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Plasma Resonance on Double Diffused Wafers

IP.com Disclosure Number: IPCOM000075167D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Adley, JM: AUTHOR [+3]

Abstract

This technique will allow the plasma resonance measurement of surface concentration (C(o)) on double-diffused wafers. Previously, this was not possible because a second diffusion on the same wafer interferes with the surface concentration measurement of the first (or likewise, the first would interfere with the second).

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Plasma Resonance on Double Diffused Wafers

This technique will allow the plasma resonance measurement of surface concentration (C(o)) on double-diffused wafers. Previously, this was not possible because a second diffusion on the same wafer interferes with the surface concentration measurement of the first (or likewise, the first would interfere with the second).

In the normal application of the plasma resonance technique, the wafer to be measured is placed in one beam of a dual-beam spectrophotometer and a trace of reflectance versus wavelength made. This trace has a minimum, which is converted to impurity concentration via a calibration curve. If two diffusions are on the same wafer, the reflectance of each interferes with the other and no determination of surface impurity concentration is possible. This problem may be overcome by use of the control wafer from one diffusion of a double-diffused device wafer to eliminate the interference of the two diffusions. The control wafer is placed in the available second spectrophotometer beam, and the spectrophotometer set to produce a trace of the difference in reflectance versus wavelength. This cancels out the interference of one diffusion and produces a plasma resonance C(o) value for the other diffusion. This process is then used with a control wafer from the second diffusion to yield the value of C(o) of the first diffusion.

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