Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) 

Destruction or Removal Efficiency (DRE) Measurement Method 

for Electronics Manufacturing: A Cooperative Evaluation with 

NEC Electronics, Inc. 

December 2008 

 

Office of Air and Radiation 

Office of Atmospheric Programs, Climate Change Division 

EPA 430-R-10-005 
Acknowledgements 

The analytical measurements, data interpretation, and report preparations were funded by the 

U.S. Environmental Protection Agency (EPA) under contract GS-10F-0124J to ICF International 

and Air Products and Chemicals, Inc. EPA and the authors wish to express their appreciation 

and thanks to NEC Electronics Inc., for their gracious support to this study by not only providing 

their facilities but also their valuable assistance and advice. EPA looks forward to continued 

collaborations with NEC Electronics Inc. and other electronics industry Partners in its 

cooperative efforts to reduce greenhouse gas emissions and advance global climate protection. 

 2 
Table of Contents 

Page 

Acknowledgements......................................................................................................3 

1.0 Introduction....................................................................................................6 

2.0 Experimental Setup...........................................................................................6 

3.0 Data Analysis...................................................................................................9 

 3.1 Determination of Scrubber Dilution...............................................................9

 3.2 Scrubber DRE Determinations....................................................................17 

 3.2.1 TecHarmonic E-HTVS DRE............................................................17 

 3.2.2 Edwards TPU DRE........................................................................21 

4.0 Conclusion ................................................................................................................................ ...23 

 3 
List of Tables 

 Page 

Table I Total equivalent flow measurements from E-HTVS determined using Xe and Kr ...... ......11 

Table II Total flow measurements from TPU determined using Xe and Kr ................................. ...12

Table III Ar concentration determined in TPU effluent during Ar flow testing.......................... .......12

Table IV Summary of the average total flow determinations for E-HTVS and TPU at NEC 

Electronics Inc. ............................................................................................................. .......13

Table V Total process flow determination for CVD Tool #1 using C2F6 tool flows.................. .......15 

Table VI Total process flow determination for CVD Tool #2 using NF3 tool flows................... .......16 

Table VII C2F6 DRE in E-HTVS during process flow calibrations .............................................. .......18 

Table VIII Integrated F-GHG process and scrubber emissions for CVD Tool #1 (process) and E-HTVS 

during chamber cleans ................................................................................21 

 4 
List of Figures 

 Page 

Figure 1 Actual sampling schematic used for E-HTVS and TPU at NEC Electronics Inc ...................7

Figure 2 QMS response to Kr (top) and Xe during QMS calibration and E-HTVS spiking of Kr and 

Xe......................... .................................................................................................... ......8

Figure 3 Regression analysis of data obtained during calibration of QMS response to 86Kr and 132Xe in 

N2............................................................................................................8

Figure 4 Calibration of FTIR response to C2F6..................................................................9

Figure 5 Xe (top) and Kr (bottom) emissions from E-HTVS during spike calibration....................12

Figure 6 Kr (top) and Xe (bottom) emissions from TPU during chemical spiking of scrubbers.........14

Figure 7 Ar emission from TPU while Ar was being flowed through the process chamber on CVD 

Tool #2......................................................................................................14

Figure 8 C2F6 emission profile for CVD Tool #1 during process flow calibration. C2F6 emissions from 

a 5 minute chamber clean are also shown ............................................................16

Figure 9 NF3 emission profile from CVD Tool #2 during NF3 process flow calibration...................17 

Figure 10 Inlet and outlet C2F6 emission profiles for E-HTVS during process flow calibration..........18 

Figure 11 FTIR spectrum of process emissions during C2F6/O2 chamber clean on CVD Tool #1.........19

Figure 12 C2F6 and CF4 emissions from CVD Tool #1 (top) and E-HTVS scrubber during chamber 

cleans......................................................................................................20

Figure 13 FTIR spectra of TPU exhaust (top) and CVD Tool #2 process exhaust (bottom) while 1.5 slm 

NF3 was flowing through the chamber .................................................................22

Figure 14 Relative CH4 and CO emissions from TPU during reduced temperature operation ............24

Figure 15 Nitric oxide emission profile during NF3 flows from CVD Tool #2 chamber through the 

TPU........................................................................................................25

 5 
1.0 Introduction 

The purpose of this study was to accurately determine the Destruction or Removal Efficiency 

(DRE) of two different commercially available Point Of Use (POU) abatement systems or 

scrubbers for process emissions fluorinated greenhouse gases (F-GHGs) such as 

perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), sulfur hexafluoride (SF6), and nitrogen 

trifluoride (NF3). A key component in accurately determining DRE was to determine the dilution 

of process exhaust occurring in each scrubber. This study used an experimental approach to 

measure the dilution across the scrubber by injecting a chemical tracer that could not react in the 

scrubber, or be produced as a by-product during scrubber operation. In this study Krypton, 

Argon and Xeon were used as chemical spiking agents, as they met the requirements for this 

application. 

