# Version 1

Protocol for Measuring Destruction or Removal Efficiency (DRE) of

Fluorinated Greenhouse Gas Abatement Equipment in Electronics Manufacturing

March 2010

Office of Air and Radiation Office of Atmospheric Programs, Climate Change Division

EPA 430-R-10-003Table of Contents

List of Tables

............................................................................................................................... .. 3 List of Figures

............................................................................................................................... . 3

PREFACE

............................................................................................................................... ....... 4

1. INTRODUCTION .................................................................................................................... 5

1.1 Protocol Purpose ........................................................................................................... 6

1.2 Protocol Objectives ....................................................................................................... 7

1.3 Protocol Scope ............................................................................................................... 7

1.4 Development of the Protocol ........................................................................................ 8

1.5 Expected Results ........................................................................................................... 8 2. MEASUREMENT PLAN, PREPARAT ION, METHODOLOGY, AND DATA

ANALYSIS

............................................................................................................................... ..... 8

2.1 Prepare Measurement Plan ......................................................................................... 8

2.1.1 Description of Ex perimental System ................................................................... 9

2.1.2 Sampling Configuration ....................................................................................... 9

2.1.3 Required Resources .............................................................................................. 9

2.1.4 Measurement Schedule ....................................................................................... 10

2.1.5 Safety .................................................................................................................... 10

2.1.6 Quality Assurance/Quality Control ................................................................... 11

2.2 Measurement Methodology ........................................................................................ 11

2.2.1 Method 1—Dilution Adjusted Concentration Measurement ......................... 12

2.2.2 Method 2—Total Volume Measurement .......................................................... 12

2.2.3 Equipment Needed .............................................................................................. 13

2.2.4 FTIR and QMS Protocols .................................................................................. 14

2.2.5 Calibration Curves .............................................................................................. 14

2.2.6 Flow and Dilution Measurements ...................................................................... 16

2.2.7 F-GHG Measurements ....................................................................................... 17

2.3 Data Treatment and Analysis .................................................................................... 18

2.3.1 Abatement System Dilution ............................................................................... 19

2.3.1.1 Total Volume Flow ........................................................................................... 19

2.3.1.2 Dilution Factor ................................................................................................. 21

2.3.2 Abatement System DRE Estimate and Relative Errors .................................. 22

2.3.2.1 Method 1—Dilution Adjusted Concentration Measurements ..................... 22

2.3.2.1.1 Concentration Measurements ......................................................................... 22

2.3.2.1.2 DRE ................................................................................................................... 23

2.3.2.2 Method 2—Total Volume Measurements ...................................................... 24

2.3.2.2.1 Total Volume Measurements .......................................................................... 24

2.3.2.2.2 DRE ................................................................................................................... 24

3. BENCHMARK RELATIVE ERROR ................................................................................. 25

3.1 Method 1—Dilution Adjusted Concentration Measurements ................................ 25

3.2 Method 2—Total Volume Measurements ................................................................. 25

4. DOCUMENTATION AND REPORTING .......................................................................... 26

5. REFERENCES ....................................................................................................................... 28

2Appendix A – History of and Revisions to the Protocol .......................................................... 30 Appendix B – Sample Calculation ............................................................................................. 32

List of Tables

Table 1. Measurement Study Equipment Needs.......................................................................... 14 Table 2. Acceptable Gases for Monitori ng Total Abatement System Flows .............................. 17 Table 3. Minimum detection levels (C MDL ) and threshold F-GHG concentrations (C * ) for measuring relative error of total fraction emitted when sample C < C * ....................................... 18

List of Figures

Figure 1. Sampling Schematic for Single and Multiple Chamber Inlet Flow(s) ........................ 10 Figure 2. Sample Calibration Curve ............................................................................................ 16

3PREFACE

The U. S. Environmental Protection Agency (EPA) in itiated preparation of th is Protocol as part

of its commitment to assist the PFC Emi ssions Reduction/Climate Partnership for the Semiconductor Industry (the Partnership) to achieve its voluntary fluorinatedgreenhouse gas (FGHG) emission reduction and reporting goals. F- GHGs include the most powerful and often persistent greenhouse gases such as perfluoroc arbons (PFCs), hydrofluorocarbons (HFCs), sulfur hexafluoride (SF 6 ), and nitrogen trifluoride (NF 3 ). The Partnership’ s reduction goal is to decrease F-GHG emissions to 10 percent belo w the 1995 base-year amounts by 2010. Several FGHG-reducing options are available, with reduc tion-efficiencies ranging from 10 to 99 percent or higher. Practical reduction strategies comprise modify ing manufacturing processes— optimizing processes and switching to alternative gases with lower emissi ons potential—as well as installing point-of-use (POU) F-GHG abatement systems. Detailed methods for measuring FGHG emissions from manufacturing processes were standardized in 1999 and are documented and continually updated in the i ndustry’s International Semiconduc tor Manufacturing Initiative (ISMI) Guidelines. Standard methods for measur ing and documenting the destruction or removal efficiencies (DREs) from POU abatement syst ems have lagged those for measuring process emissions. One objective of this document (the Protocol) is to align measurement of emissions from manufacturing processes with those from abatement systems.

The Protocol builds on three DRE measurement studies of POU F-GHG thermal abatement systems conducted onsite at three U. S. semico nductor manufacturing fac ilities, each a member of the Partnership. Air Products performed and documented the measurements under subcontract to ICF International, who was contracted by EP A to support development of the Protocol. In total, four abatement systems were tested and all were connected to plasma-enhanced chemical vapor deposition (PECVD) or etch process equipment. During the studies, DRE measurements were made with the plasma on (during wafer pro cessing) and with the plasma off. A key feature of these measurement studies was development a nd testing of a reliable method for measuring the dilution of F-GHGs during abatement.

This is the third version of the Protocol. It reflects two rounds of external reviews, one each for the first and second version. The first version, pr epared after measurements were made at two facilities, was circulated to Semiconductor Indu stry Association (SIA), Japan Electronics and Information Technology Industries Association (JEITA), and Taiwan’s Industrial Technology Research Institute (ITRI) as well as to abat ement manufacturers and industry consultants experienced in measuring the DRE of F-GHG ab atement systems. The comments and responses

to those comments were documented and discusse d with reviewers. This discussion led to the third and latest onsite measurement study, as well as to a second version of the Protocol. The second version of the Protocol was again circulat ed to a subset of the reviewers to the first version. The comments and responses to those comments were also documented and discussed

with reviewers.

A consistent theme that emerged from EPA’s tes ting and all the reviews of the Protocol is the diversity of manufacturing pract ices and conditions across the el ectronics manufacturing sector. Therefore experienced and resourceful metrologist s are central to successful DRE measurements. This Protocol is aimed for use by experienced metrologists—experienced not only in the use of

4advanced analytical measurement systems such as FTIR and QMS, but also in performing in-fab measurements of F-GHG emissions. Moreover, the Protocol does not constitute a recipe—a single approach for all circum stances—for making DRE in-fab measurements. Instead, properly construed, the Protocol permits flexibility in measurement practice provided the measurements achieve the performance standard that is integral to this Protocol

1. INTRODUCTION

Members of the U.S. Environmental Protection Agency’s PFC Emissions Reduction/Climate Partnership for the Semiconductor Industry (t he Partnership) operate under a voluntary agreement to reduce perfluorocompound (PFC, hen ceforth called fluorinated greenhouse gas, FGHG) emissions to 10 percent below the 1995 ba se-year amounts by 2010. A variety of practical F-GHG-reducing options—with reduction-efficiencies that range from 10 to >99 percent—are available. These options include process optimi zation techniques, switchi ng to alternative gases with lower emissions potentials, and point-of- use (POU) F-GHG abatement. While there are industry-standard guidelines th at set forth methods for measuring and documenting process emissions (ISMI, 2006), that is not so for measur ing the destruction-removal efficiencies (DRE) of POU F-GHG abatement systems, although published reports of DRE measurement studies are available (Beu et al., 1994; Li et al., 2001, 2002 and 2004; Lee et al., 2007).

