outgassing measurements @ asml
TRANSCRIPT
Introduction
• For the ASML NXE program, EUV lithography, outgassing rate is
an important parameter for the overall quality and costs.
• For this purpose, approximately 100 RGA qualification tools are in
place at 40 suppliers World Wide
• Total investment: ~ € 10,000,000
23 May 2017
Confidential
Slide 2
RGA Qualification Tools
Performance influenced by:
• Geometry and Dimensions
• Choice of components
• Quality/Health of Sensors
• Location/orientation sample
• Knowledge/Discipline of supplier
• Taking shortcuts
23 May 2017
Confidential
Slide 3
Qualification of RGA tools: Round Robin Method
• Round Robin Method
• Repeatability (within tool)
• Reproducibility (Compared to reference values)
• Current RR approach high impact on RGA tool availability
• POM and PE sheet material, no traceable reference value available
• 3 Measurements
• Impact 2-3 weeks per year per RGA tool
• Goal: Development International Outgassing Standard
• Primary Standard (PTB)
• Outgassing Source (Vapor) Dodecane
• Timing: 2017
• Successor for the current RR method
• Impact on RGA tool availability from 2 weeks 2 days
23 May 2017
Confidential
Slide 5
Practical Outgassing Standard: Set-up
• Every ASML related RGA tool is equipped with a
gas inlet port for calibration purposes, This port
is used to administer Dodecane.
• To generate a stable flow of Dodecane, the
following device was constructed:
• A small volume (~20 cc) filled with Dodecane
• The two valves to prevent contact between
Dodecane and the orifice during transport.
• This device, or Outgassing Source, will be
connected to the (automated) valve available on
the RGA tool.
23 May 2017
Confidential
Slide 7
3: Manual Valve
1: Manual Valve
2: Orifice
Dodecane
Liquid
Dodecane
Vapor
Outgassing standard: Characteristics
• For ASML related parts, the most commonly used RGA
qualification tool is the D&M NGQ system (40+ systems).
• With this NGQ system, first the characteristics of the Outgassing
Standard were determined
• Dynamic System Response
• Stabilization time: Dodecane concentration when valve is opened
• Recovery time: RGA tool when the supply is closed
• Mass discrimination
• How well traverse the fragments through the mass filter (ref: NIST)
23 May 2017
Confidential
Slide 8
Outgassing standard: Gage Repeatability Study
• When characterizing the system dynamics, the repeatability of the RGA tool was also studied.
• To reduce/prevent human factors, the admission of Dodecane to the RGA qualification tool is automated via an automated valve between the device and the RGA tool.
• Repeatability of the RGA tool depends on temperature effects:
• Electronic sensor drift
• Surface desorption rate
• Conductance variation
• Dodecane vapor pressure
• Contamination build-up (recovery)
• To reduce the effect of temperature fluctuations, the Repeatability study was carried out in a temperature controlled Clean Room
23 May 2017
Confidential
Slide 9
Outgassing standard: Characteristics & Gage Repeatability Study
23 May 2017
Confidential
Slide 10
Pump System
RGA
NGQ
RGA Qualification Tool
Automated
valve
QDodecane = PDodecane * Seff
Outgassing Standard: Test Sequence23 May 2017
Confidential
Slide 11
Dodecane Round Robin: Gage Repeatability Study
Pre
par
atio
nR
epea
tab
ility
Seq
uen
ceA
fter
-Car
e
Phase
Start Gage Repeatability
RGA Validation Generate BG scanBake RGA System Vent RGA SystemConnect RR
DevicePump Down RGA
SystemOpen Manual valves 1 & 2
Start RR Sequence
> 50 CyclesRR: Measure 60
minutesClose Automated
ValveBG: Measure 30
minutes
Close Manual Valves 1 & 2
Vent RGA SystemDisconnect RR
DeviceBake RGA System Generate BG scan
End Gage Repeatability
Open Automated Valve
Characteristics outgassing standard: Dynamics (1)
Observations:
1: Water level is still decreasing after 100 cycles during 70+ hours
2: Hydrocarbon levels are stable after 10 hours
3: At first sight, first five to ten cycles with RR are not stable
4: Sometimes the signal is significantly higher, cause unknown, possible timing issues
23 May 2017
Confidential
Slide 12
Characteristics outgassing standard: Dynamics (2)
Observations:
Every Cycle with Dodecane starts with a higher signal for both CxHy-v and CxHy-nv
• Cause: Flow stabilization and vapor pressure build up in the supply line while the automated valve is closed
• Data points 3, 4 and 5 used for repeatability calculations
23 May 2017
Confidential
Slide 13
1
23 4 5 6
Characteristics outgassing standard: Dynamics (3)
Observations:
For all major Dodecane peaks over
the full mass scale, background levels
drops below 1%
BG subtraction is therefore not
needed
23 May 2017
Confidential
Slide 14
Characteristics outgassing standard:
Mass Discrimination: Background
• Background information:
• Every RGA with a quadrupole mass filter will face mass discrimination.
