Width-dependent anomalous CoSix sheet resistance change by Ti and TiN capping process

In order to minimize the circuit propagation delay, self-aligned silicide (salicide) technology has been widely used to reduce source/drain/gate spreading resistance and contact resistance. Cobalt silicide (CoSi2) is the most popular silicide material beyond 0.25 μm node as it has less line width dependence than titanium silicide (TiSi2). Cobalt on silicon with TiN capping or Ti capping has been widely applied for years and demonstrates a very promising manufacturability and scalability toward 0.1 μm and below. In this work, width-dependent sheet resistance change was studied and the anomalous sheet resistance behavior was observed to be very different for these two different capping materials. The different silicide profiles around active regions and shallow trench isolation (STI) interface were identified to be the root cause for this difference. The stress built at STI and active regions played an important role for silicide formation. Experimental results can conclude that capping material selection is very crucial for deep submicron ultralarge silicon integrated (ULSI) circuit.