JP3976709B2

JP3976709B2 - Monitor device and polishing device

Info

Publication number: JP3976709B2
Application number: JP2003160252A
Authority: JP
Inventors: 治男白鳥
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 2003-06-05
Filing date: 2003-06-05
Publication date: 2007-09-19
Anticipated expiration: 2022-09-19
Also published as: JP2004104082A

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体ウエハ、特にＳＯＩ(Silicon-on-Insulator)ウエハ等の膜付きウエハの研磨に用いられるモニタ装置及び研磨装置に関する。
【０００２】
【従来の技術】
半導体ウエハ研磨では、上面に研磨布が張り付けられた定盤を回転させ、研磨布上に研磨液を滴下しながら、研磨布にウエハ支持板に固定したウエハを、ウエハ支持板により回転させつつ押し付けて、ウエハと研磨布との摩擦により研磨を進行させる方法が広く用いられている。この方法において、研磨加工量は通常、定盤の回転速度、研磨荷重、研磨液の供給量及びその温度、ウエハの回転及び揺動、等が厳しく管理された条件下で、研磨時間によって調節される。
【０００３】
研磨によるウエハ厚さの減少量と研磨時間とから平均の加工速度を求め、研磨時間の決定に用いる。通常のウエハ研磨においては、加工速度の測定はこの方法以外になく、又諸条件の変動がもたらす数％の加工速度の変動は実用上支障がないので、この方法で十分であった。
【０００４】
膜付きウエハにもこの研磨方法が適用される。通常のウエハの研磨と比較すると、研磨加工量の変動の許容幅が小さいので、研磨時間で加工量を制御しようとすれば、加工速度のわずかな変動も許さないような厳しい工程管理が必要となる。この種の研磨では膜の厚さの調節がその主な目的であって、研磨加工量の制御はその手段に過ぎない。膜の厚さは肉眼による干渉縞の観察あるいは光学的な測定によって知ることが出来るので、実験的な研磨では、研磨を時々中断して、膜厚を確認しながら研磨終了の時期を決めるのが一般的である。
【０００５】
この方法は失敗の少ない安全な方法であるが、生産のための方法としては問題が多い。即ち、研磨を中断する度にウエハの洗浄、乾燥が必要なため、１枚当たりの処理時間が長く、自動化のための機構が複雑となり研磨費用が高くなる問題がある。又、中断と中断の間の時間が短くなると、定常状態の研磨と条件が異なってくるため、予期した研磨加工量が得られず、かえって制御性が悪化してしまうという問題があった。
【０００６】
【発明が解決しようとする課題】
本発明は、研磨途中でウエハを定盤から離すことなく研磨中の膜の厚さを知ることができ、研磨の高精度な制御が効率よくできるウエハの研磨に用いられるモニタ装置及び研磨装置を提供することを課題とする。
【０００７】
【課題を解決するための手段】
本発明による課題を解決するための手段は、
（１）回転する定盤の研磨部材が設けられた面に、ウエハを接触させて研磨する際に、研磨を停止しないでウエハ研磨面の光反射状態を確認するモニタ装置であり、前記研磨部材に設けられた光透過性窓と、前記研磨部材または、前記定盤または、前記研磨部材及び前記定盤に設けられた研磨液封止部材からなるウィンドウが前記定盤の回転に伴って移動する回転路上に前記ウエハが位置し、前記ウィンドウが前記ウエハの下を通過するときに、研磨中の前記ウエハが押し付けられた研磨部材の領域により取り囲まれ、かつ前記ウィンドウと対向する前記ウエハ研磨面上の小領域の光反射状態を、前記ウィンドウを通して、かつ前記研磨液封止部材と前記小領域との間に保持される研磨液の膜を通して確認するモニタ装置、
（２）確認した前記ウエハ研磨面の光反射状態から研磨の終点を決定することを特徴とする上記のモニタ装置、
（３）前記ウエハが膜付きウエハであり、該膜付きウエハの膜面が研磨され、前記ウエハ研磨面の光反射状態が前記膜面の光反射状態であることを特徴とする上記のモニタ装置、
（４）回転する定盤の研磨部材が設けられた面に、ウエハを接触させて研磨する研磨装置において、前記研磨部材に設けられた光透過性窓と、前記研磨部材または、前記定盤または、前記研磨部材及び前記定盤に設けられた研磨液封止部材からなるウィンドウが前記定盤の回転に伴って移動する回転路上に前記ウエハが位置し、前記ウィンドウが前記ウエハの下を通過するときに、研磨中の前記ウエハが押し付けられた研磨部材の領域により取り囲まれ、かつ前記ウィンドウと対向する前記ウエハ研磨面上の小領域の光反射状態を、前記ウィンドウを通して、かつ前記研磨液封止部材と前記小領域との間に保持される研磨液の膜を通して研磨を停止しないで確認するモニタ装置が設けられていることを特徴とする研磨装置、
