Advances in Compound Semiconductor Processing
Joseph Sweeney, James Dietz, Karl Olander, Paul Marganski, Josep Arnó
ATMI, Inc.; Danbury, Connecticut, USA
jsweeney@atmi.com
phase since neither gas is soluble in or reactive with water
alone. The benefit of gas absorption is its low operating cost.
Although water usage is being scrutinized more and more, its
cost is still relatively low. In addition, the cost of an oxidizing
agent like sodium hypochlorite is not high. A disadvantage of
gas absorption is its dependence on moving parts, e.g. pumps,
in order to maintain an effective gas removal rate. The most
notable disadvantage, however, is the large volume of arsenic
laden aqueous waste that is produced. Not only must this
waste be specially treated, it represents an elevated risk within
the fab. For example, if a gas absorption system were to suffer
a large leak, the cleanup costs could be significant due to
arsenic contamination.
Abstract—Compound semiconductor manufacturers employ a
variety of techniques for managing toxic gases and solids in the
effluent of MOCVD reactors. For gas abatement, chemical wet
scrubbers, chemical dry scrubbers, and burners have been
employed with varying degrees of success. Wet scrubbers and
burners have become popular solutions due to their lower
operating costs. Unfortunately, these systems can require
frequent maintenance and generate large volumes of secondary
waste, e.g., arsenic laden waste water in the case of chemical wet
scrubbers. Dry scrubbing is the simplest and perhaps least
maintenance intensive solution for compound semiconductor
abatement of arsine and phosphine; however, efficiency
challenges at high flow rates, thermal issues due to hydrogen
reduction reactions, and material costs have limited their use.
This paper discusses new options for simplifying and improving
the abatement of gases from MOCVD reactors depositing GaAs
and InP films. The performance of several new dry scrubber
materials is presented and proven to reduce materials costs and
total operating costs when compared to existing treatment
solutions.
TABLE I.
Gas
Keywords-Compound semiconductor; abatement; effluent
treatment; chemisorption; gas adsorption, cost of ownership,
arsine, phosphine
I.
EXPOSURE GUIDELINES FOR TYPICAL COMPOUND
SEMICONDUCTOR GASES
Concentration Limits
TLV-TWA (ppm) [1]
IDLH (ppm) [2]
Arsine (AsH3)
0.05
3
Phosphine (PH3)
0.3
50
Hydrogen Chloride
(HCl)
5
50
INTRODUCTION
Various effluent treatment challenges arise in compound
semiconductor applications. First, the process gases used
typically have multiple hazards associated with them. For
example, two of the most widely used deposition gases, the
hydrides arsine and phosphine, are extremely toxic as indicated
by their respective threshold limit values (TLV’s) and
immediately dangerous to life or health values (IDLH’s); see
Table 1. In addition, phosphine is pyrophoric, meaning that it
will ignite spontaneously in air, while arsine is flammable.
Occasionally, it is necessary to use hydrogen chloride gas
(toxic and corrosive) to clean the tool chamber of unwanted
deposits.
Such hazards require effective and efficient
abatement methods.
Thermal oxidation coverts toxic and hazardous effluent
gases to their respective oxides through a reaction with oxygen
at elevated temperatures. For example, arsine is converted to
arsenic(III) oxide (As2O3), while phosphine is converted to
phosphorus pentoxide (P2O5). These oxides are still hazardous
and must be collected prior to venting to the atmosphere. A
typical collection technique is to filter the solids from the gas
stream (e.g. with a bag house filter system). As with gas
absorption, the main advantage of such a system is its relatively
low operating costs, which include fuel or electricity to operate
the oxidizer as well as the need to potentially replace filter
elements. The major disadvantage is the need to perform
frequent maintenance. The significant quantity of solids
produced in the oxidation process leads to arsenic
contamination within the exhaust ducting and may also require
frequent replacement of the filter elements. In addition, the
oxidizer unit itself may require frequent maintenance due to
solids accumulation. Another effect of using a thermal oxidizer
(which may be viewed as a positive or negative depending on
the user) is that in addition to treating the hydrides, it will also
react the hydrogen present in the gas stream. Because the
hydrogen flow rate is commonly very high (50 – 120 slpm is
typical), the oxidizer may require active cooling in the form of
large amounts of dilution air or cooling water, both of which
