Effect of Dropping Hydrofluoroether in Thermal Nanoimprint on Polycarbonate

Research Center for Ubiquitous MEMS and Micro Engineering, National Institute of Advanced Industrial Science and Technology (AIST),Tsukuba, Ibaraki 305-8564, JapanReceived November 30, 2010; revised March 10, 2011; accepted March 22, 2011; published online June 20, 2011We introduced a hydorofluoroether (HFE) liquid with a low boiling point in thermal nanoimprint lithography (T-NIL) of polycarbonate (PC) andexperimentally confirmed that molding uniformity improved at low contact pressures where conventional T-NIL had been unsuccessful. Inconventional T-NIL, the conditions to imprint on PC with a glass transition temperature of 150 C are prescribed as: heating temperature = 180 C,cooling temperature = 140 C, contact pressure = 20MPa, and contact time = 10s. With a contact pressure of 10MPa, which is half the valuenormally employed in T-NIL, imprinting on PC under such low-contact pressure resulted in incomplete fillings. To investigate the cause ofincomplete fillings, imprinting results of T-NIL in air and in vacuum were compared. As a result, we learned that defective molding can be avoidedby simply removing the residual air trapped in the mold pattern. To solve the air bubble defect problem encountered in UV-NIL when working withlow-contact pressure T-NIL, we applied a method of inserting a condensable gas into the system. In our technique, HFE gas was used, whichimproved the accuracy remarkably, and realized a complete filling at a contact pressure of 5MPa. This method of employing reduced contactpressure in T-NIL is of great advantage in large-area imprinting. # 2011 The Japan Society of Applied Physics