U.S. patent application number 10/690408 was filed with the patent office on 2005-04-21 for copper replenishment for copper plating with insoluble anode.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Hoermann, Alexander F., Kovarsky, Nicolay Y., Lubomirsky, Dmitry, Singh, Saravjeet.
Application Number | 20050082172 10/690408 |
Document ID | / |
Family ID | 34521641 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050082172 |
Kind Code |
A1 |
Kovarsky, Nicolay Y. ; et
al. |
April 21, 2005 |
Copper replenishment for copper plating with insoluble anode
Abstract
In one embodiment, the present invention generally provides an
apparatus and method for dispersing a chemical reagent into a
plating solution. The apparatus generally includes a tank for
containing the plating solution and a horizontal vessel in fluid
communication with the tank, wherein the horizontal vessel has an
input and an output. The apparatus further includes at least one
shelf contained inside the horizontal vessel, wherein the at least
one shelf extends between the input and the output and the chemical
reagent rests on the at least one shelf. In another embodiment, the
present invention generally provides an apparatus for dispersing a
chemical reagent to a plating solution comprising a tank for
containing the plating solution and a vertical vessel in fluid
communication with the tank. A lower portion of the vertical vessel
includes an inlet and an injector port and an upper portion of the
vertical vessel includes an outlet and a manifold. The chemical
reagent is positioned between the inlet and the outlet.
Inventors: |
Kovarsky, Nicolay Y.;
(Sunnyvale, CA) ; Lubomirsky, Dmitry; (Cupertino,
CA) ; Hoermann, Alexander F.; (San Jose, CA) ;
Singh, Saravjeet; (Santa Clara, CA) |
Correspondence
Address: |
MOSER, PATTERSON & SHERIDAN, LLP/
APPLIED MATERIALS, INC.
3040 POST OAK BOULEVARD, SUTIE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
34521641 |
Appl. No.: |
10/690408 |
Filed: |
October 21, 2003 |
Current U.S.
Class: |
205/101 |
Current CPC
Class: |
C25D 21/18 20130101;
C25D 21/14 20130101 |
Class at
Publication: |
205/101 |
International
Class: |
C25D 021/18 |
Claims
1. An apparatus for dispensing a chemical reagent into a plating
solution comprising: a tank for containing the plating solution; a
vessel in fluid communication with the tank, wherein the vessel has
an inlet and an outlet; at least one horizontal shelf contained
inside the vessel, wherein the at least one horizontal shelf is
positioned to hold the chemical reagent and expose the chemical
reagent to the plating solution flowing from the inlet to the
outlet.
2. The apparatus of claim 1, wherein at least one horizontal shelf
is impermeable to the plating solution.
3. The apparatus of claim 1, wherein the plating solution is an
acidic, electrochemical anolyte and includes copper ions.
4. The apparatus of claim 3, wherein a headspace is disposed above
the at least one horizontal shelf.
5. The apparatus of claim 4, wherein the headspace is in a range
from about 5 cm to about 30 cm.
6. The apparatus of claim 5, wherein the electrochemical anolyte
flows from the inlet to the outlet via the headspace.
7. The apparatus of claim 6, wherein the electrochemical anolyte is
replenished by the chemical reagent.
8. The apparatus of claim 7, wherein the chemical reagent comprises
a copper source compound selected from the group consisting of
copper hydroxide, copper carbonate, copper oxide, copper sulfate,
copper phosphate and combinations thereof.
9. The apparatus of claim 1, wherein the at least one horizontal
shelf includes a flat shelf, a longitudinally grooved shelf, a
tubular shelf or combinations thereof.
10. The apparatus of claim 9, wherein the vessel comprises at least
one porous material selected from the group consisting of a
membrane, a filter, a frit, a mesh and combinations thereof.
11. An apparatus for dispersing a chemical reagent to a plating
solution comprising: a tank for containing the plating solution;
and a vertical vessel in fluid communication with the tank,
comprising: a lower portion of the vertical vessel including an
inlet and an injector port; an upper portion of the vertical vessel
including an outlet and a manifold; and the chemical reagent
positioned between the inlet and the outlet.
12. The apparatus or claim 11, wherein the lower portion expands
radially outwardly.
13. The apparatus of claim 12, wherein the injector port is
positioned to direct the plating solution in a downward direction
away from the output.
14. The apparatus of claim 11, wherein the plating solution is an
acidic, electrochemical anolyte and includes copper ions.
15. The apparatus of claim 11, wherein a headspace is disposed
above the chemical reagent.
16. The apparatus of claim 15, wherein the headspace is in a range
from about 5 cm to about 30 cm.
17. The apparatus of claim 16, wherein the plating solution flows
from the inlet to the outlet via the headspace.
18. The apparatus of claim 17, wherein the plating solution is
replenished by the chemical reagent.
