U.S. patent application number 12/771056 was filed with the patent office on 2010-09-02 for plating apparatus and plating method.
Invention is credited to Brett Baker-O'Neal, Emanuel Cooper, Hariklia Deligianni, Kunihito Ide, Hiroyuki Kanda, Junji Kunisawa, Keiichi KURASHINA, Koji Mishima, Shinya Morisawa, Mizuki Nagai, Hidenao Suzuki, Philippe Vereecken, Satoru Yamamoto.
Application Number | 20100219078 12/771056 |
Document ID | / |
Family ID | 36205203 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100219078 |
Kind Code |
A1 |
KURASHINA; Keiichi ; et
al. |
September 2, 2010 |
PLATING APPARATUS AND PLATING METHOD
Abstract
A plating apparatus securely carries out a flattening plating of
a substrate to form a plated film having a flat surface without
using a costly mechanism, and without applying an extra plating to
the substrate. The plating apparatus includes a substrate holder; a
cathode section having a seal member for watertightly sealing a
peripheral portion of the substrate, and a cathode electrode for
supplying an electric current to the substrate; an anode disposed
in a position facing the surface of the substrate; a porous member
disposed between the anode and the surface of the substrate; a
constant-voltage control section for controlling a voltage applied
between the cathode electrode and the anode at a constant value;
and a current monitor section for monitoring an electric current
flowing between the cathode electrode and the anode, and feeding
back a detection signal to the constant-voltage control
section.
Inventors: |
KURASHINA; Keiichi; (Tokyo,
JP) ; Nagai; Mizuki; (Tokyo, JP) ; Yamamoto;
Satoru; (Tokyo, JP) ; Kanda; Hiroyuki; (Tokyo,
JP) ; Mishima; Koji; (Tokyo, JP) ; Morisawa;
Shinya; (Tokyo, JP) ; Kunisawa; Junji; (Tokyo,
JP) ; Ide; Kunihito; (Tokyo, JP) ; Suzuki;
Hidenao; (Tokyo, JP) ; Cooper; Emanuel;
(Scarsdale, NY) ; Vereecken; Philippe; (Leuven,
BE) ; Baker-O'Neal; Brett; (Sleepy Hollow, NY)
; Deligianni; Hariklia; (Tenafly, NJ) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
36205203 |
Appl. No.: |
12/771056 |
Filed: |
April 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11245490 |
Oct 7, 2005 |
7736474 |
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12771056 |
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11044375 |
Jan 28, 2005 |
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11245490 |
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Current U.S.
Class: |
205/81 |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 21/12 20130101; H01L 21/2885 20130101; C25D 5/18 20130101;
C25D 7/123 20130101; H01L 21/7684 20130101; H01L 21/76849 20130101;
C25D 5/22 20130101; C25D 17/12 20130101; C25D 17/002 20130101; H01L
21/76877 20130101; C25D 17/005 20130101; C25D 17/004 20130101 |
Class at
Publication: |
205/81 |
International
Class: |
C25D 21/12 20060101
C25D021/12; C25D 5/00 20060101 C25D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2004 |
JP |
2004-22178 |
Jan 30, 2004 |
JP |
2004-23256 |
Claims
1-37. (canceled)
38. A plating method for plating a surface, to be plated, of a
substrate to form a plated film having a flat surface while
embedding fine recesses for interconnects with the plated film, the
plating method comprising: providing a porous member composed of a
water-retentive material between the substrate and an anode;
filling a space between the surface, to be plated, of the substrate
and the anode with a plating solution; carrying out plating by
repeating contact and non-contact between the porous member and the
surface, to be plated, of the surface and applying a constant
voltage to between the surface, to be plated, of the substrate and
the anode during one of the contact time and the non-contact time
while detecting an electric current flowing between the surface, to
be plated, of the substrate and the anode; and stopping supplying
an electric current to between the surface, to be plated, of the
substrate and the anode after elapse of a predetermined period of
time from a point of time at which the electric current becomes
constant.
39. The plating method according to claim 38, wherein the plating
is carried out by applying a constant voltage to between the
surface, to be plated, of the substrate and the anode while keeping
the porous member in contact with the surface, to be plated, of the
substrate and motionless relative to the surface to be plated.
40. A plating method for plating a surface, to be plated, of a
substrate to form a plated film having a flat surface while
embedding fine recesses for interconnects with the plated film, the
plating method comprising: providing a porous member composed of a
water-retentive material between the substrate and an anode;
filling a space between the surface, to be plated, of the substrate
and the anode with a plating solution; carrying out plating by
repeating contact and non-contact between the porous member and the
surface, to be plated, of the surface and applying constant
voltages, which differ between the contact time and the non-contact
time, to between the surface, to be plated, of the substrate and
the anode while detecting an electric current flowing between the
surface, to be plated, of the substrate and the anode; and stopping
supplying an electric current to between the surface, to be plated,
of the substrate and the anode after elapse of a predetermined
period of time from a point of time at which the electric current
becomes constant.
41. The plating method according to claim 40, wherein the plating
is carried out by applying a constant voltage to between the
surface, to be plated, of the substrate and the anode while keeping
the porous member in contact with the surface, to be plated, of the
substrate and motionless relative to the surface to be plated.
42. A plating method for plating a surface, to be plated, of a
substrate to form a plated film having a flat surface while
embedding fine recesses for interconnects with the plated film, the
plating method comprising providing a porous member composed of a
water-retentive material between the substrate and an anode;
filling a space between the surface, to be plated, of the substrate
and the anode with a plating solution; carrying out plating by
repeating contact and non-contact between the porous member and the
surface, to be plated, of the surface and passing a constant
electric current between the surface, to be plated, of the
substrate and the anode during one of the contact time and the
non-contact time while detecting a voltage value between the
surface, to be plated, of the substrate and the anode; and stopping
supplying an electric current to between the surface, to be plated,
of the substrate and the anode after elapse of a predetermined
period of time from a point of time at which the voltage value
becomes constant
43. The plating method according to claim 42, wherein the plating
is carried out by passing a constant electric current between the
surface, to be plated, of the substrate and the anode while keeping
the porous member in contact with the surface, to be plated, of the
substrate and motionless relative to the surface to be plated.
44. A plating method for plating a surface, to be plated, of a
substrate to form a plated film having a flat surface while
embedding fine recesses for interconnects with the plated film, the
plating method comprising: providing a porous member composed of a
water-retentive material between the substrate and an anode;
filling a space between the surface, to be plated, of the substrate
and the anode with a plating solution; carrying out plating by
repeating contact and non-contact between the porous member and the
surface, to be plated, of the surface and passing constant electric
currents which differ between the contact time and the non-contact
time, between the surface, to be plated, of the substrate and the
anode while detecting a voltage value between the surface, to be
plated, of the substrate and the anode; and stopping supplying an
electric current to between the surface, to be plated, of the
substrate and the anode after elapse of a predetermined period of
time from a point of time at which the voltage value becomes
constant.
45. The plating method according to claim 44, wherein the plating
is carried out by passing a constant electric current between the
surface, to be plated, of the substrate and the anode while keeping
the porous member in contact with the surface, to be plated, of the
substrate and motionless relative to the surface to be plated.
Description
[0001] This is a continuation application of U.S. patent
application Ser. No. 11/044,375, filed Jan. 28, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a plating apparatus and a
plating method, and more particularly to a plating apparatus and a
plating method useful for forming interconnects by filling a
conductive metal (interconnect material) such as copper (Cu) into
fine interconnect patterns (recesses) formed in a substrate such as
a semiconductor substrate.
[0004] 2. Description of the Related Art
[0005] In recent years, instead of using aluminum or aluminum
alloys as a material for forming interconnect circuits on a
semiconductor substrate, there is an eminent movement towards using
copper (Cu) that has a low electric resistivity and high
electromigration resistance. Copper interconnects are generally
formed by forming fine recesses for interconnects, such as trenches
or via holes in a circuit form, in a semiconductor substrate,
embedding the fine recesses with copper (interconnect material) by
copper plating, and removing a copper layer (plated film) at
portions other than the fine recesses by CMP or the like. In this
damascene process, from the viewpoint of reducing loads on
subsequent CMP, it is desirable that a copper plated film be
deposited selectively in trenches or via holes in a circuit form,
and that the amount of copper plated film deposited on portions
other than the trenches or via holes be small. In order to achieve
such an object, there have heretofore been proposed various ideas
regarding a plating solution, such as composition in a bath of a
plating solution or a brightener used in a plating solution.
[0006] Upon the electroplating for forming the copper layer, a
copper sulfate plating solution containing copper sulfate and
sulfuric acid in its composition is generally employed as a plating
solution.
[0007] In recent years, more and more fine interconnects are formed
in copper interconnects forming process for semiconductor devices,
and design rules for such fine interconnects are considered to be
changing from the 0.18 .mu.m generation to the 0.13 .mu.m
generation and further to the 0.10 .mu.m generation. Depending on
circumstances, the advent of the seed-layer-less generation of
semiconductor devices may not be impossible. With those more and
more fine interconnects, unless the thickness of the seed layer is
further reduced, the seed layer overhangs at the inlets of fine
recesses, tending to produce voids in the plating process. In the
0.18 .mu.m generation of design rules, the thickness of the seed
layer is generally in the range from about 150 to 200 nm on the
flat surface of the substrate. In the 0.13 .mu.m generation of
design rules, the thickness of the seed layer is about 50 nm in
order to prevent voids from being produced in the plating process.
In the 0.10 .mu.m generation of design rules, the thickness of the
seed layer will possibly be reduced to a range from about 5 to 25
nm.
[0008] A plating apparatus having the following configuration has
been known as this type of plating apparatus used for plating to
form fine interconnects having high aspect ratios. A substrate is
held in such a state that a surface (surface to be plated) of the
substrate faces upward (in a face-up manner). A cathode electrode
is brought into contact with a peripheral portion of the substrate
so that the surface of the substrate serves as a cathode. An anode
is disposed above the substrate. While a space between the
substrate and the anode is filled with a plating solution, a
plating voltage is applied between the substrate (cathode) and the
anode to plate a surface (surface to be plated) of a substrate (for
example, see Japanese laid-open patent publication No.
2002-506489).
[0009] In a plating apparatus in which a substrate is held and
plated in single wafer processing while a surface of the substrate
faces upward, a distribution of a plating current can be made more
uniform over an entire surface of the substrate to improve
uniformity of a plated film over the surface of the substrate.
Generally, the substrate is transferred and subjected to various
processes in such a state that a surface of the substrate faces
upward. Accordingly, it is not necessary to turn the substrate at
the time of plating.
[0010] Meanwhile, in order to deposit a copper plated film
selectively in trenches in a circuit form or the like, there has
been known a method of bringing a porous member into contact with a
substrate such as a semiconductor wafer, and plating the substrate
while relatively moving the porous member in a contact direction
(for example, see Japanese laid-open patent publication No.
2000-232078).
[0011] In order to detect the endpoint of plating and determine the
timing of terminating plating in a plating apparatus of the type
described above, there are generally employed a method in which
plating is stopped when the plating time has reached a
predetermined time, a method in which the quantity of electricity
that has passed between a cathode and an anode is integrated, and
plating is stopped when the integrated value has reached a
predetermined value, and a method in which a thickness of a plated
film is measured with a film-thickness monitor provided in the
plating apparatus, and plating is stopped when the measured film
thickness has reached a predetermined value.
[0012] For performing copper electroplating on the surface of a
substrate, the outer circumferential portion of the substrate is
come in contact with electrodes (electric contacts) to pass an
electric current through the substrate. As the seed layer is
thinner, the sheet resistance becomes higher immediately after the
substrate starts to be plated, causing the plating current to
concentrate on the outer circumferential portion of the substrate.
The within-wafer thickness uniformity cannot be controlled only by
a single shield plate for electric field correction.
[0013] The applicant has proposed a plating apparatus wherein a
plating power source is connected individually to a plurality of
split anodes to increase a current density at those split anodes
positioned in a central area of the substrate to a level higher
than at those split anodes positioned in a peripheral area of the
substrate only during a certain period of time in which an initial
plated film is formed on the substrate, thereby preventing the
plating current from concentrating on the outer circumferential
portion of the substrate, but allowing the plating current to flow
to the central area of the substrate to make it possible to form a
uniform plated film even if the sheet resistance is high (for
example, see Japanese laid-open patent publication No.
2002-129383).
SUMMARY OF THE INVENTION
[0014] The method of stopping plating when the plating time has
reached a predetermined time and the method of stopping plating
when the integrated quantity of electricity has reached a
predetermined value have the advantage of being simple and low
cost. When using these methods in a so-called flattening plating
which is employed for forming interconnects by, for example, the
above-described damascene technique, however, a larger amount of
plating than the necessary plating amount must be applied to a
substrate because of the necessity of taking account of process
variation. The method using a film-thickness monitor involves the
use of a generally expensive monitor, leading to an increased cost
of the plating apparatus.
[0015] In the case of ordinary or common plating, there is no
definite law concerning a change in current value or voltage value
during plating. Accordingly, a method has not been generally
employed which involves continually monitoring a change in current
value or voltage value during plating, and stopping plating when
the current value or voltage value has reached a predetermined
value.
[0016] As the seed layer becomes thinner and eventually the seed
layer is eliminated, resulting in a higher sheet resistance.
Therefore, it is considered difficult to form a plated film of more
uniform thickness over the entire surface to be plated of the
substrate with fine interconnect recesses formed therein, only by
using the split anodes, and also to reliably embed the plated metal
within the fine recesses without forming voids therein.
[0017] The present invention has been made in view of the above
situation in the related art. It is therefore a first object of the
present invention to provide a plating apparatus and a plating
method which can securely carry out a so-called flattening plating
of a substrate to form a plated film having a flat surface without
using a costly mechanism, such as a film-thickness monitor, and
without applying an extra plating to the substrate.
[0018] It is a second object of the present invention to provide a
plating apparatus and a plating method which are capable of forming
a plated film of more uniform thickness over the entire surface to
be plated of a substrate, even if the substrate has a higher sheet
resistance, and of reliably embedding plated metal within fine
recesses without forming voids therein.
[0019] The present invention provides a plating apparatus,
comprising: a substrate holder for holding a substrate; a cathode
section having a seal member for contact with a peripheral portion
of the surface, to be plated, of the substrate held by the
substrate holder to watertightly seal the peripheral portion, and a
cathode electrode for contact with the substrate to supply an
electric current to the substrate; a vertically-movable anode
disposed in a position facing the surface, to be plated, of the
substrate; a porous member composed of a water-retentive material,
disposed between the anode and the surface, to be plated, of the
substrate; a constant-voltage control section for controlling a
voltage applied between the cathode electrode and the anode at a
constant value; and a current monitor section for monitoring an
electric current flowing between the cathode electrode and the
anode, and feeding back a detection signal to the constant-voltage
control section.
[0020] In the case of a plating method generally called flattening
plating, unlike an ordinary plating, there is a definite law
concerning current values or voltage values during plating. In
particular, when carrying out plating under a constant-current
control, the voltage value increases with the progress of plating
and becomes constant at a certain value, as shown in FIG. 1. When
carry out plating under a constant-voltage control, on the other
hand, the current value decreases with the progress of plating and
becomes constant at a certain value, as shown in FIG. 2. The reason
for this phenomenon is as follows:
[0021] When carrying out copper plating of a surface of a substrate
W having a large number of interconnect trenches 4 covered with a
seed layer (conductive film) 6, the area of the surface, to be
plated, at the beginning of plating is the surface area of the seed
layer 6 including the interior of the interconnect trenches 4, as
shown in FIG. 3A, whereas after completion of a copper layer
(plated film) 7 having a flat surface, the area of the surface, to
be plated, is the surface area of the flat copper layer 7, as shown
in FIG. 3B. Thus, the area of the surface, to be plated, gradually
decreases as the thickness of the plated film increases with the
progress of plating, and becomes substantially constant after
completion of the copper layer 7 having a flat surface.
[0022] Accordingly, by utilizing the above phenomenon, in
particular, by carrying out plating of a substrate under a
constant-voltage control, monitoring the current value during
plating to detect a point of time at which the current value
becomes constant, and stopping the plating based on the detected
point of time, it becomes possible to obtain the intended plated
film with a flat surface without applying an extra plating to the
substrate.
[0023] The constant-voltage control section and the current monitor
section may be provided independently or in combination. For
example, it is possible to use a rectifier, having a
constant-voltage control section and a current monitor section,
which automatically stops feeding of electricity according to an
installed program when a monitored current becomes constant. The
use of such a device can simplify the apparatus and may possibly
reduce the cost.
[0024] The present invention also provides another plating
apparatus, comprising: a substrate holder for holding a substrate;
a cathode section having a seal member for contact with a
peripheral portion of the surface, to be plated, of the substrate
held by the substrate holder to watertightly seal the peripheral
portion, and a cathode electrode for contact with the substrate to
supply an electric current to the substrate; a vertically-movable
anode disposed in a position facing the surface, to be plated, of
the substrate; a porous member composed of a water-retentive
material, disposed between the anode and the surface, to be plated,
of the substrate; a constant-current control section for
controlling an electric current flowing between the cathode
electrode and the anode at a constant value; and a voltage monitor
section for monitoring the voltage between the cathode electrode
and the anode, and feeding back a detection signal to the
constant-current control section.
