U.S. patent application number 11/049642 was filed with the patent office on 2005-12-15 for plating apparatus.
Invention is credited to Saito, Koji, Sameshima, Katsumi.
Application Number | 20050274604 11/049642 |
Document ID | / |
Family ID | 35459352 |
Filed Date | 2005-12-15 |
United States Patent
Application |
20050274604 |
Kind Code |
A1 |
Saito, Koji ; et
al. |
December 15, 2005 |
Plating apparatus
Abstract
A plating apparatus can form a plated film having a uniform
thickness on a surface to be plated of a substrate without
employing a complicated structure, such as a conduction detection
means capable of detecting the state of conduction (contact state)
of feeding contacts in contact with a conductive portion of the
substrate. The plating apparatus includes a substrate holder having
a plurality of feeding contacts for contact with a conductive
portion provided in a surface of a substrate, wherein the substrate
holder includes a feeding ring comprised of a single member and
having the feeding contacts disposed at regular intervals along the
circumferential direction, a plurality of substrate chucks for
contact with the substrate in the vicinity of the contact portions
of the feeding contacts with the conductive portion to support the
substrate, and a substrate deflection preventing mechanism for
preventing deflection of the substrate.
Inventors: |
Saito, Koji; (Tokyo, JP)
; Sameshima, Katsumi; (Kyoto, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
35459352 |
Appl. No.: |
11/049642 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
204/198 ;
204/297.01 |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 7/123 20130101; C25D 17/06 20130101 |
Class at
Publication: |
204/198 ;
204/297.01 |
International
Class: |
C25D 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2004 |
JP |
2004-30441 |
Mar 5, 2004 |
JP |
2004-62206 |
Claims
What is claimed is:
1. A plating apparatus comprising: a substrate holder having a
plurality of feeding contacts for contact with a conductive portion
provided in a surface of a substrate, wherein the substrate holder
includes; a feeding ring comprised of a single member and having
the feeding contacts disposed at regular intervals along the
circumferential direction, a plurality of substrate chucks for
contact with the substrate in the vicinity of the contact portions
of the feeding contacts with the conductive portion to support the
substrate, and a substrate deflection preventing mechanism for
preventing deflection of the substrate.
2. The plating apparatus according to claim 1, wherein the
substrate chucks each have a guide for stopping the peripheral end
portion of the substrate.
3. The plating apparatus according to claim 2, wherein the guide is
provided in such a position as not to interfere with the feeding
contact.
4. The plating apparatus according to claim 1, wherein the
substrate deflection preventing mechanism is comprised of an
annular flat stage.
5. The plating apparatus according to claim 4, wherein the
substrate chucks are provided around the flat stage.
6. The plating apparatus comprising: a substrate holder having a
plurality of feeding contacts for contact with a conductive portion
provided in a surface of a substrate and forming, together with the
substrate, a plating solution holding portion; an immersion member
disposed opposite the substrate, held by the substrate holder, at a
predetermined distance therefrom; and an electrode disposed on the
immersion member and opposite the substrate, held by the substrate
holder, at a predetermined distance therefrom; wherein the feeding
contacts are provided opposite the peripheral end portion of the
substrate held by the substrate holder.
7. The plating apparatus according to claim 6, wherein the feeding
contacts are provided in the form of fixed pins in an inner
peripheral end portion of the substrate holder.
8. The plating apparatus according to claim 7, wherein the feeding
contacts are provided in an inclined position and opposite to a
bevel surface of the substrate held by the substrate holder.
9. The plating apparatus according to claim 6, further comprising a
sealing member for sealing the gap between the substrate holder and
the substrate on the back surface side of the substrate when the
substrate is held by the substrate holder.
10. The plating apparatus according to claim 6, wherein the
immersion member is a non-conductive foam of the continuous cell
type.
11. The plating apparatus comprising: a substrate holder having a
plurality of feeding contacts for contact with a conductive portion
provided in a surface of a substrate; and an immersion member and
an electrode each disposed opposite the substrate, held by the
substrate holder, at a predetermined distance therefrom; wherein
the substrate holder includes a feeding ring comprised of a single
member and having the feeding contacts disposed at regular
intervals along the circumferential direction, a plurality of
substrate chucks for contact with the substrate in the vicinity of
the contact portions of the feeding contacts with the conductive
portion to support the substrate, and a substrate deflection
preventing mechanism for preventing deflection of the substrate,
wherein the diameters of the immersion member and the electrode are
set to be equal to or larger than the effective diameter of the
substrate, and wherein the feeding contacts are provided opposite
the peripheral end portion of the substrate held by the substrate
holder.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plating apparatus for use
in carrying out plating of a surface (front surface) to be plated
of a substrate, such as a semiconductor wafer, and more
particularly to a plating apparatus that can form a plated film
having a more uniform thickness on a surface to be plated of a
substrate.
[0003] 2. Description of the Related Art
[0004] With the recent progress toward higher integration of
semiconductor devices, the circuit interconnects are becoming finer
and the distance between adjacent interconnects is becoming
smaller. Especially, when forming a circuit pattern by optical
lithography with a line width of not more than 0.5 .mu.m, it
requires that surfaces on which pattern images are to be focused by
a stepper be as flat as possible because depth of focus of an
optical system is relatively small. It is therefore necessary to
flatten a surface of a substrate, such as a semiconductor wafer,
and polishing of a surface of a substrate by a chemical-mechanical
polishing (CMP) apparatus is widely practiced as a flattening
method.