19. The apparatus of claim 18, wherein the chemical reagent
comprises a copper source compound selected from the group
consisting of copper hydroxide, copper carbonate, copper oxide,
copper sulfate, copper phosphate and combinations thereof.
20. A method for replenishing copper in a plating solution
comprising: flowing the plating solution from a tank through an
inlet of a vessel, wherein the vessel comprises a chemical reagent
disposed on at least one shelf; flowing the plating solution across
the chemical reagent to enrich the plating solution with the
chemical reagent; and flowing the enriched plating solution from
the vessel through an outlet to the tank.
21. The method of claim 20, wherein at least one horizontal shelf
is impermeable to the plating solution.
22. The method of claim 20, wherein the plating solution has a pH
in a range from about 2.0 to about 4.0
23. The method of claim 22, wherein a copper concentration is
monitored and controlled as a function of the pH.
24. The method of claim 20, wherein the plating solution is an
acidic, electrochemical anolyte and includes copper ions.
25. The method of claim 20, wherein the plating solution flows
through a headspace disposed above the at least one shelf.
26. The method of claim 25, wherein the headspace is in a range
from about 5 cm to about 30 cm.
27. The method of claim 26, wherein the electrochemical anolyte
flows from the inlet to the outlet via the headspace.
28. The method of claim 24, wherein the chemical reagent comprises
a copper source compound selected from the group consisting of
copper hydroxide, copper carbonate, copper oxide, copper sulfate,
copper phosphate and combinations thereof.
29. The method of claim 28, wherein the at least one shelf includes
a flat shelf, a longitudinally grooved shelf, a tubular shelf or
combinations thereof.
30. The method of claim 29, wherein the horizontal vessel comprises
at least one porous material selected from the group consisting of
a membrane, a filter, a frit, a mesh and combinations thereof.
31. A method for monitoring and controlling a pH setting of a
plating solution in a tank comprising: transferring an aliquot of
the plating solution to a container; pressurizing the container
with a gas to transfer the aliquot to a vessel, wherein the vessel
comprises an injector, a chemical reagent and a manifold; passing
the aliquot through the injector to enrich the aliquot with a
portion of the chemical reagent; transferring the enriched aliquot
through the manifold to the plating solution in the tank;
determining a pH of the plating solution with a pH meter; and
comparing the pH to the pH setting and repeating the transferring
of the enriched aliquot to the plating solution until the pH is
equivalent to the pH setting.
32. The method of claim 31, wherein a copper concentration is
monitored and controlled as a function of the pH setting.
33. The method of claim 31, wherein the pH setting is in a range
from about 2.0 to about 4.0.
34. The method of claim 31, wherein the plating solution is an
acidic, electrochemical anolyte and includes copper ions.
35. The method of claim 31, wherein the chemical reagent comprises
a copper source compound selected from the group consisting of
copper hydroxide, copper carbonate, copper oxide, copper sulfate,
copper phosphate and combinations thereof.
36. An apparatus for dispensing a chemical reagent into a plating
solution comprising: a tank for containing the plating solution; a
vessel in fluid communication with the tank, wherein the vessel has
an inlet and an outlet; at least one impermeable shelf contained
inside the vessel, wherein the at least one impermeable shelf is
positioned to hold the chemical reagent and expose the chemical
reagent to the plating solution flowing from the inlet to the
outlet.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the invention generally relate to a metal
plating apparatus and process, namely for the replenishment of
chemical components used to electroplate copper.
[0003] 2. Description of the Related Art
[0004] Semiconductor substrates can be plated with copper by
electroplating or electroless plating processes. During the
electroplating, an anode is usually placed into an electrolyte
solution and the substrate is conductively coupled to a cathode. As
current flows, dissolved copper ions from the electrolyte solution
are reduced and plated (or deposited) on the surface of the
substrate as copper metal. Traditionally, the anode is made from
consumable copper metal and is continuously oxidized to provide
copper ions to the plating process. Due to the consumption of the
copper anode, the dimension of the copper anode is changed.
Therefore the directional electrical fields produced by the anode
also change accordingly. This alteration in the electric field
presents a challenge to precisely control the electroplating
process, especially within vias with high aspect ratios.
[0005] Another electroplating process utilizes an inert or stable
anode in place of a consumable anode. The use of an inert anode
provides excellent control for precision plating since the anode is
not consumed during the plating process. However, the inert anode
does not supply a source of copper into the electrolyte solution.
As the copper ions are reduced and plated from the electrolyte
solution to the substrate surface, the copper ion concentration in
the electrolyte solution is diminished. Therefore, as the plating
process progresses, a copper source, namely copper ions, must be
added to the electrolyte solution in order to continue the plating
process. Copper sources are generally chosen from a variety of
copper salts that include copper sulfate, copper hydroxide, copper
oxide and copper phosphate.
