标题: 于新颖负电容闸极多功能记忆体中暂态行为之实验探讨
An experimental study of transient behavior in the novel negative capacitance gated versatile memory
作者: 赖玟玮
张俊彦
Lai, Wen-Wei
Chang, Chun-Yen
电子研究所
关键字: 负电容;记忆体;暂态的;negative capacitance;memory;transient
公开日期: 2017
摘要: 近年来,随着记忆体微缩技术的发展,挥发性与非挥发性记忆体正面临许多技术上的挑战,例如动态随机记忆体的漏电与快闪记忆体的耐久性问题,但负电容铁电记忆体具有快速的切换速度、良好的耐久性及较低的操作电压,所以有希望成为新兴记忆体候选人。而最近铁电记忆体有重大的突破,由于商用高介电系数氧化铪基薄膜拥有负电容铁电特性的发现,使此新型材料制备的铁电记忆体元件受到关注,此元件具高微缩性、低功耗、良好的耐久性以及可以突破物理极限的次临界摆幅。因此,本论文提出结合负电容铁电和电荷补陷两种机制来改善新型铁电记忆体元件特性,研究内容包含基本的铁电特性、铁电效应与电荷补陷之间的交互作用以及记忆体电性。
为了改进铁电记忆体的记忆视窗与资料保存力,制作设计了铁电材料层(HfZrO)和电荷补陷层(HfON)堆叠结构。首先,我们介绍电流电压量测方法来获得铁电电容的暂态开关电流。我们应用无扫描和测量延迟的快速三角电压波形去产生暂态开关电流,并且藉由暂态开关电流的积分方法得到铁电极化-电压(P-V)迟滞环。同时我们瞭解到经由三角电压脉冲的激励,铁电电容的电流反应会出现明显的波峰,以及参杂物锆(Zr)会促进 HfO2的结晶从单斜晶相(monoclinic)转变为正交晶相(orthorhombic)。我们验证了铁电极化量与外加电场的大小和时间呈正相关,还有也验证沉积在电荷补陷层(HfON)上的铁电层(HfZrO)是确实拥有正交晶相的结晶以及铁电极化的特性。而更重要的是,利用电容的暂态电流反应,我们考究铁电效应与电荷补陷之间的相互作用,然后提出界面偶极的概念,并且证实了我们新颖的记忆体在经过写入与抹去的操作后,其铁电效应仍持续存在。
为了改善铁电记忆体的资料保存,我们运用拥有深层补陷特性的HfON材料当作电荷补陷结构,这种新颖混合式记忆体展现出优良的记忆体特性,它具有在正负10伏特直流扫描电压下4.85伏特的记忆视窗、大于1010次操作的优异耐受力、比传统铁电记忆体优良的资料保存力以及500奈秒的快速写入/抹除速度。根据实验结果,我们所提出的新颖铁电多功能型记忆体,有成为下一代记忆体应用的潜力。
In recent year, along with the development of memory scaling down technology, the volatile and non-volatile memories are facing many technological challenges such as the leakage power issue in DRAM and the endurance issue in Flash memory. The negative capacitance ferroelectric memory (NC-FRAM) is considered as a promising candidate among emerging memories due to its fast switching speed, long endurance and low operation voltage. Recently, the discovered ferroelectric properties of HfO2-based thin film open up an interesting pathway to establish highly scalable FRAM. Our studies have demonstrated one-transistor (1T) ferroelectric hybrid memories with ferroelectricity and charge-trapping mechanisms.
To improve the memory window and retention of 1T ferroelectric memory, the ferroelectric dielectric layer modulation scheme of HfZrO and HfON film stack layer was proposed. We experimentally demonstrated a novel hybrid ferroelectric/charge-trapping memory structure using HfZrO and HfON film stack. We introduced the current-voltage measurement method to obtain the transient switching current for the ferroelectric capacitors. By applying fast triangular voltage waveforms without sweeping and measuring delay, the ferroelectric polarization-voltage (P-V) hysteresis loop could be got through an integral calculation from the transient switching current. We realized the one peak of current response for each ramps will occur for ferroelectric capacitors applied by triangular pulses voltages excitation and the zirconium (Zr) can help the crystallinity of HfO2 transform from monoclinic phase to orthorhombic phase. We also confirmed the ferroelectric polarization depends on applied voltage and time, and the HfZrO film deposited on HfON trapping layer still owns the crystallinity of orthorhombic phase and ferroelectric characteristics. Importantly, the interaction between ferroelectricity and charge-trapping mechanisms was investigated by transient current response. We proposed the interface dipoles concept and verified the ferroelectric effect still exist in our memory after the program and erase operation.
The deep-trapped HfON employed as a charge-trapping structure to improve the data retention of ferroelectric HfZrO memory was investigated. This novel hybrid memory exhibited much better memory characteristics, it has a large memory window of 4.85V under ±10V DC sweep voltages, an excellent endurance of >1010 cycles, a better retention than conventional ferroelectric memory, and a fast 500ns program/erase speed. The novel ferroelectric versatile memory has the potential for the next generation memory application.
URI: http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070450176
http://hdl.handle.net/11536/142235
显示于类别:Thesis