Gate MOSCAP Studies on Electroless Deposited Nickel Boron as Word Line Candidate Metal for Future Scaled 3-D NAND Flash

Abstract

3-D NAND Flash has become the workhorse for non-volatile memory based storage. It is therefore important to develop solutions that keep NAND scaling in a sustainable path with respect to cost and performance. The memory cells in 3-D NAND are addressed by horizontal word lines (WLs) that are stacked vertically. With each technology node, the WL metallization, performed using CVD / ALD tungsten metal with a thin TiN barrier, poses a challenge in terms of WL cavity filling and WL resistance. A wet nickel boron (NiB) electroless and barrierless deposition is proposed for the next generation 3-D NAND Flash technology. Here, we investigate the memory behavior using metal / high-k / ONO / Si (MHONOS) capacitors while the resistivity and tensile stress were studied on blankets. Results indicate that the program and erase performance of the NiB devices are comparable to that of the W/TiN reference. Furthermore, the tensile stress is two times lower for the NiB integration.