Despite everyone’s best efforts, from time to time, mistakes are being made. Some of them are basically primarily annoying, some of them result in serious hardware damage and prolonged periods of downtime, and some of them can be life threatening. All mistakes are also a great opportunity for learning. We all learn from our own mistakes, the best of us are capable of learning from mistakes of others as well. Below we include examples of some of the unfortunate and common mistakes users manage to make while working in the ebeam zone of the cleanroom. We document them here with a hope that this “mini-gallery of nightmares” will serve as a learning device for all the users and will help us keep the number of incidents at the “lower than low” level.
NIGHTMARE No. 1
TMAH waste bottle full of 25% concentrated TMAH (pH=14, toxic to the nervous system, absorbs through the skin) was left open and forgotten on the wet bench.
Potential damage – DEATH !!!
Remedy – stay focused, follow procedure, close all bottles when done, and check the wet bench one more time before you leave the zone.
NIGHTMARE No. 2
The locking screw on a holder gets overturned (or turned in a wrong direction) when unloading from the alignment microscope. If not fixed by the user, the attempt to load holder with a screw in a wrong position into the ebeam tool results in a loading failure and alarm.
Potential damage – stuck loading arm, mechanical damage to tool, several weeks of downtime. About 100 000 CHF,- in damaged parts and several months of downtime have been a result of this user error in the past 10 years at CMi.
Remedy – stay focused, follow procedure, check that screw position is vertical before loading
NIGHTMARE No. 3
The small screw used normally to clamp small chips gets left sticking out about 1-2mm above the holder base plate. The clearance for loading into ebeam tool is very low, and this screw will cause loading arm to get stuck. Alarm results.
Potential damage – stuck loading arm, mechanical damage to tool, several weeks of downtime. About 60 000 CHF,- in damaged parts and several months of downtime have been a result of this user error in the past 10 years at CMi.
Remedy – stay focused, remove screws when finished, check ALL screws before loading
NIGHTMARE No. 4
The small resist bottles are left forgotten on the top of the coater (above the hotplates).
Potential damage – most resist are diluteds in solvents. Should the bottle content get spilled on top of hotplates, fire may result. In case of HSQ, CSAR62, Electra92 or eSpacer, every hour outside of the fridge (where they belong for storage) accelerates their degrade. Each bottle costs one to several thousands of CHF,- and it may take up to 16 weeks to get a replacement from the suppliers.
Remedy – DO NOT put resist bottles where they do not belong and do not forget them there !
NIGHTMARE No. 5
Hot plates are left open or not covered properly.
Potential damage – safety hazard and waste of energy
Remedy – Cover the hotplates after use properly and take couple of seconds to check.
(Better yet – check always when you enter the ebeam zone, and fix it if you see it placed wrong.)
NIGHTMARE No. 6
The main solvent waste canister is left open and the MiBK and Acetone are freely evaporating into the room.
Potential damage – safety hazard, solvent vapors are carcinogenic when inhaled over an extended period of time
Remedy – Close the canister when your are done with your waste.
(Better yet – check always when you enter the ebeam zone, and close it if you see it open.)
NIGHTMARE No. 7
The lift-off glass jar is not labeled, and/or is left around for eternity.
Potential damage – safety hazard, solvent vapors are carcinogenic when inhaled over an extended period of time – and the longer the jar is there, the higher the chance it will get dinged and the cover will slip and stuff evaporates… (besides, other users can only assume, it is acetone inside and not smtg else). Other than that, it is mostly annoyance, and the damage will be limited to the sample (and your professor’s wallet).
Remedy – Label your stuff, follow procedures, and pick your wafer promptly after lift-off finishes
NIGHTMARE No. 8
Using glassware for other purposes than it is intended. Bringing in chemicals that do not belong to the ebeam zone, causing undesired chemical reactions.
Potential damage – in the best case, the damage is limited to some unremovable residue and the glassware must be trashed. For a worse case – check-out Nightmare 9 !!!
