Detection of low-level copper contamination in p-type silicon by means ofmicrowave photoconductive decay measurements

Abstract

In order to achieve a better understanding of the behaviour of copperin p-type silicon, studies of the recombination of copper were carriedout by the microwave photoconductive decay measurement method (μPCD) using high-intensity bias light. It was observed that in the presence of smalloxygen precipitates, high-intensity light could be used to activate precipitation ofinterstitial copper. It is suggested that high-intensity light changes the charge state ofinterstitial copper from positive to neutral, which enhances the precipitation.The precipitation follows Ham’s kinetics and results in an increase in therecombination rate, which is detectable even with very low copper concentrations.This phenomenon can be used to detect low levels of copper contamination by theμPCD method. In addition, it was observed that out-diffusion as well as in-diffusionof interstitial copper could be affected by an external corona charge. Thus, it issuggested that copper atoms do not form stable bonds at the Si–SiO2 interfaceafter out-diffusion from bulk silicon.