U.S. patent application number 11/183419 was filed with the patent office on 2005-11-10 for method of plating.
Invention is credited to Akram, Salman, Hembree, David R..
Application Number | 20050247567 11/183419 |
Document ID | / |
Family ID | 31887615 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050247567 |
Kind Code |
A1 |
Akram, Salman ; et
al. |
November 10, 2005 |
Method of plating
Abstract
An apparatus and method for treating a substrate to deposit,
clean or etch material on a substrate use a first horizontal chuck
to which a plurality of substrates is attached and electrically
charged. Spaced closely to the first horizontal chuck is a
coextensive horizontal second chuck which receives and showers
reaction solution over all portions of each substrate. During the
reaction process, both chucks are substantially submerged in
reaction solution within a tank. At least one of the chucks is
attached and controllable from a control arm. At least one of the
chucks is rotated about a vertical axis at a slow speed during the
reaction process. The axes of rotation of the two chucks may be
coincident, or the axes may be offset from each other, and/or one
or both axes may be offset from the chuck centerpoint(s). One of
the chucks may also be periodically moved in a vertical direction
relative to the other chuck.
Inventors: |
Akram, Salman; (Boise,
ID) ; Hembree, David R.; (Boise, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
31887615 |
Appl. No.: |
11/183419 |
Filed: |
July 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11183419 |
Jul 15, 2005 |
|
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10228505 |
Aug 26, 2002 |
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Current U.S.
Class: |
205/145 ;
205/147 |
Current CPC
Class: |
H01L 21/67051 20130101;
H01L 21/67057 20130101; C25D 5/08 20130101; C25F 7/00 20130101;
C25D 17/001 20130101; H01L 21/67086 20130101; H01L 21/6708
20130101 |
Class at
Publication: |
205/145 ;
205/147 |
International
Class: |
C25D 005/00 |
Claims
What is claimed is:
1. A method for simultaneously depositing a material onto at least
one surface of a substrate of a plurality of substrates,
comprising: forming a deposition solution; placing said deposition
solution in a tank; attaching a plurality of substrates onto a
substantially horizontal surface of a first chuck; submerging said
first chuck in said deposition solution in said tank; submerging a
second chuck comprising a shower head in said deposition solution
in said tank for horizontally orienting at least one substrate of
said plurality of substrates parallel to said shower head and
spaced therefrom; applying a cathodic charge to at least one
substrate of said plurality of substrates and an anodic charge to
said shower head; and showering said substrates with said
deposition solution from said shower head.
2. The method in accordance with claim 1, further comprising
rotating at least one of the first chuck and the second chuck.
3. The method in accordance with claim 1, wherein one of the first
chuck and the second chuck includes a chuck rotated at a speed in
the range of from about 0.1 rpm to about 5 rpm.
4. The method in accordance with claim 1, wherein one of the first
chuck and the second chuck includes a chuck rotated at a speed in
the range of from about 0.2 rpm to about 3 rpm.
5. The method in accordance with claim 1, wherein both of the first
chuck and the second chuck includes a plurality of chucks rotated
at speeds wherein a difference in speeds is in the range of from
about 0.1 rpm to about 5 rpm.
6. The method in accordance with claim 1, wherein both of the first
chuck and the second chuck includes a plurality of chucks rotated
at speeds wherein a difference is speeds is in the range of from
about 0.2 rpm to about 3 rpm.
7. The method in accordance with claim 1, wherein the first chuck
includes a chuck rotated in a first direction and the second chuck
includes a chuck rotated in a second, opposite direction.
8. The method in accordance with claim 1, wherein all of the
plurality of substrates are equally negatively charged.
9. The method in accordance with claim 1, wherein one or more
substrates of the plurality of substrates include at least one
substrate unequally negatively charged from another substrate of
the plurality of substrates.
10. A method for simultaneously removing a material from at least a
portion of at least one surface of a substrate of a plurality of
substrates in a solution in a tank, comprising: attaching a
plurality of substrates onto a substantially horizontal surface of
a first chuck; submerging the first chuck in the solution in the
tank; submerging a second chuck comprising a shower head in the
solution in the tank for horizontally orienting at least one
substrate of the plurality of substrates parallel to the shower
head and spaced therefrom; applying a charge to the at least one
substrate of the plurality of substrates and another charge to the
shower head; and showering the substrates with the solution from
the shower head.
11. The method in accordance with claim 10, further comprising
rotating at least one of the first chuck and the second chuck.
12. The method in accordance with claim 10, wherein one of the
first chuck and the second chuck includes a chuck rotated at a
speed in the range of from about 0.1 rpm to about 5 rpm.
13. The method in accordance with claim 10, wherein one of the
first chuck and the second chuck includes a chuck rotated at a
speed in the range of from about 0.2 rpm to about 3 rpm.
14. The method in accordance with claim 10, wherein both of the
first chuck and the second chuck include a plurality of chucks
rotated at speeds wherein the difference in speeds is in the range
of from about 0.1 rpm to about 5 rpm.
15. The method in accordance with claim 10, wherein both of the
first chuck and the second chuck include a plurality of chucks
rotated at speeds wherein the difference is speeds is in the range
of from about 0.2 rpm to about 3 rpm.
