U.S. patent application number 14/497810 was filed with the patent office on 2016-03-31 for current monitoring for plating.
The applicant listed for this patent is SunPower Corporation. Invention is credited to Jose Francisco Capulong, Michael Defensor, Reynaldo Guerrero, Robert Obiles.
Application Number | 20160090662 14/497810 |
Document ID | / |
Family ID | 55582125 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160090662 |
Kind Code |
A1 |
Capulong; Jose Francisco ;
et al. |
March 31, 2016 |
Current Monitoring for Plating
Abstract
Various implementations of a method include receiving a
measurement of an electrical current provided to a component
undergoing electroplating, analyzing the current measurement, and
adjusting the current based at least on the analyzing. The
receiving, analyzing, and adjusting may be performed on a
substantially continuous ongoing basis throughout the
electroplating, and/or without interrupting the electroplating. In
various implementations, the method includes measuring a current
through a neck portion of a hangar to which the component is
affixed. The adjusting may regulate the current based on a variety
of conditions and target factors. Various implementations of a
system include a connector and a current sensor. The connector
electrically and mechanically couples a plating target to a current
bus during an electroplating operation. The sensor monitors a
current supplied to the plating target throughout a substantial
portion of the electroplating operation.
Inventors: |
Capulong; Jose Francisco;
(Lucena, PH) ; Defensor; Michael; (Metro Manila,
PH) ; Guerrero; Reynaldo; (Cagayan, PH) ;
Obiles; Robert; (Tondo, PH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SunPower Corporation |
San Jose |
CA |
US |
|
|
Family ID: |
55582125 |
Appl. No.: |
14/497810 |
Filed: |
September 26, 2014 |
Current U.S.
Class: |
205/83 ;
204/229.1 |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 17/06 20130101; C25D 21/12 20130101 |
International
Class: |
C25D 21/12 20060101
C25D021/12 |
Claims
1. A method comprising: receiving a current measurement, wherein
the current measurement represents a current provided to a
component, while the component undergoes electroplating; analyzing
the current measurement; and adjusting the current based at least
on the analyzing the current measurement.
2. The method of claim 1, wherein the receiving, the analyzing the
current measurement, and the adjusting are performed without
interrupting the electroplating.
3. The method of claim 1, wherein the component comprises a
semiconductor substrate, the method comprising: coupling the
semiconductor substrate to a hanger element; hanging the hanger
element on a supply line; immersing at least a portion of the
semiconductor substrate into an electrolyte solution; and providing
the current from the supply line, via the hanger element, to the
semiconductor substrate.
4. The method of claim 3, wherein the coupling the component to the
hanger element comprises: mounting the component on a jig; and
mounting the jig on the hanger element.
5. The method of claim 3, comprising: wirelessly transmitting the
current measurement from the hanger element to a data collection
unit, wherein the current measurement is based at least on a
Hall-effect measurement of a current flow through a
current-throttled region of the hanger element.
6. The method of claim 1, wherein the adjusting comprises: changing
a magnitude of the current to reduce large variations in the
magnitude of the current over a time segment of the
electroplating.
7. The method of claim 1, wherein the adjusting comprises:
maintaining a magnitude of the current within a predetermined
amperage range.
8. The method of claim 1, wherein the adjusting comprises:
maintaining a magnitude of the current within a predetermined
profile, wherein the predetermined profile is tailored to promote a
substantially uniform plating thickness on the component.
9. The method of claim 8, wherein the predetermined profile
comprises time-dependent parameters that vary over a time span of
the electroplating.
10. The method of claim 1, wherein the electroplating comprises one
or more of: a copper plating procedure; or a tin plating
procedure.
11. (canceled)
12. The method of claim 1, comprising: substantially simultaneously
with the receiving the current measurement, receiving a second
current measurement, wherein the second current measurement
represents a second current provided to a second component, while
the second component undergoes electroplating; and analyzing the
second current measurement, wherein the adjusting the current is
further based on the analyzing the second current measurement.
13. A system comprising: a connector, configured to electrically
and mechanically couple a plating target to a current bus during an
electroplating operation; and a current sensor mounted on the
connector, wherein the current sensor is configured to make
measurements representative of a current supplied to the plating
target throughout a substantial portion of the electroplating
operation.
