Comparison of Fourier Transform Infrared (FTIR) and Quadrupole 

Mass Spectroscopy (QMS) Methods for Determining POU 

Abatement System Effluent Flow 

International SEMATECH Manufacturing Initiative 

Technology Transfer #10095115A-ENG 
© 2011 International SEMATECH Manufacturing Initiative, Inc. 

Advanced Materials Research Center, AMRC, International SEMATECH Manufacturing Initiative, and 

ISMI are servicemarks of SEMATECH, Inc. SEMATECH and the SEMATECH logo are registered servicemarks 

of SEMATECH, Inc. All other servicemarks and trademarks are the property of their respective owners. 
Comparison of Fourier Transform Infrared (FTIR) and Quadrupole 

Mass Spectroscopy (QMS) Methods for Determining POU Abatement 

System Effluent Flow 

Technology Transfer #10095115A-ENG 

International SEMATECH Manufacturing Initiative 

October 30, 2010 

Abstract: This report documents comparison testing of quadrupole mass spectroscopy (QMS) and Fourier 

transform infrared (FTIR) spectroscopy for determining the volumetric flow of point-of-use 

(POU) abatement system effluent. The EPA Protocol for Measuring Destruction or Removal 

Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Electronics 

Manufacturing Version 1 and the International SEMATECH Manufacturing Initiative’s 2009 

Guideline for Environmental Characterization of Semiconductor Process Equipment– Revision 2

were used in this testing. The POU abatement system effluent volumetric flow rates as determined 

by FTIR and QMS were consistent with one another. The FTIR monitoring approach to determine 

POU abatement system effluent volumetric flow in ISMI’s guideline document provides a suitable 

alternative to QMS measurements.

Keywords: Flow Rates, Fourier Transform Infrared Spectroscopy, Government Regulations, Point of Use 

Abatement, Procedures, Quadrupole Mass Spectroscopy 

Authors: J. Michael Sherer, P.E., Sherer Consulting Services, Inc., Steve Hall, URS Corporation, and Bryan 

Benaway, URS Corporation 

Approvals: Steve Trammell, Project Manager 

Ron Remke, Program Manager 

Joe Draina, Director 

Laurie Modrey, Technology Transfer Team Leader 

iii 

Table of Contents 

1 EXECUTIVE SUMMARY .....................................................................................................1

1.1 POU Abatement System Effluent Flow Determination..................................................1 

1.2 Summary of Results and Conclusions ............................................................................2 

1.3 Recommendation ............................................................................................................2

2 INTRODUCTION...................................................................................................................2

3 EXPERIMENTAL SETUP......................................................................................................4

3.1 QMS-based Approach.....................................................................................................4 

3.2 FTIR-based Approach.....................................................................................................5 

3.3 Analytical Instrumentation..............................................................................................5 

3.3.1 QMS ....................................................................................................................5 

3.3.2 FTIR Spectrometer..............................................................................................7 

3.3.3 POU Abatement Systems Monitored..................................................................9 

3.3.4 Sampling System and Extraction Locations .......................................................9 

3.3.5 Tracer Injection System ....................................................................................11 

4 EXPERIMENTAL RESULTS AND DISCUSSION.............................................................12

4.1 Statistical Treatment of POU Abatement System Effluent Flow Rates........................13 

4.2 POU Abatement System Effluent Flow Determination by QMS Method....................14 

4.3 POU Abatement System Effluent Flow Determination by FTIR Method....................16 

4.4 Comparative Analysis of Tracer Release QMS and FTIR Methods.............................19 

5 SUMMARY OF RESULTS AND CONCLUSIONS ............................................................20

6 RECOMMENDATION .........................................................................................................20

7 REFERENCES......................................................................................................................20

APPENDIX A – ISMI POU ABATEMENT DEVICE VOLUMETRIC FLOW RATE 

METHODOLOGY COMPARISON TEST PLAN ...............................................................21

A.1 Introduction...................................................................................................................21 

A.2 Testing Scope................................................................................................................21 

A.3 Proposed Schedule ........................................................................................................23

APPENDIX B – EQUIPMENT CERTIFICATIONS ....................................................................24

ISMI Technology Transfer #10095115A-ENG 
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List of Figures 

Figure 1 QMS Kr Calibration Used for Effluent Flow Determinations of the POU 

Burn/Wet Systems ......................................................................................................6 

Figure 2 QMS Kr Calibration Used for Effluent Flow Determinations of the POU 

Electric Heat/Wet System...........................................................................................7 

Figure 3 FTIR SF6 Linear Calibration Curve ...........................................................................8 

Figure 4 FTIR/QMS Sampling System Diagram .....................................................................9 

Figure 5 Sample and Tracer Injection Location of POU Burn/Wet Abatement 

System #1 .................................................................................................................10 

Figure 6 Sample and Tracer Injection Location of POU Burn/Wet Abatement 

System #2 .................................................................................................................10 

Figure 7 Sample Location of POU Electric Heat/Wet Abatement System #1........................11 

Figure 8 Flow Tracer Injection Dynamics at the POU Abatement System Effluent ..............12 

Figure 9 QMS Kr Measurements at POU Burn/Wet Abatement System #1 ..........................15 

Figure 10 QMS Kr Measurements at POU Burn/Wet Abatement System #2 ..........................15 

Figure 11 QMS Kr Measurements at POU Electric Heat/Wet Abatement System #1 .............16 

Figure 12 FTIR SF6 Measurements at POU Burn/Wet Abatement System #1.........................17 

Figure 13 FTIR SF6 Measurements at POU Burn/Wet Abatement System #2.........................18 

Figure 14 FTIR SF6 Measurements at POU Electric Heat/Wet Abatement System #1............18 

Figure 15 TVF Determinations of QMS and FTIR Data (POU Burn/Wet Abatement 

System #2)................................................................................................................19 

List of Tables 

Table 1 Comparative Results for QMS and FTIR POU Abatement System Effluent 

Flow Determinations ..................................................................................................3 

Table 2 Stratification Traverse Results..................................................................................16 

Technology Transfer #10095115A-ENG ISMI 
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ISMI Technology Transfer #10095115A-ENG 

Acknowledgments 

The authors would like to acknowledge the assistance of the wafer fab personnel for use of their 

POU abatement systems, their support of the field testing, and coordination of the POU 

abatement system operations. In addition, thanks to Steve Trammell (project manager, ISMI 

ESH Technology Center) who coordinated the project as well as assisting in the field and Ron 

Remke (program manager, ISMI ESH Technology Center) for support of this project and 

assisting in the field. Finally, a well deserved thank you to Mike Sherer, Sherer Consulting 

Services, Inc., for his tireless effort in schedule coordination, testing assistance, equipment setup, 

and data review throughout the project. 

