Fabrication and characterization of n-Si/SiON/metal gate structure for future MOS technology

We present the fabrication and characterization of n-Si/SiON/metal (metal–oxide–semiconductor (MOS)) gate structure with silicon oxynitride (SiON) as insulating layer and different metal films such as Aluminium (Al), Titanium nitride (TiN) and Platinum (Pt) as gate electrode. Cheung’s method has been used to calculate the barrier height (ϕ_bo) and ideality factor (η) of these three different diodes varying in different metal electrode types. The interface state density (D_it), dielectric constant (k), effective oxide charge (Q_eff) and work function (Φ_m) have also been extracted from the capacitance–voltage (C–V) experimental data. A gradual improvement in various parameters for n-Si/SiON/metal gate stack has been observed after annealing the SiON film under controlled conditions e.g., TiN metal gate electrode shows good electrical characteristics with improved ideality factor (1.7) and barrier height (0.69 eV) over the Al and Pt/Ti gate electrodes due to the modified interface chemistry. The extracted Φ_m for TiN gate electrode is ~ 5.13 eV which is in good agreement with the previous results reported in literature. The value of D_it reduces, whereas the value of k increases upon post deposition annealing (PDA) for all the metal gate electrodes. An increase in D_it causes an increase in the η for Al and Pt/Ti metal gates as compared to TiN metal gate. The influences of PDA process on the electrical characteristics of n-Si/SiON/metal MOS diodes have also been investigated for as-deposited and annealed MOS diode.