U.S. patent application number 10/860115 was filed with the patent office on 2005-02-03 for plating apparatus, plating method and substrate processing apparatus.
Invention is credited to Fukunaga, Yukio, Kanda, Hiroyuki, Katsuoka, Seiji, Kunisawa, Junji, Makino, Natsuki, Mishima, Koji, Morisawa, Shinya, Nagai, Mizuki, Nakada, Tsutomu, Yamamoto, Satoru.
Application Number | 20050023149 10/860115 |
Document ID | / |
Family ID | 34108555 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050023149 |
Kind Code |
A1 |
Nakada, Tsutomu ; et
al. |
February 3, 2005 |
Plating apparatus, plating method and substrate processing
apparatus
Abstract
The present invention provides a plating apparatus which uses an
insoluble anode and which can perform plating of a substrate stably
while preventing oxygen gas, generated due to the use of the
insoluble anode, from causing defects in the substrate. The plating
apparatus includes: a substrate holder for holding a substrate; a
cathode section including a seal ring for contacting a peripheral
portion of a surface, to be plated, of the substrate held by the
substrate holder to seal the peripheral portion water-tightly, and
a cathode for contacting the substrate to supply current to the
substrate; a vertically-movable electrode head provided above the
cathode section, including an anode chamber housing an anode made
of an insoluble material and having a bottom opening closed with a
water-permeable porous member; a plating solution injection section
for injecting a plating solution between the anode and the surface,
to be plated, of the substrate held by the substrate holder; a
power source for applying a plating voltage between the cathode and
the anode; and a gas discharge line for discharging a gas from the
anode chamber.
Inventors: |
Nakada, Tsutomu; (Tokyo,
JP) ; Kunisawa, Junji; (Tokyo, JP) ; Kanda,
Hiroyuki; (Tokyo, JP) ; Nagai, Mizuki; (Tokyo,
JP) ; Yamamoto, Satoru; (Tokyo, JP) ; Mishima,
Koji; (Tokyo, JP) ; Morisawa, Shinya; (Tokyo,
JP) ; Katsuoka, Seiji; (Tokyo, JP) ; Makino,
Natsuki; (Tokyo, JP) ; Fukunaga, Yukio;
(Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
34108555 |
Appl. No.: |
10/860115 |
Filed: |
June 4, 2004 |
Current U.S.
Class: |
205/137 |
Current CPC
Class: |
C25D 17/06 20130101;
C25D 7/123 20130101; C25D 17/001 20130101 |
Class at
Publication: |
205/137 |
International
Class: |
C25D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 2003 |
JP |
2003-161244 |
Jun 13, 2003 |
JP |
2003-169791 |
Oct 30, 2003 |
JP |
2003-371159 |
Claims
What is claimed is:
1. A plating apparatus comprising: a substrate holder for holding a
substrate; a cathode section including a seal ring for contacting a
peripheral portion of a surface, to be plated, of the substrate
held by the substrate holder to seal the peripheral portion
water-tightly, and a cathode for contacting the substrate to supply
current to the substrate; a vertically-movable electrode head
provided above the cathode section, including an anode chamber
housing an anode made of an insoluble material and having a bottom
opening closed with a water-permeable porous member; a plating
solution injection section for injecting a plating solution between
the anode and the surface, to be plated, of the substrate held by
the substrate holder; a power source for applying a plating voltage
between the cathode and the anode; and a gas discharge line for
discharging gas from the anode chamber.
2. The plating apparatus according to claim 1, further comprising:
a control section for controlling an amount of the gas discharged
through the gas discharge line.
3. The plating apparatus according to claim 2, further comprising:
a pressure sensor for detecting the pressure in the anode chamber;
wherein the control section controls the amount of the gas
discharged through the gas discharge line based on an output of the
pressure sensor.
4. The plating apparatus according to claim 2, further comprising:
an integrator for integrating an electric current flowing between
the cathode and the anode; wherein the control section controls the
amount of the gas discharged through the gas discharge line based
on an output of the integrator.
5. A plating method comprising: providing in a plating cell an
anode and a plating solution impregnated material disposed above
the anode, and filling the plating cell with a plating solution so
that the plating solution impregnated material is immersed in the
plating solution; bringing a downwardly-facing surface, to be
plated, of a substrate into contact with the plating solution on
the plating solution impregnated material; and applying a voltage
between the anode and the surface, to be plated, of the substrate,
thereby carrying out plating of the surface, to be plated.
6. The plating method according to claim 5, wherein a contact
member is provided on the upper surface of the plating solution
impregnated material, and plating is carried out while keeping the
surface, to be plated, of the substrate in contact with the upper
surface of the contact member.
7. The plating method according to claim 6, wherein the operation
of applying a voltage between the surface, to be plated, of the
substrate and the anode while keeping the surface, to be plated, of
the substrate in contact with the upper surface of the contact
member, and the operation of detaching the surface, to be plated,
of the substrate from the upper surface of the contact member are
repeated.
8. The plating method according to claim 5, wherein the substrate
is allowed to rotate or make a scroll movement while the surface,
to be plated, of the substrate is kept in contact with the plating
solution.
9. The plating method according to claim 5, wherein the plating
solution is supplied into the plating cell from below the plating
solution impregnated material, and the plating solution is passed
through the plating solution impregnated material and supplied to
above the plating solution impregnated material.
10. The plating method according to claim 5, wherein the plating
solution is supplied from above the plating solution impregnated
material onto the upper surface of the plating solution impregnated
material.
11. A plating apparatus comprising: an anode disposed in a plating
cell; a plating solution impregnated material disposed above the
anode; a plating solution supply section for supplying and filling
a plating solution into the plating cell until the plating solution
reaches to above the plating solution impregnated material; and a
substrate holder for holding a substrate with its surface, to be
plated, facing downwardly; wherein the surface, to be plated, of
the substrate held by the substrate holder is brought into contact
with the plating solution above the plating solution impregnated
material to carry out plating of the surface, to be plated.
12. The plating apparatus according to claim 11, further
comprising: a contact member having a flat upper surface as a
contact surface, provided above the plating solution impregnated
material; and a holder drive mechanism for repeating the operation
of bringing the surface, to be plated, of the substrate held by the
substrate holder into contact with the contact surface of the
contact member and the operation of detaching the surface, to be
plated, from the contact surface of the contact member.
13. The plating apparatus according to claim 12, wherein the holder
drive mechanism includes a mechanism for vertically moving the
substrate holder, and a mechanism for allowing the substrate holder
to rotate or make a scroll movement.
14. The plating apparatus according to claim 11, wherein the
plating solution supply section includes a plating solution supply
pipe for supplying the plating solution into the plating cell from
below the anode, and a plating solution supply pipe for supplying
the plating solution to above the plating solution impregnated
material.
15. The plating apparatus according to claim 11, wherein a filter
is provided between the anode and the plating solution impregnated
material.
16. A substrate processing apparatus comprising: a
vertically-movable substrate holder for supporting a substrate in a
horizontal position and detachably holding the substrate; and a
positioning guide disposed such that it surrounds the circumference
of the substrate holder; wherein the positioning guide has a
tapered surface which, when the substrate supported horizontally by
the substrate holder is lowered or raised, contacts the peripheral
end surface of the substrate to position the substrate with respect
to the substrate holder.
17. The substrate processing apparatus according to claim 16,
wherein the positioning guide is formed in a cylindrical shape, and
the tapered surface contacts the peripheral end surface of the
substrate over substantially the entire circumference of the
peripheral end surface to position the substrate with respect to
the substrate holder.
18. The substrate processing apparatus according to claim 16,
wherein an electrode for contacting a peripheral portion of the
substrate held by the substrate holder to supply current to the
substrate, and a seal ring for pressure-contacting a peripheral
portion of the substrate to seal the peripheral portion are
provided above the substrate holder.
19. The substrate processing apparatus according to claim 18,
wherein the seal ring is composed of a composite material
comprising a metal covered with a rubber.
20. The substrate processing apparatus according to claim 16,
wherein the substrate holder is designed to hold the substrate by
vacuum attraction.
21. The substrate processing apparatus according to claim 16,
wherein a temperature control section for controlling the
temperature of the substrate holder is provided within the
substrate holder.
22. The substrate processing apparatus according to claim 21,
wherein the temperature control section comprises a fluid flow
passage for allowing a temperature-controlled heat medium to flow
therein.
23. A substrate processing method comprising: lowering or raising a
substrate supported horizontally by a substrate holder and bringing
a peripheral end surface of the substrate into contact with a
tapered surface of a positioning guide, disposed such that it
surrounds the substrate holder, to position the substrate with
respect to the substrate holder; and holding the substrate by the
substrate holder.
24. The substrate processing method according to claim 23, wherein
the tapered surface of the positioning guide is brought into
contact with the peripheral end surface of the substrate over
substantially the entire circumference of the peripheral end
surface to position the substrate with respect to the substrate
holder.
25. The substrate processing method according to claim 23, wherein
the substrate held by the substrate holder is raised so as to bring
an electrode into contact with a peripheral portion of the
substrate to supply current to the substrate, and bring a seal ring
into pressure contact with a peripheral portion of the substrate to
seal the peripheral portion.
26. The substrate processing method according to claim 25, wherein
the seal ring is composed of a composite material comprising a
metal covered with a rubber.
27. The substrate processing method according to claim 23, wherein
the substrate is held by the substrate holder by vacuum
attraction.
28. The substrate processing method according to claim 23, wherein
the temperature of the substrate is controlled.
29. The substrate processing method according to claim 28, wherein
the temperature of the substrate holder is controlled by allowing a
temperature-controlled heat medium to flow within the substrate
holder.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plating apparatus and a
plating method, and more particularly to a plating apparatus and a
plating method used for filling a fine circuit pattern formed in a
substrate, such as a semiconductor substrate, with metal
(interconnect material) such as copper so as to form
interconnects.
[0003] The present invention also relates to a substrate processing
apparatus for use as a substrate holding apparatus in the above
plating apparatus, in an etching apparatus for etching away at
least part of a thin film or the like formed on or adhering to the
surface of a substrate, or in a polishing apparatus for
mirror-polishing the surface of a substrate, or the like, and also
to a substrate processing method.
[0004] 2. Description of the Related Art
[0005] Recently, there has been employed a circuit forming method
comprising forming fine recesses for interconnects, such as
interconnect trenches (trenches) or fine holes (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 means of CMP or the like.
[0006] 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 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. 2000-232078).
[0007] 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.
[0008] It is widely practiced with such a plating apparatus to use
a soluble anode made of, for example, copper (phosphor-containing
copper) containing 0.03 to 0.05% of phosphor so as to form a
collagenous black film comprising a compound of phosphor and
chlorine, called black film, on the surface of the anode, thereby
suppressing the generation of monovalent copper ions (slime) from
the anode.
[0009] In the case of using a soluble anode, however, when
monovalent copper ions generated from the anode are deposited
excessively on the surface of a black film formed on the anode, the
black film detaches from the anode and the monovalent copper ions
easily become copper. The detached black film itself can cause
particles in the plating solution.
[0010] It may therefore be considered to use an insoluble anode.
When an insoluble anode is used, however, oxygen gas is generated
at the anode surface. The oxygen gas, when having reached a
substrate, can cause defects in the substrate. Further, the liquid
level of plating solution can change due to the pressure of the
oxygen gas acting on the surface of the plating solution, making it
impossible to carry out stable plating.
[0011] On the other hand, as shown in FIG. 1, when forming a copper
layer 7a by copper plating of the surface of a substrate W where
narrow trenches 6a with a width d.sub.1 of, for example, not more
than 0.1 .mu.m and broad trenches 6b with a width d.sub.2 of, for
example, about 100 .mu.m are co-present, the growth of the plating
film tends to be promoted over the narrow trenches 6a to raise the
copper layer 7a even when the action of the plating solution or an
additive contained in the plating solution is optimized. On the
other hand, a high-leveling growth of plating film is not possible
in the broad trenches 6b. As a result, a level difference a+b, i.e.
the sum of the height "a" of the raised portions over the narrow
trenches 6a and the depth "b" of the recessed portions over the
broad trenches 6b, is produced in the copper layer 7a deposited on
the substrate W. Accordingly, in order to flatten the surface of
the substrate W after embedding of copper in the narrow trenches 6a
and the broad trenches 6b, it is necessary to make the thickness of
the copper layer 7a sufficiently thick and polish away the copper
layer 7a by CMP in an extra amount corresponding to the level
difference a+b.
[0012] In CMP processing of a plated film, however, a larger
thickness of the plated film requires a larger polishing amount,
leading to a prolonged processing time. An increase in the CMP rate
to avoid the processing prolongation can cause dishing in broad
trenches during the CMP processing.
[0013] In order to solve these problems, it is necessary to make a
thickness of a plated film as thin as possible, and eliminate
raised portions and recesses in the plated film even when narrow
trenches and broad trenches are co-present in the surface of the
substrate to thereby enhance the flatness. At present, however,
when carrying out electroplating using, for example, an
electrolytic copper sulfate bath, it is not possible to
simultaneously decrease raised portions and recesses solely by the
action of the plating solution or an additive.
[0014] In-plane uniformity of a thickness of a plated film is a
measure for evaluating the plating performance of plating carried
out on a semiconductor substrate. It is desirable that the
thickness of a plated film formed on a surface of a substrate be
uniform over the entire surface, i.e. from the center to the
periphery, of a substrate.
[0015] According to a common standard., for example, the error
range of the diameter of a substrate, such as a 300 mm.phi.
semiconductor wafer, is about .+-.0.2 mm (300.+-.0.2 mm). It is,
therefore, necessary to provide a substrate holding apparatus for
holding such a substrate with a mechanism that can absorb about the
0.4 mm error.
[0016] FIGS. 2 through 5 schematically show a substrate holding
apparatus for use in, for example, an electroplating apparatus. As
shown in FIGS. 2 through 5, the substrate holding apparatus
includes a substrate holder 12 coupled to the upper end of a
vertically-movable spline shaft 10, and a rotating disk 16 coupled
to the upper end of a rotatable main shaft 14 surrounding the
spline shaft 10. The main shaft 14 is rotatably supported by a
housing 18 via a bearing 20, and a ball spline 22 is interposed
between the spline shaft 10 and the main shaft 14. The spline shaft
10 thus moves vertically relative to the main shaft 14, and rotates
together with the main shaft 14 and the rotating disk 16 by the
rotation of the main shaft 14.
[0017] A plurality of seats 24, each having a step portion 24a on
the inner side, is provided in the peripheral portion of the
substrate holder 12 at a given pitch along the circumferential
direction. The step portion 24a is to make contact with a
peripheral portion of the lower surface of a substrate W so as to
place thereon and support the substrate W, and is configured to
absorb, for example, about 0.4 mm error when holding a 300 mm.phi.
substrate W, as described above. A hooked chuck 26 at its center in
the length direction is rotatably supported to the seat 24, and at
the lower end is rotatably coupled to the upper end of a pressing
rod 30 which is biased downwardly by a helical spring 28.
