MEMS Shrinking Near Microscopic

PORTLAND, Ore.—Super-small inertial sensors, like microelectromechanical system (MEMS) three-axis accelerometers, are finding more-and-more uses in ultra-small Internet of Things (IoT) devices such as wearables and industrial and medical devices such as endoscopes that can navigate the smallest tracks, vessels and cavities of our bodies. The mCube Inc. (San Jose, Calif.) 0.9 cubic millimeter three-axis accelerometer—1.1-by-1.1-by-.74 millimeters—was designed specifically for these applications, by making it 75 percent smaller than the 2-by-2 and 3-by-3 millimeter accelerometers sold by its competitors. Samples of mCubes world smallest three-axis accelerometer will be shown for the first time at the MEMS Executive Congress 2015 (Napa, Calif., Nov. 4-to-6).

The three-axis accelerometer from mCube is three years ahead of the competition, according to analysts, at less than one cubic millimeter.
(Source: mCube, used with permission)

"What we call the Internet of moving things," Ben Lee, chief executive officer (CEO) of mCube told EE Times, "needs the smallest form factor possible, for many applications, and we are the only ones who can supply them today. Analysts tell us we are three years ahead of our competition."
Symmetry is another principle that mCube follows, on the advise of the founding father of MEMS, Kurt Peterson who is famous for saying "symmetry is Godlike." The original mCube three axis accelerometer was 1.6-by-1.6, the current model is 1.1-by-1.1 and its next generation model will be symmetrically sub-millimeter, according to Lee. Peterson emphasizes symmetry because it allows MEMS devices—especially those stacking the MEMS atop the application specific integrated circuit (ASIC) on the same complementary metal oxide semiconductor (CMOS) chip to run without the compensation circuitry required by non-symmetrical architectures, especially those with the MEMS and ASIC on separate chips, according to Lee.

The mCube vias between the ASIC and the MEMS on a single CMOS chip is 11-to-100 times smaller than the connections used by Invensense and Bosch respectively
(Source: mCube, used with permission)
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Throughout each shrinkage only minor changes have been made to mCube's MEMS-on-CMOS architecture which still carries the same 30 micron proof mass--which is 10 micron bigger than its competitors, according to Lee, who claims mCube's large proof mass is what makes its measurements of acceleration more accurate.
Instead of shrinking the proof mass, mCube has been going to smaller package architecture. For instance, its first 1.6 millimeter square MEMS was in a land-grid array package (LGA), the current 1.1 millimeter square device uses a Wafer Level Chip Scale Package (WLCSP) and its sub-millimeter model due out in the future will go to an even smaller chip-on-board (COB) package so small that it can be housed inside the IoT or medical device's application specific integrated circuit (ASIC) package.

The first mCube three-axis accelerometer was in a land grid array (LGA) package, but the current model downsized it by going to a wafer-scale chip scale package and in the future mCube plans to downsize more to a chip-on-board package that can fit inside other manufacturer's systems-on-chip (SoCs).
(Source: mCube, used with permission)
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The mCube MC3571 accelerometer has the same user configurable 8-,10- or 14-bit output as its predecessor which has shipped over 100 million units, with an output data rate of up to 1,024 bits-per-second over an I2C bus.

http://www.eetimes.com/document.asp?doc_id=1328125