Single-beam thermowave analysis of ion implanted and laser annealed semiconductors

Abstract

A single-beam thermowave technique is described, based on a two-frequency modulation of the laser beam used for both excitation and detection. The differential frequency content of the laser beam is used as a measure of the photothermal response. This technique provides frequency conversion to the low-frequency region and, to a certain degree, phase sensitivity without applying the lock-in detection method. By using a modulation set-up comprising two acousto-optical modulators and by applying a balance detector arrangement, an intermodulation content of 10-7 for zero response and a noise of 10-7 Hz-1/2 could be achieved. The new single-beam technique yields substantial evidence in the field of ion implantation and laser annealing of semiconductors, such as the dose of implanted species, annealing threshold, the defects generated by the ultrafast solidification and the homogeneity of the laser beam applied for irradiation.