### Comparison of Fourier Transform In frared (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 Manu facturing 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 tradem arks are the property of their respective owners.

### Comparison of Fourier Transform In frared (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 Internati onal 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, Qu adrupole Mass Spectroscopy

Authors : J. Michael Sherer, P.E., Sherer Consulting Servi ces, 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 Leaderiii

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 RESULT S AND DISCUSSION.............................................................12 4.1 Statistical Treatment of POU Abatem ent System Effluent Flow Rates........................13 4.2 POU Abatement System Effluent Flow Determination by QMS Method....................14 4.3 POU Abatement System Effluent Fl ow 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

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List of Figures

Figure 1 QMS Kr Calibration Used for Effl uent Flow Determinations of the POU Burn/Wet Systems ......................................................................................................6 Figure 2 QMS Kr Calibration Used for Effl uent Flow Determinations of the POU Electric Heat/Wet System...........................................................................................7 Figure 3 FTIR SF 6 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 SF 6 Measurements at POU Burn/Wet Abatement System #1.........................17 Figure 13 FTIR SF 6 Measurements at POU Burn/Wet Abatement System #2.........................18 Figure 14 FTIR SF 6 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

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ISMI Technology Transfer #10095115A-ENG Acknowledgments

The authors would like to acknowledge the assistan ce of the wafer fab personnel for use of their POU abatement systems , their support of the field tes ting, and coordination of the POU abatement system operations. In addition, thanks to Steve Trammell (project manager, ISMI ESH Technology Center) who coordi nated the project as well as as sisting in the field and Ron Remke (program manager, ISMI ESH Technol ogy 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 e ffort in schedule coordination, test ing assistance, equipment setup, and data review throughout the project. The authors would also like to recognize the c ontributions of Laurie B eau (project manager, ISMI ESH Technology Center) and Tom Huang (project manager, ISMI ESH Technology Center) for all of their effort s and their valuable insight.1

1 EXECUTIVE SUMMARY

Two m ethodologies for determining the total vol umetric 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 scrubb er (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 analytic al instrumentation. The two appr oaches to determine TVF were as follows:

 Injection of precise volume flow rates of sulfur hexafluoride (SF 6 ) at the POU abatement system effluent while ta king real-time measurements of SF 6 concentrations downstream of the injection point using Fourie r transform infrared (FTIR) spectroscopy.

 Injection of precise volume flow rates of krypton (Kr) in to the inlet of the POU abatement system while taking real-time meas urements of Kr concentration at the POU abatement system effluent using quadrupole mass spectroscopy (QMS). Determining TVF by QMS was performed accordi ng to the Environmental Protection Agency (EPA) Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Elec tronics Manufacturing, Version 1, March 2010 (EPA Protocol) [1] . Determining TVF by FTIR follo wed the Intern ational SEMATECH Manufacturing Initia tive’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 com parison 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 SF 6 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 th e MFCs and volumetric flow meters).

1.1 POU Abatement System Effl uent 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 m easurements ( 120 total data points) of a SF 6 tracer. The TVF for each system’s effluent was determined in triplicate by independ ently injecting three diffe rent controlled flow rates of SF 6 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 efflue nt sampling location was the same for both SF 6 tracer gas and Kr tracer gas studies.

Table 1 gives all the calculated flows in liters per m inute (lpm). As is evident from the comparison of flows, the TVFs determined by each methodology were consistent. However, both

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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 abatem ent 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 we re stable and repeatable when determined by tracer release methods ( Table 1 ).

 The tracer release/FTIR monitoring approach in the 2009 IS MI Guideline to determine POU abatement effluent flows resulted in a standa rd deviation and relative error that was, on average, 5.4 and 5.6 times better th an 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 de monstrate that the injected tracer gas is well mixed at the extraction location. This can be don e with a simple multipoint stratification test.

