JP2006186046A - Optical pulse stretch device and pulsed laser apparatus using this - Google Patents

Optical pulse stretch device and pulsed laser apparatus using this Download PDF

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JP2006186046A
JP2006186046A JP2004376777A JP2004376777A JP2006186046A JP 2006186046 A JP2006186046 A JP 2006186046A JP 2004376777 A JP2004376777 A JP 2004376777A JP 2004376777 A JP2004376777 A JP 2004376777A JP 2006186046 A JP2006186046 A JP 2006186046A
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optical path
delay optical
pulse
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JP4627185B2 (en
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Toru Suzuki
徹 鈴木
Masashi Niihori
真史 新堀
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Komatsu Ltd
Ushio Denki KK
Ushio Inc
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Ushio Denki KK
Ushio Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To reduce peak power of an individual pulse after output from an OPS while avoiding overlapping again the light pulses decomposed by the OPS. <P>SOLUTION: Pulsed light from a laser apparatus 1 is split through a beam splitter (BS) 11. Part of the light transmits the BS 11 and is incident on the next stage OPS 20 while the other light passes through a delay optical path composed of concave mirrors 12, 13, 14, 15 and is synthesized with the foregoing light and is incident on the OPS 20. For the light incident on the OPS 20 light passing through a delay optical path composed of concave mirrors 22, 23, 24, 25 and light transmitted through a BS 21 are synthesized as exit light. When the length of the longer delay optical path of the OPSs 10, 20 is assumed to be L while the length of a shorter delay optical path is assumed as S, (least common of L and S)/S≥2 and (least common of L and S)/L ≥2 are assumed. It is hereby possible to lengthen a period the light pulses are overlapped and hence to reduce individual pulse peak power. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、光学パルスストレッチ装置およびこれを用いたパルスレーザ装置に関し、更に詳細には、露光装置の光学系に与えるダメージが小さくなるように、放出されるレーザ光のパルス幅を伸長する光学パルスストレッチ装置および該光学パルスストレッチ装置を有するパルスレーザ装置に関するものである。   The present invention relates to an optical pulse stretching device and a pulse laser device using the same, and more specifically, an optical pulse for extending the pulse width of emitted laser light so as to reduce damage to an optical system of an exposure apparatus. The present invention relates to a stretching device and a pulse laser device having the optical pulse stretching device.

半導体集積回路の微細化、高集積化につれて、その製造用の露光装置においては解像力の向上が要請されている。このため、露光用光源から放出される露光光の短波長化が進められている。従来、半導体露光用光源として、波長２４８ｎｍの紫外線を放出するＫｒＦエキシマレーザ装置が用いられている。また、より短波長の露光用光源として、波長１９３ｎｍの紫外線を放出するＡｒＦエキシマレーザ装置、波長１５７ｎｍの紫外線を放出するフッ素分子（Ｆ2 ）レーザ装置の採用が検討されている。
上記パルス発振するエキシマレーザ装置、フッ素分子レーザ装置などのパルスレーザ装置は、通常、スペクトル幅を狭帯域化するための狭帯域化モジュールを備えている。
上記狭帯域エキシマレーザ又はフッ素分子レーザ等のパルスレーザ装置を光源とする半導体露光装置においては、上記光源から出力される個々のパルス光ピークパワーが高いため、レーザ出力光によって露光装置内部の光学素子がダメージを受ける問題がある。 With the miniaturization and high integration of semiconductor integrated circuits, there is a demand for improvement in resolving power in an exposure apparatus for manufacturing the semiconductor integrated circuit. For this reason, the wavelength of the exposure light emitted from the exposure light source is being shortened. Conventionally, a KrF excimer laser device that emits ultraviolet light having a wavelength of 248 nm has been used as a light source for semiconductor exposure. As an exposure light source with a shorter wavelength, the use of an ArF excimer laser device that emits ultraviolet light with a wavelength of 193 nm and a fluorine molecule (F 2 ) laser device that emits ultraviolet light with a wavelength of 157 nm are being studied.
Pulse laser devices such as the above-described pulsed excimer laser device and fluorine molecular laser device usually include a narrowband module for narrowing the spectral width.
In the semiconductor exposure apparatus using a pulse laser device such as the narrow-band excimer laser or the fluorine molecular laser as a light source, the individual pulsed light peak power output from the light source is high. Has the problem of taking damage.

そこで、光学パルスストレッチ装置（以下、ＯＰＳと言う）を用いて個々のパルス光のピークパワーレベルを下げる技術が特許文献１等により提案されている。
特許文献１に記載のものは、パルス発振するレーザ装置から出力されたひとつのパルス光に着目し、それを時間差を持つ多くのパルス光に分解して個々のパルス光のピークパワーを下げるようにしたものである。これにより露光装置内部の光学素子の受けるダメージを減らすことができる。
また、特許文献２，３には遅延光路長の相違する２台のＯＰＳを直列接続してパルス光をより多くのパルス光へ分解することにより、光学素子の受けるダメージを低減化するパルスマルチプライヤー（ＯＰＳ）を備えたエキシマレーザ装置が開示されている。
さらに、特許文献４には、４枚のミラーで遅延光路を構成し、レーザ光路中に入口側レンズとビームスプリッタ（部分反射鏡）を配置し、さらに上記４枚のミラーで囲まれる空間内のレーザ光路中に出口側レンズを配置し、上記ビームスプリッタで反射した光を４枚のミラーで構成される遅延光路で遅延させるようにしたパルス幅伸長器を備えたパルスレーザ装置が記載されている。 Thus, a technique for reducing the peak power level of each pulsed light using an optical pulse stretching device (hereinafter referred to as OPS) has been proposed in Patent Document 1 and the like.
The one described in Patent Document 1 focuses on one pulsed light output from a laser device that oscillates pulses, and decomposes it into many pulsed lights having a time difference to lower the peak power of each pulsed light. It is a thing. As a result, damage to the optical element inside the exposure apparatus can be reduced.
Patent Documents 2 and 3 disclose a pulse multiplier that reduces damage received by an optical element by connecting two OPSs having different delay optical path lengths in series to decompose pulsed light into more pulsed light. An excimer laser device with (OPS) is disclosed.
Further, in Patent Document 4, a delay optical path is constituted by four mirrors, an entrance side lens and a beam splitter (partial reflection mirror) are arranged in the laser optical path, and further, a space in a space surrounded by the four mirrors is arranged. A pulse laser device having a pulse width expander in which an exit side lens is disposed in a laser beam path and light reflected by the beam splitter is delayed by a delay beam path composed of four mirrors is described. .

