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Title: Predicting synergy in atomic layer etching

Abstract

Atomic layer etching (ALE) is a multistep process used today in manufacturing for removing ultrathin layers of material. In this article, the authors report on ALE of Si, Ge, C, W, GaN, and SiO 2 using a directional (anisotropic) plasma-enhanced approach. The authors analyze these systems by defining an “ALE synergy” parameter which quantifies the degree to which a process approaches the ideal ALE regime. This parameter is inspired by the ion-neutral synergy concept introduced in the 1979 paper by Coburn and Winters. ALE synergy is related to the energetics of underlying surface interactions and is understood in terms of energy criteria for the energy barriers involved in the reactions. Synergistic behavior is observed for all of the systems studied, with each exhibiting behavior unique to the reactant–material combination. By systematically studying atomic layer etching of a group of materials, the authors show that ALE synergy scales with the surface binding energy of the bulk material. This insight explains why some materials are more or less amenable to the directional ALE approach. Furthermore, they conclude that ALE is both simpler to understand than conventional plasma etch processing and is applicable to metals, semiconductors, and dielectrics.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Lam Research Corp., Fremont, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1376399
DOE Contract Number:
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 35; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Kanarik, Keren J., Tan, Samantha, Yang, Wenbing, Kim, Taeseung, Lill, Thorsten, Kabansky, Alexander, Hudson, Eric A., Ohba, Tomihito, Nojiri, Kazuo, Yu, Jengyi, Wise, Rich, Berry, Ivan L., Pan, Yang, Marks, Jeffrey, and Gottscho, Richard A. Predicting synergy in atomic layer etching. United States: N. p., 2017. Web. doi:10.1116/1.4979019.
Kanarik, Keren J., Tan, Samantha, Yang, Wenbing, Kim, Taeseung, Lill, Thorsten, Kabansky, Alexander, Hudson, Eric A., Ohba, Tomihito, Nojiri, Kazuo, Yu, Jengyi, Wise, Rich, Berry, Ivan L., Pan, Yang, Marks, Jeffrey, & Gottscho, Richard A. Predicting synergy in atomic layer etching. United States. doi:10.1116/1.4979019.
Kanarik, Keren J., Tan, Samantha, Yang, Wenbing, Kim, Taeseung, Lill, Thorsten, Kabansky, Alexander, Hudson, Eric A., Ohba, Tomihito, Nojiri, Kazuo, Yu, Jengyi, Wise, Rich, Berry, Ivan L., Pan, Yang, Marks, Jeffrey, and Gottscho, Richard A. Mon . "Predicting synergy in atomic layer etching". United States. doi:10.1116/1.4979019. https://www.osti.gov/servlets/purl/1376399.
@article{osti_1376399,
title = {Predicting synergy in atomic layer etching},
author = {Kanarik, Keren J. and Tan, Samantha and Yang, Wenbing and Kim, Taeseung and Lill, Thorsten and Kabansky, Alexander and Hudson, Eric A. and Ohba, Tomihito and Nojiri, Kazuo and Yu, Jengyi and Wise, Rich and Berry, Ivan L. and Pan, Yang and Marks, Jeffrey and Gottscho, Richard A.},
abstractNote = {Atomic layer etching (ALE) is a multistep process used today in manufacturing for removing ultrathin layers of material. In this article, the authors report on ALE of Si, Ge, C, W, GaN, and SiO2 using a directional (anisotropic) plasma-enhanced approach. The authors analyze these systems by defining an “ALE synergy” parameter which quantifies the degree to which a process approaches the ideal ALE regime. This parameter is inspired by the ion-neutral synergy concept introduced in the 1979 paper by Coburn and Winters. ALE synergy is related to the energetics of underlying surface interactions and is understood in terms of energy criteria for the energy barriers involved in the reactions. Synergistic behavior is observed for all of the systems studied, with each exhibiting behavior unique to the reactant–material combination. By systematically studying atomic layer etching of a group of materials, the authors show that ALE synergy scales with the surface binding energy of the bulk material. This insight explains why some materials are more or less amenable to the directional ALE approach. Furthermore, they conclude that ALE is both simpler to understand than conventional plasma etch processing and is applicable to metals, semiconductors, and dielectrics.},
doi = {10.1116/1.4979019},
journal = {Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films},
number = 5,
volume = 35,
place = {United States},
year = {Mon Mar 27 00:00:00 EDT 2017},
month = {Mon Mar 27 00:00:00 EDT 2017}
}
