Abstract

Optically transparent and electrically resistive amorphous carbon films can be deposited by photolysis of acetylene with VUV light on a substrate kept near room temperature. However, the deposited films are characterized by low refractive indices and soft. A similar result was obtained with electron-impact dissociation of acetylene. It is known that ions play important role in producing hard carbon films with high refractive indices. Therefore, we used a window-less, microwave-excited H₂ tube to dissociate acetylene. Owing to its short wavelength components and presence of active hydrogen atoms, ions are generated from the source gas injected at the exit end of the discharge tube. They are further accelerated by an applied electric field. Then, not only deposition became faster, but as expected, we could improve film quality. The films were hard and their refractive indices became as high as 2.11. The bias required to improve film quality was approximately 300 V. The substrate was silicon. The deposition rate was 700 Å/min at room temperature, and it decreased with increasing substrate temperature.

© 1987 Optical Society of America