Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-11-19
2003-12-09
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06661621
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns an inverse type compound thin film magnetic head, in which the electromagnetic induction type magnetic head for recording is formed before the magnetoresistance effect type magnetic head for reproduction.
2. Background Information
As computer performance is enhanced, there are demands for hard disk devices and other magnetic recording devices which are more compact and have greater capacities. However, because the media speed in a hard disk device depends on the disk diameter, the smaller the size of ordinary magnetic recording devices, the slower is the media speed. Because the reproduction output of inductive magnetic heads depends on the media speed, as magnetic recording devices are made smaller and media speeds are reduced, the reproduction output declines.
To counter this, the magnetoresistance effect thin film magnetic head (hereafter “MR head”) detects, as the reproduction output voltage, changes in the resistance of a magnetoresistance effect element (hereafter “MR element”) using a magnetoresistance effect film the resistivity of which changes with the magnetic field. This head has the characteristic that the reproduction output of this head does not depend on the media speed, and a high reproduction output is obtained even at low media speeds, so that small-size, large-capacity magnetic recording devices, and in particular small-size, large-capacity hard disk devices, can be realized.
Further, in order to achieve still smaller sizes and larger capacities, multilayer film giant magnetoresistive (GMR) heads and spin-valve GMR heads (SV heads), utilizing the giant magnetoresistance effect of artificial lattice multilayer films and spin-valve films, are also being developed at a rapid pace.
Because these MR heads and GMR heads are capable of reproduction only, they are combined by layering with electromagnetic induction thin film magnetic heads as heads for information recording. In these widely adopted compound thin film magnetic heads, reproduction is performed by the MR head, and recording is performed by the inductive thin film magnetic head.
Many such compound thin film magnetic heads are formed with the MR head first formed on the substrate, and then the inductive thin film magnetic head formed by layering on top; but when forming the inductive thin film magnetic head, heat treatment processing is necessary, and so considerable heat is born by the MR head as well. For example, in forming the thin film coil for recording of the inductive thin film magnetic head, in order to flatten the resist used for insulation and improve exclusion by etching so as to improve the coil shape, the resist may be baked several times at approximately 280° C. On doing so, of course, the MR head already formed beneath is also subjected to considerable heat.
When in this way the MR head is subjected to high heat, the magnetoresistance effect of the MR element is degraded. In particular, GMR elements consist of metal layered films with film thicknesses of several nm or so; diffusion occurs at the interfaces between layers, degrading the film characteristics, and greatly reducing the rate of change of magnetoresistance.
Hence there is the problem that, even using an MR head, when it is part of a compound thin film magnetic head, because of the heat treatment accompanying the formation of the inductive thin film magnetic head, high reproduction sensitivity cannot be obtained; this problem is particularly serious in GMR heads using GMR elements.
Therefore in recent years a so-called inverse type compound thin film magnetic head has been developed (see for example laid-open patent application Hei9-245321), in which after forming the inductive thin film magnetic head for recording, the MR head is then formed, to prevent degradation of the MR head reproduction sensitivity by heat treatment during formation of the inductive thin film magnetic head.
An inverse type compound thin film magnetic head is able to prevent destruction of the MR element magnetoresistance effect during manufacturing processes and degradation of the reproduction sensitivity. However, the inverse type compound thin film magnetic heads of the prior art do not take into consideration the conduction of heat arising from the MR element (the read element), and so have been problematic with respect to thermal reliability and unsuitable for practical application.
An explanation with reference to the drawings follows. Previous non-inverse type compound thin film magnetic heads were formed by successive layering on an AlTiC substrate
41
of an undercoat
42
of alumina, a lower shield layer
43
, a lower insulating layer
44
of alumina, an MR element film
45
with an MR element of permalloy or other material, an electrode layer (not shown) connected to both ends of said MR element film, an upper insulating layer
46
, and an upper shield layer
47
, as illustrated in
FIG. 5
, to comprise an MR head.
Further, the upper shield layer
47
of said MR head is common with the lower core layer of the inductive thin film magnetic head; on top of said lower core layer
47
is formed by layering an insulating layer
48
, after which an inductive coil layer
49
is formed. After covering said coil layer
49
with an insulator
50
, the upper core layer
51
is formed by layering, to comprise the electromagnetic induction thin film magnetic head. Thereafter a protective film
52
is formed by layering on the whole.
In this non-inverse type compound thin film magnetic head, the MR element
45
is positioned in proximity to the AlTiC substrate
41
, so that heat generated from said MR element
45
is dispersed in the AlTiC substrate
41
with good thermal conductivity, and thermal reliability can be secured.
On the other hand, in the structure of an inverse type compound thin film magnetic head, the inductive thin film magnetic head is formed by layering in succession on an AlTiC substrate
61
of an undercoat
62
of alumina, a lower core layer
63
, an insulator
64
, a coil
65
, a gap
66
, and an upper core layer
67
, as shown in FIG.
6
.
The upper core layer
67
of said head is common with the lower shield layer of the magnetoresistance effect thin film magnetic head; by forming in layers on top of said lower shield layer
67
, an insulating layer
68
, MR element
69
, and upper shield layer
70
, an MR head is formed.
The entire surface is then covered by forming a protective film
71
of alumina.
In this inverse type compound thin film magnetic head of the prior art, there exist thick alumina layers with low thermal conductivity above and below the MR element (the undercoat
62
and the protective film
71
), so that heat generated by the MR element is mainly transferred within the upper and lower shield layers
67
,
70
with comparatively high thermal conductivity. However, because these shield layers
67
,
70
have small thickesses, the heat transfer resistance is high, and so problems with thermal reliability occur.
SUMMARY OF THE INVENTION
A compound thin film magnetic head is disclosed. In one embodiment, the compound thin film magnetic head includes an electromagnetic induction type thin film magnetic head formed over a substrate. A first protective film is then formed over the electromagnetic induction type thin film magnetic head. A heat dispersion layer is then formed over the first protective film. The heat dispersion layer has thermal conductivity higher than the first protective film. A second protective film then formed over the heat dispersion layer.
REFERENCES:
patent: 5901021 (1999-05-01), Hirano et al.
patent: 6134079 (2000-10-01), Koshikawa
patent: 6151193 (2000-11-01), Terunuma et al.
patent: 6154346 (2000-11-01), Sasaki
patent: 6201669 (2001-03-01), Kakihara
patent: 6259585 (2001-07-01), Sasaki et al.
patent: 6266216 (2001-07-01), Hikami et al.
patent: 6278580 (2001-08-01), Sasaki
patent: 6404601 (2002-06-01), Rottmayer et al.
Burgess & Bereznak LLP
Cao Allen
Read-Rite SMI Corp.
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