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Method of Selecting CMOS Components With Hidden Defects in the Gate Oxide

IP.com Disclosure Number: IPCOM000036607D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Euen, W: AUTHOR [+3]

Abstract

A critical parameter for the life of CMOS components is the gate integrity. Slight defects in the gate oxide are initially not detected by standard test methods (yield 100 percent), although the periods for which the components operate without defects may vary later on.

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Method of Selecting CMOS Components With Hidden Defects in the Gate Oxide

A critical parameter for the life of CMOS components is the gate integrity. Slight defects in the gate oxide are initially not detected by standard test methods (yield 100 percent), although the periods for which the components operate without defects may vary later on.

The proposed method permits making visible hidden defects in the gate oxide. For this purpose, a MOS structure on each chip is subjected to a special test cycle. By a programmable current source (computer/constant current source/load and stress current), the MOS capacitor is loaded with a low current of I = 1 x 10-7 A, producing a voltage across the oxide. Upon completion of loading, a selected stress current is adjusted by a predetermined ramp. Time measurement starts after the maximum current has been reached. Voltage VBD is used to determine hidden defects revealed during current stress. A hidden defect exists if the instantaneous breakdown voltage value (which is measured, for example, every 20 ms) is reduced by 4% over the previous value.

In the case described, 15 percent of the components initially marked non- defective were found to be defective after application of the stress current for 15 seconds.

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