Spot Size Guide

Getting good results in e-beam lithography means finding the best combination of a lot of different exposure parameters. Two of the most important of these are beam spot size and pattern pixel size.

Spot Size vs. Pixel Size

Pixel size is the pixel diameter (also called “resolution” and “beam step size”) that you choose when exporting your pattern in LayoutBEAMER?. This number can be any multiple of the system’s base resolution unit (0.5 nm), all the way up to the width of your subfield, which is typically about 4 μm.

Spot size (also called “beam diameter”) is the width of the beam and is roughly proportional to the beam current. The table below gives approximate theoretical spot sizes for various beam currents set up on the 300 μm aperture, approximated using column geometry and electron physics. The chart of high-current spot sizes was empirically measured on the tool using the mss command.

For best results, some thought should be put into both of these numbers before you start writing.

Spot Size Considerations

Spot Size Table, 300um Aperture (theoretical)

Beam Current (nA) Spot Size (nm)
0.1 5
0.2 5
0.5 5
1 5
2 5
3 6
4 6
5 7
10 9
25 13
50 20
75 30
100 40

Spot Size Chart, 300um Aperture (measured)


* The above chart is only valid at the 300um aperture setting, so if you're using a different aperture make sure you measure the spot yourself with mss!