The present invention relates to the surface of a thin-film magnetic head serving as the interface between the head and a recording medium. More particularly, it relates to a thin-film head with a smooth topography interface surface which has patterned magnetic poles.
In magnetic recording devices, thin-film magnetic heads retrieve ("read") and store ("write") information to magnetic media by magneto-resistively or inductively sensing the magnetization of and creating respectively, localized magnetic domains in the media. When reading information from a magnetic medium, a thin-film head's interface surface moves over the medium at a short distance from the medium so that magnetic flux from the localized domains enters permeable material pole tips in the interface surface. This flux extends over a selected permeable material path from the surface of the pole tips at the interface surface to an electromagnetic transducer which converts the magnetic flux in the path into an electric read current. The electric read current is used by the recording device in which the head is mounted to create an electric read signal.
Thin-film heads are usually constructed using material deposition and etching techniques similar to those used in monolithic integrated circuit construction. In production, large numbers of heads are constructed on a large substrate, usually a wafer, by material deposition and etching techniques which construct the thin-film heads by layers. The heads are built up in a direction parallel to the plane of the eventual interface surface which is perpendicular to the plane of the substrate surface. This means that the basis for the eventual interface surface is located within the wafer when the deposition and etching process on the wafer is finished.
To expose the surface of the pole tips after this process, the wafer is sliced into rows near the ends of the pole tips. For each thin-film head, this creates a working surface that includes the surfaces of the pole tips. In some methods, the individual thin-film heads are simply cut from these rows and placed, as is, into magnetic recording devices with the working surfaces serving as the interface surfaces. In such methods, the shape of the pole tips is determined by the wafer-level etching and deposition procedures.
However, in other methods, the ends of the pole tips near the working surface are reshaped after the thin-film heads are cut into rows. To reshape the pole tips, the rows of thin-film heads are rotated to place the working surfaces in a common plane. Portions of the working surfaces are then masked with a layer of photoresist using known photoresist technology. A removal agent, such as an etching substance or ion milling beam, is then directed towards the masked and unmasked portions of the working surfaces. The removal agent removes material from the unmasked portions without affecting the masked portions, creating a depression around the masked portions and reshaping the ends of the pole tips near the pole tip surfaces.
When the head is placed in a magnetic recording device, the milled out depression around the patterned pole tips tends to accumulate foreign material around the pole tips during use. This foreign material often leads to device failures because of resulting mechanical damage to the pole tips. Prior approaches attempted to minimize this accumulation by opening channels in the pole tips to allow the foreign material to pass through the pole tips. This strategy has not been successful in removing all of the foreign material that accumulates in the depression and therefore has not eliminated the mechanical damage associated with the depressions.