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Semiconductor Sustainability Needs a
Whole-Fab View, Not a Point-of-Use Fix
Semiconductor sustainability discussions tend to start and stop with
high-global-warming-potential (GWP)
fluorinated gases coming off process
tools. Ahead of his presentation
at SEMICON West, Chris Jones,
Environmental Sustainability Manager
at Edwards, argues that framing
misses most of what actually drives a
fab’s environmental performance.
“Considering the fab as an ecosystem, rather than just a tool
with point-of-use abatement, is
the starting point,” Jones said.
“Emissions performance isn’t static.
Actual emissions depend on what the
tool is running, the gas flows, the
equipment condition, and whether
you have the right utilities available
at the right quality — that could be
pressure, that could be composition.”
Jones’s SEMICON West presentation uses that system-level view to
connect sustainability challenges that
are usually discussed in isolation:
Scope 1 emissions, greenhouse gas
abatement, emissions reporting, water
use, waste handling, lifecycle carbon
assessment and supply chain pressure.
The premise is that optimizing one
element of a fab in isolation can
simply move the impact somewhere
else — from air emissions to water
discharge, from reduced direct
emissions to higher energy demand,
or from an efficiency gain to more
maintenance risk.
From periodic verification
to operational control
U.S. greenhouse-gas reporting rules
provide several approaches for establishing abatement DRE, including
default, manufacturer-verified and
site-specific measured values. Where
measurement is used, periodic testing
provides a snapshot of performance
under the conditions tested.
“DRE testing is expensive, especially
for regulatory purposes, so we should
be trying to avoid both over-treating
and over-testing,” Jones said. “At the
end of the day, these are businesses.
Control needs to let every part of that
ecosystem — the process tool, the
vacuum, the abatement, the chillers —
respond as conditions change, without
just burning more energy or utilities to
hold a fixed target.”
The Scope 1/Scope 2 tradeoff
Some of the fluorinated gases used
in semiconductor manufacturing,
including CF4, C2F6 and SF6, have
very high global-warming potentials (GWP) and can be difficult
to destroy. Abatement therefore
remains critical, but Jones argues
that DRE cannot be considered in
isolation. Different abatement technologies and operating conditions
also have different requirements for
electricity, fuel and other utilities,
all contributing to scope 2, and
can produce secondary pollutants
such as NOx. “Reducing
Scope 1 is essential, but you
have to understand what
happens elsewhere in the
system,” Jones said. “The
objective is to achieve the
required emissions performance with the lowest
total environmental burden
— not simply to optimize
DRE, energy or NOx
independently.”
Figure 1. The fab is not isolated. Optimizing sustainability requires a broadbased approach that considers all aspects of the fab and the ecosystem in
which it operates.
10 | Tuesday, October 13
An overlooked source:
chiller refrigerant
Another direct greenhouse-gas source can be
fugitive
Continued on page 12
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