U.S. patent application number 13/907617 was filed with the patent office on 2014-12-04 for super shallow laminated hard mask stencil for magnetic read sensor fabrication.
This patent application is currently assigned to HGST NETHERLANDS B.V.. The applicant listed for this patent is HGST Netherlands B.V.. Invention is credited to Guomin MAO, Hicham Moulay SOUGRATI, Yi ZHENG.
Application Number | 20140353276 13/907617 |
Document ID | / |
Family ID | 51870083 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140353276 |
Kind Code |
A1 |
MAO; Guomin ; et
al. |
December 4, 2014 |
SUPER SHALLOW LAMINATED HARD MASK STENCIL FOR MAGNETIC READ SENSOR
FABRICATION
Abstract
The present invention generally relates to methods for forming a
sensor structure utilizing a shallow and narrow hard mask stencil.
In one embodiment, a sensor structure is formed by utilizing a
four-layered hard mask stencil. The four-layered hard mask stencil
includes a first mask layer, a second mask layer disposed over the
first hard mask, a third mask layer disposed over the second mask
layer, and a forth mask layer disposed over the third mask layer.
In another embodiment, a sensor structure is formed by utilizing a
three-layered hard mask stencil. The three-layered hard mask
stencil includes a first mask layer, a second mask layer disposed
over the first mask layer, and a third mask layer disposed over the
second mask layer. The sensor structure is formed with a two-step
chemical mechanical planarization (CMP) process.
Inventors: |
MAO; Guomin; (San Jose,
CA) ; SOUGRATI; Hicham Moulay; (Elk Grove, CA)
; ZHENG; Yi; (San Ramon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HGST Netherlands B.V. |
Amsterdam |
|
NL |
|
|
Assignee: |
HGST NETHERLANDS B.V.
AMSTERDAM
NL
|
Family ID: |
51870083 |
Appl. No.: |
13/907617 |
Filed: |
May 31, 2013 |
Current U.S.
Class: |
216/22 |
Current CPC
Class: |
Y10T 29/49032 20150115;
G11B 5/3163 20130101; G11B 5/398 20130101 |
Class at
Publication: |
216/22 |
International
Class: |
G11B 5/127 20060101
G11B005/127 |
Claims
1. A method for forming a read head, comprising: forming a sensor
layer on a substrate; forming a first mask layer comprising a first
material over the sensor layer; forming a bi-layer structure over a
first portion of the first mask layer and leaving a second portion
of the first mask layer exposed; forming a cap layer over the
second portion of the first mask layer and the bi-layer structure;
removing the bi-layer structure and a portion of the cap layer
disposed over the bi-layer structure to expose the first portion of
the first mask layer; forming a second mask layer comprising a
second material over the first portion of the first mask layer and
the cap layer; forming a third mask layer comprising a third
material over the second mask layer; forming a fourth mask layer
comprising a fourth material over the third mask layer; forming a
photoresist mask over the fourth mask layer; and removing a portion
of the fourth mask layer, the third mask layer, the second mask
layer, and the first mask layer to form a hard mask stencil and to
expose a portion of the sensor layer.
2. The method of claim 1, further comprising: removing the exposed
portion of the sensor layer to form one or more channels in the
sensor layer; and depositing a bias material in the channels.
3. The method of claim 1, wherein the hard mask stencil has a
height between about 30 nm and about 65 nm.
4. The method of claim 3, wherein the hard mask stencil has a width
between about 10 nm and about 30 nm.
5. The method of claim 3, wherein the first mask layer comprises
diamond-like carbon.
6. The method of claim 5, wherein the second mask layer comprises
polymer-like carbon.
7. The method of claim 6, wherein the third mask layer comprises a
material selected from the group consisting of carbon and
diamond-like carbon.
8. The method of claim 7, wherein the fourth mask layer comprises a
dielectric hard mask.
9. The method of claim 1, wherein the cap layer comprises a
dielectric material selected from the group consisting of SiN, TaO,
SiC, SiO.sub.2 and SiO.sub.xN.sub.y.
10. A method for forming a read head, comprising: forming a sensor
layer on a substrate; forming a cap layer over the sensor layer;
forming a first mask layer having a first thickness over the cap
layer; forming a second mask layer over the first mask layer;
forming a third mask layer over the second mask layer; forming a
photoresist mask over the third mask layer; removing a portion of
the third mask layer, the second mask layer, and the first mask
layer to form a stack, wherein the stack is disposed on a remaining
first mask layer having a second thickness; forming a photoresist
layer over portions of the remaining first mask layer; removing the
remaining first mask layer not covered by the stack and the
photoresist layer to form a hard mask stencil and to expose
portions of the cap layer; and removing portions of the cap layer
and the sensor layer not covered by the hard mask stencil and the
photoresist layer to form one or more channels in the sensor
layer.
11. The method of claim 10, wherein the cap layer comprises a
material selected from the group consisting of iridium and
ruthenium.
12. The method of claim 11, wherein the first mask layer comprises
diamond-like carbon and the first thickness is between about 10 nm
and about 50 nm.
13. The method of claim 11, wherein the second thickness is half of
the first thickness or less.
14. The method of claim 12, wherein the second mask layer comprises
a material selected from the group consisting of Si, SiN, SiC,
SiO.sub.xN.sub.y, SiO.sub.2 and TaO.
15. The method of claim 14, wherein the third mask layer is either
a non-silicon based BARC layer or a silicon based BARC layer.
16. The method of claim 10, wherein the hard mask stencil has a
width between about 10 nm and about 30 nm and a height between
about 20 nm and about 60 nm.
17. The method of claim 10, further comprising depositing a bias
material in the channels.
18. The method of claim 17, further comprising: forming a top
surface comprising the remaining first mask layer and the bias
material; removing a portion of the bias material to expose the
remaining first mask layer disposed over a sensor structure;
removing the remaining first mask layer to expose the cap layer,
wherein a remaining bias layer extends above the cap layer; and
planarizing the remaining bias layer so the bias layer is planar
with the cap layer.
19. A method for forming a read head, comprising: forming a top
surface comprising a mask layer and a bias layer; removing a
portion of the bias layer to expose the mask layer disposed over a
sensor structure; removing the mask layer to expose a cap layer,
wherein a remaining bias layer extends above the cap layer; and
planarizing the remaining bias layer so the bias layer is planar
with the cap layer.
20. The method of claim 19, wherein the mask layer comprises
diamond-like carbon.
