Persistent photoconductivity as a tool for monitoring oxide clusters concentration in silicon wafers

Many semiconductor devices rely on the so called “denuded zone” of the silicon wafers. It is therefore essential to have simple means to monitor the purity of this zone. It will be shown that persistent photoconductivity (PPC) can be related to the oxygen concentration in the wafer, and thus can be used to evaluate the quality of the denuded zone. A suitable 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