Diffusion Studies and Defect Spectroscopy with Isotopically Controlled Semiconductors

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

This individual investigator award will fund research focussing on self- and dopant atom transport in crystalline elemental and compound semiconductors at the atomic level. Multilayer structures consisting of different stable isotopes (e.g., 28Si and 30Si) will be doped such that the equilibrium native defect concentrations remain undisturbed by the doping process. Secondary ion mass spectrometry (SIMS) will be used to measure directly and simultaneously the concentration profiles of the host crystal isotopes and the dopant atoms as a function of depth after thermal treatment for specific times. Analysis of these concentration profiles leads to a quantitative understanding of matter transport properties. Specifically, the charge states and the diffusivity of the native defects controlling the matter transport will be determined as a function of temperature and the position of the Fermi level. The knowledge gained from these studies will be used in the formation and the study of isotopically controlled semiconductor nanostructures. Neutron transmutation will allow the doping of these crystalline nano particles at ambient temperature. The basic parameters to be determined in this research effort will benefit directly the understanding of the stability of semiconductor nano particles and the advanced modeling of future generations of semiconductor devices. Graduate and undergraduate students will be intimately involved in all aspects of this research. %%% The ever increasing performance of semiconductor devices is, in large part, due to the reduction in device dimensions and the concomitant possibility to place more functions on a chip. Introducing the dopant atoms which give semiconductor devices their functionality, is reaching limits which can only be overcome by a fundamental study of dopant atom transport at atomic dimensions. Because dopant atoms move assisted by native defects such as vacancies and/or self-interstitials, it is crucial for the understanding of the atomic transport to measure simultaneously the motion of the dopant and of the host lattice atoms. This can be achieved for the first time through the use of crystalline multilayer structures consisting of different isotopes of the host semiconductor crystal. This individual investigator award will support research using secondary ion mass spectrometry to measure dopant and isotope concentration profiles after exposure of the semiconductor structures to elevated temperatures for specific times. The results of these studies will form the basis for the advanced understanding of both matter transport parameters required for processing of future semiconductor devices and the stability of semiconductor nano particles. The graduate and undergraduate students performing this research will obtain the training required for challenging positions in the semiconductor industry and in academia. ***