U.S. patent application number 11/158976 was filed with the patent office on 2006-12-28 for multi-channel current probe.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Stephen P. LeBlanc, Gene B. Nesmith, James R. Shirck.
Application Number | 20060289299 11/158976 |
Document ID | / |
Family ID | 37565980 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060289299 |
Kind Code |
A1 |
LeBlanc; Stephen P. ; et
al. |
December 28, 2006 |
Multi-channel current probe
Abstract
A current probe for measuring electrodeposition plating
currents. The current monitoring probe includes a conductive layer
located on a front face of the current monitoring probe, an
insulating layer behind the conductive layer, and a plurality of
current sensing circuits located behind the insulating layer. The
insulating layer isolates the current sensing circuits from the
conductive layer. A plurality of apertures are formed through the
conductive layer and the insulating layer, each aperture exposing
one of the plurality of current sensing circuits to metal ions
incident to the aperture.
Inventors: |
LeBlanc; Stephen P.;
(Austin, TX) ; Nesmith; Gene B.; (Lago Vista,
TX) ; Shirck; James R.; (Austin, TX) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
37565980 |
Appl. No.: |
11/158976 |
Filed: |
June 22, 2005 |
Current U.S.
Class: |
204/229.8 |
Current CPC
Class: |
C25D 21/12 20130101;
C25D 17/10 20130101; G01N 27/42 20130101 |
Class at
Publication: |
204/229.8 |
International
Class: |
C25B 9/04 20060101
C25B009/04 |
Claims
1. A current probe for measuring electrodeposition plating
currents, the current probe comprising: a conductive layer located
on a front face of the current probe; an insulating layer located
adjacent to the conductive layer; a plurality of current sensing
circuits located adjacent to the insulating layer, wherein the
insulating layer is located between the conductive layer and the
plurality of current sensing circuits; and a plurality of apertures
formed through the conductive layer and the insulating layer,
wherein each of the plurality of apertures exposes one of the
plurality of current sensing circuits.
2. The current probe of claim 1, wherein the plurality of current
sensing circuits have equal overall resistance.
3. The current probe of claim 1, wherein each of the plurality of
current sensing circuits includes: a current sensing area, a
portion of which is exposed by one of the plurality of apertures
formed through the conductive layer and the insulating layer; and a
conductive line connecting the current sensing area to a current or
voltage measuring device.
4. The current probe of claim 3, wherein each of the plurality of
apertures exposes an equal amount of the current sensing area.
5. The current probe of claim 1, including an epoxy layer formed
adjacent to the plurality of current sensing circuits opposite the
insulating layer, the epoxy layer located on a back face of the
current probe.
6. The current probe of claim 1, wherein the conductive layer
consists of copper.
7. The current probe of claim 1, wherein the insulation layer
consists of polyimide.
8. The current probe of claim 3, wherein the conductive line and
the current sensing area of each of the plurality of current
sensing circuits consists of copper.
9. An electrodeposition measuring system, comprising: a plating
cell for holding a metal salt bath; an electrode located in the
plating cell; a current probe having a plurality of current sensing
circuits, wherein each of the plurality of current sensing circuits
senses a local electrodeposition plating current; and a computer
system connected to the current probe that determines an
electrodeposition plating thickness based on the local
electrodeposition plating currents sensed by the plurality of
current sensing circuits.
10. The electrodeposition measuring system of claim 9, including: a
plurality of plastic baffles that are adjustable to alter the
electrodeposition plating currents.
11. The electrodeposition measuring system of claim 9, wherein the
computer system further comprises: a data acquisition board
operatively connected to the current probe that converts
electrodeposition plating currents sensed by the plurality of
current sensing circuits to a plurality of digital values; a
computer operatively connected to the data acquisition board that
receives the plurality of digital values provided by the data
acquisition board; and a monitor operatively connected to the
computer for displaying the plurality of digital values provided to
the computer.
12. The electrodeposition measuring system of claim 9, wherein the
current probe further comprises: a conductive layer located on a
front face of the current probe; a insulating layer formed adjacent
to the conductive layer; and a plurality of apertures formed
through the conductive layer and the insulating layer, wherein each
of the plurality of apertures exposes one of the plurality of
current sensing circuits to local electrodeposition plating
currents generated between the electrode and the current probe.
13. The electrodeposition measuring system of claim 12, wherein
each of the plurality of current sensing circuits include: a
current sensing region, wherein a portion of the current sensing
region is exposed to electrodeposition plating currents by one of
the plurality of apertures formed through the conductive layer and
the insulating layer; and a conductive line connecting the current
sensing region to a current measuring device, wherein local
electrodeposition plating currents incident to the portion of the
current sensing region exposed by one of the plurality of apertures
is sensed by the current sensing region and provided by way of the
conductive line to the current measuring device.
