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Aqueous precursors tailored for the deposition of thin film materials are desirable for sustainable, simple, low energy production of advanced materials. Yet the simple practice of using aqueous precursors is complicated by the multitude of interactions that occur between ions and water during dehydration. Here we use lithium polyoxoniobate salts to investigate the fundamental interactions in the transition from precursor cluster to oxide film. Small-angle X-ray scattering of solutions, total X-ray scattering of intermediate gels, and morphological and structural characterization of the lithium niobate thin films reveal the atomic level transitions between these states. The studies show that 1) Lithium-[H 2 Nb 6 O 19 ] 6has drastically different solution behaviour than lithium-[Nb 6 O 19 ] 8-, linked to the precursor salt structure 2) in both compositions, the intermediate gel preserves the polyoxoniobate clusters and show similar local order and 3) the morphology and phases of deposited films reflect the ions behaviour throughout the journey from cluster solution to metal oxide.

This work complements our recent discovery of new phases derived from zirconium perchlorate by addition of hydrogen peroxide. Here, we investigate analogous reactions with hafnium perchlorate, which is found to have modifications of the Clearfield–Vaughan tetramer (CVT). For hafnium perchlorate derivatives, we find distorted versions of CVT by X-ray diffraction and study the reaction solutions by SAXS, Raman spectroscopy, and ESI-MS. Furthermore, we investigate mixed Hf–Zr solution and solid phases and find the latter resemble the zirconium family at low Hf concentrations and the hafnium family at higher hafnium contents.

Inorganic resists are promising for nanomanufacturing because of their potential for high-resolution and low line-edge roughness patterning and exceptional sensitivity to extreme ultraviolet (EUV) radiation. Hafnium oxide peroxide hydroxide sulfate (HafSO x ) is a model EUV inorganic photoresist, wherein the EUV absorption coefficients for hafnium and O are much higher than for conventional polymer resists. Absorption of EUV radiation leads to electron emission that results in the HafSO x solubility change. We used desorption-based techniques to elucidate thermal- and radiation-induced processes that contribute to the HafSO x solubility switch. We found that low kinetic energy electrons render HafSO x insoluble and result in the desorption of molecular O2. Electron-stimulated desorption and postexposure Raman spectroscopy indicate similar kinetics for peroxide loss in HafSO x . Temperature-programmed desorption studies found that peroxide ligand desorption is best characterized as first order, with a broad distribution of thermal desorption energies. Finally, a pair distribution function analysis of X-ray scattering data of HafSO x solutions and powders provides an atomic-level model of local structure within the film that is consistent with other characterization data of solutions and deposited films.

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.

A combination of ICP-OES, titration, and Raman spectroscopy was used to determine the ratio of peroxide to hafnium in the inorganic photoresist HafSOx. By using ICP-OES to determine the hafnium concentration and titration with permanganate to determine peroxide in a solution of dissolved films, the Hf:O 2 2-ratio was found to be approximately 2:1 in the films. From Raman measurements on precursor solutions, it was determined that that Hfbound peroxide saturated at this level. Film insolubility is induced through loss of approximately 75% of bound peroxide following exposure to a 30-keV electron beam.

Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxidee nables extreme UV lithographic patterning of sub-10 nm HfO 2 structures.H afnium speciation under these basic conditions (pH > 10), however,i su nknown, as studies of hafnium aqueous chemistry have been limited to acid. Here,w er eport synthesis,crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA] 6 [Hf 6 (m-O 2 ) 6 (m-OH) 6 (OH) 12 ]·38 H 2 O. The solution behavior of the cluster,i ncluding supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens anew chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing ac ritical process in single-digit-nm lithography.Water-soluble molecular oxo-hydroxo metal clusters are recognized building blocks for deposition of functional thinfilm coatings,offering low energy and "green" processing. [1][2][3] Additionally,s elected hafnium-peroxo-sulfate clusters provide unprecedented dimensional control in nanolithography. [4,5] In this lithography,u nexposed oxo-hydroxo Hf regions dissolve in base,m eaning soluble hafnium species exist at high pH.Up to now,h owever,t he aqueous chemistry of hafnium has been documented only for strongly acidic conditions.I n mildly acidic conditions (pH ! 3), gels and precipitates result from rapid hydrolysis and condensation. [6,7] At low pH, oxohydroxo hafnium clusters are commonly stabilized and isolated with capping sulfate ligands,s ometimes linking clusters into 1, 2o r3 -dimensional networks.[ [12,13] Our interest in oxo-hydroxo hafnium speciation in base arises from the development step in lithographic patterning with the water-processed hafnium material known as HafSO x , formulated Hf 4 (OH) 6.4 (O 2 ) 2 (SO 4 ) 2.8 . [4,5,14] Nanolithography allows bulk semiconductors and metals to be shaped into computing devices with sub-10 nm features.[15] New inorganic resists,such as HafSO x ,offer ultra-high-resolution patterns. [6] There are two major steps in the patterning process with HafSOx:1)exposure,which causes dissociation of the peroxo ligand and induces condensation;and 2) development, where unexposed material is selectively dissolved in concentrated aqueous tetramethylammonium hydroxide (TMAH). The nature of the species produced in these basic solutions is unknown. This dissolution, coupled with stability of asimilar peroxo-phosphato-niobium cluster observed in both basic and acidic solutions [16] has led us to propose the concept of amphoteric clusters,w herein simple ligand sets stabilize as ingle cluster or similar clusters at the extreme ends of the pH scale.T his concept broadens the approach to cluster synthesis and study,asmost common cluster types exist across limited pH ranges.[17] Forexample,Group 13 polycations are currently known to exist in the narrow range pH 3-4; [18,19] V, Mo,and Wpolyoxom...

Recently, monoalkyl oxo‐hydroxo tin clusters have emerged as a new class of metal‐oxide resist to support the semiconductor industry's transition to extreme ultraviolet (EUV) lithography. Under EUV exposure, these tin‐based clusters exhibit higher performance and wider process windows than conventional polymer materials. A promising new monoalkyl precursor, [(BuSn)12O14(OH)6][OH]2 (BuSn), is still in its infancy in terms of film formation. However, understanding potential environmental effects could significantly affect future development as a commercial product. We synthesized and explored the toxicity of nano‐BuSn in the alga Chlamydomonas reinhardtii and the crustacean Daphnia magna at exposure concentrations ranging from 0 to 250 mg/L. Nano‐BuSn had no effect on C. reinhardtii growth rate irrespective of concentration, whereas high nanoparticle concentrations (≥100 mg/L) increased D. magna immobilization and mortality significantly. To simulate an end‐of‐life disposal and leachate contamination, BuSn‐coated film wafers were incubated in water at various pH values and temperatures for 14 and 90 d to investigate leaching rates and subsequent toxicity of the leachates. Although small quantities of tin (1.1–3.4% of deposited mass) leached from the wafers, it was insufficient to elicit a toxic response regardless of pH, incubation time, or temperature. The low toxicity of the tin‐based thin films suggests that they can be an environmentally friendly addition to the material sets useful for semiconductor manufacturing. Environ Toxicol Chem 2019;38:2651–2658. © 2019 SETAC