Summary: We successfully developed the first reductive thermal ALD process for elemental gold using AuCl(PEt3) and (Me3Ge)2DHP as precursors. Highly conductive and pure gold films could be deposited at moderate temperatures of 160–180 °C. The process was proven to work on multiple substrates, although with a clear difference in nucleation that was the most favorable on a Ru surface and the least favorable on Al2O3. Furthermore, the reaction mechanism was studied and found to proceed stepwise, as expected based on the literature. The combination of high growth rate and purity of the films shows potential for many applications and furthermore proves the capabilities of the recently discovered reducing agent, (Me3Ge)2DHP.
Reductive Thermal Atomic Layer Deposition Process for Gold
Anton Vihervaara, Timo Hatanpää, Heta-Elisa Nieminen, Kenichiro Mizohata, Mykhailo Chundak, Mikko Ritala*ACS Mater. Au 2023, XXXX, XXX, XXX-XXX
In this work, we developed an atomic layer deposition (ALD) process for gold metal thin films from chloro(triethylphosphine)gold(I) [AuCl(PEt3)] and 1,4-bis(trimethylgermyl)-1,4-dihydropyrazine [(Me3Ge)2DHP]. High purity gold films were deposited on different substrate materials at 180 °C for the first time with thermal reductive ALD. The growth rate is 1.7 Å/cycle after the film reaches full coverage. The films have a very low resistivity close to the bulk value, and a minimal amount of impurities could be detected. The reaction mechanism of the process is studied in situ with a quartz crystal microbalance and a quadrupole mass spectrometer.