[0005] In order to fill fine trenches and via holes, formed in a
surface of a substrate, such as a semiconductor wafer, with an
interconnect material in advance of CMP, a technique of carrying
out the filling by metal plating, such as copper plating, has been
employed. In carrying out the plating, it is important to form a
plated film having a uniform thickness. Plating apparatuses adapted
to obtain a uniform plated film thickness for semiconductor
devices, such as LSIs, which are becoming finer and multi-level
structure, include dip-type plating apparatuses and face down-type
plating apparatuses. Though the both plating apparatuses materially
differ in their structures, they generally use an electrode
(cathode) having the same structure.
[0006] FIG. 1 shows a plating apparatus adapted to feed electricity
uniformly to a surface (surface to be plated) of a substrate, such
as a semiconductor wafer, thereby forming a plated film having a
uniform thickness (see WO 99/31304). As shown in FIG. 1, the
plating apparatus includes a plating tank 10 for holding a plating
solution Q, a substrate holder 11 for setting therein a substrate
W, such as a semiconductor wafer, and immersing it in the plating
solution Q in the plating tank 10, and an electrode (anode) 13,
facing the substrate W held in the substrate holder 11, disposed in
the plating solution Q. A plated film is formed on the surface
(surface to be plated) of the substrate W by applying a
predetermined direct-current voltage from a plating power source 14
to between the substrate holder 11 and the electrode (anode)
13.
[0007] The substrate holder 11 is provided with a feeding section
16 having a plurality of feeding contacts 15 for contacting a
surface conductive portion of the substrate W to feed electricity
thereto. When the cathode of the plating power source 14 is
connected to the feeding contacts 15 and the anode of the plating
power source 14 is connected to the electrode 13, a plating current
flows through the electrode (anode) 13, the plating solution Q, the
conductive portion of the substrate W and the feeding contacts
15.
[0008] Accordingly, if the feeding contacts 15 do not securely
contact a conductive film of the substrate W, a plated film cannot
be formed sufficiently on the conductive film of the substrate W
and the thickness of the plated film can become non-uniform.
[0009] FIG. 2 is a vertical sectional view showing an example of
the construction of the feeding section of the substrate holder 11.
As shown in FIG. 2, the feeding section includes an annular packing
18 provided on the inner side of an annular frame 17, and a feeding
ring 19 provided on the outer side of the packing 18. A plurality
of feeding contacts 15 is disposed at regular intervals in the
feeding ring 19. The end portions of the feeding contacts 15
contact, like a spring, the surface conductive portion (not shown)
of the substrate W, whereby the feeding contacts 15 and the
conductive portion of the substrate W are electrically connected.
Further, the tip of the packing 18 is pressed against the surface
of the substrate W into tight contact with it. This can prevent the
plating solution Q from leaking out of the packing 18, thus
preventing the feeding contacts 15, the feeding ring 19, etc. from
being exposed to the plating solution.
[0010] FIGS. 3 and 4 show conventional different examples of
feeding rings 19 each having feeding contacts 15 attached thereto.
According to the example shown in FIG. 3, the leaf spring-like
feeding contacts 15 are attached to the feeding ring 19 at regular
intervals. According to the example shown in FIG. 4, the feeding
ring 19 is divided into a plurality (four in FIG. 4) of divisions
electrically insulated from each other by an insulating member 20,
and the leaf spring-like feeding contact 15 is attached to each
division. FIGS. 3 and 4 are perspective views of the respective
feeding electrodes 19 with the feeding contacts 15 attached
thereto, as viewed from below.
[0011] When the plurality of leaf spring-like feeding contacts 15
are provided in the common feeding ring 19, as shown in FIG. 3,
because of a difference in the contact resistance between the
feeding contacts, some feeding contacts 15 are relatively easy to
pass electric current and some feeding contacts 15 are relatively
hard to pass electric current. Accordingly, a thin plated film is
formed in that portion of a substrate W which lies in the vicinity
of a feeding contact 15 hard to pass electric current.
[0012] When the feeding ring 19 is divided by the insulating
members 20 into a plurality of feeding divisions and the leaf
spring-like feeding contact 15 is provided in each feeding
division, as shown in FIG. 4, the feeding divisions of the feeding
ring 19 are electrically independent from each other. It is,
therefore, possible to reduce the current difference between the
feeding contacts 15 by controlling a current value supplied to each
feeding contact 15. However, an electric current is hard to flow
between a feeding contact 15 and its adjacent feeding contact 15,
whereby a thin plated film is formed in that portion of a substrate
which lies between adjacent feeding contacts 15.
[0013] In order to improve such variation in the thickness of the
plated film, a plating apparatus is disclosed which uses an
electrode having feeding contacts which, as a whole, is in the form
of a circular ring (see WO 00/03074).
[0014] FIG. 5A shows a plan view of feeding contacts provided in
the feeding section of the substrate holder of the plating
apparatus, and FIG. 5B shows an enlarged sectional view taken along
the line A-A of FIG. 5A. The feeding section comprises a plurality
(8 in FIG. 5A) of arc-shaped feeding contacts 15 which, as a whole,
form a circular ring. Each feeding contact 15a includes a plurality
(12 in FIG. 5A) of contact strips 15a which are formed integrally.
Each feeding contact 15 may be produced by subjecting a metal plate
of, for example, phosphor bronze, having elasticity and high
electric conductivity, to sheet metal processing or the like.
