New device to improve transistor quality

In a paper just published in Electronics Letters, Dr Peter Wilson and Dr Reuben Wilcock from the University's School of Electronics and Computer Science (ECS), describe the Configurable Analogue Transistor (CAT) which he and his team have developed, and for which they have a patent pending.

The CAT approach can be applied to batches of transistors which in testing after manufacture prove to have an unacceptably high variability.

According to Dr Wilson, the manufacturing process for deep submicron technologies is currently very expensive, with the cost of failed devices running into huge figures. Designers create new chip designs and generally simulate how they will perform. When the silicon wafers are produced they will then undergo rigorous electrical testing to ensure that they are working. It is at this point that the designer often realises that some of the chips do not work, which creates a problem of reduced yield, i.e. the number of chips which work out of a batch reduces. This has been an increasing problem for Integrated Circuit designers over the last few years as process technology dimensions have become increasingly small, and the corresponding variability of devices worsened.

‘One of the biggest challenges we face when shrinking devices in these new technology nodes is that there is increasing variability in the resulting devices and this is causing unacceptably poor yields in the circuits being produced – particularly in analogue and mixed signal devices where performance is at a premium,' said Dr Wilson. 'Now 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 percent can be achieved using this approach.’

According to Dr Wilson, the CAT technique can also be applied to existing products to improve their performance and longevity.

‘As technology changes over time, the CAT technique allows us to reconfigure devices so that products continue to work,’ said Dr Wilson. ‘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 copy of Dr’s Wilson and Wilcock paper can be accessed at: http://eprints.ecs.soton.ac.uk/16667/