[0018] When the pressing rod 30 moves downwardly by the elastic
force of the helical spring 28, the chuck 26 rotates such that it
closes inwardly, so that a peripheral portion of the substrate W,
placed and supported on the step portion 24a of the seat 24, is
nipped between the step portion 24a and the front end of the chuck
26. The substrate W is thus held mechanically. When the pressing
rod 30 moves upwardly against the elastic force of the helical
spring 28, the chuck 26 rotates such that it opens outwardly, so
that the nipping of the peripheral portion of the substrate W,
placed on the step portion 24a of the seat 24, between the step
portion 24a and the front end of the chuck 26 is released.
[0019] A plurality of support posts 32 is mounted on the peripheral
portion of the rotating disk 16 at a given pitch along the
circumferential direction. Cathodes 34, which comprise six parts,
for example, and a ring-shaped seal ring 36 covering the upper
surface of the cathodes 34 are mounted to the top ends of the
support posts 32. The seal ring 36 has a downwardly-extending
tapered inner peripheral portion which inclines inwardly and
downwardly.
[0020] As shown in FIG. 4, when the substrate holder 12 rises to a
plating position, the cathodes 34 presses on a peripheral portion
of the substrate W held by the substrate holder 12 and feeds
electricity to the substrate W. At the same time, the inner
peripheral end portion of the seal ring 36 comes into pressure
contact with a peripheral portion of the upper surface of the
substrate W to thereby seal that portion water-tightly, preventing
a plating solution, which has been supplied onto the upper surface
(surface to be plated) of the substrate W, from leaking out of the
peripheral portion of the substrate W and preventing the plating
solution from contaminating the cathodes 34.
[0021] An extensible bellows 38 is disposed between the substrate
holder 12 and the rotating disk 16 to prevent the plating solution
from intruding into the mechanism side where the spline shaft 10,
etc. are present.
[0022] According to the substrate holding apparatus, when the
substrate holder 12 is lowered to a position (substrate transfer
position) as shown in FIG. 2, the lower end of the pressing rod 30
comes into contact with the upper surface of the rotating disk 16
and the pressing rod 30 is lifted against the elastic force of the
helical spring 28, so that the chuck 26 moves outwardly and opens.
The apparatus is now in a condition to be able to place the
substrate W on the step portion 24a of the seat 24, or carry the
substrate W out of the step portion 24a.
[0023] When the substrate holder 12 is somewhat raised to a
position (cleaning position) as shown in FIG. 3, the pressing rod
30 is lowered by the elastic force of the helical spring 28, so
that the chuck 26 moves inwardly and closes, whereby the substrate
W at the peripheral end is mechanically held by the chuck 26. The
apparatus is now in a condition to be able to perform processing of
the substrate W, such as pre-plating processing of the substrate W
or spin-drying, while rotating the substrate holder 12 together
with the rotating disk 16 by rotating the main shaft 14.
[0024] When the substrate holder 12 is further raised to a position
(plating position) as shown in FIG. 4, the cathodes 34 come to
press on a peripheral portion of the substrate W held by the
substrate holder 12 and feed electricity to the substrate W. At the
same time, the inner peripheral end portion of the seal ring 36
comes into pressure contact with a peripheral portion of the upper
surface of the substrate W to water-tightly seal that portion. The
apparatus is now in a condition to be able to perform plating by
supplying a plating solution onto the surface (upper surface) of
the substrate W and applying a voltage between the cathodes 34 and
an anode (not shown) disposed above the cathodes 34 such that it
faces the substrate W and is immersed in the plating solution.
[0025] The seal ring 36 is generally made of a rubber, and may be
formed from, for example, a fluorocarbon rubber, a silicone rubber
or a variety of elastomers. The seal ring 36 maybe mounted to a
metal or resin holder for use.
[0026] As described above, according to the conventional substrate
holding apparatus, a substrate is fixed by the mechanical chucks on
the seats of the substrate holder which are designed in
consideration of the maximum tolerance for the diameter of the
substrate in order to absorb the dimensional error of the substrate
diameter. Accordingly, the absorbed dimensional error of the
diameter of a substrate W directly leads to an error in positioning
of the substrate W with respect to the substrate holder. For
example, when holding a substrate W having a diameter of 299.8 mm
(diametrical error: -0.2 mm) with the substrate holding apparatus
to process the substrate W, there occurs an error of about 0.4 mm
at the maximum in the contact points between the cathodes 34 and
the substrate W and in the contact portion between the seal ring 36
and the substrate W in terms of the distances from the edge of the
substrate W. When a substrate is held in a substrate holding
apparatus with such an inaccurate positioning and brought into
contact with cathodes and a seal ring disposed, for example, above
the substrate, variation (error) occurs in the contact position
between the substrate and the cathodes and in the contact position
between the substrate and the seal ring.
[0027] Such a variation (error) in the contact position between a
substrate and cathodes/seal ring, when the substrate is a
next-generation substrate having a thin-film seed layer with a
narrow interconnect width or when the substrate is plated with a
plating apparatus with a vary small distance between the substrate
and the cathodes, makes the flow of electric current at the
substrate surface non-uniform, thereby producing a significant
difference in the thickness of the plated formed on the surface of
the substrate between the central portion and the peripheral
portion of the substrate.
[0028] On the other hand, with respect to the seal ring 36, as
shown in FIG. 5, the deformation of the seal ring 36 generally made
of a rubber is large around the contact surface between the seal
ring 36 and a substrate Wand, depending upon how it is pressed
against the substrate W, a non-uniform deformation occurs in the
seal ring 36. The non-uniform deformation of the seal ring 36 can
lead to a twist in the sealing surface, causing a leak of plating
solution. Further, the distance between the peripheral end of the
substrate W and the sealing boundary can be varied, which would
adversely affect in-plane uniformity of the thickness of the plated
film after plating.
[0029] Though a substrate holding apparatus for a plating apparatus
has been described hereinabove, the same problems are involved in
substrate holding apparatuses for other electrolytic processing
apparatuses, such as an electrolytic etching apparatus, or for a
polishing apparatus, etc.
SUMMARY OF THE INVENTION
[0030] 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 which uses an
insoluble anode and which can perform plating of a substrate stably
while preventing oxygen gas, generated due to the use of the
insoluble anode, from causing defects in the substrate.
[0031] It is a second object of the present invention to provide a
plating apparatus and a plating method which can deposit a metal
plated film, such as a copper plated film, selectively in
interconnect trenches and fine holes formed in the surface of a
substrate.
[0032] It is a third object of the present invention to provide a
substrate processing apparatus and method which can hold a
substrate in a substrate holder with accurate positioning of the
substrate with respect to the substrate holder, without being
influence by a diametrical error of the substrate, and can perform
various processing processes such as electroplating.
[0033] In order to achieve the above object, the present invention
provides a plating apparatus comprising: a substrate holder for
holding a substrate; a cathode section including a seal ring for
contacting a peripheral portion of a surface, to be plated, of the
substrate held by the substrate holder to seal the peripheral
portion water-tightly, and a cathode for contacting the substrate
to supply current to the substrate; a vertically-movable electrode
head provided above the cathode section, including an anode chamber
housing an anode made of an insoluble material and having a bottom
opening closed with a water-permeable porous member; a plating
solution injection section for injecting a plating solution between
the anode and the surface, to be plated, of the substrate held by
the substrate holder; a power source for applying a plating voltage
between the cathode and the anode; and a gas discharge line for
discharging gas from the anode chamber.
[0034] The use of an anode made of an insoluble material can avoid
the need for a change of anode and, in addition, obviate the
generation of particles due to the peeling of a black film which
would occur when using a soluble anode. Further, oxygen gas
generated at the surface of the insoluble anode during plating can
be introduced into the anode chamber, and the oxygen gas in the
anode chamber can then be discharged so that the oxygen gas will
not reach the substrate.
[0035] Preferably, the plating apparatus further comprises a
control section for controlling an amount of the gas discharged
through the gas discharge line.
[0036] By controlling the amount of the gas discharged through the
gas discharge line with the control section so as to keep the
pressure in the anode chamber constant, the liquid surface level of
the plating solution in the anode chamber can be prevented from
changing, enabling stable plating.
[0037] In a preferred embodiment of the present invention, the
plating apparatus further comprises a pressure sensor for detecting
the pressure in the anode chamber, and the control section controls
the amount of the gas discharged through the gas discharge line
based on an output of the pressure sensor.
[0038] By detecting the pressure in the anode chamber with the
pressure sensor and performing a feedback control by, for example,
operating a vacuum pump in proportion to the detected pressure, the
pressure in the anode chamber can be kept constant.
[0039] In a preferred embodiment of the present invention, the
plating apparatus further comprises an integrator for integrating
an electric current flowing between the cathode and the anode, and
the control section controls the amount of the gas discharged
through the gas discharge line based on an output of the
integrator.
[0040] The amount of oxygen gas generated at the anode surface
during plating is proportional to the electric current flowing
between the substrate (cathode) connected to the cathode and the
anode. Accordingly, by integrating the electric current and
performing a feedforward control by, for example, operating a
vacuum pump in proportion to the integrated current value, the
pressure in the anode chamber can be kept constant.
[0041] The present invention also provides a plating method
comprising: providing in a plating cell an anode and a plating
solution impregnated material disposed above the anode, and filing
a plating solution into the plating cell until the plating solution
reaches to above the plating solution impregnated material;
bringing a downwardly-facing surface, to be plated, of a substrate
into contact with the plating solution above the plating solution
impregnated material; and applying a voltage between the anode and
the surface to be plated of the substrate, thereby carrying out
plating of the surface, to be plated.
[0042] By interposing the plating solution impregnated material,
which serves as a high-resistance structure, between the substrate
and the anode, it becomes possible to effect uniform plating over
the entire surface, to be plated, of the substrate. Further, by
holding the substrate with its surface, to be plated, facing
downwardly (face down), and providing the plating solution
impregnated material on the anode side, the diametrical size of the
plating solution impregnated material can be easily made large
relative to the diametrical size of the substrate, ensuring uniform
plating. Further, the plating solution impregnated material can
prevent a so-called black film, which can be formed on the anode
during plating, from moving to the substrate side.
[0043] In a preferred embodiment of the present invention, a
contact member is provided on the upper surface of the plating
solution impregnated material, and plating is carried out while
keeping the surface, to be plated, of the substrate in contact with
the upper surface of the contact member.
[0044] By thus carrying out plating while keeping the surface, to
be plated, of the substrate in contact with the upper surface of
the contact member, the plating solution can be supplied
preferentially into interconnect trenches and fine holes formed in
the surface, to be plated, of the substrate, thus making it
possible to preferentially (selectively) deposit a metal plated
film, such as a copper plated film, on the surfaces of the
interconnect trenches and fine holes. In particular, when plating
is carried out by allowing a contact member, having such fine
through-holes as to permit passage of the plating solution, in
contact with an electrical conductor layer on the surface, to be
plated, of the substrate, the plating solution flows into
interconnect trenches and fine holes, but it little flows between
the flat portion of the substrate and the contact member, resulting
in preferential deposition of a metal on the surfaces of the
interconnect trenches and the fine holes.
[0045] Preferably, the operation of applying a voltage between the
surface, to be plated, of the substrate and the anode while keeping
the surface, to be plated, in contact with the upper surface of the
contact member and the operation of detaching the surface, to be
plated, of the substrate from the upper surface of the contact
member are repeated.
[0046] When the surface, to be plated, of the substrate is detached
from the upper surface of the contact member, a fresh plating
solution can flow into interconnect trenches and fine holes on the
substrate more easily, thus facilitating selective metal plating
onto the surfaces of the interconnect trenches and the fine
holes.
[0047] Preferably, the substrate is allowed to rotate or make a
scroll movement while the surface, to be plated, of the substrate
is kept in contact with the plating solution.
[0048] By allowing the substrate to rotate or make a scroll
movement, plating can be effected move uniformly over the entire
surface, to be plated, of the substrate. The rotation or scroll
movement of the substrate may be carried out either when the
substrate is in contact with the contact member or when the
substrate is apart from the contact member.
[0049] In a preferred embodiment of the present invention, the
plating solution is supplied into the plating cell from below the
plating solution impregnated material, and the plating solution is
passed through the plating solution impregnated material and
supplied to above the plating solution impregnated material.
[0050] Even when the plating solution is supplied from below to
above the plating solution impregnated material, because of the
plating solution impregnated material (and the upper contact
member) that functions as a filter, particles, such as those coming
from a black film, produced on the anode side can be prevented from
moving to above the plating solution impregnated material (and the
upper contact member).
[0051] It is also possible to supply the plating solution from
above the plating solution impregnated material onto the upper
surface of the plating solution impregnated material.
[0052] This makes it possible to easily control the composition
(amounts of ions, amounts of additives and composition of
additives) of the plating solution on the anode side and the
composition of the plating solution above the plating solution
impregnated material and for use in plating respectively at the
optima (the two compositions may be identical).
[0053] The present invention also provides another plating
apparatus comprising: an anode disposed in a plating cell; a
plating solution impregnated material disposed above the anode; a
plating solution supply section for supplying and filling a plating
solution into the plating cell until the plating solution reaches
to above the plating solution impregnated material; and a substrate
holder for holding a substrate with its surface, to be plated,
facing downwardly; wherein the surface, to be plated, of the
substrate held by the substrate holder is brought into contact with
the plating solution above the plating solution impregnated
material to carry out plating of the surface, to be plated.
[0054] In a preferred embodiment of the present invention, the
plating apparatus further comprises a contact member having a flat
upper surface as a contact surface, provided above the plating
solution impregnated material, and a holder drive mechanism for
repeating the operation of bringing the surface, to be plated, of
the substrate held by the substrate holder into contact with the
contact surface of the contact member and the operation of
detaching the surface, to be plated, from the contact surface of
the contact member.
[0055] Preferably, the holder drive mechanism includes a mechanism
for vertically moving the substrate holder, and a mechanism for
allowing the substrate holder to rotate or make a scroll
movement.
[0056] The plating solution supply section may include a plating
solution supply pipe for supplying the plating solution into the
plating cell from below the anode, and a plating solution supply
pipe for supplying the plating solution to above the plating
solution impregnated material.
[0057] Preferably, a filter is provided between the anode and the
plating solution impregnated material.
[0058] The present invention also provides a substrate processing
apparatus comprising: a vertically-movable substrate holder for
supporting a substrate in a horizontal position and detachably
holding the substrate; and a positioning guide disposed such that
it surrounds the circumference of the substrate holder; wherein the
positioning guide has a tapered surface which, when the substrate
supported horizontally by the substrate holder is lowered or
raised, contacts the peripheral end surface of the substrate to
position the substrate with respect to the substrate holder.
