Thermal stability of sio2/cosi2/polysilicon multilayer structures improved by cavity formation

The electrical and structural stabilities of SiO2 /CoSi2 /polysilicon multilayer structures have been improved by 75 °C using 40 keV nitrogen atoms implanted in silicon before silicidation at a dose of 5E15/cm2. During the reaction process, small cavities have been created within the polysilicon layer and simultaneously pushed ahead by the poly/amorphous silicon interface created by the implant and moving toward the surface. The process has ended up with a band of big cavities located at the silicide/silicon interface. They have an average diameter of 35 nm and are preferentially located at the silicide grain boundaries. Sheet resistance measurements (Rs), Rutherford backscattering spectroscopy and transmission electron microscopy analyses have shown that these interfacial cavities have prevented the agglomeration process to occur up to 1025 °C 30 s annealing process and have reduced the driving force for silicide boundary grooving.