U.S. patent application number 11/833542 was filed with the patent office on 2008-08-28 for method of forming low-resistance metal pattern, patterned metal structure, and display devices using the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Sung Hen CHO, Sang Eun PARK, Ki Yong SONG.
Application Number | 20080206530 11/833542 |
Document ID | / |
Family ID | 39383513 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080206530 |
Kind Code |
A1 |
SONG; Ki Yong ; et
al. |
August 28, 2008 |
METHOD OF FORMING LOW-RESISTANCE METAL PATTERN, PATTERNED METAL
STRUCTURE, AND DISPLAY DEVICES USING THE SAME
Abstract
Disclosed herein is a method of forming low-resistance metal
pattern, which can be used to obtain a metal pattern having stable
and excellent characteristics by performing sensitization treatment
using a copper compound before an activation treatment for forming
uniform and dense metal cores, a patterned metal structure, and
display devices using the same.
Inventors: |
SONG; Ki Yong; (Seoul,
KR) ; CHO; Sung Hen; (Seoul, KR) ; PARK; Sang
Eun; (Yongin-si, KR) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
39383513 |
Appl. No.: |
11/833542 |
Filed: |
August 3, 2007 |
Current U.S.
Class: |
428/209 ; 216/41;
427/123; 427/124; 427/125 |
Current CPC
Class: |
H01B 13/0026 20130101;
C23C 18/1696 20130101; C23C 18/1605 20130101; H05K 3/388 20130101;
H05K 3/108 20130101; C23C 18/30 20130101; C23C 18/31 20130101; H01L
27/124 20130101; H05K 3/24 20130101; H05K 2203/072 20130101; H01L
27/1255 20130101; C23C 18/1692 20130101; Y10T 428/24917 20150115;
G02F 1/136295 20210101; H05K 2203/0716 20130101; C23C 18/1889
20130101 |
Class at
Publication: |
428/209 ; 216/41;
427/123; 427/124; 427/125 |
International
Class: |
B32B 3/00 20060101
B32B003/00; B05D 5/12 20060101 B05D005/12; B44C 1/22 20060101
B44C001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2007 |
KR |
10-2007-0020168 |
Claims
1. A method of forming a low-resistance metal pattern, in which the
metal pattern is formed by forming a plurality of metal cores by:
performing sensitization treatment of a surface of a substrate with
a copper compound, activating the sensitized surface of the
substrate by activation treatment of the substrate, and forming a
plated layer on the activated surface of the substrate.
2. The method of forming low-resistance metal pattern according to
claim 1, wherein the method comprises: forming a lower conductive
patterned film on a surface of an insulated substrate; performing
sensitization treatment on the lower conductive pattern film using
a copper compound; activating the sensitized substrate to form an
activated multi-layered catalyst film comprising a plurality of
catalyst metal cores thereon; and forming one or more plated layers
on the surface of the activated multi-layered catalyst film.
3. The method of forming low-resistance metal pattern according to
claim 2, wherein forming the lower conductive pattern film
comprises: forming a metal thin film on a surface of the insulated
substrate; forming a photosensitive film on a surface of the metal
thin film opposite the insulated substrate; patterning the
photosensitive film by selectively exposing and developing the
photosensitive film using a mask; and etching the exposed
underlying regions of metal thin film in the patterned
photosensitive film.
4. The method of forming low-resistance metal pattern according to
claim 2, wherein the copper compound is copper, a copper alloy,
copper sulfate, or copper chloride.
5. The method of forming low-resistance metal pattern according to
claim 2, wherein activating the sensitized substrate is performed
using palladium, a palladium alloy, or palladium chloride.
6. The method of forming low-resistance metal pattern according to
claim 2, wherein forming a plated layer is performed using a wet
electroless plating method or a wet electrolytic plating
method.
7. The method of forming low-resistance metal pattern according to
claim 2, wherein, in forming a plated layer, a metal for plating is
selected from the group consisting of Ni, Cu, Ag, Au, and alloys
thereof.
8. The method of forming low-resistance metal pattern according to
claim 2, wherein forming a plated layer is performed by immersing
the sensitized and activated lower conductive pattern film into a
copper electroless plating solution including a copper salt, a
complexing agent, a reductant, and a pH adjuster.
9. The method of forming low-resistance metal pattern according to
claim 3, wherein the metal thin film is formed of a conductive
material selected from the group consisting of molybdenum, nickel,
copper, titanium, tantalum, tungsten, and alloys thereof.
10. The method of forming low-resistance metal pattern according to
claim 1, further comprising forming a protective layer on the
plated layer.
11. The method of forming low-resistance metal pattern according to
claim 10, wherein the protective layer comprises nickel or a nickel
alloy.
12. The method of forming low-resistance metal pattern according to
claim 1, further comprising annealing a low-resistance metal
pattern after the formation of the low-resistance metal pattern by
forming a plated layer.
13. The method of forming low-resistance metal pattern according to
claim 12, wherein annealing is performed under a nitrogen, argon or
vacuum atmosphere at about 40 to about 400.degree. C. for about 15
to about 120 minutes.
14. A patterned metal structure, comprising: a substrate; a lower
conductive pattern film formed on a surface of the substrate; and
an upper conductive pattern film formed on a surface of the lower
conductive pattern film opposite the substrate, wherein the
patterned metal structure comprises a seed layer, including a
copper compound and a palladium compound, disposed between the
lower conductive pattern film and the upper conductive pattern
film.
