JP4681700B2 - Method for detecting crystal orientation of silicon ingot - Google Patents

Description

ここで：ｄ＝格子面間隔；θ＝ブラッグ角；ｎ＝反射次数；λ＝Ｘ線の波長；
上式で定義される。上式中の格子面間隔ｄを（０１１）面の格子面間隔に設定すると、図２に示した３つのファミリー面から（０１１）ファミリーが選別される。その結果、複数の結晶面からなるシリコン結晶体を図３に示した簡単なモデルで扱うことができる。
【００１６】
ここで、同図に示すように、シリコン結晶体を［１００］軸を中心に回転させながら、該結晶体の側面からＸ線を入射すると、９０°ごとにブラッグの条件が成立し、該シリコン結晶体を１回転させる間に４本のピークを検出することができる。このときに得られる４本のピークは、ブラッグの条件が成立した瞬間に生じる急峻な形状であるため、（０１１）ファミリーの高精度な検出が実現できる。
【００１７】
しかし、上記Ｘ線解析で得られた４本のピークは、ほとんど同じ形状および強さで得られるため、このままでは、（０１１）ファミリーを構成する４つの結晶面を特定することはできない。そこで、本発明者は、オフセットの概念を幾何学的視点から捉えて、該オフセットの積極的な利用について検討した。その検討結果を以下に示す。
【００１８】
図４は、回転軸のＨオフセットの概念を示す模式斜視図である。同図に示すように、オフセットの形態としては、まず、回転軸を（０１１）ファミリー面に対して斜めに傾けた状態が考えられる。以下、このオフセットの形態を「Ｈオフセット」と称する。次に、この傾けた回転軸と直交する方向にＸ線を入射した場合に、該Ｘ線が反射する方向について考えてみると次のようになる。
【００１９】
図５は、図４のＶ視図であり、Ｈオフセットの場合にＸ線回折光が反射する方向を示す模式側面図である。同図に示した面のうち、陰影が付された部分は紙面手前側に向いていることを示す。また、Ｘ線入射ビーム２０の先端に付された「×」印は、該Ｘ線が紙面手前から奥に向かって進行することを示す。また、Ｘ線反射ビーム２２の先端に付された「・」印は、該Ｘ線が紙面奥から手前に向かって進行することを示す。
【００２０】
同図に示すように、（０１１）面が紙面手前側に向いた状態を０°とすると、該０°では、（０１１）面が紙面右方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面右側に向かって進行する。そしてこの状態から結晶体を（１００）面に向かって時計回りに９０°回転させると、（０バー１１）面が紙面左方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面左側に向かって進行する。そしてさらに結晶体を９０°回転させると、（０バー１バー１）面は、紙面左方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面左側に向かって進行する。そしてさらに結晶体を９０°回転させると、（０１バー１）面が面右方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面右側に向かって進行する。このように、Ｈオフセットでは、Ｘ線の反射方向を２種類に分類することができる。この分類基準を合理的に定義づけると次のようになる。
【００２１】
図５に示すように、Ｘ線反射ビーム２２が紙面右側に進行するのは、（０１１）面と、（０１バー１）面である。一方、Ｘ線反射ビーム２２が紙面左側に進行するのは、（０バー１１）面と、（０バー１バー１）面である。ここで、図４を参照すると、Ｘ線反射ビーム２２が紙面右側に進行する（０１１）面と（０１バー１）面は、回転軸よりも結晶軸に近く、Ｘ線反射ビーム２２が紙面左側に進行する（０バー１１）面と（０バー１バー１）面は、結晶軸よりも回転軸に近いことがわかる。従って、Ｘ線が反射する方向は、結晶面が結晶軸側に位置するか、または、回転軸側に位置するかによって定義できる。
【００２２】
図６は、回転軸のＪオフセットの概念を示す模式斜視図である。同図に示すように、オフセットの別の形態として、回転軸を（０１１）ファミリー面に対して垂直に傾けた状態が考えられる。以下、このオフセットの形態を「Ｊオフセット」と称する。次に、この傾けた回転軸と直交する方向にＸ線を入射した場合に、該Ｘ線が反射する方向について考えてみると次のようになる。
【００２３】
図７は、図６のＶＩＩ視図であり、Ｊオフセットの場合にＸ線回折光が反射する方向を示す模式側面図である。同図に示すように、（０１１）面が紙面手前側に向いた状態を０°とすると、該０°では、（０１１）面が紙面右方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面右側に向かって進行する。そしてこの状態から結晶体を（１００）面に向かって時計回りに９０°回転させると、（０バー１１）面が紙面手前方向に現れる。その結果、Ｘ線反射ビーム２２は、紙面手前に向かって進行する。さらにこの状態から結晶体を９０°回転させると、（０バー１バー１）面が紙面左方向に傾く。その結果、Ｘ線反射ビーム２２は、紙面左側に向かって進行する。そしてさらに結晶体を９０°回転させると、（０１バー１）面が紙面手前に現れる。その結果、Ｘ線反射ビーム２２は、紙面手前に向かって進行する。このように、Ｊオフセットでは、Ｘ線の反射方向を３種類に分類することができる。この分類基準を合理的に定義づけると次のようになる。
【００２４】
図７に示すように、Ｘ線反射ビーム２２が紙面右側に進行するのは、（０１１）面である。そして、Ｘ線反射ビーム２２が紙面手前に進行するのは、（０バー１１）面と（０１バー１）面である。また、Ｘ線反射ビーム２２が紙面左側に進行するのは、（０バー１バー１）面である。ここで、図６を参照すると、Ｘ線反射ビーム２２が紙面右側に進行する（０１１）面は、回転軸よりも結晶軸に近く、Ｘ線反射ビーム２２が紙面左側に進行する（０バー１バー１）面は、結晶軸よりも回転軸に近いことがわかる。そして、Ｘ線反射ビーム２２が紙面手前に進行する（０バー１１）面と（０１バー１）面については、結晶軸と回転軸両方から同じ距離だけ離れていることがわかる。従って、Ｘ線が反射する方向は、Ｈオフセットの場合と同様に、結晶軸と回転軸に対する距離で定義できる。
【００２５】
上述したようなＸ線があるパターンで反射する現象は、Ｘ線を回転軸と平行に入射した場合でも、回転軸に対して斜めから入射した場合でも見出すことができる。また、上記説明では（０１１）ファミリー面を例として取り上げたが、反射方向に特定のパターンが生じることは、（００１）ファミリー面および（０１０）ファミリー面に対しても成立する。本発明者は、このような現象に基づいて創作行為を繰り返し、結晶面の特定に有効な構成を見出した。以下、この特徴ある新規な構成を詳細に説明する。
【００２６】
（第１の形態）
図８は、本発明の第１の形態に係る結晶面の検出方法を示す模式斜視図である。以下、同図に基づいて、本発明の第１の形態の構成を説明する。
【００２７】
シリコンインゴット１４は、結晶軸１０が中心軸１２に対してオフセットを有する。このようなインゴットは、シードの切り出し方向にオフセットを設けることによって製造できる。同図に示す例では、［１００］軸がシリコンインゴット１４の中心軸１２に対してＨオフセットを持つ。従って、オフセットウェハの周縁部に現れて、マーキングの対象となるのは、該［１００］軸を取り囲む（０１１）ファミリー面であり、結晶面を検出するにあたっては、まず、この（０１１）ファミリー面を検出対象として選定する。
【００２８】
図１を参照すればあきらかであるが、結晶軸１０の対象となるのは、［１００］軸だけでなく、［００１］軸や［０１０］軸であってもよい。これらの場合には、当該軸を取り巻く結晶面がオフセットウェハの周縁部に現れるので、この中からマーキングすべき一のファミリー面選定する。
【００２９】
次に、前記選定したファミリー面のうち、検出すべき一の結晶面を選定する。即ち、結晶軸１０の一端側（例えば、シリコンインゴットのボトム側）に視点を固定し、該視点からシリコンインゴット１４を見た場合に、結晶軸１０側に位置する結晶面または中心軸１２側に位置する結晶面のいずれか一方を選定する。これは、前述したように、Ｘ線の反射方向が結晶軸と中心軸に対する位置関係によって分類できるからである。例えば、シリコンインゴット１４の中心軸１２が図４に示すように、（０バー１バー１）面と（０バー１１）面に近接している場合には、これらの面が中心軸側に位置する面となり、他の２つの面が結晶軸側に位置する面となる。
【００３０】
次に、前記選定した側の結晶面が選定しなかった側の結晶面よりもブラッグの条件がより多く成立する位置にＸ線入射手段１６およびＸ線受光手段１８を配置する。例えば、結晶軸側に位置する（０１１）面と（０１バー１）面を選定した場合であって、図８に示すように、Ｘ線入射手段１６をＸ線が中心軸１２に対して直交方向に入射する位置に配置したときは、Ｘ線受光手段１８を第１の反射光路２６−１上に配置する。その結果、同図中に点線で示した第３の反射光路２６−３をとる（０バー１バー１）面と（０バー１１）面については、ブラッグの条件が成立せず、結晶軸側に位置する面に対してブラッグの条件が成立する。ここで、第３の反射光路２６−３は、（０バー１１）面と（０バー１バー１）面によって反射する光路である。尚、Ｘ線入射手段１６は、（０１１）面のブラッグ条件を満たすＸ線を出力する。
