U.S. patent application number 12/954437 was filed with the patent office on 2012-05-24 for method for manufacturing a narrow magnetic read width current perpendicular to plane magnetoresistive sensor.
This patent application is currently assigned to Hitachi Global Storage Technologies Netherlands B. V.. Invention is credited to Ki S. Chung, Vincent Gemena, Quang Le, Eileen Yan.
Application Number | 20120125884 12/954437 |
Document ID | / |
Family ID | 46063346 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120125884 |
Kind Code |
A1 |
Chung; Ki S. ; et
al. |
May 24, 2012 |
METHOD FOR MANUFACTURING A NARROW MAGNETIC READ WIDTH CURRENT
PERPENDICULAR TO PLANE MAGNETORESISTIVE SENSOR
Abstract
A method for manufacturing a magnetic read head having a very
narrow track width. The method includes the use of a non-Si
containing photoresist to form a mask prior to ion milling to
define the track-width of the sensor. Previously only Si-containing
resists were used. The Si in the resist turned to an oxide, which
allowed the photoresist to withstand the reactive ion etching used
for image transfer to an underlying hard mask. The Si-containing
resist, however, has limitations as to how small the mask can be
made. It has been found that a non-Si-containing resist provides
better resolution at very narrow track-width definition, and also
provides good temperature resistance. Some modifications to the
process allow the non-Si-containing resist to be used in the
construction of the magnetic read sensor.
Inventors: |
Chung; Ki S.; (Sunnyvale,
CA) ; Gemena; Vincent; (San Jose, CA) ; Le;
Quang; (San Jose, CA) ; Yan; Eileen; (San
Jose, CA) |
Assignee: |
Hitachi Global Storage Technologies
Netherlands B. V.
Amsterdam
NL
|
Family ID: |
46063346 |
Appl. No.: |
12/954437 |
Filed: |
November 24, 2010 |
Current U.S.
Class: |
216/22 |
Current CPC
Class: |
B82Y 25/00 20130101;
G11B 2005/3996 20130101; B82Y 10/00 20130101; G11B 5/3909
20130101 |
Class at
Publication: |
216/22 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Claims
1. A method for manufacturing a magnetoresistive read sensor,
comprising: depositing a plurality of sensor layers; depositing a
non-Si-containing photoresist over the plurality of sensor layers;
patterning the non-Si-containing photoresist to define a sensor
width; and performing an ion milling to remove a portion of the
plurality of sensor layers that are not protected by the
photoresist, thereby forming a magnetoresistive sensor.
2. The method as in claim 1 further comprising, after depositing
the plurality of sensor layers and before depositing the
non-Si-containing photoresist, depositing a layer of material that
is resistant to chemical mechanical polishing.
3. The method as in claim 2 wherein the material that is resistant
to chemical mechanical polishing comprises Ru, Rh, Ir or diamond
like carbon.
4. The method as in claim 1 further comprising, after performing
the ion milling: depositing a non-magnetic, electrically insulating
layer; depositing a hard magnetic layer; and performing an ion
milling at a glancing angle; and lifting off the photoresist
mask.
5. The method as in claim 3 wherein the glancing ion milling is
performed at an angle of 0-30 degrees relative to the planes of the
as deposited sensor layers.
6. The method as in claim 2 further comprising, after performing
the ion milling: depositing a layer of non-magnetic, electrically
insulating material; depositing a magnetic material over the
non-magnetic, electrically insulating material; depositing a second
layer of material that is resistant to chemical mechanical
polishing; depositing a material that is resistant to ion milling;
performing a glancing ion milling; and performing a chemical
mechanical polishing.
7. A method for manufacturing a magnetoresistive read sensor,
comprising: depositing a plurality of sensor layers; depositing a
release layer; depositing a non-Si-containing photoresist over the
plurality of sensor layers; patterning the non-Si-containing
photoresist to define a sensor width; performing a reactive ion
etching to transfer the image of the photoresist onto the release
layer; and performing an ion milling to remove a portion of the
plurality of sensor layers that are not protected by the
photoresist, thereby forming a magnetoresistive sensor.
8. The method as in claim 7 wherein the ion milling is performed in
an atomstphere that includes CO.sub.2 and an inert gas that is
chosen to slow the reactive ion etching process.
9. The method as in claim 7 wherein the release layer is a material
that can also function as a Bottom Anti-Reflective Coating
(BARC).
10. The method as in claim 7 wherein the release layer is a soluble
polyimide.
11. The method as in claim 7, further comprising: after depositing
the sensor layers and before depositing the release layer,
depositing first layer of material that is resistant to chemical
mechanical polishing; and after performing the ion milling:
depositing a layer of non-magnetic, electrically insulating
material; depositing a magnetic material over the layer of
non-magnetic, electrically insulating material; depositing a second
lager of material that is resistant to chemical mechanical
polishing; depositing a layer of material that is resistant to ion
milling over the second layer of material that is resistant to
chemical mechanical polishing; performing a glancing ion milling;
and performing a chemical mechanical polishing.
