U.S. patent application number 12/137582 was filed with the patent office on 2008-10-16 for wiring board and production method thereof.
Invention is credited to Haruo Akahoshi, Akira Chinda, Toshio Haba, Hitoshi Suzuki, Hiroshi Yoshida.
Application Number | 20080251387 12/137582 |
Document ID | / |
Family ID | 36695922 |
Filed Date | 2008-10-16 |
United States Patent
Application |
20080251387 |
Kind Code |
A1 |
Haba; Toshio ; et
al. |
October 16, 2008 |
Wiring Board and Production Method Thereof
Abstract
It is an object of the present invention to provide a wiring
board having high-density wiring with a controlled shape without
masking by a resist film and a production method thereof. In the
present invention, the production method of a wiring board having
copper wiring on an insulating substrate includes the steps of
forming a metal seed layer on the insulating substrate, the metal
seed layer having a roughened shape in a portion on which the
copper wiring or a bump is to be formed, and forming an
electroplated film of copper or an alloy of copper through
electroplating on the portion of the metal seed layer having the
roughened shape. A substance for suppressing the plating reaction
is added to a plating bath to provide an angle of 90 degrees or
smaller between a surface of the insulating substrate and a side of
the electroplated film.
Inventors: |
Haba; Toshio; (Tokai,
JP) ; Yoshida; Hiroshi; (Mito, JP) ; Akahoshi;
Haruo; (Hitachi, JP) ; Suzuki; Hitoshi;
(Hitachi, JP) ; Chinda; Akira; (Hitachi,
JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
36695922 |
Appl. No.: |
12/137582 |
Filed: |
June 12, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11205175 |
Aug 17, 2005 |
|
|
|
12137582 |
|
|
|
|
Current U.S.
Class: |
205/125 ;
257/E23.07 |
Current CPC
Class: |
H01L 2924/09701
20130101; H05K 3/108 20130101; H05K 3/241 20130101; H01L 2924/0002
20130101; H01L 23/49838 20130101; H01L 2924/0002 20130101; H01L
2924/00 20130101; H05K 3/382 20130101; H05K 3/388 20130101; H01L
21/4846 20130101 |
Class at
Publication: |
205/125 |
International
Class: |
C25D 5/02 20060101
C25D005/02; C25D 7/00 20060101 C25D007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2005 |
JP |
2005-019437 |
Claims
1. A method of producing a wiring board having copper wiring on an
insulating substrate, comprising the steps of: forming a metal seed
layer on the insulating substrate, the metal seed layer having a
roughened shape in a portion on which the copper wiring is to be
formed; and forming an electroplated copper film on the portion of
the metal seed layer having the roughened shape through
electroplating using a plating bath containing a substance for
suppressing plating reaction, wherein the electroplated copper film
is formed at an angle of 90 degrees or smaller between a surface of
the insulating substrate and a side of the electroplated copper
film.
2. The method of producing a wiring board according to claim 1,
wherein the angle between the surface of the insulating substrate
and the side of the electroplated copper film is adjusted by
controlling a current density in performing the electroplating.
3. The method of producing a wiring board according to claim 1,
wherein the metal seed layer is formed on the insulating substrate
and then the roughened shape is formed thereon, and the
electroplated copper film is formed on the metal seed layer through
the electroplating and then the metal seed layer and the
electroplated copper film are removed except their portions having
the roughened shape thereon.
4. The method of producing a wiring board according to claim 1,
wherein the metal seed layer having the roughened shape formed
thereon is formed on the insulating substrate, the roughened shape
is planarized except its portion on which the copper wiring or
bumps are to be formed, the electroplated copper film is formed
through the electroplating on the metal seed layer, and then the
metal seed layer and the electroplated copper film are removed
except their portions having the roughened shape thereon.
5. The method of producing a wiring board according to claim 1,
wherein the metal seed layer serving as a power supply layer for
the electroplating is formed, and then an insulating film serving
as the insulating substrate is formed on the metal seed layer with
a casting method, the roughened shape is formed in a portion of the
metal seed layer on which wiring or bumps are to be formed, the
electroplated copper film is formed on the metal seed layer through
the electroplating, and the metal seed layer and the electroplated
copper film are removed except their portions having the roughened
shape thereon.
6. The method of producing a wiring board according to claim 1,
wherein an arithmetic average roughness Ra, defined in JIS B0601,
of the portion having the roughened shape of the insulating
substrate or the metal seed layer is larger than an arithmetic
average roughness Ra of the remaining portion.
7. The method of producing a wiring board according to claim 1,
wherein an average length of a roughness curve element RSm, defined
in JIS B0601, of the portion having the roughened shape of the
insulating substrate or the metal seed layer is smaller than an
average length RSm of the remaining portion.
8. The method of producing a wiring board according to claim 1,
wherein the surface roughness of the portion having the roughened
shape has an arithmetic average roughness Ra, defined in JIS B0601,
of 0.01 to 4 .mu.m, and an average length of a roughness curve
element RSm of 0.005 to 8 .mu.m.
9. The method of producing a wiring board according to claim 1,
wherein the substance added to the plating bath increases the
overpotential of the metal deposition through the electroplating
when the velocity of the plating bath containing the substrate to
increases.
