Thermal-assisted switching array configuration for MRAM

Abstract

This invention provides a thermal-assisted switching magnetic memory storage device. In a particular embodiment, a cross-point array of conductive rows and columns is provided with offset tunnel junction magnetic memory cells provided proximate to the intersections between the rows and columns. A looping write conductor is provided close to, but not in electrical contact with each memory cell. The looping write conductor loops across the top and bottom of each memory cell. Each magnetic memory cell provides a magnetic data layer characterized by a material wherein the coercivity is decreased upon an increase in temperature, an intermediate layer, and a reference layer. The magnetic fields provided by the looping write conductor during a write operation are not sufficient to alter the magnetic orientation of an unheated data layer, but may alter the data layer of a memory cell warmed by a bias current tunneling through the memory cell.

Description

FIELD OF THE INVENTION [0001] This invention relates generally to magnetic memory devices and in particular to ultra-high density thermally assisted magnetic random access memory arrays (commonly referred to as “MRAM”). BACKGROUND OF THE INVENTION [0002] Today's computer systems are becoming increasingly sophisticated, permitting users to perform an ever greater variety of computing tasks at faster and faster rates. The size of the memory and the speed at which it can be accessed bear heavily upon the overall speed of the computer system. [0003] Memory for a computer system is technically any form of electronic, magnetic or optical storage; however it is generally divided up into different categories based in part upon speed and functionality. The two general categories of computer memory are main memory and mass storage. Main memory is generally comprised of fast, expensive volatile random access memory that is connected directly to the processor by a memory bus. One component of t...

AI Technical Summary

Benefits of technology

This design enhances switching efficiency, reduces power requirements, and increases memory density by allowing smaller cell sizes and closer packing, while maintaining reliable switching characteristics without the need for high-temperature manufacturing processes.

Problems solved by technology

Main memory is generally comprised of fast, expensive volatile random access memory that is connected directly to the processor by a memory bus.

This offset can result in asymmetry in the switching characteristics of the bit: the amount of switching field needed to switch the bit from parallel to anti-parallel state is different from the switching field needed to switch the bit from anti-parallel state to parallel state.

Thus, at least one disadvantage of a tunnel junction memory cell having a pinned reference layer in close and fixed proximity to the data layer is a potential reduction in the magneto-resistance ΔR / R resulting from the angular displacement.

Such manufacturing stresses may permit the reference layer to become un-pinned and lose it's set orientation if the memory is later subjected to high temperatures.

In addition, the characteristics of the data layer may be unknowingly affected by heat during some manufacturing processes.

While utilizing multiple layers may help insure that the reference layer remains pinned, it also raises the complexity of manufacturing each and every memory cell present in the magnetic memory.

As between the two fundamental operations that may be performed on a storage bit (a “write” or a “read”), the write operation is generally more complex.

Therefore, design and manufacturing issues are generally focused upon the requirements imposed by the write operation.

A large coercivity is generally undesirable, as it requires a greater magnetic field to be switched, which in turn requires a greater power source and potentially larger switching transistors.

Moreover, as the size of the magnetic memory decreases, the unused space between individual memory cells tends to increase.

Images