[0059] According to this substrate processing apparatus,
positioning of a substrate with respect to the substrate holder is
performed by bringing the peripheral end surface as a reference
into contact with the tapered surface of the positioning guide. In
this positioning, the center position of the substrate does not
change regardless of the diameter of the substrate, i.e.,
regardless of any dimensional error in the diameter. Thus,
positioning of the substrate with respect to the substrate holder
can be performed with accuracy without being influenced by the
diametrical size of the substrate. In particular, when there is a
dimensional error in the diametrical size of a substrate, though
the height position of the substrate with respect to the
positioning guide changes upon contact of the substrate in a
horizontal position with the tapered surface of the positioning
guide, the center position of the substrate with respect to the
guide does not change. Accordingly, when the substrate is attracted
and held by the substrate holder, for example, by means of a vacuum
chuck, the center of the substrate can coincide with the center of
the substrate holder.
[0060] In a preferred embodiment of the present invention, the
positioning guide is formed in a cylindrical shape, and the tapered
surface contacts the peripheral end surface of the substrate over
substantially the entire circumference of the peripheral end
surface to position the substrate with respect to the substrate
holder.
[0061] According to this embodiment, substantially the entire
circumference of the peripheral end surface of a substrate can be
utilized as a reference. This enables a more accurate positioning
of the substrate with respect to the substrate holder. The
positioning guide in a cylindrical shape may have a cut-off portion
e.g. for handling.
[0062] Preferably, an electrode for contacting a peripheral portion
of the substrate held by the substrate holder to supply current to
the substrate and a seal ring for pressure-contacting a peripheral
portion of the substrate to seal the peripheral portion are
provided above the substrate holder.
[0063] The substrate pressing apparatus, when employed in a plating
apparatus, enables accurate positioning of a substrate held by the
substrate with respect to the cathode and the seal ring. Thus, the
distances of the contact positions of the substrate with the
cathode and the seal ring from the peripheral end of the substrate
can be made uniform, whereby the in-plane uniformity of the
thickness of plated film can be enhanced for substrates of various
diametrical sizes.
[0064] The seal ring is preferably composed of a composite material
comprising a metal covered with a rubber.
[0065] The seal ring composed of such a material has an enhanced
rigidity and improved shape stability. When a substrate is sealed
with such a seal ring, the deformation of the seal ring can be
small enough to securely prevent a leak of plating solution, etc.
Further, because of the high dimensional accuracy of the seal ring,
the distance of the sealing boundary from the peripheral end
surface of the substrate can be made substantially equal
constantly.
[0066] The substrate holder is preferably designed to hold the
substrate by vacuum attraction.
[0067] The use of such a substrate holder can avoid the need to
provide an outwardly-projecting holding member, such as a
mechanical chuck, and can securely hold a substrate supported by
the positioning guide.
[0068] Preferably, a temperature control section for controlling
the temperature of the substrate holder is provided within the
substrate holder.
[0069] By controlling not only the temperature of a chemical
liquid, such as a plating solution, but also the temperature of the
substrate holder and a substrate held by the holder at a constant
temperature, the effect of a chemical liquid, which is supplied to
the substrate upon processing of the substrate, can be maximized.
The temperature control section may be comprised of, for example,
an electric heater, a Peltier device or a thermocouple.
[0070] The temperature control section, for example, comprises a
fluid flow passage for allowing a temperature-controlled heat
medium to flow therein.
[0071] A heating medium or a cooling medium is used as a heat
medium.
[0072] The present invention also provides a substrate processing
method comprising: lowering or raising a substrate supported
horizontally by a substrate holder and bringing a peripheral end
surface of the substrate into contact with a tapered surface of a
positioning guide, disposed such that it surrounds the substrate
holder, to position the substrate with respect to the substrate
holder; and holding the substrate by the substrate holder.
[0073] Preferably, the tapered surface of the positioning guide is
brought into contact with the peripheral end surface of the
substrate over substantially the entire circumference of the
peripheral end surface to position the substrate with respect to
the substrate holder.
[0074] The substrate held by the substrate holder may be raised so
as to bring an electrode into contact with a peripheral portion of
the substrate to supply current to the substrate, and bring a seal
ring into pressure contact with a peripheral portion of the
substrate to seal the peripheral portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0075] FIG. 1 is a diagram illustrating a problem in the prior art
involved in the formation of embedded interconnects by copper
plating of a substrate;
[0076] FIG. 2 is a schematic view of a conventional substrate
holding apparatus for use in an electroplating apparatus, showing
the state of the apparatus before holding of a substrate by a
substrate holder;
[0077] FIG. 3 is a schematic view of the conventional substrate
holding apparatus for use in the electroplating apparatus, showing
the state of the apparatus upon holding of the substrate by the
substrate holder;
[0078] FIG. 4 is a schematic view of the conventional substrate
holding apparatus for use in the electroplating apparatus, showing
the state of the apparatus when the substrate holder holding the
substrate is raised to a plating position;
[0079] FIG. 5 is an enlarged diagram illustrating the relationship
between the seal ring of the conventional substrate holding
apparatus for use in the electroplating apparatus and a
substrate;
[0080] FIG. 6A through 6D are views showing an example for forming
interconnects in the semiconductor device in a sequence of
steps;
[0081] FIG. 7 is a plan view of a substrate processing apparatus
provided with a plating apparatus according to an embodiment of the
present invention;
[0082] FIG. 8 is a schematic view of the main portion of the
plating apparatus shown in FIG. 7;
[0083] FIG. 9 is a schematic view of a plating apparatus according
to another embodiment of the present invention;
[0084] FIG. 10 is a systematic diagram showing an example of a
plating solution management system;
[0085] FIG. 11 is a front cross-sectional view showing an example
of a cleaning and drying apparatus shown in FIG. 7;
[0086] FIG. 12 is a plan view of FIG. 11;
[0087] FIG. 13 is a schematic view showing an example of a bevel
etching and backside cleaning apparatus shown in FIG. 7;
[0088] FIG. 14 is a plan cross-sectional view showing an example of
a heating treatment apparatus shown in FIG. 7;
[0089] FIG. 15 is a plan cross-sectional view of FIG. 14;
[0090] FIG. 16 is a front view of a pretreatment apparatus shown in
FIG. 7 at the time of substrate transfer;
[0091] FIG. 17 is a front view of the pretreatment apparatus shown
in FIG. 7 at the time of chemical treatment;
[0092] FIG. 18 is a front view of the pretreatment apparatus shown
in FIG. 7 at the time of rinsing;
[0093] FIG. 19 is a cross-sectional view showing a processing head
at the time of substrate transfer;
[0094] FIG. 20 is an enlarged view of A portion of FIG. 19;
[0095] FIG. 21 is a view corresponding to FIG. 15 at the time of
substrate fixing;
[0096] FIG. 22 is a systematic diagram of the pretreatment
apparatus shown in FIG. 7;
[0097] FIG. 23 is a cross-sectional view showing a substrate head
at the time of substrate transfer in an electroless plating
apparatus shown in FIG. 7;
[0098] FIG. 24 is an enlarged view of B portion of FIG. 23;
[0099] FIG. 25 is a view corresponding to FIG. 23 showing the
substrate head at the time of substrate fixing;
[0100] FIG. 26 is a view corresponding to FIG. 23 showing the
substrate head at the time of plating process;
[0101] FIG. 27 is a front view with partially cross-section showing
a plating tank when a plating tank cover of the pretreatment
apparatus shown in FIG. 7 is closed;
[0102] FIG. 28 is a cross-sectional view of a cleaning tank in the
pretreatment apparatus shown in FIG. 7;
[0103] FIG. 29 is a systematic diagram of the cleaning tank in the
pretreatment apparatus shown in FIG. 7;
[0104] FIG. 30 is a schematic view showing an example of a
polishing apparatus shown in FIG. 7;
[0105] FIG. 31 is a schematic front view of neighborhood of a
reversing machine in a film thickness measuring instrument shown in
FIG. 7;
[0106] FIG. 32 is a plan view of a reversing arm section of FIG.
31;
[0107] FIG. 33 is a flow chart in a substrate processing apparatus
shown in FIG. 7;
[0108] FIG. 34 is a schematic view of a plating apparatus according
to yet another embodiment of the present invention;
[0109] FIG. 35 is a diagram schematically showing the contact
surface and its vicinity when the contact member of the plating
apparatus shown in FIG. 34 is in contact with the surface, to be
plated, of a substrate;
[0110] FIG. 36 is a diagram schematically showing a current change
(A) in fine recesses of a substrate and a current change (B) in the
other surface portion of the substrate as observed in plating
carried out at a constant voltage according to a plating method of
the present invention;
[0111] FIG. 37 is an overall plan view of a plating processing
facility incorporating the plating apparatus shown in FIG. 34;
[0112] FIG. 38 is a schematic view of an electroplating apparatus
provided with a substrate processing apparatus, as a substrate
holding apparatus, according to an embodiment of the present
invention, showing the state of the plating apparatus during
plating;
[0113] FIG. 39 is a schematic view of the main portion of the
substrate holding apparatus (substrate processing apparatus) shown
in FIG. 38, showing the state of the apparatus before holding of a
substrate by a substrate holder;
[0114] FIG. 40 is a schematic view of the main portion of the
substrate holding apparatus (substrate processing apparatus) shown
in FIG. 38, showing the state of the apparatus after holding of the
substrate by the substrate holder; and
[0115] FIGS. 41A and 41B are enlarged diagrams illustrating the
relationship between the seal ring of the substrate holding
apparatus shown in FIG. 38 and a substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0116] Embodiments of the present invention will be described below
with reference to the drawings. The following embodiments show
examples in which copper as an interconnect material is embedded in
fine recesses for interconnects formed in a surface of a substrate
such as a semiconductor wafer so as to form interconnects composed
of a copper layer. However, it is of course possible to use other
kinds of interconnect materials instead of copper.
[0117] An example of forming copper interconnects in a
semiconductor device will be described with reference to FIGS. 6A
through 6D. As shown in FIG. 6A, 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 la formed on a semiconductor base 1 having
formed semiconductor devices. Fine holes (via holes) 3 and
interconnect trenches (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 feeding layer for electroplating is formed on
the barrier layer 5 by sputtering or the like.
[0118] Then, as shown in FIG. 6B, copper plating is performed on a
surface of a substrate W to fill the fine holes 3 and the
interconnect 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 make a surface of copper layer filled in the fine
holes 3 and the interconnect trenches 4, and a surface of the
insulating film 2 lie substantially on the same plane.
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. 6C.
[0119] Then, as shown in FIG. 6D, 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.
[0120] FIG. 7 is a plan view of a substrate processing apparatus
provided with a plating apparatus according to an embodiment of the
present invention. As shown in FIG. 7, the substrate processing
apparatus comprises a rectangular apparatus frame 812 to which
transfer boxes 810 such as SMIF boxes, which accommodate a number
of substrates such as semiconductor wafers, are removably attached.
Inside of the apparatus frame 812, there are disposed a
loading/unloading station 814, and a movable transfer robot 816 for
transferring a substrate to and from the loading/unloading station
814. A pair of plating apparatuses 818 is disposed on both sides of
the transfer robot 816. A cleaning and drying apparatus 820, a
bevel etching and backside cleaning apparatus 822, and a film
thickness measuring instrument 824 are disposed in alignment with
each other on one side of the transfer robot 816. On the other side
of the transfer robot 816, a heat treatment (annealing) apparatus
826, a pretreatment apparatus 828, an electroless plating apparatus
830, and a polishing apparatus 832 are disposed in alignment with
each other.
[0121] The apparatus frame 812 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 812. 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.
[0122] FIG. 8 schematically shows the plating apparatus 818. As
shown in FIG. 8, the plating apparatus 818 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. 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.
[0123] 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.
[0124] An elevating/lowering motor (not shown) comprising 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.
[0125] In this embodiment, the cathode section 506 has the cathodes
512 comprising six cathodes, and the annular seal member 514
disposed above the cathodes 512 so as to cover upper surfaces of
the cathodes 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 cathodes 512, thus
flowing current 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 cathodes 512 are thus prevented from being contaminated by the
plating solution.
[0126] 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 maybe 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.
[0127] The electrode head 502 comprises a rotatable housing 520 and
a vertically movable housing 522 which have a bottomed cylindrical
shape with a downwardly open end and are disposed concentrically.
The rotatable housing 520 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 520 is rotated together with the rotating member
524. An upper portion of the vertically movable housing 522, on the
other hand, is positioned inside the rotatable housing 520, and the
vertically movable housing 522 is rotated together with the
rotatable housing 520 and is moved relative to the rotatable
housing 520 in a vertical direction. The vertically movable housing
522 defines an anode chamber 530 by closing the lower open end of
the vertically movable housing 522 with a porous member 528 so that
a circular anode 526 is disposed in the anode chamber 530 and is
dipped in a plating solution which is introduced to the anode
chamber 530.
[0128] 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
522, and the lower open end of the vertically movable housing 522
is closed by the lower pad 534a.
[0129] 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.
[0130] The lower pad 534a is required to have the contact surface
adapted to contact the surface (surface to be plated) 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.
[0131] 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 which is growing in a
recess. 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%.
[0132] 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 a
bend elastic constant ranging from 200 to 10000 kg/cm.sup.2.
[0133] 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 (tradename)
"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.
[0134] 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.
[0135] On the other hand, the plating solution impregnated material
532 is 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 maybe 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, 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 diameterof 100 .mu.m. Theporous 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.
[0136] 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 copper
layer 7 (see FIG. 6B) 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.
[0137] 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 520 and the upper surface of the top wall of the
vertically movable housing 522, and this air bag 540 is connected
to a pressurized fluid source (not shown) through a fluid
introduction pipe 542.
[0138] 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.
[0139] A plating solution introduction pipe 544 is attached to the
vertically movable housing 522 to introduce the plating solution
into the vertically movable housing 522, and a pressurized fluid
introduction pipe (not shown) is attached to the vertically movable
housing 522 to introduce a pressurized fluid into the vertically
movable housing 522. 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).
[0140] The anode 526 is composed of an insoluble metal, such as
platinum, titanium, etc., or of an insoluble electrode comprising a
metal base plated or coated with a metal, such as platinum, for
example, an electrode comprising a titanium base and an iridium
coating. The use of the anode 526 composed of an insoluble material
(insoluble electrode) can avoid the need for a change of the anode
526 and, in addition, obviate the generation of particles due to
the peeling of a black film which would occur when using a soluble
anode. However, oxygen gas is generated at the surface of the anode
526 during plating. The oxygen gas, when it reaches the surface of
the substrate W, can cause defects in the substrate. In view of
this, the plating apparatus of this embodiment has the following
construction.
[0141] A gas discharge port 564 is mounted to the top wall of the
vertically movable housing 522 that defines the anode chamber 530,
and a gas discharge line 570, provided with a shut-off valve 566
and a vacuum pump 568, is connected to the gas discharge port 564.
