U.S. patent application number 14/931946 was filed with the patent office on 2016-05-12 for method of operating an electroless plating apparatus.
This patent application is currently assigned to EBARA CORPORATION. The applicant listed for this patent is EBARA CORPORATION. Invention is credited to Yoshitaka MUKAIYAMA, Yoichi NAKAGAWA, Kunio OISHI, Akira SUSAKI.
Application Number | 20160130702 14/931946 |
Document ID | / |
Family ID | 55911772 |
Filed Date | 2016-05-12 |
United States Patent
Application |
20160130702 |
Kind Code |
A1 |
NAKAGAWA; Yoichi ; et
al. |
May 12, 2016 |
METHOD OF OPERATING AN ELECTROLESS PLATING APPARATUS
Abstract
A method of operating an electroless plating apparatus is
disclosed. The operating method includes: storing in the
electroless plating apparatus an order of priority of the plurality
of processes which has been predetermined based on a stability of a
processed substrate with respect to pure water; supplying pure
water into the holder storage bath when any of the plurality of
processing baths malfunctions; determining whether or not a
relieving process can be performed, the relieving process being a
process of performing a higher-priority process on a substrate; if
the relieving process can be performed, performing the relieving
process and then immersing the substrate holder holding the
substrate in the pure water in the holder storage bath; and if the
relieving process cannot be performed, immersing the substrate
holder, holding the substrate, in the pure water held in the holder
storage bath without performing the relieving process.
Inventors: |
NAKAGAWA; Yoichi; (Tokyo,
JP) ; MUKAIYAMA; Yoshitaka; (Tokyo, JP) ;
SUSAKI; Akira; (Tokyo, JP) ; OISHI; Kunio;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EBARA CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
EBARA CORPORATION
Tokyo
JP
|
Family ID: |
55911772 |
Appl. No.: |
14/931946 |
Filed: |
November 4, 2015 |
Current U.S.
Class: |
427/437 |
Current CPC
Class: |
C23C 18/32 20130101;
C23C 18/163 20130101; C23C 18/1628 20130101; C23C 18/1675 20130101;
C23C 18/1632 20130101 |
International
Class: |
C23C 18/32 20060101
C23C018/32; C23C 18/16 20060101 C23C018/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2014 |
JP |
2014-228273 |
Claims
1. A method of operating an electroless plating apparatus having a
substrate holder for holding a substrate, a plurality of processing
baths for performing a plurality of processes including electroless
plating, and a holder storage bath for storing the substrate holder
when holding no substrate, comprising: storing in the electroless
plating apparatus an order of priority of the plurality of
processes which has been predetermined based on a stability of a
processed substrate with respect to pure water; supplying pure
water into the holder storage bath when any of the plurality of
processing baths malfunctions; determining whether or not a
relieving process can be performed, the relieving process being a
process of performing a higher-priority process on a substrate; if
the relieving process can be performed, performing the relieving
process and then immersing the substrate holder holding the
substrate in the pure water in the holder storage bath; and if the
relieving process cannot be performed, immersing the substrate
holder, holding the substrate, in the pure water held in the holder
storage bath without performing the relieving process.
2. The method according to claim 1, wherein the pure water is
deaerated water having a low concentration of dissolved oxygen.
3. The method according to claim 1, wherein the relieving process
is an electroless plating process of forming a metal film, having a
thickness larger than a preset target thickness, on a surface of
the substrate.
4. The method according to claim 3, wherein the metal film is a
cobalt film.
5. The method according to claim 1, wherein the plurality of
processes include pre-cleaning of the substrate, an activation
process of the substrate, and electroless plating of the substrate.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This document claims priority to Japanese Patent Application
Number 2014-228273 filed Nov. 10, 2014, the entire contents of
which are hereby incorporated by reference.
BACKGROUND
[0002] An electroless plating apparatus is known as a substrate
processing apparatus for processing a substrate, such as a wafer.
Electroless plating is a technique of forming a metal film on the
substrate by chemically reducing metal ions in a plating solution
without passing an electric current through the plating
solution.
[0003] FIG. 9 is a view showing an electroless plating apparatus.
As shown in FIG. 9, the electroless plating apparatus includes a
frame 110, loading ports 112 on which wafer cassettes, each
accommodating substrates W (e.g., wafers) therein, are placed, an
operation controller 113 for controlling operations of the
electroless plating apparatus, and an aligner 114 for aligning an
orientation flat or a notch of a substrate W in a predetermined
direction. The electroless plating apparatus further includes a
spin-rinse-drier (SRD) 116 for drying a plated substrate W by
rotating it at a high speed, a holder storage bath 118 for storing
a plurality of substrate holders 117 in a vertical position, a
substrate loader 120 in which a substrate W, to be plated, is
loaded onto a substrate holder 117 and a plated substrate W is
taken out of a substrate holder 117, and a substrate transport
robot 122 for transporting a substrate W.
[0004] A moving mechanism 115 is installed along an arrangement
direction of the loading ports 112. The substrate transport robot
122 is installed on the moving mechanism 115. The aligner 114 is
disposed adjacent to the moving mechanism 115. The substrate
transport robot 122 is configured to move on the moving mechanism
115, access the wafer cassettes set on the loading ports 112, take
a substrate W, to be plated, out of the wafer cassette, and
transfer the substrate W to the substrate loader 120.
[0005] In the frame 110, there are disposed a pre-cleaning unit 126
for pre-cleaning a surface of a substrate W (e.g., removing a
copper oxide formed on the surface of the substrate W), and a
nuclei forming unit 128 for activating the surface of the substrate
W (e.g., forming palladium nuclei on the surface of the substrate
W). The pre-cleaning unit 126 includes a pre-cleaning bath 126a for
storing a pre-cleaning liquid for pre-cleaning the surface of the
substrate W, and a first rinsing bath 126b for cleaning the
substrate W, which has been immersed in the pre-cleaning liquid,
with a cleaning liquid (e.g., pure water). The nuclei forming unit
128 includes a nuclei forming bath 128a for forming palladium
nuclei on the surface of the substrate W, and a second rinsing bath
128b for cleaning the substrate W, on which the palladium nuclei
have been formed, with a cleaning liquid (e.g., pure water).
