U.S. patent application number 09/990486 was filed with the patent office on 2002-05-16 for ruthenium and ruthenium dioxide removal method and material.
Invention is credited to Westmoreland, Donald L..
Application Number | 20020056701 09/990486 |
Document ID | / |
Family ID | 22517057 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020056701 |
Kind Code |
A1 |
Westmoreland, Donald L. |
May 16, 2002 |
Ruthenium and ruthenium dioxide removal method and material
Abstract
A method for removing at least a portion of a structure, such as
a layer, film, or deposit, including ruthenium metal and/or
ruthenium dioxide includes contacting the structure with a material
including ceric ammonium nitrate. A material for removing ruthenium
metal and amorphous ruthenium dioxide includes ceric ammonium
nitrate and may be in the form of an aqueous solution including
ceric ammonium nitrate and, optionally, other solid or liquid
solutes providing desired properties. In one application, the
method and material may be utilized to etch, shape, or pattern
layers or films of ruthenium metal and/or ruthenium dioxide in the
fabrication of semiconductor systems and their elements,
components, and devices, such as wires, electrical contacts, word
lines, bit lines, interconnects, vias, electrodes, capacitors,
transistors, diodes, and memory devices.
Inventors: |
Westmoreland, Donald L.;
(Boise, ID) |
Correspondence
Address: |
KIRKPATRICK & LOCKHART LLP
535 SMITHFIELD STREET
PITTSBURGH
PA
15222
US
|
Family ID: |
22517057 |
Appl. No.: |
09/990486 |
Filed: |
November 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09990486 |
Nov 16, 2001 |
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09675635 |
Sep 29, 2000 |
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09675635 |
Sep 29, 2000 |
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09146365 |
Sep 3, 1998 |
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6143192 |
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Current U.S.
Class: |
216/89 ; 216/101;
252/79.1; 257/E21.309 |
Current CPC
Class: |
H01L 21/32134 20130101;
Y02P 10/214 20151101; Y02P 10/20 20151101; C23C 16/4407 20130101;
C22B 11/046 20130101; C23F 1/30 20130101 |
Class at
Publication: |
216/89 ; 216/101;
252/79.1 |
International
Class: |
C23F 001/00 |
Claims
I claim:
1. A method for removing at least a portion of a structure
comprising ruthenium, the method comprising contacting the
structure with a material comprising ceric ammonium nitrate.
2. The method of claim 1 wherein the structure consists of
ruthenium metal.
3. The method of claim 1 wherein the structure consists of
amorphous ruthenium dioxide.
4. The method of claim 1 wherein the structure is selected from the
group consisting of a layer and a film.
5. The method of claim 1 wherein the material is a solution further
comprising liquid water.
6. The method of claim 1 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
7. The method of claim 6 wherein the solution further comprises
water and acetic acid.
8. The method of claim 7 wherein the solution consists of about 30
weight percent ceric ammonium nitrate, about 10 weight percent
acetic acid, and about 60 weight percent water.
9. The method of claim 5 wherein the solution is at approximately
room temperature.
10. The method of claim 5 wherein the act of contacting at least a
surface of the structure with the solution comprises immersing at
least a portion of the structure in the solution.
11. The method of claim 1 wherein the structure is disposed on at
least a portion of a substrate.
12. The method of claim 11 wherein the substrate comprises a
material selected from the group consisting of silicon, SiO.sub.2,
and BPSG.
13. The method of claim 1 wherein the structure is disposed on at
least a portion of an object.
14. The method of claim 13 wherein the object is selected from the
group consisting of a tool, a part, a component, a window, a plate,
a shield, a shower head, a collimator, and a chamber wall.
15. The method of claim 1 wherein the structure is selected from
the group consisting of a layer, a film, or a deposit.
16. A method for removing at least a portion of a ruthenium metal
structure, the method comprising contacting at least a region of a
surface of the ruthenium metal structure with a solution comprising
ceric ammonium nitrate.
17. The method of claim 16 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
18. The method of claim 16 wherein the solution further comprises
liquid water.
19. The method of claim 18 wherein the solution further comprises
acetic acid.
20. The method of claim 19 wherein the solution consists of about
30 weight percent ceric ammonium nitrate, about 10 weight percent
acetic acid, and about 60 weight percent water.
21. The method of claim 16 wherein the ruthenium metal layer is
disposed on at least a portion of a substrate.
22. The method of claim 21 wherein the substrate comprises a
material selected from the group consisting of silicon, SiO.sub.2,
and BPSG.
23. The method of claim 15 wherein the structure is disposed on at
least a portion of an object.
