JP2005135935A - Shearing interference measuring device - Google Patents
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本発明はシアリング型を利用した、高精度干渉計測装置に関するものである。 The present invention relates to a high-precision interference measurement apparatus using a shearing type.
半導体製造装置の代表である縮小投影露光装置に用いられる高精度投影光学系においては、そのパターン精度を保証する為、投影光学系全体や個々の部品の透過波面収差或いは反射波面収差を、実際の露光波長において計測する必要がある。この目的の為、露光波長と同じか、或いは露光波長とほぼ等しい波長を持つ可干渉性の高い光を用いた種々の干渉計が考案されて来た。ところが、半導体の高集積化に対応する為に、露光装置の露光波長が、高圧水銀ランプを用いたg線(436nm)からi線(365nm)へ、更にはKrFエキシマレーザ(248nm)からArFエキシマレーザ(193nm)へと短波長化した結果、露光波長付近の発振波長を持つ可干渉性の高い光源を手に入れることは困難となって来た。この問題は特にEUV光(13nm)において顕著である。その為、可干渉性の比較的低い光源でも高精度な干渉計測が行え、且つ構成が単純なシアリング(shearing)型干渉計を用いた方法が提案されている。
シアリング干渉計では、振幅分割素子を用いてひとつの波面を分割し、同じ波面形状を有するが、光軸に垂直な方向にずれた２つの光束を作り、この２つの光束を干渉させて出来る縞情報から、もとの光束の波面形状を求めるものである。
In a high-precision projection optical system used in a reduction projection exposure apparatus that is a representative of semiconductor manufacturing apparatuses, the transmission wavefront aberration or reflected wavefront aberration of the entire projection optical system or individual components is actually measured in order to guarantee the pattern accuracy. It is necessary to measure at the exposure wavelength. For this purpose, various interferometers using highly coherent light having a wavelength that is the same as or substantially equal to the exposure wavelength have been devised. However, in order to cope with higher integration of semiconductors, the exposure wavelength of the exposure apparatus changes from g-line (436 nm) to i-line (365 nm) using a high-pressure mercury lamp, and further from KrF excimer laser (248 nm) to ArF excimer. As a result of shortening the wavelength to a laser (193 nm), it has become difficult to obtain a highly coherent light source having an oscillation wavelength near the exposure wavelength. This problem is particularly noticeable in EUV light (13 nm). Therefore, a method using a shearing interferometer that can perform highly accurate interference measurement even with a light source having a relatively low coherence and has a simple configuration has been proposed.
In a shearing interferometer, an amplitude splitting element is used to divide one wavefront to produce two light fluxes that have the same wavefront shape but are shifted in a direction perpendicular to the optical axis, and these two light fluxes interfere with each other to produce fringes. The wavefront shape of the original light flux is obtained from the information.
図５は、シア方向が横方向（光軸に垂直方向）であるシアリング干渉計を説明するものである。このシアリング干渉計では、投影光学系ＰＬの物体面（例えばレチクル面Ｒ）の一点から出る球面波（測定光束Ｌ）を、投影光学系ＰＬに入射させる。この測定光束Ｌは、例えば、レチクル面Ｒにピンホール基板１１３を配置すると共に、光源から射出した光束を、ピンホール基板１１３のピンホール位置に集光させるなどして生成されたものである（図６の符号１１４は、光源から射出した光束をピンホール位置に集光する集光光学系（伝達光学系ともいう）である。）。 FIG. 5 illustrates a shearing interferometer in which the shear direction is the lateral direction (the direction perpendicular to the optical axis). In this shearing interferometer, a spherical wave (measurement light beam L) emitted from one point of the object plane (for example, reticle surface R) of the projection optical system PL is made incident on the projection optical system PL. The measurement light beam L is generated, for example, by arranging the pinhole substrate 113 on the reticle surface R and condensing the light beam emitted from the light source at the pinhole position of the pinhole substrate 113 ( Reference numeral 114 in FIG. 6 is a condensing optical system (also referred to as a transmission optical system) that condenses the light beam emitted from the light source at the pinhole position.
投影光学系ＰＬと像面（例えばウエハ面Ｗ）との間に回折格子１１１が配置されており、これによって集光する測定光束Ｌの波面が横方向に分割された２つの光束Ｌ１、Ｌ２が生成する（光束Ｌ１、及び光束Ｌ２は、例えば、回折格子１１１において生起する０次回折光、及び１次回折光である。）。この光束Ｌ１の波面、光束Ｌ２の波面の形状は、何れも、投影光学系ＰＬを通過した後の測定光束Ｌの波面形状と同じであり、シアリング干渉計が測定すべき波面である。 A diffraction grating 111 is disposed between the projection optical system PL and the image plane (for example, the wafer surface W), so that two light beams L1 and L2 obtained by dividing the wavefront of the measurement light beam L collected in the horizontal direction are obtained. (The light beam L1 and the light beam L2 are, for example, zero-order diffracted light and first-order diffracted light generated in the diffraction grating 111). The wavefront shape of the light beam L1 and the wavefront shape of the light beam L2 are both the same as the wavefront shape of the measurement light beam L after passing through the projection optical system PL, and are wavefronts to be measured by the shearing interferometer.
