Noncontact Testing of Interconnections in Film Integrated Circuits using an Electron Beam

A noncontact procedure for sensing continuity and isolation faults in large, dense interconnection patterns by means of selective deposition of charge by an electron beam is Proposed and discussed. When the accelerating potential is properly chosen, a marked variation in the secondary electron signal occurs during the charging of an electrically floating element to an equilibrium potential. This phenomenon forms the basis of the method. A laboratory system has been constructed to demonstrate the procedure. Results obtained indicate agreement with the basic theory and demonstrate the application of the technique to continuity and isolation testing of conductor films and failure analysis of encapsulated circuits. Electron beam testing has a clear advantage over mechanical probe testing in terms of speed and flexibility. The less attractive features include the need for a vacuum system and the inability to detect continuity faults when the fault resistance is less than about one megohm.