U.S. patent application number 11/339876 was filed with the patent office on 2006-06-15 for iridium oxide nanostructure.
This patent application is currently assigned to Sharp Laboratories of America, Inc.. Invention is credited to Robert A. Barrowcliff, Sheng Teng Hsu, Gregory M. Stecker, Fengyan Zhang.
Application Number | 20060124926 11/339876 |
Document ID | / |
Family ID | 36101924 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060124926 |
Kind Code |
A1 |
Zhang; Fengyan ; et
al. |
June 15, 2006 |
IRIDIUM OXIDE NANOSTRUCTURE
Abstract
A method is provided for patterning iridium oxide (IrOx)
nanostructures. The method comprises: forming a substrate first
region adjacent a second region; growing IrOx nanostructures from a
continuous IrOx film overlying the first region; simultaneously
growing IrOx nanostructures from a non-continuous IrOx film
overlying the second region; selectively etching areas of the
second region exposed by the non-continuous IrOx film; and, lifting
off the IrOx nanostructures overlying the second region. Typically,
the first region is formed from a first material and the second
region from a second material, different than the first material.
For example, the first material can be a refractory metal, or
refractory metal oxide. The second material can be SiOx. The step
of selectively etching areas of the second region exposed by the
non-continuous IrOx film includes exposing the substrate to an
etchant that is more reactive with the second material than the
IrOx.
Inventors: |
Zhang; Fengyan; (Vancouver,
WA) ; Stecker; Gregory M.; (Vancouver, WA) ;
Barrowcliff; Robert A.; (Vancouver, WA) ; Hsu; Sheng
Teng; (Camas, WA) |
Correspondence
Address: |
SHARP LABORATORIES OF AMERICA, INC.;C/O LAW OFFICE OF GERALD MALISZEWSKI
P.O. BOX 270829
SAN DIEGO
CA
92198-2829
US
|
Assignee: |
Sharp Laboratories of America,
Inc.
|
Family ID: |
36101924 |
Appl. No.: |
11/339876 |
Filed: |
January 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11013804 |
Dec 15, 2004 |
7022621 |
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11339876 |
Jan 26, 2006 |
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10971280 |
Oct 21, 2004 |
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11013804 |
Dec 15, 2004 |
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10971330 |
Oct 21, 2004 |
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11013804 |
Dec 15, 2004 |
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Current U.S.
Class: |
257/43 ;
257/E21.006; 438/734; 977/721 |
Current CPC
Class: |
H01L 21/31111 20130101;
B81C 1/00111 20130101; B82Y 10/00 20130101 |
Class at
Publication: |
257/043 ;
438/734; 257/E21.006; 977/721 |
International
Class: |
H01L 29/10 20060101
H01L029/10; H01L 21/302 20060101 H01L021/302 |
Claims
1-12. (canceled)
13. A patterned iridium oxide (IrOx) nanostructure substrate, the
patterned substrate comprising: a substrate with a first region and
a second region adjoining the first region; a first material
overlying the first region; a second material overlying the second
region; a continuous IrOx film with grown IrOx nanostructures
overlying the first material; and a non-continuous IrOx film with
grown IrOx nanostructures temporarily overlying the second
material.
14. The patterned substrate of claim 13 wherein the first material
is different than the second material.
15. The patterned substrate of claim 14 wherein the first material
is selected from the group including Ti, TiN, TaN, Ta, Nb, W, WN,
refractory metals, and refractory metal oxides.
16. The patterned substrate of claim 14 wherein the first material
has a thickness in the range of 1 to 100 nanometers (nm).
17. The patterned substrate of claim 14 wherein the second material
is SiOx.
18. The patterned substrate of claim 14 wherein the second material
overlies both the first and second regions of the substrate; and
wherein the first material overlies the second material in the
first region.
19. The patterned substrate of claim 14 wherein the second material
overlies the first region of the substrate; and wherein the first
material is formed overlying the second material, in the first
region of the substrate.
20. The patterned substrate of claim 14 wherein the non-continuous
IrOx film temporarily overlying the second region includes
non-continuous zones in the film having an area in the range
between 100 nm.sup.2 and 100 microns.sup.2, and a spacing between
zones in the range between 10 and 5000 nm.
21. The patterned substrate of claim 14 wherein IrOx nanostructures
grown from the continuous IrOx film overlying the first region have
a diameter in the range between 10 and 1000 nm, a length in the
range between 10 nm and 10 microns, and a spacing in the range
between 10 and 1000 nm.
