U.S. patent application number 12/358628 was filed with the patent office on 2009-07-30 for superconformal electrodeposition of nickel iron and cobalt magnetic alloys.
This patent application is currently assigned to GOVERNMENT OF THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE. Invention is credited to Daniel Jossel, Soo-Kil Kim, Chang Hwa Lee, Thomas P. Moffat.
Application Number | 20090188805 12/358628 |
Document ID | / |
Family ID | 40898112 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090188805 |
Kind Code |
A1 |
Moffat; Thomas P. ; et
al. |
July 30, 2009 |
SUPERCONFORMAL ELECTRODEPOSITION OF NICKEL IRON AND COBALT MAGNETIC
ALLOYS
Abstract
A process for electrodepositing at least one ferromagnetic
material into a three dimensional pattern within a substrate is
provided. The process comprises providing a substrate material,
dielectric or conductor, having a three dimensional recessed
pattern in at least one outer surface thereof, dielectric substrate
materials also having an electrical conductive seed layer at least
within the three dimensional pattern. An electrolytic bath is
prepared comprising at least one ferromagnetic material and at
least one accelerating, inhibiting, or depolarizing additive. The
at least one ferromagnetic material comprises at least one metal
cation selected from the group consisting of Ni.sup.2+, Co.sup.2+,
Fe.sup.2+, Fe.sup.3+, and combinations thereof. The substrate is
placed into the electrolytic bath and the electrolytic bath
contacts the conducting three dimensional pattern in the substrate
or the conducting seed layer within the pattern on a dielectric
substrate. A counter electrode is placed into the electrolytic
bath. An electric current is passed through the electrolytic bath
between the electrical conductive substrate or seed layer on the
three dimensional substrate and the counter electrode. At least a
portion of the ferromagnetic material is deposited into at least a
portion of the three dimensional pattern wherein the at least one
deposited ferromagnetic material is substantially void-free.
Inventors: |
Moffat; Thomas P.;
(Gaithersburg, MD) ; Lee; Chang Hwa;
(Gaithersburg, MD) ; Jossel; Daniel; (N. Potomac,
MD) ; Kim; Soo-Kil; (Seoul, KR) |
Correspondence
Address: |
Steve Witters, PLLC
930 Woodland Ridge Circle
LaGrange
KY
40031
US
|
Assignee: |
GOVERNMENT OF THE UNITED STATES OF
AMERICA, AS REPRESENTED BY THE
SECRETARY OF COMMERCE, THE NATIONAL INSTITUTE OF STANDARDS AND
TECHNOLOGY
|
Family ID: |
40898112 |
Appl. No.: |
12/358628 |
Filed: |
January 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61023593 |
Jan 25, 2008 |
|
|
|
Current U.S.
Class: |
205/119 |
Current CPC
Class: |
H01L 21/2885 20130101;
C25D 7/123 20130101; H01L 21/76877 20130101; C25D 3/20 20130101;
H01L 23/5227 20130101; C25D 3/12 20130101; G11C 11/14 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
205/119 |
International
Class: |
C25D 5/02 20060101
C25D005/02 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] This work is funded by the National Institute of Standards
and Technology under the U.S. Department of Commerce.
Claims
1. A process of electrodepositing at least one ferromagnetic metal
into a three dimensional pattern within a substrate comprising:
providing a substrate material comprising an electrical conductive
three dimensional recessed pattern in at least one surface thereof;
preparing an electrolytic bath comprising at least one
ferromagnetic metal cation selected from the group consisting of
Ni.sup.2 +, Co.sup.2+, Fe.sup.2+, Fe.sup.3+, and combinations
thereof; mixing at least one accelerating, inhibiting, or
depolarizing additive into said electrolytic bath; placing said
electrical conductive pattern of said substrate into said
electrolytic bath; contacting said electrical conductive pattern of
said substrate with said electrolytic bath; placing a counter
electrode into said electrolytic bath; passing an electrical
current through said electrolytic bath between said electrical
conductive pattern of said substrate and said counter electrode;
said electrical current being passed between said electrical
conductive pattern of said substrate and said counter electrode is
such that the potential between the said substrate and a reference
electrode is at a value negative of -0.8V SCE, or at an applied
current density in the range of 0.1 to 50 mA/cm of the area of the
electrically conductive pattern of the substrate, or both; and
depositing at least a portion of said at least one ferromagnetic
material into at least a portion of said three dimensional pattern
wherein said at least one deposited ferromagnetic material is
substantially void-free.
2. The process of claim 1 wherein said substrate is a dielectric
substrate and said process further comprises: depositing an
electrical conductive material onto said three dimensional pattern
of said dielectric substrate providing an electrical conductive
seed layer on said substrate.
3. The process of claim 1 wherein said process step of
preferentially depositing said ferromagnetic material into said
three dimensional pattern results in a superconformal bottom-up
deposition of said ferromagnetic material within said three
dimensional pattern.
4. The process of claim 1 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises a nitrogen
containing compound.
5. The process of claim 1 wherein said at least one accelerating,
inhibiting, or depolarizing additive has a compound selected from
the group consisting of cationic surfactants, anionic surfactants,
nonionic surfactants, heterocyclic benzimidazole derivatives, and
combinations thereof.
6. The process of claim 1 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises a compound selected
from the group consisting of polyethyleneimine,
2-mercapto-5-benzimidazolesulfonic acid, and combinations
thereof.
7. The process of claim 1 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises
polyethyleneimine.
8. The process of claim 1 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises
2-mercapto-5-benzimidazolesulfonic acid.
9. The process of claim 8 wherein said
2-mercapto-5-benzimidazolesulfonic acid is in said electrolytic
bath at a concentration of at least 50 .mu.mol/L.
10. The process of claim 1 wherein said three dimensional structure
has at least one trench or via with a width ranging from nanometers
to macroscopic dimensions.
11. A process of electrodepositing at least one ferromagnetic
material into a three dimensional pattern within a substrate
comprising: providing a substrate material having an electrical
conductive portion with a three dimensional recessed pattern;
preparing an electrolytic bath comprising said at least one
ferromagnetic material and at least one accelerating, inhibiting,
or depolarizing additive; said at least one ferromagnetic material
comprising at least one metal cation selected from the group
consisting of Ni.sup.2+, Co.sup.2+, Fe.sup.2+, Fe.sup.3+, and
combinations thereof; placing said electrical conductive portion of
said substrate into said electrolytic bath; contacting said
electrical conductive portion of said substrate with said
electrolytic bath; placing a counter electrode into said
electrolytic bath; passing an electrical current through said
electrolytic bath between said electrical conductive portion of
said substrate and said counter electrode; and depositing at least
a portion of said at least one ferromagnetic material into at least
a portion of said three dimensional pattern wherein said at least
one deposited ferromagnetic material is substantially
void-free.
12. The process of claim 11 wherein said process step of passing an
electrical current through said electrolytic bath between said
electrical conductive portion of said substrate and said counter
electrode is such that the potential between the said substrate and
a reference electrode is at a value negative of -0.8V SCE.
13. The process of claim 11 wherein said process step of passing an
electrical current through said electrolytic bath between said
electrical conductive portion of said substrate and said counter
electrode is at an applied current density in the range of 0.1 to
50 mA/cm2 of the area of the electrically conductive portion of the
substrate.
14. The process of claim 11 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises a nitrogen
containing compound.
15. The process of claim 11 wherein said at least one accelerating,
inhibiting, or depolarizing additive has a compound selected from
the group consisting of cationic surfactants, anionic surfactants,
nonionic surfactants, heterocyclic benzimidazole derivatives, and
combinations thereof.
16. The process of claim 11 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises a compound selected
from the group consisting of polyethyleneimine,
2-mercapto-5-benzimidazolesulfonic acid, and combinations
thereof.
17. The process of claim 11 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises
polyethyleneimine.
18. The process of claim 11 wherein said at least one accelerating,
inhibiting, or depolarizing additive comprises
2-mercapto-5-benzimidazolesulfonic acid.
19. The process of claim 18 wherein said
2-mercapto-5-benzimidazolesulfonic acid is in said electrolytic
bath at a concentration of at least 50 .mu.mol/L.
