Negative ion extractor for a plasma etching apparatus
First Claim
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1. A plasma apparatus, suitable for reactive ion etching, comprisinga vacuum enclosure including a first portion and second portion;
- means for creating a plasma of negative and positive ions and radicals in said first portion;
a substrate mounted in second portion having a surface to be contacted by said ions;
means for applying a potential between said plasma and said substrate and of a polarity for directing negative ions to said surface; and
means for generating a magnetic field between said plasma and said substrate, and across more than one aperture connecting said first and second portions, said magnetic field being of a magnitude sufficient to retain electrons in the plasma, but insufficient to prevent negative ions from passing through the apertures and reaching said surface.
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Abstract
Process and apparatus for use in extracting negative ions from a plasma which is particularly useful in reactive ion etching of metals, silicon and oxides and nitrides of silicon in the manufacture of semiconductor devices. A magnetic field is employed in the apparatus and, herein, is created by a novel grid, through which negative ions pass to a surface, such as one to be etched, while free electrons are prevented from passing through the grid and out of the plasma. The novel process utilizes negative ions which have a large fraction in the atomic state.
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9 Claims
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1. A plasma apparatus, suitable for reactive ion etching, comprising
a vacuum enclosure including a first portion and second portion; -
means for creating a plasma of negative and positive ions and radicals in said first portion; a substrate mounted in second portion having a surface to be contacted by said ions; means for applying a potential between said plasma and said substrate and of a polarity for directing negative ions to said surface; and means for generating a magnetic field between said plasma and said substrate, and across more than one aperture connecting said first and second portions, said magnetic field being of a magnitude sufficient to retain electrons in the plasma, but insufficient to prevent negative ions from passing through the apertures and reaching said surface. - View Dependent Claims (2, 3, 4, 5)
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6. In a plasma apparatus, for reactive ion etching, in which a plasma is separated from a substrate disposed in said apparatus and in which a potential is applied between said plasma and said substrate to attract species from the plasma and direct the species to said substrate, comprising the improvement of
means for establishing the polarity of said potential such that the species withdrawn from the plasma are negative ions; - and
means for generating a magnetic field between said plasma and said substrate of a magnitude sufficient to retain electrons in the plasma, but insufficient to prevent the negative ions from reaching the substrate. - View Dependent Claims (7, 8, 9)
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Specification