A SUBMICRON ELECTRON-BEAM TESTER FOR VLSI CIRCUITS BEYOND THE 4-MB DRAM

This paper describes the electron-optical low-voltage column of the submicron electron-beam tester. It can be used to produce an electron probe of 0.12-μm diameter, 2.5-nA probe current, and 1-kV beam voltage. It is shown that in the case of waveform measurements on 1.1-μm interconnection lines, the crosstalk is only approximately 3%. The voltage resolution is sufficient to allow the sense signal of 4-Mb DRAM (dynamic random access memory) to be measured. Further internal measurements with the electron probe for the chip verification of the 4-Mb DRAM are also shown which demonstrate the flexibility and the benefits of electron-beam testing. On the basis of the measured performance data and its successful use in the circuit analysis of the 4-Mb DRAM, the submicron electron-beam tester appears to be suitable also for VLSI circuits with reduced design rules, e.g., for the 16-Mb DRAM. The improvements required for such future applications are briefly discussed.