22. A patterned iridium oxide (IrOx) nanostructure substrate, the
patterned substrate comprising: a substrate with a first region and
a second region adjoining the first region; a first material
overlying the first region; a second material overlying the second
region; and a continuous IrOx film with grown IrOx nanostructures,
having an aspect ratio in the range of 1:1 and 100:1, overlying the
first material.
23. The patterned substrate of claim 22 wherein the first material
is different than the second material.
24. The patterned substrate of claim 23 wherein the first material
is selected from the group including Ti, TiN, TaN, Ta, Nb, W, WN,
refractory metals, and refractory metal oxides.
25. The patterned substrate of claim 23 wherein the second material
is SiOx.
26. The patterned substrate of claim 23 wherein the second material
overlies both the first and second regions of the substrate; and
wherein the first material overlies the second material in the
first region.
27. The patterned substrate of claim 23 wherein the second material
overlies the first region of the substrate; and wherein the first
material is formed overlying the second material, in the first
region of the substrate.
28. The patterned substrate of claim 23 wherein IrOx nanostructures
grown from the continuous IrOx film overlying the first region have
a diameter in the range between 10 and 1000 nm, a length in the
range between 10 nm and 10 microns, and a spacing in the range
between 10 and 1000 nm.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional of a pending patent
application entitled, IRIDIUM OXIDE NANOSTRUCTURE PATTERNING,
invented by Zhang et al., Ser. No. 11/013,804, filed Dec. 15,
2004.
[0002] This application is a continuation-in-part of a pending
patent application entitled, IRIDIUM OXIDE NANOTUBES AND METHOD FOR
FORMING SAME, invented by Zhang et al., Ser. No. 10/971,280, filed
Oct. 21, 2004.
[0003] This application is a continuation-in-part of a pending
patent application entitled, IRIDIUM OXIDE NANOWIRE AND METHOD FOR
FORMING SAME, invented by Zhang et al., Ser. No. 10/971,330, filed
Oct. 21, 2004.
[0004] All of the above-mentioned applications are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0005] 1. Field of the Invention
[0006] This invention generally relates to integrated circuit (IC)
fabrication and, more particularly, to patterned iridium oxide
nanostructures and an associated fabrication process.
[0007] 2. Description of the Related Art
[0008] Recently, the fabrication of nanostructures has been
explored, due to its potential importance as a building block in
nano, microelectromechanical (MEM), and nanoelectromechanical NEM
device applications. For example, researchers associated with
Charles Lieber have reported the synthesis of a variety of
semiconductor nanowires made from materials such as silicon (Si),
Si-germanium (SiGe), InP, and GaN, and use in building
nano-computing system. Other groups have reported using templates
structures to grow metallic nanowires made of materials such as Ni,
NiSi, Au, and Pt. Metallic nanowires can be used as
interconnections and the sharp tips of the nanowire make them
effective for field emission purpose. ZnO.sub.2 nanowires are
potentially useful as a light emission element.
[0009] IrO.sub.2 is a conductive metal oxide that is already widely
used in DRAM and FeRAM applications. IrO.sub.2 can be used as a
conductive electrode, as it has stable electrical and chemical
properties, even at high temperature O.sub.2 ambient conditions.
IrO.sub.2 can also be used as pH sensor material. Ir thin film can
be deposited using PVD easily with excellent polycrystalline
structure and strong (111) orientation. IrO.sub.2 can be formed
afterwards, by oxidizing the Ir film, or it can be formed directly
using reactive sputtering method at higher temperatures in oxygen
ambient. CVD methods have recently been developed to grow Ir and
IrO.sub.2 thin films. It is relatively easy to maintain good
composition control in CVD processes, and the method is know to
provide good step coverage on some materials.
[0010] No processes had been previously reported that are able to
form metallic nanowires without the use of porous material forms or
templates. The templates add a considerable degree of complexity to
the process. Thus, a more practical and commercially feasible means
of forming metallic nanowires publications is desirable. To that
end, the above-mentioned Related Applications describe the growth
of iridium oxide (IrO.sub.2) nanostructures formed using a
metalorganic chemical vapor deposition (MOCVD) method without a
template. The Related Applications describe an efficient MOCVD
process for forming nanotips and nanorods. Using these MOCVD
processes, IrO.sub.2 has been successfully grown on Ti, TiN, TaN
and SiO2 substrates. The growth length, density, and vertical
orientation can be controlled by temperature, pressure, flow,
substrates, and time.
