Hydrogenation of multicrystalline silicon from a backside silicon nitride layer

Abstract

In order to improve multicrystalline p-type silicon wafers, the authors have used the hydrogenation technique to deposit a Si/sub 3/N/sub 4/ layer containing hydrogen on a p-type surface. Silicon nitride films have been deposited by the process of mercury-sensitized photochemical vapor deposition (photo-CVD), using a gaseous mixture of SiH/sub 4/ and NH under 253.7 nm ultraviolet light irradiation. The main advantages of this technique are the low deposition temperature (100-400 degrees C) and no radiation damage compared to the plasma-enhanced CVD method. Due to the low temperature, the Si/sub 3/N/sub 4/ film could be deposited after the metallization of solar cells, provided that the back contact is a grid. On the front surface, the Si/sub 3/N/sub 4/ layer could constitute an antireflecting coating. A deposition rate of 8 nm/min and a refractive index of about two were achieved.