U.S. patent application number 10/446358 was filed with the patent office on 2004-05-06 for plating apparatus and plating method.
This patent application is currently assigned to Dainippon Screen Mfg. Co., Ltd.. Invention is credited to Matsubara, Hideaki, Mizohata, Yasuhiro.
Application Number | 20040084315 10/446358 |
Document ID | / |
Family ID | 32171276 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040084315 |
Kind Code |
A1 |
Mizohata, Yasuhiro ; et
al. |
May 6, 2004 |
Plating apparatus and plating method
Abstract
A substrate treating apparatus provided with a plating unit, a
bevel etching unit, a cassette stage on which a cassette for
accommodating a wafer and a cassette for accommodating a dummy
wafer are placed, and a transport robot for transporting the wafer
or the dummy wafer among the cassettes, the plating unit and the
bevel etching unit. The plating unit is capable of performing a
copper plating process on the wafer and the dummy wafer, and the
bevel etching unit is capable of etching a peripheral edge of the
wafer and etching away a copper film formed on the dummy wafer.
Inventors: |
Mizohata, Yasuhiro; (Kyoto,
JP) ; Matsubara, Hideaki; (Kyoto, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Dainippon Screen Mfg. Co.,
Ltd.
|
Family ID: |
32171276 |
Appl. No.: |
10/446358 |
Filed: |
May 28, 2003 |
Current U.S.
Class: |
205/82 ; 204/242;
205/291; 257/E21.175 |
Current CPC
Class: |
C25D 21/12 20130101;
C25D 7/123 20130101; C25D 21/00 20130101; C25D 17/001 20130101;
H01L 21/2885 20130101 |
Class at
Publication: |
205/082 ;
205/291; 204/242 |
International
Class: |
C25D 017/00; C25D
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2002 |
JP |
2002-318951 |
Claims
What is claimed is:
1. A plating apparatus comprising: a plating unit for performing a
plating process with the use of a plating liquid for plating a
to-be-treated substrate with copper; a dummy substrate container
for accommodating a dummy substrate having a surface formed with an
electrically conductive film; a dummy substrate transport mechanism
for transporting the dummy substrate between the plating unit and
the dummy substrate container; a substrate loading discontinuation
detecting mechanism for detecting discontinuation of loading of the
to-be-treated substrate in the plating unit; and a control section
which performs a control operation so as to transport the dummy
substrate from the dummy substrate container into the plating unit
by means of the dummy substrate transport mechanism and perform the
plating process on the surface of the dummy substrate formed with
the electrically conductive film in the plating unit in response to
the detection of the discontinuation of the loading of the
to-be-treated substrate in the plating unit by the substrate
loading discontinuation detecting mechanism.
2. A plating apparatus as set forth in claim 1, further comprising:
a film removing unit for performing a copper film removing process
for removing a copper film formed on the dummy substrate subjected
to the plating process in the plating unit, wherein the
electrically conductive film is resistant to the copper film
removing process performed in the film removing unit.
3. A plating apparatus as set forth in claim 2, wherein the
electrically conductive film is composed of gold or platinum.
4. A plating apparatus as set forth in claim 1, further comprising
a cassette stage for receiving thereon a cassette capable of
accommodating the to-be-treated substrate to be subjected to the
plating process in the plating unit, wherein the dummy substrate
container is a cassette disposed on the cassette stage.
5. A plating apparatus as set forth in claim 1, wherein the plating
unit includes a plurality of plating units, wherein the dummy
substrate includes a plurality of dummy substrates whose number is
greater than the number of the plating units, wherein the dummy
substrate container is capable of accommodating all the dummy
substrates.
6. A plating apparatus comprising: a plating unit for performing a
plating process with the use of a plating liquid for plating a
to-be-treated substrate with copper; and a film removing unit for
performing a copper film removing process for removing a copper
film formed on a dummy substrate subjected to the plating process
in the plating unit.
7. A plating method comprising: the step of detecting
discontinuation of loading of a to-be-treated substrate in a
plating unit which is adapted to perform a plating process for
plating the to-be-treated substrate with copper; the step of
transporting a dummy substrate having a surface formed with an
electrically conductive film from a dummy substrate container into
the plating unit; and a dummy plating step of performing a dummy
plating process in the plating unit for plating the surface of the
dummy substrate formed with the electrically conductive film after
the detecting step.
8. A plating method as set forth in claim 7, further comprising the
step of transporting the dummy substrate into a film removing unit
which is adapted to perform a copper film removing process, and
removing a copper film formed on the dummy substrate by the dummy
plating process in the film removing unit after the dummy plating
step, wherein the electrically conductive film is resistant to the
copper film removing process performed in the film removing
unit.
9. A plating method as set forth in claim 7, wherein the plating
unit includes a plurality of plating units, wherein the dummy
plating step comprises the step of performing the dummy plating
process simultaneously in the respective plating units.
10. A plating method comprising the steps of: transporting a dummy
substrate into a plating unit which is adapted to perform a plating
process for plating a to-be-treated substrate with copper, and
performing a dummy plating process in the plating unit for plating
the dummy substrate with copper, when the plating process is not
performed on the to-be-treated substrate in the plating unit; and
transporting the dummy substrate having a copper film formed by the
dummy plating process into a film removing unit which is adapted to
perform a copper film removing process, and removing the copper
film formed on the dummy substrate in the film removing unit after
the dummy plating step.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plating apparatus and a
plating method for plating a substrate such as a semiconductor
wafer with copper.
[0003] 2. Description of Related Art
[0004] In the production of a semiconductor device, a plating
process is often performed for plating one surface of a
semiconductor wafer (hereinafter referred to simply as "wafer"). A
typical plating apparatus for plating a wafer with copper includes
a plating vessel which contains a copper-ion-containing plating
liquid to be brought into contact with one surface of the wafer, an
anode disposed in the plating vessel, and a cathode to be brought
into contact with the wafer.
[0005] For the plating, the cathode is kept in contact with the
wafer, and one surface (lower surface) of the wafer is kept in
contact with the plating liquid filled in the plating vessel. In
this state, the anode and the cathode are electrically energized.
Thus, electrons are donated to copper ions in the plating liquid in
the interface between the surface of the wafer and the plating
liquid, so that copper atoms are deposited on the surface of the
wafer.
[0006] Exemplary methods for replenishment of copper ions consumed
by the plating in the plating liquid are to employ a dissolvable
copper anode which is per se dissolvable in the plating liquid, and
to employ an anode non-dissolvable in the plating liquid and a
copper supply source provided separately from the anode.
[0007] Where the dissolvable anode is employed, the plating process
can stably be performed with the surface of the anode being covered
with a so-called black film. The black film can be kept stable only
when the anode is electrically energized in the same cycle. When
the plating apparatus is not in use for a long period, the anode is
liable to deteriorate. Therefore, the plating process cannot
properly be performed when resumed.
[0008] To overcome this drawback, Japanese Unexamined Patent
Publication No. 2000-119900 proposes that the anode is continuously
electrically energized with a dummy cathode disposed in the plating
vessel even when a plating apparatus is not in use. In the
prior-art plating apparatus and plating method, copper is deposited
on the dummy cathode when the anode and the dummy cathode are
electrically energized. The literature states that copper deposited
on the dummy cathode is etched by the plating liquid when the dummy
cathode is not electrically energized and, therefore, no
maintenance is required without accumulation of copper on the dummy
cathode.
[0009] However, the operation (burn-in) intervals of the plating
apparatus and the amperage applied during the operation of the
plating apparatus may vary, and the etching rate at which copper
deposited on the dummy cathode is etched by the plating liquid may
vary depending on the type of the plating liquid. Therefore, it is
not always guaranteed that the dummy cathode is free from
accumulation of copper.
[0010] Further, the presence of the dummy cathode in the plating
vessel may adversely affect the uniformity of the thickness of a
plated film in the ordinary plating process. Therefore, conditions
such as the size of the dummy cathode and the position of the dummy
cathode in the plating vessel should be optimized to ensure the
uniformity of the plated film thickness. However, it is difficult
to find the optimized conditions.
[0011] When the plating apparatus is not in use for a long period,
parts of the plating apparatus supplied with the plating liquid
during the plating process are liable to dry, so that constituents
of the plating liquid may be crystallized. In a small-size droplet
of the plating liquid, the crystallization occurs in about one to
two hours. Where the plating apparatus is adapted to perform the
plating process with a peripheral edge portion of the wafer being
sealed by a cathode ring, crystals attributable to the plating
liquid are liable to grow on a sealing surface of the cathode ring,
resulting in a temporary sealing failure. In addition, the crystals
may damage the sealing surface to cause a permanent sealing
failure.
[0012] While problems associated with the use of the dissolvable
anode have been described, the use of the non-dissolvable anode
also has drawbacks. That is, when the plating apparatus is not in
use for a long period, the surface of the copper supply source is
irreversibly deteriorated. Therefore, the plating process cannot
properly be performed when resumed. If the prior-art construction
and method described in the aforesaid literature are employed, it
is expected that similar problems occur when the plating liquid is
electrically energized during the halt of the plating
apparatus.
SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to provide a
plating apparatus which is capable of properly performing a plating
process.
[0014] It is another object of the present invention to provide a
plating apparatus which comprises a sealing member for sealing a
peripheral edge portion of the wafer and is generally free from a
sealing failure of the sealing member.
[0015] It is further another object of the present invention to
provide a plating method which is capable of properly performing a
plating process.
[0016] It is still another object of the present invention to
provide a plating method which is employed in a plating apparatus
comprising a sealing member for sealing a peripheral edge portion
of the wafer and is generally free from a sealing failure of the
sealing member.
[0017] A plating apparatus (10) according to a first aspect of the
present invention comprises: a plating unit (20a to 20d) for
performing a plating process with the use of a plating liquid for
plating a to-be-treated substrate (W) with copper; a dummy
substrate container (Cd) for accommodating a dummy substrate (D)
having a surface formed with an electrically conductive film; a
dummy substrate transport mechanism (TR, 18) for transporting the
dummy substrate between the plating unit and the dummy substrate
container; a substrate loading discontinuation detecting mechanism
(155) for detecting discontinuation of loading of the to-be-treated
substrate in the plating unit; and a control section (155) which
performs a control operation so as to transport the dummy substrate
from the dummy substrate container into the plating unit by means
of the dummy substrate transport mechanism and perform the plating
process on the surface of the dummy substrate formed with the
electrically conductive film in the plating unit in response to the
detection of the discontinuation of the loading of the
to-be-treated substrate in the plating unit by the substrate
loading discontinuation detecting mechanism. The components
represented by the parenthesized alphanumeric characters are
equivalent to those to be described in the following embodiment.
However, it should be understood that the present invention be not
limited to the embodiment. This definition is also applied to the
following description.
[0018] According to this inventive aspect, the plating process can
be performed on the dummy substrate in the plating unit (this
process will be hereinafter referred to as "dummy plating process")
after the discontinuation of the loading of the to-be-treated
substrate in the plating unit. At this time, a cathode is brought
into contact with the electrically conductive film of the dummy
substrate, and an anode is provided in the plating liquid for
electrolytic plating. Therefore, copper ions are continuously
leached out of a copper supply source into the plating liquid even
when the plating process is not performed on the to-be-treated
substrate. Thus, the copper supply source can be kept in a proper
surface state.
[0019] The copper supply source may be the anode per se where a
dissolvable anode is employed as the anode, or may be provided
separately from the anode where a non-dissolvable anode is employed
as the anode. Where the copper supply source is the dissolvable
anode, a black film formed on the surface of the dissolvable anode
can be stabilized by the dummy plating process. Where the
non-dissolvable anode is employed, the dummy plating process makes
it possible to prevent irreversible deterioration of the surface of
the copper supply source provided separately from the anode.
Therefore, the to-be-treated substrate can properly be plated with
copper, when the plating process on the to-be-treated substrate is
resumed.
[0020] The discontinuation of the loading of the to-be-treated
substrate in the plating unit herein means, for example, that the
plating process on wafers in one production lot is completed. The
to-be-treated substrate may be, for example, a semiconductor wafer
(hereinafter referred to simply as "wafer").
[0021] Some plating apparatuses for the plating of the wafer
include a sealing member for sealing a peripheral edge portion of
the wafer to keep the plating liquid away from the cathode and a
portion of the wafer not to be plated. The sealing member is kept
wetted with the plating liquid during the plating process.
[0022] In this case, the sealing member is kept wetted with the
plating liquid by performing the dummy plating process when the
plating process is not performed on the to-be-treated substrate.
That is, the crystallization of constituents of the plating liquid
can be prevented, which may otherwise occur when the sealing member
wetted with the plating liquid is dried. Therefore, a sealing
failure due to the presence of crystals on the sealing member and a
sealing failure due to a damage to the sealing member by the
crystals can be suppressed. The sealing member may be provided, for
example, on a cathode ring having a cathode.
[0023] In the inventive plating apparatus, the dummy substrate is
automatically transported from the dummy substrate container to the
plating unit for the dummy plating process under the control of the
control section in response to the detection of the discontinuation
of the loading of the to-be-treated substrate in the plating unit
by the substrate loading discontinuation detecting mechanism. Since
the dummy substrate is accommodated in the dummy substrate
container in the plating apparatus, there is no need for an
operator to load the dummy substrate into the plating apparatus.
Therefore, the dummy plating process is automatically started
without the intervention of the operator, when the loading of the
to-be-treated substrate in the plating unit is discontinued.
[0024] The inventive plating apparatus may further comprise a film
removing unit (21a, 21b) for performing a copper film removing
process for removing a copper film formed on the dummy substrate
subjected to the plating process in the plating unit. In this case,
the electrically conductive film maybe resistant to the copper film
removing process performed in the film removing unit.
[0025] With this arrangement, the copper film formed on the dummy
substrate can be removed in the film removing unit. At this time,
the electrically conductive film of the dummy substrate is not
removed, because the electrically conductive film is resistant to
the copper film removing process. Since the electrolytic plating
process can be performed again via the electrically conductive
film, the dummy substrate from which the copper film has been
removed can be reused for the dummy plating process. That is, the
dummy substrate can repeatedly be used, so that the plating
apparatus obviates the need for the operator to frequently perform
a maintenance operation.
[0026] The copper film removing process, which is performed in the
film removing unit provided separately from the plating unit, does
not influence the plating process performed in the plating unit.
Therefore, the plating apparatus can properly perform the plating
process on the to-be-treated substrate. Further, the plating unit
does not influence the copper film removing process performed in
the film removing unit. Therefore, optimum conditions for complete
removal of the copper film can be employed in the copper removing
unit, so that the dummy plating process can properly be performed
with the use of the dummy substrate from which the copper film has
been completely removed.
[0027] The plating apparatus may further comprise an additional
unit for performing a process other than the plating process (e.g.,
a bevel etching unit for etching a peripheral edge of the
to-be-treated substrate subjected to the plating process). The
additional unit may function as the film removing unit.
Alternatively, the film removing unit may be a unit dedicated to
the film removing process.
[0028] The removal of the copper film may be achieved by
electrolytic etching or with the use of an etching liquid.
[0029] Exemplary materials for the dummy substrate include
semiconductors (e.g., silicon) , glass materials, ceramic
materials, resins and metals. Exemplary materials for the
electrically conductive film include gold (Au) and platinum (Pt).
Where the film removing unit performs the copper film removing
process by etching away the copper film with the use of a mixture
of sulfuric acid, a hydrogen peroxide and water (an etching
liquid), for example, the electrically conductive film of gold or
platinum has an etching resistance, i.e., a resistance to the
etching liquid.
[0030] The inventive plating apparatus may further comprise a
cassette stage (16) for receiving thereon a cassette (Cw) capable
of accommodating the to-be-treated substrate to be subjected to the
plating process in the plating unit. In this case, the dummy
substrate container may be a cassette (Cd) disposed on the cassette
stage.
[0031] With this arrangement, where the plating apparatus includes
the cassette stage, the cassette placed on the existing cassette
stage can be used as the dummy substrate container without the need
for separately providing a dedicated dummy substrate container. The
to-be-treated substrate and the dummy substrate may have the same
shape and size. In this case, the cassette for accommodating the
to-be-treated substrate can be employed as the cassette for
accommodating the dummy substrate.
[0032] The dummy substrate transport mechanism may double as a
transport mechanism for transporting the to-be-treated substrate
between the cassette placed on the cassette stage and the plating
unit.
[0033] The dummy substrate container may be a container other than
the cassette placed on the cassette stage, or a dedicated container
disposed in any other position in the plating apparatus.
[0034] In the plating apparatus having the aforesaid construction,
the plating unit may include a plurality of plating units, and the
dummy substrate may include a plurality of dummy substrates whose
number is greater than the number of the plating units. In this
case, the dummy substrate container may be capable of accommodating
all the dummy substrates.
[0035] The drying of the sealing member wetted with the plating
liquid occurs in each of the plating units. With the aforesaid
arrangement, the dummy plating process can be performed
simultaneously in the respective plating units. Therefore, the
crystallization attributable to the drying of the sealing member
can be prevented in each of the plating units. Thus, a sealing
failure of the sealing member can be suppressed in each of the
plating units.
[0036] When the plating process is performed on to-be-treated
substrates in some of the plural plating units, the dummy plating
process may be performed in the other plating units. Therefore, the
sealing failure of the sealing member can be suppressed in each of
the plating units.
[0037] A plating apparatus (10) according to a second aspect of the
present invention comprises: a plating unit (20a to 20d) for
performing a plating process with the use of a plating liquid for
plating a to-be-treated substrate (W) with copper; and a film
removing unit (21a, 21b) for performing a copper film removing
process for removing a copper film formed on a dummy substrate (D)
subjected to the plating process in the plating unit.
