Study Of Perpendicular Anisotropy In Sputtered CoFeB Thin Film

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.