JP2655097B2 - Phase difference measuring method and apparatus - Google Patents
Phase difference measuring method and apparatusInfo
- Publication number
- JP2655097B2 JP2655097B2 JP24420494A JP24420494A JP2655097B2 JP 2655097 B2 JP2655097 B2 JP 2655097B2 JP 24420494 A JP24420494 A JP 24420494A JP 24420494 A JP24420494 A JP 24420494A JP 2655097 B2 JP2655097 B2 JP 2655097B2
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- Prior art keywords
- optical path
- phase
- phase difference
- crystal
- path length
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、位相差測定方法および
装置、特にマッハツエンダ干渉計を用いた位相差測定方
法および装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a phase difference, and more particularly to a method and an apparatus for measuring a phase difference using a Mach-Zehnder interferometer.
【０００２】[0002]
【従来の技術】位相シフトマスクは、超解像露光の一方
式としてメモリ等の高集積化に有望視されている。位相
シフトマスクにおける位相シフト量は、シフタ部分とな
る薄膜の屈折率と膜厚の積で算出されるため、両者を正
確に測定することが必要である。しかしながら、露光波
長によっては、膜厚と屈折率を正確に測定する事が容易
でないため、直接位相差を測定することが望ましい。位
相差を測定する方法として最も簡易なものは、マッハツ
エンダ等の干渉光学系を組み、光路に測定試料を挿入し
た場合と、参照試料を挿入した場合とで、それぞれ生じ
る干渉フリンジのずれ量から位相差を換算する方法であ
る。この方法では明線と暗線との境界が必ずしも明確で
ないため、読み取りに誤差を生じ易く精度が低い。2. Description of the Related Art A phase shift mask is considered promising for high integration of memories and the like as one method of super-resolution exposure. Since the amount of phase shift in the phase shift mask is calculated by the product of the refractive index and the thickness of the thin film serving as the shifter portion, it is necessary to accurately measure both. However, it is not easy to accurately measure the film thickness and the refractive index depending on the exposure wavelength. Therefore, it is desirable to directly measure the phase difference. The simplest method for measuring the phase difference is to set up an interference optical system such as a Mach-Zehnder, and to determine the difference between the interference fringe displacement that occurs when the measurement sample is inserted into the optical path and when the reference sample is inserted. This is a method of converting the phase difference. In this method, since the boundary between the bright line and the dark line is not always clear, an error is likely to occur in reading and the accuracy is low.
【０００３】これに対して、フリンジが一本になるまで
厳密に光軸を調整し、干渉部分の明暗を測定する方法
は、干渉フリンジのずれ量から位相差を換算する方法よ
り精度が高い。この方法においては、光路の一方にウェ
ッジ付きの石英板等を入れ、これを手動マイクロメータ
または圧電素子でウェッジ方法に駆動することによって
光路長を変化させ、この光路または他方の光路に測定試
料を入れた場合と、参照試料を入れた場合とで発生する
干渉強度の差を０にするために必要な光路長の変化量か
ら位相量を換算することができる。しかしこの方法で
は、位相量に相当する光路長の変化量を、マイクロメー
タまたは圧電素子の駆動量から換算するので、マイクロ
メータを用いる場合はバックラッシュの影響、圧電素子
を用いる場合はヒステリシスの影響で、いずれにしても
大きな誤差要因を内包しており、複数回の連続測定にお
いて精度の再現性を得ることは困難である。On the other hand, a method of measuring the brightness of an interference portion by strictly adjusting the optical axis until one fringe is obtained has higher accuracy than a method of converting a phase difference from a shift amount of the interference fringe. In this method, a quartz plate or the like with a wedge is placed in one of the optical paths, and the optical path length is changed by driving the quartz plate or the like with a manual micrometer or a piezoelectric element in a wedge method, and the measurement sample is placed in this optical path or the other optical path. The amount of phase can be converted from the amount of change in the optical path length required to reduce the difference in interference intensity between the case where the reference sample is inserted and the case where the reference sample is inserted. However, in this method, the amount of change in the optical path length corresponding to the phase amount is converted from the driving amount of the micrometer or the piezoelectric element, so the effect of backlash when using a micrometer, and the effect of hysteresis when using a piezoelectric element. In any case, a large error factor is involved, and it is difficult to obtain reproducibility of accuracy in a plurality of continuous measurements.
【０００４】これらの他に、マッハツエンダ干渉計を用
いた測定をより高精度化したものとして、参照部分と、
これとの位相差を測定したい試料部分とを併せ持つ試料
基板を光路分岐前に挿入し、分岐後、各々の光路からそ
れぞれ試料部分透過光と参照部分透過光とを取り出して
干渉させる方法が、１９９４年フォトマスクジャパン予
稿集７０頁に発表されており、試料交換が不要なことが
大きな長所であるが、この方法でも光路長の調整はウェ
ッジ付き光学素子の微動でなされるので、同様の誤差を
免れることはできない。[0004] In addition to these, a reference portion and a measurement portion using a Mach-Zehnder interferometer are described as having higher accuracy.