• Mass discrimination leads to lower sensitivity for higher masses passing through the mass filter.
• Main driver for this effect is the lower conductance for the heavier ions, generated from the different species in the
vacuum being analyzed.
• To investigate this effect for the Dodecane in this test, the measured values were compared with the Dodecane
reference scan from NIST.
• Approach:
• Every major peak of the fragmentation pattern was normalized against the main peak, m/z = 57.
• Peaks with an m/z lower than 57 were omitted, only higher masses were of interest.
• These normalized values were compared with the NIST values.
• Investigate the relation between the mass of the ion and the deviation with the NIST spectrum
• All 50 cycles, with data points 3, 4 and 5 were taken into account.
23 May 2017
Confidential
Slide 15
Characteristics outgassing standard:
Mass Discrimination: ResultsFrom the graph it is clear that there is a linear correlation between m/z and the deviation between the ASML outgassing standard and NIST.
This correlation is then used to correct the measured intensities
The results are shown in the last column of the table
The effect of mass discrimination can be minimized using this correlation
23 May 2017
Confidential
Slide 16
m/z NIST ASML Factor ASML-corr
57 100% 100% 1.00 100%
71 54% 50% 0.94 56%
85 33% 25% 0.76 31%
99 5.9% 4.3% 0.73 6.0%
113 4.0% 2.4% 0.60 3.8%
170 5.3% 1.4% 0.27 5.6%
Round Robin Repeatability Study: First results (1)
Observations:
First two Data Points are not usable due to too large fluctuations
• The average for every Data Point is calculated
• Every Data Point is compared to this average value
23 May 2017
Confidential
Slide 17
Round Robin Repeatability Study: First results (2)
Repeatability calculations:
For the last 45 RR-cycles (cycle 6 to 50)
• The average of sample points 3, 4 and 5 is taken
• This is done for each of the top-10 masses for Dodecane
• For the 45 cycles, the average is calculated for every mass
• The variation of all masses is plotted against the average value
• There is a strong relation with the temperature
• 1 degree C ~ 10% outgassing deviation
• Probable cause: Temperature stimulated Vapor pressure in Outgassing Device
• Dodecane ΔHvap = 61,800 J/Mol
• T1=301K (28C), T2=302K (29C)
• Pvap = 18.00 19.53 Pa
• Increase of 8.5%
• Courtesy of NIST data
• Extra effect: temperature stimulated desorption of Dodecane from walls
23 May 2017
Confidential
Slide 18
Round Robin Repeatability Study: First results (3)
Strong correlation between Temperature and the outgassing of Hydrocarbons.
Correlation improves over time, the correlation during the last 25 Hrs is very strong.
Water has also a correlation between Temperature and Outgassing, but the correlation changes during the Repeatability Study
Question, can the outgassing be corrected for the temperature?
23 May 2017
Confidential
Slide 19
110%
95%
80%
110%
95%
80%
29.529.028.528.027.5
300%
200%
100%
CxH
y-v
CxH
y-n
v
Temp
H2O
Complete Data Set
110%
95%
80%
110%
95%
80%
29.529.028.528.027.5
300%
200%
100%
CxH
y-v
CxH
y-n
v
Temp
H2O
First 25 Hrs
110%
95%
80%
110%
95%
80%
29.529.028.528.027.5
100%
75%
50%
CxH
y-v
CxH
y-n
v
Temp
H2O
Between 25 and 50 Hrs
110%
95%
80%
110%
95%
80%
29.529.028.528.027.5
100%
75%
50%
CxH
y-v
CxH
y-n
v
Temp
H2O
Last 25 Hrs
Round Robin Repeatability Study:
Preliminary Conclusion
• The first tests shows:
• Due to pressure build up, 20-30 minutes is needed to stabilize the vapor flow
• RGA Tool needs stabilization time, reaching desorption/resorption equilibrium, saturation time
• Repeatability better than +/- 10%
• 8.5 % explained by the Temperature vs. Vapor pressure relation (Clausius-Clapeyron equation)
• Temperature corrected outgassing rates possible.
• Next steps
• Same experiment on other RGA tools to investigate reproducibility
23 May 2017
Confidential
Slide 20