me 381r lecture 13-14 semiconductor devices and thermal issues

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ME 381R Lecture 13-14

Semiconductor Devices and Thermal Issues

Dr. Li Shi

Department of Mechanical Engineering The University of Texas at Austin

Austin, TX 78712www.me.utexas.edu/~lishi

lishi@mail.utexas.edu

Reading: 1-7-1 & Ch. 7 in Tien et al.

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p-n Junction w/o Bias Depletion Region

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Biased p-n Junction

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Metal-Oxide-Semiconductor (MOS) Capacitor

: Electron AffinityWork Function

Energy Band Diagram before making contact

n-type

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MOS Capacitor W/O Bias (Special Case: M = S)

Energy Band Diagram after making contact

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Accumulation and Depletion of Majority Carriers

VG

Vi

eVGVS

Block Charge Diagram

Very thin

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Inversion Layer: C majority carrier >C minority carrier

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Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET)

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Ideal MOSFET

VG>0

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Pinch-Off & IV

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Thermal Circuit

Particle transport theory

Fourier’s law of heat conduction

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Joule Heating inHigh-Field Devices

Localized heat generationnear the pinch-off point

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X-Y-Z Actuator

Thermometry of Nanoelectronics

Sample

Temperature Sensor

Laser

Atomic Force Microscope (AFM) + Thermal Probe

CantileverDeflectionSensing

Thermal

X

TTopographic

X

Z

Scanning Thermal Microscope:

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Microfabricated Probes

Pt-Cr Junction

Shi, Kwon, Miner, Majumdar, J. MicroElectroMechanical Sys., 10, p. 370 (2001)

10 m

Pt Line

Cr Line

TipLaser Reflector

SiNx Cantilever

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Self Heating Effect on I-V

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Optical Phonon Emission at High Field

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Heat Transfer Path

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Governing Equations for Electro-Thermal Simulation of Devices

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Example

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Computation Scheme

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Results

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Electric Field

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Electron Temperature

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Phonon Temperature