A method in which a sample substrate having a sample portion whose phase difference is to be measured is inserted before branching the optical path, and after branching, the sample partial transmitted light and the reference partial transmitted light are taken out of each optical path and interfered with each other in 1994. Published in Photomask Japan Proceedings, p. 70.The major advantage is that sample replacement is not required.However, even with this method, the optical path length is adjusted by fine movement of the wedge-mounted optical element. I cannot escape.
【０００５】[0005]
【発明が解決しようとする課題】このように、従来の干
渉計を用いた位相差測定装置では、精度の高い測定を再
現性良く行うことが困難である。As described above, it is difficult for a phase difference measuring apparatus using a conventional interferometer to perform highly accurate measurement with good reproducibility.
【０００６】本発明の目的は、このような問題を解決し
た位相差測定方法および装置を提供することにある。An object of the present invention is to provide a phase difference measuring method and apparatus which has solved such a problem.
【０００７】[0007]
【課題を解決するための手段】本発明は、マッハツエン
ダ型干渉計の置ける２つに分岐された光路のうち一方を
光路長可変光路とし、この光路、または他方の光路に位
相差を測定しようとする２つの試料を順次挿入して合流
後の干渉強度を逐次測定し、それぞれの干渉強度を等し
くする光路長変化分を測定することから前記位相差を求
める位相差測定方法において、電気光学効果を有する結
晶を前記光路長可変光路に挿入し、前記結晶に連続的に
変化する電界を印加することによって光路長を変化させ
ることを特徴とする。SUMMARY OF THE INVENTION The present invention seeks to measure a phase difference in one of the two branched optical paths in a Mach-Zehnder interferometer, which is a variable optical path length optical path, or in the other optical path. In the phase difference measuring method for determining the phase difference by sequentially inserting the two samples to be measured and sequentially measuring the interference intensity after merging, and measuring the amount of change in the optical path length that equalizes the respective interference intensity, The optical path length is changed by inserting a crystal having the same into the variable optical path length optical path and applying a continuously changing electric field to the crystal.
【０００８】また本発明は、マッハツエンダ型干渉計に
おける２つに分岐された光路のうち一方を光路長可変光
路とし、光路の分岐前に試料を挿入して、前記試料の位
相シフタ部分と非位相シフタ部分とを一括して照射し得
るビーム形状で光を透過させ、分岐後各々の光路からそ
れぞれ位相シフタ部分透過光と非位相シフタ部分透過光
とを取り出して干渉させ、前記位相シフタの位相量を測
定する位相差測定方法において、電気光学効果を有する
結晶を前記光路長可変光路に挿入し、前記結晶に連続的
に変化する電界を印加して光路長を変化させ、既知の位
相差での干渉強度を基準として、これと強度を等しくす
るために必要とした印加電界の変化分から前記位相シフ
タの位相量を測定することを特徴とする。 The present invention also provides a Mach-Zehnder interferometer in which one of the two branched optical paths is a variable optical path length optical path, a sample is inserted before branching the optical path, and the phase shifter portion of the sample and the non-phase The light is transmitted in a beam shape capable of irradiating the shifter portion at a time, and after branching, the phase shifter partially transmitted light and the non-phase shifter partially transmitted light are taken out from each optical path and interfered, and the phase shifter Measure
Have an electro-optic effect in the phase difference measurement method
A crystal is inserted into the variable optical path length optical path, and is continuously connected to the crystal.
By applying an electric field that varies by changing the optical path length, a known position
Make the intensity equal to the interference intensity based on the phase difference.
From the change in the applied electric field required for
The phase amount of the data is measured.
【０００９】本発明は、マッハツエンダ型干渉計におけ
る２つに分岐された光路のうち一方を光路長可変光路と
し、この光路、または他方の光路に位相差を測定しよう
とする２つの試料を順次挿入して合流後の干渉強度を逐
次測定し、それぞれの干渉強度を等しくする光路長変化
分を測定することから前記位相差を求める位相差測定装
置において、前記光路長可変光路には、電気光学効果を
有する結晶が挿入され、前記結晶に連続的に変化する電
界を印加する電圧可変電源を備えることを特徴とする。According to the present invention, one of two branched optical paths in a Mach-Zehnder interferometer is a variable optical path length optical path, and two samples whose phase differences are to be measured are sequentially inserted into this optical path or the other optical path. In the phase difference measuring device to determine the phase difference by measuring the optical path length change to equalize the respective interference intensities by sequentially measuring the interference intensity after merging, the variable optical path length optical path, the electro-optic effect And a variable voltage power supply for applying a continuously changing electric field to the crystal.