12. The method as in claim 11 wherein the first and second
materials that are resistant to chemical mechanical polishing each
comprise Ru, Rh, Ir, or diamond like carbon, and the material that
is resistant to ion milling comprises Ta or Al.sub.2O.sub.3
Si.sub.3N.sub.4, SiO.sub.2, Ta.sub.2O.sub.5 or DLC.
13. The method as in claim 6 wherein the first and second materials
that are resistant to chemical mechanical polishing each comprise
Ru, Rh, Ir, or diamond like carbon, and the material that is
resistant to ion milling comprises Ta or Al.sub.2O.sub.3
Si.sub.3N.sub.4, SiO.sub.2, Ta.sub.2O.sub.5 or DLC.
14. The method as in claim 11 wherein the glancing ion milling is
performed at an angle of 0-30 degrees relative to the plane of the
as deposited sensor layers.
15. A method for manufacturing a magnetoresistive read sensor,
comprising: depositing a plurality of sensor layers; depositing a
release layer; depositing a Bottom Anti-Reflective Coating (BARC);
depositing a non-Si-containing photoresist over the plurality of
sensor layers; patterning the non-Si-containing photoresist to
define a sensor width; performing a reactive ion etching to
transfer the image of the photoresist onto the release layer; and
performing an ion milling to remove a portion of the plurality of
sensor layers that are not protected by the photoresist, thereby
forming a magnetoresistive sensor.
16. The method as in claim 15 wherein the BARC is a
carbon-containing BARC.
17. The method as in claim 15 wherein the BARC is a Si-containing
BARC.
18. The method as in claim 15 wherein the reactive ion etching is
performed in an atmosphere containing CO.sub.2 and a noble gas, the
noble gas being added in a concentration to slow the reactive ion
etching to protect the non-Si-containing photoresist.
19. The method as in claim 15, further comprising: after depositing
the sensor layers and before depositing the release layer,
depositing first layer of material that is resistant to chemical
mechanical polishing; and after performing the ion milling:
depositing a layer of non-magnetic, electrically insulating
material; depositing a magnetic material over the layer of
non-magnetic, electrically insulating material; depositing a second
layer of material that is resistant to chemical mechanical
polishing; depositing a layer of material that is resistant to ion
milling over the second layer of material that is resistant to
chemical mechanical polishing; performing a glancing ion milling;
and performing a chemical mechanical polishing.
20. The method as in claim 19 wherein the first and second layers
of material that are resistant to chemical mechanical polishing
each comprise Ru, Rh, Ir or diamond like carbon, and the layer of
material that is resistant to ion milling Ta or Al.sub.2O.sub.3,
Si.sub.3N.sub.4, SiO.sub.2, Ta.sub.2O.sub.5 or DLC.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to magnetoresistive sensors
and more particularly to a sensor manufactured by a process that
allows the sensor to be formed with a very small magnetic read
width.
BACKGROUND OF THE INVENTION
[0002] The heart of a computer is an assembly that is referred to
as a magnetic disk drive. The magnetic disk drive includes a
rotating magnetic disk, write and read heads that are suspended by
a suspension arm adjacent to a surface of the rotating magnetic
disk and an actuator that swings the suspension arm to place the
read and write heads over selected circular tracks on the rotating
disk. The read and write heads are directly located on a slider
that has an air bearing surface (ABS). The suspension arm biases
the slider into contact with the surface of the disk when the disk
is not rotating, but when the disk rotates air is swirled by 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 impressions 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.
[0003] The write head includes at least a coil, a write pole and
one or more return poles. When a current flows through the coil, a
resulting magnetic field causes a magnetic flux to flow through the
write pole, which results in a magnetic write field emitting from
the tip of the write pole. This magnetic field is sufficiently
strong that it locally magnetizes a portion of the adjacent
magnetic disk, thereby recording a bit of data. The write field,
then, travels through a magnetically soft under-layer of the
magnetic medium to return to the return pole of the write head.
[0004] A magnetoresistive sensor such as a Giant Magnetoresistive
(GMR) sensor, or a Tunnel Junction Magnetoresisive (TMR) sensor can
be employed to read a magnetic signal from the magnetic media. The
sensor includes a nonmagnetic conductive layer (if the sensor is a
GMR sensor) or a thin nonmagnetic, electrically insulating barrier
layer (if the sensor is a TMR sensor) sandwiched between first and
second ferromagnetic layers, hereinafter referred to as a pinned
layer and a free layer. Magnetic shields are positioned above and
below the sensor stack and can also serve as first and second
electrical leads so that the electrical current travels
perpendicularly to the plane of the free layer, spacer layer and
pinned layer (current perpendicular to the plane (CPP) mode of
operation). The magnetization direction of the pinned layer is
pinned perpendicular to the air bearing surface (ABS) and the
magnetization direction of the free layer is located parallel to
the ABS, but free to rotate in response to external magnetic
fields. The magnetization of the pinned layer is typically pinned
by exchange coupling with an antiferromagnetic layer.
