Chemical etching of Tungsten thin films for high-temperature surface acoustic wave-based sensor devices

  • 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 theSurface 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.show moreshow less

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Author: Mario Spindler, Steven HeroldORCiD, Jörg AckerORCiDGND, Erik BrachmannORCiD, Steffen Oswald, Siegfried Menzel, Gerd Rane
URL:http://www.sciencedirect.com/science/article/pii/S004060901630116X
DOI:https://doi.org/10.1016/j.tsf.2016.04.035
Title of the source (English):Thin Solid Films
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2016
Tag:Lift-off structuring; Magnetron sputtering; SAW devices; Tungsten electrodes; Wet-chemical etching
Volume/Year:612
First Page:322
Last Page:326
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Physikalische Chemie
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