U.S. patent application number 11/792365 was filed with the patent office on 2008-05-29 for metal thin film-forming method and metal thin film.
Invention is credited to Tsutomu Atsuki, Masaaki Oda, Kyuukou Tei.
Application Number | 20080124238 11/792365 |
Document ID | / |
Family ID | 36601619 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080124238 |
Kind Code |
A1 |
Atsuki; Tsutomu ; et
al. |
May 29, 2008 |
Metal Thin Film-Forming Method And Metal Thin Film
Abstract
A metal thin film-forming method which comprises the step of
firing metal nanoparticles each comprising a particle consisting of
at least one metal selected from Ag, Au, Ni, Pd, Rh, Ru, and Pt or
an alloy comprising at least two of these metals and an organic
substance adhered to the periphery thereof as a dispersant, under a
gas atmosphere containing water and/or an organic acid to thus form
a metal thin film. This metal thin film possesses a low resistance
value.
Inventors: |
Atsuki; Tsutomu; (Chiba-ken,
JP) ; Tei; Kyuukou; (Chiba-ken, JP) ; Oda;
Masaaki; (Chiba-ken, JP) |
Correspondence
Address: |
ARENT FOX LLP
1050 CONNECTICUT AVENUE, N.W., SUITE 400
WASHINGTON
DC
20036
US
|
Family ID: |
36601619 |
Appl. No.: |
11/792365 |
Filed: |
December 15, 2005 |
PCT Filed: |
December 15, 2005 |
PCT NO: |
PCT/JP05/23009 |
371 Date: |
June 6, 2007 |
Current U.S.
Class: |
419/10 |
Current CPC
Class: |
B22F 2998/00 20130101;
H05K 1/097 20130101; B22F 2998/00 20130101; B22F 1/0062 20130101;
B22F 1/0022 20130101; H05K 2203/122 20130101; H05K 2203/1126
20130101; H05K 3/1291 20130101; C23C 26/00 20130101; C23C 24/08
20130101 |
Class at
Publication: |
419/10 |
International
Class: |
B22F 5/00 20060101
B22F005/00; B22F 3/10 20060101 B22F003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2004 |
JP |
2004-367554 |
Claims
1. A metal thin film-forming method which comprises firing metal
nanoparticles each comprising a particle consisting of at least one
metal selected from the group consisting of Ag, Au, Ni, Pd, Rh, Ru,
and Pt or an alloy comprising at least two of these metals and an
organic substance adhered to the periphery of the metal or alloy as
a dispersant, wherein the firing step is carried out under a gas
atmosphere containing water or an organic acid, or both water and
an organic acid.
2. The metal thin film-forming method as set forth in claim 1,
wherein the organic acid is a saturated fatty acid or an
unsaturated fatty acid having not more than 4 carbon atoms.
3. A metal thin film characterized in that it is formed according
to the metal thin film-forming method as set forth in claim 1.
4. A metal thin film characterized in that it is formed according
to the metal thin film-forming method as set forth in claim 3.
Description
TECHNICAL FIELD
[0001] The present invention relates to a metal thin film-forming
method which makes use of metal nanoparticles and a metal thin
film.
BACKGROUND ART
[0002] There has been proposed a method for forming a conductive
coating film using a metal colloidal solution as a method for
forming an electrode at a low temperature (see, for instance,
Japanese Un-Examined Patent Publication 2004-207558 (claim 1,
Section Nos. 0049 to 0050)). In this case, the method is one for
forming a conductive coating film by applying a metal colloidal
solution onto the surface of a base material or a substrate
according to the ink jet printing technique, wherein the substrate
used in the application of the coating film is one provided thereon
with a layer for receiving ink jet printing ink and the drying step
is carried out at a temperature of not more than 100.degree. C.,
after the completion of the coating operation. According to this
method, a coated film formed on a sheet of paper specially designed
for the ink jet printing as a substrate has a low volume
resistivity, after the drying of the same, on the order of
4.5.times.10.sup.-6.OMEGA.cm, but a coated film formed on a sheet
of the usual paper for making a copy (i.e. the usual photocopying
paper) which is free of any coating layer has a high surface
resistance value on the order of not less than
1.0.times.10.sup.8.OMEGA./.quadrature. (this value can be converted
into the volume resistivity of not less than
4.5.times.10.sup.7.mu..OMEGA.cm on the basis of the film thickness
of 450 nm). Accordingly, the use of such a layer for receiving ink
jet printing ink should be required for the reduction of the
resistance of the coated film.
