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0 pointsamelius4y ago0 comments

He used wafers with premade structures on it.

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kens4y ago

No, Sam Zeloof started from blank silicon wafers and did four layers of photolithography to produce PMOS gates. He used boric acid for the boron diffusion. He sputtered an aluminum layer on top for the metal and etched it with phosphoric acid.

http://sam.zeloof.xyz/first-ic/

geomark4y ago

So he "only" did metal deposition to make the interconnects? I haven't read the story, but I was thinking that there's no way you would handle some of the toxic chemicals used for doping.

wrycoder4y ago

They are not really that toxic. You do have to have a chemistry background and use a fume hood and a process sink with acid neutralization capability, like you find in many chem labs.

Good dopant choices would be phosphorus oxychloride and oxidized boron nitride wafers.

As I recollect, he started with silicon wafers with an epitaxy layer. He then did the usual oxidations, diffusions, and metallization, along with all the photolithographic steps. No small feat!

geomark4y ago

Ok. I was never a process guy, but worked with some back in the day and they told me that one of their phosphorus sources was phosgene gas.

wrycoder4y ago

Silane, phosphene, and diborane gases are used to form epitaxial layers on silicon wafers. Those are truly dangerous gases. However, a simple wafer process using the reagents I mentioned can produce very credible ICs, if one buys the epi wafers.

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kens4y ago

http://sam.zeloof.xyz/first-ic/

geomark4y ago

So he "only" did metal deposition to make the interconnects? I haven't read the story, but I was thinking that there's no way you would handle some of the toxic chemicals used for doping.

wrycoder4y ago

They are not really that toxic. You do have to have a chemistry background and use a fume hood and a process sink with acid neutralization capability, like you find in many chem labs.

Good dopant choices would be phosphorus oxychloride and oxidized boron nitride wafers.

As I recollect, he started with silicon wafers with an epitaxy layer. He then did the usual oxidations, diffusions, and metallization, along with all the photolithographic steps. No small feat!

geomark4y ago

Ok. I was never a process guy, but worked with some back in the day and they told me that one of their phosphorus sources was phosgene gas.

wrycoder4y ago

j / k navigate · click thread line to collapse