JP2713190B2 - Optical property measuring device - Google Patents

Optical property measuring device

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Publication number
JP2713190B2
JP2713190B2 JP6290425A JP29042594A JP2713190B2 JP 2713190 B2 JP2713190 B2 JP 2713190B2 JP 6290425 A JP6290425 A JP 6290425A JP 29042594 A JP29042594 A JP 29042594A JP 2713190 B2 JP2713190 B2 JP 2713190B2
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Prior art keywords
light
photodetector
polarized light
optical
optical frequency
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Japanese (ja)
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JPH08128946A (en
Inventor
研 住吉
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NEC Corp
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NEC Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/23—Bi-refringence

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Testing Of Optical Devices Or Fibers (AREA)
  • Manufacturing Optical Record Carriers (AREA)

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明は光ディスク基板や液晶配
向膜等を検査する際に必要とされる複屈折を始めとし
て、二色性、旋光性、円二色性等の光学特性や、楕円偏
光（真円偏光を含む）状態の解析等を行うための光学特
性を測定するための測定装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical characteristics such as dichroism, optical rotation, circular dichroism, etc. The present invention relates to a measurement device for measuring optical characteristics for analyzing a polarization state (including a true circular polarization state).

【０００２】[0002]

【従来の技術】一般に光学要素の光学特性のうち、例え
ば微小な複屈折測定は光ディスク基板や液晶配光膜の検
査に必要な測定である。このような微小な複屈折測定方
法として、光弾性変調素子を用いた位相変調測定方法
や、横ゼーマンレーザを用いたヘテロダイン測定方法が
ある。ここでは横ゼーマンレーザを用いた測定方法の一
例を図６を参照して説明する。横ゼーマンレーザ１０１
は、直交した２つの直線偏光を出射する。この２つの直
線偏光はビート周波数と呼ばれる周波数分だけ発振周波
数が異なっている。2. Description of the Related Art Generally, among the optical characteristics of optical elements, for example, measurement of minute birefringence is a measurement necessary for inspection of an optical disk substrate and a liquid crystal light distribution film. As such a minute birefringence measuring method, there are a phase modulation measuring method using a photoelastic modulation element and a heterodyne measuring method using a transverse Zeeman laser. Here, an example of a measuring method using a lateral Zeeman laser will be described with reference to FIG. Horizontal Zeeman laser 101
Emits two orthogonal linearly polarized light beams. The two linearly polarized lights have different oscillation frequencies by a frequency called a beat frequency.

【０００３】このレーザ光はハーフミラー１０２におい
て一部が反射され、透過されたレーザ光は半波長板１０
３に入射され、この半波長板１０３によって偏光方向が
変化され、その上で試料１０４に入射される。試料１０
４を透過したレーザ光は、偏光子１０５を通過され、検
出器１０６において検出される。また、前記ハーフミラ
ー１０２で反射されたレーザ光は偏光子１０８を通され
た上で参照信号用検出器１０７において検出される。そ
して、各検出器１０６，１０７において検出された信号
は位相計１０９において位相比較される。The laser light is partially reflected by the half mirror 102 and the transmitted laser light is reflected by the half-wave plate 10.
3, the polarization direction is changed by the half-wave plate 103, and then the sample 104 is incident. Sample 10
The laser light transmitted through 4 passes through the polarizer 105 and is detected by the detector 106. The laser beam reflected by the half mirror 102 passes through a polarizer 108 and is detected by a reference signal detector 107. The signals detected by the detectors 106 and 107 are compared in phase by a phase meter 109.

【０００４】ここで、検出器１０６で検出された信号に
はビート周波数からなる交流信号が含まれており、試料
の複屈折によってこのビート周波数の位相がずれる。そ
こで、ビート周波数の位相を参照信号に対して位相計１
０９において比較し、この位相差に基づいて試料の複屈
折量を求めることができる。Here, the signal detected by the detector 106 includes an AC signal having a beat frequency, and the phase of the beat frequency is shifted due to the birefringence of the sample. Then, the phase of the beat frequency is compared with the reference signal by a phase meter 1.
At 09, the birefringence of the sample can be determined based on the phase difference.

【０００５】この場合、試料の微小な複屈折を測定する
ためには、入射偏光方位と試料面方位を変えながら測定
する必要があり、これまでは試料自身を回転させること
が行われていた。ところが、試料が大型化するに従い試
料を回転することが困難とされるため、入射偏光方位を
回転させることが行われるようになった。この入射偏光
方位を回転させる方法として、前記測定装置では半波長
板１０２を光軸回りに回転させることが行われている。
この場合、半波長板１０２はある角度（θ）回転させる
と、半波長板からの出射偏光は二倍の角度（２θ）回転
することになる。このように、半波長板１０２を回転さ
せることにより、試料面への入射偏光方位を回転させる
ことが行われている。In this case, in order to measure the minute birefringence of the sample, it is necessary to measure while changing the incident polarization direction and the sample plane direction. Until now, the sample itself has been rotated. However, since it is difficult to rotate the sample as the size of the sample increases, rotation of the incident polarization direction has been performed. As a method of rotating the incident polarization direction, the measuring device rotates the half-wave plate 102 around the optical axis.
In this case, when the half-wave plate 102 is rotated by a certain angle (θ), the polarized light emitted from the half-wave plate is rotated twice (2θ). In this manner, by rotating the half-wave plate 102, the direction of polarization incident on the sample surface is rotated.

