Temperature effect on charge density of silicon nitride films deposited in SiH4–NH3–N2 plasma

Abstract Improved surface passivation of silicon nitride films requires a high positive charge density. A neural network model of SiN charge density was used to investigate temperature effects on charge density. For a systematic modeling, the deposition process was characterized by means of a face-centered Box Wilson experiment. Prediction performance of neural network model was optimized by using genetic algorithm. Interestingly, charge density was varied little with the substrate temperature regardless of SiH 4 flow rates. Charge density variation was not sensitive to [Si–H] variation. A pronounced temperature effect at higher NH 3 flow rate or lower radio frequency (rf) power was attributed to a relatively large [N–H]. For NH 3 or rf power variation, charge density was strongly correlated to [N–H]/[Si–H].