U.S. patent application number 14/928088 was filed with the patent office on 2016-02-18 for metal plating system including gas bubble removal unit.
The applicant listed for this patent is GLOBALFOUNDRIES Inc. Invention is credited to Shafaat Ahmed, Michael P. Chudzik, Lubomyr T. Romankiw.
Application Number | 20160047058 14/928088 |
Document ID | / |
Family ID | 51522618 |
Filed Date | 2016-02-18 |
United States Patent
Application |
20160047058 |
Kind Code |
A1 |
Ahmed; Shafaat ; et
al. |
February 18, 2016 |
METAL PLATING SYSTEM INCLUDING GAS BUBBLE REMOVAL UNIT
Abstract
An electroplating apparatus includes an anode configured to
electrically communicate with an electrical voltage and an
electrolyte solution. A cathode module includes a cathode that is
configured to electrically communicate with a ground potential and
the electrolyte solution. The cathode module further includes a
wafer in electrical communication with the cathode. The wafer is
configured to receive metal ions from the anode in response to
current flowing through the anode via electrodeposition. The
electroplating apparatus further includes at least one agitating
device interposed between the wafer and the anode. The agitating
device is configured to apply a force to gas bubbles adhering to a
surface of the wafer facing the agitating device.
Inventors: |
Ahmed; Shafaat; (Ballston
Lake, NY) ; Chudzik; Michael P.; (Mountain View,
CA) ; Romankiw; Lubomyr T.; (Briancliff Manor,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GLOBALFOUNDRIES Inc |
Grand Cayman |
KY |
US |
|
|
Family ID: |
51522618 |
Appl. No.: |
14/928088 |
Filed: |
October 30, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13800201 |
Mar 13, 2013 |
|
|
|
14928088 |
|
|
|
|
Current U.S.
Class: |
204/222 ;
204/212; 204/273 |
Current CPC
Class: |
C25D 21/04 20130101;
C25D 5/08 20130101; C25D 17/001 20130101; C25D 17/008 20130101;
C25D 5/20 20130101; C25D 7/123 20130101; C25D 5/04 20130101; C25D
21/10 20130101 |
International
Class: |
C25D 21/04 20060101
C25D021/04; C25D 5/08 20060101 C25D005/08; C25D 17/00 20060101
C25D017/00; C25D 21/10 20060101 C25D021/10; C25D 5/04 20060101
C25D005/04; C25D 5/20 20060101 C25D005/20 |
Claims
1. An electroplating apparatus, comprising: an anode coupled to an
electrical voltage and an electrolyte solution; a cathode module
including a cathode coupled to a ground potential and the
electrolyte solution, the cathode module further including a wafer
in electrical communication with the cathode, the wafer configured
to receive metal ions from the anode via electrodeposition in
response to current flowing through the anode; and at least one
agitating device interposed between the wafer and the anode, the
agitating device configured to apply a force to gas bubbles
adhering to at least one of a surface, trenches, and vias of the
wafer facing the at least one agitating device.
2. The electroplating apparatus of claim 1, wherein the agitating
device is fixated within the electrolyte solution, and wherein the
cathode module is configured to rotate about an axis extending
perpendicular to the cathode.
3. The electroplating apparatus of claim 2, wherein at least one
agitating device includes a frame having an upper portion disposed
a distance beneath a center region of the wafer, the upper portion
having a slot formed therethrough to stream solution at a
predetermined velocity toward the center region of the wafer.
4. The electroplating apparatus of claim 3, wherein a velocity of
streaming electrolyte increases from an edge of the wafer to the
center region of the wafer such that a maximum velocity of the
streaming electrolyte exists at the center region.
5. The electroplating apparatus of claim 4, wherein the slot is
diamond-shaped such that a velocity of the solution streamed at a
center of the opening is greater than a velocity of the solution
streamed at ends of the opening.
