JPH0990098A - Multilayer film x-ray reflector and x-ray projection aligner - Google Patents
Multilayer film x-ray reflector and x-ray projection alignerInfo
- Publication number
- JPH0990098A JPH0990098A JP7245798A JP24579895A JPH0990098A JP H0990098 A JPH0990098 A JP H0990098A JP 7245798 A JP7245798 A JP 7245798A JP 24579895 A JP24579895 A JP 24579895A JP H0990098 A JPH0990098 A JP H0990098A
- Authority
- JP
- Japan
- Prior art keywords
- ray
- multilayer film
- optical system
- multilayer
- reflecting mirror
- 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.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、Ｘ線反射鏡として好適
な多層膜Ｘ線反射鏡、及びフォトマスク（マスクまたは
レチクル）上の回路パターンをＸ線光学系を用いたミラ
ープロジェクション方式により、投影結像光学系（以
下、結像光学系と称する場合がある）を介してウエハ等
の基板上に転写する際に好適なＸ線投影露光装置の光学
系に用いる多層膜Ｘ線反射鏡と、該多層膜Ｘ線反射鏡を
有する結像光学系を備えたＸ線投影露光装置関するもの
である。BACKGROUND OF THE INVENTION The present invention relates to a multilayer film X-ray reflecting mirror suitable as an X-ray reflecting mirror, and a circuit pattern on a photomask (mask or reticle) by a mirror projection method using an X-ray optical system. A multilayer film X-ray reflecting mirror used for an optical system of an X-ray projection exposure apparatus, which is suitable for transferring onto a substrate such as a wafer through a projection image forming optical system (hereinafter, also referred to as an image forming optical system). The present invention relates to an X-ray projection exposure apparatus having an imaging optical system having the multilayer X-ray reflecting mirror.
【０００２】[0002]
【従来の技術】従来の可視光領域の光学素子には、主に
レンズが用いられてきた。しかし、Ｘ線領域では、物質
の屈折率が１に近いため、従来のレンズは使用できな
い。そこで、Ｘ線領域では光学素子として反射鏡が用い
られる。さらに、反射鏡を直入射に近い状態で使用し
て、しかも反射鏡の反射率を向上させるために、反射鏡
の反射面に多層膜を設けることが好ましい。2. Description of the Related Art Lenses have been mainly used for conventional optical elements in the visible light region. However, the conventional lens cannot be used in the X-ray region because the refractive index of the substance is close to 1. Therefore, a reflecting mirror is used as an optical element in the X-ray region. Furthermore, it is preferable to use a multilayer mirror on the reflective surface of the reflective mirror in order to use the reflective mirror in a state of nearly direct incidence and to improve the reflectance of the reflective mirror.
【０００３】一般に、Ｘ線反射鏡に用いる多層膜は、屈
折率の大きい物質と小さい物質とを交互に薄膜状に積層
した交互多層膜であり、例えば波長13ｎｍのＸ線に対し
ては、モリブデンと珪素からなる交互多層膜が高い反射
率を有する。また、多層膜は、次式の条件を満たすとき
に高い反射率を示す。 d=λ/(2・sin θ) ここで、d は周期長であり、屈折率が大きい物質の層と
小さい物質の層一対の膜厚を示す。λはＸ線の波長を、
θは入射角を示す。Generally, a multilayer film used for an X-ray reflecting mirror is an alternating multilayer film in which a substance having a large refractive index and a substance having a small refractive index are alternately laminated in a thin film form. For example, molybdenum is used for X-rays having a wavelength of 13 nm. The alternating multilayer film made of silicon and silicon has a high reflectance. Further, the multilayer film exhibits high reflectance when the condition of the following equation is satisfied. d = λ / (2 · sin θ) where d is the period length, and indicates the film thickness of a layer of a substance having a large refractive index and a layer of a substance having a small refractive index. λ is the wavelength of X-ray,
θ indicates the incident angle.
【０００４】この式より、多層膜は使用するＸ線の波長
とその反射角（または入射角）において、反射率が高く
なるような周期長d に設定するのが好ましいことが判
る。例えば、モリブデンと珪素からなる多層膜の反射率
を図５に示す。本図には、周期長が6.63nm、6.70nm、6.
77nmの三種類の多層膜の反射率を示したが、周期長が異
なると、反射率が変化することがわかる。From this equation, it is understood that it is preferable to set the period length d so that the multilayer film has a high reflectance at the wavelength of X-rays used and its reflection angle (or incident angle). For example, FIG. 5 shows the reflectance of a multilayer film made of molybdenum and silicon. In this figure, the cycle length is 6.63 nm, 6.70 nm, 6.
The reflectivities of three types of 77 nm multilayer films are shown, and it is clear that the reflectivity changes when the period length is different.
