U.S. patent application number 12/091197 was filed with the patent office on 2008-09-18 for substrate processing method and substrate processing apparatus.
This patent application is currently assigned to Tokyo Electon Limited. Invention is credited to Kenichi Hara, Mitsuaki Iwashita, Takashi Tanaka.
Application Number | 20080226826 12/091197 |
Document ID | / |
Family ID | 38845463 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080226826 |
Kind Code |
A1 |
Tanaka; Takashi ; et
al. |
September 18, 2008 |
Substrate Processing Method and Substrate Processing Apparatus
Abstract
A substrate processing method includes applying electroless
plating of CoWB onto a Cu interconnection line formed on a wafer W,
and then performing a post-cleaning process by use of a cleaning
liquid on the target substrate or wafer before a by-product is
precipitated on the surface of the CoWB film formed by the
electroless plating to cover the Cu interconnection line.
Inventors: |
Tanaka; Takashi; (Yamanashi,
JP) ; Hara; Kenichi; (Yamanashi, JP) ;
Iwashita; Mitsuaki; (Yamanashi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Tokyo Electon Limited
Minato-ku Tokyo
JP
|
Family ID: |
38845463 |
Appl. No.: |
12/091197 |
Filed: |
June 22, 2007 |
PCT Filed: |
June 22, 2007 |
PCT NO: |
PCT/JP07/62625 |
371 Date: |
April 23, 2008 |
Current U.S.
Class: |
427/299 ; 118/52;
118/697; 257/E21.174; 427/343 |
Current CPC
Class: |
H01L 21/6723 20130101;
C23C 18/1834 20130101; H01L 2924/0002 20130101; C23C 18/1689
20130101; H01L 21/76849 20130101; H01L 2924/0002 20130101; H01L
21/288 20130101; H01L 21/67051 20130101; C23C 18/50 20130101; H01L
23/53238 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
427/299 ;
427/343; 118/52; 118/697 |
International
Class: |
B05D 3/10 20060101
B05D003/10; B05C 11/08 20060101 B05C011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2006 |
JP |
2006-174745 |
Jul 14, 2006 |
JP |
2006-194758 |
Claims
1. A substrate processing method comprising: applying electroless
plating of a Co (cobalt) alloy onto a Cu (copper) interconnection
line formed on a substrate; and performing a post-cleaning process
by use of a cleaning liquid on the substrate, before a plated
surface formed by the electroless plating is dried.
2. The substrate processing method according to claim 1, wherein
the post-cleaning process is arranged to use as the cleaning liquid
a chemical liquid acidic with a pH of 3 or more.
3. The substrate processing method according to claim 2, wherein
the chemical liquid has a pH of 3 to 4.
4. The substrate processing method according to claim 1, wherein
the post-cleaning process is arranged to use as the cleaning liquid
a chemical liquid containing a surfactant.
5. The substrate processing method according to claim 4, wherein
the chemical liquid has a surfactant concentration of 0.0001% or
more.
6. The substrate processing method according to claim 1, wherein
the post-cleaning process comprises performing a rinsing process by
use of a rinsing liquid as the cleaning liquid after the
electroless plating, and then performing a chemical liquid process
by use of a chemical liquid as the cleaning liquid.
7. The substrate processing method according to claim 1, wherein
the electroless plating is arranged to use a plating liquid
containing a surfactant.
8. The substrate processing method according to claim 1, wherein
the Co alloy is CoWB (cobalt tungsten boron) or CoWP (cobalt
tungsten phosphorous).
9. The substrate processing method according to claim 1, wherein
the method is arranged to repeat the electroless plating and the
post-cleaning process a plurality of times.
10. The substrate processing method according to claim 1, wherein
the method is arranged to further comprise performing a
pre-cleaning process on the substrate by use of a cleaning liquid
before the electroless plating, and to perform the pre-cleaning
process, the electroless plating, and the post-cleaning process
without drying a surface of the substrate
11. The substrate processing method according to claim 10, wherein
the method is arranged to repeat the pre-cleaning process, the
electroless plating, and the post-cleaning process a plurality of
times.
12. A substrate processing method for applying electroless plating
of a Co (cobalt) alloy onto a Cu (copper) interconnection line
formed on a substrate, in a substrate processing apparatus
comprising a spin chuck configured to hold and rotate the substrate
in a horizontal state, an inner surrounding member configured to
move up and down relative to the spin chuck between a surrounding
position for surrounding a peripheral edge of the substrate held on
the spin chuck and a retreat position for retreating from the
peripheral edge of the substrate, and an outer surrounding member
disposed outside the inner surrounding member and configured to
surround the peripheral edge of the substrate when the inner
surrounding member retreats from the peripheral edge of the
substrate, the method comprising: setting the substrate to be held
on the spin chuck; rotating the substrate by the spin chuck and
supplying a plating liquid onto the substrate, while surrounding
the peripheral edge of the substrate held on the spin chuck by one
of the inner surrounding member and the outer surrounding member,
thereby applying electroless plating onto the interconnection line,
while receiving the plating liquid thrown off from the substrate by
said one of the inner surrounding member and the outer surrounding
member which surrounds the peripheral edge of the substrate; and
rotating the substrate by the spin chuck and supplying a cleaning
liquid onto the substrate, while surrounding the peripheral edge of
the substrate held on the spin chuck by the other of the inner
surrounding member and the outer surrounding member at least for a
while, thereby performing a post-cleaning process on the substrate,
while receiving the cleaning liquid thrown off from the substrate
by said other of the inner surrounding member and the outer
surrounding member which surrounds the peripheral edge of the
substrate, wherein the method is arranged to perform the
post-cleaning process before a plated surface formed by the
electroless plating is dried.
13. The substrate processing method according to claim 12, wherein
the post-cleaning process comprises performing a rinsing process by
use of a rinsing liquid as the cleaning liquid after the
electroless plating, and then performing a chemical liquid process
by use of a chemical liquid as the cleaning liquid; the rinsing
process is performed by rotating the substrate by the spin chuck
and supplying the rinsing liquid onto the substrate, while
surrounding the peripheral edge of the substrate by the same one of
the inner surrounding member and the outer surrounding member as
that used in the electroless plating, thereby receiving the rinsing
liquid thrown off from the substrate by said one of the inner
surrounding member and the outer surrounding member which surrounds
the peripheral edge of the substrate; and the chemical liquid
process is performed by rotating the substrate by the spin chuck
and supplying the chemical liquid onto the substrate, while
surrounding the peripheral edge of the substrate held on the spin
chuck by the other of the inner surrounding member and the outer
surrounding member, thereby receiving the chemical liquid thrown
off from the substrate by said other of the inner surrounding
member and the outer surrounding member which surrounds the
peripheral edge of the substrate.
14. The substrate processing method according to claim 12, wherein
the post-cleaning process is arranged to use as the cleaning liquid
a chemical liquid acidic with a pH of 3 or more.
15. The substrate processing method according to claim 14, wherein
the chemical liquid has a pH of 3 to 4.
16. The substrate processing method according to claim 12, wherein
the post-cleaning process is arranged to use as the cleaning liquid
a chemical liquid containing a surfactant.
17. The substrate processing method according to claim 16, wherein
the chemical liquid has a surfactant concentration of 0.0001% or
more.
18. The substrate processing method according to claim 12, wherein
the post-cleaning process comprises performing a rinsing process by
use of a rinsing liquid as the cleaning liquid after the
electroless plating, and then performing a chemical liquid process
by use of a chemical liquid as the cleaning liquid.
19. The substrate processing method according to claim 12, wherein
the electroless plating is arranged to use a plating liquid
containing a surfactant.
20. The substrate processing method according to claim 12, wherein
the Co alloy is CoWB (cobalt tungsten boron) or CoWP (cobalt
tungsten phosphorous).
21. The substrate processing method according to claim 12, wherein
the method is arranged to repeat the electroless plating and the
post-cleaning process a plurality of times.
22. The substrate processing method according to claim 12, wherein
the method is arranged to further comprise performing a
pre-cleaning process on the substrate by use of a cleaning liquid
before the electroless plating, while surrounding the peripheral
edge of the substrate held on the spin chuck by one of the inner
surrounding member and the outer surrounding member different from
that used in the electroless plating, and to perform the
pre-cleaning process, the electroless plating, and the
post-cleaning process without drying a surface of the
substrate.
23. The substrate processing method according to claim 22, wherein
the method is arranged to repeat the pre-cleaning process, the
electroless plating, and the post-cleaning process a plurality of
times.
24. A substrate processing apparatus for applying electroless
plating of a Co (cobalt) alloy onto a Cu (copper) interconnection
line formed on a substrate, the apparatus comprising: a spin chuck
configured to hold and rotate the substrate in a horizontal state;
an inner surrounding member configured to move up and down relative
to the spin chuck between a surrounding position for surrounding a
peripheral edge of the substrate held on the spin chuck and a
retreat position for retreating from the peripheral edge of the
substrate; an outer surrounding member disposed outside the inner
surrounding member and configured to surround the peripheral edge
of the substrate when the inner surrounding member retreats from
the peripheral edge of the substrate, a plating liquid supply
mechanism configured to supply a plating liquid onto the substrate
held on the spin chuck; and a cleaning liquid supply mechanism
configured to supply a cleaning liquid onto the substrate held on
the spin chuck, wherein the apparatus is preset to rotate the
substrate by the spin chuck and supply a plating liquid onto the
substrate, while surrounding the peripheral edge of the substrate
held on the spin chuck by one of the inner surrounding member and
the outer surrounding member, thereby applying electroless plating
onto the interconnection line, while receiving the plating liquid
thrown off from the substrate by said one of the inner surrounding
member and the outer surrounding member which surrounds the
peripheral edge of the substrate; and to rotate the substrate by
the spin chuck and supply a cleaning liquid onto the substrate,
while surrounding the peripheral edge of the substrate held on the
spin chuck by the other of the inner surrounding member and the
outer surrounding member at least for a while, thereby performing a
post-cleaning process on the substrate, while receiving the
cleaning liquid thrown off from the substrate by said other of the
inner surrounding member and the outer surrounding member which
surrounds the peripheral edge of the substrate.
25. A storage medium that stores a program for execution on a
computer to control a substrate processing apparatus, wherein the
program, when executed, causes the computer to control the
substrate processing apparatus to conduct a substrate processing
method comprising: applying electroless plating onto an
interconnection line formed on a substrate; and performing a
post-cleaning process by use of a cleaning liquid on the substrate,
before a plated surface formed by the electroless plating is
dried.
26. A storage medium that stores a program for execution on a
computer to control a substrate processing apparatus comprising a
spin chuck configured to hold and rotate a substrate in a
horizontal state, an inner surrounding member configured to move up
and down relative to the spin chuck between a surrounding position
for surrounding a peripheral edge of the substrate held on the spin
chuck and a retreat position for retreating from the peripheral
edge of the substrate, and an outer surrounding member disposed
outside the inner surrounding member and configured to surround the
peripheral edge of the substrate when the inner surrounding member
retreats from the peripheral edge of the substrate, wherein the
program, when executed, causes the computer to control the
substrate processing apparatus to conduct a substrate processing
method for applying electroless plating of a Co (cobalt) alloy onto
a Cu (copper) interconnection line formed on the substrate, the
method comprising: setting the substrate to be held on the spin
chuck; rotating the substrate by the spin chuck and supplying a
plating liquid onto the substrate, while surrounding the peripheral
edge of the substrate held on the spin chuck by one of the inner
surrounding member and the outer surrounding member, thereby
applying electroless plating onto the interconnection line, while
receiving the plating liquid thrown off from the substrate by said
one of the inner surrounding member and the outer surrounding
member which surrounds the peripheral edge of the substrate; and
rotating the substrate by the spin chuck and supplying a cleaning
liquid onto the substrate, while surrounding the peripheral edge of
the substrate held on the spin chuck by the other of the inner
surrounding member and the outer surrounding member at least for a
while, thereby performing a post-cleaning process on the substrate,
while receiving the cleaning liquid thrown off from the substrate
by said other of the inner surrounding member and the outer
surrounding member which surrounds the peripheral edge of the
substrate, wherein the method is arranged to perform the
post-cleaning process before a plated surface formed by the
electroless plating is dried.
Description
TECHNICAL FIELD
[0001] The present invention relates to a substrate processing
method and substrate processing apparatus for performing a series
of steps for forming a plated film on an interconnection line
formed on a substrate, such as a semiconductor substrate.
BACKGROUND ART
[0002] As regards semiconductor devices, recently, their
integration degree thereof is required to increase owing to the
demands for a higher operation speed, and thus Cu (copper) is used
as an interconnection line metal, because Cu has a low resistivity.
Where Cu is used for an interconnection line, the current density
is increased, but therefore electro-migration (EM: migration of Cu
atoms by an electric current) can easily be caused. The
electro-migration may bring about disconnection of the
interconnection line and thereby deteriorate the reliability.
