Magnetic memory circuit with stress inducing layer
Memory circuit comprising an addressable magnetic tunnel junction (MTJ) stack, forming a magnetic storage element in the circuit. The MTJ stack comprises a tunnel oxide layer between a free layer and a fixed layer. A stress inducing layer is disposed adjacent to the free layer to provide tensile or compressive stress to the free layer, in order to manipulate a magnetic field that is required to write a bit into the MTJ stack. Method of using the memory circuit is also proposed.
1. A memory circuit comprising:
a plurality of magnetic tunnel junction (MTJ) stacks forming a corresponding plurality of magnetic storage elements in the memory circuit, wherein each of the plurality of MTJ stacks includes:
a tunnel oxide layer between a free layer and a fixed layer; and
a stress-inducing layer disposed above the free layer,
wherein:
a first free layer of a first MTJ stack of the plurality of MTJ stacks is stressed to a first extent by a first stress-inducing layer of the first MTJ stack;
a second free layer of a second MTJ stack of the plurality of MTJ stacks is stressed to a second extent by a second stress inducing layer of the second MTJ stack; and
the first extent and the second extent are different.
2. The memory circuit of claim 1 , wherein at least one of the plurality of MTJ stacks includes a dummy layer disposed between the free layer and the stress-inducing layer.
3. The memory circuit of claim 1 , wherein the stress-inducing layer of at least one of the plurality of MTJ stacks comprises a metal.
4. The memory circuit of claim 1 , wherein the stress-inducing layer of at least one of the plurality of MTJ stacks comprises titanium nitride (TiN).
5. The memory circuit of claim 1 , wherein the free layer of at least one of the plurality of MTJ stacks comprises a plurality of layers.
6. The memory circuit of claim 1 , wherein said memory circuit comprises a magnetic random access memory (MRAM) circuit.
7. The memory circuit of claim 1 , wherein:
the first stress-inducing layer comprises a first thickness;
the second stress-inducing layer comprises a second thickness; and
the first thickness and the second thickness are different.
8. The memory circuit of claim 1 , wherein:
the first stress-inducing layer comprises a first material;
the second stress-inducing layer comprises a second material; and
the first material and the second material are different.
9. The memory circuit of claim 1 , wherein:
the first stress-inducing layer was deposited using a first processing condition;
the second stress-inducing layer was deposited using a second processing condition; and
the first processing condition and the second processing condition are different.
10. The memory circuit of claim 1 , wherein:
the first stress-inducing layer is a single layer; and
the second stress-inducing layer comprises a plurality of layers.
11. The memory circuit of claim 1 , wherein at least two of the stress-inducing layers comprise different magnitudes of tensile stress.
12. The memory circuit of claim 1 , wherein:
the first stress-inducing layer provides a first magnitude of stress to the first free layer;
the second stress-inducing layer provides a second magnitude of stress to the second free layer; and
the first magnitude of stress and the second magnitude of stress are different.
13. The memory circuit of claim 1 , wherein:
a first one of the plurality of MTJ stacks includes a dummy layer disposed between the free layer and the stress-inducing layer; and
a second one of the plurality of MTJ stacks does not have a dummy layer disposed between the free layer and the stress-inducing layer.