@misc{PerezOssorioDuenasetal., author = {P{\´e}rez, Eduardo and Ossorio, {\´O}scar G. and Due{\~n}as, Salvador and Cast{\´a}n, Helena and Garc{\´i}a, Hector and Wenger, Christian}, title = {Programming Pulse Width Assessment for Reliable and Low-Energy Endurance Performance in Al:HfO2-Based RRAM Arrays}, series = {Electronics (MDPI)}, volume = {9}, journal = {Electronics (MDPI)}, number = {5}, issn = {2079-9292}, doi = {10.3390/electronics9050864}, abstract = {A crucial step in order to achieve fast and low-energy switching operations in resistive random access memory (RRAM) memories is the reduction of the programming pulse width. In this study, the incremental step pulse with verify algorithm (ISPVA) was implemented by using different pulse widths between 10 μ s and 50 ns and assessed on Al-doped HfO 2 4 kbit RRAM memory arrays. The switching stability was assessed by means of an endurance test of 1k cycles. Both conductive levels and voltages needed for switching showed a remarkable good behavior along 1k reset/set cycles regardless the programming pulse width implemented. Nevertheless, the distributions of voltages as well as the amount of energy required to carry out the switching operations were definitely affected by the value of the pulse width. In addition, the data retention was evaluated after the endurance analysis by annealing the RRAM devices at 150 °C along 100 h. Just an almost negligible increase on the rate of degradation of about 1 μ A at the end of the 100 h of annealing was reported between those samples programmed by employing a pulse width of 10 μ s and those employing 50 ns. Finally, an endurance performance of 200k cycles without any degradation was achieved on 128 RRAM devices by using programming pulses of 100 ns width}, language = {en} } @misc{OssorioVinuesaGarciaetal., author = {Ossorio, {\´O}scar G. and Vinuesa, Guillermo and Garcia, Hector and Sahelices, Benjamin and Due{\~n}as, Salvador and Cast{\´a}n, Helena and P{\´e}rez, Eduardo and Mahadevaiah, Mamathamba Kalishettyhalli and Wenger, Christian}, title = {Performance Assessment of Amorphous HfO2-based RRAM Devices for Neuromorphic Applications}, series = {ECS Transactions}, volume = {102}, journal = {ECS Transactions}, number = {2}, issn = {1938-6737}, doi = {10.1149/10202.0029ecst}, pages = {29 -- 35}, abstract = {The use of thin layers of amorphous hafnium oxide has been shown to be suitable for the manufacture of Resistive Random-Access memories (RRAM). These memories are of great interest because of their simple structure and non-volatile character. They are particularly appealing as they are good candidates for substituting flash memories. In this work, the performance of the MIM structure that takes part of a 4 kbit memory array based on 1-transistor-1-resistance (1T1R) cells was studied in terms of control of intermediate states and cycle durability. DC and small signal experiments were carried out in order to fully characterize the devices, which presented excellent multilevel capabilities and resistive-switching behavior.}, language = {en} } @misc{PerezBoschQuesadaMistroniJiaetal., author = {Perez-Bosch Quesada, Emilio and Mistroni, Alberto and Jia, Ruolan and Dorai Swamy Reddy, Keerthi and Reichmann, Felix and Castan, Helena and Due{\~n}as, Salvador and Wenger, Christian and Perez, Eduardo}, title = {Forming and resistive switching of HfO₂-based RRAM devices at cryogenic temperature}, series = {IEEE Electron Device Letters}, volume = {45}, journal = {IEEE Electron Device Letters}, number = {12}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, issn = {0741-3106}, doi = {10.1109/LED.2024.3485873}, pages = {2391 -- 2394}, abstract = {Reliable data storage technologies able to operate at cryogenic temperatures are critical to implement scalable quantum computers and develop deep-space exploration systems, among other applications. Their scarce availability is pushing towards the development of emerging memories that can perform such storage in a non-volatile fashion. Resistive Random-Access Memories (RRAM) have demonstrated their switching capabilities down to 4K. However, their operability at lower temperatures still remain as a challenge. In this work, we demonstrate for the first time the forming and resistive switching capabilities of CMOS-compatible RRAM devices at 1.4K. The HfO2-based devices are deployed following an array of 1-transistor-1-resistor (1T1R) cells. Their switching performance at 1.4K was also tested in the multilevel-cell (MLC) approach, storing up to 4 resistance levels per cell.}, language = {en} } @misc{VinuesaGarciaPerezetal., author = {Vinuesa, Guillermo and Garc{\´i}a, H{\´e}ctor and P{\´e}rez, Eduardo and Wenger, Christian and {\´I}{\~n}iguez de la Torre, Ignacio and Gonz{\´a}lez, Tom{\´a}s and Due{\~n}as, Salvador and Cast{\´a}n, Helena}, title = {On the asymmetry of Resistive Switching Transitions}, series = {Electronics}, volume = {13}, journal = {Electronics}, number = {13}, publisher = {MDPI}, issn = {2079-9292}, doi = {10.3390/electronics13132639}, pages = {11}, abstract = {In this study, the resistive switching phenomena in TiN/Ti/HfO2/Ti metal-insulator-metal stacks is investigated, mainly focusing on the analysis of set and reset transitions. The electrical measurements in a wide temperature range reveal that the switching transitions require less voltage (and thus, less energy) as temperature rises, with the reset process being much more temperature sensitive. The main conduction mechanism in both resistance states is Space-charge-limited Conduction, but the high conductivity state also shows Schottky emission, explaining its temperature dependence. Moreover, the temporal evolution of these transitions reveals clear differences between them, as their current transient response is completely different. While the set is sudden, the reset process development is clearly non-linear, closely resembling a sigmoid function. This asymmetry between switching processes is of extreme importance in the manipulation and control of the multi-level characteristics and has clear implications in the possible applications of resistive switching devices in neuromorphic computing.