E-beam Lithography

I modified my JEOL┬áscanning electron microscope to not only image tiny things, but make tiny things too. This technique is called Electron Beam Lithography. Normally, a SEM works by scanning a beam of electrons over the sample and detecting secondary electrons. In this case, I built a PC scan controller that “drives” the electron beam around and draws the image onto the sample which is coated with electron-sensitive resist.

Schematic-illustration-of-electron-beam-lithography-Electron-beam-is-focused-on-a-resistFor resist, I used SU-8 although PMMA (Acrylic) dissolved in solvent will work as well.

The scan controller uses dual 12 bit DACs. They had current outputs so a transimpedance amplifier creates +/-10v proportional to that current to drive the microscope’s external XY inputs. The controller also contains an Arduino and Altera CPLD. To turn the beam off when needed, a high voltage is generated (+2kv) and applied to a “beam blanker” inside the microscope.

I learned that the 12 bit DACs do not nearly have enough resolution, so I will be looking at upgrading to at least 18 bits hopefully. Also, the geometry of the beam blanker is not correct to create a high electric field in its center, so the beam is only partially de-focused and never fully “turns off”.

One thought on “E-beam Lithography”

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