The annealing effect on work function variation of WNxCy films deposited by remote plasma atomic layer deposition

Abstract

Tungsten-nitrogen-carbide (WNxCy) thin films were investigated as the metal gate of complementary metal-oxide-semiconductor (CMOS) devices. WNxCy thin films were deposited by employing the remote plasma atomic layer deposition (RPALD) using a bis(tert-butylimido) bis (dimethylamido) tungsten (BTBMW) precursor and hydrogen plasma as a reactant. The growth rate of the WNxCy films was about 0.12nm/cycle. X-ray diffraction (XRD) analysis indicated that the films consisted of a mixture of tungsten carbide and tungsten nitride phases. The atomic force microscope (AFM) analysis further confirmed that the WNxCy film surfaces deposited by RPALD were smooth. In addition, the chemical bonding state analysis showed that the WNxCy films consisted of WN, WC, and WO phases. To measure the work function of the WNxCy film, a MOSCAP (metal oxide semiconductor capacitor) stack was fabricated and the flat band voltage was measured by current-voltage (C-V) measurements. A WNxCy work function value of 4.91eV was suitable for p-MOS and the work function of the WNxCy films varied depending on the annealing treatment, and was higher than the work function of the as-deposited WNxCy film..