JP3647120B2 - Scanning exposure apparatus and method, and device manufacturing method - Google Patents

Description

したがって、この変換後の座標と変換前の座標との距離を計算し、かかる距離を露光エリア内の各点について発光ごとに加算し、その加算結果に対してしきい値を設けて露光不良を判断する方法や、かかる露光エリア内各点での加算結果の総和に対してしきい値を設けて露光不良を判断する方法などが考えられる。また、かかる距離の各点での加算結果に対してしきい値を設けて露光不良を判断する方法では、しきい値を超過するとその露光エリア全てを不良とするのではなく、露光エリア面内での露光不良領域を限定することができる。このため、露光エリア内でも露光不良の部分を含むチップのみを不良とすれば良くなるので、半導体チップの製造効率がさらに良くなると考えられる。なお、ここで用いた、誤差Δｘ、Δｙおよびω_Ｚは、それぞれいくつかの測定点を使用し、それらの値を平均化するなどの方法で求めた最適な値である。
【００２４】
レイヤ間の露光不良判定については、ショット上の同一位置におけるレチクル、ウエハ間の同期ずれから上述の判断基準などにより、その位置における露光状況を判断すればよい。
【００２５】
次に、別の露光不良判定方法を示す。半導体チップを露光する際に、レチクル・ウエハ間の距離のずれは、光学系の焦点距離のずれを生じさせ、露光誤差につながる。この焦点距離のずれは、露光装置でパターンを形成していく上で、そのパターンの鮮明さを左右することとなる。そして、半導体チップの露光誤差をパルス光の発光タイミングに同期させて検出するときに、焦点距離に作用する誤差Ｚ、Ｘ軸回りの回転誤差ω_Ｘ、Ｙ軸回りの回転誤差ω_Ｙなどを考慮して、露光不良を判定することが考えられる。その判定方法としては、それぞれの方向に対する誤差の絶対値を足していき、その和があらかじめ設けたしきい値を超過するかどうかを調べ、超過する場合は露光不良とすることも考えられる。また、計算の簡素化のため、それぞれの方向に対する誤差と、あらかじめ設けたそれぞれの方向の誤差しきい値とを比較し、そのしきい値を超過する場合にはその部分の露光を不良とすることが考えられる。さらには、ウエハ面の座標系を、スキャン方向をＸ、スリット長手方向をＹ、これらそれぞれの方向を軸とする回転方向をω_Ｘおよびω_Ｙ、ＸとＹとからなる平面の法線方向をＺとしたときに、ウエハの座標系にω_Ｘおよびω_Ｙなる回転誤差が加わったとすると、数２式の座標変換が作用すると考えられる。
【００２６】
【数２】

である。
【００２７】
誤差の入る前のウエハ面をＺ＝０とすると、回転誤差とＺ軸方向の誤差Δｚが入った後のウエハ面は数３式となる。
【００２８】
【数３】

したがって、露光エリア上の座標を数３式に代入し、フォーカス方向の距離（誤差）を求めてその誤差に対してしきい値を設ける方法、露光エリアの各点の誤差を足していき、その和に対してしきい値を設ける方法なども考えることができる。
【００２９】
なお、ここで用いた、誤差Δｚ、ω_Ｘおよびω_Ｙは、それぞれいくつかの測定点を使用し、それらの値を平均化するなどの方法で求めた最適な値である。
【００３０】
さらに別の露光不良判定方法を示す。半導体露光装置において、ウエハ面上の露光量はウエハに焼き付けるパターンの線幅などに影響するため、均一にしなくてはならない。図５は、パルス光源を使用した走査型半導体露光装置のウエハ上への露光量の与え方を示したものである。図５中の階段状の部分の一段一段は、スリット形状をしたパルス光を示しており、その横方向位置は露光フィールド上の位置、縦の長さはパルス光の強度を表している。図５下図のように、パルス光の発光強度とそのときの発光位置に誤差がない場合には、理想的な露光が行われ、ウエハ面上には均一な露光量を与えることができる。図５上図は、理想的な露光状態ではない場合を示したものであり、図５左上図は発光位置が少しずれた場合の露光状態を示しており、図５右上図はパルス光の発光強度が他のパルスの発光強度からずれた場合を表したものである。発光位置誤差の要因としては、レチクルステージとウエハステージの同期ずれやそれに伴う機械的なノイズなどに起因するパルス光の発光位置誤差などが、ウエハ面上での露光量を変動させる原因として考えられる。その位置誤差の方向としては、スキャン方向Ｘ、スリット長手方向Ｙ、フォーカス方向Ｚと、それぞれの方向軸に対する回転誤差ω_Ｘ、ω_Ｙ、ω_Ｚ等が考えられる。したがって、実際に走査型半導体露光装置を使用する場合は、パルス光ごとの発光強度およびそのパルス光の発光位置をパルス光の発光に同期させて検出し、それらに含まれた誤差を考慮して常にウエハ面上での露光状況を把握し、露光量誤差を常に計算しておく必要がある。静止型露光装置における露光量誤差の観点では、パルス光の発光強度のばらつきだけが露光量誤差を与える要因として考えられるので、強度誤差のみを考慮すればよい。
【００３１】
半導体露光プロセスの順番では、露光のための位置決めが行われた後で露光（パルス光の発光）を行うので、良好な露光を行うためには、露光位置についての誤差を算出し、その誤差による影響を打ち消すように露光光量の制御を行い、その部位の露光量誤差を許容値以下にすることを考慮しなくてはならない。しかし、位置誤差が大きく、露光量を制御することでその部位の露光量誤差を許容値以下にすることができない場合や、発光位置誤差は許容範囲内にあるが、発光した結果、その強度の誤差が大きく、次回以降の発光によりその誤差を補正することができない場合は、その部位を露光不良であると判定し、その露光不良部位を記憶しておき、その情報をチップの良否を判定する場合に使用する。
【００３２】
