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.