21. The method of claim 20, wherein the bias layer comprises CoFe
or NiFe.
22. The method of claim 21, wherein the cap layer comprises a
material selected from the group consisting of iridium and
ruthenium.
23. The method of claim 19, wherein the removing a portion of the
bias layer comprises a first CMP process.
24. The method of claim 24, wherein the planarizing the remaining
bias layer comprises a second CMP process.
Description
BACKGROUND
[0001] 1. Field
[0002] Embodiments of the present invention generally relate to
methods of making a magnetic read sensor. More particularly,
embodiments of the present invention relate to methods of making a
magnetic read sensor utilizing a super shallow laminated hard mask
stencil.
[0003] 2. Description of the Related Art
[0004] The heart of a computer is a magnetic disk drive which
typically includes a rotating magnetic disk, a slider that has read
and write heads, a suspension arm above the rotating disk and an
actuator arm that swings the suspension arm to place the read
and/or write heads over selected circular tracks on the rotating
disk. The suspension arm biases the slider towards the surface of
the disk when the disk is not rotating but, when the disk rotates,
air is swirled by the rotating disk and the adjacent air bearing
surface (ABS) of the slider causes the slider to ride on an air
bearing with a slight distance from the surface of the rotating
disk. When the slider rides on the air bearing, the write and read
heads are employed for writing magnetic impressions to and reading
magnetic signals from the rotating disk. The read and write heads
are connected to processing circuitry that operates according to a
computer program to implement the writing and reading
functions.
[0005] To construct a read head, a plurality of sensor layers are
deposited across the surface of a substrate. One or more mask
layers are deposited over the sensor layers and a series of
photolithographic processes and reactive ion etch (RIE) processes
are then conducted to form a mask stencil above the sensor layers.
An ion milling process then removes unmasked portions of the sensor
layers to define the shape, profile and dimension (such as track
width) of the read head sensor.
[0006] In order to achieve greater data storage density on the
magnetic media, magnetic data bits are written in increasingly
smaller sizes. The read head is therefore fabricated with a reduced
track width to properly read the smaller sized data bits.
Therefore, there is a need in the art for an improved method for
forming the narrow read head.
SUMMARY
[0007] The present invention generally relates to methods for
forming a sensor structure utilizing a shallow and narrow hard mask
stencil. In one embodiment, a sensor structure is formed by
utilizing a four-layered hard mask stencil. The four-layered hard
mask stencil includes a first mask layer, a second mask layer
disposed over the first hard mask, a third mask layer disposed over
the second mask layer, and a forth mask layer disposed over the
third mask layer. In another embodiment, a sensor structure is
formed by utilizing a three-layered hard mask stencil. The
three-layered hard mask stencil includes a first mask layer, a
second mask layer disposed over the first mask layer, and a third
mask layer disposed over the second mask layer. The sensor
structure is formed with a two-step chemical mechanical
planarization (CMP) process.
[0008] In one embodiment, a method for forming a read head is
disclosed. The method includes forming a sensor layer on a
substrate, forming a first mask layer over the sensor layer;
forming a patterned bi-layer structure over a portion of the first
mask layer, forming a RIE (reactive ion etch) stop layer over the
first mask layer and the bi-layer structure, and removing the
bi-layer structure and the portion of the RIE stop layer disposed
over the bi-layer structure to expose a portion of the first mask
layer. The area covered by the RIE stop layer is called the field
area, and the area not covered by the RIE stop layer is called the
device area.
[0009] The method further includes forming a second mask layer over
RIE stop layer (i.e., in the field area) and also over the exposed
first mask layer (i.e., in the device area), forming a third mask
layer over the second mask layer, forming a fourth mask layer over
the third mask layer, forming a patterned photoresist mask in the
device area using lithography process over the fourth mask layer,
leaving portions of the device area and the entire field area
exposed, then removing a portion of the fourth mask layer using a
first RIE with certain amount of over-etch that the fourth mask
layer is completely etched through in the area not protected by the
photoresist mask and exposing portion of the third mask layer.
[0010] The method further includes applying a second RIE process,
which capable of selectively etch the photoresist mask, the third,
the second and the first mask layer without (or with minimum) etch
to the fourth mask layer and the RIE stop layer, forming a hard
mask stencil (in the device area) consisting of four mask layers
(i.e., the fourth, the third, the second, and the first mask layer)
without photoresist residue disposed thereon. The device area is
further divided into two areas, one is the stencil, another is
channel area where the header sensor is not covered by the stencil
and is exposed. The stencil is surrounded by the channel area. The
third and second mask layer in the field area are also removed in
the second RIE process, however the first mask layer in the field
is not etched by the second RIE since the first mask layer is
protected by the RIE stop layer.
[0011] The method further includes forming a patterned photoresist
mask on the RIE stop layer and leaving device area (including
stencil and channel area) exposed. Thereafter an ion mill process
is performed, the sensor layer in the channel area is etched away,
the sensor layer under the stencil is protected by the stencil, and
a reader sensor junction shape is formed under the stencil. The
third mask layer of the stencil and partial of the second layer of
the stencil are consumed during ion mill process, and the remaining
of the second mask layer and first mask layer are still on the
stencil. The RIE stop layer and the first mask layer in the field
area is protected by the photoresist mask thus not etched by the
ion mill, however, portions of the photomask are consumed in the
ion mill.
[0012] The method further includes forming an dielectric insulation
layer (or layers) covering remaining stencil, channel areas and
photoresist in field area, forming a hard bias layer on top of the
dielectric layer, forming a cap layer on hard bias layer, removing
the cap layer, the hard bias layer and the dielectric layer in the
field area by a liftoff process to expose the RIE stop layer over
the field area, removing the cap layer, the hard bias layer, the
dielectric layer and the second mask layer of the stencil by a CMP
process, exposing the first mask layer of the stencil, at the same
time exposing the first mask layer in the field area, and partially
removing the cap layer in the channel areas. A third RIE process is
performed to remove the exposed first mask layer in both stencil
and field area and the remaining cap layer in the channel areas,
thus forming a reader junction sensor.
