U.S. patent application number 11/255855 was filed with the patent office on 2007-04-26 for adjustable dosing algorithm for control of a copper electroplating bath.
Invention is credited to Joseph F. Behnke, Thomas J. Fischenich, Yevgeniy Rabinovich, Timothy R. Webb, Bo Zheng.
Application Number | 20070089990 11/255855 |
Document ID | / |
Family ID | 37984324 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070089990 |
Kind Code |
A1 |
Behnke; Joseph F. ; et
al. |
April 26, 2007 |
Adjustable dosing algorithm for control of a copper electroplating
bath
Abstract
A method and apparatus for supplying a dose to an electrolyte
solution including measuring the time after adding fresh solution,
measuring the Amp-hours after adding fresh solution, measuring the
number of substrates processed by the solution, calculating the
volume of a dose to supply to the solution based on the time,
Amp-hours, and number of substrates processed, and adding the dose
to the solution.
Inventors: |
Behnke; Joseph F.; (San
Jose, CA) ; Webb; Timothy R.; (San Mateo, CA)
; Rabinovich; Yevgeniy; (Fremont, CA) ; Zheng;
Bo; (Saratoga, CA) ; Fischenich; Thomas J.;
(Sunnyvale, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
37984324 |
Appl. No.: |
11/255855 |
Filed: |
October 20, 2005 |
Current U.S.
Class: |
205/81 ; 205/101;
257/E21.175 |
Current CPC
Class: |
C25D 21/18 20130101;
C25D 21/14 20130101; H01L 21/2885 20130101 |
Class at
Publication: |
205/081 ;
205/101 |
International
Class: |
C25D 21/18 20060101
C25D021/18 |
Claims
1. A method for supplying a dose to an electrolyte solution,
comprising: measuring the time after adding fresh solution;
measuring the total Amp-hours used during electroplating after
adding fresh solution; measuring the number of substrates processed
after adding fresh solution; calculating a dose to supply to the
electrolyte solution based on the time, the total Amp-hours, and
the number of substrates processed; and adding the dose to the
electrolyte solution.
2. The method of claim 1, further comprising draining a small
volume of fluid from the electrolyte solution when the total
Amp-hours exceeds a set target.
3. The method of claim 2, wherein small volume is less than about 2
liters.
4. The method of claim 1, wherein calculating the dose uses
calculations that do not interrelate the Amp-hours, number of
substrates, or time.
5. The method of claim 1, further comprising resetting the time,
the total Amp-ours, and the number of substrates processed to zero
after the adding a dose to the electrolyte solution.
6. A method for supplying a dose to an electrolyte solution,
comprising: measuring the loss of a volume of fluid from a solution
vessel; measuring the time after adding fresh solution; measuring
the total Amp-hours used during electroplating after adding fresh
solution; measuring the number of substrates processed by the
electrolyte solution; calculating a dose to supply to the
electrolyte solution based on the time, the total Amp-hours, and
the number of substrates processed; and adding the dose to the
electrolyte solution.
7. The method of claim 6, further comprising draining a small
volume of fluid from the solution.
8. The method of claim 7, wherein the small volume of fluid is
about 2 liters or less.
9. The method of claim 6, wherein calculating the volume of the
dose uses calculations that do not interrelate the Amp-hours,
number of substrates, or time.
10. The method of claim 6, further comprising resetting a time
measurement.
11. The method of claim 6, further comprising resetting the
Amp-hour measurement.
12. The method of claim 6, further comprising resetting the number
of substrate measurement.
13. The method of claim 6, further comprising establishing an
initial time, Amp-hour, and substrate number measurement.
14. The method of claim 6, wherein the adding the dose to the
solution occurs when the loss of a volume of fluid is greater than
about 2 L.
15. The method of claim 6, wherein the adding the dose to the
solution occurs when the time is equal to or greater than about 2
days.
16. The method of claim 6, wherein the adding the dose to the
solution occurs when the Amp-hours is greater than about 100
Amp-hours.
17. The method of claim 6, wherein the adding the dose to the
solution occurs when the number of substrates processed is greater
than 200.
18. A method for dosing an electroplating bath, comprising:
monitoring total Amp-hours used during electroplating; monitoring
total evaporation loss during electroplating; dosing water and
chemicals to the electroplating bath after either the total
Amp-hours or the total evaporation loss exceed set targets; and
then resetting both the total Amp-hours and the total evaporation
loss to zero.
19. The method of claim 18, further comprising draining some of the
electroplating bath after the total Amp-hours exceeds the set
targets and before the dosing water and chemicals.
20. The method of claim 19, wherein the dosing the water and
chemicals restores the electroplating bath to a target
concentration of chemicals.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention generally relate to
semiconductor processing. More specifically, embodiments of the
present invention generally relate to a control scheme for
electroplating solutions.
[0003] 2. Description of the Related Art
[0004] Electroless and electroplating deposition techniques have
become an attractive option for depositing copper and copper alloys
onto semiconductor substrates and into high aspect ratio
features.