The U.S. Environmental Protection Agency (EPA) initiated preparation of this document (the Protocol) as part of its commitment to assist the Partnership in ach ieving the F-GHG emission reduction and reporting goals. The development of this Protocol builds on three DRE

measurement studies of POU F-GHG abatemen t systems conducted onsite at three U.S.

semiconductor fabrication facilitie s (fabrication facilities are he nceforth called fabs). (EPA 2008a, 2008b, and 2009)

51.1 Protocol Purpose

The purpose of the Protocol is to provide a prac tical and reliable method for measuring DREs of POU abatement systems of F-GHG gases used during the manufacture of electronics products, specifically semiconductor systems, micro-elect ro-mechanical systems (MEMS), thin film transistor (TFT) arrays and amorphous silicon (a-Si) and tandem amorphous silicon/ nanocrystaline silicon (a-Si/nc-Si) thin-film phot ovoltaic (PV) panels. 1

The Protocol sets forth two sp ecific methods for measuring abat ement system inlet and outlet flows, and hence DREs, for single or multi-ch amber process tools. These methods address measuring the mass or volume flows of F-GHGs entering and leaving the abatement system.

Both methods account for the dilution that occurs in thermal abatement systems. 2

The first and simplest, Method 1 - Dilution Ad justed Concentration Measurement, involvesmeasuring DRE when the process tool is off. This approach will produce reliable results when FGHG byproducts are not formed, for exam ple, during chamber cleaning with CF 4 , SF 6 or with

NF 3 when carbon films are not present. A variat ion of Method 1 may be used that imitate byproducts formation. This involves taking approp riate steps to add proper amounts of byproduct F-GHG to the influent abatement-sy stem flow of unutilized F-GHG(s).

The second method, Method 2 – Total Volume Flow Measurement, is the preferred method for measuring DRE when byproducts are formed. Met hod 2 measures abatement-system DRE under actual process conditions. One of two appro aches may be used when applying Method 2, dependent upon if measurements are bei ng taken sequentially or simultaneously.

Method 2, requires introducing a chemically stable material – a tracer or spiking agent that neither affects the performance of nor is aff ected by the abatement system—into the process line(s). Using this method will provide a reliable estimate of the effective dilution associated with in-fab thermal POU abatement systems 3 and, in turn, the DREs. This chemical-spiking approach is a special applic ation of ASTM E 2029 – 99 (Re- approved 2004), which provides a method for measuring volumetric or mass flow rate of a gas in a duct, pipe, etc. using a tracer dilution technique (ASTM, 2004). ASTM E 2029-99, lik e this Protocol, addr esses irregular and

non-uniform flow conditions wher e conventional pitot tube or thermal anemometer velocity measurements are difficult or inappropriate due to the absence of a suitable run of duct/pipe upstream and downstream of the measurement location.

Establishing DREs based on this Protocol wi ll (a) assure reliable comparisons of vendors’ abatement systems; (b) assure third-parties of the reliability of reported emissions; (c) improve understanding of appropriate and ne cessary system maintenance; a nd (d) serve as a starting point

1 The electronics manufacturing sector includes, but is not lim ited to those industry sub-sectors that are listed. This Protocol is applicable to all elect ronics sectors; but it was developed based on work at a semiconductor manufacturing facilities. However EPA sees no limitation on why the Protocol may not be applied when measuring

DREs at other electronics manufacturing facilities.

2 Testing for the development of the Protocol focused on POU thermal ab atement systems because dilution is greatest. It is expected the Kr tracer method is suited to POU plasma systems. However, EPA was not aware of fully operational plasma abatement sy stems in production fabs at the time of the Protocol’s publication.

3 See footnote 2.

6for emerging carbon trading opportunities (i.e ., measuring baseline and actual emission reductions). 4

1.2 Protocol Objectives

The objectives of the Protocol are to specify:

• a method for measuring and reporting F- GHG-specific DREs of installed, in-fab abatement systems that are operating during normal production processing;

• a method for measuring and reporting F-GHG-sp ecific DREs of abatement systems that

are offered to manufacturers of electroni c products that use F-GHGs during product manufacturing; and

• guidance to fab Environmental Safety &Health staff and to providers of POU abatementtesting services on best-pract ice procedures for measuring, documenting and reporting of in-fab determinations of F-GHG abatement system DREs.

1.3 Protocol Scope

The Protocol is applicable to measuring and reporting DREs of installed POU systems whose input flows may contain CF 4 , CHF 3 , CH 2 F 2 , C 2 F 6 , C 3 F 6 , C 3 F 8 , C 4 F 6 , c-C 4 F 8 , C 4 F 8 O, C 5 F 8 , NF 3 and SF 6 . These high-GWP gases may be used dire ctly in fab processes and, in some circumstances, may be formed during those processes.

The Protocol is intended to complement the guidance prepared by International SEMATECH Technology Transfer # 06124825A-ENG (December 2006); this Protocol adopts in its entirety Appendix A of SEMATECH TT # 06124825A-ENG (December 2006), which explains best known methods for measuring, among other things , F-GHG emissions. The principal difference between the 2006 updated SEMATECH guidance and this Protocol is the em phasis given here to POU abatement system DRE measurement and to measuring dilution across the abatement

system.

The Protocol institutes two practi ces to establish the veracity of reported results. The first is adoption of a benchmark metric together with a performance standard for that metric. The benchmark metric is the relative error, which is a precision metric, in th e reported true fraction emitted of which the DRE is its complement. The performance standard the relative error must meet is ±5 percent relative error. 5

, 6 The second practice is the requirement for metrologist

4 The Executive Board of the Clean Development Mechanism has final authority for approving methods for measuring emissions of greenhouse gases, for purposes of establishing a CDM project. However, CDM does not have authority in the United States..

5 The fraction emitted is chosen as th e performance metric rather than the DRE because the relative error of the

measured DRE is a function of the true fraction emitte d. As the true fraction emitted approaches one (DRE approaching zero), the relative error becomes very large even when the relative error in the true fraction is acceptably small. Similarly, when the tr ue fraction approaches zero (DRE appro aches one), the relative error in DRE can become small even when the relative error in the true fraction emitted is large. When the post-abatement concentration approaches or falls below minimum detecti on an alternative calculation is provided (vide infra).

6 Experience demonstrates that ±5 percent or better is r eadily achievable in a fab environment. In three separate studies (EPA 2008a, 2008b, and 2009), the estimated rela tive error for the true fraction emitted for four POU

7certification, certifying that the methods set forth in the Protocol were followed, including that

the conditions under which the measurements were made (with the plasma off or actual process conditions).

EPA wishes to strike an appropr iate balance between assuring reli able results and flexibility. In the remainder of the Protocol, where EPA anticipates the need for flexibility it has provided examples to demonstrate the nature and extent of the permitted flexibility. EPA will consider updating the Protocol given the availability of and access to additional testing experiences and

well-documented results.

1.4 Development of the Protocol

The Protocol has gone through five stages of development: conceptu alization, onsite tests, initial drafting, and two informal peer review processe s. During the informal peer review processes

EPA received comments from both national and in ternational parties, including semiconductor manufacturers, equipment manufacturers, gas supp liers and analytic serv ice providers. Appendix A discusses some of these comments, as well if and how the Protocol was revised to reflect

them.

1.5 Expected Results

This Protocol results in an estimate for th e DRE of F-GHG abatement systems, where the relative error of true fraction emitted estimate (the benchmark metric), measured under in-fab production processing circumstances and typical (in-fab, as-installed) POU system operating circumstances, is less than ±5 percent (the perfor mance standard). The value of relative error of the true fraction emitted is determined by the met hods outlined in the remainder of this Protocol.

2. MEASUREMENT PLAN, PREPARAT ION, METHODOLOGY, AND DATA

ANALYSIS

2.1 Prepare Measurement Plan

A measurement plan serves two main purposes. First, it provides b ackground on the tools, processes, and abatement systems to be tested ; and second, it facilita tes coordination between facility personnel and testing service providers. An understanding of the tools, processes, and abatement systems provides testing service pr oviders with background on the experimental system in preparation for the study. Coordination with facility personnel reduces the likelihood of encountering unexpected problems of m easurement execution during the study. Testing service providers should prepare a measurement pl an and submit it to facility personnel at least two weeks prior to the measurement study. At a minimum, the measurement plan should contain detailed descriptions of the experimental syst em, the sampling configuration, required/expected

systems attached to either etch or CVD process tools was below ±3 percent. Adoption of ±5 percent as a performance standard assures the accuracy of the measured true fraction emitte d will be ±5 percent or better, under the reasonable assumptions that the acc uracy of calibration gases and mass flow controllers are each ±3 percent or

better.