20. A process of electrodepositing at least one ferromagnetic
material into a three dimensional pattern within a substrate
comprising: providing a substrate material having an electrical
conductive three dimensional recessed pattern in a surface thereof;
preparing an electrolytic bath comprising said at least one
ferromagnetic material and at least one accelerating, inhibiting,
or depolarizing additive; said at least one ferromagnetic material
comprising at least one metal cation selected from the group
consisting of Ni.sup.2+, Co.sup.2+, Fe.sup.2+, Fe.sup.3+, and
combinations thereof; said at least one accelerating, inhibiting,
or depolarizing additive comprising an additive selected from the
group consisting of polyethyleneimine,
2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof;
placing said electrical conductive three dimensional recessed
pattern in said substrate into said electrolytic bath; contacting
said electrical conductive three dimensional recessed pattern in
said substrate with said electrolytic bath; placing a counter
electrode into said electrolytic bath; passing an electrical
current through said electrolytic bath between said electrical
conductive three dimensional recessed pattern in said substrate and
said counter electrode; and depositing at least a portion of said
at least one ferromagnetic material into at least a portion of said
three dimensional recessed pattern in said substrate wherein said
at least one deposited ferromagnetic material is substantially
void-free.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Application No. 61/023593,
entitled "Superconformal Electrodeposition Of Ni--Fe--Co Magnetic
Alloys", filed Jan. 25, 2008, which is hereby incorporated herein
by reference in its entirety.
ATTORNEY DOCKET NUMBER: 083 08 001ASSIGNEE: NATIONAL INSTITUTE OF
STANDARDS AND TECHNOLOGY
CERTIFICATION OF EFS-WEB TRANSMISSION UNDER 37 C.F.R. 1.10
TABLE-US-00001 [0003] I hereby certify that this New Application
and the documents referred Signature to as enclosed herein are
being deposited Steve A. Witters, 53,923 with the United States
Patent Office on Name, Reg. # date of signature via the EFS-Web
Service. Date of Signature
[0004] 1. Field
[0005] Aspects of the present invention generally relate to using
electrodeposition to fill recessed surface features of a substrate
with metals and alloys in a substantially void free manner. More
specifically, by using certain electrolyte additives void-free
electrodeposition of ferromagnetic materials onto a three
dimensional patterned substrate may be achieved.
[0006] 2. Background
[0007] As reflected in the literature, electrodeposition of
ferromagnetic materials, such as Co, Ni, Fe, and related alloys has
been used in the fabrication of recording heads and media for hard
disk drives, magnetic sensors, inductors, three-dimensional (3-D)
structures associated with ultralarge-scale integration (ULSI),
micro-electromechanical systems (MEMS), 3-D packaging and
actuators.
[0008] In the prior art, thin-film ferromagnetic microstructures
have been produced by through-mask electroplating (also known as
the LIGA). Through-mask deposition has been applied to a wide
variety of materials ranging from metals to semiconductors,
including applications in both passive and active devices. LIGA
combines template production (e.g., lithography) with
electrodeposition whereby metal deposition proceeds on the exposed
sections of the underlying conductive seed layer. Two
manifestations of this are metal plating in nanopores of a
metal-backed anodized alumina membrane and selective plating on a
metallized substrate patterned with an overlying insulating
photoresist. This process yields microstructures that are the
negative image of the template structure. The implementation of the
process is effectively two-dimensional in nature. Developing
complex multilayered three-dimensional (3-D) structures by
through-mask deposition may be problematic, particularly with
regard to electrical addressability as required for the
electrodeposition process as well as subsequent electrical and/or
thermal isolation of the final intricate structures.
[0009] The Damascene process, which is widely used for producing
multilevel Cu interconnection in ultralarge-scale integration, has
offered an alternative to the LIGA approach to building 3-D
magnetic nanostructures. The Damascene process comprises
metallizing a topographically 3-D patterned dielectric with a thin
seed layer to ensure conductivity across the entire surface
followed by metal electrodeposition across the entire surface. This
may be effectuated by the addition of accelerating and inhibiting
electrolyte additives in an electrolytic bath in combination with
the consequences of area change that accompanies deposition in the
3-D pattern. A subsequent planarization step removes the
overburden, leaving the desired metal structures embedded within
the dielectric. The process can be repeated as needed to produce
multilevel interconnected structures that may exceed ten layers.
The Damascene metallization process may provide void-free bottom-up
superconformal filling of the trenches and vias with Cu.
[0010] In the case of copper, silver, and gold, void-free
superconformal feature filling has been demonstrated by the use of
electrolyte additives that locally modify the rate of growth
leading to bottom-up filling of recessed features, such as trenches
and vias. However, such void free feature filling has not been
realized for electrodeposition of ferromagnetic materials.
[0011] In the case of ferromagnetic materials, the effect of
additives on the morphological evolution and physical properties of
the deposits has been employed in the prior art to a limited
extent. For example, the influence of dilute concentrations of
species, such as saccharin, quinoline, thiourea, and coumarian on
improving film properties such as internal stress, corrosion
resistance, and leveling of the micro-roughness, has been reported.
Among them, thiourea and coumarin are known levelers that reduce
the difference in height between protruding and recessed surface
features in large 3-D structures, over 10-100 .mu.m wide. However,
use of the Damascene process for the electroplating of
ferromagnetic materials in a 3-D patterned dielectric substrate has
been limited. Void-free filling of trenches and vias with
ferromagnetic materials remains problematic, especially in a small
scale. What is needed is a process for substantially void-free
filling of recessed surface features such as trenches and vias in
3-D patterned substrates with ferromagnetic materials.
SUMMARY
[0012] Aspects of the present invention generally relate to using
electrodeposition to fill recessed surface features of a substrate
with metals and alloys in a substantially void free manner. More
specifically, by using certain electrolyte additives, substantially
void-free electrodeposition of ferromagnetic materials within a
three dimensional patterned substrate may be achieved. The
substrate may be electrically conductive such as a metal or a doped
semiconductor. Alternatively the substrate may be a dielectric.
With a dielectric substrate, the patterned surface may first be
rendered conductive by deposition of a thin electrically conducting
seed-layer at least within the three dimensional pattern.
[0013] According to one aspect of the present invention, a process
of electrodepositing at least one ferromagnetic material into a
three dimensional pattern within a substrate is provided. The
substrate may be comprised of electrically conductive materials,
dielectric materials, or a combination thereof. A substrate
material is provided having an electrically conductive three
dimensional recessed pattern in at least one outer surface thereof.
When using a dielectric substrate, a thin electrical conductive
material is first deposited within the three dimensional pattern
and optionally the outer surface of the substrate having the three
dimensional pattern, providing a seed layer on the substrate.
Providing an electrically conductive outer surface and an
electrically conductive three dimension pattern may provide a more
efficient deposition process. An electrolytic bath comprising at
least one ferromagnetic material and at least one inhibiting,
accelerating or depolarizing additive is prepared. The at least one
ferromagnetic material comprises at least one metal cation selected
from the group consisting of Ni , Co.sup.2 +, Fe.sup.2+, Fe.sup.3+,
and combinations thereof, and the anion typically being sulfate,
chloride, sulfamate or some combination thereof. The substrate with
seed layer is placed into the electrolytic bath wherein the at
least one outer surface and three dimensional pattern is contacted
by the electrolytic bath. A counter electrode is placed into the
electrolytic bath whereby an electrical current is passed through
the electrolytic bath between the seed layer on the substrate and
the counter electrode. At least a portion of the at least one
ferromagnetic material is deposited into at least a portion of the
three dimensional pattern wherein the deposition of the at least
one ferromagnetic material is substantially void-free.
[0014] According to another aspect of the present invention, the at
least one accelerating, inhibiting, or depolarizing additive
comprises a nitrogen containing compound.
[0015] According to yet another aspect, the at least one
accelerating, inhibiting, or depolarizing additive has at least one
compound selected from the group consisting of cationic
surfactants, anionic surfactants, nonionic surfactants,
heterocyclic benzimidazole derivatives, and combinations
thereof.
[0016] According to a further aspect of the present invention, the
at least one accelerating, inhibiting, or depolarizing additive
comprises at least one compound selected from the group consisting
of polyethyleneimine (PEI), 2-mercapto-5-benzimidazolesulfonic acid
(MBIS), and combinations thereof.
[0017] According to yet a further aspect of the present invention,
the at least one accelerating, inhibiting, or depolarizing additive
comprises PEI.
[0018] According to another aspect of the present invention, the at
least one accelerating, inhibiting, or depolarizing additive
comprises MBIS.
[0019] According to yet another aspect of the present invention, a
process of electrodepositing at least one ferromagnetic metal into
a three dimensional pattern within a substrate is provided. The
process comprising: providing a substrate material comprising an
electrical conductive three dimensional recessed pattern in at
least one surface thereof; preparing an electrolytic bath
comprising at least one ferromagnetic metal cation selected from
the group consisting of N2+, Co2+, Fe2+, Fe3+, and combinations
thereof; mixing at least one accelerating, inhibiting, or
depolarizing additive into the electrolytic bath; placing the
electrical conductive pattern of the substrate into the
electrolytic bath; contacting the electrical conductive pattern of
the substrate with the electrolytic bath; placing a counter
electrode into the electrolytic bath; passing an electrical current
through the electrolytic bath between the electrical conductive
pattern of the substrate and the counter electrode; the electrical
current being passed between the electrical conductive pattern of
the substrate and the counter electrode is such that the potential
between the substrate and a reference electrode is at a value
negative of -0.8V SCE or at an applied current density in the range
of 0.1 to 50 mA/cm2 of the area of the electrically conductive
pattern of the substrate, or both; and depositing at least a
portion of the at least one ferromagnetic material into at least a
portion of the three dimensional pattern wherein the at least one
deposited ferromagnetic material is substantially void-free.
