Low-temperature plasma-enhanced atomic layer deposition growth of WN x C y from a novel precursor for barrier applicatio
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David W. Peters Praxair, Inc., Tonawanda, New York 14150
Eric T. Eisenbraun College of Nanoscale Science and Engineering, University at Albany, the State University of New York, Albany, New York 12203 (Received 14 July 2006; accepted 14 November 2006)
A low-temperature plasma-enhanced atomic layer deposition (PEALD) process has been developed for the growth of ultrathin WNxCy films, using a halide-free W precursor. A 32-nm-thick PEALD WNxCy film deposited using this process at 250 °C possesses a composition of W72C20N5, resistivity of ∼250 ⍀·cm, a root-mean-square (rms) surface roughness of 0.23 nm, and a thickness conformality of more than 80% on trench structures with a width of 120 nm and an aspect ratio of 11. The WNxCy films exhibited excellent thermal stability, whereby resistivity, thickness, surface roughness, and crystal structure were stable after 30 min anneals in 700 Torr, forming gas ambient at temperatures up to 700 °C. Copper diffusion barrier performance measurements show that a 9 nm thick WNxCy film could prevent copper diffusion after a 30 min anneal at 700 °C, while a 2-nm-thick film could prevent copper diffusion after a 30 min anneal at 500 °C.
I. INTRODUCTION
The continued downscaling of device dimensions has placed a high priority on the development of robust copper barrier/liner materials.1 Moreover, the associated processes used to deposit these materials need to be carried out at reduced temperatures (i.e., 99%) was vaporized in a stainless steel bubbler heated at 70 °C, and its vapor was delivered into the reaction chamber with the use of argon (99.999% pure) as a carrier gas. H2 (99.999% pure) was delivered into the reaction chamber through a separate delivery line. A 300 W RF plasma (13.56 MHz) was operated during H2 pulse step, but was turned off during the precursor pulse step and both Ar purge steps in all ALD cycles. Ar was used after each W precursor and H2 pulse to remove excess reactants inside the reaction chamber and ensure isolation of the reactants to avoid parasitic chemical vapor deposition (CVD) reactions from taking place.20 The chamber pressure was kept at 0.3 Torr during the entire
FIG. 1. Vapor pressure of (5-ethylcyclopentadienyl) dicarbonylnitrosyltungsten plotted as a function of 1/T. 704
ALD process. Blanket Si and SiO2 substrates were used in every run, and SiO2-coated Sematech pattern wafers were used in selected runs. III. CHARACTERIZATION TECHNIQUES
Film thickness was measured using cross-sectional scanning electron microscopy (CS-SEM) and x-ray reflectometry (XRR). CS-SEM was performed on a LEO 1550 field-emission scanning electron microscope (FE-SEM; Oberkochen, Germany) using a 20 keV electron primary beam and a sample current of 50 nA. XRR was performed on ultrathin (
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