homework4

# homework4 - -1 C/cm 3 3 A n-type MOSFET L = 1 μ m t ox =...

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Homework 4 1. A high-frequency capacitance voltage measurement of a silicon MOS structure was fitted by the following expression: C(V G ) = 6 pF + 12 pF/(1 + exp(3 V G )) a) Calculate the oxide capacitance per unit area and the oxide thickness. The area of the capacitor is 100 x 100 micron and the relative dielectric constant equals 3.9. b) From the minimum capacitance, calculate the maximum depletion layer width and the substrate doping density. c) Calculate the bulk potential. d) Calculate the flatband capacitance and the flatband voltage. e) Calculate the threshold voltage 2. Consider an aluminum-SiO 2 -silicon MOS capacitor ( Φ M = 4.1 V, ε ox / 0 = 3.9, χ = 4.05 V and N a = 10 17 cm -3 ) MOS capacitor with t ox = 5 nm. a) Calculate the flatband voltage and threshold voltage. b) Repeat for an n -type silicon substrate with N d = 10 16 cm -3 . c) Repeat with a surface charge of 10 -7 C/cm 2. d) Repeat with a charge density in the oxide of 10
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Unformatted text preview: -1 C/cm 3 . 3. A n-type MOSFET ( L = 1 μ m, t ox = 15 nm, V T = 1 V and μ n = 300 cm 2 /V-sec) must provide a current of 20 mA at a drainsource voltage of 0.5 Volt and a gate-source voltage of 5 Volt. How wide should the gate be? 4. Consider an n-channel MOSFET with n+ poly-Si gate, T oxe = 10 nm, and body doping N A =5x10 16 cm-3 . Assume W=10 μ m, V GS - V T = 3V, and Ε sat (critical electric field for velocity saturation) = 2x10 4 V/cm. a) Find V Dsat for i. L = 1 μ m. Is this a long-channel device or a short-channel device? ii. L = 0.1 μ m. Is this a long-channel device or a short-channel device? For the questions below, assume L = 0.5um. b) Without considering velocity saturation, what is I DS at V DS = 1 V? c) What is I DS at V DS = 1 V with velocity saturation? d) Calculate the subthreshold swing, S....
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