[0015] By providing the feeding contact 15 having contact strips
15a, shown in FIGS. 5A and 5B, in each feeding division of the
feeding ring 19 shown in FIG. 4, so as to bring the contact strips
15a of the feeding contact 15 into contact with a conductive
portion of a substrate W, and correcting a current value supplied
to each feeding contact 15, it become possible to uniformize
electric currents flowing through the feeding contacts 15. In the
case where the feeding contacts 15, each having the feeding strips
15a, shown in FIGS. 5A and 5B, is applied to the feeding ring shown
in FIG. 4, the distance between adjacent contact strips 15a of each
feeding contact 15 can be made extremely small. This makes it
possible to form a plated film having a uniform thickness in those
portions of a substrate which lie around the contact strips 15a and
between the contact strips 15a.
[0016] When the feeding contacts 15, having the contact strips 15a,
are connected in a ring, the pressure of the contact strips 15a on
the conductive portion of a substrate upon their contact can be
distributed uniformly, i.e., an unbalanced pressure distribution
can be prevented.
[0017] FIG. 6 shows another plating apparatus for forming a plated
film, such as a copper film, on a surface (surface to be plated) of
a substrate W, such as a semiconductor wafer, by performing
electroplating. As shown in FIG. 6, the plating apparatus 51
includes a substrate holder 11 for holding the substrate W with its
front surface facing upwardly, a plating cup 12 to be capped on the
substrate W with the open end closed with the substrate W, a
sealing member 23 for sealing between the plating cup 12 and the
substrate W held by the substrate holder 11, and an electrode
(anode) 13 disposed in the plating cup 12 and opposite to the
substrate W at a predetermined distance therefrom. The plating
apparatus 51 is provided with a plating power source 14. An
electric current is supplied from the power source 14 with the
substrate W as a cathode and the electrode 13 as an anode. A
plating solution Q is supplied into the plating cup 12 closed with
the substrate W, and a plated film, such as a copper film, is
formed on the surface of the substrate W by passing electricity
through the plating solution Q within the plating cup 12.
[0018] In such plating apparatus 51, electricity is fed to a
substrate W through mechanical contact with a conductive portion
(not shown) of the substrate W.
[0019] The conventional plating apparatus as shown in FIG. 6
necessitates a large amount of plating solution for a substrate,
such as a semiconductor wafer, and thus entails the problem of
diseconomy even if a plated film having a uniform thickness can be
formed.
[0020] A plating apparatus, as shown in FIG. 7, has therefore been
proposed as a plating apparatus directed to the solution of such a
diseconomy problem. As shown in FIG. 7, the plating apparatus 51
includes an annular frame 32 having packing properties and
comprising a metal core 29 and a rubbery sealing member 18 of a
synthetic rubber or resin material, having elasticity like a
fluorocarbon rubber and chemical resistance. The plating apparatus
51 also include an immersion member (in-liquid immersion member) 34
which is immersed in a plating solution Q, held in a plating
solution holding portion defined by the frame 32 and a substrate W,
so as to raise the liquid surface of the plating solution Q, thus
reducing the necessary amount of plating solution, a holding
assembly 33 for holding the immersion member 34 by a rubber
shielding ring 35 in order to forcibly immerse the immersion member
34 in the plating solution Q, and an electrode (anode) 13 disposed
parallel to the surface of the substrate W and on the immersion
member 34, preferably in contact with the immersion member 34 which
is disposed opposite the substrate W at a predetermined distance
therefrom.
[0021] The immersion member 34 is composed of, for example, a
continuous cell-type porous ceramic, and is non-conductive and thus
acts as a resistance. By disposing the immersion member 34 between
the substrate W and the electrode 13, and forming long channels of
plating solution in the continuous cells throughout the immersion
member 34 to thereby raise the average electric resistance, it
becomes possible to uniformize the thickness distribution of a
plated film formed on the surface of the substrate. When the
electric resistance between the electrode 13 and the substrate W is
low, electric current concentrates on the feeding contact side
(peripheral region of substrate). This is because of the high
resistance of a seed film formed in the substrate surface. The
thickness distribution of a plated film formed on the surface of
the substrate can therefore be uniformized by disposing a
resistance member, which has a higher resistance than the seed
film, such as the immersion member 34, between the electrode 13 and
the substrate W.
[0022] In this plating apparatus 51, feeding contacts 15, for
supplying an electric current from a plating power source 14 to a
conductive portion (not shown) of the substrate W, are brought into
contact with the peripheral portion of the substrate W on the outer
side of a packing portion 43 of the frame 32 by an elastic force,
whereby the conductive portion of the substrate W and the feeding
contacts 15 are electrically connected. The tip of the packing
portion 43 is pressed against the surface of the substrate W into
tight contact with it. This can prevent the plating solution Q from
leaking out of the packing portion 43, or the frame 32, thus
preventing the feeding contacts 15 from being exposed to the
plating solution Q.
[0023] FIG. 8 is a plan view showing a feeding section in which the
arc-shaped feeding contacts 15, each having a number of feeding
strips 15a, shown in FIGS. 5A and 5B, are provided in the feeding
ring 19 divided by the insulating members 20 into the feeding
sections, shown in FIG. 4, so that the feeding strips 15a of the
feeding contacts 15 are brought into contact with the conductive
portion of the substrate W, and in which substrate chucks 21, for
supporting the substrate W, are disposed each between adjacent
feeding contacts 15.
