Reexamination Certificate
1999-08-09
2002-03-12
Nguyen, Nam (Department: 1753)
C204S298320, C156S345420, C250S492100, C250S492210, C250S492220, C250S492300
Reexamination Certificate
active
06354438
ABSTRACT:
BACKGROUND
This invention relates to methods and apparatus for manufacturing improved thin-film magnetic recording heads. More specifically, the invention relates to a multi-layer lithographically fabricated device used to produce the improved thin-film recording heads. It further relates to a focused particle beam system for milling a recording head pole-tip assembly without irradiating a sensitive structure, e.g. a read head, of the recording head.
Thin-film magnetic recording heads have gained wide acceptance in the data storage industry. A thin-film recording head has a small, precisely formed pole-tip assembly. The size and shape of the pole-tip assembly, which includes features on the order of one-half a micron, in part determines the magnetic field pattern produced by the recording head. This magnetic field pattern affects how narrowly the recording head can record data tracks on the magnetic media of magnetic memory storage devices, such as computer hard disks, and digital data tape drives.
Thinner data tracks allow a storage device to store more data tracks per area of media and therefore more data per device. Accordingly, precisely forming the pole-tip assembly of the recording head results in an increase in the total data storage capacity of a magnetic memory device. Manufacturers seek to form the geometry of the pole-tip assembly with high precision, and to thereby achieve pole-tip assemblies capable of providing magnetic field patterns suitable for writing narrow tracks of recorded data.
Manufacturers presently endeavor to form the precise shape of the pole-tip assembly by employing a lithographic technique to fabricate a multi-layer device. The multi-layer device contains the structure for a recording head. As stated above, a thin-film recording head has a small pole-tip assembly. Typically, the lithographic technique deposits alternating layers of conductive and insulating materials onto a substrate by an evaporation, sputtering, plating, or other deposition technique that provides precise control of the deposition thicknesses. Chemical etching, reactive ion etching (RIE), or other mechanisms shape and form the deposited layers into a pole-tip assembly having the desired geometry. Thus, the pole-tip assembly is contained within a multi-layer lithographically fabricated device.
Although existing lithographic techniques work sufficiently well to provide pole-tip assemblies having feature sizes suitable for current data storage capacity, these lithographic techniques are limited as to the small feature sizes that they can produce. For example, present photolithographic techniques require precise application of photoresist layers. Commonly, the photoresist layer is applied to produce a topology that includes voids having 10:1 aspect ratios. Such topologies are difficult to achieve reliably using such a photoresist technique.
Thus, these lithographic techniques are poorly suited for achieving a high yield of precisely formed pole-tip assemblies. In the interest of increased areal storage density, manufacturers decrease the dimensions of a desired pole-tip assembly. As the dimensions of the desired pole-tip assembly decrease, manufacturers, using existing lithographic techniques, experience high yield loss. In other words, even if manufacturers using existing lithographic techniques are successful achieving a desired pole-tip assembly configuration, they will achieve that desired configuration with a low yield (e.g. only 20-40% of the recording heads produced using existing lithographic techniques will have the desired configuration).
The defective structures that occur during the manufacturing process are difficult to predict and are prone to wide variations. Accordingly, the application of a universal photoresist pattern to the surface of a pole-tip assembly is a generalized solution that often is ill-suited to the actual manufacturing defect of any one recording head. Therefore, current techniques for producing a magnetic recording head have several serious limitations with respect to their ability to control the physical geometry of the recording head.
Consequently, current techniques are often unacceptable for accurately shaping recording heads for use in the higher density data storage devices desired for computers. More specifically, higher density data storage devices can require micromachining of the recording head used with the devices. Manufacturers can micromachine the recording head while it is contained in a multi-layer lithographically fabricated device. The micromachining of the recording head can require accurate shaping of a second structural element, e.g. the write head, in a second layer in relation to a first structural element, e.g. the read head, in a first layer. However, the first structure can be a sensitive structure such as a Magneto-Resistive Stripe (MRS). For background information on the design and function of MRSs and inductive write heads, see Magneto-Resistive Heads, Fundamentals and Applications by John C. Mallinson (Academic Press, Inc., San Diego 1996).
It is important to note that both the MRS and the write head can each have sublayers. MRS's can include thin-film sublayers five to six angstroms thick. Thus, the focused particle beam system cannot image the first structure to determine the desired shape and location of the second structure because the first structure could be damaged by the imaging process. Furthermore, the associated layer-to-layer registration errors due to lithographic overlay tolerances are larger than the accuracy to which the system must shape the second structure.
Accordingly, it is an object of the present invention to provide methods and apparatus for manufacturing improved thin-film magnetic recording heads, and, more particularly, for precisely forming the pole-tip assembly of a magnetic recording head without irradiating a sensitive structure, e.g. a read head, in the recording head.
It is a further object of the present invention to provide a multi-layer lithographically fabricated device for manufacturing improved thin-film recording heads.
It is a further object of the present invention to provide a lithographic process for fabricating a multi-layer device for manufacturing improved thin-film recording heads.
It is yet another object of the present invention to provide methods and apparatus for manufacturing improved thin-film recording heads using a focused particle beam.
The invention is next described in connection with certain embodiments; however, it will be clear to those skilled in the art of semiconductor device fabrication that various modifications, additions and subtractions can be made to the described embodiments without departing from the spirit or scope of the invention.
SUMMARY OF THE INVENTION
One embodiment of the invention precisely forms a pole-tip assembly by milling a second structural element without irradiating a first structural element. The invention avoids irradiating the first structural element by placing a first marker element, which can be imaged and/or damaged, in the same layer of a multi-layer lithographically fabricated device as the first structural element. The marker element has a fixed spatial relationship to the first structural element. Thus, by imaging the first marker element and the second structural element, and knowing the separation between the first structural element and the first marker element, a focused particle beam system can determine the relative location of the first and second structural elements. Consequently, the focused particle beam system can determine, without irradiating the sensitive first structural element, which portions of the second structural element require milling. In this manner, the focused particle beam system mills the second structural element to produce a desired pole-tip configuration. By producing a desired pole-tip configuration, these methods and apparatus produce an improved recording head capable of higher storage density than prior art techniques.
Thus, the invention provides lithographic methods and apparat
Athas Gregory J.
Hill Raymond
Lee Randall Grafton
Libby Charles J.
Mello Russell
Cantelmo Gregg
Foley Hoag & Eliot LLP
Greenberg Robert A.
Liepmann W. Hugo
Micrion Corporation
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