}, language = {en} } @misc{VinuesaGarciaDuenasetal., author = {Vinuesa, Guillermo and Garcia, Hector and Duenas, Salvador and Castan, Helena and I{\~n}iguez de la Torre, Ignacio and Gonzalez, Tomas and Dorai Swamy Reddy, Keerthi and Uhlmann, Max and Wenger, Christian and Perez, Eduardo}, title = {Effect of the temperature on the performance and dynamic behavior of HfO2-Based Rram Devices}, series = {ECS Meeting Abstracts}, volume = {MA2024-01}, journal = {ECS Meeting Abstracts}, number = {21}, publisher = {The Electrochemical Society}, issn = {2151-2043}, doi = {10.1149/MA2024-01211297mtgabs}, pages = {1297 -- 1297}, abstract = {Over the past decades, the demand for semiconductor memory devices has been steadily increasing, and is currently experiencing an unprecedented boost due to the development and expansion of artificial intelligence. Among emerging high-density non-volatile memories, resistive random-access memory (RRAM) is one of the best recourses for all kind of applications, such as neuromorphic computing or hardware security [1]. Although many materials have been evaluated for RRAM development, some of them with excellent results, HfO2 is one of the established materials in CMOS domain due to its compatibility with standard materials and processes [2]. The main goal of this work is to study the switching capability and stability of HfO2-based RRAMs, as well as to explore their ability in the field of analogue applications, by analyzing the evolution of the resistance states that allow multilevel control. Indeed, analogue operation is a key point for achieving electronic neural synapses in neuromorphic systems, with synaptic weight information encoded in the different resistance states. This research has been carried out over a wide temperature range, between 40 and 340 K, as we are interested in testing the extent to which performance is maintained or modified, with a view to designing neuromorphic circuits that are also suitable in the low-temperature realm. We aim to prove that these simple, fast, high integration density structures can also be used in circuits designed for specific applications, such as aerospace systems. The RRAM devices studied in this work are TiN/Ti/8 nm-HfO2/TiN metal-insulator-metal (MIM) capacitors. Dielectric layers were atomic layer deposited (ALD). It has been demonstrated that the Ti coat in the top electrode acts as a scavenger that absorbs oxygen atoms from the HfO2 layer, and facilitates the creation of conductive filaments of oxygen vacancies [3]. In fact, the oxygen reservoir capability of Ti is well known, as it is able to attract and release oxygen atoms from or to the HfO2 layer during the RRAM operation [4]. The clustering of vacancies extends through the entire thickness of the oxide and, after an electroformig step, it joins the upper and lower electrodes and the device reaches the low resistance state (LRS). By applying adequate electrical signals, the filaments can be partially dissolved, which brings the device into the high-resistance state (HRS), with lower current values. The set process brings the device to the LRS state, while the reset one brings it to the HRS. The dependence of electrical conductivity on external applied electrical excitation allows triggering the device between the both states in a non-volatile manner [5]. The experimental equipment used consisted of a Keithley 4200-SCS semiconductor parameter analyzer and a Lake Shore cryogenic probe station. Fig.1 shows current-voltage cycles measured at different temperatures; the averages values at each temperature, both in logarithmic and linear scale, are also shown. The functional window increases as temperature decreases. The evolutions of set and reset voltage values with temperature are depicted in Fig.2, whereas the current values (measured at 0.1 V) corresponding to the LRS and HRS can be seen in Fig.3. LRS resistance decreases as temperature increases, in agreement with semiconductor behaviour, probably due to a hopping conduction mechanism. Both set and reset voltages decrease as temperature increases; the reset process is smoother at high temperatures. The reduction in reset voltage variability as temperature increases is very notable. Finally, Fig. 4 shows a picture of the transient behaviour; in the right panel of the same figure, the amplitudes of the current transients in the reset state have been included in the external loop. To sum up, the resistive switching phenomena is studied in a wide temperature range. The LRS shows semiconducting behavior with temperature, most likely related to a hopping conduction mechanism. Switching voltages decrease as temperature increases, with a notable reduction in reset voltage variability. An excellent control of intermediate resistance state is shown through current transients at several voltages in the reset process. REFERENCES [1] M. Asif et al., Materials Today Electronics 1, 100004 (2022). [2] S. Slesazeck et al., Nanotechnology 30, 352003 (2019). [3] Z. Fang et al., IEEE Electron Device Letters 35, 9, 912-914 (2014). [4] H. Y. Lee et al., IEEE Electron Device Letters 31, 1, 44-46 (2010). [5] D. J. Wouters et al., Proceedings of the IEEE 103, 8, 1274-1288 (2015). Figure 1}, language = {en} }