14. The system of claim 13, wherein the current sensor is
configured to make the measurements representative of the current
supplied to the plating target substantially continuously during at
least 25% of a time duration of the electroplating operation.
15. The system of claim 13, comprising: a transmitter coupled to
the current sensor and configured to transmit a value indicative of
the current supplied to the plating target.
16. The system of claim 15, wherein: the transmitter is a wireless
transmitter; the plating target comprises a semiconductor wafer;
the connector comprises a hanger configured to detachably couple to
the current bus; the connector comprises a jig configured to
detachably couple to the hanger and configured to hold the
semiconductor wafer in an electrolyte solution during the
electroplating operation; and the current sensor is mounted on a
neck portion of the hangar.
17. The system of claim 13, comprising: a feedback control unit
configured to receive the measurements representative of the
current supplied to the plating target, and adjust a current
provided to the current bus, based at least upon the measurements
representative of the current supplied to the plating target.
18. The system of claim 13, comprising: a feedback control unit
configured to adjust a current provided to the current bus, based
at least upon the measurements representative of the current
supplied to the plating target; and additional measurements
representative of currents supplied to additional plating
targets.
19. The system of claim 13, comprising: a feedback control unit
configured to adjust a current provided to a plurality of plating
targets, based at least upon the measurements representative of the
current supplied to the plating target.
20. A control system comprising: an input configured to receive
measurement data indicative of at least one current supplied to an
element undergoing an electroplating operation; a memory comprising
reference data representing target current ranges for the
electroplating operation; and a processor configured to perform a
comparison of the measurement data to the reference data and to
adjust an electrical supply unit based at least on the
comparison.
21. The control system of claim 20, wherein: the processor is
further configured to adjust the electrical supply unit based at
least on a history of the measurement data during the
electroplating operation.
Description
TECHNICAL FIELD
[0001] The present disclosure relates in general to electroplating
and in particular to techniques for monitoring and controlling an
electroplating operation.
BACKGROUND
[0002] Electroplating is used in a variety of industries for
depositing a layer of metal on a substrate. In various approaches,
a substrate and an electrode can be immersed in an electrolyte
solution. An electric voltage (electric potential) can be applied
between the substrate and the electrode. Metal ions in the
electrolyte solution are driven by the voltage toward the
substrate, where they are reduced and deposited onto the surface of
the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The benefits, features, and advantages of the present
disclosure will become better understood with regard to the
following description and accompanying drawings.
[0004] FIG. 1 illustrates one implementation of an electroplating
system.
[0005] FIGS. 2 and 3 show one implementation of a system with a
current sensor mounted on a conducting element.
[0006] FIG. 4 is a perspective view of one implementation of a
system with a current sensor mounted on a plating hangar.
[0007] FIG. 5 is a flowchart showing one implementation of a method
for controlling current delivered to an element during an
electroplating operation.
[0008] FIG. 6 illustrates a second implementation of an
electroplating system.
[0009] FIG. 7 is a block diagram of one embodiment of a computer
system for controlling an electroplating activity.
DETAILED DESCRIPTION
[0010] Electroplating can be used in the fabrication of utensils,
jewelry, decorative metal, coinage, machine parts, and other
products. Electroplating is also used in various semiconductor
manufacturing processes, such as for depositing a layer of metal
onto a silicon substrate. The substrate can be a wafer or other
component to be used in an integrated circuit or solar cell, for
example.
[0011] FIG. 1 illustrates one implementation of an electroplating
system 100. In this example, three substrates 140a, 140b, 140c
(collectively, substrates 140) are held within a plating vessel
120, immersed or partly immersed in an electrolyte solution 122. An
electrode 130 is also in contact with solution 122. An electric
current is passed through electrode 130, solution 122, and
substrates 140. With a suitable choice of electrolyte solution,
substrate material, and electrode material, the current causes a
metal film to be deposited on substrates 140.