[0003] In addition, there have also been proposed a reducing method
(see, for instance, Japanese Patent Application Serial No.
2003-317161 (Japanese Un-Examined Patent Publication 2005-081501))
and the gaseous phase evaporation technique (see, for instance,
Japanese Un-Examined Patent Publication 2002-121606 (claim 6)) as
methods for preparing metal nanoparticles.
DISCLOSURE OF THE INVENTION
Problems that the Invention is to Solve
[0004] In the methods for forming thin films which have been used
as distributing wires or electrical connections in the field of the
electric and electronic industries, the film-forming temperature
used therein has gradually been reduced recently. In addition, as a
base material used for forming a thin film thereon by applying
metal nanoparticles onto the same, drying the applied nanoparticles
and firing the same, there have been used various kinds of base
materials such as glass, polyimide, PET films, PEN films, and
polycarbonate. In addition to the methods which make use of these
base materials, metal nanoparticles have been sometimes applied
onto a substrate or a glass plate provided thereon with TFT (thin
film transistors) and accordingly, there has been desired for the
reduction of the film-forming temperature (firing temperature). The
firing temperature may vary depending on the characteristic
properties of the base material selected, but it has been desired
for the firing of the same even at a temperature of not more than
200.degree. C. in certain cases.
[0005] In consideration of these conditions, it has strongly been
desired for the formation of a thin film having a desired
thickness, while making use of a firing step carried out at a low
temperature and reducing the number of coating steps or
film-forming steps without using any heat-treatment carried out at
a high temperature. To this end, there has been desired for the
development of a method for forming a thin film having a low
resistivity, while making use of a dispersion of metal
nanoparticles having a high metal content, without using any
heat-treatment carried out at a high temperature.
[0006] Up to now, when forming a metal nanoparticle-containing thin
film used in such applications, various problems arise such that
the method requires the use of a high temperature firing step
although the resistivity of the resulting film can be reduced; and
that the method permits the use of a low temperature treatment, but
it leads to an increase in the number of coating steps. In this
respect, if the solid content of the coating solution is increased
by any means to reduce the number of coating steps, however,
problems newly arise such that the resulting coating solution is
quite instable and this results in the occurrence of a secondary
aggregation to thus cause the settlement of metal particles.
[0007] Accordingly, it is an object of the present invention to
solve the foregoing problems associated with the conventional
techniques and, more specifically, to provide a method for forming
a conductive metal thin film, using metal nanoparticles, on a
substrate free of any layer for receiving ink jet printing ink on
the surface thereon, unlike such a substrate as the paper specially
designed for the ink jet printing (i.e. a substrate provided
thereon with a layer for receiving the ink jet printing ink), which
is provided thereon with a thin film-receiving layer, which can
eliminate the use of any heat-treatment carried out at a high
temperature, and to likewise provide a metal thin film.
Means for Solving the Problems
[0008] The metal thin film-forming method according to the present
invention comprises the step of firing metal nanoparticles which
comprise particles consist of at least one metal selected from the
group consisting of Ag, Au, Ni, Pd, Rh, Ru, and Pt or an alloy
comprising at least two of these metals and an organic substance
adhered to the periphery of the metal or alloy as a dispersant,
wherein the firing step is carried out under a gas atmosphere
containing water or an organic acid, or both water and an organic
acid. The use of such a firing atmosphere would be able to form a
metal thin film having a low resistivity value.