6. The electroplating apparatus of claim 5, further comprising at
least one ultrasonic transducer coupled to the wafer, the
ultrasonic transducer configured to generate pulses at a
predetermined frequency and intensity such that the wafer
vibrates.
7. The electroplating apparatus of claim 6, further comprising a
current buffle unit interposed between the agitating device and the
anode, the current buffle unit configured to provide a current
distribution at the cathode.
8. The electroplating apparatus of claim 7, further comprising: a
power supply configured to generate the electrical current, the
power supply configured to provide the voltage and the ground
potential; and a container configured to contain the electrolyte
solution, the cathode module, and the anode immersed in the
electrolyte solution.
9. The electroplating apparatus of claim 8, further comprising a
universal joint that couples the axis to the cathode module, the
cathode module configured to rotate via axis and tilt with respect
to the axis via the universal joint.
Description
DOMESTIC BENEFIT/NATIONAL STAGE INFORMATION
[0001] This application is a divisional application of U.S.
application Ser. No. 13/800,201 filed Mar. 13, 2013, the disclosure
of which is incorporated by reference herein in its entirety.
BACKGROUND
[0002] The present disclosure relates to a metal plating system,
and more specifically, to a metal plating system including gas
bubble removal unit.
[0003] Copper metallization is a key component for integrated
circuits (ICs). As the industry demand for smaller sized ICs
increases, plating-related defects in metal vias and interconnect
lines are becoming more prominent. These plating defects ultimately
affect the reliability of the ICs.
[0004] One such plating defect that has increased over the years is
referred to as "hollow metal." Hollow metal describes various point
defects, such as voids, porosity etc., which occur in the metal
vias and connection lines of the ICs. One cause of hollow metal may
be attributed to conventional plating tools used to perform the
metallization electroplating applied to IC wafer surfaces. More
specifically, conventional plating tools dispose the wafer surface
in a metallization solution in a downward-facing position towards
an opposing anode of the plating tool. The plating process forms
various metal vias and/or metal connections on the downward-facing
surface. While the wafer is immersed, gas bubbles, such as air, may
be trapped in the trenches and via holes trapping as a result of
insufficiently fast and incomplete wetting of the trenches and vias
with plating solution before plating starts. Hydrogen and/or air
bubbles may also be formed in the solution during plating. They may
be trapped in the trenches and vias. The bubbles also rise toward
the surface and may encounter the wafer. The trapped bubbles may
not be removed when using the currently used rotating disc
configured plating tool. However, the trapped bubble may adhere to
the bottom or side wall of the trenches and vias. These bubbles may
block metal ions from reaching the conduction seed layer and
forming the metal conductor by properly filling the trenches and
vias. Accordingly, non-plated sections beneath the bubbles may
occur, which ultimately causes hollow sections in the metal lines
or vias, i.e., the hollow metal.
SUMMARY
[0005] According to an embodiment, an electroplating apparatus
includes an anode configured to electrically communicate with an
electrical voltage and an electrolyte solution. A cathode module
includes a cathode that is configured to electrically communicate
with a ground potential and the electrolyte solution. The cathode
module further includes a wafer in electrical communication with
the cathode. The wafer is configured to receive metal ions from the
anode in response to current flowing through the anode via
electrodeposition. The electroplating apparatus further includes at
least one agitating device interposed between the wafer and the
anode. The agitating device is configured to apply a uniform
agitation across a cathode module including a wafer surface and a
shearing force to gas bubbles trapped in the trenches and vias
created on a surface of the wafer facing the agitating device. In
addition this agitating device will help to maintain an uniform
diffusion layer over the large cathode i.e., wafer, surface which
eventually enables plating having a uniform metal/alloy plating
thickness. Uniform plating across the wafer surface results in
uniform planarization by chemical mechanical polishing (CMP).
