PERSISTENT PHOTOCONDUCTIVITY AS A TOOL FOR MONITORING OXIDE CLUSTER CONCENTRATION IN SILICON-WAFERS

Many semiconductor devices rely on the so-called ''denuded zone'' of t he silicon wafers. It is therefore essential to have a simple means to monitor the purity of this zone. It will be shown that persistent pho toconductivity (PPC) can be related to the oxygen concentration in the wafer, and thus can be used to evaluate the quality of the denuded zo ne. A test structure was designed and the PPC measurements performed. They clearly indicate that the intensity of the PPC effect is roughly proportional to the amount of oxygen clusters in the wafer. (C) 1998 E lsevier Science Ltd. All rights reserved.