Traditionally, there have been three common abatement
methods used in the treatment of effluent gases from compound
semiconductor processes. These are gas absorption (water
scrubbing), thermal oxidation, and gas adsorption (dry
scrubbing).
Gas absorption entails contacting the gas stream with an
aqueous stream typically over a packed bed. Although such a
system is ideal for HCl abatement, in order to effect the
removal of arsine and phosphine gases, a strong oxidizing
agent (e.g. sodium hypochlorite) must be added to the aqueous
1
add to the cost of ownership. A final disadvantage of a thermal
oxidizer is that it will not abate HCl. If left untreated, the HCl
has the potential to cause corrosion within the house exhaust
system.
scrubbing solution, as well as to further enhance our resins’
resistance to the secondary hydrogen reduction reaction.
In order to avoid using a filter unit to remove the solid
byproducts emitted from a thermal oxidizer and in order to treat
HCl, an integrated scrubber system containing a thermal
oxidizer followed by a wet gas absorption column can be
employed. Such a solution can significantly reduce the
footprint compared to a thermal oxidizer used in conjunction
with a filter system. Although an oxidizing agent is not
required, the problem and risk associated with aqueous arsenic
containing waste is the same as described for the stand-alone
gas absorption system. In addition, care must be taken in the
design such that even very small particles of arsenic oxide are
captured in the absorption column. For example, a typical gas
absorption column will only remove particles down to 2-10
microns, depending on specific process conditions [3].
Additional separations techniques may be necessary to remove
smaller particulate. Such technologies may increase the capital
cost and complexity of the equipment. Finally, as with the
thermal oxidizer solution, the integrated scrubber will require
significant cooling to manage the heat liberated from the
abatement of hydrogen gas.
In order to reduce the cost of ownership of dry scrubbing,
the focus was placed on significantly improving the capacity
(lifetime) of the chemisorbent resin media. This challenge was
tackled in three steps. First a program was developed to screen
resins of various chemistries. Second, the top performing
materials from the screening experiments were characterized
more thoroughly to determine the effect of process parameters
on the resins’ capacity and operating temperature. Third, resin
optimization techniques were evaluated.
II.
RESIN DEVELOPMENT PROGRAM
Most of the resin experiments were performed using a test
cell (Figure 1) with the following characteristics:
The final major technology used is gas adsorption –
specifically chemisorption. In chemisorption (often referred to
as dry scrubbing), the effluent gas stream is contacted with a
fixed bed containing solid particles having very high surface
areas. The chemistry of the solid material is such that a
reaction occurs when the effluent gas molecules adsorb onto
the surface. Byproducts of the reaction are non-volatile solids
and cannot be desorbed from the surface. A major benefit of
such a system is its simplicity. The system does not require
moving parts, fuel, or water, and consumes minimal electricity.
The system is passive in operation, meaning that the only
requirement for abatement is the presence of the chemisorbent
material itself. This is in stark contrast to other methods of
treatment where loss of water, air, fuel, or electricity can mean
a partial or total loss of abatement efficiency. In addition, a dry
scrubbing system contains the arsenic, phosphorus, and
hydrogen chloride waste in an isolated, well contained, and
compact vessel. The biggest disadvantage of gas adsorption
systems is their cost of operation. This arises from the need to
replace the vessels containing the chemisorption media (from
hereafter to be termed resin) on a basis prescribed by the
capacity of the given resin material in conjunction with the
total gas loading onto the resin. In addition, the relatively large
effluent flow rate common to most compound semiconductor
processes tends to reduce a resin’s capacity due to the shorter
residence time the effluent stays within the media bed. Added
to this challenge is another in which a secondary reaction can
occur between hydrogen and common metal oxide resins if the
bed temperature rises above 110-120°C. This hydrogen
reduction reaction of the resin is undesirable simply due to the
large flow of hydrogen. Not only can the resin capacity be
used up, the temperature of the bed can increase significantly.