[0005] Conventional electroplating methods generally include
positioning a substrate into an electrolytic solution. An
electrical bias is then applied between the surface of the
substrate and an anode positioned in the electrolytic solution
which operates to urge copper ions to deposit on the substrate
surface. During non-processing time periods, i.e., when substrates
are not being plated, the electrolytic solution is generally
circulated through a continual fluid path that includes a
relatively small volume plating region and a substantially larger
volume storage region. The storage region, for example, may hold
approximately 15 liters of the electrolytic solution, while the
plating region may hold approximately 2 liters of the electrolytic
solution. Additionally, the continual fluid path may include an
electrolyte replenishment device configured to replenish portions
of the electrolytic solution that may be depleted through plating
operations.
[0006] Typical electrolyte solutions used for copper electroplating
generally consist of copper sulfate solution having sulfuric acid
and copper chloride added thereto. The sulfuric acid generally
operates to modify the acidity and conductivity of the solution,
while the copper chloride provides negative chlorine ions needed
for nucleation of suppressor molecules and facilitates proper anode
corrosion. The electrolytic solutions also generally contain
various organic molecules which may be accelerators, suppressors,
levelers, brighteners, etc. These organic molecules are generally
added to the electrolytic solution in order to facilitate void-free
fill of features and planar copper deposition. Accelerators may be
sulfide-based molecules that locally accelerate electrical current
at a given voltage where they absorb. Suppressors may be polymers
of polyethylene glycol, mixtures of ethylene oxides and propylene
oxides, or block copolymers of ethylene oxides and propylene oxides
which tend to reduce electrical current at the sites where they
absorb and slow plating at those locations. Levelers may be
nitrogen containing long chain polymers which operate to facilitate
planar copper deposition.
[0007] During the plating process, copper ions are continually
being removed from and replenished to the electrolytic solution.
Thus, the copper concentration of the electrolytic solution may
change or vary over time. This concentration change may further be
affected by volume depletion of the electrolytic solution or
dissolution of the anode. The volume of water within the
electrolytic solution is also in flux as the electrolytic solution
is consumed, evaporates, and is retained by the supply piping,
volume storage region, or the plating region.
[0008] Additionally, plating operations deplete the various organic
molecules in the electrolyte solution and each organic
concentration also varies over time. For example, levelers are
known to deplete and breakdown upon exposure to oxygen containing
elements such as ambient air, oxygen absorbed into the electrolytic
solution, oxygen molecules contained in the anode metal, or
oxidation encountered during plating by incorporation into a
growing film. This breakdown process generates free radicals in the
electrolytic solution, which are undesirable because the free
radicals can deposit on a substrate and contaminate the metal
layer. Further, levelers are known to break down upon exposure to
copper, copper alloys, and platinum, all of which are typical anode
materials for electroplating systems. Similarly, accelerators and
suppressors may also suffer from depletion and breakdown
characteristics as a result of oxygen or metal exposure.
[0009] Depletion of organics is not limited to processing time
periods because the electrolyte solution in an electroplating
system is generally continually circulated through the plating
region and the volume storage region during non-processing time
periods. As a result of the circulation, the electrolyte solution
may be continually exposed to both oxygen-containing elements and
the metal anode. Thus, the organic molecules in the electrolyte
solution are continually being depleted, even though the plating
region is not in a plating or operational mode.
[0010] Because the concentration of the organics in the electrolyte
solution and the concentration of the radicals generated by the
organic molecule degradation and depletion have a substantial
effect upon the efficiency and controllability of plating
operations, replenishment of depleted organics in the electrolyte
solution to maintain specific organic concentrations is desired.
Conventional plating systems generally provide a replenishment
module configured to add fresh organics into the electrolyte
solution in order to replenish depleted organic molecules. However,
conventional organic replenishment processes generally require time
consuming organic molecule measurement processes, which decrease
the accuracy of conventional organic replenishment processes. This
variance in organic concentration may detrimentally affect the
ability to accurately control conventional electroplating
apparatus. Therefore, there exists a need for a method for
accurately replenishing organic molecules and water in an
electroplating bath during plating operations.
SUMMARY OF THE INVENTION
[0011] The present invention generally provides method and
apparatus for dosing an electrolyte solution including measuring
the time after adding fresh solution, measuring the total Amp-hours
used during electroplating after adding fresh solution, measuring
the number of substrates processed after adding fresh solution,
calculating the volume of a dose to supply to the electrolyte
solution based on the time, the total Amp-hours, and the number of
substrates processed, and adding the dose to the electrolyte
solution.
[0012] The present invention also generally provides method and
apparatus for supplying a dose to an electrolyte solution including
measuring the loss of a volume of fluid from a solution vessel,
measuring the time after adding fresh solution, measuring the total
Amp-hours used during electroplating after adding fresh solution,
measuring the number of substrates processed by the electrolyte
solution, calculating a dose to supply to the electrolyte solution
based on the time, the total Amp-hours, and the number of
substrates processed, and adding the dose to the electrolyte
solution.
[0013] The present invention also generally provides method and
apparatus for dosing an electroplating bath including monitoring
total Amp-hours used during electroplating, monitoring total
evaporation loss during electroplating, dosing water and chemicals
to the electroplating bath after either the total Amp-hours or the
total evaporation loss exceed set targets, and then resetting both
the total Amp-hours and the total evaporation loss to zero.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of 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.