（５）前記モニタ装置が確認した前記ウエハ研磨面の光反射状態から研磨の終点を決定することを特徴とする上記の研磨装置、
（６）前記ウエハが膜付きウエハであり、該膜付きウエハの膜面が研磨され、前記モニタ装置が確認する前記ウエハ研磨面の光反射状態が前記膜面の光反射状態であることを特徴とする上記の研磨装置、
にある。
【０００８】
また、特許請求の範囲の請求項としては記載しないが、本発明の別な態様として、
(7)回転する定盤の研磨布の張り付けられた面に、研磨液を滴下しつつ、ウエハ支持板に固定したウエハをウエハ支持板により回転させつつ押し付け研磨する方法において、定盤及び研磨布の回転中心と周縁との間に設けた窓からウエハの研磨面の光の反射状態を見て研磨状態を判定するウエハ研磨方法、
(8)光の反射状態を電荷結合素子を用いた撮像装置とその撮像表示装置で見るか、分光反射率測定装置で見る上記の方法、
(9)回転装置により回転する定盤と、定盤の表面に張り付けられた研磨布と、定盤の中心と周縁との間の研磨布に対面し軸方向移動可能に配置され、回転装置により回転するウエハ支持板と、定盤の中心と周縁との間の研磨布張り付け面に半径方向に延長して設けた溝と、該溝と一致させ研磨布に設けた研磨布窓と、定盤の前記溝内に設けた貫通孔と、該貫通孔を閉じる透明窓材と、定盤の前記溝を有する面の反対側で貫通孔の回転路に臨ませ配置した、前記の透明窓材を通して光をウエハ支持板に固定したウエハの研磨面に照射しその反射光を受光するプローブと、該プローブに接続した光ケーブルと、光ケーブルに接続した光ケーブルへの光供給装置と反射光観察又は評価装置とを備えているウエハ研磨装置、
(10)回転装置により回転する透明な材料からなる定盤と、定盤の表面に張り付けられた研磨布と、定盤の中心と周縁との間の研磨布に対面し軸方向移動可能に配置され、回転装置により回転するウエハ支持板と、定盤の中心と周縁との間の研磨布張り付け面に半径方向に延長して設けた溝と、該溝と一致させ研磨布に設けた研磨布窓と、定盤の前記溝を有する面の反対側で前記の溝に臨ませ配置した、前記定盤を通して光をウエハ支持板に固定したウエハの研磨面に照射しその反射光を受光するプローブと、該プローブに接続した光ケーブルと、光ケーブルに接続した光ケーブルへの光供給装置と反射光観察又は評価装置とを備えているウエハ研磨装置、
(11)定盤に設けた溝が中心から放射状に伸びる近接した２本の直線に囲まれた形状をなしている上記のウエハ研磨装置、
(12)反射光観察装置が電荷結合素子を用いた撮像装置とその撮像表示装置とからなるか、反射光評価装置が分光反射率測定装置である上記のウエハ研磨装置、
がある。
【０００９】
【発明の実施の形態】
本発明において、定盤及び研磨布の回転中心と周縁との間に設けた窓からウエハの研磨面の光の反射状態を見て研磨状態を判定すれば、研磨を中断せずに研磨状態の終点を知ることが出来るので、研磨処理の時間を短くでき、装置も簡単で済む。光の反射状態は、光ケーブルでウエハの研磨面に光を照射してその反射光をビデオカメラに用いられている電荷結合素子（ＣＣＤ）を用いた撮像装置で取り、これをブラウン管などの撮像表示装置で表示せしめ、撮像表示装置に現れた干渉縞により厚さを判断する。膜厚の場合、２μｍ以下では旧型の蛍光灯や白熱灯で縞が見え、１μｍ以下では白色灯で虹色の縞が見える。
【００１０】
又、光ケーブルでウエハの研磨面に光を照射してその反射光を分光反射率測定装置に入れ、特定の波長のピークにより所望の厚さになったことを知る。この研磨状態の判定は、研磨中に行っても、研磨を一時停止して行ってもよい。一時停止しても前記の従来の方法よりも研磨終点までの時間は極めて小さくできる。
【００１１】
本発明のウエハ研磨装置において、透明窓材とウエハとの間にできる研磨液の膜を通してウエハの研磨面に照射した光の反射光を観察あるいは評価するのであるが、研磨液は液中に微粒子が懸濁したものであり、光を散乱する性質をもっているので、透明窓材の表面とウエハの研磨面との間の間隔が小さい方が観察あるいは評価に都合がよい。
【００１２】
定盤の中心と周縁との間の研磨布張り付け面に半径方向に延長した溝を設けるのは、研磨布にだけ研磨布窓を設けたのでは、研磨液に空気が混じる恐れがあり、空気が混じると観察が困難となるので、研磨液を十分保持できるようにし、空気が混じらないようにするためである。溝に研磨液を十分保持させるため、この溝や研磨布窓は研磨加工に寄与しない領域となるので、ウエハ面内の加工量分布を乱さない形を選ぶ必要があり、定盤の中心から周辺にウエハの研磨面が同一時間で通過するように、定盤の中心から放射状に伸びる近接した２本の直線に囲まれるようにするのがよい。
【００１３】
