In-Line Copper Contamination Monitoring Using Noncontact Q ­ VSPV Techniques

Abstract

A novel approach for the sensitive detection and unequivocal identification of trace amounts of copper introduced into p-type silicon and its oxide during high-temperature processing is discussed. Noncontact surface voltage and surface photovoltage (SPV) measurements are employed to determine the impact of copper impurities on distinct bulk silicon, interface, and oxide properties. For oxidized p-type Si, the characteristic copper signature comprises an increased oxide charge and a pronounced decrease in the minority carrier recombination lifetime upon optically induced formation of copper precipitates in the silicon bulk. During illumination, out-diffusion of copper to the silicon-oxide interface occurs simultaneously with precipitation and results in an increased interface trap density. For a complete overview on the distribution of the copper impurity on the various defect states before and after optical activation, the recombination lifetime, the interface trap density, and the total oxide charge have to be monitored. © 2004 The Electrochemical Society. All rights reserved.