[0013] In another embodiment, a method for forming a read head is
disclosed. The method includes forming a sensor layer on a
substrate, forming a cap layer over the sensor layer, forming a
first mask layer having a first thickness over the cap layer,
forming a second mask layer over the first mask layer, forming a
third mask layer over the second mask layer, forming a patterned
photoresist mask using lithography process over the third mask
layer, leaving the rest of the device area exposed, removing a
portion of the third mask layer not protected by the photoresist
mask using a first reactive ion etch (RIE) with certain amount of
over-etch that both the third layer and the second layer in the
field area and in the channel area are completely etched through
and exposing portion of the first mask layer in the field area and
channel area. The first RIE process forms a stack in the device
area consisting of residual photoresist, the third and the second
mask layer, and part of the first layer. The stack is disposed on a
remaining first mask layer having a second thickness.
[0014] After forming the stack, a patterned photoresist mask is
formed on the remaining first mask layer in the field area leaving
the device area (i.e., the stack and the surrounding channel areas)
exposed. The method further includes removing a portion of the
remaining first mask layer in the channel areas using a second RIE
process to etch away the remaining first mask layer in the channel
areas, forming a hard mask stencil since the high etch selectivity
of the third mask layer on the stencil, and leaving the photoresist
mask in the field area partially etched with a remaining of
thickness that is sufficient for the liftoff process later.
Thereafter an ion mill process is performed to mill away the
exposed sensor layer in the channel areas and a reader sensor
junction shape is formed.
[0015] The method further includes forming an dielectric insulation
layer (or layers) covering the stencil, device area and photoresist
in field area, forming a side-shield layer on top of the dielectric
layer, removing the side-shield layer and the dielectric layer in
the field area by a liftoff process to expose the first mask layer
having a second thickness over the field area, removing the
side-shield layer and dielectric layer and the second mask layer of
the stencil by a first CMP process, and exposing the first mask
layer of the stencil. The exposed first mask layer in the field has
high CMP selectivity thus only partially removed. The method
further includes removing the exposed first mask layer in field and
the first mask layer on the stencil using a third RIE process to
expose the cap layer in both stencil and filed area.
[0016] The method further includes applying a second CMP to polish
the portion of the side-shield. The cap layer has higher CMP
selectivity that the bump-out side-shield is planarized and has the
same flat surface with cap layer. Then an ion mill process with the
same mill rate is used to remove the cap layer and portions of the
side-shield, and a sensor junction is formed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0018] FIG. 1 illustrates an exemplary magnetic disk drive,
according to an embodiment of the invention.
[0019] FIG. 2A is a side view of a read/write head and magnetic
disk of the disk drive of FIG. 1, according to one embodiment of
the invention.
[0020] FIG. 2B is a schematic cross-sectional view of portions of
the magnetic head according to one embodiment.
[0021] FIGS. 3A-3P illustrate the process of making a sensor
structure of FIG. 2B according to one embodiment.
[0022] FIGS. 4A-4M illustrate the process of making the sensor
structure of FIG. 2B according to another embodiment.
[0023] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation.
DETAILED DESCRIPTION
[0024] In the following, reference is made to embodiments of the
invention. However, it should be understood that the invention is
not limited to specific described embodiments. Instead, any
combination of the following features and elements, whether related
to different embodiments or not, is contemplated to implement and
practice the invention. Furthermore, although embodiments of the
invention may achieve advantages over other possible solutions
and/or over the prior art, whether or not a particular advantage is
achieved by a given embodiment is not limiting of the invention.
Thus, the following aspects, features, embodiments and advantages
are merely illustrative and are not considered elements or
limitations of the appended claims except where explicitly recited
in a claim(s). Likewise, reference to "the invention" shall not be
construed as a generalization of any inventive subject matter
disclosed herein and shall not be considered to be an element or
limitation of the appended claims except where explicitly recited
in a claim(s).
[0025] The present invention generally relates to methods for
forming a magnetic sensor structure utilizing a shallow and narrow
hard mask stencil. In one embodiment, a sensor structure is formed
by utilizing a four-layered hard mask stencil. The four-layered
hard mask stencil includes a first mask layer, a second mask layer
(a release layer), a third mask layer and a fourth mask layer. In
another embodiment, a sensor structure is formed by utilizing a
three-layered hard mask stencil. The three-layered hard mask
stencil includes a first mask layer, a second mask layer, and a
third mask layer. The sensor structure is formed with a two-step
CMP process.
[0026] FIG. 1 illustrates a top view of an exemplary HDD 100,
according to an embodiment of the invention. As illustrated, HDD
100 may include one or more magnetic disks 110, actuator 120,
actuator arms 130 associated with each of the magnetic disks, and
spindle motor 140 affixed in a chassis 150. The one or more
magnetic disks 110 may be arranged vertically as illustrated in
FIG. 1. Moreover, the one or more magnetic disks may be coupled
with the spindle motor 140.
[0027] Magnetic disks 110 may include circular tracks of data on
both the top and bottom surfaces of the disk. A magnetic head 180
mounted on a slider may be positioned on a track. As each disk
spins, data may be written on and/or read from the data track.
Magnetic head 180 may be coupled to an actuator arm 130 as
illustrated in FIG. 1. Actuator arm 130 may be configured to swivel
around actuator axis 131 to place magnetic head 180 on a particular
data track.
[0028] FIG. 2A is a fragmented, cross-sectional side view through
the center of a read/write head 200 mounted on a slider 201 and
facing magnetic disk 202. The read/write head 200 and the magnetic
disk 202 may correspond to the magnetic head 180 and the magnetic
disk 110, respectively in FIG. 1. In some embodiments, the magnetic
disk 202 may be a "dual-layer" medium that includes a perpendicular
magnetic data recording layer (RL) 204 on a "soft" or relatively
low-coercivity magnetically permeable underlayer (PL) 206 formed on
a disk substrate 208. The read/write head 200 includes an ABS, a
magnetic write head 210 and a magnetic read head 211, and is
mounted such that the ABS is facing the magnetic disk 202. In FIG.
2A, the disk 202 moves past the write head 210 in the direction
indicated by the arrow 232, so the portion of slider 201 that
supports the read/write head 200 is often called the slider
"trailing" end 203.
[0029] In some embodiments, the magnetic read head 211 is a
magnetoresistive (MR) read head that includes an MR sensing element
230 located between MR shields S1 and S2. In other embodiments, the
magnetic read head 211 is a magnetic tunnel junction (MTJ) read
head that includes a MTJ sensing device 230 located between MR
shields S1 and S2. The RL 204 is illustrated with perpendicularly
recorded or magnetized regions, with adjacent regions having
magnetization directions, as represented by the arrows located in
the RL 204. The magnetic fields of the adjacent magnetized regions
are detectable by the MR (or MTJ) sensing element 230 as the
recorded bits.