1.3 Recommendation

The 2009 ISMI Guideline tracer re lease/FTIR monitoring approach should be included in the EPA Protocol as an acceptable m ethod for dete rmining 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 homoge neity between the tracer and native effluent.

2 INTRODUCTION

To m inimize climate change, new and more st ringent 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 in stalled to mitigate ultimate GHG emissions. Very little quantitative information is availa ble 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 unde r increased scrutiny by regulatory agencies worldwide, the U.S. Environmental Protection Ag ency published a protocol for the destruction or removal efficiency (DRE) of POU abatement system s. An integral part of this protocol is the measurement of dilution across POU abatement sy stems, for which accurate determinations of the effluent flow rate are paramount. Si nce many POU abatement systems incorporate combustion/oxidation gases and purge gases, the process gases entering the abatement system become diluted. According to the EPA Protoc ol, both POU abatement system influent and effluent flows must be measure d. Historically, the small diameter ducts of these systems, the many bends and flow disturbances associated with the ducts, a nd the general inaccessibilityTable 1 Comparative Results for QMS and FTIR POUAbatement System Effluent Flow DeterminationsTracer Injection Flow RatesLocationMethodologyInfluent KrFlow (cc/min)Effluent SF6Flow (cc/min)40-Point Avg.MeasuredConc. (ppm)CalculatedFlow(lpm)Std. Dev.of Calc.Flow (lpm)TotalVolumetricFlow (lpm)Std. Dev.of TotalFlow (lpm)RelativeError (%)200—2887271701020—153367787.81500—232565895.7QMS586—86568680.46797.642.25—22.331.071916.6—43.758.175318.6Burn/WetAbatementSystem #1FTIR—64.282.977519.47461.650.441100—1609696102570—80172284.1QMS11530—3027112137119.832.77—22.132.667910.1—43.760.072812.4Burn/WetAbatementSystem #2FTIR—64.185.575017.57071.130.321030—239843657.8730—163545250.5395—89844652.2QMS224—55341045.54344.031.85—23.152.544015.7—45.4103440.214ElectricHeat/WetAbatementSystem #1FTIR—67.915344314.54411.340.611An 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 upset within the abatementor sampling systems.Note: Shaded columns are TVF and error as calculated according to EPA Protocol equations.ISMI TechnologyTransfer#10095115A-ENG34

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 iner t gas is injected and concentrations are measured of the injection location. The EPA Protocol currently desi gnates that QMS be used to m onitor 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 sta nd to benefit from using a single analytical instrument to determine both concentration and fl ow. 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 Guid eline, FTIR determination of ef fluent flow also incorporates the use of a tracer gas release. The main differenc e in how tracer releases are used in the two methodologies is the FTIR tracer is injected into the effluent ups tream of the sample extraction location whereas in the QMS approach it is inject ed into the POU abatement system inlet. The concern with using the approach incorporating e ffluent 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 Austi n, 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 sc rubbing (burn/wet) system s and a single electric heat oxidation/wet scrubbing (el ectric heat/wet) system. The te sting 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 (SF 6 ) was selected as the tracer for the FTIR-based concentration measurements. Both tr acer gases are inert and not native to the gas matrices of the processes/POU abatement systems tested.

3 EXPERIMENTAL SETUP

The EPA Pr otocol [1] , 2009 ISMI Guideline [2] , and accepted sample test plan ( Appendix A ) were followed for this study.

3.1 QMS-based Approach

 On-site QM S calibrations for Kr were performed before testing each day. The first day’s calibration consisted of a zero and five differen t 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 R 2 values for each were > 0.99.

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 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 differ ent 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

 Ef fluent emissions were initiall y analyzed to verify that SF 6 was not native to the process/POU abatement system gas matrix.

 A reference curve consisting of zero and three different referenc es was generated and fit to a linear regression. All observed SF 6 concentrations fell within th is calibration curve, and all FTIR references and sample spectra were collected at the same spectral parameters (resolution, apodization, zer o filling, etc.). Any slight pre ssure and temperature differences between the sample and reference spectra were accounted for during sample quantification.

