标题: 非挥发性氧化锆电阻式记忆元件于结构、特性与制程整合之相依性
Structures-Properties-Process Integration Interrelationship of Nonvolatile Zro2 Resistance Random Access Memory Devices
作者: 曾俊元
TSENG TSEUNG-YUEN
國立交通大學電子工程學系及電子研究所
公开日期: 2012
摘要: 随着近代消费性电子产品,如:手机、个人电脑、MP3 和數位相机等,需求愈增的脚步,非挥发
性记忆体已成为现今半导体工业之研发重点。电阻式非挥发性记忆体为“金属/电阻层/金属”的结构,具
有非破坏性讀取、多重记忆狀态、结构简单及所需面积小等优点;然而,就目前电阻式非挥发性记忆
体的研究与实际应用上,写入/抹除切换速度、操作电压、记忆保持时间和可靠度性能等方面,仍有极
大的改善空间。
以氧化物作为电阻式记忆体的电阻转态层之机制說法众說纷纭,但根据已发表的文献,以电场引
发微小缺陷区域且串聯成导电路径(通称“灯丝filament”)较为广泛接受。但由于所谓灯丝的形成或断裂
乃属机率性,故电子藉灯丝为路径所造成的导电性不易有效精准的调控。过去我们实验室对于氧化锆
(ZrO2)薄膜电阻式记忆体之研究成果显示可成功地利用活性金属钛电极有效地局限住ZrO2 薄膜中灯丝
的形成或断裂的位置,不仅大幅地改善了ZrO2 薄膜中电阻态的转换特性,且达到高可靠度的操作次
數,相关的研究成果已被报导;然而,为了进一步提升ZrO2 电阻式记忆体之效能,本计画的构想是以
ZrO2 薄膜作为电阻层,经由薄膜内掺杂金属、嵌入奈米晶粒、亦或电浆及奈米压痕等表面处理,希望
可藉由外加異质缺陷方式有效地控制电阻层中之主要缺陷形成,更清楚地局限并掌握灯丝导电路径的
形成与断裂之位置,进而降低操作电压,与提升速度、可靠度等相关性能。
本计画预定将以三年进行,第一年主要工作为利用掺杂金属離子与嵌入金属奈米晶粒于ZrO2 氧化
物薄膜,配合改变ZrO2 薄膜整体厚度以及热处理条件,欲探讨不同浓度的金属掺杂以及不同种類金属
奈米晶粒,对于电子捕捉能力的影响;并研究内含金属掺杂以及金属奈米晶粒之ZrO2 氧化物薄膜的电
流传导机制,藉以瞭解记忆体切换机制与材料特性的相依性。第二年计画以ZrO2 电阻层为主的记忆薄
膜,探讨其表面经由电浆(plasma)与奈米压痕(nano-indentation)等处理对元件记忆效应的影响,并观察
其金属电极与ZrO2 薄膜间的界面反应之于记忆效应的影响,期盼能藉此局限并控制氧化锆电阻式记忆
体的电阻转态区域于一维度与二维度空间,进而改善电阻式记忆体之整体电性、可靠度等相关性能表
现。第三年的研究中,将实现电阻式记忆体于不同电路结构中,如整合一个非挥发性电阻式记忆元件
至标准互补式金氧半电晶体制程(CMOS process)中,并搭配一个存取电晶体或二极体作为一组记忆包
(memory cell),亦或以记忆阵列(memory array)以实现电路结构。
With the arrival of Digital Age, nonvolatile memory (NVM) plays an important role in the
semiconductor industry. Resistance random access memory (RRAM) has several advantages, such as
nondestructive reading, multilevel memory, simple structure, and high density. However, there are still
various important unresolved problems, including the write/erase speed, operation voltage, retention time,
and the reliability issues, which are still needed to be improved before realizing commercial applications.
So far, the resistive switching mechanisms in RRAM are still in debate. The most general one is based
on the “conducting filaments” which consist of local defect regions induced by electric field. However, the
formation/rupture of the filaments depends on the probability. Based on our previous work in the ZrO2-based
RRAM device, we have successfully confined the formation/rupture position of the conducting filaments by
utilizing active Ti as the top electrode. Besides, we also improved the reliability performance in the
ZrO2-based device, where the relevant excellent properties have been reported. To further acquire insight into
the ZrO2-based device, we propose to dope metal ions and bury the metal nanocrystals within ZrO2, and even
use the surface treatments on the ZrO2 memory films. We hope to confine the resistive switching region in
1-D and 2-D space by artificial extrinsic defects within the ZrO2-based devices to further improve their
performance and reliability.
In the first year, we will dope metal ions and embed metal nanocrystals within ZrO2 films, further
altering the ZrO2 film thickness and the annealing conditions to control the dopant distribution and the
nanocrystal size. The capability of electron trapping for the various kinds of metal dopants and nanocrystals
will be studied. Moreover, the current conduction mechanism of the dopants and nanocrystals incorporated
ZrO2 thin films will also be investigated to understand the correlation between memory switching origin and
material characteristics. In the second year, we will study the effect of the metal electrode and the ZrO2
surface treatment, such as plasma and nano-indentation process, on the memory switching properties. We
expect to confine the resistive switching regions in 1-D and 2-D spaces by artificial extrinsic defects and
further develop high performance and high reliability for ZrO2-based RRAM devices. In the third year, the
ZrO2-based memory will be integrated into circuit level. The memory array, the access transistor and the
access diode will be adapted to implement the ZrO2-based memory cells to investigate the possibility of
practical application of nonvolatile memory.
官方说明文件#: NSC99-2221-E009-166-MY3
URI: http://hdl.handle.net/11536/98615
https://www.grb.gov.tw/search/planDetail?id=2381057&docId=377502
显示于类别:Research Plans