[0006] U.S. Pat. No. 5,516,414 teaches a method to maintain an
alkaline copper plating solution with a desired concentration of
copper ions and hydroxide ions. The '414 patent discloses adding
copper hydroxide powder from a conduit to an alkaline,
pyrophosphate solution in a dissolving tank. Once the solution has
been heated and agitated to insure that the copper hydroxide has
been dissolved, the pyrophosphate solution is transferred via a
pump to the plating solution. The plating solution is monitored
with a meter and maintained with a basic pH between 7 and 10 by
adding the alkaline, pyrophosphate solution. Though the addition of
copper hydroxide powder is adequate in the realm of electroplating
wires, this technique is unacceptable in a clean environment, such
as a semiconductor fabrication room equipped to plate substrates.
The dumping of a powdery precursor into a solution would present
contamination issues for semiconductor processing in a cleanroom
environment.
[0007] U.S. Pat. No. 5,997,712 realizes the shortcomings of the
'414 patent as applied to a cleanroom. The '712 patent avoids
dumping the powdery precursor and teaches a method to replenish
copper ions in a plating solution with the apparatus depicted in
FIG. 1A. The anolyte flows from the top of canister 2, through a
porous cartridge 4 and into a hollow cavity 6 before flowing out
the bottom of canister 2. The cartridge 4 includes a filter element
that encompasses the powdery copper source. Therefore, the anolyte
flows through the canister 2 and is enriched by copper ions via
absorbing the copper source.
[0008] However, as illustrated in FIG. 1B, the anolyte can flow
into cartridge 4 and form different phases of anolyte/copper
source. The depleted anolyte 8 enters the cartridge 4 from above
and flows downwardly to form a suspension 9 of anolyte/copper
source. As the suspension 9 flows towards the bottom of the
cartridge 4, the suspension densifies, forming a viscous cake 10 at
the bottom of the cartridge 4. Throughout the formation of cake 10,
the flow of anolyte lessens and copper ions cease to be
consistently replenished in the anolyte. Therefore, longer plate
times reduce substrate throughput with this decrease of the copper
concentration. Also, in the case when copper hydroxide is used as a
copper source, the reduction in the hydroxyl ion addition lowers
the pH of the anolyte.
[0009] Therefore, there is a need for an apparatus and method to
replenish chemical compounds within an electrolyte solution in a
consistent and reliable manner.
SUMMARY OF THE INVENTION
[0010] In one embodiment, the invention generally provides an
apparatus for dispersing chemical reagents to a plating solution
including a tank for containing the plating solution and a
cartridge in fluid communication with the tank, wherein the
cartridge has an input and an output. The apparatus further
includes at least one shelf contained inside the cartridge. The at
least one shelf may be impermeable and may extend between the input
and the output such that the chemical reagent rests on the at least
one shelf.
[0011] In another embodiment, the invention generally provides an
apparatus for dispersing a chemical reagent to a plating solution
comprising a tank for containing the plating solution and a
vertical cartridge in fluid communication with the tank. A lower
portion of the vertical cartridge includes an inlet and an injector
port and an upper portion of the vertical cartridge includes an
outlet and a manifold. The chemical reagent is positioned between
the inlet and the outlet.
[0012] In another embodiment, the invention generally provides a
method for dispersing a chemical reagent to a plating solution
including flowing the plating solution from a tank through an input
of a cartridge, wherein the cartridge comprises a chemical reagent
disposed on at least one shelf. The plating solution flows across
the chemical reagent to enrich the plating solution with the
chemical reagent, whereas the chemical agent is dissolved or
suspended within the plating solution. The enriched plating
solution flows from the cartridge through an output to the
tank.
[0013] In another embodiment, the invention generally provides a
method for monitoring and controlling a pH setting of a plating
solution in a tank including determining a pH of the plating
solution with a pH meter, transferring an aliquot of the plating
solution to a vessel and pressurizing the vessel with a gas to
transfer the aliquot to a cartridge. The cartridge includes an
injector, a chemical reagent and a manifold. The aliquot passes
through the injector, which enriches the aliquot with a portion of
the chemical reagent and the enriched aliquot transfers through the
manifold to the plating solution in the tank. A second pH of the
plating solution is determined with the pH meter and compared with
the pH setting. Enriched aliquots are transferred repeatedly to the
plating solution until the second pH is equivalent to the pH
setting.
