Method of manufacturing a thin-film magnetic head

A first magnetic layer is formed upon a non-magnetic substrate, a gap layer is formed upon the first magnetic layer, a conductor coil covered with an insulation layer is formed upon the gap layer, a second magnetic layer is formed upon the gap layer and the insulation layer, a magnetic gap being formed between the first and second magnetic layers at a front portion facing a recording medium, and the second magnetic layer being connected to the first magnetic layer at a back portion. After forming a mask made of metal oxide upon the second magnetic layer, the second magnetic layer, the gap layer, and the first magnetic layer are formed into a predetermined shape respectively at the tip portion by dry etching. Thus, a high performance thin-film magnetic head having the same widths for the first and second magnetic layers is obtained.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of manufacturing a thin-film 
magnetic head and the structure thereof, and more particularly relates to 
a method for patterning a magnetic film constituting a magnetic core and 
the structure of a thin-film magnetic head obtained by using the 
patterning method. 
The structure of an active region or element portion of a thin-film 
magnetic head is shown briefly in FIG. 1, and the method of manufacturing 
a thin-film magnetic head is generally described in the following. 
In particular, a substrate 1 is formed with an under layer 2 thereupon, and 
a lower magnetic layer 3, a gap material 4, a conductor coil 5, an 
insulation layer 6, and an upper magnetic layer 7 are in this order 
respectively formed and etched to lay one upon another. After forming a 
passivation layer 8, a block including a thin-film magnetic head is cut 
out and subjected to necessary molding processings. 
Among the above manufacturing processes, the processes for patterning the 
lower magnetic layer 3 and the upper magnetic layer 7 are required to have 
a satisfactory accuracy of dimension. In addition, it is required to make 
the track widths of the upper and lower magnetic layers as equal as 
possible, which layers appear in a finished magnetic head at a plane 
facing a recording medium, and also to attain a sufficient dimensional 
accuracy for the upper magnetic layer 7 so as to locate it entirely upon 
the lower magnetic layer 3. The improvement of those dimension accuracies 
is required particularly for a high recording density magnetic head of the 
type having the improved density of recording tracks. 
In the method for patterning a magnetic material heretofore in use (U.S. 
Pat. No. 4,219,855), upper and lower magnetic layers are independently 
patterned and formed in a superposing relation to each other. Therefore, 
as shown in FIG. 2, at the plane of a front gap portion facing the medium, 
in order to make the upper magnetic layer 7 lay completely upon the lower 
magnetic layer 3, the upper track width W.sub.1 of the lower magnetic 
layer 3 has been designed to be larger than the lower track width W.sub.2 
of the upper magnetic layer 7 by the order of 3 to 4.mu., taking into 
consideration the alignment allowance and dimension allowance. 
The magnetic head fabricated by the above method, however, has a larger 
track width of the lower magnetic layer 3 than the effective track width 
W.sub.2. As a result, for example, if the magnetic head is utilized for a 
magnetic disk, recording signals in adjacent tracks are picked up as 
noises through the lower magnetic layer 3 so that a problem of degrading 
the S/N ratio arises. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method for processing 
the track widths of upper and lower magnetic layers so as to have the same 
dimension, without degrading the magnetic layers. 
It is another object of the present invention to provide a high quality and 
performance thin-film magnetic head. 
The above objects of the present invention are achieved by a method of 
manufacturing a thin-film magnetic head wherein a magnetic core portion is 
divided into a lower magnetic layer and an upper magnetic layer, and after 
forming the upper magnetic layer in such a manner that a magnetic gap 
material, a conductor coil, and an intermediate insulation layer are 
provided between the upper and lower magnetic layers, a pattern is formed 
by etching; comprising the steps of forming on the upper magnetic layer an 
etching mask pattern made of material chemically stable and which may be 
contained in the thin-film magnetic head; and by using the mask pattern, 
trimming by ion milling both portions defining the track widths of the 
upper magnetic layer and the lower magnetic layer. 