【００３１】
ここで、Ｘ線入射手段１６とＸ線受光手段１８の配置を「ブラッグの条件がより多く成立する位置」としたのは、オフセットが小さい場合を考慮したからである。即ち、オフセットが大きい場合には、Ｘ線反射ビーム２２が左右に大きく振れるが、オフセットが小さいとＸ線反射ビーム２２の振れが小さくなる。このため、第１の反射光路２６−１上を進行するＸ線を選択的に受光することが困難になるからである。このような場合には、第１の反射光路２６−１上を進行するＸ線を第３の反射光路２６−３上を進行するＸ線よりも多く受光できる位置にＸ線受光手段１８を配置する。即ち、「ブラッグの条件がより多く成立する位置」である。
【００３２】
尚、同図中に点線で示した第２の反射光路２６−２は、Ｊオフセットの場合に（０バー１１）面と（０１バー１）面によって反射する光路である。ここでは、Ｈオフセットのケースを例に取り上げて説明しているため、Ｘ線が第２の反射光路２６−２上を進行することはないが、Ｊオフセットへの適用を容易にするために記載した。
【００３３】
次に、シリコンインゴット１４の中心軸１２を回転中心として該シリコンインゴット１４を回転させながら、Ｘ線入射手段１６を用いてＸ線入射ビーム２０を該シリコンインゴット１４に入射し、その結果得られたＸ線反射ビーム２２をＸ線受光手段１８で受光する。これにより、第１の反射光路２６−１を進行するＸ線が選択的に受光され、受光強度のパターン化が実現できる。
【００３４】
図９は、Ｈオフセットの場合のＸ線の受光パターンを示す概念図である。同図に示すように、横軸をシリコンインゴット１４の回転量、縦軸をＸ線受光手段１８が受光したＸ線回折光の強度としてグラフを作成すると、受光強度がパターン化することがわかる。Ｈオフセットの場合は、同図に示すように、９０°の間隔で２本のピークが続き、その後、２７０°の間はピークのない状態が続く。ここで、ピークが発生する位置は、第１の反射光路２６−１上を進行するＸ線であることを考慮すると、この２本のピークは、（０１バー１）面および（０１１）面であることがわかる。そしてさらに、この受光パターンが［１００］軸に向かってシリコンインゴット１４を時計まわりに回転して得られたことを考慮すると、１本目のピークは、（０１バー１）面であり、２本目のピークは、（０１１）面であることがわかる。同様に、ピークのない部分においても、結晶面が９０°ごとに現れることを考慮すれば、同図中の点線で示す部分が（０バー１１）面と（０バー１バー１）面であることがわかる。
【００３５】
上記手順により、（０１１）ファミリー面の位置が特定できたので、後は、現時点までの回転量からシリコンインゴット１４の回転開始位置から第１本目までの回転量、即ち、同図中「初期量」と示した回転量を引いて、各結晶面の位置を割り出せば、（０１１）ファミリーを構成するすべての面を特定することができる。
【００３６】
図１０は、Ｊオフセットの場合のＸ線の受光パターンを示す概念図である。Ｊオフセットの場合には、同図に示すような受光パターンが得られる。このパターンを上述した手順と同様の手順で処理すれば、Ｈオフセットの場合と同じく、各結晶面を特定することができる。
【００３７】
以上説明した本発明の第１の形態によれば、同じファミリー面であってもＸ線の反射方向にバリエーションがでるため、シリコンインゴット中の結晶面の位置をＸ線の受光パターンとして捉えることができる。その結果、任意の結晶面の検出が可能になる。
【００３８】
（第２の形態）
図１１は、本発明の第２の形態に係る結晶面の検出方法を示す模式側面図である。以下、同図に基づいて、本発明の第２の形態の構成を説明する。尚、前述した第１の形態に準ずる構成要素については、同一符号を付して説明を省略し、以下の説明では、第１の形態と異なる部分を主に説明する。
【００３９】
まず、この第２の形態では、図８に示したＸ線入射手段１６およびＸ線受光手段１８をシリコンインゴット１４の結晶軸１０と中心軸１２とが一致すると仮定した場合に、選定したファミリー面に対してブラッグの条件が成立する位置に配置する。例えば、図１１に示すように、Ｘ線の入射光路２４をシリコンインゴット１４の中心軸１２に対して垂直に設定した場合には、結晶軸１０と中心軸１２とが一致すると仮定した場合の反射光路は、第２の反射光路２６−２となる。従って、Ｘ線受光手段１８は、この第２の反射光路２６−２上を進行するＸ線を受光できる位置に配置する。このように配置する意図は、オフセットを持たないインゴットの結晶面を検出する装置に対しても本発明を適用可能にするためである。
【００４０】
次に、第１の形態と同様に、結晶軸１０の一端側に視点を固定し、該視点からシリコンインゴット１４を見た場合に、結晶軸側に位置する結晶面または中心軸側に位置する結晶面のいずれか一方を選定する。即ち、図１１に示した第１の反射光路２６−１上にＸ線を反射する結晶面か、第３の反射光路２６−３上にＸ線を反射する結晶面かを選択する。
【００４１】
そして、Ｘ線受光手段１８の受光領域２８をずらして、前記選定した側の結晶面と選定しなかった側の結晶面とを差別化する。即ち、第１の反射光路２６−１上を進行するＸ線を第３の反射光路２６−３上を進行するＸ線よりも多く受光させて、ブラッグの条件が成立する割合を調節する。ここで、第２の反射光路２６−２が受光領域２８に含まれるか否かは問題でなく、いずれの場合であっても結晶面の特定は可能である。受光領域２８をずらすという概念には、Ｘ線受光手段１８の向きを変える方法およびＸ線受光手段１８のＸ線受光ウィンドウの一部をマスクで覆って受光部分を制限する方法の双方が含まれる。
【００４２】
その後、前述した第１の形態と同様に、中心軸１２を回転中心としてシリコンインゴット１４を回転させながら、Ｘ線照射を行う。もっとも、このとき回転させるシリコンインゴット１４はオフセットを持ったものである。その結果、Ｈオフセットの場合は、図９と同じ受光パターンが得られる。
【００４３】
図１２は、本発明の第２の形態によるＪオフセットのＸ線受光パターンを示す概念図である。Ｊオフセットの場合には、反射光が図１１に示した第２の反射光路２６−２上を進行するため、Ｘ線を第３の反射光路２６−３上に反射する（０バー１バー１）面にピークがないパターンとなる。各結晶面の特定は、前述した第１の形態と同様に行う。
【００４４】
以上説明した本発明の第２の形態によれば、Ｘ線受光手段の配置がオフセットを持たないものと仮定して決定されるため、オフセットを持たないインゴットの結晶面を検出する装置に対しても本発明を適用することができる。即ち、Ｘ線受光手段の配置を変更しなくてもその受光領域をずらせば、本発明の原理が適用できる。
【００４５】
【実施例】
（要約）
Ｘ線の受光領域２８にマスク３８を被せて、第１の反射光路２６−１を第３の反射光路２６−３よりも多く受光させる。そして、オフセットを有するシリコンインゴット１４をその中心軸１２を回転中心として回転させながら、Ｘ線照射を行い、その結果得られた受光パターンに基づいて、任意の結晶面を特定する（図１４参照）。
【００４６】
（好適な実施例）
前述したように、シリコンウェハを用いて集積回路等を製造するデバイス工程では、該ウェハのオフセット方向を確認する必要がある。従って、オフセットウェハの周縁にノッチやオリエンテーションフラット等のマーキングを施し、オフセット方向の目視確認を可能にすることは、産業上非常に有用である。本発明によれば、光学的手法によって任意の結晶面が検出できるため、高精度なマーキングが可能になる。そこで、以下、シリコンインゴットにマーキングを施す方法を説明し、これを本発明の好適な実施例とする。
【００４７】
図１３は、本発明を利用した（０１１）面のマーキング方法を示す斜視図である。以下、同図に基づいて、本発明の好適な実施例に係るマーキング方法を説明する。尚、前述した本発明の各形態に準ずる構成要素については、同一符号を付して説明を省略する。
【００４８】
同図に示すシリコンインゴット１４は、［バー１００］軸を該インゴットのトップ方向に、［１００］をボトム方向に設定し、これらの結晶軸１０を中心軸１２に対して４°傾けて成長させたものである。この４°傾ける方向、即ち、オフセットの方向は、［００１］であり、その結果、（０１１）ファミリー面のうち、（０バー１１）面と（０１１）面が結晶軸側に位置したＨオフセット型の結晶体となる。従って、このシリコンインゴット１４を中心軸１２に対して垂直にスライスすれば、結晶面方位が（１００）、傾角度が［００１］方向に４°のオフセットウェハが得られる。このようにして得られたオフセットウェハのオフセット方向を明らかにするため、本実施例では、［０１１］方向にマーキングを施す。
【００４９】