【０００５】従って、反射率が高い多層膜Ｘ線反射鏡を
作製するためには、周期長分布を所望の分布にする必要
がある。そして、従来の多層膜Ｘ線反射鏡では、反射率
が十分に得られる程度の周期長分布であれば良いと考え
られてきた。例えば、モリブデンと珪素からなる多層膜
の場合、周期長分布の誤差が１％以内であれば、70％以
上の反射率が得られるので、十分であると考えられてき
た。Therefore, in order to manufacture a multilayer film X-ray reflecting mirror having a high reflectance, it is necessary to make the period length distribution a desired distribution. In the conventional multi-layer film X-ray reflecting mirror, it has been considered that the period length distribution is sufficient so that the reflectance is sufficiently obtained. For example, in the case of a multilayer film made of molybdenum and silicon, it has been considered sufficient to obtain a reflectance of 70% or more if the error of the period length distribution is within 1%.
【０００６】さて、多層膜Ｘ線反射鏡の用途の一つとし
て半導体製造用のＸ線投影露光装置がある。半導体製造
用の露光装置は、物体面としてのフォトマスク（以下、
マスクと称する）面上に形成された回路パターンを結像
光学系を介してウエハ等の基板上に投影転写する。基板
にはレジストが塗布されており、露光することによりレ
ジストが感光してレジストパターンが得られる。Now, one of the applications of the multilayer X-ray reflecting mirror is an X-ray projection exposure apparatus for semiconductor manufacturing. An exposure apparatus for semiconductor manufacturing uses a photomask as an object plane (hereinafter,
A circuit pattern formed on a surface called a mask is projected and transferred onto a substrate such as a wafer through an image forming optical system. A resist is applied to the substrate, and by exposing the resist, the resist is exposed and a resist pattern is obtained.
【０００７】露光装置の解像力w は、主に露光波長λと
結像光学系の開口数NAで決まり、次式で表される。 w=k λ/NA k:定数 従って、解像力を向上させるためには、波長を短くする
か、或いは開口数を大きくすることが必要となる。現
在、半導体の製造に用いられている露光装置は、主に波
長365nm のｉ線を使用しており、開口数約0.5 で0.5 μ
ｍの解像力が得られている。The resolving power w of the exposure apparatus is mainly determined by the exposure wavelength λ and the numerical aperture NA of the imaging optical system, and is represented by the following equation. w = k λ / NA k: constant Therefore, in order to improve the resolution, it is necessary to shorten the wavelength or increase the numerical aperture. At present, the exposure equipment used in the manufacture of semiconductors mainly uses i-line with a wavelength of 365 nm and has a numerical aperture of about 0.5 and 0.5 μm.
A resolution of m is obtained.
【０００８】開口数を大きくすることは、光学設計上困
難であるので、解像力を向上させるためには、今後は露
光光の短波長化が必要となる。ｉ線より短波長の露光光
としては、例えばエキシマレーザーが挙げられ、その波
長はKrF で248nm 、ArF で193nm であるため、KrF では
0.25μｍ、ArF では0.18μｍの解像力が得られる。そし
て、露光光としてさらに波長の短いＸ線を用いると、例
えば波長13nmで0.1 μｍ以下の解像力が得られる。Since it is difficult to increase the numerical aperture in terms of optical design, it is necessary to shorten the exposure light wavelength in the future in order to improve the resolution. As the exposure light having a shorter wavelength than the i-line, for example, an excimer laser can be mentioned. The wavelengths of KrF are 248 nm and ArF is 193 nm.
A resolution of 0.25 μm and 0.18 μm can be obtained with ArF. Then, when X-rays having a shorter wavelength are used as the exposure light, for example, a resolution of 0.1 μm or less is obtained at a wavelength of 13 nm.
【０００９】従来の、Ｘ線投影露光装置（一例）の構成
（一例）を概念的に図４に示す。露光装置は、主に光源
及び照明光学系（不図示）、マスク12、結像光学系10、
ウエハ11のステージ（不図示）により構成される。マス
ク12には描画するパターンの等倍パターンまたは拡大パ
ターンが形成されている。結像光学系10は、複数のレン
ズまたは反射鏡により構成され、マスク12上のパターン
をウエハ11上に結像するようになっている。FIG. 4 conceptually shows a configuration (an example) of a conventional X-ray projection exposure apparatus (an example). The exposure apparatus mainly comprises a light source and an illumination optical system (not shown), a mask 12, an imaging optical system 10,
It is composed of a stage (not shown) of the wafer 11. The mask 12 is formed with an equal size pattern or an enlarged pattern of the pattern to be drawn. The image forming optical system 10 is composed of a plurality of lenses or reflecting mirrors and forms an image of the pattern on the mask 12 on the wafer 11.