10. The method of producing a wiring board according to claim 1,
wherein at least one of cyanine dyes is added to the plating
bath.
11. The method of producing a wiring board according to claim 10,
wherein the cyanine dye is a compound shown in the following
formula (where X represents an anion and n represents one of the
numbers 0, 1, 2, and 3): ##STR00002##
12. The method of producing a wiring board according to claim 10,
wherein the cyanine dye has a concentration of 3 to 15
mg/dm.sup.3.
13. The method of producing a wiring board according to claim 10,
wherein the electroplating is performed with a constant current at
a current density of 0.1 to 2.0 A/dm.sup.2.
14. The method of producing a wiring board according to claim 1,
wherein at least one substance selected from a polyether, an
organic sulfur compound, and a halide ion is added to the plating
bath.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S.
application Ser. No. 11/205,175 filed Aug. 17, 2005, the contents
of which are incorporated herein by reference. This application is
related to U.S. patent application Ser. No. 11/340,570, filed Jan.
27, 2006.
INCORPORATION BY REFERENCE
[0002] The present application claims priority from Japanese
application JP2005-019437 filed on Jan. 27, 2005, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a wiring board having a
wiring made of copper or an alloy of copper, and to a production
method thereof.
[0004] Electronic devices with smaller size, lighter weight, and
lower cost are needed increasingly year after year. This requires
wiring boards used in those electronic devices to have high-density
wiring formed with low cost in order to achieve smaller size and
lighter weight. Production methods of wiring boards can be broadly
classified into two: a subtractive method and an additive method.
In the subtractive method, an etching resist is formed on a copper
foil applied to a substrate and the copper is etched away except
the portions which will serve as wiring, thereby forming wiring. In
the additive method, a resin substrate is covered with a plating
resist film except the portions which will serve as wiring and a
plated film is formed only in the portions which will serve as
wiring.
[0005] In the conventional production methods of wiring boards,
both of the subtractive method and additive methods require the
masking of the substrate surface by the resist. The masking by the
resist film needs the steps of film formation, exposure, and
development. These steps involve high cost due to the use of
chemicals and the treatment of waste liquid. In addition, the large
number of the steps cause a long processing time. Thus, the process
of masking by the resist film has been a bottleneck in producing
wiring boards with low cost in a short time.
[0006] As a solution therefor, production methods of wiring boards
have been studied which use no masking by a resist. One of them is
a known method in which a metal seeding solution layer is formed on
a substrate surface and exposed to light at an appropriate
wavelength to form a metal seed layer and then plating or the like
is performed to form a metal film (for example, JP-A-7-336018). In
another known method, a plate is used to form a chemically changed
pattern on a substrate surface and electroless plating is performed
to form wiring (for example, JP-A-2002-184752).
[0007] The conventional methods for forming a wiring board without
masking by a resist have the following problem. For example, the
method in which a metal seeding solution layer is formed on a
substrate surface and exposed to light to form a metal seed layer
and then plating or the like is performed to form a metal film has
difficulty in forming wiring with higher density since the shape of
the plated film serving as wiring is not sufficiently considered.
The reason thereof is as follows. When plating is performed without
using a resist film, the plated film is isotropically grown from
the seed layer. The isotropically grown plated film creates a
semicircular cross-section in the plated wiring to occupy a larger
area on the wiring board as compared with rectangular wiring having
the same sectional area. Therefore, the wiring with the
semicircular cross-section is disadvantageous in providing higher
density as compared with the rectangular wiring.
[0008] In the method in which a plate is used to form a chemically
changed pattern on a substrate surface and electroless plating is
performed to form wiring, the shape of the plated film serving as
the wiring is not considered sufficiently. When plating is
performed without using a resist, the plated film has a larger
width than the seed layer, which is disadvantageous in achieving
higher density in wiring. In addition, the wiring cannot be formed
with a width as designed in the underlying film.
[0009] Thus, it is an object of the present invention to provide a
wiring board having high-density wiring with a controlled shape
without masking by a resist and a production method thereof.
SUMMARY OF THE INVENTION
[0010] According to the present invention, a method of producing
wiring board includes the steps of forming a metal seed layer on an
insulating substrate, the metal seed layer having a roughened area
on which copper wiring or a bump is to be formed, and forming an
electroplated film of copper or an alloy of copper through
electroplating on the roughened area of the metal seed layer. A
substance for suppressing plating reaction is added to a plating
bath to provide an angle of 90 degrees or smaller between a surface
of the insulating substrate and a side of the electroplated
film.
[0011] According to the present invention, a wiring board includes
a metal seed layer on an insulating substrate, the metal seed layer
having a roughened area thereon, and wiring or a bump made of
copper or an alloy of copper formed through electroplating on the
portion of the metal seed layer having the roughened area. An angle
between a surface of the insulating substance and a side of the
wiring or bump is 90 degrees or smaller.
[0012] The present invention allows high-density wiring with a
controlled shape to be formed without using a resist. The angle
between the wiring side and the substrate surface set to 90 degrees
or smaller enables the formation of the wiring through
electroplating without reducing the dimensional accuracy of the
wiring.
[0013] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1(a), 1(b) and 1(c) are sectional views showing an
example of a production method of a wiring board according to the
present invention.
