JP2005268265A - Collimator optical system and illumination optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection member or collimator optical system which performs deformed illumination only by itself without installing any mechanism which needs replacement such as a shading plate and a fly eye mirror. <P>SOLUTION: The collimator optical system which is used in a reflection type illumination optical system, etc. to convert incident flux of light into parallel flux of light is constructed by a parabolic reflector divided into a plurality of parts, and performs deformed illumination by changing the arrangements of the divided parts of the parabolic reflector. Specifically, the parabolic reflector is divided into four parts, each of which is equipped with a driving mechanism, and the positions of the divided parts of the parabolic reflector are adjusted by the driving mechanisms. Thus, parallel flux of light which is necessary for various deformed illuminations such as zonal illumination and multipolar illumination is obtained by just one collimator optical system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

Currently, an exposure apparatus using EUV light (extreme ultraviolet light) having a wavelength shorter than 60 nm as a light source is being studied as a means for next-generation semiconductor lithography.
A plasma light source is used as the EUV light source, and there are two types of laser plasma light source and discharge plasma light source. The EUV light beam emitted from the EUV light source is collected by a collector optical system in a pinhole provided in the container.

  The EUV illumination optical system container is provided so that the scattered matter generated from the plasma light source does not affect other optical systems, and is scattered on the surface of the optical system such as a mirror in the subsequent optical path. This prevents the object from adhering and the reflectivity from decreasing.

  The EUV light beam that has passed through the pinhole provided in the container is converted into a parallel light beam by a collimator optical system, and this parallel light beam is incident on a reflective fly-eye optical system to form a secondary light source group. The light beam emitted from the reflective fly's eye optical system illuminates the reticle (mask) surface via a light shielding plate and a condenser optical system as necessary.

  As a mirror used in an EUV illumination optical system, an oblique incidence that can obtain a high reflectivity by making it incident at a shallow incident angle on a multilayer mirror using a Bragg reflection formed by a multilayer film and a mirror reflection surface. There are two types of type mirrors.

  In the collimator optical system, since it is necessary to suppress the loss of light amount as much as possible, the reflectance is as low as about 70%, and it is unsuitable to use a multilayer mirror that is vulnerable to contamination by debris generated from the plasma light source for the collimator optical system. . Therefore, it is generally considered that the collimator optical system is composed of an oblique incidence type mirror that can obtain a high reflectance at a shallow incident angle.

  In addition, when an extremely fine pattern is formed using an EUV illumination optical system in an exposure apparatus, it may be necessary to perform so-called annular illumination or multipolar illumination. As a method of performing modified illumination in such an EUV illumination optical system, there are a method of providing a plurality of EUV light sources and a method of forming a desired illumination pattern using a light shielding plate.

However, the method of providing a plurality of EUV light sources is not practical because the EUV light sources are larger and more expensive than ordinary light sources, leading to an increase in size and cost of the apparatus. Moreover, in the method of obtaining a desired illumination pattern with a light shielding plate, a plurality of light shielding plates are required to obtain a plurality of illumination patterns such as annular illumination, dipole illumination, quadrupole illumination, etc. There is a problem such as.

JP 2001-68410 A JP 2003-45784 A

  In addition, as another modified illumination forming method, a method of forming annular illumination or multipolar illumination by changing the position and orientation of individual micromirrors constituting the fly-eye optical system can be considered, In this case, the fly-eye optical system becomes complicated, and it is not practical from the viewpoint of control and cost.

Therefore, the present invention provides a reflecting member or collimator optical system that can be deformed and illuminated in one reflecting member or collimator optical system without providing a replacement mechanism such as a light shielding plate or a fly-eye mirror. Further, by using the collimator optical system or the reflecting member in the exposure apparatus, a simple and small exposure apparatus capable of modified illumination is provided.

The present invention has been made to solve the above problems.
A first invention is a collimator optical system for converting a light beam from a light source into a parallel light beam, wherein the collimator optical system is constituted by a split paraboloid mirror, and the paraboloid mirror is separated. This is a collimator optical system characterized in that multipolar illumination can be performed.

