Air filters for microelectronics, semiconductor, or digital technology industries produce products that would never have been developed if not for the advent of HEPA filters. All electronics from TV screens, to computers, to hard drives and more use micro circuits that can contain thousands of transistors that would fit on the head of a pin. Dimensions for the design of these circuits is now measured in terms of nanometers; one nanometer is one-billionth of one meter or 1×10-9. Nowhere is air filtration technology considered more important than in this industry as sub-micron particles can contaminate the lithography process shorting the circuits and rendering the manufactured product useless. Circuits are becoming so minute that even gaseous contaminants that are also nanometers in dimension are anticipated as being a contaminant of concern as technology advances.
The air filters used in these facilities are of the highest quality level because any type of contamination would decrease the product yield production reducing the manufacturers’ profits. Filter failures in this industry can be catastrophic in terms of financial impact. There are various stages of air filtration throughout this type of facility, from MERV 8 prefilters that remove large particles to Ultra-low Penetration Air filters (UPLA) that are certified during filter manufacture to contaminant removal efficiencies to 99,99995% on particles down to 0.1 micron in size.
Although yield consideration is the most important factor, filter performance in relation to sustained efficiency over time, long life-cycle, low carbon footprint in terms of energy usage and landfill volume, and reduced air changes (energy) required to maintain a cleanliness class level are all factors in air filter selection. Some of the defined areas requiring ultra-clean air include metallization, chemical mechanical planarization, dielectric disposition, thermal processes, ion implant, etching, and photo lithography. The microelectronics manufacturer defines the area as a class level in terms of a specific value as established by the International Organization for Standardization (ISO). Some examples include ISO Class 1 (ISO-1) which can have no more than 10 particles per cubic of air 0.1 micron in size or an ISO-5 that can have no more than 100,000 particles per cubic of air 0.1 micron in size. There are nine ISO levels of classification. US Federal Standard 209E is also referred to periodically.
Air filters typically applied in these facilities include:
- Prefilters, ASHRAE MERV 8, as a first filter stage to protect more expensive final filters from larger particles
- Secondary filters or final filters installed in the HVAC systems to prevent larger particles from reaching the next filtration stage so the principle of filtration used in the final filters can operate without compromise
- HEPA filters with factory-certified efficiencies to particle removal of at least 99.99% at 0.3 micron installed in central station air handlers or as filters in ceiling modules for low-level cleanrooms
- ULPA filters in ceiling modules with particle removal efficiencies selected based upon the process or intricacy of the product being produced, the number of air changes to the cleanroom and the total number of air filter modules used in the ceiling. Most high level processes have full ceiling coverage with the only other variables being filter efficiency and the number of air changes
- AMC or airborne molecular contamination air filters that employ special blends of carbon, other adsorbents or oxidizers to remove gaseous contaminants that may result in chemical contamination of the process
In some cases dust collection for the removal of large volumes of particulate contaminants or gas scrubbers may be used to eliminate corrosive, toxic gases, or odors, for operational security or regulatory compliance.
Your smart phone, the watch on your wrist, your cable modem, your DVR, even most medical devices we take for granted today, would not be possible without this high level of air filtration technology.