[0015] FIG. 1 is a top plan view of one embodiment of an
electrochemical plating system of the invention.
[0016] FIG. 2 is a sectional view of one embodiment of an
electrochemical process cell.
[0017] FIG. 3 is a schematic diagram of one embodiment of a plating
solution delivery system.
[0018] FIG. 4 is a schematic diagram of one embodiment of
components for a plating solution delivery system.
[0019] FIG. 5 is a flow chart of a control scheme for an
electroplating bath during plating operations.
[0020] FIG. 6 is a flow chart of an alternative control scheme for
an electroplating bath during plating operations.
DETAILED DESCRIPTION
[0021] The present invention provides a control system for
delivering electrolyte solution to electroplating baths. The
control system uses time, amp-hours, and number of substrates
processed to supply a dose of chemicals to the electrolyte solution
delivery system. Embodiments of the invention generally provide an
electrochemical plating system configured to plate conductive
materials, such as metals, on a semiconductor substrate for use in
apparatus implementing multiple chemistries or a single chemical
profile on a single plating platform. Embodiments of the invention
may be used for measuring, adding, or mixing chemical components
for various plating processes, including, but not limited to direct
plating on a barrier layer, alloy plating, alloy plating combined
with convention metal plating, plating on a thin seed layer,
optimized feature fill and bulk fill plating, plating multiple
layers with minimal defects, or any other plating process where
more than one chemistry may be beneficial to a plating process.
[0022] While the following description of the volume measurement
device is directed to use in an electrochemical processing system
(ECP), such as the SLIMCELL.TM. system available from Applied
Materials, Inc. of Santa Clara, Calif., the invention contemplates
the use of the invention where precise chemical composition of
liquids may be added to form processing composition. For example,
embodiments may be used in combination with chemical mechanical
polishing apparatus, such as the MIRRA.RTM. MESA.TM. polishing
system and the REFLEXION.TM. processing system, commercially
available from Applied Materials, Inc., of Santa Clara, Calif., wet
clean process apparatus, such as the TEMPEST.TM. wet clean
apparatus available from Applied Materials, Inc., of Santa Clara,
Calif. and other liquid processing systems.
[0023] FIG. 1 is a top plan view of one embodiment of an
electrochemical processing system (ECP) 100 of the present
invention. ECP system 100 includes a processing base 113 having a
robot 120 centrally positioned thereon. The robot 120 generally
includes one or more robot blades 122, 124 configured to support
substrates thereon. Additionally, the robot 120 and the
accompanying blades 122, 124 are generally configured to extend,
rotate, and vertically move so that the robot 120 may insert and
remove substrates to and from a plurality of processing locations
102, 104, 106, 108, 110, 112, 114, 116 positioned on the base
113.
[0024] ECP system 100 further includes a factory interface (FI)
130. FI 130 includes at least one FI robot 132 positioned adjacent
a side of the FI 130 that is adjacent the processing base 113. This
position of robot 132 allows the robot to access substrate
cassettes 134 to retrieve a substrate 126 and then deliver the
substrate 126 to one of several processing locations 114, 116 to
initiate a processing sequence. Similarly, robot 132 may be used to
retrieve substrates from one of the processing locations 114, 116
after a substrate processing sequence is complete. In this
situation, robot 132 may deliver the substrate 126 to one of the
cassettes 134 for removal from the system 100. Additionally, robot
132 is configured to access an anneal chamber 135 positioned in
communication with FI 130. The anneal chamber 135 generally
includes a two position annealing chamber, wherein a cooling plate
or position 136 and a heating plate or position 137 are positioned
adjacently with a substrate transfer robot 140 positioned between
the two stations. The robot 140 is generally configured to move
substrates between the respective heating 137 and cooling plates
136.
[0025] Generally, process locations 102, 104, 106, 108, 110, 112,
114, 116 may be any number of processing cells for use in an
electrochemical plating platform. Plating solution delivery systems
111A, 111B and a controller 115 deliver electrolyte solution to the
process locations. More particularly, the process locations may be
configured as electrochemical plating cells, rinsing cells, bevel
clean cells, spin rinse dry cells, substrate surface cleaning
cells, electroless plating cells, metrology inspection stations,
and other cells or processes that may be beneficially used in
conjunction with a plating platform.
[0026] FIG. 2 is a cross sectional view of one embodiment of an
exemplary electrochemical plating cell that may be implemented in
any one of processing locations 102, 104, 106, 108, 110, 112, 114,
116 of processing system 100 as shown in FIG. 1. Generally,
however, the exemplary processing system 100 is configured to
include four electrochemical plating cells at processing locations
102, 104, 112, and 110. Processing locations 106 and 108 are
generally configured as edge bead removal or bevel clean chambers.
Further, processing locations 114 and 116 are generally configured
as substrate surface cleaning chambers and spin rinse dry chambers,
which may be stacked one above the other. However, the invention is
not intended to be limited to any particular order or arrangement
of cells, as various combinations and arrangements may be
implemented without departing from the scope of the invention.
