3D Integration of Nonvolatile Nanomagnetic Logic
Final Report Abstract
Using the local ion irradiation technique for pNML combined with the 3D geometrical arrangements, directed signal flow and logic operation in monolithically integrated three dimensional computing systems was experimentally demonstrated within this project. A complete monolithic 3D logic family was developed and is now ready for optimization in terms of integration density, operational speed and robustness against variations. In contrast to CMOS microelectronics, pNML does not require signal and supply wiring to each gate, and it has no leakage currents. Furthermore, pNML is non-volatile, and provides an easy way for global clocking, preventing the complex wiring needed in CMOS monolithic integration. Even though computation in the ferromagnetic domain is mainly unidentified in the domain of IC design, the presented results may provide a promising technology platform for future 3D integrated circuits and systems especially when implemented in a co-processor, systolic or reconfigurable architecture. Thus, a disruptive BEOL technology for logic circuits well suited for non-charge based low-power beyond CMOS systems can be provided. Ga ions are an ion species that has been heavily used for direct magnetic patterning. However, the ion dose for fine-tuned anisotropy control in multilayer films, is somewhat extremely small. In our research, about 50 ions at 50 keV are sufficient to create artificial nucleation centers. In contrast, He ions are known to be less invasive. We speculate that the use of He ions would lead to much better control of the nucleation centers in pNML devices. The drawback is, that depth control is more difficult to achieve with He ions. But certainly, light ion irradiation with He ions combined with highest resolution lithography would be a prospective path to follow. During the project we were improving our experimental techniques for submicrosecond switching-distributions. It turned out, that an artificial nucleation center is difficult to fully understand in terms of dynamic effects. There is strong indication, that at very fast rising field-amplitudes, Arrhenius-type models for the underlying distribution come to a limit. Future research has to address second-order effects in ANC magnet reversal and should be able to time-resolve the domain-wall formation and propagation of and ANC and its surrounding. From such investigations, an optimized ANC both in position and geometry could be deduced. As pointed out earlier, for pNML circuits, the underlying distributions are essential. During this project, an optimized sputtering tool was developed and with 5 different target materials fully functional. It turned out, that low anisotropy materials like Co/Ni bilayer stacks are far more susceptible to oxidation during island etching, they are still potential for pNML devices due to larger areal magnetic moment and much higher domain wall speed. Due to the gained flexibility in available sputter materials, further research should address novel material stacks incorporating spin-hall effect sensing and switching devices as well as film compositions showing DMI. This would improve both speed, power consumption and integration density of the devices. CMOS and electronic beyond-CMOS devices are heavily researched. With 3D integrated pNML devices we were able to show, that in principle our devices in the present state are competitive. However, everyone familiar with ultimate-scaleintegration is sceptic of paradigm-changes in digital computation, simply because MOS as electronic switch is such thoroughly understood. As a consequence, we think that other, non-Boolean concepts of computation are also extremely abundant. Magnetic devices are more than attractive for such implementations, as they combine very interesting characteristics like robustness against radiation, bi-stability, scaling potential, room-temperature operation combined with rich high-frequency dynamics.
Publications
- “1-Bit Full Adder in Perpendicular Nanomagnetic Logic using a Novel 5-Input Majority Gate”, EPJ Web of Conferences 75, 05001 (2014)
Breitkreutz, S.; Eichwald, I.; Kiermaier, J.; Papp, A.; Csaba, G.; Niemier, M.; Porod, W.; Schmitt-Landsiedel, D. and Becherer, M.
(See online at https://doi.org/10.1051/epjconf/20147505001) - “Compact modeling of perpendicular nanomagnetic logic based on threshold gates”, Journal of Applied Physics 115(17), 17D104 (2014)
Breitkreutz, S.; Eichwald, I.; Kiermaier, J.; Csaba, G.; Schmitt-Landsiedel, D. and Becherer, M.
(See online at https://doi.org/10.1063/1.4857555) - “Controlled domain wall pinning in nanowires with perpendicular magnetic anisotropy by localized fringing fields”, Journal of Applied Physics 115(17), 17D506 (2014)
Breitkreutz, S.; Eichwald, I.; Kiermaier, J.; Hiblot, G.; Csaba, G.; Porod, W.; Schmitt-Landsiedel, D. and Becherer, M.
(See online at https://doi.org/10.1063/1.4864737) - “Towards on-chip clocking of perpendicular Nanomagnetic Logic”, Solid-State Electronics 102, 46-51 (2014)
Becherer, M.; Kiermaier, J.; Breitkreutz, S.; Eichwald, I.; Ziemys, G.; Csaba, G. and Schmitt-Landsiedel, D.
(See online at https://doi.org/10.1016/j.sse.2014.06.012) - “A monolithic 3D integrated nanomagnetic co-processing unit”, Solid-State Electronics 115, 74-80 (2015)
Becherer, M.; Breitkreutz-v. Gamm, S.; Eichwald, I.; Ziemys, G.; Kiermaier, J.; Csaba, G. and Schmitt-Landsiedel, D.
(See online at https://doi.org/10.1016/j.sse.2015.08.004) - “Time-dependent domain-wall nucleation probability in field-coupled nanomagnets with perpendicular anisotropy”, Journal of Applied Physics 117, 17B503 (2015)
Breitkreutz, S.; Fischer, A.; Silmi, K.; Weigl, S.; Eichwald, I.; Ziemys, G.; Schmitt-Landsiedel, D. & Becherer, M.
(See online at https://doi.org/10.1063/1.4906440) - “Towards nonvolatile magnetic crossbar arrays: a 3D-integrated field-coupled domain wall gate with perpendicular anisotropy”, Journal of Applied Physics 117, 17D507 (2015)
Breitkreutz, S.; Eichwald, I.; Ziemys, G.; Hiblot, G.; Csaba, G.; Schmitt- Landsiedel, D. and Becherer, M.
(See online at https://doi.org/10.1063/1.4913729)