8resources/support from the fab, a measuremen t schedule, address safety and a quality control/quality assurance plan (QA/QC) as descri bed in the following sect ions. In preparing the plan, attention to Appendix A of the 2006 ISMI Guid elines is essential to assuring best in-fab FTIR and QMS measuremen t practice is achieved.

2.1.1 Description of Experimental System

An understanding of the tools, pro cesses, and abatement systems to be tested prepares the testing service provider for the onsite measurement study. For example, the experimental system setup informs the study’s sampling configuration, whereas the expected dilu tion, flows, and DRE inform the type of analytical tools for data treatm ent needed for the study. To ensure that testing service providers are adequately prepared fo r conducting onsite measurements, information on the following aspects of the expe rimental system should be incl uded in the measurement plan:

• Description of the process tool and abatement system;

• Configuration of the process tool and abatement system;

• Presence of vacuum pump pur ges and additional purges;

• Process operating conditions;

• Measurement conditions (i.e., plasma off or actual process conditions);

• Gases/flow rates (when measuring with the plasma off) and/or process recipe (when measuring during actu al conditions);

• Number of process chambers served by abatement system;

• Nominal abatement system reactor temperature;

• Nominal abatement system exhaust flows;

• Nominal process exhaust flows;

• Nominal dilution factor (Note: Nominal dilution factor is defined as the ratio of the nominal abatement system exhaust flow to the nominal process exhaust flow); and

• Nominal DRE(s) for F-GHG(s) being tested.

2.1.2 Sampling Configuration

An example schematic of the sampling configurat ion, which illustrates th e configuration of the process tool and abatement system, should be de veloped by testing servic e providers prior to onsite measurements. In the schematic the planned/proposed sampling and measurement layout in relation to the process tool and abatement systems, the process tool and abatement system effluent sampling locations, and the type of sampling port (e.g., tie-in type) should be clearly labeled (see Figure 1).

2.1.3 Required Resources

One of the primary purposes of the measurement pl an is to facilitate coordination between the testing service providers and the facility pers onnel. The plan should include a sufficiently detailed description of all resources needed from the facility incl uding sampling ports and fittings, gas supplies, electrical outlets, and assistance of f acility personnel including roles, responsibility, and an anticipated schedule. Advance preparation by facility personnel is essential for maximizing the utility of testing service providers’ time at the facility.

9Figure 1. Sampling Schematic for Single and Mu ltiple Chamber Inlet Flow(s) Source: EPA, 2009. Note: Metrologists need to be mindful of recirculation issues when returning the sampled gas flows

to exhaust lines.

2.1.4 Measurement Schedule

In order to minimize any interference with f acility production, a measurement schedule should be agreed upon prior to conducti ng the onsite study. The measur ement schedule should clearly indicate the sampling start and e nd times. Additionally, the tool operator should approve and be familiar with the measurement plan and experimental system including the process tools/chambers and abatement systems, the pro cess conditions during sampling (i.e., plasma off versus actual process conditions), and the gas flow rates/process reci pe to be supplied to the tool.

2.1.5 Safety

Safety of the measurement study pa rticipants is of highest prior ity. Prior to conducting any work onsite, testing service providers will be instructed by a ppropriate fab personnel about all pertinent safety requirements and practices. For example, appropriate personal protective equipment (PPE) should be worn while conducti ng measurements in a fabrication environment (e.g., head protection, hearing protection, eye pr otection, and foot protection). Additionally, testing service providers are responsible for acquain ting themselves with the hazards that exist in the IC fabrication environment (e.g., hazardous ga ses, chemical spills, and heavy objects) and taking all steps to avoid adverse impacts. Specia l consideration should be given to the benefits and risks of mixing pyrophoric/flammable and oxi dizing gases. Most abatement systems are

10designed to prevent such mixing prior to combustion and measurem ent methodologies that defeat manfuacturers’ design goal s hould be thoroughly considered.

2.1.6 Quality Assurance/Quality Control

In preparation for the measurement study, testing service providers should gather information on the experimental system and its e xpected characteristics, such as expected reactor temperature, exhaust flows, etc (see Section 2.1.1). This information serves as a check to ensure the experimental system is functioning as expected. Testing service provider s should also be aware of any leaks or instrument malfunctioning that could nullify results of the study.

2.2 Measurement Methodology

This Protocol describes tw o methodologies for obtaining DRE measurements: Method 1 (Dilution Adjusted Concentration Measurement), wh ich is performed with the plasma off, and Method 2 (Total Volume Measurement), which measures emissions during actual production processing conditions. Two approaches may be followed when using Method 2 to measure the DRE: Sequential Single-Chamber Process Inlet Abatement System Flow Sampling (SSPISF) or Multi-Chamber Process Inlet Abatement System Flow Sampling (MPISF). Proper application of these methods (or approaches) will ensure that th e DRE measured has a relative error below ±5 percent. The relative error of the estimated true fraction emitted provides one benchmark for assessing the quality of the sampling methodology, a nd is the metric used in this Protocol to determine the acceptability of the DRE measurem ent methodology. If the relative error of the true fraction emitted is less than ±5 percent at one standard deviation the methodology used is in accordance with the best practi ces defined in this Protoc ol via Methods 1 and 2.

Whether Method 1 or Method 2 (SSPISF or MPI SF) is most applicable depends on several considerations, including the experimental system to be tested, measuremen t study objectives, and safety (cf., Sec. 2.1.5). All named methods and approaches require similar sampling and analytical methodologies, which are described in detail in this sect ion of the Protocol. Where the methods and approaches differ is Method 1 require s sampling when the process tool is off while Method 2 (SSPISF or MPISF) requires sampling under normal process conditions. The differences in sampling conditions lead to differences in data analysis and DRE calculations for Methods 1 and 2. Using alternate methodologies to the ones described here is acceptable, as long as the relative error in the true fraction emitted measurement is less than ±5 percent. If an alternate methodology is used, the bu rden falls on the testing servic e provider to demonstrate that the relative error requirement (±5 percent) is met, to provide detailed descriptions of the methodology used, and to provide the a ppropriate supporting data analysis.

In instances when concentrations exiting the ab atement system are below FTIR detection limits a modification of the performance metric is re quired. Because the concentrations exiting the abatement system cannot be measured in these instances, a predefined F-GHG concentration is used (which exceeds the lower lim it of FTIR detection) to demonstrate proper measurement. To calculate the performance metric, the relative error of that concentration is used, with the result compared to the performance standard of ±5 percent.

11Methodologies and approaches described in this Protocol make extensive use of Fourier Transform Infrared (FTIR) Spectroscopy and Qu adrupole Mass Spectrometry (QMS) techniques. Testing service providers are directed to the guidance prepared by International SEMATECH Technology Transfer #0612485A-ENG for detailed desc riptions for best practice FTIR and QMS Protocols (December, 2006). 7

2.2.1 Method 1—Dilution Adjusted Concentration Measurement

In Method 1, the process tool plasma (RF) is o ff while data are collected, so DRE measurement is made with the F-GHG and diluent gases enteri ng the abatement system. An advantage of Method 1 lies in controlling the flow rates of the F-GHGs measured, resulting in steady-state conditions, which make the subsequent data anal ysis and DRE calculations simpler than dealing with non-steady state flows. However, when th e process tool is off, by-product gas DRE's will not be measured, requiring modi fication of the process tool setup to imitate by-product gas flows. Method 2 overcomes this difficulty and is, therefore, preferred.

When using Method 1, F-GHG flows entering the abatement system should be 120 percent of the F-GHG flows entering the abatement system duri ng normal production processing to ensure the abatement tool is being tested under conditions that may occur during processing. For example, if the process flow for an F-GHG, f, is x s ccms during production processing (which corresponds to y g/sec) and the correspondi ng default utilization is U f , then the flow entering the abatement system during testing should be 1.2 * y * (1-U f ) g/sec of gas f. In a circumstance when byproducts are formed, the sum of the imitated emissions of the F-GHG and byproduct gas(es) should equal 120 percent of the value obtained using the appropriate IPCC 2006 default emission factors (Volume 3, Table 6.3).

