A direct depletion capacitance measurement technique to determine the doping profile under the gate of a MOSFET

A technique to directly measure the depletion capacitance between the inversion layer and the substrate in the determination of the doping profile under the gate of a MOS device is described. The measurement technique is less sensitive to stray capacitance and can be carried out under steady-state conditions.The technique, therefore, lends itself to direct measurement on small-area devices thus avoiding the need for large-area devices as in other techniques. Doping profiles obtained using this method on MOS transistors as small as W × L = 18.8 × 3.1 µm²are compared with profiles Obtained by the pulse method on large-area MOS capacitors. The comparison shows good agreement in the range where the technique is applicable.