1” or 2” outer diameter (0.065” wall thickness)

8” resin bed height

5-point thermocouple centered within cell

~ 1” thick insulation surrounding cell

Stainless steel construction
5-point
thermocouple
Gas Out
Resin Bed
Thermocouple
locations (in red)
Screen
Gas In
Figure 1. Test Cell used to Determine the Effectiveness of Various Resins
Tests were performed flowing either arsine or phosphine
gas in a ballast stream composed of 80% hydrogen and 20%
nitrogen by volume (this ballast stream was meant to
approximate the actual conditions in the field). All gases were
It is in this light that the authors have embarked on a major
effort to improve the cost of ownership of ATMI’s dry
2
delivered to the test cell using mass flow controllers. The
effluent of the test cell flowed through a MIDAC G2000 FTIR
(Fourier Transform Infrared Spectrometer) with a 10 cm
pathlength in order to determine the shape of the arsine or
phosphine breakthrough curve (i.e., the effluent concentration
of hydride gas as a function of time). In addition, a portable
gas detector sampled the exhaust stream to monitor for TLV
breakthrough, while a Fluke Hydra Databucket logged cell
temperatures during the experiments. Figure 2 is a simple
block diagram of the setup.
Test
Cell
FTIR
TLV
Monitor
PH3 + MOx  MyPz + P + H2O unbalanced
(2)
HCl + MOx  MyClz + H2O unbalanced
(3)
where “M” stands for a generic metal. Although chemistry of
the resin is very important in terms of dictating the resin’s
capacity, so is surface area, pore structure, density, water
content, etc. In fact, a resin screening study could be almost
limitless due to the large number of resin property variations
one could imagine. For practical purposes, we chose to focus
on only a handful of carefully selected candidates.
Because HCl flow rates are usually much smaller than the
hydride challenges in compound semiconductor processing, the
focus of this project was on the hydrides, notably arsine. In
addition, resins that abate HCl are typically lower in cost and
tend to have higher capacities than their hydride resin
counterparts. Therefore, hydride capacity improvements have
a much larger impact on cost of ownership.
Hood Dry
Scrubber
Gas In
TABLE II.
RESIN SCREENING EXPERIMENTS
Resin Capacity (moles gas per liter resin)
Figure 2. Major Components of the Experiment
Resin
The performance of any given resin was evaluated by three
criteria:

