Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) 

Destruction or Removal Efficiency (DRE) Measurement Method for 

Electronics Manufacturing: A Cooperative Evaluation with Qimonda 

March 2008 

Office of Air and Radiation 

Office of Atmospheric Programs, Climate Change Division 

EPA 430-R-08-017 
2

Acknowledgements 

The analytical measurements, data interpretation, and report preparations were funded by the 

U.S. Environmental Protection Agency under contract GS-10F-0124J to ICF International and 

Air Products and Chemicals, Inc. The authors wish to express their appreciation and thanks to 

Qimonda, for their gracious support to this study by not only providing their facilities but also 

their valuable assistance and advice. The U.S. EPA looks forward to continued collaborations 

with Qimonda and other Partners in the PFC Reduction/Climate Change Partnership for 

Semiconductors. 

 

 
3

 Table of Contents 

Page 

Acknowledgements......................................................................................................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 Determinations....................................................................11 

 3.2.1 DRE Determination During Process Calibration Flows..............................11 

 3.2.2 Determination of DRE during Wafer Processing......................................14 

4.0 Conclusion ................................................................................................................................ ...21 
4

List of Tables 

 Page 

Table I Data used to determine the total flow 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 CF4 DRE values determined during process flow calibrations ..................................... .......13

Table IV CHF3 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 CF4 DRE determined for each scrubber by comparing inlet and outlet emission volumes 

 ...................................................................................................................................... .......19 

Table VII Comparison of two methods used to determine CF4 DRE on scrubbers for AMZ17 and 

AMZ18 ......................................................................................................................... .......21 
5

List of Figures 

 Page 

Figure 1 Sampling schematic used for testing TPU PFC DRE.................................................8

Figure 2 QMS Response to 84Kr during calibration......................... ....................................... ......8

Figure 3 Regression analysis of calibration data shown in Figure 2..........................................9

Figure 4 Kr concentration determined for AMZ17 scrubber during spiking experiment.................10

Figure 5 CF4 emission concentration determined from AMZ17 chamber B while CF4 was flowed 

through chamber B with RF power off .................................................................11

Figure 6 CF4 emission profile from AMZ18 chamber B (top) and from TPU (bottom) during process 

flow calibration............................................................................................13

Figure 7 CHF3 emissions from process (top) and scrubber (bottom) during CHF3 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 CF4 emission profile from AMZ18 scrubber during processing of test wafers on Chamber B, 

and during processing of production wafers on multiple chambers................................21

Figure 12 CF4 emission profile from AMZ17 scrubber during processing of production wafers on 

Chamber B, and during processing of production wafers on multiple chambers.................21
6

1.0 Introduction 

The purpose of this study was to accurately determine 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. This 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 operation. Krypton was 

used as the chemical tracer as it met the requirements for this application. 

Testing was conducted in a fully functional semiconductor manufacturing facility, owned and 

operated by Qimonda in Richmond VA. Two tools, AMZ17 and AMZ18, each equipped with 

POU scrubbers were tested. Both tools ran the same process and used the same model of 

commercially available scrubber. The process evaluated was a contact etch process, which used 

PFC gases CF4, CHF3 and C4F6. 

2.0 Experimental Setup 

To carry out the objectives of this study it was necessary to monitor both 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 collected 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 and 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 other FTIR was equipped with a 5.6 m path length 

multi pass gas cell, and was used to sample scrubber 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 scrubber effluent during dilution determination. The 

QMS was operated in Selective Ion Monitoring (SIM) 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 sensitivity, ion signals were normalized to the signal 

obtained for the nitrogen fragment (N+), which is formed during electron impact ionization of 

N2. 

Sampling of effluent streams was done using metal 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 scrubber would not coat the FTIR internal optics, or 
7

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 response to Kr on site using a dynamic dilution 

blending system. Test atmospheres containing Kr, were created by blending a calibration 

standard containing 1% of Kr in N2 with N2 diluent. The QMS response to 84Kr 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 calibration was repeated for both tools tested. 

