Understanding effective lifetimes measured on oxidized silicon wafers with different techniques

Abstract

The interpretation of minority carrier Iifetime measurements on oxidized wafers is often difficult. Nonlinear decays in transient measurements or apparently incompatible results from different measurement techniques are observed. We present a comparison of measured results from three different techniques: photoconductance decay PCD, modulated free carrier absorption MFCA and lateral photocurrent LPC. An extended SRH formalism for the Si/SiO2, interface is used for modelling the experimental findings. With correct accounting for injection level dependent surface recombination an excellent agreement between the different methods is obtained on the basis of oxide parameters measured with MOS-techniques