[0038] According to this inventive aspect, copper ions are supplied
to the plating liquid from a copper supply source to keep the
copper supply source in a proper surface state by a dummy plating
process, even when the plating process is not performed on the
to-be-treated substrate.
[0039] Therefore, the to-be-treated substrate can properly be
plated with copper, when the plating process on the to-be-treated
substrate is resumed.
[0040] Where the plating apparatus includes a sealing member, the
sealing member is kept wetted with the plating liquid by performing
the dummy plating process even when the plating process is not
performed on the to-be-treated substrate. That is, crystallization
of constituents of the plating liquid is prevented, which may
otherwise occur when a sealing member wetted with the plating
liquid is dried. Therefore, a sealing failure due to the presence
of crystals on the sealing member and a sealing failure due to a
damage to the sealing member by the crystals can be suppressed.
[0041] Further, the copper film formed on the dummy substrate by
the plating can be removed in the film removing unit. Where the
dummy substrate has an electrically conductive film formed on one
surface thereof and having a resistance to the copper film removing
process performed in the film removing unit and the plating process
is to be performed on the surface of the dummy substrate formed
with the electrically conductive film in the plating unit, the
dummy substrate can be reused for the dummy plating process after
the removal of the copper film.
[0042] A plating method according to the present invention
comprises the steps of: detecting discontinuation of loading of a
to-be-treated substrate (W) in a plating unit (20a to 20d) which is
adapted to perform a plating process for plating the to-be-treated
substrate (W) with copper; and transporting a dummy substrate (D)
having a surface formed with an electrically conductive film from a
dummy substrate container (Cd) into the plating unit, and
performing a dummy plating process in the plating unit for plating
the surface of the dummy substrate formed with the electrically
conductive film after the detecting step.
[0043] The inventive plating method may further comprise the step
of transporting the dummy substrate into a film removing unit (21a,
21b) which is adapted to perform a copper film removing process,
and removing a copper film formed on the dummy substrate by the
dummy plating process in the film removing unit after the dummy
plating step. In this case, the electrically conductive film may be
resistant to the copper film removing process performed in the film
removing unit.
[0044] Where a plurality of plating units are provided, the dummy
plating step may comprise the step of performing the dummy plating
process simultaneously in the respective plating units.
[0045] Another plating method according to the present invention
comprises the steps of: transporting a dummy substrate (D) into a
plating unit (20a to 20d) which is adapted to perform a plating
process for plating a to-be-treated substrate (W) with copper, and
performing a dummy plating process in the plating unit for plating
the dummy substrate with copper, when the plating process is not
performed on the to-be-treated substrate in the plating unit; and
transporting the dummy substrate having a copper film formed by the
dummy plating process into a film removing unit (21a, 21b) which is
adapted to perform a copper film removing process, and removing the
copper film formed on the dummy substrate in the film removing unit
after the dummy plating step.
[0046] The foregoing and other objects, features and effects of the
present invention will become more apparent from the following
description of the preferred embodiments with reference to the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a block diagram illustrating the construction of a
substrate treating apparatus according to one embodiment of the
present invention;
[0048] FIG. 2 is a schematic plan view of a wafer treating
section;
[0049] FIG. 3(a) is a schematic plan view for explaining the
construction of a robot body provided in the wafer treating
section;
[0050] FIG. 3(b) is a schematic side view for explaining the
construction of the robot body provided in the wafer treating
section;
[0051] FIG. 3(c) is a schematic front view for explaining the
construction of the robot body provided in the wafer treating
section;
[0052] FIG. 4(a) is a schematic plan view of a cassette stage on
which a cassette is placed;
[0053] FIG. 4(b) is a schematic side view of the cassette stage on
which the cassette is placed;
[0054] FIG. 5 is a schematic front view illustrating the
construction of a plating section;
[0055] FIG. 6 is a diagram illustrating a relationship between the
concentrations of copper in plating liquid samples and measured
absorbances;
[0056] FIG. 7 is a schematic sectional view illustrating the
construction of a plating unit;
[0057] FIG. 8 is a schematic sectional view illustrating a portion
around a wafer as observed in a plating process;
[0058] FIG. 9 is a schematic sectional view illustrating the
plating unit with a spin base facing upward;
[0059] FIG. 10 is a schematic sectional view illustrating the
construction of a bevel etching unit;
[0060] FIG. 11 is a schematic sectional view illustrating the
construction of a cleaning unit;
[0061] FIG. 12 is a block diagram illustrating the construction of
a control system for the wafer treating section;
[0062] FIG. 13 is a schematic diagram illustrating the construction
of a major constituent managing section; and
[0063] FIG. 14 is a block diagram illustrating the construction of
control systems for the major constituent managing section, a minor
constituent managing section and a post-treatment agent supplying
section.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0064] FIG. 1 is a block diagram illustrating the construction of a
substrate treating apparatus 10 according to one embodiment of the
present invention.
[0065] The substrate treating apparatus 10 includes a wafer
treating section 1 for plating a surface of a semiconductor wafer
(hereinafter referred to simply as "wafer") with the use of a
plating liquid and etching (bevel-etching) a peripheral edge of the
wafer after the plating, a major constituent managing section 2
having a copper supply source for supplying copper ions to the
plating liquid for management of the concentrations of major
constituents of the plating liquid, a minor constituent managing
section 3 for managing minor constituents of the plating liquid,
and a post-treatment agent supplying section 4 for supplying a
post-treatment agent to the wafer treating section 1 for
post-treatment of the wafer after the plating. The substrate
treating apparatus 10 is disposed in a clean room.
[0066] The plating liquid for use in the wafer treating section 1
contains sulfuric acid (supporting electrolyte) copper ions (target
metal), iron (oxidizing/reducing agent) and water as major
constituents thereof. The plating liquid further contains chlorine,
a plating retarding additive and a plating accelerating additive as
minor constituents thereof.
[0067] Two plating liquid transport pipes P12a, P12b extend between
the wafer treating section 1 and the major constituent managing
section 2 for transporting the plating liquid between these
sections in opposite directions. Similarly, two plating liquid
transport pipes P13a, P13b extend between the wafer treating
section 1 and the minor constituent managing section 3 for
transporting the plating liquid between these sections in opposite
directions. Further, a post-treatment agent pipe P14 extends
between the wafer treating section 1 and the post-treatment agent
supplying section 4 for supplying the post-treatment agent from the
post-treatment agent supplying section 4 to the wafer treating
section 1.
[0068] The wafer treating section 1 includes a system controller
for controlling the entire substrate treating apparatus 10. The
wafer treating section 1 is connected to the major constituent
managing section 2, the minor constituent managing section 3 and
the post-treatment agent supplying section 4 via signal lines L12,
L13 and L14, respectively. The operations of the major constituent
managing section 2, the minor constituent managing section 3 and
the post-treatment agent supplying section 4 are controlled by the
system controller provided in the wafer treating section 1.
[0069] The plating liquid being used in the wafer treating section
1 is transported (sampled) into the minor constituent managing
section 3 through the plating liquid transport pipe P13a. The minor
constituent managing section 3 is capable of analyzing at least one
of the minor constituents through a CVS (cyclic voltammetric
stripping) analysis. The minor constituent managing section 3
includes a minor constituent management controller, which is
capable of calculating the amounts of the minor constituents to be
added to the plating liquid in the wafer treating section 1 based
on the result of the CVS analysis so as to adjust the
concentrations of the minor constituents of the plating liquid
within predetermined concentration ranges. Under the control of the
minor constituent management controller, the minor constituents are
supplied in the amounts thus calculated to the plating liquid in
the wafer treating section 1 through the plating liquid transport
pipe P13b.
[0070] The post-treatment agent supplying section 4 includes an
agent tank containing the post-treatment agent, and an agent supply
mechanism for supplying the post-treatment agent from the agent
tank to the wafer treating section 1. Examples of the
post-treatment agent include an etching liquid to be used for the
bevel etching and a cleaning liquid.
[0071] FIG. 2 is a schematic plan view of the wafer treating
section 1.
[0072] The wafer treating section 1 is adapted to perform a plating
process for forming a thin copper film on the surface of the wafer
W, then perform an etching process for etching the peripheral edge
of the wafer W, and perform a cleaning process for cleaning the
entire surfaces of the wafer W.
[0073] A wafer loading/unloading section 19 is disposed along a
first transport path 14 extending linearly horizontally. In the
wafer loading/unloading section 19, a plurality of cassette stages
16 (four cassette stages in this embodiment) which are each adapted
to receive thereon one cassette C capable of accommodating a wafer
W are arranged along the first transport path 14.
[0074] A cassette Cd disposed at one end of the wafer
loading/unloading section 19 accommodates a dummy wafer D instead
of the wafer W, and the other three cassettes Cw each accommodate a
to-be-treated wafer W. Four or more dummy wafers D are provided in
the wafer treating section 1, and the cassette Cd is capable of
accommodating all the dummy wafers D.
[0075] The wafer W has a generally round shape and, for example, is
a silicon substrate having a multiplicity of fine holes or grooves
formed in a to-be-treated surface thereof and a barrier layer and a
seed layer formed on the surface thereof. The dummy wafers D each
have the same shape and size as the wafer W and, for example, are
composed of silicon. The dummy wafers D each have an electrically
conductive film formed on one surface thereof by plating. The dummy
wafers D may be composed of a semiconductor other than silicon, a
glass material, a ceramic material, a metal or a resin
[0076] The electrically conductive film has an electrical
conductivity, and functions as a seed layer during the plating.
Further, the electrically conductive film has an etching
resistance, and is resistant to an etching liquid (e.g., a mixture
of sulfuric acid, a hydrogen peroxide aqueous solution and water)
for use in the etching of copper. The electrically conductive film
is composed of gold (Au) or platinum (Pt), for example.
[0077] A second linear transport path 15 is provided horizontally
and perpendicularly to the first transport path 14. In this
embodiment, the second transport path 15 extends from a middle
portion of the first transport path 14. A plating section 12
including four plating units 20a to 20d arranged along the second
transport path 15 is provided on one side of the second transport
path 15. Therefore, the number of the dummy wafers D provided in
the wafer treating section 1 is equal to or greater than the number
of the plating units 20a to 20d.
[0078] The plating units 20a to 20d are each adapted to plate the
surface of the wafer W or the dummy wafer D with copper. The dummy
wafers D are subjected to the plating process in the plating units
20a to 20d, when the plating process is not performed on the wafer
W.
[0079] A post-treatment section 13 including two bevel etching
units 21a, 21b and two cleaning units 22a, 22b arranged along the
second transport path 15 is provided on the other side of the
second transport path 15. The bevel etching units 21a, 21b are each
adapted to etch the peripheral edge of the wafer W and to etch away
a copper film formed on one entire surface of the dummy wafer D by
the plating. The cleaning units 22a, 22b are each adapted to clean
opposite surfaces of the wafer W.
[0080] The first transport path 14 and the second transport path 15
constitute a T-shaped transport path, and a single transport robot
TR is provided on the T-shaped transport path. The transport robot
TR includes transport guide rails 17 disposed along the second
transport path 15, and a robot body 18 movable along the transport
guide rails 17. The operation of the transport robot TR is
controlled by a transport controller 29.
[0081] The robot body 18 is capable of transporting the wafer W
along the first transport path 14 and along the second transport
path 15. Therefore, the robot body 18 can access any of the
cassettes C placed on the cassette stages 16 to load and unload a
wafer W, and access any of the plating units 20a to 20d, the bevel
etching units 21a, 21b and the cleaning units 22a, 22b to load and
unload the wafer W.
[0082] A basic wafer transport route and a basic process sequence
are as follows. First, an untreated wafer W is unloaded from one of
the cassettes Cw, then transported to the front of one of the
plating units 20a to 20d, and loaded into the plating unit 20a to
20d by the robot body 18 so as to be subjected to the plating
process. In turn, the wafer W subjected to the plating process is
unloaded from the plating unit 20a to 20d, and loaded into one of
the bevel etching units 21a, 21b by the robot body 18 so as to be
subjected to the bevel etching process.
[0083] Subsequently, the wafer W subjected to the bevel etching
process is unloaded from the bevel etching unit 21a, 21b, then
transported along the second transport path 15, and loaded into one
of the cleaning units 22a, 22b by the robot body 18 so as to be
subjected to the cleaning process.
[0084] Further, the wafer W subjected to the cleaning process is
unloaded from the cleaning unit 22a, 22b and then transported along
the second transport path 15 toward the first transport path 14 by
the robot body 18. Upon reaching the first transport path 14, the
robot body 18 starts moving along the transport path 14 to the
front of a cassette Cw placed on one of the cassette stages 16, and
loads the wafer W on the cassette C.
[0085] The wafer treating section 1 is enclosed in an enclosure so
as not to be affected by an external environment.
[0086] FIGS. 3(a) , 3(b) and 3(c) are a schematic plan view, a
schematic side view and a schematic front view, respectively, for
explaining the construction of the robot body 18.
[0087] The robot body 18 includes a base 23, a vertical articulated
arm 24 attached to the base 23, a pivotal driving mechanism 25
attached to the vertical articulated arm 24, and a substrate holder
26 to be driven pivotally about a vertical pivot axis V0 by the
pivotal driving mechanism 25 (only the substrate holder 26 is shown
in FIG. 3(a)).
[0088] The substrate holder 26 includes a body 40 having a flat
top, and a pair of retractable arms 41, 42 provided on the flat top
of the body 40. A retractable driving mechanism (not shown) for
horizontally advancing and retracting the pair of retractable arms
41, 42 is incorporated in the body 40.
[0089] The retractable arms 41 and 42 respectively include first
arm portions 41a and 42a, second arm portions 41b and 42b, and
substrate holder hands (effecters) 41c and 42c. The body 40 has a
generally round shape as seen in plan, and the first arm portions
41a, 42a are attached to a peripheral edge portion of the body 40
pivotally about vertical pivot axes thereof. The first arm portions
41a, 42a are driven pivotally about the pivot axes by the
retractable driving mechanism provided in the body 40.
[0090] The retractable arms 41, 42 each constitute a so-called
scholar robot, which is operative so that the second arm portion
41b, 42b is pivoted about a vertical pivot axis thereof in
synchronization with the pivoting of the first arm portion 41a,
42a. Thus, the first arm portion 41a, 42a and the second arm
portion 41b, 42b of the retractable arm 41, 42 are stretched and
unstretched so as to advance and retract the substrate holder hand
41c, 42c.
[0091] When the retractable arms 41, 42 are in an unstretched
state, the substrate holder hands 41c, 42c are kept in vertically
overlapped relation (FIG. 3(a)). Therefore, the substrate holder
hand 41c of the retractable arm 41 has a bent shape for prevention
of interference with the substrate holder hand 42c of the
retractable arm 42 (FIG. 3(b)).
[0092] A first arm 24a is attached to the base 23 pivotally about a
horizontal pivot axis H1 at one end thereof. A second arm 24b is
attached to the other end of the first arm 24a pivotally about a
horizontal pivot axis H2 at one end thereof. The pivotal driving
mechanism 25 is attached to the other end of the second arm 24b
pivotally about a horizontal pivot axis H3. The pivot axes H1, H2
and H3 are parallel to each other.
[0093] A motor 27 for pivoting the first arm 24a is provided n the
base 23, and a motor 28 for pivotally driving the second arm 24b is
provided in a coupling between the first arm 24a and the second arm
24b. The motor 28 is rotatable in synchronization with the motor
27. A driving force transmission mechanism (not shown) for
transmitting a driving force from the motor 28 to the pivotal
driving mechanism 25 is incorporated in the second arm 24b. Thus,
the pivotal driving mechanism 25 can constantly hold the substrate
holder 26 in the same attitude (e.g., in such an attitude as to
hold the wafer W horizontally) , even if the first arm 24a and the
second arm 24b are pivoted.
[0094] A motor (not shown) is incorporated in the pivotal driving
mechanism 25. The pivotal driving mechanism 25 receives a driving
force from this motor to pivotally drive the substrate holder 26
about the vertical pivot axis V0.
[0095] With this arrangement, the transport robot TR can move the
substrate holder hands 41c, 42c horizontally and vertically within
a range hatched in FIG. 3(c).
[0096] When the robot body 18 accesses the cassette C (the cassette
Cw or the cassette Cd) placed on one of the cassette stages 16 (see
FIG. 2), the robot body 18 is moved to ends of the transport guide
rails 17 on the side of the first transport path 14 by the
transport controller 29. In this state, the substrate holder 26 is
brought into opposed relation to the cassette C on the cassette
stage 16 by the operation of the vertical articulated arm 24. That
is, the substrate holder 26 can be moved along the first transport
path 14, while the base 23 is kept located on the transport guide
rails 17.
[0097] Then, the retractable arm 41, 42 is brought into opposed
relation to the cassette C by the operation of the pivotal driving
mechanism 25, and caused to access the cassette C by the
retractable driving mechanism not shown for loading and unloading
the wafer W with respect to the cassette C. When the wafer W is
transferred between the cassette C and the retractable arm 41, 42,
the substrate holder 26 is slightly moved up or down by the
operation of the vertical articulated arm 24.
[0098] When the robot body 18 accesses any of the plating units 20a
to 20d, the bevel etching units 21a, 21b and the cleaning units
22a, 22b (see FIG. 2) , the robot body 18 is moved to the front of
the corresponding unit on the transport guide rails 17 by a
movement mechanism not shown. In this state, the substrate holder
26 is moved up or down to the height of a substrate
loading/unloading port of the unit by the operation of the vertical
articulated arm 24, and the retractable arm 41, 42 is brought into
opposed relation to the unit by pivoting the substrate holder 26 by
means of the pivotal driving mechanism 25.
