### Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics Manufacturing: A Cooperati ve Evaluation with Qimonda March 2008

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

EPA 430-R-08-0172 

## Acknowledgements

The analytical measurements, da ta interpretation, and report pr eparations were funded by the U.S. Environmental Protection Agency under cont ract GS-10F-0124J to ICF International and Air Products and Chemicals, Inc. The authors wi sh to express their appreciation and thanks to Qimonda, for their gracious support to this study by not only providing thei r facilities but also their valuable assistance and a dvice. The U.S. EPA looks forwar d to continued collaborations with Qimonda and other Partners in the PFC Reduction/Climate Change Partnership for Semiconductors.3 

### Table of Contents Page

Acknowledgement s...................................................................................................... 2

1.0 Introduction

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

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

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

3.1 Determination of Scrubber Dilution............................................................... 8

3.2 Scrubber DRE Determin ations.................................................................... 11 3.2.1 DRE Determination During Process Calibration Flows.............................. 11 3.2.2 Determination of DRE during Wafer Processing...................................... 14

4.0 Conclusion

.............................................................................................................................. .. ... 214 

### List of Tables Page

Table I Data used to determine the total fl ow emitted from TPU systems on AMZ17 and AMZ18

............................................................................................................................. ......... ...... 9 Table II Total chamber and process pump effluent flow from chamber B on AMZ17 and AMZ18

............................................................................................................................. ............ ... 11

Table III CF 4 DRE values determined during process flow calibrations ..................................... ....... 13

Table IV CHF 3 DRE for AMZ18 scrubber based on data shown in Figure 7 .............................. ....... 14 Table V Process Utilization for etch gases used in contact etch... .............................................. ....... 17

Table VI CF 4 DRE determined for each scrubber by comparing inlet and outlet emission volumes

............................................................................................................................ .......... ....... 19 Table VII Comparison of two methods used to determine CF 4 DRE on scrubbers for AMZ17 and AMZ18 .........................................................................................................................

....... 215 

### List of Figures Page Figure 1 Sampling schematic used for testing TPU PFC DRE................................................. 8 Figure 2 QMS Response to 84 Kr during calibration......................... ....................................... ...... 8 Figure 3 Regression analysis of calibrati on data shown in Figure 2.......................................... 9 Figure 4 Kr concentration determined for AMZ17 scrubber during spiking experiment................. 10 Figure 5 CF 4 emission concentration determined from AMZ17 chamber B while CF 4 was flowed through chamber B with RF power off ................................................................. 11 Figure 6 CF 4 emission profile from AMZ18 chamber B (top) and from TPU (bottom) during process flow calibration............................................................................................ 13 Figure 7 CHF 3 emissions from process (top) and scrubber (bottom) during CHF 3 process flow calibration.................................

.................................................................. 15 Figure 8 FTIR spectra of emissions from arc etch (top) and contact main etch (bottom)................. 17 Figure 9 Emission profiles for PFC process gases (top) and plasma by-products (bottom) during contact etching of test wafers on AMZ18 chamber B................................................ 19 Figure 10 FTIR spectrum of AMZ18 scrubber emissions during test wafer processing .................... 20 Figure 11 CF 4 emission profile from AMZ18 scrubber during processing of test wafers on Chamber B, and during processing of production wafe rs on multiple chambers................................ 21 Figure 12 CF 4 emission profile from AMZ17 scrubber dur ing processing of production wafers on Chamber B, and during processing of produc tion wafers on multiple chambers................. 216 

## 1.0 Introduction

The purpose of this study was to accurately dete rmine the Destruction or Removal Efficiency (DRE) of a Point Of Use (POU) abatement system or scrubber for process emissions containing perfluorinated compounds. A key component in accurately determining DRE was to determine the dilution of process exhaust occurring in the scrubber. Th is study used an experimental approach to measure the dilution across the scrubber by injecting a chemical tracer that could not react in the scrubber, or be produced as a by- product during scrubber op eration. Krypton was used as the chemical tracer as it me t the requirements for this application.

