JP2000019316A - Period measuring method of diffraction grating - Google Patents
Period measuring method of diffraction gratingInfo
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- JP2000019316A JP2000019316A JP10191356A JP19135698A JP2000019316A JP 2000019316 A JP2000019316 A JP 2000019316A JP 10191356 A JP10191356 A JP 10191356A JP 19135698 A JP19135698 A JP 19135698A JP 2000019316 A JP2000019316 A JP 2000019316A
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- Prior art keywords
- diffraction grating
- period
- interference pattern
- angle
- interference
- Prior art date
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、主に光通信に使用
される分布帰還型半導体レーザの回折格子の周期測定方
法にする。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the period of a diffraction grating of a distributed feedback semiconductor laser mainly used for optical communication.
【０００２】[0002]
【従来の技術】近年、高密度で情報を伝達する手段とし
て、波長多重（ＷＤＭ：Wavelength Division Multiple
x ）光伝送システムが開発されている。波長多重光伝送
システムでは、広帯域に波長を可変できる光源が必要で
あり、この種の光源として共振器内で回折格子が一様に
チャーピングしている構造の半導体レーザ（例えば、Ha
rtmut Hilmer,et al.,IEEE J.Lightwave Technol.,vol.
13,no.9,pp.1905-1912）や、回折格子が周期的にチャー
ピングしている構造の半導体レーザ（例えば、Magnus O
berg,et al.,IEEE J.Lightwave Technol.,vol.13,no.1
0,pp.1892-1898 ）が開発されている。2. Description of the Related Art In recent years, as means for transmitting information at high density, wavelength division multiplexing (WDM) has been proposed.
x) Optical transmission systems are being developed. A wavelength multiplexing optical transmission system requires a light source capable of changing the wavelength over a wide band. As this type of light source, a semiconductor laser having a structure in which a diffraction grating is uniformly chirped in a resonator (for example, Ha laser).
rtmut Hilmer, et al., IEEE J. Lightwave Technol., vol.
13, no. 9, pp. 1905-1912) or a semiconductor laser having a structure in which the diffraction grating is periodically chirped (eg, Magnus O.D.
berg, et al., IEEE J. Lightwave Technol., vol.13, no.1
0, pp.1892-1898).
【０００３】このような半導体レーザの製造工程では、
半導体基板上にフォトレジスト膜を形成した後、光又は
電子ビームによりフォトレジスト膜に回折格子を描画す
る工程が必要である。回折格子の描画には、主に二光束
干渉露光法及び電子ビーム直接描画法が用いられる。電
子ビーム直接描画法では、電子ビームによりレジスト膜
に直接回折格子を描画するので、回折格子の周期を変調
して描画することは容易であるが、露光時間が膨大に長
く、生産性が悪いという欠点を有している。一方、二光
束干渉露光法では、干渉縞により回折格子を描画するの
で、露光時間を短くできるという利点がある。In the manufacturing process of such a semiconductor laser,
After forming a photoresist film on a semiconductor substrate, a step of drawing a diffraction grating on the photoresist film by light or an electron beam is required. For drawing a diffraction grating, a two-beam interference exposure method and an electron beam direct drawing method are mainly used. In the electron beam direct writing method, since the diffraction grating is drawn directly on the resist film by the electron beam, it is easy to draw by modulating the period of the diffraction grating, but the exposure time is enormously long and the productivity is poor. Has disadvantages. On the other hand, the two-beam interference exposure method has an advantage that the exposure time can be shortened because a diffraction grating is drawn by interference fringes.
【０００４】ところで、波長多重光伝送システムに使用
する半導体レーザでは、回折格子の周期分布がレーザの
波長可変特性に大きな影響を与える。このため、半導体
基板に回折格子を形成した後に、設計通りの回折格子周
期分布が形成されていることを確認することが重要であ
る。図８は、従来の回折格子の周期測定方法の一例を示
す図である。Meanwhile, in a semiconductor laser used in a wavelength division multiplexing optical transmission system, the periodic distribution of the diffraction grating has a great influence on the wavelength variable characteristics of the laser. For this reason, after forming a diffraction grating on a semiconductor substrate, it is important to confirm that a diffraction grating period distribution as designed is formed. FIG. 8 is a diagram showing an example of a conventional diffraction grating period measurement method.
【０００５】回折格子を形成した半導体基板２０にレー
ザ光（入射レーザ光）を照射し、回折格子により回折さ
れた光（回折光）の回折角を測定する。この場合、回折
格子の周期をΛとし、入射レーザ光の波長をλ、入射角
をθ0 、回折角をθ1 とすると、これらの間には下記
（１）式に示す関係がある。A semiconductor substrate 20 having a diffraction grating formed thereon is irradiated with laser light (incident laser light), and the diffraction angle of the light (diffracted light) diffracted by the diffraction grating is measured. In this case, assuming that the period of the diffraction grating is Λ, the wavelength of the incident laser light is λ, the incident angle is θ 0 , and the diffraction angle is θ 1 , there is a relationship expressed by the following equation (1).
