Contributing Editor, MEMS Investor Journal
IMEC, Europe's largest independent research center in MEMS and nanotechnology, is offering a monolithically integrated silicon-germanium (SiGe) MEMS process as a foundry service. IMEC’s new MEMS fabrication capability extends its more-than-CMOS (CMORE) initiative to include a new polysilicon-germanium process that allows both the CMOS and MEMS devices on the same chip. Polysilicon-germanium can be deposited at significantly lower temperatures than traditional polysilicon, permitting MEMS devices to be fabricated atop already finished CMOS chips without damaging their delicate circuitry.
Using this “MEMS last” technique, all of the CMOS circuitry for devices is fabricated first, after which the MEMS devices are fabricated on top of the finished CMOS wafer. IMEC claims superior performance for this approach, compared to the traditional technique of fabricating separate wafers for CMOS and MEMS and then either bonding them together or just wire-bonding the separate die inside the same package. IMEC cites superior signal-to-noise ratios, reduced interconnect parasitic capacitance and reduced power consumption as well as a smaller overall die and package sizes.
IMEC cross-sectional view showing a micromirror array on top of the six layers of interconnect.
MEMS device tuning and optimization is accomplished by varying its structural layers from 300 nanometers to 4 microns, enabling both very thin devices like micromirrors, as well as very thick mechanical structures for gyroscopes as well as other types of actuators. IMEC claims its process can also be used for silicon microphones, speakers, sensors, probe-based memories and micro-power generators.
IMEC capacitive RF MEMS switches packaged with glass caps using a BCB seal.
IMEC claims its total-solution service allows European researchers to take their design ideas from conception to fully packaged devices at a single shop. To simplify the designers task, IMEC's CMORE toolbox now includes libraries of premade silicon-germanium blocks for common devices, through silicon vias (TSVs) stacking die for 3D chip applications as well as all the necessary capping steps that protect MEMS mechanisms from contamination.
IMEC's CMORE service can perform low volume manufacturing of finished, tested designs on its own premises. And to fulfill larger orders, IMEC has already transferred the processes to its foundry partner TSMC, which will handle volume manufacturing.
Copyright 2010 MEMS Investor Journal
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