24-08-2012, 04:50 PM
Introduction to VLSI Fabrication Technologies
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Insulators
Insulatorsare usedtoisolate conductingand/or
semi-conductingmaterialsfromeachother.
MOS devicesand Capacitorsrelyon an
insulatorfortheirphysicaloperation.
The choiceof the insulators(and the conductors)
in IC design dependsheavilyon howthe materials
interactwitheachother, especiallywiththe
semiconductors.
Semiconductors
The basic semiconductor material usedin device fabrication is Silicon
The success of thismaterial isdue to:
Phisical characteristics
Abundance in nature and very low cost
Relatively easy process
Reliable high volume fabrication
Other semiconductors(e.g. GaAs) are usedforspecial applications
Overviewof Processing
Technologies
Althougha numberof processing technologiesare
available, the majority of the production isdone
withtraditionalCMOS. Otherprocessesare limited
toareaswhereCMOS isnotverysuitable
(likehigh speedRF applications)
CMOS technology
An Integrated Circuit (IC)is an electronic network fabricated in a single piece of a semiconductor material
The semiconductor surface is subjected to various processing steps in which impurities and other materials are added with specific geometrical patterns
The fabrication steps are sequenced to form three dimensional regions that act as transistors and interconnects that form the network
Single CrystalGrowth(II)
The siliconcrystal(in some casesalsocontainingdoping) ismanufacturedasa cylinder(ingot) witha diameterof
8-12 inches(1”=2.54cm).
Thiscylinderiscarefullysawedintothin(0.50-0.75 mm thick) diskscalledwafers, whichare laterpolishedand markedforcrystalorientation.