Device Photolithography: The Electron Beam Pattern Generator

The demand for integrated circuits is increasing rapidly, and projections indicate that the existing mask-making facilities will be severely overloaded in the near future. The major portion of the time required to make a mask is taken in producing the reticle. The electron beam pattern generator was originally conceived to assist the maskmaking shop by producing reticles rapidly. The use of a computer-controlled electron beam also holds promise for solving other problems. As integrated circuits become more complex, it is increasingly difficult to meet the line-width and field-size requirements of the final masks. The fundamental limits set by diffraction effects are currently being approached; moreover, the depth of focus of the lens system producing these masks is so small that severe requirements are made on material tolerances. Due to the extremely short wavelength of kilovolt electrons, diffraction effects are negligible and it is possible to write with beams a few tenths of a micron in width over small fields. A. N. Broers et al. 1 have succeeded in producing interdigital surface-wave transducers of 0.3-/un width and 0.7-jum 2077