U.S. patent application number 13/135620 was filed with the patent office on 2011-11-03 for cpp device with a plurality of metal oxide templates in a confining current path (ccp) spacer.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hideaki Fukuzawa, Min Li, Yue Liu, Hiromi Yuasa, Kunliang Zhang.
Application Number | 20110265325 13/135620 |
Document ID | / |
Family ID | 40523033 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110265325 |
Kind Code |
A1 |
Zhang; Kunliang ; et
al. |
November 3, 2011 |
CPP device with a plurality of metal oxide templates in a confining
current path (CCP) spacer
Abstract
A novel CCP scheme is disclosed for a CPP-GMR sensor in which an
amorphous metal/alloy layer such as Hf is inserted between a lower
Cu spacer and an oxidizable layer such as Al, Mg, or AlCu prior to
performing a pre-ion treatment (PIT) and ion assisted oxidation
(IAO) to transform the amorphous layer into a first metal oxide
template and the oxidizable layer into a second metal oxide
template both having Cu metal paths therein. The amorphous layer
promotes smoothness and smaller grain size in the oxidizable layer
to minimize variations in the metal paths and thereby improves
dR/R, R, and dR uniformity by 50% or more. An amorphous Hf layer
may be used without an oxidizable layer, or a thin Cu layer may be
inserted in the CCP scheme to form a Hf/PIT/IAO or Hf/Cu/Al/PIT/IAO
configuration. A double PIT/IAO process may be used as in
Hf/PIT/IAO/Al/PIT/IAO or Hf/PIT/IAO/Hf/PIT/IAO schemes.
Inventors: |
Zhang; Kunliang; (Milpitas,
CA) ; Li; Min; (Dublin, CA) ; Liu; Yue;
(Fremont, CA) ; Fukuzawa; Hideaki; (Kawasaki,
JP) ; Yuasa; Hiromi; (Kawasaki, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
TDK Corporation
|
Family ID: |
40523033 |
Appl. No.: |
13/135620 |
Filed: |
July 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11906716 |
Oct 3, 2007 |
7978442 |
|
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13135620 |
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Current U.S.
Class: |
29/887 |
Current CPC
Class: |
B82Y 25/00 20130101;
G11B 5/3106 20130101; H01L 43/08 20130101; Y10T 29/49032 20150115;
H01F 41/307 20130101; G11B 2005/3996 20130101; Y10T 29/49227
20150115; G01R 33/093 20130101; B82Y 10/00 20130101; H01F 10/3268
20130101; G11B 5/3929 20130101; H01L 43/12 20130101; B82Y 40/00
20130101; Y10T 29/49043 20150115; G11B 5/313 20130101; H01F 10/3259
20130101 |
Class at
Publication: |
29/887 |
International
Class: |
H01B 19/00 20060101
H01B019/00 |
Claims
1. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming an amorphous layer made
of metal, alloy, or metal oxide on said first Cu layer; (c)
depositing an oxidizable layer on said amorphous layer; (d)
performing a pre-ion treatment (PIT) followed by an ion-assisted
oxidation (IAO) to transform at least a portion of the first copper
layer and the amorphous layer into a first metal oxide template
having segregated Cu metal paths therein, and to transform a
portion of the first copper layer and the oxidizable layer into a
second metal oxide template having segregated Cu metal paths formed
therein; and (e) depositing a second Cu layer on the second metal
oxide template.
2. The method of claim 1 wherein the amorphous layer is made of Hf,
Zr, CoFeB, Ta, Nb, Ti, or B and has a thickness between about 1 and
15 Angstroms, and the oxidizable layer is comprised of Al, AlCu,
Mg, MgCu, Ti, Cr, Zr, Ta, Hf, or Fe and has a thickness between
about 1 and 15 Angstroms.
3. The method of claim 1 further comprised of forming a thin Cu
layer having a thickness between 0 and about 6 Angstroms on the
amorphous layer before depositing the oxidizable layer.
4. The method of claim 1 wherein the first Cu layer is from 0 to
about 10 Angstroms thick and the second Cu layer is from 0 to about
10 Angstroms thick.
5. The method of claim 1 wherein the PIT process is comprised of a
RF power between about 5 and 200 Watts, and an Ar flow rate of
about 10 to 200 sccm for a period of about 5 to 200 seconds, and
the IAO process is comprised of a RF power between about 5 and 200
Watts, an oxygen flow rate of about 0.01 to 100 sccm, and an Ar
flow rate of about 5 to 200 sccm for a period of about 5 to 2000
seconds.
6. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming an amorphous layer made
of metal, alloy, or metal oxide on said first Cu layer; (c)
performing a first PIT process followed by a first IAO process to
transform at least a portion of the first copper layer and the
amorphous layer into a first metal oxide template having segregated
Cu metal paths therein; (d) depositing an oxidizable layer on said
first metal oxide template; (e) performing a second PIT process
followed by a second IAO process to transform the oxidizable layer
into a second metal oxide template having segregated Cu metal paths
formed therein; and (f) depositing a second Cu layer on the second
metal oxide template.
7. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming a first amorphous layer
made of metal, alloy, or metal oxide on said first Cu layer; (c)
performing a first PIT process followed by a first IAO process to
transform at least a portion of the first copper layer and the
first amorphous layer into a first metal oxide template having
segregated Cu metal paths therein; (d) depositing an oxidizable
layer on said first metal oxide template; (e) depositing a second
amorphous layer on said oxidizable layer; (f) performing a second
PIT process followed by a second IAO process to transform the
oxidizable layer into a second metal oxide template having
segregated Cu metal paths formed therein and to transform the
second amorphous layer into a third metal oxide template having
segregated metal paths formed therein; and (g) depositing a second
Cu layer on the third metal oxide template.
8. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming an amorphous layer made
of a metal, alloy, or metal oxide on said first Cu layer; (c)
performing a PIT process followed by an IAO process to transform at
least a portion of the first copper layer and amorphous layer into
a first metal oxide template with segregated Cu metal paths formed
therein; and (d) depositing a second Cu layer on the first metal
oxide template.
9. The method of claim 8 wherein the amorphous layer is made of Hf,
Zr, CoFeB, Ta, Nb, Ti, or B and has a thickness between about 1 and
15 Angstroms, or the amorphous metal oxide has a thickness less
than about 15 Angstroms.
