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TRANSCRIPT
© Alexander Bol,shakov1.
Ames Research CenterNASA, MNASA, MNASA, Moooffffffett ett ett FFFiiieeeldldld,,, CACACA 940359403594035
Alexander A.Alexander A. BoBoľľshakov shakov Brett A.Brett A. Cruden Cruden
SurendraSurendra P. Sharma P. Sharma
Plasma Diagnostics for Nanoscale Fabrication
Plasma Diagnostics for Plasma Diagnostics for NanoscaleNanoscale FabricationFabrication
October 9October 920032003
© Alexander Bol,shakov2.
Presentation outlinePresentation outlineIntroduction:
micro/nano-electronics roadmapdiode lasers
Experimental setupTemperature determinationSimulation of plasma mechanismsEstimation of densities of speciesConclusions
© Alexander Bol,shakov3.
ITRS functional dimensionsITRS functional dimensions
1000
100
10
1990 1995 2000 2005 2010 2015 2020
10
100
1000
Elec
trons
per
dev
ice
Crit
ical
size
,nm
Years
16M 64M 256M 1G 4G 16GElementary devices (transistors) per chip
* International Technology Roadmap for Semiconductors
CCММOSOS
© Alexander Bol,shakov4.
NanotubeNanotube--based transistorbased transistor
Carbon nanotube
SiSiO2
Electrodes(Au)
* S.J. Wind, J. Appenzeller, R. Martel, V. Derycke, P. Avouris, J. Vac. Sci. Technol. B
© Alexander Bol,shakov5.
Carbon nanotubesCarbon nanotubes
GraphenGraphen layerlayer NanotubesNanotubes
~20 atoms in circumference, ~2 nm in diam.
Semiconducting or metallic
Useful as transistors or interconnect
© Alexander Bol,shakov6.
NanorodsNanorods/wires/wires –– nanolasersnanolasersLasing output Lasing output
ExcitationExcitationZnO
λ = 380 nm* M.H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, P. Yang, Science.
© Alexander Bol,shakov7.
Current and future needsCurrent and future needsAdvanced process control required Must be non-intrusive, compact, and simpleMonitoring of chemical species:
end-point detection process optimization and control contamination “management”
Local temperature monitoring:plasma uniformityintentionally non-uniform (!?)
© Alexander Bol,shakov8.
Semiconductor process gasesSemiconductor process gases
Inert (e.g., Ar, He, N2)
Corrosive (e.g., HCl, HBr, SF6, NF3, CF4)
Highly Toxic (e.g., AsH3, PH3)
Pyrophoric (e.g., SiH4)
Reactive (e.g., NH3, N2O, WF6, CO2, O2)
© Alexander Bol,shakov9.
Impurity transferImpurity transfer
Plasma treatment
nn--step nn+1+1--stepstep step
More than 300 technology steps for one chip
High variety of materials in use
© Alexander Bol,shakov10.
How to monitor processesHow to monitor processes??
Emission:
Absorption:
Fluorescence:
Mass spectrometry:
Electrical:
low resolution only emitting species
limited if FTIR or UV diode lasers - ideal
requires powerful lasers
intrusive, cumbersome
non-selective
© Alexander Bol,shakov11.
Commercial diode lasersCommercial diode lasers
Wavelength, µm0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3
AlGaAs/GaAs
InGaAs/GaAs
InGaAsP/InP
InGaAsP/InGaAs or InAsP
AlGaAsSb/InGaAsSb
AlGalnP/GaAs
Doubled frequency
GaNZnSe
Room temperature operation
© Alexander Bol,shakov12.
Accessible elementsAccessible elements
Probed already Possible Excited only
Al, Ba, Ca, Cr, Ag, Co, Eu, Ar, As, B, Cs, Cu, Hg, I, Fe, Ga, Gd, Br, Cl, F, H, In, K, La, Li, Mn, Hf, Ho, Lu, Kr, N, Ne,Pb, Rb, Sm, Sr, Mo, Nb, Nd, O, P, S, Si, U, Y, Zr Ni, Os, Re, Xe, Zn & etc.
Rh, Ru, Sc, Tb, Th, Ti, Tl, Tm, V, W
H2O, OH, O2,CH, CO, CO2, CH4,NH3, HCl, HBr
N2, Cl2, F2, CF, CN, SiF, AlCl and etc.
© Alexander Bol,shakov13.
Diode laser characteristicsDiode laser characteristics
Tunable over absorption features
Provide spectrally narrow linewidths
Compact and simple to use
Can be multiplexed
Commercially available
Relatively inexpensive
© Alexander Bol,shakov14.
Experimental SetupExperimental Setup
PC
DiodeLaser
FastAmplifier
Digitizer12 bit
MatchingNetwork
RF PowerSupply
ThresholdDetector
DC bias& Reset
High LimitDetector
FunctionGenerator
PulldownCircuit
Slow Ramp
Temp.Controller
Cavity modulation, 1 kHzData acquisition, 20 MHzDiode laser scan, 5 min
Start
ICP
Isolator
PD
Piezo
© Alexander Bol,shakov15.