14. The electrodeposition measuring system of claim 13, wherein
each of the plurality of apertures exposes an equal amount of the
current sensing regions of the plurality of current sensing
circuits, wherein the amount of the current sensing region exposed
and the current measured by each of the plurality of current
sensing circuits allows local electrodeposition plating current
density to be determined at each of the plurality of apertures.
15. The electrodeposition measuring system of claim 12, wherein the
current probe further comprises: an epoxy layer formed adjacent to
the plurality of current sensing circuits, the epoxy layer located
on a back face of the current monitoring probe, wherein the epoxy
layer prevents electrodeposition plating currents incident to the
back face of the probe from affecting the current sensing
circuits.
16. A method of providing real time analysis of electrodeposition
plating currents, the method comprising: A. placing a multi-channel
current probe in a plating cell; B. generating an electrodeposition
plating current; C. measuring the electrodeposition plating current
at a plurality of locations on the multi-channel current probe
using a plurality of current sensing circuits; and D. adjusting the
distribution of the electrodeposition plating current based on the
measurements taken.
17. The method of claim 16, wherein steps C and D are repeated
until the distribution of the electrodeposition plating currents
reaches a threshold level of uniformity.
18. The method of claim 16, wherein measuring the electrodeposition
plating current includes determining electrodeposition plating
current density based on the electrodeposition plating current
measured and a surface area of a current sensing region exposed to
the electrodeposition plating currents.
19. The method of claim 16, wherein adjusting the distribution of
the electrodeposition plating current based on the measurements
taken includes adjusting a plurality of plastic baffles.
20. The method of claim 16, wherein measuring the electrodeposition
plating current includes: sensing the electrodeposition plating
currents at a plurality of current sensing regions; providing the
sensed electrodeposition plating currents to a data acquisition
board via a plurality of conductive lines; and converting the
sensed electrodeposition plating currents provided to the data
acquisition board to a plurality of digital values representative
of the electrodeposition plating currents sensed at the plurality
of current sensing regions.
Description
FIELD
[0001] The present invention relates to a system and method for
monitoring and adjusting fields associated with the
electrodeposition of a metal onto a surface. More particularly, the
present invention relates to a system for monitoring the spatial
variation of the current and current density to obtain a desired
thickness of electroplated metal.
BACKGROUND
[0002] Electrodeposition of a metal onto a surface has many
applications. One such application is the deposition of a metal,
typically copper, onto a flexible substrate in order to create
interconnects on the flexible substrate. Interconnects are
essentially low-resistance transmission lines with precisely
controlled propagation characteristics. In order to control these
propagation characteristics, the thickness of the metal plating
must be precisely controlled. Typically, this requires that the
electroplated metal be deposited in uniform layers onto the
flexible substrate. Uniformity of electrodeposited layers is
influenced by the design and adjustment of the plating system,
including the current distribution seen by the flexible substrate.
If the current distribution is uneven across the flexible
substrate, then the plating thickness will also be uneven.
[0003] Typical methods of testing and measuring plating uniformity
include placing a substrate through the electroplating machine,
running the electroplater for an amount of time, removing the
substrate from the electroplating machine, and measuring thickness
variation using an X-ray fluorescence machine. The plating machine
is adjusted based on the results of the X-ray fluorescence machine,
and another trial is run until the desired distribution is
determined. However, this iterative method of plating and measuring
is both costly and time-consuming.
SUMMARY
[0004] In one aspect, the present invention provides a current
probe for measuring local electrodeposition plating currents. The
current probe comprises a conductive layer located on a front face
of the current probe, an insulating layer located adjacent to the
conductive layer, and a plurality of current sensing circuits
located adjacent to the insulating layer, wherein the insulating
layer is located between the conductive layer and the plurality of
current sensing circuits. A plurality of apertures are formed
through the conductive layer and the insulating layer, wherein each
of the plurality of apertures exposes one of the plurality of
current sensing circuits.
[0005] Another aspect of the present invention provides for an
electrodeposition monitoring system. The monitoring system is
comprised of a plating cell for holding a metal salt bath, an
electrode located in the plating cell, a probe having a plurality
of current sensing circuits, wherein each of the plurality of
current sensing circuits senses a local electrodeposition plating
current, and a computer system connected to the probe that
determines an electrodeposition plating thickness based on the
local electrodeposition plating currents sensed by the plurality of
current sensing circuits.
[0006] A further aspect of the present invention provides a method
of providing real time analysis of electrodeposition plating
currents. The method including placing a multi-channel current
probe in a plating cell, generating an electrodeposition plating
current, measuring the electrodeposition plating current at a
plurality of locations on the multi-channel current probe using a
plurality of current sensing circuits and adjusting the
distribution of the electrodeposition plating currents based on the
measurements taken.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a diagram of an exemplary embodiment of an
electrodeposition measurement system.
