Deposition and characterization of antistiction layer for nanoimprint lithography by VSAM (Vapor Self Assembly Monolayer)

Abstract

Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10 nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Torr and 110°C. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to 170°C with 0.1 ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about 110° of contact angle and under 20° of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15 mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1 nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under 110°. Also the white circles were founded in LFM images under 110°. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at 170°C, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.