Project objectives

The main objective of the project consists in the development of the first SAW temperature sensor based on AlN/Si. The sensor will be characterized "on wafer" in the 23 -150 ºC temperature range. Mounted in a special ceramic fixture with cables and SMA connectors the structure will be characterized in a cryostat, in the 5-500 K temperature range The first objective of the project consists in growing high quality AlN/Silicon layers. Thin AlN layers on high- resistivity silicon wafers using RF magnetron sputtering (RF-MS) techniques and will be developed by INCD-FM. Multi-parametric characterization methods will be employed for assessing all the AlN films properties: spectroscopic ellipsometry (SE), X-Ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), pull-out adherence tests, electrical and piezo-electrical measurements and will be developed by both teams (INCD FM and IMT).

The second objective consists in the design and modelling of the AlN/Si based SAW structure . After the solving methodology will be fixed, the optimization strategy will be established (the optimized geometry - number of fingers/ interdigit spacing, number of reflectors and their dimensions - length, width for a maximum Q of the S11 resonance). Due to the prohibitive size of the SAW structures (hundreds of digits having a width around 100 nm and a length in the range of 50 - 200 µm), the computation is extremely intensive. The most advanced technologies of high performance scientific computing (HPC) should be used in order to overcome the computational limitations. Other optimization methods available from software tools will be used (e.g. the ones offered by the optimization toolbox of Matlab which can be linked to the COMSOL Multiphysics simulation) of optimization strategies developed by PUB will be tested (such as the ones based on Particle Swarm Optimization). Finally, the output of this task will be the dependence of the resonant frequency of the AlN sensor with respect to the temperature, as well as its sensitivity.

The third major objective consists in sensor manufacturing and characterization. The major activity will consists in developing of e-beam nano-lithography and metallization for the SAW structures on AlN working in the 6-9 GHz range .It is necessary to manufacture IDTs with fingers and interdigit spacing width in the 80-150 nm range. The"on wafer" characterization of SAW based structures will be performed using the existing equipment (VNA) in IMT labs. Also structures will be characterized on a special test fixture based on a ceramic support with SMA connectors on a hot plate, (in the 23-150 ºC temperature range), oven (23-200) and cryostat (5-500K temperature range) The final objective is the manufacturing of the demonstrator for the temperature sensor based on AlN/Si SAW together with realization of an experimental wired system for data transmission from the sensor. An exploratory study for wireless transmission of the data will be performed.