[0027] Returning to FIG. 2, the electrochemical processing cell 150
generally includes a head assembly 211, an anode assembly 220, an
inner basin 272, and an outer basin 240. The outer basin 240 is
coupled to a base 160 and circumscribes the inner basin 272. The
inner and outer basins 272, 240 are typically fabricated from an
electrically insulative material compatible with process
chemistries, for example, ceramics, plastics, plexiglass (acrylic),
lexane, PVC, CPVC, or PVDF. Alternatively, the inner and outer
basins 272, 240 may be made from a metal, such as stainless steel,
nickel, or titanium, which is coated with an insulating layer, such
as Teflon.RTM., fluoropolymer, PVDF, plastic, rubber and other
combinations of materials compatible with plating fluids and can be
electrically insulated from the electrodes. The inner basin 272 is
typically configured to conform to the substrate plating surface
and the shape of the substrate being processed through the system,
generally having a circular or rectangular shape. In one
embodiment, the inner basin 272 is a cylindrical ceramic tube
having an inner diameter that has about the same dimension as or
slightly larger than the diameter of a substrate being plated in
the cell 150. The outer basin 272 generally includes a channel 248
for catching plating fluids flowing out of the inner basin 272. The
outer basin 272 also has a drain 218 that couples the channel 248
to a reclamation system for processing, recycling, or disposal of
used plating fluids.
[0028] The head assembly 211 is mounted to a head assembly frame
252. The head assembly frame 252 includes a mounting post 254 and a
cantilever arm 256. The mounting post 254 is coupled to the base
160 and the cantilever arm 256 extends laterally from an upper
portion of the mounting post 254 and rotates about a vertical axis
of the mounting post 254 to allow movement of the head assembly 211
over or clear of the basins 240, 272. The head assembly 211 is
attached to a mounting plate 260 disposed at the distal end of the
cantilever arm 256. The lower end of the cantilever arm 256 is
connected to a cantilever arm actuator 268, such as a pneumatic
cylinder, mounted on the mounting post 254. The cantilever arm
actuator 268 provides pivotal movement of the cantilever arm 256
with respect to the mounting post 254. When the cantilever arm
actuator 268 is retracted, the cantilever arm 256 moves the head
assembly 211 away from the anode assembly 220 disposed in the inner
basin 272 to provide the spacing required to remove and/or replace
the anode assembly 220 from the first process cell 150. When the
cantilever arm actuator 268 is extended, the cantilever arm 256
moves the head assembly 211 axially toward the anode assembly 220
to position the substrate in the head assembly 211 in a processing
position. The head assembly 211 may also tilt to orientate a
substrate at an angle from horizontal.
[0029] The head assembly 211 includes a substrate holder assembly
250 and a substrate assembly actuator 258. The substrate assembly
actuator 258 is mounted onto the mounting plate 260 and includes a
head assembly shaft 262 that extends downward through the mounting
plate 260. The lower end of the head assembly shaft 262 is
connected to the substrate holder assembly 250 to position the
substrate holder assembly 250 in a processing position and in a
substrate loading position. The substrate assembly actuator 258
additionally may be configured to provide rotary motion to the head
assembly 211. In one embodiment, the head assembly 211 is rotated
between about 2 rpm and about 50 rpm during an electroplating
process and often may be rotated between about 5 and about 20 rpm.
The head assembly 211 can also be rotated as the head assembly 211
is lowered to position the substrate in contact with the plating
solution in the process cell as well as when the head assembly 211
is raised to remove the substrate from the plating solution in the
process cell. The head assembly 211 may be rotated at a high speed
such as greater than 20 rpm after the head assembly 211 is lifted
from the process cell to enhance removal of residual plating
solution from the head assembly 211 and substrate.
[0030] The substrate holder assembly 250 includes a thrust plate
264 and a cathode contact ring 266. The cathode contact ring 266 is
configured to electrically contact the surface of the substrate to
be plated. Typically, the substrate has a seed layer of metal, such
as copper, deposited on the feature side of the substrate. A power
source 246 is coupled between the cathode contact ring 266 and the
anode assembly 220 and provides an electrical bias that drives the
plating process.
[0031] The thrust plate 264 and the cathode contact ring 266 are
suspended from a hanger plate 236. The hanger plate 236 is coupled
to the head assembly shaft 262. The cathode contact ring 266 is
coupled to the hanger plate 236 by hanger pins 238. The hanger pins
238 allows the cathode contact ring 266, when mated against the
inner basin 272, to move to closer to the hanger plate 236. This
allows the substrate held by the thrust plate 264 to be sandwiched
between the hanger plate 236 and thrust plate 264 during
processing, thereby ensuring good electrical contact between the
seed layer of the substrate and the cathode contact ring 266.