[0020] According to a further aspect of the present invention, a
process of electrodepositing at least one ferromagnetic material
into a three dimensional pattern within a substrate is provided.
The process comprising: providing a substrate material having an
electrical conductive portion with a three dimensional recessed
pattern; preparing an electrolytic bath comprising the at least one
ferromagnetic material and at least one accelerating, inhibiting,
or depolarizing additive; the at least one ferromagnetic material
comprising at least one metal cation selected from the group
consisting of N2+, Co2+, Fe2+, Fe3+, and combinations thereof;
placing the electrical conductive portion of the substrate into the
electrolytic bath; contacting the electrical conductive portion of
the substrate with the electrolytic bath; placing a counter
electrode into the electrolytic bath ; passing an electrical
current through the electrolytic bath between the electrical
conductive portion of the substrate and the counter electrode; and
depositing at least a portion of the at least one ferromagnetic
material into at least a portion of the three dimensional pattern
wherein the at least one deposited ferromagnetic material is
substantially void-free.
[0021] According to yet a further aspect of the present invention a
process of electrodepositing at least one ferromagnetic material
into a three dimensional pattern within a substrate is provided.
The process comprising: providing a substrate material having an
electrical conductive three dimensional recessed pattern in a
surface thereof; preparing an electrolytic bath comprising the at
least one ferromagnetic material and at least one accelerating,
inhibiting, or depolarizing additive; the at least one
ferromagnetic material comprising at least one metal cation
selected from the group consisting of N2+, Co2+, Fe2+, Fe3+, and
combinations thereof; the at least one accelerating, inhibiting, or
depolarizing additive comprising an additive selected from the
group consisting of polyethyleneimine,
2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof;
placing the electrical conductive three dimensional recessed
pattern in the substrate into the electrolytic bath; contacting the
electrical conductive three dimensional recessed pattern in the
substrate with the electrolytic bath; placing a counter electrode
into the electrolytic bath; passing an electrical current through
the electrolytic bath between the electrical conductive three
dimensional recessed pattern in the substrate and the counter
electrode; and depositing at least a portion of the at least one
ferromagnetic material into at least a portion of the three
dimensional recessed pattern in the substrate wherein the at least
one deposited ferromagnetic material is substantially
void-free.
[0022] According to another aspect of the present invention, the
process step of preferentially depositing the ferromagnetic
material into the three dimensional pattern results in a
superconformal deposition of the ferromagnetic material within the
three dimensional pattern.
[0023] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following drawings, description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1(a)-1(f) are schematic representations of different
plating structures at various stages of different electrodeposition
processes;
[0025] FIG. 2 is a series of field-emission scanning electron
microscopy (FESEM) images of 3-D structures showing the effect of
electrodeposition of Ni with an electrolytic solution containing
MBIS at different concentrations within different patterns;
[0026] FIG. 3 is a series of FESEM images of 3-D structures showing
the effect of electrodeposition of Ni with an electrolytic solution
containing MBIS at different time intervals within different
patterns;
[0027] FIG. 4 is a series FESEM images of 3-D structures showing
the effect of electrodeposition of Ni at different overpotentials
with an electrolytic solution containing MBIS within different
patterns;
[0028] FIG. 5 is a FIB-TEM image of 3-D structure showing the
morphology of Ni from the electrodeposition of Ni with an
electrolytic solution containing MBIS;
[0029] FIGS. 6(a)-6(f) are a series of FESEM images of 3-D
structures showing the effect of electrodeposition of Ni--Fe with
an electrolytic solution containing MBIS within different
patterns;
[0030] FIG. 7 is a series of FESEM images of 3-D structures showing
the effect of electrodeposition of Co with an electrolytic solution
containing MBIS within different patterns;
[0031] FIG. 8 is a series of FESEM images of 3-D structures showing
the effect of electrodeposition of Co with an electrolytic solution
containing MBIS at different time intervals within different
patterns;
[0032] FIG. 9 is a FIB-TEM image of 3-D structure showing the
morphology of Co from the electrodeposition of Co with an
electrolytic solution containing MBIS;
[0033] FIGS. 10(a)-10(f) are a series of FESEM images of 3-D
structures showing the effect of electrodeposition of Co--Fe with
an electrolytic solution containing MBIS within different
patterns;
[0034] FIGS. 11(a)-11(d) are a series of FESEM images of 3-D
structures showing the effect of electrodeposition of Ni with an
electrolytic solution containing no additive within different
patterns;
[0035] FIGS. 12(a)-12(c) are a series of FESEM images of 3-D
structures showing the effect of electrodeposition of Ni with an
electrolytic solution containing PEI within non-uniform
patterns;
[0036] FIGS. 13(a)-13(f) are a series of FESEM images of 3-D
structures showing the effect of electrodeposition of Ni with an
electrolytic solution containing PEI within different and
non-uniform patterns;
[0037] FIGS. 14(a)-14(d) are a series of FESEM images of 3-D
structures showing the inhomogeneity of Ni growth with the
electrodeposition of Ni with an electrolytic solution containing
PEI within non-uniform patterns;
DETAILED DESCRIPTION
[0038] The following detailed description is of the best currently
contemplated modes of carrying out the invention. The description
is not to be taken in a limiting sense, but is made merely for the
purpose of illustrating the general principles of the invention,
since the scope of the invention is best defined by the appended
claims.
[0039] Various inventive features are described below that can each
be used independently of one another or in combination with other
features. However, any single inventive feature may not address any
of the problems discussed above or may only address a subset of the
problems discussed above. Further, one or more of the problems
discussed above may not be fully addressed by any of the features
described below.
[0040] In at least one embodiment provided herein, a process for
bottom-up void-free filling of ferromagnetic materials within a 3-D
pattern in a substrate is provided. In at least one embodiment
provided herein, a process may provide void-free filling of
submicrometer 3-D patterns with at least one ferromagnetic
material. The products formed by the process may be suitable to
form products that may be useful as active device elements in
ultralarge-scale integration (ULSI) and micro-electromechanical
systems (MEMS). For example, 3-D structures associated with ULSI,
MEMS, 3-D packaging, actuators, ferromagnetic materials in
magnetoresistive random access memory, biomedical systems, magnetic
race track memories, contacts for semiconductors and related
devices, new semiconductor materials, electronic and spintronic
device architectures, active devices within other electronic
circuitry, and other devices as known in the art that may have an
application for the incorporation of ferromagnetic materials by
processes disclosed herein. Other products that may be produced by
the processes disclosed herein may include three-dimensional
batteries which represent a new approach for miniaturized power
sources that are purposely designed to maintain small footprint
areas and yet provide sufficient power and energy density to
operate autonomous devices. Such products are disclosed in
"Rethinking Multifunction in Three Dimensions for Miniaturizing
Electrical Energy Storage" by Bruce Dunn, Jeffrey W. Long, and
Debra R. Rolison, published in The Electrochemical Society
Interface, Fall 2008, incorporated herein in its entirety. It is
anticipated that other and additional applications of the processes
disclosed herein will become apparent to those skilled in the art
and the present disclosure shall not be limited to these examples
of products that may have applications for the presently disclosed
processes.
[0041] In addition to products benefitting from the magnetic
properties of materials deposited onto a substrate, aspects of the
invention may provide products with materials having desired
thermal expansion properties. For example, Fe--Ni INVAR alloys may
be deposited onto a patterned substrate in a void free manner which
may be beneficial for building micro-sensors, actuators, precision
instruments such as clocks, seismic creep gauges, television shadow
masks frames, valves in motors, antimagnetic watches, etc. Aspects
of the present disclosure may provide methods of building such
devices or other devices which may utilize the thermal expansion
properties of materials deposited onto a substrate. Methods of
aspects of the present disclosure may be incorporated into a
Damascene process with minimal cost.
[0042] A process of at least one embodiment herein may provide
three dimensional micromagnets for microelectromechanical devices
as well as active magnetic material components for use in a variety
of information storage devices. An embodiment may provide a means
for deposition of ferromagnetic metals as a precursor to forming
two-dimensional or three-dimensional silicide contacts in
microelectronics. In at least one embodiment provided herein, a
process may provide a variety of device geometries formed from
partially filling trenches, i.e., horseshoe magnets, or vias, i.e.,
magnetic cylinders. Trenches and vias may be completely filled and
may even provide embedded magnetically isolated structures in
nonferrous environments.
