The operations of semiconductor manufacturing and R&D present a myriad of potential industrial hygiene and safety hazards. Hazards exist in both silicon device and gallium arsenide device fabrication (fab) and laboratories.
Some semiconductor manufacturing and R&D hazards include:
- Acids such as acetic, chromic, hydrochloric, hydrofluoric, nitric, phosphoric, and sulfuric;
- Caustics such as ammonium hydroxide, hydrogen peroxide, and sodium hydroxide;
- Cryogens such as argon, carbon dioxide, oxygen and nitrogen
- Electrical and machinery;
- Gases which are corrosive, explosive, flammable, pyrophoric and/or toxic such as arsine, boron trifluoride, diborane, hydrogen chloride, phosphine, and silane;
- Ionizing and nonionizing radiation such as infrared (IR), lasers, radiofrequency (RF), and x-rays;
- Metals and/or their salts such as aluminum, antimony, arsenic, boron, chromium, gallium, gold, magnesium, mercury, nickel, silver, and phosphorus;
- Nuisance dust;
- Photoresists – positive and negative;
- Silica (crystalline) and silicon such as polycrystalline silicon, silicon dioxide, and silicon nitride;
- Solvents such as acetone, ethanol, glycol ether mixture, isopropyl alcohol, methanol, methylene chloride, methyl ethyl ketone, n-butyl acetate, 1,1,1-trichlorethane, and xylene
The above listing is not exhaustive, but illustrates the wide variety of hazards that may exist in semiconductor manufacturing and R&D.
A number of national consensus standards exist to address worker safety and health and property protection in the semiconductor industry, and are issued by Semiconductor Equipment and Materials International (SEMI) and the National Fire Protection Association (NFPA). SEMI standards exist for subjects such as process liquid heating systems, sizing and identifying flow limiting devices for gas cylinder valves, equipment safety labeling, exhaust ventilation, ergonomics engineering for equipment, and risk assessment, to name a few. NFPA 318 addresses the Protection of Semiconductor Fabrication Facilities. Due to the high density of highly flammable and easily ignitable plastics, as well as highly flammable liquids and gases in semiconductor fabs, fire and smoke are of great concern. The Semiconductor Environmental, Safety & Health Association (SESHA) promotes safety and health in the semiconductor industry.
The management of EHS in the semiconductor industry requires an EHS management systems approach. With the types of potential hazards listed above, good risk assessment is key. This requires recognition and evaluation of occupational safety and health issues by trained, competent EHS professionals. The hierarchy of controls (elimination, substitution, engineering, administrative, and personal protective equipment) needs to be utilized to reduce risks created by hazards such as those listed above. Chemical hazards need to be evaluated for potential routes of entry (dermal, inhalation, ingestion). Permanently placed fab and lab toxic gas monitors need to be periodically challenged to ascertain that they are functioning properly to protect employees and product. Job hazard/safety analysis needs to be performed to ensure safe operations, instruct employees and eliminate and/or control hazards. Process hazard assessments (i.e. what-if, hazard & operability, failure mode & effect, or fault tree) need to be conducted for significant risk operations. Employees need safety and chemical management training; process equipment needs safety and chemical labeling. A robust management of change (MOC) program needs to be incorporated into the EHS management system, since even minor process changes can add significant hazards to the workplace.
Gas safety presents special challenges in the semiconductor industry due to gas toxicity, flammability, or explosivity. Flow-limiting orifices are an industry standard with many of these specialty gases. Specialty gas cylinders are usually placed in gas cabinets within gas houses or outdoors and piped into fabs or labs; lab scale specialty gas cylinders need to be placed in ventilated enclosures or gas cabinets. Movement of specialty gas cylinders should be accompanied by periodic leak testing to ascertain that leaks have not occurred during cylinder delivery and transfer. Employees need to be trained on the hazards of the materials with which they work, and also on the elements of the gas safety program. There have been improvements in process gas delivery; sub-atmospheric toxic gas cylinders are gaining popularity in certain applications over high pressure cylinders, but their use is still not widespread.
To address these and other semiconductor safety and industrial hygiene issues, please feel free to contact:
United States Department of Labor, Occupational Safety and Health Administration, Safety and Health Topics. “Semiconductors.” https://www.osha.gov/SLTC/semiconductors/
Chelton, CF, Glowatz, M, and Mosovsky, JA. Chemical Hazards in the Semiconductor Industry. IEEE Transactions on Education, Vol 34, No 3, 1991.