U.S. patent application number 14/623462 was filed with the patent office on 2015-06-11 for method for forming solar cell with selective emitters.
The applicant listed for this patent is Industrial Technology Research Institute. Invention is credited to DIMITRE ZAHARIEV DIMITROV, CHUNG-WEN LAN, CHING-HSI LIN, DER-CHIN WU.
Application Number | 20150162482 14/623462 |
Document ID | / |
Family ID | 45933028 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150162482 |
Kind Code |
A1 |
DIMITROV; DIMITRE ZAHARIEV ;
et al. |
June 11, 2015 |
METHOD FOR FORMING SOLAR CELL WITH SELECTIVE EMITTERS
Abstract
A method for forming a solar cell with selective emitters is
provided. The method for forming a solar cell with selective
emitters includes providing a substrate; forming a first texture
structure on a first surface of the substrate; performing a doping
process to the first surface of the substrate to form a first
doping region in the substrate; forming a pattered barrier layer in
a second region on the first surface of the substrate, wherein
another portion of the substrate in a first region is exposed;
performing a second texture etching process to etch the first
region of the substrate uncovered by the patterned barrier layer;
removing the patterned barrier layer; and forming an electrode on
the second region of the substrate.
Inventors: |
DIMITROV; DIMITRE ZAHARIEV;
(HSINCHU CITY, TW) ; LIN; CHING-HSI; (HSINCHU
CITY, TW) ; LAN; CHUNG-WEN; (NEW TAIPEI CITY, TW)
; WU; DER-CHIN; (TAINAN CITY, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Industrial Technology Research Institute |
Hsinchu |
|
TW |
|
|
Family ID: |
45933028 |
Appl. No.: |
14/623462 |
Filed: |
February 16, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13165670 |
Jun 21, 2011 |
8987038 |
|
|
14623462 |
|
|
|
|
Current U.S.
Class: |
438/71 |
Current CPC
Class: |
Y02E 10/547 20130101;
Y02E 10/52 20130101; Y02P 70/521 20151101; H01L 31/068 20130101;
H01L 31/18 20130101; H01L 31/02363 20130101; H01L 31/02168
20130101; Y02P 70/50 20151101; H01L 31/1804 20130101; H01L
31/035281 20130101 |
International
Class: |
H01L 31/18 20060101
H01L031/18; H01L 31/0216 20060101 H01L031/0216; H01L 31/0352
20060101 H01L031/0352 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2010 |
TW |
099135511 |
Claims
1. A method for forming a solar cell with selective emitters,
comprising: providing a substrate; forming a first texture
structure on a first surface of the substrate; performing a doping
process to the first surface of the substrate to form a first
doping region in the substrate; forming a pattered barrier layer in
a second region on the first surface of the substrate, wherein
another portion of the substrate in a first region is exposed;
performing a second texture etching process to etch the first
region of the substrate uncovered by the patterned barrier layer;
removing the patterned barrier layer; and forming an electrode on
the second region of the substrate.
2. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the second texture etching process
treats the substrate surface in the first region to a second doping
region, and doping concentration of the second doping region is
lower than that of the first doping region.
3. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the second texture etching process
comprises: performing an electroless treatment; and performing
selective oxidizing and removing steps.
4. The method for forming a solar cell with selective emitter as
claimed in claim 3, wherein N.sub.2S.sub.2O.sub.8 is used as an
oxidizer, and AgNO.sub.3, H.sub.2O.sub.2 or NaOH are used as
catalytic agents in the electroless treatment process and the
selective oxidizing products removing steps is performed in a
solution containing HF and H.sub.2O.sub.2.
5. The method for forming a solar cell with selective emitter as
claimed in claim 1, further comprising forming an anti-reflective
layer on the substrate surface before forming the electrode.
6. The method for forming a solar cell with selective emitter as
claimed in claim 5, wherein the pattered barrier layer and the
anti-reflective layer are formed of silicon oxide silicon nitride
or aluminum oxide.
7. The method for forming a solar cell with selective emitter as
claimed in claim 5, wherein the anti-reflective layer is formed by
plasma enhanced chemical vapor deposition (PECVD).
