Investigation of electrically active defects in Si-based semiconductor structures

Abstract

A group of several methods for detailed investigation of electrically active defects (EAD) and their properties in insulator-semiconductor (IS) and metal-insulator-semiconductor (MIS) structures has been developed. It consists of different ways of analyzing EAD including precision measurements of local electrophysical properties of IS structures, mapping of defects in IS structures by means of nematic liquid crystals (NLC), application of scanning electron microscopy (SEM) in electron beam induced current (EBIC) mode for localization of EAD in the semiconductor of MIS structures. Local electrophysical measurements are carried out by using dynamic unsteady-state current–voltage characteristics (DUCVC) and their modifications which have higher sensitivity to detection of generation processes in MIS structures as compared with ordinary capacitance–voltage characteristics. Depth distributions of bulk generation lifetime of minority carriers in semiconductors, obtained by the DUCVC method, reflect normalized EAD profiles near the IS interface. The NLC method is nondestructive and makes possible to analyze lateral distribution of defects with high local conductivity in insulating films. It was shown that in the case of thin SiO 2 films on silicon EAD at semiconductor surface are also revealed by the NLC method. As a result determination of EAD coordinates opens possibility for further detailed investigation of separate EAD properties by the DUCVC method using local mercury probe 5 μm in size. Special MIS gated p–n junctions have been used for mapping of EAD with high recombination velocity in semiconductor under the metal or polysilicon gates. Combination of the described methods was applied for investigation of local EAD properties of Si-based structures, which are used for fabrication of integrated circuits. The influence of gettering on EAD concentration in Si and SiO 2 has been investigated.