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ragnar

Sat Mar 13 2010, 09:18AM

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

Jeri Ellsworth wrote ...

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.

Hi Jeri! What do you feel is the ideal HF concentration for your process?

Steve Conner

Sat Mar 13 2010, 10:24AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Jeri Ellsworth wrote ...

MinorityCarrier: HF isn't too bad when handle with care.

Good grief! Are you the real Jeri Ellsworth?
If so, welcome, it's an honour to have you on the forum.

101111

Sat Mar 13 2010, 02:17PM

Registered Member #575 Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263

Well in that case, Jeri. You are hot. I am _totally_ a fan.

TheBoozer

Sat Mar 13 2010, 03:12PM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

It's definitely an honor for her to join here. I bought over a dozen of her joysticks. I modified about 5. My Amiga friend is pushing me to make an interface for my C64 to drive my DRSSTC :

It would be for nostalgic reasons...

Rich

MinorityCarrier

Sat Mar 13 2010, 09:51PM

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

Hi Jeri, I know nothing about you, but your reputation seems to have preceeded you with many others here.

My HF warnings are aimed at people here who have no idea how hazardous HF is, it's not like the other mineral acids where you spill some on you, wash it off, maybe lose a little skin, and continue on your way. I presume you know the risks, my warnings aren't aimed at you. In my history, I have seen a process engineer lose a thumb, and a maintenance tech lose part of an index finger, to HF. Both cases due to leaky gloves. How are you growing/depositing your dielectric layers?

The time and temperature dependancey of diffusion depth makes a really deep precise dopant profile difficult without an implant. That said, Boron Nitride solid dopant works well but can cause crystallographic dislocations, and is very sensitive to moisture. I presume you will avoid Phosphorus Oxychloride and try one of the pyrophosphates. Good luck with Arsenic.

The secret to silicon epitaxy is a very clean substrate and defect free growth to prevent stacking faults, let alone polysilicon growth. Dichlorosilane/Hydrogen @ 1050C, preceded by an 1100C anhydrous HCl surface clean is the standard method. Not impossible to DIY, but very difficult. The best way is the AMAT radiant heat approach. If you intend to reproduce what Kilby and Noyce did, you shouldn't need epitaxy though.

IntraWinding

Sun Mar 14 2010, 12:50AM

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

Jeri Ellsworth

Sun Mar 14 2010, 03:44AM

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

Glad to be here! One of my friends pointed me to the forum.

Blackplasma - Whink is ~3% hf and works great even for removing the glassy layers after predep and thick oxide.
I've found that the glass etchant paste attacks the vinyl mask adhesive I use and can sometimes etch undesired areas around the edges.
Remember bare silicon is hydrophobic and water beads up, so you can use this for the end point.

MinorityCarrier - I use Emulsitone spin on dopants which come in many "flavors" including arsenic, but I have a little more to learn about arsenic before trying it. :)

I've been researching recrystallized sputtered silicon films in favor of silane. We're lucky compared to engineers in the 60's, because we can go to Ebay and purchase nearly perfect silicon with virtually no stacking faults, gettered, pure, epi layers, doped, etc.

MinorityCarrier

Sun Mar 14 2010, 04:38AM

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

I forgot about spin-on-dopants. Those go way back. Still, diffusion depth and junction profile will be a challenge. Are you using spreading resistance profilometery to check your work?

I guess you can use spin-on-glass dielectric as well for bipolar devices, but oxidation still needs to be used to clean the surface to remove defects otherwise you'll likely be fighting a lot of surface leakage.

All native oxide on silicon needs to be removed prior to epi growth, doesn't matter how defect free the substrate is. That's where the hi-temp in-situ HCl clean comes in. I don't know of a low-tech way around that. Annealing sputtered silicon into a defect-free single-crystal lattice as an alternative to epitaxial growth sounds near impossible, but then I assume you're pursuing single-crystal devices. If you're trying to build amorphous semiconductors, then never mind.

You must have amassed a lot of equipment to attempt to do all this, good luck to you.

Jeri Ellsworth

Sun Mar 14 2010, 05:06AM

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

I did gather up a lot of equipment(plasma etcher, beam line, SEM, sputtering guns, bonders, spinners), but in the end it easier than I expected thanks to help from a mentor who worked at National in the 70's.

I can make functional n-channel device with a small tube furnace, vinyl cutter for masks, dopants, conductive epoxy, dilute HF and surplus wafers. I've also made devices in my Kiln, but the tube furnace is easier to manipulate the wafer pieces.

For p-channel I use welding grade nitrogen gas feed to control the oxide growth during boron diffusion.

These are not even close to being high performance devices, but it was nice the day I made a working device and proved to all the critics that it can be done.

-Jer

Carbon_Rod

Sun Mar 14 2010, 07:05AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Nice work Jeri,
the documented refinement of these fabrication techniques will inspire others to attempt ambitious projects.

btw, that HF will have nasty long-term consequences even if minimal contact occurs.

Safe journey,
Rod

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