Allowable surface silicon thickness for fully-depleted SOI MOSFET´s

Allowable ranges for SOI (silicon-on-insulator) device parameters such as surface dopant concentration and surface silicon thickness are analyzed considering the condition that the front-gate should control inversion charges under the front-channel threshold. Two criteria for the front-gate control of the inversion charge over the back-gate are assumed in this analysis. As the SOI structure has more fixed oxide charge at the back-interface, the allowable surface silicon thickness becomes thinner compared with the normally accepted thickness for a fully-depleted SOI structure. To obtain an SOI structure with controllability of the front-gate over the back-gate and elimination of the floating substrate effect, optimal choice of the surface dopant concentration and surface silicon thickness is needed