ANALYSIS ON ACCURACY OF CHARGE-PUMPING MEASUREMENT WITH GATE SAWTOOTHPULSES

Charge-pumping (CP) measurement is performed on MOSFET's with their ga tes tied to sawtooth pulses, Influence of both rise time (t(r)) and fa ll time (t(f)) on the CP current of the devices with different channel lengths is investigated at different pulse frequencies, Results show that the dominant mechanism affecting the measurement accuracy is the energy range of interface-trap distribution D-it (E) swept by the gate signal for frequencies below 500 kHz and carrier emission for frequen cies above 500 kHz. For frequencies higher than 600 kHz, incomplete re combination could be an additional mechanism when t(f) is too short, H ence, it is suggested that low frequency is more favorable than high f requency, especially for sawtooth pulses with long t(r) and short t(f) , due to little carrier emission and negligible geometric effects even for devices as long as 50 mu m However, if high frequency (e.g., 1 MH z) is required to obtain a sufficiently large S/N ratio in the CP curr ent, sawtooth pulses with equal t(r) and t(f) should be chosen for the least carrier emission effect and thus more reliable results on inter face-state density, Moreover, for both sawtooth and trapezoidal purses with a typical amplitude of 5 V, a lower limit of 200 ns for t(r) and t(f) is necessary to suppress all the undesirable effects in devices shorter than at least 20 mu m.