【００１０】露光装置が所望の解像力を有するために
は、少なくとも結像光学系10が無収差または無収差に近
い光学系（以下、無収差光学系と称す）である必要があ
る。結像光学系10に収差があると、レジストパターンが
形成されない、レジストパターンの断面形状が劣化して
露光後のプロセスに悪影響を及ぼすという問題点の他、
像が歪んでしまうという問題点が発生する。In order for the exposure apparatus to have a desired resolving power, it is necessary that at least the imaging optical system 10 is an aberration-free or near-aberration-free optical system (hereinafter referred to as an aberration-free optical system). If the imaging optical system 10 has an aberration, other than the problems that the resist pattern is not formed and the cross-sectional shape of the resist pattern is deteriorated to adversely affect the process after exposure,
The problem that the image is distorted occurs.
【００１１】無収差の光学系と同等の性能を得るために
光学系に要求される収差の許容上限値（rms 値）は、波
長の14分の１程度の値である。従って、無収差の光学系
と同等の性能を得るためには、露光光の波長が短くなる
程、光学系の収差の値を小さくしなければならない。例
えば、露光光がｉ線の場合、収差の許容上限値は約26nm
rms である。The permissible upper limit value (rms value) of the aberration required for the optical system in order to obtain the same performance as that of the aberration-free optical system is about one quarter of the wavelength. Therefore, in order to obtain the same performance as an aberration-free optical system, the shorter the wavelength of the exposure light, the smaller the aberration value of the optical system must be made. For example, when the exposure light is i-line, the allowable upper limit of aberration is about 26 nm.
rms.
【００１２】無収差光学系を作製するためには、まず各
光学素子の形状を設計値どうりに加工しなければならな
い。即ち、形状誤差（許容上限値）は、収差（許容上限
値）と比較して少なくとも小さく、また、光学素子の数
が多くなるほど、形状誤差の許容上限値は小さくなる。
そして、光学素子が全てレンズの場合は、屈折面の数を
N とすると、形状誤差（許容上限値）は収差（許容上限
値）の1/N1/2程度の値にする必要がある。例えば露光光
がｉ線の場合、屈折面の数を30とすると、形状誤差（許
容上限値）を約5nmrmsとする必要がある。In order to manufacture an aberration-free optical system, the shape of each optical element must first be processed into a design value. That is, the shape error (allowable upper limit value) is at least smaller than the aberration (allowable upper limit value), and the allowable upper limit value of the shape error becomes smaller as the number of optical elements increases.
If all the optical elements are lenses, the number of refracting surfaces
If N, the shape error (permissible upper limit) needs to be about 1 / N 1/2 of the aberration (permissible upper limit). For example, when the exposure light is the i-line and the number of refracting surfaces is 30, the shape error (upper limit value) needs to be about 5 nmrms.
【００１３】以上のように、無収差光学系を作製するた
めには、形状精度の高い光学素子が必要であるが、従来
は高精度な加工を行うことにより、無収差光学系を作製
することができた。As described above, an optical element having a high shape accuracy is required to manufacture an aberration-free optical system, but conventionally, an aberration-free optical system is manufactured by performing highly accurate processing. I was able to.
【００１４】[0014]
【発明が解決しようとする課題】しかしながら、露光装
置の解像度を向上させるために露光光の波長を短くする
と、それに伴って収差の許容上限値も小さくなる。露光
光としてＸ線を使用し、例えば波長を13nmとすると、収
差の許容上限値は約1nmrmsとなる。この値は、ｉ線にお
ける収差の値約26nmrms と比較して非常に小さい。However, when the wavelength of the exposure light is shortened in order to improve the resolution of the exposure apparatus, the allowable upper limit value of the aberration is reduced accordingly. If X-rays are used as the exposure light and the wavelength is 13 nm, the allowable upper limit of aberration is about 1 nmrms. This value is very small compared to the aberration value at the i-line of about 26 nmrms.
【００１５】従って、Ｘ線用の無収差光学系としては、
非常に形状精度の高いものが必要となる。例えばＸ線投
影露光装置では、結像光学系に多層膜Ｘ線反射鏡を用い
るので、無収差光学系とするためには多層膜Ｘ線反射鏡
を高精度に作製しなければならない。多層膜反射鏡の作
製においては、まず基板を作製し、その表面（反射面
側）に多層膜をコーティングする。多層膜の膜厚分布
は、Ｘ線の入射角に合わせて反射率が高くなるような分
布とし、また基板形状は多層膜形成後、所望の反射面形
状が得られるような形状に加工してやればよい。Therefore, as an X-ray-free optical system,
A very precise shape is required. For example, in an X-ray projection exposure apparatus, since a multilayer X-ray reflecting mirror is used for the image forming optical system, the multilayer X-ray reflecting mirror must be manufactured with high precision in order to make it an aberration-free optical system. In the production of a multilayer-film reflective mirror, first, a substrate is produced and its surface (reflection surface side) is coated with a multilayer film. The film thickness distribution of the multilayer film should be such that the reflectance increases according to the incident angle of X-rays, and the substrate shape should be processed so that the desired reflection surface shape can be obtained after forming the multilayer film. Good.
