U.S. patent application number 10/253240 was filed with the patent office on 2004-03-25 for wafer backside electrical contact for electrochemical deposition and electrochemical mechanical polishing.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Chen, Fusen, Dordi, Yezdi, Grunes, Howard E., Lubomirsky, Dmitry, Tulshibagwale, Sheshraj, Yang, Michael X., Yu, Jick M..
Application Number | 20040055893 10/253240 |
Document ID | / |
Family ID | 31993135 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055893 |
Kind Code |
A1 |
Lubomirsky, Dmitry ; et
al. |
March 25, 2004 |
Wafer backside electrical contact for electrochemical deposition
and electrochemical mechanical polishing
Abstract
A method and apparatus for electrochemically plating on a
production surface of a substrate are provided. The apparatus
generally includes a plating cell having a plating solution
reservoir configured to contain a volume of an electrochemical
plating solution, and a substrate support member positioned above
the plating solution reservoir, the substrate support member being
configured to electrically engage a non-production side of a
substrate secured thereto. The substrate support member generally
includes a substrate support surface having at least one vacuum
channel formed therein, a plurality of electrical contact pins
extending from the substrate support surface and being positioned
to engage a perimeter of the non-production side of the substrate
secured thereto, and at least one annular seal positioned on the
substrate support surface radially outward of the plurality of
electrical contact pins, the at least one annular seal being
configured to prevent flow of the electrochemical plating solution
to the plurality of electrical contact pins. The plating cell
further includes a power supply in electrical communication with an
anode positioned in the electrochemical plating solution and the
plurality of electrical contact pins.
Inventors: |
Lubomirsky, Dmitry;
(Cupertino, CA) ; Yang, Michael X.; (Palo Alto,
CA) ; Tulshibagwale, Sheshraj; (Los Altos, CA)
; Dordi, Yezdi; (Palo Alto, CA) ; Grunes, Howard
E.; (Santa Clara, CA) ; Yu, Jick M.; (San
Jose, CA) ; Chen, Fusen; (Cupertino, CA) |
Correspondence
Address: |
PATENT COUNSEL
APPLIED MATERIALS, INC.
Legal Affairs Department
P.O. BOX 450A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
31993135 |
Appl. No.: |
10/253240 |
Filed: |
September 23, 2002 |
Current U.S.
Class: |
205/123 ;
204/252; 205/159; 257/E21.175 |
Current CPC
Class: |
H01L 21/2885 20130101;
C25D 7/123 20130101; C25D 17/06 20130101 |
Class at
Publication: |
205/123 ;
204/252; 205/159 |
International
Class: |
C25D 017/00; C25D
005/02 |
Claims
1. An electrochemical plating cell, comprising: a plating solution
reservoir configured to contain a volume of an electrochemical
plating solution; a substrate support member positioned above the
plating solution reservoir, the substrate support member being
configured to electrically engage a non-production side of a
substrate secured thereto, the substrate support member comprising:
a substrate support surface having at least one vacuum channel
formed therein, the substrate support surface facing the plating
solution reservoir; a plurality of electrical contact pins
extending from the substrate support surface and being positioned
to engage a perimeter of the non-production side of the substrate
secured thereto; and at least one annular seal positioned on the
substrate support surface radially outward of the plurality of
electrical contact pins, the at least one annular seal being
configured to prevent flow of the electrochemical plating solution
to the plurality of electrical contact pins; and a power supply in
electrical communication with an anode positioned in the
electrochemical plating solution and the plurality of electrical
contact pins.
2. The electrochemical plating cell of claim 1, wherein the volume
of the electrochemical plating solution in the plating solution
reservoir comprises between about 1.0 liters and about 5
liters.
3. The electrochemical plating cell of claim 1, wherein the volume
of the electrochemical plating solution comprises between about
1.75 liters and about 2.25 liters.
4. The electrochemical plating cell of claim 1, further comprising
a head assembly in mechanical communication with the substrate
support member, the head assembly being configured to impart at
least one of rotational, vertical, horizontal, and pivotal movement
to the substrate support member.
5. The electrochemical plating cell of claim 1, wherein the plating
solution reservoir further comprises: an inner basin; an outer
basin positioned around the inner basin and being configured to
collect overflow fluid from the inner basin; an anode positioned in
a lower portion of the inner basin; a diffusion plate positioned
above the anode; and a separation membrane positioned between the
anode and the diffusion plate.
6. The electrochemical plating cell of claim 5, wherein the inner
basin is configured to hold a volume of between about 0.5 liters
and about 5 liters of the electrolyte solution.
7. The electrochemical plating cell of claim 1, wherein the at
least one vacuum channel is selectively in fluid communication with
a vacuum source and is configured to vacuum chuck the
non-production side of the substrate to the substrate support
surface.
