Magnetoresistive random-access memory (mram)
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsYU-DER CHIH, CHIA-FU LEE
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Abstract
A method for identifying an IM state of MRAM cell writes includes providing a plurality of MRAM cells and partitioning the plurality of MRAM cells into a plurality of groups including a first group and a second group. A first MRAM cell of the first group is written from a first state to a second state and a second MRAM cell of the second group is written from the first state to the second state. The writing of the first MRAM cell is verified, including comparing a first read current of the first MRAM cell to a first reference value. The writing of the second MRAM cell is verified, including comparing a second read current of the second MRAM cell to a second reference value.
Claims20
A memory system, comprising:
- a first group having a first plurality of MRAM cells and a second group having a second plurality of MRAM cells;
- a sense amplifier configured to compare a base read current of each of the first plurality of MRAM cells and of each of the second plurality of MRAM cells to a base reference value;
- a controller configured to
- write selected ones of the first plurality of MRAM cells from a first state to a second state based on the comparing;
- write selected ones of the second group of MRAM cells from the first state to the second state based on the comparing;
- compare a first read current of each of the first plurality of MRAM cells to a first reference value different than the base reference value;
- and
- compare a second read current of each of the second plurality of MRAM cells to a second reference value different than the base reference value and the first reference value.
A memory system, comprising:
- a plurality of magnetoresistive random-access memory (MRAM) cells each including a magnetic tunnel junction (MTJ);
- a controller configured to:
- determine, for each MRAM cell of a plurality of MRAM cells, a pre-write read current associated with a first magnetic state of the MRAM cell;
- assign, to each respective MRAM cell, a corresponding verification reference value based on the pre-write read current associated with the respective MRAM cell;
- cause selected MRAM cells of the plurality of MRAM cells to be written from the first magnetic state to a second magnetic state;
- and
- determine whether a respective write operation is successful by comparing a post-write read current of each selected MRAM cell to the corresponding verification reference value assigned to the respective MRAM cell;
- and
- a sense amplifier configured to perform the comparing of the post-write read current to the corresponding verification reference value for each selected MRAM cell.
A method of operating a magnetoresistive random-access memory (MRAM) device, comprising:
- measuring, for each of a plurality of MRAM cells, a first read current corresponding to a first magnetic state;
- determining, for each respective MRAM cell, a cell-specific verification reference value based on the first read current corresponding to the respective MRAM cell;
- writing at least a subset of the plurality of MRAM cells from the first magnetic state to a second magnetic state;
- measuring, for each written MRAM cell, a second read current after the writing;
- and
- determining whether the respective MRAM cell reached the second magnetic state by comparing the second read current of the respective MRAM cell to the cell-specific verification reference value corresponding to the respective MRAM cell.
Dependencies are inferred from the claim text.