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Lithography

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Clean Room Facility

Clean Room
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

Electron Beam Lithography Supported by substantial funding of the Excellence Cluster Nanosystems Initiative Munich (NIM) the Walther-Meißner-Institute could replace its electron beam writer. The new 100 kV nB5 Electron Beam Lithography System of NanoBeam Ltd., UK, has been delivered in October 2014. With this new powerful instrument the WMI has strengthened its technological infrastructure for nanofabrication.

The nB5 main characteristics are an innovative design of the electron optics and a high degree of automation providing high throughput and reliability. The nB5 is equipped with a thermal field emitter, fast deflection speed (55 MHz deflection rate), fast beam blanking unit (rise time < 5 ns, 55 MHz blanking rate), main field and subfield writing, and advanced vibration tracking design. The electron optics provides beam voltages up to 100 kV, beam currents up to 100 nA (presently ∼ 10 nA), and a theoretical beam size of 2.3 nm.

The device is equipped with a load-lock chamber with automatic loading robotics. The loading cassette can house up to 6 chucks with a diameter of 8 inch. The nB5 system operation is highly automated. The sample geometry is converted from the GDSII format into the required data format by the pattern generation software. After defining the job in a dedicated scripting language, the sample alignment, beam focusing/adjustment, mark recognition, write field alignment/stitching, and electron beam exposure can be run in a fully automated fashion.