skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C 4F 8 and Ar/CHF 3 Plasma

Abstract

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO 2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C 4F 8 and CHF 3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32, 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have amore » strong impact on etch depth per cycle of SiO 2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF 3 has a lower FC deposition yield for both SiO 2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F 8. The thickness of deposited FC layers using CHF 3 is found to be greater for Si than for SiO 2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.« less

Authors:
 [1];  [2];  [3];  [3];  [3];  [1]
  1. Univ. of Maryland, College Park, MD (United States). Inst. for Electronics and Applied Physics, Dept. of Material Science and Engineering
  2. Univ. of Maryland, College Park, MD (United States). Inst. for Electronics and Applied Physics, Dept. of Physics
  3. IBM, Yorktown Heights, NY (United States). Thomas J. Watson Research Center
Publication Date:
Research Org.:
Univ. of Maryland, College Park, MD (United States)
Sponsoring Org.:
USDOE; National Science Foundation (NSF)
OSTI Identifier:
1294595
Alternate Identifier(s):
OSTI ID: 1322428
Grant/Contract Number:  
SC0001939; CBET-1134273
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 146; Journal Issue: 5; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Metzler, Dominik, Li, Chen, Engelmann, Sebastian, Bruce, Robert L, Joseph, Eric A, and Oehrlein, Gottlieb S. Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C4F8 and Ar/CHF3 Plasma. United States: N. p., 2016. Web. doi:10.1063/1.4961458.
Metzler, Dominik, Li, Chen, Engelmann, Sebastian, Bruce, Robert L, Joseph, Eric A, & Oehrlein, Gottlieb S. Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C4F8 and Ar/CHF3 Plasma. United States. doi:10.1063/1.4961458.
Metzler, Dominik, Li, Chen, Engelmann, Sebastian, Bruce, Robert L, Joseph, Eric A, and Oehrlein, Gottlieb S. Thu . "Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C4F8 and Ar/CHF3 Plasma". United States. doi:10.1063/1.4961458. https://www.osti.gov/servlets/purl/1294595.
@article{osti_1294595,
title = {Characterizing Fluorocarbon Assisted Atomic Layer Etching of Si Using Cyclic Ar/C4F8 and Ar/CHF3 Plasma},
author = {Metzler, Dominik and Li, Chen and Engelmann, Sebastian and Bruce, Robert L and Joseph, Eric A and Oehrlein, Gottlieb S},
abstractNote = {With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching (ALE) processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C4F8 and CHF3), and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J Vac Sci Technol A 32, 020603 (2014), and D. Metzler et al., J Vac Sci Technol A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO2 and Si, but is limited with regard to control over material etching selectivity. Ion energy over the 20 to 30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF3 has a lower FC deposition yield for both SiO2 and Si, and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F8. The thickness of deposited FC layers using CHF3 is found to be greater for Si than for SiO2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.},
doi = {10.1063/1.4961458},
journal = {Journal of Chemical Physics},
number = 5,
volume = 146,
place = {United States},
year = {Thu Sep 08 00:00:00 EDT 2016},
month = {Thu Sep 08 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 3 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process
journal, June 2005

  • Puurunen, Riikka L.
  • Journal of Applied Physics, Vol. 97, Issue 12, Article No. 121301
  • DOI: 10.1063/1.1940727

Atomic layer deposition (ALD): from precursors to thin film structures
journal, April 2002


Atomic Layer Deposition Chemistry Recent Developments and Future Challenges
journal, November 2003

  • Leskelä, Markku; Ritala, Mikko
  • Angewandte Chemie International Edition, Vol. 42, Issue 45, p. 5548-5554
  • DOI: 10.1002/anie.200301652

Atomic Layer Deposition: An Overview
journal, January 2010

  • George, Steven M.
  • Chemical Reviews, Vol. 110, Issue 1, p. 111-131
  • DOI: 10.1021/cr900056b