[0009] The foregoing organic acids are preferably saturated fatty
acids or unsaturated fatty acids having not more than 4 carbon
atoms. In this connection, if the number of carbon atoms of each
organic acid exceeds 4, various problems arise such that the
resistance value of the resulting thin film is not reduced even
when the film is fired and that an offensive odor is generated
during the firing operation.
[0010] Moreover, the metal thin film according to the present
invention is characterized in that it is formed according to the
foregoing metal thin film-forming method.
EFFECTS OF THE INVENTION
[0011] The present invention permits the achievement of such an
effect that a conductive metal thin film having a low resistance
value can be formed, using conductive metal nanoparticles, on a
substrate free of any layer for receiving ink jet printing ink on
the surface thereof, unlike such a substrate as the paper specially
designed for the ink jet printing, which is provided thereon with
such receiving layer, the thin film being prepared by a
heat-treatment, at a low temperature, within a gas atmosphere
containing water or an organic acid, or both water and an organic
acid without using any heat-treatment carried out at a high
temperature.
BEST MODE FOR CARRYING OUT THE INVENTION
[0012] According to the present invention, the metal constituting
the metal nanoparticles used in the invention is at least one
member selected from the group consisting of conductive metals such
as Ag, Au, Ni, Pd, Rh, Ru, and Pt or an alloy comprising at least
two of these metals and it may properly be selected depending on
the purposes and/or applications of the resulting thin film. In the
following description, the term "metal" used also includes the
alloys thereof. The nanoparticles constituted by the foregoing
metals each have such a structure that an organic substance is
adhered to the circumference or periphery of each nanoparticle as a
dispersant. The term "adhered to, adhesion or the like" herein used
means that an organic substance is adsorbed on the surface of a
metal nanoparticle through a metal ion in such a manner that the
organic substance would assist the stable dispersion of metal
particles in an organic dispersion medium.
[0013] The foregoing organic substance is at least one member
selected from the group consisting of fatty acids and amines.
[0014] The fatty acid may preferably be at least one member
selected from the group consisting of saturated fatty acids and
unsaturated fatty acids each having a linear or branched structure
and each having 6 to 22 carbon atoms. In this respect, if the fatty
acid has less than 6 carbon atoms, the resulting dispersion is
quite unstable and it is quite liable to undergo agglomeration and
therefore, it would be impossible to increase the metal
concentration of the dispersion. On the other hand, if the number
of carbon atoms present in the fatty acid molecule exceeds 22,
problems would arise such that the viscosity of the resulting
dispersion increases and this in turn results in the reduction of
the handling properties of the dispersion when increasing the metal
concentration of the metal nanoparticle-containing dispersion and
that carbon atoms are liable to remain in the thin film finally
obtained after the firing step and this in turn leads to an
increase in the specific resistance value of the resulting
film.
[0015] As the foregoing fatty acids, there may be listed, for
instance, hexanoic acid, heptanoic acid, octanoic acid, nonanoic
acid, decanoic acid, undecanoic acid, dodecanoic acid,
tetradecanoic acid, hexadecanoic acid, octadecanoic acid,
eicosanoic acid, docosanoic acid, 2-ethylhexanoic acid, oleic acid,
linolic acid and linolenic acid.
[0016] The foregoing amine is desirably at least one member
selected from the group consisting of aliphatic amines each having
a linear or branched structure and each having 6 to 13 carbon
atoms. In this connection, if the amine has less than 6 carbon
atoms, the following problem arises: there is observed such a
tendency that the basic properties of the amine are too strong to
thus corrode metal nanoparticles and the amine may finally dissolve
the metal nanoparticles. On the other hand, if the number of carbon
atoms present in the main chain of the alkylamine exceeds 13,
problems would arise such that the viscosity of the resulting
dispersion increases and this in turn results in the reduction of
the handling properties of the dispersion when increasing the metal
concentration of the metal nanoparticle-containing dispersion and
that carbon atoms are liable to remain in the thin film finally
obtained after the firing step and this in turn leads to an
increase in the specific resistance value of the resulting
film.