16. The method in accordance with claim 10, wherein the first chuck
includes a chuck rotated in a first direction and the second chuck
includes a chuck rotated in a second, opposite direction.
17. The method in accordance with claim 10, wherein all of the
plurality of substrates are equally charged.
18. The method in accordance with claim 10, wherein one or more
substrates of the plurality of substrates includes at least one
substrate unequally charged from another substrate of the plurality
of substrates.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of application Ser. No.
10/228,505, filed Aug. 26, 2002, pending.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to apparatus and
methods for inducing an electrochemical, chemical and/or mechanical
reaction on an article. More particularly, the invention pertains
to methods and apparatus for treating substrates including
electrodeposition of material thereonto, such as through anodizing,
etching, polishing, and cleaning.
[0004] 2. State of the Art
[0005] Semiconductor wafers, substrates and printed circuit boards
(collectively hereinafter "semiconductor substrates") are often
coated with various materials, such as metals which are etched in
later semiconductor fabrication processes to form components on the
semiconductor substrates. Techniques for coating semiconductor
substrates include electrodeposition, electron beam evaporator
deposition, chemical vapor deposition, sputter deposition,
electroless plating and the like. Electrodeposition has become a
commonly used technology.
[0006] Electrodeposition or electrolytic deposition is a process
which deposits a thin film of material, such as metal or metal
alloy, on an article. In electrodeposition, as shown in prior art
FIG. 1, an article 10 is placed in a tank 12 containing an
appropriate deposition solution, such as an electrolyte solution
14, which contains ions 16 of a metal to be deposited on the
article 10. The article 10 forms a cathode or is in electrical
contact with a cathode 18 which is immersed in the electrolyte
solution 14. The cathode 18 is connected to a negative terminal 20
of a power supply 22. A suitable anode 24 is also immersed in the
electrolyte solution 14 and connected to a positive terminal 26 of
the power supply 22. The electrical current causes an
electrochemical reaction at the surface of the article 10 which
results in the metal ions 16 in the electrolyte solution 14 being
deposited on the article 10.
[0007] With semiconductor devices, it is generally desirable to
deposit the metal film with a uniform thickness across the article
and with uniformity of composition of the metal(s) and/or other
compounds forming the metal film. However, the electrodeposition
process is relatively complex and various naturally occurring
forces may result in a degradation in the electrodeposition
process. The electrical current or flux path between the anode and
the cathode should be uniform without undesirable spreading or
curving to ensure uniform deposition. Additionally, since the metal
ions in the deposition solution are deposited on the article, the
deposition solution becomes depleted of metal ions, which degrades
the electrodeposition process. Therefore, suitable controls are
required to introduce metal ions into the deposition solution in
order to maintain consistency.
[0008] U.S. Pat. No. 5,516,412 to Andricacos et al. relates to an
electrodeposition cell having a rack for vertically supporting a
silicon substrate to be electrodeposited. An opposing wall of the
cell comprises an anode. A paddle is disposed within the cell for
agitating an electrolytic solution within the cell to maintain a
uniform distribution of deposition material within the electrolyte
solution. Furthermore, Andricacos et al. teaches that the rack can
be designed to be removable for automated handling. Although
Andricacos et al. addresses the control issues discussed above, the
rack assembly disclosed is not conducive to high-volume
manufacturing. Furthermore, Andricacos et al. does not describe,
teach, or suggest any means for improving the deposition on the
silicon substrate by the movement of either the anode or
cathode.
[0009] U.S. Pat. No. 3,798,056 to Okinaka et al. discloses a
rotating substrate holder having substrates mounted vertically
about a vertical shaft. Periodic reversal of rotation is disclosed.
The system relates to electroless autocatalytic plating and is
unrelated to electrodeposition.
[0010] U.S. Pat. No. 3,915,832 to Rackus et al. shows apparatus for
mounting and electroplating lead frames to obtain greater plate
thicknesses at the lead frame ends. Lead frames are mounted
radially about a tubular cathodic member which is rotated about a
vertical axis while an electrolytic solution is induced to flow
downwardly past the rotating mount. There is no positive control
over solution movement at the lead frame surfaces.
[0011] U.S. Pat. No. 4,855,020 to Sirbola describes the
electroplating of computer memory disks wherein disks are mounted
on a horizontal spindle and rotated in an electrolyte bath.
Coplanar anodes are spaced from each side of the disk and are
coplanar to only a portion of the disk.
[0012] U.S. Pat. No. 5,472,592 to Lowery shows an electrolytic
plating apparatus having a rotatable vertical shaft carrying a set
of anodes. Attached to the vertical shaft is an arm about which a
vertical wheel is rotated by contact with a track in the tank
floor. A substrate is mounted in a vertical configuration to the
wheel and is rotated by wheel rotation as the wheel travels about
the vertical shaft. Virtually no control of electrolyte uniformity
is exercised.