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] FIGS. 1A-B show a cartridge inside a canister as used in the
related art;
[0016] FIG. 2 shows a flow diagram for a two-sectional
electrochemical cell with catolyte and anolyte;
[0017] FIG. 3 shows a longitude sectional view of a cartridge with
horizontal shelves;
[0018] FIGS. 4A-C show cross-sectional views of cartridges with a
variety of shelves;
[0019] FIGS. 5A-C show cartridge placements into an anolyte
loop;
[0020] FIG. 6A shows a vertical sectional view of a cartridge with
a bottom injector;
[0021] FIG. 6B shows a fragmentary vertical sectional view of a
portion of the embodiment of FIG. 6A;
[0022] FIG. 7 shows a schematic diagram of a plating system
incorporating one embodiment of a cartridge with a bottom
injector;
[0023] FIG. 8 is a diagram illustrating the timing sequence of
valve operation during a plating process;
[0024] FIG. 9 shows another embodiment of a cartridge with a bottom
injector incorporated into a plating system; and
[0025] FIGS. 10A-B show embodiments of injector systems including
rotatable cups.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] The present invention comprises apparatuses and methods to
replenish chemical compounds in plating solutions in a consistent
and reliable manner. The present invention overcomes the
shortcomings of the related art as described in the background and
illustrated in FIG. 1, mainly, by not blocking anolyte flow with
cake formations. Therefore, by utilizing the various embodiments of
the apparatuses and methods of the present invention, each
substrate experiences more consistent plating times and anolyte
chemical concentrations.
[0027] Embodiments of the present invention are useful in a variety
of plating systems, including electroplating and electroless
plating systems. Further, various embodiments are also applicable
to electroplating with soluble anodes and with insoluble anodes.
FIG. 2 shows a schematic arrangement of an electroplating system
with a cell 11 containing an insoluble anode 12. The insoluble
anode 12 is made from relatively inert materials, such as platinum,
titanium, titanium with a Pt-coating, palladium, nickel, stainless
steel and/or carbon. The material of the insoluble anode 12 is
generally configured to withstand the various process conditions
involved while plating to a wafer or substrate 14. Process
conditions may have acidic or basic pH, oxidative/reductive
potentials and an assortment of chemical compounds throughout the
solution. In one embodiment, the insoluble anode 12 endures process
conditions such as acidic plating solutions and an oxidative
potential. The substrate 14 is attached to the cathode 13, usually
by a contact ring, pins, and the like (not pictured).
[0028] The insoluble anode 12 and the cathode 13 are separated by a
membrane 16 extending through cell 11. The membrane 16 is an
electroconductive membrane, such as an ion-exchange membrane,
nano-filtration membrane, ultra-filtration membrane and others
known in the art. The portion of the cell 11 containing the cathode
13 is in fluid communication with the catolyte tank 17 to
recirculate the catolyte within. The catolyte is a mixture of
compounds that may include, for copper plating, sulfuric copper
plating electrolyte or pyrophosphoric copper plating electrolyte. A
sulfuric copper plating electrolyte will generally include a
mixture of copper sulfate, sulfuric acid and various organic and
inorganic additives including suppressors, accelerators, levelers
and brighteners. Catolyte may pass through a diffuser 15 and be
more evenly distributed while flowing to the substrate 14.
[0029] The portion of the cell 11 containing the insoluble anode 12
is in fluid communication with the anolyte tank 18 and recirculates
the anolyte within. For copper plating, the anolyte is a solution
containing copper ions, often derived from dissolved copper salts,
such as copper sulfate. Other copper ion sources include copper
hydroxide, copper carbonate, copper oxide and copper phosphate.
[0030] Under copper plating electrolysis, the half reaction in
scheme (i) occurs on the insoluble anode 12:
H.sub.2O.fwdarw.2H.sup.++2e.sup.-+1/2O.sub.2(g), (i)
[0031] while Cu.sup.2+ ions migrate through the membrane 16 from
the anolyte to the catolyte and are reduced according to the half
reaction shown in scheme (ii):
Cu.sup.2++(SO.sub.4).sup.2-+2e-.fwdarw.Cu.sup.0+(SO.sub.4).sup.2-.
(ii)
[0032] The combined half reactions are represented in reaction
scheme (iii):
CuSO.sub.4+H.sub.2O.fwdarw.Cu.sup.0+H.sub.2SO.sub.4+1/2O.sub.2(g)
(iii)
[0033] Therefore, as the electroplating process proceeds, the
anolyte becomes depleted of copper ions due to the precipitation of
metallic copper as well as more acidic due to the production of
sulfuric acid. Also, water is consumed making the electrolyte more
concentrated.
[0034] The sulfuric acid formed in the anolyte penetrates through
the membrane 16 and contaminates the catolyte. The sulfuric acid
lowers the pH of the catolyte. More acidic catolyte is not
desirable because the membrane loses ion selectivity between
protons and copper ions. The lost of the membrane selectivity
permits protons to compete with copper ions while penetrating the
membrane, therefore, unbalancing the catolyte chemical
concentration. To prevent the lowering of the pH of the catolyte,
an alkaline compound is added. Copper hydroxide consists of a
copper ion source as well as a hydroxyl source and will neutralize
formed sulfuric acid, as shown by the reaction scheme (iv):
Cu.sup.2++2(OH).sup.-+H.sub.2SO.sub.4.fwdarw.CuSO.sub.4+2H.sub.2O.
