August 27, 2010

2 Min Read
DIY chip fab

I ran across Jeri Ellsworth’s home page recently, and from there found her home made chip fab photos on Flickr.  There are also a couple videos on vimeo where she talks about making transistors at home.

Details are pretty sketchy on the flickr site, but the video has good information.  She used common household supplies such as boric acid and phosphoric acid, and AquaFina bottled water.  Also not so common household items, such as silicon wafers.  It turns out that there are wafers of all sorts available on Ebay, from $5 to $15 each, depending on size and quantity.  Who knew?

She grows a layer of oxide on the wafer in a kiln by admitting small amounts of water which turn into steam.   She creates the source and drain oxide cuts by hand painting hydrofluoric acid (hobby store glass etcher) onto the wafer.  Briefly paint on some boric acid paste, then wash it off, and back to the kiln to drive the boron into the silicon.  Watch the video, it’s fascinating for its low tech cleverness.

Watching the video made me remember a book review that I read years ago in EE Times, back when it was a large format (and thick) publication.  Anyone remember that hefty weekly?  The book was a newly published history of Silicon Valley and the early days of the silocon industry.  I wish I had gotten the book back then, because I no longer recall the title and I haven’t been able to locate it on Amazon.

One of the stories I remember from the review was about a shoe salesman who heard about semiconductors and figured it was the wave of the future.  He quit his job, bought some equipment, and started manufacturing diodes in his garage.  The state of the art was such that a major advance in manufacturing was had when it was discovered that washing wafers in distilled water instead of tap water would greatly improve yields.  Exciting times indeed.

Steve Ravet

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