1. Field of the Invention
This invention relates to the fabrication of a thin-film magnetic head. In particular, it relates to a method of fabricating a stitched writer portion of such a head that is suitable for high data-rate recording of magnetic information.
2. Discussion of the Related Art
Thin film magnetic heads are used to record and retrieve data stored in the form of small magnetized regions on disks and tapes. These heads contain a read portion, which is typically a shielded magnetic field sensor of a giant magneto-resistive (GMR) type, and a write portion, consisting of a magnetic pole and yoke structure inductively energized by current carrying coils.
The need to record and retrieve data stored with increasing area densities and at increasingly higher data rates has necessitated the design of very narrow write heads with high linear resolution. The narrow write head allows data to be stored in correspondingly narrow tracks. The high linear resolution, which is achieved by the formation of a thin write gap and a strong magnetic field, allows the storage of more data per unit length of track.
An important advance in the fabrication of write heads that help to meet these stringent requirements is the so called xe2x80x9cstitched write head design.xe2x80x9d This design embodies a simplified method of forming a narrow upper magnetic pole piece by joining or xe2x80x9cstitchingxe2x80x9d together two separately deposited pole pieces, the upper pole tip and the upper pole yoke, along a pedestal formed from a portion of the upper pole tip photoresist mask. In contrast to methods that form the upper pole piece and yoke monolithically, the stitching process allows the narrow tip section to be formed within a thinner photoresist mask, which is highly advantageous in the context of the fabrication process.
The performance of the stitched writer design and the advantages inherent in the nature of its fabrication process can be further improved by overcoming several deficiencies which limit its applicability to high data-rate recording. In particular, the stitched writer head as formed by the methods of the present art has a lengthy throat region along which the magnetic flux is diminished. Thus, in order to maintain an acceptable flux level for recording at the air-bearing surface (ABS), the design requires a high saturation writing current. This, in turn, causes side erasures and adversely affects data already written on adjacent disk areas.
Several methods have been advanced to improve the flux characteristics of the stitched writer design and, indeed, to improve such other designs as have been suggested to meet the need for high recording resolution. Chang et al. (U.S. Pat. No. 5,805,391) teach a method for forming a write head with a recessed stitched yoke on a planar portion of an insulating layer. The contour of said insulating layer minimizes the flux leakage between the yoke portion and the pole tip portion stitched to it. Two inventions of Chen et al. (U.S. Pat. No. 5,652,687 and U.S. Pat. No. 5,802,700) teach methods for forming a write head having a U-shaped notch which opens out at the air-bearing surface and between whose ends is formed the upper pole tip. The structure so formed provides a parallel path for conducting the magnetic flux to said pole tip, thereby allowing the proper flux concentration for writing in narrow trackwidths. The invention of Cole et al. (U.S. Pat. No. 5,452,164) teaches a method of forming a pole tip structure that lays both above and below the write gap and has a track width of less than 1 micron. The symmetry of this arrangement supports good flux transfer with no leakage. The invention of Santini (U.S. Pat. No. 5,621,596) provides a method for improving the resolution of the photolithography process that is used to define the shape of the pole tip. Specifically, the invention teaches a method of reducing light reflections in the photolithography process by moving the point at which the pole yoke flares sufficiently far back from the position of the pole tip so that reflections from the flare do not interfere with the definition of the pole tip.
An alternative approach to improving the flux characteristics of the stitched pole design involves concentrating the flux by improving the geometry of the junction between the upper pole tip and upper pole yoke. This is presently being achieved by a design (FIG. 1) that incorporates a recessed upper pole yoke (FIG. 1 (10)) and a xe2x80x9cstepxe2x80x9d (FIG. 1 (12)) formed of non-magnetic material positioned in the rear underside of the pole tip where it contacts the write gap layer. The step effectively channels the flux through a smaller area, thereby increasing its intensity across the write gap region (FIG. 1 (14)) and enhancing the writing process. Although the use of the step provides a significant improvement in the stitched head design, its placement in the pole tip will ultimately prove to be disadvantageous as thinner pole tips and shorter throat heights are increasingly necessitated for high data-rate applications. The present invention teaches a method for fabricating a recessed yoke, stitched head writer with the flux concentrating advantages of the step formation, but without the disadvantages of the step placement in the upper pole tip.
A first object of this invention is to fabricate a stitched pole magnetic write head that is capable of recording magnetic data at high rates and increased densities.
A second object of this invention is to fabricate a stitched pole magnetic write head that has a lower saturation write current.
A third object of this invention is to fabricate a stitched pole magnetic write head with improved nonlinear transition shift performance.
A fourth object of this invention is to fabricate a stitched pole magnetic write head having improved overwrite performance.
A fifth object of this invention is to fabricate a stitched pole magnetic write head that significantly reduces the problem of side erasure.
A sixth object of this invention is to fabricate a stitched pole magnetic write head with a reduced effective throat height and upper pole thickness.
These objects will be achieved by means of a novel modification of the present stitched pole, stepped pole-piece fabrication process. The proposed modification is the removal of the step from the underside of the upper pole piece and its effective repositioning in the form of a xe2x80x9crecessed step,xe2x80x9d a non-magnetic spacer embedded into an upper layer of the lower pole of the write head, said spacer thereby being placed beneath the write gap layer of said write head. The flux concentrating region so formed is less sensitive to the position of the upper pole piece, thereby allowing the formation of a shorter throat height as will be required in future high data rate applications.