[0013] In U.S. Pat. No. 5,421,987 to Tzanavaras et al., an
electroplating cell includes a horizontally rotatable anodic spray
head. Electrolyte is sprayed through an intervening collimating
ring onto a stationary substrate to create high turbulence at the
surface. The spray head is shown with three diametrical rows of
spray nozzles which cover less than the entire substrate at any
time. Depending upon the location of a die in the substrate, each
die may receive either one, two, or six pulses of electrolyte. To
compensate, the nozzles are of differing spray design and flow
rate. The limited numbers of nozzles are varied. Although not
shown, it is stated that the substrate may alternatively be
rotated.
[0014] Systems which are used for electrodeposition may also be
used for electropolishing, electroetching, and the like. For
example, U.S. Pat. No. 5,096,550 to Mayer et al. teaches attaching
an article to a rotating anode positioned horizontally facedown in
a polishing or etching bath. However, Mayer et al. teaches only the
motion of the cathode and, since the articles are attached and
treated one at a time in the anode, the apparatus of the Mayer et
al. is not conducive to high-volume manufacturing.
[0015] In most electrodeposition techniques, the wafers are
attached to the cathode. The attachment of wafers to the cathode
can lead to significant problems, especially as the wafer
quantities are increased within a single batch, control of the
thickness of plated material may vary from semiconductor die to
semiconductor die being manufactured on any wafer. This problem
results from nonuniformity of metal ions and current density in the
electrolyte solution adjacent the wafer surface.
[0016] It is desirable to provide highly uniform thickness and
composition of deposition material on an electrodeposited article
or to uniformly polish or etch an article. Furthermore, it is also
desirable to do so in an apparatus capable of high-volume
manufacturing, preferably using automated handling equipment.
BRIEF SUMMARY OF THE INVENTION
[0017] In one embodiment, the apparatus of the present invention
may comprise a housing tank containing a reaction solution, such as
a deposition solution (e.g., an electrolyte solution). A first
chuck may be submerged in the housing tank, and articles having
surfaces to be treated are mounted on the first chuck. Article
surfaces are subjected to multiple vertical flows of reaction
solution projected in a generally normal direction to the article
surfaces. The articles may be, for example, a plurality of
semiconductor wafers, other substrates, or any articles which may
be attached to the first chuck for treatment. For articles with
generally planar surfaces to be treated, e.g., semiconductor
wafers, substrates and printed circuit boards, etc., the surfaces
are maintained by the first chuck in a substantially horizontal
position when compared to a substantially vertical position.
[0018] A second chuck with a generally planar front surface
comprises a "shower head" and contains a large number of orifices
located in, located on, or located by extending through a planar
web through which the reaction solution is showered onto the
closely spaced first chuck to intimately contact and treat the
articles mounted thereon. The planar web is generally parallel to
the substrate surfaces and is closely spaced therefrom. One or both
of the first and second chucks is/are rotated about a vertical axis
to create a relative velocity therebetween. This movement achieves
continuous, substantially complete coverage and movement of a
uniform concentration of reaction solution over each microportion
of each article on the first chuck. The chuck rotation also serves
to mix the tank contents, and blades may be attached to the
periphery of one or both chucks to enhance such mixing.
[0019] The first chuck may be positioned either below or above the
second chuck, depending upon (a) the particular application, i.e.,
electrodeposition, electroetching, electropolishing, or the like,
and (b) article topography, as well as other factors. The chucks
are closely positioned to provide the desired forced flow over the
article surfaces and rapid exit of reaction solution from the chuck
(and substrate) surfaces.
[0020] At least one of the chucks is configured to be rotated at a
relatively low speed. Such rotation mixes the reaction solution
within the housing tank to ensure uniformity. Small mixing blades
may be attached to the periphery of the rotatable chuck(s) if
desired to enhance the mixing level. The differential rotation
between the chucks also ensures that the moving sprays of solution
impinge on each microportion of all of the articles. If desired,
the direction of rotation may be reversed during the deposition
period to change the direction of solution impingement on the
substrates. In addition, chuck movement may include axial movement
to periodically widen and narrow the web-to-substrate distance.
This movement may be conducted at a high frequency by attaching an
ultrasonic device to the second chuck to enhance intimate contact
of the reaction solution with the substrates. Ultrasonic movement
may be controlled to be particularly useful in electrodeposition,
etching, polishing, and the like.
[0021] For use in electrodeposition, i.e., electroplating, the
first chuck includes conductors for connecting the attached
articles to a cathode of a power supply. The voltage and/or current
may be separately controlled for each article to achieve the
desired deposited thickness. The second chuck includes metal
electrodes in or on the second chuck. The metal electrodes are
connected to an anode of a power supply to provide contact of the
flowing reaction solution with a positively charged surface.
[0022] For use in etching or polishing, the anodic and cathodic
members may be reversed in charge. Simple etching, cleaning and
polishing may be conducted by not using, or removing, the anodic
and cathodic members from the apparatus.
[0023] The apparatus enables treatment of substrates in a
horizontal configuration or orientation with respect to a vertical
orientation wherein all substrate surfaces to be treated are fully
submerged in freshly introduced reaction solution of substantially
uniform composition for achieving uniform treatment both between
different substrates as well as differing portions of each
substrate or the same substrate.
