Ion beam sputter deposition

Nov 7, 2016 | Applications

Adding a thin film

In ion beam sputter deposition the goal is to add a thin film to the substrate surface to change its material properties. The concept of ion beam deposition is an ion beam that sputters a target in proximity to the substrate. Ion beam deposition is a physical vapor deposition (PVD) technique. Other PVD methods are for example thermal or e-beam evaporation, magnetron sputtering, and pulsed laser deposition. Each technique has its advantages. For ion beam deposition these are predominantly the flexibility and precision in the deposition parameters, low sample impact, and high quality of the deposits.

Particle energies in ion beam sputter deposition

The energy of the ion beam is typically several hundred V to several kV. Target atoms can escape the surface when they receive an energy larger than the sputtering threshold energy, or surface binding energy. This energy depends on the target and is on the order of a few eV. The average kinetic energy of the ejected atoms depends on the energy, angle and type of incoming ion, and the nature of the target material, and is typically tens of eV.

Schematic illustration of a linear collision cascade. The thick line illustrates the position of the surface, and the thinner lines the ballistic movement paths of the atoms from beginning until they stop in the material. The purple circle is the incoming ion. Dark grey, orange, light grey, and violet dots illustrate primary, secondary, tertiary and quaternary recoils, respectively. In between the ballistic collisions the ions move in a straight path.

Ion beam sputter deposition compared to other PVD methods

The workhorse of industry in terms of PVD methods is magnetron sputtering. In magnetron sputtering an inert gas is ionized in a plasma between the substrate and the target, which is confined by a magnetic field. The target is biased and gets sputtered by the positive ions that are accelerated towards it.

A big difference between ion beam sputter deposition and magnetron sputtering is that for ion beam deposition there is no plasma between the substrate and the target. This means for ion beam deposition that also sensitive substrates can be deposited on, and the sputter gas inclusion in the deposit is likely to be lower. Also, in conventional ion beam deposition there is no bias between the substrate and the target, meaning both conducting as well as non-conducting targets and substrates can be used.

Furthermore, contrary to other sputtering methods, ion beam sputtering offers the ability to control independently and over a wide range the ion energy, flux, species, and angle of incidence.

Schematic illustration of four PVD methods: evaporation, magnetron sputtering, ion beam sputter deposition and pulsed laser deposition

The evaporation deposition method uses either Joule heating or an electron beam to heat the target material up to its evaporation point. The average kinetic energy for thermal or e-beam evaporation is far less than an eV, which is much lower than that for ion beam sputtering. As a consequence, thin films deposited by ion beam sputtering are much denser (lower porosity) and smoother and more likely to be stressed compared to thin films deposited by evaporation techniques.

Pulsed laser deposition uses a laser directed at the target to vaporize the target material.

IBSD & Polygon Physics

Ion beam sputter deposition is probably the surface engineering process that Polygon Physics is most involved in. The traditional disadvantages of ion beam sputter deposition are high maintenance, high level of complexity, and difficulty to scale up. We are proud that because of our unique ECR technology these drawbacks are now part of the past.

Several of our academic clients use single cavity ion sources for ion beam sputter deposition on smaller samples in their own vacuum system. But Polygon Physics has also developed an entirely new approach to ion beam sputter deposition based on the use of multiple sources: multi beam sputter deposition. The unique geometry of this technique opens up unprecedented abilities for multi-component depositions. The Polygon Physics team has developed and fabricated several multi beam sputter deposition systems with up to 20 sources, accepting samples up to ∅ 300 mm.

Photo of Ø 400 mm Ion Beam Deposition System with 20 ion sources, for samples up to Ø 300mm