Figure 1: Sampling schematic used for testing TPU PFC DRE 

Figure 2: QMS Response to 84Kr 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 Scan

Ion Intensity

99 ppmv

79 ppmv

60 ppmv

40 ppmv

20 ppmv

air
8

Figure 3: Regression analysis 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 accurately determine the dilution that occurs when 

gas emitted from the process chamber passes through the scrubber. Dilution can occur from 

many sources including effluents from other chambers, combustion gases and by-products added 

to and generated within the scrubber, 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 

controlled flow rate added to the process exhaust duct, a total flow from the scrubber could be 

calculated: 

TF = Sf/(Can X 10-6) (1) 

Where Sf represents the spike gas flow and is reported in liters per minute, and Can represents the 

analyte concentration reported in ppmv. 

The experiment conducted to determine dilution for the scrubbers on AMZ17 and AMZ18 

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 Mass 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 during 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 Kr

Relative Ion Intessity

Y = 7.3e-6X + 2.5e-5
9

Figure 4: Kr concentration determined for AMZ17 scrubber during spiking experiment. 

Flow rates of calibration gas are indicated on the graph. 

Applying Eq. 1 to the data obtained for the scrubbers on AMZ17 and AMZ 18 yielded the total 

flows contained in Table 1. The average total flow 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 Scan

Concentration (ppmv)

1 slm

2 

3 slm

4 slm

5 slm
10

The total scrubber flow data can be combined with 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 effluent 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 into the corrosive scrubber exhaust. The experiment to measure 

the dilution of AMZ17 and AMZ18 chamber effluent consisted of flowing CF4 into the chamber 

with the RF power in the chamber turned off at several flow rates. The determined CF4

concentration in the effluent could be used to calculate the total process flow entering the 

scrubber from the following equation: 

 TPF = PGf/(CPG 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 (CPG) in ppmv. The values obtained for CF4 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: CF4 emission concentrations determined from AMZ17 chamber B while CF4 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 Scan

Concentration (ppmv)

0.200 slm

0.150 slm

0.100 slm

0.050 slm

0.025 slm
11

______________________________________________________________________________ 

Table II: Total chamber and process pump effluent flow from chamber B on AMZ17 and 

AMZ18. Values determined from the average concentration measured during each CF4

flow using Eq. 2 

ETCAMZ17 ETCAMZ18 

CF4 Flow 

(slm) 

CF4 Conc. 

(ppmv) 

Total 

Effluent 

Flow 

(slm) 

CF4 Flow 

(slm) 

CF4 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 total flow of 17.0 ± 0.7 slm for AMZ17 and 15.5 ± 0.6 

slm for AMZ18. The process flow into the scrubber combined with the total flow from the 

scrubber yielded the experimentally measured dilution for each scrubber: 

 System Dilution = TFout /TFin (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 factors 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 performance was done using two different 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 effluent during wafer processing. 

3.2.1. DRE Determination During Process Calibration Flows 

The scrubber DRE for CF4, CHF3 and C4F6 was determined during total process flow 

calibrations by comparing the steady-state inlet and outlet concentrations during the flow of each 

gas, and adjusting for the scrubber dilution. From these data a direct calculation of the scrubber 

DRE could be made. Figure 6 shows the scrubber inlet and outlet CF4 concentrations determined 

for AMZ18 while CF4 was flowing through the chamber. (These were the data used to calculate 
12

the AMZ18 process dilution.) These data were used to calculate the scrubber DRE for CF4 using 

the following equation: 

 DRE = 1 – ((CF4outX Dilution)/CF4in) (4)

Here CF4out and CF4in represent the average CF4 concentrations determined for each flow shown 

in Figure 6. Using this method of comparing concentrations into and out of the scrubber, CF4

DRE values for AMZ17 and AMZ18 are tabulated and contained in Table III. 

Figure 6: CF4 emission profile from AMZ18 chamber B (top) and from TPU (bottom) 

during process flow calibration. Each level of concentration is equivalent to a specific CF4

flow rate thru the process chamber. 

