Better Block Copolymer Lithography Stanford University by mikesanye


									Block Copolymer Lithography Made Better: Block copolymer lithography is a new approach to lithography. Block
copolymers are polymer chains made from two different bonded polymers, which inherently self-assemble into nano-
scale uniform patterns. At last year’s IEDM, Stanford researchers described how they used the technique to produce
regular, ordered 18nm contact hole patterns. But real-world circuits aren’t perfectly ordered, and so to be useful, the
technique must be able to produce non-uniform, or aperiodic, patterns. Stanford researcher will discuss how they did
just that, by using optically pre-patterned templates with dimensional scales close to the natural pitch of the polymer
self-assembly process. The pre-patterned templates physically confined the polymers, leading them to self-arrange in
specific ways, breaking the inherent uniform structure. The researchers used the technique to fabricate a realistic
contact-hole layout for a 22nm SRAM.

The top figures show the “hole-in-a-hole structure” with self-assembled holes embedded in lithographically pre-
defined contact holes. They share the same center-to-center distance of 150nm, about 3.75 times larger than the natural
40nm distance for the self-assembly. The middle image is an electron microscope view of extra holes formed next to
regularly packed self-assembled holes. The bottom views are contact-hole template designs for the SRAM cell.

(Paper #33.2, “Experimental Demonstration of Aperiodic Patterns of Directed Self-Assembly by Block Copolymer Lithography
for Random Logic Circuit Layout,” L.-W. Chang et al, Stanford University/Applied Materials)

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