【０００６】[0006]
【数１】 (Equation 1)
【０００７】従って、レーザ光の波長λ、入射角θ0 及
び回折角θ1 を測定することで回折格子の周期Λを知る
ことができる。Therefore, the period Λ of the diffraction grating can be known by measuring the wavelength λ, the incident angle θ 0 and the diffraction angle θ 1 of the laser beam.
【０００８】[0008]
【発明が解決しようとする課題】近年、微小な範囲内で
回折格子の周期を変調する技術が開発されている。しか
し、図８に示す方法では、レーザ光のビーム径が１ｍｍ
程度となるため、ビーム径よりも小さい範囲内で回折格
子の周期が変調されている場合は回折光パターンが広が
り、微小領域内での回折格子の周期の変化を厳密に測定
することができないという欠点がある。例えば、図９に
示すように、微小な範囲での回折格子の周期がΛ1 ，Λ
2 ，Λ3 （但し、Λ1 ＜Λ2 ＜Λ3 ）に変調されている
とする。この場合、入射レーザ光のビーム径が各周期の
回折格子の形成領域よりも大きいと、各周期の回折格子
からの回折光１，２，３の回折角θ1 ，θ2 ，θ3 を個
別に測定することができないため、各回折格子の周期を
正確に測定することができない。In recent years, techniques for modulating the period of a diffraction grating within a minute range have been developed. However, in the method shown in FIG. 8, the beam diameter of the laser light is 1 mm.
When the period of the diffraction grating is modulated within a range smaller than the beam diameter, the diffracted light pattern spreads, and it is not possible to exactly measure the change in the period of the diffraction grating in a minute area. There are drawbacks. For example, as shown in FIG. 9, the period of the diffraction grating in a minute range is Λ 1 , Λ
2 , Λ 3 (where に1 <Λ 2 <Λ 3 ). In this case, if the beam diameter of the incident laser beam is larger than the formation area of the diffraction grating of each period, the diffraction angles θ 1 , θ 2 , θ 3 of the diffracted lights 1, 2, 3 from the diffraction grating of each period are individually , The period of each diffraction grating cannot be measured accurately.
【０００９】本発明は、微小な領域内で回折格子の周期
が変調されている場合であっても回折格子の周期を正確
に測定することができる回折格子の周期測定方法を提供
することを目的とする。An object of the present invention is to provide a method of measuring the period of a diffraction grating, which can accurately measure the period of the diffraction grating even when the period of the diffraction grating is modulated in a minute area. And
【００１０】[0010]
【課題を解決するための手段】上記した課題は、半導体
基板に形成された回折格子の周期測定方法において、回
折格子が形成された半導体基板の前記回折格子が形成さ
れた面上にフォトレジストを塗布してフォトレジスト膜
を形成する工程と、干渉露光装置により前記フォトレジ
スト膜に干渉パターンを露光する工程と、前記フォトレ
ジスト膜を現像処理する工程と、前記現像処理により現
われるモアレ縞の角度を測定し、その角度により回折格
子の周期を求める工程とを有することを特徴とする回折
格子の周期測定方法により解決する。The object of the present invention is to provide a method for measuring the period of a diffraction grating formed on a semiconductor substrate, comprising the steps of: depositing a photoresist on a surface of the semiconductor substrate having the diffraction grating formed thereon; Forming a photoresist film by coating, exposing an interference pattern to the photoresist film by an interference exposure device, developing the photoresist film, and adjusting the angle of the moire fringes appearing by the development process. Measuring and determining the period of the diffraction grating based on the angle thereof.
【００１１】以下、作用について説明する。本発明にお
いては、干渉露光法によりフォトレジスト膜に干渉パタ
ーンを描画し、その後現像処理する。この場合、２つの
方向から入射した光による干渉パターンと、回折格子に
より回折された光による干渉パターンとにより、モアレ
縞が生じる。このモアレ縞の角度φは、入射光による干
渉パターンの周期ΛE と、回折格子に対する入射光によ
る干渉パターンの傾け角αと、回折格子の周期ΛG とに
関係する。従って、モアレ縞の角度φ、入射光による干
渉パターンの周期ΛEと、回折格子に対し入射光による
干渉パターンの傾け角αとがわかれば、回折格子の周期
ΛG を演算により求めることができる。The operation will be described below. In the present invention, an interference pattern is drawn on a photoresist film by an interference exposure method, and then developed. In this case, moire fringes are generated by an interference pattern by light incident from two directions and an interference pattern by light diffracted by the diffraction grating. The moire fringe angle φ is related to the period Λ E of the interference pattern due to the incident light, the inclination angle α of the interference pattern due to the incident light to the diffraction grating, and the period Λ G of the diffraction grating. Therefore, if the angle φ of the moire fringes, the period Λ E of the interference pattern due to the incident light, and the inclination angle α of the interference pattern due to the incident light with respect to the diffraction grating are known, the period Λ G of the diffraction grating can be obtained by calculation. .
