T-Head with Chamfered P3 Base Corners to Reduce Side-Writing and Method for Making the Same
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-20
Described is a magnetic recording head write structure that provides additional flux carrying capacity through a supplementary pole overlayer (P3) which is situated above a conventional top pole (P2) of a write element, having a lateral dimension (P3B) wider than a written track determined by a width of the top pole at a write gap (P2B), a so-called T-head structure, and yet is essentially free from side-writing anomalies that attend high fringing fields that emanate from bottom corners of P3 in proximity to P2 at an air-bearing surface (ABS). The fringing fields are reduced by chamfering the bottom corners of P3. The device structure is essentially a T-head with chamfered P3 base corners. Also, described are methods for making the same. It is known that adding a P3 layer of wider dimension than P2 has advantages for over-write performance of a write head, but it also can cause "side-writing" which appears as satellite tracks parallel to the central track written by the gap. In microtrack profiles, these satellite tracks appear as "bumps" of anomalous flux density on either side of the written track profile. As a consequence, the written track windage is increased by these side-tracks which limits areal density. The origin of these satellite tracks has been confirmed by micro-Kerr microscopy of the pole tips which shows high flux concentrations emanating from the bottom corners of P3. A preferred, first embodiment of the invention comprises a magnetic recording head write structure having a write head element with a bottom pole (P1) separated from a top pole (P2) by a write gap (G3); the top pole (P2) is disposed in proximity to and underneath a supplementary pole overlayer (P3) having a wider dimension (P3B) than a dimension (P2B) of the top pole at the write gap, giving the top pole tip a so called "T-shape"; the corners at a base of the P3 are chamfered to have a circular shape having a radius of curvature sufficiently large to lower a fringing field below a level whereby a recording medium can be written. A second embodiment comprises a magnetic recording head write structure as described above wherein the corners at a base of the P3 are chamfered simply by breaking the corners along a line that cuts a triangular portion of a corner away to lower a fringing field below a level whereby a recording medium can be written. A third embodiment comprises a magnetic recording head write structure as described above wherein the corners at a base of the P3 are chamfered by breaking the corners along a line that cuts a triangular portion of a corner away, and repeating a process of breaking corners created in a previous step so as to approximate a rounded corner with an inscribed circle having a radius of curvature sufficiently large to lower a fringing field below a level whereby a recording medium can be written. A preferred embodiment for making the same comprises a method for producing the structure of the first embodiment above by use of photolithography and plating at wafer level to produce a P3 shape with chamfered bottom corner edges. Another embodiment for making the same comprises a method for producing the structure of the second and third embodiments above by use of focused ion beam (FIB) milling at row or head level to remove triangular portions at both corners. These embodiments should not be construed to preclude such embodiments as ion-milling at row level through a photoresist mask disposed and shaped to allow milling away the P3 base corners or other similar embodiments which would be obvious to those skilled in the art.