JPH0121557Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] The invention relates to an exposure apparatus used in semiconductor manufacturing;
In particular, the present invention relates to the structure of a mirror shutter that switches and guides light from an illumination light source used in the exposure apparatus into an optical path of a projection optical system and another optical path such as an optical path of an alignment optical system.

[Background of the idea]

Conventionally, in the projection exposure apparatus used in semiconductor manufacturing, Japanese Patent Laid-Open No. 1983-42226 and Utility Model Laid-Open No. 1987-
As disclosed in Publication No. 88125, etc.
Light from an exposure light source such as an ultra-high pressure mercury lamp,
The light is focused by a condensing lens or an ellipsoidal reflector,
A mirror shutter having an aperture that transmits light and a mirror portion that reflects light is installed obliquely at the focal plane position where the light source image is focused, and the path of light from the light source is divided into two sides: one on the projection optical system side and one on the alignment optical system side. There is a known device configured to switch to . In this known projection exposure apparatus, the mirror shutter is rotated by a predetermined angle to switch the optical path so that wafer exposure and alignment are performed alternately. In order to improve this, it is desirable to increase the time it takes for the shutter to fully open and from fully opening to fully closing, that is, the rotational angular velocity and angular acceleration of the shutter as large as possible.

Now, assuming that the torque of the motor that rotates this mirror shutter is constant, in order to increase its rotational angular velocity and angular acceleration, the moment of inertia of the mirror shutter must be made as small as possible. For this purpose, it is necessary to reduce the mass of the mirror portion. If the thickness of the shutter was made thinner in order to reduce its mass, the machined surface would warp and wobble when mirror-finished with a diamond cutting tool, resulting in a decrease in surface accuracy. In addition, increasing the power supplied to the light source to increase the light intensity in order to shorten the exposure time not only shortens the life of the light source, but also shortens the life of the mirror placed at the focal point of the light source due to increased heat. There was a drawback that it decreased.

[Purpose of invention]

The present invention solves the above-mentioned drawbacks of the conventional equipment, and allows easy mirror finishing without deteriorating surface accuracy.
Moreover, the purpose is to provide a mirror shutter that is lightweight and has a small moment of inertia.

[Summary of the idea]

In order to achieve the above object, the present invention forms ribs with a honeycomb-like mesh pattern and a large number of mesh-like hollow grooves surrounded by the ribs on the back surface of the mirror shutter. The technical key point is to provide a small protrusion approximately in the center of each mesh-shaped lightening groove, and configure the end face of the small protrusion to match the mounting reference surface during mirror finishing.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a sectional view of a rotary shutter device equipped with a mirror shutter showing an embodiment of the present invention, and Fig. 2 is a back view of the mirror shutter, which constitutes the main part of the embodiment of Fig. 1. be.

A mirror shutter 1 is placed obliquely at one focal point of an elliptical mirror that focuses light from an exposure light source such as an ultra-high-pressure mercury lamp, and a mounting bracket 2 is installed in the center as shown in FIG. via motor 3
The rotary position is fixedly attached to the drive shaft of the rotor, and the rotational position is detected by the reflective photoelectric sensor 4. Further, a shutter cover 5 is provided on the front surface of the mirror shutter 1 and has an opening (not shown) only in the portion through which illumination light passes, and these motor 3, reflective photoelectric sensor 4, and shutter cover 5 are attached to a mounting base. 6, respectively. Further, a light shielding plate 7 is provided on the back surface of the mirror shutter 1 to prevent light from leaking between the shutter cover 5 and the mirror shutter 1.

The mirror shutter 1 is made of a light and highly reflective aluminum plate, and as shown in Fig. 2, the circumference is divided into eight equal parts, with an opening 8 through which the illumination light passes and a sector where the illumination light is reflected. The portions 9 are formed alternately. As shown in FIG. 2, on the back surface of each sector portion 9 of this mirror shutter 1, a hollowed-out region 9A and a photoelectric sensor reflecting portion 9B are formed by etching. As shown in FIG. 3, the lightening area 9A is lightened leaving a honeycomb-shaped rib 10 and an isolated island-shaped protrusion 11 at the center of the hexagon surrounded by the rib 10. A mesh-like lightening groove 12 is formed. In the mirror shutter 1 in this embodiment, the distance l between two opposing sides of the mesh pattern hexagon is 7 mm, and the diameter d of the protrusion 11 at the center thereof is 7 mm.
is formed to be 0.5 mm, and as shown in Figure 4,
The thickness T of mirror shutter 1 is the finished dimension.
1.2mm, the depth D of the lightening groove 12 is based on the finished dimensions.
Formed to 0.6mm.

