Application of combinatorial methodologies for work function engineering of metal gate/high-κ advanced gate stacks

This paper uses combinatorial methodologies to investigate the effect of TaN-AlN metal gate electrode composition on the work function, for (TaN-AlN)/Hf-Si-O/SiO₂/Si capacitors. We demonstrate the efficacy of the combinatorial technique by plotting work function for more than thirty Ta_1-xAl_xN_y compositions, with x varying from 0.05 to 0.50. The work function is shown to continuously decrease, from about 4.9 to about 4.7 eV, over this range. Over the same range, oxide fixed charge is seen to go from about -2.5 × 10¹² cm^-3 to about zero. The work functions reported here are about 0.1 eV higher than in a previous study, but are still about 0.2 eV smaller than required for PMOS device applications.