[0024] As apparent from FIG. 8, the distance between one feeding
strip 15a of one feeding contact 15 and an adjacent feeding strip
15a of an adjacent feeding contact 15, disposed on the opposite
sides of the substrate chuck 21, is considerably larger than the
distance between adjacent feeding strips 15a in each arc-shaped
feeding contact 15.
[0025] When the distances between contacts are not equal (not
uniformly distributed) as in this case, a plated film, having a
non-uniform thickness or variation in the film thickness, will be
formed on a surface of a substrate W, such as a semiconductor
wafer, as shown in FIG. 9.
[0026] According to the plating apparatus shown in FIG. 7, by
forcibly immersing the immersion member 34 in a plating solution Q
by using the holding assembly 33 to raise the liquid surface of the
plating solution Q, the amount of plating solution can be
materially reduced as compared to the conventional plating
apparatus shown in FIG. 6.
[0027] As apparent from FIG. 7, however, the peripheral portion of
a substrate W lies on the outer side of the packing portion 43 of
the frame 32 and does not contact the plating solution Q. This
decreases the plating area of the substrate W, and thus lowers the
efficiency in the use of substrate W.
[0028] Further, the diameter of the immersion member 34 is
considerably smaller than the diameter of the substrate W.
Accordingly, as can be seen from FIG. 7, even in the region, on the
inner side of the packing portion 43 of the frame 32, where the
plating solution Q is present, plating does not substantially
progress in that portion of the substrate W which is near the
periphery and lies in the region where the electrode 13 is not
present overhead. If plating progresses in that portion of the
substrate W, i.e., the portion lying outside the immersion member
34 or the electrode 13, it does only insufficiently as compared to
the substrate portion lying underneath the electrode 13. The poorly
plated portion cannot be utilized as a product, that is, the
effective plating area is narrowed.
[0029] Furthermore, in order to bring the frame 32 into tight
contact with a substrate W, a support (not shown) is provided on
the lower surface side of the substrate W in a position
corresponding to the frame 32, so that the substrate W is clamped
by the support and the frame 32 to bring the packing portion 43 of
the frame 32 into tight contact with the substrate W. Upon the
clamping, an intolerable force is applied to the peripheral portion
of the substrate W, which would cause warpage of the substrate W
and hinder the formation of a plated film having a uniform
thickness.
SUMMARY OF THE INVENTION
[0030] The present invention has been made in view of the above
problems in the prior art. It is therefore a first object of the
present invention to provide a plating apparatus which can form a
plated film having a uniform thickness on a surface to be plated of
a substrate without employing a complicated structure, such as a
conduction detection means capable of detecting the state of
conduction (contact state) of feeding contacts in contact with a
conductive portion of the substrate.
[0031] It is a second object of the present invention to provide a
plating apparatus which can make a considerable reduction in an
amount of plating solution and can form a plated film having a
uniform thickness over an entire surface to be plated of a
substrate, such as a semiconductor wafer.
[0032] After intensive study to achieve the above objects, it has
been found by the present inventors that variation in the thickness
of a plated film formed on a peripheral portion of a substrate,
such as a semiconductor wafer, is caused by inequality (non-uniform
distribution) in the distances between adjacent feeding contacts.
The present invention has been accomplished based on such
findings.
[0033] It has also been found that the use of an immersion member
having the same diameter as a substrate makes it possible to form a
plated film having a uniform thickness over the entire surface,
from the center to the periphery, of a substrate. The present
invention has been accomplished based on such findings.
[0034] The present invention provides a plating apparatus
comprising a substrate holder having a plurality of feeding
contacts for contact with a conductive portion provided in a
surface of a substrate, wherein the substrate holder includes a
feeding ring comprised of a single member and having the feeding
contacts disposed at regular intervals along the circumferential
direction, a plurality of substrate chucks for contact with the
substrate in the vicinity of the contact portions of the feeding
contacts with the conductive portion to support the substrate, and
a substrate deflection preventing mechanism for preventing
deflection of the substrate.
[0035] According to the present invention, feeding contacts are
disposed at regular intervals in one feeding ring. Accordingly, the
distances between adjacent feeding contacts can be equalized
(uniform distribution), whereby the contact resistances at the
contact points can be equalized. This can prevent variation in the
film thickness of a plated film formed on a peripheral portion of a
substrate, such as a semiconductor wafer, and can thus form a
plated film having a uniform thickness.
[0036] Further, the substrate, such as a semiconductor wafer, can
be held by clamping it from above and below by the integrated
feeding ring with the evenly-spaced feeding contacts mounted
thereto and the substrate deflection preventing mechanism and, in
addition, the substrate chucks are provided in the vicinity of the
contact portions of the feeding contacts of the feeding ring with
the conductive portion. This can equalize the pressures of the
feeding contacts on the substrate and, by the synergistic effect
with the uniform distribution of the feeding contacts, can
effectively reduce variation in the thickness of a plated film
formed in the peripheral region of the substrate.
[0037] The present invention also provides another plating
apparatus comprising: a substrate holder having a plurality of
feeding contacts for contact with a conductive portion provided in
a surface of a substrate and forming, together with the substrate,
a plating solution holding portion; an immersion member disposed
opposite the substrate, held by the substrate holder, at a
predetermined distance therefrom; and an electrode disposed on the
immersion member and opposite the substrate, held by the substrate
holder, at a predetermined distance therefrom; wherein the feeding
contacts are provided opposite the peripheral end portion of the
substrate held by the substrate holder.
