JP2004223651A - Plane grinding method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide grinding method and device having excellent machining efficiency by obtaining highly accurate flatness and facilitating an adjustment of a shaft. <P>SOLUTION: In this plane grinding method of an in-feed system, a wafer rotated and driven within a horizontal plane is ground by a grinding tool mounted on a lower part of a spindle head arranged in the vertical direction. Inclination components of a shaft of the spindle head are decomposed in relation to two directions of a coordinate system (X-Y) direction constituted of a direction (Y direction) along a contact arc of the grinding tool and the wafer and a direction (X direction) orthogonal to the direction to adjust relative inclination of the spindle head. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３９】
なお、式（１）及び（２）において、θ（度）は用いる砥石の直径及びウエーハの直径、及びこれらの配置により決定される。式（１）及び（２）における角度の単位も「度」でも「ラジアン」でもよい。
【００４０】
このような変換を行なうことで、正確に軸調整を行なうことができ、精度の良いウエーハ加工が行なえる。
【００４１】
特に、平面研削後に得られるウエーハ形状を「傾き成分」及び「たわみ成分」に分け計測し、これを制御パラメータとしてフィードバックすることでウエーハとスピンドルヘッドの相対的な傾きを調整すると良い。
【００４２】
このようにウエーハ形状の傾き成分及びたわみ成分をスピンドルヘッドの調整パラメータとして使用することで容易に高平坦度のウエーハが製造できる。
【００４３】
この時、平面研削後に得られるウエーハ形状の厚さ単位の「傾き成分ΔＹ’」及び「たわみ成分ΔＸ’」を下記式（３）により角度変換し、角度単位の「傾き成分ΔＹ」及び「たわみ成分ΔＸ」を得ると良い。
【００４４】
【数４】

【００４５】
ここで、ｋ_１、ｋ_３は補正係数、ｋ_２、ｋ_４は補正値であり、装置や研削条件により決まる数値で用いる装置や研削条件により決定する。なお、式（３）における角度の単位は「度」でも「ラジアン」でも良い（単位の変化に応じて係数を変える必要があることはいうまでもない）。このような関係式により得られた値を調整パラメータにすることでより制御しやすくなる。
【００４６】
なお、このようなウエーハとスピンドルヘッドの相対的な傾きの調整は研削前に実施し、研削中には砥石とウエーハの相対角度は一定に維持すると良い。
【００４７】
本発明の方法でも研削中に軸調整をすることは可能であるが、研削中に砥石とウエーハの相対角度は一定に維持することで、初めに設定した形状への制御が容易になり、また形状確認後のフィードバックも容易である。
【００４８】
また、特許文献３では本発明のようにウエーハの平坦度を直交する２軸成分に分けて制御しようとする意図がなく、主にＸ方向にしか制御しなかった為、ウエーハを高平坦度にするため研削中に砥石角度を調整するなど機構的に複雑になっていた。つまり研削中に砥石とウエーハの相対角度を制御する為、Ｘ軸の方向への相対角度を予め設定したプログラムで段階的または連続的に変化させる必要があった。本発明の軸調整方法を採用することによりウエーハ研削中の砥石角度の調整は必ずしも行なう必要が無くなり、容易に高平坦度なウエーハが製造できる。
【００４９】
本発明の平面研削装置の第１の態様は、上記のような方法を実施する為の装置であり、水平面内で回転駆動されるウエーハを、垂直方向に配置されたスピンドルヘッドの下部に取り付けられた砥石により研削するインフィード方式の研削装置において、前記スピンドルヘッドとウエーハを垂直方向であるＺ軸方向に相対移動させる駆動装置と、該砥石と該ウエーハとの接触弧に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に分解し、スピンドルヘッドを相対的に移動させる傾斜制御装置を備えたことを特徴とする平面研削装置である。
【００５０】
本発明の平面研削装置の第１の態様においては平面研削後に得られるウエーハ形状の「傾き成分」及び「たわみ成分」を入力する入力手段と、これらの値により、該砥石と該ウエーハとの接触弧に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に対するスピンドルヘッドの軸傾き成分を算出する算出手段とをさらに有するのが好ましい。
【００５１】
本発明の平面研削装置の第２の態様は、スピンドルヘッドとウエーハを垂直方向であるＺ軸方向に相対移動させる駆動機構と、砥石中心とウエーハ中心を結んだ線状の方向（α軸）とこれに直交する方向（β軸）からなる座標系（α−β）方向にスピンドルヘッドの傾斜を調整する傾斜制御装置とを有し、水平面内で回転駆動されるウエーハを、垂直方向に配置されたスピンドルヘッドの下部に取り付けられた砥石により研削するインフィード方式の平面研削装置であって、該砥石と該ウエーハとの接触弧に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）に対して座標変換する座標変換手段を有し両座標間で座標変換を行なうことでウエーハとスピンドルヘッドの相対的な傾きを調整することを特徴とする。
【００５２】
本発明の平面研削装置の第２の態様においては、平面研削後に得られるウエーハ形状の「傾き成分」及び「たわみ成分」を入力する入力手段と、これらの値により、該砥石と該ウエーハとの接触弧に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸、又は砥石中心とウエーハ中心を結んだ線状の方向（α軸）とこれに直交する方向（β軸）方向の２軸に対するスピンドルヘッドの軸傾き成分を算出する算出手段とをさらに有すると良い。
【００５３】
このようにウエーハ形状、特に傾き成分とたわみ成分を制御パラメータとして入力し、これをもとにＸ軸及びＹ軸の調整量（スピンドルヘッドの軸傾き成分）を算出することで、専門的な技術を必要とせず、容易に軸調整を行なうことができる。
【００５４】
座標変換する場合は、座標変換手段が、ウエーハ形状の厚さ単位の「傾き成分ΔＹ’」及び「たわみ成分ΔＸ’」を角度単位の「傾き成分ΔＹ」及び「たわみ成分ΔＸ」に変換し、さらに（Ｘ−Ｙ座標）から（α−β座標）に座標変換し、α軸およびβ軸の傾斜角度Δα（度）、Δβ（度）を算出するプログラム（アルゴリズム）を有すると好ましい。
【００５５】
さらに、α軸およびβ軸の傾斜角度Δα（度）、Δβ（度）を計測する角度検出器、例えば電気的なセンサーを取り付け、前記傾斜制御装置の座標変換を行なうことで得られたα軸およびβ軸の傾斜角度Δα（度）、Δβ（度）までをステッピングモータ等の駆動装置により駆動して自動的に調整する事が好ましい。必要によりΔα、Δβ（角度単位）をステッピングモータの移動距離などに変換しても良い。
【００５６】
このような軸調機構が実際に指示値通りに動作したかどうかをセンサーで確認したり、センサーの値により自動的に任意の位置まで傾斜させることにより、装置の管理が容易になる。特にセンサーの値をリアルタイムで確認しながら軸の調整を行なうような制御（フィードバック機構）システムにすると良い。
【００５７】
以上のような装置を用いることで、軸調整の為に多くの時間と専門的な技術を必要とせず、熟練した作業者で無くても容易に高平坦度なウエーハ（又は必要としている形状のウエーハ）の製造が実施できる。しかも、定期的な確認および角度調整（フィードバック）も容易である。
【００５８】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を例示的に説明する。ただし、この実施の形態に記載されている構造部品の寸法、材質、形状、相対位置などは特に特定的な記載がない限りは、この発明の範囲をそれのみに限定する趣旨ではなく、単なる説明例に過ぎない。
【００５９】
図１は本発明に係る平面研削装置の第１実施形態を示す概略説明図である。図２は図１の平面研削装置による研削時におけるウエーハと砥石との接触状態を模式的に示す上面的説明図である。図１及び図２において図１５及び図２０と同一又は類似部材は同一符号によって示される。また、図１及び図２の構成において、図１５及び図２０の構成と共通の点については再度の詳細な説明は省略し、主として相違点についての説明を行なう。
【００６０】
図１において、１０ａは本発明の第１実施形態である平面研削装置である。該平面研削装置１０ａは、水平面内で回転駆動されるウエーハ１４を、垂直方向に配置されたスピンドルヘッド２６の下部に取り付けられた砥石２２により研削するインフィード方式の研削装置であり、前記スピンドルヘッド２６とウエーハ１４を垂直方向であるＺ軸方向に相対移動させる駆動機構、例えば砥石回転軸昇降モータ４０を有し、さらに図２にその配置を示すように該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸（２方向）に分解しスピンドルヘッド２６を相対的に傾斜させる傾斜制御装置（軸調装置）３６を備えている。
【００６１】
具体的には、基台１２に固定フレーム３２が設けられ、この固定フレーム３２にスピンドルヘッド２６が傾斜制御装置（軸調装置）３６を介して配置されている。傾斜制御装置３６はスピンドルヘッド２６を該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に分解しスピンドルヘッド２６を相対的に移動させることができる。
【００６２】
スピンドルヘッド２６の先端に砥石２２が固定された回転軸２４が支持され、この回転軸２４は砥石回転軸駆動モータ２８により駆動されるようになっている。砥石２２は、固定フレーム３２の上部に設けられた砥石回転軸昇降モータ（Ｚ軸方向に相対移動させる駆動機構）４０により昇降されると共に、スピンドルヘッド２６は傾斜制御装置３６により制御されて砥石２２の回転軸２４の傾斜角を任意に設定できるようになっている。
【００６３】
基台１２にはウエーハチャック駆動モータ２０の回転軸１８に取り付けられたウエーハチャック１６が配置されている。このウエーハチャック１６上にウエーハ１４が支持固定される。このとき本発明の平面研削装置１０ａでは、スピンドルヘッド２６とウエーハチャック１６及び軸調を行なう方向の関係が、図２に示すような該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に分解し制御できるように配置・設計されている。
【００６４】
なお、本平面研削装置１０ａは、この他に装置全体を制御するＣＰＵやこのＣＰＵに制御を行なわせるためのプログラムを格納したメモリ、さらにはＸ軸、Ｙ軸の２軸に対するスピンドルヘッドの軸傾き成分を算出する算出手段などを有する加工制御部１００Ａ、及びＣＰＵに所定の動作を行なわせるため、ウエーハ形状の「傾き成分」及び「たわみ成分」を入力する入力手段などを備え、その入力指示を行なうキーボード等の操作部１００ｂ、動作表示を行なうＣＲＴや液晶デバイス等の表示部１００ｃを有している。
【００６５】
例えば、作業者がウエーハ形状の厚さ単位の「傾き成分ΔＹ’」及び「たわみ成分ΔＸ’」又は目標とする傾け角度ΔＸ（度）、ΔＹ（度）をキーボード等の操作部１００ｂによって入力してやると、傾斜制御装置３６におけるサーボモータ等の駆動装置５４、６８（図８）が指示値になるまで自動的に駆動する。
【００６６】
加工制御部１００Ａでは、スピンドルヘッド２６とウエーハ１４を垂直方向であるＺ軸方向に相対移動させる駆動機構４０や該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に分解した後の傾斜制御装置（軸調装置）３６を制御するプログラミングが収納されている。
【００６７】
次に、本発明の第２実施形態である平面研削装置を図３、図４を用い説明する。図３は本発明に係る平面研削装置の第１実施形態を示す概略説明図である。図４は図３の平面研削装置による研削時におけるウエーハと砥石との接触状態を模式的に示す上面的説明図である。図３及び図４において図１５及び図２０と同一又は類似部材は同一符号によって示される。また、図３及び図４の構成において、図１５及び図２０の構成と共通の点ついては再度の詳細な説明は省略し、主として相違点についての説明を行なう。
【００６８】
図３において、１０ｂは本発明の第２実施形態である平面研削装置である。該平面研削装置１０ｂは、スピンドルヘッド２６とウエーハ１４を垂直方向であるＺ軸方向に相対移動させる駆動機構、例えば砥石回転軸昇降モータ４０と、図４に示したように砥石中心ＯＧとウエーハ中心Ｏを結んだ線状の方向（α軸）とこれに直交する方向（β軸）方向にスピンドルヘッド２６の傾斜を調整する傾斜制御装置（軸調装置）３６を有し、水平面内で回転駆動されるウエーハ１４を垂直方向に配置されたスピンドルヘッド２６の下部に取り付けられた砥石２２により研削するインフィード方式の平面研削装置である。該平面研削装置１０ｂは、該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）に対して座標変換する座標変換手段１００ａを有し、両座標間で座標変換を行なうことでウエーハ１４とスピンドルヘッド２６の相対的な傾きを調整する。
【００６９】
具体的には、基台１２に固定フレーム３２が設けられ、この固定フレーム３２にスピンドルヘッド２６が傾斜制御装置（軸調装置）３６を介して配置されている。スピンドルヘッド２６の先端に砥石２２が固定された回転軸２４が支持され、この回転軸２４は砥石回転軸駆動モータ２８により駆動されるようになっている。砥石２２は、固定フレーム３２の上部に設けられた砥石回転軸昇降モータ（Ｚ軸方向に相対移動させる駆動機構）４０により昇降されると共に、傾斜制御装置３６により制御されて砥石２２の回転軸２４の傾斜角を任意に設定できるようになっている。
【００７０】
基台１２にはウエーハチャック駆動モータ２０の回転軸１８に取り付けられたウエーハチャック１６が配置されている。このウエーハチャック１６上にウエーハ１４が支持固定される。本平面研削装置１０ｂでは、スピンドルヘッド２６とウエーハチャック１６及び軸調を行なう方向の関係が、従来と同じように砥石中心ＯＧとウエーハ中心Ｏを結んだ線状の方向（α軸）とこれに直交する方向（β軸）方向にスピンドルヘッド２６の傾斜を調整する傾斜制御装置３６が設置されている。
【００７１】
この平面研削装置１０ｂでは、更に該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）に対して制御する為に、座標系（Ｘ−Ｙ）及び座標系（α―β）の両座標系間で座標を変換する座標変換手段１００ａが設けられており、両座標間で座標変換を自動的に行なうことができるようになっている。
【００７２】
つまり、座標変換する座標変換手段１００ａを用いることで、図４に示すような該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）の２軸に分解し正確に制御できるように設計されている。
【００７３】
なお、本平面研削装置１０ｂにおいても、この他に装置全体を制御するＣＰＵやこのＣＰＵに制御を行なわせるためのプログラムを格納したメモリ、さらにはＸ軸、Ｙ軸の２軸、又はα軸、β軸の２軸に対するスピンドルヘッドの軸傾き成分を算出する算出手段などを有する加工制御部１００Ａ、及びＣＰＵに所定の動作を行なわせるため、ウエーハ形状の「傾き成分」及び「たわみ成分」を入力する入力手段などを備え、その入力指示を行なうキーボード等の操作部１００ｂ、動作表示を行なうＣＲＴや液晶デバイス等の表示部１００ｃを有している。
【００７４】
加工制御部１００Ａでは、スピンドルヘッドとウエーハを垂直方向であるＺ軸方向に相対移動させる駆動機構４０や、該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）から、砥石中心ＯＧとウエーハ中心Ｏを結んだ線状の方向（α軸）とこれに直交する方向（β軸）に対して座標変換する座標変換手段１００ａ、砥石中心ＯＧとウエーハ中心Ｏを結んだ線状の方向（α軸）とこれに直交する方向（β軸）方向の２軸についてスピンドルヘッド２６の傾斜を調整する傾斜制御装置３６を制御するプログラミングが格納されている。
【００７５】
上記のような本発明の平面研削装置１０ａ，１０ｂを用い実際に加工する時の手順について説明する。該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ軸）およびこれに直交する方向（Ｘ軸）に対して制御する為に、本発明の平面研削装置１０ａ，１０ｂで一度テストウエーハを研削し、ウエーハの形状、特に傾き成分とたわみ成分を確認し、これを制御パラメータとして平面研削装置１０ａ，１０ｂの操作部に入力し、これをもとに加工制御部１００ＡでＸ軸及びＹ軸の調整量（スピンドルヘッド２６の軸傾き成分）を算出することで、専門的な技術を必要とせず、容易に軸調整を行なうことができる。
【００７６】
具体的には平面研削後に得られるウエーハ形状の厚さ単位の「傾き成分ΔＹ’」及び「たわみ成分ΔＸ’」を下記式（３）により角度変換し、角度単位の「傾き成分ΔＹ」及び「たわみ成分ΔＸ」に換算する。つまりウエーハを実際に研削し、測定した平坦度の成分から目標とする傾け角度ΔＸ（度）、ΔＹ（度）を決定する作業を容易にするため、測定した平坦度成分の大きさを厚さ単位で直接入力できるようにした。すなわち平坦度の成分をΔＸ’（μｍ）、ΔＹ’（μｍ）とし、これに補正係数と補正値をつけて傾け角度ΔＸ（度）、ΔＹ（度）とする。
【００７７】
【数５】