【００１０】また本発明は、マッハツエンダ型干渉計に
おける２つに分岐された光路のうち一方を光路長可変光
路とし、光路の分岐前に試料を挿入して、前記試料の位
相シフタ部分と非位相シフタ部分とを一括して照射し得
るビーム形状で光を透過させ、分岐後各々の光路からそ
れぞれ位相シフタ部分透過光と非位相シフタ部分透過光
とを取り出して干渉させ、前記位相シフタの位相量を測
定する位相差測定装置において、前記光路長可変光路に
は、電気光学効果を有する結晶が挿入され、前記結晶に
連続的に変化する電界を印加する電圧可変電源を備え、
既知の位相差での干渉強度を基準として、これと強度を
等しくするために必要とした印加電界の変化分から前記
位相シフタの位相量を測定することを特徴とする。 The present invention also provides a Mach-Zehnder interferometer in which one of the two branched optical paths is an optical path length variable optical path, and a sample is inserted before branching the optical path, and the phase shifter portion of the sample and the non-phase The light is transmitted in a beam shape capable of irradiating the shifter portion at a time, and after branching, the phase shifter partially transmitted light and the non-phase shifter partially transmitted light are taken out from each optical path and interfered, and the phase shifter Measure
In the phase difference measuring device to determine the optical path length variable optical path,
Is inserted with a crystal having an electro-optical effect, and
Equipped with a variable voltage power supply that applies a continuously changing electric field,
Based on the interference intensity at a known phase difference,
From the change in the applied electric field required to equalize
The phase shifter is characterized by measuring a phase amount of the phase shifter.
【００１１】[0011]
【作用】結晶に電界をかけると、圧電効果または電歪効
果によって結晶に変形が生じる。結晶が変形すると、光
弾性効果により屈折率が変化する。本発明は、この効果
を利用してマッハツエンダ干渉計の光路長を制御し、位
相量の測定を行うものである。When an electric field is applied to a crystal, the crystal is deformed by a piezoelectric effect or an electrostrictive effect. When the crystal is deformed, the refractive index changes due to the photoelastic effect. The present invention utilizes this effect to control the optical path length of a Mach-Zehnder interferometer and measure the amount of phase.
【００１２】マッハツエンダ型の干渉光学系において、
干渉部分の光強度は分岐した２つの光路の光路長差によ
って決定される。光路長差が波長の整数倍となるとき干
渉光強度は最も強く、半波長の奇数倍となるとき最も弱
い。従って、一方の光路（参照光路）に電気光学結晶を
挿入し、これに電界を印加することによって光路長を連
続的に変化させれば、干渉強度を変化させることができ
る。この際、もう一方の光路（試料光路）に位相差を測
定したい２つの試料のうちの１つを挿入し、あらかじめ
干渉部分の強度を測定してから、試料を交換し、再度干
渉部分の強度を測定する。この時の強度の差は、それぞ
れの試料の位相差に起因するものであるから、差がなく
なるまで結晶にかける印加電界を変化させ、強度が等し
くなった時点の印加電界から、結晶の屈折率を計算し、
位相差を換算することができる。In a Mach-Zehnder type interference optical system,
The light intensity of the interference part is determined by the optical path length difference between the two branched optical paths. The interference light intensity is strongest when the optical path length difference is an integral multiple of the wavelength, and weakest when the difference is an odd multiple of the half wavelength. Therefore, the interference intensity can be changed by inserting an electro-optic crystal in one optical path (reference optical path) and continuously changing the optical path length by applying an electric field thereto. At this time, one of the two samples whose phase difference is to be measured is inserted into the other optical path (sample optical path), the intensity of the interference part is measured in advance, the sample is exchanged, and the intensity of the interference part is again measured. Is measured. Since the difference in intensity at this time is due to the phase difference between the respective samples, the applied electric field applied to the crystal is changed until the difference disappears, and the refractive index of the crystal is calculated from the applied electric field when the intensity becomes equal. And calculate
The phase difference can be converted.
【００１３】試料を挿入する光路は、電気光学結晶を挿
入する光路と同一であっても同じ現象が起こるので、必
ずしも参照光路と試料光路とに分ける必要はない。Since the same phenomenon occurs even when the optical path for inserting the sample is the same as the optical path for inserting the electro-optic crystal, it is not always necessary to divide the optical path into the reference optical path and the sample optical path.
