### Guideline for Environmental Ch aracterization of Semiconductor Process Equipment – Revision 2

International SEMATECH Manufacturing Initiative Technology Transfer #06124825B-ENG© 2009 International SEMATECH Manufacturing Initiative, Inc. Advanced Materials Research Center

, AMRC

, International SEMATECH Manufacturing Initiative , and ISMI are servicemarks of SEMATECH, Inc. SEMATECH and the SEMATECH logo are registered servicemarks of SEMATECH, Inc. All other servicemarks and tradem arks are the property of their respective owners.

### Guideline for Environmental Ch aracterization of Semiconductor Process Equipment – Revision 2 Technology Transfer #06124825B-ENG International SEMATECH Manufacturing Initiative December 9, 2009

Abstract: This revised document from the ESHT001 project provides a guideline for suppliers of semiconductor process equipment and point-of-u se (POU) abatement devices for environmental characterization of their equipment. The characterization cons ists of quantifying air emissions, liquid effluents, and solid waste. The guideline includes a data collection template for presenting and summarizing the test data as well as recommended protocols for air emissions testing. The document is revised versions of SEMATECH Technology Transfer #01104197A-XFR and #06124825A-ENG. For this edition of the guideline, the testing protocols for process emissions and POU abatement devices were updated to pr ovide additional information for characterizing these emissions. Included with this document is the Excel data collection template.

Keywords: Design of Experiments, Emissions Control, Envi ronmental Characterization, Flow Rates, Fourier Transform Infrared Spectroscopy, Point of Use Abatement, Procedures , Quadrupole Mass Spectroscopy

Authors : Bryan Benaway and Steven Hall (URS), Curtis Laush (IMACC), Robert Ridgeway (Air Products and Chemicals), Mike Sherer (Sherer Consulti ng Services, Inc.), and Steve Trammell (ISMI)

Approvals: Steve Trammell, Author Ron Remke, Project Manager Joe Draina, Director Laurie Modrey, Technology Transfer Team Leaderiii

ISMI Technology Transfer #06124825B-ENG Table of Contents

1 EXECUTIVE SUMMARY .....................................................................................................1 1.1 Guideline Objective ........................................................................................................ 1 1.2 Background

................................................................................................................. ....1
2 EMISSIONS DA TA EXPECTATIONS................................................................................... 1 2.1 Chemical/Water Mass Balance ....................................................................................... 2 2.2 Air Emission Measurements ........................................................................................... 3 2.3 Liquid Effluent Measurements........................................................................................3 2.4 Solid Waste Measurements............................................................................................. 3
3 SELECTION OF THIRD PARTY FOR EMISSIONS MEASUREMENTS ..........................3
4 T ARGET GASEOUS EMISSIONS ........................................................................................ 4
5 EMISSIONS CHARACTERIZA TION...................................................................................6
6 TEST FOR AIR EMISSIONS ................................................................................................. 7 6.1 Process Recipe ............................................................................................................. ...7 6.2 Pump Purge Estimation................................................................................................... 7 6.3 Calibration Curves ......................................................................................................... .7 6.4 Em ission Values............................................................................................................ ..8 6.5 Volum e Closure ............................................................................................................. .9 6.6 Chemical Utilization Efficiency....................................................................................10 6.7 Process Tools Using Open/Covered Tanks/Baths ........................................................ 10 6.8 Spray Processes............................................................................................................ .11 6.9 POU Abatement Device DRE Testing.......................................................................... 11
7 TEST FOR LIQUID EFFLUENTS....................................................................................... 11 7.1 Block Diagram Showing Connections to Tool ............................................................. 12 7.2 Chemical/Water Inputs and Effluents ........................................................................... 12
8 SOLID W ASTE GENERATED DU RING WAFER PROCESSING .................................... 13
9 EMISSIONS ASSOCIA TED WITH PR EVENTIVE MAINTENANCE (PM).................... 13
10 DA TA COLLECTION TEMPLATE...................................................................................... 13 Worksheet #1 – General Inform ation .................................................................................... 14 Worksheet #2 – Tem plate for Reporting Process Air Emissions .......................................... 16 Worksheet #3 – Tem plate for Reporting Liquid Effluents.................................................... 20 Worksheet #4 – Tem plate for Reporting Solid Waste........................................................... 22 Worksheet #5 – Tem plate for Reporting Preventive Maintenance (PM) Emissions ............ 23 Worksheet #6 – Tem plate for Data Summary......................................................................... 1
APPENDIX A – TECHNICAL PR OTOCOLS FOR AIR EMISSIONS CHARACTERIZATION .........................................................................................................2 A.1 Mass Spectrometry Protocol ........................................................................................... 2 A.1.1 Introduction

......................................................................................................... 2 A.1.2 Sa mpling Conditions........................................................................................... 5 A.1.3 Operating Procedures........................................................................................ 11 A.1.4 Calculations

....................................................................................................... 11iv

Technology Transfer #06124825B-ENG ISMI A.2 Fourier Transform Infrared (FTIR) Spectroscopy Protocol.......................................... 13 A.2.1 Introduction

....................................................................................................... 13 A.2.2 Method Development........................................................................................ 13 A.2.3 Laboratory Studies ............................................................................................ 14 A.2.4 Field Studies...................................................................................................... 15 A.2.5 Method Application .......................................................................................... 18 A.2.6 Description of Extrac tive FTIR Spectrometry .................................................. 18 A.2.7 Mathematical Description of Beer’s Law ......................................................... 22 A.2.8 Mathematical Description of a Least Squares Analysis.................................... 23 A.2.9 References

......................................................................................................... 26 A.2.10 Definitions of Symbols and Terms ................................................................... 26 A.3 Modifications to QMS/FTIR Protocol s to Quantify Corrosive Air Emissions............. 28 A.4 Fluorine Chemiluminescence (FC) Protocol: Standard Quantitative Analytical Method for Measuring Gase ous Molecular Fluorine.................................................... 29 A.4.1 Theory and Practice of Chemiluminescence..................................................... 30 A.4.2 General Design and Use....................................................................................30 A.4.3 Sequence of Operation and Monitoring Procedures ......................................... 31 A.4.4 Sampling and Maintenance Considerations......................................................32 A.4.5 Examples of Field Data and Analysis ............................................................... 33
APPENDIX B – PROT OCOL FOR CHARACTERIZATION OF POINT-OF-USE ABATEMENT DEVICES .....................................................................................................35 B.1 Point-of-Use (POU) Abatement Protocol .....................................................................35 B.1.1 Representative Sampling................................................................................... 35 B.1.2 Acid Gas Analyses ............................................................................................36 B.1.3 Sequentially Varied Effluent Streams...............................................................36 B.1.4 Solid Particulates Clogging...............................................................................36 B.1.5 POU Abatement Device Dilution Factor Determination .................................. 37
APPENDIX C – ST ANDARD METHOD S FOR LIQUID AND SOLID WASTE SAMPLING AND ANALYSIS ............................................................................................. 39v

ISMI Technology Transfer #06124825B-ENG List of Figures

Figure 1 Sample Calibration Curve .......................................................................................... 7 Figure 2 FTIR CLS Calibration Curve and Fitting Errors........................................................ 8 Figure 3 Example of Process Emission Plots ........................................................................... 9 Figure 4 Connection Hookup Diagram................................................................................... 12 Figure A-1 Process Tool Exhaust Sampling System.....................................................................5 Figure A-2 Mass Spectrum for Sulfur Hexafluoride (SF 6 )...........................................................6 Figure A-3 Mass Spectrum for Nitrogen Trifluoride (NF 3 )..........................................................7 Figure A-4 Mass Spectrum for Trifluoromethane (CHF 3 )............................................................7 Figure A-5 Mass Spectrum for Carbon Tetrafluoride (CF 4 ) .........................................................8 Figure A-6 Mass Spectrum for Hexafluoroethane (C 2 F 6 ).............................................................8 Figure A-7 Mass Spectrum for Octafluoropropane (C 3 F 8 ) ...........................................................9 Figure A-8 Fully Integrated FC System Housed in a Small Container (11”  10”  5”, 5 lbs.)........................................................................................................................31 Figure A-9 FC System Monoblock............................................................................................. 31 Figure A-10 Example of a) Exhaust Emi ssions from a CVD Chamber Clean Process Chamber Clean Compounds and Byproducts and b) F 2 Byproduct......................... 34 Figure B-1 Sampling Setup to Minimize Particle Clogging....................................................... 35

List of Tables

Table 1 Required Tool Emissions Information ....................................................................... 2
T

able 2 Target Compounds Guideline (Some of Possible Species) ........................................ 5
T

able A-1 Monitored Fragment Ions...........................................................................................6vi

Technology Transfer #06124825B-ENG ISMI Acknowledgments

ISMI wishes to thank the authors of the original document: Dr. Jerry Meyer of Intel, Dr. Peter Maroulis of Air Products & Chemicals, Inc. and Dr. David Green of NIST and the authors of the first revision Mr. Mike Sherer, P.E. of Sherer Consulting Services, Inc., Dr. Curtis Laush of URS, and Dr. Walter Worth, ISMI. Special thanks to Mr. Mike Sherer, P.E. of Sherer Consulting Services, Inc., Dr. Curtis Laush of IMACC, Mr . Steven Hall of URS, Mr. Bryan Benaway of URS and Dr. Robert Ridgeway of Air Products & Chemicals, Inc. for th eir technical input for this second revision of the document.1

ISMI Technology Transfer #06124825B-ENG 1 EXECUTIVE SUMMARY

1.1 Guideline Objective

The sem iconductor industry has a responsibility to its employees and the community to minimize the environmental impact of its manufacturing processes and operations. To fulfill this responsibility, environmental performance goals have been set for its processes and operations. It is essential that equipment suppliers help the semiconductor industry achieve these goals. Equipment includes process tools, peripheral equipment, and point-of-use (POU) abatement devices. Consequently, equipment suppliers are expected to desi gn their equipment to minimize the consumption of chemicals, production of wa ste emissions, and usage of utilities such as energy and water. This document provides guidan ce to device manufacturers and e quipment suppliers on how to characterize the environmental pe rformance of their tools and pr ocesses. The characterization must include the quantification of material inputs, air emissions, liquid effluents, and solid waste generated by the process equipment (tool), pe ripheral equipment a nd point-of-use (POU) abatement device. These characterizations must be based on actual measurement data during idle and process operations. Results must be presente d in a final report that includes measurements on the baseline process recipe during wafer processing, tool id ling, and preventive maintenance activities. The guideline includes an Excel-based template for data collection consisting of six worksheets, not all of which may be required for every tool or devi ce. Also provided are protocols for the analytical methods recomm ended for collecting the data, which include quadrupole mass spectrometry (QMS), Fourier tr ansform infrared (FTIR) spectroscopy, and fluorine gas analysis based on chemiluminescence. These measurements will be customized to the specific process and the semiconductor manuf acturer will use the data provided by the equipment suppliers for several purposes, su ch as selecting equipment, securing site environmental permits, planning for exhausts and drains, handling solid waste, specifying abatement equipment, and facilitating equipment.

1.2 Background Since this guideline was first published in 2001 and revised in 2006, additional testing inform ation has become available and more regul ations have been promulgated, prompting the need to revise this document. These are a ddressed in this 2009 revision. The 2009 guideline includes process peripheral equipment (e.g., chillers, etc.), additional chemicals and byproducts, revised QMS and FTIR methodologies, and additional POU abatement device testing information.

2 EMISSIONS DATA EXPECTATIONS Table 1 is a partial list of generic tools, indicating the types of em issions information required for each tool type. In general, if the tool has any ai r emissions, liquid effluents, or solid wastes, they should all be characterized. Similarly, POU abatement devices and process pe ripheral equipment may ge nerate air emissions, liquid effluents, and solid wast es that should be reported. In addition, destruction and removal efficiency (DRE) should be measured for POU abatement devices. The DRE values reported for POU abatement devices must be measured over a range of conditions that are representative of the tool’s process or processes. Thes e conditions must be clearly documented.2

Technology Transfer #06124825B-ENG ISMI Table 1 Required Tool Emissions Information

Tool Type Air Testing Liquid Effluent Testing Solid Waste Testing Parts Clean/PMs/ Wipedowns

Diffusion Furnaces X X

Wet Hoods X X X X

Tracks X X X
CVD X X Dry Etch X X Implanters X X X
CMP X X X X Plating X X X X Metrology X

PVD X X The detailed data requirements are outlined in Section 10, which includes the Excel-based workbook, containing the following worksheets:

 Worksheet #1 – General Information (about the tool, periphe ral equipment, and POU abatement device)

 Worksheet #2 – Air Emissions

 Worksheet #3 – Liquid Effluents

 Worksheet #4 – Solid Wastes

 Worksheet #5 – Preventive Maintenance

 Worksheet #6 – Data Summary (based on the information provided in the other worksheets) The device manufacturers’ expectat ion is that when testing, the equipment supplier will complete the Data Collection Template and provide a written engine ering analysis and emission measurement report based on the data. Note this is for both process tool and POU abatement device suppliers. For each process tool, process application, and P OU abatement device that the supplier plans to offer for manufacturing, the following information must be provided.

2.1 Chemical/Water Mass Balance It is expected that a chem i cal mass balance will be conducte d unless specified otherwise by equipment purchaser. A chemical mass balance mu st show the composition and quantity of each chemical used in the supplier’s equipment and the composition and quantity discharged to each exhaust, separate chemical drain, and waste stre am. A simple block diagram showing all the gas, liquid, and solid streams entering and leaving th e process tool, periphera l equipment, and POU abatement device should be provided as part of the mass balance.

The mass balance must

 Be on a per wafer processed basis and mass per unit time basis (POU abatement devices should be reported in mass per unit time only)3

ISMI Technology Transfer #06124825B-ENG  Include chemicals used for maintenance and parts cleaning

 Be based on actual measurements

 Achieve a  90% mass closure. An example is atomic fluorine mass closure of  90% from inlet(s) to outlet(s). Note that mass clos ure of greater than 1 10% needs to also be addressed. Another definition is mass out equa ls mass in within ±10%. Some exceptions may be noted as described in Section 6.5.

2.2 Air Emission Measurements

The em issions testing methods must

 Follow an approved analytical method (i.e., FTIR, QMS, fluorine chemiluminescence, and/or ultraviolet [UV] spectroscopy). A ccepted protocols for these methods are in Appendix A.1– A.4. Appendix B provides additional information for determining DREs for POU abatem ent devices.

 Be documented in the report accompanying the Data Collection Template

.

 Include emissions resulting from peripheral equipment, maintenanc e and parts cleaning operations.

 Include a mass or volume balance that accounts for  90% and  110% of atomic fluorine, atomic chlorine, atomic bromine, a nd other constituents (if applicable). This may need to include any other effluent like liquid or solid.

2.3 Liquid Effluent Measurements

The com position and concentrations of the constituents in the liquid phase should be determined using the latest version of esta blished methods for organic and/or inorganic analytical techniques (i.e., “standard methods”) availa ble at accredited, third-party laboratories. Suggested sampling and analytical method(s) are discussed in Appendix C.

2.4 Solid Waste Measurements

The com position and concentration of the constituents in the so lid waste generated should be determined using established organic and/or i norganic analytical tech niques (i.e., “standard methods”) available at accredite d, third-party laboratories. Sugge sted sampling and analytical method(s) are discussed in Appendix C.

3 SELECTION OF THIRD PARTY FOR EMISSIONS MEASUREMENTS If the supplier does not have the in-house resources for a full equipm ent emissions characterization, a consultant s hould be engaged to make the measurements and analyses. To select a competent third party, the fo llowing questions should be asked:

 Can the third party perform a comprehensiv e environmental emissions analysis and provide a detailed emissions report for each process application you plan to offer?

 Does the third party have the internal expertise and analytical equipment required? Do the standard analytical methods (e.g., this guideline, ASTM, etc.) provide analytical data adequate for determining mass balance closure for each constituent should be used.4

Technology Transfer #06124825B-ENG ISMI  What is the third party’s previous experi ence and knowledge in conducting these types of characterization studies?

 What is the third party’s semiconducto r process and POU abatement device (if applicable) experience?

 Is the supplier using calibration st andards to quantify the results?

 What are the technical and commercia l strengths of the third party?

 What are the weaknesses, and how will the third party compensate?

 What engineering resources can the third part y provide to help determine solutions for any improvements that may be identified to meet emission goals?

 Can the third party provide POU abatement de vice inlet and outlet te sting, if required?

