Nanopatterning with Thin Polymer Films
Gila Stein
University of Houston
The most sophisticated semiconductor devices, such as microprocessors and memory chips, are
patterned with lithography. The performance of semiconductor electronics is coupled to the
resolution of the lithographic process, and to keep pace with historic growth rates (Moore's Law)
the dimensions of critical circuit elements are shrinking towards 10 nm. Our group studies the
physical and chemical variables that control pattern quality in two types of next-generation
imaging materials – block copolymers and chemically-amplified polymers, which are used for
“bottom-up” and “top-down” lithographic processes, respectively. A bottom-up image is defined
by thermodynamics, while a top-down image is controlled by exposure statistics and complex
chemical reactions. While these processes are very different, we find that imaging in both
systems is strongly affected by thin film confinement. First, I will discuss our efforts to extend
block copolymer self-assembly to integrated circuit manufacturing. We find that domain shapes
are determined by polymer-substrate interactions, and variability in domain size is controlled by
thermal fluctuations. Our work suggests that ``high chi’’ copolymers are needed for selfassembly at the 10 nm scale. Second, I will describe a new effort in our group to measure and
model reaction front propagation in chemically-amplified polymers. Our preliminary data
suggest that extent-of-reaction varies with distance from the film surface. This finding implies
that image resolution and shape are coupled to film thickness and the types of interactions at
each interface.