JP2005268359A - Mirror and lighting optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mirror from which the debris generated from a plasma light source attached to the mirror can be removed without lowering the reflectance of the mirror in an EUV optical system using plasma which prevents the drop of the reflectance even when the mirror is left in the atmosphere. <P>SOLUTION: The mirror which reflects EUV light having a wavelength of ≤60 nm is constituted of a mirror main body and a protective film. Since the refractive index and absorption factor of the material constituting the protective film at the wavelength of the EUV light are adjusted to 0.98-1.02 and ≤0.01 respectively, the surface of the mirror is not oxidized even when the mirror is left in the atmosphere, and the reflectance of the mirror is not influenced even when the debris etc., is removed physically. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a mirror as an optical element, and is mainly used for manufacturing a next-generation semiconductor having a line width of 60 nm or less, an illumination optical apparatus including the mirror, and a projection exposure apparatus including the illumination optical apparatus, The present invention relates to a method of manufacturing a micro device using the projection exposure apparatus.

  The numerical aperture and operating wavelength of a projection exposure apparatus for semiconductors tend to become larger and shorter with the increase in the density of semiconductor elements and the thinning of the target line width. The wavelength of light used shifts from mercury i-line (wavelength 365.015 nm) to KrF excimer laser (wavelength 248 nm), and a reduction projection exposure apparatus using an ArF excimer laser (wavelength 193 nm) as a light source has been put into practical use.

However, in the conventional projection optical system using the refractive optical element, the use of an F ₂ excimer laser having a wavelength of 157 nm as a light source is the limit in terms of the transmittance of the glass material constituting the lens and the like. If it is shortened, the optical system must be constituted by a reflective optical system that does not include any refractive member.

  For this reason, a reduction exposure apparatus using EUV light (extreme ultraviolet light) having a wavelength shorter than 60 nm as a light source has been studied as a means for next-generation semiconductor lithography. Currently, plasma light sources that emit light of 13.4 nm have been studied as light sources for EUV illumination optical systems, and there are two types of laser plasma light sources and discharge plasma light sources. In the discharge plasma light source, since EUV light is generated by discharging, scattered matter called debris is generated from the plasma-discharged portion, and the debris adheres to the mirror surface and the like, causing a decrease in reflectance.

  On the other hand, there are two types of mirrors used in the EUV illumination optical system: a multilayer film mirror using Bragg reflection formed by a multilayer film and a grazing incidence mirror used by being incident on the mirror reflection surface at a shallow incident angle. Is present. The multilayer mirror has a low aberration but has a low reflectance of about 70%, and is very expensive because it is made by stacking the multilayer films. On the other hand, when the oblique incidence type mirror has a relatively large aberration but is incident at a shallow angle, the reflectivity can be about 90%, and a high reflectivity can be obtained as compared with the multilayer mirror.

The oblique incidence type mirrors used in these EUV regions are arranged in the vicinity of the EUV light source of the illumination optical device because of high reflectivity and the like, and debris generated from the EUV light source is likely to adhere. For this reason, as a countermeasure for preventing debris adhesion, there is no method for drastically preventing debris adhesion without loss of light quantity, but when debris adheres, it is necessary to remove the debris.

JP2003-22950

Here, chemical or physical removal methods can be considered to remove the debris adhering to the mirror, but it is difficult to remove the debris without damaging the mirror surface in either method, and the debris is removed. Attempting to do so damages the reflecting surface of the mirror and adversely affects the reflection characteristics. Even if the bent debris is removed, the mirror cannot be used thereafter.

  For this reason, a method of repolishing after removing the debris is also conceivable, but it takes a lot of time and labor to return to the original reflecting surface of the mirror by repolishing, and in the case of a noble metal such as Ru, In some cases, the mirror is often scraped because it is a very expensive precious metal. The oblique incidence mirror is made of a material such as Mo, Rh, or Ru. In particular, Mo is easily oxidized, and an oxide film is formed when the mirror made of Mo is left in the atmosphere. This adversely affects the reflection characteristics of the oblique incidence type mirror.

  Therefore, in the present invention, even when the debris is removed by a physical or chemical method in the oblique incidence type mirror, the reflection characteristic is not adversely affected, and the oblique incidence type mirror has high reactivity such as oxidation. The present invention provides a mirror, particularly a grazing incidence reflection mirror for EUV, which is not oxidized in the atmosphere and does not deteriorate in reflection characteristics even when it is made of a material.