[0003] In light of this problem, the following method has been
proposed to improve the EM resistance of semiconductor devices (for
example, see Patent Document 1). Specifically, a plating liquid
containing, e.g., CoWB (cobalt tungsten boron) or CoWP (cobalt
tungsten phosphorous) is supplied onto the surface of a substrate
provided with a Cu interconnection line, so that a metal film of,
e.g., CoWB or CoWP, which is called a cap metal, is formed by
electroless plating to cover the Cu interconnection line.
[0004] In general, a cap metal described above is formed by
supplying a plating liquid onto the surface of a substrate provided
with a Cu interconnection line. After the cap metal is formed,
cleaning of the substrate is performed by use of a cleaning liquid
to remove the excess part of the plating liquid deposited on
portions of the substrate other than the interconnection line (for
example, see Patent Documents 2 and 3).
[0005] After the cap metal is formed, slurry-like by-products
(residues) generated by the plating reaction are normally present
on the surface of the cap metal, and are dried and precipitated in
due time. If the precipitated substances are left on the surface of
the cap metal, the leakage electric current between interconnection
lines may be increased. In order to solve this problem, cleaning of
the substrate may be performed as described above to remove the
precipitated substances. However, since the precipitated substances
strongly stick to the plated surface, the precipitated substances
may be difficult to sufficiently remove by the conventional
cleaning liquid and cleaning step. Accordingly, where a processing
method using an electroless plating step and a cleaning step after
the electroless plating is arranged according to the conventional
technique, the quality of the cap metal is inevitably lower, and
the reliability of the device may thereby be deteriorated.
[0006] Further, the substrate surface may be dried due to
deterioration of the wettability relative to a chemical liquid,
along with a change in hydrophilic/hydrophobic property. This may
cause re-oxidation of the Cu surface.
[0007] As described above, the conventional plating method entails
difficulties in forming a cap metal of high quality, and thus
cannot sufficiently improve the EM resistance of semiconductor
devices
[0008] [Patent Document 1]
[0009] Jpn. Pat. Appln. KOKAI Publication No. 2006-111938
[0010] [Patent Document 2]
[0011] Jpn. Pat. Appln. KOKAI Publication No. 2000-58487
[0012] [Patent Document 3]
[0013] Jpn. Pat. Appln. KOKAI Publication No. 2003-179058
DISCLOSURE OF INVENTION
[0014] An object of the present invention is to provide a substrate
processing method and substrate processing apparatus that can form
an electroless plated film of high quality on an interconnection
line.
[0015] According to a first aspect of the present invention, there
is provided a substrate processing method comprising: applying
electroless plating of a Co (cobalt) alloy onto a Cu (copper)
interconnection line formed on a substrate; and performing a
post-cleaning process by use of a cleaning liquid on the substrate,
before a plated surface formed by the electroless plating is
dried.
[0016] In the first aspect, the post-cleaning process may be
arranged to use as the cleaning liquid a chemical liquid acidic
with a pH of 3 or more. The chemical liquid preferably has a pH of
3 to 4. The post-cleaning process may be arranged to use as the
cleaning liquid a chemical liquid containing a surfactant. In this
case, the chemical liquid preferably has a surfactant concentration
of 0.0001% or more.
[0017] In the first aspect, the post-cleaning process may comprise
performing a rinsing process by use of a rinsing liquid as the
cleaning liquid after the electroless plating, and then performing
a chemical liquid process by use of a chemical liquid as the
cleaning liquid. The electroless plating may be arranged to use a
plating liquid containing a surfactant. The Co alloy is preferably
CoWB (cobalt tungsten boron) or CoWP (cobalt tungsten phosphorous).
The method may be arranged to repeat the electroless plating and
the post-cleaning process a plurality of times.
[0018] In the first aspect, the method is preferably arranged to
further comprise performing a pre-cleaning process on the substrate
by use of a cleaning liquid before the electroless plating, and to
perform the pre-cleaning process, the electroless plating, and the
post-cleaning process without drying a surface of the substrate The
method may be arranged to repeat the pre-cleaning process, the
electroless plating, and the post-cleaning process a plurality of
times.
[0019] According to a second aspect of the present invention, there
is provided a substrate processing method for applying electroless
plating of a Co (cobalt) alloy onto a Cu (copper) interconnection
line formed on a substrate, in a substrate processing apparatus
comprising a spin chuck configured to hold and rotate the substrate
in a horizontal state, an inner surrounding member configured to
move up and down relative to the spin chuck between a surrounding
position for surrounding a peripheral edge of the substrate held on
the spin chuck and a retreat position for retreating from the
peripheral edge of the substrate, and an outer surrounding member
disposed outside the inner surrounding member and configured to
surround the peripheral edge of the substrate when the inner
surrounding member retreats from the peripheral edge of the
substrate, the method comprising: setting the substrate to be held
on the spin chuck; rotating the substrate by the spin chuck and
supplying a plating liquid onto the substrate, while surrounding
the peripheral edge of the substrate held on the spin chuck by one
of the inner surrounding member and the outer surrounding member,
thereby applying electroless plating onto the interconnection line,
while receiving the plating liquid thrown off from the substrate by
said one of the inner surrounding member and the outer surrounding
member which surrounds the peripheral edge of the substrate; and
rotating the substrate by the spin chuck and supplying a cleaning
liquid onto the substrate, while surrounding the peripheral edge of
the substrate held on the spin chuck by the other of the inner
surrounding member and the outer surrounding member at least for a
while, thereby performing a post-cleaning process on the substrate,
while receiving the cleaning liquid thrown off from the substrate
by said other of the inner surrounding member and the outer
surrounding member which surrounds the peripheral edge of the
substrate, wherein the method is arranged to perform the
post-cleaning process before a plated surface formed by the
electroless plating is dried.
[0020] In the second aspect, the method may be arranged such that
the post-cleaning process comprises performing a rinsing process by
use of a rinsing liquid as the cleaning liquid after the
electroless plating, and then performing a chemical liquid process
by use of a chemical liquid as the cleaning liquid; the rinsing
process is performed by rotating the substrate by the spin chuck
and supplying the rinsing liquid onto the substrate, while
surrounding the peripheral edge of the substrate by the same one of
the inner surrounding member and the outer surrounding member as
that used in the electroless plating, thereby receiving the rinsing
liquid thrown off from the substrate by said one of the inner
surrounding member and the outer surrounding member which surrounds
the peripheral edge of the substrate; and the chemical liquid
process is performed by rotating the substrate by the spin chuck
and supplying the chemical liquid onto the substrate, while
surrounding the peripheral edge of the substrate held on the spin
chuck by the other of the inner surrounding member and the outer
surrounding member, thereby receiving the chemical liquid thrown
off from the substrate by said other of the inner surrounding
member and the outer surrounding member which surrounds the
peripheral edge of the substrate.
[0021] The post-cleaning process may be arranged to use as the
cleaning liquid a chemical liquid acidic with a pH of 3 or more.
The chemical liquid preferably has a pH of 3 to 4. The
post-cleaning process may be arranged to use as the cleaning liquid
a chemical liquid containing a surfactant. In this case, the
chemical liquid preferably has a surfactant concentration of
0.00010 or more.
[0022] The post-cleaning process may comprise performing a rinsing
process by use of a rinsing liquid as the cleaning liquid after the
electroless plating, and then performing a chemical liquid process
by use of a chemical liquid as the cleaning liquid. The electroless
plating may be arranged to use a plating liquid containing a
surfactant. The Co alloy is preferably CoWB (cobalt tungsten boron)
or CoWP (cobalt tungsten phosphorous). The method may be arranged
to repeat the electroless plating and the post-cleaning process a
plurality of times.
[0023] In the second aspect, the method is preferably arranged to
further comprise performing a pre-cleaning process on the substrate
by use of a cleaning liquid before the electroless plating, while
surrounding the peripheral edge of the substrate held on the spin
chuck by one of the inner surrounding member and the outer
surrounding member different from that used in the electroless
plating, and to perform the pre-cleaning process, the electroless
plating, and the post-cleaning process without drying a surface of
the substrate. The method may be arranged to repeat the
pre-cleaning process, the electroless plating, and the
post-cleaning process a plurality of times.
[0024] According to a third aspect of the present invention, there
is provided a substrate processing apparatus for applying
electroless plating of a Co (cobalt) alloy onto a Cu (copper)
interconnection line formed on a substrate, the apparatus
comprising: a spin chuck configured to hold and rotate the
substrate in a horizontal state; an inner surrounding member
configured to move up and down relative to the spin chuck between a
surrounding position for surrounding a peripheral edge of the
substrate held on the spin chuck and a retreat position for
retreating from the peripheral edge of the substrate; an outer
surrounding member disposed outside the inner surrounding member
and configured to surround the peripheral edge of the substrate
when the inner surrounding member retreats from the peripheral edge
of the substrate, a plating liquid supply mechanism configured to
supply a plating liquid onto the substrate held on the spin chuck;
and a cleaning liquid supply mechanism configured to supply a
cleaning liquid onto the substrate held on the spin chuck, wherein
the apparatus is preset to rotate the substrate by the spin chuck
and supply a plating liquid onto the substrate, while surrounding
the peripheral edge of the substrate held on the spin chuck by one
of the inner surrounding member and the outer surrounding member,
thereby applying electroless plating onto the interconnection line,
while receiving the plating liquid thrown off from the substrate by
said one of the inner surrounding member and the outer surrounding
member which surrounds the peripheral edge of the substrate; and to
rotate the substrate by the spin chuck and supply a cleaning liquid
onto the substrate, while surrounding the peripheral edge of the
substrate held on the spin chuck by the other of the inner
surrounding member and the outer surrounding member at least for a
while, thereby performing a post-cleaning process on the substrate,
while receiving the cleaning liquid thrown off from the substrate
by said other of the inner surrounding member and the outer
surrounding member which surrounds the peripheral edge of the
substrate.
[0025] According to a fourth aspect of the present invention, there
is provided a storage medium that stores a program for execution on
a computer to control a substrate processing apparatus, wherein the
program, when executed, causes the computer to control the
substrate processing apparatus to conduct a substrate processing
method comprising: applying electroless plating onto an
interconnection line formed on a substrate; and performing a
post-cleaning process by use of a cleaning liquid on the substrate,
before a plated surface formed by the electroless plating is
dried.
[0026] According to a fifth aspect of the present invention, there
is provided a storage medium that stores a program for execution on
a computer to control a substrate processing apparatus comprising a
spin chuck configured to hold and rotate a substrate in a
horizontal state, an inner surrounding member configured to move up
and down relative to the spin chuck between a surrounding position
for surrounding a peripheral edge of the substrate held on the spin
chuck and a retreat position for retreating from the peripheral
edge of the substrate, and an outer surrounding member disposed
outside the inner surrounding member and configured to surround the
peripheral edge of the substrate when the inner surrounding member
retreats from the peripheral edge of the substrate, wherein the
program, when executed, causes the computer to control the
substrate processing apparatus to conduct a substrate processing
method for applying electroless plating of a Co (cobalt) alloy onto
a Cu (copper) interconnection line formed on the substrate, the
method comprising: setting the substrate to be held on the spin
chuck; rotating the substrate by the spin chuck and supplying a
plating liquid onto the substrate, while surrounding the peripheral
edge of the substrate held on the spin chuck by one of the inner
surrounding member and the outer surrounding member, thereby
applying electroless plating onto the interconnection line, while
receiving the plating liquid thrown off from the substrate by said
one of the inner surrounding member and the outer surrounding
member which surrounds the peripheral edge of the substrate; and
rotating the substrate by the spin chuck and supplying a cleaning
liquid onto the substrate, while surrounding the peripheral edge of
the substrate held on the spin chuck by the other of the inner
surrounding member and the outer surrounding member at least for a
while, thereby performing a post-cleaning process on the substrate,
while receiving the cleaning liquid thrown off from the substrate
by said other of the inner surrounding member and the outer
surrounding member which surrounds the peripheral edge of the
substrate, wherein the method is arranged to perform the
post-cleaning process before a plated surface formed by the
electroless plating is dried.
[0027] According to the present invention, after electroless
plating is performed on an interconnection line formed on a
substrate, cleaning is performed by use of a cleaning liquid on the
substrate before the plated surface on the interconnection line is
dried, i.e., before a slurry-like by-product generated by the
plating reaction present on the plated surface is precipitated. In
this case, the by-product can be effectively removed by the
cleaning liquid before it comes to strongly stick to the plated
surface. Further, a pre-cleaning process is performed before the
electroless plating, such that the pre-cleaning process,
electroless plating, and post-cleaning process are performed
without drying the surface of the substrate. In this case, the
surface of the Cu interconnection line is prevented form being
oxidized and the morphology of the plated film is prevented form
being deteriorated. Consequently, the plated film formed by the
electroless plating on the interconnection line is improved in
quality.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 This is a plan view schematically showing the
structure of an electroless plating system including an electroless
plating unit that can be used for performing a substrate processing
method according to the present invention.
