Ion-beam-etched profile control of MTJ cells for improving the switching characteristics of high-density MRAM

Since the enhancement of write operation region is one of the key factors for realization of the high-density MRAM, the control of the astroid curve by novel MTJ shape and the reduction of the switching field distribution were examined. Although good bit yields are obtained by the 2-step-etch processing of MTJ using ion beam etching (IBE), the influence of the redeposition of magnetic materials at the time of the 1st etch step, which stops at barrier layer, on the write operating characteristic is a source of concern. By controlling the etched profile at the time of the 1st IBE step, formation of the redeposition layer is prevented and the write operation region of the MTJ array is improved.