Deposition and characterization of thin films for applications in ULSI fabrication

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Wang, Qi

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When the ever-shrinking microelectronic device dimensions scale below 100 nm, introducing new material and processing technologies are necessitated to overcome forbidding obstacles in both front-end and back-end manufacturing processes. This dissertation first addresses the deposition of an Al/Al2O3 cermet film as a potential thermal resist material for electron beam projection lithography. The films were deposited by reactive sputter deposition and their transformations were investigated by irradiation with a single 1064 nm laser pulse in ambient air and 10−2 Torr vacuum. Irradiation in vacuum led to re-distribution of components within the first ~35 nm beneath the surface. Irradiation in air increased the concentration of Al2O3 in the same region. Based on a model calculation, the observed transformations were interpreted as a result of local heating and, in air, as accompanying thermal oxidation. Second, a novel in-situ laser annealing system was developed for real time kinetic analysis on surface chemistry and thin film properties. A continuous wave CO2 infrared laser was coupled to a surface analysis system equipped for x-ray photoelectron spectroscopy and ion scattering spectroscopy. The capability is illustrated by using real time XPS and ISS to measure the reduction kinetics of a thin copper oxide (Cu2O) film. Third, research efforts were focused on deposition and characterizations of a thin ruthenium film as a new copper diffusion barrier for ultra-large scale integrated circuit (ULSI) interconnect. A thermal chemical vapor deposition route using Ru3(CO)12 was developed to form pure, uniform, and smooth Ru films on Ta and low resistivity films on SiO2. Measured using XPS and ISS and assuming smooth films, a 2.5 nm Ru film fully covers underlying Ta and SiO2. Unlike Ta, the Ru film exhibits excellent wettability by Cu even when the Ru surface is contaminated with small amounts of oxygen. A 4 nm Ru film and a 2.9 nm Ru/0.6 nm Ta composite film are effective copper diffusion barriers under 60 minutes annealing at 623 K in H2(10%)/N2 ambient.