【００７８】
ここで、ｋ_１、ｋ_３は、補正係数、ｋ_２、ｋ_４は補正値であり、装置や研削条件により決まる係数で、用いる装置などにより当初は試行錯誤で修正し決定する。このような関係式はメモリなどを有する加工制御部１００Ａにプログラミングされている。
【００７９】
実際の作業においては、作業者は先ずテストウエーハを研削し、測定したウエーハの平坦度を図５（ａ）〜（ｄ）に示す２種類の平坦度成分「傾き」および「たわみ」に分解する。
【００８０】
図５に示すように「傾き成分」（図５（ａ）（ｂ））及び「たわみ成分」は（図５（ｃ）（ｄ））、大きく分けて傾き成分２種類（以下、凸傾き、凹傾きという）、たわみ成分で２種類（以下、凸たわみ、凹たわみという）の２種類である。得られるウエーハ形状は主にこれらの組合せでありほぼ４パターンのウエーハ形状が形成される。つまり図２２に示すような凸傾きと凹たわみが合成された形状（凸傾き＋凹たわみ）や、（凸傾き＋凸たわみ）、（凹傾き＋凸たわみ）、（凹傾き＋凹たわみ）の形状のウエーハが研削される。本発明では。この傾き成分とたわみ成分に分離し、それぞれの成分に対応した軸調整を行なう。
【００８１】
ウエーハ形状の測定方法は特に限定するものではないが、接触式の粗さ計や光学式の粗さ計を用いることができる。
【００８２】
実際の手順について図６〔第１実施形態の装置：（Ｘ−Ｙ）方向に直接軸調整可能〕及び図７〔第２実施形態の装置：（Ｘ−Ｙ）方向に直接軸調整不可能、（α−β）方向に軸調整可能〕に示したフローチャートを用いて説明する。上記したように厚さ単位の「傾き成分ΔＹ’（μｍ）」及び「たわみ成分ΔＸ’（μｍ）」を計測し（ステップ２００）、これらの値を上記第１の実施の形態の平面研削装置１０ａ又は上記第２の実施形態の平面研削装置１０ｂのキーボード等の操作部１００ｂ（入力手段）によって入力する（ステップ２０２）。これを上記関係式により角度単位に変換した「傾け成分ΔＹ（度）」及び「たわみ成分ΔＸ（度）」に換算し、実際に制御すべき目標角度（傾け角度）を決定する（ステップ２０４）。なお、別に計算するなどしてあらかじめ制御すべき目標角度（「傾け成分ΔＹ（度）」及び「たわみ成分ΔＸ（度）」）がわかっていれば、その値をステップ２０４の段階でキーボード等の操作部１００ｂ（入力手段）によって入力するようにしても良い（図６及び図７）。
【００８３】
その後、第１実施形態の平面研削装置１０ａでは、図６に示すように、（Ｘ−Ｙ）方向の軸調整が直接できる構成の装置である為、そのまま傾斜制御装置３６に指示を送り（ステップ２０６）、その値をもとに駆動装置５４、６８を含む傾斜制御装置３６が指示値になるまで自動的に駆動し、軸調整を行なうようになっている。
【００８４】
一方、第２実施形態の平面研削装置１０ｂでは、図７に示すように、（Ｘ−Ｙ）方向の軸調整が直接できない構成の装置である為、ステップ２０２で制御すべき目標角度（傾け角度）を決定した後、更に角度単位の「傾け成分ΔＹ（度）」及び「たわみ成分ΔＸ（度）」を実際に制御可能な（α−β）方向の成分に座標変換し、α軸およびβ軸の傾斜角度Δα（度）、Δβ（度）を算出し（ステップ２０８）、その値をもとに傾斜制御装置３６に指示を送り（ステップ２１０）、駆動装置５４、６８を含む傾斜制御装置３６が指示値になるまで自動的に駆動し、軸調整を行なうようになっている。
【００８５】
つまり、本発明で調整を行ないたい該砥石２２と該ウエーハ１４との接触弧４４に沿った方向（Ｙ方向）およびこれに直交する方向（Ｘ方向）からなる座標系（Ｘ−Ｙ）方向と、実際に制御できる砥石中心ＯＧとウエーハ中心Ｏを結んだ線状の方向（α方向）とこれに直交する方向（β方向）からなる座標系（α−β）方向が異なる場合、座標変換手段１００ａにより座標変換し、α軸およびβ軸の傾斜角度Δα（度）、Δβ（度）を求める。
【００８６】
座標系（Ｘ−Ｙ）と座標系（α−β）の両者間には下記の簡単な座標変換式で表される幾何学的な関係がある。すなわち、角度ΔＸおよびΔＹを下記式（１）によって角度Δαおよび Δβに自動的に換算することができる。また下記式（２）によって逆方向の変換も可能である。
【００８７】
【数６】

