Film stress-related vacancy supersaturation in silicon under low-pressure chemical vapor deposited silicon nitride films

Abstract

The effect of stress in silicon nitride films, deposited by the low-pressure chemical vapor deposition process, on the point defect concentrations in silicon has been studied. The stress level in the nitride film is varied by controlling the ratio of flow rates of reactant gases R=fSiH2Cl2/fNH3, from 1/6 to 6. The stress in the nitride film is tensile and its magnitude increases with decreasing R. During anneals at 1100 °C in Ar with a high stress in the nitride, phosphorus diffusion in silicon is retarded, antimony diffusion is enhanced, and extrinsic stacking faults shrink faster than with a low stress. These results suggest that a vacancy supersaturation and a self-interstitial undersaturation exist under the nitride and that the deviation from the equilibrium point defect concentrations are closely related to the stress level in the silicon nitride film. From the phosphorus junction profiles with varying shape width, an effective vacancy diffusivity of 3×10−10 cm2/s has been obtained.