Fabrication and Simulation of Nanostructures on Silicon by Laser Assisted Direct Imprint Technique

Abstract

In this paper a newly proposed nano-patterning technology, namely laser assisted direct imprinting (LADI), is adopted with fabrication and numerical simulation for nano-scaled structures. We focused on the target material as silicon and utilized a single KrF excimer laser pulse (248nm wavelength and 30ns pulse duration) as heating source. We also demonstrated the fabrication of a positive quartz mold within micro-level and nano-level trenches by combination of conventional photolithography and novel focused ion beam (FIB) system. The influence of laser fluence and imprinting pressure on resulting nanostructure is evaluated by varying the laser fluence (0.6∼1.2 J/cm2) and imprint pressure (370∼1120 MPa). The results show that the magnitude of imprinting pressure and the laser characteristics can affect the thickness of the melted layer on the substrate surface and the morphology of the resulting nanostructures. In the other aspect, an analytical modeling of laser induced melting and solidification during LADI process was also established for the comparison between experimental results and numerical simulation. The transient temperature profiles inside the substrate, melt depth and melting duration after the irradiation of a laser pulse were evaluated by various fabrication parameters; such as materials of the substrate (silicon and copper were investigated) and the characteristics of the laser pulse (including wavelength, fluence and pulsed duration). Generally speaking, the nanostructures fabricated by LADI are quite consistent with the results of numerical simulation.