from Gas Streams
and gas distribution systems, thereby reducing the
release of metal contaminants to acceptable levels
and subsequently improving wafer yields.
Mitigating moisture contamination
High moisture levels in the corrosive gas stream
are a significant contributor to corrosion. Mitigating
moisture begins at the gas source and continues to
the transportation and storage of the gas. If moisture
can be reduced below a certain threshold (ca. 500
ppbV or greater), corrosion stops and volatile metals
inherent to the gas supply can be removed.
Moisture contamination in gas supplies can reach
hundreds of parts per billion (ppbV). By implementing a gas delivery system fitted with a mechanism that
is designed to absorb moisture from the supply, outlet
concentration can be reduced to 15 ppbV or less.
Removing contaminants from the gas supply
In addition to mitigating moisture, capturing volatile metal particulates using special filters diminish-es the occurrence of wafer contamination.
While gas delivery systems themselves feature
similar components, the process gases and the contaminants inherent to them vary from gas to gas.
As a result, different gases may require advanced
construction materials to remove contaminants. One
solution to address this is to incorporate nickel filters
in the purifier cartridge instead of stainless steel (see
Fig. 1). Nickel provides a much greater degree of corrosion resistance, as it is virtually unreactive towards
many corrosive gases. For best results, purifiers are
installed at the gas source and at the tool (see Fig. 2).
Minimizing moisture in a gas supply to 15 ppb
or below, combined with reducing on-wafer volatile
metal contaminants to < 108 atoms/cm2 is the best
strategy to improve final wafer yields, particularly
in finer nodes. To achieve both these objectives,
equipment such as Entegris’s Gatekeeper GPU cor-
rosive gas purifiers can be used. They are construct-
ed using contaminant adsorbents combined with
advanced corrosion-resistant particle filtration and
is engineered to remove volatile metal contaminants
and moisture from corrosive gas streams. The GPU
family’s moisture efficiency performance is validated
using state-of-the-art analytical instrumentation. The
purifiers can be mounted at the point of use and at
the gas supply in any physical orientation to provide
end users with flexibility when designing gas deliv-
Entegris® and GateKeeper® are trademarks of
Rocky Gipson, Ph.D., is Manager of Gas Purification
Research and Development at Entegris, Inc. www.enteg-ris.com
Fig. 2. Purification:
A process or device that
contains media designed
to “grab” molecular
(O2, H2O, N2, CO) as they
pass through a gas stream
using the principles
of chemical adsorption.
The GateKeeper GPU
family of gas purifiers