4 TARGET GASEOUS EMISSIONS

The f ollowing list and Table 2 show a sample of emission compounds that should be quantified for a particu lar process chemical. Table 2 was designed as a gui de for equipm ent suppliers; however, it may not list all the chemicals or ions that may be encountered with a specific tool and/or process, since many novel materials are continuously being introduced for the advanced technology nodes. Therefore, it is best to defi ne the possible process emissions with the equipment manufacturer before testing. A block flow diagram describing inputs and outputs to the process equipment (incl uding peripheral equipment), and POU abatement device (if applicable) can help track all substances enteri ng and leaving the tool and abatement device.

 The following target compounds should be qua ntified using calibra tion standards: NF 3 , C 3 F 8 , C 2 F 6 , CF 4 , C 4 F 8 , C 4 F 8 O, SF 6 , CHF 3 , CH 2 F 2 , CH 3 F, C 5 F 8 , CH 3 OH (methanol), C 2 H 5 OH (ethanol), CH 3 COCH 3 (acetone), (CH 3 ) 2 CHOH (isopropanol), NH(Si(CH 3 ) 3 ) 2 (HMDS), C 2 H 5 OOCCC(OH)CH 3 (Ethyl lactate), C 4 H 6 ON(CH 3 ) (NMP), CH 3 COO(CH 2 ) 3 CH 3 (butyl acetate), CH 3 O(CH 2 ) 3 OOCCH 3 (PGMEA), C 4 H 8 SO 2 (sulfolane), CH 3 (CO)C 5 H 11 (2-heptanone), HF, Cl 2, HCl, F 2 , SiF 4 , OF 2 , CO, CO 2 , NO, NO 2 , N 2 O, CH 4 , COF 2 , NH 3 , HBr, BR 2 , SO 2 , H 2 SO 4 , and fluorinated heat transfer fluids. Additional process effluents such as silane (SiH 4 ) that may require quantification.

 BrCl should be measured when Br- and Cl-containing compounds are part of the process recipe.

 During emissions testing, a survey scan must be taken. If any unident ified intensities are 10% of the height of the most intense peak attr ibuted to a process gas, then the source of that peak needs to be identified and quantified.

 If FTIR analysis is ineffective in determining NO or NO 2 emissions, then chemiluminescence methods can be used to quantity the emissions.

 If QMS analysis is ineffective in determining Cl 2 emissions, then chemiluminescence or ultraviolet absorption spectroscopy (UVAS) can be used to quantify the emissions. A testing protocol should be provide d for accurate measurements of Cl 2 , and reviewed before testing.5

ISMI Technology Transfer #06124825B-ENG  Some particulate emissions from processe s and POU abatement devices may not be quantified with the air emissions testi ng methodologies discussed here (e.g., SiO 2 , P 2 O 5 , TiO 2 , B 2 O 3 , WO 3 , NH 4 F, etc.). The equipment supplier should use an appropriate method to quantify any such emissions.

Table 2 Target Compounds Guideline (Some of Possible Species)

Process Chemicals Target Compounds to Quantify

AsH 3 AsH 3 BCl 3 Cl 2 , BCl 3 , HCl, SiCl 4 , CCl 4 , CHCl 3 , AlCl 3 Br 2 Br 2 , HBr, SiBr 4 CF 4 C 2 F 6 , CF 4 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , CO, CO 2 C 2 F 6 C 2 F 6 , CF 4 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , C 2 F 4, CO, CO 2 C 3 F 8 C 2 F 6 , CF 4 , C 3 F 8 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , C 2 F 4, CO, CO 2 C 4 F 8 , C 4 F 8 O C 2 F 6 , CF 4 , C 4 F 8 , C 4 F 8 O, C 3 F 8 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , C 2 F 4, CO, CO 2 C 5 F 8 C 2 F 6 , CF 4 , C 5 F 8 , C 4 F 8 , C 4 F 8 O, C 3 F 8 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , C 2 F 4, CO, CO 2 CHF 3 , CH 2 F 2 , CH 3 F C 2 F 6 , CF 4 , CHF 3 , CH 2 F 2 , CH 3 F, HF, F 2 , SiF 4 , OF 2 , COF 2 , C 2 F 4, CO, CO 2 CH 3 COCH 3 (Acetone) CH 3 COCH 3 CH 3 OH (Methanol) CH 3 OH
C 2 H 5 OH (Ethanol) C 2 H 5 OH (CH 3 ) 2 CHOH (Isopropanol) (CH 3 ) 2 CHOH
CH 3 O(CH 2 ) 3 OOCCH 3 (PGMEA) CH 3 O(CH 2 ) 3 OOCCH 3 C 2 H 5 OOCCC(OH)CH 3 (Ethyl lactate) C 2 H 5 OOCCC(OH)CH 3

CH 3 COO(CH 2 ) 3 CH 3 (Butyl acetate) CH 3 COO(CH 2 ) 3 CH 3 C 4 H 6 ON(CH 3 ) (NMP) C 4 H 6 ON(CH 3 )
C 4 H 8 SO 2 (Sulfolane) C 4 H 8 SO 2 CH 3 (CO)C 5 H 11 (2-Heptanone) CH 3 (CO)C 5 H 11 Cl 2 Cl 2 , HCl, SiCl 4 , CCl 4 , CHCl 3 , AlCl 3 HBr HBr, Br 2 , SiBr 4 HCl Cl 2 , HCl, SiCl 4 , CCl 4 , CHCl 3 HF HF, F 2 , SiF 4 , OF 2 , COF 2 NF 3 NF 3 , HF, F 2 , SiF 4 , OF 2 , CF 4 , COF 2 , NO, NO 2 , N 2 O

NH 3 NH 3 , NO, NO 2 , N 2 O

H 2 SO 4 H 2 SO 4 , SO 2 NH[ Si(CH 3 ) 3 ] 2 (HMDS) NH[ Si(CH 3 ) 3 ] 2 , NH 3 N 2 O N 2 O, NO, NO 2 O 3 O 3 PH 3 PH 3 SiF 4 HF, F 2 , SiF 4 , OF 2 , COF 2 SiH 4 SiH 4 SF 6 SF 6 , HF, F 2 , SiF 4 , OF 2 , COF 2 , SOF 2 , SO 2 F 2 , SO 2 Si(OC 2 H 5 ) 4 (TEOS) Si(OC 2 H 5 ) 4 , CH 3 OH, HCOOH, C 2 H 5 OH, CO, CO 26

Technology Transfer #06124825B-ENG ISMI Process Chemicals Target Compounds to Quantify PO(C 2 H 5 O) 3 (TEPO) PO(C 2 H 5 O) 3 , CH 3 OH, HCOOH, C 2 H 5 OH, CO, CO 2 B(C 2 H 5 O) 3 (TEB) B(C 2 H 5 O) 3, CH 3 OH, HCOOH, C 2 H 5 OH, CO, CO 2 TiCl 4 TiCl 4 , HCl, Cl 2 WF 6 WF 6 , HF, F 2 , SiF 4 , OF 2 , CF 4 , COF 2 Fluorinated heat transfer fluids CF 3 –(O–CF(CF3)–CF2)n–(O–CF2)m–O–CF3, CnF2n+2, CnF2n+1(O) CmF2m+1, CnF2nO, (CnF2n+1) 3 N

5 EMISSIONS CHARACTERIZATION

Worksheet #1 – General Information , of the Data Collection Template , describes the process tool, the process being run by th e tool, the POU abatement device, and peripheral equipment. It should document the following information: Type of tool tested

 Name of the baseline process, name/model of the tool, description of the process function (e.g., “deposits 1000 Å of an oxide film”)

 Batch or single-wafer tool, wafer throughput, wafer size

 POU abatement device

 Peripheral equipment that uses chemicals (lubricants, refrigera nts, heat transfer fluids, etc.) The report accompanying the Data Collection Template should document the following information for each analytical method used a nd the instrumentation parameters involved:

 The analytical methods used

 Who performed the testing (in-house or thir d party ); provide a contact number for technical questions

 Mass or wave number range; detection limits of the instrumentation for each of the analyte compounds

 Type and model name of the instrument used

 The sampling conditions for calibration a nd monitoring (source pressure, electron energy, sampling frequency, detection method and settings [Faraday or multiplier], etc.) The tool baseline recipe should be used as the basis for the tool envir onmental characterization. Emission data should be averaged ov er at least five wafers or fi ve batches for batch tools. The average for the five wafers or batches and the st andard deviation should be reported. Data should be collected for all activities associated with the tool:

 During wafer processing

 While no wafers are being processed (i.e., tool is idling or on stand-by)

 During the dry chamber clean

 During preventive maintenance7

ISMI Technology Transfer #06124825B-ENG 6 TEST FOR AIR EMISSIONS

6.1 Process Recipe The equipment supplier’s baseline process reci pe must include flows, times, radio frequency (RF) power, plasm a pressure, and spin speed. A ll sub-steps to the proc ess should be included. For example, most etching recipes consist of a st abilization, etch, and ove r-etch step. The process parameters (flows, times, etc.) listed previously should be dete rmined for each of the steps.

6.2 Pump Purge Estimation The pum p purge rate on the process tool must be determined when sampling the process exhaust downstream of the pump. Accepte d methods of determining pump purge rates can be found in the mass spectrometry protocol described in Appendix A.1.4. The pump purge rate can also be estim ated using FTIR (Appendix A.2) and a process gas such as NF 3
.
6.3 Calibration Curves

For calibra tions that are not multiv ariate (i.e., consisting of linear combinations of detector responses for multiple compounds over an array of x-axis components, as usually done in FTIR analyses), plots of signal intensity vs. analyte concentration must be provided for each of the compounds. The slope (with error), y intercept, and correlation co efficients must be provided with each plot. Figure 1 shows an example of a typical calibration cu rve. The error associated with the slope must not exceed 5%. The calibration curve should consist of at least 1 point per factor of 10 and no less than 5 points.

-2000 0 2000 4000 6000 8000 10000 12000 0 1 2 3 4 5 6 7 slope = 0.00052 ± 0.00001 y-int. = 0.10 ± 0.06

R 2 = 0.9988Intensity (a.u.)

Concentration (ppm)

Figure 1 Sample Calibration Curve8

Technology Transfer #06124825B-ENG ISMI For the usual case of cla ssical least squares (CLS) fitting ove r infrared wavelength regions when performing FTIR quantitative analyses, each cali bration will involve the linear or quadratic scaling of a series of references over its opt ical depth range (concentration times pathlength product). The lower plot in Figure 2 illustrates an example of a calibration curve for carbon monoxide. In this case, the calibration com pares the expected concentrations to CLS-computed concentrations when one of the references (hi ghlighted) is chosen as the base reference for scaling. The upper plot shows the fit errors acros s the entire curve. These errors should not exceed  10% regardless of the base reference used.

Figure 2 FTIR CLS Calibration Curve and Fitting Errors

6.4 Emission Values If the process tool uses a plasm a, then both the concentration (ppmv) vs. time plots for the no RF and wafer processing experiments must be included. Figure 3 illustrates how the concentration (ppm v) vs. time plots should be plotted. All final emission values must be expressed in g/wafer. The equation used to derive the g/wafer value from the raw signal intensities must be included. To allow a semiconductor company to relate the emission values obtained from the tool supplier to its particular process, a statistical design of experiment s (DOE) must be conducted for chemical flow, RF power (if applicable), and plas ma pressure (if applicable). For process tools that use spin coaters, spin speed should be one of the variables used in the DOE. If the DOE cannot be completed (i.e., insuffici ent resources), then the baseline recipe alone should be tested.9

ISMI Technology Transfer #06124825B-ENG All baseline emission values should be the average of at least five wa fers or five group of wafers processed (i.e., a group could be a rack of wafers or a few racks of wafers during a process run). The average as well as the standard deviation sh ould be reported. The error in the average must not exceed 10%. If a specific compound is not detected, then the detection limit of the instrumentation for that compound should be gi ven. How the detection limit was determined should also be clearly explained.

15:25:00 15:30:00 15:35:00 15:40:00 15:45:00 15:50:00 0 500 1000 1500 2000 2500Concentration (ppmv)

Time

Figure 3 Example of Pr ocess Emission Plots

6.5 Volume Closure

From the equivalent halide inlet and outlet amount s, a volume closure on the halogens (F, Cl, Br) must be calculated. The equivalent halide outlet (EHO) is calculated by Eq. [1]:

EHO (A) = Volume emitted of compound (A)  number of halides in compound (A) Eq. [1]
Similarly the equivalent halide inle t (EHI) is calculated by Eq. [2]:

EHI (A) = Volume of process compound used for compound (A) (from recipe) Eq. [2]

 number of halides present in compound (A)

The volume closure is then calculated by Eq. [3]:
Volume closure = (total amount of EHO/total amount of EHI)  100% Eq. [3]

Note that the total amount of EHO or EHI is me rely the sum of the EH for all compounds that are either emitted (outlet) or used (inlet) in the process.

– Example: A process recipe of 50 sccm (0.05 slpm) of CF 4 for 60 sec emits 30 scc (0.03 std. liters) of HF and 40 scc (0.04 std. liters) of CF 4
.10

Technology Transfer #06124825B-ENG ISMI – Total EHI = 0.05 slpm  1 min.  4 Fluorine equivalents in CF 4 = 0.20

– Total EHO = (0.03  1 Fluorine equivalent in HF) + (0.04  4 Fluorine equivalents in CF 4 ) = 0.03 + 0.16 = 0.19

– Fluorine Volume closure = 0.19/0.20  100 = 95%

The success criterion for volume closure is ≥ 90% and ≤ 110%. If the volume closure for volatile emissions is <90% or >110%, a plausible expl anation and supporting data must accompany the report. Some possible reasons for a low volume cl osure are 1) solids form ation, 2) unquantified volatile emissions, or 3) liqui d emissions. For example, if the equipment supplier gets a 60% volume closure for a specific process and belie ves it is due to solids formation, then the supplier must identify the composition of the solids.

Volume closure for additional constituen ts should be provided, as applicable.

6.6 Chemical Utilization Efficiency If the process tool uses plasm a, the utilizati on efficiency (UE) for a specific process compound must be calculated by two methods: Method #1 and Me thod #2. If the process tool does not use a plasma source, then only Method #2 needs to be used. The calculation for both methods is as follows.

 Method #1 (for process equipment that uses plasma) Method #1 uses the values from concentration vs. time plots (i.e., the raw concentrations have not been converted into grams per wafer). Utilization Efficiency = 1 – [average concentration of process compound emitted 1 /average concentration process compound input 2 ]  100%.

 Method #2 (for any process equipment) Utilization Efficiency = 1 – [m ass of process compound emitted 3 /mass of process compound used 4 ]  100%; where

1 This value is the average concentration for a single wafer for the emitted process compound from the “wafer processing” concentration vs. time plot ( Figure 3).

2 This value is the average concentration for a single wafer for the emitted process compound from the “no RF experiment ” concentration vs. time plot ( Figure 3).

3 This value is the mass of emitted process compound for a single wafer (g/wafer), which is calculated by converting the aver age concentration to average mass flow rate using the aver age gas flow rate.

4 This value is the mass of process com pound for a single wafer (g/wafer) used as calculated from the process recipe.

6.7 Process Tools Using Open/Covered Tanks/Baths

There ar e additional testing concerns when char acterizing the emissions of process tools that contain open/closed tanks/baths. The sampling poi nt for the emissions characterizations should be downstream of the process tool (i.e., somewher e on the exhaust manifold of the tool). Because the emissions from these types of tools are c ontinuous, testing must be completed when the wafer is processing and when the tool is idle . Furthermore, because data suggest that the11

ISMI Technology Transfer #06124825B-ENG emissions from these tools depend on how many wa fers are on the rack, these test must be conducted using full racks of wafers. The emissions should be reported in terms of g/wafer and mass per unit time. The emission values should be th e average of at least five racks of wafers. The equipment supplier must also clearly indi cate how many wafers are in a rack (e.g., 25 wafers, 50 wafers, etc.).

6.8 Spray Processes Spray processes are defined in this docum ent as a process that dispenses chemical onto a wafer (single-wafer tool) or group of wafers (includi ng racks of wafers). Th e chemical (e.g., acid solutions, base solutions, and organic compounds) is dispensed onto a wafer or rack of wafers through an applicator or is sprayed on. Air emi ssions can be measured in the exhaust duct from the spray chamber or application area. The e xhaust duct may be connected to a valve that automatically switches the exhaust to different centralized exhaust systems, depending on what is being sprayed (e.g., acid solution versus ammo nium hydroxide solution). Liquid drains may be segregated based on type of wastewater or solvent waste. Data should be determined for five separate runs, with a run consisting of to tal use of all chemicals in the process.