図４は上記特許文献２，３に共通して掲載されているＯＰＳの構成を示す図である。 同図に示すものは、直列接続した遅延光路長の相違する２台のＯＰＳ３０，４０から構成され、第１のＯＰＳ３０は、偏光ビームスプリッタ３１と、偏光ビームスプリッタ３１の前に配置された第１の１／４波長板３２と、遅延光路Ａに配置された第１〜第２の１／４波長板３３，３４と、第１、第２のミラー３７，３８から構成される。
また、第２のＯＰＳ４０も、上記第１のＯＰＳ３０と同様、偏光ビームスプリッタ４１と偏光ビームスプリッタ４１の前に配置された第１の１／４波長板４２と、遅延光路Ｂに配置された第１、第２の１／４波長板４３，４４と、第１、第２のミラー４７，４８から構成される。 FIG. 4 is a diagram showing the configuration of the OPS published in common in the above-mentioned Patent Documents 2 and 3. The figure is composed of two OPSs 30 and 40 having different delay optical path lengths connected in series. The first OPS 30 is a polarization beam splitter 31 and a first beam beam disposed in front of the polarization beam splitter 31. , The first and second quarter-wave plates 33 and 34 disposed in the delay optical path A, and the first and second mirrors 37 and 38.
Similarly to the first OPS 30, the second OPS 40 also includes the polarization beam splitter 41, the first quarter-wave plate 42 disposed in front of the polarization beam splitter 41, and the first OPS disposed in the delay optical path B. 1 and second quarter-wave plates 43 and 44 and first and second mirrors 47 and 48.

図４において、レーザ装置１が出力するレーザ光は、１／４波長板３２を介して第１の偏光ビームスプリッタ３１に入射し、偏光ビームスプリッタ３１で分割され、Ｐ偏光成分が偏光ビームスプリッタ３１を通過して、次段のＯＰＳ４０に入射する。また、Ｓ偏光成分は偏光ビームスプリッタ３１で反射し、１／４波長板３３を介して第１のミラー３７に入射し、ミラー３７で反射した光が１／４波長板３３を介して偏光ビームスプリッタ３１に入射する。
上記１／４波長板３３、ミラー３７、１／４波長板３３の経路を通過することによりＰ偏光光に変換された光は、偏光ビームスプリッタ３１を通過して、１／４波長板３４を介して第２のミラー３８に入射する。そして、第２のミラー３８で反射した光が１／４波長板３４に入射する。上記１／４波長板３４、ミラー３８、１／４波長板３４の経路を通過することによりＳ偏光光に変換された光は、偏光ビームスプリッタ３１で反射し、次段のＯＰＳ４０に入射する。 In FIG. 4, the laser light output from the laser device 1 enters the first polarizing beam splitter 31 via the quarter wavelength plate 32 and is split by the polarizing beam splitter 31, and the P-polarized component is converted into the polarizing beam splitter 31. , And enters the next stage OPS 40. Further, the S-polarized component is reflected by the polarization beam splitter 31, enters the first mirror 37 through the quarter wavelength plate 33, and the light reflected by the mirror 37 passes through the quarter wavelength plate 33 to obtain a polarized beam. The light enters the splitter 31.
The light converted into P-polarized light by passing through the paths of the quarter-wave plate 33, the mirror 37, and the quarter-wave plate 33 passes through the polarization beam splitter 31 and passes through the quarter-wave plate 34. Then, the light enters the second mirror 38. Then, the light reflected by the second mirror 38 enters the quarter wavelength plate 34. The light converted to S-polarized light by passing through the paths of the quarter-wave plate 34, the mirror 38, and the quarter-wave plate 34 is reflected by the polarization beam splitter 31 and enters the OPS 40 at the next stage.

次段のＯＰＳ４０に入射した光は上記と同様、１／４波長板４２を介して偏光ビームスプリッタ４１に入射し、偏光ビームスプリッタ４１で分割され、一部の光が偏光ビームスプリッタ４１を通過して出力光となる。また、偏光ビームスプリッタ４１で反射した光は、１／４波長板４３を介して第１のミラー４７に入射し、ミラー４７で反射した光が１／４波長板４３を介して第１のビームスプリッタ４１に入射し、第１のビームスプリッタ４１を通過して、１／４波長板４４を介して第２のミラー４８に入射する。
そして、第２のミラー４８で反射した光が１／４波長板４４を介して偏光ビームスプリッタ４１に入射し、偏光ビームスプリッタで反射し、出力光となる。 The light incident on the next-stage OPS 40 enters the polarization beam splitter 41 via the quarter-wave plate 42 and is split by the polarization beam splitter 41 as described above, and part of the light passes through the polarization beam splitter 41. Output light. The light reflected by the polarization beam splitter 41 enters the first mirror 47 via the quarter wavelength plate 43, and the light reflected by the mirror 47 passes through the quarter wavelength plate 43 to the first beam. The light enters the splitter 41, passes through the first beam splitter 41, and enters the second mirror 48 via the quarter wavelength plate 44.
Then, the light reflected by the second mirror 48 enters the polarizing beam splitter 41 via the quarter wavelength plate 44, is reflected by the polarizing beam splitter, and becomes output light.

図４に示すＯＰＳは、特許文献２，３に記載されるように、遅延光路Ａ，Ｂの遅延光路長がＡとＢとでそれぞれ６ｍと１２ｍである。
従って、遅延光路Ａを１巡する間の遅延時間は６ｍ÷光速（３×１０8 ｍ／ｓｅｃ）＝２０ｎｓｅｃ、遅延光路Ｂを１巡する間の遅延時間は１２ｍ÷光速（３×１０8 ｍ／ｓｅｃ）＝４０ｎｓｅｃである。
このＯＰＳの動作を図５により説明する。図５の横軸は時間軸、縦軸はレーザパルスの大きさである。
図５の太い矢印の時刻Ｔｉｎにレーザの出力パルス光が初段のＯＰＳ３０へ入射する。初段のＯＰＳ３０及び後段のＯＰＳ４０の両ビームスプリッタ３１，４１を通過して遅延光路Ａ、Ｂを経ずに出力されてくるパルス光が図５に太線で示した最大のパルスである。 なお、Ａ，Ｂいずれの遅延光路をも経ることなく出力されるまでの光路長分だけ時刻Ｔｉｎからパルス光の立ち上り時刻までの間には有限の時間があるが、その時間はＯＰＳによる遅延時間に比べて小さいため、図５には表していない。 In the OPS shown in FIG. 4, the delay optical path lengths of the delay optical paths A and B are 6 m and 12 m, respectively, as described in Patent Documents 2 and 3.
Accordingly, the delay time during one round of the delayed optical path A is 6 m ÷ light speed (3 × 10 8 m / sec) = 20 nsec, and the delay time during one round of the delayed optical path B is 12 m ÷ light speed (3 × 10 8 m / Sec) = 40 nsec.
The operation of this OPS will be described with reference to FIG. The horizontal axis in FIG. 5 is the time axis, and the vertical axis is the size of the laser pulse.
The laser output pulse light enters the first stage OPS 30 at time Tin indicated by a thick arrow in FIG. The pulse light that passes through the beam splitters 31 and 41 of the first-stage OPS 30 and the subsequent-stage OPS 40 and is output without passing through the delay optical paths A and B is the maximum pulse indicated by a thick line in FIG. Note that there is a finite time between the time Tin and the rise time of the pulsed light by the length of the optical path until the light is output without passing through any of the delay optical paths A and B, but this time is a delay time due to OPS. Therefore, it is not shown in FIG.

