JPH1020106A - Diffraction optical grating, projection optical system illumination optical system, optical aperture, exposure device and production of device - Google Patents
Diffraction optical grating, projection optical system illumination optical system, optical aperture, exposure device and production of deviceInfo
- Publication number
- JPH1020106A JPH1020106A JP17907796A JP17907796A JPH1020106A JP H1020106 A JPH1020106 A JP H1020106A JP 17907796 A JP17907796 A JP 17907796A JP 17907796 A JP17907796 A JP 17907796A JP H1020106 A JPH1020106 A JP H1020106A
- Authority
- JP
- Japan
- Prior art keywords
- optical element
- diffractive optical
- film
- optical system
- elements
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70058—Mask illumination systems
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、回折光学素子に関
し、特にバイナリ型の回折光学素子とバイナリ型の回折
光学素子を有する光学系と該光学系を有する光学装置と
に関する。The present invention relates to a diffractive optical element, and more particularly to a binary diffractive optical element, an optical system having the binary diffractive optical element, and an optical device having the optical system.
【０００２】[0002]
【従来の技術】回折光学素子を高精度に製造するため
に、最近バイナリ素子が注目を集めている。バイナリ素
子は、図１１（ａ）のようなブレーズド状の断面形状を
有する回折光学素子を図１１（ｂ）のように階段状の形
状で近似することによって作製するものである。ここで
図１２中１００，１０１が透明な基板であり、その表面
に微細な形状を有する回折格子が形成されている。回折
素子の形状を階段状に近似することによって、作製にＬ
ＳＩの製造等に用いられる半導体プロセスを適用するこ
とができるため、微細なピッチでも容易に高精度な加工
が可能になる。2. Description of the Related Art In order to manufacture a diffractive optical element with high precision, a binary element has recently attracted attention. The binary element is manufactured by approximating a diffractive optical element having a blazed cross-sectional shape as shown in FIG. 11A with a step-like shape as shown in FIG. 11B. Here, reference numerals 100 and 101 in FIG. 12 denote transparent substrates, on which a diffraction grating having a fine shape is formed. By approximating the shape of the diffraction element in a step shape, L
Since a semiconductor process used for manufacturing an SI or the like can be applied, high-precision processing can be easily performed even with a fine pitch.
【０００３】図１２に、半導体プロセスを用いて４段構
造の階段で有する回折光学素子（バイナリ素子）を製造
するプロセスを示す。図１２中、１１０は回折格子が刻
まれる透明基板、１１１は基板１１０上に塗布されたレ
ジスト、１１２は格子パターン形成用のマスクである。
図１１（ａ）の過程では、露光光１１３によってマスク
１１２を介してレジスト１１１を露光し、それにマスク
パターンの潜像を形成する。図１２（ｂ）の過程では、
現像によって露光部（潜像部）のレジストを取り除く
（ここではポジ型レジストを仮定している）。図１２
（ｃ）の過程では、反応性イオンエッチングによって基
板１１０を垂直に所定の深さまで掘り下げる。その後残
留レジストを除去して、図１２（ｄ）に示すような２段
の階段形状が作られる。次に図１２（ｅ）の過程で、基
板表面にレジスト１１４をあらためて塗布した後、マス
ク１１２上のパターンの半分のピッチを有する格子パタ
ーンが形成されたマスク１１５を用いて露光を行なう。
図１３（ｆ）、（ｇ）では、前回の露光と同様１２露光
部のレジストの除去、エッチングを行ない、残留レジス
トを取り除いて、最終的に図１２（ｈ）の４段構造の階
段を得る。更に段数を増やす場合には、マスク１１５上
のパターンの半分の周期を有するパターンから成るマス
クを用いて同様の工程を繰り返せば良い。上で説明した
方法では作製することの可能な階段の段数が２n （ｎ：
自然数）に限られてしまうが、使用するマスクの数とパ
ターン線幅を自由に選択することによって、任意の段数
から成る階段を得ることが可能になる。FIG. 12 shows a process for manufacturing a diffractive optical element (binary element) having a four-step structure using a semiconductor process. In FIG. 12, reference numeral 110 denotes a transparent substrate on which a diffraction grating is engraved, 111 denotes a resist applied on the substrate 110, and 112 denotes a mask for forming a lattice pattern.
In the process of FIG. 11A, the resist 111 is exposed by the exposure light 113 via the mask 112, and a latent image of a mask pattern is formed thereon. In the process of FIG.
The resist in the exposed portion (latent image portion) is removed by development (here, a positive type resist is assumed). FIG.
In the process (c), the substrate 110 is dug down to a predetermined depth vertically by reactive ion etching. Thereafter, the remaining resist is removed to form a two-step step shape as shown in FIG. Next, in the process of FIG. 12E, a resist 114 is newly applied to the substrate surface, and then exposure is performed using a mask 115 on which a grid pattern having a half pitch of the pattern on the mask 112 is formed.
In FIGS. 13 (f) and 13 (g), the resist is removed and etched in 12 exposed portions in the same manner as in the previous exposure to remove the residual resist, and finally the four-step staircase of FIG. 12 (h) is obtained. . To further increase the number of steps, a similar process may be repeated using a mask having a pattern having a half cycle of the pattern on the mask 115. In the method described above, the number of steps that can be produced is 2 n (n:
Although the number is limited to a (natural number), by freely selecting the number of masks to be used and the pattern line width, a step having an arbitrary number of steps can be obtained.
