U.S. patent application number 09/918908 was filed with the patent office on 2002-02-14 for methods for the lithographic deposition of materials containing nanoparticles.
Invention is credited to Bravo-Vasquez, Juan Pablo, Hill, Ross H..
Application Number | 20020018861 09/918908 |
Document ID | / |
Family ID | 22829638 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020018861 |
Kind Code |
A1 |
Hill, Ross H. ; et
al. |
February 14, 2002 |
Methods for the lithographic deposition of materials containing
nanoparticles
Abstract
A method for depositing nanoparticles in a thin film through the
dispersion of such nanoparticles in a precursor solution which is
deposited on a substrate and converted into a metal or metal oxide
film. The resulting metal or metal oxide film will contain embedded
nanoparticles. Such films can be used in a variety of applications
such as diffusion barriers, electrodes for capacitors, conductors,
resistors, inductors, dielectrics, or magnetic materials. The
nanoparticle material may be selected by one skilled in the art
based on the particular application.
Inventors: |
Hill, Ross H.; (Coquitlam,
CA) ; Bravo-Vasquez, Juan Pablo; (Burnaby,
CA) |
Correspondence
Address: |
Pennie & Edmonds, LLP
3300 Hillview Avenue
Palo Alto
CA
94304
US
|
Family ID: |
22829638 |
Appl. No.: |
09/918908 |
Filed: |
July 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60221844 |
Jul 28, 2000 |
|
|
|
Current U.S.
Class: |
427/532 ;
257/E21.273; 427/123; 427/126.3 |
Current CPC
Class: |
C23C 30/00 20130101;
G03F 7/0047 20130101; C01G 11/02 20130101; C23C 24/08 20130101;
H01L 21/02348 20130101; C23C 2/26 20130101; C23C 26/00 20130101;
H01L 21/02175 20130101; H01L 21/31695 20130101; C23C 18/143
20190501; C23C 18/06 20130101; H01L 21/02282 20130101; C23C 8/02
20130101; C23C 18/145 20190501; C23C 2/04 20130101; C23C 18/08
20130101; C23C 26/02 20130101; C23C 18/127 20130101; C23C 18/1204
20130101; H05K 3/105 20130101; H01L 21/02194 20130101; C23C 18/1283
20130101; H05K 1/162 20130101 |
Class at
Publication: |
427/532 ;
427/123; 427/126.3 |
International
Class: |
B05D 005/12 |
Claims
What is claimed is:
1. A method of depositing films comprising one or more metals or
metal oxides with embedded nanoparticles; wherein the nanoparticles
are in a metal-ligand precursor solution which is deposited on a
substrate and photochemically converted.
2. The method of claim 1 wherein the film is patterned.
3. A method of depositing films comprising one or more metals or
metal oxides with embedded nanoparticles, said method comprising:
Dispensing nanoparticles in a precursor solution of metal
complexes; Depositing the precursor solution onto a substrate; and
Converting the precursor solution deposited on the substrate to a
metal or metal oxide film with embedded nanoparticles.
4. The method of claim 3 wherein the depositing is done by spin
coating.
5. The method of claim 3 wherein the depositing is done by
spraying.
6. The method of claim 3 wherein the depositing is done by dip
coating.
7. The method of claim 3 wherein the depositing is done by
inking.
8. The method of claim 3 wherein the conversion is done
electromagnetically.
9. The method of claim 3 wherein the conversion is done
photochemically.
10. The method of claim 3 wherein the conversion is done
thermally.
11. The method of claim 3 wherein the conversion is done with a
plasma.
12. The method of claim 3 wherein the conversion is done with an
ion beam.
13. The method of claim 3 wherein the conversion is done with an
electron beam.
14. The method of claim 3 wherein the metal or metal oxide film
formed by the conversion step is patterned.
15. The method of claim 14 wherein the film is sequentially
converted in two or more steps.
16. The method of claim 14 wherein the conversion is done
electromagnetically.
17. The method of claim 14 wherein the conversion step is done
photochemically.
18. The method of claim 14 wherein the conversion is done
thermally.
19. The method of claim 14 wherein the conversion is done with a
plasma.
20. The method of claim 14 wherein the conversion is done with an
ion beam.
21. The method of claim 14 wherein the conversion is done with an
electron beam.
