Danger, Danger! Will Robinson!
Early one morning in October 1984, I walked into a dimly lit room, deep within the chemistry building at UC Berkeley. Someone had only shown me this procedure earlier in the week. But I walked up to a strange apparatus, opened it and grabbed a container of a mysterious powder, carefully measuring the correct amount onto some filter paper. This was my responsibility for the vert first time. I was terrified that I would get the proportions wrong and would be the laughing stock of both the chemistry and chemical engineering departments. I then carefully measured out the solvent for the reaction and added it to reaction apparatus. All was set, but my heart was racing. Taking a deep breath like all professionals dealing with dangerous substances do, I pushed the button to start the reaction, hoping I would get the desired result. By this point I had an audience
and I was getting anxious, much like the time s when I was 14 standing on the first tee, driving my golfball during the county golf tourney.
You see, more than my pride was at stake in this chemical reaction. Normally the chemistry graduate students performed this reaction; the chemical engineers usually stuck to their dumpy building (which by the way is still dumpy 32 years later) and didn’t perform this reaction.
Being a chemical engineer (or chemist for that matter) is indeed risky business. I feel that it is much safer today, with all the rules and regulations, but I really don’t know. This blog will take a mostly serious look at the adventures in danger that I and my research associates took to get our degrees. Many
close friends have heard some of these stories but some are coming out of the vault.
How Dangerous is it Really?
These stories are in roughly chronological order and have no particular order in severity but as you can guess they all have a moral
. Before I begin, let’s go back to the mysterious powder and water in the dimly lit room. This story ends without a disaster in either the results of the reaction or my reputation. The complex reaction was my first brew of Pete’s Coffee at the Berkeley College of Chemistry.
Caution, the rest of this story can get pretty technical…
Electrochemistry and Lasers
Besides all the cool experimental demonstrations you might see your high school teacher or college professor perform to oohs and aahs, my first experience with real industrial chemistry was creating an electroless copper plating bath. Imagine a glass caldron filled with a cool blue liquid, laced with strong acid and spinning at a very high rate. Any mistake in proportions or rotor speed meant quite a clean up. We used this bath to test plating of copper and having performed the procedure over 20 times I can say that it was messy. I was constantly cleaning up and being aware of the pH and the sulfuric acid.
As an undergraduate, I worked under a graduate student (who is now a distinguished professor at Harvey Mudd) and we were researching how to reduce the sulfur emissions of coal burning. In a process called scrubbing, the idea was to use calcium oxide to clean the sulfur and form calcium sulfide which can be disposed of or reused in a variety of ways. We built a small electrostatic containment vessel (think of a very small particle of calcium sulfide which has an electric charge being suspended by electric fields and held in place by a complex shaped electrode running alternating currents). Our ability to get a single particle suspended with the right size (mass) was a bit of a black art. We were able to figure out the mass of the particle by shin
ning a light on the particle (which emits an electric charge) and measure the change in the electrostatic field needed to suspend the particle. Through a process of exposing the suspended particle to infra-red (IR) thermal radiation (a CO2 laser) we were able to perform the chemical reaction that we were studying and measure the kinetics (the reaction speed) of the oxidation. This whole set up was on a 3 by 6 foot light table with our containment vessel, the high powered IR laser and a multitude of mirrors that we needed to get the laser aligned just right with a particle much smaller than the width of a piece of hair. Those alignment sessions were pretty difficult (kind of hard to see a head laser, so we used a common red laser to get close enough alignment).
As with many experiments, getting the conditions right has a higher priority than clean looks, or in many cases excessive safety interlocks. After all, it was just a heat laser. Being the newbie I was, having to reach onto the light table to adjust something, I can say that the puff of smoke from my arm, was my first
alert that something was wrong. Not even a moderate injury, didn’t need a band-aid , but I can still see that mark today on my arm. Note to future self: pay attention to lasers—lots of potential in the future.
Electric Shocks and Noxious Gases
My experience with the lasers at MIT gave me the right precautionary tendencies as I entered graduate school at Berkeley. Our professor was Dennis Hess, teaching and researching today at Georgia Tech. Back in the 80s as today, his research group, which we called Hess Labs worked very closely with plasmas, or electrified gases that discharge light, much like a neon lamp. Creating these plasma from exotic gases and performing reactions to either etch or deposit materials was the focus for many of my fellow graduate students. Creating the plasma required a vacuum (think large expensive vacuum vessels, complex heated electrodes, exotic and toxic gases and high electrical power, both DC, AC and RF frequencies. This was indeed like a scene out of a Frankenstein movie. It took us quite a time to design, get constructed and test the apparatus until we started getting results. Often we added very high-tech sensing equipment such as optical measurements and mass spectroscopy. Each of these experiments could cost close to $50-100k. Once your experiment started producing results, you usually did not stop taking data. In fact the main part of my thesis, the final paper, was collected over 4 days with little sleep.
Building these reactors was an exercise in trading off results for cost. We students never had enough money to do things the “right” way, so we were constantly improvising. One of my experiments needed 1000 V DC (2000 V DC can be lethal) and instead of paying a lot of money for an expensive power supply, I daisy-chained a few high voltage batteries to give me the 1000 V and saved the money for the electronics and circuits to make that voltage controllable by the computer we were using. Throughout that time, I managed to get a few minor shocks of the 1000 V as well as AC and RF
. Interestingly each of the different current types felt different to the touch, but over time I cleaned up my act and created a safer environment for the experiments through better testing and insulation.
