End-point detection during the realization of deep P+zones by Al thermomigration

A new method for creating deep junctions extending through the whole thickness of a wafer has recently been demonstrated. Applications are in the field of high power devices. The method uses the thermomigration of melted Al/Si droplets in silicon and allows function electrical isolation. This process requires a specific Rapid Thermal Processing equipment. The purpose of this paper is to discuss the control of the process by end-point detection, that is the optical in situ detection of the emergence of the melted alloy once thermomigration is completed. For this purpose, in situ laser reflectometry and video observation have been used. Experimental results are presented and discussed.