Tracer Evaluation of Hydrogen in Steam-Grown SiO[sub 2] Films

Abstract

Silicon wafers were oxidized in capsules at 1000°C with 1 atm of tritium‐tagged steam. The oxide films formed were investigated by conventional tritium counting techniques. The hydrogen profile suggested a complementary error function type in‐diffusion of water, giving a . The profile had a minimum value at around 600Aå oxide thickness. The location of this value was independent of original oxide thickness. Following this minimum, the concentration again increased as the interface was approached. The concentration of hydrogen near this interface was greater for the thinner oxide films. This observation led to the conclusion that either a hydrogen‐containing intermediate is formed by the reaction between water and silicon and that the concentration of this intermediate is dependent on the oxidation rate or that a transition region exists in the oxide film which permits segregation of the diffusant near the interface. Thermal biasing experiments followed by surface charge measurements and autoradiograms showed that mobile positive charge was present in the oxide near the interface. However, this mobile charge was not hydrogen or a hydrogen‐containing species. Out‐diffusion experiments yielded an activation energy of 15.7 kcal/mole for the tritium species.