【００１２】[0012]
【発明の実施の形態】以下、本発明の実施の形態につい
て添付の図面を参照して説明する。図１は本発明の実施
の形態の回折格子の周期測定方法を示す模式図である。
まず、図１に示すように、測定すべき回折格子が形成さ
れた基板１０を用意し、回折格子が形成された面上にフ
ォトレジストを塗布して、厚さが約１００〜２００ｎｍ
のフォトレジスト膜１０ａを形成する。Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a method for measuring the period of a diffraction grating according to an embodiment of the present invention.
First, as shown in FIG. 1, a substrate 10 on which a diffraction grating to be measured is formed is prepared, and a photoresist is applied on the surface on which the diffraction grating is formed, and the thickness is about 100 to 200 nm.
Is formed.
【００１３】その後、二光束干渉露光法により、フォト
レジスト膜１０ａを露光する。図２，図３は二光束干渉
露光法を示す模式図である。レンズ群１１は半導体レー
ザ（図示せず）から出力されたレーザビームのビーム径
を拡大するためのものであり、レンズ群１１によりビー
ム径が拡大されたレーザビームはハーフミラー１２によ
り、ハーフミラー１２で反射される光と、ハーフミラー
１２を透過する光とに分離される。Thereafter, the photoresist film 10a is exposed by a two-beam interference exposure method. 2 and 3 are schematic views showing the two-beam interference exposure method. The lens group 11 is for expanding the beam diameter of the laser beam output from the semiconductor laser (not shown). The laser beam whose beam diameter has been expanded by the lens group 11 is And the light transmitted through the half mirror 12 are separated.
【００１４】ハーフミラー１２で反射されたレーザビー
ムは、更に反射板１３により反射されて、入射角度θ10
でフォトレジスト膜１０ａに入射する。以下、入射角度
θ10でフォトレジスト膜１０ａに入射するレーザビーム
を入射光Ｐ10という。一方、ハーフミラー１２を透過し
たレーザビームは、反射板１４により反射されて、入射
角度θ20でフォトレジスト膜１０ａに入射する。以下、
入射角度θ20でフォトレジスト膜１０ａに入射するレー
ザビームを入射光Ｐ20という。The laser beam reflected by the half mirror 12 is further reflected by the reflecting plate 13 and has an incident angle θ 10
Incident on the photoresist film 10a. Hereinafter, the incident angle theta 10 in that the laser beam incident beam P 10 a that is incident on the photoresist film 10a. On the other hand, the laser beam transmitted through the half mirror 12 is reflected by the reflecting plate 14, is incident on the photoresist film 10a at an incident angle theta 20. Less than,
The laser beam incident on the photoresist film 10a at an incident angle theta 20 that the incident light P 20.
【００１５】フォトレジスト膜１０ａには、入射光Ｐ10
と入射光Ｐ20との干渉による干渉パターン（以下、「入
射光による干渉パターン」という）が露光される。ま
た、図３に示すように、入射光Ｐ10，Ｐ20が基板１０の
回折格子により回折され、回折光Ｐ11，Ｐ21が発生す
る。フォトレジスト膜１０ａには、これらの回折光
Ｐ11，Ｐ21の干渉による干渉パターン（以下、「回折光
による干渉パターン」という）も露光される。The photoresist film 10a has an incident light P 10
The interference due to the interference pattern of the incident light P 20 (hereinafter, referred to as "interference pattern due to the incident light") is exposed. Further, as shown in FIG. 3, the incident light P 10 and P 20 are diffracted by the diffraction grating of the substrate 10 to generate diffracted light P 11 and P 21 . The photoresist film 10a, these diffracted light P 11, the interference pattern due to interference of P 21 (hereinafter, referred to as "interference pattern due to the diffraction light") is also exposed.
【００１６】この場合、基板１０に形成された回折格子
に対して入射光による干渉パターンが若干傾くようにす
る。回折光による干渉パターンは基板１０に形成された
回折格子と平行に発生するので、仮に、入射光による干
渉パターンと基板に形成された回折格子とが平行である
とすると、入射光による干渉パターンと回折光による干
渉パターンとが平行になり、モアレ縞が生じない。In this case, the interference pattern caused by the incident light is slightly inclined with respect to the diffraction grating formed on the substrate 10. Since the interference pattern due to the diffracted light occurs parallel to the diffraction grating formed on the substrate 10, if the interference pattern due to the incident light and the diffraction grating formed to the substrate are parallel, the interference pattern due to the incident light The interference pattern due to the diffracted light becomes parallel, and no moiré fringes occur.