24. The method of claim 23 wherein the object is selected from the
group consisting of a tool, a part, a component, a window, a plate,
a shield, a shower head, a collimator, and a chamber wall.
25. The method of claim 16 wherein the act of contacting at least a
region of a surface of the ruthenium metal layer with the liquid
comprises immersing the region of the surface in the solution.
26. A method for removing at least a portion of an amorphous
ruthenium dioxide layer, the method comprising contacting at least
a region of a surface of the ruthenium dioxide layer with a liquid
comprising ceric ammonium nitrate.
27. The method of claim 26 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
28. The method of claim 27 wherein the solution further comprises
liquid water.
29. A method of etching at least a region of a structure comprising
ruthenium, the method comprising subjecting at least a region of a
surface of the structure to a solution comprising ceric ammonium
nitrate, acetic acid, and water.
30. The method of claim 29 wherein the solution comprises about 0.5
weight percent to about 70 weight percent ceric ammonium
nitrate.
31. A method for patterning a ruthenium metal structure, the method
comprising contacting at least a region of a surface of the
structure with an aqueous solution comprising ceric ammonium
nitrate.
32. The method of claim 31, further comprising providing a mask on
the structure prior to contacting the surface of the structure.
33. The method of claim 32, further comprising removing the mask
from the structure subsequent to contacting the surface of the
structure.
34. The method of claim 31 wherein the solution comprises about 0.5
weight percent to about 70 weight percent ceric ammonium
nitrate.
35. A method for forming a structure on a substrate, the method
comprising: providing ruthenium metal on at least a portion of a
surface of the substrate; and removing a portion of the ruthenium
metal on the surface by contacting at least a region of the
ruthenium metal with a solution comprising ceric ammonium
nitrate.
36. The method of claim 35 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
37. The method of claim 35 wherein the structure forms at least a
portion of a device.
38. The method of claim 36 wherein the solution consists of about
30 weight percent ceric ammonium nitrate, about 10 weight percent
acetic acid, and about 60 weight percent liquid water, the
percentages calculated based on the entire weight of the
solution.
39. The method of claim 35 wherein the structure is selected from
the group consisting of a layer, a film, and a deposit.
40. A method for forming a structure on a substrate, the method
comprising: providing a layer of amorphous ruthenium dioxide on at
least a portion of a surface of the substrate; and contacting at
least a region of the layer with a solution comprising ceric
ammonium nitrate.
41. The method of claim 40 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
42. A method for forming a device, the method comprising: providing
a first layer comprising ruthenium on at least a portion of a
substrate; and removing a portion of the first layer by contacting
at least a region of the first layer with a solution comprising
ceric ammonium nitrate.
43. The method of claim 42 wherein the device is selected from the
group consisting of a memory device, a capacitor, a transistor, a
diode, a wire, an electrical contact, a word line, a bit line, an
interconnect, an electrode, and a via.
44. The method of claim 42 wherein the first layer consists of at
least one of ruthenium metal and ruthenium dioxide.
45. The method of claim 42, further comprising, subsequent to the
act of removing a portion of the first layer, providing a second
layer of a material adjacent to the first layer.
46. A method for forming a device, the method comprising: providing
a first layer of ruthenium metal on at least a portion of a surface
of a substrate; oxidizing at least a portion of the ruthenium metal
in the first layer, and removing at least a portion of the first
layer by contacting at least a region of the first layer with a
solution comprising ceric ammonium nitrate.
47. A method for removing an amount of ruthenium metal from a
structure consisting of ruthenium metal, the method comprising
contacting at least a region of a surface of the structure with a
solution consisting of 30 weight percent ceric ammonium nitrate, 10
weight percent acetic acid, and 60 weight percent water.
48. A method for removing an amount of amorphous ruthenium dioxide
from a structure consisting of amorphous ruthenium dioxide, the
method comprising contacting at least a region of a surface of the
structure with a solution consisting of 30 weight percent ceric
ammonium nitrate, 10 weight percent acetic acid, and 60 weight
percent water.
49. A method for removing a deposit of a material selected from
ruthenium metal, ruthenium dioxide, and a combination of ruthenium
metal and ruthenium dioxide from a surface of an object, the method
comprising immersing at least a portion of the object in a solution
comprising about 0.5 weight percent to about 70 weight percent
ceric ammonium nitrate.
50. The method of claim 49 wherein the object is selected from the
group consisting of a tool, a part, a component, a window, a plate,
a shield, a shower head, a collimator, and a chamber wall.
