JPH05217844A - Projection aligner - Google Patents

Abstract

PURPOSE:To make an adjustment and a readjustment to an optical axis correctly and easily when the excimer laser is used as an exposure light source. CONSTITUTION:In a projection aligner which projects a pattern on a reticle 21 onto a wafer 23 through a projection optical system 22 and then exposes it, an excimer laser light source 1 for illuminating the reticle 21, a photo detector 9 which, being located in an optical path of an optical system which leads excimer laser light from the excimer laser light source to the reticle 21, detects the location of a light flux, and a light flux adjustment device 2 for adjusting the location of the light flux are provided. By monitoring the location of the excimer laser light and by making an adjustment to the location of the light flux from this information, the location of the light flux can be adjusted to the correct one easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus which uses an excimer laser as an exposure light source for forming a fine resist pattern required for manufacturing a semiconductor integrated circuit or the like.

[0002]

2. Description of the Related Art In recent years, projection exposure apparatuses have been required to create finer and finer patterns as semiconductor integrated circuits become highly integrated. In particular, when forming a 64 Mbit memory or a finer pattern of more than 64 Mbit memory, it is necessary to shorten the wavelength of the exposure light because the wavelength of the light of the exposure light source is related to the pattern to be resolved. Excimer lasers are seen as promising as a suitable light source in place of conventional mercury lamps. Hereinafter, a conventional projection exposure apparatus using a mercury lamp will be described with reference to the example disclosed in Japanese Patent Laid-Open No. 61-91662.

FIG. 8 shows the structure of a conventional projection exposure apparatus. In FIG. 8, 101 is a mercury lamp as an exposure light source. Reference numeral 102 denotes a pair of elliptical reflecting mirrors, and the mercury lamp 101 is arranged at the first focus thereof. 10
3 is a second focal point of the elliptical reflecting mirror 102, 104 is an input lens, 105 is an optical integrator, 1
Reference numeral 06 is an output lens, and 107 is a collimation lens. Reference numeral 108 is a reticle. 109 is the aperture,
110 is a filter, and 111 and 112 are cold mirrors. 113 is a lamp house, 114 is a projection optical system,
Reference numeral 115 is a wafer, and 116 is a structure of the projection exposure apparatus.

The operation of the projection exposure apparatus having the above structure will be described below. First, the light from the mercury lamp 101 is reflected by the pair of elliptical reflecting mirrors 102, and the light path is bent by the cold mirror 111.
The light is focused on the focus 103 once. After this, input lens 1
04, optical integrator 105, diaphragm 109,
The reticle 108 is illuminated through the output lens 106, the cold mirror 112, and the collimation lens 107. A fine pattern to be exposed is drawn on the reticle 108, and a semiconductor pattern is created by exposing and transferring it onto the wafer 115 by the projection optical system 114.

The mercury lamp 101 wears out with the lapse of usage time, and therefore needs to be replaced regularly. Since the mercury lamp 101 cannot be positioned at the proper position merely by exchanging it, the light deviates from the original illumination optical axis. As a result, the reticle 108 cannot be illuminated uniformly, and the exposure amount becomes uneven, causing a difference in the exposure amount of the resist applied to the wafer 115, so that a uniform pattern cannot be formed over the entire exposure region. .. Therefore, when the mercury lamp 101 is replaced, it is necessary to adjust the optical axis. The procedure is as follows. First, the mercury lamp 101 is removed, a new mercury lamp 101 is attached, and then the lamp is turned on to emit light, for example, the second focus 103. The position of the mercury lamp 101 so that it comes to the specified position.
Adjust by moving.

The adjustment of the optical axis of such a mercury lamp does not require such a difficult technique because the light emitted from the mercury lamp 101 diverges in a fairly wide range and is condensed by the elliptical reflecting mirror 102. Further, since the mercury lamp 101 is usually incorporated in the lamp house 113 above the structure 116 of the projection exposure apparatus, the relative positions of the mercury lamp 101 and the projection optical system 114 do not move.

[0007]

However, when an excimer laser is used as the exposure light source instead of the mercury lamp, the excimer laser body is much larger than the mercury lamp, and therefore it is separated from the structure of the projection exposure apparatus. Since the excimer laser beam has a very high linearity and the beam shape is small and speckles peculiar to the laser are generated, the optical system from the cold mirror 111 to the collimation lens 107 shown in FIG. However, there is a problem that the laser incident position must be adjusted more accurately than in the case of the mercury lamp. In addition, since the position of the laser beam changes daily due to electrode wear of the excimer laser, and also changes due to maintenance, there is a problem that the existing method of adjusting the position of the mercury lamp cannot handle it.