In carrying out plating, the shut-off valve 566 is opened and the
vacuum pump 568 is driven to vacuum-evacuate the anode chamber 530,
so that oxygen gas generated at the surface of the anode 526 passes
through the pores 526a of the anode 526 and reaches the top of the
anode chamber 530, and is discharged through the gas discharge line
570. In this manner, the oxygen gas is prevented from reaching the
surface of the substrate W.
[0142] The plating apparatus of this embodiment is provided with a
pressure sensor 572 for detecting the pressure in the anode chamber
530. A signal from the pressure sensor 572 is inputted into a
control section 574. Based on an output signal from the control
section 574, the operation of the vacuum pump 568 is
feedback-controlled so that the pressure in the anode chamber 530
is kept constant. By thus controlling the amount of gas discharged
through the gas discharge line 570 so as to keep the pressure in
the anode chamber 530 constant, the liquid surface level of the
plating solution in the anode chamber 530 can be prevented from
changing, enabling stable plating.
[0143] As shown in FIG. 9, instead of the pressure sensor 572, it
is also possible to provide an integrator 580 for integrating an
electric current that flows between the anode 526 and the substrate
W connected to the cathodes 512 when a voltage is applied from a
power source 550 to between the cathodes 512 and the anode 526. An
output from the integrator 580 is inputted into the control section
574, and the operation of the vacuum pump 568 is feed
forward-controlled so that the pressure in the anode chamber 530 is
kept constant.
[0144] The amount of oxygen gas generated at the surface of the
anode 526 during plating is proportional to the electric current
flowing between the substrate (cathode) W connected to the cathodes
512 and the anode 526. Accordingly, by integrating the electric
current and performing a feedforward control by operating the
vacuum pump 568 in proportion to the integrated current value, the
pressure in the anode chamber 530 can be kept constant.
[0145] The cathodes 512 and the anode 526 are electrically
connected to the cathode and the anode of the plating power source
550, respectively.
[0146] The operation of the plating apparatus in carrying out
plating will now be described. First, a substrate W is held, by
vacuum attraction, on the upper surface of the substrate holder
504, and the substrate holder 504 is raised to bring a peripheral
portion of the substrate W into contact with the cathodes 512 so as
to place the substrate in an electricity-passable condition. The
substrate holder 504 is further raised to bring a peripheral
portion of the upper surface of the substrate W into pressure
contact with the seal ring 514 to water-tightly seal the peripheral
portion of the substrate W.
[0147] The electrode head 502, on the other hand, is moved from a
position (idling position) at which idling is performed for
replacement and removal of bubbles of the plating solution to a
predetermined position (processing position) while the plating
solution is kept held in the electrode head 502. In particular, the
swing arm 500 is raised and then swung to move the electrode head
502 to a position right above the substrate holder 504. Thereafter,
the electrode head 502 is lowered and is stopped when it has
reached the predetermined position (processing position). The anode
chamber 530 is internally pressurized so as to emit the plating
solution, held in the electrode head 502, from the lower surface of
the porous pad 534. Thereafter, pressurized air is introduced into
the air bag 340 to press on the lower pad 534a downwardly.
[0148] Thereafter, the electrode head 502 and the substrate holder
504 are respectively rotated while the entire surface of the porous
member 528 (lower pad 534a) is kept in contact with the surface to
be plated of the substrate W at a uniform pressure.
[0149] Next, the cathodes 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, thereby effecting plating of
the surface to be plated of the substrate W. During the plating,
the shut-off valve 566 of the gas discharge line 570 is opened and
the vacuum pump 568 is operated while it is controlled so that the
pressure in the anode chamber 530 is kept constant, thereby
discharging gas from the anode chamber 530. This prevents oxygen
gas generated at the surface of the anode 526 during plating from
reaching the substrate W and also prevents the liquid surface level
of the plating solution in the anode chamber 530 from changing.
[0150] After carrying out plating for a predetermined time, the
cathodes 512 and the anode 526 are disconnected to the plating
power source 550, and the shut-off valve 566 is closed to return
the internal pressure of the anode chamber 530 to atmospheric
pressure. The internal pressure of the air bag 540 is also returned
to atmospheric pressure to thereby release the pressure of the
lower pad 534a on the substrate W. Thereafter, the electrode head
502 is raised.
[0151] The above operation is repeated a number of times, according
to necessity, so as to form a copper layer 7 (see FIG. 6B), having
a sufficient thickness to fill in fine interconnect recesses, on
the surface (surface to be plated) of the substrate W. Thereafter,
the electrode head 502 is swung to return it to the original
position (idling position).
[0152] 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
818. As shown in FIG. 10, a plating solution tray 600 for allowing
the electrode head 502 of the plating apparatus 818 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.
[0153] 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 620, and is then
returned to the plating solution tray 600.
[0154] 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 818. 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 818.
[0155] FIGS. 11 and 12 show an example of a cleaning and drying
apparatus 820 for cleaning (rinsing) the substrate W and drying the
substrate W. Specifically, the cleaning and drying apparatus 820
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 820
comprises a substrate holder 422 having a clamp mechanism 420 for
clamping an edge portion of the substrate W, and a substrate
mounting and removing lifting/lowering plate 424 for opening and
closing the clamp mechanism 420.
[0156] The substrate holder 422 is coupled to an upper end of a
spindle 426 which is rotated at a high speed by energization of a
spindle rotating motor (not shown). Further, a cleaning cup 428 for
preventing a treatment liquid from being scattered around is
disposed around the substrate W held by the clamp mechanism 420,
and the cleaning cup 428 is vertically moved by actuation of a
cylinder (not shown).
[0157] Further, the cleaning and drying apparatus 820 comprises a
chemical liquid nozzle 430 for supplying a treatment liquid to the
surface of the substrate W held by the clamp mechanism 420, a
plurality of pure water nozzles 432 for supplying pure water to the
backside surface of the substrate W, and a pencil-type cleaning
sponge 434 which is disposed above the substrate W held by the
clamp mechanism 420 and is rotatable. The pencil-type cleaning
sponge 434 is attached to a free end of a swing arm 436 which is
swingable in a horizontal direction. Clean air introduction ports
438 for introducing clean air into the apparatus are provided at
the upper part of the cleaning and drying apparatus 820.
[0158] With the cleaning and drying apparatus 820 having the above
structure, the substrate W is held by the clamp mechanism 420 and
is rotated by the clamp mechanism 420, and while the swing arm 436
is swung, a treatment liquid is supplied from the chemical liquid
nozzle 430 to the cleaning sponge 434, and the surface of the
substrate W is rubbed with the pencil-type cleaning sponge 434,
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 432, and the backside surface of the
substrate W is simultaneously cleaned (rinsed) with the pure water
ejected from the pure water nozzles 432. Thus cleaned substrate W
is spin-dried by rotating the spindle 426 at a high speed.
[0159] FIG. 13 shows an example of a bevel etching and backside
cleaning apparatus 822. The bevel etching and backside cleaning
apparatus 822 can perform etching of the copper layer 7 (see FIG.
6B) 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 on the surface of
the substrate. The bevel etching and backside cleaning apparatus
822 has a substrate holder 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, a center nozzle 924 placed above a nearly central
portion of the face of the substrate W held by the substrate holder
922, and an edge nozzle 926 placed above the peripheral edge
portion of the substrate W. The center nozzle 924 and the edge
nozzle 926 are directed downward. Aback 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.
[0160] 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.
[0161] Next, the method of cleaning with this bevel etching and
backside cleaning apparatus 822 will be described. First, the
substrate W is horizontally rotated together with the substrate
holder 922, with the substrate being held horizontally by the spin
chucks 921 of the substrate holder 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.
[0162] 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 anymore.
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.
[0163] 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.
[0164] 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.
[0165] FIGS. 14 and 15 show a heat treatment (annealing) apparatus
826. The annealing apparatus 826 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
1006. The annealing apparatus 26 also has a plurality of vertically
movable elevating pins 1008 penetrating the cool plate 1006 and
extending upward and downward there through for placing and holding
the substrate W on them. The annealing apparatus 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.
[0166] 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.
[0167] 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 treatment 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.
[0168] 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.
[0169] In this embodiment, 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.
[0170] FIGS. 16 through 22 show a pretreatment apparatus 828 for
performing a pretreatment of electroless plating of the substrate.
The pretreatment apparatus 828 includes a fixed frame 152 that is
mounted on the upper part of a frame 150, and a movable frame 154
that moves up and down relative to the fixed frame 152. A
processing head 160, which includes a bottomed cylindrical housing
portion 156, opening downwardly, and a substrate holder 158, is
suspended from and supported by the movable frame 154. In
particular, a servomotor 162 for rotating the head is mounted to
the movable frame 154, and the housing portion 156 of the
processing head 160 is coupled to the lower end of the
downward-extending output shaft (hollow shaft) 164 of the
servomotor 162.
[0171] As shown in FIG. 19, a vertical shaft 168, which rotates
together with the output shaft 164 via a spline 166, is inserted in
the output shaft 164, and the substrate holder 158 of the
processing head 160 is coupled to the lower end of the vertical
shaft 168 via a ball joint 170. The substrate holder 158 is
positioned within the housing portion 156. The upper end of the
vertical shaft 168 is coupled via a bearing 172 and a bracket to a
fixed ring-elevating cylinder 174 secured to the movable frame 154.
Thus, by the actuation of the cylinder 174, the vertical shaft 168
moves vertically independently of the output shaft 164.
[0172] Linear guides 176, which extend vertically and guide
vertical movement of the movable frame 154, are mounted to the
fixed frame 152, so that by the actuation of a head-elevating
cylinder (not shown), the movable frame 154 moves vertically by the
guide of the linear guides 176.
[0173] Substrate insertion windows 156a for inserting the substrate
W into the housing portion 156 are formed in the circumferential
wall of the housing portion 156 of the processing head 160.
Further, as shown in FIGS. 20 and 21, a seal ring 184 is provided
in the lower portion of the housing portion 156 of the processing
head 160, an outer peripheral portion of the seal ring 184a being
sandwiched between a main frame 180 made of e.g. PEEK and a guide
frame 182 made of e.g. polyethylene. The seal ring 184a is provided
to make contact with a peripheral portion of the lower surface of
the substrate W to seal the peripheral portion of the substrate
W.
[0174] On the other hand, a substrate fixing ring 186 is fixed to a
peripheral portion of the lower surface of the substrate holder
158. Columnar pushers 190 each protrudes downwardly from the lower
surface of the substrate fixing ring 186 by the elastic force of a
spring 188 disposed within the substrate fixing ring 186 of the
substrate holder 158. Further, a flexible cylindrical bellows-like
plate 192 made of e.g. Teflon (registered trademark) is disposed
between the upper surface of the substrate holder 158 and the upper
wall of the housing portion 156 to hermetically seal therein.
[0175] When the substrate holder 158 is in a raised position, a
substrate W is inserted from the substrate insertion window 156a
into the housing portion 156. The substrate W is then guided by a
tapered surface 182a provided in the inner circumferential surface
of the guide frame 182, and positioned and placed at a
predetermined position on the upper surface of the seal ring 184a.
In this state, the substrate holder 158 is lowered so as to bring
the pushers 190 of the substrate fixing ring 186 into contact with
the upper surface of the substrate W. The substrate holder 158 is
further lowered so as to press the substrate W downwardly by the
elastic forces of the springs 188, thereby forcing the seal ring
184a 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 56 and the substrate holder 58 to hold the
substrate W.
[0176] When the head-rotating servomotor 162 is driven while the
substrate W is thus held by the substrate holder 158, the output
shaft 164 and the vertical shaft 168 inserted in the output shaft
164 rotate together with via the spline 166, whereby the substrate
holder 158 rotates together with the housing portion 156.
[0177] At a position below the processing head 160, there is
provided an upward-open treatment tank 100 comprising an outer tank
100a and an inner tank 100b which have a slightly larger inner
diameter than the outer diameter of the processing head 160. A pair
of leg portions 104, which is mounted to a lid 102, is rotatably
supported on the outer circumferential portion of the treatment
tank 100. Further, a crank 106 is integrally coupled to each leg
portion 106, and the free end of the crank 106 is rotatably coupled
to the rod 110 of a lid-moving cylinder 108. Thus, by the actuation
of the lid-moving cylinder 108, the lid 102 moves between a
treatment position at which the lid 102 covers the top opening of
the treatment tank 100 and a retreat position beside the treatment
tank 100. In the surface (upper surface) of the lid 102, there is
provided a nozzle plate 112 having a large number of jet nozzles
112a for jetting outwardly (upwardly), electrolytic ionic water
having reducing power, as described below, for example.
[0178] Further, as shown in FIG. 22, a nozzle plate 124 having a
plurality of jet nozzles 124a for jetting upwardly a chemical
liquid supplied from a chemical liquid tank 120 by driving the
chemical liquid pump 122 is provided in the inner tank 100b of the
treatment tank 100 in such a manner that the jet nozzles 124a are
equally distributed over the entire surface of the cross section of
the inner tank 100b. A drainpipe 126 for draining a chemical liquid
(waste liquid) to the outside is connected to the bottom of the
inner tank 100b. A three-way valve 128 is provided in the drainpipe
126, and the chemical liquid (waste liquid) is returned to the
chemical liquid tank 120 through a return pipe 130 connected to one
of ports of the three-way valve 128 to recycle the chemical liquid,
as needed. Further, in this embodiment, the nozzle plate 112
provided on the surface (upper surface) of the lid 102 is connected
to a rinsing liquid supply source 132 for supplying a rinsing
liquid such as pure water. Further, a drainpipe 127 is connected to
the bottom of the outer tank 100a.
[0179] By lowering the processing head 60 holding the substrate so
as to cover or close the top opening of the treatment tank 100 with
the processing head 60 and then jetting a chemical liquid from the
jet nozzles 124a of the nozzle plate 124 disposed in the inner tank
100b of the treatment tank 100 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 126 while
preventing scattering of the chemical liquid to the outside.
Further, by raising the processing head 60 and closing the top
opening of the treatment tank 100 with the lid 102, and then
jetting a rinsing liquid from the jet nozzles 112a of the nozzle
plate 112 disposed in the upper surface of the lid 102 toward the
substrate W held in the processing head 60, 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 100a and the
inner tank 100b and is discharged through the drainpipe 127, the
rinsing liquid is prevented from flowing into the inner tank 100b
and from being mixed with the chemical liquid.
[0180] According to the pretreatment apparatus 828, the substrate W
is inserted into the processing head 160 and held therein when the
processing head 160 is in the raised position, as shown in FIG. 16.
Thereafter, as shown in FIG. 17, the processing head 160 is lowered
to the position at which it covers the top opening of the treatment
tank 100. While rotating the processing head 160 and thereby
rotating the substrate W held in the processing head 160, a
chemical liquid is jetted from the jet nozzles 124a of the nozzle
plate 124 disposed in the treatment tank 100 toward the substrate
W, thereby jetting the chemical liquid uniformly onto the entire
surface of the substrate W. The processing head 160 is raised and
stopped at a predetermined position and, as shown in FIG. 18, the
lid 102 in the retreat position is moved to the position at which
it covers the top opening of the treatment tank 100. A rinsing
liquid is then jetted from the jet nozzles 112a of the nozzle plate
112 disposed in the upper surface of the lid 102 toward the
rotating substrate W held in the processing head 160. 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.