10. The method of claim 8 wherein the first Cu layer is from 0 to
about 10 Angstroms thick and the second Cu layer is from 0 to about
10 Angstroms thick.
11. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming a first amorphous layer
made of a metal, alloy, or metal oxide on said first Cu layer; (c)
forming a thin copper layer on the first amorphous layer; (d)
forming a second amorphous layer on the thin copper layer; and (e)
performing a PIT process followed by an IAO process to transform
the first amorphous layer into a first metal oxide template with
segregated Cu metal paths formed therein and to transform the
second amorphous layer into a second metal oxide template with
segregated Cu metal paths therein. (d) depositing a second Cu layer
on the first metal oxide template.
12. The method of claim 11 wherein said thin Cu layer has a
thickness between 0 and about 6 Angstroms.
13. The method of claim 11 wherein the first metal oxide template
is comprised of a different metal than in the second metal oxide
template.
14. The method of claim 11, wherein the first metal oxide template
is comprised of the same metal as in the second metal oxide
template.
15. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming a first amorphous layer
made of a metal, alloy, or metal oxide on said first Cu layer; (c)
performing a first PIT process followed by a first IAO process to
transform said first amorphous layer into a first metal oxide
template having copper metal paths formed therein; (d) forming a
second amorphous layer on the first metal oxide template; and (e)
performing a second PIT process followed by a second IAO process to
transform the second amorphous layer into a second metal oxide
template with segregated Cu metal paths formed therein.
16. A method of forming a confining current path (CCP) spacer in a
magnetic sensor structure, comprising: (a) forming a first copper
layer on a ferromagnetic layer; (b) forming an oxidizable layer on
said first Cu layer; (c) forming an amorphous layer made of metal,
alloy, or metal oxide on said oxidizable layer; and (d) performing
a PIT process followed by an IAO process to transform the
oxidizable layer into a first metal oxide template having
segregated Cu metal paths therein and to transform the amorphous
layer into a second metal oxide template having segregated Cu metal
paths formed therein.
Description
[0001] This is a Divisional application of U.S. patent application
Ser. No. 11/906,716, filed on Oct. 3, 2007, which is herein
incorporated by reference in its entirety, and assigned to a common
assignee.
FIELD OF THE INVENTION
[0002] The invention relates to a high performance magnetic read
head element and a method for making the same, and in particular,
to an amorphous metal layer or amorphous oxide layer that is formed
on a copper spacer and subjected to a plasma treatment followed by
an ion-assisted oxidation to form a confining current path (CCP)
layer between an AP1 layer in the pinned layer stack and a free
layer and thereby improve current perpendicular to plane (CPP)
device uniformity.
BACKGROUND OF THE INVENTION
[0003] A CPP-GMR head where GMR refers to a giant magnetoresistive
effect is considered as one promising sensor to replace the
conventional CIP (current in plane) GMR head for over 200
Gb/in.sup.2 recording density. GMR spin valve stacks typically have
a configuration in which two ferromagnetic layers are separated by
a non-magnetic conductive layer (spacer). One type of CPP-GMR
sensor is called a metallic CPP-GMR that can be represented by the
following configuration in which the spacer between the AP1 pinned
layer and free layer is a copper layer and the following layers are
sequentially formed on a substrate: Seed/AFM/AP2/Ru/AP1/Cu/free
layer/capping layer. One of the ferromagnetic layers is a pinned
layer in which the magnetization direction is fixed by exchange
coupling with an adjacent anti-ferromagnetic (AFM) or pinning
layer. The pinned layer may have a synthetic anti-parallel (SyAP)
structure wherein an outer AP2 layer is separated from an inner AP1
layer by a coupling layer such as Ru. The second ferromagnetic
layer is a free layer in which the magnetization vector can rotate
in response to external magnetic fields. The rotation of
magnetization in the free layer relative to the fixed layer
magnetization generates a resistance change that is detected as a
voltage change when a sense current is passed through the
structure. In a CPP configuration, a sense current is passed
through the sensor in a direction perpendicular to the layers in
the stack. A lower resistance is detected when the magnetization
directions of the free and pinned layers are in a parallel state
("1" memory state) and a higher resistance is noted when they are
in an anti-parallel state or "0" memory state.
[0004] In a typical CPP-GMR sensor, a bottom synthetic spin valve
film stack which is generally represented as
[seed/AFM/pinned/spacer/free/cap] is employed for biasing reasons
and a CoFe/NiFe composite free layer is conventionally used
following the tradition of CIP-GMR technology.
[0005] Ultra-high density (over 100 Gb/in.sup.2) recording requires
a highly sensitive read head. To meet this requirement, the CPP
configuration is a stronger candidate than the CIP configuration
which has been used in recent hard disk drives (HDDs). The CPP
configuration is more desirable for ultra-high density applications
because a stronger output signal is achieved as the sensor size
decreases, and the magnetoresistive (MR) ratio is higher for a CPP
configuration. An important characteristic of a GMR head is the MR
ratio which is dR/R where dR is the change in resistance of the
spin valve sensor and R is the resistance of the spin valve sensor
before the change. A higher MR ratio is desired for improved
sensitivity in the device and this result is achieved when
electrons in the sense current spend more time within the
magnetically active layers of the sensor. Interfacial scattering
which is the specular reflection of electrons at the interfaces
between layers in the sensor stack can improve the MR ratio and
increase sensitivity. Unfortunately, the MR ratio is often very low
(<5%) in many CPP-GMR spin valve structures involving metal
spacers. A MR ratio of .gtoreq.10% and an RA of <0.5
ohm-um.sup.2 are desirable for advanced applications.
[0006] Another type of sensor is a so-called confining current path
(CCP) CPP GMR sensor where the current through the Cu spacer is
limited by the means of segregating metal path and oxide formation.
With a CCP-CPP scheme, the Cu metal path is limited through an
insulator template so that the MR ratio can be enhanced quite
significantly. An example of a CCP-CPP GMR sensor has the following
configuration: Seed/AFM/AP2/Ru/AP1/Cu/CCP layer/Cu/free
layer/capping layer where the CCP layer is sandwiched between two
copper layers. Typically, a CCP layer is formed by first growing an
Al or AlCu layer on a Cu layer at the top of a crystalline stack of
layers which results in rough surface morphology and large grain
size with large distributions in the Al or AlCu film. In the
ensuing pre-ion treatment (PIT) and ion-assisted oxidation (IAO)
steps where Al or AlCu is exposed to oxygen to form a current
confining path through Al.sub.2O.sub.3 and Cu segregation, it is
inevitable that a rugged Al or AlCu layer leads to a non-uniform
AlOx layer which means poor uniformity and a loss of control in
device performance.