Testing was conducted in a fully functional se miconductor manufacturing facility, owned and operated by Qimonda in Richmond VA. Two to ols, AMZ17 and AMZ18, each equipped with POU scrubbers were tested. Both tools ran th e same process and used the same model of commercially available scrubber. The process eval uated was a contact etch process, which used PFC gases CF 4, CHF 3 and C 4 F 6
. 

## 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 manometers. 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, or7 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 res ponse to Kr on site us ing a dynamic dilution blending system. Test atmospheres containi ng Kr, were created by blending a calibration standard containing 1% of Kr in N 2 with N 2 diluent. The QMS response to 84 Kr during calibration is shown in Figure 2. From regression analyses of these data a calibration curve was generated and is shown in Figure 3. This calib ration was repeated for both tools tested.

Figure 1: Sampling schematic used for testing TPU PFC DRE

Figure 2: QMS Response to 84 Kr during calibration. QMS Response to Kr

0.00E+00 1.00E-11 2.00E-11 3.00E-11 4.00E-11 5.00E-11 6.00E-11

0 100 200 300 400 500 600 700 800
QMS ScanIonIntensity 99 ppmv

79 ppmv

60 ppmv

40 ppmv

20 ppmv

ai r8 Figure 3: Regression an alysis of calibration data shown in Figure 2


## 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 en tering the scrubber at a known flow rate, and determined in the scrubber effluent stream. From the determined concentration and the controlled 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 and is reported in liters per minute, and C an represents the analyte concentration re ported in ppmv.

The experiment conducted to determine dilu tion for the scrubbers on AMZ17 and AMZ18 consisted of using the calibration system show n 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 Ma ss Flow Controller (MFC) that was calibrated for nitrogen. Five flow rates were added to the scrubber: 1, 2, 3, 4 and 5 slm. The concentration profile for Kr determined from QMS data duri ng this experiment are shown in Figure 4 for AMZ17. Regression Analysis of Kr Calibration

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

0 20 40 60 80 100 120
Concentration of added KrRelative Ion Intessity

Y = 7.3e-6X + 2.5e-59 Figure 4: Kr concentration determined fo r AMZ17 scrubber during spiking experiment. Flow rates of calibration gas are indicated on the graph.

Applying Eq. 1 to the data obtained for the sc rubbers on AMZ17 and AMZ 18 yielded the total flows contained in Table 1. The average total fl ow for each scrubber is also contained in Table 1.

______________________________________________________________________________

Table I: Data used to determine the total flow emitted from TPU systems on AMZ17 and AMZ18. AMZ17 System Total Cal Gas Flow (slm) Equivalent Kr Flow (slm) Kr Concentration measured at TPU

Outlet (ppmv) Total Flow (slm)

1.0 0.010 15.1 ± 1.4 662 ± 61 2.0 0.020 27.1 ± 2.7 738 ± 74 3.0 0.030 40.8 ± 1.8 735 ± 32 4.0 0.040 55.5 ± 1.9 723 ± 25 5.0 0.050 69.5 ± 2.0 719 ± 21 AMZ18 System Total Cal Gas Flow (slm) Ave. Total Flow for AMZ17 System 721 ± 2 1.0 0.010 14.1 ± 1.6 709 ± 80 2.0 0.020 25.5 ± 1.7 784 ± 52 3.0 0.030 38.8 ± 1.7 773 ± 34 4.0 0.040 52.2 ± 1.9 766 ± 28 5.0 0.050 65.8 ± 2.4 760 ± 28

Ave. Total Flow for AMZ18 System 765 ± 2

______________________________________________________________________________ Kr Concentration

-10.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

0 100 200 300 400 500 600 700 800 900

QMS ScanConcentration (ppmv)

