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Unformatted text preview: ECE 440 Homework XIV Spring 2006 1. Redraw Figure 6-12 of band diagrams for the ideal MOS structure in an n-type silicon at (a) thermal equilibrium (b) electron accumulation (c) electron depletion and (d) strong inversion. Also, in the drawing show a simple circuit illustrating how the biasing is applied in each case. 2. For an ideal MOS structure, the SiO 2 thickness is 300 , and the substrate is doped with 2x10 16 /cm 3 acceptors. Determine the threshold voltage, V T , required to achieve strong inversion and find the electric field in the oxide when the applied bias V=V T . Repeat for a different MOS where the SiO 2 thickness is 40 but the substrate doping is the same. For an ideal MOS, the equation to determine threshold voltage is (6-33) F i d s i d T C Q C Q V 2 + = + = So we need to calculate the three unknown quantities. 0.365V ln = = = i A F i F n N q kT E E 2 7 8 14 10 15 . 1 10 300 10 85 . 8 9 . 3 cm F d C i i...
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