[0030] The write head 210 includes a magnetic circuit made up of a
main pole 212 and a yoke 216. The write head 210 also includes a
thin film coil 218 shown in the section embedded in a non-magnetic
material 219 and wrapped around yoke 216. In an alternative
embodiment, the yoke 216 may be omitted, and the coil 218 may wrap
around the main pole 212. A write pole 220 is magnetically
connected to the main pole 212 and has an end 226 that defines part
of the ABS of the magnetic write head 210 facing the outer surface
of disk 202.
[0031] Write pole 220 is a flared write pole and includes a flare
point 222 and a pole tip 224 that includes an end 226 that defines
part of the ABS. The flare may extend the entire height of write
pole 220 (i.e., from the end 226 of the write pole 220 to the top
of the write pole 220), or may only extend from the flare point
222, as shown in FIG. 2A. In one embodiment the distance between
the flare point 222 and the ABS is between about 0 nm and about 150
nm.
[0032] The write pole 220 includes a tapered surface 271 which
increases a width of the write pole 220 from a first width W1 at
the ABS to a second width W2 away from the ABS. In one embodiment,
the width W1 may be between about 60 nm and 200 nm, and the width
W2 may be between about 120 nm and 350 nm. While the tapered region
271 is shown with a single straight surface in FIG. 2A, in
alternative embodiment, the tapered region 271 may include a
plurality of tapered surface with different taper angles with
respect to the ABS.
[0033] The tapering improves magnetic performance. For example,
reducing the width W1 at the ABS may concentrate a magnetic field
generated by the write pole 220 over desirable portions of the
magnetic disk 202. In other words, reducing the width W1 of the
write pole 220 at the ABS reduces the probability that tracks
adjacent to a desirable track are erroneously altered during
writing operations.
[0034] While a small width of the write pole 220 is desired at the
ABS, it may be desirable to have a greater width of the write pole
220 in areas away from the ABS. A larger width W2 of the write pole
220 away from the ABS may desirably increase the magnetic flux to
the write pole 220, by providing a greater thickness of the write
pole 220 in a direction generally parallel to the ABS. In
operation, write current passes through coil 218 and induces a
magnetic field (shown by dashed line 228) from the write pole 220
that passes through the RL 204 (to magnetize the region of the RL
204 beneath the write pole 220), through the flux return path
provided by the PL 206, and back to an upper return pole 250. In
one embodiment, the greater the magnetic flux of the write pole
220, the greater is the probability of accurately writing to
desirable regions of the RL 204.
[0035] FIG. 2A further illustrates one embodiment of the upper
return pole 250 that is separated from write pole 220 by a
nonmagnetic gap layer 256. In some embodiments, the upper return
pole 250 may be a trailing shield wherein substantially all of the
shield material is on the trailing end 203. Alternatively, in some
embodiments, the upper return pole 250 may be a wrap-around shield
wherein the shield covers the trailing end 203 and also wraps
around the sides of the write pole 220. As FIG. 2A is a cross
section through the center of the read/write head 200, it
represents both trailing and wrap-around embodiments.
[0036] Near the ABS, the nonmagnetic gap layer 256 has a reduced
thickness and forms a shield gap throat 258. The throat gap width
is generally defined as the distance between the write pole 220 and
the upper return pole 250 at the ABS. The upper return pole 250 is
formed of magnetically permeable material (such as Ni, Co and Fe
alloys) and gap layer 256 is formed of nonmagnetic material (such
as Ta, TaO, Ru, Rh, NiCr, SiC or Al.sub.2O.sub.3). A taper 260 in
the gap material provides a gradual transition from the throat gap
width at the ABS to a maximum gap width above the taper 260. This
gradual transition in width forms a tapered bump in the
non-magnetic gap layer that allows for greater magnetic flux
density from the write pole 220, while avoiding saturation of the
upper return pole 250.
[0037] It should be understood that the taper 260 may extend either
more or less than is shown in FIG. 2A. The taper may extend upwards
to an end of the upper return pole 250 opposite the ABS (not
shown), such that the maximum gap width is at the end of the shield
opposite the ABS. The gap layer thickness increases from a first
thickness (the throat gap width) at the ABS to greater thicknesses
at a first distance from the ABS, to a greatest thickness at a
second distance (greater than the first distance) from the ABS.
[0038] FIG. 2B is a schematic cross-sectional view of portions of
magnetic head 211 according to one embodiment. The thickness and
the width of each layer are for example only, and each layer may be
thicker/thinner and/or wider/narrower. The magnetic head 211
includes a first shield layer 231. The first shield layer 231 may
comprise a ferromagnetic material. Suitable ferromagnetic materials
that may be utilized include Ni, Fe, Co, NiFe, NiFeCo, NiCo, CoFe
and combinations thereof.
[0039] The magnetic head 211 also includes a sensor structure 205
comprising a pinned magnetic layer 233, a barrier layer 234, a free
layer 236 and an optional capping layer 238. The pinned magnetic
layer 233 may be one of several types of pinned layers, such as a
simple pinned, antiparallel pinned, self pinned or
antiferromagnetic pinned. For purposes of simplicity, the sensor
will be described herein as antiparallel pinned. The
antiferromagnetic pinned sensor has a first antiparallel pinned
layer, a second antiparallel pinned layer, and a non-magnetic,
antiferromagnetic coupling layer, such as Ru sandwiched between the
two pinned layers. The first and second antiparallel pinned layers
can be constructed of several magnetic materials, such as NiFe or
CoFe, and have magnetic moments that are pinned by exchange
coupling of the first antiparallel pinned layer with an
antiferromagnetic layer. The antiferromagnetic layer may include
materials such as PtMn, iridium, or rhodium. The barrier layer 234
may comprise an insulating material such as MgO or alumina. The
free layer 236 may comprise ferromagnetic material such as Co,
CoFe, CoFeB, NiFe or combinations thereof. The capping layer 238
may comprise a material to protect the sensor from damage such as
ruthenium, iridium, tantalum or combinations thereof.
[0040] Following the formation of the sensor structure 205
(discussed in detail below), an insulating layer 240 may be
deposited on the first shield layer 231 as well as the sidewalls of
the sensor structure 205. The insulating layer 240 may comprise an
insulating material such as aluminum oxide, silicon nitride or
silicon oxide. The insulating layer 240 may be deposited by well
known deposition methods such as atomic layer deposition (ALD),
chemical vapor deposition (CVD), sputtering, ion beam deposition
(IBD) and etc. After the insulating layer 240 is deposited, a hard
bias or a soft side-shield layer 242 is then deposited. The hard
bias layer or soft side-shield 242 may comprise a material having a
high magnetic moment such as CoFe or NiFe.
