Development and Scale Up of Precursors for Atomic Layer Deposition
Research in the Barry lab has been following two independent streams of precursor development: NHC complexes of group 11 amides for the deposition of metal films, and development of designed iminopyrrolidinates to quench low temperature thermal decomposition mechanisms. A series of novel N-heterocyclic carbene (NHC)-containing copper(I) amides have been shown to be viable ALD precursors. This family is represented by the compounds 4,5-dimethyl-1,3-diisopropyl-imidazol-2-ylidene copper hexamethyldisilazide, which was synthesized and structurally characterized. For an ALD precursor, a vapour pressure of 1 Torr is considered to be viable for precursor delivery in a commercial tool. The thermal chemistry of this series of compounds was studied by thermogravimetric (TG) analysis, and found to be reasonably volatile compounds: among the family of compounds, a vapour pressure of 1 Torr was produced at temperatures between 125°C and 165°C. The compound 1 produced 1 Torr of vapour pressure at 131 °C. Compound 1 also had no residual mass in the TG and showed long-term stability at temperatures as high as 130 °C. Copper metal with good resistivity was deposited using 1 by plasma-enhanced atomic layer deposition. The precursor demonstrated self-limiting behavior indicative of ALD, and gave a growth rate of 0.2 Å/cycle.