2.2.2 Method 2—Total Volume Measurement

Method 2 involves collecting data during actu al process conditions. Method 2 requires no modifications to the process tool for either process or byproduct gas DRE measurements. However, collecting data duri ng actual process conditions may not result in steady-state conditions, making the data analysis and DRE cal culations more involved than Method 1 (see

section 2.3 for detailed discussion of data anal ysis). Sampling to measure total F-GHG volume flow leaving the process tool and the abat ement system may be accomplished through two approaches, which are applicable to process t ools with single or multiple process chambers (reference Fig. 1).

One approach consists of sequentially measuring the F- GHG volume flow entering the abatement system from each chamber while also measuring the corresponding F-GHG volume flow leaving the abatement system. This samp ling approach is called the Sequential SingleChamber Process Inlet Abatement System Flow (SSPISF) method. The second sampling approach consists of simultaneously measuring th e volume flow from all operating chambers that

7 See Appendix A – Technical Protocols of Air Emissions Characterization of SEMATECH Technology Transfer #0612485A-ENG (December 2006). This Append ix augments EPA Test Method 320, Measurement of Vapor Phase Organic and Inorganic Emissions by Extractive Fourier Transform Infrared (FTIR) Spectroscopy , as it might apply to measuring F-GHG emissions in waste streams produced during electronic device manufacture

12is entering the abatement system while also measuring the corres ponding F-GHG volume flow exiting the abatement system. This second sa mpling approach is ca lled the Multi-chamber Process Inlet Abatement System Flow (MPISF) method. Both approaches employ sampling during actual process conditions. The SSPISF method uses a slip-str eam of the effluent from a single process chamber as its sample and the MP ISF method uses multiple slip-streams of the effluent (one for each operating chamber with e ach representing the appropriate proportion of the total process flow from all operating chambers) that are then mixed to account for actual process conditions. Sampling to measure the total F-GHG volume flow entering the abatement system may be accomplished using the MPISF method provi ded appropriate safety precautions are taken when mixing the flows of combustible gases.

2.2.3 Equipment Needed

Two FTIRs are optimal for measuring F-GHG co ncentrations in the effluent streams. 8 One FTIR is used to sample from the process effluent a nd another to sample from the abatement system effluent. Additionally, a QMS, inert gas supply, and mass flow controller (MFC) are needed to measure the dilution that occurs through the abatement system. When measuring DREs in systems that do not abate CF 4 and/or SF 6 , it is possible to measure dilution using an FTIR instead of a QMS/MFC/inert gas supply system. When a tr acer other than a noble gas is used, such as

CF 4 or SF 6 , the metrologist should provide documentati on demonstrating that less than 5 percent of the tracer gas is destroyed. Fo r purposes of testing using such tr acers, the tracer gas is treated as undestroyed. Two examples of an acceptable dem onstration are: (1) the manufacturer of the POU abatement system provides results, based on th e methods of this Protocol, that the DRE of the chemical tracer is <5 percen t under the operating c onditions being tested at the fab using the QMS and the noble gas tracer methodology or (2) in-f ab tests showing <5 percent destruction of the chemical tracer on a POU abatement sy stem (based on the QMS and noble gas tracer methodology of this Protocol for one abatement sy stem in the fab) may be used on abatement system in the facility of the same make and m odel installed and operated in the same manner as the abatement system tested.

Metal bellows sampling pumps should be instal led after each FTIR and/or QMS to collect effluent samples. Installing adju stable flow rate valves to co ntrol the sample flow rates and capacitance manometers to monitor the sample li ne pressure are recommended. A sample filter should be used in the abatement system sampling line to prevent particulate emissions from the abatement system from damaging the FTIR or QMS. Lastly, when sampling using the MPISF method, mass flow controllers (MFCs) are needed—one for each operating chamber during sampling—to create a representatively proportional slip stream composition of the total flow. Table 1 provides a summary of the equipment required and Figure 1 shows a sample schematic of the experimental setup.

8 One FTIR can be used, but it would be necessary to a lternate abatement system inlet and outlet measurements. Steady-state behavior would have to be verified by sampling for a sufficiently long period of time. It must be shown that sufficient precision can be achieved with just one FTIR system. Using one FTIR will require knowing with confidence what the abatement system load ing is. If sufficient inlet data is acquired to accomplish this, and then the FTIR is switched to the outlet of the abatement system and the same process is run on the tool then the Protocol will work just as well as using two FTIRs. The emission factors for a particular process run on the same chamber are usually reproducible. Sufficient data can be collected to achieve the desired precision.

13Table 1. Measurement Study Equipment Needs a Equipment Type Quantity Required

FTIR QMS Inert gas supply/mass flow controller (MFC) Metal bellows sampling pumps Adjustable flow rate valves Capacitance manometers Sample filter 1-2 b

0-1

0-1

2-3

2-3

2-3

1-2

MFC for exhaust streams No. of chambers tested

. a Not exhaustive

b When using 1 FTIR, it must have variable path length

2.2.4 FTIR and QMS Protocols

FTIR measurements should be taken following th e best practice guidelin es specified in the guidance prepared by Inte rnational SEMATECH Tec hnology Transfer #0612485A-ENG (December, 2006). 9 The FTIR should be operated at a resolution of 0.5 cm -1 or 1.0 cm -1

, provided that calibrations match resolution us ed during sampling. The sampling frequency for

the FTIR should be less than 3 seconds. 10 The FTIR absorbance range should be between 0.1 and 1.0; however, lower and higher absorbencies may be used provided sample data are bracketed by

calibration data. Alternate short- and long-path gas cells should be used, to ensure that the measured absorbance for process effluent con centrations and abatement system effluent

concentrations falls with in the range 0.1 to 1.

QMS measurements should be taken following th e best practice guidelin es specified in the guidance prepared by Inte rnational SEMATECH Tec hnology Transfer #0612485A-ENG (December, 2006). 11 To account for fluctuations/drift in QMS sensitivity, the ion signals should be normalized to the signal obtai ned for the nitrogen fragment N + , which is formed during

ionization of N 2

.

2.2.5 Calibration Curves

9 See Appendix A.2 – Fourier Transform Infrared (FTIR) Spectroscopy Protocol of SEMATECH Technology Transfer #0612485A-ENG (December 2006).

10 In the tests EPA performed, 4 FTIR scans were co-added for one data point, which takes 2.2 secs at 0.5 cm -1
resolution and provides adequate temporal resolution to follow time-varying process emissions. Thus, each data point requires 2.2 sec, so 40 data points requires approximately 1.5 minutes.

11 See Appendix A.1 – Mass Spectrometry Protocol of SEMATECH Technology Transfer #0612485A-ENG (December 2006).

14The Protocol permits either onsite or offsite ca libration for FTIR measur ements of F-GHGs, with both governed by the guidance provided in A ppendix A.2 of SEMATECH Technology Transfer (December 2006). In either circumstance, the ra nge in absorbance for the calibration curves should bracket the corresponding abso rbance range for the onsite measured concentrations, with a preferable range for the absorbance between 0.1 and 1. In situations where the onsite measured absorbance lies outside the 0.1 to 1 range, either (a) a calibration must be available at the high or low absorbance, (b) an alternative absorption band should be used that lies, for that specific molecule, within the 0.1 – 1 absorbance, or (c ) an alternate FTIR ga s cell should be used. 12
Further, while the measured absorbance of large molecules, like the F-GHGs of concern here, is not expected to be sensitive to reasonable differences in resolution (say, 0.5 vs. 1

cm -1 ), this concern is mitigated by requiring the use of the same resolution for calibration sampling.

For onsite calibration, the metrologist must repor t/show the calibration gr aphs and report the corresponding calibration and measurement conditions for all F-GHGs measured. The measurement conditions to report are gas temper ature and pressure, as well as the FTIR resolution used during sampling and calibra tion. When reported DREs employ offsite calibration, the metrologist must report/show ca libration graphs as well as the conditions (temperature, pressure and resolution) used for calibration and during onsite sampling. If calibration and onsite temperatures , pressures or both differ then corrections must be made to account for the change in gas number density. These corrections are often standard features of modern FTIR software packages. The calibration cu rves for both onsite and offsite testing should be generated using at least thr ee calibration points such that expected measured absorbance range is covered. Quality of calibration may be judged by proximity of R 2 to 1.00. For non-linear calibration curve, it’s important that highest observed concentra tion is within not outside the range of concentrations used to define the ca libration curve.

