Over the past few years we’ve seen several impressive projects where people try to manufacture integrated circuits using hobbyist tools. One of the most complex parts of this process is lithography: the step in which shapes are drawn onto a silicon wafer. There are several ways to do this, all of them rather complicated, but [Zachary Tong] over at Breaking Taps has managed to make one of them work quite well. He shares the results of his electron-beam lithography experiments in his latest video (embedded below).
In e-beam lithography, or EBL, shapes are drawn onto a wafer using an electron beam in a vacuum chamber. This is a slow process compared to optical lithography, as used in mass production, but it is reasonably simple and very flexible. [Zach] decided to use his electron microscope as an e-beam litho machine; although not designed for lithography, it has the same basic components as a real EBL machine and can act as a substitute with a bit of software tweaking.
The first step is to coat a wafer with a layer of e-beam resist. [Zach] used PMMA, commonly known as acrylic plastic, and applied it using spin coating after dissolving it in anisole. He then placed the wafer into the electron microscope and used it to scan an image. The image was then developed by rinsing the wafer in cold isopropyl alcohol.
[Zach] explains the whole process in detail in his video, including how he tuned all the parameters like resist thickness, beam strength, exposure time and development time, as well as the software tricks needed to persuade the microscope to function as a litho machine. In his best runs he managed to draw lines with a width of about 100 nanometers, which is seriously impressive for such a relatively simple setup.
Looks like [Sam Zeloof] got bored on his Thanksgiving break, and things got a little weird in his garage. Of course when your garage contains a scanning electron microscope, the definition of weird can include experimenting with electron-beam lithography, resulting in tiny images etched into silicon.
You’ll probably remember [Sam] from his 2018 Hackaday Superconference talk on his DIY semiconductor fab lab, which he used to create a real integrated circuit. That chip, a PMOS dual-channel differential amp, was produced by photolithography using a modified DLP projector. Photolithography imposes limits to how small a feature can be created on silicon, based on the wavelength of light.
[Sam] is now looking into using the electron beam of his SEM as a sort of CNC laser engraver to produce much finer features. The process involves spin-coating silicon wafers with SU-8, an epoxy photoresist normally used with UV light but that also turns out to be sensitive to electron beams. He had to modify his SEM to control the X- and Y-axis deflection with a 12-bit DAC and provide a custom beam blanker. With a coated wafer in the vacuum chamber, standard laser engraving software generates the G-code to trace his test images on the resist. A very quick dip in acetone develops the exposed chip.
[Sam] says these first test images are not too dainty; the bears are about 2.5 mm high, and the line width is about 10 μm. His system is currently capable of resolving down to 100 nm, while commercial electron beam lithography can get down to 5 nm or so. He says that adding a Faraday cage to the setup might help him get there. Sounds like a project for Christmas break.
The greatest bit of consumer electronics is shipping and the reviews are out: Amazon’s Alexa-enabled microwave is a capable microwave, but befuddling to the voice-controlled-everything neophyte. Voice controlled everything is the last hope we have for technological innovation; it’s the last gasp of the consumer electronics industry. This is Amazon’s first thing with a built-in voice assistant, and while this is a marginally capable microwave at only 700 Watts — fine for a college dorm, but it’s generally worth shelling out a bit more cash for a 1000 Watt unit — the controls are befuddling. The first iteration is always hard, and we’re looking forward to the Amazon Alexa-enabled toaster, toothbrush, vacuum cleaner, and Bezos shrine.
Need a laser cutter, like crowdfunding campaigns, and know literally nothing about laser cutters? Have we got something for you. The Etcher Laser crowdfunding campaign has been pinging my email non-stop, and they’ve got something remarkable: a diode laser cutter engraver for $500. It comes in a neat-looking enclosure, so it’s sure to raise a lot of money.
A while back [Paulusjacobus] released an Arduino-based CNC controller for K40 laser cutters. There were a few suggestions to upgrade this to the STM32, so now this CNC controller is running on a Blue Pill. Yes, it’s great and there’s more floating points and such and such, so now this project is a Kickstarter project. Need a CNC controller based on the STM32? Boom, you’re done. It’s also named the ‘Super Gerbil’, which is an awesome name for something that is effectively a GRBL controller. Naming things is the hardest problem in computer science, after all.
The Gigatron computer is a ‘home computer’ without a microprocessor or microcontroller. How does it do this? A metric butt-load of ROM and look-up tables. This is cool and all, but now the Gigatron logo is huge. we’re talking 18 μm by 24 μm. This was done by etching a silicon test wafer with electron beam lithography.