Analog Devices Target: MEMS Microphone Market
By Lubab Sheet, senior director emerging technologies, SEMI
With consumer electronics applications driving strong growth in MEMS devices, companies historically supplying traditional MEMS automotive markets are hoping for a piece of the action.
As the only company developing commercial MEMS products based on integrated surface micromachining, Analog Devices thinks it can serve the fast growing MEMS microphone market by integrating electronics and signal processing on-board for increased functionality. Imagine being able to use your cell phone for a conference call in a loud place, with the recipient only hearing your voice and no background noise.
There are two MEMS technologies: bulk micromachining and surface micromachining.
Bulk micromachining is the older technology in which “you just etch stuff out of silicon.” Bulk processing does not allow integration with electronics. It requires a large sensor area, has big signal to noise ratios, but design and manufacturing are simpler due to the de-coupling of the mechanical and electrical components. Bulk micromachining is harder to miniaturize and the costs might be higher.
Surface micromachining involves depositing layers of polysilicon to build the structure. Integration is feasible; sensor area is small, with lower signal to noise ratio; design and manufacturing is more complex; and costs are lower. Devices are smaller and power requirements are lower for integrated MEMS. Electronics can be integrated on the top or the bottom of surface micro-machined MEMS, with comparable performance; the choice is largely driven by intellectual property.
DRIE is the only “MEMS-centric” piece of equipment used in manufacturing, while everything else is standard, so there is not a lot of room for cost savings in this regard. Packaging and testing however, are key cost and performance drivers for MEMS. Innovation in MEMS packaging and test is needed to drive down cost. Most testers are based on electrical stimula, whereas MEMS testing requires acoustics, motion and other variables. Testers need to sense motion. “In some cases, we simply can’t test, we can only characterize.”
The information contained in this article was derived from content presented at the SEMI New England Breakfast Forum, March 7, 2007 in Billerica, Massachusetts. If you have questions or comments, feel free to contact Lubab Sheet at Lsheet@semi.org or 1.408.943.6921.