【００１７】しかし、入射光による干渉パターンを基板
１０に形成された回折格子に対し１°以上、好ましくは
１°〜１０°傾けることにより、図４に示すように、入
射光による干渉パターン（周期：ΛE ）と回折光による
干渉パターン（周期：ΛF）との間にビートパターンが
生じ、これがモアレ縞となる。このモアレ縞は、入射光
による干渉パターン及び回折光による干渉パターンの山
と山が重なった部分と、山と谷が重なった部分で露光光
量の空間分布に差が生じ、現像後のフォトレジスト膜の
厚さに差ができるために発生する。なお、図４におい
て、αは入射光による干渉パターンと回折光による干渉
パターンとのなす角度、換言すると入射光による干渉パ
ターンと基板に形成された回折格子とのなす角度であ
り、φはモアレ縞の角度、Ｌは入射光による干渉パター
ンの山と回折光による干渉パターンの山とが重なり合う
部分の間隔である。However, by tilting the interference pattern by the incident light by 1 ° or more, preferably 1 ° to 10 ° with respect to the diffraction grating formed on the substrate 10, as shown in FIG. : Λ E ) and a beat pattern between the interference pattern (period: Λ F ) due to the diffracted light, which becomes moiré fringes. This moiré fringe causes a difference in the spatial distribution of the amount of exposure light between the peak and valley overlapping portions of the interference pattern due to the incident light and the interference pattern due to the diffracted light, and the photoresist film after development. This occurs because there is a difference in the thickness of the sheet. In FIG. 4, α is the angle between the interference pattern by the incident light and the interference pattern by the diffracted light, in other words, the angle between the interference pattern by the incident light and the diffraction grating formed on the substrate, and φ is the moire fringe. , L is the interval between portions where the peak of the interference pattern due to the incident light and the peak of the interference pattern due to the diffracted light overlap.
【００１８】次いで、図４に示すモアレ縞の角度φを測
定し、この角度φから所定の演算を行って回折格子の周
期を求める。 （測定原理）以下、モアレ縞の角度φから回折格子の周
期を求めることができる原理について説明する。Next, the angle φ of the moire fringes shown in FIG. 4 is measured, and a predetermined calculation is performed from this angle φ to determine the period of the diffraction grating. (Measurement Principle) The principle by which the period of the diffraction grating can be determined from the angle φ of the moire fringes will be described below.
【００１９】二光束干渉露光装置によりフォトレジスト
膜１０ａに入射する入射光Ｐ10，Ｐ 20の入射角をそれぞ
れθ10，θ20、光源の波長をλとすると、フォトレジス
ト１０ａに露光される入射光による干渉パターンの周期
ΛE は下記（２）式で表わされる。Photoresist by two-beam interference exposure apparatus
Incident light P incident on the film 10aTen, P 20Each incident angle
Re θTen, Θ20And the wavelength of the light source is λ, the photoresist is
Of the interference pattern due to the incident light exposed on
ΛEIs represented by the following equation (2).
【００２０】[0020]
【数２】 (Equation 2)
【００２１】図３に示すように、入射光Ｐ10，Ｐ20の入
射角をθ10，θ20とし、フォトレジスト膜１０ａの屈折
率をｎとすると、スネル（ｓｎｅｌｌ）の法則により二
光束のレジスト膜内での入射角θ11，θ21は、下記
（３）式に示すようになる。As shown in FIG. 3, assuming that the incident angles of the incident light P 10 and P 20 are θ 10 and θ 20 and the refractive index of the photoresist film 10a is n, two light fluxes are obtained according to Snell's law. The incident angles θ 11 and θ 21 in the resist film are as shown in the following equation (3).
【００２２】[0022]
【数３】 (Equation 3)
【００２３】また、基板１０に形成された回折格子の周
期をΛG とすると、回折条件より下記（４）式が成り立
つ。但し、θ12，θ22は回折光Ｐ11，Ｐ21の回折角であ
る。Further, when the period of the diffraction grating formed on the substrate 10 and lambda G, the following equation (4) is satisfied from the diffraction conditions. Here, θ 12 and θ 22 are the diffraction angles of the diffracted lights P 11 and P 21 .
【００２４】[0024]
【数４】 (Equation 4)
【００２５】これらの式より、下記（５）式が導かれ
る。From these equations, the following equation (5) is derived.
【００２６】[0026]
【数５】 (Equation 5)
【００２７】また、回折光Ｐ11，Ｐ21による干渉パター
ンの周期をΛF とすると、干渉パターンの周期ΛF は下
記（６）式で表わされる。Further, assuming that the period of the interference pattern due to the diffracted light beams P 11 and P 21 is Λ F , the period 干 渉F of the interference pattern is expressed by the following equation (6).