22. The method of claim 3 wherein interdiffusion of the
nanopartioles with the metal or metal oxide can be controlled by
varying the temperature at which the conversion occurs.
23. The method of claim 3 wherein the composition or properties of
the film is altered due to the composition of the atmosphere in
which the conversion takes place.
24. A method of forming patterned films comprising one ore more
metals or metal oxides with embedded nanoparticles, said method
comprising: Dispensing nanoparticles in a precursor solution
comprising metal complexes; Depositing the precursor solution onto
a substrate; and Photochemically converting the precursor solution
deposited on the substrate to a patterned metal or metal oxide film
with embedded nanoparticles.
Description
[0001] This application claims priority to Provisional Patent
Application No. 60/221,844, filed Jul. 28, 2000, entitled "METHODS
FOR THE LITHOGRAPHIC DEPOSITION OF MATERIALS CONTAINING
NANOPARTICLES."
FIELD OF THE INVENTION
[0002] This invention is related to methods of depositing films of
metals or metal oxides with embedded nanoparticles, from metal
complexes or precursor solutions. The invention also relates to the
use of such films in a variety of applications including but not
limited to microelectronics fabrication.
DESCRIPTION OF RELATED ART
[0003] Usually films of inorganic materials are deposited by
chemical or physical vapor deposition although in some cases Sol
gel or metal organic deposition have been used.
[0004] None of these methods, however, are able to pattern films of
materials and, therefore, must be used with other methods to form
the patterned structures normally used in the construction of
microelectronic devices or circuits.
[0005] The photochemical deposition method differs from the above
two methods in that the reaction which drives off the organic
components is photochemically activated. Hybrid methods often use
light as the energy source, but the light used initiates a thermal
rather than a photochemical reaction.
[0006] U.S. Pat. No. 5,534,312 to Hill et al. discloses a method
for the deposition of a variety of metal and metal oxide systems
using photochemical deposition. This process relies upon the
construction of an optical quality film of the precursor material
in order to provide (macroscopic) optical homogeneity during the
lithographic process.
[0007] The formation of nanoscale particles of different materials
is known in the art. For example, U.S. Pat. No. 5,984,997 to
Bickmore et al., incorporated herein, discloses a process for
producing nanoscale powders by mixing an emulsion comprising all of
the elements of the desired powder composition and a combustible
fuel, and then combusting that emulsion to produce a powder. The
'997 patent process discloses the production of many types of
powders, including particles and nanowhiskers of simple, doped, and
polymetallic powders.
[0008] Forming a material with imbedded nanoparticles through use
of a precursor material is disclosed in U.S. Pat. No. 5,851,507 to
Pirzada et al., incorporated herein, where a continuous process is
used to produce nanoscale powders from different types of precursor
materials by evaporating the material and quenching the vaporized
phase in a converging-diverging expansion nozzle. However, the '507
patent does not disclose a photochemical technique of converting
the precursor material to a metal or metal oxide film with imbedded
nanoparticles. Also, M. Cahay, et al., Quantum Confinement:
Nanoscale Materials, Devices, and Systems, Electrochemical Soc.
Proceedings Volume 97-11, pp. 35-46 1997, incorporated herein,
describe embedding nanoparticles in a thermal sol gel matrix but
also does not disclose converting or patterning a thin film
deposited from a precursor material.
[0009] The use of nanoparticles or nanoscale particles in passive
components has previously been found to be beneficial. For example,
U.S. Pat. No. 5,952,040 to Yadav et al., incorporated herein,
discloses nanosize powders which are used to form the ceramic
layers of passive electronic components. The ceramic layers
containing nanoscale powders are deposited between electrodes to
form an electrode/ceramic/electrode structure. The ceramic layer is
dried at low temperatures to prevent interdiffuision problems of
the nanoscale powders. However, the '040 patent does not disclose a
means to distribute the nanoscale powders directly within a metal
or metal oxide film, nor does the '040 patent teach a photochemical
technique of converting the precursor material to a metal or metal
oxide film.
[0010] The present invention is an extension of these technologies
and discloses a means to embed nanoparticles in metal or metal
oxide films for various lithographic applications.