Testing was conducted in a fully functional semiconductor manufacturing facility, owned and 

operated by NEC Electronics Inc. in Roseville, CA. Two different process tools, referred to as 

CVD Tool #1 and CVD Tool #2, each equipped with a POU scrubber, were tested. CVD Tool 

#1 equipped with a TecHarmonic E-HTVS POU scrubber was tested, and CVD Tool #2 

equipped with an Edwards TPU POU abatement device was also tested. 

2.0 Experimental Setup 

To carry out the objectives of this study it was necessary to monitor both process and scrubber 

emissions simultaneously, and determine scrubber dilution using chemical spiking. Process and 

scrubber emissions data were collected in parallel using Fourier Transform Infrared 

Spectroscopy (FTIR). Data used to determine scrubber dilution were collected using Quadrupole 

Mass Spectrometry (QMS). A schematic showing the experimental testing set up is shown in 

Figure 1. 

Two FTIRs were used to determine process and scrubber emissions. Both systems were MKS 

2010 Multi Gas Analyzers equipped with liquid nitrogen cooled mercury cadmium telluride 

(MCT) detectors. One FTIR was equipped with a 10 cm path length single pass gas cell, and 

was used to sample process effluent. The other FTIR was equipped with a 5.6 m path length 

multi pass gas cell, and was used to sample scrubber effluent. Both FTIR were operated at 

0.5cm-1 resolution. Four scans were co-added for each data point yielding a sampling frequency 

of 2.2 sec. 

A Balzers QMS system was used to sample scrubber effluent during dilution determination. The 

QMS was operated in Selective Ion Monitoring (SIM) mode and a secondary electron multiplier 

was used to enhance sensitivity. A 1 sec sampling frequency was used for each data point. To 

account for potential changes in QMS sensitivity, ion signals were normalized to the signal 

obtained for the nitrogen fragment (N+), which is formed during electron impact ionization of 

N2. 

Sampling of effluent streams was done using metal bellows sampling pumps that were located 

after the instruments. The sample flow rate was controlled using adjustable flow rate valves. 

The sample line pressure for both FTIRs and the QMS were monitored using capacitance 

 6 
manometers. A filter was installed in the sample line used for monitoring scrubber emissions to 

ensure that particulate emissions from the scrubber would not coat the FTIR internal optics, or 

the pressure reducing orifice used for the QMS. Since the scrubber DRE determination and the 

scrubber dilution determination were independent events, it was possible to use the same sample 

line for both operations. This was accomplished by switching the instrument inlet sample fitting 

from the FTIR to the QMS. 

The QMS was calibrated to determine its response to Xe, Ar and Kr on site using a dynamic 

dilution blending system. Test atmospheres containing H2, He, Kr, Ar and Xe were created by 

blending a calibration standard containing 1% of each species in N2 with N2 diluent. The QMS 

responses to 84Kr and 132Xe during calibration are shown in Figure 2. From regression analyses 

of these data a calibration curve was generated and is shown in Figure 3. These data were used 

to quantify Kr and Xe emissions from the scrubber. 

Figure 1: Actual sampling schematic used for E-HTVS and TPU at NEC Electronics Inc. 

Schematic shows the calibration and sampling capability for each instrument. 

 7 
Kr Emissions from E-HTVS during Flow Calibration

-20

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200 1400 1600 1800

QMS Scan

Concentration (ppmv)

Calibration

Spike Flows

Xe Emissions from E-HTVS during Flow Calibrattions

-20

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200 1400 1600 1800

QMS Scan

Concentration (ppmv)

Calibration

Spike Flow

Figure 2: QMS response to Kr (top) and Xe during QMS calibration and E-HTVS spiking 

of Kr and Xe. (Note: Kr and Xe emissions in the figure titles denote the flow of tracer 

materials and have nothing to do with process emissions.) 

QMS Responser to Kr and Xe 

0.00E+00

1.00E-04

2.00E-04

3.00E-04

4.00E-04

5.00E-04

6.00E-04

7.00E-04

8.00E-04

9.00E-04

1.00E-03

0.0 20.0 40.0 60.0 80.0 100.0 120.0

Concentration of Added Kr & Xe (ppmv)

Relative Ion Intensity

amu 84/14

Predicted

amu 132/14

Predicted

Kr

Xe

Figure 3: Regression analysis of data obtained during calibration of QMS response to 86Kr 

and 132Xe in N2. These data were used to determine Kr and Xe concentration during 

chemical spiking of scrubbers. 