【００８８】
座標変換手段１００ａは上記のような関係式がメモリなどを有する加工制御部１００Ａにプログラミングされ、作業者がウエーハ形状の厚さ単位の「傾き成分ΔＹ’」及び「たわみ成分ΔＸ’」又は目標とする傾け角度ΔＸ（度）、ΔＹ（度）をキーボード等によって入力してやると、前述の式（１）によってΔα、Δβを自動的に計算するようになっており、さらにサーボモータなどの駆動装置を含む傾斜制御装置３６によってΔα、Δβが指示値になるまで軸調を制御している。
【００８９】
傾斜制御装置３６は、図１又は図３に示す固定フレーム３２とスピンドルヘッド２６の間に位置しており、図８〜図１０の模式図に示す構造を有している。なお、図８〜図１０は一例であり、本発明において採用される傾斜制御装置は特にこれに限定するものではない。図８〜図１０に示した構造は図１６〜図１８に示した構造と基本的には共通であり、再度の詳細な説明は省略し、主要な構成及び作用並びに相違点について以下に説明する。
【００９０】
図８〜図１０において、３６は第１実施形態の平面研削装置１０ａで用いられる傾斜制御装置で、Ｘ軸、Ｙ軸方向に直接、角度調整できる形態のものである。該傾斜制御装置３６は、Ｘ方向およびＹ方向に摺り割り４２、６２のついた金属製ブロック３７に固定されたサーボモータなどの駆動装置５４、６８と、これらによって駆動される駆動ロッド５２、およびリニアーゲージ式変位センサーなどの角度検出器６０、７０から成っている。±ΔＸ方向への傾斜は、加工制御部１００Ａからの信号によって駆動されるサーボモータなどの駆動装置５４により回転する駆動ロッド５２が、摺り割り４２を超えて相手方の第２ブロック部４６を押したり引いたりすることによってなされる。この変位量は駆動装置５４の近傍に固定された角度検出器６０によって検出され、角度に換算され、加工制御部１００Ａへのフィードバック信号となる。±ΔＹ方向への傾斜制御も同様にサーボモータなどの駆動装置６８と角度検出器７０によってなされる。第２実施形態の平面研削装置１０ｂで用いられる傾斜制御装置３６は、図１６〜図１８に示したα軸、β軸方向に角度調整できる形態のものと実質同様である。
【００９１】
また、必ずしも必要ではないが、サーボモータなどの駆動装置５４、６８によって電動で軸調を行った結果（場合によっては手動操作によって軸調を行ってもよい）は、Ｘ軸、Ｙ軸の実際の調整量としてディスプレー等に表示しても良い。特に座標変換した場合などは、傾け角度Δα（度）、Δβ（度）を角度検出器６０、７０によって読み取り、先に示した式（２）によってΔＸ（度）、ΔＹ（度）に自動的に換算して、Ｘ軸、Ｙ軸の調整量としてディスプレー等に表示するようにすれば制御の状況が把握しやすい。
【００９２】
本発明装置を用いウエーハ（製品ウエーハ）の研削を行なうには、まず研削前に上記制御パラメータをもとに調整量を算出し、上記傾斜制御装置３６を駆動させることによりスピンドルヘッド２６（砥石２２とウエーハ１４の相対角度）の軸調を行なう。
【００９３】
ウエーハ形状の傾き成分およびたるみ成分を目標値（一般には零）にするよう、軸調方向ＸおよびＹの傾け角度ΔＸ（度）、ΔＹ（度）を決定してやると、本発明の第１実施形態の装置１０ａでは、Ｘ軸、Ｙ軸方向に直接的にサーボモータなどの駆動装置５４、６８を駆動し、また第２実施形態の装置１０ｂでは、Δα、Δβを自動的に計算し、α軸、β軸方向にサーボモータなどの駆動装置５４、６８を駆動させることによって間接的にＸ軸、Ｙ軸方向の傾け角度を指示値になるまで正確に軸調する。
【００９４】
つまり、Ｘ軸方向及びＹ軸方向に対応する傾斜補正量を読み込んで、該補正量に対応するモータ駆動信号をサーボモータなどの駆動装置５４、６８や角度検出器６０、７０に送り、傾斜制御装置３６を駆動して砥石２２の傾斜角（ウエーハチャック１６の回転軸１８に対する傾斜角）を制御するように構成されている。
【００９５】
軸調を行なった後、実際のウエーハの研削は、従来から行なわれている方法で行なわれれば良く、例えば前記砥石回転軸昇降モータ４０を制御することにより通常の研削開始位置まで送り、研削工程時における高速切込み、低速切込み時、スパークアウト（無切込み）の三段階程度に切込み速度（研削速度）を調整して行ない高平坦度なウエーハを加工する。なお、特に研削加工中には砥石の角度等は調整しておらず、研削前に軸調した状態で研削を行なっている。
【００９６】
研削後に平坦度が目標値に達しない場合には、目標とする傾け角度ΔＸ、ΔＹに微調整を施す。それぞれの成分を目標値（一般には零）にするよう、軸調方向ＸおよびＹの傾け角度ΔＸ（度）、ΔＹ（度）を決定する。本発明ではこのようなフィードバック操作が容易に実施できる。
【００９７】
【実施例】
以下に実施例をあげて本発明をさらに具体的に説明するが、これらの実施例は例示的に示されるもので限定的に解釈されるべきでないことはいうまでもない。
【００９８】
【実験例１】
図３に示す形態の平面研削装置を用いウエーハを研削した。ウエーハは直径３００ｍｍの両頭研削（粗研削）を行った厚さ約８００μｍのシリコンウエーハを用いた。砥石は直径３５０ｍｍのレジンボンド砥石（ＳＤ＃２０００Ｂ）を用いた。
【００９９】
研削条件として、下記の三段階の切込み速度で加工した（片面研削）。全体の取り代は片面６μｍであった。
【０１００】
【表１】

【０１０１】
特に軸調整を行なわず研削した結果、図１４に示すようなウエーハ形状が得られた。なお、ウエーハ形状は黒田精工社製ナノメトロによりウエーハ面を非吸着の状態で測定した厚さむらで示したものである。
【０１０２】
図１４に示したウエーハから、傾き成分およびたわみ成分を計測した。計測した結果、傾き成分ΔＹ’＝−０．６０μｍ、たわみ成分ΔＸ’＝−０．２８μｍであった。
【０１０３】
ウエーハの平坦度成分を零にするように、この厚さ単位の傾き成分「ΔＹ’（μｍ）」およびたわみ成分「ΔＸ’（μｍ）」を角度単位の傾き成分「ΔＹ（度）」及びたわみ成分「ΔＸ（度）」に変換した。この変換は下記式（４）を用いて行った。
【０１０４】
【数７】

【０１０５】
この式（４）は、本平面研削装置、研削条件から得られた経験式である。このような式（４）より、傾き成分ΔＹ＝−０．０００２３度、たわみ成分ΔＸ＝−０．０００９５度という結果が得られた。このような角度で軸調すれば良いことがわかる。
【０１０６】
本装置では、このようなＸ軸方向、Ｙ軸方向に直接軸調できないため、下記式（１）から、実際に制御できる砥石中心とウエーハ中心を結んだ線状の方向（α方向）とこれに直交する方向（β方向）からなる座標系（α−β）に座標変換し、α軸およびβ軸の傾斜角度Δα（度）、Δβ（度）を求めた。θは、砥石の直径及びウエーハの直径から、２５．４°である。
【０１０７】
【数８】