15. The patterned metal structure according to claim 14, wherein
the structure comprises: a lower conductive pattern film disposed
on a surface of a substrate; a seed layer, including a copper
compound and a palladium compound, formed on a surface of the lower
conductive pattern film opposite the substrate; and an upper
conductive pattern film formed on a surface of the seed layer
opposite the lower conductive pattern film.
16. The patterned metal structure according to claim 14, wherein
the lower conductive pattern film is formed of a conductive
material selected from the group consisting of molybdenum, nickel,
copper, titanium, tantalum, tungsten, and alloys thereof.
17. The patterned metal structure according to claim 14, wherein
the upper conductive pattern film is formed of a conductive
material selected from the group consisting of nickel, copper,
silver, gold, and alloys thereof.
18. The patterned metal structure according to claim 14, wherein
the seed layer comprises both a copper seed layer including a
copper compound and a palladium seed layer including a palladium
compound, wherein the copper seed layer is disposed on a surface of
the lower conductive pattern film opposite the substrate, and the
palladium seed layer is disposed on a surface of the copper seed
layer opposite the lower conductive pattern film.
19. The patterned metal structure according to claim 14, wherein
the copper compound is selected from the group consisting of
copper, a copper alloy, copper sulfate, and copper chloride.
20. The patterned metal structure according to claim 14, wherein
the palladium compound is selected from the group consisting of
palladium, a palladium alloy, and palladium chloride.
21. The patterned metal structure according to claim 14, further
comprising a protective layer formed on a surface of the upper
conductive pattern film.
22. The patterned metal structure according to claim 14, wherein
the protective layer comprises nickel or a nickel alloy.
23. A display device comprising the patterned metal structure
according to claim 14.
24. The display device according to claim 23, wherein the display
device is a liquid crystal display device.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority to Korean Patent
Application No. 10-2007-0020168, filed on Feb.28, 2007, and all the
benefits accruing therefrom under 35 U.S.C. .sctn.119, the content
of which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of forming a
low-resistance metal pattern, a patterned metal structure and
display devices using the same, and, more particularly, to a method
of forming low-resistance metal pattern, which can be used to
obtain metal pattern having stable and excellent characteristics by
performing sensitization treatment using a copper compound before
activation treatment to form uniform and dense metal cores, a
patterned metal structure, and display devices using the same.
[0004] 2. Description of the Related Art
[0005] As electronic devices gradually become miniaturized and
increasingly integrated, the pattern width decreases so that the
resistance of metal pattern increases, which causes signal delayed,
thereby deteriorating the display quality of the electronic
devices. Accordingly, the problems can become significant obstacles
to the development of TFT-LCDs having high image quality and large
areas. In order to realize high-speed and highly integrated
electronic devices and products, copper (Cu), which has lower
electric resistance and higher charge mobility than conventional
aluminum, molybdenum and chromium, and thus is able to overcome the
delay of driving signals (RC delay), is useful as a pattern
material to produce such devices and products. Copper has low
specific resistance and excellent electromigration resistance.
Attempts to develop various novel technologies that take advantage
of the characteristics of copper are continuously being made.
[0006] In electronic devices, such as integrated circuits ("IC"),
liquid crystal display devices ("LCD"), and the like, metal
patterns, which are formed on a substrate, are gradually being
miniaturized to accommodate the increase in the degree of
integration required in such devices from the miniaturization of
these devices. To form metal micropatterns on a substrate by a
conventional method, a metal pattern is formed by sputtering the
entire surface of a substrate with metal, forming a pattern thereon
by a photolithography process using a photoresist, and then etching
the exposed metal to form a metal pattern, and removing the
photoresist.
[0007] Since these conventional methods of forming a metal pattern
need expensive equipment and use methods such as a sputtering
method which must be performed at a high temperature, the number of
such processing steps that are required and the investment cost for
manufacturing the necessary equipment are each high, which
increases the overall manufacturing cost.
[0008] However, among the methods of forming copper pattern, an
electroless plating method which plates a metal film by the
reaction of a reductant and an oxidant in solution to provide the
metal at the surface of an activated substrate. Advantageously,
since the electroless plating method is simultaneously performed
over the entire substrate, the manufacturing cost is low, processes
are simple, and productivity is high.
[0009] In the electroless plating method, since a metal film is
directly plated on a diffusion-preventing film using an
electrochemical method, any microstructures located at the
interface between the diffusion preventing film and the metal film,
reactions occurring on the interface, and the like, have an
influence on all of the characteristics of the metal pattern
provided thereby, including electrical properties, thermal
stability, and the like. Further, in an exemplary electroless
plating method, catalyst metal cores are formed on a lower
conductive pattern film by activating the lower conductive pattern
film before the formation of the plated metal layer. Since the
catalyst metal cores catalyze the plating process, the plating
process can thus be readily performed. Accordingly, a technology
for forming uniform and dense catalyst metal cores in an activation
process is an important aspect of the technology for forming a
stable plated layer having desirable qualities through the
electroless plating process.
[0010] To perform an activation process when the electroless
plating is conducted on an insulating film, methods of performing
sensitization treatment using SnCl.sub.2 are known. These methods
are performed for the purpose of increasing the uniformity and
density of metal cores formed by the activation process.
