Thermal stability studies for advanced Hafnium and Zirconium ALD precursors

The use of thermogravimetric analysis (TGA) to determine evaporation rates under a variety of conditions is employed to determine initial temperature regimes where decomposition may occur. More detailed studies using Nuclear Magnetic Resonance (NMR) are then conducted at fixed temperatures over a prolonged time period with regular monitoring to establish degradation effects more accurately. Our studies show similar trends between both Hf and Zr materials with the Zr derivatives less stable in all cases. Operation temperatures required to achieve suitable vapour transport in the case of MeCp2ZrMe2 have been found to lead to catastrophic decomposition after a relatively short time thus negating the usefulness of this precursor in a production environment. All other sources were deemed safe to employ under standard process conditions.