Low-resistivity ZrN_x metal gate in MOS devices

摘要

Zirconium nitride (ZrN) is presented as a metal gate candidate for future MOSFET components. Low resistivity (70 μΩ cm) of the ZrN_x thin film and n-type work function (4.0 eV) of the ZrN_x/SiO_2/p-Si MOS capacitor structure are achieved by reactively sputter depositing the ZrN_x at low nitrogen gas flows. The resistivity of the ZrN_x film is nearly un-affected by RTP annealing up to 600℃ whilst the work function increases slightly to 4.2 eV. By depositing the ZrN_x 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℃, which is almost suitable for pMOS components. At the same time, the resistivity increases to about 300 μΩ cm. These initial results make ZrN_x a promising metal gate in a gate last process, where the thermal budget is kept low.