Investigation of the Thermal Stability of Reactively Sputter-Deposited TiN MOS Gate Electrodes

Abstract

The effective work function of TiN, deposited by reactive magnetron sputtering, was found to be unaltered at /spl sim/5 eV after rapid thermal processing (RTP) annealing in nitrogen atmosphere at temperatures below 700/spl deg/C. However, further increase in the RTP temperature lowered the extracted work function by 0.4-0.5 eV to midgap values. In this brief, RTP anneals of TiN/SiO/sub 2//p-Si MOS capacitors were evaluated by extracting the metal gate TiN work function from capacitance-voltage measurements of MOS capacitors with multiple SiO/sub 2/ thicknesses. The RTP anneals were performed in nitrogen between 600/spl deg/C and 1000/spl deg/C for 30 s. The effective oxide charge density in the capacitors increased by a factor of five at RTP temperatures exceeding 800/spl deg/C. The resistivity seems to decrease slightly with increasing RTP temperature. The crystallographic orientation of the TiN films remain (111) after annealing up to 900/spl deg/C and is apparently not responsible for the change in work function. Analysis by X-ray photoelectron spectroscopy indicates no significant change in the binding states of titanium and nitrogen in the TiN/SiO/sub 2/ interface with increasing temperature.