【００１４】また参照部分と、これとの位相差を測定し
たい試料部分とを併せ持つ試料基板を光路分岐前に挿入
し、分岐後、各々の光路からそれぞれ試料部分透過光と
参照部分透過光とを取り出して干渉させる方式において
も、どちらかの光路に電気光学結晶を挿入すれば同様の
測定が可能になる。Further, a sample substrate having both a reference portion and a sample portion whose phase difference is to be measured is inserted before branching the optical path, and after branching, the sample partial transmission light and the reference partial transmission light are respectively transmitted from each optical path. In the method of taking out and causing interference, the same measurement can be performed by inserting an electro-optic crystal in either optical path.
【００１５】本発明においては、電気光学結晶として露
光波長１９３ｎｍ以上に対して十分に高い透過率を有す
る、ＫＤＰ，ＡＤＰ等を用いる。これらの結晶はいずれ
も圧電結晶であり、Ｃ軸方法（この方向をＺ軸と定め
る）に電界Ｅを印加した場合、ポッケルス効果によりＸ
軸方向の屈折率ｎX 、Ｙ軸方向の屈折率ｎY はそれぞれ
下式のように変化する。In the present invention, KDP, ADP or the like having a sufficiently high transmittance for an exposure wavelength of 193 nm or more is used as the electro-optic crystal. Each of these crystals is a piezoelectric crystal, and when an electric field E is applied in a C-axis method (this direction is defined as a Z-axis), X-rays are generated by the Pockels effect.
Refractive index of the axial n X, the refractive index n Y in the Y-axis direction is changed by the following equation, respectively.
【００１６】[0016]
【数１】 (Equation 1)
【００１７】[0017]
【数２】 (Equation 2)
【００１８】ここではγ63はポッケルス定数、ｎ0 は常
屈折率を表す。屈折率楕円体を用いた設計により、測定
光の偏光をＸ軸方向（またはＹ軸方向）に電界が振動す
る成分に限定し、電気光学結晶への入射方向をＹ軸（も
しくはＸ軸）方向とすることによって、参照光路の光路
長をｎX （またはｎY ）×［結晶の光路となる部分の長
さ］で変化させ、分岐した２つの光を同じ偏光状態に保
つことが可能であり、干渉を観測することができる。Here, γ 63 represents the Pockels constant, and n 0 represents the ordinary refractive index. Due to the design using the refractive index ellipsoid, the polarization of the measurement light is limited to a component in which the electric field oscillates in the X-axis direction (or Y-axis direction), and the incident direction to the electro-optic crystal is in the Y-axis (or X-axis) direction. Thus, the optical path length of the reference optical path can be changed by nx (or n Y ) × [the length of the portion to be the optical path of the crystal], and the two branched lights can be kept in the same polarization state. , Interference can be observed.
【００１９】電気光学結晶の電界印加によるヒステリシ
スは極めて小さく、屈折率制御の精度は十分に高い。従
って位相測定の誤差は十分に小さく、測定精度の再現性
も保持できる。The hysteresis of the electro-optic crystal due to the application of an electric field is extremely small, and the precision of the refractive index control is sufficiently high. Therefore, the error of the phase measurement is sufficiently small, and the reproducibility of the measurement accuracy can be maintained.
【００２０】[0020]
【実施例】以下、本発明をＫｒＦ露光用のレベンソン型
位相シフトマスクの位相測定に適用した実施例を図面を
参照して詳細に説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the phase measurement of a Levenson type phase shift mask for KrF exposure will be described in detail with reference to the drawings.
【００２１】図１は第１の実施例の位相差測定装置を示
す模式図である。この位相差測定装置は、マッハツエン
ダ型干渉計における２つに分岐された光路のうち一方を
光路長可変光路とし、他方の光路に位相差を測定しよう
とする測定試料を挿入して合流後の干渉強度を逐次測定
し、それぞれの干渉強度を等しくする光路長変化分を測
定することから前記位相差を求める位相差測定装置であ
って、電気光学効果を有する結晶を前記光路長可変光路
に挿入し、前記結晶に連続的に変化する電界を印加する
ことによって光路長を変化させるように構成したもので
ある。FIG. 1 is a schematic diagram showing a phase difference measuring apparatus according to the first embodiment. This phase difference measuring apparatus uses one of two branched optical paths in a Mach-Zehnder interferometer as a variable optical path length optical path, and inserts a measurement sample whose phase difference is to be measured into the other optical path, thereby causing interference after converging. A phase difference measuring device for sequentially measuring the intensities and measuring the optical path length change to equalize the respective interference intensities to obtain the phase difference, wherein a crystal having an electro-optical effect is inserted into the optical path length variable optical path. The optical path length is changed by applying a continuously changing electric field to the crystal.
【００２２】具体的には、光源１と、偏光子２と、ハー
フミラー３，８と、全反射鏡５，７と、ＫＤＰ結晶６
と、光検出器９と、電圧可変電源１０とから構成されて
いる。Specifically, the light source 1, the polarizer 2, the half mirrors 3, 8, the total reflection mirrors 5, 7, and the KDP crystal 6
, A photodetector 9 and a variable voltage power supply 10.