[0012] In the example of FIG. 1, an electric voltage is supplied by
a power source 180. In this example, power source 180 is a direct
current (DC) supply. The positive terminal of power source 180 is
coupled via a lead 184 to electrode 130, which serves as an anode
in this example. The negative terminal of power source 180 is
coupled via a lead 182 to a bus bar 105. Bus bar 105 serves as an
electrical power rail and as a mechanical support for substrates
140. In this illustrative example, substrates 140a, 140b, 140c are
connected mechanically and electrically to bus bar 105 though
holders 145a, 145b, 145c respectively (collectively, holders
145).
[0013] In this example, substrates 140 are cathodes in an
electrochemical reaction. Current flows from power source 180 to
electrode 130, through solution 122, into substrates 140, through
holders 145, through bus bar 105, and back to power source 180. In
passing from solution 122 into substrates 140, the current causes
metal ions to be reduced from aqueous phase into solid-phase atoms.
The neutral atoms are deposited onto substrates 140. In various
implementations, the source of the metal ions is the material of
electrode 130, and the electrode is gradually consumed as the
electroplating progresses. In other implementations, the source of
the metal ions is the electrolyte solution 122, which may need to
be replenished after some time to continue an effective
electroplating operation. In various examples, plating vessel 120
is large enough to accommodate large numbers of wafers, e.g., 10,
50, 160, 250, 400 wafers, for simultaneous processing in an
electroplating operation.
[0014] A variety of different forms of electroplating are used to
obtain a desired layer of material on the substrates. Different
approaches can be used depending on the substrate material and
shape, the desired type of metal layer (e.g. deposited chromium,
copper, tin, nickel, other metallic elements, or alloys), the
desired purity of the deposited layer, the desired strength of
connection between the layer and the substrate, the operating
temperature, and other factors. In various situations, multiple
plating processes may be conducted in sequence. For example, a
silicon wafer may be plated first with one metal (e.g., 30 microns
of copper) and then with a second metal (e.g., 6 microns of
tin).
[0015] In many applications, the final thickness of the deposited
layer is a relevant metric in assessing the success of the
electroplating process. Similarly, the uniformity of the layer's
thickness over the substrate can be a relevant metric in assessing
the process. These factors can be of interest in various
applications, such as the plating of metal layers onto
semiconductor substrates. In various situations, layer thickness
(e.g., ones, tens, hundreds, or thousands of microns), layer
uniformity (e.g., 1%, 2%, 5%, 8%, 10%, 15%, 20%, 30%, 40%, 60%
variations) and other factors can be controlled by monitoring the
cleanliness of the substrate, the geometry of the substrate, the
purity of the electrolyte solution, the geometry of the current
path through the solution between the electrode and the substrates,
the total time of the plating process, and other factors.
[0016] One factor that may be relevant to the quality of a plating
process is the magnitude of the current that is transmitted through
a substrate. Increases in the current level can increase the
deposition rate, and thus the overall thickness of the deposited
metal layer. This current level can be controlled by selecting an
appropriate electric voltage to be applied between the electrode
and the substrate. The current level can be monitored by a current
sensor, such as an in-line ammeter. Alternatively, an
electromagnetic sensor can be used to monitor the current without
introducing an in-line circuit element.
[0017] In FIG. 1, a hand-held clamp meter 190 is used to measure
the current that flows though substrate 140c. Clamp meter 190 has
two prongs that can be moved to engage or disengage with each other
around a conductor. When engaged around a conductor, the prongs
form a sensor loop around the conductor. Depending on the type of
clamp meter, the sensor loop employs a transformer winding,
magnetic vanes, Hall sensors, or other techniques to measure the
enclosed current. In the example of FIG. 1, clamp meter 190 is
engaged around a narrow section of holder 145c. As a result, a
display on clamp meter 190 shows the instantaneous current flowing
though substrate 140c.
[0018] A system operator may move clamp meter 190 to engage around
the holders 145a, 145b, in order to see the instantaneous current
flowing though the corresponding substrates 140a, 140b. Similarly,
the operator may move clamp meter 190 to engage around the holders
lead 182 or 184 in order to see the instantaneous total current
flowing though all of the substrates 140.
