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United States of America Patent
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-
Jan 29, 1991
Grant Date -
N/A
app pub date -
Oct 3, 1989
filing date -
Oct 3, 1989
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
Method and apparatus for determining the amount, if any, of residue remaining at the bottom of an aperture in a layer of dielectric or insulator material. A layer of electrically conducting material is positioned adjacent to the aperture bottom, an electron collector is positioned adjacent to the mouth of the aperture, and a voltage difference (optional) is impressed between the conducting material and the electron collector. The aperture bottom is illuminated with a light beam with photon energy greater than the electron work function of the conducting material, and a portion of the photons that comprise the light beam reach the conducting material and produce photoelectrons by photoemissive action. A photoelectron current is sensed by the electron collector, and the cleanliness of the aperture bottom is determined from the value of the current.
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