6.9 POU Abatement Device DRE Testing DRE testing of POU abatem ent devices should be conducted using proper analytical techniques simultaneously on the inlet and the outlet locations. Testing should be conducted during all processes including wafer processing and dry cham ber cleans. Detailed instructions for sampling inlet and outlet locations of POU abatement devices are in Appendix B, including dilution factor determ ination for POU abatement device. Any dilution effects in the POU abatement device (i.e., addition of nitrogen, air, etc. to POU abatement device) must be accounted for in DR E calculations. DRE calculated on a mass basis will remove any dilution affects. It is calculated as follows:

 % DRE = [(mass in – mass out)/(mass in)]  100% DRE should not be calculated using inlet and outlet concentrations [e.g., parts per million by volume (ppmv)] without considering the dilution factor. DRE calcu lated on a concentration basis using dilution factor is as follows:

 % DRE = {[inlet ppmv – (outlet ppmv  dilution factor)]/(inlet ppmv)}  100%

where the dilution factor is the ratio of tota l outlet gas flow rate divided by total inlet gas flow rate (i.e., dilution fact or = outlet gas flow rate/inlet gas flow rate with the gas flow rate expressed in standa rd liters per minute, where st andard refers to 25°C and one atmosphere pressure). Note that POU abatem ent device that has more than one inlet will need proper calculation using multiple inlet test data.

7 TEST FOR LIQUID EFFLUENTS

To facilitate the unders tanding of the liquid inputs and outputs fr om the tool, POU abatement device, or peripheral equipment, including a block diagram in the emissions report is recommended. The data for all liquid effluents ge nerated by the tool, POU abatement device or peripheral equipment during its ope ration must be entered into Worksheet #3 . This includes any12

Technology Transfer #06124825B-ENG ISMI liquid effluent resulting from a ny “tank pickling” operation (i.e., chemical(s) used to flush and condition the chemical bath before introduc ing the chemical used for processing).

7.1 Block Diagram Showing Connections to Tool The equipment supplier should provide a block di agram that clearly s hows all the points of connection to the process tool, POU abatement device, or peripheral equipment for both input chemicals and output liquid chemicals and wastewat er The type of drain should be labeled (i.e., solvent drain, acid wastewater drain, fluoride wastewater drain, etc.). Also the identity and concentrations of the primary constituents of the input streams and outputs streams (drains) should be included. Specific information is required for each point of connection (whether it be input chemical/water or output chemical/wastewater/ waste). Each point of connec tion should be assigned a number and purpose.

 Example: Connection point #1 is the input ultrapure water (UPW). Its purpose is to supply UPW to the process tool for wafer rinsing.

 Example: A process tool with four connec tion points (three input s [chemicals] and one output [drain]) is shown in Figure 4.

Process

Tool UPW

H 2 SO 4
HCl Acid Drain (100 ppm H 2 SO 4 , 50 ppm HCl) Input Output

Figure 4 Connection Hookup Diagram

7.2 Chemical/Water Inputs and Effluents

The volum e associated with each connection point must be included. If the chemical/water flows through the equipment, then the volume should be quantified in liters per minute (lpm). For equipment with continuous flows, an average flow rate, a maximum flow rate, and an idle flow rate along with an associated time per wafe r for each of the flows are required. If the chemical/water is used in a sta tic bath, then the volume should be expressed in liters and the dump frequency specified. If chemicals are adde d to the bath to extend bath life, then the quantity and frequency of chemical addition shou ld be specified. If th e connection point is a drain, then the outlet flow rate of the chemi cals/wastewater should be included. Finally, the primary constituents should be identified and quan tified for each of the output connection points (drains). All concentrations should be the average of at least five cycles. Both the average and standard deviation should be included. Accredit ed, standard testing methods (discussed in Appendix C) must be used for sampling and analysis of all liquid effluents.13

ISMI Technology Transfer #06124825B-ENG 8 SOLID WASTE GENERATED DURING WAFER PROCESSING The equipment supplier must identify any solid waste generated duri ng wafer processing and operation of the POU abatem ent device and peripher al equipment. The supplier must identify the composition and the quantity of solid waste ge nerated in g/wafer and must enter it in Worksheet #4 . Accredited, standard tes ting methods (discussed in Appendix C) must be used for

sam pling and analysis of all solid wastes. All quantities of soli d waste generated should be the average of at least five cycles. Both the averag e value and standard deviation should be included. Consumables such as chemical mechanical planar ization (CMP) pads, filter cartridges, sputtering targets, etc., are solid wast e items that are captured in Worksheet #5 under Preventive Maintenance

.

9 EMISSIONS ASSOCIATED WITH PR EVENTIVE M AINTENANCE (PM) Air emissions, liquid effluents, a nd solid wastes associated with preventive maintenance (PM) activities on the process tool, peripheral equipment, and POU abatement device are captured on Worksheet #5 . In addition to the air, liquid, and solid emissions, the equipment supplier must record the use of any post-PM flushing chemical (s), all consumables, and PM-associated parts cleaning data on this worksheet. All the emission s generated during the PM activities must be added to the other tool air emissions, liqui d effluents, and solid waste (Worksheets #2
, #3 , and #4 ) to arrive at total mass emissions per wafer, which are summarized in Worksheet #6

.

10 DATA COLLECTION TEMPLATE

The data collection tem plate cons ists of an Excel-based workb ook with six separate worksheets as follows:

 Worksheet #1 – General Information (about the tool, periphe ral equipment, and POU abatement device)

 Worksheet #2 – Air Emissions

 Worksheet #3 – Liquid Effluents

 Worksheet #4 – Solid Wastes

 Worksheet #5 – Preventive Maintenance

 Worksheet #6 – Data Summary

Worksheet #6 is a compilation of the information from the other worksheets. This summary will help the semiconductor manufactur er review environmental emissi ons on a per wafer basis. If mass per unit time data are needed, this information can be found in other worksheets. The soft copy version of the spreadsheets allows the supplier to add and expand rows and columns, as necessary, for the full environmenta l characterization of a particular tool, POU abatement device, and peripheral equipment.14

Technology Transfer #06124825B-ENG ISMI Worksheet #1 – General Information

Instructions The template consists of the following six worksheets:

1. Worksheet #1 asks for General Information (about your equipment)

2. Worksheet #2 pertains to Air Emissions

3. Worksheet #3 pertains to Liquid Effluents

4. Worksheet #4 pertains to Solid Waste

5. Worksheet #5 pertains to Preventive Maintenance

6. Worksheet #6 is a Data Summary of the data provided in Worksheets #1–#5 (consult before you start)

 Review all six worksheets and provide all information that applies to your specific equipment.

 For the reader’s convenience, identify the equipment name and model on each worksheet.

 Provide all data in metric units.

 Provide explanations or any additional information in the Comments column, where applicable.

 Before starting, check Worksheet #6 – Data Summary to see what data is asked for

 Indicate how the data was obtained (in-house or by third party) a nd what analytical techniques were used in the summ ary report accompanying this workbook15

ISMI Technology Transfer #06124825B-ENG Worksheet #1 – General Information

Date (form was filled out)

Supplier Name

Contact Name (telephone #)

Equipment Name/Model

Wafer Size

Process Name
Single Wafer (yes/no)
Batch (yes/no)

# of Wafers/Batch
Design Throughput (wafers/hr)

Chamber Clean (in situ or remote)
Type of Film Deposited/Etched/Cleaned

Film Thickness, Angstroms

POU Abatement Device Name/Model/Technology

Process Peripheral Equipment (List All)

NOTE: Include environmental emission s from POU abatement device and process peripheral equipment in Worksheets 2 through 6.ISMI TechnologyTransfer#06124825B-ENG16Worksheet #2 – Template for Reporting Process Air EmissionsEquipment Name:Baseline Deposition or Etch Recipe Information(Repeat forClean RecipeandSeasoning Recipe,if applicable)Parameters/StepsStep 1Step 2Step 3Time(sec)Pressure(Torr)RFPower(W)FlowofA(sccm)FlowofB(sccm)FlowofC(sccm)etc.[3]1.0 Processes such as PVD, CVD, etch, implant, etc.1.1 Emissions During Wafer ProcessingInput ChemicalVolume In(scc/wafer)Mass In(g/wafer)Mass In (g/hr)CommentsABCetc.[3]Chemical EmittedVolume Out(scc/wafer)Mass Out(g/wafer)Mass Out(g/hr)Utilization[1](%)Utilization[1](std. dev.)CommentsABCetc.[3]ISMI TechnologyTransfer#06124825B-ENG17Worksheet #2 – Template for Reporting Process Air Emissions (continued)1.2 Emissions During “Dry” Chamber CleanInput ChemicalVolume In(scc/wafer)Mass In(g/wafer)Mass In(g/hr)CommentsABCetc.[3]Chemical EmittedVolume Out(scc/wafer)Mass Out(g/wafer)Mass Out(g/hr)Utilization[1](%)Utilization[1](std. dev.)CommentsABCetc.[3]1.3 Process Component Volume Closure (i.e., halides, NH3, P, etc.)Component InDuringWaferProcessing(scc/wafer)DuringChamberClean(scc/wafer)TotalVolume In(scc/wafer)Total MassIn (g/wafer)CommentsFClBretc.[3]Component OutDuringWaferProcessing(scc/wafer)DuringChamberClean(scc/wafer)TotalVolume Out(scc/wafer)TotalVolumeClosure[2](%)VolumeClosure[2](std. dev.)Total MassOut(g/wafer)CommentsFClBretc.[3]ISMI TechnologyTransfer#06124825B-ENG18Worksheet #2 – Template for Reporting Process Air Emissions (continued)1.4 Emissions During Equipment Idle (e.g., periodic chamber cleans when wafers are NOTbeing processed)Input ChemicalMass In(g/hr)CommentsABCetc.[3]Chemical EmittedMass Out(g/hr)Utilization[1](%)Utilization[1](std. dev.)CommentsABCetc.[3]2.0 Emissions from Wet Stations/BenchesTankChemicalUsedComp. (%)TankVolume(liters)Temp. (oC)Does tankhave acover?(yes/no)% of TimeChemical isin TankType ofAgitation(e.g.,sparge,megasonic)Commentsabcetc.[3]ISMI TechnologyTransfer#06124825B-ENG19Worksheet #2 – Template for Reporting Process Air Emissions (continued)2.1 Emissions for Tank "a" (repeat for each tank)Chemical EmittedAvg.Emissionsw/o Wafers(g/hr)Avg. Emissions DuringWafer Processing (g/hr)Avg.Emissionsper WaferProcessed(g/wafer)Avg.ProcessExhaustVolume(m3/hr)[4]Average Concentration inProcess Exhaust DuringDispense (ppmv)CommentsABCetc.[3]3.0 Emissions from Spray ProcessorsInput ChemicalComp. (%)Flow Rate(sccm)Duration ofFlow (sec)Temp. (°C)% of RecipeTimeChemical isAppliedCommentsABCetc.[3]Chemical EmittedAverageEmissionsfor EachWaferProcessed(g/wafer)AverageEmissionsDuringDispense(g/sec)AverageProcessExhaustVolume(m3/hr)[4]Average Concentration inProcess Exhaust DuringDispense (ppmv)CommentsABCetc.[3]Notes:[1]= % utilization = (mass in – mass out)/mass in100%.[2]= % volume closure = volume out/volume in100%.[3]= List all chemicals used as well as any byproducts formed.[4]= 1 cfm = 1.7 m3/hrRemarks: 1. List the analytical method(s) used to obtain the data.2. Provide a copy of the third-party test report(s), where applicable.3. Provide a simplified processflow diagram showing all thestreams entering and leaving the equipment.ISMI TechnologyTransfer#06124825B-ENG20Worksheet #3 – Template for Reporting Liquid EffluentsEquipment Name:3.0 Specific Information# of connections per equipment# of recirculation loopsdrain interlocks (yes/no)drain switching capability (yes/no)drain switching capability (manual/auto)3.1 Chemical / DI Water / Wastewater /Solvent EffluentInput Chemical / Solvent/ DI Water / PurposeTime forStep (sec)ChemicalConstituent[2]Concen.(mg/L)Avg.Flow [1](lpm)MaximumFlow [1](lpm)IdleFlow [1](lpm)Volume(liters)TotalVolume(ltrs/step)SpikingAmount (%& ltrs/hr)CommentsStep 1 ABCStep 2 ABCStep 3 ABCEffluent / DrainTime forStep (sec)ChemicalConstituent[2] [4]Concen.(mg/L)Avg.Flow [1](lpm)MaximumFlow [1](lpm)IdleFlow [1](lpm)BathDischargeVolume(ltrs/step)BathDischargeFrequency(#/week)CommentsStep 1 ABCStep 2 ABCISMI TechnologyTransfer#06124825B-ENG21Worksheet #3 – Template for Reporting Liquid Effluents (continued)Effluent / DrainTime forStep (sec)ChemicalConstituent[2] [4]Concen.(mg/L)Avg.Flow [1](lpm)MaximumFlow [1](lpm)IdleFlow [1](lpm)BathDischargeVolume(ltrs/step)BathDischargeFrequency(#/week)CommentsStep 3 ABC3.2 Tank Pickling Chemistry [3]DrainChemicalConstituent[2]Concen.(mg/L)Flow [1](lpm)TotalVolume(ltrs)Duration(min)Frequency(#/month)CommentsABCNote: [1] Averaged over 5–10 wafer processing cycles.[2] Example constituents of high interest: NH3, SO4, F, Cu, TSS, organic compounds in water. All constituents should be disclosed.[3] Refers to chemical used to flush and condition the chemicalbath before introducing the chemical used for processing.[4] Include all materials etched or stripped.Remarks: 1. List the analytical methods used to obtain the data.2. Provide a copy of the third-party test report(s), where applicable.3. Provide a simplified process flow diagram showing all the streams entering and leaving the equipment.22

Technology Transfer #06124825B-ENG ISMI Worksheet #4 – Template for Reporting Solid Waste

Equipment Name/Model:

4.0 Solid Waste Produced during Wafer Processing (see 5.5 Consumables on Worksheet 5 as well)

Type of Waste Total Waste Generated (kg/24 hrs) Frequency (if intermittent) Amount Generated (g/wafer) Chemical Constituent(s) Concentration (wt%) Comments

A

B

C

Remarks: 1. List the analytical methods used to obtain the data. 2. Provide a copy of the third-party test report(s), where applicable. 3. Provide a simplified process flow diagram showing all the streams entering and leaving the equipment.ISMI TechnologyTransfer#06124825B-ENG23Worksheet #5 – Template for Reporting Preventive Maintenance (PM) EmissionsEquipment Name/Model:5.0 GeneralDescription of procedureFrequency of procedureTime between PMs (hrs)Number of wafers between PMsEstimated length of procedure5.1 Air EmissionsChemicalAmount Used(g/proc.)ConstituentConstituentConcen. (%)Mass Emitted(g/proc.)Total Mass(g/wafer)CommentsABC5.2 Liquid Chemical/Wastewater EmissionsChemicalAmount Used(ltrs/procedure)ConstituentConstituentConcentration(%)Total Mass(g/procedure)Total Mass(g/wafer)CommentsABC5.3 Solid Waste GeneratedSolid WasteAmount(g/procedure)ConstituentConstituentConcentration(%)Total mass(g/wafer)CommentsABCISMI TechnologyTransfer#06124825B-ENG24Worksheet #5 – Template for Reporting Preventive Maintenance (PM) Emissions (continued)5.4 Qualification after PMFlushing ChemicalVolume Used(g/procedure)ConstituentConcentration(%)Air Emissions(g/procedure)Liquid Waste(g/procedure)Solid Waste(g/procedure)CommentsABC5.5 ConsumablesFrequency of Replacement# Wafer PassesHours of UseQuantityContaminated?Yes/NoContaminatingConstituent(s)CommentsAnodes and CathodesTargetsCMP PadsPost-CMP BrushesFiltersBatteriesLampsGreaseIonizer Bar EmitterTipsContaminated WipesRefrigerantsHeat Transfer Fluidsetc.ISMI TechnologyTransfer#06124825B-ENG25Worksheet #5 – Template for Reporting Preventive Maintenance (PM) Emissions (continued)5.6 Parts Cleaning (include even if outsourcing is used)PartItem #1Item #2Item #3etc.CommentsAfter # of wafer passesAfter # of hours in useCleaning methodChemical usedChemical (g/clean)ConstituentConcentration (%)Air emissions (g/clean)Liquid waste (g/clean)Solid waste (g/clean)Remarks: 1. List the analytical methods used to obtain the data.2. Provide a copy of the third-party test report(s), where applicable.3. Provide a simplified process flow diagram showing all the streams entering and leaving the equipment.1

ISMI Technology Transfer #06124825B-ENG Worksheet #6 – Template for Data Summary

Equipment Name/Model:

Air Emissions [1]

Units Process Exhaust A Process Exhaust B Process Exhaust C etc. Comments HAPs g/wafer GHGs g CO2e/wafer VOCs g/wafer ODSs g/wafer

Other g/wafer
Liquid Effluents [1]

Units Effluent A Effluent B Effluent C etc. Comments

Volume ltrs/wafer Constituent 1 mg/L Constituent 2 mg/L Constituent 3 mg/L

etc. Solid Waste [1]

Units Waste A Waste B Waste C etc. Comments

Total g/wafer Constituent 1 g/wafer Constituent 2 g/wafer Constituent 3 g/wafer

etc.