[0005] When the magnetizations of the pinned and free layers are
parallel with respect to one another, scattering of the conduction
electrons is minimized and when the magnetizations of the pinned
and free layer are antiparallel, scattering is maximized. In a read
mode the resistance of the spin valve sensor changes about linearly
with the magnitudes of the magnetic fields from the rotating disk.
When a sense current is conducted through the spin valve sensor,
resistance changes cause potential changes that are detected and
processed as playback signals.
[0006] In the push to increase data density sensors have been
required to be formed with ever narrower read widths. The read
width can be determined by the width of the layers such as the
electrically conductive spacer or barrier layer sandwiched between
the pinned and free layers. However, certain manufacturing
limitations have prevented further narrowing of the read width.
Therefore, there remains a need for a method for reducing the read
width of a magnetoresistive sensor in order to further increase
track density and data density.
SUMMARY OF THE INVENTION
[0007] The present invention provides a method for manufacturing a
magnetic read head having a very narrow track width. The method
includes depositing a plurality of sensor layers, depositing a
non-Si-containing photoresist, patterning the photoresist and
performing an ion milling to define a magnetic read head.
[0008] The use of the non-Si-containing photoresist advantageously
allows the sensor to be formed with a narrow track width than would
be possible with a Si-containing photoresist as was previously used
in the construction of magnetic read heads. This is because the
non-Si-containing photoresit has better resolution and improved
depth of focus as compared with the previously used Si-containing
photoresist. The non-Si containing photoresist also provides
tolerance of high temperatures such as those needed for atomic
layer deposition and chemical vapor deposition.
[0009] Certain manufacturing process changes that make possible the
use of a non-Si-containing resist include the use of a Si
containing Bottom Anti-Reflective Coating beneath the
non-Si-containing photoresist to improve RIE selectivity during the
image transfer process. In addition, adding a noble gas to the CO,
chemistry of the reactive ion etching (during image transfer) helps
to avoid early consumption of the non-Si-containing photoresist. A
glancing ion milling assisted CMP liftoff process can also be
useful in removing the remaining mask layers at very small sensor
widths, which may not be possible using CMP alone.
[0010] These and other features and advantages of the invention
will be apparent upon reading of the following detailed description
of preferred embodiments taken in conjunction with the Figures in
which like reference numerals indicate like elements
throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a fuller understanding of the nature and advantages of
this invention, as well as the preferred mode of use, reference
should be made to the following detailed description read in
conjunction with the accompanying drawings which are not to
scale.
[0012] FIG. 1 is a schematic illustration of a disk drive system in
which the invention might be embodied;
[0013] FIG. 2 is an ABS view of a slider illustrating the location
of a magnetic head thereon;
[0014] FIGS. 3 is an ABS view of an example of a magnetoresistive
sensor that might be constructed by a method of the present
invention;
[0015] FIGS. 4-12 are ABS views of a magnetoresistive sensor in
various intermediate stages of manufacture illustrating a method of
manufacturing a magnetoresistive sensor using a single layer
mask;
[0016] FIGS. 13-20 are ABS views of a magnetoresistive sensor in
various intermediate stages of manufacture illustrating a method of
manufacturing a magnetoresistive sensor using a double layer mask;
and
[0017] FIGS. 21-28 are ABS views of a magnetoresistive sensor in
various intermediate stages of manufacture illustrating a method of
manufacturing a magnetoresistive sensor using a tri-layer mask.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The following description is of the best embodiments
presently contemplated for carrying out this invention. This
description is made for the purpose of illustrating the general
principles of this invention and is not meant to limit the
inventive concepts claimed herein.
[0019] Referring now to FIG. 1, there is shown a disk drive 100
embodying this invention. As shown in FIG. 1, at least one
rotatable magnetic disk 112 is supported on a spindle 114 and
rotated by a disk drive motor 118. The magnetic recording on each
disk is in the form of annular patterns of concentric data tracks
(not shown) on the magnetic disk 112.
[0020] At least one slider 113 is positioned near the magnetic disk
112, each slider 113 supporting one or more magnetic head
assemblies 121. As the magnetic disk rotates, slider 113 moves
radially in and out over the disk surface 122 so that the magnetic
head assembly 121 may access different tracks of the magnetic disk
where desired data are written. Each slider 113 is attached to an
actuator arm 119 by way of a suspension 115. The suspension 115
provides a slight spring force which biases slider 113 against the
disk surface 122. Each actuator arm 119 is attached to an actuator
means 127. The actuator means 127 as shown in FIG. 1 may be a voice
coil motor (VCM). The VCM comprises a coil movable within a fixed
magnetic field, the direction and speed of the coil movements being
controlled by the motor current signals supplied by controller
129.