The authors would also like to recognize the contributions of Laurie Beau (project manager, 

ISMI ESH Technology Center) and Tom Huang (project manager, ISMI ESH Technology 

Center) for all of their efforts and their valuable insight. 

1 

1 EXECUTIVE SUMMARY 

Two methodologies for determining the total volumetric flow (TVF) of various point-of-use 

(POU) abatement system effluents were studied using three systems in a wafer fab during normal 

operation. Two of the POU abatement systems were fuel-based thermal oxidation/wet scrubbers 

(burn/wet); one was an electric heat oxidation/wet scrubber (electric heat/wet). Each of the two 

methodologies used a tracer release approach to determine the TVF; the main differences were 

the injection location and analytical instrumentation. The two approaches to determine TVF were 

as follows: 

 Injection of precise volume flow rates of sulfur hexafluoride (SF6) at the POU 

abatement system effluent while taking real-time measurements of SF6 concentrations 

downstream of the injection point using Fourier transform infrared (FTIR) spectroscopy. 

 Injection of precise volume flow rates of krypton (Kr) into the inlet of the POU 

abatement system while taking real-time measurements of Kr concentration at the POU 

abatement system effluent using quadrupole mass spectroscopy (QMS). 

Determining TVF by QMS was performed according to the Environmental Protection Agency 

(EPA) Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated 

Greenhouse Gas Abatement Equipment in Electronics Manufacturing, Version 1, March 2010

(EPA Protocol) [1]. Determining TVF by FTIR followed the International SEMATECH 

Manufacturing Initiative’s (ISMI) 2009 Guideline for Environmental Characterization of 

Semiconductor Process Equipment – Revision 2 (2009 ISMI Guideline) [2]. A test plan 

(Appendix A) was prepared outlining the testing objectives and submitted to the EPA before the 

onset of the comparison study. 

Mass flow controllers (MFCs) and volumetric flow meters (VFMs) were used to deliver steady 

and precise flows of each tracer gas. Since neat Kr and SF6 were the tracer gases used, the MFCs 

(calibrated for nitrogen) were used to deliver a constant gas flow only. The tracer gas injection 

flow was determined from a DryCal DC-Lite primary flow meter; a National Institute of 

Standards and Technology (NIST)-traceable primary standard was used in which a float in the 

devices’ flow cell was timed between two sensors. (See Appendix B for calibration certifications 

for all the MFCs and volumetric flow meters). 

1.1 POU Abatement System Effluent Flow Determination 

The TVF determined at each POU abatement system effluent as calculated according to EPA 

Protocol equations is summarized in Table 1. The effluent flows were determined by FTIR 

concentration measurements (120 total data points) of a SF6 tracer. The TVF for each system’s 

effluent was determined in triplicate by independently injecting three different controlled flow 

rates of SF6 tracer gas (40 data points used for each injection flow rate). Determining the TVF by 

QMS involved injecting a Kr tracer at four precisely determined flow rates into the abatement 

system influent while performing QMS monitoring (40 data points used for each injection flow 

rate) at the effluent. Note that the effluent sampling location was the same for both SF6 tracer gas 

and Kr tracer gas studies. 

Table 1 gives all the calculated flows in liters per minute (lpm). As is evident from the 

comparison of flows, the TVFs determined by each methodology were consistent. However, both 

ISMI Technology Transfer #10095115A-ENG 
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Technology Transfer #10095115A-ENG ISMI 

the relative error and standard deviation of the flow results was, on average, six times better 

when using the FTIR approach. 

1.2 Summary of Results and Conclusions 

 The POU abatement system effluent flow rates as determined by FTIR and QMS were 

remarkably consistent with one another (9.37% relative percent difference [RPD] at 

burn/wet abatement system #1, 0.600% RPD at burn/wet abatement system #2 and 1.52% 

RPD at electric heat/wet abatement system #1). 

 The determinations of effluent flow rates were stable and repeatable when determined by 

tracer release methods (Table 1). 

 The tracer release/FTIR monitoring approach in the 2009 ISMI Guideline to determine POU 

abatement effluent flows resulted in a standard deviation and relative error that was, on 

average, 5.4 and 5.6 times better than the QMS results, respectively. 

 The tracer release/FTIR monitoring approach in the 2009 ISMI Guideline to determine POU 

abatement effluent flow provided a suitable alternative to performing mass spectroscopy 

measurements. However, it is imperative to demonstrate that the injected tracer gas is well 

mixed at the extraction location. This can be done with a simple multipoint stratification test. 

1.3 Recommendation 

The 2009 ISMI Guideline tracer release/FTIR monitoring approach should be included in the 

EPA Protocol as an acceptable method for determining POU abatement system effluent flow. 

However, a concentration stratification should be determined at various points (i.e., 25%, 50%, 

and 75%) across the effluent duct to ensure homogeneity between the tracer and native effluent. 

2 INTRODUCTION 

To minimize climate change, new and more stringent ESH initiatives and greenhouse gas (GHG) 

reporting rules for the electronics industry have been issued. Several current semiconductor 

processes that are suspected of emitting significant quantities of high global warming potential 

(GWP) gases have had POU abatement systems installed to mitigate ultimate GHG emissions. 