51. A method for forming a capacitor, the method comprising:
providing a first layer consisting essentially of ruthenium metal
on at least a portion of a substrate; etching said first layer with
an etchant solution comprising ceric ammonium nitrate to provide a
first electrode; providing a second layer consisting essentially of
ruthenium metal on at least a portion of a substrate, etching the
second layer with the etchant solution to provide a second
electrode; forming a dielectric between the first electrode and the
second electrode.
52. The method of claim 51 wherein the first layer and the second
layer consist of ruthenium metal.
53. The method of claim 52 wherein the etchant solution further
comprises acetic acid, and liquid water.
54. The method of claim 53 wherein the etchant solution comprises
about 0.5 weight percent to about 70 weight percent ceric ammonium
nitrate.
55. The method of claim 54 wherein the etchant solution consists of
about 30 weight percent ceric ammonium nitrate, about 10 weight
percent acetic acid, and about 60 weight percent liquid water, the
percentages calculated based on the entire weight of the
solution.
56. The method of claim 55 wherein the act of forming a dielectric
occurs prior to the act of providing the second layer.
57. The method of claim 51 wherein the act of forming a dielectric
comprises providing a dielectric material on at least a region of a
surface of the first electrode.
58. The method of claim 56 wherein the act of forming a dielectric
layer comprises: providing a material on at least a region of a
surface of the first electrode to provide a material deposit; and
oxidizing at least a portion of the material deposit.
59. A method for forming an electrode for a capacitor, the method
comprising: providing a layer of ruthenium metal on at least a
portion of a substrate; and patterning the layer by applying a
solution comprising ceric ammonium nitrate to at least a region of
the layer.
60. The method of claim 59 wherein the solution comprises about 0.5
to about 70 weight percent ceric ammonium nitrate.
61. The method of claim 60 wherein the solution consists of about
30 weight percent ceric ammonium nitrate, about 10 weight percent
acetic acid, and about 60 weight percent liquid water, the
percentages calculated based on the entire weight of the
solution.
62. A method of planarizing a surface, the method comprising
applying a slurry comprising ceric ammonium nitrate to the
surface.
63. The method of claim 62 wherein the method is chemical
mechanical planarization.
64. The method of claim 63 further comprising applying a frictional
force to the slurry on the surface.
65. The method of claim 64 wherein applying a frictional force
comprises applying mechanical abrasion.
66. A liquid etchant for removing ruthenium metal and ruthenium
dioxide from surfaces, the liquid etchant comprising less than 30
weight percent ceric ammonium nitrate.
67. The liquid etchant of claim 66 comprising greater than about
0.5 weight percent ceric ammonium nitrate.
68. The liquid etchant of claim 67 wherein the liquid etchant is an
aqueous solution.
69. A liquid etchant for removing ruthenium metal and ruthenium
dioxide from surfaces, the liquid etchant comprising more than 30
weight percent ceric ammonium nitrate.
70. The liquid etchant of claim 69 comprising less than about 70
weight percent ceric ammonium nitrate.
71. The liquid etchant of claim 70 wherein the liquid etchant is an
aqueous solution.
72. A chemical slurry for use in a planarization process for
planarizing a surface, the chemical slurry comprising ceric
ammonium nitrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
[0003] The present invention relates to methods of and materials
for etching, patterning, dissolving, or otherwise removing all or a
portion of a ruthenium-containing structure such as, for example, a
layer, a film, or a deposit. The present invention more
particularly relates to methods of and materials for etching,
patterning, dissolving, or otherwise removing at least a portion of
a structure composed of ruthenium metal, ruthenium dioxide, or a
combination of ruthenium metal and ruthenium dioxide, whether
disposed on an object such as a substrate or otherwise.
[0004] The methods and materials of the present invention may be
used in applications wherein it is desirable to etch, pattern,
dissolve, or otherwise remove all or a portion of a layer, film,
deposit, or other structure composed of ruthenium metal, ruthenium
dioxide, or a combination of ruthenium metal and ruthenium dioxide.
Examples of possible applications of the present methods and
materials include the removal of waste deposits of ruthenium metal
and ruthenium dioxide from the surfaces of tools, parts,
components, and apparatuses employed in chemical vapor deposition,
physical vapor deposition, and other techniques using ruthenium
metal and/or ruthenium dioxide. The present invention's methods and
materials may be incorporated into, for example, planarization
techniques such as chemical mechanical planarization, and also may
be utilized in, for example, the production of ruthenium masks,
ruthenium-coated reflective mirrors, and catalytic ruthenium
coatings, and in the fabrication of semiconductor systems and their
elements, components, and devices, such as wires, electrical
contacts, word lines, bit lines, interconnects, vias, electrodes,
capacitors, transistors, diodes, and memory devices.
