【作者】 王利；

【导师】 朱静；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 博士

【摘要】 现如今,便携式移动电子产品在人们的日常生活中应用得越来越广泛,在这些产品内部,闪存发挥着重要的作用。未来闪存技术的发展要求可以概括为:储存容量更大,读写速度更快,数据安全性更高,操作功耗更小。在此背景下,使用分散的纳米晶代替目前连续的多晶硅,作为闪存结构单元中浮动栅的结构得到了人们极大的关注。由于纳米晶浮动栅具有许多优异的性能,使得它成为目前闪存技术研究的一个热点。根据金属薄膜在氧化物介质层上生长时采用岛状生长机制这一原理。本论文利用磁控溅射制膜方法,发展了一种简单的,通过控制薄膜初始沉积厚度来制备单层纳米晶颗粒膜的实验方法。利用这种方法在二氧化硅介质层中制备得到了尺寸均一,分布均匀的银、铜以及铁镍二元合金纳米晶。证实了利用岛状生长机制制备金属和合金纳米晶的实验可行性。除此之外,还使用交替溅射的方法在二氧化硅介质层中生长了钛酸锶钡纳米晶。通过对薄膜沉积过程中溅射参数的调节,实现了对银与铜纳米晶平均粒径和分布密度一定范围内的有效控制。实验结果表明,随着沉积过程中溅射功率增加,银和铜的纳米晶平均粒径增大,分布密度则不断减小。对纳米晶生长过程中衬底温度作用的研究中发现,在纳米晶生长过程中对衬底加热可以起到与退火处理类似的效果,从而省却了后续的退火工艺,简化了纳米晶制备的实验步骤。目前对纳米晶浮动栅微观结构与宏观电荷存储性能之间的关系缺乏一个系统的说明。本文分析讨论了纳米晶材料的选择,纳米晶粒径,分布密度,绝缘介质层的相对介电常数与纳米晶浮动栅电荷存储能力之间的关系。分析结果表明,对于单个纳米晶来说,选择大功函数的材料,增大纳米晶的粒径,选择相对介电常数较大的绝缘层包裹材料,对提高它的电荷能力是有利的。增加单个纳米晶的电荷存储量,提高浮动栅中纳米晶的分布密度,可以增加纳米晶浮动栅整体的电荷存储量。更多还原

【Abstract】 Nowadays, portable electronic devices have been using more and more widely in people’s daily lives. In these devices, Flash Memory plays an important role. The development trend of future Flash Memory can be reduced to larger storage capacity, faster read/write speed, better security for data storage and lower energy consumption during operation. Under this background, a new floating gate structure using discrete nanocrystals to replace continuous polysilicon now attracts great attention. Because nanocrystals floating gate has so many advantages that more and more groups start their research work in this field.The growth of metallic films on oxide films follows Volmer-Weber mechanism. In this work, we developed a simple method to fabricate monolayer nanocrystals granular film by controlling the film’s initial deposition thickeness. With this method, we obtained well scattered Ag, Cu, FeNi binary alloy nanocrystals with uniform diameter. Besides, BST nanocrystals with ABO3 structure embedded in silicon dioxide dielectric layer are also fabricated by alternating sputtering.Ag, Cu nanocrystals’average diameter and distributing density were well controlled by adjusting magnetic sputtering conditions during films’deposition. TEM results showed that when the sputtering power during deposition increased, the average diameter of the Ag, Cu nanocrystals increased, but the distributing density decreased. We also found out that the substrate temperature during metallic films deposition had the same effection with annealing. Keeping the substrate at a proper temperature during deposition, the annealing process can be omitted, so the nanocrystal fabrication process will be simplyfized.Untill now, there are not a systemic theory to describe the relationship between the nanocrystals floating gate’s micro-structure and its charge storage capabilities. In this article, the relationship between nanocrystals’diameter, distributing density, dielectric layer’s permittivity and their charge storage capability will be analyzed. For a single nanocrystal, larger work function, bigger diameter and using dielectric layer with larger permittivity are good for improving its charge storage capability. For nanocrystals floating gate, improving a single nanocrystal’s charge storage capability and increasing nanocrystal’s distributing density are two ways to improve its charge storage capability.更多还原