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Sheet Resistance Measurement by Contactless Nondestructive IR Transmittance

IP.com Disclosure Number: IPCOM000075154D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 20K

Publishing Venue

IBM

Related People

Piscitelli, D: AUTHOR [+2]

Abstract

The description relates to a technique for utilizing infrared transmittance through a wafer to determine the diffusion sheet resistance. Since the infrared absorption occurs mainly in the diffused region due to its high-impurity concentration, the variation in wafer thickness will have only a minor effect. Only one calibration curve is required to determine the sheet resistance of the diffusion if one wavelength is used. If, however, the wavelength is changed, then another calibration curve will have to be generated. The steps of the method are as follows: 1) Use any spectrophotometer and measure the percentage transmittance at one particular wavelength (for example: Lambda = 2.5 micrometers) as a function of sheet resistance and plot the calibration curve, as shown in the figure.

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Sheet Resistance Measurement by Contactless Nondestructive IR Transmittance

The description relates to a technique for utilizing infrared transmittance through a wafer to determine the diffusion sheet resistance. Since the infrared absorption occurs mainly in the diffused region due to its high-impurity concentration, the variation in wafer thickness will have only a minor effect. Only one calibration curve is required to determine the sheet resistance of the diffusion if one wavelength is used. If, however, the wavelength is changed, then another calibration curve will have to be generated. The steps of the method are as follows: 1) Use any spectrophotometer and measure the percentage

transmittance at one particular wavelength (for example:

Lambda = 2.5 micrometers) as a function of sheet

resistance

and plot the calibration curve, as shown in the figure.

2) To measure the sheet resistance: simply measure the

percentage transmission at 2.5 micrometers and relate

it to the sheet resistance through the calibration curve.

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