【０００４】以上、基板をエッチングによって削ること
によって所望の階段形状を得る方法について説明した
が、平坦な基板上の所定箇所に段階一段分に相当する厚
さの膜を選択的にデポジッション（堆積）させる工程を
繰り返すことによって同様の形状を形成する技術も知ら
れている。A method of obtaining a desired step shape by etching a substrate by etching has been described above. A film having a thickness corresponding to one step is selectively deposited (deposited) at a predetermined position on a flat substrate. A technique for forming a similar shape by repeating the step of forming the same shape is also known.
【０００５】形状を階段状に近似することによって回折
効率は若干低下するが、８段の近似で約９５％、１６段
近似で約９９％の回折効率が得られ、実用上は問題な
い。Although the diffraction efficiency is slightly lowered by approximating the shape in a stepwise manner, about 95% is obtained by approximation of 8 steps and about 99% by approximation of 16 steps, and there is no practical problem.
【０００６】図１３は階段形状の詳細を説明するため
に、回折光学素子の一部を拡大して描いたものである。
ここで基板１２０の屈折率をｎs 、光が入射する側の媒
質１２１の屈折率をｎi とする。点線１２２が素子の理
想的な形状であり、実線１２３が、点線１２２を階段で
近似した素子の形状を表す。素子の各ピッチの境界（図
中の線Ｂ）において入射する光束に２πの不連続な位相
変化を与えるため、理想形状１２２に対する高さＤはFIG. 13 is an enlarged view of a part of the diffractive optical element for explaining the details of the staircase shape.
Here the refractive index n s of the substrate 120, the refractive index of the side of the medium 121 on which light is incident and n i. A dotted line 122 indicates an ideal shape of the element, and a solid line 123 indicates a shape of the element obtained by approximating the dotted line 122 by steps. In order to give a discontinuous phase change of 2π to the light beam incident on the boundary of each pitch of the element (line B in the figure), the height D with respect to the ideal shape 122 is
【０００７】[0007]
【外１】 となることが必要である。（λは入射光の波長）また、
階段１段の高さをｈとし、段の数をＬ（図１３では便宜
上６段で描いている）とすると、階段形状１２３に対す
る高さＥはＥ＝（Ｌ−１）ｈとなる。図中αはＤとＥの
差であり、[Outside 1] It is necessary that (Λ is the wavelength of the incident light)
Assuming that the height of one step is h and the number of steps is L (in FIG. 13, six steps are shown for convenience), the height E with respect to the step shape 123 is E = (L−1) h. In the figure, α is the difference between D and E,
【０００８】[0008]
【外２】 の関係が成り立つ。通常はα＝ｈとなるようにして、[Outside 2] Holds. Usually, α = h,
【０００９】[0009]
【外３】 の条件を課して階段の各段の高さを決定するが、これは
必ずしも必要なことではない。このような決め方をする
と、段数Ｌを決定した時点で自動的に階段１段の高さｈ
の値が決まってしまい、ｈを調整して素子の特性を操作
することができなくなってしまうので、むしろ、０＜α
＜ｈの範囲でαの値に自由度を残しておき、ｈの値を自
由に決められる方が都合が良いことが多い。そこで上記
（１）式をα＝ｋ・ｈ（０＜ｋ＜１）としてあらためて
書き換えると、[Outside 3] Is imposed to determine the height of each step of the stairs, but this is not necessary. With this method, the height h of one stair is automatically determined when the number L of steps is determined.
Is determined, and h cannot be adjusted to control the characteristics of the element.
It is often more convenient to leave a degree of freedom in the value of α in the range of < h and freely determine the value of h. Therefore, if the above equation (1) is rewritten as α = kh (0 <k < 1),
【００１０】[0010]
【外４】 が、素子の階段１段の高さｈと段数Ｌに関する条件とな
る。ここでｋは０＜ｋ＜１の範囲で任意の値をとる。[Outside 4] Is a condition relating to the height h and the number L of one staircase of the element. Here, k takes an arbitrary value in the range of 0 <k < 1.
【００１１】ところで、通常光学素子の表面には反射光
を抑えるための反射防止膜が設けられる。屈折型レンズ
の場合には、表面形状が滑らかであるため、反射防止膜
の形成は容易に行なえる。一方、バイナリ素子に関して
も、表面に反射防止膜を形成したとする報告が、例え
ば、「Ｅ．Ｐａｗｌｏｗｓｋｉ ａｎｄ Ｂ．Ｋｕｈｌ
ｏｗ，“Ａｎｔｉｒｅｆｌｅｃｔｉｏｎ−ｃｏａｔｅｄ
ｄｉｆｆｒａｃｔｉｖｅ ｏｐｔｉｃａｌ ｅｌｅｍ
ｅｎｔｓ ｆａｂｒｉｃａｔｅｄ ｂｙ ｔｈｉｎ−ｆ
ｉｌｍ ｄｅｐｏｓｉｔｉｏｎ，“Ｏｐｔ．Ｅｎｇ．３
３（１１），３５３７−３５４６（１９９４）」に記載
されている。そこで開示されている方法は、イオンビー
ムスパッタリング技術を用いて、図１４に示すように、
階段形状を有する基板１３０の上方から反射防止膜用の
物質１３１を基板１３０に対して垂直に堆積させて、薄
膜１３２を形成するものである。Incidentally, an antireflection film for suppressing reflected light is usually provided on the surface of the optical element. In the case of a refractive lens, since the surface shape is smooth, an antireflection film can be easily formed. On the other hand, regarding binary devices, reports that an antireflection film was formed on the surface have been reported, for example, in "E. Pawlowski and B. Kuhl."
