HVAC Systems online learning channel. (Heating, Ventilation n Air-conditioning)
HVAC systems for semiconductor clean rooms
Welcome
Today´s episode is about HVAC systems for semiconductor clean rooms.
How to design HVAC system for semiconductor FAB clean rooms.
Cleanroom environment is achieved through the use of appropriate HVAC (Heating, Ventilation, Air Conditioning) systems and HEPA (high efficiency particulate air) filters that maintain the correct pressurisation, temperature, and humidity of the cleanroom.
Semiconductor Fab Cleanroom
The main rooms in a semiconductor Fab is cleanrooms, FABS & Sub-FABS.
The Cleanrooms are served by the following HVAC equipment.
RAH (return air handler)- sections (heater, humidifier, Fans, filters, cooling coils).
FFU (fan filtered Units)- HEPA (High efficiency particulate air filters).
MUA (make up air unit) — sections (heater, humidifier, Fans, filters, cooling coils).
Exhaust system, very important which I discuss below.
The Cleanrooms are positive pressurised, to keep out dust particles.
HEPA or ULPA (Ultra-Low Particulate Air) filters are used in the FFU.
Pre-filters and bag filters are used in the AHU’s (air handling Unis).
The semiconductor class is ISO class 5 with above 100 ACH (air change per Hour). The room air volume to change a 100 times per hour.
The air pattern in Fabs is unidirectional airflow from ceiling to low room level return so not to cause turbulence.
Pressurisation used in Fabs is 5 to 20 Pascals. Inch water gauge(0.02” to 0.08” )
The Fab Room surfaces shall smooth and free of fissures, not to collect dust particles.
The entry of the Fab areas should be equipped with Airlocks including air showers at the entry points.
The Fab entry Doors to be self closing mechanism, to keep the areas well pressurised.
Raised floors is used in parts of the Fab areas.
HVAC Products online
Exhaust from semiconductor Fabrication areas.
These exhaust shall be separate, as it is dangerous to mix some elements.
VOC (Volatile Organic Compound) exhaust.
ACID Exhaust.
Ammonia Exhaust.
General Exhaust.
Agua Regia Exhaust -rarely used.
High ACID Exhaust.
Silane Exhaust.
General Heat Exhaust.
Pyrophoric Exhaust.
PFC Exhaust.
EPI Exhaust.
Hydrogen Exhaust.
Emergency release.
Chemical Storage and waste tanks vents
Strict Rules to follow on Exhaust.
Never mix Ammonia with acid.
Use Sloped ducts with drains, sometimes heated ducts @ 400 Celsius so no residue collects on the inside.
Use Round ducts for higher velocity.
Make sure to have High Velocity — 3000 FPM (foot per minute).
Use POU (Point of use) filtration at the process units.
Scrubbers Types.
Scrubbers are main items in exhaust.
Neutralising PH solutions for ACID or ammonia.
Chemical dosing.
Granular.
Chemical absorption.
Use drainage in the ducting as well.
Use of burners , sometimes in series.
Electrostatic Precipitator Type, that charges particles to collect on plates.
Exhaust Scrubbers online
For Design details of exhaust contact myself or exhaust specialist & partner of my recommendation.
I can be consulted on this and help you achieve your goals on site or remotely.
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