If the hexagon of the honeycomb-like mesh pattern is small, the lightening effect for reducing the mass of the sector part 9 will be reduced, so the larger the size of the hexagon, the deeper the depth D of the lightening groove 12. Moderate. However, if the island-like protrusion 11 is not formed as in a normal honeycomb shape, the distance l between the two opposing sides becomes longer, so the back surface 1a of the mirror shutter 1 (see Fig. 4) is used as the reference. When mirror-finishing the surface 1b with a diamond cutting tool, since the wall thickness t of the lightening groove 12 is thin, this thin-walled part vibrates and chatters, and the surface (mirror-finished) of this part becomes rough. The reflectance decreases, and the surface 1b
In this case, a highly reflective portion of the honeycomb-like mesh pattern corresponding to the rib 10 and a low reflectance portion corresponding to the lightening groove 12 appear. but,
By leaving the protrusion 11 at the center of the hexagon, when the mirror shutter 1 is attached to the work shaft of a processing machine (such as a diamond lathe), its back surface 1a will come into contact with the mounting surface on the work shaft side. , vibration of the hollowed out portion is suppressed by the protrusion 11. Therefore, when mirror-finishing the surface, it is possible to finish the mirror surface with high surface precision and without reducing the reflectance due to chatter.

Since the photoelectric sensor reflecting part 9B on the back side 1a of the mirror shutter 1 is not cut out, the back side 1
During the mirror finishing of a, there is no fear of chatter occurring in the reflecting portion 9B, and a mirror surface with high reflectivity can be obtained. The light shielding plate 7 is provided with an opening 7a (see FIG. 2) that exposes only one of the pair of photoelectric sensor reflecting sections 9B formed on each sector 9, and the light reflected through this opening is provided. is detected by the reflective photoelectric sensor 7, and the mirror shutter 1
The rotational position of is detected. Based on this detection signal, the motor 3 is configured to stop every time the mirror shutter 1 rotates by 45 degrees.

FIG. 5 is an optical system layout diagram of a projection type exposure apparatus incorporating the above embodiment apparatus. In FIG. 5, the mirror shutter 1 is obliquely installed at one focal position of an elliptical reflecting mirror 20, and an ultra-high pressure mercury lamp 21 is installed at the other focal position of the elliptical reflecting mirror 20. In addition, a shutter cover 5 is provided on the mirror shutter 1, and a floodlight 4A is provided on the back side.
A reflective photoelectric sensor 4 is provided, which includes a light receiver 4B and a light receiver 4B. This mirror shutter 1 is installed obliquely at the position of the primary light source image formed by the elliptical reflecting mirror 20, and the illumination light further passes through the aperture 8 (see FIG. 2) of the mirror shutter 1, and then passes through the collimator lens 22. , an optical integrator 23 consisting of a fly's eye lens, and a condenser lens 24 to illuminate a reticle 25 on a projection original plate with uniform illuminance. The pattern image of the illuminated reticle 25 is reduced by the projection lens 26 and projected onto the wafer 27 for printing.

On the other hand, the sector portion 9 of the mirror shutter 1
The illumination light reflected on the surface (mirror surface) of the relay lens 30, which constitutes the alignment illumination optical system,
optical fiber 31, relay lens 32,
The position P of the alignment mark provided on the outside of the reticle 25 is determined through the aperture 33, the semi-transmissive mirror 34, the alignment objective lens 35, and the reflecting mirror 36.
A point Q on the wafer 27 is further illuminated through the projection lens 26. In this case, the illumination optical system is arranged so that an image of the exit end surface 31a of the optical fiber 31 is formed at the position of the pupil 26a of the projection lens 26, and telecentric illumination is performed on the alignment mark on the wafer 27. It is composed of As a result, wafer 2
When the alignment mark on 7 coincides with point Q, the images of the alignment marks on both the reticle 25 and the wafer 27 are superimposed, and the images are formed on the ITV image pickup tube 37 by the alignment objective lens 35.
Through this imaging tube 37, it is observed and confirmed that the two alignment marks match, that is, the alignment is complete.

