U.S. patent number 3,662,119 [Application Number 05/051,186] was granted by the patent office on 1972-05-09 for thin film magnetic transducer head.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Lubomyr T. Romankiw, George A. Wardly.
United States Patent |
3,662,119 |
Romankiw , et al. |
May 9, 1972 |
THIN FILM MAGNETIC TRANSDUCER HEAD
Abstract
A rectangular thin film transducer head includes a magnetic core
composed of overlapping laminations of permalloy film joined
together magnetically and electrically, near an air gap, at one end
of the rectangle, between the two laminations, which gap couples
flux to the magnetic recording medium. Two electrically parallel
insulated thin film copper windings starting at the end opposite
the gap are deposited about the core joining electrically at the
end adjacent to the gap to a conductor coupled to both permalloy
laminations which conduct return current through the legs of the
core inside of the windings. Alternatively, a single series winding
passes around the core and through the gap. The head is
manufactured by means of photolithographic, vacuum, and thin film
techniques.
Inventors: |
Romankiw; Lubomyr T. (Milwood,
NY), Wardly; George A. (Yorktown Heights, NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
21969839 |
Appl.
No.: |
05/051,186 |
Filed: |
June 30, 1970 |
Current U.S.
Class: |
360/125.33;
335/297; 29/603.14; 29/603.25; G9B/5.086; G9B/5.077; G9B/5.05 |
Current CPC
Class: |
G11B
5/31 (20130101); G11B 5/313 (20130101); G11B
5/17 (20130101); Y10T 29/49044 (20150115); Y10T
29/49064 (20150115) |
Current International
Class: |
G11B
5/17 (20060101); G11B 5/31 (20060101); G11b
005/12 (); G11b 005/42 () |
Field of
Search: |
;179/1.2C,1.2CH
;346/79MC ;340/174.1F ;336/200 ;117/212 ;29/603 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Urynowicz, Jr.; Stanley M.
Assistant Examiner: Lucas; Jay P.
Claims
What is claimed is:
1. A thin film transducer head comprising a plural layer integral
core of magnetic material forming a gap between overlapping
segments thereof, said core including a central space without
magnetic material and thin film windings about said core, said
windings being electrically connected to said core adjacent to said
gap, to form an electrical circuit with said windings and said core
in series with each other.
2. Apparatus in accordance with claim 1 wherein said windings are
formed on separate layers and are generally in complementary
chevron shaped patterns with one half of each chevron stripe on a
separate layer.
3. A thin film transducer head comprising a plural layer integral
core of magnetic material forming a gap between overlapping
segments thereof, said core including a central space without
magnetic material and thin film windings about said core, and
current from said windings passing through said core.
4. A thin film transducer head comprising a plural layer integral
core of magnetic material forming a gap between overlapping
segments thereof, said core including a central space without
magnetic material and thin film windings about said core, said
windings being electrically connected in parallel, and said
windings being connected in series with said core.
5. A head in accordance with claim 4 wherein current through said
windings passes through said gap.
6. A thin film transducer head comprising a plural layer integral
core of magnetic material forming a gap between overlapping
segments thereof, said core including a central space without
magnetic material and thin film windings about said core said
windings being electrically connected in parallel, and electrical
return current passing from the windings returns through the core
passing through a winding for current flowing through an electrical
circuit including the windings of the coil and the core in
series.
7. A magnetic head comprising a magnetic core formed in a plurality
of layers and joined at one point to form a unitary magnetic core
having a gap,
a plurality of windings electrically in parallel about said core
connected to said core as an electrical return path for current
flowing through an electrical circuit including said windings and
said core connected in series.
8. A transducer head comprising a core of magnetic material
including two arms with parallel windings about both of said arms
with bridging connections between respective loops of the windings
on each arm so as to provide alternate electrical paths around the
core for improved reliability in the event of failure of at least
one loop.
9. A transducer head in accordance with claim 8 wherein said core
comprises a plural layer integral core.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electromagnetic head for providing an
electrical to magnetic transducing action to write and read
information in relation to a magnetic medium such as a tape in
response to or for producing electrical signals. This invention
also relates to thin film techniques of manufacture including
sputtering and vacuum deposition, electroless deposition or plating
(i.e. deposition by chemical rather than by electrical means) and
electroplating, and photolithography.
2. Description of the Prior Art
It has been suggested heretofore to manufacture a thin film
multitrack head including a permalloy core surrounded by silicon
dioxide and having several thin film deposited turns provided
around the permalloy core. The permalloy is deposited in layers,
with the windings wound about only one of those layers.
