One of the most important things you can do during semiconductor manufacturing is practice proper risk mitigation to reduce contamination. Contamination puts semiconductors at serious risk. It can cause them to underperform, consume too much energy, malfunction, or completely fail. This can result in profit loss, recalls, customer complaints, and damaged reputation.
The good news is that by using best practices for contamination prevention and risk mitigation, you can seriously reduce the possibility of contamination or, at least, contain it. We’ve compiled some of our best practices for risk mitigation for you to review.
Use A Cleanroom
First and foremost, use a cleanroom. This one is incredibly basic, but it needs to be said. You can only prevent contamination in a completely controlled environment. Cleanrooms are designed to minimize airborne particles, control temperature, humidity, and air quality through air filtration systems, positive air pressure, and strict access controls to prevent the entry of contaminants.
Proper Gowning
Gowning is your first line of defense against contamination. Humans are a major contamination source in cleanrooms, accounting for up to 85% of particles shed in a cleanroom. Every minute, humans shed 40,000 skin particles. We are constantly producing and shedding particles, as we generate roughly 100,000 particles that are 0.3 microns or larger per minute. That is just sitting still. When we are moving, the number of particles our skin, hair, and clothing produces increases to over 5,000,000 particles.
Thus, gowning is the line between those particles and your cleanroom.
Ensuring that your team is properly gowned and equipped with truly particle-free gowns, booties, gloves, and other necessary personal protective equipment is paramount to risk mitigation and preventing contamination during semiconductor manufacturing.
Frequent Training
The forgetting curve is very real. WIthin a day of learning something new, people, on average, forget around 75% of what they had learned. We forget most of what we learn within an hour of learning it!
Intervention, though, such as studying or informational reminders, can reinforce information and improve retention. If you repeat the information in the same way over and over again, employees will be less likely to listen and retain information. To maximize retention, make sure to spice up your training and find new ways to make training frequent and interactive.
Material Control
Contamination prevention includes careful handling and control of materials throughout the manufacturing process, as they enter the cleanroom. This involves using cleanroom-compatible packaging, storage, and transportation methods to ensure the integrity and cleanliness of materials such as wafers, chemicals, gasses, and equipment.
Equipment and Tool Maintenance
Regular maintenance and cleaning of manufacturing equipment and tools are essential to prevent contamination. Any cleanroom equipment should undergo routine inspections, cleaning, and calibration to ensure optimal performance and minimize the risk of introducing contaminants into the manufacturing process. Ideally, equipment used in a cleanroom stays in the cleanroom, but if it has to leave and re-enter, it needs to undergo additional cleaning.
Cleanliness Verification
Various techniques, such as particle counting and surface cleanliness testing, should be used to verify the cleanliness of the environment, equipment, and materials. These methods help ensure that contamination levels are within acceptable limits and enable prompt detection and mitigation of any contamination issues. While this might not prevent contamination, it is critical to risk mitigation as it assures your measures are working.
Handling and Processing Procedures
Stringent procedures are implemented for handling and processing materials in the cleanroom environment. This includes using specialized tools, robotics, or automation to minimize human contact and the introduction of contaminants. Controlled processes such as wafer cleaning, deposition, etching, and lithography are carried out with precision and under strict contamination control guidelines.
Recent regulatory updates, such as the 2020 update for GMP Annex 1, show an increased emphasis on automating cleanrooms and removing humans wherever possible to prevent contamination and create traceable processes.
Cleaning and Maintenance Protocols
Regular cleaning protocols should be implemented for cleanroom surfaces, equipment, and tools. Specialized cleaning agents, materials, and techniques are needed to remove particles, residues, and other contaminants without introducing additional contaminants. You need to establish strict cleaning schedules.
Supplier Control
Your suppliers play a large role in ensuring what enters your cleanroom is sterile. We recommend strict supplier qualification processes, quality assurance measures, and supply chain management practices to minimize the risk of receiving contaminated materials or components.
Quality Control and Testing
Rigorous quality control processes and testing should be performed throughout the manufacturing process. This includes inspection of incoming materials, in-process checks, and final product testing to detect and eliminate any defective or contaminated devices.
Contamination Monitoring
Finally, the most important thing you can do for risk mitigation is continuous monitoring of the cleanroom environment. Particle counters and air monitoring systems are used to measure and monitor airborne particles, humidity, and temperature. Rapid alarms can alert you to contamination incidents.
While this does not prevent contamination from occurring, real-time, continuous monitoring can help prevent unneeded yield loss by helping to identify exactly which semiconductors are at risk according to the contamination trends detected by the particle counter.
Here at LWS, we specialize in designing particle counters and particle counter accessories designed to make your life easier and keep your products safe. We know contamination is the worst case scenario, but when it does occur, you want to rest easy knowing that you are aware of exactly what is happening in your cleanroom.
With rapid alarms and advanced self-diagnostics, you can have confidence in the state of your cleanroom.
