Micropattern Formation by Molecular Migration via UV-induced Dehydration of Block Copolymers

A novel UV lithographic technique for the patterning of the block copolymer
(Pluronic) thin fi lms is developed. The present method is based on UVinduced
water affi nity changes in block copolymer fi lms. By water vapor posttreatment
of the fi lm, a difference in water content is established between UV
illuminated and unilluminated sections, which can induce an osmotic pressure
at the interface. This osmotic pressure drives the migration of Pluronic
molecules, resulting in formation of patterns on the block copolymer fi lms.
Remarkably, this patterning method requires neither initiators nor polymerizable
moieties which are essential for a conventional photolithographic
approach. Additionally, the etching process is bypassed, eliminating the use
of destructive acids or organic solvents and making this an environmentally
friendly patterning protocol. It is reported that Pluronic is photo-responsive to
UV exposure, which causes the dehydration of the PEO-PPO-PEO backbone.