【０１０８】
これにより、傾き成分Δα＝−０．０００９６度、たわみ成分Δβ＝０．０００２０度という結果が得られた。
【０１０９】
【実施例１】
この結果を、傾斜制御装置に送り軸調整を行なった。具体的には、実際に制御できる砥石中心とウエーハ中心を結んだ線状の方向（α方向）のサーボモータとこれに直交する方向（β方向）のサーボモータを駆動させ任意の角度まで変化させた。なお、実際にはセンサーによりΔα、Δβの値を管理し、センサーの値が上記設定値になるまで制御している。なお以上のような傾斜量の算出や傾斜制御装置の制御は加工制御部の命令で自動的に処理されている。
【０１１０】
このように調整した後、初めに研削した条件と同じ条件、つまりウエーハは直径３００ｍｍの両頭研削（粗研削）を行った厚さ約８００μｍのシリコンウエーハを用いた。砥石は直径３５０ｍｍのレジンボンド砥石（ＳＤ＃２０００Ｂ）を用いた。研削条件として、実験例１と同様の三段階の切込み速度で加工した。全体の取り代は片面６μｍであった。
【０１１１】
特にこのような軸調を行なった後のウエーハ形状は、図１３に示すような大変高平坦度なウエーハが得られた。
【０１１２】
以上のように、研削したウエーハの形状を測定し、その情報を入力すれば、簡単な操作で精度良く本来軸調したいＸ軸、Ｙ軸方向の制御が行なわれ、熟練した作業者でなくても容易に調整が行なえ、加工効率の優れた研削を行なうことが出来た。またフィードバック作業も容易である。
【０１１３】
なお、上記実施例１においては、スピンドルヘッド傾動機構としてサーボモータを用いたが、差動ねじ等を用いても良く他の構造を用いてもよい。またスピンドルヘッドを回転テーブルに対して傾ける構成について説明したが、スピンドルヘッドに代えて回転テーブルを傾ける構成でもよい。
【０１１４】
【発明の効果】
以上述べたごとく、本発明によれば、これまで専ら熟練した作業者の経験と勘に依存してきた軸調作業を、系統的かつ効率的に行なうことができるようになった。その結果、品質（ウエーハの平坦度）および作業性（軸調にかかる時間）を大幅に改善できた。
【図面の簡単な説明】
【図１】本発明の平面研削装置の第１実施形態を示す概略説明図である。
【図２】図１の平面研削装置による研削時におけるウエーハと砥石との接触状態を模式的に示す上面的説明図である。
【図３】本発明の平面研削装置の第２実施形態を示す概略説明図である。
【図４】図３の平面研削装置による研削時におけるウエーハと砥石との接触状態を模式的に示す上面的説明図である。
【図５】本発明の研削方法による研削を行なったウエーハの断面形状を示す説明図である。
【図６】第１実施形態の平面研削装置を用いた場合の本発明方法による研削手順を示すフローチャートである。
【図７】第２実施形態の平面研削装置を用いた場合の本発明方法による研削手順を示すフローチャートである。
【図８】本発明装置において用いられる角度制御機構の一例を示す斜視的概略説明図である。
【図９】図８におけるサーボモータ部分の詳細説明図である。
【図１０】図８における角度検出器部分の詳細説明図である。
【図１１】本発明の研削方法による研削を行なったウエーハの断面形状を示す説明図である。
【図１２】本発明の研削方法によるウエーハと砥石との接触状態を模式的に示す上面的説明図である。
【図１３】実験例１において研削されたウエーハ形状を示すグラフである。
【図１４】実施例１において研削されたウエーハ形状を示すグラフである。
【図１５】従来のインフィード方式の平面研削盤の構造例を示す概略説明図である。
【図１６】従来の角度制御機構の一例を示す斜視的概略説明図である。
【図１７】図１６におけるサーボモータ部分の詳細説明図である。
【図１８】図１６における角度検出器部分の詳細説明図である。
【図１９】従来のインフィード方式の平面研削盤による研削状態を誇張して示す説明図である。
【図２０】従来のインフィード方式の平面研削盤による研削時におけるウエーハと砥石との接触状態を模式的に示す上面的説明図である。
【図２１】従来のインフィード方式の平面研削盤による研削時におけるウエーハと砥石との接触状態を模式的に示す斜視的説明図である。
【図２２】従来のインフィード方式の平面研削盤によって研削したウエーハ形状を模式的に示す説明図である。
【符号の説明】
１０：従来の平面研削盤、１０ａ，１０ｂ：本発明の平面研削装置、１２：基台、１４：ウエーハ、１６：ウエーハチャック、１８：ウエーハチャック回転軸、２０：ウエーハチャック駆動モータ、２２：砥石、２２ａ： 砥石軌跡、２４：砥石回転軸、２６：スピンドルヘッド、２８：砥石回転軸駆動モータ、３０：支台、３２：固定フレーム。３４：摺動支持板、３６：傾斜制御装置（軸調装置）、３７：金属製ブロック、４０：砥石回転軸昇降モータ（駆動機構）、４２：第１摺り割り、４２ａ：第１幅広溝部、４４：接触弧、４５：第１ブロック部、４６：第２ブロック部、４８：貫通孔、５０：ネジ穴、５２：駆動ロッド、５４：第１駆動装置、５６：貫通孔、５８：ゲージプローブ、６０：第１角度検出器、６２：第２摺り割り、６２ａ：第２幅広溝部、６４：第３ブロック部、６６：第４ブロック部、６８：第２駆動装置、７０：第２角度検出器、１００Ａ：加工制御部、１００ａ：座標変換手段、１００ｂ：操作部、１００ｃ：表示部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for surface-grinding a surface of a compound semiconductor wafer such as a semiconductor silicon wafer or gallium arsenide, gallium phosphide, or indium phosphide.
[0002]
[Related technology]
With recent remarkable development of electronics technology, various semiconductor devices have been used in many electronic devices. 2. Description of the Related Art A semiconductor device is manufactured based on a single crystal of a semiconductor material such as silicon, which is sliced into a thin disk called a wafer. For example, a method for manufacturing a silicon wafer generally includes a crystal growth step of manufacturing a single crystal ingot using a Czochralski (CZ) method, a floating zone (FZ) method, or the like, and slicing the single crystal ingot. Then, a wafer processing step in which at least one main surface is processed into a mirror surface is performed. More specifically, the wafer processing step includes a slicing step of slicing a single crystal ingot to obtain a thin disk-shaped wafer, and a slicing step for preventing cracking and chipping of the wafer obtained by the slicing step. A chamfering step for chamfering the outer peripheral portion, a lapping step for flattening the wafer, an etching step for removing processing distortion remaining on the chamfered and wrapped wafer, and a polishing (polishing) step for mirror-polishing the wafer surface. And a cleaning step of cleaning the polished wafer and removing abrasives and foreign substances adhering thereto. The above-mentioned wafer processing step shows a main step, and other steps such as a heat treatment step are added, the same step is performed in multiple stages, and the order of the steps is changed.
[0003]
Particularly in recent years, a surface grinding step may be performed instead of or in combination with the lapping step. Surface grinding has the advantage that a highly flat wafer can be obtained up to the outer periphery of the wafer.
[0004]
Such a semiconductor wafer, especially a mirror-polished silicon wafer, is required to have extremely high flatness (small thickness unevenness). For this reason, it is expected that the flatness (uneven thickness) of a wafer as a raw material of a mirror-polished wafer, for example, a wafer after surface grinding, is 1 μm or less over the entire surface of the wafer.
[0005]
As a surface grinding device used for flattening a semiconductor wafer, an in-feed type surface grinding machine is mainly used. FIG. 15 schematically shows the structure of the conventional infeed type surface grinding machine. In FIG. 15, reference numeral 10 denotes an in-feed type surface grinding machine (surface grinding device) having a base 12. On the upper surface of the base 12, a wafer chuck 16 for vacuum-sucking a wafer 14 to be ground is provided. A wafer chuck rotating shaft 18 is attached to the lower surface of the wafer chuck 16. The rotation shaft 18 is rotated by a wafer chuck drive motor 20. The wafer chuck 16 is sometimes called a rotary table or a rotary table.
[0006]
Reference numeral 22 denotes a grindstone for grinding the wafer 14, and a grindstone rotating shaft 24 is attached to the upper surface thereof. The grindstone rotating shaft 24 is rotated by a grindstone rotating shaft drive motor 28 via a spindle head 26.
[0007]
Reference numeral 30 denotes an abutment provided on the upper surface of the base 12 corresponding to the wafer chuck 16, and a fixed frame 32 is further attached to the upper surface of the abutment 30. A sliding support plate 34 slidable in the vertical direction is attached to the inner surface of the fixed frame 32, and the spindle head 26 is connected to the sliding support plate 34 via an inclination control device 36. . The tilt control device 36 controls the tilt of the grindstone rotating shaft 24 as described later, and may be referred to as an axis adjusting device in the following description and drawings.
[0008]
Numeral 40 denotes a grindstone rotating shaft elevating motor provided above the fixed frame 32, and by sliding the sliding support plate 34 in the vertical direction, the inclination control device 36, the spindle head 26, the grindstone rotating shaft 24 and the grindstone 22 can be raised and lowered.
[0009]
The tilt control device 36 has a structure capable of tilting its inner surface in a predetermined direction, as described later. Therefore, the spindle head 26, the grindstone rotation shaft 24, and the grindstone 22 connected to the inner surface of the inclination control device 36 can also be inclined.
[0010]
16 to 18 are schematic explanatory views showing an example of the structure of the tilt control device (axis adjusting device) in detail. FIG. 16 is an overall perspective view of the tilt control device (axis adjusting device). FIG. 17 is a servomotor. FIG. 18 is a cross-sectional view of a portion of the angle detector, and FIG.
[0011]
In FIG. 16, reference numeral 36 denotes an inclination control device (axis adjustment device). The inclination control device 36 has a metal block 37. The spindle head 26, the grindstone rotating shaft 24, and the grindstone 22 are connected to the inner surface 37a of the metal block 37.
[0012]
Reference numeral 42 denotes a first slit for controlling the inclination of the inclination control device 36 in the α direction (toward the spindle head 26). The first slit 42 is bored in parallel with the inner surface 37a of the metal block 37. A first wide groove 42a is provided at the bottom of the slit 42. A first block portion 45 and a second block portion 46 are formed outside and inside the first slot 42, respectively.
[0013]
As shown in FIG. 17, the first block portion 45 is formed with a first through hole 48 opening to the outer surface 37b and the first slot 42, and the second block portion 46 is formed with the first through hole 48. A screw hole 50 in which a female screw portion is screwed is provided corresponding to. Reference numeral 52 denotes a first drive rod having a male screw portion threaded at the distal end thereof. The first drive rod is inserted into the through hole 48 and the distal end portion is screwed into the screw hole 50. On the outer surface 37b of the metal block 37, a first driving device 54 such as a servomotor is provided. The first driving device 54 is connected to the first driving rod 52 and controls the inclination of the inclination control device 36 in the α direction.
[0014]
As shown in FIG. 18, the first block portion 45 is further formed with an outer surface 37b and a second through hole 56 opening to the first slit 42, and a linear probe having a gauge probe 58 at a tip end. A first angle detector 60 such as a gauge type displacement sensor is provided, and measures a tilt angle in the α direction.
[0015]
The tilt control in the ± Δα direction is performed by the first wide-width groove portion 42 a when the first drive rod 52 rotated by the first drive device 54 pushes or pulls the second block portion 46 beyond the first slit 42. This is achieved by tilting the second block portion 46 with the fulcrum as a fulcrum. This displacement amount is detected by a first angle detector 60 fixed near the first driving device 54.
[0016]
Reference numeral 62 denotes a second slit for controlling the inclination of the inclination control device 36 in the β direction (the direction orthogonal to the α direction), and is provided in a direction orthogonal to the inner surface 37 a of the metal block 37. At the bottom of the second slot 62, a second wide groove 62a is provided. A third block portion 64 and a fourth block portion 66 are formed on both sides of the second slot 62, respectively.
[0017]
The structure of the second slit 62 is the same as the structure of the first slit 42 shown in FIGS. 17 and 18, and therefore, detailed description is not repeated again, and only the structure shown in FIG. Just a brief explanation. A third through-hole (not shown) is formed in the third block portion 64 so as to open to the side surface 37c and the second slot 62, and the fourth block portion 66 corresponds to the third through-hole. A screw hole (not shown) in which a female screw portion is screwed is provided. A second drive rod (not shown) having a male screw portion threaded at the tip portion is screwed into the screw hole via a third through hole. On the side surface 37c of the metal block 37, a second drive device 68 such as a servomotor is provided. The second driving device 68 is connected to the second driving rod, and controls the inclination of the inclination control device 36 in the β direction.