8. The method for forming a solar cell with selective emitter as
claimed in claim 1, wherein the doping process dopes phosphorous or
boron.
9. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the second texture etching process
treats the substrate surface in the first region to a second doping
region, wherein sheet resistance of the first doping region is
lower than that of the second doping region.
10. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the second texture etching process
removes about 50 nm-70 nm of the substrate surface in the first
region to form a second doping region.
11. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein duration of the second texture etching
process is about 60 sec.
12. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the first texture structure is formed
by alkaline etching process.
13. The method for forming a solar cell with selective emitters as
claimed in claim 1, wherein the first texture structure is formed
by acid etching process.
14. The solar cell with selective emitters as claimed in claim 1,
wherein the pattered barrier layer is formed by screen printing.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority from, and is
a divisional application of, U.S. patent application Ser. No.
13/165,670 filed on Jun. 21, 2011, entitled "Method for forming
solar cell with selective emitters", which claims the benefit of
priority from Taiwan Application No. 099135511, filed on Oct. 19,
2010 and the entirety of which is incorporated by reference
herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The disclosure relates generally to a solar cell and
fabrication thereof, and more particularly to a solar cell with
selective emitters and fabrication thereof.
[0004] 2. Description of the Related Art
[0005] A solar cell with selective emitters has improved conversion
efficiency. FIG. 1 is a cross section of a solar cell having a
selective emitter. Referring to FIG. 1, the solar cell having a
selective emitter comprises a high concentration doping region 106
in a portion of a substrate 102 under an electrode 110, a low
concentration doping region 104 in the other portion of the
substrate 102 outside of the electrode, and an anti-reflective
layer 108 on the substrate. The solar cell has a higher open
circuit voltage (Voc) and short-circuit current (Isc) than the
conventional solar cell having only one doping concentration, since
the low doping concentration doping emitter between the electrodes
can reduce carrier recombination on the surface of the solar cell
and the high concentration doping region under the electrodes can
provide good electrode contacts. Therefore, the solar cell with
selective emitters has high photoelectric conversion
efficiency.
[0006] Since the solar cell with selective emitters has a
significant advantage over the conventional solar cell having only
one doping concentration, a method for forming a solar cell with
selective emitters and fabrication thereof, having a simple process
to form high concentration doping regions under the electrodes and
low concentration doping regions in the other non-electrode regions
is required.
SUMMARY
[0007] The disclosure provides a method for forming a solar cell
with selective emitters, comprising, providing a substrate, forming
a first texture structure on a first surface of the substrate,
forming a barrier layer on the first surface of the substrate,
selectively removing a portion of the barrier layer to form an
opening exposing the substrate, wherein a portion of the substrate
under the barrier layer is a first region and another portion of
the substrate under the opening of the barrier layer is a second
region, and performing a texture etching process to the second
region to form a second texture structure under the opening of the
barrier layer, wherein the first texture structure and the second
texture structure comprise a plurality of protruding portions and
recessing portions, and the distance between neighboring protruding
portions of the first texture structure is L.sub.1, the distance
between neighboring protruding portions of the second texture
structure is L.sub.2, and L.sub.1 is about 2-20 times that of
L.sub.2. The method for forming the solar cell with selective
emitters further comprises removing the barrier layer, performing a
doping process to the first region to form a first doping region
and forming a second doping region in the second region of the
substrate, and forming an electrode on the second doping
region.
[0008] The disclosure further provides a solar cell with selective
emitters, comprising a substrate, wherein a first region on a first
surface of the substrate has a first texture structure, and a
second region on the first surface of the substrate has a second
texture structure, and the first texture structure and the second
texture structure comprise a plurality of protruding portions and
recessing portions, and the distance between neighboring protruding
portions of the first texture structure is L.sub.1, the distance
between neighboring protruding portions of the second texture
structure is L.sub.2, and L.sub.1 is 2-20 times that of L.sub.2, a
first doping region under the first region and a second doping
under the second doping region, wherein a concentration of the
second doping region is higher than that of the first doping
region, and an electrode overlies the second region.
