Ion milling induced ESD damage during MR head fabrication

An ESD-like damage mechanism relating to ion milling of MR devices at the wafer level has been identified. This failure is seen as an increased incidence of dielectric shorting between reader and shield at an in-process test point and is accompanied by an increase in MR sensor resistance. Beam neutralization conditions from a Kaufman ion source mill during particular wafer fabrication steps are shown to have been responsible for these failures. As the neutralization of the ion beam was inadequate, induced electrical potential differences can build up between the reader and the shield. Even small milling process nonuniformities then allow adequate time to differentially charge the device´s reader and shield contacts to several volts. The resulting EOS condition has led to breakdown of the read gap dielectrics. The evidence for these conclusions and the corrective actions required are presented.