CHRIS JONES, Edwards Vacuum
That the emission of greenhouse gases (GHG) is warming the planet is no longer in dispute, and industrial emissions account for about a third of the total. Though direct emissions of GHG from semiconductor manufacturing are small relative to some industries, our industry is a prodigious consumer of energy. The energy invested in a completed device can be 5.4 MJ (1.5 kWh) or more per square centimeter. Most of that energy is still generated by burning fossil fuels, the primary culprit in GHG emissions worldwide. Ultimately, the industrial sector, indeed all sectors, must transition to renewable energy sources wherever possible. But, if we want to minimize the worst effects of global warming, we must begin today to reduce energy consumption and improve energy efficiency. Fortunately, this need not be a purely altruistic effort – energy is expensive and reductions in energy consumption go directly to the bottom line, reducing costs and increasing profitability.
The SEMITM S23 guidelines describe a methodology for semiconductor equipment manufacturers and the device manufacturers who use their products to evaluate the energy used by their equipment and their manufacturing processes. Establishing a standard framework for determining energy consumption is essential to reducing it. SEMITM S23 allows device manufacturers to compare systems and consider energy efficiency in their equipment selection process, thus incentivizing equipment manufacturers to improve the efficiency of their products. And it provides an objective basis for equipment manufacturers to evaluate the success of their efforts to reduce energy consumption and promote that progress in the marketplace.
Measuring and reporting GHG
The Greenhouse Gas Protocol (GHGP) establishes comprehensive global standards for measuring and reporting greenhouse gas emissions from private and public sector operations (FIGURE 1). For convenience, emissions are reported as carbon dioxide equivalent (CO2e). The CO2e for a greenhouse gas (GHG) is the product of that gas’s global warming potential (GWP) and its mass in, for example, metric tons. The GWP100 is the integrated infra-red radiation absorbed over 100 years relative to carbon dioxide. CO2e can be used to measure the global warming impact of many gases, including those emitted during the generation of electrical power by fossil fuels, where it can be calculated from the amount of carbon dioxide, methane, and nitrous oxide emitted per unit of energy.
The GHGP categorizes emissions into three scopes:
- Scope 1 emissions are direct emissions from owned or controlled sources.
- Scope 2 emissions are indirect emissions from the generation of purchased power
- Scope 3 emissions are all indirect emissions (not included in scope 2) that occur both upstream (CO2e of incoming products and services) and downstream (CO2e of outgoing products and services) in the value chain of the reporting company.
The power consumed by a vacuum pump in use at a fab will contribute to the scope 2 emissions for the fab. A GHG abatement device will mainly reduce the scope 1 emissions of a fab while consuming power, thereby adding a small amount of scope 2 emissions. Offsite provision of utilities such as nitrogen, water, and wastewater would be regarded as scope 3 upstream. Various types of equipment and facilities in a fab are sources of direct (scope 1) and indirect (scope 2) emissions or both. Emissions from gas-fired boilers and diesel emergency generators are almost entirely scope 1 from the fuel they burn. A wet scrubber, the heating, ventilation, air conditioning (HVAC) system, the ultrapure water production system, and the provision of process cooling water generate primarily scope 2 emissions from the electrical power they consume. An ammonia oxidation system and an MBR denitrification plant generate both scope 1 and scope 2 emissions.