Furthermore, the present invention provides an illumination optical apparatus and exposure apparatus that can use the same mirror for a long period of time, reduce running costs, and can be operated stably.

  The present invention has been made to solve the above problems.

  1st invention is the mirror which reflects the light from a light source, The said mirror is comprised from the mirror main body and the protective film, The refractive index in the wavelength of the light emitted from the said light source of the material which comprises the said protective film is 0.98 or more and 1.02 or less.

A second invention is a mirror that reflects EUV light having a wavelength of 60 nm or less.
The mirror is composed of a mirror body and a protective film, and a refractive index at a wavelength of the EUV light of a material constituting the protective film is 0.98 or more and 1.02 or less. .

  According to a third invention, in the mirror of any one of the first and second inventions, the mirror body is made of Mo, Ru, Rh, MoSi, or an alloy or compound containing these. It is a featured mirror.

  According to a fourth aspect of the present invention, in the mirror that reflects EUV light having a wavelength of 60 nm or less, the mirror is composed of a substrate, a metal film, and a protective film, and a refractive index at a wavelength of the EUV light of a material constituting the protective film Is a mirror which is 0.98 or more and 1.02 or less.

  According to a fifth invention, in the mirror according to any one of the first to fourth inventions, when the mirror is used, an angle formed by the light or the EUV light and the surface of the mirror is 30 ° or less. This is a grazing incidence type mirror.

  A sixth invention is the mirror according to any one of the first to fifth inventions, wherein the material constituting the protective film has an absorption coefficient at a wavelength of the EUV light of 0.01 or less. is there.

  A seventh invention is characterized in that, in any one of the mirrors 4 to 6, the material constituting the metal film is made of Mo, Ru, Rh, MoSi, or an alloy or compound containing these. To mirror.

  According to an eighth aspect of the present invention, in any one of the mirrors according to the fourth to seventh aspects, the material constituting the metal film has a higher reflectance in the EUV light than the material constituting the substrate, and the substrate The mirror is characterized in that the material constituting the material has higher thermal conductivity than the material constituting the metal film.

  According to a ninth invention, in the mirror according to any one of the first to eighth inventions, the material constituting the protective film is any of Be, Ce, La, Pr, Rb, Si, Sr, or includes these A mirror made of an alloy or a compound.

  A tenth invention is a mirror according to any one of the first to ninth inventions, wherein the protective film or the metal film is formed by sputtering or ion plating.

  An eleventh invention is an illumination optical device comprising a light source that generates EUV light having a wavelength of 60 nm or less and an optical element for performing illumination, wherein the optical element includes any one of the mirrors of the first to tenth inventions. The illumination optical device characterized by the above.

  A twelfth aspect of the invention is an exposure apparatus for transferring a pattern image provided on a mask onto a photosensitive substrate. An illumination optical apparatus according to the eleventh aspect of the invention for illuminating the mask, and an image of the pattern of the mask. An exposure apparatus comprising: a projection optical system for forming on the photosensitive substrate.

A thirteenth invention uses the exposure apparatus of the twelfth invention to expose the mask pattern on the photosensitive substrate, and to develop the photosensitive substrate exposed by the exposure step. A method for manufacturing a microdevice.

The mirror according to the present invention can prevent deterioration of the reflecting surface of the mirror even when left in the atmosphere, and can be stored for a long period of time and used for a long period of time. Further, even a mirror with debris attached has an effect that the debris can be removed physically or chemically without affecting the reflection characteristics. Therefore, even a mirror with debris attached can be regenerated, and the regenerated mirror can be used many times. Furthermore, the illumination optical apparatus and exposure apparatus according to the present invention can be used stably at a low cost for a long time.

  Hereinafter, an embodiment of a mirror according to the present invention will be described with reference to FIG.

The mirror according to the present invention has a configuration in which a protective film 2 is formed on a mirror body 1. Specifically, the mirror body 1 is made of Mo (molybdenum) that exhibits a high reflectance when a light beam 3 having a wavelength of 13.4 nm is incident at an oblique incidence, and the mirror surface is polished so as to be a mirror surface. ing. In addition to this, the material constituting the mirror body 1 includes a light beam 3 having a wavelength of 13.4 nm.
May be made of Ru and Rh, which are materials that exhibit high reflectivity when incident at an oblique incidence. Moreover, the material which comprises the mirror main body 1 may differ with the wavelengths to be used, and is comprised with the material which becomes optimal in each wavelength.

