High-speed compare operation using magnetic tunnel junction elements including two different anti-ferromagnetic layers

摘要

A match-in-place-type compare operation utilizes a string of Magnetic Tunnel Junction (MTJ) elements including storage layers and sense layers having different anti-ferromagnetic structures respectively having higher and lower blocking temperatures. Confidential data is written into the storage layers of the MTJ elements by heating the elements above the higher blocking temperature, and then orienting the storage and sense layers in first storage magnetization directions using field lines. The elements are then cooled to an intermediate temperature between the higher and lower blocking temperatures, and the field lines are turned off, setting the sense layers to preliminary storage magnetization directions opposite to the first directions. During a pre-compare phase, an input logic pattern is written into the sense layers by heating to the intermediate temperature. During a compare operation, with the field lines turned off, resistance of the MTJ string is detected by passing a read current through the string.

主权项

1. A method for performing a high-speed compare operation to determine whether an input data bit value matches a previously stored confidential data bit value using at least one magnetic Tunnel Junction (MTJ) element including a non-volatile storage layer and a non-volatile sense layer separated by a tunnel junction layer, the method comprising:
during a write/program operation, writing said confidential data bit value into the MTJ element by fixing the non-volatile storage layer in an associated first storage magnetization direction determined by said confidential data bit value, and fixing the non-volatile sense layer in an associated preliminary storage magnetization direction that is opposite to the first magnetization direction, whereby said MTJ element exhibits a high resistance value at the end of said write/program operation; during a pre-compare phase performed subsequent to the write/program operation, writing said input data bit value into the non-volatile sense layer by fixing the sense layer in an associated final storage magnetization direction determined by said input data bit value without changing said confidential data bit value non-volatilely stored in said non-volatile storage layer, whereby at the end of said pre-compare phase, said confidential data bit value is non-volatilely stored in said non-volatile storage layer and said input data bit value is non-volatilely stored in said non-volatile sense layer, wherein said MTJ element retains said high resistance value when said final storage magnetization direction is the same as said preliminary storage magnetization direction, and said MTJ element exhibits a low resistance value when said final storage magnetization direction is opposite to said preliminary storage magnetization direction; and during a compare phase performed subsequent to the pre-compare phase, determining if the input data bit value matches the confidential data bit value by measuring a resistance of said MTJ element, wherein said MTJ element further includes an associated field line that is magnetically coupled to said storage layer and said sense layer, wherein writing said confidential data bit value comprises applying a first reference current on said field line, wherein writing said input data bit value comprises applying a second reference current on said field line, and wherein measuring said resistance of said MTJ element comprises applying a read current through the MTJ element while zero current is applied to said field line.