Lecture-04 - EEE 525: VLSI Design, L-04 Short-Channel...

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1 EEE 525: VLSI Design, L-04 Short-Channel Effects Spring 2010, ASU Yu (Kevin) Cao, yu.cao@asu.edu , GWC 336 Highlight Velocity saturation Other short-channel effects V th lowering (DIBL) Parasitic resistance Temperature effect Reading: Chapter 2 EEE525, ASU, Y. Cao Lecture 04 - 2 -
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2 Highlight Velocity saturation Other short-channel effects – V th lowering (DIBL) – Parasitic resistance – Temperature effect Reading: Chapter 2 EEE525, ASU, Y. Cao Lecture 04 - 3 - Long-Channel MOSFET V GS + V DS + Threshold voltage (V th ) n+ n+ n+ 3 4 5 6 x 10 -4 A) V GS = 2.5 V V GS = 2.0 V Linear Saturation  2 2 ds ds th gs ox ds V V V V L W C I B sb B th th V V V 2 2 0 Linear: V ds < (V gs –V th ) EEE525, ASU, Y. Cao Lecture 04 - 4 - 0 0.5 1 1.5 2 2.5 0 1 2 V DS (V) I D ( V GS = 1.5 V V GS = 1.0 V V DS = V GS -V T ) 1 ( 2 1 2 ds th gs ox ds V V V L W C I Saturation: V ds > (V gs th )
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3 Velocity Saturation For a long channel device: I ds = Q·v·W= Q inv ·( μ E )·W However, velocity saturates at high electrical fields (E v (m/s) v sat =10 5 Constant velocity high electrical fields (E) Since E V ds /L, velocity saturation is more pronounced for shorter L For short-channel transistors, velocity saturation happens before “pinch-off” E (V/ μ m) E sat Constant mobility sat E E for 1 E E E v EEE525, ASU, Y. Cao Lecture 04 - 5 - (V ds < V gs –V th ) Note: mobility μ is voltage dependent   sat E E for sat sat v 2 sat sat E v 2 sat sat v E  2 2 1 0 1 th gs th gs eff V V a V V
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Lecture-04 - EEE 525: VLSI Design, L-04 Short-Channel...

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