[0019] The use of clamp meter 190 involves some manual intervention
during the electroplating process. An operator needs to manually
engage the clamp meter, hold, observe, record, and disengage the
clamp meter for each measurement. The manual effort can be
labor-intensive for a long process (e.g., multiple hours, multiple
days). Also, the manual operation introduces some risk of
mechanical trauma--the operator may inadvertently knock or even
dislodge a substrate from bus bar 105. Similarly, clamp meter may
inadvertently be dropped into solution 122.
[0020] Other sensors can be used instead of a hand-held device. One
approach is to affix a current sensor to one or more support
structures, such as holders 145, that are used to conduct current
into the substrates.
[0021] FIGS. 2 and 3 show one implementation of a system 200 with a
current sensor 220a, 220b mounted on a conducting element 210. FIG.
2 is a perspective view and FIG. 3 is a side view of the
arrangement. The sensor has two components, 220a and 220b
(collectively, sensor 220). Each component is mounted on an
opposing side of conducting element 210. In this implementation,
the components 220a, 220b are each a Hall sensor, and are mounted
in a differential measurement configuration. In some other
implementations, a single Hall sensor is used for measuring the
current.
[0022] In this example, sensor 220 is mounted onto conducting
element 210. A connector 233 connects components 220a and 220b,
enabling comparison between components 220a and 220b. Sensor 220
may be mounted using screw holes 231 that enable the components to
be attached to conducting element 210. An electrical connector 240
supplies power to sensor 220, and communicates data measured by
sensor 220 to a computer or other monitoring device. In various
implementations, electrical connector 240 is a Universal Serial Bus
(USB) or Ethernet connector. In other implementations, sensor 220
draws power from an internal battery and electrical connector 240
is replaced by a wireless data link.
[0023] FIG. 4 is a perspective view of one implementation of a
system 400 with a current sensor 420 mounted on a plating hangar
410. In this example, a semiconductor wafer 440 is attached to a
jig 430, which in turn is attached to plating hangar 410.
[0024] In this example, hangar 410 is configured to be electrically
and mechanically connected to a bus bar (not shown). A top portion
412 of hangar 410 has a ridge 418 that can stably rest on the bus
bar. A bottom portion 416 of hangar 410 has features to which
various jigs can be connected. Jig 430 is configured to connect
with the hangar and with the wafer: a top section 432 of jig 430
has features that attach to hangar 410, and a bottom section 434 of
jig 430 has features that attach to wafer 440. In various
implementations, the holders 145 from FIG. 1 each include a hangar
410 and a jig 430.
[0025] In hangar 410, top portion 412 and bottom portion 416 are
connected to each other by a neck portion 414. Current flowing from
the bus bar to the wafer passes through neck portion 414 of hangar
410. In various implementations, neck portion 414 is relatively
narrow so that the current is throttled, concentrated, and/or
collected in neck portion 414. For example, the neck portion may be
constructed of steel, aluminum, copper, or other conductive
material with a cross section of 0.6 in..times.2.6 in. In various
other implementations, a neck portion can have other dimensions,
such as thicknesses of 0.125 in., 0.1875 in., 0.250 in., 0.3750 in.
Sensor 420 is mounted onto one face of neck portion 414. In various
implementations, a corresponding sensor (not shown) is mounted in a
differential configuration on an opposing face of neck portion 414.
In various implementations, a channel or groove can be formed or
cut into neck portion 414 to accommodate sensor 420. In various
implementations, sensor 420 is mounted in a location where it can
measure all of the current passing into a substrate, or in a
location where it can measure a substantial fraction of the current
passing into the substrate. Additionally, the location of the
sensor can be chosen so that it is not subject to jostling or other
undesired mechanical contact during regular use and storage of a
hangar.
[0026] In various situations, wafer 440 is fully immersed into an
electrolyte solution during a plating process. (For example, the
illustration in FIG. 1 showed wafers 140 being fully immersed.) In
these situations, some of the bottom section 434 of jig 430 may
also be in contact with the electrolyte solution. Depending on the
electroplating chemistry, the exposed section of a jig may be
plated or degraded, limiting the reusable lifetime of the jig. In
other situations, jig 430 is held above the surface of the
electrolyte solution. In these other situations, a top portion 442
of wafer 440 may not be exposed to the solution, while a remainder
portion 444 is immersed in the solution.
