The Research Of Reliability On Deep Submicron SONOS Nonvolatile Memory Devices

With the rapid development of portable devices, design of floating gate flash memory encounters lots of challenges, such as junction breakdown, short channel effects, area, program/erase voltage, abnormal leakage current, over erase and so on especially when feature size below 32nm node.The SONOS (Silicon-Oxide-Nitride-Oxide-Silicon) becomes one of the best solutions of deep sub-micron storage technology. It has the advantages of low-voltage, low power, easily compatible with CMOS technology. With the feature size scaling, the thickness of tunneling oxide layer is decreased. So the reliability of data retention and endurance become one of the research emphasis.This thesis focuses on 0.13μm SONOS nonvolatile memory device reliability research. The main charge leakage path of SONOS devices has been studied in the 0.13μm process based on the analysis of SONOS device structure, work and charge leakage mechanism. Optimized process methods are proposed. Lots of SONOS samples has been fabricated so that the researches on ONO stack gate annealing process, the tunneling oxide thickness optimization, the effects of flow and furnace temperature uniformity, adjustment of ONO stack temperature on ONO gate stack process could be done respectively. Finally, optimal reliability parameters are given for 0.13μm SONOS process. Process optimal methods are as follows:First, appropriate N2O annealing process is added after tunneling oxide layer formed. C-V, C-P measurements on SONOS devices showed that after annealing, the charge pump current Icp is decreased about 27.8%, and the device threshold voltage degradation rate is significantly reduced;Second, the tunneling oxide thickness and device performance is not a simple linear relationship. Different the process feature size, the optimal tunneling oxide thickness is different;Third, during ONO growth process, the gas flow and temperature uniformity in furnace affect the reliability of the device. The device life span on the top of the furnace is 5 times than that on the bottom;Fourth, appropriate ONO film growth temperature is in favour of the device reliability. By adjusting the temperature, the deterioration rate of Vte is reduced 68.4% and Vtp degradation rate is decreased 19.3%.This work not only provides a theoretical and technical support for improving the performance of SONOS device, but also lays foundations for SONOS memory researches and mass productions.