Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-10-27
2002-04-16
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603130, C029S603100, C029S593000, C451S008000, C451S005000, C360S314000
Reexamination Certificate
active
06370763
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a method for manufacturing magnetic heads for lapping magnetic head elements in order to make the height of the magnetic heads uniform after the magnetic head elements are formed on a wafer.
2. Description of the Related Art
In a magnetic head manufacturing process, after forming a magnetic head thin film, the magnetic head thin film is lapped. This lapping uniformly processes the gap length and magnetoresistive film of the magnetic head thin film. Sub-micron order precision is required for a magnetoresistive film and gap length.
FIG.
27
A and
FIG. 27B
are schematic drawings of a merged magnetic head.
As shown in
FIG. 27A
, a merged magnetic head
80
comprises a magnetoresistive element
82
and writing element
85
formed on a substrate
81
. As shown in
FIG. 27B
, the magnetoresistive element
82
comprises a magnetoresistive film
83
and a pair of conductors
84
. The resistance value of the magnetoresistive element
82
changes in the presence of an external magnetic field. This magnetoresistive element
82
is a reading element, which outputs a current equivalent in strength to the magnetic force of a track
90
on a magnetic disk.
The magnetoresistive element
82
is only used for reading, requiring that a writing element be fabricated separately. The writing element
85
is configured as an inductive head. The writing element
85
comprises a bottom magnetic pole
86
and a top magnetic pole
88
that faces the bottom magnetic pole
86
across a gap. A coil
87
, which excites these magnetic poles
86
,
88
is fabricated between the magnetic poles
86
,
88
. A non-magnetic insulation layer
89
is fabricated around the coil
87
.
In a merged magnetic head such as this, the resistance value of the magnetoresistive film
83
of the magnetoresistive element
82
must be constant for each head. However, in a magnetic head thin film manufacturing process, it is impossible to make this resistance value uniform. Consequently, after forming the magnetic head thin film, the magnetic head thin film is subjected to lapping in order to make the height (width) h of the magnetoresistive film
83
uniform thereby making the resistance values uniform.
FIGS. 28A
to
29
D provide schematic diagrams depicting the manufacturing process for such merged magnetic heads.
As shown in
FIG. 28A
, thin-film technology is used to form a plurality of merged magnetic heads
102
on a wafer
100
. Then, as shown in
FIG. 28B
, the wafer
100
is cut into strips, creating row bars, (blocks)
101
. A row bar
101
comprises one row of magnetic heads
102
. And resistance elements
102
a
for process monitoring are formed on the left end, in the middle and on the right end of the row bar
101
.
As explained previously, the magnetic heads
102
are lapped to make the height of the magnetoresistive film
83
uniform. However, the row bar is extremely thin, for example, around 0.3 millimeters. Consequently, it is impossible to mount it directly to the lapping jig. Consequently, as shown in
FIG. 28C
, a row bar
101
is bonded to a mounting jig (base)
103
using a heat-melted wax.
Then, as shown in
FIG. 29A
, the row bar
101
is placed on a lapping plate, and subjected to lapping. At this time, as pointed out in Japanese patent disclosure publication number 2-124262 (U.S. Pat. No. 5,023,991) and Japanese patent disclosure publication number 5-123960, the resistance values of the resistance elements
102
a
for monitoring the processing of the row bar
101
are constantly measured during lapping. Then, these resistance values are used to detect whether or not the magnetoresistive film
83
of the magnetic heads
102
has achieved the target height.
Lapping is terminated when the magnetoresistive film has been processed to the target height by the resistance value measurements. After that, as shown in
FIG. 29B
, a slider is formed on the bottom surface
101
-
1
of the row bar
101
.
Also, as shown in
FIG. 29C
, the row bar
101
is cut into individual magnet heads
102
while it is attached to the mounting jig
103
. Then, as illustrated in
FIG. 29D
, each magnetic head
102
is removed by heating the mounting jig
103
and melting the heat-melted wax.
A row bar
101
comprising a row of magnetic heads
102
is prepared in this way, and since lapping is performed in row bar units, the magnetoresistive film of a plurality of magnetic heads
102
can be lapped at the same time.
FIGS. 30A and 30B
provides schematic diagrams depicting the prior art.
As shown in
FIG. 30A
, the row bar
101
comprises magnetic head elements
102
and monitoring elements
102
a.
The magnetic head elements
102
, as described earlier, comprise a magnetoresistive film
83
and terminals
84
. The monitoring elements (hereafter referred to as electrical lapping guide (ELG) elements)
102
a
comprise a resistance film
1020
and terminals
1021
. This magnetoresistive film
83
and resistance film
1020
are formed from the same material.
As for this resistance film
1020
, as shown in FIG.
30
B, the lower the height ELGh of the resistance film
1020
, the higher its resistance value. Therefore, the height ELGh of the resistance film
1020
can be detected by measuring the resistance value of the resistance film
1020
of the ELG elements
102
a.
Since the height MRh of the magnetoresistive film
83
of the magnetic heads
102
is practically equivalent to the height ELGh of the resistance film
1020
, the height ELGh of the resistance film
1020
is equivalent to the height MRh of the magnetoresistive film
83
. This is used to convert the resistance value of the resistance film
1020
of the ELG elements
102
a
to the height MRh of the magnetoresistive film
83
of the magnetic heads
102
.
Further, the magnetoresistive film
83
is formed on the wafer substrate through a shield layer. Conversely, the ELG elements
102
a
are not used as magnetic heads. Consequently, since a shield is not necessary, the ELG elements
102
a
are fabricated directly on the wafer substrate.
The following problems occurred with methods like this whereby ELG elements
102
a
are fabricated on row bar
101
, and lapping is controlled by measuring the resistance of the ELG elements
102
a.
Firstly, there were variations in accuracy when aligning masks to wafers. Consequently, the position P
0
of the end of the magnetoresistive film
83
shown in
FIG. 30A
differs slightly from the position P
1
of the end of the resistance film
1020
. This is roughly a 0.1-0.2 micron difference, and for magnetic heads requiring micron order processing accuracy, this was not a problem.
However, when it comes to maintaining submicron processing accuracy, this difference poses a problem. With prior art, since the height of the ELG elements was treated as equivalent to the height of the magnetoresistive film, and the resistance values of the ELG elements were converted to the height of the magnetoresistive film, an accurate magnetoresistive film height could not be obtained. Consequently, the non-uniformity of the post-processing height of the magnetoresistive film was a problem.
Secondly, because the formation conditions for ELG elements are the same as those for magnetoresistive films, the same process used to fabricate magnetoresistive film was also used to fabricate ELG elements. However, since an ELG element is not fabricated through a shield layer, the distance from the pattern-generating stepper to the ELG element differs from the distance from the stepper to the magnetoresistive film. Consequently, the accuracy of ELG element pattern formation declines. This decline in accuracy increases the difference between the position P
0
of the end of the magnetoresistive film
83
and the position P
1
of the end of the resistance film
1020
.
With prior art, since the height of the ELG elements was treated as equivalent to the height of the magnetoresistive film, and the resistance values of the ELG elements were converted to the height of the magnetoresistive f
Sugiyama Tomokazu
Suto Koji
Watanuki Motoichi
Yanagida Yoshiaki
Yokoi Kazuo
Greer Burns & Crain Ltd.
Tugbang A. Dexter
Young Lee
LandOfFree
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