chapter 1-thin-film technology-1

Microsoft PowerPoint - Chapter 1-Thin-Film Technology-1

1. Vacuum Technology & Application
()
(Donald L. Smith)
(cluster)
cluster:
() ()

Thin film(Molecules)Physical Vapor Deposition (PVD)Chemical Vapor Deposition (CVD) Thick film(Particles)PaintingSilk ScreeningSpin-on Glass CoatingPlasma Spraying
CHENG SHIU UNIVERSITYCHENG SHIU UNIVERSITY P.5

(PVD) LiquidVaporGas
(CVD) Supply rateDeposition rate and the ratio of elements (compound) Transport VacuumSourceSubstrate(PVD) Fluid(CVD) PlasmaVacuumFluid Deposition Substrate condition
Reactivity of source material
Energy input
Analysis StructureCompositionProperties Properties Hardness of tool coatingbreakdown voltage of an isolatorthe index of refraction of an optical film
Vapor phase thin-film techniques(Liquid phase) 1.
2.
3.
Chapter 2. Gas Kinetics (T)
Vapor
a (Vapor) V↓, p↑ b (Liquid-Vapor)
V↓ c (Liquid) p↑, V↓ d (Solid-Liquid)
V↓ e (Solid) p↑, V↓ f (Solid)
Fig. 2.1p-T

3.
The pressure in a gas based on kinetic theory: xΔP
N

xvlt /2=Δ
random
2222 zyx vvvv ++= v
22222 3 xzyx vvvvv =⇒==
Maxwell-Boltzmann Distribution

Let c=vMaxwell distribution of speeds f (v)
(Mean speed)
ArMaxwell-Boltzmann

(or Pa .m3/ mol.K) NA=Avogadro’s number
=6.02x1023 mc/mol (mc = molecule)
M RT
mN TNk
m Tkc
Molecular Impingement Flux () random
vx(θ)1/2
(mc/m2.s)n(mc/m3)
A(r = 1)
( ) ( )( )
Ideal-Gas Law
(STP01 atm)22,400 cm3/mol
( ) ( ) ( ) 2 xxxxii nmv2mvnv
Molecular translational energy: εt

⇒
εr εv
(cp) >(cv)
Ummole

SI1 Pa (Pascal) = 1 Nt/m2
cgs1 dynes/cm2 = 1/10 Pa = 10-6 bar (1 bar = 750.06 mmHg)
1 psi (pound/in2) = 51.715 mmHg
1 mmHg = 101,325/760 N/m2 (Q 1 atm = 101,325 N/m2) 1 torr = 1 mmHg = 133.322 Pa 1 micron = 1 μ =10-3 mmHg 1 Pa = 7.5 mTorr (Mass Flow Rate) sccm (s: standard, cc: cm3, m: minute), sccs (s: second), slm (l: liter) Q 1 sccm = 4.48×1017 (mc/s) ∴pumpmass flow rate torr⋅l/s Pa ⋅l/s
Knudsen Equation ()
For example: M = 40 g, T = 25 , p = 10-3 Pa,
= 0.3 nm(Monomolecular LayerML)1015Accumulation rate = 2.4×1015/1015
= 2.4 (ML/s) 2.4×0.3×10-9/(1/60 ×1/60) = 2.6 μm/h 10-3 Pa ≈ 10-8 atm10-6Pa 99.9%( )

The linear deposition rate:dh/dt (h:film thickness, t:deposition time) In SI units: Jr = (mc/m2·s)
ρm= (kg/m3)
(: ρmNA/M ≈ 5×1022 mc/cm3)

Mean Free Path ()
(a) a ( « a) σm=π(a/2)2 = πa2/4 (cm2) n (mc/cm3)nσm

(b) a
(Gas Flow)
Def. Knudsen numberKn = l / L l
LSourceSubstrate
⇒
⇒ ( p < 10-2 Pa) 2. Kn < 0.01 ⇒(viscous flow regionfluid flow region)
( p) ⇒
⇒
3. 0.01 < Kn < 1 ⇒(transition region)Plasma process ⇒

Knudsen numberReynold’s number ()
(ρ)(v)(η) (d)
Def. Reynold’s numberRe = v ρd / ηη/
Kn <0.01continuum flow continuum flowReynold’s number
1. Re <1200 ⇒() 2. Re >2200 ⇒() 3. 1200 < Re < 2200 ⇒

