@misc{SpindlerHeroldAckeretal., author = {Spindler, Mario and Herold, Steven and Acker, J{\"o}rg and Brachmann, Erik and Oswald, Steffen and Menzel, Siegfried and Rane, Gerd}, title = {Chemical etching of Tungsten thin films for high-temperature surface acoustic wave-based sensor devices}, series = {Thin Solid Films}, volume = {612}, journal = {Thin Solid Films}, doi = {10.1016/j.tsf.2016.04.035}, pages = {322 -- 326}, abstract = {Surface acoustic wave devices are widely used as wireless sensors in different application fields. Recent developments aimed to utilize those devices as temperature sensors even in the high temperature range (T > N 300 degrees C) and in harsh environmental conditions. Therefore, conventional materials, which are used for the substrate and for the interdigital transducer finger electrodes such as multilayers or alloys based on Al or Cu have to be exchanged by materials, which fulfill some important criteria regarding temperature related effects. Electron beam evaporation as a standard fabrication method is not well applicable for depositing high temperature stable electrode materials because of their very high melting points. Magnetron sputtering is an alternative deposition process but is also not applicable for lift-off structuring without any further improvement of the structuring process. Due to a relatively high Ar gas pressure of about 10(-1) Pa, the sidewalls of the photoresist line structures are also covered by the metallization, which subsequently prevents a successful lift-off process. In this study, we investigate the chemical etching of thin tungsten films as an intermediate step between magnetron sputtering deposition of thin tungsten finger electrodes and the lift-off process to remove sidewall covering for a successful patterning process of interdigital transducers.}, language = {en} } @misc{BrachmannSeifertNeumannetal., author = {Brachmann, Erik and Seifert, Marietta and Neumann, Niels and Alshwawreh, Nidal and Uhlemann, Margitta and Menzel, Siegfried and Acker, J{\"o}rg and Herold, Steven and Hoffmann, Volker and Gemming, Thomas}, title = {Electroless-Deposited Platinum Antennas for Wireless Surface Acoustic Wave Sensors}, series = {Materials}, volume = {12}, journal = {Materials}, number = {7}, issn = {1996-1944}, doi = {10.3390/ma12071002}, pages = {1002 -- 1014}, abstract = {In an effort to develop a cost-efficient technology for wireless high-temperature surface acoustic wave sensors, this study presents an evaluation of a combined method that integrates physical vapor deposition with electroless deposition for the fabrication of platinum-based planar antennas. The proposed manufacturing process becomes attractive for narrow, thick, and sparse metallizations for antennas in the MHz to GHz frequency range. In detail, narrow platinum-based lines of a width down to 40 μm were electroless-deposited on γ-Al2O3 substrates using different seed layers. At first, the electrolyte chemistry was optimized to obtain the highest deposition rate. Films with various thickness were prepared and the electrical resistivity, microstructure, and chemical composition in the as-prepared state and after annealing at temperatures up to 1100 ∘C were evaluated. Using these material parameters, the antenna was simulated with an electromagnetic full-wave simulation tool and then fabricated. The electrical parameters, including the S-parameters of the antenna, were measured. The agreement between the simulated and the realized antenna is then discussed.}, language = {en} }