Very little quantitative information is available about these emissions or the subsequent 

destruction of some of these gases through POU abatement systems. Because many of the gases, 

especially those with high GWPs, are under increased scrutiny by regulatory agencies 

worldwide, the U.S. Environmental Protection Agency published a protocol for the destruction 

or removal efficiency (DRE) of POU abatement systems. An integral part of this protocol is the 

measurement of dilution across POU abatement systems, for which accurate determinations of 

the effluent flow rate are paramount. Since many POU abatement systems incorporate 

combustion/oxidation gases and purge gases, the process gases entering the abatement system 

become diluted. According to the EPA Protocol, both POU abatement system influent and 

effluent flows must be measured. Historically, the small diameter ducts of these systems, the 

many bends and flow disturbances associated with the ducts, and the general inaccessibility 
Table 1 Comparative Results for QMS and FTIR POU Abatement System Effluent Flow De

Tracer Injection Flow Rates 

Location Methodology 

Influent Kr 

Flow (cc/min) 

Effluent SF6

Flow (cc/min) 

40-Point Avg. 

Measured 

Conc. (ppm) 

Calculated 

Flow 

(lpm) 

Std. Dev. 

of Calc. 

Flow (lpm)

Total 

Volumetric 

Flow (lpm) 

200 — 288 727 170 

1020 — 1533 677 87.8 1500 — 2325 658 95.7 

QMS 

586 — 865 686 80.4 

679 

— 22.3 31.0 719 16.6 — 43.7 58.1 753 18.6 

Burn/Wet Abatement System #1 

FTIR 

— 64.2 82.9 775 19.4 

746 

1100 — 1609 696 102 

QMS 570 — 801 722 84.1 1 

1530 — 302 711 213 

711 

— 22.1 32.6 679 10.1 — 43.7 60.0 728 12.4 

Burn/Wet Abatement System #2 FTIR 

— 64.1 85.5 750 17.5 

707 

1030 — 2398 436 57.8 

730 — 1635 452 50.5 395 — 898 446 52.2 

QMS 

224 — 553 410 45.5 

434 

— 23.1 52.5 440 15.7 — 45.4 103 440.2 14 

Electric Heat/Wet Abatement System #1 

FTIR 

— 67.9 153 443 14.5 

441 

1 An additional Kr tracer flow was injected, but the results were not consistent with the other three. The cause is unknown but believed to be due to an 

or sampling systems. 

Note: Shaded columns are TVF and error as calculated according to EPA Protocol equations. ISMI Technology Transfer #10095115A-ENG 
4 

to ports using standard flow equipment made accurate determinations of effluent flow by 

conventional methodologies (EPA Test Methods 1 and 2) problematic. Consequently, tracer 

release methods have been adopted, in which a known flow of an inert gas is injected and 

concentrations are measured of the injection location. 

The EPA Protocol currently designates that QMS be used to monitor a released tracer through 

the POU abatement system to determine effluent flow and FTIR be used to measure abatement 

system influent flow as well as monitor DRE concentrations of process gases and byproducts. 

Both the semiconductor industry and the EPA stand to benefit from using a single analytical 

instrument to determine both concentration and flow. It is more cost-effective and many testing 

companies are available to collect FTIR-based measurements; very few have QMS capabilities. 

As described in the 2009 ISMI Guideline, FTIR determination of effluent flow also incorporates 

the use of a tracer gas release. The main difference in how tracer releases are used in the two 

methodologies is the FTIR tracer is injected into the effluent upstream of the sample extraction 

location whereas in the QMS approach it is injected into the POU abatement system inlet. The 

concern with using the approach incorporating effluent tracer release/FTIR measurements is twofold: 

 The effluent ducts make it difficult to obtain a properly mixed tracer/effluent gas stream 

at the sample extraction location 

 Comparative data about the two approaches are lacking 

ISMI contracted with URS Corporation in Austin, TX, to compare tracer release methods (QMS 

and FTIR) for determining POU abatement system effluent flow rates, which are subsequently 

used to determine dilution, mass emission rates and destruction or removal efficiencies. 

The QMS and FTIR tracer approaches were performed at three different POU abatement 

systems: two fuel-based thermal oxidation/wet scrubbing (burn/wet) systems and a single electric 

heat oxidation/wet scrubbing (electric heat/wet) system. The testing was performed at an 

operational wafer fab on July 27 and 28, 2010. A krypton (Kr) tracer was selected for the QMSbased concentration measurements; sulfur hexafluoride (SF6) was selected as the tracer for the 

FTIR-based concentration measurements. Both tracer gases are inert and not native to the gas 

matrices of the processes/POU abatement systems tested. 

3 EXPERIMENTAL SETUP 

The EPA Protocol [1], 2009 ISMI Guideline [2], and accepted sample test plan (Appendix A) 

were followed for this study. 

3.1 QMS-based Approach 

 On-site QMS calibrations for Kr were performed before testing each day. The first day’s 

calibration consisted of a zero and five different Kr concentrations that bracketed the Kr 

tracer concentrations observed during testing. The calibration for day 2 consisted of a zero 

and three different Kr concentrations. Each Kr calibration curve was fit to a linear 

regression; the R2

 values for each were > 0.99. 

Technology Transfer #10095115A-ENG ISMI 
5 

 Neat Kr was injected into the inlet of each POU abatement system at precisely known flow 

rates. Each Kr flow was metered using a MFC and measured using a DryCal primary 

standard volumetric flow meter. Four different flow rates were injected into each POU 

abatement system. 

 Kr concentrations were determined by QMS measurements of Kr at the POU abatement 

system effluent. The final 40 concentration measurements for each injected Kr flow were 

used to determine effluent flow and subsequent statistics. 

3.2 FTIR-based Approach 

 Effluent emissions were initially analyzed to verify that SF6 was not native to the 

process/POU abatement system gas matrix. 

 A reference curve consisting of zero and three different references was generated and fit to a 

linear regression. All observed SF6 concentrations fell within this calibration curve, and all 

FTIR references and sample spectra were collected at the same spectral parameters 

(resolution, apodization, zero filling, etc.). Any slight pressure and temperature differences 

between the sample and reference spectra were accounted for during sample quantification. 

 A neat standard of SF6 tracer gas was injected across the POU abatement system effluent 

duct using a multi-hole probe to maximize mixing. 

 A sample extraction location was selected at a minimum of eight duct diameters downstream 

of the tracer injection location. 

 A concentration stratification test was performed by FTIR monitoring of SF6 at three 

different depths into the duct to ensure homogeneity of the tracer/effluent gas. 

