Determination of technological process-induced variations of silicon recombination parameters by infrared and microwave absorption

Abstract

ABSTRACT Contactiess techniques of infrared and microwave absorption by free carriers for simultaneous determination of the setof recombination parameters by reconcilable experimental measurements and computer simulation are presented. Variations ofrecombination parameters induced by technological processes in silicon wafers are discussed.1. INTRODUCTIONCarrier lifetime is a basic electrophysical parameter of semiconductor material, which affects device characteristics andis most sensitive to defects structure. There are some well-known contactiess methods to determine earner bulk lifetime, surfacerecombination rate'3. The asymptotic relaxation time 'r averaged over the thickness ofthe sample is usually measured4'5. These methods can be easily applied when carrier lifetime is independent on the excess carrier concentration, defects of low concentration are homogeneously distributed within the depth of wafer and surfaces of wafer are passivated well. Even in wellfabricated and careflully prepared material these requirements are satisfied only in the limited range of intensities of opticalexcitation. When these conditions are nt satisfied, problems due to uncertainty of recombination parameters give rise. Lightinduced carrier concentration decay is defined by recombination on the surface and within the bulk as well as redistribution ofcarriers due to diffusion. Thus, simultaneous determination of diffusion constant (D), surface recombination velocity (s) andbulk lifetime (tb) is required. The control of crystal growth and device structure fabrication processes induced defects, theirtransformation by technological treatments is important to govern the performance of semiconductor devices.