8/16/2007

Excimer's Adventures in the Clean Room

I've decided to chronicle my adventures in the clean room, since to many, a clean room is a thing of mystery. The layperson's only real experience with a clean room is those old Intel commercials with the bunny people. Yes, people who work in microprocessor clean rooms have to wear those things, although not the flashy technicolor ones. So, without further ado, I give you a tour of a clean room.

You might be wondering, first of all, what makes a clean room clean. It's simple- the amount of particles in the air. This particular clean room I'm showing you is a class 1000 clean room. "Class 1000" refers to the number of particles in the air per cubic foot: a class 1000 clean room has, at most, 1000 particles 5µm in size per cubic foot. As comparison, the atmosphere contains millions of particles per square foot, so a clean room chops the number of particles in the atmosphere by several orders of magnitude.

While a class 1000 or 100 clean room is fine for most patterning and lithography in an academic setting, a class 100 clean room is not sufficiently particle-free for microelectronics processing. Microprocessors are typically fabricated in clean rooms with particles/ft3 that you can count on one hand. One speck of dust on an exposed microprocessor will ruin it, so extremely stringent atmospheric and climate controls are vital. However, we don't make processors here, so the regulations are less stringent. (This clean room is mainly used for photolithography.)

So where to begin our tour? Here's the door. It keeps people not privy to the wonders of the clean room out. It is made of some type of wood, probably oak.

Once you open the door, your shoes are brushed of large particles to keep the floor of the locker room clean. In the locker room, users change into their bunny suits. The bunny suits include booties, a gown, and a cap.

Two things most people notice first when entering the clean room are 1. it's really yellow and 2. the fans are loud. The yellow color is from UV filters on the lights. Since photoresist is everywhere in this clean room, and photoresist reacts with UV light, you need UV filters. Good UV filters also block out violet light, thus the light appears yellow. The HVAC system contains ridiculous HEPA and ULPA filters to remove as many particulates as it can. The air in a clean room is changed nearly 10 times an hour- that's a lot of blowing, and so the air system is rather loud.

This is the HF hood. Hydrofluoric acid is just unbelievably nasty stuff, however, it efficiently and selectively digests silicon-based materials, so it flows like wine in this clean room. So HF work is done in its own hood. Provided are thick aprons, thicker gloves, and really thick splash guards, all designed to keep HF away from you at all times. (Good thing.)

This is a mask aligner. It exposes substrates to high-intensity UV light, to pattern substrates. I'll explain how to pattern substrates on a later post.

And this, uh... is my TOTALLY MYSPACE PIC IN THE CLEAN ROOM WOOO! Note the sexy cap, sexy gown, sexy glasses, sexy headphones (a must if you're gonna be in there for extended periods of time), and decidedly unsexy fake smile. I got funny looks from people for that pic. I probably deserved them.

...so that's my tour of the clean room. Pretty exciting. Next time I'll do a short post on photolithography.

16 comments:

Chemgeek said...

I have also been in a clean room like this. I only went in there about 20 times, but I would always pretend (i.e. screw around) like I was in a James Bond movie or in a cool sci-fi movie (considering the suit, hats, goggles and shoes). The people that worked in there on a daily basis were really annoyed by that.

What can I say, I was just out of college and a full fledged moron.

Anonymous said...

Whenever I walk by that room on the way to lab (greetings from 341) I've always wondered why it's so darn yellow in there.....and now I know.

Mitch said...

I see hair, and no face mask. For shame.

Mitch

milkshake said...

Very nice. I think this calls for some Gordon Freeman jokes.

Is there a significant UV component in the common fluorescent tube light?

Colst said...

"Is there a significant UV component in the common fluorescent tube light?"

Definitely. Fluorescent lights actually work by making UV light (Hg emission) then using a fluorescent coating to shift it to longer wavelengths. A significant amount of Hg emission makes it through though. (Means you have to be extra careful about room light when you're an atomic spectroscopist looking for mercury).

John said...

"Hydrofluoric acid is just unbelievably nasty stuff..."

But the pKa of it is much less than HCl, HBr, HI... It's only its unusual affinity for silicon based materials and its systemic poisoning of humans that give it the bad rap.

Rob W. said...

That looks like the same mask aligner we have here. Old school. Were you making new photoresists, or do you just use photolithography to make something carbon-based that will get funding?

Ashutosh said...

john: that and also the great affinity of the fluoride ion for Ca2+

Excimer said...

rob, I just use the mask aligner for patterning. I can only guess what other people use it for.

Uncle Al said...

Mitch is correct. Dust is shed epithelials with a soupçon of evaporated aerosols. You should be footied, gloved, helmeted, masked, and face-shielded. No cellulose paper in a clean room, for it sheds fibers. Tyvek.

Excimer said...

mitch and uncle al- different clean rooms have different standards for clothing. keeping hair covered is sufficient- the air purifications systems are good enough to take care of sideburns or facial hair. A class 10,000 clean room would only require booties. If it were a class 10 or 1 clean room, I would be shot in the face for wearing what I wear in there. All the gowns, booties, caps, etc. are made of Tyvek. Face shields are only required when using HF.

If you actually think I'd take a picture of myself breaking the rules in a facility I use every week, you are sorely mistaken.

Mitch said...

Photolithography? A real Chemist uses a scribe and some concentration to pattern their wafers. ;)

Or at least that's what I do.

Mitch

Amanda said...

Thanks, I've always wondered what it looks like inside of a clean room. While my husband works in one almost every day (and he has even been in the particular clean room that you show in the photo), I kind of doubt that my research will ever lead me into one...

Jan said...

Some weeks ago I visited a clean room on my own. I felt like a bunny and like chemgeek said it was like being in a scifi movie but it is definetly not my world. I am a dirty bench chemist loving the smell, the dirty smell of the lab. It smells like victory when something starts to stink! My lab is surely not a clean enviroment (I am not a messy by the way) but I was raised (at least the past 15 years) in a lab and love it.
Clean labs are just so biochemical...

Ashutosh said...

The ideal clean room should demand sanitation of the kind portrayed in The Andromeda Strain. Burn your hair off please. All of it.

Ψ*Ψ said...

I always found biochem labs a little boring. Too many clear liquids. Where's the fun in that?