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