【作者】 罗强；

【导师】 游龙；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2020， 博士

【摘要】 随着物联网技术的蓬勃发展以及移动电子设备的大范围普及,快速、高密度和低功耗成为未来电子设备追求的主要目标。为了克服传统CMOS技术存在的基本能耗限制,一系列新型低功耗电子器件被提了出来,包括纳机电开关以及铁电器件等。其中,纳机电开关由于具有陡峭的电流翻转行为、趋近于零的漏电流和巨大的开关比,可以实现极低的静态功耗。另一方面,基于铁电极化翻转来工作的铁电器件,通常具有非易失性、快的翻转速度以及低的操控电压等优点。本论文中,我们提出了一种新颖的铁电畴翻转驱动的纳米裂纹开关器件,不仅具有简单的结构,而且还集成了纳机电开关和铁电器件的诸多优点。未来,这种开关器件不仅可以通过简单的方式来实现铁电极化状态的非破坏性读出操作,而且还为开发低功耗、高密度的存储和逻辑应用提供了新的可行方案。本论文主要从以下几个方面开展研究工作:首先,基于PMN-PT/Mn Pt异质结构,研究发现虽然裂纹在垂直方向的循环电场作用下可以产生并贯穿Mn Pt薄膜,然而裂纹的分布是随机性的,其位置、形状、方向和数目等都是不可控的,这极大的限制了裂纹的应用。通过将Mn Pt薄膜加工成“桥型”结构,从而可以精确控制裂纹的产生和开闭,即有且仅有一条裂纹在“桥型”结构中间有效区域的边缘产生,并沿宽度方向扩展。这种可控铁电纳米裂纹开关,具有接近于零的漏电流、巨大的开关比以及非易失的电流翻转行为,未来可用于实现非易失的低功耗存储。其次,通过在分离的两个平面电极上施加较小的面内电压,不仅可以实现有效控制裂纹产生和开闭的目的,同时还能显著降低裂纹的控制电压。通过优化器件结构,分别实现了单裂纹的非易失性开闭、双裂纹的互补开闭以及单裂纹的互补开闭三种裂纹调控模式。此外,裂纹的互补开闭行为与互补的E_Z分布有关。且随着电极间距的减小,控制电压也将显著降低。AFM和PFM测试表明,面内电场作用下裂纹的非易失性开闭过程与铁电畴的极化翻转密切相关。通过相场模拟从应变和能量的微观角度论证了裂纹动态的可逆开闭过程是由不均匀的铁电畴翻转导致的。最后,探讨了这种铁电畴翻转驱动的纳米裂纹开关在低功耗存储和逻辑方面的应用前景和潜力。一方面,由铁电畴翻转驱动的裂纹的机械式的开闭行为,具有非易失性和趋近于零的漏电流。因此,这种器件可以用来实现非易失的低功耗存储。另一方面,面内电场调控下裂纹自发的互补翻转特性,也为实现低功耗、高密度的可重构逻辑应用提供了新的方案。例如,可控互补单裂纹开关器件可用于实现非易失的反相器;可控互补双裂纹开关器件,则为开发快速、低功耗和高密度的可重构计算系统提供了新的方法和思路。更多还原

【Abstract】 With the booming development of the Internet of Things technology and the widespread popularity of mobile electronic devices,high-speed,high-density,and low-power consumption have become the main goals pursued by future electronic devices.In order to overcome the fundamental energy-efficiency limitation of conventional CMOS technology,a series of novel energy-efficient electronic devices have been proposed,including nanoelectromechanical(NEM)switch and ferroelectric devices.Among them,NEM switch has the characteristics of abrupt current switching behavior,quasi-zero leakage current and ultra-high ON/OFF ratio,and can realize ultra-low standby power consumption.On the other hand,ferroelectric devices exploit ferroelectric polarization switching to work,and usually have the advantages of non-volatility,high-speed and low control voltage.In this thesis,we proposed a novel nano-crack switching device driven by ferroelectric domain switching,which not noly has a simple structure,but also conbines the advantages both of NEM switches and ferroelectric devices.In addition,such nano-crack switches can not only realize the non-destructive readout operation of the ferroelectric olarization states in a simple manner,but also provide a new feasible way for developing of low-power,high-density memory and logic applications.This thesis mainly conducets the research work from the following several aspects:Firstly,the study found that although the cracks could be induced and then propogated through the top Mn Pt film under an out-of-plane electric field based on a PMN-PT/Mn Pt heterostructure,the distribution of the cracks was random,especially their location,shape,direction and number were uncontrollable,which greatly limited the practical application of such cracks.By processing the Mn Pt film into a“bridge-like”structure,the generation and switching of crack can be precisely controlled,that is,only one crack can be induced at the edge of the middle active area of the"bridge-like"structure,and then the crack will expand along the width direction.The controlled ferroelectric nanocrack switch has quasi-zero leakage current,ultra-high ON/OFF ratio and non-volatile current-switching behavior,which can be used to implemented the non-volatile and low-power information storage in the future.Secondly,by applying a small in-plane voltage between two separated Mn Pt electrodes on PMN-PT substrate,which can not only achieve the purpose of effectively controlling the generation and switching of cracks,but also significantly reduce the required control voltage.By optimizing the electrode layout,three modes of crack switching are constructed respectively:including non-volatile switching of single-crack,complementary switching of two-cracks,and complementary switching of single-crack.In addition,the complementary switching behavior of cracks are related to the complementary E_Z distributions.And the control voltage will be scaled down significantly as shrinking the gap width of electrodes.AFM and PFM measurements show that the nonvolatile switching of cracks is accompanied with the ferroelectric domain switching.The phase-field simulation demonstrates from the microscopic view of strain and energy that the dynamic reversible opening and closing process of the crack is caused by the non-uniform ferroelectric domain switching.Finally,the prospect and potential of such ferroelectric domain switching-induced nanocrack switching devices in low-power memory and logic applications were discussed.On the one hand,the mechanical opening and closing behavior of crack driven by ferroelectric domain switching has the feature of nonvolatility and quasi-zero leakage current,thus such device can be used to implement non-volatile and low-power memory.On the other hand,the spontaneous complementary switching characteristics of cracks under the in-plane electric field also provide a new approach for developing high-speed,low-power and high-density reconfigurable logic applications.For example,the complementary and controllrable single-crack based device can be used to implement non-volatile inverter.And also,the complementary and controllable double-crack device can be used to construct high-speed,low-power and high-density reconfigurable computing systems.更多还原