Contactless mapping of lifetime and diffusion length scan map of minority carriers in silicon wafers

The lifetime of minority carriers in crystalline silicon wafers is determin ed by means of the contactless microwave phase-shift technique, when the su rfaces of the samples are passivated using an iodine aqueous solution of po lyvidone. The stability of the passivation is sufficient in order to obtain a lifetime scan map with spatial resolution of 50 mu m, using a thin coaxi al cable which directs 9.4 GHz microwaves onto the investigated samples and a fiber coupled laser diode which generates carriers in excess. In gold co ntaminated single crystals an acceptable correlation is found between the l ifetime scan maps and the local concentrations of gold determined by deep l ever transient spectroscopy applied to an array of aluminium silicon diodes . For multicrystalline silicon wafers containing large densities of differe nt extended crystallographic defects, a good correlation is obtained betwee n the lifetime maps and the diffusion length maps obtained by the light bea m induced current technique. Both the maps display the same features of ext ended crystallographic defects and are in agreement with optical micrograph s of the scanned samples after they have been chemically etched.