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Protection of GMR Write/Read Sensor During Fabrication Process to Avoid In-line Corrosion and Electrostatic Discharge Damage Disclosure Number: IPCOM000015347D
Original Publication Date: 2002-Feb-21
Included in the Prior Art Database: 2003-Jun-20

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After rows are sliced from a quad in the GMR head slider fabrication process, bare metal of the write head and the read sensor are exposed to the ambient environment with only the nascent oxide layer as a protection layer. Subsequent to the slicing operation, the rows are often subjected to various process steps in aqueous environment such as backlap and post-backlap cleaning that can disrupt the nascent oxide layer and the metal will start to corrode. In addition, the build-in galvanic cell in the GMR read sensor with the CoFe-Cu-CoFe sandwich structure makes it particularly sensitive to corrosion in an aqueous environment. Even an adsorbed moisture layer on the bare metal may be sufficient to cause corrosion of this galvanic couple. It is thus very important to protect the bare metal with a stronger protective layer so that it can survive the ambient environment and the various aqueous processes. In addition, the GMR sensors are embedded in an alumina surrounding and is therefore susceptible to electrostatic discharge damage. The present disclosure discloses the use of a thin layer (on the order of 10A to 500A) of Al, Zn, Sn, Ti or Cr to protect the bare metal right after slicing such that the read/write sensors are protected from in-line corrosion. Since the coating is metallic in nature, it can also protect the sensors from ESD damage. Furthermore, the use of Al and Zn can serve as sacrificial anodes and cathodically protect the sensor metals, even when the surface is scratched during the various processes, and therefore Al and Zn are the most desirable protection layers. The protective layer could be applied by various vacuum processes such as sputtering. The coating process can also include sputter etch to remove the nascent oxide layer or other contamination prior to the deposition of the protective coating to ensure good adhesion. 1