[0027] FIG. 5 is a flowchart showing one implementation of a method
for controlling current delivered to an element during an
electroplating operation 500. In various implementations, some or
all of the acts in this method may employ various components
discussed with regard to the systems depicted in FIGS. 1-4 or 6-7.
For example, in the illustrated implementation, the method
commences in act 510 when an element, such as a semiconductor
wafer, is prepared for electroplating. The wafer is then mounted to
a holding jig in act 520. The jig can be, in various
implementations, a single-use or few-use component for mating a
specialized plating element to a generalized electroplating hangar.
The jig is affixed to a hangar in act 530, and the hangar is
mounted on a bus bar in act 540. The bus bar provides mechanical
support and electrical current to the wafer via the hangar and the
jig. The wafer is then immersed or partly immersed in an
electrolyte solution that is a suitable electroplating bath.
[0028] In act 550, an electric voltage is applied between the bus
bar and an electrode in the electrolyte solution. The electric
voltage causes an electric current to follow a path from the
electrolyte solution through the wafer, the jig, and the hangar. In
act 560, the current is measured. The measurement can be made, for
example, at a constricted portion of the hangar that carries all or
most of the current which passes through the wafer. The measurement
is transmitted in act 570 to a control unit. The control unit
analyzes the measurement in act 580 and determines, at decision
block 585, what adjustment (if any) needs to be made to raise or
lower the current. If no adjustment is needed, the present voltage
level (from act 550) is maintained in act 592 and the procedure
returns to act 550. Otherwise, the voltage level is adjusted in act
590 and the procedure returns to act 550.
[0029] Acts 550-560-570-580-585-590/592 form a feedback loop that
holds the current level at (or near) a desired value. The desired
value can be target constant value or can vary according to a
target profile (e.g., based on a plating rate, a desired plating
thickness, considerations of the geometry of the substrate, etc.).
The loop can terminate at any point (act 550, 560, 570, 580, 585,
590, or 592), at a time when the electroplating procedure is
complete.
[0030] FIG. 6 illustrates a second implementation of an
electroplating system 600. In this example, three substrates 640a,
640b, 640c (collectively, substrates 640) are held within a plating
vessel 620, immersed or partly immersed in an electrolyte solution
622. An electrode 630 is also in contact with solution 622. An
electric current is passed through electrode 630, solution 622, and
substrates 640. With a suitable choice of electrolyte solution,
substrate material, and electrode material, the current causes a
metal film to be deposited on substrates 640.
[0031] In this example, power source 680 is a signal-controllable
DC supply. The positive terminal of power source 680 is coupled via
a lead 684 to electrode 630. The negative terminal of power source
680 is coupled via a lead 682 to a bus bar 605. Bus bar 605 serves
as an electrical power rail and as a mechanical support for
substrates 640. In this example, substrates 640a, 640b, 640c are
connected mechanically and electrically to bus bar 605 though
holders 645a, 645b, 645c respectively (collectively, holders 645).
Current flows from power source 680 to electrode 630, through
solution 622, into substrates 640, through holders 645, through bus
bar 605, and back to power source 680. In passing from solution 622
into substrates 640, the current causes metal to be plated onto
substrates 640.
[0032] Power source 680 is controlled by a control unit 690.
Control unit 690 includes an input 692, an output 698, a processor
694, and a memory 696. Input 692 receives one or more signals that
provide information about current flowing into one or more of the
substrates 640. In the depicted example, input 692 is a wireless
receiver and is shown as receiving a wireless signal 691 that
represents a current measurement through holder 645a. This current
measurement is generated by a sensor 612 mounted on holder 645a.
Input 692 is shown as also receiving a wireless signal 697 that
represents a second current measurement, through holder 645c. This
second current measurement is generated by a second sensor 614
mounted on holder 645c. The measurement and transmission operations
(whether wireless or wired, analog or digital) can be adapted in
various implementations to tolerate electrically noisy
environments, such as those that may be present in the vicinity of
a high-current electroplating procedure.
