E-beam lithography

The principle of e-beam lithography is the same as the optical lithography. Instead of photons, high energetic electrons are used which have a much shorter wavelength and, therefore, allow to write much smaller structures. The negative resist AR-N 7500/18 from ALLRESIST is used in this thesis. After a spin-coating at 6000rpm and annealing at 85 for 2mins, the sample is exposed at 20kV in a LEO SERIES 1530 Scanning Electron Microscope (SEM) with a RAITH ELPHY PLUS lithography system. The minimal possible structure size is about 50nm and depends on the resist. For all e-beam lithography steps the developer AR 300-47 (4min) from ALLRESIST and the remover 1-Methyl-2-pyrrolidinone (1h in an ultrasonic bath at 80) from ALDRICH is used.

The SEM is also used to analyse samples [126]. The energy, the aperture and the detector type (In-lens or SE2) can be adjusted to suit the investigated sample. The nominal resolution is 1nm at 20kV. Figure 1.8 on page shows SEM images of the magnetic beads.