TLV Capacity

Dynamic Theoretical Capacity

Maximum Temperature
A
B
C
D
E
F
G
H
I
TLV capacity was defined as the amount of gas taken up
per unit volume of resin at the time when the effluent
concentration reached TLV levels as determined by the
portable gas monitor. (Note that many commercially available
gas adsorption systems are outfitted with a sensor that detects
TLV breakthrough from the fixed resin bed. At this point, the
resin bed is replaced with a new vessel containing fresh resin.
Therefore TLV capacity is directly related to cost of
ownership). Dynamic theoretical capacity was determined by
recording the full breakthrough curve using the MIDAC FTIR.
The term “full breakthrough curve” means the test was run
until the outlet concentration approached 50%+ of inlet
concentration. The area above this curve was used to
determine the total amount of hydride gas that had been
chemisorbed by the resin (note that the curve slope was
extrapolated for calculation puposes). Finally, we monitored
and logged the temperature of the cell interior at various depths
in the resin bed. For each test, we recorded the maximum
value attained.
Theoretical
1.16
0
2.47
1.00
1.02
0
0.16
0.82
0.55
3.10
NA
4.87
3.89
1.44
NA
1.53
1.13
0.82
Table II lists the results of the screening tests. Note that resin
“A” represents the material ATMI sells today for arsine and
phosphine abatement. All tests were performed using arsine as
the hydride gas; the inlet concentration was 4%, while the
superficial linear velocity through the cell was 4 cm/sec. These
test conditions are quite challenging and were chosen mainly to
decrease the testing time during the screening program. Actual
field conditions are typically 0.5% - 2% inlet gas concentration
with a linear velocity of less than 1 cm/sec (although this is
dependent on the specific design of the resin containing vessel).
Three resins were chosen for further study based on the results
of the screening program. These materials are shaded in gray
in Table II: resins A, C, and D. It is noteworthy that a
significant portion of the resins’ chemistry remained available
for further reaction at TLV breakthrough. This is evidenced by
the theoretical capacities being 2-4 times higher than TLV
capacities for the three top performers. As an example, Figure
3 plots the exhaust concentration (breakthrough curve) from the
test cell as a function of time for resin “A”. Whereas TLV
breakthrough occurred at t = 60 minutes, the outlet had not
reached 50% of the inlet concentration by t = 140 minutes.
A. Resin Screening Study
Resin screening consisted of testing various materials to
quickly determine those that showed promise. Generally,
resins are composed of various metal oxides that react with
arsine, phosphine, and HCl gases in the following fashion:
AsH3 + MOx  MyAsz + As + H2O unbalanced
TLV
(1)
3
test cases. The technique developed will be discussed in the
next section.
.
Concentration (ppm)
40000
Notes
(1) Resin "A"
(2) Column diameter = 0.87" ID
(3) Resin bed height = 8"
(4) Thermocouple (1/8" diameter)
centered in bed
(5) AsH3 flow = 34.2 sccm
(6) 80%/20% H2-N2 mix flow = 840 sccm
30000
20000
Arsine in
bypass
TABLE III.
Test Parameters
Test
1
2
3
4
5
6
10000
MDA TLV
(50 ppb, 59.5 min)
0
0
20
40
60
80
100
RESIN CHARACTERIZATION: EFFECT OF LINEAR VELOCITY
AND INLET CONCENTRATION ON CAPACITY
120
140
160
Time (min)
Conc.
%
4
4
4
2
1
1
Vel.
cm/sec
1
2
4
4
4
1
Resin Capacity for Arsine (TLV;
Theoretical)1,2
A
C
D
NA; 4.77
1.60; 3.69
1.16; 3.10
1.05; 2.07
0.85; 1.73
1.94; NA
NA; 3.49
2.26; 4.48
2.47; 4.87
1.35; 3.75
1.01; 3.66
----
------1.00; 3.89
------2.95; NA
1) Resin capacity is defined as the moles of gas treated per liter of resin.
2) All tests performed with a 1” diameter cell except for the last set, which were done with a 2” cell.
Figure 3. Breakthrough Curve for Resin “A”
TABLE IV.
RESIN CHARACTERIZATION: EFFECT OF LINEAR VELOCITY
AND INLET CONCENTRATION ON MAXIMUM TEMPERATURE RISE
B. Resin Characterization
To characterize the performance of the three candidate
resins, a simple test matrix was created to evaluate the effect of
inlet concentration and linear velocity on resin capacity and
operating temperature. In the field, the effluent flow rate is
dictated by the process recipe. Once an abatement system is in
place, there is little control over the hydride concentration or
the linear velocity of the gas as it passes through the resin bed.
Of course, in a product development sense, it is possible to
modify the resin bed geometry or add dilution nitrogen to
reduce the gas concentration. Therefore, we felt it worthwhile
to understand how these two variables affected the resins’
performance.
Test Parameters
Test
1
2
3
4
5
6
Test results for various inlet concentrations and linear
velocities are tabulated in Tables III and IV. Table III shows
how the capacities of the three candidate materials varied based
on process conditions. For example, the TLV and theoretical
capacities of resin A were observed to decrease with higher
linear velocity. In addition, for a given velocity, the capacity is
better for higher inlet arsine concentrations. For resin system
C, the effect of linear velocity was opposite that of resin A –
TLV and theoretical capacities actually increased with higher
linear velocities. The inlet concentration dependence was
analogous to resin A. Only one test was completed for resin D
in this stage of the project (test #6). This was not for lack of
interest in this material. Rather, the results from resins A and C
(as well as the screening test point for D) suggested that
changes in linear velocity and concentration only moderately
affected the TLV capacities relative to the theoretical values.
Furthermore, the dependence upon inlet concentration was
opposite to that which would be desirable from a control
standpoint. That is, the capacities decreased with lower inlet
concentration. Unfortunately, it would be much easier from an
abatement standpoint to decrease the concentration of effluent