The protective film 2 is made of a Si film and is formed by a sputtering method. Specifically, after the mirror body 1 is installed in the chamber of the sputtering apparatus, the vacuum body is evacuated to 1 × 10 ⁻⁶ Torr. In the sputtering apparatus, a Si target is placed as a sputtering target on a cathode to which an electric field can be applied, and the cathode is connected to an RF power source. Thereafter, argon gas is introduced into the chamber, and an RF electric field is applied to the cathode to generate plasma discharge. The pressure in the chamber at this time is 2 × 10 ⁻³ Torr. It is manufactured by forming a 1 μm Si film as a protective film 2 in a region to be a reflecting surface of the mirror body 1.

  In this embodiment, the film is formed by the sputtering method because it is possible to form a film having a denser and stronger adhesive force than vacuum deposition or the like. Accordingly, any film forming technique other than sputtering may be used as long as it is a dense and strong film forming technique, and film formation may be performed by ion plating or the like.

  In the present embodiment, the protective film 2 to be formed is preferably a material having a low absorption coefficient and a refractive index close to 1 at the wavelength used of 13.4 nm. This is because when the light beam 1 is incident on the protective film 2, the reflection on the surface of the protective film 2 is reduced and the absorption of the light beam in the protective film 2 is reduced. Specifically, if the absorption coefficient is 0.01 or less and the refractive index is 0.98 to 1.02, the oblique incidence type mirror can obtain almost the same optical characteristics as those without the protective film 2. In this example, Si was used as the protective film 2, but Si has a refractive index of 0.9999 and an absorption coefficient of 0.0018 at a wavelength of 13.4 nm, and is the most suitable material for the protective film 2 of the present invention. one of. Other materials that can be candidates for the protective film 2 at 13.4 nm include Be, Ce, La, Pr, Rb, and Sr.

Even if the mirror according to this example is left in the atmosphere, the surface of Mo which is a mirror surface portion of the mirror is not oxidized, and the mirror surface portion is covered with the Si film which is the protective film 2, Even if the surface of the Si film is damaged by physical debris removal, specifically ion beam etching or hand wiping, the refractive index in vacuum and the refractive index of Si are almost equal. It hardly affects the reflection characteristics of the mirror.

  An embodiment according to the present invention will be described below with reference to FIG.

  The mirror according to the present invention has a configuration in which a metal film 7 is formed on a substrate 6 and a protective film 8 is further laminated.

  Specifically, the substrate 6 is made of AlSiC having a high thermal conductivity. After the mirror surface is used as the reflective surface, the substrate 6 has a high reflectance when EUV light is incident on the oblique incidence. The Ru film shown is formed.

This Ru film is formed by sputtering. Specifically, after the substrate 6 is placed in the chamber of the sputtering apparatus, it is evacuated to 1 × 10 ⁻⁶ Torr by a vacuum pump. In the sputtering apparatus, a Ru target is placed as a sputtering target on a cathode to which an electric field can be applied, and the cathode is connected to a DC power source. Thereafter, argon gas is introduced into the chamber, and a direct current electric field is applied to the cathode to generate plasma discharge. The pressure in the chamber at this time is 2 × 10 ⁻³ Torr. A Ru film is formed to a thickness of 100 nm in a region to be a reflective surface of the substrate 6, and a Si film is further formed thereon as a protective film 8 to a thickness of about 1 μm. The Si film is formed by the method described in Example 1. In this embodiment, the Ru film was formed by the sputtering method. However, any film forming method other than sputtering may be used as long as it is a dense and strong film forming method, such as ion plating. The film may be formed by the above.

In this embodiment, Ru is used as the material of the metal film 7 to be formed. However, other than this, any material having a high reflectance at the wavelength of the light source used may be used. When used for EUV light, in addition to Ru, Rh, Pd, Mo, or an alloy or compound containing these may be used. In addition, the optimum material may differ depending on the wavelength used, and the material is optimum for each wavelength.

  Furthermore, the substrate 6 is preferably made of a material having high thermal conductivity because of the necessity of enhancing the heat dissipation effect, and needs to be made of a material having a thermal conductivity of at least 50 [W / m · K] or more. Is done. In particular, it is more preferably 150 [W / m · K] or more. From the viewpoint of the heat dissipation effect, the material to be the substrate 6 needs to be a material having a somewhat higher thermal conductivity than the material constituting the metal film 7, and the thermal conductivity of the substrate 6 according to the present invention is experienced. This is because the value can be expected to have a remarkable effect.