More particularly, the present invention features in that, the patterning 
process for the upper magnetic layer, first the upper magnetic layer is 
patterned by ion milling, and thereafter by using the same etching mask, 
the front gap portions of the gap material and the lower magnetic layer 
are trimmed, and furthermore in that metal oxide for use as a masking 
material in ion milling, such as aluminum oxide which is particularly low 
in ion milling speed, chemically stable, and which may be contained in the 
thin-film magnetic head, is used so as to eliminate a removal process of 
mask material after trimming and to prevent degrading the magnetic 
material while removing the mask material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The embodiment of the present invention will now be described in detail 
with reference to the accompanying drawings. 
FIG. 3 is a vertical cross-sectional view showing an element portion of a 
thin-film magnetic head according to an embodiment of the present 
invention. In the figure, reference numbers 1 to 6 are used to represent 
the constitutional elements identical to those shown in FIG. 1, and 
reference 7A denotes an upper magnetic layer formed over the whole surface 
of a substrate. 
On the substrate 1 made of non-magnetic ceramic material, an under layer 2 
made of metal oxide such as alumina is formed by sputtering. A lower 
magnetic layer 3 is formed by sputtering upon the under layer 2. 
Succeedingly, a gap layer 4 made of metal oxide such as alumina is formed 
by sputtering upon the lower magnetic layer 3. An intermediate insulation 
layer 6 made of organic resin such as polyimide resin is applied evenly 
upon the gap layer 4. A conductor coil 5 is formed by sputtering upon the 
intermediate insulation layer 6, and thereafter an intermediate insulation 
layer 6 is again applied upon the conductor coil 5. 
The intermediate insulation layer 6 is removed at a tip portion facing a 
recording medium. The intermediate insulation layer 6 and the gap layer 4 
are removed to expose the lower magnetic layer 3 at a portion of an end 
portion opposite to the tip portion. Succeedingly, an upper magnetic layer 
7A made of a material such as permalloy is formed by sputtering over the 
whole surface of the substrate 1. 
FIGS. 4A, 4B show the formation by sputtering of a metal oxide layer 9A 
upon the upper magnetic layer 7A, the metal oxide layer being used as a 
mask during ion milling. FIG. 4A is a plan view of the element portion, 
and FIG. 4B is a cross sectional view along line IVB--IVB of FIG. 4A. FIG. 
4B is a transverse cross-sectional view of the front gap portion of the 
finished magnetic head, and corresponds to a plane facing a recording 
medium. 
The metal oxide layer 9A may preferably be made of alumina or titania which 
are low in ion milling speed. Alumina in particular is the most suitable 
material because the ion milling speed is extraordinarily low. It is 
necessary to take into consideration the low step coverage while forming 
the metal oxide layer 9A. 
Thereafter, the metal oxide layer 9A is etched to obtain a metal oxide mask 
9 as shown in FIGS. 5A and 5B. FIG. 5A is a plan view of the element 
portion, and FIG. 5B is a cross-sectional view along line VB--VB of FIG. 
5A. It is difficult for dry etching, such as plasma etching or reactive 
sputter etching, to satisfactorily etch alumina or titania which is used 
as the material of the metal oxide layer 9. Therefore, for example, under 
CF.sub.4 gas 100%, a reactive ion milling method is preferably used. 
The details of the reactive ion milling method are described in the 
specification of Japanese Patent Application No. 58-144962. 
In the present embodiment, the reactive ion milling for etching the metal 
oxide layer 9A was performed under the following conditions, by using as a 
mask a photoresist made of novolac resin base, or a metal layer such as 
permalloy or chrome. 
Examples of the most suitable conditions for etching, for example, an 
alumina layer, are a CF.sub.4 gas pressure of 2.times.10 Torr, an 
acceleration voltage of 800V, and an ion angle of incidence of 0 degree. 
