Micro Electronic

A focus on modern silicon integrated circuit technology provides students with early exposure to up-to-date applications; a flexible organization allows professors to tailor their courses to the appropriate breadth and depth for their students. This web site is designed to make it even easier to use this innovative text.
Leading the charge at Berkeley to integrate micro-electromechanical systems (MEMS) with silicon electronics is Electrical Engineering and Computer Sciences (EECS)
MEMS are fabricated using processes similar to the way integrated circuits are manufactured. To create a three-dimensional MEMS structure, a sacrificial film is deposited on top of a silicon substrate and patterned as a sort of foundation for the structural layer that follows. Once the structural layer is deposited, the sacrificial layer is removed to leave the free-standing MEMS features. MEMS are traditionally fashioned from polycrystalline silicon, also known as polysilicon, because of the material's strength and resistance to fatigue. Today, MEMS like those in automobile airbag deployment sensors are then connected via wires to integrated circuits fabricated beside them. These interconnects, King says, can limit performance.
Stacking the MEMS and circuits is necessary to maximize performance and reduce the size of the device. The problem is that to obtain polysilicon's desirable properties, the material must be annealed, heated to a high temperature and then cooled.
Annealing burns out any electronics that are underneath the MEMS," says King, the director of Berkeley's state-of-the-art Microfabrication Laboratory and a member of the Center for Information Technology Research in the Interest of Society (CITRIS).
While custom processes for integrating MEMS and electronics are available today, they're far too impractical for mass production. No semiconductor factory, King explains, is willing to pass their wafer to a MEMS foundry and then take it back again to complete the electronics.
How many products can you make with a boutique process?" King says. "Not many. If you rely on a specialized process for every MEMS product, it will never be cost effective

King's goal is to develop a process similar to the polysilicon technologies the MEMS industry is built upon. To do it, the researchers are exploiting a material in the same column of the periodic table of the elements as silicon. Silicon combined with germanium, King explains, provides the benefits of polycrystalline silicon but can be processed at temperatures hundreds of degrees lower. It can also be patterned using conventional MEMS fabrication tools.
The Berkeley researchers have already built prototype devices using the silicon-germanium process, including an audio-frequency filter used in radio transceivers. In the future, King says, modularly integrated MEMS-electronics technology could be used to build low-power radio transceivers on a single chip.
Because the processes remain the same as those used by current commercial MEMS foundries, the factories do not need to be adapted for silicon-germanium nor does industry-standard MEMS design software need to be rewritten.