Composite SiNx/Carbon (DLC) Overcoat Barrier Layer for Improved Corrosion Resistance in Storage Devices
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-19
In conventional Carbon overcoat for slider devices in storage head , silicon/carbon (DLC) overcoat films had been used and protective overcoat material due to its excellent tribological and interface properties. In this composited structure, the thin silicon layer (10-20A) acts as an adhesion layer while the carbon film provide the desirable head/disk interface tribological properties. As the density of the storage device increases above 50 Gigabit/cm2, the overcoat layer becomes much thinner into the range of 2-4 nm. At this thickness range, the step coverage of the corrosion resistance of the overcoat becomes very important. This means that the thin adhesion layer not only must be able to provide adhesion between the substrate and the carbon layer, but also the corrosion resistance under storage device operating conditions. In recent head storage devices, ion beam deposition process has been used to deposited silicon/Diamon-like Carbon (DLC) films as overcoat protection layer. It has been known that Silicon Nitride films has a better corrosion resistance than other silicon dielectrics and has been widely used as passivation layer for integrated circuit devices (1). Hydrogen free silicon nitride films can also be sputtered on various surfaces by ion beam deposition process(2). Data showed that adhesion between silicon nitride silicon-rich silicon nitride films with DLC is quite good. Since silicon nitride films thickness must be slightly above 2 nm to be a continuous film and provide good corrosion and moisture resistance, the desirable and effective thickness for the silicon nitride layer should be at least 2 nm or above to provide good corrosion and moisture resistance. For composited SiNx/DLC and SiNx-Si/DLC overcoat on Silicon sliders, our experimental test results on corrosion dipping test for 7 hour in NaCl solution showed the SiNx films thickness of 2-2.8 nm produced good adhesion and corrosion rersistance in the SiNx/DLC composited overcoat with less than 2 fail as shown below.