### Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficien cy (DRE) Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with NEC Electronics, Inc.
December 2008

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

EPA 430-R-10-005

## Acknowledgements

The analytical measurements, da ta interpretation, and report pr eparations were funded by the U.S. Environmental Protection Agency (EPA) unde r contract GS-10F-0124J to ICF International and Air Products and Chemicals, Inc. EPA and the authors wish to express their appreciation
and thanks to NEC Electronics In c., for their gracious support to this study by not only providing
their facilities but also their valuable assistan ce and advice. EPA looks forward to continued
collaborations with NEC Electronics Inc. and other electronics indus try Partners in its cooperative efforts to reduce green house gas emissions and advan ce global climate protection.

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### Table of Contents Page

Acknowledgement s................................................

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

1.0 Introduction

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

................................................... ........................................ 6 3.0 Data Analysis

................................................................................................... 9
3.1 Determination of Scrubber Dilution............................................................... 9
3.2 Scrubber DRE Determin ations.................................................................... 17
3.2.1 TecHarmonic E-HTVS DRE............................................................ 17
3.2.2 Edwards TPU DRE........................................................................ 21

4.0 Conclusion

............................................................................................................................... . ... 23

3

### List of Tables Page

Table I Total equivalent flow measurements from E-HTVS determined using Xe and Kr ...... ...... 11
Table II Total flow measurements from TPU determined using Xe and Kr ................................. ... 12
Table III Ar concentration determined in TPU effluent during Ar flow testing.......................... ....... 12 Table IV Summary of the average total flow determinations for E-HTVS and TPU at NEC Electronics Inc. ............................................................................................................. ..

..... 13 Table V Total process flow determ ination for CVD Tool #1 using C 2 F 6 tool flows.................. ....... 15 Table VI Total process flow determ ination for CVD Tool #2 using NF 3 tool flows................... ....... 16
Table VII C 2 F 6 DRE in E-HTVS during process flow calibrations .............................................. ....... 18 Table VIII Integrated F-GHG process and scrubber emissions for CVD Tool #1 (process) and E-HTVS during chamber cleans ................................................................................ 21

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### List of Figures Page Figure 1 Actual sampling schema tic used for E-HTVS and TPU at NEC Electronics Inc ................... 7 Figure 2 QMS response to Kr (top) and Xe during QMS calibration and E-HTVS spiking of Kr and Xe......................... .................................................................................................... ...... 8 Figure 3 Regression analysis of data obtai ned during calibration of QMS response to 86 Kr and 132 Xe in N 2 ............................................................................................................ 8 Figure 4 Calibration of FTIR response to C 2 F 6 .................................................................. 9 Figure 5 Xe (top) and Kr (bottom) emissions from E-HTVS during spike calibration.................... 12 Figure 6 Kr (top) and Xe (bottom) emissions fro m TPU during chemical spiking of scrubbers......... 14 Figure 7 Ar emission from TPU while Ar was being flowed through the process chamber on CVD Tool #2....................................

.................................................................. 14 Figure 8 C 2 F 6 emission profile for CVD Tool #1 during process flow calibration. C 2 F 6 emissions from a 5 minute chamber clean are also shown ............................................................ 16 Figure 9 NF 3 emission profile from CVD Tool #2 during NF 3 process flow calibration................... 17 Figure 10 Inlet and outlet C 2 F 6 emission profiles for E-HTVS during process flow calibration.......... 18 Figure 11 FTIR spectrum of process emissions during C 2 F 6 /O 2 chamber clean on CVD Tool #1......... 19 Figure 12 C 2 F 6 and CF 4 emissions from CVD Tool #1 (top) and E-HTVS scrubber during chamber cleans...................................................................................................... 20 Figure 13 FTIR spectra of TPU exhaust (top) and C VD Tool #2 process exhaust (bottom) while 1.5 slm NF 3 was flowing through the chamber ................................................................. 22 Figure 14 Relative CH 4 and CO emissions from TPU during reduced temperature operation ............ 24 Figure 15 Nitric oxide emission profile during NF 3 flows from CVD Tool #2 chamber through the TPU........................................................................................................ 25

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## 1.0 Introduction

The purpose of this study was to accurately dete rmine the Destruction or Removal Efficiency (DRE) of two different commer cially available Point Of Use (POU) abatement systems or scrubbers for process emissions fluorinated greenhouse gases (F-GHGs) such as perfluorocarbons (PFCs), hydrofluorocarbons (HFCs) , sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). A key component in accurately determining DRE was to determine the dilution of process exhaust occurring in each scrubber. This study used an experimental approach to measure the dilution across the scrubber by injecti ng a chemical tracer that could not react in the scrubber, or be produced as a by-product dur ing scrubber operation. In this study Krypton, Argon and Xeon were used as chemical spiking agents, as they met the requirements for this application.