【００２３】測定試料４は、基板部分とシフタ部分とを
併せ持つ位相シフトマスクであり、ハーフミラー３と全
反射鏡５との光路に配置される。The measurement sample 4 is a phase shift mask having both a substrate part and a shifter part, and is arranged in the optical path between the half mirror 3 and the total reflection mirror 5.
【００２４】ＫＤＰ結晶６は、全反射鏡７とハーフミラ
ー８との間に配置され、電圧可変電源１０により電界が
印加される。The KDP crystal 6 is arranged between the total reflection mirror 7 and the half mirror 8, and an electric field is applied by a variable voltage power supply 10.
【００２５】光源１はＡｒレーザ光をＢＢＯ素子により
波長変換した２４８ｎｍのＣＷ光であり、ＫｒＦの波長
に等しい。これを偏光子２に通すことによって、電界が
Ｘ軸方向（紙面垂直方向）に振動する偏光成分のみ取り
出し、ハーフミラー３で分岐することによって、一方を
測定試料４に、他方を全反射鏡７を介してＫＤＰ結晶６
に入射させる。ＫＤＰ結晶６には、Ｃ軸方向（Ｚ軸）に
０〜２０ｋｖの電界を電圧可変電源１０により印加す
る。ＫＤＰ結晶６の透過光と全反射鏡５を介した測定試
料４の透過光は、それぞれハーフミラー８で合流させ干
渉光の強度を光検出器９で測定する。The light source 1 is CW light of 248 nm obtained by converting the wavelength of Ar laser light by a BBO element, and is equal to the wavelength of KrF. By passing this through the polarizer 2, only the polarized component whose electric field oscillates in the X-axis direction (perpendicular to the paper surface) is taken out and branched by the half mirror 3 so that one is the measurement sample 4 and the other is the total reflection mirror 7 Through the KDP crystal 6
Incident on An electric field of 0 to 20 kv is applied to the KDP crystal 6 in the C-axis direction (Z-axis) by the voltage variable power supply 10. The transmitted light of the KDP crystal 6 and the transmitted light of the measurement sample 4 via the total reflection mirror 5 are respectively combined by the half mirror 8 and the intensity of the interference light is measured by the photodetector 9.
【００２６】最初に測定試料４の基板部分を光路に挿入
し、光検出器９で干渉光強度を測定した後、測定試料４
のシフタ部分を挿入し光検出器９で測定される光強度が
基板部分挿入時と等しくなるまで、電圧可変電源１０に
よりＫＤＰ結晶６の印加電界を変える。この時の印加電
界の変化分からＫＤＰ結晶６の屈折率変化を求め、これ
にＫＤＰ結晶６の光路となる部分の長さを掛け合わせる
ことにより、測定試料４の基板部分とシフタ部分の位相
差に相当する光路長差が得られる。First, the substrate portion of the measurement sample 4 is inserted into the optical path, and the intensity of the interference light is measured by the photodetector 9.
And the electric field applied to the KDP crystal 6 is changed by the voltage variable power supply 10 until the light intensity measured by the photodetector 9 becomes equal to that when the substrate is inserted. The change in the refractive index of the KDP crystal 6 is obtained from the change in the applied electric field at this time, and the result is multiplied by the length of the portion of the KDP crystal 6 that is to be the optical path, so that the phase difference between the substrate portion and the shifter portion of the measurement sample 4 is obtained. A corresponding optical path length difference is obtained.
【００２７】この光路長差と光源波長から、±１度の精
度で位相差が換算できた。測定値のばらつきは極めて少
なく、数１０回の連続測定でも±１度の精度を保持でき
た。この精度は、位相シフトマスクが効果を発揮する上
で許容される誤差に較べて十分に小さく、位相シフト量
の検査装置として十分な精度である。From the optical path length difference and the light source wavelength, the phase difference could be converted with an accuracy of ± 1 degree. The dispersion of the measured values was extremely small, and the accuracy of ± 1 ° could be maintained even after several tens of continuous measurements. This precision is sufficiently smaller than the error allowed for the phase shift mask to exhibit its effect, and is sufficient as a phase shift amount inspection apparatus.
