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HW7_solutions

# HW7_solutions - Homework 7 1 Problem(a Consider an...

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Homework 7 1. Problem: (a) Consider an n-channel MOSFET with uniform channel doping with N A = 3 × 10 17 cm - 3 and having an oxide 10 nm thick. Calculate the sub-threshold slope at 300 K. (b) Assume now that the Si-SiO 2 interface is not ideal, but there are interface traps with density N it = 10 12 cm - 2 /eV . What is the sub-threshold slope in this case? Solution: (a) On lecture notes Part 3, the subthreshold slope is given by Eq. (280) S = k B T e ln (10)(1 + C D C ox ) (1) where C D = s W D,max and W D,max is the maximum depletion width defined by Eq. (221) W D,max = 4 s k B T ln ( N A /N i ) e 2 N A 1 / 2 = 61 . 5 nm (2) and C D = 11 . 7 × 8 . 854 × 10 - 12 F/m 61 . 5 × 10 - 9 m = 0 . 0017 F/m 2 , (3) and C ox = ox t ox = 0 . 0034 F/m 2 . Inputting the above values and finally we can get the sub-threshold slope S = 0 . 0892 . (b) When the Si-SiO 2 interface is not ideal with an interface traps density N it = 10 - 12 cm - 2 , the subthreshold slope is calculated using Eq. (282) S = k B T e ln (10)(1 + C D + C it C ox ) (4) ECE344 Fall 2009 1

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where C it is given by Eq. (226) C it = eN it = 0 . 0016 F/m 2 , (5)
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HW7_solutions - Homework 7 1 Problem(a Consider an...

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