これら光束Ｌ１の波面と光束Ｌ２の波面とが重なって干渉縞を生起する位置に、受光素子カメラ１１２などの二次元検出器の撮像面が配置される。この受光素子カメラ１１２が検出する干渉縞から、投影光学系ＰＬから出た光束の波面が復元される。 The imaging surface of the two-dimensional detector such as the light receiving element camera 112 is disposed at a position where the wavefront of the light beam L1 and the wavefront of the light beam L2 overlap to generate interference fringes. From the interference fringes detected by the light receiving element camera 112, the wavefront of the light beam emitted from the projection optical system PL is restored.
一般的に、投影光学系ＰＬを通った光束の波面は、投影光学系ＰＬの射出瞳位置における形状として評価されることが多いので、受光素子カメラ１１２の撮像面は、投影光学系ＰＬの射出瞳位置と共役な位置に配置されるのが一般的である。 In general, the wavefront of the light beam that has passed through the projection optical system PL is often evaluated as a shape at the exit pupil position of the projection optical system PL, so that the imaging surface of the light receiving element camera 112 is emitted from the projection optical system PL. Generally, it is arranged at a position conjugate with the pupil position.
上記の様な干渉計計測においては、面形状の有する非点収差の測定を高精度に行う時、測定値にばらつきが多く、信頼できる値が得られないと言う問題点があった。
本発明はこの様な従来の問題に鑑みてなされたもので、回折格子を用いたシアリング干渉計によって高精度に非点収差を測定する、新規な装置を提供することを目的としている。
In the interferometer measurement as described above, there has been a problem that when measuring astigmatism having a surface shape with high accuracy, there are many variations in measured values, and reliable values cannot be obtained.
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a novel apparatus for measuring astigmatism with high accuracy by a shearing interferometer using a diffraction grating.
本発明は非点収差を有する波面をシアリング干渉計により計測する時の位相差分布における、非点収差の分布特性を利用している。具体的に発明の基礎となる考えを以下に記す。 The present invention uses astigmatism distribution characteristics in a phase difference distribution when a wavefront having astigmatism is measured by a shearing interferometer. The idea that is the basis of the invention is described below.
観察面にＸＹ座標系をとる。非点収差は波面形状として、
A1*(Ｘ2 - Ｙ2) + 2*A2*ＸＹ (0)
という成分で表示される。 回折格子に入射する被検波面（等位相面）をＷ（Ｘ,Ｙ）＝Ｃとすると、回折格子による振幅分割を受けてＸ方向にズレた波面はＷ(Ｘ-s,Ｙ)＝Ｃとなる。ここに、sは観察面上でのＸ方向への波面のズレ量である。 観察面での２つの波面の位相差は、φ(Ｘ,Ｙ) = Ｗ(Ｘ,Ｙ) - Ｗ(Ｘ-s,Ｙ)となる。ズレ量が小さいとすると、φ= (δＷ/δＸ)*sとなり、非点収差の波面形状を代入すると、非点収差に起因する位相差分布が求まり、
φ= 2*A1*Ｘ*s + 2*A2*Ｙ*s （１）
となる。
An XY coordinate system is taken on the observation surface. Astigmatism is a wavefront shape,
A1 * (X 2 -Y 2 ) + 2 * A2 * XY (0)
It is displayed with the component. Assuming that the wavefront to be detected (equal phase plane) incident on the diffraction grating is W (X, Y) = C, the wavefront shifted in the X direction due to the amplitude division by the diffraction grating is W (X-s, Y) = C. It becomes. Here, s is the amount of deviation of the wavefront in the X direction on the observation surface. The phase difference between the two wavefronts on the observation plane is φ (X, Y) = W (X, Y) −W (X−s, Y). If the amount of deviation is small, φ = (δW / δX) * s. Substituting the wavefront shape of astigmatism gives the phase difference distribution due to astigmatism,
φ = 2 * A1 * X * s + 2 * A2 * Y * s (1)
It becomes.
