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Silicon nitride overcoats for thin-film magnetic recording heads

IP.com Disclosure Number: IPCOM000015001D
Original Publication Date: 2001-Sep-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 100K

Publishing Venue

IBM

Abstract

Disclosed are the usage of silicon nitride (SiNx) protective overcoats for head sensors of magnetic disk drives and methods to deposit them.

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Silicon nitride overcoats for thin-film magnetic recording heads

   Disclosed are the usage of silicon nitride (SiNx) protective overcoats for head sensors of magnetic disk drives and methods to deposit them.

   Continuation of the rapid increase in the recording density of magnetic disk drives necessitates the reduction of magnetic spacing between the magnetic head sensor and the disk medium. This can be partly achieved by reducing the thickness of the protective overcoat on the head sensor. The protective overcoat on the magnetic head is used to provide wear and corrosion protections during the slider processing and subsequent operations. Current magnetoresistive (MR) sensors are composed of several different metal constituents that are galvanically coupled. Of these metals, Co, Cu, and CoFe usually corrode preferentially and present a significant reliability problem. The magnetic recording industry uses variants of Diamond-like Carbon (DLC) overcoat to protect magnetic heads. While DLC can satisfactorily provide wear protection, it is porous and hence cannot provide adequate corrosion protection for MR elements. Moreover, the carbon process requires the deposition of an additional Si seed layer for adhesion purpose. As a result, the total overcoat thickness ranges from 50-120 Å. In contrast, silicon nitride (SiNx) films are denser and harder than typical carbon films produced by sputter deposition and ion beam deposition. Additionally, silicon nitride is an exceptional diffusion barrier. Hence, it is possible to reduce the thickness of the overcoat to 20-50 Å using SiNx without compromising the wear and corrosion resistance.

Ultra-thin protective overcoats need to have high hardness and low porosity. The hardness and density values of silicon nitride and carbon films are listed in the following table.

               Hardness (GPa) Density (g/cm3) Actual/Bulk Density sputtered SiNx 22-26 2.9-3.05 90-95% sputtered DLC 10-20 1.6-2.0 46-57% ion beam deposited
17-25DLC 1.7-2.1 49-60%

It is clear that sputtered SiNx films have higher hardness than sputtered DLC films. However, what dist...