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CAMBRIDGE 10 & 11th APRIL 2018
Ammonia cross contamination: FOUP to wafer evaluation and its volatile acids comparison
Paola González-Aguirre, Entegris, [email protected]é Fontaine, CEA-Leti, [email protected] In Moon, Entegris, [email protected] Phuong Tran, CEA-Leti, [email protected] Lundgren, Entegris, [email protected] Beitia, CEA-Leti, [email protected]
Surface Preparation and Cleaning Conference
| SPCC2018
OUTLINE
◦ Introduction
◦ Issues/objectives
◦ Experimental protocol
◦ Results
• Contaminant sorption by the FOUPs
• Contaminant outgassing from the FOUPs
• Contaminant transfer to wafers
◦ Conclusions
Manufacturing/Development Research
45 nm 32/28 nm 22/20 nm 16/14 nm 10 nm
2
| SPCC20183
FOUP/WAFER MOLECULAR CONTAMINATION
Demonstration of a cross-contamination chain between FOUP & wafers
FOUP contamination Transfer FOUP to wafers
FOUP equilibration
Sorption of AMCs from CR air, released from stored wafers, equipment connection…
Sensitive subsequent outgassing, transfer to wafers (promoting defectivity)
FOUPs must protect the wafer environment from AMCsCross-molecular contamination: AMCs FOUP Wafer
Wafer DEFECTIVITY
[AMC]
Time % RH
| SPCC20184
INTRODUCTION: AMC
oAirborne molecular contamination (AMC) may be responsible for severe yield losses
oAmong AMCs, HX are well known as root cause of defectiveness
Many sources of ammonia in fabs:• Staff members • Surface functionalization from priming agents• Cleaners• Polishing slurries materials
Corrosion of a Cu
1 µm
TiFx crystalgrowth on
TiN
Al lines corrosion
o Fabs feedback concerning ammoniao Photolithography (T-topping)o Crystal growth un photomasko Time dependent Hazeo Post CMP
| SPCC20185
GOALS
◦Compare critical NH3 molecular contamination behavior in two Entegris FOUP models, in terms of:
◦Contaminant, sorption and subsequent release
◦Contaminant cross-contamination on stored wafers
A300 EBM/CNT SPECTRA PC
Polycarbonate EBM/C-nanotubes
| SPCC20186
IC = Ion Chromatography, LPE = Liquid Phase ExtractionTest carried by twice
EXPERIMENTAL PROTOCOL
0) FOUP CONDITIONINGClean room equilibration
(21°C 40% RH) 7days
1) INTENTIONAL CONTAMINATION
10µL- droplet 24h
2) PURGE(N2 gun) 5 min
3) OUTGASSING MONITORING IMPINGER-IC
(once per day) 8 days
HF 2.0% 11.2ppmHCl 3.7% 11.6ppm
NH3 2,9% 14.7ppm & 0.29% 1.47ppm
3) STORAGE of Cu-WAFERS, LPE-IC
| SPCC20187
SORPTION/OUTGASSING BY PC FOUPs
Contamination phase
Outgassingphase
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 50 100 150 200 250 300 350 400
[co
nta
min
ant]
pp
bv
T(h)
0
50
100
150
200
250
300
350
400
24 44 64 84 104 124 144 164
NH3 : 22,86 A3 HCl : 22,45 A3 HF : 15,77A3
Steric effectAffinity to polymer NH3 < HCl < HF
OutgassingNH3 > HCl > HF
HCl
HF
NH3
HCl
HF
NH3
• Immediate Strong outgassing after purge, followed of a concentration equilibrium
• Solubility is the outgassing driving force
NH3 < HCl < HF
| SPCC20188
SORPTION/OUTGASSING BY EBMCNT FOUPs
Contamination phase
Outgassing phase
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 20 40 60 80 100 120 140 160 180
[co
nta
min
ant]
pp
bv
T(h)
F- EBMCNT Cl- EBMCNT NH4+ EBMCNT
-20
30
80
130
180
230
280
24 44 64 84 104 124 144 164
Affinity to polymer
NH3 < HCl < HF
OutgassingNH3 > HCl > HF
HCl
HF
NH3
HF
HCl
NH3 • Strong outgassing for HCl andNH3 after purge, followed of aconcentration equilibrium