species coming from the tool via simple dilution, as opposed to
increasing the concentration by special design and process
techniques. Something other than control techniques or design
modifications was needed to narrow the gap between the TLV
and theoretical capacities, which were quite large for nearly all
Conc.
%
4
4
4
2
1
1
Vel.
cm/sec
1
2
4
4
4
1
Maximum Temperature Rise (°C)1
A
C
D
29
50
46
39
26
24
27
49
77
41
23
----
------53
------27
(1)
All tests performed with a 1” diameter cell except for the last set, which were done with
a 2” cell.
(2)
Temperature rise is defined as the maximum observed temperature minus the room
temperature at the time of the experiment.
Figure 4. Average Ratios for Capacity and Temperature Rise Between
Candidate Resins and Resin A
As discussed in the introduction, high operation
temperatures in a dry scrubber can promote an unwanted
secondary reaction with hydrogen. In addition to improving
resin capacity, it was a second goal of this project to identify a
resin with higher resistance to a reaction with hydrogen. Table
IV shows the corresponding maximum temperature rise within
4
the test cell for each experiment. When averaged over all tests,
neither resins C nor D maintained a lower relative temperature
rise. However, resin C showed good results for all tests with
the exception of test #3. Because test #3 represents conditions
significantly outside those present in the field, it was felt that
resin C was acceptable. For the two tests performed with resin
D, the temperature rise was slightly higher than resin A.
However, resin D is known to resist the hydrogen reduction
reaction up to temperatures in the range of 180°C – much
higher than resin A (110-120°C). Therefore, it was deemed
acceptable as well. Figure 4 displays the average capacity and
temperature rise ratios between resins C and A, and D and A.
faster resin (short MTZ) acts as a polisher.
demonstrates the basic concept.
Figure 5
One can perform a mathematical analysis to evaluate the
effect of combining two such resins. Assume, for example that
the MTZ length of the high capacity resin is ½ the entire bed
length. If this is the only resin present, it stands to reason that
the capacity will be 3/4th of the resin’s theoretical limit. As
portrayed in Figure 6, this result is obtained by looking at the
area under the curve.
C/Co
C. Resin Optimization
As mentioned in the prior section, during both the screening
and the characterization testing, there always existed a large
difference between the TLV and theoretical capacities. For any
given experiment, the gap was between 100%-300% (2-4x).
These results indicated that a large percentage of the resins’
chemistry was left unutilized. In this phase of the project, a
method was investigated for improving the TLV capacities to
values closer to theoretical.
MTZ/LOB = 0.5
Column Height/Location
Figure 6. Idealized Mass Transfer Zone Equal to ½ the Column Length
Expanding on this idea, Figure 7 shows how the resin bed
utilization (defined as TLV capacity/theoretical capacity) is
affected as the MTZ:bed length ratio is varied. It is apparent
that a severe reduction in utilization occurs as the MTZ length
increases. In fact, it is obvious that the materials in Table III all
had very long MTZ lengths – some in excess of the bed length
itself. This may seem impossible, but it simply implies that the
MTZ length became longer as the bed media was consumed.
That is, an 8” bed height was not sufficient to generate a steady
state MTZ length. This corroborates data generated by Illes[4].
The authors confirmed this idea experimentally by performing
tests utilizing a bed height of 22”. The results (not shown)
indicated that the capacity was relatively unchanged relative to
the tests performed with the 8” bed height. Had the MTZ
length been constant, the use of a 22” tall bed would have
moved the system to the left and upwards on the line in Figure
7, providing for dramatically improved resin utilization.
As plotted in Figure 3, all resins display a characteristic
breakthrough curve. It is desirable to utilize resins in which the
curve is as steep (vertical) as possible so that little capacity
remains after TLV breakthrough. Said another way, there must
be a short mass transfer zone within the resin. Mass transfer
zone (MTZ) is defined as the length of adsorbent required to
remove the target contaminant from its incoming concentration
level to the level defined as the breakthrough level (TLV).
Cinlet
Breakthrough
C=0
Slow Resin
Cinlet
Breakthrough
C=0
Fast Resin
Cinlet
Breakthrough
C=0
Slow Resin
Fast Resin
Figure 5. Mass Transfer Zone Shape Through Slow and Fast Resins
Unfortunately, resins that have both high capacities and
short MTZ’s, will operate very hot and are susceptible to a
reduction reaction with hydrogen. Resins with short MTZ’s
and low capacities operate at acceptable temperature ranges,
but obviously do not last long. Finally, resins that have long
MTZ’s and high capacities tend not to be utilized well (as
indicated in Table III). The solution to this problem is to
combine a high capacity/long MTZ resin with a low
capacity/short MTZ material. Such an arrangement allows the
high capacity material to be utilized more fully because the
Figure 7. Effect of Mass Transfer Zone Length on Bed Utilization.
Therefore, the only way to attack this problem was to
somehow decrease the effective mass transfer zone of the resin.
However, because a resin that exhibits both high capacity and
short mass transfer zone tends to operate at rather high
temperatures, a different method had to be employed. This
5
TABLE V.
method as described earlier (and shown graphically in Figure
5) is to layer a small amount of “fast” polishing resin (i.e. short
MTZ) over a bed of high capacity, “slow” material. A search
began to find appropriate resins that would act as effective
polishers to the three candidates identified from the screening
study. In addition, the correct ratio in which to use the two
resins was investigated.
Resin Configuration

