Effects of humidity on nano-oxidation of silicon nitride thin film.

Effects of humidity on nanometer-scale oxidation of silicon nitride thin film using atomic force microscope in contact mode are studied at various values of relative humidity (RH) (30-70%). The shape of oxide protrusion is determined by the concentration of oxyanions under the tip apex and oxyanions diffusion laterally on the surface. At low RH (<or= 60%), the kinetics of silicon nitride oxidation has a logarithmic relationship to oxide height versus oxidation time. The threshold time decreased and initial oxidation rate increased simultaneously as humidity increased because a high concentration of oxyanions at the oxide/silicon nitride interface was generated. When a high sample voltage (9-10 V) is applied at high RH (>or= 60%), the effective electric field is decreased because of the electron being trapped in the oxide and oxyanions accumulating on the oxide surface.