A New Effective Method for Thermal Annealing of Magnetic Tunnel Junctions in Air With Ru, Au, Al2O3 as Protective Overlayers
Philip Pong, Moshe Schmoueli, F Li, William F. Egelhoff Jr.
Thermal annealing is an important process to enhance greatly the tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJs). MTJ annealing is conventionally carried out in vacuum below 10-5 Torr. However, this method involves the cost and complications of using a vacuum furnace. Pumping and venting a chamber is time-consuming; moreover, the sample temperature is difficult to measure accurately and therefore not easy to control. We have developed a method and an instrument to perform thermal annealing of MTJs in air. The method is based on protective overlayers, and the instrument has a simple structure composed of an air heat gun, thermocouple with feedback control, permanent magnets for magnetic field, and a sample holder. The influence of thermal annealing in air on MTJs properties was studied systematically on Al2O3 MTJ samples. This method has these advantages: 1) time-efficient, 2) annealing temperature can be controlled much more accurately, 3) simple and low-cost, 4) suitable for both patterned MTJs and MTJ film wafers. The samples are successfully protected from oxidation by using Ru, Au, or Al2O3 films 1-10 nm thick as protective overlayers. The Al2O3 overlayer can be removed easily with NaOH solution.
Journal of Applied Physics
, Schmoueli, M.
, Li, F.
and Egelhoff Jr., W.
A New Effective Method for Thermal Annealing of Magnetic Tunnel Junctions in Air With Ru, Au, Al<sub>2</sub>O<sub>3</sub> as Protective Overlayers, Journal of Applied Physics
(Accessed June 7, 2023)