Using polish resin S improved the capacity of resin A
by 51%. Although a significant improvement, it was
below the theoretical value of 3.1 (see Table III).

Resin V was also effective as a polishing agent when
used with resin A. The capacity of 3.12 moles/liter
could not be directly compared to a test in which TLV
capacity was measured for process conditions of 4%
arsine and 1 cm/sec velocity. However, the data and
trends displayed in Table III suggest such a
comparative data point would be < 1.94 moles/liter.

Using polish resin S with resin C actually decreased
capacity relative to C alone. Clearly, S was not
effective in this case. It is possible that certain
byproducts from the reaction of arsine with resin C
were incompatible with resin S.
Assuming S
contributed little, the lower capacity was likely due to
the smaller quantity of C present in the test cell
(compared to the test of C by itself).

Utilizing polisher V with resin C produced the best
capacity result of the program – almost 2x higher than
the next best result shown here. It is noteworthy that
the capacity far exceeded the theoretical value shown
in Table III. The reason for this is not completely
understood. However, it is suspected that the method
of calculating the dynamic theoretical capacity by
extrapolating the slope of the breakthrough curve led to
underestimated values. In fact, one can calculate an
absolute theoretical capacity simply by looking at the
reaction stoichiometry. For resin C, this value is
between 9 and 10 moles/liter.