[0006] The electroless plating apparatus further includes a first
plating unit 130 for forming a first metal film, e.g., a cobalt
(Co) film, on the surface of the substrate W by electroless
plating, and a second plating unit 132 for forming a second metal
film, e.g., a gold (Au) film, on the first metal film by
electroless plating. The first plating unit 130 includes a first
plating bath 130a for storing a plating solution, such as a cobalt
plating solution, and a third rinsing bath 130b for cleaning the
substrate W, which has been immersed in the plating solution held
in the first plating bath 130a, with a cleaning liquid (e.g., pure
water).
[0007] The second plating unit 132 includes a second plating bath
132a for storing a plating solution, such as a gold plating
solution, and a fourth rinsing bath 132b for cleaning the substrate
W, which has been immersed in the plating solution held in the
second plating bath 132a, with a cleaning liquid (e.g., pure
water).
[0008] An example of a process of plating a substrate W with use of
the above-described electroless plating apparatus will be described
with reference to FIGS. 10A through 10C. FIGS. 10A through 10e are
schematic views each showing a cross section of a substrate W. In
the example illustrated in FIG. 10A, the substrate W, to be
processed, has a photoresist 149 formed on an underlying metal film
148, and further has a copper film 150 formed in an opening of the
photoresist 149. First, the substrate W is immersed in the
pre-cleaning liquid retained in the pre-cleaning bath 126a to
remove a copper oxide from a surface of the copper film 150.
Thereafter, the substrate W is rinsed in the first rinsing bath
126b.
[0009] Next, palladium (Pd) nuclei are formed on the copper film
150 in the nuclei forming bath 128a, and the substrate W is then
rinsed in the second rinsing bath 128b. Next, the substrate W is
immersed in the cobalt (Co) plating solution in the first plating
bath 130a to form a cobalt film 151 on the surface of the copper
film 150 (see FIG. 10B). Thereafter, the substrate W is rinsed in
the third rinsing bath 130b. The substrate W is then immersed in
the gold (Au) plating solution in the second plating bath 132a to
form a gold film 152 on the cobalt film 151 (see FIG. 10C).
Thereafter, the substrate W is rinsed in the fourth rinsing bath
132b.
[0010] If any of the pre-cleaning bath 126a, the nuclei forming
bath 128a, the first plating bath 130a, and the second plating bath
132a malfunctions, it is necessary to stop processing of the
substrate W and to relieve the substrate W. A possible solution for
relieving the substrate W is to immerse the substrate W, which has
been processed in any of the pre-cleaning bath 126a, the nuclei
forming bath 128a, the first plating bath 130a, and the second
plating bath 132a, in the cleaning liquid (i.e., pure water) in any
of the rinsing baths 126b, 128b, 130b, 132b.
[0011] However, a stability of the substrate W with respect to pure
water depends on a material forming an exposed surface of the
substrate W. Therefore, when the substrate W with a low stability
is immersed in pure water in the rinsing bath, the substrate W may
become defective. For example, when palladium nuclei are formed on
the surface of the copper film 150, an exposed surface of the
copper film 150 is formed from copper (Cu) and palladium. If such
substrate W is immersed in the pure water, the copper having small
ionization energy is dissolved in the pure water. As a result, it
becomes extremely difficult to relieve the substrate W.
SUMMARY OF THE INVENTION
[0012] According to an embodiment, there is provided an operating
method of an electroless plating apparatus which can reduce the
number of substrates which become defective when any of processing
baths, including a plating bath, malfunctions.
[0013] Embodiments, which will be described below, relate to an
operating method of an electroless plating apparatus for plating a
surface of a substrate, such as a wafer.
[0014] In an embodiment, there is provided a method of operating an
electroless plating apparatus having a substrate holder for holding
a substrate, a plurality of processing baths for performing a
plurality of processes including electroless plating, and a holder
storage bath for storing the substrate holder when holding no
substrate, comprising: storing in the electroless plating apparatus
an order of priority of the plurality of processes which has been
predetermined based on a stability of a processed substrate with
respect to pure water; supplying pure water into the holder storage
bath when any of the plurality of processing baths malfunctions;
determining whether or not a relieving process can be performed,
the relieving process being a process of performing a
higher-priority process on a substrate; if the relieving process
can be performed, performing the relieving process and then
immersing the substrate holder holding the substrate in the pure
water in the holder storage bath; and if the relieving process
cannot be performed, immersing the substrate holder, holding the
substrate, in the pure water held in the holder storage bath
without performing the relieving process.
[0015] In an embodiment, the pure water is deaerated water having a
low concentration of dissolved oxygen.
[0016] In an embodiment, the relieving process is an electroless
plating process of forming a metal film, having a thickness larger
than a preset target thickness, on a surface of the substrate.
[0017] In an embodiment, the metal film is a cobalt film.
[0018] In an embodiment, the plurality of processes include
pre-cleaning of the substrate, an activation process of the
substrate, and electroless plating of the substrate.
[0019] According to the embodiments described above, the substrate,
in a state such that the stability of the substrate with respect to
pure water is as high as possible, is immersed in pure water in the
holder storage bath. As a result, the number of substrates which
become defective can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a plan view schematically showing an embodiment of
an electroless plating apparatus;
[0021] FIG. 2 is a view showing a substrate holder;
[0022] FIG. 3 is a view showing a substrate which is held by slits
of a holding arm;
[0023] FIG. 4 is a schematic view showing a pure water supply and
discharge mechanism;
[0024] FIG. 5 is a top view of a holder storage bath;
[0025] FIG. 6 is a view showing an order of priority of
processes;
[0026] FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D are views showing
processes of relieving substrates when a second plating bath
malfunctions;
[0027] FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D are views showing
processes of relieving substrates when a nuclei forming bath
malfunctions;
[0028] FIG. 9 is a view showing an electroless plating apparatus;
and
[0029] FIG. 10A, FIG. 10B, and FIG. 10C are schematic views each
showing a cross section of a substrate.