図６は、露光不良を判定するようにした１つの露光フィールドに対する露光処理のフローチャートである。同図に示すように、露光処理を開始すると、レチクルステージおよびウエハステージを移動させて露光領域に達すると、移動した位置の確認を行う（ステップＳ６１）。このときの確認事項として、Ｘ、Ｙ、Ｚ、ω_Ｘ、ω_Ｙおよびω_Ｚを計測する。そして、計測した移動位置を考慮して次回のパルス光の発光強度を計算する（ステップＳ６２）。そして、次回の発光強度を制御することによって、要求される露光誤差を満たすことができるかどうかを判断し（ステップＳ６３）、満たす場合は発光強度の計算結果に基づいてパルス光を発光させる（ステップＳ６４）。そのときのパルス光にはばらつきがあるので、そのばらつきによる発光強度を確認し（ステップＳ６５）、その誤差とステージの位置決め誤差等の誤差を加味して次回のパルス光により、前回生じた露光誤差を許容された誤差範囲内に修正することができるかどうかを判断する（ステップＳ６６）。ステップＳ６３またはＳ６６において、要求される露光誤差を満たすことができないか、修正不能と判断された場合は、その露光不良位置を記憶し（ステップＳ６７）、ステップＳ６８へ進む。ステップＳ６６において修正不能と判断されたときはただちにステップＳ６８へ進む。ステップＳ６８では、次の露光位置へレチクル・ウエハステージを移動する。そして、全ての露光が終了したかどうかを判断し（ステップＳ６９）、終了している場合は露光動作を終了する。終了していない場合は、ステップＳ６１に戻る。
【００３３】
パルス光源を用いた半導体露光装置の露光の可否を判断するときには、以上に示した誤差評価基準を独立させて採用することは事実上できないので、少なくとも２つの評価基準を組み合わせて判断することも考えられる。その際には、それらの判断基準について適切な重み等を付加して、それぞれの誤差を複合的に評価する露光不良判別法も考えられる。
【００３４】
次に、マスキングブレードとステージ系の同期誤差から露光不良と判定することも考えられる。走査露光時にはレチクルステージに照射するビーム形状の整形、ビーム照射領域の確定をするために、レチクルステージの移動すなわちレチクルの移動に同期させて、マスキングブレードを移動させる。しかし、マスキングブレードとレチクルステージとの間に同期誤差があると、それに起因する露光不良が発生する。そこで、マスキングブレードとレチクルステージの相対位置を走査露光時にモニタし、それを用いて露光状態を判断して、その露光エリアが露光不良かどうかを判断することが考えられる。相対位置要素としてはＸ、Ｙ、Ｚ、ω_X、ω_Y、ω_Z方向が考えられ、判断方法はステージの同期誤差に基づく露光不良領域判定方法と同様に、それぞれの方向に対しての許容誤差を決定しておき、判定領域内の複数の位置について同期誤差を算出し、その中で最大のものを用いて判断する方法、そのときの計測誤差の和に対し閾値を設けて露光不良を判断する方法、測定点の誤差の統計処理結果に対して閾値を設けておく方法などが考えられる。
【００３５】
これらの判定方法により、マスキングブレードとレチクルステージの同期誤差に起因する誤差から露光状態を判別し、その結果露光不良と判別された部分を記憶し、同部分を含むチップに対しては、次層以降での露光の労力を減らしたり、検査行程を省略するなどして、製造効率の向上を図ることができる。
【００３６】
走査露光時には、ステージの位置に対して投影光学系の目標縮小比の設定が行われている場合がある。そのため、ステージの位置に対して、実時間に投影光学系の縮小倍率を制御しなくてはならない。しかしながら、投影光学系の目標縮小比と実際の縮小比との間に誤差の生じることがある。図７は、スキャン露光時に投影系の縮小倍率を変化させた場合を示した図である。図７（Ａ）はスキャン位置における投影光学系の縮小倍率を示した図である。点線は目標縮小倍率が一定である場合を示しているが、実線のようにスキャン位置においてその縮小倍率を変化させる場合がある。このとき、ウエハに焼きつけられる領域としては図７（Ｂ）の実線で囲われた部分のようになる。しかし、実線の縮小倍率が図７（Ａ）の波線のようになった場合には、ウエハに焼き付けられる領域は図７（Ｂ）の波線で囲われた形となり、この波線の形が実線の形と大きく異なる場合には、露光面の局所、または、全体に像の歪みが生じることとなり、次層以降のオーバーレイに影響の生じることが考えられる。従って、投影光学系のスキャン位置における目標縮小倍率と、実際の縮小倍率との誤差から、露光状態を判定する必要が出てくる。
【００３７】
この投影光学系の誤差に対して、本発明の概念を適用し、パルス露光毎の投影光学系の実際の縮小倍率を縮小倍率検出手段により検出して、目標縮小倍率に対する投影光学系の縮小倍率の誤差が大きい場合には、露光を行わないで、再露光を行うことが考えられる。誤差の判定には、ある評価基準に対して閾値を設け、その閾値を基準に露光状態を判断することとなる。その際の閾値の設け方としては、目標縮小倍率からのズレ量そのものに設ける方法、走査フィールド上幾つかの測定点について目標値からのズレを計測し、それらを統計処理してその統計値に対して閾値を設ける方法、また回路パターンに基づき、回路パターンが他の部分と比較して複雑であったりして、より縮小倍率に対してより厳しい精度が必要である場合には各点での測定値に対し、重みをかけるなどした上で、ズレ量に対して閾値を設ける方法、統計処理を行った結果に対して閾値を設ける方法に適用することも考えられる。
【００３８】
これら一連の手法を用いることにより、投影光学系の縮小倍率の誤差に起因する露光不良を判定し、露光不良と判別された部分を記憶し、同部分を含むチップに対しては、次層以降での露光の労力を減らしたり、検査行程を省略するなどして、製造効率の向上を図ることができる。
【００３９】
図８は、半導体チップの露光を終えた後、それらを一つ一つのチップに裁断する工程のフローチャートである。上記のいずれかの方法で露光不良である位置が決定され、その露光不良を起こしている位置はあらかじめメモリなどに蓄えられているものとする。裁断工程においては、まずその露光不良位置を読み込み（ステップＳ７１）、チップの裁断を行う（ステップＳ７２）。その後、露光不良位置と現在の裁断位置とを比較して、裁断したチップが露光不良領域を含むか否かを判断する（ステップＳ７３）。裁断を行ったチップが露光領域を含むときはそのチップを捨ててから（ステップＳ７４）、含まない場合は直接、次の裁断位置へ移動する（ステップＳ７５）。そして、裁断領域内かどうかを判断し（ステップＳ７６）、裁断領域内であれば、ステップＳ７２へ戻って再び裁断を行い、裁断領域外のときには裁断を終了する。
【００４０】
さらに、ウエハ面上での露光状況は露光装置に備え付けられた表示部分に表示することにより、オペレータに知らせることができる。図９は、その表示例を示したもので、露光不良部分８０１を示すとともに、その露光不良部分を含むチップ８０２は露光不良による不良チップであることが示されている。