【００２８】[0028]
【数６】 (Equation 6)
【００２９】これに、ΛE ，ΛG に関する式を代入し
て、下記（７）式を得る。By substituting the equations for Λ E and Λ G into this, the following equation (7) is obtained.
【００３０】[0030]
【数７】 (Equation 7)
【００３１】この（７）式を変形すると、下記（８）式
が得られる。By transforming equation (7), the following equation (8) is obtained.
【００３２】[0032]
【数８】 (Equation 8)
【００３３】ここで、入射光による干渉パターンと基板
に形成された回折格子とが平行な場合、入射光による干
渉パターンと回折光による干渉パターンが平行になる。
ところが、入射光による干渉パターンを基板に形成され
た回折格子に対し僅かに傾ける（１°〜１０°程度が好
ましい）ことにより、入射光による干渉パターンと回折
格子からの回折光による干渉パターンとの間にビートパ
ターンが生じる。これがモアレ縞となってフォトレジス
ト膜に記録される。Here, when the interference pattern by the incident light and the diffraction grating formed on the substrate are parallel, the interference pattern by the incident light and the interference pattern by the diffracted light are parallel.
However, by slightly tilting the interference pattern caused by the incident light with respect to the diffraction grating formed on the substrate (preferably about 1 ° to 10 °), the interference pattern caused by the incident light and the interference pattern caused by the diffracted light from the diffraction grating can be compared. A beat pattern occurs between them. This is recorded as moire fringes on the photoresist film.
【００３４】図５は回折格子パターンの空間分布を示す
模式図であり、実線は入力光による干渉パターンを示
し、破線は回折光による干渉パターンを示す。２つの干
渉パターンの山と山とが重なる部分ではフォトレジスト
膜が強く露光され、山と谷とが重なる部分ではフォトレ
ジスト膜の露光量が少なくなる。従って、現像処理する
と露光量に応じてフォトレジスト膜の厚さに差ができる
ため、モアレ縞が発生する。FIG. 5 is a schematic diagram showing the spatial distribution of the diffraction grating pattern. The solid line shows the interference pattern due to the input light, and the broken line shows the interference pattern due to the diffracted light. The photoresist film is strongly exposed at the portion where the peaks of the two interference patterns overlap, and the exposure amount of the photoresist film is reduced at the portion where the peaks and the valleys overlap. Therefore, when the developing process is performed, the thickness of the photoresist film varies depending on the exposure amount, so that moire fringes occur.
【００３５】ここで、図４に示すように、基板１０に形
成された回折格子に対し入射光による干渉パターンを傾
ける角度をαとし、モアレ縞の角度をφ、２つの干渉パ
ターンの山と山とが重なる部分の間隔をＬとすると、Ｌ
は下記（９）式により求めることができる。Here, as shown in FIG. 4, the angle at which the interference pattern due to the incident light is inclined with respect to the diffraction grating formed on the substrate 10 is α, the angle of the moiré fringe is φ, and the peaks of the two interference patterns are two. Let L be the interval of the portion where
Can be obtained by the following equation (9).
【００３６】[0036]
【数９】 (Equation 9)
【００３７】上記（９）式をΛF について変形すると、
下記（１０）式が得られる。When the above equation (9) is modified with respect to Λ F ,
The following equation (10) is obtained.
【００３８】[0038]
【数１０】 (Equation 10)
【００３９】よって、前記（８）式に（１０）式を代入
すると、下記（１１）式が得られる。Therefore, when the equation (10) is substituted into the equation (8), the following equation (11) is obtained.
【００４０】[0040]
【数１１】 [Equation 11]
【００４１】従って、露光される回折格子パターン周期
ΛE 、傾ける角度α、モアレ縞の角度φがわかれば、基
板に形成されている回折格子の周期ΛG を算出すること
ができる。Therefore, the period Λ G of the diffraction grating formed on the substrate can be calculated by knowing the period Λ E of the diffraction grating pattern to be exposed, the inclination angle α, and the angle φ of the moire fringes.