Mass Balance

Constituent Input to Equipment (g/wafer) Air Emissions (g/wafer) Liquid Waste (g/wafer) Solid Waste (g/wafer) Mass Closure [2] (%) Comments

F ion

Cl ion

Br ion

P ion

S ion

Cu ion

NH 3 [3]

etc.
Note: [1] Includes waste generated during preventive maintenance (PM). [2] % mass closure = mass out / mass in  100%. [3] NH3 can be destroyed in process and therefore mass closure may not be 100%.
g CO 2 e = grams of carbon dioxide equivalent = g of GHG  GWP. HAP = hazardous air pollutant. VOC = volatile organic compound. ODS = ozone depleting substance. GHG = greenhouse gas GWP = global warming potential2

Technology Transfer #06124825B-ENG ISMI Appendix A – Technical Protocols for Air Emissions Characteriz ation

This appendix explains the best known met hods for conducting air emissions studies. While other analytical methods can be applied to air emissions characterization, most of these techniques have severe limitations and more supporting data must be provided to guarantee the quality of the data. The three recommended te chniques for conducting the air emissions studies are mass spectrometry (MS), Fourier transfor m infrared (FTIR) spectroscopy, and fluorine chemiluminescence. The MS protocol was writte n by Air Products and Chemicals Inc.; the FTIR protocol was written by 3M Co rporation, and modified by IMA CC and URS; and the fluorine chemiluminescence protocol was written by URS. Any alternative methodology (i.e., UV spectroscopic technique) must have a sample pr otocol associated with the methodology and be technically reviewed before sampling.

A.1 Mass Spectrometry Protocol Mass spectrom etry is a quant itative analytical method for the determination of CF 4 , C 2 F 6 , C 3 F 8 , CHF 3 , NF 3 , SF 6 , inert gases, etc., in process tool exhaust streams and POU abatement device exhaust streams.

A.1.1 Introduction This procedure can be used to determ ine fluorinated compounds such as CF 4 , C 2 F 6 , C 3 F 8 , CHF 3 , NF 3 , and SF 6 found in semiconductor processing efflue nt streams and to measure homonuclear diatomic molecules and inert gases like helium, argon and krypton (e.g., to determine the POU abatement device dilution factor). The fluorinat ed compounds are primaril y found in the effluent of chemical vapor deposition (CVD) and plasma etch applications. The method is based on using primarily quadrupole mass spectrosc opy (QMS). In QMS, the sample is typically ionized using electron impact ionization. The quadrupole mass filt er separates the ions based on their mass-tocharge ratio (m/e). A secondary electron multiplier or a Faraday plate is used as a detector for these mass separated ions. Concentrations of the individual component s in the sample are determined from QMS response factors, which ar e determined from direct calibration of the QMS response to the compounds listed above. QMS response factors are certain ly obtainable for compounds outside of the above listed fluorinated compounds. In fact, QMS is often used as a complementary monitoring technique to FTIR, when detection of homonucle ar diatomics or inerts like Cl 2 , F 2 , Ar, He, etc. (which FTIR cannot measure) is required. However, special ca re must be taken when sampling corrosive gas streams, such as exhaust streams from a pro cess tool containing signi ficant amounts of HF and/or F 2 . The QMS ionizer can become coated or degrade over time leading to calibration drift in the QMS response factors. In this case, freque nt calibration runs are n ecessary to quantify the drift and to apply appropriate corr ection factors to the sample data.

 Basic QMS Configuration The basic components of a quadrupole mass sp ectrometer system are an ionizer, a quadrupole mass filter, and a detector such as an electron multiplier.3

ISMI Technology Transfer #06124825B-ENG  Ionizer Here the molecules in the sample gas are ionized. Thermionic emission from tungsten or thoriated iridium filaments are used to produce electrons accelerated to energies of 70 eV. These electrons can ionize the molecules by the following interaction:

e - + AB x  AB x +* + 2eAB x +*  AB x-1 + + B  AB x-2 + + 2B

The molecule AB x is first ionized into an excited ionic state. Depending upon the structure of the molecule, the excited io nic state will produce different fragment ions of the type AB x + , AB x-1 + , AB x-2 + , etc. The ions produced in the ioni zer are extracted using ion optic s. A series of electrostatic lenses are used to focus the extracted ions into the entrance of the quadrupole mass filter.

 Quadrupole Mass Filter (QMF) The QMF consists of four cylindrical rods to which both RF and DC voltages are applied. The rods opposite each other are connect ed together. The voltage +(U + Vcos ω t) is applied to one set of rods, whereas the voltage -(U + Vcos  t) is applied to the other set of rods. The typical operating frequency of the RF voltage is 1.2 MHz. Under th e influence of this quadrupolar field, the equation of motion for the ions is represented by the Mathieu equation: 

#   d u
d q q

2

2 2 2   + a u = 0

u  cos Eq. [A-1]

where   = t
2 Eq. [A-2]

and a eU

m r u  4

2 2  Eq. [A-3]

where U is the DC voltage, m is mass,  is angular frequency, and r is the radius of the quadrupole and

q eV

m r u  2

2 2  Eq. [A-4]

where V is the peak amplitude of the RF voltage of angular frequency 

. The solutions to the Mathieu equation fall into either stable or unstable regions, depending upon the mass-to-charge ratio of the ion. The ions for which the solution is stable exit the quadrupole, whereas all other i ons have unstable trajectorie s and hit the rods of the quadrupole. By changing the amplitude of the RF field ( V ), different ions can be made to have stable trajectories. Thus by changing the RF field, the QMS can be tuned to transmit different masses. The resolution of the QMF is determined by the ratio U/V. For constant resolution, the ratio U/V is kept constant when the RF voltage is adjusted to change the transmitted mass.4

Technology Transfer #06124825B-ENG ISMI  Detection System The ions transmitted by the QMF are detected using either a Faraday plate or an electron multiplier. The Faraday plate is a metal plate placed at the end of the quadrupole filter. A sensitive electrometer connected to this plate records the cu rrent produced when a charged ion hits the Faraday plate. Typi cally, the electrometer is sensitiv e enough to detect current in the pico ampere range. For currents smaller than a few pico amperes, an electron multiplier is used instead of the Faraday plate. In most QMS, a continuous dynode electron multiplier is used although a discrete dynode electron multiplier could also be used. The entrance of the electron multiplier is biased at about -2000 V, wher eas the other end is connected to a groundreferenced amplifier. The positive ions exit ing the quadrupole are accelerated towards the -2000 V potential on the entrance of the electr on multiplier. When the ions strike the electron multiplier, they genera te a few secondary electrons. These secondary electrons, under the influence of the gradient in the elect ron multiplier, strike a different part of the electron multiplier. Each electron produces a few secondary electrons. These electrons will cascade down the electron multiplier. This cascading effect generates about a million electrons for every ion that strikes the entr ance of the electron multiplier. This enhanced signal is measured by the preamplifier.

 QMS Resolution A QMS is normally operated in a unit mass re solution mode meaning masses are separated by one atomic mass unit. The resolution of a QMS is defi ned by the following equation:

m /  m = (0.126)(0.1678 - U / V

) -1 Eq. [A-5]

For infinite resolution, U and V are given by the equations

U

(volts) = 1.212 mf 2 r

2 Eq. [A-6]

V

(volts) = 7.219 mf 2 r

2 Eq. [A-7]
where f is frequency. Resolution ( m /  m ) can be empirically determined by dividing the center point mass by the full width at half height of the peak for each mass of interest.

 Detection Limits The mass spectrometer chosen for this applicat ion should have the necessary sensitivity to detect the selected effluent species at a predetermined level. The typical detection limit of each component determined with the QMS used for this study was 1–10 ppmv. System detection limits can be calculated using SE MI guideline F33-0998, which describes the calculation of a regression-based limit of de tection. Two regression-based means for determining a limit of detection (LOD), ordina ry least squares (OLS), and weighted least squares (WLS) are often used. OLS analyses imp licitly assume that signal variability is the same everywhere within the calibration window. WLS analyses allow signal variability to vary over the calibration window, but require an appropriate set of weights to complete the analysis. The LOD is calculated to obtain a 3  equivalent (in probability) upper confidence limit.5

ISMI Technology Transfer #06124825B-ENG A.1.2 Sampling Conditions

 Sampling Location The sample is taken downstream of th e process tool and pump package (see Figure A-1). The exact lo cation is determined by the specifi c tool and piping conf iguration associated with the process. To prevent emissions of poten tially toxic process bypr oducts into the work space, the sample exhaust is vented back into the corrosive house ve ntilation system at a point downstream of the sample inlet location.

 Sampling Conditions Perfluorocompound (PFC) utilization efficiencies, defined as the fraction of PFC reacted in the process chamber, should be determined during actual wafer processing. For etch applications, efficiencies should be determin ed while etching a wafer (product, dummy, or test). For chemical vapor deposition (CVD) appl ications, efficiencies should be determined during a chamber clean after deposition (efficien cies should not be determined in a clean chamber). All sampling is performed non-intrus ively during wafer processing. Samples are drawn through the MS source by an external sample pump. The pressure in the exhaust is slightly below 1 atm. (~750 Torr). The pressure of the sample inlet is maintained at a lower pressure (~700–740 Torr) by throttling the samp le pump. Because of the inertness of CF 4 , C 2 F 6 , C 3 F 8 , CHF 3 , NF 3 , and SF 6 , the sample lines do not need to be heated.

Calibration System Corrosive Exhaust Line From Process Tool 700 Torr

Mass Spectrometer P
Sample Pump

Closed Ion

Source To Process Exhaust

Pump Exhaust

Figure A-1 Process Tool Exhaust Sampling System

 Mass Spectrometer Parameters Choice of specific QMS operating conditions such as electron energy, secondary electron multiplier voltage, emission current, and ion focusi ng voltage are left to the discretion of the analyst provided the QMS responses to analytes are calibrated under the same conditions. These parameters are systems-specific and will need to be determined by the analyst. To6

Technology Transfer #06124825B-ENG ISMI address questions in this ar ea, analysts should consult th e QMS manufacturer, the system manual, basic mass spectrometer textbook, and other such sources.

 Data Acquisition Mode For this application, the mass spectrometer is typically operated in the selective ion monitoring (SIM) mode where the mass filter monito rs a set of specified ions rather than the whole mass spectrum. The advantag e of operating in SIM mode is to provide more rapid and sensitive analysis. The ions chosen depend on the PFC(s) us ed in the process and the byproducts being monitored. Listed in Table A-1 are the fragment ions used to determine the PFCs typically in CVD and etch tool exhausts.

Table A-1 Monitored Fragment Ions

Compound Monitored Fragment Ion m/e

CF 4 CF 3 + 69
C 2 F 6 C 2 F 5 + 119
C 3 F 8 C 3 F 7 + 169
CHF 3 CHF 2 + 51

NF 3 NF 2 + /NF 3 + 52/71
SF 6 SF 5 + 127

To identify unknown and known co mponents in the sample, a complete mass spectrum is obtained by operating the mass spectrometer in th e full spectrum scan mode. Standard mass spectra for each of the compounds listed above are in Figure A-2 through Figure A-7. The spectra were obtained from the National Institute of Standa rds and Technology’s website

.

100

80

60

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Figure A-2 Mass Spectrum for Sulfur Hexafluoride (SF 6 )7

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Figure A-3 Mass Spectrum for Nitrogen Trifluoride (NF 3 )

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Figure A-4 Mass Spectrum for Trifluoromethane (CHF 3 )8

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Figure A-5 Mass Spectrum for Carbon Tetrafluoride (CF 4 )

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Figure A-6 Mass Spectrum for Hexafluoroethane (C 2 F 6 )9

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Figure A-7 Mass Spectrum for Octafluoropropane (C 3 F 8 )

 Flow Rates A sample flow rate of ~0.5–1.5 slm is draw n from the process tool exhaust stream under study. This typical flow rate is needed to purge the sample manifold and obtain a temporally representative sample of the process. The flow rate into the mass spectrometer source will be significantly lower and will depend on how the inle t is differentially pumped. This is usually accomplished using a Restrictive Flow Orifice (RFO) or a narrow diameter capillary.

 Sample Frequency The required sample frequency depends on the pr ocess being monitored. The software of the mass spectrometer should be capable of capturing the data at the required sample frequency. Fast processes, such as etch processes, require rapid sampling fre quencies. Typical etch sampling frequencies should be on the orde r of 0.5–1 Hz. Some CVD chamber cleaning processes are longer and can tolerate sampling frequencies of 0.25–0.5 Hz.

 Dynamic Dilution Calibration Parameters The QMS must be calibrated for both mass lo cation and response to analytes. A dynamic dilution calibration system can be used to perform both types of mass spectrometer system calibrations. The simplest type of dynamic calibration system includes appropriate tubing, fittings, and two mass flow controllers (MFC). One MFC regulates the flow rate of the standard component used to calibrate the syst em. The second MFC regulates the amount of diluent gas used to mix with the standard. The flow rates of the mass flow meters are adjusted to the appropriate settings to obtai n the required concentrations of analyte for calibrating the QMS. These data are used to generate a calibration curve for each compound of interest.10

Technology Transfer #06124825B-ENG ISMI Some Mass flow controllers (MFC ) are used to accurately re gulate the flow rates of the diluent and calibration gases. The MFC should be calibrated using the single component gas being used with them, which is typically nitrogen (N 2 ) for the diluent. MFC used with calibration mixtures should be ca librated with the cal ibration mixture bala nce gas (typically N 2 or He) if the analyte components are ~2% or less. They should be calibrated over their range of use and operated in their experi mentally determined dynamic linear range. Bringing compressed gas standards into a fab is often impractical, whether because of space, safety, or other logistical conc erns. Metered gas flows of targ et compounds into the process chamber, under no thermal or plasma conditions and with no wafer(s) present, must then be performed throughout the appropriate concentra tion ranges to derive calibration curves for the subsequent process emissions tests. This calibration method requires accurate knowledge or measurement of all the foreline roughing pump rates (and no process emissions from other tools) contributing to the sample location.

 Mass Location Calibration A mixture containing 1% He, Ar, Kr, and Xe in a balance gas of nitrogen can be used to assure the alignment of the quadrupole mass filter. This mixture covers both low and high mass ranges. The mass spectrometer should be chos en so that the mass range is sufficient to detect the predominant peaks of the components under study. Typically 1–200 amu range is sufficient. As with the dynamic dilution ca libration, inert gases or othe rs suitable as quadrupole mass standards (like SF 6 , one with a well known fragmentati on pattern over a large mass range), may need to be delivered by the process to ol, as opposed to compressed gas standards.

 QMS Response Calibration The response of the QMS to the compounds listed in Table 1 is determined by calibrating the system with test atmospheres contai ning the compounds of interest. These test atmospheres are created using dynamic gas pha se dilution techniques as described above. A calibration curve should be gene rated for each compound of interest.

 Calibration Frequency The mass spectrometer should be calibrated at the start of testing a given process. The calibration should be checked at the end of testing. This calibration frequency can detect drifts in QMS sensitivity during monitoring. It is strongly recommende d that more frequent calibrations be performed (e.g., immediately before and after a given set of test conditions) when the sample stream is known to contain a significant amount of fluorinated corrosives.

