Micro-fabrication / integration / test of BST based varactors for 5G antenna

GREMAN is a research laboratory of the University of Tours, CNRS and INSA Centre Val de Loire focusing on materials, devices and systems for the conversion and management of electrical energy with a main objective of improving energy efficiency.
Thanks to the skills of its four teams which cover materials sciences (physics and solid-state chemistry) and engineering sciences (microelectronic, acoustic, electrical engineering), activities start from the synthesis of new materials with remarkable properties until the development of components and devices, and their integration into electrical systems.

The applications relate to new microelectronic devices, transducers and ultrasonic systems, electrical energy conversion systems.
These research activities include fundamental studies using simulation tools and models developed within the laboratory. They also rely on several technological platforms, particularly on CERTeM (R&D center for microelectronics) for manufacturing and multi-physical and multi-scale characterization.

The objective of the BePolar project is to develop and optimise BST (Ba1-xSrxTiO3) based ferroelectric varactors, i.e. tunable capacitors relying on the electric field dependence of BST’s permittivity, to meet the requirement of 5G and NFC technologies. BST varactors are currently being used in 4G mobile phone applications. Going to 5G or NFC applications requires to work at higher frequency (>2 GHz) or reduced driving voltage (3V instead of 24V). To do so, the thickness of the ferroelectric layer needs to be reduced in order to push the piezoelectric resonance to higher frequencies or maintain the electrical field amplitude respectively. However, this reduction of thickness leads to an increase of the leakage current and a decrease of the tunability, both of them are unacceptable to keep reliability and usability of the component. The strategy of the BePolar project is to introduce an additional nanometric control layer between the electrodes and the BST ferroelectric material to tune the Schottky Barrier Height and reduce the interfacial ferroelectric dead layer, responsible of the decrease of the varactor performances. The development of the control layer has been done and stack optimisation is currently being fine-tuned. We are now seeking a Postdoc scientist to micro-fabricate varactor components using this refined stack in order to evaluate their performances once integrated into a prototype 5G antenna.
During this postdoc position, you mission will be :

- Micro-fabrication of the BST based varactor following an already optimised process and the initial layout used for commercial 4G varactors applications

- Optimisation of the layout to meet the antenna requirements in collaboration with Jaybeam wireless

- Participate to the prototype 5G antenna evaluation conducted by Jaybeam wireless

All the equipment required for this project are available at CERTeM technological platform (http://certem.univ-tours.fr), which is a fully equipped clean room facility and an electrical/physical characterization laboratory, hosted by STMicroelectronics Tours.

You will have a PhD in Microelectronics, or material science & engineering

You have a good knowledge of fabrication process commonly used in microelectronics (photolithography, sputtering, e-beam evaporation, ...) and in structural characterization (MEB, XRD...).

An experience in electrical engineering and high frequency measurement would be particularly welcome.

Micro-fabrication of the BST based varactor following an already optimised process and the initial layout used for commercial 4G varactors applications

Optimisation of the layout to meet the antenna requirements in collaboration with Jaybeam wireless

Participate to the prototype 5G antenna evaluation conducted by Jaybeam wireless