Structure Control of Polycrystalline Silicon Films on Glass Substrates and Their Properties

A novel technique for fabricating polycrystalline silicon thin films on glass substrates with controlling grain orientations was developed. Random, (220) or (400) preferential orientations were attained by controlling the source gas mixing ratio SiF4/H2. A remote type plasma chemical vapor deposition system was used with gas mixtures of SiF4, H2, and Ar. The randomly oriented films were obtained under a very large mixing ratio, greater than 90/5 sccm, while the (220) oriented films were obtained under a small gas flow rate ratio, less than 60/10 sccm. It was found that the (400) preferential oriented films were obtained at higher SiF4/H2 ratios (90/10 sccm). The (400) oriented crystallites have excellent crystalline regularity compared to that of the (220) oriented films; however, their electron mobility is lower than that of the (220) oriented films. The small Hall mobility of the (400) oriented films is thought to originate from large orientation fluctuation and less passivated dangling bonds at the grain boundaries. (Author)