[0007] CCP layer formation is based on a well known fact that Al
atoms have a different (higher) mobility than Cu atoms. After the
PIT treatment, Al and Cu start to segregate from each other and
when exposed to oxygen during the IAO step, Al attracts oxygen to
form amorphous AlOx. Because Cu is more chemically inert to oxygen
than Al under the process conditions, it tends to remain as a Cu
metal phase and eventually forms a metal path.
[0008] In order for the CCP-CPP GMR approach to be widely accepted
in manufacturing, a smoother CCP forming layer and one that has a
morphology which enables more uniform metal paths to be formed
during the PIT/IAO processes is required so that significant
improvement in device uniformity can be achieved. A CCP forming
layer is defined here as the one or more layers deposited on a Cu
spacer which are subsequently transformed (with Cu) into the actual
CCP layer as a result of the PIT and IAO processes.
[0009] During a routine search of the prior art, the following
references were found. In U.S. Pat. No. 7,177,121, an amorphous
metal layer made of an oxidized NiCr alloy or oxidized CoCr alloy
is formed on the sides of a magnetoresistive element and beneath a
magnetic domain control film, the magnetic characteristics of the
magnetic domain control film are improved.
[0010] U.S. Patent Application Publication No. 2005/0094317
discloses a composite layer in a MTJ stack that is comprised of a
central current control region and an insulating layer on either
side of the central region. The central current control region is
made of an oxide, nitride, or oxynitride of at least one of B, Si,
Ge, Ta, W, Nb, Al, Mo, P, V, As, Sb, Zr, Ti, Zn, Pb, Th, Be, Cd,
Sc, Y, Cr, Sn, Ga, In, Rh, Pd, Mg, Li, Ba, Ca, Sr, Mn, Fe, Co, Ni,
Rb, and rare earth metals and may contain one type of metal such as
Cu, Au, Ag, Pt, Pd, Ir, and Os.
[0011] U.S. Patent Application Publication No. 2003/0053269
describes a current confining layer made of Al.sub.2O.sub.3 or
TaO.sub.2 that is formed between a pinned layer and a free
layer.
SUMMARY OF THE INVENTION
[0012] One objective of the present invention is to provide a CCP
forming layer configuration during fabrication of a CPP device that
promotes a smoother surface morphology as well as a smaller and
more uniform grain size in the oxidizable portion of the CCP
forming layer prior to the PIT and IAO processes.
[0013] A further objective of the present invention is to form
metal oxide templates with improved uniformity during CPP device
fabrication such that the Cu metal paths formed therein are more
uniform than in a conventional CCP scheme involving segregated Cu
metal paths in AlOx templates and thereby improve dR/R, dR, and R
uniformity across the wafer.
[0014] These objectives are achieved according to the present
invention by first providing a substrate on which a CPP-GMR sensor
(CPP element) is to be fabricated. In one embodiment, the substrate
is a bottom shield in a GMR read head and a CPP stack of layers
having a bottom spin valve configuration is formed on the substrate
by sequentially forming a seed layer, AFM layer, synthetic
anti-parallel (SyAP) pinned layer, Cu spacer with CCP layer
therein, free layer, and a cap layer in a sputter deposition
system. Formation of the CCP layer is achieved by first depositing
a CCP forming layer on a lower portion of the Cu spacer. A key
feature is that the CCP forming layer is comprised of at least one
amorphous layer made of metal, an alloy, or an oxide, and, in some
embodiments has an oxidizable layer made of Al, AlCu, Mg, MgCu, Ti,
Cr, Zr, Ta, Hf, Fe, or the like, or an alloy from one of the
aforementioned elements. The amorphous layer is preferably Hf but
also may be made of Zr, CoFeB, Ta, Nb, or the like. The amorphous
layer will be oxidized to an oxide layer and its primary purpose is
to provide a small grain size with smooth surfaces that (a)
promotes more uniform Cu paths formed in a metal oxide template
derived from the amorphous layer, and (b) improves the oxidizable
layer surface morphology and reduces grain size and size
distribution therein so that a more uniform metal oxide template
derived from the overlying oxidizable layer is formed following
plasma treatment and oxidation processes. One or more layers in the
CCP forming layer is subjected to a PIT/IAO process sequence
involving pre-ion treatment (PIT) followed by an ion-assisted
oxidation (IAO), plasma oxidation, or radical oxidation step to
transform the CCP forming layer and at least a portion of the Cu
spacer into a CCP layer having one or more metal oxide templates
with segregated Cu metal paths therein. Thereafter an upper portion
of the copper spacer is deposited on the CCP layer to provide a CCP
spacer represented by Cu/CCP layer/Cu.
[0015] In one aspect, the CCP scheme disclosed in the first
embodiment may be represented by A/X/PIT/IAO where A is the
amorphous layer made of metal, alloy, or oxide, and X is the
oxidizable metal layer. PIT/IAO indicates that the NX composite
structure (CCP forming layer) was treated with a PIT step followed
by an IAO step to form a first metal oxide template from the
amorphous layer and a second metal oxide template from the
oxidizable metal layer, both having segregated Cu metal paths
therein. The first metal oxide template contacts the lower portion
of the Cu spacer while the second metal oxide template contacts the
upper portion of the Cu spacer. There may be some intermixing of
first metal oxide template with the second metal oxide template.
The first embodiment also encompasses an A/X/A/PIT/IAO
configuration in which a second amorphous layer is deposited on the
oxidizable metal layer before the PIT and IAO sequence is
performed. In this case, a second metal oxide template derived from
the "X" layer is formed between first and third metal oxide
templates that are derived from the first and second amorphous
metal or alloy layers, respectively. The present invention also
provides for an A/PIT/IAO/X/PIT/IAO configuration where the A layer
is subjected to the PIT and IAO treatments before the X layer is
deposited and treated with the PIT and IAO steps.
[0016] In a second embodiment, the amorphous layer is employed as a
CCP forming layer on the lower Cu spacer layer, and the oxidizable
X layer is omitted. This configuration is represented by A/PIT/IAO.
Alternatively, a double A layer configuration represented by
A/PIT/IAO/A/PIT/IAO may be employed wherein a first A layer formed
on the lower portion of the Cu spacer is treated with the PIT and
IAO steps before a second A layer is deposited on the resulting
metal oxide template and is subjected to the PIT/IAO sequence. The
A/PIT/IAO/A/PIT/IAO CCP configuration can lead to improved
uniformity because of more uniform oxidation at the top surface and
via the grain boundaries in the "A" layers. In the second
embodiment, the one or more A layers are transformed into a single
metal oxide template with segregated Cu metal paths formed therein
when the first and second A layers are comprised of the same metal
or alloy. In one aspect, the first A layer may be made of a
different metal or alloy than the second A layer thereby producing
a second metal oxide template on the first metal oxide
template.