【００４１】
【発明の効果】
以上説明したように本発明によれば、より効率的かつ低コストでデバイスが製造できるような露光技術を提供することができる。
【図面の簡単な説明】
【図１】 本発明の一実施例に係る露光不良部分の基本的な概念を示す図である。
【図２】 本発明の一実施例に係る半導体露光装置の構成を示す図である。
【図３】 同期ずれの誤差を示す図である。
【図４】 図３に係る誤差の概要を示す図である。
【図５】 パルス光源を使用した走査型半導体露光装置のウエハ上への露光量の与え方を示す図である。
【図６】 露光不良を判定するフローチャートである。
【図７】 スキャン露光時に投影系の縮小倍率を変化させた場合の説明図である。
【図８】 半導体チップの露光を終えた後、それらを個々のチップに裁断する際のフローチャートである。
【図９】 半導体露光装置が有する表示装置に表示された表示例を示す図である。
【符号の説明】
１：光源、２：ビーム整形光学系、３：オプティカルインテグレータ、４：コンデンサレンズ、５：ハーフミラー、６：マスキングブレード、７：結像レンズ、８：ミラー、９：レチクル、１０：投影光学系、１１：半導体基板、１２：露光量検出器、１３：レチクルステージ、１４：ウエハステージ、１５：露光量検出器、１６：トリガ信号、１７：充電電圧信号、１０１：ステージ駆動制御系、１０２：露光量演算器、１０３：レーザ制御系、１０４：主制御系、１０５：入力装置、１０６：表示部、１０７：データ出力インタフェース、１０８：照度検出信号、１０９：照度検出信号、１１０：ＡＦ光学系、１１１：ＡＦ演算器、１１２：投影レンズ駆動信号、１１３：ステージ信号、２０１：領域、２０２：露光不良部分、２０３：チップ、３０１：本来の露光位置、３０２：実際の露光位置、８０１：露光不良部分、８０２：チップ、８０３：レチクル内の回路を１／４倍した領域、８０４：ウエハの移動方向、８０５：レチクルステージの移動方向、８０６：１回のパルス光発光により露光される領域。[0001]
BACKGROUND OF THE INVENTION
  The present invention provides, for example, exposure for manufacturing a semiconductor chip.TechnologyIt is about.
[0002]
[Prior art]
Conventionally, in the manufacturing process of a semiconductor chip, when a semiconductor exposure apparatus using a pulsed light as a light source is used to expose a circuit pattern or the like of a semiconductor chip, it is normal even if there is a fatal defect in the exposure situation. The inspection is performed in the same way as the chip.
[0003]
[Problems to be solved by the invention]
However, since the inspection of the semiconductor chip is performed a plurality of times and a great deal of labor is spent on the test, if the defective chip is inspected in the same manner as a normal chip, the manufacturing efficiency decreases, As a result, the manufacturing cost increases.
[0004]
  In view of the problems of the prior art, the object of the present invention is more efficient and less expensive.deviceExposure that can be manufacturedTechnologyIs to provide.
[0005]
[Means for Solving the Problems]
  To achieve this object, the present inventionscanningThe exposure equipmentIn a scanning exposure apparatus that has a projection optical system and projects a pattern of an original plate illuminated with pulsed light onto a substrate through the projection optical system,
  Detecting means for detecting a projection magnification of the projection optical system for each pulse exposure;
  Discrimination means for discriminating an exposure failure based on a detection result of the detection means;
It is characterized by having.
[0006]
  In the scanning exposure apparatus according to the second aspect of the present invention, the determination unit determines an exposure failure based on a difference between a projection magnification detected by the detection unit and a target projection magnification.
