Via hole checker
First Claim
1. A method for determining the cleanliness of the bottom of an aperture formed in a layer of dielectric material, the method comprising the steps of:
- providing a layer of electrically conducting material adjacent to a bottom surface of the dielectric layer, where this conducting material is characterized by an electron work function W, said aperture extending downward through said dielectric layer to said layer of conducting material;
illuminating the aperture and surrounding area from above said dielectric layer with light having a wavelength component that stimulates photoemission in the underlying conducting material, thereby causing photoelectrons to be liberated from the layer of conducting material that lies beneath the aperture and nearby surrounding dielectric layer, a portion of the photoelectrons passing through any dielectric material lying at the bottom of the aperture to produce a photoelectron current, photoelectrons liberated beneath said dielectric layer being scattered by said dielectric layer and contributing little to said photoelectron current; and
determining the photoelectron current that emerges from the aperture, whereby the cleanliness of the bottom of the aperture is determined.
1 Assignment
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Accused Products
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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Citations
21 Claims
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1. A method for determining the cleanliness of the bottom of an aperture formed in a layer of dielectric material, the method comprising the steps of:
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providing a layer of electrically conducting material adjacent to a bottom surface of the dielectric layer, where this conducting material is characterized by an electron work function W, said aperture extending downward through said dielectric layer to said layer of conducting material; illuminating the aperture and surrounding area from above said dielectric layer with light having a wavelength component that stimulates photoemission in the underlying conducting material, thereby causing photoelectrons to be liberated from the layer of conducting material that lies beneath the aperture and nearby surrounding dielectric layer, a portion of the photoelectrons passing through any dielectric material lying at the bottom of the aperture to produce a photoelectron current, photoelectrons liberated beneath said dielectric layer being scattered by said dielectric layer and contributing little to said photoelectron current; and determining the photoelectron current that emerges from the aperture, whereby the cleanliness of the bottom of the aperture is determined. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. Apparatus for determining the cleanliness of the bottom of an aperture formed in a layer of dielectric material where the aperture bottom is adjacent to an underlying layer of electrically conducting material with associated work function W, the apparatus comprising:
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a light source, to provide a light beam of wavelength λ
<
λ
o =hc/W, where h=6.62×
10-27 erg-sec. and c is the speed of light;positioning means to position the light source above said aperture so that it illuminates the aperture and nearby surrounding dielectric layer with the light beam; and an electron collector, positioned adjacent to the mouth of the aperture, to collect photoelectrons that emerge from any dielectric layer residue at the aperture bottom and appear as a photoelectron current at the aperture mouth. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification