Transition Metal Complex Chemistry

Precursor Design for the Chemical Vapor Deposition of Metals

The semiconductor industry knows the advantages of copper diketonates for chemical vapor deposition to produce uniform thin films of copper on substrates such as TiN, TaN, TiSiN or SiO2. To increase their volatility currently all widely used precursors contain fluorine, which has been shown to have a potential to contaminate the resulting copper films. But not only fluorine is known to increase the volatility, but also silicon containing functional groups. We developed a wide range of silicon containing metal diketonates and also developed a corresponding chemical vapor deposition process.

The ligands were synthesized via coupling of a dithiane with a bromoketone or by Claisen type condensation. The ligands were characterized by NMR, UV/VIS, IR, MS and elemental analysis. The complexes were characterized by crystallography, DSC, TGA, UV/VIS and MS. Thin films of copper were deposited using a standalone CVD stainless steel CVD reactor equipped with mass flow controllers, a resistive heater and vacuum gauges. Usual deposition parameters included a hydrogen flow of 20 sccm and a deposition temperature of a 300 °C. The copper films were characterized by four point probe, AES, XRD, RBS, SEM, FIB, TEM and XPS.
This work was collaborative with the NYS Center for Advanced Thin Film Technology.


Catalyst Systems for the Syndiotactic Polymerization of Styrene

The syntheses, characterization and applications of cyclopentadienyltitanium triflate and bistriflimide complexes have been investigated. To pursue these aims the preparation of and structural investigations on a series of titanium triflate derivatives as well as the corresponding bistriflimide complexes of titanium has been explored. Our search for an alternative to the triflate ligand led us to the bistriflimide anion (N(SO2CF3)2 or NTf2). This anion appears to satisfy the criteria for a good, weakly-coordinating anion; i.e., it has a low overall charge of -1, a high degree of charge delocalization, good solubility and kinetic stability. This anion also has the potential for diversity with the use of its homologues or unsymmetrical imides such as the perfluoromethylsulfonyl perfluorobutylsulfonylimide reported by DesMarteau. The application of these complexes as catalysts lead to the efficient syndiotactic polymerization of styrene.