[0006] According to another embodiment, an agitating device to
remove bubbles adhered to a surface of a wafer undergoing an
electroplating process comprises a frame having an upper portion
facing a wafer and a lower portion opposing the upper portion. The
upper portion has a slot formed therethrough. The slot is
configured to stream an electrolyte solution toward and past the
surface of the wafer at an increased velocity.
[0007] Additional features are realized through the techniques of
the various embodiments described herein. For a better
understanding of the features, refer to the description and to the
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0008] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. Various forgoing and other
inventive features are apparent from the following detailed
description taken in conjunction with the accompanying drawings in
which:
[0009] FIG. 1A is a block diagram illustrating an electroplating
apparatus according to an exemplary embodiment of the present
disclosure;
[0010] FIG. 1B is a block diagram illustrating an IC wafer
according to an embodiment of the present disclosure;
[0011] FIG. 2 is a block diagram illustrating an electroplating
apparatus according to another embodiment of the present
disclosure;
[0012] FIG. 3 is a block diagram illustrating an electroplating
apparatus according to yet another embodiment of the present
disclosure;
[0013] FIG. 4 is a block diagram illustrating an electroplating
apparatus according to still another embodiment of the present
disclosure;
[0014] FIGS. 5A-B illustrate examples of an agitating device
according to an embodiment of the disclosure;
[0015] FIG. 6 illustrates an example of a plating tool including a
filter unit according to an embodiment of the disclosure;
[0016] FIG. 7 is a block diagram illustrating an electroplating
apparatus including an ultrasonic transducer according to another
embodiment of the present disclosure;
[0017] FIGS. 8A-8C illustrate a process flow of electroplating a
wafer according to an embodiment of the disclosure;
[0018] FIG. 9 is a line graph illustrating an current profile
corresponding to applying a voltage potential to the wafer during a
plating process according to an embodiment of the disclosure;
and
[0019] FIG. 10 is a flow diagram illustrating a method of
electroplating a wafer according to an embodiment of the
disclosure.
DETAILED DESCRIPTION
[0020] Referring now to FIG. 1A, an electroplating apparatus 100
according to an exemplary embodiment of the present disclosure is
illustrated. The electroplating apparatus 100 includes a power
supply 102, a container 104 and a plating tool 106. The plating
tool 106 includes an anode 108 and a cathode module 110, each in
electrical communication with the power supply 102. The anode 108
and the cathode module 110 may be formed of various shapes
including, but not limited to, square and circular.
[0021] The power supply 102 includes a positive terminal 115 and a
negative terminal 116. The power supply 102 may include a voltage
source, a current source, or a voltage source and a current source.
The power supply 102 is configured to output an electrical voltage,
a current, or a voltage and a current. The power supply 102 may
execute a voltage scan with a predetermined scan rate. The power
supply 102 may also supply a constant voltage. In addition, the
power supply 102 may generate a voltage output and then switched to
a current output or vice versa. The voltage and current output may
be a direct current (DC), a pulse or combination of different
waveforms. The current may also have a value selected to achieve a
desired current density.
[0022] The current may be supplied according to a constant
electrical potential condition, under constant electrical current
condition or combination thereof (see FIG. 9).
[0023] The container 104 may contain an electrolyte solution 117
capable of conducting an electrical current that induces a
metallization plating process. The electrolyte solution 117 may
comprise cupric ions and/or chlorine ions and sulfate ions that
render the electrolyte solution 117 to be electrically conductive.
According to at least one exemplary embodiment, the electrolyte
solution 117 includes, but is not limited, to sulfuric acid
(H.sub.2SO.sub.4), copper sulfate pentahydrate, 2N hydrochloric
acid, sodium sulfate, etc. An electrolyte solution of sulfuric acid
may range from 2-50 grams/liter (g/L), copper sulfate pentahydrate
may range from 20-300 g/L and organic additives used as
accelerator, levelers, suppressors and wetting agents. A solution
of 2N hydrochloric acid may range from 0-5 milliliters/liters
(ml/L), and a solution of sodium sulfate may range from 80-200 g/L.
