MOCVD of platinum films from (CH3)3CH3CpPt and Pt(acac)2:: Nanostructure, conformality, and electrical resistivity

A potentially manufacturable liquid-source MOCVD process was applied to deposit platinum (Pt) films (12-140 nm) on thermally oxidized Si substrates. The deposition of Pt films was carried out at a substrate temperature of 350 degreesC by oxygen-assisted pyrolysis of complex precursors in a low-pressure, hot-wall reactor. The effects of two different metal-organic precursors, a) trimethyl methyl cyclopentadienyl platinum [(CH3)(3)CH3CPPt], and b) platinum acetylacetonate [Pt(acac)(2)], on the properties of Pt films were studied. Although the polycrystalline Pt films deposited from Pt(acaC)(2) exhibited a preferred (111) orientation with a X-ray intensity ratio of I-(111)/I-(200) = 40, the films deposited from (CH3)(3)CH3CPPt were highly (111) oriented with I-(111)/I-(200) = 270. The following properties were typical of Pt films from Pt(acaC)(2) as compared to Pt films from (CH3)(3)CH3CPPt: finer grain size (25 nm vs. 50 nm), smaller root mean square (rms) surface roughness (5 nm vs. 15 nm), and better step coverage (95 % vs. 35 %). These experimental findings indicated that growth of Pt films from Pt(acaC)(2) occurred under the kinetically-limited regime, whereas the deposition of Pt from (CH3)(3)CH3CPPt was limited by the mass transport rate. Additionally, the temperature (4.2-293 K) dependence of the electrical resistivities (p) of Pt films was measured and the electron mean free paths were estimated. It was observed that p(T) deviated from Matthiessen's rule.