[0041] Once the hard bias layer or soft side-shield 242 is
deposited, a capping structure 244 may be formed. In one
embodiment, the capping structure 244 may comprise a multiple layer
structure comprising a first tantalum layer, an iridium layer, and
a second tantalum layer. After one or more planarization process, a
second shield layer 246 may be deposited over the capping structure
244 and the sensor structure 205. The second shield layer 246 may
comprise a ferromagnetic material. Suitable ferromagnetic materials
that may be utilized include Ni, Fe, Co, NiFe, NiFeCo, NiCo, CoFe
and combinations thereof.
[0042] In order to form the sensor structure 205, a hard mask
stencil is formed over the layers 233, 234, 236 and 238 to help
shaping the sensor structure 205. Typically a conventional mask
stencil has a height of about 100 nanometers (nm) and a width of
about 30 to 40 nm. As the sensor structure 205 gets narrower, a
shallower and narrower hard mask stencil with better control on
both track width and height within wafer and wafer to wafer should
be utilized. FIGS. 3A-3P illustrate the process of making the
sensor structure 205 utilizing such shallow and narrow hard mask
stencil.
[0043] As FIG. 3A illustrates, the sensor layer 302 is deposited
over the first shield layer 231. The sensor layer 302 may include
the pinned magnetic layer 233, the barrier layer 234, the free
layer 236 and the optional capping layer 238. A first mask layer
304 is deposited over the sensor layer 302. The first mask layer
304 may be a diamond-like carbon (DLC) layer that is deposited by
plasma enhanced chemical vapor deposition (PECVD), ion beam
deposition (IBD), or any other suitable deposition process. In one
embodiment, the first mask layer 304 is deposited by IBD and has a
thickness of about 3 nm to about 8 nm. One of the functions of the
first mask layer 304 is to serve as a CMP stop layer as discussed
below. In FIG. 3B, a bi-layer structure 306 is deposited over the
first mask layer 304. The bi-layer structure 306 includes a release
layer 308 and a photoresist layer 310. The release layer 308 may be
polydimethylglutarimide (PMGI) and the photoresist layer 310 may be
a polyphenolic polymer or polyvinylphenol. Gaps (or undercuts) 307
and 309 are formed between the photoresist layer 310 and the first
mask layer 304 at the bottom of the bi-layer structure 306. During
the photolithography process there is more release layer 308 being
removed and the recessed sides of the release layer 308 causes
undercuts 307 and 309 below the photoresist layer 310.
[0044] As shown in FIG. 3C, an RIE stop layer 312 (as will be
discussed in detail later) is deposited over the uncovered portions
of the first hard mask layer 304 and the photoresist layer 310. The
RIE stop layer 312 also covers the side walls of the photoresist
layer 310; however, the undercuts 307, 309 are not sealed in by the
RIE stop layer 312 because of the gap 307 and 309. The RIE stop
layer 312 may be silicon nitride (SiN), tantalum oxides (TaO,
Ta.sub.2O.sub.3, Ta.sub.2O.sub.5), silicon carbide (SiC), silicon
dioxide (SiO.sub.2), silicon oxynitride (SiO.sub.xN.sub.y), or
other suitable material. In one embodiment, the RIE stop layer 312
is SiN having a thickness of about 2 nm to 8 nm and is deposited by
ALD, PECVD, IBD, or sputtering method. Next, the bi-layer structure
306 is subjected to a photoresist stripper for dissolving the
release layer 308 and releasing the photoresist layer 310 from the
first mask layer 304. The photoresist stripper dissolves the
release layer 308 and photoresist layer 310 by entering into the
undercuts 307, 309. An exemplary photoresist stripper for the
release layer 308 and the photoresist layer 310 is N-methyl
pyrrolidone (NMP). As shown in FIG. 3D, after the removing of the
bi-layer structure 306, the RIE stop layer 312 covers portions of
the first mask layer 304, and the portions are called the field
area. The exposed portion of the first mask layer 304 not covered
by the RIE stop layer 312 is called the device area.
[0045] Next, as shown in FIG. 3E, a second mask layer 314 is
deposited on the exposed first hard mask layer 304 (device area)
and on the RIE stop layer 312 (field area). In one embodiment, the
second mask layer 314 is a polymer-like carbon (PLC), which is much
softer than DLC of the first mask layer 304, and has a thickness of
about 5 nm to about 10 nm over the first mask layer 304 and can be
deposited by either PECVD or IBD method. The second mask layer 314
serves as a release layer in the CMP process as discussed below in
detail. A third mask layer 316 is deposited over the second mask
layer 314, as shown in FIG. 3F. In one embodiment, the third mask
layer 316 is a material that has a low milling rate, such as C or
DLC and has a thickness of about 5 nm to about 10 nm. The third
mask layer 316 may be deposited by any suitable process, such as
IBD, PECVD or sputtering.
[0046] In FIG. 3G, a fourth mask layer 318 is deposited over the
third mask layer 316. The fourth mask layer 318 may be a dielectric
film or a thin metal layer. In one embodiment, the fourth mask
layer 318 is a dielectric hard mask layer. The dielectric hard mask
layer 318 may be constructed of a dielectric material and is
preferably constructed of a silicon-containing hard mask material
such as silicon oxide, silicon nitride, silicon oxynitride which
may be deposited using PECVD, IBD or sputtering method, or a
silicon-containing organic material such as SIHM.RTM. (Shin-Etsu
Chemical Co., Ltd.) or UVAS (Honeywell International Inc.) and etc,
which may be spin-coated on and cured at elevated temperature from
150 degrees Celsius to 250 degrees Celsius. In various approaches,
the thickness of the dielectric hard mask layer 318 may depend on
the total thickness of the first mask layer 304, the second mask
layer 314 and the third mask layer 316. Generally, the thicker the
total thickness of 304, 314 and 316, the thicker the dielectric
hard mask layer 318 will preferably be. The typical thickness of
the silicon containing dielectric hard mask layer 318 is about 5 nm
to about 30 nm.
