U.S. patent application number 10/308848 was filed with the patent office on 2004-06-03 for small volume electroplating cell.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Dordi, Yezdi, Edelstein, Sergio, Hey, Peter.
Application Number | 20040104119 10/308848 |
Document ID | / |
Family ID | 32392852 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040104119 |
Kind Code |
A1 |
Edelstein, Sergio ; et
al. |
June 3, 2004 |
Small volume electroplating cell
Abstract
A method and apparatus for plating a metal onto a substrate. The
apparatus generally The apparatus generally includes a substrate
support member configured to support a substrate during a plating
process, a cathode clamp ring detachably positioned to circumscribe
a perimeter of the substrate and a movable anode assembly disposed
above the substrate, wherein the anode assembly is movable in a
direction generally perpendicular the substrate. The apparatus
generally further includes a fluid inlet formed through the anode
assembly, the fluid inlet being configured to supply a plating
solution to the processing area sufficient to electrically connect
the anode assembly to the substrate. The method generally includes
supplying a plating solution to a processing chamber, the
processing chamber being defined by a movable anode assembly
disposed above the substrate and a cathode clamp ring detachably
positioned to circumscribe the perimeter of the substrate, wherein
the plating solution is supplied at a rate sufficient to
electrically connect the anode assembly to the substrate and
plating a metal from the plating solution onto the substrate.
Inventors: |
Edelstein, Sergio; (Los
Gatos, CA) ; Hey, Peter; (Sunnyvale, CA) ;
Dordi, Yezdi; (Palo Alto, 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: |
32392852 |
Appl. No.: |
10/308848 |
Filed: |
December 2, 2002 |
Current U.S.
Class: |
205/133 ;
204/198 |
Current CPC
Class: |
C25D 5/04 20130101; C25D
7/123 20130101 |
Class at
Publication: |
205/133 ;
204/198 |
International
Class: |
C25D 005/00; C25D
017/00 |
Claims
What is claimed is:
1. An apparatus for plating a metal onto a substrate surface,
comprising: a substrate support member configured to support a
substrate during a plating process; a cathode clamp ring detachably
positioned to circumscribe a perimeter of the substrate; a movable
anode assembly disposed above the substrate, wherein the anode
assembly is movable in a direction generally perpendicular the
substrate; and a fluid inlet formed through the anode assembly, the
fluid inlet being configured to supply a plating solution to the
processing area sufficient to electrically connect the anode
assembly to the substrate.
2. The apparatus of claim 1, wherein the movable anode assembly is
configured to adjust a distance between an anode plate of the anode
assembly and the substrate.
3. The apparatus of claim 2, wherein the distance is between about
2 mm and about 20 mm.
4. The apparatus of claim 1, wherein movable anode assembly
includes a disk shaped anode plate surrounded by an annular hood
member.
5. The apparatus of claim 3, wherein the hood member is
manufactured from an insulating material.
6. The apparatus of claim 4, wherein the hood member is
manufactured from a metal and is connected to a power source to
selectively control current passing between the anode plate and the
substrate.
7. The apparatus of claim 1, wherein movable anode assembly
comprises a disk shaped anode plate having an aperture formed
therein, the aperture forming the fluid inlet.
8. The apparatus of claim 7, wherein the anode plate is positioned
in parallel relationship to a plating surface of the substrate.
9. The apparatus of claim 7, further comprising an actuator
configured to actuate the anode plate toward and away from the
substrate.
10. The apparatus of claim 1, wherein the cathode clamp ring is
configured to be positioned over an upper perimeter surface of the
substrate support member in a manner such that the cathode clamp
ring electrically engages the perimeter portion of the substrate
and forms a processing volume above the substrate and within the
clamp ring.
11. The apparatus of claim 10, wherein the processing volume is as
deep as the cathode clamp ring is tall and is sized to receive an
anode plate therein.