[0011] However, a plated film formed by activation treatment
performed using tin and palladium has insufficient adhesion to the
substrate, and thus it is unsuitable for practical use.
BRIEF SUMMARY OF THE INVENTION
[0012] Accordingly, the present invention has been made to overcome
the above problems of the prior art, and in an embodiment, a method
of forming low-resistance metal pattern is provided, which can be
used to obtain an electroless plated layer having stable and
desirable characteristics by performing sensitization treatment
with a copper compound before activation treatment to form uniform
and dense metal cores in the process of forming a metal pattern
using an electroless plating method.
[0013] In another embodiment, a low-resistance metal pattern is
provided which can provide a plated layer having stable and
desirable characteristics.
[0014] In another embodiment, a display device including the metal
pattern is provided.
[0015] In an embodiment, a method of forming a low-resistance metal
pattern is provided, in which the metal pattern is formed by
forming a plurality of metal cores by performing sensitization
treatment of the substrate with a copper compound, activating a
surface of the sensitized substrate, and forming a plated layer on
the activated surface of the substrate.
[0016] In a further embodiment, the method can include forming a
lower conductive pattern film on a surface of an insulated
substrate, performing a sensitization treatment on a surface of the
lower conductive pattern film with a copper compound, activating
the sensitized surface of the substrate to form a multi-layered
catalyst film comprising a plurality of catalyst metal cores
thereon, and forming one or more plated layers on a surface of the
activated multi-layered catalyst film.
[0017] To accomplish the above, in another embodiment, a patterned
metal structure is provided, including a substrate, a lower
conductive pattern film formed on a surface of the substrate, and
an upper conductive pattern film formed on a surface of the lower
conductive pattern film opposite the substrate, wherein the
structure includes a seed layer including both a copper compound
and a palladium compound, disposed between the lower conductive
pattern film and the upper conductive pattern film.
[0018] The patterned metal structure can include a lower conductive
pattern film layered on a surface of a substrate, a seed layer
including a copper compound and a palladium compound, formed on a
surface of the lower conductive pattern film opposite the
substrate, and an upper conductive pattern film formed on a surface
of the seed layer opposite the lower conductive film.
[0019] To accomplish the above, in an embodiment, a display device
includes the patterned metal structure. In particular, the
patterned metal structure can be applied to the construction of a
liquid crystal display device such that the liquid crystal display
device comprises the patterned metal structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0021] FIG. 1 is a flow chart of the method of forming
low-resistance metal pattern according to an exemplary
embodiment;
[0022] FIG. 2 is a flow chart of the process of forming an
exemplary lower conductive pattern film by the method of forming
low-resistance metal pattern according to an embodiment;
[0023] FIG. 3 is a schematic sectional view of the structure of the
exemplary low-resistance metal pattern according to an
embodiment;
[0024] FIG. 4 is a schematic sectional view of an exemplary liquid
crystal display device according to an embodiment;
[0025] FIG. 5A to 5F are plan and side SEM (scanning electron
microscope) micrograph showing the exemplary metal pattern film
obtained in each step of Example 1;
[0026] FIG. 6 is a side SEM micrograph showing the exemplary metal
pattern film obtained in Example 1;
[0027] FIG. 7A to 7c are views showing the results of measuring the
adhesivity of the exemplary copper pattern obtained in Comparative
Examples 1 to 3;
[0028] FIG. 8 is a view showing the result of measuring the
adhesivity of the exemplary copper pattern obtained in Example
1;
[0029] FIG. 9 is a graph showing the change in thickness of plated
layers depending on reaction time in the exemplary copper pattern
obtained in Example and Comparative Examples;
[0030] FIG. 10 is a graph showing the change of specific resistance
depending on the thickness of plated layers in the exemplary copper
pattern obtained in Example and Comparative Examples; and
[0031] FIG. 11 is the X-ray diffraction spectra of the exemplary
copper pattern obtained in Example and Comparative Examples.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Hereinafter, the present invention will be described in
detail with reference to the attached drawings.
[0033] It will be understood that when an element is referred to as
being "on" another element, it can be directly on the other element
or intervening elements may be present therebetween. In contrast,
when an element is referred to as being "disposed on" or "formed
on" another element, the elements are understood to be in at least
partial contact with each other, unless otherwise specified. Terms
such as "upper", "lower", "between", and the like are labels
provided to show relative positions of elements relative to one
another, and should not be construed as absolute positions.
[0034] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. The use of the terms "first",
"second", and the like do not imply any particular order but are
included to identify individual elements. It will be further
understood that the terms "comprises" and/or "comprising," or
"includes" and/or "including" when used in this specification,
specify the presence of stated features, regions, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, regions,
integers, steps, operations, elements, components, and/or groups
thereof.
[0035] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0036] In the drawings, like reference numerals in the drawings
denote like elements and the thicknesses of layers and regions are
exaggerated for clarity.
[0037] Reference now should be made to the drawings, in which the
same reference numerals are used throughout the different drawings
to designate the same or similar components.
[0038] A method of forming low-resistance metal pattern, in which
the metal pattern is formed by forming a plurality of metal cores
by activating the surface of a patterned substrate and then forming
a plated layer thereon, which includes performing sensitization
treatment of the surface using a copper compound before the
activation treatment of the sensitized substrate.
