Posted: Nov 01, 2010

Faster inspection of micro-optical components

(Nanowerk News) The EU's SMARTHIEHS project will make the testing of MEMS structures one hundred times as fast as it is now, leading to cheaper and more reliable electronic equipment for everyone.
MEMS (MicroElectroMechanical Systems) are ultraminiature circuits which are packed in their thousands on silicon wafers.
They are used in mobile telephones, microphones and vehicles, for example as sensors in airbags and tyres.
At present, inspecting these structures is a bottleneck in the production process, as they have to be tested one at a time, which is both expensive and time-consuming.
Parallel inspection
Scientists involved in the SMARTHIEHS (SMART InspEction systems for High Speed and multifunctional testing of MEMS and MOEMS) project are developing a new test concept based on parallel inspection of circuits at wafer level.
Testing one hundred structures simultaneously will reduce the time involved from 20 minutes to less than half a minute. No only is this cheaper, but more functions can be tested at the same time.
SINTEF is coordinating the project, in which eight heavyweight European centres of expertise in micro-optics are participating. The project is already halfway to completion.
"It is the industry itself that has been asking for better and cheaper methods," explains project manager Kay Gastinger of SINTEF ICT.
"Today, electronic tyre sensors are only tested electrically, which does not guarantee full functionality. The SMARTHIEHS research programme will result in cheaper sensors and more reliable equipment."
Detects deformations and faults
The scientists use a number of interferometers in the testing process. These are instruments that are capable of identifying shape, changes of shape and vibrations in objects extremely accurately. The interferometers themselves are produced using standard microtechnology processes, which makes them highly cost-effective.
The aim of the project is to create specially manufactured glass wafers that incorporate up to 100 of these interferometers and then use them to test 100 circuits on a MEMS wafer at a stroke. The scientists will be able to measure the shape, any deformations and resonance frequencies of the MEMS structures and thus identify manufacturing faults.
"We have already produced a prototype measuring station that is capable of measuring five structures at a time," says Gastinger.
"The prototype consists of lens, mirror and beam-splitter wafers. The top wafer contains 25 microlenses, which act as tiny imaging microscopes. Small micromirrors centred on the lenses produce the interference effect."
The project is due to come to an end in 2011, by which time the demonstrator model will have been developed into a 50-channel version, in a design that can easily be further expanded to 100 channels.
Source: SINTEF