[0017] The foregoing aliphatic amine is desirably a primary,
secondary or tertiary alkylamine, but it may likewise be a
polyvalent amine such as a monoamine, a diamine or a triamine.
[0018] Specific examples of such alkylamines include primary amines
such as butylamine, hexylamine, heptylamine, n-octylamine,
nonylamine, decylamine, dodecylamine, hexa-dodecylamine,
2-ethylhexylamine, 1,3-dimethyl-n-butylamine, 1-amino-undecane and
1-amino-tridecane; secondary amines such as di-n-butylamine,
di-n-propylamine, di-isopropylamine, N-methylaniline,
di-isobutyl-amine, di-pentylamine, and di-hexylamine; and tertiary
amines such as dodecyl-dimethylamine, N,N-dibutyl-1-butaneamine,
N,N-dimethyl-butylamine, N,N-dimethyl-hexylamine, and
N,N-dimethyl-octylamine; as well as diamines such as
naphthalene-diamine, octamethylene-diamine, and nonane-diamine.
Among these amines, preferably used herein are hexylamine,
heptylamine, n-octylamine, decylamine, dodecylamine,
2-ethylhexylamine, 1,3-dimethyl-n-butyl-amine, 1-amino-undecane and
1-amino-tridecane.
[0019] In the present invention, the firing of the metal
nanoparticles is carried out in a gas atmosphere containing water
or an organic acid, or both water and an organic acid and the
firing step is not carried out at a high temperature, but at a low
temperature. This organic acid is a saturated fatty acid or
unsaturated fatty acid having not more than 4 carbon atoms and
specific examples thereof include saturated fatty acids such as
formic acid, acetic acid, propionic acid, n-butyric acid and
iso-butyric acid; and unsaturated fatty acids such as acrylic acid,
methacrylic acid, crotonic acid, isocrotonic acid, maleic acid and
fumaric acid. It is sufficient in the present invention that the
ratio of water to be mixed with an organic acid may range from (0
to 100): (100 to 0) as expressed in the unit of "% by mass". In
addition, the gas to be mixed with water and/or the organic acid
may be air, oxygen, or an inert gas such as nitrogen gas, but the
ratio of the foregoing gas is not restricted to any specific range.
According to the present invention, it is possible to form a metal
thin film having a low resistance value. Moreover, the firing
temperature is in general not less than 50.degree. C., preferably
not less than about 80.degree. C. and this would allow the
formation of a thin film having a satisfactory and practically
acceptable specific resistance value. It is sufficient to
appropriately set the upper limit of the firing temperature at a
proper level while taking into consideration, for instance, the
kind of each particular substrate selected.
[0020] The method for the preparation of the metal nanoparticles is
not likewise restricted to any particular one and specific examples
thereof are the reducing method such as that disclosed in Japanese
Patent Application Serial No. 2003-317161 (Japanese Un-Examined
Patent Publication 2005-081501)) and the gaseous phase evaporation
technique disclosed in Japanese Un-Examined Patent Publication
2002-121606.
[0021] For instance, such a reducing method comprises the steps of
dissolving at least one member selected from the group consisting
of metal compounds of the foregoing fatty acids and amines in a
non-polar solvent and then subjecting the resulting solution to a
reducing treatment by the addition of a reducing agent to thus form
metal nanoparticles.
[0022] As the foregoing reducing agents, preferably used herein
include, for instance, sodium boron hydride, dimethylamine borane,
and tertiary butylamine borane. The reducing agents usable herein
are not restricted to these specific examples, but may be other
known reducing agents insofar as they can show the same reducing
action observed for the foregoing specific examples. This reducing
reaction may likewise be carried out while introducing, into the
reaction system, hydrogen gas, carbon monoxide gas, a
hydrogen-containing gas and/or a carbon monoxide gas-containing
gas.