Testing was conducted in a fully functional se miconductor manufacturing facility, owned and operated by NEC Electronics Inc. in Roseville, CA. Two different process tools, referred to as CVD Tool #1 and CVD Tool #2, each equipped with a POU scrubber, were tested. CVD Tool #1 equipped with a TecHarmonic E-HTVS PO U scrubber was teste d, and CVD Tool #2 equipped with an Edwards TPU POU abatement device was also tested. 

## 2.0 Experimental Setup

To carry out the objectives of this study it was necessary to monitor bo th process and scrubber emissions simultaneously, and determine scrubber dilution using chemical spiking. Process and scrubber emissions data were collected in parallel using Fourier Transform Infrared Spectroscopy (FTIR). Data used to determine scrubber dilution were co llected using Quadrupole Mass Spectrometry (QMS). A schematic showing the experimental testing set up is shown in Figure 1.

Two FTIRs were used to determine process a nd scrubber emissions. Both systems were MKS 2010 Multi Gas Analyzers equipped with liquid nitrogen cooled mercury cadmium telluride (MCT) detectors. One FTIR was equipped with a 10 cm path length single pass gas cell, and was used to sample process effluent. The ot her FTIR was equipped with a 5.6 m path length multi pass gas cell, and was used to sample scr ubber effluent. Both FTIR were operated at 0.5cm -1 resolution. Four scans were co-added for each data point yielding a sampling frequency of 2.2 sec.

A Balzers QMS system was used to sample scr ubber effluent during dilution determination. The QMS was operated in Selective Ion Monitoring (S IM) mode and a secondary electron multiplier was used to enhance sensitivity. A 1 sec sampling frequency was used for each data point. To account for potential changes in QMS sensitivit y, ion signals were normalized to the signal obtained for the nitrogen fragment (N+), which is formed duri ng electron impact ionization of N 2
. Sampling of effluent streams was done using me tal bellows sampling pumps that were located after the instruments. The sample flow rate was controlled using adjustable flow rate valves. The sample line pressure for both FTIRs and the QMS were monitored using capacitance

6manometers. A filter was installed in the sample line used for monitoring scrubber emissions to ensure that particulate emissions from the scrubb er would not coat the FTIR internal optics, or the pressure reducing orifice used for the QMS. Since the scrubber DRE determination and the scrubber dilution determination were independent events, it was possible to use the same sample line for both operations. This was accomplished by switching the instrument inlet sample fitting from the FTIR to the QMS.

The QMS was calibrated to determine its respons e to Xe, Ar and Kr on site using a dynamic dilution blending system. Test atmospheres containing H 2 , He, Kr, Ar and Xe were created by blending a calibration standard containing 1% of each species in N 2 with N 2 diluent. The QMS responses to 84 Kr and 132 Xe during calibration are shown in Figure 2. From regression analyses of these data a calibration curve was generated and is shown in Fi gure 3. These data were used to quantify Kr and Xe emissions from the scrubber.

Figure 1: Actual sampling schematic used fo r E-HTVS and TPU at NEC Electronics Inc. Schematic shows the calibration and sa mpling capability for each instrument.

7Kr Emissions from E-HTVS during Flow Calibration

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QMS ScanConcentration(ppmv) Calibration

Spike Flows

Xe Emissions from E-HTVS during Flow Calibrattions

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QMS ScanConcentration (ppmv) Calibration

Spike Flow

Figure 2: QMS response to Kr (top) and Xe during QMS calibration and E-HTVS spiking of Kr and Xe. (Note: Kr and Xe emissions in the figure titles denote the flow of tracer materials and have nothing to do with process emissions.)

QMS Responser to Kr and Xe

0.00E+00 1.00E-04 2.00E-04 3.00E-04 4.00E-04 5.00E-04 6.00E-04 7.00E-04 8.00E-04 9.00E-04 1.00E-03

0.0 20.0 40.0 60.0 80.0 100.0 120.0 Concentration of Added Kr & Xe (ppmv)Relative Ion Intensity

amu 84/14 Predicted amu 132/14 Predicted Kr

Xe

Figure 3: Regression analysis of data obtained during calibration of QMS response to 86 Kr and 132 Xe in N 2 . These data were used to determine Kr and Xe concentration during chemical spiking of scrubbers.

