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Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level, 2001 by Prentice Hall,Semiconductor Manufacturing Technology,by Michael Quirk and Julian Serda,Semiconductor Manufacturing Technology,Michael Quirk & Julian Serda,October 2001 by Prentice Hall,Chapter 2,Characteristics of Semiconductor Materials,Objectives,After studying the material in this chapter, you will be able to:,1.Describe the atom, including valence shell, band theory and ions.,2.Interpret the periodic table with regards to main group elements and explain how ionic and covalent bonds are formed.,3.State the three classes of materials and describe each one with regards to current flow.,4.Explain,resistivity, resistance, capacitance and discuss their importance to wafer fabrication.,5.Describe pure silicon and give four reasons why it is the most common semiconductor material.,6.Explain doping and how the trivalent and,pentavalent,dopant elements make silicon a useful semiconductor material.,7.Explain p-type (acceptor) silicon and n-type (donor) silicon, how silicon,resistivity,changes with the addition of a dopant, and the PN junction.,8.Discuss alternative semiconductor materials, with emphasis on gallium,arsenide,.,Atomic Structure,Matter,Element,Nucleus,Proton,Neutron,Orbital Shell,Electron,Molecule,Compound,Electrons,Electron Energy,Valence Shells,Energy-Band Theory,Ions,Elementary Model of the Carbon Atom,Carbon atom:,The nucleus contains an equal number of protons (+) and neutrons (6 each). Six electrons (-) orbit around the nucleus.,Valence electron,Electron,(negative charge),Neutron,(neutral charge),Atomic number,(number of protons),Nucleus,(center of atom; contains protons and neutrons),Orbital shell,Proton,(positive charge),Valence shell,(outer shell of atom),C 6,+,+,N,N,+,N,N,+,+,N,+,N,-,-,-,-,-,-,Figure 2.1,Electron Shells in Atoms,Figure 2.2,K = 2,L = 8,M = 18,N = 32,O = 32,P = 10,Q = 2,Electron Shells for Sodium and Chlorine Atoms,-,-,-,-,-,-,-,-,-,-,-,Na 11,Sodium atom,Chlorine atom,Cl,17,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,Figure 2.3,Energy Band Gaps,Semiconductor,Conduction Band,Valence Band,Energy Gap,Electron Energy,Conduction Band,Valence Band,Insulator,Energy Gap,Electron Energy,Conduction Band,Valence Band,Overlapping bands - little energy is needed for conduction,Conductor,Electron Energy,Figure 2.4,Sodium Chloride,+ Sodium ion,A + ion is formed when an atom loses an electron.,Na 11,-,-,-,-,-,-,-,-,-,-,- Chlorine ion,A - ion is formed when an atom gains an electron.,Cl,17,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,Figure 2.5,The Periodic Table,Characteristics of Commonly Used Elements,Ionic Bonds,Covalent Bonds,The Periodic Table of the Elements,Figure 2.6,Rf,104,Ha,105,Sg,106,Uns,107,Uno,108,Une,109,IA,IIA,IIIB,IVB,VB,VIB,VIIB,IB,IIB,IIIA,IVA,VA,VIA,VIIA,VIIIA,VIIIB,Hydrogen,H,1,1.008,Beryllium,Be,4,9.012,Na,11,Sodium,22.989,Li,3,Lithium,6.939,12,24.312,Mg,Magnesium,19,K,Potassium,39.102,Ca,20,40.08,Calcium,Sc,21,Scandium,44.956,Ti,22,Titanium,47.90,V,23,Vanadium,50.942,Manganese,Mn,25,54.938,Fe,26,Iron,55.847,Co,27,Cobalt,58.933,Ni,28,Nickel,58.71,Rh,45,Rhodium,102.91,Zn,30,Zinc,65.37,As,33,Arsenic,74.922,Se,34,Selenium,78.96,Br,35,Bromine,79.909,Kr,36,Krypton,83.80,Al,13,Aluminum,26.981,Si,14,Silicon,28.086,P,15,Phosphorus,30.974,S,16,Sulfur,32.064,Cl,17,Chlorine,35.453,Ar,18,Argon,39.948,B,5,Boron,10.811,C,6,Carbon,12.011,N,7,Nitrogen,14.007,O,8,Oxygen,15.999,F,9,Florine,18.998,Ne,10,Neon,20.183,He,2,Helium,4.0026,Rb,37,Rubidium,85.47,Sr,38,Strontium,87.62,Y,39,Yttrium,88.905,Zr,40,Zirconium,91.22,Nb,41,Niobium,92.906,Molybde,-,num,Mo,42,95.94,Cr,24,Chromium,51.996,Technitium,Tc,43,99,Ru,44,Ruthenium,101.07,Cd,48,Cadmium,112.40,Cu,29,Copper,63.54,Palladium,Pd,46,106.4,Silver,Ag,47,107.87,Sm,62,Samarium,150.35,Ga,31,Gallium,69.72,In,49,Indium,114.82,Ge,32,72.59,Germaniu,m,Sn,50,Tin,118.69,Sb,51,Antimony,121.75,Te,52,Tellurium,127.60,I,53,Iodine,126.904,Xe,54,Xenon,131.30,Cs,55,Cesium,132.90,Ba,56,Barium,1137.34,La,57,Lanthanum,138.91,Hf,72,Hafnium,178.49,Ta,73,Tantalum,180.95,W,74,Tungsten,183.85,Re,75,Rhenium,186.2,Os,76,Osmium,190.2,Ir,77,Iridium,192.2,Pt,78,Platinum,195.09,Au,79,Gold,196.967,Hg,80,Mercury,200.59,Tl,81,Thallium,204.37,Pb,82,Lead,207.19,Bi,83,Bismuth,208.98,Po,84,Polonium,210,At,85,Astatine,210,Rn,86,Radon,222,Uun,110,Fr,87,Francium,223,Ra,88,Radium,226,Ac,89,227,Actinium,Ce,58,Cerium,140.12,Pr,59,Praseodym,-,ium,140.91,60,Nd,Neodym,-,ium,144.24,Pm,61,Prome,-,thium,147,Europium,Eu,63,151.96,Gd,64,Gadolin,-,ium,157.25,Tb,65,Terbium,158.92,Dy,66,Dyspro,-,sium,162.50,Ho,67,Holmium,164.93,Er,68,Erbium,167.26,Tm,69,Thulium,168.93,Yb,70,Ytterbium,173.04,71,Lu,Lutetium,174.97,Th,90,Thorium,232.04,Pa,91,Procat,-,inium,231,U,92,Uranium,238.03,Np,93,Neptunium,237,Pu,94,Plutonium,242,Americium,Am,95,243,Cm,96,Curium,247,Berkelium,Bk,97,247,Cf,98,Califor,-,nium,249,Es,99,Einstein-,ium,254,Fm,100,Fermium,253,Md,101,Mendelev,-,ium,256,102,No,Nobelium,253,Lr,103,Lawren,-,cium,257,Transition Metals,Nonmetals,Metalloids,(semimetals),Lanthanides,Actinides,Element Box of the Periodic Table,C,6,12.01115,2.0,3570,3470 s.,0.77,Carbon,atomic weight,electronegativity,symbol,acid-base,properties,atomic number,melting point (C)*,boiling point (C),atomic radius (),*,Based on carbon-12. ( ) indicates the most stable or best known isotope.,s. indicates sublimation, For representative oxides of group. Oxide is acidic if color is red, basic if color is blue, and,amphoteric,if both colors are shown. Intensity of color indicates relative strength.,Figure 2.7,Characteristics of Chemicals used in Wafer Fabrication,Continued on next slide,Table 2.1,Characteristics of Chemicals used in Wafer Fabrication(continued),Table 2.1,Ionic Bond for,NaCl,Cl,-,Na,+,Figure 2.8,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,Cl,17,-,-,-,H 1,Hydrogen atom,Chlorine atom,H +,Cl,HCl,Electron shared between two atoms to form a covalent bond.,Covalent Bond for,HCl,Figure 2.9,Classifying Materials,Conductors,Insulators,Semiconductors,Electrical Current Flow,Figure 2.10,Copper wires provide connections that allow electrons to flow from the - terminal, through the filament inside the lamp, and back into the + terminal of the battery.,e-,6 Volt,Battery,e,-,e,-,e,-,Copper atom,One electron in the valence ring,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,Cu 29,-,-,-,-,-,-,-,-,-,-,-,-,-,-,K,L,M,N,Flow of Free Electrons in Copper,Shell #,K,L,M,N,Total #,Maximum #,e,-,per shell,2,8,18,32,60,Actual #,e,-,per shell,2,8,18,1,29,Figure 2.11,How Sizes Affect Resistance,High Resistance,Low Resistance,L,A,R,=,Figure 2.12,Adding an Impurity to Water to Improve its Conductivity,Sodium and