[0009] The disclosure yet further provides a method for forming a
solar cell with selective emitter, comprising, providing a
substrate, forming a first texture structure on a first surface of
the substrate, doping the first surface of the substrate to form a
first doping region, forming a patterned barrier in a second region
on the first surface of the substrate, wherein another portion of
the substrate in a first region is exposed, performing an etching
process to etch the first region of the substrate uncovered by the
patterned barrier layer, and removing the patterned barrier layer,
and forming an electrode on the second region of the substrate.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The invention can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein,
[0011] FIG. 1 is a cross section of a conventional solar cell
having a selective emitter.
[0012] FIG. 2 is a plane view of a solar cell with selective
emitter of an embodiment of the invention.
[0013] FIG. 3A.about.FIG. 3G are intermediate cross sections of a
solar cell with selective emitter of an embodiment of the
invention.
[0014] FIG. 4 is a local enlarged view of FIG. 3D.
[0015] FIG. 5A.about.FIG. 5F are intermediate cross sections of a
solar sell with selective emitters of another embodiment of the
invention.
[0016] FIG. 6A is a diagram of a doped multicrystalline silicon
substrate with sheet resistance as a function of the etching
time.
[0017] FIG. 6B is a diagram of a doped single-crystal silicon
substrate with sheet resistance as a function of the etching
time.
[0018] FIG. 7 is a scanning electron microscope (SEM) picture of a
microtexture structure.
[0019] FIG. 8 is a scanning electron microscope (SEM) picture of a
second texture structure.
[0020] FIG. 9 is a scanning electron microscope (SEM) picture of an
interface between an electrode and the second region of the
substrate treated with second texture etching.
DETAILED DESCRIPTION
[0021] It is understood that specific embodiments are provided as
examples to teach the broader inventive concept, and one of
ordinary skill in the art can easily apply the teaching of the
present disclosure to other methods or apparatus. The following
discussion is only used to illustrate the invention, not limit the
invention.
[0022] FIG. 2 is a plane view of a solar cell with selective
emitter of an embodiment of the invention. Referring to FIG. 2, a
plurality of electrodes 202 extends along a vertical direction, and
a plurality of fingers 204 extends along a horizontal direction.
The selective emitter of an embodiment of the invention is a
structure comprising a high concentration doping region in portions
of the substrate under the electrodes 202 and the fingers 204, and
low concentration doping regions in other non-electrode regions.
The invention is not limited to the structure above. The selective
emitter of another embodiment can comprise high concentration
doping regions merely in a portion of the substrate under the
electrodes 202 and low concentration doping regions a in other
non-electrode regions.
[0023] A method for forming a solar cell having selective emitters
is illustrated in accordance with FIG. 3A.about.FIG. 3G. First,
referring to FIG. 3A, a substrate 302 is provided. The substrate
can be single-crystal silicon, polysilicon or other suitable
semiconductor materials. Next, the substrate 302 is treated with a
texturization process to form first texture structures on a first
surface 304 and a second surface 306 of the substrate 302. In order
to repair damage to a substrate 302 formed during cutting, a single
crystal substrate generally is treated with alkaline etching, such
as immersion in a NaOH solution, and a polysilicon substrate is
generally treated with acid etching, such as immersion in a
HF:HNO.sub.3:H.sub.2O solution. The alkaline etching and acid
etching forms first texture structures on surfaces of the substrate
302.
[0024] Referring to FIG. 3B, a barrier layer 308 is formed on a
first surface 304 of the substrate 302. In an embodiment of the
invention, the barrier layer comprises silicon silicon oxide,
silicon nitride or aluminum oxid, and can be formed by plasma
enhanced chemical vapor deposition (PECVD). Referring to FIG. 3C, a
portion of the barrier layer 308 at the position predetermined to
form electrodes and/or fingers is selectively removed to form
openings 310 exposing the substrate. In an embodiment of the
invention, the step of selectively removing the barrier layer 308
can be accomplished by laser irradiation or screen printing.
Thereafter, referring to FIG. 3D, a second texture etching process
is performed to the portion of the substrate 302 in the opening 310
of the barrier layer 308 to form second texture structures at the
region of the substrate 302 predetermined to form electrodes and/or
fingers. Therefore, a first surface 304 of the substrate 302
comprises second texture structures at a second region 314
predetermined to form electrodes and/or fingers and first texture
structures at a first region 312 outside of the second region 314.
