Materials and processes for microstructure fabrication

The fabrication of structures considerably smaller than the devices and circuits that are mass-produced for use in computers and other electronic equipment is the subject of this paper. Devices of <1 µm (microstructures) and <100 nm (nanostructures) minimum dimensions were made possible in a practical sense only after the introduction of electron beams and the associated processes, as lithographic tools in the early 1960s. This paper presents a historical perspective of this very important chapter in lithographic technology, primarily from the point of view of materials and processes, since electron-beam systems are covered in other papers in this issue. In addition, the important criteria that have to be considered in the fabrication of small structures, with respect to the interaction of the writing beam with the resist material and the substrate, and the subsequent pattern-transferring processes, are discussed.