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Transparent Thin Film Measurements by Visible Spectrophotometry

IP.com Disclosure Number: IPCOM000091706D
Original Publication Date: 1968-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Decobert, A: AUTHOR [+2]

Abstract

A technique to determine transparent thin-film thickness, such silicon dioxide films on silicon semiconductor devices, is VAMFO, Variable Angle Monochromatic Fringe Observation. This method allows nondestructive and precise determinations of transparent thin-film thickness over small areas of chips mounted in packages. VAMFO equipment comprises a highly sensitive spectrophotometer, an optical system, a monochromater, and a light source.

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Transparent Thin Film Measurements by Visible Spectrophotometry

A technique to determine transparent thin-film thickness, such silicon dioxide films on silicon semiconductor devices, is VAMFO, Variable Angle Monochromatic Fringe Observation. This method allows nondestructive and precise determinations of transparent thin-film thickness over small areas of chips mounted in packages. VAMFO equipment comprises a highly sensitive spectrophotometer, an optical system, a monochromater, and a light source.

A spectrophotometer is used to provide an accurate determination of light intensity variations versus the wavelength. Its two portions are a photomultiplier tube which converts light flow into electric current flow and an amplifier with an indicating meter to permit measurements of light intensity. An optical system is used for magnifying an isolating the area to be examined. In one arrangement, the optical system is a microscope with additional devices, typically an optical train, for directing the reflected light to the photomultiplier tube.

A monochromater acts as a source of varying wavelengths. It is a rotating disk with paracentric apertures. It is located in a plane conjugate to the image plane and supplies a light beam having discrete, successive and narrow ranges of wavelengths for recovering the large desired range of wavelengths. The light source can be a tungsten or zirconium filament bulb. To increase accuracy, the monochromater is replaced by a linear co...