Resistive Random Access Memory (RRAM) is considered as the most promising candidate for the next-generation nonvolatile memories due to their superior properties such as low operation voltage, fast operation speed, non-destructive read, simple metal-insulator-metal (MIM) sandwich structure, good scale-down ability. The main targets of this research are to clarify the corresponding physical mechanism, develop the potential material and structure of RRAM and stabilize the resistive switching characteristics, in which clarifying the physical mechanism will be the key factor for RRAM into production in the future. Recent research has suggested that variation of the low and high resistance states in RRAM could be caused due to the by instability in the formation and /disruption of the filament. In addition, the endurance and stability of RRAM may be related to the dissipation of oxygen ions in the switching layer. In this study, new material (Si Introduced) and structure (oxygen confined layer) are employed to improve RRAM performance and to clarify the physical mechanism. Furthermore, constant switching energy results can be used to select the optimal materials and structures also can be used to correctly allocate voltage and time to control RRAM. The detail physical mechanism is studied by the stable RRAM device (Ti/HfO2/TiN) which is offered from Industrial Technology Research Institute (ITRI). The switching process is proved as the formation/disruption of the filament. Furthermore, the dynamic switching behaviors during reset procedure in RRAM were analyzed by the sequential experimental design to illustrate the procedure of atomic quantized reaction at the ultra-cryogenic temperature.

In first part, the supercritical CO2 (SCCO2) fluid technology is employed to improve the device properties of ZnO TFT. The SCCO2 fluid exhibits liquid-like property, which has excellent transport ability. Furthermore, the SCCO2 fluid has gas-like and high-pressure properties to diffuse into the nanoscale structures without damage. Hence, the SCCO2 fluid can carry the H2O molecule effectively into the ZnO films at low temperature and passivate traps by H2O molecule at low temperature. The experimental results show that the on current, sub-threshold slope, and threshold voltage of the device were improved significantly. Next, the electrical degradation behaviors and mechanisms under drain bias stress of a-IGZO TFTs were investigated. A current crowding effect and an obvious capacitance-voltage stretch-out were observed after stress. During the drain-bias stress, the oxygen would be absorbed on the back channel near the drain region of IGZO film. Therefore, the carrier transport is impeded by the additional energy barrier near drain region induced by the adsorbed oxygen, which forms a depletion layer to generate the parasitism resistance. We also investigated the RRAM device based on IGZO film, and proposed the related physical mechanism models. The IGZO RRAM will be very promising for integration with IGZO TFTs for advanced system-on-panel display applications to be a transparent embedded system. In this part, the transparent RRAM device with ITO/IGZO/ITO structure was fabricated. The proposed device presents an excellent bipolar resistive switching characteristic and good reliability. The bipolar switching mechanism of our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path. The influence of electrode material on resistance switching characteristic is investigated through Pt/IGZO/TiN and Ti/IGZO/TiN structure. As the bias applied on the Ti or TiN, the Ti or TiN electrode can play the role of oxygen reservoir to absorb/discharge oxygen ions. Therefore, the device presents a bipolar resistive switching characteristic. However, as the bias applied on the Pt electrode, the device presents a unipolar resistive switching characteristic. Because the Pt electrode can¡¦t store the oxygen ion, the device should use the joule heating mode to rupture the conduction path and present the unipolar resistive switching characteristic. Finally, the resistive switching properties of IGZO film deposited at different oxygen content were investigated, since the resistance switching behaviors are related to the formation and rupture of filaments composed of oxygen vacancies in the IGZO matrix. Experiment results show that the HRS current decreases when the oxygen partial pressure gradually increases. Based on the XPS analysis, these phenomena are related to the non-lattice oxygen concentration. With increasing oxygen ratio, the filaments will rupture completely through the abundant non-lattice oxygen inducing oxidation, which leads to HRS current decrease and an increase in the memory window.