SUMMARY OF THE INVENTION
[0011] The present invention discloses a method for depositing
nanoparticles in a thin film. The nanoparticles are dispersed in a
precursor solution which is deposited on a substrate and converted
into a metal or metal oxide film. The precursor film may be
deposited on the surface by a variety of methods. The conversion to
metal or metal oxide film can be achieved by photochemical reaction
or by the impact of an ion or an electron beam. The resulting metal
or metal oxide film thereby contains embedded nanoparticles. By use
of a mask or a directed beam, the metal or metal oxide film can be
patterned. By altering the atmosphere in which the pattern is
formed, the composition and/or properties of the resulting metal or
metal oxide film can be altered.
[0012] Such films can be used in a variety of applications such as
diffusion barriers, electrodes for capacitors, conductors,
resistors, inductors, dielectrics, or magnetic materials. The
resulting film may be amorphous or crystalline based on the
application. The nanoparticle material may be selected by one
skilled in the art based on the particular application.
BRIEF DESCRIPTION OF THE FIGURES
[0013] FIG. 1 shows a latent image of CdS particles in manganese
(II) 2-ethylhexanoate Film
DETAILED DESCRIPTION
[0014] The present invention discloses a process of combining the
precursor solution with nanoparticles which are then deposited on a
substrate and patterned, for example, photochemically.
[0015] One of the purposes for embedding nanoparticles is to gain a
localized difference in the particular material. Nanoparticles
embedded in materials can have many practical applications,
including but not limited to, use as diffusion barriers, electrodes
for capacitors, conductors, resistors, inductors, dielectrics, and
magnetic materials, generally. Another application of these
materials is to prepare optical filters which make use of the
optical properties of the nanoparticles. Similar applications could
make use of electrochromatic nanomaterials in a suitable matrix for
optical display applications. Additionally, the use of
nanomaterials which are electro (or photo) luminescent in a matrix
would also provide low temperature routes to the assembly and
patterning of these materials.
[0016] The types of materials of which the nanoparticles are made
are tied to the application. For example, magnetic materials
composed of single domain particles could be patterned in this
process and used in memory applications. Such nanoparticles would
typically be rare earth magnets. The source of nanoparticles or the
material may be judiciously selected by a person of ordinary skill
in the art pertaining to the particular application.
[0017] Passive components, such as ferroelectrics, could be used as
well. These could be patterned for use in memory and capacitors,
for example.
[0018] The present invention uses metal complexes with
nanoparticles to form liquid crystal films, which can be converted
to metal or metal oxide films by a variety of methods, including,
but not limited to the methods described in U.S. Pat. No. 5,534,312
to Hill et al., which is incorporated herein by reference.
[0019] Typical films may be deposited on various substrates. These
include materials as wide ranging as simple salts, such as
CaF.sub.2, to semiconductor surfaces such as silicon. The nature of
the substrate is not critical for the process although it may
effect the method of deposition of the precursor film (and, if
used, the solvent for the deposition). The most commonly used
substrate has been silicon wafers. These wafers may have been
coated with other layers such as dielectric layers, photoresist or
polyimide, metal oxides, thermal oxides, conduction materials,
insulating materials, ferroelectric materials or other materials
used in the construction of electronic devices. These include
silicon single crystal wafers.
[0020] The precursor film may be deposited on the surface by a
variety of methods, one of which is spin coating the molecule from
a solvent. In this procedure, a precursor and nanoparticles are
dispersed in a solvent to form a precursor solution. The substrate
surface is then put on a surface, which can be spun. The substrate
may be held in place with a vacuum chuck such as present in a
commercial spin coater (i.e. from Headway or Laurell Corporation).
The precursor solution is dispensed onto the surface of the
substrate either before commencing spinning or while the substrate
is spinning. The substrate is then allowed to spin resulting in the
deposition of a thin film of the precursor on the surface.
[0021] The films may also be formed by other methods including but
not limited to spray on, dip coating and various inking
methods.
[0022] In one embodiment this film undergoes a photochemical
reaction resulting in the conversion of the metal complex into a
metal or metal oxide material in which the nanoparticles are
trapped. Since this process can be performed at low temperature
(ambient or below) it is possible to limit the interdiffusion of
the matrix material with the nanoparticles. By performing the
reaction at higher temperature, it is possible to interdiffuse the
two materials and lose the nanostructuring. By controlling the
temperature of the process it is possible to achieve intermediate
situations as well. This is an advantage of this system since, by
the photochemical conversion, it is possible to control the
reaction which forms the matrix independent of the thermal
interdiffusion.
