Faster inspection of MEMS possible with microinterferometer arrays

(November 1, 2010) — Scientists involved in the European Union’s "Smart inspection systems for high-speed and multifunctional testing of MEMS and MOEMS" (SMARTHIEHS) project are developing a new test concept based on parallel inspection of devices at wafer level using micro-optical systems. The intent is to make the testing of microelectromechanical systems (MEMS) and micro-optoelectromechanical systems (MOEMS) structures one hundred times as fast as it is now. Testing one hundred structures simultaneously will reduce the time involved from 20 minutes to less than half a minute.

Sintef is coordinating the project, in which eight European centers 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," says project manager Kay Gastinger of Sintef.

Interferometric detection
The scientists use a number of interferometers in the testing process. The interferometers themselves are produced using standard microtechnology processes, which makes them cost-effective.

The aim of the project is to create 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 beamsplitter wafers. The top wafer contains 25 microlenses, which act as tiny imaging microscopes. Small micromirrors centered on the lenses produce the interference effect."

The project is due to end in 2011, by which time the demonstrator model will have been developed into a 50-channel version in a design that can be further expanded to 100 channels.


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