 Once homogeneity was verified, the extraction probe was placed into the center of the duct 

and three different SF6 flow rates were injected into the effluent gas stream. FTIR spectra 

were collected every 3 sec; the final 40 spectra (per injected tracer flow rate) were quantified 

and used to determine effluent flows and subsequent statistics. 

Note that the same POU abatement system effluent location was used for QMS and FTIR 

measurements. 

3.3 Analytical Instrumentation 

3.3.1 QMS 

Traditionally, mass spectrometers have been used as analytic instruments under vacuum 

applications. Recent advancements in the technology coupled with the development of 

atmospheric samplers and closed ion sources has enabled atmospheric sampling by QMS. The 

higher pressure QMS (i.e., residual gas analyzer [RGA]) is smaller, more robust, and more 

portable than their laboratory predecessors. The RGA used for this testing was a Ferran 

Scientific Micropole Analyzer (MPA) Sensor System with a 0–100 atomic mass unit (AMU) 

range. It is mated to electronics produced by its parent company, HoribaSTEC, and is housed in 

a URS-built differentially pumped vacuum system with an atmosphere-to-analyzer chamber 

sample interface. This QMS allows sample gas, at or near atmospheric pressure, to leak into the 

QMS ionizer region under controlled rates through a precision orifice. The QMS can then scan 

over various AMU ranges or a selected few. The most sensitive Kr response was observed at 

ISMI Technology Transfer #10095115A-ENG 
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83 AMU. Since Kr was the only analyte of interest, AMU 83 was the only mass monitored. 

Since the QMS analyzer’s response factors over all the mass units depend on the ionizer’s 

chamber pressure, energy, etc., a careful calibration was performed on-site consistent with the 

configuration used for all sampling. Krypton calibration curves were generated each day by 

delivering various concentrations of Kr to the QMS sample interface. Various concentrations of 

Kr were delivered to the QMS sample interface and calibration curves generated. Figure 1 and 

Figure 2 correspond to the calibrations on 7/27/10 for the two POU burn/wet systems and 

7/28/10 for the POU electric/wet system, respectively. The linear regression equations both 

resulted in R2

 values greater than 0.98 as required by the EPA Protocol and were used to 

calculate all Kr concentrations. Sample was continuously pulled through the extractive system 

and atmospheric chamber of the QMS at a rate of ~5 lpm, from which a small volume slip stream 

was pulled into the QMS ionization chamber and analyzed. 

A Thermo-Nicolet Magna 550 FTIR bench was used for this testing. The FTIR was optically 

matched to a 0.1 m gas cell such that the IR beam propagated through the cell a single time. 

Anti-reflective zinc selenide windows transmitted the IR beam with minimal signal loss. A 

continuous flow of sample gas was delivered through the cell at ~5 lpm. As the IR beam passes 

through the sample, the molecules in the sample absorb some of its energy at particular 

frequencies. After exiting the cell, the beam is directed to a liquid-nitrogen cooled 

mercury/cadmium/telluride (MCT) detector, a photoconductive device that produces an electrical 

voltage proportional to the amount of infrared radiation that strikes it. The strength of the 

absorption at particular frequencies is a measure of the compounds’ concentrations. The total 

distance traveled by the IR beam inside the cell is the cell path length, an important parameter 

used in determining sample concentrations. 

0.0 0.2 0.4 0.6 0.8

0

500

1000

1500

2000

2500

3000

Kr Level (ppm)

% m/e = 83

ppm = 3794.81X – 149.43

R = 0.99936

Figure 1 QMS Kr Calibration Used for Effluent Flow Determinations of the POU 

Burn/Wet Systems 

Technology Transfer #10095115A-ENG ISMI 
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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

0

200

400

600

800

1000

1200

1400

1600

1800

ppm = 2404.48X – 47.43

R = 0.99435

Kr Level (ppm)

% m/e = 83

Figure 2 QMS Kr Calibration Used for Effluent Flow Determinations of the POU 

Electric Heat/Wet System 

3.3.2 FTIR Spectrometer 

The FTIR sample cell was maintained at room temperature (~23°C) throughout the testing. 

Instrumental resolution was set to 0.5 cm-1, and signal was averaged over 3-sec periods per data 

point as suggested in the EPA Protocol. A series of data points was collected at each tracer flow 

from which the final 40 datapoints were used to calculate the POU abatement system TVF and 

relative error using EPA Protocol equations. 

Figure 3 displays the FTIR calibration curve for SF6 used for all the qualitative analysis during 

sampling. The reference curve consists of a zero and three different references that were 

generated before testing and fit to a linear regression. The co-efficients (also shown in Figure 3) 

generated from this calibration curve were used in subsequent SF6 quantitative analysis during 

sampling. All observed SF6 concentrations fell within the calibration curve limits, and all FTIR 

references and sample spectra were collected at the same spectral parameters (resolution, 

apodization, etc.). Furthermore, sample quantification accounted for the slight temperature and 

pressure differences between each sample and reference spectra. 

A series of URS laboratory and on-site calibration and system checks was performed on the 

FTIRs and sampling system before testing to ensure data of known quality: 

 Infrared Detector Linearity Checks 

For best results, the infrared detector must yield a linear response throughout a 

reasonable absorbance range and all the frequencies in a set of test spectra. Linearity 

was optimized before shipment and verified just before testing. 

ISMI Technology Transfer #10095115A-ENG 
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Figure 3 FTIR SF6 Linear Calibration Curve 

 Spectral Background 

A spectral background is essentially a blank spectrum in that it does not contain any of 

the target compounds in the sample. It was created by purging the cell with POU 

abatement system effluent gas, with the process and tracer injection idle, while 

collecting a spectrum. This spectrum is then used by the analytical software to ratio 

against each sample spectrum to produce an absorbance spectrum for quantitative 

analysis. New spectral backgrounds of the non-process type were generated before each 

of the three POU abatement systems was tested. 

 SF6 Challenge 

To ensure the accuracy of the FTIR concentration measurements, a one-time challenge 

was performed. A certified standard of SF6 was directly injected into the FTIR analysis 

cell and quantified. The standard was certified at 21.9 ppm; a SF6 concentration of 

22.0 ppm was observed during the challenge. The consistency of the results 

demonstrates that the FTIR was accurately quantifying SF6. 

