Variable Interface Dipoles of Metallated Porphyrin Self-Assembled Monolayers for Metal-Gate Work Function Tuning in Advanced CMOS Technologies

This paper presents a technique for continuous tuning of the metal-gate work function (Phi(metal)) using self-assembled monolayer (SAM) of metallated porphyrins. Porphyrin SAM was prepared on SiO2 followed by Al evaporation to form MOS capacitors (MOSCAPs). The variation in the dipole moment achieved by changing the central metal ion (Zn, Cu, Ni, and Co) in metallated porphyrins has been shown as a way to modify the gate work function. Thermal gravimetric analysis (TGA) on Zn-porphyrin shows that the molecule is stable upto 450 degrees C. Temperature stability experiments on MOSCAPs show that the above method can be effectively implemented in advanced CMOS technologies involving the gate-last process.