8The FTIR was calibrated on-site using test atmospheres created through dynamic dilution blending of a 1% C 2 F 6 in N 2 standard. Several mixtures were created to calibrate the response of the FTIR equipped with the 5.6 m gas cell. Fi gure 4 shows the calibratio n curve generated for the CF 3 symmetrical deformation of C 2 F 6 (centered at 714 cm -1 ) as measured by the maximum absorbance of the R branch for each calibration poi nt. The relative error of this calibration was determined to be 3.1 %.

Absorbance for R Branch of CF 3 Symetrical Defromation (714 cm -1 ) as function of C2F6 Concentration

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

0 200 400 600 800 1000 1200 1400 Concentration of Added C2F6 (ppmv)Absorbance

Slope: 5.1E-4 ± 1.6E-5 Intercept: 0.0173 ± 0.014 R 2 : 0.996

Figure 4: Calibration of FTIR response to C 2 F 6 . Note 1: These data were generated on-site at NEC Electronics Inc. using a 1% C 2 F 6 in N 2 standard. Note 2: The least squares line is not shown in Figure, but the relevant parameters of regression line and statistics are presented. 

## 3.0 Data Analysis

3.1 Determination of Scrubber Dilution

One of the primary goals of this study was to acc urately determine the dilution that occurs when gas emitted from the process chamber passes th rough the scrubber. Dilution can occur from many sources including effluents from other ch ambers, combustion gases and by-products added to and generated within the sc rubber, vapors added as the gas stream passes through the water scrubber portion of the system, in-board leaks, and back diffusion from main headers. The method of determining dilution in this study was to use a purely experimental approach where a chemical was spiked into the gas stream entering the scrubber at a known flow rate, and determined in the scrubber effluent stream. From the determined concentration and the

9controlled flow rate added to the process exhaus t duct, a total flow from the scrubber could be calculated:

TF = S f /(C an X 10 -6 ) (1)

Where S f represents the spike gas flow a nd is reported in liters, and C an represents the analyte concentration reported in ppmv.

The experiment conducted to determine total flow from the E-HTVS scrubber consisted of using the calibration system shown in Figure 1 to add calibration gas into the process effluent through the FTIR sample line where the process effluent was monitored. While calibration gas was being added, the QMS was used to sample scrubber effluent. The flow of calibration gas was controlled with a 0 – 5 slm MFC that was calibrated for nitrogen. Five flow rates were added to the scrubber: 1, 2, 3, 4 and 5 slm. At 1% concen tration, each of these fl ows corresponded to Kr and Xe flows of 0.01, 0.02, 0.03, 0.04 and 0.05 slm, resp ectively. Concentration profiles for Xe and Kr determined from QMS data during this experiment are shown in Figure 5 for CVD Tool #1, which was the tool used for testing the E-HTVS scrubber.

Applying Eq. 1 to the data shown in Figure 5 for the E-HTVS scrubber yielded the total equivalent flows determined for both Xe and Kr, which are contained in Table I. The average total flow for each species was:

Xe: 741 ± 3 Kr: 765 ± 3

Here the reported standard deviatio ns are the best estimate of the standard deviations of the mean for total flows contained in Table I. Combining the data for Kr and Xe yielded a best estimate of effective flow of 757 ± 2 slm, which is the variance weighted average of the mean.

The precision of these measurements were ± 0.3 %. The differences between the flow values (3%) obtained for Kr and Xe could be attributable to other factors affecting accuracy, such as the accuracy of the Kr and Xe concentra tions in the calibration standards.

10_____________________________________________________________________ Table I: Total equivalent flow measurements from E-HTVS determined using Xe and Kr.

Xe/Kr Flow (slm) Xe Conc (ppmv) Total Equivalent Flow (slm) Kr Conc (ppmv) Total Equivalent Flow (slm)
0.010 12.7 ± 1.7 787 ± 122 14.4 ± 1.3 694 ± 63

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

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

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

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

______________________________________________________________________

Xe Emissions from E-HTVS during Flow Calibrattions

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QMS ScanConcentration (ppmv) Calibration

Spike Flow

Kr Emissions from E-HTVS during Flow Calibration

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QMS ScanConcentration (ppmv) Calibration

Spike Flows

Figure 5: Xe (top) and Kr (bottom) emission s from E-HTVS during spike calibration. Calibration data were generated using test atmospheres as described above.