Next, the barrier layer 308 is removed. The barrier layer 308 can
be slowly etched during the second texture etching process. The
second texture structures and the first texture structures are
described in more detail in accordance with FIG. 4 (local enlarged
view of FIG. 3D). Referring to FIG. 4, the texture structure on the
first surface 304 of the substrate 302 in the first region 312 is
referred as a first texture structure, and the texture structure on
the first surface 304 of the substrate 302 in the second region 314
is referred as a second texture structure. The first texture
structure and the second texture structure comprise a plurality of
protruding portions and recessing portions, wherein the protruding
portions and recessing portions of the second texture structure are
more concentrated than the protruding portions and recessing
portions of the first texture structure. Specifically, the distance
between neighboring protruding portions of the first texture
structure is L.sub.1, the distance between neighboring protruding
portions of the second texture structure is L.sub.2, and L.sub.1 is
about 2-20 times that of L.sub.2. In another embodiment of the
invention, L.sub.1 is about 12-15 times that of L.sub.2. In one
embodiment of the invention, L.sub.1 is about 1-10 .mu.m . FIG. 7
shows a scanning electron microscope (SEM) picture of a first
texture structure. FIG. 8 shows a scanning electron microscope
(SEM) picture of a second texture structure. Referring to FIG. 7
and FIG. 8, the distance between neighboring protruding portions of
the first texture structure L.sub.1 is at least larger than two
times that of the distance between neighboring protruding portions
of the second texture structure L.sub.2.
[0025] In an embodiment of the invention, the second texture
etching described comprises the steps as follows. First, an
electroless deposition process is performed to form silver
particles on a first surface 304 of the substrate 302, acting as a
catalytic agent. Next, a black etching process, such as immersing
the substrate in HF:H.sub.2O.sub.2:H.sub.2O, is performed. Note
that US 20090311821A1 is incorporated by reference to illustrate
the details of the second texture etching process. It is also noted
that the second texture etching process of the invention is not
limited to the etching process described, and any method which can
form a second texture structure can be applied in the
invention.
[0026] Thereafter, referring to FIG. 3E, a doping process is
performed to form a first doping region 316 in a first region 312
on the first surface 304 of the substrate 302, and a second doping
region 318 in a second region 314 on the first surface 304 of the
substrate 302. In an embodiment of the invention, the doping
process uses POCl.sub.3 as a doping source. In another embodiment
of the invention, the doping process uses boron as a doping source.
The difference in sheet resistance between the first doping region
316 and the second doping region 318 is illustrated in accordance
with table 1.
TABLE-US-00001 TABLE 1 Sheet Sheet Sheet resistance resistance
resistance (.OMEGA./sq) (.OMEGA./sq) (.OMEGA./sq) Target resistance
70 80 100 Reference (first texture 71 81 102 structure) Second
texture structure 37 43 85 Difference (.OMEGA./sq) 34 38 17
[0027] The first table shows that the second texture structure on
the surface of the substrate 302 has a relatively lower sheet
resistance (i.e. higher doping concentration) and the mircotexture
structure in the first region 312 on the surface of the substrate
302 has a relatively higher sheet resistance after the phosphorous
diffusing process. Accordingly, the doping process can form a
second doping region 318 having a relatively high doping
concentration at the second region 314 and form a first doping
region 316 having a relatively low doping concentration at the
first region 312. It is noted that the embodiment of the invention
can form doping regions (first doping region 316 and second doping
region 318) having different doping concentrations during a single
doping step. The method of the embodiment of the invention has less
process duration and costs than conventional methods of fabricating
selective emitters of a solar cell. Next, the phosphorous silicon
glass (PSG) on the surface of the substrate 302 is removed.
[0028] Following, referring to FIG. 3F, an anti-reflective layer
320 is formed on the first surface 304 of the substrate 302. In an
embodiment of the invention, the anti-reflective layer 320
comprises silicon oxide, silicon nitride or aluminum oxid, and can
be formed by plasma enhanced chemical vapor deposition (PECVD).
