U.S. patent application number 12/201840 was filed with the patent office on 2009-03-26 for production line module for forming multiple sized photovoltaic devices.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Robert Z. Bachrach, Yong-Kee Chae, Soo Young Choi, Nicholas G.J. De Vries, Yacov Elgar, Eric A. Englhardt, Michel R. Frei, Charles Gay, Parris Hawkins, Choi (Gene) Ho, James Craig Hunter, Penchala N. Kankanala, Liwei Li, Wing Hoo (Hendrick) Lo, Danny Cam Toan Lu, Fang Mei, Stephen P. Murphy, Srujal (Steve) Patel, Matthew J.B. Saunders, Asaf Schlezinger, Shuran Sheng, Tzay-Fa (Jeff) Su, Jeffrey S. Sullivan, David Tanner, Teresa Trowbridge, Brice Walker, John M. White, Tae K. Won.
Application Number | 20090077804 12/201840 |
Document ID | / |
Family ID | 40387871 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090077804 |
Kind Code |
A1 |
Bachrach; Robert Z. ; et
al. |
March 26, 2009 |
PRODUCTION LINE MODULE FOR FORMING MULTIPLE SIZED PHOTOVOLTAIC
DEVICES
Abstract
The present invention generally relates to a sectioning module
positioned within an automated solar cell device fabrication
system. The solar cell device fabrication system is adapted to
receive a single large substrate and form multiple silicon thin
film solar cell devices from the single large substrate.
Inventors: |
Bachrach; Robert Z.;
(Burlingame, CA) ; Chae; Yong-Kee; (Pleasanton,
CA) ; Choi; Soo Young; (Fremont, CA) ; De
Vries; Nicholas G.J.; (Alameda, CA) ; Elgar;
Yacov; (Sunnyvale, CA) ; Englhardt; Eric A.;
(Palo Alto, CA) ; Frei; Michel R.; (Palo Alto,
CA) ; Gay; Charles; (Westlake Village, CA) ;
Hawkins; Parris; (Los Altos, CA) ; Ho; Choi
(Gene); (Sunnyvale, CA) ; Hunter; James Craig;
(Los Gatos, CA) ; Kankanala; Penchala N.; (Santa
Clara, CA) ; Li; Liwei; (Sunnyvale, CA) ; Lo;
Wing Hoo (Hendrick); (San Francisco, CA) ; Lu; Danny
Cam Toan; (San Francisco, CA) ; Mei; Fang;
(Foster City, CA) ; Murphy; Stephen P.;
(Perrysburg, OH) ; Patel; Srujal (Steve); (San
Jose, CA) ; Saunders; Matthew J.B.; (Sunnyvale,
CA) ; Schlezinger; Asaf; (Sunnyvale, CA) ;
Sheng; Shuran; (Sunnyvale, CA) ; Su; Tzay-Fa
(Jeff); (San Jose, CA) ; Sullivan; Jeffrey S.;
(Castro Valley, CA) ; Tanner; David; (San Jose,
CA) ; Trowbridge; Teresa; (Los Altos, CA) ;
Walker; Brice; (San Juan Bautista, CA) ; White; John
M.; (Hayward, CA) ; Won; Tae K.; (San Jose,
CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
40387871 |
Appl. No.: |
12/201840 |
Filed: |
August 29, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60967077 |
Aug 31, 2007 |
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61023214 |
Jan 24, 2008 |
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61034931 |
Mar 7, 2008 |
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61023739 |
Jan 25, 2008 |
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61023810 |
Jan 25, 2008 |
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61020304 |
Jan 10, 2008 |
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61032005 |
Feb 27, 2008 |
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61036691 |
Mar 14, 2008 |
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61043060 |
Apr 7, 2008 |
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61044852 |
Apr 14, 2008 |
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Current U.S.
Class: |
29/890.033 ;
225/1; 225/96.5; 225/97; 438/462 |
Current CPC
Class: |
Y10T 225/329 20150401;
Y10T 225/10 20150401; B26F 3/002 20130101; H01L 21/67132 20130101;
H02S 50/10 20141201; B26F 3/004 20130101; H01L 31/075 20130101;
Y10T 29/5313 20150115; B65G 49/064 20130101; H01L 21/67727
20130101; Y10T 29/5317 20150115; Y10T 29/53187 20150115; B23K
26/364 20151001; H01L 31/0504 20130101; Y02E 10/548 20130101; Y02P
40/57 20151101; C03B 33/03 20130101; C03B 33/033 20130101; B65G
2249/02 20130101; Y10T 29/49355 20150115; H01L 21/67721 20130101;
Y10T 29/5196 20150115; H02S 50/00 20130101; H01L 21/67712 20130101;
H01L 21/67715 20130101; H01L 31/03921 20130101; Y10T 29/53113
20150115; Y10T 29/53417 20150115; Y10T 225/325 20150401; Y10T
29/49002 20150115; H01L 21/6776 20130101; B65G 2249/04 20130101;
H01L 21/67236 20130101; H01L 31/022425 20130101; Y10T 29/53365
20150115 |
Class at
Publication: |
29/890.033 ;
225/1; 225/96.5; 225/97; 438/462 |
International
Class: |
H01L 31/18 20060101
H01L031/18; H01L 21/304 20060101 H01L021/304; B26F 3/00 20060101
B26F003/00 |
Claims
1. A module for sectioning a solar cell device, comprising: an
inlet conveyor configured to receive commands from a system
controller and transfer a solar cell device into a scribing station
of the module; a scribing mechanism configured to receive commands
from the system controller and scribe a pattern into a first
surface of the solar cell device; a first positioning mechanism
configured to receive commands from the system controller and
accurately position the scribed solar cell device over a first
break mechanism; and a first actuator configured to receive
commands from the system controller and raise the first break
mechanism.
2. The module of claim 1, further comprising: a cross transfer
station having a conveyor and a second positioning mechanism,
wherein the conveyor is positioned to receive a section of the
solar cell device from the first positioning mechanism, and wherein
the second positioning mechanism is configured to receive commands
from the system controller and accurately position the section of
the solar cell device over a second break mechanism; a second
actuator configured to receive commands from the system controller
and raise the second break mechanism; and an exit conveyor
positioned to receive a portion of the section of the solar cell
device.
3. The module of claim 2, wherein the first and second break
mechanisms are elongated rollers.
4. The module of claim 3, wherein the first break mechanism extends
along a first axis and the second break mechanism extends along a
second axis, and wherein the first and second axes are
substantially perpendicular to one another.
5. The module of claim 1, wherein the scribing mechanism is a
mechanical scribing wheel.
6. The module of claim 1, wherein the scribing mechanism is a laser
scribing device.
7. A method for sectioning a partially processed solar cell device,
comprising: receiving a substrate having a processing surface;
forming a silicon layer on the processing surface; sectioning the
substrate into a first and a second section after forming the
silicon layer on the processing surface; and transferring the first
section into a next station for further processing.
8. The method of claim 7, wherein sectioning the substrate
comprises: scribing a first line into a surface of the substrate
after forming the silicon layer on the processing surface; and
actuating a break mechanism to break the substrate along the first
line.
9. The method of claim 8, wherein the scribing a first line
comprises scribing a line completely through the silicon layer and
into the processing surface.
10. The method of claim 8, further comprising scribing a second
line into the processing surface, wherein the second line is
substantially perpendicular to the first line.
11. The method of claim 10, further comprising positioning the
first section of the substrate adjacent a second break mechanism
such that the second scribed line is substantially in line with an
axis of the second break mechanism.
12. The method of claim 11, further comprising actuating the second
break mechanism to break the first section along the second scribed
line.
13. The method of claim 11, wherein the processing surface has a
surface area greater than about 1.4 m.sup.2.
14. A system for fabricating solar cell devices, comprising: a
substrate receiving module that is adapted to receive a substrate;
a cluster tool having a processing chamber that is adapted to
deposit a silicon-containing layer on a surface of the substrate; a
back contact deposition chamber configured to deposit a back
contact layer on a surface of the substrate; a substrate sectioning
module configured to section the substrate into two or more
sections; and a system controller for controlling and coordinating
functions of each of the substrate receiving module, the cluster
tool, the processing chamber, the back contact deposition chamber,
and the substrate sectioning module.
15. The system of claim 14, wherein the substrate sectioning module
comprises a CNC glass cutter.
16. The system of claim 14, wherein the substrate sectioning module
comprises a scribing station configured to scribe a line into a
surface of the substrate, a breaking station configured to break
the substrate along the line, and a positioning mechanism for
positioning the substrate such that the line scribed into the
substrate is substantially aligned with the breaking mechanism.