DESCRIPTION OF EMBODIMENTS
[0030] Embodiments will now be described with reference to the
drawings. The same reference numerals are denoted in FIGS. 1
through 8 to refer to the same or corresponding elements, and
duplicate descriptions thereof will be omitted.
[0031] FIG. 1 is a plan view schematically showing an embodiment of
an electroless plating apparatus. This electroless plating
apparatus is a substrate processing apparatus which can perform
various types of processes on a substrate. As shown in FIG. 1, the
electroless plating apparatus includes a frame 1, loading ports 2
on which wafer cassettes, each accommodating substrates W (e.g.,
wafers) therein, are placed, an operation controller 3 for
controlling operations of the electroless plating apparatus, and an
aligner 4 for aligning an orientation flat or a notch of a
substrate W in a predetermined direction. The electroless plating
apparatus further includes a spin-rinse-drier (SRD) 6 for drying a
plated substrate W by rotating it at a high speed, a holder storage
bath 14 for storing a plurality of substrate holders 42 in a
vertical position, a substrate loader 10 in which a substrate W, to
be plated, is loaded onto a substrate holder 42 and a plated
substrate W is taken out of a substrate holder 42, and a substrate
transport robot 12 for transporting a substrate W. The holder
storage bath 14 is configured to be able to accommodate, for
example, thirty-seven substrate holders 42.
[0032] A moving mechanism 5 is installed along an arrangement
direction of the loading ports 2. The substrate transport robot 12
is installed on the moving mechanism 5. The aligner 4 is disposed
adjacent to the moving mechanism 5. The substrate transport robot
12 is configured to move on the moving mechanism 5, access the
wafer cassettes set on the loading ports 2, take a substrate W, to
be plated, out of the wafer cassette, and transfer the substrate W
to the substrate loader 10.
[0033] In the frame 1, there are disposed a pre-cleaning unit 16
for pre-cleaning a surface of the substrate W (e.g., removing a
copper oxide formed on a surface of the substrate W), and a nuclei
forming unit 18 for activating the surface of the substrate W
(e.g., forming palladium nuclei). The pre-cleaning unit 16 includes
a pre-cleaning bath 16a for storing a pre-cleaning liquid for
pre-cleaning the surface of the substrate W, and a first rinsing
bath 16b for cleaning the substrate W, which has been immersed in
the pre-cleaning liquid, with a cleaning liquid (e.g., pure water).
The pre-cleaning bath 16a is configured to accommodate one
substrate holder 42, and the first rinsing bath 16b is also
configured to accommodate one substrate holder 42. The nuclei
forming unit 18 includes a nuclei forming bath 18a for forming
palladium nuclei on the surface of the substrate W, and a second
rinsing bath 18b for cleaning the substrate W, on which the
palladium nuclei have been formed, with a cleaning liquid (e.g.,
pure water). The nuclei forming bath 18a is configured to
accommodate one substrate 42, and the second rinsing bath 18b is
also configured to accommodate one substrate holder 42.
[0034] The electroless plating apparatus further includes a first
plating unit 20 for forming a first metal film, e.g., a cobalt (Co)
film, on the surface of the substrate W by electroless plating, and
a second plating unit 24 for forming a second metal film, e.g.,
gold (Au) film, on the first metal film by electroless plating. The
first plating unit 20 includes a first plating bath 20a for storing
a plating solution, such as a cobalt plating solution, and a third
rinsing bath 20b for cleaning the substrate W, which has been
immersed in the plating solution held in the first plating bath
20a, with a cleaning liquid (e.g., pure water). The first plating
bath 20a is configured to accommodate twenty-five substrate holders
42, and the third rinsing bath 20b is configured to accommodate one
substrate holder 42.
[0035] The second plating unit 24 includes a second plating bath
24a for storing a plating solution, such as a gold plating
solution, and a fourth rinsing bath 24b for cleaning the substrate
W, which has been immersed in the plating solution held in the
second plating bath 24a, with a cleaning liquid (e.g., pure water).
The second plating bath 24a is configured to accommodate ten
substrate holders 42. The fourth rinsing bath 24b is configured to
accommodate one substrate holder 42. The pre-cleaning unit 16, the
nuclei forming unit 18, the first plating unit 20, the second
plating unit 24, and the holder storage bath 14 are arranged in
this order in series. Hereinafter, the pre-cleaning bath 16a, the
nuclei forming bath 18a, the first plating bath 20a, and the second
plating bath 24a may be referred to as processing baths,
respectively.
[0036] Each of the first plating unit 20 and the second plating
unit 24 includes an overflow bath (not shown). The plating solution
overflows a side wall of the first plating bath 20a into the
overflow bath, and is returned through a circulation line (not
shown) to the first plating bath 20a. Similarly, the plating
solution overflows a side wall of the second plating bath 24a into
the overflow bath, and is returned through a circulation line (not
shown) to the second plating bath 24a. Each of the circulation
lines is provided with a filter and a plating solution temperature
regulator.
[0037] The substrate loader 10 is disposed adjacent to the holder
storage bath 14. The substrate loader 10 includes a table 26 on
which the substrate holder 42 is placed in a horizontal position,
and a substrate-holder tilting mechanism 28 for raising and laying
down the substrate holder 42. The substrate-holder tilting
mechanism 28 is disposed outside the table 26. The substrate-holder
tilting mechanism 28 is configured to change the substrate holder
42 from a vertical position to a horizontal position and place the
substrate holder 42 onto the table 26. The substrate W is loaded
onto and removed from the substrate holder 42 on the table 26.
