JPH0434918A - Illuminator - Google Patents

Abstract

PURPOSE:To make spatial light quantity distribution of an excimer laser light incident to an optical fiber uniform and to reduce interference by providing diffusing plates on incident and emitting surface sides of the fiber, forming the emitting surface of the fiber in a circular shape, and disposing the incident side so as to become a rectangular shape. CONSTITUTION:The light quantity distribution of a beam of an excimer laser light emitted from an excimer laser light source 1 by a diffusing plate 3 is made uniform, and the light having strong directionality is scattered to supplement the number of openings of an optical fiber 2. The fiber 2 is associated on the incident surface 2a side so as to become a slender rectangular shape similarly to the beam shape of the laser light and to efficiently guide the laser light to a condensing optical system 5. The light guided by the fiber 2 is emitted from the emitting surface 2b associated to become a circular shape, again scattered by a diffusing plate 4 to improve its uniformity, and then focused in a focusing position of an objective lens 7 through the system 5 and a half mirror 6. A light beam focused in the focusing position of the lens 7 becomes a parallel beam to uniformly throw light on a reticle 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an illumination device for uniformly illuminating a reticle using excimer laser light in a reduction projection type exposure device for semiconductor manufacturing.

2. Description of the Related Art In order to illuminate a reticle in a conventional reduction projection type exposure apparatus for semiconductor manufacturing, for example, Japanese Patent Laid-Open No. 62-1770
As described in Japanese Patent No. 5, a configuration using a mercury lamp and an optical fiber is generally known.

Hereinafter, a conventional lighting device will be described with reference to the drawings. FIG. 3 is a block diagram showing a conventional exposure apparatus.

In FIG. 3, the light emitted from the ultra-high pressure mercury lamp 501 is
Rotary mirror shutter 5 by elliptical reflector 502
After passing through the aperture provided in the rotary mirror shutter 503, the light is focused on the reflective surface of the rotary mirror shutter 503, and then passes through a collimator lens 504, an optical integrator 505 composed of a fly's eye lens, and a condenser lens 506. Illuminating the reticle 507 of the projection original,
The pattern image on the illuminated reticle 507 is formed on a wafer 509 by a reduction projection lens 508, and is printed and exposed.

On the other hand, it is reflected by the rotary mirror shutter 503,
The light beam incident on the first condensing lens 510 of the alignment optical system is transmitted to the incident end face 511 of the random optical fiber 5110.
The light is focused on a. Even a light quantity distribution in which the center of the ultra-high pressure mercury lamp is extremely reduced is averaged at the exit end face 511b of the bundle of random optical fibers 5110, and is emitted as a flat light quantity distribution. The illumination light emitted from the exit end surface 511b passes through a second condenser lens 512, a field stop 513, a half mirror 514, and a second alignment objective lens 51.
5. The alignment mark P on the reticle 507 is illuminated through the first alignment objective lens 516 and the moving mirror 517, and the wafer 5 is illuminated through the reduction projection lens 508.
Illuminate the alignment mark Q on 09. These two alignment marks P and Q are superimposed, and an image is formed on the ITV image pickup tube 51B placed behind the half mirror 514 by the alignment objective lens 516,515, and the wafer 5 is aligned with the alignment mark P on the reticle 507.
Accurate positioning of alignment mark Q on 09 is confirmed via its ITV image pickup tube 518.

Problems to be Solved by the Invention However, in the conventional configuration as described above, when using excimer laser light as an illumination light source, this excimer laser light has stronger interference than the G-line of a mercury lamp, so it does not meet the specifications. The light intensity distribution itself is uneven.

In addition, since excimer laser light has a long and narrow beam shape, it must be formed into a beam, and unlike a mercury lamp, it is a laser light and has strong directivity, so an input optical system must be set up that matches the numerical aperture of the optical fiber. . Furthermore, even if excimer laser light is incident on an optical fiber with a predetermined numerical aperture,
Since the directions of the input end face and the exit end face of each optical fiber are uneven, there are some optical fibers into which excimer laser light does not enter. Therefore, in order to compensate for this numerical aperture with the configuration of the conventional example described above, the input optical system becomes even more complicated.

Fig. 4 shows an optical fiber 51 into which excimer laser light is incident.
1 shows a schematic diagram of an exit end surface 511b of one bundle.

As is clear from FIG. 4, among the bundle of optical fibers 511, the optical fibers 511 shown in white are emitting light, and the optical fibers 511 shown in diagonal lines are not emitting light.
Alternatively, the emitted light is weak, the filled optical fiber 511 is disconnected, and significant spatial unevenness occurs in the illumination light illuminating the emitting end surface 511b, that is, the reticle.

