Magnetic random access memory with thermally stable magnetic tunnel junction cells
First Claim
1. A magnetic tunnel junction cell comprising:
- an electrically conductive underlayer comprising a first layer selected from the group consisting of a tantalum nitride and a tungsten nitride and a second layer selected from the group consisting of tantalum and tungsten located on and in contact with the first layer;
a pinned ferromagnetic layer on the second layer of the underlayer;
a free ferromagnetic layer having its magnetic moment free to rotate in the presence of an applied magnetic field;
a tunnel barrier layer located between the pinned ferromagnetic layer and the free ferromagnetic layer; and
an electrically conductive capping layer on the free ferromagnetic layer, the capping layer comprising a first layer selected from the group consisting of a tantalum nitride and a tungsten nitride and a second layer selected from the group consisting of tungsten and tantalum located on and in contact with the first layer, the first layer of the capping layer being located on and in contact with the free ferromagnetic layer.
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Accused Products
Abstract
A magnetic tunnel junction (MTJ) memory cell and a magnetic random access memory (MRAM) incorporating the cells has upper and lower cell electrodes that are formed of bilayers that provide electrical connection between the cells and the copper word and bit lines of the MRAM. The bilayers are formed of a first layer of tantalum nitride or tungsten nitride and a second layer of tantalum or tungsten. In one embodiment TaN is formed directly on the copper and low-resistivity alpha-Ta is formed directly on the TaN. If the cells use an antiferromagnetic layer to fix the moment of the pinned ferromagnetic layer, then Pt—Mn is the preferred material formed over the alpha-Ta. The bilayer can function as a lateral electrode to connect a horizontally spaced-apart cell and a copper stud in the MRAM.
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Citations
9 Claims
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1. A magnetic tunnel junction cell comprising:
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an electrically conductive underlayer comprising a first layer selected from the group consisting of a tantalum nitride and a tungsten nitride and a second layer selected from the group consisting of tantalum and tungsten located on and in contact with the first layer;
a pinned ferromagnetic layer on the second layer of the underlayer;
a free ferromagnetic layer having its magnetic moment free to rotate in the presence of an applied magnetic field;
a tunnel barrier layer located between the pinned ferromagnetic layer and the free ferromagnetic layer; and
an electrically conductive capping layer on the free ferromagnetic layer, the capping layer comprising a first layer selected from the group consisting of a tantalum nitride and a tungsten nitride and a second layer selected from the group consisting of tungsten and tantalum located on and in contact with the first layer, the first layer of the capping layer being located on and in contact with the free ferromagnetic layer. - View Dependent Claims (2, 3, 4, 5)
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6. A magnetic tunnel junction cell comprising:
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a substrate;
an electrically conductive underlayer comprising a bilayer of a tantalum nitride layer on the substrate and a layer of alpha-phase tantalum on and in contact with the tantalum nitride layer;
a layer of antiferromagnetic material on the tantalum layer of the underlayer, the antiferromagnetic material being an alloy comprising Pt and Mn;
a pinned ferromagnetic layer on and in contact with the antiferromagnetic layer and whose magnetic moment is pinned by being exchange biased with the antiferromagnetic layer;
a free ferromagnetic layer having its magnetic moment free to rotate in the presence of an applied magnetic field;
a tunnel barrier layer located between the pinned ferromagnetic layer and the free ferromagnetic layer; and
an electrically conductive capping layer comprising a bilayer of a tantalum nitride layer on the free ferromagnetic layer and a layer of alpha-phase tantalum on and in contact with the tantalum nitride layer. - View Dependent Claims (7)
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8. A magnetic memory array of magnetic tunnel junction memory cells comprising:
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a planar silicon substrate;
insulating material formed on the substrate;
a first set of copper lines in the insulating material and spaced vertically from the planar substrate, the first set of lines being electrically connected to regions of the substrate;
a second set of copper lines in the insulating material and spaced vertically from the planar substrate and from the first set of copper lines, the spacing between the first and second sets of lines defining a plurality of intersection regions;
an array of magnetic tunnel junction cells, each cell being near an intersection region and comprising an electrically conductive bilayer underlayer comprising a tantalum nitride layer electrically connected to one of the lines of the first set and a layer of alpha-phase tantalum on and in contact with the tantalum nitride layer;
a layer of antiferromagnetic material on the tantalum layer of the underlayer, the antiferromagnetic material being an alloy comprising Pt and Mn;
a pinned ferromagnetic layer on and in contact with the antiferromagnetic layer and whose magnetic moment is pinned by being exchange biased with the antiferromagnetic layer;
a free ferromagnetic layer having its magnetic moment free to rotate in the presence of an applied magnetic field;
a tunnel barrier layer located between the pinned ferromagnetic layer and the free ferromagnetic layer; and
an electrically conductive bilayer capping layer comprising a tantalum nitride layer on the free ferromagnetic layer and a layer of alpha-phase tantalum on and in contact with the tantalum nitride layer;
and wherein the tantalum layer of the capping layer is electrically connected to one of the lines of the second set. - View Dependent Claims (9)
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Specification