2-3 April, 2019
Contamination kinetics of airborne ammonia on chromium-coated wafer in cleanroom
conditions
Minh-Phuong TRAN, CEA-Leti, [email protected]é FONTAINE, CEA-Leti, [email protected] GONZÁLEZ-AGUIRRE, Entegris, [email protected] BEITIA, CEA-Leti, [email protected] MOON, Entegris, [email protected] LUNDGREN, Entegris, [email protected]
SPCC 2019 – Portland, USA
CEA–Leti, University Grenoble Aples, 17 rue des Martyrs, 38054 Grenoble, France
Entegris, SAS, Parc Centr’Alp Ouest, 196 rue du Rocher de Lorzier, 38430 Moirans, France
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OUTLINE
1. Introduction
2. Experimental setup
3. NH3 kinetics on Cr-coated wafer
Deposition kinetics vs. [NH3] and %RH
Desorption kinetics vs. %RH
4. Mathematical deposition model - Applications
5. Conclusion
SPCC 2019, Portland USA
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INTRODUCTION
NH3 sources
Wet clean/Wet etch: Salt, NH4OH, NH3/NH4Cl
CVD deposition: TiN – Tetrakis C8H24N4Ti)/NH3
CMP: basic slurries
Material out-gassing, traffic & Industrial pollution
Yield losses
Limit AMCs effect
SPCC 2019, Portland USA
Airborne molecular contaminations (AMCs)
Footing on DUV resist
Salt (NH4)2SO4, NH4Cl on lens
masks, wafers
T-topping
Salt crystal
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Knowledge of NH3 conta/outgassing
Cross-contamination FOUPs to wafers (NH3)
Test-vehicle
Mathematical deposition model
INTRODUCTION
FOUP contaminated
by wafer outgassing
NH3 contaminant outgassing from
FOUP air up to equilibrium
Contamination transfer
FOUP Air Wafer
Outgassing from wafer
FOUPs sorbed NH3
FOUPs outgassing NH3 FOUPs outgassing
Transfer NH3 to wafers
SPCC 2019, Portland USAP. González-Aguirre et al., Microelectron. Eng., (2019), 205, 53–58
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Liquid Phase Extraction
(LPE process)
Collect NH3 with DI water on
Cr surface
NH3 + H2O NH4+ + OH-
Quantify ion NH4+ by
Ionic Chromatography (IC)
NH4+ ion deposition on Cr
surface
Efficiency of LPE-IC
• Collection by LPE is >95% at first extraction (LPE1)
• LLD for Ammonia: <1.0 x 1011 ion/cm2
Cr wafer (PVD)
confined inert atmosphere (N2)
LPE- DI water
N2
N2
SPCC 2019, Portland USA
METHODOLOGY
FREE-NH3 SET-UP DEVELOPMENT
Liquid Phase Extraction (LPE process) Quantify NH3 on Cr surface
| 6Confidentiel SPCC 2019, Portland USA
Free-NH3 set-up
Con. set-up
Free-NH3 set-up helps keeping proper surface
from NH3 atmosphere in clean room (<2E11 ion.cm-2)
Free-NH3 set-up
IC analysis of blank surfaces
METHODOLOGY
FREE-NH3 SET-UP DEVELOPMENT
Free-NH3 extract protocol
Water spreading & sampling
in free-NH3 condition
| 7Confidentiel SPCC 2019, Portland USA
METHODOLOGY – SURFACE PREPARATION
N° Requirements Test-vehicle Si AlCu Cr
1 Blank – Saturation level (orders of magnitude)
2 High affinity to NH3
6 No corrosion caused by NH3
Water rinse (DIW)
Thermal desorption (350°C – 10 min)
Clean wafer contaminated
in NH3 (800ppbv – 2h)
Water rinse Thermal
X 1
00
0
x1
0
Cr-coated wafer - Best candidate as Test-vehicle Establish deposition kinetics
Cr wafer
(200mm)
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EXPERIMENTAL SETUP
c
1st
SPCC 2019, Portland USA
Thermal Desorption Chamber
Cr wafer (PVD)
Remove efficiently Clean surface
(as deposited) 2.1E11 ion.cm-2
Cleaning surface by Thermal desorption (350°C – 10 min)