Referring to FIG. 3G, a screen printing and a sintering
metallization process are performed to form electrodes 322
contacting the second doping region 318 in the second region 314.
FIG. 9 shows a scanning electron microscope (SEM) picture of an
interface between an electrode 322 and the second region 314 of the
substrate 302 treated with second texture etching. Last, an edge
isolating process is performed by laser irradiation (not
shown).
[0029] EXAMPLE 1
[0030] First, a wafer was provided. The wafer was treated with a
standard cleaning process wherein a texture structure was formed on
a surface of the wafer. A silicon nitride was formed on a surface
of the wafer by plasma enhanced chemical vapor deposition (PECVD)
to act as a barrier layer. Next, the barrier layer was selectively
removed by laser patterning to form openings having similar shapes
with a metallization pattern. An immersing alkaline solution
process was performed to remove defects on the surface of the wafer
caused by laser patterning. A second texture etching process
including the following two steps was performed. The first step
included performing an electroless treatment, wherein
Na.sub.2S.sub.2O.sub.8 was used as an oxidizer, and AgNO.sub.3,
H.sub.2O.sub.2 or NaOH was used as a catalytic agent. The second
step included performing selective oxidizing and removing processes
by using a solution containing HF and H.sub.2O.sub.2 to form a
second texture surface. Both the first and second steps were
performed at room temperature, and water based chemistries were
used. During the second texture wet chemical treating process, the
silicon nitride barrier layer was slowly removed.
[0031] Next, the wafer was cleaned using concentrated HNO.sub.3 and
HPM solutions. A single POCl.sub.3 diffusing process was performed
to form emitter, wherein the standard texture structure had sheet
resistance of about 60-80 .OMEGA./sq (for example 70 .OMEGA./sq),
and the second texture structure had a sheet resistance of about
15-50 .OMEGA./sq (for example 30 .OMEGA./sq), thereby forming
selective emitter. Next, a PECVD process was performed to form a
silicon nitride layer, which acted as an anti-reflective layer. A
screen printing process was performed to form a silver electrode at
the front side and aluminum back surface field (BSF) on the rear
side of the substrate. Thereafter, a co-firing step was performed.
Lastly, an edge isolating process was performed by laser
irradiation. A solar cell with selective emitter formed by the
method above was measured, and had a cell efficiency of 16.01%. A
comparable example of a solar cell without selective emitter being
formed was also measured, and had a cell efficiency of 15.51%.
Therefore, the technique of the embodiment indeed increased cell
efficiency of the solar cells.
[0032] A method for forming a solar cell having selective emitter
of another embodiment of the invention is illustrated in accordance
with FIG. 5A.about.FIG. 5F. First, referring to FIG. 5A, a
substrate 502 is provided. The substrate 502 can be made of a
single-crystal silicon, polysilicon or other suitable semiconductor
materials. Next, the substrate 502 is treated with a texturization
process to form first texture structures on a first surface 504 and
a second surface 506 thereof. In order to repair damage to a
substrate 502 formed during cutting, a single crystal substrate is
generally treated with alkaline etching, such as immersion in a
NaOH solution, and a polysilicon substrate 502 is generally treated
with acid etching, such as immersion in a HF:HNO.sub.3:H.sub.2O
solution. The alkaline etching and acid etching processes form
first texture structures on surfaces of the substrate 502.
Referring to FIG. 5B, a doping process is performed to form a high
doping concentration region 516 on a first surface 504 of the
substrate 502. In an embodiment of the invention, the doping
process uses POCl.sub.3 as a doping source. Next, the phosphorous
silicon glass (PSG) on the surface of the substrate 502 is removed.
Referring to FIG. 5C, a patterned barrier layer 510 having similar
shapes with the electrode pattern is formed on the first surface
504 of the substrate 502 by, for example screen printing.
Thereafter, referring to FIG. 5D, an etching back process is
performed to selectively etch a portion of the substrate 502
surface not covered by patterned barrier layer 510, thereby forming
a low concentration doping region 518 in a first region 512 not
covered by the patterned barrier layer 510, and a high
concentration doping region 516 in a second region 514 covered by
the patterned barrier layer 510.