12. A method for plating a metal onto a substrate, comprising:
supplying a plating solution to a processing volume, the processing
volume being defined by a movable anode assembly disposed above the
substrate and a cathode clamp ring detachably positioned to
circumscribe a perimeter of the substrate, wherein the plating
solution is supplied at a rate sufficient to electrically connect
the anode assembly to the substrate; and plating a metal from the
plating solution onto the substrate.
13. The method of claim 12, further comprising moving the anode
assembly to define a distance between the anode plate and the
plating surface.
14. The method of claim 12, wherein the anode assembly comprises an
anode plate including a plurality of metal segments, the plurality
of metal segments being separately controlled by a power source to
provide uniform metal deposition.
15. The method of claim 14, wherein the plurality of metal segments
are separated by an insulating material.
16. The method of claim 12, wherein the anode assembly further
comprises a hood depending from the periphery of the anode
plate.
17. The method of claim 16, further comprising releasing
electrolyte from the processing chamber through an annular opening,
the annular opening being defined by a distance between the hood
and the cathode clamp ring.
18. The method of claim 17, further comprising supplying plating
solution to the processing chamber at a rate essentially equal to
the rate of release.
19. The method of claim 12, further comprising rotating the
substrate.
20. The method of claim 12, further comprising adjusting the anode
assembly to form a cell chamber having a volume of from about 0.5 L
to about 1.9 L.
21. The method of claim 14, wherein the distance between the
substrate and the anode plate is between about 2 mm and 20 mm.
22. The method of claim 14, wherein the distance between the
substrate and the anode plate is between about 2 mm and about 10
mm.
23. An electrochemical processing cell, comprising: a substrate
support member having a circular upper substrate support surface
formed thereon; an annular cathode contact ring configured to
releasably engage an outer perimeter of the substrate support
surface and electrically contact a substrate positioned thereon;
and a disk shaped anode configured to be received within an inner
diameter of the annular cathode contact ring, the disk shaped anode
being movable between an processing position and a loading
position.
24. The processing cell of claim 23, wherein the disk shaped anode
further comprises a fluid inlet configured to deliver a processing
fluid to a processing volume defined by the anode, the cathode
contact ring, and the substrate.
25. The processing cell of claim 23, wherein the contact ring forms
an annular wall above the substrate, the annular wall being
configured to maintain a volume of a plating solution therein.
26. The processing cell of claim 23, wherein the anode further
comprises a hood member.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention generally relate to
deposition of a metal layer onto a substrate. More particularly,
the embodiments of the present invention relate to electroplating a
metal layer onto a substrate.
[0003] 2. Description of the Related Art
[0004] Metallization for sub-quarter micron sized features is a
foundational technology for present and future generations of
integrated circuit manufacturing processes. 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 interconnect features
with a conductive material, such as copper or aluminum.
Conventionally, deposition techniques such as chemical vapor
deposition (CVD) and physical vapor deposition (PVD) have been used
to fill these interconnect features. However, as 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 viable processes for filling sub-quarter micron
sized high aspect ratio interconnect features in integrated circuit
manufacturing processes.
[0005] In an ECP process sub-quarter micron sized high aspect ratio
features formed on a substrate surface 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 an anode positioned within the
electrolyte solution. The electrolyte solution is generally rich in
ions to be plated onto the surface of the substrate. Therefore, the
application of the electrical bias causes these ions to be urged
out of the electrolyte solution and to be plated as a metal on the
seed layer. The plated metal, which may be copper, for example,
grows in thickness and forms a copper layer that fills the features
formed on the substrate surface.