この式に基づき、測定結果を最小自乗法等の最適化法により（１）の平面にフィッティングさせると、A1及びA2が定まり、被検投影光学系の持つ非点収差が量的に求められる。しかしながら、実際には、回折格子と入射光束の集光点との距離の測定が困難であり、この距離の誤差が回折波の収束点のＸ方向の位置誤差になり、この誤差が上の(1)式にＸに比例する形で位相差となって生じる。即ち、回折格子と入射光束の集光点の位置誤差を含めると位相差分布は、
φ= 2*A1*Ｘ*s + 2*A2*Ｙ + kＸ （ｋは比例常数） (2)
となる。 従って、測定結果を（２）式の平面にフィッティングさせると、A2が求まることになるが、A1は求まらないことになる。本願発明者は、非点収差が正しく測定出来ない原因がこの付加項kXに有ることを見いだした。
Based on this equation, when the measurement result is fitted to the plane (1) by an optimization method such as the method of least squares, A1 and A2 are determined, and the astigmatism of the test projection optical system is quantitatively determined. However, in practice, it is difficult to measure the distance between the diffraction grating and the condensing point of the incident light beam, and the error of this distance becomes the position error in the X direction of the convergence point of the diffracted wave, and this error is This occurs as a phase difference in the form proportional to X in equation (1). In other words, including the position error of the condensing point of the diffraction grating and the incident light beam, the phase difference distribution is
φ = 2 * A1 * X * s + 2 * A2 * Y + kX (k is a proportional constant) (2)
It becomes. Therefore, when fitting the measurement result to the plane of the equation (2), A2 is obtained, but A1 is not obtained. The inventor of the present application has found that this additional term kX is the reason why astigmatism cannot be measured correctly.
そこで、本願発明者は鋭意検討の結果、回折格子を４５度回転させて同様な測定・解析を行えばｋＸの項に影響されることなく非点収差（即ち、上式(0)中のA1、A2）を求められることに到達し、本願発明をなすに至った。 Therefore, as a result of diligent study, the inventor of the present application conducted astigmatism (that is, A1 in the above equation (0) without being affected by the kX term if the diffraction grating was rotated 45 degrees and the same measurement / analysis was performed. , A2) has been obtained and the present invention has been made.
非点収差を表す式は、４５度回転したＸ'、Ｙ’座標系では, Ｘ = (Ｘ’+Ｙ’)/√2 Ｙ=(Ｘ’-Ｙ’)/ √2より
A1*(Ｘ2 - Ｙ2) + 2*A2*ＸＹ = 2*A1*Ｘ'* Ｙ’+ A2*（(Ｘ’)2−（Ｙ’）2） となる。
この座標系で回折格子によりＸ’軸方向にズレた波面と元の波面との位相差分布は、回折格子の位置誤差に起因する項を含めて、
φ= 2*A1*Ｙ’*s + 2*A2*Ｘ’*s + k’Ｘ’ （ｋ’は比例常数） （３）
となる。
The astigmatism is expressed as follows: X = (X ′ + Y ′) / √2 Y = (X′−Y ′) / √2 in the X ′ and Y ′ coordinate system rotated by 45 degrees
A1 * (X 2 −Y 2 ) + 2 * A2 * XY = 2 * A1 * X ′ * Y ′ + A2 * ((X ′) 2 − (Y ′) 2 )
In this coordinate system, the phase difference distribution between the wavefront shifted in the X′-axis direction by the diffraction grating and the original wavefront includes a term due to the positional error of the diffraction grating,
φ = 2 * A1 * Y '* s + 2 * A2 * X' * s + k'X '(k' is a proportional constant) (3)
It becomes.
この式の意味するところは、Ｘ’方向に光束を横ズレさせて位相差分布を測定し、測定結果を（３）式の平面に最小自乗法等でフィティングすると、A1が求められることになる。 This equation means that A1 is obtained when the phase difference distribution is measured by laterally shifting the light beam in the X ′ direction and the measurement result is fitted to the plane of equation (3) by the method of least squares. Become.
即ち、波面をＸ方向に横ずらしをして(2)式よりA2を求め、波面をＸ’方向に横ずらしをして(3)式よりA1を求めれば、非点収差が誤差無く求められることになる。
尚、本発明では波面の横ずらしの方向が４５度異なる方向での２つの計測より非点収差を求めているが、４５度方向に限ったものでは無くてもよい。 非点収差の面形状を任意の角度だけ回転させた座標系で表現すると、一般的にはA1(b1*Ｘ'2 + b2*Ｘ'Ｙ'+ b3*Ｙ'2) + A2(c1*Ｘ'2 + c2*Ｘ'Ｙ' + c3*Ｙ'2)となる。
従って、Ｘ'方向に横ずらしされた波面と元の波面との位相差分布より、４５度方向の横ずらしの場合と同様にして計算すると、b2*A1+c2*A2の値が求められる。b2とc2は座標系の変換常数であるので既知である。従って、先に(2)式より求めたA2とb2*A1+c2*A2の値より、A1、A2が正確に求められる。
That is, if the wavefront is laterally shifted in the X direction and A2 is obtained from the equation (2), and the wavefront is laterally displaced in the X ′ direction and A1 is obtained from the equation (3), astigmatism can be obtained without error. It will be.
