Advances in silicon surface characterisation using light beam injection techniques

The development of new integrated circuits (IC) technologies demands a deeper knowledge of the effects of wet wafer cleaning treatments on microchemical, structural and physical surface properties for better device engineering procedures. In this paper, we report and discuss the results of measurements dealing with the effect of conventional hydrochloric acid peroxide mixture (HPM), ammonia peroxide mixture (APM) and dilute hydrofluoric acid (DHF) treatments on the surface recombination rate, measured using the light beam induced current (LBIC) technique in planar configuration and on surface microroughness by scanning tunnelling microscopy (STM). The results indicate that both APM and HPM produce a stable surface, whose recombination rate (around 103 cm s−1) remains constant for days after the cleaning. In contrast, the DHF treatment results in a low surface recombination rate (less than 10 2 cm s−1), which evolves, after an induction period of several hours, to steady-state conditions characterised by surface OH termination and a recombination rate of around 103–104 cm s−1. STM images and their derived power spectra are in agreement with the interpretation of the changes in surface recombination rates before and after DHF treatments.