Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
2002-10-18
2003-12-02
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S130000, C427S131000, C427S331000, C427S402000, C427S261000, C427S264000, C427S271000, C427S595000
Reexamination Certificate
active
06656538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a magnetoresistive device including a magnetoresistive film pattern with a predetermined shape, a method of manufacturing a thin film magnetic head including such a magnetoresistive device disposed on a base, and a method of forming two or more thin film patterns with different sizes on a same base.
2. Description of the Related Art
In recent years, an improvement in performance of thin film magnetic heads has been sought in accordance with an increase in areal recording density of hard disk drives or the like. A magnetoresistive (hereinafter referred to as MR) head (MR head) including a MR device which is one of magnetic transducers is widely and commonly used as a reproducing head portion in the thin film magnetic head.
The examples of the MR device include anisotropic magnetoresistive (hereinafter referred to as AMR) devices using a magnetic film (AMR film) exhibiting an AMR effect, giant magnetoresistive (hereinafter referred to as GMR) devices using a magnetic film (GMR film) exhibiting a GMR effect and so on. A typical GMR device is a spin valve type GMR device, and the thin film magnetic head with a reproducing head portion using the spin valve type GMR device has been widely put to practical use.
Recently, the development of tunneling magnetoresistive (hereinafter referred to TMR) devices which have higher reproduction performance as compared with the spin valve type GMR devices, that is, can obtain a higher magnetoresistive ratio has been advanced. Signals stored in a recording medium having a smaller track width for high density recording can be reproduced by use of the TMR device.
In order to reduce variations in the reproduction performance of the MR head, it is required to reduce variations specifically in the dimensional accuracy of a MR height during patterning of the MR film. The MR height is a length (height) from an end on the side of a surface of the MR device facing the recording medium (air bearing surface) to the other end, and a polishing amount during processing of the air bearing surface determines the MR height.
Regarding the MR height, the applicant of the present invention has proposed a method of manufacturing a MR device capable of reducing variations in electromagnetic properties of the completed MR device and changes in the center of a distribution in electromagnetic properties of the completed MR device, and meeting predetermined specifications for magnetic reproduction in, for example, Japanese Unexamined Patent Application Publication No. 2001-006128. The method comprises the following steps.
First of all, a plurality of MR heads as well as a plurality of dummy resistive films which are thin film structures are formed on a base made of a material such as a ceramic, for example, through photolithography or the like. Then, the base is cut by use of a dicing saw or the like to form a plurality of bars each comprising a plurality of MR heads and a plurality of dummy resistive films.
Next, the plurality of bars obtained through the above step are set on a polishing apparatus or the like to mechanically polish their cut surfaces, that is, their air bearing surfaces. Mechanically polishing is not carried out while monitoring the dimension of the MR height, but while monitoring the electrical resistance of the dummy resistive films which have been already formed, in advance, on the bars. When the electrical resistance reaches a predetermined value, the polishing is stopped.
According to the above method, the processing accuracy of the MR height can be controlled, and variations in the properties of the MR device can be reduced to a certain point.
However, at present, a demand for higher density recording of hard disks, etc. has been further increased. Therefore, the adoption of a MR device using a MR film with higher sensitivity such as a TMR film has been studied, and a process of more accurately forming the dimension of the MR device applicable to a very small track width in the width direction has been in demand. It is difficult to satisfy the demands through patterning by use of the conventional photolithography, so the applicant of the invention has been pursuing the study of a method of patterning by use of electron beam (hereinafter referred to as EB) lithography.
Referring to
FIGS. 37A through 42B
, a method of forming a pattern when EB lithography is used in a method of manufacturing the MR device is described below.
FIGS. 37A
,
38
A,
39
A,
40
A,
41
A and
42
A show plan views, and
FIGS. 37B
,
38
B,
39
B,
40
B,
41
B and
42
B show cross sectional views taken along the line x—x. As shown in
FIGS. 37A and 37B
, first of all, a multilayer film
220
A is formed through sputtering or the like on a base
210
on which an insulating layer (not shown) is disposed. Then, as shown in
FIGS. 38A and 38B
, an EB resist film
71
is formed on the multilayer film
220
A. Next, as shown in
FIGS. 39A and 39B
, EB resist patterns
71
A and
71
B are selectively formed through EB lithography. The EB lithography is carried out through scanning areas where the patterns are formed while irradiating with an electron beam. After that, as shown in
FIGS. 40A and 40B
, the multilayer film
220
A is selectively etched by use of the EB resist patterns
71
A
n
and
71
B as masks through, for example, ion milling. Thereby, a MR film pattern
201
and a dummy resistive film pattern
202
are formed. Then, an insulating layer
72
is formed all over the area as shown in
FIGS. 41A and 41B
. After that, as shown in
FIGS. 42A and 42B
, the remained EB resist patterns
71
A and
71
B are removed through lift off processing, then the MR film pattern
201
and the dummy resistive film pattern
202
both having a predetermined planer shape and a predetermined size can be obtained.
Thus, by use of EB lithography, compared with the conventional photolithography, the MR film pattern
201
having a smaller dimension in the width direction can be accurately formed. However, on the other hand, much time is required to form the relatively large dummy resistive film pattern
202
, resulting in worse throughput in the manufacturing process.
Moreover, relative displacement between the MR film pattern and the dummy resistive film pattern occurs due to the electrical charge on the base on which the patterns are formed. When the base carries an electrical charge unevenly depending upon areas, the electron beam is deflected at a rate depending upon areas on the base, thereby resulting in the occurrence of the relative displacement. As the electrical charge in this case varies depending upon areas on the same base as well as individual bases, the amount of the relative displacement varies, which leads variations in the relative displacement in the base as well as among the bases. Therefore, variations in dimensions occur when processing the MR height through mechanically polishing, thereby variations in the reproduction output of the MR head become larger.
SUMMARY OF THE INVENTION
In view of the foregoing, it is a first object of the present invention to provide a method of manufacturing a magnetoresistive device and a method of manufacturing a thin film magnetic head capable of efficiently forming a magnetoresistive device having an extremely small magnetoresistive film pattern.
It is a second object of the invention to provide a method of manufacturing a magnetoresistive device and a method of manufacturing a thin film magnetic head capable of reducing variations in dimensions of a magnetoresistive film pattern.
It is a third object of the invention to provide a method of forming a thin film pattern, and more specifically efficiently forming a plurality of thin film patterns with different sizes on a same base with accuracy according to each of the plurality of thin film patterns.
In a method of manufacturing a magnetoresistive device according to the invention, the magnetoresistive device includes a magnetoresistive film pattern with a predetermined shape, and th
Kasahara Noriaki
Ohta Naoki
Sato Kazuki
Oliff & Berridg,e PLC
Pianalto Bernard
TDK Corporation
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