[0043] At least one embodiment disclosed herein provides void-free
filling of recessed surface features on non-planar conducting
surfaces with iron group magnetic materials. Specifically, the
addition of certain benzimidazole derivatives to a conventional
additive-free nickel plating baths, e.g. Watts bath
NiSO.sub.4--NiCl.sub.2 or sulfamate (SO.sub.3NH.sub.2--) bath may
result in a superconformal deposition growth mode which may provide
a manufacturable solution to problems associated with bottom-up
filling with the overall growth front propagating uniformly across
the work piece.
[0044] In at least one embodiment disclosed provides a process for
electrodepositing of ferromagnetic materials such as Ni, Co, Fe,
and alloys containing combinations thereof into trenches and/or
vias in a substrate, such as dielectric substrate containing Si or
some other element or compound. The process comprises a modified
damascene process wherein the substrate is first etched by
processes known in the art to form trenches and/or vias in a
surface thereof. This three dimensional structure may then prepared
with an adhesive material such as the physical vapor deposition of
a thin Ti adhesion layer. An electric conductive seed layer such as
Cu is then placed on the surface of the three dimensional structure
of trenches and/or vias by processes as known in the art. This
prepared substrate is then placed into an electrolytic bath
containing at least one ferromagnetic material and at least one
heterocyclic benzimidazole derivative such as MBIS. A counter
electrode is then placed into the Watts bath and an electrical
current is passed between the prepared substrate and the counter
electrode. The ferromagnetic material(s) are first preferentially
deposited at the bottom corners of the trenches and/or vias and
then the three dimensional structure in the substrate material is
filled by bottom-up filling. The filled substrate may then be
planarized to remove any overburden of the ferromagnetic
material(s). The process provides substantially void-free feature
filling of submicrometer trenches and/or vias in a dielectric
substrate with ferromagnetic materials. The product produced by
this process may be a multilevel interconnection having
ferromagnetic material(s) in trenches and/or vias with little or no
void space within the three dimensional structure.
[0045] In at least one embodiment, the substrate is electrically
conductive. Providing an electrically conductive substrate may
eliminate the steps of preparing the substrate with an adhesive
material and placing an electric conductive seed layer on the
surface of the three dimensional structure of trenches and/or
vias.
[0046] Examples of at least one embodiment are discussed in two
recently published articles. One of such articles is entitled,
"Electrodeposition of Ni in Submicrometer Trenches" by S.-K. Kim,
J. E. Bonevich, D. Josell, and T. P. Moffat, published in the
Journal of The Electrochemical Society 154 (9) D443-D451 (2007),
incorporated herein in its entirety. This article discusses the
effect of cationic, anionic, and nonionic surfactants on the rate
and morphological evolution of nickel electrodeposition. Attention
is given to the prospect for void-free filling of submicrometer
trenches. Cationic species such as polyethyleneimine (PEI) and
cetyl-trimethyl-ammonium (CTA+) were shown to yield significant
inhibition of nickel deposition. The other article entitled
"Magnetic Materials for Three-Dimensional Damascene Metallization:
Void-Free Electrodeposition of Ni and Ni.sub.70Fe.sub.30 Using
2-Mercapto-5-benzimidazolesulfonic Acid" by Chang Hwa Lee, John E.
Bonevich, Joseph E. Davies, and Thomas P. Moffat, published in the
Journal of The Electrochemical Society, 155 (7) D499-D507 (2008),
incorporated herein in its entirety. This article discusses
superconformal filling of submicrometer trenches with
electrodeposited ferromagnetic materials in an electrolyte
containing 2-mercapto-5-benzimidazolesulfonic acid (MBIS). The
process may offer the ability to build three-dimensional
magnetically active structures that may be easily integrated with
other state-of-the-art metallization schemes such as the Damascene
process.
[0047] In at least one embodiment provided herein, a process for
the electrodeposition of nickel, cobalt, iron, and alloys thereof
in 3-D structures in a dielectric material is provided. A process
of electrodepositing at least one ferromagnetic material into a
three dimensional pattern within a dielectric or metallic substrate
may comprise providing a dielectric or metallic substrate material
having a three dimensional recessed pattern in at least one outer
surface thereof. In the case of a dielectric substrate an
electrical conductive material is deposited onto the outer surface
having the 3-D pattern and within the three dimensional pattern
providing a wetting conductive seed layer on the substrate.
[0048] An electrolytic bath is prepared comprising at least one
ferromagnetic material and at least one accelerating, inhibiting,
or depolarizing additive. The at least one ferromagnetic material
has at least one of Ni.sup.2+, Co.sup.2+, Fe.sup.2+, Fe.sup.3+, and
combinations thereof. The dielectric substrate having the seed
layer is placed into the electrolytic bath where the electrolytic
bath contacts the at least one outer surface and the three
dimensional pattern having a seed layer in the case of a dielectric
substrate. A counter electrode is placed into the electrolytic bath
and an electrical current is passed through the electrolytic bath
between the seed layer on the substrate and the counter electrode.
At least a portion of the ferromagnetic material is deposited into
at least a portion of the three dimensional pattern wherein the
deposited ferromagnetic material is substantially void-free. The
electrodeposition step may provide superconformal filling of the
3-D pattern.
[0049] The at least one accelerating, inhibiting, or depolarizing
additive may comprise a nitrogen containing compound. Alternatively
or additionally, the at least one accelerating, inhibiting, or
depolarizing additive may have a compound selected from the group
consisting of cationic surfactants, anionic surfactants, nonionic
surfactants, heterocyclic benzimidazole derivatives, and
combinations thereof. Advantageously, the at least one
accelerating, inhibiting, or depolarizing additive may comprise a
compound selected from the group consisting of polyethyleneimine,
2-mercapto-5-benzimidazolesulfonic acid, and combinations thereof.
Alternatively or additionally, the at least one accelerating,
inhibiting, or depolarizing additive comprises polyethyleneimine.
Furthermore, the at least one accelerating, inhibiting, or
depolarizing additive may comprise
2-mercapto-5-benzimidazolesulfonic acid. Advantageously, the
process may provide superconformal filling of trenches, vias, and
other patterns within the dielectric substrate. It is to be
understood that other and different additives may be placed into
the electrolytic bath to provide void-free filling of the
electromagnetic material into the trenches and vias or 3-D
structure in the dielectric substrate and be within the scope of
the present invention.
[0050] Advantageously, the process disclosed herein may provide for
preferential deposition of the ferromagnetic material into the 3-D
pattern and more advantageously the process may provide for
superconformal deposition of the ferromagnetic material within the
three dimensional pattern.
[0051] At least one embodiment may provide a deposition process
that may allow void-free filling of recessed features with nickel
and related iron group alloys as well as cobalt and other alloys
and may be easily integrated with existing Damascene processes and
related tool sets. Superconformal void-free deposition of nickel,
cobalt, iron, and alloys thereof within a 3-D pattern with the
addition of heterocyclic compounds such as benzimidazole (BI),
benzotriazole (BTA), 2-mercaptobenzimidazole (MBI), a
2-mercapto-5-benzimidazolesulfonic acid (MBIS), and combinations
thereof may be achieved in a modified Damascene process.
[0052] A uniform growth profile of electromagnetic materials at the
pattern length scale of a given wafer may be achieved in at least
one process disclosed herein. The addition of heterocyclic
benzimidazole derivatives to the electrolytic bath may induce
void-free feature filling of submicrometer trenches with Ni, Co,
Fe, and alloys thereof for example. Superconformal filling of
submicrometer trenches with electrodeposited Ni may be accomplished
with an electrolytic bath comprising MBIS additions to a
conventional NiSO.sub.4--NiCl.sub.2--FeSO.sub.4 electrolytic
plating bath. The process may have the ability to build 3-D
magnetically active structures that may be easily integrated with
the conventional Damascene process as well as other
state-of-the-art metallization schemes. Although the disclosure is
not restricted to a particular mechanism, MBIS may act to inhibit
Ni(Fe) electrodeposition, for example, although under certain
conditions rapid, autocatalytic breakdown may accompany the onset
of Ni deposition. Optimal trench filling may be associated with the
positive feedback process, moderated by electrolyte
internal-resistance losses, and manifest as a hysteretic
voltammetric response on planar electrodes for an MBIS
concentration .about.100 .mu.mol/L, for example. On freshly
immersed substrates, trench filling may be characterized by an
initial period of uniform growth followed by the development of a
v-notch geometry which may be associated with transient depletion
of MBIS within the recessed feature. The finest submicrometer
features may be filled with only minimal deposition on the
neighboring free surface. Continued growth of the MBIS derived
v-notch geometry may result in void-free filling of the larger
features by geometrical leveling. Similar deposition of
electromagnetic materials, such as Fe, Ni-rich Ni--Fe alloys, Co
and Co--Fe alloys, for example, may be accomplished by at least one
embodiment. MBIS may not significantly perturb the low coercivity
of electromagnetic metals and alloys, which may be an important
attribute for prospective applications of processes disclosed
herein.