[0021] During operation of the disk storage system, the rotation of
the magnetic disk 112 generates an air bearing between the slider
113 and the disk surface 122 which exerts an upward force or lift
on the slider. The air bearing thus counter-balances the slight
spring force of suspension 115 and supports slider 113 off and
slightly above the disk surface by a small, substantially constant
spacing during normal operation.
[0022] The various components of the disk storage system are
controlled in operation by control signals generated by control
unit 129, such as access control signals and internal clock
signals. Typically, the control unit 129 comprises logic control
circuits, storage means and a microprocessor. The control unit 129
generates control signals to control various system operations such
as drive motor control signals on line 123 and head position and
seek control signals on line 128. The control signals on line 128
provide the desired current profiles to optimally move and position
slider 113 to the desired data track on disk 112. Write and read
signals are communicated to and from write and read heads 121 by
way of recording channel 125.
[0023] With reference to FIG. 2, the orientation of the magnetic
head 121 in a slider 113 can be seen in more detail. FIG. 2 is an
ABS view of the slider 113, and as can be seen the magnetic head
including an inductive write head and a read sensor, is located at
a trailing edge of the slider. The above description of a typical
magnetic disk storage system and the accompanying illustration of
FIG. 1 are for representation purposes only. It should be apparent
that disk storage systems may contain a large number of disks and
actuators, and each actuator may support a number of sliders.
[0024] FIG. 3 shows an example of a magnetoresistive sensor
structure 300 that could be constructed according to a method of
the present invention. The sensor structure 300 is seen as viewed
from the air bearing surface (ABS). The sensor 300 includes a
sensor stack 302 that is sandwiched between first and second,
electrically conductive, magnetic shields 304, 306 that also
function as electrically conductive leads.
[0025] The sensor stack 302 can include a non-magnetic layer 308
that is sandwiched between a magnetic pinned layer structure 310
and a magnetic free layer structure 312. The non-magnetic layer 308
can be an electrically conductive material, if the sensor 300 is a
Giant Magnetoresistive (GM R) sensor, and can be a thin
electrically insulating material layer if the sensor structure 300
is a Tunnel Junction Sensor (TMR).
[0026] The pinned layer structure 310 can include first and second
magnetic layers 314, 316 with a non-magnetic, antiparallel coupling
layer such as Ru 318 sandwiched between the first and second
magnetic layer 314, 318. The first magnetic layer 314 has its
magnetization pinned in a first direction perpendicular to the ABS.
This pinning is a result of exchange coupling with a layer of
antiferromagnetic material 320 such as IrMn. The second magnetic
layer 316 has its magnetization pinned in a second direction that
is antiparallel with the first direction as a result of
antiparallel coupling between the first and second magnetic layers
314, 316 across the antiparallel coupling layer 318.
[0027] The magnetic free layer 312 has a magnetization that is
biased in a direction that is generally parallel with the ABS, but
that is free to move in response to a magnetic field. The biasing
of the free layer is provided by a magnetostatic coupling with
first and second hard magnetic bias layers 322, 324. One or more
seed layers 326 may be provided at the bottom of the sensor stack
302 in order to ensure a desired grain growth of the other layers
of the sensor stack 302 deposited thereon. In addition a capping
layer such as Ta 328 may be provided at the top of the sensor stack
to protect the underlying layers during manufacture. In addition,
thin insulation layers 330 is provided at either side of the sensor
stack 302 and across at least the bottom lead/shield 304 in order
to prevent sense current from being shunted through the magnetic
bias layers 322, 324. The sensor structure 300 has a read width 322
that is determined by the width of the layers of the sensor stack
302, and especially by the width of the layers at the location of
the spacer layer 308. This read width 332 can be advantageously
made very small by a novel manufacturing process that will be
described herein below. It should be pointed out that the sensor
structure 300 is by way of example as various other forms of sensor
structure could also be manufactured by the method of the present
invention and would fall within the scope of the invention as
well.