• No detectable outgassing in HFcase LLD (low limit detection)for F- 0.62ppbv
• In the NH3 case, in respect toPC material the maximumoutgassing is detected somehours later after purge
DEBMCNT < DPC
| SPCC2018
0
1000
2000
3000
4000
5000
6000
7000
8000
0 50 100 150 200
[NH
3]
pp
bv
T(h)
NH4+ EBMCNT
NH4+ PC
0
1000
2000
3000
4000
5000
6000
7000
8000
0 50 100 150 200
[HC
l] p
pb
v
T(h)
Cl- EBMCNT
Cl- PC
0
1000
2000
3000
4000
5000
6000
7000
8000
0 50 100 150 200
HF-
] p
pb
v
T(h)
F- EBMCNT
F- PC
9
Outgassing PC > EBMCNTContaminant affinity to polymer PC > EBMCNT
Outgassing zoom
Contamination/outgassing
COMPARATIVE SORPTION/OUTGASSING FOUPs ABILITY
0
50
100
150
200
250
300
350
24 74 124 174
[HF]
pp
bv
0
50
100
150
200
250
300
350
24 74 124 174
[HC
l] p
pb
v
0
50
100
150
200
250
300
350
24 74 124 174
[NH
3]p
pb
v
HClHF NH3
| SPCC201810
[1] F. Herran, H. Fontaine, P. Gonzalez-Aguirre, C. Beitia, J. Ohlsen, J. Lundgren. A mathematical model forecasting HF adsorption onto Cu-coated wafers as a function of airborne concentration and moisture, Solid State Phenomena (2016), 255-323[2] M-P Tran, P Gonzalez-Aguirre, C Beitia, J Lundgren, S-I Moon, H Fontaine. Deposition of volatile chlorohydric acid on copper wafer depending on humidity and HCl airborne concentration, SPCC2018[3 ] H. Fontaine; G. Demenet; V. Enyedi; S. Cetre. Study of the airborne SO2 and NH3 contamination on Cr, MoSi and quartz surfaces of photomasks, Photomasks Technology 2010, Vol 7823, pp28
VEHICLE TEST FOR CONTAMINATION TRANSFER EVALUATION
Need of a proper vehicle test for ammonia cross contamination• Affinity to contaminant• Knowledge of a kinetic model
ACIDS (HF, HCl)
◦ Cu wafers
◦ AlCu wafers
BASES (NH3)
◦ Cu wafers
◦ AlCu wafers
◦ Si wafers
◦ Cr wafers
Co = 1.5E11 (ion/cm2)Cmax = 1.9E14 (ion/cm2)RH = 40%
Langmuir deposition model – Cr-NH3
𝑪 = 𝑪𝒎𝒂𝒙 − (𝑪𝒎𝒂𝒙−𝑪𝒐)𝒆−𝒌𝒂𝒅𝒔𝑪𝒈𝒕 [3]
• Cu wafers not suitable: NH4+
analysis not available• Surface AlCu is not very
sensitive to NH3.
• Si surfaces no sensitive to NH3
contamination
[F-] = [F-max]*(1 – exp(-k’t)) [1]
K=f(RH%, [HF]), F-max=f(RH%)
[Cl-] = (k*[CHCl])*[t] + [Cl0-] [2]
K= kinetic constant
| SPCC2018
0
20
40
60
80
100
120
140
24 74 124 174
[HX
] p
pb
v
Time (h)
11
CONTAMINATION TRANSFER FOUP TO WAFER
0.0E+00
3.0E+14
6.0E+14
9.0E+14
1.2E+15
0 5 10 15 20 25
X-
con
c. [
ion
s cm
-2]
Time [h]
International Roadmap for Devices and Systems (IRDS 2013) ●HF 1E14 ● HCl 1E13
PC
EBMCNT
HFHCl
HF vs HCl kinetic deposition on Cu wafer& equivalent average HX concentration
• HX transfer to Cu-coated wafers: HF > HCl• Large FOUP outgassing rates depend on HX reservoir and diffusion kinetics, and then FOUPs exhibits a strong
HCl outgassing but low transfer to copper wafers
SHCl < SHF
DEBMCNT < DPC
70 ppbv HF
0.5 ppbv HF
1.5 ppbv HCl
6.3 ppbv HClHCl PC
HCl EBMCNT
HF EBMCNT
HF PC
Outgassing phase in a empty FOUP
(static condition)
| SPCC201812
AMMONIA SORPTION/OUTGASSING OF FOUPs
NH3 kinetic deposition on Cr waferppb air Time to 90%
saturation
2 26.7h
10 5.4h
24 2.3h
73 42 min
270 12 min
0
1000
2000
3000
4000
5000
6000
7000
8000
0 20 40 60 80 100 120 140 160
con
tam
inan
t co
nc
(pp
bv)
Time (h)
NH4+ EBMCNT NH4+ PC low NH4+ EBMCNT low NH4+ PC
0
50
100
150
200
250
300
350
400
24 44 64 84 104 124 144
Time (h)
0
10
20
30
40
50
60
70
80
90
24 30 36 42 48
EBMCNT
EBMCNT
Immediately after purge!
