METHOD FOR AUTOMATIC TROUBLESHOOTING INSIDE VLSI CIRCUITS WITH AN ELECTRON PROBE AND DEVICE FOR CARRYING OUT SUCH A METHOD

摘要

1. A method of detecting faults in VLSI-circuits (IC) using an electron probe (1) which triggers secondary electrons at test points in the VLSI-circuit (IC) - with a detector which, via a secondary electron signal, determines the actual level at the test points, - with a logic simulator (CAD-system VENUS and PRIMUS C) which serve to simulate the VLSI-circuit (IC) and to determine the theoretical level which is likely to occur at the test points with predetermined test patterns, - with a test computer (4) which controls a drive unit (2) for the VLSI-circuit (IC) and co-ordinates actual value and theoretical value, characterised in that, a) test points in the VLSI-circuit (IC) are assigned co-ordinates and the test points receive a designation and that the logic-links of the test points one in relation to another are determined, b) the VLSI-circuit (IC) is tested via the external terminals and fault paths are determined on the basis of the fault picture obtained from this test, c) the electron probe (1) is positioned at a first test point of a fault path, the appropriate test pattern is applied, and with the aid of the secondary electron signal the actual value at the test point is determined, d) the actual value at the test point is compared with the theoretical value obtained for the same test pattern from the simulation of the VLSI-circuit (IC) with the assistance of the logic simulator (CAD-system VENUS and PRIMUS C), e) the next test point in the fault path is tested in a corresponding manner and that f) the testing procedure is repeated at new test points in the test path until the fault location is localised.