Laminated metal gate electrode with tunable work function for advanced CMOS

Abstract

This paper presents a novel technique for tuning the work function of metal gate electrodes. Laminated metal gate electrodes consisting of 1/spl sim/3 ultra thin (/spl sim/10 /spl Aring/) layers of Ta, TaN, Ti, TiN, Hf or HfN and bulk metal nitride gate electrodes were deposited on SiO/sub 2/, HfO/sub 2/ or HfON, followed by RTP annealing to evaluate their thermal stability. Our results show that the work function of the laminated metal gate electrodes is significantly different from their bulk electrodes counterpart. Through lamination, a TiTaN/sub x/ alloy gate is formed which exhibits NMOS compatible work function (4.35 eV) with good thermal stability up to 900/spl deg/C. Laminated metal gates consisting of 3 components exhibit pMOS compatible work function (5,0/spl sim/5.2 eV) after 1000/spl deg/C annealing and this value remains unchanged after subsequent thermal processing. Possible mechanism responsible for work function tuning using laminated gates is discussed.