[0099] In this state, the retractable arm 41, 42 is caused to
access the unit by the retractable driving mechanism for the
loading and unloading of the wafer W. When the wafer W is
transferred between the unit and the retractable arm 41, 42, the
substrate holder 26 is slightly moved up or down by the operation
of the vertical articulated arm 24.
[0100] With this arrangement, the cassette C, the plating units 20a
to 20d, the bevel etching units 21a, 21b and the cleaning units
22a, 22b can be accessed by the single robot body 18 for the
loading and unloading of the wafer W and the dummy wafer D.
[0101] The wafer W subjected to the plating process in the plating
unit 20a to 20d (hereinafter referred to as "entire-surface-plated
wafer") has a copper film formed on the entire surface thereof
including the peripheral edge thereof by the plating, before the
wafer W is subjected to the bevel etching process in the bevel
etching unit 21a, 21b. Therefore, the substrate holder hand 41c,
42c which holds the entire-surface-plated wafer is contaminated
with copper. Therefore, it is preferred that one of the substrate
holder hands 41c and 42c is dedicated to holding the
entire-surface-plated wafer. Thus, the contamination with copper is
prevented from spreading via the substrate holder hand 41c or
42c.
[0102] FIGS. 4(a) and 4(b) are a schematic plan view and a
schematic side view, respectively, of the cassette stage 16 on
which the cassette C is placed.
[0103] The cassette stage 16 includes a planar cassette base 50 for
receiving thereon the cassette C. The cassette base 50 has a
generally square shape as seen in plan. The cassette C has a
generally square shape having a smaller size than the cassette base
50 as seen in plan, and has a wafer loading/unloading opening Ce
provided on one lateral side thereof.
[0104] The cassette base 50 has cassette guides 51 provided on one
surface thereof in association with four corners of the cassette C
as seen in plan. Therefore, the cassette C can be located in
position on the cassette base 50 with its corners in contact with
the cassette guides 51. With the cassette C located in position on
the cassette base 50, the wafer loading/unloading opening Ce faces
toward the first transport path 14 (see FIG. 2).
[0105] A light emitting element 52a and a light receiving element
52b are respectively provided at generally middle points on
opposite edges of the cassette base 50 (excluding an edge having
the wafer loading/unloading opening Ce) on the surface of the
cassette base 50. The light emitting element 52a and the light
receiving element 52b constitute a transmissive photosensor 52.
When no cassette C is present on the cassette base 50, light
emitted from the light emitting element 52a is received by the
light receiving element 52b. When the cassette C is present on the
cassette base 50, the light emitted from the light emitting element
52a is blocked by the cassette C and does not reach the light
receiving element 52b. Thus, a judgment can be made on the presence
or absence of the cassette C on the cassette base 50.
[0106] There is no difference in construction between the cassette
Cw accommodating the wafer W and the cassette Cd accommodating the
dummy wafer D. Further, there is no difference in construction
between the cassette stage 16 on which the cassette Cw is placed
and the cassette stage 16 on which the cassette Cd is placed.
[0107] FIG. 5 is a schematic front view illustrating the
construction of the plating section 12.
[0108] The plating section 12 includes a plurality of plating units
(the four plating units 20a to 20d in this embodiment) for the
plating of the wafer W, and a plating liquid container 55 for
containing the plating liquid. The plating units 20a to 20d
respectively include plating cups 56a to 56d for containing the
plating liquid, and wafer holding/rotating mechanisms (treatment
heads) 74a to 74d to be located above the plating cups 56a to
56d.
[0109] The plating liquid container 55 is capable of containing the
plating liquid in a much greater amount than the plating cups 56a
to 56d (e.g., 20 times the total volume of the plating cups 56a to
56d) . Since a great amount of the plating liquid can be stored in
the plating liquid container 55, the total amount of the plating
liquid to be used in the plating section 12 can be increased. Thus,
variations in the composition of the plating liquid can be reduced
during the plating process.
[0110] The plating liquid transport pipe P12a for transporting the
plating liquid to the major constituent managing section 2 is
connected to the bottom of the plating liquid container 55 in
communication with the plating liquid container 55. The plating
liquid transport pipe P12b for introducing the plating liquid
transported from the major constituent managing section 2 into the
plating liquid container 55, the plating liquid transport pipe P13a
for transporting the plating liquid to the minor constituent
managing section 3, and the plating liquid transport pipe P13b for
introducing the plating liquid transported from the minor
constituent managing section 3 into the plating liquid container 55
are introduced into the plating liquid container 55 from the top of
the plating liquid container 55. The plating liquid transport pipes
P12b, P13a, P13b extend to a depth at which open ends thereof are
submerged in the plating liquid in the plating liquid container
55.
[0111] The plating cups 56a to 56d are located at a higher position
than the plating liquid container 55. A liquid supply pipe 57
extends from the bottom of the plating liquid container 55, and is
branched into four branch liquid supply pipes 58a to 58d. The
branch liquid supply pipes 58a to 58d extend upward to be
respectively connected to bottom center portions of the plating
cups 56a to 56d in communication with the plating cups 56a to
56d.
[0112] Pumps P1 to P4, filters 59a to 59d and flow meters 60a to
60d are provided in this order from a lower side to an upper side
in the respective branch liquid supply pipes 58a to 58d. The pumps
P1 to P4 are respectively capable of pumping the plating liquid
from the plating liquid container 55 to the plating cups 56a to
56d. The operations of the pumps P1 to P4 are controlled by the
system controller 155. The filters 59a to 59d are capable of
removing particles (contaminants) from the plating liquid. Signals
indicative of the flow rates of the plating liquid is outputted
from the flow meters 60a to 60d, and inputted to the system
controller 155.
[0113] The plating cups 56a to 56d respectively include cylindrical
plating vessels (liquid containing portions) 61a to 61d provided
inwardly thereof, and recovery vessels 62a to 62d surrounding the
plating vessels 61a to 61d. The branch liquid supply pipes 58a to
58d are connected in communication with the plating vessels 61a to
61d. Branch return pipes 63a to 63d respectively extend from bottom
portions of the recovery vessels 62a to 62d. The branch return
pipes 63a to 63d are connected in communication with a return pipe
64, which extends into the plating liquid container 55.
[0114] With the aforesaid arrangement, the plating liquid is
supplied, for example, to the plating vessel 61a from the plating
liquid container 55 through the liquid supply pipe 57 and the
branch liquid supply pipe 58a by operating the pump P1. The plating
liquid overflows from the top of the plating vessel 61a, and is fed
back into the plating liquid container 55 from the recovery vessel
62a through the branch return pipe 63a and the return pipe 64 by
gravity. That is, the plating liquid is circulated through the
plating liquid container 55 and the plating cup 56a.
[0115] Similarly, the plating liquid is circulated through the
plating liquid container 55 and the plating cup 56b, 56c or 56d by
operating the pump P2, P3 or P4. When the plating process is
performed in any of the plating units 20a to 20d, the plating
liquid is circulated through the plating cup 56a to 56d of the
corresponding plating unit 20a to 20d and the plating liquid
container 55. Thus, the plating liquid container 55 is shared by
the four plating units 20a to 20d.
[0116] One end of a bypass pipe 65 is connected to the branch
liquid supply pipe 58a between the pump P1 and the filter 59a. The
other end of the bypass pipe 65 is introduced into the plating
liquid container 55. Absorptiometers 66A, 66B for measuring
absorbances of the plating liquid at specific wavelengths of light
are provided in the bypass pipe 65. The absorptiometer 66A is
provided for determining the concentration of copper in the plating
liquid, while the absorptiometer 66B is provided for determining
the concentration of iron in the plating liquid.
[0117] When the pump P1 is operated to circulate the plating liquid
through the plating liquid container 55 and the plating cup 56a, a
part of the plating liquid flowing through the branch liquid supply
pipe 58a flows into the bypass pipe 65 due to a pressure loss by
the filter 59a. That is, the plating liquid can be introduced into
the bypass pipe 65 without provision of a dedicated pump in the
bypass pipe 65.
[0118] The absorptiometers 66A, 66B each include a cell 67A, 67B
composed of a transparent material, and a light emitting section
68A, 68B and a light receiving section 69A, 69B disposed in opposed
relation with the cell 67A, 67B interposed therebetween. The light
emitting sections 68A and 68B are respectively capable of emitting
light beams having specific wavelengths corresponding to absorption
spectra of copper and iron (e.g., 780 nm for copper). The light
receiving sections 69A and 69B are respectively capable of
measuring the intensities of the light beams emitted from the light
emitting sections 68A and 68B and transmitted through the plating
liquid in the cells 67A and 67B. The absorbances of the plating
liquid are determined on the basis of the light intensities.
Signals indicative of the absorbances are outputted from the
absorptiometers 66A, 66B, and inputted to the system controller
155.
[0119] A temperature sensor 70 and an electromagnetic conductivity
meter 71 are attached to a side wall of the plating liquid
container 55. The temperature sensor 70 and the electromagnetic
conductivity meter 71 are located at a height lower than the
surface level of the plating liquid contained in the plating liquid
container 55. Detectors of the temperature sensor 70 and the
electromagnetic conductivity meter 71 project into the plating
liquid container 55, and are respectively adapted to measure the
temperature and electrical conductivity of the plating liquid.
Output signals of the temperature sensor 70 and the electromagnetic
conductivity meter 71 are inputted to the system controller
155.
[0120] The concentrations of copper and iron in the plating liquid
can be determined by measuring the absorbances of the plating
liquid at the specific wavelengths of light. An explanation will be
given to how to determine the copper concentration on the basis of
the absorbance of the plating liquid.
[0121] For the determination of the copper concentration of the
plating liquid, a relationship between the copper concentration and
the absorbance is preliminarily determined. First, plural plating
liquid samples having different copper concentrations are prepared.
Copper sulfate is added as a copper source for the preparation of
the plating liquid samples. The plating liquid samples each have
substantially the same composition as the plating liquid actually
used for the plating process, except that the copper concentrations
thereof are different. The absorbances of the plating liquid
samples are measured by the absorptiometer 66A. Thus, the
relationship between the copper concentration and the absorbance
(copper calibration line) is determined on the basis of the known
copper concentrations and the measured absorbances of the plating
liquid samples as shown in FIG. 6.
[0122] For the determination of an unknown copper concentration of
the plating liquid, the absorbance of the plating liquid is
measured by the absorptiometer 66A. Then, the copper concentration
is determined on the basis of the measured absorbance and the
copper calibration line.
[0123] Similarly, a relationship between the iron concentration and
the absorbance (iron calibration line) is preliminarily determined
on the basis of known iron concentrations and measured absorbances
of plating liquid samples, and the concentration of iron in the
plating liquid is determined on the basis of the absorbance of the
plating liquid measured by the absorptiometer 66B and the iron
calibration line.
[0124] The system controller 155 includes a storage device storing
therein data of the copper calibration line and the iron
calibration line. The system controller 155 is capable of
determining the copper concentration on the basis of the output
signal of the absorptiometer 66A and the data of the copper
calibration line, and determining the iron concentration on the
basis of the output signal of the absorptiometer 66B and the data
of the iron calibration line.
[0125] An ultrasonic level meter 72 is provided above the plating
liquid container 55. The ultrasonic level meter 72 is capable of
detecting the surface level of the plating liquid in the plating
liquid container 55. An output signal of the ultrasonic level meter
72 is inputted to the system controller 155. A capacitive level
meter may be employed instead of the ultrasonic level meter 72.
[0126] The plating liquid container 55, the liquid supply pipe 57,
the branch liquid supply pipes 58a to 58d, the branch return pipes
63a to 63d and the return pipe 64 are disposed in a pipe chamber 73
virtually air-tightly enclosed by the enclosure and partition walls
of the wafer treating section 1. The pipe chamber 73 has an air
outlet port 32, which is connected to an air outlet duct 34. The
other end of the air outlet duct 34 is connected to an in-plant
exhauster system line. Air possibly exposed to the plating liquid
and the like in the plating section 12 is forcibly exhausted out of
the clean room. During the forcible air exhaustion, the internal
pressure of the pipe chamber 73 is kept at a negative pressure.
[0127] FIG. 7 is a schematic sectional view illustrating the common
construction of the plating units 20a to 20d. The wafer
holding/rotating mechanisms 74a to 74d are each supported by an
inversion base 181. An inversion driving section 43 is connected to
one end of the inversion base 181.
[0128] The inversion driving section 43 includes a column-shaped
vertical base 182 extending vertically, a rotary actuator 183
attached to the vertical base 182 and having a rotation shaft
perpendicular to the vertical base 182, and a toothed pulley 184
attached to the rotation shaft of the rotary actuator 183, a
toothed pulley 185 attached to a shaft extending parallel to the
shaft of the rotary actuator 183 and supported rotatably by the
vertical base 182, and a timing belt 186 stretched between the
toothed pulley 184 and the toothed pulley 185 for transmitting a
rotation force of the rotary actuator 183.
[0129] The rotary actuator 183 may be, for example, pneumatically
driven. The inversion base 181 is attached to the vicinity of the
shaft of the toothed pulley 185 perpendicularly to the toothed
pulley 185. The inversion base 181 and the wafer holding/rotating
mechanism 74a to 74d supported by the inversion base 181 can be
pivoted (inverted) about the horizontal shaft as indicated by an
arrow a in FIG. 7 by a pivotal driving force of the rotary actuator
183. Thus, the wafer W held by the wafer holding/rotating mechanism
74a to 74d can face upward or downward toward the plating cup 56a
to 56d.
[0130] The vertical base 182 is coupled to a lift mechanism 44. The
lift mechanism 44 includes a first motor 44a having a vertical
rotation shaft, a ball thread 44b attached to the first motor 44a
coaxially with the rotation shaft of the first motor 44a, and a
vertical column-shaped guide 44c. The first motor 44a maybe, for
example, a servo motor. A support member 182a having an internal
thread portion is provided in threading engagement with the ball
thread 44b in the vicinity of a lower end of the vertical base 182.
The guide 44c vertically guides the vertical base 182 while
preventing the vertical base 182 from rotating about the axis of
the ball thread 44b.
[0131] With this arrangement, the vertical base 182 can be moved
vertically by rotating the first motor 44a. Therefore, the
inversion base 181 coupled to the vertical base 182 and the wafer
holding/rotating mechanism 74a to 74d supported by the inversion
base 181 can vertically be moved up and down (in directions
indicated by an arrow b in FIG. 7).
[0132] The wafer holding/rotating mechanism 74a to 74d includes a
rotary pipe 77 and a disk-shaped spin base 78 attached to one end
of the rotary pipe 77 perpendicularly to the rotary pipe 77. The
rotary pipe 77 is supported rotatably about its axis by the
inversion base 181.
[0133] A plurality of wafer transfer pins 84 are provided on a
surface of the spin base 78 opposite from the rotary pipe 77
between the center and the peripheral edge of the spin base 78. A
plurality of support posts (e.g., four support posts) 79 are
provided in a peripheral edge portion on the surface of the spin
base 78 opposite from the rotary pipe 77. An annular cathode ring
80 is attached to distal ends of the support posts 79. The support
posts 79 have a greater length than the wafer transfer pins 84.
[0134] The cathode ring 80 has an abutment portion 80a projecting
toward the center of the cathode ring 80. The abutment portion 80a
has an inner diameter slightly smaller than the diameter of the
wafer W. The cathode ring 80 further has a projection 80p
projecting opposite from the support posts 79.
[0135] A susceptor 81 is provided coaxially with the rotary pipe
77. The susceptor 81 includes a support shaft 81b extending through
the rotary pipe 77, and a disk-shaped wafer back side press plate
81a attached to an end of the support shaft 81b (on the side of the
cathode ring 80) perpendicularly to the support shaft 81b. The
wafer back side press plate 81a is surrounded by the plurality of
support posts 79. The wafer back side press plate 81a has a
slightly smaller diameter than the wafer W. An end portion of the
support shaft 81b opposite from the wafer back side press plate 81a
projects out of the rotary pipe 77.
[0136] The susceptor 81 is coupled to a susceptor movement
mechanism 46. The susceptor movement mechanism 46 includes an air
cylinder 46a attached to the inversion base 181, and a transmission
member 46b which couples a piston of the air cylinder 46a to the
support shaft 81b. The transmission member 46b is fixed to the end
portion of the support shaft 81b projecting out of the rotary pipe
77 opposite from the wafer back side press plate 81a. The susceptor
81 can be moved along the center axis of the rotary pipe 77 by
driving the air cylinder 46a.
[0137] The wafer back side press plate 81a is formed with holes in
association with the wafer transfer pins 84. Thus, the wafer
transfer pins 84 are inserted into the holes of the wafer back side
press plate 81a, as the susceptor 81 is moved with respect to the
rotary pipe 77. With the aforesaid arrangement, the wafer W can be
held by the abutment portion 80a of the cathode ring 80 and the
wafer back side press plate 81a.
[0138] A rotative driving mechanism 45 for rotating the rotary pipe
77 about its axis is coupled to the rotary pipe 77. The rotative
driving mechanism 45 includes a second motor 45a provided on the
inversion base 181 and having a rotation shaft parallel to the axis
of the rotary pipe 77, a toothed pulley 45b fixed to the rotation
shaft of the second motor 45a, a toothed pulley 45c provided around
the rotary pipe 77, and a timing belt 45d stretched between the
toothed pulley 45b and the toothed pulley 45c for transmitting a
rotation force of the second motor 45a.