[0024] The invention will become apparent and understood from a
reading of the description of the invention when taken in
conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0025] The invention is illustrated in the following figures,
wherein:
[0026] FIG. 1 is a general cross-sectional side view of a prior art
electrodeposition apparatus;
[0027] FIG. 2 is a general isometric cross-sectional view of an
electrodeposition apparatus in accordance with the present
invention;
[0028] FIG. 3 is a plan view of an exemplary mounting surface of a
substrate-retaining cathodic chuck of the present invention;
[0029] FIG. 4 is a cutaway plan view of an exemplary shower head
chuck of an electrodeposition apparatus in accordance with the
present invention;
[0030] FIG. 5 is a cross-sectional side view of a portion of a
shower head chuck of an electrodeposition apparatus in accordance
with the present invention, as taken along line 5-5 of FIG. 4;
[0031] FIG. 6 is an enlargement of an exemplary mounting surface of
a shower head chuck of an electrodeposition apparatus of the
present invention, in accordance with portion 6 of FIG. 4;
[0032] FIG. 7 is a cross-sectional side view of a portion of
another embodiment of a shower head chuck of an electrodeposition
apparatus in accordance with the present invention, as taken along
line 5-5 of FIG. 4;
[0033] FIG. 8 is a simplified cross-sectional side view of an
electrodeposition apparatus having a rotating spray head chuck in
accordance with the present invention;
[0034] FIG. 9 is a simplified cross-sectional side view of another
embodiment of an electrodeposition apparatus having a rotating
substrate-retaining chuck in accordance with the present
invention;
[0035] FIG. 10 is a simplified cross-sectional side view of a
further embodiment of an electrodeposition apparatus having a
rotating substrate-retaining chuck and a rotating shower head chuck
in accordance with the present invention;
[0036] FIG. 11 is a simplified cross-sectional side view of an
additional embodiment of an electrodeposition apparatus having an
upper rotating substrate-retaining chuck and a nonrotating lower
shower head chuck, in accordance with the invention;
[0037] FIG. 12 is a simplified cross-sectional side view of a
further embodiment of an electrodeposition apparatus in accordance
with the invention;
[0038] FIG. 13 is a simplified partially cross-sectional side view
of another embodiment of an electrodeposition apparatus in
accordance with the invention;
[0039] FIG. 14 is a schematic front view of a production line for
making electronic devices on semiconductor wafers in a
semicontinuous line with an electrodeposition apparatus of the
invention;
[0040] FIG. 15 is a schematic plan view of a second chuck overlying
a first chuck of an electrodeposition apparatus of the invention in
a first mode;
[0041] FIG. 16 is a schematic plan view of a second chuck overlying
a first chuck of an electrodeposition apparatus of the invention in
a second mode;
[0042] FIG. 17 is a schematic plan view of a second chuck overlying
a first chuck of an electrodeposition apparatus of the invention in
a third mode; and
[0043] FIG. 18 is an isometric view of a rotatable chuck of an
electrodeposition apparatus configured to enhance bulk mixing in a
reaction tank in accordance with the invention.
BRIEF DESCRIPTION OF THE INVENTION
[0044] The apparatus of the present invention is so constructed
that a plurality of substrates such as semiconductor wafers,
substrates and printed circuit boards, etc. may be simultaneously
electroplated to achieve a highly uniform applied material
thickness.
[0045] Although the present invention may be used for
electrodeposition, etching or polishing, the following description
describes the electrodeposition of material onto a substrate. The
apparatus and method of the invention are exemplified in the
plating of a metal onto conductors of an interconnected plurality
of semiconductor dice being or having been formed on one or more
semiconductor wafers. From the following description, it will be
understood that one skilled in the art may apply the description of
the invention to etching, polishing, and the like for semiconductor
wafers, substrates, printed circuit boards, etc. and the like.
[0046] Illustrated in drawing FIG. 2 is an exemplary
electrodeposition apparatus 100 of the invention. The apparatus 100
comprises a housing tank 102 for retaining a reaction solution 108
such as an electroplating solution. The housing tank 102 is
preferably formed of a nonconductive material which does not react
with the reaction solution 108, such as poly(methyl-methacrylate)
or polypropylene, for example. The housing tank 102 preferably has
an open top 106 through which electrodeposition equipment may be
inserted and removed. The reaction solution 108 in housing tank 102
may be controlled at a desired level 118.
[0047] As shown in drawing FIG. 2, a first chuck 110 with a
horizontal planar surface 112 is adapted for holding a plurality of
substrates 120, shown here as semiconductor wafers. In this
embodiment, the first chuck 110 is supported by a vertically
oriented shaft 114 which is attached to the tank bottom 104 or
passes through a bearing seal 116 in the tank bottom for rotation
by a lower drive unit 126 (see FIG. 9, for example). The shaft 114
is hollow and contains conductors 122 which connect each substrate
120 to a cathode 124 of a controllable power supply 132 to place a
controlled negative electric charge on each substrate. The first
chuck 110 is shown as generally circular in plan view, but may have
other shapes, e.g., square, hexagonal, etc., and may optionally be
perforated to permit fluid flow from its mounting surface 112 to
its back side 113. Preferably, the first chuck 110 is circular.
