Browse Prior Art Database

Nondestructively Determining an FET Surface Leakage Source

IP.com Disclosure Number: IPCOM000081187D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Viele, AA: AUTHOR

Abstract

This process indicates whether unwanted field-effect transistor (FET) surface leakage in an electrically failing metal-oxide semiconductor FET (MOSFET) large-scale integrated (LSI) chip is associated with the thin oxide (gate region) or the thick oxide/quartz (field region).

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Nondestructively Determining an FET Surface Leakage Source

This process indicates whether unwanted field-effect transistor (FET) surface leakage in an electrically failing metal-oxide semiconductor FET (MOSFET) large-scale integrated (LSI) chip is associated with the thin oxide (gate region) or the thick oxide/quartz (field region).

The process assumes that electrical diagnostics have isolated the fail site to a particular circuit or discrete device, and shown the electrical failure to be caused by surface leakage (an inversion problem).

The figure shows the cross section of a hypothetical FET device with a contaminant trapped at the thermal oxide/quartz interface. When the chip is electrically biased, this contaminant can become polarized and spread laterally as indicated in the figure. This charge buildup can result in an image charge at the silicon surface, which causes leakage if it occurs between diffusions. However, surface leakage can occur in the channel area because of a thin oxide problem (contamination, excessive charge levels, etc.). To determine whether the surface leakage is occurring in the channel (thin oxide) or peripheral to the channel geometry, the following process can be used.

The chip is first rinsed in deionized (DI) water. A photoresist, typically positive, is applied to the quartz surface 16 and baked for five minutes at 75 degrees C. The defective area of the chip is then exposed to ultraviolet light using a microspectrophotomer for about one minute. The photoresist is developed, rinsed in DI water, and baked again for five minutes at 125 degrees
C....