Importance

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Abstract

A plasma etch apparatus (10) such as that for etching wafers in the manufacture of semiconductors includes a vacuum chamber (15) surrounded by a cylindrical dielectric wall (13). A coil (20) surrounds the chamber outside of the wall and is energized with medium frequency RF energy which is inductively coupled into the chamber to energize a plasma in the chamber to etch a semiconductor wafer (16) on a support (17) in the chamber. A generally cylindrical Faraday shield (30) surrounds the outside of the chamber in contact with the outside of the wall between the wall and the coil. The shield has a plurality of axially oriented slits (32) therein closely spaced around the shield and extending less than the height of the shield. One slit or gap (31) extends the full height of the shield and interrupts an otherwise continuous conductive path around the circumference of the chamber. The gap is about 1/8 inch wide, so that, upon initial energization of the coil, a momentary peak-to-peak RF voltage forms across the gap, which generates an electric field in the chamber in the vicinity of the gap which ignites the plasma.

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First Claim