 A neat standard of SF 6 tracer gas was injected across the POU abatement system effluent duct using a multi-hole probe to maximize mixing.

 A sample extraction location wa s selected at a minimum of eight duct diameters downstream of the tracer injection location.

 A concentration stratification test wa s performed by FTIR monitoring of SF 6 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 SF 6 flow rates were injected into th e effluent gas stream. FTIR spectra were collected every 3 sec; the final 40 spectra (p er injected tracer flow rate) were quantified and used to determine effluent flows and subsequent statistics. Note that the same POU abatement system ef fluent location was used for QMS and FTIR
measurements.

3.3 Analytical Instrumentation

3.3.1 QMS Traditionally, m ass spectrometers have been used as analytic instruments under vacuum applications. Recent advancements in the te chnology 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 it s 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 controll ed rates through a precision or ifice. The QMS can then scan over various AMU ranges or a selected few. The most sensitive Kr response was observed at

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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 ov er all the mass units depend on the ionizer’s chamber pressure, energy, etc., a careful calibra tion was performed on-site consistent with the configuration used for all sampling. Krypton ca libration 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 in terface and calibration curves generated. Figure 1 and Figure 2 correspond to the calibrations on 7/27/10 for the two POU burn/wet system s and 7/28/10 for the POU electric/wet system, respect ively. The linear regr ession equations both resulted in R 2 values greater than 0.98 as required by the EPA Protocol and were used to calculate all Kr concentrations. Sample was c ontinuously 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 th e cell a single time. Anti-reflective zinc selenide windows transmitt ed the IR beam with minimal signal loss. A continuous flow of sample gas was delivered thro ugh 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 phot oconductive device that pr oduces an electrical voltage proportional to the amount of infrared ra diation that strikes it . The strength of the absorption at particular frequencies is a meas ure 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 3000Kr Level (ppm)

% m/e = 83 ppm = 3794.81X – 149.43
R = 0.99936

Figure 1 QMS Kr Calibration Used for E ffluent Flow Determinations of the POU Burn/Wet Systems

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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 = 0.99435Kr Level (ppm)

% m/e = 83

Figure 2 QMS Kr Calibration Used for E ffluent Flow Determinations of the POU Electric Heat/Wet System

3.3.2 FTIR Spectrometer The FTIR sample cell was m aintained at room temperature (~23°C) throughout the testing. Instrumental resoluti on was set to 0.5 cm -1 , and signal was averaged ove r 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 EP A Protocol equations. Figure 3 displays the FTIR calibration curve for SF 6 used for all the qualitative analysis during sampling. The reference curve consists of a zer o and three different references that were generated before testing and f it to a linear regression. The co-efficients (also shown in Figure 3 ) generated from this calibration curv e were used in subsequent SF 6 quantitative analysis during sampling. All observed SF 6 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 a nd 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 frequenc ies in a set of test spectra. Linearity was optimized before shipment a nd verified just before testing.

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Figure 3 FTIR SF 6 Linear Calibration Curve

 Spectral Background A spectral background is essentia lly 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 we re generated before each of the three POU abatement systems was tested.

 SF 6 Challenge To ensure the accuracy of the FTIR concen tration measurements, a one-time challenge was performed. A certifi ed standard of SF 6 was directly injected into the FTIR analysis cell and quantified. The standard was certified at 21.9 ppm; a SF 6 concentration of 22.0 ppm was observed during the challeng e. The consistency of the results demonstrates that the FTIR was accurately quantifying SF 6 .