[0032] The anode assembly 220 is positioned within a lower portion
of the inner basin 272 below the substrate holder assembly 250. The
anode assembly 220 includes one or more anodes 244 and a diffusion
plate 222. The anode 244 is disposed in the lower end of the inner
basin 272 and the diffusion plate 222 is disposed between the anode
244 and the substrate held by the substrate holder assembly 250 at
the top of the inner basin 272. The anode 244 and diffusion plate
222 are maintained in a spaced-apart relation by insulative spacer
224. The diffusion plate 222 is attached to and substantially spans
the inner opening of the inner basin 272. The diffusion plate 222
is permeable to the plating solution and is fabricated from a
plastic or ceramic material, for example, an olefin such as a
spunbonded polyester film. The diffusion plate 222 operates as a
fluid flow restrictor to improve flow uniformity across the surface
of the substrate. The diffusion plate 222 also operates to damp
electrical variations in the electrochemical cell to control
electrical flux which improves plating uniformity. Alternatively,
the diffusion plate 222 may be fabricated from a hydrophilic
plastic, such as treated PE, PVDF, PP, or other porous or permeable
material that provides electrically resistive damping
characteristics.
[0033] The anode assembly 220 may include a consumable anode 244 to
serve as a metal source. Alternatively, the anode 244 may be a
non-consumable anode, and the metal to be electroplated is supplied
within the plating solution from the plating solution delivery
system 111. The anode assembly 220 may be a self-enclosed module
having a porous enclosure preferably made of the same metal as the
metal to be electroplated, such as copper. Alternatively, the
enclosure may be fabricated from porous materials, such as ceramics
or polymeric membranes. Exemplary consumable and non-consumable
anodes include copper/doped copper and platinum, respectively. The
anode 244 is metal particles, wires, a perforated sheet, or a
combination and is manufactured from the material to be deposited
on the substrate, such as copper, aluminum, gold, silver, platinum,
tungsten, copper phosphate, noble metal, or other materials which
may be electrochemically deposited on a substrate. The anode 244
may be porous, perforated, permeable, or otherwise configured to
allow passage of the plating solution. Alternatively, the anode 244
may be solid. Compared to a non-consumable anode, the consumable
(i.e., soluble) anode provides gas-generation-free plating solution
and minimizes the need to constantly replenish the metal in the
plating solution. In the embodiment depicted in FIG. 2, the anode
244 is a solid copper disk.
[0034] An electrolyte inlet 216 is formed through the inner basin
272. The plating solution entering the inner basin 272 through the
electrolyte inlet 216 flows through or around the anode assembly
220 upward toward the surface of the substrate positioned on the
upper end of the inner basin 272. The plating solution flows across
the substrate surface and through slots (not shown) in the cathode
contact ring 266 to a passage formed in the outer basin 240. The
bias between the substrate and the anode 244 causes metal ions from
the plating fluids and/or anode to deposit on the surface of the
substrate. Examples of process cells that may be adapted to benefit
from the invention are described in U.S. patent application Ser.
No. 09/905,513, filed Jul. 13, 2001, and in U.S. patent application
Ser. No. 10/061,126, filed Jan. 30, 2002, both of which
incorporated by reference.
[0035] FIG. 3 is a schematic diagram of one embodiment of the
plating solution delivery system 111A, 111B as described above in
the discussion of FIG. 1. The plating solution delivery system
111A, 111B is configured to supply a plating solution to each
processing location on system 100. The plating solution delivery
system may be further configured to supply a different plating
solution or chemistry to each of the processing locations. For
example, the delivery system may provide a first plating solution
or chemistry to processing locations 110, 112, while providing a
different plating solution or chemistry to processing locations
102, 104. Individual plating solutions are often isolated for use
with a single plating cell. There are no cross contamination issues
with the different chemistries. However, embodiments may have more
than one cell and share a common chemistry that is different from
another chemistry supplied to another plating cell on the system.
These features are advantageous, as the ability to provide multiple
chemistries to a single processing platform allows for multiple
chemistry plating processes on a single platform.
[0036] In another embodiment, a first plating solution and a
separate and different second plating solution can be provided
sequentially to a single plating cell. Typically, providing two
separate chemistries to a single plating cell requires the plating
cell to be drained and/or purged between the respective
chemistries; however, a mixed ratio of less than about 10 percent
first plating solution to the second plating solution should not be
detrimental to film properties.
[0037] More particularly, the plating solution delivery system
111A, 111B typically includes a plurality of chemical component
sources 302 and at least one electrolyte source 304 that are
fluidly coupled to each of the processing cells of system 100 via a
valve manifold 332. Typically, the chemical component sources 302
include an accelerator source 306, a leveler source 308, and a
suppressor source 310. The accelerator source 306 is adapted to
provide an accelerator material that typically adsorbs on the
surface of the substrate and locally accelerates the electrical
current at a given voltage where they adsorb. Examples of
accelerators include sulfide-based molecules. The leveler source
308 is adapted to provide a leveler material that operates to
facilitate planar plating. Examples of levelers are nitrogen
containing long chain polymers. The suppressor source 310 is
adapted to provide suppressor materials that tend to reduce
electrical current at the sites where they adsorb (typically the
upper edges/corners of high aspect ratio features). Therefore,
suppressors slow the plating process at those locations, reducing
premature closure of the feature before the feature is completely
filled and minimizing detrimental void formation. Examples of
suppressors include polymers of polyethylene glycol, mixtures of
ethylene oxides and propylene oxides, or copolymers of ethylene
oxides and propylene oxides.