このような形状とすれば、研磨中にウエハが圧縮荷重を受けて圧縮されている研磨布上から圧縮されていない研磨布の部分に乗り上げる時に、研磨布窓に引っ掛かったりしないで、研磨布窓よりくぼみを乗り越えて滑らかに研磨布に乗り上げることができる。
【００１４】
透明窓材の溝中における位置及び形状は任意である。観察または測定をウエハの中心で代表させて良い場合には、透明窓材の位置をウエハの回転中心の下に位置させてもよい。
【００１５】
アルミニウムのような光の透過しない材料で定盤が作られている時は上記のように、定盤に貫通孔を設けて研磨液が漏洩しないように透明窓材で貫通孔を閉じて光を通過させるようにするが、透明ガラスのような光の通過する材料で定盤が作られているときは、貫通孔や透明窓材を必要としない。しかし、ウエハの研磨面と、溝底との間隔を小さくするために、光を透過させる部分だけ溝底を高くするのがよい。
【００１６】
光をウエハの研磨面に照射しその反射光を受けるプローブは、研磨を停止して観察又は評価を行う場合は問題はないが、研磨中に観察又は評価を行う場合、定盤の光通過窓は回転しており、ウエハも自転しているので、ウエハの特定場所を正確に観察又は評価するのに時間を必要とするときは、ウエハの自転速度と同じ速度でプローブを光通過窓と同じ回転路において往復運動させればよい。
【００１７】
分光反射率測定装置で膜厚の評価を行う場合には、測定毎に膜厚を計算で求めることが出来るので、研磨の終点を正確に決定できる。研磨中に膜厚計算を行わず、膜が目標の厚さになったときの分光反射率を予め計算で求めておいて、測定した分光反射率の特徴が計算と一致した時点で研磨を終了してもよい。
【００１８】
【実施例】
図１、図２に示した実施例について説明する。定盤１は直径３００ｍｍ、厚さ１０ｍｍのアルミニウム製の円盤で、その中心の片面に定盤１を回転するための軸が固定してある。定盤１の軸を固定した面の反対側の面には、中心から放射状に伸びる近接した２本の直線で囲まれ、中心付近から周縁近くまで伸びた溝２が設けてある。溝２の中心側の幅は５ｍｍで周縁側の幅は１５ｍｍ、深さ１ｍｍとなっている。溝２の長手方向中央には、直径１０ｍｍの貫通孔３が設けられ、溝２の反対側では円錐状に拡大している。貫通孔３の溝２側にはパイレックス（登録商標）透明ガラス製の透明窓材４が嵌め込まれ、研磨液が漏れないようにしてある。
【００１９】
定盤１の溝２を有する面には、定盤１と同形の厚さ０.７ｍｍのローデルニッタ社製、商品名suba−500ウレタン含浸ポリエステル不織布からなる研磨布５が張り付けられ、溝２に相当する部分は溝２と同形に切り抜かれて、研磨布窓６が形成されている。透明窓材４は定盤１の表面より約０.５ｍｍ突出するが、研磨布５の弾性を考慮しても研磨布５の表面より十分低くなっている。
【００２０】
定盤１の溝２の反対側には透明窓材４の回転路に面して研磨するウエハ７の研磨面に光を照射しその反射光を受光するプローブ９が配置されている。プローブ９はピント調節用レンズを内蔵し、光ケーブル１０に接続され、その他端は二股に別れ図示していない分光反射率測定装置と測定用光源に接続されている。
【００２１】
片面に回転用の軸が固定された直径１１０ｍｍ、厚さ１０ｍｍの円盤状のアルミニウム製のウエハ支持板８に、表面に熱酸化膜を形成した２枚のシリコンウエハを、熱酸化膜を接せしめて接着し、一方のウエハを平面研削して厚さ１５μｍのシリコン膜として直径１００ｍｍのＳＯＩウエハを、平面研削加工していない面をワックスで張り付けた。
【００２２】
粒径が０.０１μｍ以下のシリカ粉末を含むアルカリ性溶液からなるローデルニッタ社製、商品名NALCO−2350を２０倍に希釈した研磨液を定盤１の研磨布５の表面に滴下しつつ、定盤１を毎分５０回転させながら、ウエハ支持板８に張り付けたウエハ７を、自転速度毎分４０回転で回転させつつ、研磨布５に、回転中心が透明窓材４の上に位置するように、研磨荷重１０ｋｇｆで押し付けて目標膜厚を１μｍにして研磨を開始した。
【００２３】
この条件では、透明窓材４の移動線速度は約５００ｍｍ／秒なので、直径１０ｍｍの透明窓材４を通してウエハ７の中心を測定出来る時間は、１回の通過に付き約１０ｍ秒である。この時間は、波長範囲６８０〜８００ｎｍ、分解能１ｎｍで行う分光反射率測定に対して十分であった。測定の参照基準には、同じ条件に置いたシリコンウエハを用いた。
【００２４】
研磨開始時、膜の分光反射率は、シリコンウエハと同一のスペクトルを示したが、研磨の進行に伴い反射率の波長に対する周期的な変動が現れ、徐々にその振幅を増した。反射光強度の個々のピークは相互の間隔を狭めながら短波長側へと移行した。個々のピークの移動により、測定波長範囲内のピークが入れ代わるにつれて、ピークの間隔は次第に広がった。
【００２５】
計算によれば、ＳＯＩの厚さ１μｍのシリコン膜の分光反射率は波長７００ｎｍと７７０ｎｍにピークを持つ。そこで、一つのピークの位置が７００ｎｍを下回った時点で次のピークの位置を読み、それが７６５ｎｍ以上であれば研磨を終了するものとし、７６５ｎｍ未満であればその位置を追跡しながら研磨を続行した。