[0025] As described above, when carrying out plating under a
constant-current control by a plating method generally called
flattening plating, the voltage value increases with the progress
of plating and becomes constant at a certain value. Accordingly, by
carrying out plating of a substrate under a constant-current
control, monitoring the voltage value during plating to detect a
point of time at which the voltage value becomes constant, and
stopping the plating based on the detected point of time, it
becomes possible to obtain the intended plated film with a flat
surface without applying an extra plating to the substrate.
[0026] The constant-current control section and the voltage monitor
section may be provided independently or in combination. For
example, it is possible to use a rectifier, having a
constant-current control section and a voltage monitor section,
which automatically stops feeding of electricity according to an
installed program when a monitored voltage becomes constant. The
use of such a device can simplify the apparatus and may possibly
reduce the cost.
[0027] The plating apparatus may further comprise a pressing
mechanism for pressing the porous member against the surface, to be
plated, of the substrate, held by the substrate holder, at a
desired pressure.
[0028] By carrying out plating while keeping the porous member
pressing on the surface, to be plated, of the substrate held by the
substrate holder, a plated film with a flatter surface can be
obtained without being influenced by variation (difference in width
and size) of the configuration of interconnect pattern.
[0029] The plating apparatus may further comprise a driving
mechanism for making a relative movement between the porous member
and the substrate.
[0030] The relative movement may be a vibrational movement
involving a repetition of contact and non-contact between the
porous member and the surface, to be plated, of the substrate.
[0031] By carrying out plating while repeating contact and
non-contact between the porous member and the surface, to be
plated, of the substrate, a plated film with a flatter surface can
be obtained without being influenced by variation of the
configuration of interconnect pattern.
[0032] Alternatively, the relative movement may be a rotational
and/or a translational movement of at least one of the porous
member and the substrate, the movement being made while the porous
member and the surface, to be plated, of the substrate are kept in
contact with each other.
[0033] By carrying out plating while, for example, rubbing the
porous member against the surface, to be plated, of the substrate,
a plated film with a flatter surface can be obtained without being
influenced by variation of the configuration of interconnect
pattern.
[0034] The present invention also provides a plating method,
comprising: providing a porous member composed of a water-retentive
material between a substrate and an anode; filling the space
between a surface, to be plated, of the substrate and the anode
with a plating solution; carrying out plating by applying a
constant voltage to between the surface, to be plated, of the
substrate and the anode while detecting an electric current flowing
between the surface, to be plated, of the substrate and the anode;
and stopping supplying an electric current to between the surface,
to be plated, of the substrate and the anode after elapse of a
predetermined period of time from a point of time at which the
current value becomes constant.
[0035] In the preferred embodiment of the present invention, the
plating is carried out by applying a constant voltage to between
the surface, to be plated, of the substrate and the anode while
rubbing the porous member against the surface, to be plated, of the
substrate.
[0036] The plating may be carried out by applying a constant
voltage to between the surface, to be plated, of the substrate and
the anode while keeping the porous member in contact with the
surface, to be plated, of the substrate and motionless relative to
the surface to be plated.
[0037] In the preferred embodiment of the present invention,
contact and non-contact between the porous member and the surface,
to be plated, of the substrate is repeated during plating, and the
plating is carried out by applying a constant voltage to between
the surface, to be plated, of the substrate and the anode during
one of the contact time and the non-contact time.
[0038] Contact and non-contact between the porous member and the
surface, to be plated, of the substrate is repeated during plating,
and the plating may be carried out by applying constant voltages,
which differ between the contact time and the non-contact time, to
between the surface, to be plated, of the substrate and the
anode.
[0039] The present invention also provides another plating method,
comprising: providing a porous member composed of a water-retentive
material between a substrate and an anode; filling the space
between the surface, to be plated, of the substrate and the anode
with a plating solution; carrying out plating by passing a constant
electric current between the surface, to be plated, of the
substrate and the anode while detecting the voltage between the
surface, to be plated, of the substrate and the anode; and stopping
supplying an electric current to between the surface, to be plated,
of the substrate and the anode after elapse of a predetermined
period of time from a point of time at which the voltage value
becomes constant.
[0040] In the preferred embodiment of the present invention, the
plating is carried out by passing a constant electric current
between the surface, to be plated, of the substrate and the anode
while rubbing the porous member against the surface, to be plated,
of the substrate.
[0041] The plating may be carried out by passing a constant
electric current between the surface, to be plated, of the
substrate and the anode while keeping the porous member in contact
with the surface, to be plated, of the substrate and motionless
relative to the surface to be plated.
[0042] In the preferred embodiment of the present invention,
contact and non-contact between the porous member and the surface,
to be plated, of the substrate is repeated during plating, and the
plating is carried out bypassing a constant electric current
between the surface, to be plated, of the substrate and the anode
during one of the contact time and the non-contact time.
[0043] Contact and non-contact between the porous member and the
surface, to be plated, of the substrate may be repeated during
plating, and the plating is carried out by passing constant
electric currents, which differ between the contact time and the
non-contact time, between the surface, to be plated, of the
substrate and the anode.
[0044] The predetermined period of time is preferably 0 second.
[0045] Stopping supplying of an electric current immediately after
the completion of a flat plated film can prevent application of an
extra plating to the substrate. On the other hand, a plated film
having a flatter surface can be obtained by stopping supplying of
an electric current after an elapse of several seconds from the
point of time at which the voltage value becomes constant to carry
out several-second additional plating.
[0046] The present invention also provides still another plating
apparatus comprising: a substrate holder for holding a substrate; a
cathode section having a seal member for contact with a peripheral
portion of a surface, to be plated, of the substrate held by the
substrate holder to watertightly seal the peripheral portion, and a
cathode electrode for contact with the substrate to supply an
electric current to the substrate; an anode disposed in a position
facing the surface, to be plated, of the substrate; a high
resistance structure made of a water-retentive material, disposed
between the anode and the surface, to be plated, of the substrate;
and a drive mechanism for making a relative movement between the
high resistance structure and the substrate; wherein the anode has
a potential gradient.
[0047] Preferably, the anode comprises an insoluble anode.
[0048] If the anode comprises an insoluble anode, then the anode is
prevented from changing its shape, and a constant discharged state
can be maintained at all times without the need for replacing the
anode.
[0049] Preferably, the anode comprises a plurality of split anodes
of desired shape.
[0050] With the above arrangement, only during a certain period in
which an initial plated film is formed on the substrate, for
example, the current densities at those split anodes which are
positioned in a central area of the substrate are made higher than
those split anodes which are positioned in a circumferential area
thereof, thus preventing a plating current from concentrating on
the outer circumferential area of the substrate, and allowing a
plating current to flow also to the central area of the substrate.
Furthermore, a large resistance is developed in the high resistance
structure that can retain the plating solution therein to the
extent that the sheet resistance of the surface of the substrate is
negligible. Therefore, even if the substrate has a higher sheet
resistance, the difference in current density over the surface of
the substrate due to the sheet resistance of the substrate are
reduced to make it possible to reliably form a plated film of more
uniform film thickness.
[0051] The split anodes may have concentric or chip shapes.
[0052] If the split anodes comprise a plurality of concentric split
anodes, for example, then the current density can be changed
between the central area and the circumferential area. If the split
anodes comprise a plurality of split anodes in the form of chips,
then current density can be changed between a certain portion of
the substrate and another portion thereof. The concentric split
anodes and the split anodes in the form of chips may be combined
with each other.
[0053] In a preferred embodiment of the present invention, at least
one of the split anodes is disposed in a position where the
distance between the one of the split anodes and the surface, to be
plated, of the substrate held by the substrate holder is different
from the distance between another one of the split anodes and the
surface, to be plated, of the substrate.
[0054] With the above arrangement, the surfaces of the split anodes
facing the substrate are staggered to make the distance between the
anode and the surface, to be plated, of the substrate different
partially, thereby making it possible to adjust the distribution of
current densities between the anode and the surface, to be plated,
of the substrate.
[0055] In a preferred embodiment of the present invention, the
plating apparatus further comprises a rectifying mechanism for
making a current or a voltage supplied between at least one of the
split anodes and the surface, to be plated, of the substrate held
by the substrate holder, different from a current or a voltage
supplied between another one of the split anodes and the surface,
to be plated, of the substrate held by the substrate holder.
[0056] The regulating mechanism is capable of changing, as desired,
a current or a voltage supplied between a desired one of the split
anodes and the surface, to be plated, of the substrate, thereby to
adjust the distribution of current densities between the anode and
the surface, to be plated, of the substrate.
[0057] The rectifying mechanism may comprise a plurality of
rectifiers associated with the respective split anodes or
respective split anode groups.
[0058] Alternatively, the rectifying mechanism may comprise a
single rectifier having elements or parts for changing a resistance
for each of the split anodes or split anode groups.
[0059] With the above arrangement, since the single rectifier is
used to change the resistance for each of the split anodes or split
anode groups, the plating apparatus is simplified in structure.
[0060] Preferably, the rectifying mechanism has a mechanism for
optimizing a distribution of currents or voltages supplied between
the split anodes and the surface to be plated of the substrate held
by the substrate holder.
[0061] With the above arrangement, the distribution of current
densities between the anode and the surface, to be plated, of the
substrate, for example, can automatically be optimized.
[0062] The present invention also provides still another plating
method comprising: providing a substrate having fine recesses
covered with a barrier layer and/or a seed layer; disposing an
anode having a plurality of split anodes in a position facing a
surface, to be plated, of the substrate which is brought into
contact with a cathode electrode so as to be supplied with an
electric current; disposing a high resistance structure made of a
water-retentive material between the substrate and the anode; and
controlling, in an initial plating stage, a distribution of
currents or voltages supplied between the split anodes and the
surface, to be plated, of the substrate so as to be large in a
central area of the substrate and small in a circumferential area
thereof, thereby filling plated metal in the fine recesses.
[0063] The present invention also provides still another plating
method comprising: providing a substrate having fine recesses
covered with a barrier layer and/or a seed layer; disposing an
anode having a plurality of split anodes in a position facing a
surface, to be plated, of the substrate which is brought into
contact with a cathode electrode so as to be supplied with an
electric current; disposing a high resistance structure made of a
water-retentive material between the substrate and the anode; and
changing a distribution of currents or voltages supplied between
the split anodes and the surface, to be plated, of the substrate
depending on an amount of plating deposition, thereby filling
plated metal in the fine recesses.
[0064] The present invention also provides still another plating
method comprising: providing a substrate having fine recesses
covered with a barrier layer and/or a seed layer; disposing an
anode having a plurality of split anodes in a position facing a
surface, to be plated, of the substrate which is brought into
contact with a cathode electrode so as to be supplied with an
electric current; disposing a high resistance structure made of a
water-retentive material between the substrate and the anode; and
changing a distribution of currents or voltages supplied between
the split anodes and the surface, to be plated, of the substrate
depending on the shape of a pattern of the fine recesses formed in
the surface of the substrate, thereby filling plated metal in the
fine recesses.
[0065] The barrier layer and/or the seed layer covering the fine
recesses may be made of Cu, Ti, V, Cr, Ni, Zr, Nb, Mo, Ta, Hf, W,
Ru, Rh, Pd, Ag, Au, Pt, or Ir, or a nitride thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] FIG. 1 is a graph showing the relationship between voltage
value and time in flattening plating as carried out under a
constant-current control;
[0067] FIG. 2 is a graph showing the relationship between current
value and time in flattening plating as carried out under a
constant-voltage control;
[0068] FIG. 3A is a cross-sectional diagram showing the state of
the substrate at the beginning of flattening plating, and FIG. 3B
is a cross-sectional diagram showing the state of the substrate
upon completion of the flattening plating;
[0069] FIG. 4A through 4D are views showing an example for forming
interconnects in the semiconductor device in a sequence of
steps;
[0070] FIG. 5 is a plan view of a substrate processing apparatus
incorporating a plating apparatus according to an embodiment of the
present invention;
[0071] FIG. 6 is a schematic view showing an essential part of the
plating apparatus shown in FIG. 5;
[0072] FIG. 7 is a schematic view showing another driving mechanism
for making a relative motion between the porous member (lower pad)
and the substrate held by the substrate stage;
[0073] FIGS. 8A through 8D are diagrams illustrating a plating
method in which contact and non-contact between the lower pad
(porous member) and the surface (surface to be plated) of a
substrate is repeated, and a current or voltage is applied during
one of the contact time and the non-contact time;
[0074] FIG. 9 is a schematic view showing an essential part of a
plating apparatus according to another embodiment of the present
invention;
[0075] FIG. 10 is a systematic diagram showing an example of a
plating solution management system;
[0076] FIG. 11 is a front cross-sectional view showing an example
of a cleaning and drying apparatus shown in FIG. 5;
[0077] FIG. 12 is a plan view showing an example of the cleaning
and drying apparatus shown in FIG. 5;
[0078] FIG. 13 is a schematic view showing an example of a bevel
etching and backside cleaning apparatus shown in FIG. 5;
[0079] FIG. 14 is a plan cross-sectional view showing an example of
a heat treatment apparatus shown in FIG. 5;
[0080] FIG. 15 is a plan cross-sectional view showing an example of
the heating treatment apparatus shown in FIG. 5;
[0081] FIG. 16 is a front view of a pretreatment apparatus shown in
FIG. 5 at the time of substrate transfer;
[0082] FIG. 17 is a front view of the pretreatment apparatus shown
in FIG. 5 at the time of chemical treatment;
[0083] FIG. 18 is a front view of the pretreatment apparatus shown
in FIG. 5 at the time of rinsing;
[0084] FIG. 19 is a cross-sectional view showing a processing head
of the pretreatment apparatus shown in FIG. 5 at the time of
substrate transfer;
[0085] FIG. 20 is an enlarged view of A portion of FIG. 19;
[0086] FIG. 21 is a view corresponding to FIG. 20 at the time of
substrate fixing;
[0087] FIG. 22 is a systematic diagram of the pretreatment
apparatus shown in FIG. 5;
[0088] FIG. 23 is a cross-sectional view showing a substrate head
of an electroless plating apparatus shown in FIG. 5 at the time of
substrate transfer;
[0089] FIG. 24 is an enlarged view of B portion of FIG. 23;
[0090] FIG. 25 is a view corresponding to FIG. 24 showing the
substrate head at the time of substrate fixing;
[0091] FIG. 26 is a view corresponding to FIG. 24 showing the
substrate head at the time of plating process;
[0092] FIG. 27 is a front view with partially cross-section showing
a plating tank of the pretreatment apparatus shown in FIG. 5 when a
plating tank cover is closed;
[0093] FIG. 28 is a cross-sectional view of a cleaning tank of the
pretreatment apparatus shown in FIG. 5;
[0094] FIG. 29 is a systematic diagram of the cleaning tank of the
pretreatment apparatus shown in FIG. 5;
[0095] FIG. 30 is a schematic view showing an example of a
polishing apparatus shown in FIG. 5; and
[0096] FIG. 31 is a flow chart in a substrate processing apparatus
shown in FIG. 5.
[0097] FIG. 32 is an overall plan view of a substrate processing
apparatus provided with a plating apparatus according to still
another embodiment of the present invention;
[0098] FIG. 33 is a plan view of the plating apparatus shown in
FIG. 32;
[0099] FIG. 34 is an enlarged sectional view of the substrate
holder and the electrode portion of the plating apparatus shown in
FIG. 32;
[0100] FIG. 35 is a front view of the pre-coating/recovering arm of
the plating apparatus shown in FIG. 32;
[0101] FIG. 36 is a plan view of the substrate holder of the
plating apparatus shown in FIG. 32;
[0102] FIG. 37 is a cross-sectional view taken along the line B-B
of FIG. 36;
[0103] FIG. 38 is a cross-sectional view taken along the line C-C
of FIG. 36;
[0104] FIG. 39 is a plan view of the electrode portion of the
plating apparatus shown in FIG. 32;
[0105] FIG. 40 is a cross-sectional view taken along the line D-D
of FIG. 39;
[0106] FIG. 41 is a plan view of the electrode arm section of the
plating apparatus shown in FIG. 32;
[0107] FIG. 42 is a schematic sectional view illustrating the
electrode head and the substrate holder of the plating apparatus
shown in FIG. 32 upon electroplating;
[0108] FIG. 43 is a plan view of an anode of the plating apparatus
shown in FIG. 32;
[0109] FIG. 44 is a cross-sectional view of a modified anode;
[0110] FIG. 45 is a plan view of another anode;
[0111] FIG. 46 is a plan view of another substrate processing
apparatus having the plating apparatus according to the present
invention; and
[0112] FIG. 47 is a block diagram of a substrate processing
sequence performed by the substrate processing apparatus shown in
FIG. 46.
DETAILED DESCRIPTION OF THE INVENTION
[0113] Preferred embodiments of the present invention will be
described below with reference to the drawings. The following
embodiments relate to the application of the present invention
useful for forming interconnects of copper by embedding copper as
an interconnect material in fine recesses for interconnects formed
in a surface of the substrate. However, it should be noted that
other kinds of interconnect materials may be used instead of
copper.
[0114] FIGS. 4A through 4D illustrate an example of forming copper
interconnects in a semiconductor device. As shown in FIG. 4A, an
insulating film 2, such as an oxide film of SiO.sub.2 or a film of
low-k material, is deposited on a conductive layer 1a formed on a
semiconductor base 1 having formed semiconductor devices. Via holes
3 and trenches 4 are formed in the insulating film 2 by performing
a lithography/etching technique so as to provide fine recesses for
interconnects. Thereafter, a barrier layer 5 of TaN or the like is
formed on the insulating film 2, and a seed layer 6 as a electric
supply layer for electroplating is formed on the barrier layer 5 by
sputtering or the like.