Simplified SetupSimplified Setup
Data acquisition, 0.1 kHz
PC
DiodeLaser PD
Etalon
Low Noisepreamplifier
Digitizer8 bit
MatchingNetwork
RF PowerSupply
LabViewsoftware
Slow Ramp
Temp.Controller ICP reactor
PD
Wafer
© Alexander Bol,shakov16.
Rate of energy loss from cavityRate of energy loss from cavityLaser АОМ DetectorCavityLaserLaser АОМАОМ DetectorDetectorCavityCavity
L
Reflectance L=50 сm L=100 сmτ (µs) τ (µs)
Number of passes
9699
99.999.99
99.999
0.040.171.67
16.67166.67
0.080.333.33
33.33333.33
25100
100010000
100000
© Alexander Bol,shakov17.
Etching ICP ReactorEtching ICP ReactorMatching NetworkRF Power Supply
Gate Valve
Turbo Pump &Backing Pump
Plasma
Gas Inlet
Throttle Valve & Roughing Pump
Coil
PoweredLowerElectrode
RF Head
Matching Network
RFPowerSupply
Turbo Pump
Backing Pump
Penning Gauge
Aperture (100 m)µ
MHV CoaxialRF FeedIon OpticsIon Source
Energy Analyzer
Quadrupole
ChanneltronIon Detector
13.56 MHz
100 kHz
© Alexander Bol,shakov18.
Diagnostics objectivesDiagnostics objectives
Determination of plasma parameters: gas temperature electron temperature degree of ionization
Identification of species in etching plasmasMeasurement of concentrations of speciesSimulation of plasma etching mechanismsbased on acquired experimental data
© Alexander Bol,shakov19.
0
200000
400000
600000
762.3 762.8 763.3 763.8 764.3
Wavelength, nm
Inte
nsity
90 mTorr50 W20 µm
25 C
35 C30 C
Laser Scan over Argon LineLaser Scan over Argon LinePlasma:
Laser:VCSELIop=4.9 mA∆ν=5 MHzPop=0.5 mW
Argon line:763.51 nm
© Alexander Bol,shakov20.
Absorption by Argon PlasmaAbsorption by Argon Plasma
0
100000
200000
300000
700 750 800 850 900 950
Time (frame number)
763.3
763.4
763.5
763.6
763.7
763.8
763.6 nm
763.4 nm
Plasma: Laser:Iop=4.9 mAT=32-20 C
Ar line:763.51 nm
200 mTorr, 100 W40 mTorr, 100 W
Wav
elen
gth,
nm450 K
550 K
Abso
rptio
n
© Alexander Bol,shakov21.
Laser wavelength calibrationLaser wavelength calibration
0
2000
4000
6000
8000
10000
762.7 762.8 762.9 763.0 763.1 763.2 763.3 763.4 763.5 763.6 763.7Wavelength, nm
Etalon fringe
Laser scan
ArPQ9 PP9
PP7PQ7PP5
PQ5
Argon and ambient airabsorption
© Alexander Bol,shakov22.
Ambient oxygen absorptionAmbient oxygen absorption
759 760 761 762 763 764 765 766Wavelength, nm
Ar 763.51
PQ9PP9
PP7PQ7
PP5
PQ5
O2 (b1Σg – X3Σg)
© Alexander Bol,shakov23.
Temperature in Ar/NTemperature in Ar/N22 plasmaplasma
0
100
200
300
400
500
600
700
800
900
0 50 100 150 200 250 300 350 400 450 500Pressure, mTorr
Tem
pera
ture
, K
300 W
100 W
100 W
0-D model
3% N2 in Ar
100% Ar
3% N2 in Ar
Doppler temperatureRotational temperature0-D simulation in Ar
45% N2 in Ar
© Alexander Bol,shakov24.
Temperature in Ar/NTemperature in Ar/N22 plasmaplasmaTe
mpe
ratu
re, K
Pressure, mTorr
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
0 50 100 150 200 250 300 350 400 450 500
300 W45% N2 in Ar
3% N2 in Ar
45% N2 in Ar
90% N2 in Ar
90% N2 in Ar
Doppler temperatureRotational temperature
© Alexander Bol,shakov25.
Argon plasma simulationArgon plasma simulation
300
400
500
600
700
800
-130 -110 -90 -70 -50 -30 -10 10 30 50 70 90 110 1300
1
2
3
4
5
6
7
Tem
pera
ture
, K
Reactor radial dimension, mm
Tgas
Ar m
etas
tabl
e de
nsity
, 101
0cm
- 3Arms
100 W100 mTorr
© Alexander Bol,shakov26.