[0018]
The third block portion 64 further has a fourth through hole (not shown) opened to the side surface 37c and the second slot 60, and has a gauge probe (not shown) at the tip. A second angle detector 70 such as a linear gauge type displacement sensor is provided, and measures the inclination angle in the β direction.
[0019]
The tilt control in the ± Δβ direction is performed by pushing or pulling the fourth block portion 66 beyond the second slit 62 by the second drive rod rotated by the second drive device 68 to move the first wide groove portion 42a. This is achieved by tilting the second block portion 46 as a fulcrum. This displacement is detected by a second angle detector 70 fixed near the second driving device 68.
[0020]
In the description of FIGS. 16 to 18, the case where the tilt control device 36 includes the angle detectors 60 and 70 has been described. However, as in the case of FIG. In most cases, the angle detectors 60 and 70 were not installed, and most depended on the skill of the operator. In general, instead of automatically controlling the feed amount of a driving lot such as a servo motor, the angle of rotation is adjusted manually by adjusting the amount of rotation of the screw, and the operator's experience and It was difficult to adjust it because it depended on intuition. Even if the angle detectors 60 and 70 are installed, it is still necessary for the operator to determine in which direction and how much the angle should be changed, and after all, there is no other way than relying on the skill of the operator. It was the current situation.
[0021]
With the configuration described above, the in-feed type surface grinding machine 10 grinds the wafer 14 vacuum-adsorbed to the wafer chuck 16 by the grindstone 22 rotating at high speed. In this grinding, the inclination direction that can be controlled by the axis adjusting device 36 is, as shown in FIGS. 20 and 21, the direction (α direction) of the line (α axis) connecting the center OG of the grinding wheel and the center O of the wafer, and This is the direction (β direction) of the orthogonal axis (β axis). In other words, the α direction is the longitudinal direction (left-right direction in FIG. 15) of the in-feed type surface grinding machine 10, and the β direction is the front-back direction of the surface grinding machine 10 (the paper surface direction in FIG. 15). .
[0022]
At this time, as shown exaggeratedly in FIG. 19, the surface of the wafer chuck 16 has a convex shape of several tens of μm, and the grindstone rotating shaft (main shaft) 24 is at a slight angle (φ = 1/100) from the wafer chuck rotating shaft 18. Since the angle is set so as to incline by about 1/10 degree, the grindstone 22 and the wafer 14 are aligned with the arc OP (that is, the wafer center O, the outer circumference of the wafer 14 and the grindstone locus 22a) shown in FIGS. The contact is made only at the portion of the arc connecting the intersection P). Hereinafter, this arc OP may be referred to as a contact arc 44. In FIG. 21, DW is the rotation direction of the wafer 14 and DG is the rotation direction of the grindstone 22.
[0023]
In order to finish the wafer 14 with high precision flatness (TTV) by the in-feed type surface grinding device, at least the inclination of the spindle head 26 in the front-rear direction with respect to the plane of the wafer chuck 16 (α direction in this specification). Needs to be adjusted with high precision. As an apparatus provided with such means, there is an apparatus described in Patent Document 1, for example. Patent Document 2 discloses a device that tilts a rotary table (wafer chuck) with respect to a spindle head, instead of tilting the spindle head with respect to the rotary table. In other words, the in-feed type surface grinding machine 10 achieves a desired flatness by adjusting the relative angle between the grinding wheel rotation shaft 24 and the wafer chuck rotation shaft 18 (hereinafter, may be abbreviated as axial adjustment). It is a device to do.
[0024]
Patent Document 3 discloses a technique for automatically changing the inclination of a spindle head in accordance with each grinding step (during grinding) to perform processing with high flatness.
[0025]
[Patent Document 1]
JP-A-61-274873
[Patent Document 2]
JP-A-8-90376
[Patent Document 3]
JP-A-10-315103
[0026]
[Problems to be solved by the invention]
However, in a current surface grinding device, for example, the above-described surface grinding machine and a device having a basic structure similar to the above, a direction (axis adjustment) in which the relative inclination between the wafer and the spindle head can be adjusted (axis adjustment). As described above, the directions that can be controlled are a linear direction (α direction) connecting the grinding wheel center OG and the wafer center O as shown in FIG. 15 and a direction orthogonal to this (β direction).
[0027]
To adjust the axis in such a direction in order to obtain a wafer with high flatness, the experience and trial and error of the operator are exclusively used. In other words, it is difficult to adjust the angle of the spindle head (or the grindstone), and a skilled technician manually adjusts the angle, requiring a lot of time and specialized skills. Moreover, even if the angle is set once, a deviation occurs during use, so that periodic confirmation and angle adjustment are required.
[0028]
In addition, in order to perform processing with a high degree of flatness, as disclosed in Patent Literature 3, it is necessary to take measures such as changing the angle of a spindle head during grinding, and control has become complicated.
[0029]
An object of the present invention is to solve such a conventional problem and to provide a highly accurate flatness, facilitate adjustment of an axis, and provide a grinding method and apparatus excellent in processing efficiency. I do.
[0030]
[Means for Solving the Problems]
As shown in FIG. 22, the wafer shape ground by the in-feed type surface grinder mainly has a “tilt” component K and a “flexure” component T superimposed. FIG. 22 schematically illustrates an example of a wafer shape (cross-sectional shape) in which a convex inclination and a concave deflection are combined. When grinding is performed by an in-feed type surface grinder, the cross-sectional shape becomes substantially symmetric from the center as shown in FIG.
[0031]
As shown in FIG. 12, such a “slope” component K and a “deflection” component T indicate the direction connecting the wafer center O and the point P along the Y axis (the direction along the contact arc 44 between the grindstone 22 and the wafer 14). ) And a direction orthogonal to the X axis, the contact arc (trajectory) 44 is tilted with respect to the X axis (that is, tilted in the Y axis direction with the X axis as the axis of symmetry), whereby the wafer shape is changed as shown in FIG. a) and (b) can be processed into the cross-sectional shape of “concave inclination” or “convex inclination”, and similarly, the contact arc (trajectory) 44 is inclined with respect to the Y axis (that is, the Y axis is By tilting the wafer in the direction of the X-axis), the wafer can be processed into a “concave” or “convex” cross-sectional shape as shown in FIGS.
[0032]
In other words, as shown in FIG. 12, the inclination components of the spindle head are decomposed into two axes of the X axis and the Y axis, and by adjusting each of these inclination angles, a flat surface without “tilt” or “deflection” is obtained. It is possible to grind the wafer. In addition, it has become clear that it is necessary to independently adjust the tilt angle with respect to the Y axis and the X axis (the direction along the contact arc and the direction orthogonal thereto) in order to perform the axial adjustment efficiently.
[0033]
Therefore, the surface grinding method of the present invention is an in-feed type surface grinding method for grinding a wafer rotationally driven in a horizontal plane with a grinding wheel attached to a lower part of a vertically arranged spindle head. The spindle head is decomposed in two directions of a coordinate system (XY) direction including a direction (Y) along a contact arc with the wafer and a direction (X) orthogonal to the direction, and the spindle head is decomposed. Is characterized by adjusting the relative inclination of.
[0034]
By precisely adjusting the axis in such a direction, a wafer having an arbitrary shape can be manufactured, and particularly, a wafer having a high flatness can be manufactured.
[0035]
In the conventional surface grinding, in order to perform the axis adjustment, generally, a linear direction (α direction in this specification) connecting the center of the grinding wheel and the wafer center and a direction perpendicular to this (β direction in this specification) are used. ). In order to perform the above-described axis adjustment with such an apparatus, a surface grinding method according to another embodiment of the present invention includes mounting a wafer rotationally driven in a horizontal plane on a lower portion of a vertically arranged spindle head. (Α-β) direction consisting of a linear direction (α direction) connecting the center of the grinding wheel and the center of the wafer and a direction (β direction) orthogonal to this direction When the spindle head axis is adjusted by resolving the inclination component of the spindle head axis, the direction along the contact arc between the grinding wheel and the wafer (Y direction) and the direction orthogonal to this (X direction) A surface grinding method for performing coordinate conversion between the two coordinate systems and adjusting a relative inclination between a wafer and a spindle head in consideration of a shift of an angle θ with respect to a coordinate system (XY) direction comprising: Is the law.
[0036]
As described above, when there is a deviation of the angle θ between the direction (α-β) in which the axis can be actually adjusted and the direction (XY) in which the axis should be originally adjusted, the deviation of the angle θ is taken into consideration, It is preferable to perform coordinate conversion between them and adjust the relative inclination between the wafer and the spindle head. Thus, even in the axis adjustment in the direction of (α-β), the components in the X-axis and Y-axis directions can be independently and accurately adjusted by an arbitrary amount.
[0037]
When the directions in which the axes can be actually adjusted are the α axis and the β axis, coordinate conversion between the coordinate system (α-β) and the coordinate system (XY) is performed by the following equation (1) or It is good to carry out by (2).
[0038]
[Equation 3]

