Crystalline and Electrical Properties of Mictamict TiSiN Gate Metal–Oxcide–Semiconductor Capacitors

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The crystal structures and electrical characteristics of Ti–Si–N metal–oxide–semiconductor (MOS) gate electrodes in the mictamict state, which is a comprehensive term referring to amorphous structures both with and without nanocrystals, were investigated. By increasing the N2 concentration of the sputtering ambient, the nitrogen (N) content of the Ti–Si–N films increased and consequently the Ti–Si–N films did not crystallize. At a N2 concentration of more than 3.0%, the N content of the films was almost constant at about 53%, which indicates that all Ti and Si atoms deposited in the form of TiN and Si3N4, respectively. In such Ti–Si–N films with a saturated N content, only 2–3-nm-grain-size nanocrystallites formed, which were embedded in amorphous layers even after post-deposition annealing (PDA) above 900 °C. At the same time, with increasing N2 concentration of the sputtering ambient, the change in the film resistivity after the PDA became smaller and the capacitance equivalent thickness (CET) fluctuation gradually ceased to occur. The work function of the mictamict Ti–Si–N gate electrodes, which were deposited in 5.0% N2 ambient and annealed at 500 °C, was determined to be 4.6 eV.
2008-04-25