- Several very toxic gases are used or generated in the semiconductor manufacturing industry.
- Toxic gases are poisonous and can affect physiological processes. These harmful gases can also be flammable and corrosive.
- The toxic gases can be grouped into process gases, acidic gases, alkaline gases, and VOC gases.
Toxic gas monitoring and control are crucial in semiconductor facilities, as they utilize substantial quantities of some of the most hazardous gases during the fabrication process. Continuous monitoring at various locations within the facilities is necessary to protect staff health and safety. Learn about the leading toxic gases in semiconductor manufacturing and their impact on health and safety.
Exposure Risks in Semiconductor Production
Many gases are used in various processes and steps during semiconductor or chip manufacturing, such as etching, vapor deposition, and ion implantation, and are referred to as process gases. These gases are supplied in gas tanks, gas tank trailers, or underground piping.
The gases used for chamber purging and cleaning are called bulk gases. Many are produced onsite in air separation plants.
Some additional toxic gases are also generated during etching and cleaning, which must be controlled. Exhaust gases can be those used for the manufacturing process or those generated as a result of the processes.
Workers can be exposed to these gases during transport through tankers, handling, storage in tanks and cylinders, processing, and disposal. Accidental leaks and spills can expose workers to toxic gases. The possibility of leaks and spills exists at pumps, valves, piping junctions, manifolds, fittings, and connections. All these potential exposure sites should be continuously monitored for toxic gases. Damage to the facility by extreme weather or terrorism can also lead to exposure.
Gases Associated with Semiconductors
The hazardous gases in the semiconductor industry can be toxic, corrosive, or flammable/ explosive.
- Toxic gases are poisonous and can have physiological effects, either through inhalation or direct contact.
- Corrosive gases attack and damage human tissue as well as metal and other materials.
- Flammable/explosive gases easily burn when mixed with air or oxygen.
Some gases, such as chlorine, can be toxic and corrosive. Some are toxic, corrosive, and flammable, like ammonia. Some can be toxic and flammable, like carbon monoxide.
According to the US system
- Class 4 gases are highly toxic
- Class 3 gases are hazardous
- Class 2 gases are moderately toxic
Gases with higher toxicity can harm or even kill people at low concentrations. Gases that must be present in higher concentrations to harm are considered less toxic. Table 1 gives the various gas concentrations in parts per million (ppm). Global systems (Globally Harmonized System GHS) use a rating, where the most dangerous gases are called class 1, followed by classes 2, 3, and 4 with lesser toxicity. See Table 1.
Table 1: Toxicity levels of gases. (LC50: It is a standard measure of the toxicity of the gas that kills 50% of the animal test population in a specified period through exposure via inhalation; NFPA: National Fire Protection Association; CFC: The California Fire Code; GHS: The Globally Harmonized System). (Credits: https://www.ehs.uci.edu/training/tango/_pdf/ToxicGasFactSheet.pdf)
The toxic gases, which are also flammable and/ or corrosive, pose additional risks to people’s health and safety.
The leading toxic gases found in the semiconductor industry are discussed below, including the process and exhaust gases.
Process Gases
The toxic process gases are arsine, phosphine, diborane, carbon monoxide, silane, and ozone. Workers can suffer severe organ damage and even death due to some process gases, and strict permissible levels control their levels in the air in the industries.
- Arsine
Arsine (AsH3) is a colorless, non-irritating, flammable, and toxic gas that has a mild garlic odor. Arsenic reacts with acids to produce arsine. The poisonous gas is not absorbed through the eyes or skin. It affects people when inhaled. It enters the blood and damages red blood cells, leading to hemolytic anemia. Permissible levels have been set by the US Occupational Safety and Health Administration (OSHA) at 0.05 ppm.