[0053] At least embodiment of a process disclosed herein may
provide a desired effect on the rate and morphological evolution of
ferromagnetic metal electrodeposition with the addition of
cationic, anionic, and nonionic surfactants to the electrolytic
bath. Cationic species such as polyethyleneimine (PEI) and
cetyl-trimethyl-ammonium (CTA+) may provide significant inhibition
of the deposition of magnetic metal, such as nickel, thereby
providing void-free filling of submicrometer trenches. For a range
of concentrations, single cationic surfactant systems may exhibit
hysteretic voltammetric curves that, when corrected for ohmic
electrolyte losses, may reveal an S-shaped negative differential
resistance. Void-free bottom-up superconformal feature filling may
be accomplished when operating at potentials within the hysteretic
regime whereby metal deposition begins preferentially in the most
densely patterned regions of the wafer followed by propagation of
the growth front laterally across the wafer surface. Alternatively,
at low overpotentials and concentrations, sulfur-bearing additives
such as thiourea (TU) may exert a depolarizing effect on nickel
deposition and negligible hysteresis. With a combination of PEI and
TU in an electrolytic bath, the suppression provided by PEI may be
diminished and feature filling may lead to more uniform deposition
on the wafer scale. Suitable combinations of PEI and TU may enable
near void-free filling of .gtoreq.230 nm wide trenches with sloping
(.about.3.5 degree inclination from vertical) sidewalls. Initial
conformal growth may be followed by geometric leveling once the
deposits on the sloping sidewalls meet. Feature filling with varied
morphological evolution may be provided with one or more embodiment
disclosed herein.
[0054] In at least embodiment, superconformal feature filling of Ni
in sub micrometer trenches with an electrolytic bath comprising
cationic surfactants, such as PEI, cetyl-trimethylammonium
chloride, and 4-picoline, may exert significant inhibition on Ni
electrodeposition at specific ranges of concentration and
overpotential. Cationic nitrogen bearing polymers that may capable
of generating superconformal feature filling having lateral
non-uniformities may be provided. In particular, the
polyelectrolyte PEI may give rise to a superconformal growth mode
whereby preferential deposition occurs at the bottom corners of the
trenches with almost negligible deposition occurring on the
neighboring free surface area, at least during the initial stages
of trench filling. Furthermore, the deposition process may be
highly heterogeneous at the pattern length scale whereby dense
arrays of narrower trenches may be filled followed by lateral
propagation of the growth front onto neighboring planar areas. An
aspect of this embodiment may provide a means to selectively fill
only the finest feature on a given level or layer while leaving the
large features open and available for deposition by a different
material such as Cu. In this aspect, Cu coils may be placed around
a ferromagnetic inductor all on one level of metallization, e.g. in
the context of Damascene processing. By appropriate patterning and
design, a variety of fully consolidated 3-D shapes and geometries
may be fabricated. The resulting structures may have potential use
as micromagnets for microelectromechanical devices as well as
active magnetic material components for use in a variety of
information storage devices. The process may also be useful in the
deposition of Ni and related metals as a precursor to forming
silicide contacts in microelectronics. The means to selectively
fill only the finest features on a given level or layer while
leaving the large features open and available for deposition by a
different material may provide for an array of metal structures
within a single layer, e.g. in the context of Damascene
processing.
[0055] FIGS. 1(a) through 1(f) show examples trench or via 2
filling within a dielectric substrate 1. The dielectric substrate 1
may be first metallized with an electric conductive material on the
surfaces adjacent to metal 3, not shown. FIG. 1(a) shows
subconformal filling of a metal 3 in trench or via 2 in a planar
region 4 of the dielectric substrate. The subconformal filling has
a greater deposition rate at pattern features such as at the top
edges 5 of trench or via 2. The subconformal growth shown in FIG.
1(a) may lead to voids 6 as shown in FIG. 1(b). As the
electrodeposition continues, the metal growth at top edges 5
continues until the metal 3 meets at point 8, forming void 6
therein as shown in FIG. 1(b). FIG. 1(c) shows an example of
conformal growth wherein metal 3 grows at a consistent rate on the
planar region 4 of the dielectric substrate, within trench or via
2, and at the top edges 5 of trench or via 2. Conformal growth as
shown in FIG. 1(c) may form a seam 8 as shown in FIG. 1(d). Seam 8
may be formed with the continued growth of metal 3 inward from the
sidewalls 7 of trench or via 2. FIG. 1(e) shows an example of
superconformal super-filling wherein metal 3 forms a "V-notch" 9
centrally oriented within trench or via 2. This is also referred to
as bottom-up filling and may produce a substantially uniform
filling of trench or via 2 with metal 3 as shown in FIG. 1(f). In
bottom up filling, metal deposition occurs preferentially in
recessed surface features, such as patterned trenches and vias 2,
thereby resulting in void-free filling, as shown in FIG. 1(f). On
freshly immersed substrates, trench filling may be characterized by
an initial period of uniform growth as shown in FIG. 1(e) followed
by the development of "v-notch" 9 geometry which may be associated
with transient depletion of an additive such as MBIS or PEI within
the recessed feature, trench or via 2. The finest submicrometer
features may be filled with only minimal deposition on the
neighboring free surfaces 10, as shown in FIG. 1(e).
EXAMPLES
[0056] The following examples are included to demonstrate
embodiments of the invention. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples that
follow represent techniques discovered by the inventors to function
in the practice of the invention, and thus can be considered to
constitute selected modes for its practice. However, those of skill
in the art should, in light of the present disclosure, appreciate
that many changes can be made in the specific embodiments that are
disclosed and still obtain a like or similar result without
departing from the spirit and scope of the invention.
Example 1
[0057] Void-free Ni deposition was shown onto a dielectric
substrate. Nickel was eletrodeposited from an electrolytic bath
comprising of 1.0 mol/L NiSO.sub.4.6H.sub.2O, 0.2 mol/L
NiCl.sub.2.6H.sub.2O, and 0.5 mol/L H.sub.3BO.sub.3, with pH 2.5 as
a base electrolyte. Separate electrolytic solutions were prepared
by adding different concentrations of MBIS, from 0 to 400
.mu.mol/L, to the base electrolyte. The sodium salt dihydrate of
MBIS, C.sub.7H.sub.5N.sub.2NaO.sub.3S.sub.2.2H.sub.2O, manufactured
by Aldrich, was used. Both planar and patterned Cu seeded Si wafers
were used as working electrodes for electrochemical analyses and
film growth. The specimens were prepared by physical vapor
deposition of a thin Ti adhesion layer followed by 100 nm of Cu.
The trenches including the barrier layer were 670 nm deep, and the
widths varied from 590 to 90 nm at the bottom and from 720 to 120
nm at the top, corresponding to sloping sidewall angle that ranged
from 6 to 2 degrees from vertical. On the basis of the average
width, the features range from 6.4 to 1.0 in aspect ratio (height
divided by average width). In this example, features are specified
by the respective bottom width.
[0058] The working electrodes were sealed with a Teflon holder
having an exposed area of 1.28 cm , facing up to the electrolyte in
order to facilitate removal of any hydrogen gas associated with
deposition. The Pt counter electrode was formed as a circular wire
of similar radius to, and suspended above, the working electrode. A
saturated calomel reference electrode (SCE) was firmly positioned
with respect to the working and counter electrode in a Teflon jig,
thereby fixing the electrical distribution and resulting
internal-resistance iR effects between different solutions. For
feature filling examples, the trench and via patterned wafer
specimens were immersed at a preset growth potential.
Field-emission scanning electron microscopy (FESEM) was used to
examine cross sectional profiles of the trench filling.
Transmission electron microscopy (TEM) was used to more closely
examine the microstructure of an array of Ni-filled trenches. The
specimen was prepared by focused ion-beam FIB sectioning. X-ray
diffraction (XRD) and atomic force microscopy (AFM) were used to
examine the crystallographic texture and the surface morphology of
the Ni films grown on planar substrates. The magnetic properties of
planar Ni and Ni--Fe films were examined by vibrating sample
magnetometer (VSM) and the saturated magnetic moment, coercivity
and squareness were evaluated as a function of MBIS concentration.
Specimens were prepared by cleaving to obtain square-shaped
samples. The specimen area and thickness were measured by an
optical scanner and FESEM, respectively.
