Contactless optical evaluation of processing effects on carrier lifetime in silicon

Contactless, optical modulation of free-carrier absorption has been used to identify minority-carrier lifetime degradation associated with both novel and common very large scale integrated circuit processing steps in p-type silicon wafers. Carrier lifetime degradation and a corresponding increase in surface recombination velocity was found to be associated with the silicon etchants ethylenediamine-pyrocatechol-water (EDP) and potassium hydroxide (KOH), prolonged exposure to hydrofluoric acid (HF and BHF), and ion bombardment associated with a variety of plasma etching steps. Knowledge of process-induced lifetime degradation obtained by this technique may offer significant input into the development of high-yield very large scale integrated circuit processes.