The rutile stoichiometric phase of RuO 2 , deposited via reactive sputtering, was evaluated as a gate electrode for Si-PMOS devices. Thermal and chemical stability of the electrodes was studied at annealing temperatures of 400 C and 600 C in N 2 . X-ray diffraction patterns were measured to study grain structure and interface reactions. Very low resistivity values were observed and were found to be a strong function of temperature. Electrical properties were evaluated on MOS capacitors, which indicated that the workfunction of RuO 2 was compatible with PMOS devices. Excellent stability of oxide thickness, flatband voltage and gate current as a function of temperature was also found. Breakdown fields were also measured for the samples before and after annealing.
Metal–oxide–semiconductor capacitors were used to study the interaction of Hf and Zr gate electrodes on SiO2, ZrSixOy, and ZrO2. A large reduction in the SiO2 equivalent oxide thickness accompanied by an increase in the leakage current was observed with Hf and Zr electrodes when subjected to anneal temperatures as low as 400 °C. The reduction in electrical thickness as observed from the capacitance–voltage measurements was attributed to the combination of (a) physical thinning of the SiO2 and (b) formation of a high-K layer. A severe instability of Zr and Hf electrodes was also observed on ZrSixOy and ZrO2 dielectrics. This behavior of Zr and Hf gates was attributed to high negative enthalpy of oxide formation and high oxygen solubility resulting in the reduction of the gate dielectric and subsequent oxygen diffusion to the gate electrode.
In this letter, the Fowler–Nordheim tunneling in TaSixNy/SiO2/p-Si structures has been analyzed. The effective barrier height at the metal–oxide interface was extracted by Fowler–Nordheim current analysis. The barrier height was found to increase with increased annealing temperature. The barrier height was correlated with the extracted work function from capacitance–voltage analysis. This indicated that the work function of TaSixNy films changes under high temperature annealing from 4.2∼4.3 eV after 400 °C anneals to ∼4.8 eV after 900 °C anneals. We believe that the mechanism that causes the work function to increase is the formation of a Ta-disilicide layer at the interface between the electrode and the dielectric.
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