1EE130: Integrated Circuit DevicesInstructor: Prof. Tsu-Jae King ([email protected])TA’s: Marie Eyoum ([email protected])Alvaro Padilla ([email protected])Web page: http://www-inst.eecs.berkeley.edu/~ee130/Newsgroup: ucb.class.ee130(online at http://webcast.berkeley.edu)Spring 2003Course Outline1. Semiconductor Fundamentals – 3 weeks2. Metal-Semiconductor Contacts – 1 week3. P-N Junction Diode –3 weeks4. Bipolar Junction Transistor – 3 weeks5. MOS Capacitor – 1 week6. MOSFET – 4 weeksSubstrateGateSource Drain2IntroductionSpring 2003Integrated-Circuit Devices4004 µPPower4 µP3Spring 2003Planar Process Technology*sequence of additive and subtractive steps with lateral patterningSi waferstartingsubstrate*planarprocessingsteps+multiple devicesmonolithically integrated=n-channel MOSFEToxidationdepositionion implantationetching lithographySpring 2003Rapid advances in IC technology have been achieved primarily by scaling down transistor lateral dimensionsIC Technology AdvancementTechnology ScalingInvestmentMarket GrowthBetter Performance/Cost2000 2005 2010 2015 2020110100GATE LENGTH (nm)YEAR LOW POWER HIGH PERFORMANCEITRS 2001 Projection4Spring 2003“Moore’s Law”# transistors/chip doubles every 1.5 to 2 yearsBenefit of Transistor Scaling1,00010,000100,0001,000,00010,000,000100,000,0001,000,000,0001970 1980 1990 2000 2010Spring 2003Generation:Intel386™ DXProcessorIntel486™ DXProcessorPentium®ProcessorPentium®II Processor1.5µ 1.0µ 0.8µ 0.6µ 0.35µ 0.25µExample: Microprocessor Evolution5Semiconductor FundamentalsOUTLINE• General material properties• Crystal structure• Bond modelRead: Chapter 1Spring 2003What is a Semiconductor?• Low resistivity => “conductor”• High resistivity => “insulator”• Intermediate resistivity => “semiconductor”– conductivity lies between that of conductors and insulators– generally crystalline in structure for IC devices• In recent years, however, non-crystalline semiconductors have become commercially very importantpolycrystalline amorphous crystalline6Spring 2003Semiconductor MaterialsElemental:Compound:Alloy:Spring 2003From Hydrogen to Silicon11s 2s 2p 3s 3p 3d1H 11s12He 21s23Li 2 11s2 2s14Be 2 21s2 2s25B 2211s2 2s2 2p16C 2221s2 2s2 2p27N 2231s2 2s2 2p38O 2241s2 2s2 2p49F 2251s2 2s2 2p510Ne 2261s2 2s2 2p611Na 22611s2 2s2 2p6 3s112Mg 22621s2 2s2 2p6 3s213Al 226211s2 2s2 2p6 3s2 3p114Si 226221s2 2s2 2p6 3s2 3p215P 226231s2 2s2 2p6 3s2 3p316S 226241s2 2s2 2p6 3s2 3p417Cl 226251s2 2s2 2p6 3s2 3p518Ar 226261s2 2s2 2p6 3s2 3p6ZName Notation23# of Electrons7Spring 2003The Silicon Atom• 14 electrons occupying the 1st 3 energy levels:– 1s, 2s, 2p orbitals filled by 10 electrons– 3s, 3p orbitals filled by 4 electronsTo minimize the overall energy, the 3s and 3p orbitals hybridize to form 4 tetrahedral 3sp orbitalsEach has one electron and is capable of forming a bond with a neighboring atomSpring 2003“diamond cubic” latticeThe Si Crystal• Each Si atom has 4 nearest neighbors• lattice constant= 5.431Å8Spring 2003Compound SemiconductorsGaAs• “zincblende” structure• III-V compound semiconductors: GaAs, GaP, GaN, etc.9important for optoelectronics and high-speed ICsSpring 2003Crystallographic Notationequivalent directions< h k l >crystal direction[ h k l ]equivalent planes{ h k l }crystal plane( h k l )InterpretationNotationh: inverse x-intercept of planek: inverse y-intercept of planel: inverse z-intercept of plane(Intercept values are in multiples of the lattice constant;h, k and l are reduced to 3 integers having the same ratio.)Miller Indices:9Spring 2003Crystallographic Planes and Si WafersSilicon wafers are usually cut along the (100) plane with a flat or notch to orient the wafer during IC fabrication: (100)plane(011)flatSpring 2003Unit cell:View in <100> directionCrystallographic Planes in SiView in <110> directionView in <111> directionlattice constant = 5.431ÅÆ 5 x 1022atoms/cm310Spring 2003Electronic Properties of Si• Silicon is a semiconductor material.– Pure Si has a relatively high electrical resistivity at room temperature.• There are 2 types of mobile charge-carriers in Si:– Conduction electrons are negatively charged;– Holes are positively charged.• The concentration (#/cm3) of conduction electrons & holes in a semiconductor can be modulated in several ways:1. by adding special impurity atoms ( dopants )2. by applying an electric field3. by changing the temperature4. by irradiationSpring 2003Bond Model of Electrons and HolesSi Si SiSi Si SiSi Si SiSi Si SiSi Si SiSi Si SiWhen an electron breaks loose and becomes a conduction electron, a hole is also created.2-D representation:11Spring 2003What is a Hole?• Mobile positive charge associated with a half-filled covalent bond– Treat as positively charged mobile particle in the semiconductor• Fluid analogy:Spring 2003The Hole as a Positive Mobile Charge12Spring 2003ni≅ 1010cm-3at room temperaturePure SiconductionSpring 2003Summary• Crystalline Si:– 4 valence electrons per atom– diamond lattice: each atom has 4 nearest neighbors–5 x 1022atoms/cm3• In a pure Si crystal, conduction electrons and holes are formed in pairs.– Holes can be considered as positively charged mobile particles which exist inside a semiconductor.– Both holes and electrons can conduct
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