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2006. 06. 26.
김 정 형jhkim86@kriss.re.kr
042-868-5644
플라즈마플라즈마 공정공정 진단진단 연구연구
플라즈마 응용분야
폐기물처리Sox, Nox, PFC,폐타이어,소각재
공기청정기:코로나방전
표면처리
핵융합
신소재합성
PDP, 전등, 네온사인
Plasma CVDDiamond,
hard film coating
반도체 공정Dry Etching,
PECVD, AshingIon Implatation
플라즈마플라즈마
여러 가지 플라즈마 I
여러 가지 플라즈마 II
Aurora
Lightening
AC Plasma
물질의 제 4의 상태인 플라즈마
[[물질의물질의 제제 44의의 상태상태]]라고라고 불리는불리는 플라즈마는플라즈마는 이온과이온과 전자와전자와 같이같이 전하를전하를 띤띤입자와입자와 중성기체가중성기체가 혼합된혼합된 상태이며상태이며 전하를전하를 띤띤 입자에입자에 의하여의하여 보통기체와는보통기체와는다른다른 성질을성질을 가지고가지고 있다있다..
가 열
Electric field
Cold electron Hot electron
NeutralPositive ion
Electrons
- --
-
-
+
+
•이온화시키기에 충분한 에너지를 전자가 갖도록 전기장을 이용하여 전자를 가열한다•전기장의 공급: DC, RF, Microwave 등
플라즈마 발생원리 (이온화 과정)
ElectronsElectrons : 물리적으로 매우 중요한 역할Mass(me)=9.1 x 10-28 gCharge=-1.6 x 10-19 Coulomb에너지 전달(이온화, 해리, 에너지상태여기(빛 방출)등) 대부분의 반응 시발점
Ions : 화학적 및 물리적 반응ex: Cl+, Cl2+, CF3+, Ar+, HF+, Cl-, O-, F-,….
Stable molecules: a collection of 2 or more atomes with fully satisfied bonding
• can be chemically active• ex: Cl2, CF4, O2, N2, SiF4,…(source gases)
Radicals (Atoms and molecules): 1 or more atoms with unsatisfied chemical bonding
• 높은 반응성으로 인한 화학적 반응• ex: F, O, N, OH, CFx(x=1-3)
플라즈마내의 각 입자의 역할
Radical에
의한 높은 반응성하전입자의
선택적 조절
Ion
Electron
Charged particlesEnergetic particlesRadicals
Plasma
고에너지 입자
Neutral
방향성전기장 및 자기장에의한 하전입자 제어
플라즈마 특성
반도체 공정
Etcher
Ar + CF4 + e
CFx ions
e- electrons
CxFy radicals
CF4, Ar molecules
wafer
Machine type, etch schemeMachine type, etch scheme
Powers, Gases, Pressure, Temp., etcPowers, Gases, Pressure, Temp., etc
Kinetic energy (IED)Ion density(ni)Angular distribution(IAD)
Electron temp.(Te), Density(ne)
Density, composition
Residence time
Etch rate, profile, selectivityEtch rate, profile, selectivity
Resistance, leakage, cap., etcResistance, leakage, cap., etc
Diagnostics of Diagnostics of process plasmaprocess plasma
External controlVariables
External controlVariables
Process outputsProcess outputs
Fine control
Optimaize processPlasmas(black box)
공정진단의 역할 및 중요성
Plasma DiagnosticsElectrical methods:
Langmuir probe: ni, Te, EEDFQMS (Quadrupole Mass Spectrometer): radical, ionsIon Energy Analyzer: IEDFRF I,V measurements: impedanceWISE probe: ni, Te
Optical methodsLIF: radical densityOES(Optical emission Spectroscopy): EPD, Te
Relative radical, ion density, partial pressureLII : dust particle Plasma emission interferometry: thin film thicknessThomson scattering: Te, EEDF, ne
Wave methodsWave Cutoff probe: neCAP(Cutoff & Absorption probe): TePlasma Oscillation probe: neWave Absorption probe:neHairpin probe: neElectromagnetic wave interferomery: ne
플라즈마 특성 진단 시스템
Load-lock
OES,LIF : radical
QMS : radical
Langmuir probe: 전자온도, 밀도
POP
Plasma
Plasma type: CCP, ICP, Sputtering
Cutoff probe: 전자 밀도,공정플라즈마 측정가능
Langmuir probe
Bsie dV
dIIIeT /)( −=
2/1
21exp ⎟⎟
⎠
⎞⎜⎜⎝
⎛⎟⎠⎞
⎜⎝⎛−== ∞
i
esisissi M
TnAvnAI
VB
I
VpVf
Quadrupole Mass Spectrometer
Quadrupolemass separator
Ion detector
TMPProcess chamber
2 4 6 8 10 12 14 16
2.00E-013
3.00E-013
4.00E-013
5.00E-013
6.00E-013
7.00E-013
8.00E-013
9.00E-013
1.00E-012
1.10E-012
1.20E-012CF3( calibrated)
QM
S o
utpu
t(a.u
.)