ow, “Antireflection-coated
diffractive optical element
ents fabricated by thin-f
ilm deposition, "Opt. Eng.
3 (11), 3537-3546 (1994) ". The method disclosed therein uses an ion beam sputtering technique, as shown in FIG.
A thin film 132 is formed by depositing a substance 131 for an anti-reflection film perpendicularly on the substrate 130 from above the stepped substrate 130.
【００１２】[0012]
【発明が解決しようとする課題】図１６は微細な階段上
にスパッタリング技術により反射防止膜を形成した時の
様子を示している。従来の技術では、階段が微細なため
に、階段上の反射防止膜の厚さが不均一となり、反射防
止の効果が低減してしまう。FIG. 16 shows a state in which an antireflection film is formed on a fine step by a sputtering technique. In the prior art, the steps are fine, so that the thickness of the antireflection film on the steps becomes uneven, and the effect of antireflection is reduced.
【００１３】また、反射型の回折光学素子上に増反射膜
を形成する時には同様の理由から増反射の効果が低減し
てしまう。Further, when a reflection-enhancing film is formed on a reflection-type diffractive optical element, the effect of the reflection enhancement is reduced for the same reason.
【００１４】[0014]
【課題を解決するための手段】本発明の第１の目的は、
効果的に反射防止を行える回折光学素子と効果的に増反
射が行える回折光学素子とを提供することにある。SUMMARY OF THE INVENTION A first object of the present invention is to:
An object of the present invention is to provide a diffractive optical element capable of effectively preventing reflection and a diffractive optical element capable of effectively increasing reflection.
【００１５】本発明の第２の目的は、上記回折光学素子
を有する投影光学系や照明光学系や光学機器や露光装置
デバイス製造方法を提供することにある。A second object of the present invention is to provide a method for manufacturing a projection optical system, an illumination optical system, an optical apparatus, and an exposure apparatus having the above-described diffractive optical element.
【００１６】本発明の回折光学素子の第１形態は、階段
状の要素を複数個の並べた回折光学素子において、前記
階段状要素全体を覆う表面が平坦な薄膜を有し、該薄膜
の作用により前記階段状要素からの反射光の強度を減少
させることを特徴とする。According to a first mode of the diffractive optical element of the present invention, in a diffractive optical element in which a plurality of step-like elements are arranged, a thin film having a flat surface covering the entire step-like element is provided. Thus, the intensity of the reflected light from the step-like element is reduced.
【００１７】本発明の回折光学素子の第２の形態は、フ
レネルレンズを構成する各レンズを階段により近似した
バイナリ型の回折光学素子において、前記階段全体を覆
う表面が平坦な薄膜を有し、該薄膜の作用により前記階
段からの反射光の強度を減少させることを特徴とする。According to a second embodiment of the diffractive optical element of the present invention, in a binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step, the surface covering the entire step is a flat thin film, The intensity of the reflected light from the step is reduced by the action of the thin film.
【００１８】本発明の回折光学素子の第３の形態は、階
段状の要素を複数個の並べた回折光学素子において、前
記階段状要素全体を覆う表面が平坦な膜を有し、該膜の
作用により前記階段状要素からの反射光の強度を増加さ
せることを特徴とする。According to a third aspect of the diffractive optical element of the present invention, in a diffractive optical element in which a plurality of step-like elements are arranged, a surface covering the entire step-like element has a flat film, and the film has a flat surface. The intensity of the reflected light from the step-like element is increased by the action.
【００１９】本発明の回折光学素子の第４の形態は、フ
レネルレンズを構成する各レンズを階段により近似した
バイナリ型の回折光学素子において、前記階段全体を覆
う表面が平坦な膜を有し、該膜の作用により前記階段か
らの反射光の強度を増加させることを特徴とする。A fourth embodiment of the diffractive optical element according to the present invention is a binary diffractive optical element in which each lens constituting the Fresnel lens is approximated by a step, wherein the surface covering the entire step is flat. The intensity of the reflected light from the step is increased by the action of the film.