The present invention solves the problems of the prior art as described above, and a projection in which an optical axis can be sufficiently adjusted even when an excimer laser is used as an exposure light source and readjustment can be easily performed. An object is to provide an exposure apparatus.

[0009]

In order to achieve the above object, the present invention provides an excimer laser light source for illuminating a reticle to project and expose a pattern on the reticle onto a wafer through a projection optical system. And a photodetector arranged in the optical path of an optical system for introducing the light beam from the light source into the reticle, for detecting the position of the light beam, and a light beam adjusting means for adjusting the position of the light beam.

[0010]

According to the present invention, with the above structure, the position of the excimer laser beam is monitored by the photodetector, and the position of the light beam is adjusted from this information by using the light beam adjusting means.
The light flux can be accurately and easily adjusted to a predetermined position.

[0011]

【Example】

(Embodiment 1) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a projection exposure apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is an excimer laser light source that emits excimer laser light, and 2 is a light flux adjusting means that adjusts the light flux of the emitted excimer laser light. The light flux adjusting means 2 includes a first reflecting mirror 3
A second reflecting mirror 4, a stage 5 for moving the first reflecting mirror 3 straight in the a direction, a stage 6 for moving the second reflecting mirror 4 straight in the b direction, and a first reflecting mirror 3 in the c direction. It includes a stage 7 for rotating and a stage 8 for rotating the second reflecting mirror 4 in the d direction.

When the traveling direction of the excimer laser light emitted from the excimer laser light source 1 is X, the direction perpendicular to it is Y, and the direction perpendicular to it is Z,
As shown in FIG. 2, the excimer laser light emitted from the excimer laser light source 1 in the X direction is reflected upward in the Z direction by the first reflection mirror 3 and reflected in the Y direction by the second reflection mirror 4. Therefore, the first reflection mirror 3 is moved in the X direction by a
When adjusted in the direction, the laser light reflected by the second reflecting mirror 4 is adjusted in the X direction, and when adjusting the second reflecting mirror 4 in the b direction which is the Z direction, the reflected light is adjusted in the Z direction. Then, by rotating the first and second reflecting mirrors 3 and 4 in the c and d directions, respectively, the direction of the reflected light can be adjusted in either direction in the three-dimensional space.

Returning to FIG. 1, reference numeral 9 denotes a photodetector. The photodetector 9 includes a partial reflection mirror 10 which reflects a part of the excimer laser light emitted from the excimer laser light source 1 and transmits a part thereof. The partial reflection mirror 11 that returns the excimer laser light to the original direction and the photoelectric detector 12 that detects the transmitted excimer laser light. The photoelectric detector 12 is 2
A dimensional sensor, for example, a CCD in which photodiodes are arranged in a two-dimensional manner having sensitivity to an ultraviolet vidicon or ultraviolet light. Reference numeral 13 is a cylindrical lens, 14 is a beam expander, 15 and 16 are cold mirrors, 17 is an integrator, 18 is a reticle blind, 19 is a sub-condenser lens, and 20 is a main condenser lens, which constitute an introduction optical system. .. Reference numeral 21 is a reticle, 22 is a projection optical system, 23 is a wafer, 24 is a wafer stage, and 25 is a projection exposure apparatus structure. Also,
Reference numeral 26 is a CCD control unit for controlling the CCD of the light source detector 12, and 27 is a monitor television for displaying the excimer laser light converted by the light source detector 12 on the screen.

The operation of the projection exposure apparatus configured as described above will be described below. First, the excimer laser light emitted from the excimer laser light source 1 passes through the first reflection mirror 3 and the second reflection mirror 4 of the light flux adjusting means 2,
The light enters the photodetector 9 in the projection exposure apparatus structure 25. In the photodetector 9, first, most of the excimer laser light is reflected by the partial reflection mirror 10, and a part of the transmitted light is incident on the photoelectric detector 12 via the partial reflection mirror 11. on the other hand,
The excimer laser light reflected by the partial reflection mirror 10 is
Since it has a rectangular shape as shown in FIG. 3A and cannot be used as it is as illumination light, it is shaped into a square shape as shown in FIG. The beam shape is expanded as shown in FIG. At this time, the excimer laser light, the cylindrical lens 13 and the beam expander 1
The positional relationship of 4 requires a high degree of accuracy. In particular, when the excimer laser light source 1 is arranged away from the projection exposure apparatus structure 25 as in the present embodiment, even a slight fluctuation of the excimer laser light source 1 causes the cylindrical lens 1 to move.
At the entrance of No. 3, there is a large displacement, and the emitted light beam is not square. For this reason, the reticle 21 cannot be uniformly illuminated, and the possibility of exposure failure becomes extremely high, so sufficient optical axis adjustment is necessary. Then cold mirror 1
5, the reticle 21 is illuminated through the integrator 17, the reticle blind 18, the sub-condenser lens 19, the cold mirror 16, and the main condenser lens 20. A pattern for semiconductor formation is drawn on the reticle 21, and this is transferred onto the wafer 23 on the wafer stage 24 through the projection optical system 22.

