Surface damage in processed silicon

The surface and sub-surface damage induced by processing is a major concern for the Si advanced sub-micron technologies. The interest in characterization techniques which allow monitoring of the modifications of the surface electrical properties of the Si wafers is, therefore, growing. The surface recombination velocity is the parameter more directly correlated to the recombination activity of the surface, and, therefore, more sensitive to the changes in the surface electronic properties, but its measurement, up to now, has not been assessed enough. We have measured the surface recombination velocity by two independent methods: the photoelectromagnetic effect (PEM) and the electron beam induced current (EBIC) mode of a scanning electron microscope (SEM), in order to test the reliability of the techniques and to correlate the macroscopic value obtained by PEM with the local values obtained by EBIC. In this work we report the results obtained on two types of processing damage: the surface modifications induced by rapid thermal annealing at 750 and 1050 °C of n-type 10 Ω cm silicon and the damage induced in the Si substrate by a SiCl4 dry etching of a 5500 Å thick polysilicon film grown on n-type 1 Ω cm CZ silicon. In both cases a very good agreement between the PEM and the EBIC values has been obtained. The correlation between the surface velocity recombination variations detected by EBIC and PEM and the data already obtained from the CV and IV characteristics and lifetime measurements has been used to understand the type and the distribution of the process induced damage.