[0033] In various implementations, signals 691 and 697 carry
information based on Hall measurements from sensors 612 and 614. In
various implementations, these measurements are indicated as total
currents (detected amperes); in other implementations, these
measurements are indicated in other physical units (e.g., detected
amperes per cm 2); in yet other implementations, these measurements
are indicated in other scalar units (e.g., a unitless 8-bit or
20-bit number that is a linear or nonlinear representation of
detected current). These indications are computed, in some
implementations, based on device calibrations stored internally in
sensors 612 and 614. For example, sensor 612 may include an analog
detector that uses a generates an output signal in the range of
-4000 mV to +4000 mV, with the output being proportional to a
detected current and a conversion constant of 4 to 4.5 mV output
per Ampere of detected current.
[0034] Processor 694 uses the received current measurements to
determine whether to change the voltage provided between bus bar
605 and electrode 630. Based on this determination, output 698
provides an output signal that increases, decreases, or maintains
the electric voltage generated by power source 680. In various
implementations, processor 694 may be configured to execute
instructions stored in memory 696 to regulate power source 680. By
executing the instructions, processor 694 may operate, for example,
to maintain a predetermined DC current level supplied to wafer
640a. This operation would be based on wireless signal 691 received
by input 692. In other examples, processor 694 and the software it
executes may be configured to regulate power source 680 based on
multiple current measurements (e.g. as received in wireless signals
691 and 697), environmental factors, or other factors, or
combinations thereof. Some additional examples of considerations
used in the regulation of a power source are discussed below.
[0035] In the example of FIG. 6, the currents through substrates
640a and 640c are measured, while the current through substrate
640b is not. Depending on the overall operation, it may not be
necessary to monitor each of the substrates in an electroplating
procedure. For example, various electroplating procedures may be
performed with multiple substrates 640 that have similar or
identical geometries, and with holders 645 that also have similar
or identical geometries. This uniformity can be helpful in
inferring that the current that flows through each of the
substrates are the same or similar. With this inference, it may not
be necessary to monitor each substrate in a batch of substrates. In
some situations it may be sufficient to monitor 90%, 75%, 50%, 20%,
10%, 5%, or 1% of the substrates in a batch. Similarly, it may be
sufficient to monitor a selected number such as 20, 10, 8, 5, 4, 3,
2, or just 1 of the substrates in a batch.
[0036] The determinations made by processor 694 can be based on
various factors in addition to the current measurement(s). These
additional factors can be encoded as comparison parameters or other
information stored, for example, in memory 696. For example,
processor 694 may be configured (using hardware, software,
firmware, or combinations thereof) to hold a current level
constant, within a fixed target range of values. For example,
historical data from past experience may indicate that a particular
process yields suitable platings if the current is held to 50
amperes through each wafer throughout a four-hour plating period.
The historical data may further show that variations of up to +/-10
amperes also yield suitable platings. Based on these observations,
processor 694 and/or the instructions that it executes may be
configured to adjust power source 680 on an ongoing basis to ensure
that the current measured at one of the sensors (e.g. sensor 614)
stays in the range of 40 to 60 amperes during the plating period.
This operation forms a feedback control loop: the adjustments made
by processor 694 lead to changes in the voltage provided by power
source 680, which affects the total current driven into bus bar
605, which affects the current that enters into wafer 640c, which
affects the measurement made by sensor 614, which can lead to
further changes by processor 694. Processor 694 and/or the
instructions that it executes can be configured to use hysteresis,
filtering, and/or other techniques to avoid positive-feedback or
other control issues, and to keep the feedback loop stable.
[0037] Processor 694 and/or the instructions that it executes can
use other approaches for determining how to control power source
680. For example, instead of maintaining a current level to be
close to a fixed value (e.g., 20, 35, 50, 65, 70 amperes)
throughout a plating procedure, a control system may be configured
with a changing temporal profile. For example, the target value of
a measured current may be 25+/-5 amperes during a first 1-hour
phase of a plating process, 65+/-15 amperes during the next
1.5-hour phase of the plating process, and 65+/-5 amperes during a
final 2-hour phase of the plating process. Other temporal profiles
may also be used. For example, various implementations of processor
694 and associated software may be configured to accept linear or
nonlinear algebraic expressions for the target value of a current
being controlled (e.g., I_target=0.5 amps.times.time_hours;
I_target=40 amps+3 amps.times.time_hours; I_target=40 amps+3
amps.times.sin(time_hours/1_hour)).