[0038] The electroless plating apparatus includes a transporter 30
for transporting the substrate holder 42, holding the substrate W,
in a horizontal direction. The transporter 30 includes a fixed base
40 extending horizontally from the substrate loader 10 to the
pre-cleaning unit 16, an arm 32 configured to be movable
horizontally on the fixed base 40, and a gripper 34 mounted to the
arm 32. A linear motor or a rack and pinion may be used as a
driving source for horizontally moving the arm 32. The gripper 34
is configured to be able to grip the substrate holder 42.
[0039] The substrate holder 42 will now be described with reference
to FIG. 2. FIG. 2 is a view of the substrate holder 42. As shown in
FIG. 2, the substrate holder 42 has projecting portions 46, 46
which project outwardly. A support arm 45 extends between these
projecting portions 46, 46. Two holding arms 44, 44 for gripping a
substrate W are secured to the support arm 45. The transporter 30
is configured to transport the substrate holder 42 with the gripper
34 gripping the support arm 45.
[0040] Each holding atm 44 has a first slit 44a, a second slit 44b,
and a third slit 44c. FIG. 3 is a view showing the substrate W
which is held by the slits 44a to 44c of each of the holding arms
44. Only one of the holding arms 44 is shown in FIG. 3. As shown in
FIG. 3, a periphery of the substrate W is inserted into the slits
44a to 44c, whereby the substrate W is held by the substrate holder
42. As shown in FIG. 2, the substrate W is slid from a position
shown by a dotted line to a position shown by a solid line, so that
the periphery of the substrate W is held by the slits 44a to 44c of
the two holding arms 44, 44. The loading of the substrate W onto
the substrate holder 42 is performed by the substrate transport
robot 12 shown in FIG. 1 or a substrate sliding mechanism (not
shown) mounted to the table 26.
[0041] Operations of the electroless plating apparatus will now be
described with reference to FIG. 1. First, the substrate holder 42
in the vertical position is taken out of the holder storage bath 14
by a bidirectional lifter 59 disposed adjacent to the holder
storage bath 14. The bidirectional lifter 59 is configured to
elevate and lower the substrate holder 42 and horizontally move the
substrate holder 42. The bidirectional lifter 59 can take out any
one of the substrate holders 42 arranged in the holder storage bath
14. The bidirectional lifter 59 transfers the substrate holder 42
to the transporter 30, and the transporter 30 transfers the
substrate holder 42 to the substrate-holder tilting mechanism 28 of
the substrate loader 10. The substrate-holder tilting mechanism 28
of the substrate loader 10 changes the substrate holder 42 from the
vertical position to the horizontal position, and places the
substrate holder 42 onto the table 26.
[0042] The substrate transport robot 12 takes one substrate W out
of the wafer cassette mounted on one of the loading ports 2, and
places the substrate W onto the aligner 4. The aligner 4 aligns an
orientation flat or a notch of the substrate W in a predetermined
direction. Thereafter, the substrate transport robot 12 removes the
substrate W from the aligner 4, and inserts the substrate W into
the substrate holder 42 on the table 26. More specifically, the
substrate transport robot 12 horizontally moves the substrate W to
a predetermined position, and slides the substrate W from the
position shown by the dotted line in FIG. 2 to the position shown
by the solid line so as to insert the substrate W into the slits
44a to 44c of the holding arm 44, thereby loading the substrate W
onto the substrate holder 42.
[0043] Next, the substrate-holder tilting mechanism 28 changes the
substrate holder 42 from the horizontal position to the vertical
position. The gripper 34 of the arm 32 grips the substrate holder
42 in the upright position, and the transporter 30 moves the
substrate holder 42 to a predetermined position above the
pre-cleaning bath 16a. A bidirectional lifter 60 is provided
adjacent to the pre-cleaning bath 16a. The bidirectional lifter 60
is configured to elevate and lower the substrate holder 42 and
horizontally move the substrate holder 42.
[0044] The bidirectional lifter 60 receives the substrate holder 42
from the transporter 30, and lowers the substrate holder 42 to
immerse the substrate W, held by the substrate holder 42, in the
pre-cleaning liquid in the pre-cleaning bath 16a. The surface of
the substrate W is pre-cleaned with the pre-cleaning liquid. This
pre-cleaning is, for example, a process of removing the copper
oxide formed on the surface of the substrate W, and is referred to
as a pre-cleaning process. After pre-cleaning of the substrate W,
the bidirectional lifter 60 elevates the substrate holder 42 to
pull the substrate W out of the pre-cleaning liquid.
[0045] The bidirectional lifter 60 horizontally moves the substrate
holder 42 to the first rinsing bath 16b adjacent to the
pre-cleaning bath 16a, and lowers the substrate holder 42 to
immerse the substrate W in the cleaning liquid (pure water) in the
first rinsing bath 16b, so that the substrate W is cleaned (i.e.,
rinsed) with the cleaning liquid. After the cleaning of the
substrate W, the bidirectional lifter 60 elevates the substrate
holder 42 to pull the substrate W out of the cleaning liquid in the
first rinsing bath 16b.
[0046] The transporter 30 receives the substrate holder 42 from the
bidirectional lifter 60, and moves the substrate holder 42 to a
predetermined position above the nuclei forming bath 18a. A
bidirectional lifter 61 is provided adjacent to the nuclei forming
bath 18a. This bidirectional lifter 61 is configured to elevate and
lower the substrate holder 42 and horizontally move the substrate
holder 42.
[0047] The bidirectional lifter 61 receives the substrate holder 42
from the transporter 30, and lowers the substrate holder 42 to
place the substrate W, held by the substrate holder 42, in the
nuclei forming bath 18a. In this nuclei forming bath 18a, nuclei
(e.g., palladium nuclei) necessary for deposition of a metal film
are formed on the surface of the substrate W. Such a process is
referred to as an activation process (or catalyst forming process).
