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Thickness Measurements of Materials Having High Refractive Index

IP.com Disclosure Number: IPCOM000075106D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Pliskin, WA: AUTHOR

Abstract

This apparatus increases the accuracy of thickness measurements in the technique known as variable angle monochromatic fringe observation VAMFO for materials having high-refractive index.

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Thickness Measurements of Materials Having High Refractive Index

This apparatus increases the accuracy of thickness measurements in the technique known as variable angle monochromatic fringe observation VAMFO for materials having high-refractive index.

In using VAMFO for refractive index and thickness measurements on high- refractive index film materials, difficulties are encountered because the change of the N with angle of incidence is less than the low-refractive index materials and the fringes become less pronounced at the higher angles of incidence due to the much greater reflectivity at the air-film interface. These effects can be limited so as to improve the VAMFO measurement by submerging the film to be measured in a liquid with a higher index of refraction than air. The apparatus shown in A has light source 10, filter 11, and half-silvered mirror 12 positioned to produce a beam of light which enters liquid 14 normal to its surface. Fixed mirror 16 reflects the beam of monochromatic light at an angle to substrate 18, immersed in liquid
14. Rotating stage 20 supports substrate 18 and is adapted to measure the angle i when the operator observes bright fringes through the microscope, not shown.

The technique can also be used with detector VAMFO's, one example of which, is shown as a horizontal cross-section in drawing B. The light from source 10 enters transparent cylinder 24 at normal incidence to the walls of 24 and the wall-liquid interface. Substrate 18...