Browse Prior Art Database

Optical Gap Meter

IP.com Disclosure Number: IPCOM000080988D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Frosch, A: AUTHOR

Abstract

A resolution pattern, e.g. a so-called Siemensstern 1, is illuminated by an arrangement comprising light source 2, lenses 3, 5, and aperture 4, and is imaged through an arrangement comprising semitransparent mirror 6, mirror 7, and objective lens 8. The latter is mounted for coarse adjustment in variable tube 9 and focuses pattern 1 either on the lower face of mask 10 or the upper face of wafer 11, depending on the adjustment of micrometer screw 12. The pattern imaged on mask 10 or wafer 11 is imaged by objective lens 8 via mirrors 7, 6, 7a in plane 12, where it can be observed through lens 13. The whole arrangement is mounted in housing 14 which is tiltably mounted on edge 15 supported by XY table 16.

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Optical Gap Meter

A resolution pattern, e.g. a so-called Siemensstern 1, is illuminated by an arrangement comprising light source 2, lenses 3, 5, and aperture 4, and is imaged through an arrangement comprising semitransparent mirror 6, mirror 7, and objective lens 8. The latter is mounted for coarse adjustment in variable tube 9 and focuses pattern 1 either on the lower face of mask 10 or the upper face of wafer 11, depending on the adjustment of micrometer screw 12. The pattern imaged on mask 10 or wafer 11 is imaged by objective lens 8 via mirrors 7, 6, 7a in plane 12, where it can be observed through lens 13. The whole arrangement is mounted in housing 14 which is tiltably mounted on edge 15 supported by XY table 16.

To measure the gap between mask 10 and wafer 11, resolution pattern 1 is optimally focussed on an opaque area adjacent to a transparent area of the lower face of mask 10, and subsequently on wafer 11 by actuating micrometer screw
12. The gap thickness can be read from the scale of micrometer screw 12.

Since the tilting of housing 14 imparts on objective lens 8 a movement having horizontal and vertical components, pattern 1 is imaged either onto the opaque area of mask 10 or alternatively through the adjacent transparent area onto wafer
11.

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