In thin film transducer heads known heretofore sensitivity has been
limited because of the core configuration employed. As a result the
number of efficient turns which could be wound upon a core was
limited because of the proximity of the totally overlapping legs of
the core which led to considerable leakage of the magnetic field
from one leg to the other which short circuits the magnetic circuit
to a degree. The reluctance of the core at an increasing distance
from the gap for a given core configuration becomes so high
relative to the reluctance of the space separating the legs, that
additional turns at greater distance produce smaller magnetic
fields at the gap and have lesser coupling to magnetic fields
passing the gap relative to turns which are closer to the gap.
In thin film technology, the number of process steps required to
manufacture a completed device determines the cost as well as the
overall efficiency of the manufacturing process in view of the fact
that the percentages of yield are less than unity and, in general,
similar reductions of overall yield result from added steps.
In cases of multiple track heads wherein cores are spaced in close
proximity, there is a possibility for flux from one winding to
thread through adjacent windings thereby leading to false response,
referred to as cross-talk, or requiring use of measures to avoid
such false response, or cross-talk, such as spacing the heads more
widely, which will greatly reduce the quantity of data stored on a
given quantity of magnetic recording medium.
SUMMARY
In accordance with this invention, a thin film transducer head is
provided comprising a ramp shaped core of magnetic material forming
a gap between its overlapping segments. The core includes a central
spacer made of non-magnetic material and thin film windings about
the core.
In another aspect of this invention, electrically parallel windings
are made along two legs of the core and the return currents are
connected back through the core.
A further aspect of this invention is that windings are provided
about the ramp core wound in an electrical series around the ramp
core.
In still another aspect of this invention, an electrical winding
turn passes between the two portions of the core forming the
magnetic gap. In still another aspect, current flows through the
core from the windings. In a further aspect of this invention,
redundancy of windings is provided and thereby fabrication yield is
increased, higher linear bit density, higher speed, and greater
track density.
An object of this invention is to produce a heat with improved
sensitivity consistent with thin film technology.
Another object of this invention is to minimize the number of
fabrication steps required to produce a thin film head having all
the above optimum features.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of a preferred embodiment of the invention, as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a partially schematic perspective view of a thin film
ramp shaped core with a pair of electrically parallel windings
connected to the core as an electrical return. A plurality of turns
is indicated. The number of turns can greatly exceed the number of
turns shown in the figure.
FIG. 2 shows an exploded view of a head including a ramp shaped
core, and a pair of electrically parallel windings about the core
having a current return path through the core. Extraneous portions
of the substrate on which the core is produced have been omitted
and the head appears here to be built on a rectangular
parallelopiped.
FIGS. 3A-3F show the thin film head of FIG. 2 manufactured in
accordance with the process of this invention in successive stages
of fabrication. Undulations in the successive layers, caused by
lower layer structures, have been omitted for facility of
illustration.
FIG. 3G shows an alternative structure with parallel
redundancy.
FIGS. 4A-4F show the patterns of masks for manufacture of the thin
film head of FIGS. 2 and 3A-3F.
FIGS. 4A-4F represent a set of masks for an individual recording
transducer. In actuality the masks consist of a plurality of such
heads packed in rows as closely, side by side, as the pattern
permits.
FIGS. 4G and 4H show alternative patterns of masks to be used as
explained in combination with those of FIGS. 4A-4E with FIG. 4H
replacing FIG. 4E.
FIGS. 5A-5G show the successive layers applied to form a thin film
head with a ramp shaped core wherein the windings are wound in
series about the two legs of the core.
FIGS. 6A-6G show the corresponding pattern masks employed for
manufacturing a thin film head corresponding to the successive
steps illustrated by FIGS. 5A-5G.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a ramp shaped core 10 having an upper lamination 11
generally rectangularly shaped with a base 23 and including a left
leg 21 and a right leg 22. There is a break 20 in lamination 11
between the left leg 21 and the base 23. Beneath the base 23, break
20 and the lower end of the left leg 21 is a lower lamination 12
which has a contact 38 that contacts the segment 34 of left leg 21
magnetically and electrically, but which is spaced by a copper
terminal 17 from the base 23. Thus a magnetic gap 14 is formed
between the base 23 and the lower lamination 12. The wire 18 is
connected to a left winding 15 wound about left leg 21 and a right
winding 16 wound about right leg 22. The windings 15 and 16 connect
together at copper terminal 17. Copper terminal 17 is electrically
connected to both the base 23 and the lower lamination 12 and the
lower lamination 12 is electrically connected to the left leg 21 so
that the return current path passes through left leg 21 and right
leg 22 as indicated by dotted lines.
While the current arrows in FIG. 1 show the direction of current
for input of current on line 18 and withdrawal of current from line
19 secured to the ramp core 10 near its apex 24, it will be
understood that current will reverse periodically and the arrows
are shown merely for convenience of explanation as to what the
current path would be for flow of current in only one
direction.
