JPS6237529B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a reduction projection exposure method used in a semiconductor manufacturing process in which patterns for semiconductor integrated circuits such as ICs and LSIs are directly formed on a wafer. This relates to improvements in equipment.

[Background of the invention]

In a conventional reduction projection exposure apparatus, relative detection of the position of the wafer 3 is performed via a photomask 1 and a reduction lens 2 using the optical system configuration shown in FIG. (see official bulletin). Normally, in a reduction projection exposure system, the photomask 1
is called a retakele, so it will be referred to as a retakele in the text below. That is, in the apparatus shown in FIG. 1, the wafer 3 is locally illuminated by the light guide 4 via the half mirror 5, the condensing lens 6, the mirror 7, the reticle 1, and the reducing lens 2. The reflected light from the wafer 3 passes through the reduction lens 2 to the alignment reference pattern 8 on the reticle 1.
is projected back onto the top. On the other hand, another light guide 9 passes the reference pattern 8 on the reticle 1 through the mirror 10, the condensing lens 11, and the mirror 12.
lighting. Then, the reflected light from the surface of the wafer 3 and the reflected light from the surface of the reticle 1 are combined and incident on the detector 16 via the mirror 7, the condensing lens 6, and the half mirror 5.

However, this method not only requires a large number of optical components as shown in FIG. Must be. As a result, the attenuation of the illumination light became significantly large, and the illumination intensity reaching the wafer 3 was about 1/10 of the intensity at the exit of the light guide 4. The condenser lens 6 also serves as an objective lens for the detector 16, but due to the configuration of the device, a lens with a long working distance must be used. As a result, the reflected light from the wafer 3 (the reflected light 20 from the pattern on the wafer 3 and the reflected light 21 from the alignment reference pattern 8 on the reticle from the wafer 3) is as shown in FIG.
However, depending on the wafer, the intensity of the reflected light 21 of the reference pattern 8 decreases as shown in FIG. 3b, and the reference pattern 8 is no longer detected. That is, there is a drawback that the contrast of the detection pattern is reduced, making it impossible to detect the reference pattern 8 on the reticle.

[Object of the Invention] Therefore, it is an object of the present invention to provide a reduction projection exposure apparatus which has a pattern detection optical system with good contrast through a reduction lens and which enables highly accurate position detection of a wafer position. There is a particular thing.

[Summary of the invention]

In order to achieve the above object, the present invention provides detection light between the reticle and the reduction lens on the optical axis connecting the alignment reference pattern on the reticle and the entrance pupil of the reduction lens. The present invention is characterized in that a reduction projection exposure apparatus is constructed by providing a half mirror for branching. Furthermore, in the present invention, a condensing lens that illuminates the pattern on the wafer and an objective lens that detects the pattern on the wafer are provided separately to realize a pattern detection optical system with good contrast, enabling high-precision pattern detection. It is characterized by the following.

[Embodiments of the invention]

An embodiment of the reduction projection exposure apparatus according to the present invention will be described below with reference to FIG. In the figure, only a light guide 4, a condensing lens 6, and a mirror 7 are provided above the reticle 1, and a half mirror 5 is provided between the reticle 1 and the reduction lens 2. Also,
An objective lens 13 and a pattern detector 16 are provided on the optical axis where the reflected light from the wafer 3 is split by the half mirror 5. Furthermore, a projection lens 14 and a mirror 15 are provided on the optical axis where the light transmitted through the reference pattern 8 on the reticle 1 by the light guide 4 is branched by the half mirror 5.

In this way, the alignment pattern 8 on the wafer 3 and reticle 1 can be detected with such a simple configuration. That is, according to this embodiment, the pattern on the wafer 3 is imaged at the focal position of the objective lens 13 by the reduction lens 2 and the half mirror 5. On the other hand, the reference pattern 8 on the reticle 1 is projected and imaged at the same focal position by the half mirror 5, the projection lens 14, and the mirror 15. At this time, a part of the projected image of the alignment reference pattern 8 on the reticle is reflected by the half mirror 5 and the mirror 15, and is transmitted to the pattern detector 16 by the objective lens 13 without being reflected by the wafer.
Therefore, the contrast of the detection pattern is good as shown in the reflected light 22 of FIG. 3c. Therefore, the composite image with the reflected light 20 from the pattern on the wafer 3 also has good contrast as shown in FIG. 3d. This composite image is magnified by the objective lens 13 and taken into the pattern detector 16. At this time, according to the present invention, an objective lens with a short working distance and a large NA can be used, so a detection optical system with good resolution and contrast can be realized. Furthermore, the illumination optical system consisting of the ride guide 4 and condensing lens 6 that illuminates the wafer 3 can now be provided with the condensing lens 6 immediately after the light guide 4, as shown in FIG. The illumination intensity is much brighter than that of the conventional configuration, and an illumination optical system having an illuminance about half that of the light guide 4 can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a reduction projection exposure apparatus including a conventional pattern detection optical system, FIG. 2 is a conceptual diagram of a reduction projection exposure apparatus including a pattern detection optical system according to the present invention, and FIG. 3 is a conventional technique. FIG. 3 is a diagram for explaining the difference in effect between the technology and the technology of the present application. 1... Reticle, 2... Reduction lens, 3...
Wafer, 4, 9... Light guide, 5... Half mirror, 6, 11... Condensing lens, 7, 10,
12, 15... Mirror, 8... Reference pattern on reticle, 13... Objective lens, 14... Projection lens, 16... Pattern detector, 20... Reflected light pattern from wafer, 21... On reticle A pattern of light reflected by the wafer of the reference pattern 22... A superposition of light reflected by the mirror of the reference pattern on the reticle and reflected light 21.

Claims (1)

[Claims] 1. A reticle is provided between the reticle and the wafer and an illumination light source that illuminates the wafer, and an optical system is provided between the reticle and the wafer to reduce a light image of a pattern on the reticle and project it onto the wafer. and further includes a photodetector for detecting an optical image of an alignment reference pattern on the reticle and an optical image of an alignment pattern on the wafer, wherein the alignment reference pattern on the reticle is The position of the alignment reference pattern on the reticle and the position of the alignment pattern on the wafer are on the optical axis connecting the position of the alignment pattern on the wafer, and between the reticle and the wafer, the illumination light is A part of the optical image of the reference pattern on the reticle is moved in the direction of the optical axis (hereinafter referred to as
a half mirror that reflects the light in a direction other than the first direction (hereinafter referred to as the second direction);
a mirror provided to reflect light in the direction toward the second direction, and in the second direction, at a position opposite to the half mirror, the mirror and a photodetector for detecting an optical image of the reference pattern on the reticle reflected by the reticle and an optical image of the alignment pattern on the wafer reflected in the second direction by the half mirror. Features of reduction projection exposure equipment.