Remedy – Do not bring any chemicals to the ebeam zone that do not belong there. Use proper glassware for any particular process. Watch out for «friends» smuggling chemicals into the ebeam zone. Do not train your master students on any tools in the ebeam zone….
NIGHTMARE No. 9
Bringing-in un-aproved chemicals, in this case an ACID, and expose equipment (and potentially people) in the zone to it and its fumes.
Potential damage – in the best case, the damage is limited to corrosion of exposed surfaces of removable parts and equipment – in our case – the sonicator had to be trashed as its back-wall and cover were completely corroded by acid fumes). Worse case scenarios include corrosion of infrastructure and its failure at later point, explosions, fire, chlorine gas release (in case of HCl being disposed of in the wrong place), and serious bodily injury by users not expecting to encounter acids in the ebeam zone.
Remedy – Do not bring ACIDs to the ebeam and use them ONLY where they belong !!!!
NIGHTMARE No. 10
Not finding the door, trying to walk through walls, leaning against the window, or plain and simple curiosity to check, if the «eye-rinsing» safety device works.
Potential damage – the «eye rinsing» device gets triggered and emptied, makes a mess on the floor, and will need to be replaced. Several hundred CHF in parts and labor.
Remedy – Walk through the door. And remember Schrodinger’s cat. You can either have a hope that the eye solution will probably be there, when you need it, or you can have a certainty, that it will not. And choose hope.
NIGHTMARE No. 11
Un-labeled samples, wafers and chips are left behind on the table in the processing room for extended periods of time.
Potential damage – mostly just an annoyance for everyone, the most likely damage will be to you, your research timeline and your advisor’s wallet, when the samples get eventually trashed for you.
Remedy – When you leave the zone, take all your stuff with you and store it properly in your designated storage box.
NIGHTMARE No. 12
Delivered resist bottles are not being picked up (sometime for months) by users who ordered them, until they are removed from the delivery tray to make space for new deliveries, or by some other user, and they disappear in the sea of other users bottles, never to be found by their original owners…
Potential damage – mostly just an annoyance for everyone, the damage is to your advisor’s wallet, who kindly and naively paid to enable your work to be done. Several hundred CHF…
Remedy – Pick up your ordered resist promptly and store it in the right place.
NIGHTMARE No. 13
Making a mess and leaving small pieces of leftover tape everywhere on the preparation desk. Especially the peeled-off plastic foil. This foil likes to cling to the holders and already once a piece ended up loaded into the tool and onto the stage.
Potential damage – If the foil gets to a wrong place, it can prevent the holder getting locked into a proper position on the stage, or it can get into the stage mechanism itself and interfere with stage movement, or it could even get blown into the column itself…
Remedy – Keep your workplace clean and clean up your mess immediately after use!
NIGHTMARE No. 14
Using a transparent plastic tape to hold the lid of the lift-off glass jar, exposing the tape to acetone and heating it in the sonicator bath.
Potential damage – The tape partially dissolves when exposed to acetone, and partially melts when heated up sufficiently inside of the sonicator bath. This creates a nasty mess with gazillions of particles that may destroy whatever micro-nano-technological devices one is trying to fabricate.
Remedy – Do not use the clear plastic tape anywhere near the acetone and thermal bath!
NIGHTMARE No. 15
Hairy event. An eyelash, an eyebrow, a hair falls on a holder during loading or alignment microscope manipulation, and travels with the holder into the ebeam chamber.
Potential damage – Hair gets under the holder pin and prevents the holder from properly locking, causing massive drift during writing, as well as pushes the surface height out of spec. Or, as happened in January 2021, lands on the o-ring of the main gate valve between the loadlock and main chamber, ruining the main chamber vacuum, triggering the EHT shutdown and one week of downtime needed to remove and inspect the valve.
Remedy – Do not pull your hair out in despair or frustration, do not touch it at all, keep the workplace clean, and carefully inspect the holder each time before you load it into the tool.
