Analytical expression of top surface charge sensitivity in fully depleted semiconductor on insulator MOS transistor

An analytical expression of free top surface charge sensitivity in FDSOI MOS structure has been established for weak inversion region and validated by TCAD numerical simulation. The influence of various FDSOI stack parameters has been analyzed. The impact of the interface trap density has been particularly emphasized, leading to a strong undesired degradation of sensitivity. This indicates that top surface passivation is a key issue for efficient charge sensing. These expressions of top surface charge sensitivity and associated threshold voltage shift should be very useful for sensor design and electrical characterization purpose.