Low-resistivity ZrNx metal gate in MOS devices

Zirconium nitride (ZrN) is presented as a metal gate candidate for future MOSFET components. Low resistivity (70 μΩ cm) of the ZrNx thin film and n-type work function (4.0 eV) of the ZrNx/SiO2/p-Si MOS capacitor structure are achieved by reactively sputter depositing the ZrNx at low nitrogen gas flows. The resistivity of the ZrNx film is nearly un-affected by RTP annealing up to 600 °C whilst the work function increases slightly to 4.2 eV. By depositing the ZrNx at higher nitrogen gas flow, the work function is found to increase to a value of 4.65 eV, closer to mid-gap of Si. Further increase to 4.9 eV occurs after RTP annealing at 600 °C, which is almost suitable for pMOS components. At the same time, the resistivity increases to about 300 μΩ cm. These initial results make ZrNx a promising metal gate in a gate last process, where the thermal budget is kept low.