Another form of Physical Vapor Deposition (PVD) is referred to as Ion Beam Deposition or Ion Beam Sputtering (IBS). Unlike conventional magnetron sputtering, where ions are generated in plasma within a cathode assembly, Ion Beam Sputtering employs a target that is external to the ion beam source. Originally developed by Dr. Harold Kaufman in his developmental work at NASA in the early 60’s as an electromagnetic ion thruster for space applications, he further refined the source for thin film deposition applications in conjunction with IBM while teaching at Colorado State University as a broad beam ion source of electrons to support a magnetically confined plasma discharge. This initial design was, and still is, the basis for almost all commercially available ion sources used for thin film deposition, ion milling, substrate cleaning, etching and ion enhanced deposition.
The Kaufman type source, as it is known, consists of a collimated, focused or defocused grid designs with a permanent magnet incorporated containing a thermionic cathode filament providing a source of electrons to facilitate a magnetically confined plasma discharge. With the use of an inert gas, such as argon, and a grid system to extract the ion beam, the source can be directed toward a “Target” with sufficient energy to dislodge atoms by breaking the individual atomic bonds. This “Target” may be in the form of a deposition material to form thin films onto a substrate, the substrate itself to provide additional energy on the surface to enhance nucleation and growth of the resultant film, or both. A second source of electrons provided by a filament (usually tungsten), a plasma bridge neutralizer or a hollow cathode electron source within the ion source provides for neutralizing the charge of the ion beam. This ion beam source is essentially a plasma source outfitted with a set of grids configured to allow a stream of ions to be extracted. The grids accelerate the ions to a high velocity. These grids contain a series of holes with designated apertures in a specific pattern which combine to form the beam with a well defined energy.
A second ion beam source can be directed toward the substrate to provide for pre-deposition substrate cleaning as well as simultaneously adding energy to the substrate surface while the initial ion beam source strikes the target surface providing impinging atoms to the substrate. This dual ion source deposition process can provide for a more stress free resultant film with better adhesion, especially for thick films.
The primary benefits of ion beam deposition include the following. Ion beam deposition allows for the independent control the ion beam energy and the ion flux independently. Ion beam sources operate at lower pressures than conventional sputtering technology allowing for lower contaminant generation and particle collisions in the plasma. With dual source processing there is better control over individual stoichiometry by controlling nucleation and growth on the substrate surface. This also provides higher density films by reducing porosity (vacant sites) and entrapped gas (argon). Provides controlled refractive indices (N) in multi layered optical films by producing films with smoother surfaces.
Plasmaterials, Inc. provides target materials for all conventional ion beam deposition systems as well as for those created independently in research laboratories and universities. This includes all sizes and compositions as well as the all metal bonding to backing plates – whether customer provided or produced by Plasmaterials, Inc. Call or email your Plasmaterials Sales Engineer with inquiries for your specific material and product needs.