In such a projection exposure apparatus, since the excimer laser light source 1 and the projection exposure apparatus structure 25 are arranged apart from each other as described above, the optical axis for accurately aligning the excimer laser light. You need to make adjustments. First, the partial reflection mirror 1 of the photodetector 9
The excimer laser light that passes through 1 and reaches the photoelectric detector 12 is photoelectrically converted and displayed on the monitor TV 27 from the CCD control unit 26. For example, when the beam spot 28 of the excimer laser light is displayed on the monitor television 27 as shown in FIG. 4A, the beam spot 28 is adjusted so as to be located at the center of the screen as shown in FIG. 4B. Next, since the excimer laser light partially reflected by the partial reflection mirror 11 is returned in the original direction, a paper is inserted near the emission port of the excimer laser light source 1 and returned with the emitted excimer laser light. Copy the excimer laser light on paper. At this time, when the respective beam spots are observed as 29 and 30 in FIG. 5A, the stages 5 and 6 of the light flux adjusting means 2 are arranged so that both beam spots overlap as shown in FIG. 5B. The first and second reflection mirrors 3 and 4 are adjusted by, the excimer laser light is moved in the horizontal and vertical directions, and the tilt in two directions is adjusted by the stages 7 and 8.

As described above, according to this embodiment, the pattern on the reticle 21 is transferred to the wafer 2 via the projection optical system 22.
In the projection exposure apparatus that projects and exposes the reticle 2
1. Excimer laser light source 1 for illuminating 1; photodetector 9 for detecting the position of the light beam arranged in the optical path of the optical system for introducing the light beam from excimer laser light source 1 into reticle 21; By providing the light beam adjusting means 2 for adjusting the position of the light beam of the excimer laser, the position of the excimer laser light is monitored, and the position of the light beam is adjusted from this information, so that the light beam can be accurately and easily brought to a predetermined position. Can be adjusted.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that the reflected light of the partial reflection mirror 10 of the photodetector 9 is guided to the photoelectric detector 12 and the transmitted light is guided to the cylindrical lens 13. A reflection mirror 31 is inserted between the partial reflection mirror 10 and the cylindrical lens 13. The function and effect are similar to those of the above embodiment.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment differs from the second embodiment described above in that the excimer laser light returned by the partial reflection mirror 11 in the photodetector 9 is not visually observed in the vicinity of the exit of the excimer laser light source 1. , Which is designed to be measured electrically. That is, the first reflection mirror 3 of the light flux adjusting means 2 is connected to the photodetector 9
The partial excimer laser light returned by the partial reflection mirror 11 of the photodetector 9 is transmitted through the partial reflection mirror 33 to replace the partial reflection mirror 33 of the photodetector 32 having the same configuration as that of the photoelectric detector 34. In the same manner as shown in FIG. 4, the output of the electric signal converted into an electric signal is displayed on the monitor television 36 through the CCD control unit 35, and the image is adjusted to the image center and the CCD control units 26 and 35 are operated. Is input to the computer 37, and the partial reflection mirror 33 of the photodetector 32 and the second reflection mirror 4 of the light flux adjusting means 2 are adjusted so that the beam position of the exposure light and the beam position of the return light coincide with each other. Adjustment is made in directions a to d by means of a motor or the like. Further, by performing calculation from the beam position, automatically controlling the motor, and feeding back the beam position to the designated position, for example, beam movement due to wear or maintenance of the electrodes of the excimer laser light source 1, external vibration, etc. It is possible to automatically follow the deviation of the beam introduction position, etc., and always maintain the optimum illumination condition.

In each of the above embodiments, the partial reflection mirror 10 of the photodetector 9 is a total reflection mirror, and this total reflection mirror is allowed to enter the optical path only when the optical axis is adjusted, and retracted from the optical path at the time of exposure. As a result, the utilization efficiency of excimer laser light during exposure can be improved. Such a retracting mechanism of the mirror can be applied to the partial reflection mirror 10 as well.