Prior to conducting measurements of the proces s and abatement system effluents, onsite QMS calibration should be completed for all compounds to be measured. The calibration curves should be generated using at least 1 zero and 5 non-zero data points. The recommended ion intensity range for the QMS should be within one decade. Calibration plots with the signal intensity versus compound concentration data points and the line of best f it should be included in the measurement report. Additiona lly, the slope, the relative erro r of the slope (one standard deviation), the y-intercept, and the correlation coefficient (i.e., R 2 ) of the correlation line should be presented and each parameter clearly labeled (see Figure 2 as an example).

To ensure that the ±5 percent benchmark relative error is achi eved, all calibration curves should meet the following criteria:

• Slope must have an error below ±5 percent; and

• Correlation coefficient must exceed 0.98

12 Some FTIR quantitative analysis software packages (e.g. AutoQuant Pro used by Midac Corporation) has the ability to shift to different absorbance peaks over several or ders of magnitude depending on the concentration of the material being measured. In this case, multiple gas cells may not be required. However, that shifting to another peak may risk influence of interferent that also absorbs at that same wave number. Using multi-path cells is best practice for this FTIR application.

15Figure 2. Sample Calibration Curve The R 2 and relative error of the slope for both calibration curves shown are >±99 percent and <±1 percent, respectively. Source: EPA, 2008a and 2008b.

2.2.6 Flow and Dilution Measurements

Determining dilution across the abatement system is a two step process. The first step is determining the total volume flow of the process effluent, and th e second step is determining the total volume flow of the abatement system effluent . The total volume flow of the process effluent can be estimated by flowing know n quantities (flows) of F-GHG through the tool with the RF turned off, while a FTIR system measures the F-GHG concentration of the process effluent. The total volume flow of the abatement system effluent can be estimated by supplying known quantities of inert gas into the process stream effluent, while a QMS system measures the inert gas concentration in the abatement system efflue nt. Controlled volume flows of inert gas can be supplied to the process effluent using a mass flow controller (MFC). When measuring DREs in systems that do not abate CF 4 and/or SF 6 it is possible to measure total abatement system flow using an FTIR instead of a QMS. In such systems CF 4 or SF 6 can be used in place of an inert gas since their DREs are zero percent. Table 2 provid es a list of acceptable gases for measuring total abatement system flows, along with their use conditions.

16Table 2. Acceptable Gases for Monito ring Total Abatement System Flows

Tracer Gas Analytical Equipment Limitations

Kr QMS None

Xe QMS May be used in some etch processes recipes.

Ar QMS Must subtract out air concentration background; cannot use if Argon is used

as a process gas.
CF 4 FTIR DRE must be zero

SF 6 FTIR DRE must be zero

To ensure that the ±5 percen t relative error is met, the fo llowing conditions should be met:

• Accuracy of calibration gases in the concentration of th e inert gas supplied to the process effluent stream shoul d be ±3 percent or less.

• 3-5 different flow rates should be supplie d to the process tool and/or abatement system, and at least 40 distinct measurements made for estimating the average

concentration at each flow rate.

• Appropriately sized MFC such that accuracy of lowest flow is ±3 percent or better

2.2.7 F-GHG Measurements

The Protocol suggests that using two FTIRs is optimal. 13 One FTIR is used to measure F-GHG concentration in the process effluent and a nother to measure F-GHG concentration in the abatement system effluent. The concentration of F-GHGs in both effluent streams should be recorded, as well as the gases/flow rates and/or process recipes that are fed into the process tool. Absorption bands should be chosen to minimize th e influence of interfer ing substances and to

hold absorbance within the range 0.1 to 1.

To ensure that the ±5 percent relative error is achieved, the fo llowing conditions should be met:

• Method 1: For each process gas tested, 3-5 di fferent flow rates should be supplied to the process tool, and at least 40 proce ss tools and abatement system effluent concentration measurements averaged for each flow rate.

• Method 2 (SSPISF and MPSIF): For each process gas tested, 3-5 data points should

be collected for total volume in and total volume out of the abatement system and at least 40 process tools and abatement system effluent concentration measurements averaged for each flow rate.

When the concentration exiting the abatement sy stem approaches or falls below the minimum detectable level the metrologist can demons trate proper measurement practice by introducing into the sampling stream a flow of that gas such that its concentration entering the abatement is

low but exceeds the minimum detection leve l. This concentration is denoted as C * . To

13 See footnote 8.

17demonstrate proper measurement of C * , the relative error of the C * measurement is used in place

of C

o (the exit concentration) to calculate th e performance metric. The precision of C * is

estimated with data from the FTIR used to measure the F-GHG exiting the abatement system.

Table 3 sets forth C * , in units of ppm-m, for the gases governed by this Protocol. Table 3 identifies the minimum detection (concentration) levels for the gases of interest at standard temperature and pressure (STP), defined as a signal to noise of 3 for a HgCdTe liquid nitrogen cooled detection, 0.5 cm -1 resolution. A single value for C * was chosen for simplicity. It is evident from comparison of the second and third column that, for the selected C * , the signal to noise ratio (S/N) w ill be much greater than 3 so the prec ision should be high. Further, for the typical long-path used in such tests, the C * concentration being sa mpled should correspond to DREs in the range 95-99%.

Table 3. Minimum detection levels (C MDL ) and threshold F-GHG concentrations (C * ) for measuring relative error of total fraction emitted when sample C < C * , ppm-m

F-GHG Typical C MDL , ppm-m C * , ppm-m Primary absorbtion band, cm -1

CF 4 0.12 10 1280

CHF 3 0.40 10 1150

C 2 F 6 0.21 10 1250

C 3 F 8 0.2 10 1150

c-C 4 F 8 0.7 10 965

NF 3 1.1 10 910

SF 6 0.1 10 943

Note: C MDL values based on calibration data using path lengths between 10 cm and 5 m,

resolution of 0.5 cm -1 , gases at STP, HgCdTe liquid c ooled detector and a S/N of 3 10 -3

absorbance units.

Of the several ways for preparing a sample stream with concentration C * , two that are acceptable

are described here. The first is to ask the process tool operator to provide a sufficiently low flow of gas such that after d ilution by the pump purge, C * is achieved at the sampling point ahead of the abatement system. For example, if the target concentration, C * , is 2 ppm and the pump purge is 50 lpm (determined previously), then 50 ppm is achieved with a process flow of C of 0.1 sccm. For process tools with MFCs that cannot de liver sufficiently low flows, the sampled slip stream can be diluted with nitrogen using either a separate MFC or need le valve. The actual concentration sampled may be within ±20 percent of C * , i.e., ±0.4 ppm in the example (vide supra).

A second approach for preparing C * is for the metrologist to have available a gas cylinder with the appropriate concentration to introduce ahead of the abatement system, which, accounting for the pump purge flow, will produce C * ±20 percent of the value ta ken from Table 3. The first approach may be preferable because it doesn’t requi re the availability of additional gas cylinders of the appropriate concentrations.

2.3 Data Treatment and Analysis

18The procedures for treating flow and concentrat ion measurements as well as calculating total flows, dilution factor and DRE of the abatement system are described in this section. Also described are the methods for consistently esti mating the precision associated with measuring gas concentrations, flows, dilution factors a nd DREs. The data treatment and analysis component consists of two sections. The first se ction addresses data used to calculate bestestimate values for flows and the abatement system dilution factor as well as their standard

deviations. The second section a ddresses the data used to ca lculate best-estimate of the abatement system DRE and associat ed relative errors, using either Method 1 or Method 2. In the following sections absolute error is referred to as σ and relative error is referred to as ε , and all relative and absolute errors are pr esented at 1 standard deviation.

When an alternative methodology, such as the Physical Flow Measurement method, to the two

described in this Protocol is used to estimate DRE, the data treatment and analysis procedure described below may not be applicable. In su ch cases, the testing service provider should determine and use the appropriate procedures to calculate both the DRE and its corresponding

error.

