Low-temperature PECVD of silicon dioxide on polymeric hydrogels

Abstract

In this work, a complex investigation of the film surface composition and nanoscale mechanical properties, i.e. hardness and elastic modulus, of plasma-modified and silica-coated hydrogel thin films was carried out. Plasma treatment was performed in a reactive ion etching chamber (SF6, CHF3) at radio frequency (rf, 13.56 MHz) and in a plasma-enhanced chemical vapor deposition chamber (SiH4/N2, NH3, N2O) at radio frequency and dual frequency (13.56 MHz/100 kHz), respectively. The use of the dual-frequency configuration comprising two power supplies and operated in a switched mode enabled the investigation of the ion-bombardment influence on the polymer properties. For the application in silicon micromachined sensors best results were obtained by using a NH3 or SiH4/N2 low-pressure plasma modification and a silica coating of the sensitive hydrogel film.