BACKGROUND OF THE INVENTION
[0005] Increasingly, ruthenium (Ru) metal is an important material
in semiconductor device fabrication, and ruthenium layers, films,
and other structures may be incorporated into semiconductor
components and elements such as wires, electrical contacts,
electrodes, capacitors, transistors, and diodes. Ruthenium also is
used in many other applications and, for example, may be employed
as building material for masks, as a coating on mirrors, to provide
a surface for catalysis, or may be applied to objects by chemical
or physical vapor deposition techniques so as to provide a surface
coating having advantageous wear or corrosion properties.
[0006] One particularly advantageous application of ruthenium metal
is its use in the formation of electrode layers in the fabrication
of oxide high dielectric capacitors, wherein the ruthenium metal is
typically applied either as a thin film by sputter deposition or as
a conformal layer by metal organic chemical vapor deposition.
Ruthenium is a conductive metal that oxidizes to form a similarly
conductive ruthenium dioxide (RuO.sub.2) layer on the surface of
the existing ruthenium metal. Therefore, when an oxide high
dielectric capacitor is formed, the surface of a ruthenium layer
provided as the electrode material will not form a secondary
dielectric layer when oxidized to RuO.sub.2 during the oxygen
anneal of the high dielectric material. The fact that ruthenium's
oxide form is conductive distinguishes it from other conductive
metal film materials such as, for example, tungsten, tantalum, and
titanium, all of which form relatively non-conductive oxide layers.
Certain other possible capacitor electrode materials do not oxidize
during the application of an oxidizing anneal to the high
dielectric material. One such capacitor electrode material is
platinum. However, ruthenium provides advantages over platinum when
used as a capacitor electrode in that platinum has a tendency to
leak charge, a property that is not exhibited to the same degree by
ruthenium.
[0007] In fabricating semiconductor devices incorporating a
ruthenium metal film, such as, for example, the above-described
oxide high dielectric capacitors, it may be necessary to etch,
pattern, dissolve, or otherwise remove at least a portion of the
ruthenium metal film or its dioxide so as to provide a suitably
configured electrode or other structure or to completely remove
such a film as an aid in recovering improperly coated devices. When
ruthenium metal is provided on an object by chemical vapor
deposition, physical vapor deposition, or other deposition
techniques, a film or other deposit ruthenium metal and/or
ruthenium dioxide may be deposited on surfaces of the tools,
components, and apparatuses used in the deposition process, and it
may be desirable to remove the ruthenium metal and/or ruthenium
dioxide therefrom.
[0008] However, both ruthenium metal and ruthenium dioxide are
resistant to removal by know wet etching techniques, and none of
the wet etchants traditionally used in semiconductor device
processing, including aqua regia and piranha, will dissolve
ruthenium. In fact, both the CRC Handbook and the Merk Index list
ruthenium metal as being insoluble in strong acids and oxidizers
and as being soluble only in molten alkali salts, harsh etchants
unsuitable for many applications, including semiconductor
processing. Currently, if a layer or film of ruthenium metal or
ruthenium dioxide must be etched or patterned in the fabrication of
a semiconductor device, one of a number of dry etch procedures is
used, including oxidizing argon plasma and O.sub.2 plasma etch
procedures. However, the use of any of those dry etch procedures to
remove ruthenium metal or ruthenium dioxide results in the
formation of the explosive compound ruthenium tetroxide
(RuO.sub.4). The ruthenium tetroxide must be removed or otherwise
prevented from building to dangerous levels during the dry etch
procedures, and this may increase the complexity and expense of
such procedures.
[0009] Although ruthenium metal and ruthenium dioxide layers,
films, and other structures are useful in semiconductor device
fabrication, the use of such structures in that application has
been limited because of the inability to satisfactorily etch or
pattern the structures using wet etch techniques and the distinct
disadvantages resulting from use of dry etch techniques. For like
reasons, it has heretofore been difficult to remove undesirable
films, layers, deposits, or other structures of ruthenium metal and
ruthenium dioxide from tools and other objects. Accordingly, a need
exists for an improved method for etching, patterning, or otherwise
removing at least a portion of a ruthenium metal or ruthenium
dioxide structure.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention addresses the above-described
deficiencies in the known techniques and materials by providing a
method for etching, patterning, dissolving, or otherwise removing
all or a portion of a film, layer, deposit, or other structure
including ruthenium metal and/or ruthenium dioxide by contacting
the structure with a material including ammonium cerium (IV)
nitrate, which also is known as ceric ammonium nitrate. The
structure may be disposed on, for example, at least a portion of a
substrate or other object.