【００１６】基板は研磨等の従来加工を高精度に施すこ
とにより、所望形状を得ることが可能である。さらに具
体的には、加工と形状測定を繰り返して、形状を徐々に
所望形状に近づけていくことにより、最終的に所望形状
を得ることができる。一方、多層膜を形成する場合は基
板加工時と異なり、多層膜形成後に再加工することが非
常に困難である。従って、多層膜の形成は基板形状を変
えないように即ち反射面形状が変化しないように、高精
度に再現性良く行なう必要がある。By subjecting the substrate to conventional processing such as polishing with high accuracy, a desired shape can be obtained. More specifically, the desired shape can be finally obtained by repeating the processing and the shape measurement to gradually bring the shape closer to the desired shape. On the other hand, when a multilayer film is formed, it is very difficult to reprocess after forming the multilayer film, unlike when processing the substrate. Therefore, it is necessary to form the multilayer film with high accuracy and good reproducibility so that the shape of the substrate is not changed, that is, the shape of the reflecting surface is not changed.
【００１７】しかし、従来のように、多層膜の反射率が
７０％以上であっても、周期長の誤差が１％程度もある
（膜厚誤差も１％程度である）と、無収差光学系として
使用できる多層膜Ｘ線反射鏡が得られないという問題点
があった。さらに、無収差光学系として使用できる多層
膜Ｘ線反射鏡が得られないためにＸ線投影露光装置の露
光性能も良くないという問題点があった。However, as in the conventional case, even if the reflectance of the multilayer film is 70% or more, if the error of the cycle length is about 1% (the film thickness error is also about 1%), the aberration-free optics will be obtained. There is a problem that a multilayer film X-ray reflecting mirror that can be used as a system cannot be obtained. Further, there is a problem that the exposure performance of the X-ray projection exposure apparatus is not good because a multilayer X-ray reflecting mirror that can be used as an aberration-free optical system cannot be obtained.
【００１８】本発明はかかる問題点に鑑みてなされたも
のであり、無収差光学系として使用できる多層膜Ｘ線反
射鏡、及び該多層膜Ｘ線反射鏡を有する投影結像光学系
を備え、露光性能を向上させたＸ線投影露光装置を提供
することを目的とする。The present invention has been made in view of the above problems, and includes a multilayer film X-ray reflecting mirror that can be used as an aberration-free optical system, and a projection imaging optical system having the multilayer film X-ray reflecting mirror. An object is to provide an X-ray projection exposure apparatus with improved exposure performance.
【００１９】[0019]
【課題を解決するための手段】そのため、本発明は第一
に「基板上に少なくとも、Ｘ線領域の光の屈折率と真空
の屈折率との差が小さい物質と大きい物質とを交互に積
層して、Ｘ線反射面を形成してなる多層膜Ｘ線反射鏡に
おいて、前記反射面を形成する多層膜の膜厚と該膜厚の
設計値との差を、該反射面上の任意点において、前記Ｘ
線の波長の六分の一以下としたことを特徴とする多層膜
Ｘ線反射鏡（請求項１）」を提供する。Therefore, the first aspect of the present invention is to "on a substrate, at least a substance having a small difference between the refractive index of light in the X-ray region and a refractive index of vacuum and a substance having a large difference are alternately laminated. Then, in a multilayer film X-ray reflecting mirror having an X-ray reflecting surface, the difference between the film thickness of the multilayer film forming the reflecting surface and the design value of the film thickness is determined by an arbitrary point on the reflecting surface. In the above X
A multilayer film X-ray reflecting mirror (claim 1) characterized in that the wavelength is less than ⅙ of the wavelength of the line.
【００２０】また、本発明は第二に、「前記多層膜が少
なくともモリブデンと珪素で構成されることを特徴とす
る請求項１記載の多層膜Ｘ線反射鏡（請求項２）」を提
供する。また、本発明は第三に「請求項１または２記載
の多層膜Ｘ線反射鏡を４個以上有する投影結像光学系を
備えたＸ線投影露光装置（請求項３）」を提供する。Further, the present invention secondly provides a "multilayer film X-ray mirror (claim 2) according to claim 1, characterized in that the multilayer film is composed of at least molybdenum and silicon. . Further, the present invention thirdly provides an "X-ray projection exposure apparatus (claim 3) having a projection imaging optical system having four or more multilayer film X-ray reflecting mirrors according to claim 1 or 2."
