In-Line Detection and Measurement of Molecular ...
Transcript of In-Line Detection and Measurement of Molecular ...
Characterization and Metrology for ULSI Technology Conference 2005 1
In-Line Detection and Measurement of Molecular Contamination in
Semiconductor Processing Solutions
Jason Wang, Michael West, Ye Han, Bob McDonald, Wenjing Yang,
Bob Ormond and Harmesh Saini
Metara Inc.Sunnyvale, CA, USA
Characterization and Metrology for ULSI Technology Conference 2005 2
OutlineIntroduction
Why the analysis of molecular contamination is important?
DiscussionUse of the Metara Trace Contamination Analyzer (TCA) for molecular contamination measurementProblem solving examples
1. A nitrogen-containing compound in H2O22. Organic additives in SC-13. Urea in UPW4. Molecular contamination in UPW5. Plasticizers in IPA6. Sulfur-containing compounds in IPA
Conclusion
Characterization and Metrology for ULSI Technology Conference 2005 3
Molecular Contamination Sources
Process equipmentImpurities in incoming process chemicalsTransfer from earlier process stepsAirborne molecular contaminationDeliberate addition of organics to process chemicals
Surfactants and chelating agents“Proprietary” additives
Characterization and Metrology for ULSI Technology Conference 2005 4
Gate Oxide Degradation Due To Organic Contamination
* HMDS Monolayer on Oxide
* HMDS =
Hexa-methyl-di-silazane
Cumulative Failure (%)
QBD = Charge-to-Breakdown
measurement
“Cost Effective Cleaning and High-quality Thin Gate Oxides”,IBM J. Res. Develop. Vol. 43, No. 3, May 1999, M. Heyns and et. al.
Characterization and Metrology for ULSI Technology Conference 2005 5
International Technology Roadmap for Semiconductor (ITRS)
Surface CarbonITRS 2004 Updated, Table 114a Technology Requirements for wafer environmental contamination control
(2003 Edition)
30% H2O2 total oxidizable carbon (ppb) - TBD TBD TBD TBD TBD TBD
IPA: High molecular weight organics (ppb) - TBD TBD TBD TBD TBD TBD
30% H2O2: Resin byproducts (ppb) - TBD TBD TBD TBD TBD TBD
ADD
ADD
Characterization and Metrology for ULSI Technology Conference 2005 6
TCA (Trace Contamination Analyzer) for Metallic, Organic and Molecular Contaminants
Electrospray Ionization Interface
Mass-Analyzer
Ion-Trap & TOF (Time of Flight)
Sample Sample Preparation Preparation ModuleModule
Mass-Spectrometer
Sample Sample Extraction UnitExtraction Unit
Trace Contaminant Analysis (TCA) Platform
..
..
..
.. ... .
.. .
• Cations
• Anions
• Metallics
• Organics
• 24/7
Bath
Characterization and Metrology for ULSI Technology Conference 2005 7
Example 1: H2O2 Excursion at a Production Fab
Contaminated H2O2 suspected to cause yield crash at a fab
Analyses of traditional lab methods show inconclusive results between the “Good” & the “Bad” H2O2 samples
ICP-MS (Inductively Coupled Plasma Mass Spectrometry), IC (Ion Chromatography), TOC (Total Oxidizable Carbon) Assay
Results of TCA showed Intensity of peak at m/z 118 was ~ 20x higher in “bad” sample than in “good” sample
Characterization and Metrology for ULSI Technology Conference 2005 8
Contaminant found from H2O2 Sample by TCA
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MassGEN( 00:03:06 : 00:05:19 )
Am
plitu
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m/z
Curve 1
“Good” Sample
Intensity of 118 peak was found to be ~ 20x higher in “Bad” sample
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MassGEN( 00:05:19 : 00:07:33 )
Am
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m/z
Curve 1
“Bad” Sample118.087
Characterization and Metrology for ULSI Technology Conference 2005 9
Identification of Contaminant in “Bad” H2O2 Sample
Possible compound: Tri-methyl-glycine
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MassGEN( 00:01:04 : 00:02:32 )
Am
plitu
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m/z
Curve 1
Suspected TMA (CH3)3NH+
m/z 60.082 m/z 118.087
m/z = 118.087
H+
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MassGEN( 00:01:20 : 00:02:32 )
Am
plitu
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m/z
Curve 1
Fragment
m/z 59.074
Higher Collision Voltage
m/z = 59.074
Characterization and Metrology for ULSI Technology Conference 2005 10
Contaminant from Ion Exchange Resin
Structure of Ion Exchange Resin
Tri-methyl-glycine-CH-CH2-CH-
CH2
H3C-N
CH-CH2-CH-
CH3 CH3
A-+
CH2
H3C-N
CH3 CH3
CH3COO -+
Characterization and Metrology for ULSI Technology Conference 2005 11
0
0.1
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0:00 2:24 4:48 7:12 9:36 12:00 14:24 16:48 19:12 21:36
Time
Peak
Are
a of 1
18 vs
inte
rnal
std
0
1
2
3
4
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6
7
Peak
Are
a of 1
92 vs
inte
rnal
std
Ratio of 118/internal stdRatio of 192/internal std
Bath Change Bath ChangeBath Change
TCA In-Line Monitoring Molecular Contamination in SC-1 (NH4OH:H2O2:H2O) Bath at a Fab
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High Organic Content in High Purity H2O2
5000 ppb max
High Organic Content
Total Organic Carbon (TOC)
Problems
10 ppt max
Low Metallic Content
Characterization and Metrology for ULSI Technology Conference 2005 13
Example 2: Deliberate Addition of Surfactant or Chelating Agents in Baths
Industrial Trend for Using Diluted Chemistry SC-1 NH4OH:H2O2:UPW from x:1:5 (x = 0.05-3), up to 1:1:500SC2 HCl:H2O2:UPW up to 1:1:1000
Addition of Surfactant or Chelating Agents in Baths
Improve Particle & Metal Removal EfficiencyImprove Surface Wetability for Uniform Wafer Surface Preparation
Characterization and Metrology for ULSI Technology Conference 2005 14
Chelating Agent found from a SC-1 (NH4OH:H2O2:H2O) by TCA
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MassGEN( 00:00:48 : 00:02:00 )
Am
plit
ud
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m/z
Curve 1
SC-1 Bath
14
14
16
1416
1414
14
19
C3H7COO-
87.044
Fragment CH2
Fragment O
4644
44
CH2CH2O = 44CH2 = 14O = 16F = 19?