[0007]
  A scanning exposure apparatus according to a third aspect of the present invention provides:SaidBy discriminating meansPoor exposureIt was determined thatMemorize the position on the boardCharacterized by having a storage means.
[0008]
  According to a fourth aspect of the present invention, there is provided a scanning exposure apparatus having an original stage for holding and moving an original and a substrate stage for holding and moving a substrate, and transferring a pattern of the original illuminated by pulsed light to the substrate. In
  A light amount detecting means for detecting a light amount for each pulse exposure;
  Calculation means for calculating an exposure amount on the substrate based on a detection result of the detection means;
  A relative position detecting means for detecting a relative position between the original stage and the substrate stage for each pulse exposure;
  And determining means for determining whether or not an exposure failure is caused by the next pulse exposure based on the calculation result of the calculating means and the detection result of the relative position detecting means.
[0009]
  A scanning exposure apparatus according to a fifth aspect of the present invention includes control means for controlling the amount of the next pulsed light based on the calculation result of the calculation means and the detection result of the relative position detection means.
  A scanning exposure apparatus according to a sixth aspect of the present invention includes storage means for storing a position on the substrate that has been determined as an exposure failure by the determination means.
[0010]
    The scanning exposure method of the present invention is a scanning exposure method for projecting a pattern of an original plate illuminated with pulsed light onto a substrate via a projection optical system.
  A detection step of detecting a projection magnification of the projection optical system for each pulse exposure;
  And a discrimination step of discriminating an exposure failure based on a detection result of the detection means.
[0011]
  Furthermore, the scanning exposure method of the present invention is characterized in that, in the determination step, an exposure failure is determined based on a difference between the projection magnification detected in the detection step and a target projection magnification.
  Furthermore, the scanning exposure method of the present invention has a step of storing in the storage means the position on the substrate determined to be an exposure failure in the determination step.
[0012]
  Furthermore, the scanning exposure method of the present invention is a scanning exposure method for transferring a pattern of an original plate illuminated with pulsed light to a substrate using an original stage holding and moving the original plate and a substrate stage holding and moving the substrate.
  A light amount detection step for detecting a light amount for each pulse exposure;
  A calculation step of calculating an exposure amount on the substrate based on a detection result in the detection step;
  A relative position detecting step for detecting a relative position between the original stage and the substrate stage for each pulse exposure;
  A discriminating step for discriminating whether or not an exposure failure is caused by the next pulse exposure based on the calculation result in the calculation step and the detection result in the relative position detection step;
  It is characterized by having.
[0013]
  Furthermore, the scanning exposure method of the present invention has a control step of controlling the amount of the next pulsed light based on the calculation result in the calculation step and the detection result in the relative position detection step.
  Furthermore, the scanning exposure method of the present invention has a step of storing in the storage means the position on the substrate determined to be an exposure failure in the determination step.
  Furthermore, the device manufacturing method of the present invention includesUsing the scanning exposure apparatus describedIt has the process of transferring the pattern of a negative | original plate to a board | substrate.
[0014]
[Action]
When exposure is performed using a semiconductor exposure apparatus using a pulsed light source, the exposure status at that time is synchronized with the light emission timing of the pulsed light, that is, the stage synchronization error between the original plate and the substrate, the deviation in the focus direction, and uneven exposure intensity. The exposure error is determined in advance by detecting various error factors that occur during exposure, and performing a specific evaluation and setting a threshold value for the evaluation result. When an exposure failure occurs, if all the chips included in the shot are discarded, the manufacturing efficiency is greatly deteriorated. Therefore, the exposure failure portion in the shot is stored and the data is output. Then, only the chip including the poorly exposed part is discarded as a defect, and the operation check or the like is not performed. That is, the portion of the shot that has become defective in exposure compared to the prior art is identified immediately, and only the chips included in the portion are excluded as defective, and the subsequent process is performed. Thereby, compared with the case where a defective chip is not excluded from the exposure state at the time of scanning exposure, the manufacturing efficiency is improved and the manufacturing cost is reduced. This is the basic concept of the present invention, and FIG. 1 is a diagram showing the basic concept of the present invention. In the figure, 201 is an area (exposure field) exposed by a single scan with a series of pulsed light, 202 is an area where an exposure failure has occurred, and 203 is a chip area including this area 202. Since the exposure failure is considered to occur partially as in the region 202, only the chip 203 is affected by the exposure failure. Therefore, the other than the chip 203 is in a good exposure state, and only the chip 203 needs to be handled as a defective product.
[0015]
【Example】
FIG. 2 is a schematic diagram showing a scanning type exposure apparatus according to an embodiment of the present invention. This apparatus includes a semiconductor device such as an IC or LSI, a liquid crystal device, an imaging device such as a CCD, or a device such as a magnetic head. It is used when manufacturing. In the figure, a light beam from a light source 1 that emits pulsed light such as an excimer laser is shaped into a desired shape by a beam shaping optical system 2 and directed to a light incident surface of an optical integrator 3 such as a fly-eye lens. The fly-eye lens is composed of a collection of a plurality of minute lenses, and a plurality of secondary light sources are formed in the vicinity of the light exit surface.