[0033] The mechanism of forming the high concentration doping
region and the low concentration doping region is illustrated in
accordance with FIG. 6A and FIG. 6B. The doping process forms a
high concentration doping region on the substrate surface. The
deeper the etching of the substrate, the lesser the doping
concentration. FIG. 6A shows a diagram of a doped multicrystalline
silicon substrate with sheet resistance as a function of etching
time. Referring to FIG. 6A, the longer the etching time, the higher
the sheet resistance of the substrate. That is, when the etching
depth is increased, the doping concentration of the substrate is
reduced. FIG. 6B shows a diagram of a doped single-crystal silicon
substrate with sheet resistance as a function of etching time. The
result shown in FIG. 6B is similar to that shown in FIG. 6A.
Therefore, the embodiment can form a low concentration doping
region 518 in the first region 512 of the substrate 502 uncovered
by the patterned barrier layer 510, while, have the unetched second
region 514 covered by the patterned barrier layer 510 not changed
from the high concentration doping region 516, thereby forming
selective emitter. In an embodiment of the invention, the etching
back process described is accomplished by a second texture etching
process. Because the second texture etching process has low etching
rate, the etching depth can be precisely controlled. The second
texture etching process comprises the steps as follows. First, an
electroless deposition process is performed to form silver
particles on a first surface 504 of the substrate 502 acting as a
catalytic agent. Next, a black etching process, such as immersion
in HF:H.sub.2O.sub.2:H.sub.2O, is performed. US 20090311821A1 is
incorporated by reference to illustrate the details of the second
texture etching process.
[0034] Thereafter, the phosphorous silicon glass (PSG) on the
surface of the substrate 502 is removed. Next, referring to FIG.
5E, an anti-reflective layer 520 is formed on the first surface 504
of the substrate 502. In an embodiment of the invention, the
anti-reflective layer 520 comprises silicon nitride, and can be
formed by plasma enhanced chemical vapor deposition (PECVD).
Referring to FIG. 5F, a screen printing and a sintering
metallization process are performed to form electrodes 522
contacting the high concentration doping region 516 in the second
region 514. Last, an edge isolating process is performed by laser
irradiation (not shown).
EXAMPLE 2
[0035] First, a wafer was provided. The wafer was treated with a
standard cleaning process wherein a texture structure was formed on
a surface of the wafer. A single POCl.sub.3 diffusing process was
performed and the doped substrate surface had a sheet resistance of
about 45 .OMEGA./sq. A patterned barrier layer, having similar
shapes with an electrode pattern, was formed on the surface of the
substrate by screen printing. A portion of the substrate uncovered
by the patterned barrier layer was etched by second texture
etching. The second texture etching process comprised the two steps
as follows. The first step included performing an electroless
treatment, wherein Na.sub.2S.sub.2O.sub.8 was used as an oxidizer,
and AgNO.sub.3, H.sub.2O.sub.2 or NaOH was used as a catalytic
agent. The second step included performing selective oxidizing and
removing processes by using a solution containing HF and
H.sub.2O.sub.2 to form second texture structures on the surface of
the substrate. The duration of the second-etching back process was
about 60 sec, and the etching process substantially removed 50-70
nm of the doping region of the substrate. The etched substrate had
high sheet resistance (i.e. lower doping concentration) and the
unetched substrate surface had low sheet resistance (i.e. higher
doping concentration) on surfaces thereof,. Therefore, selective
emitters can be formed. Next, the patterned barrier was removed.
Next, a PECVD process was performed to form a silicon nitride
layer, which acted as a passivated and anti-reflective layer. A
screen printing process was performed to form a silver electrode at
the front side of the substrate. Thereafter, a co-firing step was
performed. Lastly, an edge isolating process was performed by laser
irradiation.
[0036] While the invention has been described by way of example and
in terms of the preferred embodiments, it is to be understood that
the invention is not limited to the disclosed embodiments. It is
intended to cover various modifications and similar arrangements
(as would be apparent to those skilled in the art). Therefore, the
scope of the appended claims should be accorded the broadest
interpretation so as to encompass all such modifications and
similar arrangements.
* * * * *