8. The electrochemical plating cell of claim 1, wherein the
substrate support surface is configured to secure a substrate
thereto using only contacts on the non-production side of the
substrate.
9. The electrochemical plating cell of claim 1, wherein the
plurality of electrical contact pins are manufactured from at least
one of copper, platinum, and gold.
10. An apparatus for electrochemically plating metal onto a
substrate, comprising: a substrate support member having a
substrate support surface formed thereon, the substrate support
member being configured vacuum chuck a non-production side of the
substrate to the substrate support surface and electrically engage
non-production side of the substrate; plating bath positioned below
the substrate support member, the plating bath being configured to
contain an electrochemical plating solution and an anode therein;
and a head assembly in mechanical communication with the substrate
support member, the head assembly being configured actuate the
substrate support member in at least one of horizontally,
vertically, pivotally, and rotationally to support the substrate in
a face down configuration in the plating bath.
11. The apparatus of claim 10, wherein the plating bath comprises
an inner basin configured to contain a plating solution, the inner
basin being positioned within an outer basin that is configured to
collect overflow from the inner basin.
12. The apparatus of claim 10, wherein the substrate support
surface comprises at least one vacuum channel in fluid
communication with vacuum source.
13. The apparatus of claim 10, wherein the substrate support
surface comprises a plurality of electrical contact pins extending
therefrom.
14. The apparatus of claim 13, wherein the plurality of electrical
contact pins are positioned substantially in a circular pattern
proximate a perimeter of the substrate support surface.
15. The apparatus of claim 10, wherein the substrate support
surface comprises at least one seal positioned radially outward
from a plurality of electrical contact pins, the at least one seal
being configured to prevent the electrochemical plating solution
from flowing to the plurality of electrical contact pins during
plating operations.
16. A method for electrochemically plating metal onto a substrate,
comprising: depositing a seed layer on a production surface of the
substrate, the seed layer extending around a bevel edge of the
substrate onto at least a portion of a non-production surface of
the substrate; vacuum chucking the non-production surface of the
substrate to a substrate support member; immersing the production
surface of the substrate in an electrochemical plating solution
having an anode positioned therein; and providing an electrical
plating bias between the production surface of the substrate and
the anode via electrically connecting the portion of the seed layer
that extends onto at least a portion of the non-production surface
with a cathode terminal of a power supply and electrically
connecting the anode with an anode terminal of a power supply.
17. The method of claim 16, wherein depositing the seed layer
comprises using a first physical vapor deposition process to form a
production surface seed layer and using a second physical vapor
deposition process to form a seed layer extension that extends over
a bevel edge of the substrate and onto at least a portion of the
non-production surface of the substrate.
18. The method of claim 17, wherein the second physical vapor
deposition process comprises positioning a ring member between a
deposition target and the non-production surface of the
substrate.
19. The method of claim 16, wherein vacuum chucking the substrate
comprises providing low pressure to at least one vacuum channel
formed into a substrate support surface of the substrate support
member.
20. The method of claim 16, wherein the production surface of the
substrate is free of mechanical, electrical, and sealing
contacts.
21. The method of claim 16, wherein providing an electrical plating
bias between the production surface of the substrate and the anode
further comprises positioning a plurality of electrical contact
pins that are in electrical communication with the cathode terminal
of the power supply on the substrate support member.
22. The method of claim 16, wherein providing the electrical bias
comprises electrically engaging the non-production surface of the
substrate with a plurality of electrical contact pins positioned on
the substrate support member, the plurality of contact pins
operating to electrically engage the substrate once the substrate
is vacuum chucked to the substrate support member.
23. The method of claim 22, further comprising positioning a seal
member radially outward of the plurality of contact pins, the seal
member operating to prevent the electrochemical plating solution
from flowing to the plurality of contact pins.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the invention generally relate to an
electrochemical plating system configured to electrically contact a
back side surface of a substrate being plated on a front side.
[0003] 2. Description of the Related Art
[0004] Metallization of sub-quarter micron sized features is a
foundational technology for present and future generations of
integrated circuit manufacturing processes. More particularly, in
devices such as ultra large scale integration-type devices, i.e.,
devices having integrated circuits with more than a million logic
gates, the multilevel interconnects that lie at the heart of these
devices are generally formed by filling high aspect ratio (greater
than about 4:1, for example) interconnect features with a
conductive material, such as copper or aluminum, for example.
Conventionally, deposition techniques such as chemical vapor
deposition (CVD) and physical vapor deposition (PVD) have been used
to fill these interconnect features. However, as the interconnect
sizes decrease and aspect ratios increase, void-free interconnect
feature fill via conventional metallization techniques becomes
increasingly difficult. As a result thereof, plating techniques,
such as electrochemical plating (ECP) and electroless plating, for
example, have emerged as promising processes for void free filling
of sub-quarter micron sized high aspect ratio interconnect features
in integrated circuit manufacturing processes.
