Fabrication Of 2D Silicon Nano-mold Based On Sidewall Transfer

In this paper, the selection criterion of film deposition process and film material was established, and we selected sputtering and sputter etching to fabricate sidewalls. By combining of standard UV lithography, conformal deposition of gold by RF sputtering, argon sputter etching and deep reactive ion etching (DRIE), we developed a new method based on the sidewall transfer technique for fabricating two-dimensional (2D) nano-mold on a silicon substrate. Depositing gold on photoresist mesas greatly simplifies the fabrication process and lowers the stress between the substrate and sidewalls. This technique enables the generation of very fine geometries with nanoscale dimensions without the electron-beam (e-beam) lithography equipment or other additional lithography techniques.In order to study the effect of different exposure time and developing time on the influence of lithography, we designed four mask patterns consisting of 1-μm-wide and 2-μm-wide,2-μm-spacing and 10-μm-spacing line grating, and for better photoresist mesas a optimal conditions of exposure for 20s and developing 30s were obtained; The main process parameters of sputtering and sputter etching were studied. The thickness of deposited gold layer was precisely controlled to be 213～222 nm by sputtering and the gold was selectively removed from horizontal surfaces by argon sputter etching; Based on oxygen plasma, we optimized the main process parameters and successfully fabricated gold sidewalls after removing the photoresist mesas.Based on SF6, O2 and C4F8 plasmas, we pay much attention to the dependency of scallops and etch rate on DRIE parameters (including pressure, gas flow, substrate holder power, etching/passivation cycle duration), and as a result a vertical mold profile and a minimum scallop size of 30 nm were obtained. For smooth mold surfaces, we report and demonstrate a new mechanism of removing 'grass' obtained during DRIE etching. By tuning the substrate holder power of C4F8, the 'grass' was suppressed and removed, small scallops were obtained as well. With this technique, we have successfully fabricated very uniform 2D silicon nano-molds consisting of 200 nm-wide,200 nm-high,4.3 mm-long bar arrays.