Come up and see my etchings

	Digging micromachined trenches through etching

An improved method of etching silicon developed by Jy Bhardwaj from Surface Technology Systems Ltd (STS), Newport, UK, could side-step some of the problems facing researchers trying to build miniature motors, gearboxes, and sensors and Micro-Electro-Mechanical Systems (MEMS), from silicon on a commercial scale.

At the Royal Society of Chemistry's annual conference in April, Bhardwaj described how the slow process of wet chemical etching can only be used to make a limited range of products. STS' Advanced Silicon Etch process, however, is much faster and more flexible because it uses a plasma to etch the required features on to a silicon surface rather than acids.

In the first step, a plasma deposits a thin layer of a fluoropolymer on one face of a silicon wafer. A second plasma then decomposes the fluoropolymer releasing reactive fluorine atoms which then eat into the silicon. By switching between the deposition and etch steps, it is possible to build up a pattern of trenches in the silicon. By careful control three-dimensional structures can then be built up.

Bhardwaj told the conference that 'Recent advances made, in increasing etch rate, are driving down the cost of making devices allowing the technology to be adopted for a wide range of applications.