 8 
The FTIR was calibrated on-site using test atmospheres created through dynamic dilution 

blending of a 1% C2F6 in N2 standard. Several mixtures were created to calibrate the response of 

the FTIR equipped with the 5.6 m gas cell. Figure 4 shows the calibration curve generated for 

the CF3 symmetrical deformation of C2F6 (centered at 714 cm-1) as measured by the maximum 

absorbance of the R branch for each calibration point. The relative error of this calibration was 

determined to be 3.1 %. 

Absorbance for R Branch of CF3 Symetrical Defromation (714 cm-1) as function of C2F6 

Concentration

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 200 400 600 800 1000 1200 1400

Concentration of Added C2F6 (ppmv)

Absorbance

Slope: 5.1E-4 ± 1.6E-5 

Intercept: 0.0173 ± 0.014

R2

: 0.996

Figure 4: Calibration of FTIR response to C2F6. Note 1: These data were generated on-site 

at NEC Electronics Inc. using a 1% C2F6 in N2 standard. Note 2: The least squares line is 

not shown in Figure, but the relevant parameters of regression line and statistics are 

presented. 

3.0 Data Analysis 

3.1 Determination of Scrubber Dilution 

One of the primary goals of this study was to accurately determine the dilution that occurs when 

gas emitted from the process chamber passes through the scrubber. Dilution can occur from 

many sources including effluents from other chambers, combustion gases and by-products added 

to and generated within the scrubber, vapors added as the gas stream passes through the water 

scrubber portion of the system, in-board leaks, and back diffusion from main headers. The 

method of determining dilution in this study was to use a purely experimental approach where a 

chemical was spiked into the gas stream entering the scrubber at a known flow rate, and 

determined in the scrubber effluent stream. From the determined concentration and the 

 9 
controlled flow rate added to the process exhaust duct, a total flow from the scrubber could be 

calculated: 

TF = Sf/(Can X 10-6) (1) 

Where Sf represents the spike gas flow and is reported in liters, and Can represents the analyte 

concentration reported in ppmv. 

The experiment conducted to determine total flow from the E-HTVS scrubber consisted of using 

the calibration system shown in Figure 1 to add calibration gas into the process effluent through 

the FTIR sample line where the process effluent was monitored. While calibration gas was being 

added, the QMS was used to sample scrubber effluent. The flow of calibration gas was 

controlled with a 0 – 5 slm MFC that was calibrated for nitrogen. Five flow rates were added to 

the scrubber: 1, 2, 3, 4 and 5 slm. At 1% concentration, each of these flows corresponded to Kr 

and Xe flows of 0.01, 0.02, 0.03, 0.04 and 0.05 slm, respectively. Concentration profiles for Xe 

and Kr determined from QMS data during this experiment are shown in Figure 5 for CVD Tool 

#1, which was the tool used for testing the E-HTVS scrubber. 

Applying Eq. 1 to the data shown in Figure 5 for the E-HTVS scrubber yielded the total 

equivalent flows determined for both Xe and Kr, which are contained in Table I. The average 

total flow for each species was: 

 Xe: 741 ± 3 Kr: 765 ± 3 

Here the reported standard deviations are the best estimate of the standard deviations of the mean 

for total flows contained in Table I. Combining the data for Kr and Xe yielded a best estimate 

of effective flow of 757 ± 2 slm, which is the variance weighted average of the mean. 

The precision of these measurements were ± 0.3 %. The differences between the flow values 

(3%) obtained for Kr and Xe could be attributable to other factors affecting accuracy, such as the 

accuracy of the Kr and Xe concentrations in the calibration standards. 

 10 
_____________________________________________________________________ 

Table I: Total equivalent flow measurements from E-HTVS determined using Xe and Kr. 

Xe/Kr Flow 

(slm)

Xe Conc 

(ppmv)

Total 

Equivalent 

Flow 

(slm)

Kr Conc 

(ppmv) 

Total 

Equivalent 

Flow 

(slm)

0.010 12.7 ± 1.7 787 ± 122 14.4 ± 1.3 694 ± 63

0.020 26.9 ± 2.0 744 ± 52 28.1 ± 2.3 712 ± 58

0.030 40.1 ± 3.1 748 ± 58 37.8 ± 2.7 794 ± 57

0.040 55.4 ± 4.5 722 ± 59 50.2 ± 2.8 797 ± 44

0.050 67.6 ± 4.7 740 ± 51 64.8 ± 2.4 772 ± 29

______________________________________________________________________ 

Xe Emissions from E-HTVS during Flow Calibrattions

-20

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200 1400 1600 1800

QMS Scan

Concentration (ppmv)

Calibration

Spike Flow

Kr Emissions from E-HTVS during Flow Calibration

-20

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200 1400 1600 1800

QMS Scan

Concentration (ppmv)

Calibration

Spike Flows

Figure 5: Xe (top) and Kr (bottom) emissions from E-HTVS during spike calibration. 

