Test Circuit for Evaluating Characteristics Mismatch in Metal-Oxide-Semiconductor Field-Effect Transistor Pairs by Estimating Conductance Variation through Voltage Measurement

A procedure is described for evaluating characteristics mismatch in a pair of metal–oxide–semiconductor field-effect transistors (MOSFETs), which are nominally designed to be identical. This procedure is based on conductance variation estimation through voltage measurement. By measuring the gate voltage dependence of the voltage of the middle point of a MOSFET pair connected in series, various pieces of information on difference in characteristics (e.g., channel width difference and threshold voltage difference) in the MOSFET pair can be extracted. The applicability of the proposed procedure to fabrication process monitoring is also described and the principle of a suitable test circuit structure is illustrated.