标题: 氧化铈奈米微晶粒非挥发性记忆体元件之研究
Characteristics of Cerium Oxide Nanocrystal Nonvolatile Memory Devices
作者: 杨绍明
Shao-Ming Yang
雷添福
简昭欣
Tan-Fu Lei
Chao-Hsin Chien
电子研究所
关键字: 氧化铈;奈米微晶粒;非挥发性;记忆体;二位元;CeO2;nanocrystal;nonvolatile;memory;two-bit
公开日期: 2007
摘要: 此论文主要制作氧化铈(CeO2)奈米微晶粒的非挥发性快闪记忆体,将使用不同的退火条件制程方法来制作捕陷捕捉电荷层,以取代现今传统氮化矽 (Si3N4) 材料。在低电压下来操作快闪记忆体元件使用不同的写入/抹除的操作方式。达成电荷捕捉效率佳、有快速的写入/抹除速度、大的记忆窗口、储存资料持久性、以及写入、清除操作造成的性能退化少的非挥发性快闪记忆体。
首先,我们利用氧化铈奈米微晶粒当作捕陷电荷层来制做SONOS型非挥发性快闪记忆体。此氧化铈奈米微晶粒快闪记忆体元件在一万次的写入/抹除下,仍然拥有好的储存资料持久性、和写入、清除操作造成的性能退化少。其电荷储存方式亦可以很区域性的,利用元件制作的对称性使其一个单元储存2个位元,达到高密度之优点,适用于相关记忆体元件及半导体产业中。
其次,沉积氧化铈薄膜随着后处理环境的不同来作为捕陷电荷层制作SONOS型非挥发性快闪记忆体。我们发现到随着退火的环境的差异,氧化铈奈米微晶粒会产生的不同深能量的捕陷电荷,造成储存资料持久性变化但是基本电性的写入、清除操作的性能没有太大变化。此为退火的环境的差异下造成不同结晶额外产生的浅能量的捕陷电荷所造成。
接着,我们使用堆叠结构的穿隧氧化层来取代传统的二氧化矽氧化层,同样使用氧化铈奈米微晶粒当作捕陷电荷层来制做非挥发性快闪记忆体。主要在于改善记忆体元件在清除操作造成的二氧化矽氧化层性能退化而影响其电性。
在论文的最后,我们针对记忆体元件的写入、清除操作在基板浮接情况下,其元件操作上的差异性,在写入操作可以降低1 伏特电压亦可有相同的操作数度,对于资料保存特性不会有很大的影响。也利用电荷汲引技术(Charge-Pumping technology),来观察不同的写入操作模式在SONOS记忆体元件的边缘缺陷(border traps)进行分析。
In this thesis, we utilize cerium oxide nanoparticle as a charge-trapping layer to fabricate nonvolatile memory. The cerium oxide nanocrystals formed self-assembled under different rapid-thermal annealing (RTA) ambient. This high-k nanocrystals layer replaces the silicon nitride layer in the SONOS-type memory structure. Different program/erase (P/E) methods are also proposed low power applications. This nanocrystals nonvolatile memory device will have good properties in terms of considerably large memory window, higher P/E speed, long data retention, and good endurance.
First, we present a nonvolatile SONOS-type flash memory that using cerium oxide (CeO2) nanocrystals as the trapping storage layer. These CeO2 nanocrystal memories exhibit long data retention, and good reliability, even for the cells subjected to 10k P/E cycles. These features suggest that such cells are very useful for high-density two-bit nonvolatile flash memory applications.
Then, we demonstrate the effects of the post-deposition different annealing ambient for the CeO2 trapping layer on the performance of SONOS-type flash memories. It was found that the CeO2 nanocrystals memory with different retention time caused by annealing ambient influence the deep-trapping level. However, the basic electrical operation characteristics are similar. This was ascribed to the larger amount and the shallower energy levels of the crystallization-induced traps. Finally, in the aspect of disturbances, we show only insignificant disturbances properties presented in the normal operation.
Next, we utilized the stack tunneling layer to replace conventional SiO2 tunneling layer. A nonvolatile SONOS-type flash memory device also used CeO2 nanocrystals as a charge trapping layer. It was demonstrated that the fabricated memories exhibit higher program/erase speed and long retention time. In particular, two-bit per cell operation has been successfully demonstrated.
Finally, we study nonvolatile CeO2 nanocrystal memory with no body contact (substrate floating). The operating voltage can reduce 1 V at program mode. Nevertheless, the date retention is similar. We also measure charge-pumping current for different programming methods to observe the SONOS-type memory border traps.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT009011825
http://hdl.handle.net/11536/80669
显示于类别:Thesis


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