Description of the high-temperature RF characterization setup. (a) An orange colored langasite device about to be bounded to the chip carrier. (b) A chip carrier just placed inside the Nb block. The flat spring on the left bends it slightly upwards. The orange colored langasite device can be seen on top of the carrier, as the platinum foil strips around the carrier and the platinum plated inner tip of the RF cable. (c), (d) Respectively, top and cross-section views of one set of RF cables pair ended with a Nb hull containing the chip carrier The lid is now closed, pushing the chip carrier down to ensure electrical contact with the RFcables. (e), (f) Views of the setup showing the four sets of RF cables pair ended with a Nb hull. (g) An overview of the complete high-temperature RF characterization setup.
(a) Rocking curve for the (002) plans in the optimized AlN films. (b) Selected area electronic diffraction (SAED) pattern of the optimized AlN films. (c) 3D AFM image of the optimized AlN films. (d) Frequency response (S21 magnitude) of a SAW delay line based on optimized AlN/sapphire structure and Ir IDTs with 14 μm periodicity.
Frequency-temperature law (grey diamonds) and IL evolution (blue triangles) of Ir/AlN/sapphire SAW delay lines during the 15 h-long heating between 20 °C and 1050 °C. IL values are given relatively to their level at room temperature. Operating frequencies and IL values were obtained from time-gated S21 measurements.
Raw frequency responses (S21 magnitude) of an Ir/AlN/sapphire SAW delay line obtained at different temperatures: 25 °C, 535 °C, 908 °C, 1050 °C and after 50 h at this last temperature.
Evolution with time of operating frequency (grey diamonds) as well as IL (blue triangles) during the final plateau at 1050 °C. Black and blue dashed curves are exponential decay fitting curves of the operating frequency and IL evolution, respectively. Operating frequencies and IL values were obtained from time-gated S21 measurements.
Secondary electron SEM images of an Ir/AlN/Sapphire SAW device after the experiment: (a) tilted view, (b) plan view. The white arrows indicate the position of one finger electrode on each image for a better understanding.
Relative atomic compositions of the substrate before and after theexperiment, determined by EDXS with 5 keV-electrons and 20 keV-electrons.
(a) and (b) Cross-sectional TEM images of the device after the experiment. On top of the sample is visible the protective layer used to perform FIB cutting. (c) Electronic diffraction pattern of the upper part of the formed oxide overlayer. (d) Electronic diffraction pattern of the inner part of the formed oxide overlayer and the highly textured AlN layer.
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