Examples - 1 MOSCapacitor((1 MOS(Metal oxidesemiconductor capacitors betweenmetal(Ag,Au,Al,Heavilydoped polySi,etc,insulator(SiO2,Si3N4 etc

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
12/4/2010 1 MOS Capacitor (Metal Insulator Semiconductor junctions) (1) MOS (Metal oxide semiconductor) capacitors are made of two junctions between metal ( Ag , Au, Al , Heavily doped poly Si , etc), insulator ( SiO 2 , Si 3 N 4, etc) and semiconductors Here the thin oxide layer (insulator, 10nm 1 μ m) is sandwiched in between the metal and the semiconductor 12/4/2010 1 V G Gate An ideal MOS structure has following properties: Metallic gate is uniform & thick enough to distribute charge/voltage evenly across the oxide surface at any operational condition Oid i ft il t ith t x GND Metal-Oxide-Semiconductor (MOS) capacitor Oxide is a perfect insulator with zero current flow Oxide layer is isotropic with uniform boundary at the semiconductor interface ( no local charge centers ) Semiconductor is uniformly doped and thick enough and any applied gate voltage (V G ) is only felt near the insulator boundary Ohmic contact at back side of the semiconductor to extract charges Work functions of metal and semiconductor are equal: () SM CF at flat Band EE    Ex 1 MOS Capacitor R 1 V 1 V S V G =3V T Calculate V 1 values that put this MOS capacitor in inversion regime? (Logic in this example is relevant to the last example in lecture notes 6) In previous cases we assume substrate is grounded (V 0), no resistances. The presence of V1 and resistances change th lt d th it S x V G Gate 12/4/2010 2 R 2 GND the voltage drop across the cavacitor as V= V ,? GS G S GS V Here V is given V 2 1 12 2 1 2 1 2 1 3 (, . . 0 ) 3 2 S GS G S T GS T G T S T TT R No current flow through capacitor V V RR R VVVV V To operate in inversion regime V V it is V V i R V f substrate is grounded i e V R V V VV     MOSFET: I D V D Relationships (6) If we summarize our findings for an n channel MOSFET 12/4/2010 3  2 2 0 0 & 0 1 & 2 & 1 2 DD s a No G T D D D s a t O Dsat G T tG G T G o T T Z CV V Z CVVV V L I K W V V here V V V C L V x V       Example 1 MOS Capacitor: An MOS capacitor at T=300K with oxide thickness of 200nm and a p type substrate (bulk silicon). The bulk silicon has a acceptor density of N A =10 16 cm 3 . Calculate the reference potential (voltage) with respect to doping ( φ F ), width of the space charge region (depletion region), W, surface electric field, E S , at threshold and the threshold voltage, V T . Remember the MOS capacitor 12/4/2010 4 16 10 1/2 1/2 14 0 19 16 ln( ) 0.026 ln(10 /10 ) 0.36 2 21 1 . 78 . 8 51 0 2 2 0.36 0.962 1.6 10 10 FA i S F A kT Nn V V q K W m qN      ln( ) ln( ) Ai F Di kT pt y p e q kT Nn nt y p e q  00 0 @0 ( ) A SS A S From depletion region calculations qN dE xW dx K K qN Ex W x K At surface n  3 0 0 0 0 0 (0) 104 10 / 2 4 2 S A S OS S A TF F eed to evaluate at x EV c m Kq N Vx KK N   
Background image of page 1

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

View Full DocumentRight Arrow Icon
12/4/2010 2 Example 2
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/13/2010 for the course ELECTRICAL EECS 170A taught by Professor Ozdalboyraz during the Fall '10 term at UC Irvine.

Page1 / 6

Examples - 1 MOSCapacitor((1 MOS(Metal oxidesemiconductor capacitors betweenmetal(Ag,Au,Al,Heavilydoped polySi,etc,insulator(SiO2,Si3N4 etc

This preview shows document pages 1 - 3. Sign up to view the full document.

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