Calibration data were generated using test atmospheres as described above. 

 11 
The same approach was used for determining flow from the TPU. Figure 6 shows Xe and Kr 

emissions from the TPU during spiking of the scrubber. The same Xe and Kr flow rates of 0.01, 

0.02, 0.03, 0.04, and 0.05 slm were used. Table II contains the total flow determined for each 

species at each spike flow rate. The average total flow for each species was: 

Xe: 751 ± 3 Kr: 838 ± 2 

Here the reported standard deviations are the best estimate of the standard deviations of the mean 

for total flows contained in Table II. Combining the data for Kr and Xe yielded a best estimate 

of effective flow of 815 ± 2 slm, which is the variance weighted average of the mean. 

The precision of these measurements were ± 0.3 %. The difference between the flow values 

observed for Kr and Xe on the TPU (11%) were greater than those observed on the E-HTVS 

(3%). An additional flow determination method was deployed. 

An additional experiment using Ar was conducted on the TPU. The experiment consisted of 

flowing Ar from the CVD Tool #2 through the scrubber and determining the Ar concentration 

emitted from the scrubber. Figure 7 shows the Ar emission profile for 4 process flows: 2.0, 1.5, 

1.0 and 0.5 slm. As indicated in Figure 7, Ar background concentration was relatively high due 

to the natural atmospheric abundance of 0.94 %. This background was subtracted from the 

measured Ar concentration during the Ar flows to yield a concentration that could be attributable 

to the added Ar. Table III contains the data from this experiment. The data in Table III was 

used to determine the TPU flow by dividing the Ar process flow (in sl) by the differential Ar 

concentration (ΔAr). The weighted average total flow determined during this experiment was 

826 ± 2 slm. This value is in close agreement (± 1.5%) with the reported effective dilution for 

the Kr spike test (838 slm). 

Table II: Total flow measurements from TPU determined using Xe and Kr. 

Xe/Kr Flow 

(slm)

Xe Conc 

(ppmv) 

Total 

Equivalent 

Flow 

(slm)

Kr Conc 

(ppmv) 

Total 

Equivalent 

Flow 

(slm) 

0.010 12.3 ± 1.3 813 ± 86 12.7 ± 0.9 787 ± 56

0.020 27.2 ± 2.2 735 ± 60 22.8 ± 2.5 877 ± 95

0.030 42.2 ± 2.7 711 ± 45 35.0 ± 1.5 857± 37

0.040 51.6 ± 4.1 775 ± 62 47.6 ± 1.6 840 ± 28

0.050 63.6 ± 5.0 786 ± 62 59.9 ± 1.9 835± 26

Table III: Ar concentration determined in TPU effluent during Ar flow testing. ΔAr 

concentration is the measured concentration minus the baseline. 

Ar Process Flow 

(slm)

Ave. Ar Conc. 

(ppmv)

Δ Ar Conc 

(ppmv)

Total TPU Flow 

(slm)

 12 
Baseline 

(0)

8685 ± 22 _ _

2.0 11,098 ± 154 2413 ± 156 828 ± 53

1.5 10,302 ± 33 1617 ± 40 927 ± 23

1.0 9996 ± 27 1311 ± 35 762 ± 20

0.5 9321 ± 18 636 ± 28 786 ± 35

Baseline 

(0)

8655 ± 18 _ _

A summary comparing total flows determined for both scrubbers is contained in Table IV. 

Results for Kr and Xe on the E-HTVS scrubber were within 3%, while on the TPU system the 

difference was 11 %. In both cases the Kr based determination was higher than Xe 

determination. The dilution determined using Ar on the TPU was found to be within 1.5 % of 

the value determined using Kr. Both values were > 10 % higher than the value determined using 

Xe. Considering that using Ar supplied by the process tool is independent of the calibration 

standard accuracy for the spiking process, this result suggests that inaccuracies in the Xe 

determination may more likely have occurred. Given the relative close agreement in results for 

all flow determinations, this was not further investigated. However, the Xe discrepancy warrants 

further investigation in subsequent evaluation of the methodology. 

________________________________________________________________________ 

Table IV: Summary of the average total flow determinations for E-HTVS and TPU at 

NEC Electronics Inc. All flows reported as slm. 

