Characterization of nickel silicide transition behavior using non-contact CGS metrology

Advanced millisecond annealing technologies are being implemented to enable scaling of silicidation of Ni for contacts. There are several aspects of the millisecond annealing process that must be optimized in order to minimize defects and improve yield. One critical aspect is that NiSi agglomeration must be suppressed at higher annealing temperatures. Typically, the onset of agglomeration can be detected by microscopic observation, phase analysis or electrical measurement. This paper describes an alternate approach using the Coherent Gradient Sensing (CGS) interferometer to provide a fast, non-contact method for quickly identifying the nickel silicide agglomeration threshold. Wafers with blanket Ni films were annealing using laser spike annealing (LSA) at various temperatures. The CGS technique is demonstrated to be sensitive to changes in surface morphology associated with the nickel silicide phase transitions and agglomeration and the results correlate to more conventional metrology approaches.