Atomic layer deposited TaC(y) metal gates: Impact on microstructure, electrical properties, and work function on HfO(2) high-k dielectrics

作者：Triyoso D H^*; Gregory R; Schaeffer J K; Werho D; Li D; Marcus S; Wilk G D

来源：Journal of Applied Physics, 2007, 102(10): 104509.

DOI：10.1063/1.2817620

TaC(y) has been reported to have the appropriate work function for negative metal-oxide semiconductor metal in high-k metal-oxide field-effect transistors. As device size continues to shrink, a conformal deposition for metal gate electrodes is needed. In this work, we report on the development and characterization of a novel TaC(y) process by atomic layer deposition (ALD). Detailed physical properties of TaC(y) films are studied using ellipsometry, a four-point probe, Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). RBS and XPS analysis indicate that TaC(y) films are near-stoichiometric, nitrogen free, and have low oxygen impurities. Powder XRD spectra showed that ALD films have a cubic microstructure. XPS carbon bonding studies revealed that little or no glassy carbon is present in the bulk of the film. Excellent electrical properties are obtained using ALD TaC(y) as a metal gate electrode. Well-behaved capacitance-voltage characteristics with ALD HfO(2) gate dielectrics are demonstrated for TaC(y) thicknesses of 50, 100, and 250 A. A low fixed charge (similar to 2-4x10(-11) cm(-2)) is observed for all ALD HfO(2)/ALD TaC(y) devices. Increasing the thickness of ALD TaC(y) results in a decrease in work 4.77 to 4.54 eV) and lower threshold voltages.

• 出版日期2007-11-15