- Semiconductors’ production requires 30 specialty gases.
- Some gases are hazardous, and accidental leakage must be monitored and controlled.
- Gas detection is a crucial recommended procedure to keep people safe.
Semiconductors are a crucial element in electronics, medical devices, and transport. The fine construction of the chips is made possible by chemical reactions involving specialty gases. However, these gases need to be handled with care. Safety protocols integrating gas detection, training, protective gear, and safe work practices are necessary to keep people safe in this expanding industry.
What are Semiconductors?
Semiconductors are components of everyday electronic devices like smartphones, computers, and televisions. These are also a part of more advanced technology like medical equipment and military systems. Semiconductors are of four types- memory, microprocessors, standard chips or commodity integrated circuits, and system on chip (SOC). The components are valuable as they help in miniaturization and make devices lighter, faster, and smarter.
Semiconductors are also expected to be crucial for emerging technology like autonomous cars. Their demand is growing, and in 2022, the semiconductors market peaked at an all-time high of US$ 574 billion.
Speciality Gas Use in Semiconductors
Figure 1. “The transistor cycle in manufacturing an integrated circuit, “Emami-Naeini & Roover, 2008. (Image credits: Emami_Paper.pdf (nd.edu))
Semiconductors are crystalline solids whose electrical conductivity is intermediate between a conductor and an insulator. Semiconductors are made of silicon or gallium arsenide and whose properties are altered by treating them with dopants. Dopants can be antimony, arsenic, bismuth, and phosphorus.
Thirty specialty gases are necessary to produce the integrated circuits forming the semiconductors. The gases are involved in chemical reactions to produce characteristic semiconductor electrical properties. The gases used are pure or mixtures made for specific manufacturing processes.
Besides doping, the gases are used in other main semiconductor manufacturing processes, such as crystal growth, oxidation, etching, epitaxy formation, diffusion and ion implantation, chemical vapor deposition, metallization, die attachment, die separation, wire bonding, post-solder cleaning, and encapsulation packaging. See Figure 1 for steps in making a transistor or mini-semiconductor.
Many processes are repeated several times. So, a production process can have a chain of hundreds of steps. Between each repetition is a cleaning step.
Production is carried out in closed systems as the substances used can be carcinogenic and mutagenic. However, there are risks due to gas leakage when changing gas cylinders. These could be hydrogen, phosphine, arsine, silane, hydrogen chloride, fluoride, dichlorosilane, boron tribomide, and phosphorus oxychloride.
The most common gases used, which can be hazardous to personnel working in semiconductor manufacturing, are hydrogen fluoride, phosphine, and ozone.
Hydrogen fluoride
Hydrogen fluoride or hydrofluoric acid is used in the etching and cleaning phases of the semiconductor manufacturing process.
It is a colorless gas or liquid with a pungent, irritating odor. It is hazardous because it is highly corrosive, and even acute exposures can cause severe skin and eye burns and irritate the throat and lungs. Very high exposures can lead to permanent eye damage, respiratory problems, pulmonary edema, liver and kidney damage, fluoride poisoning, convulsions, and death. Long-term exposures cause fluorosis.
Skin contact doesn’t cause pain, and systemic poisoning can start before the affected person realizes there is an exposure.
Hydrogen fluoride can also react with water to produce toxic gases, so it should be handled and stored carefully.
According to the Occupational Safety and Health Administration (OSHA), the permissible level is over 8 hours, and according to the National Institute for Occupational Safety & Health (NIOSH), over a 10-hour exposure is three ppm. At the same time, the STEL 8 (short-term exposure level) over 15 minutes is only six ppm.
Phosphine
Phosphine is a dopant and a colorless gas with a fishy odor. It is hazardous because it is a health, fire, and explosion risk.
Breathing can irritate the nose, throat, and lungs, nausea, headache, and vomiting. Even acute but high exposures can cause pulmonary edema, coma, and death. Long-term exposure leads to bronchitis and liver and kidney damage.
OSHA and NIOSH set 0.3 ppm as the limit for a work shift, and the STEL is one ppm.
Ozone
Ozone is used extensively to clean wafers in semiconductor production. Ozone is a colorless gas with a pungent odor. It is considered hazardous and can affect people when they breathe it. It irritates the skin, eyes, and lungs, with higher exposure causing pulmonary edema. Long-term low exposure can cause lung damage.
Besides these effects, ozone can cause mutations and damage to developing fetuses and is a gas of concern.
