Uniformity improvement of a-C: H films prepared by PECVD

Being used as an advanced patterning film, hydrogenated amorphous carbon (a-C: H) is prepared in a wide range of PECVD process parameters like showerhead-to-heater spacing, process pressure, radio frequency, deposition time, and so on. We investigated the deposition non-uniformity (NU%), in-film thickness variation, optical refractive index and extinction coefficient. A multi-variable statistical design of experiment (DOE) was performed to tune key process parameters in a scientific way in order to improve uniformity and reduce thickness variation with significant cost reduction. A reduction of NU% from 1.37 to 0.89% and thickness variation from 108.69 to 70.55 Å has been achieved, which was demonstrated by both DOE estimates and experiments. Both have proven the strongest effects of process pressure on film uniformity properties.