Possible Formulation:
A Mixture of Compounds with Functioning Groups R-COO-
and -(CH2CH2)n-O
Chelating agents/surfactants Need to be completely rinsed off from wafer surface
Characterization and Metrology for ULSI Technology Conference 2005 15
Example 3: TOC (Total Oxidizable Carbon) Excursions at a Fab
Seasonal TOC excursions at a fabUrea (fertilizer) in UPW (Ultrapure Water) was suspected“No way to confirm suspicions” because “no laboratory methods available to accurately measure low ppb concentrations of urea contamination in water”*
*Ref. “Undetectable TOC in UPW can influence DUV photolithography processes”, J. Rydzewski& R. Godec, proceedings of SPWCC 2002 (Semiconductor Processing with Wet Chemicals Conference)
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TCA Quantitative Analysis of Urea in UPW
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MassGEN( 00:04:24 : 00:05:36 )
Am
plitu
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m/z
Curve 1
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MassGEN( 00:00:40 : 00:01:52 )
Am
plitu
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m/z
Curve 1
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MassGEN( 00:01:20 : 00:02:32 )
Am
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m/z
Curve 1
(NH2)2COH+
m/z = 61.041
(NH2)2COH+
(NH2)2COH+
0 ppb Urea
5 ppb Urea
10 ppb Urea
y = 1211x + 492R2 = 0.9927
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0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5ppb Urea as C12
Pea
kH
eigh
t
DL = 3σ/m = 0.084 ppb C = 84 ppt C, n = 6
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TCA Analysis of Urea by Ratio Technique
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55.0 57.5 60.0 62.5 65.0 67.5 70.0 72.5 75.0 77.5 80.0
MassGEN( 00.40275 - 01.60391 )
Am
plitude
m/z
Curve 1
0 ppb 12C Urea + 10 ppb 13C Urea
13C Urea
12C Urea
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55.0 57.5 60.0 62.5 65.0 67.5 70.0 72.5 75.0 77.5 80.0
MassGEN( 00.80258 - 02.00375 )
Am
plitude
m/z
Curve 1
13C Urea12C Urea
5 ppb 12C Urea + 10 ppb 13C Urea
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55.0 57.5 60.0 62.5 65.0 67.5 70.0 72.5 75.0 77.5 80.0
MassGEN( 00.80308 - 02.00425 )
Am
plitude
m/z
Curve 1
13C Urea12C Urea
10 ppb 12C Urea + 10 ppb 13C Urea
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Ratio Measurement of 12C Urea/13C Urea
m/z = 61 (C12)
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0 5 10 20Urea C12 (ppb)
Peak
Inte
nsity
m/z = 62 (C13)
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10 10 10 10Urea C13 (ppb)
Peak
Inte
nsity
m/z = 61 (C12)
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0 5 10 20Urea C12 (ppb)
Peak
Inte
nsity
m/z = 62 (C13)
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10 10 10 10Urea C13 (ppb)
Peak
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nsity
Ratio of 61/62
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0ppbC12/10ppbC13 5ppbC12/10ppbC13 10ppbC12/10ppbC13 20ppbC12/10ppbC13
Rat
io
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TCA Analytical Results of Urea
( Asp – Ratio ×Bsp )( Ratio ×Bs – As )
( )Cs = CspVsp
Vs
TCA Automatic Quantification
Calculated Results (10ppb C13 Urea Spike)
0.0
5.0
10.0
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20.0
25.0
0ppbC12/10ppbC13 5ppbC12/10ppbC13 10ppbC12/10ppbC13 20ppbC12/10ppbC13
Cal
cula
ted
Res
ults
(ppb
)
Well Quantified at ppb level
Calculated Results (10ppb C13 Urea Spike)
0.0
5.0
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15.0
20.0
25.0
0ppbC12/10ppbC13 5ppbC12/10ppbC13 10ppbC12/10ppbC13 20ppbC12/10ppbC13
Cal
cula
ted
Res
ults
(ppb
)
Accurately Quantified at ppb level
Characterization and Metrology for ULSI Technology Conference 2005 20
Example 4: Molecular Contamination in Pre-Gate Cleaning Processes at a Fab
Yield problems at a FabGate oxide breakdown voltage reduction
Results of TXRF and VPD-ICP/MSNo metallic contamination