[0028] A basic requirement to achieve higher areal density is to
reduce the physical magnetic read width 332 of the sensor 300. One
method that has been used to define the read width of sensors is to
use reactive ion etching (RIE) to image transfer a photo resist
mask into an ion mill hard mask and then use the ion mill to
pattern the hard mask image into the sensor. The success of this
method requires that the photoresist mask height is sufficient to
be image transferred into the ion mill hardmask. At widths of 40 nm
or greater, the current lithographic approach is to use a
silicon-containing photoresist to serve as an effective imaging
layer to pattern a hardmask that consists of a material such as
DURIMIDE.RTM. and carbon. A major advantage of silicon containing
imaging resists is RIE selectivity. In the presence of O.sub.2 or
CO.sub.2 RIE chemistries, the Si component of the imaging
photoresist will oxidize to form SiO.sub.2. In this form, the
imaging photoresist will be resistant to further etching and,
therefore, will effectively allow the patterning of the hard mask
and subsequently the patterning of the sensor. After patterning of
the sensor, ALD alumina deposition is done followed by hard
bias.
[0029] There is, however, a drawback to the above process for use
in defining sensors having very small read widths. At magnetic read
widths smaller than 40 nm, major challenges with the
silicon-containing resist result in an inability to further reduce
the read width. This is mostly due to the photoresist reaching its
resolution limit and to poor depth of focus properties of the
Si-containing photoresist, which results in more line-edge
roughness and not enough imaging photoresist to successfully image
transfer the photoresist pattern into the hard mask.
[0030] FIGS. 4-12, illustrate a method for manufacturing a
magnetoresistive sensor, according to a first embodiment of the
invention which overcomes the limitations of the above described
process. With reference to FIG. 4, a first magnetic shield/lead 402
is formed of an electrically conductive, magnetic material such as
NiFe. A series of sensor layers 404 is deposited over the first
shield/lead 402. These sensor layers 404 can correspond with the
layers of the sensor stack 302 described above, but could include
additional or other layers as well. A layer of material that is
resistant to chemical mechanical polishing (CMP stop layer) 406 is
deposited over the sensor layers 404. This layer 406 is, however,
optional. The CMP stop layer 406 can be an electrically conductive
material such as Ru, Rh, Ir or diamond like carbon (DLC).
[0031] A layer of photoresist 408 is then deposited over the mask
406. This photoresist layer 408 is a non-Si containing photoresist,
such as JSR 1891 which is available from JSR MICRO, INC.RTM.. Such
a non-Si containing photoresists achieves higher resolution than
previously used Si containing resists. In addition, such non-Si
containing photoresists have a higher heat resistance, which is
necessary to withstand chemical vapor deposition (CVD) and/or
atomic layer deposition (ALD) processes such as will be used in the
construction of the read sensor structure as will be described
herein below. Such non-Si containing photoresists also achieve
better depth of focus than Si-containing photoresists. Such a
non-Si-containing photoresist also has a better dissolution rate
than previously used photoresist, has similar reactive ion etching
selectivity to optional DLC and BARC materials (described below)
and, perhaps most importantly, is soluble in NMP solution, which
will further assist in liftoff at smaller read widths.
[0032] With reference now to FIG. 5, the photoresist layer 408 is
photolithographically patterned and developed to form a photoresist
mask having a width that defines a read width of a yet to be formed
sensor. The photoresist layer 408 is made as thin as possible to
maximize photolithographic resolution, while still being
sufficiently thick to withstand an ion milling process (described
below) for forming the sensor width. After the photoresist 408 has
been patterned as shown, a quick reactive ion etching can be
performed to transfer the image of the photoresist mask onto the
underlying CMP stop layer 406, if DLC material is used for the CMP
stop layer 406. Moreover, with or without DLC, a reactive ion
etching (RIE) using O.sub.2 or CO.sub.2 with noble gaseous such as
N.sub.2, He, Ar, Xe, etc., for example, can be used to further
reduce the photoresist mask's trackwidth (RIE slimming). A CO.sub.2
or CO.sub.2 with the noble gas is most preferred for RIE
slimming.
[0033] With reference now to FIG. 6, an ion milling is performed to
remove portions of the sensor material 404 that are not protected
by the photoresist mask layer 408 and the optional CMP stop layer
406 to form a sensor 404 with a desired read width. Then, with
reference to FIG. 7, a thin layer of non-magnetic, electrically
insulating material such as alumina 702 is deposited. This
insulation layer 702 is preferably deposited by a conformal
deposition process such as chemical vapor deposition (CVD) or
atomic layer deposition (ALD). A hard magnetic material 704 is then
deposited over the insulation layer 702. The hard magnetic material
704 provides the hard bias layers 322, 324 described above with
reference to FIG. 3, and the insulation layer 702 corresponds with
the insulation layers 330 of FIG. 3. Therefore, the insulation
layer 702 is preferably deposited thick enough to provide robust,
reliable electrical insulation between the hard magnetic material
704 and the bottom shield 402 and sensor layers 404, while also
being sufficiently thin to maximize magnetostatic coupling between
the hard magnetic material 704 and the sensor layers 404 for
improved free layer biasing.
