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Measuring Oxide Thickness on Silicon Wafers

IP.com Disclosure Number: IPCOM000042677D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Kelleher, KH: AUTHOR [+2]

Abstract

Infrared (IR) spectroscopy is used to non-destructively measure the thickness of very thin oxide films on a silicon wafer. A reflectance spectrum across a mid-IR range is measured, and thickness is determined from minimum/maximum readings associated with an artifact associated with silicon-oxide bonds. Using an IR spectrometer in a reflectance mode, IR energy is reflected from a silicon wafer having an oxide film, and the reflectance spectrum of absorbance versus wave number, in the mid-IR range, from 1600 cm-1 to 400 cm-1, is plotted. A typical plot is shown in the figure. An artifact appears in the resultant curve, which is around the wavelength of the SiO2 absorption band at 1073 cm-1 . The artifact in the curve includes a value Rmin of minimum reflection at 1220 cm-1 and a value Rmax of maximum reflection at 1070 cm-1 .

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Measuring Oxide Thickness on Silicon Wafers

Infrared (IR) spectroscopy is used to non-destructively measure the thickness of very thin oxide films on a silicon wafer. A reflectance spectrum across a mid-IR range is measured, and thickness is determined from minimum/maximum readings associated with an artifact associated with silicon-oxide bonds. Using an IR spectrometer in a reflectance mode, IR energy is reflected from a silicon wafer having an oxide film, and the reflectance spectrum of absorbance versus wave number, in the mid-IR range, from 1600 cm-1 to 400 cm-1, is plotted. A typical plot is shown in the figure. An artifact appears in the resultant curve, which is around the wavelength of the SiO2 absorption band at 1073 cm-1 . The artifact in the curve includes a value Rmin of minimum reflection at 1220 cm-1 and a value Rmax of maximum reflection at 1070 cm-1 . The quantity: AA = -log Rmin Rmax bears a linear relationship to the oxide thickness. By first plotting or calibrating such relationship, the thickness of an oxide film can be interpolated using the above quantity AA calculated from a measured spectrum. The advantages of this method are: 1) It is non-destructive. 2) It can be extended to nearly all dielectric films on silicon which show absorbance features in the mid-IR region. 3) It produces chemical bond information. 4) It is an alternate for the known ellipsometer method.

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