[0023] Typically the film may be exposed to light directed though
an optical mask used to define an image on the surface. The mask
consists of transparent and light absorbing regions. The mask may
also include an optical enhancing feature such as phase shift
technology. Exposure of the film with this light results in a
chemical reaction within the film which changes the film from
precursor to the product. This type of conversion is consistent
with that described in U.S. Pat. No. 5,534,312.
[0024] The light does not necessarily have to be directed through a
mask. For example, if it is not necessary to pattern the material,
a flood exposure may be used. Alternatively, if patterning is
desired, a direct writing approach may be used. In a common
implementation of the direct writing process laser beam is directed
in a serial fashion over the surface resulting in exposure only of
the areas where the beam was directed. Alternatively, near field
optical systems allow selective exposure of some areas of the
surface. In another alternative embodiment of the invention, the
film may be converted in multiple steps or stages where a portion
of the film is converted at a time. By using this approach, for
example, the resulting film may comprise different materials in a
pattern by sequentially converting portions of the film in
selective atmospheres.
[0025] Normally the atmosphere used for the exposure is air. It
may, for a variety of reasons, be preferable to change the
composition of the atmosphere present during exposure. One reason
is to increase the transmission of the exposing light because short
wavelength light is used which may be attenuated by air. It may
also be desirable to change the composition of the atmosphere to
alter the composition or properties of the product film.
[0026] Exposure may also be achieved with ion or electron beams.
These are normally directed in a serial write process. The ion or
electron beam is directed onto the precursor film, which causes a
reaction to produce the product film in the exposed areas. The
nature of the exposure systems for ion and electron beams are such
that these are normally done within a vacuum. The deposit from such
a process may be, depending upon the conditions, the metal which
oxidizes to form oxide upon exposure to air.
EXAMPLE 1
[0027] Nanometer scale CdS dots were prepared by the reverse
micelle method following the general procedure outlined by
Steigerwald et. al. In a typical experiment, equal volumes of
microemulsions prepared under nitrogen from of CdClO.sub.4 (0.72 mL
as a 0.4 M aqueous solution) and sodium
bis(2-ethylhexyl)sulfosuccinate (AOT) (0.2 M) in heptane (50 ml)
and Na.sub.2S (0.72 mL as a 0.3 M aqueous solution) and (AOT) (0.2
M) in heptane (50 ml) were combined in a flask and stirred under
nitrogen for 2 hours. The solvent was then removed under reduced
pressure and the product resuspended in petroleum ether. A separate
petroleum ether solution of Mn(II) 2-ethylhexanoate was prepared
and the two solutions were combined.
[0028] The resultant solution was spin coated onto a silicon wafer
and exposed to 254 .mu.m light resulting in the conversion of
Mn(II) 2-ethylhexanoate to manganese oxide. The nanoparticles were
dispersed within the manganese oxide material.
[0029] By irradiation through a mask, a patterned film could be
formed in this process. FIG. 1 shows the latent image formed from
the CdS particles in a manganese(II) 2-ethylhexanoate film.
EXAMPLE 2
[0030] In a similar experiment to Example 1, micron scale CdS
particles were prepared by a modification of the method of Dona and
Herrero. A solution of thiourea (10 mmol), cadmium acetate (10
mmol), and ethylene glycol (0.4 mL) in a 150 mL aqueous ammonium
chloride/ammonia buffer (pH 10) was prepared. A glass substrate was
inserted into the solution and this solution was heated to
80.degree. C. overnight. The solution was allowed to cool and the
adherent CdS particles were collected on the glass substrate which
was removed from the solution. These particles were suspended in
petroleum ether and combined with a Mn(II) 2-ethylhexanoate in
petroleum ether solution. This solution was spin coated onto a
silicon surface and photolysis resulted in the formation of
nanoparticles embedded on the surface of the thin manganese oxide
film.
[0031] Those skilled in the art will appreciate that variations to
the above-described methodology may occur without departing from
the scope of the invention. Thus, it follows that the invention is
not limited to the particular examples or details described
above.
* * * * *