【００２６】
このようにして１０枚のＳＯＩウエハを研磨した結果、総てのウエハにおいて中心の膜厚は０.９８〜１.００μｍの範囲に収まっていた。研磨の所要時間は３０〜４５分の範囲にあった。
【００２７】
比較例
実施例と同様の条件で同一のＳＯＩウエハのシリコン膜の研磨を行った。研磨途中での膜厚の測定は次のように観察により行った。１.研磨液の供給を停止し、研磨布に純水をかけ流した後、定盤及びウエハ支持板の回転を停止する。２.ウエハをウエハ支持板ごと取り上げ純水でゆすいで水を切る。３.照明に照らされた面光源にウエハを映して観察する。４.下記の目安で膜厚を観察する。５.ａ)研磨終了の場合、ウエハ支持板からウエハを外す。ｂ）目標より厚い場合は、研磨を再開、所定時間の後１.へ

正味の研磨時間は３０〜４０分であったが、ウエハ１枚につき２〜４回研磨を中断して膜厚測定を行ったため、平均の研磨時間としては１時間を要した。膜厚測定の結果を元に１０秒単位で研磨終了の時期を決めたが、最終的にウエハ中心の膜厚は０.９〜１.１μｍの範囲に分布した。又、研磨終了時期をこれより細かく調節しても制御性が良くなることはなく、従来法の研磨の限界精度と考えられた。
【００２８】
【発明の効果】
本発明によれば、研磨途中でウエハを定盤から離すことなく研磨中の膜の厚さを知ることができるので、研磨の高精度な制御が効率よくできる。
【図面の簡単な説明】
【図１】本発明のウエハ研磨装置の一部断面側面図である。
【図２】図１の定盤１の一部平面図である。
【符号の説明】
１定盤
２溝
３貫通孔
４透明窓材
５研磨布
６研磨布窓
７ウエハ
８ウエハ支持板
９プローブ
１０光ケーブル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a monitor device and a polishing device used for polishing a semiconductor wafer, particularly a wafer with a film such as an SOI (Silicon-on-Insulator) wafer.
[0002]
[Prior art]
In semiconductor wafer polishing, a surface plate with a polishing cloth affixed to the upper surface is rotated, and while the polishing liquid is dripped onto the polishing cloth, the wafer fixed to the polishing cloth is pressed against the wafer support plate while being rotated by the wafer support plate. Therefore, a method of advancing polishing by friction between a wafer and a polishing cloth is widely used. In this method, the polishing amount is usually adjusted by the polishing time under conditions in which the rotation speed of the platen, polishing load, supply amount and supply temperature of the polishing liquid, rotation and swinging of the wafer, etc. are strictly controlled. The
[0003]
An average processing speed is obtained from the reduction amount of the wafer thickness due to polishing and the polishing time, and is used to determine the polishing time. In normal wafer polishing, there is no measurement of the processing speed other than this method, and the variation in processing speed of several percent caused by the change in various conditions has no practical problem, so this method is sufficient.