[0139] The rotary pipe 77 can be rotated about its axis (in a
direction indicated by an arrow c in FIG. 7) by a rotative driving
force of the second motor 45a. The second motor 45a may be, for
example, a servo motor. The rotation of the rotary pipe 77 is
transmitted to the susceptor 81, while permitting the susceptor 81
to move axially of the rotary pipe 77. Therefore, the rotary pipe
77 and the susceptor 81 are rotated together. Thus, the wafer W
held by the abutment portion 80a of the cathode ring 80 and the
wafer back side press plate 81a can be rotated.
[0140] In the plating process, the wafer holding/rotating mechanism
74a to 74d is moved down by the lift mechanism 44 with the wafer W
thus held as facing downward, and a lower surface of the wafer W is
brought into contact with the plating liquid filled in the plating
vessel 61a to 61d.
[0141] FIG. 8 is a schematic sectional view illustrating a portion
around the wafer W as observed in the plating process.
[0142] Referring to FIGS. 7 to 8, a continuous fluid channel 81c is
provided in the support shaft 81b and the wafer back side press
plate 81a. The fluid channel 81c is provided as a single fluid
channel extending through the support shaft 81b along the center
axis of the support shaft 81b, and branched into a plurality of
branch channels in the wafer back side press plate 81a. The branch
channels extend from the center to the peripheral edge of the wafer
back side press plate 81a, and open in the peripheral edge of the
wafer back side press plate 81a.
[0143] A rotary joint 191 is attached to the end of the support
shaft 81b opposite from the wafer back side press plate 81a. One
end of a supply pipe 203 and one end of a leak pipe 204 are
connected to the rotary joint 191. The other end of the supply pipe
203 is branched into a cathode cleaning liquid pipe 201 and a
nitrogen gas pipe 202.
[0144] The cathode cleaning liquid pipe 201 is connected to a
cathode cleaning liquid supply source, and the nitrogen gas pipe
202 is connected to a nitrogen gas supply source. A valve 201V is
provided in the cathode cleaning liquid pipe 201, so that a cathode
cleaning liquid (e.g., deionized water) can be supplied into the
rotary joint 191 by opening the valve 201V. A valve 202V is
provided in the nitrogen gas pipe 202, so that nitrogen gas can be
supplied into the rotary joint 191 by opening the valve 202V.
[0145] Even during the rotation of the susceptor 81, the cathode
cleaning liquid and nitrogen gas can be supplied into the fluid
channel 81c from the cathode cleaning liquid supply source and the
nitrogen gas supply source on the side of a stationary system
through the rotary joint 191.
[0146] A part of the cathode cleaning liquid supplied from the
supply pipe 203 is drained through the leak pipe 204. Particles
generated around slidable members in the rotary joint 191 are
washed away into the leak pipe 204 by the cathode cleaning liquid,
thus the particles are prevented from flowing into the fluid
channel 81c.
[0147] The cathode ring 80 includes an upper ring 80u, a conduction
plate 80c and a base ring 80b arranged in this order from the side
of the spin base 78. The upper ring 80u, the conduction plate 80c
and the base ring 80b each have a ring shape. The base ring 80b is
composed of an inelastic material. The conduction plate 80c is
covered with the upper ring 80u and the base ring 80b. The
conduction plate 80c is electrically conductive. The conduction
plate 80c imparts the entire cathode ring 80 with a sufficient
strength.
[0148] The base ring 80b is provided with the abutment portion 80a.
The abutment portion 80a has a sealing surface 80s to be brought
into contact with the wafer W in opposed relation to a peripheral
edge portion of the wafer back side press plate 81a.
[0149] A plurality of fluid channels 80f are provided in the base
ring 80b as extending radially through the base ring 80b. Where the
wafer back side press plate 81a and the cathode ring 80 are located
in position in the plating process, the fluid channels 80f are
located at a lower position than the branch channels of the fluid
channel 81c. A multiplicity of notches are provided in an inner
peripheral portion of the upper ring 80u, whereby the cathode
cleaning liquid flowing out of the branch channels of the fluid
channel 81c opening in the periphery of the wafer back side press
plate 81a can be introduced into the fluid channels 80f in the
plating process.
[0150] A cathode 83 is disposed in the fluid channels 80f. The
cathode 83 is disposed within substantially the same plane as the
sealing surface 80s outwardly of the abutment portion 80a with
respect to the center of the cathode ring 80.
[0151] The cathode 83 is composed of a spring stainless steel
having a thickness of about 0.1 mm, and has a surface plated with
platinum. This prevents formation of an oxide film on the surface
of the cathode 83, and prevents dissolution of the cathode 83 even
if a reverse electric field is applied to the cathode 83. If the
platinum film of the cathode 83 is too thin, the service life of
the platinum film is reduced due to abrasion. If the platinum film
of the cathode 83 is too thick, the film is liable to be cracked
when the cathode 83 behaves resiliently. In view of these, the
thickness of the platinum film of the cathode 83 is preferably
about 0.01 .mu.m to about 2 .mu.m.
[0152] The cathode 83 has a multiplicity of contact portions 83c
arranged like a comb circumferentially of the cathode ring 80 as
extending toward the center of the cathode ring 80. The contact
portions 83c are each bent at an angle .theta. of 5 to 60 degrees
with their distal ends raised toward the wafer back side press
plate 81a. The bent contact portions 83c are restricted by the
upper ring 80u.
[0153] The cathode 83 is brought into resilient contact with a
peripheral edge portion of the wafer W or the dummy wafer D, while
the wafer W or the dummy wafer D is held between the abutment
portion 80a and the wafer back side press plate 81a. That is, the
contact portions 83c can be kept in contact with the wafer W or the
dummy wafer D at a predetermined contact pressure.
[0154] An electrically-conductive ring-shaped electrode press 80d
is disposed between the base ring 80b and the upper ring 80u in the
vicinity of the conduction plate 80c. The base ring 80b has a
groove, in which a coil spring 80e is housed. The cathode 83 is
fixed to the electrode press 80d for electrical connection, and the
electrode press 80d and the conduction plate 80c are kept in
resilient contact with each other by the coil spring 80e for
electrical connection. Thus, the electrical connection is
maintained between the electrode press 80d and the conduction plate
80c, even if the base ring 80b is pressed to be warped by the wafer
back side press plate 81a.
[0155] The support posts 79 are electrically conductive, and extend
through the upper ring 80u so as to be electrically connected to
the conduction plate 80c. O-rings 80r are provided between the
support posts 79 and the upper ring 80u (around the support posts
79) , between the upper ring 80u and the base ring 80b around the
conduction plate 80c, between the upper ring 80u and the electrode
press 80d (along the inner periphery of the electrode press 80d)
,and between the base ring 80b and the electrode press 80d (along
the outer periphery of the electrode press 80d) . This prevents the
plating liquid from intruding into the cathode ring 80. When the
cathode ring 80 is detached from the spin base 78 for cleaning
thereof, the cathode ring 80 can be immersed in the cleaning liquid
without the need for disassembling the cathode ring 80 for cleaning
thereof.
[0156] A conduction line 198 is provided within the spin base 78
and the rotary pipe 77. An electrically conductive coupling plate
78j is attached to the peripheral portion of the surface of the
spin base 78 facing toward the cathode ring 80 via an insulative
plate 78i. The conduction line 198 is electrically connected to the
coupling plate 78j via a conduction stud 78s extending through the
insulative plate 78i.
[0157] An electrically conductive coupling member 79j is attached
to ends of the support posts 79 opposite from the conduction plate
80c. The coupling member 78j has a positioning pin 78p, while the
coupling member 79j is formed with a positioning hole 79h. The
coupling member 78j and the coupling member 79j are coupled to each
other with the positioning pin 78p fitted in the positioning hole
79h. Thus, the cathode ring 80 is fixed to the spin base 78 in
proper positional relationship. Even when the cathode ring 80 is
rotated at a high speed, there is no possibility that the cathode
ring 80 is offset. When the cathode ring 80 is detached from the
spin base 78 by decoupling the coupling members 78j, 79j, the
support posts 79 serve as handles of the cathode ring 80.
[0158] With the aforesaid arrangement, the cathode 83 is
electrically connected to the conduction line 198.
[0159] An electrical connection mechanism 192 is provided between a
plating power source 82 and the conduction line 198, so that
electrical connection can be established between the conduction
line 198 rotated together with the cathode ring 80 and the plating
power source 82 provided on the side of the stationary system.
[0160] The electrical connection mechanism 192 includes an
electrically conductive pulley 193 fitted around an end portion of
the rotary pipe 77 opposite from the spin base 78, an electrically
conductive rotary shaft 194 rotatably attached to the inversion
base 181 in parallel relation to the rotary pipe 77, an
electrically conductive pulley 195 fitted around the rotary shaft
194, an electrically conductive belt 196 stretched between the
pulley 193 and the pulley 195, and a slip ring 197 attached to a
distal end of the rotary shaft 194.
[0161] The pulleys 193, 195 each have a surface plated with gold,
for example, which is kept in contact with the belt 196. The belt
196 may be a steel belt having a surface plated with gold, for
example. In this case, the electrical resistance between the pulley
193 and the pulley 195 can be reduced. The pulley 193 and the
pulley 195 are mechanically connected to each other by the belt
196. When the rotary pipe 77 is rotated by the rotative driving
mechanism 45, the rotative driving force is transmitted to the
rotary shaft 194 via the pulley 193, the belt 196 and the pulley
195, whereby the rotary shaft 194 is rotated. Even during the
rotation of the rotary pipe 77 and the rotary shaft 194, the
electrical connection between the pulleys 193 and 195 is
maintained.
[0162] The slip ring 197 is of a non-slidable type, which
establishes the electrical connection between a rotary component
and a stationary component, for example, via mercury. The slip ring
197 includes a stationary terminal and a rotary terminal for
electrical connection between the stationary system and the rotary
system.
[0163] The conduction line 198 is electrically connected to the
pulley 193. The pulley 193 is electrically isolated from the rotary
pipe 77. Further, the pulley 195 is electrically connected to the
rotary shaft 194. The rotary shaft 194 is electrically connected to
the rotary terminal of the slip ring 197. The stationary terminal
of the slip ring 197 is electrically connected to the plating power
source 82 via a conduction line 199A.
[0164] With the aforesaid arrangement, the cathode 83 and the
plating power source 82 are electrically connected to each other,
even when the rotary pipe 77 and the rotary shaft 194 are rotated.
Where the belt 196 is stretched between the pulleys 193 and 195
with a sufficiently great tensile force, the belt 196 can be
brought into non-sliding contact with the pulleys 193 and 195.
Since the slip ring 197 is of a non-slidable type, there is no
sliding contact between the plating power source 82 and the cathode
83. Therefore, the electrical connection can properly be
established between the plating power source 82 and the cathode 83,
while a noise attributable to the sliding contact such as a
so-called brush noise is suppressed.
[0165] Since the rotary joint 191 and the slip ring 197 are
respectively attached to the ends of the support shaft 81b and the
rotary shaft 194, the replacement thereof is easy. That is, when
the rotary joint 191 or the slip ring 197 is replaced, interference
between the rotary joint 191 and the slip ring 197 can be avoided,
which may otherwise occur where the rotary joint 191 and the slip
ring 197 are both attached to the support shaft 81b or the rotary
pipe 77.
[0166] Since the rotary joint 191 and the slip ring 197 are
respectively attached to the ends of the support shaft 81b and the
rotary shaft 194, the lengths of the support shaft 81b (rotary pipe
77) and the rotary shaft 194 can be reduced. Therefore, the size of
the wafer holding/rotating mechanism 74a to 74d as measured axially
of the support shaft 81b can be reduced, so that the wafer
holding/rotating mechanism 74a to 74d can be inverted with a
reduced turning radius.
[0167] The operations of the plating power source 82, the inversion
driving section 43 (rotary actuator 183), the lift mechanism 44
(first motor 44a) , the rotative driving mechanism 45 (second motor
45a) and the susceptor movement mechanism 46 (air cylinder 46a),
and the opening and closing of the valves 201V, 202V are controlled
by the system controller 155.
[0168] Next, an explanation will be given to the construction of
the plating cup 56a to 56d. The plating vessel 61a to 61d has a
cylindrical side wall having an inner diameter virtually equal to
the outer diameters of the wafer W and the dummy wafer D. A plating
liquid supply port 54 is provided in a bottom center portion of the
plating vessel 61a to 61d. The branch liquid supply pipe 58a to 58d
is connected to the plating liquid supply port 54 as slightly
projecting into the plating vessel 61a to 61d. A semispherical
shower head 75 having a multiplicity of holes is attached to an end
of the branch liquid supply pipe 58a to 58d located in the plating
vessel 61a to 61d. The plating liquid is diffusively introduced in
various directions (at various angles) into the plating vessel 61a
to 61d through the shower head 75.
[0169] A three-dimensional filter including a plurality of
fluororesin mesh members 49 stacked one on another is provided in
an upper portion of the plating vessel 61a to 61d. The mesh members
49 each have a round plan shape having an outer diameter virtually
equal to the inner diameter of the plating vessel 61a to 61d. The
plurality of stacked mesh members 49 generally entirely cover the
plating vessel 61a to 61d as viewed in plan. The plating liquid
supplied upward from the lower side of the plating vessel 61a to
61d is rectified by the mesh members 49.
[0170] A mesh anode 76 is provided at a level about one fourth the
depth of the plating vessel 61a to 61d from the bottom in the
plating vessel 61a to 61d (between the shower head 75 and the mesh
members 49) . The anode 76 is a titanium mesh member coated with
iridium oxide, and is insoluble in the plating liquid. Since the
anode 76 is mesh-shaped, the flow of the plating liquid is not
hindered by the anode 76.
[0171] The anode 76 has a round plan shape having an outer diameter
virtually equal to the inner diameter of the plating vessel 61a to
61d, and generally entirely covers the plating vessel 61a to 61d as
viewed in plan. The anode 76 is connected to the plating power
source 82 via a conduction line 199B.
[0172] A plating liquid outlet port 53 is provided in the bottom of
the plating liquid recovery vessel 62a to 62d. The branch return
pipe 63a to 63d is connected in communication with the plating
liquid recovery vessel 62a to 62d via the plating liquid outlet
port 53.
[0173] An upper edge portion of the plating vessel 61a to 61d has a
reduced wall thickness with its outer circumferential portion cut
away, and is complementary in configuration to a portion of the
cathode ring 80 (base ring 80b) which is brought into opposed
relation to the upper edge portion of the plating vessel 61a to 61d
in the plating process. This prevents the interference between the
plating vessel 61a to 61d and the cathode ring 80 in the plating
process (see FIG. 8). In the plating process, the projection 80p of
the cathode ring 80 is inserted in an upper portion of the recovery
vessel 62a to 62d.
[0174] A cathode cleaning liquid collection vessel 210 is provided
around the plating liquid recovery vessel 62a to 62d for collecting
the cathode cleaning liquid after cleaning the cathode 83. That is,
the plating cup 56a to 56d has a triple structure having the
plating vessel 61a to 61d, the plating liquid recovery vessel 62a
to 62d and the cathode cleaning liquid collection vessel 210
arranged in this order from the inside to the outside. A liquid
drain pipe 215 is connected to the bottom of the cathode cleaning
liquid collection vessel 210, so that liquid can be drained from
the cathode cleaning liquid collection vessel 210.
[0175] A liquid trap 211 is also connected to the bottom of the
cathode cleaning liquid collection vessel 210, so that a part of
the liquid (the cathode cleaning liquid and the like) flowing into
the cathode cleaning liquid collection vessel 210 can be trapped in
the liquid trap 211. A conductivity meter 212 is inserted in the
liquid trap 211. Thus, the electrical conductivity of the liquid
trapped in the liquid trap 211 can be measured. An output signal of
the conductivity meter 212 is inputted to the system controller
155.
[0176] An overflow pipe 213 is connected to an upper edge portion
of a side wall of the liquid trap 211. When the surface level of
the liquid in the liquid trap 211 rises to reach the height of the
overflow pipe 213, the liquid overflows from the overflow pipe 213.
A drain pipe 214 is connected to the bottom of the liquid trap 211.
Therefore, when the plating unit 20a to 20d is not in use, the
liquid can be drained from the liquid trap 211.
[0177] When the plating process is performed in the plating section
12, the system controller 155 first controls the inversion driving
section 43 to invert any of the wafer holding/rotating mechanisms
74a to 74d (herein assumed to be the wafer holding/rotating
mechanism 74a) with the wafer back side press plate 81a thereof
facing upward. Further, the system controller 155 controls the
susceptor movement mechanism 46 to move the wafer back side press
plate 81a toward the rotary pipe 77, so that the wafer transfer
pins 84 project out through the wafer back side press plate 81a.
This state is shown in FIG. 9.
[0178] On the other hand, an untreated wafer W is taken out of the
cassette Cw by means of the retractable arm 41 or the retractable
arm 42 of the transport robot TR (see FIGS. 3 (a) to 3 (c) ). The
wafer W is loaded onto the wafer transfer pins 84 through a space
between the support posts 79 by the transport robot TR with the
center of the wafer W coinciding with the center axis of the rotary
pipe 77.