[0006] Present designs of cells for electroplating a metal on
semiconductor substrates are generally based on a fountain plater
type configuration. FIG. 1 illustrates a cross sectional view of a
simplified exemplary fountain plater. Generally, the fountain
plater 10 includes an electrolyte container 12 having a top
opening, a substrate holder 14 disposed above the electrolyte
container 12, an anode 16 disposed at a bottom portion of the
electrolyte container 12, and a cathode 20 contacting the substrate
18. The cathode 20 includes a plurality of contact pins distributed
about the peripheral portion of the substrate 18 to provide an
electrical bias to the substrate surface. The semiconductor
substrate 18 is generally positioned a fixed distance above the
electrolyte container 12, and the electrolyte generally impinges
perpendicularly on the substrate plating surface. Because of the
possible dispersion effects of the electrical current at the
exposed edges of the substrate 18 and the possible non-uniform flow
of the electrolyte, the fountain plater 10 may provide non-uniform
current distribution, particularly at the region near the edges and
at the center of the substrate 18, which may result in non-uniform
plating on the substrate. The electrolyte flow uniformity at the
center of the substrate 18 can be improved by rotating the
substrate 18. However, the plating uniformity still may deteriorate
as the boundaries or edges of the substrate are approached.
[0007] Therefore, there remains a need for a reliable, consistent
copper electroplating technique to deposit and form copper layers
on semiconductor substrates having nanometer-sized, high aspect
ratio features. There is also a need for a face-up electroplating
system that allows fast substrate processing and increases
throughput with a small volume of plating solution. Furthermore,
there is a need for an apparatus for delivering a uniform
electrical power distribution to a substrate surface and a need for
an electroplating system that provides uniform deposition on the
substrate surface.
SUMMARY OF THE INVENTION
[0008] Embodiments of the invention generally include an apparatus
for plating a metal onto a substrate surface. The apparatus
generally includes a substrate support member configured to support
a substrate during a plating process, a cathode clamp ring
detachably positioned to circumscribe a perimeter of the substrate
and a movable anode assembly disposed above the substrate, wherein
the anode assembly is movable in a direction generally
perpendicular the substrate. The apparatus generally further
includes a fluid inlet formed through the anode assembly, the fluid
inlet being configured to supply a plating solution to the
processing area sufficient to electrically connect the anode
assembly to the substrate.
[0009] Embodiments of the invention further include a method for
plating a metal onto a substrate. The method generally includes
supplying a plating solution to a processing chamber, the
processing chamber being defined by a movable anode assembly
disposed above the substrate and a cathode clamp ring detachably
positioned to circumscribe the perimeter of the substrate, wherein
the plating solution is supplied at a rate sufficient to
electrically connect the anode assembly to the substrate and
plating a metal from the plating solution onto the substrate.
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 (Prior Art) illustrates a cross-sectional view of an
exemplary fountain plater.
[0012] FIG. 2 illustrates a cross-sectional view of an exemplary
plating cell.
[0013] FIG. 3 illustrates a cross-sectional view of an exemplary
anode assembly.
[0014] FIG. 4 illustrates a cross-sectional view of another anode
assembly.
[0015] FIG. 5 illustrates a cross-sectional view of another anode
assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 2 illustrates a cross-sectional view of an exemplary
plating cell 100 with a substrate 116 in a processing position. The
plating cell 100 generally includes an enclosure 126 having a
substrate support member 102 and an anode assembly 104. The
substrate support member 102 generally includes a conductive base
plate 130 providing a cathode connection to a cathode clamp ring
108. The substrate support member 102 is generally disposed in a
bottom portion of the enclosure 126. The anode assembly 104,
discussed in further detail below, is electrically connected to a
power supply 106 via an electrical line 128. The plating cell 102
may further include a vacuum chuck to secure the substrate 116 onto
a substrate supporting surface 132 on the substrate support member
102 during processing.
[0017] In the loading position, the cathode clamp ring 108, which
may be supported by an annular catch cup 110, is generally disposed
in a middle portion of the plating cell 100 between the substrate
support member 102 and the anode assembly 104. The cathode clamp
ring 108 is positioned in the plating cell 100 such that the
movement of the substrate support member 102 from a load/transfer
position (not shown), to the processing position lifts the cathode
clamp ring 108 slightly off the catch cup 110. The load/transfer
position is discussed in detail in U.S. Pat. No. 6,416,647, filed
on Apr. 19, 1999, which is hereby incorporated by reference.