[0115] Then, as shown in FIG. 4B, copper plating is performed on a
surface of a substrate W to fill the via holes 3 and the trenches 4
with copper and, at the same time, deposit a copper layer 7 on the
insulating film 2. Thereafter, the barrier layer 5, the seed layer
6 and the copper layer 7 on the insulating film 2 are removed by
chemical mechanical polishing (CMP) or the like so as to leave
copper filled in the via holes 3 and the trenches 4, and have a
surface of the insulating film 2 lie substantially on the same
plane as this copper. Interconnects (copper interconnects) 8
composed of the seed layer 6 and the copper layer 7 are thus formed
in the insulating film 2, as shown in FIG. 4C.
[0116] Then, as shown in FIG. 4D, electroless plating is performed
on a surface of the substrate W to selectively form a protective
film 9 of a Co alloy, an Ni alloy, or the like on surfaces of the
interconnects 8, thereby covering and protecting the surfaces of
the interconnects 8 with the protective film 9.
[0117] FIG. 5 is a plan view of a substrate processing apparatus
incorporating a plating apparatus according to an embodiment of the
present invention. As shown in FIG. 5, the substrate processing
apparatus comprises a rectangular apparatus frame 212 to which
transfer boxes 210 such as SMIF (Standard Mechanical Interface)
boxes which accommodate a number of substrates such as
semiconductor wafers, are detachably attached. Inside of the
apparatus frame 212, there are disposed a loading/unloading station
214, and a movable transfer robot 216 for transferring a substrate
to and from the loading/unloading station 214. A pair of plating
apparatuses 218 is disposed on both sides of the transfer robot
216. A cleaning and drying apparatus 220, a bevel etching and
backside cleaning apparatus 222, and a polishing apparatus 232 are
disposed in alignment with each other on one side of the transfer
robot 216. On the other side of the transfer robot 216, a heat
treatment (annealing) apparatus 226, a pretreatment apparatus 228,
and an electroless plating apparatus 230 are disposed in alignment
with each other.
[0118] The apparatus frame 212 is shielded so as not to allow a
light to transmit therethrough, thereby enabling subsequent
processes to be performed under a light-shielded condition in the
apparatus frame 212. Specifically, the subsequent processes can be
performed without irradiating the interconnects with a light such
as an illuminating light. By thus preventing the interconnects from
being irradiated with a light, it is possible to prevent the
interconnects of copper from being corroded due to a potential
difference of light that is caused by application of light to the
interconnects composed of copper, for example.
[0119] FIG. 6 schematically shows the plating apparatus 218. As
shown in FIG. 6, the plating apparatus 218 comprises a swing arm
500 which is horizontally swingable. An electrode head 502 is
rotatably supported by a tip end portion of the swing arm 500. A
substrate holder 504 for holding a substrate W in such a state that
a surface, to be plated, of the substrate W faces upwardly is
vertically movably disposed below the electrode head 502. A cathode
section 506 is disposed above the substrate holder 504 so as to
surround a peripheral portion of the substrate holder 504.
[0120] In this embodiment, the electrode head 502 whose diameter is
slightly smaller than that of the substrate holder 504 is used so
that plating can be performed over the substantially entire
surface, to be plated, of the substrate W without changing a
relative position between the electrode head 502 and the substrate
holder 504. In this embodiment, the present invention is applied to
a so-called face-up type plating apparatus in which the substrate
is held and plated in such a state that the front face of the
substrate faces upwardly. However, the present invention is, of
course, applicable to a so-called face-down type plating apparatus
in which the substrate is held and plated in such a state that a
front face of the substrate faces downwardly, or a so-called
vertical-set type plating apparatus in which the substrate is held
in a vertical direction and plated.
[0121] An annular vacuum attraction groove 504b communicating with
a vacuum passage 504a provided in the substrate holder 504 is
formed in a peripheral portion of an upper surface of the substrate
holder 504. Seal rings 508 and 510 are provided on inward and
outward sides of the vacuum attraction groove 504b, respectively.
With the above structure, the substrate W is placed on the upper
surface of the substrate holder 504, and the vacuum attraction
groove 504b is evacuated through the vacuum passage 504a to attract
the peripheral portion of the substrate W, thereby holding the
substrate W.
[0122] An elevating/lowering motor (not shown), which comprises a
servomotor, and a ball screw (not shown) are used to move the swing
arm 500 vertically, and a swinging motor (not shown) is used to
rotate (swing) the swing arm 500. Alternatively, a pneumatic
actuator may be used instead of the motor.
[0123] In this embodiment, the cathode section 506 has the cathode
electrodes 512 comprising six cathode electrodes, and the annular
seal member 514 disposed above the cathode electrodes 512 so as to
cover upper surfaces of the cathode electrodes 512. The seal member
514 has an inner circumferential portion which is inclined inwardly
and downwardly so that a thickness of the seal member 514 is
gradually reduced. The seal member 514 has an inner circumferential
edge portion extending downwardly. With this structure, when the
substrate holder 504 is moved upwardly, the peripheral portion of
the substrate W held by the substrate holder 504 is pressed against
the cathode electrodes 512, thus allowing electric current pass
through to the substrate W. At the same time, the inner
circumferential edge portion of the seal member 514 is held in
close contact with the upper surface of the peripheral portion of
the substrate W to seal a contact portion in a watertight manner.
Accordingly, a plating solution that has been supplied onto the
upper surface (surface to be plated) of the substrate W is
prevented from leaking from the end portion of the substrate W, and
the cathode electrodes 512 are thus prevented from being
contaminated by the plating solution.
[0124] In this embodiment, the cathode section 506 is not movable
vertically, but is rotatable together with the substrate holder
504. However, the cathode section 506 may be designed to be movable
vertically so that the seal member 514 is brought into close
contact with the surface, to be plated, of the substrate W when the
cathode section 506 is moved downwardly.
[0125] The above-mentioned electrode head 502 comprises a rotatable
housing 522 and a vertically movable housing 520 which have a
bottomed cylindrical shape with a downwardly open end and are
disposed concentrically. The rotatable housing 522 is fixed to a
lower surface of a rotating member 524 attached to a free end of
the swing arm 500 so that the rotatable housing 522 is rotated
together with the rotating member 524. An upper portion of the
vertically movable housing 520 is positioned inside the rotatable
housing 522, and the vertically movable housing 520 is rotated
together with the rotatable housing 522 and is moved relative to
the rotatable housing 522 in a vertical direction. The vertically
movable housing 520 defines an anode chamber 530 by closing the
lower open end of the vertically movable housing 520 with a porous
member 528 so that a disk-like anode 526 is disposed in the anode
chamber 530 and is dipped in a plating solution Q which is
introduced to the anode chamber 530.
[0126] In this embodiment, the porous member 528 has a
multi-layered structure comprising three-layer laminated porous
materials. Specifically, the porous member 528 comprises a plating
solution impregnated material 532 serving to hold a plating
solution mainly, and a porous pad 534 attached to a lower surface
of the plating solution impregnated material 532. This porous pad
534 comprises a lower pad 534a adapted to be brought into direct
contact with the substrate W, and an upper pad 534b disposed
between the lower pad 534a and the plating solution impregnated
material 532. The plating solution impregnated material 532 and the
upper pad 534b are positioned in the vertically movable housing
520, and the lower open end of the vertically movable housing 520
is closed by the lower pad 534a.
[0127] As described above, since the porous member 528 has a
multi-layered structure, it is possible to use the porous pad 534
(the lower pad 534a) which contacts the substrate W, for example,
and has flatness enough to flatten irregularities on the surface,
to be plated, of the substrate W.
[0128] The lower pad 534a is required to have the contact surface
adapted to contact the surface (surface to be contacted) of the
substrate W and having a certain degree of flatness, and to have
fine through-holes therein for allowing the plating solution to
pass therethrough. It is also necessary that at least the contact
surface of the lower pad 534a is made of an insulator or a material
having high insulating properties. The surface of the lower pad
534a is required to have a maximum roughness (RMS) of about several
tens .mu.m or less.
[0129] It is desirable that the fine through-holes of the lower pad
534a have a circular cross section in order to maintain flatness of
the contact surface. An optimum diameter of each of the fine
through-holes and the optimum number of the fine through-holes per
unit area vary depending on the kind of a plated film and an
interconnect pattern. However, it is desirable that both the
diameter and the number are as small as possible in view of
improving selectivity of a plated film that is growing in recesses.
Specifically, the diameter of each of the fine through-holes may be
not more than 30 .mu.m, preferably in the range of 5 to 20 .mu.m.
The number of the fine through-holes having such diameter per unit
area may be represented by a porosity of not more than 50%.
[0130] Further, it is desirable that the lower pad 534a has a
certain degree of hardness. For example, the lower pad 534a may
have a tensile strength ranging from 5 to 100 kg/cm.sup.2 and an
elastic bending strength ranging from 200 to 10000 kg/cm.sup.2.
[0131] Furthermore, it is desirable that the lower pad 534a is made
of hydrophilic material. For example, the following materials may
be used after being subjected to hydrophilization or being
introduced with a hydrophilic group by polymerization. Examples of
such materials include porous polyethylene (PE), porous
polypropylene (PP), porous polyamide, porous polycarbonate, and
porous polyimide. The porous PE, the porous PP, the porous
polyamide, and the like are produced by using fine powder of
ultrahigh-molecular polyethylene, polypropylene, and polyamide, or
the like as a material, squeezing the fine powder, and sintering
and forming the squeezed fine powder. These materials are
commercially available. For example, "Furudasu S (trade name)"
manufactured by Mitsubishi Plastics, Inc, "Sunfine UF (trade
name)", "Sunfine AQ (trade name)", both of which are manufactured
by Asahi Kasei Corporation, and "Spacy (trade name)" manufactured
by Spacy Chemical Corporation are available on the market. The
porous polycarbonate may be produced by passing a high-energy heavy
metal such as copper, which has been accelerated by an accelerator,
through a polycarbonate film to form straight tracks, and then
selectively etching the tracks.
[0132] The lower pad 534a may be produced by a flattening process
in which the surface, to be brought into contact with the surface
of the substrate W, of the lower pad 534a is compacted or machined
to a flat finish for thereby enabling a high-preferential
deposition in the fine recesses.
[0133] On the other hand, the plating solution impregnated material
532 may be composed of porous ceramics such as alumina, SiC,
mullite, zirconia, titania or cordierite, or a hard porous member
such as a sintered compact of polypropylene or polyethylene, or a
composite material comprising these materials. The plating solution
impregnated material 532 may be composed of a woven fabric or a
non-woven fabric. In case of the alumina-based ceramics, for
example, the ceramics with a pore diameter of 30 to 200 .mu.m is
used. In case of the SiC, the SiC with a pore diameter of not more
than 30 .mu.m, a porosity of 20 to 95%, and a thickness of about 1
to 20 mm, preferably 5 to 20 mm, more preferably 8 to 15 mm, is
used. The plating solution impregnated material 532, in this
embodiment, is composed of porous ceramics of alumina having a
porosity of 30%, and an average pore diameter of 100 .mu.m. The
porous ceramic plate per se is an insulator, but is constructed so
as to have a smaller conductivity than the plating solution by
causing the plating solution to enter its inner part complicatedly
and follow a considerably long path in the thickness direction.
[0134] In this manner, the plating solution impregnated material
532 is disposed in the anode chamber 530, and generates high
resistance. Hence, the influence of the resistance of the seed
layer 6 (see FIG. 4A) becomes a negligible degree. Consequently,
the difference in current density over the surface of the substrate
due to electrical resistance on the surface of the substrate W
becomes small, and the uniformity of the plated film over the
surface of the substrate improves.
[0135] The electrode head 502 has a pressing mechanism comprising
an air bag 540, in this embodiment, for pressing the lower pad 534a
against the surface (surface to be plated) of the substrate W held
by the substrate holder 504 under a desired pressure. Specifically,
in this embodiment, a ring-shaped air bag (pressing mechanism) 540
is provided between the lower surface of the top wall of the
rotatable housing 522 and the upper surface of the top wall of the
vertically movable housing 520, and this air bag 540 is connected
to a pressurized fluid source (not shown) through a pressurized
fluid introduction pipe 542.
[0136] Thus, the swing arm 500 is fixed at a predetermined position
(process position) so as not to move vertically, and then the inner
part of the air bag 540 is pressurized under a pressure of P,
whereby the lower pad 534a is uniformly pressed against the surface
(surface to be plated) of the substrate W held by the substrate
holder 504 under a desired pressure. Thereafter, the pressure P is
restored to an atmospheric pressure, whereby pressing of the lower
pad 534a against the substrate W is released.
[0137] A plating solution introduction pipe 544 is attached to the
vertically movable housing 520 to introduce the plating solution
into the vertically movable housing 520, and a pressurized fluid
introduction pipe (not shown) is attached to the vertically movable
housing 520 to introduce a pressurized fluid into the vertically
movable housing 520. A number of pores 526a are formed within the
anode 526. Thus, a plating solution Q is introduced from the
plating solution introduction pipe 544 into the anode chamber 530,
and the inner part of the anode chamber 530 is pressurized, whereby
the plating solution Q reaches the upper surface of the plating
solution impregnated material 532 through the pores 526a of the
anode 526, and reaches the upper surface of the substrate W held by
the substrate holder 504 through the inner part of the plating
solution impregnated material 532 and inner part of the porous pad
534 (the upper pad 534b and the lower pad 534a).
[0138] The anode chamber 530 includes gases generated by chemical
reaction therein, and hence the pressure in the anode chamber 530
may be varied. Therefore, the pressure in the anode chamber 530 is
controlled to a certain set value by a feedback control in the
process.
[0139] For example, in the case of performing copper plating, in
order to suppress slime formation, the anode 526 is generally made
of copper (phosphorus-containing copper) containing 0.03 to 0.05%
of phosphorus. The anode 526 may comprise an insoluble metal such
as platinum or titanium, or an insoluble electrode comprising metal
on which platinum or the like is plated. Since replacement or the
like is unnecessary, the insoluble metal or the insoluble electrode
is preferable. Further, the anode 526 may be a net-like anode which
allows a plating solution to pass therethrough easily.
[0140] The cathode electrodes 512 are to be electrically connected
to the cathode of a plating power source 550, and the anode 526 is
to be electrically connected to the anode of the plating power
source 550. The power source 550 is so controlled by a
constant-voltage control section 552 as to apply a constant voltage
to between the cathode electrodes 512 and the anode 526. A current
monitor section 554 is provided which, when a constant voltage is
applied between the cathode electrodes 512 and the anode 526,
monitors an electric current flowing between the cathode electrodes
512 and the anode 526. A detection signal from the current monitor
section 554 is fed back (inputted) to the constant-voltage control
section 552.
[0141] Plating is carried out by applying a constant voltage to
between the cathode electrodes 512 and the anode 526 by the
constant-voltage control section 552, i.e. under a constant-voltage
control, while an electric current flowing between the cathode
electrodes 512 and the anode 526 during plating is monitored with
the current monitor section 554. Feeding of electricity between the
cathode electrodes 512 and the anode 526 is stopped after elapse of
a predetermined period of time from a point of time at which the
current value becomes constant, thereby stopping the plating. In
particular, whether the current value detected by the current
monitor section 554 has become constant is determined, for example,
by a determination program. Upon determination of the constancy of
the current value, a signal for stopping feeding of electricity is
inputted from the constant-voltage control section 552 to the power
source 550 so as to stop feeding of electricity after elapse of a
predetermined period of time.
[0142] The period of time or time difference between the point of
time at which the current value becomes constant and the point of
time at which feeding of electricity is stopped may be set at 0
second. By thus stopping plating immediately after completion of a
flat plated film, an extra plating can be prevented from being
applied to the substrate. Alternatively, the period of time or time
difference between the point of time at which the current value
becomes constant and the point of time at which feeding of
electricity is stopped may be set at several seconds to carry out a
several-second additional plating, thereby providing a plated film
with a flatter surface.
[0143] Next, operation for performing plating by the plating
apparatus will be described. First, in such a state that the
substrate W is attracted to and held by the upper surface of the
substrate holder 504, the substrate holder 504 is raised to bring
the peripheral portion of the substrate W into contact with the
cathode electrodes 512, thus making it possible to supply current
to the substrate W. Then, the substrate holder 504 presses the seal
member 514 against the upper surface of the peripheral portion of
the substrate W, thereby sealing the peripheral portion of the
substrate W in a watertight manner.
[0144] On the other hand, the electrode head 502 is moved from a
position (idling position) where replacement of the plating
solution, removal of bubbles, and the like are conducted by idling
to a predetermined position (process position) in such a state that
the plating solution Q is held inside the electrode head 502.
Specifically, the swing arm 500 is once raised and further swung,
whereby the electrode head 502 is located right above the substrate
holder 504. Thereafter, the electrode head 502 is lowered, and when
the electrode head 502 reaches the predetermined position (process
position), the electrode head 502 is stopped. Then, the anode
chamber 530 is pressurized, and the plating solution Q held by the
electrode head 502 is discharged from the lower surface of the
porous pad 534. Next, the lower pad 534a is pressed downwardly by
introducing a pressurized air into the air bag 540 to press the
lower pad 534a against the upper surface (surface to be plated) of
the substrate W held by the substrate holder 504 under a desired
pressure.
[0145] While keeping the lower pad 534a in contact with the surface
of the substrate W, the lower pad 534a is rotated e.g. at a speed
of one revolution per second by the rotating member 524 to thereby
rub the lower pad 534a against the surface of the substrate W. It
is, of course, possible to fix the lower pad 534a and rotate the
substrate W. At the same time, the cathode electrodes 512 are
connected to the cathode of the plating power source 550 and the
anode 526 is connected to the anode of the plating power source 550
respectively, and a constant voltage is applied between the cathode
electrodes 512 and the anode 526 by the constant-voltage control
section 552 to carry out plating. During the plating, an electric
current flowing between the cathode electrodes 512 and the anode
526 is monitored with the current monitor section 554. Feeding of
electricity between the cathode electrodes 512 and the anode 526 is
stopped after elapse of a predetermined period of time, for
example, from 0 second to several seconds, from a point of time at
which a determination program or the like detects the fact that the
current value has become constant, thereby stopping the
plating.
[0146] As described above, when carrying out plating under a
constant-voltage control by a plating method generally called
flattening plating, the current value increases with the progress
of plating and becomes constant at a certain value. This phenomenon
is marked especially when carrying out plating while rubbing the
lower pad 534a, constituting the porous member 528, against the
surface, to be plated, of the substrate W held by the substrate
holder 504, because a plated film with a flat surface can be formed
regardless of variation of the configuration of interconnect
pattern. Accordingly, by carrying out plating of the substrate
under a constant-voltage control, monitoring the current value
during plating to detect a point of time at which the current value
becomes constant, and stopping the plating based on the detected
point of time, it becomes possible to obtain the intended plated
film with a flat surface without applying an extra plating to the
substrate.
[0147] After the completion of plating, the pressure in the anode
chamber 530 is returned to atmospheric pressure, and the pressure
in the air bag 540 is returned to atmospheric pressure, thereby
releasing the pressing of the lower pad 534a on the substrate W.
The electrode head 502 is raised, and returned to the idling
position.
[0148] Alternatively, plating may be carried out in the following
manner: Pressurized air is introduced into the air bag 540, as
described above, so as to press the lower pad 534a downward,
bringing it into contact with the upper surface (surface to be
plated) of the substrate W held by the substrate holder 504 under a
desired pressure. The lower pad 534a is rotated, according to
necessity, for example, at a speed of one revolution per second so
as to rub the lower pad 534a against the surface of the substrate
W. After stopping the rotation of the lower pad 534a, the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550, and a constant voltage is applied between
the cathode electrodes 512 and the anode 526 by the
constant-voltage control section 552 to carry out plating, while an
electric current flowing between the cathode electrodes 512 and the
anode 526 is monitored with the current monitor section 554.
[0149] Also in this case, by carrying out plating after stopping
the contact between the lower pad 534a, constituting the porous
member 528, and the surface, to be plated, of the substrate W held
by the substrate holder 504, a plated film with a flat surface can
be formed regardless of variation (difference in width and size) of
the configuration of interconnect pattern. Thus, when carrying out
plating under a constant-voltage control, the phenomenon that the
current value increases with the progress of plating and becomes
constant at a certain value, is marked. Accordingly, by detecting a
point of time at which the current value becomes constant and
stopping plating based on the detected point of time, it becomes
possible to obtain the intended plated film with a flat surface
without applying an extra plating to the substrate.
[0150] Though in this embodiment the lower pad 534a, constituting
the porous member 528, and the substrate W held by the substrate
holder 504 are moved relative to each other while they are kept in
contact with each other, it is also possible to vibrate the lower
pad 534a in such a manner that it repeats contact and non-contact
(detachment) with the surface, to be plated, of the substrate W
held by the substrate holder 504 (see FIG. 6), as shown in FIG. 7.
It is, of course, possible to vibrate the substrate W.
[0151] Thus, the lower pad 534a is vibrated in such a manner that
the lower pad 534a and the surface, to be plated, of the substrate
W repeat their contact and non-contact, while the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550, and a constant voltage is applied between
the cathode electrodes 512 and the anode 526 by the
constant-voltage control section 552 to carry out plating, while an
electric current flowing between the cathode electrodes 512 and the
anode 526 is monitored with the current monitor section 554.
[0152] Also in this case, by carrying out plating while repeating
contact and non-contact between the lower pad 534a, constituting
the porous member 528, and the surface, to be plated, of the
substrate W held by the substrate holder 504, a plated film with a
flat surface can be formed regardless of variation of the
configuration of interconnect pattern. Accordingly, by detecting a
point of time at which the current value becomes constant and
stopping plating based on the detected point of time, as described
above, it becomes possible to obtain the intended plated film with
a flat surface without applying an extra plating to the
substrate.
[0153] Plating may also be carried out in the following manner: The
operation of introducing pressurized air into the air bag 540 to
press the lower pad 534a downward and, after elapse of a
predetermined period of time, returning the pressure in the air bag
540 to atmospheric pressure to release the downward pressing of the
lower pad 534a is repeated, thereby repeating contact and
non-contact between the lower pad 534a and the surface of the
substrate W, as shown in FIG. 8A. As shown in FIG. 8B, only when
the lower pad 534a and the surface of the substrate are in contact
with each other, the cathode electrodes 512 are connected to the
cathode of the plating power source 550 and the anode 526 is
connected to the anode of the plating power source 550, and a
constant voltage is applied between the cathode electrodes 512 and
the anode 526 by the constant-voltage control section 552 to carry
out plating while an electric current flowing between the cathode
electrodes 512 and the anode 526 is monitored with the current
monitor section 554. The lower pad 534a and the substrate W may
either be moved relative to each other or kept motionless when they
are in contact with each other.
[0154] In this case, as shown in FIG. 8C, it is also possible to
provide a predetermined waiting time t.sub.1 so that the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550 after elapse of the waiting time t.sub.1
from the point of time at which the lower pad 534a makes contact
with the surface of the substrate.
[0155] Alternatively, as shown in FIG. 8D, it is also possible to
provide a waiting time t.sub.2 only when the lower pad 534a and the
surface of the substrate are not in contact with each other so that
a constant voltage is applied between the cathode electrodes 512
and the anode 526 to carry out plating after elapse of the waiting
time t.sub.2 from the point of time at which the contact between
the lower pad 534a and the substrate surface is released.
[0156] Furthermore, though not shown diagrammatically, it is also
possible to change the electrical conditions, that is, apply
different constant voltages between the contact time and the
non-contact time of the lower pad 534a with the surface of the
substrate.
[0157] FIG. 9 shows a plating apparatus 218 according to another
embodiment of the present invention. This embodiment differs from
the embodiment shown in FIG. 6 in that the power source 550 is so
controlled by a constant-current control section 556 as to pass a
constant electric current between the cathode electrodes 512 and
the anode 526, a voltage monitor section 558 is provided which,
when a constant electric current is passed between the cathode
electrodes 512 and the anode 526, detects the voltage value between
the cathode electrodes 512 and the anode 526, and a detection
signal from the voltage monitor section 558 is fed back (inputted)
to the constant-current control section 556.
[0158] Plating is carried out by passing a constant electric
current between the cathode electrodes 512 and the anode 526 by the
constant-current control section 556, i.e. under a constant-current
control, while the voltage value between the cathode electrodes 512
and the anode 526 is monitored with the voltage monitor section 558
during plating. Feeding of electricity between the cathode
electrodes 512 and the anode 526 is stopped after elapse of
predetermined period of time from a point of time at which the
voltage value becomes constant, thereby stopping the plating. In
particular, whether the voltage value detected by the voltage
monitor section 558 has become constant is determined, for example,
by a determination program. Upon determination of the constancy of
the voltage value, a signal for stopping feeding of electricity is
inputted from the constant-current control section 556 to the power
source 550 so as to stop feeding of electricity after elapse of a
predetermined period of time.
[0159] According to this embodiment, similarly to the
above-described embodiment, pressurized air is introduced into the
air bag 540 so as to press the lower pad 534a downward, thereby
pressing the lower pad 534a against the upper surface (surface to
be plated) of the substrate W, held by the substrate holder 504,
under a desired pressure. While keeping the lower pad 534a in
contact with the surface of the substrate W, the lower pad 534a is
rotated e.g. at a speed of one revolution per second by the
rotating member 524 to thereby rub the lower pad 534a against the
surface of the substrate W. At the same time, the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550, and a constant electric current is passed
between the cathode electrodes 512 and the anode 526 by the
constant-current control section 556 to carry out plating. During
the plating, the voltage value applied between the cathode
electrodes 512 and the anode 526 is monitored with the voltage
monitor section 558. Feeding of electricity between the cathode
electrodes 512 and the anode 526 is stopped after elapse of a
predetermined period of time, for example, 0 second to several
seconds, from a point of time at which a determination program or
the like detects the fact that the voltage value has become
constant, thereby stopping the plating.
[0160] As described above, when carrying out plating under a
constant-current control by a plating method generally called
flattening plating, the voltage value increases with the progress
of plating and becomes constant at a certain value. This phenomenon
is marked especially when carrying out plating while rubbing the
lower pad 534a, constituting the porous member 528, against the
surface to be plated of the substrate W held by the substrate
holder 504, because a plated film with a flat surface can be formed
regardless of variation of the configuration of interconnect
pattern. Accordingly, by carrying out plating of the substrate
under a constant-current control, monitoring the voltage value
during plating to detect a point of time at which the voltage value
becomes constant, and stopping the plating based on the detected
point of time, it becomes possible to obtain the intended plated
film with a flat surface without applying an extra plating to the
substrate.
[0161] Alternatively, plating may be carried out in the following
manner: Pressurized air is introduced into the air bag 540, as
described above, so as to press the lower pad 534a downward,
bringing it into contact with the upper surface (surface to be
plated) of the substrate W, held by the substrate holder 504, under
a desired pressure. The lower pad 534a is rotated, according to
necessity, for example, at a speed of one revolution per second so
as to rub the lower pad 534a against the surface of the substrate
W. After stopping the rotation of the lower pad 534a, the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550, and a constant electric current is passed
between the cathode electrodes 512 and the anode 526 by the
constant-current control section 556 to carry out plating, while
the voltage applied between the cathode electrodes 512 and the
anode 526 is monitored with the voltage monitor section 558.
[0162] Plating may also be carried out in the following manner: The
lower pad 534a, constituting the porous member 628, is vibrated in
such a manner that it repeats contact and non-contact with the
surface, to be plated, of the substrate W held by the substrate
holder 504 (see FIG. 6), as shown in FIG. 7, while the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550, and a constant electric current is passed
between the cathode electrodes 512 and the anode 526 by the
constant-current control section 556 to carry out plating while the
voltage applied between the cathode electrodes 512 and the anode
526 is monitored with the voltage monitor section 558.
[0163] Plating may also be carried out in the following manner: As
shown in FIG. 8A, contact and non-contact between the lower pad
534a and the surface of the substrate W is repeated and, as shown
in FIG. 8B, only when the lower pad 534a and the surface of the
substrate are in contact with each other, the cathode electrodes
512 are connected to the cathode of the plating power source 550
and the anode 526 is connected to the anode of the plating power
source 550, and a constant electric current is passed between the
cathode electrodes 512 and the anode 526 by the constant-current
control section 556 to carry out plating while the voltage applied
between the cathode electrodes 512 and the anode 526 is monitored
with the voltage monitor section 558.
[0164] In this case, as shown in FIG. 8C, it is also possible to
provide a predetermined waiting time t.sub.1 so that the cathode
electrodes 512 are connected to the cathode of the plating power
source 550 and the anode 526 is connected to the anode of the
plating power source 550 after elapse of the waiting time t.sub.1
from the point of time at which the lower pad 534a makes contact
with the surface of the substrate.
[0165] Alternatively, as shown in FIG. 8D, it is also possible to
provide a waiting time t.sub.2 only when the lower pad 534a and the
surface of the substrate are not in contact with each other so that
a constant electric current is passed between the cathode
electrodes 512 and the anode 526 to carry out plating after elapse
of the waiting time t.sub.2 from the point of time at which the
contact between the lower pad 534a and the substrate surface is
released.
[0166] Furthermore, though not shown diagrammatically, it is also
possible to change the electrical conditions, that is, apply
different constant currents between the contact time and the
non-contact time of the lower pad 534a with the surface of the
substrate.
[0167] FIG. 10 shows a plating solution management and supply
system for supplying a plating solution whose composition,
temperature, and the like are controlled to the plating apparatus
218. As shown in FIG. 10, a plating solution tray 600 for allowing
the electrode head 502 of the plating apparatus 218 to be immersed
for idling is provided, and the plating solution tray 600 is
connected to a reservoir 604 through a plating solution discharge
pipe 602. The plating solution discharged through the plating
solution discharge pipe 602 flows into the reservoir 604.
[0168] The plating solution, which has flowed into the reservoir
604, is introduced into the plating solution regulating tank 608 by
operating a pump 606. This plating solution regulating tank 608 is
provided with a temperature controller 610, and a plating solution
analyzing unit 612 for sampling the plating solution and analyzing
the sample solution. Further, component replenishing pipes 614 for
replenishing the plating solution with components which are found
to be insufficient by an analysis performed by the plating solution
analyzing unit 612 are connected to the plating solution regulating
tank 608. When a pump 616 is operated, the plating solution in the
plating solution regulating tank 608 flows in the plating solution
supply pipe 618, passes through the filter 618, and is then
returned to the plating solution tray 600.
[0169] In this manner, the composition and temperature of the
plating solution is adjusted to be constant in the plating solution
regulating tank 608, and the adjusted plating solution is supplied
to the electrode head 502 of the plating apparatus 218. Then, by
holding the adjusted plating solution by the electrode head 502,
the plating solution having constant composition and temperature at
all times can be supplied to the electrode head 502 of the plating
apparatus 218.
[0170] FIGS. 11 and 12 show an example of a cleaning and drying
apparatus 220 for cleaning (rinsing) the substrate W and drying the
substrate W. Specifically, the cleaning and drying apparatus 220
performs chemical cleaning and pure water cleaning (rinsing) first,
and then completely drying the substrate W which has been cleaned
by spindle rotation. The cleaning and drying apparatus 220
comprises a substrate stage 722 having a clamp mechanism 720 for
clamping an edge portion of the substrate W, and a substrate
mounting and removing lifting/lowering plate 724 for opening and
closing the clamp mechanism 720.
[0171] The substrate stage 722 is coupled to an upper end of a
spindle 726 which is rotated at a high speed by driving a spindle
rotating motor (not shown). Further, a cleaning cup 728 for
preventing a treatment liquid from being scattered around is
disposed around the substrate W held by the clamp mechanism 720,
and the cleaning cup 728 is vertically moved by actuation of a
cylinder (not shown).
[0172] Further, the cleaning and drying apparatus 220 comprises a
chemical liquid nozzle 730 for supplying a treatment liquid to the
surface of the substrate W held by the clamp mechanism 720, a
plurality of pure water nozzles 732 for supplying pure water to the
backside surface of the substrate W, and a pencil-type cleaning
sponge 730 which is disposed above the substrate W held by the
clamp mechanism 720 and is rotatable. The pencil-type cleaning
sponge 734 is attached to a free end of a swing arm 736 which is
swingable in a horizontal direction. Clean air introduction ports
738 for introducing clean air into the apparatus are provided at
the upper part of the cleaning and drying apparatus 220.
[0173] With the cleaning and drying apparatus 220 having the above
structure, the substrate W is held and rotated by the clamp
mechanism 720, and while the swing arm 736 is swung, a treatment
liquid is supplied from the chemical liquid nozzle 730 to the
cleaning sponge 734, and the surface of the substrate W is rubbed
with the pencil-type cleaning sponge 734, thereby cleaning the
surface of the substrate W. Further, pure water is supplied to the
backside surface of the substrate W from the pure water nozzles
732, and the backside surface of the substrate W is simultaneously
cleaned (rinsed) by the pure water ejected from the pure water
nozzles 732. Thus cleaned substrate W is spin-dried by rotating the
spindle 726 at a high speed.
[0174] FIG. 13 shows an example of a bevel etching and backside
cleaning apparatus 222. The bevel etching and backside cleaning
apparatus 222 can perform etching of the copper layer 7 (see FIG.
4B) deposited on an edge (bevel) of the substrate and backside
cleaning simultaneously, and can suppress growth of a natural oxide
film of copper at the circuit formation portion in the surface of
the substrate. The bevel etching and backside cleaning apparatus
222 has a substrate stage 922 positioned inside a bottomed
cylindrical waterproof cover 920 and adapted to rotate the
substrate W at a high speed, in such a state that the face of the
substrate W faces upward, while holding the substrate W
horizontally by spin chucks 921 at a plurality of locations along a
circumferential direction of a peripheral edge portion of the
substrate W, a center nozzle 924 disposed above a nearly central
portion of the face of the substrate W held by the substrate stage
922, and an edge nozzle 926 disposed above the peripheral edge
portion of the substrate W. The center nozzle 924 and the edge
nozzle 926 are directed downward, respectively. A back nozzle 928
is positioned below a nearly central portion of the backside of the
substrate W, and directed upward. The edge nozzle 926 is adapted to
be movable in a diametrical direction and a height direction of the
substrate W.
