Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-11-12
2003-08-12
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S311000, C430S312000, C430S314000, C430S394000
Reexamination Certificate
active
06605414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a magnetoresistance head and, more particularly, a method for manufacturing a magnetoresistance head including a step of forming patterns by virtue of lift-off technique.
2. Description of the Prior Art
A magnetoresistance head utilized as a reproducing head of a magnetic recording apparatus has the configuration as shown in
FIG.1
, for instance. The magnetoresistance head is implemented by forming sequentially a SAL (Soft Adjacent Layer)
102
, a nonmagnetic layer
103
, and a magnetoresistance layer (referred to as “MR layer” hereinafter)
104
on a lower gap layer
101
, then patterning these three layers as a planar rectangular pattern, and then forming antiferromagnetic layers
105
a
,
105
b
and lead terminals
106
a
,
106
b
on both sides of the rectangular pattern. A region formed between two lead terminals
106
a
,
106
b
serves as a sense region S.
A pair of lead terminals
106
a
,
106
b
are formed by lift-off process, as described below with reference to
FIGS. 2A
to
2
C.
Referring to
FIG. 2A
, a resist
107
is coated on the rectangular pattern of the SAL
102
one time, the nonmagnetic layer
103
, and the MR layer
104
and on the lower gap layer
101
. The resist
107
is then patterned by exposing and developing the resist
107
so as to expose two lead terminal forming regions and to cover the sense region S on the MR layer
104
. As shown in
FIG. 2B
, the antiferromagnetic layer
105
and the metal film
106
are formed by sputtering. In turn, the resist
107
is released to leave the metal layer
106
only on two lead terminal forming regions. The antiferromagnetic layer
105
and the metal film
106
are thus left only on two lead terminal forming regions, which are used respectively as the antiferromagnetic layers
105
a
,
105
b
and the lead terminals
106
a
,
106
b
, as shown in FIG.
2
C.
However, in the event that side portions of the patterned resist are patterned to form vertical flat surfaces, there is caused such a drawback that flashes are apt to be generated on peripheries of the lead terminals
106
a
,
106
b.
In order to suppress such flashes of the lead terminals
106
a
,
106
b
, it has been known to use the resist having a two-layered structure.
For instance, as has been recited in U.S. Pat. No 5,087,332 and Patent Application Publication (KOKAI) 3-125,311, the resist is coated two times to prepare for patterning of the gap layer in the magnetic head, then sectional shapes of the resist are formed to have a mushroom-like sectional shape by exposing and developing the resist two times, then the resist is used as a lift-off mask. In addition, the lift-off mask having such mushroom-like sectional shape in which the upper layer and the lower layer consist respectively of the resist and the Al
2
O
3
film has been recited in Patent Application Publication (KOKAI) 7-65,326.
However, if relative misalignment of mask positions occurs during exposure process since these masks are processed by two-time patterning, the mushroom-like sectional shapes may be unbalanced on the right and left sides, otherwise the resist may be curved because the upper resist layer has projected too much laterally. Hence it becomes difficult to improve manufacturing yield of the magnetic head.
Furthermore, there are some cases where the resist having the mushroom-like sectional shape is used commonly as the lift-off mask as well as the mask for forming the magnetic layer pattern. In this event, since the resist is damaged in the course of vacuum process, constituents of the resist such as the organic substance are scattered from the resist and stick to the surface of the magnetic layer. This causes defective contacts between the magnetic layer and the lead terminals.
In addition, if release liquid for the two-layered resist and other conditions are improper, the magnetic layer is also damaged.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for manufacturing a magnetoresistance head by which the films can be patterned with good precision and damage of the resist can be suppressed.
According to an aspect of the present invention, edges of pattern of an organic film formed to cut inwardly from edges of pattern of a resist film by forming the organic film on a multilayered film constituting a magnetoresistance device, then forming the resist film on the organic film, and then patterning the organic film and the resist film. A cut-into amount is defined to such an extent that particles of an upper thin film such as a magnetic film or a metal film which is formed by sputtering or vacuum evaporation on the organic film and the resist film do not stick to side portions of pattern of the organic film.
Therefore, even if the pattern is formed by virtue of lift-off while employing the organic film and the resist film as the mask so as to leave the upper thin film only on the multilayered film, no flash is generated on the pattern of the upper thin film.
If inorganic film is utilized in place of the resist film, generation of the flash can be prevented. In case the mask is also employed in ordinary photolithography, contaminants made of mask constituting substances can be suppressed from sticking to the magnetoresistance device by reducing scattering of the mask because of etching if the upper layer of the mask is formed of the inorganic film. In addition, in case the inorganic film is formed of metal and terminals are formed by virtue of lift-off, contact resistance between the terminal and the magnetoresistance device is in no way increased since the contaminants which adhere to the surface of the magnetoresistance device are metal.
In the present invention, in the mask of a two-layered structure having a pattern to cover the sense region, since the width of the mask is widened around the sense region, the upper layer of the mask is kept in a floating state even when the lower layer of the mask in the sense region is lost in the course of manufacturing the mask. Therefore, no trouble is caused in lift-off.
In case the lift-off mask having a substantial T-like sectional shape is formed, compressive stress is generated in the upper layer. For this reason, since the upper layer is curved downwardly, contaminants scattered from the mask may stick to the magnetoresistance device. If compressive stress is set within less than 0 dyn/cm
2
but more than −20.0×10
9
dyn/cm
2
, excessive curvature of the upper layer can be prevented.
Furthermore, if compressive stress in the upper layer of the mask is increased as its location in the upper layer becomes higher, curvature of the upper layer becomes small as the upper layer of the mask is etched even when the mask is employed in both patterning steps in photolithography and lift-off. Therefore, there is no trouble in succeeding with lift-off.
In the step where the lower film of the mask is formed of a photosensitive organic film and the upper film thereof is formed of the inorganic film, whole image exposure of the organic film may be effected prior to formation of the inorganic film. Thus, reduction in mask precision which is caused by degradation in photosensitivity because of heat generated in forming the inorganic film can be prevented.
According to another aspect of the present invention, since patterning is carried out after patterning of the magnetoresistance device is completed if the shielding film, etc. beneath the magnetoresistance device are patterned, the resist used when the magnetoresistance device is patterned is flattened, so that precise patterning of the magneto-resistance device can be implemented.
According to still another aspect of the present invention, since the multilayered film is patterned while employing the organic film and the resist film as another mask prior to patterning of the upper thin film by lift-off, time and labor for preparing the mask every patterning can be omitted and throughput can be improved. In this case, if the etching rate
Igarashi Miwa
Kanamine Michiaki
Kuramitsu Yoko
Namiki Takahisa
Nozaki Koji
Barreca Nicole
Fujitsu Limtied
Greer Burns & Crain Ltd.
Huff Mark F.
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