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Diagnostic Test for Defective Schottky Barrier Diodes

IP.com Disclosure Number: IPCOM000044546D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Carlson, WH: AUTHOR [+4]

Abstract

This article describes a rapid method of determining the cause of low forward voltages in Schottky barrier diodes. The method uses standard electrical test equipment and can determine whether the condition is due to structural defects or positively changed ionic contaminants. The structure of a typical Schottky barrier diode (SBD) and defects thereof are shown in the figure. During manufacture, several conditions can occur which cause the SBD to exhibit forward voltages lower than normally observed. For example, structural defects such as missing platinum silicide (PtSi) 1 or chromium (Cr) extending beyond the PtSi 2 produce a small area chromium-silicon (Cr/Si) diode in parallel with the desired PtSi/Si diode.

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Diagnostic Test for Defective Schottky Barrier Diodes

This article describes a rapid method of determining the cause of low forward voltages in Schottky barrier diodes. The method uses standard electrical test equipment and can determine whether the condition is due to structural defects or positively changed ionic contaminants. The structure of a typical Schottky barrier diode (SBD) and defects thereof are shown in the figure. During manufacture, several conditions can occur which cause the SBD to exhibit forward voltages lower than normally observed. For example, structural defects such as missing platinum silicide (PtSi) 1 or chromium (Cr) extending beyond the PtSi 2 produce a small area chromium-silicon (Cr/Si) diode in parallel with the desired PtSi/Si diode. The lower barrier height of the Cr/Si system allows preferential current flow through this path and low forward voltages. Positively charged ionic contaminants 3 remaining in the void beneath the overhanging silicon nitride will also cause low forward voltages. To determine which type of defect is causing the low forward voltage, the following test procedure is implemented using standard electrical test equipment: 1. Low current forward voltage (VF) measurement at about one microamp.
2. Reverse breakdown at about 100 microamps. 3. Repeat step 1. If the low VF is due to a structural defects 1 and 2, the forward voltage after breakdown will be unchanged. If ionic contamination 3 is the cause, the VF will...