基于二维WSex:Al薄膜小尺寸场效应晶体管的载流子输运特性

The studies of a new generation of small size, high performance XOI FET have been an urgent requirement for the further development of microelectronics technology. However, these key problems in the study of XOI p-FET need to be solved urgently such as the poor drive performance of the device,low mobility and bad stability of p-channel material, et al. This project develops a new p-type conductive two dimensional WSex:Al thin film with high mobility, good stability and uniform distribution by using atomic layer uniform deposition process. Preparation of a XOI p-FET with the channel based on WSex:Al and high-k gate dielectric based on SrHfON. This project will study the ALD processes, micro-structure and physical properties of the WSex:Al film, and investigate the influnce of micro-structure on the electrical properties of the XOI p-FET. The mapping relationship between the electrical properties of small size XOI p-FET devices and micro-structure will be established. Theoretical calculations and experiments are verified mutually to obtain the p-type conductivity characteristics of WSex:Al thin film, reveal the interfacial scattering coupling mechanism between SiO2/WSex:Al and WSex:Al/SrHfON, and clarify the variation rule of carrier transport characteristics and effect mechanism of small size XOI p-FET device. This project will provide the experimental and scientific basis for further improving the drive performance of XOI p-FET and enriching carrier transport theory of XOI p-FET.

小尺寸、高性能绝缘体上场效应晶体管（XOI FET）的研究是微电子技术发展的迫切要求。但小尺寸XOI p-FET面临驱动性能差、沟道迁移率低、稳定性差等关键问题亟待解决。本项目创新性地提出原子层沉积（ALD）均匀掺杂工艺实现Al掺杂WSe2（WSex:Al）薄膜中Al的均匀分布，获得具有高迁移率、稳定的p型导电二维WSex:Al薄膜，再以WSex:Al为沟道、以SrHfON为栅介质制备高驱动性能XOI p-FET。研究WSex:Al的ALD制备、微结构及物理特性，分析XOI p-FET的微结构及其对电学特性的影响。理论计算和实验相互验证，阐明WSex:Al薄膜p型导电特性的影响机理，揭示SiO2/WSex:Al与WSex:Al/SrHfON二元界面散射耦合作用机制，获得小尺寸XOI p-FET器件载流子输运特性的变化规律。为提高XOI p-FET驱动性能及丰富载流子输运理论提供科学依据。

针对目前小尺寸、p型绝缘体上场效应晶体管（XOI p-FET）研究中所面临的驱动性能低、稳定性差等关键问题，本项目提出并开发一种新型、稳定的、p型导电沟道材料，即Al掺杂WSe2（WSex:Al）薄膜。首先，采用第一性原理对WSex:Al薄膜的结构和电学性质进行了理论预测，揭示了Al掺杂量对WSex:Al薄膜能带结构和物理性质的影响规律。随着Al掺杂量的增加，W-Se键的共价键性减弱，WSex:Al薄膜价带上方出现杂质能级，形成深能级缺陷，为了避免形成深能级缺陷和电荷捕获陷阱，Al的掺杂浓度不宜超过5%。接下来，采用等离子体原子层沉积（PEALD）工艺成功地制备出p型导电WSex:Al薄膜，系统地研究了PEALD沉积工艺、Al掺杂量对WSex:Al薄膜成分、结构和物理性质的影响规律。随着Al掺杂量的增大，薄膜结晶质量下降；薄膜中W和Se元素含量减小，W4f、Se 2p和Al 2s的结合能向低能方向移动；薄膜的载流子浓度先增大后减小，电阻率逐渐增大。在此基础上，研究了基于WSe2薄膜和WSex:Al薄膜场效应晶体管电学特性的变化规律。WSe2薄膜FET呈双极特性，而WSex:Al 薄膜FET呈p型传导特性。随Al掺杂量的增加，p-FET的迁移率表现出先增大后减小的趋势。当Al掺杂量较低时，金属/WSex:Al界面间电荷密度增大、界面电荷转移增加，金属/WSex:Al界面间的隧道势垒和肖特基势垒都相应的减小，因而FET的迁移率随Al掺杂量的增加而增大。当Al掺杂量较大时，WSex:Al薄膜的结晶质量下降，使得晶界对载流子的散射作用增强，高的Al掺杂量也会形成深能级缺陷以及较高的费米钉扎效应，因而p-FET的迁移率随Al掺杂量的增加而降低。通过本项目的研究，获得了制备和优化p型导电WSex:Al薄膜的途径，阐明了以WSex:Al薄膜为沟道XOI p-FET器件电学特性变化规律，揭示了金属电极/WSex:Al界面微结构对XOI p-FET器件载流子输运特性的影响规律及影响机理。本项目的研究为进一步丰富p型导电沟道材料及其制备方法奠定了基础，为提高XOI p-FET器件的驱动性能及丰富XOI p-FET器件的载流子输运理论提供充实的实验和科学依据。