POU System Xe Spike Kr Spike Ar On-Tool 

E-HTVS 741 ± 3 765 ± 3 N/A 

TPU 751 ± 3 838 ± 2 826 ± 2

__________________________________________________________________ 

Kr Concentration Determiend during TPU Spike Flow Calibration 

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600

QMS Scan

Concentration (ppmv)

 13 
XeConcentration Determiend during TPU Spike Flow Calibration 

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600

QMS Sscan

Concentration (ppmv)

Figure 6: Kr (top) and Xe (bottom) emissions from TPU during chemical spiking of 

scrubbers. 

Ar Emission from TPU during NF3 DRE Testing

0

2000

4000

6000

8000

10000

12000

300 400 500 600 700 800 900

QMS Scan

Concentration (ppmv)

Ar Conc

2 

1.5 1.0 

0.5 Baselin

Ar Flow from MFC on Baselin

Figure 7: Ar emission from TPU while Ar was being flowed through the process chamber 

on CVD Tool #2. Baseline Ar concentration was close to that expected in air. 

Once the total flow from the scrubbers has been determined it was then possible to determine the 

dilution of process effluent occurring across the scrubbers. This calculation requires measuring 

the dilution that occurs as gases from the process chamber are pumped out of the chamber and 

fore line and sent into the corrosive scrubbed exhaust. The experiment to measure the dilution of 

CVD Tool #1 and CVD Tool #2 chamber effluent consisted of flowing C2F6 into the CVD Tool 

#1 chamber and NF3 into the CVD Tool #2 chamber, with the radio frequency (RF) power in the 

chambers turned off, at several flow rates. The determined C2F6 and NF3 concentrations in the 

chamber effluent could be used to calculate the total process flow entering the scrubber from the 

following equation: 

 14 
 TPF = PGf/(CPG X 10-6) (2) 

Here the total process flow (TPF) is determined from the ratio of the process gas flow (PGf) in 

slm divided by the measured concentration (CPG) in ppmv. 

Process flow data for the E-HTVS system were obtained by flowing C2F6 through the CVD Tool 

#1 chamber at several flows with the RF power turned off. Figure 8 shows the C2F6 emission 

profile for 5 different flows. From these data the total process flow was determined and is 

contained in Table V. The average total process flow was 83.58 ± 0.03 slm. Combining this 

value with the total scrubber flow yielded the effective dilution of influent gas across the EHTVS: 

Dilution Factor = (757 ± 2)/(83.58 ± 0.03) = 9.05± 0.02 

This value was used for all subsequent DRE calculations. This value represents the effective 

dilution that was determined for the E-HTVS. These data do not necessarily imply a total flow 

of 757 slm was flowing through the abatement device, but do imply that the chemical spiking 

agents were diluted to an equivalent flow of 757 slm. The source of this dilution was not 

determined, but could be attributable to factors such as in-board leaks in the duct work between 

the scrubber outlet and the sample location or mixing at the sample location from the main 

header of the scrubbed corrosive exhaust system. Having an accurate determination of this 

effective dilution is critical in determining an accurate DRE for the scrubber. 

________________________________________________________________________ 

Table V: Total process flow determination for CVD Tool #1 using C2F6 tool flows. 

C2F6 Flow 

(slm) 

Ave. C2F6 Concentration 

(ppmv) 

Total Process Flow 

(slm) 

1.0 11,714 ± 61 85.4 ± 0.4 

0.8 9461 ± 50 84.6 ± 0.4 

0.6 7232 ± 43 83.0 ± 0.5 

0.4 4889 ± 32 81.8 ± 0.5 

0.2 2500 ± 26 80.0 ± 0.8 

 15 
C2F6 Emissions from E-HTVS during Process Flow Calibrations

0

2000

4000

6000

8000

10000

12000

14000

0 100 200 300 400 500 600 700 800

FTIR Scan

Concentration (ppmv)

1.0 slm 

0.8 slm 

0.6 slm 

0.4 slm 

0.2 slm 

5 min Chamber Clean

Figure 8: C2F6 emission profile for CVD Tool #1 during process flow calibration. C2F6

emissions from a 5 minute chamber clean are also shown. 

Total process flow into the TPU was determined by flowing NF3 from the chamber with RF 

power off. Process emissions from six flows are shown in Figure 9. From these data the total 

process flow was determined to be 15.50 ± 0.01 slm. Table VI contains NF3 concentrations 

determined for each flow. The total process flow and total TPU exhaust flow were used to 

calculate the dilution occurring in the TPU: 

Dilution Factor = (831 ± 1)/(15.50 ± 0.01 ) = 53.6 ± 0.1 

Having determined the total process flow for each tool and scrubber allows determination of the 

dilution occurring across the scrubber. These data were used to determine the scrubber F-GHG 

DRE. 

