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Conundrum

Wed Mar 10 2010, 08:49PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

ok thats impressive.

Wonder if I can make anything useful from deceased e-reader backplane glass...

if anyone wants some i have some indium metal and other interesting crystals including some SiC and FeS

on the flip side, unijunctions would seem the simplest to make as they are just a bar of doped silcon with contacts at one end and an offset centre contact...

regards, -A

IntraWinding

Wed Mar 10 2010, 09:31PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

Ah! Jeri Ellsworth!
She's the prototype Geek Babe

I'm a fan.

Ben

Fri Mar 12 2010, 03:33PM

Vigilatny
Registered Member #17 Joined: Thu Feb 02 2006, 02:47PM
Location: NL
Posts: 158

It looks like it would be useful for making high power devices(because they are big). Perhaps some one will reverse engineer the big IGBT bricks everyone likes.

klugesmith

Fri Mar 12 2010, 05:38PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

IntraWinding wrote ...
Ah! Jeri Ellsworth! She's the prototype Geek Babe

Oh yeah!
I've run into her at the De Anza College electronics flea market, whose season begins tomorrow.

ragnar

Fri Mar 12 2010, 06:16PM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Could be a lot of fun... but what is the typical concentration of 'craft store' hydrofluoric acid?

Hydrofluoric Acid Burns (emedicine.medscape.com) wrote ...

Time of exposure to onset of symptoms is related to the concentration of the hydrofluoric acid:

Solutions of 14.5% and higher concentrations immediately produce symptoms.

Solutions of 12% may take up to an hour to produce symptoms.
Solutions of less than 7% may take several hours before onset of symptoms, resulting in delayed presentation, deeper penetration of the undissociated HF acid, and a more severe burn.
Concentrated solutions cause immediate pain and produce surface burns similar to those produced by other common acids (eg, erythema, blistering, necrosis).
Pain typically is described as deep, burning, or throbbing.
Pain often is disproportionate to apparent skin involvement.

Conundrum

Fri Mar 12 2010, 06:56PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

hmm.. remember that anopol HNO3/HF etching paste...
Hint:- its 1/3 full.

Probably a bad idea to even think of using this without a fume cabinet, proper gauntlets (not even gloves), calcium gluconate on hand, etc.

anyone else here ever used HF?
regards, -A

MinorityCarrier

Fri Mar 12 2010, 08:00PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

HF burns are bad news folks.

Causes tissue necrosis, destroys joint cartilage and bone, rips calcium ions out of muscle actin, extremely painful. Often leads to amputation. Excessive F-ion adsorption through skin will cause death.

I give a safety training class on use of wet etch chemicals and tell the operators to equate HF contact with the skin to being bit by a rattlesnake. They're going to the hospital for some calcium gluconate injections and hope there is no scarring.

Mattski

Sat Mar 13 2010, 12:49AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

I used HF when I took a cleanroom fab class back in undergrad. It's pretty nasty stuff. They told us you get can some on you and you might not even feel it but it will get into your bloodstream and react with the calcium, causing serious damage or death. In our lab it had its own fume hood with solutions already made up in beakers inset into the surface - it lasts for months even with regular use. Samples were rinsed for 1 minute before leaving the hood. We had the full face chemical shield, acid rated gloves, and chemical apron for that station.

But - I'm sure (I hope) the stuff they sell in the hobby store in paste form is somewhat less dangerous.

Jeri's project is pretty awesome. This video is from quite a while ago, I wonder if there's been any progress since?

MinorityCarrier

Sat Mar 13 2010, 01:13AM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

You are correct about there being no warning, it takes about an hour after HF gets on the skin before pain and discoloration appear. By then significant tissue damage may have already occurred. 2% HF will cause skin and fascia damage. Prolonged exposure will cause worse.

There were weak-HF-containing aluminum cleaners for cleaning alloy tire rims, that explicitly warned users to wear gloves, but some bubbas lost fingers 'cause they didn't read the warnings.

20:1 HF heated to 32C only etches thermal silicon dioxide at ~160 Angstroms/minute. Not particularly fast for etching thick oxide films used in power semiconductors.

Whatever this Jeri is up to, I wish her well and safe passage, she risk serious poisoning and injury. It will be interesting to see how she accomplishes deep diffusion without the use of an ion implanter.

Jeri Ellsworth

Sat Mar 13 2010, 07:45AM

Registered Member #2737 Joined: Sat Mar 13 2010, 07:34AM
Location:
Posts: 9

MinorityCarrier: HF isn't too bad when handle with care. It's available over the counter in glass etchant and Whink Rust and Stain remover.

You can achieve deep diffusion with boro and phosphosilicate dopants. The drive in step causes the dopant to diffuse laterally, which isn't always desirable. (oh and I picked up a used beam line with a large analyzer magnet that I hope to do implanting with someday)

I've been spinning my wheels for a while trying to figure out a simple way to do epi layers on top of a collector diffusion.

Overall the process is very safe. I worry more about cutting myself on the edge of the cleaved wafers than the chemicals.

-Jer

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