1 slm 2 3 slm 4 slm 5 slm10 The total scrubber flow data can be combined wi th the flow from the process chamber and pump, which go into the scrubber and is referred to as the total process flow, to determine the dilution that occurs as the process efflue nt passes through the scrubber. This calculation requires measuring the dilution that occurs as gases from the etch chamber are pumped out of the chamber and fore line and sent in to the corrosive scrubb er exhaust. The experiment to measure the dilution of AMZ17 and AMZ18 chambe r effluent consisted of flowing CF 4 into the chamber with the RF power in the chamber turned off at several flow rates. The determined CF 4 concentration in the effluent could be used to calculate the total process flow entering the scrubber from the following equation:

TPF = PG f /(C PG X 10 -6 ) (2)

Here the total process flow (TPF) is determined from the ratio of the process gas flow (slm) divided by the measured concentration (C PG ) in ppmv. The values obtained for CF 4 on AMZ17 are shown in Figure 5. From these data the total process exhaust flows for both AMZ17 and AMZ18 were calculated and are contained in Table II.

Figure 5: CF 4 emission concentrations determin ed from AMZ17 chamber B while CF 4 was flowed through chamber B with RF power off

. CF4 Emissions from ETCAMZ17 Chamber B during CF4 Chamber Flows

0 2000 4000 6000 8000 10000 12000 14000

0 100 200 300 400 500 600
FTIR ScanConcentration (ppmv) 0.200 slm

0.150 slm

0.100 slm

0.050 slm

0.025 slm11 ______________________________________________________________________________ Table II: Total chamber and process pump e ffluent flow from chamber B on AMZ17 and AMZ18. Values determined from the average concentration measured during each CF 4 flow using Eq. 2 ETCAMZ17 ETCAMZ18

CF 4 Flow (slm) CF 4 Conc. (ppmv) Total Effluent

Flow (slm) CF 4 Flow (slm) CF 4 Conc. (ppmv) Total Effluent

Flow (slm) 0.200 11,211 ± 183 17.8 ± 0.3 0.200 12,134 ± 195 16.5 ± 0.3

0.150 8780 ± 55 17.1 ± 0.2 0.150 9652 ± 121 15.5 ± 0.2 0.100 5784 ± 109 17.3 ± 0.3 0.100 6477 ± 48 15.4 ± 0.1 0.050 3024 ± 43 16.5 ± 0.2 0.050 3297 ± 32 15.2 ± 0.2 0.025 1554 ± 48 16.1 ± 0.5 0.025 1681 ± 61 14.9 ± 0.5

______________________________________________________________________________ The data in Table II yielded an average tota l flow of 17.0 ± 0.7 slm for AMZ17 and 15.5 ± 0.6 slm for AMZ18. The process fl ow into the scrubber combined with the total flow from the scrubber yielded the experimentally measured dilution for each scrubber:

System Dilution = TF out /TF in (3)

For AMZ17: Dilution = 721 ± 2/17.0 ± 0.1 = 42.4 ± 2

For AMZ18: Dilution = 765 ± 2/15.5 ± 0.1 = 49.4 ± 2

Equipped with these dilution fact ors and total flows into and out of the scrubbers it is now possible to determine the scrubbers DRE for the gases used and by-products formed during wafer processing.

3.2 Scrubber DRE Determinations

Determination of the scrubber pe rformance was done using two diffe rent testing conditions. The first was to measure the scrubber effluent of the etch process gases during the total process flow calibrations and the second was to measure the scrubber effl uent during wafer processing.

3.2.1. DRE Determination During Process Calibration Flows

The scrubber DRE for CF 4 , CHF 3 and C 4 F 6 was determined during total process flow calibrations by comparing the steady-state inlet an d outlet concentrations during the flow of each gas, and adjusting for the scrubber dilution. From these data a direct calc ulation of the scrubber DRE could be made. Figure 6 show s the scrubber inlet and outlet CF 4 concentrations determined for AMZ18 while CF 4 was flowing through the chamber. (The se were the data used to calculate12 the AMZ18 process dilution.) These data were used to calculate the scrubber DRE for CF 4 using the following equation:

DRE = 1 – ((CF 4out X Dilution)/CF 4in ) (4)

Here CF 4out and CF 4in represent the average CF 4 concentrations determined for each flow shown in Figure 6. Using this method of comparing co ncentrations into and out of the scrubber, CF 4 DRE values for AMZ17 and AMZ18 are tabulated and contained in Table III.