[0034] It can be seen in FIG. 7, that after ion milling to form the
sensor 404 and after depositing the layers 702, 704, a certain
amount of the mask material 408 remains. In order to complete the
formation of the sensor, the remaining mask layer 408 must be
removed. It can also be seen the layers 702, 704 extend over the
sensor 404, CMP stop layer 406 and remaining mask layer 408.
[0035] The mask layers 408 can be removed by a chemical liftoff
process such as by coating with a hot NMP solution (N-Methyl
Pyrrolidone) followed by snow cleaning (high pressure CO, spray) to
remove resist and fences. However, in order for such a liftoff
process to work, the NMP solution must be able to reach the mask
408. This means that a certain amount of the layers 702, 704 must
be removed or exposed to allow the NMP solution to access the mask
408.
[0036] A wrinkle bake step can be used to form cracks where NMP can
reach the mask to remove a greater portion of materials of the mask
layers 408 in the field and grid areas. Liftoff is further enhanced
by the use of the non-Si-containing resist, which is soluble in
NMP. Due to re-deposition that formed during ion milling, in the
track area it can be difficult to remove the mask layers at small
dimensions. A chemical mechanical polishing process can be used to
remove the portion of the layers 704, 702 that extend over the mask
408. This would require either inserting a CMP stop layer such as
Ta with Rh, Ru or Ir during the hard magnetic material deposition
or separately such as DLC. While CMP assisted lift-off is a
preferred method at wider read width dimensions, at very narrow
dimensions an ion milling assisted lift-off (UM) can also be used
in conjunction with CMP to remove the layers 704, 702 that extend
over the mask 408.
[0037] In this case an ion milling process in conjunction with CMP
can be used to provide access to the mask 408 for the chemical
liftoff. If ion milling is used, a bi-layer consisting of a CMP
stop layer 706 and an ion milling resistant layer 708 is deposited
on the top layer of the hard magnetic material 704. The ion milling
resistant layer 708 protects the CMP stop layer 706 on the flat
portion of the hard bias layer 704 during ion milling assisted
lift-off. The ion milling resistant layer 708 is later removed
during CMP. The CMP's slurry will remove the ion milling resistant
layer. Materials suitable for use as a CMP stop layer 406 are Rh,
Ir, and Ru. Examples of suitable materials for an ion milling
resistant layer 708 include Ta, Al.sub.2O.sub.3, Si.sub.3N.sub.4,
SiO.sub.2, Ta.sub.2O.sub.5 or DLC.
[0038] With reference to FIG. 8, an ion milling is performed at a
glazing angle as indicated by arrows 802. The glazing angle ion
milling is an ion milling that is performed at an angle that is
perpendicular with or nearly perpendicular with normal, or in other
words is parallel or nearly parallel with the plane of the as
deposited layers such as layers 402, 404, 406, 408, 702 and 704. To
this end, the ion milling can be performed at an angle of 0 to 30
degrees relative to horizontal (i.e. relative to the planes of the
as deposited layers as much as possible without damage to the
substrate fixture). This glazing angle ion milling preferentially
removes vertically aligned portions of the layer 704, thereby
removing the material 704 from the sides of the mask 408 while
leaving the desired hard bias layers 704 at the sides of the sensor
as shown in FIG. 8. The ion mill resistant layer 708 protects both
the hard bias 704 and CMP stop layer 706 during the ion milling.
After ion milling, the ion mill resistant material 708 is removed
by CMP. The CMP stop layer 706 protects the hard bias layer 704
during CMP.
[0039] A NMP solution 901 may then be applied as shown in FIG. 9 to
assist removal of the 408. This leaves a structure as shown in FIG.
10. Then, a chemical mechanical polishing process can be performed,
leaving a structure as shown in FIG. 11. In addition to removing
the ion milling resistant layer 708, the CMP also removes the
fences 1002 (as shown in FIG. 10) that may form when portions of
the alumina layer 702 extend upward after ion milling. Because the
chemical mechanical polishing (CMP) can remove the alumina layer
702, there is a choice as to whether the previous ion milling can
be used to remove the alumina 702 above the plane of the sensor
404. The ion milling can either be terminated when the alumina has
been reached (as in FIG. 8) or can be continued until this portion
of the alumina layer 702 has been removed. A reactive ion etching
(RIE) can then be performed to remove the remaining CMP stop
material 406, 706. The RIE is performed in a chemistry that is
chosen to preferentially remove the material that was chosen as the
CMP stop layers 406, 706. This leaves a structure as shown in FIG.
11, with the sensor layers 404 exposed and no fences. Then, with
reference to FIG. 12, an electrically conductive, magnetic material
such as NiFe 1202 is deposited to form a second electrically
conductive, magnetic shield/lead 1202.
[0040] The above description illustrates a method for manufacturing
a narrow read-width magnetoresistive sensor using a single layer
mask of non-silicon containing resist. A mask with an optional
Bottom Anti-Reflective Coating (BARC) formed over a CMP stop layer
can also be constructed as will be described herein below.
