Look around you. You don’t have to look far—just at the screen you’re using to read this, whether it’s your smartphone or computer. Every corner of your home is likely filled with computerized devices.
From your coffee maker and fridge to your television and car, nearly everything that runs on electronics and makes your life easier is made possible by cleanrooms.
Many gadgets contain fragile components that can easily break if mishandled. As these parts become smaller and more intricate, they also become more sensitive to damage from even the tiniest external elements, such as dust.
This is where semiconductor cleanrooms play a vital role. If you’re curious about these specialized environments and their critical importance in electronic production—and how they shape the world you live in—keep reading.
Discover the purpose of semiconductor cleanrooms, their industry applications, classifications, and common design features below.
What is a Semiconductor Cleanroom?
A semiconductor cleanroom is a specialized environment meticulously designed to prevent airborne particles, microorganisms, and contaminants from compromising semiconductor production.
In most cases, it also regulates environmental factors such as temperature, airflow, humidity, and static electricity to ensure superior product safety.
These controlled spaces play a critical role in reducing contamination risks during essential semiconductor manufacturing processes, including assembly, photolithography, wafer fabrication, semiconductor testing, and packaging.
Importance Of Semiconductor Cleanrooms
Cleanrooms are invaluable because they make semiconductor manufacturing possible while reducing the number of defective products. But what exactly are semiconductors?
Semiconductors are made from a glass-like solid material called silicon, which is shaped and cut into thin wafers. They are found in hundreds of thousands of electronic devices, embedded in microchips, memory chips, SoCs, and integrated circuits.
Silicon semiconductors are highly valued for their unique conductive properties—they conduct more electricity than insulators (like glass or rubber) but less than pure conductors (such as aluminum, brass, or copper).
They are at the core of the technology powering the world’s businesses, healthcare systems, entertainment, and much more. However, semiconductors rely on precise electrical properties to function correctly.
Contaminants as small as a single particle of pollen can alter these electrical characteristics, disrupting the semiconductor’s functionality. Without cleanrooms, contaminants could compromise the silicon’s conductivity and overall performance.
Here are some examples of industries that rely on semiconductor cleanrooms:
- Smartphone manufacturing
- Computer hardware
- Automotive building
- Aerospace and defense technologies
- Biotechnology
- Household appliance
- Robotic and automation engineering
How Do Clean Rooms Work?
Now that you understand what cleanrooms are and their importance in microelectronics, how do these controlled spaces actually work?
The goal is to minimize particulates to the lowest possible levels. To achieve this, total control over the entire environment is required, including temperature, air pressure, airflow rate, humidity, and filtration systems.
Contaminants are constantly generated by facilities, systems, equipment, and people. Therefore, the cleanroom must operate continuously to remove existing particles within the space.
Build Material
The materials used to construct cleanrooms are specially designed for easy cleaning. They’re disinfectant-resistant and have anti-shedding properties to prevent releasing particles into the atmosphere.
For example, sheet vinyl is popular for cleanroom floorings because it’s highly chemical-resistant and has minimal seams where dust and other debris can accumulate.
Walling is another important consideration that may affect the cleanroom’s performance. In many cases, the walls are made from hard steel and plastic, with some combination of soft materials like flexible polyethylene strips and curtains.
Ventilation System
A high-efficiency ventilation system is typically set up to maximize air exchange while lowering energy loss. This way, fresh air is regularly replenished to provide continuous positive pressure within the space and protect the facility in case of a breach.
The incoming air will go through filters, while outgoing air is extracted in low areas, re-filtered, and recirculated. Adding fan-filter units in the right locations generally increases the cleanliness of the space.
Higher-classification cleanrooms typically have higher air exchange rates.
The ventilation system is crucial because it regulates temperature levels. Standard cleanrooms should maintain the optimal temperature range of 70°F (21°C) and avoid exceeding or dropping higher or lower than 2 degrees.
Besides temperature, humidity should also be kept at around 30% to 40%. Incorrect relative humidity (RH) levels can lead to all sorts of problems, including microbial growth, solvent evaporation, material corrosion, and product defects.
Air Flow
Air distribution is another must-watch aspect when building a semiconductor cleanroom. Depending on your product, you may need a laminar or turbulent airflow.
Laminar airflow is characterized by its unidirectional speed and pattern. You can think of it like a smooth river, with all currents flowing in the same direction.
On the other hand, a turbulent pattern is an airflow moving at random directions and velocity. This unbalanced air distribution can come from obstacles in the current or vent fans operating at different speeds.
A turbulent pattern can be useful in less critical applications. That is, your product doesn’t require as much air filtration. Unless that’s the case, you may want to avoid turbulent airflow due to its tendency to stir up particles.
A laminar airflow is typically preferred for most standard cleanrooms because it’s more effective in sweeping particles out.
Entering and Exiting Protocols
Protocols will be in place to ensure anyone coming in and out of the cleanroom follows appropriate procedures. Often, cleanrooms require dense, chemical-resistant coveralls, gloves, masks, shoe covers, goggles, hoods, and caps.