［０１１］方向にマーキングを施すためには、シリコンインゴット１４の（０１１）面を検出する必要がある。そこで、まず、シリコンインゴット１４を中心軸１２に沿って縦に２分したときの断面を仮定し、このインゴット中心断面３０に直交する法線３２と、Ｘ線入射ビーム２０と、Ｘ線反射ビーム２２とが同一平面となる位置にＸ線入射手段１６およびＸ線受光手段１８を配置する。このとき、このＸ線入射手段１６およびＸ線受光手段１８は、（０１１）ファミリー面に対するブラッグの条件満たす位置、即ち、インゴット中心断面３０に対してブラッグ角θだけ傾けた位置に配置する。この配置は、前述した「結晶軸１０と中心軸１２とが一致すると仮定した場合に、選定したファミリー面に対してブラッグの条件が成立する位置」に相当する。
【００５０】
そして、シリコンインゴット１４の中心軸１２を真空チャッキングして、該中心軸１２に回転装置３４を設置する。回転装置３４は、１°／１，０００ の精度でシリコンインゴット１４を回転させることができる。この回転装置３４には、該回転装置３４を数値制御するコントローラ３６が接続され、このコントローラ３６は、回転装置３４の回転精度を制御するとともに、シリコンインゴット１４の回転量と、Ｘ線受光手段１８が受光したＸ線の回折強度とを対応させて記憶する。
【００５１】
図１４は、図１３に示したＸ線受光手段１８の受光領域を設定する工程を示す概念図である。同図に示すように、Ｘ線受光手段１８の受光領域２８は、第１の反射光路２６−１と第３の反射光路２６−３の両方を含む。これは、結晶軸のオフセット角が４°と小さいため、反射光路の振れも小さくなるからである。従って、Ｘ線受光手段１８の受光領域２８をそのまま用いたのでは、第１の反射光路２６−１と第３の反射光路２６−３を区別することができなくなる。そこで、この受光領域を設定する工程では、第３の反射光路２６−３の一部にマスク３８を被せて、結晶軸１０側に位置する面と、中心軸１２側に位置する面とを差別化する。具体的には、同図左下に示したグラフのように、結晶軸１０側に位置する（０バー１１）面と（０１１）面のＸ線回折強度が中心軸１２側に位置する（０１バー１）面と（０バー１バー１）面のＸ線回折強度よりも大きくなる位置にマスク３８を設置する。このＸ線回折強度のピーク差は、２倍程度あることが好ましい。このピーク差の割合は、シリコンインゴット１４を［バー１００］軸に向かって時計方向に回転させながら、実際にＸ線照射を行って決定する。
【００５２】
図１５は、（０１１）面の検出とマーキングの工程を示す概念図である。同図に示すように、まず、シリコンインゴット１４を比較的粗い精度で３６０°回転させ、その結果得られた１回転目の受光パターンを回折強度３０％前後に設定した第１のしきい値４０−１と比較する。そして、この第１のしきい値４０−１を超えるピークが４本あった場合には、当該回転させたシリコンインゴット１４の結晶軸１０が［バー１００］であると判断し、２回目の回転を行う。一方、第１のしきい値４０−１を超えるピークが４本でなかった場合には、このシリコンインゴット１４に対するマーキングを中止する。
【００５３】
２回目の回転も１回目の回転と同様に比較的粗い精度で行い、該回転の結果得られた受光パターンを回折強度７０％前後に設定した第２のしきい値４０−２と比較する。そして、この第２のしきい値４０−２を超えるピークが２本あった場合には、当該回転させたシリコンインゴット１４がＨオフセット型であると判断し、３回目の回転を行う。一方、第２のしきい値４０−２を超えるピークが２本でなかった場合には、このシリコンインゴット１４に対するマーキングを中止する。
【００５４】
３回目の回転は、（０１１）面の位置に相当する２本目のピークをねらって高精度で行う。そして、この２本目のピークが得られたら、該ピークの中心に相当する回転量を求める。ピークの中心値Ｃは、

ここで：Ｃ＝中心の回転量；Ａ＝２本目のピークと第２のしきい値４０−２との最初の交点；Ｂ＝２本目のピークと第２のしきい値４０−２との次の交点；
上式を用いて求める。そして、回転装置３４を操作して、上記求めた２本目のピークの検出位置にシリコンインゴット１４を戻し、この位置にマーキングを施す。
【００５５】
上述した実施例において、シリコンインゴット１４をチャッキングしてからマーキングするまでの工程は、自動的に行われる。この実施例を現在実施中であるが今のところ検出ミスによる不具合は発生していない。
【００５６】
尚、上記実施例では、第１のしきい値４０−１を回折強度７０％、第２のしきい値を回折強度３０％としたが、これらのしきい値は、マスク３８を被せる割合に応じて決定する。即ち、第１のしきい値４０−１は、（０１１）ファミリー面のすべてのピークを捉える値に設定し、第２のしきい値４０−２は、結晶軸１０側に位置する面と中心軸１２側に位置する面とを区別できる値に設定すればよい。
【００５７】
【発明の効果】
以上説明したように、本発明によれば、検出精度の向上と検出工程の自動化に有効なシリコンインゴットの結晶方位検出方法を提供することができる。
【００５８】
また、本発明の第１の形態によれば、同じファミリー面であってもＸ線の反射方向にバリエーションがでるため、シリコンインゴット中の結晶面の位置をＸ線の受光パターンとして捉えることができる。その結果、任意の結晶面の検出が可能になる。
【００５９】
また、本発明の第２の形態によれば、Ｘ線受光手段の配置がオフセットを持たないものと仮定して決定されるため、オフセットを持たないインゴットの結晶面を検出する装置に対しても本発明を適用することができる。即ち、Ｘ線受光手段の配置を変更しなくてもその受光領域をずらせば、本発明の原理が適用できる。
【図面の簡単な説明】
【図１】シリコン結晶体の代表的な結晶面の立体配置を示す模式的な斜視図である。
【図２】シリコン結晶体の［１００］軸を取り囲む結晶面を示す模式正面図である。
【図３】フラッグ条件を利用した（０１１）ファミリーの選定概念を示す模式斜視図である。
【図４】回転軸のＨオフセットの概念を示す模式斜視図である。
【図５】図４のＶ視図であり、Ｈオフセットの場合にＸ線回折光が反射する方向を示す模式側面図である。
【図６】回転軸のＪオフセットの概念を示す模式斜視図である。
【図７】図６のＶＩＩ視図であり、Ｊオフセットの場合にＸ線回折光が反射する方向を示す模式側面図である。
【図８】本発明の第１の形態に係る結晶面の検出方法を示す模式斜視図である。
【図９】Ｈオフセットの場合のＸ線の受光パターンを示す概念図である。
【図１０】Ｊオフセットの場合のＸ線の受光パターンを示す概念図である。
【図１１】本発明の第２の形態に係る結晶面の検出方法を示す模式側面図である。
【図１２】本発明の第２の形態によるＪオフセットのＸ線受光パターンを示す概念図である。
【図１３】本発明を利用した（０１１）面のマーキング方法を示す斜視図である。
【図１４】図１３に示したＸ線受光手段１８の受光領域を設定する工程を示す概念図である。
【図１５】（０１１）面の検出とマーキングの工程を示す概念図である。
【符号の説明】
１０…結晶軸、１２…中心軸、１４…シリコンインゴット、１６…Ｘ線入射手段、１８…Ｘ線受光手段、２０…Ｘ線入射ビーム、２２…Ｘ線反射ビーム、２４…入射光路、２６−１…第１の反射光路、２６−２…第２の反射光路、２６−３…第３の反射光路、２８…受光領域、３０…インゴット中心断面、３２…法線、３４…回転装置、３６…コントローラ、３８…マスク、４０−１…第１のしきい値、４０−２…第２のしきい値、[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a crystal orientation of a silicon ingot, and more particularly to a method for detecting a crystal orientation of a silicon ingot that is effective for improving detection accuracy and automating the detection process.
[0002]
[Prior art]
In the field of manufacturing semiconductor wafers, a semiconductor wafer having a crystal axis offset (hereinafter referred to as “offset wafer”) may be required from the device process. Conventionally, the manufacture of such an offset wafer has been performed by the following method.
[0003]