[0016]
Reference numeral 4 denotes a condenser lens, which Koehler-illuminates the masking blade 6 with a light beam from the secondary light source of the optical integrator 3. The masking blade 6 and the reticle 9 are arranged in a conjugate relationship by the imaging lens 7 and the mirror 8, and the shape and size of the illumination area in the reticle 9 are defined by the shape of the opening of the masking blade 6. It is scanned in synchronization with. A projection optical system 10 projects a circuit pattern drawn on the reticle 9 on the semiconductor substrate 11 in a reduced scale. The reticle 9 is fixed to the reticle stage 13 and aligned with the semiconductor substrate 11 fixed on the wafer stage 14 via the projection optical system 10. An exposure amount detector 15 is arranged on the wafer stage 14, and the exposure amount detector 15 can monitor the exposure amount of the laser through the optical system 10. Reference numeral 12 denotes another exposure amount detector which monitors a part of the light beam of the pulsed light divided by the half mirror 5.
[0017]
The structure of the control system is composed of a laser control system 103, an exposure amount calculator 102, a stage drive control system 101, an AF calculator 111, and a main control system 104 that supervises those calculation portions. The laser control system 103 receives the laser emission intensity and the oscillation timing signal calculated so that the target exposure amount can be obtained in the main control system 104, and the laser signal emitted from the light source 1 by the trigger signal 16 and the charging voltage signal 17. Control the pulse energy and emission interval. The exposure amount calculator 102 calculates the actual exposure by correlating the detection periods based on the illuminance detection signals 108 and 109 obtained from the exposure amount detectors 12 and 15 before the actual exposure starts. At this time, the exposure amount on the wafer is estimated only from the data from the exposure amount detector 12. The stage drive control system 101 recognizes the current positions of the reticle stage 13 and the wafer stage 14, sends the data to the main control system 104, and a stage signal based on the stage drive signal sent from the main control system 104. 113 is output to drive the stages 13 and 14. The AF calculator 111 outputs a projection lens drive signal 112 from the data obtained by the AF optical system 110 and controls the focus. The focus state at that time is transmitted to the main control system 104, and conversely, the focus target value is received from the main control system 104.
[0018]
The laser control system 103, the exposure amount calculator 102, the stage drive control system 101, and the AF calculator 111 operate in synchronization with a trigger signal for emitting pulsed light, and detect each data. The main control system 104 includes an input device 105 that inputs an exposure state, a data output interface 107 that outputs the exposure state, and a display unit 106 that graphically displays the exposure state. Further, data such as pulse light intensity, stage position, focus state, etc. are received from each control system, and a control calculation for achieving the target exposure amount input by the input device 105 is performed using them. From the result of the control calculation, a light emission intensity command signal, a stage drive signal, a focus target signal, and the like of the pulsed light are sent to each calculator and control system.
[0019]
Next, one method for determining exposure failure will be described. As a cause of the exposure failure of the semiconductor chip, firstly, a synchronous positional deviation error between the reticle 9 and the wafer 11 can be considered. FIG. 3 is a diagram showing a synchronization error. In a semiconductor exposure apparatus, a wafer (also a reticle in the case of a scanning exposure method) is moved in order to move between shots or to scan exposure light in the case of a scanning exposure method. At this time, the relative speed between the reticle and the wafer varies, or vibrations are mixed when moving the respective stages, so that the exposure area 302 is different from the exposure area 301 to be originally exposed on the wafer surface. In some cases, the reticle is applied to the wafer surface, and exposure cannot be performed at an intended position on the wafer surface.
[0020]
FIG. 4 shows an outline of errors that occur at that time. The left figure of FIG. 4 shows the result of the synchronization error between the first layer and the second layer, and the right figure shows the synchronization error between the light emission. In the figure on the left, due to the synchronization error between the first layer and the second layer, the part that must be connected between the layers would be shifted like a circled part because of the synchronization error, The circuit cannot be configured. In the right figure, a synchronization error occurs between the reticle and the wafer between the first light emission and the second light emission due to a synchronization error between shots, and a desired circuit cannot be formed. Therefore, when there is such an exposure failure by detecting these errors, the device stores the position where the exposure failure is, and prevents the semiconductor chip from performing the actual inspection at the chip inspection stage. The production efficiency can be increased.
[0021]
When calculating the exposure error in synchronization with the emission timing of the pulsed light, the X-axis direction that is the scanning direction, the Y-axis direction that is the slit longitudinal direction, the Z-axis direction that is perpendicular to the XY plane, X Rotation direction ω around the axis_X, Rotation direction ω around Y axis_Y, Rotation direction ω around Z axis_ZTherefore, it must be taken into consideration when determining a defect in manufacturing a semiconductor chip. As a method for determining the exposure failure, the error in each error direction is added to the absolute value for each emission of the pulsed light, and if the sum exceeds a preset threshold value, that portion is set as a defective exposure. A method is conceivable. In order to reduce the calculation load, a method may be considered in which a maximum error is determined in advance for each error direction, and when the value is exceeded, the exposed portion is determined to be defective.
[0022]
Also, the error in the X-axis direction is Δx, the error in the Y-axis direction is Δy, and the rotation error about the Z-axis is ω_Z  Assuming that the position in the reference exposure area plane is expressed as coordinates (x, y), if an error occurs in the X-axis, Y-axis, and Z-axis rotation directions, each point is coordinated as shown in Equation (1). Converted.
[0023]
[Expression 1]

Therefore, the distance between the coordinates after conversion and the coordinates before conversion is calculated, the distance is added for each point in the exposure area for each light emission, and a threshold value is provided for the addition result to prevent exposure failure. A method of determining, a method of determining a defective exposure by providing a threshold value for the sum of the addition results at each point in the exposure area, and the like can be considered. In addition, in the method of determining exposure failure by setting a threshold value for the addition result at each point of such distance, when the threshold value is exceeded, not all of the exposure area is determined to be defective, but in the exposure area plane. In this case, it is possible to limit the exposure failure area. For this reason, only the chip including the poorly exposed part needs to be determined as defective even in the exposure area, and it is considered that the manufacturing efficiency of the semiconductor chip is further improved. The errors Δx, Δy and ω used here_ZIs an optimum value obtained by a method such as using several measurement points and averaging the values.