_________________________________________________________________ 

Table III: CF4 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 Scan

Concentration (ppmv)

CF4 Emissions from TPU During Process Flow Calibration

0

50

100

150

200

250

2400 2500 2600 2700 2800 2900 3000

FTIR Scan

Concentration (ppmv)
13

AMZ17 

CF4 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 CF4 DRE appears higher for the AMZ17 

scrubber relative to the AMZ18 scrubber. Results for CHF3 indicated that AMZ17 abated CHF3

sufficiently to yield a concentration below the detection limit of the FTIR equipped with a 5.6m 

cell, while relatively low emissions of CHF3 were detected from AMZ18 scrubber. The CHF3

inlet and outlet profiles determined during CHF3 flows through chamber B on AMZ18 are shown 

in Figure 7. Both scrubbers abated C4F6 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 Scan

Concentration (ppmv)

200 sccm

100 sccm

25 sccm
14

Figure 7: CHF3 emissions from process (top) and scrubber (bottom) during CHF3 process 

flow calibration. 

From the data shown in Figure 7, the AMZ18 scrubber DRE was calculated for CHF3 during the 

total process flow calibration and is contained in Table IV. These data indicate a relatively high 

DRE for CHF3 on AMZ18 scrubber. The AMZ17 scrubber had a higher DRE as CHF3 was not 

detected in the effluent during the CHF3 flow calibration.

______________________________________________________________________________ 

Table IV: CHF3 DRE for AMZ18 scrubber based on data shown in Figure 7. 

CHF3 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 C4F6 was high for both AMZ17 and AMZ18 scrubbers. The estimated detection 

limit for C4F6 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 emission 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/dt = 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 Scan

Concentration (ppmv)

200 sccm

100 sccm

25 sccm
15

necessary to numerically integrate the PFC concentration 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 concentrations into volumes, the following equation was 

used: 

 VEM = ΣCiTfΔt (5)

Where the total emission volume (VEM) is the summation of each FTIR data point where the 

concentration of analyte C is determined during time interval Δt and multiplied by the total flow 

(Tf). The summation of the entire emission profile provides an emission volume for a given 

analyte during the process. During this study, these calculations were performed using standard 

spreadsheet software (Microsoft Excel). Use of this technique reinforces 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 dielectric etch process that had two distinct 

etch steps. The approximate process recipes were as follows: 

Step 1 Arc Etch: 160 sccm CF4; 100 sccm CHF3; 150 sccm Ar; 20 sccm O2 35 sec 

Step 2: Main Etch: 60 sccm C4F6; 1000 sccm Ar; 45 sccm O2 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 CF4, CHF3 and C4F6 could be detected in the process 

effluent. Many etch by-products were also detected. These included SiF4, HF, COF2, C2F4, C2F6

and CO. Figure 8 shows the FTIR spectrum of process emissions for each etch step. 
16

Figure 8: FTIR spectra of emissions from arc etch (top) and contact main etch (bottom) 

Typical emission profiles for the etch process are shown in Figure 9. These data were acquired 

on AMZ18 chamber B during the etching of test wafers. 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

C4F6
17

formed in the plasma during the process. The spikes observed in the process gas emissions are 

attributed to the stabilization flow at the beginning of the etch process, and the chamber purge of 

residual gases after the plasma has been turned 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 plasma utilization values were obtained for CF4, 

CHF3 and C4F6: 

______________________________________________________________________________ 

Table V: Process Utilization for etch gases used 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. 

CF4 Used for Process 

(sl) 

CF4 Emitted from process 

(sl) 

CF4 Process Utilization 

(%) 

0.107 0.088 18 

CHF3 Used for Process 

(sl) 

CHF3 Emitted from 

process 

(sl) 

CHF3 Process Utilization 

(%) 

0.067 0.032 52 

C4F6Used for Process 

(sl) 

C4F6 Emitted from 

process 

(sl) 

C4F6 Process Utilization 

(%) 

0.070 0.005 93 

______________________________________________________________________________ 

The data contained in Table V include emissions for both etch steps of the process. 

