Electron Beam Lithography (EBL) refers to a lithographic process that uses a focused electron beam to write patterns, in contrast with optical lithography which uses light for the same purpose. Electron lithography offers a higher resolution than optical lithography because of the shorter wavelength of the used electrons. The moving electron beam strikes only selected locations on the sample so that photo masks are not needed, in contrast with optical lithography.
The system which uses a scanning electron microscope ‘draws’ the pattern pixel per pixel over the resist using the beam as a pencil. This moving beam doesn’t allow a very fast illumination of the selected regions on the wafer. Selective etching of the illuminated positive resist (or the not illuminated negative resist) leads to a patterned wafer. After deposition of metals on this wafer and the etching of the remaining resist, the desired pattern is ready to use.Electron beam lithography is a most effective way to pattern materials at the nanoscale, especially in the case of structures, which are complex and not repeating a simple motif.
SEM lithography can be used for the fabrication of a wide variety of devices. At IMO-IMOMEC the technique is mostly used to make electrical contacts on carbon flakes or nanotubes. Other research areas include: quantum structures (single electron transistors) optical structures (binary holograms and linear/circular gratings); electro-mechanical structures (Surface Acoustic Wave (SAW) and MEMS devices).