Switching Current Fluctuation and Repeatability for MRAM With Propeller-Shape MTJ

The writing region and the repeatability of the function test and switching current fluctuation of magnetoresistive random access memory (MRAM) with a propeller shape magnetic tunnel junction (MTJ) array is evaluated. The effect of the write sequence is also investigated. The writing region is larger when the easy-axis field pulse is turned on prior to the hard-axis field than that in the case of the opposite sequence. However, the total margin in the latter sequence is larger after the repeated tests because of the smaller switching field fluctuation. The average 1-sigma value of the switching field fluctuation is 1.7%, which is mainly caused by the thermal fluctuation. The probability of the write error is estimated to be less than 10^-16 by the bit line writing region and the thermal stability