PC
PC
• Strong outgassing afterpurge, followed of aconcentration equilibrium
• Given the poor NH3 polymeraffinity (comparing with HF,HCl)Solubility: NH3 < HCl < HF
• Contaminant concentrationlocated mainly in thesurface
DNH3: DPC > DEBMCNT
Initial contamination concentration 14.7 ppmv vs 1.47ppmv
Cmax = 1.9E14 (NH4+/cm2
| SPCC201813
CONTAMINATION TRANSFER FOUP TO WAFER
Csat Cr
NH3 deposition on Cr wafer after 40min Cr wafer exposure & [NH3] required to rich this transfer
• Consequence of the NH3 Immediate PC strong outgassing respect to the belated NH3 outgassingin EBMCNT the low transfer to Cr wafers (as in HCl case) is due to a low NH3 solubility
• This transfer is in agreement to the assumption DEBMCNT < DPC
0
10
20
30
40
50
60
70
80
90
24 30 36 42 48
[NH
3]
pp
bv
Time (h)After purge 24h after purge
8.3E+13
3.9E+134.8E+13
8.6E+13
0.0E+00
2.0E+13
4.0E+13
6.0E+13
8.0E+13
1.0E+14
1.2E+14
PC EBMCNT BLANK
Blank Blank
1.7E14 (NH4+/cm2)
5.2E13 (NH4+/cm2)
1.5E14 (NH4+/cm2)
9.6E13 (NH4+/cm2)
11ppbv
21.5ppbv 22.5ppbv
8.5ppbv
| SPCC201814
K. Hatakeyama et al. Chemical recycling of polycarbonate in dilute aqueous ammonia solution under hydrothermal conditions, J. Mater. Cyces Waste Manag. 16 (2014) 124–130
PC & NH3 REACTION
PC and EBMCNT compatibility with NH3 solution (TGA characterization)
PC degradation by NH3
| SPCC2018
SUMMARY
→ Contaminant FOUP affinity : NH3 < HCl < HF, FOUP contamination f (S,D) & PC > EBMCNT
→ Contaminant outgassing after purge: NH3 > HCl > HF , mainly f (solubility) & & PC > EBMCNT
→Contaminant acid transfer to wafer: HCl < HF, mainly f(diffusivity) & PC > EBMCNT
→Assuming same vehicle test the expected contaminant transfer to wafers will follow:
NH3 < HCl < HF & PC > EBMCNT
→ PC use is not suitable in NH3 environments due it’s reactivity
15
Among the tested FOUPs, EBM/CNT is the most efficient to limit NH3, HF & HCl contamination transfer to wafers → reduced wafer
defectiveness is expected
Entegris®, the Entegris Rings Design™, Pure Advantage™ and Clarilite® are trademarks of Entegris, Inc. ©2017 Entegris, Inc. All rights reserved.
16
| SPCC201817
RESULTS ANALYSIS
- [Cont]air increases and penetrates the polymer membrane
- [Cont]surf is defined by Solubility- Penetrant’s flow governed by diffusivity- FOUP’s contamination f (D, S)
- [Cont]air increases until [Cont]surf reach the equilibrium solubility
- Outgoing diffusion continues: [Cont]surf is progressively reduced [Cont]air is pulled down
- [Cont]air is mainly solubility-dependent
- Any contaminant molecule released will be retained by the wafer
- [Cont]air 0 (cont affinity to wafer) then [Cont]surf 0 as well
- Dair >> Dpolymer Cont transfer to Cu mainly governed by Dpolymer
M Cualfield, C.W Extrand, S.I Moon, Estimating Hydrochloric acid and Ammonium Hydroxide Loss, Controlled Environments Magazine, 2011T.Q Nguyen PhD Thesis (2012)P. Gonzalez-Aguirre, H. Fontaine, R. Pastorello, C. Beitia, J. Ohlsen, J. Lundgren HF transport coefficients in polymers used for microelectronic applications. Defect and Diffusion Forum (2016), 68-76
* Public soon
• NH3 D in PFA are greater than HCl• HCl D in PC is greater than HF • HCl S in PC is lower than HF
From literature:
We postulate:
• S in PC & EBMCNT follows NH3 < HCl < HF• D & S are lower in EBMCNT than PC*