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We report a flat band voltage instability of a p+ polycrystalline-Si (poly-Si)/Al2O3/n-Si metal–oxide–semiconductor (MOS) system due to boron penetration. The flat band voltage shift of the p+ poly-Si/Al2O3/n-Si MOS capacitor determined by capacitance–voltage measurement was ∼1.54 V, corresponding to a p-type dopant level of 8.8×1012 B ions/cm2 as the activation temperature increased from 800 to 850 °C. Noticeable boron diffusion into the n-type Si channel was also observed by secondary ion mass spectroscopy with activation annealing above 850 °C. Incorporation of an ultrathin (∼5 Å) silicon oxynitride interlayer between Al2O3 and Si was effective in blocking B penetration, reducing the flat band shift to ∼90 mV.

This work demonstrates the close relationship between device scaling and the threshold voltage variation (ΔV th ) of random telegraph noise (RTN) in high-κ and metal gate (HK / MG) stacks. Statistical analysis clarifies that high temperature forming gas annealing can suppress the RTN ΔV th . And properly annealed HK FETs have smaller RTN ΔV th than SiON FETs, due mostly to fewer traps and partly to thinner inversion thickness in HK / MG stacks. Consequently, the influence of RTN on HK / MG gate stacks is less than that of random dopant fluctuation in the 22 nm generation. However, RTN may pose a difficult challenge for the 15 nm generation. In addition to the scaling dependence, we also find that characterizing hysteretic RTN behaviors due to RTN dependence on bias is essential to determine whether the observed RTN has an impact on SRAM operation or not.

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Work function and thermal stability of reactive sputtered Ti1−xAlxNy films were investigated for a metal gate electrode using a metal–oxide–semiconductor (MOS) structure. It is found that the work function (ΦM) values of Ti1−xAlxNy are ranged from 4.36 to 5.13 eV with a nitrogen partial flow rate (fN2). The ΦM values of Ti1−xAlxNy films, 4.36 eV for nMOS (n-Ti1−xAlxNy) and 5.10–5.13 eV for pMOS (p-Ti1−xAlxNy), may be applicable to dual metal gate electrodes. Excellent thermal stability up to 1000 °C was obtained on SiO2 as observed by the negligible change of capacitance equivalent thickness and Al 2p core level spectra for p-Ti1−xAlxNy (y∼1.0,fN2=50%), whereas a limited stability was attained in case of n-Ti1−xAlxNy (fN2⩽40%). The p-Ti1−xAlxNy can be a good candidate for pMOS device feasibility because of good thermal stability, while the n-Ti1−xAlxNy may be applicable for nMOS gate electrode in low thermal devices using damascene gate process.