In the present invention, astigmatism is obtained from two measurements in a direction in which the wavefront is shifted 45 degrees differently. However, the astigmatism is not limited to the 45 degree direction. When representing the surface shape of the astigmatism in a coordinate system rotated by an arbitrary angle, typically A1 (b1 * X '2 + b2 * X'Y' + b3 * Y '2) + A2 (c1 * X ′ 2 + c2 * X′Y ′ + c3 * Y ′ 2 ).
Therefore, if the calculation is performed in the same manner as in the case of the horizontal shift in the 45 degree direction from the phase difference distribution between the wavefront shifted in the X ′ direction and the original wavefront, a value of b2 * A1 + c2 * A2 is obtained. b2 and c2 are known because they are transformation constants of the coordinate system. Therefore, A1 and A2 can be accurately obtained from the values of A2 and b2 * A1 + c2 * A2 previously obtained from the equation (2).
本発明は、上記の基本的な考えを基礎に、先の課題を解決する為に以下に記す手段を用いている。
本発明の第１の手段は、
投影光学系の結像（波面収差）特性を評価するシアリング干渉計、又は点回折干渉計であって、
測定に用いる光を発する光源と、
該光源より出た光束を被検投影光学系の物点位置へ集光する為の伝達光学系と、
該物点に収束する収束光束、又は前記被検投影光学系に入射する発散光束、又は被検投影光学系から射出する収束又は発散光束を、複数の光束に分割する為の回折格子と、
分割した光束同士の干渉で生じる干渉縞を検出する為の受光素子と、
検出した干渉縞より前記被検投影光学系の波面収差を算出する為の解析手段と、を有し、
格子パターンの方向が互いに４５度傾いた２つの回折格子を切り替えて使用するようになされているシアリング干渉計である。
The present invention uses the means described below in order to solve the above problems based on the above basic idea.
The first means of the present invention is:
A shearing interferometer or a point diffraction interferometer for evaluating the imaging (wavefront aberration) characteristics of the projection optical system,
A light source that emits light used for measurement;
A transmission optical system for condensing the light beam emitted from the light source to the object point position of the test projection optical system;
A diffraction grating for dividing a convergent light beam converged on the object point, a divergent light beam incident on the test projection optical system, or a convergent or divergent light beam emitted from the test projection optical system, into a plurality of light beams;
A light receiving element for detecting interference fringes caused by interference between the divided light beams;
Analysis means for calculating the wavefront aberration of the test projection optical system from the detected interference fringes,
This is a shearing interferometer configured to switch between two diffraction gratings whose grating pattern directions are inclined by 45 degrees with respect to each other.
上述のように、測定すべき波面を第１の方向に振幅分割して互いに干渉させて出来る干渉縞の解析と、第１の方向とは４５度の角度をなす方向に被測定波面を振幅分割して互いに干渉させて出来た干渉縞の解析により容易に正確な被検投影光学系の非点収差が求められる。
本発明の第２の手段は、
第１の手段を実施する際に、
前記２つの回折格子が、その格子パターンが４５度傾けられて配置された格子板と、
該格子板を干渉計内で直線移動させて位置を変化させる切り替え機構と
を有することシアリング干渉計である。
As described above, analysis of interference fringes that can be performed by dividing the wavefront to be measured in the first direction and interfering with each other, and the measured wavefront in the direction that forms an angle of 45 degrees with the first direction Thus, the astigmatism of the test projection optical system can be easily obtained by analyzing the interference fringes generated by the interference.
The second means of the present invention is:
In implementing the first means,
A grating plate in which the two diffraction gratings are arranged with the grating pattern inclined at 45 degrees;
It is a shearing interferometer having a switching mechanism for changing the position by linearly moving the lattice plate within the interferometer.
このように２つの回折格子を、その格子パターンを互いに４５度傾けて格子板に配置し、これらを移動させる切り替え機構を有するようにしているので、２つの回折格子の切り替えが容易になる。 As described above, the two diffraction gratings are arranged on the grating plate with their grating patterns inclined by 45 degrees and have a switching mechanism for moving them, so that the two diffraction gratings can be easily switched.