[0029] FIG. 2 This is a plan view schematically showing the
electroless plating unit.
[0030] FIG. 3 This is a sectional view schematically showing the
electroless plating unit.
[0031] FIG. 4 This is a view schematically showing the structure of
a nozzle unit and a process fluid transport mechanism for supplying
process fluids, such as a plating liquid, to the nozzle unit.
[0032] FIG. 5 This is a view for explaining the movement manner of
the nozzle unit.
[0033] FIG. 6 This is a sectional view showing the structure of a
wafer to be processed in the electroless plating system.
[0034] FIG. 7 This is a flow chart for explaining a substrate
processing method according to a first embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0035] FIG. 8A This is a sectional view for explaining a step of
the substrate processing method according to the first embodiment
of the present invention.
[0036] FIG. 8B This is a sectional view for explaining a step of
the substrate processing method according to the first embodiment
of the present invention.
[0037] FIG. 8C This is a sectional view for explaining a step of
the substrate processing method according to the first embodiment
of the present invention.
[0038] FIG. 8D This is a sectional view for explaining a step of
the substrate processing method according to the first embodiment
of the present invention.
[0039] FIG. 9 This is a sectional view showing a wafer for
explaining a modification of the substrate processing method
according to the first embodiment of the present invention.
[0040] FIG. 10 This is a flow chart for explaining a substrate
processing method according to a second embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0041] FIG. 11A This is a sectional view for explaining a step of
the substrate processing method according to the second embodiment
of the present invention.
[0042] FIG. 11B This is a sectional view for explaining a step of
the substrate processing method according to the second embodiment
of the present invention.
[0043] FIG. 11C This is a sectional view for explaining a step of
the substrate processing method according to the second embodiment
of the present invention.
[0044] FIG. 11D This is a sectional view for explaining a step of
the substrate processing method according to the second embodiment
of the present invention.
[0045] FIG. 11E This is a sectional view for explaining a step of
the substrate processing method according to the second embodiment
of the present invention.
[0046] FIG. 12 This is a flow chart for explaining a substrate
processing method according to a third embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0047] FIG. 13 This is a flow chart for explaining a substrate
processing method according to a fourth embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0048] FIG. 14 This is a flow chart for explaining a substrate
processing method according to a fifth embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0049] FIG. 15 This is a flow chart for explaining a substrate
processing method according to a sixth embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
[0050] FIG. 16 This is a flow chart for explaining a substrate
processing method according to a seventh embodiment of the present
invention, performed in the electroless plating unit shown in FIGS.
2 and 3.
BEST MODE FOR CARRYING OUT THE INVENTION
[0051] Embodiments of the present invention will now be described
with reference to the accompanying drawings.
[0052] FIG. 1 is a plan view schematically showing the structure of
an electroless plating system including an electroless plating unit
that can be used for performing a substrate processing method
according to the present invention.
[0053] The electroless plating system 1 includes a process section
2 and an I/O (IN/OUT) section 3. The process section 2 is arranged
to perform an electroless plating process on a wafer W provided
with an interconnection line made of, e.g., Cu, and to perform
processes before and after the electroless plating process. The I/O
section 3 is arranged to transfer wafers W to and from the process
section 2.
[0054] The I/O section 3 includes an I/O port 4 and a wafer
transfer area 5. The I/O port 4 is provided with a table 6 for
placing thereon FOUPs (front opening unified pod) F, each of which
can store a plurality of wafers W in a horizontal state at
predetermined intervals in the vertical direction. The wafer
transfer area 5 is provided with a wafer transfer mechanism 7 for
transferring wafers W between the FOUPs F placed on the table 6 and
the process section 2.
[0055] Each FOUP F has a transfer port formed on one side for
transferring wafers W therethrough, and a lid provided on this side
for opening/closing the transfer port. The FOUP F has a plurality
of slots arrayed in the vertical direction for inserting wafers W,
wherein each of the slots supports one wafer W such that its front
surface (the surface provided with an interconnection line) faces
upward.
[0056] The table 6 of the I/O port 4 can place thereon a plurality
of, such as three, FOUPs F, which are arrayed in the width
direction (Y-direction) of the electroless plating system 1, such
that the side of each FOUP F having the transfer port faces a
partition wall 8 between the I/O port 4 and wafer transfer area 5.
The partition wall 8 has window portions 9 formed therein at
positions corresponding to the mount positions for FOUPs F. Each of
the window portions 9a is provided with a shutter 10 on the wafer
transfer area 5 side for opening/closing the window portion 9.
[0057] The shutter 10 is arranged to open/close the lid 10a of a
FOUP F at the same time when it opens/closes the window portion 9.
The shutter 10 is preferably provided with an interlock to prevent
its operation when no FOUP F is placed on the predetermined
position of the table 6. After the shutter 10 is operated to open
the window portion 9, so as to set the transfer port of the FOUP F
to communicate with the wafer transfer area 5, the wafer transfer
mechanism 7 of the wafer transfer area 5 can access the FOUP F.
[0058] The wafer transfer mechanism 7 has a transfer pick 11 for
holding a wafer W, and is movable in the Y-direction. The transfer
pick 11 is movable back and forth in the longitudinal direction of
the electroless plating system 1 (X-direction), movable up and down
in the height direction of the electroless plating system 1
(Z-direction), and rotatable in the X-Y plane. With this
arrangement, the wafer transfer mechanism 7 can transfer a wafer W
between any one of the FOUPs F placed on the table 6 and each
transit unit (TRS) 16 disposed in the process section 2.
[0059] The process section 2 includes transit units (TRS) 16,
electroless plating units (PW) 12 (substrate processing
apparatuses), hot plate units (HP) 19, cooling units (COL) 22, and
a main wafer transfer mechanism 18. Each of the transit units (TRS)
16 is arranged to temporarily place a wafer W therein when the
wafer W is transferred to and from the wafer transfer area 5. Each
of the electroless plating units (PW) 12 is arranged to perform an
electroless plating process on a wafer W, and to perform processes,
such as cleaning, on the wafer W before and after the electroless
plating process. Each of the hot plate units (HP) 19 is arranged to
perform a heating process on a wafer W before and after the
processes performed in the electroless plating units (PW) 12. Each
of the cooling units (COL) 22 is arranged to cool a wafer W heated
in one or more of the hot plate units (HP) 19. The main wafer
transfer mechanism 18 can access the respective units to transfer
wafers W between the units. The process section 2 is provided with
a filter/fan unit (not shown) at the ceiling for supplying clean
air as a down flow to the respective units and main wafer transfer
mechanism 18.
[0060] A plurality of, such as two, transit units (TRS) 16 are
stacked one on the other at a position between the wafer transfer
area 5 and the main wafer transfer mechanism 18 located essentially
at the center of the process section 2. The lower transit unit
(TRS) 16 is used to place therein a wafer W transferred from the
I/O section 3 to the process section 2. The upper transit unit
(TRS) 16 is used to place therein a wafer W transferred from the
process section 2 to the I/O section 3. A plurality of, such as
four, hot plate units (HP) 19 are stacked one on the other at each
of the opposite sides of the transit units (TRS) 16 in the
Y-direction. A plurality of, such as four, cooling units (COL) 22
are stacked one on the other at each of the opposite sides of the
main wafer transfer mechanism 18 in the Y-direction, to be adjacent
to the hot plate units (HP) 19. A plurality of, such as two,
electroless plating units (PW) 12 are stacked one on the other at
each of two positions arrayed in the Y-direction, to be adjacent to
the cooling units (COL) 22 and main wafer transfer mechanism
18.
[0061] The main wafer transfer mechanism 18 has a plurality of
transfer arms 17 disposed on, e.g., the upper and lower sides for
transferring wafers W. The transfer arms 17 are movable up and down
in the Z-direction, rotatable in the X-Y plane, and movable back
and forth in the X-Y plane. With this arrangement, the main wafer
transfer mechanism 18 can transfer wafers W between the respective
transit units (TRS) 16, electroless plating units (PW) 12, hot
plate units (HP) 19, and cooling units (COL) 22.
[0062] The electroless plating system 1 is connected to and
controlled by a process controller 31 comprising a microprocessor
(computer). The process controller 31 is connected to the user
interface 32, which includes, e.g., a keyboard and a display,
wherein the keyboard is used for a process operator to input
commands for operating the respective components or units in the
electroless plating system 1, and the display is used for showing
visualized images of the operational status of the respective
components or units in the electroless plating system 1. Further,
the process controller 31 is connected to a storage section 33 that
stores recipes with control programs and process condition data
recorded therein for the process controller 31 to control the
electroless plating system 1 so as to perform various processes. A
required recipe is retrieved from the storage section 33 and
executed by the process controller 31 in accordance with an
instruction or the like input through the user interface 32.
Consequently, the electroless plating system 1 can perform a
predetermined process under the control of the process controller
31. The recipes may be used while they are stored in a readable
storage medium, such as a CD-ROM, hard disk, or nonvolatile memory.
Alternatively, the recipes may be used online while they are
transmitted between the respective components or units in the
electroless plating system 1, or transmitted from an external
apparatus through, e.g., a dedicated line, as needed.
[0063] A wafer W to be processed in the electroless plating system
1 is structured as shown in FIG. 6, for example. Specifically, an
insulating film 101 made of a material, such as SiO.sub.2, is
formed on the surface of a plate-like substrate (not shown) made of
a material, such as Si. A groove is formed in the surface of the
insulating film 101, and is covered with a barrier metal 105. An
interconnection line 102 made of, e.g., Cu is formed on the barrier
metal 105 in the groove of the insulating film 101. In the
electroless plating system 1, a FOUP F storing wafers W to be
processed is placed at a predetermined position on the table 6 of
the I/O port 4 by a transfer robot or operator. Then, the wafers W
are taken out one by one from the FOUP F by the transfer pick 11 of
the wafer transfer mechanism 7, and each of the wafers thus taken
out is transferred into one of the transit units (TRS) 16. Where a
corrosion resistant organic film is present on the surface of the
interconnection line 102, the wafer W is transferred by one of the
transfer arms 17 of the main wafer transfer mechanism 18 from the
transit unit (TRS) 16 to one of the hot plate units (HP) 19. In
this hot plate unit (HP) 19, a pre-baking process is performed on
the wafer W, so that the organic film is sublimed. Then, the wafer
W is transferred by the main wafer transfer mechanism 18 from the
hot plate unit (HP) 19 to one of the cooling units (COL) 22, in
which the wafer W is cooled.
[0064] Then, the wafer W is transferred by the main wafer transfer
mechanism 18 to one of the electroless plating units (PW) 12. In
this electroless plating unit (PW) 12, an electroless plating
process is performed on the interconnection line 102 formed on the
wafer W, and processes, such as cleaning, are performed on the
wafer W before and after the electroless plating process. The
electroless plating units (PW) 12 will be explained later in
detail.
[0065] After the process in the electroless plating unit (PW) 12 is
finished, the wafer W is transferred by the main wafer transfer
mechanism 18 to one of the transit units (TRS) 16. Then, the wafer
W is transferred by the transfer pick 11 of the wafer transfer
mechanism 7 from the transit unit (TRS) 16 to the original slot of
the FOUP F. Alternatively, after the process in the electroless
plating unit (PW) 12 is finished, a post-baking process may be
performed on the wafer W, as needed, before the wafer W is
transferred to one of the transit units (TRS) 16. In this case, the
wafer W is transferred by the main wafer transfer mechanism 18 from
the electroless plating unit (PW) 12 to one of the hot plate units
(HP) 19. In this hot plate unit (HP) 19, a post-baking process is
performed on the wafer W to sublime organic substances contained in
the cap metal formed to cover the interconnection line 102 by the
electroless plating process, and to improve the adhesive property
of the cap metal relative to the interconnection line 102.
Thereafter, the wafer W is transferred by the main wafer transfer
mechanism 18 from the hot plate unit (HP) 19 to one of the cooling
units (COL) 22, in which the wafer W is cooled.
[0066] Next, a detailed explanation will be given of the
electroless plating units (PW) 12.
[0067] FIG. 2 is a plan view schematically showing each of the
electroless plating units (PW) 12. FIG. 3 is a sectional view
schematically showing this electroless plating unit (PW) 12.
[0068] The electroless plating unit (PW) 12 includes a housing 42,
in which an outer chamber 43 (outer surrounding member) and an
inner cup 47 (inner surrounding member) inside the outer chamber 43
are disposed. A spin chuck 46 is disposed inside the inner cup 47
to hold and rotate the wafer W in a horizontal or almost horizontal
state. A nozzle unit 51 is disposed to supply liquid and gas, such
as a plating liquid and a cleaning liquid, onto the wafer W held on
the spin chuck 46.
[0069] The housing 42 has a window portion 44a formed on the
sidewall, so that the wafer W is transferred therethrough by one of
the transfer arms 17 to and from the housing 42. The window portion
44a is provided with a first shutter 44 for opening/closing the
window portion 44a.