It can be appreciated that other solutions of acids, bases or salts
may be used as the electrolyte solution 117. In addition, the
electrolyte solution 117 may comprise either H.sub.2SO.sub.4 or
chloride (Cl), and metal ions. The electrolyte metal ions
comprises, for example, copper (Cu). In another embodiment, the
solution comprises an acid copper plating solution including (1) a
dissolved copper salt (e.g., as copper sulfate), (2) an acidic
electrolyte (e.g., as sulfuric acid) in an amount sufficient to
impart conductivity to the bath and (3) additives (e.g.,
surfactants, brighteners, levelers and suppressants). The bath may
also contain a wetting agent to increase wettability of the wafer.
Various wetting agents may be used including, but not limited to,
anionic agents, cationic agents, amphoteric wetting agents that
ionize when mixed with water, and non-ionic wetting agents.
[0024] In response to current flowing through the anode 108, metal
ions from the anode 108 are transferred to the downward-facing
surface of the wafer 113 via an electrodeposition process. As a
result, copper vias and/or copper connection lines may be formed on
the downward-facing surface of the wafer 113 and in the etched
trenches and vias which are metalized with a very thin conducting
seed layer, as discussed in greater detail below with respect to
FIG. 1B. A seed layer formed on a top of the surface of the cathode
and inside the vias and trenches. The seed layer may be formed from
tantalum nitride, tantalum copper (Cu) or Cu alloys seed like Cu
alloyed with easily oxidized metal e.g. Cu--Mn, Cu--Al, Cu--Zn,
Cu--Ga and similar alloy or other suitable conducting seed layer.
Although copper is referenced as an example when describing the
various embodiments, the plating process described herein may be
utilized with other metals including, but not limited to, gold
(Au), silver (Ag), nickel (Ni), iron (Fe), palladium (Pd), and
alloys plating thereof.
[0025] The plating tool 106 is in electrical communication with the
power supply 102 and is in fluid communication with the electrolyte
solution 117. In at least one embodiment illustrated in FIG. 1A,
the anode 108 may be connected to an inner surface of the container
104 and immersed in the electrolyte solution 117. An electrically
conductive wire 118 has one end connected to the anode 108 and an
opposing end connected to the positive terminal 115 of the power
supply 102. The anode 108 may be formed of any metal configured to
transfer metal ions to the downward-facing surface of the wafer 113
via electro deposition. In at least one exemplary embodiment, the
anode 108 is formed of copper (Cu).
[0026] The cathode module 110 includes a cathode 111 coupled to a
supporting plate 112. Various means may be used to connect the
cathode 111 to the supporting plate 112 including, but not limited
to, mechanical pins, fasteners, and a non-soluble conductive
adhesive. Further, the cathode 111 may be connected to the
supporting plate 112 using a universal joint 400. The universal
joint 400 allows the cathode module 110 to move in a plurality of
directions with respect to the axis (A). For example, the cathode
module 110 may rotate about the axis, while still capable of
tilting left, right or moving up and down.
[0027] The supporting plate 112 may be configured to rotate about
an axis (A) extending perpendicular to cathode module 110. Hence,
the cathode 111 may be rotated when the plate 112 rotates. The
cathode module 110 further includes an interconnect (IC) wafer 113
connected in electrical communication to the cathode 111. A
conductive alloy seed layer 114 may be formed on the IC wafer.
Accordingly, the IC wafer 113 may rotate along with the supporting
plate 112 and the cathode 111. In at least one embodiment, the
supporting plate 112 may be selectively rotated. The cathode module
110, including the wafer 113, may be formed in various shapes
including, but not limited to square, circular and other.