【００２０】[0020]
〔実施例１〕本発明の実施例１について図面を用いなが
ら説明を行う。図１は階段を複数個並べた回折光学素子
（バイナリ素子）の表面に、反射防止膜を適用した状態
を示す。図２中、１が複数個の階段が形成された透明基
板（屈折率：ｎs ）であり、ガラスまたはプラスチック
より成る。２は反射防止膜の材料（屈折率：ｎ）であ
る。ここで光３は、上方から入射する。光入射側の媒質
は空気（屈折率：１）である。本実施例の特徴は、バイ
ナリ素子の表面全体に反射防止用の部材を充填して階段
全体を表面が平坦な薄膜で覆い、階段の各段において反
射防止の条件が満たされるように階段の一段の高さと反
射防止膜材料２の屈折率ｎs 等を最適化している点であ
る。Embodiment 1 Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 shows a state in which an antireflection film is applied to the surface of a diffractive optical element (binary element) in which a plurality of steps are arranged. In FIG. 2, reference numeral 1 denotes a transparent substrate (refractive index: ns ) on which a plurality of steps are formed, and is made of glass or plastic. 2 is a material (refractive index: n) of the antireflection film. Here, the light 3 enters from above. The medium on the light incident side is air (refractive index: 1). This embodiment is characterized in that the entire surface of the binary element is filled with an anti-reflection member to cover the entire stairs with a thin film having a flat surface, and that each step of the stairs satisfies the anti-reflection condition. And the refractive index n s of the antireflection film material 2 are optimized.
【００２１】本反射防止膜の動作原理の説明を行うため
にまず反射防止を実現させるために必要な条件をまとめ
ておく。最も基本的な単層の反射防止膜について図２の
ように屈折率ｎs を有する透明基板１０と空気の界面に
おける反射防止条件を考える。透明基板１０上に、屈折
率ｎ、厚さｄの透明な単層膜１１が形成されている際の
波長λの光に対する反射防止条件は、In order to explain the principle of operation of the antireflection film, first, conditions necessary for realizing antireflection will be summarized. For the most basic single-layer anti-reflection film, anti-reflection conditions at the interface between the transparent substrate 10 having a refractive index n s and air as shown in FIG. 2 will be considered. When a transparent single layer film 11 having a refractive index n and a thickness d is formed on a transparent substrate 10, the antireflection conditions for light having a wavelength λ are as follows:
【００２２】[0022]
【外５】 となる。ここで（３）式は位相条件と、（４）式は振幅
条件と呼ばれる。（３）式においてはｍを変化させるこ
とにより膜厚ｄが[Outside 5] Becomes Here, equation (3) is called a phase condition, and equation (4) is called an amplitude condition. In the equation (3), the film thickness d is changed by changing m.
【００２３】[0023]
【外６】 と複数の値で反射防止の条件が満たされることが分か
る。一方（４）式の条件からは基板の屈折率として通常
の硝子の値（例えばｎs ＝１．５２）を仮定するとｎ＝
１．２３となるが、しかしながら、このような物質で実
用になるものは存在しないため、通常は、より屈折率の
大きなＭｇＦ2 （ｎ＝１．３８）を用いることになり、
そのため多少の残留反射率は避けられない。[Outside 6] It can be seen that the condition of antireflection is satisfied with a plurality of values. On the other hand (4) from the condition of assuming the values of normal glass as the refractive index of the substrate (e.g., n s = 1.52) n =
However, since there is no such material that can be practically used, MgF 2 (n = 1.38) having a larger refractive index is usually used,
Therefore, some residual reflectance cannot be avoided.
【００２４】本実施例では、（３）式と（４）式で示し
た反射防止膜の膜厚の条件をバイナリ素子の階段一段の
高さの条件に合わせることにより、階段の各段で反射防
止の条件を満たすことができる厚さの反射防止膜を設け
る。そのための条件を決める方法を図３を用いて説明す
る。ここでは階段一段あたりの高さをｈとし、ｈに対す
る最適化を行う。反射防止の条件から階段の最上部の位
置における反射防止膜の膜厚ｋ1 はλ／（４ｎ）とな
り、一段下がった位置での膜厚ｋ2 は３λ／（４ｎ）、
更に一段下がった位置での膜厚さｋ3 は５λ／（４ｎ）
というように隣り合う段でλ／（２ｎ）の膜厚差があれ
ばよいことが分かる。そしてこの値が基板の階段一差の
値ｈと等しくなれば、全ての階段部分で反射防止の条件
が達成されることになる。この条件をｎi ＝ｎとして上
記の（２）式に代入するとIn this embodiment, the condition of the film thickness of the antireflection film shown in the equations (3) and (4) is adjusted to the condition of the height of one step of the binary element, so that the reflection at each step of the step is performed. An anti-reflection film having a thickness that can satisfy the anti-reflection condition is provided. A method for determining conditions for that will be described with reference to FIG. Here, the height per one stair is h, and optimization for h is performed. Thickness k 1 of the antireflection film in the uppermost position of the stairway from the condition of antireflection lambda / (4n), and the film thickness k 2 in one step lower position 3 [lambda] / (4n),
The film thickness k 3 at the position further lowered by one step is 5λ / (4n).
Thus, it is sufficient if there is a difference in film thickness of λ / (2n) between adjacent stages. If this value is equal to the value h of the difference between the steps of the substrate, the antireflection condition is achieved in all the steps. Substituting this condition into the above equation (2) with n i = n
【００２５】[0025]
【外７】 となる。実際の値として、ｎs ＝１．５２，ｎ＝１．３
８を代入してみるとＬ＝２０となり、２０段のバイナリ
構造で、反射防止効果が実現される。[Outside 7] Becomes As actual values, n s = 1.52, n = 1.3
When 8 is substituted, L = 20, and the antireflection effect is realized by a binary structure having 20 steps.
