SURFACE DAMAGE IN PROCESSED SILICON

The surface and sub-surface damage induced by processing is a major co ncern for the Si advanced sub-micron technologies. The interest in cha racterization techniques which allow monitoring of the modifications o f the surface electrical properties of the Si wafers is, therefore, gr owing. The surface recombination velocity is the parameter more direct ly correlated to the recombination activity of the surface, and, there fore, more sensitive to the changes in the surface electronic properti es, but its measurement, up to now, has not been assessed enough. We h ave measured the surface recombination velocity by two independent met hods: the photoelectromagnetic effect (PEM) and the electron beam indu ced current (EBIC) mode of a scanning electron microscope (SEM), in or der to test the reliability of the techniques and to correlate the mac roscopic value obtained by PEM with the local values obtained by EBIC. In this work we report the results obtained on two types of processin g damage: the surface modifications induced by rapid thermal annealing at 750 and 1050 degrees C of n-type 10 Omega cm silicon and the damag e induced in the Si substrate by a SiCl4 dry etching of a 5500 Angstro m thick polysilicon him grown on n-type 1 Omega cm CZ silicon. In both cases a very good agreement between the PEM and the EBIC values has b een obtained. The correlation between the surface velocity recombinati on variations detected by EBIC and PEM and the data already obtained f rom the C-V and I-V characteristics and lifetime measurements has been used to understand the type and the distribution of the process induc ed damage.