(iv)
[0035] Therefore, schemes (iii) and (iv) are combined and the
proportional amount of copper hydroxide is added to the anolyte.
The summed reaction is depicted in scheme (v), namely copper is
consistently deposited while water and oxygen are formed as
byproducts, such as:
Cu(OH).sub.2.fwdarw.Cu.sup.0+H.sub.2O+1/2O.sub.2(g). (v)
[0036] FIG. 3 shows a longitudinal sectional view of an embodiment
of a cartridge system 20 including a cartridge 22 containing one
embodiment of shelves 24 of the invention. The shelves 24 are
vertically spaced apart and extend longitudinally between input 32
and output 34. The shelves 24 may number in a range from about 1 to
about 50, though preferably from about 2 to about 10. FIGS. 3 and
4A illustrate four horizontal substantially flat top shelves. The
cartridge 22 and the shelves 24 may be made from an assortment of
materials, such as plastics or metals, including stainless steel,
aluminum, titanium, nickel-coated steel and various alloys, amongst
others.
[0037] Chemical reagents 26 are distributed across each of the
shelves 24. The chemical reagents are exposed to plating solution
28 (depicted with arrows) flowing through the cartridge 22. The
plating solution 28 enters the cartridge at least partially
depleted of various chemical components, but is enriched by flowing
over the chemical reagents 26 contained within the cartridge 22.
The enriching process includes the dissolving and/or suspending of
chemical reagents 26 within the plating solution 28. The chemical
reagents 26 usually have a solid state of matter (e.g., powder,
pellets, crystalline), but could also be a viscous liquid or a
suspension. Therefore, enriched plating solution 29 emerges from
the output 34. A progressive and consistent transformation or
enrichment of the plating solution occurs as plating solution 28
flows across chemical reagents 26. In one example, the shelves 24
are impermeable to liquids (e.g., metal plate with no holes or no
porosity), so the plating solution 28 passes along and not through
the shelves 24. In another example, the shelves 24 are permeable to
liquids, such as ceramic or mesh, so the plating solution 28 passes
along and/or through the shelves 24.
[0038] Chemical reagents 26 are compounds or mixtures of compounds
selected for the process requirements of the plating solution.
Plating solutions include electroless plating solutions and
electroplating solutions, wherein the latter is usually the anolyte
or the catolyte. Electroplating systems are utilized to deposit
materials such as copper, zinc, cadmium, nickel and other metals.
In one preferred embodiment, the plating solution is an anolyte
within an electroplating system used to plate copper.
[0039] Chemical reagents 26 useful for copper ion replenishment in
a plating solution include copper hydroxide, copper oxide, copper
carbonate, copper sulfate and copper phosphate and combinations
thereof, preferably copper hydroxide. Generally, plating solutions,
enriched or depleted, have a copper ion concentration in a range
from about 5 g/L to about 70 g/L.
[0040] Chemical reagents 26 are also used to replenish plating
solutions of other depleted compounds and ions. In one embodiment,
chemical reagents are used to control the pH of the plating
solution. The pH of the solution can be raised or lowered by adding
a basic or acidic compound, respectively. Chemical reagents 26 for
replenishing hydroxyl ions to increase the pH include copper
hydroxide, ammonium salts, sodium hydroxide, potassium hydroxide,
lithium hydroxide, cesium hydroxide, magnesium hydroxide, calcium
hydroxide, amongst others, and combinations thereof. Therefore, in
one embodiment, copper hydroxide is used to replenish copper ions
and hydroxyl ions.
[0041] Porous material 25 is optionally placed at either or both
ends of the cartridge 22 and include porous plastics, metals,
ceramics, filters, frits, membranes, wool (e.g., glass or metal),
packed inert media (e.g., silica or alumina) and the like.
Generally, the porous material has pores that are penetrable for
enriched plating solution (suspensions), but prevents chemical
reagents 26 from uncontrollably passing through the cartridge 22.
The porous material has pores with a diameter in the range from
about 10 .mu.m to about 2,000 .mu.m.
[0042] FIGS. 4A-C show cross-sectional views of cartridge system 20
with a variety of geometries for cartridges and shelves. FIG. 4A
shows the four flat shelves 24 of FIG. 3 as described above. FIG.
4B shows shelves with longitudinal grooves 36. The grooves 36
further segregate the chemical reagents 26 into various rows
running along each shelf. FIG. 4C shows a cylindrical cartridge 37
containing tubular shelves 38. Tubular shelves 38 also hold
chemical reagents 26 in segregated rows. The shelves distribute
(i.e., provide more surface area) chemical reagents 26. Time
exposure between the plating solution and the chemical reagent
varies the degree of enrichment the plating solution endures.