【００２６】次に、図１に示した反射防止膜を作製する
方法について図４を用いて説明を行う。図４（ａ）は透
明基板１上に反射防止膜２を設ける前の状態である。図
４（ｂ）は反射防止膜用の物質をイオンビームスパッタ
リング等の技術によって透明基板１上にデポジション
（堆積）した後の状態を示す。図４（ｂ）の状態では、
反射防止膜２は基板１の階段の凹凸に影響されてその表
面が平坦になっていない。従って、この状態から反射防
止膜２の表面を研磨することにより図４（ｃ）に示すよ
うに階段の最も高い位置における膜厚がｄ＝λ／（４
ｎ）になるようにし、最終的に図１に示したような反射
防止膜とする。Next, a method of manufacturing the antireflection film shown in FIG. 1 will be described with reference to FIG. FIG. 4A shows a state before the antireflection film 2 is provided on the transparent substrate 1. FIG. 4B shows a state after a substance for an antireflection film is deposited (deposited) on the transparent substrate 1 by a technique such as ion beam sputtering. In the state of FIG.
The surface of the antireflection film 2 is not flat due to the unevenness of the steps of the substrate 1. Therefore, by polishing the surface of the antireflection film 2 from this state, the film thickness at the highest position of the stairs is d = λ / (4) as shown in FIG.
n) and finally an antireflection film as shown in FIG.
【００２７】〔実施例２〕実施例１では単層の膜により
反射防止膜を形成した。そのため多少の残留反射率が避
けられない。そこで第２の実施例では、反射光をほぼ完
全に消滅させることが可能な２層構造の反射防止膜を適
用した例について説明を行う。Example 2 In Example 1, an antireflection film was formed by a single layer film. Therefore, some residual reflectance cannot be avoided. Therefore, in a second embodiment, an example will be described in which an antireflection film having a two-layer structure capable of almost completely eliminating reflected light is applied.
【００２８】まず２層の反射防止膜の構成例を示す。図
５に示すように、屈折率ｎs を有する透明基板５０と空
気の界面における反射防止条件を考える。ここで第１層
目の透明膜５１の厚さをｄ1 、その屈折率をｎ1 、第２
層目の透明膜５２の厚さをｄ2 、その屈折率をｎ2 と
し、１＜ｎ1 ＜ｎ2 ＞ｎs の条件を与えると、位相に対
する条件First, a configuration example of a two-layer antireflection film will be described. As shown in FIG. 5, consider an antireflection condition at an interface between a transparent substrate 50 having a refractive index n s and air. Here, the thickness of the first transparent film 51 is d 1 , its refractive index is n 1 ,
The thickness d 2 of the transparent film 52 of the layer first, and the refractive index n 2, 1 <when n 1 gives the condition <n 2> n s, conditions for phase
【００２９】[0029]
【外８】 と、振幅に対する条件[Outside 8] And conditions for amplitude
【００３０】[0030]
【外９】 が決まる。（５）式と（６）式の条件は膜厚の制御によ
り満たすことができ、（７）式の条件は現実的な物質と
して、例えば第１層目にＭｇＦ2 （ｎ＝１．３８）を、
第２層目にＡｌ2 Ｏ3 （ｎ＝１．６２）を用いることに
すればほぼ満たされる。[Outside 9] Is determined. The conditions of the expressions (5) and (6) can be satisfied by controlling the film thickness. The condition of the expression (7) is a realistic substance, for example, MgF 2 (n = 1.38) in the first layer. To
The use of Al 2 O 3 (n = 1.62) for the second layer is almost satisfied.
【００３１】次に上記の２層膜を本発明に適用するため
の条件について図６を用いて説明を行う。図６中、６０
は多数階段より成るバイナリ素子が形成された基板であ
り、反射防止膜は膜６１及び膜６２により構成される。
ここで、膜６１の屈折率をｎ1 、厚さをｒとすると、そ
れらの間の関係は（５）式で規定される。一方、膜６２
に対して反射防止の条件である（６）式が成り立つ必要
があることから、膜６２の屈折率をｎ2 とすると、階段
の最上部の位置における反射防止膜の膜厚ｓ1はλ／
（４ｎ2 ）、一段下がった位置での膜厚ｓ2 は３λ／
（４ｎ2 ）、更に一段下がった位置での膜厚ｓ3 は５λ
／（４ｎ2 ）というように、隣り合う段でλ／（２ｎ
2 ）の膜厚差があればよいことが分かる。尚、λは入射
の波長である。そしてこの値が基板の階段段差の値ｈと
等しくなれば各段で反射防止の条件が達成される。これ
を式で書くと、Ｌとｋの記号は実施例１で用いたものと
同様の意味であるとして、Next, the conditions for applying the above two-layer film to the present invention will be described with reference to FIG. In FIG.
Is a substrate on which a binary element composed of many steps is formed, and the antireflection film is composed of a film 61 and a film 62.