[0038] In order to prevent situations where a chemical component
source runs out and to minimize chemical component waste during
containers replacement, each of the chemical component sources 302
generally includes a bulk or larger storage container coupled to a
smaller buffer container 316. The buffer container 316 is generally
filled from the containers 306, 308, and 310, and therefore, the
containers 306, 308, and 310, may be removed for replacement
without affecting the operation of the fluid delivery system, as
the associated buffer container may supply the particular chemical
component to the system while the containers are being replaced.
The volume of the buffer container 316 is less than the volume of
the containers 306, 308, and 310. The containers 306, 308, and 310
are sized to contain enough chemical components for 10 to 12 hours
of uninterrupted operation. This provides sufficient time for
operators to replace the containers when the containers are empty.
If the buffer container was not present and uninterrupted operation
was still desired, the containers would have to be replaced prior
to being empty, thus resulting in significant chemical component
waste.
[0039] In the embodiment depicted in FIG. 3, the fluid delivery
system includes a volume measurement module 312 coupled between the
plurality of chemical component sources 302 and the plurality of
processing cells (not shown). The volume measurement module 312
generally includes at least a vessel, an ultrasonic sensor disposed
in a position to monitor the level or volume in the vessel, a
controller coupled to the ultrasonic sensor, a liquid inlet port
315, a liquid outlet line 340, a purge port 317, a gas inlet, and a
vent 316. The volume measurement module 312 may be adapted to
receive liquids from one or more sources and adapted for providing
volumes of individual liquids and mixtures of liquids. Additional
information about the volume measurement system may be found in
U.S. patent application Ser. No. 10/683,917, Patent Application
Publication 2005-0077182, filed Oct. 10, 2003, which is hereby
incorporated by reference herein.
[0040] A first liquid inlet port 315 is coupled to a chemical
component dosing pump 311 disposed between the volume measurement
module 312 and the chemical component sources 306, 308, and 310.
The chemical component dosing pump 311 provides the chemical
components to the module 312 via the pump line 319 and may also be
adapted to provide additional liquids, such as electrolyte 304,
deionized water 342, and/or a purge gas 344. The chemical component
dosing pump 311 may be a rotary metering pump, a solenoid metering
pump, a diaphragm pump, a syringe, a peristaltic pump, a piston
pump, or other positive displacement volumetric device. The
chemical component dosing pump 311 may used in conjunction with the
volume measurement module 312 and/or the controller described
herein as well as used singularly or coupled to a flow sensor. For
example, in one embodiment, the chemical component dosing pump 311
includes a rotating and reciprocating ceramic piston that drives
0.32 ml per cycle of a predetermined chemical component.
Alternatively, the dosing pump 311 may be replaced by a pressurized
fluid delivery process or a vacuum delivery system, which draws
chemical components into the module 312 by a vacuum source at port
317 or another port. The electrolyte source 304 may also be fluidly
coupled to the module 312 by the dosing pump 311.
[0041] A first outlet port 330 of the volume measurement module 312
is generally coupled to the processing cells via valve or valve
manifold 332 by an output line 340. Chemical components, such as at
least one or more accelerators, levelers and/or suppressors, may be
mixed or delivered for combining with an electrolyte flowing
through a first delivery line 350 from the electrolyte source 304,
to form the first or second plating solutions as desired. The purge
port 317 is generally coupled to the module 312. The purge port 317
may be used to purge module 312 when necessary to recover from
chemical component delivery errors that are detected by the volume
measurement module 312.
[0042] FIG. 4 is a schematic diagram of a fluid delivery system 400
to each processing system. In operation, the sensor 420 measures
the level of any fluids located in the vessel 410. Chemical
components from source 401 are then introduced through the vessel
410 to the recirculation pump 411 and through the pump line 419
into the plating cell 413. The sensor 420 measures the level of the
liquid in the vessel 410 either continuously, periodically, or as a
level sensor, until a specified volume is measured. The sensor 420
may also measure the discharging liquid volume. The liquid
recirculates from the plating cell 413 through valve 405 and
recirculation line 406 to the vessel 410. Occasionally, fluid may
be drained from vessel 410 through the drain 407.
[0043] While an embodiment volume measurement module is described
herein for processing chemical components for electrolyte
solutions, the invention contemplates that the volume measurement
module may be used for processing additional liquids used in
plating operations, including electrolytes, cleaning agents, such
as water, etchants, or dissolving agents, among others.
[0044] While not shown, the invention also contemplates additional
components using in fluid systems, including bypass valves, purge
valves, flow controllers, or temperature controllers.
[0045] In another embodiment of the invention the fluid delivery
system may be configured to provide a second completely different
plating solution and associated chemical components. As such,
multiple volume measurement modules may be disposed in the system
to connect to one or more of the plating cells to provide the
necessary plating solutions. For example, in this embodiment a
different base electrolyte solution (similar to the solution
contained in container 304 of FIG. 3) may be implemented to provide
the processing system 100 with the ability to use plating solutions
from two separate manufacturers. Further, an additional set of
chemical component containers may also be implemented to correspond
with the second base plating solution. Therefore, this embodiment
of the invention allows for a first chemistry (a chemistry provided
by a first manufacturer) to be provided to one or more plating
cells of system 100, while a second chemistry (a chemistry provided
by a second manufacturer) is provided to one or more plating cells
of system 100. Each of the respective chemistries will generally
have their own associated chemical components, however, cross
dosing of the chemistries from a single chemical component source
or sources is not beyond the scope of the invention.