ひとつのパルスの発光時間が４０ｎｓｅｃであれば、遅延光路Ａを１巡する間の遅延時間が２０ｎｓｅｃであるから、初段のＯＰＳ３０の遅延光路Ａのみを経て後段のＯＰＳ４０のビームスプリッタ４１を通過してくるパルス光は、図５に太線で示すように２０ｎｓｅｃ毎に現われるパルスの列Ｐ２１，Ｐ２２，…である。
一方、遅延光路Ｂを１巡する間の遅延時間が４０ｎｓｅｃであるから、初段ＯＰＳ３０のビームスプリッタ３１を通過して後段のＯＰＳ４０の遅延光路Ｂのみを経て出力されるパルス光は、図５に細い線で示すように４０ｎｓｅｃ毎に現われるパルスの列Ｐ１１，Ｐ１２，Ｐ１３…である。
以上のパルス光以外にも２台のＯＰＳの最終出力パルス光にはＡ，Ｂの各遅延光路を両方経由してくるものもある。それらのパルスは図５に示したいずれかのパルスと重複し、重複したタイミングにおけるパルス光エネルギーは各重複したパルス光のエネルギーの積算値である。なぜなら遅延光路Ａ，Ｂの光路長比が２（整数）だからである。
特開平９−２８８２５１号公報 特開２０００−９１６８４号公報 特許３３４３５３３号公報 特開平４−２６１０８３号公報 If the light emission time of one pulse is 40 nsec, the delay time during one round of the delay optical path A is 20 nsec, so that it passes through the beam splitter 41 of the subsequent OPS 40 only through the delay optical path A of the first OPS 30. The coming pulsed light is a pulse train P21, P22,... That appears every 20 nsec as shown by a thick line in FIG.
On the other hand, since the delay time during one round of the delay optical path B is 40 nsec, the pulse light that passes through the beam splitter 31 of the first-stage OPS 30 and is output only through the delay optical path B of the subsequent-stage OPS 40 is thin in FIG. As indicated by the lines, the pulse trains P11, P12, P13... Appear every 40 nsec.
In addition to the above pulsed light, the final output pulsed light of the two OPSs may pass through both the A and B delayed optical paths. These pulses overlap with any one of the pulses shown in FIG. 5, and the pulsed light energy at the overlapping timing is an integrated value of the energy of each overlapping pulsed light. This is because the optical path length ratio between the delay optical paths A and B is 2 (integer).
Japanese Patent Laid-Open No. 9-288251 JP 2000-91684 A Japanese Patent No. 3343533 Japanese Unexamined Patent Publication No. Hei 4-2611083

特許文献２，３によれば、特許文献１のＯＰＳに比べてパルス光の分解が進んでいるのでＯＰＳ出力後の個々のパルス光ピークパワーは一層小さくなっている。しかし、分解後のパルスの多くは再び重複する場合が多い。この重複を出来るだけ少なくすれば、ＯＰＳ出力後の個々のパルスのピークパワーを小さくすることができ、光学素子の受けるダメージを減らすことができる。
本発明は、上記事情に鑑みなされたものであって、ＯＰＳにより分解したパルス光が再び重複することをなるべく避けて、ＯＰＳ出力後の個々のパルスピークパワーをより一層小さくすることができる光学パルスストレッチ装置およびこれを用いたパルスレーザ装置を提供することを課題とする。 According to Patent Documents 2 and 3, since the decomposition of the pulsed light is advanced compared to the OPS of Patent Document 1, the individual pulsed light peak power after OPS output is further reduced. However, many of the pulses after decomposition often overlap again. If this overlap is reduced as much as possible, the peak power of each pulse after OPS output can be reduced, and damage to the optical element can be reduced.
The present invention has been made in view of the above circumstances, and it is possible to avoid the overlapping of pulse lights decomposed by OPS as much as possible, and to further reduce the individual pulse peak power after OPS output. It is an object to provide a stretch device and a pulse laser device using the same.

上記課題を本発明においては、次のように解決する。
（１）遅延光学路長が異なる長さの２台の光学パルスストレッチ装置（ＯＰＳ）を直列接続し、各パルスストレッチ装置（ＯＰＳ）の長い方の遅延光学路長をＬ，短い方の遅延光学路長をＳとしたとき、ＬとＳを以下の式を満たすように定める。
［ＬとＳの最小公倍数］／Ｓ≧２、かつ、［ＬとＳの最小公倍数］／Ｌ≧２
（２）パルス発振するレーザ装置のレーザ光出力側に、上記光学パルスストレッチ装置（ＯＰＳ）を少なくとも２台直列接続する。
図４に示した特許文献１，２に記載されるものでは、前記したように遅延光路Ａ．Ｂの遅延光路長比Ｌ／Ｓが２（整数）であり、このため分解後のパルスの多くは再び重複する場合が多かったが、本発明では、上記遅延光路長比Ｌ／Ｓを整数以外の値とした。
すなわち、遅延光路長ＬとＳを上記のように［ＬとＳの最小公倍数］／Ｓ≧２、かつ、［ＬとＳの最小公倍数］／Ｌ≧２となるように定めた。なお、ここで問題となるのは、上記Ｌ，Ｓの比であり、例えば、１０ｍと５．５ｍのように上記Ｌ，Ｓが整数でない場合には、Ｌ’＝２０，Ｓ’＝１１として、［Ｌ’とＳ’の最小公倍数］を求めればよい。つまり、ＬとＳが整数で表されるようにＬ，ＳをＮ倍し、最小公倍数を求めればよい。 In the present invention, the above problem is solved as follows.
(1) Two optical pulse stretchers (OPS) having different lengths of delay optical path lengths are connected in series, and the longer delay optical path length of each pulse stretcher (OPS) is L, and the shorter delay optical path When the road length is S, L and S are determined so as to satisfy the following expression.
[Least common multiple of L and S] / S ≧ 2 and [Least common multiple of L and S] / L ≧ 2
(2) At least two optical pulse stretch devices (OPS) are connected in series to the laser beam output side of the pulsed laser device.
In the devices described in Patent Documents 1 and 2 shown in FIG. The delay optical path length ratio L / S of B is 2 (integer). Therefore, many of the pulses after decomposition often overlap again, but in the present invention, the delay optical path length ratio L / S is not an integer. The value of
That is, the delay optical path lengths L and S are determined so that [the least common multiple of L and S] / S ≧ 2 and [the least common multiple of L and S] / L ≧ 2 as described above. The problem here is the ratio of L and S. For example, when L and S are not integers such as 10 m and 5.5 m, L ′ = 20 and S ′ = 11. , [Least Common Multiple of L ′ and S ′]. That is, L and S are multiplied by N so that L and S are represented by integers, and the least common multiple is obtained.

