Water Quality and the Semiconductor Industry

Understanding Water Quality

Water quality describes the condition of water resources, including their chemical, physical, and biological characteristics. Standards used to address overall water quality typically involve monitoring and assessing the extent of water pollution, drinking water sources, human water contact safety, and the health of aquatic ecosystems. Federal water quality standards (WQS) refer to federal, state, territorial, tribal, or local laws or regulations approved by EPA that govern the desired condition of a water body and how that condition will be protected or achieved.

Water Demand at Semiconductor Manufacturing Facilities

Semiconductor facilities are heavy water users with a typical semiconductor facility using between 2 and 10 million gallons of ultra-pure water per day, which is essential for rinsing of silicon chips during fabrication and ensuring they are free from contaminants. 

Water demand at semiconductor manufacturing facilities typically falls into five categories.

1. Process Water: Used directly in the manufacturing process.

2. Cooling Water: Used to cool equipment and maintain optimal operating conditions. 

3. Abatement Technologies: Used to remove hazardous gases from semiconductor manufacturing equipment. 

4. Ultra-Pure Water (UPW) Treatment Losses: Used in the production of ultra-pure water.

5. Non-Industrial Use: General facility operations that include water for kitchens, toilets, and other typical water demand for office buildings. 

CHIPS projects are encouraged to reduce, recycle, and treat process wastewater to the maximum extent possible. Reductions in water use can be achieved by: 

• Replacing wet processes with dry processes 
• Improving UPW production efficiency
• Optimizing tools and procedures utilizing UPW
• Reusing rinse water and other wastewater streams from existing production processes. 

Water Quality Regulations

At the federal level, the Clean Water Act (CWA) is the primary statute regulating water quality, aiming to restore and maintain the chemical, physical, and biological integrity of US waters. Key sections of the CWA include:  

• Section 303(d): Requires states to develop a list of impaired waster bodies and establish plans to restore degraded areas. 
• Section 305 (b): Requires state to report on the overall condition of aquatic resources. 
• Section 301: Authorizes the EPA to develop effluent limitation guidelines and standards for existing sources of water pollution.
• Section 307: Establishes national pretreatment standards to control pollutants that pass through or interfere with wastewater treatment processes at POTWs.
• Section 402: Establishes the National Pollution Discharge Elimination System (NPDES), a permit program designed to regulate discharges of water pollutants from point sources, like semiconductor fabrication facilities.
• Section 404: Prevents the discharge of dredge or fill material into federal waters without a permit.

For more information see: Summary of the Clean Water Act | US EPA 

Wastewater Discharge Regulations

Indirect Discharges

Semiconductor facilities that discharge their wastewater to a publicly owned treatment works (POTW) will be required to obtain a permit from the local POTW and will be required to pretreat their industrial wastewater through processes like acid neutralization or chemical precipitation prior to discharging. The actual pretreatment requirements will vary based upon the receiving POTW but will need to conform to federal standards for industrial wastewater. 

A recent EPA report found that a majority of U.S. semiconductor fabrication facilities discharge their wastewater to local or regional POTWs as opposed to directly into surface waters. 

For more information see: 

 Pretreatment Standards and Requirements-Categorical Pretreatment Standards | US EPA 

11197_EEC Study Report_508.pdf (epa.gov) 

Direct Dischargers

Direct discharging facilities are facilities who have obtained a permit to directly discharge their wastewater to a water source. These facilities will have to obtain a discharge permit with strict guidelines as to the monitoring and testing of the discharge at the discharge point. These facilities will use treatment processes such as solvent management, neutralization, chemical precipitation with clarification, filtration, and in-process control for specific pollutants to conform with their discharge permit. 

For more information see: National Pollutant Discharge Elimination System (NPDES) | US EPA 

Per-and polyfluoroalkyl substances (PFAS) in the Semiconductor Industry

The Role of PFAS

PFAS chemistries are essential in various stages of the semiconductor fabrication process. Although the semiconductor industry only accounts for a small portion of the world’s PFAS use, these chemicals are critical for ensuring the precision and quality required in chip manufacturing.

PFAS are most utilized during the lithography, etching, and deposition processes. These chemicals are used for: 

• Enabling surface coat uniformity 
• Ensuring complete resist removal with low effectivity 
• Improving line roughness 
• Reducing line collapse

Environmental Concerns and Industry Response

PFAS is used in small quantities in the semiconductor manufacturing process, and PFAS can be found in semiconductor wastewater streams. With the exception of the National Drinking Water Standards and a few state laws, there has been little regulation of PFAS to date. PFAS does raise environmental and health concerns, and over the past two decades, the semiconductor industry has made significant efforts to replace or reduce specific PFAS chemicals. For example, due to concerns in the early 2000s about perfluorooctane sulfonic acid (PFOS), the global semiconductor industry worked to phase out non-essential use of PFOS and ultimately eliminated its use. While there are currently no known substitutes for many PFAS chemistries, there is an ongoing research and development effort across the industry to reduce and ultimately eliminate PFAS use.

As part of the 2022 CHIPS Act, $11 billion was set aside to advanced U.S. leadership in semiconductor research and development (R&D) which includes the establishment of the CHIPS National Semiconductor Technology Center (NTSC) Program. As part of the NTSC program, PFAS Abatement strategies are being studied with industry partners to prototype solutions that capture and destroy PFAS without disrupting existing processes.

For more information see: 

National Semiconductor Technology Center | NIST 

Ensuring Compliance

The Environmental Division works with CHIPS projects to ensure compliance with water and wastewater quality regulations and to implement effective water and wastewater quality control measures. Through Best Management Practices (BMPs) and proactive engagement with the industry, the Environmental Division aims to minimize the industry’s environmental impact while it continues to innovate and produce essential technologies.   

For more information on water quality regulations and the semiconductor industry visit the EPA’s Summary of the Clean Water Act | US EPA page. 

For more information on industrial wastewater regulations visit the EPA’s Industrial Effluent Guidelines | US EPA. 

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