TOKYO, June 23 /Kyodo JBN-AsiaNet/ -- Asahi Glass Co., Ltd. (Headquarters:
Tokyo; President: Masahiro Kadomatsu) has succeeded in the development of "QC-
i" a synthetic quartz photomask(1) substrate, which complies with the liquid
immersion technology used in ArF (argon fluoride) laser steppers(2) that use
ArF lasers as a light source for photolithography in semiconductor production.
QC-i can be mass-produced due to substantially reduced production costs, which
makes it the world's first substrate for ArF immersion photolithography(3) to
be mass-produced. This development is expected to dramatically advance the
ultra-fine processing technology that is indispensable for semiconductor
As more advanced, sophisticated integration and ultra-fine techniques for
devices mounted on LSI chips are required for semiconductor manufacturers,
they seek shorter wavelength light sources for the photolithography process by
which semiconductor patterns are formed. These manufacturers recently have
begun to use 248 nanometer(4) KrF (krypton fluoride) lasers and 193nm ArF
lasers, as light sources.
Meanwhile, the semiconductor device manufacturers(5), aiming to further
advance ultra-fine processing technologies, are developing photolithography
processes using much shorter wavelength lasers such as the 157nm-F2 (fluoride
dimmer) and 13nm-EUV (extreme ultraviolet) lasers. Asahi Glass in 1999
developed photomask substrate and pellicle materials for F2 lasers, and is
currently developing photomask materials for EUV lasers jointly with
International Sematech of the U.S. (Headquarters: Austin, Texas). Through
these efforts, Asahi Glass has strived to shorten the wavelength of light
sources. Although development of materials for an F2-laser photolithography
process has progressed much, manufacturing costs, including equipments, are
still a major barrier to commercialization. It is expected to take from four
to six more years before mass-production of an EUV photolithography process is
realized, considering the progress of development of peripheral materials.
Therefore, the most pressing task for the industry is to develop a
photolithography process that can be commercialized at an earlier date and
requires less investment.
Facing such circumstances, semiconductor device manufacturers began using
conventional ArF laser steppers to develop a liquid-immersion photolithography
process that can improve the accuracy of ultra-fine processing, and they are
nearing commercialization. In the liquid immersion photolithography process,
pure water is put between the stepper lens and silicon wafer to significantly
refract the light passed through the lens, so that ultra-fine processing on
the wafer is made possible. Synthetic quartz photomask substrates for liquid
immersion photolithography require the "low birefringence(6)" property that
minimizes irregularities in light polarization(7).
Leveraging development expertise in dealing with lens materials for ArF
laser steppers that the Company has accumulated for years, Asahi Glass has
succeeded in the development of synthetic quartz photomask substrate QC-i
which can be used in the ArF liquid immersion photolithography on a commercial
basis. The characteristics of QC-i are as follows:
1. The birefringence is 1nm or less, compared with the 4 to 5nm for
conventional synthetic quartz photomask substrates for ArF
2. As production costs are remarkably reduced, QC-i can be mass-produced.
(Annual production at Asahi Glass is estimated at 50,000 substrates of
6 x 6 inch square, with a thickness of 0.25 inch.)
3. Component technologies include a high-performance planarizing
technique conventionally applied in photomask materials for the F2
lithography, and a technique to reduce defects at scales of 100nm or
Semiconductor stepper manufacturers are expected to launch mass-produced
ArF liquid immersion steppers in 2005 and 2006, and demand for photomask
materials for ArF liquid immersion lithography is forecast to grow remarkably.
Asahi Glass estimates sales of QC-i at 1 billion yen in fiscal 2008, by coping
with the rising demand through the mass production. The Company will continue
to develop and produce high quality, high performance materials matching
various light sources used in the photolithography process, so that it can
offer optimum solutions to its customers.
An patterned original sheet needed to transfer LSI circuit patterns to
silicon wafers and others in the photolithography. A copy of the photomask
pattern forms on the mask blank, which is a substrate for the fabrication of
(2) ArF laser stepper
Typical equipment for photographic exposure which is used to transfer
photomasking patterns to wafers in IC chip manufacturing process. Also called
"reduction-projection exposure device." The ArF laser stepper uses an 193nm
ArF laser for its light source.
The general term for processes of transferring LSI circuit patterns to a
silicon wafer and others. Ultraviolet and other short wavelength light sources
are used to form fine circuits.
A nanometer is one billionth of a meter.
(5) Semiconductor device manufacturers
Manufacturers of the fundamental devices that constitute electronic
circuits, including transistors, ICs and LSIs.
A phenomenon in which each ray of light entering an object is split into
two refractions. Quartz glass causes double refraction, birefringence, due to
the distortion caused by strains in the material and other causes.
Birefringence disturbs light polarization in ArF liquid immersion exposure
equipment, resulting in deteriorated performance.
(7) Polarization of light
Polarization is occurred when light waves are aligned so that they vibrate
in the same direction. In the exposing process to transfer photomask patterns
to wafers, polarization of the light source improves the contrast when resist
materials are exposed, enabling an easier transfer of finer patterns to the
SOURCE Asahi Glass Co., Ltd.