A second invention is a collimator optical system according to the first invention, wherein the parabolic mirror is divided into two or four parts.
A third invention is a collimator optical system according to any one of the first and second inventions, wherein the wavelength of the light source is 60 nm or less.

A fourth invention is the collimator optical system according to any one of the first to third inventions,
The collimator optical system includes a split paraboloid mirror and a light shielding member provided at a central portion.

According to a fifth invention, in the collimator optical system according to any one of the first to fourth inventions, the parabolic mirror is made of Ru, Mo, MoSi ₂ or a material containing them. This is a characteristic collimator optical system.

  According to a sixth invention, in the collimator optical system according to any one of the first to fifth inventions, a drive mechanism is provided in each of the divided paraboloid mirrors constituting the collimator optical system. The collimator optical system is characterized in that the parabolic mirror is movable.

A seventh invention is a collimator optical system according to the sixth invention, wherein the drive mechanism is a drive mechanism not using oil.
According to an eighth aspect of the present invention, there is provided an illumination optical apparatus including a light source that generates EUV light having a wavelength of 60 nm or less and a collimator optical system that converts a light beam of the EUV light into a parallel light beam. An illumination optical device comprising the collimator optical system according to any one of the inventions.

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

A tenth 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 ninth 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 collimator optical system according to the present invention has a simple structure, and a plurality of modified illumination patterns can be formed with a single collimator optical system.
For this reason, when the collimator optical system according to the present invention is used in an exposure apparatus, there is an effect that a modified illumination can be performed without requiring an element for forming a plurality of modified illuminations. Therefore, there is an effect that an EUV exposure apparatus capable of forming a fine pattern can be simplified, downsized, and made inexpensive.

  Examples of the collimator optical system according to the present invention will be described below.

FIG. 2 shows a collimator optical system according to the present embodiment.
FIG. 2A shows an optical path followed by a light beam viewed from the side of the collimator optical system according to the present embodiment, and FIG. 2B shows a cross-section of the collimator optical system when cut by a broken line MN. Show. The collimator optical system of the present embodiment is constituted by paraboloidal mirrors 41, 42, 43 and 44 obtained by dividing one parabolic mirror made of molybdenum (Mo) into four parts. When the divided parabolic mirrors are arranged as shown in FIG. 2, the light beams spreading from the condensing point S are four parallel light beams by the four divided parabolic mirrors 41, 42, 43, 44. Each of the illumination light sources is converted into a light source, and a light beam passing through the central portion can be used for illumination.

  FIG. 3 shows an arrangement of parabolic mirrors when tripolar illumination is performed using the collimator optical system according to the present embodiment. FIG. 3A shows an optical path followed by a light beam as viewed from the side of the collimator optical system according to the present embodiment, and FIG. 3B shows a cross section of the collimator optical system when cut by a broken line PQ. Show. Specifically, as shown in FIG. 3B, the parabolic mirrors 41 and 43 divided into four parts are combined, and the parabolic mirrors 42 and 44 are combined to form two parabolic mirrors. It becomes the collimator optical system comprised by these. In the collimator optical system having such a configuration, the light spreading from the condensing point S is converted into two parallel light fluxes by the two parabolic mirrors combined to form respective illumination light sources. The light beam passing through the part can also be used for illumination, and becomes a light source for tripolar illumination.

  FIG. 4 shows the arrangement of parabolic mirrors when conventional illumination is performed using the collimator optical system according to the present embodiment. 4A shows an optical path followed by a light beam as viewed from the side of the collimator optical system according to the present embodiment, and FIG. 4B shows a cross section of the collimator optical system when cut along a broken line RT. Show. When performing conventional illumination, the collimator optical system of this embodiment combines all the parabolic mirrors 41, 42, 43, 44 divided into four as shown in FIG. It becomes a collimator optical system constituted by an object mirror. In the collimator optical system having such a configuration, the light spreading from the condensing point S is converted into a uniform parallel light beam by a parabolic mirror, and becomes a light source for conventional illumination. At this time, an optimal parallel light beam can be obtained by moving either the condensing point S or the entire collimator optical system.