The FIGS. 1-6G make no attempt to show the transmission lines which
supply current to the heads or receive signals from the heads.
Neither do they show possible adjacent heads. Electrical contact
pads are shown to which contact can be made by wires, however,
transmission lines can be fabricated concurrently with the head.
The figures would then be modified in obvious ways to show twin
line, strip line or twisted pair transmission lines. In these cases
the contact pads would then be integral with the chosen
transmission line and insulation patterns would be modified.
By way of example, referring to FIG. 2, a typical recording head is
fabricated with a track width along magnetic gap 14 of between 1
and 10 mils, gap 14 thickness defined by a copper layer 28 of
between 1 and 4.mu. meters, the magnetic ramp core 10 is, in part,
comprised of legs 21 and 22 between 5 and 50 mils long, each leg
0.5 to 4 mils wide and copper conductors 31, 30, etc. between 0.1
and 0.5 mil wide. The number of chevrons 15, 16 or barber poles
(turns) around the magnetic ramp core 10 is determined by the width
of the copper conductors and by the length of the legs 21 and 22.
The gap thickness and track width are dependent on the ultimate
application of the head which may be used with storage devices such
as a disk, drum, strip file, tape, or other equivalent storage
device. The selected gap thickness and track width determine all
other lateral dimensions as well as the individual layer
thicknesses. They are usually chosen to result in maximum
efficiency of the head based on its final intended application.
Although FIG. 2 shows two individual cores forming chevron stripes,
the cores can be formed by connecting opposite bars 42 and 43 and
30 and 31. The current divides equally around cores 21 and 22 by
virtue of equal impedance characteristics of the geometrically
opposing cores. This provides redundancy with respect to random
failure of individual windings.
Referring to FIG. 2 an exploded perspective view of a magnetic head
incorporating the features of FIG. 1 is shown. A cutout portion of
a silicon substrate 26 includes a thin film of silicon dioxide 27
upon which the lower lamination 12 of the ramp core 10 is
deposited. Over lamination 12 is deposited a copper layer 28
including a lower terminal 29. A plurality of lower halves of
windings 30 and 31 are combined with the upper halves of windings
42 and 43 discussed below to provide entire helical windings and
the copper terminal 17 which lies in electrical contact with and
above the lower permalloy lamination 12 leaving overlapping
magnetic contact 38 uncovered. It will be noted again that the
copper film of terminal 17 also provides the minimum spacing
between the lower lamination 12 and the base 23 forming the
magnetic gap 14. Above the copper layer 28 is the upper lamination
11 of the ramp core 10 which is comprised of permalloy. The left
leg 21, the apex 24, the right leg 22 and the base 23 of lamination
11 are shown. The base 23 has end 35 which electrically contacts
terminal 17, otherwise base 23 is spaced from terminal 17 by
insulation layer 44 shown in FIG. 3C, etc. which is provided
between the copper and permalloy layers except below segment 34 and
end 35 which are in electrical and physical contact with the
permalloy lower lamination 12 at contact 38 on the one hand and the
copper terminal 17 on the other hand.
At the top level is a layer of copper 36 composed of an end
terminal 37 and copper sections 42 and 43 comprising upper half
windings which are of U-shaped cross sections and which connect
between the lower terminal 29 and the lower halves of windings 31
to the copper terminal 17 by means of helical windings about the
legs 21 and 22, respectively, on the permalloy ramp core 10. All of
the windings are formed about the upper lamination 11 of core
10.
It should be understood, that the actual elevations and formations
of the layers of the materials used will vary slightly from what is
shown here which is simplified for convenience of illustration and
for convenience of drawing. For example, the terminal layer 17
would have a slightly different shape from that which is shown. It
is shown as being flat on its entire surface but actually would be
bent down over the lower lamination 12.
The end terminal 37 is in electrical and mechanical contact with
the apex 24 of the upper lamination 11. Thus the end terminal 37
may conduct current passing through the legs 21 and 22 of the upper
lamination out to the second wire 19 for connection to the circuit
controlling the head.
It will be understood also that, in general, insulation is provided
between the copper windings and the permalloy core, on both levels,
as will be shown hereinafter except at the points where it is
indicated that there is actual mechanical and electrical contact
between the segments of the ramp core 10 and the electrical
circuit.
It will also be noted that the formation of the conductors by the
segments 30 and 31 as well as 42 and 43 is in the form of sets of
chevron stripes. This will be seen particularly clearly with
reference to FIGS. 3B and 3F which will be described in greater
detail hereinafter.