In each of the above embodiments, the photoelectric detector 12
In (and 34), a two-dimensional sensor is used, but even if a plurality of one-dimensional sensors are arranged or the point sensors are two-dimensionally arranged, signal processing becomes slightly complicated, but similar results are obtained. ..

Further, the photodetectors 9 may be arranged in front of and behind the cylindrical lens 13 to directly observe the beam shape.

[0022]

As described above, according to the present invention, in order to project and expose a pattern on a reticle onto a wafer through a projection optical system, an excimer laser light source for illuminating the reticle, and a light flux from this light source. Is arranged in the optical path of the optical system for introducing the light into the reticle, and is equipped with a photodetector for detecting the position of the light flux and a light flux adjusting means for adjusting the position of the light flux, so that the position of the excimer laser light is monitored. The position of the light flux can be adjusted based on this information, and an excellent projection exposure apparatus that can accurately and easily adjust the light flux to a predetermined position can be realized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a projection exposure apparatus in a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a light flux adjusting means in the first embodiment.

FIG. 3 is a schematic diagram showing a beam shape transition of excimer laser light in the first embodiment.

FIG. 4 is a schematic diagram showing an example of a screen on a monitor TV which displays an excimer laser beam in the first embodiment.

FIG. 5 is a schematic diagram showing beam spots of emitted light and returned light of excimer laser light in the first embodiment.

FIG. 6 is a schematic configuration diagram of a projection exposure apparatus in a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a projection exposure apparatus in a third embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing an example of a conventional projection exposure apparatus.

[Explanation of symbols]

 1 Excimer Laser Light Source 2 Luminous Flux Adjusting Means 3 First Reflecting Mirror 4 Second Reflecting Mirror 5, 6, 7, 8 Stage 9 Photo Detector 10, 11 Partial Reflecting Mirror 12 Photoelectric Detector 13 Cylindrical Lens 14 Beam Expander 15, 16 Cold mirror 17 Integrator 18 Reticle blind 19 Sub-condenser lens 20 Main condenser lens 21 Reticle 22 Projection optical system 23 Wafer 24 Wafer stage 25 Projection exposure device structure 26 CCD control unit 27 Monitor TV 31 Reflection mirror 32 Photodetector 33 Partial reflection mirror 34 Photoelectric detector 35 CCD control unit 36 Monitor TV 37 Computer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihito Nakanishi 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (7)

[Claims] 1. An excimer laser light source for illuminating the reticle for projecting and exposing a pattern on the reticle onto a wafer via a projection optical system, and an optical system for introducing a light beam from the light source into the reticle. Placed in the optical path,
A projection exposure apparatus comprising a photodetector for detecting the position of a light beam and a light beam adjusting means for adjusting the position of the light beam. 2. The projection exposure apparatus according to claim 1, wherein the photodetector includes a partial reflection mirror for sampling a part of the light flux and a photoelectric detector for photoelectrically converting the light flux transmitted through the partial reflection mirror. 3. A photodetector photoelectrically converting the transmitted light flux, and a partial reflection mirror for sampling a part of the light flux, a partial reflection mirror for returning the light flux transmitted through the partial reflection mirror to the original direction. The projection exposure apparatus according to claim 1, further comprising a photoelectric detector. 4. The projection exposure according to claim 1, wherein the photoelectric detector is a two-dimensional array photoelectric detector, a two-dimensional array point type photoelectric detector or a two-dimensional array one-dimensional photoelectric detector. apparatus. 5. The projection exposure apparatus according to claim 1, wherein the light flux adjusting means includes means for moving the light flux parallel to the two directions and means for adjusting the angle in the two directions. 6. The photodetector according to claim 1, further comprising a partial reflection mirror or a total reflection mirror for sampling a part of the light beam, and means for moving the partial reflection mirror or the total reflection mirror forward or backward on the optical path. 6. The projection exposure apparatus according to any one of 5. 7. An excimer laser light source for illuminating the reticle for projecting and exposing a pattern on the reticle onto a wafer through a projection optical system, and an optical system for introducing a light beam from the light source into the reticle. Placed in the optical path,
A first photodetector for detecting the position of the light beam, a light beam adjusting means for adjusting the position of the light beam, a unit for returning the light beam to the original direction, and a first position for detecting the position of the returned light beam. And a control means for controlling the light flux adjusting means so that the light flux emitted from the light source and the returned light flux match based on the output of the second photodetector. Projection exposure device.