Backyard foundry - Page 1
Forum section: electronics / projects

author: blueskull
author_rank: Unknown
timestamp: May 20, 2019, 06:12:25 am
content: This is probably my most audacious and stupid proposal, but allow me to explain.This proposal is about building a CMOS processing all-in-one tool at home, so not Grant Thompson's aluminum melter.Modern CMOS processes are based on a collaboration of multiple devices, there are special equipment for lithography/spinning/baking/developing, special equipment for etching, special equipment for implanting, and special equipment for deposition.In between, there are cleaning, planarization and handling equipment, and all of them housed in a clean room.My proposal is to build a single ion beam (E field lens and linear accelerator) based equipment that can scan patterns to etch, deposit and implant, using both additive and subtractive methods, driven by a configurable ion source (mass spectrometer and electric field ionization source) that spits noble gas ions, dopant ions and protons.A second beam of scanning electrons gives real time image feedback of the process to control focus of the ion beam as well as to profile depth and to do close loop compensation of deflection caused by mechanical vibration and H field. With controlled e beam irradiation, antenna effect can also be negated, thus allowing designs that were not possible previously.When massive quantity of material is needed for deposition, the wafer can be heated and gas being introduced for CVD, the excess can be etched by focused (with adjustable focal length) ion beam in a DRIE atmosphere.The wafer stays in place from cleaned and mounted virgin wafer to finished wafer waiting for dicing, so alignment requirement is minimum, plus the SEM can provide image feedback for fine adjustment to compensate contraction/expansion, vibration and other sources of misalignment.The only other equipment needed is a sputter machine, which deposits Ti/Ni/Au triple layer to make die bump pads, with a relatively low resolution stencil. Sputtering is moved away due to its messiness, I think everyone worked in a clean room knows how messy this process is.The finished product can then be diced either in house or sent to a packaging house to do dicing, testing, bumping and C4 with encapsulation.---------------------------Do you guys think this is a viable solution that will allow the more advanced hobbyists to make 0.35um chips at home for less than, say, $50k investment?Since everything is scanning based, rather than lithography based, this is no where close to production throughput, but just for prototyping niche ideas, I think this is a viable solution.

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 06:34:28 am
content: Just the flow/pressure hardware is going to take up 10-20% of your budget if you buy it (i.e. gas tank regulators), cylinders, manifolds, etc.If you need to mix gases even more (thousands of dollars for a gas mixer).i.e.https://www.bakersgas.com/MIL299-011-1C.html?gdffi=f2209edff2b34307a7a9da4e7fe2627a&gdfms=F1B0F4710B1F4663A535E49F45C1256D&campaign=258286922&adgroup=19042135802&feeditem=&keyword=&matchtype=&device=c&network=g&gclid=CjwKCAjw_YPnBRBREiwAIP6TJ-qcGOOP61l_zYiUN97sq1yqPmHkk-MzVTMrsBkkZr6GfdQgdgUQqhoC2FsQAvD_BwE&creative=56953834202&gclid=CjwKCAjw_YPnBRBREiwAIP6TJ-qcGOOP61l_zYiUN97sq1yqPmHkk-MzVTMrsBkkZr6GfdQgdgUQqhoC2FsQAvD_BwEThats manual stuff too.And I think you will need extremely high quality plumbing to keep stuff clean, expensive gas filters etc

author: AndyC_772
author_rank: Super Contributor
timestamp: May 20, 2019, 06:44:29 am
content: I've no idea about the technical viability, but the idea of marketing something like this at "hobbyists" is deeply bizarre to me.If it's viable at all, it'll be in the context of a service bureau, who have this equipment, the consumables it requires, the 3rd party contacts who can package the finished silicon, and above all, the design capability to turn schematics and specifications into a usable form. (What do the requisite Cadence licences cost these days?)I could give you a spec right now for a bespoke chip or two that I can't buy off the shelf, and which would be of genuine commercial value to me in quantities of 10's. It might be because there's no commercial demand for such a device, so nobody lists it as a standard part, or it might be that it's simply not technically possible. (It's not particularly complicated, but the temperature rating might raise a chuckle).I'm not going to devote lab space to such a device, or learn from scratch how to be a semiconductor designer / process engineer, but I might send a spec off to a custom silicon supplier and ask them if it can be made and at what cost. The service I'd be looking for would be one whereby I agree technical requirements, cost and time scale, and receive back a tray of parts.Can that be done today? Is anyone doing it already?