______________________________________________________________________ 

Table VI: Total process flow determination for CVD Tool #2 using NF3 tool flows. 

NF3 Flow 

(slm) 

Ave. NF3 Concentration 

(ppmv) 

Total Process Flow 

(slm) 

0.50 31,735 ± 157 15.8± 0.1 

1.00 67,886 ± 974 14.7 ± 0.1 

1.50 93,964 ± 685 16.0 ± 0.1 

0.20 13,098 ± 83 15.3 ± 0.1 

0.25 16,147 ± 50 15.5 ± 0.1 

0.30 19,020 ± 41 15.8 ± 0.1 

 16 
NF3 Emissions from AMAT HDP during Process Flow Calibration

0

20000

40000

60000

80000

100000

120000

0 100 200 300 400 500 600

FTIR Scan

Concentration (ppmv)

0.500 

1.000 

1.500 

0.200 0.250 

0.300 

Figure 9: NF3 emission profile from CVD Tool #2 during NF3 process flow calibration. 

3.2 Scrubber DRE Determinations 

Determination of the E-HTVS scrubber performance was performed using two different testing 

conditions. The first was to measure the scrubber effluent of C2F6 during the total process flow 

calibrations and the second was to measure the scrubber effluent during C2F6/O2 chamber cleans. 

Two chamber cleans were monitored. The first was a short 5-minute clean of a chamber that was 

relatively clean (little tungsten accumulation in the chamber). The second clean was longer and 

was performed after an accumulation of approximately (ca.) 20 μm of film that had built up in 

the chamber. This clean used an optical end-point mechanism to determine the length of the 

clean. The process recipe for the chamber clean was to flow 1.2 slm C2F6 and 1.2 slm O2. 

Determination of the TPU performance could only be done using NF3 flows from the tool gas 

delivery system, as the tool chosen for this project was not operational at the time of testing. 

Several NF3 flows were sent through the process chamber to determine NF3 DRE. However, no 

process wafers could be run and the system could not be evaluated under manufacturing 

conditions. 

3.2.1 TecHarmonic E-HTVS DRE 

The E-HTVS DRE for C2F6 was determined during process flow calibrations. Figure 10 shows 

C2F6 emissions from process and scrubber during the flow calibration. Using the average 

measured C2F6 concentration for both inlet and outlet samples from each step and applying the 

dilution correction yields the C2F6 DRE for the E-HTVS scrubber during process flow 

determination. These averages for each C2F6 flow are contained in Table VII. The associated 

DRE values for each C2F6 flow are also contained in Table VII. 

________________________________________________________________________ 

 17 
Table VII: C2F6 DRE in E-HTVS during process flow calibrations. Dilution adjustment 

was based total measured flows into and out of the scrubber. 

C2F6 Flow 

(slm) 

C2F6 Conc. In 

Process 

Effluent 

(ppmv) 

C2F6 Conc. In 

E-HTVS 

Effluent 

(ppmv) 

Dilution 

Adjusted C2F6

Concentration 

(9.05X in ppmv) 

DRE 

(%) 

1.0 11,714 ± 61 1288 ± 10 11,656 0 % 

0.8 9461 ± 50 1064 ± 10 9629 -2 % 

0.6 7232 ± 43 736 ± 10 6661 8 % 

0.4 4889 ± 32 505 ± 8 4570 7 % 

0.2 2500 ± 26 250 ± 4 2263 9 % 

________________________________________________________________________ 

 

From the data contained in Table VII above, a 95% Confidence Interval (CI) is determined 

to be 5.0 ± 4.4 % indicating that all values in Table VII are statistically zero at the 95 % CI. 

C2F6 Emissions from E-HTVS during Process Flow Calibrations

0

2000

4000

6000

8000

10000

12000

14000

0 50 100 150 200 250 300 350 400 450 500

FTIR Scan

Concentration (ppmv)

1.0 slm 

0.8 slm 

0.6 slm 

0.4 slm 

0.2 slm 

C2F6 Emissions from E-HTVS during Process Flow Calibration

0

200

400

600

800

1000

1200

1400

0 50 100 150 200 250 300 350 400 450 500

FTIR Scan

Concentration (ppmv)

1.0 

0.8 

0.6 

0.4 

0.2 

Figure 10: Inlet and outlet C2F6 emission profiles for E-HTVS during process flow 

calibration. 

