Studies of thin-film growth of sputtered hydrogenated amorphous silicon

Abstract

The role of a number of physical and chemical sputtering effects in the thin film growth of hydrogenated amorphous silicon has been investigated. Charged particle bombardment was found to affect the film microstructure more than neutral particle bombardment. The roles of electron and Ar + ion bombardment have been identified. Control of the hydrogen bonding is accomplished through bias sputtering. Positive substrate bias (electron bombardment) favors hydrogen in the 2000 cm − mode. Negative substrate bias (Ar + ion bombardment) favors hydrogen in the 2100 cm −1 mode. However, the density of states in the middle of the gap and the recombination properties do not depend on the mode of the hydrogen bonding, but rather on the total amount of hydrogen in the film. Experimental evidence is produced that the SiH x compound formation moves progressively from the substrate to the target as the hydrogen pressure in the discharge increases. Evidence of the importance of chemical etching of the growing film by H-plasma is produced.