【０００６】[0006]

【発明が解決しようとする課題】しかしながら、一般的
にみて、半波長板はその位相精度が低いという問題があ
る。半波長板は進相軸方位の偏光と、遅相軸方位の偏光
との間に１８０°の位相差をもたらすものであり、この
位相差が正確に１８０°であるならば、入射直線偏光を
回転した出射直線偏光を得ることができる。ところが、
１８０°からずれた場合には出射光は楕円偏光となって
しまい、このように場合には前記した測定には不向きと
なる。通常、半波長板の位相精度は１°程度であり、こ
の位相精度によって測定される複屈折量に誤差が生じ
る。特に、測定する試料としての光ディスク基板や液晶
配向膜の複屈折量は１°以下である場合が多く、このよ
うな半波長板の位相誤差によって微小な複屈折の測定が
できなくなることがある。However, generally, there is a problem that the half-wave plate has low phase accuracy. The half-wave plate provides a 180 ° phase difference between the polarized light in the fast axis direction and the polarized light in the slow axis direction. If the phase difference is exactly 180 °, the incident linear polarization is changed. Rotated outgoing linearly polarized light can be obtained. However,
If the angle deviates from 180 °, the emitted light becomes elliptically polarized light, and in such a case, it is not suitable for the above-described measurement. Usually, the phase accuracy of a half-wave plate is about 1 °, and an error occurs in the amount of birefringence measured by this phase accuracy. In particular, the amount of birefringence of an optical disc substrate or a liquid crystal alignment film as a sample to be measured is often 1 ° or less, and a minute birefringence measurement may not be possible due to such a phase error of the half-wave plate.

【０００７】また、一方では、半波長板の回転軸と光軸
が正確に一致していなければ、半波長板による位相誤差
が一定でなくなり、この原因によっても測定される複屈
折量に誤差が生じる。更に、横ゼーマンレーザの発振光
が直線偏光からずれ、楕円偏光化することもある。この
楕円偏光化はレーザ発振管の状態に強く左右されるもの
であり、毎回毎回の測定時に一定になるとは限らない。
この楕円率が測定誤差となり、正確に試料の複屈折量を
測定することができなくなる。On the other hand, if the rotation axis and the optical axis of the half-wave plate do not exactly coincide with each other, the phase error due to the half-wave plate will not be constant. Occurs. Furthermore, the oscillation light of the transverse Zeeman laser may deviate from linearly polarized light and become elliptically polarized light. This elliptically polarized light strongly depends on the state of the laser oscillation tube, and is not always constant at every measurement.
This ellipticity becomes a measurement error, and it becomes impossible to accurately measure the birefringence of the sample.

【０００８】[0008]

【発明の目的】本発明の目的は、試料の微小な複屈折量
や二色性、旋光性、円二色性等の光学特性を正確にしか
も高精度に測定することが可能な測定装置を提供するこ
とにある。また、本発明の他の目的は、楕円偏光状態の
解析を行うための光特性を測定するための測定装置を提
供することにある。SUMMARY OF THE INVENTION It is an object of the present invention to provide a measuring apparatus capable of accurately and precisely measuring optical characteristics such as minute birefringence, dichroism, optical rotation, and circular dichroism of a sample. To provide. Another object of the present invention is to provide a measuring device for measuring optical characteristics for analyzing an elliptically polarized light state.

【０００９】[0009]

【課題を解決するための手段】本発明において、前記し
た光学特性を測定するための第１の測定技術は、楕円偏
光された光を偏光子によって直線偏光とし、この直線偏
光を試料および光周波数変調器に入射させ、これらから
出射された光を検光子を通して光検出器にて検出し、前
記偏光子を光軸回りに回転させながら光検出器にて検出
された交流信号の位相に基づいて試料の複屈折量を測定
することに基づく。In the present invention, a first measurement technique for measuring the above-described optical characteristics is to convert elliptically polarized light into linearly polarized light by a polarizer, and to convert the linearly polarized light into a sample and an optical frequency. It is made to enter into a modulator, the light emitted from these is detected by a photodetector through an analyzer, and based on the phase of the AC signal detected by the photodetector while rotating the polarizer around the optical axis. Based on measuring the birefringence of the sample.

