An MOS device for AC measurement of surface impedance with application to moisture monitoring

A surface impedance measurement (SIM) device fabricated using a metal-gate n-channel depletion-mode MOS process is reported. The device serves as the basis of an ac instrumentation system for the measurement of sheet resistances as high as 10
¹⁶
Ω/square in the frequency range 1 Hz to 10 kHz. Results are presented illustrating the use of the device as a moisture monitor.