After the activation process, the bidirectional lifter 61 elevates
the substrate holder 42 to pull the substrate W out of the nuclei
forming bath 18a. The bidirectional lifter 61 then horizontally
moves the substrate holder 42 to the second rinsing bath 18b
adjacent to the nuclei forming bath 18a, and lowers the substrate
holder 42 to immerse the substrate W in the cleaning liquid (pure
water) in the second rinsing bath 18h. The substrate W is cleaned
(i.e., rinsed) with the cleaning liquid. After the cleaning of the
substrate W, the bidirectional lifter 61 elevates the substrate
holder 42 to pull the substrate W out of the cleaning liquid in the
second rinsing bath 18b.
[0048] The transporter 30 receives the substrate holder 42 from the
bidirectional lifter 61, and moves the substrate holder 42 to a
predetermined position above the first plating bath 20a. A
substrate-holder transporting mechanism 70 is provided adjacent to
the first plating bath 20a. The substrate-holder transporting
mechanism 70 is configured to horizontally move the substrate
holder 42 while keeping the substrate W immersed in the plating
solution in the first plating bath 20a. A unidirectional lifter 65
is provided outside the substrate-holder transporting mechanism 70.
The unidirectional lifter 65 is configured to elevate and lower the
substrate holder 42.
[0049] The unidirectional lifter 65 receives the substrate holder
42 from the transporter 30, and lowers the substrate holder 42 to
transfer the substrate holder 42 to the substrate-holder
transporting mechanism 70. The substrate-holder transporting
mechanism 70 advances the substrate holder 42 from a holder put-in
position "IN" to a holder takeout position "OUT" while keeping the
entirety of the substrate W immersed in the plating solution in the
first plating bath 20a. While the substrate W thus moves in the
plating solution, electroless plating is performed on the surface
of the substrate W. This electroless plating is, for example,
cobalt (Co) plating (i.e., a cobalt plating process).
[0050] A bidirectional lifter 62 is provided outside the
substrate-holder transporting mechanism 70. This bidirectional
lifter 62 elevates the substrate holder 42 that has reached the
holder takeout position "OUT" to pull the substrate W out of the
plating solution. The bidirectional lifter 62 then horizontally
moves the substrate holder 42 to the third rinsing bath 20b
adjacent to the first plating bath 20a, and lowers the substrate
holder 42 to immerse the substrate W in a cleaning liquid (pure
water) in the third rinsing bath 20b. The substrate W is cleaned
(i.e., rinsed) with the cleaning liquid. After the cleaning of the
substrate W, the bidirectional lifter 62 elevates the substrate
holder 42 to pull the substrate W out of the cleaning liquid in the
third rinsing bath 20b.
[0051] The transporter 30 receives the substrate holder 42 from the
bidirectional lifter 62, and horizontally moves the substrate
holder 42 to a predetermined position above the second plating bath
24a. A substrate-holder transporting mechanism 71 is provided
adjacent to the second plating bath 24a. A unidirectional lifter 66
is provided outside the substrate-holder transporting mechanism
71.
[0052] The unidirectional lifter 66 receives the substrate holder
42 from the transporter 30, and lowers the substrate holder 42 to
transfer the substrate holder 42 to the substrate-holder
transporting mechanism 71. The substrate-holder transporting
mechanism 71 advances the substrate holder 42 from a holder put-in
position "IN" to a holder takeout position "OUT" while keeping the
entirety of the substrate W immersed in the plating solution in the
second plating bath 24a. While the substrate W thus moves in the
plating solution, electroless plating is performed on the surface
of the substrate W. This electroless plating is, for example, gold
(Au) plating (i.e., a gold plating process). In this manner, two
types of plating processes are sequentially performed on the
substrate W in the first plating unit 20 and the second plating
unit 24, so that different metal films are sequentially formed on
the surface of the substrate W. In this embodiment, since the gold
plating process is performed after the cobalt plating process, the
gold film is formed on the cobalt film.
[0053] A bidirectional lifter 63 is provided outside the
substrate-holder transporting mechanism 71. The bidirectional
lifter 63 elevates the substrate holder 42 that has reached the
holder takeout position "OUT" to pull the substrate W out of the
plating solution. The bidirectional lifter 63 then horizontally
moves the substrate holder 42 to the fourth rinsing bath 24b
adjacent to the second plating bath 24a, and lowers the substrate
holder 42 to immerse the substrate W in the cleaning liquid (pure
water) in the fourth rinsing bath 24b. The substrate W is cleaned
(i.e., rinsed) with the cleaning liquid. After the cleaning of the
substrate W, the bidirectional lifter 63 elevates the substrate
holder 42 to pull the substrate W out of the cleaning liquid in the
fourth rinsing bath 24b. The transporter 30, the bidirectional
lifters 59, 60, 61, 62, 63, the unidirectional lifters 65, 66, and
the substrate-holder transporting mechanisms 70, 71 may
collectively be referred to as transporting device.
[0054] The transporter 30 receives the substrate 42 from the
bidirectional lifter 63, horizontally moves the substrate holder
42, and transfers the substrate holder 42 to the substrate-holder
tilting mechanism 28. The substrate-holder tilting mechanism 28
places the substrate holder 42 onto the table 26. The substrate
transport robot 12 removes the substrate W from the substrate
holder 42 by sliding the substrate W from the position shown by the
solid line in FIG. 2 to the position shown by the dotted line.
[0055] Thereafter, the substrate transport robot 12 transports the
substrate W to the spin-rinse-dryer 6. The spin-rinse-dryer 6 dries
the substrate W by rotating it at a high speed. The substrate
transport robot 12 removes the dried substrate W from the
spin-rinse-dryer 6 and returns it to the wafer cassette on the
loading port 2, whereby processing of the substrate W is
completed.