Approximately 10% of the total CF4 emission was observed during the C4F6 process step, where 

CF4 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 Scan 

Concentration (ppmv)

TRIFLUOROMET

HANE 150C

CARBON

TETRAFLUORIDE

150C

C4F6 Qimonda

AMZ18 Process

Flow 150C

Arc Etch

Main 
18

Figure 9: Emission profiles for PFC process 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 wafer processing included primarily CF4. Figure 10 shows 

an FTIR spectrum obtained during test wafer processing on AMZ18. Low level CHF3 and C2F6 

emissions were detected. The CF4 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 other chambers is not 

accounted for. CF4 emissions from the test wafers were integrated and used to calculate DRE by 

comparing to the integrated process emissions reported above. Figure 12 shows CF4 emissions 

from AMZ17 scrubber. Again multiple chambers were being used on the tool. CF4 emissions 

for the last 9 wafers were integrated to yield total CF4 emission for 9 wafers and compared to the 

integrated process emissions for the same 9 wafers. 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 Scan

Concentration (ppmv)

HF 150C

SiF4rp100C

COF2 105C

C2F6 120C

C2F4

CO LOW PPM 150C

ARC 

Main 
19

______________________________________________________________________________ 

Table VI: CF4 DRE determined for each scrubber by comparing inlet and outlet emission 

volumes. 

AMZ17 

Integrated CF4 Process 

Emissions for 9 wafers 

(sl) 

Integrated CF4 Scrubber 

Emissions for 9 wafers 

(sl) 

Scrubber CF4 DRE 

(%) 

0.920 0.716 22 

AMZ18 

Integrated CF4 Process 

Emissions for 5 test wafers 

(sl) 

Integrated CF4 Scrubber 

Emissions for 5 test wafers

(sl) 

Scrubber CF4 DRE 

(%) 

0.445 0.425 4 

______________________________________________________________________________ 

Emissions of C2F6 and CHF3 from the AMZ18 scrubber during test wafer processing were 

integrated and used to estimate minimum DRE values of > 98 % for C2F6 and > 98.7 % for 

CHF3. Actual DRE values are presumed to be higher. The minimum DRE for C2F6 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 CHF3 is based on an integrated per wafer process emission of 

0.033 sl and an integrated scrubber emission of < 0.001 sl. CHF3 and C2F6 were not detected in 

the effluent of the scrubber on AMZ17. 

Figure 10: FTIR spectrum of AMZ18 scrubber emissions 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 C2F6
20

Figure 11: CF4 emission profile from AMZ18 scrubber during processing of test wafers on 

Chamber B, and during processing of production wafers on multiple chambers. 

Figure 12: CF4 emission profile from AMZ17 scrubber during processing of production 

wafers on Chamber B, and during processing of production wafers on multiple chambers. 

III: Comparison of CF4 DRE Determinations:

Both methods of determining the scrubber DRE for CF4 on AMZ17 and AMZ18 are compared in 

Table VII. Both methods are in reasonable agreement and both indicate a relatively low DRE 

for CF4 on the scrubbers tested. Higher DRE were obtained for etch gases CHF3 and C4F6, and 

process by-product C2F6. The AMZ17 scrubber appears to be more effective at abating all PFCs. 

It was noted during testing that the AMZ17 scrubber was operating at a higher reported 

temperature than the AMZ18 scrubber, however, temperature data were not collected.1

 

1

 Observations of temperature during the study indicated that AMZ17 was running at approximately 885 to 905 oC, 

whereas, AMZ18 was running at approximately 800 to 815 oC. It is believed that the noted temperatures refer to the 

external wall temperature of the combustion 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 Scan

Concentration (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 Scan

Concentration (ppmv)

Multiple Chambers Running

Chamber B Running
21

______________________________________________________________________________ 

Table VII: Comparison of two methods used to determine CF4 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 scrubbers 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 results indicated very high DRE for most PFC process 

gases and PFC by-products. Only CF4 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 scrubber exhaust duct. In this study, 

the dilution was determined by using a chemical tracer, Kr, which was injected into the scrubber 

inlet of one process chamber, and subsequently determined in the scrubber 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 scrubber effluent data were corrected for dilution. Wafer processing 

emissions were also used to calculate DRE by integrating 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 reasonable agreement. The latter method could be 

needed in cases where the effluent data do not appear 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 would not present in method 1. This would include 

any particulates that may be present in the etch effluent stream.