【００２１】[0021]
【実施の態様】Ｘ線投影露光装置の光学系、特に結像光
学系の光学素子は、全て多層膜Ｘ線反射鏡とすることが
好ましい。また、無収差光学系を得るためには、光学設
計の観点から反射面は４個以上とすることが好ましい。
従って、結像光学系は４個以上の多層膜Ｘ線反射鏡で構
成されることが好ましい。BEST MODE FOR CARRYING OUT THE INVENTION It is preferable that all optical elements of an X-ray projection exposure apparatus, particularly optical elements of an image forming optical system, are multilayer X-ray reflecting mirrors. Further, in order to obtain an aberration-free optical system, it is preferable to have four or more reflecting surfaces from the viewpoint of optical design.
Therefore, it is preferable that the imaging optical system is composed of four or more multilayer film X-ray reflecting mirrors.
【００２２】反射面の形状誤差は、屈折の場合の半分の
値が要求されるので、反射面の数をN とすると、形状誤
差の許容上限値は収差の許容上限値の1/（2N1/2 ）とな
る。ここで、収差の許容上限値、即ち無収差光学系の収
差上限値は、Ｘ線波長の１／１４である。従って、反射
面の数を４とすると、波長13nmのＸ線を使用する場合、
反射面の形状誤差（許容上限値）は0.23nmrms となる。Since the shape error of the reflecting surface is required to be half the value in the case of refraction, assuming that the number of reflecting surfaces is N, the allowable upper limit of the shape error is 1 / (2N 1 / 2 ). Here, the allowable upper limit value of aberration, that is, the upper limit value of aberration of the aberration-free optical system is 1/14 of the X-ray wavelength. Therefore, assuming that the number of reflecting surfaces is 4, when using X-rays with a wavelength of 13 nm,
The shape error (allowable upper limit) of the reflecting surface is 0.23 nmrms.
【００２３】このように、Ｘ線投影露光装置では、結像
光学系の収差として極めて小さな値が要求される。例え
ば、波長13nmのＸ線を使用する場合には、反射面の数が
４の結像光学系では、光学素子の形状誤差は少なくとも
2.3nm 以下であることが要求される。即ち、光学素子の
形状誤差を波長の約６分の１以下とする必要がある。そ
こで、本発明では、多層膜Ｘ線反射鏡の基板のように、
加工と形状測定を繰り返して、形状を徐々に所望形状に
近づけていくことにより、最終的に所望形状とすること
が非常に困難である多層膜について、その形状誤差（膜
厚誤差）をＸ線波長の約６分の１以下とすることによ
り、無収差光学系が得られるようにした（請求項１）。As described above, in the X-ray projection exposure apparatus, an extremely small value is required as the aberration of the image forming optical system. For example, when an X-ray with a wavelength of 13 nm is used, in an imaging optical system with four reflecting surfaces, the shape error of the optical element is at least
It is required to be 2.3 nm or less. That is, it is necessary to reduce the shape error of the optical element to about 1/6 or less of the wavelength. Therefore, in the present invention, like the substrate of the multilayer X-ray reflecting mirror,
By repeating processing and shape measurement to gradually bring the shape closer to the desired shape, it is very difficult to finally obtain the desired shape. By setting the wavelength to about 1/6 or less, an aberration-free optical system can be obtained (claim 1).
【００２４】例えば、波長13nmのＸ線を反射する多層膜
Ｘ線反射鏡の多層膜として、モリブデンと珪素からなる
多層膜を作製し、その周期長を6.7nm 、周期数を50周期
とすると、多層膜の膜厚は335nm となる。従来の多層膜
Ｘ線反射鏡における１％という膜厚誤差の場合には、膜
厚の１％は3.4nm となり、無収差光学系に必要な膜厚誤
差2.3nm よりかなり大きい。従って、従来の多層膜Ｘ線
反射鏡では、無収差光学系を得ることができない。For example, if a multilayer film made of molybdenum and silicon is prepared as a multilayer film of a multilayer X-ray reflecting mirror that reflects X-rays having a wavelength of 13 nm, and its cycle length is 6.7 nm and the number of cycles is 50 cycles, The thickness of the multilayer film is 335 nm. In the case of a film thickness error of 1% in the conventional multilayer X-ray reflecting mirror, 1% of the film thickness is 3.4 nm, which is considerably larger than the film thickness error of 2.3 nm required for the aberration-free optical system. Therefore, a conventional multilayer X-ray reflecting mirror cannot provide an aberration-free optical system.