[0015] FIGS. 2(a), 2(b) and 2(c) are sectional views showing
another example of the production method of a wiring board
according to the present invention.
[0016] FIGS. 3(a), 3(b), 3(c) and 3(d) are sectional views showing
yet another example of the production method of a wiring board
according to the present invention.
[0017] FIGS. 4(a), 4(b), 4(c) and 4(d) are sectional views showing
still another example of the production method of a wiring board
according to the present invention.
[0018] FIGS. 5(a), 5(b), 5(c) and 5(d) are sectional views showing
a further example of the production method of a wiring board
according to the present invention.
[0019] FIGS. 6(a), 6(b), 6(c), 6(d) and 6(e) are sectional views
showing a still further example of the production method of a
wiring board according to the present invention.
[0020] FIGS. 7(a), 7(b), 7(c), 7(d), 7(e) and 7(f) are sectional
views showing a yet further example of the production method of a
wiring board according to the present invention.
[0021] FIGS. 8(a), 8(b), 8(c) and 8(d) are sectional views showing
another example of the production method of a wiring board
according to the present invention.
[0022] FIG. 9 shows an evaluation method of the sectional shape of
wiring.
[0023] FIGS. 10(a), 10(b) and 10(c) are sectional views showing the
sectional shapes of wiring provided in Examples of the present
invention.
[0024] FIG. 11 is a plan view showing a wiring board viewed from an
electroplated copper film.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present inventors have found that an appropriate
roughened area is formed on a metal seed layer for electroplating
and plating conditions are optimized to allow the controlled
deposition shape of the plated film in the portion having the
roughened area. An effective approach to control of the deposition
conditions of the plated film is to add a compound, as an additive,
which suppresses the plating reaction and loses the plating
reaction suppressing effect as the plating reaction proceeds. The
property of suppressing the plating reaction can be seen from the
fact that the addition of the additive increases the metal
deposition overpotential. The property of losing the plating
reaction suppressing effect as the plating reaction proceeds can be
seen from the fact that the metal deposition rate is decreased with
a higher flow rate of a plating bath, that is, with quicker supply
of the additive to the metal surface. When the additive loses the
plating reaction suppressing effect, the additive may be decomposed
into different substrates, or reduced to a substrate with a
different oxidation number.
[0026] When plating is performed with the plating bath containing
such an additive, the additive loses its effect on the surface of
the metal seed layer as the plating reaction proceeds, so that the
effective concentration of the additive contributing to the plating
reaction decreases. The portion of the metal seed layer of the
roughened shape has a relatively larger surface area to consume the
additive at a higher rate as compared with the portion without any
roughened shape, which results in an even lower concentration of
the additive near the surface of the metal seed layer of the
roughened area. Thus, in the portion of the roughened shape on the
metal seed layer, the additive effect of suppressing the plating
reaction is reduced to increase the plating rate. Since the plating
rate depends on the concentration of the additive on the surface of
the metal seed layer, the shape of the plated film changes with the
distribution of the additive concentration.
[0027] Since the distribution of the additive concentration can be
changed by controlling the plating conditions, the shape of the
plated film can also be changed by controlling the plating
conditions. The distribution of the additive concentration is
provided on the basis of the balance between the diffusion of the
additive over the metal seed layer and the reaction rate thereof on
the surface of the metal seed layer. Thus, controlling either the
diffusion of the additive over the metal seed layer or the reaction
rate thereof on the surface of the metal seed layer enables control
of the shape of the plated film in the portion of the roughened
shape.
[0028] The diffusion rate of the additive over the metal seed layer
is largely affected by the concentration of the additive in the
plating bath, and the reaction rate of the additive on the metal
seed layer is largely affected by the current density during
plating. Thus, changing the additive concentration in the plating
bath or the current density during the plating can control the
distribution of the additive concentration, thereby making it
possible to achieve preferential deposition of the plated film on
the roughened area and control of the shape of the plated film.
[0029] Description will hereinafter be made for aspects of a
production method of a wiring board of the present invention.
[0030] According to one aspect, the production method includes the
steps of forming the metal seed layer on the insulating substrate,
forming the rough area on the metal seed layer including the
portion on which wiring or a bump is to be formed, forming the
electroplated film made of copper or an alloy of copper on the
rough area of the metal seed layer through the electroplating, and
removing the seed metal layer and the electroplated copper film
except their portions having the rough area thereon. The substance
for suppressing the plating reaction is added to the plating bath
to provide an angle of 90 degrees or smaller between the surface of
the insulating substrate and the side of the electroplated
film.
[0031] According to another aspect, the production method includes
the steps of forming the metal seed layer having the rough area
formed thereon on the insulating substrate, planarizing the
roughened shape on the metal seed layer except its portion on which
the copper wiring or bumps are to be formed, forming the
electroplated film made of copper or an alloy of copper through the
electroplating on the metal seed layer, and removing the metal seed
layer and the electroplated film except their portions having the
roughened area thereon. The substance for suppressing the plating
reaction is added to the plating bath to provide an angle of 90
degrees or smaller between the surface of the insulating substrate
and the side of the electroplated film.
