Recessed SiO2 or Si3N4 overcoat for GMR head in magnetic disk drive

摘要

A giant magnetoresistive (GMR) head contains an overcoat layer consisting of silicon dioxide or silicon nitride. These materials have a coefficient of thermal expansion (CTE) that is less than alumina, which is conventionally used for the overcoat layer. As a result, the overcoat layer exhibits a smaller temperature-induced protrusion when the head heats up from friction with the passing air stream. The process of forming the head includes forming a recess in the overcoat layer that reduces the stress on the poles and improves the performance of the head. The process includes depositing a seed layer over the overcoat layer in preparation to plating a metal mask layer with an opening where the recess is to be formed, wet chemical etching the seed layer through the opening in the mask layer and performing an ion milling process to remove any remaining traces of the seed layer. With the seed layer completely removed, a trench having smooth sidewalls and bottom can be etched in the overcoat layer by a reactive ion etch (RIE) process. The saw that is used to separate the head elements in the wafer can be passed through the clean trench without contacting the overcoat layer, thereby avoiding the chipping and cracking that might otherwise result from the use of a silicon dioxide or silicon nitride overcoat layer.