On-line extraction of model parameters of a long buried-channel MOSFET

A buried-channel depletion MOS transistor has an implanted neutral conducting channel between the source and drain due to which the device works in a variety of modes such as accumulation, accumulation-depletion, depletion, inversion-depletion, inversion, etc., and presents a more complex structure than an enhancement-mode device. For precise circuit simulation, accurate and on-line extraction of model parameters has assumed significant importance. It is found that representing the implanted buried channel by an equivalent box with average doping and junction depth gives a convenient trade-off between simplicity in modeling and accuracy in device characterization. The present work proposes a method of deriving the necessary model parameters through the measurement of a single device parameter, namely drain conductance under different operating conditions. The on-line measurements carried on a boron-implanted relatively long buried-channel MOSFET have been used to predict the best box for the profile and give other model parameters necessary for circuit simulation. It is shown that the method is most insensitive to measurement conditions compared to other techniques.