【００２８】図２は第２の実施例の位相差測定装置を示
す模式図である。この位相差測定装置は、マッハツエン
ダ型干渉計における２つに分岐された光路のうち一方を
光路長可変光路とし、光路の分岐前に測定試料を挿入し
て、測定試料の位相シフタ部分と非位相シフタ部分とを
一括して照射し得るビーム形状で光を透過させ、分岐後
各々の光路からそれぞれ位相シフタ部分透過光と非位相
シフタ部分透過光とを取り出して干渉させ、既知の位相
差での干渉強度を基準として、これと強度を等しくする
ために必要な光路長変化分から前記位相シフタの位相量
を測定する位相差測定装置であって、電気光学効果を有
する結晶を前記光路長可変光路に挿入し、前記結晶に連
続的に変化する電界を印加することによって光路長を変
化させるように構成したものである。FIG. 2 is a schematic diagram showing a phase difference measuring apparatus according to a second embodiment. This phase difference measuring apparatus uses one of the two branched optical paths in a Mach-Zehnder interferometer as a variable optical path length optical path, inserts a measurement sample before branching the optical path, and connects the phase shifter portion of the measurement sample with the non-phase The light is transmitted in a beam shape that can irradiate the shifter part collectively, and after branching, the phase shifter partially transmitted light and the non-phase shifter partially transmitted light are taken out from each optical path and caused to interfere with each other, with a known phase difference. A phase difference measuring device that measures a phase amount of the phase shifter from a change in an optical path length necessary to make the intensity equal to the interference intensity, wherein a crystal having an electro-optical effect is transmitted to the optical path length variable optical path. The structure is such that the optical path length is changed by inserting and applying a continuously changing electric field to the crystal.
【００２９】具体的には、光源１と、偏光子２と、グレ
ーティングアパーチャ１４と、コンデンサレンズ１５
と、対物レンズ１６と、石英光路１７と、像分離素子１
８と、ＫＤＰ結晶６と、電圧可変電源１０と、石英光路
１１と、イメージセンサ１２と、ピンホールスリット１
３と、光検出器９とから構成されている。Specifically, the light source 1, the polarizer 2, the grating aperture 14, and the condenser lens 15
, Objective lens 16, quartz optical path 17, image separation element 1
8, a KDP crystal 6, a voltage variable power supply 10, a quartz optical path 11, an image sensor 12, and a pinhole slit 1.
3 and a photodetector 9.
【００３０】測定試料４は、基板の掘り込みによる位相
シフタ部分を有し、コンデンサレンズ１５と対物レンズ
との間の光路に配置される。The measurement sample 4 has a phase shifter portion formed by digging a substrate, and is arranged on an optical path between the condenser lens 15 and the objective lens.
【００３１】石英光路１７と１１との間の光路長可変光
路には、ＫＤＰ結晶６が配置され、電圧可変電源１０に
より電界が印加される。The KDP crystal 6 is disposed in the optical path length variable optical path between the quartz optical paths 17 and 11, and an electric field is applied by the variable voltage power supply 10.
【００３２】この位相差測定装置では、光源１からの２
４８ｎｍ光を偏光子２に通した後、グレーティングアパ
ーチャ１４により分割し（分割された光を実線と点線で
示す）、コンデンサレンズ１５によって測定試料４のシ
フタ部分と基板部分（非シフタ部分）の両方を透過する
ように照射する。透過光は対物レンズ１６によって平行
光とした後、石英光路１７によって２つに分岐する。こ
のうち一方を、ＫＤＰ結晶６によって光路長を可変とし
た光路に導き、石英光路１１透過後にピンホールスリッ
ト１３により非シフタ部分透過光のみを透過させる。他
の一方は、石英光路１１を介してシフタ部分透過光のみ
がピンホールスリット１３を透過するようにイメージセ
ンサ１２を観察しつつ像分離素子１８を回転調整する。In this phase difference measuring device, two
After passing the 48 nm light through the polarizer 2, the light is split by the grating aperture 14 (the split light is indicated by a solid line and a dotted line), and both the shifter portion and the substrate portion (non-shifter portion) of the measurement sample 4 are measured by the condenser lens 15. Irradiation so as to transmit light. The transmitted light is collimated by the objective lens 16 and then split into two by the quartz optical path 17. One of them is led to an optical path whose optical path length is variable by the KDP crystal 6, and after transmitting through the quartz optical path 11, only the non-shifter partially transmitted light is transmitted through the pinhole slit 13. The other adjusts the rotation of the image separation element 18 while observing the image sensor 12 so that only the shifter partially transmitted light passes through the pinhole slit 13 via the quartz optical path 11.
【００３３】ピンホールスリット１３を透過した、シフ
タ部分透過光と非シフタ部分透過光は干渉し合い、光検
出器９ではこの干渉光強度を測定する。位相差が既知の
試料をあらかじめ測定しておき、この時の干渉光強度と
同じ強度を得るために必要な光路長変化量から位相シフ
タの位相量を測定することができる。The partially transmitted light of the shifter and the partially transmitted light of the non-shifter transmitted through the pinhole slit 13 interfere with each other, and the photodetector 9 measures the intensity of the interference light. A sample whose phase difference is known is measured in advance, and the phase amount of the phase shifter can be measured from the optical path length change amount necessary to obtain the same intensity as the interference light intensity at this time.