[0005] In an ECP process, for example, sub-quarter micron sized
high aspect ratio features formed into the surface of a substrate
(or a layer deposited thereon) may be efficiently filled with a
conductive material, such as copper, for example. ECP plating
processes are generally two stage processes, wherein a seed layer
is first formed over the surface features of the substrate, and
then the surface features of the substrate are exposed to an
electrolyte solution, while an electrical bias is simultaneously
applied between the substrate and a copper anode positioned within
the electrolyte solution. The electrolyte solution is generally
rich in ions to be plated onto the surface of the substrate, and
therefore, the application of the electrical bias causes these ions
to be urged out of the electrolyte solution and to be plated onto
the seed layer.
[0006] Conventional ECP systems generally utilize a cathode contact
ring to electrically contact the production surface (the surface
being plated or the front side of the substrate) during plating
operations. However, one challenge associated with front or
production side contact-type plating systems is that the
combination of the electrical contacts and the associated seals
utilized in these configurations generally takes up several
millimeters, generally between about 3 and about 7 millimeters, of
the perimeter surface area of the production surface of the
substrate. Since this surface area is used to make electrical and
seal contacts, the area cannot be used to support device formation.
Further, several modern semiconductor processing techniques rely
upon low k materials, which are easily damaged, i.e., cracked, via
physical contact. As such, when these low k layers are deposited on
a substrate and plated over, the electrical contact with the
surface has been shown to crack and/or otherwise damage the low k
material layer.
[0007] Therefore, there is a need for an apparatus for
electrochemically plating substrates, wherein the apparatus
minimizes or eliminates contact with the production surfaces of the
substrates being plated.
SUMMARY OF THE INVENTION
[0008] Embodiments of the invention generally provide an
electrochemical plating cell configured to electrically contact the
backside of a substrate being plated. The plating cell generally
includes a plating solution reservoir configured to contain a
volume of an electrochemical plating solution, and a substrate
support member positioned above the plating solution reservoir, the
substrate support member being configured to electrically engage a
non-production side of a substrate secured thereto. The substrate
support member generally includes a substrate support surface
having at least one vacuum channel formed therein, a plurality of
electrical contact pins extending from the substrate support
surface and being positioned to engage a perimeter of the
non-production side of the substrate secured thereto, and at least
one annular seal positioned on the substrate support surface
radially outward of the plurality of electrical contact pins, the
at least one annular seal being configured to prevent flow of the
electrochemical plating solution to the plurality of electrical
contact pins. The plating cell further includes a power supply in
electrical communication with an anode positioned in the
electrochemical plating solution and the plurality of electrical
contact pins.
[0009] Embodiments of the invention further provide an apparatus
for electrochemically plating metal onto a substrate, wherein the
apparatus includes a substrate support member having a substrate
support surface formed thereon, the substrate support member being
configured vacuum chuck a non-production side of the substrate to
the substrate support surface and electrically engage
non-production side of the substrate. The apparatus further
includes a plating bath positioned below the substrate support
member, the plating bath being configured to contain an
electrochemical plating solution and an anode therein. Further, the
apparatus includes a head assembly in mechanical communication with
the substrate support member, the head assembly being configured
actuate the substrate support member in at least one of
horizontally, vertically, pivotally, and rotationally.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0011] FIG. 1 illustrates a general partial perspective and
sectional view of an exemplary plating cell of the invention.
[0012] FIG. 2 illustrates a perspective view of an exemplary head
assembly of the invention.
[0013] FIG. 3 illustrates a detailed sectional view of an exemplary
plating cell of the invention.
[0014] FIG. 4 is a perspective view of an exemplary substrate
support member of the invention.
[0015] FIG. 5 is a general sectional view of an exemplary
deposition chamber configured to deposit the backside conductive
layer of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Embodiments of the invention generally provide an
electrochemical plating cell configured to electrically contact a
back side surface of a substrate being plated. The electrochemical
plating cell of the invention generally utilizes a vacuum
chuck-type substrate holder configured to secure a substrate
thereto with the back side of the substrate (the non-production
side of the substrate) being in contact with the vacuum chuck and
the production side (the side of the substrate being plated) being
exposed to an electrolyte solution. In this configuration, the
production surface of the substrate is free of physical contact
from the plating cell hardware, i.e., electrical contacts, seals,
or other contact devices that may be used to secure the substrate
to the substrate support member. The lower surface of the vacuum
chuck-type substrate support member is configured to electrically
contact the backside of the substrate being chucked thereto via a
plurality of electrical contact pins extending outwardly from the
lower surface of the vacuum chuck. The plurality of pins are
generally configured to physically contact the backside of the
substrate secured to the substrate support member. Therefore, since
at least a backside of the substrate generally includes a
conductive layer deposited thereon that is in electrical
communication with the production surface of the substrate, the
plurality of backside electrical contact pins may be used to supply
an electrical plating bias to the production surface of the
substrate without actually contacting the production surface.
