Optimization of tunneling magnetoresistance of MgO based tunnel junctions by tuning the stage impedance for radio frequency sputtering of the barrier

摘要

In this article, we describe a method to maximize the tunneling magnetoresistance of magnetic tunnel junctions with MgO tunneling barrier by optimizing the stage impedance for the RF MgO deposition. The impedance can be varied continuously using a matchbox that is in place to apply a RF bias to the stage. It is measured by means of a network analyzer connected to a dummy wafer on the stage. For positive stage reactance, both resistance area product and tunneling magnetoresistance are observed to drop, related to the stage impedance resonating with the plasma sheath capacitance. At high negative stage reactance, resputtering is minimized and tunneling magnetoresistance maximized.