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Stabilizer Grid for Contrast Enhancement in Contactless Testing of MLC Modules

IP.com Disclosure Number: IPCOM000046051D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Golladay, SD: AUTHOR [+3]

Abstract

A stabilizer grid is provided for contrast enhancement in contactlesstesting of multilayer ceramic (MLC) modules.

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Stabilizer Grid for Contrast Enhancement in Contactless Testing of MLC Modules

A stabilizer grid is provided for contrast enhancement in contactlesstesting of multilayer ceramic (MLC) modules.

It is known that contactless electrical testing of MLC substratesmay be achieved by the generation of voltage contrast through interaction of beam electrons at various energy levels with the specimen. Typically, systems for implementing such a scheme rely upon multiple guns which allow simultaneous application of electron beams with different energies on the top and bottom side of the MLC test sample. In one application, a flood gun injects charge into the sample and establishes a distribution of surface potentials which are then analyzed by a directed "reading" beam. In order to charge the three- dimensional conductor network negatively, the flood gun energy must be higher than the second crossover of the secondary electron emission yield of the conductor material. For molybdenum conductors, the secondary crossover is approximately 1.8 kV. Beam energies required for this material are of such a magnitude that the beam also causes charging effects in the insulating material (typically, A1/2/O/3/) surrounding the conductor and impacts the voltage contrast.

It has been found that the energy of the flood beam electrons may be reduced to a few hundered volts (200-500 V) if a negatively charged "stabilizer grid" is placed between the flood gun and the sample. The negative potential of the grid is transferred to the conductors via low energy electrons and secondary electrons around the first crossover of molybdenum. Fig. 1A shows a layer of Al/2/O/3/ insulating material 1 with molybdenum conductors 3. A 1.4 kV read beam is shown top side. Fig. 1B shows the secondary emission (SE) ratio of the A1/2/O/3/ and molybdenum conductor, from which it can be seen that both surfaces will tend to charge positively.

Fig. 2A shows the insulator and conductor arrangement shown in Fig. 1A with a flood beam only on the bottom side of the insulator.

The stabilizer grid is shown biased to -50 volts. Fig. 2B shows the secondary emission ratio characteristics with the flood beam biased ...