Referring to FIG. 3A, a portion of the substrate 26 is shown with
the silicon dioxide coating 27 thereon coated with the permalloy
lower lamination 12. It will be seen by reference to the mask in
FIG. 4A that the shape of the lower lamination 12 is nearly
identical to that of the mask of FIG. 4A. The masks of FIGS. 4A-4F
are somewhat extended beyond the final desired gap location in
order to provide for final polishing of the substrate and to a
desired flushness. The method employed to form the permalloy lower
lamination 12 is a photolithographic method in which the entire
surface 27 is coated with permalloy after additional preparatory
coatings described below in detail. Then, by photolithography, the
unwanted permalloy is removed leaving the lower permalloy
lamination 12.
FIG. 3B shows the product of FIG. 3A with the addition of a copper
layer 28 in the form of the mask of FIG. 4B including the lower
terminal 29, the left and right lower halves of windings 30, 31 and
the copper terminal 17.
One corner 46 of lower terminal 29 in FIGS. 2, 3B and 4B is
connected by a left, upper half winding 73, one of the windings 42,
to the first end 47 of the first chevron 30 on the left side. The
second end 48 of the first chevron 30 is connected by a second
upper half winding 71 to the first end 49 of the second chevron
30.
We note again that overlapping magnetic contact 38 on the top of
lamination 12 is the surface of lamination 12 which is not covered
by copper terminal 17 in FIGS. 2 and 3B.
FIG. 3C shows the product of FIG. 3B with the addition of an
insulating layer 44 in the form of the mask in FIG. 4C including a
window 45 for the lower terminal 29, and windows 50 for corners 46
and 70 of the terminal 29 and the ends of the chevron lower halves
of the windings 30 and 31 such as ends 47, 48 and 49. Window 51 is
provided for the corner 46 of the terminal 29. Window 52 is
provided for the first end 47 of the first chevron 30. Window 53 is
provided for the second end 48 of the first chevron 30. Window 54
is provided for the first end 49 of the second chevron 30. Window
55 above segments 67 of the terminal 17 is provided for connection
of the upper halves 42, 43 of the last turns 72 of the windings to
the segment 67 of terminal 17. Window 56 is provided for connection
of the upper permalloy segment 34 to the magnetic contact 38 as
will be described in connection with FIG. 3D.
Referring to FIG. 3D, the permalloy, upper lamination 11 of core 10
is shown with the apex 24 directed towards the terminal 29, and the
base 23 overlying the terminal 17, with the end 35 of base 23
extending down into electrical contact with the copper terminal 17.
The left leg 21 of permalloy lamination 11 extends between the
windows 51, 53 and 52, 54, respectively, and the other lefthand
windows 50 so that the upper half windings 42 will pass over it.
Winding 73 passes from window 51 to window 52 over the left leg 21
and winding 71 passes from window 53 to window 54 over the left leg
21 also. Similarly, all of the remaining windows 50 will be
connected in like fashion by upper half windings 42, 43, about legs
21 and 22, respectively. The segment 34 extends downwardly into the
window 56 for electrical and magnetic connection of the upper
permalloy segment 34 to the magnetic contact 38 of FIG. 3B to
provide both electrical and magnetic continuity. The lower
permalloy lamination 12 and the upper permalloy lamination 11 are
thereby formed into one continuous ramp core 10 which has magnetic
continuity and which provides the return path for the electrical
currents as was described in connection with FIG. 1 an as will be
shown in greater detail in connection with FIG. 3F. It will be seen
by reference to FIG. 4D that the mask shown therein is of the same
configuration as the upper permalloy layer although the elevations
provided by the lower layers alter the three dimensional form of
the shape.
Referring to FIG. 3E, the second insulating layer 57, a mask for
which is shown in FIG. 4E, is deposited upon the product of FIG.
3D. A window 58 is provided and is coextensive with window 45 above
the lower terminal 29. A window 59 is provided for a second contact
terminal 37 (deposited in FIG. 3F) with a segment of the apex 24 of
the upper permalloy lamination 11 of the core 10 extending into the
space defined by the window 59. Windows 60, corresponding to
windows 50, are provided above and in alignment with windows 50,
with windows 61, 62, 63 and 64 above, and corresponding to, and in
alignment with windows 51, 52, 53, and 54. Window 65 overlies and
is in alignment with windows 55 above the segment 67 of terminal 17
which is adapted to be connected to windings 42 and 43 of the last
turns 72.
FIG. 3F shows the topmost, copper layer deposited upon the product
of FIG. 3E in the form shown in FIG. 4F with a terminal 37 in
window 59 electrically connected to the underlying apex 24 of
lamination 11 of core 10. The wire 19 is connected to terminal 37.
The upper half windings 42 are shown with a portion of the
structure partially cut away to show the entire connection to left
lower halves 30. Upper half winding 73 connects corner 46 of lower
terminal 29 and the first end 47 of chevron lower half winding 30.