Therefore, the flow of the plating solution through cartridge 22
varies in a range from about 0.5 L/min to about 10 L/min, depending
on the bath volume and performance.
[0043] The flow of the plating solution is maintained due to part
of headspace 30 provided above the top surface of the chemical
reagents 26. Generally, headspace 30 has a height in the range from
about 1 cm to about 50 cm, preferably from about 5 cm to about 30
cm. Headspace 30 changes throughout the process with respect to
time, since the chemical reagents 26 are consumed by the plating
solution and the height of headspace increases. Also, headspace 30
changes throughout the process with respect to certain segments
along the shelves. Besides consumption, chemical reagents 26 also
migrate and erode along the shelves.
[0044] In several examples, as depicted in FIGS. 5A-C, cartridge
system 20 is placed into anolyte loops with various configurations.
In one embodiment, FIG. 5A shows cartridge system 20 placed into a
single anolyte loop. As anolyte requires replenishment of chemical
reagents (e.g., Cu.sup.2+ or OH.sup.-), pump 120 draws depleted
anolyte from the anolyte tank 110. With control valve 130 open,
pump 120 pushes the depleted anolyte through cartridge system 20.
The anolyte emerges from the cartridge system 20 enriched with the
specific chemical reagents required for the plating process (e.g.,
Cu(OH).sub.2). Upon exiting the cartridge system 20, anolyte flows
to the electroplating cell 100, where the plating process
commences, forming depleted anolyte, which is transferred back to
the anolyte tank 110. This cycle resumes as the anolyte is
recirculated throughout the anolyte loop.
[0045] In another embodiment, FIG. 5B shows cartridge system 20
placed into an anolyte loop also including a bypass line. The
bypass line is useful when the anolyte is only partially depleted
of the necessary chemical reagents. Though depleted anolyte will
contain some essential chemical reagents, the concentration of the
reagents is too low and affects the plating process. However,
partially depleted anolyte is suited to be recirculated and used in
the electroplating process prior to being enriched by cartridge
system 20. Depleted or partially depleted anolyte is determined per
process parameters. As anolyte requires replenishment of chemical
reagents (e.g., Cu.sup.2+ or OH.sup.-), pump 120 draws depleted
anolyte from the anolyte tank 110. With control valve 130 open and
control valve 135 closed, pump 120 pushes the depleted anolyte
through cartridge system 20. The anolyte emerges from the cartridge
system 20 enriched with the specific chemical reagents required for
the plating process (e.g., Cu(OH).sub.2). Upon exiting the
cartridge system 20, anolyte flows to the electroplating cell 100.
However, with control valve 130 closed and control valve 135
opened, pump 120 pushes the partially depleted anolyte through a
bypass around the cartridge system 20 and directly to the
electroplating cell 100. Upon the commencement of the plating
process, depleted anolyte is transferred back to the anolyte tank
110. This cycle resumes as the anolyte is recirculated throughout
the anolyte loop.
[0046] The anolyte cycle system depicted in FIG. 5B has an
advantage over the system depicted in FIG. 5A due to the cartridge
bypass line, namely, more control of the supplemental chemical
reagent addition. Since the system of FIG. 5B has the bypass line,
anolyte is recirculated with the option to pass through cartridge
system 20. For any of the anolyte loops depicted in FIGS. 5A-C, the
capacity of anolyte tank 110 can be increased to slow the anolyte
dilution from the addition of depleted anolyte coming from cell
100.
[0047] The system depicted in FIG. 5C includes several anolyte
loops linked together via the anolyte tank 110. One loop includes
the electroplating cell 100 in fluid communication with the anolyte
tank 110. Pump 120 circulates the anolyte within this loop.
However, an auxiliary loop is also linked with the anolyte tank
110. The auxiliary loop includes the cartridge system 20 connected
to a control valve 134 and a pump 125. In one aspect, pump 125 is a
high-pressure pump. Also incorporated to the auxiliary loop is a
bypass line managed by control valve 132. Therefore in one aspect,
with control valve 134 opened and control valve 132 closed, anolyte
can be circulated between the anolyte tank 110 and cartridge system
20 to be enriched with chemical reagents, while the anolyte is
circulated between the anolyte tank 110 and the electroplating cell
100. In another aspect, control valve 134 is closed while control
valve 132 is opened and cartridge system 20 does not replenish the
supplemental chemical reagents to the system.
[0048] In another embodiment, FIGS. 6A-B show cartridge 40 as a
vertical vessel in which a lower portion of the interior of the
vessel expands upwardly to form an inverted conical bottom 42. The
cartridge 40 includes top 39 as a portion of housing 41, both made
from an assortment of materials, such as plastics or metals,
including stainless steel, aluminum, titanium, nickel-coated steel,
various alloys amongst others.
