I. Ion-Solid Interactions with Markers. II. Oxidation Phenomena in Silicides and Aluminides

Citation

Kim, Sung Joon (1988) I. Ion-Solid Interactions with Markers. II. Oxidation Phenomena in Silicides and Aluminides. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/av5j-xe20. https://resolver.caltech.edu/CaltechETD:etd-11062007-081348

Abstract

This thesis consists of two main topics: a) study of ion-solid interactions, or "ion mixing", by markers and b) oxidation phenomena of metal silicides and gold aluminides.

There are many well-developed theories describing atomic collisions in solids. However, the basic aspects of ion mixing, such as the magnitude of atomic relocation and the formation of certain compounds, have proven elusive to theoretical understanding. We have conducted experiments that provide a data base for an understanding of atomic motion during ion irradiation. In these experiments the so-called "marker" sample configuration was used, where a layer of about 10 Å of an impurity is buried in an otherwise homogeneous medium. When the sample is irradiated, the layer is dispersed. This irradiation-induced spreading of marker layer is measured by backscattering spectrometry. The different amount of spreading in different samples under various experimental conditions yields insight into the atomic displacement mechanisms.

Three major mechanisms are known to contribute to the atomic displacements during ion irradiation on solids: a) collisional displacements, b) intermixing by a thermal spike and c) radiation-enhanced diffusion (see chap. 1 for definitions). At low temperatures only the first two mechanisms play role in the atomic displacements; at high temperatures radiation-enhanced diffusion is significant. The irradiations were conducted at temperatures ranging from 7 to 500 K using Kr and Xe ions of energies from 0.3 to 1.0 MeV. The matrix atoms studied range in mass from C to Au. The marker impurities used go from Al to Bi.

At low temperatures, the effects of material properties and parameters such as -vmass and cohesive energy of the target, damage energy density in the material, thermal diffusivity, and heat of mixing are investigated. At high temperatures, the effects of the defect creation rate in the material by irradiation and the diffusion mechanisms are studied.

The second part of the thesis deals with oxidation phenomena The oxidation of Co and Ni disilicides on SiO₂ substrates is investigated. The motivation of this work is the desire to produce an elemental metal film encapsuled by a protective insulating SiO₂ layer for low resistivity interconnection in VLSI circuits. Electrical, chemical, and morphological properties of the oxidized films were investigated as a function of oxidation duration under various oxidation conditions and Si content in the silicide films.

The oxidation of Au aluminides was also investigated. Gold bonds on aluminum metallization for semiconductor devices are under constant physical and chemical changes due to joule heating, electromigration and outgassing of packaging materials. Water and oxygen are some of the main undesirable components in the outgassing of packaging material. We investigate the effects of 50, 70, and 100° C water and wet oxidation at 773 K on thin films of Al and of all five existing binary Au-Al compounds (AuAl₂, AuAl, AU₂Al, Au₅Al₂, and Au₄Al) on SiO₂ substrates.

Thesis Files