【００１０】図１は本発明の第１の測定装置の基本構成
を示す図であり、光源１からは楕円偏光された光Ｌを出
射し、この楕円偏光の光Ｌを偏光子２によって直線偏光
とする。この偏光子２は回転手段３によって光軸回りに
回転させることが可能である。そして、この偏光子２か
らの光を試料４に入射させ、さらに試料４を透過した光
をＸ方向とＹ方向の偏光間にビート周波数の差を付ける
光周波数変調器５に入射させる。そして、この光周波数
変調器５から出射される光の所定方向の直線偏光の成分
を検光子６により検出させ、この検光子６を透過された
光を電気量として光検出器７により検出する。しかる上
で、位相計８において前記光検出器７で検出された電気
量の交流信号の位相を検出し、所定の演算を行うことで
試料の複屈折量を測定する。FIG. 1 is a diagram showing a basic configuration of a first measuring apparatus according to the present invention, in which a light source 1 emits elliptically polarized light L, and this elliptically polarized light L is linearly polarized by a polarizer 2. And The polarizer 2 can be rotated around the optical axis by the rotation means 3. Then, the light from the polarizer 2 is made incident on the sample 4, and the light transmitted through the sample 4 is made incident on an optical frequency modulator 5 which gives a difference in beat frequency between the polarizations in the X and Y directions. Then, an analyzer 6 detects a linearly polarized component of light emitted from the optical frequency modulator 5 in a predetermined direction, and the light transmitted through the analyzer 6 is detected by the photodetector 7 as an electric quantity. Then, the phase meter 8 detects the phase of the alternating current signal of the electric quantity detected by the photodetector 7 and performs a predetermined calculation to measure the birefringence of the sample.

【００１１】一方、本発明において、楕円偏光の状態を
解析するための第２の測定技術は、楕円偏光の光を光周
波数変調器を透過させ、透過された光を検光子を通して
光検出器にて検出し、この光検出器にて検出された交流
信号の位相に基づいて楕円偏光の状態を解析することに
基づく。On the other hand, in the present invention, a second measurement technique for analyzing the state of elliptically polarized light is to transmit elliptically polarized light through an optical frequency modulator and transmit the transmitted light to a photodetector through an analyzer. To analyze the state of elliptically polarized light based on the phase of the AC signal detected by this photodetector.
Based .

【００１２】図２は本発明の第２の測定装置の基本構成
を示している。即ち、被測定対象である楕円偏光の光Ｌ
Ｘは、この光に対してＸ方向とＹ方向の偏光間にビート
周波数の差を付ける光周波数変調器５に入射され、この
光周波数変調器５から出射される光の所定方向の直線偏
光の成分を検光子６によって透過させ、この検光子６を
透過された光を電気量として光検出器７により検出す
る。そして、位相計８においてこの光検出器７で検出さ
れた電気量の交流信号の位相を検出して所定の演算を行
うことで、楕円偏光の状態を解析することが可能とな
る。[0012] Figure 2 shows the basic configuration of the second measuring device of the present invention. That is, the elliptically polarized light L to be measured is
X is incident on an optical frequency modulator 5 that imparts a beat frequency difference between the polarized light in the X direction and the Y direction to the light, and the linearly polarized light in a predetermined direction of the light emitted from the optical frequency modulator 5 is emitted. The components are transmitted by the analyzer 6, and the light transmitted through the analyzer 6 is detected by the photodetector 7 as an electric quantity. Then, by detecting the phase of the AC signal of the electric quantity detected by the photodetector 7 in the phase meter 8 and performing a predetermined calculation, the state of the elliptically polarized light can be analyzed.

【００１３】[0013]

【作用】図１に示した第１の測定装置を用いて試料の複
屈折量を測定する例を説明する。光源１からの円偏光ま
たは楕円偏光の光、ここでは楕円偏光は偏光子２を透過
して直線偏光とされる。この直線偏光は、ジョーンズペ
クトルを用いると、（数１）で示される。An example of measuring the birefringence of a sample using the first measuring device shown in FIG. 1 will be described. Circularly or elliptically polarized light from the light source 1, here elliptically polarized light, passes through the polarizer 2 and becomes linearly polarized light. This linearly polarized light is expressed by (Equation 1) using Jones spectrum.

【００１４】[0014]

【数１】 ここで、Ａｘ，Ａｙは、入射される楕円偏光によって決
まる実数の量である。(Equation 1) Here, Ax and Ay are real numbers determined by the incident elliptically polarized light.

【００１５】この直線偏光は、試料４および光周波数変
調器５に順次入射される。試料４の複屈折量をδとする
と、試料４に入射された直線偏光の光ジョーンズベクト
ルは（数２）のように計算される。The linearly polarized light is sequentially incident on the sample 4 and the optical frequency modulator 5. Assuming that the birefringence of the sample 4 is δ, the optical Jones vector of the linearly polarized light incident on the sample 4 is calculated as (Equation 2).

