JP2005259949A - Mirror and illumination optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive mirror for EUV light, capable of efficient dissipation of the heat caused using irradiation of beams, an illumination optical device, and an exposure device using it. <P>SOLUTION: The oblique incidence type mirror for reflecting EUV light with a wavelength of 60 nm or shorter is provided with a substrate and a reflecting film. For the reflectivity in the EUV light, the reflectivity of the material constituting the reflective film is higher than that of the material constituting the substrate; whereas, for the thermal conductivity, the thermal conductivity of the material constituting the substrate is higher than that of the material constituting the reflecting film. In this way, the oblique incidence type mirror for reflecting the EUV light can be produced with high efficiency in heat dissipation and at a low cost. Moreover, it can prevent changes in the shape of the mirror surface caused due to heat, as much as possible. The illumination optical device and the exposure device mounting it can be used stably over a long time, and with little change in the illumination conditions and exposure conditions, even if they are used over a long term. <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, a plasma light source that emits 13.4 nm light has been studied as a light source of an EUV illumination optical system, and a multilayer that uses Bragg reflection formed by a multilayer film is used as a mirror that is used in an EUV illumination optical system. Two types of oblique incidence type mirrors that can obtain high reflectivity by being incident at a shallow incident angle with respect to the film mirror and the mirror reflection surface have been studied.

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, the oblique incidence type mirror has a relatively large aberration, but if it is incident at a shallow angle, the reflectivity can be about 90%, so that the reflectivity is higher than that of the multilayer mirror. For this reason, as the illumination optical system, the use of a grazing incidence type mirror having a relatively high reflectivity results in less light loss and higher throughput.

JP 2001-28332 A

  However, the reflectivity of the oblique incidence type mirror changes depending on the incident angle, and even if the reflectivity is high, it is at most about 90%, and the reflectivity of the mirror currently used in the visible light region. Is about 98%, which is extremely low. That is, in the EUV region, unlike the visible light region, there is no mirror having a high reflectivity with little light loss.

  Thus, most of the light not reflected by the oblique incidence type mirror is absorbed by the mirror and becomes heat. Therefore, the lower the reflectance, the more the mirror generates heat. When a grazing incidence type mirror is used as an optical element for illumination of an exposure apparatus, the mirror body is heated and deformed by thermal expansion due to long-term use, and the shape of the mirror surface changes, making it impossible to perform desired illumination. End up. For this reason, a method of cooling the mirror from the back side by water cooling or a Peltier element is also conceivable, but if the thermal conductivity of the mirror body is low, it is extremely difficult to cool the entire mirror uniformly, and the temperature distribution on the mirror surface is difficult. It will be further deformed. Therefore, it is desired that the thermal conductivity of the mirror body is as high as possible.

  On the other hand, Mo, Ru, Rh, and the like are known as materials for a grazing incidence type mirror having a high reflectivity in the EUV region. Among them, Ru and Rh are very expensive, and if the entire mirror is made of these materials, the apparatus price becomes enormous and a practical exposure apparatus cannot be made as a production apparatus.

Therefore, the present invention provides an inexpensive mirror in which the mirror body has high heat conduction and the surface is not deformed by heat. Moreover, the illumination optical apparatus and exposure apparatus which can be used for a long time using EUV light as a light source are provided at low cost.

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 board | substrate and the reflecting film, and the said reflecting film is comprised rather than the material which comprises the said board | substrate about the light from the said light source. The mirror is characterized in that the material to be formed has a higher reflectance, and the material constituting the substrate has a higher thermal conductivity than the material constituting the reflective film.

A second invention is a mirror that reflects EUV light having a wavelength of 60 nm or less.
The mirror is composed of a substrate and a reflective film, and the material constituting the substrate has a higher thermal conductivity than the material constituting the reflective film.

  According to a third 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 and a reflective film, and in the wavelength of the irradiated EUV light, the material constituting the substrate is The material constituting the reflective film is a mirror having a higher reflectance.

  A fourth invention is a mirror that reflects EUV light having a wavelength of 60 nm or less, wherein the mirror is composed of a substrate and a reflective film, and in the wavelength of the EUV light that is irradiated, the material that constitutes the substrate, The mirror is characterized in that the material constituting the reflective film has a higher reflectivity, and the material constituting the substrate has a higher thermal conductivity than the material constituting the reflective film. is there.

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

  According to a sixth invention, in the mirror according to any one of the first to fifth inventions, the reflective film is made of a material made of Mo, Ru, Rh, MoSi, or an alloy containing these. It is a featured mirror.