[0039]
In Expressions (1) and (2), θ (degree) is determined by the diameter of the grindstone used, the diameter of the wafer, and their arrangement. The unit of the angle in the expressions (1) and (2) may be “degree” or “radian”.
[0040]
By performing such a conversion, the axis can be accurately adjusted, and a highly accurate wafer processing can be performed.
[0041]
In particular, it is preferable to measure the wafer shape obtained after the surface grinding separately into a “slope component” and a “deflection component”, and to feed back this as a control parameter to adjust the relative tilt between the wafer and the spindle head.
[0042]
As described above, a wafer having a high flatness can be easily manufactured by using the inclination component and the deflection component of the wafer shape as adjustment parameters of the spindle head.
[0043]
At this time, the “tilt component ΔY ′” and “flexure component ΔX ′” of the thickness unit of the wafer shape obtained after the surface grinding are angle-converted by the following equation (3), and the “tilt component ΔY” and “deflection” It is preferable to obtain the component ΔX ”.
[0044]
(Equation 4)

[0045]
Where k ₁ , K ₃ Is the correction coefficient, k ₂ , K ₄ Is a correction value, which is determined by an apparatus and grinding conditions used as numerical values determined by the apparatus and grinding conditions. The unit of the angle in the expression (3) may be “degree” or “radian” (it is needless to say that the coefficient needs to be changed according to the change of the unit). By using a value obtained by such a relational expression as an adjustment parameter, control becomes easier.
[0046]
The adjustment of the relative inclination between the wafer and the spindle head is performed before grinding, and the relative angle between the grindstone and the wafer is preferably kept constant during grinding.
[0047]
Although the method of the present invention can also perform axis adjustment during grinding, by maintaining the relative angle between the grinding wheel and the wafer constant during grinding, control to the initially set shape is facilitated, and Feedback after shape confirmation is also easy.
[0048]
Further, in Patent Document 3, there is no intention to control the flatness of the wafer by dividing it into two orthogonal components as in the present invention, and the wafer is controlled only in the X direction. For this purpose, the angle of the grindstone was adjusted during the grinding, and the mechanism was complicated. That is, in order to control the relative angle between the grinding wheel and the wafer during grinding, it is necessary to change the relative angle in the X-axis direction stepwise or continuously by a preset program. By employing the axis adjusting method of the present invention, it is not always necessary to adjust the grinding wheel angle during wafer grinding, and a wafer with high flatness can be easily manufactured.
[0049]
A first aspect of the surface grinding apparatus of the present invention is an apparatus for performing the above method, in which a wafer rotationally driven in a horizontal plane is attached to a lower portion of a vertically arranged spindle head. In a grinding apparatus of an in-feed system for grinding with a grinding wheel, a driving device for relatively moving the spindle head and the wafer in a vertical Z-axis direction, and a direction along a contact arc between the grinding wheel and the wafer (Y-axis) ) And an inclination control device for disassembling the spindle head into two axes in a direction (X-axis) orthogonal to the direction, and relatively moving the spindle head.
[0050]
In the first aspect of the surface grinding apparatus of the present invention, the input means for inputting the "tilt component" and the "deflection component" of the wafer shape obtained after the surface grinding, and the contact between the grinding wheel and the wafer is determined by these values. It is preferable that the apparatus further includes a calculation unit that calculates an axial inclination component of the spindle head with respect to two axes in a direction along the arc (Y axis) and a direction perpendicular to the arc (X axis).
[0051]
A second aspect of the surface grinding apparatus of the present invention is a drive mechanism for relatively moving a spindle head and a wafer in a vertical Z-axis direction, and a linear direction (α-axis) connecting a grinding wheel center and a wafer center. A tilt control device that adjusts the tilt of the spindle head in a coordinate system (α-β) direction consisting of a direction (β axis) orthogonal to this direction, and a wafer that is rotationally driven in a horizontal plane is disposed in a vertical direction. An in-feed type surface grinding device for grinding with a grindstone attached to a lower part of a spindle head, wherein a direction along a contact arc between the grindstone and the wafer (Y axis) and a direction perpendicular to the direction (X axis) ) Has a coordinate conversion means for performing coordinate conversion, and performs coordinate conversion between the two coordinates to adjust the relative inclination between the wafer and the spindle head.
[0052]
In the second aspect of the surface grinding apparatus of the present invention, the input means for inputting the “inclination component” and the “deflection component” of the wafer shape obtained after the surface grinding, and by using these values, the grinding wheel and the wafer are Two axes, a direction along the contact arc (Y axis) and a direction orthogonal thereto (X axis), or a linear direction (α axis) connecting the center of the grinding wheel and the center of the wafer and a direction orthogonal to this (β axis) And calculating means for calculating the axis inclination components of the spindle head with respect to the two axes in the direction (1).
[0053]
As described above, the wafer shape, in particular, the tilt component and the deflection component are input as control parameters, and the X-axis and Y-axis adjustment amounts (axis tilt components of the spindle head) are calculated based on the input parameters. And the axis can be easily adjusted.
[0054]
In the case of performing coordinate conversion, the coordinate conversion unit converts the “tilt component ΔY ′” and “flexure component ΔX ′” of the thickness unit of the wafer shape into the “tilt component ΔY” and “flexure component ΔX” of the angle unit, Further, it is preferable to have a program (algorithm) for converting the coordinates from (XY coordinates) to (α-β coordinates) and calculating the inclination angles Δα (degrees) and Δβ (degrees) of the α-axis and β-axis.
[0055]
Further, an angle detector for measuring the inclination angles Δα (degrees) and Δβ (degrees) of the α-axis and β-axis, for example, an electric sensor is attached, and the α-axis obtained by performing coordinate conversion of the inclination control device. It is preferable to automatically adjust the inclination angles Δα (degrees) and Δβ (degrees) of the β axis by driving a driving device such as a stepping motor. If necessary, Δα and Δβ (in units of angle) may be converted into a moving distance of the stepping motor or the like.
[0056]
The device can be easily managed by checking with a sensor whether such an axis adjustment mechanism actually operates according to the indicated value, or by automatically inclining to an arbitrary position based on the value of the sensor. In particular, a control (feedback mechanism) system that adjusts the axis while checking the value of the sensor in real time may be used.
[0057]
By using the above-mentioned device, a lot of time and specialized skills are not required for axis adjustment, and a highly flat wafer (or a required shape) can be easily obtained without a skilled operator. Manufacturing of wafers). In addition, regular confirmation and angle adjustment (feedback) are also easy.
[0058]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative positions, and the like of the structural components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified. It is only an example.
[0059]
FIG. 1 is a schematic explanatory view showing a first embodiment of the surface grinding apparatus according to the present invention. FIG. 2 is an explanatory top view schematically showing a contact state between a wafer and a grindstone during grinding by the surface grinding apparatus of FIG. 1 and 2, the same or similar members as those in FIGS. 15 and 20 are denoted by the same reference numerals. Further, in the configurations of FIG. 1 and FIG. 2, detailed description of points common to the configurations of FIG. 15 and FIG. 20 will not be repeated, and only the differences will be described.
[0060]
In FIG. 1, reference numeral 10a denotes a surface grinding apparatus according to a first embodiment of the present invention. The surface grinding device 10a is an in-feed type grinding device that grinds a wafer 14 rotationally driven in a horizontal plane with a grindstone 22 attached to a lower part of a vertically arranged spindle head 26. A drive mechanism for relatively moving the wafer 26 and the wafer 14 in the Z-axis direction which is a vertical direction, for example, a grindstone rotating shaft elevating motor 40, and further, as shown in FIG. 2, the contact between the grindstone 22 and the wafer 14 An inclination control device (axis adjusting device) 36 is provided which disassembles the spindle head 26 relatively in two directions (two directions) of a direction (Y axis) along the arc 44 and a direction (X axis) orthogonal thereto. ing.
[0061]
Specifically, a fixed frame 32 is provided on the base 12, and the spindle head 26 is disposed on the fixed frame 32 via an inclination control device (axis adjusting device) 36. The tilt controller 36 disassembles the spindle head 26 into two axes, a direction along the contact arc 44 between the grinding wheel 22 and the wafer 14 (Y axis) and a direction orthogonal to this (X axis), and separates the spindle head 26 relative to the axis. Can be moved.
[0062]
A rotating shaft 24 to which the grindstone 22 is fixed is supported at the tip of the spindle head 26, and the rotating shaft 24 is driven by a grindstone rotating shaft drive motor 28. The grindstone 22 is moved up and down by a grindstone rotating shaft elevating motor (a driving mechanism for relatively moving in the Z-axis direction) 40 provided above the fixed frame 32, and the spindle head 26 is controlled by the inclination control device 36 to control the grindstone 22. Can be set arbitrarily.
[0063]
On the base 12, a wafer chuck 16 mounted on a rotating shaft 18 of a wafer chuck drive motor 20 is arranged. The wafer 14 is supported and fixed on the wafer chuck 16. At this time, in the surface grinding apparatus 10a according to the present invention, the relationship between the spindle head 26, the wafer chuck 16 and the direction in which the axis is adjusted is the direction along the contact arc 44 between the grinding wheel 22 and the wafer 14 as shown in FIG. It is arranged and designed so that it can be disassembled and controlled into two axes (Y axis) and a direction (X axis) orthogonal thereto.
[0064]
The surface grinding apparatus 10a further includes a CPU that controls the entire apparatus, a memory that stores a program for causing the CPU to perform control, and an axis inclination of the spindle head with respect to two axes of the X axis and the Y axis. In order to cause the CPU to perform a predetermined operation, a processing control unit 100A having a calculating means for calculating a component, etc., and input means for inputting a “tilt component” and a “deflection component” of a wafer shape, and the like are provided. An operation unit 100b such as a keyboard for performing the operation and a display unit 100c such as a CRT or a liquid crystal device for displaying an operation are provided.
[0065]
For example, the operator inputs “tilt component ΔY ′” and “flexure component ΔX ′” of the wafer-shaped thickness unit or target tilt angles ΔX (degrees) and ΔY (degrees) using the operating unit 100b such as a keyboard. Then, the driving devices 54 and 68 (FIG. 8) such as servo motors in the tilt control device 36 are automatically driven until the indicated value is reached.
[0066]
In the machining control unit 100A, the drive mechanism 40 for relatively moving the spindle head 26 and the wafer 14 in the vertical Z-axis direction, the direction along the contact arc 44 between the grinding stone 22 and the wafer 14 (Y-axis), and The programming for controlling the tilt control device (axis adjusting device) 36 after being disassembled into two axes in the direction (X axis) perpendicular to the direction is stored.
[0067]
Next, a surface grinding apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic explanatory view showing a first embodiment of the surface grinding apparatus according to the present invention. FIG. 4 is an explanatory top view schematically showing a contact state between a wafer and a grinding wheel at the time of grinding by the surface grinding apparatus of FIG. 3 and 4, the same or similar members as those in FIGS. 15 and 20 are denoted by the same reference numerals. Also, in the configurations of FIGS. 3 and 4, the same points as the configurations of FIGS. 15 and 20 will not be described again in detail, and mainly the differences will be described.
[0068]
In FIG. 3, reference numeral 10b denotes a surface grinding apparatus according to a second embodiment of the present invention. The surface grinding device 10b includes a driving mechanism for relatively moving the spindle head 26 and the wafer 14 in the vertical Z-axis direction, for example, a grinding wheel rotating shaft elevating motor 40, and a grinding wheel center OG and a wafer center as shown in FIG. It has an inclination control device (axis adjusting device) 36 for adjusting the inclination of the spindle head 26 in a linear direction (α axis) connecting O and a direction (β axis) orthogonal thereto, and is driven to rotate in a horizontal plane. This is an in-feed type surface grinding apparatus for grinding a wafer 14 to be processed by a grindstone 22 attached to a lower part of a spindle head 26 arranged in a vertical direction. The surface grinding device 10b has coordinate conversion means 100a for performing coordinate conversion in a direction (Y axis) along a contact arc 44 between the grinding wheel 22 and the wafer 14 and a direction (X axis) orthogonal thereto. By performing coordinate conversion between the two coordinates, the relative inclination between the wafer 14 and the spindle head 26 is adjusted.
[0069]
Specifically, a fixed frame 32 is provided on the base 12, and the spindle head 26 is disposed on the fixed frame 32 via an inclination control device (axis adjusting device) 36. A rotating shaft 24 to which the grindstone 22 is fixed is supported at the tip of the spindle head 26, and the rotating shaft 24 is driven by a grindstone rotating shaft drive motor 28. The grindstone 22 is moved up and down by a grindstone rotating shaft elevating motor (a driving mechanism for relatively moving in the Z-axis direction) 40 provided on an upper portion of the fixed frame 32, and controlled by a tilt control device 36 to rotate the grindstone 22. Can be set arbitrarily.
[0070]
On the base 12, a wafer chuck 16 mounted on a rotating shaft 18 of a wafer chuck drive motor 20 is arranged. The wafer 14 is supported and fixed on the wafer chuck 16. In the present surface grinding apparatus 10b, the relationship between the spindle head 26, the wafer chuck 16 and the direction in which the axis is adjusted is, as in the conventional case, the linear direction (α axis) connecting the grinding wheel center OG and the wafer center O, and An inclination control device 36 for adjusting the inclination of the spindle head 26 in a direction (β axis) orthogonal to the direction is provided.
[0071]
In the surface grinding device 10b, a coordinate system (X-axis) is used to control the direction (Y-axis) along the contact arc 44 between the grinding wheel 22 and the wafer 14 and the direction (X-axis) orthogonal thereto. -Y) and a coordinate conversion means 100a for converting coordinates between the two coordinate systems (α-β) are provided so that coordinate conversion can be automatically performed between the two coordinates. .
[0072]
That is, by using the coordinate conversion means 100a for performing coordinate conversion, the direction along the contact arc 44 between the grinding wheel 22 and the wafer 14 as shown in FIG. 4 (Y axis) and the direction orthogonal to this (X axis) It is designed so that it can be disassembled into two axes and controlled accurately.
[0073]
In the surface grinding apparatus 10b, a CPU for controlling the entire apparatus and a memory for storing a program for causing the CPU to perform control are further provided. Further, two axes of X axis and Y axis, or α axis, In order to cause the CPU to perform a predetermined operation, the processing control unit 100A having a calculating means for calculating the axis inclination component of the spindle head with respect to the two axes of the β-axis, and the wafer-form “tilt component” and “flexure component” are input. An operation unit 100b such as a keyboard for inputting instructions and a display unit 100c for displaying an operation, such as a CRT or a liquid crystal device, are provided.
[0074]
In the machining control unit 100A, a driving mechanism 40 for relatively moving the spindle head and the wafer in the vertical Z-axis direction, a direction along the contact arc 44 between the grinding wheel 22 and the wafer 14 (Y-axis), and A coordinate conversion means 100a for performing coordinate conversion from a direction (X axis) orthogonal to a linear direction (α axis) connecting the center OG of the grinding wheel and the center O of the wafer and a direction (β axis) orthogonal thereto; The programming for controlling the inclination control device 36 for adjusting the inclination of the spindle head 26 in two directions of a linear direction (α axis) connecting the OG and the wafer center O and a direction (β axis) perpendicular to the linear direction is stored. ing.
[0075]
A procedure for actually processing using the above-described surface grinding apparatuses 10a and 10b of the present invention will be described. In order to control the direction (Y axis) along the contact arc 44 between the grinding wheel 22 and the wafer 14 and the direction (X axis) orthogonal thereto, a test is performed once with the surface grinding devices 10a and 10b of the present invention. The wafer is ground and the shape of the wafer, particularly the inclination component and the deflection component, are confirmed and input as control parameters to the operation units of the surface grinding machines 10a and 10b. By calculating the adjustment amount of the Y-axis (axial tilt component of the spindle head 26), it is possible to easily perform the axis adjustment without requiring any specialized technique.
[0076]
Specifically, the “tilt component ΔY ′” and “flexure component ΔX ′” of the thickness unit of the wafer shape obtained after the surface grinding are angle-converted by the following equation (3), and the “tilt component ΔY” and “ To the deflection component ΔX ”. That is, in order to facilitate the work of actually grinding the wafer and determining the target tilt angles ΔX (degrees) and ΔY (degrees) from the measured flatness components, the magnitude of the measured flatness component is determined by the thickness. Added support for direct input in units. That is, the components of the flatness are represented by ΔX ′ (μm) and ΔY ′ (μm), and the correction coefficients and the correction values are added thereto to obtain the inclination angles ΔX (degree) and ΔY (degree).
[0077]
(Equation 5)

