Accurate characterization of surface recombination velocities of silicon wafers with differential nonlinear photocarrier radiometry

The surface recombination velocity (SRV), which reflects the fundamental characteristics of surface defects of semiconductor wafers, is an important parameter in evaluating the quality of surface passivation and electrical performance of surface devices. In conventional photocarrier radiometry (PCR) used for characterizing the electronic transport properties of electronically thick silicon wafers, the rear SRV usually cannot be determined directly due to the relatively low sensitivity of PCR signal to the rear SRV. On the other hand, the determination of front SRV is also very sensitive to the experimental measurement error, especially the measurement error of instrumental frequency response, which is not always easy to be accurately measured in the experiment. In this paper, the front and rear SRVs of silicon wafers are extracted simultaneously with high accuracy by a differential PCR via multi-parameter fitting of the experimental frequency dependences of amplitude ratio and phase difference of PCR signals obtained from the regular measurements and measurements with wafers being flipped respectively to a corresponding differential nonlinear PCR model. The comparison between the front and rear SRVs determined by the conventional and differential PCRs indicates that the differential PCR is highly accurate for the simultaneous determination of the front and rear SRVs of silicon wafers.