[0028] Referring now to FIG. 1B, an IC wafer 300 is illustrated
according to an embodiment. The IC wafer 300 may be formed from a
semiconductor material, such as silicon. The IC wafer 300 includes
a base layer 302 and a dielectric layer 304. The base layer 302 and
dielectric layer 304 may be insulated from one another by an
insulating layer 306 interposed therebetween. One or more trenches
308 and/or vias 309 may be formed in the dielectric layer 304. In
at least one embodiment, the vias 309 may extend through the
insulating layer 306 and into the base layer 302. The trenches 308
and/or vias 309 may be lined with a liner 310. The liner 310 may be
formed from tantalum (Ta) or tantalum nitride (TaN). A copper (Cu)
seed layer 312 may be formed on top of the liner 310. Accordingly,
one or more air and/or hydrogen bubbles 314 may become trapped
against the lower surface of the wafer 300, in a trench 308, and/or
inside a via 309.
[0029] Referring again to FIG. 1A, the cathode 111 is in electrical
communication with the negative terminal 116 of the power supply
102 via a second electrically conductive wire 119. An
electrochemical circuit may be achieved when the anode 108 and the
cathode 111 are introduced to the electrolyte solution 117 as
described above. Accordingly, the electrical current output from
the power supply 102 travels through the electrolyte solution 117
and to the anode 108, which induces an electrochemical
metallization plating process such that metal ions from the anode
108 are transferred to the downward-facing surface of the wafer 113
via electrodeposition. As a result, metal vias and/or metal
connection lines are formed on the downward-facing surface the
wafer 113.
[0030] The plating tool 106 further includes at least one agitating
device 120 configured to prevent air, hydrogen and/or other gas
bubbles from becoming trapped inside the trenches and vias located
beneath the cathode module 110 and adhering to the downward-facing
surface of the wafer 113. The agitating device 120 may include a
static agitating device that remains fixed or a dynamic agitating
device that moves. When the wafer 113 is static, the dynamic
agitating device will remove one or more bubbles from the wafer
113. When the wafer 113 is dynamic, a static agitation device will
also maintain a constant well defined diffusion layer across the
plating surface of the wafer 113.
[0031] Referring to at least one embodiment illustrated in FIG. 1A,
for example, the agitating device 120 is fixated within the
solution 117 and is disposed a predetermined distance below the
wafer 113. The distance between the agitating device 120 and the
wafer 113 may range from about 1 millimeter (mm) to about 5 mm. In
at least one embodiment, the agitating device 120 may include a
slot 122. The slot 122 is configured to flow one or more streams of
solution 117 therethrough and toward the downward-facing surface of
the wafer 113. The streamed solution 117 dislodges and directs
bubbles away from the cathode module 110. Further, the flowed
solution exerts a force on bubbles adhered to the downward-facing
surface the wafer 113. The force causes the bubbles to loosen from
the downward-facing surface and escape from beneath the cathode
module 110. Accordingly, the wafer 113 may be plated without the
formation of hollow metal since the bubbles 314 are removed from
the downward-facing surface.
[0032] The plating system 106 may further include a pump configured
to force the electrolyte solution through the slot 122.
Accordingly, the stream generated by the pump may have an increased
velocity that weakens the adhering force of the bubbles against the
down-facing surface of the wafer 113. However, it is appreciated
that the pump may be located outside of the container 104, and may
include a tube system (not shown) that conveys solution to the slot
122. Although the pump may assist in flowing the stream of solution
through the slot 122, it is appreciated that the pump is not
required. For example, the rotation of the cathode module 110 may
generate a shearing force that induces a partial vacuum between the
wafer 113 and the agitating device 120 such that solution and gas
bubbles are drawn from the vias and trenches.
[0033] The electroplating apparatus 100 may further include a
filter unit 123 that is disposed between the anode 108 and the
cathode module 110, and that extends between opposing inner walls
of the container 104. The filter unit 123 may include a sac filter
or a membrane, and is configured to separate a solution inside the
container into a plating solution including additives and a virgin
made solution (VMS) excluding the additives. The anode 108 may be
disposed in the VMS, while the cathode module 110 is disposed in
the plating solution 117. The additives may include brightener,
suppressor, leveler, surfactant, wetting agent.