[0011] It would be advantageous if iridium oxide nanostructures,
however formed, could be selectively formed or patterned on a
substrate.
[0012] It would be advantageous if iridium oxide nanostructures
could be selectively formed on a substrate, taking advantage of the
differences in characteristics of adjoining substrate
materials.
[0013] It would be advantageous if iridium oxide nanostructures
could be selectively formed on a substrate, taking advantage of the
differences in the manner in which iridium oxide covers adjoining
substrate materials.
SUMMARY OF THE INVENTION
[0014] Now that it has been shown that nanotips and nanorods can be
efficiently formed using conventional CMOS processes, the next step
is to investigate means of forming practical iridium oxide nanotip
structures. To that end, this application describes a process for
patterning IrO2 nanorods, so that they can be seamlessly integrated
into CMOS, IC, and liquid crystal display (LCD) devices.
[0015] Accordingly, a method is provided for patterning iridium
oxide (IrOx) nanostructures. The method comprises: forming a
substrate first region adjacent a second region; growing IrOx
nanostructures from a continuous IrOx film overlying the first
region; simultaneously growing IrOx nanostructures from a
non-continuous IrOx film overlying the second region; selectively
etching areas of the second region exposed by the non-continuous
IrOx film; lifting off the IrOx nanostructures overlying the second
region; and, in response to lifting off the IrOx nanostructures
overlying the second region, forming a substrate with
nanostructures overlying the first region.
[0016] Typically, the first region is formed from a first material
and the second region from a second material, different than the
first material. For example, the first material can be a refractory
metal, or refractory metal oxide. The second material can be
SiOx.
[0017] The step of selectively etching areas of the second region
exposed by the non-continuous IrOx film includes exposing the
substrate to an etchant that is more reactive with the second
material than the IrOx. For example, if the first material is a
refractory metal and the second material is SiO2, then HF or
buffered oxide etches (BOE) are suitable etchants.
[0018] In one aspect, the step of forming a substrate first region
adjacent a second region includes: conformally depositing the
second material overlying the first and second regions; and,
selectively forming the first material overlying the second
material in the first region. In a second aspect, the step of
forming a substrate first region adjacent a second region includes:
conformally depositing the second material overlying the first and
second regions; selectively forming the first material with a
surface overlying the second material in the first region;
conformally depositing the second material overlying the first and
second regions; and, chemical-mechanical polishing (CMP) the second
material to the level of the first material surface.
[0019] Additional details of the above-described method and a
corresponding patterned substrate with IrOx nanostructures are
described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a partial cross-sectional view of a patterned
iridium oxide (IrOx) nanostructure substrate.
[0021] FIG. 2 is a partial cross-sectional view of a variation of
the patterned substrate of FIG. 1.
[0022] FIGS. 3A and 3B are partial cross-sectional and plan views,
respectively, of the patterned substrate of FIG. 1 in a prior
process step.
[0023] FIGS. 4A and 4B are scanning electron microscope (SEM)
photographs depicting the growth of IrO2 on different substrate
materials.
[0024] FIGS. 5A and 5B depict a first method for selectively
etching off the IrO2 nanorods.
[0025] FIGS. 6A and 6B depict a second method for selectively
etching IrOx nanostructures.
[0026] FIG. 7 is a flowchart illustrating a method for patterning
IrOx nanostructures.
DETAILED DESCRIPTION
[0027] FIG. 1 is a partial cross-sectional view of a patterned
iridium oxide (IrOx) nanostructure substrate. The patterned
substrate 100 comprises a substrate 102 with a first region 104 and
a second region 106 adjoining the first region 104. A first
material 108 overlies a second material 110 in the first region
104. A continuous IrOx film 112 with grown IrOx nanostructures 114,
having an aspect ratio in the range of 1:1 to 100:1, overlies the
first material 108.
[0028] An "aspect ratio" is defined herein to be the length 116 of
the nanostructures 114 with respect to the nanostructure diameter
118. IrOx is defined herein to be any iridium oxide compound, where
"x" is any value between (and including) the values of zero and 2.
In another aspect, the "x" value in the continuous IrOx film 112 is
different than the "x" value in the nanostructures. For example,
the continuous IrOx film 112 can be Ir (x=0), while the
nanostructures 114 are IrOx, where x is greater than zero.
