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This page contains a single entry from the blog posted on August 25, 2009 10:20 AM.

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MS Defense - John Lacis

John successfully defended his masters thesis on August 25, 2009

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

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.