[0078]
Where k ₁ , K ₃ Is the correction coefficient, k ₂ , K ₄ Is a correction value, which is a coefficient determined by the apparatus and grinding conditions, and is initially corrected and determined by trial and error depending on the apparatus used. Such a relational expression is programmed in the processing control unit 100A having a memory and the like.
[0079]
In an actual operation, an operator first grinds a test wafer and decomposes the measured flatness of the wafer into two types of flatness components “slope” and “bend” shown in FIGS. 5A to 5D. .
[0080]
As shown in FIG. 5, the "slope component" (FIGS. 5 (a) and 5 (b)) and the "flexure component" (FIGS. 5 (c) and (d)) can be roughly divided into two types of tilt components (hereinafter, convex slope, There are two types of deflection components (hereinafter, referred to as convex deflection and concave deflection). The obtained wafer shapes are mainly combinations of these, and almost four patterns of wafer shapes are formed. That is, as shown in FIG. 22, the shape (convex inclination + concave deflection), (convex inclination + convex deflection), (concave inclination + convex deflection), and (concave inclination + concave deflection) in which the convex inclination and the concave deflection are combined. The shaped wafer is ground. In the present invention. The component is separated into the tilt component and the deflection component, and the axis adjustment corresponding to each component is performed.
[0081]
The method for measuring the wafer shape is not particularly limited, but a contact roughness meter or an optical roughness meter can be used.
[0082]
6 [Apparatus of the first embodiment: direct axis adjustment in (XY) direction] and FIG. 7 [Apparatus of the second embodiment: direct axis adjustment in (XY) direction impossible, Adjustable in (α-β) direction]. As described above, the “inclination component ΔY ′ (μm)” and the “deflection component ΔX ′ (μm)” of the thickness unit are measured (step 200), and these values are used as the surface grinding device of the first embodiment. An input is made by the operation unit 100b (input means) such as a keyboard of the surface grinding device 10a or the surface grinding device 10b of the second embodiment (Step 202). This is converted into “tilt component ΔY (degree)” and “flexure component ΔX (degree)” converted into angle units by the above relational expression, and a target angle (tilt angle) to be actually controlled is determined (step 204). . If the target angles to be controlled (“tilt component ΔY (degree)” and “deflection component ΔX (degree)”) are known in advance by, for example, calculating separately, the values are input to the keyboard or the like in step 204. The information may be input by the operation unit 100b (input means) (FIGS. 6 and 7).
[0083]
Thereafter, as shown in FIG. 6, in the surface grinding device 10a of the first embodiment, since the axis can be directly adjusted in the (X-Y) direction, an instruction is directly sent to the inclination control device 36 (step S10). 206), based on the value, the inclination control device 36 including the drive devices 54 and 68 is automatically driven until the indicated value is reached, and the axis is adjusted.
[0084]
On the other hand, in the surface grinding apparatus 10b of the second embodiment, as shown in FIG. 7, since the axis adjustment in the (X-Y) direction cannot be directly performed, the target angle (tilt angle) to be controlled in step 202 ) Is determined, the “tilt component ΔY (degree)” and the “flexure component ΔX (degree)” in angular units are coordinate-converted into components in the (α-β) direction that can be actually controlled, and the α axis and β The inclination angles Δα (degrees) and Δβ (degrees) of the shafts are calculated (step 208), and an instruction is sent to the inclination control device 36 based on the values (step 210), and the inclination control devices including the driving devices 54 and 68 are provided. The drive is automatically performed until 36 reaches the indicated value, and the axis is adjusted.
[0085]
That is, a coordinate system (XY) direction including a direction (Y direction) along the contact arc 44 between the grinding wheel 22 and the wafer 14 to be adjusted in the present invention and a direction (X direction) orthogonal thereto. If the coordinate system (α-β) direction composed of a linear direction (α direction) connecting the wheel center OG and the wafer center O, which can be actually controlled, and a direction (β direction) orthogonal thereto, are different, the coordinate conversion means is used. 100a, coordinate conversion is performed, and inclination angles Δα (degrees) and Δβ (degrees) of the α axis and the β axis are obtained.
[0086]
There is a geometric relationship represented by the following simple coordinate conversion equation between both the coordinate system (XY) and the coordinate system (α-β). That is, the angles ΔX and ΔY can be automatically converted into the angles Δα and Δβ by the following equation (1). The conversion in the reverse direction is also possible by the following equation (2).
[0087]
(Equation 6)

[0088]
The coordinate transformation means 100a is programmed such that the above-mentioned relational expression is programmed in the machining control section 100A having a memory or the like, and the operator can set the “tilt component ΔY ′” and “flexure component ΔX ′” or the target in the thickness unit of the wafer shape. When the inclination angles ΔX (degrees) and ΔY (degrees) to be input are input by a keyboard or the like, Δα and Δβ are automatically calculated by the above-described equation (1). The inclination control device 36 controls the axial tone until Δα and Δβ become the indicated values.
[0089]
The tilt control device 36 is located between the fixed frame 32 and the spindle head 26 shown in FIG. 1 or FIG. 3, and has a structure shown in the schematic diagrams of FIGS. 8 to 10 are examples, and the tilt control device employed in the present invention is not particularly limited to this. The structure shown in FIGS. 8 to 10 is basically the same as the structure shown in FIGS. 16 to 18, and a detailed description thereof will be omitted, and the main configuration, operation, and differences will be described below. .
[0090]
8 to 10, reference numeral 36 denotes an inclination control device used in the surface grinding apparatus 10a according to the first embodiment, which is capable of directly adjusting the angle in the X-axis and Y-axis directions. The tilt control device 36 includes driving devices 54 and 68 such as servo motors fixed to a metal block 37 having slits 42 and 62 in the X and Y directions, a driving rod 52 driven by these devices, and It consists of angle detectors 60 and 70 such as linear gauge type displacement sensors. The inclination in the ± ΔX direction may be caused by the fact that the drive rod 52 rotated by the drive device 54 such as a servomotor driven by a signal from the machining control unit 100A pushes the second block 46 of the other party beyond the slit 42. It is done by pulling. This displacement amount is detected by an angle detector 60 fixed near the driving device 54, converted into an angle, and becomes a feedback signal to the processing control unit 100A. Similarly, tilt control in the ± ΔY direction is performed by a drive device 68 such as a servomotor and an angle detector 70. The inclination control device 36 used in the surface grinding device 10b of the second embodiment is substantially the same as the one in which the angle can be adjusted in the α-axis and β-axis directions shown in FIGS.
[0091]
Although it is not always necessary, the result of the axial adjustment performed by the driving devices 54 and 68 such as servomotors (in some cases, the axial adjustment may be performed manually) is based on the actual X-axis and Y-axis. May be displayed on a display or the like as the adjustment amount of. In particular, when coordinate transformation is performed, the inclination angles Δα (degrees) and Δβ (degrees) are read by the angle detectors 60 and 70, and are automatically converted to ΔX (degrees) and ΔY (degrees) according to equation (2) shown above. If the control amounts are displayed on a display or the like as the adjustment amounts of the X axis and the Y axis, the control situation can be easily grasped.
[0092]
In order to grind a wafer (product wafer) using the apparatus of the present invention, first, before grinding, an adjustment amount is calculated based on the above-mentioned control parameters, and the inclination control device 36 is driven to thereby drive the spindle head 26 (the grinding wheel 22). (The relative angle between the wafer 14 and the wafer 14).
[0093]
When the inclination angles ΔX (degrees) and ΔY (degrees) of the axial adjustment directions X and Y are determined so that the inclination component and the sag component of the wafer shape become target values (generally zero), the first embodiment of the present invention The device 10a drives the driving devices 54 and 68 such as servo motors directly in the X-axis and Y-axis directions, and the device 10b of the second embodiment automatically calculates Δα and Δβ, By driving the driving devices 54 and 68 such as servomotors in the β-axis direction, the tilt angles in the X-axis and Y-axis directions are indirectly accurately adjusted until they reach the indicated values.
[0094]
That is, the tilt correction amounts corresponding to the X-axis direction and the Y-axis direction are read, and the motor drive signals corresponding to the correction amounts are sent to the drive devices 54 and 68 and the angle detectors 60 and 70 such as servo motors, and the tilt control is performed. The apparatus 36 is driven to control the inclination angle of the grindstone 22 (the inclination angle of the wafer chuck 16 with respect to the rotation axis 18).
[0095]
After the axial adjustment, the actual grinding of the wafer may be performed by a conventional method. For example, the wafer is moved to a normal grinding start position by controlling the grinding wheel rotating shaft elevating motor 40, and the grinding process is performed. The cutting speed (grinding speed) is adjusted to about three stages of high-speed cutting, low-speed cutting, and spark-out (no cutting) at the time of processing to process a wafer with high flatness. In particular, the angle of the grindstone is not adjusted during the grinding, and the grinding is performed with the shaft adjusted before the grinding.
[0096]
If the flatness does not reach the target value after grinding, fine adjustments are made to the target tilt angles ΔX and ΔY. The inclination angles ΔX (degrees) and ΔY (degrees) in the axial adjustment directions X and Y are determined so that the respective components have target values (generally zero). In the present invention, such a feedback operation can be easily performed.
[0097]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. However, it is needless to say that these Examples are illustrative and should not be construed as limiting.
[0098]
[Experimental example 1]
The wafer was ground using a surface grinding apparatus having the form shown in FIG. As the wafer, a silicon wafer having a thickness of about 800 μm which had been subjected to double-head grinding (rough grinding) with a diameter of 300 mm was used. As the grindstone, a resin bond grindstone (SD # 2000B) having a diameter of 350 mm was used.
[0099]
The grinding was performed at the following three cutting speeds (single-side grinding). The overall allowance was 6 μm on one side.
[0100]
[Table 1]

[0101]
In particular, as a result of grinding without adjusting the axis, a wafer shape as shown in FIG. 14 was obtained. In addition, the wafer shape is indicated by thickness unevenness measured in a non-adsorbed state on the wafer surface by Nano Metro manufactured by Kuroda Seiko Co., Ltd.
[0102]
From the wafer shown in FIG. 14, a tilt component and a deflection component were measured. As a result of the measurement, the inclination component ΔY ′ = − 0.60 μm and the deflection component ΔX ′ = − 0.28 μm.
[0103]
The tilt component “ΔY ′ (μm)” and the deflection component “ΔX ′ (μm)” of the thickness unit and the deflection component “ΔY (degree)” of the angle unit are set so that the flatness component of the wafer becomes zero. It was converted to the component “ΔX (degree)”. This conversion was performed using the following equation (4).
[0104]
(Equation 7)