本発明の第３の手段は、
投影光学系の結像（波面収差）特性を評価するシアリング干渉計、又は点回折干渉計であって、
測定に用いる光を発する光源と、
該光源より出た光束を被検投影光学系の物点位置へ集光する為の伝達光学系と、
該物点に収束する収束光束、又は前記被検投影光学系に入射する発散光束、又は被検投影光学系から射出する収束又は発散光束を、複数の光束に分割する為の回折格子と、
分割した光束同士の干渉で生じる干渉縞を検出する為の受光素子と、
検出した干渉縞より前記被検投影光学系の波面収差を算出する為の解析手段と、を有し、
前記回折格子を、干渉計の光軸の周りに４５度回転可能に保持する回転機構を有するシアリング干渉計である。
The third means of the present invention is:
A shearing interferometer or a point diffraction interferometer for evaluating the imaging (wavefront aberration) characteristics of the projection optical system,
A light source that emits light used for measurement;
A transmission optical system for condensing the light beam emitted from the light source to the object point position of the test projection optical system;
A diffraction grating for dividing a convergent light beam that converges on the object point, a divergent light beam incident on the test projection optical system, or a convergent or divergent light beam emitted from the test projection optical system, into a plurality of light beams;
A light receiving element for detecting interference fringes caused by interference between the divided light beams;
Analysis means for calculating the wavefront aberration of the test projection optical system from the detected interference fringes,
A shearing interferometer having a rotation mechanism that holds the diffraction grating so as to be rotatable by 45 degrees around the optical axis of the interferometer.
後述するように、測定すべき波面を第１の方向に振幅分割して互いに干渉させて出来る干渉縞の解析と、第１の方向とは４５度の角度をなす方向に被測定波面を振幅分割して互いに干渉させて出来た干渉縞の解析により容易に正確な被検投影光学系の非点収差が求められる。 As will be described later, analysis of interference fringes that can be performed by splitting the wavefront to be measured in the first direction and interfering with each other, and splitting the measured wavefront in a direction that forms an angle of 45 degrees with the first direction Thus, the astigmatism of the test projection optical system can be easily obtained by analyzing the interference fringes generated by the interference.
また、ひとつの干渉計を４５度回転して２度目の測定を行うので部材点数が低減され、全体価格を低く出来る。
本発明の第４の手段は、
前記第１乃至３のいずれかの手段を実施する際に、
干渉させる２つの回折波を選択するための次数選択窓を有し、
２つの回折波を通過させる窓の並び方向又は窓の広がり方向が互いに４５度傾いている次数選択窓を切り替えて使用するようになされているシアリング干渉計。
In addition, since one interferometer is rotated 45 degrees and the second measurement is performed, the number of members is reduced and the overall price can be reduced.
The fourth means of the present invention is:
When implementing any one of the first to third means,
An order selection window for selecting two diffracted waves to interfere with each other;
A shearing interferometer configured to switch and use an order selection window in which the arrangement direction of windows through which two diffracted waves pass or the spread direction of the windows are inclined by 45 degrees.
本発明の第５の発明は、
前記第４の手段を実施する際に、
２つの次数選択窓の並び方向、又は次数選択窓の広がり方向が互いに４５度傾いている２組の次数選択窓が配置された窓保持板と、
該窓保持板を干渉計内で窓を切り替えるために直線的に移動させる窓移動装置とを有するシアリング干渉計である。
本発明の第６の手段は、
前記第１乃至３のいずれかの手段を実施する際に、
干渉させる２つの回折波を選択するための次数選択窓と、
該窓を干渉計の光軸の周りに４５度回転させる、窓回転手段と、を有するシアリング干渉計である。 これら、第４から第６の手段は、２つの回折格子の格子パターンが互いに４５度をなすことにより、回折波のズレの方向も４５度だけ異なってくる事に対応する手段で有り、いずれも有効な手段である。
The fifth invention of the present invention is:
In carrying out the fourth means,
A window holding plate on which two sets of order selection windows in which the arrangement direction of the two order selection windows or the spreading direction of the order selection windows is inclined by 45 degrees from each other;
A shearing interferometer having a window moving device that linearly moves the window holding plate in order to switch windows within the interferometer.
The sixth means of the present invention includes
When implementing any one of the first to third means,
An order selection window for selecting two diffracted waves to interfere with each other;
A shearing interferometer having window rotating means for rotating the window by 45 degrees around the optical axis of the interferometer. These fourth to sixth means are means corresponding to the fact that the direction of the deviation of the diffracted wave differs by 45 degrees when the grating patterns of the two diffraction gratings form 45 degrees with each other. It is an effective means.
尚、次数選択に対しては、単独次数を選択するために２つの窓を設けたものと、隣り合う次数を選択するためにひとつの窓を設けたものがある。 上記「窓の並び方向」とは、２つの窓を設ける型の場合の窓の並び方向（窓を結ぶ線分方向）であり、「窓の広がり方向」とはひとつの窓に入る２つの回折波の収束点を結ぶ線分方向である。 For order selection, there are two types in which two windows are provided to select a single order, and one type in which one window is provided to select adjacent orders. The above "window alignment direction" is the window alignment direction (direction of the line segment connecting the windows) in the case of a type having two windows, and "window expansion direction" is two diffractions that enter one window. The direction of the line segment connecting the convergence points of the waves.