前記図４において、第１のＯＰＳ３０の遅延光路Ａを１巡、２巡、３巡・・・して第２のＯＰＳ４０の遅延光路を経ずにビームスプリッタを通過したパルス光ＰＡと、第１のＯＰＳ３０の遅延光路Ａを経ずに第２のＯＰＳ４０の遅延光路Ｂを１巡、２巡、３巡・・・したパルス光ＰＢは、ＬとＳの公倍数の長さの光路をパルス光が通過する時刻毎に重複する。
例えば、前記したように遅延光路Ａの遅延光路長Ｓを６ｍ（遅延時間２０ｎｓ）、遅延光路Ｂの遅延光路長Ｌを１２ｍ（遅延時間４０ｎｓ）とすると、最小公倍数は１２であり、１２ｍ÷光速（３×１０8 ｍ／ｓｅｃ）＝４０ｎｓｅｃ毎に重複する。
一方、例えば、遅延光路Ａの遅延光路長Ｌを１２ｍ（遅延時間４０ｎｓ）、遅延光路Ｂの遅延光路長Ｓを８ｍ（遅延時間２７ｎｓ）とすると、最小公倍数は２４であり、２４ｍ÷光速（３×１０8 ｍ／ｓｅｃ）＝８０ｎｓｅｃ毎に重複する。
すなわち、［ＬとＳの最小公倍数］／Ｌを２より大きくするとともに、［ＬとＳの最小公倍数］／Ｓを２より大きくすることで、上記パルスＰＡとＰＢの重複を、パルス光が遅延光路長Ｌ，Ｓを通過する時間の２倍以上の周期とすることができる。
前記図４で説明したＯＰＳでは、上記［ＬとＳの最小公倍数］／Ｌは、１２／１２＝１であり、上記パルスＰＡとＰＢは遅延光路長Ｌをパルスが通過する時間の１倍（４０ｎｓ）の時間毎に重複する。また、上記［ＬとＳの最小公倍数］／Ｓは、１２／６＝２であり、上記パルスＰＡとＰＢは遅延光路長Ｓをパルスが通過する時間の２倍（４０ｎｓ）の時間毎に重複する。
一方、遅延光路Ａの遅延光路長Ｌを１２ｍ（遅延時間４０ｎｓ）、遅延光路Ｂの遅延光路長Ｓを８ｍ（遅延時間２７ｎｓ）とすると、上記［ＬとＳの最小公倍数］／Ｌは、２４／１２＝２であり、上記パルスＰＡとＰＢは遅延光路長Ｌをパルスが通過する時間の２倍（８０ｎｓ）の時間毎に重複する。また、上記［ＬとＳの最小公倍数］／Ｓは、２４／８＝３であり、上記パルスＰＡとＰＢは遅延光路長Ｓをパルスが通過する時間の３倍（２７ｎｓ×３＝８１ｎｓ）の時間毎に重複する。
ＯＰＳの遅延光路を巡環するパルス光は時間が経過するほど減衰するので、上記のように［ＬとＳの最小公倍数］／Ｓ≧２、かつ、［ＬとＳの最小公倍数］／Ｌ≧２とすることで、重複する周期を長くすることができ、ＯＰＳ出力後の個々のパルスピークパワーをより一層小さくすることができる。 In FIG. 4, the pulse light PA that has passed through the beam splitter without passing through the delay optical path of the second OPS 40 after passing through the delay optical path A of the first OPS 30 through the first, second, third,. The pulsed light PB, which has passed through the delayed optical path B of the second OPS 40 without going through the delayed optical path A of the second OPS 30, is transmitted through the optical path of the common multiple of L and S. It overlaps every time it passes.
For example, as described above, when the delay optical path length S of the delay optical path A is 6 m (delay time 20 ns) and the delay optical path length L of the delay optical path B is 12 m (delay time 40 ns), the least common multiple is 12, 12 m ÷ light speed (3 × 10 8 m / sec) = Overlapping every 40 nsec.
On the other hand, for example, if the delay optical path length L of the delay optical path A is 12 m (delay time 40 ns) and the delay optical path length S of the delay optical path B is 8 m (delay time 27 ns), the least common multiple is 24, and 24 m ÷ light speed (3 × 10 8 m / sec) = Overlapping every 80 nsec.
That is, by setting [Least Common Multiple of L and S] / L to be greater than 2 and [Least Common Multiple of L and S] / S to be greater than 2, the pulse light is delayed by overlapping the pulses PA and PB. The period can be set to be twice or more as long as the time of passing through the optical path lengths L and S.
In the OPS described with reference to FIG. 4, the above [L and S Least Common Multiple] / L is 12/12 = 1, and the pulses PA and PB are one time the pulse passing through the delay optical path length L ( 40 ns). In addition, [the least common multiple of L and S] / S is 12/6 = 2, and the pulses PA and PB overlap every two times (40 ns) of the time that the pulse passes through the delay optical path length S. To do.
On the other hand, when the delay optical path length L of the delay optical path A is 12 m (delay time 40 ns) and the delay optical path length S of the delay optical path B is 8 m (delay time 27 ns), the above [L and S least common multiple] / L is 24 / 12 = 2, and the pulses PA and PB overlap each other at a time twice as long as the pulse passes through the delay optical path length L (80 ns). Further, the [Least Common Multiple of L and S] / S is 24/8 = 3, and the pulses PA and PB are three times (27 ns × 3 = 81 ns) as long as the pulse passes through the delay optical path length S. Duplicate every hour.
Since the pulsed light that circulates in the OPS delay optical path is attenuated as time elapses, [the least common multiple of L and S] / S ≧ 2 and [the least common multiple of L and S] / L ≧ as described above. By setting it to 2, the overlapping period can be lengthened, and the individual pulse peak power after OPS output can be further reduced.

本発明においては、遅延光学路長が異なる長さの２台のＯＰＳを直列接続し、２台のＯＰＳの長い方の遅延光学路長をＬ，短い方の遅延光学路長をＳとしたとき、［ＬとＳの最小公倍数］／Ｓ≧２、かつ、［ＬとＳの最小公倍数］／Ｌ≧２となるようにしたので、
重複する周期を長くすることができ、ＯＰＳ出力後の個々のパルスピークパワーをより小さくすることができる。
このため、レーザ出力光によって生ずる、露光装置等の内部の光学素子のダメージを小さくすることができる。 In the present invention, when two OPSs with different delay optical path lengths are connected in series, the longer delay optical path length of the two OPSs is L, and the shorter delay optical path length is S. Since [Least Common Multiple of L and S] / S ≧ 2 and [Least Common Multiple of L and S] / L ≧ 2,
The overlapping period can be lengthened, and the individual pulse peak power after OPS output can be made smaller.
For this reason, damage to the optical elements inside the exposure apparatus or the like caused by the laser output light can be reduced.

