Analytical tools for the characterization of power devices

Since power devices require an electrically active, thick n-type silicon la yer with high resistivity and a large area, their electrical characteristic s are extremely sensitive to contamination. If transition metals diffuse in to the wafers during the high temperature steps required for device fabrica tion, an uncontrolled increase in leakage Current and on state voltage can be observed. Further more, current filamentation and instabilities of the e lectrical data can occur. As a consequence of the low doping level of the n -base, the blocking voltage and the failure rate due to cosmic radiation ar e sensitive to contaminating atoms acting as donors or accepters. To obtain information about the sources and the extent of the contamination, a conta mination check was performed after each high temperature step. Moreover, th e dependence of the carrier lifetime on temperature and injection level was analyzed for typical operation conditions of power devices. The results pr oved to be important in finding ways of keeping contamination and silicon d efect densities as low as possible and to ensure that good electrical data with adequate stability could be obtained. (C) 2000 The Electrochemical Soc iety. S0013-4651(00)05-045-X. All rights reserved.