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Automatic Diffused Angle, Multiple Position Oblique Light Illumination Station

IP.com Disclosure Number: IPCOM000034323D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 6 page(s) / 172K

Publishing Venue

IBM

Related People

Chan, SA: AUTHOR [+6]

Abstract

A technique is described whereby an automatic mechanism illuminates a semiconductor wafer, so as to enable inspection without a manual setup. The mechanism automatically positions an illuminated observation station so that defect coordinates can be automatically recorded. The station utilizes diffused angle multiple positioning oblique light (DAMPOL), attached to a stereomicroscope, to highlight surface defects of the wafer. Typically, a large field microscope is used to detect particles and defects on the surface of wafers. Employing DAMPOL enables the surface defects to be highlighted, as shown in Fig. 2. With the wafer at zero degrees and the microscope at ninety degrees, light at any angle, other than ninety degrees, will be oblique.

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Automatic Diffused Angle, Multiple Position Oblique Light Illumination Station

A technique is described whereby an automatic mechanism illuminates a semiconductor wafer, so as to enable inspection without a manual setup. The mechanism automatically positions an illuminated observation station so that defect coordinates can be automatically recorded. The station utilizes diffused angle multiple positioning oblique light (DAMPOL), attached to a stereomicroscope, to highlight surface defects of the wafer. Typically, a large field microscope is used to detect particles and defects on the surface of wafers. Employing DAMPOL enables the surface defects to be highlighted, as shown in Fig. 2. With the wafer at zero degrees and the microscope at ninety degrees, light at any angle, other than ninety degrees, will be oblique. Without surface defects, nothing is seen through the microscope, the field of view is black, and no reflective light is entered into the microscope, as shown in Fig. 1. However, when surface depressions and particles above the wafer surface are present, oblique light at thirty degrees is

(Image Omitted)

reflected, and the remaining field of view is black.

Particles above the wafer surface, when subjected to oblique light at zero degrees, are seen because of the reflective light, as shown in Fig. 3, while surface depressions and the remaining field of view are black. Light at zero degrees above the wafer requires adjustment of the Z-axis, as shown in Fig. 4, to provide illumination of the particle. With a fixed centerline of the microscope, the X-Y axis also requires positioning. So as to eliminate the manual positioning procedure, the concept described herein provides an automatic positioning device for viewing the particle and surface defects on the wafer. The automatic station consists of the following components: o Stage assembly for controlling the X-Y movement of chuck,

wafer and zero-degree illumination device.

o Chuck assembly to position and hold the wafer and guides.

It also holds a zero-degree illumination device and sensors.

o Thirty-degree device to illuminate the wafer surface defects

depressions and particles.

o Zero-degree device to illuminate the wafer surface particles.

o Stereomicroscope with a large field of view.

(Image Omitted)

o Stage control to provide power and signals to the stage

mechanism.

o Grippers to hold and release the zero-degree device.

o DC stepping motor to provide Z-axis movement

o Support weldment to house the DC motor and hold the zero-

1

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and thirty-degree devices incorporating the grippers and the

microscope.

(Image Omitted)

Light is illuminated from the thirty-degree illumination device, as shown in Fig. 5a, when light from fiber optic cable bundle 10 splits into twelve equally-spaced openings 11 in housing 12. The light exits from openings 11 at an angle, as shown in Fig. 5b, so that if housing 12 remains parallel to the wafer, the light will always hit the wafer at...