Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-06-30
2002-02-26
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S312000, C430S314000, C430S320000, C430S324000, C427S128000, C360S313000
Reexamination Certificate
active
06350556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming a thin film pattern, and particularly to a method of forming a metal film having a fine pattern. Furthermore, the present invention relates to a method of manufacturing a thin film magnetic head having an inductive type thin film magnetic head element, and particularly to a method of forming a pole portion of an inductive type thin film magnetic head element.
2. Description of Related Art
A method of forming a thin film pattern of the present invention can be applied to formation of a high-density wiring pattern in various circuit elements, integrated circuits and the like. Sine the method is particularly suitable for forming a pole portion of an inductive type thin film magnetic head element which is faced to a magnetic record medium, a method of forming such a pole portion will be described in the following. In a thin film magnetic head used in a magnetic disk unit constituting a storage in a computer, a combination type thin film magnetic head in which an inductive type thin film magnetic head element is used as a writing element and a magnetoresistive element (MR element) is used as a reading element has made the main current.
In a combination type thin film magnetic head including a writing inductive type thin film magnetic head element stacked on a reading MR element, the inductive type thin film magnetic head comprises a bottom magnetic film serving also as a top shield for the MR reading element, a gap film, a gap film, a top magnetic film, a thin film coil supported by an insulating film made of an organic resin, and the like.
The end portions of the bottom magnetic film and the top magnetic film have respectively a bottom pole portion and a top pole portion facing each other via the gap film having a very small thickness, and a writing operation is performed by these bottom pole portion and top pole portion.
The bottom magnetic film and the top magnetic film are magnetically coupled with each other at the opposite side to the abovementioned bottom pole portion and top pole portion to form a magnetic circuit. This magnetically coupled portion is called also a back gap portion. The thin film coil is formed such that the coil is wound around the back gap portion.
In order to attain a high recording density using a thin film magnetic head of this kind, it is necessary to increase an amount of data to be recorded in unit area (surface recording density) of a magnetic disk. The surface recording density is governed by the ability of the writing element. The surface recording density can be improved by making small the gap length between the bottom pole portion and the top pole portion in the writing element. However, since shortening the gap length causes a reduction in the intensity of a magnetic flux passing through these pole portions, it is naturally limited.
Another means for improving the surface recording density is to increase the number of data tracks recordable on the magnetic disk. The number of data tracks recordable on a magnetic disk is usually represented by TPI (Tracks Per Inch).
The TPI of the writing element can be increased by making small a head size determining a width of a data track. The head size is usually called a track width of head.
Since an inductive type thin film magnetic head element performs the writing operation in the bottom and top pole portions facing each other via the gap film having a very small thickness, in order to reduce the track width of head determining a width of a data track, it is necessary to reduce a width (a size of the pole portion measured in parallel with the gap) of at least one of the bottom pole portion and the top pole portion.
In case of forming a pole portion, up to now, a photoresist film is formed and then a cut-out pattern is formed therein by a photolithography process. Next, a magnetic film containing a desired pattern of the pole portion is formed in the cut-out pattern by means of an electroplating and the like. Therefore, the accuracy of the pattern of the magnetic film including the pole portion is influenced by the performance of the photoresist film, and the resolution, focus and the like of an exposure light source. Heretofore, the head size of he pole portion has been made narrow and small by selecting a high-performance material as photoresist and shortening a wavelength of the exposure light source. However such a known method could not make a width of the pole portion smaller than a limit size determined by the optical performance of an exposing apparatus used in a photolithography process.
Furthermore, since the photoresist film is formed to have a substantially constant thickness, as a track width of head determining a width of a data track becomes smaller, the aspect ratio (height/width) of a height (thickness) of the photoresist film to a width of the cut-out pattern becomes larger. When this aspect ratio becomes large, even if a high-performance photoresist material is utilized and an exposure light source having a short wavelength is used, the cut-out pattern could not be accurately formed. In such a way, in the conventional manufacturing method, it has been considered that there would be a limit to make narrow and small a track width of head and a thin film magnetic head having a track width of 1 &mgr;m or less is difficult to obtain.
Moreover, in the thin film magnetic head of the kind mentioned above, the insulating film supporting the thin film coil in such a condition that the thin film coil is supported in an insulated and isolated manner, forms a step having an abruptly increasing height. Due to this step, in a photolithography process for forming the top yoke, a photoresist is liable to be deposited have a large thickness at said step. Therefore, the top pole portion has to be formed by patterning a very thick portion of the photoresist deposited on a root of the step, and thus the aspect ratio becomes remarkably high. Due to this, a reduction in a size of the track width of head has a certain limitation.
A technique of minimizing the track width of pole portion by applying an ion beam milling process has been known. However, it is difficult to attain a track width of 1 &mgr;m or less even by using such a technique. Moreover, it is difficult to mill vertically both side walls of the pole portion viewed in a direction of the track width of pole portion and both side walls are liable to form tapered faces spreading slightly wider toward the bottom. When the pole portion has such tapered faces, a problem of side fringing occurs.
In order to prevent the side walls of the pole portion from being tapered, a method of irradiating the side walls with an ion beam at a certain angle is disclosed in the specification of U.S. Pat. No. 5,438,747 issued to Krounbi et al., on Aug. 8th, 1995. However, since this method could not easily form vertical side walls of the pole portion, it is difficult to manufacture a thin film magnetic head having a track width of 1 &mgr;m or less.
In addition to the above described method of forming the pole portion of the inductive type thin film magnetic head, in a method of forming a wiring pattern in various circuit elements, integrated circuits or the like, after a photoresist film has been formed on a substrate, a cut-out pattern is formed by a photolithography process and a wiring metal film having a given pattern defined by the cut-out pattern is formed. Also in such a method, it is difficult to make a line width of a metal film smaller than a limit size determined by the optical performance of an exposing apparatus used in the photolithography process. And such a problem occurs in the same way not only in case of forming a metal film pattern but also in case of forming a thin film pattern of another material.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of forming a thin film pattern, said method being capable of forming a thin film pattern, particularly, a metal film pattern whose width is set at a very small value
Barreca Nicole
Huff Mark F.
Oliff & Berridg,e PLC
TDK Corporation
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