Process Integration Issues on Mo-Metal-Gated MOSFETs with HfO_2 High-k Gate Dielectrics

摘要

We investigate a MoN_x/HfO_2 gate stack fabricated using a gate-first process flow. We ideally etch the MoN_x/HfO_2 gate stack using a Cl_2-O_2 gas system. The work function variation of MoN_x gates is more than 0.7 eV. The work function can extensively cover the energy of the band gap of Si except that near the conduction band. In addition, we show issues on thermal budget from N diffusion in Mo and the reaction of Mo with HfO_2. We propose that thin-SiN insertion between MoN_x and HfO_2, and a decrease in Mo thickness are useful in fabricating process windows. On the basis of the results, we fabricate metal-oxide -semiconductor (MOS) devices and show their excellent characteristics.