  Typical examples of such materials include gold, silver, copper, aluminum, AlN, SiC, Si, and the like. However, when the temperature of the mirror becomes high due to the irradiation of EUV light, if the thermal expansion coefficients of the materials constituting the substrate 6 and the metal film 7 are greatly different, the film may be peeled off, causing damage to the mirror. . For this reason, it is desirable that the thermal expansion coefficients of the substrate 6 and the metal film 7 are as close as possible. In this embodiment, AlSiC, which is a material having a thermal expansion coefficient relatively close to Ru, is used as the material of the substrate 6. . Other candidate materials include alloy materials such as W-Cu.

When the EUV light ray 9 is incident obliquely on the mirror according to the present embodiment, the light ray 9 passes through the protective film 8 and is reflected by the surface of the reflective film 7, and again passes through the protective film 8 to become reflected light. The Ru film serving as the reflective surface is covered with the Si film that is the protective film 8, and the Si film that is the protective film 8 is damaged by physical debris removal, specifically by ion beam etching or hand wiping. However, the Ru film as the reflective film 7 is not damaged, and the refractive index in vacuum and the refractive index of Si are almost equal, so that the reflective characteristics of the mirror according to the present embodiment are hardly affected. .

  An embodiment of the illumination optical apparatus according to the present invention will be described below with reference to FIG.

  In the present embodiment, since the EUV light is used, the entire illumination optical device is incorporated into the vacuum chamber and exhausted by a vacuum pump (not shown). A plasma light source is installed as the EUV light source 11 in such a vacuum chamber. This plasma light source generates plasma by applying an electric field to an electrode and discharging it while flowing Xe gas. From this plasma light source, EUV light having a wavelength of 13.4 nm is emitted. In this embodiment, a discharge plasma light source is used as the EUV light source 11, but a laser plasma light source may be used.

The EUV light emitted from the EUV light source 11 is collected by a grazing incidence collector optical system 12. The collector optical system 12 is an oblique incidence type mirror in which a plurality of conical surfaces are concentrically arranged, and is constituted by a mirror having Mo as a mirror body and Si as a protective film formed on a reflection surface. The EUV light source 11 and the collector optical system 12 are housed in one container 13, and a pinhole P is provided in the vicinity of the position where the EUV light is collected by the collector optical system 12. EUV light generated from the can be extracted. Further, the pressure inside the container 13 is set to be lower than that outside the container, and the pressure is adjusted so that the scattered matter generated from the EUV light source 11 does not scatter outside the container 13. The EUV light emitted from the pinhole P of the container 13 enters the collimator optical system 14.

  The EUV light incident by the collimator optical system 14 is converted into a parallel light beam having a uniform distribution and emitted. In this embodiment, the mirror in the collimator optical system 14 uses AlSiC for the substrate, and after forming a Ru film as a metal film on the reflection surface, a Si film is formed thereon as a protective film. It is an incident type mirror, and is installed so that the incident angle of the EUV light beam is incident at an angle of about 10 degrees with respect to the mirror surface. When the EUV light beam is incident on the oblique incidence type mirror at this angle, the reflectivity is about 90%, and the reflectivity of the multilayer mirror is about 70%, whereas the reflectivity is high.

  The parallel EUV light emitted from the collimator optical system 14 is then incident on an oblique incidence type reflective fly's eye optical system 15 to generate a secondary light source group. The oblique incidence type reflective fly-eye optical system 15 is composed of a pair of a fly-eye mirror on the incident side and a fly-eye mirror on the exit side. In this embodiment, the reflective fly-eye optical system 15 uses AlSiC for the substrate, and after forming a Ru film as a metal film on the reflective surface, an oblique incidence type in which a Si film is formed thereon as a protective film It is a mirror and is installed so that the incident angle of the EUV light beam is incident at an angle of about 10 degrees with respect to the mirror surface.

The EUV light beam emitted from the reflective fly-eye optical system 15 illuminates the reticle 17 after passing through the condenser optical system 16. The condenser optical system 16 uses AlSiC as a substrate, and is composed of a grazing incidence type mirror in which a Ru film is formed as a metal film on a reflection surface and a Si film is formed thereon as a protective film.

