Effect of boron dose and post-thermal budget on electrical properties of MOS-capacitors with a W/WN_x/poly-Si_1-xGe_x gate stack

We investigated the effect of boron dosage and post-thermal budget on the electrical properties such as capacitance-voltage (C-V), gate leakage current-voltage (I-V), and charge-to-breakdown (Q_BD) of metal oxide semiconductor (CMOS) capacitors with W/WN_x/poly-Si_1-xGe_x gates stack. The C-V curve of the MOS-capacitors with the W/WN_x/poly-Si_0.4Ge_0.6 stack had a lower flatband voltage (V_FB) and showed less gate depletion effect (GDE), compared with that of the W/WN_x/poly-Si_0.8Ge_0.2 stack due to the decrease of gate electrode work function and the increase of dopant activation rate with the increase of Ge content, respectively. Although the I-V curves of MOS-capacitors with W/WN_x/poly-Si_1-xGe_x gates stack exhibited similar behaviors regardless of Ge content, the beginning of conduction in the I-V curves accelerated with the increase of Ge content due to the decrease of the gate electrode work function. The Q_BD of W/WN_x/poly-Si_0.4Ge_0.6 gates stack was much higher than that of the W/WN_x/poly-Si gates stack due to the reduced boron penetration in the gate oxide. We also found that annealing temperatures between 800 and 850°C has no influence on the electrical properties of MOS capacitors with W/WN_x/poly-Si_1-xGe_x gates stack.