CF4/O2 inductively coupled plasma etching of silicate glass for antifogging applications

Abstract

Fogging of glass surfaces is a highly undesirable phenomenon that significantly impairs optical transmittance. This paper demonstrates inductively coupled plasma reactive ion etching (ICP-RIE) of silicate glass in the mixture of CF4 and O2 gases with the aim of rendering the glass surface superhydrophilic and antifogging. Maskless ICP-RIE as well as ICP-RIE of the glass surface through the lithographic Al masks with design periods of 400 and 500 nm was performed. The optical transmittance of the etched glass in the range of 350–900 nm was at least 85%. The maskless etching increased the water wettability of the glass, but the superhydrophilic state was still not achieved. However, real-time fogging experiments have demonstrated the usefulness of maskless etching for reduction of the glass fogging. The ICP-RIE of the glass surface through the lithographic masks resulted in pillar-like and pit-like textures. The average roughness of the textured glass surface, compared to the maskless etching, increased more than 10 times. Both textures were suitable to impart superhydrophilicity (Θ < 1°) to the silicate glass surface and ensured at least 85% optical transmittance during real-time fogging tests.