EPA has supported the semiconductor industry's (including stakeholders in the semiconductor manufacturing industry, the Semiconductor Industry Association and device manufacturers) voluntary efforts to reduce high global warming potential (GWP) greenhouse gas (GHG) emissions.
Semiconductor manufacturers use a variety of high GWP gases to create intricate circuitry patterns upon silicon wafers and to rapidly clean chemical vapor deposition (CVD) tool chambers. Semiconductor manufacturing processes use high GWP fluorinated compounds including perfluorocarbons (e.g., CF4, C2F6 and C3F8), hydrofluorocarbons (CHF3, CH3F and CH2F2), nitrogen trifluoride (NF3) and sulfur hexafluoride (SF6). Semiconductor manufacturing processes also use fluorinated heat transfer fluids and nitrous oxide (N2O).
Although the use of fluorinated GHGs did not begin until the late 1980s, their application facilitated the development of significantly more complex and faster processing semiconductors. The continued availability and use of these gases is considered to be critical to the future success of the industry.
Estimating fluorinated GHG emissions from semiconductor manufacture is complicated and has required a significant and coordinated effort by the industry and governments. It was historically assumed that the majority of these chemicals were consumed or transformed in the manufacturing process. It is now known that under normal operating conditions, anywhere between 10 to 80 percent of the fluorinated GHGs pass through the manufacturing tool chambers unreacted and are released into the air.
In addition, fluorinated GHG emissions vary depending on a number of factors, including gas used, type/brand of equipment used, company-specific process parameters, number of fluorinated GHG-using steps in a production process, generation of fluorinated GHG by-product chemicals, and whether appropriate abatement equipment has been installed. Companies’ product types, manufacturing processes and emissions also vary widely across semiconductor fabs.
Many companies in the semiconductor manufacturing have successfully identified, evaluated and implemented a variety of technologies that protect the climate and improved production efficiencies. Solutions have been investigated and successfully implemented in the following key technological areas:
- Process improvements/source reduction
- Alternative chemicals
- Capture and beneficial reuse
- Destruction technologies
Technical Papers and Reports
- EPA's Protocol for Measuring Destruction or Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Electronics Manufacturing
- Developing a Reliable Fluorinated Greenhouse Gas
- Uses and Air Emissions of Liquid PFC Heat Transfer Fluids from the Electronics Sector
- Reduction of Perfluorocompound (PFC) Emissions: 2005 State-of-the-Technology Report
- Estimating the Impact of Migration to Asian Foundry Production on Attaining the WSC 2010 PFC Reduction Goal
- How do semiconductor manufacturers use fluorinated GHGs?
Fluorinated GHGs are used for both etching intricate circuitry features on silicon wafers and for cleaning chemical vapor deposition (CVD) tool chambers. Fluorinated GHGs are energized and dissociated in plasmas to provide reactive fluorine atoms in the manufacturing tool chambers. In the case of plasma etching, the free fluorine atoms selectively react with and remove insulating and/or conductive materials from the exposed surface of a silicon wafer to create the intricate circuitry patterns found on modern semiconductors. In CVD tool chamber cleaning applications, the fluorine atoms react with and remove excess materials from the surface of the tool chambers themselves.
Semiconductor manufacturers also use fluorinated heat transfer fluids and nitrous oxide. Fluorinated heat transfer fluids are used to cool process equipment, control temperature during device testing, clean substrate surfaces and other parts, and for soldering. Nitrous oxide is used for CVD and other manufacturing processes such as chamber cleaning.
- Can fluorinated GHG emissions from semiconductor manufacturing be reduced?
Yes, fluorinated GHG emissions from semiconductor manufacturing can be reduced. Companies in the industry have implemented a variety of emission reduction strategies, such as optimizing (i.e., fine tuning) their production processes to use and emit fewer fluorinated GHGs and switching to alternative input gases (for example, NF3), which are utilized more efficiently in the process, thereby emitting fewer fluorinated GHGs into the exhaust stream.
- Will companies continue to report their GHG emissions data to EPA?
Yes, under subpart I of EPA’s Greenhouse Gas Reporting Program (40 CFR Part 98), owners or operators of electronics manufacturing facilities that emit equal to or greater than 25,000 metric tons of CO2e per year from fluorinated GHG and N2O emissions from cleaning and etch processes, heat transfer use, and other source categories (e.g., CO2 from stationary combustion facilities) must report GHG emissions from all electronics manufacturing processes and any other source category at the facility for which methods are defined in the rule. Covered facilities were required to begin monitoring GHG emissions on January 1, 2011 in accordance with the methods specified in the rule. The first report was due to EPA by September 28, 2012; subsequent reports are due annually thereafter by March 31. Reporters submit their data to EPA electronically through EPA’s Electronic Greenhouse Gas Reporting Tool (e-GGRT).
- Will fluorinated GHG emissions from semiconductor manufacturing grow in the future?
Demand for semiconductors and other electronics products manufactured using fluorinated GHGs (e.g., flat panel displays, micro-electro-mechanical systems and photovoltaic cells) is expected to continue to rise given high demand for high-tech products and renewable energy. Therefore, it is likely that emissions from electronics manufacturing sectors will grow in the future.