Abstract
Stress in dry, thermal oxides grown on silicon in the thickness range of about 20 nm to 110 nm has been studied as a function of exposure to ionizing radiation, and other processing conditions. The average total stress, measured at room temperature, for dry thermal oxides grown at 1000°C with 0.0% 
was found to be 
. For thermal oxides grown at this same temperature with 4.5% 
, the average total stress was slightly lower at 
. At 800°C, however, the presence of 
had little or no effect on the total stress. Oxides grown with 0.0% 
and 4.5% 
at 800°C both exhibited average total stresses of 
. Annealing of the thermal oxides for extended periods of time in Ar at the growth temperatures resulted in significant stress relaxation. The nature of this relaxation suggests a viscous flow mechanism. None of the as‐grown or annealed thermal oxides showed any change in stress after exposure to 
rad 
ionizing radiation (
x‐rays). This irradiation resulted in a copious increase in net fixed positive charge up to a plateau level of about 1012/cm2. Together with the annealing data mentioned above, this indicates strongly that the formation of fixed positive charge does not represent the breaking of strained bonds, as has been postulated by others. It was found that approximately 50% of the wafers used to grow thermal oxides plastically deformed during oxidation at 800°C and 1000°C. Furthermore, about 75% of the oxidized wafers that were annealed at their growth temperature plastically deformed as a result of one or more of the high‐temperature processing steps.