OT: a chip fab at home - detailed explanation

[BigEd]

We've talked from time to time about the economics of chip fabrication[1]... here's someone who has bought some equipment and knows how chips work and how they are made, and is prepared to spend some time explaining, on video:
Semiconductor Fabrication Basics - Thin Film Processes, Doping, Photolithography, etc.



More on his web site (http://sam.zeloof.xyz/):

• Homemade Insulated Gate Field Effect Transistor (MOSFET)
• Introduction to Semiconductor Fabrication at Home
• High Vacuum Experiments – Physical Vapor Deposition, Plasma Cleaning/Etching, etc.
• Homemade Photovoltaics – DIY Silicon PN Junction Solar Cells
• Maskless Photolithography with DLP Projector – 10um Feature Sizes

[via hackaday]

[1] We've had one or two excursions as to whether custom chips could be designed and made or whether a small fab could be constructed. My own take is that fabrication is very capital-intensive. With older equipment which should be cheaper you can make only the older less dense technologies. Without high volume, your chips will need to be priced in the thousands, and you are going to struggle to find customers with such deep pockets. Design is also rather expensive: to get from a sketch to mask data takes a lot of effort, skill, and tools. To get from mask data to masks is expensive too.

[White Flame]

I've always thought it would be interesting to attempt to replace masks with LCD panels and lensing, for limited run devices. Great to see a variant on that is being done, and I didn't think of DLP with its truer blacks.

[BigEd]

Sam has published his slides from a recent presentation (maybe his third?) - lots of good detail in them, about how semiconductors work and how they are made.
"Home Chip Fab"
https://goo.gl/e5H9sd
(67 slides)

Edit: link died, but see https://sam.zeloof.xyz/category/semiconductor/

[DerTrueForce]

I had a quick look at that, and all the images and most of the content is missing from them.
I'm using Chrome.

[BigEd]

Works for me... but here's a PDF anyhow.

[DblDragon]

I thought fabbing chips involved a number of polluting substances which is why there was only a handful of chip fab facilities.
Ya mean it can be done at home ?

[BigEd]

You need to be not too worried about using interesting chemicals, and yes, you should dispose of them correctly when you're done.

[BigEd]

Sam's latest video is a short one, summarising that last year he was able to make a few chips with a 5 micron PMOS process and a total of 6 transistors in the form of a differential amplifier. Details from his website:

Quote:

I designed the Z1 amplifier looking for a simple chip to test and tweak my process. Layout was done in Magic VLSI for a 4 mask PMOS process (active/doped area, gate oxide, contact window, and top metal.) PMOS has advantages over NMOS as far as mobile ionic contamination that lends it to being fabricated in a garage.
The feature (gate) size is approximately 175μm although there are test features as small as 2μm on the chip. Each amplifier section (center and right) contain 3 transistors (2 for long-tailed differential pair and one as current source/load resistor) which means a total of 6 FETs on the IC. The left portion of the IC contains resistors, capacitors, diodes, and other test features used to characterize the fabrication process.

Some of the early HP calculator chips were PMOS - it's a simple and robust process, not especially fast or power efficient. It's a long way from 6 transistors to a CPU, let alone a very specific CPU like the 6502, but it will be interesting to follow Sam's progress.

Quote:

...to do this at home I've had to build and acquire quite a lot of specialized equipment ... this project was great because I got to learn so much about so many different fields ... I also had to deal with a number of hazardous chemical like hydrofluoric acid phosphoric acid sulfuric acid hydrochloric acid and number of others

[Chromatix]

Hydrofluoric acid is a particularly nasty one, I understand. Fluorine compounds are… "special".

[BigEd]

Jeri Ellsworth has some amusing words about jelly bones. Apparently it's very painful indeed. And the stuff gets through gloves:
Making Microchips at Home - Cooking with Jeri Part1

More seriously:
Safe HF Etching at Home with an Etch Chamber

Quote:

Hydrofluoric Acid (HF) can cause terrible burns, dissolve bones or even die from fluorides in your blood stream. Be sure to research HF handling and make containment chamber like this.

[drogon]

Chromatix wrote:

Hydrofluoric acid is a particularly nasty one, I understand. Fluorine compounds are… "special".

If you want to waste an afternoon reading about fluorines, then I can thoroughly recommend getting hold of "Ignition!: An Informal History of Liquid Rocket Propellants" but first read the most excellent blog "In the Pipeline", starting with: Sand wont save you this time: https://blogs.sciencemag.org/pipeline/a ... _this_time

-Gordon

[BigEd]

FOOF!

[Chromatix]

Yes, precisely my point.