Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-09-13
2003-05-13
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06563669
ABSTRACT:
TECHNICAL FIELD
The present invention is related to the field of thin filmed magnetic write transducer structures and methods of fabrication.
BACKGROUND ART
Magnetic storage media uses increasingly narrower track widths to increase the amount of data that can be recorded per square inch. Narrow track widths require tight control of the dimension and shape of the magnetic transducer's poles near and at a write gap. As the magnetic write transducer and magnetic media move relative to each other, it is generally the trailing pole of the magnetic write transducer that determines the effective size of the track width written in the magnetic media.
Two widely used methods of controlling pole width and pole sidewall profiles during wafer fabrication are electroplating and ion milling. Optically patterned photoresist layers produce well defined, steep sidewall profiles that make excellent electroplating templates. In an electroplating process, an electrically conductive seedlayer is deposited on the wafer before the photoresist. The photoresist is then deposited, exposed, and developed. Plating is then performed with the seedlayer carrying the plating current. After plating, the photoresist is stripped and a quick etch removes the unwanted areas of the seedlayer. A drawback to this process is that the plated poles tend to be softer than vacuum deposited poles. This results in a shorter life span for thin film magnetic heads in tape applications where the poles wear against the magnetic tape medium causing pole tip recession.
Vacuum deposited poles can be made of harder materials thus resulting in a longer life span for the thin film magnetic write transducer. A problem with vacuum deposited poles, however, is controlling the size and shape of the top pole. The magnetic material used to create the top pole is usually deposited to a thickness of three to five micrometers. Chemical etching of unwanted material is generally quick and simple to perform, but results in sloped sidewalls and average control of the top pole's longitudinal width. Precision removal of unwanted material at these thicknesses generally requires ion or focused electron beam milling. These techniques can produce steep sidewalls with good longitudinal dimension control. However, ion milling through five microns of a hard material can be time consuming and expensive. Furthermore, control of the dimensions at the bottom of the layer being milled decreases as ion milling depth increases.
A variation on ion milling during wafer level fabrication is to perform the milling at the device level. Individual transducers, or arrays of transducers, are fabricated and then cut from the wafer. The side of the transducers that is to become the air bearing surface (in magnetic disk applications) or tape bearing surface (in magnetic tape applications) is then polished to produce the media (tape or air) bearing surface. Ion milling takes place into the media bearing surface to trim the top pole, and usually part of the bottom pole adjoining the write gape. Voids left by the ion milling are filled in tape media applications, and left open in environmentally sealed magnetic disk drive applications. Here, the milling can be shallower than cutting through the entire top pole layer giving better dimensional control. Media bearing surface milling can also be performed over a small area resulting in less debris being redeposited elsewhere. However, handling each individual/array of magnetic transducers for milling is time consuming and expensive. Furthermore, errors in the milling process that results in scrapping of the magnetic transducers occur after many other fabrication steps have been completed. Scrapping a transducer at this point is costly.
DISCLOSURE OF INVENTION
The present invention is a method of fabrication, and the resulting structure for a thin film magnetic transducer having two poles separated by a gap. A bottom pole and top pole are fabricated where the longitudinal dimension of the bottom pole is smaller than the top pole in a zero throat region resulting in an “inverted” structure, as compared with convention designs. An upper portion of the bottom pole is ion milled in at least the zero throat region early in wafer-level fabrication to produce a precise width adjoining the gap layer. The trimmed upper pole portion of the bottom pole results in an improved write pole geometry that produces tightly defined data tracks.
In a preferred embodiment, a planarization layer is deposited over the bottom pole after patterning of the bottom pole is complete. This planarization layer is then lapped to expose the underlying bottom pole. Lapping may also remove part of the upper portion of the bottom pole. Partial removal of the upper portion reduces the effective thickness of the upper portion from a target upper portion thickness to a final upper portion thickness.
Accordingly, it is an object of the present invention to provide a method for fabricating a magnetic transducer, and resulting magnetic transducer structure wherein the top pole is wider than the bottom pole, and the bottom pole has an even narrower upper portion adjoining the gap layer that controls track width.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.
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Biesecker John P.
Cates James C.
Daby Larry E.
Brooks & Kushman P.C.
Evans Jefferson
Storage Technology Corporation
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