Fabrication and Characterization of Smooth Si Mold for Hot Embossing Process

Abstract

In this paper, we propose a fabrication and characterization of silicon mold for PMMA hot embossing process. Silicon molds were fabricated from silicon wafer with thickness of 500μm. First, DRIE technique was performed after optimized etching time and deposition (passivation) time to obtain a depth of 30μm with positive tapered sidewall of 1°. This is very important for de-molding process while hot embossing. Second, in order to reduce scalloping steps on the sidewall after DRIE, silicon molds were soaked in the TMAH solution 20% at 80°C for 10 minutes without magnetic stirrer. Third, to further reduce the friction coefficient between sidewall surface and PMMA substrate while de-molding, the post-passivation technique was applied to create a thin layer of Teflon-like material on the surface of the sidewall of silicon mold. These smooth silicon molds were used to emboss several models of PMMA patterns and comb-drive actuators, as well as applications in Micro Conveyer System. The PMMA patterns obtained after hot embossing process had very sharp edge and aspect ratio of 15 with minimum feature sized of 2μm.