Figure 6: CF 4 emission profile from AMZ18 cham ber B (top) and from TPU (bottom) during process flow calibration. Each level of concentration is equivalent to a specific CF 4 flow rate thru the process chamber.

_________________________________________________________________

Table III: CF 4 DRE values determined during process flow calibrations. CF4 Emissions from ECTAMZ18 Chamber B During Process Flow Calibration

0 2000 4000 6000 8000 10000 12000 14000 16000

900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400
FTIR ScanConcentration (ppmv)

CF4 Emissions from TPU During Process Flow Calibration

0 50 100 150 200 250

2400 2500 2600 2700 2800 2900 3000
FTIR ScanConcentration (ppmv)13 AMZ17 CF 4 Flow (slm) Ave Process Emiss. Conc. (ppmv) Ave Scrubber Emiss. Conc. (ppmv) Dilution Adjusted Concentration (ppmv) DRE (%)

0.200 11,121 ± 183 191 ± 2.5 8098 27.8 ± 0.6 0.150 8783 ± 55 151 ± 1.5 6402 27.1 ± 0.4 0.100 5811 ± 109 104 ± 0.6 4410 23.6 ± 0.5 0.050 3028 ± 43 51 ± 0.4 2162 28.5 ± 0.5 0.025 1551 ± 48 27 ± 0.5 1145 26.3 ± 1.0 AMZ18 0.200 12,134 ± 195 200 ± 2.0 9880 18.6 ± 0.4 0.150 9652 ± 121 162 ± 0.8 8005 17.1 ± 0.2 0.100 6477 ± 48 113 ± 0.5 5582 13.8 ± 0.2 0.050 3297 ± 32 59 ± 0.3 2915 11.6 ± 0.2 0.025 1681 ± 61 30 ± 0.2 1482 11.8 ± 0.5

______________________________________________________________________________
From the data contained in Table III the scrubber CF 4 DRE appears higher for the AMZ17 scrubber relative to the AMZ18 scrubber. Results for CHF 3 indicated that AMZ17 abated CHF 3 sufficiently to yield a concentration below the de tection limit of the FTIR equipped with a 5.6m cell, while relatively low emissions of CHF 3 were detected from AMZ18 scrubber. The CHF 3 inlet and outlet profiles determined during CHF 3 flows through chamber B on AMZ18 are shown in Figure 7. Both scrubbers abated C 4 F 6 sufficiently to yield an outlet concentration not detected by the FTIR.

CHF3 Emissions from AMZ18 Chamber B during Process Flow Calibration

0 2000 4000 6000 8000 10000 12000 14000

1100 1200 1300 1400 1500 1600 1700
FTIR ScanConcentration (ppmv) 200 sccm

100 sccm

25 sccm14 Figure 7: CHF 3 emissions from process (top) and scrubber (bottom) during CHF 3 process flow calibration.

From the data shown in Figure 7, the AMZ18 scrubber DRE was calculated for CHF 3 during the total process flow calibration and is contained in Table IV. Thes e data indicate a relatively high DRE for CHF 3 on AMZ18 scrubber. The AMZ17 sc rubber had a higher DRE as CHF 3 was not detected in the effluent during the CHF 3 flow calibration.