[0023] The foregoing reducing treatment is preferably carried out
under such a condition that the reaction system is subjected to a
bubbling treatment while stirring the same, and/or refluxing the
reaction system at room temperature or with heating.
[0024] As has been described above, the foregoing metal compound is
subjected to a reducing treatment in a non-polar solvent to thus
form metal colloidal particles in the present invention, but
impurities or contaminants (such as boron atoms included in the
reducing agent) are present in the reaction liquid. For this
reason, deionized water is added to the reaction liquid and then
the resulting mixture is stirred, followed by allowing the mixture
to stand for a predetermined time period to thus recover the
supernatant. Among the impurities present in the reaction liquid,
hydrophilic ones are transferred to the aqueous phase at this stage
and this accordingly permits the reduction of the content of
impurities in the reaction liquid. In this respect, a polar solvent
having the smaller number of carbon atoms may be substituted for
the deionized water. In addition, the reaction liquid treated as
described above can be concentrated through filtration, for
instance, ultrafiltration to thus remove the excess fatty acids,
fatty acid esters and/or amines and to thus increase the purity and
the metal concentration of the resulting product. As a result, a
dispersion can be obtained, which comprises metal nanoparticles in
a concentration of not less than 5% by mass and not more than 90%
by mass.
[0025] The non-polar solvent described above and preferably used
herein may be, for instance, an organic solvent whose main chain
includes 6 to 18 carbon atoms and which has a low polarity. If
using an organic solvent whose main chain includes less than 6
carbon atoms, the polarity of the solvent is high to ensure the
formation of a desired dispersion or the resulting dispersion
suffers from a problem concerning the handling properties and this
is because, the coated layer thereof would be dried within an
extremely short period of time. On the other hand, if the number of
carbon atoms included in the main chain of such an organic solvent
exceeds 18, a problem arises such that carbon atoms are liable to
remain in the resulting film during the firing step due to possible
increases of, for instance, the viscosity of the liquid and/or the
boiling point thereof. As such solvents, usable herein include, for
instance, long chain alkanes such as hexane, heptane, octane,
decane, undecane, dodecane, tridecane and trimethyl pentane; cyclic
alkanes such as cyclohexane, cycloheptane and cyclooctane; aromatic
hydrocarbons such as benzene, toluene, xylene, trimethyl benzene
and dodecyl benzene; and alcohols such as hexanol, heptanol,
octanol, decanol, cyclohexanol and terpineol. These solvents may be
used alone or in the form of a mixed solvent. For instance, the
solvent may be mineral spirit which is a mixture of long chain
alkanes.
[0026] Moreover, as the gaseous phase evaporation method, an
example thereof includes one which comprises the steps of
evaporating a metal in a vacuum atmosphere in the presence of the
vapor of an organic solvent comprising at least one known organic
solvent used for forming metal nanoparticles according to the
gaseous phase evaporation method or in the presence of a mixed
vapor comprising the vapor of such an organic solvent and the vapor
of at least one member selected from the group consisting of, for
instance, fatty acids and amines serving as a dispersant to thus
bring the metal vapor into close contact with the vapor of the
organic solvent or the mixed vapor; cooling the resulting gaseous
mixture; and recovering the metal nanoparticles to thus give a
liquid containing the metal nanoparticles or a desired dispersion
thereof. In this respect, when bringing the metal vapor into
contact with only the organic solvent vapor, it is also possible to
obtain a desired dispersion by the addition of at least one member
selected from the group consisting of, for instance, fatty acids
and amines serving as a dispersant to the recovered liquid
containing the metal nanoparticles. The method comprising the
foregoing steps would permit the formation of a metal
nanoparticle-containing dispersion in which metal nanoparticles
each having a particle size of not more than 100 nm are separately
or individually dispersed.