本発明の第７の手段は、
前記第１乃至第６のいずれかの手段を実施する際に、
前記回折格子を、格子パターンに垂直な方向に移動させる走査手段を有するシアリング干渉計である。 この回折格子走査手段により干渉縞の解析方法として縞走査法を採用することが出来、干渉波面の位相差分布を正確に、容易に求めることが出来る。
The seventh means of the present invention is:
When implementing any one of the first to sixth means,
A shearing interferometer having scanning means for moving the diffraction grating in a direction perpendicular to the grating pattern. With this diffraction grating scanning means, the fringe scanning method can be adopted as an interference fringe analysis method, and the phase difference distribution of the interference wave front can be accurately and easily obtained.
本発明に示した様な、格子パターンが互いに４５度の方向をなす２つ回折格子を切り替えて使用できる干渉計を用いることによって、被検投影光学系の非点収差が容易に、且つ精度良く求められることになる。 By using an interferometer that can be used by switching two diffraction gratings whose directions are 45 degrees to each other as shown in the present invention, the astigmatism of the test projection optical system can be easily and accurately performed. It will be required.
以下は、本発明の実施例を図面に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
図４は本発明に関わるシアリング干渉計の全体概略図である。
光源１より射出した光束は伝達光学系２によって被検投影光学系の物点位置を特定する為のピンホール３へ入射する。（この物点位置を特定するピンホールは測定光学系の構成によって必要ないものもある。）ピンホール３を透過した光束は計測対象である被検投影光学系４を経由した後、回折格子２３（２３ａ又は２３ｂ）によって複数の回折次数の光束に分割される。分割された光束は計測に用いられる２種類の次数の光束のみ透過する次数選択窓（窓保持板３１に設けられている）によって次数選択された後、受光素子７上に干渉縞を生成する。 本例では＋１次(Ｄ(+1))、−１次(Ｄ(-))の回折光を透過させ、０次回折光波吸収するような次数選択窓を用いている。
FIG. 4 is an overall schematic diagram of a shearing interferometer according to the present invention.
The light beam emitted from the light source 1 enters the pinhole 3 for specifying the object point position of the projection optical system under test by the transmission optical system 2. (Some pinholes for specifying the position of the object point are not necessary depending on the configuration of the measurement optical system.) The light beam that has passed through the pinhole 3 passes through the projection optical system 4 to be measured, and then the diffraction grating 23. (23a or 23b) is divided into light beams of a plurality of diffraction orders. The divided light beams are selected by the order selection window (provided on the window holding plate 31) that transmits only two kinds of light beams used for measurement, and then interference fringes are generated on the light receiving element 7. In this example, an order selection window that transmits + 1st order (D (+1)) and −1st order (D (−)) diffracted light and absorbs 0th order diffracted light waves is used.
干渉縞情報は受光素子７により光電変換され、解析手段（不図示）へ転送される。
本装置の回折格子は図１に示すような構成を有している。回折格子２３ａ及び２３ｂは回折格子保持部材２２ａ及び２２ｂに保持され、保持部材は同一の格子板２１に取り付けられている。この時、図に示すように、二つの回折格子の格子パターン（細い開口スリット群）は互いに４５度だけ傾いて配置されている。そして、この二つの回折格子を干渉計内で切り替えるために図４に示す切り替え機構２５が設けられている。この機構により、４５度だけ格子の方向が異なる二つの回折格子の切り替えが容易に行える。(請求項１，２に対する実施例である)
The interference fringe information is photoelectrically converted by the light receiving element 7 and transferred to analysis means (not shown).