[0004]
This polishing method is also applied to a wafer with a film. Compared to normal wafer polishing, the tolerance of fluctuations in the amount of polishing processing is small, so if you want to control the amount of processing with the polishing time, you need strict process control that does not allow slight fluctuations in the processing speed. Become. In this type of polishing, the adjustment of the thickness of the film is the main purpose, and the control of the polishing amount is only the means. The thickness of the film can be determined by observing interference fringes with the naked eye or by optical measurement, so in experimental polishing, it is sometimes necessary to interrupt the polishing from time to time and determine when to finish polishing while checking the film thickness. It is common.
[0005]
Although this method is a safe method with few failures, there are many problems as a method for production. That is, each time polishing is interrupted, the wafer needs to be cleaned and dried, so that the processing time per sheet is long, the automation mechanism is complicated, and the polishing cost is increased. Further, if the time between interruptions is shortened, the conditions differ from those in steady-state polishing, so that the expected polishing amount cannot be obtained, and the controllability is deteriorated.
[0006]
[Problems to be solved by the invention]
The present invention provides a monitor device and a polishing apparatus used for polishing a wafer, which can know the thickness of a film being polished without separating the wafer from the surface plate during polishing, and can efficiently perform high-precision control of polishing. The issue is to provide.
[0007]
[Means for Solving the Problems]
Means for solving the problems according to the present invention include:
(1) A monitor device for confirming a light reflection state of a wafer polishing surface without stopping polishing when the wafer is brought into contact with the surface of the rotating surface plate on which the polishing member is provided, and the polishing member And a window made of the polishing member, the surface plate, or the polishing liquid sealing member provided on the polishing member and the surface plate moves as the surface plate rotates. When the wafer is positioned on a rotation path and the window passes under the wafer, the wafer being polished is surrounded by a region of the polishing member pressed against the wafer and is on the wafer polishing surface facing the window. A monitoring device for confirming the light reflection state of the small area of the liquid crystal through the window and the polishing liquid film held between the polishing liquid sealing member and the small area,
(2) The above monitoring apparatus, wherein an end point of polishing is determined from the light reflection state of the confirmed wafer polishing surface,
(3) The monitor device described above, wherein the wafer is a film-coated wafer, the film surface of the film-coated wafer is polished, and the light reflection state of the wafer polishing surface is the light reflection state of the film surface. ,
(4) In a polishing apparatus for polishing by bringing a wafer into contact with a surface of a rotating surface plate on which a polishing member is provided, a light transmissive window provided on the polishing member, the polishing member, or the surface plate or The wafer is positioned on a rotation path in which a window composed of the polishing member and a polishing liquid sealing member provided on the surface plate moves as the surface plate rotates, and the window passes under the wafer. Sometimes the light reflecting state of a small area on the wafer polishing surface which is surrounded by the area of the polishing member pressed against the wafer being polished and which faces the window is passed through the window and sealed with the polishing liquid. A polishing apparatus, characterized in that a monitoring device is provided for confirming without stopping polishing through a film of polishing liquid held between the member and the small region;
(5) The above polishing apparatus, wherein the polishing end point is determined from the light reflection state of the wafer polishing surface confirmed by the monitor device,
(6) The wafer is a film-coated wafer, the film surface of the film-coated wafer is polished, and the light reflection state of the wafer polishing surface confirmed by the monitor device is the light reflection state of the film surface. The above polishing apparatus,
It is in.
