JPH04142546A - Projection exposure device - Google Patents

Abstract

PURPOSE:To measure illuminance distributions corresponding to various wafer processes by using pinhole plates which have the same reflection factors as process wafers for an illuminance meter according to the respective wafer processes. CONSTITUTION:A specific mask pattern is formed on a wafer made of the same material as a wafer to be processed and a pinhole 15 is formed by etching. A thin film is adhered by the same process with the wafer to be processed and the cut to desired size to manufacture a pinhole plate 11. The wafer for the pinhole plate is made to correspond to each process, so wafers as many as the wafer processes are prepared and thinned out by one each time one process is passed to form the pinhole plate of the wafer. The pinhole plate 11 is mounted on a horizontal part 12a with the processed surface up. The pinhole plate 11 is positioned with a pin 13 and light passed through the pinhole 15 is detected by a photodetector without being eclipsed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a projection exposure apparatus equipped with an illuminance meter that measures the illuminance distribution on an exposure surface by an illumination light emitting section.

"Prior Art" A projection exposure apparatus for IC manufacturing is equipped with an illuminance meter that measures the illuminance within the exposure field because uneven illuminance adversely affects the characteristics of manufactured devices. An example of a projection exposure apparatus equipped with such an illuminometer is disclosed in Japanese Patent Publication No. 1-39207. This configuration will be briefly explained based on FIGS. 4 and 5.

A reticle 2 is illuminated by illumination light that has passed through a condenser lens 1, and the IC pattern on the reticle 2 is reduced and projected onto a wafer 6 placed on a sample stage 5 that moves two-dimensionally by a reduction projection lens 3. be done. In this way, the IC pattern is exposed onto the wafer 6. This sample stage stage 5
An illuminometer 7 is installed above to measure the illuminance within the exposure field. The illuminance distribution can be obtained by opening the shutter with the reticle removed, dividing the exposure field into a plurality of regions, and measuring the illuminance by sequentially moving the illuminance meter 7 to the grid points. In this case, the upper photometric surface of the illuminance meter 7 and the upper surface of the wafer 6 are configured to be on the same plane so that the true light intensity on the exposure surface can be measured (see FIG. 5). ).

"Problem that the invention attempts to solve" However, the above conventional technology has the following drawbacks.

The illuminance of the wafer during the wafer exposure stage is composed of light that first enters the wafer, and light that is reflected by the wafer, reflected from the illumination system (light source) and the reduction optical system, and re-enters the wafer. The light incident on the wafer for the first time does not depend on the reflectance of the wafer, or the light that enters the wafer again depends on the reflectance of the wafer. The reflectance of this wafer depends on the wafer process, and the reflectance varies greatly depending on the process. Therefore, in actual exposure, the illuminance distribution changes depending on the wafer process. On the other hand, since the conventional illuminance meter has a fixed photometric surface (fixed reflectance to one), its measurement results are only an index for rough judgment in a certain state. That is, the measured illuminance distribution, which has only a certain tendency, and the actual tendency of pattern line width variations may not match depending on the wafer process.

Furthermore, as line widths become finer, it becomes necessary to accurately grasp the aspects of illuminance distribution for each process.
Conventional equipment could not perform measurements according to the wafer process.

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus equipped with an illuminance meter that can measure illuminance distribution according to each wafer process.

"Means for Solving the Problems" In order to solve the above problems, the projection exposure apparatus of the present invention provides an illuminance system for measuring the illuminance distribution within the exposure field of the exposure apparatus that transfers a pattern formed on a mask onto a wafer. The projection exposure apparatus is characterized in that the irradiation surface of the pinhole plate of the illuminance meter has the same reflectance as the irradiation surface of the wafer to be exposed.

``Operation'' Using the fact that the illuminance distribution on the wafer surface changes depending on the reflectance of the wafer, the reflectance of the pinhole plate of the illumination meter can be adjusted to be the same as the reflectance of each exposed wafer. It is configured so that

"Example" Hereinafter, an example of the present invention will be specifically described based on the accompanying drawings.