Where the substrates are of other shapes, the first chuck 110 may
be of any useful shape, even reticulated. The substrate-retaining
chuck 110 may comprise an anode, or the first chuck 110 and shaft
114 may be formed of a nonconductive material, or insulated to
prevent their participation in the electrolytic reactions. In this
variant, a positive charge may be placed on the substrates 120 via
conductors 122. The charge voltages and currents may be controlled
individually for each substrate 120 for achieving differing
deposition thicknesses. The charge on an individual substrate 120
may be controlled to avoid deposition altogether.
[0048] A second chuck 130 is shown in drawing FIG. 2 as a shower
head with a hollow core 140 and a substantially planar spray web
136 with a large number of flow orifices 138 leading from the
hollow core 140 to the exterior of second chuck 130. The size of
the second chuck 130 is such that its spray pattern will completely
uniformly cover the substrates 120 mounted on the first chuck 110
with a continuous flow of reaction solution 108. The second chuck
130 is attached to a hollow drive shaft 150 which is shown
suspended from a drive 128 which may be controlled to rotate the
drive shaft 150 about upper axis of rotation 172. The drive 128 is
motivated by motor 145 and is, in turn, mounted on a control arm
146 for aligning and maintaining the second chuck 130 at a desired
position in the horizontal X axis and Y axis as well as the
vertical Z axis and to maintain a specific web-to-substrate spacing
148 (see FIG. 8). One or more conductors 152 are connected between
an anode 134 of controllable power supply 132 or another power
supply and pass through hollow drive shaft 150 to contact a portion
of the second chuck 130 to form and maintain a positive charge
thereon. Where a shaft(s) is to be rotated, the electric
conductor(s) will include brush sets, not shown, or other devices
as known in the art, for making electrical connection to portions
of the attached chuck(s). The flow orifices 138 may be suitable
flow nozzles located on surface 137 of the second chuck 130, or in
recesses in the surface 137 of the second chuck 130 (see FIG.
4).
[0049] It is important that at least one of the first chuck 110 and
the second chuck 130 be rotated substantially continuously during
the electrodeposition period. The spacing 148 between the planar
spray web 136 and substrates 120 should be sufficiently limited to
increase the solution velocity over the substrates. In depositing
materials on semiconductor wafers, substrates, printed circuit
boards, and the like, the substrates 120 should not be exposed to
the bulk liquid in the housing tank 102, inasmuch as the bulk
liquid will, in general, have a slightly lower titer than the
incoming reaction solution 108, even if the latter is not augmented
to increase its titer. Thus, the ionic solution strength in contact
with the substrates 120 is maintained at a high level, maximizing
the deposition rate and providing a high level of uniformity in
deposition depth. The spacing 148 between the planar spray web 136
and substrates 120 may generally vary from about 1 mm to about 10
mm. For most purposes, the first 110 and second 130 chucks are
maintained in a submerged position during the particular treatment
process.
[0050] The rotation rate required to achieve high uniformity in
electrodeposition is very low when compared to existing apparatus.
A rotation rate may vary from about 0.1 to about 3 rpm, or somewhat
higher. The net rotation velocity may be achieved by rotating the
first chuck 110, rotating the second chuck 130, or rotating both
chucks 110 and 130 to achieve a differential velocity. For example,
the two chucks may be counter-rotated (relative to each other) at
slow speeds, wherein the net differential velocity is the total of
the two rotative velocities relative to the housing tank 102.
[0051] As depicted in drawing FIG. 2, reaction solution 108 may be
recirculated through the electrodeposition housing tank 102, where
solution is passed through drain 154 to a pump 156, which
recirculates the solution via tube 162 to a rotating fitting 158 on
hollow drive shaft 150. The recirculated reaction solution 108
passes through the hollow drive shaft 150 to supply the shower head
of the second chuck 130 with recirculated reaction solution 108.
Typically, the depleted reaction solution 108 draining from the
housing tank 102 may be filtered to remove solids, such as by
filter 160, as known in the art. Fresh materials may also be fed to
the recirculated solution to replenish materials lost by deposition
onto the substrates 120. Apparatus for replenishing the titer of
depleted solutions is well known in the art and will not be further
discussed here.
[0052] Turning now to drawing FIG. 3, depicted is an example of a
first chuck 110 specifically configured for electrodeposition on
substrates 120 comprising multi-chip. semiconductor wafers. The
first chuck 110 may be of any desirable size to accommodate, for
example, a substantial number of wafers 120. For example, all
wafers 120 originating from a specific boule may be processed
together as a batch. As shown in drawing FIG. 3, seven wafers of
the same general size are affixed to the surface 112 of first chuck
110 by clips 164. The clips 164 may also serve as electrical
connectors to place a charge on the substrates 120. Each substrate
120 (wafer) may be electrically biased individually to achieve a
desired deposition thickness. The configuration of the first chuck
110 may vary widely but will, in general, retain a plurality of
substrates in the shower stream from the second chuck 130. It may
be noted that substrates 120 may be attached to a first chuck 110
by any suitable attachment device. For example, wafers may be
attached with clips as shown, with clamp rings which are tightened
or with other devices as known in the art.