[0008]
Moreover, although not described as a claim in the scope of claims, as another aspect of the present invention,
(7) A surface plate and a polishing cloth in a method in which a polishing liquid is dropped on a surface of a rotating surface plate attached to a polishing cloth and a wafer fixed to the wafer support plate is pressed and polished while being rotated by the wafer support plate. A wafer polishing method for judging a polishing state by looking at a reflection state of light on a polishing surface of a wafer from a window provided between a rotation center and a peripheral edge of
(8) The above method of viewing the reflection state of light with an imaging device using a charge coupled device and its imaging display device, or with a spectral reflectance measurement device,
(9) A surface plate that is rotated by a rotating device, an abrasive cloth affixed to the surface of the surface plate, and an abrasive cloth between the center and the periphery of the surface plate are arranged so as to be movable in the axial direction. A rotating wafer support plate, a groove extending in a radial direction on a polishing cloth attaching surface between a center and a peripheral edge of the surface plate, a polishing cloth window provided on the polishing cloth so as to coincide with the groove, and a surface plate A through-hole provided in the groove, a transparent window member that closes the through-hole, and the transparent window member that is disposed facing the rotation path of the through-hole on the opposite side of the surface of the surface plate having the groove. A probe for irradiating the polished surface of the wafer fixed to the wafer support plate and receiving the reflected light; an optical cable connected to the probe; a light supply device to the optical cable connected to the optical cable; and a reflected light observation or evaluation device; A wafer polishing apparatus comprising:
(10) A surface plate made of a transparent material rotated by a rotating device, an abrasive cloth affixed to the surface of the surface plate, and an abrasive cloth between the center and the periphery of the surface plate so as to be movable in the axial direction. A wafer support plate that is rotated by a rotating device, a groove provided in a radial direction on a polishing cloth attaching surface between a center and a peripheral edge of the surface plate, and a polishing cloth provided on the polishing cloth so as to coincide with the groove A probe that irradiates the polishing surface of the wafer fixed to the wafer support plate through the surface plate and receives the reflected light, which is arranged facing the groove on the opposite side of the window and the surface having the groove of the surface plate. A wafer polishing apparatus comprising: an optical cable connected to the probe; a light supply device to the optical cable connected to the optical cable; and a reflected light observation or evaluation device.
(11) The wafer polishing apparatus described above, wherein the groove provided on the surface plate has a shape surrounded by two adjacent straight lines extending radially from the center,
(12) The above wafer polishing apparatus, in which the reflected light observation device is composed of an imaging device using a charge coupled device and its imaging display device, or the reflected light evaluation device is a spectral reflectance measurement device,
There is.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, if the polishing state is judged by observing the light reflection state of the polishing surface of the wafer from the window provided between the rotation center and the periphery of the surface plate and the polishing cloth, the polishing state is not interrupted without interruption. Since the end point can be known, the polishing process time can be shortened and the apparatus can be simplified. The light reflection state is obtained by irradiating the polished surface of the wafer with an optical cable and taking the reflected light with an imaging device using a charge-coupled device (CCD) used in a video camera, which is displayed on an imaging display such as a cathode ray tube. The thickness is determined by the interference fringes appearing on the imaging display device. When the film thickness is 2 μm or less, stripes can be seen with old fluorescent lamps and incandescent lamps, and when it is 1 μm or less, rainbow-colored stripes can be seen with white lights.
[0010]
Further, light is irradiated onto the polished surface of the wafer with an optical cable, and the reflected light is put into a spectral reflectance measuring device, and it is known that the desired thickness is obtained due to a specific wavelength peak. The determination of the polishing state may be performed during polishing or may be performed after the polishing is temporarily stopped. Even if it is temporarily stopped, the time until the polishing end point can be made extremely smaller than that of the conventional method.
[0011]
In the wafer polishing apparatus of the present invention, the reflected light of the light irradiated on the polishing surface of the wafer through the film of polishing liquid formed between the transparent window material and the wafer is observed or evaluated. Is suspended and has the property of scattering light. Therefore, it is convenient for observation or evaluation that the distance between the surface of the transparent window member and the polished surface of the wafer is small.
[0012]
The groove extending in the radial direction is provided on the polishing cloth application surface between the center and the periphery of the surface plate. If the polishing cloth window is provided only on the polishing cloth, air may be mixed into the polishing liquid. This is because it becomes difficult to observe if there is a mixture of particles, so that the polishing liquid can be sufficiently retained and air is not mixed. Since this groove and polishing cloth window are areas that do not contribute to the polishing process in order to hold the polishing liquid sufficiently in the groove, it is necessary to select a shape that does not disturb the processing amount distribution in the wafer surface, from the center of the surface plate to the periphery In addition, it is preferable that the wafer is surrounded by two adjacent straight lines extending radially from the center of the surface plate so that the polishing surface of the wafer passes in the same time.
[0013]
With such a shape, the polishing cloth window does not get caught in the polishing cloth window when it rides on the uncompressed polishing cloth portion from the polishing cloth that is compressed under the compressive load during polishing. You can get over the dent more smoothly and get on the polishing cloth.
[0014]
The position and shape in the groove | channel of a transparent window material are arbitrary. When observation or measurement may be represented by the center of the wafer, the position of the transparent window material may be positioned below the center of rotation of the wafer.