[0018] The cathode clamp ring 108 preferably includes an outer
portion having a downwardly sloping surface 166 that overlaps an
inner terminus 168 of the catch cup 110 to assist the plating
solution flow into the catch cup 110. The inner terminus 168
includes a ridge 170 corresponding to a recess 172 on the bottom
surface 174 of the cathode clamp ring 108. The ridge 170 supports
the cathode clamp ring 108 when the substrate support member 102 is
not engaged in a deposition position. When the substrate support
member 102 is engaged in the deposition position, the cathode clamp
ring 108 is lifted from the ridge 170 and is supported on the
substrate deposition surface 176.
[0019] The electrical power is delivered by the cathode clamp ring
108 to the substrate deposition surface 176 through a contact
portion 178 of the cathode clamp ring 108. To provide electrical
power to the cathode clamp ring 108, one or more cathode contacts
180 are fixedly secured to a bottom surface 146 of the conductive
base plate 130 of the substrate support member 102 and extend
radially outward to electrically contact a bottom surface 174 of
the cathode clamp ring 108. Upon rotation, the electrical power is
conducted through the rotating shaft 134 to the conductive base
plate 130, then through one or more cathode contacts 180 secured
onto the conductive base plate 130, and then to a bottom surface
174 of the cathode clamp ring 108. Alternatively, the cathode clamp
ring 108 is fixedly connected to the power supply 106 through
connection wires (not shown).
[0020] The rotating shaft 134 extends through a lift pin platform
136 having a plurality of lift pins 138 disposed thereon. A lift
platform actuator 142 moves the lift pin platform 136 vertically to
lift and lower a substrate 116 for transfer into and out of the
plating cell 100. A flexible bellow 144, preferably made of
polyethylene, is disposed around each lift pin 138, to provide a
splash seal against plating solutions, rinsing solutions, and other
processing chemicals. The flexible bellow 144 is attached from a
top surface of the lift pin platform 136 to a bottom surface of the
conductive base plate 146 of the substrate support member 102. The
flexible bellow 144 compresses when the lift pin platform 136 is
elevated by the lift platform actuator 142 and stretches when the
lift pin platform 136 is resting on a platform ridge 148. Each
flexible bellow 144 also maintains a seal when subjected to a
slight side load, such as when the substrate support member 102
rotationally accelerates or decelerates.
[0021] To prevent plating solutions, rinsing solutions, and other
process chemicals from contacting components disposed in the
central portion of the plating cell 100, such as the lift platform
actuator 142 and the shaft sleeve 150, a splash guard 152 is
generally attached to an outer portion of a lower surface of the
lift pin platform 136. The splashguard 152 includes a cylindrical
downward extension that is disposed radially outward of an upwardly
extending inner container wall 154. The inner container wall 154 is
a cylindrical upward extension from the enclosure bottom 156 of the
plating cell 100 that holds the process solutions to be pumped out
of the system through a solution outlet 114.
[0022] To provide rotational movement to the substrate support
member 102, a rotary actuator 158 is disposed on an actuator
platform 160 and connected to the rotating shaft 134. The rotary
actuator 158 rotates the rotating shaft 134 freely within the shaft
sleeve 150. During deposition, the rotary actuator 158 rotates or
oscillates the substrate support member 102 about a central axis
through the rotating shaft 134. Generally, the rotary actuator 158
rotates the support member 102 at between about 10 revolutions or
cycles per minute to about 50 RPM or cycles per minute. The
rotation or oscillation of the substrate support member 102
provides uniform exposure of the plating solution to the substrate
deposition surface 176 promoting uniform metal deposition. In the
alternative, the anode assembly 104 may be rotated. Deposition
uniformity is further promoted by continuous cathode electrical
contact provided by the cathode clamp ring 108. The cathode clamp
ring 108 operates to distribute a uniform current density across
the substrate deposition surface 176.