[0034] Referring to FIG. 2, a plating tool 106' is illustrated
according to another embodiment. The plating tool 106' operates
similar to the plating tool 106 described above. In this
embodiment, however, the cathode module 110 is not rotated and
remains stationary. Further, the agitating device 120 is disposed a
short distance beneath a center region of the wafer 113. The
agitating device 120 is configured to reciprocate at a
predetermined frequency in a lateral direction with respect to the
surface of the wafer 113. In at least one embodiment, the agitating
device 120 may reciprocate at substantially the center of the
cathode module 110. According to another the embodiment, the
agitating device 120 may reciprocate and move all the way past,
i.e., beyond, the edge of the wafer 113. The agitating device 120
may be reciprocated at frequency ranging from about 0.01 Hertz (Hz)
to about 5 Hz, and more specifically 0.5 Hz-1.0 Hz. In the
embodiment of FIG. 2, the agitating device 120 excludes a slot such
that the portion near the wafer 113 is uniformly solid. The motion
of the agitating device 120 induces waves in the solution 117,
which exerts a force on bubbles trapped against the downward-facing
surface of the wafer 113. As a result, the bubbles may be removed
from the vias and trenches and forced away from beneath the wafer
113 such that they may continue rising toward the upper surface of
the solution 117. In at least one embodiment, the agitating device
120 is coupled to an electrical motor (not shown) that is
configured to reciprocate the agitating device 120 back and forth
as described above.
[0035] In another embodiment, a plating tool 106'' may include a
plurality of agitating devices 120A-120C, as illustrated in FIG. 3.
Each agitating device 120A-120C may be spaced apart from one
another by a predetermined distance and may reciprocate back and
forth similar to the agitating device 120 described with respect to
FIG. 2. However, the reciprocal motion of the plurality of
agitating devices 120A-120C generates a greater shear force onto
bubbles trapped beneath the wafer 113 and in the trenches and vias
compared to the force generated by the single agitating device 120
illustrated in FIG. 2. The increased shear force, therefore,
further weakens the adhesion force of bubbles against the wafer
113, and may further prevent hollow metal from forming during the
plating process.
[0036] Referring to FIG. 4, a plating tool 106''' is illustrated
according yet another embodiment. The plating tool 106''' operates
similar to the plating tool 106' described above with respect to
FIG. 2. In this embodiment, however, the agitating device 120 is
configured to move dynamically from one end of the wafer 113 to an
opposing end. The agitating device 120 may also move all the past,
i.e., beyond, the edge of the wafer 113. More specifically, the
agitating device 120 is shown in phantom traveling beneath from a
first end of the wafer 113 to an opposite end. As a result, the
agitating device 120 can exert a shearing force across the entire
downward-facing surface of the wafer 113, thereby increasing the
possibility that bubbles trapped along the entire downward-facing
surface can be pulled out and forced away from the wafer 113. In at
least one embodiment, the agitating device 120 is coupled to an
electrical motor (not shown) that is configured to sweep the
agitating device 120 between opposing ends of the wafer 113.
[0037] Turning now to FIGS. 5A-5B, various agitating devices to
prevent adherence of air and/or hydrogen bubbles to a wafer, e.g.,
inside one or more trenches and/or vias, during a plating process
are illustrated. FIG. 5A illustrates an agitating device 500
according to a first embodiment. The agitating device 500 includes
opposing first and second ends 510. A slotted portion 502 is
connected deliberately between the first and second ends 510 The
agitating device 500 may be formed from various electrically
insulated materials including, but not limited to, plastic or metal
coated with plastic/polymer such as, for example, Teflon.TM.. The
upper and lower sections of paddle 504, 506 may each have a
triangular cross-section where the outer edges of the section
extend toward the slotted portion 502. The triangular cross-section
permits minimal resistance against the solution.
