- 1 -

()

1.0

III IV VB CAl Si PGa Ge AsIn Sb

()

Elemental Semiconductors: Ge, Si()

Ge: 1950, High Leakage Current(Eg=0.67eV), Germanium Oxide =>

=> .

Si: 1960, Low Leakage Current(Eg=1.1eV), SiO2 => High Quality, Thermally

Grown, Device Isolation

((Si (>95%): 1) (O2, 25%), 2) Low Leakage

Current (Eg=1.1eV), 3) High Quality SiO2))

((Si : 1) =14, 2) Atomic Weight=28.1, 3) Diamond Structure, 4)

Lattice Constant=5.43, 5) =5X1022atoms/cm3, 6) Eg=1.1eV))

Diamond Structure: Ge, Si

Atomic Bonding=Covalent Bonding(): Si 4

4 Si . Si Core = Si Atom +

10 Electrons

1.1-2 ,

(1) Principle of Energy Quanta by Plank:

Thermal Radiation Discrete Packets

of Energy" = Quanta .

- 2 -

(2) Pauli Exclusion Principle Quantum State

. 2

Quantum State(n=1) Quantum

State(n=1) . N N

Quantum State(n=1) . .

,

1 2 N

- 3 -

1.3

: n=1 2 , n=2 8 Si

. n=3 8 4 ( ).

(Crystal) (Covalent Bonding)

. , n=3 s p Quantum State

(Crystal) .

Valence Band Conduction Band.

Forbidden Band.

- 4 -

1.4

(Electrical Conduction):

: (E>Eg),

. , Valence Band Conduction Band .

.

: (+ )

. Valence Band

. + . (Hole)

.

- 5 -

1.5 (n-type p-type)

3 4 5

B C N

Al Si P

Ga Ge As

(1) Intrinsic : , n0=p0=ni=1010cm-3 @T=300K

(2) Extrinsic : ()

(donor): P, As, Sb 5 , , n-type

(acceptor): B, Al, Ga, In 3 , , p-type

N

P

- 6 -

1.6 , ,

1.6x Carrier Action

NonEquilibrium Carrier Action

(1) Drift: Electric Field Charged-Particle

MicroScopic MacroScopic

Thermal Motion:32kT=

12m *v2th

vth107cm/s @T=300K

Thermal Velocity( vth):

Drift Velocity( vd):

(Net Velocity)

(2) Diffusion:

.

(3) Recombination-Generation

Recombination:

Generation:

- 7 -

1.7 PN

Basic Structure(P N

)

Diffusion . ( n-type

p-type )

=> Diffusion

Space Charge .

=> Charge Electric Field

Drift

, Electric Field

Diffusion .

=> Diffusion

Drift

.

PN 3 .

(1)p-QNR(Quasi-Neutral Region): Quasi-Neutral p-type .

Uniform Doping Quasi-Neutral Electric Field .

Drift Current = 0 .

(2) SCR(Space Charge Region)( Depletion ): Diffusion

Space Charge . Diffusion Current = Drift Current.

(3) n-QNR: Quasi-Neutral n-type . p-QNR .

- 8 -

P N

I-V

(1)

n-QNR potential barrier

p+-QNR

diffusion.(Jn,diff,eq)

p+-QNR n-QNR

drift.(Jn,drift,eq)

Jn,eq = Jn,diff,eq + Jn,drift,eq = 0

,

Jp,eq = Jp,diff,eq + Jp,drift,eq = 0

(2) (VA>0)

potential barrier

. ( - n

.)

n-QNR potential barrier

(thermal equilibrium )

p+-QNR

diffusion.(Jn,diff>Jn,diff,eq)

p+-QNR n-QNR drift.

(Jn,drift=Jn,drift,eq)

Jn = Jn,diff + Jn,drift > 0

,

Jp = Jp,diff + Jp,drift > 0

potential barrier eqVA/kT

(Fermi function, p+n diode)

J eqVA/kT

- 9 -

(3) (VA AC DC .

- 10 -

v

+

-

Resistor

i=v/r

Trans-Resistor=Transistor

+

-

i= vc/rt = gm vc

vc

+

-

i=gm vcvc rc

1.8

?

