Numerical Investigation of Phase-Changing Heat Transfer for Laser-Assisted Direct Nano Imprint Processing
F-B Hsiao, D-B Wang, C-P Jen, Y-C Lee and C-H Chuang
National Cheng Kung University, TW
nanoimprinting, pulsed laser, heat conduction, phase change
Laser-Assisted Direct Imprinting (LADI), a novel and promising technique, has been proposed since 2002 to utilize an excimer laser to irradiate and heat the silicon surface through a highly-transparent quartz mold preloaded onto the silicon. For this fabrication, the molten depth, melting duration and preloading pressure are key issues to obtain a satisfactory imprinting pattern. The present study develops an efficient numerical method to deal with the phase-changing heat transfer during the imprinting process to acquire the effect of laser fluence for the transient response both in temperature and molten depth. According to simulation results and SEM photography, this study proposed a “fluence window” for the laser irradiation (about 0.6~0.9 J/cm^2), which guarantees not only the melting of silicon but also an undamaged shape of the quartz mold. Simulation regarding thermal-fluid-stress coupling will also be undertaken in the coming future to investigate more completely about the stuffing situation and stress concentration of silicon inside the mold during imprinting process.
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Nanotech 2005 Conference Program Abstract