[0032] According to yet another aspect, the production method
includes the steps of forming the metal seed layer serving as a
power supply layer for the electroplating, forming an insulating
film serving as the insulating substrate on the metal seed layer
with a casting method, forming the rough area in a portion of the
metal seed layer on which wiring or a bump is to be formed, forming
the electroplated film made of copper or an alloy of copper through
the electroplating on the portion of the metal seed layer having
the rough area, and removing the metal seed layer and the
electroplated film except their portions having the rough area
thereon. The substance for suppressing the plating reaction is
added to the plating bath to provide an angle of 90 degrees or
smaller between the surface of the insulating substrate and the
side of the electroplated film.
[0033] In the present invention, an arithmetic average roughness Ra
(defined in JIS B0601) of the portion having the rough area of the
substrate or the metal seed layer is set to be larger than Ra in
the remaining portion. Alternatively, an average length of a
roughness curve element RSm (defined in JIS B0601) of the portion
having the rough area of the substrate or the metal seed layer is
set to be smaller than RSm in the remaining portion.
[0034] It is desirable that the surface roughness of the portion
having the rough area of the metal seed layer on which the plated
film is preferentially formed has an arithmetic average roughness
Ra (defined in JIS B0601) of 0.01 to 4 .mu.m and has an average
length of a roughness curve element RSm of 0.005 to 8 .mu.m. More
specifically, it is desirable that the surface roughness of the
portion having the roughened shape of the metal seed layer has an
arithmetic average roughness Ra (defined in JIS B0601) of 0.1 to 1
.mu.m and has an average length of a roughness curve element RSm of
0.05 to 2 .mu.m.
[0035] The substance added to the plating bath desirably increases
the deposition overpotential of the metal deposition through the
plating when the flow rate of the plating bath to which the
substrate is added increases. As an example of such a substrate, at
least one of cyanine dyes is desirably added. A particularly
desirable cyanine dye is a compound shown in the formula below (X
represents an anion and n represents one of the numbers 0, 1, 2,
and 3).
##STR00001##
[0036] The cyanine dye desirably has a concentration of 3 to 15
mg/dm.sup.3. In the present invention, at least one substance
selected from a polyether, an organic sulfur compound, and a halide
ion can be added to an electrolytic copper plating bath.
[0037] The electrolytic copper plating in forming the copper film
is desirably performed with a constant current at a current density
of 0.1 to 2.0 A/dm.sup.2.
[0038] Next, description will be made for aspects of the wiring
board of the present invention.
[0039] According to one aspect, the wiring board has the metal seed
layer on the insulating substrate, the metal seed layer having the
rough area thereon, and wiring or bumps formed through
electroplating on the portion of the metal seed layer having the
rough area. An angle between a surface of the insulating substance
and a side of the wiring or bump is 90 degrees or smaller. An
arithmetic average roughness Ra, defined in JIS B0601, of the
portion having the rough area of the substrate or the metal seed
layer is larger than an arithmetic average roughness Ra of the
remaining portion.
[0040] According to one aspect, the wiring board has the metal seed
layer on the insulating substrate, the metal seed layer having the
rough area thereon, and wiring or bumps of copper or an alloy of
copper formed through electroplating on the portion of the metal
seed layer having the rough area. An angle between a surface of the
insulating substance and a side of the wiring or bump is 90 degrees
or smaller. An average length of a roughness curve element RSm,
defined in JIS B0601, of the portion having the rough area of the
substrate or the metal seed layer is smaller than an average length
RSm of the remaining portion.
[0041] It is desirable that the surface roughness of the portion
having the rough area of the metal seed layer has an arithmetic
average roughness Ra (defined in JIS B0601) of 0.01 to 4 .mu.m, or
an average length of a roughness curve element RSm of 0.005 to 8
.mu.m. More specifically, Ra desirably has a value of 0.1 to 1
.mu.m and RSm desirably has a value of 0.05 to 2 .mu.m. It is most
desirable that both of them fall within the abovementioned
ranges.
[0042] The angle between the surface of the insulating substrate
and the side of the wiring or bump is desirably equal to or larger
than one degree.
[0043] In the wiring board, the plated copper or an alloy of copper
desirably has a surface in parallel with the surface of the
insulating substrate.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0044] Examples of the present invention will hereinafter be
described. First, table 1 shows the results of Examples 1 to 22 and
Comparative Example 1.
TABLE-US-00001 TABLE 1 Additive Concentration Current Density No.
