Ion milling-induced ESD damage during MR head fabrication

An ESD-like damage mechanism relating to ion milling of MR devices at the w afer level has been identified. This failure is seen as an increased incide nce of dielectric shorting between the reader and shield at an in-process t est point and is accompanied by an increase in MR sensor resistance. Beam n eutralization conditions from a Kaufman ion source mill during particular w afer fabrication steps are shown to have been responsible for these failure s. Because the neutralization of the ion beam was inadequate, induced elect rical potential differences can build up between the reader and the shield. Even small nonuniformities in the milling process then allow adequate time to differentially charge the device's reader and shield contacts to severa l volts. The resulting EOS condition has led to breakdown of the read gap d ielectrics. The evidence for these conclusions and the corrective actions r equired will be presented. (C) 1999 Published by Elsevier Science B.V. All rights reserved.