Here, assuming that the refractive index of the film 61 is n 1 and the thickness is r, the relationship between them is defined by the equation (5). On the other hand, the film 62
Since the expression (6), which is an antireflection condition, needs to be satisfied with respect to the above, if the refractive index of the film 62 is n 2 , the film thickness s 1 of the antireflection film at the uppermost position of the step is λ /
(4n 2 ), the film thickness s 2 at the position one step lower is 3λ /
(4n 2 ), and the film thickness s 3 at the position further lowered by one step is 5λ.
/ (4n 2 ), λ / (2n
It can be seen that the difference in film thickness 2 ) is sufficient. Here, λ is the wavelength of the incident light. If this value becomes equal to the value h of the step of the substrate, the antireflection condition is achieved at each stage. When this is expressed by an equation, it is assumed that the symbols of L and k have the same meanings as those used in the first embodiment.
【００３２】[0032]
【外１０】 となる。実際の値としてｎs ＝１．５２、Ｎ2 ＝１．６
２を代入してみるとＬ＝３３となり、３３段のバイナリ
構造で反射防止効果が実現されることが分かる。第２層
目の膜６２を図４を用いて説明した方法で作製し、その
上に通常の方法で第１層目の膜６１を成膜することによ
り、本実施例の反射防止膜を作製することができる。[Outside 10] Becomes As actual values, n s = 1.52, N 2 = 1.6
By substituting 2, it becomes L = 33, and it can be seen that the antireflection effect is realized by the binary structure of 33 steps. The second-layer film 62 is formed by the method described with reference to FIG. 4, and the first-layer film 61 is formed thereon by a normal method to form the anti-reflection film of the present embodiment. can do.
【００３３】ここまでの説明は、単層及び２層構造によ
る反射防止膜について説明を行った。反射防止膜の機能
として、入射光の波長が変動した場合或いは入射角度が
変動した場合にも優れた反射防止効果を持たせるために
は、更に多くの層数が必要になることが知られている。
そのような多層の反射防止膜に対しても、基板に接した
最も下の表面が平坦な層（膜）の屈折率を考慮してバイ
ナリ素子の階段の高さを決定することにより本発明をそ
のまま適用することができる。In the description so far, the antireflection film having a single-layer structure and a two-layer structure has been described. As a function of the anti-reflection film, it is known that a larger number of layers is required to have an excellent anti-reflection effect even when the wavelength of incident light fluctuates or the incident angle fluctuates. I have.
The present invention is also applied to such a multilayer antireflection film by determining the height of the staircase of the binary element in consideration of the refractive index of a layer (film) having the lowest flat surface in contact with the substrate. It can be applied as it is.
【００３４】以上の実施例では、バイナリ素子の表面に
垂直に入射する光の反射率が最小になる条件として階段
一段の高さ及び段数の最適化を行った。が、垂直以外の
ある角度を持って斜入射する光の反射率が最小となるよ
うに、階段一段の高さ及び段数の最適化を行うことが可
能である。In the above embodiment, the height and the number of steps are optimized as a condition for minimizing the reflectance of the light perpendicularly incident on the surface of the binary element. However, the height and the number of steps can be optimized so that the reflectance of light obliquely incident at an angle other than perpendicular is minimized.
【００３５】回折光学素子として、透過光の位相を周期
的にπだけ不連続に変化させるフレネルゾーンプレート
が知られているが、この構成は、２段の階段構造を有す
るバイナリ素子そのものであり、本発明の反射防止技術
がそのまま適用できる。As a diffractive optical element, a Fresnel zone plate that periodically changes the phase of transmitted light discontinuously by π is known, but this configuration is a binary element itself having a two-step structure. The anti-reflection technique of the present invention can be applied as it is.
【００３６】以上の説明は、透過型のバイナリ型光学素
子の反射防止技術に関して行ったが、反射型のバイナリ
型素子に対して本発明を適用して増反射膜を形成するこ
とが可能である。The above description has been made with respect to the antireflection technique of a transmission type binary optical element. However, the present invention can be applied to a reflection type binary optical element to form an enhanced reflection film. .
【００３７】以上説明した回折光学素子のうち反射防止
膜を形成するものは、透明基板の一方の面に階段構造を
形成して他方の面に平面または球面を形成する形態や、
透明基板の一方の面に階段構造を形成して他方の面に非
球面を形成する形態や、透明基板の両面に階段構造を形
成する形態等が採れる。Among the diffractive optical elements described above, those which form an anti-reflection film include those in which a stepped structure is formed on one surface of a transparent substrate and a flat surface or a spherical surface is formed on the other surface,
A configuration in which a staircase structure is formed on one surface of the transparent substrate and an aspheric surface is formed on the other surface, and a configuration in which a staircase structure is formed on both surfaces of the transparent substrate are adopted.
【００３８】図７は上記回折光学素子のいずれかを有す
る投影光学系を示す図である。図７において、８１は球
面または非球面を有する通常のレンズ、８２は本発明の
回折光学素子である。回折光学素子８２は通常のレンズ
８１と協力して系の各種収差（色収差ザイデルの５収
差）を補正する。尚、通常のレンズ８１の表面には反射
防止膜が形成されている。FIG. 7 is a view showing a projection optical system having any of the above-described diffractive optical elements. In FIG. 7, reference numeral 81 denotes a normal lens having a spherical or aspherical surface, and reference numeral 82 denotes a diffractive optical element of the present invention. The diffractive optical element 82 corrects various aberrations (chromatic aberration Seidel's five aberrations) of the system in cooperation with the ordinary lens 81. Incidentally, an antireflection film is formed on the surface of the normal lens 81.