______________________________________________________________________________

Table IV: CHF 3 DRE for AMZ18 scrubber based on data shown in Figure 7. CHF 3 Flow (slm) Ave Process Emiss. Conc. (ppmv) Ave Scrubber Emiss. Conc. (ppmv) Dilution Adjusted Concentration (ppmv) DRE (%)

0.200 12,820 ± 170 3.1 ± 0.1 153 98.8 0.100 6538 ± 74 1.4 ± 0.06 69 98.9 0.025 1601 ± 15 0.4 ± 0.01 20 98.8

______________________________________________________________________________
The DRE for C 4 F 6 was high for both AMZ17 and AMZ18 sc rubbers. The estimated detection limit for C 4 F 6 was 0.5 ppmv with the 5.6m gas cell based on a signal to noise ratio of 3. Thus, based on a 0.100 slm process flow (0.100 slm was the maximum flow possible with the installed MFC), which yielded an average process emissi on of 6474 ± 59 ppmv on AMZ18, the minimum DRE would be 99.6 %.

3.2.2 Determination of DRE during Wafer Processing

Determining the scrubber DRE under wafer processing conditions can be much more challenging, particularly if the PFC effluent concentration does not reach a steady state condition (here a steady state condition is defined as dC/d t = 0, where the concentration (C) is not changing over a relatively short period of time, as shown in Figure 6). Under these conditions it may be CHF3 Emissions from Scrubber during CHF3 Process Flow Calibration

0 1 2 3 4 5 6 7 8 9 10

2700 2750 2800 2850 2900 2950 3000 3050 3100
FTIR ScanConcentration (ppmv)

200 sccm

100 sccm

25 sccm15 necessary to numerically integrate the PFC con centration over time to yield an emission volume, which can be compared to the integrated process emission volume entering the scrubber for a given analyte. To convert measured concentr ations 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 is de termined 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.

The process tested on AMZ17 and AMZ18 was a di electric etch process that had two distinct etch steps. The approximate process recipes were as follows:

Step 1 Arc Etch: 160 sccm CF 4 ; 100 sccm CHF 3 ; 150 sccm Ar; 20 sccm O 2 35 sec Step 2: Main Etch: 60 sccm C 4 F 6 ; 1000 sccm Ar; 45 sccm O 2 65 sec

In addition to the etch times listed above, up to 5 sec of additional chamber stabilization time is required to turn the process gases on and set the chamber pressure prior to turning on the process plasma.

During the etch processes etch gases CF 4 , CHF 3 and C 4 F 6 could be detected in the process effluent. Many etch by-products were also detected. These included SiF 4 , HF, COF 2 , C 2 F 4 , C 2 F 6 and CO. Figure 8 shows the FTIR spectrum of process emissions for each etch step.16 Figure 8: FTIR spectra of emissions from ar c etch (top) and contact main etch (bottom)

Typical emission profiles for the etch process ar e shown in Figure 9. These data were acquired on AMZ18 chamber B during the etching of test wa fers. The top graph shows PFC process gas emissions during both etch steps for three wafers . The bottom graph shows the etch by-products 0 .5 1 1.5

1000 1500 2000 2500 3000 3500 4000 4500

Arbitrary Y / Wavenumber (cm-1) 10/23/2007 1:39 PM Res=None CF4

CHF3 SiF4 CO HF

COF2 CHF3

CF4

0 .05 .1 .15 .2 .25 .3

1000 1500 2000 2500 3000 3500 4000 4500

Arbitrary Y / Wavenumber (cm-1) Paged Y-Zoom CURSOR

File # 1 = QIMOND~1 10/23/2007 1:39 PM Res=None CF4

C2F4

SiF4 COF2 CO

HF COF2/C2F6

CHF3

C2F6 C2F4

C4F617 formed in the plasma during the process. The spikes observed in the process gas emissions are attributed to the stabilization fl ow at the beginning of the etch process, and the chamber purge of residual gases after the plasma has been tu rned off at the conclusion of etching.

