JPS6348819A - Exposure device - Google Patents

Abstract

PURPOSE:To assure the areal precision of a mirror surface while enabling an image surface and a wafer surface to be finely aligned and corrected by a method wherein air pads floatingly holding a parallel plane glass holding a dichromirror of exposure device of a semiconductor as well as a changing means of air pressure of air pads are provided. CONSTITUTION:Exposure light is reflected by a dichromirror 2 held by a parallel plane glass 3 in the 90 deg. direction. The parallel plane glass 3 is floatingly held by three pairs of opposing air pads 8-1-8-3 making gaps of air pads by air pressure. The gaps between the plane glass 3 and the air pads 8-1-8-3 are adjusted by controlling the air pressure of respective air pads using servovalves 9-1-9-6 and pressure sensers 10-1-10-6. An alignment detecting system 7 observes an alignment mark of a reticle 1 and a wafer 5 to transmit detecting signals of any slippage of the mark to a control circuit 12. In such a constitution, the attitude and direction of plane glass 3 are processed by said signals to transmit signals to the servovalves of corresponding air pads so that the attitude and direction of plane glass 3 may be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an exposure apparatus used in a photolithography process in the manufacturing process of semiconductor devices (IC, LSI, etc.).

Specifically, it is a device that projects and exposes a pattern on a reticle onto a semiconductor substrate (wafer) using a projection optical system, and uses a dichroic mirror (hereinafter referred to as a dichroic mirror) to perform alignment using multi-wavelength light. The present invention relates to an exposure apparatus that maintains high surface accuracy of a dichroic mirror, and further enables minute coincidence between the image plane of a projection lens and the surface of a sea urchin, and correction of minute distortion.

[Description of the Prior Art] Conventionally, reduction projection exposure apparatuses have been used to determine the relative relationship between a pattern drawn on a reticle, which is a photographic original plate, through a projection lens and a pattern on the surface of a substrate to be exposed, which is a sea urchin. Regarding the process of alignment and subsequent exposure, efforts have been made to find a way to accomplish the process accurately, reliably, and quickly, and to provide an easy-to-use apparatus.

For this reason, attempts have been made to solve the problem of axial chromatic aberration by installing a dichroic mirror that separates exposure light and non-exposure light between the projection lens of the exposure device and the original plate such as a reticle, and performing multi-wavelength alignment. ing. The present applicant previously filed a patent application (Japanese Patent Application No. 1983-12
No. 8171 and Japanese Patent Application No. 149892/1982).

[Problems to be Solved by the Invention] Conventionally, mirrors in such exposure apparatuses have been held by mechanically fixing them or by using adhesives.

However, all of these holding methods have the problem that external force (curing strain on the presser plate or adhesive) is applied directly to the mirror, which generates internal stress in the mirror and deteriorates the surface accuracy of the mirror.

The first object of the present invention is to provide a dichroic mirror that separates exposure light and non-exposure light to perform multi-wavelength alignment as an effective means for solving problems such as axial chromatic aberration, in view of the above-mentioned problems with the conventional type. In a reduction projection exposure device,
It is an object of the present invention to provide an exposure apparatus that can maintain the attitude and position of a dichroic mirror that separates light while maintaining the surface precision of the dichroic mirror surface, and that has high precision as a whole.

Furthermore, a second object of the present invention is to enable minute alignment between the image plane of the projection lens and the surface of the sea urchin and correction of minute distortion by controlling the attitude of the dichroic mirror, and to provide a new means of minute positioning for alignment. and to provide an exposure apparatus with additional correction functions.

[Means and Operations for Solving the Problems] In order to achieve the above object, the exposure apparatus of the present invention covers the entire exposure light between the projection lens and the photographic original plate (hereinafter referred to as a reticle). It includes a dichroic mirror arranged so as to bend a light beam, three or more sets of air pads for floating and holding parallel plane glass holding the dichroic mirror, and means for varying the air pressure of each of the air pads.

As a result, the air pressure of each air pad can be changed, so the attitude of the parallel plane glass holding the dichroic mirror can be controlled.

The present invention is applied to an exposure apparatus that relatively aligns a pattern drawn on a reticle with a pattern on a substrate (hereinafter referred to as a wafer), and then projects and exposes the pattern of the reticle onto the wafer using a projection lens. be done. and,
The dichromirror is configured so that light having a wavelength different from the exposure wavelength is input into or taken out from the exposure light beam from a portion of the dichromirror.

Furthermore, in the exposure apparatus of the present invention, the means for varying the air pressure of the air pad can be used as a means for micro-alignment between the imaging plane of the reticle pattern by the projection lens and the surface of the sea urchin, thereby controlling the attitude of the parallel plane glass. By doing this, it is possible to match this pattern (lj) with the surface of the sea urchin with high precision.

Furthermore, in the exposure apparatus of the present invention, by changing the air pressure of the air pad and controlling the attitude of the parallel plane glass to align the image plane within the focal depth of the projection lens, for example, the regular four sides drawn on the reticle can be The shape can be changed to a trapezoid or a diamond, or in the opposite direction of deformation. This makes it possible to correct minute distortions.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of a dichroic mirror holding and attitude control mechanism in an exposure apparatus according to an embodiment of the present invention.