Additive Type [mg/dm.sup.3] [A/dm.sup.-2] Ra RSm .theta. [degree]
Example 1 A-2 7.0 1.25 0.01 0.02 83 Example 2 A-2 7.0 1.25 0.05
0.04 83 Example 3 A-2 7.0 1.25 0.4 1.1 85 Example 4 A-2 7.0 1.25
1.5 1.4 80 Example 5 A-2 7.0 1.25 2.0 4.0 86 Example 6 A-2 7.0 1.25
0.5 0.6 83 Example 7 A-2 7.0 1.25 1.0 1.1 89 Example 8 A-2 7.0 1.25
0.4 3.1 85 Example 9 A-2 2.5 1.0 0.4 1.1 86 Example 10 A-2 5.0 1.0
0.4 1.1 85 Example 11 A-2 7.5 1.0 0.4 1.1 32 Example 12 A-2 10 1.0
0.4 1.1 19 Example 13 A-2 7.0 0.50 0.4 1.1 10 Example 14 A-2 7.0
1.5 0.4 1.1 89 Example 15 A-2 10 1.25 0.4 1.1 28 Example 16 A-2 10
1.37 0.4 1.1 45 Example 17 A-2 10 1.50 0.4 1.1 52 Example 18 A-1
7.0 1.25 0.4 1.1 80 Example 19 A-3 4.0 1.25 0.4 1.1 83 Example 20
A-4 5.0 1.0 0.4 1.1 79 Example 21 A-1 7.0 1.5 0.4 1.1 68 A-2 5.0
Example 22 A-2 7.0 1.0 0.4 1.1 34 B-1 100 C-1 2 Comparative A-2 7.0
1.25 0.007 10 135 Example 1 Various symbols in the columns
"Additive Type" in Table 1 represent the following chemical
substances. A-1:
2-[(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-methyl]-1,3,3-tri-
methyl-3H-indolium perchlorate A-2:
2-[3-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1-propenyl]-1,3-
,3-trimethyl-3H-indolium chloride A-3:
2-[5-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1,3-pentadienyl-
]-1,3,3-trimethyl-3H-indolium iodide A-4:
2-[7-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-1,3,5-heptatrie-
nyl]-1,3,3-trimethyl-3H-indolium iodide B-1: Polyethylene glycol
(average molecular weight 3000) C-1:
bis(3-sulfopropyl)disulfide
EXAMPLE 1
[0045] A solution containing dispersed silver particles with an
average diameter of 20 nm was sprayed with an ink jet technique
onto a surface of an insulating substrate 1 (Kapton EN made by Du
Pont-Toray Co., Ltd.) made of polyimide film with a thickness of 25
.mu.m shown in FIG. 1(a) to form a metal seed layer 2 with a wiring
width of 20 .mu.m and a thickness of 0.2 .mu.m as shown in FIG.
1(b). Then, the insulating substrate was heated to a temperature of
200.degree. C. to fuse the silver particles. As the insulating
substrate, it is possible to use not only the polyimide but also a
resin of polyester, class epoxy, phenol, and aramid, ceramics, and
glass. As the particles, it is possible to use metal particles of
platinum, gold, copper, nickel, tin and the like, other than
silver. The roughness on the surface of the metal seed layer formed
by the silver particles was measured with a surface roughness
measuring apparatus. The measurement showed that the surface
roughness of the metal seed layer had an arithmetic average
roughness Ra (defined in JIS B0601) of 0.01 .mu.m and an average
length of a roughness curve element RSm of 0.02 .mu.m.
[0046] Electroplating was performed immediately after the formation
of the metal seed layer to form an electroplated copper film 3 as
shown in FIG. 1(c). The electroplating was performed by using a
plating bath having a composition shown in Table 2 to which a
substrate shown in Table 1 is added as an additive. The
electroplating was performed for 40 minutes at a current density of
1.25 A/dm.sup.2 with the plating bath at a temperature of
25.degree. C. Phosphorus copper was used as an anode.
TABLE-US-00002 TABLE 2 Component Concentration (g/dm.sup.3) Copper
Sulfate Pentahydrate 64 Sulfuric Acid 180 Chloride Ion 70 .times.
10.sup.-3
[0047] The cross-section of the wiring board was observed after the
plating to measure an angle .theta. between the side wall of the
electroplated copper film and the polyimide film substrate as shown
in FIG. 9, and an angle of 83 degrees was found.
[0048] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the metal seed layer including the silver particles.
It should be noted that the plan view of the wiring board viewed
from the electroplated copper film 3 is as shown in FIG. 11, and
this applies to the following Examples.
EXAMPLE 2
[0049] A metal seed layer 2 with a wiring width of 10 .mu.m was
formed as shown in FIG. 2(a) through a mask with a sputtering
technique on a surface of an insulating substrate 1 (Upilex S made
by Ube Industries Ltd.) made of polyimide film with a thickness of
25 .mu.m shown in FIG. 2(a). The metal seed layer was made of two
layers: a nickel film with a thickness of 0.01 .mu.m formed on the
substrate and a copper film with a thickness of 0.5 .mu.m formed on
the nickel film. As the metal seed layer, it is possible to use not
only the stacked film of nickel and copper but also a stacked film
of chromium and copper. Then, copper roughening processing was
performed to form a roughened shape on the surface of the copper
film as shown in FIG. 2(b). The metal seed layer in FIG. 2(b) is
made of the two layers, although not shown. The copper roughening
processing was performed by using MultiBond made by Nippon
MacDermid Co., Inc. in accordance with steps shown in Table 3. As a
solution used copper roughening process, it is possible to use MEC
etch BOND made by Mec Co., Ltd., Circubond made by Shipley Far East
Ltd., Alpha Prep made by Alpha Metals Ltd. and the like, other than
the abovementioned one.
