Study On Performance And Mechanism Of Hgafium - Based Impedance Memory

In the non-volatile storages’field, with the shrinking of the technology node of the integrated circuit, the traditional Flash memory which is the mainstream of the storage market encounters a series of problems that are difficult to overcome, leading to it’s application faced a serious challenges. Therefore, the next generation of nonvolatile memories began to enter into the research areas, including Ferroelectric Memory (FeRAM), Phase Change Memory (PCM), Magnetic Memory (MRAM) and Resistive Memory (RRAM), and obtained a rapid development.In these all new non-volatile memories, RRAM is considered as the most promising candidate in next generation of "common" memory, because it’s simple structure, fast writing and reading speed, long retention times, high storage density, low voltage operation, the nondestructive read operation, the strong ability of scaling down, narrow and low power consumption and excellent compatibility with traditional CMOS process, In all the resistive materials, the transition metal oxides have become the most promising candidate because of its low cost, easy preparation, simple composition and stable performance. But, the physical mechanism about the RRAM is not completely clear, so lots of research work still need to be done.Based on atomic layer deposition technology, this thesis studied the hafnium oxidation (HfO2) material resistance from the performance of electrical and material properties, doing a series of researches. First, we introduce the ALD process about its principle, classification and system. Second, according to the RCB model and its simulation for the relationship between the forming and rupture of the filaments and the electric field distribution, we put forward a thin low K/thick high K stack structure to improve the stability of the switching voltages and reduce the switching voltages’ values for the device with a single high K film. When applying the external voltage on the device, the low k/high k structure makes the electronic field distributed in the A12O3film stronger than that in the HfO2film by the Gauss Theorem, as a result, the filament’s forming and rupture behaviors were controlled in the Al2O3film near the anode rather than randomly happened in the whole resistive materials. The experimental results realize our objective. And the comparison between the device with thinner Al2O3film and thicker Al2O3film show the stability of the device’s switching voltages with the thinner low-k Al2O3film is significantly improved, the values of the switching voltages are reduced and the resistance ratio window become larger. Then, to address the influence of nitrogen incorporation into the surface of the resistive switching of HfO2film, we compare the characteristics between the devices with HfO2nitrided and the other one is not nitride. The results show that the device is not resistive after nitridation. And the current leakage characteristics change from SCLC to PF.Finally, this paper summarized the work of the experiments and make the prospect for the research and application of the RRAMs.