dopant

2 Articles

Two clear phials are shown in the foreground, next to a glass flask. One phial is labelled “P,” and the other is labelled “N”.

Designing A Hobbyist’s Semiconductor Dopant

May 18, 2025 by 3 Comments

[ProjectsInFlight] has been on a mission to make his own semiconductors for about a year now, and recently shared a major step toward that goal: homemade spin-on dopants. Doping semiconductors has traditionally been extremely expensive, requiring either ion-implantation equipment or specialized chemicals for thermal diffusion. [ProjectsInFlight] wanted to use thermal diffusion doping, but first had to formulate a cheaper dopant.

Thermal diffusion doping involves placing a source of dopant atoms (phosphorus or boron in this case) on top of the chip to be doped, heating the chip, and letting the dopant atoms diffuse into the silicon. [ProjectsInFlight] used spin-on glass doping, in which an even layer of precursor chemicals is spin-coated onto the chip. Upon heating, the precursors decompose to leave behind a protective film of glass containing the dopant atoms, which diffuse out of the glass and into the silicon.

After trying a few methods to create a glass layer, [ProjectsInFlight] settled on a composition based on tetraethyl orthosilicate, which we’ve seen used before to create synthetic opals. After finding this method, all he had to do was find the optimal reaction time, heating, pH, and reactant proportions. Several months of experimentation later, he had a working solution.

After some testing, he found that he could bring silicon wafers from their original light doping to heavy doping. This is particularly impressive when you consider that his dopant is about two orders of magnitude cheaper than similar commercial products.

Of course, after doping, you still need to remove the glass layer with an oxide etchant, which we’ve covered before. If you prefer working with lasers, we’ve also seen those used for doping. Continue reading “Designing A Hobbyist’s Semiconductor Dopant” →

Laser doping silicon wafer

Laser Doping His Way To Homemade Silicon Chips

December 28, 2021 by 8 Comments

It’s a pity that more electronics enthusiasts haven’t taken the hobby to its ultimate level: making your own semiconductors. There are plenty of good reasons for that: chief among them is the huge expense involved in obtaining the necessary equipment. But for the sufficiently clever, there are ways around that.

[Zachary Tong] is dipping his toes into the DIY semiconductor world, and further to the goal of keeping costs to a hobbyist scale, is experimenting with laser doping of silicon. Doping is the process of adding impurities to silicon wafers in a controlled manner to alter the electrical properties of the semiconductor. [Zach]’s doping method is a more localized version of the simple thermal diffusion method, which drives a dopant like phosphorus into silicon using high temperatures, but instead of using a tube furnace, he’s using a fiber laser.

The video below shows his two-step process, which first blasts the silicon oxide layer off the wafer before doping with the laser shining through a bath of phosphoric acid. The process is admittedly fussy, and the results were mixed at best. [Zach]’s testing seems to suggest that some doping occurred, and it even looks like he managed to make something reasonably diode-like using the method.

Although the jury is still out on [Zach]’s method, we thought the effort was the important bit here. Granted, not everyone has a fiber laser kicking around to replicate his results, but it’s always good to see progress in the DIY semiconductor field. Here’s hoping [Zach]’s work, along with the stuff that [Sam Zeloof] is doing, kicks off a spate of garage semiconductor fabs.

Continue reading “Laser Doping His Way To Homemade Silicon Chips” →