The first method is a method of obtaining an offset wafer by obliquely cutting a silicon ingot pulled up with a crystal axis, for example, a [100] axis as a central axis. The second method is a method of growing a silicon ingot by tilting the crystal axis from the beginning. Here, in the first method, since both ends of the silicon ingot are wasted, the second method is generally used. By using this second method, a silicon ingot having a crystal axis offset from the central axis can be obtained. Then, the silicon ingot is cut vertically to obtain a plurality of offset wafers from the silicon ingot.
[0004]
When a device such as an integrated circuit is manufactured using the offset wafer, the tilt direction of the crystal axis, that is, the offset direction is important. Therefore, when supplying an offset wafer, notches and orientation flats are formed on the periphery of the offset wafer so that the offset direction can be specified in the device process.
[0005]
The notch and the orientation flat are generally formed with respect to a crystal plane located in the offset direction among a plurality of crystal planes surrounding the crystal axis. Therefore, when forming a notch or an orientation flat, it is necessary to detect a crystal plane located in the offset direction. Conventionally, such detection of a crystal plane has been performed based on a mirror plane generated when the silicon ingot is pulled up.
[0006]
[Problems to be solved by the invention]
However, since the mirror surface is a physical shape generated at the top of the silicon ingot, the crystal plane cannot be specified after the top of the silicon ingot is cut off. Since the silicon ingot slicing step is generally performed after both ends of the silicon ingot are cut off, it is necessary to form notches and orientation flats before cutting the upper portion of the silicon ingot.
[0007]
Further, since it is necessary to visually determine the position of the mirror surface, it is difficult to automate marking. In addition, high-precision detection cannot be expected by visual determination.
[0008]
Accordingly, an object of the present invention is to provide a silicon ingot crystal orientation detection method that is effective in improving detection accuracy and automating the detection process.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a method for detecting a crystal orientation of a silicon ingot (14) in which the crystal axis (10) is offset from the central axis (12), the crystal A step of selecting a family plane of a plurality of crystal planes surrounding the axis, a step of selecting a crystal plane of the selected family plane, and a Bragg condition for the selected crystal plane. An X-ray incident means (16) and an X-ray light receiving means (18) are arranged at a position where they are established, and further, an X-ray reflected beam (22) output from the X-ray incident means (16) and reflected by the selected one crystal plane. ) only The X-ray receiving means (18) is disposed at a position where the X-ray receiving means (18) can be selectively received, and the X-ray incident beam ( 20) is incident on the silicon ingot, and the resulting X-ray reflected beam (22) is received by the X-ray light receiving means, the intensity of the received X-ray reflected beam, and the X-ray reflected beam. And determining the crystal orientation of the silicon ingot based on the amount of rotation of the silicon ingot when the light is received.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(Summary of Invention)
A feature of the present invention is that when a silicon ingot whose crystal axis is offset with respect to the central axis is rotated, the inclination of the crystal plane appearing on the side surface of the silicon ingot changes, and an arbitrary crystal plane is optically converted. Is to detect automatically. When X-rays are incident on the crystal plane whose inclination changes as described above, the X-rays are reflected depending on the tilt direction of the crystal plane. If attention is paid to the X-ray reflection direction, the crystal plane can be specified.
