Investigation of the anti-adhesion layers for nanoimprint molding

Abstract

To realize the anti-adhesion issue between silicon mold and nanostructures of hard polydimethylsiloxane (H-PDMS), anti-adhesion layers were coated on molds to improve the H-PDMS grating structure with half-pitch below 200 nm. Various deposition methods such as liquid immersion method, vapor deposition method, and plasma-enhanced chemical vapor deposition were used to coat various anti-adhesion layers, respectively. Three anti-adhesion layers including diamond-like carbon (DLC) film, fluorine-doped diamond-like carbon (F-DLC) film, and perfluorooctyl-trichlorosilane (PFOTCS) were investigated. PFOTCS was functioned as a mold-releasing agent using the liquid immersion and vapor deposition methods, respectively. The effect of those anti-adhesion layers on the molding process was characterized. The results show that the PFOTCS anti-adhesion layer coated by vapor deposition method exhibits the best separability among all of the anti-adhesion layers. The maximum contact angle using PFOTCS is about 115° under 0.5 h of heating time. Compared to DLC, the F-DLC anti-adhesion layer shows good separability when the line width exceeds 100 nm, and does not require recoating again after each use. In addition, atomic force microscopy (AFM) was adopted to measure the adhesion force between the H-PDMS and the anti-adhesion layers.