| 학회 | 한국재료학회 |
| 학술대회 | 2018년 가을 (11/07 ~ 11/09, 여수 디오션리조트) |
| 권호 | 24권 2호 |
| 발표분야 | A. 전자/반도체 재료 분과 |
| 제목 | Design of High Thermal Stability Perpendicular Magnetic Anisotropy Structure using Co2Fe6B2 and [Co/Pt]n Multilayers as Free Layer for Below 10-nm-scale Memory Cell |
| 초록 | Recently, perpendicular-spin-transfer torque magnetic random access memory (p-STT MRAM) has received considerable attention as the next-generation memory to replace dynamic random access memory (DRAM). It has fast write and read speed with non-volatility. In addition, it has less electric energy consumption to maintain its data (~1 pJ/bit) [1]. However, p-STT MRAM has several challenges for tera-bit-level integration. They require a high tunneling magnetoresistance (TMR) ratio (＞150%), high thermal stability (Δ＞60), and a low switching current (Jc~1×102 MA/cm2) [2],[3]. For the p-STT MRAM to be commercialized as a memory, high retention time (＞10 years) must be satisfied which is closely related to the thermal stability(Δ=(KuV)/(kBT)). However, this becomes problematic as the p-STT MRAM cells are scaled down as Δ is proportional to the volume of the magnetic free layer. At sub-20nm diameters for general structure, Δ drops below 60 [4]. However, the device size should be smaller than 10nm×10nm size for tera-bit-level integration. In our presentation, we suggest a new PMA(perpendicular magnetic anisotropy) structure for high Δ using Co2Fe6B2 free layer and [Co/Pt]n multilayer. The new structure has coupling between [Co/Pt]n multilayer by W bridge layer. Consequently, magnetic moment is increased as n increases so it can retain Δ for 10nmx10nm. If device size is 10nm×10nm, the new structure has Δ greater than 60 for [Co/Pt]7 multilayer. We will report the effect of coupling between [Co/Pt]n multilayer and free layer. In addition, we will demonstrate the enhanced Δ as the number of [Co/Pt]n multilayer increases. The thermal stability were calculated by estimating the PMA magnetic moment using the vibrating sample magnetometer (VSM). Acknowledgment This work was supported by a Basic Science Research Program grant from the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP) (No. 2017R1A2A1A05001285) and the Brain Korea 21 PLUS Program in 2014. Reference [1] Y. Huai, “Spin-Transfer Torque MRAM (STT-MRAM): Challenges and Prospects,” AAPPS Bull., 18, 33 (2008). [2] J. G. Park. et al. Challenging issues for terra-bit-level perpendicular STT-MRAM. IEEE Int. Electron Devices Meet. 19.2.1–19.2.4 (2014). [3] H. Honjo. et al. 10 nmϕ perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction with over 400°C high thermal tolerance by boron diffusion control. Symposium on VLSI Technology, T160–T161 (2015). [4] N. Perrissin. et al. A highly thermally stable sub-20nm magnetic random-access memory based on perpendicular shape anisotropy. Nanoscale, 10, 12187-12195 (2018) |
| 저자 | 정선화, 전한솔, 최진영, Kondo Kei, 백종웅, 박재근 |
| 소속 | 한양대 |
| 키워드 | STT-MRAM; Thermal stability; Perpendicular Magnetic Anisotropy |
