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Spin Torque Oscillators for Wireless and Radar Applications

Final Report Summary - SPINAPPS (Spin Torque Oscillators for Wireless and Radar Applications)

Wireless devices generally utilise a classical inductor-capacitor (LC) circuit with on-chip inductors and capacitors. The size and shape of the inductor typically defines the characteristics of the oscillator. As a consequence, its size cannot be scaled down with its surrounding microelectronic devices (e.g. transistors). The inductor is thus a bottleneck for further miniaturisation. The core technology of the SPINAPPS project is a novel inductor-free oscillator technology, the so-called spin torque oscillator (STO). However, this novel technology also has its challenges. The output power is still below the necessary requirements and both frequency stability (phase noise) and frequency control need to be better addressed.

SPINAPPS brought together a French mmall and medium enterprise (SME), SpinRoc SAS, and a world leading research institution, The Royal Institute of Technology (KTH). Both partners are active in the research and development of STOs. The goal of SPINAPPS was to transfer both vital scientific / technical knowledge and market-driven business needs. The project seconded people between Sweden and France and between the academic and industrial sectors.

The project has now ended and successfully completed all its work packages (WPs) and milestones. Highlights include the following:

- The realisation of a Cadence based simulation environment where STO circuits can be simulated with active and passive devices in any semiconductor technology that Cadence can support. The impact on STOs of known semiconductor noise and temperature dependence can hence be investigated and novel circuit solutions can be tried out for enhanced STO performance.
- A thorough analysis of which application spaces the STO has the most potential for and in which emerging ultra-high frequency ranges it might do particularly well.
- The development and optimisation of a highly robust nano-contact STO process on 4'' Si wafers.
- Demonstration of single and synchronised nano-contact STOs, both in-plane magnetised and out-of-plane magnetised devices with different material choices and nano-contact geometries.
- Design of two types of stand-alone STO demonstrators: a first based on MTJ-STOs on a PCB, and a second based on GMR-STOs inside an electromagnet package with substantial frequency tunability using both magnetic field and current.

The obtained results have been extremely valuable to the competitiveness of the consortium partners and has had a profound impact on their ongoing and future activity within this research field and technology area. The results are also expected to serve as an inspiration well outside the consortium. Both partners have benefited from the other partner's network and have been able to established new contacts both in France and in Sweden.