Additionally, one or more seals may be positioned on the lower
surface of the vacuum chuck to prevent to electrolyte used in
plating operations from traveling to the backside of the substrate,
and more particularly, to prevent the electrolyte from reaching the
electrical contact pins and causing plating thereon.
[0017] FIG. 1 illustrates a general partial perspective and
sectional view of an exemplary plating cell and head assembly 100
of the invention. Cell and head assembly 100 generally includes a
support arm 101 configured to support a head assembly 102 at a
position above a plating bath 104 in a manner that allows the head
assembly 102 to position a substrate in a plating bath for
processing. The head assembly 102 is generally attached to a
substrate support member 103 at a lower portion thereof, and is
configured to provide vertical, rotational, and angular movement
thereto. The substrate support member 103, which will be described
in further detail herein, is generally configured to support a
substrate on a lower surface thereof, i.e., wherein the lower
surface is defined as the surface of the substrate support member
positioned adjacent the plating bath 104. Additionally, the lower
surface is configured to electrically contact the backside of the
substrate supported thereon to facilitate electrochemical plating
on the production surface of the substrate, and therefore, the
electrical current supplied to the substrate is generally conducted
around the bevel edge of the substrate to the plating/production
surface by a conductive layer deposited on the front side, the
bevel edge, and a portion of the backside of the substrate, as will
be described herein.
[0018] The plating bath 104 is generally contained within an inner
basin 105, which is separated into two distinct regions: first, an
anode region; and second, a cathode region, both of which will be
further described herein. The inner basin 105 generally resides
within a larger diameter outer basin 106, which operates to collect
and drain fluids received from the inner basin 105 via a fluid
drain. An anode assembly 107, which may be a consumable or
non-consumable-type anode, for example, is generally positioned
within a lower portion (anode region) of the inner basin 105. A
membrane 108 is generally positioned across the diameter of inner
basin at a position above the anode assembly 107, and as such,
membrane 108 generally operates to separate the cathode region from
the anode region. The membrane may be, for example, a cation
membrane, an anion membrane, an uncharged-type membrane, or a
multilayer diffusion differentiated permeable membrane, as
described in commonly assigned U.S. patent application Ser. No.
10/194,160 filed on Jul. 11, 2002, which is hereby incorporated by
reference in its entirety. The upper portion of the inner basin 105
(the cathode region) generally includes an electrolyte solution
fluid inlet 109 configured to supply a plating electrolyte solution
to the cathode region, while a separate fluid inlet 110 generally
operates to supply a fluid solution exclusively to the anode
region. Both of the respective fluid inlets will be further
described herein.
[0019] FIG. 2 illustrates a perspective view of an exemplary head
assembly 102 of the invention. Head assembly 102 generally includes
an upper actuation portion 201 and a lower substrate support
portion 202. The upper actuation portion 201, which is in
mechanical communication with the lower substrate support portion
202, generally operates to control the position of substrate
support portion 202. For example, upper actuation portion 201
generally operates to rotate substrate support portion 202, raise
and lower substrate support portion 202 in a direction
perpendicular to the substrate support surface, i.e., along the
vertical axis of the upper actuation portion 201, and vary the
angular position of the substrate support surface, such as during
an angular immersion process. The substrate support portion 202
generally includes a disk shaped substrate support member 400,
which is shown in perspective in FIG. 4. The disk shaped substrate
support member 400 includes a substrate lower support surface 401
configured to receive and secure a substrate thereto during and
electoral plating process. The substrate support surface generally
includes a plurality of vacuum channels 402 formed therein. The
vacuum channels are generally in fluid communication with a vacuum
source (not shown), and are therefore, configured to vacuum chuck a
substrate to the substrate support surface 401 for processing when
a vacuum is applied to the vacuum channels 402. The substrate
support surface 401 further includes a plurality of electrical
contact pins 403 extending therefrom. The plurality of electrical
contact pins, which may be positioned in a circular pattern, for
example, are generally configured to electrically contact the
backside of the substrate being plated when the substrate is vacuum
chucked to the substrate support surface 401. Power is supplied to
the plurality of pins via a power supply (not shown). The power
supply may supply electrical power to all of the pins 403
cooperatively, banks or groups of pins individually, or to the
individual pins 403. In embodiments where current is supplied to
groups or individual pins, a current control system may be employed
to control the current applied to each group or pin. The substrate
support surface 401 further includes one or more seals 404
positioned proximate the plurality of electrical contact pins 403.
