Metal gate CMOS capacitors were formed using a metal interdiffusion process at RIT. First silicon dioxide was grown on the wafer. The first metal, titanium, was deposited. Then the second metal, nickel, was deposited. The nickel was selectively etched away from the top of half the capacitors to form the different work function regions. The wafers were then heated so that the nickel diffused into the titanium. The work function could not be determined of the metal gates because the MOS capacitors did not function correctly. The capacitance stayed constant across the allowable gate voltage. This is likely due to contamination of the silicon surface from spin on dopant.
"Fabrication of Interdiffused Dual work Function Metal Gate CMOS Capacitors,"
Journal of the Microelectronic Engineering Conference: Vol. 12:
1, Article 13.
Available at: https://repository.rit.edu/ritamec/vol12/iss1/13