Numerical investigation of relationship between micro-scale pattern, interfacial plasma structure and feature profile during deep-Si etching in two-frequency capacitively coupled plasmas in SF6/O2

Fukutaro Hamaoka, Takashi Yagisawa, Toshiaki Makabe

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The feature profile of deep-Si etching in the presence of plasma moulding in two-frequency capacitively coupled plasmas in SF6/O2 has been numerically simulated to investigate the relationship between the micro-scale pattern on a Si wafer, the interfacial structure of the plasma (i.e. the sheath) and the etching profile. We have also discussed the deep-Si etching profile as functions of the SF6/O2 gas mixture ratio and the total gas pressure. The result shows that the plasma moulding has no influence on the sheath structure when the sheath thickness is an order of magnitude longer than the width of the hole pattern. In the presence of a large number of F radicals, the chemical etching of Si causes isotropic etching with a significant undercut profile, reducing the plasma moulding's influence on the etching profile due to the F radicals' much higher Si etching rate compared with the rate of etching by ions. On the other hand, with the increase in the oxygen mixture ratio, a passivation layer grows up on the inside wall, and the removal of the layer at the bottom corner is strengthened by the distorted ion by plasma moulding. Thus, the etching is enhanced particularly at the bottom corner. As the pattern width decreases and the oxygen mixture ratio increases, the etching profile becomes anisotropic by the formation of the passivation layer at the sidewall. In addition, the bottom profile becomes flat because of the uniform ion flux under the reduced influence of the plasma moulding.

Original languageEnglish
Article number075201
JournalJournal of Physics D: Applied Physics
Volume42
Issue number7
DOIs
Publication statusPublished - 2009

Fingerprint

Etching
etching
Plasmas
profiles
Molding
sheaths
Plasma sheaths
Ions
Passivation
passivity
Oxygen
ions
oxygen
Gas mixtures
gas pressure
gas mixtures
Gases
wafers
Fluxes
causes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films

Cite this

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title = "Numerical investigation of relationship between micro-scale pattern, interfacial plasma structure and feature profile during deep-Si etching in two-frequency capacitively coupled plasmas in SF6/O2",
abstract = "The feature profile of deep-Si etching in the presence of plasma moulding in two-frequency capacitively coupled plasmas in SF6/O2 has been numerically simulated to investigate the relationship between the micro-scale pattern on a Si wafer, the interfacial structure of the plasma (i.e. the sheath) and the etching profile. We have also discussed the deep-Si etching profile as functions of the SF6/O2 gas mixture ratio and the total gas pressure. The result shows that the plasma moulding has no influence on the sheath structure when the sheath thickness is an order of magnitude longer than the width of the hole pattern. In the presence of a large number of F radicals, the chemical etching of Si causes isotropic etching with a significant undercut profile, reducing the plasma moulding's influence on the etching profile due to the F radicals' much higher Si etching rate compared with the rate of etching by ions. On the other hand, with the increase in the oxygen mixture ratio, a passivation layer grows up on the inside wall, and the removal of the layer at the bottom corner is strengthened by the distorted ion by plasma moulding. Thus, the etching is enhanced particularly at the bottom corner. As the pattern width decreases and the oxygen mixture ratio increases, the etching profile becomes anisotropic by the formation of the passivation layer at the sidewall. In addition, the bottom profile becomes flat because of the uniform ion flux under the reduced influence of the plasma moulding.",
author = "Fukutaro Hamaoka and Takashi Yagisawa and Toshiaki Makabe",
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