As described above, by changing the arrangement of the parabolic mirrors divided into four, it is possible to change the illumination conditions such as conventional illumination, tripolar illumination, and pentapolar illumination.
In this embodiment, the collimator optical system uses a parabolic mirror divided into four parts. However, the number of parts divided is not limited to this, and is divided into six parts, eight parts, 12 parts, 16 parts. It may be divided or the like.

  Next, each of the parabolic mirrors 41, 42, 43, and 44 obtained by dividing the collimator optical system according to the first embodiment into four is provided with a drive mechanism, and collimator optics capable of deformed illumination by automatic control from the control system. An example of the system is shown.

  FIG. 5 is a cross-sectional view of the collimator optical system according to the present embodiment. Each of the four parabolic mirrors 41, 42, 43, 44 is divided into drive mechanisms 51a, 51b, 52a, 52b, 53a, 53b, 54a, 54b that can be moved linearly by an oil-free vacuum motor. Is provided. Specifically, the parabolic mirror 41 is provided with a driving mechanism 51a that can be linearly driven left and right and a 51b that can be linearly driven up and down, and the parabolic mirror 41 and the parabolic mirror 42 are provided. In the case of coupling, the parabolic mirrors 41 and 42 are coupled by the driving mechanism 51 b and the driving mechanism 52 b provided on the parabolic mirror 42. Further, when the parabolic mirror 41 and the parabolic mirror 43 are coupled, the parabolic mirrors 41 and 43 are coupled by the driving mechanism 51 a and the driving mechanism 53 a provided in the parabolic mirror 43. .

These drive mechanisms such as the drive mechanism 51a are controlled by an external signal, and a light source for modified illumination can be formed continuously. Note that the light source moves as necessary to supply parallel light beams in accordance with these drive mechanisms.

FIG. 6 shows another embodiment of the collimator optical system according to the present invention.
In this embodiment, in the collimator optical system of Embodiment 1, a light shielding member 45 is provided at the central portion. By adopting such a configuration, it becomes possible to freely perform modified illumination from annular illumination to multipolar illumination.

  FIG. 6A shows an optical path followed by a light beam as viewed from the side of the collimator optical system according to the present embodiment. Similar to the collimator optical system of the first embodiment, the collimator optical system of the present embodiment has four parabolic mirrors 41, 42, 43, and 44 each made of one parabolic mirror made of molybdenum. The light shielding member 45 is used.

  FIG. 6A shows the arrangement of the parabolic mirrors divided when performing dipole illumination or quadrupole illumination. When performing quadrupole illumination, the parabolic mirrors divided into four are arranged separately, and when performing dipole illumination, the parabolic mirrors divided into four are adjacent to each other. Each of the two parabolic mirrors is combined to form a collimator optical system including two combined parabolic mirrors. In this embodiment, unlike the case of the first embodiment, the light beam that has passed through the central portion of the collimator optical system from the condensing point S is blocked by the light blocking member 45.

  FIG. 6B shows an arrangement of the parabolic mirrors divided into four when performing annular illumination. The four parabolic mirrors that have been divided all combine to form one parabolic mirror. The light beam that has passed through the central portion of the collimator optical system from the condensing point S is reflected and becomes a parallel light beam by the parabolic mirror. Therefore, the shape of the illumination obtained by this is annular illumination.

As described above, by moving the divided paraboloidal mirror, it is possible to vary the annular illumination, the dipole illumination, and the quadrupole illumination. Moreover, it is also possible to use in the vacuum chamber by externally controlling the drive mechanism 51a provided in each parabolic mirror 41 shown in FIG.

An embodiment of an 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 1 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 the present embodiment, a discharge plasma light source is used as the EUV light source 1, but a laser plasma light source may be used.

