High energy electron fluxes in dc-augmented capacitively coupled plasmas. II. Effects on twisting in high aspect ratio etching of dielectrics

Journal Article · Fri Jan 15 00:00:00 EST 2010 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3290873· OSTI ID:21476102

Mingmei, Wang ^[1]; Kushner, Mark J ^[2]

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1. Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50010 (United States)
2. Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)

In high aspect ratio (HAR) plasma etching of holes and trenches in dielectrics, sporadic twisting is often observed. Twisting is the randomly occurring divergence of a hole or trench from the vertical. Many causes have been proposed for twisting, one of which is stochastic charging. As feature sizes shrink, the fluxes of plasma particles, and ions in particular, into the feature become statistical. Randomly deposited charge by ions on the inside of a feature may be sufficient to produce lateral electric fields which divert incoming ions and initiate nonvertical etching or twisting. This is particularly problematic when etching with fluorocarbon gas mixtures where deposition of polymer in the feature may trap charge. dc-augmented capacitively coupled plasmas (dc-CCPs) have been investigated as a remedy for twisting. In these devices, high energy electron (HEE) beams having narrow angular spreads can be generated. HEEs incident onto the wafer which penetrate into HAR features can neutralize the positive charge and so reduce the incidence of twisting. In this paper, we report on results from a computational investigation of plasma etching of SiO{sub 2} in a dc-CCP using Ar/C{sub 4}F{sub 8}/O{sub 2} gas mixtures. We found that HEE beams incident onto the wafer are capable of penetrating into features and partially neutralizing positive charge buildup due to sporadic ion charging, thereby reducing the incidence of twisting. Increasing the rf bias power increases the HEE beam energy and flux with some indication of improvement of twisting, but there are also changes in the ion energy and fluxes, so this is not an unambiguous improvement. Increasing the dc bias voltage while keeping the rf bias voltage constant increases the maximum energy of the HEE and its flux while the ion characteristics remain nearly constant. For these conditions, the occurrence of twisting decreases with increasing HEE energy and flux.

• OSTI ID: 21476102
• Journal Information: Journal of Applied Physics, Vol. 107, Issue 2; Other Information: DOI: 10.1063/1.3290873; (c) 2010 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ASPECT RATIO
BUILDUP
DEPOSITION
DIELECTRIC MATERIALS
DIRECT CURRENT
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTRON BEAMS
ELECTRONS
ETCHING
IONS
MIXTURES
PLASMA
SILICON OXIDES
STOCHASTIC PROCESSES
TRAPS
BEAMS
CHALCOGENIDES
CHARGED PARTICLES
CURRENTS
DIMENSIONLESS NUMBERS
DISPERSIONS
ELECTRIC CURRENTS
ELEMENTARY PARTICLES
FERMIONS
LEPTON BEAMS
LEPTONS
MATERIALS
OXIDES
OXYGEN COMPOUNDS
PARTICLE BEAMS
SILICON COMPOUNDS
SURFACE FINISHING