[0053] Illustrated in drawing FIGS. 4 and 5 is the discharge end
144 of an exemplary second chuck 130 with a cutaway view of the
spray web 136. The second chuck 130 is shown with a body 176 which
includes a peripheral ring 177 surrounding a solid plate 178. Drive
shaft 150 is centrally joined to the solid plate 178 about axis
172. The space between the body 176 and the spray web 136 comprises
the hollow core 140. Pumped reaction solution, not shown, passes
into the hollow core 140 from the hollow drive shaft opening 151
and passes to each orifice 138 for discharge onto the substrates
and nonsubstrate portions of the first chuck 110. In this version,
the spray web 136 contains a large number of closely spaced flow
orifices 138 in a regular pattern substantially covering its
generally planar exit surface 137. As shown in drawing FIG. 6, the
spacing 139 between the orifices 138 in the X and Y axes on the
surface 137 of the second chuck 130 approximately corresponds to
the spacing of plurality of dice 170 (FIG. 3) on any substrate 120
of the plurality of substrates 120, but may vary, as long as a
uniform flow of reaction solution 108 floods all portions of the
substrate in a uniform manner. In general, the spacing between
orifices 138 in a regular pattern may vary from about 3 to 35 mm,
and preferably about 3 to about 25 mm. Instead of orifices 138
formed in the web, multiple spray nozzles may be used as known in
the art located on surface 137 or within recesses within surface
137. However, conventional nozzles typically have a spray pattern
which may be uneven in coverage. In addition, the typical diameter
of spray nozzles is many times the diameter of the nozzle opening
and may severely restrict the number and spacing of nozzles which
may be fixed to a shower-producing surface, i.e., the spray
web.
[0054] Referring again to drawing FIGS. 4 and 5, an electrical
charge may be provided to the second chuck 130 in various ways. As
shown, conductive (e.g., metal) members 166 may be attached within
the hollow core 140. Illustrated in drawing FIG. 4 is a plurality
of electrically chargeable members 159 in the shape of sectors of a
pie surrounding the opening of the hollow drive shaft 150. These
members 159 may be charged by connection of each connector 168 to a
single conductor 152 (as shown), or each member 159 may be
individually charged as desired by connection to a separate
conductor 152.
[0055] In another embodiment illustrated in drawing FIG. 7, the
spray web 136 may comprise a conductive material which is connected
by conductor 152 to an anode 134 (not shown in this figure) whereby
the web becomes positively charged. The conductor 152 passes
through the hollow drive shaft opening 151 of drive shaft 150.
[0056] As already mentioned, it is important that the spray web 136
is of a size such that all substrates 120 on the first chuck 110
will be fully flooded with newly introduced reaction solution,
rather than the bulk solution in housing tank 102. This is unlike
many electrodeposition methods in which the substrates are
contacted fully or partially by the bulk reaction solution. In
these prior art instances, the titer of the solution contacting the
substrates 120 at any moment differs from place to place, even on a
single wafer.
[0057] Turning now to drawing FIGS. 8, 9 and 10, electrodeposition
apparatus 100 having three differing rotational configurations is
shown. In each figure, a housing tank 102 containing a reaction
solution 108 is shown. A first chuck 110 on which substrates 120
are substantially horizontally mounted with respect to the vertical
is supported by shaft 114 to be closely positioned below a second
chuck 130. The web-to-substrate spacing 148 may vary from about 1
to about 10 mm, or may be higher, depending on the flow rate of
reaction solution from the second chuck 130. The second chuck 130
comprises a shower head to flood the first chuck 110 with a shower
190 of recycled reaction solution 108. The first chuck 110 is fully
submerged and the second chuck 130 is at least partially submerged,
i.e., below liquid level 118. The second chuck 130 is generally
coextensive with the first chuck 110, or may be slightly larger to
ensure complete flooding of each substrate 120. Conductors 122 and
152 from the cathode and anode, respectively, of a power supply 132
provide a negative charge to the first chuck 110 and a positive
charge to the second chuck 130 to enable an electrolytic reaction
therebetween. Reaction solution 108 from the housing tank 102 is
shown as being recycled through piping 180 to a filter 160. The
filtered solution is pumped by pump 156 to a rotary fitting 158 on
the drive shaft 150 and into the second chuck 130, from which a
shower 190 of solution exits to impinge upon the substrates 120. A
conventional drain line 182 for draining housing tank 102 and a
conventional feed line 184 for adding fresh solution, water or
other liquid 108 to the second chuck 130 are also illustrated in
drawing FIG. 8.
[0058] In drawing FIG. 8, the first chuck 110 is stationary while
the second chuck 130 is rotated about substantially vertical axis
172 by a controllable drive 128 with a motor 145. The rotational
speed may vary from about 0.1 rpm to about 3 rpm, or even higher,
e.g., 5 gpm. In general, the rotational velocity is preferred to be
relatively slow, e.g., about 0.2 to about 2 rpm, depending on the
chuck diameters and other factors, so that laminar flow of the
reaction solution 108 is maintained over the substrate
surfaces.