OSHA and NIOSH prescribe a permissible level of 0.1 ppm over a work shift.
Figure 2: Protective gear necessary during ork in the semiconductor manufacture process, Emami-Naeini & Roover, 2008. (Image credits: Emami_Paper.pdf (nd.edu))
Best Practices to Reduce Risks
To control and reduce accidental gas emissions and their impact, safety managers should integrate the following suggestions:
Monitoring and Reporting
Monitoring the sources of toxic gas emissions used in the semiconductor factory should be continuous and part of the work protocol. The data should be analyzed and reviewed regularly to check that gas levels are within permissible. Otherwise, necessary corrective actions should be initiated. Records of monitoring data results should be maintained and shared with the concerned authorities as required.
Instruments that can detect these minute quantities can be stationary and portable. For example,
- Interscan’s AccuSafe is suitable for installation and continuous monitoring at one or more points. Each controller is connected to ten sensors. Modbus TCP/IP communications allow a considerable distance between the sensor and controller. Data acquisition is built in and requires no additional software. Devices for hydrogen fluoride and phosphine can be custom-made to suit the precision needs of each factory. Ozone devices that detect 0-2000 ppb and 0-20 ppm are available.
- Interscan’s GasD® 8000 portable gas analyzer is for surveys. They can also be customized for hydrogen fluoride and phosphine. Ozone sensors with detection ranges of 0-5 ppm, 0-50 ppm, and 0-20 ppm are available.
Storage and Handling
Cylinders of the hazardous gases should be fitted with leak detection devices. Well-designed emergency protocols should be in place to activate them in case of accidents, leaks, and spillage. Point-of-use control systems like wet scrubbers can control the toxic emissions of the chemicals used in semiconductor factories.
Provide Adequate Information, Protection, and Training
People working in semiconductor factories should be informed of the risks of common toxic gases, be trained in emergency measures, and know the proper procedures to handle them. The staff should also wear prescribed protective gear during manufacturing and tackling emergencies; see Figure 2.
The semiconductor manufacturing process also produces hazardous gas emissions and liquid and solid effluents which are a risk to the environment and people, like ozone-depleting substances, acids, organic solvent vapors, ammonia, chlorine, metals, stannic oxide, fluorides, fluoborates, sulfates, and solder dross, hydroxide metals, etc. Safety managers must also deal with them.
Using Speciality Gases Carefully
The semiconductor is a vast global industry, and the use of gases and demand for these commodities is rising. The specialty gas market was worth 12.14 billion in 2022 and is expected to grow at a CAGR of 7.9% by 2030 to reach a value of USD 22.30 billion. However, its use must be accompanied by due caution and care to safeguard workers’ health and lives.
Vijayalaxmi Kinhal
Science Writer, CID Bio-Science
Ph.D. Ecology and Environmental Science, B.Sc Agriculture
Sources
Deloitte. (n.d.). Semiconductor Industry Outlook 2024. Retrieved from https://www2.deloitte.com/content/dam/Deloitte/us/Documents/technology-media-telecommunications/us-tmt-semiconductor-industry-outlook-2024.pdf
Emami-Naeini, A &de Roover, D. (2008). Control in Semiconductor Wafer Manufacturing. Retrieved from https://www3.nd.edu/~pantsakl/Archive/WolovichSymposium/files/Emami_Paper.pdf.
Multilateral Investment Guarantees Agency. (n.d.). Environmental Guidelines for
Electronics Manufacturing. Retrieved from https://www.miga.org/sites/default/files/archive/Documents/ElectronicsManufacturing.pdf
New Jersey Department of Health and Senior Services. (n.d.). Hazardous substances fact sheet- Hydrogen fluoride. Retrieved from https://nj.gov/health/eoh/rtkweb/documents/fs/3759.pdf
New Jersey Department of Health and Senior Services. (n.d.). Hazardous substances fact sheet- Phosphine. Retrieved from https://nj.gov/health/eoh/rtkweb/documents/fs/1514.pdf
New Jersey Department of Health and Senior Services. (n.d.). Hazardous substances fact sheet- Ozone. Retrieved from https://nj.gov/health/eoh/rtkweb/documents/fs/1451.pdf
SNS Insider. (2023, October). Specialty Gas Market Size, Share & Segmentation By Product (Noble Gases, Ultra-high Purity Gases, Carbon Gases, Halogen Gases, and Others), By Application (Manufacturing, Healthcare, Electronics, Institutions, and Others), By Region and Global Forecast for 2023-2030