With the reactive ion beam etching incorporated for the etching of the 
metal oxide layer 9A, the etching selectivity between the metal oxide 
layer 9A and the photoresist or metal mask is large, and moreover side 
etching is hardly brought about. Therefore, the taper angle at edges of a 
pattern becomes sharp so that a good dimensional accuracy may 
advantageously be obtained. 
Succeedingly, by ion milling using argon gas, the upper magnetic layer 7A 
is dry etched to obtain such a shape as shown in FIG. 6. Thereafter, in 
succession, the front gap portion at the lower magnetic layer 3 is trimmed 
through dry etching. In this case, the element portion except the front 
gap portion has to be prevented from being etched. Therefore, as shown in 
FIGS. 7A and 7B, photoresist is applied to form a photoresist mask 10 
which exposes only a part of the intermediate insulation layer 6 generally 
made of organic resin and the front gap portion. 
FIG. 7A is a plan view of the element portion, and FIG. 7B is a 
cross-sectional view along line VIIB--VIIB of FIG. 7A. By again ion 
milling using argon gas following the step in FIG. 7, only the exposed 
portion is etched, and the gap layer 4, lower magnetic layer 3, and metal 
oxide mask 9 are trimmed. 
Since the gap layer 4 made of metal oxide such as alumina is formed thinly, 
the ion milling using argon gas can sufficiently be used for the etching. 
It is apparent that if required, the gap layer 4 and the lower magnetic 
layer 3 can again be trimmed through reactive ion milling using freon gas. 
FIGS. 8A, 8B show cross-sectional views of the element portions wherein the 
photoresist mask has been removed by submerging in acetone liquid after 
the above trimming process. FIG. 8A is a vertical cross-sectional view, 
and FIG. 8B is a cross-sectional view along line VIIIB--VIIIB of FIG. 8A. 
Thus, as shown in the figures, it is possible to make the track widths of 
the lower magnetic layer 3 and the upper magnetic layer 7 substantially 
equal to each other. Thereafter, without removing the metal oxide mask 9, 
a passivation mask 8 made of metal oxide such as alumina is formed by 
sputtering, and the surface of the passivation mask 8 is processed to make 
it smooth and even to obtain a shape shown in FIGS. 9A and 9B. To obtain a 
finished magnetic head, the element portion is cut along line IXB--IXB. 
FIG. 9A is a vertical cross sectional view of the element portion, and 
FIG. 9B is a cross sectional view along line IXB--IXB. 
In the above embodiment, if all of the under layer 2, gap layer 4, 
passivation layer 8, and metal oxide mask 9 are made using alumina which 
is a stable metal oxide, a highly reliable magnetic head may 
advantageously be obtained which has high stability against erosion, 
abrasion, and the like. The reason for this is that the magnetic material 
appears, at the medium facing plane of the finished magnetic head, in the 
form fully embedded in the alumina layers. 
Further, it is obvious that instead of the metal oxide mask, other 
materials may be used which pose no obstacles even if left in the magnetic 
head. 
As described above, the construction of the present invention features a 
method of manufacturing a thin-film magnetic head wherein a magnetic core 
portion is divided into a lower magnetic layer and an upper magnetic 
layer, and after forming the upper magnetic layer in such a manner that a 
magnetic gap material, a conductor coil, and an intermediate insulation 
layer are provided between the upper and lower magnetic layer, a pattern 
is formed by etching; comprising the steps of forming on the upper 
magnetic layer an etching mask pattern made of material chemically stable 
and which may be contained in the thin-film magnetic head; and by using 
the mask pattern, trimming by ion milling both portions defining the track 
widths of the upper magnetic layer and the lower magnetic layer. 
Therefore, even if the accuracy of alignment between the upper and lower 
magnetic layers is poor in the manufacturing processes, the final widths 
of the upper and lower magnetic layers appearing at the medium facing 
plane are not deviated in position from each other, and moreover can be 
processed to have the same dimensions. Thus, it is possible to fabricate a 
high quality and high performance magnetic head with ease.