[0046] In order to implement the fluid delivery system capable of
providing two separate chemistries from separate base electrolytes,
a duplicate of the fluid delivery system illustrated in FIG. 3 is
connected to the processing system. More particularly, the fluid
delivery system illustrated in FIG. 3 is generally modified to
include a second set of chemical component containers 302 and
separate sources for virgin makeup solution/base electrolyte 304
are also provided. The additional hardware is set up in the same
configuration as the hardware illustrated in FIG. 3, however, the
second fluid delivery system is generally in parallel with the
illustrated or first fluid delivery system. Thus, with this
configuration implemented, either base chemistry with any
combination of the available chemical components may be provided to
any one or more of the processing cells of system 100.
[0047] The valve manifold 332 is typically configured to interface
with a bank of valves 334. Each valve of the valve bank 334 may be
selectively opened or closed to direct fluid from the valve
manifold 332 to one of the process cells of the plating system 100.
The valve manifold 332 and valve bank 334 may optionally be
configured to support selective fluid delivery to additional number
of process cells. In the embodiment depicted in FIG. 3, the valve
manifold 332 and valve bank 334 include a sample port 336 that
allows different combinations of chemistries or component thereof
utilized in the system 100 to be sampled without interrupting
processing.
[0048] In some embodiments, it may be desirable to purge the volume
measurement module 312, output line 340 and/or valve manifold 332.
To facilitate such purging, the plating solution delivery system
111A, 111B is configured to supply at least one of a cleaning
and/or purging fluid. In the embodiment depicted in FIG. 3, the
plating solution delivery system 111A, 111B includes a deionized
water source 342 and a non-reactive gas source 344 coupled to the
first delivery line 350. The non-reactive gas source 344 may supply
a non-reactive gas, such as an inert gas, air or nitrogen through
the first and second delivery lines 350 and 352 to flush out the
valve manifold 332. Deionized water may be provided from the
deionized water source 342 to flush out the valve manifold 332 in
addition to, or in place of non-reactive gas. Electrolyte from the
electrolyte sources 304 may also be utilized as a purge medium.
[0049] In an alternative embodiment of the system, a second
delivery line 352 is tied between the first gas delivery line 350
and the dosing pump 311. A purge fluid of a purge liquid includes
at least one of an electrolyte, deionized water or other suitable
liquid from the respective sources, such as 304 and 342, may be
diverted from the first delivery line 350 through the second gas
delivery line 352, and through the dosing pump 311 to the volume
measurement module 312. A purge fluid of a purge gas, such as
nitrogen gas, from the respective sources 344 may be diverted from
the first delivery line 350 through the second gas delivery line
352 and purge gas line 351 to the volume measurement module 312.
The purge fluid is driven through the volume measurement module 312
and out the output line 340 to the valve manifold 332. The valve
bank 334 typically directs the purge fluid out a drain port 388 to
the reclamation system 232. The various other valves, regulators
and other flow control devices have not been described and/or shown
for the sake of brevity.
[0050] In one embodiment of the invention, chemical components for
a first chemistry may be provided to promote feature filling of
copper on a semiconductor substrate. The first chemistry may
include between about 30 and about 65 g/l of copper, between about
35 and about 85 ppm of chlorine, between about 20 and about 40 g/l
of acid, between about 4 and about 7.5 ml/L of accelerator, between
about 1 and 5 ml/L of suppressor, and no leveler. The chemical
components for the first chemistry is delivered from the valve
manifold 332 to a first plating cell 150 to enable features
disposed on the substrate to be substantially filled with metal. As
the first chemistry generally does not completely fill the feature
and has an inherently slow deposition rate, the first chemistry may
be optimized to enhance the gap fill performance and the defect
ratio of the deposited layer.
[0051] A second chemistry makeup with a different chemistry from
the first chemistry may be provided to another plating cell on
system 100 via valve manifold 332, wherein the second chemistry is
configured to promote planar bulk deposition of copper on a
substrate. The second chemistry may include between about 35 and
about 60 g/l of copper, between about 60 and about 80 ppm of
chlorine, between about 20 and about 40 g/l of acid, between about
4 and about 7.5 ml/L of accelerator, between about 1 and about 4
ml/L of suppressor, and between about 6 and about 10 ml/L of
leveler, for example. The chemical components for the second
chemistry is delivered from the valve manifold 332 to the second
process cell to enable an efficient bulk metal deposition process
to be performed over the metal deposited during the feature fill
and planarization deposition step to fill the remaining portion of
the feature. Since the second chemistry generally fills the upper
portion of the features, the second chemistry may be optimized to
enhance the planarization of the deposited material without
substantially impacting substrate throughput. Thus, the two steps,
different chemistry deposition process allows for both rapid
deposition and good planarity of deposited films to be realized.