[0011]
(Invention process)
First, the present inventor examined not a method for visually confirming a physical shape such as a mirror surface but a method for optically detecting a crystal plane. Detection of crystal planes by an optical method is actively performed in the field of X-ray analysis, and is widely known as a method for realizing detection of crystal planes with high accuracy. If such an optical method can be applied to a crystal plane having an offset, an improvement in accuracy and automation of the detection process can be expected. Therefore, the present inventor has reviewed the principle of the known X-ray analysis method in order to find out the applicability of the optical technique. Hereinafter, a known X-ray analysis method will be described.
[0012]
FIG. 1 is a schematic perspective view showing a three-dimensional arrangement of a typical crystal plane of a silicon crystal. As shown in the figure, the silicon crystal body has 26 crystal orientations, and each orientation is represented by a three-digit numerical value indicating its configuration. A crystal plane belonging to each orientation is expressed by enclosing a 3-digit numerical value in parentheses, and a crystal axis penetrating each crystal plane is expressed by enclosing a 3-digit numerical value in parentheses. Among these three-digit numerical values, the symbol “-” written above 1 means inversion of the axis, and the numerical value with the inversion symbol is hereinafter referred to as “bar 1”.
[0013]
Each crystal plane is grouped by the same kind of crystal orientation. In the case of a silicon crystal, there are seven groups (001), (010), (011), (100), (101), (110), and (111). Hereinafter, the group classified in this way is referred to as “family face”. Since the (100) plane is generally used as the plane orientation of the silicon wafer, the crystal plane surrounding the [100] axis is a formation target of notches and orientation flats. Therefore, in the following description, the detection of the crystal plane surrounding the [100] axis will be described in mind.
[0014]
FIG. 2 is a schematic front view showing a crystal plane surrounding the [100] axis of the silicon crystal. As shown in the figure, the [100] axis is surrounded by three family planes: (001) family, (010) family, and (011) family. Here, the (001) family consists of two crystal planes, the (001) plane and the (00 bar 1) plane, and the (010) family consists of two crystal planes, the (010) plane and the (0 bar 10) plane. The (011) family is composed of four crystal planes: (011) plane, (0 bar 11) plane, (0 bar 1 bar 1) plane, and (01 bar 1) plane. In the known X-ray analysis method, these three family planes are distinguished by using the flag condition. Here, a method of selecting the (011) family using the Bragg condition will be described.
[0015]
FIG. 3 is a schematic perspective view showing the concept of selecting the (011) family using the flag condition. As shown in the figure, when an X-ray incident beam 20 satisfying the Bragg condition with respect to the (011) plane is incident at a Bragg angle θ from the side surface of the [100] axis, the X-ray incident beam 20 is (011) An X-ray reflected beam 22 reflected on the family surface is obtained. The above Bragg condition is

Where: d = lattice spacing; θ = Bragg angle; n = reflection order; λ = X-ray wavelength;
It is defined by the above formula. When the lattice plane interval d in the above equation is set to the lattice plane interval of the (011) plane, the (011) family is selected from the three family planes shown in FIG. As a result, a silicon crystal composed of a plurality of crystal planes can be handled with the simple model shown in FIG.
[0016]
Here, as shown in the figure, when an X-ray is incident from the side of the crystal while rotating the silicon crystal around the [100] axis, the Bragg condition is satisfied every 90 °, and the silicon crystal Four peaks can be detected during one rotation of the crystal. Since the four peaks obtained at this time have a steep shape that occurs at the moment when the Bragg condition is satisfied, the (011) family can be detected with high accuracy.
[0017]
However, since the four peaks obtained by the X-ray analysis are obtained with almost the same shape and intensity, the four crystal planes constituting the (011) family cannot be specified as they are. Therefore, the present inventor considered the concept of offset from a geometrical viewpoint, and examined the positive use of the offset. The examination results are shown below.
[0018]
FIG. 4 is a schematic perspective view showing the concept of the H offset of the rotating shaft. As shown in the figure, as a form of offset, first, a state in which the rotation axis is inclined obliquely with respect to the (011) family surface can be considered. Hereinafter, this form of offset is referred to as “H offset”. Next, when X-rays are incident in a direction orthogonal to the inclined rotation axis, the direction in which the X-rays are reflected is as follows.
[0019]
FIG. 5 is a V side view of FIG. 4 and is a schematic side view showing a direction in which X-ray diffracted light is reflected in the case of H offset. Of the surface shown in the figure, the shaded portion is directed to the front side of the page. In addition, the “x” mark attached to the tip of the X-ray incident beam 20 indicates that the X-ray travels from the front to the back of the page. Further, the “·” mark attached to the tip of the X-ray reflected beam 22 indicates that the X-ray travels from the back of the paper toward the front.
[0020]
As shown in the figure, when the state where the (011) plane faces the front side of the sheet is 0 °, the (011) plane is inclined rightward on the sheet at 0 °. As a result, the X-ray reflected beam 22 travels toward the right side of the page. Then, when the crystal is rotated 90 ° clockwise toward the (100) plane from this state, the (0 bar 11) plane tilts to the left in the drawing. As a result, the X-ray reflected beam 22 travels toward the left side of the page. When the crystal is further rotated by 90 °, the (0 bar 1 bar 1) plane is inclined to the left in the drawing. As a result, the X-ray reflected beam 22 travels toward the left side of the page. When the crystal is further rotated by 90 °, the (01 bar 1) plane tilts to the right of the plane. As a result, the X-ray reflected beam 22 travels toward the right side of the page. Thus, with the H offset, the X-ray reflection direction can be classified into two types. A rational definition of this classification criterion is as follows.
[0021]
As shown in FIG. 5, it is the (011) plane and the (01 bar 1) plane that the X-ray reflected beam 22 travels to the right side of the page. On the other hand, it is the (0 bar 11) plane and the (0 bar 1 bar 1) plane that the X-ray reflected beam 22 travels to the left side of the page. Here, referring to FIG. 4, the (011) plane and the (01 bar 1) plane in which the X-ray reflected beam 22 travels to the right side of the paper are closer to the crystal axis than the rotation axis, and the X-ray reflected beam 22 is on the left side of the paper. It can be seen that the (0 bar 11) plane and the (0 bar 1 bar 1) plane proceeding to 1 are closer to the rotation axis than the crystal axis. Therefore, the direction in which X-rays are reflected can be defined by whether the crystal plane is located on the crystal axis side or the rotation axis side.
[0022]
FIG. 6 is a schematic perspective view showing the concept of J offset of the rotating shaft. As shown in the figure, as another form of offset, a state in which the rotation axis is inclined perpendicularly to the (011) family plane can be considered. Hereinafter, this form of offset is referred to as “J offset”. Next, when X-rays are incident in a direction orthogonal to the inclined rotation axis, the direction in which the X-rays are reflected is as follows.