[0039] FIG. 1 is a flow chart of the method of forming
low-resistance metal pattern, and FIG. 2 is a flow chart of the
process of forming a lower conductive pattern film.
[0040] Referring to FIG. 1, in a method of forming a low-resistance
metal pattern, a lower conductive pattern film 101 is formed on a
surface of an insulating substrate 10. This lower conductive
pattern film is formed by patterning a metal thin film 20 on the
substrate 10. A copper seed layer 30 is formed on the metal thin
film 20 opposite substrate 10 to form the lower conductive pattern
film 101, and thereby sensitization treatment of the metal thin
film 20 is performed. Subsequently, the sensitized substrate is
activated using a palladium compound, to provide a palladium seed
layer 40 layered on a surface of the copper seed layer 30 opposite
the metal thin film 20, to form a plurality of catalyst metal
cores. The catalyst metal cores constitute a multi-layered catalyst
film 102 having two or more layers. For example, when the
sensitization treatment is performed using a copper compound and
the activation treatment is performed using a palladium compound, a
two-layered catalyst film, consisting of a copper catalyst film and
a palladium catalyst film, can be formed. Finally, the
low-resistance metal pattern 103 can be formed by forming one or
more plated layers 50 on a surface of the activated multi-layered
catalyst film 102 opposite the substrate 10.
[0041] Hereinafter, each step will be described in more detail with
reference to FIGS. 1 and 2.
[0042] (i) Forming a Lower Conductive Pattern Film
[0043] A lower conductive pattern film may be formed according to
general methods of forming metal pattern film. In an exemplary
embodiment, in FIG. 2, a metal thin film (metal catalyst film) 220
is first formed on a surface of a substrate 210.
[0044] The substrate material that can be used is not limited, but
a plastic substrate or a glass substrate is desirably used as the
substrate 210.
[0045] Metal thin film materials that can be used to form a lower
conductive pattern film include, but are not limited to,
molybdenum, nickel, copper, titanium, tantalum, tungsten and alloys
thereof. The metal thin film may be deposited to a thickness of
about 5 to about 500 nm.
[0046] Subsequently, a photosensitive film 230 is formed on a
surface of the metal thin film 220 by applying a photoresist
composition thereon. The photosensitive film 230 is selectively
UV-exposed using a photo mask 240, developed, and thus patterned to
form a photoresist pattern 231. In this case, usable photoresist
compositions, exposure conditions and the like are not limited. The
metal catalyst 220 that is exposed in the opened regions 232 of the
photoresist pattern 231 are etched to expose the underlying surface
of substrate 210 and create a metal catalyst pattern 221 using an
etchant, and subsequently, the photosensitive film comprising the
photoresist pattern 231 remaining undesirably over the metal
catalyst pattern 221 is removed. For the etching process, in an
embodiment, an etchant whose main component is nitric acid,
hydrochloric acid, phosphoric acid, acetic acid or hydrogen
peroxide may be used.
[0047] (ii) Sensitization Treatment
[0048] Electroless plating proceeds by autocatalytic nucleation and
growth, and requires seeds, i.e., small metal particles, to
initiate a reaction to plate the metal. Since most metals cannot
themselves function as their own catalysts, it is necessary to form
metal cores for the growth of metal by performing sensitization and
activation treatment before metal can be deposited by electroless
plating.
[0049] When the lower conductive pattern film is formed,
sensitization treatment of the surface of the lower conductive
pattern film is performed by use of a copper compound. In this
case, the copper compound can be, but is not limited to, copper, a
copper alloy, copper sulfate, or copper chloride.
[0050] The sensitization treatment can be performed by immersing
the lower conductive pattern film into a sensitization solution
that includes the copper compound. In an exemplary embodiment, 0.01
M to 0.1 M aqueous copper sulfate can be used for the sensitizing
solution. The sensitization treatment may be performed at a
temperature of about 20 to about 80.degree. C. for about 5 to about
100 seconds. When the sensitization treatment is completed, the
lower conductive pattern film can be washed using deionized water
in order to remove the remaining sensitization solution.
[0051] Before the sensitization treatment, the lower conductive
pattern film can be pretreated using an acid solution, such as
nitric acid, or the like, to increase the contact between the metal
catalyst of the lower conductive pattern film and the copper thin
film formed by the sensitization treatment, by selectively
increasing the roughness of the surface of the lower conductive
pattern film. In an exemplary embodiment, an aqueous solution of 10
to 30% (v/v) of nitric acid is used.
[0052] Copper seeds are formed on the lower conductive pattern film
by the sensitization treatment process, thereby increasing the
number of nucleation sites available in the activation treatment
process, which is a post-process. Accordingly, the density and
uniformity of the metal cores provided after treatment using the
activation treatment process can each increase, thereby improving
the characteristics, such as electrical conductivity, adhesivity
and the like, of the plated layer formed thereon through the
subsequent electroless plating process.
[0053] (iii) Activation Treatment
[0054] After the sensitization treatment, activation treatment is
performed on the sensitized layer to form an active layer for
plating on the surface of metal cores. Generally, the activation
treatment is performed by immersing the sensitized pattern film
into an activation solution containing an activation treatment
metal, such as palladium, at about room temperature for a
predetermined time of, in an embodiment, 5 to 200 seconds. Upon
activation treatment, a plurality of metal cores that act as a
catalyst surface, are formed on the surface of the lower conductive
pattern film, thereby providing a suitable surface on which to
perform the electroless plating process.