 Calibration Range The mass spectrometer is typically calibrated over the expected concentration range of analytes. A multi-level calibration is performe d using a minimum of five concentrations including a zero. The zero point is defined as diluent contai ning no added analyte. Ideally the QMS should be calibrated over the expect ed concentration range of analytes in the process effluent.11

ISMI Technology Transfer #06124825B-ENG A.1.3 Operating Procedures

1. Perform a qualitative mass calibration by running a standard (or by flowing chamber gases under non-process conditions) cont aining stable components such as Ar, Kr and Xe that provide predominant signals at m/e values dist ributed throughout the mass range to be used. This will ensure the mass locations are properl y identified and that the m/e values of the mass fragments are correctly identified. Adjust the quadrupole mass filter as needed to align with the inert gas fragments.

2. Quantitatively calibrate the QMS for each analyt e of interest. The analyte concentrations during calibration should include the expected concentrations in the process effluent. The calibration should be performed under the same operating conditions, such as inlet pressure, as when sampling process exhaust. One way to do this is to carefully regulate the inlet pressure during calibration and sampling using a flow controlling va lve and monitoring the pressure using a capacitance manometer. If th e calibration inlet pressure differs from the sampling inlet pressure than the relations hip between inlet pressure and QMS signal response must be empirically determined and ap plied to correct for any differences between calibration and process emissions monitoring data.

3. To determine the response time of the instrument to changes in a process, a process gas such as C 2 F 6 should be turned on at the process tool for a fixed period of time. This should be a relatively short period (e.g., 20 seconds), after wh ich the gas is shut off. The amount of time it takes for the QMS to respond to this proce ss gas appearing and di sappearing should be observed. The response should be relatively ra pid with the signal increasing to a constant concentration within a few sec onds, and decreasing to background levels also within a few seconds. If this is not observed, the samp le flow rate through the system should be increased.

4. Sample process effluent through the QMS and acquire data for the required amount of time to track the process. The sample frequency is set to monitor the changes in the process. Repeat this for at least five wafers on the sa me process to obtain an average and standard deviation of the analyte concentration.

5. Repeat quantitative calibration at the conclusion of sampling to identify any drifts in QMS sensitivity. If significant drift is observed, use of an internal standard can be used to correct for changes in sensitivity. For semiconductor emissions monitoring nitrogen fragment (N + ) observed at m/e 14 works well for monitoring dr ift. All analyte signals can normalized to N + , including those obtained during quantitative calibration. This will help to negate changes in sensitivity caused by reduced flow into th e QMS source, which can occur quite easily when monitoring processes emitti ng particles that can clog or obscure flow through a RFO or thin capillary.

A.1.4 Calculations

 Calibration Plot ion intensity vs. analyt e concentration for a given co mpound obtained when calibrating the analytical system. Determine the slope and intercept for each calib rated species to obtain response factors with which to calculate concentrations in the sample. For an acceptable calibration, the R 2 value of the calibration curv e should be at least 0.98.12

Technology Transfer #06124825B-ENG ISMI  Sample Analysis To determine the concentration of a specifi c component in the sample, divide the ion intensity of the sample response by the calib rated response factor. Repeat this for each component.

 Deconvolution of Interfering Peaks Interfering peaks must be deconvolved to obtai n accurate results. As an example of this, C 2 F 6 and CF 4 have common fragments in their mass spectra (CF 3 + , CF 2 + , CF + , and F + ). CF 4 does not produce a fragment that is not observed in the mass spectra for C 2 F 6 . Thus the contribution of fragment ions attributable to C 2 F 6 must be deconvoluted from the ions attributable to CF 4 at a common mass such as m/e 69. Deconvolution can be achieved by using a prominent peak, such as C 2 F 5 + (m/e 119), which is not common to both molecules. Contributions to m/e 69 from C 2 F 6 can be subtracted by using the m/e 69/ m/e 119 ion intensity ratio obtained when C 2 F 6 is present alone. For example, to determine the CF 4 concentration in the presence of C 2 F 6 , the following expression can be used: 

#     B = 119

62 69 Total 69 4 FC CF SSS

 Eq. [A-8] 

#     C SR

CF CF CF

4 69 4 69 4 69 = Eq. [A-9]

where S is QMS signal, C is concentration, R is the response factor of the QMS to CF 4 determined from the calibration curve, superscripts are amu values, and B is the branching ratio defined by

B C F 2 6 69

119 C2F6

C2F6 S
S  Eq. [A-10]

If other compounds are present that contribute to the signal at m/e = 69, they must also be included in the calculation.

 Determining Total Process Flow (Including Pump) Semiconductor process pumps typically have nitrogen purges to pr otect the pump from corrosion and to prevent process effluents fr om accumulating. To calculate dilution of process emissions occurring in the pump, PFC s can be used. This is typically done by flowing PFCs at the process flow rate thr ough the chamber with RF power in the chamber turned off. From the PFC concentration and known process flow, the dilution in the process exhaust and pump can be determined. The cal culation below shows an example of how to determine pump purge dilution. Assume 50 sccm of CF 4 in the process tool yielded 500 ppmv average CF 4 effluent concentration with the RF power off. 

##       1
1
4 6 1 CF4 min L 100 L 10500 minL 050.0





 

  FlowTotal
FlowTotal CF L Eq. [A-11]

Note that it is necessary to ensure RF power is off and that the compound chosen is thermally stable at the chamber temperature.13

ISMI Technology Transfer #06124825B-ENG These data can be used to determine the proc ess emission volumes and/or emission factors. The emission volumes are obtained by integratin g the emission concentration over time with the total process flow. The emission factors ar e determined from the ratio of a volume of PFC added to chamber relative to the volum e of PFC emitted from the chamber. For PFC based byproducts, such as CF 4 produced during C 2 F 6 chamber cleans, the CF 4 emission factor would be the volume of emitted CF 4 relative to the volume of C 2 F 6 used for the chamber clean. Mass emission factors can also be calculated by converting volumes to mass using molecular weight and ideal gas law.

A.2 Fourier Transform Infrared (FTIR) Spectroscopy Protocol This is a protocol for FTIR measurements of sp ecies that are not diatomic molecules and inert gases like argon, helium, and krypton in semiconductor process tool exhaust.

A.2.1 Introduction This section provides procedural and quality assurance and qual ity control (QA/QC) bases for gaseous concentration measurements of fluorinat ed compounds by extractive FTIR spectrometry. Some of the compounds of interest are SF 6 , NF 3 , C 2 F 6 , C 3 F 8 , CF 4 , and CHF 3 . Other compounds can be measured using FTIR such as N 2 O, CH 4 , CO, NO, NO 2 , SiH 4 , HF and HCl. Compounds are to be measured in enclosed samples extracted from the effl uent of semiconductor tools; the analytes are typically in a mixt ure of oxygen and nitrogen with lo w moisture content (less than 0.1% by volume). Typical concentrations of th e six analytes are in the 100–50,000 ppmv range. Because the tool effluent concentrations can change rapidly, measurements must be made at least twice per minute or several times per minute, if possible. This requirement places special emphasis on the sampling and data acquisi tion operations for this application. Substantial field experience in the use of FT IR spectroscopy gained in previous SEMATECH studies (see Reference [1] in Appendix A.2.9) was used in the prepar ation of this protocol. The

nom enclature is adopted from Reference [2]. Appendix A.2.10 lists several salient definitions. The intende d audience is the technical commun ity familiar with process tool operation and standard emission testing methodologies. However, because FTIR spectrometry is a relatively new emissions testing technique, it is briefly described in Appendix A.2. Additional

m athematical details of the tech nique are provided in Appendices A.2.7 and A.2.8.

A.2.2 Method Development The general procedure for developing and documenti ng an extractive, FTIR-based analysis of the effluent from semiconductor process tools is largely based on studies by SEMATECH and 3M Corporation. Developing an FTIR method consists of two dist inct phases: 1) a laboratory study phase and 2) a field study phase. In pr actice, portions of these de velopmental phases may occur simultaneously, and some adjusts in the order and/or repetition of some activities may be
necessary.14

Technology Transfer #06124825B-ENG ISMI A.2.3 Laboratory Studies

 Proposed Spectroscopic Conditions Propose a set of spectroscopic c onditions under which the field studies and subsequent field applications are to be carried out. These incl ude the minimum instrumental linewidth (MIL), spectrometer wavenumber range, sample gas te mperature, sample gas pressure, absorption pathlength, maximum sampling system volume (including the absorption cell), minimum sample flow rate, and maximum allowable tim e between consecutive infrared analyses of the effluent.

 Criteria for Reference Spectral Libraries On the basis of previous emissions test results and/or proce ss knowledge, estimate the maximum concentrations of all of the anal ytes in the effluent and their minimum concentrations of interest (those concentrations below which the measurement of the compounds is of no importance to the analys is). Values between the maximum expected concentration and the minimum concentration of interest are referred to below as the “expected concentration range.” A minimum of f our reference spectra must be available for each analyte. When the set of spectra is or dered according to abso rbance, the absorbance levels of adjacent reference spec tra should not differ by more than a factor of six. Optimally, reference spectra for each analyte should be avai lable at absorbance levels that bracket the analyte’s expected concentration range; mini mally, the spectrum whose absorbance exceeds each analyte’s expected maximum c oncentration or is within 30% of it must be available. It is imperative that the reference spectra be co llected at or near the same temperature and pressure that the sample is to be analyzed under. Furthermore, the gas sample pressure and temperature must be continuously monitored duri ng testing. Most modern analysis software packages can auto-correct for temperature and pressure differences between the sample and reference spectra. However, the corrections w ill not account for major pressure differences (~50%) or major temperature differences (~70oC ); under vastly different temperatures or pressures, the absorption profiles of these compounds will be significantly different and quantification errors will be significant if not fit to references of similar temperature and
pressure. If reference spectral libraries meeting these cr iteria do not exist for all the analytes and interferants or cannot be accura tely generated from existing libraries exhibiting lower MIL values than those proposed for the testing, prepare the required spect ra according to the procedures below.

 Preparation of Reference Spectra When practical, reference spectra at the same absorbance level (to within 10%) of independently prepared samples should be recorded. The reference samples should be prepared from neat forms of the analyte or from gas standards of the highest quality commonly available from commercial sources. Either barometric or volumetric methods may be used to dilute the reference samples to the required concentrations, and the equipment used should be periodically calibra ted in some independent fashion to ensure suitable accuracy. Dynamic and static referenc e sample preparation methods are acceptable, but dynamic preparations are more likely than st atic methods to give consistent results for reactive analytes. Any well characterized ab sorption pathlength may be employed in15

ISMI Technology Transfer #06124825B-ENG recording reference spectra, but the temperat ure and pressure of the reference samples should match as closely as possible those of the proposed spectroscopic conditions. If an MCT or other po tentially non-linear det ector (i.e., a detector whose response vs. total infrared power is not a linear function over the range of resp onses employed) is used for recording the reference spectra, the effects of this type of re sponse on the resulting concentration values should be examined and co rrected for. Spectra of a calibration transfer standard (CTS) should also be recorded period ically with the laboratory spectrometer system to verify the absorption pathlength and othe r aspects of the system performance. All reference spectral data should be recorded in interferometric form and stored digitally.

 Sampling System Preparation Construct a sampling system suitable for deliver ing the proposed sample flow rate from the effluent source to the infrared absorption cell. Fo r the compounds of inte rest, the surfaces of the system exposed to the effluent stream s hould be limited to stainless steel and Teflon; because of the potential for generation of inor ganic automated gases, glass surfaces within the sampling system and absorption cell shoul d be Teflon-coated. Demonstrate that the system, when sampling from a simulated source at the estimated effluent source pressure, delivers a volume of sample at least four times the maximum sampling system volume in a time shorter than the proposed minimum time between consecutive infrared analyses. This may be difficult for rapidly changing proce sses in which case the sample retention time should be determined.

 Preliminary Analytical Routines For the proposed absorption path length to be used in actual emissions testing, prepare an analysis method containing of all the effl uent compounds at their expected maximum concentrations plus the field CTS compound at 20% of its full concentration. Common to most all FTIR software are analytical routines for calculating the six analyte concentrations plus the CTS compound (and their uncertainties) from a sample spectrum using a subset of the analyte and interferant reference spectra.

 Documentation The laboratory techniques used to generate refe rence spectra and to c onvert sample spectral information to compound concentrations shoul d be thoroughly documented. The required level of detail for the documentation is that which allows an independent analyst to reproduce the results from the documentati on and the stored interferometric data.

A.2.4 Field Studies The performance of the proposed spectroscopic system, sampling system, and analytical method should be rigorously examined during and after a field study. Several itera tions of the analysis method may need to be applied depending on obser ved concentrations, ab sorbance intensities, and interferences. During the field study, all th e sampling and analytical procedures envisioned for future field applications should be documen ted. Additional procedures not required during routine field applications, notably dynamic sp iking studies of the analyte gases, may be performed during the field study. These additional pr ocedures need to be performed only once if the results are acceptable and if the effluent sour ces in future field applications prove suitably similar to those chosen for the field study. If sign ificant changes in the effl uent sources in future applications are noted and requi re substantial changes to the analytical equipment and/or16

Technology Transfer #06124825B-ENG ISMI procedures, a separate field study should be pe rformed for the new set of effluent source conditions. Ideally, all data taken during the stud y should be carefully stored and documented, and all spectral information should be perm anently stored in interferometric form.

 System Installation The spectroscopic and sampling sub-systems shoul d be assembled and installed according to the manufacturers’ recommendations. For the field study, the length of the sample lines used should exceed the maximum length envisioned for future field applications. The system should be given sufficient time to stabilize before testing begins.

 Pre-Test Calibration Record a suitable background spectrum using pure ni trogen gas; alternatively, if the analytes of interest are in a sample matrix consistent with ambient air (e.g., from an open bath hood), it is beneficial to use an ambient air bac kground to control interfer ences from water and carbon dioxide. Introduce a sample of the CTS gas directly into the absorption cell at the expected sample pressure and record its ab sorbance spectrum (the “initial field CTS spectrum”). Compare it to the laboratory CTS spectra to determine the effective absorption pathlength. If possible, record spectra of fi eld calibration gas standa rds (single component standards of the analyte compounds) and determin e their concentrations using the reference spectra and analytical rou tines developed in Appendix A.2.3; these spectra may be used instead of the reference s pectra in actual concentration and uncertainty calculations. The CTS gas may be derived by flowing appr opriate semiconductor tool chamber gases under non-process conditions (no thermal or plasma conditions and with no wafer(s) present) if compressed gas sta ndards cannot be brought on-site.

 Reactivity and Response Time Checks While sampling ambient air and continuously recording absorbance spectra, suddenly replace the ambient air flow with CTS gas intr oduced as close as possible to the probe tip. Examine the subsequent spectra to determin e whether the flow rate and sample volume allow the system to respond quickly enough to changes in the sampled gas. Should a corrosive or reactive gas be of interest in th e sample matrix it would be beneficial to determine the reactivity in a similar fashion, if practical. Examine the subsequent spectra to ensure that the reactivities of the analytes wi th the exposed surfaces of the sampling system do not limit the time response of the analytical sy stem. If a pressure co rrection routine in not automated, monitor the absorption cell temperatur e and pressure; verify that the (absolute) pressure remains within 2% of the pressure specified in the proposed system conditions.

 Analyte Spiking If practical, analyte spiking should be performed. While sampling actual source effluent, introduce a known flow rate of CT S gas into the sample stream as close as possible to the probe tip or between the probe and extraction line. Measure and monitor the total sample flow rate, and adjust the spike flow rate until it represents 10% to 20% of the total flow rate. After waiting until at least four absorption cell volumes have been sampled, record four spectra of the spiked effluent, terminate the CTS spike flow, pause until at least four cell volumes are sampled, and then record four (unspiked) spectra. Repeat this process until three spiked and three unspiked spectra have be en obtained. If a pre ssure correction routine is not automated, monitor the absorption cell temperature and pressure; verify that the17

ISMI Technology Transfer #06124825B-ENG pressure remains within 2% of the pressure specified in the proposed system conditions. Calculate the expected CTS co mpound concentrations in the spectra and compare them to the values observed in the spectrum. This pr ocedure is best perfor med using a spectroscopic tracer to calculate d ilution (as opposed to measured flow rates) of the in jected CTS (or analyte) standard. The spectrosc opic tracer should be a component not in the gas matrix that is easily detectable and maintains a linear absorbance over a large concentration range. The gas spike is delivered by an MFC, and the e xpected concentration of analyte of interest (AOI Theoretical ) is calculated as follows:

AOI Theoretical = 

##     native cylinder sample cylinder cylinder sample Tracer Tracer
Tracer Tracer AOI 1 AOI                   

where

AOI Theoretical = Theoretical analyte of interest concentration (ppm);

Tracer sample = Tracer concentration (ppm) as s een by the FTIR during spiking;

Tracer cylinder = The concentration (ppm) of tracer recorded during direct injection of the cylinder to the FTIR cell;

AOI cylinder = The supplier-certified concentra tion (ppm) of the analyte of interest gas standard; and

AOI native = The native AOI concentration (ppm ) of the effluent during stable conditions.