As described above, in this projection exposure apparatus, exposure and alignment of the wafer 27 are performed alternately, and at that time, the exposure optical path lE and the alignment optical path
lA are alternately switched by rotating the mirror shutter 1 by 45 degrees. In this case, the sector portion 9 of the mirror shutter 1 is hollowed out in a mesh pattern with protrusions to reduce the moment of inertia, so that the rotational angular velocity and angular acceleration can be increased. Moreover, the surface 1a of the sector portion 9
Since there is no reduction in surface precision or reflectance due to surface wobbling, the alignment marks on both the reticle 25 and the wafer 27 can be illuminated with sufficient illumination light and there is no illumination unevenness. Able to accurately observe the situation.

Further, the sector portion 9 of the mirror shutter 1 is placed at the focal point of the elliptical reflecting mirror 20, and strong illumination light from the ultra-high pressure mercury lamp 21 is focused at this position. Therefore, the sector portion 9 is heated by the strong illumination light and its temperature increases. but,
The heat dissipation area is increased by the mesh pattern ribs 10 surrounding the relatively deep lightening grooves 12 on the back surface and the columnar protrusions 11, so that heat is not accumulated and the temperature is maintained at a relatively low temperature. Therefore, the durability of the mirror shutter is improved, and the cycle of parts replacement can be lengthened.

Note that the mesh pattern for thinning formed on the back surface of the mirror shutter 1 is honeycomb-shaped as shown in FIG. I don't mind if you do that. Further, the projection 11 provided in the central portion is not limited to one location, but may be provided in several locations depending on the size of the lightening groove. Furthermore, although this mirror shutter 1 is constructed as a rotary shutter having a sector portion 9, it is of a type in which it is inserted into and removed from the illumination optical path by swinging motion, like a movable mirror in a single-lens reflex camera, to switch the illumination optical path. Alternatively, it goes without saying that a mirror shutter of a type that can be inserted into and removed from the illumination optical path by linear movement may be constructed. In addition, in FIG. 2, the reason why the reflecting parts 9B are provided at both ends of one sector part 9 is to maintain the dynamic balance of the mirror shutter 1, and originally only one reflecting part 9B would be formed. Just leave it there.

[Effect of idea]

As described above, according to the present invention, since the lightening groove with a mesh pattern with protrusions is provided on the back surface of the mirror shutter, there is no risk of surface wobbling or chattering during mirror finishing, and weight reduction is possible, and the moment of inertia is reduced. can be easily reduced and the optical path switching speed can be increased. Therefore, it is possible to increase the speed of the mirror drive device, shorten the shutter opening/closing time, and furthermore, due to the heat dissipation effect due to the increased surface area, durability is increased and the replacement cycle of parts is lengthened.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a rotary shutter device equipped with a mirror shutter showing an embodiment of the present invention;
Figure 2 is a rear view of the mirror shutter in Figure 1, Figure 3 is an enlarged view of the mesh pattern with protrusions showing details of the lightening groove of the mirror shutter in Figure 1, and Figure 4 is the same as in Figure 3. FIG. 5, an enlarged cross-sectional view taken along line A-A, is a layout diagram of the optical system of a projection exposure apparatus equipped with the rotary shutter device shown in FIG. Explanation of symbols of main parts, 1...mirror shutter, 1a...back surface, 1b...mirror surface, 8...opening, 9...sector part, 9A...lightening area, 1
0...Rib, 11...Protrusion, 12...Removed groove.

Claims (1)

[Scope of utility model registration request] In an exposure apparatus having a mirror shutter that switches a light beam from an illumination light source and guides it to an exposure optical path and another optical path, a rib with a mesh pattern is provided on the back surface of the mirror shutter on the opposite side from the mirror surface. A large number of surrounded mesh-like lightening grooves are formed, and a small protrusion is provided near the center of each of the mesh-like lightening grooves, and the end surface of the small protrusion is used as a mounting reference surface during mirror finishing. A mirror shutter for an exposure device, characterized in that the mirror shutters are configured so as to match each other.