Recent advances in the semiconductor industry have created an exigency for processes that allow to deposit and etch material in conformal matter in three-dimensional devices. While conformal deposition is achieved using atomic layer deposition (ALD), conformal etching can be accomplished by thermal atomic layer etching (ALE) which, like ALD, proceeds via a binary sequence of self-limiting reactions. This study explores ALE of TiO2 and ZrO2 using WF6 as a fluorinating agent, and BCl3, TiCl4, or SOCl2 as a co-reactant. The effect of co-reactant chemistry was studied using atomic force microscopy, in situ ellipsometry, and in vacuo Auger electron spectroscopy measurements along with thermodynamic modeling. All three co-reactants exhibited saturation and etch rates increasing with temperature. At 170 °C, TiO2 can be etched using WF6 with BCl3, TiCl4, or SOCl2, and the etching proceeds at 0.24, 0.18, and 0.20 nm/cycle, respectively. At 325 °C, ZrO2 ALE can occur using these same reactants, proceeding at 0.96, 0.74, and 0.13 nm/cycle, respectively. A higher temperature is needed for ZrO2 ALE versus TiO2 because the ZrCl4 product is less volatile than the corresponding TiCl4. During ZrO2 and TiO2 etching using BCl3 or TiCl4, boron oxide or titanium oxide intermediate layers, respectively, were formed on the surface, and they were subsequently removed by WF6. In contrast, for ALE of TiO2 using SOCl2, a similar intermediate layer is not observed. This study broadens the understanding of co-etchants role during thermal ALE and expands the range of reactants that can be used for vapor etching of metal oxides.
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July 2023
Research Article|
June 20 2023
Comparison of BCl3, TiCl4, and SOCl2 chlorinating agents for atomic layer etching of TiO2 and ZrO2 using tungsten hexafluoride
Special Collection:
Celebrating the Achievements and Life of Joe Greene
Holger Saare;
Holger Saare
(Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing)
1
Department of Physics, North Carolina State University
, Raleigh, North Carolina 27695
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Wenyi Xie
;
Wenyi Xie
(Conceptualization, Formal analysis, Investigation, Methodology, Writing – review & editing)
2
Department of Chemical and Biomolecular Engineering, North Carolina State University
, Raleigh, North Carolina 27695
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Gregory N. Parsons
Gregory N. Parsons
a)
(Conceptualization, Funding acquisition, Project administration, Supervision, Writing – review & editing)
1
Department of Physics, North Carolina State University
, Raleigh, North Carolina 276952
Department of Chemical and Biomolecular Engineering, North Carolina State University
, Raleigh, North Carolina 27695a)Author to whom correspondence should be addressed: gnp@ncsu.edu
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a)Author to whom correspondence should be addressed: gnp@ncsu.edu
Note: This paper is part of the Special Topic Collection Celebrating the Achievements and Life of Joe Greene.
J. Vac. Sci. Technol. A 41, 042602 (2023)
Article history
Received:
March 22 2023
Accepted:
May 12 2023
Citation
Holger Saare, Wenyi Xie, Gregory N. Parsons; Comparison of BCl3, TiCl4, and SOCl2 chlorinating agents for atomic layer etching of TiO2 and ZrO2 using tungsten hexafluoride. J. Vac. Sci. Technol. A 1 July 2023; 41 (4): 042602. https://doi.org/10.1116/6.0002708
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