【数２】 (Equation 2)

【００１６】この後、光周波数変調器５に入射され、直
線偏光のＸ方向とＹ方向の偏光間にビート周波数ω差が
付けられる。このときの光周波数変調器５による位相差
をωｔとすると、（数３）のように計算される。Thereafter, the light is incident on the optical frequency modulator 5 and a beat frequency ω difference is provided between the linearly polarized light in the X direction and the Y direction. Assuming that the phase difference by the optical frequency modulator 5 at this time is ωt, it is calculated as in (Equation 3).

【数３】 (Equation 3)

【００１７】その後、４５°方向に調整された検光子６
を通過する。これによる変化は（数４）のように計算さ
れる。Thereafter, the analyzer 6 adjusted in the 45 ° direction is used.
Pass through. The change due to this is calculated as in (Equation 4).

【数４】 したがって、光検出器７において検出される透過光量は
（数５）で現される。(Equation 4) Therefore, the amount of transmitted light detected by the photodetector 7 is expressed by (Equation 5).

【００１８】[0018]

【数５】 (Equation 5)

【００１９】これから、透過光量は周波数ωの交流信号
をもつことが判る。また、この交流信号の位相差を位相
計８において測定することにより、試料４の複屈折量δ
を測定することができる。From this, it can be seen that the transmitted light amount has an AC signal of frequency ω. Further, by measuring the phase difference of this AC signal with the phase meter 8, the birefringence δ of the sample 4 is obtained.
Can be measured.

【００２０】また、図２に示した第２の測定装置により
第２の測定方法を説明する。試料が存在していないた
め、前記した複屈折量δは０となり、透過光量は入射さ
れる楕円偏光の成分によって決まる。これより、透過光
の時間変化を測定すれば、Ａｘ，Ａｙが決定できる。し
たがって、任意の楕円偏光の状態を決定することが可能
となる。ただし、この場合ＡｘとＡｙの位相差を考慮す
る必要がある。The second measuring method will be described with reference to the second measuring device shown in FIG. Since the sample does not exist, the above-mentioned birefringence amount δ becomes 0, and the transmitted light amount is determined by the incident elliptically polarized light component. From this, Ax and Ay can be determined by measuring the time change of the transmitted light. Therefore, it is possible to determine an arbitrary elliptically polarized light state. However, in this case, it is necessary to consider the phase difference between Ax and Ay.

【００２１】即ち、解析対象とする楕円偏光を（数６）
のように表記する。That is, the elliptically polarized light to be analyzed is expressed by (Equation 6)
Notation as follows.

【数６】 (Equation 6)

【００２２】ここで、φとΔが決定されれば、楕円偏光
状態が解析できることになる。そこで、第１の測定方法
の場合と同様に（数７）の計算を行う。Here, if φ and Δ are determined, the elliptically polarized light state can be analyzed. Therefore, the calculation of (Equation 7) is performed as in the case of the first measurement method.

【数７】 (Equation 7)

【００２３】この結果、透過光量は（数８）のように求
められる。As a result, the amount of transmitted light is obtained as shown in (Equation 8).

【数８】 (Equation 8)

【００２４】これより、透過光量の交流信号の位相差を
測定することにより、Δが決定できる。また、交流信号
と直流信号の比を測定することでφを決定することがで
きる。したがって、楕円偏光状態の解析が可能となる。From this, Δ can be determined by measuring the phase difference of the AC signal of the amount of transmitted light. Also, φ can be determined by measuring the ratio of the AC signal to the DC signal. Therefore, it is possible to analyze the elliptically polarized light state.

【００２５】[0025]

【実施例】次に、本発明の実施例を図面を参照して説明
する。図３は第１の測定方法及び測定装置の具体例を示
す図である。この構成においては、光源１として発振波
長６３３ｎｍの周波数安定化ＨｅＮｅレーザ１１（日本
科学エンジニアリング社製，ＭＯＤＥＬ−４３０）を用
いた。レーザ発振光は直線偏光である。水晶板からなる
１／４波長板１２の進相軸をレーザ発振光の直線偏光方
位に対して４５°の位置をなすように配置した。１／４
波長板１２からの出射光は円偏光となる。この出射光を
偏光子であるグラントムソンプリズム２に入射させる。
このグラントムソンプリズムは回転手段であるステッピ
ングモータ３によって回転させることができる。Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a specific example of the first measuring method and the measuring device. In this configuration, a frequency-stabilized HeNe laser 11 having an oscillation wavelength of 633 nm (MODEL-430, manufactured by Nippon Kagaku Engineering Co., Ltd.) was used as the light source 1. The laser oscillation light is linearly polarized light. The fast axis of the quarter-wave plate 12 made of a quartz plate was arranged at 45 ° with respect to the linear polarization direction of the laser oscillation light. 1/4
The light emitted from the wave plate 12 is circularly polarized. The emitted light is made incident on a Glan-Thompson prism 2 as a polarizer.
This Glan-Thompson prism can be rotated by a stepping motor 3 which is a rotating means.

