Magnetic tunnel junction with improved tunneling magneto-resistance

Abstract

A magnetic tunnel element that can be used, for example, as part of a read head or a magnetic memory cell, includes a first layer formed from an amorphous material, an amorphous tunnel barrier layer, and an interface layer between the first layer and the tunnel barrier layer. The interface layer is formed from a material that is crystalline when the material is in isolation from both the first layer and the tunnel barrier layer. Alternatively, the thickness of the interface layer is selected so that the interface layer is not crystalline. The first layer is formed from at least one material selected from the group consisting of amorphous ferromagnetic material, amorphous ferrimagnetic materials, and amorphous non-magnetic materials. The interface layer is formed from a material selected from the group consisting of a ferromagnetic material and a ferrimagnetic material.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to Magnetic Tunnel Junction (MTJ) Magnetoresistive (TMR) devices for use as magnetic field sensors, such as read heads for reading magnetically recorded data, as memory cells in nonvolatile magnetic random access memory (MRAM) cells, and for magnetic logic and spintronic applications. More particularly, the present invention relates to magnetic tunneling elements and MTJ devices having significantly improved magnetoresistance. [0003] 2. Description of the Related Art [0004] Magnetic Tunnel Junctions (MTJ) are promising candidates for memory storage cells by enabling a nonvolatile, high performance Magnetic Random Access Memory (MRAM). An MTJ-based MRAM has the potential to rival conventional Dynamic Random Access Memory (DRAM) in density and cost, and conventional Static Random Access Memory (SRAM) in speed. In addition, MRAM is truly nonvolatile, that is, the state of the memory is mai...

AI Technical Summary

Benefits of technology

[0014] The advantages of the present invention are provided by a magnetic tunnel element having a first layer formed from an amorphous material, an amorphous tunnel barrier layer, such as Al2O3, and an interface layer between the first layer and the tunnel barrier layer. According to the present invention, the interface layer is formed from a material that is typically crystalline and typically not amorphous when the material is in isolation from both the first layer and the tunnel barrier layer. For a limited range of thickness of the interface layer, the magneto-tunneling characteristics of the magnetic tunneling element are improved. For example, the thickness of the interface layer is preferably less than ˜25 Å when comprised of an alloy of Co and Fe. Alternatively, the thickness of the interface layer is selected so that the interface layer is not crystalline. The first layer is preferably formed from at least one material selected from the group consisting of an amorphous ferromagnetic material and an amorphous ferrimagnetic material. For example, the first layer can be a CoFeB alloy of the form (CO70Fe30)100−xBx in which x is between about 15 and 20. Alternatively, the first layer is an alloy of the form CoFeX or CoFeXY, in which X and Y are chosen from the group consisting of B, Hf, Zr, C, Be, Si, Ge, P and Al, so that at least one of X and Y of the alloy causes the alloy to be amorphous. The interface layer is advantageously formed from at least one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials. For example, the interface layer can be an Fe-containing alloy, such as CoFe containing between about 10 atomic percent and 60 atomic percent Fe. As another alternative, the Fe-containing alloy is NiFe. Or as another alternative, the Fe-containing alloy can be formed from a CoNiFe alloy.

Problems solved by technology

One of the most challenging problems for the successful development of MTJ memory storage cells is to obtain sufficiently uniform switching fields for a large array of MTJ cells.

One clear limitation on the AQF is the polycrystalline nature of the MTJ materials, which becomes especially important for high density MRAM in which the size of the MTJ element is so small that the MJT element contains only a small number of crystalline grains.

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