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Scaling of MOS Circuits

EE213 VLSI Design

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Scaling

• VLSI technology is constantly evolving

towars s!aller line withs

• "euce feature si#e generally leas to

 $  %etter & faster 'erfor!ance

 $ More gate & chi'

• More accurate escri'tion of !oerntechnology is (LSI )ultra large scale

integration

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Scaling *actors

• In our iscussions we will consier 2 scaling

factors+ , an -

• 1& - is the scaling factor for VDD an o.ie

thic/ness D

• 1& , is scaling factor for all other linear

i!ensions• 0e will assu!e electric fiel is /e't constant

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Scaling *actors for Device

ara!eters• Si!'le erivations showing the effects of scaling are erive in uc/nell an

Eshraghian 'ages 12 124

• It is i!'ortant that you unerstan how the following 'ara!eters are effecte

 %y scaling• 5ate 6rea

• 5ate Ca'acitance 'er unit area

• 5ate Ca'acitance

• Charge in Channel

• Channel "esistance

• 7ransistor Delay

• Ma.i!u! O'erating *re8uency• 7ransistor Current

• Switching Energy

• ower Dissi'ation er 5ate )Static an Dyna!ic9

• ower Dissi'ation er (nit 6rea

• ower S'ee rouct

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Scaling of Interconnects

• "esistance of trac/ " : L & wt

• " )scale9 : )L & ,9 & ) )w& , 9; )t

&,99

• ")scale9 < ," 

• therefore resistance increases with

scaling

t w L

6

=

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Scaling 7i!e Constant

• 7i!e constant of trac/ connecte to gate+

• 7 < " ; Cg

• 7)scale9 < , " ; )- & ,2

9 ;Cg < )- & ,9 ;";Cg• Let - < ,+ therefore 7 is unscale>

• 7herefore elays in trac/s on?t reuce with scaling

• 7herefore as trac/s get 'ro'ortionately larger+ effect gets

worse• Cross tal/ %etween connections gets worse %ecause of

reuce s'acing