[0059] In the embodiment of the invention illustrated in drawing
FIG. 8, as in the other embodiments of apparatus 100, the control
arm 146 is movable in a vertical direction 186 and/or a pivotal
direction 188 wherein the second chuck 130 is alternately placed in
housing tank 102 and removed therefrom. The control arm 146 may
also be configured to move in other directions, not shown, for
optional placement of the second chuck 130 in any of a line of
processing tanks.
[0060] Illustrated in drawing FIG. 9, another embodiment of an
electrodeposition apparatus 100 similar to that illustrated in
drawing FIG. 8 is depicted in which the first chuck 110 is rotated
about vertical axis 174 by lower drive unit 126 while the second
chuck 130 is supported by control arm 146 in a stationary position
during the electrodeposition process.
[0061] Illustrated in drawing FIG. 10 is an embodiment of an
electrodeposition apparatus 100 in which both of the first and
second chucks 110, 130 are rotatable. The rotational speed of each
chuck 110, 130 may be controlled to simultaneously achieve (a) a
desired differential speed between the two chucks, (b) a desired
centrifugal force, and (c) a desired degree of mixing of tank
contents.
[0062] In all of the embodiments of the invention considered thus
far, it may be noted that the first chuck 110 is below the second
chuck 130, and the substrates face upwardly into the discharge end
144 of the second chuck. Illustrated in drawing FIGS. 11 and 12 are
further embodiments of an electrodeposition apparatus 100 in which
the first chuck 110 and second chuck 130 are reversed in position.
Inasmuch as the reaction solution is then "showered" upwardly at
the substrate surfaces, the tendency for particles to settle in
substrate recesses is negated. The same general alternatives of the
present invention as illustrated in drawing FIGS. 8 through 10 are
applicable here. For example, the rotated chuck(s) may comprise the
first chuck 110 only, the second chuck 130 only, or both chucks
together. Such alternatives are illustrated in drawing FIGS. 11 and
12.
[0063] As shown in drawing FIG. 11, the stationary first chuck 110
carrying substrates 120 is uppermost, with the substrates 120
facing downwardly toward the closely spaced spray web 136 of the
second chuck 130. Both pumped reaction solution 108 and electrical
connections are made through one or two rotating connectors 192,
the latter being known in the art. The first chuck 110 is supported
by control arm 146, which may be raised or pivoted, or moved in
other directions (but not rotated) to remove substrates 120 from
the housing tank 102. The control arm movement may enable
sequential submersion of the substrate-carrying first chuck 110 in
a line of processing tanks. Inasmuch as the solution from the spray
web 136 has a relatively low velocity of a shower, solution will
not be forced into the air above the liquid surface 118 around the
periphery of the first chuck 110.
[0064] As illustrated in drawing FIG. 12, the embodiment of the
present invention has a movable first chuck 110 which is uppermost
and a movable second chuck 130 which is below the first chuck. The
first chuck 110 is rotated by drive 128 and the second, i.e.,
lower, chuck 130 is rotated by lower drive unit 126. The drive
speeds may be controlled over a relatively wide speed range to
achieve the desired differential speed, centrifugal force at the
substrate surfaces and tank mixing.
[0065] An embodiment of an electrodeposition assembly 200 of the
present invention is especially adapted to an automatic process
line and is shown in drawing FIG. 13. The assembly includes a
single control arm 146, from which two chucks 110 and 130 are
suspended. This permits placement into a housing tank 102 (not
shown) or removal therefrom as a single unit by actuation of a
single control arm 146. In this embodiment of the invention, one of
the first chuck 110 and second chuck 130 has a rotatable drive
shaft 114 or 150, respectively, for rotation thereby. In the
embodiment of the invention illustrated in drawing FIG. 13, a drive
shaft 114 for driving the first (substrate-carrying) chuck 110 is
bearingly mounted coaxially within a stationary hollow drive shaft
150 of a second (spray-head) chuck 130, coincident with center axis
224. The annular space 206 between drive shaft 114 and drive shaft
150 has bearings and fluid seals 208 at its upper and lower ends.
Drive shaft 114 is controllably rotatively driven by drive 202
shown movably mounted on linear drive shaft 216 of linear actuator
220. While drive motor 226 rotates drive shaft 216 about center
axis 224, the drive shaft 216 is also configured to be vertically
movable by actuator 220 to control the web-to-substrate spacing 222
or provide a vertical vector to shaft movement.
[0066] The first chuck 110 comprises a thin planar member having
center axis 224 and devices 228 for attaching a plurality of
substrates 120 to an upper mounting surface 112 of the chuck. The
figure shows exemplary substrates 120 as semiconductor wafers which
are attached to the upper mounting surface 112 by devices 228 shown
as clips. Other suitable devices 228 may be used for substrate
attachment, depending upon the substrate shape. The substrates 120
are provided with a negative electrical charge from a power supply,
not shown, via conductors 214 which pass through a rotating
connection fitting 248 (such as use brushes) into conductors in the
hollow drive shaft 114 and through clips or other connectors 228 to
the substrates.