[0015]
When the surface plate is made of a material that does not transmit light such as aluminum, as described above, the through hole is provided in the surface plate and the through hole is closed with a transparent window material so that the polishing liquid does not leak. However, when the surface plate is made of a material through which light passes, such as transparent glass, no through hole or transparent window material is required. However, in order to reduce the distance between the polishing surface of the wafer and the groove bottom, it is preferable that the groove bottom is raised only in the portion that transmits light.
[0016]
There is no problem with a probe that irradiates light onto the polished surface of the wafer and receives the reflected light. When the observation or evaluation is performed after the polishing is stopped, there is no problem. Since the wafer is rotating and the wafer is rotating, when it takes time to accurately observe or evaluate a specific location of the wafer, the probe is moved at the same speed as the rotation speed of the wafer and is the same as the light passage window. What is necessary is just to make it reciprocate in a rotation path.
[0017]
When the film thickness is evaluated with the spectral reflectance measuring device, the film thickness can be obtained by calculation for each measurement, so that the polishing end point can be accurately determined. Without calculating the film thickness during polishing, the spectral reflectance when the film reaches the target thickness is calculated in advance, and the polishing is finished when the measured spectral reflectance characteristics match the calculation. May be.
[0018]
【Example】
The embodiment shown in FIGS. 1 and 2 will be described. The surface plate 1 is an aluminum disk having a diameter of 300 mm and a thickness of 10 mm, and a shaft for rotating the surface plate 1 is fixed to one surface at the center. On the surface opposite to the surface on which the axis of the surface plate 1 is fixed, a groove 2 is provided which is surrounded by two adjacent straight lines extending radially from the center and extending from near the center to near the periphery. The width on the center side of the groove 2 is 5 mm, the width on the peripheral side is 15 mm, and the depth is 1 mm. A through hole 3 having a diameter of 10 mm is provided at the center in the longitudinal direction of the groove 2, and is expanded conically on the opposite side of the groove 2. A transparent window material 4 made of Pyrex ( registered trademark ) transparent glass is fitted into the groove 2 side of the through hole 3 so that the polishing liquid does not leak.
[0019]
The surface of the surface plate 1 having the groove 2 is affixed with a polishing cloth 5 made of Rodernitta, which has the same shape as the surface plate 1 and having a thickness of 0.7 mm and made of a non-woven polyester fabric impregnated with urethane-500. The portion to be cut is cut out in the same shape as the groove 2 to form a polishing cloth window 6. The transparent window member 4 protrudes about 0.5 mm from the surface of the surface plate 1, but is sufficiently lower than the surface of the polishing pad 5 even when the elasticity of the polishing pad 5 is taken into consideration.
[0020]
A probe 9 is disposed on the opposite side of the groove 2 of the surface plate 1 to irradiate the polishing surface of the wafer 7 that faces the rotation path of the transparent window member 4 and receives the reflected light. The probe 9 incorporates a focus adjustment lens and is connected to an optical cable 10, and the other end is bifurcated and connected to a spectral reflectance measurement device and a measurement light source (not shown).
[0021]
Two silicon wafers with a thermal oxide film formed on the surface are brought into contact with a disk-shaped aluminum wafer support plate 8 having a diameter of 110 mm and a thickness of 10 mm with a rotation shaft fixed on one side. Then, one wafer was subjected to surface grinding, and an SOI wafer having a diameter of 100 mm as a silicon film having a thickness of 15 μm was pasted with wax on the surface not subjected to surface grinding.
[0022]
A surface plate is prepared by dripping a polishing solution, which is manufactured by Rodel Nitta Co., Ltd. made of an alkaline solution containing silica powder having a particle size of 0.01 μm or less, diluted 20 times with the trade name NALCO-2350 onto the surface of the polishing cloth 5 of the surface plate 1 While rotating 1 at 50 rotations per minute, while rotating the wafer 7 attached to the wafer support plate 8 at a rotation speed of 40 rotations per minute, the center of rotation is positioned on the transparent window 4 on the polishing pad 5. Then, the polishing was started at a target film thickness of 1 μm by pressing with a polishing load of 10 kgf.
[0023]
Under this condition, the moving linear velocity of the transparent window material 4 is about 500 mm / second, so the time during which the center of the wafer 7 can be measured through the transparent window material 4 having a diameter of 10 mm is about 10 milliseconds per pass. This time was sufficient for the spectral reflectance measurement performed in the wavelength range of 680 to 800 nm and the resolution of 1 nm. A silicon wafer placed under the same conditions was used as a reference standard for measurement.
