Copper filling contact process to realize low resistance and low cost production fully compatible to SOC devices

A copper filling contact process that does not cause any device characteristic degradation or reliability degradation is demonstrated. Optimization of the barrier layer realizes lower and small variation contact resistance with enough prevention of copper diffusion from the contact hole. Copper filling realizes a 65% reduction of contact resistance in 0.16 /spl mu/m diameter contacts and very small contact depth dependence. There is no degradation of junction leakage current and no difference in reliability characteristics compared to a conventional tungsten filling process. Gate oxide TDDB and hot carrier injection test results are shown. Another benefit of the copper filling process is lower production cost. Dual damascene structures for contact and metal-1 reduce process steps by 40%. Furthermore, investment for tungsten filling machines is saved because BEOL processes can be switched to copper filling for 0.13 /spl mu/m generations. Especially, in a 300 mm wafer fabrication line, the decrease in the varieties of machines will be significant.