Memory system having thermally stable perpendicular magneto tunnel junction (MTJ) and a method of manufacturing same

Abstract

A spin-torque transfer magnetic random access memory (STTMRAM) element employed to store a state based on the magnetic orientation of a free layer, the STTMRAM element is made of a first perpendicular free layer (PFL) including a first perpendicular enhancement layer (PEL). The first PFL is formed on top of a seed layer. The STTMRAM element further includes a barrier layer formed on top of the first PFL and a second perpendicular reference layer (PRL) that has a second PEL, the second PRL is formed on top of the barrier layer. The STTMRAM element further includes a capping layer that is formed on top of the second PRL.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Application No. 61 / 483,314 and is a continuation of U.S. patent application Ser. No. 12 / 965,733, which is a continuation-in-part of previously-filed U.S. patent application Ser. No. 12 / 965,733 filed on Dec. 10, 2010, by Zhou et al., and entitled “Enhanced Magnetic Stiffness and Method of Making Same”.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to a memory system having spin transfer torque (STT) switched magneto tunnel junctions (MTJs) and more particularly, a method to reduce the effective damping of magnetic layer and increase tunneling magneto-resistive ratio (TMR), and a method and apparatus for improving the perpendicular anisotropy and thermal stability of the low switching current perpendicular magneto tunnel junctions (pMTJs).[0004]2. Description of the Prior Art[0005]Spin transfer torque magnetic random access memory (...

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Benefits of technology

[0011]Additionally, this invention describes a method to reduce damping and increase stiffness in the magnetic layers of STTMRAM and simultaneously achieving higher TMR, which is applicable to both in-plane MTJs and pMTJs.

Problems solved by technology

The main hurdles associated with field-switched-MRAM are its more complex cell architecture with high write current [currently in the order of milliamps (mA)] and poor scalability (limited to 65 nm process node) attributed to its inherent field write scheme used in these devices.

One of the challenges for implementing STT is a substantial reduction of the intrinsic current density to switch the magnetization of the free layer while maintaining high thermal stability, which is required for long-term data retention.

Incorporation of conventional perpendicular anisotropy materials, such as FePt, into STTMRAM causes a high damping constant leading to undesirably high switching current density.

Furthermore, during manufacturing, conventional higher ordering transformation temperature required for forming L10 order structure could degrade the tunneling magneto-resistance (TMR) performance and make MTJ deposition process more demanding and complicated (such as elevated substrate temperatures during MTJ film deposition)

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