## LSU Historical Dissertations and Theses

#### Title

Chemical Vapor Deposition of Copper Films.

1997

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### Department

Chemical Engineering

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$\sp{-1}$).

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