Thermally Stable NiSi Gate Electrode with TiN Barrier Metal for High-Density NAND Flash Memory Devices

Abstract

As a gate word line, Ni silicide with a TiN barrier metal has been investigated and demonstrated for NAND flash memory devices with a 24 nm technology node. In addition, physical vapor deposition (PVD) and atomic layer deposition (ALD) TiN layers are compared as diffusion barrier metals. Results show that the carbon impurity in the TiN barrier layer may be one of the factors that affect the quality of the barrier layer at 900 °C. It is also found that Ni diffusion and the discontinuity of Ni silicide induced by the grain growth of polycrystalline silicon (poly-Si) are effectively suppressed by the PVD TiN layer of 20 nm inserted into the control gate. As a result, no significant sheet resistance increase is observed even at a narrow gate line of 24 nm width, and its thermal stability is maintained up to 900 °C.