[0059] Ni deposition from the additive-free electrolytic bath was
examined by cyclic voltammetry (CV). The onset of metal deposition
was evident near 0.7 V, followed by a rapid increase in the current
with the applied potential that tends toward a linear response at
higher current densities.
[0060] A series of samples were feature filled as a function of
MBIS concentration. Ni was deposited at -0.925 V SCE (i.e., voltage
defined relative to saturated calumel reference electrode, SCE) for
3 min, and then the specimens were cross sectioned for FESEM
analysis. Images of trench arrays with four different dimensions
are shown in FIG. 2 wherein trench widths of 520 nm are shown in
column (1), trench widths of 260 nm are shown in column (2), trench
widths of 150 nm are shown in column (3), and trench widths of 90
nm are shown in column (4). The trench widths are reported as the
dimension of the bottom of the trench and these different
dimensions offer a representative sample of filling behavior. The
concentrations of MBIS were 0 .mu.mol/L, shown in row (a), 50
.mu.mol/L, shown in row (b), 80 .mu.mol/L, shown in row (c), 100
.mu.mol/L, shown in row (d), and 150 .mu.mol/L, shown in row (e).
The dark contrast 103 at the bottom 118 of the trench 102 and on
the free surface 104 between the trenches is associated with the
copper seed layer. In the absence of MBIS, a large seam 106 is
apparent in the narrowest trenches, shown in FIG. 2, column (4),
while voids are sometimes evident at the top of all but the widest
features, as in row (a) of FIG. 2. The upper surface 110 of the
deposition on free surface 104 is also notably rough relative to
the dimension of the trenches 102 and overburden 112. Thus,
conformal deposition coupled with high surface roughness may lead
to the formation of voids and/or seams 106 when the rough opposing
side walls impinge.
[0061] Deposition in the presence of 50 .mu.mol/L MBIS, shown in
row (b) of FIG. 2, results in smoother overburden 110 above the
widest trench, as shown in FIG. 2, row (b), column (1); however,
centerline voids and/or seams 106 appear near the top of the
smallest trenches shown in column (4). Increasing the MBIS
concentration to 80 .mu.mol/L, shown in row (c) of FIG. 2, yields a
smoother free surface 110; however, voids and/or seams 106 are
still evident at the top of finest trenches shown in row (c),
column (4), although they are smaller than for the 50 .mu.mol/L
shown in row (b) of FIG. 2. A further increase in the MBIS
concentration to 100 .mu.mol/L, shown in row (d) of FIG. 2, leads
to void-free filling for all features shown. Comparison between the
additive-free, 50, 80, and 100 .mu.mol/MBIS concentrations shown in
rows (a), (b), (c), and (d) respectively, performed for the same
duration and potential, show progressively less overburden 112
above the filled features 102, which may show the inhibition
provided by MBIS. This effect is most notable over the widest
features, shown in column (1) of FIG. 2. A further increase of MBIS
concentration to 150 .mu.mol/L, shown in row (e) of FIG. 2, was
shown to lead to a sharp decrease in the overall deposition rate.
In row (e) of FIG. 2, very limited deposition occurred on the free
surface 104 while substantial filling of the trenches 102 occurred.
The smaller trenches 102 shown in columns (2)-(4) of FIG. 2, row
(e), are completely filled while the growth front in the widest
features shown in column (1) of FIG. 2, row (e), has a well-defined
v-notch shape 114. This shows a superconformal film growth mode in
column (1), row (e), of FIG. 2; whereby the effect of a linear
gradient of the sidewall 116 growth velocity with trench depth is
evident and deposition at the bottom 118 of the trench 102 is
substantially progressed compared to the neighboring free surface
104.
[0062] In order to show a more detailed view of shape evolution
during feature filling, a series of samples were examined as a
function of deposition time at -0.925 V SCE in the 100 .mu.mol/L
MBIS electrolytic solution. The results for five different trench
widths as shown in FIG. 3 wherein row (a) has a trench width of 590
nm, row (b) has a trench width of 520 nm, row (c) has a trench
width of 305 nm, row (d) has a trench width of 160 nm, and row (e)
has a trench width of 130 nm. For reference purposes, the Cu-seeded
substrate t=0 is shown prior to Ni deposition in the column (1) of
FIG. 3 for each trench width. The columns, from left to right, show
the deposition of Ni after 0 seconds in column (1), 25 seconds in
column (2), 50 seconds in column (3), 100 seconds in column (4),
150 seconds in column (5), 200 seconds in column (6), and 300
seconds respectively in column (7). The buildup of Cu 202 on the
top 204 and bottom 206 surfaces, relative to the sidewalls 208,
reflects the nature and limitations of the physical vapor
deposition or sputtering process used to form the seed layer 210.
Examination of the filling images after 25 seconds of deposition
show a substantially conformal Ni layer 212 along the entire
surface profile, where the height 214 of the bottom surface 206 and
the sidewall 208 thickness 216 are almost the same. The extent of
Ni deposition in the recessed regions 218 may be compared to the
integrated deposition charge derived from the chronoamperometry
transient. Because the surface area changes significantly during
feature filling, a comparison of nominal thickness value may be
only considered for the first 25 seconds and the last 100 seconds
from 200 to 300 seconds, assuming that there is minor area change
occurring for the respective cases.
[0063] Between 25 seconds and 50 seconds, shown in column (2) and
column (3) respectively, the two finest features, shown in rows (d)
and (e), are shown to be filled while almost negligible Ni
deposition has occurred on the top surface 204. The geometry of the
feature filling is such that electrode area change effects may be
most strongly during the filling of the smallest and highest aspect
ratio features. In the three wider trenches shown in rows (a), (b),
and (c), a gradient in the deposition rate on the sidewalls 208 has
clearly developed as a function of width, similar to that noted
earlier in row (e) of FIG. 2 The amount of Ni deposited on the
bottom surface 206 is shown to be substantially the same to that on
the sidewalls 208 immediately adjacent to the bottom 206. Notably,
the amount of Ni deposited on the sidewalls 208 of the larger
features may exceed half of the width of the two narrowest
trenches, shown in rows (d) and (e), consistent with those features
which may have already been filled by sidewall collision, followed
by a geometric zipping process The transient depletion of MBIS
within the trench may result in the sloping sidewalls or v-notch
shape and may be critical to the overall void-free filling
process.
[0064] Between 50 seconds and 100 seconds, as shown in columns (3)
and (4) of FIG. 3, growth continues on the bottom 206 and sidewalls
208 of the 305 nm wide trench shown in row (c) of FIG. 3. The slope
associated with sidewalls 208 did not change substantially between
50 seconds and 100 seconds, as shown in columns (3) and (4), row
(c), of FIG. 3. This may show a transition back to a conformal
growth mode as reflected by the constant sidewall growth velocity
during this time increment. Evolution of the growth front in the
widest trench, shown in row (a) of FIG. 3, may also support this.
In the absence of any compositional gradients, continued growth on
such a v-notched surface geometry may result in a planar surface by
an effect known as geometrical leveling. Indeed, following trench
filling, significant growth is shown to begin on the adjacent free
surface 204 and the remaining cusp shape in the larger features is
filled congruent with geometric leveling.
[0065] FIG. 3 shows that trench filling may be associated with
three stages, a brief period of near conformal growth, followed by
the development of sloping sidewalls, and the subsequent onset of
impingement of opposing sidewalls. The remaining cusp or v-notch
shape may then be filled by geometric leveling. A key role of MBIS
may be the development of sloping sidewalls, which may be
associated with transient depletion of the MBIS flux within the
trench. Deposition in the presence of MBIS was shown to be
substantially uniform on the pattern density length scale, making
the MBIS process a viable manufacturing solution in the context of
conventional Damascene processing
[0066] The potential dependence of trench filling is shown in FIG.
4 for a fixed MBIS concentration of 100 .mu.mol/L and a fixed
deposition time of 300 seconds. The results for four different
trench widths as shown in FIG. 4 wherein column (1) has a trench
width of 520 nm, column (2) has a trench width of 305 nm, column
(3) has a trench width of 160 nm, and column (4) has a trench width
of 90 nm. The rows, from top to bottom, show the deposition
potential wherein row (a) has an potential of -0.850 V SCE, row (b)
has an potential of -0.875 V SCE, row (c) has an potential of
-0.900 V SCE, row (d) has an potential of -0.925 V SCE, and row (e)
has an potential of -0.950 V SCE.
[0067] At -0.850 V SCE, shown in row (a) of FIG. 4, the deposition
potential was so low that the transition to the activated surface
300 and the MBIS passivated one is substantially negligible.