[0017] There is a third embodiment similar to the second embodiment
except a thin Cu layer is inserted between the two A layers. This
configuration is represented by A/PIT/IAO/Cu/A/PIT/IAO. In this
case, a Cu layer is deposited on the first metal oxide template
generated by performing PIT and IAO processes on the first A layer.
Then a second A layer is deposited on the Cu layer and PIT and IAO
processes are performed a second time to produce a second metal
oxide template on the first metal oxide template. In one aspect,
the same metal or alloy is employed in both the first and second A
layers to give essentially a single CCP layer having a metal oxide
template and Cu metal paths therein. However, the first A layer may
be comprised of a different metal or alloy than the second layer
which would result in a composite CCP structure where the first
metal oxide template derived from the first A layer is different
than the second metal oxide template formed from the second A
layer. Thereafter, the upper portion of the Cu spacer is deposited
on the second metal oxide template to form a CCP spacer having a
Cu/CCP layer/Cu configuration. Optionally, the third embodiment may
have an A/Cu/A/PIT/IAO configuration in which a thin Cu layer is
deposited on the first A layer followed by deposition of the second
A layer on the thin Cu layer before the PIT and IAO steps are
performed.
[0018] In a fourth embodiment, the CCP configuration of the first
embodiment is modified by inserting a thin Cu layer between the A
layer and the X layer as in A/Cu/X/PIT/IAO. Alternatively, the A
layer may be subjected to PIT and IAO process steps before a Cu
layer is deposited on the resulting first metal oxide template
derived from the A layer. Then the X layer is deposited on the thin
Cu layer followed by PIT and IAO process steps to generate a second
metal oxide template on the first metal oxide template in which
both metal oxide templates have Cu paths therein. This scheme is
represented by A/PIT/IAO/Cu/X/PIT/IAO.
[0019] The present invention also encompasses a method of forming
the CPP-GMR element comprised of the aforementioned Cu/CCP layer/Cu
spacer configurations. All layers in the CPP-GMR element are
preferably formed in a sputter deposition system that includes one
or more sputter deposition chambers and at least one oxidation
chamber. The PIT process may be performed in a sputter deposition
chamber followed by an IAO process in an oxidation chamber of a
sputter deposition mainframe. After all layers in the CPP-GMR
element are laid down on the substrate, a conventional patterning
and etching sequence may then be followed to define the shape of
the CPP-GMR element. Subsequently, a dielectric layer and a hard
bias layer may be formed adjacent to the sidewalls of the CPP-GMR
element in the CCP-CPP GMR sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a cross-sectional view of a CPP-GMR sensor with a
stack of layers in which a confining current path (CCP) spacer is
formed between an AP1 pinned layer and the free layer according to
one embodiment of the present invention.
[0021] FIG. 2 is a cross-sectional view of a read head comprised of
a CPP-GMR sensor according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention is a confining current path scheme for
a CCP spacer between a pinned layer and a free layer in a
magnetoresistive element such as a CPP-GMR sensor. The drawings are
provided by way of example and are not intended to limit the scope
of the invention. Although the exemplary embodiments describe a
bottom spin valve structure, the confining current path scheme of
the present invention may also be employed in a top spin valve
structure or a multilayer spin valve configuration in a CPP-GMR
element as appreciated by those skilled in the art. The present
invention is also a method of making a CCP-CPP GMR sensor with
improved uniformity compared with a conventional CCP-CPP GMR design
involving Cu paths in a metal oxide template. The terms "device",
"sensor", and "element" may be used interchangeably.
[0023] It is well known in conventional CCP schemes that the top
surface of an oxidizable Al or AlCu layer formed on a Cu spacer is
rough prior to the PIT and IAO process sequence. Furthermore, when
the Al or AlCu layer is oxidized to form AlOx templates for the Cu
metal paths, the volume of the CCP layer may expand by as much as
30% which increases surface roughness on the metal oxide template.
Since the Cu metal paths are formed through the grain boundaries of
the rough AlOx templates, the Cu metal paths have a large variation
in terms of width and length thereby leading to large variations in
RA and dR/R for the plurality of sensor devices fabricated across
the wafer. The inventors have discovered that by first depositing
an amorphous layer made of metal, alloy, or oxide on the Cu spacer,
the overlying oxidizable portion of the CCP forming layer will have
a smoother surface and smaller grain size to promote more uniform
Cu metal paths in the resulting metal oxide template following the
PIT and IAO process steps. Moreover, an amorphous layer made of
metal or alloy that is oxidizable and formed on a Cu spacer may be
employed without an overlying oxidizable layer in a CCP scheme with
similar improvement in device uniformity.
[0024] Referring to FIG. 1, one embodiment of the present invention
is shown that relates to a CCP-CPP GMR sensor 1 having a bottom
spin valve structure. The view in FIG. 1 is from a cross-section
along an air bearing surface (ABS) in the read head. A substrate 8
is shown that may be a first magnetic shield (S1) in a read head.
For example, the substrate 8 may be comprised of a 2 micron thick
layer of an electroplated permalloy. There is a seed layer 9 that
may be comprised of a lower Ta layer and an upper Ru layer (not
shown) formed on the substrate 8. The seed layer 9 promotes a
smooth and uniform crystal structure in the overlying AFM and
pinned layers that enhances the MR ratio in the CCP-CPP GMR sensor
1.
[0025] An AFM layer 10 is formed on the seed layer 9 and is
preferably comprised of IrMn having a composition of about 18 to 22
atomic % Ir and a thickness of about 50 to 75 Angstroms.
Alternatively, the AFM layer 10 may be made of MnPt having a
composition between about 55 to 65 atomic % manganese and with a
thickness of about 125 to 175 Angstroms. Those skilled in the art
will appreciate that other materials such as NiMn, OsMn, RuMn,
RhMn, PdMn, RuRhMn, or PtPdMn may also be employed as the AFM layer
10 which is used to pin the magnetization direction in an overlying
ferromagnetic (pinned) layer 14.