[0011] The present invention also provides a material that includes
ceric ammonium nitrate and that may be utilized in the method of
the invention to remove all or a portion of a structure including
ruthenium metal and/or ruthenium dioxide. According to one aspect
of the invention, the material is an aqueous solution including
ceric ammonium nitrate, and the solution may include other
components such as, for example, components that provide the
solution with desired properties.
[0012] The material and method of the present invention do not
result in the formation of the tetroxide form of ruthenium when
used to etch, pattern, dissolve, or otherwise remove ruthenium
metal and/or ruthenium dioxide from structures including those
materials and provide an alternative to known dry etch procedures
for removing ruthenium metal and ruthenium dioxide from structures
including those materials.
DETAILED DESCRIPTION OF THE INVENTION
[0013] As described herein, a method is provided for etching,
patterning, dissolving, or otherwise removing all or a portion of a
film, layer, deposit, or other structure composed of ruthenium
metal and/or ruthenium dioxide. In the method, at least a portion
of a structure comprising ruthenium and/or ruthenium dioxide
(whether deposited on at least a portion of a substrate or an
object, or otherwise provided) is removed by contacting at least a
region of a surface of the structure with a material comprising
ceric ammonium nitrate. The inventor has discovered that material
comprising ceric ammonium nitrate will remove ruthenium metal or
amorphous ruthenium dioxide without the formation of the explosive
tetroxide form of ruthenium.
[0014] Accordingly, the material of the invention for removing
ruthenium metal and/or ruthenium dioxide includes an amount of
ceric ammonium nitrate. The material of the invention may be, for
example, a solution of ceric ammonium nitrate. The material may be
in the form of a liquid etchant solution, and, in one form, the
solution may be an aqueous solution wherein ceric ammonium nitrate
and, optionally, other solutes, are dissolved in liquid water. Such
other solutes may include, for example, acetic acid and other
liquid or solid solutes such as agents for buffering or enhancing
dissolution of the ceric ammonium nitrate in the solvent. Other
additional components that may be added to the solution will be
apparent to those having ordinary skill in the art. In one form,
the material of the invention may include about 0.5 to about 70
weight percent ceric ammonium nitrate. As used in the method of the
present invention, the material of the present invention may be,
for example, an aqueous solution including about 30 weight percent
ceric ammonium nitrate, about 10 weight percent acetic acid, and
about 60 weight percent water.
[0015] When the ceric ammonium nitrate material of the invention is
applied as a liquid solution, it may be applied to the structure
using any suitable technique for contacting a surface with a
liquid, including immersion and spray techniques. The solution also
may be applied to the surface as a component of a slurry. Once
apprised of the details of the invention as described herein, one
of skill in the art will readily comprehend additional methods for
applying the material of the invention, whether in liquid form or
otherwise, to a structure. When applied by an immersion or similar
technique, the immersion bath may be agitated in order to enhance
the contact of the ceric ammonium nitrate with the ruthenium metal
and/or ruthenium dioxide to be removed. The ceric ammonium nitrate
material, whether a solution or otherwise, may be applied to the
ruthenium metal and/or ruthenium dioxide structure at room
temperature, if desired, and one manner of contacting at least a
surface of the structure is to immerse at least a portion of the
structure in an aqueous ceric ammonium nitrate solution.
[0016] As used herein, the term "structure" refers to any
monolithic mass of a material, including one or more layers, films,
or deposits of any configuration, including active or operable
portions of a semiconductor device. The term "substrate" as used
herein refers to any thing on or in which a structure may be
provided. For example, substrates include silicon-based materials,
such as silicon, silicon dioxide (SiO.sub.2), and
borophosphosilicate glass (BPSG), and also include other materials,
including stainless steel, quartz, and insulators such as sapphire.
Substrates also refer to one or more layers that may include all or
a portion of a structure. When a structure is formed on a
substrate, it may be formed directly on the substrate or it may be
formed on the substrate with one or more intermediate layers
between it and the substrate. A substrate is often the lowest layer
of material in a wafer. The present invention may be utilized with
a doped silicon substrate, or with other structures and
technologies, such as silicon-on-insulator, silicon-on-sapphire,
and thin film transistors.