【００２６】被測定物である試料４として、ラビング配
向膜、すなわちガラス基板上に成膜したポリイミド薄膜
（日本合成ゴム社製，ＡＬ１０５１）をレーヨン布でラ
ビングしたものを用いた。この試料４を例えば試料ステ
ージに取り付けて、レーザ光を入射させる。更に、光周
波数変調器としてコントローラ１３により制御される光
周波数シフタ５（ＨＯＹＡ−ＳＣＨＯＴＴ社製，Ｗ−２
１０）を用いた。ビート周波数として５０ＫＨｚを選ん
だ。As the sample 4 to be measured, a rubbing alignment film, that is, a polyimide thin film (AL1051 manufactured by Nippon Synthetic Rubber Co., Ltd.) formed on a glass substrate was rubbed with a rayon cloth. The sample 4 is attached to, for example, a sample stage, and a laser beam is made incident. Further, an optical frequency shifter 5 (manufactured by HOYA-SCHOTT, W-2, which is controlled by the controller 13 as an optical frequency modulator)
10) was used. 50 kHz was selected as the beat frequency.

【００２７】光周波数シフタ５からの出射光を検光子で
あるグラントムソンプリズム６に入射させ、それからの
出射光を光検出器であるシリコンフォトダイオード７に
入射させた。フォトダイオード７の光電流は、電流電圧
変換器１４（ケースレイ社製，４２８型）に通して電圧
に変換した後、位相計８（ドラネッツ社製，３０５Ｃ）
に入力した、位相計８の参照信号は、光周波数シフタ５
のコントローラ１３から供給した。位相計８のアナログ
出力を電圧計１５（ケースレイ ２００１型）に入力し
た。The light emitted from the optical frequency shifter 5 is made incident on a Glan-Thompson prism 6 which is an analyzer, and the light emitted therefrom is made incident on a silicon photodiode 7 which is a photodetector. The photocurrent of the photodiode 7 is converted into a voltage by passing it through a current / voltage converter 14 (manufactured by Keithley Corp., type 428), and then converted into a voltage by a phase meter 8 (manufactured by Dranez Corp., 305C).
The reference signal of the phase meter 8 input to the optical frequency shifter 5
Supplied from the controller 13. The analog output of the phase meter 8 was input to the voltmeter 15 (Kaysley 2001 type).

【００２８】具体的な測定は、試料４を挿入前にグラン
トムソンプリズム２をステッピングモータ３により回転
させながら電圧計１５の出力を測定した。この後、試料
４を挿入し、同様の測定を行った。そして、２つの測定
結果の差を求めた。結果を図４に示す。このように、偏
光子としてのグラントムソンプリズム２の一回転に対し
て二倍の周期での変化を示す結果が得られた。この二倍
周期の振幅は０．４°程度である。これから、測定した
ラビング配向膜の複屈折量は０．４ｎｍであることが判
った。Specifically, the output of the voltmeter 15 was measured while the Glan-Thompson prism 2 was rotated by the stepping motor 3 before the sample 4 was inserted. Thereafter, sample 4 was inserted and the same measurement was performed. Then, the difference between the two measurement results was determined. FIG. 4 shows the results. As described above, a result showing a change in a cycle twice as long as one rotation of the Glan-Thompson prism 2 as the polarizer was obtained. The amplitude of this double cycle is about 0.4 °. From this, it was found that the measured birefringence of the rubbing alignment film was 0.4 nm.

【００２９】また、この実施例によれば、グラントムソ
ンプリズム２で構成される偏光子の偏光度は非常に高い
ため、半波長板におけるような位相精度が低いことによ
る誤差が発生することはない。更に、レーザ光を出力す
る光源１に変調機能をもたせる必要がないため、レーザ
光源の偏光状態によらずに安定した測定が可能となる。Further, according to this embodiment, since the degree of polarization of the polarizer constituted by the Glan-Thompson prism 2 is very high, no error occurs due to low phase accuracy as in a half-wave plate. . Further, since it is not necessary to provide the light source 1 that outputs laser light with a modulation function, stable measurement can be performed regardless of the polarization state of the laser light source.

【００３０】なお、前記実施例では偏光子２からの光が
先に試料４に入射され、次に光周波数変調器５に入射さ
れているが、この逆に、先に光周波数変調器５に入射さ
れ、後に試料４に入射されるようにしてもよい。In the above embodiment, the light from the polarizer 2 is first incident on the sample 4 and then on the optical frequency modulator 5, but conversely, the light is first incident on the optical frequency modulator 5. The light may be incident on the sample 4 later.