[0070] The outer chamber 43 has a cylindrical or box-like shape
with an opening at the bottom and a sidewall configured to surround
the wafer W held on the spin chuck 46. The sidewall of the outer
chamber 43 has a tapered portion 43c with an inner wall inclined
inward and upward at a height level essentially the same as the
wafer W held on the spin chuck 46. The tapered portion 43c has a
window portion 45a formed therein to face the window portion 44a of
the housing 42, so that the wafer W is transferred therethrough by
one of the transfer arms 17 to and from the outer chamber 43. The
window portion 45a is provided with a second shutter 45 for
opening/closing the window portion 45a.
[0071] The upper wall of the outer chamber 43 is provided with a
gas supply port 89 for supplying nitrogen gas (N.sub.2) or clean
air to form a down flow into the outer chamber 43. The annular
bottom wall of the outer chamber 43 is provided with a drain 85 for
discharging exhaust gas and drainage.
[0072] The inner cup 47 has a cylindrical shape with openings at
the top and bottom. The inner cup 47 is movable up and down by an
elevating mechanism, such as a gas cylinder, between a process
position (see the solid lines in FIG. 3) for surrounding the wafer
W held on the spin chuck 46 and a retreat position (see the phantom
lines in FIG. 3) for retreating below the wafer W held on the spin
chuck 46. The inner cup 47 has a tapered portion 47a inclined
inward and upward at the upper end corresponding to the tapered
portion 43c of the outer chamber 43. The annular bottom wall of the
inner cup 47 is provided with a drain 88 for discharging exhaust
gas and drainage. When the inner cup 47 is set at the process
position, the tapered portion 47a is present at a height level
essentially the same as the wafer W held on the spin chuck 46.
[0073] The inner cup 47 is set at the process position, when the
electroless plating process is performed on the wafer W held on the
spin chuck 46. In this state, the plating liquid supplied from the
nozzle unit 51 onto the wafer W, as described later, and dropping
from the wafer W, bouncing from wafer W, or thrown off from the
wafer W by rotation of the spin chuck 46 is received by the tapered
portion 47a of the inner cup 47 and so forth, so that the plating
liquid is prevented from scattering around the inner cup 47. The
inner wall of the inner cup 47 is preferably provided with
corrosion resistant means, such as a hydrogen fluoride resin
coating, corresponding to the plating liquid, so that the inner
wall is protected from corrosion due to deposition of the plating
liquid. The plating liquid received by the inner cup 47 is guided
to the drain 88. The drain 88 is connected to a collection line
(not shown), so that the plating liquid is collected through the
collection line and is recycled or discarded (disposal of
drainage).
[0074] The inner cup 47 is set at the retreat position, when the
wafer W is transferred between one of the transfer arms 17 and spin
chuck 46, or when cleaning is performed on the wafer W by use of a
chemical liquid. Accordingly, when cleaning is performed on the
wafer W by use of a chemical liquid, the wafer W held on the spin
chuck 46 is surrounded by the outer chamber 43. In this state, the
chemical liquid supplied from the nozzle unit 51 onto the wafer W,
as described later, and dropping from the wafer W, bouncing from
wafer W, or thrown off from the wafer W by rotation of the spin
chuck 46 is received by the tapered portion 43c of the outer
chamber 43 and so forth, so that the plating liquid is prevented
from scattering around the outer chamber 43. At this time, the
chemical liquid is also received by the outer wall of the tapered
portion 47a of the inner cup 47. The inner wall of the outer
chamber 43 and the outer wall of the tapered portion 47a of the
inner cup 47 are preferably provided with corrosion resistant
means, such as a hydrogen fluoride resin coating, corresponding to
the chemical liquid, so that they are protected from corrosion due
to deposition of the chemical liquid. The chemical liquid received
by the outer chamber 43 is guided to the drain 85. The drain 85 is
connected to a collection line (not shown), so that the chemical
liquid is collected through the collection line and is recycled or
discarded (disposal of drainage).
[0075] The spin chuck 46 includes a rotary cylindrical body 62
rotatable in the horizontal direction, and an annular rotary plate
61 extending in the horizontal direction at the top of the rotary
cylindrical body 62. The peripheral portion of the rotary plate 61
is provided with support pins 63 for supporting the wafer W placed
thereon and pusher pins 64 for contacting and pushing the edge of
the wafer W supported by the support pins 63. The wafer W is
transferred between one of the transfer arms 17 and spin chuck 46
by use of the support pins 63. In order to reliably support the
wafer W, the support pins 63 are preferably disposed at intervals
at three or more positions in the annular direction.
[0076] The pusher pins 64 are arranged not to obstruct the
operation for transferring the wafer W between the transfer arm 17
and spin chuck 46. For this purpose, a pushing mechanism (not
shown) is disposed to push the portions of the pusher pins 64 below
the rotary plate 61 toward the rotary plate 61, so that the upper
ends (distal ends) of the pusher pins 64 are inclined out of the
rotary plate 61. In order to reliably hold the wafer W, the pusher
pins 64 are also preferably disposed at intervals at three or more
positions in the annular direction.
[0077] A belt 65 is wound around the outer surface of the rotary
cylindrical body 62 and is arranged to be driven by a motor 66.
With this arrangement, the rotary cylindrical body 62 can be
rotated to rotate the wafer W held by the support pins 63 and
pusher pins 64 in a horizontal or almost horizontal state. The
position of the barycenter of the pusher pins 64 can be adjusted,
so that the pushing force on the wafer W during rotation of the
wafer W is adjusted. For example, where the barycenter is set at a
position below the rotary plate 61, a centrifugal force is applied
to a portion below the rotary plate 61 and causes the upper end to
move inward, so the pushing force on the wafer W is increased.
[0078] An under plate 48 for adjusting the temperature of the wafer
W is disposed to face the back surface of the wafer W held on the
spin chuck 46 and to be movable up and down. The under plate 48 is
maintained at a predetermined temperature by a heater (not shown)
built therein. The under plate 48 is disposed in a space on the
rotary plate 61 and surrounded by the support pins 63 and pusher
pins 64, and is connected to a shaft 67 extending through the
rotary cylindrical body 62. The shaft 67 is connected to an
elevating mechanism 69, such as an air cylinder, through a
horizontal plate 68 disposed below the rotary cylindrical body 62,
so that the shaft 67 is movable up and down by the elevating
mechanism 69. For example, the upper surface of the under plate 48
has a plurality of process fluid supply ports 81 formed therein to
supply a process fluid, such as purified water or a drying gas,
toward the back surface of the wafer W. A process fluid supply
passage 87 is formed in the under plate 48 and shaft 67 to supply a
process fluid, such as purified water used as a
temperature-adjusting fluid or nitrogen gas used as a drying gas to
the process fluid supply ports 81. The process fluid supply passage
87 is provided with a heat exchanger 84 formed in the shaft 67, so
that a process fluid flowing through the process fluid supply
passage 87 is heated to a predetermined temperature by the heat
exchanger 84 and is supplied from the process fluid supply ports 81
toward the back surface of the wafer W.
[0079] When the wafer W is transferred between the spin chuck 46
and one of the transfer arms 17, the under plate 48 is moved down
to a position adjacent to the rotary plate 61 so as not to
interfere with the transfer arm 17 (see the solid lines in FIG. 3).
When the electroless plating process is performed on the
interconnection line 102 on the wafer W held on the spin chuck 46,
the under plate 48 is moved up to a position adjacent to the wafer
W (see the phantom lines in FIG. 3).
[0080] The nozzle unit 51 extends in a horizontal or almost
horizontal state, and a predetermined portion on the distal end
side thereof (the side for delivering a plating liquid and so forth
onto the wafer W) can be placed in a nozzle shed 50 formed to
communicate with the outer chamber 43. The nozzle unit 51 includes
a cleaning nozzle 51a, a drying nozzle 51b, and a plating liquid
nozzle 51c integrated with each other. The cleaning nozzle 51a is
arranged to selectively supply a chemical liquid used as a cleaning
liquid, purified water used as a cleaning liquid or rinsing liquid,
and nitrogen gas onto the wafer W. The drying nozzle 51b is
arranged to supply nitrogen gas used as a drying gas onto the wafer
W. The plating liquid nozzle 51c is arranged to supply a plating
liquid onto the wafer W. The cleaning nozzle 51a, drying nozzle
51b, and plating liquid nozzle 51c are arrayed in parallel with
each other in a horizontal or almost horizontal direction. The
cleaning nozzle 51a, drying nozzle 51b, and plating liquid nozzle
51c respectively has nozzle tips 52a, 52b, and 52c at their distal
ends bent downward. The cleaning nozzle 51a, drying nozzle 51b, and
plating liquid nozzle 51c are connected to a process fluid supply
mechanism 60 for supplying fluids, such as the plating liquid,
cleaning liquid, and N.sub.2 gas.
[0081] FIG. 4 is a view schematically showing the structure of the
nozzle unit 51 and the process fluid transport mechanism for
supplying process fluids, such as a plating liquid, to the nozzle
unit 51.
[0082] As shown in FIG. 4, the process fluid supply mechanism 60
includes a cleaning liquid supply mechanism 70 for supplying a
chemical liquid to the cleaning nozzle 51a, and a plating liquid
supply mechanism 90 for supplying a plating liquid to the plating
liquid nozzle 51c.
[0083] The cleaning liquid supply mechanism 70 includes a chemical
liquid storage tank 71, a pump 73, and a valve 74a. The chemical
liquid storage tank 71 stores the chemical liquid while heating and
adjusting it to a predetermined temperature. The pump 73 is
arranged to pump up the chemical liquid from inside the chemical
liquid storage tank 71. The valve 74a is arranged to switch the
transportation of the chemical liquid pumped up by the pump 73 to
the cleaning nozzle 51a. The cleaning nozzle 51a can be supplied
not only with the chemical liquid from the cleaning liquid supply
mechanism 70 but also with purified water and nitrogen gas both
being heated and adjusted to a predetermined temperature. By
switching the opening/closing of the valves 74a, 74b, and 74c, any
one of the chemical liquid, purified water, and nitrogen gas can be
selectively supplied to the cleaning nozzle 51a. For example, a
common source may be used for supplying nitrogen gas to the
cleaning nozzle 51a and drying nozzle 51b, while supply of nitrogen
gas to the drying nozzle 51b is adjusted by opening/closing a valve
74d additionally disposed.
[0084] The plating liquid supply mechanism 90 includes a plating
liquid storage tank 91, a pump 92, a valve 93, and a heating source
94. The plating liquid storage tank 91 stores the plating liquid.
The pump 92 is arranged to pump up the plating liquid from inside
the plating liquid storage tank 91. The valve 93 is arranged to
switch the transportation of the plating liquid pumped up by the
pump 92 to the plating liquid nozzle 51c. The heating source 94 is
arranged to heat the plating liquid supplied through the valve 93
to the plating liquid nozzle 51c to a predetermined temperature.
For example, the heating source 94 is formed of a heater or heat
exchanger.
[0085] The nozzle unit 51 is held by a nozzle holder 54 having an
essentially annular or cylindrical shape and provided on a wall 50a
serving as the outer wall of the nozzle shed 50. The nozzle holder
54 includes three plate-like members 54a, 54b, and 54c disposed at
predetermined intervals on the outer periphery, so that the nozzle
holder 54 is arranged to close a through hole 57 formed in the wall
50a and to be slidable in the vertical direction. On the other
hand, the through hole 57 of the wall 50a is provided with an
engaging portion 50b along the edge, which engages with the
plate-like members 54a, 54b, and 54c in a sealing state in the
thickness direction. Since the engaging portion 50b engages with
the plate-like members 54a, 54b, and 54c, the atmosphere inside the
nozzle shed 50 can be hardly leaked outside.
[0086] The nozzle holder 54 is connected to a nozzle elevating
mechanism 56a through an essentially L-shaped arm 55 outside the
nozzle shed 50, so that the nozzle unit 51 can be moved up and down
by the nozzle elevating mechanism 56a. The nozzle holder 54
includes a bellows 54d that surrounds the nozzle unit 51 inside the
nozzle shed 50. The nozzle unit 51 is slidable in a horizontal
direction by a nozzle slide mechanism 56b, while the bellows 54d
extends/contracts along with slide of the nozzle unit 51.
[0087] The wall at the boundary between the nozzle shed 50 and
outer chamber 43 has a window portion 43a formed therein, so that
the nozzle unit 51 can move therethrough. The window portion 43a is
provided with a door mechanism 43b for opening/closing the window
portion 43a. Where the window portion 43a is set open and the
nozzle unit 51 is set at a height level corresponding to the window
portion 43a by the nozzle elevating mechanism 56a, the distal end
side of the nozzle unit 51 can be moved into and out of the outer
chamber 43 by the nozzle slide mechanism 56b.
[0088] FIG. 5 is a view for explaining the movement manner of the
nozzle unit.
