PHOTON STIMULATED OXIDATION OF SILICON (SURFACE PHYSICS, SPECTROSCOPIC ANALYSIS, SEMICONDUCTOR, LASER OXIDATION, THERMAL)

This research employed visible (2.4-2.7 eV) and ultraviolet (4-6.4 eV) light to selectively probe atomic level process mechanisms possibly operative during silicon oxidation.;Within a given photon energy regime, light stimulation concurrent with typical dry thermal oxidation processing enhanced the oxide growth rate in direct proportion to the absorbed photon flux. Enhancement was driven by photon-generated excess electrons rather than holes, it increased with decreasing processing temperature, and was sensitive to silicon crystal orientation and sample thickness.;In the visible regime, optical and thermal enhancement components were differentiated. These depended on light power density level, shifting toward a thermal effect as that level increased. An oxidation rate constants analysis revealed numerous process kinetic features, particularly demonstrating how much more the photon flux stimulated parabolic compared to linear domain kinetics, plus how, surprisingly, silicon crystal orientation affected that parabolic domain activity. Pulsing the photon flux decreased enhancement somewhat over an equivalent flux of continuous stimulation, while spatially layering light-on versus light-off segments during thermal oxide growth affected the resulting enhancements.;In the ultraviolet regime, several photon energies were "spectroscopically" employed to reveal both electronic and molecular activity contributions to silicon oxidation kinetics. Normalized to the visible stimulation level, enhancement increased 10X for photon energies exciting electrons from the silicon to silicon dioxide conduction band, and by an additional 30X for higher photon energies which stimulated molecular oxygen dissociation.;Finally, an Electron-Active Oxidation Process Scenario (EAOPS) is presented. Its main supposition, evolving from key experimental results, is that collisional dissociation of molecular oxygen occurs near the oxidizing interface region in response to a hot electron flux emitted from the silicon out into the silicon dioxide. The kinetics associated with this reaction correlate well with thermal oxide growth. The EAOPS may help explain several currently unresolved though important phenomena associated with silicon oxidation such as very thin oxide growth and the charged-versus-neutral oxidant controversy. From a more general photochemical perspective, implications from this research readily carry over to photonic stimulations associated with other surface and interface reactions such as plasma processing and rapid thermal annealing.