The PFC emissions data shown in Figure 9 (top) were integrated to determine the total emission volume for each gas, and used to calculate the process utilization for each molecule. Using the process recipe shown above the following PFC pl asma utilization values were obtained for CF 4 , CHF 3 and C 4 F 6 :

______________________________________________________________________________ Table V: Process Utilization for etch gases us ed in contact etch. The volumes reported as being used were calculated from the process recipe and assumed a stabilization flow of 5 seconds. Data reported per wafer processed. CF 4 Used for Process (sl) CF 4 Emitted from process (sl) CF 4 Process Utilization (%) 0.107 0.088 18 CHF 3 Used for Process (sl) CHF 3 Emitted from process (sl) CHF 3 Process Utilization (%)

0.067 0.032 52 C 4 F 6 Used for Process (sl) C 4 F 6 Emitted from process (sl) C 4 F 6 Process Utilization (%)

0.070 0.005 93

______________________________________________________________________________
The data contained in Table V include emissi ons for both etch steps of the process. Approximately 10% of the total CF 4 emission was observed during the C 4 F 6 process step, where CF 4 was formed as a by-product.

PFC Emissions during Contact Etch on AMZ18

0 2000 4000 6000 8000 10000 12000 14000 16000

2700 2750 2800 2850 2900 2950 3000 3050 3100
FTIR ScanConcentration (ppmv) TRIFLUOROMET HANE 150C

CARBON TETRAFLUORIDE 150C

C4F6 Qimonda AMZ18 Process Flow 150C Arc Etch

Main18 Figure 9: Emission profiles for PFC proce ss gases (top) and plasma by-products (bottom) during contact etching of test wafers on AMZ18 chamber B. The ARC and Main etch portions are labeled in the figures

. Emissions from the scrubber during wa fer processing included primarily CF 4 . Figure 10 shows an FTIR spectrum obtained during test wa fer processing on AMZ18. Low level CHF 3 and C 2 F 6 emissions were detected. The CF 4 emission profile from the scrubber is shown in Figure 11. Only the data for the test wafers was used to calculate a DRE as emissions from multiple chambers confound the DRE determination if the scrubber loading from ot her chambers is not accounted for. CF 4 emissions from the test wafers were integrated and used to calculate DRE by comparing to the integrated process emissi ons reported above. Figure 12 shows CF 4 emissions from AMZ17 scrubber. Again multiple cham bers were being used on the tool. CF 4 emissions for the last 9 wafers were integrated to yield total CF 4 emission for 9 wafers and compared to the integrated process emissions for the same 9 wafe rs. The results for both scrubbers are contained in Table VI below: By-product Emissions from Contact Etch on AMZ18

0 500 1000 1500 2000 2500 3000 3500 4000 4500

2700 2750 2800 2850 2900 2950 3000 3050 3100
FTIR ScanConcentration (ppmv) HF 150C SiF4rp100C COF2 105C C2F6 120C C2F4 CO LOW PPM 150C ARC Main19 ______________________________________________________________________________

Table VI: CF 4 DRE determined for each scrubber by comparing inlet and outlet emission volumes. AMZ17 Integrated CF 4 Process Emissions for 9 wafers (sl) Integrated CF 4 Scrubber Emissions for 9 wafers (sl) Scrubber CF 4 DRE (%)

0.920 0.716 22 AMZ18 Integrated CF 4 Process Emissions for 5 test wafers (sl) Integrated CF 4 Scrubber Emissions for 5 test wafers (sl) Scrubber CF 4 DRE (%)

0.445 0.425 4

______________________________________________________________________________
Emissions of C 2 F 6 and CHF 3 from the AMZ18 scrubber durin g test wafer processing were integrated and used to estimate mi nimum DRE values of > 98 % for C 2 F 6 and > 98.7 % for CHF 3. Actual DRE values are presumed to be higher. The minimum DRE for C 2 F 6 is based on an integrated per wafer process emission of 0.010 sl and an integrated scrubber emission of < 0.001 sl. The minimum DRE for CHF 3 is based on an integrated per wafer process emission of 0.033 sl and an integrated scr ubber emission of < 0.001 sl. CHF 3 and C 2 F 6 were not detected in the effluent of the scrubber on AMZ17.

