Browse Prior Art Database

Dual Layer Overcoat Disclosure Number: IPCOM000013482D
Original Publication Date: 2001-Aug-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue



Disclosed is a new overcoat process on wafer level. The modification allows reducing significantly the amount of redeposited metallic material. Especially copper redeposition in the pole zone may act as a starting point for corrosion or may lead to copper protrusion. Redeposition is caused by pre sputter etching and occurs on surfaces where the etching rate is less compared to the deposition rate of previously removed material. Typically, this occurs at the sidewalls of pronounced features of a surface. Here a dual layer overcoat process is described to overcome redeposition issues. The first overcoat is thin and reactively sputtered and can be deposited without a presputter etch. This avoids redeposition below the overcoat 1. Furthermore, overcoat 1 covers all metallic material including copper. Overcoat 2 is deposited including an intense sputter etch step. In contrast to the situation before, the redeposited material is no more metallic but alumina. Therefore the visible redeposition vanishes completely or is reduced significantly. An overcoat made of alumina (Al2O3) is used for packaging of magnetic read write heads. The alumina coats mechanically and chemically sensitive structures like the pole tips and copper leads. These structures are not planar but show strong topography including perpendicular walls. During a sputter etch step, most likely, redeposited copper will contaminate the surface left and right of the poletip. Indeed, copper is found on the sidewalls of the poletip 2 at the ABS (Air Bearing Surface). Corrosion and/or protrusion are possible consequences of presence of copper. For example this may lead to incorrect flight height control. Fig: 1. ABS view of a write head using standard overcoat process (left) and modified overcoat process (right). Only a tiny residual of the redeposited material can be detected at the modified head. Strong copper redeposition is remaining using the standard process. Processing the dual layer overcoat the amount of copper is dramatically reduced. In Fig. 1 the result of both processes is compared. Both pictures show electron micrographs from the ABS at row level. The headtypes shown in the pictures are not identical but similar. Attention should be focused at the bright lines left and right of the sidewalls of the poletip. These lines are metallic. An EDX analysis verified that this material is copper. Obviously, the disclosed dual layer overcoat process results in a