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Developments in the market for UHP hydrogen purifiers
Long treated as the Cinderella material of
semiconductor processing, with limited usage in silicon semiconductor, LCD and GaAs
manfacture, hydrogen and in particular ultra-high-purity hydrogen is becoming an increasingly
important ingredient in new and high-growth areas of semiconductor processing technologies,
says Noel Leeson of Power & Energy Inc.
semiconductorTODAY Compounds&AdvancedSilicon • Vol. 6 • Issue 4 •
May/June 2011
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here to download the
article in PDF
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by Noel Leeson
The dramatic growth in LED production since 2008 has attracted much
scrutiny and many articles have been written about the growth in metal-organic chemical vapor
deposition (MOCVD) tool demand, the challenges faced by the substrate makers, and the rush to
expand the production capacity of inorganometalic chemicals and of high-purity NH3, a critical
gallium nitride (GaN) precursor.
Less well publicized has been the need to improve the supply of UHP
hydrogen (the gas that transports all the organometalic chemicals into the MOCVD reaction
chambers). For the highest-performance GaN devices, for example, the need to eliminate oxygen from
GaN epitaxial layers means that typically the hydrogen must reliably and consistently contain
<<1ppb (parts per billion) of both oxygen and H2O impurities. As supplied, hydrogen typically
contains far higher levels of impurities when it is delivered to the fab, GaN epitaxy processors
must purify the hydrogen on-site.
Since the early days of the MOCVD industry, most processors have used H2
purifiers that work by diffusion through a hot palladium membrane (Figure 1). Each MOCVD tool would
typically have been equipped with its own palladium (Pd) purifier.
Modern GaN epi facilities typically operate many MOCVD tools, and
facilities engineers are increasingly adopting a centralized purification model, where several
purifiers are installed in parallel to supply a group of tools or even an entire fab.
Fig 1. Principle of palladium purification of
hydrogen.
This approach allows a facilities manager to build redundancy into the purifier
system design by installing an additional stand-by purifier (Figure 2), increasing reliability and
uptime while reducing capital and operating costs by making use of larger capacity purifiers.With
this philosophy, facilities managers are also able to pace purification capacity additions to match
the tool installation and production ramp of the fab, thereby optimizing cash flow. Pd purifiers
capable of purifying hydrogen from 97% to 99.9999999% are now available with nominal flow
capacities of up to 160NM3/Hr, a capacity unthinkable a couple of years ago.
Fig 2. Centralized purification layout.
While there are alternatives to Pd for the purification of hydrogen, Pd remains
the technology of choice, as it is the only technology that provides absolute purification, i.e.
only H2 can diffuse across the Pd membrane. All other technologies work by adsorbing some
proportion of the impurities from the H2 stream and struggle to contain the impurity spikes to
which all hydrogen systems are prone, particularly those fed by H2 of variable consistency such as
the H2 supplied in much of China, India and other parts of Asia. Given the high cost of an impurity
excursion in terms of lost epiwafers, down-time for tool clean-up, and the cost for replacement of
contaminated MOCVD chemistry, few facilities managers are willing to give up the security provided
by palladium. Also, with the lower unit costs achieved through the adoption of the centralized
purification model, there is little economic incentive for a facilities manager to take a risk on
an alternative technology.
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Modern GaN epi facilities typically operate many MOCVD tools... Pd
purifiers capable of purifying hydrogen from 97% to 99.9999999% are now available with
nominal flow capacities of up to 160NM3/Hr, a capacity unthinkable a couple of years
ago
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Pd purifiers use either the traditional ‘outside-in’ approach to purification or
the more modern ‘insideout’ micro-channel technology (Figure 3). Each approach has its advocates,
but currently only insideout micro-channel technology purifiers are available in nominal capacities
of greater than 60NM3/hr.
In addition to the demand from LED production, thinfilm silicon
photovoltaic (PV) cell production processes require large volumes of UHP hydrogen. China-based
producers are increasingly turning to Pd technology to protect
their processes from variability in quality of the the local hydrogen supply. For these
thin-film processes, N2 and O2 are particularly unwelcome impurities. Unlike other purification
technologies, Pd purifiers can reliably maintain sub-ppb impurity levels even in the face of
large spikes of contamination possible from routine operations such as tube trailer change-over
or from leaking fittings.
