Evaluation of silicide morphology by near-infrared-laser optical-beam-induced-current technique

We found that the near-infrared-laser optical-beam-induced-current (IR-OBIC ) technique was very useful for the evaluation of silicide morphology in ul tralarge-scale integrated (ULSI) devices. By this technique, it is possible to detect the cohesion points of silicide as two-dimensional images by sca nning a near-infrared laser from the back of the chip. The cohesion points appear as bright spots. We confirmed that the number and intensity of brigh t spots changed according to the extent of cohesion for some different samp les upon varying the silicide layer thickness or thermal treatment time aft er silicide formation. Furthermore. other experiments were performed to cla rify the image formation mechanism at cohesion points. It was demonstrated that the electromotive current wits generated upon irradiation by the near- infrared-laser, and Schottky junctions were formed at cohesion points. Thus . it wits clarified that the images obtained at cohesion points by this tec hnique are a result of the electromotive current generated due to the carri ers (electrons or holes) that are excited over the Schottky barrier formed at cohesion points. The IR-OBIC technique can be used to detect tile silici de morphology nondestructive ly without the need to remove the upper layers of the silicide layer. This study reveals a novel application of the IR-OB IC method which is a very useful technique for tile evolution of the self-a ligned silicide (SALICIDE) process or structure in future ULSIs.