Organic or molecular contamination was proposedNo significant suspect by routine lab methods
Characterization and Metrology for ULSI Technology Conference 2005 21
Contaminants Found from HQDR (Hot Quick Dump Rinse) UPW by TCA
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MassGEN( 00:00:32 : 00:01:44 )
Am
plitude
m/z
Curve 1
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MassGEN( 00:00:32 : 00:01:52 )
Am
plitude
m/z
Curve 1
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MassGEN( 00:01:04 : 00:02:16 )
Am
plitude
m/z
Curve 1
HQDR UPW_2
HQDR UPW_3
HQDR UPW_4NMP-H+
100.076
Scale Different
(H3PO4)H+
98.987
Urea (NH2)2COH+
m/z = 61.040
Characterization and Metrology for ULSI Technology Conference 2005 22
Possible Contamination Sources in Fab
NMP = N-Methyl-2-pyrrolidone (C5H9NO m/z = 99.068)
• Photoresist stripper• Wafer cleaning• Semi-aqueous defluxing• Degreasing• Coatings (polyamide, epoxy, & polyurethane)
H3PO4 Incomplete rinse from nitride etching?
Urea Source water, re-cycling or reclaimed water?
Characterization and Metrology for ULSI Technology Conference 2005 23
TCA In-Line Monitoring Phosphorus Species in SC-1 Bath at a Production Fab
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Time
Rat
io
Bath Change Bath Change Bath ChangeBath Change
Proposed as H3PO4NH4+ m/z=106.011
Characterization and Metrology for ULSI Technology Conference 2005 24
Example 5: Phthalate (Plasticizer) Contamination in IPA (Isopropyl Alcohol)
It has been reported:
Dibutyl phthalate (DBP) in high density polyethylene (HDPE) containers leaching into IPAPlasticizers deposit inside the gas nozzles and chamber in a dryer
Phthalates have deleterious effects on wafers
Characterization and Metrology for ULSI Technology Conference 2005 25
TCA Analysis of Dioctyl Phthalate (DOP) and Dibutyl Phthalate (DBP) in IPA
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MassGEN( 00:00:40 : 00:01:52 )
Am
plitude
m/z
Curve 1
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MassGEN( 00:00:32 : 00:01:44 )
Am
plitude
m/z
Curve 1
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MassGEN( 00:00:32 : 00:01:44 )
Am
plitude
m/z
Curve 1
DOP H+
m/z=391.285DBP H+
m/z=279.160
Blank
5 ppb
10 ppb
DOP H+
m/z=391.285
DOP H+
m/z=391.285
DBP H+
m/z=279.160
DBP H+
m/z=279.160
Characterization and Metrology for ULSI Technology Conference 2005 26
Example 6: Molecular Contamination in IPA (Isopropyl Alcohol) at a Fab
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MassGEN( 00.80250 - 02.00366 )
Am
plitude
m/z
Curve 1
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MassGEN( 00.67033 - 01.87158 )
Am
plitude
m/z
Curve 1
IPA lot 1, 2, 3
(CH3)2CHOSO3-
m/z = 139.007
• IPA from lot 1,2 3 suspected causing multiple excursions
• No significant difference between lot 1,2,3 and lot 4,5,6 by routine lab methods
(CH3)2CHOSO2-
m/z = 123.012
HSO4-
m/z = 96.960
IPA lot 4, 5, 6
Characterization and Metrology for ULSI Technology Conference 2005 27
Contamination Sources from IPA Manufacturing Processes
di-isopropyl sulfate
(CH3)2CH CH(CH3)2O-S-O=O
=O
isopropyl sulfate
+ (CH3)2CH
m/z = 139.007
_O-S-O=O
=O
propene gas
CH3CH=CH2 + H2SO4
hydrolysed w/ H2O
(CH3)2CHOH
IPAFinal Product =
Isopropyl sulfate is a highly suspect in IPA lot 1, 2, 3
Characterization and Metrology for ULSI Technology Conference 2005 28
Summary
Using the TCA we have demonstrated the ability to:
Analyze molecular contamination in a variety of process solutions including UPW, SC-1 and IPAIdentify specific molecular contaminantsProvide quantitative concentration measurementMake measurements in-line and in near real-timeProvide process chemistry trends that correlate to Wafer Fab yield problems
Characterization and Metrology for ULSI Technology Conference 2005 29
Conclusion
We believe this new measurement capability will:
Enable statistically valid real-time process chemistry control decisions Provide advanced warning of excursionsEnable chemical specifications and bath life decisions based on process data and yield correlation