PSG Flow in High-Pressure Steam

Abstract

Phosphosilicate glass (PSG) flow in high-pressure gas ambient is examined. PSG flow is enhanced with increasing pressure of steam ambient. Annealing temperature can be reduced by 80°C or the phosphorous concentration can be decreased by about 2 wt% by increasing the steam partial pressure from 0.95 kg/cm² to 8.5 kg/cm² from the viewpoint of planarization. The increase in pressure of dry N₂ or dry O₂ as ambient gas is not effective in enhancing PSG flow. The newly developed LSI (large scale integration) circuit process where a silicon nitride film underlies the PSG film is effective in preventing the oxidation of polysilicon and substrate during the flow in high-pressure steam. The FTIR result indicates that PSG films annealed in high-pressure steam absorb much less water than PSG films annealed in dry O₂.