Magnetic Tunnel Junction (MTJ) Patterning for Magnetic Random Access Memory (MRAM) Process Applications

We have developed a top free type magnetic tunnel junction (MTJ) patterning technique that involves tunnel barrier etching with enough time margins for chemical assisted ion etching (CAIE). The approximately 1 nm thick tunnel barrier enables stopping the etching process in a shorter time margin. We have found that no aluminum-oxide barrier shorting by re-deposition occurred in chlorine based CAIE, when the etching depth into anti-ferromagnetic IrMn layer was less than 5 nm. The magnetoresistance (MR) ratio of the whole MTJ patterns reached 35% on a 6-inch wafer. The time margin of the etching was 120 s, which is long enough for an magnetic random access memory (MRAM) process.