quiz230B-2_2010_solution

# quiz230B-2_2010_solution - Solutions(a Scale length Î = W...

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ECE 230B Quiz-2 (Winter 2010) Assume silicon, room temperature, complete ionization. Consider the design of a 100 nm (channel length) nMOSFET. Assume a gate oxide thickness of 3 nm. (a) What substrate doping (assume uniform) is needed for control of short- channel effects? (b) Estimate the mobility at V gs - V t = 1 V based on universal mobility (Hint: First calculate the depletion charge density at maximum depletion width). (c) In (b), estimate the saturation current (per device width) using the n = 1 velocity saturation model.
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Unformatted text preview: Solutions: (a) Scale length Î» = W dm + 3t ox ~ L/2 = 50 nm. So W dm ~ 40 nm and N a ~ 8x10 17 cm-3 (from Fig. 3.25). (b) Vertical field ~ q N a W dm / Îµ si + (V gs-V t )/6t ox ~ 1 MV/cm. So Î¼ eff ~ 250 cm 2 /V-s from Fig. 3.15. (c) m = 1 + 3t ox /W dm ~ 1.25. v sat ~ 10 7 cm/s. So 2 Î¼ eff (V gs-V t )/(mv sat L) ~ 4, and I dsat ~ 4.4 A/cm. I C Wv V V V V mv L V V mv L dsat ox sat g t eff g t sat eff g t sat =-+--+-+ ( ) ( ) / ( ) ( ) / ( ) 1 2 1 1 2 1 Î¼...
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