In this way, uniform illumination of the reticle depends largely on the manufacturing precision of the optical fiber.

Therefore, when using excimer laser light as the illumination light source,
The above configuration has a problem in that it is difficult to illuminate the reticle uniformly compared to the G-line of a mercury lamp.

The present invention solves the problems of the prior art as described above, and aims to provide an illumination device that can uniformly illuminate a reticle using excimer laser light. .

Means for Solving the Problems The technical solution of the present invention for achieving the above object is as follows:
An excimer laser light source, a deformed bundle-shaped optical fiber arranged so that the incident surface side has a rectangular shape that is almost the same as the beam pattern of the excimer laser light, and an exit surface side that has a circular shape, and this optical fiber. a diffuser plate disposed on the incident surface side of the optical fiber to scatter the excimer laser light; a diffuser plate disposed on the exit surface side of the optical fiber to scatter the excimer laser light emitted from the optical fiber; and a diffuser plate disposed on the exit surface side of the optical fiber to scatter the excimer laser light emitted from the optical fiber. It is equipped with an optical system for uniformly illuminating a reticle with light and observing an image of the reticle.

The optical system includes a condensing optical system that condenses the excimer laser light scattered by the diffuser plate, a half mirror that reflects the condensed excimer laser light, and a condensing optical system that condenses the excimer laser light scattered by the diffuser plate, and a half mirror that reflects the condensed excimer laser light, and directs the reflected excimer laser light to the reticle. It can be composed of an objective lens that uniformly illuminates the reticle, and an imaging lens that forms an image of the reflected light from the reticle on an observation means via the objective lens and a half mirror. Vidicon can be used.

Therefore, according to the present invention, diffusers are provided on the entrance surface side and the exit surface side of the optical fiber, and the exit surface of the optical fiber is arranged in a circular shape, and the entrance surface side is arranged in a rectangular shape. By arranging and matching the beam shape of the excimer laser beam, even if the illumination light source is an excimer laser beam with strong coherence and directivity, the optical fiber can be easily uniformizes the spatial light intensity distribution of excimer laser light incident on the laser beam, reduces coherence,
Furthermore, by widening the numerical aperture, it is possible to make the excimer laser beam enter all of the optical fiber bundles with irregular directions.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

1 and 2 show an epi-illumination type illumination device according to an embodiment of the present invention, in which FIG. 1 is an overall configuration diagram and FIG. 2 is a perspective view of an optical fiber.

In FIG. 1, 1 is a pulsed excimer laser light source that is an illumination light source, and 2 is a bundle-shaped optical fiber that guides the excimer laser light emitted from the excimer laser light source. The fibers 2 are arranged so as to have an elongated rectangular shape in accordance with the beam shape of the excimer laser light emitted from the excimer laser light source 1 on the side of the entrance surface 2a, and are arranged so as to have a circular shape on the side of the exit surface 2b. It has a deformed shape that is arranged in combination. In FIG. 1, reference numerals 3 and 4 are diffuser plates provided on the entrance surface 2a side and the exit surface 2b side of the optical fiber 2, respectively, which scatter the excimer laser beam 3 and make the light quantity distribution uniform. 5 is a condensing optical system that condenses the excimer laser beam that has been made uniform by the diffuser plate 4; 6 is a half mirror that reflects the condensed excimer laser beam; and 57 is a reticle that converts the condensed excimer laser beam into parallel light. 9 is an objective lens of a magnification imaging system that uniformly illuminates the reticle 8; 9 is an imaging lens of a magnification imaging system that images the reflected light from the reticle 8 via an objective lens 7 and a half mirror 6; 10 is an objective lens This is an ultraviolet vidicon that observes the image formed at 9.

The operation of the above configuration will be described below.

In FIG. 1, the excimer laser light emitted from the excimer laser light source 1 is uniformized in the light intensity distribution by the diffuser plate 3, and the highly directional excimer laser light is scattered and spread, and the numerical aperture of the optical fiber 2 is As mentioned above, the optical fibers 2 are combined to form an elongated rectangular shape on the incident surface 2a side, similar to the beam shape of the excimer laser light (see Figure 2), so that the excimer laser light can be efficiently transmitted. The light can be well guided to the condensing optical system 5.