【００２５】これに対して、本発明では膜厚誤差を波長
（13nm）の約６分の１以下（約2.3nm以下）としている
ので、無収差光学系を得ることができる。図１は本発明
にかかる多層膜Ｘ線反射鏡の一例を示している。多層膜
Ｘ線反射鏡は、基板１と多層膜２により構成され、反射
面に多層膜２が形成されている。多層膜Ｘ線反射鏡にＸ
線が入射すると（以下、入射Ｘ線３と称する）、入射Ｘ
線３は多層膜２により反射される（以下、反射されたＸ
線を反射Ｘ線４と称する）。On the other hand, in the present invention, the thickness error is about 1/6 or less of the wavelength (13 nm) (about 2.3 nm or less), so that an aberration-free optical system can be obtained. FIG. 1 shows an example of a multilayer film X-ray reflecting mirror according to the present invention. The multilayer X-ray reflecting mirror is composed of a substrate 1 and a multilayer film 2, and the multilayer film 2 is formed on the reflecting surface. X for multilayer X-ray mirror
When a ray is incident (hereinafter referred to as incident X-ray 3), the incident X-ray
The line 3 is reflected by the multilayer film 2 (hereinafter, the reflected X
The rays are referred to as reflected X-rays 4).
【００２６】このとき、入射Ｘ線３の波面５の形状は、
反射Ｘ線４の波面６の形状に変化する。そして、多層膜
Ｘ線反射鏡が所望形状に作製できていれば、反射Ｘ線４
の波面６も所望形状になる。一方、多層膜Ｘ線反射鏡が
所望形状に作製できていないと、反射Ｘ線４の波面形状
が所望形状と異なってしまい、この反射鏡により構成し
た光学系の収差の原因となる。At this time, the shape of the wavefront 5 of the incident X-ray 3 is
The shape of the wavefront 6 of the reflected X-ray 4 changes. Then, if the multilayer X-ray reflecting mirror can be manufactured in a desired shape, the reflected X-ray 4
The wavefront 6 of also has a desired shape. On the other hand, if the multilayer film X-ray reflecting mirror is not manufactured in a desired shape, the wavefront shape of the reflected X-ray 4 will be different from the desired shape, which will cause aberration of the optical system configured by this reflecting mirror.
【００２７】つまり、所望形状の波面が得られない多層
膜Ｘ線反射鏡により構成した光学系、さらにその光学系
を結像光学系として具備した投影露光装置は十分な解像
度を示さない。従って、多層膜Ｘ線反射鏡は、その反射
面を所望形状にすることが好ましい。多層膜Ｘ線反射鏡
の反射面形状を所望形状とするためには、少なくとも反
射鏡の基板が所望形状に作製されていることが好まし
い。さらに、多層膜の膜厚分布が所望の分布になってい
れば、所望形状の反射面が得られる。That is, an optical system composed of a multilayer film X-ray reflecting mirror that does not provide a wavefront having a desired shape, and a projection exposure apparatus equipped with the optical system as an imaging optical system do not show sufficient resolution. Therefore, it is preferable that the reflecting surface of the multilayer X-ray reflecting mirror has a desired shape. In order to make the shape of the reflecting surface of the multilayer X-ray reflecting mirror into a desired shape, it is preferable that at least the substrate of the reflecting mirror is made into a desired shape. Furthermore, if the thickness distribution of the multilayer film has a desired distribution, a reflecting surface having a desired shape can be obtained.
【００２８】例えば図２に示すように、多層膜Ｘ線反射
鏡の反射面形状が平面で、入射Ｘ線３の波面５の形状が
平面であれば、反射Ｘ線４の波面６の形状は平面とな
る。このような所望の波面形状が得られる多層膜Ｘ線反
射鏡により光学系を作製すれば、光学系の収差は十分小
さくなるので好ましい。一方、多層膜Ｘ線反射鏡の基板
が所望形状に作製されているとしても、多層膜の膜厚分
布が所望の分布からずれている場合は、反射面の形状も
所望形状からずれてしまう。For example, as shown in FIG. 2, if the reflection surface of the multilayer X-ray reflecting mirror is flat and the wavefront 5 of the incident X-ray 3 is flat, the shape of the wavefront 6 of the reflected X-ray 4 is. It becomes a plane. It is preferable to manufacture an optical system using a multilayer film X-ray reflecting mirror that can obtain such a desired wavefront shape, because the aberration of the optical system will be sufficiently small. On the other hand, even if the substrate of the multilayer X-ray reflecting mirror is formed in a desired shape, if the thickness distribution of the multilayer film deviates from the desired distribution, the shape of the reflecting surface also deviates from the desired shape.
【００２９】例えば図３に示すように、所望形状（平
面）の基板１に多層膜２を成膜した多層膜Ｘ線反射鏡に
おいて、多層膜２の膜厚分布が所望の分布（平面）でな
い場合には、多層膜Ｘ線反射鏡の反射面の形状も所望形
状（平面）からずれてしまう。従って、反射Ｘ線の波面
も所望の形状からずれてしまう。本発明にかかる多層膜
としては、使用するＸ線に対する反射率が高いものが好
ましい。例えば、波長13nmにおいてはモリブデンと珪素
を交互に積層した多層膜が反射率が高くなるので好まし
い（請求項２）。For example, as shown in FIG. 3, in a multilayer film X-ray mirror in which a multilayer film 2 is formed on a substrate 1 having a desired shape (planar), the film thickness distribution of the multilayer film 2 is not the desired distribution (planar). In this case, the shape of the reflecting surface of the multilayer X-ray reflecting mirror also deviates from the desired shape (flat surface). Therefore, the wavefront of the reflected X-ray also deviates from the desired shape. The multilayer film according to the present invention preferably has a high reflectance for the X-ray used. For example, at a wavelength of 13 nm, a multilayer film in which molybdenum and silicon are alternately laminated is preferable because the reflectance is high (claim 2).
