Many materials that are scaled for use in semiconductor manufacturing contain toxic dialkyl- and trialkyltin compounds. Here, we explored monoalky-tin as a substitute precursor for the semiconductor industry as mono-substituted tin species are less toxic than tri- or di-substituted species. We synthesized mono-alkyl tin in the form of nano-clusters, (BuSn)12(OH)6, and used them to make solution-processed thin films. The butyl tin oxo hydroxo compound was dissolved in 2-heptanone solvent at a concentration of approximately 0.04 M. Films spun from this solution appeared optically smooth and free of major defects. Analysis of this film by SEM showed high surface uniformity. In order to test for potential environmental impacts of these alternative materials, pure crystal toxicity was assessed in the single cell algae Chlamydomonas reinhardtii and the freshwater planktonic crustacean Daphnia magna. Both organisms are well-established aquatic models for toxicity evaluations and are ubiquitous in natural bodies of water. In accordance with international standards, we assessed the growth inhibition of C. reinhardtii (OECD 2002, Test No. 201) and the immobilization and mortality of D. magna (OECD 2004, Test No. 202) in response to pure nanocluster at exposure concentrations ranging from 50 to 250 mg/L. No impacts on C. reinhardtii growth rate were identified at any concentration, whereas D. magna immobilization and mortality were significantly increased at high exposure concentrations, ≥100 mg/L. To test the solution-processed thin films for potential impacts, we designed a study to simulate an end-of-life disposal and possible landfill leachate. In this study, we incubated control wafers and (BuSn)12(OH)6-coated wafers in water for 14 days under 4 different environmental conditions. Films were incubated in water with varied pH (5.6, 7.0) and temperature (20, 37°C) to generate leachate for toxicity evaluation. Low concentrations of tin (25 to 128 µg/L) leached from the wafers but not enough to elicit a toxic response from either C. reinhardtii or D. magna, regardless of the pH or temperature. Overall, the low toxicity observed to the test species suggests that (BuSn)12(OH)6 thin films would be more sustainable and environment-friendly than currently used di- and trialky tin compounds for applications in the semiconductor field.

Alternative organotin clusters for thin films: Low environmental impacts under simulated environmental conditions

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.