[0055] The activation solution can include a palladium compound,
such as palladium, a palladium alloy, or palladium chloride. The
activation solution further comprises a solvent, such as for
example, sulfuric acid, hydrochloric acid, hydrogen peroxide, or
the like, but not limited thereto. In an embodiment, concentration
of palladium compound in the solution is 1 to 100 mg/L. When the
activation treatment is completed, the lower conductive pattern
film may be washed using deionized water in order to remove the
remaining activation solution.
[0056] When the sensitization and activation treatments are
performed, metal cores are formed as a multi-layered catalyst film.
These metal cores serve as catalysts for accelerating the growth of
metal crystals in the subsequent plating process.
[0057] (iv) Forming a Plated Layer
[0058] A low-resistance metal pattern is then fabricated by forming
one or more plated layers on a surface of the activated
multi-layered catalyst film by an electroless plating process. In
the plating step, metal crystals are grown from the plurality of
metal cores formed on the lower conductive pattern film, thereby
forming a metal pattern on a surface of the patterned activated
multi-layered catalyst film. That is, the metal cores formed on the
lower conductive pattern film aggregate with each other during
growth of the crystals, and thus form islands, and these islands in
turn combine with each other during further growth, thereby forming
a continuous plated film.
[0059] During plating, a multi-layered metal pattern may be formed
by growing two or more kinds of metals sequentially in a stepwise
method. This plating treatment can be performed using either a wet
electroless plating method or a wet electrolytic plating
method.
[0060] Herein, when the sensitization treatment is performed using
a copper compound and the activation treatment is performed using a
palladium compound, the resulting metal pattern film having
particles of palladium metal deposited at the surface of the metal
pattern film has sufficient catalyst activity to accelerate the
growth of crystals by a plating process, performed using an
electroless plating solution, thereby providing a more precise
metal pattern on the metal pattern film.
[0061] As a metal used for plating, Cu, Ni, Ag, Au, or alloys
thereof can be selectively used depending on the use of the metal
pattern. In order to obtain a highly conductive metal pattern, it
is preferred that a copper metal compound solution or a silver
metal compound solution be used.
[0062] Electroless plating or where desired, electrolytic plating,
can be performed using conventional commonly known methods. For
example, copper electroless plating is described below. The copper
plating is performed by immersing the activated lower conductive
pattern film into a plating solution containing 1) a copper salt,
2) a complexing agent for suppressing liquid phase reaction by
forming a ligand with copper ions, 3) a reductant for reducing
copper ions, 4) a pH adjuster for maintaining a suitable pH to
oxidize the reductant, 5) a pH buffer, and 6) a modifier, for a
predetermined time.
[0063] Specifically,
[0064] 1) The copper salt may include, but is not limited to,
copper chloride, copper nitrate, copper sulfate, or copper cyanide.
In a specific embodiment, copper sulfate is used as the copper
salt.
[0065] 2) The reductant includes NaBH.sub.4, KBH.sub.4,
NaH.sub.2PO.sub.2, hydrazine, formalin, or a polysaccharide such as
glucose. In a specific embodiment, formalin or a polysaccharide
such as glucose is used as the reductant.
[0066] 3) The complexing agent includes a chelator such as an
ammonia solution, acetic acid, guanic acid, a salt of tartaric
acid, ethylenediamine tetraacetic acid ("EDTA"), Rochelle salt and
the like, or an organic amine compound. In a specific embodiment, a
chelator such as EDTA, a salt thereof, or the like is used as the
complexing agent.
[0067] 4) The pH adjuster can include an acidic compound such as,
for example, H.sub.2SO.sub.4, or a basic compound such as, for
example, sodium carbonate or sodium hydroxide, and 5) the pH buffer
can include various organic acids such as formic acid or acetic
acid, and weakly acidic inorganic compounds such as ammonium
acetate or ammonium sulfate.
[0068] 6) The modifier is a compound for improving the coating and
flatness characteristics of a plated layer, and includes
surfactants such as for example poly(ethylene glycol) polymers, or
poly(ethylene glycol-propylene glycol) copolymers, and adsorptive
materials such as for example bis(3-sulfopropyl)disulfide,
3-mercapto-1-propane sulfonic acid, 2-mercaptopyridine,
4-mercaptopyridine, and the like, for adsorbing components that
suppress the growth of crystals.
[0069] Where an electrolytic plating method is used for growing
copper metals, the plating can be performed by immersing the lower
conductive pattern film into a plating composition containing 1) a
copper salt, 2) a complexing agent, 3) a pH adjuster, 4) a pH
buffer, and 5) a modifier.
[0070] Herein, an annealing process can be performed if desired in
order to remove water remaining in low-resistance metal pattern
obtained by forming a plated layer and to improve the electrical
properties and adhesivity of the plated layer. The annealing
process may be performed in a nitrogen, argon or vacuum atmosphere
at a temperature of about 40 to about 400.degree. C. for about 15
to about 120 minutes.
[0071] Further, after the formation of the plated layer, a
protective layer can be formed to protect the low-resistance
pattern. The protective layer can be formed of nickel or a nickel
alloy.