[0089] As shown in FIG. 5, when the nozzle unit 51 is retreated
most, the distal end side is placed inside the nozzle shed 50 (see
the solid lines). On the other hand, when the nozzle unit 51 is
projected most, the nozzle tips 52a, 52b, and 52c are placed
essentially above the center of the wafer W (see the phantom
lines). The nozzle unit 51 is moved up and down by the nozzle
elevating mechanism 56a while the nozzle tips 52a, 52b, and 52c are
placed inside the inner cup 47, so that the distance of the distal
ends of the nozzle tips 52a, 52b, and 52c and the wafer W is
adjusted. The nozzle unit 51 is moved by the nozzle slide mechanism
56b to linearly slide the nozzle tips 52a, 52b, and 52c between the
essential center and peripheral edge of the wafer W, so that the
plating liquid or another fluid is supplied onto a target position
of the wafer W in the radial direction.
[0090] The nozzle unit 51, the inner wall of the nozzle shed 50,
and other various members, such as the under plate 48, disposed
inside the outer chamber 43 are also preferably provided with
corrosion resistant means, such as acid and alkali resistant means,
e.g., a fluorocarbon resin coating, corresponding to the chemical
liquid and plating liquid. The nozzle shed 50 is preferably
provided with a cleaning mechanism for cleaning the distal end side
of the nozzle unit 51.
[0091] As shown in FIG. 2, the respective components of the
electroless plating unit (PW) 12 are connected to and controlled by
a unit controller 34 (control section) connected to the process
controller 31. As needed, a required recipe is retrieved from the
storage section 33 and executed by the process controller 34 in
accordance with an instruction or the like input through the user
interface 32.
[0092] Next, an explanation will be given of several methods
according to embodiments for processing a wafer W in the
electroless plating unit (PW) 12. The following explanation will be
exemplified by a case where an interconnection line 102 is plated
with a CoWB film as a cap metal.
[0093] Where plating of a CoWB film is performed in the electroless
plating unit (PW) 12, the window portion 44a and window portion 45a
are set open, and a wafer W is transferred by one of the transfer
arms 17 of the main wafer transfer mechanism 18 through the window
portion 44a and window portion 45a into the housing 42 and outer
chamber 43. Then, the wafer W is placed on the support pins 63 of
the spin chuck 46 and is held on the spin chuck 46 by the pusher
pins 64 that push the edge of the wafer W. Then, the transfer arm
17 are retreated out of the housing 42, and the window portion 44a
and window portion 45a are set closed by the first shutter 44 and
second shutter 45. Further, the window portion 43a is set open, and
the distal end side of the nozzle unit 51 is moved into the outer
chamber 43 and placed above the wafer W. In this state, a process
is started.
FIRST EMBODIMENT
[0094] FIG. 7 is a flow chart showing in outline a processing
method of a wafer W according to a first embodiment, performed in
the electroless plating unit (PW) 12. FIG. 8A to 8D are sectional
views for explaining steps of this process.
[0095] At first, purified water is supplied from the cleaning
nozzle 51a onto a wafer W in the state shown in FIG. 8A to perform
pre-wetting of the wafer W, thereby setting the surface of the
wafer W to be hydrophilic (Step 1: hydrophilic step). With this
operation, a cleaning liquid used in a subsequent pre-cleaning
process is prevented from being repelled on the surface of the
wafer W, and a plating liquid used in electroless plating is
prevented from dropping from the wafer, even where an inter-level
insulating film present on the wafer surface is made of a
hydrophobic material, such as a low dielectric constant film (Low-k
film). For example, the pre-wetting of the wafer W is performed as
follows. Specifically, a process liquid, such as purified water, is
supplied onto the wafer W to form a puddle of purified water on the
wafer W, while the wafer W is set in a stationary state or is
slowly rotated by the spin chuck 46. This state is maintained for a
predetermined time. Then, the wafer W is rotated at a predetermined
rotational speed and purified water is supplied onto the wafer W,
while the nozzle unit 51 is moved for the nozzle tip 52a of the
cleaning nozzle 51a to linearly scan the portion between the center
and peripheral edge of the wafer W. In the cleaning process,
rinsing process, and electroless plating process described later,
the same method as that of the pre-wetting can be used, while the
rotational speed of the wafer W is suitably selected in accordance
with the process conditions of the cleaning process, electroless
plating process, and so forth.
[0096] The hydrophilic process performed by this pre-wetting also
serves to remove contaminants on the surface of the wafer W and to
remove bubbles easily generated at the interface between liquid and
solid. In this case, the delivery flow rate of purified water is
preferably adjusted in accordance with the hydrophobic level of the
surface of the wafer W, such that the delivery flow rate is set
larger with a higher hydrophobic level. The rotational speed of the
wafer W is also preferably adjusted in accordance with the
hydrophobic level, such that the rotational speed is set lower with
a higher hydrophobic level. The process time is also preferably
adjusted in accordance with the hydrophobic level of the wafer
surface.
[0097] After the pre-wetting of the wafer W is finished and
purified water deposited on the wafer W is thrown off to some
extent by rotation of the spin chuck 46, a chemical liquid used as
a cleaning liquid is supplied from the cleaning nozzle 51a onto the
wafer W to perform a chemical liquid process as a pre-cleaning
process of the wafer W (Step 2: chemical liquid process step
(pre-processing step)). With this operation, the Cu oxide film and
contaminants are removed from the surface of the interconnection
line 102 formed on the wafer W. The chemical liquid used in this
step is not limited to a specific one and it may be a chemical
liquid commonly used. However, in order to enhance the effect of
removing the Cu oxide film from the surface of the interconnection
line 102, an organic acid aqueous solution may be used, for
example. Specifically, where an organic acid is used for the
pre-cleaning, the copper oxide is removed from the copper
interconnection line without causing corrosion, so that the nucleus
formation density is increased in the subsequent plating process,
and the surface morphology is thereby improved. At this time, the
chemical liquid received by the outer chamber 43 is collected
through the drain 85.
[0098] This chemical liquid process step serving as a
pre-processing step is preferably performed while the wafer surface
is kept wetted. With this operation, purified water on the wafer
surface is efficiently replaced with the chemical liquid, and the
cleaning effect of the chemical liquid is improved. The chemical
liquid process step serving as a pre-cleaning step is performed
while the chemical liquid is supplied at a flow rate set to
efficiently remove a Cu oxide protection film, a Cu oxide film,
and/or metal components remaining between interconnection lines. At
this time, the rotational speed of the wafer W needs to be suitably
set, because an excessively low speed deteriorates the removal
efficiency, while an excessively high speed causes the wafer W to
be at least partly dried and deteriorates the morphology of the
plated film due to re-oxidation of the Cu surface. The process time
is preferably set to be about 10 to 60 seconds, because an
excessively long process time causes Cu used as the metal of the
interconnection line to be dissolved too much, and brings about
problems, such as an increase in the resistivity of the
interconnection line.
[0099] Then, purified water is supplied from the cleaning nozzle
51a onto the wafer W, to perform a rinsing process as a
pre-processing step on the wafer W by use of purified water (Step
3: rinsing process step (pre-cleaning step)). This rinsing process
step is performed to replace the chemical liquid with purified
water to prevent the following problem. Specifically, where the
chemical liquid, which is acidic, remains on the surface of the
wafer W after the chemical liquid cleaning, the chemical liquid is
mixed with the plating liquid, which is alkaline, used in a
subsequent step. Consequently, a neutralization reaction is caused,
so the pH of the plating liquid is changed and particles are
generated, thereby bringing about plating faults. Further, the
rinsing process step needs to be performed to prevent the surface
of the wafer W from being dried, because Cu is oxidized if the
wafer W is dried.]]]
[0100] In the rinsing process of the wafer W or after the rinsing
process, the under plate 48 is moved up to a position near the
wafer W. Then, purified water heated at a predetermined temperature
is supplied from the process fluid supply ports 81 to heat the
wafer W to a predetermined temperature.
[0101] After the rinsing process of the wafer W is finished and
purified water deposited on the wafer W is thrown off to some
extent by rotation of the spin chuck 46, the inner cup 47 is moved
up to the process position. Then, as shown in FIG. 8B, a plating
liquid 106 heated at a predetermined temperature by the heating
source 94 is supplied, from the plating liquid nozzle 51c set at a
predetermined position above the wafer W, onto the wafer W
(insulating film 101) heated at a predetermined temperature to
perform an electroless plating process on the interconnection line
102 (Step 4: electroless plating step). With this operation, as
shown in FIG. 8C, CoWB of the plating liquid 106 is precipitated on
the surface of the interconnection line 102 (including the barrier
metal 105), so the interconnection line 102 is covered with a CoWB
film 103 (cap metal).
[0102] In this electroless plating process, while the wafer W is
rotated at about 100 rpm, the plating liquid is supplied onto the
wafer W to replace the rinsing liquid (purified water) present on
the wafer W with the plating liquid. Thereafter, the rotational
speed of the wafer W is decreased to a very low value to pool the
plating liquid on the wafer W. Then, while the wafer W is kept
rotated at the very low speed, the plating liquid is supplied to
promote the plating process, so as to form the CoWB film 103.
[0103] Immediately after the CoWB film 103 is formed, a slurry-like
by-product 104 generated by the plating reaction is present on the
surface of the CoWB film 103. The plating liquid received by the
inner cup 47 during the electroless plating process is collected
through the drain 88.
[0104] The plating liquid used in the electroless plating process
is not limited to a specific one, and it may be a plating liquid
commonly used. For example, the plating liquid may be prepared such
that it contains, as main components, a Co-containing salt, such as
cobalt chloride, a W-containing salt, such as tungsten acid
ammonium, and a reducing agent, such as dimethylamineborane (DMAB),
which is a derivative of sodium borohydride (SBH), and further
contains, as auxiliary components, a complexing agent, a
pH-adjusting agent, a buffering agent, and so forth. The plating
liquid preferably contains a surfactant, which is not limited to an
acidic or alkali surfactant, but is preferably an anionic,
nonionic, ampho-ionic, cationic, or polymer surfactant. Where a
plating liquid containing such a surfactant is used, the effect of
removing the by-product 104 present on the surface of the CoWB film
103 is enhanced by the surface-activation effect of the surfactant
in a post-cleaning process described below.
[0105] In the electroless plating process step, the rinsing liquid
(purified water) remaining on the surface of the wafer W needs to
be replaced in a short time, so the wafer W is preferably rotated
at a rotational speed that realizes replacement in a predetermined
time. However, if the rotational speed of the wafer W is too high,
the wafer can be easily dried due to a high viscosity of the
plating liquid, and may deteriorate the morphology or bring about
plating faults. Since the plating liquid needs to be uniformly
pooled all over the surface of the wafer W after purified water
used as the rinsing liquid is replaced with the plating liquid, the
rotational speed is preferably lower. However, it is not preferable
to set the rotational speed at zero, because the frequency of
supplying the plating liquid to the peripheral portion of the wafer
W becomes too low and the wafer W may be thereby dried. Where the
wafer W is kept rotated after the liquid pooling, the thermal
influence from the backside of the wafer W is uniformized, so that
the planar uniformity in plating rate is improved.
[0106] Since the plating liquid pooled on the wafer W is discharged
through the peripheral portion of the spin chuck 46 and/or wafer W,
the surface of the wafer W may thereby be dried and deteriorate the
morphology. Accordingly, the plating liquid is preferably supplied
during the plating process. Further, when the liquid on the surface
of the wafer W is replaced with the plating liquid to start the
plating process, the temperature of the wafer W needs to be set at
the precipitation temperature of CoWB. If the precipitation cannot
be promoted due to an excessively low temperature, the alkali
plating liquid may cause hydroxylation of the surface of the Cu
interconnection line, which inhibits the plating even if the
temperature is increased thereafter. In order to solve this
problem, warmed purified water is preferably supplied onto the
wafer back surface to heat the wafer W before the start of the
plating.
[0107] After the electroless plating process is finished, the
supply of warmed purified water from the process fluid supply ports
81 is stopped. Then, purified water is supplied from the cleaning
nozzle 51a onto the wafer W to perform a rinsing process as
post-cleaning of the wafer W (Step 5: first rinsing process step
(post-process step). With this operation, the excess part of the
plating liquid 106 deposited on portions of the wafer W other than
the interconnection line 102 is partly or mostly removed, and the
part of the plating liquid deposited on the inner wall of the inner
cup 47 is also removed. On the other hand, the by-product 104
present on the surface of the CoWB film 103 should be removed as
soon as possible, because the by-product 104 has a high viscosity
and is dried with a lapse of time to be a precipitated substance
strongly sticking to the CoWB film 103. This rinsing process
prevents the by-product 104 from being dried, and thereby delays
precipitation of the by-product 104. At this time, the rotational
speed of the wafer W needs to be set at a suitable value, because
an excessively high rotational speed causes the surface of the
wafer W to be partly dried, thereby decreasing the efficiency of
the post-cleaning in removing residues generated by the plating
process. The supply of purified water from the process fluid supply
ports 81 may be stopped after the rinsing process.