本発明においては、パルス発振するエキシマレーザ又はフッ素分子レーザのレーザ光出力側に少なくとも２台のＯＰＳを直列接続したものを設置する。それら複数のＯＰＳのうち少なくとも２台は互いに異なる光路長を有する。
以下の説明はパルス発振繰返し数が４ＫＨｚ、パルス発光時間が４０ｎｓｅｃ、ＯＰＳを２台有する場合を例にしているが、２台以上のＯＰＳが直列接続されていてもよい。
レーザ光の光路は、ＫｒＦエキシマレーザ（波長はおよそ２４８ｎｍ）の場合は気体のよる光吸収が少ないので空気中でよい。ＡｒＦエキシマレーザ（波長はおよそ１９３ｎｍ）、フッ素分子レーザ（波長はおよそ１５７ｎｍ）の場合は酸素による光吸収が大きいので光路を酸素パージして真空、窒素ガス雰囲気、希ガス雰囲気のいずれかが望ましい。光路雰囲気が前記どれであっても屈折率はほぼ１であるから、光速ｃはおよそｃ＝３×１０８ｍ／ｓｅｃである。 In the present invention, a laser light output side of a pulsed excimer laser or fluorine molecular laser having at least two OPSs connected in series is installed. At least two of the plurality of OPSs have different optical path lengths.
In the following description, the case where the pulse oscillation repetition rate is 4 KHz, the pulse emission time is 40 nsec, and two OPSs are provided is an example, but two or more OPSs may be connected in series.
In the case of a KrF excimer laser (wavelength is approximately 248 nm), the optical path of the laser light may be in the air because light absorption by the gas is small. In the case of an ArF excimer laser (wavelength is about 193 nm) or a fluorine molecular laser (wavelength is about 157 nm), light absorption by oxygen is large. Therefore, it is desirable to purge the optical path with oxygen and to use a vacuum, a nitrogen gas atmosphere, or a rare gas atmosphere. Since the refractive index is approximately 1 regardless of the optical path atmosphere, the speed of light c is approximately c = 3 × 10 8 m / sec.

図１は、本発明の第１の実施例の構成を示す図である。同図において、１はエキシマレーザ又はフッ素分子レーザ等のパルス発振するレーザ装置であり、レーザ装置の光出力側に遅延光路長の異なる２台のＯＰＳ１０，２０が接続されている。
ＯＰＳ１０において、１１はビームスプリッタ、１２〜１５は凹面ミラーであり、これらで遅延光学系を構成する。なお、凹面ミラーの代りに、平凸レンズを用いてもよい。
レーザ装置１からの入射光はビームスプリッタ１１で分割されて、一部の光はビームスプリッタ１１を通過して次段のＯＰＳ２０に入射する。また、他の一部の光はビームスプリッタ１１で入射した光軸と直交方向に折り返され、凹面ミラー１２→凹面ミラー１３→凹面ミラー１４→凹面ミラー１５の経路でビームスプリッタ１１に入射し、ビームスプリッタ１１で入射光と同一方向に折り返され、ビームスプリッタ１１で合成されＯＰＳ１０から出射する。
また、ＯＰＳ２０において、２１はビームスプリッタ、２２〜２５は上記凹面ミラーである。
ＯＰＳ１０からの入射光はビームスプリッタ２１で分割され一部の光はビームスプリッタ２１を通過して出射光となる。また、他の一部の光は、ビームスプリッタ２１で、入射した光軸と直交方向に折り返され、凹面ミラー２２→凹面ミラー２３→凹面ミラー２４→凹面ミラー２５の経路でビームスプリッタ２１に入射し、ビームスプリッタ２１で入射光と同一方向に折り返され、ビームスプリッタ２１で合成されＯＰＳ２０から出射する。 FIG. 1 is a diagram showing the configuration of the first exemplary embodiment of the present invention. In the figure, reference numeral 1 denotes a laser device that performs pulse oscillation such as an excimer laser or a fluorine molecular laser, and two OPSs 10 and 20 having different delay optical path lengths are connected to the light output side of the laser device.
In the OPS 10, reference numeral 11 denotes a beam splitter, and 12 to 15 denote concave mirrors, which constitute a delay optical system. A plano-convex lens may be used instead of the concave mirror.
Incident light from the laser device 1 is split by the beam splitter 11, and part of the light passes through the beam splitter 11 and enters the next-stage OPS 20. The other part of the light is folded back in the direction orthogonal to the incident optical axis by the beam splitter 11, and enters the beam splitter 11 through the path of the concave mirror 12 → the concave mirror 13 → the concave mirror 14 → the concave mirror 15. It is folded back in the same direction as the incident light by the splitter 11, and is combined by the beam splitter 11 and emitted from the OPS 10.
In OPS 20, 21 is a beam splitter, and 22 to 25 are the concave mirrors.
Incident light from the OPS 10 is split by the beam splitter 21, and part of the light passes through the beam splitter 21 to become outgoing light. The other part of the light is folded back in the direction perpendicular to the incident optical axis by the beam splitter 21 and enters the beam splitter 21 through the path of the concave mirror 22 → the concave mirror 23 → the concave mirror 24 → the concave mirror 25. The beam splitter 21 is folded in the same direction as the incident light, and is combined by the beam splitter 21 and emitted from the OPS 20.

上記直列接続された２台のＯＰＳ１０，２０のうち、レーザに近い方のＯＰＳ１０内の遅延光路長Ｌを１２ｍとする。
ＯＰＳ１０内を一巡して出力されるパルス光は、ＯＰＳ１０への入力パルス光に対して１２÷ｃ（光速）＝１２÷（３×１０8 ）＝４０ｎｓｅｃだけ遅れる。よって、ＯＰＳ１０内をＮ巡して出力されるパルス光はＯＰＳ１０への入力パルス光に対してＮ×４０ｎｓｅｃだけ遅れるから、ＯＰＳ１０より出力されるパルス光はそれらの４０ｎｓｅｃ毎に現われるパルス光の列になる。
一方、２台のＯＰＳ１０，２０のうち、レーザ装置１から遠い方のＯＰＳ２０内の遅延光路長Ｓを８ｍとすると、そのＯＰＳ２０内を１巡して出力されるパルス光は、ＯＰＳ２０への入力パルス光に対して８÷ｃ（光速）＝８÷（３×１０8 ）≒２７ｎｓｅｃだけ遅れる。
よって、ＯＰＳ２０内をＮ巡して出力されるパルス光はＯＰＳ２０への入力パルス光に対しておよそＮ×２７ｎｓｅｃだけ遅れるから、ＯＰＳ２０より出力されるパルス光はそれらのおよそ２７ｎｓｅｃ毎に現われるパルス光の列になる。 Of the two OPSs 10 and 20 connected in series, the delay optical path length L in the OPS 10 closer to the laser is 12 m.
The pulsed light output in a round in the OPS 10 is delayed by 12 ÷ c (light speed) = 12 ÷ (3 × 10 8 ) = 40 nsec with respect to the input pulse light to the OPS 10. Therefore, since the pulse light output N times within the OPS 10 is delayed by N × 40 nsec with respect to the input pulse light to the OPS 10, the pulse light output from the OPS 10 becomes a pulse light train that appears every 40 nsec. Become.
On the other hand, if the delay optical path length S in the OPS 20 farther from the laser device 1 out of the two OPSs 10 and 20 is 8 m, the pulsed light output once in the OPS 20 is the input pulse to the OPS 20. 8 ÷ c (speed of light) = 8 ÷ (3 × 10 8 ) ≈27 nsec behind the light.
Therefore, since the pulse light output N times in the OPS 20 is delayed by about N × 27 nsec with respect to the input pulse light to the OPS 20, the pulse light output from the OPS 20 is a pulse light that appears every approximately 27 nsec. Become a column.

