5652
Chem. Mater. 2006, 18, 5652-5658
Articles Reactive Deposition of Conformal Ruthenium Films from Supercritical Carbon Dioxide Adam O’Neil and James J. Watkins* Departments of Chemical Engineering and Polymer Science and Engineering, UniVersity of Massachusetts, Amherst, Massachusetts 01003 ReceiVed January 19, 2006. ReVised Manuscript ReceiVed July 11, 2006
High-purity Ru films were deposited from supercritical carbon dioxide onto the native oxide of Si wafers and onto Ta films supported on Si wafers using a batch, cold wall deposition reactor. Ru(0) and Ru(II) precursors were effective at substrate temperatures between 175 and 300 °C and pressures between 20 and 25 MPa. Hydrogen-assisted deposition of Ru from triruthenium dodecacarbonyl (Ru3(CO)12), tris(2,2,6,6-tetramethyl-heptane-3,5-dionato)ruthenium (Ru(tmhd)3), and bis(2,2,6,6-tetramethyl heptane3,5-dionato)(1,5-cyclooctadiene)ruthenium (Ru(tmhd)2cod) proceeded readily to yield highly reflective thin films with resistivities as low as 22 µΩ-cm for a 33 nm thick film. H2-assisted depositions using ruthenocene were not successful on oxide surfaces at temperatures up to 300 °C, but proceeded readily on Au. Thermal depositions from (Ru3(CO)12) yielded reflective, but highly resistive, films. Excellent step coverage of high-purity films was achieved within 200 nm × 300 nm trenches on patterned tantalumcoated surfaces and within 2 µm × 30 µm and 300 nm × 1.2 µm via structures on etched silicon wafers by H2-assisted deposition using Ru3(CO)12 and Ru(tmhd)2cod, respectively. Analysis by X-ray diffraction and X-ray photoelectron spectroscopy indicated that the films were polycrystalline and free of oxygen contamination.
Introduction The preparation of conformal Ru films is of broad interest for applications in microelectronics including electrodes for dynamic random access memory (DRAM), nonvolatile ferroelectric memory (FeRAM), and potentially as conducting diffusion barriers in Cu interconnect structures for integrated circuits. Each of these applications requires conformal step coverage in high aspect ratio features. Additional integration requirements include low deposition temperatures (