[0017] According to one aspect of the invention, the method and
material of the invention may be applied to etch, shape, or pattern
structures of ruthenium metal and/or ruthenium dioxide during the
fabrication of semiconductor systems and their elements,
components, and devices, including the fabrication of wires,
electrical contacts, word lines, bit lines, interconnects, vias,
electrodes, capacitors, transistors, diodes, and memory devices.
The method and material of the present invention also may be used
to etch, shape, or pattern ruthenium metal or ruthenium dioxide
structures in other applications such as, for example, fabrication
of ruthenium masks, ruthenium-coated reflective mirrors, and
catalytic ruthenium coatings. Because the present material may be
applied to a structure as a liquid solution and does not result in
the formation of ruthenium's explosive tetroxide form, it provides
an advantageous alternative to existing ruthenium dry etch
procedures.
[0018] The method and material of the invention also may be used to
remove waste deposits of ruthenium metal and ruthenium dioxide from
the surfaces of tools, parts, components, and apparatuses employed
in chemical vapor deposition, physical vapor deposition, and other
techniques for providing ruthenium metal and/or ruthenium dioxide
on a substrate or other object. As an example, after completing a
chemical vapor deposition process of coating ruthenium metal onto
an object, ruthenium metal also may coat the several components of
the deposition apparatus. Such components include the surfaces of
the deposition chamber, the quartz susceptor window in the bottom
of the deposition chamber, any plates or shields, and the shower
head. As another example, after completion of a sputter process of
coating ruthenium metal on an object, the ruthenium metal may coat
the sputter shields, collimator, sputter target, and deposition
chamber. After either process, everything but the object that is to
be coated must be cleaned and may be done so conveniently by the
present invention. Accordingly, the present invention is directed
to a method for removing a layer, film, coating, or other deposit
of ruthenium metal or ruthenium dioxide from an object including,
for example, a tool, a part, a component, a window, a plate, a
shield, a shower head, a collimator, or a chamber wall. In that
process, the object is contacted with the material of the invention
using a technique such as, for example, a spray or immersion
technique.
[0019] The ceric ammonium nitrate material of the present
invention, whether in solution form or otherwise, also may be used
as an active chemical component of a slurry used in a planarization
process for planarizing a surface. In such an application, the
material of the invention is applied to the surface and acts to
remove ruthenium metal and/or ruthenium dioxide from the surface
that is planarized. The planarization process may be a chemical
mechanical planarization process, which may include application of
a frictional force, such as mechanical abrasion, to the slurry on
the surface. Other parameters of the planarization process may be
readily determined by or will be apparent to those of ordinary
skill.
[0020] Accordingly, the present invention also provides for a
slurry for use in planarization processes, including chemical
mechanical planarization, and that includes an amount of ceric
ammonium nitrate. The slurry form of the present invention provides
selective application of the material of the invention so as to
restrict the region from which ruthenium metal and/or ruthenium
dioxide is removed. The slurry may include, for example, an amount
of the material of the present invention in a form suitable for
incorporation into the slurry.
[0021] The present invention also is directed to a method for
forming a structure on a substrate wherein ruthenium metal is
provided on at least a portion of a surface of the substrate and a
portion of the ruthenium metal is removed therefrom by contacting
at least a region of the ruthenium metal with the material of the
present invention, as described above and including, for example,
applying the material by spray or immersion techniques, so as to
remove a portion of the ruthenium metal. The ruthenium metal may be
provided on the substrate by any known technique for providing
ruthenium metal on a surface, including chemical vapor deposition,
physical vapor deposition, and sputter techniques, and may form all
or a portion of a device.
[0022] The present invention also encompasses a method for forming
a structure wherein a layer of amorphous ruthenium dioxide is
provided on a substrate and the amorphous ruthenium dioxide is
contacted with the material of the invention, as described above
and including, for example, applying the material by spray or
immersion techniques, so as to remove a portion of the ruthenium
dioxide. The amorphous ruthenium dioxide may be provided by any
method known to those of ordinary skill in the art and may form all
or a portion of a device.
[0023] In addition, the present invention includes a method for
forming a device wherein a first layer including ruthenium metal
and/or ruthenium dioxide is provided on at least a portion of a
substrate, and a portion of the first layer is subsequently removed
by contacting at least a region of the first layer with the ceric
ammonium nitrate-containing material of the invention, as described
above. The device may be, for example, a memory device, a
capacitor, a transistor, a diode, a wire, an electrical contact, a
word line, a bit line, an interconnect, an electrode, or a via.
Subsequent to removal of a portion of the first layer by the
present invention's material, a second layer of ruthenium metal
and/or ruthenium dioxide, or of some other material, may be
provided adjacent to the first layer. The first and second layers
may be provided by any known method.