以上のパルス光列について、図２を用いて更に詳細に説明する。
図２中のＰ１、Ｐ２１等は２台のＯＰＳ１０，２０を経て出力されてくる個々のパルス光を表している。横軸は時間軸である。
なお、図２は、Ｐ１、Ｐ２１等のパルス光を図に書ける範囲内で書いたものであって、時間経過に従って更に多くの後続パルス光が存在している。
太い矢印の時刻Ｔｉｎにレーザの出力パルス光がＯＰＳ１０へ入射する。図２中のＰ１はＯＰＳ１０及びＯＰＳ２０のビームスプリッタ１１，２１（以下、ビームスプリッタをＢＳと略記する）を透過し、いずれの遅延光路をも経ることなく出力されるパルス光である。
このパルス光にあっては、時刻ＴｉｎからＯＰＳ２０を通過するまでの光路長分だけパルス光Ｐ１の立ち上り時刻とＴｉｎとの間には有限の時間があるが、その時間はＯＰＳによる遅延時間に比べて小さいため、図２には表していない。このＰ１はレーザ出力直後のパルス光から両ＯＰＳのビームスプリッタ１１，２１で分離された光を差引いたパルスエネルギーを持つ。 The above pulse light train will be described in more detail with reference to FIG.
P1, P21, etc. in FIG. 2 represent individual pulse lights output through the two OPSs 10, 20. The horizontal axis is the time axis.
Note that FIG. 2 shows pulse lights P1, P21, etc. written within the range that can be written in the figure, and there are more subsequent pulse lights as time passes.
Laser output pulse light enters the OPS 10 at time Tin indicated by a thick arrow. P1 in FIG. 2 is pulsed light that passes through the beam splitters 11 and 21 of the OPS 10 and OPS 20 (hereinafter, the beam splitter is abbreviated as BS) and is output without passing through any delay optical path.
In this pulsed light, there is a finite time between the rising time of the pulsed light P1 and Tin by the optical path length from the time Tin to passing through the OPS 20, but this time is compared with the delay time due to OPS. Therefore, it is not shown in FIG. This P1 has pulse energy obtained by subtracting the light separated by the beam splitters 11 and 21 of both OPS from the pulse light immediately after laser output.

太線で表したＰ１ｎ（ｎ＝１，２，３・・・）は、それぞれＯＰＳ１０の遅延光路を１巡、２巡、３巡、・・・してＯＰＳ２０の遅延光路を経ずにＢＳ２１を通過したパルス光であり、細い線で表したＰ２ｎ（ｎ＝１，２，３・・・）はそれぞれＯＰＳ２０の遅延光路を経ずに、ＢＳ１１を通過してＯＰＳ２０の遅延光路を１巡、２巡、３巡・・・したパルスである。時刻Ｔｉｎから４０ｎｓｅｃと２７ｎｓｅｃの公倍数の時刻毎にＰ１ｎとＰ２ｎは重複する。例えばＰｓｐ＝Ｐ１２＋Ｐ２３はＰ１２とＰ２３とが重複することを意味する。
以上のパルス光以外にも２台のＯＰＳ１１，２０の最終出力パルス光にはＯＰＳ１０とＯＰＳ２０の各遅延光路を経由してくるものもあり、例えばＰ１１２はＯＰＳ１０の遅延光路を１巡したパルス光Ｐ１１が更にＯＰＳ２０の遅延光路を１巡して出力されたパルス光を示す。２台のＯＰＳの最終出力パルス光はこうした様々な光路を経て来るパルス光の列である。 P1n (n = 1, 2, 3...) Indicated by a bold line passes through the BS 21 without passing through the OPS 20 delay optical path through the OPS 10 delay optical path 1 round, 2 rounds, 3 rounds,. P2n (n = 1, 2, 3,...) Represented by thin lines passes through the BS 11 without going through the OPS 20 delay optical path, and travels through the OPS 20 delay optical path once or twice. This is a three-round pulse. P1n and P2n overlap each time of common multiples of 40 nsec and 27 nsec from time Tin. For example, Psp = P12 + P23 means that P12 and P23 overlap.
In addition to the above pulsed light, the final output pulsed light of the two OPSs 11 and 20 may pass through the delay optical paths of OPS10 and OPS20. For example, P112 is a pulsed light P11 that makes one round of the delayed optical path of OPS10. Shows the pulsed light output after making a round of the delay optical path of the OPS 20. The final output pulsed light of the two OPSs is a train of pulsed light that passes through these various optical paths.

以上説明してきた実施例のＯＰＳ１０，２０において遅延光路長をそれぞれＬ，Ｓとすると、［ＬとＳの最小公倍数］／Ｌは２、［ＬとＳの最小公倍数］／Ｓは３となる。すなわち、［ＬとＳの最小公倍数］／Ｌ≧２、［ＬとＳの最小公倍数］／Ｓ≧２となっており、上記パルスが重複する周期は、遅延光路長Ｌ，Ｓをパルス光が通過する時間の２倍以上の周期（８０ｎｓ）となる。
前記図４で説明したＯＰＳでは、［ＬとＳの最小公倍数］／Ｌは１、［ＬとＳの最小公倍数］／Ｓは２であり、上記パルスＰＡとＰＢは遅延光路長Ｓをパルスが通過する時間の２倍（遅延光路長Ｌをパルスが通過する時間の１倍）の時間（４０ｎｓ）毎に重複する。 このため、本実施例のＯＰＳを使用することにより、ＯＰＳの最終出力パルス光の分解が一層進み、露光装置へ向かうパルス光列の個々のパルス光ピークパワーは図４に示したものより小さくなっている。 In the OPSs 10 and 20 of the embodiments described above, assuming that the delay optical path lengths are L and S, respectively, [the least common multiple of L and S] / L is 2, and [the least common multiple of L and S] / S is 3. That is, [the least common multiple of L and S] / L ≧ 2 and [the least common multiple of L and S] / S ≧ 2, and the period in which the pulses are overlapped is determined by the delay light path lengths L and S with the pulsed light. The period (80 ns) is at least twice as long as the passing time.
In the OPS described with reference to FIG. 4, [Least Common Multiple of L and S] / L is 1, [Least Common Multiple of L and S] / S is 2, and the pulses PA and PB have the delay optical path length S as the pulse. It overlaps every time (40 ns) twice as long as passing time (1 time as long as the pulse passes through the delay optical path length L). For this reason, by using the OPS of this embodiment, the decomposition of the final output pulse light of the OPS further proceeds, and the individual pulse light peak powers of the pulse light train directed to the exposure apparatus become smaller than those shown in FIG. ing.

