JPH04367213A - Projection-type aligner - Google Patents

Abstract

PURPOSE:To make an illuminance distribution uniform on a work face and to obtain a high-accuracy pattern by a method wherein an aspherical lens wherein the principal-ray tilted angle characteristic of a radiant illumination ray as the radiant ray of an illumination system coincides with the principal-ray tilted angle characteristic of an incident ray by the projection lens of a projection system is installed in the illumination system. CONSTITUTION:The following are installed with reference to a pattern mask 5: an illumination system S which is constituted of a light source 1 for exposure use, a shutter 2, a fly-eye lens 3, a collimator lens 4 and the like; and a projection system T constituted of a projection lens 6. In such a projection-type aligner, an aspherical lens 8 wherein the inclination of the principal ray of exposure light coincides with that of an incident ray by the projection lens 6 is installed in the illumination system S. Thereby, the exposure light for irradiating a work face through the projection lens does not deviate from an ideal principal ray with reference to the projection lens. Consequently, the work face is irradiated at a uniform illumination distribution.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for forming graphic patterns on semiconductor wafers and other electronic circuits.

0002

2. Description of the Related Art As a conventional technique of a projection type exposure apparatus that projects a circuit pattern drawn on a pattern mask onto a work surface such as a wafer for exposure, there is a technique disclosed in Japanese Patent Application Laid-open No. 185319/1983. As shown in FIG. 5, in this conventional technology, illumination light from a light source 1 equipped with a condensing mirror 10 is guided from a first reflecting mirror 9 to a fly-eye lens 3 via a shutter 2. After making the illuminance distribution uniform in step 3, the illuminance is guided by the second reflecting mirror 9, and while the illuminance distribution is kept uniform with the collimator lens 4, the focus is accurately corrected and the pattern mask 5 is irradiated. The transmitted projection light is focused by a projection lens 6 and irradiated onto a work surface 7, which is a wafer surface, thereby exposing the work surface 7.

In the above-mentioned prior art, the collimator lens 4 is constituted by a condenser lens group 12 that is a combination of a plurality of concave lenses and convex lenses, and by appropriately setting the combination of concave lenses and convex lenses, By mutually correcting the spherical aberrations of the concave lens and the convex lens, the pattern mask 5 is irradiated with uniform illuminance, and a light source image is created at the center of the entrance pupil 11 of the projection lens 6 without blurring, thereby achieving high precision. The aim is to obtain excellent resolution.

0004

[Problem to be Solved by the Invention] The projection lens 6, which is constructed by combining a large number of concave lenses and convex lenses, has a characteristic of the principal ray inclination angle α (see FIG. 4) of the incident light ray that the projection lens 6 has. Rather than changing linearly or in an increasing function from the lens center O toward the lens periphery L like the characteristic curve d shown by the imaginary line in FIG. 3, for example, the characteristic curve c shown by the solid line in FIG. As shown in FIG. 2, the angle increases almost linearly from the center O to the lens periphery L, but as it approaches the lens periphery L, the inclination angle α decreases, which is not a linear or increasing function change. do.

As described above, since the circumferential ray inclination angle characteristic of the incident ray of the projection lens does not change linearly or in an increasing function manner, the collimator lens is formed by a condenser lens group consisting of a plurality of concave lenses and convex lenses. It is extremely difficult to mutually correct the spherical aberrations of the concave and convex lenses to make the illuminance distribution of the illumination light beam uniform on the pattern mask, and to create a complete optical image at the center of the entrance pupil of the projection lens without blurring it. It is difficult or impossible for the illumination light beam irradiated from the mask surface to the projection lens to deviate from the linear or increasing functional change in the principal ray inclination angle characteristic of the incident light beam of the projection lens, and to Therefore, the illuminance distribution becomes non-uniform, which causes a problem in that a highly accurate pattern cannot be obtained.

It is possible to correct the deviation to a certain extent by combining a large number of concave lenses and convex lenses with respect to the linear or increasing function change in the principal ray inclination angle characteristic of the incident ray of the projection lens. , it is impossible to completely correct it, and therefore it has not been possible to fully satisfy the high resolution that has been increasingly demanded in recent years.

Therefore, the present invention was devised to solve the problems in the prior art described above. In a projection exposure apparatus, the principal ray inclination angle of the illumination light beam emitted from the illumination system that irradiates the pattern mask is The technical problem is to match the characteristics with the principal ray inclination angle characteristics of the incident light beam of the projection lens that constitutes the projection system, and the purpose is to make the illuminance distribution on the work surface uniform.

[0008]

[Means for Solving the Problems] The means of the present invention for solving the above technical problems is to provide an illumination system for a pattern mask, which includes an exposure light source, a shutter, a fly-eye lens, a collimator lens, etc. and a projection system consisting of a projection lens, the projection lens of the projection system having a principal ray inclination angle characteristic of the exit illumination ray that is the exit ray from the illumination system. The aim is to provide an illumination system with an aspherical lens that matches the principal ray inclination angle characteristic of the incident light beam.

[0009]

[Operation] The principal ray inclination angle characteristics of the incident light rays of the projection lens constituting the projection system of the projection exposure apparatus are measured in advance.
Based on this measurement result, an aspherical lens is manufactured that has principal ray inclination angle characteristics of the exiting ray that match the principal ray inclination angle characteristic of the incident ray of the projection lens, and this aspherical lens is used as an exposure light source, shutter, and fly eye. It is provided in an illumination system comprising a lens, a collimator lens, etc.