[0049] At the base of the conical bottom 42, an injector 43 is
positioned in a vertical arrangement. The conical bottom 42
collects the settling chemical reagents 26 by gravitational forces.
This settling process maintains the chemical reagents 26 in contact
with the injector 43. The injector has an input 45 that is in fluid
communication with the electroplating system. Depleted electrolyte
28 combined with or without gas (e.g., air) passes through the
input 45 and is introduced into the cartridge 40 through at least
one output 47 of injector 43. In one embodiment, there are multiple
outputs 47 in a single injector 43. The orifice that provides the
output 47 generally has a diameter in the range from about 0.1 mm
to about 1 mm. As depicted in FIG. 6B, outputs 47 are less than
normal (i.e., <90.degree.) relative to the plane of the axis of
the conical bottom 42. That is, the outputs 47 generally point
downward, towards the conical bottom 42 and extend through the
sides 48 of injector 43. However, in one embodiment (not shown),
the channels are normal or pointing upward, but have an optional
flap in order to keep chemical reagent from descending into the
outputs.
[0050] Plating solution or electrolyte is administered into the
cartridge 40 through the injector 43. Chemical reagents 26 are
disposed within the cartridge 40, so the electrolyte travels
through the chemical reagents 26 and into a headspace 49. An under
pressure (e.g., vacuum system) and/or an over pressure (e.g.,
compressed gas) is utilized to assist the migration of the
electrolyte through the cartridge 40. The electrolyte becomes
enriched with the chemical reagents 26, (i.e., dissolved or
suspended) while passing through the cartridge 40. The enriched
electrolyte 29 accumulates near or at the headspace 49, and then
proceeds to exit the cartridge 40 through the manifold 44. In one
embodiment, the headspace 49 has enriched anolyte 29 as well as
accumulated gas 46 or air. The accumulated gas 46 is bled from the
headspace prior or during the flow of enriched anolyte 29. In
another embodiment, a porous material (not shown), such as sponges,
porous plastics, metals, ceramics, filters, frits, membranes, wool
(e.g., glass or metal), packed inert media (e.g., silica or
alumina) and the alike is displaced below the manifold 44 to
inhibit any large particulate of chemical reagents 26 from leaving
the cartridge 40.
[0051] In another embodiment, FIG. 7 shows a plating system 50 that
includes a cartridge 40 of the invention. The enriched electrolyte
29 is added to anolyte tank 52, which is in fluid communication
with an electroplating cell 56 and pump 58 within an anolyte loop.
Anolyte is depleted of reagent chemical (e.g., CU.sup.2+ and
OH.sup.-) during the plating process within the electroplating cell
56. Pump 58 drives the circulation of depleted anolyte to the
anolyte tank 52 and enriched anolyte from the anolyte tank 52 to
the electroplating cell 56.
[0052] A pH controller 54, pH sensor 57 and a computer 55 monitor
and regulate the pH of the anolyte within the anolyte tank 52. A pH
controller may be selected from a variety of commercially available
models, such as dTRANSpH 01 from JUMO Process Control Inc., DP24-E
Process Meter from Omega, EMIT-pH from Pathfinder Instruments, and
LED pH/ORP indicator/controller from Kemko Instruments. In one
embodiment, the pH is maintained in the range from about 1.0 to
about 5.0, preferably, from about 2.0 to about 4.0 and more
preferably from about 2.8 to about 3.0. In another embodiment, the
pH is maintained at less than 3.4 to prevent chemical precipitants
(e.g., copper hydroxide) from forming and clouding the anolyte.
[0053] As the pH of the anolyte becomes too low, an aliquot of the
anolyte is transferred from anolyte tank 52 to canister 53 via
three-way valve 60. Generally, three-way valve 61 is positioned to
pressurize anolyte tank 52 with compressed gas (e.g., air) and
three-way valve 60 is positioned as to accept the aliquot from the
anolyte tank 52 to the canister 53. Once the aliquot is
transferred, then both valves 60 and 61 are turned off.
Subsequently, three way valve 61 is positioned to pressurize the
canister 53 containing the aliquot of the anolyte while three-way
valve 60 is positioned to permit the flow of the aliquot into the
cartridge 40 via the injector 43. The enriched anolyte emerges from
the cartridge 40 via the manifold 44 and into the anolyte tank 52.
As the enriched anolyte combines with the depleted anolyte, acidic
protons are neutralized by the incoming hydroxyl ions and copper
ions become more concentrated. In practice, the concentration of
the anolyte will not vary much since control of the replenishment
is occurring real time. That is, when valves 60 and 61 are timed
and positioned correctly, the anolyte will reach a relatively
constant pH with minimal flux (e.g., about 0.5 pH units). The
compressed gas is delivered from a source 62, such as a tank or an
in-house line and may include air, N.sub.2, Ar, He, H.sub.2 and
combinations thereof.