2.3.1 Abatement System Dilution

2.3.1.1 Total Volume Flow

Total volume flow (TVF) is the to tal volume of gas that flows acro ss a process tool or abatement system, and is generally measured in standard li ters per minute (slm). For both Methods 1 and 2, measurements of TVF entering and exiting th e abatement system are needed. TVF or 

### F is calculated using Equation 1:

6 10

− × =

ef f

C S F (1)

where,



### F = total volume flow based on a sing le concentration data point [slm]

f 

### S = spike gas flow into the proce ss tool/abatement system [slm]

ef 

### C = measured concentration of standard gas in the process tool/abate ment system effluent

[ppmv]

To ensure that the e rror of TVF is low enough to meet th e relative error requirement of ±5 percent, TVF measurements should be collected during at least thr ee different standard gas flow rates. During each gas flow rate, at least 40 concentration measurements (FTIR or QMS scans) should be collected at the effluent side of the pr ocess tool/abatement system. For example, when measuring the TVF exiting the proce ss tool, a process gas such as C 2 F 6 should be fed into the process tool at multiple flow rates (e.g., 0.2, 0.6, and 1.0 slm), and during each flow rate, a minimum of 40 concentration data points of th e process effluent shoul d be collected using a FTIR. Similarly, when measuring the TVF exiting th e abatement system, an inert gas such as Kr should be spiked into the abatement system at multiple flow rates (e.g., 0.010, 0.030, and 0.050

19slm), and during each flow rate a minimum of 60 c oncentration data points of the inert gas in the abatement effluent should be measured using a QMS.

The measurements above will result in at leas t 120 TVF data points, which will need to be

averaged appropriately. A simple average, denoted as 

### F determines the average TVF and corresponding standard deviation during each flow rate applied, de noted by subscript m (see Equation 2 and Equation 3).

m F =

1 n i 

### F

n 

# ∑ (2)

where,

m F = simple average of TVF [slm] for the m th flow

n = number of concentration measurements taken while at a constant standard gas flow (e.g., 40 concentration data points collected du ring a 0.2 slm standard gas flow rate)

mF 

### σ 

# ( ) ∑

− = n

m i FF

n 1 2 1 (3)

The TVF simple average (

m F ) only applies to values that are collected during the same standard gas flow rate. Therefore, if three different stan dard gas flow rates are collected, three different simple averages must be derived.

When combining the multiple TVF simple average (

m F ) values for each flow rate into a single

average TVF, a variance weighted average must be applied (denoted as 

### F ˆ ). The equations for determining the variance weighted average and its corresponding standard deviation, are shown in Equations 4 and 5.

ˆ

g F = 2

1

2

1 1 m

m M

m

F

M

F F

σ

σ 

## ∑

∑ (4)

where,

ˆ

g F = variance weighted average TVF [slm] for flow standard gas, g

M = number of flow rates used per standard gas, g



### =

g F ˆ 

### σ 2 1

1 2 

### 11 − 

### ⎟ ⎟
⎠ ⎞
⎜ ⎜
⎝ ⎛

× 

# ∑ M

F m 

### n σ (5)

20where,

n = number of concentration measurements

The variance weighted TVF average ( 

### F ˆ ) can only be calculated using average TVF values ( 

### F ) obtained using the same standard gas. For exam ple, if two different standard gases are used, then a variance weighted average is calculated for each standard gas.

Equation 5 assumes that the number of concentration measurements during each flow rate is constant (i.e., is the same for each simple average). If varies for each simple average, then Equation 5 must be altered to account fo r variations in n. Alternatively, when varies, the

lowest can be used in Equation 5 to generate a c onservative estimate of the standard deviation (i.e., the standard deviation will err on the larger side). n n

n

n

In the case when multiple standard gases (e.g., Kr and Xe for abatement system or C 2 F 6 and CF 4 for process tool) are used to calculate TV F, then the variance weighted average ( ˆ

g F ) for each

gas, g, can be combined to determine a TVF best estimate (denoted as F ) and its corresponding error as shown below (see Equations 6 and 7).



## ∑ ∑

= G

F G

F g

g g F

F

1 2

ˆ 1 2

ˆ

1 ˆ

σ σ (6)

where,

F = Best estimate for TVF [slm]

G = number of standard gases used to determine TVF

2 1

1 2

ˆ 1 −
⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

= 

## ∑ G

F F

g σ σ (7)

The absolute errors or standard devia tions obtained from equations 3, 5 and 7 measure the precision of each standard gas flow for each gas, for all flows for each gas, and for all gases, respectively, when more than one gas is used (e .g., if Xe and Kr were both used). The overall accuracy is determined by the accuracy of the calibration, calibration standard gas concentrations, and mass flow controller. In orde r to obtain a DRE relative error of less than ±5 percent, the concentration standard gas should have a relative error of less than 3 percent of the designated concentration, and the accuracy of the MFC should be less th an 3 percent for the lowest flow rate used during the measurements.

2.3.1.2 Dilution Factor

21The dilution factor describes the total volumet ric dilution that occurs across an abatement

system. The dilution factor is determined by calculating the best estimate for TVF into ( in 

### F )

and out of the abatement system ( out 

### F ). (See Section 2.3.1 for determining the best estimate for TVF). The TVF exiting the abatement system divided by the TVF entering the abatement system defines the dilution factor as shown in E quation 8. The standard de viation or precision of the dilution factor is determined by the standa rd deviation of each TVF measurement, and is estimated using error propagati on techniques (See Equation 9).

D F

in out



### F F

= (8)

where,

D F = Best estimate for dilu tion factor [dimensionless]

out 

### F = Best estimate for TVF exiting abatement system [slm]

in 

### F = Best estimate for TVF entering the abatement system [slm]

)(

DF ε 2 2

⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

+ ⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

=

in F

out F

FF in out σσ (9)

where,

ε D F = The relative error of D F (the standard deviation di vided by the mean value)

out F 

### σ = The standard deviation of out 

### F [slm] (see Equation 7)

in F 

### σ = The standard deviation of in 

### F [slm] (see Equation 7)

.3.2 2 Abatement System DRE Estimate and Relative Errors

The formulas for calculating DRE depend on the method used. For Method 1, the ratio of the

measured effluent concentration to measured influent concentration is multiplied by the measured dilution factor (i.e., dilution adjusted concentration fraction, whic h equals the mass- or volume-emitted fraction). For Method 2, the ratio of effluent to influent gas volumes is used (i.e., volume fraction); the affect of d ilution is accounted for when calculating total flows. For either method it can be shown that, for the formulas given below, the calculated DRE is a bestestimate, i.e., statistically unbias ed. The subscripts 1 and 2 diffe rentiate formulas for Method 1

nd 2, respectively. a

.3.2.1 2 Method 1—Dilution Adjusted Concentration Measurements

2.3.2.1. 1 Concentration Measurements

22During Method 1, the concentration of process gas entering and exiting the abatement system is monitored, while the process tool is off, and whil e a known flow rate of process gas is fed into the abatement system. For each flow rate, the concentration of process gas in the abatement influent and effluent is in steady state. For each process gas at least three different process gas

flow rates should be used to coll ect a minimum of 60 concentration data points per flow rate, to

ensure relative error is achieve d. As described in section 2.2, an FTIR should be used to monitor concentration of process gases, and the FTIR s absorbance signal should be converted to a concentration using a calibration curve. The relative error of each concentration data points measured by the FTIR is equal to rela tive error of the calibration curve slope. 14 Using the concentration data points, the variance we ighted average and corresponding error for concentration can be estimated using a procedure analogous to that shown for total volume flow (see Section 2.3.1.1; Equations 1 to 5). The variance weighted aver age is considered the best

estimate for F-GHG concentration enteri ng and exiting the abatement system.

2.3.2.1.2 DRE

1 

### DRE 

# ( )

percent C DFC

in out 100 1 × ⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

×

−= (10)

where,

1 

### DRE = Best estimate for Destruction and Removal Efficiency [percent]

out 

### C = Best estimate for concentration of F-GHG exiting the abatement system [ppm]

in 

### C = Best estimate for concen tration of F-GHG entering th e abatement system [ppm]



# ( ) DF DF DRE

C C

λ λ

ε

− = 1 )( 1 2 2
⎟ ⎟
⎠ ⎞
⎜ ⎜
⎝ ⎛

+ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

DF DF

C C σ

λ σ λ (11)

where,

in out

C 

### C C

= λ

)( C λ ε 2 2

⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

+ ⎟ ⎟

⎠ ⎞

⎜ ⎜

⎝ ⎛

=

in C

out C

C C in out σ σ

c λ σ = The standard deviation of λ

c

DF σ = The standard deviation of DF

14 The relative error of the calibration curv e slope should not exceed ±5 percent (a t one standard deviation) to ensure the Protocol benchmark error of ±5 percent is obtained.

