In clean rooms where people work on things like nanoscale semiconductors, the occupants typically wear suits, caps, and masks to prevent the shedding of hairs and fibers that could ruin their work. But I often see that this gear leaves their eyes and the surrounding portion of their face exposed. It’s a small portion of a person’s total surface area, and so the total risk of contamination has been greatly reduced by covering most of their body - but at the same time, a person’s face is often positioned close to whatever it is that they’re working on. Also, the surgical-style mask worn over their mouth and nose would appear to have limited ability to contain particles generated while sneezing, coughing, or even talking.
Some health care workers during the pandemic were seen to be wearing a powered air purifying respirator (PAPR). This forms a pretty good seal around the worker’s face while a battery-powered blower pushes air through a HEPA filter to provide them with uncontaminated breathing air. Their exhaled air is filtered too, although presumably not quite as well because the seal around their face isn’t perfect. It seems like the same tech could be used in reverse to assure that clean room workers don’t shed any particulate at all: instead of filtering the incoming air, the system would filter exhaled air before blowing it back into the room (presumably using something like ULPA instead of HEPA).
With clean room workers having exposed upper faces and not-perfectly-sealed/filtered respiratory tracts as I described above, how often does clean room work get contaminated? Do people really never cough, sneeze, or shed skin cells or eyebrow hairs while they’re in clean rooms?
Although many of them are wearing safety glasses, these don’t appear to provide a full seal over all of their skin, and I wonder about the ability of their masks to fully contain a sneeze or a cough.
I worked as a equipment maintenance technician for Digital Equipment Corporation [RIP…] at their fab in Hudson, MA back in the early 1980’s. Bunny suits, hoods and slippers but no face masks at that time. They wanted to promote me to technician supervisor for a new class 10 clean room they were setting up - ‘just show up next Monday with a shorter haircut and clean-shaven, so we can start your training’. I quit.
That was a million years ago in digital time. I imagine by now they’re trying to remove pesky humans from the process altogether any way they can.
I’ve worked in and around clean rooms for a big portion of my career, always in research, not production. But I’ve kept track on the state of the art.
The largest source of particulates in a clean room is people.
Bunny suits, masks, gloves, etc. help contain the particulates, but don’t entirely stop them.
If you look closely, you’ll see that the floors of the clean room have a mesh of holes in them every few fest. That’s the air return. Clean rooms are three stories. On the top is a big clean plenum leading into HEPA filters feeding the working area. In the middle is the working area, where the air flows straight down, entraining particles and directing them to the floor. The bottom floor is another plenum, where the dirty air is taken out.
Finally, in a modern production area, all the wafers are contained in their own environment through the process. The exposure to any human handling and the clean room is minimal to non-existent. The bunny suits are to minimize the potential for particulates to find their ways into the equipment.
And yes, bunny suits are a real hassle to put on (you need to follow a precise order), they are hot and confining to wear for extended periods, and workers have to obey strict cleanliness guidelines (no makeup, beards are frowned on, and smokers are discouraged).
Final note: Most people don’t realize how loud clean rooms are. There’s a sonic penalty (and visual exhaustion due to the artificial yellow or red light) that comes with the work.
With a single silicone wafer containing hundreds to thousands of IC chips, I’d expect the companies have already compared the cost of contamination damaging one or a few of them vs. the cost in equipment and lost productivity of having tighter clean room attire for workers.
And as vbob said, companies are probably putting their efforts into mechanizing this manufacturing and removing people as much as possible.
It should also be remembered, of course, that there are multiple levels of clean rooms. For the least strict, you basically just need to wipe your feet and wear a mask and gloves. For the most, you’re in something resembling a hazmat suit.