Technology Transfer #10095115A-ENG ISMI 
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3.3.3 POU Abatement Systems Monitored 

The comparative tests were performed at three different POU abatement systems. All had two 

stages of abatement. The first two systems tested had a first stage natural gas-fueled thermal 

oxidation system, followed by a second stage wet scrubbing section. The third system consisted 

of an electrically heated oxidation section followed by a wet scrubbing section. 

3.3.4 Sampling System and Extraction Locations 

Figure 4 illustrates the sampling system used in this study for both FTIR and QMS systems. 

Figure 5 to Figure 7 are photographs of the effluent ducts and sample locations for the three POU 

abatements systems. The QMS and FTIR measurements were not performed simultaneously 

since the same extraction location was required for both. Although the ductwork of each system 

varied, the extractive setup was diagrammatically identical: the extraction location was between 

eight and nine duct diameters downstream of the SF6 injection location. Sample was extracted 

from each effluent by a probe positioned in the center of the duct. The sample then was pulled 

through unheated, 1⁄4-inch perfluoroalkoxy copolymer (PFA) tubing at ~ 5 lpm using Venturi 

pumps. While the QMS differentially pumped a slipstream of less volume for analysis, the FTIR 

pulled the entire 5 lpm sample through its 0.1 m cell. A rotometer was attached to the FTIR cell 

to ensure adequate flow through the system during testing. After passing through the FTIR or 

QMS, the sample gas mixed with the Venturi pump motive gas before exiting the sampling 

system through 3/8-inch PFA tubing into facility exhaust. 

Effluent Duct 

(POU) Abatement 

System

FTIR or 

QMS

POU Abatement System

Effluent Stream

Sample Port 

~ 1⁄4" Hole

~20 psi Motive 

Pressure for 

External Venturi 

Pump Venturi Sample Pump

3/8" PFA FTIR Exhaust

~ 5 lpm

Figure 4 FTIR/QMS Sampling System Diagram 

ISMI Technology Transfer #10095115A-ENG 
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Figure 5 Sample and Tracer Injection Location of POU Burn/Wet Abatement 

System #1 

Figure 6 Sample and Tracer Injection Location of POU Burn/Wet Abatement 

System #2 

Technology Transfer #10095115A-ENG ISMI 
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Figure 7 Sample Location of POU Electric Heat/Wet Abatement System #1 

3.3.5 Tracer Injection System 

The injection system for the QMS-based approach, depicted in Figure 8, consisted of a neat Kr 

standard, a 0–5000 sccm MFC, 1⁄4-inch Teflon tubing, and a volumetric flow meter (VFM). The 

injection system for the FTIR approach was identical except that SF6 was used, the MFC had a 

0–500 sccm range, and a 3/8-inch multi-holed stainless steel probe was used to inject the tracer 

across the effluent duct. Using the MFC to stabilize flow through the calibrated VFM, precise 

amounts of SF6 were injected through the multi-holed probe across the effluent duct for the FTIR 

measurements; similarly, precise amounts of Kr were injected into the POU abatement system 

inlet for the QMS measurements. The SF6 injection port was located ~1 foot downstream of the 

POU abatement system exit but well upstream of the effluent sample port. 

ISMI Technology Transfer #10095115A-ENG 
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0.5 L 

MFC

POU Effluent 

Flow

POU System

~ 1"

Volumetric 

Flow Meter

SF6 Tracer Gas

5 L 

MFC

Kr Tracer Gas

Volumetric 

Flow Meter

Main Header

Venturi Pump 

(~5 lpm)

FTIR 

or 

QMS

Figure 8 Flow Tracer Injection Dynamics at the POU Abatement System Effluent 

4 EXPERIMENTAL RESULTS AND DISCUSSION 

QMS monitored the POU abatement system effluent gas for a Kr tracer that was injected into the 

POU abatement system influent. Krypton is inert and passes through the POU abatement system 

unabated. Monitoring was performed in strict accordance with the EPA Protocol. FTIR 

monitored the effluent downstream of the controlled SF6 tracer release. The sample extraction 

point was a minimum of eight duct diameters downstream of the tracer injection. Monitoring was 

performed in strict accordance with the 2009 ISMI Guideline [2]. Table 1 compares the results of 

these two methods. 

Tracer release-based flow measurements were performed by injecting a controlled flow of inert 

gas, SF6 and Kr, at the POU abatement system effluent and influent, respectively. By measuring 

the diluted tracer concentrations, the effluent flows can be determined using the following 

equation from the EPA Protocol (Equation 1) [1], 

6 10*  

ef

f

C

S

F Eq. [1] 

where: F = TVF based on a single concentration data point 

Sf = Tracer gas flow into the sample duct 

Cef = Measured concentration of the tracer gas 

Technology Transfer #10095115A-ENG ISMI 
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This technique is described in both the EPA Protocol [1] and the 2009 ISMI Guideline [2]. The 

only difference is that the 2009 ISMI Guideline also allows this method to be used to measure 

POU abatement system effluent flows (Section B.1.5) by injecting the tracer into the POU 

effluent once it has been verified that the effluent has no native concentration of the tracer. 

Conversely, the EPA Protocol states that to determine effluent flow the tracer must be injected 

into the POU abatement system inlet and pass through it with 0% or less than 5% DRE (Table 2 

and Section 2.2.3 of the EPA Protocol). 

4.1 Statistical Treatment of POU Abatement System Effluent Flow Rates 

Equation 1 applies to individual concentration measurements. The SF6 and Kr concentrations 

reported in Table 1 (column 5) are simple averages using the last 40 data points corresponding to 

each injected tracer flow rate (columns 3 and 4). However, the final estimated flow rates listed in 

column 6 were calculated by averaging the flow rates predicted by each concentration data point 

using the following equation (Equation 2 of the EPA Protocol), not by plugging the average 

concentration into Eq. [1],

 

n

i m

n

F

F

1

 Eq. [2] 

Where: The effluent flow rate calculated for the ith  data point using Fi Eq. [1]. 

