contact is formed, the optical semiconductor at the metal thin film It is not necessary to form the electrode pattern of the element on the two surfaces of the optical path changer, and an optical module with excellent reliability can be provided in which the metal thin film is not broken at the edge of the optical path changer.
[0069]
Then, according to the optical modules described in 請 Motomeko 7. The light emitted from the surface emitting element is efficiently optically connected to the optical transmission member, moreover possible to provide a highly reliable high optical module.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically illustrating a reference embodiment in which a light receiving element is removed from an optical path changer and an optical module according to the present invention.
FIG. 2 is a plan view for schematically explaining the method of manufacturing the optical path changer according to the present invention.
FIG. 3 is a cross-sectional view taken along line AA ′ in FIG. 2;
The engagement Ru optical path converter to the present invention; FIG is a perspective view illustrating schematically.
The optical module engaging Ru in the present invention; FIG is a perspective view illustrating schematically.
[Explanation of symbols]
1: Substrate 1a: Lower position surface 1b of substrate 1: Mounting groove 2: Optical path changer 2a, 2b: Upper and lower surfaces 2c of the optical path changer: Inclined surface 3 of the optical path changer: Surface light emitting element 4: Optical transmitter 4a : Tip 5 of optical transmission body 5: optical semiconductor element (light receiving element, photodiode)
5a: light receiving part 5b: electrode pad 6: adhesive member (adhesive surface)
7: Electric signal line 8: Current supply line 9: Bonding wire 10, 13: Both main surfaces 11 of single crystal wafer W 11: Photoresist 12: V-groove 14, 15: Optical path changer columnar parts 20, 21: Impurity diffusion Regions M1, M2: optical module L1: outgoing light L2: reflected light W: single crystal wafers θ1, θ2: inclination angle of etching surface

Claims

The upper and lower surfaces of the main body made of columnar single crystal silicon are (111) planes formed by anisotropic etching or equivalent flat surfaces thereof .
The non-etched portion on the side surface of the main body is a surface inclined by 4.7 ° to 14.7 ° in the [110] direction from the (100) surface, or an equivalent surface thereof, and receives incident light. element arrangement surface der the light receiving elements are arranged which by reflecting part of the light to the optical path conversion in a predetermined direction is,
Between the lower surface and the element arrangement surface of the body, the optical path converter which is characterized that you have impurity diffusion region for ohmic contact is formed.

The light receiving element reflects light on a surface that is perpendicular to the lower surface of the main body and has a light path changed at an angle of 90 ° with respect to incident light from the lower surface side. optical path converting element according to claim 1, characterized in that.

The optical path changer according to claim 1, wherein the light receiving element is made of a compound semiconductor material of InGaAs / InP.

By subjecting both main surfaces of the single crystal wafer to anisotropic etching, a plurality of V-grooves alternately positioned on the two main surfaces are formed, and the cross-sections formed on both sides of the V-groove are parallel four sides. Non-etching of the column-shaped main body including a step of forming columnar portions having different thicknesses alternately in shape and a step of separating the columnar portion having a larger thickness by removing the columnar portion having a smaller thickness while receiving incident light a portion of the surface, a manufacturing method of the element arrangement surface and the optical path converter to provide an optical semiconductor device a portion of the light is reflected Ru is the optical path conversion in a predetermined direction.

By subjecting both main surfaces of the single crystal wafer to anisotropic etching, a plurality of V-grooves alternately positioned on the two main surfaces are formed, and the cross-sections formed on both sides of the V-groove are parallel four sides. Non-etching of the column-shaped main body including a step of forming columnar portions having different thicknesses alternately in shape and a step of separating the columnar portion having a larger thickness by removing the columnar portion having a smaller thickness A method of manufacturing an optical path changer, wherein a part of the surface is a light reflecting surface for changing the optical path of incident light in a predetermined direction.

Forming an impurity diffusion region of a semiconductor at a boundary portion between one main surface of the single crystal wafer and the element disposition surface; and forming the optical semiconductor element in ohmic contact with the impurity diffusion region on the element disposition surface side The manufacturing method of the optical path changer of Claim 3 further including a process.

The surface light emitting element and the optical path changer according to any one of claims 1 to 3 , wherein the surface light emitting element and the light emitted from the surface light emitting element are reflected on a low position surface having a height difference and a low position surface of the substrate on which the high position surface is formed. And an optical transmission body for allowing reflected light from the optical path changing body to enter the high position surface.