[0056] In a case where any of the processing baths 16a, 18a, 20a,
and 24a malfunctions when the electroless plating apparatus is in
operation, pure water is supplied into the holder storage bath 14.
Specifically, the electroless plating apparatus includes a pure
water supply and discharge mechanism 35 which supplies pure water
into the holder storage bath 14 and discharges the pure water from
the holder storage bath 14. The operation controller 3 is
configured to control an operation of the pure water supply and
discharge mechanism 35.
[0057] The pure water supply and discharge mechanism 35 will be
described with reference to FIG. 4. FIG. 4 is a schematic view
showing the pure water supply and discharge mechanism 35. As shown
in FIG. 4, the pure water supply and discharge mechanism 35
includes a supply line 75 coupled to a bottom of the holder storage
bath 14, an ON-OFF valve 76 coupled to the supply line 75, and a
discharge line 77 coupled to the bottom of the holder storage bath
14. The supply line 75 is coupled to a pure water supply line (not
shown). When the ON-OFF valve 76 is opened, the pure water is
supplied through the supply line 75 into the holder storage bath
14. The pure water is discharged from the holder storage bath 14
through the discharge line 77.
[0058] FIG. 5 is a top view of the holder storage bath 14. The
holder storage bath 14 is configured to be able to accommodate all
of the substrate holders 42 which are present in the electroless
plating apparatus, and has the same number of compartments 36 as
the number of processes to be performed on the substrate W (in this
embodiment, four processes, i.e., the pre-cleaning process, the
activation process, the cobalt plating process, and the gold
plating process). The compartments 36 are completely separated by
partitions 37 so that the pure water does not flow between the
compartments 36. The number of substrate holders 42, which can be
accommodated in each of the compartments 36, corresponds to the
maximum number of substrate holders 42 which can be accommodated in
each of the processing baths 16a, 18a, 20a, 24a, respectively. The
pure water supply and discharge mechanism 35 is configured to
supply the pure water into the compartments 36. When a
predetermined amount of the pure water is held in each compartment
36, the supply of the pure water is stopped. The pure water to be
supplied into the holder storage bath 14 may preferably be
deaerated water having a low concentration of dissolved oxygen.
[0059] When a malfunction has occurred in any one of the processing
baths 16a, 18a, 20a, 24a, the substrate W, together with the
substrate holder 42, is transported to the holder storage bath 14
by the transporting device, and is immersed in the pure water
retained in the holder storage bath 14. However, as described
above, the stability of the substrate W with respect to the pure
water varies depending on a material forming an exposed surface of
the substrate W. Therefore, if the substrate W with a low stability
is immersed in the pure water, the substrate W becomes defective.
Hereinafter, the stability of the substrate W with respect to the
pure water will be described.
[0060] When palladium nuclei are formed on the surface of the
copper film (see the symbol 150 in FIGS. 10A through 10C), the
exposed surface of the substrate W is constituted by copper (Cu)
and palladium. When such substrate W is immersed in the pure water,
copper having small ionization energy is dissolved in the pure
water. As a result, it becomes extremely difficult to relieve the
substrate W. Therefore, the stability of the substrate W having the
copper film and palladium nuclei formed thereon with respect to the
pure water is extremely low.
[0061] When a substrate W plated with cobalt is immersed in the
pure water, a surface of the cobalt film is oxidized, and as a
result, a cobalt oxide film is formed on the surface of the cobalt
film. Unless the cobalt oxide film is removed, processing of the
substrate W cannot be resumed after the electroless plating
apparatus is returned to a normal operating condition. Therefore,
the stability of the substrate W plated with cobalt with respect to
the pure water is low.
[0062] When a pre-cleaned substrate W is immersed in pure water, a
copper oxide is formed on the surface of the substrate W. However,
by immersing the substrate W in the pre-cleaning liquid again, the
copper oxide on the surface of the substrate W can be removed.
Therefore, the stability of the pre-cleaned substrate W with
respect to the pure water is high. A substrate W plated with gold
is not adversely affected even when such a substrate W is immersed
in pure water. Therefore, it is highly probable that the substrate
W can be relieved. Accordingly, the stability of the substrate W
plated with gold with respect to the pure water is extremely
high.
[0063] The operation controller 3 has stored therein in advance an
order of priority of the processes which has been determined based
on the stability of a processed substrate W with respect to pure
water. In this embodiment, a process with a highest priority is the
gold plating process, a process with a second highest priority is
the pre-cleaning process, a process with a third highest priority
is the cobalt plating process, and a process with a lowest priority
is the activation process. That is, the order of priority is (1)
the gold plating process, (2) the pre-cleaning process, (3) the
cobalt plating process, and (4) the activation process.
[0064] A method of relieving a substrate W in a case where the
second plating bath 24a malfunctions will now be described with
reference to FIG. 6 and FIGS. 7A through 7D. FIG. 6 is a view
showing the order of priority of the processes. FIGS. 7A through 7D
are views showing processes of relieving substrates W when the
second plating bath 24a malfunctions.
[0065] When the second plating bath 24a malfunctions, first, a
loading of an unprocessed substrate W onto the substrate holder 42
in the substrate loader 10 is stopped. Next, the pure water supply
and discharge mechanism 35 supplies the pure water into the holder
storage bath 14. The operation controller 3 determines whether or
not a relieving process can be performed based on the stored order
of priority (i.e., (1) the gold plating process, (2) the
pre-cleaning process, (3) the cobalt plating process, (4) the
activation process). The relieving process is a process of
performing a higher-priority process on a substrate W. If the
operation controller 3 has determined that the relieving process
can be performed, the relieving process is performed on the
substrate W, and the substrate W is then immersed in the pure water
held in the holder storage bath 14.