[0072] In the method disclosed herein, patterns are formed and
etched by vacuum deposition and photolithography only in the step
of forming a lower conductive pattern film. Subsequently, the lower
conductive pattern film is plated by a wet plating technology,
which is a wet film formation technology, in which the processing
cost is lower than that of vacuum deposition technology, thereby
decreasing the total manufacturing cost. Further, in the wet film
formation technology, since a film is formed in an aqueous
solution, the temperature for the film formation is 100.degree. C.
or lower, and thus energy consumption is lower than for a dry film
formation technology. Further, when the substrate being coated with
a film is large, fewer restrictions on equipment are encountered
compared to in the dry process, so that large metal pattern can be
easily formed on a variety of substrates of different sizes.
[0073] In another embodiment, a patterned metal structure having
excellent electrical properties, adhesivity, and processability is
provided. The patterned metal structure includes a substrate, a
lower conductive pattern film formed on a surface of the substrate,
and an upper conductive pattern film formed on a surface of the
lower conductive pattern film opposite the substrate, wherein the
structure includes a seed layer, including a copper compound and a
palladium compound, disposed between the lower conductive pattern
film and the upper conductive pattern film.
[0074] FIG. 3 is a schematic sectional view of a patterned metal
structure according to an embodiment. The patterned metal structure
according to an embodiment can in general include a lower
conductive pattern film layered on a surface of a substrate 10, a
seed layer, including a copper compound and a palladium compound,
formed on a surface of the lower conductive pattern film opposite
the substrate 10, and an upper conductive pattern film formed on a
surface of the seed layer opposite the lower conductive film.
Specifically, in FIG. 3, the lower conductive pattern film is
prepared by forming a metal thin film 20 on a surface of substrate
10, and the seed layer can include a combination of a copper seed
layer 30 formed on a surface of metal thin film 20 opposite
substrate 10, and a palladium seed layer 40 formed on a surface of
copper seed layer 30 opposite metal thin film 20. The upper
conductive pattern film, formed on a surface of the seed layer
(i.e., palladium seed layer 40 in the present embodiment),
corresponds to plated layer 50.
[0075] In the patterned metal structure, the metal thin film 20 is
formed of a conductive material selected from the group consisting
of molybdenum, nickel, copper, titanium, tantalum, tungsten, and
alloys thereof. Meanwhile, the plated layer 50 forming the upper
conductive pattern film can include, but is not limited to, a
conductive material selected from the group consisting of nickel,
copper, silver, gold and alloys thereof.
[0076] A seed layer placed between the lower conductive pattern
film and an upper conductive pattern film includes a copper
compound and a palladium compound. The seed layer can include a
copper seed layer 30 which includes a copper compound, and a
palladium seed layer 40 which includes a palladium compound. The
copper compound constituting the copper seed layer 30 may be
selected from the group consisting of copper, a copper alloy,
copper sulfate, and copper chloride; and the palladium compound
constituting the palladium seed layer 40 may be selected from the
group consisting of palladium, a palladium alloy, and palladium
chloride; but are not limited thereto.
[0077] The patterned metal structure can further include a
protective layer (not shown), which is composed of nickel, a nickel
alloy, or the like, formed on a surface of the upper conductive
pattern film opposite the seed layer to protect the upper
conductive pattern film.
[0078] In the patterned metal structure, the combination of strong
adhesivity of the copper seed layer and the improved uniformity of
the palladium seed layer provide the patterned metal structure with
a low specific resistance of about 3.0 .mu..OMEGA./cm or less, so
that the structure has high electroconductivity and improved gloss,
and the adhesivity of a plated film is improved.
[0079] The patterned metal structure can be used for various
display devices, such as liquid crystal display ("LCD"), plasma
display panels ("PDP"), electro luminescent displays ("ELD") and
electrochromic displays ("ECD"), as well as flat sensor such as
X-ray imaging device, and the like. In particular, where the
patterned metal structure is used for liquid crystal displays,
advantages realized include reduced manufacturing costs of the
liquid crystal display, and large-sized liquid crystal displays can
be manufactured.
[0080] Generally, a liquid crystal display device includes gate
lines formed in a transverse direction, data lines formed in a
longitudinal direction that intersect the gate lines, and thin film
transistors that are formed at intersections of the gate lines and
the data lines. Pixel electrodes connected with the thin film
transistors through drain contact holes are formed in pixel
regions, which are defined as the intersecting regions of the gate
lines and the data lines. The thin film transistor includes gate
electrodes branching from the gate lines, a semiconductor layer
covering the gate electrodes, source electrodes which overlap both
ends of the semiconductor layer at regular intervals and branch
from the data lines, and drain electrodes which are spaced apart
from the source electrodes and connect the pixel electrodes with
the thin film transistor.
[0081] FIG. 4 is a schematic sectional view of a liquid crystal
display device including the patterned structure of an embodiment.
As shown in FIG. 4, the liquid crystal device according to the
embodiment includes a transparent substrate 11; gate electrodes 12
formed on a surface of the substrate 11; a gate insulating film 15,
formed on a surface of the gate electrodes 12 opposite substrate
11; and a semiconductor layer 17, formed on the surface portion of
the gate insulating film 15 covering the gate electrodes 12. Source
electrodes 32 and drain electrodes 34, spaced apart from each other
at intervals (not shown in the cross-sectional view of FIG. 4), are
formed on the semiconductor layer 17, and channels 33 are formed in
the gaps between the source electrodes 32 and the drain electrodes
24. The semiconductor layer 17 includes an active layer 17a formed
of pure amorphous silicon (a-Si), and an ohmic contact layer 17b
formed of impure amorphous silicon (n+a-Si) and placed on a surface
of the active layer 17a. A protective layer 27, having drain
contact holes 28 for partially exposing the drain electrodes 34, is
formed in the upper portion of the thin film transistor, and pixel
electrodes 40 connected with the drain electrodes 34 through the
drain contact holes 28 are formed in pixel regions located in the
upper portion of the protective layer 27. The liquid crystal
display device is not limited to this structure, and can be
variously modified, added to and substituted by those skilled in
the art.
