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Electron-Beam Injected Current Testing

IP.com Disclosure Number: IPCOM000035710D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 98K

Publishing Venue

IBM

Related People

Lukianoff, GV: AUTHOR

Abstract

The techniques described provide a method of testing chips, substrates, and modules, using multiple electron-beam instrumentation. Testing possibilities are: line conductor continuity, linear resistance, introduction of AC currents, and contactless circuit current excitation.

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Electron-Beam Injected Current Testing

The techniques described provide a method of testing chips, substrates, and modules, using multiple electron-beam instrumentation. Testing possibilities are: line conductor continuity, linear resistance, introduction of AC currents, and contactless circuit current excitation.

Referring to Fig. 1, electron-beam 10 produces a positive potential at one end of conductor 11, and electron-beam 12 produces a negative potential at the other end of conductor 11 at the points of impingement. Both beam currents and conductor current 1E are equal; as a result, the conductor remains neutral. When a conductor discontinuity 12 is present, a pronounced gray shade contrast is produced at the discontinuity by the opposite polarities. Line scan response of a scanning reading beam 13 reveals the discontinuity.

(Image Omitted)

Equipment required for the injected current technique consists of a multiple beam column unit with separate, independent tool controls, beam current monitors, and secondary electron emission monitors. The beam columns provide multiple beams for either spot probing or a scanning mode of operation. The beam current and emission controls are needed to maintain a predetermined balance of the positive and negative charges in order to maintain specimen neutral and keep the required injected current at a constant level. A continuous sensing of both these factors, beam current and emissivity, and means of their adjustments have to be introduced into the instrumentation. A block diagram of the system is shown in Fig. 2.

Referring to Fig. 3, resistance measurements can be performed by the use of three electron-beams. Beam 30 provides a positive potential on the resistor 31, and beam 32 a negative potential at the points of impingement. Both provide a current through the resistor 31. Scanning beam 33 measures the resultant voltage drop 34 along the resistor length.

Both electron-beams IE1 and IE2 (Fig. 4) have a constant energy and are blanked and unblanked at the same time. Direction of injected current flow (I injected) during the pulses, depends upon the polarities produced by the beams at the points of beam impingement.

(Image Omitted)

Double polarity injected currents IE can be achieved by reversing beam polarities at each end of conductor 50 (See Fig. 5). Directions of injected current flow depends upon beam polarities at the points of impingement. Three methods for low, intermediate and high frequency operation follow: Low frequency AC injected currents are introduced in conductor 50 by stationary electron-beams E1 and E2, having opposite polarity. Accelerating potentials of the electron-beams ar...