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3.3.3 POU Abatement Systems Monitored

The com parative tests were performed at three different POU abatement systems. All had two stages of abatement. The first two systems test ed 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 th is study for both FTIR and QMS systems. Figure 5 to Figure 7 are photographs of the effluent ducts and sam ple locations for the three POU abatements systems. The QMS and FTIR measurements were not performed simultaneously since the same extraction locat ion 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 SF 6 injection location. Sample was extracted from each effluent by a probe positioned in the ce nter of the duct. The sample then was pulled through unheated, 1⁄4-inch perfluoroalkoxy copolym er (PFA) tubing at ~ 5 lpm using Venturi pumps. While the QMS differentially pumped a s lipstream 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 thr ough the system during testing. Afte r 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

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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

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Figure 7 Sample Location of POU El ectric Heat/Wet Abatement System #1

3.3.5 Tracer Injection System The injec tion system for the QM S-based approach, depicted in Figure 8 , consisted of a neat Kr standard, a 0–5000 sccm MFC, 1⁄4-inch Teflon tubi ng, and a volumetric flow meter (VFM). The injection system for the FTIR approach was identical except that SF 6 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 stab ilize flow through the calibrated VFM, precise amounts of SF 6 were injected through the multi-holed pr obe 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 SF 6 injection port was located ~1 foot downstream of the POU abatement system exit but well ups tream of the effluent sample port.

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0.5 L MFC POU Effluent Flow

POU System ~ 1" Volumetric Flow Meter

SF 6 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 m onitored the POU abatement system effluent ga s for a Kr tracer that was injected into the POU abatement system influent. Krypton is iner t and passes through the POU abatement system unabated. Monitoring was performed in strict accordance with the EPA Protocol. FTIR monitored the effluent downs tream of the controlled SF 6 tracer release. The sample extraction point was a minimum of eight duc t diameters downstream of the tracer injection. Monitoring was performed in strict accordan ce with the 2009 ISMI Guideline [2]

. Table 1 compares the results of these two methods.

Tracer release-based flo w measurements were perf ormed by injecting a controlled flow of inert gas, SF 6 and Kr, at the POU abatement system efflue nt and influent, respectively. By measuring the diluted tracer concentrations, the effluent flows can be determined using the following equation from the EPA Pr otocol (Equation 1) [1]

,

6 10*  
ef f C S F Eq. [1]

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

f = Tracer gas flow into the sample duct C

ef

= Measured concentration of the tracer gas

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This technique is describe d in both the EPA Protocol [1] and the 2009 ISMI Guideline [2] . The only difference is that the 2009 ISMI Guideline also allows this m ethod to be used to measure POU abatement system effluent flows (Secti on B.1.5) by injecting th e tracer into the POU effluent once it has been verified that the effl uent 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 th rough 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 Abatem ent Syste m Effluent Flow Rates Equation 1 applies to individual c oncentration measurements. The SF 6 and Kr concentrations reported in Table 1 (column 5) are simple averages usi ng the last 40 data points corresponding to each in jected 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 th e 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 i th data point using  i F Eq. [1]

.

 m F Simple average of TVF for the m th injected tracer gas flow rate. Number of concentration measurements taken while at the m th constant tracer gas flow rate.  n

Once the av erage effluent flow was determined using Eq. [2] , a standard deviation for the mth injected tracer gas flow rate was determ ined using Eq. [3] (Equation 3 of the EPA Protocol). This is a m easure of the stability and precisi on of the sampling system (column 7). 

#   

   n

i m i F FF
n i

m 1 2  Eq. [3]

where: 

m F  Standard deviation of m F

.

To arrive at a single calculated effluent flow rate , each of the individual flows ( m F ) was used in Eq. [4] (Equation 4 of the EPA Protocol). This eq uation calcu lates a variance weighted average of average effluent flow rates calculated using Eq. [2] . Results are presented as the total volum etric flow in the 8 th column of Table 1

.



#  

 M

F M

F m

g

m m F

F

1 2 1 2

1 ˆ

  Eq. [4]

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

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

 g F ˆ

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Finally, for each effluent flow rate calculated using Eq. [4] , a standard error of the mean was calcu lated using Eq. [5] (Equation 5 of the EPA Protocol). To both sim plify 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 m easure of precisi on; it relates only to the mean and that

g F ˆ  will often be lower than any of the

m F 

.