【００３９】このような投影光学系は、各種カメラや、
一眼レフカメラに取り付ける交換レンズや、複写機等の
事務機や、液晶パネル製造用の投影露光装置や、ＩＣ，
ＬＳＩ等の半導体チップ製造用の投影露光装置に用いら
れる。Such a projection optical system includes various cameras,
Interchangeable lenses attached to single-lens reflex cameras, office machines such as copiers, projection exposure equipment for manufacturing liquid crystal panels, ICs,
It is used for a projection exposure apparatus for manufacturing a semiconductor chip such as an LSI.
【００４０】図８は上記投影露光装置を示す外略図であ
る。図８において、９１は露光光を供給する照明光学
系、９２は照明光学系により照明されるマスク、９３は
マスク９２に描かれたデバイスパターンの像を投影する
投影光学系、９３はレジストが塗布されたガラス基板や
シリコン基板を示す。投影光学系９３は本発明の回折光
学素子を有し、照明光学系９１も本発明の回折光学素子
を有する。そして、照明光学系９１や投影光学系を構成
するレンズはその表面に反射防止膜が形成してある。FIG. 8 is a schematic view showing the projection exposure apparatus. 8, reference numeral 91 denotes an illumination optical system for supplying exposure light; 92, a mask illuminated by the illumination optical system; 93, a projection optical system for projecting an image of a device pattern drawn on the mask 92; 1 shows a glass substrate or a silicon substrate that has been etched. The projection optical system 93 has the diffractive optical element of the present invention, and the illumination optical system 91 also has the diffractive optical element of the present invention. The lens constituting the illumination optical system 91 and the projection optical system has an anti-reflection film formed on the surface thereof.
【００４１】[0041]
【発明の効果】以上、本発明によれば、効果的に反射防
止が行える。また、本発明によれば、効果的に増反射が
できる。As described above, according to the present invention, reflection can be effectively prevented. Further, according to the present invention, it is possible to effectively increase reflection.
【図１】本発明の一実施例であるバイナリ型回折光学素
子の断面図である。FIG. 1 is a sectional view of a binary diffractive optical element according to an embodiment of the present invention.
【図２】単層反射防止膜の機能を説明するための説明図
である。FIG. 2 is an explanatory diagram for explaining a function of a single-layer antireflection film.
【図３】第１実施例のバイナリ型光学素子の断面図であ
る。FIG. 3 is a sectional view of the binary optical element according to the first embodiment.
【図４】反射防止膜の製造方法を説明するための説明図
である。FIG. 4 is an explanatory diagram for explaining a method for manufacturing an antireflection film.
【図５】二層反射防止膜の機能を説明するための説明図
である。FIG. 5 is an explanatory diagram for explaining a function of a two-layer antireflection film.
【図６】第２実施例のバイナリ型回折光学素子の断面図
である。FIG. 6 is a sectional view of a binary diffractive optical element according to a second embodiment.
【図７】投影光学系を示す図である。FIG. 7 is a diagram showing a projection optical system.
【図８】投影露光装置を示す図である。FIG. 8 is a view showing a projection exposure apparatus.
【図９】半導体デバイスの製造フローを示す図である。FIG. 9 is a diagram showing a manufacturing flow of the semiconductor device.
【図１０】図９のウエハプロセスを示す図である。FIG. 10 is a view showing a wafer process of FIG. 9;
【図１１】従来の回折素子とバイナリ型回折素子の断面
を比較した図である。FIG. 11 is a diagram comparing cross sections of a conventional diffraction element and a binary diffraction element.
【図１２】バイナリ型回折素子の製造方法を説明するた
めの説明図である。FIG. 12 is an explanatory diagram for describing the method for manufacturing the binary diffraction element.
【図１３】バイナリ素子の階段の高さの決め方を説明す
るためめの説明図である。FIG. 13 is an explanatory diagram for explaining how to determine the height of the staircase of the binary element.
【図１４】従来の反射防止膜の製造方法を説明するため
の説明図である。FIG. 14 is an explanatory diagram for explaining a conventional method for manufacturing an antireflection film.
【図１５】従来の反射防止膜の状態を説明するための説
明図である。FIG. 15 is an explanatory diagram for explaining a state of a conventional antireflection film.
１ 階段が形成された基板 ２ 階段全体を覆う反射防止用薄膜 ３ 入射光 1 Substrate with steps formed 2 Antireflection thin film covering the whole steps 3 Incident light
Claims (20)
素子において、前記階段状要素全体を覆う表面が平坦な
膜を有し、該膜の作用により前記階段状要素からの反射
光の強度を減少させることを特徴とする回折光学素子。1. A diffractive optical element in which a plurality of step-like elements are arranged, wherein a surface covering the whole of the step-like elements has a flat film, and reflected light from the step-like elements by the action of the film. A diffractive optical element having a reduced intensity.