The expectations for growth of power
semiconductor devices are also high, driven by the exploding growth in wired and wireless data
transmission capacity, increasing adoption of non-traditional grid-linked electricity
generation, and the general growth in electric vehicles. Power devices can be based on silicon
technology but increasingly devices are being designed on gallium nitride
(GaN) or silicon carbide (SiC) epiwafers. Like GaN, SiC epi is grown using an MOCVD process but,
in addition to removing oxygen, nitrogen must be controlled to < 1ppb. Pd once again is the
ideal technology to consistently achieve the demanding hydrogen purity needed by SiC producers.
Inside-out micro-channel purifiers employ identical membrane elements in all sizes of
purifier.
 
Fig 3. ‘Outside-in’ and ‘inside-out’ purification schematic
designs.
Fig 4. ‘Lab to fab’ using identical purification
elements.
Researchers and producers can eliminate one source
of variation by using consistent hydrogen purification at all stages of technology deployment,
from R&D through pilot operations into mass production (Figure 4).
As we approach the sub-20nm generation of silicon
semiconductor processing, tolerance for impurities in silicon epi layers and in the superthin
gate structures is also decreasing, continuing the requirement for employing UHP hydrogen in
these critical process steps.
The surging demand in traditional and new
applications for UHP hydrogen, coupled with the move to centralized purification systems, is
driving growth and change in the market for hydrogen purifiers. Manufacturers are responding by
increasing the capacity of Pd purifiers from 60NM3/hr up to 160NM3/hr and higher, thereby
allowing a semiconductor manufacturer to reduce unit costs and ensure process uptime while
guaranteeing that only the highest-purity hydrogen consistently reaches the process
chamber.
Author: Noel Leeson, president & chief
operating officer, Power & Energy Inc, Ivyland (Warminster), PA, USA www.powerandenergy.com
semiconductorTODAY Compounds&AdvancedSilicon • Vol. 6 • Issue 4 •
May/June 2011 www.semiconductor-today.com
Click here to
read this article at
semiconductorTODAY.
About Power+Energy
Power & Energy is headquartered in
Pennsylvania, USA. Established in 1993, the company's mission is to enable the hydrogen economy
and promote energy efficiency through the application of micro-channel technologies. The company
provides a full range of micro-channel hydrogen purifiers to ultra-high purity users across the
U.S., Asia and Europe.
Power & Energy is leading the way to the
hydrogen economy with proprietary manufacturing and patented hydrogen purification, separation
and generation technologies. Power & Energy's Micro-Channel palladium-alloy hydrogen
purifiers purify any grade of hydrogen to nine-nines purity, meeting the most stringent
requirements for semiconductor fabrication processes, including light emitting diode
manufacture, solar cell manufacture and the manufacture of other compound and silicon
semiconductors. Power & Energy's Micro-Channel hydrogen purifiers are also ideal for
metallurgy, R&D, and instrumentation applications. Power & Energy's Micro-Channel
membrane systems can also be used to efficiently separate hydrogen from reformed fuels and
synthesis gas mixtures.
Power & Energy is now applying its hydrogen expertise to the fuel cell vehicle refueling
market. Power & Energy has recognized that highly compact, low cost, and efficient hydrogen
generators that can convert existing liquid fuels to hydrogen at the refueling station will enable
the rapid development of the hydrogen refueling infrastructure that fuel-cell vehicles will
require. The company's expertise in the design and manufacture of micro-channel gas processors
provides the basis for this exciting new venture.
For further information, contact Al Stubbmann, Power & Energy Inc., 106
Railroad Avenue, Ivyland, PA 18974-1449, e-mail al.s@powerandenergy.com or call
+1-610-217-0193.
CONTACT:
Albert Stubbmann
Power & Energy, Inc.
106 Railroad Drive
Ivyland, PA 18974-1449
USA
PHONE. 215-942-4600 ext 17
FAX. 215-942-9300
EMAIL: al.s@powerandenergy.com
WEB: http://www.powerandenergy.com
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