- Phosphine
Phosphine (PH3) is a toxic, flammable, and explosive gas. It is a colorless gas at ambient temperature with a garlic or decaying fish odor. PH3 is very harmful when inhaled, even in low concentrations. Heating can cause explosions. Health effects are nausea, vomiting, diarrhea, abdominal pain, chest tightness, dyspnea, muscle pain, thirst, chills, stupor, and pulmonary edema. Exposure to 400 to 600 ppm for half to one hour can cause death. Even exposures of 5-10 ppm result in severe effects. Hence, the permissible OSHA levels for phosphine are 0.3 ppm.
- Diborane
Diborane (B₂H₆) is colorless and has a sickly sweet odor. The gas is toxic and highly flammable. At high concentrations, it can react with oxygen in the air to ignite spontaneously. Diborane vapors are heavier than air and collect in low-lying areas. Diborane irritates moist tissues like eyes, skin, and the respiratory tract, causing burns. Effects are more serious in poorly ventilated rooms and can lead to ulceration and even death.
- Carbon monoxide
Pure carbon monoxide is used in semiconductor factories to regulate the etch rate, providing better control over etching profiles. Carbon monoxide (CO) is an odorless, colorless gas that is very poisonous. The CO symptoms are headache, dizziness, vomiting, chest pain, and confusion. Higher concentrations of CO can lead to loss of consciousness and death, as it replaces oxygen in the bloodstream. Carbon monoxide (CO) accumulation is possible in areas without proper ventilation or in confined spaces.
- Silane
Silane (SiH4) is a colorless, flammable, and poisonous gas with a strong, repulsive odor. It is easily ignited in air, reacts with oxidizing agents, is very toxic by inhalation, and is a strong irritant to skin, eyes, and mucous membranes. Silane is lighter than air.
- Ozone
Ozone is used for cleaning in semiconductor production. Ozone (O3) is a colorless gas with a pungent odor. It irritates the skin, eyes, and lungs, and high concentrations can lead to pulmonary edema. Ozone is mutagenic and can damage fetuses. Due to the high risks involved,
OSHA has established a permissible exposure limit of 0.1 ppm in workplaces.
Exhaust Acidic Gases
The toxic exhaust gases can be acidic, alkaline, and volatile organic compounds.
Strong acids like sulphuric acid, hydrogen chloride, nitric acid, hydrogen fluoride, and hydrogen peroxide (H2O2) are used for cleaning and etching, and produce significant amounts of these vapors in bulk gases. These acidic vapors pose a health threat and have a negative environmental impact, such as acid rain.
- Sulphuric acid
Sulphuric acid (H2SO4) fumes are toxic and corrosive and are produced in the wet-itching processes. Inhalation can cause respiratory distress. Epidemiological studies suggest it could be related to laryngeal cancer. Occupational exposure to strong mists of H2SO4 is considered carcinogenic.
- Hydrogen chloride
Hydrogen chloride (HCL) gas is produced in the diffusion process. It is colorless to slightly yellow and is nonflammable, non-toxic, and non-corrosive. It forms corrosive fumes when the gas comes in contact with air and hydrochloric acid when in contact with water. At high concentrations, the gas irritates the respiratory tract, such as the nose, throat, and lungs, as well as the eyes and skin. Acute exposure to high levels can lead to chronic problems. Death can follow after severe pulmonary damage. Long-term exposure to low gas levels can lead to respiratory problems, skin and eye irritation, and discoloration of the teeth.
- Nitric Acid
Nitric acid (HNO3) is toxic, strongly oxidizing, and corrosive. It can be present as vapor, mist, or fumes. Nitric acid fumes can also cause immediate pain in the stomach, lungs, head, and loins, dizziness, and nausea. Nitric acid fumes also cause respiratory tract irritation that requires a lengthy recovery period. It can also cause bronchitis, pulmonary edema, and pneumonitis.
