White Paper: Perspectives On Microsensor Systems: Past, Present, And Future

By Stephen D. Senturia Professor of Electrical Engineeering, Emeritus, Massachusetts Institute of Technology Chairman and Chief Technology Officer, Polychromix, Inc.

The word Microsensor is typically used to mean a sensing device that is fabricated using microelectronic technology, either based on silicon integrated circuit technology, thin-film electroforming technology, or thick-film hybrid-circuit technology. The field of Microsensors has a fifty-year history starting with several key developments in the 1950's:

• The invention of integrated circuits.
• The discovery of piezoresistance in silicon.
• The discovery of selective etching of single-crystal silicon.
• The development of thin-film read heads for magnetic recording.

Pioneers in the 1960's and 1970's developed silicon diaphragm pressure sensors with piezoresistive readout, ceramic gas sensors, ion-sensitive field-effect transistors, Hall-effect magnetic sensors, and various specialty devices. But it was only in the early 1980's that the field of Solid-State Sensors and Actuators became identified as a clear discipline, with its own special technologies and capabilities, expanded now to include not only etching into silicon wafers to make interesting shapes but also the use of what is now called surface micromaching: deposition, patterning, and selective etching to remove sacrificial materials, creating complex structures attached to a substrate wafer.

In November 1981, the Materials Research Society meeting in Boston included a seminar on Solid-State Sensors. It drew about 80 people from Japan, Europe, and the US. Along with the pressure sensors, Hall-effect sensors, and gas sensors, there were some interesting specialty sensors: a dielectric sensor for monitoring the cure of resins, and an ISFET fabricated on the tip of a needle. This meeting was a turning point in the development of Solid-State Sensors, because at that meeting, the decision was made to set up the International Steering Committee on Solid-State Sensors and Actuators, the governing body for the highly successful series of biennial international conferences, starting with Transducers 83 in Delft, and rotating between Europe, the US, and Asia on a six-year cycle. This meeting now attracts roughly 1000 persons from all over the world.