# Flatband and Threshold Voltages

An Al-silicon dioxide-silicon MOS capacitor has an oxide thickness of 450Angstroms and a doping of Na=10^15 cm^-3. The oxide charge density is Q'ss=3x10^11cm^-2. Calculate (a) the flat-band voltage and (b) the threshold voltage. Sketch the electric field through the structure at the onset of inversion.

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#### Solution Preview

These problems require some effort. I have referred to some papers to find the missing data and provided the reference links to them as well.

I haven't calculated the numbers as once the concepts are clear and we come up with a well defined formula, all it takes is plugging in numbers in a calculator and coming up with an answer. I have left that much portion to the student.

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You can use the following two formulate to calculate the two quantities.

a) V fb = Phi (metal-semiconductor) - (Qf/Cox)

Cox = Eox/tox ...

#### Solution Summary

An Al-silicon dioxide-silicon MOS capacitor has an oxide thickness of 450Angstroms and a doping of Na=10^15 cm^-3. The oxide charge density is Q'ss=3x10^11cm^-2. Calculate (a) the flat-band voltage and (b) the threshold voltage. Sketch the electric field through the structure at the onset of inversion.