Method of manufacturing thin film magnetic head

A method of manufacturing thin film magnetic heads. One embodiment of the present method features the step of placing a separating layer on a substrate and placing subsequent element layers of one or more thin film magnetic heads on the separating layer. Upon imposition of separating conditions, the thin film magnetic head is released, allowing the substrate to be reused.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of manufacturing a thin film magnetic 
head. Thin film magnetic heads are used in a magnetic disc drives and 
magneto-optical disc drives. 
2. Description of Related Art 
Thin film magnetic heads are manufactured in a manner similar to a 
semiconductor integrated circuit elements, by film forming techniques such 
as vapor deposition, sputtering or the like or lithography such as 
photoengraving processes, etching, etc. These methods are advantageous in 
producing high-accuracy heads in large quantities. 
There are two types of thin film magnetic heads hitherto known, i.e., a 
vertical head wherein a magnetic gap is formed in a direction 
perpendicular to a substrate surface (film thickness direction) and a 
horizontal head wherein a magnetic gap is formed along the substrate 
surface. 
The vertical head is put to practical use because in the process of making 
vertical heads, it is easy to form a gap and vertical heads exhibit 
resistance against the sliding movement of a medium. On the other hand, 
the horizontal head makes it possible to complete whole processes, such as 
air bearing surface processing, in a substrate, since the surface of the 
head normally oriented to the medium is on the substrate side. Moreover, 
the depth of the magnetic gap is determined by the thickness of the film 
in the horizontal head, so that the depth of the gap is easily controlled 
during manufacture. 
The procedures are generally carried out independently in the individual 
vertical head after the head is cut and separated from the substrate. 
Performing such procedures on individual vertical heads makes such heads 
more expensive generally than horizontal heads. 
FIG. 1 is a cross sectional view depicting a horizontal thin film magnetic 
head described in "A NEW APPROACH TO MAKING THIN FILM HEAD SLIDER DEVICES" 
by IBM at IEEE INTEGRAM '89. As illustrated in FIG. 1, the thin film 
slider is comprised of the following elements: substrate 1, a protecting 
film 2, a magnetic gap 3, a lower magnetic core 4, an insulating layer 5, 
a coil 6, an upper magnetic core 7, a coil leading conductor 8, an 
insulative protecting film 9, a slider wafer 10 and a connecting conductor 
11. The connecting connector 11 is within the slider wafer 10. The 
protecting film 2 protects the magnetic gap 3 and lower magnetic core 4 
from sliding motions. 
The manufacturing method and operation of the head shown in FIG. 1 will be 
described below. 
First, the protecting film 2, comprising a metallic film and as a plating 
substrate, and the magnetic gap 3 are formed on the substrate 1. The 
magnetic gap 3 is formed with a submicron width through electron beam 
exposure. The gap is completed by the resist, or by etching a preformed a 
gap film (generally, inorganic insulative film) on the substrate using the 
resist as a mask. 
A narrow gap width is considerably important to enhance the linear density 
in magnetic recording. It is thus required to form the pattern with a 
submicron width. 
Next, the lower magnetic core 4 is formed through plating. At this time, 
the magnetic film is not formed on the part of the magnetic gap having the 
resist or insulative film. The insulating layer 5, coil 6, upper magnetic 
core 7 and coil leading conductor 8 are sequentially formed on the lower 
magnetic core 4 by films and lithography. 
Then, the insulative protecting layer 9 is laminated and ground until a 
connecting part of the coil leading conductor 8 is exposed. The slider 
wafer 10 is bonded which serves not only to connect the coil terminals to 
the outside but to support the head elements. 
Thereafter, the substrate 1 is dissolved through etching and removed, 
whereby the magnetic gap surface is exposed. The exposed surface is 
photoengraved and processed with a facing by ion beams or the like (to 
form an air bearing surface in a hard disc head). 
The above-discussed method has such advantages that the gap of a submicron 
width is easily formed on a surface because the surface is flat and 
eventually the gap surface is made flat, and facing process of the head 
surface can be processed simultaneously for every substrate including 
several hundred heads without being separated into individual heads. 