[0179] Then, the system controller 155 controls the susceptor
movement mechanism 46 to move the wafer back side press plate 81a
apart from the rotary pipe 77. Thus, the wafer back side press
plate 81a presses the peripheral edge portion of the lower (back)
surface of the wafer W, and the peripheral edge portion of the
upper surface of the wafer W is pressed against the abutment
portion 80a of the cathode ring 80. That is, the wafer W is held
between the wafer back side press plate 81a and the abutment
portion 80a of the cathode ring 80. Thus, the peripheral edge
portion of the upper surface of the wafer W is sealed by the
sealing surface 80s of the abutment portion 80a, while the cathode
83 is biased toward the wafer W into contact with the peripheral
edge portion of the upper surface of the wafer W.
[0180] The system controller 155 controls the inversion driving
section 43 to invert the wafer holding/rotating mechanism 74a so
that the wafer W faces downward. Then, the pump P1 is actuated
under the control of the system controller 155 to supply the
plating liquid into the plating vessel 61a at a flow rate of 10
1/min (see FIG. 5). Thus, the plating liquid is slightly raised
from the edge of the plating vessel 61a to overflow into the
recovery vessel 62a.
[0181] In turn, the system controller 155 controls the lift
mechanism 44 to lower the wafer holding/rotating mechanism 74a. The
lowering rate of the wafer holding/rotating mechanism 74a is
reduced when a distance between the lower surface of the wafer W
and the surface of the plating liquid is reduced to not greater
than several millimeters. Then, the lower surface of the wafer W is
gradually brought into contact with the surface of the plating
liquid filled in the plating vessel 61a. A period from the start of
the contact of the wafer W with the plating liquid to the
completion of the contact should be such that the seed layer formed
on the lower surface of the wafer W is hardly dissolved in the
plating liquid. When the distance between the lower surface of the
wafer W and the surface of the plating liquid is reduced to several
millimeters, the system controller 155 controls the plating power
source 82 to apply a first voltage between the anode 76 and the
cathode 83.
[0182] With the lower surface of the wafer W in contact with the
surface of the plating liquid, the wafer W is spaced about 0.3 mm
to about 1 mm from the upper edge of the plating vessel 61a.
[0183] Subsequently, the system controller 155 controls the
rotative driving mechanism 45 to rotate the wafer W at a relatively
low rotation speed (e.g., 10 rpm to 100 rpm), and then controls the
plating power source 82 to apply a second voltage (plating voltage)
between the anode 76 and the cathode 83 for electrical energization
for several minutes. Thus, electrons are donated to copper ions in
the plating liquid in an interface between the plating liquid and
the lower surface of the wafer W connected to the cathode 83, so
that copper atoms are deposited on the lower surface of the wafer
W. That is, the lower surface of the wafer W is plated with
copper.
[0184] Iron ions as an oxidizing/reducing agent are present in the
form of divalent or trivalent iron ions in the plating liquid. In
this embodiment, the mesh anode 76 has a sufficiently great surface
area (e.g., a surface area two to ten times the area to be plated)
. Further, the plating liquid can be applied to the entire anode 76
at a sufficiently high flow rate by the shower head 75. Therefore,
a sufficient amount of divalent iron ions can be supplied to the
anode 76 to promote a reaction in which the divalent iron ions
donate electrons to the anode 76 thereby to be turned into
trivalent iron ions.
[0185] Thus, the iron ions cyclically experience the oxidization
and the reduction, so that the amount of electrons transferred
between the plating liquid and the anode 76 is virtually balanced
with the amount of electrons transferred between the cathode 83 and
the plating liquid.
[0186] Therefore, the plating process is free from bubbles of
active oxygen, which may otherwise be generated when the
oxidizing/reducing agent is not used. Thus, oxidative decomposition
of the additives contained in the plating liquid can be retarded.
Further, it is possible to eliminate the possibility that the
oxygen bubbles adhere on the lower surface of the wafer W and fill
the fine holes or grooves formed in the surface (lower surface) of
the wafer W to hinder the plating.
[0187] The plating liquid is drawn by the rotating wafer W in the
vicinity of the interface between the plating liquid and the wafer
W, and subjected to a centrifugal force. However, the plating
liquid can assuredly be introduced into the recovery vessel 62a to
62d by the projection 80p of the cathode ring 80.
[0188] Upon the electrical energization of the plating power source
82, the valve 201V is opened under the control of the system
controller 155. Thus, the cathode cleaning liquid is introduced
into the fluid channel 81c. The cathode cleaning liquid flows out
of the peripheral openings of the wafer back side press plate 81a,
and is introduced into the cathode cleaning liquid collection
vessel 210 through the fluid channels 80f (see FIG. 8). Thus, the
cathode 83, which is disposed in the fluid channels 80f, is cleaned
with the cathode cleaning liquid.
[0189] The plating liquid is present opposite from the cathode 83
with respect to the wafer W and the abutment portion 80a.
Therefore, where the wafer W is properly sealed by the sealing
surface 80s of the abutment portion 80a, the plating liquid does
not flow to the cathode 83. On the other hand, if the sealing
between the wafer W and the abutment portion 80a is insufficient,
the plating liquid flows into a gap between the wafer W and the
abutment portion 80a to reach the cathode 83. If the electrically
energized cathode 83 is kept in contact with the plating liquid,
the cathode 83 is liable to be damaged (plated).
[0190] The plating liquid reaching the cathode 83 is washed away by
the cathode cleaning liquid, and flows into the liquid trap 211
from the cathode cleaning liquid collection vessel 210. Since the
cathode cleaning liquid and the mixture of the cathode cleaning
liquid and the plating liquid differ in electrical conductivity,
the system controller 155 can detect the plating liquid reaching
the cathode 83 on the basis of the output signal of the
conductivity meter 212.
[0191] Then, the system controller 155 controls the plating supply
source 82 to stop the electrical energization between the anode 76
and the cathode 83, and controls the lift mechanism 44 to lift the
wafer W so that the lower surface of the wafer W is spaced several
millimeters apart from the surface of the plating liquid filled in
the plating vessel 61a.
[0192] Further, the system controller 155 controls the rotative
driving mechanism 45 to rotate the wafer W at a relatively high
speed (e.g., 200 rpm to 1000 rpm) for several tens seconds. Thus,
the plating liquid is laterally spun off from the lower surface of
the wafer W. At this time, the plated surface of the wafer W is
kept covered with a film of the plating liquid rather than
completely dried. Thus, the plated surface of the wafer W is
prevented from being corroded during transportation of the wafer
W.
[0193] Under the control of the system controller 155, the valve
201V is closed and the valve 202V is opened. Thus, the cathode
cleaning liquid remaining in the fluid channel 81c is purged by
nitrogen gas, and the cathode cleaning liquid in the fluid channels
80f is laterally drained by a centrifugal force. The cathode
cleaning liquid remaining in the leak pipe 204 may be sucked to be
drained by an ejector not shown.
[0194] In turn, the system controller 155 controls the rotative
driving mechanism 45 to stop the rotation of the wafer W, and
controls the lift mechanism 44 to lift the wafer holding/rotating
mechanism 74a to a predetermined position. Then, the system
controller 155 controls the inversion driving section 43 to invert
the wafer holding/rotating mechanism 74a so that the wafer W faces
upward.
[0195] Thereafter, the system controller 155 controls the susceptor
movement mechanism 46 to move the wafer back side press plate 81a
toward the rotary pipe 77, whereby the wafer W is disengaged from
the wafer back side press plate 81a. At this time, the wafer W is
smoothly released from the sealing surface 80s by the resilience of
the cathode 83, so that the wafer W is supported on the wafer
transfer pins 84 as shown in FIG. 9. Since the cathode cleaning
liquid is not present in the fluid channels 80f, the cathode
leaning liquid does not drip on the upper surface (plated surface)
of the wafer W.
[0196] After the wafer W is moved apart from the abutment portion
80a, the plating liquid remaining on the plated surface of the
wafer W is sucked through a gap between the sealing surface 80s and
the wafer W, so that the sealing surface 80s and the contact
portions 83c of the cathode 83 are contaminated with the plating
liquid. However, the plating liquid adhering to the contact
portions 83c is rinsed off with the cathode cleaning liquid when
the plating process is performed on the next wafer W (or the dummy
wafer D). On the other hand, the plating liquid adhering to the
sealing surface 80s cannot be rinsed off with the cathode cleaning
liquid, but remains on the sealing surface 80s. However, this
presents no particular problem, as long as the plating process is
sequentially performed with the sealing surface 80s kept wetted
with the plating liquid.
[0197] The treated wafer W is unloaded through the space between
the support posts 79 by the retractable arm 42 or the retractable
arm 41 of the transport robot TR. Thus, the plating process on the
single wafer W is completed.
[0198] The plating process maybe performed simultaneously in the
plating cups 56a to 56d by simultaneously actuating the four pumps
P1 to P4, or in some of the plating cups 56a to 56d by actuating
corresponding ones of the pumps P1 to P4.
[0199] FIG. 10 is a schematic sectional view illustrating the
common construction of the bevel etching units 21a, 21b.
[0200] A spin chuck 86 for generally horizontally holding and
rotating the wafer W is provided in a generally cylindrical cup 85.
The spin chuck 86 is adapted to hold the wafer W by sucking a
center portion of the lower surface of the wafer W without
contacting the peripheral edge of the wafer W. The spin chuck 86
has a vertical rotation shaft 87, and a rotative driving force is
transmitted from a rotative driving mechanism 88 to the rotation
shaft 87. A lift mechanism 89 for moving up and down the spin chuck
86 is coupled to the spin chuck 86, so that the spin chuck 86 can
be brought into a state where its upper portion is accommodated in
the cup 85 and into a state where its upper portion is located
above an upper edge of the cup 85.
[0201] The cup 85 includes three cups 85a to 85c coaxially
arranged. The outermost one 85a of the cups 85a to 85c has an upper
edge located at the highest position, and the middle cup 85b has an
upper edge located at the lowest position. An annular treatment
liquid guide plate 85d as seen in plan is coupled to an upper edge
of the innermost cup 85c. An outer edge of the treatment liquid
guide plate 85d is bent to be inserted into a space between the cup
85a and the cup 85b.
[0202] A treatment liquid collection vessel 97 having an open top
is defined between the cup 85a and the cup 85b, and an air outlet
vessel 98 is defined between the cup 85b and the cup 85c. A liquid
drain port 97a is provided in the bottom of the treatment liquid
collection vessel 97, and an air outlet port 98a is provided in the
bottom of the air outlet vessel 98.
[0203] A rinse nozzle 90A and an etching nozzle 90B are provided
above the cup 85. A rinse liquid pipe 91 is connected in
communication with the rinse nozzle 90A, and a rinse liquid supply
source 92 is connected to the rinse liquid pipe 91. A valve 91V is
provided in the rinse liquid pipe 91. By opening the valve 91V, the
rinse liquid can be discharged through the rinse nozzle 90A to be
supplied to the upper surface of the wafer W held by the spin chuck
86. The rinse liquid may, for example, deionized water.
[0204] The etching nozzle 90B is connected via the post-treatment
agent pipe P14 to an etching liquid supply source 96 disposed in
the post-treatment agent supply section 4 (see FIG. 1) and
containing the etching liquid. A valve 90BV is provided in the
post-treatment agent pipe P14 between the etching liquid supply
source 96 and the etching nozzle 90B. By opening the valve 90BV,
the etching liquid can be supplied onto the upper surface of the
wafer W held by the spin chuck 86 through the etching nozzle 90B.
The flow rate of the etching liquid can also be adjusted by the
valve 90BV. The etching liquid may be, for example, a mixture of
sulfuric acid, a hydrogen peroxide and water.
[0205] Another rinse nozzle 99 extends through the treatment liquid
guide plate 85d from the lower side. A rinse liquid pipe 100 is
connected in communication with the rinse nozzle 99, and the rinse
liquid supply source 92 is connected to the rinse liquid pipe 100.
A valve 100V is provided in the rinse liquid pipe 100. By opening
the valve 100V, the rinse liquid can be discharged through the
rinse nozzle 99 to be supplied to the lower surface of the wafer W
held by the spin chuck 86.
[0206] An etching pipe 93 is provided generally vertically above
the cup 85. The etching pipe 93 has a groove 94 provided in a lower
end portion thereof as opening horizontally toward the center of
the cup 85 in association with the surface of the wafer W held by
the spin chuck 86. The peripheral edge of the wafer W can be
inserted in the groove 94. The inner space of the groove 94 and the
inner space of the etching pipe 93 communicate with each other.
[0207] A movement mechanism 95 is coupled to the etching pipe 93.
The etching pipe 93 can be moved vertically and radially of the cup
85 by the movement mechanism 95. Thus, the etching pipe 93 can be
moved between a treatment position at which the peripheral edge of
the wafer W is inserted in the groove 94 and a retracted position
at which the etching pipe 93 is retracted from the treatment
position apart from the wafer W. The etching pipe 93 can also be
retracted laterally beyond the cup 85.
[0208] The etching pipe 93 is connected via the post-treatment
agent pipe P14 to the etching liquid supply source 96 disposed in
the post-treatment agent supplying section 4 (see FIG. 1) and
containing the etching liquid. A valve 93V is provided in the
post-treatment agent pipe P14 between the etching pipe 93 and the
etching liquid supply source 96. By opening the valve 93V, the
etching liquid can be supplied to the inner space of the groove 94.
The flow rate of the etching liquid can also be adjusted by the
valve 93V.
[0209] The operations of the rotative driving mechanism 88, the
lift mechanism 89 and the movement mechanism 95, and the opening
and closing of the valves 90BV, 91V, l00V, 93V are controlled by
the system controller 155.
[0210] When the peripheral edge of the wafer W is to be etched by
the bevel etching unit 21a, 21b, the system controller 155 first
controls the movement mechanism 95 to retract the etching pipe 93
at the retracted position.
[0211] In turn, the system controller 155 controls the lift
mechanism 89 to move up the spin chuck 86 so that the upper portion
of the spin chuck 86 is located above the upper edge of the cup 85.
The wafer W subjected to the plating process in the plating section
12 is loaded into the bevel etching unit 21a or 21b by the
retractable arm 41 or the retractable arm 42 of the transport robot
TR (see FIGS. 3(a) to 3(c)), and held by the spin chuck 86 by
suction with the center of the wafer W coinciding with the center
axis of the rotation shaft 87. The surface of the wafer W subjected
to the plating process faces upward.
[0212] Thereafter, the system controller 155 controls the lift
mechanism 89 to move down the spin chuck 86. Thus, the wafer W held
by the spin chuck 86 is surrounded by the cup 85a. Then, the system
controller 155 controls the rotative driving mechanism 88 to rotate
the wafer W held by the spin chuck 86. The rotation speed of the
wafer W is, for example, about 500 rpm.
[0213] In this state, the valves 91V and 100V are opened under the
control of the system controller 155. Thus, the rinse liquid is
supplied to the upper and lower surfaces of the wafer W from the
rinse nozzles 90A and 99. The rinse liquid spreads toward the
peripheral edge of the wafer W by a centrifugal force, and flows
over the entire upper surface of the wafer W and the lower surface
of the wafer W except a portion thereof in contact with the spin
chuck 86. Thus, the wafer W is cleaned.
[0214] The rinse liquid is spun off laterally of the wafer W by the
centrifugal force, and flows over the interior of the cup 85a and
the upper surface of the treatment liquid guide plate 85d down into
the treatment liquid collection vessel 97. The rinse liquid is
introduced into a collection tank not shown through the liquid
drain port 97a. Further, gas is exhausted from the cup 85 through
the air outlet port 98a by an air exhauster system not shown. Thus,
mist of the rinse liquid and the like are prevented from scattering
out of the cup 85.
[0215] After the rinsing process is performed for a predetermined
period, the valves 91V, 100V are closed under the control of the
system controller 155. The wafer W is continuously rotated, whereby
the rinse liquid remaining on the wafer W is mostly spun off.
[0216] Subsequently, the system controller 155 controls the
movement mechanism 95 to move the etching pipe 93 to the treatment
position. Thus, the peripheral edge of the wafer W is inserted in
the groove 94 as shown in FIG. 10. At this time, the rotation speed
of the wafer W may be, for example, about 500 rpm. Then, the valve
93V is opened under the control of the system controller 155. The
flow rate of the etching liquid may be, for example, 20 ml/min.
Thus, the etching liquid is supplied into the groove 94 from the
etching liquid supply source 96. The etching liquid flows out of
the groove 94, so that the groove 94 is virtually filled with the
etching liquid.
[0217] Since the peripheral edge of the wafer W is inserted in the
groove 94, a part of the thin copper film formed on the peripheral
edge of the wafer W is dissolved by the etching liquid. With the
wafer W being rotated, the peripheral edge of the wafer W is moved
relative to the etching pipe 93 located at the treatment position.
As a result, the entire peripheral edge of the wafer W is etched.
An etching width is determined by an insertion depth of the wafer W
in the groove 94, so that the etching process can accurately be
performed with a desired etching width.
[0218] Like the rinse liquid, the etching liquid spun off laterally
of the wafer W by a centrifugal force is once collected in the
collection vessel 97, and then introduced into the collection tank
not shown through the liquid drain port 97a. During this period,
gas is continuously exhausted through the air outlet port 98a, so
that mist of the etching liquid is prevented from scattering out of
the cup 85.
[0219] After the etching liquid is continuously supplied for a
predetermined period (e.g., several tens seconds) for the etching
of the thin copper film on the peripheral edge of the wafer W, the
valve 93V is closed under the control of the system controller 155
to stop the supply of the etching liquid to the groove 94. Thus,
the etching process for etching the peripheral edge of the wafer W
is completed in the absence of the etching liquid in the groove
94.
