Performance Enhancement of Large Crossbar Resistive Memories With Complementary and 1D1R-1R1D RRAM Structures

The paper proposes novel solutions to improve the signal and thermal integrity of crossbar arrays of Resistive Random-Access Memories, that are among the most promising technologies for the 3D monolithic integration. These structures suffer from electrothermal issues, due to the heat generated by the power dissipation during the write process. This paper explores novel solutions based on new architectures and materials, for managing the issues related to the voltage drop along the interconnects and to thermal crosstalk between memory cells. The analyzed memristor is the 1 Diode - 1 Resistor memory. The two architectural solutions are given by a reverse architecture and a complementary resistive switching one. Compared to conventional architectures, both of them are also reducing the number of layers where the bias is applied. The electrothermal performance of these new structures is compared to that of the reference one, for a case-study given by a 4 × 4 × 4 array. To this end, a full-3D numerical Multiphysics model is implemented and successfully compared against other models in literature. The possibility of changing the interconnect materials is also analyzed. The results of this performance analysis clearly show the benefits of moving to these novel architectures, together with the choice of new materials

Electro-Thermal Parameters of Graphene Nano-Platelets Films for De-Icing Applications

This paper provides a study of some relevant electro-thermal properties of commercial films made by pressed graphene nano-platelets (GNPs), in view of their use as heating elements in innovative de-icing systems for aerospace applications. The equivalent electrical resistivity and thermal emissivity were studied, by means of models and experimental characterization. Macroscopic strips with a length on the order of tens of centimeters were analyzed, either made by pure GNPs or by composite mixtures of GNPs and a small percentage of polymeric binders. Analytical models are derived and experimentally validated. The thermal response of these graphene films when acting as a heating element is studied and discussed

Signal and Thermal Integrity Analysis of 3-D Stacked Resistive Random Access Memories

In this article, a 3-D electrothermal numerical model is used to perform the signal and thermal integrity analysis of 3-D stacked Resistive-switching random access memory (RRAM) arrays. Two main issues are found: voltage drop along the interconnects and thermal crosstalk between the memory cells. Possible solutions to these issues are here thoroughly investigated, based either on new biasing schemes or new materials. Especially, conventional nickel bars are replaced by interconnects made by copper (Cu) and carbon nanotubes (CNTs), whose electrical and thermal parameters are here described using physically based models. The analysis is performed on a $5 imes 5 imes5$ array, under a real case of a RESET switching, which is the worst case scenario from the electrothermal point of view. Simulation results show that the use of CNTs reduces the voltage drop in both word and bitline (BL) interconnects, thermal crosstalk, and the maximum working temperature; hence, it mitigates many of the crucial issues in the roadmap for the large-scale monolithic 3-D RRAM integration

Thermal and Signal Integrity Analysis of Novel 3D Crossbar Resistive Random Access Memories

The resistive random access memory (RRAM) device is a fundamental building block of novel nonvolatile memories. This paper addresses the design of suitable 3D crossbar structures, in view of their monolithic integration into large memory modules. In fact, a full 3D electro-thermal model is here adopted to simulate and study the thermal and signal integrity of a 1Diode-1Resistor RRAM x-point crossbar structure. These analysis are carried out by considering different RESET biasing schemes and heatsink locations. In addition, two different materials are considered for realizing the contact electrode material wires of the 3D crossbar: Nickel and/or Carbon nanotubes. In particular, we investigate the worst-case scenario in the electro-thermal analysis by comparing the performance results in terms of resistive voltage drop and of temperature distribution. The achieved simulation results demonstrate that the use of carbon interconnects not only provides excellent signal and thermal integrity performances, but also enables the simplest solutions for an effective biasing scheme

Electrothermal analysis of 3D memristive 1D-1RRAM crossbar with carbon nanotube electrodes

Resistive random access memory (RRAM) is a promising candidate for the next generation nonvolatile memory technology. Conventional materials so far used for RRAM technology suffer from a severe issue related to the temperature increase. In this paper, we investigate the possibility of mitigating such a problem by exploiting the excellent properties of novel nanostructured materials, such as the Carbon Nanotubes (CNTs). To this end, a 3D 1Diode-1RRAM crossbar is here analyzed, comparing conventional Ni metal electrodes to novel CNT ones. Accurate temperature-dependent electrical and thermal conductivities are used to simulate the behavior of the materials. An electrothermal analysis performed by means of a full 3D numerical model of such a structure provides the voltage and temperature distributions over the 3D 1D-1RRAM crossbar. The use of CNT electrodes is demonstrated to provide excellent uniformity in the voltage distribution, good electrical current pathways distribution and a temperature reduction more than 300K over the baseline crossbar design