Investigation of optical and compositional properties of thin SiNx:H films with an enhanced growth rate by high frequency PECVD method

Hydrogenated thin silicon nitride (SiNx:H) films were deposited by high frequency plasma enhanced chemical vapor deposition techniques at various NH3 and SiH4 gas flow ratios [R = NH3/(SiH4 + NH3)], where the flow rate of NH3 was varied by keeping the constant flow (150 sccm) of SiH4. The deposition rate of the films was found to be 7.1, 7.3, 9 and 11 Å/s for the variation of R as 0.5, 0.67, 0.75 and 0.83, respectively. The films were optically and compositionally characterized by reflectance, photoluminescence, infrared absorption and X-ray photoelectron spectroscopy. The films were amorphous in nature and the refractive indices of the films were varied between 2.46 and 1.90 by changing the gas flow ratio during the deposition. The PL peak energy was increased and the linear band tails become broad with the increase in R. The incorporation of nitrogen takes place with the increase in R.

► The SiNx:H films were incorporated in the solar cell application as an AR coating.
► SiNx:H films were deposited by high power and very high frequency (60 MHz) PECVD technique.
► With increasing gas flow ratio [R = NH3 / (SiH4 + NH3)] from 0.5 to 0.83, the refractive index was decreased widely from 2.46 to 1.90.
► The low temperature growth with the adjustable refractive index can make SiNx:H films be suitable for the solar cell application.