Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2002-02-05
2003-07-15
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S330000, C430S945000, C430S967000, C264S002500
Reexamination Certificate
active
06593067
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a microstructure by using a high energy light source; and, more particularly, to a method for manufacturing a microlens or a microstructure having a predetermined pattern by using synchrotron radiation.
DESCRIPTION OF THE PRIOR ART
Recently, high energy synchrotron radiation has been widely used in the field of X-ray lithography in the semiconductor industry and also in manufacturing microstructures by using the so-called LIGA (X-ray deep etching molding) process first developed in Germany in the course of manufacturing a slot nozzle to separate a uranium isotope.
The synchrotron radiation is a high energy light source, tens of thousand times stronger than other light sources. It has a low dispersion due to excellent parallel beam characteristics and also has the continuous energy spectrum and further is a highly clean light source to radiate under high vacuum. Accordingly, a lithographic exposure time can be significantly reduced by way of using the synchrotron radiation, when compared with other light sources. The microstructure having a high aspect ratio can be manufactured by the synchrotron radiation due to its low dispersion characteristic. The synchrotron radiation also can be an optimum X-ray light source in the LIGA method since it can increase the degree of freedom in the selection of a photomask by choosing an appropriate wavelength range therefor.
One of the applications of the LIGA process can be found in the field of a microlens. The microlens is used as an important element in an optical system, wherein the structure of the microlens needs to be controlled so as to obtain desired optical properties.
One of the conventional microlens manufacturing schemes, proposed by N. Moldovan in “LIGA AND ALTERNATIVE TECHNIQUE FOR MICROOPTICAL COMPONENTS”, IEEE, page 149~152, 1997, will now be described with reference to
FIGS. 1A
to
1
D.
As shown in
FIG. 1A
, a photosensitive material, e.g., (PMMA: polyMethylMethAcrylate),
12
is coated on a substrate
10
. Thereafter, an X-ray exposure process is performed using an X-ray photomask
14
. The PMMA is often used as the photosensitive material
12
since the transparency of the lens manufactured by the PMMA is about 90% better than those of other prior art plastic lenses and other optical characteristics thereof are also closer to those of a glass.
Thereafter, a cylindrical pattern
16
is obtained by eliminating a portion of the PMMA exposed to the X-ray, as shown in
FIG. 1B
, by a developing process.
The whole cylindrical pattern
16
is then exposed to a second X-ray of a lower intensity provided through a membrane filter (not shown) located thereabove, as shown in FIG.
1
C.
By exposing the pattern
16
to the weaker second X-ray, only a surface portion
16
a
of the pattern
16
is affected to have a lower glass transition temperature (T
g
) than that of the nonexposed portion.
Finally, as shown in
FIG. 1D
, the cylindrical pattern
16
is heat-treated at a predetermined temperature so that only the affected surface portion
16
a
of the exposed cylindrical pattern
16
having low T
g
melts and deforms to form a microlens
16
b
having a hemispherical top portion by a surface tension. Here, the diameter of the microlens
16
b
is determined by the diameter of the original pattern
16
, while the height thereof is determined by the heat-treatment temperature and the height and the diameter of the pattern
16
.
However, the conventional microlens manufacturing method described above has some drawbacks in that the manufacturing schemes require two X-ray exposure processes together with a developing process, complicating the whole process.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a simplified microstructure manufacturing method by using only one X-ray exposure process, without being subjected to a developing process.
In accordance with the present invention, there is provided a method for manufacturing a microstructure by using a high energy light source, which includes the steps of selectively exposing a portion of a photosensitive material to the high energy light source and performing a heat-treatment for melting and deforming only an upper portion of the exposed portion of the photosensitive material.
REFERENCES:
patent: 4572611 (1986-02-01), Bellman et al.
patent: 4877717 (1989-10-01), Suzuki et al.
patent: 5604635 (1997-02-01), Lawandy
patent: 5665136 (1997-09-01), Komachi
patent: 6387578 (2002-05-01), Lian et al.
patent: 8-171099 (1996-07-01), None
Borrelli et al., “Photolytic Technique for Producing Microlenses in Photosensitive Glass”, Applied Optics vol. 24, No. 16, pp. 2520-2525, Aug. 15, 1985.
Lee Kwang-Cheol
Lee Seung Seob
Lee Sung-Keun
Bacon & Thomas PLLC
McPherson John A.
Postech Foundation
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