[0108] In the rinsing process of the wafer W or after the rinsing
process, the inner cup 47 is moved down to the retreat position.
Where the inner cup 47 is moved down in the rinsing process,
purified water for the rinsing process thrown off from the wafer W
can be sprayed onto the inner cup 47 to scan it from the lower side
to the upper side, so that the entire inner wall of the inner cup
47 is efficiently washed out.
[0109] After the rinsing process is finished, a chemical liquid is
supplied as a cleaning liquid from the cleaning nozzle 51a onto the
wafer W to perform a chemical liquid process as a post-cleaning
process of the wafer W (Step 6: chemical liquid process step
(post-cleaning step)). This chemical liquid process is arranged to
remove residues generated by the plating precipitation reaction and
to remove plated films abnormally precipitated between lines. The
chemical liquid process is preferably performed while the wafer
surface is not dried but kept wetted. If the wafer surface is
dried, precipitated substances generated by the plating process can
easily remain on the wafer surface and deteriorate the cleaning
effect. In this embodiment, this chemical liquid process can be
started at a very short interval that is defined by a switching
time of valves from purified water for the rinsing process to the
cleaning liquid for the post-cleaning process, after the rinsing
process described above. Consequently, this process can be
performed before the plated surface is dried, i.e., before the
by-product 104 is dried to be a precipitated substance strongly
sticking to the surface of the CoWB film 103. In other word, as
shown in FIG. 8D, the by-product 104 is reliably removed by this
chemical liquid process, when the sticking force thereof to the
CoWB film 103 is still weak. Further, the residues of the excess
part of the plating liquid 106 deposited on the wafer W are also
removed by this post-cleaning process to prevent contamination. If
the wafer W is dried, the post-cleaning effect is deteriorated,
because by-products (residues) generated by the plating process can
easily remain on the surface of the wafer W and strongly stick to
the surface.
[0110] In the chemical liquid process, the cleaning liquid received
by the outer chamber 43 and the outer wall of the tapered portion
47a of the inner cup 47 is collected through the drain 85. In this
embodiment, a rinsing process is performed before the chemical
liquid process, so that the excess part of the plating liquid 106
deposited on portions of the wafer W other than the interconnection
line 102 is partly or mostly removed. Consequently, the chemical
liquid is collected in a state having a high purity, so the
chemical liquid can be recycled.
[0111] The chemical liquid (cleaning liquid) used in the chemical
liquid process is not limited to a specific one and it may be a
chemical liquid commonly used. However, an acidic liquid is
preferably used, because an acidic cleaning liquid can enhance the
effect of dissolving the by-product 104 by acid, thereby removing
the by-product 104 more effectively. However, where the chemical
liquid is strong acid with a pH of less than 3, the liquid may
infiltrate into the portion between the interconnection line 102
and barrier metal 105 and cause galvanic corrosion (corrosion due
to contact between heterogeneous metals). Further, in this case,
the adhesive property of particles relative to the wafer may become
stronger and thereby decrease the process yield. Accordingly, the
chemical liquid is preferably an acid with a pH of 3 or more, and
more preferably with a pH of 3 to 4, such as diluted sulfuric
acid.
[0112] Where the chemical liquid is an acid with a pH of 3 to 4,
the by-product 104 can be dissolved and removed from the surface of
the CoWB film 103 by an acid of the chemical liquid, even if the
by-product 104 has a high adhesive property relative to the surface
of the CoWB film 103.
[0113] In an experiment, the chemical liquid process was performed
on a by-product deposited on the surface of a CoWB film, by use of
chemical liquids with pH 3, pH 4, and pH 5, respectively, to
confirm whether the by-product was removed from the surface of the
CoWB film. As a result, it was confirmed that, where the chemical
liquid with pH 5 was used, the by-product was not sufficiently
removed, while, where the chemical liquids with pH 3 and pH 4 were
used, the by-product was removed (see Table 1).
TABLE-US-00001 TABLE 1 Cleaning liquid pH Removal of by-product 3
.largecircle. (Complete) 4 .largecircle. (Complete) 5 .DELTA.
(Insufficient)
[0114] The chemical liquid used in the chemical liquid process
serving as a post-cleaning process is preferably contains a
surfactant. In this case, as shown in FIG. 9, the chemical liquid
process is performed such that a surfactant layer 110 is present
between the CoWB film 103 and by-product 104 and peels off the
by-product 104 by its surface-activation effect, thereby removing
the by-product 104 more effectively (the surfactant layer 110 is
removed along with the by-product 104). Further, where the chemical
liquid for the post-cleaning process contains a surfactant, the
chemical liquid has high wettability relative to the surface of the
wafer W and thereby prevents the surface of the wafer W from being
dried.
[0115] Particularly, where the cleaning liquid has a surfactant
concentration of 0.0001% or more, the by-product 104 is peeled off
and removed from the surface of the CoWB film 103 by the
surface-activation effect of the surfactant, even if the by-product
104 has a high adhesive property relative to the surface of the
CoWB film 103.
[0116] Where the cleaning liquid is acidic particularly with a pH
of 3 to 4 and contains a surfactant particularly in a concentration
of 0.0001% or more, the dissolution effect of the acid is combined
with the peeling effect of the surfactant, thereby providing a
further enhanced effect.
[0117] In an experiment, the cleaning process was performed on a
by-product deposited on the surface of a CoWB film, by use of
cleaning liquids with surfactant concentrations of 0.001%, 0.0001%,
and 0.00001%, respectively, to confirm whether the by-product was
removed from the surface of the CoWB film. As a result, it was
confirmed that, where the cleaning liquid with a surfactant
concentration of 0.00001% was used, the by-product was not
sufficiently removed, while, where the cleaning liquids with
surfactant concentrations of 0.001% and 0.0001% were used, the
precipitated substance was removed (see Table 2). As the
surfactant, RS-710 (manufactured by TOHO Chemical Industry Co.,
LTD) was used, and DIW was added thereto to dilute the surfactant
to a target concentration.
TABLE-US-00002 TABLE 2 Surfactant concentration (%) Removal of
by-product 0.001% .largecircle. (Complete) 0.0001% .largecircle.
(Complete) 0.00001% .DELTA. (Insufficient)
[0118] Where the cleaning liquid is acidic particularly with a pH
of 3 to 4 and contains a surfactant particularly in a concentration
of 0.0001% or more, the dissolution effect of the acid is combined
with the peeling effect of the surfactant, thereby providing a
further enhanced effect.
[0119] As described above, where a plating liquid containing a
surfactant is used in the electroless plating process, as shown in
FIG. 9, the post-cleaning process is performed such that a
surfactant layer 110 is present between the CoWB film 103 and
by-product 104 and peels off the by-product 104 by its
surface-activation effect, thereby removing the by-product 104 more
effectively. Further, in this case, the surfactant prevents the
plating liquid from bubbling and improves the wettability of the
plating liquid.
[0120] After the chemical liquid process step serving as a
post-cleaning process of the wafer W is finished, purified water is
supplied from the cleaning nozzle 51a onto the wafer W to perform a
rinsing process of the wafer W (Step 7; second rinsing process). In
this rinsing process or after this rinsing process, the under plate
48 is moved down and separated from the wafer W.
[0121] After the second rinsing process is finished, the wafer W is
rotated by the spin chuck 46, and nitrogen gas is supplied from the
cleaning nozzle 51a onto the wafer W to dry the wafer W (Step 8).
The drying process of the wafer W is arranged such that nitrogen
gas is supplied onto the back surface of the wafer W from the
process fluid supply ports 81 of the under plate 48 that has been
moved down, and then the under plate 48 is moved up to be close to
the wafer W again. Further, for example, this drying process may be
performed such that the wafer W is rotated at a low rotational
speed for a predetermined time and then rotated at a high
rotational speed for a predetermined time.
[0122] After the drying process of the wafer W is finished, the
nozzle unit 51 is moved to a predetermined height by the nozzle
elevating mechanism 56a, as needed, then the distal end side of the
nozzle unit 51 is moved into the nozzle shed 50 by the nozzle slide
mechanism 56b, and then the window portion 43a is closed. Then, the
under plate 48 is moved down and separated from the wafer W, and
the wafer W is released from the pushing force of the pusher pins
64 and is supported only by the support pins 63, while the window
portion 44a and window portion 45a are opened. Thereafter, one of
the transfer arms 17 is moved into the outer chamber 43, receives
the wafer W from the support pins 63, and transfers it outside.
[0123] In the electroless plating unit (PW) 12, the electroless
plating process of the interconnection line 102 formed on the wafer
W and the cleaning process (post-cleaning process) of the wafer W
after this electroless plating process can be performed at the same
site without transferring the wafer W. In this case, the by-product
104 can be removed by the post-cleaning process, before the
by-product 104 turns into a precipitated substance on the surface
of the CoWB film 103 formed by the electroless plating process to
cover the interconnection line 102.
[0124] It is often the case that a plating liquid used for an
electroless plating process differs from a cleaning liquid used for
a post-cleaning process, such that the plating liquid is alkaline
and the cleaning liquid is acidic. Conventionally, this difference
makes it difficult to perform the electroless plating process and
post-cleaning process in the same unit, due to, e.g., the corrosion
resistant relative to the plating liquid and cleaning liquid.
Accordingly, it takes a long time to start the post-cleaning
process after the electroless plating process is finished, because
a wafer W needs to be transferred after the electroless plating
process from an electroless plating unit to a cleaning unit to
perform the post-cleaning process. Further, in order to prevent a
transfer mechanism for transferring the wafer W from being
contaminated by the plating liquid and so forth, the wafer W needs
to be dried after the electroless plating process and before the
post-cleaning process. Consequently, a by-product turns into a
precipitated substance on the surface of a CoWB film formed by the
electroless plating process before the post-cleaning process,
wherein this precipitated substance is very difficult to remove by
the post-cleaning process.
[0125] In light of the problem described above, the electroless
plating unit (PW) 12 according to this embodiment includes the
outer chamber 43 and the inner cup 47 movable up and down inside
the outer chamber 43. When the electroless plating process is
performed, the plating liquid thrown off from the wafer W is
received by the inner cup 47. When the post-cleaning process is
performed, the cleaning liquid thrown off from the wafer W is
received by the outer chamber 43. Where the plating liquid and
cleaning liquid have different natures, the inner cup 47 and outer
chamber 43 are provided with corrosion resistant means
corresponding to the plating liquid and cleaning liquid,
respectively, so that they are prevented from being corroded by
deposition of the plating liquid and cleaning liquid. Further, the
alkaline plating liquid and the acidic cleaning liquid are
separately collected or discharged, so that the electroless plating
process and post-cleaning process can be sequentially performed
while the wafer W is kept held on the spin chuck 46. Specifically,
when the post-cleaning process is performed after the electroless
plating process, the wafer W does not need to be transferred, and
thus the electroless plating process and post-cleaning process can
be performed at a short interval. Accordingly, the post-cleaning
process can be performed before the plated surface is dried, to
effectively remove the by-product 104 on the surface of the CoWB
film 103, thereby improving the quality of the CoWB film 103
serving as a cap metal.
[0126] As in the electroless plating process, the hydrophilic
process and pre-cleaning process before the plating process are
performed by use of the spin chuck 46, so the pre-cleaning process
and electroless plating process can be performed at a short
interval while the wafer surface is not dried but kept wetted.
Where the wafer W is prevented from being dried also before the
plating process, the pre-cleaning is efficiently performed, and Cu
re-oxidation is restrained so as not to deteriorate the morphology
of the plated film, as described above.
[0127] As described above, the post-cleaning is preferably
performed on the wafer W by use of a cleaning liquid before the
plated surface formed by the electroless plating is dried. In
addition, the plating process is preferably performed before the
surface of the wafer W is dried after the pre-cleaning. Most
preferably, the processes from the pre-wetting process (hydrophilic
process) to the drying process are performed while the wafer is
kept wetted. With this arrangement, a series of processes is
completed without causing problems due to the surface of the wafer
W being dried.
[0128] As described above, the post-cleaning process may employ an
acidic cleaning liquid particularly with a pH of 3 to 4.
Alternatively, the post-cleaning process may employ a cleaning
liquid containing a surfactant and particularly acidic or neutral
with a surfactant concentration of 0.0001% or more. Further, the
electroless plating process may employ a plating liquid containing
a surfactant. In any of these cases, the effect of removing the
by-product 104 is very high in the post-cleaning process, so the
post-cleaning process can be shortened and the cleaning liquid
consumption can be decreased.
