Diffusion Control Techniques for TiN Stacked Metal Gate Electrodes for p-Type Metal Insulator Semiconductor Field Effect Transistors

We have investigated a polycrystalline silicon (poly-Si)/chemical vapor deposited titanium nitride (CVD-TiN) stacked structure as a metal gate with a high-k for p-type metal insulator semiconductor field effect transistors (p-MISFETs). A divided-CVD method provided an appropriate effective work function (4.9–5.2 eV) on HfSiON for p-MISFETs. However, the deposition of poly-Si on CVD-TiN films shifted the effective work function to a midgap (~4.6 eV), and Ti, Hf, and Si diffused into poly-Si/CVD-TiN/high-k structures during poly-Si deposition. Then, we found that an increase in the deposition temperature of CVD-TiN films and the insertion of a physical vapor deposited (PVD)-TiN film between the poly-Si and CVD-TiN layers are effective in suppressing these diffusions. In particular, the insertion of the PVD-TiN film provided an appropriate effective work function of 4.9 eV. Therefore, we found that the diffusion control techniques for poly-Si/TiN/high-k stacked structures are highly effective for obtaining the appropriate work function for p-MISFETs.