LED Fabrication from Wafer to Light

Building a circuit to blink an LED is the hardware world’s version of the venerable “Hello, world!” program — it teaches you the basics in a friendly, approachable way. And the blinky light project remains a valuable teaching tool right up through the hardware wizard level, provided you build your own LEDs first.

For [emach1ne], the DIY LED was part of a Master’s degree course and began with a slice of epitaxial wafer that goes through cleaning, annealing, and acid etching steps in preparation for photolithography. While gingerly handling some expensive masks, [emach1ne] got to use some really cool tools and processes — mask aligners, plasma etchers, and electron beam vapor deposition. [emach1ne] details every step that led to a nursery of baby LEDs on the wafer, each of which was tested. Working arrays were cut from the wafer and mounted in a lead frame, bonded with gold wires, and fiat lux.

The whole thing must have been a great experience in modern fab methods, and [emach1ne] should feel lucky to have access to tools like these. But if you think you can’t build your own semiconductor fab, we beg to differ.

[via r/engineering]

18 thoughts on “LED Fabrication from Wafer to Light

    1. Actually, that phrase comes from the Bible– it’s Latin for “let there be light” (Genesis 1:3). But it’s telling that people think it comes from an obscure science fiction novel. Apparently, the Bible is not taught anymore, or Latin.

        1. Darren,

          Are you really so insecure or intimidated about the Bible that you feel compelled to discount it? Have you nothing better to do than make sophomoric attempts to insult others’ beliefs?

  1. Something I don’t quite get from the process is when the P-N junction is formed. I assume the wafer is P doped on the surface and the first etch removes the P material from the unwanted zones. Is this correct?

    1. The actual diode part was already on the wafer he started with (likely grown using some sort of vapour deposition process), all that he needed to do was isolate a device and add contacts. One if my fluorite demos working with LED wafers was touching a probe to the top of an unprocessed wafer, which causes a large area to glow dimly.

  2. “If I had dropped one of these I probably would have stood up, walked out, and never returned.”

    no you wouldnt you would go back to the start and etched a new one and then raised the price of the leds made from that plate by a factor of double to make up for the loss of the previous plate.

    or salvaged the unbroken etchings and then only raised the price of the difference between unsalvagable etchings and the value of a perfect plate

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