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Memristive Devices: Fabrication, Modeling, and Electrical Characterization of HfOx Devices
By:
Prajwal Prakash
M.Sc. student under the supervision of Prof. Arie Ruzin
Abstract
Nonvolatile memory, particularly memristor-based nonvolatile memory, holds great potential for advancing computer technology. There is stiff competition among leading research groups to develop alternatives to DRAM (Dynamic Random Access Memory) and NAND Flash. According to the semiconductor industry, the newly developed memory technology with memristor will be faster, denser, and more durable than existing memory.
This research addresses fundamental scientific and practical technological aspects in developing metal-oxide-metal devices for nonvolatile memory applications. The objective is to gain a comprehensive understanding of the switching mechanisms in these devices, particularly the filamentary nature of the switching process. The assumption is that the switching is controlled by the creation and destruction of conductive channels, which will be verified under different electrical conditions. In the technological aspect of creating dense memory, the crossbar architecture is the most promising. Devices using this type of architecture must have a high level of nonlinearity in their current-voltage characteristics.
This work, HfO2 thin films were synthesized, and their memristive behavior is seen through the ON/OFF states in a switching cycle. Key contributions include controlled synthesis of hafnium oxide, fabrication of Ti/Pt/HfO2/Au memristor using novel architectures (single device or stand-alone element and crossbar arrays), and its electrical characterization. In this work, various fabrication procedures were implemented to fabricate arrays of memristors on a chip. The memristive characteristics were studied for HfOx-based memristors. Two different-sized devices, 10×10 µm2 and 100×100 µm2 (denoted as CB10 and CB100, respectively), were fabricated using magnetron sputtering. The primary objective is to develop a characterization methodology that optimizes the measurement parameters for achieving moderate to high ON/OFF ratios and bipolar switching in all the fabricated memristor devices. A physical model based on experimental results will also be developed to better understand the device’s behavior. The research also aims to examine the influence of current compliance on the electroforming process and device-switching mechanisms. Bipolar memristive characteristics were obtained and were consistent with the combined electric field and temperature-dependent oxygen migration in the filament formation mechanism. The contact geometry is shown to play an important role in the device characteristics. The devices exhibited moderate to high ON/OFF ratios, retention, and endurance.
This research provides insights into the electroforming process and electrical characterization of the HfOx-based memristors. It enables the fabrication of reliable devices with controlled electroforming behavior to explore new possibilities and expand their practical implementation in various fields.