【００３１】図５は前記した本発明の第２の測定装置を
利用し、これに第１の測定装置と同様に偏光子２を付加
することで、楕円偏光状態の解析を行うと共に、試料４
の複屈折量の測定を可能にした実施例を示す図である。
発振波長６３３ｎｍの周波数安定化ＨｅＮｅレーザ１１
（日本科学エンジニアリング社製，ＭＯＤＥＬ−４３
０）からの光は、１／４波長板１２を通過して楕円偏光
とされ、その上で偏光子であるグラントムソンプリズム
２を通過させ直線偏光とする。FIG. 5 shows the analysis of elliptically polarized light by using the second measuring device of the present invention and adding a polarizer 2 to the same as in the first measuring device.
FIG. 4 is a diagram showing an example in which the measurement of the amount of birefringence of the present invention is enabled.
Frequency stabilized HeNe laser 11 having an oscillation wavelength of 633 nm
(Model-43 manufactured by Nippon Kagaku Engineering Co., Ltd.
The light from 0) passes through the quarter-wave plate 12 and is converted into elliptically polarized light, and then passes through the Glan-Thompson prism 2 as a polarizer to be converted into linearly polarized light.

【００３２】その後、レーザ光を試料４の表面に入射角
７０°で入射させる。このときの入射偏光方位を試料４
の入射面から４５°の角度となるように調整する。試料
面からの反射光は光周波数変調器としての光周波数シフ
タ（ＨＯＹＡ−ＳＣＨＯＴＴ社製，Ｓ−２１０）５を通
過させる。試料４としては、シリコンウェハの表面に成
膜した薄いシリコン酸化膜を用いる。試料の反射光は検
光子であるグラントムソンプリズム６を通過した後、光
検出器としてのシリコンフォトダイオード７に入射され
る。Thereafter, a laser beam is incident on the surface of the sample 4 at an incident angle of 70 °. At this time, the incident polarization direction was set to Sample 4.
Is adjusted so as to be at an angle of 45 ° from the incident surface. The light reflected from the sample surface is passed through an optical frequency shifter (HOYA-SCHOTT, S-210) 5 as an optical frequency modulator. As the sample 4, a thin silicon oxide film formed on the surface of a silicon wafer is used. The reflected light of the sample passes through a Glan-Thompson prism 6 as an analyzer, and then enters a silicon photodiode 7 as a photodetector.

【００３３】更に、シリコンフォトダイオード７で検出
された光電流は電流電圧変換器（ケースレイ社製，４２
８型）によって電圧に変換される。この電圧波形をスト
レージオシロスコープ１６で記録する。この記録した電
圧波形をパーソナルコンピュータ１７に入力し、解析を
行う。Further, the photocurrent detected by the silicon photodiode 7 is supplied to a current-to-voltage converter (42, manufactured by Keithley Co., Ltd.).
(Type 8). This voltage waveform is recorded by the storage oscilloscope 16. The recorded voltage waveform is input to the personal computer 17 for analysis.

【００３４】この結果、（数８）から判るように、電圧
波形は直流成分と交流成分とよりなり、試料挿入前後の
交流成分の位相差を読み取ることにより、Δを２７０°
と決定することができる。更に、交流信号成分の振幅と
直流信号成分の比を求めることによりφを７４°と決定
することができる。そして、通常のエリプソメトリの計
算に従い、このφ及びΔよりシリコン酸化膜の厚さを１
５０ｎｍと決定できた。As a result, as can be seen from (Equation 8), the voltage waveform is composed of a DC component and an AC component, and by reading the phase difference between the AC components before and after the sample is inserted, Δ is set to 270 °.
Can be determined. Further, by determining the ratio between the amplitude of the AC signal component and the DC signal component, φ can be determined to be 74 °. Then, according to the normal ellipsometry calculation, the thickness of the silicon oxide film is set to 1 from these φ and Δ.
It was determined to be 50 nm.

【００３５】[0035]

【発明の効果】以上説明したように本発明の第１の測定
装置によれば、楕円偏光された光を偏光子によって直線
偏光とし、これを試料および光周波数変調器に入射さ
せ、これらから出射された光を検光子を通して光検出器
にて検出し、かつ偏光子を回転させながら光検出器にて
検出された交流信号の位相に基づいて試料の複屈折量を
測定することにより、試料の複屈折を始めとする光学特
性を測定することができる。これにより、半波長板が不
要となり、測定する複屈折量の誤差を低減することがで
きる。As described above, the first measurement of the present invention
According to the apparatus , the elliptically polarized light is converted into linearly polarized light by a polarizer, and the linearly polarized light is made incident on a sample and an optical frequency modulator. By measuring the amount of birefringence of the sample based on the phase of the AC signal detected by the photodetector while rotating the element, it is possible to measure the optical characteristics of the sample including birefringence. This eliminates the need for a half-wave plate and reduces errors in the amount of birefringence to be measured.