[0105]
Equation (4) is an empirical equation obtained from the surface grinding apparatus and the grinding conditions. From the equation (4), the result was obtained that the gradient component ΔY = −0.00023 degrees and the flexural component ΔX = −0.00095 degrees. It is understood that the axis should be adjusted at such an angle.
[0106]
In this apparatus, since the axis cannot be directly adjusted in the X-axis direction and the Y-axis direction, a linear direction (α direction) connecting the center of the grinding wheel and the center of the wafer which can be actually controlled is calculated from the following equation (1). Were converted into a coordinate system (α-β) consisting of a direction (β direction) orthogonal to the above, and the inclination angles Δα (degrees) and Δβ (degrees) of the α-axis and β-axis were obtained. θ is 25.4 ° from the diameter of the grindstone and the diameter of the wafer.
[0107]
(Equation 8)

[0108]
As a result, a result was obtained in which the inclination component Δα = −0.00096 degrees and the deflection component Δβ = 0.00020 degrees.
[0109]
Embodiment 1
The feed axis was adjusted based on the result by a tilt control device. Specifically, the servomotor in the linear direction (α direction) connecting the center of the grinding wheel and the center of the wafer, which can be actually controlled, and the servomotor in the direction perpendicular to the direction (β direction) are driven to change to an arbitrary angle. Was. Actually, the values of Δα and Δβ are managed by sensors, and control is performed until the values of the sensors reach the above-mentioned set values. The calculation of the tilt amount and the control of the tilt control device as described above are automatically processed by the command of the machining control unit.
[0110]
After the adjustment as described above, the same conditions as those of the first grinding, that is, a silicon wafer having a thickness of about 800 μm which had been subjected to double-head grinding (rough grinding) with a diameter of 300 mm were used. As the grindstone, a resin bond grindstone (SD # 2000B) having a diameter of 350 mm was used. As the grinding conditions, processing was performed at the same three-stage cutting speed as in Experimental Example 1. The overall allowance was 6 μm on one side.
[0111]
In particular, a wafer having such a high degree of flatness as shown in FIG.
[0112]
As described above, if the shape of the ground wafer is measured and the information is input, the X-axis and Y-axis directions which are originally required to be axially adjusted with a simple operation can be accurately controlled. It was also possible to easily make adjustments and perform grinding with excellent processing efficiency. Feedback work is also easy.
[0113]
In the first embodiment, the servo motor is used as the spindle head tilting mechanism. However, a differential screw or the like may be used, or another structure may be used. Further, the configuration in which the spindle head is tilted with respect to the rotary table has been described, but a configuration in which the rotary table is tilted instead of the spindle head may be used.
[0114]
【The invention's effect】
As described above, according to the present invention, it has become possible to systematically and efficiently perform the axial adjustment work that has relied solely on the experience and intuition of a skilled worker. As a result, the quality (the flatness of the wafer) and the workability (the time required for the axial adjustment) were significantly improved.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a first embodiment of a surface grinding device of the present invention.
FIG. 2 is an explanatory top view schematically showing a contact state between a wafer and a grinding wheel during grinding by the surface grinding apparatus of FIG. 1;
FIG. 3 is a schematic explanatory view showing a second embodiment of the surface grinding apparatus of the present invention.
4 is an explanatory top view schematically showing a contact state between a wafer and a grinding wheel during grinding by the surface grinding apparatus of FIG. 3;
FIG. 5 is an explanatory view showing a cross-sectional shape of a wafer ground by the grinding method of the present invention.
FIG. 6 is a flowchart showing a grinding procedure according to the method of the present invention when the surface grinding device of the first embodiment is used.
FIG. 7 is a flowchart showing a grinding procedure according to the method of the present invention when the surface grinding device of the second embodiment is used.
FIG. 8 is a schematic perspective explanatory view showing an example of an angle control mechanism used in the apparatus of the present invention.
FIG. 9 is a detailed explanatory view of a servo motor part in FIG. 8;
FIG. 10 is a detailed explanatory view of an angle detector in FIG. 8;
FIG. 11 is an explanatory view showing a cross-sectional shape of a wafer ground by the grinding method of the present invention.
FIG. 12 is a top explanatory view schematically showing a contact state between a wafer and a grindstone according to the grinding method of the present invention.
FIG. 13 is a graph showing the shape of a wafer ground in Experimental Example 1.
FIG. 14 is a graph showing a wafer shape ground in Example 1.
FIG. 15 is a schematic explanatory view showing a structural example of a conventional infeed type surface grinding machine.
FIG. 16 is a schematic perspective view showing an example of a conventional angle control mechanism.
FIG. 17 is a detailed explanatory view of a servo motor part in FIG. 16;
FIG. 18 is a detailed explanatory view of an angle detector in FIG.
FIG. 19 is an explanatory diagram exaggeratingly showing a state of grinding by a conventional infeed type surface grinding machine.
FIG. 20 is an explanatory top view schematically showing a contact state between a wafer and a grindstone during grinding by a conventional in-feed type surface grinder.
FIG. 21 is a perspective explanatory view schematically showing a contact state between a wafer and a grindstone during grinding by a conventional in-feed type surface grinder.
FIG. 22 is an explanatory view schematically showing a wafer shape ground by a conventional in-feed type surface grinding machine.
[Explanation of symbols]
10: conventional surface grinder, 10a, 10b: surface grinding device of the present invention, 12: base, 14: wafer, 16: wafer chuck, 18: wafer chuck rotating shaft, 20: wafer chuck drive motor, 22: grinding wheel , 22a: grinding wheel locus, 24: grinding wheel rotating shaft, 26: spindle head, 28: grinding wheel rotating shaft drive motor, 30: abutment, 32: fixed frame. 34: sliding support plate, 36: tilt control device (axis adjusting device), 37: metal block, 40: grinding wheel rotating shaft elevating motor (drive mechanism), 42: first slit, 42a: first wide groove portion, 44: contact arc, 45: first block portion, 46: second block portion, 48: through hole, 50: screw hole, 52: drive rod, 54: first drive device, 56: through hole, 58: gauge probe , 60: first angle detector, 62: second slot, 62a: second wide groove, 64: third block, 66: fourth block, 68: second drive, 70: second angle detection 100A: processing control unit, 100a: coordinate conversion means, 100b: operation unit, 100c: display unit.

Claims (13)

In an in-feed type surface grinding method of grinding a wafer rotationally driven in a horizontal plane by a grindstone attached to a lower part of a vertically arranged spindle head, a direction along a contact arc between the grindstone and the wafer The tilt component of the axis of the spindle head is decomposed in two directions of a coordinate system (XY) consisting of a direction (Y direction) and a direction (X direction) orthogonal thereto, and the relative tilt of the spindle head is resolved. Surface grinding method characterized by adjusting the surface roughness. In a surface grinding method of an in-feed system in which a wafer rotationally driven in a horizontal plane is ground by a grindstone attached to a lower part of a vertically arranged spindle head, a line connecting the center of the grindstone and the center of the wafer The inclination component of the axis of the spindle head is decomposed in two directions of a coordinate system (α-β) direction consisting of a shape direction (α direction) and a direction (β direction) orthogonal to the direction, and the axis of the spindle head is decomposed. In performing the adjustment, a deviation of an angle θ with respect to a coordinate system (XY) direction including a direction (Y direction) along a contact arc between the grinding wheel and the wafer and a direction (X direction) orthogonal to the direction is considered. A surface grinding method comprising: performing coordinate conversion between both coordinate systems to adjust a relative inclination between a wafer and a spindle head. 3. The surface grinding method according to claim 2, wherein coordinate conversion is performed between the coordinate system (α-β) and the coordinate system (XY) by the following equation (1) or (2). .

The wafer shape obtained after surface grinding is measured by dividing it into "tilt component" and "flexure component", and the relative tilt between the wafer and the spindle head is adjusted by feeding back this as a control parameter. The surface grinding method according to claim 1. The “tilt component ΔY ′” and “flexure component ΔX ′” of the thickness unit of the wafer shape obtained after surface grinding are angle-converted by the following equation (3), and the “tilt component ΔY” and “flexure component ΔX” of the angle unit are obtained. 5. The surface grinding method according to claim 4, wherein

(In the equation (3), k ₁ and k ₃ are correction coefficients, and k ₂ and k ₄ are correction values, which are determined by equipment and grinding conditions.) The adjustment of the relative inclination between the wafer and the spindle head is performed before grinding, and the relative angle between the grinding wheel and the wafer is maintained constant during grinding. 2. The surface grinding method according to claim 1. In an in-feed type surface grinding apparatus for grinding a wafer rotationally driven in a horizontal plane with a grindstone attached to a lower part of a vertically arranged spindle head, a Z-axis in which the spindle head and the wafer are vertically aligned And a drive mechanism for relatively moving the spindle head in two directions: a direction along the contact arc between the grinding wheel and the wafer (Y axis) and a direction orthogonal to this (X axis) to adjust the inclination of the spindle head. A surface grinding device, comprising: Input means for inputting a "tilt component" and a "deflection component" of a wafer shape obtained after surface grinding, and by using these values, a direction along a contact arc between the grinding wheel and the wafer (Y axis) and a direction orthogonal thereto. 8. The surface grinding apparatus according to claim 7, further comprising: calculation means for calculating an axis inclination component of the spindle head with respect to two directions (X-axis). A drive mechanism for relatively moving the spindle head and the wafer in the vertical Z-axis direction, and a coordinate system consisting of a linear direction (α-axis) connecting the center of the grinding wheel and the wafer and a direction (β-axis) orthogonal thereto. An inclination control device for adjusting the inclination of the spindle head in the (α-β) direction, wherein the wafer, which is rotationally driven in a horizontal plane, is attached to a lower part of the spindle head arranged in a vertical direction. Coordinate system (XY) comprising a direction (Y-axis) along a contact arc between the grinding wheel and the wafer and a direction (X-axis) perpendicular to the direction of contact arc between the grinding wheel and the wafer. Coordinate conversion means for performing coordinate conversion on the wafer and the spindle head by performing coordinate conversion between both the coordinate system (α-β) and the coordinate system (XY). Adjust the tilt DOO surface grinding apparatus according to claim. Input means for inputting a "tilt component" and a "deflection component" of a wafer shape obtained after surface grinding, and by using these values, a direction along a contact arc between the grinding wheel and the wafer (Y axis) and a direction orthogonal thereto. Axis inclination component of the spindle head with respect to two axes (X axis), or two axes in a linear direction (α axis) connecting the grinding wheel center and the wafer center and a direction (β axis) orthogonal to this. 10. The surface grinding apparatus according to claim 9, further comprising a calculating unit that performs the calculation. The coordinate conversion means converts the “tilt component ΔY ′” and “flexure component ΔX ′” in the thickness unit of the wafer shape into the “tilt component ΔY” and “flexure component ΔX” in angle units, and further converts the coordinate system (X 11. The surface grinding apparatus according to claim 10, wherein coordinates are converted from -Y) to a coordinate system (α-β) to calculate inclination angles Δα (degrees) and Δβ (degrees) of the α axis and the β axis. The surface grinding apparatus according to claim 11, further comprising an angle detector that measures inclination angles Δα (degrees) and Δβ (degrees) of the α axis and the β axis. The inclination control device automatically adjusts the inclination of the spindle head until the inclination angles Δα (degree) and Δβ (degree) of the α-axis and the β-axis obtained by performing the coordinate transformation. The surface grinding device according to claim 11.

Images