Deposition on the trench pattern was limited, but preceded
conformally, and the roughness that developed on the sidewalls 308
of the finest feature in column (4) of FIG. 4 lead to incipient
occlusion of voids 315 along the centerline of the finest features,
as shown in row (a), column (4) of FIG. 4. Increasing the
overpotential by 0.025 V to -0.875 V SCE placed the system within
the positive feedback hysteretic voltammetric regime. Void-free
filling of the finest features was shown along with the development
of sloping sidewalls 308 in the wider trenches, as shown in row (b)
of FIG. 4. When the overpotential is increased further by 0.025 V
to -0.900 V SCE, sloping sidewalls 317 are readily evident in the
widest trench shown in row (c), column (1) of FIG. 4 while the
remaining trenches are filled and void-free, as shown in row (c),
columns (2)-(4) of FIG. 4. For growth at -0.925 V SCE and -0.950 V
SCE, all features are shown to be void-free and the overburden
thickness 313 increased sharply as shown in rows (d) and (e) of
FIG. 4.
[0068] FIG. 5 shows a FIB-TEM cross sectional image of a 160 nm
width trench filled by Ni electrodeposition in the presence of 100
.mu.mol/L MBIS where the deposition was performed at -0.925 V SCE
for 150 seconds. FIG. 5 shows that the addition of MBIS enables
void-free trench filling. FIG. 5 shows that the volume of materials
associated with the free surface 404 between the trenches 401 is
mostly Cu 403, which is only covered with a thin 25 nm thick Ni
layer 405. In contrast, the 160 nm wide trench 401 is entirely
filled with Ni 402 and free of any obvious voids. A microstructural
seam 407 may exist along the top two-thirds of the trench. This
seam 407 or consolidated boundary may be formed during deposition
in a manner analogous to grain boundary generation associated with
grain coalescence during Volmer-Weber film growth. The bright-field
contrast shows an average grain size on the order of about 30-40
nm, although certain grains are shown to be larger with
well-defined twins or stacking faults evident.
Example 2
[0069] Void-free Ni--Fe deposition was shown onto a dielectric
substrate 500 is shown in FIGS. 6(a)-(e). The extension and
efficacy of MBIS for inducing superconformal deposition of Ni--Fe
alloys is shown. Permalloy, a Ni.sub.80Fe.sub.20 alloy that has a
rich history in the development of magnetic storage devices was
electrodeposited onto a dielectric substrate 500 with the process
of Example 1. The electrolytic bath comprised 1 mol/L
NiSO.sub.4.6H.sub.20+0.2 mol/L NiCl.sub.2.6H.sub.2O+0.05 mol/L
FeSO.sub.4+0.5 mol/L H.sub.3BO.sub.3. 100 .mu.mol/L of MBIS was
added to the solution and the Ni--Fe alloy was electroplated onto
the 3-D seeded surfaces of the dielectric substrates with an
electric potential of about -0.950 V (SCE) for about 300 seconds.
Cross-sectional FESEM images of various patterned trenches showing
the deposition of the Ni--Fe alloy 502 are shown in FIGS. 6(a)-(e).
Void-free feature filling is clearly shown in each pattern in FIGS.
6(a)-(e). The presence of iron in the electrolytic solution showed
a decrease in the deposition rate as compared to that of Example 1.
The magnetic properties of the Ni--Fe alloy films were shown not to
be significantly altered by MBIS additions in the plating bath.
Example 3
[0070] Void-free Co deposition was shown onto a patterned
substrate. The effect of MBIS for inducing void-free deposition of
cobalt is shown in FIGS. 7-9. Cobalt was electrodeposited onto a
dielectric substrate with the process of Example 1. The
electrolytic bath comprised 0.4 mol/L CoSO.sub.47H.sub.2O+0.01
mol/L CoCl.sub.2+0.5 mol/L H.sub.3BO.sub.3. Various amounts of MBIS
were added to the solution and the Co was electroplated onto the
3-D surfaces of the substrates with various electric potentials for
various periods of time.
[0071] FIG. 7 shows cross-sectional FESEM images of various
patterned trenches showing the deposition of Co 602 in an
additive-free deposition at -0.86 V for 300 seconds in rows (a) and
(b) for various trench widths, ranging between 720 and 90 nm. Rows
(c) and (d) show the deposition of cobalt 602 with an electrolytic
solution comprising 200 .mu.mol/L MBIS at -0.86 V for 300 seconds
for various trench widths, ranging between 720 and 90 nm. The
smaller trenches in the additive-free deposition have void spaces
615, as shown in row (a) column (3) and row (b) columns (1)-(3), of
FIG. 7. This is contrasted with the void-free deposition of Co 602
shown in each trench in rows (c) and (d), having MBIS.
[0072] FIG. 8 shows the deposition of cobalt 602 with an
electrolytic solution comprising 200 .mu.mol/L MBIS at -0.87 V for
25 seconds in column (1), 50 seconds in column (2), 100 seconds in
column (3), 180 seconds in column (4), and 300 seconds in column
(5) for various trench widths in each row (a)-(e). The trench
widths in FIG. 8 are as follows; row (a) had a trench width of 720
nm, row (b) had a trench width of 280 nm, row (c) had a trench
width of 215 nm, row (d) had a trench width of 200 nm, and row (e)
had a trench width of 140 nm. Void free deposition of Co 602 in a
range of trench widths was shown. In each pattern shown in rows
(a)-(e), superconformal filling of Co 602 was exhibited as
shown.
[0073] FIG. 9 shows TEM for Co 602 filling using the process of
Example 1. The electrolytic bath comprised 200 .mu.mol/L MBIS and
the Co 602 was deposited onto the dielectric substrate 601 at an
overpotential of -0.86 V SCE. The TEM shows that the
micro-structure is void-free with a low density grain boundary
marking the 603 center line.
Example 4
[0074] Void-free Co--Fe deposition was shown onto a patterned
substrates. FIGS. 10(a)-(f) show Co.sub.80Fe.sub.20 702 trench
filling using the process of Example 1 but in a base electrolyte of
0.4 mol/L CoSO.sub.4.sup.-7H.sub.2O+0.01 mol/L CoCl.sub.2+0.5 mol/L
H.sub.3BO.sub.3+0.01 mol/L FeSO.sub.4. The electrolytic bath
contained 200 .mu.mol/L MBIS and the alloy was deposited onto the
patterned dielectric substrates 703 at an overpotential of -0.87 V
for 300 seconds. The patterns varied, having trench widths between
726 nm in FIG. 10(a) and 134 nm in FIG. 10(f). A superconformal
void-free deposition of Co.sub.80Fe.sub.20 702 was shown in each of
the patterns of FIG. 10(f).
[0075] In each of the Examples 1-4, the addition of MBIS to the
electrolytic solution yielded a smoother outer surface with little
or no measurable effect on the saturated magnetization (Ms) of the
ferromagnetic materials deposited onto the dielectric
substrate.
[0076] Examples 1-4 show superconformal electrodeposition of Ni,
Ni--Fe, Co, and Co--Fe alloys using a single benzimidazole
derivative, MBIS, as an additive to the respective sulfate/chloride
mixed electrolyte. The process may offer integration of the
ferromagnetic materials into Damascene processes,
microelectromechanical systems and related thin-film derived
technologies. Feature filling at potentials within the
voltammetrically identified critical regimes resulted in void-free
superconformal film growth. For freshly immersed specimens, trench
filling initially proceeded with a period of conformal growth
followed by the development of sloping sidewalls which may be
associated with transient depletion of MBIS within the recessed
features. The resulting v-notch growth front then evolved in a
manner that is difficult to distinguish from geometric leveling.
Stabilization of the feature filling process within the
voltammetrically identified critical domain is provided by a
decrease in the overpotential for metal deposition that accompanies
the flow of current in the resistive electrolyte.
Example 5
[0077] A survey of the effect of various electrolyte additives on
the nickel deposition kinetics, as revealed by voltammetric and
chrono-amperometric measurements was conducted. The effect of
molecular size and function on the metal deposition were examined.