[0038] According to the present invention, by forming the plating
solution holding portion with the substrate holder and a substrate
held by the substrate holder, the necessary amount of plating
solution for a substrate can be materially reduced. Furthermore,
since the immersion member is immersed in a plating solution during
plating, the amount of plating solution, corresponding to the
amount excluded by the immersion member, can be further reduced.
Because of the small amount of plating solution used, the plating
solution can be used batchwise, though it may be reused in a
circulatory manner.
[0039] By clamping the peripheral portion of a substrate with the
substrate holder, and forming the plating solution holding portion
with the substrate holder and the substrate, the entire surface of
the substrate can be brought into contact with the plating
solution. Further, in carrying out plating with the electrode on
the immersion member as an anode and the substrate disposed below
the immersion member as a cathode, the use of the immersion member
and the electrode, whose diameters are equal to or larger than the
effective diameter of the substrate, can broaden the effective
plating area of the substrate. The immersion member is made of, for
example, a continuous cell-type porous ceramic, and is
non-conductive and thus acts as a resistance. By forming long
channels of plating solution in the continuous cells throughout the
immersion member, a plated film having a uniform thickness can be
formed over the entire surface of the substrate. When copper
plating is carried out, a copper plate is used as the electrode.
The term "effective diameter of substrate" refers to the diameter
of the peripheral end of that portion of the substrate which is in
contact with a plating solution.
[0040] During plating, the feeding contacts are in contact with a
plating solution. The feeding contacts are conventionally made of a
material that can corrode when exposed to a plating solution. In
view of this, a protective film, which is non-conductive and
corrosion resistant, may be formed on that portion of each feeding
contact which is to contact a plating solution. The protective film
allows an electric current to flow easily between the feeding
contact and the conductive substrate holder serving as a feeding
electrode. Further, the corrosion prevention method, as compared to
other conventional methods, can simplify the electrode structure.
Such a protective film cannot be formed on that portion of the
feeding contact which directly contacts a substrate. Therefore, a
plated film grows gradually on that portion of the feeding contact.
The plated film, however, can be removed, for example, by applying
a voltage, which is reverse to the voltage applied upon plating,
between the substrate and the electrode to etch away the plated
film.
[0041] Further, with such an electrode structure, the substrate can
be clamped from above and below without a stress that causes
deflection or warpage of the substrate. This can stabilize the
state of electricity feeding, thus stably forming a plated film
having a uniform thickness.
[0042] The present invention also provides yet another plating
apparatus comprising: a substrate holder having a plurality of
feeding contacts for contact with a conductive portion provided in
a surface of a substrate; and an immersion member and an electrode
each disposed opposite the substrate, held by the substrate holder,
at a predetermined distance therefrom, wherein the substrate holder
includes a feeding ring comprised of a single member and having the
feeding contacts disposed at regular intervals along the
circumferential direction, a plurality of substrate chucks for
contact with the substrate in the vicinity of the contact portions
of the feeding contacts with the conductive portion to support the
substrate, and a substrate deflection preventing mechanism for
preventing deflection of the substrate, wherein the diameters of
the immersion member and the electrode are set to be equal to or
larger than the effective diameter of the substrate, and wherein
the feeding contacts are provided opposite the peripheral end
portion of the substrate held by the substrate holder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a diagram schematically showing the construction
of a conventional plating apparatus;
[0044] FIG. 2 is a cross-sectional view showing the construction of
a feeding section of a conventional substrate holder;
[0045] FIG. 3 is a perspective view, as viewed from below, of a
conventional feeding section including a feeding ring having
feeding contacts mounted thereto;
[0046] FIG. 4 is a perspective view, as viewed from below, of
another feeding section including a feeding ring having feeding
contacts mounted thereto, the feeding contacts being electrically
insulated from each other;
[0047] FIG. 5A is a plan view showing the construction of feeding
contacts provided in the feeding section of the substrate holder of
a conventional plating apparatus, and FIG. 5B is a cross-sectional
view taken along the line A-A of FIG. 5A;
[0048] FIG. 6 is a schematic diagram showing the construction of
another conventional plating apparatus;
[0049] FIG. 7 is a schematic cross-sectional view showing the main
portion of yet another conventional plating apparatus adapted to
reduce an amount of plating solution;
[0050] FIG. 8 is a plan view showing yet another feeding section of
a substrate holder of a plating apparatus;
[0051] FIG. 9 is a graph showing the distribution of a thickness of
a plated film in a peripheral portion of a substrate as the plated
film is formed on a surface of the substrate by using the feeding
section of FIG. 8;
[0052] FIG. 10 is a plan view (taken along the line A-A of FIG. 12)
showing a feeding ring and feeding contacts, together constituting
the feeding section of the substrate holder of a plating apparatus
according to an embodiment of the present invention;
[0053] FIG. 11 is a bottom view of the feeding ring shown in FIG.
10;
[0054] FIG. 12 a cross-sectional view showing the state of
electricity feeding from the feeding ring and the feeding contacts
shown in FIG. 10;
[0055] FIG. 13 is a perspective view of the substrate chuck shown
in FIG. 12;
[0056] FIG. 14 is a perspective view, partly broken away, showing
part of the substrate holder of the plating apparatus according to
the embodiment of the present invention;
[0057] FIG. 15 is a graph showing the distribution of a thickness
of a plated film in a peripheral portion of a substrate as the
plated film is formed on a surface of the substrate by using the
plating apparatus according to the embodiment of the present
invention;
[0058] FIG. 16 is a schematic cross-sectional view showing the main
portion of a plating apparatus according to another embodiment of
the present invention; and
[0059] FIG. 17 is a schematic cross-sectional view showing the main
portion of a plating apparatus according to yet another embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0060] Preferred embodiments of the present invention will now be
described with reference to the drawings. In the drawings, the same
parts or members as those shown in FIGS. 1 through 8 are shown with
the same reference numerals.