Transport Properties: Mass (diffusion), Momentum (viscous shear) and Energy (heat conduction)
Transport is always described by an equation of the form: (flux of A) = − (proportionality factor) × (gradient in A)
Diffusion: AB Diffusion flux JA(net) = J (down at x) − J (up at x+l) =
AB
(cf. Table 2.1) p ↓ ⇒ DAB ↑p
Kn>1 ()
Viscosity: u
= (J) ×()
η(viscosity) kg/m·s = N·s/m2 = Pa ·s (SI) g/cm ·s = Poise (cgs)
( ) dx du
dx dumcn
4 1umJ η==Δ×=τ∴ l
⇒1. T ↑ ⇒ η ↑ () 2. p (Kn>1η)
Heat conduction: Heat flux () Φ (J/s·cm2 = W/cm2)
(Thermal conductivity)

∴Φp
substrate
⇒
(He) (thermal accommodation factor)
(W/cm2·K) (heat transfer coefficient) (hc)
( ) ( ) ( )shcshv 4
sh A
Def. The thermal accommodation coefficient γ () Th
Trs:
Trh:
( γHe ≈ 0.1 ~ 0.4 ) ⇒γ < 1γ ′
⇒γ = 0.2 γ ′ = 0.11(He)
hrs
rhrs
Arhcb
Chapter 3. Vacuum Technology
(1)(rough vacuum)1 atm ~ 1 torr (2)(medium vacuum)1 torr ~ 10-3 torr (3)(high vacuum)10-3 torr ~ 10-7 torr (4)(ultra-high vacuum)10-7 torr
(vacuum pump)() pump

(pump)

1.
2.
Pump selection: 1. Process vacuum level. 2. The properties of the vapors to be handled. 3. The pump operate well at the desired process pressure. 4. The cost (depend on pumping speed, liter/s).
1.
2.
Vacuum pump
()
Sputtering ion pump

(Mechanical pump)
2.
(Vapor steam pump):(Vapor pump) ()
(Chemical adsorption pump) (reactive substance) (getter) (vacuum tube) (Ta) ()
(Sorption pump) (physical sorption)
(Cryopump) (non-reactive metal) (liquid helium)
1664 36
(Rotary oil-sealed pump) (rotor) (vane) (stator) (flap valve) 10-4 torr
(Rotary oil-sealed pump)
(Rotary oil-sealed pump)
Gas ballast valve Rotary pump gas ballast gas ballast gas ballast gas ballast
Gas ballast
Rotary pump Rotary pump pump pump pump Roatry pump
(Ultimate pressure)
Rotary pump (pump)
(Pumping speed)
(Rotary blower pump)(Roots pump) 0.1 mm 1010-2torr 10-4 torr (booster pump)
Roots pump
(Dry pump)
Dry pump

(Multi-stage roots pump)

(Claw pump)
Claw pump

1. Inlet exposed 2. Inlet isolated 3. Exhaust exposed 4. Exhaust isolated

(Mechanical molecular pump)

1
(Molecular drag pump) 0.005
5 0.5
(Turbo-molecular pump) 24000 60000 10-2 torr 10-9 torr10-10 torr

(Diffusion pump) (silicone oil) (nozzle) (pump fluid)
( )

Foreline pressure
too high

(Baffle)(Cryotrap)

1. Rotary pump(foreline valve)
2.Rotary pump Rotary pump(roughing valve)Rotary pump (U-VAC valve)
3.10-2 torrroughing valve foreline valvecyrotrap U-VAC valve,
(Steam ejector pump) (expansion chamber)
101
(Steam ejector pump)

(Diffusion-ejector pump)
()
(Sorption pump) (absorption) (physical adsorption)(chemisorption) (Von der Waals forces) (chemical bond force) (absorbate)(absorbent) (absorption energy)

(Cryogenic pump)

(Dewar flask)
(Gettering pump) (getter) (85%15%) () () (titanium sublimation pumpTSP) 10-2 torr10-10 torr
(Gettering ion pump) (evaporate ion pump) (heated post) () (1660)
(grid)
(Sputtering ion pump)

()(sputter)

(4)
( )
(7)CH4CH2

(Gas throughputQ) Flow rate
(Pa·l /s torr ·l /s )
(ConductanceC):
(ImpedanceW): ( s / l )
t pVQ =