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 06:45:49 am
content: how do you ensure correct vapor concentrations? you would need to filter aresols too if you are bubblingrun it to a bypass and switch it in while its correct? keep in mind stuff like bubbling gasses through a liquid will increase its temperature after a while because of friction most likely and change concentrationsYou would need heated plumbing then to prevent condensation and probobly actually create vapor densities over what is required then dilute and mix them because it might be easier to control the concentration that way then control it with the bubbler.It's like sparging. How do you ensure your mixture evaporates uniformly rather then being distilled ? I think you would need to bubble gas through each chemical separately then combine them in the correct ratios if you need more then one. Then you still need to do a combiner? Or does the process just require one at a time?

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 06:53:16 am
content: and keep in mind if a pressure regulator fails what can happen is your evaporator can explode if its filled with something pyrophoric. poison gas might be better lol

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:00:08 am
content: how do you ensure correct mixture? how do you measure vapor concentrations when its running?what do you do with the hydrogen/vapor mixture if its too concentrated while tuning it during startup ?

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:01:21 am
content: do you just adjust each one, hope it stays good then go to the next one and try to run the process without continuous metering?

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:05:48 am
content: is the mixture of reactants stable in the condenser protecting the pump ? might need more then one

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:16:02 am
content: you mentioned organometallicsI thought you are sparging organometallics into a chamber. That means there will be organometallics condensing in your protection.

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:20:37 am
content: how do you prevent backflow of ions from the red hot material under vacuum back into your controlled chamber? that can contaminateI think you would need to condense each reactant seperately or at least make sure their compatible with each other if condensed in the same thing. And that thing will be dangerous if air reaches it because it will be filled with organometallic compounds that can ignite

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:23:16 am
content: and it can clog up on you

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:26:05 am
content: I feel like with a turbomollecular pump you can run the semiconductor toxic gasses through it OK. I don't know if you can run a hot turbomollecular pump.I also don't know how they deal with them, do they just let em into the oil (pick a nonreactive one) that they gas out of ?what do you normally do with this shit? maybe the clean gasses can react with something, if you have organic attached to it, it seems like it would soot up? getting some fucking pump oil infused with pyrophoric chemicals sounds like a new recipe for napalm

author: jeremy
author_rank: Super Contributor
timestamp: May 20, 2019, 07:29:36 am
content: I’ve always wanted to do something like this, but having HF or pirhana around people who don’t know the dangers (ie, in a garage) worried me too much. That’s not even counting any of the wacky dopants like phosgene, etc.What do you plan on doing for the vacuum? Chamber, seals, flanges, gauges, etc? Turbopump, diffusion pump, etc? I feel as though it would be easy to burn a big hole in your budget on vacuum equipment alone. The obvious answer is to scavenge on eBay for used stuff, but that basically just means that nobody can replicate your system.

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 07:30:32 am
content: are you sure your not gonna end up with barrels full of shady ass pump oil? return of the living dead part 2

author: jeremy
author_rank: Super Contributor
timestamp: May 20, 2019, 07:38:41 am
content: Quote from: blueskull on May 20, 2019, 07:32:29 amCould you link a pump kit? I am curious. I look forward to any updates on this project.Also, what is TBLi? I assume some sort of crazy solvent, but googling reveals nothing useful.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: May 21, 2019, 08:28:46 am
content: How does your business model work? One problem I see is getting your customers to commit significant (to them) resources in time and money upfront.