Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2002-11-18
2004-12-28
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
Reexamination Certificate
active
06835509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a mask used in an exposure apparatus, and more particularly, to a mask for estimating aberration in a projection lens system of an exposure apparatus.
2. Description of the Related Art
Typically, an exposure apparatus is used to form photoresist patterns on a semiconductor wafer in the manufacture of semiconductor devices. Specifically, the exposure apparatus is used to realize patterns on a mask on a photoresist layer. A projection lens system, which reduces and projects patterns on a mask on a semiconductor wafer using light characteristics, is installed in the exposure apparatus. Thus, an estimation of aberration in the projection lens system of the exposure apparatus is necessary.
Referring to
FIG. 1
, a conventional method for estimating aberration in a projection lens system of an exposure apparatus can best be seen. The mask
11
for estimating is divided into a portion marked with the letter “K”.
FIG. 2
is an enlarged view of the section “K” of FIG.
1
and shows where a lens array
19
and a transparent layer
21
are formed.
In
FIG. 1
, reference numeral
13
denotes the mask plane (i.e., mask surface). Light emitted from a light source in the exposure apparatus passes through lenses
16
a
and
16
b
of a projection lens system
15
, and image patterns are formed on an image plane
17
of a semiconductor wafer.
Light A′, C′, E′, A″, C″, and E″ passing through a portion of the mask
11
in which the transparent layer
21
is not formed creates reference pattern
23
with respect to the entire projection lens system
15
in the image plane
17
. Light A, B, C, D, and E traveling through a portion of the mask
11
in which the transparent layer
21
is formed, passes through a desired position of the projection lens system
15
through a pin hole
25
of the transparent layer
21
and forms measurement pattern
27
.
In particular, light marked D in
FIG. 1
is light passing through the projection lens system
15
without aberration, and light marked D
ab
is light passing through the projection lens system
15
with aberration. The aberration is estimated by comparing the reference pattern
23
with the measurement pattern
27
. In
FIG. 1
, reference numerals
29
and
31
denote an aperture plane and an aperture stop, respectively.
The lens array
19
should be manufactured at the backside of a mask that is used in the conventional method for estimating aberration in the projection lens system of the exposure apparatus. In addition, the transparent layer
21
in which the pin hole
25
is formed should be manufactured at the front side of the mask. Further, it costs a great deal to manufacture the mask used in the conventional method for estimating aberration in a projection lens system of an exposure apparatus. Consequently, it is therefore desirable to provide a mask for estimating aberration in a projection lens that overcomes the disadvantages of the known prior art.
SUMMARY OF THE INVENTION
At least one exemplary embodiment of the present invention provides a mask for estimating aberration in a projection lens system of an exposure apparatus by changing mask patterns.
In at least one exemplary embodiment of the present invention there is provided a mask for estimating aberration in a projection lens system of an exposure apparatus. The mask includes a mask substrate and mask patterns arranged on the mask substrate such that a critical dimension (CD), represented by the width of each of the mask patterns, and a phase of the mask patterns have a size proportional to a SINC function. Preferably, the distance between the centers of the mask patterns is substantially uniform. The phase of each of the mask patterns may be provided by etching the mask substrate.
According to at least one exemplary embodiment of the present invention, the size and phase of light transmitted to the projection lens system during an exposure step are substantially uniform, and thus an aberration value in each portion of the projection lens system depending on each mask pattern is not distorted and is uniform.
REFERENCES:
patent: 2003/0123052 (2003-07-01), Ausschnitt et al.
Harness Dickey
Rosasco S.
Samsung Electronics Co,. Ltd.
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