Hydrogen‐related memory traps in thin silicon nitride films

The internal photoelectric‐effect technique in combination with multiple internal reflection measurements has been used for quantitative measurement of impurities and defect‐related traps in the thin Si₃N₄ insulating film of a metal–nitride–oxide–semiconductor device, and their correlation with film processing conditions. The hydrogen content in the film showed an increase of approximately 3% for a decrease of deposition temperatures from 950 to 700 °C and corresponding increase in trapped electron density from 0.55×10¹⁸ to 2.0×10¹⁸ cm³. The multiple internal reflection measurements indicated that the variation in the hydrogen content in the Si₃N₄ film was predominantly related to a variation in hydrogen‐to‐silicon bonding while the hydrogen bonded to nitrogen was relatively constant. The results suggest that hydrogen, in addition to excess silicon, and perhaps other structural defects, plays a role in determining trapped electron densities in silicon nitride.