DOC PREVIEW
UT Arlington EE 5340 - Semiconductor Device Theory

This preview shows page 1-2-17-18-19-36-37 out of 37 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 37 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Slide 1Ideal 2-terminal MOS capacitor/diodeMOS surface states** p- substr = n-channelMOS Bands at OSI p-substr = n-channelEquivalent circuit for accumulationEquivalent circuit for Flat-BandEquivalent circuit for depletionEquivalent circuit above OSIDifferential charges for low and high freqIdeal low-freq C-V relationshipComparison of low and high freq C-VEffect of Q’ss on the C-V relationshipFlat band condition (approx. scale)Flat-band parameters for n-channel (p-subst)Flat-band parameters for p-channel (n-subst)Typical fms valuesFlat band with oxide charge (approx. scale)Inversion for p-Si Vgate>VTh>VFBApproximation concept “Onset of Strong Inv”MOS Bands at OSI p-substr = n-channelComputing the D.R. W and Q at O.S.I.Calculation of the threshold cond, VTEquations for VT calculationFully biased n-MOS capacitorMOS energy bands at Si surface for n-channelComputing the D.R. W and Q at O.S.I.Q’d,max and xd,max for biased MOS capacitorFully biased n- channel VT calcn-channel VT for VC = VB = 0Fully biased p- channel VT calcp-channel VT for VC = VB = 0n-channel enhancement MOSFET in ohmic regionConductance of inverted channelBasic I-V relation for MOS channelI-V relation for n-MOS (ohmic reg)ReferencesComputing the D.R. W and Q at O.S.I.EE 5340Semiconductor Device TheoryLecture 25 – Spring 2011Professor Ronald L. [email protected]://www.uta.edu/ronc©rlc L25-21Apr20112Ideal 2-terminalMOS capacitor/diodex-xox0SiO2silicon substrateVgateVsubconducting gate,area = LWtsub0yL©rlc L25-21Apr20113MOS surface states**p- substr = n-channelVGSsSurf chg Carr DenVGS < VFB < 0s < 0 Accum. ps > NaVGS = VFB < 0s = Neutral ps = NaVFB < VGSs > 0 Depletion ps < NaVFB < VGS < VThs = |p| I ntrinsic ns = ps = niVGS < VThs > |p| Weak inv ni< ns < NaVGS = VThs = 2|p| O.S.I . ns = Na©rlc L25-21Apr20114MOS Bands at OSIp-substr = n-channelFig 10.9*2q|fp|qfpxd,max©rlc L25-21Apr20115Equivalent circuitfor accumulation•Accum depth analogous to the accum Debye length = LD,acc = [eVt/(qps)]1/2•Accum cap, C’acc = eSi/LD,acc•Oxide cap, C’Ox = eOx/xOx•Net C is the series combOxacctot'C1'C1'C1C’OxC’acc©rlc L25-21Apr20116Equivalent circuitfor Flat-Band•Surface effect analogous to the extr Debye length = LD,extr = [eVt/(qNa)]1/2•Debye cap, C’D,extr = eSi/LD,extr•Oxide cap, C’Ox = eOx/xOx•Net C is the series combOxextr,Dtot'C1'C1'C1C’OxC’D,extr©rlc L25-21Apr20117Equivalent circuitfor depletion•Depl depth given by the usual formula = xdepl = [2eSi(Vbb)/(qNa)]1/2•Depl cap, C’depl = eSi/xdepl•Oxide cap, C’Ox = eOx/xOx•Net C is the series combOxdepltot'C1'C1'C1C’OxC’depl©rlc L25-21Apr20118Equivalent circuitabove OSI•Depl depth given by the maximum depl = xd,max = [2eSi|2fp|/(qNa)]1/2•Depl cap, C’d,min = eSi/xd,max•Oxide cap, C’Ox = eOx/xOx•Net C is the series combOx,mindtot'C1'C1'C1C’OxC’d,min©rlc L25-21Apr20119Differential chargesfor low and high freqFrom Fig 10.27*high freq.