Optimal design of self-damped lossy transmission l

OptimalDesignofSelf-DampedLossyTransmissionLinesinaTreeNetworkforMultichipModuleJimmyS.-H.WangandWayneW.-M.DaiUCSC-CRL-92-11April6,1992BoardofStudiesinComputerEngineeringUniversityofCalifornia,SantaCruzSantaCruz,CA95064abstractThispaperaddressessomeoftheproblemsencounteredinpropagatinghigh-speedsignalsthroughlossytransmissionlinesonthesubstratesofsilicon-on-siliconthin-lmmultichipmodules(MCM).Insteadofterminatedbyresistors,thelossylinesonthethin-lmmultichipmodulescanbestructuredtocriticallydampoutthesignalresonances,theyarethuscalledoptimal,self-dampedlossytransmissionlines.Itiseasiesttomanufactureinterconnectionlineswithxedmetalanddielectricthicknesses,andvaryonlythelinewidth.Thisresultsinspecicdependencyoflinewidthonlengthforself-dampedlines.Inthispaper,wepresentasimpleandrobustmethodofdesigningself-dampedlossytransmissionlinesinatreenetworkformultichipmodule.Wevarythewidthofeachbranchofthenetworktomeetcertainelectricaldampingcriteria.Thisresultsinstableoperationaslongasthelossytransmissionlineisshorterthanthequarterwavelengthofthehighestfrequencycomponentofinterests.Thelengthsoflinesonthesilicon-on-siliconthin-lmMCMsubstrateusuallydoesnotexceedthislimit.Ifcertaindesignsrequirelargersubstrateorhigherspeed,thematerialsandstructuralpropertiesofthesubstrate(forexamplethedielectricthickness)ischangedaccordingtothemethod.Keywords:transmissionline,lossy,self-damped,criticaldamped,multichipmod-ule,multi-terminalnetwork,distributedtermination1.TableofContents11TableofContentsContents1TableofContents:::::::::::::::::::::::::::::::::12ListofTablesandFigures::::::::::::::::::::::::::::23Introduction::::::::::::::::::::::::::::::::::::34OptimalDesignofSelf-DampedLossyTransmissionLineforPoint-To-PointNet:::::::::::::::::::::::::::::::::::::::::45OptimalDesignofSelf-DampedLossyTransmissionLinesforMulti-TerminalNet:::::::::::::::::::::::::::::::::::::::::116Example::::::::::::::::::::::::::::::::::::::157ConcludingRemarks:::::::::::::::::::::::::::::::168Acknowledgment:::::::::::::::::::::::::::::::::18References::::::::::::::::::::::::::::::::::::::::1822.ListofTablesandFigures2ListofTablesandFiguresListofFigures4.1Typicalphysicalstructureofmultichipmoduleinterconnections.Itshowstwolayerofembeddedmicrostriptransmissionlines.Themetalstripsinbothlayersaremadeof2mthickaluminum.Theupperlayerhas5micronsofdielectricabovethelineand10micronsbelow.Thelowerlayerhas10micronsofdielectricabovethelineand5micronsbelow.Therelativedielectricconstantis3.5.:::::::::::::::::::::::::::::54.2Point-To-PointNet.Circuitdiagramofapoint-to-pointnetrepresentedinthedistributedlumpedRLCmodel.:::::::::::::::::::::74.33Dplotofthesolutionandtheapproximationerror.Thisgureshowsthe3Dplotofsolutionin(a).Thex-axisisRsZ0,they-axisisZ0ZL,andthez-axisisRlZ0.Theapproximationerrorisplottedin(b).Becausethefeasiblesolutionisonlyfoundabovethex-yplane,wecanignorerighthalfoftheerrorplot.:::::::::::::::::::::::::::::::::105.1TypicalMicrowaveStructure.Atypicalmicrowavestructureisshownin(a),anditstwoportz-parameterrepresentationisshownin(b).:::::115.2ExampleofaMulti-TerminalTreeNetworkandItsDecomposition.Thetreetopologynetworkin(a)isdecomposedintothreepoint-to-pointsegmentsin(b).::::::::::::::::::::::::::::::::::146.1SimulationResultsforTwoMulti-TerminalTreeNetworks.Thetopologiesofthetwoexampleareshownin(a)and(c).Thesimulationresultsofinput,underdamped,criticallydamped,andoverdampedwaveformsareshowin(b)and(d).Thewaveformsin(b)arethatoftreenetworkin(a),andwaveformsin(d)arethatoftreenetworkin(c).:::::::::::::173.Introduction33IntroductionThelimitingfactorforhighperformancesystemsissetbyinterconnectiondelayratherthanbytransistorswitchingspeed.Inhighperformancesystems,50percentofthetotalsystemdelayisusuallycontributedbypackaging.Thisnumbermayriseto80percentbytheyear2000.Astheoperatingfrequencyarepushedabove50MHz,delaylimitedbythepackagingtechnologybecomesthepacingitemforsystemclockspeed.WhilehybridandPrintedCircuitBoard(PCB)havetechnicallimitationsinproducingnelinegeometries,thick-lmmethodsandmultilayerceramictechnologiesyieldhighsub-stratepermittivity.Anewrevolutioninpackagingtechnologycalledthemultichipmodule(MCM)avoidsmanyofthelimitationsofsinglechippackages.Amultichipmodulehasseveralbarechipsmountedandinterconnectedonasubstrate.Byeliminatingtheindivid-ualchippackages,chipsareplacedclosertogetherresultinginshorterinterconnectlengths.Althoughmultichippackagingisnotnew,thethinlmmultilayerinterconnecttechnologyallowsarevolutionaryadvanceintheperformanceofmultichippackaging[BST87][BMH89].Comparedtoconventionalpackaging,MCM’scanimprovethesystemoperatingfrequencybyafactorofthree,reduceareabyafactorofseven,andreducepowerconsumptionby30%[Ohs89].Multichipmodulepackagingisusedtodesignveryhighspeedsystems,andituseslessspacethantheconventionalpackagingtechniques.Byemployingthin-lminterconnectlines,thenumberofsignallayersarereducedsubstantially(usuallytwosignallayerswithapowerandagroundplane).Thelinesbecomelossyduetoreduceddimensions,andbehavedierentlyfromthecomparativel