Characteristics of Resistive Switching in Strontium Zirconate Based Memory Devices
2007
Hochschulschrift
Zugriff:
95
Due to the popularity of portable equipment, such as mobile phone and MP3 player, the requirements of nonvolatile memory (NVM) increase significantly in the semiconductor industry. The mainstream of NVM nowadays is the Flash memory; however, the Flash memory has some issues such as high operation voltage, low operation speed, and poor retention time and coupling interference effect during the memory scaling down. Therefore, some new-type Flash memories, such as charge-trapping (SONOS) Flash and band-engineered SONOS Flash are studied to replace the traditional Flash memory. Besides, researchers are eagerly finding one kind of next-generation NVM possessing the advantages of high density, high speed, and nonvolatility of DRAM, SRAM, and Flash memory, respectively. One of the promising candidates of next-generation NVMs is the resistive random access memory (RRAM) owing to its low operation voltage and power, high operation speed, high scalability, good endurance, small size, etc. Resistive switching properties have been observed in many kinds of materials, such as doped SrZrO3 (SZO) and doped SrTiO3, transition metal oxides, Pr1-XCaXMnO3 and La1-XCaXMnO3, and organic and polymer materials. In this dissertation, the resistive switching properties and mechanisms of the SZO-based memory devices are studied in depth. In this dissertation, Chapter 1 introduces the memories, especially for the RRAM. Chapter 2 shows the experimental procedures of the devices indicated in this dissertation. Chapter 3 presents the properties of the SZO-based memory devices with LaNiO3¬¬ (LNO) bottom electrode and Al top electrode (Al/SZO/LNO, ERE devices), which have bipolar resistive switching characteristics. The doping effects of the SZO-based ERE devices are investigated, indicating that a proper concentration of doping into the SZO film can improve the resistive switching properties, such as resistance ratio and stability. The resistance ratio between high resistance state (HRS) and low resistance state (LRS) of the 0.3%-V:SZO ERE device is over 104, and retains 1000 after applying 100 voltage sweeping cycles. This device has stable resistive switching properties even when the measurement is performed at 100oC. The retention time of the device is longer than 107s, and the nondestructive readout property of the device is also examined. Chapter 4 presents the properties of the SZO-based memory devices with Pt bottom electrode, LNO buffer layer, and Al top electrode (Al/SZO/LNO/Pt, ERBE devices), which possess nonpolar resistive switching characteristics. The nonpolar switching is considered as an intrinsic property of the SZO-based memory devices, while the electrode materials employed in the devices would determined the resistive switching polarities. The operation voltages of the 0.3%-V:SZO ERBE device are less than 7V, and the resistance ratio of the device is higher than 107. This device with Pt bottom electrode has lower resistive switching voltages and higher resistance ratio comparison with the 0.3%-V:SZO ERE device with LNO bottom electrode. The resistive switching speed of the 0.3%-V:SZO ERBE device is 10ns, which is the fastest speed in comparison with that of the previous reports. The device has stable resistive switching properties even when the measurement is performed at 150oC. The nondestructive readout property of the device is also demonstrated, and the retention time of the device is longer than 107s. The resistive switching mechanism of the SZO-based memory devices are considered as the formation and disruption of the current paths, which possibly attributed to the storage and release of electrons in the trap states of the SZO film. The conduction mechanisms of both LRS and HRS currents of the SZO-based memory devices are dominated by Ohmic conduction and Frenkel-Poole emission, respectively. Consequently, the SZO-based memory device with good resistive switching characteristics including low operation voltage, low power consumption, high operation speed, long retention time, nondestructive readout, and simple structure is a promising candidate for next-generation NVM applications. Finally, the experimental results and discussion are summarized in chapter 5. Some suggestions for future work are also provided in this chapter.
Titel: |
Characteristics of Resistive Switching in Strontium Zirconate Based Memory Devices
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Autor/in / Beteiligte Person: | Lin, Chun-Chieh ; 林群傑 |
Link: | |
Veröffentlichung: | 2007 |
Medientyp: | Hochschulschrift |
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