John successfully defended his masters thesis on August 25, 2009

TITLE:
Atomic Layer Deposition of TiO₂ on Si and GaAs Substrates Using TDMATi and H₂O Precursors

ABSTRACT:
Atomic Layer Deposition (ALD) has emerged as an effective method for depositing high-quality, conformal thin films with thickness control on the monolayer level. With a homemade hot-wall, flowtube ALD reactor, TiO₂ films were deposited on Si and GaAs substrates using TDMATi and H₂O precursors. Spectroscopic ellipsometry (SE) measurements show an optimal growth rate at a furnace temperature of 200°C. SE was also used to measure the index of refraction of the films. XPS analysis indicates that the films have very little bulk contamination and are slightly over-oxidized. FTIR and XRD were used to examine film crystallization. RBS measurements of the coverage of Ti atoms were conducted over a comprehensive range of film thicknesses. AFM produced topographical images of the film surfaces that indicate RMS values of 3-4% of the film thickness.

Interfacial oxide layers are an undesired consequence of many metal-oxide/semiconductor stacks. Analysis of the films deposited on GaAs substrates focused on the interfacial native oxide layer. Films that were grown on top of a 25Å native oxide layer consumed the oxide during deposition almost completely. This “self-cleaning” effect has been attributed to methylamino ligands of the TDMATi precursor molecules.