course230B4new

course230B4new - MOSFET Scaling Device scaling: Simplified...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: MOSFET Scaling Device scaling: Simplified design goals/guidelines for shrinking device dimensions to achieve density and performance gains, and power duction in VLSI. reduction in VLSI. Issues: Short-channel effect, Power density, Switching delay, Reliability. The principle of constant-field scaling lies in scaling the device voltages and the device dimensions (both horizontal nd vertical) by the same factor ) such that the electric 2/22/2010 1 and vertical) by the same factor, ( > 1), such that the electric field remains unchanged . Rules of Constant Field Scaling MOSFET Device and Circuit Parameters Multiplicative Factor ( > 1) caling evice imensions / Scaling assumptions Device dimensions ( t ox , L , W , x j ) Doping concentration ( N a , N d ) Voltage ( V ) 1/ 1/ Derived scaling Electric field ( E ) 1 behavior of device parameters Carrier velocity ( v ) Depletion layer width ( W d ) Capacitance ( C = A / t ) 1 1/ 1/ Inversion layer charge density ( Q i ) Current, drift ( I ) Channel resistance ( R ch ) 1 1/ 1 Derived scaling behavior of circuit parameters Circuit delay time ( CV / I ) Power dissipation per circuit ( P VI ) Power-delay product per circuit ( P ) ircuit density ( / 1/ 1/ 2 1/ 3 2 2/22/2010 2 Circuit density ( 1/ A ) Power density ( P / A ) 1 Scaling of Depletion Width W V qN D si bi dd a = + 2 ( ) Maximum drain depletion width: or nd For N a N a and V dd V dd / , W D W D / if V dd >> bi . W qN S si bi a = 2 However, the source depletion width, is indep. of V d and only scales as W W / . dd S S Furthermore, the maximum gate depletion width, cales even less than 1/ W kT N n q N dm si a i a 2 4 = ln( / ) 2/22/2010 3 scales even less than 1/ . Generalized Scaling Allows electric field to scale up by ( E E ) while the device dimensions scale down by , e voltage scales by i.e., voltage scales by / ( V ( / ) V ). More flexible than constant-field scaling, ut has reliability and power concerns but has reliability and power concerns. To keep Poissons equation invariant under the p q transformation, ( x , y ) ( x , y )/ and /( / ) within the depletion region: 2 2 ( / ) ( / ) qN N a should be scaled to ( ) N a . 2 2 ( ) ( / ) ( ) ( / ) x y q a si + = 2/22/2010 4 Constant Voltage Scaling Special case of = in generalized scaling: The only mathematically correct scaling as far as 2D Poisson eq. and boundary conditions are concerned. N a 2 N a , kT N n 4 ln( / ) therefore, the maximum depletion width, scales down by . oth the short hannel ll ff W q N dm si a i a 2 = ( ) t ox L W t dm ox + 24 2 3 / Both the short-channel V t roll-off, and the threshold voltage, V W V e t dm bi bi ds = + ( ) V V qN V C t f b B si a B bs ox = + + + 2 2 2 ( ) remain unchanged for constant-voltage scaling....
View Full Document

Page1 / 72

course230B4new - MOSFET Scaling Device scaling: Simplified...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online