Electron Beam Lithography for nano-patterning

Electron beam lithography is a versatile tool for fabrication of nano-sized patterns. The patterns are generated by scanning a focused beam of high-energy electrons onto a substrate coated with a thin layer of electron-sensitive polymer (resist), i.e. by directly writing custom-made patterns in a polymer. Electron beam lithography is a suitable method for nano-sized production, research, or development of semiconductor components on a low-volume level. Here, we present electron beam lithography available at DTU Danchip. We expertize a JEOL 9500FZ with electrons accelerated to an energy of 100keV and focused to a beam spot size down to ^~5nm. The electron beam can scan across the substrate with a speed of 100MHz and can write areas of 1mm x 1mm without stitching. In order to ensure high-precision patterning, the beam position on the substrate is controlled by a two-stage deflector system and substrates are mounted on a stage which is positionally controlled by laserinterferometry. This results in a resolution of 10 nm and stitching accuracy of 10 nm. The electron beam writer is located in a class 10 (ISO 4) cleanroom which is vibrationally and electromagnetically screened from the surroundings. Furthermore, the room temperature is controlled to an accuracy of 0.1 degrees in order to minimize the thermally induced drift of the beam during pattern writing. We present process results in a standard positive tone resist and pattern transfer through etch to a Silicon substrate. Even though the electron beam is below 10 nm, the feature and pitch resolution in resist is limited by forward and backward scattering of the electrons. The scattering depends on the energy of the electrons, type and thickness of resist and type of substrate. Also, when patterning on a non-conductive substrate, the accumulation of electrons in the substrate will influence the patterning. We present solutions to overcome these obstacles.