 18 
The E-HTVS DRE for C2F6 was also determined during chamber cleans. Emissions from the 

chamber clean included significant levels of tetrafluoromethane (CF4), which was formed as byproduct. Other chamber clean by-products included carbonyl fluoride (COF2), tungsten 

hexafluoride (WF6) and carbon monoxide (CO) as identified in the FTIR spectrum shown in 

Figure 11. Emission profiles of CF4 and C2F6 for two chamber cleans are shown in Figure 12. 

Emission profiles of CF4 and C2F6 from the E-HTVS are also shown in Figure 12. These data 

were numerically integrated over time to yield emission volumes. Comparison of the CF4 and 

C2F6 emission volume entering the scrubber with that emitted from the scrubber can be used to 

directly calculate DRE for each compound. 

To convert measured concentrations into volumes, the following equation was used: 

 VEM = ΣCiTfΔt (5)

Where the total emission volume (VEM) is the summation of each FTIR data point where the 

concentration of analyte Ci is determined during time interval Δt and multiplied by the total flow 

(Tf). The summation of the entire emission profile provides an emission volume for a given 

analyte during the process. During this study, these calculations were performed using standard 

spreadsheet software (Microsoft Excel). Use of this technique reinforces the importance of 

accurately determining the total process and scrubber flows as described in the sections above. 

-.4

-.2

0

.2

.4

.6

.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

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C2F6

CF4

WF6

COF2

CO

Figure 11: FTIR spectrum of process emissions during C2F6/O2 chamber clean on CVD 

Tool #1. 

 19 
C2F6 and CF4 Emissions from LPW108 During Chamber Clean

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C2F6 and CF4 Emissions from E-HTVS during Chamber Cleans

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C2F6 EPA 5.6m

cell 150C

CF4 EPA 5.6m

cell 150C

Figure 12: C2F6 and CF4 emissions from CVD Tool #1 (top) and E-HTVS scrubber during 

chamber cleans. The first clean was timed for 5 minutes. The second clean was for a 

tungsten accumulation of ca. 20μm and was run until end point. 

Integration of the emission profiles shown in Figure 12 yielded emission volumes contained in 

Table VIII for both process and scrubber emissions. These integrated emission volumes were 

compared directly to determine F-GHG DRE during the chamber cleans, which are also included 

in Table VIII. The results are close in value to those presented for C2F6 during the process flow 

calibrations shown above. 

The results for CF4 yielded an average DRE of 9.5 % with a 95 % CI of ± 9.8 %. Use of these 

two data points yields DRE‘s in the range of -0.3 – 19.3 %, which includes zero. Therefore, we 

cannot reject the hypothesis that the DRE equals zero. Given that CF4 is more difficult to abate 

than C2F6 due to higher bond energy of C-F compared to C-C, a zero DRE would be expected 

and the data indicates statistically that this is the case. The actual deviation from a zero DRE as 

 20 
determined in this study can be attributable to the propagation of errors associated with all the 

factors used in calculating the values contained in Table VIII. 

_______________________________________________________________________ 

Table VIII: Integrated F-GHG process and scrubber emissions for CVD Tool #1 (process) 

and E-HTVS during chamber cleans. Details on the cleans provided in text 

Clean #1 Clean #2 

C2F6 Process Emission (sl) 3.914 8.266 

C2F6 E-HTVS Emission (sl) 3.723 8.802 

C2F6 DRE 5 % -5 % 

CF4 Process Emission (sl) 1.011 1.730 

CF4 E-HTVS Emission (sl) 0.952 1.494 

CF4 DRE 6 % 13 % 

The data contained in Table VIII can also be used to determine the process DRE for C2F6 and the 

process emission factor for CF4. The process DRE is defined as the ratio of C2F6 emitted from 

the process to the total C2F6 added to the process. For clean #1 the total C2F6 added to the 

process was 6.0 sl based on a 1.2 slm process flow and 5 minute chamber clean, thus the C2F6 

process DRE was 35 % for this clean. For clean #2, which reached end point at 11.1 minutes, 

the C2F6 process DRE was 38% based on a total process flow of 13.3 sl. 

The CF4 emission factor is defined as the ratio of CF4 volume emitted from the process to the 

C2F6 volume added to the process. For cleans #1 and #2 these values were 17 and 13%, 

respectively. The slight differences between cleans 1 and 2 were attributed to clean #2 being 

done when the chamber had more tungsten film accumulation in the chamber. 

All of the DRE values reported for C2F6 and CF4 indicate that the E-HTVS system does not abate 

these gases under the operating conditions tested. The result obtained for CF4 is statistically 

equivalent to zero at the 95 % CI. 