[0220] Thereafter, the valves 91V, 100V are opened again under the
control of the system controller 155 to supply the rinse liquid to
the surfaces of the wafer W. Thus, the etching liquid remaining on
the peripheral edge portion of the wafer W is rinsed away with the
rinse liquid. During this period, the system controller 155
controls the movement mechanism 95 to move the etching pipe 93 to
the retracted position.
[0221] After the rinse liquid is continuously supplied for a
predetermined period (e.g., about one minute), the valves 91V, 100V
are closed under the control of the system controller 155 to stop
the supply of the rinse liquid. The system controller 155 controls
the rotative driving mechanism 88 to rotate the spin chuck 86 at a
high rotation speed (e.g., about 1000 rpm) for a predetermined
period (e.g., several tens seconds) for spinning off the rinse
liquid from the wafer W for drying. Then, the rotation of the spin
chuck 86 is stopped.
[0222] Subsequently, the system controller 155 controls the lift
mechanism 89 to move up the spin chuck 86 so that the wafer W held
by the spin chuck 86 is located above the upper edge of the cup 85.
Then, the wafer W is released out of the suction-held state.
[0223] In turn, the treated wafer W is unloaded by the retractable
arm 42 or the retractable arm 41 of the transport robot TR. Thus,
the etching process for the etching of the peripheral edge of the
single wafer W is completed. Since no thin copper film is present
on the peripheral edge of the treated wafer W, there is no
possibility that copper adheres on the substrate holder hand 41c,
42c when the peripheral edge of the wafer W is held by the
substrate holder hand 41c, 42c (see FIG. 3(a)) in the subsequent
steps.
[0224] In this embodiment, the cup 85 is fixed, and the spin chuck
86 is adapted to be moved up and down by the lift mechanism 89.
However, it is merely necessary to vertically move the spin chuck
86 and the cup 85 relative to each other. For example, the spin
chuck 86 may vertically be fixed, and the cup 85 may be adapted to
be moved up and down. Even in this case, the upper portion of the
spin chuck 86 can be located above the upper edge of the cup 85, so
that the wafer W can be loaded and unloaded by the retractable arm
41 or the retractable arm 42.
[0225] The dummy wafer D having one surface plated with copper in
the plating unit 20a to 20d is subjected to an etching process in
the bevel etching unit 21a, 21b for removal of the copper film
formed by the plating, so that the dummy wafer D can be reuse for
the plating. For the removal of the copper film on the dummy wafer
D, the dummy wafer D is held by the spin chuck 86 so that the
surface of the dummy wafer D plated in the plating section 12 faces
upward as in the case of the bevel etching of the wafer W. The
etching process for removing the entire copper film formed on the
dummy wafer D is performed in substantially the same manner as in
the aforesaid bevel etching process, except that the etching liquid
is not ejected from the etching pipe 93 but from the etching nozzle
90B.
[0226] More specifically, the valve 90BV is opened for a
predetermined period under the control of the system controller 155
to supply the etching liquid over the upper surface of the dummy
wafer D. At this time, the system controller 155 controls the
rotative driving mechanism 88 to stop the rotation of the spin
chuck 86 or rotate the spin chuck 86 at a low speed. Thus, no
centrifugal force or a reduced centrifugal force is exerted on the
etching liquid on the dummy wafer D. Therefore, a greater amount of
the etching liquid remains in a raised state on the dummy wafer D
as compared with the case where the spin chuck 86 is rotated at a
high speed. Thus, the copper film can efficiently be etched by the
etching liquid, so that the etching liquid is saved.
[0227] For the supply of the etching liquid, the etching liquid may
continuously be supplied by keeping the valve 90BV open.
Alternatively, the etching of the copper film on the dummy wafer D
may be achieved by repeating such a process that the etching liquid
is supplied to be raised on the entire surface of the dummy wafer D
standing still or rotated at a low speed, then the valve 90BV is
closed to stop the supply of the etching liquid and, after a lapse
of a predetermined period, the spin chuck 86 is rotated at a high
speed to spin off the etching liquid.
[0228] By thus performing the etching process, the copper film
formed on the dummy wafer D can completely be removed (or
stripped). Since the units for removing the copper film formed on
the dummy wafer D are provided separately from the plating units
20a to 20d, the plating process can properly be performed in the
plating units 20a to 20d without any influence of the etching
process. Further, it is possible to completely remove the copper
film from the dummy wafer D, because the conditions for the removal
of the copper film formed on the dummy wafer D are not constrained
by the plating units 20a to 20d.
[0229] After the removal of the copper film by the etching liquid,
the dummy wafer D is rinsed with the rinse liquid, and the rinse
liquid is spun off for drying as in the bevel etching process.
[0230] FIG. 11 is a schematic sectional view illustrating the
common construction of the cleaning units 22a, 22b.
[0231] A spin chuck 102 for generally horizontally holding and
rotating the wafer W is provided in a generally cylindrical cup
101. The spin chuck 102 includes a vertical rotation shaft 102a and
a disk spin base 102b provided at an upper end of the rotation
shaft 102a perpendicularly to the rotation shaft 102a. A plurality
of chuck pins 102e are provided upright on a peripheral edge
portion of an upper surface of the spin base 102b in
circumferentially spaced relation. The chuck pins 102e
cooperatively support a peripheral edge portion of the lower
surface of the wafer W in abutment against the peripheral surface
(circumferential surface) of the wafer W for holding the wafer
W.
[0232] A rotative driving force is transmitted to the rotation
shaft 102a of the spin chuck 102 from a rotative driving mechanism
103. A lift mechanism 104 for moving up and down the spin chuck 102
is coupled to the spin chuck 102, so that the spin chuck 102 can be
brought into a state where its upper portion is accommodated in the
cup 101 and into a state where its upper portion is located above
an upper edge of the cup 101.
[0233] The cup 101 includes three cups 101a to 101c coaxially
arranged. The outermost one 101a of the cups 101a to 101c has an
upper edge located at the highest position, and the middle cup 101b
has an upper edge located at the lowest position. An annular
treatment liquid guide plate 101d as seen in plan is coupled to an
upper edge of the innermost cup 101c. An outer edge of the
treatment liquid guide plate 101d is bent to be inserted into a
space between the cup 101a and the cup 101b.
[0234] A treatment liquid collection vessel 105 having an open top
is defined between the cup 101a and the cup 101b, and an air outlet
vessel 106 is defined between the cup 101b and the cup 101c. A
liquid drain port 105a is provided in the bottom of the treatment
liquid collection vessel 105, and an air outlet port 106a is
provided in the bottom of the air outlet vessel 106.
[0235] A nozzle 107 is provided above the cup 101. The nozzle 107
is connected in communication with the rinse liquid supply source
via a valve 107V. By opening the valve 107V, the rinse liquid can
be discharged toward the wafer W held by the spin chuck 102 from
the nozzle 107.
[0236] The rotation shaft 102a has a treatment liquid supply
channel 102c extending axially therethrough, and an open upper end
serving as a treatment liquid outlet port 102d. The cleaning liquid
can be supplied into the treatment liquid supply channel 102c
through the post-treatment agent pipe P14 from a cleaning liquid
supply source provided in the post-treatment agent supplying
section 4 (see FIG. 1) The rinse liquid can also be supplied into
the treatment liquid supply channel 102c from the rinse liquid
supply source. The cleaning liquid maybe, for example, a mixture of
sulfuric acid, a hydrogen peroxide and water.
[0237] A valve 108V is provided between the treatment liquid supply
channel 102c and the cleaning liquid supply source. A valve 109V is
provided between the treatment liquid supply channel 102c and the
rinse liquid supply source. By closing the valve 109V and opening
the valve 108V, the cleaning liquid can be discharged from the
treatment liquid outlet port 102d. By closing the valve 108V and
opening the valve 109V, the rinse liquid can be discharged from the
treatment liquid outlet port 102d. Thus, the cleaning liquid or the
rinse liquid can be supplied to the center of the lower surface of
the wafer W held by the spin chuck 102.
[0238] The operations of the rotative driving mechanism 103 and the
lift mechanism 104, and the opening and closing of the valves 107V,
108V, 109V are controlled by the system controller 155.
[0239] When the wafer W is to be cleaned in the cleaning unit 22a
or 22b, the system controller 155 first controls the lift mechanism
104 to move up the spin chuck 102 so that the upper portion of the
spin chuck 102 is located above the upper edge of the cup 101. The
wafer W subjected to the bevel etching process in the bevel etching
unit 21a or 21b is loaded into the cleaning unit 22a or 22b by the
retractable arm 41 or the retractable arm 42 of the transport robot
TR (see FIGS. 3(a) to 3(c)), and mechanically held by the chuck
pins 102e with the center of the wafer W coinciding with the center
axis of the rotation shaft 102a.
[0240] Thereafter, the system controller 155 controls the lift
mechanism 104 to move down the spin chuck 102. Thus, the wafer W
held by the spin chuck 102 is surrounded by the cup 101a. Then, the
system controller 155 controls the rotative driving mechanism 103
to rotate the wafer W held by the spin chuck 102. The rotation
speed of the wafer W is, for example, about 500 rpm. Gas is
exhausted from the cup 101 through the air outlet port 106a by the
exhauster system not shown.
[0241] In this state, the valves 107V, 108V are opened under the
control of the system controller 155. Thus, the rinse liquid and
the cleaning liquid are discharged toward the wafer W from the
nozzle 107 and the treatment liquid outlet port 102d, respectively.
The rinse liquid and the cleaning liquid supplied to the surfaces
of the wafer W spread toward the peripheral edge of the wafer W by
a centrifugal force. Thus, the entire lower surface of the wafer W
is cleaned.
[0242] The rinse liquid and the cleaning liquid are spun off
laterally of the wafer W by the centrifugal force, and flows over
the interior of the cup 101a and the upper surface of the treatment
liquid guide plate 101d down into the treatment liquid collection
vessel 105. The rinse liquid and the cleaning liquid are introduced
into the collection tank not shown through the liquid drain port
105a. Further, gas is exhausted from the cup 101. Thus, mist of the
cleaning liquid can be exhausted through the air outlet port 106a
so as to be prevented from scattering out of the cup 101.
[0243] After this process is performed for a predetermined period,
the valve 108V is closed and the valve 109V is opened under the
control of the system controller 155. Thus, the rinse liquid is
discharged toward the lower surface of the wafer W from the
treatment liquid outlet port 102d. The supply of the rinse liquid
to the upper surface of the wafer W from the nozzle 107 is
continued. Thus, the cleaning liquid is rinsed away from the lower
surface of the wafer W. After this process is continued for a
predetermined period (e.g., about one minute), the valves 107V and
109V are closed under the control of the system controller 155 to
stop the supply of the rinse liquid to the wafer W.
[0244] Subsequently, the system controller 155 controls the
rotative driving mechanism 103 to rotate the wafer W held by the
spin chuck 102 at a high speed, for example, at about 2000 rpm.
Thus, the rinse liquid remaining on the wafer W is mostly spun off
for drying the wafer W. After the high-speed rotation of the wafer
W is continued for a predetermined period (e.g., several tens
seconds), the system controller 155 controls the rotative driving
mechanism 103 to stop the rotation of the wafer W.
[0245] In turn, the system controller 155 controls the lift
mechanism 104 to move up the spin chuck 102 so that the wafer W
held by the spin chuck 102 is located above the upper edge of the
cup 101. Thus, the wafer W is released from the chuck pins
102e.
[0246] Then, the treated wafer W is unloaded by the retractable arm
42 or the retractable arm 41 of the transport robot TR. Thus, the
cleaning process for the cleaning of the single wafer W is
completed.
[0247] In this embodiment, the cup 101 is fixed, and the spin chuck
102 is adapted to be moved up and down by the lift mechanism 104.
However, it is merely necessary to vertically move the spin chuck
102 and the cup 101 relative to each other. For example, the spin
chuck 102 may vertically be fixed, and the cup 101 may be adapted
to be moved up and down. Even in this case, the spin base 102b can
be located above the upper edge of the cup 101, so that the wafer W
can be loaded and unloaded by the retractable arm 41 or the
retractable arm 42.
[0248] FIG. 12 is a block diagram illustrating the construction of
a control system for the wafer treating section 1.
[0249] The system controller 155 controls the wafer treating
section 1, the major constituent managing section 2, the minor
constituent managing section 3 and the post-treatment agent
supplying section 4 to comprehensively manage the entire plating
apparatus 10. More specifically, the system controller 155 monitors
the states of the respective sections, issues proper control
commands to the respective sections, generates data for the
respective sections, and takes in data from the respective
sections.
[0250] Hardware of the system controller 155 includes a central
processing unit (CPU) having a processing capability of 10 MIPS
(million instructions per second) or more, a semiconductor memory
having a storage capacity of 10 Mbytes or more, a magnetic memory
having a storage capacity of 1 Mbyte or more, RS-232C compatible
serial ports, RS-485 compatible serial ports, and a plurality of
printed circuit boards. The magnetic memory may be, for example, a
hard disk (HD) incorporated in a hard disk drive (HDD), or a
flexible disk (FD) to be inserted in a flexible disk drive
(FDD).
[0251] Software employed in the system controller 155 includes an
operating system, and application programs which are at least
partly described in a high-level language. These programs are
stored in a storage device 155M provided in the system controller
155. The application programs include recipes for performing the
plating process, the bevel etching process, the cleaning process,
the process employing the dummy wafer D, and the like.
[0252] The system controller 155 is connected to a display 156, a
keyboard 157, a pointing device (e.g., a mouse) 156p, so that the
operator can interact with the system controller 155 for inputting
and outputting information. The system controller 155 is further
connected to an audible alarm generator 158. When a certain event
occurs, e.g., when the residual amount of the copper supply source
(copper tube) for supplying copper ions to the plating liquid is
reduced below a predetermined level, an audible alarm is given, and
information on the alarm is displayed on the display 156.
[0253] The system controller 155 is connected to the transport
controller 29 (see FIG. 2), the major constituent managing section
2 and the minor constituent managing section 3 via the RS-232C
compatible serial ports by cables. The system controller 155 is
further connected to a motor controller 159 by a pulse-string
input/output cable, and connected to a pump controller 160, the
flow meters 60a to 60d and the absorptiometers 66A and 66B by
analog signal cables.
[0254] Thus, the system controller 155 is capable of controlling
motors provided in the rotative driving mechanisms 45, 88, 103 (see
FIGS. 7, 10 and 11), for example, via the motor controller 159, and
controlling the operations of the pumps P1 to P4 (see FIG. 5) in
the plating section 12, for example, via the pump controller 160.
Signals indicative of the flow rates from the flow meters 60a to
60d (see FIG. 5) are inputted as analog signals to the system
controller 155. Further, the system controller 155 controls the
operations of the absorptiometers 66A, 66B (e.g., light emission of
the light emitting sections 68A, 68B) on an analog signal basis,
and receives analog signals outputted from the light receiving
sections 69A, 69B.
[0255] The system controller 155 is further connected to the major
constituent managing section 2, the post-treatment agent supplying
section 4 and serial/parallel converters 161a, 161b via the RS-485
compatible serial ports by cables. In FIG. 12, only two
serial/parallel converters 161a, 161b are shown, but the system
controller 155 may be connected to a greater number of
serial/parallel converters.
[0256] The serial/parallel converters 161a and 161b are
respectively connected to electromagnetic valves 162a and 62b, and
sensors 163a and 163b (e.g., the temperature sensor 70, the
electromagnetic conductivity meter 71, the ultrasonic level meter
72 (see FIG. 5)) via parallel cables. The electromagnetic valves
162a, 162b are capable of controlling air valves (e.g., the valves
91V, 100V (see FIG. 10) and the valve 107V (see FIG. 11)).
[0257] Information on a production plan can be inputted to the
storage device 155M of the system controller 155 via the keyboard
157 or the pointing device 156p as an inputting device. More
specifically, the number of wafers W intended to be plated (in each
production lot) can be inputted. Further, the system controller 155
counts the number of actually treated wafers W out of the intended
wafers W on the basis of a control history of the transport robot
TR.
[0258] Therefore, the system controller 155 can detect the
discontinuation of the loading of the wafer W in the plating units
20a to 20d by comparing the number of the wafers W loaded to be
plated with the number of the treated wafers W. Where the
production plan includes a plurality of production lots,
information indicative of whether or not these lots are to be
sequentially dealt with can be inputted to the system controller
155. Thus, the system controller 155 can predict whether or not the
loading of the wafer W in the plating units 20a to 20d is
discontinued after each of the lots.
[0259] FIG. 13 is a schematic diagram illustrating the construction
of the major constituent managing section 2.
[0260] The major constituent managing section 2 includes at least
one copper dissolution tank (two copper dissolution tanks 110a,
110b in this embodiment) containing copper tubes 146 (copper supply
source) for supplying copper ions to the plating liquid, a buffer
container 111 for supplying a replacement liquid to one of the
copper dissolution tanks 110a, 110b not in use, and an undiluted
replacement liquid supplying section 112 for supplying an undiluted
replacement liquid as a source of the replacement liquid to the
buffer container 111.
[0261] The copper dissolution tanks 110a, 110b each have a
cylindrical sealed structure having a closed bottom and a generally
vertical axis. The copper dissolution tank 110a, 110b is placed on
a weight meter 154a, 154b, which is adapted to measure the total
weight of the copper dissolution tank 110a, 110b including its
content.
[0262] The copper dissolution tank 110a, 110b includes an outer
pipe 116a, 116b constituting a side wall thereof, and an inner pipe
117a, 117b provided in the outer pipe 116a, 116b. An inner space of
the inner pipe 117a, 117b communicates with a space (hereinafter
referred to as "annular space 145") defined between the outer pipe
116a, 116b and the inner pipe 117a, 117b in a lower portion of the
copper dissolution tank 110a, 110b. Copper tubes are placed in the
annular space 145.