The seals 404 are generally positioned radially outward of the
contact pins 403, so that a dry contact configuration is created.
Generally, the seals are configured to prevent electrolyte solution
from traveling through the seals and contacting the electrical
contact pins 403, as contact between electoral contact pins 403 and
electrolyte solution generally causes plating on the pins, which
alters the pin resistance and has a negative effect on the
substrate plating uniformity. Both the electrical contact pins 403
and the seals 404 are configured to engage the backside of the
substrate being plated, and therefore, the frontside contact
configurations of conventional plating cells is eliminated.
[0020] FIG. 3 illustrates a detailed sectional view of an exemplary
plating cell 104 of the invention. As briefly described with
respect to FIG. 1, the exemplary plating cell 104 generally
includes an inner basin 105 positioned radially inward from an
outer basin 106. The inner basin 105 generally operates to contain
a plating solution therein in a manner that allows the substrate
support member 103 to position a substrate within the plating
solution during plating operations. The inner basin 105 generally
includes sloped sides that terminate at a common upper point 306,
and therefore, the electrolyte solution supplied to the area within
inner basin 105 may flow over the common upper point in order to
create a substantially planar upper fluid surface and maintain a
constant volume of electrolyte solution in the inner basin 105. The
electrolyte solution flowing over the common upper point 306 is
received in the outer basin 106 and drained therefrom. The central
portion of inner basin 105 generally includes an open volume or
bath 307 where the electrolyte solution used for plating operations
is contained. The lower portion of volume 307 is generally bounded
by a diffusion plate 308, which generally consists of a disk shaped
plate having a plurality of pores or holes formed therein to
facilitate fluid flow therethrough. Additionally, diffusion plate
308 may be configured to provide some degree of control over
plating parameters, such as deposition uniformity for example,
through material selection, positioning of the diffusion plate, and
the pore size selection for the diffusion plate. The pores in the
diffusion plate 308, for example, may be between about 1 micron in
diameter and about 10 microns in diameter, and the materials used
to manufacture the diffusion plate may be insulators, such as,
ceramics, plastics, and other materials known in the electroplating
art to be insulators and non-reactive with electroplating
solutions.
[0021] Immediately below diffusion plate 308 is a second open
volume 309, where the electrolyte solution used for plating
operations is introduced into prior to traveling through diffusion
plate 308 to contact the substrate for plating operations. Fluid
for plating operations, i.e., the electrolyte plating solution, is
generally supplied to open area 309 via an electrolyte solution
inlet 314, which is generally in fluid communication with an
electrolyte supply source (not shown).
[0022] An anode assembly is generally positioned below open space
309 and is configured to supply metal ions to the plating solution
for plating operations. The anode assembly may be separated from
the open volume 309 via a membrane 310. The anode assembly
generally includes a disk shaped metal member 311, which may be
copper or copper phosphate, for example, in a copper electoral
plating system. The positioning of membrane 310 generally operates
to provide an open volume between the lower surface of membrane 310
and an upper surface of anode 311. This space between membrane 310
and the upper surface of anode 311 is generally in fluid
communication with a second fluid inlet 312 configured to supply a
fluid solution to the volume immediately above the anode 311 and
below the membrane 310. Additionally, the area below membrane 310
and above anode 311 may also be in fluid communication with a fluid
drain 313 configured to remove fluid from the area. As such,
cooperative operation of fluid supply inlet 312 and fluid drain 313
allows for the fluid introduced into the region immediately above
anode 311 to be removed therefrom by fluid drain 313, without the
fluid transferring through the membrane 310 into open area 309.
This configuration allows for isolation of the anode assembly from
the cathode region of the plating cell, and more particularly,
allows for isolation of contaminants generated at the surface of
the anode, i.e., organic additive breakdown, copper balls, etc.,
from traveling from the anode surface and depositing on the
production surface of the substrate and generating a defect.
