The silicon nitride films were deposited by means of high-density inductively coupled plasma chemical vapor deposition in a planar coil reactor. The process gases used were pure nitrogen and a mixture of silane and helium. Passivated by silicon nitride, solar cells show efficiency above 13%. Strong H-atom release from the growing SiN film and Si-N bond healing are responsible for the improved electrical and passivation properties of SiN film. This paper presents the optimal refractive index of SiN for single layer antireflection coating as well as double layer antireflection coating in solar cell applications. (C) 2002 Elsevier Science B.V. All rights reserved.