[0263] The buffer container Ill has a cover 120 having piping ports
for piping, and is virtually sealed. Upper and lower portions of
the buffer container 111 are connected in communication with each
other by a bypass pipe 125 vertically extending along the exterior
of the buffer container 111. A constant volume check sensor 126 is
provided at a predetermined height on a lateral side of the bypass
pipe 125 for detecting the presence or absence of liquid at this
predetermined height within the bypass pipe 125.
[0264] The liquid (e.g., the replacement liquid) is allowed to
freely flow between the buffer container 111 and the bypass pipe
125, so that a liquid surface level in the buffer container 111 is
virtually equal to a liquid surface level in the bypass pipe 125.
Thus, the presence or absence of the liquid at the predetermined
height in the buffer container 111 can be detected by the constant
volume check sensor 126.
[0265] One end of a circulation pipe 118 is connected to the bottom
of the buffer container 111 via a piping port for communication
between the circulation pipe 118 and the buffer container 111. The
other end of the circulation pipe 118 is branched into branch
circulation pipes 121, 122 at a branch point Bi. The branch
circulation pipe 121 is further branched into branch circulation
pipes 121a, 121b, while the branch circulation pipe 122 is further
branched into branch circulation pipes 122a, 122b.
[0266] The branch circulation pipes 121a and 121b are respectively
connected to upper portions of the inner pipes 117a and 117b of the
copper dissolution tanks 110a and 110b. The branch circulation
pipes 122a and 122b are respectively connected to liquid outlet
pipes 149a and 149b provided in the copper dissolution tanks 110a
and 110b. Valves AV3-2 and AV4-2 are provided in the branch
circulation pipes 121a and 121b, respectively. Valves AV3-3 and
AV4-3 are provided in the branch circulation pipes 122a and 122b,
respectively.
[0267] Branch circulation pipes 119a and 119b are respectively
connected in communication with the annular spaces 145. Valves
AV3-1 and AV4-1 are provided in the branch circulation pipes 119a
and 119b, respectively. The branch circulation pipes 119a, 119b are
connected to one end of a circulation pipe 119. The other end of
the circulation pipe 119 is branched into branch circulation pipes
119d and 119e at a branch point B2.
[0268] The valves AV3-1, AV3-2, AV3-3, AV4-1, AV4-2, AV4-3 are
collectively disposed in a copper dissolution tank channel
switching section 153.
[0269] The branch circulation pipe 119d extends into the buffer
container 111 through the cover 120 (through the piping port formed
in the cover 120). A valve AV2-2 is provided in the branch
circulation pipe 119d .
[0270] One end of a channel switching pipe 115 is connected to the
circulation pipe 118 at a branch point B3. Liquid can be drained
from the other end of the channel switching pipe 115. A valve AV1-4
is provided at the other end of the channel switching pipe 115. The
plating liquid transport pipes P12a and P12b are connected to the
channel switching pipe 115 via valves AV1-3 and AV1-2,
respectively.
[0271] A valve AV1-1 is provided in the circulation pipe 118
between the buffer container 111 and the branch point B3. A valve
AV1-5, a pump P5 and a flow meter 123 are provided in the
circulation pipe 118 between the branch point B3 and the branch
point B1 in this order from the branch point B3. An emptiness check
sensor 127 is provided on a lateral side of the circulation pipe
118 in the vicinity of the buffer container 111 (between the buffer
container 111 and the branch point B3) . The emptiness check sensor
127 is capable of detecting the presence or absence of the liquid
at the height of the emptiness check sensor 127 in the circulation
pipe 118. This makes it possible to determine whether or not the
buffer container 111 is empty.
[0272] The valves AV1-1, AV1-2, AV1-3, AV1-4, AV1-5 are
collectively disposed in an inlet-side main channel switching
section 113.
[0273] The branch circulation pipe 119e is connected to the plating
liquid transport pipe P12b at a branch point B4. A valve AV2-1 is
provided in the branch circulation pipe 119e. The valves AV2-1,
AV2-2 are collectively disposed in an outlet-side main channel
switching section 114.
[0274] The undiluted replacement liquid supplying section 112
includes an undiluted replacement liquid tank 128 containing the
undiluted replacement liquid, and a measure cup 129 for dispensing
a predetermined amount of the undiluted replacement liquid. The
undiluted replacement liquid may be, for example, concentrated
sulfuric acid. The measure cup 129 has a cover 129a, and is
virtually sealed. The measure cup 129 has a bottom having an
inverted cone shape. An undiluted replacement liquid transport pipe
130 extends from an upper portion of the measure cup 129 into a
bottom portion of the undiluted replacement liquid tank 128. A
valve AV6-3 is provided in the undiluted replacement liquid
transport pipe 130.
[0275] The undiluted replacement liquid supplying section 112 is
connected to the buffer container 111 by an undiluted replacement
liquid supply pipe 124. The undiluted replacement liquid supply
pipe 124 extends to the upper portion of the measure cup 129
through the cover 129a. One end of an undiluted replacement liquid
transport pipe 131 is connected to the bottom of the measure cup
129. The other end of the undiluted replacement liquid transport
pipe 131 is connected to the undiluted replacement liquid supply
pipe 124 at a branch point B5. A valve AV6-1 is provided in the
undiluted replacement liquid supply pipe 124 between the branch
point B5 and the measure cup 129. A valve AV6-2 is provided in the
undiluted replacement liquid transport pipe 131.
[0276] A leak pipe 132 extends through the cover 129a to be
connected in communication with the measure cup 129. A valve AV6-4
is provided in the leak pipe 132 outside the measure cup 129. By
opening the valve AV6-4, the internal pressure of the measure cup
is set at the atmospheric pressure.
[0277] A constant volume check sensor 133 is provided at a
predetermined height on a lateral side of the measure cup 129 for
detecting the presence or absence of liquid at this predetermined
height in the measure cup 129. An emptiness check sensor 134 is
provided on a lateral side of the undiluted replacement liquid
transport pipe 131 in the vicinity of the measure cup 129. The
emptiness check sensor 134 is capable of detecting the presence or
absence of liquid at the height of the emptiness check sensor 134
in the undiluted replacement liquid transport pipe 131. This makes
it possible to determine whether or not the measure cup 129 is
empty.
[0278] A deionized water supply pipe 135 extends through the cover
120 to be connected in communication with the buffer container 111.
Thus, deionized water can be supplied to the buffer container 111
from a deionized water supply source not shown. A valve AV7-1 is
provided in the deionized water supply pipe 135.
[0279] An air inlet/outlet pipe 136 is introduced into the buffer
container 111 through the cover 120. An air pump 137 is connected
to an end of the air inlet/outlet pipe 136 outside the buffer
container 111. A three-way valve AV8-3 is provided in the air
inlet/outlet pipe 136. The three-way valve AV8-3 is adapted to
selectively establish air communication between the buffer
container 111 and the air pump 137 and between the buffer container
111 and the atmosphere.
[0280] The air pump 137 has an air exhaustion pipe 138 and an air
supply pipe 139. The air inlet/outlet pipe 136 is connected in
communication with the air exhaustion pipe 138 and the air supply
pipe 139. A three-way valve AV8-1 is provided in the air exhaustion
138, while a three-way valve AV8-2 is provided in the air supply
pipe 139. The three-way valves AV8-1, AV8-2, AV8-3, which may be
air valves, are collectively disposed in a pressure
increasing/reducing section 164.
[0281] Air can be supplied into the buffer container 111 by
establishing communication between the atmosphere and the air pump
137 through the three-way valve AV8-1 and between the air pump 137
and the air inlet/outlet pipe 136 through the three-way valve
AV8-2, and actuating the air pump 137. Gas can be exhausted from
the buffer container 111 by establishing communication between the
air inlet/outlet pipe 136 and the air pump 137 through the
three-way valve AV8-1 and between the air pump 137 and the
atmosphere through the three-way valve AV8-2, and actuating the air
pump 137.
[0282] The opening and closing of the valve AV7-1 and the valves in
the inlet-side main channel switching section 113, the outlet-side
main channel switching section 114, the copper dissolution tank
channel switching section 153, the undiluted replacement liquid
supplying section 112 and the pressure increasing/reducing section
164, and the operations of the pump P5 and the air pump 137 are
controlled by the system controller 155 of the wafer treating
section 1 via the serial/parallel converter 165. Output signals of
the constant volume check sensors 126, 133, the emptiness check
sensors 127, 134, the flow meter 123 and the weight meters 154a,
154b are inputted to the system controller 155 of the wafer
treating section 1 via the serial/parallel converter 165.
[0283] FIG. 14 is a block diagram illustrating the construction of
control systems for the major constituent managing section 2, the
minor constituent managing section 3 and the post-treatment agent
supplying section 4.
[0284] The major constituent managing section 2 includes the
serial/parallel converter 165 and an operation panel 166. The
system controller 155 provided in the wafer treating section 1 is
connected to the serial/parallel converter 165 via the RS-485
compatible serial port by a cable, and connected to the operation
panel 166 via the RS-232C compatible serial port by a cable.
[0285] Electromagnetic valves 167 and sensors 168 (e.g., the
constant volume check sensors 126, 133, the emptiness check sensors
127, 134 and the weight meters 154a, 154b (see FIG. 13)) are
connected in parallel to the serial/parallel converter 165. The
electromagnetic valves 167 are capable of controlling air valves
(e.g., the valve AV1-1 and the like (see FIG. 13)). The operator
can input and output information on the major constituent managing
section 2 by means of the operation panel 166.
[0286] The minor constituent managing section 3 includes a minor
constituent management controller 169, so that a control operation
can be performed independently of the system controller 155
provided in the wafer treating section 1. The minor constituent
management controller 169 is connected to the system controller 155
via the RS-232C compatible serial port by a cable.
[0287] A display 170, a keyboard 171, a potentiostat (power source)
172, a syringe pump 173 and a serial/parallel converter 174 are
connected to the minor constituent management controller 169. The
display 1.70 and the keyboard 171 permit the operator to interact
with the minor constituent management controller 169 for inputting
and outputting information.
[0288] The syringe pump 173 is capable of adding an indicator and
the like dropwise to a sampled plating liquid when the
concentrations of the minor constituents of the plating liquid are
measured. Further, the syringe pump 173 is capable of
quantitatively dispensing replenishment liquids respectively
containing the minor constituents in required amounts.
[0289] Electromagnetic valves 175 and sensors 176 (e.g., surface
level sensors) are connected to the serial/parallel converter 174
by parallel cables. The electromagnetic valves 175 are capable of
controlling air valves.
[0290] The post-treatment agent supplying section 4 includes a
serial/parallel converter 177. The system controller 155 provided
in the wafer treating section 1 is connected to the serial/parallel
converter 177 via the RS-485 compatible serial port by a cable.
Electromagnetic valves 178 and sensors 179 are connected to the
serial/parallel converter 177 by parallel cables. The
electromagnetic valves 178 are capable of controlling air valves
(e.g., the valve 93V (see FIG. 10) and the valve 108V (see FIG.
11)).
[0291] With reference to FIG. 13, an explanation will hereinafter
be given to the operation of the major constituent managing section
2 during the plating process performed in the plating section
12.
[0292] Prior to the plating process, the system controller 155
determines which of the copper dissolution tanks 110a, 110b is to
be used. One of the copper dissolution tanks 110a, 110b which
contains tubes 146 whose total weight is the lightest is used. The
other copper dissolution tank is not used, but reserved as a
spare.
[0293] Data of the net weights of the respective copper dissolution
tanks 110a, 110b and the weights of the respective copper
dissolution tanks 110a, 110b measured when the plating liquid is
filled therein is preliminarily inputted into the memory of the
system controller 155. The system controller 155 calculates the
weights of copper tubes 146 in the copper dissolution tanks 110a,
110b on the basis of the output signals of the weight meters 154a,
154b.
[0294] It is herein assumed that the weight of the copper tubes 146
in the copper dissolution tank 110a is judged to be the lightest
and sufficient to supply copper ions to the plating liquid for a
predetermined period. In this case, a flow channel is established
for circulating the plating liquid through the plating section 12
and the copper dissolution tank 110a under the control of the
system controller 155. More specifically, the valves AV1-3, AV1-5,
AV3-2, AV3-1, AV2-1 are opened, and the other valves are
closed.
[0295] In this state, the pump P5 is actuated under the control of
the system controller 155. Thus, the plating liquid is supplied
into the copper dissolution tank 110a from the plating section 12,
flows over the interior and exterior surfaces of the copper tubes
146 in the copper dissolution tank 110a, and returned into the
plating section 12. In the copper dissolution tank 110a, the copper
tube 146 is deprived of electrons by trivalent iron ions in the
plating liquid, whereby the trivalent iron ions are reduced to
divalent iron ions. Copper ions are leached into the plating liquid
from the copper tubes 146 deprived of the electrons.
[0296] Thus, the copper ions are supplied from the copper tubes
146, while being consumed on the lower surface of the wafer W or
the dummy wafer D during the plating process. On the other hand,
the trivalent iron ions are reduced to the divalent iron ions in
the vicinity of the copper tubes 146, while the divalent iron ions
are oxidized into trivalent iron ions in the vicinity of the anode
76.
[0297] Where the concentrations of the copper ions, the divalent
iron ions and the trivalent iron ions in the plating liquid are not
within the predetermined concentration ranges, the plating process
cannot properly be performed with a poorer capability of filling
the holes or grooves formed in the surface of the wafer W with
copper. Therefore, the concentrations of the copper ions and the
divalent and trivalent iron ions in the plating liquid should be
kept at the predetermined concentration levels (within the
predetermined concentration ranges). That is, the amount of the
copper ions consumed on the lower surface of the wafer W or the
dummy wafer W should substantially be equalized with the amount of
the copper ions leaching out of the copper tubes 146, and the
amount of the divalent iron ions occurring in the vicinity of the
anode 76 should substantially be equalized with the amount of the
trivalent iron ions occurring in the vicinity of the copper tubes
146.
[0298] The copper ion consumption rate at which the copper ions are
consumed in the plating liquid by the plating is determined by the
operation statuses of the respective plating units 20a to 20d. The
copper ion leaching rate at which the copper ions leach into the
plating liquid from the copper tubes 146 in the copper dissolution
tank 110a is determined by the surface area of the copper tubes 146
in contact with the plating liquid, the flow rate of the plating
liquid flowing in the vicinity of the copper tubes 146 and the
concentration of the trivalent iron ions in the plating liquid.
[0299] The inner and outer peripheral surface areas of the copper
tube 146 account for a major percentage of the total surface area
of the copper tube 146. As the dissolution of the copper tube 146
proceeds, the thickness and length of the copper tube 146 are
reduced. However, the reduction rate of the length is negligible.
Therefore, the outer and inner peripheral surface areas of the
copper tube 146 (the total surface area of the copper tube 146) are
considered to be virtually constant before complete dissolution of
the copper tube 146, even if the dissolution of the copper tube 146
proceeds. Whether or not the copper tube 146 is very close to the
complete dissolution is determined on the basis of the output
signal of the weight meter 154a, 154b. The flow rate of the plating
liquid flowing into the copper dissolution tank 110a may be
employed as the flow rate of the plating liquid flowing in the
vicinity of the copper tubes 146.
[0300] Therefore, the system controller 155 determines the pumping
rate of the pump P5 on the basis of the operation statuses of the
plating units 20a to 20d and the output signal of the
absorptiometer 66B indicative of the concentration of the iron
ions. The pumping rate of the pump P5 is regulated at a
predetermined level on the basis of the feedback of the output
signal of the flow meter 123 to the system controller 155. Under
such control, the amount of the copper ions supplied to the plating
liquid is balanced with the amount of the copper ions consumed in
the plating liquid to keep the copper ion concentration virtually
constant in the plating liquid.
[0301] If the dissolution of the copper tubes 146 in the copper
dissolution tank 110a proceeds to an extremely high level, the
total surface area of the copper tubes 146 is rapidly reduced,
making it difficult to supply the copper ions to the plating liquid
at a constant rate. To avoid such an event, the supply of the
plating liquid to the copper dissolution tank 110a is stopped when
the weight of the copper tubes 146 in the copper dissolution tank
110a is reduced below a predetermined level (e.g., 20% to 30% of
the initial weight). Then, the supply of the plating liquid to the
copper dissolution tank 110b is started.
[0302] More specifically, when the system controller 155 judges on
the basis of the signal of the weight meter 154a that the weight of
the copper tube 146 in the copper dissolution tank 110a is reduced
below the predetermined level, the valves AV4-1 and AV4-2 are
opened and the valves AV3-1 and AV3-2 are closed under the control
of the system controller 155. Thus, the plating liquid is
circulated through the plating section 12 and the copper
dissolution tank 110b. Where the copper tubes 146 contained in the
copper dissolution tank 110b have a sufficient weight, the copper
ions can stably be supplied into the plating liquid.
[0303] Since the two copper dissolution tanks 110a, 110b are
provided in the major constituent managing section 2, the copper
ions can constantly be supplied to the plating liquid without
excess and deficiency. Thus, the surface of the wafer W can
properly be copper-plated with the fine holes or grooves thereof
properly filled with copper.