[0181] The lowermost position of the processing head 160 may be
adjusted to adjust the distance between the substrate W held in the
processing head 160 and the nozzle plate 124, whereby the region of
the substrate W onto which the chemical liquid is jetted from the
jet nozzles 124a of the nozzle plate 124 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
pretreatment 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 liquid 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 the above.
[0182] FIGS. 23 through 29 show an electroless plating apparatus
830. This electroless plating apparatus 830, which is provided to
form the protective film 9 shown in FIG. 6D, includes a plating
tank 200 (see FIGS. 27 and 29), and a substrate head 204, disposed
above the plating tank 200, for detachably holding a substrate
W.
[0183] As shown in detail in FIG. 23, the processing head 204 has a
housing 230 and a head portion 232. The head portion 232 mainly
comprises a suction head 234 and a substrate receiver 236 for
surrounding the suction head 234. The housing 230 accommodates
therein a substrate rotating motor 238 and substrate receiver drive
cylinders 240. The substrate rotating motor 238 has an output shaft
(hollow shaft) 242 having an upper end coupled to a rotary joint
244 and a lower end coupled to the suction head 234 of the head
portion 232. The substrate receiver drive cylinders 240 have
respective rods coupled to the substrate receiver 236 of the head
portion 232. Stoppers 246 are provided in the housing 230 for
mechanically limiting upward movement of the substrate receiver
236.
[0184] The suction head 234 and the substrate receiver 236 are
operatively connected to each other by a splined structure such
that when the substrate receiver drive cylinders 240 are actuated,
the substrate receiver 236 vertically moves relative to the suction
head 234, and when the substrate rotating motor 238 is energized,
the output shaft 242 thereof is rotated to rotate the suction head
234 and the substrate receiver 236 in unison with each other.
[0185] As shown in detail in FIGS. 24 through 26, a suction ring
250 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 234 by a presser ring 251. The suction ring 250
has a recess 250a continuously defined in a lower surface thereof
in a circumferential direction and in communication with a vacuum
line 252 extending through the suction head 234 by a communication
hole 250b that is defined in the suction ring 250. When the recess
250a is evacuated, the substrate W is attracted to and held by the
suction ring 250. Because the substrate W is attracted under vacuum
to the suction ring 250 along a radially narrow circumferential
area provided by the recess 250a, any adverse effects such as
flexing caused by the vacuum on the substrate W are minimized. When
the suction ring 250 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 250 by
introducing N.sub.2 into the vacuum line 252.
[0186] The substrate receiver 236 is in the form of a downwardly
open, hollow bottomed cylinder having substrate insertion windows
236a defined in a circumferential wall thereof for inserting
therethrough the substrate W into the substrate receiver 236. The
substrate receiver 236 also has an annular ledge 254 projecting
inwardly from its lower end, and an annular protrusion 256 disposed
on an upper surface of the annular ledge 254 and having a tapered
inner circumferential surface 256a for guiding the substrate W.
[0187] As shown in FIG. 24, when the substrate receiver 236 is
lowered, the substrate W is inserted through the substrate
insertion window 236a into the substrate receiver 236. The
substrate W thus inserted is guided by the tapered surface 256a of
the protrusion 256 and positioned thereby onto the upper surface of
the ledge 254 in a predetermined position thereon. The substrate
receiver 236 is then elevated until it brings the upper surface of
the substrate W placed on the ledge 254 into abutment against the
suction ring 250 of the suction head 234, as shown in FIG. 25.
Then, the recess 250a in the vacuum ring 250 is evacuated through
the vacuum line 252 to attract the substrate W while sealing the
upper peripheral edge surface of the substrate W against the lower
surface of the suction ring 250. In order to plate the substrate W,
as shown in FIG. 26, the substrate receiver 236 is lowered several
mm to space the substrate W from the ledge 254, keeping the
substrate W attracted only by the suction ring 250. 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 254.
[0188] FIG. 27 shows the details of the plating tank 200. The
plating tank 200 is connected at the bottom to a plating solution
supply pipe 308 (see FIG. 29), and is provided in the peripheral
wall with a plating solution recovery groove 260. In the plating
tank 200, there are disposed two current plates 262, 264 for
stabilizing the flow of a plating solution flowing upward. A
thermometer 266 for measuring the temperature of the plating
solution introduced into the plating tank 200 is disposed at the
bottom of the plating tank 200. Further, on the outer surface of
the peripheral wall of the plating tank 200 and at a position
slightly higher than the liquid level of the plating solution held
in the plating tank 200, there is provided a jet nozzle 268 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 232 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 268 toward the
substrate W to cool the substrate W, thereby preventing progress of
plating by the plating solution remaining on the substrate W.
[0189] Further, at the top opening of the plating tank 200, there
is provided an openable/closable plating tank cover 270 which
closes the top opening of the plating tank 200 in a non-plating
time, such as idling time, so as to prevent unnecessary evaporation
of the plating solution from the plating tank 200.
[0190] As shown in FIG. 29, a plating solution supply pipe 308
extending from a plating solution storage tank 302 and having a
plating solution supply pump 304 and a three-way valve 306 is
connected to the plating tank 200 at the bottom of the plating tank
200. With this arrangement, during a plating process, a plating
solution is supplied into the plating tank 200 from the bottom of
the plating tank 200, and the overflowing plating solution is
recovered by the plating solution storage tank 302 through the
plating solution recovery groove 260. Thus, the plating solution
can be circulated. A plating solution return pipe 312 for returning
the plating solution to the plating solution storage tank 302 is
connected to one of the ports of the three-way valve 306. 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 302 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.
[0191] Particularly, in this embodiment, by controlling the plating
solution supply pump 304, 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.
[0192] The thermometer 266 provided in the vicinity of the bottom
of the plating tank 200 measures a temperature of the plating
solution introduced into the plating tank 200, and controls a
heater 316 and a flow meter 318 described below.
[0193] Specifically, in this embodiment, there are provided a
heating device 322 for heating the plating solution indirectly by a
heat exchanger 320 which is provided in the plating solution in the
plating solution storage tank 302 and uses water as a heating
medium which has been heated by a separate heater 316 and has
passed through the flow meter 318, and a stirring pump 324 for
mixing the plating solution by circulating the plating solution in
the plating solution storage tank 302. 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.
[0194] FIG. 28 shows the details of a cleaning tank 202 provided
beside the plating tank 200. At the bottom of the cleaning tank
202, there is provided a nozzle plate 282 having a plurality of jet
nozzles 280, attached thereto, for upwardly jetting a rinsing
liquid such as pure water. The nozzle plate 282 is coupled to an
upper end of a nozzle lifting shaft 284. The nozzle lifting shaft
284 can be moved vertically by changing the position of engagement
between a nozzle position adjustment screw 287 and a nut 288
engaging the screw 287 so as to optimize the distance between the
jet nozzles 280 and a substrate W located above the jet nozzles
280.
[0195] Further, on the outer surface of the peripheral wall of the
cleaning tank 202 and at a position above the jet nozzles 280,
there is provided a head cleaning nozzle 286 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 232 of the substrate head 204.
[0196] In operating the cleaning tank 202, the substrate W held in
the head portion 232 of the substrate head 204 is located at a
predetermined position in the cleaning tank 202. A cleaning liquid
(rinsing liquid), such as pure water, is jetted from the jet
nozzles 280 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 286 to clean at least a portion, which was in
contact with the plating solution, of the head portion 232 of the
substrate head 204, thereby preventing a deposit from accumulating
on that portion which was immersed in the plating solution.
[0197] According to this electroless plating apparatus 830, when
the substrate head 204 is in a raised position, the substrate W is
held by vacuum attraction in the head portion 232 of the substrate
head 204 as described above, while the plating solution in the
plating tank 200 is allowed to circulate.
[0198] When plating is performed, the plating tank cover 270 of the
plating tank 200 is opened, and the substrate head 204 is lowered,
while the substrate head 204 is rotating, so that the substrate W
held in the head portion 232 is immersed in the plating solution in
the plating tank 200.
[0199] After immersing the substrate W in the plating solution for
a predetermined time, the substrate head 204 is raised to lift the
substrate W from the plating solution in the plating tank 200 and,
as needed, pure water (stop liquid) is immediately jetted from the
jet nozzle 268 toward the substrate W to cool the substrate W, as
described above. The substrate head 204 is further raised to lift
the substrate W to a position above the plating tank 200, and the
rotation of the substrate head 204 is stopped.
[0200] Next, while the substrate W is held by vacuum attraction in
the head portion 232 of the substrate head 204, the substrate head
204 is moved to a position right above the cleaning tank 202. While
rotating the substrate head 204, the substrate head 204 is lowered
to a predetermined position in the cleaning tank 202. A cleaning
liquid (rinsing liquid), such as pure water, is jetted from the jet
nozzles 280 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 286 to clean at least a portion, which was in
contact with the plating solution, of the head portion 232 of the
substrate head 204.
[0201] After completion of cleaning of the substrate W, the
rotation of the substrate head 204 is stopped, and the substrate
head 204 is raised to lift the substrate W to a position above the
cleaning tank 202. Further, the substrate head 204 is moved to the
transfer position between the transfer robot 816 and the substrate
head 204, and the substrate W is transferred to the transfer robot
816, and is transported to a next process by the transfer robot
816.
[0202] As shown in FIG. 29, the electroless plating apparatus 830
is provided with a plating solution management unit 330 for
measuring an amount of plating liquid held by the electroless
plating apparatus 830 and for 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 330, signals indicative of the
analysis results are processed to replenish insufficient components
from a replenishment tank (not shown) to the plating solution
storage tank 302 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.
[0203] The plating solution management unit 330 has a dissolved
oxygen densitometer 332 for measuring dissolved oxygen in the
plating solution held by the electroless plating apparatus 830 by
an electrochemical method, for example. According to the plating
solution management unit 330, dissolved oxygen concentration in the
plating solution can be controlled at a constant value on the basis
of indication of the dissolved oxygen densitometer 332 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.
[0204] 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.
[0205] FIG. 30 shows an example of a polishing apparatus (CMP
apparatus) 832. The polishing apparatus 832 comprises a polishing
table 842 having a polishing surface composed of a polishing cloth
(polishing pad) 840 which is attached to the upper surface of the
polishing table 842, and a top ring 844 for holding a substrate W
with its to-be-polished surface facing the polishing table 842. In
the polishing apparatus 832, the surface of the substrate W is
polished by rotating the polishing table 842 and the top ring 844
about their own axes, respectively, and supplying a polishing
liquid from a polishing liquid nozzle 846 provided above the
polishing table 842 while pressing the substrate W against the
polishing cloth 840 of the polishing table 842 at a given pressure
by means of the top ring 844. It is possible to use a fixed
abrasive type of pad containing fixed abrasive particles as the
polishing pad.
[0206] The polishing power of the polishing surface of the
polishing cloth 840 decreases with a continuation of a polishing
operation of the CMP apparatus 832. In order to restore the
polishing power, a dresser 848 is provided to conduct dressing of
the polishing cloth 840, for example, at the time of replacing the
substrate W. In the dressing, while rotating the dresser 848 and
the polishing table 842 respectively, the dressing surface
(dressing member) of the dresser 848 is pressed against the
polishing cloth 840 of the polishing table 842, 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 842 may be provided with a monitor for monitoring
the surface state of the substrate to detect in situ an end point
of polishing, or with a monitor for inspecting in situ the finish
state of the substrate.
[0207] FIGS. 31 and 32 show the film thickness measuring instrument
824 provided with a reversing machine. As shown in the FIGS. 31 and
32, the film thickness measuring instrument 824 is provided with a
reversing machine 339. The reversing machine 339 includes reversing
arms 353, 353. The reversing arms 353, 353 put a substrate W
therebetween and hold its outer periphery from right and left
sides, and rotate the substrate W through 180.degree., thereby
turning the substrate over. A circular mounting base 355 is
disposed immediately below the reversing arms 353, 353 (reversing
stage), and a plurality of film thickness sensors S are provided on
the mounting base 355. The mounting base 355 is adapted to be
movable upward and downward by a drive mechanism 357.
[0208] During reversing of the substrate W, the mounting base 355
waits at a position, indicated by solid lines, below the substrate
W. Before or after reversing, the mounting base 355 is raised to a
position indicated by dotted lines to bring the film thickness
sensors S close to the substrate W gripped by the reversing arms
353, 353, thereby measuring a film thickness.
[0209] According to this embodiment, since there is no restriction
such as the arms of the transfer robot, the film thickness sensors
S can be installed at arbitrary positions on the mounting base 355.
Further, the mounting base 355 is adapted to be movable upward and
downward, so that the distance between the substrate W and the
sensors S can be adjusted at the time of measurement. It is also
possible to mount plural types of sensors suitable for the purpose
of detection, and change the distance between the substrate W and
the sensors each time measurements are made by the respective
sensors. However, the mounting base 355 moves upward and downward,
thus requiring certain measuring time.
[0210] An eddy current sensor, for example, may be used as the film
thickness sensor S. The eddy current sensor measures a film
thickness by generating an eddy current and detecting the frequency
or loss of the current that has returned through the substrate W,
and is used in a non-contact manner. An optical sensor may also be
suitable for the film thickness sensor S. The optical sensor
irradiates a light onto a sample, and measures a film thickness
directly based on information of the reflected light. The optical
sensor can measure a film thickness not only for a metal film but
also for an insulating film such as an oxide film. Places for
setting the film thickness sensor S are not limited to those shown
in the drawings, but the sensor may be set at any desired places
for measurement in any desired numbers.
[0211] Next, a sequence of processing for forming copper
interconnects on the substrate having the seed layer 6 shown in
FIG. 6A, which is carried out by the substrate processing apparatus
having the above structure, will be described with reference to
FIG. 33.
[0212] First, the substrate W having the seed layer 6 formed in its
surface is taken out one by one from a transfer box 810, and is
carried in the loading/unloading station 814. The substrate W,
which has carried in the loading/unloading station 814, is
transferred to the thickness measuring instrument 824 by the
transfer robot 816, and an initial film thickness (film thickness
of the seed layer 6) is measured by the thickness measuring
instrument 824. Thereafter, if necessary, the substrate is inverted
and transferred to the plating apparatus 818. In the plating
apparatus 818, as shown in FIG. 6B, the copper layer 7 is deposited
on the surface of the substrate W to embed copper.
[0213] Then, the substrate W having the copper layer 7 formed
thereon is transferred to the cleaning and drying apparatus 820 by
the transfer robot 816, 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 818, the substrate W
is spin-dried (removal of liquid) in the plating apparatus 818, and
then the dried substrate is transferred to the bevel etching and
backside cleaning apparatus 822.
