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Jpn. J. Appl. Phys. 39 (2000) pp. 1583-1596  |Next Article|  |Table of Contents|
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Invited Review Paper

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. Donnelly1 and Mikhail V. Malyshev1

Silicon Systems Research Laboratories, NEC Corporation, 34 Miyukigaoka Tsukuba, Ibaraki 305-8501, Japan
1Bell Laboratories, Lucent Technologies, 600 Mountain Ave. Murray Hill, NJ 07974, USA

(Received January 25, 1999; revised manuscript revised September 1, 1999; accepted for publication January 6, 2000)

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 30 cm. 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 20 mTorr), 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 20 mTorr 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.

KEYWORDS: discharge frequency, ultrahigh-frequency plasma, inductively coupled plasma, electron energy distribution function, plasma etching
URL: http://jjap.ipap.jp/link?JJAP/39/1583/
DOI: 10.1143/JJAP.39.1583


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