2 1

1 2 tan 2 1

2 ˆ 11 1 

         

  

        

 

#   M

F tconsn

F m F

m m g n n    Eq. [5]

Where: 

g F 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 tim e were QMS data used with FTIR concentr ation data to determin e 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 Fl ow Determination by QMS Method The EPA Protocol (Section 2.2.6) and 2009 ISMI Gu ideline (Section A.1) were strictly followed for the QMS-based flow determinations. A neat ga s standard of Kr was injected into the POU abatement system inlet at precisely known volum es. 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 w ould create a well mixed sample stream at the POU abatement system effluent. Four different tr acer 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 sta ndard deviations from the QMS Method tests are shown in Table 1

. The QMS data for each set of injected Kr flow s consisted of the final 40 Kr concentration

m easurements, which were used to calculate the e ffluent flow for each inje cted 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 th is inconsistency is unknown. Sin ce 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 occurr ed in the calibration curve associated with the POU electric heat/wet abatement system #1 te sts. 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 inje ction 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 poin t. If this were removed, the TVF for the POU electric heat/wet abatement system #1 would not change signif icantly (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 th e three POU abatement systems. Figure 9 through Figure 11 plot the to tal QMS data sets for each injected tracer flow at each POU abatement system.

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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

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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 PO U Electric Heat/Wet Abatement System #1

4.3 POU Abatement System Effluent Fl ow Determination by FTIR Method

A controlled SF 6 tracer release was used simultaneous ly with the FTIR concentration measurements to determine flow at each POU ab atement system effluent. Sections A.2 and B.1.5 of the 2009 ISMI Guideline were followed without de viation as they pertained to the testing. The SF 6 tracer was not native to any of the processe s/POU abatement systems used for this study. Three different flow rates of SF 6 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 abatem ent system, the sample gas was extract ed from a port between eight and nine duct diameters downstream from the SF 6 injection location. Before TV F measurements, a series of stratification tests was performed by monitoring the SF 6 at various depths (25%, 50%, and 75%) into the duct to demonstrate homogeneity of th e tracer/effluent gas. The results from the stratification tests, summarized in Table 2 , are consistent in concentration at each point across the ducts, demonstrating hom oge neity of the effluent and SF 6 gases for each system.

Table 2 Stratification Traverse Results

POU Abatement System Traverse Position % into Duct SF 6 Conc. (ppm)

25 58.7
50 60.8 Burn/Wet #1

75 58.3
25 57.5
50 57.1 Burn/Wet #2

75 61.2
25 108.9
50 107.5 Electric/Wet #1

75 109.3

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The low standard deviations in Table 1 show that the SF 6 concentrations were extremely consistent throughout monitoring. Figure 12 through Figure 14 plot the FTIR SF 6 concentration results for each of the injected flows into each POU abatement system effluent.

The SF 6 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 calib rated for nitrogen and was not as precise as the VFM. The repeatability of these experiments demons trates that the FTIR method can produce accurate results and is app licable 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 F6C oncentration (pp

Figure 12 FTIR SF 6 Measurements at POU Burn /Wet Abatement System #1

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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)SF6Concentration (ppm)

Figure 13 FTIR SF 6 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 SF 6 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

m ethodology collected concentration da ta 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 determin ed by QMS and FTIR agreed favorably. The relative percent difference (RPD ) in effluent flows determin ed 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. Th e remarkable consistency between the two methodologies suggests that either approach is acceptable for determining POU abatement system effluent flow. However, when analyzi ng the data scatter and error of each methodology, FTIR clearly provided much more stable and preci se results. Comparison of the relative error (a report requirement of the EPA Pr otocol) 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, th e 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 th at although their TVFs agreed, the FTIR data had m uch less variability.