11The same approach was used for determining fl ow from the TPU. Figure 6 shows Xe and Kr emissions from the TPU during spiking of the scr ubber. The same Xe and Kr flow rates of 0.01, 0.02, 0.03, 0.04, and 0.05 slm were used. Table II contai ns the total flow determined for each species at each spike flow rate. The av erage total flow for each species was:

Xe: 751 ± 3 Kr: 838 ± 2

Here the reported standard deviatio ns are the best estimate of the standard deviations of the mean for total flows contained in Table II. Combining the data for Kr and Xe yielded a best estimate of effective flow of 815 ± 2 slm, which is the variance weighted average of the mean.

The precision of these measurements were ± 0.3 %. The difference between the flow values observed for Kr and Xe on the TPU (11%) were greater than those observed on the E-HTVS (3%). An additional flow determination method was deployed.

An additional experiment using Ar was conducte d on the TPU. The experiment consisted of flowing Ar from the CVD Tool #2 through the sc rubber and determining the Ar concentration emitted from the scrubber. Figure 7 shows the Ar emission profile for 4 process flows: 2.0, 1.5, 1.0 and 0.5 slm. As indicated in Figure 7, Ar background concentration was relatively high due to the natural atmospheric abundance of 0.94 %. This background was subtracted from the measured Ar concentration during the Ar flows to yield a concentration that could be attributable to the added Ar. Table III contains the data fr om this experiment. The data in Table III was used to determine the TPU flow by dividing the Ar process flow (in sl ) by the differential Ar concentration ( Δ Ar). The weighted average total flow determined during this experiment was 826 ± 2 slm . This value is in close agreement (± 1.5%) with the reported effective dilution for the Kr spike test (838 slm).

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

Xe/Kr Flow (slm) Xe Conc (ppmv) Total Equivalent Flow (slm) Kr Conc (ppmv) Total Equivalent Flow (slm )

0.010 12.3 ± 1.3 813 ± 86 12.7 ± 0.9 787 ± 56 0.020 27.2 ± 2.2 735 ± 60 22.8 ± 2.5 877 ± 95 0.030 42.2 ± 2.7 711 ± 45 35.0 ± 1.5 857± 37 0.040 51.6 ± 4.1 775 ± 62 47.6 ± 1.6 840 ± 28 0.050 63.6 ± 5.0 786 ± 62 59.9 ± 1.9 835± 26

Table III: Ar concentration determined in TPU effluent during Ar flow testing. Δ Ar concentration is the measured co ncentration minus the baseline.

Ar Process Flow (slm) Ave. Ar Conc. (ppmv) Δ Ar Conc (ppmv) Total TPU Flow (slm)

12Baseline (0) 8685 ± 22

_ _
2.0 11,098 ± 154 2413 ± 156 828 ± 53 1.5 10,302 ± 33 1617 ± 40 927 ± 23 1.0 9996 ± 27 1311 ± 35 762 ± 20 0.5 9321 ± 18 636 ± 28 786 ± 35 Baseline (0) 8655 ± 18

_ _

A summary comparing total flows determined for both scrubbers is contained in Table IV. Results for Kr and Xe on the E-HTVS scrubber we re within 3%, while on the TPU system the difference was 11 %. In both cases the Kr based determination was higher than Xe determination. The dilution determined using Ar on the TPU was found to be within 1.5 % of the value determined using Kr. Both values were > 10 % higher than the value determined using Xe. Considering that using Ar supplied by the process tool is independent of the calibration standard accuracy for the spiking process, this result suggests that inaccuracies in the Xe determination may more likely have occurred. Gi ven the relative close agreement in results for all flow determinations, this was not further inve stigated. However, the Xe discrepancy warrants further investigation in subseque nt evaluation of the methodology.

________________________________________________________________________ Table IV: Summary of the average total fl ow determinations for E-HTVS and TPU at NEC Electronics Inc. All flows reported as slm. POU System Xe Spike Kr Spike Ar On-Tool

E-HTVS 741 ± 3 765 ± 3 N/A TPU 751 ± 3 838 ± 2 826 ± 2

__________________________________________________________________
Kr Concentration Determiend during TPU Spike Flow Calibration

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QMS ScanConcentration (ppmv)

13XeConcentration Determiend during TPU Spike Flow Calibration

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Figure 6: Kr (top) and Xe (bottom) emissi ons from TPU during chemical spiking of scrubbers.

