SAW devices polished off in Nottingham

Researchers at Nottingham Trent University have purchased an Engis polishing and lapping machine to assist their work into the use of acoustic wave devices for use in sensors.

Researchers at Nottingham Trent University have purchased an Engis polishing and lapping machine to assist their work into the use of acoustic wave devices for use in sensors.

Dr Michael Newton, Reader in Experimental Physics at the University, explained: "Surface acoustic wave devices are used extensively in radio frequency electronics such as mobile phones, but they have additional properties, one of which is mass sensitivity, making them potentially useful in sensor applications".

The current three-year research project, led by Dr Newton, supported by Professor McHale and assisted by PhD student Carl Evans, investigates surface acoustic wave device designs using thinned wafers.

It has been established that if the wafer is sufficiently thin, the metal interdigital transducers (IDT) can be fabricated on its reverse surface from the one used for sensing, thus obviating the problems associated with electrical shorting of the IDT when used in a liquid environment.

It is in the creation of these very thin wafers that the Engis lapping and polishing equipment is being used.

The three materials currently being used for the wafers are quartz, lithium niobate and lithium tantalate.

The wafers themselves are polished from a starting thickness of approximately 0.5mm to a finished thickness of 100-150 microns.

In this particular application extreme flatness is not important because the sensing devices have an area of only 1cm2.

One of the aspects of the Engis machine that was most attractive to the research group was its very small footprint.

As in many research laboratories, at Nottingham Trent space is at a premium, and the fact that the equipment could provide both lapping and polishing functions while taking up very little bench-space has proved to be most valuable.

The School of Biomedical and Natural Sciences at Nottingham Trent undertakes wide-ranging and thriving research activities for which a major focus has been the recent formation of the Interdisciplinary Biomedical Research Centre (IBRC).

Research into the potential use of acoustic wave sensors in cancer research screening, using the Engis equipment for wafer polishing and lapping, is due to start in January.

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