Ruthenium films by digital chemical vapor deposition: Selectivity, nanostructure, and work function

Ruthenium electrodes were selectively deposited on photoresist-patterned HfO2 surface [deposited on a SiOx/Si wafer by atomic layer deposition (ALD)] by a manufacturable, digital chemical vapor deposition (DCVD) technique. DCVD of Ru was carried out at 280-320 degreesC using an alternate delivery of Bis (2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)Ru (dissolved in tetrahydrofuran) and oxygen. The as-deposited Ru films were polycrystalline, dense, and conducting (resistivity similar to20.6 muOmega cm). However, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and high-resolution electron microscopy results indicate the presence of an amorphous RuOx at the Ru grain boundaries and at the DCVD-Ru/ALD-HfO2 interface. The estimated work function of DCVD-Ru on ALD-HfO2 was similar to5.1 eV. Moreover, the equivalent oxide thickness, hysteresis in capacitance-voltage, and leakage current density at -2 V of the HfO2/SiOx dielectric, after forming gas (95% N-2+5% H-2) annealing at 450 degreesC for 30 min, were 1.4 nm, 20 mV, and 7.4x10(-7) A cm(-2), respectively. (C) 2004 American Institute of Physics.