【００４２】（回折格子が変調されている場合の回折格
子の周期測定）以下、回折格子の周期が変調されている
場合の回折格子の周期測定に本発明を適用した例につい
て説明する。図１に示すように、半導体基板１０に形成
された回折格子の周期がΛ1 ，Λ2，Λ3 と変調されて
いるとする。まず、半導体基板１０の回折格子が形成さ
れている面にフォトレジストを塗布してフォトレジスト
膜１０ａを形成する。そして、二光束干渉露光法によ
り、フォトレジスト膜に異なる方向から同一波長のレー
ザ光を照射して、干渉パターンを描画する。このとき、
例えば光源として波長が３２５ｎｍのＨｅ−Ｃｄレーザ
を用い、入射角θ10，θ20はいずれも４２°３７’と
し、回折格子に対する入射光による干渉パターンの傾け
角αを５°とする。このとき、入射光による干渉パター
ンの回折格子周期ΛE は、前記（２）式より計算する
と、２４０ｎｍであることがわかる。(Measurement of Period of Diffraction Grating when Modulation of Diffraction Grating) An example in which the present invention is applied to measurement of the period of a diffraction grating when the period of the diffraction grating is modulated will be described below. As shown in FIG. 1, the period of the diffraction grating formed on the semiconductor substrate 10 is lambda 1, lambda 2, and is modulated and lambda 3. First, a photoresist is applied to the surface of the semiconductor substrate 10 on which the diffraction grating is formed to form a photoresist film 10a. Then, by a two-beam interference exposure method, the photoresist film is irradiated with laser beams of the same wavelength from different directions to draw an interference pattern. At this time,
For example, a He-Cd laser having a wavelength of 325 nm is used as a light source, the incident angles θ 10 and θ 20 are both 42 ° 37 ′, and the tilt angle α of the interference pattern due to the light incident on the diffraction grating is 5 °. At this time, the diffraction grating period Λ E of the interference pattern due to the incident light is found to be 240 nm when calculated from the above equation (2).
【００４３】このようにしてフォトレジスト膜に干渉パ
ターンを露光した後、フォトレジストを現像すると、例
えば図６のように、回折格子の周期Λ1 ，Λ2 ，Λ3 に
応じて角度φ1 ，φ2 ，φ3 が変化したモアレ縞が現わ
れる。このモアレ縞の角度φ1 ，φ2 ，φ3 を測定した
結果、それぞれの角度が例えばφ1 ＝−４．５°、φ2
＝３．５°、φ3 ＝１２．６°であったとする。これら
の値を用いて前記（１１）式により回折格子周期Λ1 ，
Λ2 ，Λ3 を求めると、それぞれの回折格子周期Λ1 ，
Λ2 ，Λ3 は、下記の値となる。 Λ1 ＝２３９．６ｎｍ Λ2 ＝２４１．１ｎｍ Λ3 ＝２４２．８ｎｍ このように、本発明においては、二光束干渉露光法によ
りフォトレジスト膜を露光した後、現像処理してフォト
レジスト膜に現われるモアレ縞の角度から回折格子の周
期を求めるので、微小な範囲内で回折格子の周期が変調
されている場合であっても、各回折格子の周期を正確に
知ることができる。[0043] After exposing the interference pattern in the photoresist film in this manner, when developing the photoresist, for example, as shown in FIG. 6, the period of the diffraction grating lambda 1, lambda 2, the angle phi 1 according to lambda 3, Moire fringes in which φ 2 and φ 3 have changed appear. As a result of measuring the angles φ 1 , φ 2 , φ 3 of the moire fringes, the respective angles are, for example, φ 1 = −4.5 °, φ 2
= 3.5 ° and φ 3 = 12.6 °. Using these values, the diffraction grating period Λ 1 ,
When Λ 2 and Λ 3 are obtained, the diffraction grating periods Λ 1 and
Λ 2 and Λ 3 have the following values. Λ 1 = 239.6 nm Λ 2 = 241.1 nm Λ 3 = 242.8 nm As described above, in the present invention, after the photoresist film is exposed by the two -beam interference exposure method, it is developed and appears on the photoresist film. Since the period of the diffraction grating is obtained from the angle of the moiré fringes, the period of each diffraction grating can be accurately known even when the period of the diffraction grating is modulated within a minute range.
【００４４】なお、上述した実施の形態では、回折格子
の周期が回折格子に垂直な方向に変調されている場合に
ついて説明したが、回折格子の周期が回折格子と平行な
方向に変調されている場合や、基板面内で任意に分布し
ている場合にも適用することができる。また、回折格子
の任意の位置に位相シフトが存在したとしてもモアレ縞
の角度は位相シフトによっては変化しない。従って、回
折格子の任意の位置に位相シフトが存在したとしても、
モアレ縞の角度で回折格子周期を知ることができるとと
もに、モアレ縞のシフト量で位相シフト量を知ることが
できる。例えば、図７は回折格子と平行な方向に周期が
変調されており、かつ回折格子に垂直な方向に位相がシ
フト（シフト量π）している場合のモアレ縞を示す図で
ある。この図で、ΛF1，ΛF2はそれぞれ回折格子からの
回折光による干渉パターンの周期を示し、ΛE は入射光
による干渉パターンの周期を示す。この図７に示すよう
に、回折格子が変調されているとともに位相がシフトし
ている場合も、各回折格子の周期及びシフト量を個別に
求めることができる。In the above embodiment, the case where the period of the diffraction grating is modulated in the direction perpendicular to the diffraction grating has been described. However, the period of the diffraction grating is modulated in the direction parallel to the diffraction grating. The present invention can also be applied to the case and the case where the particles are arbitrarily distributed in the substrate surface. Further, even if a phase shift exists at an arbitrary position on the diffraction grating, the angle of the moiré fringes does not change due to the phase shift. Therefore, even if there is a phase shift at an arbitrary position on the diffraction grating,
The diffraction grating period can be known from the angle of the moiré fringes, and the phase shift amount can be known from the shift amount of the moiré fringes. For example, FIG. 7 is a diagram illustrating moiré fringes when the period is modulated in a direction parallel to the diffraction grating and the phase is shifted (shift amount π) in a direction perpendicular to the diffraction grating. In this figure, Λ F1 and Λ F2 each indicate the period of the interference pattern due to the diffracted light from the diffraction grating, and Λ E indicates the period of the interference pattern due to the incident light. As shown in FIG. 7, even when the diffraction grating is modulated and the phase is shifted, the period and shift amount of each diffraction grating can be obtained individually.
