Effects of deposition parameters on the refractive index in plasma polymerized methyl methacrylate thin films

Abstract

Plasma polymerization can be used to deposit thin films whose properties significantly differ from those of conventionally synthesized linear or cross-linked polymers. We investigate the plasma polymerization of methyl methacrylate for use in microelectronic and photonic applications. The deposition system is a 13.56 MHz parallel plate reactor. The effects of varying rf power and neutral pressure on deposition rate and refractive index in the visible are examined. It is found that the deposition rate can be varied from 50–500 Å/min over a pressure range of 40–300 mT. In addition, the refractive index can be varied from 1.5 to 1.6 in the visible by varying the rf power from 10 to 50 W. Possible applications in photonics include smoothly varying graded index and multilayer structures.