Effects of initial layer surface roughness on GMR performance of Si/Cu/NiFe/Cu/Co/Cu/NiFe dual spin-valves for MRAM

The effects of initial layer surface roughness on GMR performance for magnetoresistance random access memory (MRAM) have been investigated as a function of Cu buffer layer thickness and input sputtering power of Si/Cu/NiFe/Cu/Co/Cu/NiFe dual spin valves. The GMR ratio increased up to 4.5% as Cu buffer layer thickness decreased from 30 nm to 5 nm and input sputtering power increased from 50 to 300 W. According to ex-situ atomic force microscopy and Auger electron spectroscopy analyzes, the higher GMR ratio is mainly due to smoother interfacial roughness of the multilayers and smaller oxygen content inside the GMR stacks. It is revealed that the initial layer surface roughness is dependent upon the deposition parameters and film thickness plays a key role in determining the surface roughness and magnetic coupling of subsequent magnetic multilayers.