17. The system of claim 16, wherein the substrate sectioning module
further comprises a second positioning mechanism for positioning
one of the sections of the substrate adjacent a second breaking
mechanism, such that the second breaking mechanism is substantially
aligned with a second line scribed into the substrate.
18. A method of processing a solar cell device, comprising:
cleaning a substrate to remove one or more contaminants from a
surface of the substrate; depositing a photoabsorbing layer on the
surface of the substrate; removing at least a portion of the
photoabsorbing layer from a region on the surface of the substrate;
depositing a back contact layer on the surface of the substrate;
sectioning the substrate into two or more sections; performing an
edge deletion process on a surface of one of the sections; bonding
a back glass substrate to the surface of one of the sections to
form a composite structure; and attaching a junction box to the
composite structure.
19. The method of claim 18, wherein the sectioning the substrate
comprises cutting the substrate with a CNC glass cutter.
19. The method of claim 18, wherein sectioning the substrate
comprises scribing a first line into the substrate, aligning the
first line with a first break mechanism, and breaking the substrate
along the first line.
20. The method of claim 19, wherein sectioning the substrate
further comprises scribing a second line into the substrate,
aligning the second line with a second break mechanism, and
breaking the substrate along the second line, wherein the first
line is substantially perpendicular to the second line.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 60/967,077, filed Aug. 31, 2007 (Attorney
Docket No. APPM/011141 L), U.S. Provisional Patent Application Ser.
No. 61/023,214, filed Jan. 24, 2008 (Attorney Docket No.
APPM/12959L), U.S. Provisional Patent Application Ser. No.
61/034,931, filed Mar. 7, 2008 (Attorney Docket No. APPM/12959L02),
U.S. Provisional Patent Application Ser. No. 61/023,739, filed Jan.
25, 2008 (Attorney Docket No. APPM/12960L), U.S. Provisional Patent
Application Ser. No. 61/023,810, filed Jan. 25, 2008 (Attorney
Docket No. APPM/12961L), U.S. Provisional Patent Application Ser.
No. 61/020,304, filed Jan. 10, 2008 (Attorney Docket No.
APPM/12962L), U.S. Provisional Patent Application Ser. No.
61/032,005, filed Feb. 27, 2008 (Attorney Docket No. APPM/13160),
U.S. Provisional Patent Application Ser. No. 61/036,691, filed Mar.
14, 2008 (Attorney Docket No. APPM/13177L02), U.S. Provisional
Patent Application Ser. No. 61/043,060, filed Apr. 8, 2008
(Attorney Docket No. APPM/13321L), and U.S. Provisional Patent
Application Ser. No. 61/044,852, filed Apr. 14, 2008 (Attorney
Docket No. APPM/13322L), which are all incorporated by reference in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the present invention generally relate to a
module of a production line used to form multiple sized solar cell
devices.
[0004] 2. Description of the Related Art
[0005] Photovoltaic (PV) devices or solar cells are devices which
convert sunlight into direct current (DC) electrical power. Typical
thin film type PV devices, or thin film solar cells, have one or
more p-i-n junctions. Each p-i-n junction comprises a p-type layer,
an intrinsic type layer, and an n-type layer. When the p-i-n
junction of the solar cell is exposed to sunlight (consisting of
energy from photons), the sunlight is converted to electricity
through the PV effect. Solar cells may be tiled into larger solar
arrays. The solar arrays are created by connecting a number of
solar cells and joining them into panels with specific frames and
connectors.
[0006] Typically, a thin film solar cell includes active regions,
or photoelectric conversion units, and a transparent conductive
oxide (TCO) film disposed as a front electrode and/or as a back
electrode. The photoelectric conversion unit includes a p-type
silicon layer, an n-type silicon layer, and an intrinsic type
(i-type) silicon layer sandwiched between the p-type and n-type
silicon layers. Several types of silicon films including
microcrystalline silicon film (.mu.c-Si), amorphous silicon film
(a-Si), polycrystalline silicon film (poly-Si), and the like may be
utilized to form the p-type, n-type, and/or i-type layers of the
photoelectric conversion unit. The backside electrode may contain
one or more conductive layers. There is a need for an improved
process of forming a solar cell that has good interfacial contact,
low contact resistance and provides a high overall electrical
device performance.
[0007] With traditional energy source prices on the rise, there is
a need for a low cost way of producing electricity using a low cost
solar cell device. Conventional solar cell manufacturing processes
are highly labor intensive and have numerous interruptions that can
affect the production line throughput, solar cell cost, and device
yield. For instance, particular solar cell device sizes are needed
for particular applications. Conventional solar cell lines are
either capable of producing only a single sized solar cell device
or require significant downtime to manually convert the solar cell
production line processes to accommodate a different substrate size
and produce a different sized solar cell device. Thus, there is a
need for a production line that is able to perform all phases of
the fabrication process for producing multiple sized solar cell
devices from a single large substrate.
SUMMARY OF THE INVENTION
[0008] In one embodiment of the present invention, a module for
sectioning a solar cell device comprises an inlet conveyor
configured to receive commands from a system controller and
transfer a solar cell device into a scribing station of the module,
a scribing mechanism configured to receive commands from the system
controller and scribe a pattern into a first surface of the solar
cell device, a first positioning mechanism configured to receive
commands from the system controller and accurately position the
scribed solar cell device over a first break mechanism, and a first
actuator configured to receive commands from the system controller
and raise the first break mechanism.
[0009] In another embodiment of the present invention, a method for
sectioning a partially processed solar cell device comprises
receiving a substrate having a processing surface, forming a
silicon layer on the processing surface, sectioning the substrate
into a first and second section after forming the silicon layer on
the processing surface, and transferring the first section into a
next station for further processing.
[0010] In another embodiment of the present invention, a system for
fabricating solar cell devices comprises a substrate receiving
module that is adapted to receive a substrate, a cluster tool
having a processing chamber that is adapted to deposit a
silicon-containing layer on a surface of the substrate, a back
contact deposition chamber configured to deposit a back contact
layer on a surface of the substrate, a substrate sectioning module
configured to section the substrate into two or more sections, and
a system controller for controlling and coordinating functions of
each of the substrate receiving module, the cluster tool, the
processing chamber, the back contact deposition chamber, and the
substrate sectioning module.
[0011] In yet another embodiment of the present invention, a method
of processing a solar cell device comprises cleaning a substrate to
remove one or more contaminants from a surface of the substrate,
depositing a photoabsorbing layer on the surface of the substrate,
removing at least a portion of the photoabsorbing layer from a
region on a surface of the substrate, depositing a back contact
layer on the surface of the substrate, sectioning the substrate
into two or more sections, performing an edge deletion process on a
surface of one of the sections bonding a back glass substrate to
the surface of one of the sections to form a composite structure,
and attaching a junction box to the composite structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0013] FIG. 1 illustrates a process sequence for forming a solar
cell device according to one embodiment described herein.
[0014] FIG. 2 illustrates a plan view of a solar cell production
line according to one embodiment described herein.
[0015] FIG. 3A is a side cross-sectional view of a thin film solar
cell device according to one embodiment described herein.
[0016] FIG. 3B is a side cross-sectional view of a thin film solar
cell device according to one embodiment described herein.
[0017] FIG. 3C is a plan view of a composite solar cell structure
according to one embodiment described herein.
[0018] FIG. 3D is a cross-sectional view of along Section A-A of
FIG. 3C.
[0019] FIG. 3E is a side cross-sectional view of a thin film solar
cell device according to one embodiment described herein.
[0020] FIGS. 4A-4E are schematic plan views illustrating the
sequencing of a sectioning module according to one embodiment of
the present invention.
[0021] FIGS. 5A-5C are schematic side views of portions of the
sectioning module illustrating a sequence of sectioning a substrate
according to one embodiment of the present invention.
DETAILED DESCRIPTION
[0022] Embodiments of the present invention generally relate to a
system used to form solar cell devices using processing modules
adapted to perform one or more processes in the formation of the
solar cell devices. In one embodiment, the system is adapted to
form thin film solar cell devices by accepting a large unprocessed
substrate and performing multiple deposition, material removal,
cleaning, sectioning, bonding, and testing processes to form
multiple complete, functional, and tested solar cell devices that
can then be shipped to an end user for installation in a desired
location to generate electricity. In one embodiment, the system is
capable of accepting a single large unprocessed substrate and
producing multiple smaller solar cell devices. In one embodiment,
the system is capable of changing the sizes of the solar cell
devices produced from the single large substrate without manually
moving or altering any of the system modules. While the discussion
below primarily describes the formation of silicon thin film solar
cell devices, this configuration is not intended to be limiting as
to the scope of the invention since the apparatus and methods
disclosed herein can also be used to form, test, and analyze other
types of solar cell devices, such as III-V type solar cells, thin
film chalcogenide solar cells (e.g., CIGS, CdTe cells), amorphous
or nanocrystalline silicon solar cells, photochemical type solar
cells (e.g., dye sensitized), crystalline silicon solar cells,
organic type solar cells, or other similar solar cell devices.
