Electron beam testing: Problems in practice

Electron beam testing has now become an almost indispensable design verification aid for very large scale ICs. The test preparations for circuit analysis are very important as the purpose of these preparation is to ensure that the integrated circuit is driven as it was during characterization on the computerized test system. The same applies when the circuit is being irradiated by the electron beam. This involves the use of preparation techniques such as plasma etching and plasma cleaning, the development of measuring equipment, determining suitable parameters for the electron probe and constantly checking how the circuit is functioning. The actual circuit analysis is carried out in two stages – first the defective block is located and then the individual circuit responsible for the design weakness pinpointed. Cases may arise where measurements on interconnections covered by an oxide layer are required. It might also be necessary to impress signals on certain nodes using a mechanical probe or to separate the circuits.