Interface characterization by C(V) measurements of three-terminal MOSOS capacitors

It is shown that with knowledge of quantities, such as front interface charges, film doping concentration, and film thickness, the back interface properties can be determined easily by using the C (V) characteristics for a depleted back interface, since the charges located at the boundary between silicon film and buried oxide now have a strong influence on the capacitance. To illustrate this quantitatively, the simulated front and back surface potentials for a MOSOS capacitor with specified properties and a silicon film doping concentration of 5×10¹⁶ cm^-3 are shown as functions of the front gate voltage V_G. Typical values for the back interface charge density (5×10¹¹ to 1×10¹² cm^-2) result in a positive offset of the back surface potential thus giving rise to the onset of strong inversion at the back interface, when the gate voltage reaches V_T1 and before the front channel is formed at V _G=V_T2. Extraction of the back interface charge density can be performed by a simple data fitting algorithm in conjunction with an accurate numerical model