r(cm)
300 W 500 W 700 W 1000 W
0 2 4 6 8 10 12 14 16
3.00E-012
3.50E-012
4.00E-012
4.50E-012
5.00E-012
5.50E-012
6.00E-012CF4 distributions
300 W 500 W 700 W 1000 W
QM
S ou
tput
(a.u
.)
r(cm)
3.00E-012
4.00E-012
5.00E-012
6.00E-012
7.00E-012
8.00E-012
9.00E-012
1.00E-011
1.10E-011
0 W
LIF(Laser Induced Fluorescence)
FILTER
ICCDCAMERA
Nd-YAG DYE
FREQUENCYDOUBLER
SHEETBEAM
CCDCAMERA
DYECELL
BEAMDUMP
CAMERACONTROLLER
GATECONTROLLER
LASERCONTROLLER
MONOCHROMATORPM-TUBE
PM-TUBEPOWER
I/V
BOXCAR
CCDCONTROLLER
QUARTZPLATE
Scanning LIF
2D Planar LIF
Optical Emission Spectroscopy
250 300 350 400 450 5000.0
0.5
1.0
1.5
ExcitationA + e => A* + eAB + e => A* + B + e
De-excitationA* => A** +hν
Emission Intensity
Sig
nal(A.U
.)
Wavelength(nm)
emission LIF+emission
][AnkI eAA ∝si
gnal
inte
nsity
start of etchfilm clears
etchant
substrateproduct
filmproduct
power ontime
A B
End point detection
Laser Thomson Scattering
To measure the electron propertiesNo perturbation of the plasmaThomson scattering: from free electronsRayleigh scattering: from the bound electrons in the atoms and ionsStray scattering: from the surfaces and windows of the chamber
2
2
2
)2/(sin8)( ⎟⎟
⎠
⎞⎜⎜⎝
⎛λλΔ
θ=λΔ
L
ee
cmE
e
eLT m
kTc
22
sin2⎟⎠⎞
⎜⎝⎛ θλ
=λΔ
In-situ film thickness monitoring system
Matching Box
Substrate holder
Plasma
Heater(~500C) RF bias
Monochromator I-V converter
PMT
Boxcar
Lens
-20 0 20 40 60 80 100 120 140 160 180
0
1
2
3
4
Inte
rfere
nce
sign
al(a
.u.)
time(s)
박막: DUV PR(n=1.6, thickness=7000A)
플라즈마조건: O2= 100 sccm, N2=50 sccm, p=20 mTorr, Prf=1000 W
선택파장: 556 nm(emitted from N atom)
두께변화율: dTpr/dt = λ(n2-sin2θ)-1/2(2T)-1
T=15 secθ=5 degreesdTpr/dt = 6959 A/min
Microwave Interferometer
Refractive index:
Phase shift:)/(1/1 2
1222cep nnN −≈−= ωω
∫=Δ dlncn e
c2ωφ
W.E. Mlynko and D.W. Hess, J. Vac. Sci. Technol. A3, 499(1985)
Measurements of Impedance
K. Ukai and K. Hanazawa, J. Vac. Sci. Technol. 16, 385(1979)
Oscillation Probe Structure
2/1
0
2
⎟⎟⎠
⎞⎜⎜⎝
⎛ε
=ωe
epe m
en
Plasma oscillation
Filament E-beam
antenna
Vb
e-
Spectrum Analyzer
T. Shirakawa and H. Sugai, Jpn. J. Appl. Phys. Vol. 32(1993) 5129
Plasma frequency
POP results
Surface Wave Absorption Probe
dp
SW
εωω
+=
11
K. Nakamura et al., J. Vac. Sci. Technol. A, Vol. 21, 325(2003)
Coaxial CableDielectric Tube
Network Analyzer(10kHz ~ 3GHz)
13.56 MHz inductive discharge
plasmasheathantenna
•Te 를 따로 측정해서 알고 있어야 함.•경향성을 볼수는 있으나 절대값을 얻기는 힘듦.
