Real impact of W/WNx/Poly-Si gate stack in volume production of high density DRAM

We have investigated the feasibility for volume production of high density DRAMs employing a polymetal gate stack(W/WNx/Poly-Si). Especially, based on the fully matured production level, DRAM devices gated with polymetal stack were directly compared to those with conventional polycide stack (WSix/Poly-Si) with respect to the impact of gate etch post-cleaning and selective oxidation. Also, we proposed the best solution to overcome the critical issues related to tungsten (W) process, still keeping comparable product performance to conventional polycide gate stack.