The other part of the reactor besides all the electronics and vacuum apparatus (we used multiple vacuum pumps, some scavenged around campus, others purchased, still other donated by companies) was the gas systems. A typical research experiment involved 4 to 6 different gases used at different times. Nitrogen, Oxygen, Nitrogen Triflouride, Tungsten Hexaflouride, Silane, Xenon, Helium, Hydrogen and so on. Most of these gases were flammable, toxic and some were explosive. Additionally we used a number of wet chemicals to do other items on the research docket. We used cold traps and liquid nitrogen to trap out some of the waste products to help increase the amount of vacuum and reduce the impurities in our experiments.
I intentionally lived close to campus so I could make the daily late night run to fill up the part of my apparatus with liquid nitrogen so that I could start right in during the morning with experimentation. It took me a while to figure out that I could use an old fashioned light timer to automatically fill up the dewar with liquid nitrogen. At the end of the week I was left with a small amount of highly reactive leftover sludge at frozen temperatures and no easy way to get rid of them.
Usually when the reaction is going on, the exhaust of the reactor goes up the hood and out into the air. So my big realization that the best way to get rid of this was to heat it up and vent it out the hood/top of the building. Great news, instead of dealing with toxic fumes in my lab, we sent it up into the Berkeley air. It was a small amount, so we did not worry, but I am sure modern systems have scrubbers in place.
I did hear that in the previous generations,
people got rid of leftover reactants or byproducts with slightly similar but with more exciting results. I was told a story that a graduate student needed to get rid of something similar to what I had, but it was enclosed in a glass ampule. This graduate student asked a more senior graduate student about what to do with the byproducts. The answer was to meet him in the lab at midnight that night (never a good sign). They met at the designated location at midnight and the younger graduate student looked at his senior colleague and asked what they were going to do. The older student took the vial and unceremoniously chucked it off the roof. The younger student looked over the edge of the roof and to his surprise the vial with the excess reactant chemical exploded on contact. No damage, just some glass to clean up. Well that was a creative solution to the problem. I think nowadays there are better ways to solve this problem, but it certainly had its shock value in the day.
Reactor Implosion and Two Explosions
Unfortunately this next section is quite serious as you can tell by the title. The bane of our existence in our lab group was the fact that we could not etch or deposit materials with high uniformity across the substrate wafers we were using (which could be silicon, glass, sapphire and other materials). One of our hypotheses was that the gas flow lines in our reactors where not uniform enough and we expended a lot of effort to try to make everything symmetrical. One of the Masters student’s goal was to look at deposition with a quartz reactor that was designed to be square versus a round time. The gas flow was supposed to be more uniform. He designed and had built a square quartz reaction. In retrospect we know that nature abhors off shapes.
Have you ever seen a square soap bubble? Well this student achieved many of the goals of his research work. I honestly don’t know if the thin films being deposited were more uniform than the circular reactors. As I was an early riser, I was usually the first student to enter the lab in the morning. One morning, however, something was not right. As I entered the building, I noted that our end of the hallway had some smoke (not enough to set off the smoke alarms) and when I opened the door of the lab, it was completely filled with white smoke and a burning oil smell. I immediately knew something was not right. As a graduate student whose next few years and future career depended on his experimental apparatus, I immediately went into my lab alcove to see if my stuff was damaged, and luckily it was not. The student with the square quartz reactor was in trouble as his square vacuum glass reactor had imploded, sending all sorts of glass shards into the vacuum pumping system and
as you can imagine, the pump was pulverized with glass and was burning oil.
Reactor implosions can be dangerous; luckily the event happened at night. We wore safety gear back then but looking back on it, we could have been more careful. This next story is about a wet chemical reaction in another lab and in that situation there was a small explosion and one of the chemicals was hydrofluoric acid. Hydrogen and fluorine together as a molecule is highly reactive and a wonder chemical when performing physical chemistry. Hydrofluoric acid however can dissolve calcium. If you get the acid on your skin, you don’t get the normal acid burn, but the hydruofluo
ric acid will seep into your body and dissolve your bones. A fellow student had this happen to him from this small explosion and luckily the standard procedure was to inject calcium into his skin so that the acid was dissolved, and not his bones. This story had a good outcome.
The third reactor story was one that started with a small bang, but escalated quickly to a few of us having to make an assessment as to whether we needed to call the fire department. One of the lab students was doing a project in etching and was using nitrogen triflouride, a very reactive gas that can oxide (burn) most anything. He was using a very small amount of the gas and at some point for some reason we heard a pop and the gas started burning the gas line with a small flame. When I say burning the gas line, the gas was burning the stainless steal line – which was a sight not even chemical engineers see very often. It was like a slow fuse, burning the stainless steel line back to the small cylinder. After a quick calculation or two and measuring the speed of the “fuse”, we figure this explosion would burn it self out, which it did about 2 minutes later. I remarked later that it was good that we had about 8-12 people in our lab group with at least half of the folks around at most times. Strength in numbers was good thing for this incident to help determine the right course of action.
The Big Leagues of Integrated Circuit Manufacturing
After school, when I started at HP’s fabrication facility, I learned that dangerous chemicals and gases where all over the place in our lab. I also saw industrial-level safety procedures and interlocks. I never saw anyone with any injury during my HP career. But we always knew that by the time you would smell some of the very toxic gases, you would already be on your way to death. Thankfully our global society and technology companies have for the most part solved the danger of modern science and engineering during fabrication. We are left however with other problems such as exploding batteries…