Chip tweaking

Manufacturing deep submicron integrated circuits is an expensive business and keeping the yield of those integrated circuits at acceptable levels is a serious issue for chip manufacturers.

One way of improving that yield has recently been unveiled by researchers Dr Peter Wilson and Dr Reuben Wilcock from the School of Electronics and Computer Science (ECS) at Southampton University.

The pair has jointly developed what they are calling the Configurable Analogue Transistor (CAT), for which they have a patent pending.

The CAT comprises a transistor that is connected up to a series of other adjustment devices, allowing any circuitry built on the concept to be tweaked after it has been manufactured to ensure that its characteristics meet a desired specification.

The researchers believe that such a calibration process could easily be built in to an existing chip test environment, meaning that instead of losing a significant proportion of bad devices off the production line, scrap devices could be retuned back to their original specification.

Dr Wilson said: 'With CAT we can take whole batches of chips and tighten their performance characteristics, resulting in massive improvements in yield.

‘Improvements in variability of up to 80 per cent can be achieved using this approach.'

Dr Wilson sees a particular benefit of the technology for remote or hostile environments, such as military and space applications.

The CAT has been developed so its silicon overhead, or the extra area on a die needed to implement it, is relatively small.

Dr Wilson claims that the overhead is in fact typically less than a couple of per cent for a complete circuit and because of this he believes that approach will make it commercially attractive for less demanding applications.

In an exclusive interview with The Engineer Online, Dr Wilson said there are other benefits to the approach.

'As technology changes over time, the CAT technique allows us to reconfigure devices so that products continue to work.

'For example, remote circuits in satellites and sensor devices can be reprogrammed and effectively recalibrated to take account of changing characteristics over time and environmental conditions.'

A more detailed technical explanation of the CAT can be found at: http://eprints.ecs.soton.ac.uk/16667/1/v14.pdf