A low-temperature thermal ALD process for nickel utilizing dichlorobis(triethylphosphine)nickel(II) and 1,4-bis(trimethylgermyl)-1,4-dihydropyrazine

Anton Vihervaara; Timo Hatanpää; Kenichiro Mizohata; Mykhailo Chundak; Georgi Popov; Mikko Ritala

doi:10.1039/d2dt01347a

A low-temperature thermal ALD process for nickel utilizing dichlorobis(triethylphosphine)nickel(II) and 1,4-bis(trimethylgermyl)-1,4-dihydropyrazine

Dalton Trans. 2022 Jul 26;51(29):10898-10908. doi: 10.1039/d2dt01347a.

Authors

Anton Vihervaara¹, Timo Hatanpää¹, Kenichiro Mizohata², Mykhailo Chundak¹, Georgi Popov¹, Mikko Ritala¹

Affiliations

¹ Department of Chemistry, University of Helsinki, P. O. Box 55, FI-00014 Helsinki, Finland. mikko.ritala@helsinki.fi.
² Department of Physics, University of Helsinki, P. O. Box 43, FI-00014 Helsinki, Finland.

PMID: 35792068
DOI: 10.1039/d2dt01347a

Abstract

In this work, we developed a new ALD process for nickel metal from dichlorobis(triethylphosphine)nickel(II) (NiCl₂(PEt₃)₂) and 1,4-bis(trimethylgermyl)-1,4-dihydropyrazine ((Me₃Ge)₂DHP). A series of phosphine adducts of nickel and cobalt halides were synthesized and characterized for their volatility and thermal stability. Also (Me₃Ge)₂DHP is a novel reducing agent in ALD. Smooth nickel films were deposited on different substrate materials at 110 °C, which is the lowest deposition temperature for Ni metal found in the literature. The growth rate is 0.2 Å per cycle when the film is not continuous and decreases to 0.1 Å per cycle after the film becomes pinhole-free. Besides a small amount (7 at%) of carbidic carbon, the films have only small amounts of impurities. Most notably, the chlorine content is below 0.2 at%, indicating efficient reduction. Furthermore, we think that (Me₃Ge)₂DHP can open new avenues for the ALD of other metals at low temperatures.