Reactive Sputtering Process Development

Centrum Partners:

• Tomas Nyberg, Oliver Kappertz, Tomas Kubart, Sören Berg, Ilia Katardjiev, Lina Liljeholm, Ulf Jansson, Urban Wiklund (Uppsala)
• Ulf Helmersson (Linköping)

External Partners

• Fraunhofer Institute (Braunschweig)
• RWTH (Aachen).

Scientific Objectives

• Understand the sputtering process on Complex Targets for complex phase growth.

Technology Transfer Objectives

• International cooperation funded by the Volkswagen-Stiftung involving Applied Films in Frankfurt.

Research plan:

In the work of optimizing sputtering-based processes – in particular finding means of eliminating the hysteresis for reactive sputtering processes - we have recently discovered that such conditions may be obtained in a mixed nitrogen/oxygen processing environment for deposition of oxide films. The cause of this favorable behavior seems to be strongly related to the difference in reactivity between oxygen and nitrogen with the sputtered metal. We intend to study this phenomena, experimentally as well as theoretically, and also investigate whether nitride targets may be used as the metal source for metal oxide formation in reactive sputtering deposition processes.
Moreover, the electrical properties of the sputtering plasma has so far been neglected in our modeling work. We know, however, that the target voltage in many cases easily may drop from - 400V to –250V when shifting from metal to poisoned mode. It is evident that this may cause a significant contribution to the overall processing behavior. Target voltage is one processing parameter that is easily measurable. We therefore believe that we will find out new correlations for voltage variations vs processing conditions. Detailed studies experiments/modeling will be carried out.

We will study also the transient behaviour of the process. Preliminary results indicate that it may be possible to resolve the different target poisoning effects (reactive gas ion implantation and chemisorption) by studying on-off sequences in reactive sputtering processes. Pulsed sputtering has been along for some time to discharge insulating layers at the target surface to decrease the arcing effect.

In collaboration with prof Ulf Helmersson we intend to carry out studies on HIPIMS operating in the reactive sputtering mode. This has not been done in any detail before. The HIPIMS will represent a true transient reactive sputtering system thus fitting directly into our intended studies of such phenomena.

In addition to the above, we are interested in fabrication of the compound AlBXN in order to find thin films having piezoelectric properties superior to AlN but still compatible with integration onto IC-chips. Thin films of this material will be fabricated and their  proerties vs the value of x will be carefully investigated. Theoretical predictions will assist in the fabrication experiments. The goal will be to jointly develop a sensor based on AlBN.