What to do with some Silicon Wafers - Page 1
Forum section: electronics / general

author: calexanian
author_rank: Super Contributor
timestamp: July 25, 2019, 07:03:19 pm
content: While doing some gear trading I came to be the owner of about 20 pieces of 200 mm by 1.5 mm Boron doped P type wafers still in their sealed package. As far as I can tell nothing has been done to them since slicing.Any thoughts other than art project type things on what to do with? Can they be used as a base for some kind of demonstration such as a diode or photocell or some such thing? Seems an awful waste to just let them sit around till accidentally broken and just toss them in the bin. I do some hobby plating and vacuum coating so i'm not afraid of basic chemicals. Just don't want to get into the totally nasty sniff it and your dead type stuff, but acids, bases and vacuum coating metals is well within my ability.

author: calexanian
author_rank: Super Contributor
timestamp: July 25, 2019, 07:04:43 pm
content: Oh, I also got some phosphors for making scope tubes and such too. I plan on making a basic CRT when it cools down enough for me to work in the garage again.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 25, 2019, 07:30:19 pm
content: Hm, should be able to make diodes by, say, etching the surface (remove SiO2), aluminizing, annealing (diffusion), then hopefully some kind of passivation (hot steam? parylene? polyimide?). Which could be done with masks, allowing a planar diode process without worrying about the junction going to the edge.Jeri Ellsworth fabbed MOSFETs with a similar process, and silver epoxy for contacts. Sam Zeloof is doing planar ICs, with rather more sophisticated hardware:http://sam.zeloof.xyz/Preferably you'll want very pure water and etchant, especially avoiding sodium (mobile ions in oxide) and transition metals (introduce energy bands in the middle of the bandgap, ruining various properties like carrier lifetime, leakage and polarity).Tim

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 25, 2019, 08:28:42 pm
content: Quote from: T3sl4co1l on July 25, 2019, 07:30:19 pmThat requires concentrated hydrofluoric acid, doesn't it? OP better have some calcium gluconate on hand just in case he gets any - and I mean *any* on his skin.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 25, 2019, 09:54:07 pm
content: Concentrated -- no, glass etchant is commercially available and uses a low percentage. Much less deadly, only ordinary precautions needed.Not that the commercial product would be pure enough to make reasonable MOSFETs, but is probably fine for diodes and BJTs.Also, sorry, not aluminum, it would have to be phosphorous doped of course.Probably a phos compound can be sputtered or evaporated, otherwise, deposition from solution is traditional.Tim

author: calexanian
author_rank: Super Contributor
timestamp: July 25, 2019, 10:55:40 pm
content: I think maybe Sam or somebody mentioned Armor Etch is an alternative, but I cannot remember the details. Darn my leaky brain. I think they said its avaliable at craft stores for etching drinking glasses or something like that.

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 25, 2019, 10:56:23 pm
content: Quote from: T3sl4co1l on July 25, 2019, 09:54:07 pmIANADr, but my understanding is that HF is unique in its ability to wreak havoc on biological tissues despite its relatively weak acidity, so being diluted doesn't help much. It really is unbelievably nasty stuff.That said, the OP has p-doped silicon so while it would be possible to make a Schottky diode from it, it still wouldn't perform nearly as well as its n-doped counterpart. I say turn them into coasters.

author: edavid
author_rank: Super Contributor
timestamp: July 26, 2019, 01:11:23 am
content: You might actually be able to sell them:http://www.novawafers.com/purchasing.html

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 26, 2019, 01:21:36 am
content: There's a young guy on youtube that really went all out and spent a lot of money and can do some serious transistor making. IDK if he's making ICs, but he could I think.There's a lot of chemicals needed tho even for basic stuff, even if you use your kitchen oven