Cryogenic temperature deposition of high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions on 300 mm wafers

TL;DR

This paper presents a cryogenic temperature deposition process for CoFeB/MgO/CoFeB magnetic tunnel junctions on 300 mm wafers, significantly enhancing their magnetic and magneto-transport properties compared to room-temperature deposition.

Contribution

The study introduces a cryogenic deposition method that improves interface quality and magnetic properties of MTJs, advancing manufacturing techniques for next-generation MRAM.

Findings

Enhanced PMA and VCMA at 100 K deposition

Improved interfacial qualities such as reduced intermixing and oxidation

Potential for standard manufacturing process in MRAM production

Abstract

We developed a cryogenic temperature deposition process for high-performance CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) on 300 mm thermally oxidized silicon wafers. The effect of the deposition temperature of the CoFeB layers on the nanostructure, magnetic and magneto-transport properties of the MTJs were investigated in detail. When CoFeB was deposited at 100 K, the MTJs exhibited a perpendicular magnetic anisotropy (PMA) of 214 uJ/m2 and a voltage-controlled magnetic anisotropy (VCMA) coefficient of -45 fJ/Vm, corresponding to 1.4- and 1.7-fold enhancements in PMA and VCMA, respectively, compared to the case of room-temperature deposition of CoFeB. The improvement in the MTJ properties was not simply due to the morphology of the MTJ films. The interface-sensitive magneto-transport properties indicated that interfacial qualities such as intermixing and oxidation states at the MgO/CoFeB interfaces were improved by the cryogenic temperature deposition. Cryogenic-temperature sputtering deposition is expected to be a standard manufacturing process for next-generation magnetoresistive random-access memory.