[0047] In one embodiment, an optional bottom anti-reflective
coating (BARC) may be deposited over the dielectric hard mask layer
318. The determination of whether a BARC layer is desirable depends
on the requirements of the photolithograph and on the material used
for the dielectric hard mask layer 318. For example, if the
dielectric hard mask layer 318 is a material that acts as a BARC,
then no BARC layer is deposited. Such materials include silicon
oxynitride, SIHM.RTM. (Shin-Etsu Chemical Co., Ltd.), UVAS
(Honeywell International Inc.), and etc. In other cases, some form
of BARC is desirable to control photolithography parameters such as
reflective swing and photo CDs, and a BARC layer is deposited by
any suitable deposition method such as spin coating and then
baking. For simplicity, hereafter the dielectric hard mask layer
318 represents both the mask layer and the BARC layer if any.
[0048] Next in FIG. 3H, a photoresist layer 352 is deposited over
the dielectric hard mask layer 318. A photolithography process is
then performed to form a photoresist mask in which only a small
portion of the photoresist layer 352 remains on the dielectric hard
mask layer 318 in the device area, as shown in FIG. 3H, and the
remaining portion of the dielectric hard mask layer 318 is
exposed.
[0049] Next, a first RIE process is performed to remove portions of
the dielectric hard mask layer 318 that are not protected by the
photoresist mask 352, as shown in FIG. 3I. The RIE may use
fluorocarbon based gas chemistry mixed with other gases as etchants
to perform the etching. In one approach, this RIE may preferably be
performed in a fluorine containing plasma chemistry such as one
that contains CF.sub.4, CHF.sub.3, Ar, He, O.sub.2 and etc., a
combination thereof, or any other compound which would be apparent
to one skilled in the art upon reading the present description. It
is preferable that both CF.sub.4 and CHF.sub.3 gas flows are in the
range of 5 sccm to 50 sccm, the He gas flow is no more than 30
sccm, and the oxygen gas flow is between 1 sccm to 10 sccm.
According to an illustrative approach, the first RIE may
additionally include transferring the image of the photoresist mask
352 onto the under-lying dielectric hard mask layer 318 by removing
portions of the dielectric hard mask layer 318 that are not
protected by the photoresist mask 352, leaving a structure as shown
in FIG. 3I.
[0050] While any suitable tool known in the art may be used, one
plasma tool especially suitable for the RIE process to etch the
dielectric hard mask material and polymer mask under-layer is
Plasma-Therm's VERSALOCK.RTM. etcher, which is an inductively
coupled plasma (ICP) etch system in which the plasma is generated
by means of inductively coupling 2 MHz RF power (the source power)
while independently controlling the ion energy directed toward the
substrate via 13.56 MHz bias power. This separate power control
allows a wider range of RIE processes to be performed, ranging from
highly chemical processes to highly physical processes. The
VERSALOCK.RTM. etcher is equipped with an Optical Emission
Spectrometry (OES) endpoint system that allows precise control of
the over-etch amount via the determination of etch endpoint.
[0051] Many other ICP etchers equipped with both source and bias
power supplies, such as TCP9400DFM.RTM. from Lam Research Inc., or
DPS.RTM. from Applied Materials Inc., can also be used for RIE the
dielectric hard mask material and polymer mask under-layer. It is
expected that the RIE process presented herein can be used in
conjunction with many different ICP etchers.
[0052] In the first RIE process, to ensure all of the dielectric
hard mask 318 in the area not protected by the photoresist 352 is
completely removed, or the third mask layer 316 is completely
exposed in the area not protected by the photoresist mask 352, a
certain amount of over-etch is applied, the percentage of the over
etch time can be ranging from 20% to 60%. At the end of the first
RIE process, the pattern of the photoresist mask layer 352 is
transferred onto the dielectric hard mask layer 318, and part of
the photoresist mask 352 is consumed during the first RIE.
[0053] Referring to FIG. 3J, the image of the dielectric hard mask
318 may be transferred onto the layer disposed thereunder (i.e.,
layers 316, 314 and 304) using a second RIE which may have a
different material selectivity than the first RIE, to form a
stencil consisting of layers 318, 316, 314 and 304. In one
approach, the second RIE is an oxygen or carbon dioxide based RIE.
The preferable oxygen gas flow is about 5 sccm to 20 sccm, and the
carbon dioxide gas flow is about 15 sccm to 50 sccm. Since the
second RIE uses oxygen based plasma, the photoresist layer 352
remaining from the first RIE (and optional BARC layer if any) is
etched away completely during the second RIE. Since the dielectric
hard mask layer 318 has much slower etch rate (or high etch rate
selectivity), only a small portion of the dielectric hard mask 318
is consumed, thus the mask pattern of the dielectric hard mask
layer 318 is transferred to the third mask layer 316, the second
mask layer 314 and the first mask layer 304, the portion of these
three layers which are not protected by the dielectric hard mask
layer 318 are etched away in the device area, and the remaining
layers in the device area form a hard mask stencil 320. In
addition, since the cap layer 312 is a kind of dielectric layer and
also has high etch selectivity (i.e., it doesn't etch by oxygen
based plasma), the second RIE stops on the cap layer 312 in the
field area, thus the first mask layer 304 under the cap layer 312
is not etched, as shown in FIG. 3J. As a result of the two RIE
processes, the hard mask stencil 320 is formed in the device area,
as shown in FIG. 3J. Portions of the sensor layer 302 are exposed
while the remaining portions of the sensor layer 302 are covered by
the hard mask stencil 320 (in device area) and the first mask layer
304 (in field area). The resulting hard mask stencil 320 includes
four layers and has a height (thickness) between about 30 nm and
about 65 nm and a width between about 10 nm to about 30 nm. In one
embodiment, the hard mask stencil 320 has a height of about 45 nm.
The hard mask stencil 320 provides better wafer to wafer and within
wafer control on mill stencil CD uniformity and height by combining
both low RIE and low milling etch rate mask layers. The reduced
height of the hard mask stencil 320 helps with symmetric junction
shape formation and the narrow width of the hard mask stencil 320
helps with narrow track width read sensor fabrication.
