Effects of discharge frequency in plasma etching and ultrahigh-frequency plasma source for high-performance etching for ultralarge-scale integrated circuits

Seiji Samukawa, Vincent M. Donnelly, Mikhail V. Malyshev

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

A low-temperature, uniform, high-density plasma is produced by applying ultrahigh-frequency (UHF) power through a spokewise antenna. The plasma is uniform within ±5% over a diameter of 30cm. No magnetic field is needed to maintain the high-density plasma. Consequently, the plasma source is fairly simple and lightweight. This plasma creates a high electron density and a low degree of dissociation of the feed gas at the same time because the electron energy distribution function is not Maxwellian (bi-Maxwellian distributions). The plasma characteristics are highly suitable for the precise etching of Al and gate electrodes. Additionally, by the combination of bi-Maxwellian electron energy distribution in the UHF plasma and new fluorocarbon gas chemistries (C2F4, CF3I), selective radical generations of CF2 and CF3 could be realized for high-aspect contact hole patterning of SiO2. A high ion density and a high-energy tail in the electron energy distribution can also be maintained over a wide range of pressure (from 3 to 20mTorr), whereas in conventional inductively coupled plasma (ICP: 13.56 MHz), the ion density and number of high-energy electrons are drastically reduced when the gas pressure is increased. This indicates that the ionization in the UHF plasma does not depend significantly on gas pressures between 3 and 20mTorr because the discharge frequency is higher than the frequency of electron collisions in the plasma. As a result, the UHF plasma provides a process window for high-performance etching that is wider than the one provided by an ICP.

Original languageEnglish
Pages (from-to)1583-1596
Number of pages14
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume39
Issue number4 A
Publication statusPublished - 2000 Dec 1
Externally publishedYes

Keywords

  • Discharge frequency
  • Electron energy distribution function
  • Inductively coupled plasma
  • Plasma etching
  • Ultrahigh-frequency plasma

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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