| Summary: | 博士 === 國防大學中正理工學院 === 國防科學研究所 === 94 === A solid state memory device based on electrical manipulation of charges for binary data storage is one of the most convenient methods for recording information and storing data. Due to the advantage of fast erasing method, operating time can be saved from the Flash memory. The conventional material for storing carriers in a floating gate memory is a conductor, and the memories won’t work when the tunnel oxide is worn out because the leakage causes carriers loss constantly. A SONOS (Polysilicon-Oxide-Nitride-Oxide-Silicon) structure is one of the best candidates for the next generation product due to simpler processes, lower operation voltage, higher density and better radiation hardiness. However, the oxide degradation in a thinner tunnel oxide and the poor trapping efficiency in a nitride layer obstruct the mass production of the SONOS in the market. To this end, the dissertation focuses on the performance and reliability improvements of the SONOS devices.
This dissertation is divided into three major topics. The first topic is to optimize the tunnel oxide and nitride by different processes and the optimal condition can be obtained by comparing the performance and reliability of the devices. The second topic discusses the results of the radiation effect and the operation of the two-bit per cell in devices. The last topic is to compare the quality of different dielectrics for the blocking oxide structures. Experimental results show that the oxynitride grown in N2O ambient and high temperature exhibits excellent properties. For the nitride layer, the non-uniform nitride structure has better trapping efficiency and reliability due to larger barrier heights that reduce the chance of back tunneling. Furthermore, the radiation test indicates the non-uniform nitride has better endurance than that of the standard nitride, and the operation of the two-bit per cell can be indeed executed in the non-uniform nitride device. Finally, the non-uniform composition of the nitride exhibits the lowest leakage and the smallest hysteresis in all test samples.
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