Cr wafer (PVD)
confined inert atmosphere (N2)N2
N2
Heating source
350°C, 10 min
Quartz chamber
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EXPERIMENTAL SETUP
NH3 gas
1 ppm
200 mm Chamber
Concentration: 10, 15 and 35-ppbv
(21oC and 1 atm)
Outlet
Dilution air
(Controlled %RH)
NH3 generator
Constant CNH3
cCr coated-wafer – 100 nm PVD
2nd
o Cr-coated wafers: Physical Vapor Deposition (PVD) - 100nm Cr
o Diluted NH3 gas by clean air, controlled humidity
SPCC 2019, Portland USA
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Saturation at 1.9E14 (ion.cm-2)
Cmax and Kads independent on CNH3-gas
𝐶 = 𝐶𝑚𝑎𝑥 − (𝐶𝑚𝑎𝑥 − 𝐶𝑜)exp[−𝑘𝑎𝑑𝑠𝐶𝑔𝑡]
RESULTS – NH3 DEPOSITION ON Cr WAFER
NH3 Deposition Kinetics on Cr at 40%RH, varying NH3 concentration
SPCC 2019, Portland USA
𝐶 = 𝐶𝑚𝑎𝑥 − 𝐶𝑜 𝑘𝑎𝑑𝑠𝐶𝑔𝑡 − 𝐶𝑜
Type Langmuir deposition
Kads determined from slope (short time)
0 2 4 6 8 10 12 14 16 18 20
0
5E13
1E14
1,5E14
2E14
2,5E14
Exp. 10 ppbv
Exp. 15 ppbv
Exp. 35 ppbv
Calcul. 10 ppbv
Calcul. 15 ppbv
Calcul. 35 ppbv
NH
3 a
mo
un
t (N
H4
+ /c
m2)
Time (h)
Kads=0.04 ± 30% ppbv-1.h-1
Saturation: Cmax=1.9E14 (ion.cm-2)
40%RH
Co=2.1E11 (ion.cm-2)Kads=0.04 ± 30% ppbv-1.h-1
time
NH3 gas concen. (ppbv)
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0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
0
5E13
1E14
1,5E14
2E14
2,5E14
40RH Exp.
20RH Exp.
<1RH Exp.
40RH Calcul.
20RH Calcul.
<1RH Calcul.
NH
3 a
mou
nt
(NH
4+/c
m2)
Time (h) Saturation level, Cmax depending on %RH
Increase %RH increasing Cmax & decrease Kads
H2Ovapor favors NH3 deposition
Agreement with HF deposition on Cu-coated
surface [Ref]
𝐶 = 𝐶𝑚𝑎𝑥 − (𝐶𝑚𝑎𝑥 − 𝐶𝑜)exp[−𝑘𝑎𝑑𝑠𝐶𝑔𝑡]
Deposition Kinetics on Cr at 15-ppbv, varying %RH (Humidity)
SPCC 2019, Portland USA
Type Langmuir deposition
Kads determined from slope (short time)
Co=2.09E11 (ion.cm-2)
40%RH: Cmax=1.95E14 (ion.cm-2)
15-ppbv
20%RH: Cmax=1.78E14 (ion.cm-2)
<1%RH: Cmax=1.21E14 (ion.cm-2) 𝐶 = 𝐶𝑚𝑎𝑥 − 𝐶𝑜 𝑘𝑎𝑑𝑠𝐶𝑔𝑡 − 𝐶𝑜
F. Herrán, H. Fontaine et al., Solid State Phenomena, 2016, vol. 255, pp. 323–328
Kads
RESULTS – NH3 DEPOSITION ON Cr WAFER
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Langmuir modified model
– Deposition
Cmax (ion.cm-2) = 1.65E12(RH) + 1.32E14
MATHEMATICAL MODEL
Experimental results
𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]
𝑪𝒎𝒂𝒙 independent on Cg at %RH = 40
𝑪𝒎𝒂𝒙 linearly dependent on %RH at Cg= 15 (ppbv)
SPCC 2019, Portland USA
Cmax (ion.cm-2)
Cg (NH3)
1.9E14 (ion.cm-2)
Cmax (ion.cm-2)
%RH
A = 1.65E12
B = 1.32E14
Csurface = f (RH, Cg, t)
[NH3]surf = f( RH, CNH3, time)
(1)
RESULTS – NH3 DEPOSITION ON Cr WAFER
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Kads (ppbv-1.h-1) = -7.06E-4(RH) + 7.28E-2
Experimental results
𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]
𝑲𝒂𝒅𝒔 independent on Cg at %RH = 40
𝑲𝒂𝒅𝒔 linearly dependent on %RH at Cg= 15 (ppbv)
SPCC 2019, Portland USA
𝑲𝒂𝒅𝒔 (ppbv-1.h-1)
Cg (NH3)
0.04
%RH
A’ = -7.06E-4
B’ = 7.28E-2
Csurface = f (RH, Cg, t)
[NH3]surf = f( RH, CNH3, time)
(2)
𝑲𝒂𝒅𝒔 (ppbv-1.h-1)
MATHEMATICAL MODEL
RESULTS – NH3 DEPOSITION ON Cr WAFER
Langmuir modified model
– Deposition
| 14Confidentiel SPCC 2019, Portland USA
𝑪 = 1.65E12RH+1.32E14− (1.65E12RH+1.32E14 − 𝑪𝒐)𝒆𝒙𝒑[−(−7.06E−4)RH +7.28E−2)𝑪𝒈𝒕]
𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]
Csurface = f (RH, Cg, t)
