Enhancement of Magnetic and Electric Transport Performance of Perpendicular Spin-Orbit Torque Magnetic Tunnel Junction by Stop-on-MgO Etching Process

Abstract

We investigate the magnetic and electric transport performance of the spin-orbit torque magnetic tunnel junction (SOT-MTJ) with perpendicular magnetic anisotropy (PMA) by stop-on-MgO etching process. This process etches away the hard mask (HM), synthetic antiferromagnetic layer (SAF) and reference layer (RL) while keeping the MgO barrier layer and free layer (FL) retained. Compared with the SOT-MTJ without stop-on-MgO etching process, the SOT-MTJ with stop-on-MgO etching process exhibits nearly zero offset field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${H}_{\text {off}}{)}$ </tex-math></inline-formula> and lower critical switching current density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{c}{)}$ </tex-math></inline-formula> with higher thermal stability factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {)}$ </tex-math></inline-formula> . Although the magnetic property of the FL underneath the MgO is retained, the switching speed can still reach as fast as 1 ns. Furthermore, the SOT-MTJ with stop-on-MgO etching process presents much more concentrated distribution of the statistical coercivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${H}_{c}{)}$ </tex-math></inline-formula> , tunneling magnetoresistance (TMR), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${H}_{\text {off}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{c}$ </tex-math></inline-formula> . The resistance-based MTJ yield can raise up to 100%, which is advantageous in the high-speed and large-scale memory application.