Projects

Future agile wireless multi standard communication systems and sensors need new tunable micro-wave components like phase shifters or matching networks. They are needed to adapt power amplifiers and antennas or can be used to operate adjustable multiband antennas. Tunable components have to fulfill different, partially opposing needs depending on the desired application. This is a wiring challenge, which available semiconductor components and RF-MEMS can fulfill only insufficiently or with a lot of technical effort. Therefore research efforts around the world aim at the development of new functional components, e.g. based on tunable ferroelectric films. Basic components for the desired functional components are tunable varactors. They can be designed as tunable, vertical Metal Insulator Metal (MIM)-structures. Up to now these tunable MIM-structures are made by physical vapor deposition and chemical vapor deposition of ferroelectric thin films with a thickness of up to 400 nm. Ferroelectric films with high piezoelectric coefficients and high permittivity, like lead-zirconate-titanate (PbZrxTi1−xO3, PZT) or barium-strontium-titanate (BaxSr1-xTiO3, BST) films with perovskite structure are widely used in the fields of sensors, energy harvesting capacitors and FERAMs. Especially barium-strontium-titanate has great potential to be used as structured thin films for HF-applications. The main aim of this project is the development of a new deposition and micro structuring process for the micro fabrication of electronically tunable varactors made of micro structured perovskite barium-strontium-titanate thin films with high permittivity. For this purpose a direct UV-photolithographic sol-gel process should be developed. In a first step a known demonstrator system, based on an UV-photopatternable lead-zirconate-titanate sol, should be investigated. The purpose is to learn about the difficulties, e.g. crackformation during thermal treatment. A better understanding of the complete process of the generation of micro structured ceramic layers by direct UV-lithography of metal organic sols is sought. In a second step it is planned to expand the available materials of this process to tunable dielectrics like lead-strontium-titanate and barium-strontium-titanate. Finally the generation of simple electronic components, e.g. varactors or transistors, should show the suitability of the developed process to generate micro structured thin films for applications in microsystem engineering.