  The EUV light emitted from the EUV light source 1 is collected by a grazing incidence collector optical system 2. The collector optical system 2 is an oblique incidence type mirror made of molybdenum (Mo) having a plurality of conical surfaces arranged concentrically. The EUV light source 1 and the collector optical system 2 are housed in one container 3, and a pinhole P is provided in the vicinity of the position where the EUV light is collected by the collector optical system 2. EUV light generated from the can be extracted. Further, the pressure inside the container 3 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 1 is not scattered outside the container 3. The EUV light emitted from the pinhole P of the container 3 enters the collimator optical system 4.

  The collimator optical system 4 is composed of four divided parabolic mirrors as described in the first embodiment, and each of the divided parabolic mirrors is provided with a driving mechanism. .

In this embodiment, molybdenum is used as a material constituting the mirror, but ruthenium (Ru) or MoSi ₂ may also be used. Molybdenum or ruthenium is suitable as a material when it is desired to increase the width of the incident angle, but MoSi ₂ is suitable as a material when it is desired to reduce polarization.

  The EUV light incident by the collimator optical system 4 is converted into a parallel light beam having a uniform distribution and emitted. In this embodiment, the mirrors in the collimator optical system 4 are all oblique incidence type mirrors, and are arranged so that the incident angle of the light beam is incident on each mirror surface at an angle of about 10 degrees. When the EUV light beam is incident on the molybdenum 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 4 is then incident on an oblique incidence type reflective fly-eye optical system 5 to generate a secondary light source. The oblique incidence type reflective fly-eye optical system 5 is an oblique incidence type mirror made of molybdenum composed of a pair of a fly-eye mirror on the incident side and a fly-eye mirror on the exit side. It is installed so as to be incident at an angle of 10 degrees with respect to the mirror surface.

The EUV light beam emitted from the reflective fly-eye optical system 5 illuminates the reticle 7 after passing through the condenser optical system 6 constituted by a grazing incidence condenser mirror made of molybdenum.

  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 microdevice 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. 7, 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 illumination optical apparatus using the collimator optical system which concerns on this invention. 1 is a diagram illustrating a configuration of a collimator optical system according to Example 1. FIG. It is a figure which shows the structure which moved the parabolic mirror about the collimator optical system which concerns on Example 1. FIG. It is a figure which shows the structure which moved the parabolic mirror about the collimator optical system which concerns on Example 1. FIG. 6 is a diagram illustrating a collimator optical system according to Example 2. FIG. 6 is a diagram illustrating a collimator optical system according to Example 3. FIG. 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

41, 42, 43, 44 Divided parabolic mirror S Condensing point

Claims (10)

In a collimator optical system that converts a light beam from a light source into a parallel beam,
A collimator optical system, wherein the collimator optical system is constituted by a divided parabolic mirror, and multipolar illumination can be performed by separating the parabolic mirror.
In the collimator optical system according to claim 1,
A collimator optical system, wherein the parabolic mirror is divided into two or four.
The collimator optical system according to any one of claims 1 and 2,
A collimator optical system, wherein the light source has a wavelength of 60 nm or less.
The collimator optical system according to any one of claims 1 to 3,
The collimator optical system includes a split paraboloid mirror and a light shielding member provided at a central portion.
The collimator optical system according to any one of claims 1 to 4,
A collimator optical system, wherein the parabolic mirror is made of Ru, Mo, MoSi ₂ or a material containing them.
The collimator optical system according to any one of claims 1 to 5,
A collimator optical system, wherein a drive mechanism is provided for each of the divided parabolic mirrors constituting the collimator optical system, and each of the parabolic mirrors is movable.
The collimator optical system according to claim 6,
A collimator optical system, wherein the drive mechanism is a drive mechanism that does not use oil.
A light source that generates EUV light having a wavelength of 60 nm or less;
In the illumination optical apparatus having a collimator optical system for converting the EUV light beam into a parallel beam,
An illumination optical apparatus, wherein the collimator optical system is configured by the collimator optical system according to any one of claims 1 to 7.
In an exposure apparatus for transferring a pattern image provided on a mask onto a photosensitive substrate,
An illumination optical apparatus according to claim 8 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 9 and a developing process for developing the photosensitive substrate exposed by the exposure process. A manufacturing method of a microdevice characterized by the above.