[0129] After the post-cleaning process, back surface cleaning and
end surface cleaning may be performed on the wafer. In the back
surface cleaning and end surface cleaning, the rotational speed of
the wafer is first increased to dry the process target surface of
the wafer. This is conceived to prevent a back surface cleaning
liquid from flowing onto the wafer front surface. Then, the back
surface cleaning is performed. In the back surface cleaning, while
the wafer W is rotated at a low speed, purified water is supplied
onto the wafer back surface to perform a hydrophilic process on the
wafer back surface, so that a back surface cleaning liquid can be
uniformly spread on the wafer back surface. Then, a chemical liquid
for the back surface cleaning is supplied onto the wafer back
surface to remove residues deposited on the back surface during the
plating process. Thereafter, the end surface cleaning is performed.
In the end surface cleaning, purified water is supplied on the
wafer back surface, and is kept supplied in the subsequent steps.
Then, while purified water is supplied onto the wafer center, the
back surface nozzle is placed at the wafer peripheral edge and is
used to perform the end surface cleaning by use of the back surface
cleaning liquid (chemical liquid). Thereafter, the back surface
cleaning liquid is stopped, and only purified water is supplied to
perform a rinsing process.
[0130] Where the back surface cleaning and end surface cleaning are
performed, a drying step is performed thereafter.
SECOND EMBODIMENT
[0131] FIG. 10 is a flow chart showing in outline a processing
method of a wafer W according to a second embodiment, performed in
the electroless plating unit (PW) 12. FIG. 11A to 11E are sectional
views for explaining steps of this process.
[0132] At first, purified water is supplied from the cleaning
nozzle 51a onto a wafer W in the state shown in FIG. 8A to perform
pre-wetting of the wafer W, thereby setting the surface of the
wafer W to be hydrophilic (Step 11: hydrophilic step). With this
operation, the wettability of the surface of the wafer W is
improved. The pre-wetting of the wafer W is performed in the same
way as that of the first embodiment. Specifically, for example, a
process liquid, such as purified water, is supplied onto the wafer
W to form a puddle of purified water on the wafer W, while the
wafer W is rotated by the spin chuck 46. This state is maintained
for a predetermined time. Then, the wafer W is rotated at a
predetermined rotational speed and purified water is supplied onto
the wafer W, while the nozzle unit 51 is moved for the nozzle tip
52a of the cleaning nozzle 51a to linearly scan the portion between
the center and peripheral edge of the wafer W. At this time, the
rotational speed of the wafer W is suitably selected in accordance
with the process conditions of the cleaning process, electroless
plating process, and so forth. As in the first embodiment, the
cleaning processes using a chemical liquid and purified water and
electroless plating process may be performed in the same way, while
the rotational speed of the wafer W is suitably selected in
accordance with the process conditions of the cleaning process,
electroless plating process, and so forth.
[0133] After the hydrophilic step (pre-wetting) of the wafer W is
finished and purified water deposited on the wafer W is thrown off
to some extent by rotation of the spin chuck 46, a chemical liquid
is supplied from the cleaning nozzle 51a onto the wafer W to
perform a chemical liquid process as a pre-cleaning process (Step
12: chemical liquid process step (pre-cleaning step)). With this
operation, the Cu oxide film and contaminants are removed from the
surface of the interconnection line 102 formed on the wafer W. This
step is performed essentially in the same way as that of the first
embodiment. Further, the chemical liquid used in this step is not
limited to a specific one and it may be a chemical liquid commonly
used, as in the first embodiment. However, in order to enhance the
effect of removing the Cu oxide film from the surface of the
interconnection line 102, an organic acid aqueous solution may be
used, for example. Further, the chemical liquid process step is
preferably performed while the wafer surface is kept wetted, as in
the first embodiment.
[0134] After the chemical liquid cleaning step is finished,
purified water is supplied from the cleaning nozzle 51a onto the
wafer W, to perform a rinsing process as cleaning or rinsing of the
wafer W by use of purified water (Step 13: rinsing process step
(pre-cleaning step)). With this operation, the chemical liquid
deposited on the water W is removed, and the chemical liquid
deposited on the outer chamber 43 is also washed out. This rinsing
process is performed in the same way as that of the first
embodiment, and is preferably performed to prevent the surface of
the wafer W from being dried, because Cu is oxidized if the wafer W
is dried, as in the first embodiment. In the cleaning of the wafer
W by use of purified water or after the cleaning, the under plate
48 is moved up to a position near the wafer W, as in the first
embodiment. Then, purified water heated at a predetermined
temperature is supplied from the process fluid supply ports 81 to
heat the wafer W to a predetermined temperature.
[0135] After the cleaning process using purified water is finished
and purified water deposited on the wafer W is thrown off to some
extent by the centrifugal force of rotation of the spin chuck 46,
the inner cup 47 is moved up to the process position. Then, as
shown in FIG. 8B, a plating liquid 106 heated at a predetermined
temperature by the heating source 94 is supplied from the plating
liquid nozzle 51c onto the wafer W heated at a predetermined
temperature to perform an electroless plating process on the
interconnection line 102 (Step 14: electroless plating step). For
example, the plating liquid used in this step may be prepared as in
the first embodiment such that it contains, as main components, a
Co salt, such as cobalt chloride, a W salt, such as tungsten acid
ammonium, and a reducing agent, such as dimethylamineborane (DMAB),
which is a derivative of sodium borohydride (SBH), and further
contains, as auxiliary components, a complexing agent, a
pH-adjusting agent, a buffering agent, and so forth. With this
electroless plating, as shown in FIG. 8C, CoWB of the plating
liquid 106 is precipitated on the surface of the interconnection
line 102, so the interconnection line 102 is covered with a CoWB
film 103. The plating liquid received by the inner cup 47 during
the electroless plating process is collected through the drain
88.
[0136] After the electroless plating process of the interconnection
line 102 is finished, the supply of warmed purified water from the
process fluid supply ports 81 is stopped. Then, purified water is
supplied from the cleaning nozzle 51a onto the wafer W to perform a
rinsing process as post-cleaning of the wafer W (Step 15: first
rinsing process step (post-process step). With this operation, the
excess part of the plating liquid 106 deposited on portions of the
wafer W other than the interconnection line 102 is partly or mostly
removed, and the part of the plating liquid deposited on the inner
wall of the inner cup 47 is also removed. The supply of purified
water from the process fluid supply ports 81 may be stopped after
the rinsing process.
[0137] In the electroless plating step of Step 14 described above,
hydrogen gas is generated due to decomposition of the reducing
agent contained in the plating liquid 106 when the plating reaction
is caused. Consequently, as indicated in the enlarged view of FIG.
11A showing a portion corresponding to the interconnection line
102, voids 107 are formed in the CoWB film 103 by the hydrogen gas
bubbles, and damage the continuity of the CoWB film 103 at this
time. Further, voids may be formed due to bubbling of gas dissolved
in the plating liquid, thereby damaging the continuity of the CoWB
film 103. Where the rinsing process of Step 15 described above is
performed in this state, the rinsing process can not only remove
the excess part of the plating liquid 106 as described above, but
also remove hydrogen gas adsorb on the CoWB film 103, which is a
cause of the voids 107, as shown in FIG. 11B.
[0138] However, some voids 107 in the CoWB film 103 are still left,
and Cu of the interconnection line 102 may be diffused from these
voids 107.
[0139] In light of this, according to this embodiment, the
electroless plating step of Step 14 described above and the first
rinsing step of Step 15 serving as the post-process step described
above are repeated a predetermined number of times (Step 16). For
this purpose, the unit controller 34 is used to make a judgment of
whether or not Steps 14 and 15 have been repeated a predetermined
number of times.
[0140] When the electroless plating step of Step 14 is performed
again, the plating liquid 106 is supplied onto the CoWB film 103
and forms a state shown in FIG. 11C. When the electroless plating
process is performed for the first time, the CoWB film 103 includes
voids 107 formed therein, so Cu of the interconnection line 102 may
be diffused from these voids 107. On the other hand, when the
plating liquid 106 is supplied on the CoWB film 103 for the second
time, a CoWB film 103' is formed on the surface of the CoWB film
103, as show in FIG. 11D, so that the voids 107 formed in the CoWB
film 103 are filled with part of the CoWB film 103'. Further, even
where voids formed by bubbling of gas dissolved in the plating
liquid are present in the CoWB film 103, these voids are filled
with part of the CoWB film 103'. Further, since the CoWB film 103
is poly-crystalline and thus has crystal grain boundaries, Cu may
be diffused from pinholes 108 at the crystal grain boundaries.
Where the plating step is repeatedly performed, the openings of the
pinholes 108 formed at the crystal grain boundaries of the CoWB
film 103 are also filled with the CoWB film 103'.
[0141] Accordingly, the barrier property of the CoWB film is
improved to prevent Cu diffusion. Further, recessed portions 109
may be formed in the CoWB film 103' at positions corresponding to
the voids 107 of the CoWB film 103, but the recessed portions 109
are sufficiently smaller than the voids 107 and do not damage the
quality of the CoWB film. Further, pinholes 108' are also formed in
the CoWB film 103' at the crystal grain boundaries, but the
pinholes 108' are very unlikely to communicate with the pinholes
108 at the crystal grain boundaries of the CoWB film 103.
[0142] The CoWB film 103' includes voids 107' formed therein due to
hydrogen gas, so the first rinsing step (Step 15) is performed
again after this electroless plating step is finished.
Consequently, as shown in FIG. 11E, hydrogen gas is removed from
inside the voids 107' along with the plating liquid 106.
[0143] As described above, the electroless plating step of the
interconnection line 102 (Step 14) and the cleaning of the wafer W
by use of purified water (Step 15) are repeated a plurality of
times. Consequently, voids formed by hydrogen gas and pinholes at
crystal grain boundaries, which may cause Cu diffusion, are closed,
and hydrogen gas adsorb on the CoWB film is removed, while the cap
metal is formed.
[0144] The number of repetitions is preferably set to be 2 to 10,
so that the plating process is performed in a practical period of
time, while the coverage of the CoWB film is improved and Cu
diffusion is prevented.
[0145] The time period of the electroless plating step, such as the
time for supplying the plating liquid, may be set by use of the
number of repetitions of the plating step. For example, the process
time of one cycle of the plating step is preferably set to be 1/n
of the process time of conventional electroless plating performed
only once. Specifically, where the process time of conventional
electroless plating is set at about 100 seconds, the process time
of the plating step repeated twice is set at about 50 seconds, and
the process time of the plating step repeated 10 times is set at
about 10 seconds.
[0146] The unit controller 34 makes a judgment of whether the
electroless plating step (Step 14) and the first rinsing process
step (Step 15) serving as a post-cleaning step have been repeated a
predetermined number of times. If the answer is yes, the unit
controller 34 moves down the inner cup 47 to the retreat position
in the first rinsing process or after the first rinsing process is
finished. Where the inner cup 47 is moved down in the cleaning,
purified water thrown off from the wafer W can be sprayed onto the
inner cup 47 to scan it from the lower side to the upper side, so
that the entire inner wall of the inner cup 47 is efficiently
washed out. After the cleaning of the wafer W by use of purified
water is finished, a chemical liquid is supplied from the cleaning
nozzle 51a onto the wafer W to perform a chemical liquid process as
a post-cleaning process (Step 17: chemical liquid process step
(post-cleaning step)). With this operation, residues of the excess
part of the plating liquid 106 deposited on the wafer W are removed
to prevent contamination. Further, a by-product generated by the
plating reaction of the plating step on the surface of the CoWB
film is removed. In general, the by-product generated by the
plating reaction has a high viscosity and is dried with a lapse of
time to be a precipitated substance strongly sticking to the CoWB
film, which may increase the leakage electric current between the
interconnection line 102 and another interconnection line. However,
where this chemical liquid process serving as a post-cleaning step
is performed, the by-product is removed, thereby decreasing the
leakage electric current.
[0147] This chemical liquid cleaning process is preferably
performed before the plated surface formed by the electroless
plating is dried, as in Step 6 of the first embodiment. As in the
first embodiment, this chemical liquid process can be started at a
very short interval that is defined by a switching time of valves
from purified water for the rinsing process to the cleaning liquid
for the post-cleaning process, after the first rinsing process.
Consequently, this process can be performed before the plated
surface is dried, i.e., before the by-product 104 is dried to be a
precipitated substance strongly sticking to the surface of the CoWB
film 103. In other word, as shown in FIG. 8D, the by-product 104 is
reliably removed by this chemical liquid process, when the sticking
force thereof to the CoWB film 103 is still weak.
[0148] The chemical liquid used in this step is not limited to a
specific one and it may be a chemical liquid commonly used.
However, in order to enhance the effect of removing the by-product,
an acidic aqueous solution may be used, for example. At this time,
the chemical liquid received by the outer chamber 43 is collected
through the drain 85.
[0149] After the chemical liquid process step is finished, purified
water is supplied again from the cleaning nozzle 51a onto the wafer
W to perform a rinsing process of the wafer W by use of purified
water as a part of the post-cleaning step (Step 18: second rinsing
process step (post-cleaning step)). With this operation, the
chemical liquid deposited on the water W is removed, and the
chemical liquid deposited on the outer chamber 43 is also washed
out. This rinsing process is also performed in the same way as that
of the first embodiment. In the cleaning or after the cleaning, the
under plate 48 is moved down and separated from the wafer W.