[0082] Hereinafter, exemplary embodiments of the invention will be
described in detail with reference to Examples. Here, these
Examples are set forth to illustrate the invention, but should not
to be construed as limiting thereto.
EXAMPLES
Example 1
[0083] Molybdenum was deposited to a thickness of 50 nm on a glass
substrate, and then the glass substrate, with the molybdenum thin
film so formed, was spin-coated with an AZ1512 photoresist
(Clariant Corp. positive tone photoresist). Subsequently, the
photoresist-coated glass substrate was exposed through a photo mask
using broadband UV exposure (equipment manufactured by Oriel Corp.)
as a light source for 7 seconds so that the output of broad band UV
resulted in a dose of 13 mJ/cm.sup.2 in the exposed regions defined
by the photomask, and was developed using a TMAH developer and
patterned and the exposed molybdenum thin film etched using AT10
(manufactured by Dongwoo Fine-Chem Co. Ltd.) as an etchant, thereby
obtaining a lower conductive pattern film.
[0084] 800 ml of deionized water was added to a 1.5 L vessel, 5.99
g of CuSO.sub.4.5H.sub.2O was added thereto, and the mixture was
then stirred. Subsequently, 26.99 g of EDTA.4Na was added thereto
and stirred, and 7.47 ml of HCHO (37 wt % aqueous solution) was
added thereto. Next, the pH of a plating solution was adjusted to
12.6 using sodium hydroxide (NaOH), and 5 ml of a 2,2-dipyridyl
solution was then added thereto, to prepare a sensitization
solution having the composition shown in (a) of the following Table
1. The sensitization solution was bubbled and simultaneously heated
to a temperature of 60.degree. C. After the bubbling and heating of
the sensitization solution was stopped, the lower conductive
pattern film was immersed into the sensitization solution for
seconds, removed therefrom, and washed with water. FIG. 5A to 5B
show plan and side SEM micrograph of the resulting sensitized metal
pattern film.
[0085] A 2 l beaker was filled with 1 L of deionized water, 2 ml of
conc. (aq.) HCl, and then 0.03 g of PdCl.sub.2 was added thereto
and stirred thoroughly until dissolved, to prepare the palladium
activation solution having a composition shown in (b) of the
following Table 1. This activation solution was stirred for about 1
hour, and was then introduced into a copper electroless double
boiling apparatus, and then the sensitized pattern film obtained in
the previous step was immersed therein for 60 seconds.
[0086] FIG. 5C and 5D show plan and side SEM micrograph of the
metal pattern film, activated for 10 seconds, and FIG. 5E and 5F
show plan and side SEM micrographs of the metal pattern film,
activated for 60 seconds. Referring to FIG. 5A to 5F, it can be
seen that metal cores were sparsely formed on the lower conductive
pattern film during the first stage, but grew when the activation
treatment was performed, so that they combined with each other to
form a continuous thin film.
[0087] The metal pattern film so obtained was immersed into an
electroless copper plating solution having the composition shown in
(c) in the following Table 1 at a temperature of 65.degree. C. for
5 minutes, so that copper metal crystals were grown on the lower
conductive pattern film, thereby obtaining a copper pattern
film.
[0088] FIG. 6 showed a side SEM micrograph of the obtained metal
pattern film plated with copper. As shown in FIG. 6, it can be seen
that the plated film so obtained does not exhibit separation at the
interface, and has high adhesivity.
TABLE-US-00001 TABLE 1 (a) Sensitization solution (b) Pd activation
solution (c) Copper plating solution Deionized water 800 ml
Deionized water 1 l Copper sulfate 3.5 g CuSO.sub.4.cndot.5H.sub.2O
5.99 g Conc. hydrochloric acid 2 ml Salt of tartaric acid 8.5 g
EDTA.4Na 26.99 g PdCl.sub.2 0.03 g Formalin (37%) 22 ml HCHO (37 wt
%) 7.47 ml Thiourea 1 g 2,2-dipyridyl solution 5 ml Ammonia 40
g
Comparative Example 1
[0089] A copper pattern film having a predetermined pattern was
obtained as in Example 1, except that the activation treatment was
not performed using a palladium compound, and only the
sensitization treatment was performed. The material properties of
the copper pattern film so obtained were evaluated, and the results
thereof are given in the following Table 2.
Comparative Example 2
[0090] A copper pattern film having a predetermined pattern was
obtained as in Example 1, except that the sensitization treatment
was not performed, and the activation treatment was performed using
only the palladium activation solution used in Example 1. The
material properties of the comparative copper pattern film so
obtained were evaluated, and the results thereof are given in the
following Table 2.