[0026] There is a synthetic anti-parallel (SyAP) pinned layer 14
formed on the AFM layer 10 that preferably has an AP2/coupling
layer/AP1 configuration. The AP2 layer 11 in the pinned layer may
be comprised of CoFe with a composition of about 75 to 90 atomic %
cobalt and a thickness of about 20 to 50 Angstroms and is formed on
the AFM layer 10. The magnetic moment of the AP2 layer 11 is pinned
in a direction anti-parallel to the magnetic moment of the AP1
layer 13. For example, the AP2 layer may have a magnetic moment
oriented along the "+x" direction while the AP1 layer has a
magnetic moment in the "-x" direction. The AP2 layer 11 may be
slightly thicker than the AP1 layer to produce a small net magnetic
moment for the pinned layer 14. Exchange coupling between the AP2
layer 11 and the AP1 layer 13 is facilitated by a coupling layer 12
that is preferably comprised of Ru with a thickness of about 7.5
Angstroms. Optionally, Rh or Ir may be employed as the coupling
layer 12.
[0027] The AP1 layer 13 may be a composite with a
[CoFe/Cu].sub.k/CoFe configuration wherein k=1, 2, or 3. In an
embodiment where k=1, the AP1 layer 13 may be comprised of a stack
wherein the first and third layers (not shown) are made of CoFe
with a Fe content of 50 to 90 atomic % and a thickness between 10
and 20 Angstroms, and preferably 18 Angstroms, and the second
(middle) layer is made of Cu with a thickness of 0.5 to 4 Angstroms
and preferably 2 Angstroms. The use of a laminated AP1 layer to
improve CPP-GMR properties is well known in the art. All of the
CoFe and Cu layers in the AP1 layer 13 have a magnetic moment in
the "-x" direction when the AP1 layer has a magnetic moment along
the "-x" axis in the exemplary embodiment. Optionally, the AP1
layer 13 may be made of CoFe or a composite comprised of CoFe and
CoFeB.
[0028] A key feature of the present invention is a CCP spacer 18
formed on the AP1 layer 13. The CCP spacer 18 is a composite
comprised of a confining current path (CCP) layer sandwiched
between two Cu layers 15, 17 each having a thickness from 0 to
about 10 Angstroms. It should be understood that the first step in
forming the CCP spacer 18 is depositing a first Cu layer 15 on the
AP1 layer 13. Alternatively, in a top spin valve, the CCP spacer 18
may be formed on a free layer. In a first embodiment, a CCP forming
layer (not shown) is formed on the first Cu layer 15 and is
comprised of at least one amorphous layer made of a metal, alloy,
or an oxide and hereafter referred to as the "A" layer, and an
oxidizable layer comprised of Al, AlCu, Mg, MgCu, Ti, Cr, Zr, Ta,
Hf, Fe, or the like, or an alloy from one of the aforementioned
elements and hereafter referred to as the "X" layer. The A layer
made of metal or alloy has a thickness from 1 to 15 Angstroms while
the X layer has a thickness from about 1 to 15 Angstroms. When the
A layer is an amorphous oxide, the preferred thickness is less than
15 Angstroms.
[0029] In one aspect, the X layer is formed above the A layer. The
A layer may be made of Hf, Zr, CoFeB, Ta, Nb, Ti, or B for example,
and serves to promote a smoother surface morphology and smaller
grain size in an overlying X layer. Thus, in a subsequent process
sequence involving PIT and IAO steps, the metal oxide template
resulting from oxidation of the X layer will have a smoother
surface texture and the Cu metal paths formed at the grain
boundaries will have improved uniformity compared with the Cu metal
paths formed within typical AlOx templates. Preferably, the A layer
is also oxidizable and is believed to form an oxide template with
Cu metal paths therein. The amorphous nature of the A layer means
the small grain size and smooth surfaces in the A layer promote the
formation of uniform Cu metal paths therein in subsequent PIT and
IAO processing. There may be a gradual transition from a metal
oxide template made of essentially oxidized A layer near the
interface with the first Cu layer 15 to a metal oxide template made
of essentially oxidized X layer at the top of the CCP layer 16
following the PIT/IAO steps. Thereafter, a second Cu layer 17 is
deposited on the CCP layer 16 to complete the CCP spacer 18. It
should be understood that at least a portion of the first Cu layer
15 reacts to form the Cu paths in the metal oxide templates.
Preferably, a portion of the first Cu layer 15 remains on the AP1
layer 13 following the IAO process to serve as an oxygen barrier so
that the magnetic material in the AP1 layer is not oxidized which
could lower the MR ratio and otherwise degrade the performance of
the CCP-CPP GMR sensor 1.
[0030] The CCP forming layer in the first embodiment may be
represented by an A/X/PIT/IAO configuration which indicates the A
layer is formed on the first Cu spacer layer 15 and the X layer is
deposited on the A layer prior to performing the PIT and IAO
processes. During the PIT/IAO processes, the CCP forming layer and
a portion of the first Cu layer 15 are transformed into the CCP
layer 16. In one aspect, the lower Cu layer 15 is about 2 to 8
Angstroms thick and preferably 5.2 Angstroms thick, and the upper
Cu layer 17 has a thickness between 2 and 6 Angstroms and is
preferably 3 Angstroms thick. The first metal oxide template in the
CCP layer 16 may have a thickness of 2 to 15 Angstroms and the
second metal oxide template may have a thickness of 2 to 15
Angstroms.
[0031] A typical PIT process is performed in a sputter deposition
chamber within a sputter deposition mainframe that preferably
contains at least one sputter deposition chamber and at least one
oxidation chamber. One example of a PIT process employed by the
inventors comprises a RF power of 5 to 200 Watts and an Ar flow of
10 to 200 standard cubic centimeters per minute (sccm) for 5 to 200
seconds. The IAO process may be performed in an oxidation chamber
of a sputter deposition mainframe and may be comprised of an Ar
flow rate of 5 to 200 sccm, an oxygen flow rate of 0.01 to 100
sccm, and a RF power of 5 to 200 Watts for 5 to 2000 seconds.
[0032] The first embodiment also encompasses an A/X/A/PIT/IAO
configuration in which a second amorphous (A) layer is deposited on
the X layer before the PIT and IAO sequence is performed. For
example, when A is Hf and X is Mg, then a first hafnium oxide
template is formed on the first Cu layer 15 and a MgO template is
formed on the first hafnium oxide template. There is also a second
hafnium oxide template formed on the MgO template with segregated
Cu metal paths formed within each of the three aforementioned metal
oxide templates. Optionally, the amorphous metal or amorphous alloy
selected for the second A layer may be different than the material
in the first A layer. As a result, each of the three metal oxide
templates in the CCP layer 16 may be comprised of a different metal
and has a thickness of 1 to 15 Angstroms. It should be understood
that the boundaries between adjacent metal oxide layers may not be
clearly defined since some intermixing of metal oxide templates can
occur during the PIT and IAO processes. Furthermore, the Cu density
in the second and third metal oxide templates may be less than in
the first metal oxide template since the Cu must migrate a greater
distance to reach the second and third metal oxide templates.
