Electron lithography for the fabrication of microelectronic devices

Electron lithography is a technique which is in widespread use for making masks and reticles for the manufacture of integrated circuits. It is also commonly used in research laboratories for exposing micron or sub-micron patterns directly on wafers. In addition, direct exposure is used, to a limited extent, in manufacturing plants, although generally at coarser resolutions. The reasons for using electron lithography in these applications are explained, and a history of the technique's evolution is given. The two major types of instrument-the scanning instrument and the projection instrument-are described and their limitations are pointed out. Interactions between electrons with energies of tens of keV (the energies typically used in electron lithography), the substrate (wafer or mask plate) and the resist material (in which a latent image is formed) are discussed. It is shown how these interactions affect the quality of the resist image before and after development.