Comparative Example 3
[0091] A copper pattern film having a predetermined pattern was
obtained as in Example 1, except that a tin chloride solution (a
mixed solution of 10 g/L SnCl.sub.2 and 40 ml/L of conc. HCl (37 wt
% aq.) in water) was used as a sensitization solution instead of an
aqueous copper sulfate solution. The material properties of the
comparative copper pattern film so obtained were evaluated, and the
results thereof are given in the following Table 2.
Experiment Example 1
Measurement of Adhesivity
[0092] In the patterned metal structure (thickness 4500 .ANG.,
width 7 .mu.m) obtained in Example 1, the adhesivity of the plated
layer was tested by tape pull test using adhesive tape, and the
results thereof are shown in FIG. 8. Meanwhile, the adhesivity of
the plated layer obtained in Comparative Examples 1 to 3 was
evaluated, and the results thereof were shown in FIG. 7A to 7C.
[0093] As shown in FIG. 7A to 7C and 8, in the case of Comparative
Example 1, the adhesivity of a plated layer was good, but the
specific resistance of the plated layer was undesirably high since
Cu.sub.2O was formed on the plated layer. In the case of
Comparative Example 2, in which only the activation treatment was
performed using palladium, it was found that the adhesivity of the
plated layer was insufficiently low, so that the plated layer
completely peeled off when the adhesive tape adhered thereto was
pulled to separate it from the plated layer. Meanwhile, in the case
of Comparative Example 3, in which a tin compound was used as a
sensitizing agent and the activation treatment was performed using
a palladium activation solution, the adhesivity was somewhat
improved compared to Comparative Example 2, but was insufficient
compared to Example 1. That is, in the case of Example 1, in which
a copper compound was used as a sensitizing agent and the
activation treatment was performed using a palladium compound, the
adhesivity of the plated layer was best.
Experimental Example 1
Measurement of Specific Resistance
[0094] The specific resistances of each of the metal pattern film
obtained in Example 1 and Comparative Example 1 to 3 were measured
at thicknesses of both 300 nm and 450 nm, and the results thereof
are given in Table 2. The thickness thereof was measured using a
Surface profiler P-10, manufactured by Tencor corp., and the
specific resistance thereof was measured using a 4 point probe. The
change in the thickness of a plated layer was measured by observing
the change in the reaction time in Example 1 and Comparative
Example 1 to 3, and the results thereof are shown in FIG. 9.
Further, the change in the specific resistance of a plated layer
was measured depending on the thickness thereof, and the results
thereof are shown in FIG. 10.
TABLE-US-00002 TABLE 2 Specific resistance Specific resistance
(.mu.ohm-cm) (.mu.ohm-cm) Thickness of plated Thickness of plated
Examples layer 300 nm layer 450 nm Peeling test Comparative 3.0 2.8
0/140 Example 1 (Cu) Comparative Measurement Measurement 88/140
Example 2 impossible impossible (Pd) Comparative 2.9 2.4 69/140
Example 3 (Sn/Pd) Example 1 2.6 2.5 24/140 (Cu/Pd)
[0095] As shown in Table 2 and FIG. 9 to 10, the growth rate of the
copper electroless plated layer in Example 1 was similar to that in
Comparative Examples 1 to 3. However, the specific resistance in
Comparative Example 1 was the highest, and the specific resistance
in Comparative Example 2, in which the plated layer includes
palladium, was similar to that of Example 1. In the case of
Comparative Example 2, in which the activation treatment was
performed using a palladium compound, the specific resistance of
the plated layer could not be measured due to a strong peeling
phenomenon.
[0096] FIG. 11 is a graph showing the results of X-ray diffraction
analysis of copper pattern films obtained in Example 1 and
Comparative Examples 1 and 3. As shown in FIG. 11, in the case of
Comparative Example 1, since copper oxide (CuO.sub.2) peaks exist
at a 2.THETA. of 36.6.degree. (111) and 42.5.degree. (200), and
copper (Cu) peaks exist at a 2.THETA. of 43.3.degree. (111) and
50.5.degree. (200), it is predicted that the plated layer includes
Cu.sub.2O in addition to Cu. However, in the case of Comparative
Example 3 and Example 1, in which the activation treatment was
performed using palladium, the oxide peaks did not exist.
[0097] As seen in the above results in which, at the time of
electroless plating, a copper compound was used as the
sensitization agent and a palladium compound was used as the
activation agent, the adhesivity and specific resistance of the
plated film prepared thereby were found to provide the best
results.
[0098] According to the method of forming metal pattern, a
low-resistance metal pattern can be obtained efficiently by a wet
film formation process without undergoing a conventional sputtering
process, which requires high-temperature and high-vacuum
conditions. Accordingly, the present invention can be used to
reduce equipment investment and manufacturing costs. Moreover, the
method of forming metal pattern can also be applied to a flexible
substrate, and the metal pattern can be continuously produced by a
roll-to-roll process, thereby significantly improving
productivity.
[0099] The metal pattern has improved adhesivity and specific
resistance for the plated layer relative to a plated layer prepared
without the sensitization treatment using a copper compound and the
activation treatment of the substrate, so that the reliability and
price competitiveness of display devices using the patterned metal
structure of the present invention can also be improved.
[0100] As described above, although the preferred embodiments of
the present invention have been disclosed for illustrative
purposes, those skilled in the art will appreciate that various
modifications, additions and substitutions are possible, without
departing from the scope and spirit of the invention as disclosed
in the accompanying claims.
* * * * *