[0027] When bringing the metal vapor into contact with only the
organic solvent vapor in the foregoing gaseous phase evaporation
technique, a polar solvent having a low molecular weight used for
the removal of the organic solvent may be added to the resulting
metal nanoparticle-containing dispersion to thus precipitate the
metal nanoparticles, after the addition of at least one member
selected from the group consisting of, for instance, fatty acids
and amines serving as a dispersant to the liquid containing the
metal nanoparticles recovered through cooling, followed by the
removal of the supernatant to thus substantially remove the organic
solvent and the subsequent addition, to the resulting precipitates,
of at least one solvent for ensuring the solvent-solvent exchange
to thus form a dispersion in which the metal nanoparticles thus
precipitated are separately or individually dispersed. On the other
hand, when bringing the metal vapor into close contact with the
mixed vapor, the polar solvent having a low molecular weight used
for the removal of the organic solvent may be added to the liquid
containing the metal nanoparticles recovered through cooling to
thus precipitate the metal nanoparticles, followed by the removal
of the supernatant to thus substantially remove the organic solvent
and the subsequent addition, to the resulting precipitates, of at
least one solvent for ensuring the solvent-solvent exchange to thus
form a dispersion in which the metal nanoparticles thus
precipitated are separately or individually dispersed.
[0028] The foregoing polar solvent having a low molecular weight is
a solvent having the small number of carbon atoms and specific
examples thereof preferably used herein are methanol, ethanol and
acetone.
[0029] The substrate onto which the metal nanoparticles can be
applied according to the method of the present invention may
appropriately be selected while taking into consideration the
purposes and applications of the resulting thin film and examples
thereof include a variety of substrates such as glass substrates;
resin substrates made of, for instance, polyimide, PET films, PEN
films and polycarbonate; and substrates such as glass plates
provided thereon with TFT layers. The methods for applying a metal
nanoparticle-containing dispersion onto such a substrate are not
restricted to specific ones and they may be the spin-coating
technique and the ink jet printing technique.
[0030] The present invention will hereunder be described in more
specifically with reference to the following Examples.
EXAMPLE 1
[0031] In this Example, Ag was selected as a metal material and the
metal nanoparticles used herein were Ag nanoparticles comprising
octanoic acid having 8 carbon atoms and 2-ethylhexylamine having 8
carbon atoms, both adhered to the periphery of these Ag
nanoparticles. These Ag nanoparticles were dispersed in toluene and
the dispersion had a metal concentration of 40% by mass. The Ag
nanoparticles used herein were prepared according to the gaseous
phase evaporation method.
[0032] This Ag nanoparticle-containing dispersion was applied onto
the surface of a glass substrate according to the usual
spin-coating technique to thus form a film, followed by firing the
same at 120.degree. C. for 30 minutes in an atmosphere formed by
evaporating a water: formic acid mixed liquid [90:10 (% by mass)]
in the air. After the completion of the firing step, the surface of
the resulting thin film had a gloss tinged with silver. The
specific resistance of the resulting film was determined using Low
resistance measurement unit (available from Mitsubishi Chemical
Co., Ltd.) and the measurement was carried out for three points on
the thin film. In this respect, the surface resistance values were
determined, and then the thickness of the thin film was determined
for converting the same into the corresponding specific resistance.
The results thus obtained are summarized in the following Table
1.
TABLE-US-00001 TABLE 1 Surface Resistance Film Thickness Specific
Resistance (.OMEGA./.quadrature.) (.mu.m) (.OMEGA. cm) 0.1228 0.37
4.54 .times. 10.sup.-6 0.1106 0.37 4.09 .times. 10.sup.-6 0.1228
0.37 4.54 .times. 10.sup.-6
[0033] The data listed in the foregoing Table 1 clearly indicate
that the specific resistance of the resulting Ag
nanoparticle-containing thin film is nearly equal to that observed
for the pure Ag (1.59.times.10.sup.-6.OMEGA.cm).
