Radiation hardness comparison of MOS capacitors using tungsten polycide and cobalt polycideas gate electrode materials

We investigate the radiation hardness of metal-oxide-semiconductor (MOS) capacitors with tungsten polycide (WSi/sub x/) and those with cobalt polycide (CoSi₂) as gate electrode materials. CoSi₂ has been considered as a gate/contact material for MOS devices in 0.18 μm integrated circuit fabrication due to its low resistivity and good thermal stability. However, we found that MOS capacitors with a CoSi₂ gate electrode exhibited an increase in radiation-induced interface trap density shift of more than one order of magnitude, and more than eighteen times larger in radiation-induced flatband voltage shifts compared with those with the WSi/sub x/ gate electrode, after 1 Mrad Co/sup 60/ /spl gamma/-ray irradiation under no applied bias.