[0033] The first embodiment also provides for an
A/PIT/IAO/X/PIT/IAO configuration where the A layer is subjected to
the PIT and IAO treatments before the X layer is deposited and
treated with the PIT and IAO steps. In this case, a first metal
oxide template made of oxidized A layer is formed on the first Cu
layer 15 and a second metal oxide template made of oxidized X layer
is formed on the first metal oxide template. The concentration of
metal paths formed in the first metal template may be greater than
in the second metal oxide template since Cu from the lower Cu layer
15 must migrate a larger distance to reach the second metal oxide
template.
[0034] In another aspect, the X layer may be formed on the lower Cu
layer 15 followed by deposition of the A layer on the X layer.
Thus, the first embodiment also encompasses an X/A/PIT/IAO
configuration in which an amorphous A layer is deposited on the X
layer before the PIT and IAO processes are performed. For example,
a Mg/Hf/PIT/IAO configuration may be used to form a MgO template on
the lower Cu layer 15 and a hafnium oxide template on the MgO
template. As a result of the PIT/IAO sequence, both metal oxide
templates contain Cu metal paths. Thereafter, the upper Cu layer 17
is deposited on the resulting CCP layer 16.
[0035] In a second embodiment, at least one A layer is employed and
the X layer is omitted in the CCP forming layer. This configuration
may be represented by A/PIT/IAO. The A layer formed on the first Cu
layer 15 is treated with PIT and IAO processes to form a metal
oxide template with Cu metal paths therein to produce a CCP layer
16 having a thickness of about 5 to 25 Angstroms on the remaining
portion of first Cu layer 15. An important requirement for
formation of a segregated Cu metal path in a metal oxide template
is that the metal should be more readily oxidized than Cu and
should have a different mobility than Cu. Preferably, the A layer
metal or alloy has a higher mobility than Cu, but in principle, an
A layer material that has a lower mobility than Cu is also
acceptable. Thereafter, the second Cu layer 17 is deposited on the
CCP layer 16.
[0036] Alternatively, a double A layer configuration represented by
A/PIT/IAO/A/PIT/IAO may be employed wherein a first A layer (not
shown) formed on the first Cu layer 15 is treated with the PIT and
IAO steps to form a first metal oxide template before a second A
layer is deposited on the first metal oxide template having
segregated Cu metal paths therein and is subjected to the PIT/IAO
sequence to form a second metal oxide template having segregated Cu
metal paths therein. When the first A layer is comprised of the
same material as in the second A layer, then the resulting CCP
layer 16 has essentially the same metal oxide composition
throughout. Depending on the thicknesses of the two A layers, a
lower portion of the CCP layer 16 may have a higher concentration
of Cu metal paths than an upper portion because the first A layer
is closer to the first Cu layer 15 during the PIT/IAO sequence. The
A/PIT/IAO/A/PIT/IAO CCP configuration can lead to improved
uniformity because of more uniform oxidation at the top surface and
via the grain boundaries in the two A layers. It should be
understood that the second A layer may be made of a different
amorphous material than in the first A layer. The first metal oxide
template has a thickness of 2 to 15 Angstroms and the second metal
oxide template has a thickness of 2 to 15 Angstroms.
[0037] There is a third embodiment similar to the second embodiment
except a thin Cu layer (not shown) is inserted between the two A
layers. The thin Cu layer has a thickness from 0 to 6 Angstroms and
preferably less than 3 Angstroms. This configuration may be
represented by A/PIT/IAO/Cu/A/PIT/IAO. In this case, a thin Cu
layer is deposited on the first metal oxide template generated by
performing PIT and IAO processes on the first A layer. Then a
second A layer is deposited on the thin Cu layer and PIT and IAO
processes are performed a second time to produce a second metal
oxide template on the first metal oxide template. In one aspect,
the same metal or alloy is employed in both the first and second A
layers to give a CCP layer 16 having essentially a single metal
oxide template and Cu metal paths therein. However, the first A
layer may be comprised of a different metal or alloy than the
second A layer which would result in a composite CCP structure
where the first metal oxide template in a lower portion of the CCP
layer 16 is different than the second metal oxide template in an
upper portion of the CCP layer. Thereafter, the upper portion of
the Cu spacer is deposited on the CCP layer 16 to complete the CCP
spacer 18. Optionally, the third embodiment may have a
A/Cu/A/PIT/IAO configuration in which a thin Cu layer is deposited
on the first A layer followed by deposition of the second A layer
on the thin Cu layer before the PIT and IAO steps are performed.
This configuration is believed to generate a CCP layer 16 having a
more uniform Cu metal path distribution throughout since the Cu
used to form metal paths in the second metal oxide template does
not need to migrate through the first A layer.
[0038] In a fourth embodiment, the CCP configuration of the first
embodiment is modified by inserting a thin Cu layer from 0 to 6
Angstroms thick between the A layer and the X layer to give an
A/Cu/X/PIT/IAO scheme. In this case, the CCP layer 16 is comprised
of a first metal oxide template formed from the A layer and a
second metal oxide template formed from the X layer as a result of
the PIT. and IAO process sequence. Alternatively, the A layer may
be subjected to PIT and IAO process steps before a thin Cu layer is
deposited on the resulting first metal oxide template made from the
A layer. Then the X layer is deposited on the thin Cu layer
followed by PIT and IAO process steps to generate a second metal
oxide template on the first metal oxide template wherein both metal
oxide templates have Cu metal paths formed therein. This scheme is
represented by A/PIT/IAO/Cu/X/PIT/IAO. In this example, the first
metal oxide template in the CCP layer 16 has a different
composition than the second metal oxide template.
[0039] Above the CCP spacer 18 is a free layer 19 that may be
comprised of CoFe. Alternatively, the free layer 19 may be a
composite in which a bottom layer made of CoFe is formed on the CCP
spacer 18 and a NiFe layer is disposed on the CoFe layer. The
present invention also anticipates that other soft magnetic
materials may be employed as the free layer 19 in the GMR-CPP
sensor 1.
[0040] At the top of the CPP-GMR sensor stack is a cap layer 20
that may be a composite comprised of a lower Ru layer on the free
layer 19 and a Ta layer on the Ru layer. Optionally, the cap layer
20 may be comprised of a composite such as Ru/Ta/Ru or other
suitable capping layer materials used by those skilled in the
art.