[0024] The present invention also is directed to a method for
forming a device wherein a first layer of ruthenium metal and/or
ruthenium dioxide is provided on at least a portion of a surface of
a substrate, at least a portion of the ruthenium metal in the first
layer is oxidized, and at least a portion of the first layer is
removed by contacting at least a region of the first layer with the
material of the present invention so as to remove ruthenium metal
and/or ruthenium dioxide form the first layer. The first layer may
be oxidized by any known means for oxidizing ruthenium metal,
including a rapid thermal anneal process.
[0025] A method for patterning a ruthenium metal structure also is
provided and includes contacting at least a region of a surface of
a structure of ruthenium metal with the material of the invention,
as described above. The method also may include the act of
providing a mask on the ruthenium metal structure prior to
contacting the surface of the structure with the material of the
invention. The method also may include the step of removing the
mask subsequent to contacting the surface of the structure with the
material of the invention. The ruthenium metal structure and the
mask may be provided, and the mask may be removed, using techniques
known to those of skill in the art.
[0026] As discussed above, one application of ruthenium metal is as
the electrode in a capacitor. Accordingly, the present invention
also includes a method for forming a capacitor wherein:
[0027] a first layer including ruthenium metal is provided on at
least a portion of a substrate;
[0028] the first layer is etched using the ceric ammonium
nitrate-containing material of the present invention to provide a
first electrode;
[0029] a second layer including ruthenium metal is provided on at
least a portion of the substrate;
[0030] the second layer is etched using the ceric ammonium
nitrate-containing material of the invention to provide a second
electrode; and
[0031] a dielectric is formed between the first and second
electrodes.
[0032] In the foregoing method for forming a capacitor, the act of
forming the dielectric may occur prior to the act of providing the
second layer and, also, may include providing the dielectric on at
least a region of a surface of the first electrode. More
particularly, the act of forming the dielectric may encompass
providing a material on at least a region of a surface of the first
electrode and then oxidizing at least a portion of the material to
provide the desired dielectric properties.
[0033] In a more basic form, the present invention includes a
method for forming an electrode for a capacitor and wherein a layer
of ruthenium metal is provided on at least a portion of a
substrate, and the layer is subsequently patterned by applying the
material of the invention to at least a region of the layer.
[0034] The results achieved by use of the method of the present
invention and by conventional etch methods on ruthenium metal films
and ruthenium oxide films are provided in the examples below.
EXAMPLE 1
[0035] Samples of ruthenium metal deposited by chemical vapor
deposition on SiO.sub.2 were placed in baths of the following
materials: aqua regia (3 parts hydrochloric acid and 1 part nitric
acid) at approximately 100.degree. C.; piranha solution (a mixture
of 1 part of a 50 weight % peroxide aqueous solution and 1 part of
98-99% sulfuric acid) at approximately 100.degree. C.; HCl/peroxide
at approximately 85.degree. C.; 85% phosphoric acid solution at
approximately 150.degree. C.; ammonium hydroxide/peroxide (50/50 by
weight) at approximately 100.degree. C.; pure 100% liquid bromine
at room temperature (approximately 20-25.degree. C.); 10% by weight
bromine (Br.sub.2) in water at approximately 20-25.degree. C.; and
KOH aqueous solution (approximately 30 weight % KOH at
approximately 85.degree. C.). Each of the foregoing materials were
allowed to contact the ruthenium metal deposit for at least 30
minutes and in each case a detectable amount of ruthenium metal was
not removed from the SiO.sub.2 substrate.
[0036] The runs of Example 1 show that several know wet etching
materials, as well as other, harsher materials, will not remove
ruthenium from a layer of that metal at a commercially significant
rate.
EXAMPLE 2
[0037] Samples of ruthenium and ruthenium dioxide films on silicon,
its thermal oxide (SiO.sub.2), and borophosphosilicate glass (BPSG)
were immersed in a room temperature (approximately 20-25.degree.
C.) bath of CR-14 Chrome Etchant obtained from Cyantek Corporation,
Fremont, Calif. The CR-14 Chrome Etchant consisted of 30% by weight
ceric ammonium nitrate, 10% by weight acetic acid, and 60% by
weight water and is commonly used for etching chromium and chromium
dioxide. The parameters and results of each run are provided below
in Table 1. It will be seen that the CR-14 Chrome Etchant removed
ruthenium metal from each of the three substrates. The estimated
ruthenium metal etch rates achieved were as high as 11.67 A/sec.
(Ru on 8K thermal oxide) and as low as 2.63 A/sec. (Ru on BPSG).