[0023] The positioning of membrane 310 generally operates to
isolate the anode 311 from the substrate being plated, which is
essentially the cathode. As such, the volume proximate the
substrate being plated may generally be characterized as a cathode
chamber, while the volume proximate the anode, i.e., the volume
below membrane 310 and above the upper surface of anode 311, may
generally be characterized as an anode chamber. As noted above, the
isolation of anode 311 from the substrate being plated generally
operates to prevent additives in the plating solution that degrade
upon contact with the anode from traveling to the substrate being
plated and causing plating defects. The positioning of the membrane
310 between the anode and the substrate allows for the capture or
prevention of these degraded solution additives from traveling from
the anode to the substrate surface. Furthermore, the implementation
of fluid inlet 312 in conjunction with fluid drain 313, both of
which are exclusively in fluid communication with the anode
compartment, i.e., the volume immediately above the anode surface
and immediately below the lower surface of membrane 310, further
facilitates prevention of degraded solution additives from
traveling from the anode to the substrate being plated. More
particularly, inasmuch as the fluid provided to the anode
compartment is circulated out of the anode compartment without
traveling into the cathode compartment, degraded solution additives
are removed from the plating cell altogether before they have a
chance to circulate through the membrane 310 into the cathode
compartment and cause defects on the plating surface. Further
still, the plating solution provided to the anode compartment may
be a solution that does not include the plating additives, i.e.,
the solution may be a copper sulfate solution without additives,
and therefore, the solution that contacts the anode may not even
have the additives that react with the anode therein.
[0024] Additionally, plating cell 104 is generally configured as a
low-volume plating cell. More particularly, the volume of
electrolyte solution contained within inner basin 105, i.e., the
volume of electrolyte solution within basin 105 is used for plating
operations, is generally less than about one liter for a basin
having a diameter of about 300 mm, which is substantially smaller
than convention cells that generally hold about 6 liters.
Therefore, given the diameter of inner basin 105 of about 300 mm,
the depth of the electrolyte solution with in inner basin 105
having about 1 liter of electrolyte solution therein will generally
be less than about one inch. More particularly, the depth of the
electrolyte solution within inner basin 105 may be between about 1
mm and about 10 mm, for example. As such, when head assembly 102
operates to position a substrate for plating operations within the
electrolyte solution contained by inner basin 105, the surface of
the substrate being plated will generally be positioned between
about 1 mm and about 10 mm away from the upper surface of diffusion
plate 308. The low-volume plating cell 104 provides several
advantages, namely, reduced electrolyte solution required for
plating. Additionally, the low-volume, which requires low clearance
between the substrate being plated and the diffusion plate 308,
operates to eliminate head recalibration processes when an anode is
replaced or changed out.
[0025] In operation, the plating cell of the invention is generally
configured to electrochemically plate a metal onto a production
surface of a substrate, while making electrical and seal contacts
with the substrate on a nonproduction surface of the substrate.
Therefore, inasmuch as conventional electrochemical plating systems
generally make electrical contact with a conductive seed layer
formed on the production surface of the substrate during plating
operations, embodiments of the invention include extending the
conductive seed layer formed on the production surface to a portion
of the non production surface. For example, the conductive seed
layer may be extended around the bevel edge of the substrate to an
outer perimeter annular region of the non-production surface of the
substrate. More particularly, embodiments of the present invention
are generally configured to electrically contact the nonproduction
surface of the substrate near the perimeter of the substrate, i.e.,
in a circular pattern near the bevel edge of the substrate on the
backside thereof. Therefore, in order to extend the conductive seed
layer around the bevel edge of the substrate being plated to the
back side thereof, embodiments of the invention contemplate
utilizing a deposition chamber configured to deposit an annular
region, band, or ring shaped conductive layer onto a portion of the
backside of the substrate. Since the backside electrical contact
pins of the invention are generally positioned near the outer
perimeter of the backside of the substrate, the annular band
deposited on the backside of the substrate is generally deposited
near the perimeter of the substrate so that the conductive band
will align with the plurality of electrical contact pins extending
from the substrate support member. For example, FIG. 5 illustrates
an exemplary PVD chamber configured to deposit a narrow band of
conductive material onto the backside and bevel edge of the
substrate near the perimeter. This narrow band of conductive
material, which is generally referred to as a seed layer extension,
may then be used by the electrical contact pins of the invention to
electrically contact the backside of the substrate being plated via
electrical engagement between the backside electrical contact pins
and the conductive seed layer extension on the backside of the
substrate. The electrical bias applied to the seed layer extension
layer on the backside may then be conducted to the production
surface via the conductive seed layer extension layer.
[0026] The exemplary PVD chamber 500 illustrated in the FIG. 5
generally operates to deposit the seed layer extension layer across
the bevel edge and onto the backside of the substrate to be plated.
