B a c kg r o u n d
Testing
Dutch Meteoriet con sortium tackles MEMS testing bottleneck Currently, MEMS testing basically comes in two flavors: highly automated but tailored to a very specific device that’s manufactured in high volumes, and, essentially, manual inspection for everything else. A consortium of ‘neighboring’ companies and research institutes aims to bridge that gap by developing an all-electric, universal MEMS testing solution suitable for all volumes. Paul van Gerven
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no mistake, though: large manufacturers stand to benefit, too, as their testing time per unit can be reduced. All in all, the new testing methods will remove a major bottleneck for the adoption and application of MEMS technology.
Great value
Most chips only need to have electrical signals run through them to find out whether they work as intended. MEMS, on the other hand, require another type of physical input for testing, such as a temperature Credit: University of Twente
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magine having to discard a product at the final stages of its production process because it turns out a chip is malfunctioning. This doesn’t happen very often in the electronics industry because chips are rigorously tested before they’re mounted. But not all companies, particularly manufacturers of specialized MEMS chips, have the luxury of low-cost and highly automated testing procedures. Because of their mechanical nature, MEMS are more complex to test than electrical ICs. Large MEMS manufacturers like Analog Devices and Bosch can afford to develop highly specialized testing equipment, but for companies with lower volumes, sometimes as low as a few thousand devices per year, that’s never going to be costeffective. Nor are there any specific ‘MEMS testing houses’ to outsource to. These companies have to resort to labor-intensive ‘manual’ testing, which often isn’t enough to prevent that a percentage of the final assembled product won’t work. Three companies and two research institutes, all located in the east of the Netherlands, have partnered up to solve this problem. Co-financed by the European investment fund OP-Oost, the Meteoriet consortium is looking to develop a universal MEMS testing technology. Make
An early version of the MEMS chip Meteoriet will be using for calibration.
increase, a movement or a changing magnetic field. A MEMS airbag sensor chip, for example, is tested by subjecting it to a massive deceleration. And a MEMS microphone device is exposed to a range of sound frequencies. Each type of device requiring a different physical stimulus makes MEMS testing hard to standardize. But perhaps it doesn’t need to be. The Meteoriet partnership is convinced that it’s possible to test MEMS chips the same way regular ICs are tested: by electrical means only. “The movement in a MEMS chip is associated with electrical signals, which can be measured and used to obtain information about the displacement that has occurred. It’s also possible to induce the desired movement electrically. Taking together, you can test a MEMS chip electrically,” explains Paul van Ulsen, CEO of test technology company Salland Engineering, which spearheads Meteoriet. An all-electrical MEMS test could look like this: an electrical stimulus is applied to induce a displacement of a particular mechanical part of the chip. Next, an appropriate electrical measurement is performed to verify whether the displacement did indeed take place. Other functionalities, such as temperature sensors or heaters, can be tested in a similar fashion.