Entering the controlled space may also mean going through a changing room, and removing or covering your external clothing with approved apparel. Ultimately, it protects both you and the facility from harmful contaminants.
Semiconductor Cleanroom Classifications
Because of the sensitive processes involved, semiconductor cleanrooms typically run non-stop throughout the day. To lower contamination risks, rigorous guidelines must be followed throughout manufacturing.
ISO Cleanroom Classification
Semiconductor clean room classifications are divided by level of cleanliness per the ISO classification system set up to ensure optimal safety and performance. This is measured according to the number and size of particles per unit volume of air.
For your reference:
ISO classes are generally divided into 9 categories. ISO 1 is the “cleanest” classification typically used in industries that demand ultra-fine particulate processing. Some examples include microelectronics and the sciences.
ISO 9 is considered the “dirtiest” classification, with a maximum particulate amount of 35,200,000 per cubic meter sized 0.5 microns or larger. Still, although considered the dirtiest, ISO 9 spaces are far cleaner than regular rooms.
Semiconductor Cleanroom ISO Standard
Strictly speaking, semiconductor cleanrooms must comply with ISO Class 4 to 6 stipulated in ISO 14644-1. In this classification, the space should only have a maximum particle count of 352-35,200 particles sized 0.5 microns or smaller.
In addition to meeting ISO’s particle-to-air recommendations, cleanrooms must comply with ISO 14644-2. The document outlines the quality control guidelines to maintain the optimal conditions for cleanroom operations.
That said, it’s important to remember that not all production processes demand stringent control. In fact, many semiconductor cleanrooms that deal with testing, assembly, and packaging are only classified as ISO 7 or ISO 8.
Of course, unique industry standards will apply besides the required ISO classification. For instance, aerospace-related products will have to comply with NASA’s criteria. Similarly, automotive manufacturers will need to follow ASTM guidelines.
Common Semiconductor Cleanroom Design Features
With rigorous guidelines and standards involved, semiconductor cleanrooms need extensive planning and designing. Here are some essential features to consider for high-quality and optimally performing cleanrooms.
HEPA and ULPA Filters
Cleanroom demands fresh, high-quality air to prevent particulate ingress. This is where high-efficiency particulate air (HEPA) filters come in handy.
According to the US Environmental Protection Agency, HEPA filters can eliminate 99.97% of dust, pollen, mold, and bacteria from the air, making them a staple in cleanrooms. Not to mention they can remove particulates as small as 0.3 microns.
In situations where the tiniest speck can potentially disrupt production, ultra-low particulate air (ULPA) filters may be needed. Compared to HEPA, ULPA can filter particles as small as 0.12 microns, eliminating 99.9995% of air contaminants.
Humidity and Temperature Control
Humidity control is crucial because it directly impacts static electricity. Set it too high and bacteria can flourish or metal equipment can start to corrode. Cleanrooms with high RH are also prone to photolithographic degradation and condensation issues.
Controlling humidity directly ties to temperature. The lower the temperature inside the facility, the lower the RH. That means you want to maintain a relatively low temperature, so air conditioning is usually installed to dehumidify a clean room.
Some people also use HVAC systems in combination with desiccant cooling systems. These are heat-driven cooling devices that absorb moisture in the air. They act as a dehumidifier and extend your HVAC system’s lifespan by sharing the workload.
ESD Control
Electrostatic discharge (EDS) occurs when two oppositely charged materials are brought close together. This causes a sudden surge of electricity. Common examples of ESD include the shock we experience when we touch something metallic after walking across a carpet.
Although insignificant in an everyday setting, the electricity in an ESD is enough to harm small electronic components often found inside semiconductor cleanrooms.
While it sounds complicated, preventing ESD is quite simple. You can do this by choosing conductive and dissipative materials when building or using the cleanroom.
Conductive objects prevent static charge buildup by quickly dispersing electricity away from important components and equipment.
On the other hand, dissipative materials drain electric charge, preventing sudden shocks from happening. Static-dissipative floorings made of vinyl and epoxy are especially useful in managing ESD. Proper grounding must also be observed at all times.
Airflow Management
Airflow is massively important if you want to maintain a controlled environment. Generally, you want a uniform (laminar) airflow to remove particles consistently within the space.
For the best air management, HEPA fan filter units are placed strategically on ceilings, blowing air downward. Low-wall air ducts then catch the contaminated air and recirculate it to the filtration system.
The uniformly downward airflow prevents the dirty air from shooting up and stirring particulates in your working space. Although simple, this technique is also great for avoiding dead zones where air can’t circulate properly and accumulates contaminants.
Challenges in Maintaining Semiconductor Cleanrooms
It’s virtually impossible to create a 100% particle-free space, especially in a semiconductor cleanroom that’s heavily used. Contaminants from your personnel, facility equipment, raw materials, and environment are the hardest to prevent.
Still, having extensive contamination protocol training can significantly lower the risks. Strict gowning procedures, frequent equipment maintenance, careful product handling, and observing clean behaviors all cut down particle invasion by a lot!