TABLE-US-00003 TABLE 3 Temperature Time Step Processing Liquid
(.degree. C.) (Seconds) 1 5 vol % Sulfuric Acid 25 30 2 Pure Water
(Running Water) 22 60 3 2 vol % MB-100B 25 30 2.9 vol % MB-100C 4 5
vol % Sulfuric Acid 32 15 15 vol % MB-100A 2 vol % MB-100B 2.9 vol
% MB-100C 5 Pure Water (Running Water) 22 60
[0050] The rough area on the surface of the copper film after the
copper roughening processing was measured with a surface roughness
measuring apparatus. The measurement showed that the surface
roughness of the metal seed layer had an arithmetic average
roughness Ra (defined in JIS B0601) of 0.05 .mu.m and an average
length of a roughness curve element RSm of 0.04 .mu.m.
Electroplating was performed immediately after the formation of the
roughened shape on the surface of the copper film in the metal seed
layer 2 to form an electroplated copper film 3 as shown in FIG.
2(c). The electroplating was performed by using the same
composition of a plating bath and the same plating conditions as
those in Example 1. The cross-section of the wiring board was
observed after the plating to measure an angle .theta. between the
side wall of the electroplated copper film and the polyimide film
substrate as shown in FIG. 9, and an angle of 83 degrees was
found.
[0051] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the copper film formed with the sputtering
technique.
EXAMPLE 3
[0052] As shown in FIG. 3(a), a nickel film with a thickness of 0.1
.mu.m formed on a surface of an insulating substrate 1 made of
glass epoxy resin and a copper film with a thickness of 1.0 .mu.m
was formed with the sputtering technique on the nickel film. Next,
copper roughening processing was performed to form a rough area in
the portion of the copper surface on which wiring was to be formed,
thereby providing the shape shown in FIG. 3(b). The rough area was
formed with sandblast. The sandblast was performed by spraying
alumina particles onto the copper surface through a mask pattern
with a wiring width of 8 .mu.m. The roughened shape on the copper
surface after the sandblast processing was measured with a surface
roughness measuring apparatus. The measurement showed that the
surface roughness of the metal seed layer had an arithmetic average
roughness Ra (defined in JIS B0601) of 0.4 .mu.m and an average
length of a roughness curve element RSm of 1.1 .mu.m.
Electroplating was performed immediately after the formation of the
roughen area on the copper surface to form an electroplated copper
film 3 as shown in FIG. 3(c). The electroplating was performed by
using the same composition of a plating bath and the same plating
conditions as those in Example 1. Next, a copper etchant (MECBRITE
made by Mec Co., Ltd) was used to etch away the portions of the
electroplated copper film 3 and the copper seed layer on which the
rough area was not formed. In addition, MEC REMOVER made by Mec
Co., Ltd was used to remove a portion of the nickel seed layer to
provide the structure shown in FIG. 3(d). The cross-section of the
wiring board was observed after the plating to measure an angle
.theta. between the side wall of the copper film and the substrate
as shown in FIG. 9, and an angle of 85 degrees was found.
[0053] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the copper seed layer having the roughen area formed
thereon through the sandblast.
EXAMPLE 4
[0054] As shown in FIG. 4(a), a surface of an insulating substrate
1 made of polyimide film with a thickness of 25 .mu.m was treated
with a surface modification solution shown in Table 4 at a
temperature of 25.degree. C. for two minutes and then plating was
performed with an electroless copper plating bath (CUST-2000 made
by Hitachi Chemical Co., Ltd.) to form a metal seed layer 2. After
the plating, the substrate was washed with running water and vacuum
drying was performed thereon at 25.degree. C. for two hours. The
copper film had a thickness of approximately 300 nm at that point.
The roughness on the surface of the copper seed layer after the
plating was measured with a surface roughness measuring apparatus.
The measurement showed that the surface roughness of the metal seed
layer had an arithmetic average roughness Ra (defined in JIS B0601)
of 1.5 .mu.m and an average length of a roughness curve element RSm
of 1.4 .mu.m.
TABLE-US-00004 TABLE 4 Component Concentration (g/dm.sup.3) Sodium
Hydroxide 100 Ethylenediamine 70 Ethanol 100
[0055] Next, a solution containing dispersed copper particles was
sprayed onto the metal seed layer 2 except the portion which would
serve as wiring with a width of 10 .mu.m, that is, the portion on
which wiring was not to be formed. Then, annealing was performed in
vacuum at 350.degree. C. for 30 minutes. The surface roughness of
the portion sprayed with the copper particles was measured with a
surface roughness measuring apparatus. The measurement showed that
the surface roughness had an arithmetic average roughness Ra
(defined in JIS B0601) of 0.005 .mu.m and an average length of a
roughness curve element RSm of 11 .mu.m, which demonstrated that
the surface of the copper film was planarized. FIG. 4(b) shows the
structure at that point.
[0056] Next, electroplating was performed to form an electroplated
copper film 3 as shown in FIG. 4(c). The electroplating was
performed by using the same composition of a plating bath and the
same conditions as those in Example 1 except the plating time set
to 20 minutes. Then, a copper etchant (MECBRITE made by Mec Co.,
Ltd) was used to etch away the portions of the electroplated copper
film and the copper seed layer in which the roughened shape was
planarized, thereby providing the structure shown in FIG. 4(d). The
cross-section of the wiring board was observed after the plating to
measure an angle .theta. between the side wall of the electroplated
copper film and the polyimide film substrate as shown in FIG. 9,
and an angle of 80 degrees was found.
[0057] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the copper seed layer having the rough area formed
thereon.