In the conventional manufacturing method of the thin film magnetic head, it 
is necessary to dissolve the substrate through etching, and therefore the 
material for the substrate is limited to one that can be etched. Moreover, 
it takes a long time to dissolve the substrate through etching. In 
addition, the substrate cannot be recycled, thereby causing a waste of 
resources and additional expense. 
For example, in the case where Si of 4 inch diameter is used as the 
substrate, it should be 0.6 mm thick or so from the viewpoint of the 
strength, and not shorter than several hours is required to dissolve the 
substrate in a solution of sodium hydroxide. 
Si substrate is not suitable in some cases since the coefficient of linear 
expansion thereof is smaller as compared with that of a magnetic film 
generally used in the magnetic core (it is desirable that the coefficient 
of linear expansion of the substrate in a thin film laminated body such as 
a thin film magnetic head is close to that of the magnetic film). Even if 
the other material is selected for the substrate, the material is 
restricted to such one that can be dissolved through etching. Therefore, 
this presents great limitation as to the choice of material for use as 
substrate. 
Further, since the surface of the element on the substrate side after the 
substrate is separated is completely flat, positioning of the mask is 
quite difficult when the surface is processed to form an air bearing 
surface through photoengraving process. In general, a groove is formed 
about 10 .mu.m deep to form the air bearing surface. Therefore, it is 
necessary for the resist as a mask to be 10 .mu.m or more thick to form 
the groove through ion beam etching, thus making it hard to position the 
mask by recognizing the differences in index of reflection of the surface 
material (magnetic core, gap, protecting film against the sliding motion). 
SUMMARY OF THE INVENTION 
This invention has been devised to solve the aforementioned problems 
encountered in the prior art. 
A first object of this invention is to provide a manufacturing method of a 
thin film magnetic head, whereby a separating layer is provided on a 
substrate to separate the substrate later, on which head elements are 
laminated, so that the substrate can be divided only be removing the 
separating layer, offering a wide range of selection for the substrate 
material and enabling recycling of the substrate. 
A second object of this invention is to provide a manufacturing method of a 
thin film magnetic head, whereby one surface of a substrate is processed 
beforehand to fit with the surface shape of head elements and a slider on 
the side of confronting a medium, on which a separating layer and head 
elements are laminated, thereby making it unnecessary to process an air 
bearing surface and round treatment after the substrate is separated. 
The above and further objects and features of the invention will more fully 
be apparent from the following detailed description with accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A manufacturing method of a preferred embodiment of this invention will be 
discussed below with reference to the accompanying drawings. FIGS. 2(A) 
through (D) are cross sectional views showing a manufacturing method 
according to a preferred embodiment of this invention, in which numeral 21 
indicates a substrate, 22 a protecting film against sliding motion, 23 a 
magnetic gap, 24 a lower magnetic core, 25 an insulating layer, 26 a coil, 
27 an upper magnetic coil, 28 a coil leading conductor, 29 an insulative 
protecting film, 30 a slider wafer, 31 a connecting conductor provided 
within the slider wafer, 32 a separating layer and 33 a groove for 
separation, respectively. 
Referring to FIG. 2(A), the separating layer 32 made of Cu is provided 
about 30 .mu.m thick on the substrate 21 separating layer 32 has 
protrusions and recesses the reverse of those in the slider processing 
(for example, a groove is formed 300 .mu.m wide and 10 .mu.m deep on the 
substrate). This separating layer is formed by plating, sputtering, etc. 
FIG. 2(B) shows the next step following that of FIG. 2(A). Elements of a 
horizontal thin film head are formed on the substrate in a general manner 
of manufacturing a thin film magnetic head similar to that in the document 
cited in the prior art. In the method, the surface is ground to be flat, 
so that the connecting part is exposed, then, the slider wafer 30 also 
serving as an electric connection is bounded. The substrate 21 is not flat 
all over the surface thereof, but is recessed 10 .mu.m deep where the head 
elements are formed, inversely corresponding to the surface shape of the 
element. However, since the forming area of the head elements is flat, a 
photoengraving device of electron beam exposure type or reflection 
projection exposure type may easily be focused on this area. 