  A method for exposing a micro device with the exposure apparatus including the illumination optical apparatus described above will be described below. This exposure apparatus illuminates a mask (or reticle) with an illumination optical apparatus (illumination process), and exposes a transfer pattern formed on the mask using a projection optical system onto a photosensitive substrate (exposure process). Micro devices (semiconductor elements, imaging elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. An example of a technique for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using this exposure apparatus will be described with reference to the flowchart of FIG.

  First, in step 101 of FIG. 4, a metal film is deposited on one lot of wafers. In the next step 102, a photoresist is applied on the metal film on one lot of wafers. Thereafter, in step 103, using the exposure apparatus of the above-described embodiment, the image of the pattern on the mask is sequentially exposed to each shot area on the wafer of one lot via the projection optical system (projection optical module). Transcribed. Thereafter, in step 104, the photoresist on the wafer is developed for the lot, and in step 105, the resist pattern is etched on the wafer in the lot to obtain a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a circuit pattern is formed on the upper layer to manufacture a device such as a semiconductor element. According to the semiconductor device manufacturing method described above, it is possible to manufacture a semiconductor device having an extremely fine circuit pattern.

In the exposure apparatus of the above-described embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate).

It is a block diagram of the mirror which concerns on Example 1 of this invention. It is a block diagram of the mirror which concerns on Example 2 of this invention. It is a block diagram of the illumination optical apparatus which concerns on Example 3 of this invention. It is a figure which shows the process which produces a microdevice with the projection exposure apparatus which concerns on this invention.

Explanation of symbols

1 Mirror body 2 Protective film 3 Light beam 6 Substrate 7 Reflective film 8 Protective film 9 Light beam

Claims (13)

In the mirror that reflects the light from the light source,
The mirror is composed of a mirror body and a protective film,
A mirror having a refractive index at a wavelength of light generated from the light source of a material constituting the protective film of 0.98 or more and 1.02 or less.
In a mirror that reflects EUV light with a wavelength of 60 nm or less,
The mirror is composed of a mirror body and a protective film,
A mirror having a refractive index at a wavelength of the EUV light of a material constituting the protective film of 0.98 or more and 1.02 or less.
The mirror according to claim 1 or 2,
A mirror characterized in that the mirror body is made of Mo, Ru, Rh, MoSi, or an alloy or compound containing these.
In a mirror that reflects EUV light with a wavelength of 60 nm or less,
The mirror is composed of a substrate, a metal film, and a protective film,
A mirror having a refractive index at a wavelength of the EUV light of a material constituting the protective film of 0.98 or more and 1.02 or less.
The mirror according to any one of claims 1 to 4,
The oblique incidence type mirror, wherein when the mirror is used, an angle formed by the light or the EUV light and the surface of the mirror is 30 ° or less.
The mirror according to any one of claims 1 to 5,
The mirror according to claim 1, wherein the material constituting the protective film has an absorption coefficient of 0.01 or less at the wavelength of the EUV light.
The mirror according to any one of claims 4 to 6,
A mirror characterized in that the material constituting the metal film is made of Mo, Ru, Rh, MoSi, or an alloy or compound containing these.
A mirror according to any one of claims 4 to 7,
The material constituting the metal film has a higher reflectance in the EUV light than the material constituting the substrate, and
The mirror characterized in that the material constituting the substrate has higher thermal conductivity than the material constituting the metal film.
The mirror according to any one of claims 1 to 8,
A mirror characterized in that the material constituting the protective film is made of any one of Be, Ce, La, Pr, Rb, Si, Sr, or an alloy or compound containing these.
The mirror according to any one of claims 1 to 9,
The mirror, wherein the protective film or the metal film is formed by sputtering or ion plating.
A light source that generates EUV light having a wavelength of 60 nm or less;
In an illumination optical device comprising an optical element for performing illumination,
An illumination optical apparatus comprising the mirror according to any one of claims 1 to 10 in the optical element.
In an exposure apparatus for transferring a pattern image provided on a mask onto a photosensitive substrate,
An illumination optical apparatus as claimed in claim 11 for illuminating the mask;
An exposure apparatus comprising: a projection optical system for forming an image of the mask pattern on the photosensitive substrate.
13. An exposure process for exposing the pattern of the mask onto the photosensitive substrate using the exposure apparatus according to claim 12, and a development process for developing the photosensitive substrate exposed by the exposure process. A manufacturing method of a microdevice characterized by the above.

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