Effective channel length estimation using charge-based capacitance measurement

An effective channel length is estimated from the capacitance-voltage (C-V) curves of actual size MOSFETs which are measured using charge-based capacitance measurement (CBCM). To evaluate the accurate capacitances between the gate and the channel of sample MOSFETs, their parasitic capacitances are removed by using the test MOSFETs having various channel size and special test structure. A good linear relation between the gate-channel capacitance and the design channel length is obtained and then, the effective channel length is estimated from it. It is found that the obtained effective channel length is shorter than that extracted by the conventional channel resistance method.