A seventh invention is the mirror according to any one of the first to sixth inventions, wherein the material constituting the substrate has a thermal conductivity of 50 [W / m · K] or more. .
According to an eighth invention, in the mirror according to any one of the first to seventh inventions, the thermal expansion coefficient of the material constituting the substrate is not less than 1/2 and not more than twice the thermal expansion coefficient of the material constituting the reflective film. It is a mirror characterized by being.

  According to a ninth invention, in the mirror of any one of the first to eighth inventions, the substrate is made of gold, silver, copper, aluminum, AlN, SiC, AlSiC, Si, or an alloy or compound containing these. It is a mirror characterized by being comprised.

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

  An eleventh invention is an illumination optical apparatus comprising a light source and an optical element for illuminating, wherein the optical element includes the mirror according to any one of the first to tenth inventions.

  A twelfth aspect of the invention is an illumination optical device comprising a light source that generates EUV light with a wavelength of 60 nm or less and an optical element for performing illumination, wherein the optical element includes the mirror according to any one of the first to tenth aspects of the invention. The illumination optical device is characterized.

  A thirteenth invention is an exposure apparatus for transferring a pattern image provided on a mask onto a photosensitive substrate, the illumination optical apparatus according to any one of the eleventh or twelfth invention for illuminating the mask, and the mask And an optical projection system for forming an image of the pattern on the photosensitive substrate.

A fourteenth aspect of the invention is an exposure step of exposing the pattern of the mask onto the photosensitive substrate using the exposure apparatus of the thirteenth aspect of the invention, and a developing step of developing the photosensitive substrate exposed by the exposure step. A method for manufacturing a microdevice.

  The mirror according to the present invention has high heat conduction and can enhance the heat dissipation effect, and can reduce deformation of the mirror surface due to heat. Thereby, there is an effect that desired illumination can be performed for a long time. Further, since the mirror is used in the EUV region, there is an effect that the mirror can be made inexpensive.

Furthermore, the illumination optical apparatus and exposure apparatus using the EUV light source according to the present invention have the effect of reducing variations in illumination conditions and exposure conditions due to heat as much as possible even when used for a long time. Moreover, there is an effect that the illumination optical device and the exposure device can be made inexpensive.

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

The mirror according to this embodiment is configured by forming a reflective film 1 on a substrate 2.
Specifically, the substrate 2 is made of AlSiC having a high thermal conductivity, and after the surface to be a reflective surface is polished to be a mirror surface, the reflective film 1 is highly reflective when incident with EUV light at an oblique incidence. A Ru film showing the rate is formed.

This Ru film is formed by sputtering. Specifically, after the substrate 2 is placed in the chamber of the sputtering apparatus, the vacuum is exhausted to 1 × 10 ⁻⁶ Torr. In a 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. Argon gas is introduced into the chamber, an electric field is applied to the cathode to generate plasma discharge on the target, and a Ru film is formed to a thickness of 100 nm in a region to be a reflective surface of the substrate 2. The pressure in the chamber at this time is 2 × 10 ⁻³ Torr.

  The mirror in this embodiment forms a film by a sputtering method because it is possible to form a film that is denser and has a stronger adhesive force than a film formation method such as vacuum deposition. 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 this embodiment, Ru is used as the material of the reflective film 1 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, the reflective film 1 may be Rh, Pd, Mo, or the like in addition to Ru. In addition, the material which comprises the reflecting film 1 may differ with the wavelengths used.

  Furthermore, in the present invention, the substrate 2 needs to be made of a material having high thermal conductivity because of the necessity of enhancing the heat dissipation effect, and is made of a material having a thermal conductivity of at least 50 [W / m · K]. Is required, and is preferably 150 [W / m · K] or more. This is because a sufficient heat radiation effect cannot be expected unless the material for the substrate 2 is a material that exhibits a somewhat higher thermal conductivity than the material constituting the reflective film 1.

Typical examples of such materials include gold, silver, copper, aluminum, AlN, SiC, Si, and the like.
As these materials are shown in Table 1, metal materials such as copper and aluminum tend to have a high coefficient of thermal expansion, and compound materials such as AlN and SiC tend to have a low coefficient of thermal expansion. The coefficient of thermal expansion of Ru is different from that of Ru. If the thermal expansion coefficients of the materials constituting the substrate 2 and the reflective film 1 are different, the film may be peeled off when the mirror is heated to a high temperature by irradiation with EUV light, which causes damage to the mirror. For this reason, it is desirable that the thermal expansion coefficients of the substrate 2 and the reflective film 1 are made of materials that are as close as possible. In consideration of this point, in this embodiment, AlSiC (thermal expansion coefficient 10), which is a material relatively close to the thermal expansion coefficient 9.1 of Ru constituting the reflective film 1, is used as the substrate 2 material. Other materials having a similar coefficient of thermal expansion include alloys such as W-Cu (8.3). In addition, about alloy materials, such as W-Cu, it is possible to make it substantially correspond with the thermal expansion coefficient of the reflecting film 1 by changing a composition of an alloy material.