Figure 10: FTIR spectrum of AMZ18 scrubber emissi ons during test wafer processing. -.15 -.1 -.05 0 .05 .1 .15 .2 .25

880 900 920 940 960 980 1000 1020 1040 1060 1080 1100 1120 1140 1160 1180 1200 1220 1240 1260 1280 1300 1320 1340 1360

Arbitrary Y / Wavenumber (cm-1) Paged X-Zoom CURSOR

File # 2 = AMZ18O~1 10/24/2007 1:31 PM Res=None CF4

CHF3 C2F620 Figure 11: CF 4 emission profile from AMZ18 scrubber during processing of test wafers on Chamber B, and during processing of pro duction wafers on multiple chambers.

Figure 12: CF 4 emission profile from AMZ17 scrubb er during processing of production wafers on Chamber B, and during processing of production wafers on multiple chambers.

III: Comparison of CF 4 DRE Determinations: Both methods of determin ing the scrubber DRE for CF 4 on AMZ17 and AMZ18 are compared in Table VII. Both methods are in reasonable agreement and both indicat e a relatively low DRE for CF 4 on the scrubbers tested. Higher DR E were obtained for etch gases CHF 3 and C 4 F 6 , and process by-product C 2 F 6 . The AMZ17 scrubber appears to be more effective at abating all PFCs. It was noted during testing th at the AMZ17 scrubber was oper ating at a higher reported temperature than the AMZ18 scrubber, howev er, temperature data were not collected. 1

1 Observations of temperature during the study indicated that AMZ17 was running at approximately 885 to 905 o C, whereas, AMZ18 was running at approximately 800 to 815 o C. It is believed that the noted temperatures refer to the external wall temperature of the combustio n chamber within the abatement device. CF4 Emissions from TPU During Process Flow Calibration

0 50 100 150 200 250

3000 3200 3400 3600 3800 4000 4200 4400 4600
FTIR ScanConcentration (ppmv) Test Wafers Chamber B Multiple Chambers Processing Production Wafers

CF4 Emissions from TPU During AMTZ17 Wafer Processing

0 50 100 150 200 250

700 900 1100 1300 1500 1700
FTIR ScanConcentration (ppmv) Multiple Chambers Running

Chamber B Running21 ______________________________________________________________________________ Table VII: Comparison of two methods used to determine CF 4 DRE on scrubbers for AMZ17 and AMZ18 Scrubber CF4 DRE determined from Process Gas flow Calibrations (average of 5) (%) CF4 DRE from Integrated Process Emissions (%)

ETCAMZ17 27 22 ETCAMZ18 15 4

______________________________________________________________________________ 

## 4.0 Conclusion

Determination of the DRE of PFCs by POU scr ubbers has been conducted for a contact etch process at Qimonda. Two scrubbers of the same make and model were tested. The processes tested were the same on each tool. The result s indicated very high DR E for most PFC process gases and PFC by-products. Only CF 4 was determined to have a low DRE on both systems.

One key element of this study was to accurately determine the dilution that occurs to process effluent as it passes through the scrubber into the corrosive scrubbe r exhaust duct. In this study, the dilution was determined by using a chemical tr acer, Kr, which was inj ected into the scrubber inlet of one process chamber, and subsequently determined in the sc rubber effluent. The effluent Kr concentration was determined by using a QMS, which was calibrated on-site for its response to Kr. The choice of Kr for chemical spiking was dictated by the need for a tracer that would not react in or be produced by the scrubber.

Two methods of determining process gas DRE were investigated. Use of a continuous flow of PFC gases permitted a steady state emission of PFC from both the process chamber and scrubber (provided the DRE was < 100%). This allowed direct comparison of emission concentrations from tool and scrubber after scr ubber effluent data were correc ted for dilution. Wafer processing emissions were also used to calculate DRE by in tegrating the emission concentrations over time and total flow to yield emission volumes into and out of the scrubber. The comparison of these methods yielded DRE values that were in reason able agreement. The latter method could be needed in cases where the effluent data do not app ear to reach a steady state, particularly for the scrubber effluent. The fundamental difference between the two methods is that etch by-products would be present in method 2, whereas they woul d not present in method 1. This would include any particulates that may be presen t in the etch effluent stream.