F m  Simple average of TVF for the mth injected tracer gas flow rate. 

 Number of concentration measurements taken while at the mth constant tracer 

 gas flow rate. 

n 

Once the average effluent flow was determined using Eq. [2], a standard deviation for the mth 

injected tracer gas flow rate was determined using Eq. [3] (Equation 3 of the EPA Protocol). This 

is a measure of the stability and precision of the sampling system (column 7). 

  

 

n

i

i m F FF

n

i

m

1

2

 Eq. [3] 

where:  F m  Standard deviation of F m . 

To arrive at a single calculated effluent flow rate, each of the individual flows ( F m ) was used in 

Eq. [4] (Equation 4 of the EPA Protocol). This equation calculates a variance weighted average 

of average effluent flow rates calculated using Eq. [2]. Results are presented as the total 

volumetric flow in the 8th column of Table 1. 





 M

F

M

F

m

g

m

m

F

F

1

2

1

2

1

ˆ





 Eq. [4] 

Where: Variance weighted average TVF for the standard tracer gas (g). 

M = Number of flow rates used per standard tracer gas (g). 

Fˆ

g 

ISMI Technology Transfer #10095115A-ENG 
14 

Finally, for each effluent flow rate calculated using Eq. [4], a standard error of the mean was 

calculated using Eq. [5] (Equation 5 of the EPA Protocol). To both simplify and provide the most 

conservative figure, n was taken to be constant and equal to the lowest n encountered in Eq. [2]. 

Again, this was strictly a measure of precision; it relates only to the mean and that 

Fg

 ˆ will often be lower than any of the F m . 

2

1

1

2

tan

2

1

ˆ 2

1 11 



















    















  

M

F

tconsn

m F

F

m m

g n  n 

 Eq. [5] 

Where:  Fg ˆ The standard error (uncertainty) of the mean (average) TVF (Table 1, column 9). 

Note that Eq. [2]–Eq. [5] were used identically on both the QMS and FTIR data independently. 

At no time were QMS data used with FTIR concentration data to determine TVF. Relative errors 

reported for the effluent flow in Table 1, column 10 are based on a 95% confidence interval. 

4.2 POU Abatement System Effluent Flow Determination by QMS Method 

The EPA Protocol (Section 2.2.6) and 2009 ISMI Guideline (Section A.1) were strictly followed 

for the QMS-based flow determinations. A neat gas standard of Kr was injected into the POU 

abatement system inlet at precisely known volumes. During Kr injections, QMS monitored Kr at 

the effluent sampling location. Krypton was not native to the system; it was assumed that 

injecting at the POU abatement system inlet would create a well mixed sample stream at the 

POU abatement system effluent. Four different tracer flows were injected at three different POU 

abatement systems. An outline of the tracer injection and sample extraction system is 

diagrammed in Figure 8. The TVFs, corresponding relative errors, and standard deviations from

the QMS Method tests are shown in Table 1. 

The QMS data for each set of injected Kr flows consisted of the final 40 Kr concentration 

measurements, which were used to calculate the effluent flow for each injected tracer flow. Note 

that one of the four injected tracer flows at the burn/wet abatement system #2 resulted in a 

calculated effluent flow that was inconsistent with the other three and was omitted from the TVF 

determination. The cause of this inconsistency is unknown. Since the EPA Protocol states a 

criterion of three tracer injections per effluent flow determination, the TVF of the burn/wet 

abatement system #2 still complies with the protocol. 

Another minor issue with the QMS sampling occurred in the calibration curve associated with 

the POU electric heat/wet abatement system #1 tests. The highest Kr concentration observed 

during the testing was outside the range of the QMS calibration curve. The average Kr 

concentration during the high flow tracer injection was ~30% greater than the highest 

concentration of the calibration curve for that day. The calibration curve is fit to a linear 

regression and was extrapolated to include this point. TVF and relative error calculations for this 

POU abatement system also included this data point. If this were removed, the TVF for the POU 

electric heat/wet abatement system #1 would not change significantly (0.47 lpm less or 0.1% 

RPD). 

The compilation of the effluent flows determined from each tracer injection was then used to 

calculate the TVF of each of the three POU abatement systems. Figure 9 through Figure 11 plot 

the total QMS data sets for each injected tracer flow at each POU abatement system. 

Technology Transfer #10095115A-ENG ISMI 
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-100

400

900

1400

1900

2400

2900

3400

18:40:19 18:43:12 18:46:05 18:48:58 18:51:50 18:54:43 18:57:36

Time (hh:mm:ss)

Kr Concentration (ppm)

Figure 9 QMS Kr Measurements at POU Burn/Wet Abatement System #1 

0

500

1000

1500

2000

2500

18:12:58 18:14:24 18:15:50 18:17:17 18:18:43 18:20:10 18:21:36 18:23:02 18:24:29 18:25:55 18:27:22 18:28:48

Time (hh:mm:ss)

Kr Concentration (ppm)

Figure 10 QMS Kr Measurements at POU Burn/Wet Abatement System #2 

ISMI Technology Transfer #10095115A-ENG 
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0

500

1000

1500

2000

2500

3000

3500

10:36:29 10:39:22 10:42:14 10:45:07 10:48:00 10:50:53 10:53:46 10:56:38

Time (hh:mm:ss)

Kr Concentration (ppm)

Figure 11 QMS Kr Measurements at POU Electric Heat/Wet Abatement System #1 

4.3 POU Abatement System Effluent Flow Determination by FTIR Method 

A controlled SF6 tracer release was used simultaneously with the FTIR concentration 

measurements to determine flow at each POU abatement system effluent. Sections A.2 and B.1.5 

of the 2009 ISMI Guideline were followed without deviation as they pertained to the testing. The 

SF6 tracer was not native to any of the processes/POU abatement systems used for this study. 

Three different flow rates of SF6 were injected into each system effluent ~1 foot above the POU 

abatement system housing. The injection system is depicted in Figure 8. For each POU 

abatement system, the sample gas was extracted from a port between eight and nine duct 

diameters downstream from the SF6 injection location. Before TVF measurements, a series of 

stratification tests was performed by monitoring the SF6 at various depths (25%, 50%, and 75%) 

into the duct to demonstrate homogeneity of the tracer/effluent gas. The results from the 

stratification tests, summarized in Table 2, are consistent in concentration at each point across 

the ducts, demonstrating homogeneity of the effluent and SF6 gases for each system. 