Tests using resin D indicated that polishing agents T,
U, and V all provided significant improvements over
resin D by itself. For example, the D/V combination
was 2.5x better than D alone. The theoretical capacity
at these process conditions of 3.89 moles/liter (Table
III) indicates that there may be even more room to
improve.

Resin D displayed similar performance for the
abatement of phosphine as it did for arsine. In
addition, other test results (not included here) indicated
that the capacity for phosphine was always
approximately the same as for arsine.
Test Parameters1,2,3
Performance
A
A
A
Polish
Bed
---S
V
Conc.
(%)
4
4
4
Vel.
cm/sec
4
4
1
C
C
C
---S
V
4
4
4
4
4
1
2.47
2.20
6.97
D
D
D
D
D
D
D
---J
V
U
U
U
T
4
4
4
4
4
4
1
4
4
4
4
1
1
1
1.00
0.94
2.49
2.04
3.39
3.28
3.67
Main Bed
Various tests were performed using each of the three main
resin candidates in which the effect of using different polishing
resins was evaluated. The results are shown in Table V. A
number of comments can be made regarding these data.
THE SEARCH FOR A POLISHING RESIN
TLV Capacity
(1)
Grayed row denotes a test in which phosphine was used instead of arsine
(2)
Percent polisher was 20% for all tests
(3)
TLV Capacity defined as moles gas abated per liter resin
1.16
1.75
3.12
The next step in the resin development program was to
evaluate the effect of varying the amount of polish material.
For this we chose resin D with polisher U. We set up a simple
2 level, 2 factor design of experiments in which we varied the
resin bed height and the percentage of polisher. The test results
are plotted in Figure 8. The data show a major dependence on
the quantity of polisher present within the bed, and a small
dependence on the bed height. An optimum polish layer
percent is known to exist because the capacity of the polishing
resin itself (100% polish) was less than any of the four points
plotted in Figure 8. The actual maximum location cannot be
determined from these data; other test results (not presented
here) suggest it is somewhere in the 20-30% range.
Figure 8. Effect of Polish Layer Percent and Bed Height on TLV Capacity.
D. Resin Development – Concluding Remarks
Through the resin screening, characterization, and
optimization efforts, significant achievements were made in
6
identifying new resins with improved capacities and better
thermal characteristics.
Resin combination D/V had a
maximum capacity of 3.67 moles/liter, while C/V achieved a
value of 6.97. This compares to a capacity of 1.94 moles/liter
for a standard material available today.
III.
The model provides a useful basis for understanding the
relative cost of using carbon resin in the TGA system as well as
the targeted cost for new chemisorption resins under
development. As Figure 10 shows, the model predicts the
mean cost of carbon abatement to be $12.81 per mole hydride
treated. Depending on the particular conditions, the range in
carbon abatement costs is approximately $8.60 – $18.37 per
mole hydride abated, at a 90% confidence level. Therefore,
from the end-user standpoint, the cost of the C/V or D/V resins
must be equivalent or better to this distribution of existing
carbon costs. The development of C/V and D/V resins
included the specific target to achieve a 10-20% improvement
in TCO for TGA carbon users, based upon new resin pricing
and reduction of disposal quantities, labor, and time. For the
beta versions of C/V and D/V resins, this appears to be entirely
possible.
RESIN COST OF OWNERSHIP
Two key customer deliverables of resin development were
improving the Total Cost of Ownership (TCO) for existing
users of chemisorption abatement systems and providing
existing users of carbon abatement systems a higher
performing, cost-effective alternative. The C/V and D/V resin
combinations show good promise to meet these goals. For the
purpose of this discussion, we focus on the potential TCO
improvements for existing users of carbon treatment systems
for arsine and phospine abatement of III-V processes.
Forecast: Carbon Cost
A TCO model was developed to analyze the impact of
switching from carbon to C/V and D/V layered resins. The
model incorporates the main variables that were thought to
impact resin consumption, maintenance, and tool downtime
based upon the operation of the so-called “Toxic Gas
Absorber” (TGA) carbon systems on the Emcore toolset. The
main variables, assumptions cells, were:

