Paper TF-ThP39
Alkali Halide Assisted Atomic Layer Etching of Metal Oxides

Thursday, November 2, 2017, 6:30 pm, Room Central Hall

The authors previously reported on the development and application of an atomic layer etching (ALE) procedure based on alternating exposures of trimethylaluminum (TMA) and anhydrous hydrogen fluoride (HF) implemented to controllably etch aluminum oxide. We have shown that conditioning the chamber with a thin film of lithium fluoride (LiF) enhances the ALE process, resulting in higher etch rates and better uniformity. We have hypothesized that the LiF participates in an intermediate reaction that promotes the loss of fluorine surface species and results in conformal layer-by-layer etching of aluminum oxide films. Etch properties were explored over a temperature range of 225–300 °C with the Al₂O₃ etch rate increasing from 0.8 to 1.2 Å per ALE cycle at a fixed HF exposure of 60 ms per cycle. We have since extended this work to include a variety of substrates (metal oxides) and etch enhancers (alkali halides). Preliminary results suggest that the TMA/HF chemistry is effective at etching hafnium oxide. Additionally, other alkali halide materials (e.g. KBr) behave as oxide etch enhancers, in some cases resulting in even higher etch rates than what was previously achieved with LiF.

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