In-process control of Co silicide formation by RTA

Abstract

The results of in-situ monitoring of laser reflectivity during Rapid Thermal Annealing (RTA) of cobalt layers on silicon are presented. 120 nm thick cobalt films were deposited. The wafers were implanted with silicon to ion beam mix the interface. Annealings at 820°C were conducted, to correlate sample reflectivity changes with the formation of particular silicide phases. It is shown that changes in reflectivity of the above samples, correspond to the appearance at the surface of a particular silicide phase. A new concept, that is “software sensing”, is also presented. It uses an advanced algorithm calculating in real-time the transfer function of the processor/wafer system. Results about the use of this algorithm to detect the formation of a particular silicide phase are presented.