[0041] With reference now to FIGS. 13 through 20, a method is
described for using a bi-layer mask structure to construct a
magnetoresistive sensor having a further reduced read-width. With
particular reference to FIG. 13, a first or lower magnetic,
electrically conductive shield/lead 402 is formed, and a plurality
of sensor layers 404 are deposited over the shield/lead 402 as
described earlier. Also as described earlier, a CMP stop layer 406
is deposited over the sensor layers 404, and as before, the CMP
stop layer 406 can be constructed of a material such as Ru, Rh, It
or Diamond Like Carbon (DLC). A bi-layer mask 1302 is deposited
over the CMP stop layer 406. The bi-layer mask includes a first
layer 1304 which serves as a release layer, an ion milling mask
layer, and which may also be a material that can function as a
bottom-antireflective coating (BARC) layer. The layer 1304 may also
function as an image transfer layer as will be seen. The layer 1304
can be a soluble polyimide material such as DURAMIDE.RTM. or a
soluble spin-on carbon material such as SIUL.RTM. from SHIN ETSU. A
layer of non-silicon-containing photoresist 1306 is then deposited
over the first layer 1304.
[0042] Then, the photoresist layer is photolithographically
patterned to form a read width defining mask as shown in FIG. 14.
Because the layer 1304 acts as an image transfer layer to withstand
the future ion milling that will be used to construct the sensor,
the photoresist layer 1306 can be made thinner than with the
previously discussed method. This reduced photoresist thickness
means that the photoresist layer can be patterned with greater
resolution than with the previously described method, allowing
further reduction of read-width. The presence of a bottom
antireflective coating (BARC) further improves photolithographic
resolution, allowing even further reduced read width. As with the
previously described method, the use of a non-silicon containing
photoresist provides improved resolution at narrow read width and
improved temperature resistance.
[0043] With reference now to FIG. 15, a reactive ion etching (RIE)
is performed to remove portions of the layer 1304 that are not
protected by the photoresist mask 1306 in order to transfer the
image of the photoresist layer 1306 onto the underlying layer 1304.
The RIE may also be used to further transfer the image of the
photoresist mask onto the underlying CMP stop layer 406. Moreover,
the RIE can be used to further reduce the read width (RIE slimming)
using, as mention previously, O.sub.2, CO.sub.2 or CO.sub.2 with
noble gases as mention above. The addition of the noble gas to the
CO, can be used to slow the rate of the reactive ion etching. This
is useful when patterning with a non-Si-containing resist, which
has less resistance to reactive ion milling. In prior art processes
that used Si-containing resist, the Si formed an oxide which
provided robustness against reactive ion etching. Since the present
invention uses a non-Si-containing resist, 1302, the slowing of the
etching by the addition of a noble gas helps to ensure that the
resist mask 1306 will be sufficiently able to withstand the RIE to
allow the mask and sensor to be patterned. Moreover, because the
photoresist 1306 is a non-Si-containing photoresist, the etch
selectivity is similar to 1304 and 406 which enables uniformity
slimming of the stencil (1306, 1304, and 406).
[0044] With reference now to FIG. 16, an ion milling is performed
to define the sensor width, and then a thin layer of insulation
1602 such as alumina and a layer of hard magnetic bias material
1604 are deposited. As with previously discussed embodiment, the
insulation layer 1602 can be deposited by chemical vapor deposition
or atomic layer deposition. The hard magnetic bias layer is
preferably deposited thicker than the insulation layer and
preferably to a thickness that is at least level with the top of
the sensor layers 404. As discussed above, a chemical mechanical
polishing process can be used to remove the remaining mask 1304.
This would require either inserting a CMP stop layer such as Ta
with Rh, Ru or Ir, or separately depositing a CMP stop layer such
as DLC.
[0045] However, as discussed previously, an optional ion milling
assisted lift-off in conjunction with CMP can be used to remove the
remaining mask 1304 at very small sensor widths. Again, if such an
ion milling assisted lift off process is performed, a second layer
of CMP resistant material 1606 is deposited, followed by a layer of
ion milling resistant material 1608. The materials for layers 1606,
1608 can be the same materials described above with reference to
layers 706, 708 of FIG. 7. With reference now to FIG. 17, an ion
milling is performed at a glancing angle to remove hard bias
material 1604 from the sides of the remaining mask structure 1304.
