An MOS chip for surface impedance measurement and moisture monitoring

Surface impedance measurements are employed in a variety of applications such as moisture sensing (1), (2). Sheet resistances as high as 10¹⁶Ohms/sq are often encountered (3), and reliable measurements are difficult to obtain. This paper reports a planar MOS device and associated measurement technique that can be used to make AC sheet resistance measurements in the frequency range 1 Hz - 10 kHz, and which yields reproducible measurements for sheet resistances as high as 10¹⁶Ohms/sq.