[0023] The system is generally an arrangement of automated
processing modules and automation equipment used to form solar cell
devices that are interconnected by an automated material handling
system. In one embodiment, the system is a fully automated solar
cell device production line that is designed to reduce and/or
remove the need for human interaction and/or labor intensive
processing steps to improve the device reliability, process
repeatability, and the cost of ownership of the formation process.
In one configuration, the system is adapted to form multiple
silicon thin film solar cell devices from a single large substrate
and generally comprises a substrate receiving module that is
adapted to accept an incoming substrate, one or more absorbing
layer deposition cluster tools having at least one processing
chamber that is adapted to deposit a silicon-containing layer on a
processing surface of the substrate, one or more back contact
deposition chambers that is adapted to deposit a back contact layer
on the processing surface of the substrate, one or more material
removal chambers that are adapted to remove material from the
processing surface of each substrate, one or more sectioning
modules used to section the processed substrate into multiple
smaller processed substrates, a solar cell encapsulation device, an
autoclave module that is adapted to heat and expose a composite
solar cell structure to a pressure greater than atmospheric
pressure, a junction box attaching region to attach a connection
element that allows the solar cells to be connected to external
components, and one or more quality assurance modules adapted to
test and qualify each completely formed solar cell device. The one
or more quality assurance modules generally include a solar
simulator, a parametric testing module, and a shunt bust and
qualification module.
[0024] FIG. 1 illustrates one embodiment of a process sequence 100
that contains a plurality of steps (i.e., steps 102-142) that are
each used to form a solar cell device using a novel solar cell
production line 200 described herein. The configuration, number of
processing steps, and order of the processing steps in the process
sequence 100 is not intended to be limiting to the scope of the
invention described herein. FIG. 2 is a plan view of one embodiment
of the production line 200, which is intended to illustrate some of
the typical processing modules and process flows through the system
and other related aspects of the system design, and is thus not
intended to be limiting to the scope of the invention described
herein.
[0025] In general, a system controller 290 may be used to control
one or more components found in the solar cell production line 200.
The system controller 290 is generally designed to facilitate the
control and automation of the overall solar cell production line
200 and typically includes a central processing unit (CPU) (not
shown), memory (not shown), and support circuits (or I/O) (not
shown). The CPU may be one of any form of computer processors that
are used in industrial settings for controlling various system
functions, substrate movement, chamber processes, and support
hardware (e.g., sensors, robots, motors, lamps, etc.), and monitor
the processes (e.g., substrate support temperature, power supply
variables, chamber process time, I/O signals, etc.). The memory is
connected to the CPU, and may be one or more of a readily available
memory, such as random access memory (RAM), read only memory (ROM),
floppy disk, hard disk, or any other form of digital storage, local
or remote. Software instructions and data can be coded and stored
within the memory for instructing the CPU. The support circuits are
also connected to the CPU for supporting the processor in a
conventional manner. The support circuits may include cache, power
supplies, clock circuits, input/output circuitry, subsystems, and
the like. A program (or computer instructions) readable by the
system controller 290 determines which tasks are performable on a
substrate. Preferably, the program is software readable by the
system controller 290 that includes code to perform tasks relating
to monitoring, execution and control of the movement, support,
and/or positioning of a substrate along with the various process
recipe tasks and various chamber process recipe steps being
performed in the solar cell production line 200. In one embodiment,
the system controller 290 also contains a plurality of programmable
logic controllers (PLC's) that are used to locally control one or
more modules in the solar cell production, and a material handling
system controller (e.g., PLC or standard computer) that deals with
the higher level strategic movement, scheduling and running of the
complete solar cell production line. An example of a system
controller, distributed control architecture, and other system
control structure that may be useful for one or more of the
embodiments described herein can be found in the U.S. Provisional
Patent Application Ser. No. 60/967,077, which has been incorporated
by reference.
[0026] Examples of a solar cell 300 that can be formed using the
process sequence(s) illustrated in FIG. 1 and the components
illustrated in the solar cell production line 200 are illustrated
in FIGS. 3A-3E. FIG. 3A is a simplified schematic diagram of a
single junction amorphous or micro-crystalline silicon solar cell
300 that can be formed and analyzed in the system described below.
As shown in FIG. 3A, the single junction amorphous or
micro-crystalline silicon solar cell 300 is oriented toward a light
source or solar radiation 301. The solar cell 300 generally
comprises a substrate 302, such as a glass substrate, polymer
substrate, metal substrate, or other suitable substrate, with thin
films formed thereover. In one embodiment, the substrate 302 is a
glass substrate that is about 2200 mm.times.2600 mm.times.3 mm in
size. The solar cell 300 further comprises a first transparent
conducting oxide (TCO) layer 310 (e.g., zinc oxide (ZnO), tin oxide
(SnO)) formed over the substrate 302, a first p-i-n junction 320
formed over the first TCO layer 310, a second TCO layer 340 formed
over the first p-i-n junction 320, and a back contact layer 350
formed over the second TCO layer 340. To improve light absorption
by enhancing light trapping, the substrate and/or one or more of
the thin films formed thereover may be optionally textured by wet,
plasma, ion, and/or mechanical processes. For example, in the
embodiment shown in FIG. 3A, the first TCO layer 310 is textured,
and the subsequent thin films deposited thereover generally follow
the topography of the surface below it. In one configuration, the
first p-i-n junction 320 may comprise a p-type amorphous silicon
layer 322, an intrinsic type amorphous silicon layer 324 formed
over the p-type amorphous silicon layer 322, and an n-type
microcrystalline silicon layer 326 formed over the intrinsic type
amorphous silicon layer 324. In one example, the p-type amorphous
silicon layer 322 may be formed to a thickness between about 60
.ANG. and about 300 .ANG., the intrinsic type amorphous silicon
layer 324 may be formed to a thickness between about 1,500 .ANG.
and about 3,500 .ANG., and the n-type microcrystalline
semiconductor layer 326 may be formed to a thickness between about
100 .ANG. and about 400 .ANG.. The back contact layer 350 may
include, but is not limited to a material selected from the group
consisting of Al, Ag, Ti, Cr, Au, Cu, Pt, alloys thereof, and
combinations thereof.
[0027] FIG. 3B is a schematic diagram of an embodiment of a solar
cell 300, which is a multi-junction solar cell that is oriented
toward the light or solar radiation 301. The solar cell 300
comprises a substrate 302, such as a glass substrate, polymer
substrate, metal substrate, or other suitable substrate, with thin
films formed thereover. The solar cell 300 may further comprise a
first transparent conducting oxide (TCO) layer 310 formed over the
substrate 302, a first p-i-n junction 320 formed over the first TCO
layer 310, a second p-i-n junction 330 formed over the first p-i-n
junction 320, a second TCO layer 340 formed over the second p-i-n
junction 330, and a back contact layer 350 formed over the second
TCO layer 340. In the embodiment shown in FIG. 3B, the first TCO
layer 310 is textured, and the subsequent thin films deposited
thereover generally follow the topography of the surface below it.
The first p-i-n junction 320 may comprise a p-type amorphous
silicon layer 322, an intrinsic type amorphous silicon layer 324
formed over the p-type amorphous silicon layer 322, and an n-type
microcrystalline silicon layer 326 formed over the intrinsic type
amorphous silicon layer 324. In one example, the p-type amorphous
silicon layer 322 may be formed to a thickness between about 60
.ANG. and about 300 .ANG., the intrinsic type amorphous silicon
layer 324 may be formed to a thickness between about 1,500 .ANG.
and about 3,500 .ANG., and the n-type microcrystalline
semiconductor layer 326 may be formed to a thickness between about
100 .ANG. and about 400 .ANG.. The second p-i-n junction 330 may
comprise a p-type microcrystalline silicon layer 332, an intrinsic
type microcrystalline silicon layer 334 formed over the p-type
microcrystalline silicon layer 332, and an n-type amorphous silicon
layer 336 formed over the intrinsic type microcrystalline silicon
layer 334. In one example, the p-type microcrystalline silicon
layer 332 may be formed to a thickness between about 100 .ANG. and
about 400 .ANG., the intrinsic type microcrystalline silicon layer
334 may be formed to a thickness between about 10,000 .ANG. and
about 30,000 .ANG., and the n-type amorphous silicon layer 336 may
be formed to a thickness between about 100 .ANG. and about 500
.ANG.. The back contact layer 350 may include, but is not limited
to a material selected from the group consisting of Al, Ag, Ti, Cr,
Au, Cu, Pt, alloys thereof, and combinations thereof.
