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Scratch and Line Defect Detention System using Oblique Light Modified to Detect Preferentially Scattered Light

IP.com Disclosure Number: IPCOM000088440D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 4 page(s) / 56K

Publishing Venue

IBM

Related People

Flamholz, AL: AUTHOR [+2]

Abstract

The detection of scratches and/or line defects on wafers is useful and necessary in many instances.

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Scratch and Line Defect Detention System using Oblique Light Modified to Detect Preferentially Scattered Light

The detection of scratches and/or line defects on wafers is useful and necessary in many instances.

In the past, oblique light has been effectively used for the detection of point defects. However, scratches and line defects are not always detected by conventional oblique light techniques. This is due to the difference in scattering characteristics of the defects. The point defects are isotropic scatterers which scatter light equally well in all directions. This is different from the line or scratch defect which preferentially scatters light in a direction perpendicular to itself.

The technique here described takes into account the preferential scattering characteristics of scratch and line defects by effectively detecting scattered light in all possible preferential scattering planes. This is accomplished by the simultaneous rotation of the wafer and detection of scattered light in the plane of detection. The plane of detection is the plane formed by the incident and reflected light beam and the detector. Scattered light from any scratch or line defect on the wafer will be detected when the preferential scattering plane of the line and the plane of detection coincide. The rotation of the wafer allows the detection plane to coincide with all possible preferential scattering planes and, thereby, with scratches or line defects in all possible directions.

The set-up in Fig. 5 was used to demonstrate this technique. The resulting data consists of two sets of photographs. In order to visualize the system, consider the three dimensional coordinate system such that the photographs of the wafers are in the X-Y plane (X - horizontal, Y - vertical) and the Z-axis is perpendicular to the wafer surface. In the diagram, the X-axis and the Z-axis are shown and the Y-axis, which is not shown, is perpendicular to the plane of the paper.

Procedure:
(1) Insert the test wafer as shown in Fig. 5.
(2) Illuminate the wafer with a high...