In the figure, a projection lens 4 and a dichroic mirror 2 are arranged to project and expose the pattern of a reticle 1 onto the surface of a wafer 5. The dichroic mirror 2 is held by a parallel plane glass 3 and is set at an angle of 45 degrees with respect to the projection optical axis. In other words, the projection exposure optical axis is bent by 90° in the dichroic mirror 2, and the exposure light is reflected in the 90° direction by the dichroic mirror 2. On the other hand, the light with the alignment wavelength is reflected by the dichroic mirror 2. It's like passing through.

The air pad has the characteristics of high rigidity in the gap direction and low moment rigidity. The holding parallel plane glass 3 of the dichroic mirror 2 utilizes the characteristics of such air pads to attach three sets of opposing air pads 8-1 to 8-8.
-3, the parallel plane glass 3 is floated and held by air pressure so that the gap between the parallel plane glass 3 and the air pad is 10 to 15 μm on one side, and the planar direction of the parallel plane glass 3 is regulated by a stopper (not shown). In addition, the air pressure of each air pad is controlled by servo valves 9-1 to 9-6 and pressure sensors 10-1 to 10-, respectively.
6, and by controlling the air pressure, the gaps between the parallel plane glass 3 and the air pads 8-1 to 8-3 can be adjusted.

Furthermore, air is supplied to the air pads 8-1 to 8-3 from an air source 11, but this air is clean and has been passed through a filter and a dryer.

Next, a method of alignment by controlling the attitude of the parallel plane glass 3 will be explained.

First, set the standards for the reticle and stage as follows. In FIG. 1, the alignment mark (not shown) on the reticle 1 and the reference mark (not shown) on the movable stage 6 are observed by the alignment detection system 7 through the projection lens 4, and the stage 6 is moved to the B position. to align the reticle 1 side with the alignment mark of the stage 6. At this time, the air pad 8- which holds the parallel plane glass 3
The air pressures 1 to 8-3 are set to their respective reference pressures.

Next, alignment between the reticle and the wafer chip will be explained.

The stage 6 moves the wafer 5 to the exposure position, the alignment detection system 7 observes the alignment marks (not shown) on the reticle 1 and the wafer 5, detects the amount of deviation of the marks, and sends a detection signal to the control circuit 12. . The attitude direction of the parallel plane glass 3 is calculated based on the sent signal, and a signal is sent to the servo valve of the air pad corresponding to each direction to control the attitude direction of the parallel plane glass 3.

At this time, since the optical path of the alignment system for the non-exposure wavelength changes as the attitude of the parallel plane glass 3 changes, it is necessary to calculate a correction value in the direction of attitude change of the parallel plane glass 3 and correct the servo valve control signal. .

Note that when using an excimer projection lens, the glass materials that can be used for the lens are limited to two types, which makes it difficult to achieve achromatization due to lens design, and the difference between the exposure wavelength and alignment wavelength becomes large. Naturally, the longitudinal chromatic aberration will increase. At this time, in the conventional configurations shown in FIGS. 2 and 3, a large take-out mirror 200 or chromatic aberration correction lens 201 is required, and as a result, the exposed area becomes vignetted (hatched in the figure). section), it is unacceptably narrowed. Therefore, in an excimer exposure apparatus, it is necessary to use a mirror type that covers the entire exposure light beam and to introduce alignment light from the outside. Therefore,
If the present invention is applied, it is possible to maintain the surface accuracy of the dichroic mirror, and it is also possible to perform minute alignment and correction of minute distortion.

[Effects of the Invention] As explained above, according to the present invention, in an exposure apparatus that projects and exposes a pattern drawn on a reticle onto a wafer using a projection lens, the entire exposure light flux is disposed between the projection lens and the reticle. The parallel plane glass holding the dichroic mirror that covers the exposure beam and bends the exposure light beam is held floating by three or more sets of air pads, each with variable air pressure, so the posture and position of the dichroic mirror can be adjusted. It can be held while maintaining surface accuracy, and the exposure apparatus as a whole has high precision.

Furthermore, by controlling the attitude, it becomes possible to perform minute alignment between the image plane of the projection lens and the surface of the sea urchin, and to correct minute distortions.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a dichroic mirror holding and attitude control mechanism in an exposure apparatus according to an embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of the prior art. 1 Reticle, 2: Dichroic mirror, 3: Parallel plane glass, 4: Projection lens, 5: Wafer, 6: Motion stage, 7: Observation microscope, 8-1 to 8-3 = Air pad, 9-1 to 9-6: Servo valve, 10-1 to 10-8: Pressure sensor, 11: Air source, 12: Control circuit. o〇- Figure 3

Claims (1)

[Scope of Claims] 1. An exposure apparatus that projects and exposes a pattern drawn on a photographic original plate onto a substrate using a projection lens, wherein the entire exposure light beam is covered between the projection lens and the photographic original plate, and the exposure light beam is A dichroic mirror arranged so as to be bent, three or more sets of air pads for floating and holding parallel plane glass holding the dichroic mirror, and means for varying the air pressure of each of the air pads. Characteristic exposure equipment. 2. The exposure apparatus according to claim 1, wherein the air pressure variable means enables minute alignment between the image plane of the pattern on the photographic original plate by the projection lens and the surface of the substrate. 3. The exposure apparatus according to claim 1 or 2, wherein the air pressure variable means agitates the image plane within the focal depth of the projection lens to correct minute distortion.