[NH3]surf = f ( RH, CNH3, time)
(1)
Co = 2.1E11 ion.cm-2
Model validation: <1% – 40%RH (Humidity) & 1 – 35-ppbv (NH3 airborne concentration)
Initial Clean surface: Co = 2.1E11 ion.cm-2
MATHEMATICAL MODEL
RESULTS – NH3 DEPOSITION ON Cr WAFER
Langmuir modified model
– Deposition
Cmax (ion.cm-2) = 1.65E12(RH) + 1.32E14
Kads (ppbv-1.h-1) = -7.06E-4(RH) + 7.28E-2 (2)
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RESULT
NH3 DESORPTION FROM AMMONIA SATURATED CR WAFEREL
SPCC 2019, Portland USA
NH3-saturated surface of Cr waferFree-NH3 flow (<1% or 40%RH)
Free-NH3 flow
Set-up: Desorption Chamber (Polymer)
Varying RH (<1% and 40%)
1180 mL/min
Desorption kinetics slower vs. Deposition
Not fully desorption (plateau 1.1E13 ion.cm-2)
• 40%RH: 160h desorption
• <1%RH: 260h desorption
• Plateau ~6% of saturated amount
60% removal NH3 in 20h (40%RH)
Model application at 160h @40%RH
~ 5-pptv NH3 concentration (cannot control)
At 40%RH: higher efficient in removing NH3
from saturated-Cr wafers
Agreement with desorption HF on Cu [Ref]0 50 100 150 200 250 300 350 400 450 500
0,0E+00
5,0E+13
1,0E+14
1,5E+14
2,0E+14
2,5E+14
40 RH Desorption
<1 RH Desorption
NH
3 a
mo
un
t (N
H4+/c
m2)
Time (h)
40%RH
<1%RH
Blank level 1.1E13 (ion.cm-2)
NH3 saturation
1.95E14 (ion.cm-2) at 40%RH
F. Herrán, H. Fontaine et al., Solid State Phenomena, 2016, vol. 255, pp. 323–328
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APPLICATION OF MATHEMATICAL MODEL
SPCC 2019, Portland USA
Example 1: Cr-coated surface serves as Test-vehicle
FOUPs (PC, PEI, EBM, EBMCNT)
Calculation of average-NH3 airborne concentration (Cg) in FOUPs
Example 2: Calculation of time for appearance of haze or salt crystals on Photomask (Cr)
at specification of Cg (ppbv) of NH3 and %RH in lithography zones or in equipment
Calculate time from mathematical model
P. González-Aguirre et al., Microelectron. Eng., (2019), 205, 53–58
FOUPs outgassing
Transfer NH3 to wafer
[NH3]surf = f ( RH, CNH3, time)
Agreement experimental data
FOUPs
transfer NH3
to Cr wafers
Calculation
Conta.
Purge (5 min)
Outgassing
21.5 ppbv
11 ppbv8.5 ppbv
22.5 ppbv
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Development of free-NH3 set-up for LPE-IC protocol avoid cross conta. from clean room air
Establishment of NH3 deposition kinetics knowledge of NH3 contamination model
Cmax (saturation level) and Kads (adsorption coefficient)
Dependent on humidity (%RH)
Independent on (Cg)
Langmuir modified deposition model
Desorption
Humid condition favors desorption (vs. Dry)
Desorption kinetic: Slower than Deposition
No full desorption presence of few pptv of NH3 in desorption chamber
Apply model to calculate average-Cg and time in mini-enviroment
Dry condition is highly recommended in sensible zones to AMCs
CONCLUSIONS
C=[NH3]surf
t
40%RH
Cmax=1.95E14 ion.cm-2𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙 − 𝑪𝒐)𝒆𝒙𝒑[−𝑲𝒂𝒅𝒔𝑪𝒈𝒕]
[NH3]surf = f (RH, Cg-NH3 , t)Kads = A’(RH) + B’
Cmax = A(RH) + B
Co = 2.1E11 ion.cm-2
Langmuir deposition model
Cg = 0 – 35 (ppbv)
%RH = 0 - 40
SPCC 2019, Portland USA
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Univ. Grenoble Alpes, CEA, LETI
Sylviane CÊTRENicolas CHEVALIERCarmelo CASTAGNAGarcia ROLANDPierre LEYGNAC
SPCC 2019, Portland USA
Thanks for your attention
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