Fusor Forums

Maybe of limited usefulness, but:

I accumulated a batch of bad Edwards/BOC AIM style CCG sensors from work (I just hated to just throw them out). Rework illusions aside, they are basically KF25 nipples -- the innards are captured inside a KF25 nipple with a couple of circlips. Maybe some folks here also have access to similar CCG's. The sensors have a couple of pins on the exterior of the tube to install them into the AIM body, so it would be necessary to file them off, or cut off the portion of tube they're on (I can turn them down with my lathe). I will use two for connecting my rotary pump to a DP so it's basically a zero-cost situation. Just sayin.

Some might wonder why I have a number of these. The CCG's came out of a couple of focused ion beam machines. We use them for doing circuit edit and failure analysis on IC's, which required metal deposition -- in our case, putting down tungsten using a tungsten hexacarbonyl (W (CO)6)) precursor. The gallium ion beam breaks down the tungsten carbonyl and the tungsten is left behind. The CCG's in these tools are turned on all the time so they also are exposed to the W(CO)6, and as a result the CCG eventually becomes contaminated with tungsten. Increased leakage current due to the tungsten being deposited on insulator surfaces causes the CCG to become less and less accurate, to the point where the system S/W throws up its hands and stops the tool. We had to replace them about every 6 months. I know how to selectively etch tungsten so wanted to try reworking these guys but never got around to trying it....

Mark

Sounds interesting and potentially useful. Cold cathode gauges have more than just the KF nipple...

However, I understand that metallic carbonyls can be extremely toxic. They're clean, right? (IIRC carbonyls are also volatile...)

Nice, a friend of mine is a Prof of Nanotech at PSU. He gave me a crash course on his Plasma FIB, I have been trying to get into FEI for years.

If I remember right you can use ammonium hydroxide to clean the built up tungsten on wehnelts. I have not tried it yet on my SEM.

It is true that many carbonyls are extremely toxic. W(CO)6 is a solid at RT and has relatively low vapor pressure so it's not the baddest. The FIB system performs a very thorough purge before venting so it's pretty safe. In use the W(CO)6 pops the chamber pressure up to about 3E-5 torr (thank goodness for differential pumping!). It sublimes, no liquid phase is present.

It may be possible to clean W-contaminated CCG's using a mixture of hydrogen peroxide and ammonium hydroxide. We use that combination to etch tungsten in the FA lab (many IC processes use a tungsten alloy as part of the metallization system). This etch is highly selective, only attacking a few metals -- tungsten, gallium, copper, tin and (slowly) tantalum nitride. The etch is not stable, particularly after it's been contaminated with meal ions so it should be disposed of soon after use. Fresh or used, NEVER store it in a sealed container! We use 30% H2O2 but 3% or 6% probably would work, just more slowly.

I hadn't thought of using some of the other CCG components, but now you mention it, the electrode assembly would make a decent feedthrough (once the insulator is cleaned up). Thanks for the comment!

Mark

Hi Jerry,

I think I know the gentleman at PSU as well. Tony, right? He worked in our lab for a short time. We also have used his services at PSU -- TEM work for the most part.

Mark

No, Erik Sanchez, he pretty much owns the physics department at PSU, literally. Almost everything there is his personal stuff. He has a couple FE SEMs, a few regular FIBs, the new PFIB, and just about everything else.

The new PFIB FEI gave it to him, it is a prototype machine that was used kind of a test bed.
5D3_4228 by Jerry Biehler, on Flickr

A PFIB! Very nice indeed. I have heard of folks using different gasses like neon and helium. If the tool can focus He+ maybe it could focus D+. Not sure how many neutrons you'd get -- IIRC PFIB beam
currents max out at 20uA or less. Doesn't sound like a lot until you consider the current density at the focus.

I haven't met Eric, at least to my knowledge.

-Mark

This machine was originally set up for Xe but if you have seen the price of that... So he us using Kr, much cheaper. And it is insane how little gas it actually uses, he cracks the valve on the little lab cylinder and the thing will run for days on what is just in the line. Its taken some work to get the thing going, but FEI has decided to help him out and has sent some techs to get things moving on it. I did etch a little Si with it when I was playing around. I cant remember the max current, I think it was pretty high, well, for a FIB.

26-28% H2O2 is readily purchased rather inexpensively from local swimming pool supply stores as "pool shock". Note they only have it in 1gallon jugs during the pool season for obvious reasons to folks who know H2O2. For those who don't know H2O2, do not let one drop of this high percentage nasty get on your skin!! I have had most every nasty acid get on my skin at one time of another and nothing begins to compare with the instant pain of a drop or two of high percentage H2O2.

Richard Hull

You can also get it from beauty supply places.

H2O2 is not as bad as you make it, we used 30% plus at a tofu plant I worked at and at most it will do is give you white spots on your skin. It takes a lot stronger than 30-35% to do you damage. Get much stronger than that and you will be unhappy, though.

30% H2O2, once it's got something to destabilize it, decomposes in an exothermic reaction. Even 50mL in a beaker is enough to experience thermal runaway -- right up to the boiling point. Boiling peroxide, mmm. Anyone using this concentration or higher should know what they''re doing, and NEVER return any unused peroxide into the original bottle. Serious badness could occur.

Mark