Ar Emission from TPU during NF3 DRE Testing

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Ar Conc 2

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Baselin Ar Flow from MFC on

Figure 7: Ar emission from TPU while Ar was being flowed through the process chamber on CVD Tool #2. Baseline Ar concentratio n was close to that expected in air.

Once the total flow from the scr ubbers has been determined it was then possible to determine the dilution of process effluent occurring across the scrubbers. This calculation requires measuring the dilution that occurs as gases from the pr ocess chamber are pumped out of the chamber and fore line and sent into the corrosive scrubbed exha ust. The experiment to measure the dilution of CVD Tool #1 and CVD Tool #2 chambe r effluent consisted of flowing C 2 F 6 into the CVD Tool #1 chamber and NF 3 into the CVD Tool #2 chamber, with the radio frequency (RF) power in the chambers turned off, at several flow rates. The determined C 2 F 6 and NF 3 concentrations in the chamber effluent could be used to calculate the total process flow entering the scrubber from the following equation:

14T PF = PG f /(C PG X 10 -6 ) (2)

Here the total process flow (T PF ) is determined from the rati o of the process gas flow (PG f ) in slm divided by the measured concentration (C PG ) in ppmv.

Process flow data for the E-HTVS system were obtained by flowing C 2 F 6 through the CVD Tool #1 chamber at several flows with the RF power turned off. Figure 8 shows the C 2 F 6 emission profile for 5 different flows. From these data the total process flow was determined and is contained in Table V. The average total process flow was 83.58 ± 0.03 slm. Combining this value with the total scrubber flow yielded the effectiv e dilution of influent gas across the EHTVS:

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

This value was used for all subsequent DRE calcu lations. This value represents the effective dilution that was determined for the E-HTVS. Th ese data do not necessarily imply a total flow of 757 slm was flowing through the abatement devi ce, but do imply that the chemical spiking agents were diluted to an equivalent flow of 757 slm. The source of this dilution was not determined, but could be attributable to factors such as in-board leaks in the duct work between the scrubber outlet and the sample location or mixing at the sample location from the main header of the scrubbed corrosive exhaust system . Having an accurate determination of this effective dilution is critical in determ ining an accurate DRE for the scrubber.

________________________________________________________________________ Table V: Total process flow de termination for CVD Tool #1 using C 2 F 6 tool flows. C 2 F 6 Flow (slm) Ave. C 2 F 6 Concentration (ppmv) Total Process Flow (slm) 1.0 11,714 ± 61 85.4 ± 0.4 0.8 9461 ± 50 84.6 ± 0.4 0.6 7232 ± 43 83.0 ± 0.5 0.4 4889 ± 32 81.8 ± 0.5 0.2 2500 ± 26 80.0 ± 0.8

15C2F6 Emissions from E-HTVS during Process Flow Calibrations

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FTIR ScanConcentration (ppmv) 1.0 slm

0.8 slm

0.6 slm

0.4 slm

0.2 slm 5 min Chamber Clean

Figure 8: C 2 F 6 emission profile for CVD Tool #1 dur ing process flow calibration. C 2 F 6 emissions from a 5 minute ch amber clean are also shown.

Total process flow into the TPU was determined by flowing NF 3 from the chamber with RF power off. Process emissions from six flows ar e shown in Figure 9. From these data the total process flow was determined to be 15.50 ± 0.01 slm. Table VI contains NF 3 concentrations determined for each flow. The total process flow and total TPU exhaust flow were used to calculate the dilution occurring in the TPU:

Dilution Factor = (831 ± 1)/(15.50 ± 0.01 ) = 53.6 ± 0.1 Having determined the total process flow for each tool and scrubber allows determination of the dilution occurring across the scrubber. These da ta were used to dete rmine the scrubber F-GHG DRE.

