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Non-Destructive Method to Measure the Defect Free Zone In Situ

IP.com Disclosure Number: IPCOM000049170D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Zunino, P: AUTHOR

Abstract

Semiconductor products use silicon wafers coming from crystals pulled by the Czochralski method. The particularity of these crystals is contamination by oxygen (10/17/ to 10/18/ at/cm/3/). During subsequent heat treatments of the semiconductor processes, the oxygen precipitates and, consequently, defects are generated which contribute to the gettering effect. Near the active face, the oxygen concentration decreases by out-diffusion in lowering the defect formation. A zone with a very low density of defects is measurable beneath the active face.

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Non-Destructive Method to Measure the Defect Free Zone In Situ

Semiconductor products use silicon wafers coming from crystals pulled by the Czochralski method. The particularity of these crystals is contamination by oxygen (10/17/ to 10/18/ at/cm/3/). During subsequent heat treatments of the semiconductor processes, the oxygen precipitates and, consequently, defects are generated which contribute to the gettering effect. Near the active face, the oxygen concentration decreases by out-diffusion in lowering the defect formation. A zone with a very low density of defects is measurable beneath the active face.

Bevel methods are examples of the prior characterization techniques that have been used up to now to measure this defect free zone; unfortunately, they only give a macroscopic view of the physical phenomenon, they are destructive, and they take place at the end of semiconductor processing. The most important feature is to have an electrical defect free zone to ensure semiconductor yields.

Disclosed herein is a novel and non-destructive method to measure the defect-free zone, which involves the use of a very common device, i.e., the MOS capacitor, and which allows the control of the active surface at any processing step.

The method consists in applying different steps of voltage to the gate of the MOS capacitor to deplete majority carriers from the active face. As minority carriers are generated in a region in the order of the diffusion length of the depletion layer, they are swept to the surface to form the inversion layer. The majority carriers flow to the edge of the depletion layer and neutralize the ionized impurity sites, reducing the width of the depletion layer.

In other words,...