- Hydrogen fluoride
Hydrogen fluoride (HF) is a colorless and very poisonous gas produced by its fuming liquid state. It is made during chemical vapor deposition processes in the semiconductor industry. It dissolves in water to give corrosive hydrofluoric acid. HF gas manages to seep easily into the skin and tissue, damaging cells, leading to severe pain, rashes, and deep burns that take a long time to heal. Inhalation of even small quantities can irritate the respiratory system and cause chronic health issues. Higher concentrations can cause death. Eye exposure to HF can lead to chronic or permanent vision problems or the breakdown of eye tissue.
- Phosphoric acid
Phosphoric acid (H3PO4) is produced in the epitaxy process. It is a solid or liquid at room temperature and is a problem when heated or misted. Inhalation of mist can irritate the throat and nose.
- Hydrogen peroxide (H2O2)
Hydrogen peroxide is a colorless, nonflammable liquid whose fumes are toxic. It is a strong oxidizer and can cause spontaneous combustion when in contact with organic matter. It is poisonous and corrosive when inhaled. Skin contact is not dangerous. Since it is odorless, even high concentrations cannot be detected by smell. Inhalation irritates the nose and throat and causes pulmonary edema. The gas is heavier than air and accumulates in low-lying areas. It causes asphyxiation in closed or low-lying areas. Children are more vulnerable to the same concentration as adults, due to their shorter stature and higher surface area-to-mass ratio.
Exhaust Alkaline Gases
Alkaline gases are ammonia and ammonium hydroxide and are formed during cleaning and etching. Alkaline emissions also have adverse environmental impacts, such as ecosystem alkalization. Critical loads of atmospheric pollutants in terrestrial systems can increase the pH of soils, which is harmful to the growth of most trees by limiting the availability of nutrients.
- Ammonia
Ammonia (NH3) is the primary alkaline emission in the semiconductor factories and is used during silicon nitride deposition. It is a colorless gas with a strong odor and is toxic, corrosive, and flammable. Ammonia irritates the respiratory tract, leading to pulmonary edema. It also irritates the skin and eyes. Therefore, the National Institute for Occupational Safety and Health (NIOSH) requires that NH3 emissions be kept below 25 ppm.
- Ammonium hydroxide
Ammonium hydroxide, a colorless solution of ammonia in water (NH4OH), is used for cleaning purposes. It is not flammable, but in the event of a fire, it produces ammonia gas that can cause explosions. It is very corrosive and irritates the skin and eyes. It can damage the eyes, and repeated exposure causes dermatitis. Ammonium hydroxide also affects the respiratory system, leading to pulmonary edema.
Electrochemical-based gas sensors can detect alkaline and acidic gases.
Exhaust Volatile Organic Compounds
Volatile Organic Compounds (VOCs) are toxic and also have adverse environmental effects because they can react with nitrogen oxides and carbon monoxide to form ozone or smog.
- Volatile Organic Compounds
VOC emissions are generated during wafer cleaning, photoresist stripping, and photolithography processes. The main compounds producing the VOCs are methanol, acetone, isopropyl alcohol, propylene glycol, ethyl acetate, and monomethyl ether acetate. VOC exposure irritates eyes, nose, and throat and can cause nose, eyes, and throat problems, breathing difficulties, and central nervous system damage. VOCs are also carcinogenic.
Besides these toxic gases, the semiconductor factories also use or produce flammable, corrosive, and greenhouse gases that are non-toxic, but must also be monitored.
Detecting the Toxic Gases
It is vital to detect gases so that their levels can be monitored and maintained below prescribed levels to avoid harm to people working in the facilities. Sensors that are sensitive enough to detect gas traces in ppm and ppb (parts per billion) concentrations are necessary, considering the low levels that are permitted for most of the toxic gases in the semiconductor industry. Various technologies will be required to detect the wide range of gases found in these facilities based on the characteristics of the chemicals. One of the standard technologies used is electrochemical sensing. Interscan offers electrochemical sensors for over 20 hazardous gases, some of which are present in the semiconductor industry. Fixed and portable types are available for continuous monitoring and for checking gas levels in closed, confined spaces, respectively.