The seed layer extension deposition process generally includes
positioning a substrate 501 above a disk shaped ring member 502,
wherein the ring is configured to support the substrate 501 with
the outer perimeter of the substrate extending beyond the outer
perimeter of the ring 502. The substrate is generally positioned in
a face up manner, i.e., the production surface of the substrate is
facing away from a deposition target positioned below the ring
member 502, and therefore, the backside of the substrate is facing
towards the deposition target. The ring member 502 is positioned
above the deposition target 503, and therefore, when a PVD
deposition process is conducted, the outer perimeter portion of the
substrate extending beyond the outer perimeter portion of the ring
member 502 will be plated with the target material. Additionally,
one or more magnetic field generation devices may be positioned
near the chamber 500 and may be used to control the directionality
of the deposition process to facilitate the seed layer extension
deposition. The deposition process used to form a conductive seed
layer on the production surface of the substrate and to form the
seed layer extension on the non-production surface of the substrate
may include using one or more deposition chambers. For example, the
seed layer may be deposited on the production surface in a first
PVD or CVD chamber, and then the substrate may be transferred to a
second deposition chamber (PVD or CVD) where the seed layer
extension (the bevel edge and non-production surface layer) may be
deposited. Alternatively, a single deposition chamber, i.e., a PVD
or a CVD chamber, may be configured to deposit both the production
surface seed layer and the non-production surface/bevel edge seed
layer extension layer.
[0027] Once the seed layer extension is deposited on the substrate,
the substrate may then be transported to a backside contact-type
plating cell of the invention. The backside contact plating cell,
such as plating cell 100 illustrated in FIG. 1, for example, will
generally receive with the substrate in a face down position, i.e.,
the backside of the substrate to be plated is received and secured
to a substrate support member in a manner such that the production
surface is exposed and the backside is engaged with the substrate
support member. If the substrate to be processed in the backside
contact electrochemical plating cell of the invention is not in the
proper orientation, then the substrate may be flipped over by a
flipper robot, for example. The process of securing the substrate
to be plated to the substrate support member further includes both
electrically contacting the seed layer extension on the backside of
the substrate, as well as mechanically engaging the backside of the
substrate with one or more seals to prevent electrolyte solution
from traveling to the area on the backside of the substrate where
the electrical contact pins engage the seed layer extension.
Embodiments of the invention generally utilize a vacuum chuck type
operation to secure the substrate to be plated to the substrate
support member. For example, prior to plating operations, a
substrate to be plated is brought to a position proximate the
substrate support surface. Thereafter, the substrate support
surface may be lowered to a position nearly in contact with the
backside of the substrate. A vacuum source in fluid communication
with a plurality of grooves formed into the substrate support
surface may then be activated such that the backside of the surface
is drawn into engagement with the substrate support surface as a
result of a negative pressure region generated between the
substrate and the substrate support surface. The end result is that
the backside of the substrate is vacuum chucked to the substrate
support surface. However, inasmuch as the substrate support surface
may include a plurality of electrical contact pins extending
therefrom, when the backside of the substrate is vacuum chucked to
the substrate support surface, the electrical contact pins
inherently contact/engage the backside of the substrate. As such,
the electrical contact pins are generally positioned around or
proximate the perimeter of the substrate support surface, i.e., in
an area adjacent the seed layer extension layer deposited on the
backside of the substrate. Therefore, since the seed layer
extension is in electrical communication with the seed layer
deposited on the production surface of the substrate, when the
electrical contact pins are caused to engage the seed layer
extension, the electrical contact pins become in electrical
communication with the seed layer on the production surface of the
substrate. Therefore, the electrical contact pins may be used to
provide an electrical plating bias to the production surface of the
substrate sufficient to facilitate electrochemical plating
operations, even though the electrical contacts are in electrical
communication with the backside or nonproduction side of the
substrate being plated.
[0028] Further, since it is known in electrical chemical plating
systems that contact between the contact pins and the electrolyte
plating solution results in metal being plated directly on the
electrical contact pins, it is desirable to isolate the electrical
contact pins from the electrolyte solution during plating
operations. More particularly, for example, the electrical contact
pins may be positioned radially around the perimeter of the
substrate support surface in a circular pattern configured to
mirror the annular seed layer extension deposited on the backside
of the substrate being plated. In this configuration, an annular
seal may be positioned radially outward of the electrical contact
pins near the perimeter of the substrate support surface. In this
configuration, when a substrate to be plated is vacuum chucked to
the substrate support surface, the electrical contact pins will
engage the seed layer extension layer, while the annular seal will
simultaneously engage the perimeter of the backside of the
substrate just outside of the electrical contact pins. Inasmuch as
the annular seal is positioned radially outward from the electrical
contact pins, the electrolyte solution used for plating operations
must first pass through the annular seal in order to reach the
contact pins. As such, the annular seal generally operates to
generate a dry contact configuration via preventing the electrolyte
from passing through or around the seal, which minimizes or
eliminates plating on the electrical contact pins, and therefore,
reduces plating uniformity problems associated therewith.
