Influence of post-annealing on the performance of BST thin film varactors

This paper presents the material and microwave characterisation of BST thin films on sapphire substrates. The influence of post-annealing the BST thin films in vacuum and air is investigated. RF magnetron sputtering was utilised to deposit the films and different analytical techniques were employed to characterise the as-grown and annealed BST thin films. Fabrication of the BST thin film varactors using standard photolithography processes and eventually gold electroplating for the electrodes are outlined. Microwave characterisations are performed on both unannealed and annealed devices and the correlation between the microwave and material properties of the BST thin films are discussed.