Air preparation

Most of the cost of maintaining the operability of the technology center is spent precisely on “air”, i.e. to ensure a constant influx of thousands of cubic meters per hour of highly purified air, the creation of its laminar flow in the cleanest areas of the technological center, the provision of overpressure, the precise control of temperature and humidity, as well as the provision of various types of exhaust. Moreover, this system works 24/7, i.e. round the clock without days off and holidays.

FMN Laboratory is benefiting from a three-stage air purification, which provides output filtering of dust particles up to 0.3 microns in size with an efficiency of no worse than 99.999% (in all areas with a cleanliness class up to ISO5) and 99.9995% (in areas with a cleanliness class ISO5 and higher). Air at the last stage of cleaning (directly on the ceiling of the clean room) is supplied at a speed of 0.3 - 0.5 m/s through HEPA or ULPA filters into the clean area, passes from the ceiling to the floor, blowing people and equipment, and is discharged to service rooms zones through the air grilles. The number of such grilles is calculated based on the air balance of the supply air, all types of exhaust, and the need to maintain excess pressure.
The need to maintain excess pressure is also associated with the special purity of the technological center sections, the higher the cleanliness class of the technological center section, the higher the pressure maintained in this section. So, when opening a door from a less clean room to a cleaner one, the airflow will always be directed to a less clean area, which allows not introducing additional pollution into the cleanest areas of the technological center. To maintain a given level of overpressure, a certain (calculated during design) number of air grilles are equipped with actuators that can regulate the amount of air passing through them by closing/opening the grille shutters. This automatic system combines the air preparation system, control of technological hoods, access control to rooms into a single mechanism and provides feedback.

For example, when opening a door from a clean corridor (low-pressure area) to any technological area (high-pressure area), the pressure “tends” to equalize. At this moment, the air preparation control system, firstly, drives the louvers of the air grates, equalizing the indoor pressure to their set values. Secondly, it provides control over heat exchangers and steam generators, maintaining temperature and humidity at predetermined limits. At the same time, the access control system blocks all other doors, realizing local locking to prevent air mixing (and therefore particle generation) between different clean zones. At the same time, fire extinguishing and gas analysis systems in real time receive information on the status of all of the listed subsystems, preparing at any time to “help” in case of emergencies. 

In this case, one of the main tasks of the air preparation system is to ensure the conditions for the regular implementation of technological processes. Almost all high-precision technological and metrological operations at the сenter are extremely sensitive to changes in temperature and humidity. The air preparation system and local climate control systems maintain the temperature with an accuracy of ± 0.1° C in areas of high temperature stability requirements, such as, for example, a section of electron beam lithography. Humidity is maintained with an accuracy of ± 5%.

When carrying out technological operations, the center uses a wide range of solvents, acids, alkalis, chemicals, gases, etc. To prevent their possible interaction after technological processes, the hood is divided into three subsystems: chemically resistant, for flammable substances and a separate hood from gas cabinets. Such a separation makes it possible to exclude even the hypothetical possibility of mixing waste with the formation of emergencies. Moreover, all hazardous products of reactions and technological processes must be fed to a scrubber before being discharged into the hood, where hazardous substances are neutralized.