[0066] As shown in FIG. 7A, if the malfunction has occurred in the
second plating bath 24a during the gold plating of a substrate W,
the gold plating process cannot be completed in the second plating
bath 24a. However, if the substrate W stays immersed in the plating
solution, an excessive gold film is formed on the substrate W, and
as a result, the substrate W should be scrapped. Thus, in order to
relieve the substrate W, the substrate W in the second plating bath
24a is transported together with the substrate holder 42 to a
compartment 36 by the transporter 30, and the substrate W is
immersed in the pure water in this compartment 36. As shown by
dotted arrows in FIG. 7A, the substrate W may be immersed in the
cleaning liquid (e.g., pure water) in the fourth rinsing bath 24b,
and the substrate W may be then transported into the compartment
36.
[0067] As shown in FIG. 7B, if the malfunction has occurred in the
second plating bath 24a during cobalt plating processing of a
substrate W, the substrate W plated with cobalt cannot be
transported to the second plating bath 24a. Therefore, first, the
substrate W in the first plating bath 20a is transported to the
third rinsing bath 20b, and the substrate W is immersed in the
cleaning liquid (pure water) in the third rinsing bath 20b.
Thereafter, the substrate W, together with the substrate holder 42,
is transported to a compartment 36 by the transporter 30, and the
substrate W is immersed in the pure water in this compartment 36.
The substrate W plated with cobalt is accommodated in the
compartment 36 which is different from the compartment 36 in which
the substrate W plated with gold is accommodated. Since the
compartments 36 are completely separated, the gold plating solution
and the cobalt plating solution attached to the substrates W and
the substrate holders 42 are not mixed with each other.
[0068] As shown in FIG. 7C, if the malfunction has occurred in the
second plating bath 24a during the activation process of a
substrate W, the substrate W that has been processed in the nuclei
forming bath 18a is transported to the second rinsing bath 18b, and
is cleaned (i.e., rinsed) with the cleaning liquid in the second
rinsing bath 18b. Thereafter, the substrate W, together with the
substrate holder 42, is transported to the first plating bath 20a
by the transporter 30, and the substrate W is plated with cobalt.
According to the order of priority that has been stored in the
operation controller 3, the cobalt plating process has a higher
priority than the activation process. Therefore, after the
activation process of the substrate W is completed, the cobalt
plating process is performed on the substrate W. The stability of
the substrate W plated with cobalt with respect to the pure water
is higher than the stability of the substrate W that has been
subjected to the activation process with respect to the pure water.
Therefore, in the embodiment illustrated in FIG. 7C, the cobalt
plating process is the relieving process of the substrate W.
[0069] The substrate W plated with cobalt is cleaned (or rinsed) in
the third rinsing bath 20b and is transported, together with the
substrate holder 42, to the compartment 36 by the transporter 30.
The substrate W is then immersed in the pure water held in this
compartment 36.
[0070] As shown in FIG. 7D, if the malfunction has occurred in the
second plating bath 24a during pre-cleaning of a substrate W, the
relieving process of the substrate W is not performed. That is, the
activation process and the cobalt plating process are not performed
on the pre-cleaned substrate W. This is because the pre-cleaning
process has a higher priority than the activation process and the
cobalt plating process. Therefore, the pre-cleaned substrate W,
together with the substrate holder 42, is transported to a
compartment 36 by the transporter 30, and is immersed in the pure
water in this compartment 36. The pre-cleaned substrate W is
accommodated in the compartment 36 which is different from the
compartments 36 in which the substrate W plated with cobalt and the
substrate W plated with gold are accommodated. As shown by a dotted
arrow in FIG. 7D, the substrate W may be immersed in the cleaning
liquid (or pure water) in the first rinsing bath 16b adjacent to
the pre-cleaning bath 16a, instead of transporting the substrate W
to the compartment 36.
[0071] As described above, the number of substrate holders 42,
which can be accommodated in each of the compartments 36 in the
holder storage bath 14, corresponds to the maximum number of
substrate holders 42 which can be accommodated in each of the
processing baths 16a, 18a, 20a, 24a. If the electroless plating
apparatus malfunctions, the substrates W, which are being processed
in the respective processing baths, are transported to the
compartments 36 assigned in advance to the respective processing
baths, and are accommodated in the respective compartments 36.
Since the holder storage bath 14 is partitioned for each one of the
processing baths, it is possible to prevent an adverse effect which
could occur as a result of reactions between the substrates W and
small amounts of processing solution components attached to the
substrates W and the substrate holders 42 that have been subjected
to different processes.
[0072] Next, a method of relieving a substrate W in a case where
the nuclei forming bath 18a malfunctions will be described with
reference to FIGS. 8A through 8D. FIGS. 8A through 8D are views
showing processes of relieving substrates W when the nuclei forming
bath 18a malfunctions.
[0073] If the malfunction has occurred in the nuclei forming bath
18a, first, a loading of an unprocessed substrate W onto the
substrate holder 42 in the substrate loader 10 is stopped. Next,
the pure water supply and discharge mechanism 35 supplies the pure
water into the holder storage bath 14. The operation controller 3
determines whether or not a relieving process can be performed
based on the stored order of priority. The relieving process is a
process of performing a higher-priority process on a substrate W.
If the operation controller 3 has determined that the relieving
process can be performed, the relieving process is performed on the
substrate W, and the substrate W is then immersed in the pure water
held in the holder storage bath 14.
[0074] As shown in FIG. 8A, if the malfunction has occurred in the
nuclei forming bath 18a during the gold plating process of the
substrate W, the gold plating process is allowed to be completed.
The substrate W plated with gold is transported, together with the
substrate holder 42, to a compartment 36 by the transporter 30, and
the substrate W is then immersed in the pure water in this
compartment 36. As shown by dotted arrows in FIG. 8A, the substrate
W may be immersed in the cleaning liquid (or pure water) in the
fourth rinsing bath 24b, and the substrate W may be then
transported to the compartment 36.
