Magnetic reversal and thermal stability of CoFeB perpendicular magnetic tunnel junction arrays patterned by block copolymer lithography

Abstract

Dense arrays of pillars, with diameters of 64 and 25 nm, were made from a perpendicular CoFeB magnetic tunnel junction thin film stack using block copolymer lithography. While the soft layer and hard layer in the 64 nm pillars reverse at different fields, the reversal of the two layers in the 25 nm pillars could not be distinguished, attributed to the strong interlayer magnetostatic coupling. First-order reversal curves were used to identify the steps that occur during switching, and the thermal stability and effective switching volume were determined from scan rate dependent hysteresis measurements.

Magnetic Domain Wall Based Synaptic and Activation Function Generator for Neuromorphic Accelerators

“…Figure 3b shows the complete switching of a 200 nm × 400 nm MTJ from parallel to antiparallel state at different bias fields. The pinning field from the reference layer is maximum at the edges of the reference layer 30 . A combination of bias field and spin torque from the current pulse translates the domain wall under the MTJ, switching the state of the MTJ.…”

“…The pinning field from the reference layer is maximum at the edges of the reference layer. 32 A combination of bias field and spin torque from the current pulse translates the domain wall under the MTJ, switching the state of the MTJ. The current density required to switch the MTJ increases with a decrease in the amplitude of the bias field; see Figure 3b.…”

Solvent Vapor Annealing, Defect Analysis, and Optimization of Self-Assembly of Block Copolymers Using Machine Learning Approaches

“…[1][2][3][4][5][6][7][8][9][10] When integrated with sparse guiding morphological or chemical features produced via traditional lithography, these low cost polymer processing methods enable the generation of templates for production of sub-10 nm features with a high degree of long range order. 11 This combination of self-assembly with lithography is termed directed self-assembly (DSA) and has been primarily directed towards applications in microelectronics, including memory storage materials, 6,12,13 finFET, 5,14,15 and vias. [16][17][18] These nanopatterned substrates have also seen use as catalysts for growth of ordered nanowire arrays, [19][20][21] as a platform for protein detection, 22,23 separation membranes, [24][25][26][27] surface enhanced Raman spectroscopy (SERS) substrates, [28][29][30] anti-reflective coatings in photovoltaics, [31][32][33] and chemical and biomedical sensors.…”

Tailoring sidewall profiles of magnetic tunnel junctions fabricated with various etching conditions

“…With a high magnetic field sensitivity, MgO-based MTJs are the best candidates for logic and memory device applications. [20][21][22][23][24] Moreover, the possibility of developing a new generation of ultra-sensitive magnetic sensors based on the MgO/CoFeB layers with low noise has also been discussed. [25][26][27] However, many remaining issues that are related to fabrication processes, i.e.…”

“…TMR ratio largely reduces at high annealing temperatures, effects of diffusion, migration and texture, are simultaneously included. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Despite the extensive research effort in MgO-MTJ structures, a better understanding on each MTJ and its fabrication processes at the microscopic level is indispensable. Therein, the transport properties of MTJs are largely dictated by their underlying microstructures, i.e.…”