The etchant also removed ruthenium dioxide from each of the three
substrates if the ruthenium dioxide was deposited on the substrate
in an amorphous form. No crystalline ruthenium dioxide was removed
by the CR-14 Chrome Etchant.
1TABLE 1 Film Deposition Method/ Characteristics of Approximate
Deposition Deposited Ru or Film Thick- Estimated Estimated Etch
Material Temperature RuO.sub.2 Film ness (.ANG.) Etch Time Rate
(.ANG./sec.) Comments Ru on Si CVD/200.degree. C. crystalline 400
<2 min. 3.33 Ru film flaked off immediately in etchant bath, but
dissolved in etchant within 2 min. Ru on Si CVD/250.degree. C.
crystalline 1100 <2 min. 9.17 Ru film flaked off immediately in
etchant bath, but dissolved in etchant within 2 min. Ru on Si
CVD/350.degree. C. crystalline 320 30 sec. 10.67 Ru film etched off
without flaking. Ru on 8K (8000 .ANG.) CVD/200.degree. C.
crystalline 500 <30 min. thermal oxide (SiO.sub.2) Ru on 8K
CVD/200.degree. C. crystalline 350 30 sec. 11.67 Ru film flaked off
immediately in thermal oxide (SiO.sub.2) etchant bath, but
dissolved within etchant within 30 sec. Ru on BPSG CVD/200.degree.
C. crystalline 790 <5 min. 2.63 Ru film flaked off immediately
in etchant bath, but dissolved within etchant within 5 min.
RuO.sub.2 on Si CVD/150.degree. C. amorphous 375 <1 min. 6.25
RuO.sub.2 film did not flake. RuO.sub.2 on Si CVD/150.degree. C.
amorphous 250 <4 min. 1.04 RuO.sub.2 film did not flake.
RuO.sub.2 on Si CVD/300.degree. C. crystalline 125 no etch 0
RuO.sub.2 film did not appear to etch within 30 min. RuO.sub.2 on
8K CVD/150.degree. C. amorphous 375 <1.5 min. 4.17 RuO.sub.2
film did not flake. thermal oxide (SiO.sub.2) RuO.sub.2 on BPSG
CVD/150.degree. C. amorphous 950 <1 min. 15.83 RuO.sub.2 film
did not flake. RuO.sub.2 on BPSG CVD/300.degree. C. crystalline
<100 no etch 0 RuO.sub.2 film did not appear to etch within 20
min.
EXAMPLE 3
[0038] Samples of ruthenium and ruthenium dioxide provided on
silicon substrates were annealed using a rapid thermal process
(RTP) in which the samples were quickly heated from room
temperature to 750.degree. C. and were then immersed in a room
temperature (20-25.degree. C.) bath of the CR-14 Chrome Etchant.
The methods by which the ruthenium films were deposited on the
substrates and then annealed are provided in Table 2. Table 2 also
provides the estimated times during which etching occurred and an
estimated etch rate for each run. As was observed with the
RuO.sub.2 films in Example 2 that were not annealed, the annealed
crystalline ruthenium dioxide film was not etched in the
procedure.
2TABLE 2 Film Deposition Method/ Characteristics of Approximate
Estimated Deposition Deposited Ru or Film Thickness Estimated Etch
Rate Material Temperature RuO.sub.2 Film (.ANG.) Anneal Procedure
Etch Time (A/sec.) Comments RuO.sub.2 on Si CVD/150.degree. C.
amorphous 250 RT Pin N.sub.2 @ 4 min. 1.04 A conductive RuO.sub.2
layer existed 850.degree. C. under the material etched away. for 30
sec. RuO.sub.2 on Si CVD/300.degree. C. crystalline 600 RT Pin
O.sub.2 @ no etch 0 Film did not appear to be etched 850.degree. C.
within 10 min. for 30 sec. Ru on Si CVD/200.degree. C. crystalline
400 RT Pin N.sub.2 @ 10 min. 0.67 Film flaked off immediately and
850.degree. C. most of the flakes dissolved in the for 30 sec.
etchant in less than 10 min., but a residue remained at 10 min.
[0039] Accordingly, the present invention provides an improved
method and material for etching, patterning, dissolving, or
otherwise removing at least a portion of a structure including
ruthenium metal and/or ruthenium dioxide.
[0040] The present invention has been described in connection with
certain embodiments thereof. Those of ordinary skill in the art
will recognize that many modifications and variations may be
employed. All such modifications and variations are intended to be
covered by the foregoing description and the following claims.
* * * * *