PFC Gas Management

200 mm semiconductor facility
• 3 types of cylinder operations:

– Auto-crossover

– Manual crossover

– Manual single cylinder change

• Real time, 24/7 monitoring of every cylinder

• Pre-determined cylinder changeout triggers by weight or by 

pressure, depending on gas type

• Auto-paging of on-site technicians for alarms:

– Low alarm notification – ensure next cylinder is on-site for changeout

when needed

– Low-low alarm – prepare to monitor auto-crossover, conduct manual 

crossover, or ensure tool is secure for single cylinder change at trigger 

point (coordination with fab)

• Cylinder changeouts happen as close to trigger point as possible

– Too soon = waste of expensive gas

– Too late = jeopardy of process interruption due to extreme sensitivity of 

gas delivery integrity

General Gas Cylinder Monitoring
Cylinder Changeout Triggers

* Change trigger is either PSIG or lb

N2O 60 12 20%

SF6 50 12 24%

NF3 CVD 1450 40 3%

NF3 etch (c) 1450 60 4%

NF3 etch (m) 1450 85 6%

CF4 1800 180 10%

CHF3 70 17.6 25%

C4F8 88 5 6%

C4F8 16 1 6%

C4F6 11 1 9%

C2F6 95 7 7%

Heel 

Factor

Change 

Gas PSIG lb Trigger

m = manual configuration

c = crossover configuration
C4F8 88 lb 5 lb Manual 4 99.5 7.4

NF3 1450 psig 85 psig Manual 46 91.9 22.1

NF3 1450 psig 60 psig Auto 76 100.0 1.2

NF3 1450 psig 40 psig Auto 72 100.5 4.2

NF3 1450 psig 40 psig Auto 68 100.0 9.1

NF3 1450 psig 40 psig Manual 68 103.0 18.1

C2F6 95 lb 7 lb Manual 19 110.8 10.4

C2F6 95 lb 7 lb Manual 11 111.6 12.1

C2F6 95 lb 7 lb Manual 9 110.5 12.9

C2F6 95 lb 7 lb Manual 8 113.4 8.6

CF4 1800 psig 180 psig Manual 30 102.1 15.7

CF4 1800 psig 180 psig Manual 35 101.6 6.3

CF4 1800 psig 180 psig Manual 31 98.8 10.7

CF4 1800 psig 180 psig Manual 41 105.0 10.6

Accuracy % St. Dev %

Change

outs

Equipment

Type

Changeout

Gas Type Full cylinder Trigger

Preliminary Analysis of Cylinder Changes

Accuracy & St. Dev. analysis around actual cylinder change point vs. target point
Example Cylinder Changeout History

C/O Date C/O PSI

9/28/2009 40

9/16/2009 40

9/5/2009 40

8/28/2009 40

8/17/2009 40

8/6/2009 40

7/28/2009 40

7/19/2009 80

7/7/2009 40

6/27/2009 40

6/16/2009 40

6/7/2009 40

5/29/2009 40

5/20/2009 40

5/10/2009 40

4/29/2009 40

4/18/2009 40

4/8/2009 40

3/30/2009 40

3/21/2009 40

3/9/2009 40

3/1/2009 40

2/20/2009 40

2/12/2009 40

2/5/2009 39

1/28/2008 40

1/20/2008 39

1/12/2008 40

1/4/2008 40

NF3

C/O Date C/O PSI

9/19/2009 8.5

9/4/2009 8.1

8/19/2009 9.5

7/29/2009 6.4

7/7/2009 6.9

6/8/2009 8.8

5/5/2009 6.6

3/17/2009 7.2

2/16/2009 7.4

1/3/2009 8

11/24/2008 9.4

10/24/2008 8.1

9/21/2008 7.8

8/29/2008 8.6

8/7/2008 6.8

6/29/2008 8

5/27/2008 8.1

4/22/2008 7.6

3/29/2008 11.4

3/5/2009 8.1

2/6/2008 8.2

1/4/2008 9.7

C2F6

C/O Date C/O PSI

9/29/2009 108

8/29/2009 189

8/12/2009 160

7/30/2009 193

7/5/2009 188

6/10/2009 183

5/18/2009 184

4/24/2009 180

4/4/2009 180

3/12/2009 187

2/8/2009 180

1/26/2009 187

1/11/2009 185

12/25/2008 307

12/8/2008 189

11/24/2008 180

11/11/2008 191

10/26/2008 194

10/11/2008 180

9/24/2008 190

9/11/2008 178

8/31/2008 169

8/17/2008 187

8/3/2008 182

7/22/2008 165

7/10/2008 180

6/28/2008 180

6/17/2008 185

6/7/2008 150

5/25/2008 202

CF4

Target = 180 psi

Target = 8 lb

Target = 40 psi
Control Room Monitoring

Real-time monitoring of every gas cylinder

Technician can select room, cabinet, or individual cylinder details
C2F6 Cylinder Monitoring

(by weight)

Cylinder 

weight at

Installation

95 lbs

Cylinder

changeout

or crossover

trigger at

7 lbs

Cylinder idle

Until crossover
NF3 Cylinder Monitoring

(by pressure)

Cylinder 

installed at

1450 psig

Cylinder

ready for

crossover

(idle)

Cylinder

changeout

trigger at

60 psig
NF3 Cylinder Monitoring

Pressure is monitored

at cylinder and point

of delivery to tool

Technician can see all information at the cabinet or remotely in the control room
NF3 Cabinets

Primarily auto-crossover due to high usage

Stored in exhausted cabinets due to hazardous properties
NF3 in Auto-Crossover Cabinet

Cabinet display shows same data as Control Room display
Panel Inside NF3 Auto-Crossover Cabinet
CHF3 Cylinders – Monitored by Scale, Single & Crossover
CHF3 Manual Crossover Panel

Switch over valves – valve switching occurs w/in seconds 

Open

Closed
CF4 Cylinders Monitored by Pressure
CF4 Crossover Panel
N2O Cylinders monitored

by scales
N2O Crossover Panel
C4F8 Modification

Originally had multiple small cylinders

that, with low usage, could have product go

beyond expiration date.

Converted to manifolded crossover

configuration of larger cylinders

feeding several etch tools