The diffusion of selected transition metals in silicon during short anneals

Douglas Ray Sparks, Purdue University

Abstract

Transition metals have been known to degrade semiconductor device performance for over twenty years. While the diffusion of transition metals in silicon has been the subject of much research for a longer period of time, the observations made in this study during short anneals (5-300 seconds) suggests that the diffusion of certain transition metals in silicon can occur much more rapidly than is predicted in the literature. The objective of the current study is to gain a better understanding of the diffusion of transition metals in silicon during short anneals. Transition metals such as nickel, iron, copper, cobalt, vanadium and palladium were examined. This is the first study of the diffusion of transition metals during short anneals. Experimental techniques such as neutron activation analysis, and secondary ion mass spectroscopy, were employed to examine the low concentrations of metals in silicon ($<$10$\sp{18}$ atoms/cc). U-shaped diffusion profiles for Ca, Cu, Ni and Pd were observed for first time. Such profiles in single crystal material may indicate that amphoteric diffusion is occurring. For the first time a multi-component diffusion approach was taken towards the theoretical treatment of amphoteric diffusion. Unlike all other approaches both vacancies and self-interstitials along with the interstitial and substitutional chemical impurities are combined in the same equations. Several new applications of this study to semiconductor processing were made. This work will aid in the understanding of the behavior transition metals in silicon which should lead to improvements in semiconductor processing.

Degree

Ph.D.

Advisors

Dayananda, Purdue University.

Subject Area

Materials science

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