The two chemistries may be provided sequentially from the same
volume measurement module 312.
[0052] When utilized with a process cell requiring anolyte
solutions such as the process cell 150 of FIG. 2, the plating
solution delivery system 111 generally includes an anolyte fluid
circuit (not shown) that is coupled to the inlet 216 of the plating
cell 150. The anolyte fluid circuit may include a plurality of
chemical component sources (not shown) coupled by a dosing pump to
a manifold (not shown) that directs chemical components (typically
not utilized) selectively metering from one or more of the sources
and combined with an anolyte in the manifold to those process cells
(such as the cell 150) requiring anolyte solution during the
plating process. The anolyte may be provided by an anolyte source
and a volume measurement module may be used to provide the
selectively metering chemical components.
[0053] Upon starting the system with a fresh batch of electrolyte
solution, the controller 115 waits until a set limit is reached in
Amp-hours, such as 100, or maximum evaporation loss in the fluid
delivery system 400, such as 2 L. If the evaporation loss is
reached first, then the controller follows the process as
illustrated by FIG. 5. If the Amp-hour limit is reached, the
controller follows the process detailed by FIG. 6.
[0054] FIG. 5 is a flow chart of a control scheme for an
electroplating bath during plating operations. Initially, the
sensor 420 provides a volume measurement for the vessel 410 in step
501 to determine if the maximum evaporation loss has occurred.
Based on the number of substrates processed, the amp-hours the
solution has been in service, and the length of time the solution
has been in service, the controller calculates the degradation
during step 502. The controller next calculates drag-out losses
based on the number of substrates during step 503. The controller
calculates the water lost over time and amp-hour during step 504.
Then, the controller commands the individual component feed
mechanisms to provide one aliquot of the desired components based
on the combined calculated volume of fluid loss and chemical
consumption in step 505. Note that the calculations are separate,
individual calculations. The volume lost to evaporation and the
volume lost to drag out do not relate to each other mathematically,
nor do the additive calculations interrelate the time of operation
to the Amp-hours of operation. The final intermediate dose that is
introduced into the system contains a one time addition of material
based on the three separate, independent sources of information and
not on the actual in-line chemical component measurements or volume
loss. How the depletion methods interact with each other is
factored out of these calculations to create independent depletion
equations.
[0055] FIG. 6 is a flow chart of an alternative control scheme for
an electroplating bath during plating operations. Initially, the
controller measures the number of amp-hours the system has been in
operation since the previous solution change during step 601. Next,
draining the vessel 410 of a small volume, 0.1 to 2 liters may be
selected to address volume measurement concerns or to remove system
impurities during step 602. Then, calculating the organic loss,
drag-out, and water loss to evaporation is performed in steps 603,
604, and 605, much like steps 502, 503, and 504 described above. In
response to the calculations performed in steps 603, 604, and 605,
the controller manipulates the system to provide one aliquot of the
desired components to the electrolyte solution in step 606. Again,
the calculations are separate, individual calculations. The volume
lost to evaporation and the volume lost to drag out do not relate
to each other mathematically, nor do the additive calculations
interrelate the time of operation to the Amp-hours of operation.
The calculated intermediate dose that is introduced into the system
contains additional material based on the three separate,
independent sources of information and not on the actual in-line
chemical component measurements or volume loss.
[0056] Steps 505 and 606 are single dosing events. The additives
and water are configured to provide one intermediate dose to the
electrolyte solution to prolong the life of the electrolyte
solution. Prolonging the life of the solution means providing
enough fresh chemical components and water to the system to delay
the need to dispose of the depleted solution and replace the
solution with fresh solution. The volume of solution that is sent
to the individual cells is approximately 15 L per bath. However,
there can be a 0.5 L volume difference between the cell baths
because of piping volume differences between the different cells.
An individual, intermediate dose to the electrolyte solution is
about 2 L. This volume is selected to provide at least 1 L of
solution at the first and last of the solution addition to the
individual cells. If the volume is too high, there is a risk of
wasting fresh chemicals. If the volume is too low, there is a risk
that the one dose of material will not prolong the life of the
solution. Multiple doses at one time are also undesirable as they
can lead to an overall solution increase that will alert the volume
indicator on the vessel to shut down the system.
[0057] Multiple doses over a long period of time may also result in
an overall volume increase in the system, specifically the volume
in the vessel 410. If that volume is too high, the controller may
stop the entire system. Also, the overall effectiveness of the
system may decrease as the intermediate doses are based on an
overall volume of solution that does not increase. Thus,
occasionally, as the controller continues to provide intermediate
doses to the system, a small volume of fluid may be removed from
the vessel to prevent over-filling the vessel.
[0058] Marathon testing was performed to examine the effectiveness
of this system. Over 700 amp-hours, one system exhibited acceptable
accelerator, suppressor, and leveler when a dose was added every
100 amp-hours throughout the entire 700 amp-hours. Another system
farther away from the main vessel had similar results, with
slightly less variation in the concentration of the leveler. Over
the course of the marathon testing, the constants for the algorithm
to calculate the fresh dose components drifted less than 0.2
mL/amp-hour.
[0059] 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.
* * * * *