Brian Fletcher, a semiconductor equipment specialist talks us through the evolution of cleanrooms
A cleanroom is a controlled environment where pollutants like dust, airborne microbes, and aerosol particles are filtered out in order to provide the cleanest area possible. Most cleanrooms are used for manufacturing products such as electronics, pharmaceutical products, and medical equipment. A cleanroom can be classified into different levels of contamination depending on the number of particles allowed in the space, per cubic meter. Cleanrooms also control variables like temperature, airflow, and humidity.
So, what makes a cleanroom clean? You may know what a cleanroom is, but do you know when they started and why? Although no exact date can be pinpointed to when the first cleanroom existed, it is known that the high-efficiency particulate air (HEPA) filters were being used throughout cleanrooms by the mid-19th century when sterilized environments were being used in hospital operating rooms.
The very first cleanroom’s purpose was to solely blow the clean air over the machine or instrument you were working on. Most historians agree that the HEPA filter was developed during World War II where they were used to produce and manufacture weapons in a sterile and safe environment and became available for industrial use in the early 1950s. Laminar flow technology was formulated in 1961 by a team of Sandia Laboratories researchers led by Willis Whitfield.
We asked our expert Brian Fletcher to tell us more about the changes he has witnessed over the years:
Brian Fletcher, a true cleanroom expert and IES Field Service Engineer who has worked in the semiconductor industry for over 50 years and has seen the changes first-hand. Brian is currently a semiconductor equipment specialist based in Sweden. His experience in the industry spans over five decades, in a variety of roles from Junior Technician to Cleanroom Fab Maintenance Manager, and his engineering skills have taken him around the world.
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If there is a person to quiz on the various nuances of microelectronics around the world, it is Brian. He is very well-travelled and has experience in cleanrooms of all shapes and sizes. He has seen microelectronics develop from the frontline, and today’s industry is almost unrecognisable from the one which he remembers in the 1970s.
“It’s a completely different world,” Brian confirms. “There used to be four chips on a half-inch silicon wafer. You could have made them in your garage. Today on a 200mm wafer there can be 20,000 chips, and one speck of dust will destroy that chip.”
Let’s take a look at some of the other changes that Brian feels have allowed the high-technology industry of semiconductors to continue to flourish and provide devices to keep up with our demanding technology needs.
Change in classifications
Cleanrooms are classified according to the cleanliness level of the air inside the controlled environment. This is measured by the number of particles per volume of air and there are very specific (and rightly so) requirements for how many particles are permitted in that space. The ISO classification standards range from ISO 1 to ISO 9. ISO 1 is the “cleanest” class and ISO 9, the “dirtiest” class.
“In 1971, the air only had to be clean when blowing over the machine you worked on and was Class 100,000, which is 100,000 particles per cubic metre of air. Today, the general standard in a manufacturing cleanroom is Class 1- 1 particle per cubic metre of air! Cleanrooms are different to what they used to be. To get clean air you must use HEPA filters which uses an innovative membrane technology – a vast upgrade from the car filter like options once widely used,” said Brian.
A change in airflow
There has been a massive change in airflow over the years, when cleanrooms first originated it is said to be air was flowing 10 feet a minute but today air flows around 50,000 feet a minute. This equates to air being changed 1,000 times a minute. There are multiple fans and blowers above the filters, the airflow path goes through the ceiling and out through the floor.
To prevent external air from contaminating the sterile environment, the room is kept pressurised. For example, when the door is opened, there is only air movement from inside to outside the room and not in the opposite direction. By that, only clean air leaves the room, without letting the “dirty” air enter. In the past, there was no need for temperature, humidity, and static electricity control, but in today’s cleanrooms, these factors play a vital part in the regulation of airflow.
Brian educated us on the temperature within a cleanroom and the contributing variables “The temperature needs to be 18 degrees +/- 2 degrees, this is, however, dependant on the type of cleanroom you’re working in, the types of devices you are manufacturing and the tools you’re working on. The dew point needs to be low as the environment within a cleanroom needs to be extremely dry.” In today’s modern cleanrooms, drinking machines have had to be installed to ensure the employees stay hydrated. Dryness is key - if the humidity is high, static electricity is dramatically increased which can destroy semiconductor devices.
IES offers a complete service for semiconductor tools. With our trusted turnkey solutions and provision of legacy parts, we meet the semiconductor industry’s requirements for equipment that offers high performance and predictability.
Designs changing with the times
The design layout and structure of cleanrooms has also progressively changed throughout the years. The rooms of today are known as bays and modular rooms. A modular cleanroom is a freestanding structure that can convert an existing facility into a classified clean environment. It is a fully scalable solution, as it can easily be extended or relocated to adapt to a change in demand. The modular nature of the design means a modular cleanroom can be made to any size - from just a few square meters to hundreds of square meters. It can also be installed in and around existing machinery. They can withstand the high volume of airflow required to achieve ISO-classified, ultra-clean environments.
However, Brian tells us that the industry's way forward is to look at using “ballrooms” as their standard cleanroom, it is structured around a wide-open floor, with suspended plenums above, and a separate floor below (a “subfab”) to house all the support equipment. All the pumps, chillers, filters, gas cabinets, and so on are in the subfab where they don’t contaminate the cleanroom (or vibrate it), and only sealed production equipment is located in the cleanroom itself. This solution obviously minimises the further risk of any dust, and “dirty” air particles coming into the room.
Another benefit of a ballroom design is more open space for the large tools needed in manufacturing environments that are much larger than they used to be. Having fewer walls to manoeuvre around and planning the layout when adding new equipment makes life much easier.
Cleanroom moves are not always straightforward. Read how IES provided a range of engineering services to relocate tools from one building to another at Bristol University.
People in the cleanroom
Unfortunately, the dirtiest thing in a cleanroom is the people. When it comes to the cleanroom, new technology has meant that ever more precautions must be taken, states Brian: “The dirtiest thing in a cleanroom is the people that are in it. So, we must cover almost every part of our body to make sure we don’t shed skin, any particles from our hair, or anything. There are Fabs in the world where you can’t have any parts of the body showing, so faces and eyes must be completely covered – we don’t have that in Europe thankfully.”
Just from the normal shedding of human skin and movement, we can emit around 100 million particles into the air which catastrophically contaminates the air. And remember when we said the air is so dry due to ideal manufacturing temperatures? If the engineers need to take advantage of the water drinking facilities, then the face masks can only be down for a split second!
In the past, engineers and technicians have just doubled up on masks and gloves, as well as their normal bunny suit to help reduce risk, but with devices getting smaller and more sensitive, automation and robots are today's answer.
Adopting industry 4.0 ensures a cleanroom is cleaner than ever by severely limiting the number of people working within the cleanroom environment. Day-to-day operations, diagnostics and electronic repairs can be controlled from any computer, anywhere.
Regardless of when cleanrooms were established, contamination was the problem, and manufacturers needed a solution to ensure their sensitive devices were protected at all stages of the process. Continually growing and constantly changing for the betterment of projects, research, and performance, cleanrooms, as we know them today, are recognised for their low levels of pollutants and contaminants and the future will no doubt see further advancements in the classifications, filtering technology, layouts and automation.
IES is an experienced partner to many companies within high-technology industries where cleanrooms are common, including semiconductor and pharmaceutical. If you’d like to discuss your cleanroom equipment moves, semiconductor equipment installation and requirements, get in touch today via our contact form.
