US 9,177,627 B2Granted

Method for improving the stability, write-ability and manufacturability of magneto-resistive random access memory

AssigneeLaurence Lujun Chen

InventorsLaurence Lujun Chen, Di (Laura) Chen, Michael Meng Chen

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Abstract

This invention provides the method to overcome 4 backwards which limit the manufacturability or production yield rate of Magneto-resistive random access memory (MRAM). The key points of this invention are: (1) providing method to improve the manufacturability through reducing bias variation, by using a compensation module to correct the bias point of extreme cells; (2) providing method to improve the manufacturability through removing outlier cells (called bad cells), by using “writing jump-over” and “reading exclusion” to exclude bad-cells; (3) providing method to reduce the bias point, amplitude and asymmetry variation, using shared fixed-magnetic-reference-layer and proper shape anisotropy; (4) providing method to improve the write-ability, using flipping-assistant-field to speed up STT flipping process by large current, and using heating resistance and heating cells by the same current (including global heating, row heating, column heating, or local cell heating, i.e. heating with conventional thermal nature or heating with thermagnonic spin-transfer torque).

Claims17

Dependent claims

A method for improving manufacturability or production yield rate of magneto-resistive random access memory (MRAM) comprise at least one the following steps:

(1) compensating bias or operation point by using cell-selection circuit board and compensation module through bias compensation method, so as to reduce bias distribution range and increase bias uniformity;
(2) excluding outlier cells and bad cells when reading by using cell-selection circuit board and exclusion module for reading through the reading exclusion method;
(3) excluding outlier cells and bad cells when writing by using write-jump-over management circuit blocks and exclusion module for writing through write jump-over method;
(4) improve stability and uniformity by optimizing magnetic and geometric design of MRAM cells through using shared PL (pinned layer) and AFC (ferro-magnetically coupled layers) with smaller AFM (anti-ferro-magnetism) grain size to increase uniformity, and adjusting FL (free layer) shape anisotropy;
and
(5) improving write-ability by using same heating current for both heating cells and providing flipping-assistant-field to doubly speed up flipping process of cells.

3 more elements

Dependencies are inferred from the claim text.