chlorine ions from ordinary table salt provide electrical path for current flow in water.,e,-,e,-,e,-,e,-,+,-,6 Volt,Battery,Na,+,Cl,-,H,2,O,Figure 2.13,Basic Capacitor Structure,K, dielectric constant in farads/cm,A, plate area in cm,2,S, spacing between plates in cm,KA,S,C =,Formula for Capacitance,conductor,(metal plate),conductor,(metal plate),dielectric,(glass),wire connection,wire connection,Schematic symbol for Capacitor,Figure 2.14,Battery Charges a Capacitor,1.5 V,Switch,(+) Positive charged plate,(-) Negative charged plate,electrostatic,field,e,-,e,-,e,-,e,-,e,-,1.5 V,Battery,Figure 2.15,Capacitor Holds a Charge,(-) Negative charged plate,Electrostatic field,1.5 V,(+) Positive charged plate,Figure 2.16,Low-,k,Dielectric Material,Metal 2,Dielectric material*,Metal 1,Capacitance,* Low K dielectric reduces capacitance between metal layers.,Figure 2.17,Silicon,Pure Silicon,Why Use Silicon?,Doped Silicon,Dopant Materials,n-type Silicon,p-type Silicon,Resistivity,of Doped Silicon,pn,Junctions,Semiconductors,Group IVA,C, Carbon6,Si, Silicon14,Ge, Germanium32,Sn, Tin50,Pb, Lead 82,Group IVA Elemental Semiconductors,Figure 2.18,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Silicon atoms share valence electrons to form insulator-like bonds.,Covalent Bonding of Pure Silicon,Figure 2.19,Silicon dioxide (SiO,2,),Silicon wafer,SiO,2,on Silicon Wafer,Figure 2.20,Doping of Silicon,P,Si,Si,Si,Si,Si,Si,P,P,P,P,dopant dispenser,wafer,dopant layer,diffusion of dopant atoms through silicon,Deposition Step,Drive-in & Diffusion Step,wafer substrate,Activation,Step,Figure 2.21,Group III (p-type),Boron5,Aluminum13,Gallium31,Indium49,Group IV,Carbon6,Silicon14,Germanium32,Tin50,Group V (n-type),Nitrogen7,Phosphorus15,Arsenic33,Antimony51,Acceptor Impurities,Donor Impurities,Semiconductor,* Items underlined are the most commonly used in silicon-based IC manufacturing.,Silicon,Dopants,Figure 2.22,Donor atoms provide excess electrons,to form n-type silicon.,Phosphorus atom serves as n-type dopant,Excess electron (-),Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,P,P,P,Electrons in N-Type Silicon with Phosphorus Dopant,Figure 2.23,Conduction in n-Type Silicon,Free electrons flow toward positive terminal.,Positive terminal from power supply,Electron Flow,Negative terminal from power supply,Figure 2.24,Acceptor atoms provide a deficiency,of electrons to form p-type silicon.,+ Hole,Boron atom serves as p-type dopant,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,Si,B,Si,Si,Si,Si,Si,Si,B,B,Holes in p-Type Silicon with Boron Dopant,Figure 2.25,Conduction in p-Type Silicon,Electron Flow,Hole Flow,Positive terminal from voltage supply,Negative terminal from voltage supply,+Holes flow toward negative terminal,-Electrons flow toward positive terminal,Figure 2.26,Silicon,Resistivity,Versus Dopant Concentration,Redrawn from,VLSI Fabrication Principles, Silicon and Gallium,Arsenide, John Wiley & Sons, Inc.,Dopant Concentration (atoms/cm,3,),Electrical,Resistivity,(ohm-cm),10,21,10,20,10,19,10,18,10,17,10,16,10,15,10,14,10,13,10,-3,10,-2,10,-1,10,0,10,1,10,2,10,3,n-type,p-type,Figure 2.27,p-type,Si,n-type,Si,Cross Section of Planar,pn,Junction,Figure 2.28,Alternative Semiconductor Materials,Table 2.3,Chapter 2 Review,Summary 41,Key Terms41,Review Questions42,References42,
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