【００３０】さらに、本発明にかかる多層膜Ｘ線反射鏡
により構成された光学系は、多層膜Ｘ線反射鏡の形状精
度が十分小さいので、無収差に近い性能を有する。さら
に、この光学系を結像光学系として具備したＸ線投影露
光装置は高い解像力を有するので好ましい（請求項
３）。以下、本発明を実施例により更に詳細に説明する
が、本発明はこの例に限定されるものではない。Further, the optical system constituted by the multilayer X-ray reflecting mirror according to the present invention has a performance close to aberration-free since the shape accuracy of the multilayer X-ray reflecting mirror is sufficiently small. Further, an X-ray projection exposure apparatus equipped with this optical system as an imaging optical system has a high resolving power and is preferable (claim 3). Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
【００３１】[0031]
【実施例】図１は、本実施例の多層膜Ｘ線反射鏡を示し
ている。多層膜Ｘ線反射鏡は、基板１と多層膜２により
構成され、反射面に多層膜２が形成されている。多層膜
２は、モリブデンと珪素を交互に積層した交互多層膜で
あり、波長13nmのＸ線を高反射率で反射するように、周
期長を6.7nm 、周期数を50とした。EXAMPLE FIG. 1 shows a multilayer film X-ray reflecting mirror of this example. The multilayer X-ray reflecting mirror is composed of a substrate 1 and a multilayer film 2, and the multilayer film 2 is formed on the reflecting surface. The multilayer film 2 is an alternating multilayer film in which molybdenum and silicon are alternately stacked, and has a period length of 6.7 nm and a number of periods of 50 so as to reflect X-rays having a wavelength of 13 nm with high reflectance.
【００３２】基板１は、その表面が高精度な非球面に加
工されている。さらに、その表面に形成された多層膜２
は、多層膜Ｘ線反射鏡の反射面上の各点（任意点）にお
ける多層膜の膜厚の値と該膜厚の設計値との差が2nm 以
下であるような膜厚分布を有している。この値は、Ｘ線
の波長の1/6 以下であり、多層膜の膜厚の0.6 ％以下で
ある。The surface of the substrate 1 is processed into a highly accurate aspherical surface. Furthermore, the multilayer film 2 formed on the surface thereof
Has a film thickness distribution such that the difference between the film thickness value of the multilayer film at each point (arbitrary point) on the reflecting surface of the multilayer film X-ray reflecting mirror and the design value of the film thickness is 2 nm or less. ing. This value is 1/6 or less of the wavelength of X-rays and 0.6% or less of the film thickness of the multilayer film.
【００３３】この多層膜Ｘ線反射鏡に、波長13nmのＸ線
をほぼ垂直に入射すると、Ｘ線は反射され、その波面の
所望の波面に対する誤差は0.23nmrms 以下であった。さ
らに同様に、異なる非球面形状の多層膜Ｘ線反射鏡を３
枚作製した。つまり、これらの表面に形成された多層膜
は、多層膜Ｘ線反射鏡の反射面上の各点における多層膜
の膜厚の値と該膜厚の設計値との差が2nm 以下であるよ
うな膜厚分布を有している。When an X-ray having a wavelength of 13 nm was made to enter the multilayer X-ray reflecting mirror substantially vertically, the X-ray was reflected, and the error of the wavefront with respect to the desired wavefront was 0.23 nmrms or less. Further, similarly, a multi-layer film X-ray mirror having different aspherical shapes is used.
Were produced. In other words, the multi-layer film formed on these surfaces is such that the difference between the thickness of the multi-layer film at each point on the reflecting surface of the multi-layer film X-ray reflecting mirror and the design value of the thickness is 2 nm or less. It has a wide film thickness distribution.
