【作者】 周勇；

【导师】 钟智勇；

【作者基本信息】 电子科技大学 ， 电子科学与技术， 2015， 硕士

【摘要】 半导体技术的发展引起了信息技术的高速发展,存储器作为系统的核心部件之一,已经引发了多次技术革命,使存储器件朝着集成度更高、存储密度更大、读写速度更快、功耗更小的方向发展。自旋转移磁矩随机存储器(STT-RAM)因为其高的热稳定性、非易失性、写入功耗低、与CMOS晶体管搭配工作时有低的开关电流,而被人们视为受欢迎的可靠存储器件。如何进一步降低存储器功耗这一问题已经呈现在人们面前,首先考虑的方式就是降低开关电流,降低磁存储垂直结构中的磁性层阻尼系数。此外,如果能够使用电压来控制磁化,那么对磁性存储必然带来革命性的突破。本文根据上述背景,主要研究降低Co20Fe60B20薄膜的吉尔伯特阻尼系数,以及对Co20Fe60B20薄膜与Ti O2薄膜之间的垂直各向异性进行表征。本文的主要工作有:调研了采用不同CoFe B靶材配方将会影响吉尔伯特阻尼系数,实验中采用Co20Fe60B20的靶材配方。研究了薄膜的制备工艺对Co20Fe60B20薄膜金属软磁性能的影响。获得了最佳的Co20Fe60B20磁性薄膜的工艺参数:背底真空压强为8.0 10 Pa,溅射功率为90 W,氩气流量为20 sccm,溅射压强为0.4 Pa,靶材与基片距离为6 cm。同时,研究了Cu、Ta、Ti不同缓冲层对Co20Fe60B20金属软磁性能以及吉尔伯特阻尼系数的影响,并探究了其影响机理。研究表明CoFeB磁性薄膜与氧化层薄膜之间的界面效应将会影响CoFeB薄膜的垂直各向异性,实验中选择了TiO2薄膜。研究了薄膜制备工艺对TiO2薄膜的性能影响。得出了最佳的TiO2薄膜的工艺参数:背底真空压强为8.0 10 Pa,溅射功率为150 W,氩气流量为40 sccm,氧气流量为2 sccm,溅射压强为0.5 Pa。同时,当基片温度为400℃时,会促进金红石结构TiO2薄膜的形成。研究了霍尔条(Hall Bar)的制备方式,设计出硬质掩膜板来制备多层膜样品结构,搭建出利用反常霍尔效应表征Co20Fe60B20与Ti O2之间的垂直各向异性的测试系统,并和振动样品强磁计(VSM)的测试结果进行相应的对比验证。结论是当Co20Fe60B20层厚度达到1.7 nm时,多层膜结构Si/Ta/Co20Fe60B20/TiO2的垂直各向异性最佳。更多还原

【Abstract】 The development of semiconductor technology has caused the rapid development of information technology. As one of the core components of the system, memory has led to a number of technological revolutions and developed in the direction toward a higher degree of integration, a greater degree of storage density, a faster speed of reading and writing, less power.Because of high thermal stability, non-volatile, low critical current when it works with CMOS transistors, STT-RAM is considered as a popular and reliable storage device. The issue how to further reduce memory consumption has been presented. The first method for considering is to reduce the critical current and Gilbert damping factor of magnetic layer in perpendicular magnetic tunnel junctions(P-MTJs). In addition, if the magnetization can be controlled by voltage, it is will be revolutionary breakthrough for magnetic storage. Based on the above background, the main study of this thesis is to reduce Gilbert damping of Co20Fe60B20 film and improve perpendicular anisotropy between Co20Fe60B20 film and TiO2 film. The main works are as following:Research shows that different components of CoFeB target will influence the gilbert damping. We adopt Co20Fe60B20 target material formula in the experiment.The deposition conditions of Co20Fe60B20 film using magnetron sputtering system were optimized. The optimal deposition conditions are as following: base vacuum pressure is 8.0 10‐ Pa, sputter power is 90 W, argon gas flow rate is 20 sccm, sputter pressure is 0.4 Pa, the distance between the target and the substrate is 6 cm. Meanwhile, different buffer layers(Cu, Ta, Ti) have different impacts on the soft magnetic properties and Gilbert damping of Co20Fe60B20 film, where the mechanism are studied.Research shows that the interface effect between the CoFeB magnetic thin film and oxide film will influence the perpendicular anisotropy of CoFeB film, we choose TiO2 thin film.The deposition conditions of TiO2 film using magnetron sputtering system were optimized. The optimum deposition conditions are as following: base vacuum pressure is 8.0 10‐ Pa, sputter power is 150 W, argon gas flow rate is 40 sccm, Oxygen gas flow rate is 2 sccm, and sputter pressure is 0.5 Pa. Meanwhile, the deposition temperature of the substrate is 400℃ can promote the formation of rutile structure.The preparation method of Hall Bar is studied. Etch mask is designed to fabricate a multilayer film structure of the sample. A test system of charactering perpendicular anisotropy between Co20Fe60B20 film and TiO2 film is designed and the results is a compared with results of VSM. It concludes that when the thickness of Co20Fe60B20 film is 1.7 nm, perpendicular anisotropy of multilayer film structure(Si/Ta/ Co20Fe60B20/TiO2) is maximized.更多还原