Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
1996-04-18
2001-06-12
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
C430S022000, C355S077000, C250S201200, C250S548000
Reexamination Certificate
active
06245470
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection aligner for use in a large-scale integrated circuit (LSI) manufacturing process. Moreover, the present invention relates to an aberration estimating (or evaluating) mask pattern for estimating aberration included in an optical system of a projection aligner, an aberration quantity (namely, quantity-of-aberration) estimating method, and an aberration eliminating filter for eliminating the aberration. Furthermore, the present invention relates to a semiconductor manufacturing method for manufacturing a semiconductor device by transferring a circuit pattern while eliminating the aberration.
2. Description of the Related Art
Projection aligners for projecting a circuit pattern of a semiconductor device, which is formed on a mask, onto a wafer are required to have high resolution so as to achieve the transferring of a micro or fine pattern thereon. Generally, in proportion as the numerical aperture (NA) of a projection lens (or projecting lens) increases, or in proportion as the wavelength of exposure light decreases, the resolution is improved. The method of increasing the NA of the projection lens, however, causes a reduction in the focal depth (namely, the depth of focus) thereof at the time of transferring the pattern. Thus, there is a limit to the improvement of the resolution. On the other hand, the use of exposure light having short wavelength requires an extensive modification of the transferring process. The method of decreasing the wavelength of exposure light is, therefore, unpractical.
Thus, in Japanese Patent Laid-Open Nos. 4-251914 and 4-179213, there have been proposed projection aligners, by each of which the resolution can be enhanced by increasing the NA but, simultaneously, the focal depth can be enlarged, by the applicant of the present application. As illustrated in
FIG. 19
, in this projection aligner, a fly-eye lens
3
is placed diagonally to the front of a lamp house or lamp housing
1
by interposing a mirror
2
therebetween. Further, an aperture
4
is positioned in front of the fly-eye lens
3
. Moreover, a blind
6
is placed in front of the aperture
4
by putting a condensing lens or condenser lens
5
therebetween. Furthermore, a photomask
10
, on which a desired circuit pattern is formed, is disposed diagonally to the front of the blind
6
by interposing a condensing lens
7
, a mirror
8
and a condensing lens
9
therebetween. In addition, a wafer
12
is placed in front of the photomask
10
by interposing a projection optical system or projecting lens system
11
therebetween. The contrast of an image at the time of defocusing is improved by putting a phase shift member, which is operative to cause a phase difference between light passing through the central portion of a transmitting zone or area and light passing though the peripheral area thereof, onto the pupillary surface or pupil plane of the projection optical system
11
. Consequently, the focal depth is increased effectively.
However, in the case of the aforementioned conventional projection aligner, the aberration of the optical system is not taken into consideration. Generally, actual or practical optical systems have various aberrations. Typical aberrations are a spherical aberration, an astigmatism aberration, a field curvature and a coma aberration. It is known that theses aberrations can be expressed, as illustrated in
FIGS. 20A
to
20
E, by being converted into wavefront aberrations, respectively. In these figures, &phgr; denotes a shift quantity or distance of a wavefront; &rgr; a radius on a pupillary surface (namely, &eegr;&xgr;E -plane); &thgr; an angle of rotation with respect to the axis &eegr;; y
0
coordinates on a wafer surface; and B to F constants. The details of these aberrations are described in various literatures, for example, “Principle of Optics I to III” (published by Tokai University Press.).
Because the optical systems of the conventional projection aligners have such aberrations, the conventional projection aligners have the problems that the image quality thereof is degraded and that the accuracy of transferring a circuit pattern is deteriorated.
The present invention is accomplished to solve such problems of the conventional projection aligners.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a projection aligner which can eliminate the influence of the aberrations of the optical system thereof and can achieve the high-accuracy transfer of a (circuit) pattern.
Moreover, another object of the present invention is to provide an aberration estimating mask pattern for estimating the aberration of the optical system of a projection aligner, and to further provide a method for estimating an aberration quantity by using this aberration estimating mask pattern.
Furthermore, still another object of the present invention is to provide an aberration eliminating filter for compensating for an aberration of the optical system of the projection aligner.
Additionally, yet another object of the present invention is to provide a semiconductor manufacturing method for manufacturing a semiconductor device by transferring a circuit pattern while eliminating the influence of the aberration of the optical system of a projection aligner.
To achieve the foregoing objects, in accordance with an aspect of the present invention, there is provided a projection aligner which comprises: a light source; an aperture for shaping illumination light and forming a secondary light source plane; a blind having an opening portion for setting an exposure area; a photomask which has a circuit pattern and is illuminated with illumination light emanating from the secondary light source plane; a projection optical system for projecting a circuit pattern of the photomask by forming an image on an exposed substrate from diffraction light diffracted by the photomask; and an aberration eliminating filter, placed on a pupillary surface of the projection optical system, for eliminating an aberration.
Further, in accordance with another aspect of the present invention, there is provided an aberration estimating mask pattern which comprises: a transparent substrate; a plurality of micro patterns selectively formed on the transparent substrate; and a plurality of larger patterns which are formed selectively on the transparent substrate. Further, in this aberration estimating mask pattern, each of the micro patterns and a corresponding one of the larger patterns are combined with each other. Furthermore, a plurality of such combinations (or sets) of micro patterns and a larger pattern are placed on the transparent substrate.
Moreover, in accordance with a further aspect of the present invention, there is provided an aberration quantity (namely, a quantity-of-aberration) estimating method which comprises the steps of: exposing aberration estimating mask patterns; observing a plurality of finished (or obtained) patterns; finding a best focus position or a finishing position of each of the patterns; and estimating a quantity of an aberration from a quantity of a change in the best focus position or in the finishing position of each of the patterns.
Furthermore, in accordance with yet another aspect of the present invention, there is provided an aberration eliminating filter that is a filter, which is placed on a pupillary surface (namely, a pupil plane) of a projection optical system, for eliminating an aberration. This filter is provided with a transparent substrate and a wavefront regulating (or adjusting) transparent multi-layer film formed on at least one principal plane.
Additionally, in accordance with a further aspect of the present invention, there is provided a semiconductor manufacturing method which comprises the steps of: forming a secondary light source plane by shaping illumination light emanating from a light source; establishing an exposure area; illuminating a photomask with illumination light emanating from a secondary light source plane; forming an ima
Angebranndt Martin
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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