Table 2 Stratification Traverse Results 

POU Abatement 

System 

Traverse Position % 

into Duct SF6 Conc. (ppm) 

25 58.7 

Burn/Wet #1 50 60.8 

75 58.3 

25 57.5 

Burn/Wet #2 50 57.1 

75 61.2 

25 108.9 

Electric/Wet #1 50 107.5 

75 109.3 

Technology Transfer #10095115A-ENG ISMI 
17 

The low standard deviations in Table 1 show that the SF6 concentrations were extremely 

consistent throughout monitoring. Figure 12 through Figure 14 plot the FTIR SF6 concentration 

results for each of the injected flows into each POU abatement system effluent. 

The SF6 flow was set and controlled by the MFC, measured by the VFM, and injected across the 

POU abatement system effluent flow using a multi-point probe. All reported tracer gas flows in 

Table 1 were taken from the VFM, not the MFC, as the MFC was calibrated for nitrogen and was 

not as precise as the VFM. The repeatability of these experiments demonstrates that the FTIR 

method can produce accurate results and is applicable for measuring flows such as these. 

0

10

20

30

40

50

60

70

80

90

100

16:59:31 17:02:24 17:05:17 17:08:10 17:11:02 17:13:55 17:16:48 17:19:41 17:22:34 17:25:26 17:28:19

Time (mm:hh:ss)

S F6 C oncentration (pp

Figure 12 FTIR SF6 Measurements at POU Burn/Wet Abatement System #1 

ISMI Technology Transfer #10095115A-ENG 
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0

10

20

30

40

50

60

70

80

90

100

17:48:29 17:51:22 17:54:14 17:57:07 18:00:00 18:02:53 18:05:46 18:08:38

Time (hh:mm:ss)

SF6 Concentration (ppm)

Figure 13 FTIR SF6 Measurements at POU Burn/Wet Abatement System #2 

0

20

40

60

80

100

120

140

160

180

12:14:24 12:17:17 12:20:10 12:23:02 12:25:55 12:28:48 12:31:41 12:34:34 12:37:26

Time (hh:mm:ss)

SF6 Concentration (ppm)

Figure 14 FTIR SF6 Measurements at POU Electric Heat/Wet Abatement System #1 

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4.4 Comparative Analysis of Tracer Release QMS and FTIR Methods 

Table 1 compares measurements using the both QMS and FTIR tracer approaches. Each 

methodology collected concentration data sets at specific tracer gas injection rates that were then 

used to calculate POU abatement system effluent flow rates. For each of the three different POU 

abatement systems studied, the TVF determined by QMS and FTIR agreed favorably. The 

relative percent difference (RPD) in effluent flows determined by each methodology was 9.37% 

at burn/wet abatement system #1, 0.600% at burn/wet abatement system #2, and 1.52% at 

electric heat/wet abatement system #1. The remarkable consistency between the two 

methodologies suggests that either approach is acceptable for determining POU abatement 

system effluent flow. However, when analyzing the data scatter and error of each methodology, 

FTIR clearly provided much more stable and precise results. Comparison of the relative error (a 

report requirement of the EPA Protocol) shows a 5.1, 8.6, and 3.1 times improvement in FTIR 

over QMS data for the burn/wet abatement system #1, burn/wet abatement system #2, and 

electric heat/wet abatement system #1, respectively. In short, the relative error as calculated 

according to the EPA Protocol requirements is on average 5.6 times lower when using the FTIRbased approach. This is easily seen in Figure 15 for POU abatement system burn/wet #2; a plot 

of both the QMS and FTIR flows over the entirety of a 120-point test shows that although their 

TVFs agreed, the FTIR data had much less variability. 

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 12

Data Point

TVF (lpm)

0

QMS FTIR

Figure 15 TVF Determinations of QMS and FTIR Data (POU Burn/Wet Abatement 

System #2) 

ISMI Technology Transfer #10095115A-ENG 
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5 SUMMARY OF RESULTS AND CONCLUSIONS 

 The POU abatement system effluent flow rates as determined by FTIR and QMS were 

remarkably consistent with one another (9.37% RPD at burn/wet abatement system #1, 

0.600% RPD at burn/wet abatement system #2, and 1.52% RPD at electric heat/wet 

abatement system #1). 

 The determinations of POU abatement system effluent flow rates were stable and repeatable 

when determined using tracer release methods (Table 1). 

 The 2009 ISMI Guideline tracer release/FTIR monitoring approach to determine effluent 

flows resulted in a standard deviation and relative error that was on average 5.4 and 5.6 

times better than the QMS results, respectively. 

 The 2009 ISMI Guideline tracer release/FTIR monitoring approach provided a suitable 

alternative to performing mass spectroscopy measurements. However, the injected tracer gas 

must be well mixed at the extraction location. A simple multipoint stratification test can 

verify this. 

6 RECOMMENDATION 

Results indicate that the 2009 ISMI Guideline tracer release/FTIR monitoring approach should 

be included in the EPA Protocol as an acceptable method of determining POU abatement system 

effluent flow. However, a concentration stratification determination must be performed at 

various points (i.e., 25%, 50%, and 75%) across the effluent duct to ensure homogeneity between 

the tracer and native effluent. 

7 REFERENCES 

[1] EPA Version 1 (March, 2010), EPA 430-R-10-003, Protocol for Measuring Destruction or 

Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in 

Electronics Manufacturing, Office of Air and Radiation Office of Atmospheric Programs, 

Climate Change Division, U.S Environmental Protection Agency, Washington D.C. 

[2] International SEMATECH Manufacturing Initiative (2009). Guideline for Environmental 

Characterization of Semiconductor Process Equipment – Revision 2. Technology Transfer 

# 06124825B-ENG, December 9, 2009. 

Technology Transfer #10095115A-ENG ISMI 
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Appendix A – ISMI POU Abatement Device Volumetric Flow Rate Methodology 

Comparison Test Plan

A.1 Introduction 

ISMI will be conducting comparison testing at a wafer fab between two tracer-based 

methodologies for determining POU abatement device total outlet volumetric flow rate: 

 Using a non-reactive gas at POU abatement device outlet; and 

 Quadrupole mass spectroscopy (QMS) and noble gas method (using krypton) through 

POU abatement device. 

