Charge trapping and interface states in hydrogen annealed HfO 2–Si structures

Abstract

Metal–oxide–semiconductor (MOS) capacitors based on HfO 2 gate stacks with Al and TiN gates are compared to study the effect of the gate electrode material to the properties of insulator–semiconductor interface. The structures under study were shown to contain interface trap densities of around 2 × 10 11 cm −2 eV −1 for Al gate and up to 5.5 × 10 12 cm −2 eV −1 for TiN gate. The peak in the surface state distribution was found at 0.19 eV above the valence band edge for Al electrode. The respective capture cross-section is 6 × 10 −17 cm 2 at 200 K. The charge injection experiments have revealed the presence of hole traps inside the dielectric layer. The Al-gate structure contains traps with effective capture cross-section of 1 × 10 −20 cm 2, and there are two types of traps in the TiN-gate structure with cross-sections of 3.5 × 10 −19 and 1 × 10 −20 cm 2. Trap concentration in the structure with Al electrode was considerably lower than in the structure with TiN electrode.