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As the semiconductor industry grapples with escalating scaling challenges associated with the floating gate MOSFET, alternative memory technologies like Resistive Random Access Memory (ReRAM) are gaining prominence in the scientific community. Boasting a straightforward device structure, ease of fabrication, and compatibility with CMOS (Complementary Metal-oxide Semiconductor) Back-end of Line (BEOL), ReRAM stands as a leading candi- date for the next generation of non-volatile memory (NVM). ReRAM devices feature nanoionics-based filamentary switching, outperforming flash memory in terms of power consumption, scalability, retention, ON/OFF ratio, and endurance. Furthermore, integrating ReRAMs within the CMOS BEOL/low-k Cu interconnect system not only reduces latency between the connectivity constraints of logic and memory modules but also minimizes the chip footprint. However, investigations have revealed a significant concern surrounding ReRAMs—specifically, their electro-thermal reliability. This research provides evidence highlighting the critical influence of material properties, deposition effects, and thermal transport on the device's performance and reliability. Various material systems have undergone in this work scrutiny to comprehend the impact of intrinsic material properties such as thermal conductivity, specific heat capacity, thermal diffusivity, and deposition effects like surface roughness on the electroforming voltages of ReRAM devices. The reference device structure considered in this work is Cu/TaOx/Pt, which has been compared with alternative configurations involving metals like Ru and Co as potential substitutes for Pt. Additionally, a new vehicle has been introduced to quantify cell degradation resulting from thermal cross-talk in crossbar Resistive Random Access Memory (ReRAM) arrays. Furthermore, a novel methodology has been presented to predict cell degradation due to remote heating, taking into account the cell's location, the material properties of the device, and geometry of its electrodes. The experimental results presented in this study showcase filament rupture caused by remote heating, along with spontaneous filament restoration ensuing from the subsequent cooling of the ReRAM cell. / Doctor of Philosophy / As the demand for compact, high-speed logic-memory modules continues to surge, the diminishing silicon real estate in our gadgets poses a challenge in extending Moore's law to meet the scaling needs of the semiconductor device industry. To tackle this challenge, emerging memory technologies like Resistive Random Access Memory (ReRAM) are positioned as promising successors to flash memory. ReRAM devices offer distinct advantages over flash memory, showcasing superior power consumption, scalability, long retention, a high ON/OFF ratio, and good endurance. Their compatibility with current CMOS (Complementary Metal-oxide Semiconductor) technology facilitates seamless integration. However, a significant concern associated with ReRAMs is their electro-thermal reliability. This research delves into how material properties comprising a ReRAM device and fabrication factors, such as the surface roughness of the material, can impact the electrical and thermal reliability of a ReRAM cell. In this context, a novel methodology has been introduced to predict cell degradation within ReRAM crossbar arrays induced by thermal cross-talk, considering material properties and the geometry of the device. The new methodology has been thoroughly verified on manufactured ReRAM arrays with various composite electrodes. The study also presents experimental results demonstrating the rupture of cell filaments due to remote heating, along with instances of spontaneous filament restoration due to subsequent cooling.

With CMOS technology scaling reaching its limitations rigorous research of alternate and competent technologies is paramount to push the boundaries of computing. Spintronic and resistive memories have proven to be effective alternatives in terms of area, power and performance to CMOS because of their non-volatility, ability for logic computing and easy integration with CMOS. However, deeper investigations to understand their physical phenomenon and improve their properties such as writability, stability, reliability, endurance, uniformity with minimal device-device variations is necessary for deployment as memories in commercial applications. Application of these technologies beyond memory and logic are investigated in this thesis i.e. for security of integrated circuits and systems and special purpose memories. We proposed a spintonic based special purpose memory for search applications, present design analysis and techniques to improve the performance for larger word lengths upto 256 bits. Salient characteristics of RRAM is studied and exploited in the design of widely accepted hardware security primitives such as Physically Unclonable Function (PUF) and True Random Number Generators (TRNG). Vulnerability of these circuits to adversary attacks and countermeasures are proposed. Proposed PUF can be implemented within 1T-1R conventional memory architecture which offers area advantages compared to RRAM memory and cross bar array PUFs with huge number of challenge response pairs. Potential application of proposed strong arbiter PUF in the Internet of things is proposed and performance is evaluated theoretically with valid assumptions on the maturity of RRAM technology. Proposed TRNG effectively utilizes the random telegraph noise in RRAM current to generate random bit stream. TRNG is evaluated for sufficient randomness in the random bit stream generated. Vulnerability and countermeasures to adversary attacks are also studied. Finally, in thesis we investigated and extended the application of emerging non-volatile memory technologies for search and security in integrated circuits and systems.