[0024]
Regarding the exposure failure determination between layers, the exposure status at that position may be determined from the reticle at the same position on the shot and the synchronization deviation between the wafers according to the above-described determination criteria.
[0025]
Next, another exposure failure determination method will be described. When the semiconductor chip is exposed, a shift in the distance between the reticle and the wafer causes a shift in the focal length of the optical system, leading to an exposure error. This deviation in focal length affects the sharpness of the pattern when the pattern is formed by the exposure apparatus. Then, when detecting the exposure error of the semiconductor chip in synchronization with the light emission timing of the pulsed light, the error Z acting on the focal length, the rotation error ω around the X axis_X, Rotation error ω around Y axis_YIt is conceivable to determine the exposure failure in consideration of the above. As a determination method, it is conceivable that the absolute value of the error in each direction is added and it is checked whether or not the sum exceeds a predetermined threshold value. Also, for simplification of calculation, an error for each direction is compared with an error threshold value for each direction provided in advance, and if the threshold value is exceeded, the exposure of that portion is regarded as defective. It is possible. Further, the coordinate system of the wafer surface is set such that the scanning direction is X, the slit longitudinal direction is Y, and the rotation direction around each of these directions is ω._XAnd ω_Y, Where the normal direction of the plane consisting of X and Y is Z,_XAnd ω_YIf the rotation error is added, it is considered that the coordinate transformation of Formula 2 works.
[0026]
[Expression 2]

It is.
[0027]
Assuming that the wafer surface before the error enters is Z = 0, the wafer surface after the rotation error and the error Δz in the Z-axis direction are expressed by Equation (3).
[0028]
[Equation 3]

Therefore, by substituting the coordinates on the exposure area into Equation 3, the distance (error) in the focus direction is obtained and a threshold is set for the error, and the error at each point in the exposure area is added. A method of setting a threshold value for the sum can also be considered.
[0029]
The errors Δz and ω used here_XAnd ω_YIs an optimum value obtained by a method such as using several measurement points and averaging the values.
[0030]
Still another exposure failure determination method will be described. In a semiconductor exposure apparatus, the exposure amount on the wafer surface affects the line width of the pattern to be printed on the wafer, and so must be made uniform. FIG. 5 shows how to give an exposure amount on a wafer of a scanning semiconductor exposure apparatus using a pulse light source. Each step of the stepped portion in FIG. 5 shows the pulse light having a slit shape, the horizontal position indicates the position on the exposure field, and the vertical length indicates the intensity of the pulse light. As shown in the lower diagram of FIG. 5, when there is no error between the light emission intensity of the pulsed light and the light emission position at that time, ideal exposure is performed, and a uniform exposure amount can be given on the wafer surface. The upper diagram in FIG. 5 shows a case where the exposure state is not ideal, the upper left diagram in FIG. 5 shows the exposure status when the light emission position is slightly shifted, and the upper right diagram in FIG. 5 shows the emission of pulsed light. This shows the case where the intensity deviates from the emission intensity of other pulses. As a cause of the light emission position error, the light emission position error of the pulsed light caused by the synchronization shift of the reticle stage and the wafer stage and the accompanying mechanical noise can be considered as the cause of fluctuation of the exposure amount on the wafer surface. . The direction of the position error includes a scanning direction X, a slit longitudinal direction Y, a focus direction Z, and a rotation error ω with respect to each direction axis._X, Ω_Y, Ω_ZEtc. are considered. Therefore, when actually using a scanning semiconductor exposure apparatus, the emission intensity for each pulsed light and the emission position of the pulsed light are detected in synchronization with the emission of the pulsed light, taking into account the errors contained in them. It is necessary to always grasp the exposure state on the wafer surface and always calculate the exposure amount error. From the viewpoint of the exposure amount error in the static exposure apparatus, only the variation in the light emission intensity of the pulsed light can be considered as a factor giving the exposure amount error, so that only the intensity error needs to be considered.
[0031]
In order of the semiconductor exposure process, exposure (emission of pulsed light) is performed after positioning for exposure. Therefore, in order to perform good exposure, an error about the exposure position is calculated, and the error depends on the error. The amount of exposure light must be controlled so as to cancel the influence, and it must be taken into consideration that the exposure amount error at that portion is less than the allowable value. However, if the position error is large and the exposure amount error cannot be reduced below the allowable value by controlling the exposure amount, or the light emission position error is within the allowable range, If the error is large and the error cannot be corrected by light emission from the next time onward, it is determined that the part is defective in exposure, the defective part of exposure is stored, and the information is used to determine whether the chip is good or bad. Use when.
