Effect of some technological parameters on Fowler-Nordheim injection through tunnel oxides for non-volatile memories
Résumé
In this work the effects of various technological parameters on Fowler-Nordheim injection through thin (around 7.2 nm) silicon dioxide films in metal-oxide-semiconductor capacitors have been studied. Attention has been paid to the effect of gate geometry (round or strip gate) and area, substrate doping type (boron or phosphorus one), polycrystalline silicon gate structure (simple polysilicon or polysilicon-oxide-nitride-oxide-polysilicon structure) and tunnel oxide type (standard or nitrided silicon dioxide). The effect of all these parameters on Fowler-Nordheim tunneling injection and on the potential barrier height at both oxide injecting interfaces are usually neglected in literature and moreover the tunnel coefficients obtained from a simple capacitor are used in the simulation of programmable operations of electrically erasable programmable read only memories. Quasi-static capacitance (voltage) and current (voltage) measurements have been performed and the latter have been simulated by using a constant effective barrier height at the injecting interface. We have found that Fowler-Nordheim tunneling parameters and potential barrier height at both oxide injecting interfaces are affected by the substrate doping type, oxide type, gate geometry and gate structure but they are not affected by the gate area. Moreover in all structures, a difference between the barrier heights at the two injecting interfaces has been observed. The variation induced by the studied technological parameters on the potential barrier height are comparable to the variation induced by considering a constant (classical theory) or electrical field dependent (quantum theory) barrier height as reported in literature.