[0061] FIG. 10 is a plan view (taken along the line A-A of FIG. 12)
showing a feeding ring 19 and feeding contacts 15, together
constituting the feeding section of the substrate holder 11 (see
FIG. 1) of a plating apparatus according to an embodiment of the
present invention. The feeding ring 19, together with the feeding
contacts 15 mounted thereto, forms, as a whole, the circular
ring-shaped feeding section. FIG. 10 shows the connection between
the feeding ring 19 and the feeding contacts 15. FIG. 11 is a
bottom view (as viewed from below) of the feeding ring 19. A
sealing member 23 covering the upper surface of the feeding ring 19
appears between the feeding contacts 15. Each feeding contact 15
can be produced by subjecting a metal plate of, for example,
phosphor bronze, having elasticity and high electric conductivity,
to sheet metal processing or the like. Though not shown in FIG. 11,
holes are formed in the lower surface of the feeding ring 19 at the
positions of feeding contacts 15 so that the feeding contacts 15
are screwed up. Instead of the feeding contacts 15, it is also
possible to mount the circular ring-shaped feeding contacts 15,
each having a plurality of contact strips 15a integrally formed
with the feeding contact, which has the same construction shown in
FIG. 5A, to the feeding ring 19.
[0062] FIG. 12 is a cross-sectional view showing the state of
electricity feeding from the feeding ring 19 and the feeding
contacts 15 to a substrate W. Six substrate chucks 21 are provided
at regular intervals around an annular flat stage 22 (see FIG. 14)
provided to support the peripheral portion of the substrate W from
below. The peripheral end portion of the substrate W is placed on
the substrate chucks 21 to hold the substrate W by pressing it from
above. By holding the substrate W in this manner, the substrate W
can be prevented from warping or deflecting. The flat stage 22 is
one example of a substrate deflection preventing mechanism.
According to this embodiment, the substrate W is adapted to be held
by clamping the substrate W from above and below by the sealing
member 23 and the flat stage (substrate deflection preventing
mechanism) 22. The feeding contacts 15 project from a lower portion
of the feeding ring 19, and their tips contact the substrate W to
feed electricity to the substrate W.
[0063] The substrate chuck 21 has a structure as shown in FIG. 13.
The feeding contact 15 passes between guides 24, which are provided
for stopping the peripheral end portion of the substrate W, so that
the guides 24 and the feeding contacts 15 do not interfere with
each other, and electricity can be fed to the substrate W even at
the site of substrate chuck 21, thus avoiding non-uniform feeding
of electricity to the substrate W.
[0064] FIG. 14 is a perspective view illustrating the electrode
structure of the above-described substrate holder. As shown in FIG.
14, the feeding contacts 15 mounted to the feeding ring 19 contact
a conductive portion (not shown) formed in the surface of the
peripheral portion of the substrate W, which is held by clamping of
the peripheral portion from above and below by the substrate chucks
21, the flat stage 22 and the sealing member 23, whereby the
conductive portion and the feeding contacts 15 are electrically
connected. FIG. 14 shows the substrate holder when the substrate W
is on the flat stage 22. Therefore, the flat stage 22, lying under
the substrate W, is not visible and hence is shown by broken lines.
The feeding contacts 15, lying under the feeding ring 19, are also
invisible and are shown by broken lines. However, the feeding ring
19 is partly broken away to show the substrate chucks 21, and the
substrate W is also broken away as shown. As can be seen from FIG.
14, the feeding contact 15 passes between the guides 24 of the
substrate chuck 21.
[0065] FIGS. 10 and 11 clearly show that the electrode contacts 15
are uniformly distributed in the circumferential direction. As a
result, as shown in FIG. 15, variation in the thickness of a plated
film formed on a peripheral portion of a substrate, such as a
semiconductor wafer, is considerably improved, or reduced as
compared to variation in the thickness of a plated film as formed
by use of the feeding section in which the distances between
adjacent contacts are not equal (non-uniform distribution of
contacts), as shown in FIG. 9. Thus, a plated film with
sufficiently small thickness variation can be formed on a
peripheral portion of a substrate, such as a semiconductor
wafer.
[0066] The substrate holder (electrode) of the plating apparatus,
described hereinabove, can be advantageously employed not only for
a dip-type plating apparatus, but also for a face down-type plating
apparatus or a variant thereof equally as well. With respect to a
plating solution, besides a copper sulfate plating solution for
copper plating, a plating solution for other metal plating can, of
course, be used.
[0067] The plating apparatus of the present invention, which, owing
to the substrate holder, can form a plated film having a uniform
thickness on a substrate, such as a semiconductor wafer, is useful
in the field of semiconductor manufacturing, etc. Further, because
of the capability to form a plated film having a uniform thickness,
the plating apparatus can easily form copper interconnects which
have a larger current capacity than aluminum interconnects or the
like. The present plating apparatus can therefore be advantageously
used especially for the production of semiconductor devices which
need fine interconnects.