[0038] Moreover, the target profile may be adjusted based on the
history of a plating process. For example, various implementations
of processor 694 and associated software may be configured so that
if a plating current has consistently been measured at the upper
range of acceptable values through the first half of a plating
process, then the current is subsequently maintained in the lower
range of acceptable values for the second half of the plating
process. Similarly, the duration of a plating process can be
shortened (or extended) if the plating current has largely been
measured on the high side (or on the low side) of acceptable
values.
[0039] Also, various implementations of processor 694 and the
instructions it executes (or both) may be configured or programmed
so that the target current is based on other measured factors
(e.g., ambient temperature) or input parameters (the target
thickness of the plating layer, the desired tolerance of that
target thickness, the number of substrates in a plating bath, the
locations of the substrates in a plating bath, the arrangement of
hangars on a bus bar, the volume or other geometry of an
electrolyte bath, the cleanliness of the plating solution, whether
the plating solution is fresh or has been used for a previous
plating, or other factors).
[0040] As another example, various implementations of processor 694
and associated software can be configured to monitor the currents
supplied to multiple wafers (e.g. wafers 640a and 640c, as depicted
in FIG. 6), and to attempt to keep all of the measured currents
within a target range. For example, consider a situation where
memory 696 indicates that a target range is 50 amperes with a
tolerance of +/-5 amperes, and processor 694 determines that wafer
640a is consistently receiving a little more current than wafer
640c. Such a situation may arise, for example, due to a faulty
mounting, an adverse mounting position in the electrolyte bath for
one of the wafers, or other reasons. In that situation, processor
694 may adjust power source 680 so that wafer 640a receives 52
amperes and wafer 640c receives 48 amperes of current. In effect,
this mode of operation involves some degree of compromise among the
measured values, with both of the measured values being kept within
the tolerances. Similar compromises may be configured for three or
more wafers.
[0041] In some situations, processor 694 may determine that a
compromise is not possible. For example, consider a situation where
a target current is 60 amperes, with a tolerance of +/-3 amperes.
If processor 694 detects that five wafers in a batch are each
receiving 62 amperes of current (just a bit more than the target
value) while one anomalous wafer is receiving 47 amperes
(substantially less than the target value), the processor may be
unable to compensate in a way that keeps all the wafers in range.
In such a situation the processor may adjust the power supply in a
manner that deliberately sacrifices the anomalous wafer. For
example, processor 694 may adjust the power source so that the five
wafers receive the optimal 60 amperes, while the one anomalous
wafer receives only 44 amperes. Alternatively, or in addition, the
processor may trigger an alarm signal, alerting an operator that
the anomalous wafer may need attention or adjustment.
[0042] In various implementations, processor 694 converts the
information received in signals 691 and 697 based on system
calibrations that are stored in memory 696. For example, after
sensor 612 is affixed to holder 645a, an operator may perform an
initial calibration procedure. In the calibration procedure, the
operator can compare the measurements that are received in signal
691 against clamp-meter measurements for a variety of operating
conditions. These comparisons can be used to generate a lookup
table for use during subsequent electroplating operations.
[0043] In the illustrated example, control unit 690 is depicted
with a single processor and a single memory. In other
implementations, a control unit includes a data collection unit
(e.g., having an input, a processor, and a memory) and also
includes a feedback control unit (e.g., having an output, a
processor, and a memory) that responds to information received by
the data collection unit.
[0044] In various implementations, electroplating system 600
operates so that control unit 690 monitors a current and provides
feedback control during an entire time duration of a plating
process. In other implementations, a plating process may be
performed with the monitoring during only a portion of the plating
process. For example, the monitoring may operate substantially
continuously during at least 25%, 40%, 50%, 75%, 90%, 98%, or 100%
of a full duration of an electroplating activity. Similarly,
automated feedback control may be used for all or part of a time
duration of a plating process, such as substantially continuously
during at least 15%, 25%, 35%, 40%, 50%, 75%, 80%, 90%, 95%, 98%,
or 100% of a full duration of an electroplating activity.