[0150] After the second rinsing process for cleaning the wafer W by
use of purified water is finished, the wafer W is rotated by the
spin chuck 46, and nitrogen gas used as a drying gas is supplied
from the cleaning nozzle 51a onto the wafer W to dry the wafer W
(Step 19: drying step). The drying process of the wafer W is
arranged such that nitrogen gas is supplied onto the back surface
of the wafer W from the process fluid supply ports 81 of the under
plate 48 that has been moved down, and then the under plate 48 is
moved up to be close to the wafer W again. Further, this drying
process may be performed such that the wafer W is rotated at a high
rotational speed for a predetermined time.
[0151] After the drying process of the wafer W is finished, the
distal end side of the nozzle unit 51 is moved into the nozzle shed
50 by the nozzle slide mechanism 56b, and then the window portion
43a is closed. Then, the under plate 48 is moved down and separated
from the wafer W, and the wafer W is released from the pushing
force of the pusher pins 64 and is supported only by the support
pins 63, while the window portion 44a and window portion 45a are
opened. Thereafter, one of the transfer arms 17 is moved into the
outer chamber 43, receives the wafer W from the support pins 63,
and transfers it outside.
[0152] According to this embodiment, the electroless plating is
repeated a plurality of times on the interconnection line 102
formed on the wafer W, along with the cleaning of the wafer W
interposed therebetween by use of purified water. In this case,
hydrogen gas adsorbed on the CoWB film in each plating step is
removed, while voids due to the hydrogen gas and pinholes at
crystal grain boundaries, present in the CoWB film formed by the
previous plating step, are filled with part of the CoWB film formed
by the subsequent plating step. Consequently, the quality of the
CoWB film is improved, and Cu diffusion from the voids and/or
pinholes is prevented from being caused in the interconnection line
102, so that the EM resistance thereof is remarkably improved.
Accordingly, the reliability of the wafer W is maintained at a high
level for a long time.
[0153] Also in this embodiment, the post-cleaning of the wafer W by
use of a cleaning liquid is preferably performed before the plated
surface formed by the electroless plating is dried, as described
above in the first embodiment. In addition, the plating process is
preferably performed before the surface of the wafer W is dried
after the pre-cleaning. Most preferably, the processes from the
pre-wetting process (hydrophilic process) to the drying process are
performed while the wafer is not dried but kept wetted. With this
arrangement, a series of processes is completed without causing
problems due to the surface of the wafer W being dried in the
processes.
[0154] In this embodiment, the electroless plating step (Step 14)
and the first rinsing process step (Step 15) serving as a
post-cleaning step are repeated a plurality of times.
Alternatively, the electroless plating step and first rinsing
process step may be repeated a plurality of times along with other
several steps.
[0155] Next, an explanation will be given of third to sixth
embodiments in which steps are repeated. In the third to sixth
embodiments, a hydrophilic step, a chemical liquid process step
serving as a pre-cleaning step, a rinsing process step serving as a
pre-cleaning step, an electroless plating step, a first rinsing
process step serving as a post-cleaning step, a chemical liquid
process step serving as a post-cleaning step, a second rinsing
process step serving as a post-cleaning step, and a drying step may
be respectively performed in the same ways as those of the second
embodiment. Further, also in these embodiments, the post-cleaning
of the wafer W by use of a cleaning liquid is preferably performed
before the plated surface formed by the electroless plating is
dried. In addition, the plating process is preferably performed
before the surface of the wafer W is dried after the pre-cleaning.
Most preferably, the processes from the pre-wetting process
(hydrophilic process) to the drying process are performed while the
wafer is not dried but kept wetted.
THIRD EMBODIMENT
[0156] FIG. 12 is a flow chart showing in outline a processing
method of a wafer W according to a third embodiment, performed in
the electroless plating unit (PW) 12.
[0157] In this embodiment, at first, a hydrophilic step (Step 21),
a chemical liquid process step (Step 22) serving as a pre-cleaning
step, and a rinsing process step (Step 23) serving as a
pre-cleaning step are sequentially performed. Then, an electroless
plating step (Step 24), a first rinsing process step (Step 25)
serving as a post-cleaning step, a chemical liquid process step
(Step 26) serving as a post-cleaning step, and a second rinsing
process step (Step 27) serving as a post-cleaning step are
sequentially preformed. These steps (Steps 24 to 27) are repeated a
predetermined number of times (Step 28). For this purpose, the unit
controller 34 is used to make a judgment of whether or not Steps 24
to 27 have been repeated a predetermined number of times. After the
steps are repeated a predetermined number of times, a drying step
(Step 29) is performed.
[0158] In the third embodiment, the chemical liquid process using a
chemical liquid, such as an acidic aqueous solution, serving as a
post-cleaning step is repeated along with the plating step a
plurality of times. Consequently, voids due to hydrogen gas and
pinholes at crystal grain boundaries present in the CoWB film are
closed up, and the by-product generated by the plating reaction on
the surface of a CoWB film formed by each plating step is removed
by the chemical liquid, such as an acidic aqueous solution, so that
the quality of the CoWB film is further improved. Accordingly, the
long-term reliability of the wafer W is enhanced by that much. When
the electroless plating step (Step 24) is performed again after the
second rinsing process step (Step 27) serving as a post-cleaning
step, the inner cup 47 is moved up before the electroless plating
step.
FOURTH EMBODIMENT
[0159] FIG. 13 is a flow chart showing in outline a processing
method of a wafer W according to a fourth embodiment, performed in
the electroless plating unit (PW) 12.
[0160] In this embodiment, at first, a hydrophilic step (Step 31)
is performed. Then, a chemical liquid process step (Step 32)
serving as a pre-cleaning step, a rinsing process step (Step 33)
serving as a pre-cleaning step, an electroless plating step (Step
34), and a first rinsing process step (Step 35) serving as a
post-cleaning step are sequentially performed. These steps (Steps
32 to 35) are repeated a predetermined number of times (Step 36).
For this purpose, the unit controller 34 is used to make a judgment
of whether or not Steps 32 to 35 have been repeated a predetermined
number of times. After the steps are repeated a predetermined
number of times, a chemical liquid process step (Step 37) serving
as a post-cleaning step, a second rinsing process step (Step 38)
serving as a post-cleaning step, and a drying step (Step 39) are
sequentially preformed.
[0161] In the fourth embodiment, the chemical liquid process using
a chemical liquid, such as an organic acid aqueous solution,
serving as a pre-cleaning step is repeated along with the plating
step a plurality of times. Consequently, voids due to hydrogen gas
and pinholes at crystal grain boundaries present in the CoWB film
are closed up. Accordingly, the long-term reliability of the wafer
W is enhanced by that much.
FIFTH EMBODIMENT
[0162] FIG. 14 is a flow chart showing in outline a processing
method of a wafer W according to a fifth embodiment, performed in
the electroless plating unit (PW) 12.
[0163] In this embodiment, at first, a hydrophilic step (Step 41)
is performed. Then, a chemical liquid process step (Step 42)
serving as a pre-cleaning step, a rinsing process step (Step 43)
serving as a pre-cleaning step, an electroless plating step (Step
44), a first rinsing process step (Step 45) serving as a
post-cleaning step, a chemical liquid process step (Step 46)
serving as a post-cleaning step, and a second rinsing process step
(Step 47) serving as a post-cleaning step are sequentially
preformed. These steps (Steps 42 to 47) are repeated a
predetermined number of times (Step 48). For this purpose, the unit
controller 34 is used to make a judgment of whether or not Steps 42
to 47 have been repeated a predetermined number of times. After the
steps are repeated a predetermined number of times, a drying step
(Step 49) is performed.
[0164] In the fifth embodiment, the chemical liquid process using a
chemical liquid, such as an acidic aqueous solution, serving as a
post-cleaning step and the chemical liquid process using a chemical
liquid, such as an organic acid aqueous solution, serving as a
pre-cleaning step are repeated along with the plating step a
plurality of times. Consequently, the functions and effects of the
third embodiment and fourth embodiment are complexly obtained, so
that the quality of the CoWB film is further improved. Accordingly,
the long-term reliability of the wafer W is further enhanced by
that much.
SIXTH EMBODIMENT
[0165] FIG. 15 is a flow chart showing in outline a processing
method of a wafer W according to a sixth embodiment, performed in
the electroless plating unit (PW) 12.
[0166] In this embodiment, at first, a hydrophilic step (Step 51)
and a chemical liquid process step (Step 52) serving as a
pre-cleaning step are sequentially preformed. Then, a rinsing
process step (Step 53) serving as a pre-cleaning step, an
electroless plating step (Step 54), a first rinsing process step
(Step 55) serving as a post-cleaning step, a chemical liquid
process step (Step 56) serving as a post-cleaning step, a second
rinsing process step (Step 57) serving as a post-cleaning step, and
a drying step (Step 58) are sequentially preformed. These steps
(Steps 53 to 58) are repeated a predetermined number of times (Step
59). For this purpose, the unit controller 34 is used to make a
judgment of whether or not Steps 53 to 58 have been repeated a
predetermined number of times. The rinsing process serving as a
pre-cleaning step in the second cycle or thereafter, performed
after the drying step, can serve to set the wafer W to be
hydrophilic.
[0167] In the sixth embodiment, the chemical liquid process using a
chemical liquid, such as an acidic aqueous solution, serving as a
post-cleaning step and the drying step are repeated along with the
plating step a plurality of times. Consequently, the same functions
and effects as the third embodiment are obtained. Further, even if
hydrogen gas adsorbed on the CoWB film by the post-cleaning step is
not sufficiently removed, this hydrogen gas is reliably removed by
each drying step, so that the quality of the CoWB film is further
improved. Accordingly, the long-term reliability of the wafer W is
further enhanced by that much.
SEVENTH EMBODIMENT
[0168] FIG. 16 is a flow chart showing in outline a processing
method of a wafer W according to a seventh embodiment, performed in
the electroless plating unit (PW) 12.
[0169] In this embodiment, a hydrophilic step (Step 61), a chemical
liquid process step (Step 62) serving as a pre-cleaning step, a
rinsing process step (Step 63) serving as a pre-cleaning step, an
electroless plating step (Step 64), a first rinsing process step
(Step 65) serving as a post-cleaning step, a chemical liquid
process step (Step 66) serving as a post-cleaning step, a second
rinsing process step (Step 67) serving as a post-cleaning step, and
a drying step (Step 68) are sequentially preformed. These steps
(Steps 61 to 68) are repeated a predetermined number of times (Step
69). For this purpose, the unit controller 34 is used to make a
judgment of whether or not Steps 61 to 68 have been repeated a
predetermined number of times. After the processes are repeated a
predetermined number of times, the sequence is finished
[0170] In the seventh embodiment, the chemical liquid process using
a chemical liquid, such as an acidic aqueous solution, serving as a
post-cleaning step, the chemical liquid process using a chemical
liquid, such as an organic acid aqueous solution, serving as a
pre-cleaning step, and the drying step are repeated along with the
plating step a plurality of times. Consequently, the functions and
effects of the third embodiment and sixth embodiment are complexly
obtained, so that the quality of the CoWB film is remarkably
improved. Accordingly, the long-term reliability of the wafer W is
remarkably enhanced by that much.
[0171] The plated film formed by the electroless plating step in
the embodiments described above may be made of another Co alloy,
such as CoWP, in place of CoWB.
[0172] The present invention is not limited to the embodiments
described above, and it may be modified in various manners. For
example, in the embodiments described above, a rinsing process
serving as a post-cleaning step is performed after the electroless
plating step. Alternatively, for example, after the electroless
plating step, a chemical liquid process serving as a post-cleaning
step may be performed without a rinsing process performed in
advance. In this case, the plating step and the chemical liquid
process serving as a post-cleaning step may be repeated a plurality
of times.
[0173] In the embodiments described above, the substrate held on
the spin chuck is surrounded by the inner surrounding member in the
electroless plating step, and the substrate held on the spin chuck
is surrounded by the outer surrounding member in the chemical
liquid cleaning step. Alternatively, for example, the substrate
held on the spin chuck may be surrounded by the outer surrounding
member in the electroless plating step, and the substrate held on
the spin chuck may be surrounded by the inner surrounding member in
the post-cleaning process. Further, in place of the inner
surrounding member, the spin chuck may be moved up and down, or the
outer surrounding member may be moved up and down.
[0174] In the embodiments described above, a series of steps are
sequentially performed in the same unit. However, the present
invention encompasses a case where the pre-cleaning process,
electroless plating process, and post-cleaning process are
respectively performed in different units.
[0175] Further, the present invention should be construed to
encompass arrangements obtained by suitably combining some of the
components of the embodiments described above or excluding some of
the components of the embodiments described above, as long as they
do not depart from the spirit or scope of the present
invention.
* * * * *