Thermal Stability Enhancement of Nickel Monosilicides by Addition of Iridium

We fabricated thermal evaporated 10 nm-Ni/(poly)Si and 10 nm-Nill nm-Ir/(poly)Si films to investigate the thermal stability of nickel minosilicide at the elevated temperatures by rapid annealing them at the temperatures of 300 similar to 1200 degrees C for 40 seconds. Silicides for salicide process was formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester is used for sheet resistance. Scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An x-ray diffractometer and an auger depth profile scope were used for phase and composition analysis, respectively. Nickel silicides with iridium on single crystal silicon actives and polycrystalline silicon gates showed low resistance up to 1200 degrees C and 800 degrees C, respectively, while the conventional nickel monosilicide showed low resistance below 700 degrees C. The grain boundary diffusion and agglomeration of silicides led to lower the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.