Ion Tracks and Microtechnology

The penetration of heavy charged particles through matter has been the subject of investigations since the early days of Bohr's atomic model. Much later it was found that the resulting traces have dimensions close to the atomic scale and can be revealed in the form of fme patterns. Quite recently, this characteristic attracts applications in micro­ electronics and -mechanics, biology and medicine, surface and membrane technology, magneto-optics and low temperature physics - applications which require a high subtlety of geometric control on a microscopic scale. Progress in advanced technologies depends crucially on the refinement of the available tools. On the road into the submicron regime, customary lithographies using visible and ultraviolet light, x rays, and electrons are steadily nearing their physical limits. A central point in the search for better tools is the improvement of irradiation technology. Ions have a well-defined range of penetration, a high local confmement of the deposited energy and can be generated conveniently in great quantity. The generated dam­ age zones can be stored indefmitely in many insulators and be used to initiate a phase transformation process that changes, removes, or collects material along the latent tracks. Up to now the most common development process is track etching, which acts as a chemical amplifier that dissolves the damaged zone of the latent tracks preferentially and creates etch pits or channels that can be extremely fine, starting around 10 nm and in­ creasing .linearly with the etching time.