23o

out C 

### σ = The standard deviation of

ut [ppm] 

### C

in C 

### σ = The standard deviation of in 

### C [ppm]

2.3.2.2 M ethod 2—Total Volume Measur ements

ady

tal ess, the best estimate and error of the total olume measurement is equal to the simple av erage and its standard deviation, which are

tions 2 and 3 in Section 2.3.1.1.

2.3.2.2.2 DRE 2.3.2.2.1 Total Volume Measurements

When measuring the DRE using Method 2, the concen tration of the gas in the abatement influent and effluent is monitored while the process tool is on, and cannot be assumed to be at ste state. Therefore, the total vol ume of process gas entering and ex iting the abatement system must be estimated by integrating the FTIR signal over time (The absorbance signal should be converted to concentration using the calibration curv e, prior to integration) . When multiple to volume measurements are collected for a single pr oc

v analogous to Equa

percent
V V DRE 2 =

in ⎠ ⎝

re, out 100 1 × ⎟ ⎟ ⎞

⎜ ⎜ ⎛

− (12)

whe

out 

### V = Best estimate for total volume of F-GHG exiting the abatement system [sl]

in 

### V = Best estimate for total volume of F-GHG entering the abatement system [sl].

i 

### V =

, , 1 1 ( ) N N

i ij j i ij j j j Vi t FC t F C t

= = = Δ= Δ



## ∑ ∑ ∫ (13)

where i denotes either the outlet or inlet F-GHG ga s, F denotes the corre sponding inlet or outlet

ow, T

0

j 

### t Δ denotes the integration interval, is the concentration of F-GHG either entering or

, i j 

### C fl

exiting the abatement system and the sum is taken over the period, T , of production processing.



## ( )

V V DRE λ σ

ε ( 2 λ

− = 1 )
(14) where,

out

V

in V

V λ =

)

(
V λ ε 2 2

out in V V

out in V V = + ⎜ ⎟⎜ ⎟ ⎝ ⎠⎝ ⎠

σ σ ⎛ ⎞⎛ ⎞

out V 

### σ out 

### V [slm] = The standard deviation

24in V 

### σ = The standard deviation of in 

### V [slm].

It can be shown that

V λ 

### ε , the relative error in the true fraction of em itted F-GHG estimated using

Method 2 is, to a very good approximation, governed by relative error in the effluent process and abatement system flows, or the relative error in the dilution factor. This simplification occ because, in calculating the volume flow, integrati ng the measured concentrations over the perio of production processing averages out the uncertainties in FT IR measured concentrations compared to the 15 urs d

corresponding measured flow rates. The relative error for Method 2 may be stimated, to a very good approximation, as the re lative error in the dilu tion factor, which is

an e given by Eq. 9.

3. BENCHMARK RELATIVE ERROR

For Protocol to be considered valid, the relative error for true fraction emitted must be less th ±5 percent. Presented below are the form ulas for estimating relative error (i.e., 

### ( ) TFE ε ) of
true fraction emitted for both Method 1 (Equation 14) and Method 2 (Equation 15). All the parameters used to estimate the relative error of true fraction emitted have been defined in section 2.3, and therefore, are not redefined here. These formulas may not be applicable when alternative methodologies to those the

pr esented in this Protocol are us ed, and in such cases, testing rvice providers should determ ine and use the appropriate formulas to calculate the relative

3.1 Method 1—Dilution Adjusted Concentration Measurements se

err or of the true fraction emitted.

= )( 1 TFE ε 2 2
⎟ ⎟
⎠ ⎜ ⎝ ⎞ ⎜ ⎛

+ ⎟ ⎟ ⎞ ⎜ ⎜ ⎛

DF C σ σ λ (15)

3.2 Method 2—Total Volume Measurements ⎠⎝ DF C λ 

### 5 percent ≤

2 2

⎟ ⎟ ⎜ ⎜
+ ⎟ ⎟ ⎜ ⎜ V V

V V in out 

### 5 perc ≤ = )( 2 TFE ε ⎠ ⎞

⎝ ⎛

⎠ ⎞

⎝ ⎛

in out σ σ (16)

those instances where the concentr ations exiting the abatement system, C out in the equations is placed with C *

, so λ

c is calculated using C *

. 

### ent

which may be estimated using Eq. 9.

In

re

15 This can be shown using the expression for )(
V λ ε given in Eq. 14 and noting that relative errors, 2

O V ε and 2

I V ε

, are each the sums in quadrature of the relative errors of the outlet/inlet flows and outlet/inlet concentrations

, respectively. Using the method of simulation to estimate th e relative error in the outlet or inlet concentrations, it

becomes evident that the relative error in measured outlet or inlet concentration is more than an order of magnitude

less than the relative error in the corresponding measured abatement system outlet or inlet flows. The reduced relative error in the integrated concentration profile occurs because in the course of integrating over the measured FTIR concentration profile the error in each FTIR measurement is reduced through averaging.

254. DOCUMENTATION AND REPORTING

Proper documentation and reporting ensures tran sparency of the DRE measurement process allowing users of DREs and third-parties to re view and understand the measurements collec

as well as the data treatment a nd analysis conducted. Therefore, it is important that test , ted ing ervice providers adequately document their analyses, and presen t the results in a clear and

he Protocol also requires certification by the te sting provider. The fina l report should contain s concise report. A suggested structure for the report is presented in the text box below.

T the following language together with the appropriate signature.

The tester/metrologist principally responsible for the measurements and content presented in this report and obtained during the period ____ to _____ at (name of facility) hereby certifies th

methods and calculations set forth in the Protocol were followed a nd that material departures o deviations therefrom, if any, are fully documented in this report dated, ___________. The tester/metrologist also certifies that th at the

r

e calculations and benchmark relative error presented in this report properly and accurately reflect the actual measurements made at the facility during the

ation.

Date ____________________ test period noted in this certific

Signed __________________

2627 Final Report Structure

I. Introduction

a. General information about testing

II. Experimental Setup

a. Actual sampling/tes ting configuration

b. Description of how measurements are taken (reference to Protocol encouraged)

c. Sampling Configuration

III. Data Analysis

a. Documentation

i. Formulas Used

ii. Figures showing calibration curves for each F-GHG and tracer gas (the regression equation should be displayed for each. calibration curve along with relati ve error of the slope and yintercept).

iii. Figures showing the FTIR spectra at the abatement inlet and outlet, which each F-GHG peak clearly labeled.

iv. Figures showing the temporal concentration profiles of the

abatement inlet and outlet concentration for each F-GHG and

tracer gas.

v. Tables showing the means and standard deviations of the FGHG and tracer gas inlet and out let concentrations and/or volumes (see Section 2.3 for de scription of the means and standard deviations appropriate for each quantity).

vi. Tables showing the mean and sta ndard deviation of the dilution

factor and DRE for each F-GHG.

b. Comparison of estimated DRE error with the 5 percent benchmark

relative error.

IV. Discussion

V. Metrologist certification that repor ted results conform to Protocol. Appendix A: Measurement Plan5. REFERENCES

40 CFR 60. 1998. Appendix A, Method 2, as amended. U.S. Environmental Protection Agency, Method 2 - Determination of Stack Gas Velocity and Volumetric Flow Rate. U.S. Code of Federal Regulations.

40 CFR 52. 1998. Appendix E, Performance Specifications and Specification Test Procedures for Monitoring Systems for Effluent Stream Gas Volumetric Flowrate. U.S. Code of Federal Regulations.

ASTM. (2004) Standard Test Method for Volumetric and Mass Flow Rate Measurement in a Duct Using Tracer Gas Dilution. Designation E 2029 – 99 (Reapproved 2004).

Beu. Laurie S. International Sematech Manufacturing Initiative (ISMI 2005). Reduction of Perfluorocompound (PFCF-GHG) Emissions: 2005 State-of-the-Technology Re port. International Sematech Document ID 05104693A-ENG, December 1, 2005.

Beu, L. et al.(1994)., Results of Delatech Cont rolled Decomposition/Oxidation (CDO) Unit Testing for Perfluorocompound (PFC) Emission Abatement A pplications, SEMATECH Technology Transfer #94092543A, October 1994.