Upper half winding 71 connects second end 48 of the first lower
half winding 30 and first end 49 shown in FIG. 3B. The last turns
72 are connected through windows 55 and 65 to the segment 67 of
copper terminal 17 in order to connect the windings about legs 21
and 22 to a common point, electrically. It will be noted that
terminal 17 is connected directly to lower lamination 12 and upper
lamination 11 and, as described in FIG. 1, provides return current
paths therethrough. Wire 18 is connected through windows 58 and 45
down to terminal 29 to connect the opposite ends of the windings 15
and 16 to an outside source as shown in FIGS. 1 and 2.
In another variation of the structure one can protect the chevron
wired transducer against random faulty contacts between the upper
copper " Chevron" half windings 42-43 and the lower half windings
30-31 in FIGS. 3B-3F, by adding shorting bars 90 in FIG. 1 which
are shown there as dashed connections between geometrically
opposing windings. This is accomplished by taking the product of
FIG. 3E and depositing the layer of copper 36 and etching or
electroforming it by use of the mask in FIG. 4H in place of the
mask in FIG. 4F which yields the product in FIG. 3F. Additional
copper 90 in FIG. 3G is deposited between geometrically opposing
upper half windings 42, 43. The connections 90 between
geometrically opposing windings 30-42 and 31-43 have no effect on
the electrically parallel current in the windings around core legs
21 and 22 unless there is a fault in an upper or lower half winding
42-43-30-31 or a fault in the electrical connections between some
half winding pairs 40-42 and 31-43. The interconnections areas 90
lend a redundancy of electrical connection which is used to
increase the yield of the fabrication processes. Thus, if an open
circuit fault occurs in one half winding pair 30-42 or 31-43, the
complementary or geometrically opposing half winding pair 31-43 or
30-42, respectively, will conduct current for both of the
geometrically opposing or complementary winding pairs 30-42 and
31-43.
Referring to FIG. 5A, a portion of a substrate 126 is shown which
may be composed of a material such as silicon molybdenum, or other
metal with a thin film of silicon dioxide or other insulating film
127 covering the entire surface of the wafer. Alternatively, the
substrate 126 may be made of sapphire, glass, alumina or other
insulating material. Deposited above the insulative surface 127 is
the lower permalloy lamination 112 having an overlapping magnetic
contact area 138 at the end thereof distal from the upper end of
the wafer 126. The mask shown in FIG. 6A is employed for the
purpose of photolithographically selecting the permalloy 112 to be
retained during etching away of the surplus permalloy.
Referring to FIG. 5B, the product of FIG. 5A is overlaid with an
insulating layer 75 employing the photolithographic mask shown in
FIG. 6B.
Subsequently as shown in FIG. 5C a layer 128 of conducting material
which may be copper or other conductive material is deposited upon
the product of FIG. 5B. Copper terminal 117 overlies the insulating
layer 75 and the lower permalloy lamination 112 with the
overlapping magnetic contact 138 extending beyond the end of the
terminal 117. The magnetic gap will, eventually after polishing and
lapping, occur along the dashed line 114 near one end of substrate
portion 126 which has been isolated for drawing purposes. The gap
will exist where permalloy 111 and permalloy 112 totally overlap
and are spaced by copper terminal 117. One set of lower half
windings 130 are shown along with the other set of half windings
131 and arranged in a "barber pole" fashion instead of the
"chevron" arrangement which was shown in the previous embodiment.
The two sets of windings are to be connected in series rather than
in parallel, in this case. A terminal segment 76 is shown in the
lower left hand corner in FIG. 5C. In the manufacture of this
layer, first the entire surface is coated with copper. The mask
shown in FIG. 6C then is used to provide photolithographic resist
techniques for etching away the surplus copper or for additively
forming the copper conductors in order to produce the configuration
shown in FIG. 6C.
The product of FIG. 5C is shown in FIG. 5D with the addition of
insulating layer 144 of silicon dioxide or resist which has been
etched away in accordance with the mask of FIG. 6D to provide
coupling window 83 for area 80 of the terminal 117 for coupling a
turn including terminal segment 117 and coupling segment 81 in FIG.