【００３６】また、本発明の第１の測定装置は、楕円偏
光された光を出射する光源に対して光軸回りに回転可能
な偏光子と、偏光子からの光に対してＸ方向とＹ方向の
偏光間にビート周波数の差を付ける光周波数変調器と、
この光周波数変調器から出射される光の所定偏光方向の
成分を透過させる検光子と、この検光子を透過された光
を電気量として検出する光検出器と、この光検出器で検
出された電気量の交流信号の位相を検出して所定の演算
を行う手段とを備えることにより、光周波数変調器の前
段或いは後段に介挿配置した試料の複屈折量を始めとす
る光学特性を高精度に測定することができる。Further, the first measuring apparatus of the present invention comprises a polarizer rotatable around an optical axis with respect to a light source which emits elliptically polarized light, an X direction and a Y direction with respect to the light from the polarizer. An optical frequency modulator for providing a beat frequency difference between polarizations in directions,
An analyzer that transmits a component in a predetermined polarization direction of light emitted from the optical frequency modulator, a photodetector that detects light transmitted through the analyzer as an electric quantity, and a photodetector that is detected by the photodetector. Means for detecting the phase of an AC signal of an electric quantity and performing a predetermined calculation, thereby achieving high-precision optical characteristics such as the birefringence of a sample interposed and arranged before or after the optical frequency modulator. Can be measured.

【００３７】ここで、光源を直線偏光のレーザ光を出射
する周波数安定化レーザと、この出射されるレーザ光を
円偏光とする１／４波長板とで構成することで、安定し
た楕円偏光を出力することができ、測定精度を高めるこ
とができる。また、偏光子をグラントムソンプリズムで
構成することで、偏光度の高い偏光を得ることができ、
半波長板のような位相精度による測定誤差が発生するこ
とはない。Here, the light source is constituted by a frequency-stabilized laser for emitting linearly polarized laser light and a quarter-wave plate for making the emitted laser light circularly polarized, so that stable elliptically polarized light can be obtained. Can be output, and the measurement accuracy can be increased. Also, by configuring the polarizer with a Glan-Thompson prism, it is possible to obtain polarized light having a high degree of polarization,
A measurement error due to phase accuracy unlike a half-wave plate does not occur.

【００３８】本発明の第２の測定装置によれば、楕円偏
光の光を光周波数変調器を透過させ、透過された光を検
光子を通して光検出器にて検出し、この光検出器にて交
流信号の位相にを検出することで、楕円偏光の状態を解
析することができる。 According to the second measuring device of the present invention, the elliptically polarized light is transmitted through the optical frequency modulator, and the transmitted light is detected by the photodetector through the analyzer. By detecting the phase of the AC signal, the state of the elliptically polarized light can be analyzed.

【００３９】また、本発明の第２の測定装置は、楕円偏
光の光に対してＸ方向とＹ方向の偏光間にビート周波数
の差を付ける光周波数変調器と、この光周波数変調器か
ら出射される光の所定偏光方向の成分を透過させる検光
子と、この検光子を透過された光を電気量として検出す
る光検出器と、この光検出器で検出された電気量の交流
信号の位相を検出して所定の演算を行う手段とを備える
ことにより、楕円偏光の状態を解析することかできる。
また、偏光子を付加することで、第１の測定方法を実行
することも可能である。Further, the second measuring device of the present invention comprises an optical frequency modulator for giving a difference in beat frequency between the polarization in the X direction and the polarization in the Y direction with respect to the elliptically polarized light, and an output from the optical frequency modulator. An analyzer that transmits a component of a predetermined polarization direction of light to be transmitted, a photodetector that detects light transmitted through the analyzer as an electric quantity, and a phase of an AC signal of the electric quantity detected by the photodetector And means for performing a predetermined operation by detecting the state of the elliptically polarized light.
Further, by adding a polarizer, it is possible to execute the first measurement method.

【図面の簡単な説明】[Brief description of the drawings]

【図１】本発明の第１の測定方法と測定装置の基本構成
を示す図である。FIG. 1 is a diagram showing a basic configuration of a first measuring method and a measuring device of the present invention.

【図２】本発明の第２の測定方法と測定装置の基本構成
を示す図である。FIG. 2 is a diagram illustrating a basic configuration of a second measuring method and a measuring apparatus according to the present invention.

【図３】本発明の第１の測定装置の一実施例の構成を示
す図である。FIG. 3 is a diagram showing a configuration of one embodiment of a first measuring device of the present invention.

【図４】本発明の第１の測定方法による測定結果の一例
を示す図である。FIG. 4 is a diagram showing an example of a measurement result by the first measurement method of the present invention.

【図５】本発明の第２の測定装置を応用して第１の測定
方法及び第２の測定方法を行う構成を示す図である。FIG. 5 is a diagram showing a configuration for performing a first measurement method and a second measurement method by applying the second measurement device of the present invention.

【図６】従来の複屈性測定装置の一例の構成を示す図で
ある。FIG. 6 is a diagram showing a configuration of an example of a conventional birefringence measuring device.

