lectures_2013_2014_A analog

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Course:

Analog Circuit Design

Time schedule:Mo 11.00-13.00We 14.00-16.00

Th 14.00-16.00

Office hours:Th 16.00-18.00

Exams:Feb. (2), Jun.-Jul. (2), Sep. (2)Oral examination

Additional course material:ftp://ftp.dii.unisi.it/pub/users/vignoli/Analog_Circuit_Design


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References:

F. MalobertiAnalog Design for CMOS VLSI SystemsKluwer 2001

J. Millman, C. HalkiasIntegrated Electronics: Analog and Digital Circuit and SystemsMcGraw-Hill 1972

R. Spencer, M. Ghausi

Introduction to Electronic Circuit DesignPrentice Hall 2003

P. Gray, R MeyerAnalysis and Design of Analog Integrated Circuits (3rd ed.)Wiley 1993

M.S. TyagiIntroduction to Semiconductor Material and Devices

Wiley 1991


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MATERIALS: electric behavior

semiconductor Insulator conductor


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In semiconductors EF is in the Band-Gap

SEMICONDUCTORS: electric behavior

kTEE F

eEf

+

=

1

1)(

Fermi-Dirac distribution: occupation probability for the energy level E


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NC is the number of available states (per cm-3) in the conduction band

kT

EE

CkT

EE

deii

FcFc

eNekThmdEEfENpn

=

==

2/3

2'

241)()(

where Ne(E) is Energetic State Density function in the material.

Intrinsic Semiconductors: free carriers


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DOPING

The Fermi energy

moves with doping

EF n-type

EF p-type

T effect

ACCEPTORDONOR


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Also PVD


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Single crystal silicon SCS Anisotropic crystal Semiconductor, great heat conductor

Silicon dioxide is created by interaction between silicon and oxygenor water vapor Si + O

2= SiO

2or Si + 2H

2O = SiO

2+ 2H

2 Excellent thermal and electrical insulator protects surface from contaminants forms insulating layer between conductors

forms barrier to dopants during diffusion or ion implantation grows above and into silicon surface

Thermal oxide, LTO, PSG: different names for different depositionconditions and methods

Polycrystalline silicon polysilicon Mostly isotropic material Semiconductor also a conductor, but with much more resistance than metal or diffused layers created when silicon is epitaxially grown on SiO2 commonly used (heavily doped) for gate connections in most MOS processes

Silicon nitride Si3N4 Excellent electrical insulator

Aluminum Al Metal excellent thermal and electrical conductor

Materials


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PHOTOLITOGRAPHY

Photoresist

spin.-coating

Thick film: 1 mm

EXPOSITION:The mask is transferred to

the photoresist

Uv - X-ray


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The photoresist chemically reacts and dissolves in thedeveloping solution, only on the parts that were notmasked during exposure (positive method).

Development is performed with an alkalinedeveloping solution.

After the development, photoresist is left on the

wafer surface in the shape of the mask pattern.Masked photoresist

solvents remove exposed (unexposed) resistEtching removes material from wafer surface where resist has beenremoved


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Wet etching

Dry etching


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EFFECT OF FLATBAND VOLTAGE VFB (VFB < 0)


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VGB = 0


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GATEPolisilicon

OXIDESiO2

SUBSTRATEP-type Si

SUBSTRATE CONTACTPolisilicon

- -

Space charge regions

x-tOX 0 xD

x-tOX 0 xD

PotentialVGB-VFB

-VFB

VGB

VOX

s(0)

+

VOX


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STRONG INVERSION CONDITION


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SMALL SIGNAL EQUIVALENT CIRCUIT OF A MOS TRANSISTOR

lectures_2013_2014_A analog

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