A study of the electrical performances of isolation structures

The electrical properties of field oxide isolation structures are investigated from the device physics point of view. The importance of the potential barrier formation mechanism is clearly demonstrated through the derivation of an analytical formulation of the subthreshold current. The current independence on the isolation device length is clearly established. A large range of ideal field oxide geometries is systematically characterized to demonstrate the effect of two key parameters: the amount of buried oxide and the bird´s-beak slope. The predicted isolation performances are verified on semirecessed and fully recessed structures by means of process/device simulations and experimental data. Good agreement is found between measured and calculated subthreshold currents