Repeat this spiking process with all efflue nt compounds that are pot entially reactive with either the sampling system component s or with other effluent compounds.

 Post-Test Calibration At the end of a sampling run and at the end of the field study, record the spectrum of the CTS gas. The resulting “final field CTS spectru m” should be compared to the initial field CTS spectrum to verify suitable stability of the spectroscopic system throughout the course of the field study.

 Amendment of Analytical Routines The presence of unanticipated interferant compounds and/or the obs ervation of compounds at concentrations outside thei r expected concentration ranges may necessitate the repetition of portions of the Appendix A.2 procedures. Such amendments are allowable before final analysis of the data, but must be represented in the docum enta tion required in next section.

 Documentation The sampling and spiking techniques used to ge nerate the field study spectra and to convert sample spectral information to concentra tions should be thoroughly documented. The required level of detail for the documentation is that which allows an independent analyst to reproduce the results from the documentati on and the stored interferometric data.18

Technology Transfer #06124825B-ENG ISMI A.2.5 Method Application When the required laboratory and fi eld studies have been complete d and if the results indicate a suitable degree of accuracy, the methods developed may be applied to practical field measurement tasks. During field applications, the procedures demonstrated in the field study (see Appendix A.2.4) should be adhered to as closely as possible, w ith the following exceptions:

1. Ideally, the sampling lines employed should be as short as practically possible and not longer than those used in the field study.

2. Analyte spiking and reactivity checks are requi red only after the installation of or major repair to the sampling system or major change in sample matrix. However, it is always good practice to perform three sp iked/unspiked samples with CTS or a surrogate analyte on a daily basis if time permits and gas st andards are easy to obtain and get on-site.

3. Sampling and other operational data should be recorded and documented as during the field study, but not all the in terferometric data need be stored permanently. Store only the amount interferometric data to sufficient ly reproduce actual te st and spiking data. The format of this data does not necessarily need to be interferograms but could be absorbance spectra or single beams if desired.

A.2.6 Description of Extractive FTIR Spectrometry

 Molecular Rotation-Vibration Absorption and Beer’s Law The energy of a molecule associ ated with its vibrational and rotational motions is quantized (i.e., it may take on only particular, discrete va lues). The allowed values are determined by the molecular structure, the atomic masses, and certain other internal molecular interactions. A molecule can (but need not) absorb light when the energy of an incident photon closely matches the energy spacing between two of its allowed energy levels. For most molecular structures, the allowed vibr ational/rotational energy leve l spacings correspond to the energies of photons in the mid-infrared rang e; therefore, most molecules exhibit some degree of absorption in that spectral range. Th e probability of an absorption occurring in a bulk sample containing a large number of si milar molecules depends on several factors besides the incident infrared photon energy, including (but not limited to) the number of absorbing molecules, the total gas pressure, th e gas temperature, and the distance the photon is allowed to travel through the sample. The energy of a photon is proportion al to its frequency; mathem atically, the energy is given by E = h  , where h is Planck’s constant and  is the frequency of the photon;  is related to the speed of light c and the photon wavelength (  ) through the relation c =  . In infrared spectroscopy, radiation is customar ily described by its wavenumber (  ), defined by the relation    1 / ; when  is expressed in centimeters, the units of  are cm -1 . These units, which are proportional to the frequency and to the energy of the photon, are used almost exclusively in the remainder of this document . The spectral range of interest, namely the mid-infrared region, is usually between 400–5000 cm -1

. FTIR spectrometers rapidly provide accurate es timates to the total energy in an infrared beam at hundreds to tens of thousands of particular wavenumber values across the midinfrared region. These estimates are arranged in wavenumber order to form a “single beam spectrum” of the infrared power versus wavenumber. In extractive spectroscopy, two such19

ISMI Technology Transfer #06124825B-ENG spectra are used to determine molecular concen trations. The first spectrum, recorded using a non-absorbing gas as the sample, is called th e “background” spectrum; its value at the i th
wavenumber value is referred to here as B i . The second, or “sample,” spectrum is recorded under the same conditions using the sample gas of interest; its value at the i th wavenumber value is referred to here as S i . It is the direct availability of the quantities B i , measured under the same conditions as the quantities Si, whic h most clearly differentiates extractive FTIR spectroscopy from other types de scribed in the literature (e .g., “remote” or “open path” FTIR spectroscopy). The “transmittance” spectrum of the sample, representing the fraction of the incident infrared power transmitted by the sample at each wavenumber value, is calculated point-bypoint from the sample and background single-beam spectra according to

i i i B S T  Eq. [A-12]

The “absorbance” of the sample at each wavenumber value ( A i ) is calculated according to the definition

i i T A 10 log

  . Eq. [A-13]

The absorbance of the sample is the quantity of greatest interest in quantitative analyses because it is linearly related to the gaseous concentrations of the absorbing species. The following equation, often referred to as Beer’s Law, relates several FTIR experimental parameters to the concentrations in a gaseous mixture of compounds:

 

 M

j jiji LCaA
1 , Eq. [A-14]

where: i = an index labeling the wavenumber va lues represented in an FTIR spectrum j = an index labeling the abso rbing compounds in the mixture M = the number of absorbing compounds in the mixture

a ij = the absorptivity of the j th compound at the i th wavenumber value L

= the absorption pathlength (length of interaction of radi ation and sample) C

j = the volumetric concentration of the j th compound in the mixture Instrumentation and techniques for determining the quantities in Eq. [A-14] are found in the following three sections. A modern and more complete description of the molecular physics related to qualitative and quantitativ e molecular spectroscopy is found ref. [3].

 Spectroscopic Instrumentation Modern FTIR spectrometers are availabl e from many manufact urers and in many configurations. However, most spectrometers for gas phase anal ysis consist of the several standard components. Broad-band, collimated IR radiation is produced in a glowbar or other thermal source and directed into an interferometer. The interf erometer optically processes the infrared beam, which consists of radiation containing all wavenumbers (wavelengths) across the mid-infrared region. The interferomet er contains at least one moving element; this motion is responsible for the amplitude modulati on of the infrared radiation. The modulated IR beam is directed through one or more enclosed sample volumes such as a series20

Technology Transfer #06124825B-ENG ISMI combination of a multiple-pass (white) sample cell and two single-pass sample cells. After interacting with the sample, the infrared b eam exits the sample region and illuminates a square-law infrared detector. A computer records the detect or response as a function of the position of the moving element. The resulting plot of the detector response (total infrare d power) versus position (more accurately, the optical retardation) is referred to as an “i nterferogram.” Through appropriate mathematical manipulations and a fast Fourier transform (FFT), the same computer (effectively) digitally demodulates the interferogram, and the resulting singlebeam spectrum accurately represents the power in the beam versus wavenumber. Note that, as is characteristic of the Fourier transform, the independent variable in the original function (position, in units of cm) is the inverse of the independent variab le in the transformed function (wavenumber, in units of cm -1 ). Two single beam spectra (recorded with and without the sample present in the cell) yield the absorb ance of the sample in a straightforward calculation. Many operational parameters are available for the analyst to adjust and optimize the spectrometer system. Discussions of most of these parameters are beyond the scope of this work, but are available in ref. [4] and from many other sources. Of greatest importance to the cur rent application are the choices of integration time, absorption pathlength, and spectral resolution.

– Integration Time Under optimal conditions (i.e., when “white” noise in the detector limits the system performance), the signal-to-noise ratio (S/N ) in a single beam spectrum is proportional to the square root of the time spent averagi ng the detector signal during collection of the interferogram, referred to here as the “int egration time.” In typical systems, the integration time is proportional to the number of “scans” (res ults of a single motion of the interferometer’s moving element or indivi dual spectrum) that ar e co-added to form a complete interferogram (spectrum). The time required for a single scan depends on details of the detector res ponse speed and the chosen spect ral resolution (see below), but is typically between 0.1 and 3.0 seconds. As long as the composition of the sample gas changes slowly on the time scale of a single scan, the result of an integration over multiple scans represents a time-average (over the integration time) of the sample composition. Because the generation of ab sorbance spectra requi res two single beam spectra, it is important that the integrati on time used in collec ting both the background and sample interferograms is suitably long; in practice, the b ackground integration is usually carried out over at as many scans as the subsequent sample interferograms, so that the noise in the background spectrum is not dominant.

– Absorption Pathlength As stated in Eq. [A-14], the absorbance of a given sample is proportional to the length (the “absorption pathlength”) over which the infrared beam is allowed to interact with the sample. If all other spectral properties are held constant, including the S/N, the lowest concentration of a single gaseous component at which its absorbance is detectable in the spectral noise is inversely proportional to the absorption pathlength. For samples containing multiple analytes over a large range of concentrations, a single absorption pathlength may not allow optimal measurement of all the components. In typical systems, the absorption pathlength ca nnot be quickly and eas ily varied. Rather21

ISMI Technology Transfer #06124825B-ENG than changing the pathlength of a single ab sorption cell, the operator can direct the sample stream through one of three cells while the others are purged with a nonabsorbing gas. This allows a relatively rapid adjustment of the absorption pathlength, limited only by the rate at which the sample and purge gases can be replaced in each cell.

– Minimum Instrumental Linewidth For a given set of operating parameters pert aining to the interferometer and FFT, an FTIR spectrometer exhibits a lower limit to the full width at half-maximum (FWHM) of absorption features in an absorbance spectrum. This lower limit is referred to as the “minimum instrumental linewidth” (MIL). Significantly lowering the MIL, or “improving the spectral resolution” of th e system, is possible only by increasing the physical length over which a given interferom eter’s moving element is displaced during a single scan. For a given interf erometer, there is always an upper limit to this physical length and therefore a lower limit to the MIL. Careful consideration must be given to choosing an MIL for a given application, since decreasing the MI L introduces severe costs in both interferometer fragility a nd S/N achieved per integration time. It is generally accepted that 0.5 cm -1 is currently the lowest practical MIL value for gas phase spectroscopic field applications. Howeve r, if the spectrometer hardware allows both a larger MIL and optimization of the effective infrared source size (usually by adjusting an aperture or “J acquinot stop” located somewher e in the beam path), the achievable S/N per integration time can be improved significantly.

 Sampling of Effluent Gases The direct availability of a background spectrum B i , measured under the same conditions as the sample single beam spectrum S i , is an advantage of extractive spectroscopy. However, this advantage comes at the sometimes c onsiderable cost of extracting a truly representative sample. Interactions between th e components of the gas and th e sampling system can change the composition of some samples and lead to ina ccurate results. The rate and temperature at which gas is extracted from the effluent source, relative to the volume of sample required for the analysis, must also be taken into account when the concentrations of the components change over time. The gas matrix of current interest consists ma inly of compounds that do not react with the materials used in standard gas extraction systems and are stable over normal temperature regimes (25–185°C). However, because of the po ssibility of reactions between these and other, unanticipated sample constituents or with condensed water vapor, both suitable delivery efficiency and integrity of the sa mpling system should be considered for each sample matrix. Standard components of a gas sampling system suitable for this application consist of a stainless steel sample probe, Teflon sample lines, calibration gas source, and a pump. The pump attaches to the outlet of the infrared absorption cell; maintains a slight negative pressure throughout the absorption cell, sample lines, and probe; and provides a sample gas flow rate of suitable for the testing (commonl y 1–20 lpm). With a calibrated MFC or meter, the operator can introduce known rates of bot h nitrogen-balance cal ibration and “spike” gases into the sample stream through the calibration line, whic h feeds into the probe through a standard “tee” fitting. This al lows replacement of any desired fraction of the actual sample22

Technology Transfer #06124825B-ENG ISMI flow with known concentrations of analytes or other compounds. Procedures for calibrating and dynamically spiking analytes into the sample stream are discussed in Appendix A.2.4.

 Data Acquisition and Analysis Equation A.14 (Beer’s Law) represents the basis for nearly all quantitative analyses of midinfrared spectra recorded with a known abso rption pathlength. The literature (e.g., refs. [4], [5], [6]) contains substantial discussion and comp arison of several types of algorithm s used to derive estimates of multi-component gas sa mple concentrations from a sample spectrum using libraries of reference spectr a. These spectral libraries are also referred to as “training sets.” Examples of techniques described in th e literature are the “P-matrix,” “K-matrix” (or “classical least squares”), “principal component regression,” and “partial least squares” algorithms. A simplified classical least squa res analysis is described in Appendix A.2.8. Experienced analysts can also employ visual subtraction techniques to obtain accurate concentration data and uncertainties. In most cases, the choice of an appropriate te chnique for determining sample concentrations is a matter of both trial and error and of c onvenience. Important features of an acceptable method of spectral analysis include the following:
1. Careful preparation of multiple reference spectra for each compound of interest, and characterization of the extent to which the quality of the reference spectral data may limit the overall accuracy and uncertainty from sample spectrum analyses.

2. Generation of both concentration data and an estimate of the associated error or uncertainty in the determined values for each individual spectrum analyzed.

3. Complete documentation of the processing of the acquired field data, at the level of detail allowing an independent analyst to reproduce quoted concen tration results and uncertainties from the interferometric data.

A.2.7 Mathematical Description of Beer’s Law Direct calculation of the probability of absorption fo r a particular molecular structure is complex, but can be characterized for a bulk sample and radiation at a pa rticular wavenumber (  ) by the absorption coefficient   , defined through the relation

               

 zd zPd
P

o )( 1

  Eq. [A-15]

Here, the radiation travels in the z-direction, is incident on the sample with power P O at z = 0, and has power P ( z ) as a function of locati on along the z axis. If the sample includes a single molecule with non-zero absorption coefficient   , integration of Eq. [A-15] from z = 0 to z = L leads to the following expression for the fraction of the incident power left in the incident radiation after the “ab sorption pathlength” ( L ), defined as the transmittance  T :

 
 L

o e P zP T          

 )( Eq. [A-16]23

ISMI Technology Transfer #06124825B-ENG If two species (1 and 2) in the sample both absorb radiation at the wavenumber (  ), with absorption coefficients (  1 and  2 ), the fraction of power transmitted after distance ( L ), can be seen from Eq. [A-16] to be 

#       21 2 1    
 

     L LL eeeT Eq. [A-17]

This relation represents the efficacy of measuring  T for a sample containing a mixture of
compounds, since contributions to the logarithm of  T from the different compounds are

additive. It can be shown from first principles 3,4 that the quantities  j in gaseous samples are proportional to the average concentrations (per unit volume) of the absorbing species, labeled here by the index j. By defining the “abso rbance” at some discrete (i th ) wavenumber through Ai = -log 10 T i , the following simple relation for the abso rbance of a mixture of M compounds with concentrations C j can be written:

 

 M

j jiji LCaA
1 Eq. [A-18]

Here, the absorption coefficients for the j th compound at the i th wavenumber have been replaced by the “absorptivity” ( a ij ), to which it is proportional. Eq. [A-18] is often referred to as the “Beer-Lambert Relation,” or simply as “Beer’s La w.” It is rigorously tr ue for gas samples only when all its quantities are perfect ly measured at a given sample (equilibrium) pressure, and when the effects of spontaneous emission are small enough to be neglected. A useful practical strategy, and one often used in conjunction with FTIR spectrometry, is to determine the absorptivities ( a ij ) for single components at a large number of wavenumber values under well-characterized experimental conditions. B eer’s Law can then be used to determine the concentrations ( C j ) for a gaseous mixture from the absorp tion pathlength L and the mixture’s observed absorbance ( A i ). As described in Appendix A.2.3, FTIR spectrometers rapidly estimate several thousand values of A i (at various wavenumber values), providing a statistically powerful means for determining a large number of gaseous concentrations from a single sample spectrum.