1,000 Trials
Hydride gas flow (both arsine and phosphine)

Hours of operation per day using arsine and phosphine

Process conversion of arsine and phosphine

TGA carbon change out time (days)

Tool downtime per TGA change

Carbon cost

Disposal costs

Labor costs
Frequency Chart
988 Displayed
.025
25
.019
18.75
.013
12.5
.006
6.25
M ean = $1 2.81
.000
0
$6.55
$10.10
$13.64
$17.18
$20.72
$ / m ol hy dri de treated
Figure 10. Distribution of carbon costs ($ / mol hydride treated)
The results of the model show several advantages of C/V
and D/V resins over carbon in the operation of the TGA.
Regarding disposal volumes, the increased capacities of the
C/V and D/V resins result in a decrease in average disposal
volumes of approximately 72.7%, which allows for significant
environmental and safety benefits. Figures 11 and 12 present
the pertinent output data from the model regarding carbon
versus C/V and D/V resin disposal volumes. In addition to
reducing disposal volumes, labor and time savings are realized,
the latter of which can lead to additional tool time for
production, if need be. Figure 13 presents the additional tool
time gain, or downtime savings when switching from carbon
resin to D/V resin.
Based upon these assumptions and known parameters, the
model was used to determine the operating cost of the TGA,
i.e., $ per mole hydride treated, using a static model of single
point estimates for the assumption cells and a dynamic model
using Monte-Carlo simulation.
For the Monte-Carlo
simulation, Crystal Ball, an Excel add-in, was used to generate
distributions of likely values for the assumption cells (Figure
9). Likewise, the same base model was used to assess the
operating cost of using C/V and D/V resins in place of carbon
in the TGA system.
Forecast: Carbon disposal v olume
1,000 Trials
Frequency Chart
999 Displayed
.022
22
.017
16.5
.011
11
New resin cap acity (mo l h yd rid e / liter)
.006
5.5
Mean = 3,655
.000
0
2,927
3,271
3,615
3,959
Liters
3 .0
3 .5
4 .0
4 .5
5 .0
Figure 11. Carbon Disposal Volume (liters)
Figure 9. Distribution of expected new resin capacity (mol / liter)
7
4,303
IV.
Forecast: Total v olume of resin
1,000 Trials
Frequency Chart
Through an extensive test program involving resin
screening, characterization, and optimization aspects,
significant improvements were made in treatment capacity for
hydride gases. Specifically, a resin layering technique was
developed and optimized that improved resin capacities
approximately 2-3½ times.
988 Displayed
.029
29
.022
21.75
.015
14.5
.007
7.25
Using a Monte-Carlo simulation, the two top candidate
resins appear to enable reductions in Total Cost of Ownership
for current users of carbon treatment systems.
Mean = 996
.000
0
440
731
1,022
1,312
1,603
REFERENCES
Figure 12. Chemisorption Resin Disposal Volume (liters)
[1]
[2]
.
Forecast: Annual dow ntime sav ings
1,000 Trials
Frequency Chart
988 Displayed
.029
29
.022
21.75
.015
14.5
.007
7.25
[3]
[4]
.000
0
10.6
27.2
43.7
60.3
CONCLUSION
76.8
(hours)
Figure 13. Annual Downtime Savings (hours) – chemisorption over carbon
8
American Conference of Governmental Industrial Hygienists (ACGIH)
website, http://www.acgih.org.
National Institute for Occupational Safety and Health (NIOSH) website,
http://www.cdc.gov/niosh/homepage.html.
Calvert, S., Goldshmid, J., Leith, D., and Mehta, D., Wet Scrubber
System Study, Scrubber Handbook, vol. 1, Report No. EPA-R2-72118a, PB 213 016.
Illes, V., MAFKI Report 233, 1961.