[0067] The second chuck 130 has a discharge end 144 and comprises
an annular disk having a nonconductive body 230 of a solid annular
upper plate 232, outer peripheral ring 234 and inner peripheral
ring 236. The lower planar surface comprises a web 240 which is
perforated with flow orifices (not shown) for passage of reaction
solution 108 therethrough as a shower 190.
[0068] A recirculation pump 204 is attached to the control arm 146.
Reaction solution 108 from the housing tank 102 enters the pickup
end 250 of conduit 210 and is filtered by filter 244 to remove
solid particles before being pumped to a slightly elevated pressure
by recirculation pump 204. The filtered reaction solution 108 is
pumped through one or more conduits 246 into the hollow core 212
within the second chuck 130. Pressurized reaction solution 108 is
forced through a pattern of flow orifices 138 (see FIG. 4) in spray
web 136 in accordance with the specifications of the invention. A
conductor 218 carries a cathodic charge from a distal power supply
132, not shown in this figure, to the spray web 136 or other
chargeable surface on the second chuck 130.
[0069] In an alternative arrangement, not shown, the recirculated
reaction solution 108 may be directed by a conduit 246 to the
annular space 206 between the two drive shafts 114, 150. Conduits
between the annular space 206 and the hollow core 212 will then
enable filling the hollow core to create the shower 190. Rotating
bearings with seals 208 will prevent reaction solution 108 from
escaping from the annular space 206.
[0070] It may be noted that the first chuck 110 and the second
chuck 130 may be reversed in position, the first chuck 110 being
positioned above the second chuck 130. Thus, shaft 114 of the first
chuck 110 must be larger in diameter than drive shaft 150 of the
second chuck, so that drive shaft 150 may rotatively pass through
it. In this configuration, the substrates 120 will be attached to
the lower surface 112 of the first chuck 110. Pumped reaction
solution 108 will be passed through shaft 114 to the second chuck
130 and will be discharged upwardly to impinge upon the substrates
120.
[0071] Some of the features of apparatus 200 of the present
invention are:
[0072] 1. the apparatus for supporting, rotating, vertical
movement, solution pickup and pumping are all mounted on a single
control arm;
[0073] 2. the processing tanks require no rotating shaft seals;
[0074] 3. substrates may be readily attached and removed from the
apparatus;
[0075] 4. multiple substrates may be processed simultaneously under
identical conditions; and
[0076] 5. application to a continuous or semicontinuous processing
line is enhanced. For example, as shown in drawing FIG. 14, the
apparatus 200 may be readily moved as indicated at 253 from station
A to station I in a continuous sequence 252, where each station A
through I may comprise, for example, a station for
electrodeposition, washing, etching, and a variety of other
processes, both "wet" and "dry," without removal of substrates from
the first chuck 110.
[0077] It will be evident from the above discussion that the
electrodeposition apparatus 200 may be further enhanced by
providing a rotation drive for both of the chucks 110 and 130. In
this embodiment, it is possible to simultaneously (a) achieve a
desired relative velocity between the two chucks, (b) provide a
desired mixing of the tank contents, and (c) achieve a desired
centrifugal force on each chuck.
[0078] In each of the embodiments of the electrodeposition
apparatus 100, 200 considered so far, the rotational axes 172 and
174 have been shown as being coaxial. However, the system may be
designed to have offset axes of rotation. For example, as shown in
drawing FIG. 15, the first chuck 110 and second chuck 130 rotate
about their centers 254, 256, respectively. The centers 254, 256
are offset a distance 258 from each other (FIG. 16), and the second
chuck 130 is shown as having a diameter 260 somewhat greater than
the diameter 262 of the first chuck 110 to provide complete
coverage thereof by its shower 190.
[0079] In drawing FIG. 16, second chuck 130 is rotatable about its
center 256 while the first chuck 110 has an axis of rotation 266
displaced from its center 254 by displacement distance 264. Again,
diameter 260 is greater than diameter 262.
[0080] Illustrated in drawing FIG. 17, both chucks 110 and 130 are
shown as having respective axes of rotation 266, 268 which are
displaced from their centers 254, 256 (not shown), respectively. In
this mode, the difference in diameters 262, 260 of the first and
second chucks is generally greatest.
[0081] Displacement and/or offset of the chucks 110, 130 may be
useful to ensure that every tiny portion of the substrates is
subjected to equivalent contact with the reaction solution. The
"path" taken by each shower orifice 138 over a substrate 120 on the
first chuck 110 will constantly vary to ensure complete
coverage.
[0082] With respect to each of the rotatable chucks 110, 130,
agitation of reaction solution 108 in the housing tank 102 is
enhanced by attaching a relatively small number of stirring blades
270 to the periphery 272 or nonactive planar surface 113 of the
rotatable chuck(s) or alternatively to a submerged portion of a
rotatable shaft 114 such as that positioned below a lower chuck
(for example, see FIG. 12). Preferably, the stirring blades 270 are
planar and mounted in a balanced radial alignment for generally
equivalent mixing irrespective of the direction of rotation. The
blades may take various shapes, and a preferred embodiment is
generally shown in drawing FIG. 18. The number of blades 270 on a
chuck may vary from about 4 for a small chuck up to about 15 for a
larger chuck of about five foot diameter.
* * * * *