[0038] Referring to FIG. 5B, an agitating device 500' is
illustrated, which is similar to the agitating device 500 described
above with respect to FIG. 5A. The agitating device 500' of FIG.
5B, however, includes one or more slots formed in the agitating
device 500'. According to the embodiment illustrated in FIG. 5B, a
slot 508 is formed through the upper section of the paddle 504.
When utilized with the plating tool 106, the slot 508 permits
surrounding solution 117 to stream therethrough at an increased
velocity and toward the downward-facing surface of the wafer 113.
As discussed above, the streamed fluid exerts a force on bubbles
adhered to the downward-facing surface and in the trenches and
vias. The force from the stream causes the bubbles to dislodge and
to break away from the downward-facing surface and escape from
beneath the wafer 113. Accordingly, the wafer 113 may be plated
without the formation of hollow metal since the bubbles are removed
from the downward-facing surface. Although not illustrated,
additional slots may be formed in the agitating device 120.
[0039] In at least one embodiment, the slot 508 is shaped such that
a slot opening increases as the slot 508 extends toward the middle
of the upper section 504. The slot 508, for example, may be formed
to have a diamond-shape such that the slot-opening gradually
increases as the slot 508 extends toward the center. Bubbles which
adhere to the downward-facing surface of the wafer 113 congregate
most at the center of the wafer. Forming a slot 508 having a slot
opening that increases at the center of the upper section 504
permits the agitating device 500' to be positioned such that
maximum velocity of the stream flowing through the slot 508 is
focused at the center of the downward-facing wafer 113 where the
highest concentration of bubbles typically exist. It is appreciated
that the slot 508 may have a shape other than the described above.
The slot 508 is shaped in such a fashion so that a substantially
uniform shear force is generated between the solution and the wafer
when the wafer is rotated throughout the entire 360.degree. circle.
For example, the slot may 508 be shaped in such a way that the
plating solution velocity is highest near the center of the wafer.
The slot 508 may also be formed such that a force may be delivered
therethrough to dislodge any bubbles on the downward facing
surface.
[0040] Referring now to FIG. 6, a plating tool 106 is provided with
a buffle unit 600 which is configured to provide more uniform
current distribution between the anode 108 and the cathode module
110 of the plating tool 106. As a result of the increase in uniform
current distribution, a resistance drop in a seed layer between an
edge and a center of the wafer is compensated, e.g., reduced. More
specifically, the buffle unit 600 is interposed between the anode
108 and the lower section 506 of the agitating device 120. The
buffle unit 600 may be formed from any electrically insulated
material including, but not limited to, plastic. The buffle unit
600 includes a plurality of holes that are sized to assure a higher
current in the center of the wafer to compensate for the drop of
current in the very thin seed layers between the edge and center of
the cathode module 110.
[0041] Turning to FIG. 7, a plating tool 106''' is illustrated
according to yet another embodiment. The plating tool 106'''
operates similar to the plating tool 106' described above with
respect to FIG. 2. However, the cathode module 110 further includes
one or more ultrasonic transducers 700 coupled thereto. The
ultrasonic transducer 700 may convert electricity into sound
waves/pulses at a predetermined frequency and intensity. As the
wafer 113 is immersed in the solution 117, ultrasonic transducer
700 may generate the sound waves, which vibrate the wafer 113. The
vibrations weaken the adhesion force of the bubbles attached to the
downward facing surface of the wafer 113, thereby dislodging
bubbles such that they may be separated and removed from the wafer
113. The ultrasonic transducer 700 may be combined with the
reciprocating agitating device 120 and/or the high velocity
solution steamed through the slot 508 to assist in further
weakening the adhesion force of the bubbles.