FIG. 1 is a sectional view of an illuminance meter 10 provided in a projection exposure apparatus according to the present invention. Note that since the projection exposure apparatus of the present invention has a feature in the illuminance meter portion, only the illuminance meter portion is illustrated. The outline of the projection exposure apparatus has almost the same configuration as that shown in FIG. 4, and the details thereof will be omitted.

The illumination meter 10 is provided in an area off the center area of the wafer stage 14 on which a semiconductor wafer to be processed is placed. A cylindrical body portion 12 protrudes from the wafer stage 14, and the upper inner periphery thereof has a horizontal portion 12a whose upper surface is parallel to the surface of the wafer stage 14. A rectangular pinhole plate 11 is placed on the upper surface of this horizontal portion 12a. The main body 1 is placed so that the upper surface of the pinhole plate 11 and the upper surface of the wafer to be processed are approximately at the same height.
The height of 2 is preset. This pinhole plate 11 is manufactured, for example, as follows. First, a predetermined mask pattern is formed on a wafer made of the same material as the wafer to be processed, and pinholes 15 are made by etching. After a thin film is deposited using the same process as the wafer to be processed, the wafer is cut to a desired size.

In this case, in order to correspond to each process, as many pinhole plate wafers as there are in the wafer process are prepared in advance, and one wafer is thinned out after each process. The pinhole plate produced in this manner is placed on the horizontal portion 12a with the processed side facing upward.

In the horizontal portion 12a, an opening 1 larger than the pinhole 15 is provided directly below the pinhole 15 of the pinhole plate 11 placed on the pinhole plate 11.
6 is provided. A photodetector 17 is fixed to the back surface of the horizontal portion 12 below the opening 16 so as to close the opening 16. Further, in the horizontal portion 12a, an opening 1 is provided.
An air groove 18 for vacuum suction for suctioning the pinhole plate 11 is dug in the upper surface of the horizontal portion 12a around the pinhole plate 11.

There is a 90° angle near the main body 12 on the wafer stage 14.
Two positioning pins 13 are provided to protrude from each other with an interval of . By abutting two adjacent sides of the rectangular pinhole plate 11 against these bottles, the pinhole plate 11 can be positioned on the horizontal portion 12a.

The configuration is such that when the pinhole plate 11 is placed on the horizontal portion 12a and abuts against the positioning bin 13, the light passing through the pinhole 15 can be detected by the photodetector 17 without being obstructed.

The wafer stage 14 can be moved two-dimensionally within its horizontal plane by a laser interferometer (not shown). To set the illumination meter 10, move the wafer stage 14 to a position where it can be easily replaced, release the vacuum suction, and
The pinhole plate 11 is placed on the horizontal portion 12a with the processed side facing upward, and placed so as to abut against the positioning bin 13, and vacuum suction is performed again. That is, each time a mask pattern is formed using a reticle, the illumination meter 10 can be replaced with a pinhole plate 11 having the same reflectance.

FIGS. 2A and 2B show the relationship between the pinhole plate 11 and the exposure field 20 during illuminance distribution measurement. Second
Figure A shows the center of the exposure field being measured, and Figure 2B shows the edge of the exposure field being measured. When measuring illuminance distribution, if the size of the pinhole plate is small, the area that reflects the exposure field will be different when measuring the edges of the exposure field and when measuring the center, and the reflection conditions of the base will change. . Therefore, when measuring the center of the exposure field (the pinhole 15 of the pinhole plate 11
In order to prevent the conditions of the pinhole plate from changing between (when the pinhole 15 of the pinhole plate 11 is located at the center of the exposure field 20) and edge measurement (when the pinhole 15 of the pinhole plate 11 is located at the corner of the exposure field 20), The size of the hole plate 11 is about four times that of the exposure field 20.

FIG. 3 is a sectional view showing a second embodiment of the illuminance meter 10 provided in the projection exposure apparatus according to the present invention. In this figure, the same parts as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, the light incident on the photodetector is configured to be detected via an optical fiber 25. The pinhole plate 11 is provided with a pinhole 15 having a diameter larger than the diameter of the optical fiber 25, and the tip of the optical fiber 25 can be inserted into this pinhole 15.