段により近似したバイナリ型の回折光学素子において、
前記階段全体を覆う表面が平坦な膜を有し、該膜の作用
により前記階段からの反射光の強度を減少させることを
特徴とする回折光学素子。2. A binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step,
A diffractive optical element, wherein a surface covering the entire step has a flat film, and the action of the film reduces the intensity of light reflected from the step.
満足されるように前記階段の段数と一段の高さと前記膜
の屈折率とが定められることを特徴とする請求項１また
は２の回折光学素子。3. The diffraction according to claim 1, wherein the number of steps, the height of one step, and the refractive index of the film are determined so that the antireflection condition is satisfied for each step of the steps. Optical element.
形成し、複数層の膜の作用により前記反射光の強度を減
少させることを特徴とする請求項１または２の回折光学
素子。4. The diffractive optical element according to claim 1, wherein at least one layer of the film is formed on the film, and the intensity of the reflected light is reduced by the action of a plurality of layers.
し、前記透明基板の他方の面に非球面を形成したことを
特徴とする請求項１−４のいずれかの回折光学素子。5. The diffractive optical element according to claim 1, wherein the step is formed on one surface of the transparent substrate, and an aspherical surface is formed on the other surface of the transparent substrate.
たことを特徴とする請求項１−４のいずれかの回折光学
素子。6. The diffractive optical element according to claim 1, wherein said step structure is formed on both sides of a transparent substrate.
成し、前記透明基板の他方の面に平面または球面を形成
したことを特徴とする請求項１−４のいずれかの回折光
学素子。7. The diffractive optical element according to claim 1, wherein the step structure is formed on one surface of the transparent substrate, and a flat surface or a spherical surface is formed on the other surface of the transparent substrate. .
徴とする請求項１−７のいずれかの回折光学素子。8. The diffractive optical element according to claim 1, wherein said transparent substrate is made of glass.
とを特徴とする請求項１−７のいずれかの回折光学素
子。9. The diffractive optical element according to claim 1, wherein said transparent substrate is made of plastic.
学素子において、前記階段状要素全体を覆う表面が平坦
な膜を有し、該膜の作用により前記階段状要素からの反
射光の強度を増加させることを特徴とする回折光学素
子。10. A diffractive optical element in which a plurality of step-like elements are arranged, wherein a surface covering the whole of the step-like elements has a flat film, and the film acts to reflect reflected light from the step-like elements. A diffractive optical element characterized by increasing the intensity.
階段により近似したバイナリ型の回折光学素子におい
て、前記階段全体を覆う表面が平坦な膜を有し、該膜の
作用により前記階段からの反射光の強度を増加させるこ
とを特徴とする回折光学素子。11. A binary diffractive optical element in which each lens constituting a Fresnel lens is approximated by a step, the surface covering the entire step has a flat film, and the light reflected from the step by the action of the film. A diffractive optical element characterized by increasing the intensity of light.
満足されるように前記階段一段の高さ前記膜の屈折率と
が定められること特徴とする請求項１０または１１の回
折光学素子。12. The diffractive optical element according to claim 10, wherein the height of one step of the stairs and the refractive index of the film are determined so that the reflection increasing condition is satisfied for each floor of the steps.
層を形成し、複数層の膜の作用により前記反射光の強度
を増加させることを特徴とする請求項１０または１１の
回折光学素子。13. The diffractive optical element according to claim 10, wherein at least one film layer is formed on the thin film, and the intensity of the reflected light is increased by the action of a plurality of layers.
素子を有することを特徴とする投影光学系。14. A projection optical system comprising the diffractive optical element according to claim 1.
を特徴とする光学機器。15. An optical apparatus comprising the projection optical system according to claim 14.
を特徴とする露光装置。16. An exposure apparatus comprising the projection optical system according to claim 14.
素子を有することを特徴とする照明光学系。17. An illumination optical system comprising the diffractive optical element according to claim 1.
を特徴とする光学機器。18. An optical apparatus comprising the illumination optical system according to claim 17.
を特徴とする露光装置。19. An exposure apparatus comprising the illumination optical system according to claim 17.
光装置により基板上にデバイスパターンを転写する段階
を有することを特徴とするデバイス製造方法。20. A device manufacturing method, comprising a step of transferring a device pattern onto a substrate by the exposure apparatus according to claim 16.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17907796A JPH1020106A (en) | 1996-07-09 | 1996-07-09 | Diffraction optical grating, projection optical system illumination optical system, optical aperture, exposure device and production of device |
| US08/889,859 US5995285A (en) | 1996-07-09 | 1997-07-08 | Multilevel optical diffraction device with antireflection film and exposure apparatus |
| US09/359,044 US6327086B1 (en) | 1996-07-09 | 1999-07-23 | Optical diffraction device and exposure apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17907796A JPH1020106A (en) | 1996-07-09 | 1996-07-09 | Diffraction optical grating, projection optical system illumination optical system, optical aperture, exposure device and production of device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1020106A true JPH1020106A (en) | 1998-01-23 |
Family
ID=16059690
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17907796A Withdrawn JPH1020106A (en) | 1996-07-09 | 1996-07-09 | Diffraction optical grating, projection optical system illumination optical system, optical aperture, exposure device and production of device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1020106A (en) |
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Legal Events
| Date | Code | Title | Description |
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| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20031007 |