Lithography

Clean Room Facility

For the fabrication of nanostructures and superconducting as well as spintronic devices the WMI operates a class 1000 clean room facility with an area of about 50 square meters. This clean room facility is subdivided into two parts for optical lithography and electron beam lithography, respectively. The clean room facility is equipped with the standard tools for optical lithography such as resist coaters, hot plates, wet benches, a Karl Süss MJB3 mask aligner and an optical projection lithography system. The clean room also is equipped with a reactive ion etching system, Plasmalab 80 Plus with ICP plasma source (Oxford Instruments Plasma Technology). The technical infrastructure for the clean room is located in the basement of the WMI directly below the clean room area.

Optical Lithography

For optical lithography a Karl Süss MJB 3 maskaligner or an optical microscope based projection system are used. The maskaligner is operating in the 1 : 1 soft or hard contact mode and is using chromium metal masks. In the projection system the mask pattern is demagnified by a factor of 5 to 100. Therefore, cheap foil masks can be used. With both systems microstructures with a lateral dimension down to 1 µm can be fabricated.

Electron Beam Lithography

The Electron Beam Lithography System is installed in one part of the clean room facility. It consists of a Philips XL 30 SFEG scanning electron microscope (SEM) with a Raith Elphy Plus electron beam lithography system and a laser interferometer table for precise stitching of writing fields. The SEM is equipped with a hot field emitter and typically provides a beam diameter of less than 1.5 nm at > 10 keV or about 2.5 nm at 1 keV. The lithography unit allows the fabrication of nanostructures down to about 10 nm. We have realized the controlled fabrication of metallic strip patterns with a strip width of about 20 nm. The electron beam lithography is used for the fabrication of nanostructures in metallic (eg. superconducting flux qubits) and oxide systems required for the study of quantum effects in mesoscopic samples.