400 600 800 1000 1200 1400 1600

0 20 40 60 80 100 12

Data PointTVF (lpm)

0 QMS FTIR

Figure 15 TVF Determinations of QMS a nd FTIR Data (POU Burn/Wet Abatement System #2)

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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 effl uent flow rates were stable and repeatable when determined using tracer release methods ( Table 1 ).

 The 2009 ISMI Guideline tracer release/FTIR monitoring appro ach 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 ma ss spectroscopy measurements. Howe ver, 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 tr acer release/FTIR monitoring approach should be included in the EPA Protocol as an accepta ble method of determining POU abatement system effluent flow. However, a concentration stratif ication determination must be performed at various points (i.e., 25%, 50%, and 75%) across th e 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 O ffice of Atmospheric Programs, Climate Change Division, U.S Environmen tal Protection Agency, Washington D.C. [2] International SEMATECH Manuf acturing Initiative (2009). Guideline for Environmental Characterization of Semiconductor Process Equipment – Revision 2 . Technology Transfer # 06124825B-ENG, December 9, 2009.

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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 volum etric flow rate:

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

 Quadrupole mass spectroscopy (QMS) and nobl e 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 comp are two methodologies for determining POU abatement device outlet volumetric flow rate using semiconduc tor production processes and POU abatement devices located at a wafer fab. The two met hodologies for determining outlet volumetric flow
rate are:

 Injecting non-reactive gas (SF 6 ) at POU abatement device outlet while utilizing realtime concentration FTIR measurements downs tream of the injection location; and

 Injecting krypton through POU abatement de vice while monitoring the POU abatement device outlet for krypton using QMS. This testing will be conducted in accordance with pertinent sec tions of the 2009 Guideline for Environmental Characterization of Semiconduc tor Equipment (ISMI Gu ideline) and EPA's Protocol for Measuring Destru ction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gases Abatement Equipment in Electronics Manuf acturing (Version 1) (EPA Protocol). Sherer Consulting Services, Inc. (SCS) will be the testing coordinator, working directly with ISMI, wafer fab, and testing company URS Corporatio n. 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 ensu re that site is prepared for testing. URS Corporation personnel will review testing locations when they arrive Monday morning (see later schedule).

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It is planned at this time that the following three processe s 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 electr ic heat oxidation/wet scrubb ing 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 s hould allow for good mixing in POU abatement device and subsequent krypton measurement at ou tlet of POU abatement device. The same POU abatement device outlet location will be utili zed 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 Protoc ol and ISMI Guide line will be approved by SCS and URS Corporation before use. The te sting will be conducted in series for each process/POU abatement device tandem as follows:

1. Determine each POU abatement device total in let 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 SF 6 tracer gas at POU abatement device outlet. Using SF 6 tracer gas at POU abatement device outle t methodology is presented below from ISMI Guideline, with an addition of the upstream diam eter from any exhaust la teral connection. This method will accurately flow SF 6 into POU abatement device outlet at known volumetric flow rates using mass flow mete r while measuring the SF 6 concentration downstream (by FTIR). This methodology requires the following criteria to be utilized:

 The POU abatement device outlet must be samp led to ensure that the non-reactive gas is not present.

 SF 6 must be injected across the POU abat ement device outlet duct. This can be accomplished by using an injection probe with equally spaced holes.

 The location selected for downstream non-reactiv e gas analysis must be at least eight duct diameters downstream from SF 6 tracer gas injection location. In addition, this location will be at least two duct diameters ups tream from an exhaus t lateral connection.

 The location selected for downstream SF 6 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 conc entration across the duct is uniform.

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A.3 Proposed Schedule Monday: URS Corporation to arrive on-site for safety orientation, re view 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 test ing at first POU abatement device is scheduled to begin at 9:00 AM, and s econd 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.

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Appendix B – Equipment Certifications

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Technology Transfer #10095115A-ENG ISMIInternational SEMATECH Manufacturing Initiative Technology Transfer 2706 Montopolis Drive Austin, TX 78741
http://ismi.sematech.org e-mail: info@sematech.org