We have used contactless photoconductance decay measurements to monito
r cleaning processes, surface contamination, and surface roughness. Ch
anges in surface chemistry are evidenced by a degradation (increase) i
n the surface recombination velocity (decrease in measured decay time)
. We have applied the tool to monitor cleaning effectiveness, surface
cleanliness, and roughness during tell processing. Iodine in methanol
achieves a superior passivation of Si than H in 48% HF. The measured m
inority carrier lifetime in this solution is higher than in 48% HF. We
illustrate that I-terminated silicon surfaces are more stable than H-
terminated surfaces. We confirm that deionized water is responsible fo
r the roughening of silicon surfaces. We show that NH4F is a superior
alternate clean to dilute HF.