Thursday, March 2, 2017

Etch Rates for Micromachining Processing

When designing a microfabrication process, the etch rate of each material to be etched must be known. Knowing the etch rates of other materials that will be exposed to the etch, such as masking films and underlying layers, enables an etch process to be chosen for good selectivity (high ratio of etch rate of the target material to etch rate of the other material)—if one exists. These two papers compare the etch rates of different materials in various etchants

K. R. Williams and R. S. Muller, "Etch rates for micromachining processing," in Journal of Microelectromechanical Systems, vol. 5, no. 4, pp. 256-269, Dec 1996.

K. R. Williams, K. Gupta and M. Wasilik, "Etch rates for micromachining processing-Part II," in Journal of Microelectromechanical Systems, vol. 12, no. 6, pp. 761-778, Dec. 2003.
doi: 10.1109/JMEMS.2003.820936


Sunday, February 12, 2017

2D thermal MEMS accelerometer

A 2D thermal MEMS accelerometer uses a monolithic approach that integrates the sensor and electronics onto the IC which is then hermetically sealed in a package. The silicon die includes a heating element and thermopiles suspended over a cavity etched into the die. Instead of using capacitance to measure force, the thermal sensor uses the movement of the heated gas molecules to detect acceleration. With acceleration, the heated molecules move in the direction of acceleration, and with zero acceleration the heated gas is symmetrical above the heater. These devices have no flexing or moving parts, which make them more durable and delivers very high measurement repeatability.