[0041] All of the layers in the CPP stack in CCP-CPP GMR sensor 1
may be laid down in a sputter deposition system. For instance, the
CPP-GMR stack of layers may be formed in an Anelva C-7100 thin film
sputtering system or the like which typically includes three
physical vapor deposition (PVD) chambers each having 5 targets, an
oxidation chamber, and a sputter etching chamber. At least one of
the PVD chambers is capable of co-sputtering. Typically, the
sputter deposition process involves an argon sputter gas and the
targets are made of metal or alloys to be deposited on a substrate.
All of the CPP layers may be formed after a single pump down of the
sputter system to enhance throughput.
[0042] The present invention also encompasses an annealing step
after all of the CPP-GMR layers have been deposited. For example,
the CPP-GMR stack comprised of seed layer 9, AFM layer 10, pinned
layer 14, CCP spacer 18, free layer 19, and cap layer 20 may be
annealed by applying a magnetic field of about 10K Oe in magnitude
along a certain axis for about 0.5 to 20 hours at a temperature
between 250.degree. C. and 350.degree. C. The annealing process may
also comprise an annealing step along a hard axis and an annealing
step along an easy axis.
[0043] Referring to FIG. 2, a CCP-CPP GMR head 30 having a CPP-GMR
element comprised of layers 9-20 and with sidewalls 21 and a top
surface 20a may be fabricated by coating and patterning a
photoresist layer (not shown) on the cap layer surface 20a after
all of the layers in the CPP-GMR stack are deposited. The
photoresist layer serves as an etch mask during an ion beam etch
(IBE) or reactive ion etch (RIE) sequence that transfers the
pattern through the CPP-GMR stack of layers to form the sidewalls
21 that are typically sloped so that the top surface 20a has a
smaller width along the x-axis than that of the seed layer 9. Once
the etch sequence is complete, the photoresist layer may be removed
by a conventional stripping process known to those skilled in the
art.
[0044] Thereafter, a first dielectric layer 22 made of
Al.sub.2O.sub.3 or the like with a thickness of about 100 to 150
Angstroms is deposited on the bottom shield 8 and along the
sidewalls 21 of the CPP-GMR element by a chemical vapor deposition
(CVD) or physical vapor deposition (PVD) method. Optionally, a seed
layer (not shown) such as TiW, Cr, CrTi, or CrMo may be formed on
the first dielectric layer. Next, a hard bias layer 23 that may be
comprised of CoCrPt or FePt is deposited on the first dielectric
layer 22 (or seed layer) by an ion beam deposition (IBD) or PVD
process. In an alternative embodiment, a soft magnetic underlayer
such as NiFe, CoFe, CoNiFe, FeTaN, or FeAlN is formed on a seed
layer to promote good lattice matching between the seed layer and
hard bias layer 23. Then a second dielectric layer 24 is deposited
on the first dielectric layer 22 and on the hard bias layer 23 with
a CVD or PVD method, for example. In one embodiment, the hard bias
layer 23 has a thickness of about 200 to 400 Angstroms and the
second dielectric layer 24 has a thickness between about 150 and
250 Angstroms. A planarization step such as a chemical mechanical
polish (CMP) process may be employed to make the second dielectric
layer 24 coplanar with the top surface 20a of the cap layer 20. An
upper shield 25 is disposed on the top surface 20a of the cap layer
20 and on the second dielectric layer 24. The upper shield 25 may
be a composite layer such as Ta/NiFe as appreciated by those
skilled in the art.
[0045] The advantages of incorporating a CCP layer 16 as described
herein within a CCP spacer in a CPP GMR sensor are improved dR/R,
dR, and R uniformity over CCP schemes involving conventional metal
oxide templates with segregated Cu metal paths. Moreover, the
amorphous layer inserted into the CCP forming layer is believed to
minimize the threat of oxygen diffusion from the metal oxide
template derived from the oxidizable metal into the AP1 layer and
thereby avoids degradation in sensor performance. Several examples
of CCP configurations in accordance with the present invention are
described below.
COMPARATIVE EXAMPLE 1
[0046] An experiment was conducted to demonstrate the improved
performance of a CPP-GMR stack of layers comprised of a seed layer,
IrMn AFM layer, SyAP pinned layer, CCP spacer of the present
invention, free layer, and cap layer that were sequentially formed
on a AlTiC substrate. In this example, the seed layer has a 10
Angstrom thick Ta lower layer and a 10 Angstrom thick Ru upper
layer, the IrMn AFM layer has a thickness of 70 Angstroms, the AP2
trilayer has a
Fe.sub.10Co.sub.90/Fe.sub.70Co.sub.30/Fe.sub.10Co.sub.90
configuration, the AP1 layer is a
Fe.sub.70Co.sub.30/Cu/Fe.sub.70Co.sub.30 laminate, the free layer
is a Fe.sub.25Co.sub.75/CoFeB/Ni.sub.90Fe.sub.10 composite, and the
cap layer has a Ru/Ta/Ru configuration. The value next to each
layer in the reference configuration below indicates the film
thickness in Angstroms. The reference sample labeled BTF2B3N has a
CCP layer with AlOx and Cu metal paths therein and is formed by
treating a Cu/Al/PIT/IAO configuration with a PIT process comprised
of a RF power of 20 Watts and an Ar flow rate of 50 sccm for 35
seconds, and an IAO process comprised of a RF power of 27 Watts, an
Ar flow rate of 35 sccm and an oxygen flow rate of 0.56 sccm for 40
seconds. The uniformity data for the reference CCP-CPP GMR sensor
structure represented by
Ta10/Ru10/IrMn70/Fe.sub.10Co.sub.908/Fe.sub.70Co.sub.3010.5/Fe.sub.10Co.s-
ub.9016/Ru7.5/Fe.sub.70Co.sub.3012/Cu2/Fe.sub.70Co.sub.3012/Cu5.2/AlCu8.6/-
PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru10/Ta60/Ru-
30 is provided in Table 1.
TABLE-US-00001 TABLE 1 dR/R, dR, and R uniformity data for various
device sizes for BTF2B3N under a conventional PIT/IAO process dR/R
dR BTF2B3N Uniformity Uniformity R Uniformity device size FLL Area
(%) (%) (%) 2B 0.61 0.288 11.232 25.323 15.679 2A 0.49 0.189 8.658
22.605 16.747 1D 0.80 0.515 12.062 23.766 13.726 1C 0.37 0.105
9.031 26.497 19.982 1B 0.30 0.073 7.437 26.446 20.916 1A & 2C
0.24 0.047 8.814 23.631 22.290
[0047] Typically, the 1 sigma uniformity data across the wafer
ranges from 7% to 15% for dR/R, 20% to 30% for dR, and 15% to 30%
for R. These large values for conventional CCP schemes are due to
large variations in Cu metal paths formed within the rugged and
non-uniform aluminum oxide templates generated during the PIT/IAO
processes.
