Spontaneous etching of B2O3by HF gas studied using infrared spectroscopy, mass spectrometry, and density functional theory

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-03-01
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Language
en
Pages
11
Series
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, Volume 40, issue 2
Abstract
The spontaneous etching of boron oxide (B2O3) by hydrogen fluoride (HF) gas is important during thermal atomic layer etching after BCl3 converts the surface of various metal oxides to a B2O3 layer. In this study, the chemical vapor etching (CVE) of B2O3 by HF was experimentally monitored using Fourier transform infrared (FTIR) spectroscopy and quadrupole mass spectrometry (QMS). The spontaneous etching of B2O3 by HF gas was also analyzed using density functional theory (DFT). B2O3 films were grown using B2O3 atomic layer deposition with BCl3 and H2O as the reactants at 40 °C. FTIR spectroscopy then observed the CVE of B2O3 by HF at 150 °C. B2O3 etching was monitored by the loss of absorbance for B-O stretching vibration in B2O3 films. FTIR spectroscopy studies also observed B-F stretching vibrations from BFx species on the B2O3 surface after HF exposures. In addition, the QMS analysis was able to identify the etch products during the spontaneous etching of B2O3 by HF gas at 150 °C. The QMS studies observed the main volatile etch products as BF3, BF2(OH), and H2O. Additional volatile etch products were also detected including B3O3F3 and other boroxine ring compounds. The DFT predictions were consistent with the spontaneous etching of B2O3 by HF gas. DFT confirmed that CVE was likely because the energetics of the spontaneous etching reaction B2O3(s) + 6HF(g) → 2BF3(g) + 3H2O(g) were more favorable than the self-limiting reaction B2O3(s) + 6HF(g) → 2BF3(s) + 3H2O(g). The spontaneous etching of B2O3 was predicted at temperatures above-163 °C for an HF reactant pressure of 0.2 Torr and BF3 and H2O product pressure of 0.01 Torr.
Description
Funding Information: The FTIR studies were funded by Intel through a member specific research grant through the Semiconductor Research Corporation (SRC). Support for the new QMS reactor and the QMS investigations was provided by Lam Research. S.K.N. and S.D.E. acknowledge the Irish Centre for High-End Computing (Project Code No. tiche077c) and the Science Foundation Ireland funded computing cluster at Tyndall for computer time. Publisher Copyright: © 2022 Author(s).
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Citation
Cano , A M , Kondati Natarajan , S , Partridge , J L , Elliott , S D & George , S M 2022 , ' Spontaneous etching of B 2 O 3 by HF gas studied using infrared spectroscopy, mass spectrometry, and density functional theory ' , Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films , vol. 40 , no. 2 , 022601 . https://doi.org/10.1116/6.0001542