Browse Prior Art Database

Macroscope Dark Field Illumination System

IP.com Disclosure Number: IPCOM000086465D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Ellsworth, RK: AUTHOR [+2]

Abstract

In dark field illumination systems, conventional practice is to utilize a microscope for direct viewing of the subject target, for example, a semiconductor wafer 10. The target is illuminated at a high angle so that the light impinging thereon does not reflect back to the objective lens of the microscope, unless there is an obstruction or some reflective surface on the target which causes light to be scattered from the target back onto the objective lens.

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Macroscope Dark Field Illumination System

In dark field illumination systems, conventional practice is to utilize a microscope for direct viewing of the subject target, for example, a semiconductor wafer 10. The target is illuminated at a high angle so that the light impinging thereon does not reflect back to the objective lens of the microscope, unless there is an obstruction or some reflective surface on the target which causes light to be scattered from the target back onto the objective lens.

The drawing illustrates schematically a "macroscope" low-angle dark field illumination apparatus. A macroscope is nothing more than a low-powered microscope. The apparatus comprises an enlarged objective lens 11 which permits axial margin rays 12 and 13 to pass through the periphery thereof from a lamp condenser 14, after reflection from a mirror 15.

The central portion 16 of the mirror is open, so that direct light from the lamp condenser 14 will pass therethrough and not be focused onto the central portion 17 of the objective lens system 11. Therefore, the outer portion of the objective lens is used to angle light rays 12 and 13 to provide the dark field illumination of the target 10.

In this manner, the central portion 17 of the objective lens 11 of the macroscope is utilized to receive the light which is reflected (if any) and scattered by the angled illumination of the target 10 impinging upon a defect in the target surface. As shown in the drawing, the wafer image...