SONOS存储器保持特性模型及存储层退火工艺研究

发布时间：2018-01-13 02:13

本文关键词：SONOS存储器保持特性模型及存储层退火工艺研究　出处：《华中科技大学》2013年硕士论文　论文类型：学位论文

【摘要】：随着对存储要求的增加，非挥发性存储器的市场增长速度非常快，，尤其是闪存存储器，因此闪存存储器的发展越来越受大家的关注。SONOS存储器可避免悬浮栅存储器的缺点如耦合率显著降低、浮栅干扰严重、工作电压偏高和漏电严重等，且具有工艺简单、操作速度快、保持时间长、存储密度高等特点，是未来存储器发展的方向。因此改善其性能参数成为目前研究的热点之一。本文是以SONOS存储器为研究对象，通过采用高k存储层材料和不同淀积后退火工艺来研究存储器的特性，并建立电荷保持特性模型，分析存储层陷阱空间分布。本文采用了反应溅射法制备了LaTiON和HfLaON作为存储层的MONOS电容存储器，研究了不同退火工艺对存储特性的影响。实验结果表明LaTiON样品中，Ti-NH3样品具有较好的电荷保持特性和编程/擦除速度，但疲劳特性较差；HfLaON样品中，Hf-NH3样品具有更好的存储特性；二者比较发现Hf-NH3样品具有最好的存储特性，NH3退火HfLaON是最具潜力的存储层材料。本文首先分析了隧穿层厚度、陷阱深度和温度对最主要两种电荷泄漏机制(陷阱-衬底导带隧穿和热发射)的影响，得出常温下陷阱-衬底导带隧穿是最主要的电荷泄漏机制；建立了考虑陷阱分布对电荷保持特性影响的电荷保持特性模型；分析了陷阱空间和能量分布对电荷保持特性的影响。结果表明陷阱空间分布为局域分布有助于改善电荷保持特性；当隧穿层厚度较薄时，陷阱能量分布为局域分布利于改善电荷保持特性；当隧穿层厚度较厚时，陷阱能量分布为三角形分布有助于改善电荷保持特性。利用模型分析实验中两组样品的存储层陷阱空间分布发现LaTiON样品的存储层陷阱空间分布为均匀分布；Hf-no样品和Hf-NH3样品的存储层陷阱空间分布为局域分布，而Hf-N2样品的存储层陷阱空间分布为均匀分布。该结论进一步说明N2退火调整了HfLaON样品的陷阱分布。根据修正因子，推断出NH3退火LaTiON样品的陷阱深度最深。HfLaON样品的陷阱深度比LaTiON样品浅。
[Abstract]:With the increasing demand for storage, the market of non-volatile memory is growing very fast, especially flash memory. Therefore, the development of flash memory has attracted more and more attention. SONOS memory can avoid the disadvantages of suspended gate memory, such as significantly reduced coupling rate, serious floating gate interference, high working voltage and serious leakage. The utility model has the advantages of simple process, fast operation speed, long retention time and high storage density. It is the direction of memory development in the future. Therefore, improving its performance parameters has become one of the research hotspots. This paper takes SONOS memory as the research object. The characteristics of the memory are studied by using high-k storage layer materials and different post-deposition annealing processes, and the charge-retention characteristic model is established to analyze the spatial distribution of storage layer traps. In this paper, MONOS capacitive memory with LaTiON and HfLaON as storage layer was fabricated by reactive sputtering method. The effects of different annealing processes on the storage characteristics were studied. The experimental results showed that the Ti-NH3 samples in LaTiON samples had better charge retention characteristics and programming / erasure rate, but the fatigue characteristics were poor. The Hf-NH _ 3 sample of HfLaON has better storage characteristics. It is found that Hf-NH3 samples have the best storage properties and NH3 annealed HfLaON is the most promising storage layer material. In this paper, the effects of tunneling layer thickness, trap depth and temperature on the two main charge leakage mechanisms (trap-substrate conduction tunneling and thermal emission) are analyzed. It is concluded that the main mechanism of charge leakage is trap-substrate conduction tunneling at room temperature. A charge-retention model considering the effect of trap distribution on charge-retention characteristics is established. The effects of trap space and energy distribution on charge retention characteristics are analyzed. When the thickness of tunneling layer is thin, the local distribution of trap energy is helpful to improve the charge retention characteristics. When the tunneling layer thickness is thicker, the trap energy distribution is triangular, which is helpful to improve the charge retention characteristics. The spatial distribution of storage layer traps of LaTiON samples was found to be uniform by using the model analysis of the two groups of samples. The storage layer trap spatial distribution of Hf-no and Hf-NH3 samples is localized. However, the storage layer trap spatial distribution of Hf-N2 samples is uniform. This conclusion further indicates that N2 annealing adjusts the trap distribution of HfLaON samples. It is inferred that the trap depth of LaTiON sample annealed by NH3 is the deepest. The trap depth of HF Laon sample is lower than that of LaTiON sample.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

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