Browse Prior Art Database

Double Pass Grazing Incidence Scanner

IP.com Disclosure Number: IPCOM000082801D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Seebe, NB: AUTHOR

Abstract

Light scanner 10 is particularly useful for illuminating the surface of a semiconductor wafer W being inspected for particulate matter. It uses an irradiating beam directed at the grazing angle or near grazing angle incident to the surface to be observed. The irradiating beam is collimated with minimum beam spread, thus requiring a minimal cross-sectional beam diameter and thereby allowing greater concentration of beam power.

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Double Pass Grazing Incidence Scanner

Light scanner 10 is particularly useful for illuminating the surface of a semiconductor wafer W being inspected for particulate matter. It uses an irradiating beam directed at the grazing angle or near grazing angle incident to the surface to be observed. The irradiating beam is collimated with minimum beam spread, thus requiring a minimal cross-sectional beam diameter and thereby allowing greater concentration of beam power.

The collimated light beam 1 from a source of beam-forming optics, not shown, is formed in coincident parallel relationship with center axis 2 of beam 1. Axis 2 is normal to the surface of W.

Rotating beam deflecting prism 3 deflects beam 1 at a right angle to axis 2, i.e., in a radial direction, cf. beam 1A. The 90 Degrees -conical mirror surface 4 of upper concentric ring reflector 5 diverts beam 1A another 90 Degrees, cf. beam 1B onto the 90 Degrees -conical mirror surface 6 of lower concentric ring reflector 7.

Surface 6 directs beam 1C diametrically across the surface of W to be irradiated.

On the opposite side, i.e., left as viewed in the figure, beam 1C passes via conical mirror surfaces 6, 4 onto the retro-mirror surface 8, which is rigidly mounted to the back of rotating beam deflecting prism 3. The resultant beam 1D reflected by surface 8 follows the reverse path and is directed by surface 6 diametrically across the surface of W, cf. beam 1E, at or near the grazing angle.

The interaction of beams 1C and 1E re...