Browsing by Subject "RRAM"
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Item Memristor based arithmetic circuit design(2016-12) Revanna, Nagaraja; Swartzlander, Earl E., Jr., 1945-; Valvano, Jonathan; Akinwande, Deji; Gerstlauer, Andreas; Schulte, MichaelThe revolution in electronics enabled by Moore’s Law has been driven historically by the ability to fabricate ever smaller features lithographically on planar semiconductor platforms. In recent years, this has been slowing down due to the myriad of problems in short channel CMOS technologies. Research is now focusing on realizing Moore’s law by architectural innovation, involving novel circuits and computation paradigms. There has been intense interest and activity directed towards designing logic circuits with memory elements. This is mainly driven by ideas like in-memory compute where logic operations are performed at the memory location in order to overcome the memory-wall bottleneck. Resistive-switching random-access memory (RRAM)/ memristors has a great potential to be the future of non-volatile memory owing to its CMOS compatibility, read-write endurance, power and speed. We describe novel high speed logic circuits for adders and multipliers built with RRAM to support the concept of logic-in-memory. These circuits have significant speed/area/power improvements over the existing designs. The complexity involved in computation in terms of controlling the basic gates, sequence of operations etc. has been significantly reduced. RRAM properties are exploited with the help of a well-known analog element called current mirror. Previously known logic-implication technique to realize digital gates comes with a serious limitation of limited fan-out. By using current mirrors, this limitation can be overcome, enabling more logic operations to run in parallel. Results show that the delay for even an XOR operation can be reduced to 1 cycle, compared to the 5 cycles taken by logic implication. Spice simulations are done with known RRAM models. Simulation results show significant improvement in power consumed over the existing designs. The design of different adders and multipliers are also described. Metrics like area, power and latency are compared, and it shows significant improvement over the state-of-the-art.Item Process integration and logic applications of SiOx based resistive memory(2015-12) Zhou, Fei, 1984-; Lee, Jack Chung-Yeung; Banerjee , Sanjay K; Register, Leonard F; Yu, Edward T; Fowler , Burt WFlash memory has been the fastest growing non-volatile memory technology, and it has been widely used in many portable electronic products. Due to its charge based memory mechanism, there are more and more challenges scaling down the flash memory device. Researchers have been looking for new memory materials and novel structures for non-volatile memory devices to replace the conventional floating gate flash. Resistive switching memory stands out from other leading contenders such as phase change memory, magnetic random access memory, and spintronic random access memory. Resistive switching memory has the advantages of non-charge based memory mechanism, simple two-terminal device structure, and fast switching speed. Therefore, it demonstrates great potential for replacing NAND flash and even DRAM to become the next-generation non-volatile memory. A comprehensive investigation on amorphous silicon oxide (SiOx) based resistive memory, starting from fabrication and material analysis, to performance optimization, then to advanced characterization, and finally ending with novel logic circuit applications, have been presented in this dissertation. New device structure and encapsulation process are developed to enable SiOx based resistive memory to operate in air ambient. External resistance effect and substrate optimization have been made to achieve good switching window, low endurance variation. Current sweep technique was used to study the Set process, which simplified multiple resistance level operation of SiOx based resistive memory. Characterization of resistive switching behavior at elevated temperature showed that SiOx resistive material has great potential for high temperature memory applications. Random Telegraph Noise and Energetic Dispersive Spectroscopy provided insights into the physical model of the resistive switching phenomenon. Finally, bidirectional implication scheme using SiOx based resistive memory was proposed and tested, which forms the corner stone of memristor based logic operations. Taking one step further, one bit full adder logic function was theoretically realized on a logic circuit consisting of 4 × 4 crossbar structure resistive memory 1D-1R array and select transistors, the findings show pros and cons of memory enabled logic circuit. In summary, this work presents the optimization and application researches on SiOx based resistive switching memory.Item SiOx-based resistive switching memory integrated in nanopillar structure fabricated by nanosphere lithography(2014-08) Ji, Li, active 21st century; Yu, Edward T.; Ekerdt, John G.A highly compact, one diode-one resistor (1D-1R) SiOx-based resistive switching memory device with nano-pillar architecture has been achieved for the first time using nano-sphere lithography. The average nano-pillar height and diameter are 1.3 μm and 130 nm, respectively. Low-voltage electroforming using DC bias and AC pulse response in the 50ns regime demonstrate good potential for high-speed, low-energy nonvolatile memory. Nano-sphere deposition, oxygen-plasma isolation, and nano-pillar formation by deep-Si-etching are studied and optimized for the 1D-1R configurations. Excellent electrical performance, data retention and the potential for wafer-scale integration are promising for future non-volatile memory applications.