[0028] FIG. 3C is a plan view that schematically illustrates an
example of the rear surface of a formed solar cell 300 that has
been produced in the production line 200. FIG. 3D is a side
cross-sectional view of portion of the solar cell 300 illustrated
in FIG. 3C (see section A-A). While FIG. 3D illustrates the
cross-section of a single junction cell similar to the
configuration described in FIG. 3A, this is not intended to be
limiting as to the scope of the invention described herein.
[0029] As shown in FIGS. 3C and 3D, the solar cell 300 may contain
a substrate 302, the solar cell device elements (e.g., reference
numerals 310-350), one or more internal electrical connections
(e.g., side buss 355, cross-buss 356), a layer of bonding material
360, a back glass substrate 361, and a junction box 370. The
junction box 370 may generally contain two connection points 371,
372 that are electrically connected to portions of the solar cell
300 through the side buss 355 and the cross-buss 356, which are in
electrical communication with the back contact layer 350 and active
regions of the solar cell 300. To avoid confusion relating to the
actions specifically performed on the substrates 302 in the
discussion below, a substrate 302 having one or more of the
deposited layers (e.g., reference numerals 310-350) and/or one or
more internal electrical connections (e.g., side buss 355,
cross-buss 356) disposed thereon is generally referred to as a
device substrate 303. Similarly, a device substrate 303 that has
been bonded to a back glass substrate 361 using a bonding layer 360
is referred to as a composite solar cell structure 304.
[0030] FIG. 3E is a schematic cross-section of a solar cell 300
illustrating various scribed regions used to form the individual
cells 382A-382B within the solar cell 300. As illustrated in FIG.
3E, the solar cell 300 includes a transparent substrate 302, a
first TCO layer 310, a first p-i-n junction 320, and a back contact
layer 350. Three laser scribing steps may be performed to produce
trenches 381A, 381B, and 381C, which are generally required to form
a high efficiency solar cell device. Although formed together on
the substrate 302, the individual cells 382A and 382B are isolated
from each other by the insulating trench 381C formed in the back
contact layer 350 and the first p-i-n junction 320. In addition,
the trench 381B is formed in the first p-i-n junction 320 so that
the back contact layer 350 is in electrical contact with the first
TCO layer 310. In one embodiment, the insulating trench 381A is
formed by the laser scribe removal of a portion of the first TCO
layer 310 prior to the deposition of the first p-i-n junction 320
and the back contact layer 350. Similarly, in one embodiment, the
trench 381B is formed in the first p-i-n junction 320 by the laser
scribe removal of a portion of the first p-i-n junction 320 prior
to the deposition of the back contact layer 350. While a single
junction type solar cell is illustrated in FIG. 3E this
configuration is not intended to be limiting to the scope of the
invention described herein.
General Solar Cell Formation Process Sequence
[0031] Referring to FIGS. 1 and 2, the process sequence 100
generally starts at step 102 in which a substrate 302 is loaded
into the loading module 202 found in the solar cell production line
200. In one embodiment, the substrates 302 are received in a "raw"
state where the edges, overall size, and/or cleanliness of the
substrates 302 are not well controlled. Receiving "raw" substrates
302 reduces the cost to prepare and store substrates 302 prior to
forming a solar device and thus reduces the solar cell device cost,
facilities costs, and production costs of the finally formed solar
cell device. However, typically, it is advantageous to receive
"raw" substrates 302 that have a transparent conducting oxide (TCO)
layer (e.g., first TCO layer 310) already deposited on a surface of
the substrate 302 before it is received into the system in step
102. If a conductive layer, such as TCO layer, is not deposited on
the surface of the "raw" substrates then a front contact deposition
step (step 107), which is discussed below, needs to be performed on
a surface of the substrate 302.
[0032] In one embodiment, the substrates 302 or 303 are loaded into
the solar cell production line 200 in a sequential fashion, and
thus do not use a cassette or batch style substrate loading system.
A cassette style and/or batch loading type system that requires the
substrates to be un-loaded from the cassette, processed, and then
returned to the cassette before moving to the next step in the
process sequence can be time consuming and decrease the solar cell
production line throughput. The use of batch processing does not
facilitate certain embodiments of the present invention, such as
fabricating multiple solar cell devices from a single substrate.
Additionally, the use of a batch style process sequence generally
prevents the use of an asynchronous flow of substrates through the
production line, which is believed to provide improved substrate
throughput during steady state processing and when one or more
modules are brought down for maintenance or due to a fault
condition. Generally, batch or cassette based schemes are not able
to achieve the throughput of the production line described herein,
when one or more processing modules are brought down for
maintenance, or even during normal operation, since the queuing and
loading of substrates can require a significant amount of overhead
time.
[0033] In the next step, step 104, the surfaces of the substrate
302 are prepared to prevent yield issues later on in the process.
In one embodiment of step 104, the substrate is inserted into a
front end substrate seaming module 204 that is used to prepare the
edges of the substrate 302 or 303 to reduce the likelihood of
damage, such as chipping or particle generation from occurring
during the subsequent processes. Damage to the substrate 302 or 303
can affect device yield and the cost to produce a usable solar cell
device. In one embodiment, the front end seaming module 204 is used
to round or bevel the edges of the substrate 302 or 303. In one
embodiment, a diamond impregnated belt or disc is used to grind the
material from the edges of the substrate 302 or 303. In another
embodiment, a grinding wheel, grit blasting, or laser ablation
technique is used to remove the material from the edges of the
substrate 302 or 303.
[0034] Next the substrate 302 or 303 is transported to the cleaning
module 206, in which step 106, or a substrate cleaning step, is
performed on the substrate 302 or 303 to remove any contaminants
found on the surface of thereof. Common contaminants may include
materials deposited on the substrate 302 or 303 during the
substrate forming process (e.g., glass manufacturing process)
and/or during shipping or storing of the substrates 302 or 303.
Typically, the cleaning module 206 uses wet chemical scrubbing and
rinsing steps to remove any undesirable contaminants.
[0035] In one example, the process of cleaning the substrate 302 or
303 may occur as follows. First, the substrate 302 or 303 enters a
contaminant removal section of the cleaning module 206 from either
a transfer table or an automation device 281. In general, the
system controller 290 establishes the timing for each substrate 302
or 303 that enters the cleaning module 206. The contaminant removal
section may utilize dry cylindrical brushes in conjunction with a
vacuum system to dislodge and extract contaminants from the surface
of the substrate 302. Next, a conveyor within the cleaning module
206 transfers the substrate 302 or 303 to a pre-rinse section,
where spray tubes dispense hot DI water at a temperature, for
example, of 50.degree. C. from a DI water heater onto a surface of
the substrate 302 or 303. Commonly, since the device substrate 303
has a TCO layer disposed thereon, and since TCO layers are
generally electron absorbing materials, DI water is used to avoid
any traces of possible contamination and ionizing of the TCO layer.
Next, the rinsed substrate 302, 303 enters a wash section. In the
wash section, the substrate 302 or 303 is wet-cleaned with a brush
(e.g., perlon) and hot water. In some cases a detergent (e.g.,
Alconox.TM., Citrajet.TM., Detojet.TM., Transene.TM., and Basic
H.TM.), surfactant, pH adjusting agent, and other cleaning
chemistries are used to clean and remove unwanted contaminants and
particles from the substrate surface. A water re-circulation system
recycles the hot water flow. Next, in a final rinse section of the
cleaning module 206, the substrate 302 or 303 is rinsed with water
at ambient temperature to remove any traces of contaminants.
Finally, in a drying section, an air blower is used to dry the
substrate 302 or 303 with hot air. In one configuration a
deionization bar is used to remove the electrical charge from the
substrate 302 or 303 at the completion of the drying process.
[0036] In the next step, or step 108, separate cells are
electrically isolated from one another via scribing processes.
Contamination particles on the TCO surface and/or on the bare glass
surface can interfere with the scribing procedure. In laser
scribing, for example, if the laser beam runs across a particle, it
may be unable to scribe a continuous line, and a short circuit
between cells will result. In addition, any particulate debris
present in the scribed pattern and/or on the TCO of the cells after
scribing can cause shunting and non-uniformities between layers.
Therefore, a well-defined and well-maintained process is generally
needed to ensure that contamination is removed throughout the
production process. In one embodiment, the cleaning module 206 is
available from the Energy and Environment Solutions division of
Applied Materials in Santa Clara, Calif.