【符号の説明】[Explanation of symbols]

１ 光源 ２ 偏光子 ３ 回転手段 ４ 試料 ５ 光周波数変調器 ６ 検光子 ７ 光検出器 ８ 位相計 １１ 周波数安定化ＨｅＮｅレーザ １２ １／４波長板 １３ コントローラ １４ 電流電圧変換器 １５ 電圧計 １６ ストレージオシロスコープ １７ パーソナルコンピュータ Reference Signs List 1 light source 2 polarizer 3 rotating means 4 sample 5 optical frequency modulator 6 analyzer 7 photodetector 8 phase meter 11 frequency stabilized HeNe laser 12 quarter-wave plate 13 controller 14 current-voltage converter 15 voltmeter 16 storage oscilloscope 17 Personal computer

Claims (3)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 楕円偏光された光を出射する光源と、こ
の光源からの光を直線偏光とする偏光子と、この偏光子
を光軸回りに回転させる手段と、前記偏光子からの光に
対してＸ方向とＹ方向の偏光間にビート周波数の差を付
ける光周波数変調器と、この光周波数変調器から出射さ
れる光の所定偏光方向の成分を透過させる検光子と、こ
の検光子を透過された光を電気量として検出する光検出
器と、この光検出器で検出された電気量の交流信号の位
相を検出して所定の演算を行う手段とを備え、前記光周
波数変調器の前段或いは後段に試料を介挿配置すること
を特徴とする光学特性測定装置。1. A light source that emits elliptically polarized light, a polarizer that converts the light from the light source into linearly polarized light, a unit that rotates the polarizer around an optical axis, and a light source that emits the light from the polarizer. On the other hand, an optical frequency modulator for giving a beat frequency difference between the polarizations in the X direction and the Y direction, an analyzer for transmitting a component in a predetermined polarization direction of light emitted from the optical frequency modulator, and the analyzer A photodetector for detecting the transmitted light as an electric quantity, and means for detecting a phase of an alternating current signal of the electric quantity detected by the photodetector and performing a predetermined operation, and the optical frequency modulator An optical characteristic measuring apparatus characterized in that a sample is interposed and arranged at a front stage or a rear stage. 【請求項２】 光源は直線偏光のレーザ光を出射する周
波数安定化レーザと、この出射されるレーザ光を円偏光
とする１／４波長板とで構成され、偏光子と検光子はグ
ラントムソンプリズムで構成され、光周波数変調器は光
周波数シフタで構成され、光検出器はフォトダイオード
で構成され、位相を検出する手段は電流電圧変換器と位
相計或いはコンピュータで構成されてなる請求項１の光
学特性測定装置。2. A light source comprises: a frequency-stabilized laser for emitting linearly polarized laser light; and a quarter-wave plate for converting the emitted laser light to circularly polarized light. The polarizer and analyzer are Glan Thompson. is composed of a prism, an optical frequency modulator is composed of an optical frequency shifter, the photodetector is a photodiode, according to claim 1 means for detecting a phase composed consists of a current-voltage converter and a phase meter or computer Optical property measuring device. 【請求項３】 楕円偏光の光に対してＸ方向とＹ方向の
偏光間にビート周波数の差を付ける光周波数変調器と、
この光周波数変調器から出射される光の所定偏光方向の
成分を透過させる検光子と、この検光子を透過された光
を電気量として検出する光検出器と、この光検出器で検
出された電気量の交流信号の位相を検出して所定の演算
を行う手段とを備えることを特徴とする光学特性測定装
置。3. An optical frequency modulator for providing a beat frequency difference between the polarization in the X direction and the polarization in the Y direction for elliptically polarized light;
An analyzer that transmits a component in a predetermined polarization direction of light emitted from the optical frequency modulator, a photodetector that detects light transmitted through the analyzer as an electric quantity, and a photodetector that is detected by the photodetector. Means for detecting a phase of an AC signal of an electric quantity and performing a predetermined calculation.
JP6290425A 1994-10-31 1994-10-31 Optical property measuring device Expired - Lifetime JP2713190B2 (en)

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JP6290425A JP2713190B2 (en) 1994-10-31 1994-10-31 Optical property measuring device

Applications Claiming Priority (1)

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JP6290425A JP2713190B2 (en) 1994-10-31 1994-10-31 Optical property measuring device

Publications (2)

Publication Number Publication Date
JPH08128946A JPH08128946A (en) 1996-05-21
JP2713190B2 true JP2713190B2 (en) 1998-02-16

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US6300954B1 (en) 1997-09-12 2001-10-09 Meiryo Tekunika Kabushiki Kaisha Methods and apparatus for detecting liquid crystal display parameters using stokes parameters
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JPH0612333B2 (en) * 1988-09-20 1994-02-16 有限会社ユニオプト Automatic birefringence measuring device
JPH0438455A (en) * 1990-06-01 1992-02-07 Sekisui Chem Co Ltd Apparatus for inspecting surface state
JPH0721534B2 (en) * 1990-07-11 1995-03-08 株式会社ピーエフユー Battery test method in power supply circuit
JP3340145B2 (en) * 1991-12-20 2002-11-05 日本分光株式会社 Stork meter

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005068957A1 (en) * 2004-01-15 2005-07-28 Tokyo Denki University Stress measuring method and instrument
US7639348B2 (en) 2004-01-15 2009-12-29 Tokyo Denki University Stress measuring method and instrument

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