EPA (2008a). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electroni cs Manufacturing: A Cooperative Evaluation with
NEC Electronics, Inc. (EPA 430-R-10-005). Office of Air and Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection Agency, Washington, DC. http://www.epa.gov/semiconductor-pfc/documents/qimonda_report.pdf

EPA (2008b). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with Qimonda (EPA 430-R-08-017). Office of Air and Radiati on Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection Agency, Washington, DC. http://www.epa.gov/semiconductor-pfc/documents/qimonda_report.pdf

EPA (2009). Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electroni cs Manufacturing: A Cooperative Evaluation with

IBM (EPA 430-R-10-004), Office of Air and Radiation Office of Atmospheric Programs, Climate Change Division, U.S. Environmental Protection Agency, Washington, DC. http://www.epa.gov/semiconductorpfc/documents/ibm_report.pdf

International Sematech (2006). Guideline for Char acterization of Semiconductor Process equipment. International Sematech, Technology Transfer # 06124825A -ENG, December 22, 2006. Note that this is an update to previous guideline, TT from Interna tional Sematech # 01104197A-XFR, December 2001.

IPCC Guidelines for National Greenhouse Gas Invent ories. 2006. Volume 3 Industrial Processes and Product Use. Chapter 6, Electronics Industry Emissions.

Laush, Curtis, Mike Sherer and Walter Worth. Inte rnational Sematech Manufact uring Initiative (ISMI 2006). Guideline for Environmental Characterization of Semiconductor Process Equipment. International Sematech Document ID 06124825A-ENG, December 20, 2006.

Lee et al. (2007). Evaluation Method on Destructi on and Removal Efficiency of Perfluorocompounds from Semiconductor and Display Manufacture. Bull. Korean Chem. Soc. 28 (8), 1383-1388 (2007).

28Li et al., (2001). Improved Technique for Evalua ting Point-of-use Abatemen t Systems. Semiconductor Fabtech, 14th Edition, June 2001.

Li et al., (2002). FTIR spectrometers measure scrubber ab atement Efficiencies. Solid-State Technology, July

2002.

Li et al.,(2004). Default values appear to be ove restimating F-GHG emissions from fabs. Solid-State Technology, Sep. 2004.

Stuart L. Meyers (1974). Data Analysis for Scientists and Engineers . John Wiley & Sons, Inc., New York 1974. Page 146-147.

29Appendix A – History of and Revisions to the Protocol

The Protocol has gone through five stages of development: conceptu alization, onsite tests, initial drafting, and two informal peer review processe s. During the informal peer review processes

EPA received comments from both national and in ternational parties, including semiconductor manufacturers, equipment manufacturers, gas su ppliers and analytic service providers. EPA addressed these comments directly with reviewers in verbal and written form.

Modifications were made to the Protocol to ad dress this feedback. In addition to specific technical issues that reviewers raised, an overa rching concern emerged that the Protocol provide as much flexibility as possi ble without compromising the in tegrity of the Protocol’s measurement process. Calls for flexibility stemme d from the diversity of fab environments, as well as from the diversity of established measur ement practices and tech nologies. International reviewers were unanimous in seeking acceptabl e alternatives to QMS systems (used for measuring abatement system dilution via the gas tracer method of chemical spiking) for onsite testing, although central to the met hod favorably evaluated by Lee et al. (Lee, 2007) is the use of a magnetic type precision gas mass spectromete r rather than a quadrupole mass spectrometer (QMS). To provide for more flexibility and to a ddress the technical issues that reviewers raised, EPA considered and made substantive changes to the Protocol:

• Removal of suggested temperature limitations at which a POU system would not abate

CF 4 or SF 6 in reference to instances where CF 4 or SF 6 may be used as tracers gases to measure flow across the abatement system

• Allowance of off-site Fourier Transform Infrared (FTIR) Spectrometer calibration

• Consideration of alternative DRE measur ement methods. The alternative methods

considered were:

o The Multi-chamber Process Inlet Flow Sampling (MPIFS) Method

o The Physical Flow Measurement Method 16

o The Abatement system De-tuning Method 17

o The Post-abatement Flow Tracer Method

Of these listed methods, the Protocol expands Method 2 to include the MPIFS method. The

MPIFS method was tested in December 2008. The results using the MPIFS method agreed with results obtained using the Sequential Single-Ch amber Process Inlet Flow Sampling (SSPIFS). 18

. The Physical Flow Measurement Study, because it is already an EPA method, is allowable under

16 Physical Flow Measurement Methods are allowable per th e Protocol to measure the Total Volume Flow in order to determine DRE. Acceptable flow measurement methods would be those that have pre-determined specified measurement standards in place, such as EPA Appendix A Method 2 and EPA Appendix E. However, these methods are not preferred because often they require laminar flow regimes, where that is often not the case in in-fab testing. When using a physical method for measuring gas flow rate, the performance benchmark metric and standard given in Section 3 applies.

17 The Abatement system De-tuning Method involves either turning off the methane or oxygen flow to the burner of the abatement system, lowering the temp erature of the abatement system, or a combination of the two. The Protocol does not permit this method because to do so would defeat the purpose of the abatement system and intentionally release F-GHG emissions to the atmosphere during testing.

18 EPA cautions, however, that the MPIFS method holds potential safety risks when mixing pyrophoric/flammable and oxidizing gases.

3031 this Protocol; and the Abatement system De-T uning Method in not permitted under this Protocol. The Post-abatement Flow Tracer Method, while theo retically attractive, has not been compared to the pre-abatement tracer method used in the Pr otocol and is therefore not permitted under this

Protocol. 19

19 While the Post-abatement Flow Tracer Method is not perm itted in the Protocol, EPA is interested in learning more, through in-fab testing, about the validity of this method.Appendix B – Sample CalculationStep 1 Determine the Mean Total FlowDataCalculations: Data Treatmentn =60Measured effluent flowsVariance weighted mean of effluent flowKrFlow(slm)Avg KrConc(ppm)Avg EffluentFlow, F(slm)Standard deviation inmeasured effluentflow,σ(slm)Variance inmeasured effluentflow,σ2(slm2)1/σ2F/σ2Units0.0114.1709.28064000.00015630.110816NA0.0225.5784.35227040.00036980.290057NA0.0338.8773.23411560.00086510.668855NA0.0452.2766.3287840.00127550.977402NA0.0565.8759.9287840.00127550.969233NASum of F/σ2=3.01636slm-1Sum of 1/σ2=0.0039421slm-2Mean total flow=765slm(Sum of 1/σ2)-1/2=15.927slm-1Sqrt (1/n)=0.129099dimensionlessσof effluent flow2slm95% CI4slmUpper bound of mean flow=769slmLower bound of mean flow=761slmRelative error, %=0.5%dimensionlessStep 2 Determine the Dilution FactorDataCalculations: Dilution FactorTF(slm)σTF(slm)σTF/TF(σTF/TF)2UnitsOut76520.00261440.0000068NAIn15.50.10.00645160.0000416NADF=49.35483871dimensionlessSum of (σTF/TF)2=0.0000485dimensionlessRelative Error=0.7%dimensionless32Step 3 For Method 1: Determine the Relative Error of the TFE*The TFE error must meet the+/- 5% performance standardDataCalculations:λ, DRE, and True Fraction EmittedValueσσ/Best Estimate(σ/Best Estimate)2UnitsCO20020.01000000.0001NACI12,1341950.01607050.000258262NADF49.420.04052290.001642103NAλC=0.0167450dimensionlessσλ=0.0001033dimensionlessλ* DF=0.8264455dimensionless1 - (λ* DF)=0.1735545dimensionlessSum of (σCO/CO)2and (σCI/CI)2=0.0003583dimensionlessσλ/λC=0.0061710dimensionless(σλ/λC)2=0.0000381dimensionlessSum of (σλ/λC)2and (σDF/DF)2=0.0016802dimensionlessRelative Errorλ=1.9%dimensionlessDRE, %=19%dimensionlessRelative Error DRE=20%dimensionlessRelative Error of TFE=4%dimensionless33Step 3 For Method 2: Determine the Relative Error of the TFE*The TFE error must meet the+/- 5% performance standardDataCalculations:λ, DRE, and True Fraction EmittedBest Est.V(slm)σV(slm)σV/V(σV/V)2UnitsOut0.4250.0050.01104480.00012198847956824NAIn0.4430.0060.01273180.0001620981711280NAλV=0.958843303dimensionlessσλ=0.016194732dimensionless1 -λV=0.041156697dimensionlessSum of (σV/V)2=0.0002841dimensionlessRelative Errorλ=1.7%dimensionlessDRE, %=4%dimensionlessRelative Error DRE=2%dimensionlessRelative Error TFE=2%dimensionless34