[0023]
FIG. 7 is a view taken along the line VII of FIG. 6 and is a schematic side view showing a direction in which X-ray diffracted light is reflected in the case of J offset. As shown in the figure, when the state where the (011) plane faces the front side of the sheet is 0 °, the (011) plane is inclined rightward on the sheet at 0 °. As a result, the X-ray reflected beam 22 travels toward the right side of the page. Then, when the crystal is rotated 90 ° clockwise toward the (100) plane from this state, the (0 bar 11) plane appears in the front direction of the page. As a result, the X-ray reflected beam 22 travels toward the front of the page. Further, when the crystal body is rotated 90 ° from this state, the (0 bar 1 bar 1) plane tilts to the left in the drawing. As a result, the X-ray reflected beam 22 travels toward the left side of the page. When the crystal is further rotated by 90 °, the (01 bar 1) plane appears in front of the page. As a result, the X-ray reflected beam 22 travels toward the front of the page. Thus, with the J offset, the X-ray reflection direction can be classified into three types. A rational definition of this classification criterion is as follows.
[0024]
As shown in FIG. 7, it is the (011) plane that the X-ray reflected beam 22 travels to the right side of the page. And the X-ray reflected beam 22 is Before this page The (0 bar 11) plane and the (01 bar 1) plane proceed to. Further, the X-ray reflected beam 22 travels to the left side of the drawing on the (0 bar 1 bar 1) plane. Here, referring to FIG. 6, the (011) plane in which the X-ray reflected beam 22 travels to the right side of the page is closer to the crystal axis than the rotation axis, and the X-ray reflected beam 22 travels to the left side of the page (0 bar 1). It can be seen that the bar 1) plane is closer to the rotational axis than the crystal axis. Then, it can be seen that the (0 bar 11) plane and the (01 bar 1) plane where the X-ray reflected beam 22 travels in front of the page are separated by the same distance from both the crystal axis and the rotation axis. Therefore, the direction in which X-rays are reflected can be defined by the distance between the crystal axis and the rotation axis, as in the case of H offset.
[0025]
The phenomenon in which X-rays are reflected in a certain pattern as described above can be found whether X-rays are incident in parallel to the rotation axis or obliquely incident on the rotation axis. In the above description, the (011) family plane is taken as an example, but the occurrence of a specific pattern in the reflection direction is also true for the (001) family plane and the (010) family plane. The inventor of the present invention repeated the creative action based on such a phenomenon, and found an effective configuration for specifying the crystal plane. Hereinafter, this characteristic new configuration will be described in detail.
[0026]
(First form)
FIG. 8 is a schematic perspective view showing a crystal plane detection method according to the first embodiment of the present invention. The configuration of the first embodiment of the present invention will be described below with reference to FIG.
[0027]
In the silicon ingot 14, the crystal axis 10 has an offset with respect to the central axis 12. Such an ingot can be manufactured by providing an offset in the seed cutting direction. In the example shown in the figure, the [100] axis has an H offset with respect to the central axis 12 of the silicon ingot 14. Therefore, it is the (011) family plane that surrounds the [100] axis that appears at the peripheral edge of the offset wafer and is the (011) family plane for detecting the crystal plane. Is selected as the detection target.
[0028]
As is apparent from FIG. 1, the target of the crystal axis 10 may be not only the [100] axis but also the [001] axis and the [010] axis. In these cases, since the crystal plane surrounding the axis appears at the peripheral edge of the offset wafer, one family plane to be marked is selected from these.
[0029]
Next, one crystal plane to be detected is selected from the selected family planes. That is, when the viewpoint is fixed to one end side of the crystal axis 10 (for example, the bottom side of the silicon ingot) and the silicon ingot 14 is viewed from the viewpoint, the crystal plane is located on the crystal axis 10 side or the central axis 12 side. Select one of the crystal planes located. This is because, as described above, the X-ray reflection direction can be classified according to the positional relationship between the crystal axis and the central axis. For example, when the central axis 12 of the silicon ingot 14 is close to the (0 bar 1 bar 1) plane and the (0 bar 11) plane as shown in FIG. 4, these planes are positioned on the central axis side. The other two surfaces are surfaces located on the crystal axis side.
[0030]
Next, the X-ray incident means 16 and the X-ray light receiving means 18 are arranged at a position where the Bragg condition is more satisfied in the selected crystal face than in the non-selected crystal face. For example, when the (011) plane and the (01 bar 1) plane located on the crystal axis side are selected, the X-ray incidence means 16 is orthogonal to the central axis 12 as shown in FIG. When arranged at a position incident in the direction, the X-ray light receiving means 18 is arranged on the first reflected light path 26-1. As a result, for the (0 bar 1 bar 1) plane and the (0 bar 11) plane taking the third reflected light path 26-3 indicated by the dotted line in FIG. Bragg's condition holds for the surface located at. Here, the third reflected light path 26-3 is an optical path reflected by the (0 bar 11) plane and the (0 bar 1 bar 1) plane. The X-ray incident means 16 outputs X-rays that satisfy the Bragg condition of the (011) plane.
[0031]
Here, the reason why the arrangement of the X-ray incident means 16 and the X-ray light receiving means 18 is “a position where more Bragg conditions are satisfied” is because the case where the offset is small is taken into consideration. That is, when the offset is large, the X-ray reflected beam 22 is greatly shaken from side to side, but when the offset is small, the shake of the X-ray reflected beam 22 is reduced. For this reason, it is difficult to selectively receive X-rays traveling on the first reflected light path 26-1. In such a case, the X-ray light receiving means 18 is arranged at a position where more X-rays traveling on the first reflected light path 26-1 can be received than X-rays traveling on the third reflected light path 26-3. To do. That is, “a position where more Bragg conditions are satisfied”.
[0032]
The second reflected light path 26-2 indicated by a dotted line in the figure is an optical path reflected by the (0 bar 11) plane and the (01 bar 1) plane in the case of J offset. Here, since the case of the H offset is taken as an example, the X-ray does not travel on the second reflected light path 26-2, but it is described for easy application to the J offset. did.
[0033]
Next, while rotating the silicon ingot 14 around the central axis 12 of the silicon ingot 14, the X-ray incident beam 20 is incident on the silicon ingot 14 using the X-ray incident means 16 and obtained as a result. The X-ray reflected beam 22 is received by the X-ray light receiving means 18. As a result, X-rays traveling in the first reflected light path 26-1 are selectively received, and the pattern of received light intensity can be realized.
[0034]
FIG. 9 is a conceptual diagram showing an X-ray light receiving pattern in the case of H offset. As shown in the figure, when the graph is created with the horizontal axis representing the rotation amount of the silicon ingot 14 and the vertical axis representing the intensity of the X-ray diffracted light received by the X-ray light receiving means 18, it can be seen that the received light intensity is patterned. In the case of the H offset, as shown in the figure, two peaks continue at an interval of 90 °, and thereafter there is no peak for 270 °. Here, considering that the positions where the peaks occur are X-rays traveling on the first reflected light path 26-1, the two peaks are the (01 bar 1) plane and the (011) plane. I know that there is. Furthermore, considering that this light receiving pattern is obtained by rotating the silicon ingot 14 clockwise toward the [100] axis, the first peak is the (01 bar 1) plane, and the second peak It can be seen that the peak is the (011) plane. Similarly, in consideration of the fact that a crystal plane appears every 90 ° even in a portion without a peak, the portions indicated by dotted lines in the figure are the (0 bar 11) plane and the (0 bar 1 bar 1) plane. I understand that.