The process of FIG. 2(B) is followed by the step shown in FIG. 2(C), 
wherein the groove 33 is formed to separate the substrate 21. The groove 
33 extends only within the Cu layer 32, but not to the substrate surface. 
The groove 33 is intended to allow easy separation of the substrate; 
however, the groove 33 is not necessarily formed depending on the kind of 
means for separating the substrate. 
FIG. 2(D) illustrates the head after dissolving the Cu separating layer 32 
through etching. The magnetic property of the element and resistance of 
the coil are checked before separating the element from the substrate. 
When NiFe alloy is used for the magnetic core, it is possible to dissolve 
Cu alone in a solution of NH.sub.4 OH and ammonium persulfate. Owing to 
the grooves 33 formed as shown in FIG. 2(C), dissolution proceeds from 
each side of the exposed Cu provided at the bottom of the element, so that 
the element can be quickly and perfectly separated from the substrate. As 
above, the head elements are obtained in the order shown in FIGS. 2(A) 
through 2(D). 
Although the separating layer is provided on the substrate having the 
surface preliminarily processed according to the foregoing embodiment, 
even in the case where the separating layer is provided on a general flat 
substrate, the substrate may be used again. 
Moreover, although the separating layer made of Cu which selectively 
dissolved against the magnetic core is employed as separating means of the 
substrate in the foregoing embodiment, this invention is not particularly 
restricted to the above. Any separating layer may be possible so along as 
it can selectively etched against the magnetic film and protecting film, 
e.g., aluminum may by employed for the separating layer and dissolved in a 
solution of sodium hydroxide or the like. 
If the separating layer is impossible to be selectively etched, a 
protecting film may be arranged on the element surface, which is to be 
remove after the substrate is separated. 
Such process as above is made clear from FIGS. 3(A) through 3(D). Numeral 
34 denotes a protecting film in FIGS. 3(A) through (D). The other parts 
are designated by the same reference numerals as in FIG. 2. 
By way of example, in the case where the magnetic core is made of NiFe and 
the separating layer is made of Cu using acid as an etching solution, 
since both the magnetic core and separating layer are to be etched 
together, the protecting film is formed in order to avoid etching of the 
magnetic core. An Si.sub.2 or Si.sub.3 N.sub.4 film is applied to the 
protecting film, or a set resist film is provided between the separating 
layer and element. After the Cu is removed through etching thereby to 
separate the element, the protecting film 34 at the exposed surface is 
easily removed through plasma etching by use of CF.sub.4 gas for the 
SiO.sub.2 or Si.sub.3 N.sub.4 protecting film, or by the use of O.sub.2 
gas for the resist protecting film without a damage to the element. 
Meanwhile, an organic resin may be used as the separating layer with plasma 
etching or thermal decomposition using CF.sub.4 gas may be carried out to 
separate the substrate in the example of FIG. 2. In another way, an alloy 
of a low melting point may be used as the separating layer and melted. 
When NiFe is applied to the magnetic core by plating, Pb-Sn alloy or the 
like having a melting point not higher than 300.degree. C. is used for the 
separating layer. It is not necessary to form the grooves when heat is 
used to separate the substrate, contrary to the case where chemical 
reaction is used for that purpose. 
Although the separating layer is described as between the substrate and the 
air bearing surface, which separating layer is placed beforehand on the 
substrate according to the above embodiments, as part of a continuous 
process, the separating layer may be applied independently to the 
substrate in a noncontinuous batch-type process. 
When the protecting film against the sliding motion is more difficult to 
process in comparison with the substrate material, by preliminary 
processing of the surface shape being the reverse of that in the slider 
processing, the surface processing of the head element after dissolving 
the substrate by etching is unnecessary. That is the case where when Si is 
used for the substrate and alumina is used for the protecting film against 
the sliding motion. Alumina is chemically etched more easily than Si. 
As this invention may be embodied in several forms without departing from 
the spirit of essential characteristics thereof, the present embodiment is 
therefore illustrative and not restrictive, since the scope of the 
invention is defined by the appended claims rather than by the description 
preceding them, and all changes that fall within the metes and bounds of 
the claims, or equivalence of such metes and bounds thereof are therefore 
intended to be embraced by the claims.