JPS62283629A - Light source position controller - Google Patents

Abstract

PURPOSE:To reduce an illuminance irregularity of a light source position controller by directly monitoring the intensity distribution of an optical integrator of a secondary light source to symmetrically form the intensity distribution of the secondary source. CONSTITUTION:The light of an optical integrator of a secondary light source is reflected by a half mirror 2, and condensed through a condenser lens 3 on the surface of a mask 4. Luminous fluxes 8a, 8b passed through the mirror 2 are condensed by the lens 3 to pass a pinhole plate 6 having pinholes at a point conjugate with the center of the mask 4 to be incident on a photodetector 7. When matched to a lamp position, lamp is so regulated at its position that the luminous fluxes 8a, 8b symmetrical with respect to an optical axis become the same intensity at the lamp position while monitoring the output of the detector 7. Quadrant photodetectors are used as the photodetector, and the intensities of the lights incident to the dividing surfaces A and C, B and D are qualified so that the intensity distribution of the secondary source becomes symmetrical. Thus, the lamp as a light source can be accurately and easily positioned at the position where the illuminance distribution on the irradiated surface is symmetrical and not irregular.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Technical Field to Which the Invention Pertains] The present invention relates to a device for monitoring the position of a light source in an illumination optical system, such as a device for monitoring the position of a light source in an illumination optical system of a semiconductor exposure apparatus. The present invention relates to a light source position control device suitable for adjusting the position of a light source.

[Prior Art] Conventionally, as shown in FIG. 6, the positioning of a lamp in a semiconductor exposure apparatus is carried out by visually observing the image of the cathode or anode of the lamp using a pinhole plate 13 and an arc monitor plate 14, and positioning the lamp at a predetermined position. I took a method to suit the situation.

That is, in the figure, a part of the luminous flux from the lamp 9 is transmitted through a half mirror (or cold mirror) 11, is taken out, is reflected by a mirror 12, and then passes through a pinhole in a pinhole plate 13, and is emitted from the lamp. If 9 is in the correct position, an image is formed on the arc monitor plate 14. The arc monitor plate 14 and the pinhole plate 13 are arranged so that when the lamp 9 comes to a position where the intensity distribution of the optical integrator l, which is a secondary light source, is symmetrical, an image is formed at a predetermined position on the arc monitor plate. There is. If the intensity distribution of the secondary light source is asymmetrical, image performance will be adversely affected. Therefore, the operator used the image of the cathode or anode of the lamp to adjust this earth position. By doing so, it is possible to eliminate uneven illuminance on the mask 4 surface of light that is reflected by the half mirror 11, passes through the optical integrator 1, is reflected by the mirror 2, and is focused on the mask 4 surface by the condenser lens 3.

However, this method uses an optical light source, which is a secondary light source.
Since the intensity distribution of the integrator l is not directly monitored, there is a drawback that the intensity distribution of the secondary light source may not be symmetrical even if the lamp 9 is in the correct position on the arc monitor plate 14. . This is the optical axis from the focal point of the elliptical mirror 10 to the center of the optical integrator l, the mirror 12, and the pinhole plate 13.
This can also occur if the axis of the arc monitor plate 14 is deviated from the axis due to, for example, changes in the optical system over time or changes in the environment.

Furthermore, the image on the arc monitor plate 14 was not clear, and it was extremely difficult to align the image to an accurate position just by visual inspection.

Furthermore, if the lamp is not precisely in the correct position, the unevenness of the illuminance on the four surfaces of the mask will be so large that it cannot be ignored. Lamp positioning was quite troublesome because the lamp position was finely adjusted while measuring the illuminance distribution on the four sides.

[Object of the Invention] In view of the problems with the conventional type described above, the present invention directly monitors the intensity distribution of the optical integrator, which is a secondary light source, and makes the intensity distribution of the secondary light source symmetrical. It is an object of the present invention to provide a light source position control device that makes it possible to accurately and easily adjust the lamp position so that the illuminance distribution on a surface is symmetrical, the unevenness of illuminance is reduced, and the illuminance is maximized. .

[Embodiment] FIG. 1 shows a schematic diagram of a detection unit according to an embodiment of the present invention. l
2 is an optical integrator which is a secondary light source, and 2 is a half mirror with a transmittance of 1 to 2%. The light reflected by the half mirror 2 is focused by the condenser lens 3 onto the surface of the mask 4. Furthermore, the light beams 8a and 8b transmitted through the half mirror 2 are condensed by a condenser lens 5, pass through a pinhole plate 6 having a pinhole at a point conjugate to the center of the surface of the mask 4, and enter the light receiving element 7. . When adjusting the lamp position, the lamp position may be adjusted while monitoring the output of the light receiving element 7 so that the light beams 8a and 8b, which are symmetrical with respect to the optical axis, have the same intensity.

FIG. 2 shows an example of how the light receiving element 7 is used. Here, an example is shown in which a four-divided fort detector as shown in FIG. 2(a) is used as a light receiving element. In order for the intensity distribution of the secondary light source to be symmetrical, it is sufficient that the intensities of the light incident on the dividing planes A, CSB, and D of the four-divided photodetector shown in FIG. 2(,a) are equal. Specifically, as shown in FIG. 2(b), the lamp position is adjusted by inputting the fort detector output to the analysis section 20 and comparing the outputs A-C and B as the width analysis results.
-D and A+B+C+D are monitored, and the positions in the orthogonal axial directions in the plane perpendicular to the optical axis are adjusted so that A-C and B-D become 0, and A+B+C+D becomes the maximum in the optical axis direction. Adjust as follows. The light receiving element 7 is installed in advance at a position where A-C and B-D are O when the light source is at the normal position. By maximizing A+B+C+D, you can increase the absolute illuminance and improve the lighting efficiency.