[0037] Referring to FIGS. 1 and 2, in one embodiment, prior to
performing step 108 the substrates 302 are transported to a front
end processing module (not illustrated in FIG. 2) in which a front
contact formation process, or step 107, is performed on the
substrate 302. In one embodiment, the front end processing module
is similar to the processing module 218 discussed below. In step
107, the one or more substrate front contact formation steps may
include one or more preparation, etching and/or material deposition
steps that are used to form the front contact regions on a bare
solar cell substrate 302. In one embodiment, step 107 generally
comprises one or more PVD steps that are used to form the front
contact region on a surface of the substrate 302. In one
embodiment, the front contact region contains a transparent
conducting oxide (TCO) layer that may contain metal element
selected from a group consisting of zinc (Zn), aluminum (Al),
indium (In), and tin (Sn). In one example, a zinc oxide (ZnO) is
used to form at least a portion of the front contact layer. In one
embodiment, the front end processing module is an ATON.TM. PVD 5.7
tool available from Applied Materials in Santa Clara, Calif. in
which one or more processing steps are performed to deposit the
front contact formation steps. In another embodiment, one or more
CVD steps are used to form the front contact region on a surface of
the substrate 302.
[0038] Next the device substrate 303 is transported to the scribe
module 208 in which step 108, or a front contact isolation step, is
performed on the device substrate 303 to electrically isolate
different regions of the device substrate 303 surface from each
other. In step 108, material is removed from the device substrate
303 surface by use of a material removal step, such as a laser
ablation process. The success criteria for step 108 are to achieve
good cell-to-cell and cell-to-edge isolation while minimizing the
scribe area. In one embodiment, a Nd:vanadate (Nd:YVO.sub.4) laser
source is used ablate material from the device substrate 303
surface to form lines that electrically isolate one region of the
device substrate 303 from the next. In one embodiment, the laser
scribe process performed during step 108 uses a 1064 nm wavelength
pulsed laser to pattern the material disposed on the substrate 302
to isolate each of the individual cells (e.g., reference cells 382A
and 382B) that make up the solar cell 300. In one embodiment, a 5.7
m.sup.2 substrate laser scribe module available from Applied
Materials, Inc. of Santa Clara, Calif. is used to provide simple
reliable optics and substrate motion for accurate electrical
isolation of regions of the device substrate 303 surface. In
another embodiment, a water jet cutting tool or diamond scribe is
used to isolate the various regions on the surface of the device
substrate 303. In one aspect, it is desirable to assure that the
temperature of the device substrates 303 entering the scribe module
208 are at a temperature in a range between about 20.degree. C. and
about 26.degree. C. by use of an active temperature control
hardware assembly that may contain a resistive heater and/or
chiller components (e.g., heat exchanger, thermoelectric device).
In one embodiment, it is desirable to control the device substrate
303 temperature to about 25+/-0.5.degree. C.
[0039] Next the device substrate 303 is transported to the cleaning
module 210 in which step 110, or a pre-deposition substrate
cleaning step, is performed on the device substrate 303 to remove
any contaminants found on the surface of the device substrate 303
after performing the cell isolation step (step 108). Typically, the
cleaning module 210 uses wet chemical scrubbing and rinsing steps
to remove any undesirable contaminants found on the device
substrate 303 surface after performing the cell isolation step. In
one embodiment, a cleaning process similar to the processes
described in step 106 above is performed on the device substrate
303 to remove any contaminants on the surface(s) of the device
substrate 303.
[0040] Next, the device substrate 303 is transported to the
processing module 212 in which step 112, which comprises one or
more photoabsorber deposition steps, is performed on the device
substrate 303. In step 112, the one or more photoabsorber
deposition steps may include one or more preparation, etching,
and/or material deposition steps that are used to form the various
regions of the solar cell device. Step 112 generally comprises a
series of sub-processing steps that are used to form one or more
p-i-n junctions. In one embodiment, the one or more p-i-n junctions
comprise amorphous silicon and/or microcrystalline silicon
materials. In general, the one or more processing steps are
performed in one or more cluster tools (e.g., cluster tools
212A-212D) found in the processing module 212 to form one or more
layers in the solar cell device formed on the device substrate 303.
In one embodiment, the device substrate 303 is transferred to an
accumulator 211A prior to being transferred to one or more of the
cluster tools 212A-212D. In one embodiment, in cases where the
solar cell device is formed to include multiple junctions, such as
the tandem junction solar cell 300 illustrated in FIG. 3B, the
cluster tool 212A in the processing module 212 is adapted to form
the first p-i-n junction 320 and cluster tools 212B-212D are
configured to form the second p-i-n junction 330. Information
regarding the hardware and processing methods used to deposit one
or more layers in the p-i-n junctions is further described in U.S.
patent application Ser. No. 12/178,289 [Attorney docket # APPM
11709.P3], filed Jul. 23, 2008, and U.S. patent application Ser.
No. 12/170,387 [Attorney docket # APPM 11710], filed Jul. 9, 2008,
which are both herein incorporated by reference.
[0041] In one embodiment of the process sequence 100, a cool down
step, or step 113, is performed after step 112 has been performed.
The cool down step is generally used to stabilize the temperature
of the device substrate 303 to assure that the processing
conditions seen by each device substrate 303 in the subsequent
processing steps are repeatable. Generally, the temperature of the
device substrate 303 exiting the processing module 212 could vary
by many degrees Celsius and exceed a temperature of 50.degree. C.,
which can cause variability in the subsequent processing steps and
solar cell performance.
[0042] In one embodiment, the cool down step 113 is performed in
one or more of the substrate supporting positions found in one or
more accumulators 211. In one configuration of the production line,
as shown in FIG. 2, the processed device substrates 303 may be
positioned in one of the accumulators 211B for a desired period of
time to control the temperature of the device substrate 303. In one
embodiment, the system controller 290 is used to control the
positioning, timing, and movement of the device substrates 303
through the accumulator(s) 211 to control the temperature of the
device substrates 303 before proceeding down stream through the
production line.
[0043] Next, the device substrate 303 is transported to the scribe
module 214 in which step 114, or the interconnect formation step,
is performed on the device substrate 303 to electrically isolate
various regions of the device substrate 303 surface from each
other. In step 114, material is removed from the device substrate
303 surface by use of a material removal step, such as a laser
ablation process. In one embodiment, an Nd:vanadate (Nd:YVO.sub.4)
laser source is used ablate material from the substrate surface to
form lines that electrically isolate one solar cell from the next.
In one embodiment, a 5.7 m.sup.2 substrate laser scribe module
available from Applied Materials, Inc. is used to perform the
accurate scribing process. In one embodiment, the laser scribe
process performed during step 108 uses a 532 nm wavelength pulsed
laser to pattern the material disposed on the device substrate 303
to isolate the individual cells that make up the solar cell 300. As
shown in FIG. 3E, in one embodiment, the trench 381B is formed in
the first p-i-n junction 320 layers by used of a laser scribing
process. In another embodiment, a water jet cutting tool or diamond
scribe is used to isolate the various regions on the surface of the
solar cell. In one aspect, it is desirable to assure that the
temperature of the device substrates 303 entering the scribe module
214 are at a temperature in a range between about 20.degree. C. and
about 26.degree. C. by use of an active temperature control
hardware assembly that may contain a resistive heater and/or
chiller components (e.g., heat exchanger, thermoelectric device).
In one embodiment, it is desirable to control the substrate
temperature to about 25+/-0.5.degree. C.
[0044] In one embodiment, the solar cell production line 200 has at
least one accumulator 211 positioned after the scribe module(s)
214. During production accumulators 211C may be used to provide a
ready supply of substrates to a contact deposition chamber 218,
and/or provide a collection area where substrates coming from the
processing module 212 can be stored if the contact deposition
chamber 218 goes down or can not keep up with the throughput of the
scribe module(s) 214. In one embodiment it is generally desirable
to monitor and/or actively control the temperature of the
substrates exiting the accumulators 211C to assure that the results
of the back contact formation step 120 are repeatable. In one
aspect, it is desirable to assure that the temperature of the
substrates exiting the accumulators 211C or arriving at the contact
deposition chamber 218 are at a temperature in a range between
about 20.degree. C. and about 26.degree. C. In one embodiment, it
is desirable to control the substrate temperature to about
25+/-0.5.degree. C. In one embodiment, it is desirable to position
one or more accumulators 211C that are able to retain at least
about 80 substrates.