Potential suppressor or rate inhibiting species included were
dodecyltrimethylammonium chloride [DTAC,
CH.sub.3(CH.sub.2).sub.11N.sup.+(CH.sub.3).sub.3Cl.sup.-;
manufactured by Fluka], dodecyltrimethylammonium bromide [DTAC,
CH.sub.3(CH.sub.2).sub.11N.sup.+(CH.sub.3).sub.3Br.sup.-;
manufactured by Fluka]; sodium dodecyl sulfate [SDS, ,
CH.sub.3(CH.sub.2).sub.11OSO.sub.3.sup.-Na.sup.+; manufactured by
Fisher], 2-butyne-1,4-diol [2-B-1,4-D, HOCH.sub.2C.dbd.CCH.sub.2OH,
manufactured by Aldrich], saccharin [C.sub.7H.sub.5N0.sub.3S,
manufactured by Aldrich], sodium benzenesulfonate [SBS,
C.sub.6H.sub.5SO.sub.3.sup.-Na.sup.+, manufactured by Aldrich],
cetyltrimethylammonium chloride [CTAC,
CH.sub.3(CH.sub.2).sub.15N.sup.+(CH.sub.3).sub.3Cl.sup.-;
manufactured by Alfa Aesar], polyethyleneimine
{PEI,-[NH.sub.2.sup.+CH.sub.2CH.sub.2NH.sup.+(CH.sub.2CH.sub.2NH.sub.3.su-
p.+)CH.sub.2CH.sub.2.sup.-].sub.n, 1800 Mw; branched, manufactured
by Fluka Alfa Aesarl}, 4-picoline (CH.sub.3C.sub.5H.sub.4N,
manufactured by Alfa Aesar), polyethylene glycol [PEG,
(--CH.sub.2CH.sub.2O--).sub.n, 3400 Mw; manufactured by Aldrich).
Some sulfur-containing organic additives, such as thiourea (TU,
H.sub.2NCSNH.sub.2, manufactured by Alfa Aesar),
3-mercapto-1-propane sulfonic acid, sodium salt [MPS,
HS(CH.sub.2).sub.3SO.sub.3--Na.sup.+, manufactured by Raschig],
bis(3-sulfopropyl) disulfide, sodium salt [SPS,
Na.sub.2.sup.+(SO.sub.3.sup.-(CH.sub.2).sub.3S).sub.2, manufactured
by Raschig], and 3-N,N-dimethylaminodithiocarbamoyl-1-propane
sulfonic acid, sodium salt [DPS,
Na.sup.+SO.sub.3.sup.-(CH.sub.2).sub.3SCSN (CH.sub.3).sub.2,
manufactured by Raschig] were investigated as potential
accelerating or depolarizing additives.
[0078] This example shows feature filling with a range of effects
on morphological evolution. Filling examples were performed at
potentials and current densities where negligible depletion of the
nickel cations occurred. The following examples were performed at
pH 3, which minimized the parasitic effects of hydrogen evolution
on the voltammetric measurements and avoided potential
complications associated with the H.sub.2 bubbles that form readily
in more acidic electrolytes.
[0079] Ni electrodeposition onto a dielectric substrate metallized
with thin Cu seed layer was performed with an electrolytic bath
comprising 1 mol/L NiS0.sub.4.6H.sub.2O, 0.2 mol/L
NiCl.sub.2.6H.sub.2O, and 0.5 mol/L H.sub.3B0.sub.3 dissolved in 18
M.OMEGA. cm deionized water. A nickel plate and a saturated calomel
electrode (SCE) were used as the counter and reference electrodes,
respectively. The cell for the electrochemical experiments was a
Teflon cylinder of 5 cm diameter and 8.5 cm height with parallel,
vertically oriented working and counter electrodes separated by a
distance of 1.3 cm. The SCE reference electrode was fixed midway
between the working and counter electrode but laterally positioned
so as not to interfere with the current distribution between the
other electrodes. A distance of 1.8 cm separated the working and
reference electrode and impedance measurements revealed an
uncompensated ohmic resistance of 9.35 .OMEGA.cm.sup.2.
[0080] The concentrations of the suppressors were fixed at 100
.mu.mol/L with the exception of PEI which was found to exhibit
similar inhibition as the other additives at much lower
concentrations. In order to more fully characterize the effect of
PEI the concentration was varied from 2 to 200 .mu.mol/L. For
comparison to the rate-suppressing additives, accelerating
sulfur-bearing species were surveyed using a fixed concentration of
100 .mu.mol/L. Feature filling was examined using Cu-seeded
trenches approximately 770 nm deep and 5 .mu.m to 210 nm wide to
probe the effect of the suppressing and accelerating additives as
well as combinations thereof. Depositions were conducted at -0.9 V
vs. SCE for 3 min in the base electrolyte with designated
concentrations of the additives. In order to minimize seed-layer
corrosion, the specimens were immersed into the electrolyte with
the potential applied. Feature filling was also examined as a
function of deposition time. Specimen cross sections obtained by
mechanical polishing followed by ion milling were examined by field
emission scanning electron microscopy (FESEM). A subset of samples
was also prepared by a single-step focus ion beam milling and
examined by SEM. Filled features were also examined by transmission
electron microscopy of cross sections prepared using traditional
dimpling and ion-milling methods.
[0081] PEI was shown to exhibit superior void-free feature filling
over the other additives screened. For context the results are
compared to those obtained from an additive-free nickel plating
electrolyte.
[0082] FIG. 11 shows a cross-sectional image of a Ni
electrodeposition grown in additive-free solution for 3 min at -0.9
V SCE. Ni was deposited on 5 .mu.m wide trenches 802, 700 nm wide
trenches 804, 400 nm wide trenches 806 and 230 nm wide trenches
808. The Ni deposit 810 on the 5 .mu.m wide trench 802 was
conformal. The slightly smaller thickness 812 on the sidewalls 814
reflects the difference between the seed-layer 816 thickness on the
sidewalls 814 versus the free surface 818 and bottom 820 due to
line-of-sight constraints during physical vapor deposition (PVD)
preparation. The growth front exhibits noticeable roughness 822.
The two widest, low-aspect-ratio trenches 802 and 804 may be
void-free while voids 824 are clearly evident in the narrower
high-aspect-ratio features of trenches 806 and 808, shown in FIGS.
11(c) and 11(d).
[0083] Additions of PEI were shown to induce significant changes in
the feature-filling dynamics. Conformal filling of an .about.1
.mu.m wide trench 902 in the additive-free electrolyte is shown in
FIG. 12a. The addition of 5 .mu.mol/L PEI yields superconformal
film growth, as shown in FIG. 12b, by preferential deposition at
the bottom 904 and on the deeper sections of the sidewall surfaces
906 of trench 904, while more limited deposition occurs on the
neighboring wall surface 908. Preferential deposition of nickel is
also evident in the bottom corners 910 of the larger features such
as that shown in FIG. 12(c). It is shown that void-free filling of
the trenches 904 may persists up to an aspect ratio of at least 2.3
for a mid-height trench width greater than 300 nm.
[0084] Ni electrodeposition grown in an electrolytic bath
comprising 10 .mu.mol/L PEI for 3 min at -0.9 V showed further
evidence of preferential deposition toward the bottoms of the finer
features, as shown in FIG. 13(a)-FIG. 13(c). The sloping deposits
on the sidewalls 1002 suggests a PEI depletion effect in the higher
aspect ratio features that may be congruent with a
consumption-driven leveler depletion mechanism, as shown in FIG.
13(b). Limited nickel deposition occurs on the top surfaces 1004,
1006, 1008, and 1010 between the trenches 1005, 1007, 1009, and
1011, as shown in FIG. 13(a)-FIG. 13(d) such that the convex bumps
1012, 1014, 1016, and 1018 are substantially comprised of the
copper seed layer. In FIG. 13(e), feature filling and planarity are
obtained with modest overburden 1020. However, significant
dispersion in the feature-filling dynamics was shown in FIG.
13(f).
[0085] In addition to the superconformal feature-filling mode,
deposition from 10 .mu.mol/L PEI electrolyte showed a variety of
interesting pattern--density-dependent effects. For example,
specimens grown at -0.9 V SCE for 3 min showed multiple examples of
preferential nucleation and bottom-up growth occurring in the
finest and most densely packed trench arrays with negligible
deposition evident on neighboring planar or lower feature density
regions. Four examples of this behavior are shown in FIGS.
14(a)-14(d). These figures show distinct active and passive areas.
The inhomogeneity in growth, a manifestation of self-patterning,
enables selective deposition triggered by the nonuniform substrate
topography. For example, FIG. 14(d) shows a greater film growth
proximate the center of the pattern and lesser film growth
proximate each end of the pattern.
[0086] Cationic species such as protonated, nitrogen-bearing PEI
were shown to substantially inhibit Ni deposition. The addition of
PEI to the electrolytic bath was shown to yield bottom-up
superconformal feature-filling that also included pattern scale
effects whereby feature filling began preferentially in the most
densely patterned (high-surface area) regions and was followed by
lateral propagation of the metal nucleation and growth fonts.
Patterning and designing a three dimensional recess in a dielectric
substrate may provide a desired three dimensional shapes and
configurations of a ferromagnetic material deposited on the
dielectric substrate.
[0087] The addition of PEI to the electrolytic bath provided a
deposition of the magnetic material with a smooth outer surface and
little or no measurable effect on the magnetic properties.
[0088] It should be understood that the foregoing relates to
exemplary aspects of the invention and that modifications may be
made without departing from the spirit and scope of the invention
as set forth in the following claims.
* * * * *