[0042] Referring now to FIGS. 8A-8C, a process flow illustrates a
process of electroplating a wafer 113 according to an embodiment of
the disclosure. As illustrated in FIG. 8A, a cathode module 110 is
coupled to an axis (A) via a universal joint (400). The cathode
module 110 includes a wafer 113, which rotates when the cathode
module 110 rotates about the axis (A). The cathode module 110 may
be rotated at a predetermined speed, for example 90 rotations per
minute (RPM).
[0043] Turning to FIG. 8B, the cathode module 110 may be tilted
while continuing to rotate about the axis (A) via a universal joint
400. As the cathode module 110 is titled, the cathode module 110
may be moved toward a plating solution 117. Prior to contacting the
cathode module 110 with the plating solution 117, a constant biased
potential may be applied to the wafer 113. In addition, one or more
ultrasonic transducers 700 can be mechanically attached at the back
of the wafer by a lever 800, which may be initiated to output
pulses at a predetermined frequency that vibrate the cathode module
110. Accordingly, the wafer 113 may be vibrated at a predetermined
frequency prior to being immersed in the plating solution 117.
[0044] Referring to FIG. 8C, the cathode module 110 may be
introduced into the plating solution 117 while tilted, vibrating
and biased at the predetermined electrical potential. After the
wafer 113 is immersed in the plating solution 117, the cathode
module 110 may be leveled and the ultrasonic transducers 700 may be
switched off. Accordingly, the cathode module 110 may continue to
rotate such that the wafer 113 is rotated while being
electroplated, as discussed in detail above.
[0045] The wafer 113 may be electroplated according to an
electrical current profile. An example of a current profile is
illustrated in FIG. 9. More specifically, FIG. 9 shows an initial
increase of current due to the potentiostatic entry of a wafer into
a plating solution, such as a copper bath. The potentiostatic entry
of the wafer assists to protect the seed layer from corrosion by
the plating solution. At the end of potentiostatic entry, a short
pulse (for example 0.01-0.5 seconds) is used to achieve optimum
nucleation and liner seed repairing. The high current density is
used for plating overburden followed by a low current density step
to fill trenches and vias. Accordingly, the majority of trapped air
bubbles will be removed when the wafer is still in the tilted
position.
[0046] Turning now to FIG. 10, a flow diagram illustrates a method
of electroplating a wafer according to an embodiment of the
disclosure. At operation 1000, the wafer is rotated at a
predetermined speed, such as 90 RPMs. At operation 1002, the wafer
is tilted at a predetermined angle. For example, the wafer may be
tilted at an angle ranging from 0.5-5 degrees with respect to the
plating solution. At operation 1004, a constant potential may be
applied to the wafer. For example, the wafer may be biased with a
constant potential that is less than the hydrogen evolution
over-potential. At, operation 1006, the wafer may be vibrated at a
predetermined frequency and intensity. For example, one or more
ultrasonic transducers may generate ultrasonic waves that vibrate
the wafer. At operation 1008, the wafer is introduced into the
plating solution while the wafer is tilted, rotated, electrically
biased, and vibrating. Accordingly, a potentiostatic entry,
referred to as a "hot entry," is achieved. At operation 1010, the
wafer may be leveled with respect to the plating solution when a
predetermined amount of the wafer is immersed in the plating
solution. At operation 1012, the wafer continues to rotate while
being electroplated until the method ends. Accordingly, the surface
of the wafer may be uniformly plated, while preventing the
formation of hollow metal.
[0047] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, element components, and/or groups thereof.
[0048] The flow diagrams depicted herein are just one example.
There may be many variations to this diagram or the operations
described therein without departing from the scope of the claims.
For instance, the operations may be performed in a differing order
or steps may be added, deleted or modified. All of these variations
are considered a part of the scope of the claimed features.
[0049] While various embodiments have been described, it will be
understood that those skilled in the art, both now and in the
future, may make modifications to the embodiments which fall within
the scope of the following claims. These claims should be construed
to maintain the proper protection for the invention.
* * * * *