Emission from Ar plasmaEmission from Ar plasma
0
0.2
0.4
0.6
0.8
1
Rel
ativ
e in
tens
ity
Pressure, mTorr
763.5 nm
602.5 nm
603.2 nm667.7 nm
© Alexander Bol,shakov27.
Passive Optical Cavity Passive Optical Cavity
CF4
ArMFC
MFC
DiodeLaser
Plasma
Top View
λ = 2.12 µmIsolator
PD
Back Mirroron Piezomount
FrontMirror Planar ICP Reactor
© Alexander Bol,shakov28.
Composite Spectrum of CFComposite Spectrum of CFXX
2.0 2.5 3.0 4.0 5.0 7.0 10 15
5000 4000 3000 2000 1000
Wavenumber, cm-1
Wavelength, µm
100
102
104
106
108
CFCFCFCF22CFCF33CFCF44
Fundamental, overtone and combination bands
Band
inte
nsity
, m-2
atm
-1
© Alexander Bol,shakov29.
Cavity Modes and Laser LineCavity Modes and Laser LineLaser is slowly scanned throughout ~400 GHzCavity length is fast modulated within ±100 MHz
Frequency, MHz
<100 MHz
laser scan
200 MHz
50 kHz
Doppler-broadened line~1GHz
© Alexander Bol,shakov30.
Detection of plasma speciesDetection of plasma speciesHigh anisotropy & selectivity in etching of Siover SiO2 or SiN3 is necessary; research in CFx radicals plasmachemistry is neededAbsolute densities of CxHy, CFx radicals and kinetics in plasma can be measured by cavity absorption spectroscopy at ~1 km of the equivalent optical pathlengthUseful for diagnostics, analysis, monitoring and control of both nano- and microelectronic fabrication processes and development of micro- and nanodevice-based sensors
© Alexander Bol,shakov31.
Spot Size at MirrorsSpot Size at Mirrors
1
0
2
3
1 10 1000.1Radius of curvative, m
Spot
siz
e, m
m
Cavity length:0.5 m0.7 m1.0 m
λ = 2 µm; λ = 3 µm
Con
cent
ric
Confocal configuration
© Alexander Bol,shakov32.
νν33 Fundamental Band of CFFundamental Band of CF44
OnOnOffOff
Plasma:
0.05 Torr100 W
Q0
Q1
Q2
R branch
0.8
0.6
Abso
rban
ce
0.4
0.2
0.01270 1275 1280 1285 1290
Wavenumber, cm-1
* B.A.Cruden, M.V.V.S.Rao, S.P.Sharma, M.Meyyappan, Plasma Sci. Source Technol.
© Alexander Bol,shakov33.
Emission from CFEmission from CF44 PlasmaPlasma
185 195 205 215 225
CCF
Si
Species detected include C, C2, F, CF, Si, O, COWavelength, nm
Inte
nsity
0.03 Torr, 0.3 kW
* B.A.Cruden, M.V.V.S.Rao, S.P.Sharma, M.Meyyappan, J. Vac. Sci. Technol. B
© Alexander Bol,shakov34.
Impurity AbsorptionImpurity Absorption
Wavelength, µm1.0 1.5 2.0 2.5 3.0
H2O
CO2
CO
10-210-1
10-3
10-2
10-4
10-2
10-5
10-3
10-4Line
stre
ngth
, cm
-2at
m-1
Interference-free window between 2.1– 2.2 µm* M.E.Webber, J.Wang, S.T.Sanders, D.S.Baer, R.K.Hanson, Proc. 28 Int. Symp.Combustion
© Alexander Bol,shakov35.
Sensitivity EstimatesSensitivity Estimates
Minimum absorption coeff. ~10-10 cm-1Hz-½
CFx radicals detection limit ~1011 cm-3
(λ = 2.12 µm; Cavity leakout time =100 µs)
Single molecule absorption can in principlebe detected at strong fundamental bands
(α ~10-15 cm-1Hz-½; λ = 8 µm)
© Alexander Bol,shakov36.
ConclusionsConclusions
Diode lasers operating in the 0.3 - 2.3 µm region are convenient, compact, inexpensive, tunable, of spectrally narrow bandwidth, and require no cryogenic coolingLocal and averaged temperature can be determined with different thermometric speciesAbsolute densities of atoms, radicals and molecules can be monitoredMulti-parametric measurements possible
© Alexander Bol,shakov37.
ConclusionsConclusionsChecking overall chamber health in real timeChamber clean-up/ fast start-up optimizationEnd-point for small features, cost-effectively Dopant species detection for end-pointingMonitoring atomic metal species in ALDReplacing the slow techniques (TXRF, SIMS) B and P implants detection in gate etch Aerosol detection in photoresist processing
© Alexander Bol,shakov38.
AcknowledgementsAcknowledgements
Alexander Boľshakov held NRC senior re-search associateship award at NASA AmesResearch Center while performing this work
Brett Cruden’s work was contracted throughEloret Corporation