Improving metal step coverage with Ar sputtering

Ar sputtering is applied to taper contact side-walls; experimental results show that metal step coverage is significantly improved as compared to conventional wet+dry contact etching without reflow. The sputtering improves the metal step coverage by rounding off the sharp corners on contact side-walls without contact CD loss nor degrading device performance. This approach is extremely useful for shallow junction formation and titanium or tungsten silicide processes which can not tolerate high temperature reflow. The depth limitation for 0.8 μm contacts on metal step coverage improvement is found to be around 1.0 um