Nano-Optics Graz Methods

Electron Beam Lithography


Electron beam lithography (EBL) is a flexible and versatile tool for the fabrication of a wide range of micro- and nanostructures on a substrate.

Principle

Sample fabrication by EBL in schematically illustrated in the figure below. Starting point is a usually flat substrate that is conducting to prevent charging. For optical applications calling for transperancy indium-tin-oxide covered glass plates have become widely used. The substrate is spin coated with an electron sensitive resist, typically 100 nm thick. Resists as polymethylmethacrylate (PMMA) consist of macromolecules that are modified upon exposure to high-energy electrons, resulting in a changed solubility. A desired sample pattern can thus be transferred to the resist by writing the pattern with an electron beam and subsequent wet chemical development. The resulting patterned resist layer serves as a mask for depositing the sample material by vacuum evaporation. Finally, a lift-off step removes the resist mask and excess material on top of it, leaving the sample structures on the surface.


Technology

For research purposes commercial scanning electron microscopes (SEMs) are an practical and appealing base for EBL in terms of flexibility and cost. Here in Graz we use a RAITH 100-2 turnkey system (see press release) based on a ZEISS Gemini field emission SEM and a JEOL 6400 tungsten cathode SEM equipped with a RAITH Quantum lithography unit.

        Modified 5.5.2007