Switching Properties in Spin Transper Torque MRAM with sub-5Onm MTJ size

Abstract

Magnetic random access memory using spin-transfer torque effect has been developed with 30 nm sized magnetic tunnel junction (MTJ) cells. In this paper, we will describe the switching properties of sub-50 nm sized MTJ patterned by conventional lithography and etching process. Low switching current density (Jc) of 1.63×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with 10 ns pulse was achieved by optimizing magnetic materials and MTJ structure including MgO tunnel barrier. One sigma (σ) value of switching voltage distribution within 9 chips was about 6.2% of average value, which was much narrower than that of conventional field induced switching scheme. Also, as cell width decreased from 65 nm to 30 nm, switching current decreased from 133 μA to 25 μA. This indicates that STT-MRAM has an excellent scalability as well as the feasibility of low power and high density.