[0214] In the bevel etching and backside cleaning apparatus 822,
unnecessary copper attached to the bevel (edge) 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 820 by the transfer robot 816, 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 822, the substrate W is
spin-dried in the bevel etching and backside cleaning apparatus
822, and then the dried substrate is transferred to the heat
treatment apparatus 826 by the transfer robot 816.
[0215] In the heat treatment apparatus 826, heat treatment
(annealing) of the substrate W is carried out. Then, the substrate
W after the heat treatment is transferred to the film thickness
measuring instrument 824 by the transfer robot 816, and the film
thickness of copper is measured by the film thickness measuring
instrument 824. The film thickness of the copper layer 7 (see FIG.
6B) is obtained from the difference between this measured result
and the measured result of the above initial film thickness. Then,
for example, plating time of a subsequent substrate is adjusted
according to the measured film thickness. If the film thickness of
the copper layer 7 is insufficient, then additional formation of
copper layer is performed by plating again. Then, the substrate W
after the film thickness measurement is transferred to the
polishing apparatus 832 by the transfer robot 816.
[0216] As shown in FIG. 6C, unnecessary copper layer 7, the seed
layer 6 and the barrier layer 5 deposited on the surface of the
substrate W are polished and removed by the polishing apparatus 832
to flatten the surface of the substrate W. At this time, for
example, the film thickness or the finishing state of the substrate
is 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
820 by the transfer robot 816, 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 820. After this
spin-drying, the substrate W is transferred to the pretreatment
apparatus 828 by the transfer robot 816.
[0217] In the pretreatment apparatus 828, 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 820 by the
transfer robot 816, 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 828, the
substrate W is spin-dried (removal of liquid) in the pretreatment
apparatus 828, and then the dried substrate is transferred to the
electroless plating apparatus 830 by the transfer robot 816.
[0218] In the electroless plating apparatus 830, as shown in FIG.
6D, for example, electroless Co--W--P plating is applied to the
surfaces of the exposed interconnects 8 to form a protective film
(plated film) 9 composed of Co--W--P 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.
[0219] After the electroless plating, the substrate W is
transferred to the cleaning and drying apparatus 820 by the
transfer robot 816, 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. After the
spin-drying, the substrate W is returned into the transfer box 810
via the loading/unloading station 814 by the transfer robot
816.
[0220] In this embodiment, copper is used as an interconnect
material. However, besides copper, a copper alloy, silver, a silver
alloy, and the like may be used.
[0221] As described in detail hereinabove, according to the present
invention, the use of an anode made of an insoluble material can
avoid the need for a change of anode and, in addition, obviate the
generation of particles due to the peeling of a black film which
would occur when using a soluble anode. Further, oxygen gas
generated at the surface of the insoluble anode during plating can
be introduced into the anode changer, and the oxygen gas in the
anode chamber can then be discharged so that the oxygen gas will
not reach the substrate. This can prevent the oxygen gas from
causing defects in the substrate.
[0222] FIG. 34 shows a plating apparatus according another
embodiment of the present invention. The plating apparatus 700
includes a plating cell 710 for storing a plating solution Q, an
anode 720 provided in the plating cell 710, a plating solution
impregnated material 730 disposed above the anode 720, a filter 740
provided between the plating solution impregnated material 730 and
the anode 720, a plurality of plating solution supply pipes 751,
753, 755 for supplying the plating solution Q into the plating cell
710 and circulating the plating solution Q, a contact member 760
provided on the upper surface of the plating solution impregnated
material 730, a substrate holder 770 for holding a substrate W with
its front surface (surface to be plated) facing downwardly, and a
holder drive mechanism 790 for vertically moving and rotating or
scroll-rotating the substrate holder 770. The plating solution
supply pipes 751, 753, 755 all together constitute a plating
solution supply section.
[0223] The plating cell 710 is formed in the shape of an
upwardly-open container, and an overflow tank 711 is provided
around the upper portion of the outer circumferential surface of
the plating cell 710. The lower chamber, partitioned by the filter
740, in the plating cell 710 constitutes an anode chamber 713 in
which the anode 720 is disposed.
[0224] The anode 720 may be composed of the same metal as the metal
to be plated, or an insoluble metal such as platinum, titanium,
etc., or an insoluble electrode comprising a metal base plated with
e.g. platinum. As with the preceding embodiment, because of no
necessity for a change, etc., an insoluble metal or an insoluble
electrode is preferred. The anode 720 is housed in an anode cup
721, and is to be connected to the anode of a plating power source
797. Though the anode 720 of this embodiment is tabular, it is also
possible to house a plurality of ball-shaped anodes in the anode
cup 721.
[0225] The plating solution impregnated material 730 may be
composed of the same material as the plating solution impregnated
material 532 (see e.g. FIG. 8) of the preceding embodiment and,
when impregnated with the plating solution (electrolytic solution),
constitutes a high-resistance structure having a lower electric
conductivity than the electric conductivity of the plating
solution. Since the plating solution impregnated 730, which serves
as the high-resistance structure, is disposed on the plating cell
710 side, its diametrical size can be made larger than the
diametrical size of the substrate W.
[0226] A membrane filter having numerous fine holes (holes with a
diameter of e.g. about 0.1 .mu.m), an ion-exchange resin membrane,
a filter composed of PP or PE fibers compressed into the form of a
sheet, etc. may be used as the filter 740. The filter 740 has a
function of passing the plating solution Q therethrough, but
blocking passage of particles, such as those coming from a
so-called black film.
[0227] The plating solution supply section includes a plating
solution supply pipe 751 that passes through the center of the
bottom of the plating cell 710 and penetrates through the center of
the anode 720, and is inserted centrally into the plating solution
impregnated material 730, a plurality of plating solution supply
pipes 753 for supplying the plating solution Q from the bottom of
the plating cell 710 into the plating cell 710 on the side below
the anode 720, and a plating solution supply pipe 755 for supplying
the plating solution Q from above the contact member 760 provided
in an upper position in the plating cell 710. Thus, the plating
solution supply pipe 751 supplies the plating solution Q directly
into the plating solution impregnated material 730, the plating
solution supply pipes 753 supply the plating solution Q into the
anode chamber 713 of the plating cell 710, and the plating solution
supply pipe 755 supplies the plating solution Q directly onto the
upper surface of the contact member 760. The plating solution Q,
supplied into the plating cell 710 via the plating solution supply
pipes 751, 753, 755, is discharged out of the plating cell 710 via
a plurality of discharge pipes 757, provided in the sidewall of the
plating cell 710, and the overflow tank 711 and is circulated.
[0228] With respect to the contact member 760, as with the lower
pad 534a (see e.g. FIG. 8) of the preceding embodiment, its surface
(upper surface) to make contact with the surface (surface to be
plated), having an electrical conductor layer (seed layer 6 shown
in FIG. 6A), of the substrate W should have a high smoothness and
have fine through-holes that permit passage therethrough of the
plating solution Q. Further, in order to avoid plating deposition
on the contact member 760 itself, at least the contact surface
should be made of an insulator or a material having high insulating
properties. Furthermore, in order to firmly hold a flat surface of
the substrate W and suppress plating deposition on the contact
portion to a minimum, the contact surface should have a certain
level of hardness. The smoothness required for the contact member
760 is not more than several tens of .mu.m in terms of the maximum
roughness (RMS). The fine through-holes required for the contact
member 760 are preferably round through-holes in order to keep
flatness of the contact surface with the substrate W. Though the
optimum hole size (diameter), the number of holes per unit area,
etc. of the fine through-holes vary depending upon the quality of a
plated film and the interconnect pattern, the selectivity of the
growth of a plated film in recesses and raised portions is enhanced
with a smaller hole size and a smaller number of holes. The
thickness of the contact member 760 is preferably 0.01 to 20 mm,
more preferably 0.1 to 5 mm.
[0229] The material of the contact member 760 that meets the above
requirements may be the same as the above-described lower pad
534a.
[0230] The substrate holder 770 holds the substrate W with its
front surface (surface to be plated) facing downwardly. According
to this embodiment, the substrate holder 770 attracts and holds the
substrate W by vacuum-attracting or electrostatically attracting
the back surface of the substrate W. In a peripheral portion of the
lower surface of the substrate holder 770 is provided a cathode 771
for feeding electricity from the peripheral bevel portion of the
substrate W to the electrical conductor layer of the surface to be
plated of the substrate W. The cathode 771 is to be connected to
the cathode of the plating power source 796.
[0231] The holder drive mechanism 790 includes a rotational drive
shaft 791 connected to the center of the upper surface of the
substrate holder 70, a scroll drive shaft 793 for causing the
rotational drive shaft 791 to make a scroll movement, and a drive
section 795 for rotationally driving the shafts 791, 793 and
driving the substrate holder 770 to move vertically. With the
provision of the holder drive mechanism 790, it is possible to
rotate or scroll-rotate the substrate W, held by the substrate
holder 770, by the drive section 795, and lower the substrate
holder 770 so as to bring the surface to be plated of the substrate
W into contact with the plating solution Q over the upper surface
of the contact member 760 or bring the surface to be plated into
pressure contact with the upper surface of the contact member
760.
[0232] The plating power source 796 is to apply a plating voltage
between the anode 720 and the electrical conductor layer of the
surface to be plated of the substrate W, as described above, and
generally applies a positive potential to the anode 720 and a
negative potential to the substrate W. Depending upon the manner of
using the plating apparatus 700, the plating power source 796 may
be designed to be able to switch between positive potential
application and negative potential application.
[0233] A method for metal-plating the surface to be plated of the
substrate W by the plating apparatus 700 having the above-described
construction will now be described.
[0234] First, the plating solution Q is supplied from the plating
solution supply pipes 753 into the plating cell 710, the plating
solution Q is supplied from the plating solution supply pipe 751
into the plating solution impregnated material 730 and the contact
member 760, and the plating solution Q is also supplied from the
plating solution supply pipe 755 onto the upper surface of the
contact member 760. At the same time, the plating solution Q is
discharged out of the plating cell 710 via the discharge pipes 757
and the overflow tank 711. The discharged plating solution Q, after
removing impurities from it by, for example, passing it through a
filter, is returned into the plating cell 710 via the plating
solution supply pipes 751, 753, 755. In this manner, the plating
solution Q is circulated.
[0235] Since the interior of the plating cell 710 is partitioned by
the plating solution impregnated material 730, the plating solution
Q supplied from the plating solution supply pipes 753 mainly fills
the anode chamber 713, the plating solution Q supplied from the
plating solution supply pipe 751 mainly fills the interior of the
plating solution impregnated material 730 and the interior of the
contact member 760, and the plating solution Q supplied from the
plating solution supply pipe 755 mainly fills the space above the
contact member 760. The plating solution Q in each of the above
regions can pass through the filter 740, the plating solution
impregnated material 730 and the contact member 760 into the other
region. However, the amount of such transferring plating solution
is small. Accordingly, it is easily possible to vary the
compositions of the respective plating solutions Q to be supplied
from the plating solution supply pipes 751, 753, 755 so as to meet
the intended uses of the respective regions.
[0236] In particular, with respect to the plating solution Q to be
supplied from the plating solution supply pipe 755, a plating
solution may be used which contains a suitable additive for
embedding a plating metal into the interconnect trenches and fine
holes of the substrate W. With respect to the plating solution Q to
be supplied from the plating solution supply pipes 551, 553, a
plating solution not containing the above additive or a plating
solution having a different composition from that of the above
plating solution may be used. Instead of the supply of the plating
solution Q onto the upper surface of the contact member 760 via the
plating solution supply pipe 755, it is also possible to omit the
plating solution supply pipe 755 and supply the plating solution Q
from the plating solution supply pipes 751, 753 through the plating
solution impregnated material 730 and the contact member 760 onto
the upper surface of the contact member 760.
[0237] Next, while circulating the plating solution Q in the
above-described manner, the substrate holder 770, holding the
substrate W face down on the lower surface of the holder 770, is
lowered by the holder drive mechanism 790 to bring the surface to
be plated of the substrate W into contact with the plating solution
Q. A voltage is applied from the plating power source 796 to
between the anode 720 and the electrical conductor layer of the
substrate W to pass electric current therebetween, thereby
effecting plating (e.g. copper plating) onto the electrical
conductor layer of the substrate surface. During the plating, the
surface to be plated of the substrate W is allowed to be in contact
with the contact member 760 in the below-described manner.
[0238] According to this embodiment, plating is carried out while
keeping the surface to be plated of the substrate W in contact with
the contact member 760. While the surface to be plated of the
substrate W is kept in contact with the contact member 760, it is
possible to rotationally drive the substrate holder 770 so as to
slide the surface to be plated of the substrate W on the surface of
the contact member 760. It is also possible to repeat the contact
and non-contact between the contact member 760 and the surface to
be plated of the substrate W at appropriate time intervals during
plating.
[0239] By thus carrying out plating while keeping the surface to be
plated of the substrate W in contact with the contact member 760,
it becomes possible to supply the plating solution Q preferentially
into the interconnect trenches and fine holes of the substrate W,
thereby depositing the metal preferentially onto the surfaces of
the interconnect trenches and the fine holes.
[0240] FIG. 35 schematically shows the contact surface and its
vicinity when the contact member 760 is in contact with the surface
to be plated of the substrate W. Though not shown in FIG. 35, the
electrical conductor layer (seed layer 6) has been formed by a
common method on the surface to be plated of the substrate W, as
shown in FIG. 6A. The contact member 760 having a high surface
flatness is in contact with the surface of the electrical conductor
layer. Since the contact member 760 is formed of an insulator or a
material having high insulating properties, only the portions of
the numerous fine through-holes 761 of the contact member 760 are
electrically conductive. Thus, the plating solution in the fine
recesses (fine holes 3 and interconnect trenches 4 shown in FIG.
6A) W1 of the substrate W communicates with the plating solution
under the contact member 760 only through the fine through-holes
761, and an electric current flows only through the fine
through-holes 761 to effect plating.
[0241] When application of current is started in the state shown in
FIG. 35, plating is effected selectively only in the fine recesses
W1 filled with the plating solution. Though metal ions in the fine
recesses W1 are consumed with the process of plating, a fresh
plating solution is supplied through the fine through-holes 761 of
the contact member 760 into the fine recesses W1, whereby plating
proceeds. After filling in the fine recesses W1 with the plated
film, the application of current is stopped and the substrate
holder 770 is raised by the holder drive mechanism 790 to separate
the contact member 760 and the substrate W. The substrate W is then
subjected to the next process step, such as cleaning.
[0242] If the contact and non-contact between the contact member
760 and the substrate W are repeated during plating, a fresh
plating solution Q favorably can enter the fine recesses W1 more
easily when the contact member 760 and the substrate W are
apart.