In addition, a CCD area sensor may be used as the light receiving element.

FIG. 3 shows an example in which the present invention is implemented in a semiconductor exposure apparatus. Reference numeral 9 denotes a mercury lamp as a light source, and the arc center of the lamp 9 is located at the first focus of an elliptical mirror 10.An optical integrator 1 is placed at the second focus of the elliptical mirror 10. The configuration from the optical integrator 1 to the analysis section 20 is as described above.Below the mask 4 in the figure is a member, not shown, that holds the wafer to be printed.

A signal outputted from the light receiving element 7, amplified and analyzed by the input light analysis section 2o, and outputted is inputted to the slide drive source control section 30 via the signal transmission means 28.

The control unit 30 controls the slide drive source 25 in the drive unit 40 in response to the input signal. 26. A command signal is sent to 27 via signal transmission means 29. FIG. 4 shows a detailed diagram of an example of the drive unit 40. Drive sources 25, 26, and 27 each drive and control the slides 22, 23, and 24 for one-way sliding in the sliding direction according to command signals. The drive source drives the slide by, for example, pushing or pulling a nut attached to the slide in the sliding direction using a ball screw system. The slide 22 has a guide (not shown) for sliding the slide 23 in the Z direction in the drawing, and also fixedly supports a drive source 26. Similarly, the slide 24 has a guide (not shown) for sliding the slide 22 in the Y direction in the drawing, and also fixedly supports a drive source 25. Slide 24
A guide and a drive source 27 for sliding the device in the direction
0 or fixedly supported. Konoyou Nisrai F22, 23. 24+tx, y, z slide system. The guide may for example be a linear bearing system. Here, the slide direction of the slide 23 is parallel to the optical axis, the slide directions of the slides 22 and 24 are perpendicular to the optical axis and perpendicular to each other, and the A-C direction of the dividing plane of the light receiving element 7 and the n- The D direction is A by the light from the light source 9 when the slides 22 and 24 move respectively.
, C, B, and D, the directions are adjusted so that each output ratio change is the largest. The control unit 30 is A-C
>O, the drive source 25 is controlled to drive the slide 22 in a direction in which the output of A is relatively smaller than the output of C, and A-C is monitored during this movement, and A-C,= When the value becomes 0, the drive source 25 is stopped. I went too far at this time A-
When C<0, the slide 22 may be driven in the opposite direction and stopped when A-C=0.

Alternatively, a certain tolerance range may be set, and the operation may be stopped when the tolerance range is within this range. First, when A-C<O, control is performed in the opposite manner. Further, when B-D≠0, the control unit 30 controls the drive source 27 in the same manner as described above. Furthermore, the control unit 30 controls the drive source 26 so that the light source 9 moves in a predetermined certain section in the optical axis direction, stores the values of A+B+C+D at each point at that time, and calculates the maximum value among them. is determined and stored, and the light source 9 is moved again for a certain period while monitoring the value of A+B+D, and the light source 9 is stopped when the value of A+B+C+D reaches the stored maximum value. A means for detecting the position information of the slide 23 such as a linear potentiometer (not shown) is provided at the opposing portion of the slides 23 and 22, and the position information is sent to the control section 30 via the signal transmission means 31, and based on this information, the control section 30 drives the drive source 26 so that the light source 9 moves within a certain range. The fixed section is sized and positioned so that at least the point with the maximum absolute intensity is always included. The above control method is shown in FIG.

The subsequent steps in the control method shown in FIG. 5 may be omitted if unnecessary. In this case, if you create a loop that returns to the 5TART state immediately after completing the process up to this point, you can constantly monitor and control the position of the light source, and even if the light source moves out of the allowable range due to an unexpected accident, for example. There is no possibility of returning to the range immediately, and throughput is improved.

[Effects of the Invention] As explained above, according to the present invention, the direct light from the secondary light source is received by the light receiving element, and the position of the lamp is automatically adjusted based on the output of the light receiving element. It has become possible to accurately and easily align the illuminance distribution on the irradiation surface, for example, the mask surface, to a symmetrical and even position.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a light receiving section of a light source position control device according to an embodiment of the present invention, FIG. 2(a) is a plan view of an example of a light receiving element of the same embodiment, and FIG. FIG. 3 is a schematic diagram showing a semiconductor exposure apparatus using a light source position control device according to an embodiment of the present invention, and FIG. 4 is a perspective view showing an example of a light source driving section. , FIG. 5 is a flowchart showing the operating method of the control device of the first embodiment, and FIG. 6 is a schematic diagram of a conventional semiconductor exposure apparatus having means for adjusting the position of the light source. In the figure; t: optical integrator 5: condenser lens 6: pinhole plate 7: light receiving element 9: lamp lO: elliptical mirror 20: analysis section 30: drive source control section 40: light source drive section.

Claims (3)

[Claims] (1) It has a detection means for detecting the illuminance state of light incident on a specific part of the illuminated surface of an illumination optical system including a light source, and a control means for changing the position of the light source based on a signal from the detection means. A light source position control device characterized by: (2) The light source position according to claim 1, wherein the detection means has a plurality of light receiving elements for detecting the difference in illuminance on both sides of the optical axis in a direction perpendicular to the optical axis. Control device. (3) The light source position control device according to claim 2, wherein the control means changes the light source position so that the illuminance difference is substantially eliminated.