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Grazing Angle Illumination Scattering Apparatus

IP.com Disclosure Number: IPCOM000039876D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Batchelder, JS: AUTHOR

Abstract

Micron size, particulate contamination on patterned semiconductor wafers can be detected by microscopic examination using grazing illumination from more than one source and aspect ratio gradation. In the figure, two lasers, 1 and 2, having different wavelengths, illuminate the area of the wafer 3 under inspection at oblique incidence from nearly opposite directions. The resulting scattered light is magnified and imaged by a microscope objective 4 onto a slit 5 and passes through a dispersive prism 6. This light is then imaged by a lens 7 onto a detector array plane 8 wherein two parallel images of a narrow band of the silicon wafer surface are seen. The intensities of light in these bands correspond to the intensities of the light reflected by one particular area element on the wafer.

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Grazing Angle Illumination Scattering Apparatus

Micron size, particulate contamination on patterned semiconductor wafers can be detected by microscopic examination using grazing illumination from more than one source and aspect ratio gradation. In the figure, two lasers, 1 and 2, having different wavelengths, illuminate the area of the wafer 3 under inspection at oblique incidence from nearly opposite directions. The resulting scattered light is magnified and imaged by a microscope objective 4 onto a slit 5 and passes through a dispersive prism 6. This light is then imaged by a lens 7 onto a detector array plane 8 wherein two parallel images of a narrow band of the silicon wafer surface are seen. The intensities of light in these bands correspond to the intensities of the light reflected by one particular area element on the wafer. The detector plane is designed to produce an output only when both optical wavelengths are simultaneously scattered from a point or points on the surface (such as particles). One of the key characteristics in identifying the particulate contamination is the contaminants ratio between its height and width, which is defined as its aspect ratio. Particulate contamination is defined as reflections with aspect ratios of approximately 1 or greater. By using two light sources, if the reflection is of the same intensity and position from illumination by both sources, then the reflection is indicated as being from a particulate.

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