The diffraction grating of this apparatus has a configuration as shown in FIG. The diffraction gratings 23 a and 23 b are held by diffraction grating holding members 22 a and 22 b, and the holding members are attached to the same grating plate 21. At this time, as shown in the figure, the grating patterns (thin aperture slit groups) of the two diffraction gratings are arranged so as to be inclined by 45 degrees with respect to each other. A switching mechanism 25 shown in FIG. 4 is provided to switch the two diffraction gratings in the interferometer. With this mechanism, it is possible to easily switch between two diffraction gratings having different grating directions by 45 degrees. (Example for claims 1 and 2)
また、回折格子保持部材は格子板上で格子パターンに少なくとも垂直な方向（図１中の回折格子の脇に記された矢印の方向）に移動可能に取り付けられており、走査手段２４（２４ａ及び２４ｂ）により縞走査が容易になされるようになっている。駆動法としては、例えば電歪素子を用いる方法である。（請求項７に対する実施例である。）この操作手段は、少なくとも格子パターンに垂直な移動を可能にするものであれば良く、例えば、効率の面を無視すれば格子パターンに垂直ではなく、垂直な方向にも移動する、格子パターンに対して４５度方向に移動させても良い。 一方、回折光が収束する面には図３に示すような窓保持板３１が配置され、さらにこれを移動させて窓３２を切り替える窓移動装置２８が設けられている。この窓の切り替えは、回折格子の切り替えに伴って生じる回折光の収束点の変化に対応するためである。（請求項４，５の実施例である。）
次数窓の切り替えに関しては、測定光学系の光軸を中心にして次数窓を４５度回転する手段を用いることも可能である。この場合、窓部材の構成が簡単になる。（請求項６に対する実施例である。）
The diffraction grating holding member is mounted on the grating plate so as to be movable at least in the direction perpendicular to the grating pattern (in the direction of the arrow written on the side of the diffraction grating in FIG. 1). 24b) facilitates the fringe scanning. As a driving method, for example, an electrostrictive element is used. (This is an embodiment corresponding to claim 7.) The operation means is only required to be movable at least perpendicular to the lattice pattern. For example, if the efficiency is ignored, the operation means is not perpendicular to the lattice pattern. It may also be moved in the direction of 45 degrees with respect to the lattice pattern. On the other hand, a window holding plate 31 as shown in FIG. 3 is disposed on the surface on which the diffracted light converges, and a window moving device 28 for switching the window 32 by moving the window holding plate 31 is provided. This is because the switching of the windows corresponds to the change in the convergence point of the diffracted light that occurs with the switching of the diffraction grating. (Examples of claims 4 and 5)
For switching the order window, it is possible to use means for rotating the order window by 45 degrees around the optical axis of the measurement optical system. In this case, the configuration of the window member is simplified. (Example for claim 6)
図２には、回折格子の切り替え手段の他の手段を示すものである。回折格子はひとつであるが、図４中の回折格子切り替え機構の代わりに、回折格子を４５回転させる回転機構を設ける。図２中、回折格子４３は回折格子保持板４２によって保持され、保持板４２は移動可能なように格子板に取り付けられている。（請求項３に対応する実施例である。）図１中の走査手段と同様の走査手段４４が取り付けられていて、縞走査が可能になされている。
これにより容易に回折波のズレ方向が４５だけ異なる波面が得られることになる。
FIG. 2 shows another means for switching the diffraction grating. Although there is only one diffraction grating, a rotation mechanism for rotating the diffraction grating 45 times is provided instead of the diffraction grating switching mechanism in FIG. In FIG. 2, the diffraction grating 43 is held by a diffraction grating holding plate 42, and the holding plate 42 is attached to the grating plate so as to be movable. (Embodiment corresponding to claim 3) A scanning means 44 similar to the scanning means in FIG. 1 is attached to enable fringe scanning.
As a result, wavefronts whose diffraction wave misalignment directions are different by 45 are easily obtained.
１：光源
２：伝達レンズ
３：ピンホール
４：被検レンズ
７：受光素子
２１、４１：格子板
２２、４２：回折格子保持部材
２３、４３：回折格子
２４、４４：走査機構
２５：切り替え手段
２８：窓移動装置
３１：窓保持板
３２：次数選択窓
1: Light source 2: Transfer lens 3: Pinhole 4: Test lens 7: Light receiving element 21, 41: Grating plate 22, 42: Diffraction grating holding member 23, 43: Diffraction grating 24, 44: Scanning mechanism 25: Switching means 28: Window moving device 31: Window holding plate 32: Order selection window
Claims (7)
測定に用いる光を発する光源と、
該光源より出た光束を被検投影光学系の物点位置へ集光する為の伝達光学系と、
該物点に収束する収束光束、又は前記被検投影光学系に入射する発散光束、又は被検投影光学系から射出する収束又は発散光束を、複数の光束に分割する為の回折格子と、
分割した光束同士の干渉で生じる干渉縞を検出する為の受光素子と、
検出した干渉縞より前記被検投影光学系の波面収差を算出する為の解析手段と、を有し、
格子パターンの方向が互いに４５度傾いた２つの回折格子を切り替えて使用するようになされていることを特徴とするシアリング干渉計。 A shearing interferometer for evaluating the imaging characteristics of a projection optical system,
A light source that emits light used for measurement;
A transmission optical system for condensing the light beam emitted from the light source to the object point position of the test projection optical system;
A diffraction grating for dividing a convergent light beam that converges on the object point, a divergent light beam incident on the test projection optical system, or a convergent or divergent light beam emitted from the test projection optical system, into a plurality of light beams;
A light receiving element for detecting interference fringes caused by interference between the divided light beams;
Analysis means for calculating the wavefront aberration of the test projection optical system from the detected interference fringes,
2. A shearing interferometer, wherein two diffraction gratings whose grating pattern directions are inclined by 45 degrees are switched and used.
前記２つの回折格子が、その格子パターンが４５度傾けられて配置された格子板と、
該格子板を干渉計内で直線移動させて位置を変化させる切り替え機構と
を有することを特徴とするシアリング干渉計。 The interferometer according to claim 1, wherein
A grating plate in which the two diffraction gratings are arranged with the grating pattern inclined at 45 degrees;
A shearing interferometer, comprising: a switching mechanism that changes the position of the lattice plate by linearly moving the grating plate in the interferometer.