【００４５】[0045]
【発明の効果】以上説明したように、本発明によれば、
干渉露光法により半導体基板上に形成したレジスト膜に
干渉パターンを露光し、現像により現われるモアレ縞の
角度を測定して回折格子の周期を求めるので、微小な領
域で回折格子が変調されている場合であっても、各回折
格子の周期を正確に求めることができる。As described above, according to the present invention,
Exposure of the interference pattern to the resist film formed on the semiconductor substrate by the interference exposure method, and measuring the angle of the moiré fringes appearing during development to determine the period of the diffraction grating. However, the period of each diffraction grating can be accurately obtained.
【図１】本発明の実施の形態の回折格子の周期測定方法
を示す模式図である。FIG. 1 is a schematic view showing a method of measuring a period of a diffraction grating according to an embodiment of the present invention.
【図２】二光束干渉露光法を示す模式図である。FIG. 2 is a schematic view showing a two-beam interference exposure method.
【図３】二光束露光法による回折光の干渉を示す模式図
である。FIG. 3 is a schematic diagram showing interference of diffracted light by a two-beam exposure method.
【図４】回折光による干渉パターンと入射光による干渉
パターンとにより発生するモアレ縞を示す図である。FIG. 4 is a diagram showing moire fringes generated by an interference pattern caused by diffracted light and an interference pattern caused by incident light.
【図５】回折格子パターンの空間分布を示す模式図であ
る。FIG. 5 is a schematic diagram showing a spatial distribution of a diffraction grating pattern.
【図６】回折格子が変調されているときのモアレ縞を示
す図である。FIG. 6 is a diagram showing moire fringes when the diffraction grating is modulated.
【図７】回折格子が変調されているとともに位相シフト
しているときのモアレ縞を示す図である。FIG. 7 is a diagram showing Moiré fringes when the diffraction grating is modulated and phase-shifted.
【図８】従来の回折格子の周期測定方法の一例を示す図
である。FIG. 8 is a diagram showing an example of a conventional diffraction grating period measurement method.
【図９】従来の回折格子の周期測定方法の問題点を示す
図である。FIG. 9 is a view showing a problem of a conventional diffraction grating period measurement method.
１０，２０ 半導体基板、 １０ａ フォトレジスト膜、 １１ レンズ群、 １２ ハーフミラー、 １３，１４ 反射板。 10, 20 semiconductor substrate, 10a photoresist film, 11 lens group, 12 half mirror, 13, 14 reflector.
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 2F065 AA22 AA32 CC19 FF06 FF48 FF52 GG04 HH12 HH14 LL12 LL46 2H049 AA07 AA34 AA48 AA51 AA59 AA62 AA66 5F073 AA63 BA02 HA12 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA22 AA32 CC19 FF06 FF48 FF52 GG04 HH12 HH14 LL12 LL46 2H049 AA07 AA34 AA48 AA51 AA59 AA62 AA66 5F073 AA63 BA02 HA12
Claims (4)
測定方法において、 回折格子が形成された半導体基板の前記回折格子が形成
された面上にフォトレジストを塗布してフォトレジスト
膜を形成する工程と、 干渉露光装置により前記フォトレジスト膜に干渉パター
ンを露光する工程と、前記フォトレジスト膜を現像処理
する工程と、 前記現像処理により現われるモアレ縞の角度を測定し、
その角度により回折格子の周期を求める工程とを有する
ことを特徴とする回折格子の周期測定方法。1. A method of measuring a period of a diffraction grating formed on a semiconductor substrate, wherein a photoresist is applied to a surface of the semiconductor substrate on which the diffraction grating is formed on which the diffraction grating is formed to form a photoresist film. Steps, a step of exposing the photoresist film to an interference pattern by an interference exposure apparatus, a step of developing the photoresist film, and measuring an angle of a moiré fringe appearing by the development processing,
Determining the period of the diffraction grating from the angle.