56 through the core.at end 89. Window 82 is provided for the
overlapping magnetic contact 138 of the lower permalloy lamination
112. Windows 150 are provided for connection of the upper half
windings 142 and 143 in FIG. 5G, down to the lower half windings
130 and 131. FIG. 6D shows the mask which was employed in providing
the product of FIG. 5D by photolithographic resist techniques. The
product of FIG. 5D is further modified as shown in FIG. 5E by the
addition of an upper permalloy lamination 111 so that the end 123
of the lamination 111 overlaps the end of lower lamination 112,
thereby providing a magnetic gap of a head ultimately along the
dotted line 114 of the gap in FIG. 5 which will be a real substrate
edge after polishing away excess substrate and head material above
line 114. Then as can be seen the legs 122 and 121 extend between
the windows 150 and as can be visualized the legs 121 and 122
extend between the ends of lower windings 130 and 131,
respectively. The upper permalloy layer 111 is insulated from
electrical and magnetic contact except through the window 82
whereby it makes magnetic and electrical contact with the lower
lamination 112 overlapping magnetic contact 138 which is shown in
phantom along with the lower lamination 112 and except for contact
with the copper lamination, 111 adjacent to the final dotted line
114 of the magnetic gap 114. Thus, copper lamination 117 provides
the minimum spacing between permalloy legs 122 in the vicinity of
the gap 114. Manifestly the mask of FIG. 6E is employed to make the
upper permalloy lamination 111.
The product of FIG. 5E is further modified employing the mask of
FIG. 6F to provide an additional insulation layer 157 which
provides an additional window 86 which overlies window 83 so that
the contact areas 80 for coupling the turn through the core is
capable of making electrical contact with the next layer.
Similarly, windows 160 are provided overlying windows 150 in order
to permit contact to be made with the lower half windings 130 and
131 and the terminal 117. One of the windows 78 will connect to the
corner 79 of an upper right terminal segment 77 composed of copper,
for example. This upper insulating layer 157 may also be composed
of silicon dioxide, an insulating photoresist or some other organic
or inorganic insulation.
The product of FIG. 5F is further processed as shown in FIG. 5G
employing the mask configuration of FIG. 6G to provide an upper
coupling segment 81 having an end 89 extending down through the
windows 86 and 83 into contact with the end 80 of lower terminal
117. The upper half windings 142 and 143 are shown with the
respective ends thereof extending down through windows 160 to
contact the lower half windings 130 and 131 as will be understood
particularly with reference to the procedure employed in the
previous embodiment. Also, as will be understood, the windings are
electrically in series. The upper terminal segment 77 connects to
the first lower winding on the lower level through end 79 and
window 78. Assuming that current enters terminal segment 76, it
will then move upwardly towards the right and then will flow into
the winding 143 in the lower left hand corner of FIG. 5G at its
right end towards its upper end and then down into the first
winding 131 shown in FIG. 5C up to the right hand corner of that
winding and then back up into FIG. 5G in the lower right hand
corner of the second winding 143 shown in FIG. 5G, etc. A helical
current flow is produced. Thus, employing the right hand rule to
this circulating current one would place his hand around the
enclosed leg 122 shown in FIG. 5E with his thumb extending
downwardly. This downward direction being that of the induced
magnetic field in the core leg 122. At the top of FIG. 5G, the
current would then pass through the winding of the left hand corner
down into winding 117 and then to edges 80 and 89 up to segment 81
and from 81 down through the window 160 in the upper right hand
corner in FIG. 5F and rise back through the window 160 to the left
and a little below the upper rightmost window 160 and would travel
across the upper right hand winding 142 from left to right, etc. A
helical current flow then surrounds core leg 120 so that employing
the right hand rule, the induced magnetic field would be directed
upwardly towards the top of the page in FIG. 5G in core leg 121.
Thus, with the above sign conventions, a counterclockwise magnetic
flux is induced in the core 111 in FIG. 5E by the current. The
current then passes from the first winding 130 through window 78
into the edge 79 of the upper terminal 77. Current would be taken
to/from lower terminal 76 and from/to upper terminal 77 by means of
wires connected to them shown in FIG. 5G as wires 118 and 119,
respectively.
Again, wires 118 and 119 may take the form of twin lead, strip line
or twisted pair transmission line fabricated simultaneously with
the head. And again, the terminals 76 and 77 would be continuous
with and leading into the transmission line. The masks for copper
and insulation layers would then be extended and modified in ways
that are known to produce the desired transmission line.
The "barber pole" embodiment is more susceptible to interference
from closely spaced adjacent heads because it contains an open
current loop whereby current approaches the gap line 114 via
conductors 131-143 and recedes via the conductors 130-142. The
resulting "cross-talk" of this embodiment can be nulled by a
compensating transmission line. The insulating layer 25 provides
additional separation of the composite leg 121-112 and leg 122
where they overlap until they are adjacent to the location of the
magnetic gap to be formed by polishing the completed structure in
FIG. 5G to the gap line 114.
This extra insulating layer was not used in the description of the
chevron striped head so that both approaches could be demonstrated.