[0029] Typically, the first material 108 is different than the
second material 110. For example, the first material can be Ti,
TiN, TaN, Ta, Nb, W, or WN. More generally, the first material 108
can be a refractory metal or a refractory metal oxide. Typically,
the second material 110 is SiOx, where "x" is any value greater
than zero and less than, or equal to 2. Note, the patterned
substrate 100 is not necessarily limited to just the listed
materials. It is expected that other materials with similar
properties can also be used.
[0030] FIG. 2 is a partial cross-sectional view of a variation of
the patterned substrate of FIG. 1. In this aspect, the second
material 110 overlies both the first region 104 and the second
region 106 of the substrate 102. The first material 108 is formed
overlying the second material 110 in the first region 104 of the
substrate.
[0031] Specifically referencing FIG. 1, although the same analysis
can also be applied to FIG. 2, IrOx nanostructures 114 grown from
the continuous IrOx film 112 overlying the first region 104 have a
diameter 118 in the range between 10 and 1000 nm, a length 116 in
the range between 10 nm and 10 microns, and a spacing 120 in the
range between 10 and 1000 nm. In one aspect, the first material 108
has a thickness 122 in the range of 1 to 100 nanometers (nm). It
should be understood that above-described patterned substrate can
be formed with a wide variety of grown nano-type IrOx structures,
regardless of whether they are called nanotips, nanowires,
nanotubes, or nanorods. Typically, nanorods are understood to be
rod structures that do not have to have a sharp tip. Nanotips do
not have to have rod shape; they can be any shape with a sharp tip.
Likewise, the patterned substrate is not necessarily limited to
just the above-mentioned exemplary nanostructure dimensions.
[0032] Note, although the nanostructures 114 are shown as having
relatively uniform lengths, diameters, and spacings, the variation
is length 116 can be between 100 nm to 10 microns, the variation in
diameter 118 can be between 10 nm and 1000 nm, and the variation in
spacing 120 can be between 10 nm and 10 microns.
[0033] FIGS. 3A and 3B are partial cross-sectional and plan views,
respectively, of the patterned substrate of FIG. 1 in a prior
process step. In one aspect seen in FIG. 3A, a non-continuous IrOx
film 300, with grown IrOx nanostructures 114, temporarily overlies
the second material 110. As shown, the nanostructures 114 are shown
as having been grown from a collection of non-continuous "island"
structures. However, in other aspects, the diameters 118 of at
least some of the nanostructures 114 can be equal to island
diameters 304. That is, the non-continuous film areas 304 can be
defined by the nanostructures diameter 118. If a large percentage
of the film areas are defined by nanostructure diameters, then "the
non-continuous film with grown IrOx nanostructures" maybe
alternately be considered to be a discontinuous filed of IrOx
nanostructures. Also as shown, not all the film area need
necessarily be non-continuous.
[0034] The non-continuous IrOx film 300 includes non-continuous
zones 302 in the film having an area (shown in cross-hatch, see
FIG. 3B) in the range between 100 nm.sup.2 and 100 microns.sup.2,
and a spacing 306 between zones 302 in the range between 10 and
5000 nm. The significance of the above-mentioned non-continuous
film 300 is described below.
[0035] Although not specifically shown here, the non-continuous
IrOx film, with nanostructures, can be formed as a prior process
step in the fabrication of the structure of FIG. 2. The details of
a damascene patterned structure are essentially the same as the
details shown in FIGS. 3A and 3B (see FIGS. 6A and 6B).
Functional Description
[0036] FIGS. 4A and 4B are scanning electron microscope (SEM)
photographs depicting the growth of IrO2 on different substrate
materials. As can be seen, the growth mechanism is different for
the two substrates. The material of the left in each figure is TiN,
the material on the right is SiO2. FIG. 4B is a higher
magnification than FIG. 4A.
[0037] Substrates made with a thin layer of Ti, TiN, or TaN, with a
thickness range from 1 nm to 100 nm, promote the growth of a
continuous Ir-IrO2 film. IrO2 nanorods are grown on the
Ir-IrO.sub.2 film. With the adjoining SiO2 substrate, the IrO2
nanorods grow directly on the SiO2 surface. Alternately stated, a
continuous Ir-IrO.sub.2 need not be formed between the SiO2 layer
and the nanostructures. The spaces between the nanorods on SiO2
make it possible for etching chemicals, such as HF solutions, to
attack the underneath SiO2 layer and lift off the overlying IrO2
nanorods.