次に、ピークパワーとビームスプリッタ（ＢＳ）１１，ビームスプリッタ（ＢＳ）２１の透過率の関係について説明する。
レーザ装置１が出力するレーザ光のピークパワーをｈ０とし、ＯＰＳ１０のＢＳ１１の透過率をＴ１，ＯＰＳ２０のＢＳ２１の透過率をＴ２とすると、２台のＯＰＳ１０，２０を巡回せずに出力されるパルスＰ１のピークパワーｈ１はｈ０×Ｔ１×Ｔ２となる。 一方ＯＰＳ１０のみにより遅延されたパルス光列のピークパワーｈ１はｈ０×（１−Ｔ１）2 ×Ｔ２であらわせ、Ｎ巡した場合のピークパワーｈ１ｎはｈ０×（１−Ｔ１）2 ×Ｔ１(N-1) ×Ｔ２となる。
同様にＯＰＳ１０は通過してＯＰＳ２０をＮ巡した場合のピークパワーｈ２ｎはｈ０×（１−Ｔ２）2 ×Ｔ２(N-1) ×Ｔ１となる。
最終的にＯＰＳ１０、ＯＰＳ２０を通過して得られるピークパワーはこれらの総和で表現され、その総和の波形のピークが最も低くなる波形が望ましい。また、総和の波形は二つのＢＳ１１，２１の透過率Ｔ１，Ｔ２の値に大きく影響を受けるため、総和の波形のピークが最も低くなるようＴ１，Ｔ２を決定することが望ましい。 Next, the relationship between the peak power and the transmittance of the beam splitter (BS) 11 and the beam splitter (BS) 21 will be described.
When the peak power of the laser beam output from the laser device 1 is h0, the transmittance of the BS11 of the OPS 10 is T1, and the transmittance of the BS 21 of the OPS 20 is T2, the pulse that is output without going through the two OPSs 10 and 20 The peak power h1 of P1 is h0 × T1 × T2. On the other hand, the peak power h1 of the pulse light train delayed only by the OPS 10 is expressed as h0 × (1-T1) 2 × T2, and the peak power h1n in the case of N rounds is h0 × (1-T1) 2 × T1 (N− 1) xT2.
Similarly, the peak power h2n when the OPS 10 passes through the OPS 20 N times is h0 × (1-T2) 2 × T2 (N−1) × T1.
The peak power finally obtained by passing through OPS10 and OPS20 is expressed as the sum of these, and the waveform in which the peak of the waveform of the sum is the lowest is desirable. Since the sum waveform is greatly influenced by the transmittances T1 and T2 of the two BSs 11 and 21, it is desirable to determine T1 and T2 so that the peak of the sum waveform is the lowest.

本発明で使用されるＯＰＳとしては上記第１の実施例に示したもののほか、例えば前記特許文献２，３に記載されている構成のものを使用することもできる。
図３は、本発明を前記図４に示したＯＰＳに適用した本発明の第２の実施例の構成を示す図である。
図３に示すように、本実施例のＯＰＳは、直列接続した遅延光路長の相違する２台のＯＰＳ３０，４０から構成され、第１のＯＰＳ３０は、偏光ビームスプリッタ３１と、偏光ビームスプリッタ３１の前に配置された第１の１／４波長板３２と、遅延光路Ａに配置された第１〜第２の１／４波長板３３，３４と、第１、第２の凹面ミラー３５，３６から構成される。また、第２のＯＰＳ４０も、上記第１のＯＰＳ３０と同様、偏光ビームスプリッタ４１と偏光ビームスプリッタ４１の前に配置された第１の１／４波長板４２と、遅延光路Ｂに配置された第１、第２の１／４波長板４３，４４と、第１、第２の凹面ミラー４５，４６から構成される。なお、凹面ミラー代え、平凸レンズを用いてもよい。 As the OPS used in the present invention, in addition to the one shown in the first embodiment, for example, the one described in Patent Documents 2 and 3 can be used.
FIG. 3 is a diagram showing a configuration of a second embodiment of the present invention in which the present invention is applied to the OPS shown in FIG.
As shown in FIG. 3, the OPS of the present embodiment is composed of two OPSs 30 and 40 having different delay optical path lengths connected in series. The first OPS 30 includes a polarization beam splitter 31 and a polarization beam splitter 31. The first quarter wave plate 32 disposed in front, the first to second quarter wave plates 33 and 34 disposed in the delay optical path A, and the first and second concave mirrors 35 and 36. Consists of Similarly to the first OPS 30, the second OPS 40 also includes the polarization beam splitter 41, the first quarter-wave plate 42 disposed in front of the polarization beam splitter 41, and the first OPS disposed in the delay optical path B. 1 and second quarter-wave plates 43 and 44 and first and second concave mirrors 45 and 46. Instead of the concave mirror, a plano-convex lens may be used.

図３に示すＯＰＳの動作は前記図４で説明したものと同様であり、
図４において、レーザ１が出力するレーザ光は、１／４波長板３２を介して第１の偏光ビームスプリッタ３１に入射し、偏光ビームスプリッタ３１で分割され、Ｐ偏光成分が偏光ビームスプリッタ３１を通過して、次段のＯＰＳ４０に入射する。
また、Ｓ偏光成分は偏光ビームスプリッタ３１で反射し、１／４波長板３３→第１の凹面ミラー３５→１／４波長板３３→偏光ビームスプリッタ３１→１／４波長板３４→第２の凹面ミラー３６→１／４波長板３４の経路で偏光ビームスプリッタ３１に入射し、偏光ビームスプリッタ３１で反射し、次段のＯＰＳ４０に入射する。
次段のＯＰＳ４０に入射した光は上記と同様、１／４波長板４２介して偏光ビームスプリッタ４１に入射し、偏光ビームスプリッタ４１で分割され、一部の光が偏光ビームスプリッタ４１を通過して出力光となる。また、偏光ビームスプリッタ４１で反射した光は、１／４波長板４３→第１の凹面ミラー４５→１／４波長板４３→第１のビームスプリッタ４１→１／４波長板４４→第２の凹面ミラー４６→１／４波長板４４の経路で偏光ビームスプリッタ４１に入射し、偏光ビームスプリッタで反射し、出力光となる。 The operation of the OPS shown in FIG. 3 is the same as that described in FIG.
In FIG. 4, the laser light output from the laser 1 is incident on the first polarizing beam splitter 31 via the quarter-wave plate 32 and is split by the polarizing beam splitter 31, and the P-polarized component passes through the polarizing beam splitter 31. Passes through and enters the OPS 40 in the next stage.
Further, the S-polarized component is reflected by the polarization beam splitter 31, and the ¼ wavelength plate 33 → the first concave mirror 35 → the ¼ wavelength plate 33 → the polarization beam splitter 31 → the ¼ wavelength plate 34 → the second wave plate. The light enters the polarization beam splitter 31 through the path of the concave mirror 36 → the quarter wavelength plate 34, is reflected by the polarization beam splitter 31, and enters the OPS 40 at the next stage.
The light incident on the next-stage OPS 40 enters the polarization beam splitter 41 via the quarter-wave plate 42 and is split by the polarization beam splitter 41 as described above, and a part of the light passes through the polarization beam splitter 41. Output light. The light reflected by the polarization beam splitter 41 is a quarter wavelength plate 43 → the first concave mirror 45 → the quarter wavelength plate 43 → the first beam splitter 41 → the quarter wavelength plate 44 → the second wavelength. The light enters the polarization beam splitter 41 through the path of the concave mirror 46 → ¼ wavelength plate 44, is reflected by the polarization beam splitter, and becomes output light.