[0175] The width of movement L of the edge nozzle 926 is set such
that the edge nozzle 926 can be arbitrarily positioned in a
direction toward the center from the outer peripheral end surface
of the substrate, and a set value for L is inputted, according to
the size, usage, or the like of the substrate W. Normally, an edge
cut width C is set in the range of 2 mm to 5 mm. In the case where
a rotational speed of the substrate is a certain value or higher at
which the amount of liquid migration from the backside to the face
is not problematic, the copper layer and the like within the edge
cut width C can be removed.
[0176] Next, the method of cleaning with this bevel etching and
backside cleaning apparatus 222 will be described. First, the
substrate W is horizontally rotated integrally with the substrate
stage 922, with the substrate W being held horizontally by the spin
chucks 921 of the substrate stage 922. In this state, an acid
solution is supplied from the center nozzle 924 to the central
portion of the face of the substrate W. The acid solution may be a
non-oxidizing acid, and hydrofluoric acid, hydrochloric acid,
sulfuric acid, citric acid, oxalic acid, or the like is used. On
the other hand, an oxidizing agent solution is supplied
continuously or intermittently from the edge nozzle 926 to the
peripheral edge portion of the substrate W. As the oxidizing agent
solution, one of an aqueous solution of ozone, an aqueous solution
of hydrogen peroxide, an aqueous solution of nitric acid, and an
aqueous solution of sodium hypochlorite is used, or a combination
of these is used.
[0177] In this manner, the copper layer, or the like formed on the
upper surface and end surface in the region of the edge cut width C
of the substrate W is rapidly oxidized with the oxidizing agent
solution, and is simultaneously etched with the acid solution
supplied from the center nozzle 924 and spread on the entire face
of the substrate, whereby it is dissolved and removed. By mixing
the acid solution and the oxidizing agent solution at the
peripheral edge portion of the substrate, a steep etching profile
can be obtained, in comparison with a mixture of them which is
produced in advance being supplied. At this time, the copper
etching rate is determined by their concentrations. If a natural
oxide film of copper is formed in the circuit-formed portion on the
face of the substrate, this natural oxide is immediately removed by
the acid solution spreading on the entire face of the substrate
according to rotation of the substrate, and does not grow any more.
After the supply of the acid solution from the center nozzle 924 is
stopped, the supply of the oxidizing agent solution from the edge
nozzle 926 is stopped. As a result, silicon exposed on the surface
is oxidized, and deposition of copper can be suppressed.
[0178] On the other hand, an oxidizing agent solution and a silicon
oxide film etching agent are supplied simultaneously or alternately
from the back nozzle 928 to the central portion of the backside of
the substrate. Therefore, copper or the like adhering in a metal
form to the backside of the substrate W can be oxidized with the
oxidizing agent solution, together with silicon of the substrate,
and can be etched and removed with the silicon oxide film etching
agent. This oxidizing agent solution is preferably the same as the
oxidizing agent solution supplied to the face, because the types of
chemicals are decreased in number. Hydrofluoric acid can be used as
the silicon oxide film etching agent, and if hydrofluoric acid is
used as the acid solution on the face of the substrate, the types
of chemicals can be decreased in number. Thus, if the supply of the
oxidizing agent is stopped first, a hydrophobic surface is
obtained. If the etching agent solution is stopped first, a
water-saturated surface (a hydrophilic surface) is obtained, and
thus the backside surface can be adjusted to a condition that will
satisfy the requirements of a subsequent process.
[0179] In this manner, the acid solution, i.e., etching solution is
supplied to the substrate W to remove metal ions remaining on the
surface of the substrate W. Then, pure water is supplied to replace
the etching solution with pure water and remove the etching
solution, and then the substrate is dried by spin-drying. In this
way, removal of the copper layer in the edge cut width C at the
peripheral edge portion on the face of the substrate, and removal
of copper contaminants on the backside are performed simultaneously
to thus allow this treatment to be completed, for example, within
80 seconds. The etching cut width of the edge can be set
arbitrarily (from 2 to 5 mm), but the time required for etching
does not depend on the cut width.
[0180] FIGS. 14 and 15 show a heat treatment (annealing) apparatus
226. The annealing apparatus 226 comprises a chamber 1002 having a
gate 1000 for taking in and taking out the substrate W, a hot plate
1004 disposed at an upper position in the chamber 1002 for heating
the substrate W to e.g. 400.degree. C., and a cool plate 1006
disposed at a lower position in the chamber 1002 for cooling the
substrate W by, for example, flowing cooling water inside the
plate. The annealing apparatus 26 also has a plurality of
vertically movable elevating pins 1008 penetrating the cool plate
1006 and extending upward and downward therethrough for placing and
holding the substrate W on them. The annealing apparatus 226
further includes a gas introduction pipe 1010 for introducing an
antioxidant gas between the substrate W and the hot plate 1004
during annealing, and a gas discharge pipe 1012 for discharging the
gas which has been introduced from the gas introduction pipe 1010
and flowed between the substrate W and the hot plate 1004. The
pipes 1010 and 1012 are disposed on the opposite sides of the hot
plate 1004.
[0181] The gas introduction pipe 1010 is connected to a mixed gas
introduction line 1022 which in turn is connected to a mixer 1020
where a N.sub.2 gas introduced through a N.sub.2 gas introduction
line 1016 containing a filter 1014a, and a H.sub.2 gas introduced
through a H.sub.2 gas introduction line 1018 containing a filter
1014b, are mixed to form a mixed gas which flows through the line
1022 into the gas introduction pipe 1010.
[0182] In operation, the substrate W, which has been carried in the
chamber 1002 through the gate 1000, is held on the elevating pins
1008 and the elevating pins 1008 are raised up to a position at
which the distance between the substrate W held on the lifting pins
1008 and the hot plate 1004 becomes about 0.1 to 1.0 mm, for
example. In this state, the substrate W is then heated to e.g.
400.degree. C. through the hot plate 1004 and, at the same time,
the antioxidant gas is introduced from the gas introduction pipe
1010 and the gas is allowed to flow between the substrate W and the
hot plate 1004 while the gas is discharged from the gas discharge
pipe 1012, thereby annealing the substrate W while preventing its
oxidation. The annealing may be completed in about several tens of
seconds to 60 seconds. The heating temperature of the substrate may
be selected in the range of 100 to 600.degree. C.
[0183] After the completion of the annealing, the elevating pins
1008 are lowered down to a position at which the distance between
the substrate W held on the elevating pins 1008 and the cool plate
1006 becomes 0 to 0.5 mm, for example. In this state, by
introducing cooling water into the cool plate 1006, the substrate W
is cooled by the cool plate 1006 to a temperature of 100.degree. C.
or lower in about 10 to 60 seconds. The cooled substrate is
transferred to the next step.
[0184] A mixed gas of N.sub.2 gas with several percentages of
H.sub.2 gas is used as the above antioxidant gas. However, N.sub.2
gas may be used singly.
[0185] FIGS. 16 through 22 show a pretreatment apparatus 228 for
performing a pretreatment of electroless plating of the substrate.
The pretreatment apparatus 228 includes a fixed frame 252 that is
mounted on the upper part of a frame 250, and a movable frame 254
that moves up and down relative to the fixed frame 252. A
processing head 260, which includes a bottomed cylindrical housing
portion 256, opening downwardly, and a substrate holder 258, is
suspended from and supported by the movable frame 254. In
particular, a servomotor 262 for rotating the head is mounted to
the movable frame 254, and the housing portion 256 of the
processing head 260 is coupled to the lower end of the
downward-extending output shaft (hollow shaft) 264 of the
servomotor 262.
[0186] As shown in FIG. 19, a vertical shaft 268, which rotates
together with the output shaft 264 via a spline 266, is inserted in
the output shaft 264, and the substrate holder 258 of the
processing head 260 is coupled to the lower end of the vertical
shaft 68 via a ball joint 270. The substrate holder 258 is
positioned within the housing portion 256. The upper end of the
vertical shaft 268 is coupled via a bearing 272 and a bracket to a
fixed ring-elevating cylinder 274 secured to the movable frame 254.
Thus, by the actuation of the cylinder 274, the vertical shaft 268
moves vertically independently of the output shaft 264.
[0187] Linear guides 276, which extend vertically and guide
vertical movement of the movable frame 254, are mounted to the
fixed frame 252, so that by the actuation of a head-elevating
cylinder (not shown), the movable frame 254 moves vertically by the
guide of the linear guides 276.
[0188] Substrate insertion windows 256a for inserting the substrate
W into the housing portion 256 are formed in the circumferential
wall of the housing portion 256 of the processing head 260.
Further, as shown in FIGS. 20 and 21, a seal ring 284 is provided
in the lower portion of the housing portion 256 of the processing
head 260, an outer peripheral portion of the seal ring 284a being
sandwiched between a main frame 280 made of e.g. PEEK and a guide
frame 282 made of e.g. polyethylene. The seal ring 284a is provided
to make contact with a peripheral portion of the lower surface of
the substrate W to seal the peripheral portion.
[0189] On the other hand, a substrate fixing ring 286 is fixed to a
peripheral portion of the lower surface of the substrate holder
258. Columnar pushers 290 each protrudes downwardly from the lower
surface of the substrate fixing ring 286 by the elastic force of a
spring 288 disposed within the substrate fixing ring 286 of the
substrate holder 258. Further, a flexible cylindrical bellows-like
plate 292 made of e.g. Teflon (registered trademark) is disposed
between the upper surface of the substrate holder 258 and the upper
wall of the housing portion 256 to hermetically seal therein.
[0190] When the substrate holder 258 is in a raised position, a
substrate W is inserted from the substrate insertion window 256a
into the housing portion 256. The substrate W is then guided by a
tapered surface 282a provided in the inner circumferential surface
of the guide frame 282, and positioned and placed at a
predetermined position on the upper surface of the seal ring 284a.
In this state, the substrate holder 258 is lowered so as to bring
the pushers 290 of the substrate fixing ring 286 into contact with
the upper surface of the substrate W. The substrate holder 258 is
further lowered so as to press the substrate W downwardly by the
elastic forces of the springs 288, thereby forcing the seal ring
284a to make pressure contact with a peripheral portion of the
front surface (lower surface) of the substrate W to seal the
peripheral portion while nipping the substrate W between the
housing portion 256 and the substrate holder 258 to hold the
substrate W.
[0191] When the head-rotating servomotor 262 is driven while the
substrate W is thus held by the substrate holder 258, the output
shaft 264 and the vertical shaft 268 inserted in the output shaft
264 rotate together via the spline 266, whereby the substrate
holder 258 rotates together with the housing portion 256.
[0192] At a position below the processing head 260, there is
provided an upward-open treatment tank 300 comprising an outer tank
300a and an inner tank 300b which have a slightly larger inner
diameter than the outer diameter of the processing head 260. A pair
of leg portions 304, which is mounted to a lid 302, is rotatably
supported on the outer circumferential portion of the treatment
tank 300. Further, a crank 306 is integrally coupled to each leg
portion 306, and the free end of the crank 306 is rotatably coupled
to the rod 310 of a lid-moving cylinder 308. Thus, by the actuation
of the lid-moving cylinder 308, the lid 302 moves between a
treatment position at which the lid 302 covers the top opening of
the inner tank 300b of the treatment tank 300 and a retreat
position beside the inner tank 300b of the treatment tank 300. In
the surface (upper surface) of the lid 302, there is provided a
nozzle plate 312 having a large number of jet nozzles 312a for
jetting outwardly (upwardly), electrolytic ionic water having
reducing power, for example.
[0193] Further, as shown in FIG. 22, a nozzle plate 324 having a
plurality of jet nozzles 324a for jetting upwardly a chemical
liquid supplied from a chemical liquid tank 320 by driving the
chemical liquid pump 322 is provided in the inner tank 300b of the
treatment tank 300 in such a manner that the jet nozzles 324a are
equally distributed over the entire surface of the cross section of
the inner tank 300b. A drainpipe 326 for draining a chemical liquid
(waste liquid) to the outside is connected to the bottom of the
inner tank 300b. A three-way valve 328 is provided in the drainpipe
326, and the chemical liquid (waste liquid) is returned to the
chemical liquid tank 320 through a return pipe 330 connected to one
of ports of the three-way valve 328 to recycle the chemical liquid,
as needed. Further, in this embodiment, the nozzle plate 312
provided on the surface (upper surface) of the lid 302 is connected
to a rinsing liquid supply source 332 for supplying a rinsing
liquid such as pure water. Further, a drainpipe 327 is connected to
the bottom of the outer tank 300a.
[0194] By lowering the processing head 260 holding the substrate so
as to cover or close the top opening of the inner tank 300b of the
treatment tank 300 with the processing head 260 and then jetting a
chemical liquid from the jet nozzles 324a of the nozzle plate 324
disposed in the inner tank 300b of the treatment tank 300 toward
the substrate W, the chemical liquid can be jetted uniformly onto
the entire lower surface (surface to be processed) of the substrate
W and the chemical liquid can be discharged out from the discharge
pipe 326 while preventing scattering of the chemical liquid to the
outside. Further, by raising the processing head 260 and closing
the top opening of the inner tank 300b of the treatment tank 300
with the lid 302, and then jetting a rinsing liquid from the jet
nozzles 312a of the nozzle plate 312 disposed in the upper surface
of the lid 302 toward the substrate W held in the processing head
260, the rinsing treatment (cleaning treatment) is carried out to
remove the chemical liquid from the surface of the substrate.
Because the rinsing liquid passes through the clearance between the
outer tank 300a and the inner tank 300b and is discharged through
the drainpipe 327, the rinsing liquid is prevented from flowing
into the inner tank 300b and from being mixed with the chemical
liquid.
[0195] According to the pretreatment apparatus 228, the substrate W
is inserted into the processing head 260 and held therein when the
processing head 260 is in the raised position, as shown in FIG. 16.
Thereafter, as shown in FIG. 17, the processing head 260 is lowered
to the position at which it covers the top opening of the inner
tank 300b of the treatment tank 300. While rotating the processing
head 260 and thereby rotating the substrate W held in the
processing head 260, a chemical liquid is jetted from the jet
nozzles 324a of the nozzle plate 324 disposed in the inner tank
300b of the treatment tank 300 toward the substrate W, thereby
jetting the chemical liquid uniformly onto the entire surface of
the substrate W. The processing head 260 is raised and stopped at a
predetermined position and, as shown in FIG. 18, the lid 302 in the
retreat position is moved to the position at which it covers the
top opening of the inner tank 300b of the treatment tank 300. A
rinsing liquid is then jetted from the jet nozzles 312a of the
nozzle plate 312 disposed in the upper surface of the lid 302
toward the rotating substrate W held in the processing head 260.
The chemical treatment by the chemical liquid and the rinsing
treatment by the rinsing liquid of the substrate W can thus be
carried out successively while avoiding mixing of the two
liquids.
[0196] The lowermost position of the processing head 260 may be
adjusted to adjust the distance between the substrate W held in the
processing head 260 and the nozzle plate 324, whereby the region of
the substrate W onto which the chemical liquid is jetted from the
jet nozzles 324a of the nozzle plate 324 and the jetting pressure
can be adjusted as desired. Here, when the pretreatment liquid such
as a chemical liquid is circulated and reused, active components
are reduced by progress of the treatment, and the pretreatment
liquid (chemical liquid) is taken out due to attachment of the
treatment liquid to the substrate. Therefore, it is desirable to
provide a pretreatment liquid management unit (not shown) for
analyzing composition of the pretreatment liquid and adding
insufficient components. Specifically, a chemical liquid used for
cleaning is mainly composed of acid or alkali. Therefore, for
example, a pH of the chemical liquid is measured, a decreased
content is replenished from the difference between a preset value
and the measured pH, and a decreased amount is replenished using a
liquid level meter provided in the chemical storage tank. Further,
with respect to a catalytic liquid, for example, in the case of
acid palladium solution, the amount of acid is measured by its pH,
and the amount of palladium is measured by a titration method or
nephelometry, and a decreased amount can be replenished in the same
manner as described above.
[0197] FIGS. 23 through 29 show an electroless plating apparatus
230. This electroless plating apparatus 230, which is provided to
form the protective layer 9 shown in FIG. 4D, includes a plating
tank 400 (see FIGS. 27 and 29) and a substrate head 404, disposed
above the plating tank 400, for detachably holding a substrate
W.
[0198] As shown in detail in FIG. 23, the processing head 404 has a
housing portion 430 and a head portion 432. The head portion 432
mainly comprises a suction head 434 and a substrate receiver 436
for surrounding the suction head 434. The housing portion 430
accommodates therein a substrate rotating motor 438 and substrate
receiver drive cylinders 440. The substrate rotating motor 438 has
an output shaft (hollow shaft) 442 having an upper end coupled to a
rotary joint 444 and a lower end coupled to the suction head 434 of
the head portion 432. The substrate receiver drive cylinders 440
have respective rods coupled to the substrate receiver 436 of the
head portion 432. Stoppers 446 are provided in the housing portion
430 for mechanically limiting upward movement of the substrate
receiver 436.
[0199] The suction head 434 and the substrate receiver 436 are
operatively connected to each other by a splined structure such
that when the substrate receiver drive cylinders 440 are actuated,
the substrate receiver 436 vertically moves relative to the suction
head 434, and when the substrate rotating motor 438 is energized,
the output shaft 442 thereof is rotated to rotate the suction head
434 and the substrate receiver 436 in unison with each other.
