Interface reactions at TiN/HfSiON gate stacks: Dependence on the electrode structure and deposition method

摘要

We systematically investigated intrinsic and extrinsic thermal reactions at TiN/HfSiON gate stacks. The formation of an ultrathin TiO₂ interlayer was found to be an intrinsic reaction at the metal/insulator interface, but growth of SiO₂ underlayers between HfSiON and Si substrates, which determines the electrical thickness of metal-oxide-semiconductor (MOS) devices, depends on the structure and deposition method of the gate electrodes. Physical vapor deposition (PVD) grown TiN electrodes covered with W overlayers exhibited excellent thermal stability at up to 1000?°C. Formation of ultrathin TiO₂ interlayers reduced gate leakage current (I_g), and growth of the oxide underlayer was suppressed by less than a few angstroms even for 1000?°C annealing. In contrast, we found that halogen impurities within CVD-grown metal electrodes enhance interface SiO₂ growth, resulting in deterioration of equivalent oxide thickness (EOT) versus I_g characteristics of the gate stacks.