[0035]
With the above procedure, the position of the (011) family plane has been identified, and thereafter, the rotation amount from the rotation start position of the silicon ingot 14 to the first one from the rotation amount up to the present time, that is, “initial amount” in FIG. If the position of each crystal plane is determined by subtracting the amount of rotation indicated by “”, all planes constituting the (011) family can be specified.
[0036]
FIG. 10 is a conceptual diagram showing an X-ray light receiving pattern in the case of J offset. In the case of J offset, a light receiving pattern as shown in the figure is obtained. If this pattern is processed in the same procedure as described above, each crystal plane can be specified as in the case of H offset.
[0037]
According to the first embodiment of the present invention described above, since the X-ray reflection direction varies even in the same family plane, the position of the crystal plane in the silicon ingot can be regarded as the X-ray light receiving pattern. it can. As a result, an arbitrary crystal plane can be detected.
[0038]
(Second form)
FIG. 11 is a schematic side view showing a crystal plane detection method according to the second embodiment of the present invention. The configuration of the second embodiment of the present invention will be described below with reference to FIG. In addition, about the component according to the 1st form mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted, and the following description mainly demonstrates a different part from a 1st form.
[0039]
First, in the second embodiment, when the X-ray incident means 16 and the X-ray light receiving means 18 shown in FIG. 8 are assumed that the crystal axis 10 and the central axis 12 of the silicon ingot 14 coincide with each other, the selected family surface For the position where the Bragg condition is satisfied. For example, as shown in FIG. 11, when the incident optical path 24 of X-rays is set perpendicular to the central axis 12 of the silicon ingot 14, the reflection when it is assumed that the crystal axis 10 and the central axis 12 coincide with each other. The optical path is the second reflected optical path 26-2. Therefore, the X-ray light receiving means 18 is arranged at a position where X-rays traveling on the second reflected light path 26-2 can be received. The intention to arrange in this way is to make the present invention applicable to an apparatus for detecting a crystal plane of an ingot having no offset.
[0040]
Next, as in the first embodiment, when the viewpoint is fixed to one end side of the crystal axis 10 and the silicon ingot 14 is viewed from the viewpoint, the crystal axis is positioned on the crystal plane side or the central axis side. Select one of the crystal planes. That is, the crystal plane that reflects X-rays on the first reflected light path 26-1 shown in FIG. 11 or the crystal face that reflects X-rays on the third reflected light path 26-3 is selected.
[0041]
Then, the light receiving region 28 of the X-ray light receiving means 18 is shifted to differentiate the selected crystal face from the non-selected crystal face. That is, X-rays traveling on the first reflected light path 26-1 are received more than X-rays traveling on the third reflected light path 26-3, and the rate at which the Bragg condition is satisfied is adjusted. Here, it does not matter whether the second reflected light path 26-2 is included in the light receiving region 28, and in any case, the crystal plane can be specified. The concept of shifting the light receiving region 28 includes both a method of changing the direction of the X-ray light receiving means 18 and a method of covering a part of the X-ray light receiving window of the X-ray light receiving means 18 with a mask to limit the light receiving portion. .
[0042]
Thereafter, as in the first embodiment described above, X-ray irradiation is performed while rotating the silicon ingot 14 around the central axis 12 as a rotation center. However, the silicon ingot 14 rotated at this time has an offset. As a result, in the case of H offset, the same light receiving pattern as that in FIG. 9 is obtained.
[0043]
FIG. 12 is a conceptual diagram showing a J-offset X-ray light receiving pattern according to the second embodiment of the present invention. In the case of J offset, since the reflected light travels on the second reflected light path 26-2 shown in FIG. 11, the X-ray is reflected on the third reflected light path 26-3 (0 bar 1 bar 1). ) The pattern has no peak on the surface. Each crystal plane is specified in the same manner as in the first embodiment.
[0044]
According to the second embodiment of the present invention described above, since the arrangement of the X-ray light receiving means is determined on the assumption that there is no offset, the apparatus for detecting a crystal plane of an ingot having no offset. The present invention can also be applied. That is, the principle of the present invention can be applied by shifting the light receiving area without changing the arrangement of the X-ray light receiving means.
[0045]
【Example】
(wrap up)
The X-ray light receiving region 28 is covered with a mask 38 so that the first reflected light path 26-1 receives more light than the third reflected light path 26-3. Then, X-ray irradiation is performed while rotating the silicon ingot 14 having an offset around the center axis 12 as a rotation center, and an arbitrary crystal plane is specified based on the light receiving pattern obtained as a result (see FIG. 14). .
[0046]
(Preferred embodiment)
As described above, in the device process of manufacturing an integrated circuit or the like using a silicon wafer, it is necessary to confirm the offset direction of the wafer. Therefore, it is very useful industrially to provide markings such as notches and orientation flats on the periphery of the offset wafer to enable visual confirmation of the offset direction. According to the present invention, since an arbitrary crystal plane can be detected by an optical method, highly accurate marking is possible. Therefore, a method for marking a silicon ingot will be described below, and this is a preferred embodiment of the present invention.
[0047]
FIG. 13 is a perspective view showing a method for marking the (011) plane using the present invention. Hereinafter, a marking method according to a preferred embodiment of the present invention will be described with reference to FIG. In addition, about the component according to each form of this invention mentioned above, the same code | symbol is attached | subjected and description is abbreviate | omitted.
[0048]
The silicon ingot 14 shown in the figure is grown by setting the [bar 100] axis in the top direction of the ingot and [100] in the bottom direction, and tilting these crystal axes 10 with respect to the central axis 12 by 4 °. It is a thing. The direction tilted by 4 °, that is, the offset direction is [001]. As a result, in the (011) family plane, the (0 bar 11) plane and the (011) plane are located on the crystal axis side. It becomes a crystal of type. Therefore, if this silicon ingot 14 is sliced perpendicularly to the central axis 12, an offset wafer having a crystal plane orientation of (100) and an inclination angle of 4 ° in the [001] direction can be obtained. In order to clarify the offset direction of the offset wafer thus obtained, in this embodiment, marking is performed in the [011] direction.
[0049]
In order to perform marking in the [011] direction, it is necessary to detect the (011) plane of the silicon ingot 14. Accordingly, first, a cross section when the silicon ingot 14 is vertically divided into two along the central axis 12 is assumed, and a normal line 32 orthogonal to the ingot central cross section 30, an X-ray incident beam 20, and an X-ray reflected beam are assumed. The X-ray incident means 16 and the X-ray light-receiving means 18 are arranged at a position where 22 is on the same plane. At this time, the X-ray incident means 16 and the X-ray light receiving means 18 are arranged at a position satisfying the Bragg condition with respect to the (011) family plane, that is, a position inclined by the Bragg angle θ with respect to the ingot center section 30. This arrangement corresponds to the above-described “position where the Bragg condition is satisfied with respect to the selected family plane when it is assumed that the crystal axis 10 and the central axis 12 coincide with each other”.
[0050]
Then, the central shaft 12 of the silicon ingot 14 is vacuum chucked, and the rotating device 34 is installed on the central shaft 12. The rotating device 34 can rotate the silicon ingot 14 with an accuracy of 1 ° / 1,000. A controller 36 that numerically controls the rotating device 34 is connected to the rotating device 34. The controller 36 controls the rotational accuracy of the rotating device 34, and the rotation amount of the silicon ingot 14 and the X-ray light receiving means 18. Is stored in correspondence with the diffraction intensity of the received X-rays.