[0054] To assist the liftoff process discussed below, a photoresist
mask layer 330 is fabricated. The field area which is protected by
the cap layer 312 is completely covered by the photoresist 330, and
the device area (including the stencil 320) is exposed and has no
photoresist over it at all, as shown in FIG. 3K. The thickness of
the photoresist 330 is about 150 nm to 300 nm. After the formation
of photoresist mask 330, an ion milling process with desired angle,
time, strength and operation mode is performed to remove portions
of the sensor layer 302 that are not protected by the hard mask
stencil 320 and the photoresist mask 330. As a result of the ions
milling through the sensor layer 302 and exposing the first
shielding layer 231, channels 332, 334 are formed in the sensor
layer 302, and a tapered reader sensor stack 205 is formed under
the stencil 320, as shown in FIG. 3L. During the ion milling, the
entire fourth mask layer 318 and a portion of the third mask layer
316 of the hard mask stencil 320 are consumed as a result of the
ion milling process, and portions of the photoresist mask 330 are
also removed in the ion mill. Thus the thickness of the photoresist
mask 330 is reduced but still sufficient enough for liftoff process
as discussed below. The remaining thickness of the photoresist mask
layer 330 is about 50 nm to about 200 nm.
[0055] After the formation of sensor stack 205, as shown in FIG.
3M, an insulation dielectric layer 338 is first deposited as an
insulation layer, followed by a magnetic hard bias (or soft
side-shield) material 340 deposition into the channels 332, 334 and
over the photoresist layer 330 and the top of the hard mask stencil
320. The insulation layer 338 and the hard bias (or soft
side-shield) material 340 also cover side walls of the stencil 320,
side walls of sensor 205 and side walls of photoresist mask 330.
The suitable materials for the insulation layer can be various
dielectric films such as silicon nitride, alumina, silicon oxide,
tantulum oxide, silicon carbride, with thickness from about 2 nm to
about 10 nm, and can be deposited by sputtering, PECVD or IBD
method. The hard bias (or soft side-shield) material 340 may be a
material that has a high magnetic moment such as CoFe or NiFe which
can be deposited by sputtering method.
[0056] Another optional layer 360 may be deposited over the hard
bias (or soft side-shield) material 340. The optional layer 360 may
be diamond-like carbon, and has a thickness of about 2 nm to about
10 nm. As shown in FIG. 3N, the photoresist mask 330 along with the
optional layer 360, the hard bias (or soft side-shield) material
340, and the insulation layer 338 covering the top and the side of
the photoresist mask 330 may be removed. The removal may be
achieved by first baking the structure at elevated temperature such
as about 90 degrees Celsius to about 180 degrees Celsius and then
cooling the structure rapidly, followed by one or more rounds of
hot NMP liftoff. During heating and cooling, cracks are formed on
the optional layer 360, the hard bias (or soft side-shield)
material 340 and insulation layer 338, thus allowing the hot NMP at
temperature from about 60 degrees Celsius to about 90 degrees
Celsius to reach the covered photoresist mask 330 to liftoff the
photoresist mask 330 and everything on the photoresist mask 330 in
the field area. After the liftoff, the RIE stop layer 312 and the
first mask layer 304 are remaining in the field area. The sensor
205, stencil 320, insulation layer 338, hard bias layer (or soft
side-shield) 340 and optional layer 360 are still remaining in the
device area.
[0057] Following the liftoff of photoresist mask 330, a CMP process
is performed. In the field area, the CMP process removes the RIE
stop layer 312 and stops on the first mask layer 304 since the
dielectric material of the RIE stop layer 312 can be polished much
faster than the DLC material of the first mask layer 304. In the
channels 332, 334, the CMP is only removing a small portion of the
optional layer 360 since the optional layer 360 is DLC material,
thus protects the hard bias (or soft side-shield) material 340. On
the stencil 320, since the second mask layer 314 is a polymer like
carbon which is much soft than the DLC material of the first mask
layer 304, when a CPM process is applied, the stencil breaks at the
interface between the second mask layer 314 and the first mask
layer 304. Anything on the stencil 320 above the first mask layer
304 is removed. As a result of this CMP process, the exposed
surface in the channels 332 and 334 of the device area comprises
the optional layer 360, the exposed surface of the stencil
comprises the first mask layer 304, and the exposed surface in the
field also comprises the first mask layer 304, as illustrated in
FIG. 3O. The above discussed removal process is achieved by a CMP
process and thus is called CMP assisted liftoff. The resulting
planar surface includes the first mask layer 304 (in both field
area and on the sensor) and the optional layer 360.
[0058] After the CMP assisted liftoff, the remaining DLC film of
the first mask layer 304 and the optional layer 360 are removed by
an oxygen based RIE process, exposing the cap layer of the sensor
structure 205 in device area, the hard bias (or soft side-shield)
layer 340 and the sensor layer 302 in the field area. The top
magnetic shield layer composed with NiFe is then deposited with
sputtering method or metal plating method, and more subsequent
processes are performed to fabricate a magnetic recording
sensor.
[0059] FIGS. 3A-3P illustrate one manner of making a sensor
structure utilizing a shallow and narrow hard mask stencil. FIGS.
4A-4M illustrate an alternative way of making the sensor structure
utilizing a different shallow and narrow hard mask stencil. As
shown in FIG. 4A, the sensor layer 302 is deposited over the first
shield layer 231. A cap layer 402 is deposited over the sensor
layer 302, and a first mask layer 404 is deposited over the cap
layer 402. In one embodiment, the cap layer 402 is iridium (Ir) and
has a thickness of about 2 nm to about 6 nm and can be deposited
using sputtering method. However, other suitable materials may also
be used, such as ruthenium (Ru) with similar thickness. The first
mask layer 404 may be a diamond-like carbon layer having a
thickness between about 10 nm and about 50 nm and can be deposited
using either PECVD or IBD process.
[0060] As shown in FIGS. 4B and 4C, a second mask layer 406 is
deposited over the first mask layer 404 and a third mask layer 408
is deposited over the second mask layer 406. In one embodiment, the
second mask layer 406 is a dielectric material such as silicon
oxide and has a thickness of about 5 nm to about 20 nm. However,
other suitable dielectric materials may also be used, such as
silicon, silicon nitride, silicon carbide, silicon oxynitride or
tantalum oxide. The dielectric material 406 can be deposited using
PECVD, IBD or sputtering method. The third mask layer 408 may be a
regular non-silicon based BARC layer or a silicon based BARC layer
such as SIHM.RTM. (Shin-Etsu Chemical Co., Ltd.), UVAS (Honeywell
International Inc.) and etc., with a thickness ranging from about
20 nm to 60 nm. A photoresist layer is coated and baked over the
third mask layer 408, a photolithography process is performed, and
a photoresist mask 409 is formed on the third mask layer 408,
exposing portions of the third mask layer, as shown in FIG. 4C.
