Browse Prior Art Database

Film Thickness Measurement Correction

IP.com Disclosure Number: IPCOM000051968D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Case, WR: AUTHOR [+2]

Abstract

Described is a technique for correction for different NA (numerical aperture) objective lenses when film thickness is measured by interferometric means through a microscope such as described by Fried, et al., in "Thickness Measurement of Silicon Dioxide Films Over Small Geometrics," Journal of Applied Physics 5732-5735 (November 1968).

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Film Thickness Measurement Correction

Described is a technique for correction for different NA (numerical aperture) objective lenses when film thickness is measured by interferometric means through a microscope such as described by Fried, et al., in "Thickness Measurement of Silicon Dioxide Films Over Small Geometrics," Journal of Applied Physics 5732-5735 (November 1968).

An effect of using a microscope with objective lenses to achieve small spot measurement is the varying of the incident angle (theta(1)) away from the normal. For incident light which is not normal, the relation between film thickness is: See Original. where: n(f) = index of refraction of the film being measured theta(1) = angle between incident light and the normal to

the film

The effective angle (theta(1)) for a lens is unknown. However, it can be determined empirically by measuring the same film with objective lenses of different numerical apertures and assuming that the angle (theta(1)) is proportional to the arc tangent of the numerical aperture. See Original.

Finally, the correction for the numerical aperture of the objective lens may be computed: See Original.

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