[0054] FIG. 8 is a diagram illustrating a timing sequence of valves
60 and 61 during an electroplating process useful in the plating
system 50 depicted in FIG. 7. The timing of valves 60 and 61 is
controlled by the pH controller 54 in combination with a computer
55. The valves 60 and 61 change positions every second or so and
remain synchronized as described above. When the pH of the anolyte
drops to a lower limit (LL), the compressed gas (e.g., air) moves
the electrolyte from canister 53 into cartridge 40. The time
t.sub.1 is slightly longer (e.g., about a second) than that
required to push all of the anolyte from canister 53, so that a
small amount of air also penetrates in to the cartridge 40. The air
provides a thorough mixing of the chemical reagents with the
anolyte and enriches the suspension (e.g., copper hydroxide) near
the top of the cartridge 40 within headspace 49. This thorough
mixing with the air and the conical shape of the bottom of the
cartridge prevents cake formation. During time t.sub.2, compressed
air is stopped by closing valve 61 and canister 53 is refilled with
anolyte through valve 60. During t.sub.3, the anolyte is injected
into cartridge 40 with the timing quick enough to prevent
penetration of air into the canister 53, about a second. Canister
53 is refilled with anolyte that is subsequently injected into the
cartridge 40. Thereafter, an enriched anolyte is transferred from
the cartridge 40 to the anolyte tank 52. This cycle continues until
the pH reaches a higher limit (HL), then ceases until the pH of the
anolyte within the anolyte tank reaches the LL. The overall
sequence repeats during the electroplating process.
[0055] In another embodiment, FIG. 9 shows a plating system 70 that
includes a cartridge 40. The enriched electrolyte 29 is added to
anolyte tank 52, which is in fluid communication with an
electroplating cell 56 and pump 58 within an anolyte loop. Anolyte
is depleted of reagent chemical (e.g., Cu.sup.2+ and OH.sup.-)
during the plating process within the electroplating cell 56. Pump
58 drives the circulation of depleted anolyte to the anolyte tank
52 and enriched anolyte from the anolyte tank 52 to the
electroplating cell 56. The depleted anolyte is temporally
contained within a section 71 of the anolyte tank 52. Section 71 is
separated by partition 80 and will gather depleted anolyte as well
as enriched anolyte, before flowing over into the main compartment
of anolyte tank 52.
[0056] A pH controller 54, pH sensor 57 and a computer 55 monitors
and regulates the pH of the anolyte within section 71. In one
embodiment, the pH is maintained in the range from about 1.0 to
about 5.0, preferably, from about 2.0 to about 4.0 and more
preferably from about 2.8 to about 3.0. In another embodiment, the
pH is maintained at less than 3.4 to prevent chemical precipitants
(e.g., copper hydroxide) from forming and clouding the anolyte.
[0057] As the pH of the anolyte becomes too low, an aliquot of the
anolyte is transferred from anolyte tank 52 to canister 53 via
two-way valve 76. Pump 58 helps push the anolyte to canister 53.
Once the aliquot is transferred, then two-way valve 72 is
positioned to pressurize the canister 53 containing the aliquot of
the anolyte while two-way valve 78 is positioned to permit the flow
of the aliquot into the cartridge 40. The enriched anolyte flows
from the cartridge 40 to section 71 of the anolyte tank 52. As the
enriched anolyte combines with the depleted anolyte, acidic protons
are neutralized by the incoming hydroxyl ions and copper ions
become more concentrated. Two-way valve 74 is positioned open and
gas flow agitates the enriched anolyte with the depleted with the
flow of gas. In practice, the concentration of the anolyte will not
vary much since the replenishment is occurring in real time. That
is, when valves 72, 74, 76 and 78 are timed and positioned
correctly, the anolyte will reach a relatively constant pH with
minimal flux (e.g., about 0.5 pH units). The compressed gas is
delivered from a source 62, such as a tank or an in-house line and
may include air, N.sub.2, Ar, He, H.sub.2 and combinations
thereof.
[0058] In one embodiment depicted in FIG. 10A, injector system 82
includes an injector 84 with output holes 85 and a cup 86 with
output holes 87. Cup 86 is rotatable as to line-up the output holes
85 with output holes 87. Once lined-up, anolyte will pass through
holes 85 and 87 and into the cartridge. To remove cartridge 40,
output holes 85 and 87 are misaligned to turn off the excess of
chemical reagents 26 from escaping the cartridge 40. FIG. 10A
illustrates cup 86 disposed within the injector 84, while in
another embodiment, FIG. 10B shows an injector 94 disposed within a
cup 96 as part of injector system 92. Also, injector 94 contains
output holes 95 and cup 96 contains output holes 97. The output
holes 85 and 87 generally point horizontal while the output holes
95 and 97 point in a downwardly direction.
[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.
* * * * *