測定に用いる光を発する光源と、
該光源より出た光束を被検投影光学系の物点位置へ集光する為の伝達光学系と、
該物点に収束する収束光束、又は前記被検投影光学系に入射する発散光束、又は被検投影光学系から射出する収束又は発散光束を、複数の光束に分割する為の回折格子と、
分割した光束同士の干渉で生じる干渉縞を検出する為の受光素子と、
検出した干渉縞より前記被検投影光学系の波面収差を算出する為の解析手段と、を有し、
前記回折格子を、干渉計の光軸の周りに４５度回転可能に保持する回転機構を有することを特徴とするシアリング干渉計。 A shearing interferometer for evaluating the imaging characteristics of a projection optical system,
A light source that emits light used for measurement;
A transmission optical system for condensing the light beam emitted from the light source to the object point position of the test projection optical system;
A diffraction grating for dividing a convergent light beam converged on the object point, a divergent light beam incident on the test projection optical system, or a convergent or divergent light beam emitted from the test projection optical system, into a plurality of light beams;
A light receiving element for detecting interference fringes caused by interference between the divided light beams;
Analysis means for calculating the wavefront aberration of the test projection optical system from the detected interference fringes,
A shearing interferometer, comprising: a rotation mechanism that holds the diffraction grating so as to be rotatable by 45 degrees around the optical axis of the interferometer.
干渉させる２つの回折波を選択するための次数選択窓を有し、
２つの回折波を通過させる窓の並び方向又は窓の広がり方向が互いに４５度傾いている次数選択窓を切り替えて使用するようになされていることを特徴とするシアリング干渉計。 A shearing interferometer according to any one of claims 1 to 3,
An order selection window for selecting two diffracted waves to interfere with each other;
A shearing interferometer, wherein an order selection window in which the arrangement direction of windows through which two diffracted waves pass or the spreading direction of windows is inclined by 45 degrees is switched.
該窓保持板を干渉計内で窓を切り替えるために直線的に移動させる窓移動装置とを有することを特徴とするシアリング干渉計。 The interferometer according to claim 4, wherein a window holding plate in which two sets of order selection windows in which the arrangement direction of the two order selection windows or the spreading direction of the order selection windows is inclined by 45 degrees from each other is disposed;
A shearing interferometer, comprising: a window moving device that linearly moves the window holding plate in order to switch windows in the interferometer.
干渉させる２つの回折波を選択するための次数選択窓と、
該窓を干渉計の光軸の周りに４５度回転させる、窓回転手段と、を有することを特徴とするシアリング干渉計。 A shearing interferometer according to any one of claims 1 to 3,
An order selection window for selecting two diffracted waves to interfere with each other;
A shearing interferometer, comprising: window rotating means for rotating the window by 45 degrees around the optical axis of the interferometer.
前記回折格子を、少なくとも格子パターンに垂直な方向に、移動させる走査手段を有することを特徴とするシアリング干渉計。 A shearing interferometer according to any one of claims 1 to 6,
A shearing interferometer, comprising: scanning means for moving the diffraction grating at least in a direction perpendicular to the grating pattern.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101943570A (en) * | 2009-07-03 | 2011-01-12 | 株式会社高永科技 | 3-d shape measurement equipment |
| US10374221B2 (en) | 2012-08-24 | 2019-08-06 | Sila Nanotechnologies, Inc. | Scaffolding matrix with internal nanoparticles |
| JP2020534565A (en) * | 2017-09-20 | 2020-11-26 | カール・ツァイス・エスエムティー・ゲーエムベーハー | Wafer-holding device and projection microlithography system |
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2003
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101943570A (en) * | 2009-07-03 | 2011-01-12 | 株式会社高永科技 | 3-d shape measurement equipment |
| CN102840840A (en) * | 2009-07-03 | 2012-12-26 | 株式会社高永科技 | Three dimensional shape measuring apparatus |
| US8754936B2 (en) | 2009-07-03 | 2014-06-17 | Koh Young Technology Inc. | Three dimensional shape measurement apparatus |
| US10374221B2 (en) | 2012-08-24 | 2019-08-06 | Sila Nanotechnologies, Inc. | Scaffolding matrix with internal nanoparticles |
| JP2020534565A (en) * | 2017-09-20 | 2020-11-26 | カール・ツァイス・エスエムティー・ゲーエムベーハー | Wafer-holding device and projection microlithography system |
| JP7288896B2 (en) | 2017-09-20 | 2023-06-08 | カール・ツァイス・エスエムティー・ゲーエムベーハー | Wafer holding device and projection microlithography system |
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