Date of Award

1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Gregory L. Griffin

Abstract

We have studied the kinetics of copper chemical vapor deposition (CVD) for interconnect metallization using hydrogen (H$\sb2$) reduction of the Cu(hfac)$\sb2$ (copper(II) hexafluoroacetylacetonate) precursor. Steady-state deposition rates were measured using a hot-wall microbalance reactor. For base case conditions of 2 Torr Cu(hfac)$\sb2$, 40 Torr H$\sb2$, and 300$\sp\circ$C, a growth rate of 0.5 mg cm$\sp{-2}$ hr$\sp{-1}$ (ca. 10 nm min$\sp{-1}$) is observed. Reaction order experiments suggest that the deposition rate passes through a maximum at partial pressure of 2 Torr of Cu(hfac)$\sb2$. The deposition rate has an overall half-order dependence on H$\sb2$ partial pressure. A Langmuir-Hinshelwood rate expression is used to describe the observed kinetic dependencies on Cu(hfac)$\sb2$, H$\sb2$, and H(hfac). Based on the rate expression a mechanism is proposed in which the overall rate is determined by the surface reaction of adsorbed Cu(hfac)$\sb2$ and H species. Additionally, the role of alcohols in enhancing the deposition rate has been investigated. Addition of isopropanol results in a six fold enhancement to yield a deposition rate of 3.3 mg cm$\sp{-2}$ hr$\sp{-1}$ (ca. 60 nm min$\sp{-1}$) at 5 Torr of isopropanol, 0.4 Torr Cu(hfac)$\sb2$, 40 Torr H$\sb2$, and 300$\sp\circ$C. Ethanol and methanol give lower enhancements of 1.75 and 1.1 mg cm$\sp{-2}$ hr$\sp{-1}$, respectively. A mechanism based on the ordering of the aqueous pK$\sb{\rm a}$ values of the alcohols is proposed to explain the observed results. Lastly, we have built a warm-wall Pedestal reactor apparatus to demonstrate copper CVD on TiN/Si substrates. The apparatus includes a liquid injection system for transport of isopropanol-diluted precursor solutions. At optimized conditions of precursor and substrate pre-treatments, we have deposited uniform films of copper on TiN/Si substrates at an average deposition rate of 3.0 mg cm$\sp{-2}$ hr$\sp{-1}$ (ca. 60 nm min$\sp{-1}$).

ISBN

9780591723793

Pages

185

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