[0068] FIG. 16 shows a cross-sectional view of the main portion of
a plating apparatus according to another embodiment of the present
invention.
[0069] This plating apparatus forms a copper film by electroplating
on a substrate, such as a semiconductor wafer for a semiconductor
device, in particular an LSI which is becoming finer and
multi-level structure to meet the demand for higher speed and lower
power consumption. As shown in FIG. 16, the plating apparatus 51
includes a substrate holder 11 for holding a substrate W with its
front surface facing upwardly. A plating solution holding portion
for holding a plating solution Q is formed by the substrate holder
11 and the substrate W held by the substrate holder 11. The plating
apparatus 51 includes an immersion member (in-liquid immersion
member) 34 disposed opposite the substrate W, held by the substrate
holder 11, at a predetermined distance therefrom, which is to be
immersed in the plating solution Q held in the plating solution
holding portion to exclude the plating solution Q, a holding
assembly 33 for holding the immersion member 34 by a rubber
shielding ring 35 in order to forcibly immerse the immersion member
34 in the plating solution Q, an electrode (anode) 13 located
within the plating solution holding portion and preferably attached
to the upper surface of the immersion member 34,and a sealing
member 18 for sealing the gap between the substrate W and the
substrate holder 11 on the back surface side of the substrate
W.
[0070] In the thus-constructed plating apparatus 51, a plurality of
feeding contacts 15 for feeding electricity from a plating power
source 14 (see FIG. 6) to a conductive portion of the substrate W
are mounted, in the form of fixed pins, to a projecting portion 54,
projecting into the plating solution Q, of the substrate holder 11.
The feeding contacts 15 contact the peripheral end portion of the
front surface of the substrate W to feed electricity to the
conductive portion of the substrate W. This construction makes it
possible to plate a wide area, except the peripheral end portion,
of the surface of the substrate W. The feeding contacts 15 are
immersed in the plating solution Q when they are in contact with
the peripheral end portion of the surface of the substrate W. In
this regard, corrosion resistance can be imparted to the feeding
contact 15 by the provision of a corrosion resistant coating or by
the use of a corrosion resistant material. The feeding contact 15
can be much shorter than the conventional ones shown in FIG. 7. The
feeding contact 15 may not necessarily be of the shape of a pin,
but may be of the shape of a continuous ring extending over the
inner circumference of the substrate holder 11.
[0071] In the plating apparatus 51, an electric current is supplied
from the plating power source 14 (see FIG. 6) with the substrate W
as a cathode and the electrode 13 as an anode. A plating solution Q
is supplied into the plating solution holding portion formed by the
substrate W and the substrate holder 11, and a copper film is
formed on the surface of the substrate W by passing electricity
through the plating solution Q in the plating solution holding
portion.
[0072] In the plating apparatus 51, the immersion member 34 needs
to achieve the objective of reducing the amount of plating solution
Q held in the plating solution holding portion formed by the
substrate W and the substrate holder 11. The immersion member 34 is
composed of, for example, a continuous cell-type porous ceramic,
and is non-conductive and thus acts as a resistance. By disposing
the immersion member 34 between the substrate W and the electrode
13, and forming long channels of plating solution in the continuous
cells throughout the immersion member 34 to thereby raise the
average electric resistance, it becomes possible to uniformize the
thickness distribution of a plated film formed on the surface of
the substrate. When the electric resistance between the electrode
13 and the substrate W is low, electric current concentrates on the
feeding contact side (peripheral region of substrate). This is
because of the high resistance of a seed film formed in the
substrate surface. The thickness distribution of a plated film
formed on the surface of the substrate can therefore be uniformized
by disposing a resistant material, having a higher resistance than
the seed film, i.e., the immersion member 34, between the electrode
13 and the substrate W. A ceramic, a synthetic resin, a rubber,
etc. can be preferably used as a material for the immersion member
34. A foamed material may be used when a lightweight member is
desired. The formed material should be one durable to the plating
solution.
[0073] An elastic material, such as a synthetic rubber or resin, is
preferably used for the sealing member 18 for sealing the gap
between the substrate W and the substrate holder 11 in order to
prevent leakage of the plating solution Q in the plating solution
holding portion formed by the substrate holder 11 and the substrate
W held by the substrate holder 11. A fluorocarbon rubber having
excellent elasticity, heat resistance and chemical resistance is
most preferably used.
[0074] Examples of the fluorocarbon rubber include a propylene
hexafluoride-chlorotrifluoroethylene-vinylidene fluoride terpolymer
rubber, a tetrafluoroethylene-propylene copolymer rubber, a
fluorine-containing polyacrylate rubber, a fluorine-containing
polyester rubber, and a fluorinated phosphazene rubber.
[0075] A description will now be given of feeding of electricity to
a substrate W in the plating apparatus 51.
[0076] In the plating apparatus 51, a substrate W is held by the
substrate holder 11 by clamping the peripheral portion, as
described above. In the plating apparatus 51, the plurality of
fixed pin-shaped feeding contacts 15, mounted to the projecting
portion 54 of the substrate holder 11 as an electrode, lie between
the projecting portion 54 and the substrate W, and contact a
conductive portion (not shown) of the substrate W to feed
electricity thereto. The feeding contacts 15 are disposed at
regular intervals over the peripheral portion of the substrate W so
that they make point contact or line contact with the surface
conductive portion of the substrate W in the entire peripheral area
of the substrate W.