【００３４】本実施例においては、印加電界によるヒス
テリシスの少ない電気光学結晶を用いているので、測定
の再現性および精度に優れている。In the present embodiment, since the electro-optic crystal having little hysteresis due to the applied electric field is used, the reproducibility and accuracy of the measurement are excellent.
【００３５】以上の各実施例ではＫＤＰ結晶を用いる場
合についてのみ説明したが、ＡＤＰ結晶でも同様な測定
が可能である。また本実施例では光源として２４８ｎｍ
光を用いた場合についてのみ説明したが、水銀ランプｉ
線，ｇ線、および狭帯域化されたＡｒＦレーザ光（１９
３ｎｍ）でも同様に測定できる。In each of the embodiments described above, only the case where a KDP crystal is used has been described, but the same measurement can be performed with an ADP crystal. In this embodiment, the light source is 248 nm.
Although only the case using light has been described, the mercury lamp i
Line, g line, and narrowed band ArF laser light (19
3 nm).
【００３６】[0036]
【発明の効果】以上説明したように本発明の位相差測定
方法および装置によれば、±１度の高い精度で位相シフ
トマスクの位相差を測定することができる。また測定の
再現性も優れており、この精度は複数回の連続測定でも
変化しない。As described above, according to the phase difference measuring method and apparatus of the present invention, the phase difference of the phase shift mask can be measured with high accuracy of ± 1 degree. Also, the reproducibility of the measurement is excellent, and this accuracy does not change even in a plurality of continuous measurements.
【図１】本発明を適用した第１の実施例を示す模式図で
ある。FIG. 1 is a schematic diagram showing a first embodiment to which the present invention is applied.
【図２】本発明を適用した第２の実施例を示す模式図で
ある。FIG. 2 is a schematic diagram showing a second embodiment to which the present invention is applied.
１ 光源 ２ 偏光子 ３，８ ハーフミラー ４ 測定試料 ５，７ 全反射鏡 ６ ＫＤＰ結晶 ９ 光検出器 １０ 電圧可変電源 １１，１７ 石英光路 １２ イメージセンサ １３ ピンホールスリット １４ グレーティングアパーチャ １５ コンデンサレンズ １６ 対物レンズ １８ 像分離素子 Reference Signs List 1 light source 2 polarizer 3,8 half mirror 4 measurement sample 5,7 total reflection mirror 6 KDP crystal 9 photodetector 10 voltage variable power supply 11,17 quartz optical path 12 image sensor 13 pinhole slit 14 grating aperture 15 condenser lens 16 objective Lens 18 Image separation element
Claims (4)
岐された光路のうち一方を光路長可変光路とし、この光
路、または他方の光路に位相差を測定しようとする２つ
の試料を順次挿入して合流後の干渉強度を逐次測定し、
それぞれの干渉強度を等しくする光路長変化分を測定す
ることから前記位相差を求める位相差測定方法におい
て、 電気光学効果を有する結晶を前記光路長可変光路に挿入
し、 前記結晶に連続的に変化する電界を印加することによっ
て光路長を変化させることを特徴とする位相差測定方
法。1. One of two branched optical paths in a Mach-Zehnder interferometer is a variable optical path length optical path, and two samples whose phase differences are to be measured are sequentially inserted into this optical path or the other optical path. Measure the interference intensity after merging sequentially,
In the phase difference measuring method for determining the phase difference by measuring an optical path length change amount that equalizes the respective interference intensities, a crystal having an electro-optical effect is inserted into the variable optical path length optical path, and the crystal is continuously changed. A phase difference measuring method, wherein an optical path length is changed by applying a changing electric field.
分岐された光路のうち一方を光路長可変光路とし、光路
の分岐前に試料を挿入して、前記試料の位相シフタ部分
と非位相シフタ部分とを一括して照射し得るビーム形状
で光を透過させ、分岐後各々の光路からそれぞれ位相シ
フタ部分透過光と非位相シフタ部分透過光とを取り出し
て干渉させ、前記位相シフタの位相量を測定する位相差
測定方法において、電気光学効果を有する結晶を前記光
路長可変光路に挿入し、前記結晶に連続的に変化する電
界を印加して光路長を変化させ、既知の位相差での干渉
強度を基準として、これと強度を等しくするために必要
とした印加電界の変化分から前記位相シフタの位相量を
測定することを特徴とする位相差測定方法。 2. A method according to claim 1, wherein one of the two branched optical paths in the Mach-Zehnder interferometer is a variable optical path length optical path, and a sample is inserted before branching the optical path. Is transmitted in a beam shape that can collectively irradiate the phase shifter partially transmitted light and the non-phase shifter partially transmitted light from the respective optical paths after branching and interfere with each other to measure the phase amount of the phase shifter. Phase difference
In the measuring method, the crystal having the electro-optical effect is
The crystal is inserted into the variable-length optical path,
A field is applied to change the optical path length, causing interference at a known phase difference
Required to make this equal to the strength based on the strength
From the change in the applied electric field, the phase amount of the phase shifter is calculated.