When additional spacing of legs 121 and 122 is not mandatory,
insulating layer 75 may be removed entirely from the above
discussion. Likewise, when additional spacing is required, layer 75
is used. The "chevron striped" embodiment does not consider similar
additional spacing between the permalloy lamination and the
terminal layer 17 in FIG. 3B. This additional spacing can be
achieved by interposing an additional insulator lamination between
the laminations 12 and 17 shown deposited in FIG. 3A and FIG. 3B.
Thus, a photolithographic deposition of insulator 275 is masked by
the mask in FIG. 4G. The mask windows 256 and 235 in FIG. 4G are
thus positioned beneath the mask windows 56 and 135 in FIG. 4C.
The process steps for the fabrication of the preferred embodiments
are described below. The two processes basically differ in that
steps 4 and 5 for the series wound head deposit the insulation
layer 75 in FIG. 5B, whereas these steps are omitted in the
fabrication of the "chevron head." Thus, step 6 of the "barber
pole" head fabrication process (the second-described process below)
is essentially the same as step 4 of the "chevron head" fabrication
process (the first one below).
As mentioned above, insulation layer 75 of the "barber pole" head
can be eliminated. Also, the insulation layer 275
photolithographically deposited with the use of the mask in FIG. 4G
can be included in the "chevron" head. Steps 4 and 5 of the "barber
pole" head fabrication process are then interposed between steps 3
and 4 of the "chevron" head fabrication process with the
substitution by the words "seventh mask shown in FIG. 4G" in place
of the words "...second mask shown in FIG. 5B."
In fabrication of the head in accordance with the first preferred
embodiment of FIGS. 2, 3A-3F, and 4A-4F, a number of steps are
required as follows:
1. Deposit a titanium or a chromium film as an adhesion layer
either in vacuum or by sputtering or any other acceptable
metallization technique to the thickness of 150-500A and a copper
or permalloy film of approximately 300-500A are both placed upon a
silicon dioxide surface upon a silicon wafer or other similar
substrate.
2. Electroplate permalloy (or deposit it using any equivalent
technique) upon the entire surface of the metallized film coatings
to the thickness of from 1.5-5 microns.
3. Apply a photoresist coating to the entire surface of the
permalloy. Employ the first mask shown in FIG. 4A, and expose the
photoresist through it and etch with ferric chloride or any other
suitable etchant to yield the first permalloy lamination in the
shape of FIG. 4A. Etch the titanium underlayer using 1% HF
solution.
4. Evaporate approximately 150-500 A of titanium and 300- 500A of
copper all over the wafer as in step (1).
5. Apply Shipley* (*Shipley Co. Inc., Wellesley, Mass.) positive
photoresist everywhere with a thickness of 2-4 microns and then use
the second mask shown in FIG. 4B to remove resist where it is
desired to apply a plurality of copper chevrons, etc., over what
remains of the permalloy and the metallized silicon dioxide
surface.
6. Electroplate 1 to 3 microns of copper through the apertures
formed by the second mask.
7. Electrolessly plate or electroplate 1,000- 2000A of gold on top
of the copper.
8. Remove the Shipley mask using acetone or other acceptable
technique.
9. Etch the underlying copper with ammonium per sulphate and
underlying titanium with 1% HF in order to separate the chevron
segments which would be connected by the copper applied in step
(1).
10. Deposit a new layer of insulation composed of SiO.sub.2, KTFR**
(**Eastman Kodak Co., Rochester, New YOrk) (negative) photoresist
or Shipley photoresist to a thickness of 1-3 microns. When using
KTFR or Shipley bake resist at a temperature greater than
170.degree. C to thermally stabilize and polymerize the resist.
11. Etch holes in the insulation with the third mask in FIG. 4C
using hydrogen fluoride for silicon dioxide insulation (solution
may be buffered with ammonium hydroxide) and if KTFR or Shipley is
used, expose and develop the photoresist using an appropriate
developer.
12. Evaporate a very thin layer of titanium 150- 500A and then
evaporate a very thin layer of permalloy 400-500A, or metallize the
entire surface using any other acceptable means.
13. Electroplate 2-4 microns of permalloy on the very thin
metallized layer (plating it in a sheet form).
14. Apply Shipley or KTFR expose and develop resist and etch both
parts of the second layer of permalloy after using the fourth mask,
in FIG. 4D. Etch Ti underlayer as described in step (9).
15. Apply KTFR or Shipley photoresist or apply SiO.sub.2 and bake
the photoresist, if used, to form a second insulator. Expose the
fifth mask shown in FIG. 4E and etch using buffered hydrogen
fluoride if SiO.sub.2 has been used in the preceding step, or
expose and develop if KTFR or Shipley photoresist has been used.
This opens the connections to the contacts.
16. Evaporate a thin film of titanium and a thin film of copper as
in step (4) upon the areas exposed by the fifth mask in FIG. 4E and
all other areas of the coated wafer.
