1. © 2013 ANSYS, Inc. September 10, 20161
ANSYS CFD simulation the nitrogen
concentration in eFEM
徐子正 Tj Hsu

2. © 2013 ANSYS, Inc. September 10, 20162
The N2 is difficult to be measured, we
can use CFD to predict the result
• We concern human safety near the eFEM which is
very high concentration of N2.
• It’s difficult to measure the concentration of N2
inside the eFEM or FOUP.
• Using CFD simulation is the only way to get the N2
concentration profile in eFEM.

3. © 2013 ANSYS, Inc. September 10, 20163
Configuration: eFEM , FOUP and N2 blade
eFEM
FOUP
N2 blade
1. N2 blade is place
inside of eFEM, which
N2 is flow into FOUP
2. There are two N2 inlet
ports on the FOUP
bottom, and two outlet
ports too.

4. © 2013 ANSYS, Inc. September 10, 20164
For safety issue, the N2 concentration in
eFEM is necessary to know
• Too high nitrogen gas in air means too less oxygen gas,
which cause people suffer suffocation
N2 concentration
indicator
eFEM
FOUP
N2 blade

5. © 2013 ANSYS, Inc. September 10, 20165
The nitrogen flow into eFEM and FOUP
• Two ways for N2 flow into FOUP and FOUP
1. One is N2 blade
2. The other is bottom ports for input
N2 blade
100% N 2
bottom ports

6. © 2013 ANSYS, Inc. September 10, 20166
Geometry and Boundary conditions
• Two inlets
1. One is N2 blade
2. The other is bottom ports
for input
• Two outlets
1. One way is on bottom
ports of FOUP
2. The other is bottom
exhaust of eFEM
Purge port on
FOUP bottom
N 2 Blade with 100% N 2
(2) Inlet
100% N 2
(1) outlet
(2) Exhaust with -10 Pa
on bottom
(1) Air with laminar flow 80% N 2+20% O 2
eFEM
space

7. © 2013 ANSYS, Inc. September 10, 20167
Simulation Result

8. © 2013 ANSYS, Inc. September 10, 20168
Input conditions
2.
Purge
port on
FOUP
bottom
5. N 2 Blade
Inlet
100% N 2
3. outlet
4. Exhaust
with -10 Pa on
bottom
1. Air with laminar flow
80% N 2+20% O 2
eFEM
space
Description component Area, flow rate, exhaust
pressure
1 Air with
laminar flow
on eFEM top
80% N2
+20% O 2
Rectangle 600mm x
650mm with 1.4m/s
2 Purge port on
FOUP bottom
100% N2 Circle, diameter=25mm
with 5m/s
3 Snokel from
FOUP bottom
100% N 2 Rectangle 1mm x
270mm with 0 m/s
3 Exhaust on
FOUP bottom
purge port
100% N 2 Circle, diameter=25mm
with -5 Pa
4 Exhaust on
eFEM bottom
80% N2
+20% O 2
Rectangle 600mm x
650mm with -10 Pa
5 N2 blade (left)
in eFEM
100% N 2 Rectangle 1mm x
270mm with 0 m/s
6 N2 blade (right)
in eFEM
100% N 2 Rectangle 1mm x
270mm with 0 m/s

9. © 2013 ANSYS, Inc. September 10, 20169
Result the N2 concentration
Exceed 0.778
Higher than 0.778 is dangerous for human safety concern
(Unit convert: For N2 , the mass fraction 0.778 = Mole fraction 0.805)
Region of dangerous

10. © 2013 ANSYS, Inc. September 10, 201610
CFD simulation can delivery the gas
concentration during the N2 purge
• We can get the gas concentration by CFD simulation.
– Distribution by 3D space.
– Could by different input condition to optimization.
• The gas concentration is difficult using methodology tools
to measured.

11. © 2013 ANSYS, Inc. September 10, 201611
Detail description for FOUP
FOUP
wafer
eFEM
Purge port on
FOUP bottom
Inlet
100% N 2
Inlet
100% N 2outlet
outlet

12. © 2013 ANSYS, Inc. September 10, 201612
Simulation result for loading 3 wafers inside
FOUP with bottom purge
N2 mass fraction 0.77 ~ N2 mole fraction 0.8
N2 mass fraction 0.782 ~ N2 mole fraction 0.805

13. © 2013 ANSYS, Inc. September 10, 201613
The Simulation result for loading 3
wafers inside FOUP with bottom purge

14. © 2013 ANSYS, Inc. September 10, 201614
Two results by different flow rate for
moisture purge
• Low purge flow rate
• High purge flow rate

15. © 2013 ANSYS, Inc. September 10, 201615
Simulation under
low flow rate purge

16. © 2013 ANSYS, Inc. September 10, 201616
Humidity 40%
Humidity 3.9%
Humidity <0.1%
Humidity <0.01%

17. © 2013 ANSYS, Inc. September 10, 201617
Humidity distribution by 3D space

18. © 2013 ANSYS, Inc. September 10, 201618
Simulation under
high flow rate purge

19. © 2013 ANSYS, Inc. September 10, 201619
High flow rate of nitrogen purge
Humidity 40%
Humidity 3.9%
Humidity <0.1%

20. © 2013 ANSYS, Inc. September 10, 201620
Humidity distribution by 3D space
Humidity 40%
Humidity 3.9%
Humidity <0.1%