  • This paper explores the atomic layer deposition (ALD) of indium oxide (In{sub 2}O{sub 3}) films using cyclopentadienyl indium (InCp) and combinations of both molecular oxygen and water as the co-reactants. When either O{sub 2} or H{sub 2}O were used individually as the oxygen source the In{sub 2}O{sub 3} growth was negligible over the temperature range 100-250 C. However, when oxygen and water were used in combination either as a simultaneous exposure or supplied sequentially, In{sub 2}O{sub 3} films were deposited at growth rates of 1.0-1.6 {angstrom}/cycle over the full range of deposition temperatures. In situ quadrupole mass spectrometry and quartzmore » crystal microbalance measurements revealed that water serves the function of releasing ligands from the surface while oxygen performs the role of oxidizing the indium. Since both processes are necessary for sustained growth, both O{sub 2} and H{sub 2}O are required for the In{sub 2}O{sub 3} ALD. The electrical resistivity, mobility, and carrier concentration of the In{sub 2}O{sub 3} films varied dramatically with both the deposition temperature and co-reactant sequence and correlated to a crystallization occurring at {approx}140 C observed by X-ray diffraction and scanning electron microscopy. Using this new process we successfully deposited ALD In{sub 2}O{sub 3} films over large area substrates (12 in. x 18 in.) with very high uniformity in thickness and resistivity.« less
  • This paper explores the atomic layer deposition (ALD) of indium oxide (In 2O 3) films using cyclopentadienyl indium (InCp) and combinations of both molecular oxygen and water as the co-reactants. When either O 2 or H 2O were used individually as the oxygen source the In 2O 3 growth was negligible over the temperature range 100-250 °C. However, when oxygen and water were used in combination either as a simultaneous exposure or supplied sequentially, In 2O 3 films were deposited at growth rates of 1.0-1.6 Å/cycle over the full range of deposition temperatures. In situ quadrupole mass spectrometry and quartzmore » crystal microbalance measurements revealed that water serves the function of releasing ligands from the surface while oxygen performs the role of oxidizing the indium. Since both processes are necessary for sustained growth, both O 2 and H 2O are required for the In 2O 3 ALD. The electrical resistivity, mobility, and carrier concentration of the In 2O 3 films varied dramatically with both the deposition temperature and co-reactant sequence and correlated to a crystallization occurring at ~140 °C observed by X-ray diffraction and scanning electron microscopy. Using this new process we successfully deposited ALD In 2O 3 films over large area substrates (12 in. × 18 in.) with very high uniformity in thickness and resistivity.« less
  • We describe controlled, self-limited etching of a polystyrene polymer using a composite etching cycle consisting of sequential deposition of a thin reactive layer from precursors produced from a polymer-coated electrode within the etching chamber, modification using O{sub 2} exposure, and subsequent low-pressure Ar plasma etching, which removes the oxygen-modified deposited reactive layer along with Almost-Equal-To 0.1 nm unmodified polymer. Deposition prevents net etching of the unmodified polymer during the etching step and enables self-limited etch rates of 0.1 nm/cycle.
  • Angstrom-level plasma etching precision is required for semiconductor manufacturing of sub-10 nm critical dimension features. Atomic layer etching (ALE), achieved by a series of self-limited cycles, can precisely control etching depths by limiting the amount of chemical reactant available at the surface. Recently, SiO{sub 2} ALE has been achieved by deposition of a thin (several Angstroms) reactive fluorocarbon (FC) layer on the material surface using controlled FC precursor flow and subsequent low energy Ar{sup +} ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO{sub 2} frommore » the surface. In the present article, the authors describe controlled etching of Si{sub 3}N{sub 4} and SiO{sub 2} layers of one to several Angstroms using this cyclic ALE approach. Si{sub 3}N{sub 4} etching and etching selectivity of SiO{sub 2} over Si{sub 3}N{sub 4} were studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Surface chemistries of Si{sub 3}N{sub 4} were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si{sub 3}N{sub 4} has a lower physical sputtering energy threshold than SiO{sub 2}, Si{sub 3}N{sub 4} physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si{sub 3}N{sub 4} to SiO{sub 2} ALE etching selectivity was observed for these FC depleted conditions. By optimization of the ALE process parameters, e.g., low ion energies, short ESLs, and/or high FC film deposition per cycle, highly selective SiO{sub 2} to Si{sub 3}N{sub 4} etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si{sub 3}N{sub 4} surfaces. This highly selective etching is explained by a lower carbon consumption of Si{sub 3}N{sub 4} as compared to SiO{sub 2}. The comparison of C{sub 4}F{sub 8} and CHF{sub 3} only showed a difference in etching selectivity for FC depleted conditions. For FC accumulation conditions, precursor chemistry has a weak impact on etching selectivity. Surface chemistry analysis shows that surface fluorination and FC reduction take place during a single ALE cycle for FC depleted conditions. A fluorine rich carbon layer was observed on the Si{sub 3}N{sub 4} surface after ALE processes for which FC accumulation takes place. The angle resolved-XPS thickness calculations confirmed the results of the ellipsometry measurements in all cases.« less