SONOS存储器中隧穿氧化层淀积预清洗工艺研究

Study on the Pre-Cleaning Process of Tunnel Oxide Deposition of SONOS Memory

介绍了当今业界流行的两种隧穿氧化层淀积预清洗工艺:改进的RCA预清洗工艺以及HF-last预清洗工艺。通过实验对比各自优缺点,分析差异产生的根本原因。相对于改进的RCA预清洗工艺,HF-last预清洗工艺使SONOS存储器阈值电压窗口增大约600mV。但可靠性测试结果表明,HF-last工艺会降低器件的耐烘烤和耐擦写循环能力。进一步的电荷泵对比实验结果表明,HF-last工艺引起的耐烘烤和耐擦写循环能力的降低,分别由Si-SiO2界面态增加和隧穿氧化层变薄引起。

Two kinds of current popular process of tunnel oxide pre-cleaning were introduced, which were improved RCA pre-cleaning process and HF last pre-cleaning process. By comparing their advantages and disadvantages, the fundamental reasons of the differences were analyzed. Compared with the improved RCA pre- cleaning process, the HF-last pre-eleaning process could increase the threshold voltage window of a SONOS memory about 600 mV. But the reliability test showed that, the HF-last technology would reduce the device＇s performance in baking and endurance test. The charge pump experiment showed that, in the HF-last process, performance loss in baking test was caused by inducing Si SiO2 interface states, while performance loss in endurance test was caused by tunnel oxide thinning.