:

.

TRs => Bipolar Junction Transistor(BJT), (NPN, PNP)

Field-Effect Transistor(FET), (n-Ch p-Ch MOSFET, JFET)

(Transistor) = Transferred + Resistor

Transferred= , Resistor=

Transconductance(gm)=1/Transresistance(rt)

rc = r for BJTs

= for MOSFETs

- 11 -

-xp xn

SCRp+-QNR n-QNR

0

JJp

Jp

Jn

Jn

-xp xn

SCRp+-QNR n-QNR

0

JJp

Jn

-xp xn

SCRp+-QNR

n-QNR

0

JJp

Jn

SCR p-QNR

Base Current

CollectorCurrent

-xp xn

x'x'=0

p+ nnarrow-base

xc'

xcLp

p+ n

xc'

p BJTSCR

SCR

SCR

SCR

1.9 BJT(Bipolar Junction Transistor)

BJT

Narrow-Base => BJT

BJT = Narrow-base diode +

( Jn/Jp )

Terminology & Symbols

- 12 -

ElectroStatics

- 13 -

(Active Region)

(i) :

EBJ

=> n ()

, EF

Junction Barrier .

(VJ=Vbi-VA).

=> Barrier

( IEp).

=>

Diffusion .

(

WBL p

,

B=W2B/ 2D p - BJT )

=> BCJ() SCR ( ICp).

.

(ii) :

Barrier (Back Injection).

=> Diffusion .

( IEn=IB1). ( >>

)

IC=ISeVBE/VT, IB=

IC

- 14 -

:

- 15 -

1.10 MOSFET

MOS Energy-Band Diagram

( ) ( )

(1) Flat-Band

VG=VFB=M-S=MS=-0.8V

(Flat-Band Voltage)

FLAT .

(2) Depletion

Si

Bulk .

VG>VFB

- 16 -

(3) Inversion(VG>VFB)

Depletion

Depletion

(Inversion

Charge) Si .

( Depletion

Generation

) =>MOSFET ON

(Threshold Voltage, VT):

Inversion .

~1V

MOSFET

Field Oxide: (Isolation) (~5000)

Gate: Polysilicon (W/L=0.5/0.5m)

Gate Oxide: Gate Channel (~100)

- 17 -

MOSFET

(a) VG>VT, VD=small(0.1V):

Inversion Layer , Simple Linear

Resistor, ID VD

(b) VG>VT, VD : Channel

Drain Inversion Layer

(Oxide Field ). Nonlinear

Resistor. ID f(VD)

(c) VG>VT, VD=VDsat=VG-VT: y=L

Pinch-Off , ID = IDsat

(d) VG>VT, VD>VDsat: VD

Pinch-Off .

ID = Drift Current Ey

= VDsat/Leff = Const = IDsat

L L Leff

ID . (Channel-Length

Modulation)

IDsat=12

nC oxWL

(VG-VT)2

( VG>VT, VD > VDsat )

: BJT

- 18 -

1.11 DRAM/Flash Memory

Volatile Memory

1) DRAM(Dynamic Random Access Memory)

2) SRAM(Static Random Access Memory)

NonVolatile Memory

1) ROM (Mask Programmable Read Only Memory)

- 19 -

2) EPROM(UV Erasable Programmable ROM)

Floating Gate, Hot Electron Injection Program, UV Erase

3) EEPROM(Electrically Erasable and Programmable ROM)

Program/Erase: FN(Fowler-Nordheim) Tunneling

4) Flash EEPROM

Erased at one time like EPROM

cf. EEPROM: Byte Erase

- 20 -

NOR Flash

Intel Introduced in 1988

One end to GND, the other end to Bit Line

Acts like NOR Gate: If One of the Word Lines High, the Storage Transistor

pulls Bit Line Low

NAND Flash

Toshiba (Dr. Masuoka) Introduced in 1980

Resembles a NAND Gate: If All word lines High, the Bit Line Pulled Low

Denser Layout than NOR Flash

FN Tunneling for Write/Erase

USB Flash Drives, Memory Cards, Solid-State Drives

- 21 -

NOR/NAND

- 22 -