EFFECT OF ULTRAVIOLET-LIGHT IRRADIATION ON NONCONTACT LASER MICROWAVE LIFETIME MEASUREMENT

An ultraviolet (UV) irradiation effect on minority-carrier recombination lifetime measured by a noncontact laser/microwave (LM) method is investigated for silicon wafers with native oxide. After UV irradiation, the surface recombination velocity greatly decreased resulting in the increase in the effective recombination lifetime (tau(eff)). The effect disappears rapidly with time after the irradiation, and tau(eff) recovers to the initial value after several minutes at room temperature. Since the UV irradiation process is noncontact and nondestructive, the irradiation is proposed to minimize the surface effect of sample, in turn, to obtain the bulk lifetime (tau(b)) with a noncontact LM lifetime measurement method.