(Q = C⋅Δp)

Q P W I V R

() Input + Generation = Output + Accumulation ⇒ Qs + Qi = Q0
(Chamber walls)
⇒×
⇒CA
2.
⇒ For air at R.T. ⇒ Cm= 12.3 φ3/L (l/s) ⇒φ(cm)L(cm)L>> φ
Fig.3.3foreline tubeC1 pumpC0tubeforeline tube
pumpQs

The unthrottled case: (cf.Fig.3.3 & Eq.3.3) Qi:pi= Qi/Co
The throttled case: (fixed pressure p2 with a throttle)
⇒ Qsp2p2throttle (C2)pi
⇒p2
)QQ( Q Q
⇒Let t=0p2= p2o
V/Co
Exp: For a typical case of a 100 l chamber and a 10 l/s roughing pump, the time constant is 10 s. This means that evacuation of the air from 1 atm to 10-5 Pa would take place in a mere 4 min. Contamination Source:
(Au)

=
Oil backstreaming (backstreaming) (pv)
⇒ For example, a typical rotary pump oil has a pv of 10-4 Pa at 25 but a pv of 10-1 Pa at a pump operating temperature of 85.
⇒
⇒
⇒Oil backstreaming behavior in molecular flow and fluid flow:
Kn>1 process chamber

()
() ()
⇒Cooled baffle
Process chamberValve

⋅ =−
2) 2
A = tube cross-sectional area, cm2
Q = gas mass flow rate, Pa·cm3/s (at 25⇒ Q = sccm × 1837)
p = total pressure in the tube (Pa)
Ar⇒ cf: Table 2.1D(Ar-Ar) (p.26)
⇒ D = 0.19×105/p (cm2/s)
Gas evolution () (Outgassing) Source(Bulk)
⇒
1. Oil( )(ACETCE IPA)
2. Water Baking() Desorb()
[(CH3-CH2)4Pb] 2,2,4-()100 92%(95%)92%(95%) 92(95)92(95)()
⇒1 monolayer 1 monolayer1015 mc/cm21 m2
1019 mc:
( ) ( ) ( ) ( )s4000
⇒40 Pa·l1 atm (~105Pa) 10 slm (l/m)1 ppmPump =10(l/m)/106=10×103(cm3/m)/106=10−2 cm3/m:
)m(40 )Pa(10)m(10
)Pa(40 )atm(1)mcm(10
)Pa(40t 55-32- = ⋅ ⋅
⇒ (O-rings) O-rings O-rings 10−6 Pa (O-rings 10−8 Pa)
⇒ (Zn)(Cd)(Pb)(Sb) (P)303(S)(Se)
⇒304(L)316(L)(Fe-Ni-Cr )SSe L(Carbon)
⇒450 (Mn) MBEMnTrapGaAs (W)(Ta) (Mo)Ta WmpPv()
⇒Virtual-leak problemcf: Fig. 3.5

Dust ()
(Submicrod <10−4 cm)
(Clean Room)1001(Class One) 0.1
Class One0.5μm1
Pressure Measurement
2.(vacuum gauge) ()
⇒
⇒
⇒(Thermocouple GaugeTC Gauge)
3.
Thermocouple Gage

⇒(Pirani GaugeTC Gauge)
Pirani Gauge
TC Gauge TC Gauge
⇒(Capacitance Manometer) (pr)(p3) 10-41 Torr
⇒(Ion Gauge)

⇒-(Bayard-Alpert Ion Gauge)
B-A
⇒(Penning Cold Cathode Gauge)
3.
4.
⇒(Penning Cold Cathode Gauge)
Penning gauge
Penning gauge

foreline O-ring(Gasket) (Flapper)O-ring 300O-ringBuna-N80 Viton200
⇒
⇒ Gate valves Gate valve Gate valve Gate valve Gate valve
Flapper O-ring
⇒ Right-angle and block valves
⇒ Straight-through valves
⇒ Ball valves
⇒ Butterfly valves
Flapper
⇒ Leak valves

⇒ O-ring
⇒O-ring
O-ring O-ring
⇒O-ring

⇒O-ring
O-ring O-ring KF
⇒
O-ringO-ring GasketAlCuNi Gasket Gasket Gasket
⇒(Mass Flow Controller MFC )

⇒ :
⇒
(1)VCR
⇒
⇒

chapter 1-thin-film technology-1

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