EXAMPLE 2
[0034] The same procedures used in Example 1 were repeated except
that the firing temperature was set at 80.degree. C. to thus form a
thin film and then the electric characteristic properties of the
resulting thin film were determined under the same conditions used
in Example 1. The results thus obtained are summarized in the
following Table 2.
TABLE-US-00002 TABLE 2 Surface Resistance Film Thickness Specific
Resistance (.OMEGA./.quadrature.) (.mu.m) (.OMEGA. cm) 0.2020 0.28
5.66 .times. 10.sup.-6 0.1863 0.28 5.22 .times. 10.sup.-6 0.1885
0.28 5.28 .times. 10.sup.-6
[0035] The data listed in the foregoing Table 2 clearly indicate
that the specific resistance of the resulting Ag
nanoparticle-containing thin film is slightly greater than that
observed for the thin film prepared in Example 1, but the thin film
still has a specific resistance value on the order of
10.sup.-6.OMEGA.cm, even when the firing temperature was
reduced.
[0036] FIG. 1 shows an SEM image illustrating the cross-sectional
view of the Ag thin film obtained after the firing step carried out
at 80.degree. C. and prepared in Example 2. As will be seen from
this FIGURE, it can be confirmed that particles are partially
sintered in the resulting film.
[0037] The results obtained in the following Examples 3 to 18 and
Comparative Examples 1 to 12 are summarized in the following Tables
3 and 4. In Examples 3 to 18, the same procedures used in Example 1
were repeated except that the metal species, dispersants and firing
conditions used were variously changed to thus form thin films of
these Examples and then the electric characteristic properties of
the resulting thin films were likewise determined or evaluated
under the same conditions used in Example 1. In this connection,
the mixing ratio of water to formic acid or acetic acid was set at
a level of 90:10 (% by mass) and it was evaporated in the air, but
the concentration in the resulting atmosphere was not particularly
controlled. Moreover, in Comparative Examples 1 to 12, the same
procedures used in Example 1 were repeated except that the firing
step was carried out in an atmosphere simply comprising the air and
then the electric characteristic properties of the resulting thin
films were likewise determined or evaluated under the same
conditions used in Example 1.
TABLE-US-00003 TABLE 3 Metal Conc. Ex. Metal Organic Substance
(Dispersant) (% by No. Sp. Fatty acids Amines mass) 3 Ag Dodecanoic
acid (C12) Octylamine (C8) 40 4 Ag Decanoic acid (C10) Hexylamine
(C6) 40 5 Ag Octanoic acid (C8) Dodecylamine (C12) 40 6 Ag Oleic
acid (C18) Decylamine (C10) 40 7 Ag Dodecanoic acid (C12)
Octylamine (C8) 40 8 Ag Dodecanoic acid (C12) -- 40 9 Ag Decanoic
acid (C10) -- 40 10 Ag Octanoic acid (C8) -- 40 11 Ag Oleic acid
(C18) -- 40 12 Au Dodecanoic acid (C12) Octylamine (C8) 40 13 Au
Octanoic acid (C8) Decylamine (C10) 40 14 Au Decanoic acid (C10)
Dodecylamine (C12) 40 15 Ag Octanoic acid (C8) -- 40 16 Ag Oleic
acid (C18) -- 40 17 Au Decanoic acid (C10) Octylamine (C8) 40 18 Au
Octanoic acid (C8) Dodecylamine (C12) 40 Surface Film Firing
Conditions Resist- Thick- Specific Ex. Temp Time ance ness
Resistance No. (.degree. C.) (min) Atm. (.OMEGA./.quadrature.) (nm)
(.mu..OMEGA. cm) 3 120 30 Water + formic acid 0.26 250.00 6.40 4
120 30 Water + formic acid 0.23 250.00 5.80 5 100 30 Water + acetic
acid 0.28 250.00 7.00 6 130 30 Water + acetic acid 0.80 250.00
