MEMS Technology
"A sensor is the gateway between the three-dimensional world and an information system. You can't measure phenomena of the 3D-world efficiently and accurately without resorting to 3D-technology. This is why VTI has created 3D MEMS for its motion and pressure sensors."
Heikki Kuisma, Director, Advanced Development
firstname [dot] lastname [at] vti [dot] fi
VTI's silicon capacitive sensors are made of single crystal silicon and glass. These materials ensure exceptional reliability, unprecedented accuracy and excellent stability over time and temperature. Manufacturing technologies are borrowed from semiconductor industry, which provides mass production capability and cost efficiency. Additional MEMS-specific technologies include wafer bonding and deep reactive ion etching of silicon.
VTI is using the simple and stable capacitive detection principle. It is based on the variation of the distance between two surfaces. The capacitance, or charge storage capacity of a pair of surfaces, depends on their distance and on the overlapping surface area. VTI's 3D MEMS sensors are robust structures that are very sensitive to inertial forces and pressure but are insensitive to other environmental variables and causes of failure. Symmetry and other sound design principles of the accelerometers and gyroscopes help to improve stability, linearity, cross-axis sensitivity and susceptibility to vibrations.
VTI's 3D MEMS are capped, i.e. inherently hermetically sealed in a wafer level process for reduced packaging requirements. No particles or chemicals can enter the capped sensor, a fact that ensures reliability. VTI is a pioneer in utilizing through-silicon vias in the capping wafer. This saves device area and simplifies the packaging process.
Depending on the needs of the application the accelerometer, gyroscope and pressure sensor elements can be designed for a specific sensitivity, measuring range and frequency response. Accelerometer and gyroscope elements are available for both in-plane and z-axis measurement as well as for 3-axis sensing. Gyroscopes can be used for signals as small as earth's rotation and as large as tracking the motion of a human hand.
System-in-package technologies are used to combine one or more sensing elements with signal processing circuits. Very robust and reliable moulded cavity plastic packages are used for automotive and industrial products. For consumer electronics sensors wafer level packaging technologies are used that guarantee smallest possible device size and cost.