Chap.3-handout

Chap.3-handout - 9/14/2010 Chap.3 Semiconductors (5th ed:...

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9/14/2010 1 1 Chap.3 Semiconductors (5 th ed: Sec.3.7-3.9) 2 Figure A.2 Conceptual illustration of a step-and-repeat reduction technique to facilitate the mass production of integrated circuits. i) Introduction Silicon is Semiconductor and is the basis material for Integrated Circuits
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9/14/2010 2 3 i) Introduction Silicon is Semiconductor and is the basis material for Integrated Circuits Figure A.1 Photolithography using positive or negative photoresist. 4 Figure A.5 A modern twin-well CMOS process flow with shallow trench isolation (STI). i) Introduction Silicon is Semiconductor and is the basis material for Integrated Circuits
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9/14/2010 3 5 Figure A.14 A CMOS inverter schematic and its layout. CMOS Inverter LAYOUT 6 Interactive animated applet for Nwell process for CMOS Inverter: http://jas.eng.buffalo.edu/education/fab/invFab/index.html LAYOUT : Cross-sectional View: CMOS IC Layout and Device Cross-section
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9/14/2010 4 PN Junction Diode 7 The Si atom shares/receives FOUR Additional electrons with/from the Four nearest neighbors to stabilize the Outermost shell with 8 electrons. ii) Physical Operation of Diodes PN Junction Diode 8 ii) Physical Operation of Diodes
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9/14/2010 5 2x2x2=8 unitcells Showing only the Ga and As atoms Single unitcell of GaAs 9 http://jas.eng.buffalo.edu/education/ solid/unitCell/home.html http://jas.eng.buffalo.edu/education/ solid/genUnitCell/750.html T=0K 10 Intrinsic = chemically pure material, without any chemical impurities. T=300K At an elevated temperature, a few of those Covalent bonds are broken. A broken covalent Bond means that an electron, originally fixed In the bond, is now broken off and FREE to move Around in the Si crystal. mobile Electron Hole are generated. 3.1 Intrinsic Silicon
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9/14/2010 6 11 n =electron concentration p =hole concentration n = p =n i = intrinsic carrier concentration n i = 1.5x10 10 cm -3 at T=300K, is a function of Temperature = BT 3/2 exp(-E g /2kT) where, B=material-dep. constant=7.3x10 15 cm -3 K -3/2 for silicon E g = bandgap energy = 1.12 eV for silicon k= Boltzman’s const = 8.62x10 -5 eV/K Ex) Find intrinsic carrier density ni for silicon at T=100K and 400K Ans) Assume that Eg is indept. of Temperature (which is not true) T=100K: n i = 7.3x10 15 (100) 3/2 exp[-1.12/(2*8.62E-5*100)] = 7.3E18*e -64.965 =4.46E-10 cm -3 T=400K: n i =7.3E15*(400) 3/2 *exp[-1.12/(2*8.62E-5*400)]=5.84E19*e -16.24 =5.16E12 cm -3 3.1 Intrinsic Silicon 3.2 Doped Semiconductor: Extrinsic, n-type or p-type Donor Acceptor 12 n-type p-type
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Chap.3-handout - 9/14/2010 Chap.3 Semiconductors (5th ed:...

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