As described above, it is necessary to select a material for the substrate 2 in consideration of the physical properties of the material used as the reflective film 1 to produce a mirror.

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 the EUV light source 11, 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 in which a Ru film is formed as a reflection film on a reflection surface of a substrate made of W-Cu. 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. The mirror in the collimator optical system 14 is a grazing incidence type mirror in which a Ru film is formed as a reflective film on the reflective surface of a substrate made of AlSiC. It is installed so that. When the EUV light beam is incident on the oblique incidence type mirror at this angle, the reflectance is about 90%.

  The EUV light of the parallel light beam emitted from the collimator optical system 14 is then incident on the oblique incidence type reflective fly-eye optical system 15 to generate a secondary light source. 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. The mirror constituting the reflective fly-eye optical system 15 is an oblique incidence type mirror in which a Ru film is formed as a reflective film on the reflective surface of a substrate made of AlSiC, and the incident angle of the light beam is about 10 degrees with respect to the mirror surface. It is installed to be incident at an angle.

  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 is composed of a grazing incidence type mirror in which a Ru film is formed as a reflective film on a reflective surface of a substrate made of AlSiC.

All the mirrors are provided with a cooling mechanism (not shown) for cooling from the back surface, and can be cooled by water cooling, a Peltier element or the like.

  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 based on the flowchart of FIG.

  First, in step 101 of FIG. 3, 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 this invention. It is a block diagram of the illumination optical apparatus which concerns on 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 Reflective film 2 Substrate 3 Light beam

Claims (14)

In the mirror that reflects the light from the light source,
The mirror is composed of at least a substrate and a reflective film;
For the light from the light source, the material constituting the reflective film has a higher reflectance 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 reflective film.
In a mirror that reflects EUV light with a wavelength of 60 nm or less,
The mirror is composed of at least a substrate and a reflective film;
The mirror characterized in that the material constituting the substrate has higher thermal conductivity than the material constituting the reflective film.
In a mirror that reflects EUV light with a wavelength of 60 nm or less,
The mirror is composed of at least a substrate and a reflective film;
The mirror characterized in that the material constituting the reflective film has a higher reflectance than the material constituting the substrate at the wavelength of the EUV light to be irradiated.
In a mirror that reflects EUV light with a wavelength of 60 nm or less,
The mirror is composed of at least a substrate and a reflective film;
In the wavelength of the irradiated EUV light, the material constituting the reflective film has a higher reflectance 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 reflective film.
The mirror according to any one of claims 1 to 4,
An oblique incidence type mirror characterized in that an angle formed by a EUV light beam incident on the mirror and the surface of the mirror is 30 ° or less.
The mirror according to any one of claims 1 to 5,
The mirror characterized in that the reflective film is made of a material made of Mo, Ru, Rh, MoSi or an alloy containing these.
The mirror according to any one of claims 1 to 6,
The mirror characterized in that the material constituting the substrate has a thermal conductivity of 50 [W / m · K] or more.
The mirror according to any one of claims 1 to 7,
The mirror, wherein the material constituting the substrate has a thermal expansion coefficient of ½ to 2 times the thermal expansion coefficient of the material constituting the reflective film.
The mirror according to any one of claims 1 to 8,
A mirror characterized in that the substrate is made of gold, silver, copper, aluminum, AlN, SiC, AlSiC, or Si, or an alloy or compound containing these.
The mirror according to any one of claims 1 to 9,
The mirror, wherein the reflective film is formed by sputtering or ion plating.
In an illumination optical apparatus having a light source and an optical element for performing illumination,
An illumination optical apparatus comprising the mirror according to any one of claims 1 to 10 in an optical element.
A light source that generates EUV light having a wavelength of 60 nm or less;
In an illumination optical apparatus having an optical element for performing illumination,
An illumination optical apparatus comprising the mirror according to any one of claims 1 to 10 in an optical element.
In an exposure apparatus for transferring a pattern image provided on a mask onto a photosensitive substrate,
The illumination optical apparatus according to any one of claims 11 and 12, for illuminating the mask,
An exposure apparatus comprising: a projection optical system for forming an image of the mask pattern on the photosensitive substrate.
An exposure process for exposing the pattern of the mask onto the photosensitive substrate using the exposure apparatus according to claim 13, and a development process for developing the photosensitive substrate exposed by the exposure process. A manufacturing method of a microdevice characterized by the above.