[0008] FIG. 2A is a front view of an exemplary embodiment of a
current probe used in the current probe measurement system.
[0009] FIG. 2B is a back view of an exemplary embodiment of the
current probe.
[0010] FIG. 3 is a cross-sectional view of an exemplary embodiment
of the current probe.
[0011] FIG. 4 is a diagram of an exemplary embodiment of a single
channel within the current probe.
DETAILED DESCRIPTION
[0012] FIG. 1 shows an exemplary embodiment of electrodeposition
measuring system 10, which includes plating cell 12, plating bath
14 contained within plating cell 12, electrode 16, current probe 18
which includes a plurality of apertures 20a, 20b, . . . 20N
("apertures 20"), plastic baffles 22a and 22b, data acquisition
board 23, and computer system 24.
[0013] To measure the spatial distribution of plating currents,
current probe 18 is placed in plating cell 12, submerged in plating
bath 14. In this exemplary embodiment, plating bath 14 includes
copper ions (Cu.sup.2+). A potential difference is created between
electrode 16 (which in this exemplary embodiment, acts as an anode)
and current probe 18 (which in this embodiment acts as a cathode).
The potential difference causes copper ions (Cu.sup.2+) located in
plating bath 14 to flow toward current probe 18. Copper ions
flowing toward current probe 18 eventually come into contact with
current probe 18, where the ionic charge is neutralized and the
copper ions plate onto the surface of current probe 18. The flow of
positive charge to current probe 18 caused by the copper ions
results in current being generated at current probe 18. The
magnitude of the current, and more specifically of current density,
is directly related to the thickness of copper plating deposited on
current probe 18. Variations in current density across the area of
current probe 18 result in varying plating thickness. By detecting
and measuring current magnitude and/or current density at a number
of locations along current probe 18, the plating thickness at each
location can be determined.
[0014] In an exemplary embodiment, current associated with copper
ions incident to the plurality of apertures 20 is detected by
current sensing circuits, the details of which are described below
with respect to FIG. 2B. Currents detected at the plurality of
apertures 20 are provided to data acquisition board 23. Data
acquisition board 23 measures currents detected at the plurality of
apertures 20 by measuring a voltage drop across each current
sensing circuit. The measured current value associated with each of
the plurality of apertures 20 is converted by the data acquisition
board to a digital value, which can be displayed or stored by
computer system 24. Knowing the area of each aperture 20 (in one
embodiment, each aperture 20 is of equal area) allows either data
acquisition board 23 or a processor to calculate current density
associated with each aperture 20. In this way, electrodeposition
measuring system 10 provides real time data concerning current
and/or current density sensed at a number of locations along
current probe 18. Based on this data, a user can manipulate the
mechanics of plating cell 12 or plating bath 14 to achieve the
desired current distribution along current probe 18. In the
exemplary embodiment shown, plastic baffles 22a and 22b may be
manipulated to alter the current distribution. Current distribution
can be measured again using current probe 18, and further
adjustments can be made.
[0015] FIGS. 2A-2B are diagrams of the front and back faces,
respectively, of current probe 18. FIG. 2A shows conductive layer
26 located on the front face of current probe 18, along with a
plurality of apertures 20a, 20b, . . . 20N ("apertures 20").
Conductive layer 26 acts as an electrode (in this example, a
cathode) in the electrodeposition process. During testing of
electrodeposition current distribution, a potential difference is
created between conductive layer 26 and electrode 16 (shown in FIG.
1), causing metal ions to travel toward conductive layer 26.
Connector tabs 28a and 28b, discussed in more detail below, may be
connected to a power supply capable of providing a potential to
conductive layer 26. Apertures 20 are small openings in conductive
layer 26 that extend through conductive layer 26 (as well as an
insulating layer shown in FIG. 3) to one of the plurality of
current sensing circuits 32a, 32b, . . . 32N. ("current sensing
circuits 32") formed on the back face of current probe 18, as shown
in FIG. 2B. Metal ions incident to apertures 20 travel through the
apertures and plate onto current sensing circuits 32. The current
created at each of the current sensing circuits 32 by incident
metal ions allows current probe 18 to determine the magnitude
and/or density of current at each of the plurality of apertures
20.
[0016] FIG. 2B is a diagram of the back face of current probe 18,
including a plurality of current sensing circuits 32a, 32b, . . .
32N, deposited on an insulating layer 34. A current measuring
device 35 (in one embodiment, current measuring device 35 is
included within data acquisition board 23 (FIG. 1)) connects to
probe 18 by way of connector tabs 28a and 28b. In this embodiment,
there are eight current sensing circuits, each providing a channel
of data to current measuring device 35. Each current sensing
circuit 32 intersects with one of the plurality of apertures 20
shown in FIG. 2A and is extended to the edge of connector tabs 28a
and 28b. Current measuring device 35 is connected between connector
tabs 28a and 28b, which closes the circuit between points A and B
for each current sensing circuit 32 and allows current measuring
device 35 to measure current by determining a voltage drop between
points A and B.