[0200] As shown in detail in FIGS. 24 through 26, a suction ring
450 for attracting and holding a substrate W against its lower
surface to be sealed is mounted on a lower circumferential edge of
the suction head 434 by a presser ring 451. The suction ring 450
has a recess 450a continuously defined in a lower surface thereof
in a circumferential direction and in communication with a vacuum
line 452 extending through the suction head 434 by a communication
hole 450b that is defined in the suction ring 450. When the recess
450a is evacuated, the substrate W is attracted to and held by the
suction ring 450. Because the substrate W is attracted under vacuum
to the suction ring 450 along a radially narrow circumferential
area provided by the recess 450a, any adverse effects such as
flexing caused by the vacuum on the substrate W are minimized. When
the suction ring 450 is dipped in the plating solution (treatment
liquid), not only the surface (lower surface) of the substrate W,
but also its circumferential edge, can be dipped in the plating
solution. The substrate W is released from the suction ring 450 by
introducing N.sub.2 into the vacuum line 452.
[0201] The substrate receiver 436 is in the form of a downwardly
open, hollow bottomed cylinder having substrate insertion windows
436a defined in a circumferential wall thereof for inserting
therethrough the substrate W into the substrate receiver 436. The
substrate receiver 436 also has an annular ledge 454 projecting
inwardly from its lower end, and an annular protrusion 456 disposed
on an upper surface of the annular ledge 454 and having a tapered
inner circumferential surface 456a for guiding the substrate W.
[0202] As shown in FIG. 24, when the substrate receiver 436 is
lowered, the substrate W is inserted through the substrate
insertion window 436a into the substrate receiver 436. The
substrate W thus inserted is guided by the tapered surface 456a of
the protrusion 456 and positioned thereby onto the upper surface of
the ledge 454 in a predetermined position thereon. The substrate
receiver 436 is then elevated until it brings the upper surface of
the substrate W placed on the ledge 454 into abutment against the
suction ring 450 of the suction head 434, as shown in FIG. 25.
Then, the recess 450a in the vacuum ring 450 is evacuated through
the vacuum line 452 to attract the substrate W while sealing the
upper peripheral edge surface of the substrate W against the lower
surface of the suction ring 450. In order to plate the substrate W,
as shown in FIG. 26, the substrate receiver 436 is lowered several
mm to space the substrate W from the ledge 454, keeping the
substrate W attracted only by the suction ring 450. The substrate W
now has its lower peripheral edge surface prevented from not being
plated because it is held out of contact with the ledge 454.
[0203] FIG. 27 shows the details of the plating tank 400. The
plating tank 400 is connected at the bottom to a plating solution
supply pipe 1308 (see FIG. 29), and is provided in the peripheral
wall with a plating solution recovery groove 460. In the plating
tank 400, there are disposed two current plates 462, 464 for
stabilizing the flow of a plating solution flowing upward. A
thermometer 466 for measuring the temperature of the plating
solution introduced into the plating tank 400 is disposed at the
bottom of the plating tank 400. Further, on the outer surface of
the peripheral wall of the plating tank 400 and at a position
slightly higher than the liquid level of the plating solution held
in the plating tank 400, there is provided a jet nozzle 468 for
jetting a stop liquid which is a neutral liquid having a pH of 6 to
7.5, for example, pure water, inwardly and slightly upwardly in the
normal direction. After plating, the substrate W held in the head
portion 432 is raised and stopped at a position slightly above the
surface of the plating solution. In this state, pure water (stop
liquid) is immediately jetted from the jet nozzle 468 toward the
substrate W to cool the substrate W, thereby preventing progress of
plating by the plating solution remaining on the substrate W.
[0204] Further, at the top opening of the plating tank 400, there
is provided a plating tank cover 470 capable of opening and closing
for closing the top opening of the plating tank 400 in a
non-plating time, such as idling time, so as to prevent unnecessary
evaporation of the plating solution from the plating tank 400.
[0205] As shown in FIG. 29, a plating solution supply pipe 1308
extending from a plating solution storage tank 1302 and having a
plating solution supply pump 1304 and a three-way valve 1306 is
connected to the plating tank 400 at the bottom of the plating tank
400. With this arrangement, during a plating process, a plating
solution is supplied into the plating tank 400 from the bottom of
the plating tank 400, and the overflowing plating solution is
recovered by the plating solution storage tank 1302 through the
plating solution recovery groove 460. Thus, the plating solution
can be circulated. A plating solution return pipe 1312 for
returning the plating solution to the plating solution storage tank
1302 is connected to one of the ports of the three-way valve 1306.
Thus, the plating solution can be circulated even in a standby
condition of plating, and a plating solution circulating system is
constructed. As described above, the plating solution in the
plating solution storage tank 1302 is always circulated through the
plating solution circulating system, and hence a lowering rate of
the concentration of the plating solution can be reduced and the
number of the substrates W, which can be processed, can be
increased, compared with the case in which the plating solution is
simply stored.
[0206] Particularly, in this embodiment, by controlling the plating
solution supply pump 1304, the flow rate of the plating solution
which is circulated at a standby of plating or at a plating process
can be set individually. Specifically, the amount of circulating
plating solution at the standby of plating is in the range of 2 to
20 litter/minute, for example, and the amount of circulating
plating solution at the plating process is in the range of 0 to 10
litter/minute, for example. With this arrangement, a large amount
of circulating plating solution at the standby of plating can be
ensured to keep a temperature of the plating bath in the cell
constant, and the flow rate of the circulating plating solution is
made smaller at the plating process to form a protective film
(plated film) having a more uniform thickness.
[0207] The thermometer 466 provided in the vicinity of the bottom
of the plating tank 400 measures a temperature of the plating
solution introduced into the plating tank 400, and controls a
heater 1316 and a flow meter 1318 described below.
[0208] Specifically, in this embodiment, there are provided a
heating device 1322 for heating the plating solution indirectly by
a heat exchanger 1320 which is provided in the plating solution in
the plating solution storage tank 1302 and uses water as a heating
medium which has been heated by a separate heater 1316 and has
passed through the flow meter 1318, and a stirring pump 1324 for
mixing the plating solution by circulating the plating solution in
the plating solution storage tank 1302. This is because in the
plating, in some cases, the plating solution is used at a high
temperature (about 80.degree. C.), and the structure should cope
with such cases. This method can prevent very delicate plating
solution from being mixed with foreign matter or the like unlike an
in-line heating method.
[0209] FIG. 28 shows the details of a cleaning tank 402 provided
beside the plating tank 400. At the bottom of the cleaning tank
402, there is provided a nozzle plate 482 having a plurality of jet
nozzles 480, attached thereto, for upwardly jetting a rinsing
liquid such as pure water. The nozzle plate 482 is coupled to an
upper end of a nozzle lifting shaft 484. The nozzle lifting shaft
484 can be moved vertically by changing the position of engagement
between a nozzle position adjustment screw 487 and a nut 488
engaging the screw 487 so as to optimize the distance between the
jet nozzles 480 and a substrate W located above the jet nozzles
480.
[0210] Further, on the outer surface of the peripheral wall of the
cleaning tank 402 and at a position above the jet nozzles 480,
there is provided a head cleaning nozzle 486 for jetting a cleaning
liquid, such as pure water, inwardly and slightly downwardly onto
at least a portion, which was in contact with the plating solution,
of the head portion 432 of the substrate head 404.
[0211] In operating the cleaning tank 402, the substrate W held in
the head portion 432 of the substrate head 404 is located at a
predetermined position in the cleaning tank 402. A cleaning liquid
(rinsing liquid), such as pure water, is jetted from the jet
nozzles 480 to clean (rinse) the substrate W, and at the same time,
a cleaning liquid such as pure water is jetted from the head
cleaning nozzle 486 to clean at least a portion, which was in
contact with the plating solution, of the head portion 432 of the
substrate head 404, thereby preventing a deposit from accumulating
on that portion which was immersed in the plating solution.
[0212] According to this electroless plating apparatus 230, when
the substrate head 404 is in a raised position, the substrate W is
held by vacuum attraction in the head portion 432 of the substrate
head 404, as described above, while the plating solution in the
plating tank 400 is allowed to circulate.
[0213] When plating is performed, the plating tank cover 470 is
opened, and the substrate head 404 is lowered, while the substrate
head 404 is rotating, so that the substrate W held in the head
portion 432 is immersed in the plating solution in the plating tank
400.
[0214] After immersing the substrate W in the plating solution for
a predetermined time, the substrate head 404 is raised to lift the
substrate W from the plating solution in the plating tank 400 and,
as needed, pure water (stop liquid) is immediately jetted from the
jet nozzle 468 toward the substrate W to cool the substrate W, as
described above. The substrate head 404 is further raised to lift
the substrate W to a position above the plating tank 400, and the
rotation of the substrate head 404 is stopped.
[0215] Next, while the substrate W is held by vacuum attraction in
the head portion 432 of the substrate head 204, the substrate head
404 is moved to a position right above the cleaning tank 402. While
rotating the substrate head 404, the substrate head 404 is lowered
to a predetermined position in the cleaning tank 402. A cleaning
liquid (rinsing liquid), such as pure water, is jetted from the jet
nozzles 480 to clean (rinse) the substrate W, and at the same time,
a cleaning liquid such as pure water is jetted from the head
cleaning nozzle 486 to clean at least a portion, which was in
contact with the plating solution, of the head portion 432 of the
substrate head 404.
[0216] After completion of cleaning of the substrate W, the
rotation of the substrate head 404 is stopped, and the substrate
head 404 is raised to lift the substrate W to a position above the
cleaning tank 402. Further, the substrate head 404 is moved to the
transfer position between the transfer robot 216 and the substrate
head 404, and the substrate W is transferred to the transfer robot
216, and is transported to a next process by the transfer robot
216.
[0217] As shown in FIG. 29, the electroless plating apparatus 230
is provided with a plating solution management unit 1330 for
measuring an amount of the plating solution held in the electroless
plating apparatus 230, and analyzing composition of the plating
solution by an absorptiometric method, a titration method, an
electrochemical measurement, or the like, and replenishing
components which are insufficient in the plating solution. In the
plating solution management unit 1330, signals indicative of the
analysis results are processed to replenish insufficient components
from a replenishment tank (not shown) to the plating solution
storage tank 1302 using a metering pump, thereby controlling the
amount of the plating solution and composition of the plating
solution. Thus, thin film plating can be realized in a good
reproducibility.
[0218] The plating solution management unit 1330 has a dissolved
oxygen densitometer 1332 for measuring dissolved oxygen in the
plating solution held by the electroless plating apparatus 230 by
an electrochemical method, for example. According to the plating
solution management unit 1330, dissolved oxygen concentration in
the plating solution can be controlled at a constant value on the
basis of indication of the dissolved oxygen densitometer 1332 by
deaeration, nitrogen blowing, or other methods. In this manner, the
dissolved oxygen concentration in the plating solution can be
controlled at a constant value, and the plating reaction can be
achieved in a good reproducibility.
[0219] When the plating solution is used repeatedly, certain
components are accumulated by being carried in from the outside or
decomposition of the plating solution, resulting in lowering of
reproducibility of plating and deteriorating of film quality. By
adding a mechanism for removing such specific components
selectively, the life of the plating solution can be prolonged and
the reproducibility can be improved.
[0220] FIG. 30 shows an example of a polishing apparatus (CMP
apparatus) 232. The polishing apparatus 232 comprises a polishing
table 822 having a polishing surface composed of a polishing cloth
(polishing pad) 820 which is attached to the upper surface of the
polishing table 822, and a top ring 824 for holding a substrate W
with its to-be-polished surface facing the polishing table 822. In
the polishing apparatus 232, the surface of the substrate W is
polished by rotating the polishing table 822 and the top ring 824
about their own axes, respectively, and supplying a polishing
liquid from a polishing liquid nozzle 826 provided above the
polishing table 822 while pressing the substrate W against the
polishing cloth 820 of the polishing table 822 at a given pressure
by the top ring 824. It is possible to use a fixed abrasive type of
pad containing fixed abrasive particles as the polishing pad.
[0221] The polishing power of the polishing surface of the
polishing cloth 820 decreases with a continuation of a polishing
operation of the CMP apparatus 232. In order to restore the
polishing power, a dresser 828 is provided to conduct dressing of
the polishing cloth 820, for example, at the time of replacing the
substrate W. In the dressing, while rotating the dresser 828 and
the polishing table 822 respectively, the dressing surface
(dressing member) of the dresser 828 is pressed against the
polishing cloth 820 of the polishing table 822, thereby removing
the polishing liquid and chips adhering to the polishing surface
and, at the same time, flattening and dressing the polishing
surface, whereby the polishing surface is regenerated. The
polishing table 822 may be provided with a monitor for monitoring
the surface state of the substrate to detect in situ the end point
of polishing, or with a monitor for inspecting in situ the finish
state of the substrate.
[0222] A description will now be given of a series of process steps
for forming copper interconnects in a substrate, having a seed
layer 6 formed in the surface as shown in FIG. 4A, by the substrate
processing apparatus having the above construction, by referring
also to FIG. 31.
[0223] First, substrate W having the seed layer 6 thereon is taken
one by one out of the transfer box 210, and the substrate W is
carried in the loading/unloading station 214. The substrate W is
then reversed, if necessary, and transferred to the plating
apparatus 218. In the plating apparatus 218, a copper layer 7 is
deposited by plating on the surface of the substrate W, thereby
effecting embedding of copper, as shown in FIG. 4B. The plating is
carried out under a constant-voltage control or a constant-current
control. In the case of constant-voltage control, the current value
during plating is monitored, and feeding of electricity is stopped
after elapse of a predetermined period of time from a point of time
at which the current value becomes constant, thereby stopping
plating. In the case of constant-current control, the voltage value
during plating is monitored, and feeding of electricity is stopped
after elapse of a predetermined period of time from a point of time
at which the voltage value becomes constant, thereby stopping
plating. Such a manner of controlling the end point of plating
makes it possible to obtain the intended plated film with a flat
surface without applying an extra plating to the substrate.
[0224] Then, the substrate W having the copper layer 7 formed
thereon is transferred to the cleaning and drying apparatus 220 by
the transfer robot 216, and the substrate W is cleaned by pure
water and spin-dried. Alternatively, in a case where a spin-drying
function is provided in the plating apparatus 218, the substrate W
is spin-dried (removal of liquid) in the plating apparatus 218. The
dried substrate is then transferred to the bevel etching and
backside cleaning apparatus 222.
[0225] In the bevel etching and backside cleaning apparatus 222,
unnecessary copper attached to the bevel (edge) portion of the
substrate W is removed by etching, and at the same time, the
backside surface of the substrate is cleaned by pure water or the
like. Thereafter, as described above, the substrate W is
transferred to the cleaning and drying apparatus 220 by the
transfer robot 216, and the substrate W is cleaned by pure water
and spin-dried. Alternatively, in a case where a spin-drying
function is provided in the bevel etching and backside cleaning
apparatus 222, the substrate W is spin-dried in the bevel etching
and backside cleaning apparatus 222. The dried substrate is then
transferred to the heat treatment apparatus 226 by the transfer
robot 216.
[0226] In the heat treatment apparatus 226, heat treatment
(annealing) of the substrate W is carried out. The heat-treated
substrate is then transferred to the polishing apparatus 232 by the
transfer robot 216.
[0227] As shown in FIG. 4C, unnecessary copper layer 7 and the seed
layer 6 deposited on the surface of the substrate W are polished
and removed by the polishing apparatus 232 to planalize the surface
of the substrate W. At this time, for example, the film thickness
and the finishing state of the substrate are inspected by a
monitor, and when an end point is detected by the monitor,
polishing is finished. Then, the substrate W which has been
polished is transferred to the cleaning and drying apparatus 220 by
the transfer robot 216, and the surface of the substrate is cleaned
by a chemical liquid and then cleaned (rinsed) with pure water, and
then spin-dried by rotating the substrate at a high speed in the
cleaning and drying apparatus 220. After this spin-drying, the
substrate W is transferred to the pretreatment apparatus 228 by the
transfer robot 216.
[0228] In the pretreatment apparatus 228, a pretreatment before
plating comprising at least one of attachment of Pd catalyst to the
surface of the substrate and removal of oxide film attached to the
exposed surface of the substrate, for example, is carried out.
Then, the substrate after this pretreatment, as described above, is
transferred to the cleaning and drying apparatus 220 by the
transfer robot 216, and the substrate W is cleaned by pure water
and spin-dried. Alternatively, in a case where a spin-drying
function is provided in the pretreatment apparatus 228, the
substrate W is spin-dried (removal of liquid) in the pretreatment
apparatus 228. The dried substrate is then transferred to the
electroless plating apparatus 230 by the transfer robot 216.
[0229] In the electroless plating apparatus 230, as shown in FIG.
4D, for example, electroless CoWP plating is applied to the
surfaces of the exposed interconnects 8 to form a protective film
(plated film) 9 composed of CoWP alloy selectively on the exposed
surfaces of the interconnects 8, thereby protecting the
interconnects 8. The thickness of the protective film 9 is in the
range of 0.1 to 500 nm, preferably in the range of 1 to 200 nm,
more preferably in the range of 10 to 100 nm. At this time, for
example, the thickness of the protective film 9 is monitored, and
when the film thickness reaches a predetermined value, i.e., an end
point is detected, the electroless plating is finished.