図３に示すＯＰＳ３０の遅延光路長Ｌは、ＯＰＳ４０の遅延光路長Ｓは前記したように、［ＬとＳの最小公倍数］／Ｌ≧２、［ＬとＳの最小公倍数］／Ｓ≧２となるように設定され、例えば、前記第１の実施例と同様、遅延光路長Ｌは１２ｍ、遅延光路長Ｓは例えば８ｍに設定される。
このため、前記したようにパルスが重複する周期は、遅延光路長Ｌ，Ｓをパルス光が通過する時間の２倍以上の周期（８０ｎｓ）となり、露光装置へ向かうパルス光列の個々のパルス光ピークパワーを小さくすることができる。
なお、ＯＰＳとしては、上記第１、第２の実施例に示したものの外、既に公開されている種々の構成のＯＰＳを利用することができる。また、ＯＰＳの台数も２台に限定する必要はなく、複数台のＯＰＳを用いたものに適用することもできる。
また、上記実施例では、ＯＰＳ１０の遅延光路長Ｌを１２ｍ、ＯＰＳ２０の遅延光路長Ｓを８ｍとしたが、２台のＯＰＳの遅延光路長差は上記実施例に限られることはなく、前記したように［ＬとＳの最小公倍数］／Ｓ≧２、かつ、［ＬとＳの最小公倍数］／Ｌ≧２であればよい。 The delay optical path length L of the OPS 30 shown in FIG. 3 is [the least common multiple of L and S] / L ≧ 2 and [the least common multiple of L and S] / S ≧ 2, as described above. For example, similarly to the first embodiment, the delay optical path length L is set to 12 m, and the delay optical path length S is set to 8 m, for example.
For this reason, as described above, the period in which the pulses overlap is a period (80 ns) that is twice or more the time during which the pulse light passes through the delay optical path lengths L and S, and the individual pulse lights of the pulse light train directed to the exposure apparatus Peak power can be reduced.
As the OPS, OPS having various configurations already disclosed can be used in addition to those shown in the first and second embodiments. Further, the number of OPSs need not be limited to two, and can be applied to one using a plurality of OPSs.
In the above embodiment, the delay optical path length L of the OPS 10 is 12 m, and the delay optical path length S of the OPS 20 is 8 m. However, the delay optical path length difference between the two OPSs is not limited to the above embodiment. Thus, [the least common multiple of L and S] / S ≧ 2 and [the least common multiple of L and S] / L ≧ 2 may be satisfied.

本発明の第１の実施例の構成を示す図である。It is a figure which shows the structure of the 1st Example of this invention. 図１に示すＯＰＳの動作を説明する図である。It is a figure explaining operation | movement of OPS shown in FIG. 本発明の第２の実施例の構成を示す図である。It is a figure which shows the structure of the 2nd Example of this invention. 従来のＯＰＳの構成の一例を示す図である。It is a figure which shows an example of a structure of the conventional OPS. 図４に示すＯＰＳの動作を説明する図である。It is a figure explaining operation | movement of OPS shown in FIG.

符号の説明Explanation of symbols

１ レーザ装置
１０ ＯＰＳ
１１ ビームスプリッタ（ＢＳ）
１２−１５ 凹面ミラー
２０ ＯＰＳ
２１ ビームスプリッタ（ＢＳ）
２２−２５ 凹面ミラー
３０ ＯＰＳ
３１ ビームスプリッタ（ＢＳ）
３２−３４ １／４波長板
３５−３６ 凹面ミラー
４０ ＯＰＳ
４１ ビームスプリッタ（ＢＳ）
４２−４４ １／４波長板
４５−４６ 凹面ミラー 1 Laser equipment 10 OPS
11 Beam splitter (BS)
12-15 Concave mirror 20 OPS
21 Beam splitter (BS)
22-25 Concave mirror 30 OPS
31 Beam splitter (BS)
32-34 1/4 wavelength plate 35-36 Concave mirror 40 OPS
41 Beam splitter (BS)
42-44 1/4 wavelength plate 45-46 Concave mirror

Claims (2)

直列接続された少なくとも２台の光学パルスストレッチ装置であって、各パルスストレッチ装置の遅延光学路長が異なる長さであって、長い方の遅延光学路長をＬ，短い方の遅延光学路長をＳとしたときに、（ＬとＳ最小公倍数）／Ｓ≧２、かつ、（ＬとＳ最小公倍数）／Ｌ≧２である
ことを特徴とする光学パルスストレッチ装置。 At least two optical pulse stretch devices connected in series, each of which has a different delay optical path length, the longer delay optical path length being L, and the shorter delay optical path length An optical pulse stretcher, wherein (L and S least common multiple) / S ≧ 2 and (L and S least common multiple) / L ≧ 2, where S is S. パルス発振するレーザ装置のレーザ光出力側に少なくとも２台の光学パルスストレッチ装置を直列接続し、
各パルスストレッチ装置の遅延光学路長が異なる長さであって、長い方の遅延光学路長をＬ，短い方の遅延光学路長をＳとしたときに、（ＬとＳ最小公倍数）／Ｓ≧２、かつ、（ＬとＳ最小公倍数）／Ｌ≧２である
ことを特徴とするパルスレーザ装置。









At least two optical pulse stretch devices are connected in series on the laser beam output side of the laser device that oscillates pulses,
When the delay optical path lengths of the respective pulse stretching devices are different, where the longer delay optical path length is L and the shorter delay optical path length is S, (L and S least common multiple) / S ≧ 2, and (L and S least common multiple) / L ≧ 2.









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JP7482225B2 (en) 2020-05-27 2024-05-13 ギガフォトン株式会社 Laser device and method for manufacturing electronic device

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