Amphoteric Aqueous Hafnium Cluster Chemistry

Sara Goberna-Ferrón; Deok-Hie Park; Jenn M Amador; Douglas A Keszler; May Nyman

doi:10.1002/anie.201601134

Amphoteric Aqueous Hafnium Cluster Chemistry

Angew Chem Int Ed Engl. 2016 May 17;55(21):6221-4. doi: 10.1002/anie.201601134. Epub 2016 Apr 20.

Authors

Sara Goberna-Ferrón¹, Deok-Hie Park¹, Jenn M Amador¹, Douglas A Keszler¹, May Nyman²

Affiliations

¹ Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA.
² Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA. may.nyman@oregonstate.edu.

PMID: 27094575
DOI: 10.1002/anie.201601134

Abstract

Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography.

Keywords: cluster compounds; hafnium; mass spectrometry; peroxides; small-angle X-ray scattering.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.