______________________________________________________________________ Table VI: Total process flow de termination for CVD Tool #2 using NF 3 tool flows. NF 3 Flow (slm) Ave. NF 3 Concentration (ppmv) Total Process Flow (slm) 0.50 31,735 ± 157 15.8± 0.1 1.00 67,886 ± 974 14.7 ± 0.1 1.50 93,964 ± 685 16.0 ± 0.1 0.20 13,098 ± 83 15.3 ± 0.1 0.25 16,147 ± 50 15.5 ± 0.1 0.30 19,020 ± 41 15.8 ± 0.1

16NF3 Emissions from AMAT HDP during Process Flow Calibration

0 20000 40000 60000 80000 100000 120000

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FTIR ScanConcentration (ppmv)

0.500 1.000 1.500

0.200 0.250 0.300

Figure 9: NF 3 emission profile fr om CVD Tool #2 during NF 3 process flow calibration.

3.2 Scrubber DRE Determinations

Determination of the E-HTVS scrubber performa nce was performed using two different testing conditions. The first was to meas ure the scrubber effluent of C 2 F 6 during the total process flow calibrations and the second was to m easure the scrubber effluent during C 2 F 6 /O 2 chamber cleans. Two chamber cleans were monitored. The first wa s a short 5-minute clean of a chamber that was relatively clean (little tungsten accumulation in the chamber). The second clean was longer and was performed after an accumulation of approximately (ca.) 20 μm of film that had built up in the chamber. This clean used an optical end- point mechanism to determine the length of the clean. The process recipe for the chamber clean was to flow 1.2 slm C 2 F 6 and 1.2 slm O 2
. Determination of the TPU performance could only be done using NF 3 flows from the tool gas delivery system, as the tool chosen for this pr oject was not operational at the time of testing. Several NF 3 flows were sent through the pr ocess chamber to determine NF 3 DRE. However, no process wafers could be run and the system could not be evaluated under manufacturing conditions.

3.2.1 TecHarmonic E-HTVS DRE

The E-HTVS DRE for C 2 F 6 was determined during process fl ow calibrations. Figure 10 shows C 2 F 6 emissions from process and scrubber durin g the flow calibration. Using the average measured C 2 F 6 concentration for both inlet and outlet sa mples from each step and applying the dilution correction yields the C 2 F 6 DRE for the E-HTVS scrubber during process flow determination. These averages for each C 2 F 6 flow are contained in Table VII. The associated DRE values for each C 2 F 6 flow are also contained in Table VII.

________________________________________________________________________

17Table VII: C 2 F 6 DRE in E-HTVS during process flow calibrations. Dilution adjustment was based total measured flows into and out of the scrubber. C 2 F 6 Flow (slm) C 2 F 6 Conc. In Process Effluent (ppmv) C 2 F 6 Conc. In E-HTVS Effluent (ppmv) Dilution Adjusted C 2 F 6 Concentration (9.05X in ppmv) DRE (%)

1.0 11,714 ± 61 1288 ± 10 11,656 0 % 0.8 9461 ± 50 1064 ± 10 9629 -2 % 0.6 7232 ± 43 736 ± 10 6661 8 % 0.4 4889 ± 32 505 ± 8 4570 7 % 0.2 2500 ± 26 250 ± 4 2263 9 %

________________________________________________________________________ From the data contained in Table VII above, a 95% Confidence Interval (CI) is determined to be 5.0 ± 4.4 % indicating that all values in Table VII are stat istically zero at the 95 % CI.

C2F6 Emissions from E-HTVS during Process Flow Calibrations

0 2000 4000 6000 8000 10000 12000 14000

0 50 100 150 200 250 300 350 400 450 500
FTIR ScanConcentration (ppmv) 1.0 slm

0.8 slm

0.6 slm

0.4 slm

0.2 slm

C2F6 Emissions from E-HTVS during Process Flow Calibration

0 200 400 600 800 1000 1200 1400

0 50 100 150 200 250 300 350 400 450 500
FTIR ScanConcentration(ppmv) 1.0

0.8

0.6

0.4

0.2

Figure 10: Inlet and outlet C 2 F 6 emission profiles for E- HTVS during process flow calibration.

18The E-HTVS DRE for C 2 F 6 was also determined during chamber cleans. Emissions from the chamber clean included significant le vels of tetrafluoromethane (CF 4 ), which was formed as byproduct. Other chamber clean by-pr oducts included carbonyl fluoride (COF 2 ), tungsten hexafluoride (WF 6 ) and carbon monoxide (CO) as identif ied in the FTIR spectrum shown in Figure 11. Emission profiles of CF 4 and C 2 F 6 for two chamber cleans are shown in Figure 12. Emission profiles of CF 4 and C 2 F 6 from the E-HTVS are also shown in Figure 12. These data were numerically integrated over time to yield emission volumes. Comparison of the CF 4 and C 2 F 6 emission volume entering the scrubber with that emitted from the scrubber can be used to directly calculate DRE for each compound.

