Electron Beam Evaporation: Overview
Electron beam (e-beam) evaporation is a time tested deposition technology for producing dense, high purity coatings.
During an e-beam evaporation process, current is first passed through a tungsten filament which leads to joule heating and electron emission. High voltage is applied between the filament and the hearth to accelerate these liberated electrons towards the crucible containing the material to be deposited. A strong magnetic field focuses the electrons into a unified beam; upon arrival, the energy of this beam of electrons is transferred to the deposition material, causing it to evaporate (or sublimate) and deposit onto the substrate. Adding a partial pressure of reactive gas, such as oxygen or nitrogen to the chamber during evaporation can be used to reactively deposit non-metallic films.
Electron beam evaporation has many advantages over resistive thermal evaporation. First, the e-beam source is capable of heating materials to much higher temperatures than is possible using a resistive boat or crucible heater. This allows for very high deposition rates and evaporation of high temperature materials and refractory metals such as tungsten, tantalum, or graphite. Second, films deposited by electron beam evaporation can better maintain the purity of the source material; water cooling of the crucible tightly confines the electron beam heating to only the area occupied by the source material, eliminating any unwanted contamination from neighbouring components. Finally, electron beam evaporation sources are available in a variety of sizes and configurations including single or multiple pockets. Pocket indexing using a motorized carousel allows one source to deposit many materials from a single source location.
E-beam evaporation is available on a variety of PVD platforms and for many applications, including metallization, dielectric coating, optical coatings, and Josephson junctions.