17. Apply Shipley photoresist.
18. Expose the sixth mask pattern shown in FIG. 4F.
19. Plate copper through the mask as in step (6).
20. Electroplate or electrolessly plate copper with 1,000- 2,000A
thick layer of gold as in step (7).
21. Remove the Shipley photoresist mask and etch the copper and
titanium underlayers as in steps (8) and (9).
22. Connect wires to the pads in the structure, polish head
structure and substrate to make the substrate edge flush with the
desired magnetic gap position 14 in FIG. 2.
In fabrication of the head shown in FIGS. 5A-5G a similar set of
steps is required as follows:
1. Deposit a titanium or a chromium film as an adhesion layer
either in vacuum or by sputtering or any other acceptable
metallization technique to the thickness of 150-500A and a copper
or permalloy film of approximately 300-500A are both placed upon a
silicon dioxide surface upon a silicon wafer or other similar
substrate.
2. Electroplate permalloy (or deposit it using any equivalent
technique) upon the entire surface of the metallized film coatings
to the thickness of from 1.5-5 microns.
3. Apply a photoresist coating to the entire surface of the
permalloy. Employ the first mask shown in FIG. 5A, and expose the
photoresist through it and etch with ferric chloride or any other
suitable etchant to yield the first permalloy lamination in the
shape of FIG. 5A. Etch the titanium underlayer using 1% HF
solution.
4. Deposit a layer of insulation composed of SiO.sub.2, KTFR etc
(same as 12 below).
5. Etch the insulation with the second mask shown in FIG. 5B using
hydrogen fluoride for silicon dioxide insulator (solution may be
buffered with ammonia) and if KTFR of Shipley is used, expose and
develop the photoresist using an appropriate developer.
6. Evaporate approximately 150-500 A of titanium and 300-500A of
copper all over the wafer as in step (1).
7. Apply Shipley* (*Shipley Co., Inc., Wellesley, Mass.) positive
photoresist everywhere with a thickness of 2-4 microns and then use
the second mask shown in FIG. 5C to remove resist where it is
desired to apply a plurality of copper stripes, etc., over what
remains of the permalloy and the metallized silicon dioxide
surface.
8. Electroplate 1 to 3 microns of copper through the apertures
formed by the mask.
9. Electrolessly plate or electroplate 1,000-2,000A of gold on top
of the copper.
10. Remove the Shipley mask using acetone or other acceptable
technique.
11. Etch the underlying copper with ammonium per sulphate and
underlying titanium with 1% HF in order to separate the copper
segments which would be connected by the copper applied in step
(1).
12. Deposit a new layer of insulation composed of SiO.sub.2, KTER**
(**Eastman Kodak Co., Rochester, N. Y.) (negative) photoresist or
Shipley photoresist to a thickness of 1-3 microns. When using KTFR
or Shipley bake the resist at a temperature greater than
170.degree. C to thermally stabilize the resist.
13. Etch holes in the insulation with the fourth mask in FIG. 5D
using hydrogen fluoride for silicon dioxide insulation (solution
may be buffered with ammonium hydroxide) and if KTFR or Shipley is
used, expose and develop the photoresist using an appropriate
developer.
14. Evaporate a very thin layer of titanium 150-500A and then
evaporate a very thin layer of permalloy 400-500A, or metallize the
entire surface using any other acceptable means.
15. Electroplate 2-4 microns of permalloy on the very thin
metallized layer (plating it in a sheet form).
16. Apply Shipley or KTFR expose and develop resist and etch both
parts of the second layer of permalloy after using the fifth mask,
in FIG. 5E. Etch Ti underlayer as described in step (9).
17. Apply KTFR or Shipley photoresist or apply SiO.sub.2 and bake
the photoresist, if used, to form a second insulator. Expose the
fifth mask shown in FIG. 4E and etch using buffered hydrogen
fluoride if SiO.sub.2 has been used in the preceding step, or
expose and develop if KTFR or Shipley photoresist has been used.
This opens the connections to the contacts.
18. Evaporate a thin film of titanium and a thin film of copper as
in step (4) upon the areas exposed by the sixth mask in FIG. 5F and
all other areas of the coated wafer.
19. Apply Shipley photoresist.
20. Expose the seventh mask pattern shown in FIG. 5G.
21. Plate copper through the mask as in step (8).
22. Electroplate or electrolessly plate copper with 1,000-2,000A
thickness of gold as in step (9).
23. Remove the Shipley photoresist mask and etch the copper and
titanium underlayers as in steps (10) and (11).
24. Connect wires to the pads in the structure, polish head
structure and wafer to form the magnetic gap at the proper location
(line 114 in FIGS. 5A-G) and make the substrate edge flush with the
desired gap location.
* * * * *