This comparison testing will provide data that is requested in the EPA's Protocol for Measuring 

Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gases Abatement 

Equipment in Electronics Manufacturing (Version 1) (EPA Protocol), Page 31: "While the Postabatement Flow Tracer Method is not permitted in the Protocol, EPA is interested in learning 

more, through in-fab testing, about the validity of this method." The testing will provide 

technical data for EPA to support addition of the volumetric flow determination methodology of 

utilizing non-reactive gas at POU abatement device outlet to next version of EPA protocol. The 

dates for this testing are Tuesday, July 27, 2010 and Wednesday, July 28, 2010, and will occur in 

the Phoenix, Arizona area. 

A.2 Testing Scope 

The testing will directly compare two methodologies for determining POU abatement device 

outlet volumetric flow rate using semiconductor production processes and POU abatement 

devices located at a wafer fab. The two methodologies for determining outlet volumetric flow 

rate are: 

 Injecting non-reactive gas (SF6) at POU abatement device outlet while utilizing realtime concentration FTIR measurements downstream of the injection location; and 

 Injecting krypton through POU abatement device while monitoring the POU abatement 

device outlet for krypton using QMS. 

This testing will be conducted in accordance with pertinent sections of the 2009 Guideline for 

Environmental Characterization of Semiconductor Equipment (ISMI Guideline) and EPA's 

Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse 

Gases Abatement Equipment in Electronics Manufacturing (Version 1) (EPA Protocol). Sherer 

Consulting Services, Inc. (SCS) will be the testing coordinator, working directly with ISMI, 

wafer fab, and testing company URS Corporation. EPA and their representatives are welcome 

and encouraged to attend this testing. Safety and additional subfab training will be provided for 

all personnel involved, as required by the wafer fab company. 

SCS will work with wafer fab personnel to ensure that site is prepared for testing. URS 

Corporation personnel will review testing locations when they arrive Monday morning (see later 

schedule). 

ISMI Technology Transfer #10095115A-ENG 
22 

It is planned at this time that the following three processes and corresponding POU abatement 

devices will be selected for the testing. 

 CVD process with POU thermal oxidation (using fuel)/wet scrubbing system (one 

inlet). 

 CVD process with POU thermal oxidation (using fuel)/wet scrubbing system (two 

inlets). 

 CVD process with POU electric heat oxidation/wet scrubbing system (two inlets). 

Two planned POU abatement devices will have two process inlets and one planned POU 

abatement device will have one process inlet. Each inlet will have volumetric flow rate 

determination conducted. The injection of krypton will be done into one of the two inlets for 

each two-inlet POU abatement device. This should allow for good mixing in POU abatement 

device and subsequent krypton measurement at outlet of POU abatement device. The same POU 

abatement device outlet location will be utilized for all QMS and FTIR measurements for 

volumetric flow rate determination; the QMS and FTIR measurements will not be performed 

simultaneously as each methodology should be conducted separately. 

Any deviation from methodologies stated in EPA Protocol and ISMI Guideline will be approved 

by SCS and URS Corporation before use. The testing will be conducted in series for each 

process/POU abatement device tandem as follows: 

1. Determine each POU abatement device total inlet volumetric flow rate using a chamber 

clean gas with the tool plasma off. 

2. QMS analysis of krypton through POU abatement device. 

3. FTIR analysis of SF6 tracer gas at POU abatement device outlet. 

Using SF6 tracer gas at POU abatement device outlet methodology is presented below from ISMI 

Guideline, with an addition of the upstream diameter from any exhaust lateral connection. This 

method will accurately flow SF6 into POU abatement device outlet at known volumetric flow 

rates using mass flow meter while measuring the SF6 concentration downstream (by FTIR). This 

methodology requires the following criteria to be utilized: 

 The POU abatement device outlet must be sampled to ensure that the non-reactive gas is 

not present. 

 SF6 must be injected across the POU abatement device outlet duct. This can be 

accomplished by using an injection probe with equally spaced holes. 

 The location selected for downstream non-reactive gas analysis must be at least eight 

duct diameters downstream from SF6 tracer gas injection location. In addition, this 

location will be at least two duct diameters upstream from an exhaust lateral connection. 

 The location selected for downstream SF6 tracer gas measurements must also be used 

for QMS and noble gas method measurements. 

 It is recommended that the downstream tracer gas analysis location duct be traversed 

with the sampling probe at a few locations to ensure the tracer gas is well mixed. For 

example, if the duct is 4 inches, the duct can be traversed in 1-inch increments (25%, 

50% and 75%) to prove that the concentration across the duct is uniform. 

Technology Transfer #10095115A-ENG ISMI 
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A.3 Proposed Schedule 

Monday: URS Corporation to arrive on-site for safety orientation, review testing locations, 

and set-up equipment at first testing location. 

Tuesday: EPA and their representatives arrive on-site by 7:30 AM for safety orientation. 

POU abatement flow rate comparison testing at first POU abatement device is 

scheduled to begin at 9:00 AM, and second POU abatement device at 2:00 PM. 

Move to third POU abatement device. 

Wednesday: POU abatement volumetric flow rate comparison testing at third POU abatement 

device at 9:00 AM; testing completed by noon. 

ISMI Technology Transfer #10095115A-ENG 
24 

Appendix B – Equipment Certifications 

Technology Transfer #10095115A-ENG ISMI 
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ISMI Technology Transfer #10095115A-ENG 
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Technology Transfer #10095115A-ENG ISMI 
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ISMI Technology Transfer #10095115A-ENG 
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Technology Transfer #10095115A-ENG ISMI 
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ISMI Technology Transfer #10095115A-ENG 
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Technology Transfer #10095115A-ENG ISMI 

International SEMATECH Manufacturing Initiative 

Technology Transfer 

2706 Montopolis Drive 

Austin, TX 78741 

http://ismi.sematech.org 

e-mail: info@sematech.org