[0061] Next in FIG. 4D, a first RIE process containing fluorocarbon
such as CF.sub.4/CHF.sub.3 mixed with other gases such as oxygen,
argon and helium is performed. Portions of the third mask layer 408
not protected by the photoresist mask 409 is etched away, and with
continuing of the RIE, a portion of the second mask layer 406 and a
portion of the first mask layer 404 not protected by the
photoresist mask 409 are also removed. Although the third mask
layer 408 and the second mask layer 406 are etched through in the
area not protected by the photoresist mask 409, the first mask
layer is not etched through. The RIE process stops on the first
mask layer 404, and the etch depth of the first mask layer 404
depends on the total over etch amount of the third and second mask
layers 408, 406. A portion of the photoresist mask 409 is consumed
in the first RIE and the thickness is reduced. As the result of the
first RIE, the remaining photoresist mask 409, the third mask 408,
the second mask layer 406, and a portion of the first mask layer
404 form a stack 411. A portion of the first mask layer 404 having
the entire width "W" and depth "D" is not affected by this first
RIE and is labeled with 410. Thus, the stack 411 sits on a mask
layer 410 that has a thickness less than the first mask layer 404.
In one embodiment, the thickness of the mask layer 410 is half of
the first mask layer 404. The remaining photoresist layer 409 may
or may not be removed by a wet strip process depending on the
needs.
[0062] A photoresist layer is then coated and baked, and a
photolithography is performed to form a photoresist assisted CMP
(PAC) photoresist mask 412 on the first mask layer 410, as shown in
FIG. 4E. The photoresist mask 412 covers only the field area,
leaving the stack 411 and surrounding area (i.e., channel areas
formed in the ion mill as discussed later) exposed. The channel
areas (i.e., the portions of the mask layer 410 neither protected
by the photoresist layer 412 nor the stack 411) is removed by a
second RIE process based on the oxygen plasma chemistry, exposing
the cap layer 402 in the channel areas. Since the PAC photoresist
mask 412 is applied with enough thickness that there is sufficient
remaining PAC photoresist mask 412 leftover in the field area. The
remaining photoresist mask 409 is completely removed in the second
RIE process, and the second RIE is stopped on the third mask layer
408 if the third mask layer 408 is a silicon based BARC material
such as SIHM.RTM. (Shin-Etsu Chemical Co., Ltd.), UVAS (Honeywell
International Inc.), which has high etch selectivity so only a
small amount of the top portion is etched away. If the third mask
layer 408 is a regular non-silicon based BARC layer, the third mask
layer 408 is completely removed in the second RIE process, and
since the second mask layer 406 is a dielectric based mask layer,
the second RIE will not etch the second mask layer 406, protecting
the underneath mask layer 404 from being etched. A hard mask
stencil 420, consisting of the third mask layer 408, the second
mask layer 406 and the first mask layer 404, is formed, as shown in
FIG. 4F. The hard mask stencil 420 has a width between about 10 nm
and about 30 nm and a height between about 20 nm and about 60 nm.
In one embodiment, the hard mask stencil 420 has a height of about
40 nm.
[0063] To form the sensor structure, an ion milling is performed to
remove portions of the cap layer 402 and the sensor layer 302 not
protected by the photoresist layer 412 and the hard mask stencil
420. Channels 432 and 434 in the sensor layer 302 are formed and
portions of the first shield layer 231 are exposed, as shown in
FIG. 4G. In addition, the third mask layer 408, the second mask
layer 406, and a portion of the first mask layer 404 of the hard
mask stencil 420 are also consumed as a result of the ion milling
process. Thus, disposed above the sensor structure 205 is a mask
layer 436, which is the remaining portion of the first mask layer
404 and the cap layer 402. Portion of the photoresist mask layer
412 is also consumed but there is still enough thickness left over
for the later liftoff process.
[0064] Next, an insulation layer 414 such as silicon nitride,
alumina, or silicon oxide, or silicon carbide is deposited with a
thickness from 2 nm to 10 nm, covering the top and side walls of
the PAC photoresist mask 412, the top and side walls of the mask
layer 436, the side walls of the sensor 205, and the exposed
channel areas 432 and 434. The insulation layer 414 can be
deposited using IBD or PECVD method. Then a side-shield layer (or a
hard bias layer) 440 is deposited on the insulation layer 414, as
shown in FIG. 4H. The side-shield or hard bias layer 440 may be a
NiFe which can be deposited by sputtering method or a hard bias
material that has a high magnetic moment such as CoFe.
[0065] A liftoff process using hot NMP is performed to remove the
PAC photoresist layer 412 and portions of the bias layer 440
covering the top and the sides of the PAC photoresist layer 412,
exposing the first mask layer 410 in the field area, as shown in
FIG. 4I. The removal process leaves an uneven surface of the bias
layer 440, as shown in FIG. 4I. The uneven surface of the bias
material 440 is then planarized by a CMP process. The resulting
bias layer 440 is planar and has a surface 450 that is below the
mask layers 410, 436, as shown in FIG. 4J. The mask layers 410,
436, which are carbon based films, are subsequently removed by an
oxygen based RIE process, exposing the cap layer 402. As shown in
FIG. 4K, since the side-shield or hard bias layer 440 is not etched
by the oxygen based plasma, the side-shield or the bias layer 440
now extends above the cap layer 402. The portions of the
side-shield or the hard bias layer 440 extending above the cap
layer 402 are then removed by another CMP process, and the cap
layer 402 serves as the CMP stop layer so that only the side-shield
(the hard bias) layer 440 is removed. This second CMP process is
controlled in such way that the remaining bias layer 440 and the
cap layer 402 are planar, as shown in FIG. 4L. Lastly, the cap
layer 402 and a top portion of the side-shield (or hard bias) 440
which had been oxidized in the oxygen plasma are removed by an ion
milling process, exposing the sensor structure 205 and the sensor
layer 302, as shown in FIG. 4M. The method of forming a sensor
structure utilizing a hard mask stencil, as illustrated by FIGS.
4A-4M, does not including utilizing a release layer. Instead, the
method includes a two-step CMP process.
[0066] In summary, a shallow and narrow hard mask stencil is
utilized to form a sensor structure. In one embodiment, the hard
mask stencil includes four distinct layers. In another embodiment,
the hard mask stencil includes three layers of different materials
and utilizes a two-step CMP process in the forming of the sensor
structure.
[0067] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *