MONITORING AND OPTIMIZATION OF SILICON SURFACE QUALITY

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.