Frequency spectra
1 2 3-20
-19
-18
-17
-16
-15
-14
-13
-12
-11
-10
-9
Ref
lect
ion
Coe
ffici
ent(d
B)
Frequency(GHz)
-95
-90
-85
-80
-75
-70
-65
-60
ωabs/2π
ωp/2π
Osc
illat
ion
Am
plitu
de(a
.u.)
επωπω
πω
πω
+=
=
=
12/2/
2/
2/
pesw
abs
pe
Prf= 300 WpAr= 15 mTorrPAP
POP
1.708 GHz
2.396 GHz
096.178.31/396.2
=+=
Cutoff Probe Structure
l
d
Coaxial Cable
Dielectric Tube
Network Analyzer(10kHz ~ 3GHz)
13.56 MHz inductive discharge
20
2
,e
mn ep
epcutoff
εωωω ==Plasma
•Plasma frequency에 해당하는 주파수를 가진 전자파는 플라즈마를 통과하지못하는 현상을 이용
Frequency Spectra of measured signals
Absorptionfrequency Cutoff frequency
Oscillationfrequency
(Cutoff probe)
(Oscillationprobe)
(Absorptionprobe)
Some results
0 100 200 300 400
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Ar=25 sccm, CH4=25 sccm, p=20 mT, p=300 W
I sat(m
A)
time(s)
0
1
2
f sw(G
Hz)
Dispersion relation of surface wave
plasma sheath
antenna
s
ab d
Where Km and Im are modified Bessel functions, β=2π/λ, λ=2d, d is antenna length,a is sheath radius from the antenna center, b is antenna radius.a=b+s, s is sheath width
Obtaining Ne and Te
Electron density ne <= plasma frequency(cutoff frequency)
Electron temperature <= ne & absorption frequency
Dispersion relation of surface wave (Absorption frequency)
20
2
,e
mn ep
epcutoff
εωωω ==
Where Km and Im are modified Bessel functions, β=2π/λ, λ=2d, d is antenna length,a is sheath radius from the antenna center, b is antenna radius.a=b+s, s is sheath width, s=nλd , λd=(ε0Te/nee2)1/2
• Since we know the values of d, a, b, s(n=2), and ne(from ωc), we can get Te using the dispersion relation of surface wave.
Ne and Te in Ar plasma
5 10 15 20 255.00E+010
1.00E+011
1.50E+011
2.00E+011
2.50E+011
3.00E+011
3.50E+011
4.00E+011
Ele
ctro
n de
nsity
(cm
-3)
Pressure (mTorr)
ne from EEDF of SLP ne from IV of SLP ne from fc
5 10 15 20 25
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
Ele
ctro
n Te
mpe
ratu
re (e
V)
Pressure (mTorr)
Te from EEDF of SLP Te from IV of SLP Te from fc and fa
Comparison
Thin film depo. on
tip
RF fluctuation
Mixed gases
Te
공간
분포
Wide range of pressure
Absolute density
O x
O
O
x
O
O
x
x
cutoff O O O x O O
Langmuir probe x x O O
U-wave interferometer
O O O x x
POP O O O x O
PAP O O O x O
Tools
Environs
Integration of FTIR on ULVAC CVD
Ref: Maryland Univ.
Acoustic Sensing of Reactor Gases
Ref: Maryland Univ.
Summary
공정플라즈마 진단의 필요성미세공정 제어
미세공정변화모니터링
최적공정조건
공정 플라즈마 진단 요건공정에의 영향: 무
공정에 의한 영향(증착 식각 등): 무
RF에 의한 영향: 무
공정변화에 민감
혼합가스플라즈마 적용
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