Further, in the horizontal portion 12a, a through hole 16a having a diameter almost the same as the diameter of the optical fiber 25 is provided directly below the pinhole 15.
An optical fiber 2 is provided in this through hole 16a.
5 is inserted. The tip of the optical fiber 25 slightly protrudes from the surface of the horizontal portion 12a, and is configured at a height that does not protrude from the upper surface of the pinhole plate 11 when the pinhole plate 11 is placed thereon. Further, the rear end of the optical fiber 25 is connected to a photodetector. As a result, the tip of the optical fiber 25 fulfills the function of positioning the pinhole plate 11, making it unnecessary to provide the positioning bin 13 described above, simplifying the configuration, and enabling accurate placement of the pinhole plate 11. becomes.

To set up the illuminance meter, move the wafer stage 14 to a position where it can be easily replaced, release the vacuum suction, and place the pinhole plate 11 on the horizontal part 12a with the processed side facing up.
The pinhole plate 11 is placed so as to be inserted into the tip of the optical fiber 25 protruding from the optical fiber 25, and the pinhole plate 11 is vacuum-adsorbed.

Since the pinhole plate uses the same process as the wafer being processed, it naturally has a resist on its surface.

The absorptance of the resist for exposure light depends on the degree of exposure, so if the illuminance is measured without exposing the resist, changes in the absorptance will be involved in the measurement results. Therefore, when measuring illuminance, if the resist on the pinhole plate is unexposed,
Before measurement, a process is included in which the resist is fully exposed to light using exposure light. Also, before placing the pinhole board on the horizontal part,
It is also possible to use another UV source for exposure.

In the above example, a wafer made of the same material as the wafer to be processed was used to create the pinhole plate using the same process, but other substrates may have the same reflectance at the exposure wavelength as the desired wafer. However, a thin film with a transmittance of 0 may be attached as a substitute. in this case,
Since there is no resist on the pinhole plate, the step of exposing the resist to light is omitted when measuring the illuminance distribution. Of course, it is also possible to use a material whose transmittance is 0 and whose reflectance at the exposure wavelength is the same as that of the desired wafer.

"Effects of the Invention" As is clear from the above description, the projection exposure apparatus of the present invention is equipped with an illuminance meter using a pinhole plate having the same reflectance as the process wafer, depending on each wafer process. ing. Therefore, it is possible to measure the illuminance distribution according to various wafer processes.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of the illuminance meter used in the projection exposure apparatus according to the present invention, FIGS. 2A and 2B are diagrams showing the relationship between the pinhole plate and the exposure field, and FIG. An enlarged sectional view showing a second embodiment of the illuminance meter used in the projection exposure apparatus according to the present invention, FIG. 4 shows the conventional projection exposure apparatus, and FIG. FIG. 3 is an enlarged cross-sectional view of the illuminance meter portion. ...Pinhole board. 4...Wafer steppin hole. ...Photodetector. 5...Optical fiber

Claims (5)

[Claims] (1) In a projection exposure apparatus equipped with an illuminance meter for measuring the illuminance distribution within an exposure field of a projection exposure apparatus that transfers a pattern formed on a mask onto a wafer, the irradiation surface of the pinhole plate of the illuminance meter is A projection exposure apparatus characterized in that the projection exposure apparatus has the same reflectance as the reflectance of the irradiation surface of the wafer to be exposed. (2) The projection exposure apparatus according to claim 1, wherein the illuminance meter has mounting means for placing the pinhole plate on the illuminance meter main body and making it replaceable. (3) The projection exposure apparatus according to claim 2, wherein the pinhole plate is created by the same process as the wafer to be exposed. (4) The pinhole plate is a substrate different from the wafer that is actually exposed, and is coated with a thin film whose reflectance is the same as that of the wafer to be exposed and whose transmittance is 0. 3. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is formed by attaching a plurality of layers to each other. (5) The projection exposure apparatus according to any one of claims 1 to 4, wherein the exposure field always remains on the surface of the pinhole plate when the illuminance is measured by the illuminance meter.