Area-selective polymer deposition on micro-area framed by trenches with falling liquid film

Additional formation of functional films on the defined micro-areas on the microstructure is often complicated and need advanced control technique. Any simple and faster deposition processes are favorable. In this paper, we propose a simple processing method to form thin films on the defined areas by falling dispersion liquid containing the coating materials on a tilted silicon substrate with trench frames. We attempted to hold the coating solution and to form a thin film within the framed micro-area. We fabricated 500 nm-wide trench frames on silicon substrates, and flew a diluted photoresist (PR) solution, as the coating solution, on the tilted surface with the frames. PR film was successfully formed on the framed area for the substrate modified with hexamethyldisilazane (HMDS). However, the area-selective PR deposition was difficult in case the substrate was not treated with HMDS. It is likely that lower contact angle for the substrate without HMDS treatment is unfavorable for the area-selective PR deposition for the excess adhesive properties of the coating solution to the surface. The effectiveness of the frames as the guide to hold a liquid droplet within the defined area was considered.