Chapter 1: Cleanroom

A cleanroom, often known as a clean room, is a constructed area that is designed to keep the concentration of airborne particles at an extremely low level. In addition to being actively cleansed, it is also well isolated and kept under control against contamination. It is normal practice to require such rooms for the purpose of conducting scientific research and for industrial production of all nanoscale operations, including the creation of semiconductors. The purpose of a cleanroom is to prevent any and all particles, including dust, airborne organisms, and vaporized particles, from entering the space, and consequently, from contaminating the item that is being handled within the cleanroom.

Furthermore, a cleanroom has the ability to stop the escape of materials. Within the fields of hazardous biology, nuclear work, pharmaceutics, and virology, this is frequently the major objective.

A cleanroom is typically equipped with a level of cleanliness that is measured in terms of the number of particles per cubic meter at a molecular measurement that has been determined in advance. Within a typical urban location, the ambient outside air includes 35,000,000 particles per cubic meter that fall within the size range of 0.5 µm and larger. This amount of particles is similar to the amount found in an ISO 9 certified cleanroom. As a point of contrast, a cleanroom that is certified to ISO 14644-1 level 1 does not allow any particles to be present in that size range, and it only allows 12 particles per cubic meter that are 0.35 micrometers or smaller. When it comes to semiconductor facilities, level 7 or level 5 is typically sufficient, however level 1 facilities are extremely few and far between.

By the middle of 1963, more than two hundred industrial plants in the United States had such specially constructed facilities, which were referred to as "White Rooms," "Clean Rooms," or "Dust-Free Rooms" at the time. These facilities included the Radio Corporation of America, McDonnell Aircraft, Hughes Aircraft, Sperry Rand, Sylvania Electric, Western Electric, Boeing, and North American Aviation. Beginning in February of 1961, RCA initiated the process of converting a portion of its facilities located in Cambridge, Ohio. It was utilized to prepare control equipment for the Minuteman intercontinental ballistic missiles, and it had a total area of 70,000 square feet.

MicroAire, PureAire, and Key Plastics all contributed to the majority of the integrated circuit production facilities in Silicon Valley. These three businesses were responsible for the majority of the facilities. Laminar flow units, glove boxes, cleanrooms, and air showers were some of the products that these competitors manufactured. Additionally, they manufactured chemical tanks and benches that were utilized in the "wet process" construction of integrated circuits. It was these three businesses that were the first to employ Teflon in the fabrication of integrated circuits, airguns, chemical pumps, scrubbers, water guns, and other devices that were necessary for the manufacturing of integrated circuits. The Honorable William C. The designs that McElroy Jr. created contributed 45 original patents to the technology that was available at the time. He worked for all three companies as an engineering manager, drawing room supervisor, quality assurance and quality control, and designer. Additionally, McElroy penned a four-page paper for the MicroContamination Journal, as well as training manuals for wet processing, equipment manuals for cleanrooms, and wet processing training manuals.

In the production of semiconductors and rechargeable batteries, as well as in the life sciences and any other discipline that is extremely sensitive to environmental contamination, a cleanroom is an absolute necessity.

It is possible for cleanrooms to be as small as very small or as vast as very large. There are two types of cleanrooms: on the one hand, a single-user laboratory can be constructed to cleanroom standards inside a few square meters, and on the other hand, complete production plants can be enclosed within a cleanroom with factory floors covering thousands of square meters. There are also modular cleanrooms that are located between the large and the tiny cleanrooms. Additionally, it has been stated that they are less prone to catastrophic failure and that they reduce the expenses associated with scaling the technology.

There is a vast range of applications for cleanrooms, hence not all cleanrooms follow the same pattern. To give an example, the rooms that are used in the manufacturing of semiconductors may not necessarily need to be sterile (that is, free of uncontrolled bacteria), yet the rooms that are used in biotechnology typically need to be sterile. Operating rooms, on the other hand, do not necessarily need to be completely free of nanoscale inorganic salts like rust, whereas nanotechnology necessitates that they be completely free of such salts. The stringent control of airborne particulates is something that is shared by all cleanrooms. This control may also include secondary decontamination of the air, surfaces, workers entering the room, utensils, chemicals, and machines.

In certain circumstances, such as when conducting research on potentially harmful viruses or when dealing with radioactive materials, particulates that are released from the compartment might also be a cause for concern.

To begin, the air from the outside that is brought into a cleanroom is filtered and cooled by multiple exterior air handlers that use filters that are progressively thinner in order to eradicate dust.

For the purpose of removing impurities that are produced internally, the air is continuously recirculated through fan units that contain high-efficiency particle absorbing filters (HEPA) and/or ultra-low particulate air (ULPA) filters. With the goal of reducing the amount of airborne particles that are produced, specialized lighting fixtures, walls, equipment, and other materials are utilized. Whenever the design of the cleanroom is of the laminar airflow type, plastic sheets can be utilized to reduce the amount of air turbulence encountered.

For the reason that they have an impact on the effectiveness and methods of air filtration, the temperature and humidity levels of the air inside a cleanroom are subject to stringent regulation. It is possible to control static electricity in a specific room by, for example, putting controlled amounts of charged ions into the air through the use of a corona discharge. This is the case if the humidity in that space needs to be low enough to prevent static electricity from occurring. Static discharge is a particular problem in the electronics sector since it has the potential to ruin components and circuitry in an instant.

The equipment that is inside of a cleanroom is designed to produce the least amount of air contamination possible. In order to ensure that the building of a cleanroom does not result in the production of any particles, it is recommended that the floor coating be either monolithic epoxy or polyurethane. Rather than using iron alloys, which are prone to rusting and flaking, sandwich partition panels and ceiling panels made of powder-coated mild steel or buffed stainless steel are utilized. By providing a coved surface, corners such as wall to wall, wall to floor, and wall to ceiling can be avoided. Additionally, all joints must be sealed with epoxy sealant in order to prevent any particles from being deposited or generated at the joints as a result of vibration and friction. There are several cleanrooms that feature a "tunnel" architecture, which means that there are areas that are referred to as "service chases." These areas function as air plenums, transporting air from the bottom of the room to the top of the cleanroom. This allows the air to be recirculated and filtered at their highest point.

Filters that use either HEPA or ULPA and operate according to the principles of laminar or turbulent airflow are utilized in cleanrooms in order to keep the air free of particulates. Laminar airflow systems, also known as unidirectional airflow systems, are designed to ensure that filtered air is directed downward or horizontally in a continuous stream towards filters that are situated on walls close to the cleanroom floor or through raised perforated floor panels in order to be recirculated. In order to ensure that the air processing in a cleanroom is consistent, laminar airflow systems are often installed across eighty percent of the ceiling. In order to prevent an excessive amount of particles from entering the air, laminar airflow filters and hoods are constructed using materials such as stainless steel or other materials that do not shed. Turbulent airflow, also known as non-unidirectional airflow, is a method of maintaining air in a cleanroom in a state of continual motion, while not all of the air is moving in the same direction. This method makes use of laminar airflow hoods and nonspecific velocity filters. In order to remove particles from the cleanroom environment, the rough air is designed to capture any particles that may be present in the air and force them towards the floor, where they are then captured by filters. The Food and Drug Administration (FDA) of the United States and the European Union (EU) have established severe criteria and limits to guarantee that pharmaceutical products are free from microbial contamination. As an additional option, sticky mats and plenums can be utilized in the space between the fan filter units and the air handlers.

In addition to the usage of air filters, ultraviolet light is another method that can be utilized in cleanrooms to disinfect the air. For the purpose of irradiating air and eliminating potentially infectious particles,...