[0304] Next, an explanation will be given to the operation of the
major constituent managing section 2 after the completion of the
plating process in the plating section 12. If the plating liquid is
circulated through the plating liquid container 55 and the copper
dissolution tank 110a or 110b when the plating process is not
performed in any of the plating units 20a to 20d, the concentration
of the copper ions in the plating liquid is increased beyond the
proper concentration range. This is because the copper ions are
continuously supplied to the plating liquid from the copper tubes
146, though the copper ions are not consumed.
[0305] If the circulation of the plating liquid is stopped, the
surfaces of the copper tubes 146 in the copper dissolution tank
110a, 110b are irreversibly deteriorated. Therefore, the surface of
the wafer W cannot properly be copper-plated with a poorer
capability of filling the fine holes or grooves thereof with
copper, when the plating process is performed again in any of the
plating units 20a to 20d by resuming the circulation of the plating
liquid.
[0306] To cope with this, the plating liquid in the copper
dissolution tank 110a, 110b is replaced with the replacement liquid
for prevention of the increase in the concentration of the copper
ions in the plating liquid and the deterioration of the surfaces of
the copper tubes 146 upon the completion of the plating process in
the plating section 12. It is herein assumed that the plating
liquid in the copper dissolution tank 110a is replaced with the
replacement liquid.
[0307] The deterioration of the surfaces of the copper tubes 146
may occur within several hours. On the other hand, the plating
process is often resumed immediately after the completion of the
plating process in the plating section 12 due to a change in the
production plan. In this case, if the plating liquid in the copper
dissolution tank 110a is already replaced with the replacement
liquid, the replacement liquid in the copper dissolution tank 110a
should be replaced again with the plating liquid. The time required
for the replacement of the plating liquid in the copper dissolution
tank 110a is about 5 minutes to about 10 minutes, so that the
productivity is reduced. Therefore, the plating liquid in the
copper dissolution tank 110a is replaced with the replacement
liquid after a lapse of a 2- to 3-hour standby period from the
completion of the plating process in the plating section 12.
[0308] If the plating process is less likely to be resumed
immediately after the completion of the plating process in the
plating section 12, the plating liquid in the copper dissolution
tank 110a may be replaced with the replacement liquid immediately
after the completion of the plating process.
[0309] First, the pump P5 is stopped and all the valves in the
major constituent managing section 2 are closed under the control
of the system controller 155. In turn, the system controller 155
controls the pressure increasing/reducing section 164 to supply air
into the buffer container 111. Thus, the internal pressure of the
buffer container 111 is increased. Then, the valves AV2-2, AV3-1,
AV3-2, AV1-5, AV1-2 are opened under the control of the system
controller 155. Thus, air pressurized in the buffer container 111
is introduced into the annular space 145 through the branch
circulation pipe 119a, so that the plating liquid is forced out of
the copper dissolution tank 110a into the plating liquid container
55 in the plating section 12 through the branch circulation pipe
121a.
[0310] The system controller 155 calculates the weight of the
plating liquid in the copper dissolution tank 110a on the basis of
the output signal of the weight meter 154a, and maintains the
aforesaid conditions until it is judged that almost all the plating
liquid is expelled from the copper dissolution tank 110a. When the
system controller 155 judges that almost all the plating liquid is
expelled from the copper dissolution tank 110a, the valve AV3-3 is
opened for a predetermined period under the control of the system
controller 155. Thus, the plating liquid remaining in the bottom
portion of the copper dissolution tank 110a is virtually completely
discharged through the liquid outlet pipe 149a.
[0311] Subsequently, the valve AV7-1 is opened under the control of
the system controller 155 to introduce deionized water into the
buffer container 111. When it is judged on the basis of the output
signal of the constant volume heck sensor 126 that the surface of
deionized water rises o reach the predetermined level in the buffer
container 111, the valve AV7-1 is closed under the control of the
system controller 155. Thus, a predetermined amount of deionized
water is contained in the buffer container 111.
[0312] In turn, the valves in the major constituent managing
section 2 except the three-way valves AV8-1, AV8-2, AV8-3 are
closed, and air is exhausted from the buffer container 111 by the
pressure increasing/reducing section 164 under the control of the
system controller 155. Thus, the internal pressure of the buffer
container 111 is reduced. Then, the valves AV6-1, AV6-3 are opened
under the control of the system controller 155. Thus, the internal
pressure of the measure cup 129 is also reduced, so that the
undiluted replacement liquid is sucked into the measure cup 129
from the undiluted replacement liquid tank 128 through the
undiluted replacement liquid transport pipe 130.
[0313] During this period, the system controller 155 monitors the
output signal of the constant volume check sensor 133, and judges
whether the surface of the undiluted replacement liquid in the
measure cup 129 reaches the predetermined level. If it is judged
that the surface of the undiluted replacement liquid reaches the
predetermined level, the valves AV6-3, AV6-1 are closed under the
control of the system controller 155. Thus, a predetermined volume
of the undiluted replacement liquid is dispensed in the measure cup
129.
[0314] Then, the valves AV6-2, AV6-4 are opened under the control
of the system controller 155. Thus, the internal pressure of the
measure cup 129 is set at the atmospheric pressure, so that the
undiluted replacement liquid is transported from the measure cup
129 into the buffer container 111 having a lower internal pressure
through the undiluted replacement liquid transport pipe 131 and the
undiluted replacement liquid supply pipe 124 and mixed with the
deionized water in the buffer container 111. When it is judged by
the system controller 155 on the basis of the output signal of the
emptiness check sensor 134 that the measure cup 129 is empty, the
valves AV6-2, AV6-4 are closed under the control of the system
controller 155.
[0315] Thus, the replacement liquid which has a predetermined
composition and a predetermined concentration (e.g., 10% sulfuric
acid aqueous solution) is prepared in the buffer container 111.
[0316] In turn, the system controller 155 controls the valve AV8-3
to establish communication between the buffer container 111 and the
atmosphere. Thus, the internal pressure of the buffer container 111
is set at the atmospheric pressure. Thereafter, the valves AV1-1,
AV1-5, AV3-2, AV3-1, AV2-2 are opened, and the pump P5 is actuated
under the control of the system controller 155. At this time, the
pump P5 is operated only for a predetermined period, or operated
until it is judged on the basis of the output signal of the weight
meter 154a that the copper dissolution tank 110a is filled with the
replacement liquid.
[0317] Thereafter, the pump P5 is stopped, and all the valves in
the major constituent managing section 2 are closed under the
control of the system controller 155. Then, the valves AV1-1, AV1-4
are opened under the control of the system controller 155, whereby
the replacement liquid remaining in the buffer container 111 is
drained. Thus, the replacement of the plating liquid in the copper
dissolution tank 110a with the replacement liquid is completed.
[0318] Thus, the increase in the copper ion concentration of the
plating liquid can be prevented. Further, the deterioration of the
surfaces of the copper tubes 146 can be prevented. Therefore, when
the plating process is performed again in any of the plating units
20a to 20d by circulating the plating liquid through the plating
section 12 and the copper dissolution tank 110a (110b) , the
surface of the wafer W can properly be copper-plated with the fine
holes and grooves thereof properly filled with copper. Even if a
small amount of the replacement liquid of the sulfuric acid aqueous
solution is mixed in the plating liquid, the replacement liquid
does not adversely affect the plating liquid because sulfuric acid
is a supporting electrolyte of the plating liquid.
[0319] In the replacement of the plating liquid with the
replacement liquid, deionized water maybe introduced into and
discharged from the copper dissolution tank 110a before the
introduction of the replacement liquid after the plating liquid is
discharged from the copper dissolution tank 110a. Thus, the copper
dissolution tank 110a is cleaned with deionized water, so that the
amount of the plating liquid mixed in the replacement liquid can be
reduced. The introduction of the deionized water into the copper
dissolution tank 110a can be achieved in substantially the same
manner as the introduction of the replacement liquid into the
copper dissolution tank 110a, except that only deionized water is
introduced into the buffer container 111 from the deionized water
supply source (but the undiluted replacement liquid is not
introduced after the introduction of the deionized water).
[0320] When the replacement liquid filled in the copper dissolution
tank 110a, 110b is replaced again with the plating liquid, the
following operation is performed. First, the replacement liquid is
expelled from the copper dissolution tank 110a, 110b in
substantially the same manner as when the plating liquid is
expelled from the copper dissolution tank 110a, 110b for the
replacement of the plating liquid with the replacement liquid. In
this operation, however, the expelled replacement liquid is drained
by closing the valve AV1-2 and opening the valve AV1-4 under the
control of the system controller 155. Thereafter, all the valves in
the major constituent managing section 2 are closed, and then the
valves AV1-2, AV1-5, AV3-2, AV3-1, AV2-1, for example, are opened
under the control of the system controller 155. Thus, the plating
liquid is introduced into the copper dissolution tank 110a.
[0321] Next, an explanation will be given to an operation to be
performed by the plating section 12 after the completion of the
plating process in the plating section 12.
[0322] Upon detection of the discontinuation of the loading of the
wafer W in the plating unit 20a to 20d, the system controller 155
controls the transport controller 29 to take one of the dummy
wafers D out of the cassette Cd and transport the dummy wafer D
into one of the plating units 20a to 20d. The dummy wafers D are
transported into the respective plating units 20a to 20d in the
same manner.
[0323] In turn, the dummy wafers D are subjected to the plating
process in the respective plating units 20a to 20d according to the
program (recipe) stored in the storage device 155M under the
control of the system controller 155. Where the electrically
conductive film of the dummy wafer D is composed of gold or
platinum, there is no possibility that impurities are leached into
the plating liquid because only the electrically conductive film of
the dummy wafer D is kept in contact with the plating liquid.
[0324] At this time, the amount of the electricity applied between
the cathode 83 and the anode 76 by the plating power source 82 is
reduced to the minimum level required to keep the copper tubes 146
in a proper surface state. That is, an energization period is
limited (for example, by intermittent energization) , or the
amperage of the electric current is reduced as compared with the
plating process performed on the wafer W. This allows for power
saving.
[0325] In this case, the pumping rate of the plating liquid
supplied by the pump P5 (see FIG. 13) is automatically adjusted
correspondingly to the amount of the copper ions consumed on the
dummy wafer D under the control of the system controller 155. Thus,
the copper ion concentration and the divalent and trivalent iron
ion concentrations in the plating liquid are kept generally
constant.
[0326] When the plating process is continued in the plating units
20a to 20d for a predetermined period or when a command for
treating wafers W of another lot is applied to the system
controller 155, the plating of the dummy wafer D is interrupted. In
such a case, the system controller 155 controls the transport
controller 29 to load the dummy wafer D into the bevel etching unit
21a, 21b for removal of the copper film formed on the dummy wafer
D.
[0327] The bevel etching units 21a, 21b can merely deal with two
dummy wafers D at a time, while the plating units 20a to 20d can
perform the plating process on the four dummy wafers D at a time.
Therefore, the copper film removing process is performed twice, for
example, in the respective bevel etching units 21a, 21b for the
removal of the copper films on the four dummy wafers D. Where the
copper films each have a reduced thickness due to the application
of a reduced amount of electricity in the plating process, the
removal of the copper films in the bevel etching units 21a, 21b can
be achieved in a short time. The electrically conductive gold or
platinum films of the dummy wafers D can completely be exposed by
the etching.
[0328] Thereafter, the upper and lower surfaces of the dummy wafers
D are rinsed with the rinse liquid. As required, the dummy wafers D
are loaded into the cleaning units 22a, 22b thereby to be further
cleaned under the control of the system controller 155.
[0329] Where the command for the treatment of wafers W of another
lot is issued, the system controller 155 thereafter controls the
transport controller 29 to accommodate all the dummy wafers D in
the cassette Cd and then start the treatment of the wafers W.
[0330] On the other hand, where the command for the treatment of
wafers W of another lot is not issued, the system controller 155
controls the transport controller 29 to return the dummy wafers D
into the plating units 20a to 20d to perform the plating process
again on the dummy wafers D.
[0331] Thus, the plating process and the copper film removing
process are repeatedly performed on the dummy wafers D, until the
command for the treatment of wafers W of another lot is inputted to
the system controller 155. When the command for the treatment of
wafers W of another lot is issued during the plating process on the
dummy wafers D, the dummy wafers D are subjected to the copper film
removing process and the cleaning process and then accommodated in
the cassette Cd.
[0332] Even during discontinuation of the plating process on the
wafer W, copper ions are continuously leached out of the copper
tubes 146 in the copper dissolution tank 110a, 110b by performing
the plating process on the dummy wafers D. Thus, the deterioration
of the surfaces of the copper tubes 146 can be prevented.
Therefore, the surface of the wafer W can properly be copper-plated
with the fine holes or grooves thereof properly filled with copper,
whenever the plating process on the wafer W is resumed.
[0333] As described above, it is also possible to prevent the
deterioration of the surfaces of the copper tubes 146 (copper
supply source) by replacing the plating liquid with the replacement
liquid in the copper dissolution tank 110a, 110b. In this case,
there is no need for the electrical energization between the anode
76 and the cathode 83, so that the energy is saved and the
deterioration of the plating liquid is prevented. In this case,
however, time is required for replacing the plating liquid with the
replacement liquid and replacing the replacement liquid with the
plating liquid in the copper dissolution tank 110a, 110b as
described above. Therefore, the treatment of the wafer W cannot
immediately be started when the replacement liquid is contained in
the copper dissolution tanks 110a, 110b. Further, about 200 ml to
about 300 ml of the plating liquid, for example, is wasted for the
replacement.
[0334] In contrast, where the plating process is performed on the
dummy wafers D to keep the copper tubes 146 in a proper surface
state, the plating process on the wafer W can be started
immediately after the dummy wafers D are subjected to the copper
film removing process, then cleaned and dried, and accommodated in
the cassette Cd. The wafer W may be transported into the plating
unit 20a to 20d so as to start the plating process on the wafer W
during the copper film removing process on the dummy wafers D in
the bevel etching units 21a, 21b. Further, the waste of the plating
liquid can be eliminated which maybe entailed where the plating
liquid is replaced with the replacement liquid.
[0335] On the other hand, the plating process on the dummy wafers D
entails energy consumption for the electrical energization between
the anode 76 and the cathode 83 and the deterioration of the
plating liquid. Since the aforesaid two methods for keeping the
copper tubes 146 in a proper surface state each have an advantage
and a disadvantage, these methods may selectively be employed.
Where the plating process on the wafer W is discontinued for two,
three or more hours, for example, the plating liquid may be
replaced with the replacement liquid in the copper dissolution tank
110a, 110b. Where the plating process on the wafer W is
discontinued for a shorter period, the plating process on the dummy
wafers D may be performed.
[0336] By keeping the dummy wafer D in contact with the surface of
the plating liquid filled in the plating vessel 61a to 61d, the
plating vessel 61a to 61d is lidded with the dummy wafer D.
Therefore, the evaporation of the plating liquid can be prevented
thereby to mitigate a change in the composition of the plating
liquid, even when the apparatus is not electrically energized.
[0337] By continuously performing the plating process on the wafer
W or the dummy wafer D in the plating unit 20a to 20d, the
crystallization of the effective constituents of the plating liquid
is prevented which may other wise occur due to the drying of the
plating liquid adhering onto the sealing surface 80s of the cathode
ring 80. Where the plating process is discontinued for a long
period, the effective constituents of the plating liquid are liable
to be crystallized on the sealing surface 80s. The crystals of the
effective constituents prevent intimate contact between the wafer W
and the abutment portion 80a when the plating process on the wafer
W is resumed. In addition, the crystals damage the sealing surface
80s, resulting in a permanent sealing failure. Such events can be
avoided by continuously performing the plating process for
prevention of the drying of the sealing surface 80s. Thus, the
plaiting liquid is prevented from leaking from a gap between the
abutment portion 80a and the wafer W.
[0338] The plating process on the dummy wafer D is performed in the
respective plating units 20a to 20d, so that the abutment portions
80a in the plating units 20a to 20d are less liable to suffer from
the sealing failure.
[0339] The plating process on the dummy wafer D is automatically
started upon the discontinuation of the loading of the wafer W in
the plating unit 20a to 20d, so that the operator does not have to
perform any operation for discontinuation of the plating process on
the wafer W. The dummy wafers D are each repeatedly used in the
plating section 12 until the service life of the electrically
conductive film thereof ends due to wear-out. Hence, there is no
need to frequently perform a maintenance operation.
[0340] While one embodiment of the present invention has thus been
described, the invention may be embodied in any other ways. The
dummy wafers D are accommodated in the cassette C placed on the
cassette stage 16 in the plating apparatus in accordance with the
embodiment described above. However, a place for accommodating the
dummy wafers D is not limited to the cassette C placed on the
cassette stage 16, but may be any place which is accessible by the
transport robot TR within the wafer treating section 1.
[0341] The units for removing the copper film formed on the dummy
wafer D (for refreshing the dummy wafer D) are not limited to the
bevel etching units 21a, 21b. For example, components required for
the removal of the copper film may be attached to the plating units
20a to 20d or the cleaning units 22a, 22b. Alternatively, units
(chambers) dedicated to the removal of the copper film may be
provided in any position accessible by the transport robot TR. The
method for the removal of the copper film formed on the dummy wafer
D is not limited to the chemical etching, but may be an
electrolytic etching, for example.
[0342] While the present invention has been described in detail by
way of the embodiment thereof, it should be understood that the
foregoing disclosure is merely illustrative of the technical
principles of the present invention but not limitative of the same.
The spirit and scope of the present invention are to be limited
only by the appended claims.
[0343] This application corresponds to Japanese Patent Application
No. 2002-318951 filed with the Japanese Patent Office on Oct. 31,
2002, the disclosure of which is incorporated herein by
reference.
* * * * *