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

V EM = Σ C i T f Δ t (5)

Where the total emission volume (V EM ) is the summation of each FTIR data point where the concentration of analyte C i is determined during time interval Δ t and multiplied by the total flow (T f ). The summation of the entire emission pr ofile provides an emission volume for a given analyte during the process. Duri ng this study, these calculations were performed using standard spreadsheet software (Microsoft Excel). Use of this technique reinfo rces the importance of accurately determining the total process and scrubber flows as described in the sections above.

-.4 -.2 0 .2 .4 .6 .8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

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File # 2 = NEC_1343 9/25/2007 4:36 PM Res=None C2F6 CF4

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Figure 11: FTIR spectrum of process emissions during C 2 F 6 /O 2 chamber clean on CVD Tool #1.

19C2F6 and CF4 Emissions from LPW108 During Chamber Clean

0 2000 4000 6000 8000 10000 12000 14000

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FTIR ScanConcetration C2F6 EPA 5.6m cell 150C

CF4 EPA 5.6m cell 150C

C2F6 and CF4 Emissions from E-HTVS during Chamber Cleans

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FTIR ScanConcentration (ppmv)
C2F6 EPA 5.6m cell 150C

CF4 EPA 5.6m cell 150C

Figure 12: C 2 F 6 and CF 4 emissions from CVD Tool #1 (top) and E-HTVS scrubber during chamber cleans. The first clean was timed for 5 minutes. The second clean was for a tungsten accumulation of ca. 20μm and was run until end point.

Integration of the emission prof iles shown in Figure 12 yielded emission volumes contained in Table VIII for both process and scrubber emission s. These integrated emission volumes were compared directly to determine F-GHG DRE duri ng the chamber cleans, which are also included in Table VIII. The results are clos e in value to those presented for C 2 F 6 during the process flow calibrations shown above.

The results for CF 4 yielded an average DRE of 9.5 % with a 95 % CI of ± 9.8 %. Use of these two data points yields DRE‘s in the range of -0.3 – 19.3 %, which includes zero. Therefore, we cannot reject the hypothesis that th e DRE equals zero. Given that CF 4 is more difficult to abate than C 2 F 6 due to higher bond en ergy of C-F compared to C-C, a zero DRE would be expected and the data indicates statistically that this is the case. The actual deviation from a zero DRE as

20determined in this study can be at tributable to the propagation of errors associated with all the factors used in calculating the va lues contained in Table VIII.

_______________________________________________________________________ Table VIII: Integrated F-GHG process and scrubber emissions for CVD Tool #1 (process) and E-HTVS during chamber cleans. Deta ils on the cleans provided in text Clean #1 Clean #2 C 2 F 6 Process Emission (sl) 3.914 8.266 C 2 F 6 E-HTVS Emission (sl) 3.723 8.802 C 2 F 6 DRE 5 % -5 % CF 4 Process Emission (sl) 1.011 1.730 CF 4 E-HTVS Emission (sl) 0.952 1.494 CF 4 DRE 6 % 13 %

The data contained in Table VIII can also be used to determine the process DRE for C 2 F 6 and the process emission factor for CF 4 . The process DRE is defined as the ratio of C 2 F 6 emitted from the process to the total C 2 F 6 added to the process. For clean #1 the total C 2 F 6 added to the process was 6.0 sl based on a 1.2 slm process fl ow and 5 minute chamber clean, thus the C 2 F 6 process DRE was 35 % for this clean. For clean #2, which reached end point at 11.1 minutes, the C 2 F 6 process DRE was 38% based on a total process flow of 13.3 sl.

The CF 4 emission factor is defi ned as the ratio of CF 4 volume emitted from the process to the C 2 F 6 volume added to the process. For cleans #1 and #2 these values were 17 and 13%, respectively. The slight differences between clea ns 1 and 2 were attributed to clean #2 being done when the chamber had more tungsten film accumulation in the chamber.

All of the DRE values reported for C 2 F 6 and CF 4 indicate that the E-HTVS system does not abate these gases under the operating conditions te sted. The result obtained for CF 4 is statistically equivalent to zero at the 95 % CI.