[0024]
At the start of polishing, the spectral reflectance of the film showed the same spectrum as that of the silicon wafer, but as the polishing progressed, periodic fluctuations with respect to the wavelength of the reflectance appeared, and the amplitude gradually increased. The individual peaks of reflected light intensity shifted to the short wavelength side while narrowing the mutual interval. As the peaks in the measurement wavelength range were replaced by movement of individual peaks, the peak spacing gradually increased.
[0025]
According to the calculation, the spectral reflectance of the silicon film having an SOI thickness of 1 μm has peaks at wavelengths of 700 nm and 770 nm. Therefore, when the position of one peak falls below 700 nm, the position of the next peak is read. If it is 765 nm or more, polishing is terminated. If it is less than 765 nm, polishing is continued while tracking the position. did.
[0026]
As a result of polishing 10 SOI wafers in this way, the central film thickness of all the wafers was within the range of 0.98 to 1.00 μm. The time required for polishing was in the range of 30 to 45 minutes.
[0027]
Comparative Example The silicon film of the same SOI wafer was polished under the same conditions as in the example. The film thickness during polishing was measured by observation as follows. 1. Stop supplying the polishing liquid, pour pure water over the polishing cloth, and then stop the rotation of the surface plate and the wafer support plate. 2. Pick up the wafer together with the wafer support plate, rinse with pure water and drain the water. 3. The wafer is projected on a surface light source illuminated by illumination and observed. 4. Observe the film thickness according to the following guidelines. 5. a) When polishing is completed, remove the wafer from the wafer support plate. b) If it is thicker than the target, resume polishing and go to 1. after a predetermined time.

Although the net polishing time was 30 to 40 minutes, the average polishing time was 1 hour because polishing was interrupted 2 to 4 times per wafer and the film thickness was measured. The time for finishing polishing was determined in units of 10 seconds based on the results of film thickness measurement. Finally, the film thickness at the center of the wafer was distributed in the range of 0.9 to 1.1 μm. Further, even if the polishing end time is adjusted more finely than this, the controllability is not improved, which is considered to be the limit accuracy of the conventional method.
[0028]
【The invention's effect】
According to the present invention, since the thickness of the film being polished can be known without separating the wafer from the surface plate during polishing, high-precision control of polishing can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional side view of a wafer polishing apparatus of the present invention.
FIG. 2 is a partial plan view of the surface plate 1 of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surface plate 2 Groove 3 Through-hole 4 Transparent window material 5 Polishing cloth 6 Polishing cloth window 7 Wafer 8 Wafer support plate 9 Probe 10 Optical cable

Claims

When the wafer is brought into contact with the surface of the rotating surface plate where the polishing member is provided, it is a monitoring device for checking the light reflection state of the wafer polishing surface without stopping the polishing, and is provided on the polishing member. A window made of a light transmissive window and the polishing member, the surface plate, or a polishing liquid sealing member provided on the polishing member and the surface plate moves on a rotation path along with the rotation of the surface plate. When the wafer is located and the window passes under the wafer,
The light reflection state of a small area on the wafer polishing surface that is surrounded by the area of the polishing member pressed against the wafer being polished and that faces the window is passed through the window and the polishing liquid sealing member and the A monitoring device that confirms through a film of polishing liquid held between small areas.

The monitoring apparatus according to claim 1, wherein an end point of polishing is determined from the confirmed light reflection state of the wafer polishing surface.

The said wafer is a wafer with a film | membrane, the film | membrane surface of this wafer with a film | membrane is grind | polished, The light reflection state of the said wafer polishing surface is a light reflection state of the said film | membrane surface, The Claim 1 or 2 characterized by the above-mentioned. Monitoring device.

In a polishing apparatus for polishing by bringing a wafer into contact with a surface of a rotating platen on which a polishing member is provided, a light transmissive window provided on the polishing member, the polishing member, the platen, or the polishing When the wafer is positioned on a rotation path in which a window composed of a member and a polishing liquid sealing member provided on the surface plate moves along with the rotation of the surface plate, and when the window passes under the wafer,
The light reflection state of a small area on the wafer polishing surface that is surrounded by the area of the polishing member pressed against the wafer being polished and that faces the window is passed through the window and the polishing liquid sealing member and the A polishing apparatus, characterized in that a monitoring device for checking without stopping polishing through a film of polishing liquid held between the small area and a small region is provided.

The polishing apparatus according to claim 4, wherein an end point of polishing is determined from a light reflection state of the wafer polishing surface confirmed by the monitor device.

The wafer is a film-coated wafer, a film surface of the film-coated wafer is polished, and a light reflection state of the wafer polishing surface confirmed by the monitor device is a light reflection state of the film surface. Item 6. The polishing apparatus according to Item 4 or 5.