[0023] To move the substrate support member 102 vertically, a
vertical actuator 162 extends and retracts a shaft 164 connected to
the actuator platform 160. The vertical actuator 162 is disposed
outside of the cell 100 on the cell bottom 156, and the shaft 164
extends through the cell bottom 156 and is attached to a bottom
surface of the actuator platform 160. These actuators may be fluid
cylinders, screw-type actuators, or any other actuator capable of
producing longitudinal movements. In addition, a substrate transfer
actuator 122 vertically adjusts the anode assembly 104 to set an
anode assembly 104 to substrate 116 distance. The distance may be
from about 2 mm to about 20 mm. The anode assembly 104 may be sized
to recess within the contact ring 108 upon vertical adjustment,
e.g., during plating, so that the anode assembly 104 is in
electrical contact with the plating solution. In addition, plating
solution may flow through the anode assembly 104 to provide
additional plating solution or to provide movement within the
existing plating solution. Alternatively, the anode assembly 104
may be sized to rest upon the contact ring 108 upon vertical
adjustment. When the anode assembly 104 rests upon the contact ring
108, an insulator may be utilized to separate the anode assembly
104 and the contact ring 108.
[0024] The cell 100 additionally includes a sidewall 124 having a
slit 118 formed therein for receiving and discharging a substrate
116, e.g., loading and transferring the substrate 116. The
plurality of lift pins 136 extends through vertical bores in the
substrate support member 102 and lifts the substrate 116 above a
robot blade (not shown). The robot blade then retracts out of the
cell 100 and the slit valve 120 closes the slit opening 118. Once
the substrate 116 is in the processing position, a plating solution
pump (not shown), which is connected to a plating solution inlet
112, pumps plating solution from a plating solution reservoir (not
shown) into the plating cell 100. Generally, a plating solution
outlet 114 is connected to a plating solution drain (not shown)
formed in the catch cup 110 to return the plating solution back to
the plating solution reservoir to be re-circulated to the plating
cell 100.
[0025] The plating solution fills a processing area defined by the
substrate 116, i.e., the processing area bottom, and the contact
ring 108, i.e., the sidewalls. Therefore, the volume of the
processing area and the resulting volume of the plating solution
utilized are dependent upon the size of the substrate 116 and the
height of the contact ring 108. In addition, the volume is
dependent upon the distance of the anode assembly 104 from the
substrate 116. Generally the anode assembly 104 is from about 2 mm
to about 20 mm from the substrate 116. Preferably, the anode
assembly 104 is from about 2 mm to about 10 mm from the substrate
116.
[0026] FIG. 3 illustrates a cross-sectional view of an exemplary
anode assembly 200. The anode assembly 200 may be used in the
plating cell 100 described above, or another plating cell capable
of processing semiconductor substrates in the face-up position. The
anode assembly 200 and the substrate 116 and clamp ring 108 define
a cell chamber 208, e.g., a processing area. The cell chamber 208
generally has a volume of from about 0.5 L to about 1.9 L.
[0027] The anode assembly 200 generally includes an anode plate 202
and a hood 204. The anode plate 202 generally has a circular
cross-section. The anode plate 202 preferably includes a consumable
metal that can dissolve in the electroplating solution to provide
the metal particles to be deposited onto the substrate deposition
surface. The hood 204, which is electrically insulated from the
anode plate 202, depends from the outer periphery of the anode
plate 202 and may be made of anodic material, which is the same or
different from the material of the anode plate 202. For example,
the anode plate 202 may be formed of a mesh material.
Alternatively, the anode plate 202 and hood 204 are each made of
consumable metal particles encased in a fluid permeable membrane
such as a porous ceramic plate. An alternative to the consumable
anode plate is a non-consumable anode plate that is perforated or
porous for passage of the electroplating solution therethrough.