As described above, since the aspherical lens having the principal ray inclination angle characteristic matching the principal ray inclination angle characteristic of the incident light ray of the projection lens is provided in the illumination system, the light beam passes through the pattern mask and enters the projection lens. The inclination angle of the incident light ray is corrected according to the principal ray inclination angle characteristic of the incident ray of the projection lens, and the incident light ray becomes an exit illumination ray and enters the projection lens.

[0011] As a result, the emitted projection light ray irradiated onto the work surface through the projection lens becomes a light beam with no deviation in angle from the ideal principal ray with respect to the projection lens, so that it is uniform with respect to the work surface. It will be irradiated with an illuminance distribution.

0012

Embodiment FIG. 1 shows an embodiment of the present invention. The projection exposure apparatus shown in FIG. 1 includes an illumination system S that includes a light source 1 for exposure, a shutter 2, a fly's eye lens 3, two reflecting mirrors 9, a collimator lens 4, and an aspherical lens 8 for a pattern mask 5. and a projection system T with the projection lens 6.
It consists of

An ultra-high pressure mercury lamp is used as the light source 1 for exposure, and the illumination light from this light source 1 is directed to a condensing mirror 10.
The light is condensed and irradiated toward the fly's eye lens 3.

The illumination light emitted from this light source 1 passes through a shutter 2 that sets an exposure time, and then is transmitted through a fly-eye lens 3 to the light necessary to achieve exposure at a set illuminance distribution intensity. The amount of light is extracted and enters the collimator lens 4.

The illumination light incident on the collimator lens 4 is corrected into parallel light beams by the collimator lens 4, and is then incident on the aspherical lens 8.

The aspherical lens 8 has a principal ray inclination angle characteristic that matches the principal ray inclination angle characteristic of the incident light beam of the projection lens 6 constituting the projection system T. Therefore, the aspherical lens 8 has a pattern mask. The exit illumination beam b irradiated on 5
has a tilt angle distribution that matches the principal ray tilt angle characteristic of the incident light ray of the projection lens 6.

Since the aspherical lens 8 is manufactured to have a principal ray inclination angle characteristic that matches the principal ray inclination angle characteristic of the incident ray of the projection lens 6, its structure is such that the angle of inclination of the incident light of the projection lens 6 It is determined according to the principal ray inclination angle characteristics of the light ray.

For example, when a telecentric projection lens having the exit projection ray inclination characteristic shown in curve c in FIG. 3 is used as the projection lens 6, the structure of the aspherical lens 8 used is as shown in FIG. In addition, one surface R1 is a flat surface, and the other surface R2 has a slightly bulged and curved central portion.

That is, the aspherical lens 8 shown in FIG. 2 has a diameter of 116 mm, and the diameter of the other surface R2 is 105 mm.
．． The area within the 1 mm range is a curved surface defined by Equation 1, and Table 1 shows an example of the dimensions of the actual aspherical lens 8 obtained using Equation 1. In addition, in FIG. 2, Z is the distance in the thickness direction from the center point of the other surface R2, Y is the distance in the radial direction from the center of the aspherical lens 8, and the distance Z outside the diameter of 105.1 mm is It is a constant value of 2.0196 mm.

[Math 1]

[Table 1]

[0020]

[Effects of the Invention] Since the present invention has the above-mentioned configuration, it produces the following effects. Since the illumination system of the projection exposure apparatus is provided with an aspherical lens having a principal ray inclination angle characteristic that matches the principal ray inclination angle characteristic of the incident light ray of the projection lens constituting the projection system of the projection exposure apparatus, the illumination The influence of the principal ray inclination angle characteristic of the incident ray of the projection lens on the actual incident light from the system to the projection lens can be eliminated,
This makes it possible to make the illuminance distribution on the work surface uniform, thereby making it possible to obtain a pattern with high resolution and high precision.

Since the light incident on the projection lens is given an inclination in advance that matches the principal ray inclination angle characteristic of the incident light ray of this projection lens, vignetting of the light within the projection lens can be eliminated. The illuminance on the work surface can be set accurately.

[0022] In order to correct the principal ray inclination angle characteristic of the incident ray of the projection lens, it is sufficient to use only one aspherical lens without combining a large number of concave and convex lenses. It is possible to reduce the number of lenses constituting the illumination system in the projection exposure apparatus, thereby simplifying the structure of the illumination system of the projection exposure apparatus, and achieving a significant reduction in manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a side view showing an example of the structure of an aspherical lens used in the device of the present invention.

FIG. 3 is a diagram showing an example of the exit projection ray inclination angle characteristic of a telecentric projection lens.

FIG. 4 is an explanatory diagram for explaining FIG. 3;

FIG. 5 is a configuration diagram showing an example of a conventional projection exposure apparatus.

[Explanation of symbols]

1; light source
2; Shutter 3; Fly-eye lens 4
; Collimator lens 5 ; Pattern mask
6; Projection lens 7; Work surface
8; Aspherical lens 9; Reflector
10; Condensing mirror 11; Entrance pupil
12; Condenser lens group S; Illumination system
T; projection system a; exit projection ray b; exit illumination ray O; lens center
L: Lens periphery

Claims (2)

[Claims] 1. An illumination system (S) for a pattern mask (5), which includes an exposure light source (1), a shutter (2), a fly's eye lens (3), a collimator lens (4), etc. ) and a projection system (T) consisting of a projection lens (6), the principal ray inclination angle characteristic of the exit illumination ray (b), which is the exit ray, is determined by the projection lens (6). ) Aspherical lens that matches the principal ray tilt angle characteristics of the incident ray (8)
A projection exposure apparatus comprising: the illumination system (S). 2. The projection exposure apparatus according to claim 1, wherein the projection lens (6) is of a telecentric type.