[0230] After the electroless plating, the substrate W is
transferred to the cleaning and drying apparatus 220 by the
transfer robot 216, and the surface of the substrate is cleaned by
a chemical liquid, and cleaned (rinsed) with pure water, and then
spin-dried by rotating the substrate at a high speed in the
cleaning and drying apparatus 220. After the spin-drying, the
substrate W is returned into the transfer box 210 via the
loading/unloading station 214 by the transfer robot 216.
[0231] According to this embodiment, copper is used as a
interconnect material. Besides copper, a copper alloy, silver, or a
silver alloy, or the like may be used as a interconnect
material.
[0232] According to the present invention, the so-called flattening
plating can be carried out securely until completion of a plated
film having a flat surface. Further, the present invention can
avoid application of an extra plating to a substrate, thereby
reducing the material cost and also reducing the cost and the
technical burden of a later polishing process. In addition, the
present invention can eliminate the need for a costly mechanism,
such as a film-thickness monitor, thus lowering the cost of the
plating apparatus.
[0233] FIG. 32 is a plan view showing a substrate processing
apparatus incorporating a plating apparatus according to the
present invention. As shown in FIG. 32, this substrate processing
apparatus has a apparatus frame which houses therein two
loading/unloading units 10 for housing a plurality of substrates W
therein, two plating apparatuses 12 for performing plating process,
a transfer robot 14 for transferring substrates W between the
loading/unloading units 10 and the plating apparatuses 12, and
plating solution supply equipment 18 having a plating solution tank
16.
[0234] The plating apparatus 12, as shown in FIG. 33, is provided
with a substrate processing section 20 for performing plating
process and processing incidental thereto, and a plating solution
tray 22 for storing a plating solution is disposed adjacent to the
substrate processing section 20. There is also provided an
electrode arm portion 30 having an electrode head 28 which is held
at a front end of a pivot arm 26 swingable about a rotating shaft
24, and which is swung between the substrate processing section 20
and the plating solution tray 22. Furthermore, a
pre-coating/recovering arm 32, and fixed nozzles 34 for ejecting
pure water or a chemical liquid such as ion water, and also a gas
or the like toward a substrate are disposed laterally of the
substrate processing section 20. In this embodiment, three of the
fixed nozzles 34 are disposed, and one of them is used for
supplying pure water.
[0235] The substrate processing section 20, as shown in FIG. 34,
has a substrate holder 36 for holding a substrate W with its
surface (surface to be plated) facing upwardly, and a cathode
section 38 located above the substrate holder 36 so as to surround
a peripheral portion of the substrate holder 36. Further, a
substantially cylindrical bottomed cup 40 surrounding a periphery
of the substrate holder 36, for preventing scatter of various
chemical liquids used during processing, is provided so as to be
vertically movable by an air cylinder (not shown).
[0236] The substrate holder 36 is adapted to be raised and lowered
by the air cylinder 44 to and from a lower substrate transfer
position A, an upper plating position B, and a
pretreatment/cleaning position C that is intermediate these
positions A and B. The substrate holder 36 is also adapted to
rotate, at an arbitrary acceleration and an arbitrary velocity,
integrally with the cathode section 38 by a rotating motor and a
belt (not shown). Substrate carry-in and carry-out openings (not
shown) are provided in confrontation with substrate transfer
position A in a side panel of the plating apparatus 12 facing the
transfer robot 14. When the substrate holder 36 is raised to
plating position B, a seal member 90 and cathode electrodes 88 (to
be described below) of the cathode section 38 are brought into
contact with a peripheral portion of substrate W held by the
substrate holder 36. On the other hand, the cup 40 has an upper end
located below the substrate carry-in and carry-out openings, and
when the cup 40 ascends, the upper end of the cup 40 reaches a
position above the cathode section 38 closing the substrate
carry-in and carry-out openings, as shown by imaginary lines in
FIG. 34.
[0237] The plating solution tray 22 serves to wet a below-described
high resistance structure 110 and an anode 98 of the electrode arm
portion 30 with a plating solution, when plating has not been
performed. The plating solution tray 22 is set at a size in which
the high resistance structure 110 can be accommodated, and the
plating solution tray 22 has a plating solution supply port and a
plating solution drainage port (not shown). A photo-sensor is
attached to the plating solution tray 22, and can detect brimming
with the plating solution in the plating solution tray 22, i.e.,
overflow, and drainage.
[0238] The electrode arm portion 30 is vertically movable by a
vertical movement motor 132, which is a servomotor, and a ball
screw 134, and swingable between the plating solution tray 22 and
the substrate processing section 20 by a swing motor, in this
embodiment, as described bellow. A pneumatic actuator may be
used.
[0239] As shown in FIG. 35, the pre-coating/recovering arm 32 is
coupled to an upper end of a vertical support shaft 58. The
pre-coating/recovering arm 32 is swingable by a rotary actuator 60
and is also vertically moveable by an air cylinder (not shown). The
pre-coating/recovering arm 32 supports a pre-coating nozzle 64, for
discharging a pre-coating liquid, on its free end side, and a
plating solution recovering nozzle 66, for recovering the plating
solution, on a portion closer to its proximal end. The pre-coating
nozzle 64 is connected to a syringe that is actuatable by an air
cylinder, for example, for intermittently discharging a pre-coating
liquid from the pre-coating nozzle 64. The plating solution
recovering nozzle 66 is connected to a cylinder pump or an
aspirator, for example, to draw the plating solution on the
substrate from the plating solution recovering nozzle 66.
[0240] As shown in FIGS. 36 through 38, the substrate holder 36 has
a disk-shaped substrate stage 68 and six vertical support arms 70
disposed at spaced intervals on the circumferential edge of the
substrate stage 68 for holding a substrate W in a horizontal plane
on respective upper surfaces of the support arms 70. A positioning
plate 72 is mounted on an upper end one of the support arms 70 for
positioning the substrate by contacting the end face of the
substrate. A pressing finger 74 is rotatably mounted on an upper
end of the support arm 70, which is positioned opposite to the
support arm 70 having the positioning plate 72, for abutting
against an end face of the substrate W and pressing the substrate W
to the positioning plate 72 when rotated. Chucking fingers 76 are
rotatably mounted on upper ends of the remaining four support arms
70 for pressing the substrate W downwardly and gripping the
circumferential edge of the substrate W.
[0241] The pressing finger 74 and the chucking fingers 76 have
respective lower ends coupled to upper ends of pressing pins 80
that are normally urged to move downwardly by coil springs 78. When
the pressing pins 80 are moved downwardly, the pressing finger 74
and the chucking fingers 76 are rotated radially inwardly into a
closed position. A support plate 82 is disposed below the substrate
stage 68 for engaging lower ends of the opening pins 80 and pushing
them upwardly.
[0242] When the substrate holder 36 is located in substrate
transfer position A shown in FIG. 34, the pressing pins 80 are
engaged and pushed upwardly by the support plate 82, so that the
pressing finger 74 and the chucking fingers 76 rotate outwardly and
open. When the substrate stage 68 is elevated, the opening pins 80
are lowered under the resiliency of the coil springs 78, so that
the pressing finger 74 and the chucking fingers 76 rotate inwardly
and close.
[0243] As shown in FIGS. 39 and 40, the cathode section 38
comprises an annular frame 86 fixed to upper ends of vertical
support columns 84 mounted on the peripheral portion of the support
plate 82 (see FIG. 38), a plurality of, six in this embodiment,
cathode electrodes 88 attached to a lower surface of the annular
frame 86 and projecting inwardly, and an annular seal member 90
mounted on an upper surface of the annular frame 86 in covering
relation to upper surfaces of the cathode electrodes 88. The seal
member 90 is adapted to have an inner peripheral edge portion
inclined inwardly downwardly and progressively thin-walled, and to
have an inner peripheral end suspending downwardly.
[0244] When the substrate holder 36 has ascended to plating
position B, as shown FIG. 43, the cathode electrodes 88 are pressed
against the peripheral portion of the substrate W held by the
substrate holder 36 for thereby allowing electric current to pass
through the substrate W. At the same time, an inner peripheral end
portion of the seal member 90 is brought into contact with an upper
surface of the peripheral portion of the substrate W under pressure
to seal its contact portion in a watertight manner. As a result,
the plating solution supplied onto the upper surface (surface to be
plated) of the substrate W is prevented from seeping from an end
portion of the substrate W, and the plating solution is prevented
from contaminating the cathode electrodes 88.
[0245] In the present embodiment, the cathode section 38 is
vertically immovable, but rotatable with the substrate holder 36.
However, the cathode section 38 may be arranged such that it is
vertically movable and the seal member 90 is pressed against the
surface, to be plated, of the substrate W when the cathode section
38 is lowered.
[0246] As shown in FIGS. 41 and 42, the electrode head 28 of the
electrode arm section 30 includes a housing 94 which is coupled via
a ball bearing 92 to the free end of the pivot arm 26, and a high
resistance structure (plating solution impregnated material) 110
which is disposed such that it closes the bottom opening of the
housing 94 and composed of a water-retentive material. The housing
94 has at its lower end an inwardly-projecting portion 94a, while
the high resistance structure 110 has at its top a flange portion
110a. The flange portion 110a is engaged with the
inwardly-projecting portion 94a and a spacer 96 is interposed
therebetween. The high resistance structure 110 is thus held with
the housing 94, while a hollow plating solution chamber 100 is
defined in the housing 94.
[0247] The high resistance structure (plating solution impregnated
material) 110 is composed of porous ceramics such as alumina, SiC,
mullite, zirconia, titania or cordierite, or a hard porous material
such as a sintered compact of polypropylene or polyethylene, or a
composite material comprising these materials. The high resistance
structure 110 may be composed of a woven fiver or non-woven fiber.
In case of the alumina-based ceramics, for example, the ceramics
with a pore diameter of 30 to 200 .mu.m is used. In case of the
SiC, SiC with a pore diameter of not more than 30 .mu.m, a porosity
of 20 to 95%, and a thickness of about 1 to 20 mm, preferably 5 to
20 mm, more preferably 8 to 15 mm, is used. The high resistance
structure 110, in this embodiment, is constituted of porous
ceramics of alumina having a porosity of 30%, and an average pore
diameter of 100 .mu.m. The porous ceramic plate per se is an
insulator, but has a lower electric conductivity than a plating
solution by causing plating solution to enter its interior
complicatedly and follow a considerably long path in the thickness
direction.
[0248] The high resistance structure (plating solution impregnated
material) 110, which has the high resistance, is disposed in he
plating solution chamber 100. Hence, the influence of sheet
resistance of the surface of the substrate, such as seed layer 7
(see FIG. 4A), becomes a negligible degree. Consequently, the
difference in current density over the surface of the substrate due
to sheet resistance on the surface of the substrate W becomes
small, and the uniformity of the plated film over the surface of
the substrate improves.
[0249] In the plating solution chamber 100, there is disposed an
anode 98 held in abutment against an lower surface of a plating
solution introduction pipe 104 disposed above the anode 98. The
plating solution introduction pipe 104 has a plating solution
introduction port 104a connected to a plating solution supply pipe
102 which extends from the plating solution supply unit 18 (see
FIG. 32). A plating solution discharge port 94b provided in an
upper plate of the housing 94 is connected to an plating solution
discharge pipe 106 communicating with the plating solution chamber
100.
[0250] A manifold structure is employed for the plating solution
introduction pipe 104 so that the plating solution can be supplied
uniformly onto the plating surface of the substrate. In particular,
a large number of narrow tubes (not shown), communicating with the
plating solution introduction pipe 104, are connected to the pipe
104 at predetermined positions along the long direction of the pipe
104. Further, small holes are provided in the anode 98 and the high
resistance structure 110 at positions corresponding to the narrow
tubes. The narrow tubes extend downwardly in the small holes and
reach the lower surface or its vicinity of the high resistance
structure 110.
[0251] Thus, the plating solution, introduced from the plating
solution supply pipe 102 into the plating solution introduction
pipe 104, passes through the narrow tubes and reaches the bottom of
the high resistance structure (plating solution impregnated
material) 110, and pass through the high resistance structure 110
and fills the plating solution chamber 100, whereby the anode 98 is
immersed in the plating solution. The plating solution is
discharged from the plating solution discharge pipe 106 by
application of suction to the plating solution discharge pipe
106.
[0252] The anode 98 may have a number of vertically through holes
for allowing a plating solution introduced into the plating
solution chamber 100 to flow through the through holes to the high
resistance structure 110.
[0253] In order to suppress slime formation, the anode 98 is
generally made of copper (phosphorus-containing copper) containing
0.03 to 0.05% of phosphorus. In this embodiment, an insoluble
anode, which comprises an insoluble metal such as platinum or
titanium, or an insoluble electrode comprising metal on which
platinum or the like is plated, is used as the anode 98. By using
an insoluble anode as the anode 98, the anode 98 is prevented from
changing its shape by being dissolved, and a constant discharged
state can be maintained at all times without the need for replacing
the anode 98.
[0254] The anode 98 comprises, in this embodiment, four concentric
split anodes 98a through 98d with ring-shaped insulating members
99a through 99c interposed between split surfaces of the split
anodes 98a through 98d. Specifically, the anode 98 comprises a
first split anode 98a in the form of a solid disk that is
positioned centrally, a second split anode 98b in the form of a
hollow disk that is positioned in surrounding relation to the first
split anode 98a, a third split anode 98c in the form of a hollow
disk that is positioned in surrounding relation to the second split
anode 98b, and a fourth split anode 98d in the form of a hollow
disk that is positioned in surrounding relation to the third split
anode 98c. The ring-shaped insulating members 99a through 99c are
interposed between the first and second split anodes 98a, 98b, the
second and third split anodes 98b, 98c, and the third and fourth
split anodes 98c, 98d. The split anodes 98a through 98d and the
ring-shaped insulating members 99a through 99c are disposed in a
planar configuration.
[0255] The cathode electrodes 88 are electrically connected to the
cathode of a plating power source 114 and the anode 98 is
electrically connected to the anode of the plating power source
114. The plating power source 114 is arranged to be able to change
the direction of an electric current which flows, as desired. In
this embodiment, the plating apparatus has a rectifier 115 serving
as a rectifying mechanism. The rectifier 115 has elements or parts
for individually adjusting voltages or currents as desired that are
supplied between the first split anode 98a and the surface to be
plated of the substrate, the second split anode 98b and the surface
to be plated of the substrate, the third split anode 98c and the
surface to be plated of the substrate, and the fourth split anode
98d and the surface to be plated of the substrate.
[0256] In an initial plating period, for example, the electric
current is adjusted to make the current density thereof
progressively higher at central areas of the anode 98 than at
circumferential areas thereof, i.e., progressively higher
successively from the fourth split anode 98d to the third split
anode 98c to the second split anode 98b to the first split anode
98a, to pass the plating current to a central area of the substrate
W. Furthermore, a large resistance is developed in the high
resistance structure 110 which retains the plating solution therein
to the extent that the sheet resistance of the surface of the
substrate is negligible. Therefore, even if the substrate has a
higher sheet resistance, within-wafer differences of the current
density due to the sheet resistance of the substrate are reduced to
make it possible to reliably form a plated film of more uniform
film thickness.
[0257] As shown in FIG. 44, the split anodes 98a through 98d may be
arranged such that they have staggering surfaces facing the
substrate W, to make the distance H between the anode 98 and the
substrate W differently partially, i.e., at the split anodes 98a
through 98d, for thereby adjusting the distribution of current
densities between the anode 98 and the substrate W. Furthermore,
although not shown, the split anodes 98a through 98d may be
associated with respective rectifiers (rectifying mechanisms),
instead of the above rectifier 115. The rectifier 115 preferably
have a mechanism for optimizing the distribution of currents or
voltages supplied between the anode 98 and the surface to be plated
of the substrate. In this manner, the distribution of current
densities between the anode 98 and the surface to be plated of the
substrate can automatically be optimized.
[0258] The ball bearing 92 is coupled to the pivot arm 26 via a
support member 124. The pivot arm 26 is vertically movable by a
vertical movement motor 132, which is a servomotor, and a ball
screw 134. It is also possible to use a pneumatic actuator to
constitute a vertical movement mechanism.
[0259] When carrying out electroplating, the substrate holder 36 is
positioned at plating position B (see FIG. 43). The electrode head
28 is lowered until the distance between the substrate W held by
the substrate holder 36 and the high resistance structure 110
becomes e.g. about 0.1 to 3 mm. A plating solution is supplied from
the plating solution supply pipe 102 to the upper surface (surface
to be plated) of the substrate W while impregnating the high
resistance structure 110 with the plating solution and filling the
plating solution chamber 100 with the plating solution to carry out
plating of the surface to be plated of the substrate W.
[0260] The operation of the substrate processing apparatus
incorporating the above-described plating apparatus will now be
described.
[0261] First, a substrate W to be plated is taken out from one of
the loading/unloading units 10 by the transfer robot 14, and
transferred, with the surface to be plated facing upwardly, through
the substrate carry-in and carry-out opening defined in the side
panel, into one of the plating apparatuses 12. At this time, the
substrate holder 36 is in lower substrate transfer position A.
After the hand of the transfer robot 14 has reached a position
directly above the substrate stage 68, the hand of the transfer
robot 14 is lowered to place the substrate W on the support arms
70. The hand of the transfer robot 14 is then retracted through the
substrate carry-in and carry-out opening.