【００３４】そして、これらの反射鏡４枚により光学系
を作製したところ、光学系の波面収差は1nmrms以下と、
ほぼ無収差であった。さらに、この光学系を結像光学系
として具備したＸ線投影露光装置により露光を行なった
ところ、パターンサイズ0.1μm のレジストパターンが
得られた。一方、従来の多層膜Ｘ線反射鏡（膜厚誤差１
％）を用いたＸ線投影露光装置により露光した場合に
は、パターンサイズ0.1 μm のレジストパターンが得ら
れなかった。Then, when an optical system was manufactured by using these four reflecting mirrors, the wavefront aberration of the optical system was 1 nmrms or less,
There was almost no aberration. Further, when exposure was carried out by an X-ray projection exposure apparatus equipped with this optical system as an imaging optical system, a resist pattern having a pattern size of 0.1 μm was obtained. On the other hand, the conventional multilayer X-ray reflecting mirror (film thickness error 1
%), A resist pattern with a pattern size of 0.1 μm could not be obtained.
【００３５】[0035]
【発明の効果】以上説明したように、本発明の多層膜Ｘ
線反射鏡は、無収差光学系として使用できる。また、本
発明の多層膜Ｘ線反射鏡を有する投影結像光学系を備え
たＸ線投影露光装置は高い解像力を有し、その結果、高
いスループットで、マスクのパターンを忠実に基板上に
転写することができる。As described above, the multilayer film X of the present invention
The line reflector can be used as an aplanatic optical system. Further, the X-ray projection exposure apparatus having the projection imaging optical system having the multilayer film X-ray reflecting mirror of the present invention has a high resolving power, and as a result, the mask pattern is faithfully transferred onto the substrate at a high throughput. can do.
【図１】は、実施例の多層膜Ｘ線反射鏡を示す概略構成
図である。FIG. 1 is a schematic configuration diagram showing a multilayer X-ray reflecting mirror of an example.
【図２】は、本発明にかかる多層膜Ｘ線反射鏡（一例）
を示す概略構成図である。FIG. 2 is a multilayer film X-ray reflecting mirror according to the present invention (an example).
FIG.
【図３】は、従来の多層膜Ｘ線反射鏡（一例）を示す概
略構成図である。FIG. 3 is a schematic configuration diagram showing a conventional multilayer X-ray reflecting mirror (an example).
【図４】は、従来の投影露光装置（一例）を示す概略構
成図である。FIG. 4 is a schematic configuration diagram showing a conventional projection exposure apparatus (one example).
【図５】は、多層膜の周期長と反射率との関係を示すデ
ータ図である。FIG. 5 is a data diagram showing the relationship between the cycle length and the reflectance of a multilayer film.
１・・・基板 ２・・・多層膜 ３・・・入射Ｘ線 ４・・・反射Ｘ線 ５・・・入射Ｘ線の波面 ６・・・反射Ｘ線の波面 10・・・結像光学系 11・・・ウエハ 12・・・マスク 13・・・露光光 以 上 1 ... Substrate 2 ... Multilayer film 3 ... Incident X-ray 4 ... Reflected X-ray 5 ... Incident X-ray wavefront 6 ... Reflected X-ray wavefront 10 ... Imaging optics System 11 ・ ・ ・ Wafer 12 ・ ・ ・ Mask 13 ・ ・ ・ Exposure light
Claims (3)
折率と真空の屈折率との差が小さい物質と大きい物質と
を交互に積層して、Ｘ線反射面を形成してなる多層膜Ｘ
線反射鏡において、 前記反射面を形成する多層膜の膜厚と該膜厚の設計値と
の差を、該反射面上の任意点において、前記Ｘ線の波長
の六分の一以下としたことを特徴とする多層膜Ｘ線反射
鏡。1. A multilayer structure in which a substance having a small difference between the refractive index of light in the X-ray region and a refractive index of vacuum is alternately laminated on a substrate to form an X-ray reflecting surface. Membrane X
In the line reflection mirror, the difference between the film thickness of the multilayer film forming the reflection surface and the design value of the film thickness is set to one sixth or less of the wavelength of the X-ray at an arbitrary point on the reflection surface. A multilayer film X-ray reflecting mirror characterized by the above.
素で構成されることを特徴とする請求項１記載の多層膜
Ｘ線反射鏡。2. The multilayer X-ray reflecting mirror according to claim 1, wherein the multilayer film is composed of at least molybdenum and silicon.
鏡を４個以上有する投影結像光学系を備えたＸ線投影露
光装置。3. An X-ray projection exposure apparatus comprising a projection imaging optical system having four or more multilayer film X-ray reflecting mirrors according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7245798A JPH0990098A (en) | 1995-09-25 | 1995-09-25 | Multilayer film x-ray reflector and x-ray projection aligner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7245798A JPH0990098A (en) | 1995-09-25 | 1995-09-25 | Multilayer film x-ray reflector and x-ray projection aligner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0990098A true JPH0990098A (en) | 1997-04-04 |
Family
ID=17138999
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7245798A Pending JPH0990098A (en) | 1995-09-25 | 1995-09-25 | Multilayer film x-ray reflector and x-ray projection aligner |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0990098A (en) |
-
1995
- 1995-09-25 JP JP7245798A patent/JPH0990098A/en active Pending
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