Within the next few years, your watch, television, and computer may all contain microelectromechanical systems (MEMS), micron-size machines being developed at Sandia.
Jim Smith, Manager of Intelligent Micro- machine Dept. 1725, together with colleagues from Sandia and Trey Roessig, Al Pisano, and Roger Howe from the University of California at Berkeley, have built a MEMS prototype that functions as a clock source. The minuscule machines with moving parts the size of a pollen grain perform the same job as quartz crystals, the traditional technology used in timing devices in all digital electronics.
THE TIMING IS RIGHT - Jim Smith, Manager of Intelligent Micromachine Dept. 1725, looks through a high-power microscope at a MEMS prototype that functions as a clock source. (Photo by Randy Montoya)
Roessig, accompanied by Jim, made the first public announcement of the prototype in June at the Solid State Sensor and Actuator Workshop in Hilton Head, S.C.
Micromachines are made from polysilicon, which is the same material used in manufacturing integrated circuits, the building blocks of digital electronics. Because of this, the micromachines and integrated circuits can be constructed on one chip.
The system-on-a-chip concept, only about three years old, embeds the micromachines in a shallow trench on a silicon wafer. These wafers with the microelectromechanical devices are then used as the starting material for the conventional complementary metal oxide semiconductor (CMOS) manufacturing process of integrated circuits. The integrated circuits are built on the surface of the wafer, while the MEMS are sealed in the trench.
The prototype also acts somewhat differently from other micromachines used in products currently on the market - such as sensors for pressure and acceleration - that are minute moving gears and pins.
The frequencies provide the constant timing signals necessary for the digital electronics device to operate. Because of the low noise, the signals are constant and not disrupted, resulting in more accuracy.
Collaboration with Berkeley
Jim says his efforts build on work done at the University of California at Berkeley by Howe and Clark Nguyen (now at the University of Michigan).
He adds that having the clock source on the same chip as other electronic circuitry is one of the building blocks toward developing complete electromechanical systems in a single monolithic piece of silicon.