©rlc L25-21Apr201110Ideal low-freqC-V relationshipFig 10.25*©rlc L25-21Apr201111Comparison of lowand high freq C-VFig 10.28*©rlc L25-21Apr201112Effect of Q’ss onthe C-V relationshipFig 10.29*©rlc L25-21Apr201113Flat band condition (approx. scale)Ec,OxEvAlSiO2p-Siq(fm-cox)= 3.15 eVEFmEFpEcEvEFiq(cox-cSi)=3.1eVEg,ox~8eVcond band-flat forVVV8.0 VeV8.0EETheneV85.0EEIfsgMSfpfmFBfpfmfpcqffp= 3.95eV©rlc L25-21Apr201114Flat-band parametersfor n-channel (p-subst)0nNlnVq2EnNNlnV gate, Si-poly n a Forden chg Ox/Si the is 'Q ,x'C'C'QV :substratepiatg2iactmssmsssOxOxOxOxssmsFB©rlc L25-21Apr201115Flat-band parametersfor p-channel (n-subst)0nNlnVq2EnNNlnVqE gate, Si-poly p a Forden chg Ox/Si the is 'Q ,x'Cchange) (no 'C'QV :substratenidtg2idvtmsgsmsssOxOxOxOxssmsFB©rlc L25-21Apr201116Fig 10.15*fms(V)NB (cm-3)Typical fms values©rlc L25-21Apr201117Flat band with oxidecharge (approx. scale)EvAlSiO2p-SiEFmEc,OxEg,ox~8eVEFpEcEvEFi'Ox'ssmsOxmsFBOxOxcOx'ssxssmssCQVVxVdxdEq1QEsurface gate the onis Q'Q' chargea cond FB at thenbound, Ox/Si the atis Q' charge a Ifq(ffp-cox)q(Vox)q(fm-cox)q(VFB)VFB= VG-VB, when Si bands are flatEx+<--Vox-->-©rlc L25-21Apr201118Inversion for p-SiVgate>VTh>VFBVgate> VFBVsub = 0EOx,x> 0inversion for threshold above E Induced depletes 0 E Induced 0xVESiSiOxOxx,Ox--AcceptorsDepl Reg e- e- e- e- e-©rlc L25-21Apr201119Approximation concept“Onset of Strong Inv”•OSI = Onset of Strong Inversion occurs when ns = Na = ppo and VG = VTh•Assume ns = 0 for VG < VTh•Assume xdepl = xd,max for VG = VTh and it doesn’t increase for VG > VTh •Cd,min = eSi/xd,max for VG > VTh •Assume ns > 0 for VG > VTh©rlc L25-21Apr201120MOS Bands at OSIp-substr = n-channelFig 10.9*2q|fp|qfpxd,max©rlc L25-21Apr201121Computing the D.R. W and Q at O.S.I.ExEmaxxaSixNqdxdE apSidqNx22,maxparea 2,max,max'dadxqNQ ©rlc L25-21Apr201122Calculation of thethreshold cond, VTOx the across Q' induce to addedvoltage the isV where V,VVsub)-p sub,-(n xNqQ' ischarge extra the and x of value the reached has region depletionThe inverted. is surface the whenreached is condition threshold Thed,maxFBTd,maxBd,maxd,max©rlc L25-21Apr201123Equations forVT calculationsubstr-n for 0 substr,- p for 0VqN22x ,xNqQ' 0nNV 0NnVCQ2VV substrnpdanpd,maxd,maxa,dd,maxidtnaitpOxdnpFBT,,',max,,ln,ln':,©rlc L25-21Apr201124Fully biased n-MOScapacitor0yLVGVsub=VBEOx,x> 0AcceptorsDepl Reg e- e- e- e- e- e- n+ n+VSVD p-substrateChannel if VG > VT©rlc L25-21Apr201125MOS energy bands atSi surface for n-channelFig 8.10**©rlc L25-21Apr201126Computing the D.R. W and Q at O.S.I.ExEmaxxaSixNqdxdE aSBpSidqNVVx)(22,max)(2SBpVVarea ,maxda,maxdxqNQ ©rlc L25-21Apr201127Q’d,max and xd,max forbiased MOS capacitorFig 8.11**xd,max(mm))2-d,max(cmqQ'©rlc L25-21Apr201128Fully biased n-channel VT calc  0V ,qNVV22x ,xNqQ' ,0NnlnVVV'C'Q2VVVVV


View Full Document

UT Arlington EE 5340 - Semiconductor Device Theory

Download Semiconductor Device Theory
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Semiconductor Device Theory and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Semiconductor Device Theory 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?