Hiroshi Ito talks with
ScienceWatch.com and answers a few questions about
this month's Fast Moving Front in the field of Materials
Science. The author has also sent along images of
Article: Chemical amplification resists for
Journal: ADVAN POLYM SCI, 172: 37-245 2005
Addresses: IBM Corp, Almaden Res Ctr, 650 Harry Rd, San
Jose, CA 95120 USA.
IBM Corp, Almaden Res Ctr, San Jose, CA 95120 USA.
Why do you think your paper is highly
As the co-inventor of chemical amplification resists, I am considered an
expert in this area. All of today's advanced semiconductor devices are
manufactured using chemical amplification resists, and my article presents
the most comprehensive review to date in this area.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Yes, my article describes a new discovery, development of new resist
materials, new lithographic processes, and new methodology, as well as
accumulated knowledge in microlithography.
Would you summarize the significance of your paper
in layman's terms?
"Microlithography technology and the
semiconductor industry will continue to grow
and evolve, and as we continue to innovate,
technology will continue to impact our
society and the world."
The chemical amplification resists I
invented in collaboration with C. Grant Willson and
Jean Fréchet have enabled the semiconductor industry make
electronics devices smaller, cheaper, and more powerful—keeping
pace with Moore's Law, a prediction made in 1965 by Gordon Moore,
cofounder of Intel, stating that the number of transistors occupying a
square inch of integrated circuit material had doubled each year since
the invention of the integrated circuit and that the multiplication of
circuitry would continue.
My paper describes the advancement of chemical amplification resists from
the time of their inception to worldwide implementation in device
manufacture, and the further development to support next-generation
lithography (NGL), citing more than 500 references. I believe that my
article is now considered to be a textbook of chemical amplification
How did you become involved in this research and
were any particular problems encountered along the way?
When I joined IBM in 1980, I began working on several projects, one of
which aimed at a drastic increase in the resist sensitivity to support deep
UV lithography. Use of a photochemical acid generator to induce an
acid-catalyzed reaction achieved the goal and also provided a solution to
the other two projects. As the three systems were characterized with a gain
mechanism, we decided to call these acid-catalyzed resist systems "chemical
View three slides of Hiroshi Ito's
The most serious and devastating problem which chemical amplification
resists encountered was the formation of a skin or T-shaped profile in
developed positive images, due to neutralization of the photochemically
generated acid with airborne basic substances absorbed in a top layer of
the resist film upon standing, after UV exposure. I was able to solve the
problem by reducing the free volume in the resist film through annealing
near its glass transition temperature to prevent airborne basic
contaminants from diffusing into the film. This resist gained worldwide
acceptance, was a workhorse in device manufacture at a 250 nm feature size,
and introduced the era of chemical amplification.
Where do you see your research leading in the
The chemical amplification resist has enabled the technology industry to
keep pace with Moore's Law and benefited the world economy for the last 15
years. In all likelihood, the chemical amplification resist will continue
to be employed in subsequent generations of device manufacture down to a 20
nm resolution through innovations in materials and processes and through
concerted efforts among diverse disciplines of microlithography.
Do you foresee any social or political implications
for your research?
Microlithography technology and the semiconductor industry will continue to
grow and evolve, and as we continue to innovate, technology will continue
to impact our society and the world. New breakthroughs in chip technology
have enabled things we couldn't have even imagined 30 years ago, like
handheld devices capable of storing 40 gigabytes or more. And in turn, the
breakthroughs we are making today will enable future advances that are
still beyond our imagination.
Hiroshi Ito, Ph.D.
San Jose, CA, USA
Keywords: chemical amplification resists,
next-generation lithography, acid-catalyzed resist systems,
microlithography technology, semiconductor industry, breakthroughs in chip