'Sensing is Believing'

"At last we have a noninvasive method of diagnosing sick chips"

(Article Precis, 15/Aug/1998, Issue 2147, p20)
Sharon Ann Holgate reports on a new technique for tesing chips, developed by researchers at the University of Sussex. The new system permits the observation of electricity moving through integrated circuits, without affecting the operation of the circuit.

Existing techniques involve touching probes to a chip's surface, but this limits one to analysing only a few places out of possibly millions - quality control is thus not as good as might be desired. Faulty components can be spotted, but not the problems which caused the faults. Other techniques cannot tell the difference between different material types. Common to them all, current is taken from the circuit during the measuring process, altering the way the circuit works.

The researchers at Sussex have developed a 'scanning electric potential microscope' (SEPM); using a tungsten tip and a special voltmeter, the device creates a capacitance between its tip and the test circuit - an AC current flowing below the tip changes the capacitance, which can be measured. Using very high resitances (in the order of 10^17 ohms), the device is designed to cause current changes in the circuit of no more than 10^-15 amps - currents this small do not change the circuit's operation.

Work continues to improve the system; the resistances used must be increased still further in order to allow the scanning of components in the nanometre range. A spokesman for Motorola said that any system which can quickly analyse extremely small components without damaging them would be welcomed by the industry.

Note: In order to comply with copyright law, I have ommited some details from the original article. Thus, for a complete insight into the topic covered here, please either consult your local library for the issue concerned, purchase the relevant issue from your local newsagent, or back-order it from the publishers.

Precised by Ian Mapleson, 16/Aug/1998.