して１°乃至１０°傾くように露光することを特徴とす
る請求項１に記載の回折格子の周期測定方法。2. The method according to claim 1, wherein the exposure is performed so that the interference pattern is inclined by 1 ° to 10 ° with respect to the diffraction grating.
周期が変調されていることを特徴とする請求項１に記載
の回折格子の周期測定方法。3. The method according to claim 1, wherein the period of the diffraction grating formed on the semiconductor substrate is modulated.
周期をΛG 、前記回折格子に対する入射光の干渉パター
ンの傾け角をα、前記モアレ縞の角度をφ、入射光の干
渉パターンの周期をΛE とすると、回折格子の周期ΛG
は下記数式 ΛG ＝ΛE （２ｃｏｓφ）／｛ｃｏｓ（α＋φ）＋ｃｏ
ｓφ｝ により算出することを特徴とする請求項１に記載の回折
格子の周期測定方法。4. The period of the diffraction grating formed on the semiconductor substrate is Λ G , the inclination angle of the interference pattern of the incident light with respect to the diffraction grating is α, the angle of the moiré fringe is φ, the period of the interference pattern of the incident light Let Λ E be the period of the diffraction grating Λ G
Is given by the following equation: Λ G = Λ E (2 cos φ) / ｛cos (α + φ) + co
The method for measuring the period of a diffraction grating according to claim 1, wherein the period is calculated by sφ｝.
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|---|---|---|---|
| JP19135698A JP3916773B2 (en) | 1998-07-07 | 1998-07-07 | Method for measuring period of diffraction grating |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19135698A JP3916773B2 (en) | 1998-07-07 | 1998-07-07 | Method for measuring period of diffraction grating |
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| Publication Number | Publication Date |
|---|---|
| JP2000019316A true JP2000019316A (en) | 2000-01-21 |
| JP3916773B2 JP3916773B2 (en) | 2007-05-23 |
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|---|---|---|---|
| JP19135698A Expired - Lifetime JP3916773B2 (en) | 1998-07-07 | 1998-07-07 | Method for measuring period of diffraction grating |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002095457A2 (en) * | 2001-05-22 | 2002-11-28 | Bookham Technology Plc | Method of defining grating patterns for optical waveguide devices |
| JP2009085615A (en) * | 2007-09-27 | 2009-04-23 | Sumitomo Electric Ind Ltd | Shape evaluation method of diffraction grating |
| WO2013084906A1 (en) | 2011-12-09 | 2013-06-13 | 株式会社 日立ハイテクノロジーズ | Exposure device, and production method for structure |
| US8824842B2 (en) | 2010-03-19 | 2014-09-02 | Fujitsu Limited | Optical semiconductor device and method for fabricating the optical semiconductor device |
| CN117804349A (en) * | 2024-03-01 | 2024-04-02 | 中国科学技术大学 | Grating displacement sensor debugging method based on moire fringe correlation calculation |
| CN117804349B (en) * | 2024-03-01 | 2024-04-30 | 中国科学技术大学 | Grating displacement sensor debugging method based on moire fringe correlation calculation |
-
1998
- 1998-07-07 JP JP19135698A patent/JP3916773B2/en not_active Expired - Lifetime
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2002095457A2 (en) * | 2001-05-22 | 2002-11-28 | Bookham Technology Plc | Method of defining grating patterns for optical waveguide devices |
| WO2002095457A3 (en) * | 2001-05-22 | 2003-03-20 | Bookham Technology Plc | Method of defining grating patterns for optical waveguide devices |
| JP2009085615A (en) * | 2007-09-27 | 2009-04-23 | Sumitomo Electric Ind Ltd | Shape evaluation method of diffraction grating |
| US8824842B2 (en) | 2010-03-19 | 2014-09-02 | Fujitsu Limited | Optical semiconductor device and method for fabricating the optical semiconductor device |
| US9184558B2 (en) | 2010-03-19 | 2015-11-10 | Fujitsu Limited | Optical semiconductor device and method for fabricating the optical semiconductor device |
| WO2013084906A1 (en) | 2011-12-09 | 2013-06-13 | 株式会社 日立ハイテクノロジーズ | Exposure device, and production method for structure |
| JPWO2013084906A1 (en) * | 2011-12-09 | 2015-04-27 | 株式会社日立ハイテクノロジーズ | Exposure apparatus and structure production method |
| US9104118B2 (en) | 2011-12-09 | 2015-08-11 | Hitachi High-Technologies Corporation | Exposure device and method for producing structure |
| CN117804349A (en) * | 2024-03-01 | 2024-04-02 | 中国科学技术大学 | Grating displacement sensor debugging method based on moire fringe correlation calculation |
| CN117804349B (en) * | 2024-03-01 | 2024-04-30 | 中国科学技术大学 | Grating displacement sensor debugging method based on moire fringe correlation calculation |
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