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Detection of Non-Conductive Contact Holes in Semiconductor Devices Through Electrical Testing

IP.com Disclosure Number: IPCOM000059939D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Scrivner, CH: AUTHOR

Abstract

In the testing of semiconductor devices it is necessary to detect electrically open contacts in transistors. Existing approaches have involved wiring contacts in series using alternating metal straps and diffusion patterns, but this does not separate broken metal or diffusion patterns from non-conductive contacts. This proposal uses a chain of transistors wired in parallel to minimize potential fail modes not related to open contacts. In the prior system using metal lands and silicon alternately as the conductors between contact holes, the test was sensitive to non- conductive contact holes. However, since it was also sensitive to missing or broken segments in the metal and silicon conductors the sum of all three defect types would often be mistaken for non-conductive contact hole defects.

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Detection of Non-Conductive Contact Holes in Semiconductor Devices Through Electrical Testing

In the testing of semiconductor devices it is necessary to detect electrically open contacts in transistors. Existing approaches have involved wiring contacts in series using alternating metal straps and diffusion patterns, but this does not separate broken metal or diffusion patterns from non-conductive contacts. This proposal uses a chain of transistors wired in parallel to minimize potential fail modes not related to open contacts. In the prior system using metal lands and silicon alternately as the conductors between contact holes, the test was sensitive to non- conductive contact holes. However, since it was also sensitive to missing or broken segments in the metal and silicon conductors the sum of all three defect types would often be mistaken for non-conductive contact hole defects. This solution allows for segregation of different failure mechanisms so that non-conductive contacts may be monitored exclusively. The proposed non- conductive contact hole monitor can be made by contacting a large number of NPN transistors in parallel, as shown in the figure. A key element of the design is a single metal land connecting all base contact holes in series with a pad at each end. The base pads are indicated as 1 and 2, the collector pad as 3 and the emitter pad as 4. The testing procedure requires normal transistor breakdown tests such as BVcbo (breakdown voltage collector to base--emitter open), BVebo (breakdown voltage emitter to base--collector open), and BVceo (breakdown voltage collector to emitter--base open) to screen out defects that render the transistor group inoperable. Next, is to test the continuity of the base cont...