[0032]
FIG. 6 is a flowchart of an exposure process for one exposure field in which an exposure failure is determined. As shown in the figure, when the exposure process is started, the reticle stage and wafer stage are moved to reach the exposure area, and the moved position is confirmed (step S61). As confirmation items at this time, X, Y, Z, ω_X, Ω_YAnd ω_ZMeasure. Then, the emission intensity of the next pulsed light is calculated in consideration of the measured movement position (step S62). Then, it is determined whether or not the required exposure error can be satisfied by controlling the next light emission intensity (step S63), and if satisfied, the pulse light is emitted based on the calculation result of the light emission intensity (step S63). S64). Since there is a variation in the pulsed light at that time, the light emission intensity due to the variation is confirmed (step S65), and the error caused by the next pulsed light is taken into account by taking into account the error and errors such as the positioning error of the stage. Is determined to be within the allowable error range (step S66). If it is determined in step S63 or S66 that the required exposure error cannot be satisfied or cannot be corrected, the exposure failure position is stored (step S67), and the process proceeds to step S68. If it is determined in step S66 that correction is not possible, the process immediately proceeds to step S68. In step S68, the reticle / wafer stage is moved to the next exposure position. Then, it is determined whether or not all exposures have been completed (step S69). If the exposure has been completed, the exposure operation is terminated. If not completed, the process returns to step S61.
[0033]
When judging whether a semiconductor exposure apparatus using a pulsed light source can be exposed or not, it is virtually impossible to adopt the above error evaluation criteria independently, so it is also possible to judge by combining at least two evaluation criteria. It is done. In that case, an exposure defect discrimination method in which appropriate errors are added to these judgment criteria and each error is evaluated in combination is also conceivable.
[0034]
Next, it can be considered that the exposure failure is determined from the synchronization error between the masking blade and the stage system. At the time of scanning exposure, the masking blade is moved in synchronization with the movement of the reticle stage, that is, the movement of the reticle, in order to shape the shape of the beam irradiated onto the reticle stage and to determine the beam irradiation area. However, if there is a synchronization error between the masking blade and the reticle stage, an exposure failure due to that occurs. Therefore, it is conceivable to monitor the relative position between the masking blade and the reticle stage during scanning exposure, and use it to determine the exposure state to determine whether or not the exposure area is defective. X, Y, Z, ω as relative position elements_X, Ω_Y, Ω_ZThe direction is considered, and the determination method is the same as the method for determining the poor exposure area based on the synchronization error of the stage. The allowable error for each direction is determined and the synchronization error is calculated for a plurality of positions in the determination area. A method of judging using the largest one of them, a method of judging a exposure failure by providing a threshold for the sum of measurement errors at that time, and a threshold for a statistical processing result of measurement point error The method of putting it is considered.
[0035]
By these determination methods, the exposure state is determined from the error caused by the synchronization error between the masking blade and the reticle stage, and as a result, the portion that is determined to be defective in exposure is stored. The production efficiency can be improved by reducing the subsequent exposure labor or omitting the inspection process.
[0036]
At the time of scanning exposure, a target reduction ratio of the projection optical system may be set for the position of the stage. Therefore, the reduction magnification of the projection optical system must be controlled in real time with respect to the stage position. However, an error may occur between the target reduction ratio of the projection optical system and the actual reduction ratio. FIG. 7 is a diagram showing a case where the reduction magnification of the projection system is changed during scan exposure. FIG. 7A shows the reduction magnification of the projection optical system at the scan position. The dotted line shows the case where the target reduction magnification is constant, but the reduction magnification may be changed at the scan position as shown by the solid line. At this time, the region burned on the wafer is a portion surrounded by a solid line in FIG. However, when the reduction ratio of the solid line is as shown by the wavy line in FIG. 7A, the region to be baked on the wafer is surrounded by the wavy line in FIG. 7B, and the shape of this wavy line is the solid line. When the shape is significantly different from the shape, image distortion occurs locally or entirely on the exposure surface, and it is considered that the overlay on the subsequent layers is affected. Therefore, it is necessary to determine the exposure state from the error between the target reduction magnification at the scanning position of the projection optical system and the actual reduction magnification.
[0037]
The concept of the present invention is applied to the error of the projection optical system, the actual reduction magnification of the projection optical system for each pulse exposure is detected by the reduction magnification detection means, and the reduction magnification of the projection optical system with respect to the target reduction magnification If there is a large error, it is conceivable to perform re-exposure without performing exposure. In determining the error, a threshold is set for a certain evaluation criterion, and the exposure state is determined based on the threshold. In this case, the threshold value is set by the method of setting the deviation amount from the target reduction magnification itself, the deviation from the target value at several measurement points on the scanning field, and statistically processing them to obtain the statistical value. On the other hand, if the circuit pattern is more complex than the other parts based on the method of providing a threshold for the circuit pattern, or if more precise precision is required for the reduction ratio, It is also conceivable to apply a method of setting a threshold for the amount of deviation and a method of setting a threshold for the result of statistical processing after applying a weight to the measured value.
[0038]
By using these series of methods, it is possible to determine an exposure failure caused by an error in the reduction magnification of the projection optical system, store a portion determined as an exposure failure, and for chips including the same portion, the subsequent layers It is possible to improve the manufacturing efficiency by reducing the labor of exposure in the process or omitting the inspection process.
[0039]
FIG. 8 is a flowchart of a process of cutting the semiconductor chips into individual chips after the exposure of the semiconductor chips. It is assumed that a position where exposure is defective is determined by any of the above methods, and the position where the exposure failure occurs is stored in a memory or the like in advance. In the cutting process, first, the exposure failure position is read (step S71), and the chip is cut (step S72). Thereafter, the exposure failure position is compared with the current cutting position to determine whether or not the cut chip includes an exposure failure area (step S73). If the cut chip includes the exposure area, the chip is discarded (step S74). If not included, the chip is directly moved to the next cutting position (step S75). Then, it is determined whether or not it is within the cutting area (step S76). If it is within the cutting area, the process returns to step S72 to perform cutting again, and when it is outside the cutting area, the cutting ends.