[0045] Sensors 612, 614 may each incorporate a Hall sensor or a
differentially-aligned pair of Hall sensors. The signal from the
sensor can be conditioned by an amplifier, converted from analog to
digital form, and possibly pre-processed by a microcontroller for
transmission or local storage. A variety of technologies are
contemplated for transmitting wireless links 691 and 697. In
various implementations, wired links can be used instead of
wireless links.
[0046] In various implementations of an electroplating system, the
data can be logged in a unit on the holder instead of (or in
addition to) being transmitted to a control unit. In such
implementations, a holder or hangar can be equipped with a memory
that stores current measurements for future reading. In various
situations, an operator may manually remove the memory during a
plating process for analysis and possible adjustment or fine-tuning
of the plating process. In yet other implementations, current
readings are stored in a memory buffer on a hangar, and are
intermittently transmitted to a control unit.
[0047] FIG. 7 is a block diagram of one embodiment of a computer
system 700 for controlling an electroplating activity. For example,
computer system 700 may be an embodiment of control unit 690.
Computer system 700 may include a processor 710 and a memory 720
coupled together by a communications bus 705. Processor 710 may be
a single processor or a number of individual processors working
together. Memory 720 is typically random access memory (RAM), or
some other dynamic storage device, and is capable of storing data
726 and instructions to be executed by the processor, e.g.,
operating system 722 and applications 724. The applications 724 and
operating system 722 may include software, firmware, and/or ROM
instructions. Memory 720 may also be used for storing temporary
variables or other intermediate information during the execution of
instructions by the processor 710. In various situations, computer
instructions, such as those used by processor 694 or other
instructions used in a plating operation, may be stored on a
non-transitory computer-readable storage medium.
[0048] Computer system 700 may also include input devices such as a
keyboard, mouse, or touch screen 750, a USB interface 752,
communications input and output components 754, output devices such
as graphics & display 756, a magnetic memory storage such as
hard disk 758, an optical memory storage such as CD-ROM 760, and a
semiconductor memory storage such as removable flash memory card
770, all of which are coupled to processor 710, e.g., by
communications bus 705. It will be apparent to those having
ordinary skill in the art that computer system 700 may also include
numerous elements not shown in the figure, such as additional
storage devices, communications devices, input devices, and output
devices.
[0049] The flow chart of FIG. 5 illustrates some of the many
operational examples of the techniques disclosed in the present
application. Those having ordinary skill in the art will readily
recognize that certain steps or operations illustrated in FIG. 5
may be eliminated or taken in an alternate order, or with alternate
configurations such as various electroplating arrangements or
alternating or reversed current flows. Moreover, various aspects of
these steps or operations can be implemented as one or more
software programs for a computer system (e.g., computer system 700)
and are encoded in a computer readable medium (e.g., memory 720) as
instructions executable on one or more processors (e.g., processor
710). A tangible computer readable medium may include, for example,
an electronic storage medium, a magnetic storage medium, or an
optical storage medium, or combinations thereof. The software
programs may also be carried in a communications medium conveying
signals encoding the instructions. Separate instances of these
programs may be executed on separate computer systems, e.g., in a
multi-processor architecture. Thus, although certain steps have
been described as being performed by certain devices or software
programs, this need not be the case and a variety of alternative
implementations will be understood by those having ordinary skill
in the art.
[0050] Those having ordinary skill in the art will readily
recognize that the techniques and methods discussed below may be
implemented in software using a variety of computer languages,
including, for example, traditional computer languages such as
assembly language, Pascal, and C; object oriented languages such as
C++, C#, and Java; and scripting languages such as Perl and Python.
Additionally, software 724 may be provided to the computer system
via a variety of computer readable media including electronic media
(e.g., flash memory), magnetic storage media (e.g., hard disk 758,
a floppy disk, etc.), optical storage media (e.g., CD-ROM 760 or
DVD-ROM), other tangible storage media, and communications media
conveying signals encoding the instructions (e.g., via a wired or
wireless network coupled to communications input and output
components 754).
[0051] Although the present disclosure has been described in
connection with several embodiments, the disclosure is not intended
to be limited to the specific forms set forth herein. On the
contrary, it is intended to cover such alternatives, modifications,
and equivalents as can be reasonably included within the scope of
the disclosure as defined by the appended claims.
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