Again, this ion milling can be performed at an angle of 0 to 30
degrees relative horizontal (i.e. relative to the plane of the as
deposited layers as much as possible without damage to the
substrate fixture). A wrinkle bake step can be performed, and a hot
NMP solution 1802 can be applied as shown in FIG. 18. The hot NMP
removes the remaining mask 1304, leaving a structure such as shown
in FIG. 19. A buff CMP can then be performed to remove the
remaining CMP resistant layers 708, 1606, leaving a structure as
shown in FIG. 20. A reactive ion etching (RIE) can be performed to
remove the remaining CMP stop layers 406, 1606 if DLC is used as
the CMP stop layers. A magnetic layer can then be deposited to form
a second magnetic shield/lead layer 1202 as described above with
reference to FIG. 12.
[0046] FIGS. 21-28 illustrate yet another method for manufacturing
a magnetoresistive sensor. According to this method a tri-layer
mask structure is used to even further reduce read width. With
reference to FIG. 21, a first magnetic, electrically conductive
shield/lead layer 402 is formed, a series of sensor layers 404 are
deposited over the shield/lead layer 402, and a CMP stop layer 406
is deposited over the sensor layers 404. The CMP stop layer can be
Ru, Rh, Ir or DLC as before.
[0047] A tri-layer mask 2102 is deposited over the sensor layers
404 and CMP stop layer 406. The tri-layer mask includes a release
layer 2104 formed at the bottom of the mask structure 2102. The
release layer can be a soluble polyimide material such as
DURIMIDE.RTM. and in addition to functioning as a release layer for
assisting in lifting off the mask 2102 also functions as an image
transfer layer. A bottom antireflective coating (BARC) 2106 is
deposited over the release layer 2104. The BARC layer 2106 can be a
Si containing BARC or can be a carbon-only BARC. A non-silicon
containing photoresist layer 2108 is deposited over the BARC 2106.
A major function of the BARC is to improve resolution of the
imaging of the photoresist layer 2106 and may also improve RIE
selectivity between the BARC layer 2106 and the release layer 2104.
RIE selectivity allows for adjustment of the height of the
release/image-transfer layer 2104 to serve as an effective hard
mask to pattern the sensor layers 404 and assist in lift-off. A
BARC 2106 consisting of carbon only is used to improve photoresist
resolution and also reduce faceting during RIE, while silicon
containing BARC offers better imaging resolution and also RIE
selectivity between the BARC 2106 and the underlying lift off layer
2104.
[0048] With reference to FIG. 22, the non-Si-containing photoresist
layer 2108 is photolithographically patterned. Then, a reactive ion
etching is performed to transfer the image of the photoresist layer
2108 onto the underlying mask layers 2106, 2104 and possibly the
CMP stop layer 406 as well, leaving a structure as shown in FIG.
23. CO1 or CO.sub.2 with noble gaseous RIE chemistries as mention
previously is used for layers 2104 and 406 while CF.sub.4,
CHF.sub.3 or their mixture is used for layer 2104. Then, an ion
milling is performed using the mask 2102 as a stencil to form the
sensor 404 that are not protected by the mask 2108, 2106, 2104,
thereby defining a sensor width and leaving a structure as shown in
FIG. 24. The height of the overall mask 2102 is chosen to achieve
the narrowest dimension while also being sufficiently thick for
patterning of the sensor by ion milling and liftoff.
[0049] A thin insulation layer such as alumina 2502 is then
deposited, preferably by chemical vapor deposition or atomic layer
deposition, and a hard magnetic material 2504 is deposited over the
insulation layer 2502, leaving a structure as shown in FIG. 25,
with a bump 2506 formed over the sensor structure 404. A thin CMP
resistant material 2506, and thin ion milling resistant material
2508 are also deposited as shown in FIG. 25. A chemical mechanical
polishing can be used to remove the bump 2506 and to remove the
remaining mask 2104. As discussed above, this CMP alone can remove
the bump and mask for relatively large sensor widths. However, at
very small sensor widths (less than 40 nm) the correspondingly
small bump 2504 cannot be removed by CMP alone, and an ion milling
assisted CMP lift-off process such as that described above can be
used.
[0050] An ion milling is performed at a glazing angle as indicated
by arrows 2602. This glazing angle is nearly perpendicular to
normal or nearly parallel with the planes of the deposited layers.
For example, the glazing ion milling can be performed at an angle
of 0-30 degrees relative to the planes of the as deposited layers
as much as possible without damage to the substrate fixture. This
removes the magnetic material 2504 from the sides of the sensor
2104 as shown in FIG. 26. Then, a hot NMP solution can be applied
to lift off the mask 2104, and a chemical mechanical polishing can
be performed as described above, leaving a structure a shown in
FIG. 27. A reactive ion etching can be performed to remove the CMP
resistant layers 406, 2506, leaving a structure as shown in FIG.
28.
[0051] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only and not limitation. Other embodiments falling within
the scope of the invention may also become apparent to those
skilled in the art. Thus, the breadth and scope of the invention
should not be limited by any of the above-described exemplary
embodiments, but should be defined only in accordance with the
following claims and their equivalents.
* * * * *