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()
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
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-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
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(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
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NOR/NAND
- 22 -
Recommended