[0045] Next, the device substrate 303 is transported to the
processing module 218 in which one or more substrate back contact
formation steps, or step 118, are performed on the device substrate
303. In step 118, the one or more substrate back contact formation
steps may include one or more preparation, etching, and/or material
deposition steps that are used to form the back contact regions of
the solar cell device. In one embodiment, step 118 generally
comprises one or more PVD steps that are used to form the back
contact layer 350 on the surface of the device substrate 303. In
one embodiment, the one or more PVD steps are used to form a back
contact region that contains a metal layer selected from a group
consisting of zinc (Zn), tin (Sn), aluminum (Al), copper (Cu),
silver (Ag), nickel (Ni), and vanadium (V). In one example, a zinc
oxide (ZnO) or nickel vanadium alloy (NiV) is used to form at least
a portion of the back contact layer 305. In one embodiment, the one
or more processing steps are performed using an ATON.TM. PVD 5.7
tool available from Applied Materials in Santa Clara, Calif. In
another embodiment, one or more CVD steps are used to form the back
contact layer 350 on the surface of the device substrate 303.
[0046] In one embodiment, the solar cell production line 200 has at
least one accumulator 211 positioned after the processing module
218. During production, the accumulators 211D may be used to
provide a ready supply of substrates to the scribe modules 220,
and/or provide a collection area where substrates coming from the
processing module 218 can be stored if the scribe modules 220 go
down or can not keep up with the throughput of the processing
module 218. In one embodiment it is generally desirable to monitor
and/or actively control the temperature of the substrates exiting
the accumulators 211D to assure that the results of the back
contact formation step 120 are repeatable. In one aspect, it is
desirable to assure that the temperature of the substrates exiting
the accumulators 211D or arriving at the scribe module 220 are at a
temperature in a range between about 20.degree. C. and about
26.degree. C. In one embodiment, it is desirable to control the
substrate temperature to about 25+/-0.5.degree. C. In one
embodiment, it is desirable to position one or more accumulators
211C that are able to retain at least about 80 substrates.
[0047] Next, the device substrate 303 is transported to the scribe
module 220 in which step 120, or a back contact isolation step, is
performed on the device substrate 303 to electrically isolate the
plurality of solar cells contained on the substrate surface from
each other. In step 120, material is removed from the substrate
surface by use of a material removal step, such as a laser ablation
process. In one embodiment, a Nd:vanadate (Nd:YVO.sub.4) laser
source is used ablate material from the device substrate 303
surface to form lines that electrically isolate one solar cell from
the next. In one embodiment, a 5.7 m.sup.2 substrate laser scribe
module, available from Applied Materials, Inc., is used to
accurately scribe the desired regions of the device substrate 303.
In one embodiment, the laser scribe process performed during step
120 uses a 532 nm wavelength pulsed laser to pattern the material
disposed on the device substrate 303 to isolate the individual
cells that make up the solar cell 300. As shown in FIG. 3E, in one
embodiment, the trench 381C is formed in the first p-i-n junction
320 and back contact layer 350 by use of a laser scribing process.
In one aspect, it is desirable to assure that the temperature of
the device substrates 303 entering the scribe module 220 are at a
temperature in a range between about 20.degree. C. and about
26.degree. C. by use of an active temperature control hardware
assembly that may contain a resistive heater and/or chiller
components (e.g., heat exchanger, thermoelectric device). In one
embodiment, it is desirable to control the substrate temperature to
about 25+/-0.5.degree. C.
[0048] Next, the device substrate 303 is transported to the quality
assurance module 222 in which step 122, or quality assurance and/or
shunt removal steps, are performed on the device substrate 303 to
assure that the devices formed on the substrate surface meet a
desired quality standard and in some cases correct defects in the
formed device. In step 122, a probing device is used to measure the
quality and material properties of the formed solar cell device by
use of one or more substrate contacting probes. In one embodiment,
the quality assurance module 222 projects a low level of light at
the p-i-n junction(s) of the solar cell and uses the one more
probes to measure the output of the cell to determine the
electrical characteristics of the formed solar cell device(s). If
the module detects a defect in the formed device, it can take
corrective actions to fix the defects in the formed solar cells on
the device substrate 303. In one embodiment, if a short or other
similar defect is found, it may be desirable to create a reverse
bias between regions on the substrate surface to control and or
correct one or more of the defectively formed regions of the solar
cell device. During the correction process the reverse bias
generally delivers a voltage high enough to cause the defects in
the solar cells to be corrected. In one example, if a short is
found between supposedly isolated regions of the device substrate
303 the magnitude of the reverse bias may be raised to a level that
causes the conductive elements in areas between the isolated
regions to change phase, decompose, or become altered in some way
to eliminate or reduce the magnitude of the electrical short. In
one embodiment of the process sequence 100, the quality assurance
module 222 and factory automation system are used together to
resolve quality issues found in a formed device substrate 303
during the quality assurance testing. In one case, a device
substrate 303 may be sent back upstream in the processing sequence
to allow one or more of the fabrication steps to be re-performed on
the device substrate 303 (e.g., back contact isolation step (step
120)) to correct one or more quality issues with the processed
device substrate 303.
[0049] Next, the device substrate 303 is optionally transported to
the substrate sectioning module 224 in which a substrate sectioning
step 124 is used to cut the device substrate 303 into a plurality
of smaller device substrates 303 to form a plurality of smaller
solar cell devices. In one embodiment of step 124, the device
substrate 303 is inserted into substrate sectioning module 224 that
uses a CNC glass cutting tool to accurately cut and section the
device substrate 303 to form solar cell devices that are a desired
size. In one embodiment, the device substrate 303 is inserted into
the cutting module 224 that uses a glass scribing tool to
accurately score the surface of the device substrate 303. The
device substrate 303 is then broken along the scored lines to
produce the desired size and number of sections needed for the
completion of the solar cell devices.
[0050] In one embodiment, the solar cell production line 200 is
adapted to accept (step 102) and process substrate 302 or device
substrates 303 that are 5.7 m.sup.2 or larger. In one embodiment,
these large area substrates 302 are partially processed and then
sectioned into four 1.4 m.sup.2 device substrates 303 during step
124. In one embodiment, the system is designed to process large
device substrates 303 (e.g., TCO coated 2200 mm.times.2600
mm.times.3 mm glass) and produce various sized solar cell devices
without additional equipment or processing steps. Currently
amorphous silicon (a-Si) thin film factories must have one product
line for each different size solar cell device. In the present
invention, the manufacturing line is able to quickly switch to
manufacture different solar cell device sizes. In one aspect of the
invention, the manufacturing line is able to provide a high solar
cell device throughput, which is typically measured in Mega-Watts
per year, by forming solar cell devices on a single large substrate
and then sectioning the substrate to form solar cells of a more
preferable size.
[0051] In one embodiment of the production line 200, the front end
of the line (FEOL) (e.g., steps 102-122) is designed to process a
large area device substrate 303 (e.g., 2200 mm.times.2600 mm), and
the back end of the line (BEOL) is designed to further process the
large area device substrate 303 or multiple smaller device
substrates 303 formed by use of the sectioning process. In this
configuration, the remainder of the manufacturing line accepts and
further processes the various sizes. The flexibility in output with
a single input is unique in the solar thin film industry and offers
significant savings in capital expenditure. The material cost for
the input glass is also lower since solar cell device manufacturers
can purchase a larger quantity of a single glass size to produce
the various size modules.
[0052] In one embodiment, steps 102-122 can be configured to use
equipment that is adapted to perform process steps on large device
substrates 303, such as 2200 mm.times.2600 mm.times.3 mm glass
device substrates 303, and steps 124 onward can be adapted to
fabricate various smaller sized solar cell devices with no
additional equipment required. In another embodiment, step 124 is
positioned in the process sequence 200 prior to step 122 so that
the initially large device substrate 303 can be sectioned to form
multiple individual solar cells that are then tested and
characterized one at a time or as a group (i.e., two or more at a
time). In this case, steps 102-121 are configured to use equipment
that is adapted to perform process steps on large device substrates
303, such as 2200 mm.times.2600 mm.times.3 mm glass substrates, and
steps 124 and 122 onward are adapted to fabricate various smaller
sized modules with no additional equipment required. A more
detailed description of an exemplary substrate sectioning module
224 is presented below in the section entitled, "Substrate
Sectioning Module and Processes."
[0053] Referring back to FIGS. 1 and 2, the device substrate 303 is
next transported to the seamer/edge deletion module 226 in which a
substrate surface and edge preparation step 126 is used to prepare
various surfaces of the device substrate 303 to prevent yield
issues later on in the process. In one embodiment of step 126, the
device substrate 303 is inserted into seamer/edge deletion module
226 to prepare the edges of the device substrate 303 to shape and
prepare the edges of the device substrate 303. Damage to the device
substrate 303 edge can affect the device yield and the cost to
produce a usable solar cell device. In another embodiment, the
seamer/edge deletion module 226 is used to remove deposited
material from the edge of the device substrate 303 (e.g., 10 mm) to
provide a region that can be used to form a reliable seal between
the device substrate 303 and the backside glass (i.e., steps
134-136 discussed below). Material removal from the edge of the
device substrate 303 may also be useful to prevent electrical
shorts in the final formed solar cell.
