An alternative method for measuring flatband voltage in MOS devices

摘要

The present paper describes an experimental method that can be used to measure the flatband voltage value in MOS devices. The method is based on the detection of the non-steady-state/steady-state transition of the surface potential at the Si-SiO_2 interface when it is pulsed by a voltage signal. This detection is evidenced as follows. A set of current versus signal frequency measurements, for different voltage amplitudes, are performed. The frequency values corresponding to the maximum measured current (optimal frequencies) are read. Various plots of gate voltage signal (V_G) versus critical frequencies (f_m -V_G) are performed for voltage values comprised in the range 0.2 to 2 V stepped by a 0.1 V increment. The f_m -V_G curves are found to undergo an abrupt change of slope at a specific gate voltage value. The value of the flatband voltage is extracted from the former curves. Experiments have been carried out on a variety of devices. The values of flatband voltage obtained are compared to that obtained by the conventional C-V method and that specified by device manufacturers. The results are found to be in quite good agreement.