Towards memristor-based cryogenic control electronics for solid-state quantum systems

Significance 

A quantum device can be defined as a device whose functionality or principle of operation depends essentially on quantum mechanical effects. Quantum devices are inescapable nowadays, primarily to satiate the ever-increasing appetite for slimmer gadgets. As such, the ever-increasing improvement of nanofabrication processes has led to promising demonstration of high-quality solid-state quantum devices functioning at sub-Kelvin temperatures. In particular, efforts are currently focused towards the development of silicon-based quantum systems that could be operated above 1 K. Such progress has paved way for the realization of truly scalable quantum bit architectures leveraging mature complementary metal-oxide-semiconductor (CMOS) technologies. However, current classical electronic tools and rack-scale instruments used to control few-qubit systems from outside the cryostat cause major scalability, automation and performance issues hindering the fabrication of full-scale quantum computers. Overcoming these pitfalls therefore requires fully integrated cryogenic quantum–classical interfaces able to control qubits from inside refrigerators. Literature has it that such an interface would be composed of CMOS-based digital and analog electronics, enabling mixed-signal control systems. In that scope, non-volatile cryogenic memory technologies hold a key role to store data related to qubit states and error correction algorithms. To this end, standard dynamic random-access memory-based cryogenic systems have been investigated at 77 K; nonetheless, it has been hypothesized that emerging nanoscale resistive memory devices with better scalability could play a key role to enable largescale quantum systems.

Generally, non-volatile resistive switching devices are considered as prime candidates for next-generation memory applications operating at room temperature and above, such as resistive random-access memories or brain-inspired in-memory computing. However, their operability in cryogenic conditions remains to be mastered to adopt these devices as building blocks enabling large-scale quantum technologies via quantum–classical electronics co-integration. To address this, University of Sherbrooke researchers: Pr. Yann Beilliard, Dr. François Paquette, Dr. Frederic Brousseau, Pr. Serge Ecoffey, Pr. Fabien Alibart and Pr. Dominique Drouin investigated multilevel resistive switching of TiN/Al2O3/TiO2-x/Ti/TiN memory devices conducted at 1.5 K. Their work is currently published in the research journal IOP Nanotechnology.

In their approach, full switching cycles were first performed between 300 and 1.5 K, revealing metal-insulator transition-induced negative differential resistance effects below 110 K. Analysis of the current-voltage (I–V) curves was then conducted for the multilevel SET and RESET processes, showing that space-charge limited current and trap-assisted tunneling to be dominant for specific field ranges and resistance states.

The research team reported the carrier transport analysis of all multilevel switching I–V curves showed that while the insulating regime follows the space charge limited current (SCLC) model for all resistance states, the conduction in the metallic regime was dominated by SCLC and trap-assisted tunneling for low- and high-resistance states respectively. Moreover, a non-monotonic conductance evolution was observed in the insulating regime, as opposed to the continuous and gradual conductance increase and decrease obtained in the metallic regime during the multilevel SET and RESET operations. The research team suggest the non-monotonic conductance evolution in the insulating regime was due to the combined effects of longitudinal and radial variations of the Ti4O7 conductive filament during the DC switching. This behavior could be the result of the interplay between temperature- and field-dependent geometrical and physical evolution of the filament.

In summary, the study reported on successful multilevel resistive switching of CMOS compatible TiN/Al2O3/TiO2-x/Ti/TiN memory devices at 1.5 K, exhibiting a Joule-heating-induced MIT at a critical ambient temperature of 110 K. Remarkably, the conductance increase/decrease in the metallic regime was seen to be continuous and gradual, contrary to the insulating regime characterized by a non-monotonic conductance evolution. In a statement to Advances in Engineering, Professor Yann Beilliard explained that their findings not only bring a new light on the resistive switching mechanisms of TiO2-based memory devices, but also pave the way towards memristor-based cryogenic electronics dedicated to control solid-state quantum systems.

Conductive filament evolution dynamics revealed by cryogenic (1.5 K) multilevel switching of CMOS-compatible Al2O3/TiO2 resistive memories - Advances in Engineering

About the author

Yann Beilliard is an Adjunct Professor in the Department of Electrical and Computer Engineering at the Interdisciplinary Institute for Technological Innovation (3IT) of Université de Sherbrooke (QC, Canada). He received his PhD in microelectronics in 2015 from Université Grenoble Alpes (France), in collaboration with STMicroelectronics, CEA Leti and SIMaP laboratory. He joined 3IT in 2015 to work on advanced packaging and integration technologies for high-performance computing. Since 2017, his main research interests are focused on developing emerging memory devices and neuromorphic hardware for energy-efficient machine learning and bio-inspired computing applications.

About the author

Serge Ecoffey received the Master’s degree in material science and the PhD degree in electrical engineering from the Swiss Federal Institute of Technology Lausanne. Since 2009, he has been with the Université de Sherbrooke where he became an Adjunct Professor in 2012. He was a member of the Process and Manufacturing Technology and Advanced Logic Technology sub-committees of the IEDM International Electron Devices Meeting. His research focuses on microfabrication, process integration, electron devices, MEMS and the development of chemical mechanical planarization processes.

About the author

Prof. Dominique Drouin is a holder of NSERC/IBM Industrial Research Chair on High-Performance Heterogeneous Integration and Professor at the Department of Electrical and Computer Engineering of the Université de Sherbrooke since 1999. He received his electrical engineering degree in 1994 and his PhD in mechanical engineering in 1998. He has expertise in the fields of nanoelectronics devices and advanced packaging.

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Reference

Yann Beilliard, François Paquette, Frederic Brousseau, Serge Ecoffey, Fabien Alibart, Dominique Drouin. Conductive filament evolution dynamics revealed by cryogenic (1.5 K) multilevel switching of CMOS-compatible Al2O3/TiO2 resistive memories. Nanotechnology: volume 31 (2020) 445205.

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