[0038] FIGS. 5A and 5B depict a first method for selectively
etching off the IrO2 nanorods. The first material (i.e., TiN, TaN,
Ti, Ta, Nb, W, or WN) is patterned. The IrO2 nanorods are grown on
the wafer, then the wafer is dipped in an HF solution for just
enough time to lift off the IrO2 nanorod without sacrificing too
much of SiO2 layer. This technique may cause some undercutting
under the first material.
[0039] FIGS. 6A and 6B depict a second method for selectively
etching IrOx nanostructures. After patterning the first material
(i.e., Ti, TiN) layer, SiO2 is deposited by CVD and CMP is
performed. The sidewall of the first material layer is protected by
the SiO2 when the wafer is dipped into the HF solution. As a
result, there is less likelihood of undercutting the first
material.
[0040] For either method, a photoresist can be added overlying the
nanostructures growing from the continuous film, when wafer is
dipped in the HF solution. Then, the first material and IrOx
nanostructures overlying the device region can be better protected
from unintentional etching. In this manner, a faster acting, but
less selective etchant can be used.
[0041] FIG. 7 is a flowchart illustrating a method for patterning
IrOx nanostructures. Although the method is depicted as a sequence
of numbered steps for clarity, no order should be inferred from the
numbering unless explicitly stated. It should be understood that
some of these steps may be skipped, performed in parallel, or
performed without the requirement of maintaining a strict order of
sequence. The method starts at Step 700.
[0042] Step 702 forms a substrate first region adjacent a second
region. Step 704 grows IrOx nanostructures from a continuous IrOx
film overlying the first region. Step 706 simultaneously (with Step
704) grows IrOx nanostructures from a non-continuous IrOx film
overlying the second region. Step 708 selectively etches areas of
the second region exposed by the non-continuous IrOx film. Step 710
lifts off the IrOx nanostructures overlying the second region. Step
712, in response to lifting off the IrOx nanostructures overlying
the second region, forms a substrate with nanostructures overlying
the first region.
[0043] Typically, forming the substrate first region adjacent the
second region (Step 702) includes forming the first region from a
first material and the second region from a second material,
different than the first material. For example, the first material
can be Ti, TiN, TaN, Ta, Nb, W, WN, refractory metals, or
refractory metal oxides. The second material can be SiOx. In
another aspect, Step 702 forms the first material with a thickness
in the range of 1 to 100 nanometers (nm).
[0044] In one aspect, selectively etching areas of the second
region exposed by the non-continuous IrOx film (Step 708) includes
exposing the substrate to an etchant that is more reactive with the
second material than the IrOx. Ideally, the IrOx has no reaction
with the etchant. For example, HF or buffered oxide etches (BOE)
can be used. BOE is understood to be a mixture of HF with water or
ammonium. For example, (NH(INF/4)F) is an example of BOE. If the
second material is different than SiO2, another etchant might be
used.
[0045] In one aspect, forming a substrate first region adjacent a
second region in Step 702 includes substeps. Step 702a conformally
deposits the second material overlying the first and second
regions, and Step 702b selectively forms the first material
overlying the second material in the first region, see FIGS. 5A and
5B. Alternately, Step 702c conformally deposits the second material
overlying the first and second regions. Step 702d selectively forms
the first material with a top surface overlying the second material
in the first region. Step 702e conformally deposits the second
material overlying the first and second regions. Step 702f
chemical-mechanical polishes (CMPs) the second material to the
level of the first material top surface, see FIGS. 6A and 6B.
[0046] In another aspect, simultaneously growing IrOx
nanostructures from the non-continuous IrOx film overlying the
second region (Step 706) includes forming non-continuous zones in
the film having an area in the range between 100 nm.sup.2 and 100
microns.sup.2, and a spacing between zones in the range between 1
and 5000 nm.
[0047] In one aspect, growing IrOx nanostructures from the
continuous IrOx film overlying the first region (Step 704) includes
forming nanostructures having a diameter in the range between 10
and 1000 nm, a length in the range between 10 nm and 10 microns,
and a spacing in the range between 10 and 1000 nm. Note, the
nanostructures grown overlying the temporary non-continuous film
have approximately the same dimensions.
[0048] A method for patterning a substrate of IrOx nanostructures,
and a resulting patterned substrate have been provided. Examples of
dimensions and materials have been used to help illustrate the
invention. However, it should be understood that the invention is
not limited to merely these examples. Other variations and
embodiments of the invention will occur to those skilled in the
art.
* * * * *