3.2.2. Edwards TPU DRE 

As stated above the CVD Tool #2 was not operational. This prevented evaluating the 

performance of the TPU during wafer processing. It was possible to flow NF3 from the process 

chamber through the TPU. The five flow rates used to collect the data in Figure 9 (data collected 

at the inlet to the TPU) yielded undetectable levels of NF3 in the TPU effluent. Figure 13 shows 

FTIR spectra obtained at the inlet and outlet of the TPU while 1.5 slm NF3 was flowing from the 

process chamber. These data can be used to report a TPU DRE of > 99.9 % based on an 

estimated FTIR detection limit of 0.5 ppmv, an average inlet concentration of 93,964 ± 685 

ppmv and a dilution factor of 53.6 X: 

 21 
 Diluted NF3: 93,964/53.6 = 1750 ppmv fully diluted 

 Undetected NF3: 0.5/1750 = 0.00029 

 DRE (1.000 – 0.00029)x100 = 0.99971 = 99.971%

The TPU was proven to be effective at abating any NF3 potentially emitted from the process 

under the conditions with which it was operated. The TPU thermocouple temperature gauge 

reported an operating temperature of ca. 820o

 C. An experiment was conducted to determine if 

the NF3 DRE would be reduced if the TPU operating temperature was reduced. Temperature 

reduction was done by reducing the natural gas flow by ca. 10 and 20 %, which yielded 

operating conditions of 665o C and 480o

 C, respectively. Under these operating conditions NF3

was not detected in the TPU effluent suggesting that it may be possible to operate the TPU at 

lower temperatures if its sole purpose is to abate NF3. One observed consequence of operating at 

lower temperatures was an increase in CO and CH4 emissions from the TPU relative to those 

observed at 820o

 C. Figure 14 shows CO and CH4 increased emissions while the temperature 

was reduced. 

Another by-product observed during NF3 abatement was nitric oxide (NO). Figure 15 shows NO 

emission profile during testing. NO emissions are correlated with NF3 flows from the tool. 

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NF3 NF3

Process Exhaust

TPU Exhaust

Figure 13: FTIR spectra of TPU exhaust (top) and CVD Tool #2 process exhaust (bottom) 

while 1.5 slm NF3 was flowing through the chamber. NF3 emissions from TPU were below 

the detection limit of the FTIR (0.5 ppmv). The process emissions were ca. 94,000 ppmv. 

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4.0 Conclusion 

The purpose of this study was to accurately determine the DRE of F-GHGs in two commercially 

available POU abatement systems used in semiconductor manufacturing. A critical component 

of an accurate DRE was to determine the dilution of process effluent occurring in the scrubbers. 

Chemical spiking of inert gases was used to determine the dilution. Kr and Xe were used for the 

TecHarmonic E-HTVS scrubber. It was determined that both Xe and Kr yielded statistically 

equivalent effective dilution for the E-HTVS. Kr, Ar and Xe were used to determine the 

effective dilution occurring in the Edwards TPU scrubber. All three chemicals yielded similar 

results. The effective dilution for each system was combined with the process emission data to 

determine the DRE of each scrubber for F-GHGs C2F6 and CF4 on the E-HTVS and for NF3 on 

the TPU. 

The DRE determined for C2F6 and CF4 on the E-HTVS were very low. The results indicate a 

statistically zero DRE was obtained for both C2F6 and CF4 on the E-HTVS. 

The TPU was determined to have a very high DRE, > 99.9%, for NF3 when accounting for the 

dilution occurring in the scrubber. The data also demonstrated that the TPU can be operated at 

lower temperatures while maintaining a high DRE for NF3. While other process and operating 

parameters may need to be considered before reducing the temperature, it could be possible to 

operate at lower natural gas flows and maintain a high NF3 DRE. 

The process DRE for C2F6 during tungsten chamber clean was determined to be 35 - 38 %, 

which was in close agreement with the 2006 IPCC reported value of 40 %. A CF4 emission 

factor of 13 – 17 % was determined, which was also in close agreement to the 2006 IPCC 

reported value of 20 %. 

 23 
CH4 Emissions from TPU During NF3 Breakthrough Testing

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CH4 Decreased to 20 

CH4 Flow at 22 slm TPU at 

CH4 Flow Decreased to 18 

TPU cooled to 478 

CH4 Flow raised to 22 

CO Emissions from TPU During NF3 Breakthrough Study

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Concentration (ppmv)

CH4 20 

CH4 22 

CH4 18 

CH4 22 

Figure 14: Relative CH4 and CO emissions from TPU during reduced temperature 

operation. The temperature was reduced by lowering the CH4 flow into the system. 

 24 
NO Emissions from TPU During NF3 Breaktrhough Test

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Figure 15: Nitric oxide emission profile during NF3 flows from CVD Tool #2 chamber 

through the TPU. NO emissions are correlated with NF3 flow rate 

 25