The promising role resistive random-access memory (RRAM) plays in the imminent reality of wearable electronics calls for a new, updated physical model of their operating mechanism. Their high applicability as the next-generation flexible non-volatile memory (NVM) devices has promoted the recent emergence of a novel ultra-thin (< 5nm) organic/inorganic hybrid dielectric RRAM. A deep understanding of their resistive switching (RS) behavior is required to unlock their suitability in future electronics applications. However, the extremely reduced thicknesses bring about new challenges in terms of material characterization sample processing, while the RS observations through electrical characterization techniques lack uniformity in the key switching parameters, thus hindering the identification of any clear trends.  This work studies the RS mechanism in ultra-thin Al/Hf-hybrid/Ni RRAM devices through uniformity-improved electrical observations. First, the focus is to implement a ramped-pulse train method during the reset process to reduce the dispersion of the voltage and resistance fluctuations at different starting voltage amplitudes and pulse widths. After finding the optimal electrical programming conditions for reduced parameter dispersions, a temperature test was performed to study the contributions of the metal ions and oxygen vacancies (V2+) in the switching layer. Finally, a physical model describing the operating mechanism in flexible RRAM is proposed after the close observation and study of the processed devices. The model is based on the coexistence of a hetero-metallic portion composed of Al and Hf3Al2, and a V2+ portion connected to form the hybrid conducting filament (CF) and turning the device on. The CF forming processes emphasize the strong presence of these vacancies partaking in RS, as the temperature dependence results suggest the majority of their concentration to be generated during this step. Also, the different electrical potential, temperature, and concentration gradients influencing the V2+ migration during RS may explain some of the failure mechanisms in the rupture and the re-forming of the filament. Additionally, the possible presence of a thin Al-oxide layer in the Al/Hf-hybrid interface may give a reason for leaky on-states. A detailed physical model of the RS mechanism in next-generation flexible RRAMs is key to learn to unlock a range of emerging technologies fitted to today’s needs. / Den senaste introduktionen av ultratunn (<5 nm) organisk-oorganisk hybrid dielektrisk RRAM som nästa generations icke-flyktiga minnesenheter kräver en djup förståelse för hybridskiktresistiv växling (RS). Den extremt reducerade tjockleken hindrar emellertid deras bearbetbarhet för materialkarakteriseringstekniker. Dessutom hindrar den dåliga enhetligheten i viktiga omkopplingsparametrar fortfarande i RRAM att alla trender kan definieras tydligt genom elektrisk karakterisering. Detta arbete använder elektrisk manipulation genom en RPS-metod (ramped-pulse series) för att förbättra spännings- och motståndsfluktuationerna i återställningsprocessen för ultratunna Al/Hf-hybrid/Ni-enheter vid olika spänningsamplitud, pulsbredd och temperaturförhållanden. Från de erhållna RPS-optimerade resultaten föreslås en ny och detaljerad fysisk modell som beskriver driftsmekanismen. Samexistensen i den ledande filamenten (CF) av en hybridmetalldel, sammansatt av Al och Hf3Al2, och en syrevakansdel bekräftas. Vår modell betonar vakansbidraget i RS, där majoriteten genereras under CF-formningsprocessen och deltar i olika grad i filamentbrottet för RPS och ingen RPS-bearbetade enheter via Joule-uppvärmning, drift och Fick-krafter. Dessutom förklaras kopplingsfelhändelser baserat på närvaron av ett Al2O3-lager i Al/Hf-hybridgränssnittet.