[0054] In one embodiment, a diamond impregnated belt is used to
grind the deposited material from the edge regions of the device
substrate 303. In another embodiment, a grinding wheel is used to
grind the deposited material from the edge regions of the device
substrate 303. In another embodiment, dual grinding wheels are used
to remove the deposited material from the edge of the device
substrate 303. In yet another embodiment, grit blasting or laser
ablation techniques are used to remove the deposited material from
the edge of the device substrate 303. In one aspect, the
seamer/edge deletion module 226 is used to round or bevel the edges
of the device substrate 303 by use of shaped grinding wheels,
angled and aligned belt sanders, and/or abrasive wheels.
[0055] Next the device substrate 303 is transported to the
pre-screen module 228 in which optional pre-screen steps 128 are
performed on the device substrate 303 to assure that the devices
formed on the substrate surface meet a desired quality standard. In
step 128, a light emitting source and probing device are used to
measure the output of the formed solar cell device by use of one or
more substrate contacting probes. If the module 228 detects a
defect in the formed device it can take corrective actions or the
solar cell can be scrapped.
[0056] Next the device substrate 303 is transported to the cleaning
module 230 in which step 130, or a pre-lamination substrate
cleaning step, is performed on the device substrate 303 to remove
any contaminants found on the surface of the substrates 303 after
performing steps 122-128. Typically, the cleaning module 230 uses
wet chemical scrubbing and rinsing steps to remove any undesirable
contaminants found on the substrate surface after performing the
cell isolation step. In one embodiment, a cleaning process similar
to the processes described in step 106 is performed on the
substrate 303 to remove any contaminants on the surface(s) of the
substrate 303.
[0057] Next the substrate 303 is transported to a bonding wire
attach module 231 in which step 131, or a bonding wire attach step,
is performed on the substrate 303. Step 131 is used to attach the
various wires/leads required to connect the various external
electrical components to the formed solar cell device. Typically,
the bonding wire attach module 231 is an automated wire bonding
tool that is advantageously used to reliably and quickly form the
numerous interconnects that are often required to form the large
solar cells formed in the production line 200. In one embodiment,
the bonding wire attach module 231 is used to form the side-buss
355 (FIG. 3C) and cross-buss 356 on the formed back contact region
(step 118). In this configuration the side-buss 355 may be a
conductive material that can be affixed, bonded, and/or fused to
the back contact layer 350 found in the back contact region to form
a good electrical contact. In one embodiment, the side-buss 355 and
cross-buss 356 each comprise a metal strip, such as copper tape, a
nickel coated silver ribbon, a silver coated nickel ribbon, a tin
coated copper ribbon, a nickel coated copper ribbon, or other
conductive material that can carry the current delivered by the
solar cell and be reliably bonded to the metal layer in the back
contact region. In one embodiment, the metal strip is between about
2 mm and about 10 mm wide and between about 1 mm and about 3 mm
thick. The cross-buss 356, which is electrically connected to the
side-buss 355 at the junctions, can be electrically isolated from
the back contact layer(s) of the solar cell by use of an insulating
material 357, such as an insulating tape. The ends of each of the
cross-busses 356 generally have one or more leads that are used to
connect the side-buss 355 and the cross-buss 356 to the electrical
connections found in a junction box 370, which is used to connect
the formed solar cell to the other external electrical components.
Further information on soldering bus wire to thin film solar
modules is disclosed in U.S. Provisional Patent Application Ser.
No. 60/967,077, U.S. Provisional Patent Application Ser. No.
61/023,810, and U.S. Provisional Patent Application Ser. No.
61/032,005, which are incorporated by reference herein.
[0058] In the next step, step 132, a bonding material 360 (FIG. 3D)
and "back glass" substrate 361 are prepared for delivery into the
solar cell formation process (i.e., process sequence 100). The
preparation process is generally performed in the glass lay-up
module 232, which generally comprises a material preparation module
232A, a glass loading module 232B and a glass cleaning module 232C.
The back glass substrate 361 is bonded onto the device substrate
303 formed in steps 102-130 above by use of a laminating process
(step 134 discussed below). In general, step 132 requires the
preparation of a polymeric material that is to be placed between
the back glass substrate 361 and the deposited layers on the device
substrate 303 to form a hermetic seal to prevent the environment
from attacking the solar cell during its life. Referring to FIG. 2,
step 132 generally comprises a series of sub-steps in which a
bonding material 360 is prepared in the material preparation module
232A, the bonding material 360 is then placed over the device
substrate 303, the back glass substrate 361 is loaded into the
loading module 232B and is washed by use of the cleaning module
232C, and the back glass substrate 361 is placed over the bonding
material 360 and the device substrate 303.
[0059] In one embodiment, the material preparation module 232A is
adapted to receive the bonding material 360 in a sheet form and
perform one or more cutting operations to provide a bonding
material, such as Polyvinyl Butyral (PVB) or Ethylene Vinyl Acetate
(EVA) that is sized to form a reliable seal between the backside
glass and the solar cells formed on the device substrate 303. In
general, when using bonding materials 360 that are polymeric, it is
desirable to control the temperature (e.g., 16-18.degree. C.) and
relative humidity (e.g., RH 20-22%) of the solar cell production
line 200 where the bonding material 360 is stored and integrated
into the solar cell device to assure that the attributes of the
bond formed in the bonding module 234 are repeatable and the
dimensions of the polymeric material is stable. It is generally
desirable to store the bonding material prior to use in temperature
and humidity controlled area (e.g., T=6-8.degree. C.; RH=20-22%).
The tolerance stack up of the various components in the bonded
device (Step 134) can be an issue when forming large solar cells,
therefore accurate control of the bonding material properties and
tolerances of the cutting process are required to assure that a
reliable hermetic seal is formed. In one embodiment, PVB may be
used to advantage due to its UV stability, moisture resistance,
thermal cycling, good US fire rating, compliance with Intl Building
Code, low cost, and reworkable thermo-plastic properties. In one
part of step 132, the bonding material 360 is transported and
positioned over the back contact layer 350, the side-buss 355 (FIG.
3C), and the cross-buss 356 (FIG. 3C) elements of the device
substrate 303 using an automated robotic device. The device
substrate 303 and bonding material 360 are then positioned to
receive a back glass substrate 361, which can be placed thereon by
use of the same automated robotic device used to position the
bonding material 360, or a second automated robotic device.
[0060] In one embodiment, prior to positioning the back glass
substrate 361 over the bonding material 360, one or more
preparation steps are performed to the back glass substrate 361 to
assure that subsequent sealing processes and final solar product
are desirably formed. In one case, the back glass substrate 361 is
received in a "raw" state where the edges, overall size, and/or
cleanliness of the substrate 361 are not well controlled. Receiving
"raw" substrates reduces the cost to prepare and store substrates
prior to forming a solar device and thus reduces the solar cell
device cost, facilities costs, and production costs of the finally
formed solar cell device. In one embodiment of step 132, the back
glass substrate 361 surfaces and edges are prepared in a seaming
module (e.g., seamer 204) prior to performing the back glass
substrate cleaning step. In the next sub-step of step 232 the back
glass substrate 361 is transported to the cleaning module 232B in
which a substrate cleaning step, is performed on the substrate 361
to remove any contaminants found on the surface of the substrate
361. Common contaminants may include materials deposited on the
substrate 361 during the substrate forming process (e.g., glass
manufacturing process) and/or during shipping of the substrates
361. Typically, the cleaning module 232B uses wet chemical
scrubbing and rinsing steps to remove any undesirable contaminants
as discussed above. The prepared back glass substrate 361 is then
positioned over the bonding material and partially device substrate
303 by use of an automated robotic device.
[0061] Next the device substrate 303, the back glass substrate 361,
and the bonding material 360 are transported to the bonding module
234 in which step 134, or lamination steps are performed to bond
the backside glass substrate 361 to the device substrate formed in
steps 102-130 discussed above. In step 134, a bonding material 360,
such as Polyvinyl Butyral (PVB) or Ethylene Vinyl Acetate (EVA), is
sandwiched between the backside glass substrate 361 and the device
substrate 303. Heat and pressure are applied to the structure to
form a bonded and sealed device using various heating elements and
other devices found in the bonding module 234. The device substrate
303, the back glass substrate 361 and bonding material 360 thus
form a composite solar cell structure 304 (FIG. 3D) that at least
partially encapsulates the active regions of the solar cell device.
In one embodiment, at least one hole formed in the back glass
substrate 361 remains at least partially uncovered by the bonding
material 360 to allow portions of the cross-buss 356 or the side
buss 355 to remain exposed so that electrical connections can be
made to these regions of the solar cell structure 304 in future
steps (i.e., step 138).