However, when a non-consumable anode plate is used, the
electroplating solution requires a metal particle supply to
continually replenish the metal particles to be deposited in the
process.
[0028] As described above, the contact ring 108 is in electrical
communication with the cathode terminal of a power supply (not
shown). The power source discussed in reference to FIG. 2 generally
includes controls for varying the voltage and polarity of the anode
plate 202 and the hood 204. For example, to ensure plating in a
central portion of the substrate, the hood 204 may be electrically
isolated to prevent ions from plating on the hood 204.
[0029] The hood 204 generally is secured to the anode plate 202 by
an insulating ring 206. The hood 204 is sized to substantially
cover the substrate 116 and the clamp ring 108 from the outer edges
of the anode plate 202 extending downward towards the substrate
116.
[0030] The flow of electrolyte through the processing chamber 208
is controlled by the size of an annular opening 210, e.g., the
distance between the hood 204 and the clamp ring 108. The annular
opening 210 is sized in relation to the electrolyte flow rate to
maintain the electrolyte in the chamber 208 at a predetermined
level during the plating process. Generally, the flow of plating
solution continues during plating to retain electrical contact
between the anode plate 202 and the substrate 116. In addition, the
flow of electrolyte into the processing chamber 208 is generally
equal to the flow of electrolyte out of the processing chamber
through the annular opening 210 and the consumption of electrolyte
due to plating on the substrate. Generally, the processing chamber
208 is full of electrolyte throughout plating to maintain an
electrical connection between the anode and the substrate.
[0031] In operation, the plating cell provides a small volume
(electrolyte volume) processing chamber 208 that may be used for
copper electrochemical plating processes, for example. A substrate
116 is first immersed into a plating solution contained within the
processing chamber 208. Once the substrate is immersed in the
plating solution, which generally contains copper sulfate,
chlorine, and one or more of a plurality of plating additives
(levelers, suppressors, accelerators, etc.) configured to control
plating parameters, an electrical plating bias is applied between a
seed layer on the substrate and the anode 202 positioned above the
substrate 116. The electrical plating bias generally operates to
cause metal ions in the plating solution to deposit on the cathodic
substrate surface 116. The plating solution is continually
circulated through the processing chamber 208 via fluid inlets and
outlets.
[0032] FIG. 4 illustrates a cross-sectional view of another anode
assembly 300. The embodiment shown in FIG. 3 includes the same
components as the embodiment shown in FIG. 2, except that the anode
plate 304 does not include a hood. Thus, the cell chamber 302 is
defined by the downwardly facing surface of the anode plate 304,
the upwardly facing surface of the substrate 116, and the clamp
ring 108, e.g., the clamp ring 108 operates as sidewalls for the
chamber 302, thereby defining the volume of the chamber 302. The
distance of the anode plate 304 from the substrate 116 is generally
minimized. For example, the distance may be from about 2 mm to
about 20 mm, resulting in a small chamber volume. Alternatively,
the distance may be from about 2 mm to about 10 mm. The precise
volume of the chamber is determined by the vertical actuator
setting.
[0033] FIG. 5 illustrates yet another embodiment of an anode
assembly 400. The anode assembly 400 includes an anode plate 402.
The anode plate 402 generally includes a plurality of annular anode
segments that are separated by insulators 404. The insulators 404
may be annular spaces, plastic rings, or other means capable of
insulating the anode segments from one another. The individual
anode segments allow selective plating operation by providing
individual voltage control for each anode segment. Selective
operation provides control over the flow of cations adhering and
flowing to the cathode/substrate 116, thereby resulting in uniform
plating upon the substrate 116. Although the anode assembly 400 may
be used alone, the anode assembly 400 may also be used in
conjunction with either of the embodiments illustrated in FIGS. 2
and 3.
[0034] 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.
* * * * *