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Tri-Potential Method for Testing Electrical Opens and Shorts in Multilayer Ceramic Packaging Modules

IP.com Disclosure Number: IPCOM000048883D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Chang, TP: AUTHOR [+4]

Abstract

A scanning electron beam is used to address test points on the top side of a multilayer ceramic packaging module at two different potentials, one for charging and one for detection, while a second beam, which can be a scanning beam or a flood beam, is used to charge the back side at a third potential.

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Tri-Potential Method for Testing Electrical Opens and Shorts in Multilayer Ceramic Packaging Modules

A scanning electron beam is used to address test points on the top side of a multilayer ceramic packaging module at two different potentials, one for charging and one for detection, while a second beam, which can be a scanning beam or a flood beam, is used to charge the back side at a third potential.

A functional electrical test of a multilayer ceramic packaging module is concerned with detection of unintended open circuits and unintended short circuits within or between networks of interconnected electrically conducting lines. In general, there are networks which contain only top to top interconnections and networks which contain top to bottom interconnections. An open circuit could occur in any top to top interconnection or in any top to bottom interconnection. A short circuit could occur between top to top interconnections, between top to bottom interconnections, or between one of each. A tri-potential electron beam method can be used to detect all of these defects.

The basic principle of the tri-potential technique is shown in the figure. A scanning beam is used to address test points on the top side of the sample at two different potentials, one for charging and one for inspection, while a second beam, which can be a scanning beam or a flood beam, representing the two charged states (T/S and B/S) and the uncharged state, can be detected by the inspection beam, thus allowing top to top networks and top to bottom networks to be identified and tested independently.

The charging mechanism is based on secondary electron yield (Eta) characteristics at different beam incident potentials. It is well known in the literature that secondary electron yield initially increases with increasing beam potential and eventually reaches a peak value, thereafter decreasing with further increase in beam potential. Two cross-over potentials (V(0),V(2)) exist at which the secondary electron yield equals unity. The second cross-over potential V(2) is the stable one (typically 1 to 2 kV).

Charging of network lines is accomplished by operating the electron beam at a potential different from a cross-over potential. In the figure, as an example, the backside charging is performed at a beam potential V(1), which is lower than the second cross-over potential V(2). At this potential, the secondary electron yield is higher than unity and positive charging occurs creating a surface potential change (Delta)V(1). As a result, when this charged area or any other area in electrical contact with this area is subsequently inspected by an inspection bea...