The Study of Silane-Free SiC[sub x]N[sub y] Film for Crystalline Silicon Solar Cells

Abstract

We deposited plasma-enhanced chemical vapor deposition silicon carbon nitride (SiCxNy) antireflection coating and passivation layers using a silane-free process. We used a solid polymer source developed at SiXtron Advanced Materials to eliminate the storage and handling of dangerous pyrophoric silane gas. We used ammonia flow rate as a control for the chemical and optical properties in the silane-free process. As NH3 flow rate increases, the carbon content, refractive index, extinction coefficient, and surface charge density of the film decrease. At an ammonia flow rate of 3000 sccm, which is similar to the conventional SiNx, the extinction coefficients for the two films were similar. This led to an emitter dark saturation current density (Joe) of 404 fA/cm2 for the two films on 45 Ohm/ emitters. However, a stack passivation of SiO2/SiCxNy on an 80 Ohm/ emitter resulted in an emitter dark saturation current density of 95 fA/cm2, which is enough to provide a good surface passivation for high efficiency solar cells. An energy conversion efficiency of 17.4% was obtained for a 149 cm2 textured Czochralski screen-printed solar cell with this stack passivation. For a 156 cm2 nontextured multicrystalline silicon, with only SiCxNy and a 45 Ohm/ emitter, we obtained 14.9% efficiency.