[0077] The substrate holder 11 for holding the substrate W by
clamping its peripheral portion, together with the feeding contacts
15 disposed between the projecting portion 54 and the surface
conductive film of the peripheral portion of the substrate W,
constitutes a feeding section. Accordingly, the substrate holder 11
is formed of a conductive material, preferably a metal. The
substrate holder 11 protrudes to above the surface of the substrate
W at such a height as to sufficiently hold the plating solution Q
even when the plating solution Q is excluded by the immersion
member 34 and the liquid surface rises. The substrate holder 11 has
a tapered inner surface, and the projecting portion 54 for mounting
the fixed pin-shaped feeding contacts 15 thereto is formed at the
lower end of the tapered surface. The feeding contacts 15 are
formed of, for example, copper or a noble metal such as gold,
silver or platinum.
[0078] In this plating apparatus 51, when the substrate W is held
by the substrate holder 11, the feeding contacts 15 come into
contact with the surface conductive portion of the peripheral
portion of the substrate W, whereby electricity is fed to the
surface of the substrate W from the peripheral portion of the
substrate W through the conductive portion.
[0079] According to the plating apparatus 51, by thus carrying out
feeding of electricity to the surface (surface to be plated) of the
substrate W from the peripheral side of the substrate W and by the
evenly-spaced feeding contacts 15, stable feeding with a uniform
current density distribution becomes possible. Accordingly, it
becomes possible with the plating apparatus 51 to form, by
electroplating, a copper film having a uniform thickness on the
surface (surface to be plated) of the substrate W.
[0080] Further, unlike the conventional plating apparatus as shown
in FIG. 7, there is no need to provide a support on the back
surface side of a substrate and clamp the peripheral portion of the
substrate by the support and the packing portion of a frame for
tight contact of the packing portion with the substrate. There is,
therefore, no fear of distortion or warpage of the substrate W,
enabling the formation of a plated film having a uniform thickness
over the entire surface of the substrate W.
[0081] In addition, the diameters of the immersion member 34 and
the electrode 13 are equal to or larger than the effective diameter
of the substrate W, and the plating solution Q is present over the
entire surface of the substrate W. This can broaden the effective
plating area as compared to the conventional plating apparatus
shown in FIG. 7, and enables the formation of a plated film having
a uniform thickness over the entire surface of the substrate W.
[0082] FIG. 17 shows a cross-sectional view of the main portion of
a plating apparatus according to yet another embodiment of the
present invention.
[0083] The plating apparatus 51 only differs in electrical
connection between a substrate W and a substrate holder 11 from the
plating apparatus shown in FIG. 16. Since the other construction is
the same, a description thereof is omitted, and a description is
made only of the electrical connection.
[0084] Referring to FIG. 17, a substrate holder 11 for clamping the
periphery of a substrate W, together with feeding contacts 15
mounted to the substrate holder 11, constitutes a feeding section.
The feeding contacts 15 are for contact with the bevel portion
(upper peripheral inclined surface) 46 of the substrate W. As
apparent from FIG. 17, the inner surface of the substrate holder 11
is only tapered and thus simplified as compared to the substrate
holder of FIG. 16. Though the feeding contacts 15 are preferably
provided on the tapered surface of the substrate holder 11, it is
also possible to place the feeding contacts 15, in the form of a
ring as a whole, on the bevel portion 46 of the substrate W so that
they come into electrical contact upon holding of the substrate W
by the substrate holder 11.
[0085] The feeding contacts 15 may only be provided at regular
intervals on the tapered surface of the annular substrate holder
11. Further, feeding of electricity to the substrate W can be
carried out in the bevel portion of the substrate W, and not the
front surface for which flatness is required in the manufacturing
of semiconductor device. Accordingly, the electricity feeding to
the substrate W according to this embodiment exerts no adverse
influence on flattening of the front surface.
[0086] Further, by simply clamping the feeding contacts 15, each in
the form of a plate-like strip, between the bevel portion of the
substrate W and the lower inclined surface of the substrate holder
11, electrical connection can be made more securely as compared to
the case shown in FIG. 16.
[0087] In the embodiments shown in FIGS. 16 and 17, it is also
possible to use, as the feeding contacts 15 provided in the
substrate holder 11, the feeding contacts 15 of the feeding ring 19
used in the embodiment shown in FIGS. 10 to 14. Further, the
plating apparatuses of the embodiments shown in FIGS. 16 and 17 may
also include the substrate chucks 21 and the flat stage 22 as a
substrate deflection preventing mechanism, both used in the
embodiment shown in FIGS. 10 to 14.
[0088] This can equalize the contact resistances at the contact
points, thereby preventing variation in the film thickness of a
plated film formed on a peripheral portion of a substrate, such as
a semiconductor wafer. A plated film having a uniform thickness can
thus be formed over the broadened effective plating area of the
substrate.
[0089] The plating apparatus of the present invention, which can
form a plated film having a uniform thickness on a substrate and
can take a broad plating area, is useful in the field of the
production of articles with a mirror-like surface where the
formation of a metal film having a uniform thickness on the surface
(surface to be plated) of a substrate, such as a semiconductor
wafer, a quartz substrate or a glass substrate, is required.
[0090] The plating apparatus of the present invention, which can
form a uniform plated film over the entire surface of a substrate
and can take a broad plating area, is especially useful for the
production at a low cost of semiconductor devices, in particular
LSIs, for use in electronics which are required to be small-sized,
high-performance and multifunctional ones.
* * * * *