[0062] Next the composite solar cell structure 304 is transported
to the autoclave module 236 in which step 136, or autoclave steps
are performed on the composite solar cell structure 304 to remove
trapped gasses in the bonded structure and assure that a good bond
is formed during step 134. In step 134, a bonded solar cell
structure 304 is inserted in the processing region of the autoclave
module where heat and high pressure gases are delivered to reduce
the amount of trapped gas and improve the properties of the bond
between the device substrate 303, back glass substrate, and bonding
material 360. The processes performed in the autoclave are also
useful to assure that the stress in the glass and bonding layer
(e.g., PVB layer) are more controlled to prevent future failures of
the hermetic seal or failure of the glass due to the stress induced
during the bonding/lamination process. In one embodiment, it may be
desirable to heat the device substrate 303, back glass substrate
361, and bonding material 360 to a temperature that causes stress
relaxation in one or more of the components in the formed solar
cell structure 304.
[0063] Next the solar cell structure 304 is transported to the
junction box attachment module 238 in which junction box attachment
steps 138 are performed on the formed solar cell structure 304. The
junction box attachment module 238, used during step 138, is used
to install a junction box 370 (FIG. 3C) on a partially formed solar
cell. The installed junction box 370 acts as an interface between
the external electrical components that will connect to the formed
solar cell, such as other solar cells or a power grid, and the
internal electrical connections points, such as the leads, formed
during step 131. In one embodiment, the junction box 370 contains
one or more connection points 371, 372 so that the formed solar
cell can be easily and systematically connected to other external
devices to deliver the generated electrical power.
[0064] Next the solar cell structure 304 is transported to the
device testing module 240 in which device screening and analysis
steps 140 are performed on the solar cell structure 304 to assure
that the devices formed on the solar cell structure 304 surface
meet desired quality standards. In one embodiment, the device
testing module 240 is a solar simulator module that is used to
qualify and test the output of the one or more formed solar cells.
In step 140, a light emitting source and probing device are used to
measure the output of the formed solar cell device by use of one or
more automated components that are adapted to make electrical
contact with terminals in the junction box 370. If the module
detects a defect in the formed device it can take corrective
actions or the solar cell can be scrapped.
[0065] Next the solar cell structure 304 is transported to the
support structure module 241 in which support structure mounting
steps 141 are performed on the solar cell structure 304 to provide
a complete solar cell device that has one or more mounting elements
attached to the solar cell structure 304 formed using steps 102-140
to a complete solar cell device that can easily be mounted and
rapidly installed at a customer's site.
[0066] Next the solar cell structure 304 is transported to the
unload module 242 in which step 142, or device unload steps are
performed on the substrate to remove the formed solar cells from
the solar cell production line 200.
[0067] In one embodiment of the solar cell production line 200, one
or more regions in the production line are positioned in a clean
room environment to reduce or prevent contamination from affecting
the solar cell device yield and useable lifetime. In one
embodiment, as shown in FIG. 2, a class 10,000 clean room space 250
is placed around the modules used to perform steps 108-118 and
steps 130-134.
Substrate Sectioning Module and Processes
[0068] The substrate sectioning module 224 and processing sequence
performed during the substrate sectioning step 124 are used to
section a large, partially processed device substrate 303 (i.e., a
substrate having one or more thin silicon films deposited thereon)
into two or more device substrates 303 for further processing into
a solar module. In one embodiment, the substrate sectioning module
receives a 2600 mm.times.2200 mm device substrate 303 and sections
it into two 1300 mm.times.2200 mm device substrates 303 for further
processing. In one embodiment, the substrate sectioning module
receives a 2600 mm.times.2200 mm device substrate 303 and sections
it into two 2600 mm.times.1100 mm device substrates 303 for further
processing. In one embodiment, the substrate sectioning module
receives a 2600 mm.times.2200 mm device substrate 303 and sections
it into four 1300 mm.times.1100 mm device substrates 303 for
further processing.
[0069] In one embodiment, the system controller 290 (FIG. 2)
controls the number and size of the sections of the device
substrates 303 produced by the substrate sectioning module 224.
Accordingly, the system controller 290 sends commands to all
downstream processes in the sequence 100 (FIG. 1) for coordinating
both the processes and adjustments to the downstream modules to
accommodate and further process sections of the device substrate
303 produced by the substrate sectioning module regardless of the
size of the sections produced.
[0070] FIGS. 4A-4E are top plan, schematic views illustrating a
sequence of sectioning a device substrate 303 according to one
embodiment of the substrate sectioning module 224. Referring to
FIG. 4A, an inlet conveyor 410 transports the device substrate 303
into a scribing station 420. In one embodiment, the side of the
device substrate 303 having thin films deposited thereover is
facing upward. A scribing conveyor 422 positions the device
substrate in the scribing station 420 for scribing. In the scribing
station 420, as shown in FIG. 4B, a pattern is scribed on the upper
surface of the device substrate 303 via a scribing mechanism 424
according to the programmed sectioning of the device substrate 303.
In one embodiment, the inlet conveyor 410, the scribing conveyor
422, and the scribing mechanism 424 are controlled and coordinated
with each other as well as other operations in the sequence 100
(FIG. 1) via the system controller 290 (FIG. 2).
[0071] In one embodiment, the scribing mechanism 424 is a
mechanical scribing mechanism, such as a mechanical scribing wheel.
In one embodiment, the scribing mechanism 424 is an optical
scribing mechanism, such a laser scribing mechanism. Regardless of
the type of scribing mechanism 424 employed, it should be noted
that the scribing mechanism must cut completely through any films
deposited on the processing surface of the device substrate 303 and
cleanly score the upper surface of the underlying glass.
[0072] The scored device substrate 303 is then transported via the
scribing station conveyor 422 partially onto a cross transfer
station 430 as shown in FIG. 4C. A first transfer station conveyor
432 is coordinated with the scribing station conveyor 422 via the
system controller 290 to properly position the device substrate
303. FIGS. 5A-5C schematically illustrate a process for breaking
the scored device substrate 303 according to one embodiment of the
present invention. Referring to FIGS. 4C and 5A, the scored device
substrate 303 is positioned over a roller 426 such that a line
scribed along the X-axis is located directly above the roller 426.
The roller 426 is then raised and placed in contact with the lower
surface of the device substrate 303 as schematically shown in FIG.
5B. As schematically depicted in FIG. 5C, the roller 426 is raised
exerting a lifting force on the lower surface of the device
substrate 303 along the scribed line and perpendicular to the plane
of the device substrate 303 resulting in a clean break along the
scribed line.
[0073] In one embodiment, the roller 426 is a padded cylindrical
roller extending the length of the device substrate 303. The roller
426 is raised by an actuator 428.
[0074] In one embodiment, the actuator 428 may be an electric,
hydraulic, or pneumatic motor. In one embodiment, the actuator 428
may be a hydraulic or pneumatic cylinder. In one embodiment, the
actuator 428 is controlled and coordinated by the system controller
290.
[0075] Next, shown in FIG. 4D, a first section 303A of the
substrate device 303 is fully loaded into the cross transfer
station 430 via the first transfer conveyor 432. Next, a second
transfer conveyor 434, in conjunction with an exit conveyor 440,
transfers the first section 303A partially onto the exit conveyor
440 as shown in FIG. 4E. The second transfer station conveyor 434
is coordinated with the exit conveyor 440 via the system controller
290 to properly position the device substrate section 303A.
Referring to FIGS. 4E and 5A, the scored sectioned device substrate
303A is positioned over the roller 426 such that a line scribed
along the Y-axis is located directly above the roller 426. The
roller 426 is then raised and placed in contact with the lower
surface of the sectioned device substrate 303A as schematically
shown in FIG. 5B. As schematically depicted in FIG. 5C, the roller
426 is raised to exert a lifting force on the lower surface of the
device substrate section 303A along the scribed line and
perpendicular to the plane of the device substrate section 303A
resulting in a clean break along the scribed line. As a result the
substrate section 303A is sectioned into two smaller device
substrate sections 303C and 303D. Each of the substrate sections
303C and 303D are then transferred via the second transfer conveyor
434 and the exit conveyor 440 into a subsequent module for further
processing. The above processes are then repeated for the device
substrate section 303B.
[0076] Although the above-described embodiment illustrates
processes and apparatus for sectioning a single substrate device
303 into four smaller sections, it should be evident that the
embodiment works equally well for sectioning a single substrate
device 303 into two smaller sections by adjusting the scribing
mechanism 424 to scribe only a single line on either the X-axis or
the Y-axis and performing only a single break process.
[0077] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *