负电容场效应晶体管研究

This project aims to explore and implement the fabrication of negative capacitance FETs (NCFET); focuses on the key scientific issues of HfZrOx ferroelectric multi-domain effects and the effect of material parameters on the performance of NCFETs, and develops the research on the device models, the growth and characterization of HfZrOx, the devices design and implementation of NCFET, the negative capacitance effect and transistor characterization. The method of introducing HfZrOx multi-domain effect and defect-induced charge trapping/detrapping model to NCFET two-dimensional self-consistent model will be investigated. The improvement of electrical performance of NCFET by changing the material composition, the thickness and the ferroelectric parameters of HfZrOx will be demonstrated. The underlying mechnism of the influence of HfZrOx material parameters on negative capacitance and NCFET device characteristics will be clarified by utilizing I-V and C-V measurement at different temperatures and different frequencies techniques. Through the combination of theoretical simulation and experimental testing, the impacts of negative capacitance effect and charge trapping/detrapping process on the key characteristics such as subthreshold swing and operating current of the device are clarified. After further correction of parameters of device model and further optimization of the process, NCFETs with the steep subthreshold swing (<40 mV/decade) and controllable hysteresis characteristics will be achievedt. By means of researching this topic, theoretical and experimental guidance are provided for the development of low-power CMOS logic devices.

本项目以探索并实现负电容场效应晶体管（NCFET）器件为目标，围绕HfZrOx铁电多畴效应、材料参数对NCFET器件性能影响等关键科学问题，开展器件模型、HfZrOx材料生长与表征、NCFET器件的设计与实现、负电容效应及晶体管特性表征等方面的研究。探索在NCFET二维自洽模型中引入HfZrOx多畴效应、缺陷引起的电荷俘获释放模型的方法；探测通过改变HfZrOx材料组分、厚度以及铁电参数提高NCFET电学性能的工艺；探测通过变温、变频技术证明HfZrOx材料参数对负电容和NCFET器件特性影响规律的测试方法。通过理论模拟与实验测试相结合，阐明负电容效应、电荷俘获释放过程等对器件亚阈值摆幅和工作电流等关键特性的影响机制；进一步修正模型参数，优化工艺，最终实现陡峭亚阈值摆幅（<40 mV/dec）和可控回滞特性的NCFET。通过本课题的研究，为低功耗CMOS逻辑器件的发展提供理论和实验指导。

本项目深入研究了负电容场效应晶体管（NCFET）器件制备、性能表征和理论模型，并开展了新型铁电薄膜NCFET器件和基于铁电掺杂的可重构晶体管研究。.1）开发不同Zr组分的HfZrOx薄膜工艺制备NCFET器件，Zr组分较低的Hf0.67Zr0.33O2 NCFET获得无回滞的窗口和较大的导通电流。.2）实验研究探索NCFET物理机制，发现NCFET栅极电压增益的实验值和引入去极化电场的理论计算值高度吻合，从而明确了负电容效应的物理机制是去极化电场。实验证明无回滞NCFET的极化行为模式为渐变型连续响应，证明无回滞NCFET工作的物理机制是铁电极子的不完全翻转。.3）理论上研究准反铁电NC-FinFET模型，发现准反铁电材料零极化值点附近P-V曲线负斜率区的存在使得准反铁电NC-FinFET的器件性能相较于传统FinFET得到了明显的提升。.4）实验发现了新型超薄铁电薄膜-绝缘层内嵌纳米晶以及不定型类铁电栅介质，验证了其在NCFET方面的应用。实现了小于60 mV/decade的陡峭亚阈值摆幅，通过周期性直流循环扫描和升温测试验证了器件中由纳米晶铁电薄膜引起的负电容效应的稳定性。.5）理论上提出基于铁电的静电掺杂技术，实现具有非易失可重构特性的铁电掺杂晶体管；并进一步提出可重构的铁电静电掺杂负电容纳米片场效应晶体管（Fe-ED NCFET），发现Fe-ED NCFET可以实现低于60 mV/decade的亚阈值摆幅，跨导提高约40%。该结构有望成为超低功率和超高功能密度电子器件的关键推动力之一。.本项目的研究结果，为负电容晶体管的发展和进一步实用化提供理论指导和技术支撑！