A phase difference measuring method characterized by measuring.
岐された光路のうち一方を光路長可変光路とし、この光
路、または他方の光路に位相差を測定しようとする２つ
の試料を順次挿入して合流後の干渉強度を逐次測定し、
それぞれの干渉強度を等しくする光路長変化分を測定す
ることから前記位相差を求める位相差測定装置におい
て、 前記光路長可変光路には、電気光学効果を有する結晶が
挿入され、 前記結晶に連続的に変化する電界を印加する電圧可変電
源を備えることを特徴とする位相差測定装置。3. One of the two branched optical paths in the Mach-Zehnder interferometer is a variable optical path length optical path, and two samples whose phase differences are to be measured are sequentially inserted into this optical path or the other optical path. Measure the interference intensity after merging sequentially,
In a phase difference measuring device that obtains the phase difference by measuring an optical path length change amount that equalizes the respective interference intensities, a crystal having an electro-optical effect is inserted in the optical path length variable optical path, and the crystal is continuously connected to the crystal. A phase difference measuring device comprising a voltage variable power supply for applying a changing electric field.
分岐された光路のうち一方を光路長可変光路とし、光路
の分岐前に試料を挿入して、前記試料の位相シフタ部分
と非位相シフタ部分とを一括して照射し得るビーム形状
で光を透過させ、分岐後各々の光路からそれぞれ位相シ
フタ部分透過光と非位相シフタ部分透過光とを取り出し
て干渉させ、前記位相シフタの位相量を測定する位相差
測定装置において、前記光路長可変光路には、電気光学
効果を有する結晶が挿入され、前記結晶に連続的に変化
する電界を印加する電圧可変電源を備え、既知の位相差
での干渉強度を基準として、これと強度を等しくするた
めに必要とした印加電界の変化分から前記位相シフタの
位相量を測定することを特徴とする位相差測定装置。 4. A method according to claim 1, wherein one of the two branched optical paths in the Mach-Zehnder interferometer is a variable optical path length optical path, a sample is inserted before branching of the optical path, and a phase shifter portion and a non-phase shifter portion of the sample are inserted. Is transmitted in a beam shape that can collectively irradiate the phase shifter partially transmitted light and the non-phase shifter partially transmitted light from the respective optical paths after branching and interfere with each other to measure the phase amount of the phase shifter. Phase difference
In the measuring apparatus, the optical path length variable optical path includes an electro-optical
A crystal having an effect is inserted and changes continuously to the crystal
A variable voltage power supply that applies an electric field
The interference intensity at
From the change in the applied electric field required for
A phase difference measuring device for measuring a phase amount.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24420494A JP2655097B2 (en) | 1994-10-07 | 1994-10-07 | Phase difference measuring method and apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24420494A JP2655097B2 (en) | 1994-10-07 | 1994-10-07 | Phase difference measuring method and apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08110266A JPH08110266A (en) | 1996-04-30 |
| JP2655097B2 true JP2655097B2 (en) | 1997-09-17 |
Family
ID=17115324
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24420494A Expired - Lifetime JP2655097B2 (en) | 1994-10-07 | 1994-10-07 | Phase difference measuring method and apparatus |
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| Country | Link |
|---|---|
| JP (1) | JP2655097B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3067697B2 (en) * | 1997-06-25 | 2000-07-17 | 日本電気株式会社 | Phase difference measuring device |
| JP4698992B2 (en) * | 2004-09-14 | 2011-06-08 | 浜松ホトニクス株式会社 | Sample measuring apparatus and measuring method |
| CN103148949B (en) * | 2013-03-08 | 2015-07-01 | 深圳奥比中光科技有限公司 | Dynamic phase acquisition device |
| CN103499429B (en) * | 2013-08-28 | 2016-09-21 | 中国科学院上海光学精密机械研究所 | Transmission-type heavy-calibre element Method for Phase Difference Measurement |
| JP2015102537A (en) * | 2013-11-28 | 2015-06-04 | キヤノン株式会社 | Optical interference tomograph meter |
| CN104062096B (en) * | 2014-06-27 | 2017-01-04 | 哈尔滨工业大学深圳研究生院 | A kind of method that crystal optical index is affected by voltage compensation temperature |
| CN113777035A (en) * | 2021-08-26 | 2021-12-10 | 五邑大学 | Crystal refractive index measuring method and device and storage medium |
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| JP3006260B2 (en) * | 1992-01-24 | 2000-02-07 | 株式会社ニコン | Photomask inspection method and apparatus |
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