Scanning Microscopy


By fundamental experiments and theoretical treatments a detailed understanding of the capacitive coupling voltage contrast {CCVC) has been gained, demonstrating that this technique is, in principle, applicable to a non-destructive testing of passivated integrated circuits (IC) by means of electron beams. In fact, however, several problems have to be eliminated in order to introduce this testing technique into a production line procedure.

In a first step, preconditions have to be met. These are a primary electron (PE) energy where the electron yield is greater than one and a sufficiently low extraction field above the IC. Secondly, as CCVC vanishes within a certain time span caused by charge compensation during electron irradiation, several precautions have to be undertaken. To obtain unfalsified CCVC-micrographs a fast image recording and processing system has to be realized; for IC-internal waveform measurements suitable sampling electronics have to be developed. Besides this, the resulting measurement errors are classified and determined. These are the error due to charge compensation on the passivation layer during electron irradiation, the error due to an incomplete coupling of the line potential to the passivation surface and the error due to capacitive coupling cross talk from neighboring lines.

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