[0029] Once the substrate to be plated is chucked to the substrate
support surface and electrically contacted by the electrical
contact pins, the substrate support surface is generally lowered
into the plating cell containing an electrolyte solution configured
to facilitate electrochemical plating operations. For example, as
illustrated in FIG. 1, head assembly 102 may lower the substrate
support assembly 103 into plating cell 104, where an electrolyte
plating solution may be contained by an inner base and 105. The
substrate may be lowered into the plating solution in a manner
configured to prevent bubbles from forming or attaching to the
substrate surface during the immersion process. For example, had
assembly 102 may be configured to immerse the substrate to be
plated into the plating solution at an angle so that any bubbles on
the substrate surface may be urged upward via the angle and off or
away from the substrate surface. Further still, had assembly 102
may be configured to rotate the substrate during the immersion
process to further facilitate the removal of bubbles from the
substrate surface. Regardless of the particular immersion process,
embodiments of the invention generally provide advantages over
conventional electrochemical plating cells, as the present
invention do not utilize any sort of front side substrate contact.
This is an important feature the invention, as conventional
electrochemical plating cells utilizing front side contacts, i.e.,
contact seals, electrical contacts, or mechanical contacts used to
secure the substrate to a support surface, are known to cause
bubble formation on the substrate surface during the immersion
process, as the contacts trap bubbles at the surface during
immersion. These trapped bubbles lead to uniformity problems, as
the bubbles have a different conductivity than the electrolyte
plating solution, and therefore, the substrate surface below the
bubbles will plate differently than the substrate surface in
contact with the electrolyte solution. Additionally, during the
immersion process, an electrical bias may be applied to the
substrate, as the electrolyte solutions are generally acidic, and
therefore, will catch the conductive seed layer deposited on the
substrate. The application of the electrical bias generally
operates to offset the chemical etching process with a slight
plating process, and therefore, prevents damage to the seed layer
during the immersion process as a result of acidic etching.
[0030] Once the immersion process is completed and the production
surface of the substrate is in contact with the electrolyte
solution, then an electrical plating bias may be applied to the
production surface of the substrate by the backside electrical
contacts. More particularly, the backside electrical contacts
extending from the substrate support surface are in electrical
engagement with the seed layer extension deposited on the backside
of the substrate, and therefore, the backside electrical contacts
may be utilized to supply electrical bias to the production surface
of the substrate in order to facilitate electrochemical plating
thereon. The electrical bias, which is supplied to the backside
electrical contact pins by a power supply (not shown), generally
travels from the backside electrical contact pins into the
conductive seed layer extension deposited on the backside and bevel
edge of the substrate being plated. The electrical bias, therefore,
travels through the seed layer extension and around the bevel edge
of the substrate into the seed layer formed on the production
surface of the substrate. Since the seed layer is in fluid
communication with the electrolyte solution, the electrical bias
causes metal ions in the electrolyte solution to plate on the seed
layer as a result of the polarity of the electrical bias applied
thereto. For example, in a copper electrochemical plating system of
the invention, the electrolyte solution may contain a copper rich
solution, such as copper sulfate, for example, and the backside
electrical contact pins may be in electrical communication with the
cathode of a power supply, while the anode of the power supply may
be in electrical communication with an anode positioned in the
electrolyte solution. In this configuration, the seed layer of the
substrate being plated is biased as a cathode, and therefore,
attracts the positive copper ions in the electrolyte solution to
plate on the seed layer. During the plating process, the head
assembly may rotate, tilt, or otherwise move the substrate support
surface (and the substrate supported thereon) in the electrolyte
solution to obtain desired flow or circulation properties of the
electrolyte solution to the production surface of the
substrate.
[0031] Once the desired electrochemical plating processing recipe
has been executed and the metal layer deposited on the production
surface of the substrate, head assembly 102 may retract the
substrate support 103 from the electrolyte solution. Once the
substrate is retracted from the solution, it may be removed from
the substrate support 103 and transferred to an adjacent position
for cleaning, rinsing, drying, and/or bevel material removal
process, as desired for the particular process. In particular,
since the seed layer extension layer was deposited onto the bevel
edge and backside of the substrate in order to allow the backside
contact pins to be in electrical communication with the production
surface seed layer, the substrate will generally be transported to
a bevel edge cleaning chamber configured to remove the seed layer
extension layer once the plating process is complete. Generally, a
bevel edge cleaning chamber will include one or more nozzles
configured to dispense an acidic or etchant solution onto the seed
layer extension layer while the substrate is rotated. The solution
operates to etch away the seed layer extension layer, thus leaving
a clean bevel edge and backside of the substrate. It will be
understood by those skilled in the art that generally all
conventional electrochemical processing parameters, such as plating
voltages, current densities, rotation rates, plating durations,
solution chemical compositions, etc. may be applied to the
processing of substrates in the plating cell of the present
invention, and therefore, these parameters will not be discussed in
detail.
[0032] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
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