[0262] After the hand of the transfer robot 14 is retracted, the
cup 40 is elevated. Then, the substrate holder 36 is lifted from
substrate transfer position A to pretreatment/cleaning position C.
As the substrate holder 36 ascends, the substrate W placed on the
support arms 70 is positioned by the positioning plate 72 and the
pressing finger 74, and then reliably gripped by the chucking
fingers 76.
[0263] On the other hand, the electrode head 28 of the electrode
arm portion 30 is in a normal position over the plating solution
tray 22 now, and the high resistance structure 110 or the anode 98
is positioned in the plating solution tray 22. At the same time
that the cup 40 ascends, plating solution starts being supplied to
the plating solution tray 22 and the electrode head 28. Until the
step of plating the substrate W is initiated, the new plating
solution is supplied, and the plating solution discharge pipe 106
is evacuated to replace the plating solution in the high resistance
structure (plating solution impregnated material) 110 and remove
air bubbles from the plating solution in the high resistance
structure 110. When the ascending movement of the cup 40 is
completed, the substrate carry-in and carry-out openings in the
side panel is closed by the cup 40, isolating the atmosphere in the
side panel and the atmosphere outside of the side panel from each
other.
[0264] When the cup 40 is elevated, the pre-coating step is
initiated. Specifically, the substrate holder 36 that has received
the substrate W is rotated, and the pre-coating/recovering arm 32
is moved from the retracted position to a position confronting the
substrate W. When the rotational speed of the substrate holder 36
reaches a preset value, the pre-coating nozzle 64 mounted on the
tip end of the pre-coating/recovering arm 32 intermittently
discharges a pre-coating liquid which comprises a surface active
agent, for example, toward the plating surface of the substrate W.
At this time, since the substrate holder 36 is rotating, the
pre-coating liquid spreads all over the plating surface of the
substrate W. Then, the pre-coating/recovering arm 32 is returned to
the retracted position, and the rotational speed of the substrate
holder 36 is increased to spin the pre-coating liquid off and dry
the plating surface of the substrate W.
[0265] After the completion of the pre-coating step, the plating
step is initiated. First, the substrate holder 36 is stopped
against rotation, or the rotational speed thereof is reduced to a
preset rotational speed for plating. In this state, the substrate
holder 36 is lifted to plating position B. Then, the peripheral
portion of the substrate W is brought into contact with the cathode
electrodes 88, when it is possible to pass an electric current, and
at the same time, the seal member 90 is pressed against the upper
surface of the peripheral portion of the substrate W, thus sealing
the peripheral portion of the substrate W in a water-tight
manner.
[0266] Based on a signal indicating that the pre-coating step for
the loaded substrate W is completed, the electrode arm portion 30
is swung in a horizontal direction to displace the electrode head
28 from a position over the plating solution tray 22 to a position
over the plating processing position. After the electrode head 28
reaches this position, the electrode head 28 is lowered toward the
cathode section 38. At this time, the high resistance structure 110
does not contact with the surface to be plated of the substrate W,
but is held closely to the surface to be plated of the substrate W
at a distance ranging from 0.1 mm to 3 mm. When the descent of the
electrode head 28 is completed, the plating process is
initiated.
[0267] That is, the cathode of the plating power source 114 is
connected to the cathode electrodes 88 and the anode of the plating
power source 114 is connected to the split anodes 98a through 98d,
and a constant voltage control process is performed for applying a
constant voltage between the cathode electrodes 88 and the split
anodes 98a through 98d. At the same time, the plating solution is
supplied from the plating solution supply pipe 102 into the
electrode head 28 to fill the plating solution chamber 100 with the
plating solution from the upper surface (surface to be plated) of
the substrate W while impregnating the high resistance structure
110 with the plating solution. At this time, if necessary, the
voltage applied between the split anodes 98a through 98d and the
cathode electrodes 88 is adjusted.
[0268] By thus supplying the plating solution while performing the
constant voltage control process for applying a constant voltage
between the cathode electrodes 88 and the split anodes 98a through
98d, the seed layer 6 (see FIG. 1A) is prevented from being
dissolved into the plating solution when the substrate W is brought
into contact with the plating solution.
[0269] After the introduction of the plating solution is finished,
a constant current control process is performed for passing a
constant current between the cathode electrodes 88 and the split
anodes 98a through 98d to deposit a plated film on the surface (the
seed layer 7) of the substrate. In the initial plating stage, as
described above, the electric current is adjusted to make the
current density thereof progressively higher at central areas of
the anode 98 than at circumferential areas thereof, i.e.,
progressively higher successively from the fourth split anode 98d
to the third split anode 98c to the second split anode 98b to the
first split anode 98a, to pass the plating current to a central
area of the substrate W, thereby forming a plated film. When the
thickness of the plated film is increased and the sheet resistance
is lowered, the current densities at the four split anodes 98a
through 98d are equalized. At this time, if necessary, the
substrate holder 36 is rotated at a low speed.
[0270] In this manner, even if the substrate has a high sheet
resistance, a plated film of more uniform film thickness can be
formed on the entire surface to be plated of the substrate to embed
plated metal in the fine recesses including contact holes 3 and
trenches 4 (see FIG. 4B) without developing voids therein.
[0271] When the film thickness of the plated film has reached a
predetermined value, the current (voltage) may be switched to
convert the cathode electrodes 88 into anodes and the split anodes
98a through 98d into cathode electrodes, and a constant current may
be passed between the cathode electrodes (anodes) 88 and the split
anodes (cathode electrodes) 98a through 98d to etch the surface of
the plated film into a flat surface, after which the current
(voltage) may be switched to convert the cathode electrodes 88 back
into cathode electrodes and the split anodes 98a through 98d back
into anodes.
[0272] When the plating process is completed, the electrode arm
portion 30 is raised and then swung to return to the position above
the plating solution tray 22 and to lower to the ordinary position.
Then, the pre-coating/recovering arm 32 is moved from the retreat
position to the position confronting to the substrate W, and
lowered to recover the remainder of the plating solution on the
substrate W by a plating solution recovering nozzle 66. After
recovering of the remainder of the plating solution is completed,
the pre-coating/recovering arm 32 is returned to the retreat
position, and pure water is supplied from the fixed nozzle 34 for
supplying pure water toward the central portion of the substrate W
for rinsing the plated surface of the substrate. At the same time,
the substrate holder 36 is rotated at an increased speed to replace
the plating solution on the surface of the substrate W with pure
water. Rinsing the substrate W in this manner prevents the
splashing plating solution from contaminating the cathode
electrodes 88 of the cathode section 38 during descent of the
substrate holder 36 from plating position B.
[0273] After completion of the rinsing, the washing with water step
is initiated. That is, the substrate holder 36 is lowered from
plating position B to pretreatment/cleaning position C. Then, while
pure water is supplied from the fixed nozzle 34 for supplying pure
water, the substrate holder 36 and the cathode section 38 are
rotated to perform washing with water. At this time, the seal
member 90 and the cathode electrodes 88 can also be cleaned,
simultaneously with the substrate W, by pure water directly
supplied to the cathode portion 38, or pure water scattered from
the surface of the substrate W.
[0274] After washing with water is completed, the drying step is
initiated. That is, supply of pure water from the fixed nozzle 34
is stopped, and the rotational speed of the substrate holder 36 and
the cathode section 38 is further increased to remove pure water on
the surface of the substrate W by centrifugal force and to dry the
surface of the substrate W. The seal member 90 and the cathode
electrodes 88 are also dried at the same time. Upon completion of
the drying, the rotation of the substrate holder 36 and the cathode
section 38 is stopped, and the substrate holder 36 is lowered to
substrate transfer position A. Thus, the gripping of the substrate
W by the chucking fingers 76 is released, and the substrate W is
just placed on the upper surfaces of the support arms 70. At the
same time, the cup 40 is also lowered.
[0275] All the steps including the plating step, the pretreatment
step accompanying to the plating step, the cleaning step, and the
drying step are now finished. The transfer robot 14 inserts its
hand through the substrate carry-in and carry-out opening into the
position beneath the substrate W, and raises the hand to receive
the plated substrate W from the substrate holder 36. Then, the
transfer robot 14 returns the plated substrate W received from the
substrate holder 36 to one of the loading/unloading units 10.
[0276] FIG. 45 shows another anode. The anode 150 shown in FIG. 14
comprises a plurality of insulating members 154 disposed in a grid
pattern in a cylindrical housing 152, and a plurality of split
anodes 156 in the form of rectangular chips disposed individually
in respective cells defined by the insulating members 154. A
rectifier 160 serving as a rectifying mechanism connected to a
plating power source 158 has elements or parts for individually
adjusting voltages or currents as desired that are supplied between
the split anodes 156 and the surface to be plated of the
substrate.
[0277] If the anode 150 thus constructed is used in place of the
anode 58 of the plating apparatus 12 shown in FIGS. 32 through 42,
then the current density may be changed between a certain portion
of the substrate facing the anode 150 and another portion thereof.
Depending on an amount of plating electrolysis (plating
deposition), for example, the distribution of currents or voltages
supplied between the split anodes 156 and the surface to be plated
of the substrate may be changed to fill fine recesses with plated
metal, or depending on the shape of a pattern of fine recesses
formed in the surface of the substrate, the distribution of
currents or voltages supplied between the split anodes 156 and the
surface to be plated of the substrate may be changed to fill fine
recesses with plated metal.
[0278] At this time, in the same manner as described above, the
rectifier 160 may have a mechanism for optimizing the distribution
of currents or voltages supplied between the split anodes 156 and
the surface to be plated of the substrate, so that the distribution
of current densities between the split anodes 156 and the surface
to be plated of the substrate can automatically be optimized.
[0279] In this embodiment, the voltages or currents supplied
between the split anodes 156 and the surface to be plated of the
substrate can individually be adjusted as desired. However, the
split anodes 156 may be divided into split anode groups each
comprising a plurality of split anodes, and the voltages or
currents supplied between the split anode groups and the surface to
be plated of the substrate may individually be adjusted as
desired.
[0280] The split anodes in the form of chips are not limited to a
rectangular shape, but may be of any desired shapes such as a
triangular shape. Alternatively, the concentric split anodes as
described above and the split anodes in the form of chips may be
combined with each other.
[0281] FIG. 46 shows an overall layout plan of another substrate
processing apparatus provided with a plating apparatus according to
the present invention. The substrate processing apparatus includes
two loading/unloading sections 1202 for carrying a substrate in and
out a main frame 1200. Inside the main frame 1200 are disposed a
heat treatment apparatus 1204 for heat treatment (annealing) a
plated film formed on the substrate, a bevel-etching apparatus 1206
for removing a plated film formed on or adhering to a peripheral
portion of the substrate, two cleaning and drying apparatuses 1208
for cleaning the surface of the substrate with a cleaning liquid,
such as a chemical liquid or pure water, and spin-drying the
cleaned substrate, a substrate stage 1210 for temporarily placing
the substrate thereon, and two plating apparatuses 1212. Inside the
main frame 1200 are also provided a movable first transfer robot
1214 for transferring the substrate between the loading/unloading
sections 1202 and the substrate stage 1210, and a movable second
transfer robot 1216 for transferring the substrate between the
substrate stage 1210, the heat treatment apparatus 1204, the
bevel-etching apparatus 1206, the cleaning and drying apparatuses
1208 and the plating apparatuses 1212. According to this
embodiment, the plating apparatus 1212 has a similar construction
to that of the plating apparatus 12 shown in FIGS. 32 through
42.
[0282] The main frame 1200 has been made light-shielding so that
the following process steps can be carried out under light-shielded
conditions in the main frame 1200, i.e. without irradiation of a
light, such as an illuminating light, onto the interconnects of the
substrate. This prevents corrosion of interconnects of e.g. copper
due to potential difference that would be produced by light
irradiation onto the interconnects.
[0283] Positioned beside the main frame 1200, there is provided a
plating solution management apparatus 1224 which includes a plating
solution tank 1220 and a plating solution analyzer 1222, and which
analyzes and manages the components of a plating solution for use
in the plating apparatuses 1212 and supplies the plating solution
of a predetermined composition to the plating apparatuses 1212. The
plating solution analyzer 1222 includes an organic material
analysis section for analyzing an organic material by cyclic
voltammetry (CVS), liquid chromatography, etc., and an inorganic
material analysis section for analyzing an inorganic material by
neutralization titration, oxidation-reduction titration,
polarography, electrometric titration, etc. The results of analysis
by the plating solution analyzer 1222 are fed back to adjust the
components of the plating solution in the plating solution tank
1220. The plating solution management apparatus 1224 may also be
disposed inside the main frame 1200.
[0284] An example of the formation of copper interconnects by the
substrate processing apparatus, as illustrated in FIG. 47, will now
be described.
[0285] First, substrates W each having a seed layer 6 (see FIG. 1A)
as a electric supply layer formed on a surface are prepared, and a
substrate cassette housing the substrates is mounted in the
loading/unloading section 1202. One substrate W is taken by the
first transfer robot 1214 out of the cassette mounted in the
loading/unloading section 1202, and the substrate is carried in the
main frame 1200, transferred to the substrate stage 1210, and
placed and held on the substrate stage 1210. The substrate held on
the substrate stage 1210 is transferred by the second transfer
robot 1216 to one of the plating apparatuses 1212.
[0286] In the plating apparatus 1212, as with the above-described
embodiment, a pre-plating treatment, such as pre-coating, of the
surface (surface to be plated) of the substrate W is first carried
out. Thereafter, plating of the substrate is carried out. During
the plating, the composition of the plating solution in the plating
solution tank 1220 is analyzed by the plating solution analyzer
1222, and a shortage of a component is replenished in the plating
solution in the plating solution tank 1220 so that the plating
solution of a constant composition is supplied to the plating
apparatus 1212. After completion of the plating, as with the
above-described embodiment, the plating solution remaining on the
substrate is recovered and the plated surface of the substrate is
rinsed, and the surface of the substrate is cleaned (water-washed)
with e.g. pure water. The substrate after cleaning is transferred
by the second transfer robot 1216 to the bevel-etching apparatus
1206.
[0287] In the bevel-etching apparatus 1206, while rotating the
substrate which is held horizontally, an acid solution is supplied
continuously to the central portion of the front surface of the
substrate and an oxidizing agent solution is supplied continuously
or intermittently to a peripheral portion of the front surface. The
acid solution may be of any non-oxidative acid, such as
hydrofluoric acid, hydrochloric acid, sulfuric acid, citric acid,
oxalic acid, etc. Examples of the oxidizing agent solution include
ozone water, hydrogen peroxide solution, nitric acid solution, and
sodium hypochlorite solution, and a combination thereof. Copper,
etc. formed on or adhering to a peripheral portion (bevel portion)
of the substrate W is rapidly oxidized by the oxidizing agent
solution, and the oxidized product is etched and dissolved out by
the acid solution which is supplied to the central portion of the
substrate and spreads over the entire surface of the substrate.
[0288] During the above etching processing, an oxidizing agent
solution and an etching agent for silicon oxide film may be
supplied simultaneously or alternately to the central portion of
the back surface of the substrate, thereby oxidizing copper etc. in
elemental form adhering to the back surface of the substrate W,
together with the silicon of the substrate, with the oxidizing
agent solution and etching away the oxidized product with the
etching agent.
[0289] The substrate after bevel-etching is transferred by the
second transfer robot 1216 to one of the cleaning and drying
apparatuses 1208, where the surface of the substrate is cleaned
with a cleaning liquid, such as a chemical liquid or pure water,
followed by spin-drying. The dried substrate is transferred by the
second transfer robot 1216 to the heat treatment apparatus
1204.
[0290] In the heat treatment apparatus 1204, heat treatment
(annealing) of the copper layer 7 (see FIG. 1B) formed on the
surface of the substrate W is carried out, thereby crystallizing
the copper layer 7 for forming interconnects. The heat treatment
(annealing) is carried out by heating the substrate, for example,
at 400.degree. C. for about a few tens of seconds to 60 seconds. At
the same time, if necessary, a gas for oxidation inhibition is
introduced into the heat treatment apparatus 1204 and is allowed to
flow along the surface of the substrate to prevent oxidation of the
surface of the copper layer 7. The heating temperature of the
substrate is generally 100 to 600.degree. C., preferably 300 to
400.degree. C.
[0291] The substrate W after heat treatment is transferred by the
second transfer robot 1216 to the substrate stage 1210 and held on
the substrate stage 1210. The substrate on the substrate stage 1210
is returned by the first transfer robot 1214 to the cassette of the
loading/unloading section 1202.
[0292] Thereafter, extra metal formed on the insulating film and
the barrier layer are removed by method such as chemical mechanical
polishing (CMP) so as to flatten the surface, whereby forming
interconnects 8 composed of the seed layer 6 and the copper layer
6, as shown in FIG. 17C.
[0293] In the above embodiments, the barrier layer is made of TaN,
TiN, or the like, and the seed layer is made of copper. However,
they may be made of Ti, V, Cr, Ni, Zr, Nb, Mo, Ta, Hf, W, Ru, Rh,
Pd, Ag, Au, Pt, or Ir, or a nitride thereof.
[0294] According to the present invention, the high resistance
structure made of a water-retentive material is disposed between
the anode and the surface to be plated of the substrate, and the
anode is given a potential gradient. Even if the substrate has a
high sheet resistance, a plated film of more uniform film thickness
can be formed on the entire surface to be plated of the substrate
to reliably the plated metal within the fine recesses without
forming voids therein.
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