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Explore the significance of metal properties on silicon chips, including thermal expansion failures, chip cooling, heat capacity, thermal conductivity, and more. Delve into electrical current flow, resistance in interconnects, and the role of electrons in conduction. Learn fundamentals like Ohm's Law and Drude's theory for a comprehensive understanding.
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Lecture 4.0 Properties of Metals
Importance to Silicon Chips • Metal Delamination • Thermal expansion failures • Chip Cooling- Device Density • Heat Capacity • Thermal Conductivity • Chip Speed • Resistance in RC interconnects
Electrical Current • Flow of Charged Particles due to applied voltage • Solids • Ions/holes are large and slow • electrons are small and fast • Electrons are often responsible for conduction
Ohm's Law • Current density, J=I/A==/ • =electric field[V/cm] • =Conductivity, [=1/] =Resistivity • =ne, =mobility, e=electron charge, n=#/vol. • Resistance, R= L/A • V=IR
Drude’s theory electron scattering by lattice Mobility, e/me = average time between collisions of electron with ions Bloch’s Quantum theory no electron scattering in perfect lattice only in a imperfect lattice Scattering lattice vibrations impurities dislocations Metal Conduction
• • 1s 1s • • Remember Molecular Orbitals • New Energy • Bonding • Anti Bonding
Energy Bands Partially Filled
Distribution of Electrons in Band • Fermi-Dirac distribution • Probability, • F(E)=1/(exp{[E-Ef]/kBT}+1) • Ef is the Fermi Energy
Eletrical Conductivity • =ne • =mobility, e=electron charge, n=#/vol. • =(N/V) F(E)G(E) e2/me,
Thermal Properties - Chapter 7 • Thermal Conductivity • Thermal Expansion • Heat Capacity • Thermoelectric effect • thermocouple
Thermal Properties - Chapter 7 • Thermal Vibrations-phonons • Displacement, xmax=(3kBT/Yao)1/2 • Y ao is the spring constant • Thermal Expansion • (l/lo)(1/T), also volume->(V/Vo)(1/T) • Heat Capacity • Cp=1/2 kBT per degree of freedom • 6 degrees of freedom per ion, Cp=3R • kinetic and potential • Variation of Conductivity with Temp. d /dT
Heat Capacity-Effect of Phonons/electrons • Einstein Model • Debye Model • Electrons • density of occupied states En=(n+1/2)h <E>= h/(exp(h/kBT)-1) g()= 2V/(22v3)
Thermal Conduction • Transport of Phonons (vibrations) • kthermal/(T)=constant • thermal conductivity scales with electrical conductivity • kthermal=kelectrons + kphonons
Thermal Conductivity-Phonon • kphonons= Ne Cp ph Vph/3 • Ne number e-/volume, • Cp=heat capacity of atoms =3kB • ph =mean free path, • Vph=velocity
Thermal Conductivity - Electron • ke= Ne Ce e Ve/3 • Ne number e-/volume, • Ce=heat capacity of electrons • e =mean free path, • Ve=velocity
Phonon Interactions • With other phonons • With impurities • depends upon phonon wavelength • With imperfections in Crystal • depends upon phonon wavelength • Phonons travel at speed of sound