Find out more about Interscan gas analyzers and sensors for your toxic gas monitoring needs.
Sources
ATSDR. (2002). Hydrogen chloride. Retrieved from https://www.atsdr.cdc.gov/toxfaqs/tfacts173.pdf
ATSDR. (2014, Oct 14). Medical Management Guidelines for Diborane. Retrieved from https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=964&toxid=202
CDC. (2024, April 17) Carbon Monoxide Poisoning Basics. Retrieved from https://www.cdc.gov/carbon-monoxide/about/index.html
CDC. (2004, Sept 6). Chemical emergencies. Retrieved from https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/hydrogen-fluoride.html
CDC. (2014, Oct 21). Medical Management Guidelines for Hydrogen Peroxide. Retrieved from https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=304&toxid=55
Committee on Acute Exposure Guideline Levels; Committee on Toxicology; Board on Environmental Studies and Toxicology; Division on Earth and Life Studies; National Research Council. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 14. Washington (DC): National Academies Press (US). (2013, April 26). 5, Nitric Acid: Acute Exposure Guideline Levels. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK201482/
Hess, J. C. (2024, June 20). Chip Production’s Ecological Footprint: Mapping Climate and Environmental Impact. Retrieved from https://www.interface-eu.org/publications/chip-productions-ecological-footprint
Mayo Clinic. Carbon monoxide poisoning. Retrieved from https://www.mayoclinic.org/diseases-conditions/carbon-monoxide/symptoms-causes/syc-20370642
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 944, Nitric Acid. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Nitric-Acid.
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 24823, Ozone. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Ozone.
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 24404, Phosphine. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Phosphine.
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 1004, Phosphoric Acid. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Phosphoric-Acid.
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 23953, Silane. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Silane.
National Center for Biotechnology Information (2025). PubChem Compound Summary for CID 1118, Sulfuric Acid. Retrieved May 6, 2025 from https://pubchem.ncbi.nlm.nih.gov/compound/Sulfuric-Acid.
Nguyen, M. T. N., & Lee, J. S. (2024). Development of a Chemical Sensor Device for Monitoring Hazardous Gases Generated in the Semiconductor Manufacturing Process. Chemosensors, 12(11), 233. https://doi.org/10.3390/chemosensors12110233
Nguyen, Q.H. (n.d.). PFAS Reduction in Semiconductor Manufacturing. Retrieved from https://www.emft.fraunhofer.de/en/projects-fraunhofer-emft/pfas-semiconductor-manufacturing.html
NJ Health. (2016). Hazardous Substance Fact Sheet- Ammonia. Retrieved from https://nj.gov/health/eoh/rtkweb/documents/fs/0084.pdf
NJ Health. (2016). Hazardous Substance Fact Sheet- Hydrogen Peroxide. Retrieved from https://nj.gov/health/eoh/rtkweb/documents/fs/1015.pdf
NRC (US). (2009). Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants: Volume 3. Washington (DC): National Academies Press (US); 2009. 3, Hydrogen Chloride. Available from: https://www.ncbi.nlm.nih.gov/books/NBK219917/
OSHA. (n.d.). Toxic Exhaust Gases. Retrieved from https://www.osha.gov/semiconductors/solutions/toxic-gases
Peng, J. L., Yeh, M. P., Liu, K. H., Chen, T., Chuang, T. S., Lee, S. L., & Tung, K. L. (2025). Source and characteristics of inorganic acidic gases and aerosol emissions in a semiconductor plant. Separation and Purification Technology, 354, 128806.
Tattar, T. A. (2012). Diseases of shade trees. Elsevier.
UAB.edu. (2019, June 19). Corrosive Compressed Gases. Retrieved from https://www.uab.edu/ehs/images/docs/gen/Corrosives_06192019.pdf
Wald, P. H., & Becker, C. E. (1986). Toxic gases used in the microelectronics industry. Occupational medicine (Philadelphia, Pa.), 1(1), 105–117.
