Master Thesis - Co-sputtering of ternary and quaternary piezoelectric materials for BAW RF filters (f/m/d)

Silicon Austria LabsVillach,Österreich Abschlussarbeitvor 1 Monat

Recent years have seen increasing mobile wireless traffic resulting in increasing numbers of RF filters in smartphones. RF filters based on Bulk Acoustic Waves (BAW) devices could play a significant role in enabling 5G technology’s higher data rates if the devices succeeded in operating at higher frequencies (between 3.5 GHz and 6 GHz). While currently used piezoelectric materials like AlScN provide high performance, Sc is costly and alternative materials have to be found to realize cheaper devices. Theoretical studies (DFT simulations) of different authors have identified several material combinations that could provide comparable piezoelectric performance at reduced material costs.

The objective of this thesis is to select one of these ternary or quaternary material combinations (AlX1X2N) and to investigate it experimentally. Using AlN as a starting point, the piezo-layers will be fabricated by co-sputtering of up to three materials on a metal electrode, with the aim of maximizing the doping concentration without diminishing crystallinity. The layers will be characterized in terms of stress, roughness, granularity, orientation, piezoelectric coefficient (d33), and stiffness. Successful materials will be used to fabricate and characterize BAW test resonators on a suitable Bragg mirror (SMR mounted).

In particular, the candidate will:

  • Gain fundamental understanding of growth principles in thin film sputtering and influence of process parameters.
  • Experimentally characterize thin films (mechanical profilometer, ellipsometry, SEM, EDX, XRD).
  • Use single layer lithography to fabricate test-structures to measure piezoelectric properties and to realize and characterize simple BAW resonators.


  • Master student in material science, microsystem technology, physics, semiconductor technologies or similar fields.
  • Experience in cleanroom would be appreciated.
  • Experience with experimental data processing software (e.g. Matlab, Python,…) is also beneficial.
  • Autonomous, well orga­nized and enjoys working in a dynamic and multi­cul­tural team.
  • Oral and written commu­ni­ca­tion skills in English.


  • Start date: March 2021.
  • Duration: 6 Months.
  • Payment: 1500€ gross (38.5 Hours/Week).
  • Additional Benefits: free coffee/milk, € 4.- food allowance per working day in restaurants, homeoffice, no coretime...
  • State-of-the-art laboratories and equipment, including the opportunity to work in a cleanroom environment.
  • An international scientific environment and contacts with our industrial network.
  • Opportunity to work on a hot topic with industrial collaborations.

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