Steamer vs. torch in PV manufacturing—a cost of ownership comparison
or explosion. In addition to permitting chance of explosion. steam and then purify the steam creates a
issues, infrastructure investment is new paradigm in the technique to create
high for the tank farm installation as cost calculator steam for wet oxidation. The benefits of
well as the piping of all welded high Many factors go into the cost of ownership eliminating hydrogen include safety, material
purity stainless steel lines. In some areas calculation, making it difficult for the typical cost reduction, and increased growth rate
double containment may be required. manufacturer to get a quick comparison of and uniformity. Steam generation using the
Installation costs can run over $200 per the options available. RASIRC has built Steamer creates both top and bottom line
foot and piping may extend hundreds or a calculator that takes a dozen inputs and improvement through increased good die
thousands of feet in larger installations. presents an immediate calculation of the and reduced operating cost.
Point of Use (POU) installation ROI period, total annual savings, and
places a gas cabinet near the tool or throughput enhancement provided by the references
in a chase area. For oxide thicker than Steamer. This calculator can be found at 1. Spiegelman, Jeff. “Alternative Method
100 nm, hydrogen and oxygen usage www.RASIRC.com\roi\torch.php. and Device to Purify and Deliver Water
can require frequent cylinder change Inputs are grouped into: Vapor”.
out. The cost of the gases often is less 2. Spiegelman, Jeff. “Urea and Ammonia
• Wafer Processing: Process value/wafer,
than the labor required to change out Removal from De-Ionized Water via
wafers/furnace run and hours to grow
and purge the lines. When dealing with Steam Purification”.
oxide
pyrophoric gases, two operators may be 3. Spiegelman, Jeff. “Improved Oxide
• Process Gas Volumes and Power
needed to meet safety regulations. The Growth Rate and Uniformity through
Consumption: H2, O2, Power and CDA
same piping costs generally still apply New Steam Delivery Method”.
• Costs: H2, O2, CDA, Electrical cost and
as well as hydrogen safety interlocks 4. Deal B. E. and Grove A. S. 1965 J. Appl.
spares
to prevent excessive hydrogen from Phys. 36 3770
reaching the tool without the matching Behind the scenes, these inputs are 5. Geib, K.M., Choquette K.D., Hou
oxygen flows. Because cylinders must be calculated to estimate the incremental value H.Q., and Hammons, B.E. “Fabrication
changed out frequently, storage within of the Steamer over Torches. Based on issues of oxide-confined VCSELS”.
the building may be limited, requiring the results, manufacturers can decide for Center for Compound Semiconductor
additional space external to the building themselves whether the potential reduction Technologies. Sandia National
for flammable gas storage. Permitting in cost of ownership is worth pursuing. Laboratories
can again become a problem and limit A simplified example is given in Table 1
or slow the expansion of the facility to for a 2.7 micron thick oxide film run. The Jeffrey Spiegelman is the president of RASIRC
add wet thermal oxidation capacity. Steamer was set to 16 slm and the torch and has a BS in bioengineering and MS in
• Steamer. The DI water plant was set to a 15 slm hydrogen and 8.5 slm Applied Mechanics from University of California
infrastructure can be used without oxygen flow. The enhanced growth rate and at San Diego. He has over 50 international
incurring significant additional costs. reduced operated cost generated a $127,000 patents and publications. Previously, he was
The DI water for each Steamer is savings over the torch. This hydrogen cost founder and president of Aeronex until it was
less than 1.5 liters per hour which is based on bulk rates. Gas cylinder rates purchased by Entegris in 2003. In 2005, he
should not affect the DI water plant. would be five times higher. founded RASIRC to address process purity and
Lines can be run ¼” or 6 mm PFA delivery issues around next generation chemistries,
tubing. Installations can typically be conclusion with an initial focus on water vapor.
done at minimal cost by in-house The ability to turn water directly into
facility engineers or local mechanical
contractors without extensive permits
Wafer Processing Steamer 101 Torch
and safety issues.
Hours to grow oxide lasyer 12.00 12.84
Cost of safe operation
Total process time, in hours (including ramp up/down) 15.00 15.84
Safety is a big concern for manufacturers.
Wafers/run 144.00 144.00
Processes that involve volatile gases are
inherently more dangerous than those Wafers/hour 9.60 9.09
that do not. The cost associated with safe
Wafers/week 1612.80 1527.27
operations is higher for processes that
involve such gases.
Process value/wafer 25.00 25.00
• Pyrolytic Torch. This process is
Total wafer value processed/week 40,320.00 38,181.82
inherently dangerous because of the
Total utilities cost, weekly 27.23 294.50
high temperature and volatile gases.
Total maintenance costs, annually 2900.00 13,100.00
Additional oxygen is required to
ensure that the hydrogen is sufficiently Annual utilities + maintenance cost 4,315.79 28,413.93
saturated.
Annual throughput 2,090,895.78 1,963,696.14
• Steamer. Inherently safe
Annual throughput loss relative to steamer 0.00 127,199.64
The torch has a higher cost of safe
operations due to the use of oxygen to Total annual cost difference 0.00 -127,199.64
dampen the hydrogen. This excess oxygen
serves no other purpose than to reduce the
Table 1. Cost comparison of torch vs. steamer.
www.globalsolartechnology.com
Global Solar Technology – May/June 2009 – 9
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