20.00 7 80 30 Water + formic acid 0.16 250.00 4.00 8 120 30 Water +
acetic acid 0.27 250.00 6.86 9 120 30 Water + formic acid 0.20
250.00 5.00 10 100 30 Water + acetic acid 0.34 250.00 8.40 11 130
30 Water + acetic acid 0.38 250.00 9.40 12 120 30 Water + formic
acid 3.40 250.00 85.00 13 80 30 Water + acetic acid 4.16 250.00
104.00 14 100 30 Water + formic acid 4.40 250.00 110.00 15 100 60
Water 0.40 250.00 9.90 16 130 30 Formic acid 0.37 250.00 9.30 17
120 60 Water 3.88 250.00 97.00 18 80 30 Formic acid 5.20 250.00
130.00
TABLE-US-00004 TABLE 4 Metal Conc. Comp. Metal Organic Substance
(Dispersant) (% by Ex. No. Sp. Fatty acids Amines mass) 1 Ag
Dodecanoic acid (C12) Octylamine (C8) 40 2 Ag Decanoic acid (C10)
Hexylamine (C6) 40 3 Ag Octanoic acid (C8) Decylamine (C10) 40 4 Ag
Oleic acid (C18) Dodecylamine (C12) 40 5 Ag Dodecanoic acid (C12)
Octylamine (C8) 40 6 Ag Dodecanoic acid (C12) -- 40 7 Ag Decanoic
acid (C10) -- 40 8 Ag Octanoic acid (C8) -- 40 9 Ag Oleic acid
(C18) -- 40 10 Au Dodecanoic acid (C12) Octylamine (C8) 40 11 Au
Octanoic acid (C8) Decylamine (C10) 40 12 Au Decanoic acid (C10)
Dodecylamine (C12) 40 Film Firing Conditions Surface Thick-
Specific Comp. Temp Time Res. ness Res. Ex. No. (.degree. C.) (min)
Atm. (.OMEGA./.quadrature.) (nm) (.mu..OMEGA. cm) 1 120 30 The
atmosphere 7.20 250.00 180 2 120 30 The atmosphere 6.60 250.00 165
3 100 30 The atmosphere 4.80 250.00 120 4 130 30 The atmosphere
9780.00 250.00 244500 5 80 30 The atmosphere 5.24 250.00 131 6 120
30 The atmosphere 5.04 250.00 126 7 120 30 The atmosphere 3.60
250.00 90 8 100 30 The atmosphere 7.60 250.00 190 9 130 30 The
atmosphere 8.00 250.00 200 10 120 30 The atmosphere 420.00 250.00
10500 11 80 30 The atmosphere 2600.00 250.00 65000 12 100 30 The
atmosphere 1656.00 250.00 41400
[0038] The data listed in the foregoing Tables 3 and 4 indicate
that the firing in the atmosphere containing either or both of
water and an organic acid can form a thin film having a resistance
value lower than that observed for the thin film formed through the
use of a firing step carried out in an atmosphere comprising the
simple air, under the same temperature condition.
[0039] Moreover, even when using the foregoing conductive metals
other than Ag and Au as the foregoing metal species, and even when
using dispersants selected from the foregoing fatty acids and
amines other than those used in the foregoing Examples, one can
prepare metal thin films each having a low resistance value similar
to those observed for the foregoing Examples.
INDUSTRIAL APPLICABILITY
[0040] The present invention can provide a metal thin film having a
sufficient and practically acceptable specific resistance by making
use of the low temperature firing treatment carried out under the
presence of water and/or an organic acid. Accordingly, the present
invention can effectively be used in or applied to the fields,
which require the formation of metal thin films at a low
temperature, for instance, in the fields of electric and electronic
industries. For instance, the present invention can be applied to
the formation of metal distributing wires or metal electrical
connections used in the fields of display machinery and tools such
as flat panel display devices and in the fields of printed
wirings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 shows an SEM image illustrating the cross-sectional
view of the Ag thin film prepared in Example 2.
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