[0051]
FIG. 14 is a conceptual diagram showing a process of setting a light receiving region of the X-ray light receiving means 18 shown in FIG. As shown in the figure, the light receiving region 28 of the X-ray light receiving means 18 includes both a first reflected light path 26-1 and a third reflected light path 26-3. This is because since the offset angle of the crystal axis is as small as 4 °, the fluctuation of the reflected light path is also small. Therefore, if the light receiving region 28 of the X-ray light receiving unit 18 is used as it is, the first reflected light path 26-1 and the third reflected light path 26-3 cannot be distinguished. Therefore, in the step of setting the light receiving region, the mask 38 is covered with a part of the third reflected light path 26-3 to discriminate between the surface located on the crystal axis 10 side and the surface located on the central axis 12 side. Turn into. Specifically, as shown in the graph shown in the lower left of the figure, the X-ray diffraction intensities of the (0 bar 11) plane and (011) plane located on the crystal axis 10 side are located on the central axis 12 side (01 bar). 1) A mask 38 is placed at a position where the X-ray diffraction intensity of the surface and the (0 bar 1 bar 1) surface is greater. The peak difference in X-ray diffraction intensity is preferably about twice. The ratio of this peak difference is determined by actually performing X-ray irradiation while rotating the silicon ingot 14 clockwise toward the [Bar 100] axis.
[0052]
FIG. 15 is a conceptual diagram showing steps of (011) plane detection and marking. As shown in the figure, first, the silicon ingot 14 is rotated 360 ° with a relatively coarse accuracy, and the first light receiving pattern obtained as a result of the first rotation is set to a diffraction intensity of about 30%. Compare with -1. When there are four peaks exceeding the first threshold value 40-1, it is determined that the crystal axis 10 of the rotated silicon ingot 14 is [bar 100], and the second rotation is performed. I do. On the other hand, when the number of peaks exceeding the first threshold value 40-1 is not four, marking on the silicon ingot 14 is stopped.
[0053]
Similar to the first rotation, the second rotation is performed with a relatively coarse accuracy, and the light receiving pattern obtained as a result of the rotation is compared with the second threshold value 40-2 set to around 70% diffraction intensity. If there are two peaks exceeding the second threshold value 40-2, it is determined that the rotated silicon ingot 14 is of the H offset type, and the third rotation is performed. On the other hand, when the number of peaks exceeding the second threshold value 40-2 is not two, the marking on the silicon ingot 14 is stopped.
[0054]
The third rotation is performed with high accuracy aiming for the second peak corresponding to the position of the (011) plane. When the second peak is obtained, the rotation amount corresponding to the center of the peak is obtained. The center value C of the peak is

Where: C = center rotation amount; A = first intersection of the second peak and the second threshold 40-2; B = second peak and the second threshold 40-2 Next intersection;
Calculate using the above formula. Then, by operating the rotating device 34, the silicon ingot 14 is returned to the detected position of the second peak obtained above, and marking is performed at this position.
[0055]
In the embodiment described above, the process from chucking the silicon ingot 14 to marking is performed automatically. This embodiment is currently being implemented, but so far no malfunctions have occurred due to detection errors.
[0056]
In the above embodiment, the first threshold value 40-1 is set to the diffraction intensity of 70%, and the second threshold value is set to the diffraction intensity of 30%. Decide accordingly. That is, the first threshold value 40-1 is set to a value that captures all peaks of the (011) family plane, and the second threshold value 40-2 is centered on the plane located on the crystal axis 10 side. What is necessary is just to set to the value which can distinguish from the surface located in the axis | shaft 12 side.
[0057]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a silicon ingot crystal orientation detection method that is effective in improving detection accuracy and automating the detection process.
[0058]
In addition, according to the first embodiment of the present invention, since the X-ray reflection direction varies even in the same family plane, the position of the crystal plane in the silicon ingot can be grasped as the X-ray light receiving pattern. . As a result, an arbitrary crystal plane can be detected.
[0059]
Further, according to the second embodiment of the present invention, since the arrangement of the X-ray light receiving means is determined on the assumption that there is no offset, the apparatus for detecting a crystal plane of an ingot having no offset is also provided. The present invention can be applied. That is, the principle of the present invention can be applied by shifting the light receiving area without changing the arrangement of the X-ray light receiving means.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a three-dimensional configuration of a typical crystal plane of a silicon crystal body.
FIG. 2 is a schematic front view showing a crystal plane surrounding a [100] axis of a silicon crystal body.
FIG. 3 is a schematic perspective view showing a concept of selecting a (011) family using flag conditions.
FIG. 4 is a schematic perspective view showing a concept of H offset of a rotation shaft.
5 is a schematic side view showing a direction in which X-ray diffracted light is reflected in the case of H offset, which is a view from V in FIG.
FIG. 6 is a schematic perspective view showing a concept of J offset of a rotation shaft.
FIG. 7 is a schematic side view showing the direction in which X-ray diffracted light is reflected in the case of J offset in the VII view of FIG.
FIG. 8 is a schematic perspective view showing a crystal plane detection method according to the first embodiment of the present invention.
FIG. 9 is a conceptual diagram showing an X-ray light receiving pattern in the case of H offset.
FIG. 10 is a conceptual diagram showing an X-ray light receiving pattern in the case of J offset.
FIG. 11 is a schematic side view showing a crystal plane detection method according to the second embodiment of the present invention.
FIG. 12 is a conceptual diagram showing an X-ray light receiving pattern of J offset according to the second embodiment of the present invention.
FIG. 13 is a perspective view showing a method for marking the (011) plane using the present invention.
14 is a conceptual diagram showing a process of setting a light receiving region of the X-ray light receiving means 18 shown in FIG.
FIG. 15 is a conceptual diagram showing steps of (011) plane detection and marking.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Crystal axis, 12 ... Center axis, 14 ... Silicon ingot, 16 ... X-ray incident means, 18 ... X-ray light-receiving means, 20 ... X-ray incident beam, 22 ... X-ray reflected beam, 24 ... Incident optical path, 26- DESCRIPTION OF SYMBOLS 1 ... 1st reflected light path, 26-2 ... 2nd reflected light path, 26-3 ... 3rd reflected light path, 28 ... Light-receiving area, 30 ... Ingot center cross section, 32 ... Normal, 34 ... Rotating device, 36 ... Controller, 38 ... Mask, 40-1 ... First threshold value, 40-2 ... Second threshold value,

Claims (1)

A method for detecting a crystal orientation of a silicon ingot (14) having a crystal axis (10) having an offset relative to a central axis (12),
Selecting one family plane of a plurality of crystal planes surrounding the crystal axis;
Selecting one crystal face of the selected family face;
An X-ray incident means (16) and an X-ray light receiving means (18) are arranged at a position where the Bragg condition is established with respect to the selected crystal plane, and further output from the X-ray incident means (16) and the selected one. Disposing the X-ray receiving means (18) at a position where only the X-ray reflected beam (22) reflected by the crystal plane can be selectively received;
The X-ray incident beam (20) is incident on the silicon ingot using the X-ray incident means while rotating the silicon ingot around the central axis, and the X-ray reflected beam (22) obtained as a result is incident on the silicon ingot. Receiving the light by the X-ray light receiving means;
Identifying the crystal orientation of the silicon ingot based on the intensity of the received X-ray reflected beam and the amount of rotation of the silicon ingot when the X-ray reflected beam is received. Direction detection method.

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