Dopant profiles determined from enhancement-mode MOSFET dc measurements

Simplified algorithms are described which allow the determination of the dopant profile in the gate region of a four-terminal enhancement-mode metal-oxide-silicon field-effect transistor (MOSFET). The method calls for the dc measurement of the source-body voltage VSB as a function of the gate-source voltage VGS for a fixed minority-carrier channel current. The profile depth is proportional to dVSB/dVGS and the dopant density is inversely proportional to d2VSB/dV2GS. Only the oxide and silicon dielectric constants and the oxide thickness are needed in the computations. The data acquisition was computerized and includes the use of an operational amplifier circuit. The method is illustrated by the profile of a phosphorus layer implanted in an n-type silicon substrate.