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Method of Creating a Field-Induced Guard Ring for Retention Time Measurement

IP.com Disclosure Number: IPCOM000047535D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bakeman, P: AUTHOR

Abstract

This article describes a technique for controlling the wafer surface potential during the taking of retention time measurements on MOS devices. It involves depositing a fixed charge on the oxidized surface of the MOS devices and trapping it there during the measurement period. The silicon surface potential needs to be controlled during the characterization of wafers or processes for making MOS devices, to prevent the surface generation of charges from affecting the leakage of the MOS capacitors used in the testing. In the past, monitor wafers have been characterized by first applying a -80-volt bias to the dot for approximately 20 minutes prior to taking any retention time measurements.

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Method of Creating a Field-Induced Guard Ring for Retention Time Measurement

This article describes a technique for controlling the wafer surface potential during the taking of retention time measurements on MOS devices. It involves depositing a fixed charge on the oxidized surface of the MOS devices and trapping it there during the measurement period. The silicon surface potential needs to be controlled during the characterization of wafers or processes for making MOS devices, to prevent the surface generation of charges from affecting the leakage of the MOS capacitors used in the testing. In the past, monitor wafers have been characterized by first applying a -80-volt bias to the dot for approximately 20 minutes prior to taking any retention time measurements. Using the presently proposed technique for a p-type wafer, a negative surface charge can be applied by "spraying" electrons on the surface of the wafer. This can be accomplished by biasing positively the entire wafer and using a corona-type discharge, or any other source of ionizing radiation, to create free electrons in the space above the wafer. The potential of the wafer will then drop due to the accumulation of negative charge on its surface. Removing the ionization source in the presence of a dry atmosphere will then trap the electrons on the surface of the oxide, forming a field-induced guard ring which will remain in place throughout the measurement period and will prevent the charge generation on ...