The excimer laser light guided to the optical fiber 2 is emitted from the exit surface 2b side which is combined to form a circular shape, and this excimer laser light is again scattered by the diffuser plate 4 to improve uniformity. An image is formed at the imaging position of the objective lens 7 by the condensing optical system 5 and the half mirror 6. Objective lens 7
The light beam formed at the imaging position becomes parallel light, and the reticle 8
Evenly illuminate the top. The reflected light from the reticle 8 is guided to the objective lens 7, the half mirror 6, and the imaging lens 9, and is imaged on the ultraviolet vidicon 10 for magnified observation.

Next, specific examples of the present invention will be described.

Excimer laser light (KrF) with a wavelength of 248n- is emitted from an excimer laser light source 1, and is scattered by a diffuser plate 3 made of frosted quartz glass with a thickness of 2 cm to equalize the light intensity distribution. On the other hand, the light is made to enter a bundle of ultraviolet light optical fibers 2 that are placed in close contact with the incident surface 2a side or are placed slightly apart from each other.

This optical fiber 2 is constructed by combining each optical fiber 2 on the incident surface 2a side so as to form an elongated rectangular shape that matches the beam shape of the excimer laser light, thereby efficiently transmitting the excimer laser light into the bundle-shaped optical fiber 2. The excimer laser light emitted from the exit surface 2b side of each optical fiber 2 combined into a circular shape is scattered again by the same diffuser plate 4 as described above, and a condensing optical system consisting of a plurality of assembled lenses is formed. 5 and a half mirror 6 whose reflectance and transmittance are approximately equal, the image is focused at an imaging position within an ultraviolet objective lens 7 made up of a plurality of lens sets.The incident light that is focused at the focal position is emitted as parallel light. Therefore, a desired area on the reticle 8 placed at the focal length of the ultraviolet objective lens 7 can be uniformly illuminated. Therefore, the light passes through the ultraviolet objective lens 7, the half mirror 6, and the imaging lens 9, and is imaged on the light-receiving surface of the ultraviolet vidicon 10, so that a uniform image 10 times larger than that of the reticle 8 can be observed.

Effects of the Invention As described above, according to the present invention, a diffusion plate is provided on the entrance surface side and the exit surface side of the optical fiber, the exit surface side of the optical fiber is combined into a circular shape, and the entrance surface side is used for excimer laser light. By combining a rectangular shape that matches the beam shape of the optical fiber, even if an excimer laser beam with strong coherence and directivity is used as illumination light, the optical fiber can be easily It is possible to make the spatial light intensity distribution of the excimer laser light incident on the laser beam uniform, reduce coherence, and widen the numerical aperture, thereby making it possible to make the excimer laser light incident on all the optical fiber bundles having irregular directions. Therefore, even if excimer laser light is used as an illumination light source, the reticle can be uniformly illuminated, thereby enabling reticle alignment by image processing or the like.

[Brief explanation of drawings]

1 and 2 show a lighting device according to an embodiment of the present invention, FIG. 1 is an overall configuration diagram, FIG. 2 is a perspective view of an optical fiber, and FIGS. 3 and 4 are conventional lighting devices. shows,
FIG. 3 is an overall configuration diagram, and FIG. 4 is a schematic diagram of the exit end face of the optical fiber. l...Excimer laser light source, 2...Optical fiber, 2a...Incidence surface, 2b...
Output surface, 3.4...Diffusion plate, 5...Condensing optical system, 6...Half mirror 7...
Objective lens, 8... Reticle, 9...
Imaging lens, IO...UV vidicon. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 1 Figure a Figure of plane of incidence

Claims (3)

[Claims] (1) The excimer laser light source is arranged so that the incident surface side has a rectangular shape that is almost the same as the beam pattern of the excimer laser light, and the exit surface side is arranged so that it has a circular shape,
A deformed bundle of optical fibers, a diffuser plate disposed on the incident surface side of the optical fiber to scatter the excimer laser beam, and an excimer laser beam emitted from the optical fiber disposed on the exit surface side of the optical fiber. An illumination device includes a diffuser plate that scatters excimer laser light, and an optical system that uniformly illuminates a reticle with the scattered excimer laser light and observes an image of the reticle. (2) The optical system includes a condensing optical system that condenses the excimer laser light scattered by the diffuser, a half mirror that reflects the condensed excimer laser light, and a uniform distribution of the reflected excimer laser light onto the reticle. 2. The illumination device according to claim 1, further comprising: an objective lens for illuminating the reticle; and an imaging lens for forming an image of the reflected light from the reticle onto observation means via the objective lens and a half mirror. (3) The illumination device according to claim 2, wherein the observation means is an ultraviolet vidicon.