Multi-state spin-torque transfer magnetic random access memory

Abstract

A multi-state spin-torque transfer magnetic random access memory (STTMRAM) is formed on a film and includes a first magnetic tunneling junctions (MTJ) having a first fixed layer, a first sub-magnetic tunnel junction (sub-MTJ) layer and a first free layer. The first fixed layer and first free layer each have a first magnetic anisotropy. The STTMRAM further includes a non-magnetic spacing layer formed on top of the first MTJ layer and a second MTJ formed on top of the non-magnetic spacing layer. The second MTJ has a second fixed layer, a second sub-MTJ layer and a second free layer. The second fixed and second free layers each have a second magnetic anisotropy, wherein at least one of the first or second magnetic anisotropy is perpendicular to the plane of the film.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 11 / 678,515 filed on Feb. 23, 2007, by Rajiv Yadav Ranjan and entitled “A High Capacity Low Cost Multi-State Magnetic memory” and U.S. patent application Ser. No. 11 / 866,830, filed on Oct. 3, 2007, by Rajiv Yadav Rajiv and entitled “An Improved High Capacity Low Cost Multi-State Magnetic Memory” and U.S. application Ser. No. 11 / 860,467, filed on Sep. 24, 2007, by Rajiv Yadav Ranjan and entitled “Low Cost Multi-State Magnetic Memory” and a continuation-in-part of U.S. patent application Ser. No. 11 / 674,124 entitled “Non-Uniform Switching Based Non-Volatile Magnetic Base Memory”, filed on Feb. 12, 2007, the disclosure of which is incorporated herein by reference, as though set forth in full.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to non-volatile magnetic memory and particularly to multi-state magnetic...

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Benefits of technology

[0011]To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a ...

Problems solved by technology

Such MLCs suffer from low density and therefore higher costs.

One of the key challenges for such type of designs using in-plane magnetization is that they cannot be scaled to lower feature sizes such as below 65 nm.

This is primarily because as the feature size reduces, the reduced memory bit size (for example: for 90 nm, the memory bit size is 90 nm×180 nm, but for 45 nm this would be 45 nm×90 nm) becomes thermally unstable due to the reduction in the volume.

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