[0048] The inventors have achieved a substantial improvement in
uniformity by inserting an amorphous layer (Hf) between a lower Cu
spacer and an oxidizable Al layer in a CCP scheme represented by
A/X/PIT/IAO where A=Hf and X.dbd.Al according to one embodiment of
the present invention. In other words, a thin amorphous Hf layer is
deposited on the lower Cu spacer before an Al layer is grown. The
same PIT and IAO process conditions were employed as in the
reference to form a CCP layer. The CCP-CPP GMR sensor (BTF3A0) with
improved uniformity fabricated from a CCP forming layer
configuration Hf/Al/PIT/IAO is represented by
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/Al7/P-
IT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru10/Ta60/Ru3-
0. Results are shown in Table 2. Note that dR/R, R, and dR one
sigma uniformity are reduced by 50% or more for all device sizes
compared with the reference data in Table 1.
TABLE-US-00002 TABLE 2 dR/R, dR, and R uniformity data for various
device sizes for BTF3A0 under the new CCP scheme with amorphous
layer insertion before PIT/IAO processing. dR/R dR BTF3A0
Uniformity Uniformity R Uniformity device size FLL Area (%) (%) (%)
2B 0.61 0.288 4.370 6.687 6.439 2A 0.49 0.189 4.350 7.401 3.574 1D
0.80 0.515 3.048 3.382 4.761 1C 0.37 0.105 4.466 8.551 4.486 1B
0.30 0.073 3.916 10.564 7.597 1A & 2C 0.24 0.047 4.781 10.847
6.848
[0049] In another example that represents an A/X/A/PIT/IAO CCP
scheme, a CCP-CPP GMR sensor (BTF3FG) was formed with the following
structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/Al2/H-
f3/PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru10Ta60/-
Ru30. In this embodiment, a first Hf layer is deposited on a lower
Cu spacer followed by deposition of an Al layer and then a second
Hf layer before the PIT/IAO sequence is performed. An upper Cu
spacer is deposited on the resulting CCP layer having a stack of
three metal oxide templates before the free layer is formed. In
another example that represents an A/X/A/PIT/IAO CCP scheme where
Al is replaced by Mg as the oxidizable "X" layer, a CCP-CPP GMR
sensor (BTF39J) was formed with the following structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/Mg4/H-
f3/PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru.sub.10-
/Ta60/Ru30. In this embodiment, a first Hf layer is deposited on a
lower Cu spacer followed by deposition of a Mg layer and then a
second Hf layer before the PIT/IAO sequence is performed. An upper
Cu spacer is deposited on the resulting CCP layer before the free
layer is formed. In the two A/X/A/PIT/IAO examples, the amorphous
like Hf/Al/Hf or Hf/Mg/Hf trilayer configuration is treated with a
PIT/IAO process sequence. Since the grain size is further decreased
in the CCP forming layer compared with the A/X/PIT/IAO embodiment,
more uniform oxidation and better uniformity can be realized.
[0050] In another example that represents an A/PIT/IAO CCP scheme,
a CCP-CPP GMR sensor (BTF3C6) was formed with the following
structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf8/PIT/I-
AO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru10/Ta60/Ru30.
In this embodiment, a Hf layer is treated with the PIT/IAO sequence
without an overlying Al or AlCu layer. Since Hf is amorphous, the
oxidation will be more uniform from the top surface and via the
grain boundary than when an A/X/PIT/IAO scheme is employed.
Therefore, better uniformity can be realized.
[0051] In an example that represents an A/PIT/IAO/A/PIT/IAO CCP
scheme according to the present invention, a CCP-CPP GMR sensor was
formed with the following structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/P
IT/IAO/Hf3/PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/-
Ru10/Ta60/Ru30. A first amorphous Hf layer is deposited on the
lower Cu spacer and is treated with a PIT/IAO sequence to give a
hafnium oxide template with Cu metal paths therein before a second
amorphous Hf layer is deposited on the first hafnium oxide template
and a second PIT/IAO sequence is performed to generate a second
hafnium oxide template with Cu paths therein. In effect, the
A/PIT/IAO/A/PIT/IAO scheme represents a double nano-oxidation layer
(NOL) process. The first and second amorphous hafnium layers
replace the Al or AlCu layer in a conventional CCP design. Since
both amorphous hafnium layers were subjected to the PIT/IAO
processes, the amorphous nature of the Hf layer results in a more
uniform oxidation from the top surface and via the grain
boundaries. Therefore better uniformity can be realized.
[0052] A modification of the previous sample that represents an
A/PIT/IAO/Cu/A/PIT/IAO CCP scheme according to one embodiment of
the present invention is shown in the following structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.3018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/PIT/I-
AO/Cu/Hf3/PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru-
10/Ta60/Ru30. The thin Cu layer formed on the first hafnium oxide
template is believed to form a more uniform concentration of Cu
metal paths in the resulting CCP layer and thereby improves
uniformity.
[0053] In yet another modification of the A/PIT/IAO CCP scheme, a
thin Cu layer is inserted between two A layers prior to performing
the PIT/IAO sequence. For example, a first Hf layer, a thin Cu
layer, and a second Hf layer are sequentially deposited on a lower
Cu spacer before applying the PIT/IAO process steps. A structure
formed according to an A/Cu/A/PIT/IAO embodiment of the present
invention is represented by the structure:
Ta10/Ru20/IrMn70/Fe.sub.10Co.sub.9012/Fe.sub.70Co.sub.3017/Fe.sub.10Co.su-
b.9024/Ru7.5/Fe.sub.70Co.sub.2018/Cu2/Fe.sub.70Co.sub.3018/Cu5.2/Hf3/Cu2/H-
f3/PIT/IAO/Cu3/Fe.sub.25Co.sub.7512/CoFeB10/Ni.sub.90Fe.sub.1035/Ru10/Ta60-
/Ru30. The thin Cu layer formed between the two amorphous hafnium
layers is believed to form a more uniform concentration of Cu metal
paths in the resulting CCP layer and thereby improves
uniformity.
[0054] While this invention has been particularly shown and
described with reference to, the preferred embodiment thereof, it
will be understood by those skilled in the art that various changes
in form and details may be made without departing from the spirit
and scope of this invention.
* * * * *