Obic Modelling, Numerical Computation and Measurement of Silicon Parameters in The Presence of Defects

Abstract

AbstractIn recent years the use of non-destructive techniques involving the generation of minority carriers by means of an electron beam (EBIC) or a LASER beam (OBIC) have proven to be useful in the study of the electrical properties of process-induced defects in bulk silicon. The development of a model and algorithm to obtain the diffusion length L, the surface recombination ratio S and the defect-increased recombination, by collecting the LASER-Beam-Induced-Current scanning the sample using a Schottky diode is presented. First a model to obtain the probability of collection of an electron-hole-pair generated by a point source is derived. The finite size of the collecting junction, L and S make the solution of the diffusion equation available only in integral form; it is therefore necessary to perform a numerical integration. Then a least-squares algorithm for identifying L and S in the case of bulk silicon without defects is obtained. Lastly the effect of a finite size generation volume and the increased recombination due to a line defect is taken into account. The effect of S and the distance of the defect from the surface on the signal contrast is analysed. This determines the information depth of the collected signal. It is shown how a high value of surface recombination ratio reduces the contrast and therefore impairs the possibility of detecting low-strength defects.An analysis of the experimental results is performed and they are found to be in good agreement with the model.