EXAMPLE 5
[0058] Roughening processing was performed on a surface of an
insulating substrate 1 made of polyimide film with a thickness of
25 .mu.m shown in FIG. 5(a) to form a rough area as shown in FIG.
5(b). The roughening processing was performed in accordance with
steps shown in Table 5. As a roughening liquid, it is possible to
use not only a mixed solution of potassium permanganate solution
and sodium hydroxide but also a mixed solution of chromic acid and
sulfuric acid, a mixed solution of chromic acid and fluoroboric
acid and the like.
TABLE-US-00005 TABLE 5 Temperature Step Processing Liquid (.degree.
C.) Time (Seconds) 1 50 g/dm.sup.3 Potassium 80 5 Permanganate
Solution 1 mol/dm.sup.3 Sodium Hydroxide 2 0.5 vol % Sulfuric Acid
40 5 0.2 vol % Hydroxylamine Sulfate
[0059] Next, a solution containing dispersed copper particles with
an average diameter of 10 nm was sprayed onto the surface of the
insulating substrate 1 to form a metal seed layer 2 with a wiring
width of 30 .mu.m and a thickness of 0.03 .mu.m as shown in FIG.
5(c). The roughness on the surface of the metal seed film formed by
the copper particles was measured with a surface roughness
measuring apparatus. The measurement showed that the metal seed
layer had an arithmetic average roughness Ra (defined in JIS B0601)
of 2.0 .mu.m and an average length of a roughness curve element RSm
of 4.0 .mu.m.
[0060] Electroplating was performed immediately after the formation
of the metal seed layer 2 to form an electroplated copper film 3 as
shown in FIG. 5(d). The electroplating was performed by using the
same composition of a plating bath and the same conditions as those
in Example 1. The cross-section of the wiring board was observed
after the plating to measure an angle .theta. between the side wall
of the electroplated copper film and the polyimide film substrate
as shown in FIG. 9, and an angle of 86 degrees was found.
[0061] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the metal seed layer formed of the copper
particles.
EXAMPLE 6
[0062] As shown in FIG. 6(a), a mold 4 made of silicon which has a
250 nm pitch protrusion with a width of 250 nm and a height of 400
nm over a width of 10 .mu.m was pushed onto a surface of an
insulating substrate 1 made of epoxy resin to form a roughened
shape. The mold was pushed onto the insulating substrate 1 while it
was heated to near the glass-transition temperature, thereby
softening the epoxy resin substrate 1 for deformation to the shape
corresponding to the mold. After the insulating substrate 1 and the
mold 4 was cooled to 25.degree. C., the mold 4 was separated from
the substrate 1. Thus, the rough area was able to be formed on part
of the surface of the insulating substrate 1 as shown in FIG. 6(b).
Next, a nickel/chromium film made of nickel and chromium at a ratio
of 1:1 was formed with a thickness of 10 nm with the sputtering
technique on the surface of the insulating substrate 1. A copper
film was formed thereon with a thickness of 100 nm through a
chemical vapor deposition technique. The nickel/chromium film and
the copper film constituted a metal seed layer 2. FIG. 6(c) shows
the structure at that point. The observation of the rough area on
the surface of the metal seed layer 2 revealed that the metal seed
layer 2 maintained the roughened shape of the insulating
substrate.
[0063] Electroplating was performed immediately after the formation
of the metal seed layer 2 to form an electroplated copper film 3 as
shown in FIG. 6(d). The electroplating was performed by using the
same composition of a plating bath and the same conditions as those
in Example 1 except the plating time set to 90 minutes. Next, a
solution containing sulfuric acid and hydrogen peroxide was used to
remove the portions of the electroplated copper film and the copper
film of the metal seed layer on which the rough area was not
formed. In addition, a solution containing potassium permanganate
solution was used to remove a portion of the nickel/chromium film.
The cross-section of the wiring board was observed after the
plating to measure an angle .theta. between the side wall of the
electroplated copper film and the substrate as shown in FIG. 9, and
an angle of 83 degrees was found.
[0064] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the copper seed layer having the roughened shape
formed thereon.
EXAMPLE 7
[0065] As shown in FIG. 7(a), roughening processing was performed
on a surface of an insulating substrate 1 made of polyimide film
with a mixed solution of chromic acid and sulfuric acid to form a
rough area. The surface roughness of the portion having the rough
area was measured with a surface roughness measuring apparatus. The
measurement showed that the surface roughness had an arithmetic
average roughness Ra (defined in JIS B0601) of 1.0 .mu.m and an
average length of a roughness curve element RSm of 1.1 .mu.m. Next,
as shown in FIG. 7(b), a mold 4 made of silicon which has a concave
portion with a width of 10 .mu.m was pushed onto the surface of the
insulating substrate 1 to planarize the roughened shape in the
portion on which no wiring was to be formed. The mold was pushed
onto the insulating substrate 1 while it was heated to near the
glass-transition temperature, thereby softening the insulating
substrate for deformation to the shape corresponding to the mold.