A.2.8 Mathematical Description of a Least Squares Analysis Virtually all quantitative analyses of FTIR absorption spectra are based on Beer’s Law or some physically reasonable adaptation of Beer’s La w indicated by the pe rtinent experimental constraints. For convenience, this equation and the definitions of its quantities are restated here:

 

 M

j jij La 1 i C A
, i = 1, 2,

 N Eq. [A-19]24

Technology Transfer #06124825B-ENG ISMI where: M = the number of compounds assumed to abso rb in the spectral region analyzed (with index j ) N

= the number of infrared frequencie s used in the analysis (with index i ) A i = the observed sample absorbance at the i th infrared frequency C

j = the (unknown) volumetri c concentration of the j th component of the mixture L

= the absorption path length used in recording the sample spectrum

a ij = the absorptivity of the j th compound at the i th infrared frequency

Once the absorbance of a sample gas ( A i ) and the absorptivities are determined, many mathematical techniques are suitable for an i nversion of Eq. [A-19]. The technique described here is a simple least-squares analysis using a single reference spectrum for each component in the mixture. The following approach to estimating the quantities C j in Eq. [A-19] is similar in most respects to one described in Refs. [5], [6], and [7]. The following treatment follows the notation of Ref. [8] and rewrites Beer’s law as

 

 M

j jijii S i A
1 S++ +  Eq. [A-20]

where: The measurements of the sample absorbances ( A i S ) are made at absolute temperature ( T ), absorption path length ( L ) (meters), and pressure ( p ) (atm)

i  = the wavenumber value of the i th absorbance point

i    +

= a linear baseline error in Beer’s Law for the selected (contiguous) data points

ε i = the non-baseline error in Beer’s Law at  i S

j = a “scaling factor” for the j th compound included in the analysis The quantity  ij in Eq. [A-20] is defined as the “reduced absorptivity” of the j th compound at the frequency (  i ). For the purposes of the present calculation, it may be estimated by

R ij A R jjj j ij CpL T

  Eq. [A-21]

where: A ij R = the absorbance of a single refe rence spectrum of the (pure) j th compound, recorded with absorption path length ( L j ) (meters) at absolute temperature ( T j ) and pressure ( p

j )(atm), and concentration ( C j R ) (ppmv). If Eq. [A-20] is used to form least squares estimates of  ,  , and the scaling factors ( S j )

, denoted by  ,  , and j S , then the desired least squares es timates of the concentrations ( C j ) are given by

jj S Lp T C  Eq. [A-22]25

ISMI Technology Transfer #06124825B-ENG The least squares estimates  ,  , and S j can be formulated from the linear model of Eq. [A-19] as follows (ref. [8]): form the “design matrix” D of with M+2 columns and N rows; each the first M columns of D corresponds to the j th compound, and consists of the N values  ij . The (M+1) th column consists of N entries of any non-zero co nstant, representing the c onstant baseline offset term (  ), the (M+2) th column consists of the N values  i . If similar vector A is defined to represent the values A i , X to represent the M+2 unknown quantities {S 1 , S 2 ,... S M ,  ,  }, and E to represent the errors ( ε i ), the linear model in Eq. [A-22] takes the form

EDXA   Eq. [A-23]
In the over-determined case of interest ( N  M+2), assume the errors ( ε i ) posses a joint distribution with zero means, and a vari ance-covariance matrix of the form

    

 

    

 

    



2 11 2 1 1221 11 1221 2 1

N NN NN

f M

   

Eq. [A-24]

Assume further that M f is known only to within a scaling factor (  2 ):

NM 2   f Eq. [A-25]

Denoting the matrix transpose with the superscrip t “t” and the matrix inverse with superscript “-1,” the least squares estimate to the desired quantity X is given simply by 

#   ANDDND=X 1-t 1 1-t  Eq. [A-26]

The matrix ( N -1 ) is the “weight matrix.” In the simple st case where all the observed quantities A i have equal variances  2

, N -1 is the identity matrix I , and M f =  2 I

. Least squares estimates of several other important quantities are available from X , including the errors in the components of X itself, that is, the errors in the scaling factor estimates. Calculate the residual vector

XD-AV  Eq. [A-27]

which gives the point-by-point di fference between the measured A i S and its least squares estimate according to the linear model; from V , the parameter moment matrix ( M X ) can be estimated according to 

#   1 1-t 1-t DND VNV M         

  3 MN X Eq. [A-28]

and the uncertainty  i in the parameter estimate X i is given by 

#   ii X M 

i Eq. [A-29]26

Technology Transfer #06124825B-ENG ISMI The least squares estimates of the concentrations and the uncertainties in these estimates are obtained by combining Eq. [A-22], Eq. [A-26], and Eq. [A-29] for the appropriate elements of the set {S 1 , S 2 ,... S M ,  ,  }.

A.2.9 References [1] M.D. Tucker et al., S68 Final Report: Template Met hodology and Lessons Learned for Sampling and Analyzing Tool Effluents , SEMATECH Technology Transfer #95123039ATR, 1995. [2] “Protocol for the Use of Extractive Fourier Transform Infrared (FTIR) Spectrometry for the Analyses of Gaseous Emissions From Stationary Sources,” U.S. EPA Emission Measurement Center, EPA-TTN EMC-FTIR Technology. [3] P. Bernath, Spectra of Atoms and Molecules , Oxford Press, New York, 1995. [4] P. Griffiths and J. de Haseth, Fourier Transform Infrared Spectroscopy , John Wiley and Sons, New York, 1986. [5] D.M. Haaland and R.G. Easterling, “Improved Sensitivity of Infrared Spectroscopy by the Application of Leas t Squares Methods,” Appl. Spectrosc . 34(5):539–548, 1980. [6] D.M. Haaland and R.G. Easterling, “Applicat ion of New Least-Squares Methods for the Quantitative Infrared Analysis of Multicomponent Samples,” Appl. Spectrosc . 36(6):665– 673, 1982. [7] D.M. Haaland, R.G. Easterling, and D.A. V opicka, “Multivariate Least-Squares Methods Applied to the Quantitative Spectral An alysis of Multicomponent Samples,” Appl. Spectrosc . 39(1):73–84, 1985. [8] W.C. Hamilton, Statistics in Physical Science , Ronald Press Co., New York, Chapter 4, 1964.

A.2.10 Definitions of Symbols and Terms absorbance ( A ) – The logarithm to the base 10 of the reciprocal of the transmittance ( T ).

T T A log - = 1 log = 10 10      

absorption band – A contiguous wavenumber region of a spectrum (equivalently, a contiguous set of absorbance spectrum data points) in wh ich the absorbance passes through a maximum or a series of maxima. absorption pathlength – In a spectrophotometer, the distan ce, measured in the direction of propagation of the beam of radiant energy, be tween the surface of th e specimen on which the radiant energy is incident and the surface of the specimen from which it is emergent. apodization – Modification of the instrument line shape function (ILS) by multiplying the interferogram by a weighing function whose magnitude va ries with retardation. background spectrum – The single beam spectrum obtaine d with all system components without sample present.27

ISMI Technology Transfer #06124825B-ENG baseline – Any line drawn on an absorption spectrum to establish a reference point that represents a function of the radiant power incident on a sa mple at a given wavelength.

Beer’s law – The direct proportionality of the absorbance of a sample to the concentrations of its constituent compounds (see Eq. [A-14]). calibration transfer standard (CTS) gas – A gas standard of a compound used to achieve and/or demonstrate suitable quant itative agreement between sample spectra and the reference spectral library. compound – A substance possessing a distin ct, unique molecular structure. concentration ( c ) – The quantity of a compound contained in a unit quantity of sample. The unit “ppmv” (parts-per-million volume) employed in this document is equivalent under the assumption of ideal gases to the same quantity expressed on a number, or molar, basis. double beam spectrum – A transmission or absorbance spectrum derived by dividing the sample single beam spectrum by the background spectrum.

Note : The term “double-beam” is used elsewhere to denote a spectrum in which the sample and background interferograms are collected simultane ously along physically distinct absorption paths. Here, the term denotes a spectrum in wh ich the sample and background interferograms are collected at different times along the same absorption path. fast Fourier transform (FFT) – A method of accelerating the computation of a discrete FT by factoring the data into sparse matrices containing mostly zeros. Fourier transform (FT) – The mathematical process for converting an amplitude-time spectrum to an amplitude-frequency spectrum, or vice versa. Fourier transform infrared (FTIR) spectrometer – An analytical system that employs a source of mid-infrared radiation, an interferom eter, an enclosed sample cell of known absorption pathlength, an infrared detector, optical elemen ts that transfer infr ared radiation between components, and a computer system. The time- domain detector response (interferogram) is processed by a Fourier transform to yield a representation of the detector response vs. infrared frequency.

Note : When FTIR spectrometers are interfaced with other instrument s, a slash should be used to denote the interface (e.g., GC/FTIR; HPCL/FTIR, and the use of FTIR should be explicit) (i.e., FTIR not IR). frequency ( v ) – The number of cycles per unit time.

infrared – The portion of the electromagnetic sp ectrum containing wavelengths from ~0.78– 800 μm. interferogram ( I (  )) – A record of the modulated com ponent of the interference signal measured as a function of retardation by the detector.

interferometer – A device that divides a beam of ra diant energy into two or more paths, generates an optical path difference between the beams, and recombines them to produce repetitive interference maxima and minima as the optical retardation is varied.

linewidth – The full width at half maximum of an absorption band in units of wavenumbers (cm -1 ).28

Technology Transfer #06124825B-ENG ISMI minimum instrumental linewidth (MIL) – The minimum linewidth (observed in absorbance spectra) exhibited by the FTIR, in wavenumbers.

Note : The MIL of a system can be determined by observing an absorption band known (through higher resolution examinations) to be narrowe r than indicated by the system. The MIL is fundamentally limited by the reta rdation of the interferometer, but is also affected by other operational parameters (e.g., the choice of apodization function).

mid-infrared – The region of the electromagnetic spectrum from ~400–5000 cm -1

. reference spectra – Absorption spectra of gases with know n chemical compositions, recorded at a known absorption pathlength, that are used in the quantitative analysis of gas samples.
retardation (  – Optical path difference between two beams in an interferometer; also known as “optical path difference” or “optical retardation.”

scan – Digital representation of the detector out put obtained during one co mplete motion of the interferometer's moving assembly or assemblies. single beam spectrum – Fourier-transformed interferogram , representing the detector response vs. wavenumber.

Note : The term “single-beam” is used elsewhere to denote any spectrum in which the sample and background interferograms are recorded on the same physical absorption path; such usage differentiates such spectra from those gene rated using interferograms recorded along two physically distinct absorption pa ths (see “double-beam spectrum” a bove). Here, the term applies (for example) to the two spectra used directly in the calculation of tr ansmission and absorbance spectra of a sample.

T

R – Absolute temperature of gases used in recording reference spectra.

T

S – Absolute temperature of sample ga s as sample spectra are recorded. transmittance ( T ) – The ratio of radiant power transmitted by the sample to the radiant power incident on the sample. Estimated in FTIR spect roscopy by forming the ratio of the single-beam sample and background spectra.
wavenumber (  ) – The number of waves per unit length.

Note : The usual unit of wavenumber is the reciprocal centimeter, cm -1 . The wavenumber is the reciprocal of the wavelength,  , when  is expressed in centimeters.

A.3 Modifications to QMS/FTIR Protocols to Quantify Corrosive Air Emissions The two technical protocols specifically addre ss the quantification of PFC emissions. Several issues must be addressed for these protocols to effectively quantify corrosive air emissions: material compatibilities and passivation of the an alytical system. The four main corrosive air emissions of interest are HF, HCl, Cl 2 , and F 2 , but are not limited to these compounds (e.g., HBr, NH 3 , etc., may be of interest). Due to the co rrosiveness and reactivity of these compounds, special precautions must be taken to ensure th e quality of the emissions data. For material compatibility, all of the parts of the analytical equipment (i.e., sample lines, roughing, and turbo pumps, exhaust lines, etc.) must be compatible w ith these four gases. It is recommended that stainless steel and ceramic parts be used whenev er possible and that Teflon and Viton parts be minimized. For passivation, these gases should be r un through the analytical system until a stable signal is achieved (i.e., the system is “passiva ted”). This can be done by either running the29

ISMI Technology Transfer #06124825B-ENG corrosive compounds through the system without running wafers (if the compounds are used in the process) or by running wafers through the system until the signals are stable (if the compounds are byproducts). Furthermore, all parts of the instrumentation in contact with these compounds should be heated
to 1. Drive out any water from the system

2. Limit the reactivity of the corrosive co mpounds with the analytical system
It should not be assumed that if the system is passivated with one of the compounds that it is passivated with the other three compounds. Passi vation times can range from 15 minutes to 2 hours depending on the condition/length of the samp le lines, temperature of the sample lines, and nature of the compound. In general, the pass ivation time of the analytical system is longest for HF and shortest for Cl 2 . During emissions testing, extreme car e must be taken to ensure that the temperature of the heated sa mple lines is the same during th e calibration steps as it is during the wafer processing steps. In addition, the chemistry between process gase s and byproducts may play a role in employing the proper sampling system, one that minimi zes compound conversion or loss before being analyzed. Examples include process emissions a ssociated with silicon-based depositions using silane (SiH 4 ) or tetraethyl orthosilicat e (TEOS). Significant amounts of silicon oxide particulates and aerosols are typically produced, which could coat the FTIR optics and/or QMS filaments/lenses and lead to biasing of quantitative values. Proper filtering as close to the point of sample extraction as possible and at temper atures above dew points becomes especially important.

A.4 Fluorine Chemiluminescence (FC) Protocol : Standard Quantitative Analytical Method for Measuring Gaseous Molecular Fluorine This analytical technique and measurement pr ocedure was developed specifically to allow accurate, real-time emissions mon itoring of molecular fluorine (F 2 ), a compound that cannot be measured by FTIR (F 2 does not absorb mid-IR radiati on) and is problematic for QMS (F 2 is quite reactive and corrosive in nature , especially when combined with moisture, which leads to significant filament degradation and calibration drift). The FC measurement mechanism entails the calibrated response to light emitted from a s ubstance that chemically interacts upon exposure to F 2 . The FC measurement system should be designed to respond to varying F 2 concentrations in a fast (response times within seconds, or better) and sensit ive (sub-ppmv detection limits) fashion. If a field calibration that brackets observed concentration levels is not possible because precisely known gas standards ar e not practical or obtainable, then pre- and post-field test calibrations under laboratory cond itions are recommended. If interfer ants are in the sampled gas streams, whether they lead to false positive sign als or artificially suppress/augment the calibrated FC signals, they must be identified and characterized.30

Technology Transfer #06124825B-ENG ISMI A.4.1 Theory and Practice of Chemiluminescence Chemiluminescence is produced when a chemical reaction yields an electronically excited species, which emits light as it returns to its ground state. A simple type of chemiluminescent reaction is

A + B → C* + D

C* → C + h  where C* represents the excited state of a sp ecies. The instrumentation for chemiluminescence measurements is quite simple and may cons ist primarily of a reaction vessel and a photomultiplier tube. No wavelength separation, or modulation, device is n ecessary (as in FTIR) because the only source of radiation is the chemical reaction between the analyte and reagent. In most cases, the relationship between signal and concentration is lin ear over a concentration range of several orders of magnitude, thus offering a wide dynamic range. For F 2 sensing, materials have been developed that produce a nearly instantaneous reaction (providing real-time response to F 2 ) that is highly sensitive (providing F 2 detection limits below 10 ppbv). The “substrate” materials for chemiluminescence sens ors vary greatly in composition and can take gaseous, liquid, or solid forms. The example FC mate rial described in this protocol is an organic substrate mixed as a slurry and deposited on a surface as hydrophobic paste.

A.4.2 General Design and Use The FC measurement system requires a desi gn that enables reproduc ible and calibrated measurements of very low levels of emitted radiation. System portability and a simple means to introduce gas streams into the chemiluminescence reaction chamber are also recommended. An example of a fully integrated FC system is pictured in Figure A-8. It can be operated as a standalone device since the dete ctor signal (the system houses an integrated photon-counting module) is digitally handled by a microprocesso r and interfaced to a multi-function keypad and LCD display. The system can also be remotely driven by laptop using Ethernet or RS232 and some pre-developed software applications. For in stance, real-time data tr ending and archival are done through a LabView-based application, and system calibra tion plus curve fitting is automated through a C ++ -based utility. A relay contact has b een integrated to allow the user to change process states based on pre-defined alarm thre sholds. Additional analog data outputs are available as 4–20 mA or 0–10 V, as well. Of critical importance is that the FC system maintains the integrity of the gas matrix being sampled; no interactions of F 2 with the system upstream of the chemiluminescence substrate material are acceptable. In the system descri bed above, the actual chemiluminescence sensing module is a compact nickel-coated steel monobl ock gas delivery system mated to the photoncounter (the integrated PMT). The 3-D drawing in Figure A-9 depicts the module’s design. The monoblock contains an internal Venturi pum p to extract gas sample flow and a gas-substrate contact area near a sapphire window (behind whic h sits the PMT). A substrate paste has been deposited on a nickel-coated aluminum surface th at allows a continuous and uniform interaction flow. The “top-hat” shaped subs trate holder can be serviced, as needed, without disassembling any other part that makes up the system.31

ISMI Technology Transfer #06124825B-ENG Note: The gas fittings and pressure transducer are attached and shown on the right-hand side.

