Electron Beam Fabrication of Micron Transistors

For high-speed performance as well as high packing density, it is desirable to make the components in integrated circuits as small as possible. One of the fundamental problems in making smaller components is that of limitations in the optical technology. This paper describes an experimental process and the results obtained by using an electron-optical system to fabricate small transistors. Planar bipolar transistors with emitter and base contact windows one micron wide have been fabricated, with the electron beam exposure system used to open all the diffusion windows as well as to expose the metallization patterns. Conventional etching techniques are unable to provide 1-µm wide metal paths in half-to one-micron thick metal layers; therefore the lift-off process is used. The dc and ac characteristics presented compare favorably, for the first time using this fabrication process, with the best bipolar transistors produced by optical masking processes. These characteristics provide a guide for refinement in future micron transistor design.