maboudianlab - John Kluth

Alumnus - Ph. D.

Ph.D. in Chemical Engineering, University of California, Berkeley, 1997

B.S. in Chemical Engineering, Georgia Institute of Technology, 1993

gjkluth (at) worldnet.att.net

Current Position:

Senior Device Engineer

Advanced Micro Devices

One AMD Place

P.O. Box 3453, MS 49

Sunnyvale, CA 94088

Structure and Stability of Surface Passivation Layers on Semiconductor Materials (Ph.D. Thesis Abstract)

The structure and stability of passivating layers on silicon surfaces have been examined on the molecular level using the methods of surface science. Hydrogen-terminated surfaces were prepared through wet chemical treatment with ammonium fluoride. The oxidation of these surfaces was studied using high resolution electron energy loss spectroscopy (HREELS), which showed that oxidation occurred through oxygen insertion in silicon backbonds, while the hydrogen termination remained intact. Oxygen was observed in both the surface layer and bulk layers, suggesting that initial oxidation was not restricted to layer-by-layer growth. Because the surface did oxidize with time, other passivating treatments, specifically self-assembled monolayers, were examined.

The thermal stability of alkylsiloxane monolayers on oxidized Si(100) was studied in vacuum. Using HREELS it was found that the monolayers were stable up to 740 K. Above that temperature, they began to decompose through cleavage of C-C bonds, resulting in a reduction in chain length. The thermal stability of alkyl monolayers, which form directly on silicon without requiring an oxide layer, was also examined. These monolayers were stable to 620 K, significantly lower than the alkylsiloxane monolayers. Desorption was accompanied by the appearance of Si-H bonds, suggesting that desorption took place through a hydrogen elimination reaction.

The thermal behavior of these two different monolayers highlighted the importance of bonding between the surface and the chains. The bonding of alkylsiloxane monolayers was examined in more detail by forming them on both SiO2 and Si3N4. It was found that cross linking between adjacent head groups was critical to the formation of high quality monolayers. Bonding between the chains and the surface was of secondary importance, but played a key role in the initial stages of growth, when nucleation occurred.

The chemical stability of alkylsiloxane monolayers on oxidized silicon was also examined through exposure in vacuum to atomic hydrogen (deuterium). Initially, the H/D exchange reaction occurred readily, then slowed due to steric effects. In addition, it was proposed that etching and cross linking of the chains occurred. The molecular-level understanding developed in this work can be used to make rational improvements in the application of these passivating layers.

Ph.D. Thesis

Structure and Stability of Surface Passivation Layers on Semiconductor Materials (1993)

Advisors: Prof.'s Roya Maboudian