[0243] In some cases, it is possible to carry out ordinary plating
in the plating solution Q while keeping the substrate W apart from
the contact member 760 before, after or during plating carried out
by allowing the substrate W to be in contact with the contact
member 760. For example, after carrying out plating for a short
time while keeping the surface to be plated of the substrate W
apart from the contact member 760, the surface to be plated is
brought into contact with the contact member 760 to carry out the
above-described plating.
[0244] According to this embodiment, because of the presence of the
plating solution impregnated material 730 as a high-resistance
structure between the substrate W and the anode 720, uniform
plating over the entire surface to be plated of the substrate W can
be effected whether plating is carried out while keeping the
substrate W in contact with the contact member 760 or while keeping
the substrate W apart from the contact member 760. In particular,
electricity is fed to the peripheral bevel portion of the substrate
W. Without the plating solution impregnated material 730, since the
electric resistance of the electrical conductor layer increases
with the distance from the periphery of the substrate W, potential
variation is produced in the surface of the substrate W, resulting
in variation of the plating rate. The presence of the plating
solution impregnated material 730, which has such a large
resistance as to make the electric resistance difference in the
surface of the substrate W negligible, can equalize the plating
rate. Further according to this embodiment, the substrate W is held
face down, and the plating solution impregnated material 730 is
provided on the plating cell 710 side. Accordingly, the diametrical
size of the plating solution impregnated material 730 can be made
larger than the diametrical size of the substrate W with ease,
whereby more uniform plating can be effected.
[0245] Further, by rotating or scroll-rotating the substrate W in
this embodiment, even more uniform plating becomes possible over
the entire surface to be plated of the substrate W. The rotation or
scroll movement of the substrate W may be performed either when
plating is carried out while keeping the substrate W in contact
with the contact member 760 or when plating is carried out while
keeping the substrate W apart from the contact member 760.
[0246] During plating, a so-called black film produced at the anode
720 floats in the plating solution Q in the anode chamber 713.
However, the plating solution impregnated material 730 and,
according to this embodiment, also the contact member 760 and the
filter 740 can prevent the movement of the black film to the
substrate W side.
[0247] As described above, since the anode chamber 713 is defined
by the filter 740 (or by the plating solution impregnated material
730 in case of not providing the filter 740) in the plating
apparatus 700, it is possible to easily control the composition
(amount of ions, amounts of additives and composition of additives)
of the plating solution Q in the anode chamber 713 and the
composition of the plating solution Q above the contact member 760
for use in plating of the substrate W respectively at the optima
(the two compositions may be identical).
[0248] As another method to promote the growth of plated film in
the fine recesses W1, it is possible to employ a method which
involves a repetition of the contact and non-contact between the
contact member 760 and the substrate W, and an intermittent power
supply in accordance with the contact/non-contact, in particular a
method which comprises supplying a power only when the substrate W
is in contact with the contact member 760 (or a method which
comprises supplying a higher power when the substrate W is in
contact with the contact member 760).
[0249] FIG. 36 schematically shows a current change A in the fine
recesses W1 of the substrate W and a current change B in the other
surface portion of the substrate W as observed in plating carried
out at a constant voltage. The graph in FIG. 36 is made only in
consideration of the balance between supply and consumption of
copper ions, while the adsorption, decomposition, consumption, etc.
of an additive is not taken into account.
[0250] In electroplating, when there is a plenty of fresh plating
solution over a portion to be plated, the plating solution contains
metal ions in a large amount and thus has a low electric
resistance. Accordingly, a high electric current flows in the
plating solution. However, if the supply of plating solution is
insufficient, the resistance of the plating solution increases with
the consumption of the metal ions in the plating solution, whereby
the electric current decreases. The amount of plating solution
differs greatly between the space surrounded by the surface portion
of the substrate W and the surface of the contact member 760 and
the space surrounded by the fine recesses W1 and the surface of the
contact member 760, and therefore there is a difference in the time
at which the resistance of plating solution begins to increase.
Thus, the current value begins to decrease at an earlier time
(a.sub.1) in the surface portion of the substrate W, while the
current value begins to decrease at a considerably later time
(a.sub.2) in the fine recesses W1. The respective currents become
constant after the times (b.sub.1, b.sub.2) at which the supply and
consumption of the metal ions (copper ions) become balanced. The
time at which the current becomes constant and the constant current
value vary depending upon the width, the hole size, the number,
etc. of the fine recesses W1. In the case of a constant current
control, a rise in the voltage occurs in response to the above
current decrease.
[0251] By applying a voltage or electric current in a pulsed manner
(i.e. on/off or decrease/increase of voltage/current in a pulsed
manner) in synchronization with the cycle of contact/non-contact
between the contact member 760 and the substrate W, it becomes
possible to further promote the growth of plated film in the fine
recesses W1 compared to the surface portion of the substrate W. In
this case, it is most effective to make the pulse width equal to
the time period (a.sub.2) until the current begins to decrease in
the fine recesses W1. Further, since a fresh plating solution is
supplied into the fine recesses W1 upon the contact/non-contact
operation, there is no need to make the current density small for
the purpose of ensuring the film quality, hence there is no
significant lowering of the throughput. In order to improve the
in-plane film thickness distribution of the plated film formed on
the substrate W, it is possible to change the relative position
between the contact member 760 and the substrate W by the holder
drive mechanism 790 during the non-contact time, as described
above.
[0252] As yet another method to promote the growth of plated film
in the fine recesses W1, instead of the repetition of
contact/non-contact between the contact member 760 and the
substrate W (or in combination with the contact/non-contact between
the contact member 760 and the substrate W), it is possible to
employ a method which comprises changing the pressure of the
substrate W on the contact member 760 upon contact from a
relatively high pressure to a low pressure and, at the same time,
changing the voltage application condition according to the change
in pressure. The change of the voltage application condition
includes an intermittent voltage application, an increase/decrease
of applied voltage (repetition of high voltage and low voltage),
etc. The voltage application may be application of a simple
direct-current voltage, application of a pulse voltage as a group
of pulses, or application of a sine-wave voltage. A method of
carrying out plating by employing the change of the voltage
application condition in association with a change of pressing
condition of the substrate W on the contact member 760 may be
carried out in the following two manners:
[0253] The first manner relates to the case where the change of the
pressing condition is a change of the intensity of the pressure of
the surface to be plated of the substrate W on the contact member
760 and the change of the voltage application condition is an
intermittent voltage application. According to this manner, for
example, a voltage is applied when the above pressure is relatively
high to carry out plating, whereas a voltage is not applied when
the pressure is relatively low to stop plating and a fresh plating
solution is supplied between the fine recesses W1 of the substrate
W and the contact member 760.
[0254] The second manner relates to the case where the change of
the pressing condition is a change of the intensity of the pressure
of the surface to be plated of the substrate W on the contact
member 760 and the change of the voltage application condition is a
change of the intensity of applied voltage. According to this
manner, for example, a high voltage is applied when the above
pressure is relatively high to carry out plating, whereas a low
voltage is applied when the pressure is relatively low and a fresh
plating solution is supplied to replace the plating solution in the
fine recesses W1 which was consumed upon the high voltage
application.
[0255] As a method for solving the above-described problem
illustrated in FIG. 1 and improving the flatness of a plated film
formed on the electrical conductor layer of the surface to be
plated of the substrate W, it is possible to employ a method which
comprises electrolytically plating the electrical conductor layer
of the substrate W by any one of the above-described methods or by
an ordinary plating method in which the substrate W is not
contacted with the contact member 760, and electrolytically etching
the electrical conductor layer of the substrate W while allowing
the substrate W to be in contact with the contact member 760 and
slide on the contact member 760. According to this method,
electrolytic etching can be performed while polishing the surface
of the substrate W with the contact member 760. Thus, it becomes
possible to rub off a thin film at the topmost layer of a raised
portion of the plated film formed over a narrow trench, and
selectively etch away the exposed plated layer, thereby improving
the flatness of the plated film. In this case, at least the surface
of the contact member 760 that is to make contact with the
substrate W should preferably be made of a flexible and durable
material. The following is a specific manner of carrying out this
method.
[0256] When carrying out electroplating by the plating apparatus
700 shown in FIG. 34, as described above, the operation of bringing
the surface to be plated of the substrate W into contact with the
contact member 760 and the operation of detaching the surface to be
plated from the contact member 760 are repeated, or the pressure of
the substrate W on the contact member 760 is changed during
plating. Alternatively, plating is carried out by a common method,
that is, by applying current while keeping the surface to be plated
of the substrate W apart from the contact member 760 at a given
distance with the plating solution interposed therebetween.
[0257] When carrying out electrolytic etching, on the other hand,
the positive and the negative of the plating power source 796 are
reversed so as to make the electrical conductor layer of the
substrate W an anode and change the anode 720 to a cathode.
Thereafter, the holder drive mechanism 790 is driven to lower the
substrate holder 770 so as to press the surface to be plated of the
substrate W on the contact member 760 at a predetermined pressure
while the substrate holder 770 is rotated, thereby etching the
surface to be plated of the substrate W while rubbing the surface
to be plated with the surface of the contact member 760. By thus
performing electrolytic etching during plating and carrying out the
electrolytic etching while pressing the surface to be plated of the
substrate W on the surface of the contact member 760 and moving the
both surfaces relative to each other, it becomes possible to
selectively etch away raised portions of the plated film formed
over narrow trenches on the surface to be plated of the substrate
W, thereby improving the flatness of the plated film. Thus, the
above-described problem illustrated in FIG. 1 can be solved.
[0258] FIG. 37 is a schematic overall plan view of a plating
processing facility 300 incorporating the plating apparatus 700
shown in FIG. 34. As shown in FIG. 37, the plating processing
facility 300 includes three loading/unloading sections 301 for
housing substrates W, four plating apparatuses 700, two transfer
robots 303, 305 for transferring a substrate W between the
loading/unloading sections 301 and the plating apparatuses 700, a
bevel and back surface cleaning unit 307, a spin-drying unit 309,
and a temporary substrate storage stage 311.
[0259] The transfer robot 303 takes a substrate W before plating
out of a substrate cassette set in one of the loading/unloading
sections 301 and places the substrate W on the temporary substrate
storage stage 311. The other transfer robot 305 takes the substrate
W on the temporary substrate storage stage 311 and transfers it to
one of the plating apparatuses 700, where plating of the substrate
W is carried out in the above-described manner. After completion of
the plating, the substrate W is taken by the transfer robot 305 out
of the plating apparatus 700 and transferred to the bevel and back
surface cleaning unit 307, where the substrate W is cleaned. The
substrate W is then transferred by the transfer robot 303 to the
spin-drying unit 309, where the substrate W is dried. Thereafter,
the substrate W is transferred by the transfer robot 303 to a
substrate cassette set in one of the loading/unloading sections 301
and is housed in the cassette, whereby a series of plating
processes of the substrate W is completed.
[0260] As described in detail hereinabove, the present invention
makes it possible to plate a substrate uniformly over the entire
surface to be plated of the substrate. Further, a metal plated
film, such as a copper plated film, can be deposited selectively in
interconnect trenches and fine holes formed in a substrate
surface.
[0261] FIG. 38 is a schematic view of an electroplating apparatus
provided with a substrate processing apparatus according to an
embodiment of the present invention, showing the state of the
plating apparatus during plating, FIG. 39 is a schematic view of
the main portion of the substrate holding apparatus (substrate
processing apparatus), showing the state of the apparatus before
holding of a substrate, and FIG. 40 is a schematic view of the main
portion of the substrate holding apparatus, showing the state of
the apparatus after holding of the substrate. Though in this
embodiment the substrate processing apparatus of the present
invention is employed as a substrate holding apparatus in an
electroplating apparatus, the present substrate processing
apparatus can also be employed as a substrate holding apparatus in
other electrolytic processing apparatus, such as an electrolytic
etching apparatus, or in a polishing apparatus. Further, though in
this embodiment a substrate is held with its front surface (surface
to be processed) facing upwardly (face up) in processing of the
substrate, it is, of course, possible to hold and process a
substrate with its front surface facing downward (face down). In
the following description, the same or equivalent members as or to
the members shown in FIGS. 2 through 4 are given the same reference
numerals, and a duplicate description thereof is omitted.
[0262] As shown in FIG. 38, the electroplating apparatus is mainly
comprised of a substrate holding apparatus (substrate processing
apparatus) 40 and an electrode head 42. The substrate holding
apparatus 40 includes a generally disk-shaped substrate holder 12
coupled to the upper end of a vertically-movable spline shaft 10. A
vacuum passage 12a, having a number of suction ports opening at the
upper surface of the substrate holder 12, is provided within the
substrate holder 12. The vacuum passage 12a communicates with a
vacuum passage 10a that vertically penetrates the spline shaft 10,
and the vacuum passage 10a is connected to a vacuum line 46
extending from a vacuum source 44, such as a vacuum pump. A
substrate W, supported on the upper surface of the substrate holder
12, is attracted and held on the substrate holder 12 through
vacuuming of the vacuum passage 12a, provided within the substrate
holder 12, by the vacuum source 44. The holding by attraction of
the substrate W is released by breaking the vacuum.
[0263] The use of the substrate holder 12, which holds a substrate
W by vacuum attraction, can avoid the need to provide an
outwardly-projecting holding member, such as a mechanical chuck,
and can securely hold the substrate which is supported by a
positioning guide, as will be described later.
[0264] A fluid flow passage 12b as a temperature control section
for allowing a heat medium to flow in it so as to control the
temperature of the substrate holder 12 at a constant temperature is
provided within the substrate holder 12. The fluid flow passage 12b
communicates at one end with one fluid flow passage 10b that
vertically penetrates the spline shaft 10 and at the other end with
the other fluid flow passage 10c that vertically penetrates the
spline shaft 10. The fluid flow passage 10b is connected to a heat
medium supply line 50 extending from a heat medium supply source
48, and the fluid flow passage 10c is connected to a heat medium
discharge line 52 extending from the heat medium supply source 48.
A heat medium, which may be a heating medium or a cooling medium,
whose temperature is controlled by the heat medium supply source
48, is thus supplied into the fluid flow passage 12b within the
substrate holder 12 and flows in one direction along the fluid flow
passage 12b in a circulative manner, thereby controlling the
temperature of the substrate holder 12 and also the temperature of
the substrate W held by the substrate holder 12 at a constant
temperature.
[0265] By thus controlling not only the temperature of a chemical
liquid, such as a plating solution, but also the temperature of the
substrate holder 12 and a substrate W held by the substrate holder
12 at a constant temperature, the effect of a chemical liquid,
which is supplied to the substrate W upon processing of the
substrate, can be maximized. Though in this embodiment the
temperature control section is comprised of the fluid flow passage
12b, the temperature control section may also be comprised of, for
example, an electric heater, a Peltier device or a
thermocouple.