3.2.2. Edwards TPU DRE

As stated above the CVD Tool #2 was not ope rational. This prevented evaluating the performance of the TPU during wafer pro cessing. It was possible to flow NF 3 from the process chamber through the TPU. The five flow rates used to collect the data in Figure 9 (data collected at the inlet to the TPU) yiel ded undetectable levels of NF 3 in the TPU effluent. Figure 13 shows FTIR spectra obtained at the inlet and outlet of the TPU while 1.5 slm NF 3 was flowing from the process chamber. These data can be used to report a TPU DRE of > 99.9 % based on an estimated FTIR detection limit of 0.5 ppmv, an average inlet concen tration of 93,964 ± 685 ppmv and a dilution factor of 53.6 X:

21Diluted NF 3 : 93,964/53.6 = 1750 ppmv fully diluted Undetected NF 3 : 0.5/1750 = 0.00029 DRE (1.000 – 0.00029)x100 = 0.99971 = 99.971%

The TPU was proven to be e ffective at abating any NF 3 potentially emitted from the process under the conditions with which it was operate d. The TPU thermocouple temperature gauge reported an operating temperature of ca. 820 o C. An experiment was conducted to determine if the NF 3 DRE would be reduced if the TPU operati ng temperature was reduced. Temperature reduction was done by reducing the natural ga s flow by ca. 10 and 20 %, which yielded operating conditions of 665 o C and 480 o C, respectively. Under th ese operating conditions NF 3 was not detected in the TPU effluent suggesting that it may be possible to operate the TPU at lower temperatures if its sole purpose is to abate NF 3 . One observed consequence of operating at lower temperatures was an increase in CO and CH 4 emissions from the TPU relative to those observed at 820 o C. Figure 14 shows CO and CH 4 increased emissions while the temperature was reduced.

Another by-product observed during NF 3 abatement was nitric oxide (NO). Figure 15 shows NO emission profile during testing. NO emissions are correlated with NF 3 flows from the tool.

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Figure 13: FTIR spectra of TPU exhaust (to p) and CVD Tool #2 process exhaust (bottom) while 1.5 slm NF 3 was flowing through the chamber. NF 3 emissions from TPU were below the detection limit of the FTIR (0.5 ppmv) . The process emissions were ca. 94,000 ppmv.

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## 4.0 Conclusion

The purpose of this study was to accurately dete rmine the DRE of F-GHGs in two commercially available POU abatement systems used in semi conductor manufacturing. A critical component of an accurate DRE was to determ ine the dilution of process efflue nt occurring in the scrubbers. Chemical spiking of inert gases wa s used to determine the dilution. Kr and Xe were used for the TecHarmonic E-HTVS scrubber. It was determined that both Xe and Kr yielded statistically equivalent effective dilution for the E-HTVS. Kr, Ar and Xe were used to determine the effective dilution occurring in the Edwards TPU sc rubber. All three ch emicals yielded similar results. The effective dilution for each system was combined with the process emission data to determine the DRE of ea ch scrubber for F-GHGs C 2 F 6 and CF 4 on the E-HTVS and for NF 3 on the TPU.

The DRE determined for C 2 F 6 and CF 4 on the E-HTVS were very low. The results indicate a statistically zero DRE was obtained for both C 2 F 6 and CF 4 on the E-HTVS.

The TPU was determined to have a very high DRE, > 99.9%, for NF 3 when accounting for the dilution occurring in the scrubber. The data also demonstrated that the TPU can be operated at lower temperatures while maintaining a high DRE for NF 3 . While other process and operating parameters may need to be considered before reducing the temperature, it could be possible to operate at lower natural gas flows and maintain a high NF 3 DRE.

The process DRE for C 2 F 6 during tungsten chamber clean was determined to be 35 - 38 %, which was in close agreement with the 2006 IPCC reported value of 40 %. A CF 4 emission factor of 13 – 17 % was determined, which was also in close agreement to the 2006 IPCC reported value of 20 %.

23CH4 Emissions from TPU During NF3 Breakthrough Testing

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CO Emissions from TPU During NF3 Breakthrough Study

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Figure 14: Relative CH 4 and CO emissions from TPU during reduced temperature operation. The temperature wa s reduced by lowering the CH 4 flow into the system.

24NO Emissions from TPU During NF3 Breaktrhough Test

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Figure 15: Nitric oxide emission profile during NF 3 flows from CVD Tool #2 chamber through the TPU. NO emis sions are correlated with NF 3 flow rate

25