Susan L. Cohen

Mechanisms of copper chemical vapor deposition

The mechanism of copper chemical vapor deposition from Cu(II)bis‐hexafluoroacetylacetonate [Cu(hfac)2] and 1,5‐cyclooctadiene‐Cu(I)‐hexafluoroacetylacetonate (COD‐Cu‐hfac) has been determined. The results explain the different processing conditions required for deposition from the precursors. Both molecules react at room temperature on Ag to form a similar Cu(I)‐hfac surface intermediate. Subsequent reaction of the COD‐Cu‐hfac fragment can lead to loss of the organic ligands leaving clean Cu. In contrast, for Cu(hfac)2, the presence of one extra surface hfac requires the addition of an external reductant to produce a ligand‐free Cu film.

Selectivity in copper chemical vapor deposition

The fundamental surface chemistry underlying selectivity in copper chemical vapor deposition (CVD) from COD‐Cu‐hfac and Cu(hfac)2 has been determined. Both electronic and chemistry contributions strongly influence the precursor reactivity on oxide as compared to metal surfaces. These results have important implications regarding the role of surface preparation and cleaning for initiating and maintaining selective deposition.

Surface analysis studies of copper chemical vapor deposition from 1,5‐cyclooctadiene‐copper(I)‐hexafluoroacetylacetonate

The chemical vapor deposition of Cu from the 1,5‐cyclooctadiene copper(I) hexafluoroacetylacetonate (COD‐Cu‐hfac) precursor has been studied using x‐ray photoelectron spectroscopy, high‐resolution electron energy‐loss spectroscopy, and in situ reactor growth. Cu films are reproducibly grown on a Ag seed layer with resistivities of 2.0–2.4 μΩ cm with a deposition rate of 30–80 A/min at 180 °C. After deposition, the surface of the Cu is covered by some adsorbed precursor fragments and residual hydrocarbon. Upon heating in vacuum, the precursor desorbs leaving behind about 3–5 A carbon. Incorporation of carbon, oxygen, and fluorine into the bulk of the Cu films is limited to 1% or less. The reactive sticking coefficient of the COD‐Cu‐hfac molecule during deposition is estimated to be ∼ 1 × 10−3 at 180 °C. Cu grows somewhat selectively on metal relative to oxide surfaces at 180 °C. Room temperature adsorption of the precursor on Ag leads to dissociation of the molecule and loss of the COD ligand. The stoichio...

Characterization of the surface oxidation and magnetic properties of MnFe thin films

There is considerable interest in understanding the surface oxidation reactions of transition‐metal alloys with potentially useful magnetic properties. These reactions can either lead to passivation or corrosion of the magnetic film under normal atmospheric conditions. Little is known, however, about the surface oxidation reactions of MnFe. In the present study, thin films of MnFe prepared by dc magnetron sputter deposition onto Si, Cu, and Ni80Fe20 have been characterized magnetically by superconducting quantum interference device (SQUID) and vibrating sample magnetometer measurements and their surface chemistry has been followed by angle resolved x‐ray photoelectron spectroscopy and ellipsometry. The reactivity of the clean MnFe surface with O2, H2O, and N2 was investigated. The interaction of MnFe with O2 proceeds by preferential oxidation and surface segregation of Mn oxide. The final products of oxidation after a 66 000‐L exposure are MnO and Fe2O3, in agreement with thermodynamic considerations. Com...