[0266] On the upper surface of a rotating disk 16 coupled to the
upper end of a main shaft 14, a positioning guide 54, which is
generally cylindrical and has a downwardly-tapering tapered surface
54a, is provided concentrically with the substrate holder 12 such
that it surrounds the circumference of the substrate holder 12. The
diameter D.sub.1 of the upper end opening of the tapered surface
54a of the positioning guide 54 is set to be larger than the sum of
the diameter of a substrate W to be held by the substrate holder 12
and the maximum error for the substrate W. In particular, in the
case of a .phi.300 mm substrate, the diameter D.sub.1 is larger
than the sum of 300 m and the maximum error +0.2 mm, i.e. 300.2 mm.
Thus, with a necessary margin added to the sum, the diameter
D.sub.1 is set at e.g. about 302 to 310 mm. The diameter D.sub.2 of
the lower end opening of the tapered surface 54a is set to be
smaller than the sum of the diameter of the substrate W to be held
by the substrate holder 12 and the minimum error for the substrate
W. In particular, in the case of a .phi.300 mm substrate, the
diameter D.sub.2 is smaller than the sum of 300 mm and the minimum
error -0.2 mm, i.e. 299.8 mm. Thus, with a necessary margin added
to the sum, the diameter D.sub.2 is set at e.g. about 290 to 299
mm. The inclination angle .theta. of the tapered surface 54a is set
at e.g. 5 to 30.degree..
[0267] As the substrate holder 12 descends, as described below, the
substrate W supported on the substrate holder 12 enters smoothly
into the inside of the positioning guide 54 without interfering
with the positioning guide 54. As the substrate holder 12 further
descends, the substrate W comes to be supported by the positioning
guide 54, without falling off the positioning guide 54, and only
the substrate holder 12 continues to descent.
[0268] The positioning guide 54, in consideration of chemical
resistance, low friction, strength, processibility, etc., is formed
of a PEEK material. Other resin materials, such as PTFE, PCTFE,
PVC, PP, etc., may also be employed. A metal material, such as a
stainless steel or titanium, is of course usable as a material for
the positioning guide 54. The positioning guide 54 is subjected to
water cleaning, cleaning with a chemical and spin-drying after the
completion of plating, and therefore is desirably of a well-drained
shape. Further, it is desirable that water cleaning or chemical
cleaning of the substrate W and the positioning guide 54 be carried
out while they are positioned such that the distance between them
is smallest.
[0269] The positioning guide 54 rotates together with the substrate
holder 12 by the rotation of the main shaft 14. The positioning
guide 54 is not provided with a movable member for positioning, and
positioning of the substrate W with respect to the substrate holder
12 is completed merely by placing the substrate W on the surface of
the positioning guide 54.
[0270] Support posts 32 are mounted on the peripheral portion of
the rotating disk 16, and at the top of the support posts 32 are
provided, as shown in FIG. 38, inwardly-projecting cathodes 34
which, when the substrate W is in a raised position (plating
position), make contact with a peripheral portion of the substrate
W to feed electricity to the substrate, and an inwardly-projecting
ring-shaped seal ring 36 which makes pressure contact with a
peripheral portion of the substrate W in the plating position to
seal the peripheral portion. The seal ring 36 is composed of a
composite material comprising a core 56 of metal covered with a
covering material 58 of rubber having elasticity. A material having
good corrosion resistance, such as a stainless steel, titanium or
Hasteloy, is preferred as the core (metal) 56. A fluorocarbon
rubber, a silicone rubber or a resin elastomer is preferred as the
covering material (rubber). It is, of course, possible to use other
metals and rubbers depending upon the chemical used, etc.
[0271] The seal ring 36 composed of such a composite material
comprising a metal covered with a rubber has an enhanced rigidity
and improved shape stability. When the substrate W is sealed with
the seal ring 36, as shown in FIGS. 41A and 41B, the deformation of
the seal ring 36 can be small enough to securely prevent a leak of
plating solution. Further, because of the high dimensional accuracy
of the seal ring 36, the distance S of the sealing boundary from
the peripheral end surface of the substrate W can be made
substantially equal constantly.
[0272] When attracting and holding the substrate W by the substrate
holding apparatus 40, the substrate W is first placed on the upper
surface of the substrate holder 12, which is in a somewhat raised
position, so that the substrate W is supported horizontally on the
upper surface. The substrate W is in a condition to be movable
horizontally along the upper surface of the substrate holder 12.
While keeping the substrate W in a horizontal position, the
substrate holder 12 is lowered to bring the peripheral end surface
of the substrate W into contact with the tapered surface 54a of the
positioning guide 54 over substantially the entire circumference of
the peripheral end surface, as shown in FIG. 39. The substrate
holder 12 is further lowered so as to shift the support of the
substrate W by the substrate holder 12 to support of the substrate
W by the tapered surface 54a of the positioning guide 54, thereby
positioning the substrate W with respect to the substrate holder
12.
[0273] According to necessity, the substrate holder 12 is again
raised so as to horizontally support and raise the substrate W
which has been supported by the tapered surface 54a of the
positioning guide 54, and the substrate holder 12 is then lowered
so as to shift the support of the substrate W by the substrate
holder 12 to the support of the substrate W by the tapered surface
54a of the positioning guide 54. This operation may be repeated one
or more times.
[0274] Next, while keeping the substrate holder 12 in a condition
to attract and hold the substrate W, i.e. while vacuuming the
vacuum passage 12a provided within the substrate holder 12 via the
vacuum source 44, the substrate holder 12 is raised and when the
upper surface of the substrate holder 12 contacts the substrate W
supported by the tapered surface 54a of the positioning guide 54,
the substrate W is attracted and held on the upper surface of the
substrate holder 12, as shown in FIG. 40. The substrate holder 12
is further raised and stopped.
[0275] According to this embodiment, positioning of the substrate W
with respect to the substrate holder 12 is thus performed by
bringing the peripheral end surface of the substrate W as a
reference into contact with the tapered surface 54a of the
positioning guide 54. In this positioning, the center position of
the substrate W does not change regardless of the diameter of the
substrate W, i.e., regardless of any dimensional error in the
diameter. Thus, positioning of the substrate W with respect to the
substrate holder 12 can be performed with accuracy without being
influenced by the diametrical size of the substrate W. In
particular, when there is a dimensional error in the diametrical
size of the substrate W, though the height position of the
substrate W with respect to the positioning guide 54 changes
(substrate W with a larger diameter is supported in an upper
position by the tapered surface 54a) upon contact of the substrate
W in a horizontal position with the tapered surface 54a of the
positioning guide 54 to hold the substrate W, the center position
of the substrate W with respect to the guide 54 does not change.
Accordingly, when the substrate W is attracted and held by the
substrate holder 12, for example, by means of a vacuum chuck, the
center of the substrate W can coincide with the center of the
substrate holder 12.
[0276] Further according to this embodiment, the positioning guide
54 has a cylindrical shape, and the tapered surface 54a contacts
the peripheral end surface of the substrate W over substantially
the entire circumference of the peripheral end surface to position
the substrate W with respect to the substrate holder 12. This
enables a more accurate positioning of the substrate W with respect
to the substrate holder 12. The cylindrical positioning guide 54
may have a cut-off portion e.g. for handling.
[0277] The electrode head 42 includes a housing 62 mounted to a
vertically-movable support plate 60, and a high-resistance
structure 64 disposed such that it closes the bottom opening of the
housing 62. The housing 62 has at its bottom an inwardly-projecting
portion 62a and the high-resistance structure 64 has at its top a
flange portion 64a. The high-resistance structure 64 is held by the
housing 62 with the flange portion 64a caught on the
inwardly-projecting portion 62a. A hollow plating solution chamber
66 is thus defined inside the housing 62.
[0278] The high-resistance structure 64 of this embodiment is
composed of the same material as the plating solution impregnated
materials 532 (see e.g. FIG. 9) and 730 (see e.g. FIG. 34), and is
designed to exhibit a lower electric conductivity than the electric
conductivity of a plating solution by allowing the plating solution
to flow into it and run along complicated, considerably long paths
in the thickness direction.
[0279] The provision of the high-resistance structure 64, which
exhibits a high electric resistance, makes it possible to make the
influence of the resistance of e.g. the seed layer 6 (see FIG. 6A)
formed on the surface of the substrate W negligibly small and make
an in-plane difference in current density due to the electric
resistance at the surface of the substrate W smaller, thereby
enhancing the in-plane uniformity of plated film.
[0280] An anode 68 is disposed in the plating solution chamber 66,
and a plating solution introduction pipe (not shown) for
introducing a plating solution 70 into the plating solution chamber
66 is mounted to the housing 62. The plating solution 70,
introduced from the plating solution supply pipe into the plating
solution chamber 66, immerses the anode 68, passes through the
high-resistance structure 64 and reaches to below the
high-resistance structure 64.
[0281] In the case of performing copper plating, for example, in
order to suppress the formation of slime, the anode 68 may be
composed of copper (phosphor-containing copper) containing 0.03 to
0.05% of phosphor. The anode 68 may also be composed of an
insoluble metal such as platinum, titanium, etc., or an insoluble
electrode comprising a metal base plated with e.g. platinum.
Because of no necessity for a change, an anode composed of an
insoluble metal or an insoluble electrode is preferred. Further,
because of permeability to plating solution, the anode 68 may have
a net form.
[0282] The cathode 34 and the anode 68 are to be electrically
connected to the cathode and the anode of a plating power source,
respectively.
[0283] The operation of the plating apparatus in carrying out
plating will now be described.
[0284] First, after performing accurate positioning of a substrate
W in the above-described manner, the substrate W is attracted and
held by the substrate holder 12. The substrate W is raised to a
raised portion (plating position) as shown in FIG. 38 so as to
bring the cathodes 34 into contact with a peripheral portion of the
substrate W and, at the same, bring the seal ring 36 into pressure
contact with a peripheral portion of the substrate W to seal that
portion. Thereafter, the electrode head 42 is lowered, and the
lowering of the electrode head 42 is stopped when the lower surface
of the high-resistance structure 64 of the electrode head 42 has
reached a position as close as about 0.1 to 3 mm to the surface of
the substrate W. On the other hand, the plating solution 70 has
been introduced into the plating solution chamber 66, and the
high-resistance structure 64 has been impregnated with the plating
solution.
[0285] In this state, the gap between the substrate W and the
high-resistance structure 64 is filled with the plating solution 70
in an amount of e.g. not more than about 10 cc, and the cathodes 34
and the anode 68 are electrically connected to the cathode and the
anode of the plating power source, respectively, thereby performing
plating of the surface of the substrate W. During plating, the main
shaft 14 is rotated, according to necessity, to rotate the
substrate holder 12 at a rotational speed of e.g. 1-40 min.sup.-,
thereby reducing localized plating on the substrate which would be
caused by electric field concentration due to the shape of the
electrode and enhancing the in-plane uniformity of the film
thickness of the plated film formed. Further, according to
necessity, a heat medium (heating medium or cooling medium) is
allowed to flow in the fluid flow passage 12b during plating so as
to control (by heating or cooling) the temperature of the substrate
holder 12 and the substrate W held by the substrate holder 12 at a
constant temperature, as described above, thereby enhancing the
plating performance. After completion of the plating, the electrode
head 42 is raised and is moved to a retreat position.
[0286] Next, the plating solution 70 remaining on the substrate W
is recovered, for example, by means of an aspirator nozzle, which
is movable over the substrate W, until the amount of the residual
liquid becomes e.g. about several cc. After the recovery of plating
solution, the aspirator nozzle is returned to a retreat
position.
[0287] Thereafter, while rotating the substrate holder 12 by
rotating the main shaft 14, pure water is supplied to the surface
of the substrate W to clean the surface of the substrate W with
pure water. During the cleaning, the several cc of plating solution
remaining on the surface of the substrate W is cleaned off with
pure water, falling off the periphery of the seal ring 36 by
centrifugal force. In order to minimize scattering of the diluted
plating solution, the rotational speed of the substrate holder 12
is preferably controlled at several tens to a hundred and several
tens min.sup.-1.
[0288] Next, the substrate holder 12 is lowered to a position
(cleaning position) as shown in FIG. 40 to thereby separate the
substrate W from the seal ring 36 and the cathodes 34. Thereafter,
while rotating the substrate holder 12 by rotating the main shaft
14, pure water is supplied to the surface of the substrate W to
clean the surface of the substrate W with pure water and, at the
same, clean the positioning guide 54. The rotational speed of the
substrate holder 12 is preferably high enough to perform effective
cleaning.
[0289] After the completion of water cleaning, the supply of pure
water is stopped, and the rotational speed of the substrate holder
12 is increased to spin-dry the substrate W and the positioning
guide 54.
[0290] After the spin-drying of the substrate W, the rotation of
the substrate holder 12 is stopped, and the substrate holder 12 is
lowered to a position (substrate transfer position) as shown in
FIG. 39. Upon the lowering, the vacuum in the vacuum passage 12a
provided within the substrate holder 12 is broken. Thus, the
substrate W, upon contact with the tapered surface 54a of the
positioning guide 54, detaches from the substrate holder 12 and, as
described above, is supported by the tapered surface 54a of the
positioning guide 54 with accurate positioning.
[0291] Next, the substrate holder 12 is raised to support
horizontally and raise the substrate W which has been supported by
the tapered surface 54a of the positioning guide 54, and the
substrate W is sent to the next process step.
[0292] In this embodiment, the substrate processing apparatus
according to the present invention is employed as a substrate
holding apparatus in the electroplating apparatus. The substrate
processing apparatus, when thus used as a substrate holding
apparatus in an electroplating apparatus, can make the contact
positions of a substrate, held by the substrate holder, with a
cathode and a seal ring more accurate and can enhance the in-plane
uniformity of the thickness of plated film regardless of an error
in the diameter of the substrate. Further, margins that have
conventionally been allowed for cathode contact position and seal
ring contact position can be made smaller, for example, from 2.5 mm
to 2.0 mm, thus making it possible to enlarge the effective area of
a substrate.
[0293] The substrate processing apparatus can be employed as a
substrate holding apparatus in an electrolytic etching apparatus by
reversing the above-described anode and cathode, and using an
etching liquid instead of a plating solution. It is, of course,
possible to use the substrate processing apparatus as a substrate
holding apparatus in a polishing apparatus.
[0294] According to the substrate processing apparatus of the
present invention, the accuracy of positioning of a substrate with
respect to a substrate holder can be enhanced without being
influenced by a dimensional error in the diameter of the substrate.
Thus, the substrate processing apparatus, when used as a substrate
holding apparatus in an electroplating apparatus, can make the
contact positions of a substrate, held by the substrate holder,
with a cathode and a seal ring more accurate and can therefore
enhance the in-plane uniformity of the thickness of plated film
regardless of an error in the diameter of the substrate. Further,
margins that have conventionally been allowed for cathode contact
position and seal ring contact position can be made smaller, for
example, from 2.5 mm to 2.0 mm, thus making it possible to enlarge
the effective area of a substrate. This will contribute much to
increasing the product yield now and in future years when the
diametrical sizes of substrates are becoming increasingly
large.
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