Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
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134 Chapter7. <strong>Model</strong>-<strong>Driven</strong>Migration<br />
x<br />
@Measure<br />
Figure 7.2:Simplifiedlayout<strong>of</strong>awaferscanner<br />
7.3.2 RunningExample:AWaferScanner<br />
@Expose<br />
InthischapterweconsidertheASMLwaferscannerasarepresentative<br />
example<strong>of</strong>anadvancedmanufacturingmachine.Waferscannersareused<br />
inthesemiconductorindustry<strong>and</strong>performthemostcriticalstepinthe<br />
manufacturingprocess<strong>of</strong>integratedcircuits(ICs).Figure7.2illustratesa<br />
scanner<strong>and</strong>itssubsystems.<br />
Aneighbouringmachine,thetrack(TR),performspre-processingsteps<br />
<strong>and</strong>deliverssiliconwaferstothepre-alignmentsystem(PA),wherethe<br />
waferorientation<strong>and</strong>alignmentaredetermined<strong>and</strong>adjusted. Next,the<br />
loadrobot(LR)transportsthewafertoone<strong>of</strong>thetwowaferstages(WS:0<br />
or WS:1). Here,thewafercharacteristicsaremeasured. Aftermeasurement,thewaferstagesareswapped<strong>and</strong>themeasuredwaferisexposed.<br />
Duringexposure,alaserprojectsanimage<strong>of</strong>therequiredICpatternonto<br />
thewafer’ssurfacethroughademagnificationlens.Awaferisexposedina<br />
scanningfashion,similartotheprocessusedinaphoto-copier.Eventually,<br />
thewafercomestoholdhundreds<strong>of</strong>smallcopies(i.e.,dies)<strong>of</strong>thispattern.<br />
Afterexposure,thestagesswapback<strong>and</strong>theunloadrobot(UR)transportstheexposedwafertothedischargeunit(DU)whereitisbuffered.Next,thewaferispickedupbythetrackagaintoundergovariouspostprocessingsteps.<br />
Now,thewaferisreadyforanotherexposureifneeded;<br />
theprocessisre-entrant.Witheachpassing,anotherlayerisaddedtoeach<br />
die.Oncethewaferhasbeenfullyprocessed<strong>and</strong>inspected,itisdicedinto<br />
individualdiesthatarepackagedt<strong>of</strong>ormICssuchasmicroprocessors.<br />
FortheSMCcomponent<strong>of</strong>thewaferscannerdepictedinFigure7.2,we<br />
canidentifythe‘processwaferw’manufacturingrequest,whichsupports<br />
concurrentmeasuring<strong>and</strong>exposing<strong>of</strong>twowafers.Toperformthisrequest<br />
manufacturingactivitiessuchas‘loadwaferwontowaferstageWS:0’<strong>and</strong><br />
‘unloadwaferwfromwaferstageWS:1’areexecuted.Forinstance,aftera
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