【作者】 张宇；

【导师】 李沫； 郭旗；

【作者基本信息】 电子科技大学 ， 电子信息（专业学位）， 2024， 硕士

【摘要】 进入后摩尔时代以后,由于短沟道效应等物理限制,基于传统硅基晶体管的集成电路发展遇到重大瓶颈,人们一方面不断提出新的器件结构和提高半导体加工水平,另一方面也在不断寻找具有优异特性的新材料作为替代。二硫化钼（MoS₂）作为一种典型的过渡金属二硫化物,具备超薄的原子层厚度和较高的载流子迁移率,基于其制备的场效应晶体管（FET）等电子器件既有较强的栅控能力又能有效地抑制短沟道效应,在后摩尔时代集成电路领域有着极大的潜力。此外,MoS₂FET因为具有高迁移率、高开关比以及较强的栅极调控能力等性质,在航空航天与核工业领域具有极大的应用潜力。但上述场景中存在电离辐照效应与位移辐照效应等辐射因素,必须对MoS₂及其FET的辐照效应进行研究。目前关于MoS₂及其FET的辐照效应多集中在伽马射线、电子、质子辐照等引起的总剂量效应和单粒子效应,关于中子和各种离子引发的辐照位移效应研究较少。因此,本文开展了重离子、快中子对MoS₂及其FET的位移辐照效应研究,并且分析了注量、能量、粒子种类对辐照损伤的影响。本文的主要内容包括,首先研究了MoS₂的电离辐照效应与位移辐照效应机理,随后,制备了高质量的层状MoS₂材料,优化了MoS₂光刻与反应离子刻蚀技术等工艺实现了MoS₂FET的制备,并对晶体管的沟道材料以及晶体管电学性能进行了表征测试,为后续实验的开展奠定了良好的器件基础。随后,利用聚焦离子束以及高能重离子加速器开展了低能镓离子（Ga⁺）与两种高能重离子的辐照实验,结合TRIM仿真不同能量的重离子辐照前后FET的性能变化,得出不同能量重离子辐照单层与多层MoS₂及其FET的物理机理。本文发现,低能重离子辐照MoS₂时主要引起位移损伤,包括Ga⁺引起的初级碰撞产生的初级反冲原子与空位缺陷,注量增大时会产生复合缺陷和纳米孔,此外,MoS₂层数越多,低能重离子造成的损伤就越小。对器件而言,空位较多时会减小晶体管的迁移率,另一方面晶体管的衬底也会对缺陷密度产生影响,溅射的衬底原子会与反冲原子会加剧晶格损伤,使器件的开关比和迁移率等性能下降。高能重离子在辐照MoS₂FET时会产生两种损伤:位移损伤与电离损伤,位移损伤会破坏晶体管沟道的晶格结构,电离损伤产生的电子空穴对以及电子的转移会对导电沟道的电子浓度产生影响,都会影响晶体管的迁移率、导通电流与阈值电压等参数。进一步地,本论文开展了不同注量的快中子辐照单双层MoS₂FET实验,发现MoS₂FET本身对中子的抗辐照性能良好,且双层MoS₂FET的抗中子辐照能力比单层MoS₂FET更强,尤其是低注量中子辐照时,只会产生较少的硫空位,甚至在特定的中子注量下会出现空位的修复,单硫空位的产生会减小晶体管的迁移率、开关比,空位数量越多晶体管性能下降越严重,高注量的中子会产生较多的硫、钼空位和空位的氧化取代,空位的产生与修复对晶体管性能有不同的影响。此外,中子辐照实验周期较长,空气环境对MoS₂的影响不可忽视,晶体管性能的变化并不只是来源于辐照产生的影响,而是中子与空气环境的复合影响。本研究丰富了MoS₂及其FET的重离子、中子辐照效应的基本认识,为全面评估MoS₂及其FET的抗辐照特性提供了重要的依据,为推动MoS₂及其电子器件在辐照环境下的集成电路应用奠定了基础。更多还原

【Abstract】 After entering the post-Moore era,the development of integrated circuits based on traditional silicon-based transistors has encountered major bottlenecks due to physical limitations such as the short-channel effect,and people have continued to put forward new device structures and improve the level of semiconductor processing on the one hand,and on the other hand,they also continue to look for new materials with excellent characteristics as a substitute.As a typical transition metal disulfide,molybdenum disulfide（MoS₂）has ultra-thin atomic layer thickness and high carrier mobility,based on which electronic devices such as field effect transistors（FET）are prepared with strong gate control capability and effective suppression of short-channel effect,which has great potential in the field of integrated circuits in the post-Moore era.In addition,MoS₂FET have great potential for application in aerospace and nuclear industries because of their high mobility,high switching ratio,and strong gate control capability.However,there are radiation factors such as ionizing irradiation effect and displacement irradiation effect in the above scenarios,and the irradiation effect of MoS₂and its FET must be investigated.At present,the irradiation effects of MoS₂and its FET are mostly focused on the total dose effect and single-particle effect caused by gamma rays,electrons,proton irradiation,etc.,and the irradiation displacement effects triggered by neutrons and various ions are less studied.Therefore,this paper carries out a study on the displacement irradiation effects of heavy ions and fast neutrons on MoS₂and its FET,and analyses the effects of the injection amount,energy,and particle species on the irradiation damage.The main content of this paper includes,firstly,studying the mechanism of ionizing irradiation effect and displacement irradiation effect of MoS₂,then,preparing high-quality layered MoS₂materials,optimizing the MoS₂photolithography and reactive ion etching technology to achieve the preparation of MoS₂FET,and carrying out characterization tests on the channel material of the transistor and the electrical performance of the transistor,which lays a good device foundation for the subsequent experiments.The characterization of the channel material and the electrical properties of the transistor were tested,laying a good foundation for subsequent experiments.Subsequently,low-energy gallium ion（Ga⁺）and two kinds of high-energy heavy ion irradiation experiments were carried out using a focused ion beam and a high-energy heavy ion accelerator,combined with TRIM to simulate the performance changes of the FET before and after irradiation with different energies of heavy ions,and to find out the physical mechanisms of irradiation of single-layer and multi-layer MoS₂and its FET with different energies of heavy ions.In this paper,it is found that low-energy heavy-ion irradiation of MoS₂mainly causes displacement damage,including primary recoil atoms and vacancy defects generated by Ga⁺induced primary collisions,and composite defects and nanoholes are generated when the injection volume is increased,and in addition,the more the number of MoS₂layers is,the smaller the damage caused by low-energy heavy ions is.For the device,more vacancies will reduce the mobility of the transistor,on the other hand,the substrate of the transistor will also have an impact on the defect density,sputtered substrate atoms and recoil atoms will exacerbate the lattice damage,so that the device’s switching ratio and mobility and other properties of the device decreased.The irradiation of MoS₂FETs with high-energy heavy ions produces two types of damage:displacement damage and ionization damage,which destroys the lattice structure of the transistor channel,and ionization damage,which produces electron-hole pairs and transfers electrons to the electron concentration of the conductive channel,which affects parameters such as transistor mobility,on-current and threshold voltage.Further,in this thesis,experiments on single and double-layer MoS₂FET irradiated by fast neutrons with different injection amounts were carried out,and it was found that the MoS₂FET themselves have good resistance to neutron irradiation,and the double-layer MoS₂FET are more resistant to neutron irradiation than the single-layer MoS₂FET,especially when irradiated by neutrons with a low injection amount,which would produce only fewer sulphur vacancies,and even the repair of vacancies occurs at a specific neutron injection amount.The generation of single sulfur vacancies decreases the mobility and switching ratio of the transistor,and the more the number of vacancies,the more serious the transistor performance degradation,and the high injection amount of neutrons generates more sulfur and molybdenum vacancies and oxidative substitution of the vacancies,and the generation and repair of the vacancies have different effects on the transistor performance.In addition,the neutron irradiation experimental period is long,and the influence of the air environment on MoS₂cannot be neglected,and the change of transistor performance does not only originate from the irradiation-generated effects,but is a composite effect of the neutrons and the air environment.This study enriches the basic understanding of the heavy ion and neutron irradiation effects of MoS₂and its FET,provides an important basis for comprehensively evaluating the anti-irradiation characteristics of MoS₂and its FET,and lays a foundation for promoting the application of MoS₂and its electronic devices to the integrated circuits in irradiated environments.更多还原