The maximum operating voltage of an NMOS integrated circuit is 10 V and substrate doping level in the region between the MOSFETs (the field region) is NA = 5 x 10^17 cm-3. Determine the minimum oxide thickness in the field region (the field-oxide thickness) needed to prevent current leakage between neighboring MOSFETs. Neglect the oxide charge, and consider aluminum gate (the worst-case scenario).
Hint: The field oxide can be considered as the fate oxide of a parasitic MOSFET that should be kept off (the maximum operating voltage should be below the threshold voltage) to prevent a possible leakage.