Static random access memory with magnetic tunnel junction cells
View Patent ↗Disclosed herein are related to a memory cell including magnetic tunneling junction (MTJ) devices. In one aspect, the memory cell includes a first layer including a first transistor and a second transistor. In one aspect, the first transistor and the second transistor are connected to each other in a cross-coupled configuration. A first drain structure of the first transistor may be electrically coupled to a first gate structure of the second transistor, and a second drain structure of the second transistor may be electrically coupled to a second gate structure of the first transistor. In one aspect, the memory cell includes a second layer including a first MTJ device electrically coupled to the first drain structure of the first transistor and a second MTJ device electrically coupled to the second drain structure of the second transistor. In one aspect, the second layer is above the first layer.
1. A memory cell comprising:
a first transistor and a second transistor connected to each other in a cross-coupled configuration, wherein the memory cell does not include a P-type transistor;
a third transistor coupled to a first drain structure of the first transistor and coupled to a bit line of the memory cell; and
a first magnetic tunnel junction (MTJ) device electrically coupled to the first drain structure of the first transistor and a second MTJ device electrically coupled to a second drain structure of the second transistor,
wherein the first MTJ device and the second MTJ device are each coupled to a common node, the first MTJ device includes a free layer structure electrically coupled to the common node, and voltage is applied across each of the first MTJ device and the second MTJ device via the common node.
2. The memory cell of claim 1 , further comprising a first layer including the first transistor and the second transistor.
3. The memory cell of claim 2 , further comprising a second layer including the first MTJ device and the second MTJ device.
4. The memory cell of claim 3 , wherein the second layer is above the first layer.
5. The memory cell of claim 1 , wherein:
the first drain structure of the first transistor is electrically coupled to a first gate structure of the second transistor, and
the second drain structure of the second transistor is electrically coupled to a second gate structure of the first transistor.
6. The memory cell of claim 1 , wherein the first MTJ device includes a pinned layer structure electrically coupled to the first drain structure of the first transistor.
7. The memory cell of claim 1 , further comprising a fourth transistor electrically coupled between a second bit line and the second drain structure of the second transistor.
8. The memory cell of claim 7 , wherein the first transistor, the second transistor, the third transistor, and the fourth transistor are each defined on a first layer of the memory cell.
9. A memory cell comprising:
a first layer comprising a first transistor, a second transistor, and a third transistor, the first transistor and the second transistor connected to each other in a cross-coupled configuration, the first transistor and the third transistor sharing a first drain structure; and
a second layer comprising:
a first magnetic tunnel junction (MTJ) device coupled to the first drain structure of the first transistor, and
a second MTJ device electrically coupled to a second drain structure of the second transistor,
wherein voltage is applied across each of the first MTJ device and the second MTJ device via a common node, and the first MTJ device comprises a free layer structure electrically coupled to the common node.
10. The memory cell of claim 9 , wherein the first MTJ device is disposed above the first drain structure of the first transistor.
11. The memory cell of claim 9 , wherein the first MTJ device is disposed above a first gate structure of the first transistor.
12. The memory cell of claim 10 , wherein the third transistor is electrically coupled between a first bit line and the first drain structure.
13. The memory cell of claim 10 , wherein the first transistor, the second transistor, and the third transistor are N-type transistors.
14. The memory cell of claim 9 , wherein the first MTJ device is electrically coupled to the first drain structure via one or more contacts.
15. The memory cell of claim 9 , wherein the first MTJ device includes a pinned layer structure electrically coupled to the first drain structure of the first transistor.
16. A method of operating a memory cell comprising:
applying, by a memory controller, a first voltage to a first magnetic tunnel junction (MTJ) device of the memory cell;
applying, by the memory controller, a second voltage to a second MTJ device of the memory cell while the first voltage is applied to the first MTJ device, the first MTJ device electrically coupled to a first drain structure of a first transistor and the second MTJ device electrically coupled to a second drain structure of a second transistor, wherein the first transistor and the second transistor are cross-coupled, wherein the second voltage is applied to the second MTJ device via a third transistor electrically coupled to the second MTJ device at the second drain structure, and wherein the first MTJ device and the second MTJ device are electrically coupled to a common node; and
applying, by the memory controller, a reference voltage to the common node while the first voltage and the second voltage are applied.
17. The method of claim 16 , wherein the second voltage is applied to the second MTJ device via a bit line coupled to the third transistor.
18. The memory cell of claim 6 , wherein the pinned layer structure is a first pinned layer structure, and the second MTJ device includes a second pinned layer structure electrically coupled to the second drain structure of the second transistor.
19. The memory cell of claim 6 , wherein the pinned layer structure is disposed closer to the first transistor than the free layer structure.
20. The memory cell of claim 15 , wherein the pinned layer structure is a first pinned layer structure, and the second MTJ device includes a second pinned layer structure electrically coupled to the second drain structure of the second transistor.