During the step, the mold 4 was placed such that its concave
portion was out of contact with the insulating substrate 1. Then,
after the insulating substrate 1 and the mold 4 was cooled to
25.degree. C., the mold 4 was separated from the substrate 1. Thus,
the rough area was able to be planarized except part of the surface
of the insulating substrate 1 as shown in FIG. 7(c). The surface
roughness of the portion where the rough area was planarized was
measured with a surface roughness measuring apparatus. The
measurement showed that the surface roughness had an arithmetic
average roughness Ra (defined in JIS B0601) of 0.006 .mu.m and an
average length of a roughness curve element RSm of 9 .mu.m.
[0066] Next, a nickel/chromium film made of nickel and chromium at
a ratio of 1:1 was formed with a thickness of 10 nm through the
sputtering technique on the surface of the insulating substrate 1.
A copper film was formed thereon with a thickness of 100 nm through
the chemical vapor deposition technique. The nickel/chromium film
and the copper film constituted a metal seed layer 2. FIG. 7(d)
shows the structure at that point. The surface roughness of the
portion of the metal seed layer 2 on which the roughened shape was
formed was measured with a surface roughness measuring apparatus.
The measurement showed that the surface roughness had an arithmetic
average roughness Ra (defined in JIS B0601) of 1.0 .mu.m and an
average length of a roughness curve element RSm of 1.1 .mu.m. The
measurement demonstrated that the metal seed layer 2 maintained the
roughened shape of the insulating substrate.
[0067] Electroplating was performed immediately after the formation
of the metal seed layer 2 to form an electroplated copper film 3 as
shown in FIG. 7(e). The electroplating was performed by using the
same composition of a plating bath and the same conditions as those
in Example 1. Next, a solution containing sulfuric acid and
hydrogen peroxide was used to remove the portions of the
electroplated copper film 3 and the copper of the metal seed layer
on which the rough area was not formed. Subsequently, a solution
containing potassium permanganate solution was used to remove a
portion of nickel/chromium film. The cross-section of the wiring
board was observed after the plating to measure an angle .theta.
between the side wall of the electroplated copper film and the
polyimide film substrate as shown in FIG. 9, and an angle of 89
degrees was found.
[0068] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the metal seed layer having the roughened shape formed
thereon.
EXAMPLE 8
[0069] As shown in FIG. 8(a), an insulating substrate 1 made of
polyimide with a thickness of 25 .mu.m was formed with a casting
method on a mat surface of a metal seed layer 2 made of
electrolytic copper foil with a thickness of 8 .mu.m. Next, copper
roughening processing was performed to form a rough area in a
portion of a surface of the metal seed layer on which wiring was to
be formed as shown in FIG. 8(b). The roughened shape was formed
with sandblast. The sandblast was performed by spraying alumina
particles onto the surface of the metal seed layer through a mask
pattern with a wiring width of 10 .mu.m. The roughened shape on the
surface of the metal seed layer after the sandblast processing was
measured with a surface roughness measuring apparatus. The
measurement showed that the surface roughness had an arithmetic
average roughness Ra (defined in JIS B0601) of 0.4 .mu.m and an
average length of a roughness curve element RSm of 1.1 .mu..
Electroplating was performed immediately after the formation of the
roughened shape on the copper surface to form an electroplated
copper film 3 as shown in FIG. 8(c). The electroplating was
performed by using the same composition of a plating bath and the
same plating conditions as those in Example 1. Next, a copper
etchant (MECBRITE made by Mec Co., Ltd) was used to etch away the
portions of the electroplated copper film 3 and the copper foil on
which the rough area was not formed, thereby providing the
structure shown in FIG. 8(d). The cross-section of the wiring board
was observed after the plating to measure an angle .theta. between
the side wall of the electroplated copper film and the polyimide
film substrate as shown in FIG. 9, and an angle of 85 degrees was
found.
[0070] As a result, it was possible to produce the wiring board in
which copper wiring having a generally rectangular wiring section
is formed on the metal seed layer having the roughened shape formed
thereon with the sandblast.
EXAMPLE 9 to 22
[0071] As shown in Table 1, wiring boards of Examples 9 to 22 were
produced in the same manner as in Example 3 except the additive
concentration and plating current density. The observation of the
cross-sections of the wiring boards after plating showed that the
angle .theta. between the side wall of the electroplated copper
film and the substrate as shown in FIG. 9 depended on the additive
concentration and plating current density, and therefore the angle
.theta. can be controlled by changing those conditions. As a
result, wiring boards were able to be produced to have wiring or
bumps with a rectangular, trapezoidal, or triangular section as
shown in FIG. 10(a), 10(b), or 10(c). In addition, in Examples 9 to
22, the ratio of the height of the side wall of the wiring to the
width of the bottom of the wiring can be set to one or higher and
the wiring boards can be produced with high electromigration
resistance.
COMPARATIVE EXAMPLE 1
[0072] Wiring was formed by performing electroplating in the same
manner as in Example 2 except that no roughening processing was
performed. The cross-section of the wiring board was observed after
the plating to measure an angle .theta. between the side wall of an
electroplated copper film and a substrate as shown in FIG. 9, and
an angle of 135 degrees was found. The wiring with a width of 10
.mu.m before the electroplating had a wiring width of 18 .mu.m
after the electroplating, and short-circuit was found.
[0073] Since plating can be performed on a fine pattern without
masking by a resist, the present invention is applicable not only
to the formation of wiring or bumps but also to the formation of a
device mounted on a wiring board such as a passive device.
[0074] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *