THE EFFECTS OF CHEMICAL, THERMAL, AND ION BEAM PROCESSING ON THE PHYSICS OF CHARGE TRANSPORT IN POLYCRYSTALLINE SILICON (GRAIN BOUNDARIES, SEMICONDUCTORS)

Charge transport in polycrystalline silicon has been studied as a function of low energy (LlkeV) ion processing utilizing both oxygen and hydrogen. As previous investigations have found H is a powerful grain boundary barrier passivant. It has been shown here for the first time that H alters the temperature power law dependence of the charge transport scattering mechanisms. Also demonstrated for the first time is that ion implanted oxygen acts as a grain boundary barrier passivant on n type Wacker polycrystalline silicon while acting to increase the barrier height on p type Wacker polycrystalline silicon. A model for this behavior of oxygen in the Wacker polycrystalline silicon is presented. Spreading resistance measurements have been used to demonstrate the existence of decreased resistivity in the vicinity of scratched and grain boundaries on p type silicon and an increased resistivity in the vicinity of the same surface distortions on n type silicon. A band structure model is presented to explain this previously undocumented phenomena.;Electron paramagnetic resonance was used to determine the paramagnetic spin center density which was found to be well correlated with grain boundary activation energy in LPCVD grown polycrystalline silicon. This demonstrates for the first time direct correlation between decrease in spin center density--due to grain regrowth--and decreased grain boundary barrier height (activation energy). Further investigation has shown the possible existence of a thermally induced oxygen donor defect center appearing after a 30 minute 725(DEGREES)C N(,2) thermal anneal which corresponds to a significant increase in grain boundary activation energy (barrier height).;Thermal cycling experiments were performed and charge transport monitored through the various cycling steps. It was found that oxygen donor formation and neutralization plays a significant role in the variation of the charge transport mechanisms. Annealing ambient (O(,2) or N(,2)) was found to have an insignificant effect upon determining the charge transport mechanism(s) in Wacker polycrystalline silicon.