[0017] Insulating layer 34 isolates current sensing circuits 32
from conductive layer 26 located on the front face of current probe
18. Therefore, apertures 20 are formed through conductive layer 26
as well as insulating layer 34 to expose a conductive portion of
current sensing circuit 32 to incoming metal ions. In order for the
sensing circuits 32 to sample representative plating currents on
electrode 26, current sensing circuits 32 are held at nearly the
same cathodic potential as electrode 26. Current generated in each
of the current sensing circuits 32 by incoming metal ions is
provided to current measuring device 35.
[0018] The conductive lines (having a thickness and depth) making
up each current sensing circuit 32 are formed by pattern plating
copper onto insulating layer 34. As shown in FIG. 2B, the
conductive line length of each current sensing circuit 32 varies
depending on the distance to connector tabs 28a and 28b. This
varying length of each current sensing circuit 32 can result in
varying overall resistance values of each current sensing circuit
32. For example, the conductive line length of current sensing
circuit 32a is shorter than the conductive line length of current
sensing circuit 32b, which results in current sensing circuit 32a
having a lower overall resistance than current sensing circuit 32b.
Varying overall resistances of each current sensing circuit 32 must
be taken into account when current measuring device 35 measures the
voltage drop between points A and B.
[0019] In one exemplary embodiment, the conductive line of each of
the number of current sensing circuits 32 is designed such that
each current sensing circuit 32 is of equal resistance. By varying
the thickness and/or width of the conductive lines making up each
current sensing circuit 32, the overall resistance of each current
sensing circuit 32 can be made equal. Configuring current sensing
circuits 32 to have equal overall resistance allows for easier
measuring and comparison of currents by current measuring device
35. For instance, if currents associated with each current sensing
circuit 32 are determined by measuring a voltage drop between
points A and B, then the measured voltages can be directly compared
without having to employ external resistors to take into account
the differences in resistance of current sensing circuits 32.
[0020] FIG. 3 is a cross sectional view taken along dashed line 37
in FIG. 2B, illustrating the locations of conductive layer 26,
insulating layer 34, current sensing circuit 32a, and epoxy layer
36 within a portion of current probe 18. The resistance of current
sensing circuit 32a is made sufficiently small so that conductive
layer 26 and current sensing circuit 32a are at nearly the same
cathodic potential. Aperture 20a is formed through conductive layer
26 and insulating layer 34 to expose current sensing circuit 32a to
incident or incoming metal ions (e.g., Cu.sup.2+). Insulating layer
34 separates conductive layer 26 from current sensing circuit 32a.
Epoxy layer 36 prevents current incident to the back face of
current probe 18 from affecting current sensing circuit 32a. During
the measuring process, metal ions will plate onto current sensing
circuit 32a. However, this does not have any significant effect on
the overall resistance of current sensing circuit 32a, and
therefore does not affect current magnitude or density
measurements. Therefore, a single current probe 18 can be used a
number of times to measure current magnitude and/or density
distribution despite some amount of metal plating being deposited
on each of the number of current sensing circuits 32, provided
metal plating deposited on current sensing circuit 32a does not
extend up to conductive layer 26, resulting in a short circuit
condition.
[0021] FIG. 4 is a schematic diagram of current sensing circuit 32a
located on current probe 18. Current sensing circuit 32a includes
current sensing area 40a and conductive line 42a and 42b, which
provides sensed currents to current measuring device 35 connected
between connecting tabs 28a and 28b. It should be noted that each
current sensing circuit 32a-32N will include similar current
sensing area and conductive line connecting the current sensing
area to connector tabs 28a and 28b. Aperture 20a is formed through
conductive layer 26 (shown in FIG. 3) and insulating layer 34
(shown in FIG. 3) to expose a portion of current sensing area 40a
to incident currents. It is important that the area exposed by
aperture 20a be entirely within current sensing area 40a. If a
portion of aperture 20a exposes an area outside of current sensing
area 40a, any current incident to this outside area will not
generate current within current sensing circuit 32a. Knowing the
amount of current sensing area 40a exposed by aperture 20a allows
current density to be determined along with the magnitude of the
current measured. If each of the plurality of current sensing
circuits 32 employed have an equal amount of current sensing area
exposed, then current densities of each can be compared without the
need for additional compensation or calculations.
[0022] A multi-channel current probe has been described. Although
the current probe described with reference to FIGS. 1-4 is a
current probe with eight apertures and corresponding current
sensing circuits located in vertical fashion, it should be
understood that any number of apertures and corresponding current
sensing circuits may be employed and may be located in any pattern
order to gather information relevant to a particular
application.
[0023] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *