Pinhole imaging in magnetic tunnel junctions

Magnetic tunnel junctions may experience failure due to local short cuts in the insulating layer of such devices. The thicknesses of the insulating layers need to be reduced, which will likely make this problem more prevalent. To develop low resistance magnetic tunnel junctions, the density of pinholes must be analyzed. Using the electrodeposition of copper, we have developed a method for the imaging of pinholes. With the selective nucleation of copper at pinhole sites, structures are formed which can be visualized by conventional microscopy techniques. The potential applied for electrodeposition might cause dielectric breakdown of weak spots in the insulator layer. Variation of the applied voltage will allow identification of such sources of device failure. (C) 2000 American Institute of Physics. [S0021-8979(00)54108-5].