Figure A-8 Fully Integrated FC System Housed in a Small Container (11”  10”  5”, 5 lbs.) Figure A-9 FC System Monoblock

A.4.3 Sequence of Operation and Monitoring Procedures The following sequence is recommended when m onitoring sample or calibration gas streams with an FC system. Although these steps are specif ically for the FC system described above, they would accurately apply to other FC methods after modifications:

1. Attach tubing of appropriate material (PFA Teflon, stainless steel, or monel) to the gas fitting at the exhaust port of the FC system. The exhaust line should always be vented to an appropriate abatement or exhaust system to avoid any human exposure to residual fluorine.

2. Attach a high pressure line from the gas fitting at the Ventur i pump port on the FC system to a compressed dry air (CDA) or N 2 source capable of de livering up to 1 scfm through the system’s Venturi pump. Add a shut-off valve and high pressure gauge (capable of reading 30–100 ps ig) to easily control samp le flow and shut-off or activation of the pump.

3. Attach a length of tubing of appropriate mate rial (PFA Teflon, stainless steel, or monel) to the gas fitting at the inlet port on the FC system. Attach the other end to the source to be sampled. The FC system is now ready for continuous monitoring.

4. Power the FC system and allow its PMT (or other light detection device) to thermally stabilize. The dark current (# of photon counts per second) decr eases and stabilizes to an average baseline value on the order of 500 cts/sec, or less. This “warm up” time is typically 10–15 minutes.

5. After warm up, activate the Venturi pump to begin a sample draw through the inlet port (and the chemiluminescence chamber).32

Technology Transfer #06124825B-ENG ISMI 6. The FC system is usually initially factor y-calibrated, but most systems can be (and should be) recalibrated at any time. It is st rongly recommended that a system calibration check be performed immediately before and di rectly after field testing. The calibration check should entail exposing the FC chamber to F 2 gas standards at three concentration levels: at a low, mid, and high level re lative to the expected (or observed) F 2 field concentrations. Should the calibration check points not agree to within ±30% per point with the pre-set calibration curve, a more thorough PMT response to F 2 concentration curve is in order . Rest the FC system calibration befo re field testing or appropriately adjust field data (if possibl e) if the post-test calibration check reveals a well behaved calibration drift. Therefore, it is advantageous to perform F 2 calibration checks while on-site. Since this is not al ways feasible, however, a laboratory gas mixing/delivery system (or simply a set of gas standards in cylinders) can be used.

A.4.4 Sampling and Maintenance Considerations The following points should be well understood wh en sampling with the FC system. These will help ensure accurate and reproducible results throughout the lifetime of each chemiluminescence substrate. Again, some of these points apply specifically to the FC system described in Appendix A.4.2, but must be considered when using other FC m ethods, as well.

 O 2 Signal Suppression

Consideration must be taken when the FC system is sampling an air source versus a predominantly nitrogen (or some other inert ga s, such as argon) stream. The presence of oxygen in the sample stream interacts with th e substrate surface and will partially quench the chemiluminescence. Given the geom etry of FC chamber (see Appendix A.4.2), the

am ount of PMT signal suppression has been experi mentally characterized to be on the order of 65% for any given F 2 concentration in dry air (containing 21% O 2 ) vs. the same concentration in nitrogen. Because the suppres sion factor decreases linearly with % O 2 , and has been found to be reproducible and well defined under field conditions, a correction factor is included in the system software util ity to account for it. Ente r the percentage of O 2 known to be in the sample stream (e.g., for sampling ambient air, enter 21 ) before field data collection. Alternatively, if field testing is known to entail the m onitoring of only ambient air exhaust streams, the FC system can be cal ibrated with zero air gas mixtures. Then, no correction factor is necessary.

 Substrate Aging The substrate, consisting of an organic salt in the example FC system described in Appendix A.4.2, is known to age over extended periods (many m onths or years). To maintain the substrate’s life, it is recommended th at the sensor be purge d with a dry gas, like house N 2 , then capped off before extended storage.

 Protecting the Light Detector Never expose the PMT to intense light sources, such as room light, with its power on. The PMT is an extremely sensitive light measuri ng device; intense sources, producing signals greater than 30 million cts/sec, will da mage its performance. Therefore, do not open the FC chamber without shutting down the power to the system beforehand . High concentrations of F 2 , even those exceeding 200,000 ppmv, are known to be safe to the PMT since their signals still do not reach the 30 MHz threshold.33

ISMI Technology Transfer #06124825B-ENG  Cross Interferences Very few signals generated by cross interference compounds have been observed from the FC system described in Appendix A.4.2. Commonly encountered po llutants, such as HF, SiF 4 , SiH 4 , NF 3 , HCl, Cl 2 , PFCs, VOCs, NO x , SO x , N 2 O, and O 2 , do not register a response from the system. The only potentially inte rfering compound seen to date has been OF 2 , which appeared to produce a signal of intensity equivalent to 3% of a F 2 signal of similar concentration. This is still being investigat ed, however, because it was unknown whether the small signal was due to OF 2 or a F 2 byproduct in the OF 2 gas standard.

 FC Substrate Lifetime If the chemiluminescence reaction for a give n FC system is known to be irreversible (i.e., the substrate material does not regenerate after contact with F 2 ), then the substrate within the FC chamber will have a finite lif etime, thus requiring periodic recalibration and/or replacement. The FC system described in Appendix A.4.2 still maintains a

m easurable response to F 2 beyond 775,000 ppmv  min of exposure, but needs recalibration at that point, after which the calibration drift becomes more substantial. Other FC systems will require substrate replacement/recalibration at different time intervals.

A.4.5 Examples of Field Data and Analysis The FC method is an excellent complementary meas urement tool to FTIR or QMS, as shown in Figure A-10. The field data shown below i nvolve the abatement of CVD cham ber clean compounds and byproducts as a function of water scrubbing and steam injection. As with the FTIR ( Figure A-10a), the FC system provide s real-tim e emissions profiling ( Figure A-10b) at the
ppm v levels exhibited in this particular exhaust system.34

Technology Transfer #06124825B-ENG ISMI a)

b) Note: The color legend corresponding to compound trace in the upper left-hand corner of each plot. Y-axes are in ppm, X-axes in time-of-day. Generic abatement conditions are also noted.
Figure A-10 Example of a) Exhaust Emis sions from a CVD Chamber Clean Process Chamber Clean Compounds and Byproducts and b) F 2 Byproduct35

ISMI Technology Transfer #06124825B-ENG Appendix B – Protocol for Characterization of Point-of-Use Abatement Devices

B.1 Point-of-Use (POU) Abatement Protocol Depending on the specific character istics of the gas stream analyzed, the sampling technique can be as important as the analyti cal instrument used. In many cas es, traditional sampling methods fail and custom designed techniques are needed to minimize analyte loss or distorted results. The following are some techniques used to characterize specific, problematic t ool effluent streams. They will serve as the first of a compilation of different, application-specific analytical sampling methods used to characterize semiconductor processing effluent streams. As additional methods are reviewed and qualified, they will be added to this document.

B.1.1 Representative Sampling Collecting gas samples from pipes, especially th ose with laminar flow characteristics, requires special attention. Sampling from a fitting bored into a pipe can result in wall effects that cause false or inaccurate results. This is especially true when sampling the outlet of wet scrubbers as moisture tends to condensate on the inner walls of exhaust pipes; disproportionate levels of moisture and dissolved gases are drawn into analyzers leading to incorrect gas phase composition characterization. One way to minimize these effects is to introduce a probe bent at 90  to collect samples concentrically and concurrent with respect to the direction of the gas flow from the center of the pipe (see Figure B-1).

3-Way Valve

3-Way Valve

3-Way Valve Filter 1 Filter 2

To FTIR N 2 From Sampling Port Exhaust Duct

Figure B-1 Sampling Setup to Minimize Particle Clogging36

Technology Transfer #06124825B-ENG ISMI B.1.2 Acid Gas Analyses This can include measurement of acid gases at the exhaust of a metal etch tool (BCl 3 , HCl, and Cl 2 ) using a QMS or FTIR and in water va por saturated conditions (HF, HCl, F 2 , Cl 2 after a water scrubber) using FTIR spectrometers, QMS, and/or fluorine chemiluminescence. In acid gas sampling and analysis, materials compatibility can be a dominant concern. The two main materials used for sampling are heated stainless steel and Teflon. The disadvantage with heated stainless steel is limited flexibility and evidence of reactions between Cl 2 and F 2 with the walls of the sampling lines when water is present. The disadvantage with Teflon lines is evidence of an interaction of HF and F 2 with Teflon. Ensure that the choice of sampling lines does not affect the accuracy or reproducibility of the emissions measurements. In extreme wet conditions, it is recommended that an inline permeation dryer (e.g., PERMA-PURE) be considered, which can eliminate 90% of the moisture in the gas stream . Studies of analyzer responses (QMS and FTIR spectroscopy) with and without the dryer in line have shown no analyte was lost in the water removal process (i.e., the dryer is selective and does not rem ove any acids). This technique proved effective for measuring the acid gase s at the outlets of wet scrubbers, and for characterizing SiF 4 and HF emissions during a wet HF clean of an atmospheric pressure CVD tool. Note, however, that before implementing any of these sample conditioning techniques, a specific effluent stream needs to be thoroughly test ed. For instance, further tests have determined that some polar organic compounds, ammoni a, and TEOS permeate out of the dryer.

B.1.3 Sequentially Varied Effluent Streams In performing mixed effluent charact erization studies, it is helpful to install three-way valves at the sampling ports. One end is connected to the tool exhaust duct, the other is connected to purging dry nitrogen, and the common port is directed to the analyzer. This setup allows either the purging nitrogen or sample stream to be transferred to the FTIR, QMS, or fluorine chemiluminescence analyzer. Dry nitrogen is used to collect background or ba seline spectra or to clean the lines and spectrometer between runs. Wh enever the port is remote or inaccessible, the three-way valve can include a pneumatic actuator to switch be tween the sample or nitrogen stream collection. This can be useful when characterizing varied exhaust streams (e.g., measurements inside an ion impl anter processing arsine, phosphine, boron trifluoride, and silicon tetrafluoride).

B.1.4 Solid Particulates Clogging Many processes in the semiconductor industry releas e solid particulates. For example, silane and TEOS often generate silicon dioxide (SiO 2 ), TEB and diborane generate boric oxide (B 2 O 3 ), and TEPO and phosphine generate phosphorus pentoxide (P 2 O 5 ). These solids not only hinder material balance calculations but can also obstruct sampling lines, analytical tools, and sampling valves. To allow continuous analysis, a sampling system has been designed to minimize particle (e.g., SiO 2 ) interference with the analysis. This system has been shown to be very effective in characterizing the tool effluent composition an d concentration of species released during APCVD TEOS/ozone process. The setup (see Figure B-1) includes a 1⁄4-inch Teflon-lined stainless steel probe bent at 90  to collect samples concentrically and concurrent with respect to the direction of the gas flow. Inte rference from solid particles is further minimized using a filter setup (2 μm pore size). Solid particulates with in the gas stream are removed by filter #1 before entering the analyzer. When filter #1 becomes sa turated with solids, two pneumatically actuated three-way valves direct the sample stream to filter #2, allowing the re placement of the clogged37

ISMI Technology Transfer #06124825B-ENG filter. This setup can result in trouble-free anal ysis of particulate-laden streams throughout an extended testing period.

B.1.5 POU Abatement Device Dilution Factor Determination This section provides methodologies for determin ing the POU abatement device inlet and outlet total volume flows to calculate the dilution factor . The total process volume flow into the POU abatement device can be done by accur ately flowing a process gas like NF 3 with tool process power off, and then measuring the concentration (u sually with FTIR) at outlet of pump (inlet to POU abatement device). It is important that the location for determin ing this total volume process flow is the same as the loca tion for sampling the process effluent. Once the total volume flow for all POU abatement device inlets is known, the POU abatement device total outlet (exhaust) volum e flow needs to be determined. Three methods can be used:

1. Using inert gas through POU abatement device

2. Using a gas at POU abatement device outlet

3. Using a gas through POU abatement device with a known 0% DRE

 Using Inert Gas Through POU Abatement Device This methodology is to accurately flow an inert gas (e.g., Ar, Kr, Xe) that is not used in the process into the process tool effluent and to measure the POU abatement device outlet concentration for that specie (usually by QMS). Care must be taken to subtract out any of these inert gases that are in the air (e.g., argon) supplied to the POU abatement device. Furthermore, the inert gas must not also be supplied as a pr ocess gas. The background for the inert gas to be used in the POU abatement device inlet and out let sampling locations must be measured. The outlet concentration measurement point for dete rmining total outlet volume flow must be the same as the POU abatement device exhaust sampling location.

 Using a Gas at POU Abatement Device Outlet Another methodology is to accurately flow a non-reactive gas (e.g., CF 4 ) into the POU abatement device outlet and measure the concen tration downstream (usually by FTIR). The following criteria must be fulfilled when using this methodology:
1. The POU abatement device outlet must be samp led to ensure that the non-reactive gas is not present.

2. The non-reactive gas must be injected acr oss the POU abatement device outlet duct. This can be done using an injection probe with equally spaced holes.

3. The location selected for downstream non-reactiv e gas analysis must be at least eight duct diameters downstream from the non-reactive gas inj ection location.

4. The location selected for downstream non-reactive gas sampling must also be used for POU abatement device outlet sampling. This will ensure that any dilution from POU abatement device outlet to this samp ling location will be accounted for.

5. The downstream non-reactive gas analysis loca tion duct should be traversed with the sampling probe at a few locations to ensure the non-reactive gas is well mixed. For example, if the duct is 10 centimeters, the duct can be traversed in 2 centimeter increments to prove that the concentration across the duct is uniform.38

Technology Transfer #06124825B-ENG ISMI  Using a Gas Through POU Abatement Device with a Known 0% DRE Another possible methodology is to accura tely flow a process gas (e.g., CF 4 ) that has 0% destruction and removal efficiency (DRE) through the POU abatement device and measure (usually by FTIR) the outlet concentration. It is critical to document there is a 0% DRE for the process gas being used and no CF 4 in the gas stream from other sources (e.g., CF 4 is not generated as a byproduct in POU abatement device) . The outlet concentration measurement point for determining total outlet volume flow must be the same as the POU abatement device exhaust sampling location.

The calculation for POU abatement device dilution factor is as follows: Dilution Factor = (total POU abatement device outlet flow/total POU abatement device inlet flow) For example, if the total POU abatement devi ce inlet volume flow is 400 slm and total outlet volume flow is 4,000 slm, the dilution factor is 10. Using dilution factor, % DRE w ould be calculated as follows: % DRE = {[inlet ppmv – (outlet ppmv  dilution factor)]/(inlet ppmv)}  100% Caution is required for the concentration measur ement and this DRE calculation when there is more than one POU abatement device inlet. The POU abatement device inlet flow(s) and total outlet flow can be used to calculate mass rates into and out of POU abatement device. In this case, DRE can be calculated as follows: % DRE = [(total mass in – total mass out)/(total mass in)]  100% The total mass in can be calculated by summing all mass rates from all POU abatement device inlets.39

ISMI Technology Transfer #06124825B-ENG Appendix C – Standard Methods for Liquid and Solid Waste Sampling and Analysis

Standard methods for liquid and solid waste sampli ng should be used whenever determining data for mass balances. Personnel shoul d use standard methods as pres cribed by local or national regulatory agencies, credible st andards development organization, etc., for the country where these sampling and analytical efforts are being performed.International SEMATECH Manufacturing Initiative Technology Transfer 2706 Montopolis Drive Austin, TX 78741

http://ismi.sematech.org e-mail: info@sematech.org