[0075] As shown in FIG. 8B, if the malfunction has occurred in the
nuclei forming bath 18a during the cobalt plating process of the
substrate W, the cobalt plating process is allowed to be completed,
because the cobalt plating process is not affected by the
malfunction of the nuclei forming bath 18a. The substrate W in the
first plating bath 20a is transported to the third rinsing bath
20b, and is immersed in the cleaning liquid (or pure water) in the
third rinsing bath 20b. Thereafter, the substrate W, together with
the substrate holder 42, is transported to the second plating bath
24a by the transporter 30, and the substrate W is immersed in the
gold plating solution so that the substrate W is plated with gold.
The stability of the substrate W plated with gold with respect to
pure water is higher than the stability of the substrate W plated
with cobalt with respect to pure water. Therefore, in the
embodiment illustrated in FIG. 8B, the gold plating process is the
relieving process of the substrate W.
[0076] The substrate W plated with gold is transported to the
compartment 36 by the transporter 30, and is immersed in the pure
water held in the compartment 36. As shown by dotted arrows in FIG.
8B, the substrate W may be immersed in the cleaning liquid (or pure
water) in the fourth rinsing bath 24b, and the substrate W may be
then transported to the compartment 36.
[0077] As shown in FIG. 8C, if the malfunction has occurred in the
nuclei forming bath 18a during the activation process of the
substrate W, the substrate W cannot go to the next process step as
long as the activation process of the substrate W is completed.
Therefore, in this case, the substrate W is transported to a
compartment 36 without performing the relieving process. The
substrate W is accommodated in this compartment 36 which is
different from compartments 36 that accommodate substrates W that
have been subjected to the processes, other than the activation
process.
[0078] As shown in FIG. 8D, if the malfunction has occurred in the
nuclei forming bath 18a during the pre-cleaning process of the
substrate W, the substrate W cannot go to the next process step, as
long as the pre-cleaning process of the substrate W is completed.
Therefore, in this case, the substrate W is transported to a
compartment 36 without performing the relieving process. The
substrate W is accommodated in this compartment 36 which is
different from compartments 36 that accommodate substrates W that
have been subjected to the processes, other than the pre-cleaning
process. As shown by dotted arrow in FIG. 8D, the substrate W may
be immersed in the cleaning liquid in the first rinsing bath 16b
adjacent to the pre-cleaning bath 16a without transporting the
substrate W to the compartment 36.
[0079] According to this embodiment, the substrate W is immersed in
the pure water in the holder storage bath 14 in a state such that
the stability of the substrate W with respect to the pure water is
as high as possible. As a result, it is possible to reduce the
number of substrates W which become defective.
[0080] If the substrate W is pulled out of the pure water in the
holder storage bath 14, is dried in the spin-rinse-dryer 6, and is
then returned to the wafer cassette by the substrate transport
robot 12, the operations of the substrate transport robot 12
increase. As a result, relieving of all substrates W is delayed.
Therefore, the substrate W, with the substrate holder 42 holding
the substrate W, is stored in the pure water in the holder storage
bath 14.
[0081] When the electroless plating apparatus is returned to the
normal operating condition, the pure water held in the holder
storage bath 14 is discharged through the discharge line 77, and
processing of the substrates W is then resumed.
[0082] When the substrate W is plated with cobalt as the relieving
process of the substrate W, it is preferable to form a cobalt film
having a larger thickness than a preset target thickness. In the
case where a plurality of substrates W are plated with cobalt,
plating times of these substrates W are controlled such that cobalt
films having the same thickness are formed on all of the substrates
W. Specifically, the operation controller 3 controls transporting
times of the substrates W in the substrate-holder transporting
mechanism 70 so that immersion times of all of the substrates W in
the plating solution are the same.
[0083] When the substrate W plated with cobalt is immersed in pure
water, a cobalt oxide film is formed on the surface of the
substrate W. Therefore, after the relieving process of the
substrate W, the substrate W is transported to a cobalt oxide film
removing device 80 (see FIG. 1). The cobalt oxide film removing
device 80 is a device capable of removing the cobalt oxide film by,
for example, a hydrogen reduction method. Specifically, the
substrate W is heated in a hydrogen atmosphere formed in the cobalt
oxide film removing device 80, so that the cobalt oxide film is
removed. After the removal of the cobalt oxide film, the substrate
W is transported to an etching device 81 (see FIG. 1). The cobalt
film formed thicker than the target thickness is etched so as to
have the target thickness. Etching of the substrate W may be
performed by an etching device (not shown) which is provided
outside the electroless plating apparatus. The etched substrate W
is transported to the second plating bath 24a, and is then plated
with gold.
[0084] A plating reaction depends on a temperature of a plating
solution. If a heater for heating the plating solution
malfunctions, the temperature of the plating solution is gradually
lowered, and a plating rate is also lowered with a decrease in the
temperature. As a result, a thickness of a metal film formed on a
substrate W cannot be estimated from a plating time of the
substrate W. Thus, it is desirable to measure the thickness of the
metal film formed on the substrate W by using a film-thickness
measuring device 82 for measuring the thickness of the metal film.
The film-thickness measuring device 82 may be a non-contact type
thickness measuring device using fluorescence X-rays. The thickness
of the metal film formed on the substrate W is measured by the
film-thickness measuring device 82, and a thickness to be added or
to be reduced is determined based on the measured thickness of the
metal film. If the measured thickness of the metal film is less
than the target thickness, the substrate W is plated again. If the
measured thickness of the metal film is larger than the target
thickness, the metal film is etched by the etching device 81.
[0085] While the present invention has been described with
reference to the embodiments thereof, it should be understood that
the present invention is not limited to the particular embodiments
described above, and that other modifications may be made within
the technical concept of the present invention.
* * * * *