[0040]
Furthermore, the operator can be informed of the exposure status on the wafer surface by displaying it on a display portion provided in the exposure apparatus. FIG. 9 shows an example of the display, which shows an exposure failure portion 801 and that a chip 802 including the exposure failure portion is a defective chip due to exposure failure.
[0041]
【The invention's effect】
  As described above, the present inventionAccording to,Providing exposure technology that enables devices to be manufactured more efficiently and at lower costbe able to.
[Brief description of the drawings]
FIG. 1 is a view showing a basic concept of a defective exposure portion according to an embodiment of the present invention.
FIG. 2 is a view showing a configuration of a semiconductor exposure apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram showing an error in synchronization.
FIG. 4 is a diagram showing an outline of errors according to FIG. 3;
FIG. 5 is a view showing how to give an exposure amount on a wafer of a scanning semiconductor exposure apparatus using a pulse light source;
FIG. 6 is a flowchart for determining an exposure failure.
FIG. 7 is an explanatory diagram when the reduction magnification of the projection system is changed during scan exposure.
FIG. 8 is a flowchart when cutting the semiconductor chips and cutting them into individual chips.
FIG. 9 is a view showing a display example displayed on a display device included in the semiconductor exposure apparatus.
[Explanation of symbols]
1: light source, 2: beam shaping optical system, 3: optical integrator, 4: condenser lens, 5: half mirror, 6: masking blade, 7: imaging lens, 8: mirror, 9: reticle, 10: projection optical system , 11: semiconductor substrate, 12: exposure amount detector, 13: reticle stage, 14: wafer stage, 15: exposure amount detector, 16: trigger signal, 17: charge voltage signal, 101: stage drive control system, 102: Exposure amount calculator, 103: Laser control system, 104: Main control system, 105: Input device, 106: Display unit, 107: Data output interface, 108: Illuminance detection signal, 109: Illuminance detection signal, 110: AF optical system , 111: AF computing unit, 112: projection lens drive signal, 113: stage signal, 201: region, 202: defective exposure portion, 203: 301: Original exposure position, 302: Actual exposure position, 801: Unexpected exposure portion, 802: Chip, 803: Area obtained by ¼ times the circuit in the reticle, 804: Moving direction of wafer, 805: Movement direction of the reticle stage, 806: an area exposed by one-time pulse light emission.

Claims (13)

In a scanning exposure apparatus that has a projection optical system and projects a pattern of an original plate illuminated with pulsed light onto a substrate through the projection optical system ,
Detecting means for detecting a projection magnification of the projection optical system for each pulse exposure ;
Scanning exposure apparatus characterized by have a discriminating means for discriminating defective exposure based on a detection result of said detecting means. The scanning exposure apparatus according to claim 1, wherein the determination unit determines an exposure failure based on a difference between a projection magnification detected by the detection unit and a target projection magnification. The scanning exposure apparatus according to claim 1 , further comprising a storage unit that stores a position on the substrate that has been determined to be an exposure failure by the determination unit . In a scanning exposure apparatus having an original stage holding and moving an original plate and a substrate stage holding and moving a substrate, and transferring a pattern of the original plate illuminated with pulsed light to the substrate,
A light amount detecting means for detecting a light amount for each pulse exposure;
Calculation means for calculating an exposure amount on the substrate based on a detection result of the detection means;
A relative position detecting means for detecting a relative position between the original stage and the substrate stage for each pulse exposure;
A discriminating unit for discriminating whether or not an exposure failure is caused by the next pulse exposure based on the calculation result of the calculating unit and the detection result of the relative position detecting unit;
A scanning exposure apparatus comprising: 5. The scanning exposure apparatus according to claim 4, further comprising control means for controlling the amount of the next pulsed light based on the calculation result of the calculation means and the detection result of the relative position detection means. 6. The scanning exposure apparatus according to claim 4, further comprising storage means for storing a position on the substrate that has been determined as an exposure failure by the determination means. In a scanning exposure method for projecting a pattern of an original plate illuminated with pulsed light onto a substrate via a projection optical system ,
A detection step of detecting a projection magnification of the projection optical system for each pulse exposure ;
Scanning exposure method, characterized by chromatic and discrimination step of discriminating a defective exposure based on a detection result of said detecting means. 8. The scanning exposure method according to claim 7, wherein in the determination step, an exposure failure is determined based on a difference between the projection magnification detected in the detection step and a target projection magnification. Scanning exposure method according to claim 7 or 8, wherein further comprising the step of storing a position on the substrate that has been judged as defective exposure in the discriminating step in a storage means. In a scanning exposure method of transferring a pattern of an original plate illuminated with pulsed light to a substrate using an original stage holding and moving the original plate and a substrate stage holding and moving the substrate,
A light amount detection step for detecting a light amount for each pulse exposure;
A calculation step of calculating an exposure amount on the substrate based on a detection result in the detection step;
A relative position detecting step for detecting a relative position between the original stage and the substrate stage for each pulse exposure;
A discriminating step for discriminating whether or not an exposure failure is caused by the next pulse exposure based on the calculation result in the calculation step and the detection result in the relative position detection step;
A scanning exposure method characterized by comprising: The scanning exposure method according to claim 10, further comprising a control step of controlling a light amount of the next pulsed light based on a calculation result in the calculation step and a detection result in the relative position detection step. Claim 10 or 11 scanning exposure method wherein further comprising the step of storing a position on the substrate that has been judged as defective exposure in the discriminating step in a storage means. A device manufacturing method comprising a step of transferring a pattern of an original plate to a substrate using the scanning exposure apparatus according to claim 1 .

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