Method for constructing miniature micro circuits is based upon the same steps as photolithography:
Electron beam writing substrate covered with a sensitive polymer paste is exposed to the electron beam moving in desired patterns.
Developing exposed areas of the polymer are more soluble in solvents and after etching those parts remain as a channels in the polymer layer.
Metal coating metal particles are sputtered onto the sample, but they are attached directly to the substrate only in channels.
Lift-off by using more aggressive solvent the rest of the polymer is etched off the substrate, while the metal layer remains on the substrate in desired patterns.
Some advantages of e-beam lithography over photolitography are:
– electron optics allows for better quality of the writing beam;
– electron writer can also be used as a regular scanning electron microscope;
– the smallest features are bellow 100nm in size, which presents the limit for photolitography.
Scaning electron microscope image of a cross section of a polymer paste after developing.
Atomic force microscope image of a 300 nm wide channel between two electodes.
Scanning electron microscope image of a transistor constructed by using e-beam lithography.