Analysis of the deep depletion MOSFET and the use of the d.c. characteristics for determining bulk-channel charge-coupled device parameters

A qualitative and quantitative analysis of the deep depletion MOSFET operated in the regimes of depletion, enhancement and depletion/enhancement, is presented. The quantitative analysis presented here does not make any of the simplifications made in some earlier papers, applicable to shallow channel depletion MOSFETs, and uses a four terminal device model so as to provide a complete set of characterisation equations for each mode of operation. It is demonstrated that the device parameters of flatband voltage, implanted channel doping and depth, and bulk and surface carrier mobilities, can easily be determined by use of some of the characteristics equations in conjunction with simple measurements made directly from the drain current/drain voltage characteristics. Furthermore these parameters are applicable to bulk-channel charge-coupled devices fabricated under the same implantation and drive-in conditions. As the device parameters are determined from the drain current/drain voltage characteristics the techniques presented offer an attractive alternative to the more complicated C- V methods used for bulk-channel charge-coupled device characterisation. The validity of the model and the techniques used to determine the device parameters is demonstrated by the good agreement between calculated and measured results obtained from fabricated devices.