Characteristics of TaSixNy thin films as gate electrodes for dual gate Si-complementary metal-oxide-semiconductor devices

Reactively sputtered TaSixNy films have been investigated as gate electrodes for dual gate Si-complementary metal-oxi e-semiconductor devices. The as-deposited TaSixNy films were amorphous over a wide range of compositions. After annealing at 1000degreesC, Ta30Si33N37 film became crystalline, however Ta26Si28N52 film remained amorphous. The x-ray photoelectron spectroscopy shows a significant increase of Si-N bonding in the TaSixNy films with increasing N content. The presence of Si-N bonds is attributed to cause the amorphous nature of the high N containing TaSixNy films. The work functions of TaSixNy films were extracted by capacitance-voltage analysis. The work function values for TaSixNy films with varying N contents range from 4.26 to 4.35 eV after forming gas annealing at 400 degreesC for 30 min, suggesting that TaSixNy films have work functions appropriate for n-type metal-oxide-semiconductor devices. However, it was observed, after 1000 degreesC anneals, that the work function of TaSixNy films increased to -4.8 eV. We believe that the mechanism that causes the work function to increase is the formation of a Ta-disilicide layer at the inter-face of the electrode and the dielectric. Current-voltage characteristics of the TaSixNy gates showed lower gate leakage compared to the TaSix gates, due to the retarding formation of an interface layer in the TaSixNy/SiO2/p-Si structures. (C) 2004 American Vacuum Society.