A silicon MOS magnetic field transducer of high sensitivity

Abstract
A structure has been devised which converts magnetic flux density change to a change in output current. The structure is essentially a P-channel MOST with the drain diffusion split into two halves. A magnetic field normal to the silicon surface deflects device current towards one half-drain. By operating the MOST in the "pinched-off" mode (VDS> VGS-VT) the output impedance is made high, so that large output voltage swings may be obtained. A theoretical study of the voltage and current distributions in the MOST channel has given data on the influence of device geometry on sensitivity. Experimental results indicate a linear relationship between output current and magnetic flux density, and an unexplained nonlinear variation of output with device current. Comparison of experimental results with theory indicates a carrier Hall mobility in the channel of 116 cm2/V.s.